Ophthalmologic imaging apparatus, control method, and program

Abstract

To provide an ophthalmologic imaging apparatus capable of easily adjusting a position relative to an eye to be examined when acquiring a tomographic image.SOLUTION: An ophthalmologic imaging apparatus includes: an examination optical system for examining a subject's eye, which is equipped with an objective lens facing the subject's eye; a driving unit that can adjust a relative position between the subject's eye and the objective lens; and a control unit to control the driving unit such that the relative position becomes a second relative position further separated from a first relative position for fundus imaging by a distance corresponding to a focal distance of the subject's eye.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an ophthalmic imaging device, which can be used as a fundus camera, an OCT device, or a combination of these. [Background technology]

[0002] As an ophthalmic imaging device, a device for acquiring a two-dimensional image of the fundus of an eye to be examined (hereinafter referred to as a fundus camera device) has been put to practical use. Also, as an ophthalmic imaging device, an OCT device for acquiring a tomographic image of the eye to be examined by optical coherence tomography (OCT) has been put to practical use.

[0003] The OCT device can acquire a tomographic image at any location by scanning a light beam. Patent Document 1 discloses a device that performs OCT imaging of the anterior segment and the posterior segment of the eye. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-126361 Summary of the Invention [Problem to be solved by the invention]

[0005] When using an OCT system to obtain tomographic images of the subject's eye, the relative positional relationship between the eye and the system, particularly the distance between the eye and the system in the direction of the system's optical axis, must be appropriate. However, adjusting the relative positional relationship between the eye and the system is time-consuming and a burden for the technician.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide an ophthalmologic imaging apparatus that can easily adjust the relative position with respect to the subject's eye when acquiring a tomographic image. [Means for solving the problem]

[0007] In view of the above problems, the ophthalmologic imaging device of the present application is characterized by comprising an examination optical system for examining a subject's eye, the examination optical system having an objective lens facing the subject's eye, a drive unit capable of adjusting the relative position between the subject's eye and the objective lens, and a control unit that controls the drive unit so that the relative position becomes a second relative position that is further separated from a first relative position for fundus photography by a distance corresponding to the focal length of the subject's eye. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an ophthalmologic imaging apparatus that can easily adjust the relative position with respect to the subject's eye when acquiring a tomographic image. [Brief explanation of the drawings]

[0009] [Figure 1] 1 illustrates an ophthalmic imaging device and its optical system; [Figure 2] FIG. 2 is a diagram illustrating a configuration of a control unit of the ophthalmologic imaging apparatus. [Figure 3] FIG. 2 is a diagram illustrating an operation flow of the ophthalmologic imaging apparatus. [Figure 4] 4(a) is a diagram for explaining the working distance when photographing the fundus, and FIG. 4(b) is a diagram for explaining the working distance when photographing the anterior segment. [Figure 5] Fig. 5(a) is a diagram showing the alignment between the optical head unit and the subject's eye as viewed from above. Fig. 5(b) is a diagram showing an image of the anterior eye segment observed. Fig. 5(c) is a diagram showing the alignment between the optical head unit and the subject's eye as viewed from above. Fig. 5(d) is a diagram showing an image of the anterior eye segment observed. Fig. 5(e) is a diagram showing the alignment between the optical head unit and the subject's eye as viewed from above. Fig. 5(f) is a diagram showing an image of the anterior eye segment observed. [Figure 6] Fig. 6(a) is a diagram showing the state before alignment when photographing the anterior eye segment, and Fig. 6(b) is a diagram showing the state after alignment when photographing the anterior eye segment. [Figure 7]7(a) shows an OCT image of the anterior segment adjusted to the target position, and FIG. 7(b) shows an OCT image of the anterior segment shifted from the target position. [Figure 8] FIG. 10 is a diagram illustrating a preview of anterior segment OCT imaging. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the embodiments of the present invention with reference to the accompanying drawings. The claimed invention is not limited to the configurations described in the embodiments. Modifications, such as replacing or omitting parts of the configuration or processing, may be made within the scope of achieving similar effects.

[0011] (Example) <Configuration of ophthalmic imaging device> The schematic configuration of an ophthalmologic apparatus will be described with reference to Fig. 1. Fig. 1 is a diagram showing an ophthalmologic imaging apparatus and its optical system. In the following description, the direction that approximately coincides with the line of sight of the subject's eye E is referred to as the Z direction. Furthermore, the plane perpendicular to the Z direction is referred to as the XY plane, the horizontal direction is referred to as the X direction, and the vertical direction is referred to as the Y direction.

[0012] The ophthalmic device (ophthalmic imaging device) 10 used in this embodiment includes a fundus image capturing unit (fundus image capturing function) that captures two-dimensional fundus images, and a tomographic image capturing unit (tomographic image capturing function) that captures three-dimensional tomographic images of the fundus of the subject's eye using information based on optical interference.

[0013] The ophthalmologic apparatus 10 includes an optical head 100, a spectroscope 200, and a control unit 300.

[0014] The optical head 100 is composed of a measurement optical system for capturing two-dimensional images and tomographic images of the anterior segment Ea of the subject's eye E and the fundus Ef of the subject's eye.

[0015] The spectroscope 200 is an optical system for separating the interference light obtained in the OCT imaging and obtaining a tomographic image.

[0016] The control unit 300 is a controller that performs overall control of the ophthalmologic apparatus 10. The control unit 300 includes a CPU as an arithmetic processing circuit, and ROM and RAM as memories. The control unit 300, for example, loads a program stored in the ROM into the RAM, and the CPU executes the program to realize various controls. Note that the control unit 300 may use an MPU or ASIC as the arithmetic processing circuit instead of the CPU. Furthermore, the control unit 300 may use a storage medium such as an SSD or HDD instead of the ROM.

[0017] The configurations of the optical head 100, the spectrometer 200, and the control unit 300 will be described below in order.

[0018] <Configuration of optical head and spectrometer> The optical head 100 is an examination optical system that includes an objective lens 101 and is arranged opposite the subject's eye E. A first dichroic mirror 102 and a second dichroic mirror 103 that function as optical path separation units are arranged on the optical axis L1 of the objective lens 101. These dichroic mirrors separate the optical path of the anterior eye observation system (optical axis L2), the optical path of the fundus photography system (optical axis L3), and the optical path of the OCT interference system (optical axis L5) for each wavelength band. The working distances of these optical systems are designed to be approximately the same.

[0019] A lens 120, a prism 121, an aperture 122, a lens 123, and an image sensor 124 are arranged on an optical axis L2 in the reflection direction of the dichroic mirror 103. The image sensor 124 is a monochrome sensor sensitive to the infrared range. An anterior eye observation optical system for observing the anterior eye segment is configured by these optical members and the like arranged on the optical axis L2. The image sensor 124 is connected to a control unit 300. Each pixel value acquired by the image sensor 124 is output to a display unit 310 via the control unit 300. An anterior eye observation light source 125 arranged near the objective lens 101 illuminates the anterior eye segment of the subject's eye E.

[0020] A perforated mirror 131, a photographing aperture 132, a focus lens 133, an imaging lens 134, a third dichroic mirror 135, and an image sensor 136 are arranged on an optical axis L3 in the transmission direction of the dichroic mirror 102. The perforated mirror 131 has an aperture in its center. The focus lens 133 adjusts the focus by moving its position on the optical axis L3. The optical path on the optical axis L3 is branched by the third dichroic mirror 135 into two optical paths, one leading to the image sensor 136 and the other leading to the fixation lamp 137, according to wavelength band. The image sensor 136 is a fundus image sensor that is sensitive to visible and infrared light and is capable of both video observation and still image capture. The fixation lamp 137 is positioned conjugate to the image sensor 136 and emits visible light to prompt the subject to fixate. The optical head 100 also includes an aperture (not shown) for filtering the light beam required for fundus photography.

[0021] A corneal baffle 140, a relay lens 141, a focus index unit 142, a lens 143, and a ring slit 144 are arranged in this order on an optical axis L4 in the reflection direction of the perforated mirror 131. The corneal baffle 140 has a light-blocking point in the center. The ring slit 144 has a ring-shaped slit opening. Also arranged on the optical axis L4 are a crystalline lens baffle 145 as a light-blocking member having a light-blocking point, and a dichroic mirror 146 that has the property of transmitting infrared light and reflecting visible light. The focus index unit 142 is movable along the optical axis L4 and can be inserted into and removed from the optical axis L4.

[0022] A condenser lens 147 and a white LED light source 148 are arranged in the reflection direction of the dichroic mirror 146. The white LED light source 148 is a photography light source in which multiple white LEDs that emit visible pulsed light are arranged. A condenser lens 149 and an infrared LED light source 150 are arranged in the transmission direction of the dichroic mirror 146. The infrared LED light source 150 is an observation light source in which multiple infrared LEDs that emit constant infrared light are arranged. The objective lens 101, the dichroic mirror 146, the optical members between them, and the condenser lenses 147 and 149 constitute an illumination optical system that illuminates the fundus. Light from the white LED light source 148 or the infrared LED light source 150 illuminates the fundus of the subject's eye via this illumination optical system.

[0023] A lens 151, a mirror 152, an OCTX scanner 153-1, an OCTY scanner 153-2, and lenses 154 and 155 are arranged on an optical axis L5 in the reflection direction of the dichroic mirror 102. The OCTX scanner 153-1 and the OCTY scanner 153-2 are configured, for example, with mirrors, and function as a scanning unit that scans the fundus Ef of the subject's eye with measurement light. Furthermore, the OCTX scanner 153-1 and the OCTY scanner 153-2 have centers that are optically conjugate with the position of the pupil of the subject's eye E. Note that the OCTX scanner 153-1 and the OCTY scanner 153-2 each scan with measurement light in a main scanning direction and a sub-scanning direction perpendicular to the main scanning direction, but the scanning directions are not limited to these.

[0024] The measurement light source 157 is a light source that emits light to obtain measurement light to be incident on the measurement optical path. In this embodiment, the measurement light in the OCT optical system is emitted from the fiber end as a light source, and the fiber end of the optical fiber 156-2 has an optically conjugate relationship with the fundus Ef of the subject's eye E. The lens 154 is a focus adjustment lens and is driven by a motor (not shown) in the optical axis direction indicated by the arrow in the figure. The focus of the measurement light is adjusted so that the measurement light emitted from the fiber end acting as the light source is imaged on the fundus Ef. The lens 154, which functions as a focus adjustment unit, is disposed between the fiber end serving as the measurement light source and the OCTX scanner 153-1 and OCTY scanner 153-2 functioning as scanning units. The focus adjustment described above allows the image of the measurement light emitted from the fiber end to be imaged on the fundus Ef of the subject's eye E, and allows the return light from the fundus Ef to be efficiently returned to the optical fiber 156-2.

[0025] In FIG. 1, the optical paths between the OCTX scanner 153-1 and the OCTY scanner 153-2 are arranged side by side within the plane of the paper, but in reality they are arranged side by side in the direction perpendicular to the plane of the paper.

[0026] Next, the optical path from the measurement light source 157, the reference optical system, and the spectrometer 200 will be described. The measurement light source 157, optical coupler 156, optical fibers 156-1 to 156-4, lens 158, dispersion compensation glass 159, reference mirror 160, and spectrometer 200 constitute a Michelson interferometer. The optical fibers 156-1 to 156-4 are single-mode optical fibers connected to and integrated with the optical coupler 156. Light emitted from the measurement light source 157 is guided to the optical coupler 156 via optical fiber 156-1. The light guided to the optical coupler 156 is split by the optical coupler 156 into measurement light on the optical fiber 156-2 side and reference light on the optical fiber 156-3 side. The measurement light is irradiated onto the fundus Ef of the subject's eye E, which is the object of observation, via the optical path of the OCT optical system (tomographic imaging optical system) described above, and reaches the optical coupler 156 again via the same optical path due to reflection and scattering by the retina.

[0027] Meanwhile, the reference light passes through optical fiber 156-3, lens 158, and dispersion compensation glass 159, which is inserted to match the dispersion of the measurement light and the reference light, and reaches and is reflected by reference mirror 160. The reference light reflected by reference mirror 160 returns along the same optical path and reaches optical coupler 156 again. The reference light and measurement light (returned light) that reach optical coupler 156 again are combined (synthesized) by optical coupler 156. Here, when the optical path lengths of the measurement light and the reference light become approximately the same, this combination causes interference between the respective lights. The reference mirror 160 is held in an adjustable position along the optical axis indicated by the arrow in the figure by a motor and drive mechanism (not shown). The optical path length of the reference light can be adjusted to match the optical path length of the measurement light, which varies depending on the subject's eye E, by using this motor, etc. The resulting interference light is guided to spectrometer 200 via optical fiber 156-4.

[0028] The spectrometer 200 includes a lens 201, a diffraction grating 202, a lens 203, and a line sensor 204. Interference light emitted from the optical fiber 156-4 becomes approximately parallel light via the lens 201, is then dispersed by the diffraction grating 202, and is imaged on the line sensor 204 by the lens 203. Each element in the line sensor 204, which serves as a light receiving unit, outputs a signal corresponding to the received light. The control unit 300 samples this signal at a predetermined timing using the image acquisition unit 304 (described later), and performs predetermined signal processing to generate a tomographic image.

[0029] Next, the measurement light source 157 and its surroundings will be described. In this embodiment, the measurement light source 157 is an SLD (SupEf Luminescent Diode), a typical low-coherence light source. The light emitted from the measurement light source 157 has a central wavelength of 880 nm and a wavelength width of approximately 60 nm. The wavelength width is an important parameter because it affects the resolution of the resulting tomographic image in the optical axis direction. Although an SLD was selected as the light source here, any light source capable of emitting low-coherence light can also be used, such as an amplified spontaneous emission (ASE). Considering that the measurement light is being performed on the eye, near-infrared light is appropriate for the central wavelength of the measurement light. Furthermore, due to the characteristics of the dichroic mirrors 102 and 103, the optical path (optical axis L3) of the fundus photography system and the optical path (optical axis L5) of the OCT interference system are branched into wavelength bands. It is necessary to provide a certain degree of wavelength difference from the wavelengths used in each optical path of the anterior eye observation optical path (optical axis L2). From this perspective, the above wavelengths were selected as the SLD wavelengths. Although a Michelson interferometer is used as the interferometer in this embodiment, a Mach-Zehnder interferometer may also be used.

[0030] Furthermore, the optical head 100 includes a head driving unit 170. The head driving unit 170 is composed of three motors (not shown) and is configured to be able to move the optical head 100 in three-dimensional (X, Y, Z) directions relative to the subject's eye E. This makes it possible to align the optical head 100 with the subject's eye E.

[0031] <Controller configuration> Next, the control unit 300 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of the control unit of the ophthalmologic imaging apparatus.

[0032] The control unit 300 has various functional blocks that are realized by the CPU executing a program.

[0033] The control unit 300 includes an imaging control unit 301, a storage unit 302, an output control unit 303, an image acquisition unit 304, and an image processing unit 305. The control unit 300 is also connected to the optical head 100, the spectrometer 200, an input unit 340, a display unit 310, and an audio output unit 350.

[0034] The imaging control unit 301 is connected to the storage unit 302, the optical head 100, and the input unit 340. Based on an input signal from the input unit 340, the imaging control unit 301 controls each unit of the optical head 100 so that an examination sequence including an alignment operation stored in the storage unit 302 is executed. For example, in capturing an anterior eye observation image, the imaging control unit 301 causes the anterior eye observation light source 125 to emit light, receives the light with the image sensor 124, and reads a signal. The read signal is sent to the image acquisition unit 304.

[0035] In addition, when capturing an infrared fundus observation image using a fundus camera, the imaging control unit 301 causes the infrared LED light source 150 to emit light, and performs fundus infrared observation image capturing, which serves as both a fundus observation means and a tracking imaging means. Then, the imaging control unit 301 drives the focus index unit 142 to acquire diopter information of the subject's eye, and then drives the focus lens 133 to match the diopter information. After that, the image sensor 136 receives light, reads a signal, and sends the read signal to the image acquisition unit 304. The image acquisition unit 304 generates an infrared fundus observation image using an image processing unit 305.

[0036] When photographing a fundus image using a fundus camera, the photographing control unit 301 changes the position of the focus lens 133 so that it matches the diopter position obtained by applying aberration correction to the detected diopter information of the subject's eye. The aberration correction corrects for aberrations caused by the difference in wavelength between the infrared LED light source 150 and the representative wavelength of the white LED light source 148, which is the photographing light source. The photographing control unit 301 causes the white LED light source 148 to emit visible pulsed light, which is received by the image sensor 136 and reads the signal. The read signal is sent to the image acquisition unit 304.

[0037] In tomographic imaging, the imaging control unit 301 drives the focus lens 154 based on diopter information detected by the focus index unit 142. The imaging control unit 301 also sends scanning control signals to the OCTX scanner 153-1 and the OCTY scanner 153-2 to scan the subject's eye Er in the X and Y directions with measurement light from the measurement light source 157. The imaging control unit 301 then reads a signal received by the line sensor 204. The read signal is sent to the image acquisition unit 304.

[0038] The image acquisition unit 304 uses the image processing unit 305 to perform a Fourier transform on the signal obtained from the line sensor 204. By converting the data thus obtained into brightness or density information, an image of the subject's eye in the depth direction (Z direction) can be obtained. Obtaining this data in the depth direction is called an A-scan, and the obtained tomographic image is called an A-scan image.

[0039] The measurement light for this A-scan is scanned in a predetermined transverse direction on the fundus of the subject's eye Er by the OCTX scanner 153-1 and the OCTY scanner 153-2, thereby obtaining multiple A-scan images. The image processing unit 305 then generates a tomographic image from the multiple A-scan images and the scanning information. For example, scanning in the X direction obtains a tomographic image in the XZ plane, and scanning in the Y direction obtains a tomographic image in the YZ plane. Scanning the measurement light in a predetermined transverse direction on the subject's eye Er in this way is called a B-scan, and the resulting tomographic image is called a B-scan image. Multiple B-scan images can be obtained by repeatedly scanning a predetermined imaging range on the subject's eye Er in a predetermined direction with the OCTX scanner 153-1 and the OCTY scanner 153-2. For example, repeating a B-scan in the XZ plane in the Y direction can obtain three-dimensional information in the XYZ space. Such data acquisition is called a C-scan, and data consisting of the obtained multiple B-scan images is called three-dimensional data. From this three-dimensional data, a frontal image (two-dimensional image) of the fundus of the subject's eye Er can be obtained using the method described below. This is called a C-scan image.

[0040] The storage unit 302 stores the anterior eye observation image, fundus infrared observation image, fundus image, B-scan image which is a tomographic image, 3D data, and OCT fundus front image (2D image) acquired by the image acquisition unit. The storage unit 302 also stores various programs and the like for executing various controls. Examples of control include an examination sequence which defines a series of control procedures for performing an examination multiple times, generated images of the subject's eye, image analysis results, imaging conditions at the time of image acquisition, so-called patient information about the subject's eye, and the like. The storage unit 302 also controls the above-mentioned anterior eye observation image capture, fundus infrared observation image capture and fundus image capture by a fundus camera, tomographic image capture, and the like.

[0041] The output control unit 303 is connected to a display unit 310 such as a display, and displays the anterior eye observation image, fundus infrared observation image, fundus image, B-scan image which is a tomographic image, 3D data, and OCT fundus front image stored in the memory unit 302.

[0042] <Image for observing the anterior eye> Next, an anterior eye observation image will be described with reference to Fig. 5(a) to (f). Fig. 5(a) is a diagram showing the alignment between the optical head unit and the subject's eye as viewed from above. Fig. 5(b) is a diagram showing the anterior eye observation image. Fig. 5(c) is a diagram showing the alignment between the optical head unit and the subject's eye as viewed from above. Fig. 5(d) is a diagram showing the anterior eye observation image. Fig. 5(e) is a diagram showing the alignment between the optical head unit and the subject's eye as viewed from above. Fig. 5(f) is a diagram showing the anterior eye observation image.

[0043] The pupil Ep of the subject's eye E is observed through the objective lens 101. In Fig. 5(a), a visual angle 501 and a visual angle 502 each represent an apparent angle when the pupil Ep is observed from a virtual viewpoint due to the prism effect of the prism 121 in Fig. 2.

[0044] A beam of reflected and scattered light from the anterior segment of the subject's eye E is imaged once on the prism 121 and then imaged again on the image sensor 124. FIG. 5(a) shows a state when the optical head 100 and the subject's eye E are aligned. FIG. 5(b) shows an anterior segment observation image acquired by the image sensor 124 at this time. The anterior segment observation image is divided by the prism 121 into an upper half partial region 503 and a lower half partial region 504. The pupils in the partial region 503 and the partial region 504 represent the pupils observed at the viewing angles 501 and 502 in FIG. 5(a), respectively. When the optical head 100 and the subject's eye E are aligned as shown in FIG. 5(a), the prism 121 and the image sensor 124 are positioned so that the pupil appears in the center. The distance from the objective lens 101 to the corneal vertex of the subject's eye when the pupils reflected in the upper and lower partial areas 503 and 504 divided by the prism 121 are aligned is defined as the working distance WD.

[0045] FIG. 5(c) shows a case where the optical head 100 and the subject's eye E are not aligned in the optical axis direction (the vertical direction on the paper), resulting in a working distance longer than the ideal distance WD. In this case, the visual angle 511 moves to the right of the visual angle 501, and the visual angle 512 moves to the left of the visual angle 502. Therefore, the anterior-segment observation image at this time is as shown in FIG. 5(d). The pupil in partial region 513 moves to the right in response to the visual angle 511, and the pupil in partial region 514 moves to the left in response to the visual angle 512. Therefore, the anterior-segment observation image in FIG. 5(d) shows that the distance between the optical head 100 and the subject's eye E is too long and the alignment is not correct. If the distance between the optical head 100 and the subject's eye E is too short, the anterior-segment observation image will split in the opposite direction to that shown in FIG. 5(d).

[0046] FIG. 5(e) shows a case where the optical head 100 and the subject's eye E are not aligned perpendicular to the optical axis and the working distance is longer than the ideal distance WD. In this case, compared to FIG. 5(c), the viewing angle 521 moves leftward from the viewing angle 511, and the viewing angle 522 moves leftward from the viewing angle 512. Therefore, the anterior eye observation image at this time is as shown in FIG. 5(f). The pupil in partial region 523 moves leftward in accordance with the viewing angle 521, and the pupil in partial region 524 also moves leftward in accordance with the viewing angle 522. At this time, as in FIG. 5(d), the pupils are separated between the upper and lower partial regions, indicating a deviation from the working distance WD. It can also be seen that the midpoint between the pupil center estimated from the pupil seen in partial region 523 and the pupil center estimated from the pupil seen in partial region 524 is shifted leftward from the center of the anterior eye observation image. 5(e), if the subject's eye E is shifted to the right, the midpoint of the pupil center that can be estimated from the pupil visible in the upper and lower partial regions will be shifted to the right. If the subject's eye E is shifted in the direction perpendicular to the paper surface, the midpoint of the pupil center will be shifted in the vertical direction in the anterior eye observation image. Therefore, it is possible to determine from the anterior eye observation image in which direction and to what extent the alignment between the optical head 100 and the subject's eye E is shifted.

[0047] <Shooting operation> A series of imaging procedures for performing OCT imaging of the anterior segment after performing OCT imaging of the fundus (posterior segment) will be described with reference to Fig. 3. Fig. 3 is a diagram showing the operation flow of the ophthalmologic imaging apparatus.

[0048] In step S301, a process is performed to move the optical head 100 to a position where the fundus is photographed. The control unit 300 acquires an anterior-segment observation image, and calculates and determines the relative positional relationship between the optical head 100 and the subject's eye E as described above. The control unit 300 then drives the head driving unit 170 to correct the calculated amount of deviation. As a result, the relative positional relationship between the optical head 100 and the subject's eye E is adjusted so that the pupils displayed in the upper and lower partial regions of the anterior-segment observation image overlap and are located at the center of the image, as shown in FIG. 5(b).

[0049] In step S302, a process of adjusting the focus is performed to obtain a clearer fundus observation image. The control unit 300 drives the focus index unit 142 to acquire diopter information of the subject's eye, and then drives the focus lens 133 to adjust the focus to match the diopter information (focus adjustment). Similarly, the control unit 300 drives the lens 154, which is a lens for adjusting the focus of the OCT, to adjust the focus to match the diopter information. During this focus adjustment, it is desirable to turn on the fixation lamp 137 to encourage the subject to fixate in order to stabilize the fixation of the subject's eye E.

[0050] In step S303, OCT imaging processing is performed, but detailed description thereof will be omitted as it is not the main purpose of this embodiment.

[0051] In step S304, processing for photographing the fundus is performed, but detailed description thereof will be omitted since it is not the main point of this embodiment.

[0052] If a change in the relative positional relationship with the subject's eye E is detected between S301 and S304, the position may be adjusted by driving the head driving unit 170. The change in the relative positional relationship can be realized by continuously monitoring the anterior eye segment observation image.

[0053] In step S305, the optical head 100 is moved backward (away from the subject's eye E) by a predetermined distance L mm. In this embodiment, the optical head 100 is moved an appropriate distance to ensure a working distance suitable for photographing the anterior segment. At the end of step S304, the optical head 100 and the subject's eye E are adjusted to the working distance WD (FIG. 4(a)). If the optical head 100 is moved backward by, for example, 33.3 mm from this working distance WD, the distance between the subject's eye E and the objective lens 101 becomes WD+33.3 mm.

[0054] In step S306, a process is performed to achieve a focus state suitable for photographing the anterior segment. In step S305, if the lens has been moved a predetermined distance L mm away from the working distance WD, the focus is adjusted to a focus position suitable for the subject's eye at 1000 / L diopter (D). Specifically, since the lens has been moved a predetermined distance (33.3 mm rearward in the above example) from the working distance WD in step S305, the desired focus is 1000 / 33.3≒30D (diopter: refractive power). The control unit 300 performs the focus adjustment by driving the focus lens 133 of the fundus camera and / or the focus lens 154 of the OCT.

[0055] In fundus camera photography and OCT photography, the objective lens 101 is spaced a working distance WD from the subject's eye E. Focus adjustment using the focus lenses 133 and 154 is performed to match the refractive power of the subject's eye. The unit of refractive power (D: diopter) = 1000 / focal length (f [mm]) is typically used to represent the refractive power of the eye. For a subject's eye with a refractive power of 30D, the focal length is approximately 33.3 mm at the focus position where the fundus is in focus. Therefore, in steps S305 and S306, the optical head is moved back 33.3 mm, and the focus adjustment is set to 30D. Thus, the movement amount in step S305 and the focus adjustment in step S306 are interrelated. Therefore, if the maximum retraction amount of the optical head needs to be reduced to reduce the installation size of the ophthalmic equipment, the maximum adjustment amount of the focus adjustment needs to be increased. On the other hand, if the focus adjustment amount relative to the lens movement amount is reduced to increase the sensitivity and reduce the maximum focus adjustment amount in order to improve the accuracy of the focus adjustment, the maximum retraction amount of the optical head must be increased.

[0056] For example, if it is desired to set the maximum retraction amount from the fundus imaging position to 20 mm, the maximum focus adjustment amount should be set to 1000 / 20 = 50 D. As described above, if the maximum adjustment range of the focus adjustment mechanism on the positive diopter side is D, it is desirable that the maximum retraction amount of the optical head from the fundus imaging position can be moved a distance of 1000 / D [mm] or more.

[0057] In step S307, an image acquired by the image sensor 136 is used to perform alignment for anterior-segment imaging in directions perpendicular to the optical axis (X and Y directions in FIG. 1). The image sensor 136 is a fundus image sensor that can both observe and capture still images of the fundus. The control unit 300 illuminates the subject's eye E by emitting light from the infrared LED light source 150, which serves as an observation light source, and acquires an anterior-segment observation image using the image sensor 136. The anterior-segment observation image data is sent from the image sensor 136 to the image acquisition unit 304. The control unit 300 extracts the pupil position of the subject's eye from the anterior-segment observation image data using the image processing unit 305. The control unit 300 then drives the drive unit 170 to adjust the position of the optical head 100 so that the pupil is at the center of the anterior-segment observation image. FIG. 6(a) shows the state before alignment for anterior-segment imaging. FIG. 6(b) shows the state after alignment for anterior-segment imaging. For example, in steps S305 and S306, if the state is as shown in FIG. 6(a), the optical head 100 is moved so that the pupil is positioned at the center as shown in FIG. 6(b).

[0058] Incidentally, it is desirable to keep the infrared LED light source 150 on from step S305 to step S307 (during the period when the relative positions of the optical head 100 and the subject's eye E are changing). This is because the infrared LED light source 150 can serve as a fixation lamp and stabilize the subject's fixation. At a working distance suitable for fundus photography, the light from the infrared LED light source 150 illuminates the entire fundus, but when the optical head 100 is moved backward, only a portion of the illuminated angle of view reaches the fundus. Therefore, it appears as a point to the subject and can be used in place of a fixation lamp.

[0059] In step S308, a preview process for OCT imaging of the anterior segment is performed. Fig. 7(a) shows an OCT image of the anterior segment adjusted to the target position. Fig. 7(b) shows an OCT image of the anterior segment shifted from the target position.

[0060] By moving the optical head 100 in step S305, the subject's eye E is now positioned at an appropriate distance. At this time, the OCT preview tomographic image 701 shows a tomographic image of the anterior segment of the subject's eye E. The control unit 300 adjusts the reference mirror 160 so that the apex (predetermined feature) of the cornea Ec of the subject's eye E is positioned at the corneal position adjustment target 710 (target position), as shown in FIG. 7(a). The position of this reference mirror 160 is adjusted in accordance with the change in the optical path length of the measurement light caused by moving the reference mirror 160 backward a predetermined distance in step S305. This allows the optical path length of the reference light to be similarly changed.

[0061] Whether imaging with the image sensor 136 or OCT imaging, if the position in the optical axis direction is shifted with respect to a fixed imaging angle of view, this will lead to fluctuations in the magnification of the captured image in the X and Y directions. Therefore, when performing measurements using a captured image, it is desirable to perform adjustment by moving the optical head 100 to correct for deviations in the Z direction.

[0062] For example, between steps S305 and S308, the subject may move their face, causing the position of the subject's eye E to move in the optical axis direction (Z direction in FIG. 1). In this case, as shown in FIG. 7B, the tomographic image of the anterior segment is displaced in the depth direction relative to the corneal position adjustment target 710. In such a case, the control unit 300 causes the image processing unit 305 to extract the corneal position from the tomography of the anterior segment displayed in the OCT tomographic preview. The control unit 300 then calculates the amount of displacement in the depth direction relative to the corneal position adjustment target 710. The control unit 300 corrects the relative positional relationship between the subject's eye E and the optical head 100 by moving the optical head 100 so as to correct the calculated amount of displacement in the depth direction.

[0063] Alternatively, even when there are individual differences in the distance from the corneal apex to the pupil (anterior chamber depth), the relative relationship is corrected by moving the optical head 100. The ophthalmic apparatus 10 of the present application considers that the Z direction has been adjusted by aligning the upper and lower partial regions 503 and 504 of the anterior eye observation image. In other words, the position of the pupil is adjusted in the Z direction relative to the optical head 100. However, when there are individual differences in the anterior chamber depth, the corneal apex position may differ from the position assumed during the design stage of the apparatus (for example, a position 3.5 mm away from the pupil). Therefore, even if the pupil is positioned as intended (assumed position), the corneal apex may deviate from the corneal position adjustment target 710. In such cases, it is desirable to adjust the position of the optical head 100 so that the corneal apex is aligned with the corneal position adjustment target 710.

[0064] In step S309, OCT imaging of the anterior segment is performed, but detailed description thereof will be omitted as it is not the main focus of this embodiment.

[0065] In step S310, the anterior segment is photographed. The anterior segment may be photographed using visible light by pulsating the white LED light source 148, as in photographing the fundus, or may be photographed using illumination from the infrared LED light source 150. Infrared photography is known to have the advantage of making it easier to see the meibomian glands when photographing the inside of the eyelid, and so the light source used may be changed depending on the application.

[0066] This completes the process of photographing the fundus and the anterior segment in a series.

[0067] <Effects> As described above, the ophthalmologic apparatus of this embodiment can easily adjust the relative positional relationship between the subject's eye E and the optical head 100 when photographing the anterior segment of the eye. This reduces the burden on the examiner.

[0068] Furthermore, the ophthalmologic apparatus of this embodiment can acquire images by photography and can drive each optical element in the optical head 100. Therefore, it is possible to automate each step by applying image recognition technology to the images acquired by photography and making various judgments. For example, by making judgments regarding alignment from acquired image information, it is possible to automate everything from alignment when photographing the fundus to alignment and photography of the anterior segment. This reduces the amount of work required by the examiner, and reduces the burden on the examiner.

[0069] Furthermore, the ophthalmic apparatus of this embodiment can maintain a constant imaging range. This allows for highly reproducible length measurements to be performed from the imaging results. By checking the angle of view through optical adjustment during the manufacture of the ophthalmic apparatus 10, the actual size and length of the subject's eye can be measured from the size on the image.

[0070] For example, when using an image obtained by photographing the anterior segment, it is also possible to measure the size (width d mm, height h mm, etc.) of a pterygium portion 801 using an examinee's eye with a pterygium, as shown in Figure 8. Figure 8 is a diagram for explaining the preview of anterior segment OCT photography.

[0071] The corneal thickness distribution may also be measured from a tomographic image, such as that shown in FIG. 7( a), obtained by OCT imaging of the anterior segment of the eye. Corneal thickness measurement can be achieved by extracting the front and rear surfaces of the cornea using known layer extraction techniques and calculating the thickness from the incident angle of the light beam, the imaging range, and the imaging depth. Corneal thickness can be calculated using the stable imaging range image obtained in this embodiment, the incident angle of the OCT measurement light on the cornea, the OCT depth scale, and other factors. The incident angle of the OCT measurement light and the OCT depth scale are confirmed by design values ​​and optical adjustments during manufacturing of the ophthalmic device 10. Such measurements may be performed visually by a user based on the image obtained by imaging, or may be performed automatically using image processing.

[0072] (Other Examples) Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Inventions modified within the scope of the present invention and inventions equivalent to the present invention are also included in the present invention. For example, not all of the combinations of features described in the above embodiments are necessarily essential to the solution of the present invention. Some features may be replaced with other features or deleted as long as the effects of the present invention are obtained. Furthermore, the dimensions, materials, shapes, and relative positions of components described in the above embodiments are merely examples and can be changed as appropriate depending on the conditions. Furthermore, the above-described embodiments and modifications can be combined as appropriate within the scope of the present invention.

[0073] In the embodiment, the flow for photographing one eye of the subject has been described, but both eyes may also be photographed. In this case, the optical head 100 may be made movable in the left-right direction relative to the subject, and the other eye to be inspected may be photographed. In this case, it is desirable to also adjust the relative positional relationship between the optical head 100 and the eye E to be inspected in S301 for the other eye to be inspected.

[0074] In the examples, the order of photographing the entire series of images is described as OCT fundus photography, fundus camera photography, anterior segment OCT photography, and anterior segment photography. However, the order, type, and number of photographs may be changed as appropriate, as long as the process includes moving the optical head back a predetermined distance from a Z-direction position suitable for fundus photography to photograph the anterior segment. However, if photographing the anterior segment using visible light from a white LED light source is performed before fundus photography, the glare of the illumination can cause miosis in the subject's eye. If fundus camera and fundus OCT photography is performed in a miotic state, vignetting by the pupil is likely to occur. Therefore, it is considered a more preferable photographing order to photograph the anterior segment, which is not affected by miosis, after photographing the fundus.

[0075] In the embodiment, a flow for capturing two-dimensional images (fundus camera, anterior segment imaging) using the image sensor 136 and capturing tomographic images using OCT, as well as capturing both fundus and anterior segment images, is described. However, the combination of imaging is not limited to this. For example, only capturing two-dimensional images using an image sensor may be performed using an ophthalmic device without OCT functionality. That is, OCT imaging in steps S303 and S308 and S309 may not be performed. Furthermore, after adjusting the working distance in the Z direction to a value suitable for fundus imaging, only the anterior segment may be imaged without capturing the fundus. When it is desired to capture only the anterior segment using ophthalmic equipment, the anterior segment is imaged without capturing unnecessary fundus images. Therefore, steps S302, S303, and S304 may not be performed, and step S305, which moves the optical head, may be started after step S302 (focus adjustment).

[0076] In the embodiment, step S305 of moving the optical head and step S306 of adjusting the focus are described as steps that are executed in this order, but both steps may be executed simultaneously or in reverse order.

[0077] The present invention can also be realized by providing a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions. A computer may have one or more processors or circuits, and may include multiple separate computers or a network of multiple separate processors or circuits to read and execute computer-executable instructions.

[0078] The processor or circuitry may include a central processing unit (CPU), a microprocessing unit (MPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), or a field programmable gateway (FPGA). The processor or circuitry may also include a digital signal processor (DSP), a data flow processor (DFP), or a neural processing unit (NPU).

[0079] (Addendum) This specification includes the following disclosure.

[0080] [Appendix 1] an examination optical system for examining an eye to be examined, the examination optical system including an objective lens facing the eye to be examined; a driving unit capable of adjusting a relative position between the eye to be examined and the objective lens; and a control unit that controls the drive unit so that the relative position becomes a second relative position that is further separated from a first relative position for fundus photography by a distance corresponding to the focal length of the subject's eye.

[0081] [Appendix 2] 2. The ophthalmologic imaging device according to claim 1, wherein the distance according to the focal length of the subject's eye is a distance corresponding to a diopter obtained by focus adjustment for photographing the fundus.

[0082] [Appendix 3] The ophthalmologic imaging device described in Appendix 2, characterized in that the examination optical system has a focus index unit for acquiring diopter information of the test eye, and a focus lens that can be moved to a position according to the diopter information.

[0083] [Appendix 4] 3. The ophthalmologic imaging apparatus according to claim 2, wherein when the value of the diopter is D, the distance corresponding to the diopter is 1000 / D mm.

[0084] [Appendix 5] a means for acquiring a two-dimensional image of the anterior segment of the subject's eye, 5. The ophthalmologic imaging apparatus according to claim 1, wherein the first relative position for photographing the fundus is determined based on the two-dimensional image.

[0085] [Appendix 6] 6. The ophthalmologic imaging device according to claim 1, wherein the anterior segment of the subject's eye is photographed after the relative position is adjusted to the second relative position.

[0086] [Appendix 7] the inspection optical system has a tomographic image optical system, The tomographic image optical system includes: a light receiving unit that receives interference light obtained by combining the return light from the subject's eye and the reference light; means for generating a tomographic image based on a signal output from the light receiving unit; 7. An ophthalmologic imaging device according to any one of claims 1 to 6, comprising:

[0087] [Appendix 8] means for extracting a feature from the tomographic image; and means for acquiring a deviation amount of the position of the characteristic portion from a preset target position, 8. The ophthalmologic imaging apparatus according to claim 7, wherein the control unit controls the drive unit based on the amount of deviation.

[0088] [Appendix 9] An ophthalmologic imaging device according to any one of appendices 1 to 8, characterized in that processing between multiple steps including a step of capturing a two-dimensional image of the fundus of the subject's eye, a step of capturing a tomographic image of the fundus of the subject's eye, a step of capturing a two-dimensional image of the anterior segment of the subject's eye, and a step of capturing a tomographic image of the anterior segment is automatically performed.

[0089] [Appendix 10] a light source that illuminates the subject's eye when photographing the fundus, 10. The ophthalmologic imaging device according to claim 1, wherein the light source is turned on during a period in which the relative position transitions from the first relative position to the second relative position.

[0090] [Appendix 11] An ophthalmic imaging apparatus having an examination optical system for examining an eye to be examined, the examination optical system including an objective lens facing the eye to be examined, A control method characterized by comprising a step of adjusting the relative position of the subject's eye and the objective lens to a second relative position that is further separated from a first relative position for fundus photography by a distance corresponding to the focal length of the subject's eye. [Explanation of symbols]

[0091] 10 Ophthalmological equipment 100 Optical Head 170 Head drive unit 200 spectrometer 300 control section

Claims

1. an examination optical system for examining an eye to be examined, the examination optical system including an objective lens facing the eye to be examined; a driving unit capable of adjusting a relative position between the eye to be examined and the objective lens; and a control unit that controls the drive unit so that the relative position becomes a second relative position that is further separated from a first relative position for fundus photography by a distance corresponding to the focal length of the subject's eye.

2. 2. The ophthalmologic imaging apparatus according to claim 1, wherein the distance according to the focal length of the subject's eye is a distance corresponding to a diopter obtained by focus adjustment for photographing the fundus.

3. 3. The ophthalmologic imaging apparatus according to claim 2, wherein the examination optical system includes a focus index unit for acquiring diopter information of the subject's eye, and a focus lens that can be moved to a position according to the diopter information.

4. 3. The ophthalmologic imaging apparatus according to claim 2, wherein when the value of the diopter is D, the distance corresponding to the diopter is 1000 / D mm.

5. a means for acquiring a two-dimensional image of the anterior segment of the subject's eye, 2. The ophthalmologic imaging apparatus according to claim 1, wherein the first relative position for photographing the fundus is determined based on the two-dimensional image.

6. 2. The ophthalmologic imaging apparatus according to claim 1, wherein an image of the anterior segment of the subject's eye is captured after the relative position is adjusted to the second relative position.

7. the inspection optical system has a tomographic image optical system, The tomographic image optical system includes: a light receiving unit that receives interference light obtained by combining the return light from the subject's eye and the reference light; means for generating a tomographic image based on a signal output from the light receiving unit; 2. The ophthalmologic imaging apparatus according to claim 1, further comprising:

8. means for extracting a feature from the tomographic image; and means for acquiring a deviation amount of the position of the characteristic portion from a preset target position, The ophthalmologic imaging apparatus according to claim 7 , wherein the control unit controls the drive unit based on the amount of deviation.

9. 2. The ophthalmologic imaging device according to claim 1, wherein processing between a plurality of steps including a step of capturing a two-dimensional image of the fundus of the subject's eye, a step of capturing a tomographic image of the fundus of the subject's eye, a step of capturing a two-dimensional image of the anterior segment of the subject's eye, and a step of capturing a tomographic image of the anterior segment is automatically performed.

10. a light source that illuminates the subject's eye when photographing the fundus, The ophthalmologic imaging apparatus according to claim 1 , wherein the light source is turned on during a period in which the relative position transitions from the first relative position to the second relative position.

11. An ophthalmic imaging apparatus having an examination optical system for examining an eye to be examined, the examination optical system including an objective lens facing the eye to be examined, A control method characterized by comprising a step of adjusting the relative position of the test eye and the objective lens to a second relative position that is further separated from a first relative position for fundus photography by a distance corresponding to the focal length of the test eye.

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