JP6355930B2 - 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.

However, since the cornea is irradiated obliquely with slit light, the range of corneal endothelial cells to be irradiated is narrow, and the corneal endothelial cells can be observed and photographed only within this narrow range. For this reason, when there is a lesion in a part of corneal endothelial cells, there is a problem that the lesion is overlooked.

With respect to this problem, Patent Document 1 discloses a corneal endothelial cell imaging apparatus that can observe and capture corneal endothelial cells over a wide range.

The imaging apparatus disclosed in Patent Document 1 includes a plurality of fixation lamps that are targets for which the subject is directed to the line of sight, and changes the fixation lamp that is turned on after the completion of one imaging. The process of shooting again with the direction of the line of sight changed is repeated. Then, a plurality of images obtained in this way are combined to create a wide-range corneal endothelial cell image.

However, since photographing is repeated in a plurality of gaze directions by changing the fixation lamp, it takes a very long time to acquire one wide range image. This places a heavy burden on the subject.

In other words, after performing alignment of the apparatus with the subject fixed to one fixation lamp, imaging processing is performed, and another fixation lamp is turned on to examine the subject's line of sight. The imaging process is performed again after the apparatus is aligned by directing it toward the other fixation lamp. Since such a process is repeated a plurality of times, it takes a long time to complete one wide-range image capturing process.

Furthermore, for each gaze position, the subject will continue to see the fixation light that is lit, and thus, the method according to the patent document is very burdensome for the subject. is there.

In addition, it is inevitable that a time difference occurs between the acquired images having different imaging positions, and the state of the subject's eye that is a living body changes during imaging of the plurality of images, so that a wide range of high quality corneal endothelium is obtained. There was also a risk that cell images could not be obtained.

In order to solve the above problem, Patent Document 2 discloses an apparatus that can acquire a wide range of corneal endothelial cell images in a short time so that a subject is not burdened.

The imaging apparatus disclosed in Patent Document 2 has a structure that can rotate and move an inspection optical system for imaging a corneal endothelial cell of a subject. That is, in order to acquire a corneal endothelial cell image in a predetermined range (wide range), the inspection optical system is rotated by a predetermined (for panoramic imaging) rotation angle.

According to this configuration, in a state in which the subject is fixed with one fixation target, the examination optical system is rotated to acquire a plurality of corneal endothelial cell images at different imaging positions, and the plurality of corneal endothelial cells A wide range of corneal endothelial cell images can be acquired by synthesizing images.

In other words, by performing the rotational movement of the inspection optical system at high speed, it is possible to acquire corneal endothelial cell images with different imaging positions in a short time, thereby reducing the burden on the patient and further acquiring the acquired imaging position. Since a plurality of images having different values have little time difference, a high-quality wide-range corneal endothelial cell image can be created.

Japanese Patent No. 2580464 JP 2013-169233 A

As described above, in the method according to Patent Document 1, since it takes too much time to generate one wide-range corneal endothelial cell, an excessive burden is placed on the subject, and a plurality of acquired images have a time difference. Therefore, it has been difficult to acquire a wide range of corneal endothelial cell images obtained by synthesis with high quality.

On the other hand, since the method according to Patent Document 2 can acquire corneal endothelial cell images having different imaging positions in a single fixation state and in a short time, the burden on the subject is reduced. Since the acquired images have a small time difference, a wide range of high-quality corneal endothelial cells can be acquired.

However, the method according to Patent Document 2 for rotating the inspection optical system has a complicated structure. That is, since it is necessary to rotate the inspection optical system in a state where it is focused on the position of the corneal endothelium of the subject, very accurate control is required, and there is a space for rotating the inspection optical system. As a result, the size of the device itself is increased, and as a result, there is a problem that the cost is increased.

The present invention solves the above-described problems, and provides a cornea imaging apparatus capable of acquiring a wide range of high-quality corneal endothelial cells without burdening the subject and without cost. 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 cornea photographing apparatus including a driving unit, a plurality of captured images having different front and rear positions (Z-axis coordinates) are acquired by emitting light a plurality of times while the apparatus body is moving in the approaching or separating direction, and the plurality of acquired imaging In the image, an extraction means for extracting a cell wall in the whole or a predetermined region, a calculation means for calculating a relative position of XY coordinates between a plurality of captured images from the cell wall extracted from the extraction means, and a calculation means By superimposing the plurality of captured images based on the obtained relative position, characterized by comprising a generating means for generating a wide range image.

A plurality of (corneal endothelial cell) captured images acquired during the alignment operation of the corneal endothelial cell in-focus position of the eye to be examined (Z-axis coordinate) are X-axis coordinates of the corneal endothelial cell (left-right position of the eye to be examined). It is an image acquired by moving little by little. In other words, since the images are continuously different in position with respect to the X-axis coordinates, for each image of a plurality of corneal endothelial cell images acquired continuously at positions before and after the in-focus position of the corneal endothelial cells of the eye to be examined. Then, the cell wall is extracted in the whole or in a predetermined area, and the relative position of the XY coordinates (left and right and up and down positions of the eye to be examined) between the acquired plurality of corneal endothelial cell images is calculated from the extracted cell wall. Based on the relative position, a plurality of acquired corneal endothelial cell images are superimposed to generate a wide-range image of corneal endothelial cells. Therefore, a wide-range image as disclosed in Patent Document 1 or Patent Document 2 is used. Because there is no need to perform another operation (changing the fixation target or moving the inspection optical system) to acquire the image, there is no burden on the subject and no special configuration is required, so the cost is also low. Wide Generating a corneal endothelial cell image of circumference can be achieved.

According to a second aspect of the present invention, in the corneal imaging device according to the first aspect, a two-dimensional pattern matching process is performed on the extracted cell wall to obtain a plurality of acquired corneal endothelial cell images. The relative position of XY coordinates is obtained.

By performing a two-dimensional pattern matching process on the extracted cell wall, the relative position of the XY coordinates between the corneal endothelial cell images can be determined with higher accuracy, so a wide range of higher quality corneal endothelial cell images can be obtained. Can be generated.

According to a third aspect of the present invention, in the corneal imaging device according to the first or second aspect, when a wide-range corneal endothelial cell image is generated, an addition process is performed on a region where the images overlap. It is characterized by that.

By performing the addition process, it is possible to improve the S / N ratio and generate a wide-range corneal endothelial cell image with higher contrast.

According to a fourth aspect of the present invention, in the corneal imaging device according to any one of the first to third aspects, the corneal endothelial cell images are continuously obtained before and after the focal position of the corneal endothelial cell of the eye to be examined. Is acquired, at least one position information among XYZ position information (coordinate information) obtained from the XY alignment signal and / or the Z alignment signal is simultaneously acquired and stored.

For example, when acquiring corneal endothelial cell images, by acquiring and storing XY position information (coordinate information) at the same time, when obtaining the relative positions of XY coordinates between the acquired plurality of corneal endothelial cell images, Since it is not necessary to obtain the relative position by the processing, it is possible to generate a wide range of corneal endothelial cell images in a shorter time.

Further, by using the stored XY position information (coordinate information) together with the above-described relative position calculation means, the relative position can be calculated with higher accuracy.

As described above, the cornea imaging apparatus according to the present invention can acquire a wide range of high-quality corneal endothelial cells without imposing a burden on the subject and without cost.

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 the selection method of an image. Explanatory drawing for demonstrating the structure of each layer of a cornea. Explanatory drawing for demonstrating the position and captured image of the image | photographed corneal endothelial cell (en) at the time of the continuous imaging | photography of a corneal endothelial cell image in one Embodiment of this invention. Example of a plurality of corneal endothelial cell images (a) taken continuously during movement in the Z-axis direction and obtained from different Z coordinates and a wide range of corneal endothelial cell images (b) obtained by synthesizing a plurality of corneal endothelial cell images Explanatory drawing which showed. The flowchart which shows the procedure for synthesize | combining the several image | photographed corneal endothelial cell image continuously image | photographed and acquiring a wide range of corneal endothelial cell images.

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).

Then, the deceleration operation in S5 is started, and in S6, continuous imaging of the corneal endothelium image detected by the CCD 28 is started. Such continuous imaging is performed by inputting captured images (images) received by the CCD 28 to the image selection circuit 122 at predetermined time intervals (for example, 1/30 seconds). As a result, a plurality of cornea images having different times and positions are input to the image selection circuit 122. Along with such continuous imaging, the image selection circuit 122 selects the input image and stores it in the storage device 124. Thus, in this embodiment, the continuous imaging means and the image selection means are comprised including S6 and the image selection circuit 122. FIG.

9 and 10 illustrate an image selection method in the image selection circuit 122. FIG. First, in the same manner as the detection of corneal endothelial cells in S5 described above, as shown in FIG. 9, one or more (in this embodiment, five) horizontal lines in the image 132 acquired by the CCD 28: 11 to 15 Get the brightness value of each pixel above.

And as shown in FIG. 10 and Formula 1, with respect to the pixels (X _{1 to} X _n ) of the acquired horizontal lines: l1 to l5, the horizontal lines: l1 to l5 are based on Formula 1, respectively. (I) The absolute value of the luminance value difference between adjacent pixels is obtained, and (ii) the sum of the luminance value differences is obtained.

And the average value of the sum total of the luminance value difference calculated | required for each horizontal line: l1-l5 based on Numerical formula 1 is calculated | required. It is recognized that the larger this value is, the wider the range of the corneal endothelial cell image. That is, as schematically shown in FIG. 11 and FIG. 6 described above, for example, in the captured image of the anterior chamber a, the irradiation light beam is transmitted through the aqueous humor and almost no reflected light beam is obtained. The image becomes dark. Further, since the cornea substance s is transparent, the photographed image of the cornea substance s is transmitted through the irradiation light beam in the same manner as the anterior chamber a, and becomes a dark image as a whole. Furthermore, since the amount of reflected light is large in the corneal epithelium e, the entire image becomes bright and uniform. Therefore, in the image of these parts, the difference in luminance value between adjacent pixels becomes small. On the other hand, in the corneal endothelium en, the contrast between the central part of the endothelial cells and the cell wall clearly appears, and the difference in luminance value between adjacent pixels increases, so that the corneal endothelial cell en is imaged over a wide range. In this case, the sum of the luminance value differences becomes large. Therefore, an image in which a corneal endothelial cell image is effectively obtained by storing in the storage device 124 only the image in which the average value of the sum of the luminance value differences obtained for each of the horizontal lines: l1 to l5 is a predetermined value or more. Only can be selected.

In particular, in the present embodiment, before performing the above determination, pixels having a luminance value of 240 or more are continuously within a range of about 50 μm to 100 μm on a predetermined horizontal line (for example, the horizontal lines: 11 to 15). If it exists, the image is excluded. That is, when a part of the corneal epithelium is shown in the image, a large luminance value difference occurs on the boundary line between the corneal epithelium and the corneal stroma. Therefore, if the sum of the luminance value difference in the corneal endothelium becomes small because the in-focus position with the corneal endothelial cell cannot be obtained correctly (out of focus), the luminance value difference is affected by the boundary line with the corneal stroma. May increase, and an image obtained by imaging the corneal epithelium may be selected. Therefore, by using the above judgment criterion, an image showing a part of the corneal epithelium can be excluded.

Next, the deceleration operation is started in S5, and the apparatus optical system 10 is moved backward at such a relatively slow speed from a time point (P4 in FIG. 8) when a relatively slow speed described later is reached. Then, continuous imaging and image selection in S6 are performed over a predetermined range (P4 to P6 in FIG. 8) from the time when deceleration is completed. Note that the in-focus position with the corneal endothelial cell (P5 in FIG. 8) is also included in the range of P4 to P6.

Here, the relatively slow moving speed at which the deceleration in S5 is completed takes into consideration the range in which continuous imaging is performed while moving at a low speed (P4 to P6 in FIG. 8), the time for capturing images by the CCD 28, the number of images to be captured, and the like. It is determined appropriately. For example, as a range in which continuous imaging is performed by moving at a low speed, a range of 200 μm or more can be suitably adopted in consideration of the fine movement of the eye E to be examined. Then, assuming that the image capture time of the CCD 28 is 1/30 second per sheet and the continuous imaging range is 200 μm, 600 μm / sec when capturing 10 images, 300 μm / sec when capturing 20 images, 30 200 μm / sec is set when capturing a single image, 150 μm / sec when capturing 40 images, and 100 μm / sec when capturing 50 images. Therefore, a speed of 100 to 300 μm / sec is preferably employed in order to reliably acquire a corneal endothelium image by continuous imaging. As described above, in the present embodiment, the image capturing time by the CCD 28 is made substantially constant, and the moving speed of the apparatus optical system 10 is changed, whereby the number of images captured by continuous imaging is adjusted. The number of images to be captured may be adjusted by changing the interval of image capturing time by the CCD 28 based on the detection of the reflected light from the corneal endothelium in S5 with the moving speed of the apparatus optical system 10 constant. It is also possible to control both the moving speed and the capture time.

Then, at a time point (P6 in FIG. 8) that has moved backward by a predetermined distance (for example, 200 μm in the present embodiment) from the start position of low-speed movement and continuous imaging (P4 in FIG. 8), acceleration is performed in S7. Is started, and the apparatus optical system 10 is accelerated to the speed before the deceleration is started. Note that, as a criterion for determining the acceleration start position, not only the moving distance but also acceleration is performed at the stage where the corneal endothelial reflected light is not detected according to the same method as the detection procedure of the corneal endothelial reflected light in S5 described above, for example. The acceleration may be started or acceleration may be started when a predetermined time has elapsed from the start of imaging, or may be used in combination as appropriate.

When the apparatus optical system 10 is accelerated and reaches a relatively fast speed before decelerating is started (P7 in FIG. 8), in S8, for example, 100 μm is considered in consideration of the fine movement of the eye E. After being retracted to a certain extent, the backward operation is stopped, the imaging light source 40 is turned off, and imaging is terminated (P8 in FIG. 8).

Here, the plurality of images continuously captured and acquired in S6 are acquired by continuously changing the Z coordinate of the corneal endothelial cell position (the front-rear direction of the eye to be examined), and the plurality of corneas having different Z coordinate positions. It is an endothelial cell image.

FIG. 12 is an explanatory diagram for explaining the position of a corneal endothelial cell (en) to be imaged during continuous imaging of a corneal endothelial cell 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. 2 shows the corneal endothelial cell position of the eye to be imaged when the in-focus position is at the corneal endothelial cell position on the optical axis O1, and (c) shows the in-focus position in the imaging optical system on the optical axis O1. 2 shows the corneal endothelial cell position of the eye to be imaged when it is in front of the corneal endothelial cell position. (D) is a corneal endothelial cell image captured at each position in (a), (e) in (b), and (f) in (c). As the apparatus optical system 10 sequentially moves away from the cornea C of the eye to be examined (retreats in the Z-axis direction), the position of the corneal endothelial cell en of the eye to be imaged moves in the X-axis direction (downward in FIG. 12). I can see that (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.)

That is, in corneal endothelial cell image continuous imaging in one embodiment of the present invention, by continuously acquiring corneal endothelial cell images while moving the focus position in the imaging optical system in the Z-axis direction, FIG. As shown in a), corneal endothelial cell images with different X-coordinate positions obtained by continuously shifting the corneal endothelial cell position of the eye to be examined in the X-axis direction (left-right direction in the eye to be examined) are acquired and stored. .

Then, by performing a synthesis process for superposing and synthesizing the acquired plurality of corneal endothelial cell images, a wide-ranging corneal endothelial cell image that spreads in the left-right direction, particularly with respect to the eye to be examined, as shown in FIG. 13B. Can be generated.

In a plurality of corneal endothelial cell images acquired continuously, the Y-coordinate deviation is ideally 0 (zero). However, in actuality, when moving in the Z-axis direction, it is slightly shifted in the Y-axis direction. Therefore, when these corneal endothelial cell images are superimposed, it is necessary to calculate the relative position of the XY coordinates between the corneal endothelial cell images and to superimpose based on the calculated relative position.

FIG. 14 is a flowchart showing a procedure until a wide range of corneal endothelial cell images are synthesized from a plurality of continuously acquired corneal endothelial cell images and the synthesized image is displayed.

First, edge processing is performed on the endothelial cell region portion with respect to each of a plurality of corneal endothelial cell images acquired successively (S10). The edge processing is appropriately performed, such as binarization processing and smoothing processing that are generally performed in image processing.

Next, a cell wall extraction process for extracting a corneal endothelial cell wall is performed on each corneal endothelial cell image edge-processed in S10 (S11). Thereby, each cell shape in the corneal endothelial cell image is drawn and determined.

Next, the relative position of the XY coordinates of each image is calculated using the cell wall extracted in S11 (S12). As a method of calculating the relative position of the XY coordinates between the corneal endothelial cell images, various methods as conventionally performed can be used.

For example, a two-dimensional pattern matching process generally used in image processing may be used. By performing the two-dimensional pattern matching process, an accurate relative position of the XY coordinates can be calculated. Alternatively, a characteristic part existing in the acquired plurality of corneal endothelial cell images may be detected, and the relative position of the XY coordinates may be calculated from the position of the characteristic part.

Next, based on the relative position of the XY coordinates between the corneal endothelial cell images calculated in S12, the images are arranged in an XY plane (S13), and the images are superimposed (S14).

Then, the images superimposed in S14 are synthesized (S15). As a synthesis method, addition processing may be simply performed in a superposed state. By performing the addition process, the S / N ratio of a wide-range corneal endothelial cell image finally obtained is improved, and a high-contrast cell image can be obtained.

In addition, with respect to the overlapping area portions in a plurality of images, the luminance information of the overlapping area portions of each image (for example, the total value of the pixel value differences between adjacent pixels) is obtained, and the overlapping information is obtained from the luminance information. The region portion may be synthesized using one selected image. That is, it is possible to obtain a wide range of corneal endothelial cell images with high quality by selecting the best image for the overlapping region and synthesizing using the selected image.

Alternatively, an image having a predetermined condition is selected from the luminance information of the overlapped area portions of the respective images, and the luminance values of the overlapped area portions are averaged for the selected one or more images. You may use for. By using this method, a wide range of high quality corneal endothelial cell images can be obtained.

Finally, a wide-range corneal endothelial cell image generated by the synthesis process is displayed on the display screen 110 (S16).

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, the edge processing region may be the entire endothelial cell region or a predetermined region determined in advance. The predetermined area may be, for example, an overlapping area of images whose positions are adjacent to each other.

In the above-described embodiment, the method for calculating the relative position of the XY coordinates is disclosed. However, when the plurality of corneal endothelial cell images are acquired, the XY coordinate positions obtained from the alignment detection sensor 88 may be stored simultaneously. Good. By simultaneously storing the XY coordinate positions when acquiring a corneal endothelial cell image, it is possible to superimpose the images without calculating the relative positions of the XY coordinates of the images. Also, by using such XY coordinate position information, the relative position of the XY coordinates can be calculated more easily when the relative position of the XY coordinates is calculated by the relative position calculation method of the XY coordinates according to the above.

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 .. Light source for imaging, 44 .. Line sensor, 54 .. Light source for observation, 64 .. Fixation target optical system, 66 .. Alignment optical system, 74. Light source, 82..Alignment light source, 84..Alignment detection optical system, 88..Alignment detection sensor

Claims (4)

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 And
In the cornea photographing apparatus provided with 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 in-focus,
The apparatus main body is caused to emit light a plurality of times while moving in the approaching or separating direction, and a plurality of captured images having different front and rear positions (Z-axis coordinates) are acquired . Extraction means for extracting cell walls in the overlapping region ;
Calculating means for calculating a relative position of XY coordinates among a plurality of captured images from the cell wall extracted from the extracting means;
A cornea imaging apparatus comprising: a generating unit that generates a wide range image by superimposing the plurality of captured images based on a relative position obtained from a calculating unit.
2. The cornea photographing apparatus according to claim 1, wherein the calculating unit obtains relative positions in the XY coordinates of a plurality of captured images from a two-dimensional pattern matching process on the extracted cell wall. The cornea imaging apparatus according to claim 1, wherein the generation unit generates a wide-range image from a plurality of captured images by performing addition processing on a region where the captured images overlap. 4. At least one position information among XYZ position information obtained from an XY alignment signal and / or a Z alignment signal is simultaneously acquired when acquiring a plurality of captured images. The cornea photographing device described in 1.