JP2013128800A - Ophthalmologic apparatus and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a distance between a plurality of light beams to be obtained by dividing light beams from cornea bright spot image while maintaining alignment accuracy.SOLUTION: An ophthalmologic apparatus includes: a projection optical system which projects an alignment index to a cornea of an eye to be examined; aperture members which have a plurality of apertures which divide light beams of corneal reflection images using the alignment index into a plurality of light beams to make the light beams pass through; optical members which shorten a distance between a plurality of light beams passing through the apertures; and an imaging lens which images the shortened plurality of light beams on an imaging unit.

Description

  The present invention relates to an ophthalmologic apparatus and a control method thereof.

  In general, in an ophthalmologic apparatus that measures the corneal thickness of an eye to be examined or measures intraocular pressure, the alignment between the eye to be examined and the apparatus is in the vertical direction, the left-right direction, and the working distance direction (front-back direction). , In a direction toward or away from the eye to be examined).

  In the corneal thickness measuring apparatus described in Patent Document 1, a first projection / light receiving system that performs vertical and horizontal alignment, and a second that performs alignment in the working distance direction and is also used for measuring corneal thickness. Alignment is performed by the projection / light receiving system. Here, for alignment in the working distance direction, reflected light of an alignment index projected from the outside of the optical axis facing the eye to be examined toward the cornea is used. When performing alignment in the working distance direction by such a method, two sets of projection / light receiving systems are required for alignment and for measurement of corneal thickness. Therefore, there is a problem that the optical system of the apparatus cannot be simplified, resulting in an increase in size and cost of the apparatus.

  Here, in the alignment method of the non-contact tonometer described in Patent Document 2, there is one projection system (shared for alignment and corneal thickness measurement) and two light receiving systems (one for the target). The apparatus is composed of a light receiving system for measuring the corneal thickness disposed at a position off the optical axis facing the optometry, and alignment in the vertical, horizontal, and working distance directions is performed using the corneal bright spot image. The corneal bright spot image is an image formed when the alignment index is illuminated toward the cornea of the eye to be examined and the reflected light is received through the prism from the optical axis facing the eye to be examined. .

Japanese Patent No. 3597274 JP 2006-334441 A

  Here, in the case of alignment using a corneal bright spot image, a light beam from the corneal bright spot image is divided into a plurality of light fluxes, and a plurality of corneal bright spot images are captured through a prism. In this case, the alignment accuracy is determined by the distance between the light beams. That is, if the distance between the light beams is increased, the alignment can be realized with higher accuracy, but the apparatus becomes larger. On the other hand, if the distance between the light beams is shortened in order to reduce the size of the apparatus, the alignment accuracy is lowered.

  The present invention has been made in view of the above problems, and enables to shorten the distance between a plurality of light beams obtained by dividing a light beam from a corneal bright spot image while maintaining alignment accuracy. The purpose is to do.

In order to achieve the above object, an ophthalmic apparatus according to one aspect of the present invention has the following configuration. That is,
A projection optical system that projects an alignment index onto the cornea of the eye to be examined; and
An opening member including a plurality of openings that divide the light beam of the corneal reflection image by the alignment index into a plurality of light beams and allow the plurality of light beams to pass;
An optical member that changes a distance between the plurality of light beams that have passed through the plurality of openings to a short distance;
An imaging lens that forms an image on the imaging unit with the plurality of light fluxes changed to the short distance.

  According to the present invention, it is possible to shorten the distance between a plurality of light beams obtained by dividing a light beam from a corneal bright spot image while maintaining alignment accuracy.

The block diagram which shows the structural example of the measurement part of the ophthalmologic apparatus by embodiment. (A) is a diagram showing the prism diaphragm 11, (b) is a diagram showing the slit plate 24, (c) is a diagram showing the distance D between the aperture diaphragms. The figure which shows the distance D to the front-end | tip part of the cornea of the cornea Ec by the cornea bright spot alignment, and a nozzle. The figure which shows the imaging to the image pick-up element 28 of the scattered light from the cornea Ec with an average radius of a cornea curvature. The figure which shows the imaging to the image pick-up element 28 of the scattered light from the cornea Ec whose radius of a cornea curvature is larger than an average. The figure which shows the imaging to the image pick-up element 28 of the scattered light from the cornea Ec whose radius of a cornea curvature is larger than an average. (A), (b) is a figure which shows the positional relationship of the width of the image on an image pick-up element in an corneal-thickness-measuring optical system, and an image. (A)-(d) is a figure explaining the relationship between two cornea luminescent spot images imaged in corneal bright spot alignment, and a working distance. It is a flowchart which shows operation | movement of the ophthalmologic apparatus by embodiment. (A) is a diagram showing an imaging relationship due to a difference in WD, (b) is a diagram illustrating alignment accuracy due to a difference in distance between aperture stops, and (c) is while maintaining alignment accuracy by using an optical member. The figure which shows corresponding to size reduction. (A), (b) is a figure which shows the positional relationship of a corneal bright spot by the difference in WD. (A) is a diagram showing different configurations of an aperture stop, an optical member, and a prism, and (b) is a diagram showing a configuration in which the aperture stop is integrated.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

(First embodiment: the measured corneal thickness is corrected by using a correction value corresponding to an error caused by the curvature of the cornea in the measured corneal thickness)
FIG. 1 is a block diagram illustrating a configuration example of a measurement unit in the ophthalmologic apparatus according to the present embodiment. The ophthalmologic apparatus of this embodiment has both functions of a corneal thickness measuring apparatus that measures the corneal thickness of the eye to be examined and a non-contact tonometer that measures intraocular pressure.

  On the optical axis L1 facing the cornea Ec of the eye E, a parallel plane glass 1 and an objective lens 3 are arranged, and a nozzle 2 is provided on the central axis thereof. The air chamber 4, the observation window 5, the dichroic mirror 10, the prism diaphragm 11, the imaging lens 12, and the image sensor 13 are sequentially arranged on the rear side. These constitute an observation system and an alignment detection system for the eye E.

  The plane-parallel glass 1 and the objective lens 3 are supported by an objective lens tube 9, and external eye illumination light sources 6a and 6b for illuminating the eye E to be examined are arranged on the outside thereof. The external illumination light sources 6a and 6b are arranged at positions symmetrical with respect to the optical axis L1. The dichroic mirror 10 transmits light having a wavelength emitted from the external eye illumination light sources 6a and 6b, and reflects the light except for a part of light having a wavelength from an LED light source which will be described later for both intraocular pressure measurement and alignment. Yes.

  The prism diaphragm 11 has three openings as shown in FIG. 2A, and prisms 11a and 11b for deflecting light beams in different left and right directions are provided in the upper and lower openings. In practice, these openings are arranged side by side, and the light beams are deflected in the vertical direction by the prisms 11a and 11b. Furthermore, a filter having spectral characteristics that absorbs the wavelength light from the external illumination light sources 6a and 6b and transmits the wavelength light from the LED light source for both intraocular pressure measurement and alignment is provided in the upper and lower openings of the prism diaphragm 11. Is provided. The number of aperture stops is not limited to two, and may be three or more. On the other hand, the central aperture of the prism diaphragm 11 is provided with a filter that absorbs the wavelength light from the LED light source for both intraocular pressure measurement and alignment and transmits the wavelength light from the external illumination light sources 6a and 6b.

  A relay lens 14, a half mirror 15, a dichroic mirror 16, an aperture 17, and a light receiving element 18 are disposed on the optical axis L2 in the reflection direction of the dichroic mirror 10, and these detect corneal deformation detection that detects changes in the amount of reflected light from the cornea. The system is configured. The dichroic mirror 16 has a characteristic of transmitting near-infrared wavelengths and reflecting visible light wavelengths.

  On the optical axis L3 in the reflection direction of the half mirror 15, the half mirror 19, the projection lens 20, and the above-described LED light source 21 for both intraocular pressure measurement and alignment are arranged, and an intraocular pressure measurement light projection system and an alignment index projection system are configured. Has been. Further, on the optical axis L4 in the reflection direction of the half mirror 19, a fixation light source 22 presenting a fixation lamp for fixing the eye E to be examined is disposed.

  On the optical axis L5 in the reflection direction of the dichroic mirror 16, a projection lens 23, a slit plate 24, and an LED light source 25 used for measuring the corneal thickness are arranged. As shown in FIG. 2B, the slit plate 24 has a rectangular aperture that is long in the direction perpendicular to the paper surface.

  On the other hand, a filter 26, an imaging lens 27, and an image sensor 28 that transmit light in the corneal scattered light wavelength region of the LED light source 25 are disposed on the optical axis L6 in the obliquely downward direction of the eye E to be examined. It is composed. As will be described later, in the corneal thickness measurement optical system, the corneal cross section of the eye E is imaged by the imaging device 28 based on the return light from the eye E illuminated with the measurement light, and the obtained corneal cross-sectional image is the cornea. Used for thickness measurement. The optical axis L1 and the optical axis L6 intersect at the corneal apex of the eye cornea Ec to be examined. Further, the slit plate 24, the cornea Ec, and the image sensor 28 are in a substantially conjugate relationship. The output of the image sensor 28 is connected to a corneal thickness calculator 31, and in addition, a corneal thickness correction data unit 32 is connected to the corneal thickness calculator 31.

  A piston 7 that is pushed up by driving of a solenoid 34 is slidably fitted into a cylinder 33 in the air chamber 4. The nozzle 2, the air chamber 4, the solenoid 34, and the piston 7 constitute a pressurizing unit. A pressure sensor 8 for monitoring the internal pressure is arranged in the air chamber 4.

  The control unit 29 controls the entire apparatus, and is connected to the image sensor 13, a measurement start switch 30 for starting measurement, and a corneal thickness calculation unit 31. Further, the control unit 29 includes an external illumination light source 6a, 6b, a light receiving element 18, an LED light source 21 for intraocular pressure measurement and alignment, a fixation light source 22, an LED light source 25 for corneal thickness measurement, and a pressure sensor 8. The solenoid 34 is connected.

  1 is mounted on a stage unit (not shown) and is driven in a triaxial direction with respect to the eye E to be examined in the direction of the optical axis L1 and the direction perpendicular to the optical axis L1. It has come to be.

  Next, the operation of the ophthalmologic apparatus according to the present embodiment will be described with reference to the flowchart of FIG. The process shown in FIG. 9 is a process executed by the control unit 29 and the corneal thickness calculation unit 31. In the measurement, the control unit 29 turns on the fixation light source 22 to cause the eye E to be examined to fixate the fixation light source 22. In this state, when the measurement start switch 30 is pressed by the examiner, the control unit 29 aligns the eye to be examined and the apparatus main body. This alignment is performed in two stages: coarse alignment and alignment using corneal bright spots. First, the control unit 29 performs rough alignment (step S901). More specifically, the control unit 29 turns on the external illumination light sources 6a and 6b, and illuminates the anterior eye portion of the eye E with illumination light beams from these light sources. The illumination light beam reflected and scattered by the anterior eye part is made substantially parallel light by the parallel plane glass 1 and the objective lens 3, passes through the central opening of the observation window 5, the dichroic mirror 10, and the prism diaphragm 11, and forms the imaging lens 12. As a result, an image is formed on the image sensor 13.

  The control unit 29 performs binarization processing with an appropriate threshold value from the anterior ocular segment image obtained from the image sensor 13 to detect the pupil and obtain the pupil center. Then, the control unit 29 drives the stage so that the relative position between the optical axis L1 and the eye pupil to be examined falls within the allowable range within the plane in the xy direction perpendicular to the optical axis L1 of the measurement unit. Move and perform coarse alignment. In the present embodiment, the optical system for performing the rough alignment as described above is referred to as a first alignment optical system. The first alignment optical system includes the flat glass 1 to the imaging element 13 on the optical axis directed to the cornea and the external illumination light sources 6a and 6b indicated by L1.

  When the rough alignment using the first alignment optical system is completed, the control unit 29 performs alignment using corneal bright spots (steps S902 to S904). First, the control unit 29 turns on the LED light source 21 and projects an alignment index onto the cornea (step S902). The luminous flux from the LED light source 21 is once imaged in the nozzle 2 by the projection lens 20, the half mirror 19, the half mirror 15, the relay lens 14, the dichroic mirror 10, and the objective lens 3, and reaches the eye E to be examined. Reflected. The reflected light beam at the cornea Ec is collected by the parallel plane glass 1 and the objective lens 3, and after passing through the observation window 5, several percent of the light beam passes through the dichroic mirror 10. Of the three apertures of the prism diaphragm 11, only the light beams of the prisms 11 a and 11 b of the light beam transmitted through the dichroic mirror 10 are imaged on the image sensor 13 by the imaging lens 12. At this time, the light beams that have passed through the upper and lower openings of the prism diaphragm 11 are deflected by the prisms 11a and 11b in the direction toward the back of the paper and the direction toward the front, respectively. Therefore, the light from the LED light source 21 becomes a corneal bright spot image divided into two on the image pickup device 13, and the positional relationship thereof changes depending on the relative position between the eye E and the measurement unit. Therefore, the control unit 29 knows the positional relationship between the eye E and the measuring unit by detecting the positional relationship between the two corneal bright spot images divided from the image obtained by the imaging device 13. (Step S903). Here, the alignment using this corneal bright spot image is called corneal bright spot alignment.

  As described above, the optical system for executing the corneal bright spot alignment is referred to as a second alignment optical system. Therefore, the second alignment optical system detects an index projection system that follows the optical axis L3 → L2 → L1 for projecting the alignment index toward the cornea of the eye to be examined, and an alignment index projected on the cornea. And an index detection system along the optical axis L1. The configuration on the optical axis L1 is a configuration that the first alignment optical system and the second alignment optical system have in common.

  8A to 8D show two corneal bright spot images picked up by the image pickup device 13 in the execution of the corneal bright spot alignment described above. Here, T1 (x1, y1) and T2 (x2, y2) indicate two corneal bright spot images, and the corneal bright spot image on the imaging element 13 in front of the paper surface is T1 (x1, y1), the corneal bright light at the back of the paper surface. The point image is T2 (x2, y2). Further, the central coordinates T (xt, yt) of the line segment connecting these two corneal bright spot images T1 (x1, y1) and T2 (x2, y2) coincide with the optical axis L1. The center of the cornea Ec is indicated by an intersection C (x0, y0) between the x coordinate and the y coordinate.

  FIG. 8A shows a case where the working distance between the eye E and the measurement unit is longer than a predetermined distance, and FIG. 8B shows a case where the working distance between the eye E and the measurement unit is closer than the predetermined distance. Yes. FIG. 8C shows the case where the positional relationship between the eye E and the measurement unit is shifted in the y direction. FIG. 8D shows that the corneal bright spot alignment is completed between the eye E and the measurement unit. Shows the case.

  For example, when the working distance between the eye E and the measuring unit is longer than a predetermined distance, as shown in FIG. 8A, the corneal bright spot image T2 (x2, y2) The image T1 (x1, y1) moves upward. On the other hand, when the working distance between the eye E and the apparatus measuring unit is shorter than the predetermined distance, as shown in FIG. 8B, the corneal bright spot image T2 (x2, y2) is upward, The point images T1 (x1, y1) move downward. Further, when there is a deviation in the y direction in the positional relationship between the eye E and the measurement part, as shown in FIG. 8C, y1 and y2 coincide with each other, and the center C (x0, y0) of the cornea Ec. ) Matches x0 and xt, but y0 and yt are different. On the other hand, when the corneal bright spot alignment is completed between the eye E and the measurement unit, as shown in FIG. 8D, two corneal bright spot images T1 (x1, y1), T2 (x2, y2 ) Are arranged at equal intervals from the center of the cornea Ec and on the x axis, and the center coordinates T1 (x1, yt) and the cornea Ec center C (x0, y0) coincide.

  As described above, in the corneal bright spot alignment, the control unit 29 obtains the misalignment between the eye E and the apparatus measuring unit as shown in FIGS. 8A to 8C, and the position of the corneal bright spot image is shown. The stage is driven to reach the position shown in FIG. 8 (d) (step S904).

  It should be noted here that, when corneal bright spot alignment is performed, as shown in FIG. 3, the surface of the cornea Ec has different curvatures (hereinafter, the curvature of the surface of the cornea Ec is referred to as the corneal curvature). The distance D from the corneal apex to the tip of the nozzle 2 changes. In the corneal bright spot alignment, the virtual image Ei created when the light beam projected from the LED light source 21 is reflected by the cornea Ec and the distance D ′ to the tip of the nozzle 2 are determined by the eye E having any corneal curvature. Even if it exists, it is operating so as to be the same distance. Therefore, the distance D from the corneal apex of the cornea Ec to the tip of the nozzle 2 varies depending on the corneal curvature.

  When the corneal bright spot alignment is completed as described above, the corneal thickness is then measured (steps S905 to S907). In the measurement of the corneal thickness, the control unit 29 turns off the LED light source 21 and turns on the LED light source 25 for measuring corneal thickness (step S905). Then, the control unit 29 instructs the corneal thickness calculation unit 31 to calculate the corneal thickness (step S906).

  In the measurement of corneal thickness, slit light formed by the LED light source 25 illuminating the slit plate 24 passes through the projection lens 23, the dichroic mirror 16, the half mirror 15, the relay lens 14, the dichroic mirror 10, and the nozzle 2. The image is formed on the cornea Ec. The slit light imaged on the cornea Ec is scattered by the cornea Ec, and the scattered light passes through the filter 26 and the imaging lens 27 arranged along the optical axis L6 and is imaged by the imaging element 28. The corneal thickness calculation unit 31 calculates the corneal thickness using the image data output from the image sensor 28 and the data stored in the corneal thickness correction data unit 32. When the control unit 29 receives the measurement result of the corneal thickness from the corneal thickness calculation unit 31 (step S907), the control unit 29 subsequently starts measuring the intraocular pressure (step S908).

As described above, the calculation of the corneal thickness is
The corneal thickness measurement light for measuring the corneal thickness is shared by a part of the first and second alignment optical systems on the optical axis (optical axis L1) toward the cornea and directed toward the cornea of the eye to be examined. A projection optical system for projecting (an optical system following L5 → L2 → L1),
A light receiving optical system (optical axis) that images scattered light from the cornea of the corneal thickness measurement light projected onto the cornea by the projection optical system outside the optical axis and captures an image corresponding to the corneal thickness of the cornea And an optical system that follows an optical axis L6 outside L1).

  In the measurement of intraocular pressure, the LED light source 21 is turned on (the LED light source 25 is turned off), an airflow is blown from the nozzle 2 toward the cornea of the eye to be examined, the cornea is deformed, and the reflected light changes according to the deformation of the cornea. The intraocular pressure value is measured by detecting. Hereinafter, the measurement of intraocular pressure will be described in more detail. The control unit 29 drives the solenoid 34. Then, the air in the air chamber 4 is compressed by the piston 7 pushed up by the solenoid 34 and is ejected from the nozzle 2 toward the cornea Ec of the eye E as pulsed air. The cornea Ec gradually begins to deform according to the strength of the air.

  At this time, the light receiving element 18 receives a light beam emitted from the LED light source 21 and reflected from the cornea Ec through the aperture 17. The aperture 17 is arranged so as to be substantially conjugate with the LED light source 21 when the radius R of curvature of the cornea Ec of the eye to be examined is substantially infinite. For this reason, the amount of light received by the light receiving element 18 increases as the corneal curvature radius R increases due to the pulsating air, and the corneal curvature radius R is approximately infinite, that is, the cornea Ec is approximately planar. The amount of received light is a peak value. The light receiving element 18 detects a peak value when the cornea Ec becomes a flat surface by air emitted in a pulse shape. The control unit 29 calculates the intraocular pressure value of the eye E from the peak value of the light receiving element 18 and the value of the pressure sensor 8 at that time. The control unit 29 takes into account the measurement result of the corneal thickness calculated from the corneal thickness calculation unit 31 when calculating the intraocular pressure value of the eye E, that is, based on the measurement result of the corneal thickness. The final intraocular pressure value is obtained by correcting the obtained intraocular pressure (step S909).

The optical system for measuring the intraocular pressure of the eye to be examined as described above is referred to as an intraocular pressure measuring optical system in the present embodiment. This tonometry optical system
An optical system (LED light source) having the first and second alignment optical systems on the optical axis L1 in common and projecting the tonometry light for measuring the intraocular pressure of the eye to be examined toward the eye to be examined. 21 → L3 → L2 → L1)
An optical system that detects reflected light from the cornea of the intraocular pressure measurement light (an optical system that follows L1 → L2 → the light receiving element 18).

  In the ophthalmologic apparatus of the present embodiment as described above, calculation of the corneal thickness by the corneal thickness calculation unit 31 and the corneal thickness correction data unit 32 will be described with reference to FIGS. 4 to 7 and FIG.

  The corneal thickness calculation unit 31 waits for a corneal thickness measurement instruction from the control unit 29 (step S921). When receiving a corneal thickness measurement instruction from the control unit 29, the corneal thickness calculation unit 31 acquires an image for measuring the corneal thickness from the image sensor 28 (step S922).

  4 to 6 are views showing how the scattered light from the cornea Ec is imaged on the image sensor 28 by the LED light source 25. FIG. 4 to 6 show the vicinity of the corneal apex of the cornea Ec, and only the configuration necessary for the description to be described later is shown. Moreover, the same number is attached | subjected about the structure same as the structure shown in FIG.

  In addition, in FIGS. 4 to 6, the radius R of the corneal curvature is different. 4 shows the case where the radius R of the corneal curvature is an average eye to be examined (corneal curvature as a reference when designing the optical system), FIG. 5 shows the case where the radius R of the corneal curvature is larger than the average, and FIG. The case where the radius R is smaller than the average is shown. In FIGS. 5 and 6, the measurement state of the corneal thickness shown in FIG. Here, Pw is the corneal thickness, T is the front surface of the cornea, B is the back surface of the cornea, and Ls is the illumination light from the nozzle 2 of the LED light source 25. However, the corneal thickness Pw shown in FIGS. 4 to 6 is the same for all three examples.

  As described with reference to FIG. 3, in the corneal bright spot alignment, the distance between the tip of the nozzle 2 and the corneal apex changes depending on the corneal curvature. 4 to 6, the distance D between the corneal vertex of the cornea Ec and the tip of the nozzle 2 after alignment of the corneal bright spot is in a relationship of Db <Da <Dc due to the difference in the radius R of the corneal curvature. As a result, the angle of the optical axis L6 that receives the scattered light from the cornea and the optical path length to the image sensor 28 are different, and the image on the image sensor 28 is blurred.

  When the radius R of the corneal curvature is an average eye to be examined (FIG. 4), larger than the average (FIG. 5), or smaller than the average (FIG. 6), the width of the image and the position of the image on the image sensor 28 The relationship is as shown in FIG. The horizontal axis in FIG. 7A indicates the position of the image on the image sensor 28 as viewed in the Ad direction in FIGS. For the image positions Xa, Xb, and Xc, points where scattered light from the corneal apex of the cornea Ec by the LED light source 25 forms an image on the imaging surface of the image sensor 28 are used. 4 shows Xa, FIG. 5 shows Xb, and FIG. 6 shows Xc. The vertical axis in FIG. 7A indicates the width of the image on the image sensor 28.

  In the case of an eye to be examined having an average corneal curvature radius R, the position of the image is Xa, the width of the image is Sa, and the image is not blurred (FIG. 4). On the other hand, when the radius R of the corneal curvature is larger than the average, the position of the image is Xb and the width of the image is Sb (FIG. 5), and when the radius R of the corneal curvature is smaller than the average, the position of the image is Xc, The width of the image is Sc (FIG. 6), and in all cases, the image is blurred. Therefore, as shown in FIG. 7A, it can be seen that the width of the image increases when the radius R of the corneal curvature is large or small (Sb> Sa, Sc> Sa). On the other hand, it can be seen that when the radius R of the corneal curvature is large, the address of the image position becomes large (Xb> Xa). It can be seen that when the radius R of the corneal curvature is small, the address of the image position is small (Xc> Xa).

  When receiving the image data output from the image sensor 28, the corneal thickness calculation unit 31 reads the address of the image width and the image position. On the other hand, the correction value of the width of the image corresponding to the address is stored in the corneal thickness correction data section 32. For example, the corneal thickness correction data unit 32 has a correction value table that holds the position of the image captured by the image sensor 28 in the light receiving optical system for measuring the corneal thickness and the correction value in association with each other. Therefore, the corneal thickness calculation unit 31 acquires a corresponding correction value from the corneal thickness correction data unit 32 (for example, a correction value table) using the position of the image indicating the corneal thickness (step S923). The corneal thickness calculation unit 31 corrects the width of the image read from the image sensor 28 using the correction value of the width of the image read from the image sensor 28 and the width of the image read from the corneal thickness correction data unit 32. (Step S924). The width of the image may be measured by binarizing the image read from the image sensor 28 with an appropriate threshold value. The corneal thickness calculation unit 31 notifies the control unit 29 of the measurement value of the corneal thickness corrected in this way (step S925).

  For example, it is assumed that the corneal thickness calculation unit 31 receives image data output from the image sensor 28 and acquires Xb as the position of the image corresponding to the corneal thickness (address on the image sensor 28). This is a case where the radius R of the corneal curvature is larger than the average. In this case, the corneal thickness calculation unit 31 reads the correction value corresponding to the address Xb of the image from the corneal thickness correction data unit 32. In the calculation of the corneal thickness, Sa / Sb is acquired as a correction value, and the corneal thickness calculation unit 31 corrects the corneal thickness acquired from the image data using this correction value. For example, the corneal thickness correction data unit 32 has a correction value data table as shown in FIG. 7A, and the corneal thickness calculation unit 31 has the address Xa with Sb acquired according to the address Xb. A value obtained by dividing Sa in (Sa / Sb) is set as a correction value. The corneal thickness calculation unit 31 obtains the corrected corneal thickness by multiplying the correction value obtained in this way by the value of the corneal thickness measured from the image data.

On the other hand, it is assumed that the radius R of the corneal curvature is smaller than the average, and the corneal thickness calculation unit 31 acquires Xc as the address of the position of the image corresponding to the corneal thickness from the image data output from the image sensor 28. In this case, the corneal thickness calculation unit 31 reads a correction value corresponding to the address Xc of the image position from the corneal thickness correction data unit 32. In the calculation of the corneal thickness, Sa / Sc is acquired as the correction value, and the corneal thickness calculation unit 31 corrects the corneal thickness acquired from the image data using this correction value. For example, the corneal thickness calculator 31 obtains a value (Sa / Sc) obtained by dividing Sa at the address Xa by Sc acquired according to the address Xc from the correction value data table as shown in FIG. The correction value. Then, the corneal thickness calculation unit 31 obtains the corrected corneal thickness by multiplying the correction value obtained in this way by the value of the corneal thickness measured from the image data.
In the above description, the correction value is calculated using one type of characteristic as shown in FIG. 7A. However, the present invention is not limited to this. For example, as shown in FIG. 7B, a plurality of types of characteristic values (characteristic curves 701, 702, and 703 in FIG. 7B) are prepared, and the positions of the measured images and the measured images are measured. A correction value may be obtained by selecting the most appropriate characteristic curve from the width. For example, in FIG. 7B, when the position of the image is Xb and the width of the image is an X mark 704, the characteristic curve 702 closest to this measured value is selected, and the value (Sb) of the characteristic curve 702 at Xb is selected. A correction value is obtained using ') and the value (Sa') in Xa.

  As described above, the corneal thickness calculator 31 corrects the width of the image in this way, and calculates the corneal thickness Pw of the eye to be examined from the corrected image width, lens imaging magnification, and the like. According to the corneal thickness measurement configuration described above, by correcting the width of the detected image with a correction value corresponding to the detection position of the image, the corneal curvature of the subject having the same corneal thickness can be measured. Even in the optometry, the width of the image corresponding to the corneal thickness can be made the same.

  As described above, the ophthalmologic apparatus having both functions of measuring the corneal thickness of the eye to be examined and measuring the intraocular pressure has been described as an example, but the present invention may be an ophthalmologic apparatus having only the function of measuring the corneal thickness of the eye to be examined. . In the case of an ophthalmologic apparatus having only the function of measuring the corneal thickness of the eye to be examined, for example, from the configuration of the above embodiment, the parallel flat glass 1, the nozzle 2, the air chamber 4, the observation window 5, the piston 7, and the pressure sensor 8 are used. The solenoid 34, the aperture 17, and the light receiving element 18 may be omitted.

  As described above, in the ophthalmologic apparatus of this embodiment having at least the function of measuring the corneal thickness of the eye to be examined, the second alignment optical system (projection system / light receiving system for corneal bright spot alignment) and the corneal thickness measurement The projection optical system mainly includes the optical axis L1. In addition, the light receiving optical system for measuring the corneal thickness can mainly include the optical axis L6. For this reason, a measuring apparatus for corneal thickness can be configured with a simple optical system configuration. Further, since corneal thickness measurement is performed using corneal bright spot alignment, the image on the image sensor 28 is blurred due to the difference in corneal curvature of the eye to be examined, and an error occurs in the measured value of corneal thickness. Resulting in. This is because the angle of the optical axis of the light receiving system that receives scattered light from the cornea and the optical path length to the light receiving element differ depending on the difference in corneal curvature. However, according to the above embodiment, an accurate corneal thickness can be obtained by correcting the measured value of the corneal thickness based on the position of the image on the image sensor 28. In addition, according to the said embodiment, it can correct | amend not only about the error of the measured value of the corneal thickness caused by the difference in the corneal curvature, but also about the error of the measured value of the corneal thickness caused by the alignment in the Z direction. That is, according to the embodiment, in the ophthalmologic apparatus having a function of measuring the corneal thickness, it is possible to simplify the configuration of the optical system and realize more accurate measurement of the corneal thickness.

  Further, in the case of an ophthalmologic apparatus having both functions of measuring the corneal thickness of the eye to be examined and measuring the intraocular pressure, the second alignment optical system, the projection optical system for measuring the corneal thickness, the intraocular pressure measuring optical system (for measuring the intraocular pressure) The projection system / light receiving system) can be configured mainly with the optical axis L1. In addition, as described above, the light receiving system for measuring the corneal thickness can mainly include the optical axis L6. For this reason, it is possible to measure the corneal thickness, the intraocular pressure, and both functions with a simple optical system configuration.

  Furthermore, when calculating the intraocular pressure value of the eye E, the intraocular pressure value can be corrected using the calculation result of the corneal thickness, so that a more accurate intraocular pressure value can be obtained with a simple optical system. An ophthalmic device that can be provided can be provided.

  In the embodiment described above, the optical axis L6 is arranged in the obliquely downward direction of the eye E, but the optical axis L6 may be outside the optical axis L1 facing the eye E. That is, the corneal thickness measurement optical system (the filter 26, the imaging lens 27, and the image sensor 28) may be configured such that the optical axis thereof is arranged at a predetermined angle with respect to the optical axis L1.

  The control unit 29 and the corneal thickness calculation unit 31 execute, for example, a predetermined program by the CPU to realize the processing shown in FIG. May be implemented. Further, part or all of the processing executed by the control unit 29 and / or the corneal thickness calculation unit 31 may be realized by dedicated hardware or a logic circuit.

  In the above embodiment, the control unit 29 automatically performs the corneal bright spot alignment. However, the user may move the apparatus main body and perform the alignment while watching the monitor of the corneal bright spot. .

(Second Embodiment: Compact optical member for alignment)
Next, a second embodiment will be described. In recent years, as the size of an image pickup device has been reduced, the lens of an imaging optical system has also been reduced in size, and the restrictions on manufacturing the lens and the back focus have become shorter, making it difficult to dispose the lens. Further, when the lens is miniaturized, the distance between the aperture stops cannot be increased in an apparatus that captures a corneal reflection image by an alignment index from two directions by two aperture stops and performs alignment based on the positional relationship between the two images. This is because it is necessary to put the light beam taken in by the aperture stop into the imaging lens. Therefore, if the distance between the aperture stops cannot be increased, the alignment accuracy cannot be maintained.

  Japanese Patent Laid-Open No. 2000-060801 proposes to provide an alignment index projection system and a light receiving optical system outside the optical axis. In Japanese Patent Laid-Open No. 2000-060801, an index is projected onto the eye cornea to be examined, and an imaging position of a regular reflection light by the cornea on a sensor provided in a light receiving optical system is detected, and the detected imaging position and reference position are detected. Alignment of the distance (working distance) from the eye cornea to the device based on the amount of deviation from the eye. However, in this configuration, an optical system for alignment must be provided, which causes a problem that the apparatus becomes large. In the second embodiment, an alignment optical system will be described in which the apparatus configuration is not complicated and the alignment performance is not impaired even when the imaging device and the imaging lens are downsized.

  FIG. 10A is a diagram showing the extracted parts of the prism diaphragm 11, the imaging lens 12, and the image sensor 13 on the optical axis L1. The solid line in FIG. 10A shows a case where the eye to be examined and the measurement unit are at an appropriate distance (d = WD). Ec is the cornea of the eye to be examined, and Ei is a reflection image formed by projecting the LED light source 21 as an alignment index onto the cornea by the alignment index projection system described above. For simplification, the plane parallel glass 1, the nozzle 2, the objective lens 3, the air chamber 4, and the observation window 5 existing on the optical axis L1 are omitted.

  Since the position of the approximate focal length of the objective lens 3 is designed to be the reflected image position when the distance in the optical axis direction between the eye cornea to be examined and the measurement unit is a normal distance (d = WD), The light beam transmitted through the objective lens becomes substantially parallel light. The light beam is deflected by the prism, and the light beam that has passed through the upper and lower aperture stops of the prism stop 11 forms an image on the image sensor 13 via the imaging lens 12. The imaging element 13 is disposed at a position substantially at the focal length of the imaging lens 12.

  At that time, a monitor that displays an image obtained by the image sensor 13 is displayed as shown in FIG. Reflected images (T1, T2) transmitted through the upper and lower aperture stops and deflected by the prism are arranged in a line on the x plane including the optical axis. On the other hand, the dotted line shows the luminous flux when the WD is shifted and far (d> WD). Since the object point (corneal reflection image) is far from the measurement unit, the light beam is imaged on the imaging lens 12 side from the image sensor 13, and the reflected image (T1, T2) is blurred on the image sensor 13, In addition, as shown in FIG. 11B, the position is point-symmetric with respect to the optical axis.

  As described above, when the distance in the optical axis direction between the eye cornea to be examined and the measurement unit is changed from the normal distance (WD), the two reflected images are shifted in opposite directions. This occurs because the light beam passing through the two aperture stops has an angle with respect to the optical axis by the prisms 11a and 11b, so that the intersection position of the image sensor 13 and the light beam changes when WD changes. Using this principle, the ophthalmic apparatus disclosed in the present case performs alignment.

  The accuracy in the optical axis direction is determined by the distance D between the two aperture stops shown in FIG. 2C if the number of pixels of the image sensor 13 with respect to the sensor size is constant. In order to explain that the resolution in the WD distance direction changes depending on the size of the lens diameter, the light beam when the imaging lens 36 having a small lens size is used in FIG. 10B is shown by a solid line, and FIG. The luminous flux when the imaging lens 12 having the described lens size is used is indicated by a dotted line. The prism diaphragm 11 'has a short distance between the aperture diaphragms in order to make the light beam enter a small lens (D' in the figure). When the distance D between the upper and lower aperture stops of the prism stop 11 is made small, the angle at which the aperture stop takes out the reflected image light beam becomes small with respect to a minute change in WD, so the change becomes small, and the reflection on the image sensor 13 is reduced. The moving amount of the image is also reduced, and the alignment accuracy is lowered.

  An example in which an optical member 37 made of, for example, resin is arranged in the prism diaphragm 11 in which two pairs of total reflection mirrors of approximately 45 degrees are paired in order to cope with a downsized optical system while maintaining the distance D between the aperture diaphragms. Is shown in FIG. The optical member 37 is provided on the optical path of the light beam that has passed through the aperture stop. In FIG. 10C, the distance D between the aperture stops of the prism diaphragm 11 is the same as that of the imaging lens 12 of FIG. A configuration that is downsized to 13 'is employed.

  The optical member 37 offsets the light beam taken by the prism diaphragm 11 at the distance D between the aperture diaphragms to the optical axis side. Thus, by shortening the distance between the light beams corresponding to the distance D between the aperture stops, the light beam is made incident on the miniaturized imaging lens 36 while maintaining the distance D between the aperture stops. The optical member 37 completely covers the openings at both ends of the prism diaphragm 11 and has such a size that the light beams deflected by the prisms 11a and 11b cannot be lost. The distance between the aperture stops is a distance at which the principal ray is not blocked by the nozzle 2 for injecting air to the eye cornea to be examined, and the optical member 37 is designed so that the distance between the light beams that have passed through the aperture stop is shortened. Change the optical path of the luminous flux.

  In the second embodiment, the prisms 11a and 11b, the aperture stop of the prism stop 11, and the optical member are arranged in this order, but the present invention is not limited to this. For example, as shown in FIG. 12 (a), two aperture stops 11 'having a distance D between the aperture stops without a prism, an optical member 37, and prisms 11a' and 11b 'may be configured in this order. In other words, the prisms 11 a ′ and 11 b ′ that are deflecting means may be arranged on the exit side of the optical member 37.

  The shapes of the prisms 11a 'and 11b' are the same as those of the prisms 11a and 11b, and play the role of deflecting the light beam. The optical members 37 provided in each aperture stop may be arranged as separate parts as shown in FIG. 12A, but the two optical members 37 arranged up and down as shown in FIG. 12B. It is good also as a structure which shape | molded integrally.

  As described above, according to the second embodiment, even when the imaging element and the imaging lens are downsized, the apparatus configuration is not complicated and the alignment performance is not impaired.

  Although the embodiment has been described in detail above, the present invention can take an embodiment as a system, apparatus, method, program, storage medium, or the like. Specifically, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of a single device.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (24)

A projection optical system that projects an alignment index onto the cornea of the eye to be examined; and
An opening member including a plurality of openings that divide the light beam of the corneal reflection image by the alignment index into a plurality of light beams and allow the plurality of light beams to pass;
An optical member that changes a distance between the plurality of light beams that have passed through the plurality of openings to a short distance;
An ophthalmologic apparatus, comprising: an imaging lens that forms an image on the imaging unit with the plurality of light fluxes changed to the short distance.   The ophthalmologic apparatus according to claim 1, wherein a distance between the plurality of light beams that have passed through the plurality of openings corresponds to a distance between the plurality of openings.   3. The ophthalmic apparatus according to claim 1, wherein the plurality of openings are arranged at a predetermined distance at substantially symmetrical positions around the optical axis in the opening member.   The ophthalmologic apparatus is a non-contact tonometer, and a distance between the plurality of openings is a distance at which a principal ray is not blocked by a nozzle for injecting air to the cornea of the eye to be examined. The ophthalmic apparatus according to any one of claims 1 to 3. A deflection member that deflects the plurality of light beams in different directions;
5. The ophthalmologic apparatus according to claim 1, wherein the optical member changes a distance between the deflected light beams to a short distance. 6.   The ophthalmic apparatus according to claim 5, wherein the deflecting member, the opening member, and the optical member are arranged in this order from the cornea toward the imaging unit.   The ophthalmic apparatus according to claim 5, wherein the opening member, the optical member, and the deflection member are arranged in this order from the cornea toward the imaging unit.   The ophthalmologic apparatus according to claim 7, wherein the optical member and the deflection member are integrally formed and configured as a plurality of members separately disposed in the plurality of openings.   The ophthalmic apparatus according to claim 7, wherein the optical member and the deflection member are integrally formed and configured as one member. The optical member is two pairs of reflecting members arranged in each opening in the plurality of openings,
10. The ophthalmologic apparatus according to claim 1, wherein each of the reflecting members of the two pairs of reflecting members is disposed at approximately 45 degrees with respect to an optical axis of the imaging lens. .   The ophthalmologic apparatus according to claim 1, wherein the optical member includes a resin.   12. The apparatus according to claim 1, further comprising a control unit configured to perform alignment by driving a stage on which the imaging unit is mounted based on the plurality of light beams formed on the imaging unit. The ophthalmic apparatus according to item 1.   13. The ophthalmologic apparatus according to claim 12, wherein the control unit starts corneal thickness measurement of the eye to be examined after the alignment is completed.   14. The ophthalmologic apparatus according to claim 13, wherein when the alignment is completed, the control unit turns off a light source for projecting the index and turns on a light source for measuring the corneal thickness.   The ophthalmologic apparatus according to claim 13 or 14, wherein the control unit starts measuring the intraocular pressure of the eye to be examined after the corneal thickness measurement is completed.   16. The ophthalmologic apparatus according to claim 15, wherein when the corneal thickness measurement is completed, the control means turns off the light source for measuring the corneal thickness and turns on the light source for measuring the intraocular pressure. .   The ophthalmologic apparatus according to claim 15, wherein the control unit corrects the result of the intraocular pressure measurement using the result of the corneal thickness measurement. An ophthalmologic apparatus control method for controlling the ophthalmologic apparatus according to any one of claims 1 to 11,
An ophthalmologic apparatus control method comprising a step of performing alignment by driving a stage on which the imaging unit is mounted based on the plurality of light beams formed on the imaging unit.   The method for controlling an ophthalmologic apparatus according to claim 18, further comprising a step of starting measurement of corneal thickness of the eye to be inspected after the alignment is completed.   20. The method of controlling an ophthalmologic apparatus according to claim 19, further comprising a step of turning off a light source for projecting the index and turning on a light source for measuring the corneal thickness when the alignment is completed. .   The method for controlling an ophthalmologic apparatus according to claim 19 or 20, further comprising a step of starting intraocular pressure measurement of the eye to be examined after the corneal thickness measurement is completed.   The ophthalmic apparatus according to claim 21, further comprising a step of turning off the light source for measuring the corneal thickness and turning on the light source for measuring the intraocular pressure when the corneal thickness measurement is completed. Control method.   The method for controlling an ophthalmologic apparatus according to claim 21 or 22, further comprising a step of correcting the result of the intraocular pressure measurement using the result of the corneal thickness measurement.   24. A program for causing a computer to execute each step of the method for controlling an ophthalmologic apparatus according to any one of claims 18 to 23.

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