JP2024104924A - Ophthalmic device, method for controlling ophthalmic device, and program - Google Patents

Abstract

To provide a new technology for reducing costs of an ophthalmologic apparatus.SOLUTION: An ophthalmologic apparatus includes an acquisition part, a ring image center position identifying part, a polar coordinate conversion part, a filter processing part, and a calculation part. The acquisition part projects a ring-shaped light to an eye to be tested and receives return light from the eye to be tested to acquire a ring image. The ring image center position identifying part identifies a center position of the ring image. The polar coordinate conversion part performs polar coordinate conversion of the ring image around the center position. The filter processing part performs noise reduction processing on a polar coordinate conversion image of the ring image on which polar coordinate conversion is performed by the polar coordinate conversion part. The calculation part calculates refractive power value of the eye to be tested on the basis of the noise reduced image on which the noise reduction processing has been performed by the filter processing part.SELECTED DRAWING: Figure 3

Description

This invention relates to an ophthalmic device, a control method for an ophthalmic device, and a program.

Conventionally, ophthalmic devices capable of measuring the refractive power of a test eye have been known. This type of ophthalmic device projects a ring-shaped light onto the fundus of the test eye, identifies the ring image obtained by receiving the return light from the test eye, and is capable of calculating the refractive power value by analyzing the identified ring image.

The ring image formed based on the result of receiving the return light from the subject's eye contains noise components, which reduces the accuracy of the analysis results of the ring image. For example, Patent Documents 1, 2, and 3 disclose methods for optically reducing noise in the ring image using a rotary prism.

Japanese Patent Application Publication No. 10-014876 International Publication No. 2003/022138 JP 2004-081725 A

If the rotary prism could be eliminated, the configuration and drive control of the ophthalmic device would be simplified. This could potentially lead to lower costs for the ophthalmic device.

The present invention was made in consideration of these circumstances, and its purpose is to provide a new technology for reducing the cost of ophthalmic devices.

One aspect of the embodiment is an ophthalmic device including: an acquisition unit that acquires a ring image by projecting ring-shaped light onto the test eye and receiving return light from the test eye; a ring image center position identification unit that identifies the center position of the ring image; a polar coordinate conversion unit that converts the ring image into polar coordinates with the center position as the center; a filter processing unit that performs noise reduction processing on the polar coordinate converted image of the ring image converted into polar coordinates by the polar coordinate conversion unit; and a calculation unit that calculates the refractive power value of the test eye based on the noise-reduced image that has been subjected to the noise reduction processing by the filter processing unit.

Another aspect of the embodiment is a control method for an ophthalmic device that projects ring-shaped light onto a test eye and acquires a ring image by receiving return light from the test eye. The control method for the ophthalmic device includes a ring image center position identification step for identifying the center position of the ring image, a polar coordinate conversion step for polar coordinate conversion of the ring image with the center position as the center, a filter processing step for performing noise reduction processing on the polar coordinate converted image of the ring image converted in the polar coordinate conversion step, and a calculation step for calculating the refractive power value of the test eye based on the noise-reduced image that has been subjected to the noise reduction processing in the filter processing step.

Yet another aspect of the embodiment is a program that causes a computer to execute each step of the above-mentioned method for controlling an ophthalmic device.

The present invention provides a new technology for reducing the cost of ophthalmic devices.

1 is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic apparatus according to an embodiment. 2 is a schematic diagram illustrating an example of the configuration of a processing system of an ophthalmic apparatus according to an embodiment. FIG. 2 is a schematic diagram illustrating an example of the configuration of a processing system of an ophthalmic apparatus according to an embodiment. FIG. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 10A and 10B are schematic diagrams for explaining an operation of an ophthalmologic apparatus according to a comparative example of an embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5 is a flowchart illustrating an example of the operation of the ophthalmologic apparatus according to the embodiment. 5 is a flowchart illustrating an example of the operation of the ophthalmologic apparatus according to the embodiment. FIG. 13 is a schematic diagram illustrating an example of the configuration of a processing system of an ophthalmologic apparatus according to a modified example of the embodiment. 10 is a flowchart showing an example of the operation of an ophthalmologic apparatus according to a modified example of an embodiment.

Examples of embodiments of an ophthalmic device, a control method for an ophthalmic device, and a program according to the present invention will be described in detail with reference to the drawings. Note that the contents of the documents cited in this specification and any publicly known technology may be incorporated into the following embodiments.

The ophthalmic device according to the embodiment is configured to project a ring-shaped light onto the fundus of the test eye, acquire a ring image by receiving the return light from the test eye, and calculate the refractive power value of the test eye based on the acquired ring image. In some embodiments, the ophthalmic device includes an optical system configured to project a ring-shaped light onto the fundus of the test eye and receive the return light from the test eye, and calculates the refractive power value of the test eye by analyzing the ring image acquired using the optical system. In some embodiments, the ophthalmic device acquires a ring image acquired by an external device from the device via a network or the like, and calculates the refractive power value of the test eye by analyzing the acquired ring image.

The ophthalmic device identifies the center position of the acquired ring image, performs polar coordinate transformation on the ring image centered on the identified center position of the ring image to generate a polar coordinate transformed image, and performs noise reduction processing on the generated polar coordinate transformation. The ophthalmic device calculates the refractive power value of the test eye based on the noise-reduced image that has been subjected to noise reduction processing. In some embodiments, the ophthalmic device performs inverse polar coordinate transformation on the noise-reduced image to generate an inverse polar coordinate transformed image (a ring image that has been subjected to noise reduction processing), and calculates the refractive power value of the test eye based on the generated inverse polar coordinate transformed image.

This makes it possible to reduce noise in the ring image (polar coordinate conversion image) without providing a rotary prism, and improves the analysis accuracy of the ring image. As a result, the configuration and control of the ophthalmic device are simplified, making it possible to reduce the cost of the ophthalmic device.

The ophthalmic device according to the embodiment realizes the functions of the ophthalmic information processing device according to the embodiment. The ophthalmic information control method according to the embodiment is executed by a processor (computer) and includes one or more steps for realizing processing for controlling the ophthalmic device according to the embodiment. The program according to the embodiment causes the processor to execute each step of the ophthalmic device control method according to the embodiment. The recording medium (storage medium) according to the embodiment is a non-transitory recording medium (storage medium) readable by a computer in which the program according to the embodiment is recorded (stored).

In this specification, the term "processor" refers to a circuit such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), or a programmable logic device (e.g., an SPLD (Simple Programmable Logic Device), a CPLD (Complex Programmable Logic Device), or an FPGA (Field Programmable Gate Array)). The processor realizes the functions of the embodiment by, for example, reading and executing a program stored in a memory circuit or a storage device.

The following describes the ophthalmic apparatus according to the embodiment in a case where the ophthalmic apparatus performs median filter processing as noise reduction processing on a ring image (a polar coordinate transformed image obtained by polar coordinate transforming the ring image). However, the ophthalmic apparatus according to the embodiment can also be applied to cases where noise reduction processing other than median filter processing is performed.

The ophthalmic apparatus according to the embodiment includes an optical system (refractive power measurement optical system, refractive power measurement optical system) capable of performing refractive power measurement (refractive power measurement). The ophthalmic apparatus according to some embodiments further includes a subjective test optical system for performing subjective tests, and an objective measurement system for performing other objective measurements.

Subjective testing is a measurement technique that obtains information using responses from the subject. Subjective testing includes subjective refraction measurements such as distance testing, near testing, contrast testing, and glare testing, as well as visual field testing.

Objective measurement is a measurement technique that obtains information about the subject's eye primarily using physical methods, without reference to responses from the subject. Objective measurement includes measurement to obtain characteristics of the subject's eye and photography to obtain images of the subject's eye. Other objective measurements include corneal shape measurement, intraocular pressure measurement, fundus photography, optical coherence tomography (OCT) measurement, etc.

Hereinafter, the fundus conjugate position is a position that is approximately optically conjugate with the fundus of the test eye when alignment is complete, and refers to a position that is optically conjugate with the fundus of the test eye or its vicinity. Similarly, the pupil conjugate position is a position that is approximately optically conjugate with the pupil of the test eye when alignment is complete, and refers to a position that is optically conjugate with the pupil of the test eye or its vicinity.

The direction of the optical axis of the optical system is defined as the z direction (front-to-back direction), the horizontal direction perpendicular to (or intersecting with) the optical axis of the optical system is defined as the x direction (left-to-right direction), and the vertical direction perpendicular to the optical axis of the optical system is defined as the y direction (up-down direction).

<Configuration of Optical System>
1 shows an example of the configuration of an optical system of an ophthalmic apparatus 1000 according to an embodiment. The ophthalmic apparatus 1000 includes an optical system for measuring the refractive power of the subject's eye E (refractive index measurement optical system), an optical system for observing the subject's eye E, an optical system for performing other tests on the subject's eye E, and a dichroic mirror for wavelength separation of the optical paths of these optical systems. An anterior eye observation system 5 is provided as the optical system for observing the subject's eye E. A corneal shape measurement optical system is provided as the optical system for performing other tests on the subject's eye E.

The ophthalmic device 1000 includes, as the above optical systems, a Z alignment system 1, an XY alignment system 2, a keratometry system 3, a fixation projection system 4, an anterior segment observation system 5, a reflex measurement projection system 6, and a reflex measurement light receiving system 7. In the following, for example, the anterior segment observation system 5 uses light of 940 nm to 1000 nm, the reflex measurement optical system (reflex measurement projection system 6, reflex measurement light receiving system 7) uses light of 830 nm to 880 nm, and the fixation projection system 4 uses light of 400 nm to 700 nm.

(Anterior Eye Observation System 5)
The anterior-segment observation system 5 captures a moving image of the anterior segment of the subject's eye E. In the optical system passing through the anterior-segment observation system 5, the imaging surface of the image sensor 59 is disposed at a pupil conjugate position. The anterior-segment illumination light source 50 irradiates illumination light (e.g., infrared light) onto the anterior segment of the subject's eye E. In some embodiments, the function of the anterior-segment illumination light source 50 is realized by a keratinizing light source 32 described below, and the ophthalmic apparatus 1000 has a configuration in which the anterior-segment illumination light source 50 is omitted.

The light reflected by the anterior segment of the subject's eye E passes through the objective lens 51, the dichroic mirror 52, passes through a hole formed in the aperture (telecentric aperture) 53, and passes through the half mirror 23. The light that passes through the half mirror 23 passes through the relay lenses 55 and 56, and passes through the dichroic mirror 76. The dichroic mirror 52 combines (separates) the optical path of the reflex measurement optical system and the optical path of the anterior segment observation system 5. The dichroic mirror 52 is arranged such that the optical path combining surface that combines these optical paths is inclined with respect to the optical axis of the objective lens 51. The relay lens 56 may be movable along the optical axis of the anterior segment observation system 5 (or the optical axis of the relay lens 56). The light that passes through the dichroic mirror 76 is imaged on the imaging surface of the image sensor 59 (area sensor) by the imaging lens 58. The image sensor 59 captures images and outputs signals at a predetermined rate. The output (video signal) of the imaging element 59 is input to a processing unit 9 described below. The processing unit 9 displays an anterior eye image E' based on this video signal on a display screen 10a of a display unit 10 described below. The anterior eye image E' is, for example, an infrared moving image.

(Z alignment system 1)
The Z alignment system 1 projects light (infrared light) for alignment in the optical axis direction (front-back direction, z direction) of the anterior eye observation system 5 onto the subject's eye E. The Z alignment light source 11 projects light onto the cornea Cr of the subject's eye E from a position away from the optical axis of the anterior eye observation system 5. The light output from the Z alignment light source 11 is projected onto the cornea Cr of the subject's eye E, reflected by the cornea Cr, and imaged onto the sensor surface of the line sensor 13 by the imaging lens 12. When the position of the corneal apex changes in the optical axis direction of the anterior eye observation system 5, the projection position of the light (reflected light of the cornea Cr) on the sensor surface of the line sensor 13 changes. The processing unit 9 obtains the position of the corneal apex of the subject's eye E based on the projection position of the light on the sensor surface of the line sensor 13, and performs Z alignment by controlling a mechanism for moving the optical system based on the position.

(XY alignment system 2)
The XY alignment system 2 irradiates the subject's eye E with light (infrared light) for alignment in directions (left-right direction (x direction) and up-down direction (y direction)) perpendicular to the optical axis of the anterior eye observation system 5. The XY alignment system 2 includes an XY alignment light source 21 and a collimator lens 22 provided on an optical path branched off from the optical path of the anterior eye observation system 5 by a half mirror 23. The light output from the XY alignment light source 21 passes through the collimator lens 22, is reflected by the half mirror 23, and is projected onto the subject's eye E through the anterior eye observation system 5. The light reflected by the cornea Cr of the subject's eye E is guided to the image sensor 59 through the anterior eye observation system 5.

The image (bright spot image) Br based on this reflected light is included in the anterior eye image E'. The processing unit 9 displays the anterior eye image E' including the bright spot image Br and the alignment mark AL on the display screen of the display unit. When performing manual XY alignment, the user moves the optical system so as to guide the bright spot image Br into the alignment mark AL. When performing automatic alignment, the processing unit 9 controls the mechanism for moving the optical system so that the displacement of the bright spot image Br relative to the alignment mark AL is canceled.

(Kerato measurement system 3)
The keratometry system 3 projects ring-shaped light (infrared light, kerato-ring light) onto the cornea Cr to measure the shape of the cornea Cr of the subject's eye E. The kerato-plate 31 is disposed between the objective lens 51 and the subject's eye E. The kerato-plate 31 is provided with a kerato-ring light source 32 on the rear side (objective lens 51 side) of the kerato-plate 31. The kerato-plate 31 has an arc-shaped or circumferential transmission pattern formed around a position corresponding to the optical axis of the optical system (kerato-measurement system 3, anterior eye observation system 5). In the embodiment, the kerato-plate 31 has two concentric transmission patterns formed around the optical axis, but one circular transmission pattern or three or more child-centered transmission patterns may be formed around the optical axis.

By illuminating the keratography plate 31 with light from the keratography light source 32, a ring-shaped light beam (an arc-shaped or circumferential measurement pattern, keratography light) is projected onto the cornea Cr of the subject's eye E. The reflected light (keratography image) from the cornea Cr of the subject's eye E is detected by the imaging element 59 together with the anterior segment image E'. The processing unit 9 performs known calculations based on this keratography image to calculate corneal shape parameters that represent the shape of the cornea Cr.

(Reflection measurement projection system 6, reflection measurement light receiving system 7)
The refraction measurement optical system includes a refraction measurement projection system 6 and a refraction measurement light receiving system 7 used for refractive power measurement. The refraction measurement projection system 6 projects a light beam (e.g., a ring-shaped light beam) (infrared light) for refractive power measurement onto the fundus Ef. The refraction measurement light receiving system 7 receives the return light of this light beam from the subject's eye E. The refraction measurement projection system 6 is provided on an optical path branched by an aperture prism 65 provided on the optical path of the refraction measurement light receiving system 7. The hole formed in the aperture prism 65 is arranged at the pupil conjugate position. In the optical system passing through the refraction measurement light receiving system 7, the imaging surface of the image sensor 59 is arranged at the fundus conjugate position.

In some embodiments, the reflex measurement light source 61 is a superluminescent diode (SLD) light source, which is a high-brightness light source. The reflex measurement light source 61 is movable in the optical axis direction. The reflex measurement light source 61 is arranged at a fundus conjugate position. The light output from the reflex measurement light source 61 passes through the relay lens 62 and enters the conical surface of the conical prism 63. The light that enters the conical surface is deflected and exits from the bottom surface of the conical prism 63. The light that exits from the bottom surface of the conical prism 63 passes through a ring-shaped light-transmitting portion formed in the ring aperture 64. The light (ring-shaped light beam) that passes through the light-transmitting portion of the ring aperture 64 is reflected by a reflecting surface formed around the hole of the hole prism 65 and is reflected by the dichroic mirror 67. Here, the hole formed in the hole prism 65 can be arranged at a pupil conjugate position. The light reflected by the dichroic mirror 67 is reflected by the dichroic mirror 52, passes through the objective lens 51, and is projected onto the subject's eye E.

The return light of the ring-shaped light beam projected on the fundus Ef passes through the objective lens 51 and is reflected by the dichroic mirror 52 and the dichroic mirror 67. The return light reflected by the dichroic mirror 67 passes through the hole of the aperture prism 65, passes through the relay lens 71, is reflected by the reflecting mirror 72, and passes through the relay lens 73 and the focusing lens 74. The focusing lens 74 can move along the optical axis of the reflex measurement light receiving system 7. The light transmitted through the focusing lens 74 is reflected by the reflecting mirror 75, is reflected by the dichroic mirror 76, and is imaged on the imaging surface of the imaging element 59 by the imaging lens 58. The processing unit 9 calculates the refractive power value of the subject eye E by performing a known calculation based on the output from the imaging element 59. For example, the refractive power value includes spherical power, cylindrical power and cylindrical axis angle, or equivalent spherical power.

(Fixation Projection System 4)
The fixation projection system 4 is provided in an optical path that is wavelength-separated from the optical path of the reflex measurement optical system by a dichroic mirror 67 .

The fixation projection system 4 presents a fixation target to the subject's eye E. A fixation unit 40 is disposed in the optical path of the fixation projection system 4. The fixation unit 40 is controlled by a processing unit 9, which will be described later, and is movable along the optical path of the fixation projection system 4. The fixation unit 40 includes a liquid crystal panel 41.

The liquid crystal panel 41, controlled by the processing unit 9, displays a pattern representing a fixation target. The liquid crystal panel 41 is capable of displaying a fixation target pattern representing a fixation target for keratometry or reflex measurement (e.g., a landscape chart).

In some embodiments, the fixation target includes two or more fixation targets having different visual angles. In this case, the liquid crystal panel 41 displays a pattern representing one of the two or more fixation targets having different visual angles so as to selectively present the two or more fixation targets to the subject's eye E.

The fixation position of the subject's eye E can be changed by changing the display position of the pattern on the screen of the liquid crystal panel 41. Fixation positions of the subject's eye E include a position for acquiring an image centered on the macular portion of the fundus Ef, a position for acquiring an image centered on the optic disc, and a position for acquiring an image centered on the center of the fundus between the macular portion and the optic disc. The display position of the pattern representing the fixation target can be changed as desired.

Light from the liquid crystal panel 41 passes through the relay lens 42, passes through the relay lens 43, is reflected by the reflecting mirror 44, passes through the dichroic mirror 67, and is reflected by the dichroic mirror 52. The light reflected by the dichroic mirror 52 passes through the objective lens 51 and is projected onto the fundus Ef. In some embodiments, the liquid crystal panel 41 and the relay lens 42 can each be moved independently in the optical axis direction.

In some embodiments, instead of the liquid crystal panel 41, a transmissive or reflective optotype chart and an illumination light source for illuminating the optotype chart are provided. A fixation target pattern representing a fixation target is printed on the optotype chart. The fixation target is presented to the subject's eye E by illuminating the optotype chart with the illumination light source. Two or more optotype charts on which fixation target patterns with different visual angles are printed may be selectively illuminated by the illumination light source.

The processing unit 9 calculates the refractive power value from the measurement results obtained using the refraction measurement optical system, and based on the calculated refractive power value, moves the refraction measurement light source 61 and the focusing lens 74 in the optical axis direction to a position where the fundus Ef, the refraction measurement light source 61, and the image sensor 59 are conjugate. In some embodiments, the processing unit 9 moves the liquid crystal panel 41 (fixation unit 40) in the optical axis direction in conjunction with the movement of the refraction measurement light source 61 and the focusing lens 74.

<Processing system configuration>
The configuration of the processing system of the ophthalmic apparatus 1000 will be described.

Figures 2 and 3 show schematic diagrams for explaining the configuration of the processing system of the ophthalmic device 1000. Figures 2 and 3 show block diagrams of an example of the functional configuration of the processing system of the ophthalmic device 1000.

Figure 2 shows an example of a functional block diagram of the processing system (control system) of the ophthalmic device 1000. In Figure 2, parts similar to those in Figure 1 are given the same reference numerals, and descriptions will be omitted as appropriate. Figure 3 shows an example of a functional block diagram of the data processing unit 223 in Figure 2.

The processing unit 9 controls each part of the ophthalmic device 1000. The processing unit 9 can also execute various types of arithmetic processing. The processing unit 9 includes a processor. The processing unit 9 realizes the functions according to the embodiment, for example, by reading and executing a program stored in a memory circuit or a storage device.

The processing unit 9 is an example of an "ophthalmological information processing device" according to the embodiment. In other words, a program for realizing the functions of the processing unit 9 is an example of a "program" according to the embodiment.

The processing unit 9 includes a control unit 210 and an arithmetic processing unit 220. The functions of the processing unit 9 are realized by one or more processors. In some embodiments, the functions of the processing unit 9 are realized by multiple processors provided for each functional block constituting the processing unit 9 (arithmetic processing unit 220). In some embodiments, the functions of the processing unit 9 are realized by a single processor. The ophthalmic device 1000 also includes a movement mechanism 200, a display unit 270, an operation unit 280, and a communication unit 290.

The moving mechanism 200 is a mechanism that moves the head unit, which houses optical systems such as the Z alignment system 1, XY alignment system 2, keratometry system 3, fixation projection system 4, anterior eye observation system 5, reflex measurement projection system 6, and reflex measurement light receiving system 7, in the left-right direction (x direction), up-down direction (y direction), and front-back direction (z direction). For example, the moving mechanism 200 is provided with an actuator that generates a driving force for moving the head unit, and a transmission mechanism that transmits this driving force. The actuator is, for example, a pulse motor. The transmission mechanism is, for example, a combination of gears or a rack-and-pinion. The control unit 210 (main control unit 211) controls the moving mechanism 200 by sending a control signal to the actuator.

(Control unit 210)
The control unit 210 includes a processor and controls each unit of the ophthalmic apparatus. The control unit 210 includes a main control unit 211 and a storage unit 212. The storage unit 212 stores in advance computer programs for controlling the ophthalmic apparatus. The computer programs include a light source control program, an optical system control program, an arithmetic processing program, and a user interface program. The main control unit 211 operates according to such computer programs, causing the control unit 210 to execute control processing.

The main control unit 211 performs various controls of the ophthalmic apparatus as a measurement control unit. The control of the Z alignment system 1 includes control of the Z alignment light source 11 and control of the line sensor 13. The control of the Z alignment light source 11 includes turning the light source on and off, adjusting the light amount, and adjusting the aperture. As a result, the Z alignment light source 11 is switched on and off, and the light amount is changed. The control of the line sensor 13 includes exposure adjustment, gain adjustment, and detection rate adjustment of the detection element. The main control unit 211 takes in a signal detected by the line sensor 13, and specifies the projection position of light on the line sensor 13 based on the taken in signal. The main control unit 211 controls the calculation processing unit 220 to specify the position of the corneal apex of the test eye E based on the specified projection position, and based on this, controls the moving mechanism 200 to move the head unit in the z direction (Z alignment).

The control of the XY alignment system 2 includes control of the XY alignment light source 21. The control of the XY alignment light source 21 includes turning the light source on and off, adjusting the amount of light, and adjusting the aperture. This causes the XY alignment light source 21 to be switched on and off, or to change the amount of light. The main control unit 211 captures the signal detected by the image sensor 59, identifies the bright spot image based on the captured signal, and controls the movement mechanism 200 based on the displacement of the position of the bright spot image relative to the alignment reference position (e.g., the position corresponding to the optical axis of the optical system) to move the head unit in the x and y directions (XY alignment).

The control of the keratometry system 3 includes the control of the keratometry light source 32. The control of the keratometry light source 32 includes turning the light source on and off, adjusting the light intensity, and adjusting the aperture. This causes the keratometry light source 32 to be switched on and off, and changes the light intensity. The main control unit 211 causes the calculation processing unit 220 to execute known calculations on the keratometry image detected by the imaging element 59. This allows corneal shape information of the subject's eye E to be obtained.

Control of the fixation projection system 4 includes control of the liquid crystal panel 41 and control of the movement of the fixation unit 40. Control of the liquid crystal panel 41 includes turning on and off the display of the pattern representing the fixation target, switching the pattern representing the fixation target, and switching the display position of the pattern representing the fixation target. Switching the pattern representing the fixation target includes switching between a pattern representing a fixation target with a small visual angle and a pattern representing a fixation target with a large visual angle.

For example, the fixation projection system 4 is provided with a moving mechanism that moves the liquid crystal panel 41 (or the fixation unit 40) in the optical axis direction. Like the moving mechanism 200, this moving mechanism is provided with an actuator that generates a driving force for moving the moving mechanism, and a transmission mechanism that transmits this driving force. The main control unit 211 controls the moving mechanism by sending a control signal to the actuator, and moves at least the liquid crystal panel 41 in the optical axis direction. This adjusts the position of the liquid crystal panel 41 so that the liquid crystal panel 41 and the fundus Ef are optically conjugate.

Control of the anterior eye observation system 5 includes control of the anterior eye illumination light source 50 and control of the image sensor 59. Control of the anterior eye illumination light source 50 includes turning the light source on and off, adjusting the light amount, and adjusting the aperture. This allows the anterior eye illumination light source 50 to be switched on and off, and the light amount to be changed. Control of the image sensor 59 includes adjustment of the exposure, gain, and detection rate of the image sensor 59. The main control unit 211 captures signals detected by the image sensor 59, and causes the calculation processing unit 220 to perform processing such as forming an image based on the captured signals.

The control of the reflex measurement projection system 6 includes the control of the reflex measurement light source 61. The control of the reflex measurement light source 61 includes turning the light source on and off, adjusting the light amount, and adjusting the aperture. This causes the reflex measurement light source 61 to be switched on and off, or the light amount to be changed. For example, the reflex measurement projection system 6 includes a movement mechanism that moves the reflex measurement light source 61 in the optical axis direction. Similar to the movement mechanism 200, this movement mechanism is provided with an actuator that generates a driving force for moving the movement mechanism, and a transmission mechanism that transmits this driving force. The main control unit 211 controls the movement mechanism by sending a control signal to the actuator, and moves the reflex measurement light source 61 in the optical axis direction.

The control of the reflex measurement light receiving system 7 includes the control of the focusing lens 74. The control of the focusing lens 74 includes the control of the movement of the focusing lens 74 in the optical axis direction. For example, the reflex measurement light receiving system 7 includes a moving mechanism that moves the focusing lens 74 in the optical axis direction. This moving mechanism is provided with an actuator that generates a driving force for moving the moving mechanism, and a transmission mechanism that transmits this driving force, similar to the moving mechanism 200. The main control unit 211 controls the moving mechanism by sending a control signal to the actuator, and moves the focusing lens 74 in the optical axis direction. The main control unit 211 can move the reflex measurement light source 61 and the focusing lens 74 in the optical axis direction, for example, according to the refractive power of the test eye E, so that the reflex measurement light source 61, the fundus Ef, and the image sensor 59 are optically conjugate.

Furthermore, as a display control unit, the main control unit 211 is capable of displaying various information on the display unit 270. For example, the main control unit 211 causes the display unit 270 to display images (anterior eye image, fundus image) of the subject's eye E obtained by the image sensor 59, a graphical user interface for realizing the functions of the operation unit 280 by a touch panel, and information corresponding to the processing results of the arithmetic processing unit 220. The processing results of the arithmetic processing unit 220 include the refractive power value of the subject's eye E calculated by the ocular refractive power calculation unit 221, the corneal shape information of the subject's eye E calculated by the corneal shape information calculation unit 222, the processing results of the data processing unit 223, and the like.

Furthermore, the main control unit 211 performs processes for writing data to the memory unit 212 and reading data from the memory unit 212.

(Memory unit 212)
The storage unit 212 stores various data. Examples of data stored in the storage unit 212 include measurement results of objective measurements (refractive measurements, keratometric measurements), image data of fundus images, subject eye information, and subject information. The subject eye information includes information about the subject eye, such as identification information of the left eye/right eye. The subject information includes information about the subject, such as a patient ID, name, subject age, sex, height, and weight. In some embodiments, the subject information is information acquired from an electronic medical record. In some embodiments, the subject eye information and subject information are information input by the examiner or subject using the operation unit 280. In addition, the storage unit 212 stores various programs and data for operating the ophthalmic device.

(Calculation processing unit 220)
The arithmetic processing unit 220 includes an eye refractive power calculation unit 221 , a corneal shape information calculation unit 222 , and a data processing unit 223 .

(Eye refractive power calculation unit 221)
The ocular refractive power calculation unit 221 calculates the refractive power value of the test eye E by analyzing a ring image (pattern image) obtained by receiving, by the image sensor 59, the return light of a ring-shaped light beam (ring-shaped measurement pattern) projected onto the fundus Ef by the reflex measurement projection system 6. In this embodiment, a noise-reduced image of the ring image is obtained by performing noise reduction processing, which will be described later, on the ring image obtained by receiving the return light by the image sensor 59. The ocular refractive power calculation unit 221 calculates the refractive power value of the test eye E by analyzing the noise-reduced image of the ring image.

The eye refractive power calculation unit 221 can determine the refractive power value of the test eye E by specifying the size and shape of the acquired ring image, as disclosed in, for example, Japanese Patent Application Laid-Open No. 63-275318. Here, the size of the ring image changes according to the refraction of the test eye E, and the shape of the ring image changes from a perfect circle to an ellipse according to the degree of astigmatism. At this time, when the ring image has a major axis and a minor axis and is an ellipse whose major axis forms a predetermined angle with respect to the reference axis, the size of the ellipse corresponds to the spherical power, the refractive power of the strong meridian of the astigmatism corresponds to the major axis, the refractive power of the weak meridian of the astigmatism corresponds to the minor axis, and the astigmatism axis angle corresponds to the angle. In this embodiment, the eye refractive power calculation unit 221 specifies the major axis, minor axis, and angle of the approximate ellipse of the ring image from the image after polar coordinate conversion obtained by converting the ring image into polar coordinates with the center position (or center of gravity) of the ring image as the center. More specifically, the eye refractive power calculation unit 221 identifies the major axis, minor axis, and angle of the approximate ellipse of the ring image from the noise-reduced image obtained by performing noise reduction processing on the image after polar coordinate conversion.

The ocular refractive power calculation unit 221 determines the size of the approximate ellipse from the major axis, minor axis, and angle, and calculates the spherical power S corresponding to the determined size of the ellipse based on a predetermined reference circle. The ocular refractive power calculation unit 221 also determines the difference in refractive power between the major axis corresponding to the strongest meridian and the minor axis corresponding to the weakest meridian as the cylindrical power C, and determines the angle with respect to the reference axis as the cylindrical axis angle A. In some embodiments, the equivalent spherical power SE (= S + C/2) is calculated as the refractive power value.

In some embodiments, the ocular refractive power calculation unit 221 performs an approximate ellipse fitting process on the ring image in the xy plane as disclosed in, for example, Japanese Patent Application Laid-Open No. 63-275318, to obtain a general formula for the approximate ellipse of the ring image, "αx ² +βy ² +γxy=1" (α, β, γ are coefficients). Since the coefficients α, β, and γ can be expressed by the major axis, minor axis, and angle, the ocular refractive power calculation unit 221 can calculate the major axis, minor axis, and angle from the coefficients α, β, and γ. In other words, the ocular refractive power calculation unit 221 can calculate the major axis, minor axis, and angle from the ring image in the xy coordinate system before polar coordinate conversion.

In some embodiments, the ocular refractive power calculation unit 221 calculates the spherical power S, the cylindrical power C and the cylindrical axis angle A, or the spherical equivalent power SE, based on the deformation and displacement of the ring image relative to the reference pattern.

(Cornea shape information calculation unit 222)
The corneal shape information calculation unit 222 receives reflected light from the anterior segment onto which the keratometry system 3 projects the keratometry light beam, and calculates a ring pattern image (keratometry image) acquired by the anterior segment observation system 5. The corneal shape information includes the corneal refractive power, the degree of corneal astigmatism, and the corneal astigmatism axis angle. For example, the corneal shape information calculation unit 222 analyzes a keratinogram image. In this way, the corneal radius of curvature of the principal meridian and the minor meridian on the anterior surface of the cornea is calculated, and the above-mentioned corneal shape information is calculated based on the corneal radius of curvature.

(Data processing unit 223)
The data processing unit 223 performs various types of data processing (image processing) and analysis processing on the image obtained by the imaging element 59. For example, the data processing unit 223 executes correction processing such as luminance correction and dispersion correction of the image.

The data processing unit 223 also identifies a ring image for calculating the refractive power value of the test eye E, performs polar coordinate transformation on the identified ring image, and performs noise reduction processing on the image after polar coordinate transformation to generate a noise-reduced image.

As shown in FIG. 3, the data processing unit 223 includes a ring image identification unit 230, a ring image center position identification unit 240, a polar coordinate conversion unit 250, and a filter processing unit 260.

The functions of the data processing unit 223 are realized by a processor. In some embodiments, the functions of the data processing unit 223 are realized by multiple processors provided for each functional block that constitutes the data processing unit 223. In some embodiments, the functions of the data processing unit 223 are realized by a single processor.

(Ring image identifying unit 230)
The ring image identification unit 230 analyzes the fundus image of the test eye E obtained by the image sensor 59 in the reflex measurement light receiving system 7, and identifies the ring image formed by the return light of the ring-shaped light beam projected onto the fundus Ef by the reflex measurement projection system 6.

For example, the ring image identification unit 230 determines the luminance distribution of the acquired fundus image, determines the central position or center of gravity position of the ring image from the determined luminance distribution, and determines the luminance distribution along multiple meridian directions extending radially from the determined central position or center of gravity position. The ring image identification unit 230 identifies the ring image from the determined luminance distribution.

(Ring image center position specifying unit 240)
The ring image center position identifying section 240 identifies the center position of the ring image identified by the ring image identifying section 230 .

For example, the ring image center position identifying unit 240 identifies four meridians in the cross direction from the brightness distribution of the identified ring image, and identifies the position on the four identified meridians that is approximately equal in distance from the inner or outer diameter of the ring image as the center position of the ring image.

In some embodiments, the ring image center position identifying section 240 identifies the center position of the ring image from the luminance distribution of the fundus image obtained by the ring image identifying section 230. In some embodiments, the ring image center position identifying section 240 identifies the center position of the ring image identified by the ring image identifying section 230.

In some embodiments, the ring image center position identification unit 240 performs an ellipse approximation process on the ring image, and identifies the center position of the approximated ellipse, which is the intersection point of the major axis and minor axis of the obtained approximated ellipse, as the center position of the ring image.

In some embodiments, the ring image center position identification unit 240 identifies the center position of the ring image from an image obtained by applying noise reduction processing such as a Gaussian filter to the ring image identified by the ring image identification unit 230.

(Polar coordinate conversion unit 250)
The polar coordinate conversion unit 250 performs polar coordinate conversion processing on the ring image identified by the ring image identifying unit 230, centered around the center position of the ring image identified by the ring image center position identifying unit 240, to generate a polar coordinate converted image of the ring image.

Figures 4 and 5 show explanatory diagrams of the operation of the polar coordinate conversion unit 250. Figure 4 shows an example of a ring image in the xy coordinate system identified by the ring image identification unit 230. Figure 5 shows an example of a polar coordinate converted image of the ring image generated by the polar coordinate conversion unit 250.

The ring image center position identifying unit 240 identifies the center position O of the ring image from the ring image IMG0 in the xy coordinate system as shown in FIG. 4. The polar coordinate conversion unit 250 performs polar coordinate conversion on the ring image IMG0 in the xy coordinate system with the center position O as the origin, centered on the center position O. As a result, the polar coordinate conversion unit 250 can generate a ring image (polar coordinate converted image) IMG1 in the polar coordinate system as shown in FIG. 5, which is defined by the radius (radius) r from the center position O and the deflection angle (angle) θ with respect to a reference direction (e.g., the x direction).

In some embodiments, the polar coordinate conversion unit 250 performs polar coordinate conversion on the image obtained by applying noise reduction processing such as a Gaussian filter to the ring image IMG0 identified by the ring image identification unit 230.

(Filter Processing Unit 260)
The filter processing unit 260 performs noise reduction processing on the polar coordinate conversion image IMG1 generated by the polar coordinate conversion unit 250. Examples of noise reduction processing include median filtering, average filtering, Gaussian filtering, and LoG (Laplacian of Gaussian) filtering. In this embodiment, the filter processing unit 260 can perform one-dimensional or two-dimensional median filtering on the polar coordinate conversion generated by the polar coordinate conversion unit 250. For example, the filter processing unit 260 performs one-dimensional median filtering on the polar coordinate conversion image for each pixel block having one pixel in a radial (radial) direction centered on the center position of the ring image identified by the ring image center position identification unit 240 and having a first number of pixels in an angular (deflection) direction centered on the center position.

Figures 6 and 7 are diagrams illustrating the operation of the filter processing unit 260. Figure 6 is a schematic representation of an example of a pixel block (processing unit) on which median filter processing is performed. Figure 7 is a schematic representation of the processing contents of the median filter processing performed on the pixel block of Figure 6. Figure 7 shows the processing contents of one-dimensional median filter processing, but two-dimensional median filter processing is similar.

Median filter processing is a process in which the pixel value of each pixel of interest is replaced with the median of the pixel values of two or more pixels surrounding the pixel of interest while sequentially changing the pixel of interest. In one-dimensional median filter processing, the processing unit is a pixel block (a group of pixels adjacent in one dimension) that includes two or more pixels adjacent in the angular direction around the pixel of interest. In two-dimensional median filter processing, the processing unit is a pixel block (a group of pixels adjacent in two dimensions) that includes two or more pixels adjacent in the radial and angular directions around the pixel of interest.

The filter processing unit 260 sequentially acquires data blocks DT including groups of pixels adjacent in the angular direction from a predetermined acquisition start line that extends in the angular direction (circumferential direction) of the polar coordinate transformed image IMG1. The filter processing unit 260 sequentially acquires pixel blocks DS from the acquired data blocks DT so that the pixel of interest moves in the angular direction, and performs median filter processing on each pixel block DS.

Because the polar coordinate converted image IMG1 is an image obtained by polar coordinate conversion of the ring image, each of the radial pixels at an angle of 360 degrees in the polar coordinate converted image IMG1 corresponds to a radial pixel at an angle of 0 degrees. Therefore, if the pixels angularly adjacent to the pixel of interest in the pixel block do not fit into the data block DT, the pixel block is obtained to include adjacent pixels in the positive direction from an angle of 0 degrees or the negative direction from an angle of 360 degrees.

For example, as shown in FIG. 6, the data block DT includes pixels d1 to d9 arranged in the angular direction. When the filter size of the one-dimensional median filter process is 1 pixel (radial direction, r direction) × 5 pixels (angular direction, θ direction), the filter processing unit 260 performs median filter process on pixels d1 to d5 adjacent in the angular direction to the pixel of interest d3. Next, the filter processing unit 260 performs median filter process on pixels d2 to d6 adjacent in the angular direction to the pixel of interest d4, performs median filter process on pixels d3 to d7 adjacent in the angular direction to the pixel of interest d5, ..., performs median filter process on pixels d5 to d9 adjacent in the angular direction to the pixel of interest d7. Furthermore, the filter processing unit 260 performs median filter process on pixels d6 to d9 and d1 adjacent in the angular direction to the pixel of interest d8, and performs median filter process on pixels d7 to d9 and d1 to d2 adjacent in the angular direction to the pixel of interest d9.

Here, the pixel values of the pixels d1 to d9 constituting a given data block DT0 in the polar coordinate transformed image IMG1 before median filter processing are assumed to have the pixel values shown in Figure 7. Note that in Figure 7, a pixel value of "0" is assumed to be a black pixel, and a pixel value of "1" is assumed to be a white pixel.

First, the filter processing unit 260 obtains a pixel block DS0 including pixels d1 to d5 surrounding the pixel of interest d3 from the data block DT0. Next, the filter processing unit 260 executes a sorting process to sort the pixels d1 to d5 constituting the obtained pixel block DS0 in ascending (or descending) order of pixel value (sorting process block DS0s). The filter processing unit 260 identifies the pixel value "74", which is the median of the pixel values in the sorting process block DS0s, and replaces the pixel value of the pixel of interest d3 in the pixel block DS0 with the identified pixel value "74" (data block DT01).

Next, the filter processing unit 260 obtains a pixel block including pixels d2 to d6 surrounding the pixel of interest d4 from the data block DT0, and similarly replaces the pixel value of the pixel of interest d4. This process is repeated until all pixels constituting the data block DT0 become pixels of interest.

When the pixel of interest is pixel d9, the filter processing unit 260 acquires a pixel block DSn from the data block DT0, which includes pixels d7 to d8 and d1 to d2 surrounding the pixel of interest d9. Next, the filter processing unit 260 executes a sorting process on the pixels d7 to d9 and d1 to d2 that make up the acquired pixel block DSn (sorting process block DSns). The filter processing unit 260 identifies the pixel value "74", which is the median of the pixel values in the sorting process block DSns, and replaces the pixel value of the pixel of interest d9 in the pixel block DSn with the identified pixel value "74".

As described above, the filter processing unit 260 converts the data block DT0 into the data block DT1 after the median filter processing. The filter processing unit 260 acquires a data block from the next acquisition line adjacent in the radial direction, for example, and repeats the above process until, for example, all pixels of the polar coordinate conversion image IMG1 become pixels of interest.

When the filter processing unit 260 performs two-dimensional median filtering, the filter processing unit 260 can change the radial size of the pixel block in the data block of the topmost or bottommost radial line of the polar coordinate converted image. In some embodiments, the filter processing unit 260 is configured not to perform two-dimensional median filtering on a data block in which no pixels constituting a pixel block exist, such as a data block of the topmost or bottommost radial line of the polar coordinate converted image. In some embodiments, when a two-dimensional pixel block of a predetermined size cannot be configured, such as a data block of the topmost or bottommost radial line of the polar coordinate converted image, the data block is filled with a predetermined pixel value, and two-dimensional median filtering is performed with all pixels of the polar coordinate converted image as the target pixel.

Figure 8 shows an example of a polar coordinate converted image after noise reduction processing performed by the filter processing unit 260. Figure 8 shows an example of a noise reduced image IMG2 obtained by performing median filter processing on the polar coordinate converted image IMG1 shown in Figure 6.

The noise-reduced image IMG2 shown in FIG. 8 has reduced noise compared to the polar coordinate converted image IMG1. The eye refractive power calculation unit 221 identifies the major axis, minor axis, and angle of the approximate ellipse of the ring image from the noise-reduced image IMG2, and calculates the spherical power S, cylindrical power C, and cylindrical axis angle A from the identified major axis, minor axis, and angle.

In other words, according to the embodiment, it is possible to calculate the refractive power value of the test eye E with high accuracy without providing a rotary prism.

In some embodiments, the filter processing unit 260 acquires data blocks within a predetermined radial range, and performs median filter processing within the acquired data blocks within the predetermined radial range. Here, the predetermined range is uniquely determined by the range of spherical power, the range of cylindrical power, and the range of cylindrical axis angle that can be measured by the ophthalmic device 1000. This makes it possible to reduce the load of the median filter processing.

However, if the subject eye E has astigmatism, when polar coordinate transformation is performed on the acquired ring image, the shape of the ring image after polar coordinate transformation as shown in Figure 5 is not a straight line extending in the angular direction.

Figure 9 shows an example of a polar coordinate transformed image of a ring image when the subject's eye E has astigmatism.

Light is projected onto the fundus Ef of the test eye E, which is an astigmatic eye, and the shape of the ring image formed based on the returned light is elliptical. When polar coordinate transformation is performed on such a ring image, the ring image after polar coordinate transformation has a wave-like shape that changes radially as the angular direction increases.

In this case, if one-dimensional median filtering is performed on the polar coordinate transformed image IMG3 having the shape shown in Figure 9, stripes may appear in the radial direction.

Figure 10 shows an example of a noise-reduced image obtained by performing one-dimensional median filter processing on a polar coordinate transformed image in a comparative example of an embodiment.

As shown in FIG. 10, when one-dimensional median filter processing is performed on the polar coordinate converted image IMG3, the noise reduction effect differs for each diameter (line), and stripes appear in inclined parts where the diameter changes with the change in angle. In this case, it is desirable for the filter processing unit 260 to perform two-dimensional median filter processing on the polar coordinate converted image IMG3 so as to perform noise reduction processing in the radial direction as well.

Figure 11 is an explanatory diagram of the operation of two-dimensional median filter processing according to the embodiment.

In FIG. 11, the polar coordinate converted image IMG5 is an enlarged view of a portion of the polar coordinate converted image IMG3 in FIG. 9. At this time, the filter processing unit 260 performs two-dimensional median filter processing for each pixel block set to include pixels that make up the inclined portion of the polar coordinate converted image IMG5. At this time, the pixel block has a pixel number fsy in the radial direction and a pixel number fsx in the angular direction. This allows uniform noise reduction processing to be performed across the ring width of the ring image, making it possible to suppress the appearance of stripes in the inclined portion, as shown in the polar coordinate converted image IMG6. As a result, it becomes possible to reduce noise in the ring image, and the refractive power value of the test eye E can be calculated with higher accuracy.

Here, each of the pixel numbers fsx and fsy (i.e., the size of the pixel block) can be determined in advance based on the range of spherical power, cylindrical power, and cylindrical axis angle that can be measured by the ophthalmic device 1000. This makes it possible to significantly reduce the noise of the ring image without providing a rotary prism, even if the size and shape of the ring image change within the range of measurable refractive power values.

Specifically, the pixel counts fsx and fsy are determined based on the radial ring width of the ring image, the outer diameter in the short diameter direction of the ring image, and the outer diameter in the long diameter direction of the ring image, which are uniquely determined by the measurement range of the refractive power value (including the degree of astigmatism and the angle of the astigmatism axis) of the test eye by the ophthalmic device 1000.

Figures 12 and 13 show schematic diagrams of ring images obtained when the subject's eye E is an astigmatic eye. Figure 12 shows a schematic diagram of a ring image IMG10 in an xy coordinate system. Figure 13 shows a schematic diagram of a polar coordinate transformed image IMG11 obtained by performing polar coordinate transformation on the ring image IMG10 in Figure 12, and an enlarged view of the inclined portion of the ring image.

As shown in Figure 12, the number of pixels corresponding to the radial ring width of the ring image is d, the number of pixels corresponding to the outer diameter of the ring image in the long diameter direction is L, and the number of pixels corresponding to the outer diameter of the ring image in the short diameter direction is M. In this case, as shown in Figure 13, the number of pixels f corresponding to the angular ring width at the inclined portion of the ring image can be expressed as arccos(2d x (L - M)).

That is, if no stripes are generated in the radial direction by the polar coordinate transformation, the filter processing unit 260 can perform one-dimensional median filter processing on the polar coordinate transformed image for each pixel block having one pixel in the radial direction and a first number of pixels in the angular direction. Here, the first number of pixels is determined based on the ring width in the radial direction of the ring image, the outer diameter in the major axis direction of the ring image, and the outer diameter in the minor axis direction of the ring image. By making the first number of pixels larger than the number of pixels f in FIG. 12, it becomes possible to effectively reduce noise near the boundary of the ring image in the inclined portion.

On the other hand, if stripes occur in the radial direction due to the polar coordinate transformation, the filter processing unit 260 can perform two-dimensional median filter processing on the polar coordinate transformed image for each pixel block that has a number of pixels in the radial direction greater than the number of pixels d corresponding to the ring width and has a first number of pixels in the angular direction. Here, the first number of pixels is determined based on the ring width in the radial direction of the ring image, the outer diameter in the major axis direction of the ring image, and the outer diameter in the minor axis direction of the ring image. As with the one-dimensional median filter processing, the first number of pixels can be made greater than the number of pixels f in FIG. 12.

As shown in FIG. 13, from the polar coordinate converted image (noise reduced image) IMG11 that has been subjected to noise reduction processing, the ocular refractive power calculation unit 221 can determine the number of pixels L that corresponds to the outer diameter in the major axis direction of the approximation ellipse of the ring image, the number of pixels M that corresponds to the outer diameter in the minor axis direction, and the angle θ of the major axis. For example, for the ring image in the polar coordinate converted image IMG11, twice the longest diameter (outer diameter) in the radial direction is determined as the number of pixels L that corresponds to the outer diameter in the major axis direction, twice the shortest diameter (outer diameter) in the radial direction is determined as the number of pixels M that corresponds to the outer diameter in the minor axis direction, and the angle in the angular direction determined as the outer diameter in the major axis direction is determined as the angle θ.

If the number of pixels L corresponding to the outer diameter in the long axis direction of the approximate ellipse of the ring image, the number of pixels M corresponding to the outer diameter in the short axis direction, and the angle θ can be identified, the eye refractive power calculation unit 221 can calculate the spherical power S, the cylindrical power C, and the cylindrical axis angle A from the identified long axis, short axis, and angle, as described above.

(Display section 270, operation section 280)
The display unit 270 serves as a user interface unit and displays information under the control of the control unit 210. The display unit 270 includes the display unit 10 shown in FIG.

The operation unit 280 is used as a user interface unit to operate the ophthalmic device. The operation unit 280 includes various hardware keys (joystick, buttons, switches, etc.) provided on the ophthalmic device. The operation unit 280 may also include various software keys (buttons, icons, menus, etc.) displayed on the touch panel display screen 10a.

At least a portion of the display unit 270 and the operation unit 280 may be configured as an integrated unit. A typical example of this is a touch panel type display screen 10a.

(Communication unit 290)
The communication unit 290 has a function for communicating with an external device (not shown). The communication unit 290 has a communication interface according to the connection form with the external device. Examples of the external device include a refractive power measurement device capable of refractive power measurement, or a spectacle lens measurement device for measuring the optical characteristics of a lens. The refractive power measurement device, like the ophthalmic device 1000, projects light onto the fundus of the subject's eye and receives return light from the subject's eye to obtain a ring image. The ophthalmic device 1000 captures the ring image obtained by the external refractive power measurement device via the communication unit 290, performs polar coordinate conversion processing and noise reduction processing on the captured ring image as described above to generate a noise-reduced image, and can calculate the refractive power value of the subject's eye from the generated noise-reduced image. The spectacle lens measurement device measures the degree of the spectacle lens worn by the subject, and inputs the measurement data into the ophthalmic device 1000. The external device may be any ophthalmologic device, a device (reader) that reads information from a recording medium, or a device (writer) that writes information to a recording medium. Furthermore, the external device may be a hospital information system (HIS) server, a DICOM (Digital Imaging and Communication in Medicine) server, a doctor's terminal, a mobile terminal, a personal terminal, a cloud server, etc. The communication unit 290 may be provided in the processing unit 9, for example.

The reflex measurement projection system 6 and the reflex measurement light receiving system 7, or the communication unit 290 are an example of an "acquisition unit" according to the embodiment. The eye refractive power calculation unit 221 is an example of a "calculation unit" according to the embodiment.

<Example of operation>
The operation of the ophthalmologic apparatus 1000 according to the embodiment will be described.

FIGS. 14 and 15 show an example of the operation of the ophthalmic device 1000. FIG. 14 shows a flow diagram of an example of the operation of the ophthalmic device 1000. FIG. 15 shows a flow diagram of an example of the operation of step S3 in FIG. 14. The memory unit 212 stores a computer program for realizing the processing shown in FIG. 14 and FIG. 15. The main control unit 211 executes the processing shown in FIG. 14 and FIG. 15 by operating according to this computer program.

(S1: Alignment)
With the subject's face fixed on a face receiving unit (not shown), the examiner performs a predetermined operation on the operation unit 280, causing the ophthalmic device 1000 to start presenting a fixation target to the subject's eye E. Specifically, the main control unit 211 controls the fixation projection system 4 to cause the liquid crystal panel 41 to display a fixation target pattern representing a predetermined fixation target.

In addition, the examiner performs a specified operation on the operation unit 280, and the ophthalmic device 1000 performs alignment.

Specifically, the main controller 211 turns on the XY alignment light source 21 and the Z alignment light source 11. The main controller 211 controls the image sensor 59 to identify the bright spot image formed by the light output from the XY alignment light source 21, and controls the moving mechanism 200 based on the displacement of the bright spot image relative to the alignment reference to perform XY alignment. The main controller 211 also controls the line sensor 13 to identify the projection position of the reflected light from the cornea Cr, and performs Z alignment for the identified projection position. As a result, the optical system shown in FIG. 1 is moved to the examination position of the subject's eye E. The examination position is a position where the examination of the subject's eye E can be performed with sufficient accuracy.

The main control unit 211 also moves the reflex measurement light source 61, the focusing lens 74, and the fixation unit 40 (liquid crystal panel 41) along their respective optical axes to their origin positions (e.g., a position corresponding to 0D).

The operation of the ophthalmic device 1000 transitions to step S2 in response to an instruction from the main control unit 211 or a user operation or instruction to the operation unit 280.

(S2: Corneal shape measurement)
Next, the main controller 211 executes corneal shape measurement.

Specifically, the main control unit 211 causes the corneal shape information calculation unit 222 to analyze an anterior segment image in which light from the keratinizing light source 32 is projected onto the anterior segment.

The corneal shape information calculation unit 222 performs a predetermined arithmetic process on the keratinizing image to calculate the corneal radius of curvature, and calculates the corneal refractive power, the degree of corneal astigmatism, and the corneal astigmatism axis angle from the calculated corneal radius of curvature. In the control unit 210, the calculated corneal refractive power, etc. are stored in the memory unit 212.

The operation of the ophthalmic device 1000 proceeds to step S3 in response to an instruction from the main control unit 211 or a user operation or instruction to the operation unit 280.

(S3: Refractive power measurement)
Next, the main controller 211 executes the refractive power measurement. Details of step S3 will be described later.

(S4: Subjective test)
Next, the main controller 211 displays the desired target by controlling the liquid crystal panel 41 based on, for example, a user's instruction to the operation unit 280. The main controller 211 also moves the fixation unit 40 to a position according to the result of the refractive power measurement. The main controller 211 may also move the fixation unit 40 to a position according to the user's instruction to the operation unit 280.

The subject responds to the visual target projected onto the fundus Ef. For example, in the case of a visual target for measuring visual acuity, the visual acuity value of the subject's eye is determined by the subject's response. Selection of the visual target and the subject's response to it are repeated at the discretion of the examiner or the main control unit 211. The examiner or the main control unit 211 determines the visual acuity value or prescription value (S, C, A) based on the response from the subject.

This completes the operation of the ophthalmic device 1000 (end).

Step S3 in FIG. 14 is executed according to the flow shown in FIG. 15.

(S11: Projecting a ring pattern)
In the refractive power measurement in step S3, the main controller 211 projects a ring pattern (ring-shaped measurement pattern light beam) for refractive power measurement onto the subject's eye E (fundus Ef) as described above. A ring image based on the return light of the ring pattern from the subject's eye E is formed on the imaging surface of the imaging element 59.

First, as a provisional measurement, the main controller 211 determines whether or not a ring image based on the return light from the fundus Ef detected by the image sensor 59 has been acquired. For example, the main controller 211 detects the edge position (pixels) of the image based on the return light detected by the image sensor 59, and determines whether or not the width of the image (difference between the outer diameter and the inner diameter) is equal to or greater than a predetermined value. Alternatively, the main controller 211 may determine whether or not a ring image has been acquired by determining whether or not a ring can be formed based on points (images) that are equal to or greater than a predetermined height (ring diameter).

When it is determined that a ring image has been obtained by provisional measurement, the eye refractive power calculation unit 221 analyzes the ring image based on the return light of the measurement pattern light beam projected onto the subject's eye E using a known method (or the method described above) to determine a provisional spherical power S and provisional cylindrical power C. Based on the determined provisional spherical power S and cylindrical power C, the main control unit 211 moves the reflex measurement light source 61, the focusing lens 74, and the fixation unit 40 (liquid crystal panel 41) to a position of the equivalent spherical power (S+C/2) (a position corresponding to the provisional far point).

The main control unit 211 further moves the fixation unit 40 (liquid crystal panel 41) from the position of the identified spherical equivalent power (S+C/2) to the cloud position.

When it is determined that the ring image cannot be obtained, the main controller 211 takes into consideration the possibility that the patient has a severe refractive error and moves the reflex measurement light source 61 and the focusing lens 74 in preset steps to the negative power side (e.g., -10D) and the positive power side (e.g., +10D). The main controller 211 controls the reflex measurement light receiving system 7 to detect the ring image at each position. When it is still determined that the ring image cannot be obtained, the main controller 211 executes a specified measurement error process. The controller 210 stores information indicating that the reflex measurement result could not be obtained in the memory unit 212.

(S12: Acquire ring image)
Next, as the main measurement, the main control unit 211 controls the reflex measurement projection system 6 and the reflex measurement light receiving system 7 to obtain a ring image again.

The main control unit 211 controls the ring image identification unit 230 to identify the ring image as described above (see Figures 4 and 12).

(S13: Identify the center position)
Next, the main control unit 211 controls the ring image center position identifying unit 240 to identify the center position of the ring image identified in step S12 as described above.

(S14: Polar coordinate conversion)
Next, the main control unit 211 controls the polar coordinate conversion unit 250 to perform polar coordinate conversion processing on the ring image in the xy coordinate system acquired in step S12, with the central position identified in step S13 as the center.

The polar coordinate conversion unit 250 generates a polar coordinate conversion image as shown in FIG. 5 or FIG. 9 from a ring image in an xy coordinate system as shown in FIG. 4 or FIG. 12. The generated polar coordinate conversion image is stored in the memory unit 212.

In some embodiments, between steps S13 and S14, a known noise reduction process such as Gaussian filtering is applied to the ring image in the xy coordinate system.

(S15: Obtain pixel block)
Next, the main control unit 211 controls the filter processing unit 260 to sequentially obtain data blocks including groups of pixels that are adjacent at least in the angular direction from the polar coordinate transformed image obtained in step S14, and to sequentially obtain pixel blocks within the data blocks.

(S16: Median filter processing)
Next, the main control unit 211 controls the filter processing unit 260 to perform the median filter process as described above on the pixel block acquired in step S15.

(S17: Next pixel block?)
Next, the main control unit 211 determines whether or not to obtain the next pixel block from the data block. For example, the main control unit 211 determines whether or not to obtain the next pixel block from the data block by determining whether or not a pixel block has been extracted with all pixels in the polar coordinate converted image as the pixel of interest. Alternatively, the main control unit 211 determines whether or not to obtain the next pixel block from the data block by determining whether or not a pixel block has been extracted with all pixels in a predetermined filter processing range in the polar coordinate converted image as the pixel of interest.

When it is determined that the next pixel block is to be acquired (S17: Y), the process of step S3 proceeds to step S15. When it is determined that the next pixel block is not to be acquired (S17: N), the process of step S3 proceeds to step S18.

(S18: Calculate refractive power value)
When it is determined that the next pixel block should not be acquired (S17: N), the main control unit 211 controls the ocular refractive power calculation unit 221 to calculate the refractive power value of the test eye E based on the noise-reduced image of the polar coordinate converted image acquired by repeating steps S15 to S17.

As described above, the ocular refractive power calculation unit 221 determines the number of pixels L corresponding to the outer diameter in the major axis direction for the ring image in the noise-reduced image, which is twice the longest diameter in the radial direction, determines the number of pixels M corresponding to the outer diameter in the minor axis direction, and determines the angle in the angular direction determined as the outer diameter in the major axis direction as the angle θ. The ocular refractive power calculation unit 221 calculates the spherical power S, the cylindrical power C, and the cylindrical axis angle A from the determined number of pixels L corresponding to the outer diameter in the major axis direction, the number of pixels M corresponding to the outer diameter in the minor axis direction, and the angle θ.

This completes the processing of step S3 in FIG. 14 (END).

As described above, according to the embodiment, the acquired ring image is converted into polar coordinates, and the obtained polar coordinate converted image is subjected to median filter processing as noise reduction processing, and the refractive power value of the test eye E is calculated from the obtained noise reduced image. This makes it possible to calculate the refractive power value of the test eye E with high accuracy without providing a rotary prism, contributing to reducing the cost of the ophthalmic apparatus.

(Modification)
In the above embodiment, the size of the pixel block to which the median filter process is applied is determined in advance. However, the configuration according to the embodiment is not limited to this. For example, for each ring image of the eye E, the noise-reduced image of the ring image may be analyzed to determine the ring width of the ring image, the outer diameter in the outer diameter direction, and the outer diameter in the inner diameter direction of the ring image, and the size of the pixel block may be determined.

The configuration of the ophthalmic device according to the modified embodiment differs from the configuration of the ophthalmic device 1000 according to the embodiment in that a data processing unit 223a is provided instead of the data processing unit 223, and the control unit 210 (main control unit 211) is configured to control the data processing unit 223a instead of the data processing unit 223.

The following describes the configuration and control of the modified embodiment, focusing mainly on the differences between the configuration and control of the embodiment.

Figure 16 shows an example of a functional block diagram of a configuration example of a data processing unit 223a according to a modified embodiment. In Figure 16, parts similar to those in Figure 3 are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

The configuration of the data processing unit 223a differs from the configuration of the data processing unit 223 in that a ring width determination unit 251, an outer diameter determination unit 252, and a filter size calculation unit 253 have been added to the configuration of the data processing unit 223.

(Ring width specification unit 251)
The ring width specifying unit 251 specifies the number of pixels d that corresponds to the radial width of the ring image specified by the ring image specifying unit 230 .

For example, the ring width determination unit 251 determines the boundary position on the outer diameter side and the boundary position on the inner diameter side of the ring image, and determines the number of pixels corresponding to the distance between the determined boundary positions on the outer diameter side and the inner diameter side as the number of pixels d corresponding to the radial width of the ring image. In some embodiments, the ring width determination unit 251 determines the number of pixels corresponding to two or more widths of the ring image (for example, the width at the position where the major axis passes and the width at the position where the minor axis passes), and determines the average value of the determined two or more numbers of pixels as the number of pixels d.

The ring image to be processed by the ring width determination unit 251 may be a ring image in an xy coordinate system, or a ring image in a polar coordinate conversion image converted by the polar coordinate conversion unit 250.

(Outer diameter specifying section 252)
The outer diameter specifying unit 252 specifies the number of pixels corresponding to the outer diameter in the major axis direction of the ring image specified by the ring image specifying unit 230, and the number of pixels corresponding to the outer diameter in the minor axis direction.

For example, as shown in FIG. 13, the outer diameter determination unit 252 determines the number of pixels L corresponding to the outer diameter in the long diameter direction for the ring image in the polar coordinate conversion image as twice the longest diameter in the radial direction, and determines the number of pixels M corresponding to the outer diameter in the shortest diameter direction as twice the longest diameter in the radial direction.

The ring image to be processed by the outer diameter determination unit 252 may be a ring image in the xy coordinate system before polar coordinate conversion.

(Filter size calculation unit 253)
The filter size calculation unit 253 calculates the size of a pixel block as a filter size based on the number of pixels d corresponding to the ring width of the ring image specified by the ring width specification unit 251, the number of pixels L corresponding to the outer diameter in the major axis direction of the ring image specified by the outer diameter specification unit 252, and the number of pixels M corresponding to the outer diameter in the minor axis direction. As described above, the size of a pixel block is defined by the number of pixels in the radial direction and the number of pixels in the angular direction in the polar coordinate converted image.

When the filter processing unit 260 performs one-dimensional median filter processing, the filter size calculation unit 253 calculates the filter size so that it has one pixel in the radial direction centered on the center position of the ring image, and a first number of pixels in the angular direction centered on this center position. Here, the first number of pixels is a number of pixels greater than arccos(2d×(L-M)), as described above. For example, the first number of pixels is the smallest integer greater than arccos(2d×(L-M)), or an integer obtained by adding a predetermined margin value to arccos(2d×(L-M)).

When the filter processing unit 260 performs two-dimensional median filter processing, the filter size calculation unit 253 calculates the filter size so that the number of pixels d corresponding to the ring width in the radial direction centered on the center position of the ring image and the first number of pixels in the angular direction centered on this center position are calculated. Here, the first number of pixels is a number of pixels greater than arccos(2d×(L-M)) as described above. For example, the first number of pixels is the smallest integer greater than arccos(2d×(L-M)), or an integer obtained by adding a predetermined margin value to arccos(2d×(L-M)). In some embodiments, the filter size calculation unit 253 calculates the filter size so that the number of pixels d corresponding to the ring width in the radial direction centered on the center position of the ring image and the first number of pixels in the angular direction centered on this center position are calculated. In some embodiments, the filter size calculation unit 253 calculates the filter size so that the number of pixels d corresponding to the ring width in the radial direction centered on the center position of the ring image and the first number of pixels in the angular direction centered on this center position are calculated.

The filter processing unit 260 uses the filter size (size of the pixel block) calculated by the filter size calculation unit 253 to perform median filter processing on the polar coordinate transformed image to generate a noise-reduced image.

Next, we will explain the operation of the ophthalmic device according to this modified example.

The operation of the ophthalmic apparatus according to this modified example is almost the same as the operation example of the ophthalmic apparatus 1000 according to the embodiment shown in FIG. 14. However, in this modified example, the processing in step S3 in FIG. 14 differs from the processing of the ophthalmic apparatus 1000 according to the embodiment.

Figure 17 shows a flow diagram of an example of the operation of step S3 in Figure 14 in the ophthalmologic apparatus according to this modified example. The storage unit 212 stores a computer program for implementing the processes shown in Figures 14 and 17. The main control unit 211 operates according to this computer program to execute the processes shown in Figures 14 and 17.

In this modified example, step S3 in FIG. 14 is executed according to the flow shown in FIG. 17.

(S21: Project the ring pattern)
In the refractive power measurement in step S3, the main controller 211 projects a ring pattern (ring-shaped measurement pattern light beam) for refractive power measurement onto the subject's eye E (fundus Ef) as described above, in the same manner as in step S11. A ring image based on the return light of the ring pattern from the subject's eye E is formed on the imaging surface of the imaging element 59.

(S22: Acquire ring image)
Next, as the main measurement, the main control unit 211 controls the reflex measurement projection system 6 and the reflex measurement light receiving system 7 to obtain a ring image again, similarly to step S12.

(S23: Identify the center position)
Next, similarly to step S13, the main control unit 211 controls the ring image center position identifying unit 240 to identify the center position of the ring image identified in step S22 as described above.

(S24: Polar coordinate conversion)
Next, similar to step S14, the main control unit 211 controls the polar coordinate conversion unit 250 to perform polar coordinate conversion processing on the ring image in the xy coordinate system acquired in step S22, centered on the central position identified in step S23.

The polar coordinate conversion unit 250 generates a polar coordinate conversion image as shown in FIG. 5 or FIG. 9 from a ring image in an xy coordinate system as shown in FIG. 4 or FIG. 12. The generated polar coordinate conversion image is stored in the memory unit 212.

In some embodiments, between steps S23 and S24, a known noise reduction process such as Gaussian filtering is applied to the ring image in the xy coordinate system.

(S25: Identify ring width)
Next, the main control unit 211 controls the ring width specifying unit 251 to specify the number of pixels corresponding to the radial width of the ring image acquired in step S22.

As described above, the ring width determination unit 251 determines the number of pixels that corresponds to the radial width of the ring image.

(S26: Identify the outer diameter)
Next, the main control unit 211 controls the outer diameter specifying unit 252 to specify the number of pixels corresponding to the outer diameter in the major axis direction of the ring image acquired in step S22 and the number of pixels corresponding to the outer diameter in the minor axis direction.

As described above, the outer diameter determination unit 252 determines the number of pixels corresponding to the outer diameter in the long diameter direction of the ring image and the number of pixels corresponding to the outer diameter in the short diameter direction.

(S27: Calculate filter size)
Next, the main control unit 211 controls the filter size calculation unit 253 to calculate a filter size (size of a pixel block) based on the number of pixels corresponding to the ring width identified in step S25, the number of pixels corresponding to the outer diameter in the long diameter direction of the ring image identified in step S26, and the number of pixels corresponding to the outer diameter in the short diameter direction.

The filter size calculation unit 253 calculates the filter size (size of the pixel block) as described above.

(S28: Obtain pixel block)
Next, similarly to step S15, the main control unit 211 controls the filter processing unit 260 to sequentially obtain data blocks including groups of pixels that are adjacent at least in the angular direction from the polar coordinate transformed image obtained in step S24, and sequentially obtain pixel blocks within the data blocks.

(S29: Median filter processing)
Next, similarly to step S16, the main control unit 211 controls the filter processing unit 260 to perform the median filter process as described above on the pixel block acquired in step S28.

(S30: Next pixel block?)
Next, the main control unit 211 determines whether or not to obtain the next pixel block from the data block, similarly to step S17.

When it is determined that the next pixel block is to be acquired (S30: Y), the process of step S3 proceeds to step S28. When it is determined that the next pixel block is not to be acquired (S30: N), the process of step S3 proceeds to step S31.

(S31: Calculate refractive power value)
When it is determined that the next pixel block should not be acquired (S30: N), the main control unit 211, similar to step S18, controls the ocular refractive power calculation unit 221 to calculate the refractive power value of the test eye E based on the noise-reduced image of the polar coordinate converted image acquired by repeating steps S28 to S30.

As described above, the ocular refractive power calculation unit 221 determines the number of pixels L corresponding to the outer diameter in the major axis direction for the ring image in the noise-reduced image, which is twice the longest diameter in the radial direction, determines the number of pixels M corresponding to the outer diameter in the minor axis direction, and determines the angle in the angular direction determined as the outer diameter in the major axis direction as the angle θ. The ocular refractive power calculation unit 221 calculates the spherical power S, the cylindrical power C, and the cylindrical axis angle A from the determined number of pixels L corresponding to the outer diameter in the major axis direction, the number of pixels M corresponding to the outer diameter in the minor axis direction, and the angle θ.

This completes the processing of step S3 in FIG. 14 for this modified example (END).

As described above, according to this modified example, the acquired ring image is converted to polar coordinates, and median filter processing is performed as noise reduction processing on the polar coordinate converted image according to the subject's eye E, and the refractive power value of the subject's eye E is calculated from the obtained noise-reduced image. This makes it possible to calculate the refractive power value of the subject's eye E with higher accuracy than the embodiment without providing a rotary prism, contributing to reducing the cost of the ophthalmic apparatus.

[Action]
An ophthalmic apparatus, a control method for the ophthalmic apparatus, and a program according to an embodiment will be described.

A first aspect of some embodiments is an ophthalmic device (1000) including an acquisition unit (refractive index measurement projection system 6 and reflex measurement light receiving system 7, or a communication unit 290), a ring image center position identification unit (240), a polar coordinate conversion unit (250), a filter processing unit (260), and a calculation unit (ocular refractive power calculation unit 221). The acquisition unit projects ring-shaped light (ring pattern, ring-shaped measurement pattern light beam) onto the test eye (E) and acquires a ring image by receiving return light from the test eye. The ring image center position identification unit identifies the center position (O) of the ring image. The polar coordinate conversion unit converts the ring image into polar coordinates with the center position as the center. The filter processing unit performs noise reduction processing on the polar coordinate converted images (IMG1, IMG3) of the ring image converted into polar coordinates by the polar coordinate conversion unit. The calculation unit calculates the refractive power value of the test eye based on the noise-reduced images (IMG2, IMG6) that have been subjected to noise reduction processing by the filter processing unit.

According to this aspect, the acquired ring image is converted into polar coordinates, the obtained polar coordinate converted image is subjected to noise reduction processing, and the refractive power value of the test eye is calculated from the obtained noise reduced image. This makes it possible to calculate the refractive power value of the test eye with high accuracy without providing a rotary prism, which contributes to reducing the cost of the ophthalmic device.

In a second aspect of some embodiments, in the first aspect, the noise reduction process includes median filtering.

According to this aspect, the refractive power value of the test eye can be calculated with high accuracy using simple median filter processing without the need for a rotary prism, contributing to lower costs of ophthalmic devices.

In a third aspect of some embodiments, in the first or second aspect, the filter processing unit performs one-dimensional median filtering on the polar coordinate transformed image for each pixel block having one pixel in a radial direction centered on the central position and a first number of pixels in an angular direction centered on the central position.

According to this aspect, the refractive power value of the test eye can be calculated with high accuracy using simple processing that uses one-dimensional median filter processing, without the need for a rotary prism, thereby contributing to reducing the cost of ophthalmic devices.

In a fourth aspect of some embodiments, in the third aspect, the first number of pixels is determined based on the radial ring width of the ring image, the outer diameter of the ring image in the major axis direction, and the outer diameter of the ring image in the minor axis direction.

According to this aspect, even if the subject eye is astigmatic, the refractive power value of the subject eye can be calculated with high accuracy by simple processing using one-dimensional median filter processing, which contributes to reducing the cost of ophthalmic devices.

In a fifth aspect of some embodiments, in the first or second aspect, the filter processing unit performs two-dimensional median filtering on the polar coordinate transformed image for each pixel block having a number of pixels greater than the number of pixels corresponding to the ring width in the radial direction centered on the central position and a first number of pixels in the angular direction centered on the central position.

According to this aspect, the refractive power value of the test eye can be calculated with high accuracy using simple processing that uses two-dimensional median filter processing, without the need for a rotary prism, thereby contributing to reducing the cost of ophthalmic devices.

In a sixth aspect of some embodiments, in the fifth aspect, the first number of pixels is determined based on the radial ring width of the ring image, the outer diameter of the ring image in the major axis direction, and the outer diameter of the ring image in the minor axis direction.

According to this aspect, even if the subject eye is astigmatic, the refractive power value of the subject eye can be calculated with high accuracy by simple processing using two-dimensional median filter processing, which contributes to reducing the cost of ophthalmic devices.

In a seventh aspect of some embodiments, in the sixth aspect, when the number of pixels corresponding to the ring width is d, the number of pixels corresponding to the outer diameter in the major axis direction is L, and the number of pixels corresponding to the outer diameter in the minor axis direction is M, the first number of pixels is a number of pixels greater than arccos(2d×(L-M)).

According to this aspect, even if the ring image in the polar coordinate conversion image has an inclined portion, the noise in the ring image can be effectively reduced without causing stripes in the radial direction, making it possible to calculate the refractive power value of the test eye with higher accuracy.

An eighth aspect of some embodiments includes a ring width determination unit (251) that determines the ring width of the ring image based on the ring image or the polar coordinate converted image in the first or second aspect. The filter processing unit performs noise reduction processing on the polar coordinate converted image using the ring width determined by the ring width determination unit.

According to this aspect, noise reduction processing is performed on the polar coordinate converted image according to the astigmatism of the test eye, and the refractive power value of the test eye is calculated from the obtained noise-reduced image. This makes it possible to calculate the refractive power value of the test eye with higher accuracy without providing a rotary prism.

A ninth aspect of some embodiments is the eighth aspect, which includes an outer diameter determination unit (252) that determines the outer diameter in the major axis direction of the ring image and the outer diameter in the minor axis direction of the ring image based on the ring image or the polar coordinate converted image. The filter processing unit performs noise reduction processing on the polar coordinate converted image using the ring width determined by the ring width determination unit and the outer diameter in the major axis direction and the outer diameter in the minor axis direction determined by the outer diameter determination unit.

According to this aspect, noise reduction processing is performed on the polar coordinate converted image according to the astigmatism of the test eye, and the refractive power value of the test eye is calculated from the obtained noise-reduced image. This makes it possible to calculate the refractive power value of the test eye with higher accuracy without providing a rotary prism.

A tenth aspect of some embodiments is a control method for an ophthalmic device (1000) that projects ring-shaped light (ring pattern, ring-shaped measurement pattern light beam) onto a test eye (E) and acquires a ring image by receiving return light from the test eye. The control method for the ophthalmic device includes a ring image center position identification step, a polar coordinate conversion step, a filter processing step, and a calculation step. The ring image center position step identifies the center position of the ring image. The polar coordinate conversion step converts the ring image into polar coordinates with the center position as the center. The filter processing step performs noise reduction processing on the polar coordinate converted image of the ring image converted in the polar coordinate conversion step. The calculation step calculates the refractive power of the test eye based on the noise-reduced image that has been subjected to noise reduction processing in the filter processing step.

According to this method, the acquired ring image is converted to polar coordinates, the obtained polar coordinate converted image is subjected to noise reduction processing, and the refractive power value of the test eye is calculated from the obtained noise reduced image. This makes it possible to calculate the refractive power value of the test eye with high accuracy without providing a rotary prism, contributing to reducing the cost of ophthalmic equipment.

In an eleventh aspect of some embodiments, in the tenth aspect, the noise reduction process includes a median filter process.

This method uses simple median filter processing to calculate the refractive power value of the test eye with high accuracy without the need for a rotary prism, contributing to lower costs of ophthalmic equipment.

In a twelfth aspect of some embodiments, in the tenth or eleventh aspect, the filtering step applies one-dimensional median filtering to the polar coordinate transformed image for each pixel block having one pixel in a radial direction centered on the central position and a first number of pixels in an angular direction centered on the central position.

This method uses simple one-dimensional median filter processing to calculate the refractive power value of the test eye with high accuracy without the need for a rotary prism, contributing to lower costs of ophthalmic equipment.

In a thirteenth aspect of some embodiments, in the twelfth aspect, the first number of pixels is determined based on the radial ring width of the ring image, the outer diameter of the ring image in the major axis direction, and the outer diameter of the ring image in the minor axis direction.

According to this method, even if the subject eye is astigmatic, the refractive power value of the subject eye can be calculated with high accuracy using simple processing using one-dimensional median filter processing, which can contribute to reducing the cost of ophthalmic equipment.

In a fourteenth aspect of some embodiments, in the tenth or eleventh aspect, the filtering step applies two-dimensional median filtering to the polar coordinate transformed image for each pixel block having a number of pixels greater than the number of pixels corresponding to the ring width in the radial direction centered on the central position and a first number of pixels in the angular direction centered on the central position.

This method uses simple two-dimensional median filter processing to calculate the refractive power value of the test eye with high accuracy without the need for a rotary prism, contributing to lower costs of ophthalmic equipment.

In a fifteenth aspect of some embodiments, in the fourteenth aspect, the first number of pixels is determined based on the radial ring width of the ring image, the outer diameter of the ring image in the major axis direction, and the outer diameter of the ring image in the minor axis direction.

According to this method, even if the subject eye is astigmatic, the refractive power value of the subject eye can be calculated with high accuracy through simple processing using two-dimensional median filter processing, which contributes to reducing the cost of ophthalmic equipment.

In a sixteenth aspect of some embodiments, in the fifteenth aspect, when the number of pixels corresponding to the ring width is d, the number of pixels corresponding to the outer diameter in the major axis direction is L, and the number of pixels corresponding to the outer diameter in the minor axis direction is M, the first number of pixels is a number of pixels greater than arccos(2d×(L-M)).

With this method, even if the ring image in the polar coordinate conversion image has an inclined portion, it is possible to effectively reduce noise in the ring image without generating radial stripes, and to calculate the refractive power value of the test eye with higher accuracy.

A seventeenth aspect of some embodiments of the tenth or eleventh aspect includes a ring width determination step of determining a ring width of the ring image based on the ring image or the polar coordinate converted image. The filtering step performs noise reduction processing on the polar coordinate converted image using the ring width determined in the ring width determination step.

According to this method, noise reduction processing is performed on the polar coordinate converted image according to the astigmatic eye to be examined, and the refractive power value of the eye to be examined is calculated from the obtained noise-reduced image. This makes it possible to calculate the refractive power value of the eye to be examined with higher accuracy without providing a rotary prism.

An 18th aspect of some embodiments is the 17th aspect, which includes an outer diameter determination step of determining the outer diameter of the ring image in the major axis direction and the outer diameter of the ring image in the minor axis direction based on the ring image or the polar coordinate converted image. The filtering step performs noise reduction processing on the polar coordinate converted image using the ring width determined in the ring width determination step and the outer diameter in the major axis direction and the outer diameter in the minor axis direction determined in the outer diameter determination step.

According to this method, noise reduction processing is performed on the polar coordinate converted image according to the astigmatic eye to be examined, and the refractive power value of the eye to be examined is calculated from the obtained noise-reduced image. This makes it possible to calculate the refractive power value of the eye to be examined with higher accuracy without providing a rotary prism.

A nineteenth aspect of some embodiments is a program that causes a computer to execute each step of the method for controlling an ophthalmic device according to any one of the tenth to eighteenth aspects.

According to such a program, the acquired ring image is converted into polar coordinates, the obtained polar coordinate converted image is subjected to noise reduction processing, and the refractive power value of the test eye is calculated from the obtained noise reduced image. This makes it possible to calculate the refractive power value of the test eye with high accuracy without providing a rotary prism, contributing to reducing the cost of ophthalmic equipment.

＜Other＞
The embodiment described above is merely one example for carrying out the present invention. Anyone who wishes to carry out the present invention may make any modifications, omissions, additions, etc. within the scope of the gist of the present invention.

Reference Signs List 6 Refractive index measurement projection system 7 Refractive index measurement light receiving system 9 Processing section 210 Control section 211 Main control section 220 Arithmetic processing section 221 Eye refractive power calculation section 223, 223a Data processing section 230 Ring image determination section 240 Ring image center position determination section 250 Polar coordinate conversion section 251 Ring width determination section 252 Outer diameter determination section 253 Filter size calculation section 260 Filter processing section 1000 Ophthalmic apparatus E Eye to be examined

Claims (19)

an acquisition unit that projects a ring-shaped light onto the subject's eye and acquires a ring image by receiving return light from the subject's eye;
a ring image center position identifying unit that identifies a center position of the ring image;
a polar coordinate conversion unit that converts the ring image into polar coordinates with the central position as a center;
a filter processing unit that performs noise reduction processing on the polar coordinate converted image of the ring image that has been polar coordinate converted by the polar coordinate conversion unit;
a calculation unit that calculates a refractive power value of the subject's eye based on a noise-reduced image that has been subjected to the noise reduction processing by the filter processing unit;
13. An ophthalmic device comprising: The ophthalmic apparatus according to claim 1 , wherein the noise reduction process includes a median filter process. 3. The ophthalmic apparatus according to claim 1, wherein the filter processing unit performs one-dimensional median filter processing on the polar coordinate transformed image for each pixel block having one pixel in a radial direction centered on the central position and a first number of pixels in an angular direction centered on the central position. The ophthalmologic apparatus according to claim 3 , wherein the first number of pixels is determined based on a ring width in a radial direction of the ring image, an outer diameter in a major axis direction of the ring image, and an outer diameter in a minor axis direction of the ring image. 3. The ophthalmic apparatus according to claim 1, wherein the filter processing unit performs two-dimensional median filter processing on the polar coordinate transformed image for each pixel block having a number of pixels greater than a number of pixels equivalent to a ring width in a radial direction centered on the central position and a first number of pixels in an angular direction centered on the central position. The ophthalmologic apparatus according to claim 5 , wherein the first number of pixels is determined based on a ring width in a radial direction of the ring image, an outer diameter in a major axis direction of the ring image, and an outer diameter in a minor axis direction of the ring image. 7. The ophthalmic device according to claim 6, wherein, when a number of pixels corresponding to the ring width is d, a number of pixels corresponding to an outer diameter in the major axis direction is L, and a number of pixels corresponding to an outer diameter in the minor axis direction is M, the first number of pixels is a number of pixels larger than arccos(2d×(L−M)). a ring width specifying unit that specifies a ring width of the ring image based on the ring image or the polar coordinate converted image,
The ophthalmologic apparatus according to claim 1 , wherein the filtering unit performs noise reduction processing on the polar coordinate converted image by using the ring width specified by the ring width specifying unit. an outer diameter specifying unit that specifies an outer diameter in a major axis direction of the ring image and an outer diameter in a minor axis direction of the ring image based on the ring image or the polar coordinate converted image,
The ophthalmic apparatus according to claim 8, wherein the filter processing unit performs noise reduction processing on the polar coordinate transformed image using the ring width specified by the ring width specifying unit and the outer diameter in the major axis direction and the outer diameter in the minor axis direction specified by the outer diameter specifying unit. A method for controlling an ophthalmic apparatus that projects a ring-shaped light onto a subject's eye and acquires a ring image by receiving return light from the subject's eye, comprising the steps of:
a ring image center position specifying step of specifying a center position of the ring image;
a polar coordinate conversion step of converting the ring image into polar coordinates with the central position as a center;
a filtering step of performing noise reduction processing on the polar coordinate converted image of the ring image converted in the polar coordinate conversion step;
a calculation step of calculating a refractive power value of the subject's eye based on a noise-reduced image obtained by performing the noise reduction process in the filtering step;
A method for controlling an ophthalmic device, comprising: The method for controlling an ophthalmic apparatus according to claim 10 , wherein the noise reduction process includes a median filter process. 12. The method of controlling an ophthalmic apparatus according to claim 10, wherein the filtering step performs one-dimensional median filtering on the polar coordinate transformed image for each pixel block having one pixel in a radial direction centered on the central position and a first number of pixels in an angular direction centered on the central position. The control method for an ophthalmic apparatus according to claim 12, wherein the first number of pixels is determined based on a ring width in a radial direction of the ring image, an outer diameter in a major axis direction of the ring image, and an outer diameter in a minor axis direction of the ring image. 12. The method for controlling an ophthalmic apparatus according to claim 10, wherein the filtering step performs two-dimensional median filtering on the polar coordinate transformed image for each pixel block having a number of pixels greater than a number of pixels equivalent to a ring width in a radial direction centered on the central position and a first number of pixels in an angular direction centered on the central position. The control method for an ophthalmic apparatus according to claim 14, wherein the first number of pixels is determined based on a ring width in a radial direction of the ring image, an outer diameter in a major axis direction of the ring image, and an outer diameter in a minor axis direction of the ring image. 16. The method for controlling an ophthalmic device according to claim 15, wherein the first number of pixels is a number of pixels larger than arccos(2d×(L−M)), where d is the number of pixels corresponding to the ring width, L is the number of pixels corresponding to the outer diameter in the major axis direction, and M is the number of pixels corresponding to the outer diameter in the minor axis direction. a ring width specifying step of specifying a ring width of the ring image based on the ring image or the polar coordinate converted image,
12. The method of controlling an ophthalmic apparatus according to claim 10, wherein the filtering step performs noise reduction processing on the polar coordinate converted image by using the ring width specified in the ring width specifying step. an outer diameter specifying step of specifying an outer diameter in a major axis direction of the ring image and an outer diameter in a minor axis direction of the ring image based on the ring image or the polar coordinate converted image,
The control method for an ophthalmic apparatus according to claim 17, characterized in that the filtering step performs noise reduction processing on the polar coordinate transformed image using the ring width identified in the ring width identifying step and the outer diameter in the major axis direction and the outer diameter in the minor axis direction identified in the outer diameter identifying step. A program that causes a computer to execute each step of the method for controlling an ophthalmic device according to claim 10 or 11.

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