JP2024142796A - Optical Coherence Tomography Equipment - Google Patents

Abstract

To achieve adjustment of an optical coherence tomography (OCT) measurement condition on a spectrometer by simple configuration and control.SOLUTION: An OCT device generates interference light by superposing return light of measurement light projected onto a sample on reference light, and detects it by a spectrometer. The spectrometer separates input light into a plurality of wavelength components by a dispersion element, and detects the wavelength components separately by a photodetector. An image forming lens system including a movable lens moved by a lens moving mechanism is provided between the dispersion element and the photodetector. The OCT device changes the position of the movable lens by controlling the lens moving mechanism on the basis of the output from the photodetector.SELECTED DRAWING: Figure 2

Description

This disclosure relates to an optical coherence tomography device.

Optical coherence tomography (OCT) is a technology that uses the coherence of light to image the inside of a sample with micrometer-level resolution, and has been put to practical use in a variety of fields, including medical imaging and non-destructive testing (see, for example, Patent Document 1).

The OCT technology described in Patent Document 1 aims to achieve both high-speed measurement and an expanded measurement range (depth range) in the depth direction, and is configured to change the depth range by moving the variable magnification lens in the spectrometer in the optical axis direction to change the focal length, and also by moving the cylindrical lens and light-receiving element (photodetector) in the optical axis direction. Therefore, in order to put this technology into practical use, a complex and large-scale driving mechanism and complex and precise synchronous driving control are required. Note that when the optical elements (variable magnification lens, cylindrical lens, photodetector) are moved to change the depth range, conditions other than the depth range also change, which may adversely affect the OCT measurement. However, the technology described in Patent Document 1 cannot solve this problem.

JP 2006-101927 A

One objective of this disclosure is to achieve adjustment of OCT measurement conditions for a spectrometer with a simple configuration and control.

The optical coherence tomography device according to the embodiment is configured to generate interference light by superimposing return light of measurement light projected onto a sample on a reference light, and detect the generated interference light with a spectroscope. The spectroscope includes a dispersive element, a photodetector, and an imaging lens system. The dispersive element separates the input light into a plurality of wavelength components. The photodetector separately detects the plurality of wavelength components generated from the incident light by the dispersive element. The imaging lens system is composed of a plurality of lenses arranged between the dispersive element and the photodetector. At least one of the plurality of lenses of the imaging lens system is a movable lens. The optical coherence tomography device according to the embodiment includes a lens movement mechanism and a first control unit. The lens movement mechanism is configured to move a movable lens of the imaging lens system. The first control unit is configured to control the lens movement mechanism based on an output from the photodetector.

According to the embodiment, it is possible to adjust the OCT measurement conditions for the spectrometer with a simple configuration and control.

1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 1 is a schematic diagram for explaining an example of processing executed by an optical coherence tomography apparatus (ophthalmic apparatus) according to an embodiment. 4 is a flowchart showing an example of an operation of the optical coherence tomography apparatus (ophthalmic apparatus) according to the embodiment.

Some non-limiting aspects of the embodiments of the present disclosure are described in detail below with reference to the drawings.

Any known technology may be combined with any aspect of the present disclosure. For example, any matter disclosed in the documents cited in this specification may be combined with any aspect of the present disclosure. In addition, any known technology in the technical field related to the present disclosure may be combined with any aspect of the present disclosure. For example, any technical matter disclosed by the applicant of the present application (matters disclosed in patent applications, papers, etc.) regarding technology related to the present disclosure or technology applicable to the technology may be incorporated in any aspect of the present disclosure.

Any two or more of the various aspects described in this disclosure may be combined, at least in part.

At least a portion of the functionality of the elements described in this disclosure is implemented using circuitry or processing circuitry. The circuitry or processing circuitry may be a general purpose processor, a special purpose processor, an integrated circuit, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), a Field Programmable Gate Array (FPGA), or a combination of a number of different devices configured and/or programmed to perform at least some of the disclosed functions. Array), conventional circuitry, and any combination thereof. A processor is considered to be a processing circuitry or circuitry, including transistors and/or other circuitry. In this disclosure, a circuitry, unit, means, or similar term is hardware that performs at least some of the disclosed functions or hardware that is programmed to perform at least some of the disclosed functions. The hardware may be hardware disclosed herein, or may be known hardware that is programmed and/or configured to perform at least some of the described functions. If the hardware is a processor that can be considered as a type of circuitry, the circuitry, unit, means, or similar term is a combination of hardware and software, and the software is used to configure the hardware and/or the processor.

Some aspects of the embodiments of the present disclosure are listed below. These are merely examples and are not intended to limit the embodiments of the present disclosure. In addition, any of the matters related to the present disclosure or any known technology can be combined with any of the aspects exemplified below.

As described above, the invention described in Cited Document 1 moves optical elements in a spectrometer to change the depth range of OCT measurement. This movement of optical elements may worsen conditions other than the depth range. For example, a change in the relative position between a lens (variable lens, cylindrical lens) and a photodetector may cause a decrease in the intensity of light incident on the photodetector or a shift in the projection position of light on the photodetector. The embodiments of the present disclosure provide several techniques for correcting measurement conditions that have deteriorated in this way, and in particular, achieve this with a simpler configuration and control than the invention described in Patent Document 1.

A first non-limiting aspect of the embodiment is configured to detect interference light generated by superimposing return light of measurement light projected onto a sample on a reference light with a spectroscope. The spectroscope includes a dispersive element that separates input light into a plurality of wavelength components, a photodetector that separately detects the plurality of wavelength components, and an imaging lens system consisting of a plurality of lenses arranged between the dispersive element and the photodetector. The optical coherence tomography device of this aspect includes a lens movement mechanism and a first control unit. The lens movement mechanism is configured to move a movable lens that is at least one of the plurality of lenses of the imaging lens system. The first control unit is configured to control the lens movement mechanism based on the output from the photodetector.

According to a first non-limiting aspect, measurement conditions other than the depth range (conditions that change the state of spectrum detection by the spectrometer) can be automatically adjusted by moving a movable lens in the spectrometer based on the output from the photodetector. In particular, automatic adjustment of measurement conditions can be achieved by a simple configuration and control of moving a movable lens.

The input light may be of any type as long as it is light input to the spectrometer. In some aspects, the input light may be light generated by a light source (see, for example, the fifth non-limiting aspect described below). In this case, the light from the light source can be guided to the spectrometer through the reference arm by disabling the sample arm of the OCT optical system. The sample arm is disabled, for example, by controlling an optical scanner provided in the sample arm or by placing a light-shielding member in the sample arm. In some other aspects, the input light may be interference light generated by superimposing the return light of the measurement light projected onto the test eye or the model eye on the reference light. In still other aspects, the input light may be light guided from an external light source for adjusting the measurement conditions.

A second non-limiting aspect of the embodiment is an optical coherence tomography device of the first non-limiting aspect, in which the first control unit is configured to control the lens movement mechanism based on the amount of light detected by the photodetector of the spectrometer.

According to a second non-limiting aspect, feedback control can be performed in which the amount of light detected by the photodetector of the spectrometer is used to control the movement of the movable lens. This makes it possible to automatically adjust (calibrate) the amount of light detected by the photodetector. For example, it is possible to automatically adjust the amount of light detected by the photodetector to maximize it.

It is anticipated that maximizing the amount of detected light may result in saturation of the amount of detected light, but typical optical coherence tomography devices are provided with a light amount adjustment component (attenuator) that can prevent saturation of the amount of detected light. If a light amount adjustment component is not provided or if saturation of the amount of detected light occurs, this embodiment can automatically adjust to "optimize" the amount of detected light by the photodetector.

A third non-limiting aspect of the embodiment is an optical coherence tomography device according to the first or second non-limiting aspect, in which the first control unit may be configured to control the lens movement mechanism to move the movable lens in a direction perpendicular to the optical axis of the movable lens.

According to a third non-limiting aspect, it is possible to provide one aspect of automatic adjustment of the spectral detection state by the spectrometer. More specifically, it is possible to automatically adjust the measurement conditions that change by moving the movable lens in a direction perpendicular to the optical axis of the movable lens.

A fourth non-limiting aspect of the embodiment is an optical coherence tomography device according to any one of the first to third non-limiting aspects, in which the photodetector of the spectroscope includes at least one light receiving element array consisting of a plurality of light receiving elements arranged in a line. Furthermore, the first control unit of this aspect may be configured to control the lens movement mechanism to move the movable lens in a direction (first direction) perpendicular to the arrangement direction of the plurality of light receiving elements that make up the light receiving element array.

According to the fourth non-limiting aspect, when the projection position of light on the photodetector is shifted in a first direction from the appropriate position, this shift can be automatically corrected. This makes it possible to cause a photodetector having one or more light receiving element rows to properly detect a spectrum. More specifically, when the projection position of light on the photodetector is shifted in the first direction from the appropriate position, part or all of the light to be detected by the spectrometer is projected to a position away from the light receiving elements, reducing the detection efficiency of the spectrometer, but it is possible to restore the detection efficiency of the spectrometer by using the fourth non-limiting aspect.

An invention for adjusting the projection position of light on a photodetector is disclosed in JP 2008-203246 A. This known invention is called Y-axis auto-adjustment, etc., and is configured to move the output end of an optical fiber that guides interference light to a spectrometer. The fourth non-limiting aspect can be adopted as an alternative to this Y-axis auto-adjustment.

The fourth non-limiting aspect differs from known Y-axis auto-adjustment at least in that the light projection position is adjusted using an element for changing the depth range.

The fourth non-limiting aspect is more advantageous than known Y-axis auto-adjustment at least in that the depth range and the light projection position are changed using a common element. In other words, according to the fourth non-limiting aspect, a function equivalent to Y-axis auto-adjustment can be added without adding dedicated hardware, so the device configuration does not become complicated or large-scale.

Some non-limiting aspects may include both a configuration for performing the function of the fourth non-limiting aspect and a configuration for performing known Y-axis auto-adjustment, and may be configured to perform these two functions alternatively and/or simultaneously.

The fourth non-limiting aspect of the photodetector may be, for example, a line sensor (single line sensor, one-dimensional sensor) having a single row of light receiving elements, a multi-line sensor having multiple rows of light receiving elements, or an area sensor (two-dimensional sensor) in which multiple light receiving elements are arranged vertically and horizontally.

A fifth non-limiting aspect of the embodiment is an optical coherence tomography device according to the fourth non-limiting aspect, in which the first control unit may be configured to control the lens movement mechanism to move the movable lens in a direction (first direction) perpendicular to the arrangement direction of the multiple light receiving elements that form the light receiving element row, based on information (intensity information) indicating the intensity of a spectrum obtained by detecting, with a spectrometer, the light output from a light source for generating the measurement light and the reference light.

According to the fifth non-limiting aspect, the light output from the light source can be used to actually obtain spectral intensity information by the photodetector of the spectrometer, and the movement of the movable lens can be controlled. Therefore, it is possible to adjust the position of the movable lens so that the spectral intensity detected by the photodetector becomes an appropriate value. More specifically, if the projection position of light on the photodetector is shifted in the first direction from the appropriate position, the detection efficiency of each light receiving element in the light receiving element row of the photodetector decreases, but by using the fifth non-limiting aspect, the detection efficiency of each light receiving element can be restored, and thus the detection efficiency of the spectrometer can be restored. The fifth non-limiting aspect provides one specific example of an alternative means for Y-axis auto adjustment.

A sixth non-limiting aspect of the embodiment is an optical coherence tomography device according to any one of the first to fifth non-limiting aspects, in which the photodetector of the spectrometer includes at least one light receiving element array consisting of a plurality of light receiving elements arranged in a line. This photodetector is similar to that of the fourth non-limiting aspect. Furthermore, the first control unit may be configured to control the lens movement mechanism to move the movable lens in a direction (second direction) parallel to the arrangement direction of the plurality of light receiving elements that make up the light receiving element array.

The second direction is a direction perpendicular to the first direction in the fourth and fifth non-limiting aspects. The first and second directions may be referred to as the Y and X directions, respectively. Note that the "direction perpendicular to the optical axis of the movable lens" in the third non-limiting aspect may be any direction defined by a two-dimensional coordinate system (XY coordinate system) spanned by the X and Y directions (in other words, a direction indicated by any vector expressed as a linear combination of a unit vector in the X direction and a unit vector in the Y direction). The direction perpendicular to the optical axis of the movable lens may be referred to as the XY direction.

According to the sixth non-limiting aspect, when the projection position of light on the photodetector is shifted in the second direction from the appropriate position, this shift can be automatically corrected. This makes it possible to allow a photodetector having one or more light receiving element rows to properly detect a spectrum. More specifically, when a photodetector having a light receiving element row is used, a specific spectral component (specific wavelength, specific frequency) is assigned in advance to each light receiving element of the light receiving element row, thereby generating a spectral intensity distribution (intensity information). If the projection position of light on the photodetector is shifted in the second direction from the appropriate position, each light receiving element detects a spectral component other than the pre-assigned spectral component. This generates an inaccurate spectral intensity distribution that is shifted in the wavelength direction. By using the sixth non-limiting aspect, it is possible to eliminate such a shift in the wavelength direction of the spectral intensity distribution.

A seventh non-limiting aspect of the embodiment is an optical coherence tomography device according to the sixth non-limiting aspect, in which the first control unit may be configured to control the lens movement mechanism to move the movable lens in a direction (second direction) parallel to the arrangement direction of the multiple light receiving elements that form the light receiving element array, based on information (position information) indicating the position of the spectrum obtained by detecting the light output from the light source for generating the measurement light and the reference light using a spectrometer.

According to the seventh non-limiting aspect, the movement of the movable lens can be controlled by actually acquiring spectral position information using the light output from the light source by the photodetector of the spectroscope, so that the position of the movable lens can be adjusted so that each light receiving element of the photodetector detects the appropriate spectral component (appropriate wavelength). In addition, the seventh non-limiting aspect has the advantage that it is not necessary to provide dedicated hardware for causing each light receiving element of the photodetector to detect the appropriate spectral component.

An eighth non-limiting aspect of the embodiment is an optical coherence tomography device according to any one of the first to seventh non-limiting aspects, in which the first control unit may be configured to control the lens movement mechanism to move the movable lens in a direction parallel to the optical axis of the movable lens (third direction). The third direction is a direction perpendicular to both the first direction (Y direction) in the fourth and fifth non-limiting aspects and the second direction (X direction) in the sixth and seventh non-limiting aspects. The third direction may be referred to as the Z direction.

According to the eighth non-limiting aspect, when the imaging position (focal position) of light is misaligned with respect to the photodetector (light receiving element), this misalignment can be automatically corrected. This makes it possible to recover the decrease in detection efficiency of the spectrometer caused by the misalignment of the imaging position of the light. To explain more specifically, if the imaging state of the light projected onto the photodetector is poor and the imaging position of this light is misaligned from the position of the light receiving element, some of the light that should be detected by the light receiving element will not be detected, and as a result, the detection efficiency of the spectrometer will decrease. By using the eighth non-limiting aspect, the imaging state of the light projected onto the photodetector can be corrected, making it possible to eliminate the decrease in detection efficiency caused by the misalignment of the imaging position.

A ninth non-limiting aspect of the embodiment is the optical coherence tomography device of the eighth non-limiting aspect, in which the first control unit may be configured to control the lens movement mechanism to move the movable lens in a direction parallel to the optical axis of the movable lens (third direction) based on spectral intensity information obtained by detecting light output from a light source for generating the measurement light and the reference light using a spectrometer.

According to a ninth non-limiting aspect, the movement of the movable lens can be controlled by actually acquiring spectral intensity information using the light output from the light source with the photodetector of the spectroscope, so that the position of the movable lens can be adjusted so that the spectral intensity detected by the photodetector becomes an appropriate value.

The fifth non-limiting aspect and the ninth non-limiting aspect are common in that they recover the reduction in the spectral intensity obtained by the spectroscope by performing a spectral intensity measurement using light from a light source, but they differ from each other in terms of the cause of the reduction in the spectral intensity. That is, the fifth non-limiting aspect recovers the reduction in the spectral intensity caused by the misalignment of the light projected onto the photodetector, while the ninth non-limiting aspect recovers the reduction in the spectral intensity caused by the poor imaging state of the light projected onto the photodetector. Therefore, by combining the fifth non-limiting aspect and the ninth non-limiting aspect, the spectral intensity can be corrected more appropriately than when either of them is applied alone. Similarly, it is also possible to combine the fourth non-limiting aspect and the eighth non-limiting aspect.

More generally, the fourth or fifth non-limiting aspect may be combined with the sixth or seventh non-limiting aspect, the fourth or fifth non-limiting aspect may be combined with the eighth or ninth non-limiting aspect, the sixth or seventh non-limiting aspect may be combined with the eighth or ninth non-limiting aspect, or the fourth or fifth non-limiting aspect may be combined with the sixth or seventh non-limiting aspect and the eighth or ninth non-limiting aspect. Also, the fourth or fifth non-limiting aspect, the sixth or seventh non-limiting aspect, the eighth or ninth non-limiting aspect, and any combination of two or more of these may be combined with the third non-limiting aspect.

A tenth non-limiting aspect of the embodiment is an optical coherence tomography device according to any one of the first to ninth non-limiting aspects, in which the imaging lens system may include a first lens group consisting of one or more lenses arranged between the dispersion element and the photodetector, and a second lens group consisting of one or more lenses that are inserted and removed between the dispersion element and the photodetector. Furthermore, the focal position of the imaging lens system when the second lens group is inserted (placed) in the optical path between the dispersion element and the photodetector may be the same as the focal position of the imaging lens system when the second lens group is retracted from the optical path (when the second lens group is not placed in the optical path). In addition, the focal length of the imaging lens system when the second lens group is inserted (placed) in the optical path may be different from the focal length of the imaging lens system when the second lens group is retracted from the optical path (when the second lens group is not placed in the optical path). The second lens group that can be added to the spectrometer optical system may be called an additional lens group, lens unit, etc. Also, each lens included in the second lens group may be called an additional lens.

According to a tenth non-limiting aspect, the second lens group, which is designed and configured to change the focal length of the spectrometer optical system without changing the focal position of the spectrometer optical system, can be inserted and removed from the optical path between the dispersive element of the spectrometer and the photodetector, so that the depth range can be changed without moving the photodetector. This makes it possible to change the depth range of the OCT measurement without using a complex and large-scale driving mechanism or complex and precise synchronous driving control.

An eleventh non-limiting aspect of the embodiment is the optical coherence tomography device of the tenth non-limiting aspect, in which the movable lens may include one or more lenses in a second lens group that is removably inserted into the optical path between the dispersive element and the photodetector. That is, one or more additional lenses may be used as the movable lens.

According to an eleventh non-limiting aspect, it is possible to correct and/or compensate for misalignment of the second lens group inserted between the dispersion element and the photodetector. This misalignment is an error (deviation) of the actual insertion position from the designed insertion position of the spectrometer optical system. In the eleventh non-limiting aspect, by moving the additional lens used as a movable lens, the misalignment of this additional lens can be corrected and/or the misalignment of another additional lens can be compensated for.

A twelfth non-limiting aspect of the embodiment is the optical coherence tomography device of the tenth non-limiting aspect, in which the second lens group may include two or more lenses.

By reducing the number of lenses included in the second lens group, the overall dimensions of the second lens group can be reduced, the distance between the second lens group and the photodetector can be increased, and the movement distance of the second lens group can be shortened. This makes it possible to reduce the scattering and flying of dust that occurs when the second lens group is inserted into the optical path or removed from the optical path, and to reduce the inconvenience caused by this. For example, it is possible to reduce the risk of dust adhering to the detection surface of the photodetector. The inventors' research has revealed that the second lens group that satisfies the condition related to the tenth non-limiting aspect (i.e., the focal position of the imaging lens system is equal and the focal length is different when the second lens group is used and when it is not used) includes at least two lenses as in the twelfth non-limiting aspect. The second lens group may include a lens (e.g., a cemented lens) in which two or more lenses are integrally formed.

A thirteenth non-limiting aspect of the embodiment is the optical coherence tomography device of the twelfth non-limiting aspect, in which the movable lens may be a part of two or more lenses in the second lens group. In other words, when the second lens group includes N lenses (N is an integer equal to or greater than 2), in this aspect, at most N-1 lenses out of these N lenses are used as movable lenses.

According to the thirteenth non-limiting aspect, the driving force required to move the movable lens is smaller than when all of the lenses in the second lens group are moved, thereby reducing the labor required to move the movable lens.

A fourteenth non-limiting aspect of the embodiment is the optical coherence tomography device of the twelfth non-limiting aspect, in which the movable lenses may be all of the two or more lenses in the second lens group. In other words, when the second lens group includes N lenses (N is an integer equal to or greater than 2), in this aspect, all of these N lenses are used as movable lenses.

According to the fourteenth non-limiting aspect, the mechanism for inserting and removing the second lens group into and from the optical path and the mechanism for moving the movable lens (the second lens group itself) (lens movement mechanism) can be made common, which makes it possible to simplify the device configuration.

Here, we will explain some non-limiting points (features, variations, etc.) related to the tenth to fourteenth non-limiting aspects.

The optical coherence tomography device according to the first non-limiting item of the tenth to fourteenth non-limiting aspects includes a lens unit (second lens group) and a mechanism. The lens unit is designed and configured to change the focal length of the spectrometer optical system without changing the focal position of the spectrometer optical system. The mechanism is configured to insert and remove the lens unit between the dispersion element and the photodetector.

In other words, the lens unit is designed and constructed to satisfy the following two conditions (1) and (2).

Condition (1): The focal length (composite focal length) of the optical system (composite optical system) combining the lens unit and the imaging lens is different from the focal length of the imaging lens alone.

Condition (2): The focal position (composite focal position) of the composite optical system of the lens unit and the imaging lens is equal to the focal position of the imaging lens alone. In other words, the focal position of the spectrometer optical system in a state where the lens unit is disposed between the dispersion element and the photodetector coincides with the focal position of the spectrometer optical system in a state where the lens unit is not disposed between the dispersion element and the photodetector. In further other words, the focal position of the spectrometer optical system does not change even when the lens unit is inserted into the optical path between the dispersion element and the photodetector, and the focal position of the spectrometer optical system does not change even when the lens unit is moved out of the optical path between the dispersion element and the photodetector.

According to this first non-limiting feature, a lens unit designed and configured to change the focal length of the spectrometer optical system without changing the focal position of the spectrometer optical system is configured to be insertable and detachable between the dispersive element of the spectrometer and the photodetector, so that it is possible to change the depth range without moving the photodetector. Therefore, it is possible to achieve an advantageous effect that cannot be achieved with conventional technology, that is, the depth range of optical coherence tomography can be changed without using a complex and large-scale driving mechanism or complex and precise synchronous driving control.

The optical coherence tomography device according to the second non-limiting item of the tenth to fourteenth non-limiting aspects has, in addition to the first non-limiting item, that the lens unit includes at least two lenses. Here, the lens unit may include a lens in which two or more lenses are integrally formed (e.g., a cemented lens).

By reducing the number of lenses included in the lens unit, it is possible to reduce the dimensions of the lens unit, increase the distance between the lens unit and the photodetector, and shorten the distance the lens unit moves by the mechanism, which makes it possible to reduce the scattering and flying of dust caused by the movement of the lens unit and to reduce the inconvenience caused by this. As a specific example, it becomes possible to reduce the risk of dust adhering to the detection surface of the photodetector.

The optical coherence tomography device according to the third non-limiting item of the tenth to fourteenth non-limiting aspects has, in addition to the second non-limiting item, at least two lenses included in the lens unit are configured to be inserted between the imaging lens and the photodetector by a mechanism.

According to the third non-limiting aspect, one example of the insertion position of the lens unit into the spectrometer can be provided. Some effects that can be achieved based on the third non-limiting aspect will be described later.

The optical coherence tomography device according to the fourth non-limiting item of the tenth to fourteenth non-limiting aspects includes, in addition to the third non-limiting item, at least two lenses included in the lens unit include a first convex lens and a concave lens disposed between the first convex lens and the photodetector.

According to the fourth non-limiting item, the light passing through the imaging lens passes through a convex lens and a concave lens in this order to be guided to the photodetector, so the dimensions of the lens unit can be made smaller than when the light passes through a concave lens and a convex lens in this order. In fact, in a configuration in which the light passing through the imaging lens passes through a concave lens and a convex lens in this order to be guided to the photodetector, contrary to the fourth non-limiting item, a convex lens with a large diameter must be provided to allow the light passing through the concave lens to enter the photodetector, resulting in a large dimension of the lens unit. In addition, an optical system configured so that the light passing through the imaging lens passes through two convex lenses to be guided to the photodetector is also conceivable, but the distance between the two convex lenses is larger than the distance between the convex lens and the concave lens in the fourth non-limiting item, so the dimensions of the lens unit are also large.

The optical coherence tomography device according to the fifth non-limiting item of the tenth to fourteenth non-limiting aspects includes, in addition to the fourth non-limiting item, that the lens unit further includes a second convex lens. The second convex lens is disposed between the concave lens and the photodetector, and is designed and configured to reduce the angle of incidence of the multiple wavelength components on the photodetector.

According to the fifth non-limiting feature, the angle of incidence on the photodetector can be reduced (i.e., light can be projected from a direction close to perpendicular to the detection surface of the photodetector), thereby improving the light receiving efficiency of the spectrometer. For example, the light receiving efficiency of the spectrometer can be optimized by designing and configuring the lens unit so that it is telecentric with respect to the photodetector.

The optical coherence tomography device according to the sixth non-limiting item related to the tenth to fourteenth non-limiting aspects is designed and configured such that, in addition to the third to fifth non-limiting items, the focal length f1 of the imaging lens, the focal length f2 of the lens unit, the distance d1 between the rear principal point of the imaging lens and the front principal point of the lens unit, the distance d2 between the rear principal point of the lens unit and the photodetector, and the combined focal length f of the imaging lens and the lens unit satisfy the following two equations: d1=f1+f2-f1×f2/f, and f=d2+f×d1/f1.

According to the sixth non-limiting item, when at least two lenses included in the lens unit are inserted between the imaging lens and the photodetector, it is possible to provide one specific conditional formula for the lens unit to satisfy the above-mentioned conditions (1) and (2). Note that the specific conditional formula related to the sixth non-limiting item is one example, and is not limited to this.

The optical coherence tomography device according to the seventh non-limiting item of the tenth to fourteenth non-limiting aspects has, in addition to the second non-limiting item, at least two lenses included in the lens unit are configured to be inserted between the dispersive element and the imaging lens by a mechanism.

According to the seventh non-limiting feature, it is possible to provide one example of the position at which the lens unit can be inserted into the spectrometer. In addition, according to the seventh non-limiting feature, it is possible to position the lens unit and mechanism away from the photodetector, which makes it possible to reduce the scattering and flying of dust caused by the movement of the lens unit, and thus to reduce the inconvenience caused thereby. As a specific example, it is possible to reduce the risk of dust adhering to the detection surface of the photodetector.

An optical coherence tomography device according to an eighth non-limiting feature of the tenth to fourteenth non-limiting aspects has, in addition to the seventh non-limiting feature, at least two lenses included in the lens unit include a convex lens and a concave lens disposed between the convex lens and the imaging lens.

According to the eighth non-limiting item, the light that has passed through the dispersion element (for example, transmitted or reflected) passes through the convex lens and the concave lens in this order and is guided to the imaging lens, so the size of the lens unit can be made smaller than when the light passes through the concave lens and the convex lens in this order. In fact, in a configuration in which the light that has passed through the dispersion element passes through the concave lens and the convex lens in this order and is guided to the imaging lens, contrary to the eighth non-limiting item, a convex lens with a large diameter must be provided to allow the light that has passed through the concave lens to enter the imaging lens, resulting in a large size of the lens unit. In addition, in a configuration opposite to the eighth non-limiting item, it is possible to provide a large diameter imaging lens instead of a large diameter convex lens, but this would result in another problem of the size of the spectroscope becoming large. In this way, according to the eighth non-limiting item, it is possible to compact both the spectroscope and the lens unit. It is also possible to consider an optical system in which light passing through a dispersion element passes through two convex lenses and is directed to an imaging lens; however, the distance between the two convex lenses would be greater than the distance between the convex and concave lenses in the eighth non-limiting item, so the dimensions of the lens unit would still be large.

The optical coherence tomography device according to the ninth non-limiting item related to the tenth to fourteenth non-limiting aspects has, in addition to the seventh or eighth non-limiting item, at least two lenses designed and configured as an afocal system.

In addition, in the ninth non-limiting aspect, the light immediately after passing through the dispersive element is parallel light, and when the lens unit is not disposed in the optical path of the spectrometer optical system, the imaging lens converts the parallel light into convergent light.

According to the ninth non-limiting feature, since parallel light that has passed through the dispersion element enters the lens unit and is emitted from the lens unit, it is possible to switch the depth range simply by inserting and removing the lens unit into the optical path of the spectrometer optical system. In other words, it is possible to switch the depth range without performing operations other than inserting and removing the lens unit, such as moving the photodetector or controlling the imaging lens (e.g., moving the imaging lens, inserting and removing at least one lens included in the imaging lens, etc.). In addition, it is possible to reduce deterioration of the optical performance of the spectrometer caused by decentering or tilting (tilting) of the lens unit.

The optical coherence tomography device according to the tenth non-limiting item of the tenth to fourteenth non-limiting aspects is designed and configured such that, in addition to the ninth non-limiting item, the focal length f1 of the imaging lens, the focal length fa on the dispersive element side of the lens unit and the focal length fb on the imaging lens side, and the combined focal length f of the imaging lens and the lens unit satisfy the following formula: f = (fa/|fb|) x f1.

Here, the absolute value of the focal length fb on the imaging lens side of the lens unit means that either a convex lens or a concave lens can be used arbitrarily. In the case of a convex lens, the above formula becomes: f = (fa/fb) x f1. On the other hand, in the case of a concave lens, the above formula becomes: f = [fa/(-fb)] x f1.

According to the tenth non-limiting item, when at least two lenses included in the lens unit are inserted between the dispersion element and the imaging lens, it is possible to provide one specific conditional formula for the lens unit to satisfy the above-mentioned conditions (1) and (2). Note that the specific conditional formula related to the tenth non-limiting item is one example, and is not limited thereto.

In some embodiments of the present disclosure, a configuration may be adopted that at least partially combines any of the third to sixth non-limiting items with any of the seventh to tenth non-limiting items.

For example, in one embodiment combining the third non-limiting feature and the seventh non-limiting feature, the lens unit includes a first lens group including one or more lenses and a second lens group including another one or more lenses, the first lens group being configured to be inserted between the imaging lens and the photodetector by a mechanism, and the second lens group being configured to be inserted between the dispersion element and the imaging lens by a mechanism. According to such an embodiment, the third non-limiting feature and the seventh non-limiting feature can be selectively applied, and these advantageous effects can be selectively provided. In addition, this embodiment can be combined with any of the fourth to sixth non-limiting features, any of the eighth to tenth non-limiting features, any feature related to the present disclosure, any known technology, etc.

Another embodiment combining the third non-limiting feature and the seventh non-limiting feature is configured to selectively insert at least two lenses included in the lens unit between the imaging lens and the photodetector and between the dispersion element and the imaging lens by a mechanism. With such an embodiment, the third non-limiting feature and the seventh non-limiting feature can also be selectively applied, and these advantageous effects can be selectively provided. In addition, this embodiment can be combined with any of the fourth to sixth non-limiting features, any of the eighth to tenth non-limiting features, any feature related to the present disclosure, any known technology, etc.

An optical coherence tomography device according to an eleventh non-limiting item related to the tenth to fourteenth non-limiting aspects is designed and configured such that, in addition to the first to tenth non-limiting items, the quotient β obtained by dividing the combined focal length of the imaging lens and the lens unit by the focal length of the imaging lens satisfies 1<β≦5.

According to the eleventh non-limiting item, one quantitative condition for achieving the advantageous effect of the embodiment can be provided. Since the depth range and the resolution are in a trade-off relationship with each other, the effectiveness of the embodiment can be evaluated from the viewpoints of both of them.

The optical coherence tomography device according to the twelfth non-limiting item related to the tenth to fourteenth non-limiting aspects is designed and configured such that, in addition to the eleventh non-limiting item, the quotient β obtained by dividing the combined focal length of the imaging lens and the lens unit by the focal length of the imaging lens satisfies 1.5≦β≦3.

According to the twelfth non-limiting item, a more preferable quantitative condition can be provided for achieving the advantageous effects of the embodiment.

As an alternative to the tenth to fourteenth non-limiting aspects (and the variations thereof described above), the fifteenth non-limiting aspect, the sixteenth non-limiting aspect, or the seventeenth non-limiting aspect described below may be adopted.

A fifteenth non-limiting aspect of the embodiment is an optical coherence tomography device according to any one of the first to ninth non-limiting aspects, in which the imaging lens system may include a zoom lens with a variable focal length.

A sixteenth non-limiting aspect of the embodiment is an optical coherence tomography device according to the fifteenth non-limiting aspect, which may further include a photodetector moving mechanism that moves the photodetector, and a second control unit that controls the coordination between the zoom lens and the photodetector moving mechanism.

The fifteenth and sixteenth non-limiting aspects have disadvantages compared to the tenth to fourteenth non-limiting aspects, such as the need to provide additional hardware (zoom lens, photodetector movement mechanism, etc.) and the need to control the movement of the photodetector. However, it is possible to change the depth range of the OCT measurement using a configuration different from the tenth to fourteenth non-limiting aspects.

It is possible to at least partially combine the configuration according to any one of the tenth to fourteenth non-limiting aspects with the configuration according to the fifteenth or sixteenth non-limiting aspect. In addition, it is possible to control these two configurations to operate selectively or in conjunction with each other.

A seventeenth non-limiting aspect of the embodiment is an optical coherence tomography device according to any one of the first to sixteenth non-limiting aspects, in which the imaging lens system may include a liquid lens with a variable focal length. The liquid lens may be, for example, but is not limited to, a known liquid lens that utilizes electrowetting technology that changes wettability by applying an electric field to a surface.

In the seventeenth non-limiting aspect, although extremely precise control is required to operate the liquid lens, it also has some advantages, such as being able to miniaturize the second lens group and reducing the scattering and flying of dust.

It is possible to at least partially combine the configuration according to any one of the non-limiting aspects of the tenth to sixteenth embodiments with the configuration according to the non-limiting aspect of the seventeenth embodiment. In addition, it is possible to control these two configurations to operate selectively or in conjunction with each other.

Explanatory embodiments according to the present disclosure will be described. In the following embodiments, spectral domain OCT will be described. Spectral domain OCT is an imaging technology in which light from a low-coherence light source (broadband light source) is split into measurement light and reference light, return light of the measurement light from the sample is superimposed on the reference light to generate interference light, the spectral intensity distribution of this interference light is detected by a spectrometer, and an image is constructed by performing signal processing such as Fourier transform on the detected spectral intensity distribution.

Figure 1A shows an example of the configuration of an ophthalmic device that functions as an optical coherence tomography device according to one embodiment. The ophthalmic device 1 performs imaging of a living eye, and is a multi-modality device that combines an optical coherence tomography device and a fundus camera.

The ophthalmic apparatus 1 as an optical coherence tomography device optically collects data of the subject eye E by applying an OCT scan to the subject eye E. The ophthalmic apparatus 1 collects OCT data (interference signals) by scanning a target area of the subject eye E (e.g., the fundus, the anterior segment, etc.). The ophthalmic apparatus 1 can generate an image of the target area (OCT image) based on the collected OCT data.

Types of OCT images include cross-sectional images (section images), three-dimensional images, frontal images, and functional images. Cross-sectional images include B-scan images. Three-dimensional images include stack data and volume data (voxel data). Frontal images include C-scan images, en-face images, shadowgrams, and projection images. Functional images include motion contrast images (OCT angiography images), hemodynamic images, phase images, and elastography images (OCT elastography images).

The ophthalmic device 1 as a fundus camera photographs the subject's eye E to generate a digital photograph. A digital photograph generated by photographing the fundus Ef is called a fundus image, and a digital photograph generated by photographing the anterior segment is called an anterior segment image. Fundus images include a fundus photograph, which is a still image, and a fundus observation image, which is a moving image. Anterior segment images include an anterior segment photograph, which is a still image, and an anterior segment observation image, which is a moving image.

In another embodiment, instead of a fundus camera, an ophthalmic modality such as a scanning laser ophthalmoscope (SLO), a slit lamp microscope, or a surgical microscope may be provided. Yet another embodiment may be a single modality device (optical coherence tomography device) rather than a multi-modality device. Yet another embodiment may be an ophthalmic device that combines an optical coherence tomography device with a device that measures the optical characteristics of a living eye (ophthalmic measurement device). Ophthalmic measurement devices include a refractometer, a keratometer, a tonometer, a wavefront analyzer, a specular microscope, a perimeter, and the like. Yet another embodiment may be an ophthalmic device that combines an optical coherence tomography device with a device used to treat a living eye (ophthalmic treatment device). Ophthalmic treatment devices include a laser treatment device, a cataract surgery device, a vitreous surgery device, and the like.

As shown in FIG. 1A, the ophthalmologic apparatus 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic and control unit 200. The fundus camera unit 2 includes elements for generating digital photographs of a living eye. The OCT unit 100 includes elements for performing an OCT scan. The arithmetic and control unit 200 includes elements for performing various types of processing. The processing performed by the arithmetic and control unit 200 includes calculation, control, image processing, analysis processing, etc.

The fundus camera unit 2 shown in FIG. 1A is provided with an optical system for acquiring a two-dimensional image (fundus image) showing the surface morphology of the fundus Ef of the subject's eye E. The fundus observation image is, for example, a monochrome moving image generated by video shooting using near-infrared light as illumination light. The fundus photograph is, for example, a color image generated by still image shooting using flashed visible light as illumination light, or a monochrome still image generated by still image shooting using flashed near-infrared light or visible light as illumination light. The fundus camera unit 2 may be capable of generating other types of images than the images exemplified here. Such images include fluorescein fluorescence angiography images (FA images), indocyanine green fluorescence angiography images (ICGA images), and spontaneous fluorescence angiography images.

The fundus camera unit 2 is provided with a chin rest and a forehead rest to support the subject's face. The fundus camera unit 2 is further provided with an illumination optical system 10 and a photographing optical system 30. The illumination optical system 10 projects illumination light onto the subject's eye E. The photographing optical system 30 guides the return light of the illumination light projected onto the subject's eye E to the image sensor 35 or the image sensor 38. The image sensors 35 and 38 may be CCD image sensors or CMOS image sensors. The photographing optical system 30 also guides the measurement light incident on the fundus camera unit 2 from the OCT unit 100 to the subject's eye E, and guides the return light of the measurement light from the subject's eye E to the OCT unit 100.

The observation light source 11 of the illumination optical system 10 may be, for example, a halogen lamp or a light-emitting diode (LED). The light (observation illumination light) output from the observation light source 11 is reflected by a reflecting mirror 12 having a curved reflecting surface, passes through a condenser lens 13, and the near-infrared component is extracted by a visible cut filter 14. The observation illumination light consisting of the near-infrared component is once focused near the imaging light source 15, reflected by a mirror 16, passes through a relay lens 17, a relay lens 18, an aperture 19, and a relay lens 20, is reflected by a hole mirror 21 (a mirror around the hole), passes through a dichroic mirror 46, is refracted by an objective lens 22, and is projected onto the subject's eye E. The return light of the observation illumination light is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through a hole formed in the central region of the hole mirror 21, passes through the dichroic mirror 55, passes through the focusing lens 31, is reflected by the mirror 32, passes through the half mirror 33A, is reflected by the dichroic mirror 33, and is imaged on the light receiving surface of the image sensor 35 by the imaging lens 34. The image sensor 35 detects the return light, for example, at a predetermined frame rate. The display device 3 displays an image based on the output from the image sensor 35 (for example, an anterior eye observation image or a fundus observation image).

The imaging light source 15 may be, for example, a xenon lamp or an LED. Light output from the imaging light source 15 (imaging illumination light) is projected onto the subject's eye E through the same path as the observation illumination light. The return light of the imaging illumination light is guided to the dichroic mirror 33 through the same path as the return light of the observation illumination light, passes through the dichroic mirror 33, is reflected by the mirror 36, and is imaged on the light receiving surface of the image sensor 38 by the imaging lens 37. An image based on the output from the image sensor 38 (for example, an anterior segment photograph or a fundus photograph) is displayed on the display device 3.

The liquid crystal display (LCD) 39 displays information presented to the subject's eye E. This information includes a fixation target, visual acuity measuring index, etc. The light output from the LCD 39 (part of it) is reflected by the half mirror 33A, reflected by the mirror 32, passes through the focusing lens 31 and the dichroic mirror 55, passes through the hole in the hole mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus Ef. The direction of fixation (fixation position) can be changed by changing the display position of the fixation target.

The fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60. The alignment optical system 50 generates an index (alignment index) for positioning (aligning) the device optical system with respect to the subject's eye E. The focus optical system 60 generates an index (split index) for focusing on the subject's eye E.

The light (alignment light) output from the LED 51 of the alignment optical system 50 passes through the aperture 52, the aperture 53, and the relay lens 54, is reflected by the dichroic mirror 55, passes through the hole of the hole mirror 21, transmits the dichroic mirror 46, and is projected onto the subject's eye E by the objective lens 22. The return light of the alignment light (for example, corneal reflected light or fundus reflected light) passes through the objective lens 22, the dichroic mirror 46, and the hole of the hole mirror 21, transmits the dichroic mirror 55, passes through the focusing lens 31, is reflected by the mirror 32, transmits the half mirror 33A, is reflected by the dichroic mirror 33, and is imaged on the light receiving surface of the image sensor 35 by the imaging lens 34. The light receiving image (alignment index) by the image sensor 35 is displayed on the display device 3 together with the observation image. Manual alignment and/or auto alignment can be performed using the alignment index.

When performing focus adjustment, the reflecting surface of the reflecting rod 67 is obliquely installed on the optical path of the illumination optical system 10. The light (focusing light) output from the LED 61 of the focus optical system 60 passes through the relay lens 62, is split into two beams by the split index plate 63, passes through the two-hole diaphragm 64, is reflected by the mirror 65, is imaged once on the reflecting surface of the reflecting rod 67 by the condenser lens 66, is reflected, passes through the relay lens 20, is reflected by the hole mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E. The return light of the focus light (for example, corneal reflected light or fundus reflected light) is guided to the image sensor 35 through the same path as the return light of the alignment light and is detected. The received light image (split index) by the image sensor 35 is displayed on the display device 3 together with the observation image. Manual focusing and/or autofocusing can be performed using the split index.

The dichroic mirror 46 combines the optical path for digital photography and the optical path for OCT (sample arm). The dichroic mirror 46 reflects light in the wavelength band used for OCT scanning and transmits light in the wavelength band used for digital photography. The sample arm is provided with, in order from the OCT unit 100 side, a collimator lens unit 40, an optical path length changer 41, an optical scanner 42, a focusing lens 43, a mirror 44, and a relay lens 45. The focusing lens 43 is movable in a direction along the optical axis of the sample arm.

The optical path length changing unit 41 is configured to be movable in the direction of the arrow shown in FIG. 1A, thereby changing the length (optical path length) of the sample arm. Changing the optical path length of the sample arm is used for correcting the optical path length according to the axial length of the subject's eye E, adjusting the interference state, and so on. The optical path length changing unit 41 includes, for example, a corner cube and a mechanism for moving it.

The optical scanner 42 is aligned to be positioned optically conjugate with the pupil of the subject's eye E. The optical scanner 42 deflects the measurement light passing through the sample arm. By changing the direction in which the measurement light is deflected, scanning of the subject's eye E using the measurement light is achieved. The optical scanner 42 includes, for example, a galvanometer mirror that deflects the measurement light in the x direction (horizontal direction) and a galvanometer mirror that deflects the measurement light in the y direction (vertical direction). Such an optical scanner 42 makes it possible to deflect the measurement light in any direction on the xy plane.

One embodiment of the OCT unit 100 is shown in FIG. 1B. The OCT unit 100 is provided with elements (optical system, mechanism, etc.) for applying an OCT scan to the subject's eye E. The OCT unit 100 of this embodiment includes elements 101 to 115 similar to those of a known spectral domain type optical coherence tomography device, as well as elements unique to this embodiment (lens unit 120, lens unit moving mechanism 130, lens moving mechanism 140, etc.). Note that the interferometer included in the OCT unit 100 of this embodiment is a Michelson type, but another type of interferometer (e.g., a Mach-Zehnder type interferometer) may also be used.

To perform spectral domain OCT, the OCT unit 100 is configured to split light (low coherence light) emitted by a broadband light source (low coherence light source) into reference light LR and measurement light LS, provide the measurement light LS to the fundus camera unit 2, receive from the fundus camera unit 2 the return light of the measurement light LS projected onto the subject's eye E, superimpose the return light of the measurement light LS and the reference light LS that has passed through the reference light path (reference arm) to generate interference light LC, and detect the spectral intensity distribution of the interference light LC. The result of detecting the spectral intensity distribution of the interference light LC (detection signal, interference signal) is sent to the arithmetic and control unit 200.

The light source unit 101 outputs a wideband low-coherence light L0. The low-coherence light L0 includes, for example, a wavelength band in the near-infrared region (approximately 800 nm to 900 nm) and has a temporal coherence length of approximately several tens of micrometers. Note that a wavelength band that is not visible to the human eye, for example, near-infrared light having a central wavelength of approximately 1040 to 1060 nm, may be used as the low-coherence light L0. The light source unit 101 includes any light output device, for example, any of a superluminescent diode (SLD), an LED, and a semiconductor optical amplifier (SOA).

The low-coherence light L0 output from the light source unit 101 is guided by the optical fiber 102 to the fiber coupler 103, where it is split into the measurement light LS and the reference light LR.

The reference light LR generated by the fiber coupler 103 is guided through the optical fiber 104 to the attenuator 105 where the light amount is adjusted, and is then guided through the optical fiber 104 to the polarization controller 106 where the polarization state is adjusted and then guided to the fiber coupler 109.

The measurement light LS generated by the fiber coupler 103 is guided to the collimating lens unit 40 through the optical fiber 107 and emitted as parallel light, and is guided to the dichroic mirror 46 via the optical path length change unit 41, the optical scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45, where it is reflected, refracted by the objective lens 22, and projected onto the subject's eye E. The measurement light LS is scattered and reflected at various depth positions in the subject's eye E (particularly the fundus Ef), generating backscattered light. The return light of the measurement light LS from the subject's eye E travels in the opposite direction along the same path as the outward path and is guided to the fiber coupler 103, and is guided to the fiber coupler 109 via the optical fiber 108.

The fiber coupler 109 generates interference light LC by superimposing the return light of the measurement light LS and the reference light LR that has passed through the reference arm. The interference light LC is emitted from the output end 111 of the optical fiber 110 and converted into parallel light by the collimating lens 112. The interference light LC converted into parallel light enters the spectroscope. That is, the interference light LC converted into parallel light is dispersed (spectrally resolved) by the dispersive element 113 and converted from parallel light to convergent light by the imaging lens 114. The interference light LC that has been spectrally resolved and converted into convergent light is guided to the image sensor 115 via the lens unit 120 if the lens unit 120 is arranged in the optical path of the spectroscope, and is guided to the image sensor 115 without passing through the lens unit 120 if the lens unit 120 is not arranged in the optical path of the spectroscope. The spectroscope in this embodiment includes the dispersive element 113, the imaging lens 114, the lens unit 120, and the image sensor 115.

The dispersion element 113 may be, for example, a transmissive diffraction grating or a reflective diffraction grating. The imaging lens 114 is composed of one or more lenses and is also called an imaging lens system, a zoom lens system, a Fourier transform lens system, etc. The image sensor 115 is, for example, a photodetector such as a line sensor, a multi-line sensor, or an area sensor, and detects multiple spectral components (wavelength components) of the interference light LC separately using a light receiving element array to generate a detection signal. The generated detection signal is sent to the arithmetic and control unit 200.

Lens unit 120 is an optical unit that includes at least a lens, for example, two or more lenses. Lens unit 120 is designed and configured to satisfy the above-mentioned conditions (1) and (2). In other words, lens unit 120 is designed and configured to change the focal length of the spectrometer optical system without changing the focal position of the spectrometer optical system.

In other words, the lens unit 120 is designed and configured so that the focal length (composite focal length) of the composite optical system of the imaging lens 114 and the lens unit 120 is different from the focal length of the imaging lens 114, and the focal position (composite focal position) of this composite optical system coincides with the focal position of the imaging lens 114.

In other words, the lens unit 120 is designed and configured so that the composite focal length of the imaging lens 114 and the lens unit 120 is different from the focal length of the imaging lens 114, and so that the focal position of the spectrometer optical system is the same regardless of whether the lens unit 120 is disposed between the imaging lens 114 and the image sensor 115.

In other words, the lens unit 120 is designed and configured so that the composite focal length of the imaging lens 114 and the lens unit 120 is different from the focal length of the imaging lens 114, so that the focus of the spectrometer optical system does not shift even when the lens unit 120 is inserted into the optical path between the imaging lens 114 and the image sensor 115, and so that the focus of the spectrometer optical system does not shift even when the lens unit 120 is removed from the optical path between the imaging lens 114 and the image sensor 115.

The movement of the lens unit 120 is performed by the lens unit movement mechanism 130. The lens unit movement mechanism 130 may include, for example, an actuator that operates under the control of the control unit 210 described below, and a transmission mechanism that transmits the driving force generated by the actuator to move the lens unit 120. Alternatively, the lens unit movement mechanism 130 may include a transmission mechanism that transmits the driving force applied by the user to move the lens unit 120.

An example of the configuration of the control system and processing system of the ophthalmic device 1 is shown in FIG. 2. The arithmetic control unit 200 is provided with a control unit 210, an image construction unit 220, and a data processing unit 230. Although not shown in the figure, the ophthalmic device 1 may also include a communication device, a drive device (reader/writer), etc.

The control unit 210 executes various types of control. The control unit 210 includes a main control unit 211 and a memory unit 212. The main control unit 211 includes a processor, and controls the elements of the ophthalmic device 1 (the elements shown in FIG. 1A and the elements shown in FIG. 1B). The main control unit 211 is realized by cooperation between hardware including a processor and control software. The memory unit 212 includes a storage device such as a hard disk drive or solid state drive, and stores data.

The main controller 211 executes control of the elements provided in the fundus camera unit 2, for example, controlling the image sensors 35 and 38, the LCD 39, the optical path length changer 41, the optical scanner 42, the focusing drive units 31A and 43A, etc. The optical path length changer 41 changes the optical path length of the sample arm by moving a reflector (retroreflector) provided in the optical path of the sample arm under the control of the main controller 211. The focusing drive unit 31A changes the focusing position (focal position) of the photographing using the illumination optical system 10 and the photographing optical system 30 by integrally or synchronously moving the focusing lens 31 provided in the photographing optical path and the focus optical system 60 provided in the illumination optical path under the control of the main controller 211. The optical scanner 42 sequentially deflects the measurement light LS according to a preset scan pattern under the control of the main controller 211 in order to apply an OCT scan according to this scan pattern to the subject's eye E. The focusing driver 43A, under the control of the main controller 211, moves the focusing lens 43 provided on the sample arm to change the focusing position (focal position) of the measurement light LS, that is, the depth position (z position) of the beam waist of the measurement light LS.

The moving mechanism 150 is configured to move the optical system of the ophthalmic device 1 three-dimensionally. The main control unit 211 executes control of the moving mechanism 150 for, for example, alignment and tracking. Tracking is an operation of moving the optical system of the device in real time in response to the movement of the subject's eye E, and is executed to maintain an appropriate alignment state and an appropriate focusing state for the subject's eye E.

The main control unit 211 controls the elements provided in the OCT unit 100, such as the light source unit 101, the attenuator 105, the polarization controller 106, and the image sensor 115. Under the control of the main control unit 211, the light source unit 101 switches between on and off, changes the intensity (light amount) of the low-coherence light L0 output, and changes the wavelength of the low-coherence light L0 output. Under the control of the main control unit 211, the attenuator 105 adjusts the light amount of the reference light LR. Under the control of the main control unit 211, the polarization controller 106 adjusts the polarization state of the reference light LR.

The OCT unit 100 of this embodiment further includes a lens unit 120, a lens unit moving mechanism 130, and a lens moving mechanism 140. As described above, the lens unit 120 is configured to change the focal length without changing the focal position of the spectrometer optical system. Some examples of the lens unit 120 will be described later. The lens unit moving mechanism 130 is configured to move the lens unit 120, thereby inserting the lens unit 120 into the optical path of the spectrometer optical system and retracting the lens unit 120 from the optical path of the spectrometer optical system. The lens moving mechanism 140 is configured to move a specific lens (called a movable lens) among the lenses included in the lens unit 120.

The movable lenses may be all the lenses included in the lens unit 120, or only some of the lenses. When all the lenses included in the lens unit 120 are movable lenses, that is, when all the lenses included in the lens unit 120 are moved by the lens movement mechanism 140, the lens movement mechanism 140 and the lens unit movement mechanism 130 may be common elements or may be separate elements. In the former case, the configuration of the OCT unit 100 is simplified. Here, the mode in which the lens movement mechanism 140 and the lens unit movement mechanism 130 are configured as common elements is classified into the following four cases: a first case in which the entire lens movement mechanism 140 and the entire lens unit movement mechanism 130 are configured as common elements; a second case in which a part of the lens movement mechanism 140 and the entire lens unit movement mechanism 130 are configured as common elements; a third case in which the entire lens movement mechanism 140 and a part of the lens unit movement mechanism 130 are configured as common elements; and a fourth case in which a part of the lens movement mechanism 140 and a part of the lens unit movement mechanism 130 are configured as common elements. A person skilled in the art would be able to understand the mechanical configurations that can be used in each case, taking into account that the lens movement mechanism 140 is used to fine-tune the position of the movable lens, and that the lens unit movement mechanism 130 is used to insert and retract the entire lens unit 120 into and from the optical path of the spectrometer optical system.

The lens movement mechanism 140 may be configured as an element of the lens unit 120, or as an element of the lens unit movement mechanism 130 (at least a part of the lens unit movement mechanism 130), or may be configured in a different manner.

The direction in which the movable lens is moved by the lens movement mechanism 140 may be a direction perpendicular to the optical axis of the movable lens (the optical axis of the lens unit 120, the optical axis of the spectrometer) (XY direction) and/or a direction parallel to the optical axis of the movable lens (Z direction).

When the image sensor 115 is a line sensor (or a multi-line sensor or an area sensor), the direction in which the movable lens is moved by the lens movement mechanism 140 may be a direction (X direction) corresponding to the arrangement direction (line direction) of the light receiving element group, and/or a direction (Y direction) corresponding to a direction perpendicular to the line direction. Here, the correspondence between the movement direction of the movable lens and the movement direction of the projection position of the interference light LC on the image sensor 115 is as follows: the movement of the movable lens in the X direction corresponds to the movement of the projection position of the interference light LC in the line direction; the movement of the movable lens in the Y direction corresponds to the movement of the projection position of the interference light LC in the direction perpendicular to the line direction. When no optical deflector is disposed between the movable lens and the image sensor 115, the X direction and the line direction spatially coincide, and the Y direction and the direction perpendicular to the line direction spatially coincide. In contrast, when an optical deflector is disposed between the movable lens and the image sensor 115, the X direction and the line direction may not spatially coincide, and the Y direction and the direction perpendicular to the line direction may not spatially coincide.

The lens unit moving mechanism 130 moves the lens unit 120 under the control of the main control unit 211 to insert the lens unit 120 into the optical path of the spectrometer optical system and to retract the lens unit 120 from the optical path of the spectrometer optical system.

The lens movement mechanism 140 moves the movable lens in the lens unit 120 under the control of the main control unit 211. Some non-limiting examples of the configuration of the lens unit 120 and the manner in which the movable lens moves will be described later.

The image construction unit 220 constructs OCT image data of the subject's eye E based on the signal (OCT data representing the spectral intensity distribution) provided by the image sensor 115. The constructed OCT image data is one or more A-scan image data, for example, B-scan image data (two-dimensional cross-sectional image data) consisting of multiple A-scan image data. The image construction unit 220 is realized by the cooperation of hardware including a processor and image construction software.

To construct OCT image data from the OCT data provided by the image sensor 115, the image construction unit 220 performs signal processing on the spectral intensity distribution based on the OCT data for each A-line to generate a reflection intensity profile (A-line profile) for each A-line, as in conventional spectral domain OCT, images each A-line profile to generate multiple A-scan image data, and arranges these A-scan image data according to a scan pattern (arrangement of multiple scan points). Signal processing for generating the A-line profile includes noise reduction (denoising), filtering, fast Fourier transform (FFT), etc. When a different signal processing method is used, a known OCT image data construction process corresponding to that method can be adopted.

The image construction unit 220 may be configured to construct three-dimensional image data that represents a three-dimensional region (volume) of the subject's eye E. Three-dimensional image data is image data in which the positions of pixels are defined by a three-dimensional coordinate system, and examples of such data include stack data and volume data. Stack data is image data constructed by arranging multiple cross-sectional images obtained along multiple scan lines according to the positional relationships of these scan lines. Volume data is image data in which pixels are three-dimensionally arranged voxels, and is constructed, for example, by applying an interpolation process or a voxelization process to stack data, and is also called voxel data.

The image constructor 220 can create new OCT image data from the OCT image data constructed in this manner. In some non-limiting aspects, the image constructor 220 can apply rendering to the three-dimensional image data. Examples of rendering include volume rendering, surface rendering, maximum intensity projection (MIP), minimum intensity projection (MinIP), multiplanar reconstruction (MPR), etc.

In some non-limiting aspects, the image constructor 220 may be configured to construct an OCT front image from the three-dimensional image data. For example, the image constructor 220 may construct projection data by projecting the three-dimensional image data in the z direction (A-line direction, depth direction). The image constructor 220 may also construct projection data from partial data (e.g., slabs) of the three-dimensional image data. This partial data may be specified automatically using, for example, image segmentation (also simply referred to as segmentation), or may be specified manually by a user. This segmentation method may be any method, and may include, for example, image processing such as edge detection and/or segmentation using machine learning. This segmentation is performed, for example, by the image constructor 220 or the data processor 230.

The ophthalmic device 1 may be capable of performing OCT motion contrast imaging. OCT motion contrast imaging is a functional imaging technique for extracting the movement of liquids and particles present in the eye. OCT motion contrast imaging is used, for example, in OCT angiography (OCTA) for depicting blood vessels.

The data processing unit 230 is configured to apply specific data processing to the image of the subject's eye E. The data processing unit 230 is realized, for example, by cooperation between hardware including a processor and data processing software.

The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes the display device 3. The operation unit 242 includes various operation devices and input devices. The user interface 240 may include a device that integrates a display function and an operation function, such as a touch panel. It is also possible to construct an embodiment that does not include at least a part of the user interface 240. For example, the display device may be an external device connected to the ophthalmic apparatus 1.

Lens unit 120A, which is one example of lens unit 120, will be described with reference to FIG. 3. FIG. 3 shows the state in which lens unit 120A is arranged in the optical path of the spectrometer. Lens unit 120A includes two lenses 121 and 122, and is retractably inserted between imaging lens 114 and image sensor 115 by lens unit movement mechanism 130.

The focal length of the spectrometer optical system can be changed without moving the focal position of the spectrometer optical system by moving the lens unit 120A, which is arranged outside the optical path of the spectrometer optical system, to a position between the imaging lens 114 and the image sensor 115. Conversely, the focal length of the spectrometer optical system can be changed without moving the focal position of the spectrometer optical system by moving the lens unit 120A, which is arranged between the imaging lens 114 and the image sensor 115, to a position outside the optical path of the spectrometer optical system.

The two lenses 121 and 122 included in the lens unit 120A are a convex lens 121 and a concave lens 122. That is, the lens unit 120A includes a convex lens 121 and a concave lens 122 arranged between the convex lens 121 and the image sensor 115. In other words, of the two lenses 121 and 122 included in the lens unit 120A arranged between the imaging lens 114 and the image sensor 115, the lens 121 arranged on the imaging lens 114 side is a convex lens, and the lens 122 arranged on the image sensor 115 side is a concave lens. By adopting such a configuration, it is possible to make the lens unit 120A more compact.

Either or both of the convex lens 121 and the concave lens 122 included in the lens unit 120A are movable lenses. The convex lens 121 and/or the concave lens 122 as movable lenses are moved by the lens movement mechanism 140 under the control of the main control unit 211. The direction in which the movable lens is moved by the lens movement mechanism 140 may be any one, any two, or all three of the X, Y, and Z directions.

Here, the Z direction is a direction parallel to the optical axis of the spectrometer optical system (the optical axis of the lens group in the lens unit 120, the optical axis of the movable lens), the X direction is a direction corresponding to the line direction of the image sensor 115, and the Y direction is a direction perpendicular to both the X direction and the Z direction.

In some aspects, it may be assumed that the orientation of the optical axis of the spectrometer optical system and the orientation of the optical axis of the movable lens are substantially the same. However, in some other aspects, it is assumed that the orientation of the optical axis of the spectrometer optical system and the orientation of the optical axis of the movable lens are substantially different. In such cases, the ophthalmic device 1 may be configured to change the orientation of the optical axis of the movable lens by the lens unit movement mechanism 130, the lens movement mechanism 140, or another mechanism to align it with the orientation of the optical axis of the spectrometer optical system.

When the moving direction of the movable lens includes two or more directions, the movable lenses to be moved may be the same or different. For example, when the lens moving mechanism 140 is configured to be able to move the movable lens in the X direction, the Y direction, and the Z direction, the movable lens moved in the X direction (X movable lens), the movable lens moved in the Y direction (Y movable lens), and the movable lens moved in the Z direction (Z movable lens) may each be selected in advance from a lens group consisting of a convex lens 121 and a concave lens 122. Specifically, the X movable lens may be a convex lens 121 and/or a concave lens 122, the Y movable lens may be a convex lens 121 and/or a concave lens 122, and the Z movable lens may be a convex lens 121 and/or a concave lens 122. Note that the X movable lens, the Y movable lens, and the Z movable lens do not need to be fixed, and any of them may be selected at the time of correction.

In some embodiments, the main controller 211 may be configured to control the lens movement mechanism 140 based on the output from the image sensor 115. The image sensor 115 is configured to separately detect multiple spectral components (wavelength components) of the interference light LC using a light receiving element array. The output from the image sensor 115 is an electrical signal (detection signal, interference signal) that represents the spectral intensity distribution of the interference light LC.

The main control unit 211 is configured to control the lens movement mechanism 140 based on a predetermined parameter of the detection signal generated by the image sensor 115. This parameter may be, for example, a parameter indicating intensity information (light amount information) of the detected spectral intensity distribution, a parameter indicating wavelength information, a parameter indicating phase information, etc.

The main control unit 211 optimizes the detection state of the spectral intensity distribution by the image sensor 115 by controlling the lens movement mechanism 140 to move the movable lens based on the detection signal output from the image sensor 115. That is, the main control unit 211 adjusts the position of the movable lens based on the detection state of the spectral intensity distribution, thereby performing feedback control to optimize the detection state of the spectral intensity distribution.

For example, the main control unit 211 controls the optical scanner 42 to block the optical path of the measurement light LS and turns on the light source unit 101. This causes the low-coherence light L0 output from the light source unit 101 to be guided to the spectroscope through the reference arm. The spectroscope detects the spectral intensity distribution of the low-coherence light L0 and outputs a detection signal.

When the X direction is included in the moving direction of the movable lens, the main control unit 211 may be configured to, for example, obtain spectral position information from the detection signal generated by the spectrometer, and control the lens moving mechanism 140 to move the movable lens in the X direction based on this spectral position information. A specific example of the process for moving the movable lens in the X direction will be described later.

When the Y direction is included in the moving direction of the movable lens, the main control unit 211 may be configured to, for example, obtain spectral intensity information from the detection signal generated by the spectrometer, and control the lens moving mechanism 140 to move the movable lens in the Y direction based on this spectral intensity information. A specific example of the process for moving the movable lens in the Y direction will be described later.

Similarly, when the moving direction of the movable lens includes the Z direction, the main control unit 211 may be configured to, for example, obtain spectral intensity information from the detection signal generated by the spectrometer, and control the lens moving mechanism 140 to move the movable lens in the Z direction based on this spectral intensity information. A specific example of the process for moving the movable lens in the Z direction will be described later.

Note that moving the movable lens in the Y direction is equivalent to correcting the deviation of the projection position of the interference light LC on the image sensor 115 (deviation in the direction perpendicular to the line direction). In contrast, moving the movable lens in the Z direction is equivalent to correcting the deviation of the focus of the interference light LC on the image sensor 115. Both corrections are performed with reference to the spectral intensity information detected by the spectrometer, but it should be noted that the mechanisms that deteriorate the spectral intensity are different.

One example of the design and configuration of a spectrometer optical system in which the lens unit 120A is used will be described with further reference to FIG. 4. FIG. 4 includes three diagrams (top, middle, and bottom). The top diagram of FIG. 4 shows a state in which the lens unit 120A is not arranged in the optical path of the spectrometer optical system. The middle diagram of FIG. 4 shows a state in which the lens unit 120A is arranged in the optical path of the spectrometer optical system. The bottom diagram of FIG. 4 shows a state in which the lens unit 120A is arranged in the optical path of the spectrometer optical system, with the imaging lens 114 and the lens unit 120A expressed as a composite optical system.

As shown in the top and middle diagrams of FIG. 4, the position of the front principal point of the imaging lens 114 is indicated by H1, and the position of the rear principal point of the imaging lens 114 is indicated by H1'. Also, as shown in the middle diagram of FIG. 4, the position of the front principal point of the lens unit 120A (the group of lenses that make up the lens unit 120A) is indicated by H2, and the position of the rear principal point of the lens unit 120A is indicated by H2'. Also, as shown in the top, middle, and bottom diagrams of FIG. 4, the position of the image sensor 115 (its light receiving surface) is indicated by K.

As shown in the upper diagram of FIG. 4A, the focal length of the imaging lens 114 (e.g., the composite focal length of the lens group that constitutes the imaging lens 114) is f1. In order to focus (image) the parallel light emitted from the dispersion element 113 on the image sensor 115, the imaging lens 114 is designed and configured so that the distance H1'K between the rear principal point position H1' of the imaging lens 114 and the light receiving surface position K of the image sensor 115 is equal to the focal length f1 of the imaging lens 114. The imaging lens 114 is designed based on, for example, the shooting range (e.g., depth range), parameters related to the collimator lens 112, parameters related to the dispersion element 113, etc.

The focal length of lens unit 120A (for example, the composite focal length of the lens group that constitutes lens unit 120A, more specifically, the composite focal length of convex lens 121 and concave lens 122) is f2. As shown in the middle diagram of FIG. 4, the distance H1'H2 between the rear principal point position H1' of imaging lens 114 and the front principal point position H2 of lens unit 120A is d1. Also, as shown in the middle diagram of FIG. 4, the distance H2'K between the rear principal point H2' of lens unit 120A and the light receiving surface position K of image sensor 115 is d2. These distances d1 and d2 are determined based on the optical configuration of lens unit 120A, its insertion position into the optical path of the spectrometer optical system, and the like.

As shown in the lower diagram of FIG. 4, the focal length (composite focal length) of the composite optical system of the imaging lens 114 and the lens unit 120A is f. If the zoom magnification of the lens unit 120A is β, the zoom magnification β is expressed as the quotient obtained by dividing the composite focal length f of the imaging lens 114 and the lens unit 120A by the focal length f1 of the imaging lens 114: β=f/f1.

As can be seen from the middle and bottom diagrams in Figure 4, the composite focal length f of the focal length f1 of the imaging lens 114 and the focal length f2 of the lens unit 120A, that is, the focal length f of the composite optical system of the imaging lens 114 and the lens unit 120A, is expressed by the following formula: f = (f1 x f2) / (f1 + f2 - d1). In addition, the distance δ2 between the rear principal point position H2' of the lens unit 120A and the rear principal point position H' of the composite optical system of the imaging lens 114 and the lens unit 120A is expressed by the following formula: δ2 = f x d1 / f1.

From the above, the condition for the focal position of the imaging lens 114 when the lens unit 120A is not placed in the optical path of the spectrometer optical system to coincide with the focal position of the composite optical system of the imaging lens 114 and the lens unit 120A when the lens unit 120A is placed in the optical path of the spectrometer optical system, in other words, the condition for these two focal positions to both be located at the light receiving surface position K of the image sensor 115, or further in other words, the condition for the focal position of the spectrometer optical system not to change when the lens unit 120A is inserted or removed from the optical path of the spectrometer optical system, can be expressed as follows: f = H2'K + δ2 = d2 + f × d1/f1.

In addition, the above formula for the focal length of the composite optical system of the imaging lens 114 and the lens unit 120A, f = (f1 x f2)/(f1 + f2 - d1), can be rearranged to d1 = f1 + f2 - f1 x f2/f.

Therefore, in order to change the focal length of the spectrometer by inserting or removing the lens unit 120A into or from the optical path of the spectrometer without changing the focal position of the spectrometer, the optical system of the spectrometer in this example is designed and configured so that the focal length f1 of the imaging lens 114, the focal length f2 of the lens unit 120A, the distance d1 between the rear principal point of the imaging lens 114 and the front principal point of the lens unit 120A, the distance d2 between the rear principal point of the lens unit 120A and the image sensor 115, and the composite focal length f of the imaging lens 114 and the lens unit 120A satisfy the following two equations: d1 = f1 + f2 - f1 x f2/f, and f = d2 + f x d1/f1.

One specific example is shown in FIG. 5. The parameters in this specific example are set as follows: focal length f1 of the imaging lens 114 = 107.7 mm; focal length f2 of the lens unit 120A = -58.4 mm; composite focal length f of the imaging lens 114 and the lens unit 120A = 214 mm; distance d1 between the rear principal point of the imaging lens 114 and the front principal point of the lens unit 120A = 78.6 mm; distance d2 between the rear principal point of the lens unit 120A and the image sensor 115 = 57.8 mm; distance δ2 between the rear principal point position H2' of the lens unit 120A and the rear principal point position H' of the composite optical system of the imaging lens 114 and the lens unit 120A = 156.2 mm. In this case, d2 + δ2 = 214 = f, and the above conditional formula f = d2 + f × d1 / f1 is satisfied.

The value of the quotient β obtained by dividing the combined focal length f of the imaging lens 114 and the lens unit 120A by the focal length f1 of the imaging lens 114, i.e., the zoom magnification β of the lens unit 120A, may be greater than 1 and less than or equal to 5 (1<β≦5). As mentioned above, there is a trade-off between the depth range and the resolution, but when both parameters are taken into consideration, if the zoom magnification β is outside this range (1<β≦5), there is a risk that the condition of one of the parameters may be insufficient for practical use, for example, in OCT measurement for ophthalmic diagnosis.

In order to make both the depth range and the resolution practically sufficient, the zoom magnification β may be 1.5 or more and 3 or less (1.5≦β≦3). In this case, the range of the focal length f2 of the lens unit 120A is f2 = -1.1×f1 to -0.3×f1. If the focal length of the convex lens 121 is f3 and the focal length of the concave lens 122 is f4, the ratio (f3/f4) of these focal lengths f3 and f4 is in the range of about -1.5 to 5.0. Here, using the focal length f1 and the zoom magnification β of the imaging lens 114, f1×f3/(f4×β) = about -200 to -150. The range of the depth range and the range of the resolution may be determined arbitrarily depending on the type of sample and the use of the data obtained by the OCT measurement.

The Abbe number of lenses 121 and 122 that make up lens unit 120A can be determined based on the wavelength range of light used for OCT measurement (e.g., 840±50 nanometers).

Lens unit 120B, another example of lens unit 120, will be described with reference to FIG. 6. FIG. 6 shows the state in which lens unit 120B is arranged in the optical path of the spectrometer. Lens unit 120B includes three lenses 123, 124, and 125, and is retractably inserted between imaging lens 114 and image sensor 115 by lens unit movement mechanism 130.

By moving the lens unit 120B, which is disposed outside the optical path of the spectrometer optical system, to a position between the imaging lens 114 and the image sensor 115, the focal length of the spectrometer optical system can be changed without changing the focal position of the spectrometer optical system. Conversely, by moving the lens unit 120B, which is disposed between the imaging lens 114 and the image sensor 115, to a position outside the optical path of the spectrometer optical system, the focal length of the spectrometer optical system can be changed without changing the focal position of the spectrometer optical system.

The three lenses 123 to 125 included in the lens unit 120B are a convex lens 123, a concave lens 124, and a convex lens 125. That is, the lens unit 120B includes a convex lens 123, a concave lens 124 arranged between the convex lens 123 and the image sensor 115, and a convex lens 125 arranged between the concave lens 124 and the image sensor 115. In other words, of the three lenses 123 to 125 included in the lens unit 120B arranged between the imaging lens 114 and the image sensor 115, the lens 123 arranged on the imaging lens 114 side is a convex lens, the lens 125 arranged on the image sensor 115 side is also a convex lens, and the lens 124 arranged between them is a concave lens. By adopting such a configuration, it is possible to make the lens unit 120B more compact, as in the example of FIG. 3.

Unlike the lens unit 120A in FIG. 3, which is composed of a convex lens 121 and a concave lens 122, the lens unit 120B in FIG. 6 includes a further convex lens 125 in addition to the convex lens 123 and the concave lens 124. The convex lens 125 is disposed between the concave lens 124 and the image sensor 115, and acts to reduce the angle of incidence of light to the image sensor 115. By reducing the angle of incidence of light to the image sensor 115, in other words, by projecting light from a direction close to perpendicular to the light receiving surface of the image sensor 115, the light receiving efficiency of the spectrometer is improved. In particular, the light receiving efficiency of the spectrometer can be optimized by designing and configuring the lens unit 120B to be telecentric with respect to the image sensor 115.

At least one of the convex lens 123, concave lens 124, and convex lens 125 included in lens unit 120B is a movable lens. The movable lens in lens unit 120B is moved in at least one of the X direction, Y direction, and Z direction by lens movement mechanism 140 under the control of main control unit 211. Unless otherwise specified, the manner of movement of the movable lens may be the same as in lens unit 120A.

The lens unit 120B in Figure 6 may be designed and constructed to satisfy the above conditional expressions (d1 = f1 + f2 - f1 x f2/f, f = d2 + f x d1/f1). One specific example is shown in Figure 7. The parameters in this specific example are set as follows: focal length f1 of the imaging lens 114 = 107.7 mm; focal length f2 of the lens unit 120B = -388.7 mm; composite focal length f of the imaging lens 114 and the lens unit 120B = 214 mm; distance d1 between the rear principal point of the imaging lens 114 and the front principal point of the lens unit 120B = -85.4 mm; distance d2 between the rear principal point of the lens unit 120B and the image sensor 115 = 383.7 mm; distance δ2 between the rear principal point position H2' of the lens unit 120B and the rear principal point position H' of the composite optical system of the imaging lens 114 and the lens unit 120B = 169.7 mm. In this case, d2 + δ2 = 214 = f, and the above conditional formula f = d2 + f × d1 / f1 is satisfied.

The value of the quotient β obtained by dividing the combined focal length f of the imaging lens 114 and the lens unit 120B by the focal length f1 of the imaging lens 114, i.e., the zoom magnification β of the lens unit 120B, may be greater than 1 and less than or equal to 5 (1<β≦5). Furthermore, the zoom magnification β may be greater than or equal to 1.5 and less than or equal to 3 (1.5≦β≦3). This makes both the depth range and the resolution sufficient for practical use, for example, in an optical coherence tomography device (ophthalmic device 1) for ophthalmic diagnosis.

Another embodiment of the OCT unit 100 is shown in FIG. 8. The OCT unit 100 in FIG. 1B is configured so that the lens unit 120 is retractably inserted between the imaging lens 114 and the image sensor 115, but the OCT unit 100A of this embodiment is configured so that the lens unit 120 is retractably inserted between the dispersion element 113 and the imaging lens 114. According to this embodiment, in which the lens unit 120 is inserted between the dispersion element 113 and the imaging lens 114, the distance between the image sensor 115 and the lens unit 120 is larger than when the lens unit 120 is inserted between the imaging lens 114 and the image sensor 115, so the risk of dust adhering to the image sensor 115 is reduced.

Except for the insertion position of the lens unit 120 and the optical configuration of the lens unit 120 (e.g., lens parameters, lens arrangement, etc.), the configuration of the OCT unit 100A in this embodiment may be similar to the configuration of the OCT unit 100 in FIG. 1B.

Lens unit 120C, which is an example of the lens unit 120 mounted on the OCT unit 100A in FIG. 8, will be described with reference to FIG. 9. FIG. 9 shows the state in which lens unit 120C is disposed in the optical path of the spectrometer. Lens unit 120C includes two lenses 126 and 127, and is retractably inserted between the dispersion element 113 and the imaging lens 114 by the lens unit moving mechanism 130.

The focal length of the spectrometer optical system can be changed without changing the focal position of the spectrometer optical system by moving the lens unit 120C, which is arranged outside the optical path of the spectrometer optical system, to a position between the dispersion element 113 and the imaging lens 114. Conversely, the focal length of the spectrometer optical system can be changed without changing the focal position of the spectrometer optical system by moving the lens unit 120C, which is arranged between the dispersion element 113 and the imaging lens 114, to a position outside the optical path of the spectrometer optical system.

The two lenses 126 and 127 included in lens unit 120C are convex lens 126 and concave lens 127. That is, lens unit 120C includes convex lens 126 and concave lens 127 arranged between convex lens 126 and imaging lens 114. In other words, of the two lenses 126 and 127 included in lens unit 120C arranged between dispersion element 113 and imaging lens 114, lens 126 arranged on the dispersion element 113 side is a convex lens, and lens 127 arranged on the imaging lens 114 side is a concave lens. By adopting such a configuration, it is possible to make lens unit 120C more compact.

The convex lens 126 and concave lens 127 included in the lens unit 120C are designed and configured as an afocal system. In other words, the light incident on the lens unit 120C is parallel light, and the light emitted from the lens unit 120C is also parallel light. Thus, in this embodiment, the light emitted from the dispersion element 113 is parallel light, this parallel light enters the lens unit 120C, the light emitted from the lens unit 120C is parallel light, the parallel light emitted from the lens unit 120C enters the imaging lens 114, the light emitted from the imaging lens 114 is convergent light, and the convergent light emitted from the imaging lens 114 forms an image (converges) on the light receiving surface of the image sensor 115.

Furthermore, lens unit 120C may be designed and configured to act as a demagnification beam expander. In this case, lens unit 120C is an afocal lens system, and the beam diameter of the emerging parallel light is smaller than the beam diameter of the incoming parallel light.

The configuration of the lens system included in the lens unit that is retractably inserted between the dispersion element 113 and the imaging lens 114 is not limited to an afocal system. For example, the two lenses 128 and 129 (convex lens 128 and concave lens 129) included in the lens unit 120D shown in FIG. 10 are not an afocal system.

As shown in FIG. 9, by adopting a configuration in which an afocal lens unit 120C is inserted at a point (parallel light section) where parallel light is guided in the optical path of the spectrometer optical system, it is possible to reduce the deterioration of optical performance due to decentering or tilt (tilt) of the lens unit 120C, which acts as a beam expander with a reduced magnification. Therefore, although it is possible to adopt a lens unit that is not an afocal system, such as the lens unit 120D in FIG. 10, in some embodiments, it is considered that there are great advantages to adopting an afocal lens unit, such as the lens unit 120C in FIG. 9.

Either or both of the convex lens 126 and the concave lens 127 included in the lens unit 120C are movable lenses. The movable lens in the lens unit 120C is moved in at least one of the X direction, Y direction, and Z direction by the lens movement mechanism 140 under the control of the main control unit 211. Unless otherwise specified, the manner of movement of the movable lens may be the same as in the case of the lens unit 120A. When the lens unit 120D is adopted, the convex lens 126 and the concave lens 127 included therein may also be the same.

We will explain some examples of the design and configuration of the spectrometer optical system equipped with lens unit 120C.

Figure 11 includes two diagrams (top and bottom diagrams). The top diagram in Figure 11 shows an afocal lens unit that includes a convex lens with focal length fa arranged on the dispersive element 113 side, and a convex lens with focal length fb arranged on the imaging lens 114 side, and is retractably inserted between the dispersive element 113 and the imaging lens 114. In the lens unit of this example, the distance between the two convex lenses is the sum of the two focal lengths, fa + fb, so the dimensions of the lens unit are relatively large.

On the other hand, the lower diagram of FIG. 11 shows an afocal lens unit that includes a convex lens with focal length fa (>0) arranged on the dispersion element 113 side and a concave lens with focal length fb (<0) arranged on the imaging lens 114 side and is inserted between the dispersion element 113 and the imaging lens 114 in a retractable manner. Here, the focal length fa of the convex lens is greater than the absolute value of the focal length fb of the concave lens (fa>|fb|). In the lens unit of this example, the distance between the two lenses is the difference fa-|fb| between the focal length fa of the convex lens and the absolute value |fb| of the focal length fb of the concave lens, so that the dimensions of the lens unit can be made smaller than when two convex lenses are included as in the upper diagram of FIG. 11. The lens unit 120C in FIG. 9 and the lens unit 120D in FIG. 10 are examples of the lens unit of this example.

Figure 12 includes two diagrams (top and bottom). The top diagram of Figure 12 shows a state in which the lens unit is not placed in the optical path of the spectrometer optical system. The bottom diagram of Figure 12 shows a state in which the lens unit is placed in the optical path of the spectrometer optical system.

The lens unit in this example is an afocal lens unit that includes a convex lens with focal length fa (>0) arranged on the dispersion element 113 side and a concave lens with focal length fb (<0) arranged on the imaging lens 114 side, and is retractably inserted between the dispersion element 113 and the imaging lens 114.

In the following, the lens unit in this example is assumed to be lens unit 120C in FIG. 9. Lens unit 120C is an afocal lens unit that includes a convex lens 126 with a focal length fa (>0) arranged on the dispersion element 113 side, and a concave lens 127 with a focal length fb (<0) arranged on the imaging lens 114 side, and is retractably inserted between the dispersion element 113 and the imaging lens 114.

The focal length of the imaging lens 114 (e.g., the composite focal length of the lens group that constitutes the imaging lens 114) is denoted by f1. Also, the focal length (composite focal length) of the composite optical system consisting of the imaging lens 114 with focal length f1 and the lens unit 120C that includes the convex lens 126 with focal length fa and the concave lens 127 with focal length fb is denoted by f.

If the zoom magnification of lens unit 120C is β, the zoom magnification β is expressed as the quotient of the combined focal length f of imaging lens 114 and lens unit 120C divided by the focal length f1 of imaging lens 114: β = f/f1. Furthermore, if the angular magnification of lens unit 120C as a reduction magnification expander is γ, the angular magnification γ is equal to the zoom magnification β: γ = β = f/f1. Here, the angular magnification γ is assumed to be greater than 1: γ > 1. In other words, in this example, the depth range of OCT measurement is expanded by inserting lens unit 120C into the optical path of the spectrometer optical system.

In view of the above, the optical system of the spectrometer in this example is designed and configured so that the focal length f1 of the imaging lens 114, the focal length fa on the dispersion element 113 side of the lens unit 120C and the focal length fb on the imaging lens 114 side of the lens unit 120C, and the composite focal length f of the imaging lens 114 and the lens unit 120C satisfy the following formula: f = (fa/|fb|) x f1. As mentioned above, the absolute value of the focal length fb on the imaging lens 114 side of the lens unit 120C means that either a convex lens or a concave lens can be selected.

One specific example is shown in Figure 13. The parameters in this specific example are set as follows: focal length f1 of imaging lens 114 = 107.7 mm; focal length fa of lens unit 120C on the dispersive element 113 side = 94.202; focal length fb of lens unit 120C on the imaging lens 114 side = -47.101; angular magnification γ of lens unit 120C = fa/|fb| = 2.0; combined focal length f of imaging lens 114 and lens unit 120C = γ x f1 = 215.4. According to this specific example, the focal length of the spectrometer can be changed without changing the focal position of the spectrometer by inserting or removing lens unit 120C into or from the optical path of the spectrometer.

The value of the quotient β obtained by dividing the composite focal length f of the imaging lens 114 and the lens unit 120C by the focal length f1 of the imaging lens 114, that is, the zoom magnification β of the lens unit 120B, may be greater than 1 and less than or equal to 5 (1<β≦5). Furthermore, the zoom magnification β may be greater than or equal to 1.5 and less than or equal to 3 (1.5≦β≦3). This allows, for example, an optical coherence tomography device (ophthalmic device 1) for ophthalmic diagnosis to have both a depth range and a resolution that are sufficient for practical use. In addition, the Abbe number of the lenses 126 and 127 that constitute the lens unit 120C can be determined based on the wavelength range of light used in OCT measurement (e.g., 840±50 nanometers).

Next, we will explain some specific examples of the processes performed to move the movable lens.

First, a specific example of the process executed to move the movable lens in the X direction corresponding to the line direction of the image sensor 115 of the spectrometer will be described. In this example, the main controller 211 controls the optical scanner 42 to block the optical path of the measurement light LS and turns on the light source unit 101. This causes the low-coherence light L0 output from the light source unit 101 to be guided to the spectrometer through the reference arm. The image sensor 115 of the spectrometer detects the spectral intensity distribution of the low-coherence light L0. The main controller 211 determines spectral position information from the detected spectral intensity distribution, and controls the lens movement mechanism 140 to move the movable lens in the X direction based on this spectral position information.

An example of a detection signal output from the image sensor 115 that detects the low coherence light L0 is shown in FIG. 14. The curve indicated by the symbol SD represents the spectral intensity distribution of the low coherence light L0. The spectral intensity distribution of the low coherence light L0, that is, the output wavelength distribution from the light source unit 101, is predetermined. In particular, the shortest wavelength and the longest wavelength of the low coherence light L0 are predetermined. The shortest wavelength is the shortest wavelength among the wavelengths whose intensity is non-zero, and the longest wavelength is the longest wavelength among the wavelengths whose intensity is non-zero. As described above, the image sensor 115 includes a plurality of light receiving elements arranged in a line direction, and each light receiving element is assigned a detection wavelength. Therefore, the light receiving element corresponding to the shortest wavelength of the low coherence light L0 and the light receiving element corresponding to the longest wavelength are predetermined. The symbols P1 and P2 in FIG. 14 respectively indicate the identifier (pixel address) of the light receiving element corresponding to the shortest wavelength of the low-coherence light L0 and the identifier of the light receiving element corresponding to the longest wavelength.

As described above, the line direction of the image sensor 115 corresponds to the X direction. If there is a positional misalignment of the optical elements in the spectrometer (for example, misalignment of the optical axis of the lens), the projection position of the spectrum of the low-coherence light L0 on the image sensor 115 is displaced in the X direction from the predetermined position, and each light receiving element detects a spectral component other than the pre-assigned spectral component. In this case, one of the light receiving element at pixel address P1, where the detected spectral intensity should be substantially zero, and the light receiving element at pixel address P2, where the detected spectral intensity should be substantially zero, detects a substantially non-zero spectral intensity. Here, "substantially zero" may be zero or a value equal to or less than a predetermined threshold. Also, "substantially non-zero" may be a value exceeding a predetermined threshold.

By utilizing this phenomenon, it is possible to detect and evaluate the positional misalignment of the optical elements in the spectrometer in the X direction. For example, the main control unit 211 obtains the detection intensity of the light receiving element at pixel address P1 and the detection intensity of the light receiving element at pixel address P2 from the spectral intensity distribution generated by the image sensor 115 that detects the low-coherence light L0, and determines whether these detection intensities are substantially zero.

If it is determined that both detection intensities are substantially zero, the main control unit 211 determines that there is no positional misalignment of the optical elements in the spectrometer in the X direction. In this case, no control is performed to move the movable lens in the X direction.

In contrast, if one of the detected intensities is determined to be substantially non-zero, the main control unit 211 determines that there is a positional deviation in the X direction of the optical element in the spectrometer. In this case, the main control unit 211 executes control to move the movable lens in the X direction.

For example, the main control unit 211 performs control to move the movable lens in the X direction so as to move the projection position of the spectrum of the low coherence light L0 in the direction opposite to the pixel address where the detected intensity is determined to be substantially non-zero. As a specific example, when the detected intensity by the light receiving element of pixel address P1 is substantially non-zero, the main control unit 211 performs control to move the movable lens in the X direction so as to move the projection position of the spectrum of the low coherence light L0 (spectral intensity distribution of the low coherence light L0) toward the light receiving element of pixel address P2.

In some aspects, the moving distance of the movable lens in the X direction may be a predetermined distance. By repeating the process and control for moving the movable lens in the X direction while gradually decreasing the moving distance in the X direction, the movable lens can be guided to an optimal position (a position of the movable lens where the deviation of the spectral intensity distribution in the X direction is substantially zero). In other words, by alternately performing the movement of the movable lens in the X direction and the process and control for moving the movable lens in the X direction while gradually decreasing the moving distance in the X direction, the movable lens can be guided to an optimal position.

In some other aspects, the main control unit 211 can determine the movement distance in the X direction based on the spectral intensity distribution SD of the low-coherence light L0 and the magnitude of the detected non-zero detection intensity value. By alternately performing this movement distance determination process and control for moving the movable lens in the X direction, the movable lens can be guided to an optimal position.

Next, a specific example of a process executed to move the movable lens in the Y direction corresponding to the direction perpendicular to the line direction of the image sensor 115 of the spectrometer will be described. In this example, the main controller 211 controls the optical scanner 42 to block the optical path of the measurement light LS and turns on the light source unit 101. As a result, the low-coherence light L0 output from the light source unit 101 is guided to the spectrometer through the reference arm. The image sensor 115 of the spectrometer detects the spectral intensity distribution of the low-coherence light L0. The main controller 211 obtains spectral intensity information from the detected spectral intensity distribution, and controls the lens movement mechanism 140 to move the movable lens in the Y direction based on this spectral intensity information.

The spectral intensity information may be any information representing signal intensity generated from the spectral intensity distribution, such as the maximum intensity value in the spectral intensity distribution, the integral value of the spectral intensity distribution, or the intensity value of a spectral component detected by a light receiving element at a specified pixel address.

In some aspects, the operation of moving the movable lens in the Y direction is performed by carrying out processing and control similar to the Y-axis auto adjustment disclosed in JP 2008-203246 A. For example, the main control unit 211 can lead the movable lens to an optimal position (a position of the movable lens where the deviation in the Y direction of the projection position of the low-coherence light L0 on the image sensor 115 is substantially zero, and a position of the movable lens where the value indicated by the spectral intensity information is maximum) by repeating processing and control for moving the movable lens in the Y direction while gradually decreasing the moving distance in the Y direction. In other words, the movable lens can be led to an optimal position by alternately moving the movable lens in the Y direction and processing and control for moving the movable lens in the Y direction while gradually decreasing the moving distance in the Y direction.

Next, a specific example of a process executed to move the movable lens in the Z direction parallel to the optical axis of the spectrometer (the optical axis of the lens unit 120, the optical axis of the movable lens) will be described. In this example, the main controller 211 controls the optical scanner 42 to block the optical path of the measurement light LS and turns on the light source unit 101. As a result, the low-coherence light L0 output from the light source unit 101 is guided to the spectrometer through the reference arm. The image sensor 115 of the spectrometer detects the spectral intensity distribution of the low-coherence light L0. The main controller 211 obtains spectral intensity information from the detected spectral intensity distribution, and controls the lens movement mechanism 140 to move the movable lens in the Z direction based on this spectral intensity information.

The spectral intensity information for moving the movable lens in the Z direction may be any information representing signal intensity generated from the spectral intensity distribution, and may be, for example, the same information as the spectral intensity information for moving the movable lens in the Y direction.

In some aspects, the main control unit 211 can guide the movable lens to an optimal position (a position of the movable lens where the focus deviation of the low-coherence light L0 relative to the image sensor 115 is substantially zero, and a position of the movable lens where the value indicated by the spectral intensity information is maximum) by repeating processing and control for moving the movable lens in the Z direction while gradually decreasing the distance of movement in the Z direction. In other words, the movable lens can be guided to an optimal position by alternately performing movement of the movable lens in the Z direction and processing and control for moving the movable lens in the Z direction while gradually decreasing the distance of movement in the Z direction.

The operation performed by the ophthalmic device 1 according to this embodiment will be described. Figure 15 shows an example of the operation of the ophthalmic device 1.

First, the ophthalmic device 1 performs alignment and focus adjustment for the subject eye E (fundus Ef) (S1).

Next, the depth range for the OCT measurement is set (S2).

In one aspect, the depth range is set using the user interface 240. The main control unit 211 displays an operation screen on the display unit 241. The operation screen is provided with a graphical user interface (GUI) for setting the depth range. The user can set the depth range using this GUI and the operation unit 242.

In another aspect, the ophthalmic device 1 is provided with hardware (e.g., a lever, button, etc.) for changing the depth range. The user can set the depth range by manipulating this hardware.

In yet another aspect, the ophthalmic device 1 is provided with software for automatically setting the depth range, and is configured to execute the setting of the depth range based on, for example, the subject's attributes, the subject's examination data, the subject's diagnostic data, the subject's attributes, the subject's examination data, the subject's diagnostic data, etc. These reference data are obtained, for example, from electronic medical record data, image interpretation reports, image data, etc.

In this operation example, the state in which the lens unit 120 is placed in the optical path of the spectrometer optical system corresponds to a wide depth range (wide range), and the state in which the lens unit 120 is not placed in the optical path of the spectrometer optical system corresponds to a narrow depth range (narrow range).

If the wide range is selected in the depth range setting in step S2 (S3: wide range), the main controller 211 controls the lens unit moving mechanism 130 to insert the lens unit 120 into the optical path of the spectrometer optical system (S4). Once the lens unit 120 is inserted into the optical path, the process proceeds to step S5.

If narrow range is selected in the depth range setting in step S2 (S3: narrow range), processing proceeds to step S7 with the lens unit 120 retracted from the optical path.

When the wide range is selected in the depth range setting in step S2 and the lens unit 120 is inserted into the optical path of the spectrometer optical system in step S4, the main control unit 211 determines whether or not to adjust the position of the movable lens in the lens unit 120 (S5).

For example, the main control unit 211 controls the optical scanner 42 to block the sample arm and turn on the light source unit 101, thereby guiding the low-coherence light L0 output from the light source unit 101 to the spectrometer. Furthermore, the main control unit 211 obtains spectral intensity information and/or spectral position information from the spectral intensity distribution acquired by the image sensor 115 of the spectrometer. The main control unit 211 can determine whether or not to adjust the position of the movable lens in the X direction based on the spectral position information, and can also determine whether or not to adjust the position of the movable lens in the Y direction and/or whether or not to adjust the position of the movable lens in the Z direction based on the spectral intensity information. These determinations include, for example, threshold processing (comparison with a predetermined threshold).

If it is determined in step S5 that the position of the movable lens is not to be adjusted (S5: No), the process proceeds to step S7. On the other hand, if it is determined in step S5 that the position of the movable lens is to be adjusted (S5: Yes), the main control unit 211 adjusts the position of the movable lens in the manner described above (S6). When the position adjustment of the movable lens is completed, the process proceeds to step S7.

Next, the ophthalmic apparatus 1 applies an OCT scan to the subject eye E (fundus Ef) (S7). This OCT scan is performed within the depth range set in step S2 and under the suitable OCT measurement conditions achieved in step S6.

Next, the ophthalmic device 1 generates OCT image data based on the data collected by the OCT scan in step S7 (S8).

Next, the ophthalmologic apparatus 1 displays an OCT image on the display unit 241 based on the OCT image data generated in step S8 (S9). This is the end of this operation example (END).

Some functions and effects of the ophthalmic device 1 according to this embodiment will be described.

The ophthalmic device 1 functions as an optical coherence tomography device configured to detect, with a spectroscope, the interference light LC generated by superimposing the return light of the measurement light LS projected on the subject's eye E (sample) and the reference light LR. The spectroscope includes a dispersion element 113, an image sensor 115 (photodetector), and an imaging lens system (imaging lens 114 and lens unit 120). The dispersion element 113 separates the input light into multiple wavelength components. The imaging lens system includes multiple lenses arranged between the dispersion element 133 and the image sensor 115 for imaging the multiple wavelength components generated by the dispersion element 113 on the light receiving surface of the image sensor 115. The image sensor 115 detects the multiple wavelength components generated by the dispersion element 113 separately. Furthermore, the ophthalmic device 1 includes a lens movement mechanism 140 and a main control unit 211 (first control unit). The lens movement mechanism 140 is configured to move a movable lens, which is at least one of the multiple lenses in the imaging lens system of the spectrometer. The main control unit 211 controls the lens movement mechanism 140 based on the output from the image sensor 115.

With this type of ophthalmic device 1, the optical axis misalignment of the lens in the spectroscope and the focus misalignment of the spectroscope can be corrected by moving the movable lens based on the output from the image sensor 115, making it possible to adjust the OCT measurement conditions related to the spectroscope with a simple configuration and control.

In this embodiment, the main control unit 211 may be configured to control the lens movement mechanism 140 based on the amount of light detected by the image sensor 115.

In this embodiment, the main control unit 211 may be configured to control the lens movement mechanism 140 to move the movable lens in directions perpendicular to the optical axis of the movable lens (XY directions).

In this embodiment, the image sensor 115 may include at least one light receiving element row consisting of a plurality of light receiving elements arranged in a line. In this case, the main controller 211 may be configured to control the lens movement mechanism 140 to move the movable lens in a first direction (Y direction) perpendicular to the arrangement direction (line direction) of the plurality of light receiving elements. Furthermore, the main controller 211 may be configured to control the lens movement mechanism 140 to move the movable lens in the Y direction based on the spectral intensity information obtained by detecting the low coherence light L0 output from the light source unit 101 for generating the measurement light LS and the reference light LR using a spectroscope.

In this embodiment, the image sensor 115 may include at least one light receiving element row consisting of a plurality of light receiving elements arranged in a line. In this case, the main controller 211 may be configured to control the lens movement mechanism 140 to move the movable lens in a second direction (X direction) parallel to the arrangement direction (line direction) of the plurality of light receiving elements. Furthermore, the main controller 211 may be configured to control the lens movement mechanism 140 to move the movable lens in the X direction based on the spectral position information obtained by detecting the low coherence light L0 output from the light source unit 101 for generating the measurement light LS and the reference light LR using a spectrometer.

In this embodiment, the main controller 211 may be configured to control the lens movement mechanism 140 to move the movable lens in a third direction (Z direction) parallel to the optical axis of the movable lens. In this case, the main controller 211 may be configured to control the lens movement mechanism 140 to move the movable lens in the Z direction based on spectral intensity information obtained by detecting, by a spectrometer, the low-coherence light L0 output from the light source unit 101 for generating the measurement light LS and the reference light LR.

In this embodiment, the imaging lens system of the spectrometer may include an imaging lens 114 (first lens group) consisting of one or more lenses arranged between the dispersion element 113 and the image sensor 115, and a lens unit 120 (second lens group) consisting of one or more lenses that are inserted into and removed from the optical path between the dispersion element 113 and the image sensor 115. Here, the focal position of the imaging lens system when the lens unit 120 is inserted into the optical path is the same as the focal position of the imaging lens system when the lens unit 120 is retracted from the optical path, and the focal length of the imaging lens system when the lens unit 120 is inserted into the optical path is different from the focal length of the imaging lens system when the lens unit 120 is retracted from the optical path. In other words, the lens unit 120 is configured to change the focal length of the spectrometer without changing the focal position of the spectrometer. The insertion and retraction of the lens unit 120 into and from the optical path is performed by the lens unit moving mechanism 130.

In this embodiment, the movable lens may include one or more lenses in lens unit 120.

In this embodiment, the lens unit 120 may include two or more lenses. In this case, the movable lens may be a portion of the two or more lenses in the lens unit 120 (one or more lenses). Alternatively, the movable lens may be all of the two or more lenses in the lens unit 120.

We will explain some modified examples of the ophthalmic device according to this embodiment.

The ophthalmic device 1 (optical coherence tomography device) according to the above embodiment is configured to change the depth range of the OCT measurement without moving the photodetector (image sensor 115) by using a novel lens unit 120 that changes the focal length without moving the focal position of the spectrometer optical system. On the other hand, one feature of the embodiment according to the present disclosure is that the movement of the movable lens is controlled based on the output from the photodetector. Optical coherence tomography devices having this feature are not limited to those equipped with a lens unit such as the above embodiment.

For example, the ophthalmic device described in Patent Document 1 is an optical coherence tomography device configured to detect interference light generated by superimposing the return light of the measurement light projected on the sample on the reference light with a spectroscope, and the spectroscope includes a dispersion element that separates the input light into a plurality of wavelength components, a photodetector that detects these wavelength components separately, and a zoom lens (variable magnification lens system) with a variable focal length arranged between the dispersion element and the photodetector. Furthermore, the ophthalmic device described in Patent Document 1 includes a photodetector moving mechanism that moves the photodetector, and a second control unit. The second control unit is configured to execute control of the zoom lens of the spectroscope and control of the photodetector moving mechanism in cooperation with each other. It will be understood by those skilled in the art that it is possible to combine one characteristic feature of the embodiment of the present disclosure, "control of the movement of the movable lens based on the output from the photodetector," with such a conventional ophthalmic device. In other words, by combining a lens moving mechanism for moving the movable lens with a first control unit that controls the lens moving mechanism based on the output from the photodetector, it is possible to achieve the same action and effect as the ophthalmic device 1 according to the above embodiment.

The embodiments and aspects described in this disclosure are merely examples. Anyone who wishes to implement the invention disclosed herein may make any modifications (omissions, substitutions, additions, etc.) within the scope of the gist of the invention.

1. Ophthalmic equipment (optical coherence tomography equipment)
101 Light source unit 113 Spectroscopic element 114 Imaging lens 115 Image sensor 120 Lens unit 130 Lens unit moving mechanism 140 Lens moving mechanism 211 Main control unit

Claims (17)

An optical coherence tomography device configured to detect interference light generated by superimposing a return light of a measurement light projected onto a sample on a reference light, the optical coherence tomography device comprising:
The spectrometer includes:
a dispersive element for separating input light into a plurality of wavelength components;
a photodetector that detects the plurality of wavelength components separately;
an imaging lens system including a plurality of lenses disposed between the dispersive element and the photodetector;
a lens moving mechanism for moving a movable lens, which is at least one of the plurality of lenses;
a first control unit that controls the lens moving mechanism based on an output from the photodetector.
Optical coherence tomography device. the first control unit performs the control of the lens moving mechanism based on the amount of light detected by the photodetector.
2. The optical coherence tomography device of claim 1. the first control unit controls the lens moving mechanism to move the movable lens in a direction perpendicular to an optical axis of the movable lens;
2. The optical coherence tomography device of claim 1. the photodetector includes at least one light receiving element row including a plurality of light receiving elements arranged in a line;
the first control unit controls the lens moving mechanism to move the movable lens in a first direction perpendicular to an arrangement direction of the plurality of light receiving elements;
2. The optical coherence tomography device of claim 1. the first control unit controls the lens moving mechanism to move the movable lens in the first direction based on intensity information of a spectrum obtained by detecting light output from a light source for generating the measurement light and the reference light using the spectroscope;
5. The optical coherence tomography apparatus of claim 4. the photodetector includes at least one light receiving element row including a plurality of light receiving elements arranged in a line;
the first control unit controls the lens moving mechanism to move the movable lens in a second direction parallel to an arrangement direction of the plurality of light receiving elements;
2. The optical coherence tomography device of claim 1. the first control unit controls the lens moving mechanism to move the movable lens in the second direction based on position information of a spectrum obtained by detecting light output from a light source for generating the measurement light and the reference light using the spectroscope;
7. The optical coherence tomography device of claim 6. the first control unit controls the lens moving mechanism to move the movable lens in a third direction parallel to an optical axis of the movable lens;
The optical coherence tomography device of claim 1 . the first control unit controls the lens moving mechanism to move the movable lens in the third direction based on intensity information of a spectrum obtained by detecting light output from a light source for generating the measurement light and the reference light using the spectroscope;
9. The optical coherence tomography device of claim 8. The imaging lens system includes:
a first lens group of one or more lenses disposed between the dispersive element and the photodetector;
a second lens group including one or more lenses that are inserted and removed between the dispersive element and the photodetector;
a focal position of the imaging lens system when the second lens group is inserted is the same as a focal position of the imaging lens system when the second lens group is retracted,
a focal length of the imaging lens system when the second lens group is inserted is different from a focal length of the imaging lens system when the second lens group is retracted;
2. The optical coherence tomography device of claim 1. the movable lens includes one or more lenses in the second lens group;
The optical coherence tomography device of claim 10. the second lens group includes two or more lenses;
The optical coherence tomography device of claim 10. the movable lens is a part of the two or more lenses in the second lens group;
13. The optical coherence tomography device of claim 12. the movable lenses are all of the two or more lenses in the second lens group;
13. The optical coherence tomography device of claim 12. The imaging lens system includes a zoom lens having a variable focal length.
2. The optical coherence tomography device of claim 1. a photodetector moving mechanism for moving the photodetector;
and a second control unit that controls the zoom lens and the photodetector moving mechanism in cooperation with each other.
16. The optical coherence tomography device of claim 15. The imaging lens system includes a liquid lens having a variable focal length.
2. The optical coherence tomography device of claim 1.

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