Ophthalmic devices

Abstract

To provide an ophthalmologic apparatus equipped with an index imaging optical system in which an examined eye side is non-telecentric, capable of acquiring an examination result accurately.SOLUTION: An ophthalmologic apparatus includes: an index projection optical system for projecting a first index and a second index on different projection conditions; an index imaging optical system for imaging an observation image including the first index and the second index, which is non-telecentric on an examined eye side; an examination part including the index projection optical system and the index imaging optical system; alignment adjusting means for adjusting the position in an operation distance direction of the examination part; and correction means for acquiring an actual error from an appropriate operation distance and making correction accordingly on the basis of correspondence information in which position information on the positions of the first index image and the second index image in the observation image is associated beforehand for the error of the operation distance with respect to the appropriate operation distance, the error being attributed to the cornea curvature of the examined eye and the non-telecentric property of the index imaging optical system, and position information on a current position in the operation distance direction of the examination part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an ophthalmic apparatus for examining an eye to be examined. [Background technology]

[0002] There is known an ophthalmic apparatus that examines an eye by aligning the eye to be examined with an ophthalmic examination unit in the working distance direction using alignment targets projected onto the cornea under different projection conditions. For example, the apparatus disclosed in Patent Document 1 uses an infinity target and a finite target as alignment targets to align the eye to be examined in the working distance direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-127581 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, alignment in the working distance direction is performed using a target imaging optical system that is telecentric on the side of the subject's eye, but no consideration has been given to alignment in the working distance direction using a target imaging optical system that is non-telecentric on the side of the subject's eye.

[0005] In view of the above-described conventional technology, the present disclosure has as its technical object to provide an ophthalmic apparatus that is equipped with a target imaging optical system that is non-telecentric on the side of the subject's eye and that can obtain accurate examination results. [Means for solving the problem]

[0006] an ophthalmic device for examining an eye to be examined, the ophthalmic device comprising: an index projection optical system that projects a first index and a second index onto the cornea of the eye to be examined under different projection conditions; an index photographing optical system that is non-telecentric on the side of the eye to be examined and that photographs an observation image including a first index image which is a corneal reflection image of the first index and a second index image which is a corneal reflection image of the second index; an examination unit including the index projection optical system and the index photographing optical system; an alignment adjustment means that adjusts the positional relationship between the eye to be examined and the examination unit at least in a working distance direction; and a correction means that acquires and corrects an actual error from the appropriate working distance based on correspondence information in advance regarding positional information on the positions of the first index image and the second index image in the observation image, the error of the working distance from the appropriate working distance being an error caused by the corneal curvature of the eye to be examined and the non-telecentricity of the index photographing optical system, and the positional information at the current position of the examination unit in the working distance direction. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an external view of an ophthalmic apparatus. [Figure 2] FIG. 1 is a schematic diagram of a photographing optical system. [Figure 3] 10 is an example of an anterior eye image captured with an alignment target projected thereon. [Figure 4] FIG. 2 is a block diagram showing a control system of the ophthalmologic apparatus. [Figure 5] FIG. 10 is a diagram illustrating misalignment of the working distance. [Figure 6] FIG. 10 is a diagram showing the correspondence between the interval La of the first target images and the ratio Lb / La for each radius of curvature of the cornea. [Figure 7] FIG. 10 is a diagram showing the correspondence between the ratio Lb / La and the misalignment Δz for each radius of corneal curvature. [Figure 8] FIG. 4 is a flowchart showing the operation of the ophthalmologic apparatus. [Figure 9] FIG. 10 is a diagram illustrating image misalignment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [overview] An embodiment of an ophthalmic device according to the present disclosure will be described. Items grouped in < > below can be used independently or in conjunction with each other.

[0009] An ophthalmic apparatus (e.g., ophthalmic apparatus 1) of this embodiment examines an eye to be examined. For example, the ophthalmic apparatus includes an examination unit (e.g., an imaging unit 2). For example, the ophthalmic apparatus includes an alignment adjustment unit (e.g., a drive unit 5). For example, the ophthalmic apparatus includes a correction unit (e.g., a control unit 71).

[0010] <Inspection Department> In this embodiment, the examination unit is provided to photograph or measure the subject's eye. The examination unit includes a target projection optical system (e.g., an alignment target projection optical system 50) and a target photographing optical system (e.g., an anterior segment observation optical system 200).

[0011] The target projection optical system projects the first target and the second target onto the cornea of the subject's eye under different projection conditions. For example, the first target and the second target may be projected so that at least their coordinates (pixel positions) in an observation image (described later) are different.

[0012] The projection condition may be the state of the light beam of the index. In this case, the state of the light beam of the index differs between the first index and the second index. As an example, the index projection optical system may project a first index at infinity and a second index at a finite distance. In such a configuration, the difference between the amount of change in the position of the index image of the first index and the amount of change in the position of the index image of the second index increases with a change in working distance, making it easier to perform precise alignment. Also, as an example, the index projection optical system may project a first index at a finite distance and a second index at a finite distance. In this case, as the finitely distant index, one of the first index and the second index may be projected as convergent light, and the other as divergent light.

[0013] For example, the first index and the second index may differ in the amount of change in the position of the index image with respect to the change in working distance.

[0014] For example, in the target projection optical system, when the projection conditions of the first target and the second target are different, the positional relationship between the first target and the second target changes depending on at least one of the corneal curvature of the test eye and the distance between the test eye and the examination unit in the working distance direction. In this embodiment, a correction unit described later performs accurate correction using the positional relationship between the first target and the second target.

[0015] The target imaging optical system is a target imaging optical system that is non-telecentric on the subject's eye side. In other words, it is a target imaging optical system that is non-telecentric on the object side. The target imaging optical system may be a telecentric optical system or a non-telecentric optical system on the image side. The target projection optical system captures an observation image including a first target image that is a corneal reflection image of the first target and a second target image that is a corneal reflection image of the second target. For example, the observation image may be an image obtained by capturing only the first target image and the second target image. For example, the observation image may be an image obtained by capturing the first target image and the second target image together with the anterior segment of the subject's eye (e.g., anterior segment observation image 84).

[0016] The examination unit may include an examination optical system for acquiring examination information of the subject's eye. The examination optical system may be an imaging optical system for imaging the subject's eye, or a measurement optical system for measuring the subject's eye. The examination optical system may include at least one of an imaging optical system and a measurement optical system.

[0017] For example, the examination optical system may be an OCT optical system (e.g., the OCT optical system 300) that detects an interference signal between the measurement light irradiated onto the fundus of the subject's eye and the reference light. In this case, OCT data may be acquired as the examination information. In addition, in this case, the axial length may be acquired as the examination information. Of course, the examination optical system may be an optical system different from the OCT optical system, and the examination information may be information different from the OCT data and the axial length.

[0018] In this embodiment, the optical path of the target imaging optical system and the optical path of the inspection optical system may be made into a common optical path by an optical path combining member. For example, the optical path combining member may be composed of at least one optical member such as a beam splitter, a dichroic mirror, a half mirror (e.g., half mirror 201), etc.

[0019] <Alignment adjustment method> In this embodiment, the alignment adjustment means adjusts the positional relationship between the subject's eye and the examination unit at least in the working distance direction. For example, the alignment adjustment means may adjust the relative positional relationship between the subject's eye and the examination unit in the working distance direction by moving the examination unit relative to the subject's eye. Furthermore, for example, the alignment adjustment means may adjust the relative positional relationship between the subject's eye and the examination unit in the working distance direction by moving a face support means (e.g., face support unit 110) that supports the subject's face relative to the examination unit. Of course, the relative positional relationship may be adjusted by moving both the examination unit and the face support means.

[0020] The alignment adjustment means may adjust the positional relationship between the subject's eye and the examination unit in the left-right direction in addition to the positional relationship in the working distance direction. Furthermore, the alignment adjustment means may adjust the positional relationship between the subject's eye and the examination unit in the up-down direction in addition to the positional relationship in the working distance direction. Of course, the positional relationship in both the left-right direction and the up-down direction may also be adjusted.

[0021] <Correction means> In this embodiment, the correction means acquires and corrects the actual error based on correspondence information that associates position information regarding the positions of the first and second target images in the observation image with the error in the working distance, and position information of each target image obtained at the current position of the inspection unit in the working distance direction. Note that the correspondence information is, for example, predetermined.

[0022] For example, the position information regarding the position of each target image may be information expressed as coordinates (pixel position) in the observed image, image height, the ratio of the interval between the first target images to the interval between the second target images, etc. Furthermore, for example, the working distance error may be the error of the working distance with respect to the appropriate working distance, which may be an error caused by the corneal curvature of the subject's eye and non-telecentricity of the target imaging optical system. Furthermore, for example, the actual error may be the error between the appropriate working distance for the subject's eye and the actual working distance at the current position of the examination unit.

[0023] For example, such correspondence information may be stored in a memory as a lookup table or an arithmetic expression (e.g., a function) that associates the above-mentioned position information with the error in advance. The correction means may acquire and correct the actual error by using at least one of the lookup table and the arithmetic expression.

[0024] The correspondence information may be obtained in advance by measuring and associating position information regarding the positions of the first and second target images with the error in the working distance using a model eye. Of course, the present invention is not limited to this, and the correspondence information may be obtained in advance, for example, by simulation.

[0025] When the target imaging optical system on the subject's eye side is telecentric, if an infinite target is projected, the position information of the target image on the observation image changes depending on the difference in corneal curvature, but the position information of the target image hardly changes regardless of the change in the distance between the subject's eye and the examination unit. However, when the target imaging optical system on the subject's eye side is non-telecentric, as in this embodiment, the position information of the target image on the observation image changes depending on the difference in corneal curvature as well as the distance between the subject's eye and the examination unit, whether the target is an infinite target or a finite target. Therefore, by performing correction taking into account errors caused by non-telecentricity, accurate examination results can be obtained even when a non-telecentric target imaging optical system is used on the subject's eye side.

[0026] The correction means may correct the actual error by removing the influence of the actual error from the examination information acquired by the examination optical system based on the correspondence information. For example, after adjusting the positional relationship between the subject's eye and the examination unit, measurement results may be acquired that take into account the error between the appropriate working distance for the subject's eye and the actual working distance at the current position of the examination unit. This allows for accurate examination results to be obtained without having to adjust the alignment position again. This also reduces the time required for realignment.

[0027] Furthermore, the correction unit may drive the alignment adjustment unit based on the correspondence information to align the eye to the examination unit with the appropriate working distance, thereby correcting the actual error. For example, after adjusting the positional relationship between the eye to be examined and the examination unit, the positional relationship may be readjusted so that the error between the appropriate working distance for the eye to be examined and the actual working distance at the current position of the examination unit becomes zero. This allows the alignment position to be corrected even if the distance between the eye to be examined and the examination unit is significantly different from the appropriate working distance. Therefore, accurate examination results can be obtained.

[0028] <Method for acquiring axial length> The ophthalmologic apparatus of this embodiment may further include an axial length acquisition means (e.g., the control unit 71). The axial length acquisition means acquires the axial length of the subject's eye as examination information. The axial length acquisition means may acquire the axial length using an OCT optical system. In this case, for example, the axial length may be acquired based on the difference in optical path length between the measurement light and the reference light, the detection result of the interference signal, and the position of the examination unit in the working distance direction.

[0029] [Example] An example of this embodiment will be described with reference to the drawings.

[0030] Fig. 1 is an external view of an ophthalmic apparatus 1. As shown in Fig. 1, in this embodiment, the ophthalmic apparatus 1 includes an operation unit 8, a monitor 73, a base 101, a movable table 102, a drive unit 5, a face support unit 110, an imaging unit 2, a control unit 71, and the like.

[0031] The operation unit 8 inputs signals for operating the imaging unit 2. For example, when the operation unit 8 is tilted, a movement signal is input for moving the movable stage 102 in at least one of the left-right direction (X direction) and the front-back direction (Z direction) relative to the base 101. Furthermore, for example, when a knob (not shown) of the operation unit 8 is rotated, a movement signal is input for moving the imaging unit 2 in the up-down direction (Y direction) relative to the base 101.

[0032] The monitor 73 displays an anterior segment image, a front image, OCT data, etc. of the subject's eye E1 on its screen. The monitor 73 also functions as a touch panel that doubles as the operation unit 8. That is, a movement signal for moving the imaging unit 2 is also input by operating the monitor 73.

[0033] The driving unit 5 moves the imaging unit 2 in the left-right, up-down, and front-back directions. For example, the driving unit 5 is a slide mechanism. As an example, the slide mechanism may include a motor, gears, guide rails, etc.

[0034] The face support unit 110 supports the face of the subject. The face support unit 110 has a forehead rest 111 and a chin rest 112. The forehead of the subject is placed against the forehead rest 111. The chin of the subject is placed on the chin rest 112.

[0035] <Photography Department> The photographing unit 2 has an optical system (see FIG. 2) therein for photographing the subject's eye E1.

[0036] In this embodiment, the photographing unit 2 includes an OCT optical system 300 , an SLO optical system 500 , a binocular observation optical system 600 , an alignment target projection optical system 50 , and an anterior eye photographing optical system 200 .

[0037] In this embodiment, the optical path of the OCT optical system 300 and the optical path of the anterior-segment observation optical system 200 are coupled by a half mirror 201. That is, the optical axis (and optical path) L1 of the OCT optical system 300 and the optical axis (and optical path) L2 of the anterior-segment observation optical system 200 are made coaxial by the half mirror.

[0038] Also, the optical axis L1 of the OCT optical system 300 and the optical axis (and optical path) L3 of the SLO optical system 500 are made coaxial by the dichroic mirror 12. An objective lens 11 is disposed on the common optical path 10 (common optical axis) of the OCT optical system 300, the anterior eye observation optical system 200, and the SLO optical system 500.

[0039] <OCT optical system> The OCT optical system 300 is used, for example, to image a tomographic image of the tissue of the subject eye E1. The OCT optical system may include, in addition to the objective lens 11, the dichroic mirror 12, and the half mirror 201, an OCT light source that emits low-coherence light, an optical splitter that splits the light emitted from the light source into measurement light and reference light, a measurement optical system that guides the measurement light to the subject eye E1, a scanning unit that scans the measurement light in the transverse direction on the fundus of the subject eye E1, a reference optical system that generates reference light, a detector that detects an interference signal by combining the measurement light and the reference light, and the like. Of course, the OCT optical system may have a configuration different from these. For details of the OCT optical system 300, reference may be made, for example, to the configuration disclosed in Japanese Patent Application Laid-Open No. 2019-134896.

[0040] For example, the OCT optical system 300 splits the OCT light emitted from the OCT light source into measurement light and reference light by an optical splitter. The measurement light reaches the fundus of the subject eye E1 through the half mirror 201, the dichroic mirror 12, and the objective lens 11. The OCT optical system 300 receives the interference light between the measurement light reflected from the fundus of the subject eye E1 and the reference light, thereby acquiring the OCT signal of the fundus of the subject eye E1 and inputting it to the control unit 71. The control unit 71 may generate an OCT image of the fundus Er based on the input signal and store it in the storage unit 72. The control unit 71 may display the generated frontal image on the monitor 73.

[0041] In addition, in this embodiment, the OCT optical system 300 may be used to measure the axial length of the eye to be examined. For example, in this case, the axial length of the eye to be examined may be obtained based on the optical path length of the measurement light, the optical path length of the reference light, the detection result of the interference signal, and the actual operating distance of the imaging unit 2 with respect to the eye to be examined (details will be described later).

[0042] <SLO optical system> The SLO optical system 500 is used, for example, to capture a frontal image of the fundus of the eye to be examined E1. The SLO optical system may include, in addition to the objective lens 11 and the dichroic mirror 12, a laser light source that emits laser light, a focusing lens for focusing on the eye to be examined, a scanning unit for scanning the laser light, a light receiving element for receiving the return light reflected from the fundus of the eye to be examined, a perforated mirror for transmitting the light emitted from the laser light and reflecting the return light to guide it to the light receiving element side, a confocal aperture for blocking the return light reflected outside the focus position, and the like. Of course, the SLO optical system 500 may have a configuration different from these. For details of the SLO optical system 500, for example, reference may be made to the configuration disclosed in Japanese Patent Application Laid-Open No. 2019-134896.

[0043] <Binocular observation optical system> The binocular observation optical system 600 is provided for observing both eyes of the eye to be examined when aligning the imaging unit 2 and the eye to be examined E1. In this embodiment, a binocular camera 80 is provided as the binocular observation optical system 600. As shown in FIG. 2, for example, the binocular camera 80 is provided on the subject side of the imaging unit 2 and captures an image of the subject's face supported by the face support unit 110. The binocular observation image captured by the binocular camera 80 is displayed on the monitor 73 or the like by a control unit described later. Of course, other members may be provided in the binocular observation optical system 600.

[0044] <Alignment index projection optical system> The alignment target projection optical system 50 projects an alignment target light beam onto the subject's eye E1. As shown in the diagram within the dotted line at the bottom left of Fig. 2, the alignment target projection optical system 50 has a plurality of infrared light sources arranged at 45-degree intervals on a concentric circle centered on the optical axis L1. The ophthalmic apparatus in this embodiment mainly includes a first target projection optical system (0 degrees and 180 degrees) and a second target projection optical system.

[0045] The first target projection optical system projects a first target at infinity onto the cornea of the subject's eye E1. The first target projection optical system has an infrared light source 51 and a collimating lens 52. The infrared light sources 51 are arranged symmetrically across a vertical plane passing through the optical axis L1. The second target projection optical system projects a second target at a finite distance onto the cornea of the subject's eye E1. The second target projection optical system is arranged at a different position from the first target projection optical system and has six infrared light sources 53. For example, the infrared light sources 53 may be arranged vertically or diagonally around the optical axis L1. Of course, the angles at which the targets are projected in the first target optical system and the second target optical system are not limited to these. For convenience, FIG. 2 shows only the first target projection optical system (0 degrees and 180 degrees) and a portion of the second target projection optical system (45 degrees and 135 degrees).

[0046] <Anterior segment observation optical system> The anterior-segment observation optical system 200 is used to capture an image of the anterior segment of the subject's eye E1 and obtain an anterior-segment image.

[0047] The anterior-segment observation optical system 200 includes an anterior-segment illumination light source 204. The anterior-segment observation optical system 200 also mainly includes a half mirror 201, a relay lens 202, and a light-receiving element 203 on the reflecting side of the dichroic mirror 12. The anterior eye illuminated by the anterior-segment illumination light source 204 is received by the light-receiving element 203 via the objective lens 11, the dichroic mirror 12, and the half mirror through the optical system of the relay lens 202. In this way, an anterior-segment image is captured.

[0048] The anterior-segment observation optical system 200 also serves as an optical system for detecting alignment target images formed on the cornea of the subject's eye E1. That is, the anterior-segment observation optical system 200 acquires an anterior-segment image obtained by capturing the first target image and the second target image formed on the cornea of the subject's eye E1 as well as the anterior segment of the subject's eye E1.

[0049] 3 is an example of an anterior-segment image. When a first index is projected onto the cornea of the subject's eye E1, first index images Ia1 and Ia2, which are corneal reflection images of the first index, appear in the anterior-segment image. Furthermore, when a second index is projected onto the cornea of the subject's eye E1, second index images Ib1 to Ib6, which are corneal reflection images of the second index, appear in the anterior-segment image.

[0050] In this embodiment, the anterior-eye-segment observation optical system 200 is a non-telecentric optical system on the subject's eye side (in other words, on the object side) relative to the objective lens 11. More specifically, in this embodiment, the non-telecentric optical system extends from the subject's eye to the objective lens 11. This is because part of the optical path of the anterior-eye-segment observation optical system 200 is shared with the optical path of the OCT optical system 300.

[0051] For example, in the ophthalmic apparatus 1 of this embodiment, the focal position of the objective lens 11 is between the objective lens 11 and the dichroic mirror 12. In this case, it may be difficult to secure space to place an aperture at the focal position of the objective lens 11. Even if an aperture can be placed at the focal position of the objective lens 11, when the measurement light is scanned during imaging using the OCT optical system 300, the measurement light may be blocked by the aperture, making it impossible to obtain appropriate OCT data. For this reason, the anterior eye observation optical system 200 is configured as a non-telecentric optical system on the side of the eye to be examined.

[0052] In this embodiment, the case where the anterior eye observation optical system 200 and the OCT optical system 300 are shared has been described, but the present invention is not limited to this. For example, even if the anterior eye observation optical system 200 and the SLO optical system 500 or the like share an optical path, the same problem may occur.

[0053] <Control unit> The control system of the ophthalmic apparatus 1 will be described with reference to Fig. 4. Fig. 4 is a block diagram showing the control system of the ophthalmic apparatus 1. Each part of the ophthalmic apparatus 1 is controlled by a control unit 71. The control unit 71 is a processing device (processor) having electronic circuits that perform control processing of each part of the ophthalmic apparatus 1 and arithmetic processing. The control unit 71 is realized by a CPU (Central Processing Unit) or the like. The control unit 71 is electrically connected to a memory unit 72 via a bus or the like.

[0054] For example, the control unit 71 is electrically connected to each of the components, such as the drive unit 5, the operation unit 8, the monitor 73, the infrared light source 51, the infrared light source 53, the light receiving element 203, the anterior eye illumination light source 204, and the binocular camera 80. The control unit 71 is also electrically connected to each of the components, such as a laser light source (not shown) and an image sensor (not shown), provided in the SLO optical system 500. The control unit 71 is also electrically connected to each of the components, such as an OCT light source (not shown) and a detector (not shown), provided in the OCT optical system 300.

[0055] In this embodiment, the control unit 71 also controls the drive unit 4 to align the imaging unit 2 with the subject's eye E1 in the XY directions (see FIG. 1) and in the working distance direction (Z direction in FIG. 1).

[0056] [Operation] The operation of the ophthalmologic apparatus 1 having the above-described configuration will be described with reference to the flowchart of Fig. 8. As shown in Fig. 8, in this embodiment, an OCT image is taken and the axial length is measured.

[0057] <S101:ラフなアライメント> First, the control unit 71 roughly adjusts the positions of the photographing unit 2 and the eye E1 to be examined.

[0058] When the subject places their forehead on the forehead rest 111 and their chin on the chin rest 112, a detection signal is output from a detector (not shown), and the control unit 71 starts capturing an image of the subject's face with the binocular camera 80. The examiner instructs the subject to gaze at a fixation target projected by a fixation target projection unit (not shown), and then touches the center of the pupil of one of the subject's eyes while viewing a binocular observation image including both of the subject's eyes captured by the binocular camera 80 on the monitor 73. The control unit 71 drives the drive unit 5 based on the signal from the monitor 73 to move the imaging unit 2 so that the optical axis L1 is positioned at the touched position on the binocular observation image. For example, the control unit 70 calculates the drive amounts in the X and Y directions from the coordinates of the touch on the monitor 73 and drives the drive unit 5 in the X and Y directions. After completing the movement of the imaging unit 2 in the X and Y directions, the control unit 71 may advance the imaging unit 2 until an alignment target image is detected.

[0059] When the photographing unit 2 approaches the subject's eye E1, an anterior-segment observation image 84 (see FIG. 3) photographed by the anterior-segment observation optical system 200 appears on the monitor 73. Note that in the anterior-segment observation image 84, first target images Ia1 and Ia2 and second target images Ib1 to Ib6 appear as alignment target images.

[0060] <S102:XYアライメント> Next, when the control unit 71 detects each target image from the anterior eye observation image 84, it starts automatic alignment control and aligns the imaging unit 2 in the X and Y directions with respect to the eye to be examined.

[0061] For example, the control unit 71 detects the XY coordinates of the center of a circle formed by the first target images Ia1, Ia2 and the second target images Ib1 to Ib6 as approximately the center of the cornea, and moves the imaging unit 2 so that the center coincides with an alignment reference position in the XY directions set on the light receiving element 203 (for example, the intersection of the imaging surface of the light receiving element 203 and the optical axis L2). Note that this method of alignment in the XY directions is just one example. For example, the method described in Japanese Patent Application Laid-Open No. 2016-67795 may be referred to for the alignment method in the XY directions.

[0062] <S103: Alignment in the Z direction> Next, the control unit 71 aligns the position of the imaging unit 2 in the Z direction (operating distance direction) with respect to the eye to be examined based on the anterior eye observation image 84. For example, the imaging unit 2 is moved so that the distance from the eye to be examined to the imaging unit 2 (objective lens 11) becomes the appropriate operating distance.

[0063] For example, the control unit 71 analyzes the anterior eye observation image 84 (see FIG. 3) that is captured in real time by the anterior eye observation optical system 200, and obtains the ratio (hereinafter referred to as ratio Lb / La) of the interval La between the first index images Ia1 and Ia2 and the interval Lb between the second index images Ib1 and Ib3. Also, for example, the control unit 71 adjusts the positional relationship between the eye to be examined E1 and the imaging unit 2 so that the ratio Lb / La becomes a predetermined value P (for example, 0.7). The predetermined value P is the value of the ratio Lb / La when the imaging unit 2 is arranged so as to have the appropriate operating distance WD1 (for example, 25 mm) shown in FIG. 5(a) when the corneal radius of curvature is the reference value (for example, 7.8 mm), and is a predetermined value. The predetermined value P of the ratio Lb / La is stored in the storage unit 72.

[0064] As shown in FIG. 5(b), even when alignment is performed so that the ratio Lb / La becomes the predetermined value P, there may be an error caused by the corneal radius of curvature (hereinafter referred to as alignment deviation Δz) between the actual operating distance WD2 and the appropriate operating distance WD1. Here, in the prior art exemplified in Patent Document 1, the position of the index image of the infinity index obtained via a telecentric anterior eye observation optical system on the eye to be examined side corresponds one-to-one with the corneal radius of curvature, and the corneal radius of curvature and the error (alignment deviation) caused by the corneal radius of curvature have been obtained.

[0065] However, in this embodiment, the anterior eye observation optical system 200 is a non-telecentric optical system on the eye to be examined side. Therefore, the position of the first index image, which is the index image of the infinity index (in this embodiment, the interval La), changes according to the position of the imaging unit 2 in the Z direction. Also, the position of the first index image changes according to the corneal radius of curvature. Thus, in this embodiment, the position of the first index image, which is the index image of the infinity index, is affected by the combined influence of the position of the imaging unit 2 in the Z direction and the corneal radius of curvature, so the alignment deviation Δz cannot be obtained by the same method as in the prior art.

[0066] In contrast, in this embodiment, the control unit 71 obtains the alignment deviation Δz and performs correction as described below.

[0067] <S104: Detection of alignment deviation Δz> In order to obtain the alignment deviation Δz, the control unit 71 obtains the corneal radius of curvature R of the eye to be examined by using the positional relationship between the first index image and the second index image in addition to the position information of the first index image.

[0068] As an example, the control unit 71 obtains the corneal radius of curvature R based on the height position of the first index image and the positional relationship between the first index image and the second index image. In this embodiment, the interval La between the first index images Ia1 and Ia2 is used as the height position of the first index image (see FIG. 3). Of course, the height position of the first index image is not limited to this, and for example, coordinates on the anterior eye observation image 84 may be used. Instead of the height position of the first index image, it is also possible to use the height position of the second index image (for example, the interval Lb between the second index images Ib1 and Ib3).

[0069] In this embodiment, for each corneal radius of curvature R, the correspondence relationship Cr1 between the interval La of the first index images and the ratio Lb / La is stored in the storage unit 72 as a function as shown in FIG. 6. For example, this correspondence relationship Cr1 may be determined in advance based on experiments, simulations, etc. for a plurality of corneal radii of curvature (here, corneal radii of curvature R1 and R2). Therefore, the control unit 71 can obtain the corneal radius of curvature R by referring to the correspondence relationship Cr1 using the interval La of the first index images and the ratio Lb / La detected from the anterior segment observation image 84 of the subject eye E1. Of course, FIG. 6 is an example of a function and is not limited thereto.

[0070] Next, the control unit 71 detects the alignment deviation Δz using the obtained corneal radius of curvature R.

[0071] In this embodiment, for each corneal radius of curvature R, the correspondence relationship Cr2 between the ratio Lb / La and the alignment deviation Δz is stored in the storage unit 72 as a function as shown in FIG. 7. For example, this correspondence relationship Cr2 may be determined in advance based on experiments, simulations, etc. for a plurality of corneal radii of curvature. Therefore, the control unit 71 uses the ratio Lb / La detected from the anterior segment observation image 84 of the subject eye E1 and the corneal radius of curvature R obtained above, and by referring to the correspondence relationship Cr2, obtains how much the actual operating distance WD2 deviates from the appropriate operating distance WD1 as the alignment deviation Δz. Of course, FIG. 7 is an example of a function and is not limited thereto.

[0072] By the above operations, even when the subject eye side uses the non-telecentric index imaging optical system 200, it is possible to appropriately obtain the alignment deviation Δz from the appropriate operating distance that occurs when actually performing alignment in the Z direction.

[0073] <S105: Adjustment of OCT optical system> When the alignment in the XYZ directions of the imaging unit 2 with respect to the subject eye E1 is completed, the control unit 71 adjusts the OCT optical system 300. At this time, for example, the control unit 71 adjusts the optical path length difference between the reference optical system and the measurement optical system.

[0074] In addition, in this embodiment, the optical path length of the reference optical system is defined as the optical path length from the light divider until the reference light reaches the detector. The optical path length of the reference optical system in this embodiment is a fixed value. Also, in this embodiment, the optical path length of the measurement optical system is defined as the optical path length from the light divider until the measurement light is reflected by the eye under test and reaches the detector.

[0075] In this embodiment, while irradiating the eye under test with measurement light, the control unit 71 adjusts the optical path length of the measurement optical system by controlling a pulse motor (not shown) provided in the measurement optical system. For example, the control unit 71 adjusts the optical path length of the measurement optical system so that an interference signal between the returned light reflected by the fundus by the measurement light and the reference light is detected. More specifically, it is adjusted so that an image of the fundus based on the interference signal is depicted within a predetermined interval from zero delay.

[0076] <S106: Obtain the axial length of the eye under test> Next, the control unit 71 obtains the axial length. In this embodiment, for the axial length AL1 of the eye under test, a model eye with a known axial length (for example, the axial length is AL2) is placed at an appropriate operating distance WD1, and while adjusting the optical path length difference between the measurement optical system and the reference optical system as described above and photographing the model eye, the axial length is obtained as follows based on the state of the device. Note that photographing of the model eye may be performed in advance at the time of factory shipment. At that time, parameters for specifying the state of the device when photographing the model eye are stored in the memory.

[0077] First, the control unit 71 obtains the difference Δp in the correction amount of the optical path length difference between the reference optical system and the measurement optical system. Δp is expressed by the following formula.

[0078] Δp = p2 - p1 ··· (1) Here, p1 indicates the correction amount of the optical path length difference in the process of S105. p2 indicates the correction amount of the optical path length difference when photographing the model eye. The correction amount of the optical path length difference may be derived based on the driving amount (the driving amount from the initial value) of the aforementioned pulse motor.

[0079] Next, the control unit 71 acquires a fundus tomographic image 800 as shown in Fig. 9 in a state in which the optical path length difference has been corrected by the process of S105. Also, the control unit 71 acquires an image shift Δd.

[0080] As shown in Fig. 9, the image shift Δd represents the amount of shift in the Z direction between the position d1 of the fundus image in the fundus tomographic image 800 and the position d2 of the fundus image of the model eye when the model eye is photographed. Note that d2 is a known value based on photographing the model eye. The control unit 71 analyzes the fundus tomographic image 800, determines the position d1 of the fundus image, and calculates the difference from position d2. In this way, the image shift Δd is obtained.

[0081] Here, if the test eye is positioned at an appropriate working distance WD1, the axial length AL1 of the test eye is expressed by the following equation using the axial length AL2 of the model eye, the difference Δp in the correction amount of the optical path length, and the image shift Δd.

[0082] AL1=AL2+Δp+Δd (2) Since AL2 is known, and the difference Δp in the correction amount of the optical path length and the image shift Δd can be calculated as described above, the control unit 71 can calculate the axial length AL1 of the subject's eye by substituting the respective values into equation (2).

[0083] However, as mentioned above, since the photographing optical system is an optical system that is non-telecentric on the object side, the actual working distance WD2 at which the subject's eye is positioned is shifted by a shift amount Δz from the appropriate working distance WD1.

[0084] Therefore, the axial length AL2 based on (2) is corrected for the alignment deviation Δz. Specifically, the corrected axial length AL3 of the subject's eye can be calculated using the following equation (3).

[0085] AL3 = AL1 + Δz (3) According to this method, even when alignment is performed using a non-telecentric optical system, the alignment deviation Δz from the appropriate working distance can be corrected, and the axial length of the subject's eye can be determined with high accuracy.

[0086] In this embodiment, an example has been described in which the axial length of the eye is obtained once and the alignment deviation Δz is corrected for the obtained value of the axial length, assuming that the test eye is placed at the position of the proper operating distance WD1. Of course, even if the axial length of the eye is not obtained once, the alignment deviation Δz may be corrected to obtain the axial length of the test eye. That is, the corrected axial length AL3 may be obtained by the following formula.

[0087] AL3 = AL2 + Δp + Δd + Δz ··· (4) As described above, even if the ophthalmic apparatus 1 of this embodiment has a target imaging optical system 200 in which the test eye side is non-telecentric, the alignment deviation Δz in the operating distance direction due to the corneal curvature (corneal curvature radius R) of the test eye and the positional relationship between the test eye and the imaging unit 2 is obtained, and by correcting this alignment deviation Δz, an inspection result can be obtained with high accuracy. Note that the method for obtaining the axial length described above is only an example and is not limited thereto.

[0088] In addition, the ophthalmic apparatus 1 of this embodiment corrects the alignment error by removing the influence of the alignment deviation Δz from the proper operating distance that occurs when performing alignment in the Z direction from the measurement result. For example, the alignment deviation Δz is obtained using the interval La between the first target images and the ratio Lb / La of the interval La between the first target images and the interval Lb between the second target images, and the measurement result of the axial length is corrected. As a result, the measurement result can be accurately obtained without performing alignment again considering the alignment deviation Δz. In addition, it is possible to suppress an increase in the measurement time.

[0089] <S107: OCT Image Acquisition> In this embodiment, the control unit 71 captures an OCT image of the subject's eye after measuring the axial length. For example, the control unit 71 captures an OCT image of the subject's eye based on a release signal input from the outside (for example, by the user of the ophthalmologic apparatus 1). When the acquisition of the axial length and the capture of the OCT image are performed as part of a series of measurements, in this embodiment, in order to correct the effect of the alignment misalignment Δz on the axial length, the imaging unit 2 is not moved again to perform the correction, but rather a correction calculation is performed on the axial length value, allowing the imaging to proceed smoothly and the overall measurement time to be shortened.

[0090] For ease of explanation, in this embodiment, the acquisition of the alignment error (S104) and the acquisition of the axial length (S106) are performed with the adjustment of the OCT optical system (S105) sandwiched between them. However, considering changes in the alignment state due to eye movement, it is desirable that there is no time lag between the acquisition of the alignment error (S104) and the acquisition of the axial length (S106), so the acquisition of the alignment error (S104) may be performed after the adjustment of the OCT optical system (S105).

[0091] The order of obtaining the axial length and capturing the OCT image is not limited to that of this embodiment, and either may be performed first. Also, only obtaining the axial length may be performed without capturing the OCT image.

[0092] [Example of transformation] In this embodiment, the control unit 71 performs alignment in the X, Y, and Z directions (automatic alignment), but this is not limiting. For example, the examiner may manually perform alignment in the X, Y, and Z directions by operating the operation unit 8.

[0093] In this embodiment, the controller 71 corrects the measurement result (here, the axial length) based on the alignment shift Δz to eliminate the influence of the alignment shift Δz. However, the controller 71 may also eliminate the influence of the alignment shift Δz by adjusting the alignment in the working distance direction based on the alignment shift Δz. For example, the controller 71 may move the imaging unit 2 relative to the subject's eye E1 and adjust the working distance so as to cancel out the determined alignment shift Δz.

[0094] This allows the distance from the subject's eye E1 to the imaging unit 2 to be adjusted to the appropriate working distance, thereby obtaining accurate examination results. Note that if the current working distance is significantly different from the appropriate working distance due to differences in the corneal curvature radius R, etc., adjusting the alignment rather than correcting the measurement results may provide better measurement accuracy. For this reason, this configuration is effective, particularly when the alignment deviation Δz is large.

[0095] In this embodiment, the corneal radius of curvature R of the subject's eye E1 is calculated after aligning the imaging unit 2 with the subject's eye in the XY directions and the working distance direction. However, the control unit 71 may calculate the corneal radius of curvature R after alignment in the XY directions and before alignment in the working distance direction. In this case, the control unit 71 acquires the ratio Lb / La and the distance La between the first target images from the anterior segment observation image 84 at the time of completing alignment in the XY directions, and calculates the corneal radius of curvature R based on the correspondence relationship Cr1. Furthermore, the control unit 71 calculates the value of Lb / La when the eye with the corneal radius of curvature R has an appropriate working distance WD1 based on the corneal radius of curvature R, and moves the imaging unit 2 in the working distance direction to a position where Lb / La is obtained. For example, this can also cancel out the misalignment Δz that may occur during alignment and position the imaging unit 2 at the appropriate working distance.

[0096] The control unit 71 may directly determine the misalignment Δz without acquiring the corneal radius of curvature R of the subject's eye. In this case, for example, a correspondence relationship between the ratio Lb / La and the interval La and the misalignment Δz may be stored in advance in the storage unit 72. For example, such a correspondence relationship may be determined by linking the corneal radius of curvature R determined by the correspondence relationship Cr1 with the corneal radius of curvature R used in the correspondence relationship Cr2.

[0097] Furthermore, in this embodiment, the case where the misalignment Δz is calculated from the ratio Lb / La and the corneal radius of curvature R has been described, but the present invention is not limited to this. For example, the misalignment Δz may be calculated from the interval La between the first target images and the corneal shape R. In this case, for example, the correspondence relationship between the interval La and the misalignment Δz for each corneal radius of curvature R may be stored in the storage unit 72. Furthermore, the misalignment Δz may be calculated from the interval Lb between the second target images and the corneal shape R. In this case, for example, the correspondence relationship between the interval Lb and the misalignment Δz for each corneal radius of curvature R may be stored in the storage unit 72. [Explanation of symbols]

[0098] 1 Ophthalmology equipment 2. Filming Department 5 Drive unit 50 Alignment target projection optical system 71 Control Unit 200 Anterior segment observation optical system

Claims

1. In an ophthalmic apparatus for examining an eye to be examined, an index projection optical system that projects a first index and a second index onto the cornea of the subject's eye under different projection conditions; a target photographing optical system that is non-telecentric on the subject's eye side and photographs an observation image including a first target image that is a corneal reflection image of the first target and a second target image that is a corneal reflection image of the second target; an inspection unit including the target projection optical system and the target photographing optical system; an alignment adjustment means for adjusting the positional relationship between the eye to be examined and the examination unit at least in the working distance direction; a correcting means for acquiring and correcting an actual error from the appropriate working distance based on correspondence information in which position information on the positions of the first target image and the second target image in the observation image is previously associated with an error of the working distance from the appropriate working distance, the error being due to the corneal curvature of the subject's eye and the non-telecentricity of the target photographing optical system, and the position information of the current position of the examination unit in the working distance direction; An ophthalmic apparatus comprising:

2. The ophthalmic apparatus of claim 1, the examination unit includes an examination optical system for acquiring examination information of the subject's eye, an ophthalmic device characterized in that the correction means corrects the actual error by removing the influence of the actual error from the examination information based on the position information at the current position of the examination unit in the working distance direction and the correspondence information.

3. In the ophthalmic device of claim 2, An ophthalmic apparatus, characterized in that the optical path of the target photographing optical system and the optical path of the examination optical system are made into a common optical path by an optical path combining member.

4. In the ophthalmic device of claim 2 or 3, The ophthalmologic apparatus is characterized in that the examination optical system is an OCT optical system that detects an interference signal between a measurement light irradiated onto the fundus of the subject's eye and a reference light.

5. In the ophthalmic device of claim 4, an axial length acquisition means for acquiring the axial length of the subject's eye as the examination information based on the optical path length difference between the optical path length of the measurement light and the optical path length of the reference light, the detection result of the interference signal, and the position of the examination unit in the working distance direction.

6. In the ophthalmic device of any one of claims 1 to 5, an ophthalmic device characterized in that the correction means drives the alignment adjustment means based on the position information at the current position of the examination unit in the working distance direction and the correspondence information, and corrects the actual error by aligning the test eye and the examination unit to the appropriate working distance.

7. In the ophthalmic device of any one of claims 1 to 6, An ophthalmic apparatus, characterized in that the target projection optical system projects the first target at infinity and the second target at a finite distance.

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