JPS6150449B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ophthalmological measuring device, and particularly to an ophthalmological measuring device that can selectively measure the corneal shape and diopter (eye refractive power) of an eye to be examined using the same device.

A keratometer that measures the shape of the cornea is generally used to measure the three elements of the corneal curvature, degree of astigmatism, and astigmatism axis direction of the eye to be examined, but it can also be used to test the base curve of contact lenses by measuring the curvature of the cornea. Applied.

In addition to commercially available keratometers called ophthalmometers or keratometers, there are
There are those described in JP-A-56-18837, JP-A-56-66235, and the applicant's earlier application, JP-A-55-82516 and JP-A-57-9431. On the other hand, when measuring diopter, the eye to be examined often has astigmatism, so the diopter in the meridian direction, that is, the spherical diopter, where the diopter reaches its extreme value, and the diopter that changes with the change in the meridian direction, that is, Three elements are required: the degree of astigmatism and the direction of the meridian when the diopter reaches its extreme value, that is, the axis of astigmatism.
An eye refractometer for measuring this was developed in Japanese Patent Application Publication No. 1986-
Publication No. 110531, patent application filed in 1983, which is the applicant's earlier application.
-64443 There are those described in Japanese Patent Application Laid-Open No. 56-161031. Generally, several types of contact lenses are prepared in advance as sets of curvature and diopter of the lens surface facing the cornea, and if the corneal curvature and diopter are measured, a lens suitable for the eye to be examined can be provided.

However, the current situation is that the diopter of the eye to be examined is generally measured separately from the corneal shape measurement by ophthalmologists, opticians, and the like.

Moreover, when the above-mentioned off-salmometer or keratometer is used as a keratometer, measurement takes time and errors occur due to movement of the eye to be examined.

In other words, an ophthalmometer or keratometer projects an inspection mark onto the cornea and observes the reflected image with a microscope, and measures the amount of adjustment until the reflected image reaches a predetermined state, or it measures concentric marks on the cornea. It projects, photographs the reflected image, and analyzes the distortion of the image. For example, a device that uses a microscope to read the size of the light source reflected image by the cornea is equipped with a means to measure two meridian directions perpendicular to each other. First, the direction of corneal astigmatism was determined by observing the reflected image, and then optical elements such as prisms were sequentially moved in the meridian direction and the meridian direction perpendicular to the meridian direction, and the radius of curvature was determined from the amount of movement.

The present invention performs corneal shape measurement by shortening measurement time and eliminating error factors caused by movement of the eye to be examined.
Moreover, it is an object of the present invention to provide an ophthalmological measuring device that enables selective eye diopter measurement using the same device.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram of an embodiment of the invention. Here, for convenience, the corneal shape measurement system will be described first, and then the diopter measurement system will be described.

In the figure, 1a and 1b are light sources for corneal shape measurement, such as infrared light emitting diodes, flash discharge lamps, etc.
Although only two are shown in Figure 1, in reality,
As shown in Fig. 2, three sets of two pieces, each spaced at an equal distance from the optical axis, are placed on three meridians R ₁ , R ₂ , and R ₃ that pass through the measurement optical axis light source 1
a, 1b, 1c, 1d, 1e, and 1f are arranged. Here, each light source has at least a predetermined length in the circumferential direction, and may further be an annular light source that is integrated in the circumferential direction.

The reason for choosing three meridians here is that when the center of the cornea is regarded as a toric surface, the change in the meridian direction of the corneal curvature becomes sinusoidal, so at least three
This is because if the value in the meridian direction is known, the value in any other meridian direction can be calculated, and as a result, the corneal astigmatism axis direction can also be calculated. This point will be further explained in the diopter measurement section described later.

2a and 2b are slits corresponding to the light sources 1a and 1b, and may be annular slits integrally formed in the circumferential direction.

3a and 3b are collimating lenses for light source 1
The speed of light that exits from the slits 2a and 2b and enters the cornea is converted into a parallel beam of light toward the cornea. That is, the slits 2a, 2b are placed at the focal positions of the collimating lenses 3a, 3b.

The collimating lenses 3a and 3b correspond to the light sources 1a and 1b, respectively, but may be annular lenses whose cross-sectional shapes are integral in the circumferential direction as shown in the figure.

2a' and 2b' are light source images (virtual images) generated as a result of the corneal Ee surface acting as a convex mirror, and light sources 1a and 1b
is formed within the same cross section.

4 is an objective lens, 5 is an aperture plate, 6 is a prism,
7ab is a one-dimensional photodiode array (hereinafter referred to as an array) such as a CCD.

4 is a lens for projecting the light source images 2a', 2b' onto the array 7ab;
Connect the sensing surface of ab to the conjugate.

As shown in FIG. 3, the array 7 is provided in three radial directions 7ab, 7cd, and 7ef corresponding to the three meridian directions with respect to the measurement optical axis X.

The diaphragm plate 5 is provided at the back focal position of the objective lens 4, and constitutes a telecentric system. That is, the imaging principal ray is parallel to the optical axis X within the plane of the paper in FIG.

Since the illumination light fluxes from the light sources 1a and 1b are parallel light fluxes, and the imaging principal ray is parallel to the optical axis X, the subject moves in the optical axis X direction, and the light source image 2
Even if a' and 2b' are displaced in the optical axis X direction, that is, even if the working distance changes, the size of the image formed on the array 7ab does not change, and no measurement error occurs. .

Now, the functions of the aperture plate 5 and the prism 6 will be explained.

As shown in FIG.
Corresponding to a, 1b, 1c, 1d, 1e, 1f,
Openings 5a, 5b, 5c, 5e, and 5f are provided.

What should be noted here is that the apertures 5a and 5b corresponding to the light sources 1a and 1b are not located in the same direction as the light sources 1a and 1b, but are provided perpendicularly to each other and are formed by prisms 6a and 6b shown in FIG. This means that the light beam is two-dimensionally deflected and directed toward the array 7ab.

If the apertures 5a and 5b are arranged in the same direction as the light sources 1a and 1b, the imaging chief ray will form an oblique angle with respect to the optical axis X, and will no longer form a telecentric system, resulting in a change in working distance. This results in measurement errors. This connects the apertures 5a and 5b to the light source 1.
This is the reason for making it orthogonal to the directions a and 1b.

Here, the light beam from the light source image 2a' passes through the aperture 5a and is deflected onto the array 7ab by the prism 6a.
The light beam that passes through b and is deflected by the prism 6b heads out of the effective range in the arrangement direction of the array 7ab,
The light fluxes that pass through the apertures 5c, 5d, 5e, and 5f and are respectively deflected by the prisms 6c, 6d, 6e, and 6f head in a direction that is significantly different from the arrangement direction of the array 7ab, and in the end, only the light flux that passes through the aperture 5a. contributes to the measurement. Similarly, of the light flux from the light source image 2b', only the light flux passing through the aperture 5b contributes to the measurement. Further, among the light beams from the light source images 2c', 2d', 2e', and 2f', only the beams passing through the apertures 5c, 5d, 5e, and 5f, respectively, contribute to the measurement. Here, the openings 5a, 5
The prisms 6a and 6b corresponding to b move diagonally upward by 2
Configured to dimensionally deflect light. That is, the light beams passing through the apertures 5a and 5b are deflected by prisms 6a and 6b, respectively, toward a predetermined point in the arrangement direction of the array 7ab.

Similarly, other prisms 6c and 6d, 6e and 6f deflect light two-dimensionally toward arrays 7cd and 7ef, respectively.

In summary, the light beams from the light source images 2a', 2b' are respectively apertures 5a, 5b, 5c, 5d, 5e, 5
The re-projected images of the light source that do nothing overlap and cannot be detected, but by configuring the prism 6 into six parts as shown in Figure 5 and deflecting each of the light beams, , only the light flux from the light source image 2a' passes through the aperture 5a, and only the light flux from the light source image 2b' passes through the aperture 5b,
As shown in FIG.
They are imaged separately as a″ and 2b″.

FIG. 6 shows light source images 2a', 2 with the optical axis X as the center.
FIG. 7 is a schematic diagram when a virtual circle passing through the position b' is projected onto the array surface.

The virtual circles passing through the light source images 2a' and 2b' become 8a and 8a, respectively, due to the predetermined deflection action of the prisms 6a and 6b, respectively.
It is projected onto array 7ab as a circle 8b. The same applies to the other light source images 2c', 2d', 2e', and 2f'.

FIG. 7 shows the measurement points on each array.

This is the projected image 8a, 8 of the virtual circle in FIG.
This is the point where b and array 7ab intersect. array 7
The same applies to CD and 7EF. In array 7ab,
When each photodiode is scanned and signals are taken out sequentially, since there is a peak in the light distribution in the elements of real images 2a'' and 2b'', an electric signal train corresponding to the peak is obtained. From this signal train, a processing circuit (not shown) detects the interval between peaks and converts it into a radius of curvature in the meridian _R1 direction. Similarly, since the radii of curvature in the other meridian R ₂ and R ₃ directions can be collected from the signals obtained from the other arrays 7cd and 7ef, the angle and value of each meridian from the reference position can be determined. Become.

Here, if the alignment is not sufficient, a cylindrical lens 8ab is placed in front of the array 7ab to guide the re-formed real image to the scanning plane even if it deviates from the scanning plane of the array 7ab, and to allow a setting error.
It is good to set up The generatrix of the cylindrical lens 8ab and the scanning direction of the array 7ab are arranged to match. A system (plan view) viewed from the scanning direction of array 7ab is shown in FIG. 12, which will be described later. Corneal curvature, degree of corneal astigmatism, and corneal astigmatism axis are determined by coordinate measurement in three meridian directions using arrays 7ab, 7cd, and 7ef.

Next, diopter measurement will be explained. This is shown in Japanese Patent Application No. 55-64443, which is the applicant's earlier application. As mentioned above, when measuring diopter, the eye to be examined often has astigmatism, so the diopter in the meridian direction, that is, the spherical diopter, where the diopter reaches its extreme value, and the diopter that accompanies changes in the meridian direction. It is necessary to measure three elements: the change in power, that is, the degree of astigmatism, and the direction of the meridian, that is, the axis of astigmatism when the diopter reaches its extreme value, or data equivalent to these.

Here, we will explain why all the necessary information can be obtained by measuring the refractive power in the three meridian directions. First, if the change in diopter in the meridian direction in astigmatism is regarded as changing sinusoidally, the diopter can be expressed as a function of the angle in the meridian direction, for example, as follows.

D=Asin(2θ+α)+B However, D represents the diopter, θ represents the angle in the meridian direction, and the constants A, B, and α correspond to the degree of astigmatism, the average diopter, and the astigmatism direction, respectively.

Since three constants are required to be determined here, it is sufficient to provide at least three measured values in the meridian direction.

In FIG. 8, a system as an eye refractometer will be explained. Here, FIG. 8 is equivalent to the diopter measurement system shown in FIG. 1. When the illumination light source 9 is turned on, the light source 9
The emitted infrared rays illuminate the projection mask 11 in such a manner that they are converged onto the relay lens 13 by the action of the condensing lens 10. The light beams emitted from the slits 11a, 11b, and 11c of the mask 11 as shown in FIG.
3, it is reflected by the spot mirror 14, and a chart image is formed on F, and then,
It is collimated by the objective lens 4 and is directed from a predetermined region of the pupil toward the fundus Er, where a chart image is formed. The light beam scattered and reflected by the fundus Er exits the subject's eye, is imaged by the objective lens 4, is then imaged by the relay lens 15, and passes through the aperture of the six-hole diaphragm plate 16 as shown in FIG. and is deflected by prisms 17a and 17b as shown in FIG.
Array 7 via cylindrical lens 8ab
Form a chart image on ab. Here opening 16
The direction connecting the centers of prisms a and 16b is the same as the arrangement direction of array 7ab, and prisms 17a and 17b
deflects the light beam one-dimensionally and directs it to the effective area of array 7ab. 17c, 17d, 17e, 17f
The same is true. Cylindrical lens 8ab is
As shown in FIG. 12, the aperture position of the diaphragm plate 16 is provided along the arrangement direction of the array 7ab at a position where an image is approximately formed on the array 7ab, allowing for setting errors and further increasing the amount of light. useful for.

When the array 7ab is activated and the photodiodes are sequentially scanned, an electrical signal train corresponding to the light intensity is output.This signal train is subjected to electrical processing to detect the positions of peaks P and Q, and the width of this peak is determined. and calculate the refractive power from its width. If the subject is myopic, the light beams passing through the aperture are convergent, and the peak positions of the two light beams are close to each other, so the peak width is smaller than that of an emmetropic eye, indicating that the subject is myopic. is identified, and the degree of refractive error can be measured from the degree of reduction. The opposite is true if you are farsighted.

Next, a case where corneal shape measurement and diopter measurement are selectively used will be described in detail.

First, when used as an eye refractometer or refractometer, the infrared light emitted from the light source 9 in FIG. 18, the light is further reflected by the optical path selection member 19 and enters the fundus Er of the eye E to be examined through the objective lens 4, and the image of the mask 11 is projected onto the fundus Er. If the light source 9 is highly directional, the condenser lens 10, relay lens 13, and mask 11 can be omitted, and the image of the light source 9 is projected onto the fundus Er, which can serve as an index when measuring diopter.

The light reflected from the fundus Er returns to the outside of the spot mirror 14 and passes through the relay lens 15 provided at a position conjugate with the pupil Ep of the eye to be examined, the apertures 16a and 16b of the six-hole diaphragm plate 16, and the prism 17.
a, 17b, mirror 20, optical path selection member 2
1 and is imaged onto array 7ab via cylindrical lens 8ab.

On the other hand, when measuring the corneal shape, the light sources 1a, 1
The luminous flux emitted from b passes through slits 2a, 2 in the circumferential direction.
b, Image 2 is captured by the cornea Ee through the collimating lenses 3a and 3b (or toric lens).
Connect a′ and 2b′. The light reflected by the cornea heads toward the objective lens 4 as if it were emitted from the images 2a' and 2b', passes through the optical path selection member 19, and passes through the aperture plate 5,
The array 7 passes through the prism 6, passes through the optical path selection member 21, and passes through the cylindrical lens 8ab.
imaged on ab.

By using dichroic mirrors as the optical path selection members 19 and 21, the light source 9, the light source 1a,
The light flux from 2a (or the annular light source) can be efficiently separated.

For example, as the optical path selection members 19 and 21, dichroic mirrors that reflect light in the red range and transmit light in the blue range are used, and as the light source 9, one that emits light in the red range, and the light sources 1a and 2a (or circular If a ring-shaped light source that emits light in the blue region is used, the diopter measurement system and the corneal shape measurement system can be separated by reflection and transmission from a dichroic mirror.

Here, as a dichroic mirror, 2
If a color-separating device is used, infrared light can be used as illumination light for both corneal shape measurement and diopter measurement, eliminating problems during measurement due to blinking of the subject's eyes, etc.

In addition, the diopter measurement system and the corneal shape measurement system can be adjusted by using a so-called quick return method in which normal mirrors are used as the optical path selection members 19 and 21 and are inserted into the optical path or removed from the optical path. It can also be separated.

If the light source for corneal topography measurement and the light source for diopter measurement are both turned on here, the corneal image and fundus image will overlap on the array, so depending on the corneal topography measurement and diopter measurement, It shall be turned on selectively. However, in the case of the quick return method, for example, the first
Considering the system in which the optical path selection members 19 and 21 are inserted into the optical path in the figure, the light reflected by the cornea is reflected by the optical path selection members 19 and 21 and goes toward the array 7ab, but depending on the optical design, it may be defocused. Alternatively, the corneal shape measurement system can be virtually ignored due to the vignetting caused by the spot mirror 14 and the aperture plate 16, so that the light source for corneal shape measurement and the light source for diopter measurement can be selectively turned on. It is possible to keep both lights on at all times even if the lights are not turned on.

In addition, in the present invention, a corneal topography measurement system,
The means for separating the diopter measurement system is not limited to this embodiment, and may be other means such as one using polarization characteristics.

As described above, according to the present invention, the corneal shape and diopter of the eye to be examined can be selectively measured using the same device.

Furthermore, it is possible to provide a simple ophthalmological measuring device that can perform measurements in a short period of time.

In addition, according to the present invention, corneal shape and diopter can be measured almost continuously, so changes in the subject's eye that are difficult to avoid when measuring each independently (such as changes in the surrounding environment, eye strain, etc.) It is possible to remove most of the elements (various changes associated with the measurement) and has the effect of making it possible to trust the correlation between both measurement values.

On the other hand, if separate measuring devices are used, the subject will
It is necessary to move to the device and perform new alignment and working distance adjustment, etc.
The present invention eliminates this type of complicated operation and waste of time, so it is particularly effective for children, the elderly, and the sick.

Furthermore, since the present invention has a structure in which the photoelectric detector and other components are shared, the apparatus is compact and simple, unlike a system in which both measuring instruments are simply superimposed.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an embodiment of the present invention, FIG. 2 is a layout diagram of a light source for corneal shape measurement viewed from the optical axis X direction, and FIG. 3 is an array layout diagram viewed from the optical axis X direction. Figures 4 and 5 are views of the aperture plate and prism for corneal shape measurement viewed from the optical axis X direction, and Figure 6 is a view centered on the optical axis X and passing through the position of each light source image Schematic diagram when a virtual circle is projected onto each array,
FIG. 7 is a diagram showing the measurement points on each array, FIG. 8 is an explanatory diagram of the diopter measurement system, FIG. 9 is an explanatory diagram of the projection mask, and FIGS. 10 and 11 are, respectively. Figure 12 is an explanatory diagram of the cylindrical lens. In the figure, 1a and 1b are the light sources for corneal shape measurement, and 2
a and 2b are slits, 3a and 3b are collimating lenses, 2a' and 2b' are light source images, 4 is an objective lens, 5 is a diaphragm plate, 6 is a prism, 7ab is an array, 8ab is a cylindrical lens, and 9 is a visual field. A light source for power measurement, 10 a condenser lens, 11 a projection mask, 12 an aperture plate, 13 a relay lens, 14
is a spot mirror, 15 is a relay lens, 16 is an aperture plate, 17a, 17b are prisms, 18, 20
is a mirror, and 19 and 21 are optical path selection members.

Claims (1)

[Scope of Claims] 1. In an ophthalmological measurement device that measures the diopter and corneal shape of an eye to be examined by projecting a fundus reflection image and a corneal reflection image obtained by projecting an index onto the eye to be examined onto a predetermined sensor using a projection system. . An ophthalmological measuring device comprising: a selection means for selectively projecting a fundus reflection image and a corneal reflection image onto the array. 2. The ophthalmological measuring device according to claim 1, wherein the selection means selects the fundus reflection optical path and the corneal reflection optical path. 3. The ophthalmological measuring device according to claim 2, wherein the selection means is a wavelength selection member. 4. The ophthalmological measuring device according to claim 3, wherein the wavelength selection member is a dichroic mirror that separates two colors in the infrared region. 5. The ophthalmological measuring device according to claim 1, wherein a fundus reflection image and a corneal reflection image are selectively formed on the subject's eye. 6. The ophthalmological measuring device according to claim 2, wherein the selection means is a mirror that is inserted into or removed from the optical path. 7. The ophthalmological measuring device according to claim 1, wherein the array is a one-dimensional array provided corresponding to at least three meridian directions. 8. The ophthalmological measuring device according to claim 1, wherein the projection system is a telecentric system.