JP6355952B2 - Corneal imaging device - Google Patents

Description

The present invention relates to a cornea imaging apparatus that captures a cornea image by irradiating illumination light to a subject's eye and receiving reflected light from the cornea of the subject's eye.

Conventionally, the cell state of the cornea, particularly the corneal endothelium, has been observed when determining the presence or absence of an eye disease or diagnosing the postoperative course of the eye.

When observing the cell state of such corneal endothelium, a corneal imaging apparatus that can image corneal endothelial cells in a non-contact manner with respect to an eye to be examined is known. In this cornea photographing device, a slit-shaped illumination light is irradiated obliquely to the cornea of an eye to be examined by an illumination optical system, and reflected light from the cornea is received by an imaging optical system to image corneal endothelial cells. Yes.

By the way, since the corneal endothelial cell has a small thickness dimension, the corneal imaging apparatus has a problem that it is difficult to obtain a clear focused image of the corneal endothelial cell. In particular, since the corneal imaging apparatus employs slit-shaped illumination light, in order to avoid the adverse effects of reflected light from the corneal epithelium or corneal stroma and obtain a clear corneal endothelial cell, the illumination optical system and The in-focus position in the imaging optical system needs to be accurately aligned with the position of the corneal endothelial cell, and in particular, alignment in the Z direction (front-rear direction) with respect to the corneal endothelial cell is important. Endothelial cells have been considered difficult because of their small thickness.

In Patent Document 1, the corneal surface (corneal epithelium) is irradiated with alignment light, the reflected light (bright spot) is detected by an alignment detection sensor inside the main body, the XY position is aligned, and another alignment light is emitted. Incidently incident on the cornea of the eye to be examined, the reflected image is received by a one-dimensional CCD, the in-focus position (Z coordinate) of the illumination optical system and the imaging optical system is detected from the received light signal, and the detected focus is detected. Once the position is moved to the back of the cornea (the position filled with aqueous humor behind the corneal endothelial cells), the optical system is moved backward to move the in-focus position to the front (corneal direction). A method is disclosed in which corneal imaging is started based on detection of reflected light on the rear end side of the cornea while moving the position in the forward direction (Z direction), and a plurality of images are continuously captured.

And it is supposed that a highly accurate corneal endothelium image can be acquired by selecting a photographed image based on the light level and contrast of a plurality of photographed images.

As described above, according to the configuration according to Patent Document 1, the in-focus position is moved over the entire area of the corneal endothelial cell from the rear end of the cornea (the lowermost end portion of the corneal endothelial cell), and continuous corneal imaging is performed. By performing and selecting a plurality of photographed images, a corneal endothelial cell image can be imaged with high accuracy and excellent efficiency.

Japanese Patent No. 4916255

However, in the XY alignment using the bright spot of the corneal epithelium as in Patent Document 1, the apex position of the corneal epithelium and the apex position (XY coordinate) of the corneal endothelial cell do not necessarily coincide with each other. It was difficult to obtain images of corneal endothelial cells at

Moreover, it is necessary to perform XY alignment during imaging of corneal endothelial cells, and in Patent Document 1, it is performed between imaging of corneal endothelial cells. In this case, it is necessary to always perform switching control of the light source for the illumination light for imaging and the XY alignment light so that the XY alignment light does not enter the corneal endothelial cells.

Furthermore, a plurality of images are taken continuously at predetermined time intervals while moving in the front-rear direction (Z-axis direction), and a good image is selected from the plurality of taken images based on the light level and contrast. This method does not necessarily obtain an image at the optimum position of the Z position.

The present invention solves the above-described problems, and provides a cornea imaging apparatus capable of acquiring a corneal endothelium image at an optimal position (X, Y, Z coordinates) by a simple method without performing special control. The purpose is to do.

In order to achieve the above object, an invention according to claim 1 is directed to an illumination optical system including an illumination light source that irradiates a slit light beam obliquely to the eye to be examined, and a reflected light beam from the cornea of the eye to be examined by the slit light beam. And an optical imaging system that includes a photoelectric element that captures a corneal image and moves the illumination optical system and the imaging optical system as a whole toward or away from the eye to be focused. In a corneal imaging apparatus including a driving unit, an acquisition unit that continuously acquires a corneal endothelium image at a position where a corneal endothelium image can be acquired, an analysis unit that analyzes the acquired corneal endothelium image, and an analysis unit The present invention is characterized by comprising a calculation means for calculating the amount of deviation of each of the X and Y coordinates based on the analysis result, and an alignment means for performing XY alignment based on the calculation result.

Conventional XY alignment using the bright spot of corneal epithelium is performed until the position where corneal endothelial cells can be acquired, and corneal endothelial images are continuously acquired at the positions where corneal endothelial cells can be acquired. By performing XY alignment based on the current XY coordinate position shift amount from the analysis result, it is possible to acquire an image of the corneal endothelial cell at the optimum position.

According to a second aspect of the present invention, in the corneal imaging device according to the first aspect, the calculation method of the amount of deviation of the X (Z) coordinates is based on the acquired corneal endothelial image (slit image). It is characterized in that the positions of both end edges of the image are detected and calculated from the detection result.

The left and right (X direction) edge positions of the corneal endothelial cell image are detected, the center position is obtained in the left and right direction of the corneal endothelial cell image from the detected left and right edge positions, and the difference between the position and the center position of the acquired cell image By calculating the quantity, precise X (Z) coordinate alignment is possible.

According to a third aspect of the present invention, in the corneal imaging apparatus according to the first or second aspect, the method for calculating the amount of Y-coordinate deviation is the Y-coordinate direction of the acquired corneal endothelium image (the eye to be examined). It is calculated from the distribution state of the luminance value in the vertical direction).

For each predetermined area (for example, about 10 pixels) in the Y coordinate direction, the total value of the pixel values in that area is used as the luminance value of each predetermined area, the distribution state in the Y coordinate direction is detected, the position of the peak value of the luminance value and the cell By calculating the amount of deviation from the center position of the image in the Y coordinate direction (vertical direction), precise Y coordinate alignment is possible.

According to a fourth aspect of the present invention, in the corneal imaging apparatus according to the first or second aspect, the method for calculating the amount of Y-coordinate deviation is the Y-coordinate direction of the acquired corneal endothelium image (the eye to be examined). (Up and down direction) of the contrast value is calculated.

The distribution value in the Y coordinate direction is detected using the sum of absolute values of differences between adjacent pixels in a predetermined region (for example, about 10 pixels) in the Y coordinate direction as the contrast value of each predetermined region, and the peak value of the contrast value By calculating the amount of deviation between the position of and the center position of the cell image in the Y-coordinate direction (vertical direction), precise Y-coordinate alignment is possible.

According to a fifth aspect of the present invention, in the corneal imaging device according to the first or second aspect, the method for calculating the amount of deviation of the Y coordinate is such that the luminance value of the acquired corneal endothelium image is a predetermined value. The area of the above region is calculated.

Accurate Y coordinate alignment is possible by calculating the area of a region where the luminance value of the acquired corneal endothelium image is equal to or greater than a predetermined value and performing Y coordinate alignment at a position where the area is maximized.

As described above, the corneal imaging device according to the present invention can acquire a corneal endothelium image at an optimum position (X, Y, Z coordinates) by a simple method without performing special control.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing for demonstrating the optical system as one Embodiment of this invention. Explanatory drawing for demonstrating the cornea imaging device as one Embodiment of this invention. Explanatory drawing for demonstrating the control circuit etc. which are connected to the optical system shown in FIG. The flowchart which shows the imaging | photography procedure of a cornea imaging device. Explanatory drawing for demonstrating the anterior eye part displayed on a display screen. Explanatory drawing for demonstrating the reflected light beam in each layer of a cornea. Explanatory drawing which shows light quantity distribution detected by a light quantity detection means. Explanatory drawing which shows a change in the moving speed of an apparatus optical system. Explanatory drawing for demonstrating the detection method of corneal-endothelium reflected light, and the selection method of an image. Explanatory drawing for demonstrating arrangement | positioning of the pixel in an image. Explanatory drawing for demonstrating the structure of each layer of a cornea. Explanatory drawing for demonstrating the X (Z) alignment method using the corneal endothelium image in one Embodiment of this invention. Explanatory drawing for demonstrating the Y alignment method using the corneal endothelium image in one Embodiment of this invention.

Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows an apparatus optical system 10 as an embodiment of a cornea photographing apparatus according to the present invention. The apparatus optical system 10 includes an imaging illumination optical system 14 and a position detection optical system 16 on one side with an observation optical system 12 for observing the anterior eye portion of the eye E to be examined, and a position detection illumination on the other side. The optical system 18 and the imaging optical system 20 are provided. In particular, in the present embodiment, the illumination optical system is configured to include the imaging illumination optical system 14 and the position detection illumination optical system 18.

The observation optical system 12 is configured such that a half mirror 22, an objective lens 24, a half mirror 26, a cold mirror 27, and a CCD 28 as a photoelectric element are provided on the optical axis O1 in order from a position close to the eye E. Further, a plurality (two in the present embodiment) of observation light sources 30 and 30 are arranged in front of the eye E to be examined. As the observation light sources 30, 30, for example, infrared LEDs that emit infrared light beams are used. The cold mirror 27 transmits infrared light while reflecting visible light, and the reflected light beam emitted from the observation light sources 30 and 30 and reflected by the anterior eye portion of the eye E is examined. The image is formed on the CCD 28 through the objective lens 24 and the cold mirror 27.

The imaging illumination optical system 14 includes a projection lens 32, a cold mirror 34, a slit 36, a condensing lens 38, and an imaging light source 40 in order from a position close to the eye E. The imaging light source 40 is, for example, an LED that emits a visible light beam. The cold mirror 34 transmits infrared light while reflecting visible light. Then, the light beam emitted from the imaging light source 40 is converted into a slit light beam through the objective lens 38 and the slit 36, reflected by the cold mirror 34, and then irradiated to the cornea C from the oblique direction through the projection lens 32. It is like that.

The position detection optical system 16 has a part of its optical axis aligned with the optical axis of the imaging illumination optical system 14, and is provided with a projection lens 32, a cold mirror 34, and a line sensor 44 in order from a position close to the eye E. Is configured. A light beam emitted from an observation light source 54 to be described later and reflected by the cornea C is imaged on the line sensor 44 through the projection lens 32 and the cold mirror 34.

On the other hand, the position detection illumination optical system 18 includes an objective lens 46, a cold mirror 48, a condenser lens 52, and an observation light source 54 as a position detection light source in order from a position close to the eye E. . As the observation light source 54, for example, an infrared light source such as an infrared LED is suitably employed. The infrared light beam emitted from the observation light source 54 is irradiated to the cornea C from an oblique direction. Note that the observation light source 54 may be configured by combining a visible light source such as a halogen lamp or visible light LED and an infrared filter, for example. However, the observation light source 54 is not necessarily an infrared light source, and a visible light source such as a halogen lamp or a visible light LED may be used. When a visible light source is used, the illuminance is preferably made smaller than the illuminance of the imaging light source 40. Thereby, it is possible to reduce the burden on the subject when irradiating the light beam from the observation light source 54 such as alignment.

The imaging optical system 20 has a part of its optical axis aligned with the optical axis of the position detection illumination optical system 18, and the objective lens 46, cold mirror 48, slit 56, magnification change in order from the position close to the eye E to be examined. A lens 58, a focusing lens 60, a cold mirror 27, and a CCD 28 are provided. Then, the light beam irradiated from the imaging light source 40 and reflected by the cornea C is reflected by the cold mirror 48 through the objective lens 46, and then converted into a parallel light beam by the slit 56. The light is reflected by the cold mirror 27 through the lens 60 and imaged on the CCD 28.

The half mirror 22 provided on the observation optical system 12 constitutes a part of the fixation target optical system 64 and the alignment optical system 66.

The fixation index optical system 64 includes a half mirror 22, a projection lens 68, a half mirror 70, a pinhole plate 72, and a fixation target light source 74 in order from a position close to the eye E. The fixation target light source 74 is a light source that emits visible light, such as an LED, and the light beam emitted from the fixation target light source 74 is transmitted through the pinhole plate 72 and the half mirror 70 and then converted into a parallel light beam by the projection lens 68. Then, it is reflected by the half mirror 22 and irradiated to the eye E.

The alignment optical system 66 includes a half mirror 22, a projection lens 68, a half mirror 70, a diaphragm 76, a pinhole plate 78, a condenser lens 80, and an alignment light source 82 in order from a position close to the eye E. . Infrared light is emitted from the alignment light source 82, and the infrared light is collected by the condenser lens 80, passes through the pinhole plate 78, and is guided to the diaphragm 76. The light that has passed through the diaphragm 76 is reflected by the half mirror 70, converted into a parallel light beam by the projection lens 68, reflected by the half mirror 22, and applied to the eye E.

Further, the half mirror 26 provided on the observation optical system 12 constitutes a part of the alignment detection optical system 84.

The alignment detection optical system 84 includes a half mirror 26 and an alignment detection sensor 88 capable of detecting the position in order from a position close to the eye E. The light beam emitted from the alignment light source 82 and reflected by the cornea C is reflected by the half mirror 26 and guided to the alignment detection sensor 88.

The apparatus optical system 10 having such a structure is accommodated in the cornea photographing apparatus 100 shown in FIG. The cornea photographing apparatus 100 is configured such that a main body 104 is provided on a base 102, and a case 106 is provided on the main body 104 so as to be movable back and forth, right and left, and up and down. The base 102 has a built-in power supply device and is provided with an operation stick 108 so that the case 106 can be driven by operating the operation stick 108. Further, the main body unit 104 accommodates control circuits and the like described later, and a display screen 110 including a liquid crystal monitor, for example.

Further, as shown in FIG. 3, the cornea photographing apparatus 100 is provided with a driving unit that moves the apparatus optical system 10 toward or away from the eye E by driving the case 106. . These driving means are constituted by, for example, a rack and pinion mechanism, and in this embodiment, an X-axis driving mechanism 112 that drives the apparatus optical system 10 in the vertical X direction in FIG. 3, and a paper surface in FIG. A Y-axis drive mechanism 114 that drives in the vertical Y direction and a Z-axis drive mechanism 116 that drives in the left-right Z direction in FIG. 3 are provided.

Further, the cornea photographing apparatus 100 is provided with an imaging control circuit 117 serving as an imaging control unit that performs operation control of imaging of the cornea image by the apparatus optical system 10. The X-axis drive mechanism 112, the Y-axis drive mechanism 114, and the Z-axis drive mechanism 116 are connected to the imaging control circuit 117, and are driven based on a drive signal from the imaging control circuit 117. Yes. The alignment detection sensor 88 is connected to an XY alignment detection circuit 118, and the XY alignment detection circuit 118 is connected to an imaging control circuit 117. The line sensor 44 is connected to the Z alignment detection circuit 120, and the Z alignment detection circuit 120 is connected to the imaging control circuit 117. Thereby, detection information of the alignment detection sensor 88 and the line sensor 44 is input to the imaging control circuit 117. In addition, although illustration is abbreviate | omitted, the imaging control circuit 117 is also connected to each illumination light source 30,40,54,74,82, and it can control these light emission.

Further, the cornea photographing apparatus 100 is provided with an image selection circuit 122 that receives an image received by the CCD 28 and selects the image, and stores the image selected by the image selection circuit 122. A storage device 124 is provided as a means.

Next, in the corneal imaging device 100 having such a structure, an outline of the corneal endothelium imaging procedure executed by the imaging control circuit 117 is shown in FIG.

First, in S1, the alignment (XY alignment) of the apparatus optical system 10 in the X direction and the Y direction is performed on the eye E. During such XY alignment, the fixation target light emitted from the fixation target light source 74 is guided to the eye E. Then, by fixing the fixation target light applied to the subject, the optical axis direction of the eye E can be matched with the direction of the optical axis O1 of the observation optical system 12. Under such a state, the light beam irradiated from the observation light sources 30 and 30 and reflected by the anterior eye portion of the eye E is guided onto the CCD 28. As a result, as shown in FIG. 5, the anterior segment of the eye E is displayed on the display screen 110.

Further, on the display screen 110, for example, an alignment pattern 125 having a rectangular frame shape generated by a superimpose signal or the like is displayed over the eye E. At the same time, the light beam emitted from the alignment light source 82 toward the subject eye E is reflected by the anterior eye portion of the subject eye E and guided to the CCD 28, so that the display screen 110 has the dotted alignment light 126. It is displayed. Then, the operator operates the operation stick 108 to drive the apparatus optical system 10 and adjust the position of the apparatus optical system 10 so that the alignment light 126 enters the frame of the alignment pattern 125.

A part of the light beam irradiated from the alignment light source 82 and reflected by the anterior eye portion of the eye E is reflected by the half mirror 26 and guided to the alignment detection sensor 88. The alignment light source 82 emits an infrared beam that is not recognized by the subject, thereby reducing the burden on the subject. Here, the alignment detection sensor 88 can detect the position of the alignment light 126 in the X direction and the position of the Y direction when the alignment light 126 enters the frame of the alignment pattern 125. The X direction position and the Y direction position are input to the XY alignment detection circuit 118. The XY alignment detection circuit 118 drives the X-axis drive mechanism 112 so that the optical axis O1 of the observation optical system 10 approaches the optical axis of the eye E based on the positional information in the X direction, and uses the positional information in the Y direction. Based on this, the Y-axis drive mechanism 114 is driven so that the optical axis O1 of the observation optical system 10 approaches the optical axis of the eye E to be examined. Thereby, the alignment of the apparatus optical system 10 with respect to the eye E in the XY directions is performed. As will be described later, such XY alignment is performed at an appropriate timing even during imaging. Particularly in the present embodiment, the alignment light source 82 and the observation light sources 30 and 30 are alternately blinked in a short time, and detection by the alignment detection sensor 88 is performed in accordance with the lighting timing of the alignment light source 82. ing. As a result, the infrared light beams of the observation light sources 30 and 30 are not affected during the XY alignment. The blinking of the alignment light source 82 and the observation light sources 30 and 30 is performed at a higher speed than the conversion speed of the CCD 28 into the light reception signal. 30 is not recognized by blinking, and the light source 82, 30 is recognized as being continuously lit.

Next, in S <b> 2, the Z-axis drive mechanism 116 is driven, and the apparatus optical system 10 is moved forward in a direction approaching the eye E to be examined. Thus, in the present embodiment, the pre-imaging advance control means is configured including S2 and the Z-axis drive mechanism 116. Then, the observation light source 54 is caused to emit light, and the infrared light beam irradiated from the observation light source 54 is irradiated obliquely onto the cornea C of the eye E, and the light beam reflected from the cornea C is Light is received by the sensor 44. In particular, in this embodiment, since the light beam emitted from the observation light source 54 is an infrared light beam, the burden on the subject is reduced.

The infrared light beam from the observation light source 54 is reflected with a different amount of reflected light for each layer of the cornea C, such as epithelial cells of the cornea C, corneal stroma, and corneal endothelium. As schematically shown in FIG. 6, the infrared light beam L from the observation light source 54 is first reflected by the epithelial cells e that form the boundary surface between the air and the cornea C. Further, a part of the light beam transmitted through the epithelial cell e is reflected by the corneal stroma s and the corneal endothelium en. The amount of the reflected light beam e ′ reflected by the epithelial cell e is the largest, the amount of the reflected light beam en ′ reflected by the corneal endothelium en is relatively small, and the reflected light beam s ′ reflected by the corneal substance s. The light intensity is the smallest. Further, since the anterior chamber a is filled with aqueous humor, the infrared light beam L is hardly reflected in the anterior chamber a.

These reflected light beams are detected by the line sensor 44, and the light quantity distribution as shown in FIG. In FIG. 7, the first peak portion 128 having the largest amount of light indicates the reflected light from the corneal epithelium. Next, the second peak portion 130 with the largest amount of light indicates the reflected light from the corneal endothelium. Then, the imaging control circuit 117 drives the Z-axis drive mechanism 116 to set the device at a predetermined distance D1 in consideration of the physiological corneal thickness variation of the human eye from the position of the corneal epithelium detected by the line sensor 44. The optical system 10 is driven forward in a direction approaching the cornea C. The moving distance from the corneal epithelium is appropriately set within a range of 1000 to 1500 μm, for example. Thereby, the focus position of the imaging optical system 20 in the apparatus optical system 10 is positioned behind the endothelial cells in the cornea C. A position behind the corneal epithelium by a predetermined distance: D1 is set as the inversion position of the apparatus optical system 10.

Next, when the apparatus optical system 10 is positioned at the reversal position, in S3, the Z-axis drive mechanism 116 is driven in the opposite direction, so that the apparatus optical system 10 moves away from the eye E on the Z-axis. It can be operated backwards. As described above, in the present embodiment, the reversal operation control means and the imaging reverse control means are configured including S3 and the Z-axis drive mechanism 116. Here, the apparatus optical system 10 is configured such that the reverse speed is changed from when the reverse operation is started from the inversion position to when the imaging is completed. FIG. 8 shows changes in the moving speed in the backward operation of the apparatus optical system 10.

First, as described above, the apparatus optical system 10 starts to move backward from the reverse position (P1 in FIG. 8). Such reverse operation is performed at a relatively high speed of, for example, about 500 μm to 3000 μm / sec, more preferably about 2000 μm / sec. Then, in S4, the observation light sources 30, 30 are turned off and the imaging light source from the time when the position reaches the rear position (P2 in FIG. 8) by a predetermined distance: D2 (see FIG. 7) from the corneal endothelial cell position. 40 light emission starts. In the present embodiment, the predetermined distance from the corneal endothelial cell: D2 is determined from a predetermined threshold at which the light amount distribution detected by the line sensor 44 is slightly smaller than the second peak portion 130. The separation distance is. Further, the specific value of the predetermined distance: D2 is preferably a value having a certain margin so that the corneal endothelial cells can be reliably captured in consideration of the detection accuracy of the line sensor 44 and the positional deviation of the eye E to be examined. However, when the predetermined distance: D2 increases, the light emission time of the imaging light source 40 becomes longer, increasing the burden on the subject. Therefore, the predetermined distance: D2 is preferably a value in the range of 200 to 500 μm. Is done. The imaging light source 40 is flashed at predetermined short intervals, and the XY alignment in S1 is simultaneously performed at the timing when the imaging light source 40 is turned off.

Then, while the apparatus optical system 10 is moved backward at a relatively high speed, the reflected light from the endothelial cells of the cornea C is detected by the CCD 28 in S5 (P3 in FIG. 8). Deceleration starts. The detection of the reflected light from the endothelial cells in S5 is performed, for example, as shown in FIG. 9, one or more (in this embodiment, five) appropriate horizontal lines in the image 132 taken by the CCD 28: 11 to 15 From the luminance value of the upper pixel, it is determined that the reflected light from the corneal endothelial cell is detected based on the number of pixels having a luminance value equal to or higher than a predetermined value. In the present embodiment, the luminance value of each pixel in the image 132 is detected with 255 gradations (luminance value 1 is the darkest and luminance value 255 is the brightest) from luminance value 1 to luminance value 255, and unevenness of the endothelial reflected light is detected. In consideration of the above, the luminance values of the respective pixels on the five horizontal lines: l1 to l5 on the image 132 are detected. Then, the number of pixels having a luminance value of 25 to 255 in each pixel on the horizontal lines: l1 to l5 is counted. Note that the luminance values 25 to 255 are amounts of light that can recognize reflected light that is clearly visible. And the average value of the number of pixels counted in the horizontal lines: l1 to l5, or the maximum value of the number of pixels counted in the horizontal lines: l1 to l5 is approximately 30 μm in terms of the distance on the corneal endothelium. The position corresponding to the amount of reflected light is the deceleration start point (P3 in FIG. 8).

Since the deceleration operation is started in S5 and a relatively slow speed (for example, a speed of 100 to 300 μm / sec) is reached (P4 in FIG. 8), the apparatus optical system 10 is at such a relatively slow speed. It can be operated backwards. Then, from the time when the deceleration is completed, a time point PZ0 (FIG. 12) when the in-focus position in the apparatus optical system 10 enters the position adjustment region including the position of the center (P5) of the X position of the corneal endothelial cell shown in FIG. The retreat operation is stopped at a position where both end edges of the corneal endothelium image can be detected in the acquired slit image F as shown in FIG. 6, and in S6, imaging of the corneal endothelium image detected by the CCD 28 is started. Note that the position adjustment region in FIG. 8 (range of PZ0 to PZ1, shaded portion) indicates a region where the backward and forward operations are performed during X alignment.

The corneal endothelium image taken after stopping the retreat operation is stored in the temporary storage device 124, analyzed by a computing device (not shown) in S7, and the deviation amount of the X (Z) position is calculated in S8.

FIG. 12 is an explanatory diagram for explaining an X (Z) alignment method using a corneal endothelium image (en) at the time of continuous photographing of a corneal endothelium image including the imaging illumination optical system 14 and the imaging optical system 20. (A) shows the corneal endothelial cell position of the eye to be imaged when the in-focus position in the imaging optical system is behind the corneal endothelial cell position on the optical axis O1, and (b) shows the imaging optical system. 3 shows the position of the corneal endothelial cell of the eye to be imaged when the in-focus position is on the optical axis O1, that is, the center of the target corneal endothelial cell in the X direction, and (c) shows the imaging optical system. 2 shows the position of the corneal endothelial cell of the eye to be imaged when the in-focus position is ahead of the position of the corneal endothelial cell on the optical axis O1. (In practice, the luminous flux of the imaging light source 40 is slightly refracted by the corneal epithelium e when incident on the cornea C and when the reflected luminous flux from the endothelial cells is emitted from the cornea C. The state is omitted.)

As can be seen from FIGS. 12A to 12C, when the apparatus optical system 10 is moved in the Z-axis direction (left-right direction in the figure), the position of the corneal endothelial cell to be imaged is in the X-axis direction (up-down direction in the figure). ) That is, alignment in the X-axis direction is performed by adjusting the apparatus optical system 10 in the Z-axis direction. In S8 of FIG. 4, “X position deviation amount calculation” is described, but this is the same as “Z position deviation amount calculation”. Hereinafter, regarding X alignment using a corneal endothelium image, the meaning of Z alignment is assumed. Is also included.

(D) of FIG. 12 is a corneal endothelium image taken at each position of (a), (e) of (b), and (f) of (c), that is, a slit image F ((d ) To (f) F). In the analysis in S7, the positions Xe0 and Xe1 of both ends (left and right ends in the figure) of the bright area of the corneal endothelial cell are detected from the slit image F by using, for example, edge processing, and the center position XP is calculated. To do. In S8, the difference between the slit image F and the center position X0 in the X direction is obtained as a deviation amount ΔX of the X position.

In S9, it is determined whether or not the deviation amount ΔX of the X position obtained in S8 is equal to or less than a preset value. If the X position deviation amount ΔX is 0 or less than a preset value, it is determined that the current X position is an appropriate position (the center of the corneal endothelial cell in the X direction), and the next Y position of S10 The amount of deviation is calculated. If the X position deviation amount ΔX is larger than a preset value, the apparatus optical system 10 is moved in the Z axis direction by the Z-axis drive mechanism 116 by the distance calculated from the X position deviation amount ΔX in S14. , Return to S6 again, take a picture, and repeat S7 to S9 until the X position deviation amount ΔX is equal to or less than a preset value.

When the X alignment of S6 to S9 is completed, the displacement amount of the Y position is calculated in S10.

FIG. 13 is an explanatory diagram for explaining an example of a Y alignment method using a corneal endothelium image. (A) when the Y position is shifted downward in the figure, (b) when the Y position is shifted upward in the figure, and (c) when the Y position is the Y axis of the corneal endothelial cell The graph which plotted the value of the luminance value with respect to the Y axis of each slit image F and the slit image F in the center (Y0) is shown. Y0 represents the center of the Y axis of the slit image F, YP represents the Y position of the peak of the luminance value, and the difference between Y0 and YP is calculated to obtain the Y position deviation amount ΔY.

If the displacement amount ΔY of the Y position is 0 or less than a preset value in S11, the XY alignment in S6 to S11 ends, the captured image is stored in S12, and the imaging ends.

If the displacement amount ΔY of the Y position is larger than the preset value in S11, the apparatus optical system 10 is moved in the Y-axis direction by the Y-axis drive mechanism 114 by the distance calculated from the displacement amount ΔY of the Y position in S15. Move, return to S6, and take a picture. And X alignment of said S6-S9 is performed again. The X alignment is performed again because the corneal endothelial cell has the same curvature as the corneal epithelium, so that the Z position (X position) is shifted when the Y position is moved. As described above, when the X and Y alignments in S6 to S11 are completed, the captured image is stored in S12 as described above, the imaging light source 40 is turned off, and imaging is terminated.

In FIG. 13C, (Y position deviation amount) ΔY = 0 is illustrated, but it is not strictly necessary that ΔY = 0, and may be equal to or less than a preset value as described above. In addition, the luminance value graph shown in FIG. 13 may use a luminance value at a predetermined X position (left and right direction of the slit image F) of the taken slit image F, for example, the center of the X position, or may be in the X direction. The sum total of the pixel values arranged in a line may be used as the luminance value. Further, it may be an average value of pixel values arranged in the X direction, a sum of pixel values in a predetermined range in the X direction, or an average value thereof. That is, any value can be used as long as the distribution of luminance values at the Y position can be grasped and the peak position can be obtained.

As mentioned above, although one embodiment of the present invention has been described in detail, the present invention is not limited in any way by the specific description in the embodiment, and various changes, modifications, and modifications based on the knowledge of those skilled in the art. Needless to say, the present invention can be implemented in a mode with improvements and the like, and all such modes are included in the scope of the present invention without departing from the gist of the present invention.

For example, in the above embodiment, during the X alignment, the center position XP of the bright region is obtained from the positions Xe0 and Xe1 of the bright edge of the corneal endothelial cell in the slit image F, but the positions Xe0 and Xe1 of the double edge are obtained. ΔX1 (difference between the left end position of the slit image F in FIG. 12 and Xe0) and ΔX2 (difference between the right end position of the slit image F in FIG. 12 and Xe1) from the both end positions of the slit image F are calculated as ΔX1 X alignment may be performed with the difference of ΔX2 as ΔX.

In the above embodiment, the luminance value distribution in the Y-axis direction (vertical direction) is used during Y alignment, but the contrast distribution in the Y-axis direction may be used. For example, a total value or an average value of differences between adjacent pixels in a range of a predetermined number of pixels in the Y-axis direction (for example, about 10 pixels) is obtained, plotted against the Y-axis, and the peak value The difference between the position and the position of the Y-axis center may be calculated as ΔY.

Alternatively, the captured slit image F can be binarized with a predetermined luminance value, the area of a region having a predetermined luminance value or more can be calculated, and Y alignment can be performed. In this case, it is conceivable to perform alignment at the Y position where the area is maximized.

It is also possible to combine several Y alignment methods shown above. In such a case, it is possible to perform stricter Y alignment.

10: device optical system, 12: observation optical system, 14: imaging illumination optical system, 16: position detection optical system, 18: position detection illumination optical system, 20: imaging optical system, 28: CCD, 30: light source for observation, 40: imaging light source, 44: line sensor, 54: observation light source, 64: fixation target optical system, 66: alignment optical system, 74: fixation target light source, 82: alignment light source, 84: alignment detection optical system, 88: Alignment detection sensor

Claims (5)

An imaging optical system including an illumination optical system including an illumination light source that irradiates the slit light beam obliquely to the eye to be examined, and a photoelectric element that receives a reflected light beam from the cornea of the eye to be examined by the slit light beam and captures a corneal image A corneal imaging apparatus including a driving unit that moves the illumination optical system and the imaging optical system as a whole toward or away from the eye to be focused.
An acquisition means for continuously acquiring a corneal endothelium image at a position where the corneal endothelium image can be acquired;
An analysis means for individually analyzing the acquired corneal endothelium image,
Calculation means for calculating the amount of deviation of each of the X and Y coordinates based on the analysis result obtained from the analysis means;
A cornea photographing apparatus comprising: an alignment unit that performs XY alignment based on a calculation result. 2. The method of calculating a deviation amount of an X (Z) coordinate includes detecting both end edge positions of a corneal endothelial cell from an acquired corneal endothelium image (slit image), and calculating from the detection result. Cornea photographing device. The corneal imaging according to claim 1 or 2, wherein a calculation method of a deviation amount of the Y coordinate is calculated from a distribution state of luminance values in the Y coordinate direction (vertical direction of the eye to be examined) of the acquired corneal endothelium image. apparatus. The corneal imaging according to claim 1 or 2, wherein a calculation method of a deviation amount of the Y coordinate is calculated from a distribution state of contrast values in the Y coordinate direction (up and down direction of the eye to be examined) of the acquired corneal endothelium image. apparatus. The corneal imaging apparatus according to claim 1, wherein the Y coordinate shift amount calculation method calculates an area of a region where the luminance value of the acquired corneal endothelium image is a predetermined value or more.