JP2013244364A - Fundus photographing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fundus photographing apparatus capable of keeping a patient's eye and a photographing unit at a proper operation distance.SOLUTION: A fundus photographing apparatus includes: a fundus illuminating optical system for illuminating the fundus of the eye; an alignment means which has a light source for projecting an alignment index onto the cornea via an objective lens; a focus means which has a diopter correction lens and which adjusts a focus of the fundus of the eye; a photographing optical system which comprises an imaging element for taking a reflected image of the alignment index and a reflected image of the fundus of the eye, illuminated by the illuminating optical system, via the objective lens; an eye information acquisition unit which acquires the corneal curvature or spherical diopter power of the eye from the reflected image of the alignment index; and an operation distance acquisition means for acquiring a corrected value with respect to a proper operation distance of the photographing unit with respect to the eye on the basis of at least one of the corneal curvature and the spherical diopter power, acquired by the eye information acquisition unit. Furthermore, the fundus photographing apparatus also includes a drive unit which moves the photographing unit with respect to the eye on the basis of the corrected value acquired by the operation distance acquisition means.

Description

  The present invention relates to a fundus imaging apparatus that images the fundus of a patient's eye.

  In fundus imaging using the fundus imaging apparatus, alignment, which is a relative alignment between the patient's eye and the imaging unit, is performed in order to effectively make the illumination light beam enter the fundus. For example, a light beam emitted from a plurality of target light sources arranged in contrast around the optical axis is projected onto the corneal surface of the patient's eye via the objective lens, and the index image is obtained from the light reception result of the index image reflected on the corneal surface. There is a fundus imaging apparatus that moves the imaging unit so that the focus state of the image is appropriate and aligns the working distance between the patient's eye and the apparatus (see, for example, Patent Document 1). As a fundus imaging apparatus, there is known a fundus imaging apparatus that projects a visual inspection target on different local regions on the fundus and performs a visual function test based on a patient's response (for example, see Patent Document 2).

JP 2011-36273 A JP 2003-235800 A

  However, if the working distance between the patient's eye and the fundus camera is not appropriate, the size of the ring slit image projected onto the patient's eye changes, and flare is likely to be mixed, resulting in a reduction in image quality. Further, in the fundus imaging apparatus that can perform the visual field inspection as disclosed in Patent Document 2, if the working distance between the patient's eye and the imaging unit is not appropriate, the light flux of the inspection target (stimulation light) projected around the fundus image is drawn. As a result, there arises a problem that the angle of view at which the visual field inspection can be performed with an appropriate light amount becomes narrow. Therefore, the fundus imaging apparatus is required to adjust with higher accuracy with respect to the working distance.

  An object of the present invention is to provide a fundus imaging apparatus capable of maintaining the patient's eye and the imaging unit at an appropriate working distance in view of the above-described problems of the prior art.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) In a fundus imaging apparatus including an imaging unit that images the fundus of a patient's eye and a drive unit that moves the imaging unit relative to the patient's eye, the imaging unit illuminates the fundus. An alignment unit having a light source for projecting an alignment index onto the cornea of the patient's eye via an objective lens, a focusing unit having a diopter correction lens and focusing the fundus, and a reflected image of the alignment index An imaging optical system including an imaging element that captures a reflected image of the fundus illuminated by the illumination optical system via the objective lens, a corneal shape acquisition unit that obtains a corneal curvature of a patient's eye from the reflected image of the alignment index, and An eye information acquisition unit having at least one of a diopter information acquisition unit that obtains spherical power based on diopter correction by the diopter correction lens, and an angle obtained by the eye information acquisition unit A working distance acquisition unit that obtains a correction value for an appropriate working distance of the imaging unit with respect to the patient's eye based on at least one of a film curvature and a spherical power, and the drive unit acquires the correction acquired by the working distance acquisition unit The imaging unit is moved with respect to the patient's eye based on the value.
(2) In the fundus imaging apparatus according to (1), the corneal shape acquisition unit obtains the corneal curvature based on an imaging magnification of a reflection image of the alignment index imaged by the imaging element.
(3) In the fundus imaging apparatus according to (2), the alignment unit includes a plurality of light sources arranged symmetrically with respect to an optical axis, and the cornea shape acquisition unit calculates an imaging magnification of a reflected image of the alignment index. It is obtained from the interval between the plurality of alignment indices imaged by the image sensor.

  According to the present invention, the patient's eye and the imaging unit can be maintained at an appropriate working distance.

  In FIG. 1, a fundus imaging apparatus 1 includes a base 1a, a movable base 2 provided so as to be movable in the left and right direction (X direction) and the front and rear (working distance) direction (Z direction) with respect to the base 1a. An imaging unit (apparatus) movably provided in the left / right direction (X direction), the up / down direction (Y direction), and the front / rear direction (X direction) with respect to the patient's eye (eye) E by the drive unit 6 provided on the table 2. Main body) 3 and a face support unit 5 fixed to the base 1a for supporting the patient's face. Note that an optical system and a control system, which will be described later, are housed inside the photographing unit 3.

  A joystick 4, a control unit 7a, and a monitor 8 are provided on the examiner side of the imaging unit 3. The joystick 4 is used to move the photographing unit 3 relative to the eye E. When the joystick 4 is tilted, the moving base 2 slides in the XZ direction on the base 1a by the sliding mechanism. A joystick 4 has a rotation knob 4a on the side surface and a switch 4b on the top. The drive unit 6 is driven by the rotation operation of the rotation knob 4a, and the photographing unit 3 moves in the Y direction. In addition, a fundus image is captured by an input signal from the switch 4b.

The control unit 7a is an input means for setting various photographing / inspection conditions and the like, and a mouse, a keyboard, a touch panel (attached to the monitor 8) and the like are used.
In addition to the observation / photographed image of the eye E, various inspection results are displayed on the monitor 8. For example, a fundus observation screen, an anterior ocular segment observation screen, a visual field inspection screen, and the like are displayed on the monitor 8.
On the patient side of the imaging unit 3, there are provided an imaging window 9 through which the patient looks into the apparatus, and a response button 7b for the patient to input a response signal at the time of visual function inspection of the eyes (retina).

  In FIG. 2, the optical system includes an illumination optical system 10, an observation / imaging optical system 30 for observing and photographing the fundus and anterior segment of a patient's eye, and focus index projection optics for projecting a focus index (focus index) on the fundus. The system 40 includes an alignment index projection optical system that projects an alignment index light beam onto the anterior eye part, and a visual target presentation optical system 70 that guides the line of sight of the patient (eye E).

<Illumination Optical System> The illumination optical system 10 includes a photographing illumination optical system and an observation illumination optical system. The photographing illumination optical system includes a photographing light source 14 that emits a visible light beam, a condenser lens 15, a ring slit 17 having a ring-shaped opening, a relay lens 18, a mirror 19, a black spot plate 20 having a black spot at the center, a relay lens 21, It has a perforated mirror (ring slit) 22 and an objective lens 25.
The observation illumination optical system includes an illumination light source 11 that emits a near-infrared light beam, an infrared filter 12 that transmits near-infrared light, a condenser lens 13, and a dichroic disposed between the condenser lens 13 and the ring slit 17. An optical system from the mirror 16 and the ring slit 17 to the perforated mirror 22 and an objective lens 25 are provided.

  <Observation / Photographing Optical System> The observation / photographing optical system 30 includes a fundus observation optical system, a fundus photographing optical system, and an anterior ocular segment observation optical system. The fundus oculi observation optical system includes an objective lens 25, a photographing aperture 31 located in the vicinity of the aperture of the perforated mirror 22, a diopter correction lens (focusing lens) 32 movable in the optical axis direction, an imaging lens 33, and a flip-up mirror 34. Is provided. In the optical path in the reflection direction of the flip-up mirror 34, a dichroic mirror 37 having infrared light reflection / visible light transmission characteristics, a relay lens 36, and an observation two-dimensional imaging device 38 having sensitivity in the infrared region are disposed. A fundus image illuminated with an infrared light source is taken. The flip-up mirror 34 is inserted into the optical path when observing the fundus, and is retracted from the optical path by the insertion / removal mechanism 39 when photographing the fundus.

  The fundus photographing optical system shares the objective lens 25 and the optical system from the photographing aperture 31 to the imaging lens 33 with the fundus observation optical system. The fundus photographing optical system includes a photographing two-dimensional imaging element 35 having sensitivity in the visible range, and photographs a fundus image illuminated by the visible light source 14. The photographing aperture 31 is disposed at a position substantially conjugate with the pupil of the eye E with respect to the objective lens 25, and the focusing lens 32 is moved in the optical axis direction by a moving mechanism 49 including a motor.

  With the above configuration, when observing the fundus, the luminous flux emitted from the illumination light source 11 is once converged near the pupil of the eye E by the objective lens 25 and then diffused to illuminate the fundus. Reflected light from the fundus is obtained through an imaging element 38 via an objective lens 25, an aperture of a perforated mirror 22, a photographing aperture 31, a focusing lens 32, an imaging lens 33, a flip-up mirror 34, a dichroic mirror 37, and a relay lens 36. To form an image. At the time of photographing the fundus, the reflected light from the fundus illuminated by the photographing light source 14 passes through the objective lens 25, the aperture of the perforated mirror 22, the photographing aperture 31, the focusing lens 32, and the imaging lens 33, and the two-dimensional image sensor 35. To form an image.

  The anterior ocular segment observation optical system includes light sources 35 a and 35 b that emit infrared light, an objective lens 25, and an anterior ocular segment observation auxiliary lens 26 (hereinafter referred to as an auxiliary lens), from the perforated mirror 22 to the image sensor 38. This optical system is shared with the fundus observation optical system. The infrared light sources 35a and 35b are a pair of rectangular LEDs arranged symmetrically with the imaging optical axis L1 in between, and a finite index (patient) by a divergent light beam at a predetermined projection angle toward the cornea of the eye E. A rectangular index extending in a direction perpendicular to the eye) is projected. Thereby, the alignment state of the eye E and the imaging | photography part 3 in the three-dimensional direction is shown, and the whole anterior eye part is illuminated.

  The auxiliary lens 26 is inserted into and removed from the optical path by driving of the driving means 26a, and when the auxiliary lens 20 is placed on the optical axis L1, the anterior eye portion and the image sensor 38 are in a substantially conjugate relationship. That is, at the time of observing the anterior segment, the anterior segment captured by the image sensor 38 with the auxiliary lens 26 placed on the optical axis L1 is displayed on the monitor 8. On the other hand, at the time of fundus observation, the auxiliary lens 26 is retracted from the optical path by driving of the driving unit 26 a, the imaging element 38 and the fundus are in a substantially conjugate relationship, and the photographed fundus image is displayed on the monitor 8.

  In this way, in the configuration in which the visual target test of the eye is performed by projecting the test target on the fundus, the anterior ocular segment observation optical system and the fundus observation optical system are used in order to suppress the influence of noise light during the test and increase the test accuracy. A configuration in which and are used by switching is preferable. On the other hand, in this embodiment, when the anterior ocular segment observation optical system is switched to the fundus oculi observation optical system, alignment by the infrared light sources 35a and 35b used in the anterior ocular segment observation optical system cannot be performed. Therefore, when switching to the fundus oculi observation optical system, alignment is performed by the light source 27 placed near the aperture of the perforated mirror 22 and at the pupil conjugate position.

  For example, the point light source 27 is formed at the output end of the optical fiber, and the optical fiber guides light from a halogen lamp (not shown) to the perforated mirror 22. When the point light source 27 is turned on during fundus observation, the light beam from the point light source 27 is projected onto the cornea surface of the patient's eye via the objective lens 25, and the reflected light forms an image again via the objective lens 25. Then, based on the light reception result of the image of the point light source 27 by the image sensor 38, the photographing unit 3 is moved in the working distance direction so that the point light source 27 image is in focus, and alignment in the working distance direction is performed. In a state where the working distance between the patient's eye and the objective lens 25 is determined to be appropriate, the image of the point light source 27 and the fundus reflection image are formed in the conjugate plane.

  By the way, the proper working distance of alignment is designed in accordance with a standard corneal curvature and diopter (spherical power) such as a model eye. Therefore, in a patient eye having a specific corneal curvature and spherical power, the corneal curvature or spherical power The imaging position of the working distance of the point light source 27 image changes depending on the difference. As a result, when the size of the image of the perforated mirror 22 projected onto the patient's eye changes, flare may easily be mixed into the fundus image. Also, in visual function inspections such as visual field inspection, the field of view is narrowed by changing the imaging position of the working distance (the fundus image to be photographed is small), and the angle of view that can properly project the inspection target is small (The amount of light of the inspection target projected around the fundus image may be vignetted).

  Therefore, in the present invention, the corneal curvature and spherical power of the patient's eye are acquired in advance before fundus photography (observation) or visual field inspection, and a correction value for the proper working distance of alignment based on at least one of the acquired corneal curvature and spherical power. Ask for. More preferably, the correction value is obtained based on both the corneal curvature and the spherical curvature. Then, fundus photographing (observation) or eye examination is performed at an appropriate working distance after correction for each patient eye. A detailed description of the correction of the appropriate working distance will be described later.

<Focus Index Projection Optical System> The focus index projection optical system 40 is provided obliquely on the optical path of the infrared light source 41, the slit index plate 42, the two declination prisms 43 attached to the slit index plate 42, and the illumination optical system 10. Lever 45, spot mirror 44 attached to lever 45 and placed at the conjugate position of the fundus, rotary solenoid 46, and projection lens 47.
The lever 45 is placed on the optical axis, and the spot mirror 44 is attached to the tip of the lever 45 so as to be placed at a position avoiding the optical axis. As a result, during observation of the fundus, the reflected light from the spot mirror 44 is projected to a position on the fundus that avoids the optical axis L1.

  The luminous flux of the slit indicator plate 42 is separated by the deflection prism 43 and then reflected by the spot mirror 44 via the projection lens 47, and then passes through the relay lens 21, perforated mirror 22, dichroic mirror 24, and objective lens 25. Projected on. When the fundus is out of focus, the index images (focus indices S1, S2) on the slit index plate 42 are not conjugated to the fundus and are projected separately on the fundus. In this case, the focusing lens 32 and the focus target projection optical system 40 are moved in the optical axis direction in conjunction with the drive of the drive mechanism 49 based on the detection result of the separation state of the focus targets S1 and S2. On the other hand, when the fundus is in focus, the focus indices S1 and S2 are in conjugate positions with the fundus. When fundus photographing is performed in a focused state, the lever 45 is retracted from the optical path by the rotation of the shaft of the rotary solenoid 46.

  <Target Display Optical System> The target display optical system 70 shares the objective lens 25 to the flip-up mirror 34 of the observation / photographing optical system 20, and further includes a two-dimensional scanning projector 71, a screen 72, and a lens 73. Prepare. Although illustration is omitted here, the projector 71 includes a plurality of laser light sources that irradiate laser beams of predetermined colors (for example, red, green, and blue), a collimator lens that collimates each laser beam, and a collimator A dichroic mirror that collimates each laser beam that has been collimated by a lens, a lens that is moved on the optical axis to change the irradiation diameter of the laser beam that has been collimated, and a screen that displays the laser beam that has passed through the lens. The control unit 80 described later controls the lighting state of each light source and drive control of the scanning unit.

  By using a laser light source for the optotype presenting optical system 70, the size, shape, etc. of the optotype projected onto the fundus can be arbitrarily changed. Further, by combining laser beams emitted from laser light sources, not only monochrome but also color targets can be presented, and various types of visual function tests can be performed with one unit.

  In the present embodiment, an image (target) projected on the screen 72 placed at a position substantially conjugate with the fundus is imaged on the fundus via an intermediate optical system. Various visual targets may be formed by projecting light directly onto the fundus. Alternatively, a known liquid crystal display or the like may be used as the target presentation optical system 70, and the target may be formed by driving pixels.

  <Control System> The control unit 80 is connected to the above-described optical system and control system and performs various operation controls. The control unit 80 is connected to a memory 83 as a storage unit, and various programs are stored in advance. The memory 83 stores information on the diopter and corneal curvature of the acquired patient's eye.

  For example, the control unit 80 detects an alignment index from the anterior segment image captured by the image sensor 38. Further, the fundus image captured by the image sensor 35 is displayed on the monitor 8 and the fundus is focused based on the separation state of the focus index. Furthermore, in this embodiment, the diopter (spherical power) of the patient's eye is obtained from the position of the focusing lens 32 at the time of focusing. Further, the corneal curvature of the patient's eye is obtained from the inter-image distance of the working dot W that is the point light source 27 image detected by the image sensor 38. Then, based on at least one of the obtained spherical power and corneal curvature, a correction value for the appropriate working distance of the imaging unit 3 (objective lens 25) is obtained. Then, by determining an appropriate working distance for each patient eye based on the correction value, the working distance between the patient eye and the imaging unit 3 (objective lens 25) is appropriately set regardless of the difference in corneal curvature and spherical power of the patient eye. Adapted. In the following description, an example in which the correction value is obtained based on both the spherical power and the corneal curvature will be described.

An operation of the fundus imaging apparatus having the above configuration will be described. Here, an operation of photographing the fundus after performing an eye visual field inspection will be described.
When the visual field inspection mode is set by operating the control unit 7a, a visual field inspection screen is displayed on the monitor 8. The controller 80 drives the driving unit 26a to position the auxiliary lens 26 on the optical axis L2 and turn on the light sources 35a and 35b. When the patient looks into the inside of the apparatus from the imaging window 9 in this state, the anterior segment is illuminated and a rectangular alignment index is projected onto the cornea.

  On the other hand, the control unit 80 forms a fixation target on the screen 72 by driving control of the projector 71. That is, the output of the laser beam is adjusted according to the scanning angle of the scanning unit to form a high-luminance fixation target on a low-luminance background. Specifically, the output (luminance) of the laser beam from each light source is increased at the fixation target presentation position corresponding to the optical axis L1, and the output (luminance) of the laser beam is decreased at other background portions. As a result, a bright (high luminance) fixation target is formed on the screen 72 on a dark background (low luminance). The image (fixed target) formed on the screen 72 is projected from the lens 73, the flip-up mirror 34, and the relay lens 33 through the objective lens 25 onto the fundus of the patient at a substantially conjugate position with the screen 72.

  With the eye E guided by the fixation target, alignment using the anterior segment image is performed. FIG. 3 shows an example of an anterior segment image displayed on the monitor 8. When rectangular alignment indexes M1 and M2 appear on the anterior eye image F1, the control unit 80 aligns the imaging unit 3 and the eye E based on the light reception results of the alignment indexes M1 and M2.

  The control unit 80 moves the imaging unit 3 in the up, down, left, and right (XY) directions so that the intermediate position obtained from the alignment indices M1 and M2 and the pupil center obtained from the anterior segment image coincide. In addition, the imaging unit 3 is moved in the front-rear (Z) direction with respect to the eye E so that the alignment index M1 and M2 are spaced apart from each other, thereby aligning the working distance direction. For details of the alignment operation, refer to International Publication No. 2008/062527.

  If the control unit 80 determines that the alignment in the three-dimensional direction is within the alignment allowable range, the control unit 80 turns off the light sources 35a and 35b, turns the light source 11 and on by retracting the auxiliary lens 26 from the optical path. Then, the display on the monitor 8 is switched to the fundus image captured by the image sensor 38, and the fundus is focused using the focus index projection optical system 40.

  FIG. 4 shows an example of a fundus image displayed on the monitor 8. FIG. 4A shows a state where the fundus is out of focus, and FIG. 4B shows a state where the fundus is in focus. The control unit 80 specifies the positions of the focus indexes S1 and S2 based on the luminance distribution in the imaging range of the imaging element 38. Then, the distance (separation state) between the detected focus indices S1 and S2 is obtained, and focusing based on the detection result is performed.

  When the focus is not achieved as shown in FIG. 4A, the control unit 80 moves the focusing lens 32 on the optical axis L1 so that the focus targets S1 and S2 are matched. When the control unit 80 determines that the focus is appropriate, the focus adjustment is completed. The control unit 80 obtains the spherical power of the patient's eye from the position of the focusing lens 32 on the optical axis L in a focused state. The spherical power is obtained by associating the position of the focusing lens 32 (the driving amount of the moving mechanism 49) and the spherical power in the memory 83 in advance.

  When the fundus focusing is completed, the light source 27 is turned on and the working dot W is projected onto the patient's eye E. The control unit 80 detects the position of the working dot W by performing image processing on the fundus image captured by the image sensor 38, and aligns the working distance so that the focus of the pair of working dots W is the best. When the alignment is completed, the control unit 80 analyzes the imaging magnification of the working dot W from the interval (distance) between the pair of working dots W projected symmetrically via the optical axis, and obtains the corneal curvature of the patient's eye. . The distance between the bright spots of the working dots W can be obtained by a well-known center of gravity analysis or the like.

  When the spherical power and the corneal curvature of the patient's eye are obtained as described above, the control unit 80 obtains a correction value for the appropriate working distance between the patient's eye and the imaging unit 3 (objective lens 25). The correction value is obtained as follows.

  FIG. 5 is an explanatory diagram for calculating the correction value of the appropriate working distance. In FIG. 5, the corneal surface CS (corneal surface), the objective lens 25 (surface), the point light source image 27a, the focal point FP (focal point), the corneal apex p, the corneal curvature radius r, the working distance WD, the objective lens 25 A distance C from the point light source image 27a (constant), a distance s from the point light source image 27a to the corneal apex p, and a distance s1 from the corneal apex p to the reflected image 27b of the point light source 27.

  When the radius of curvature of the cornea of the patient's eye is r, the working distance WD at which the point light source image 27a is conjugate with the imaging optical system is expressed by Expression (1).

・・・式（１）
式（１）をテイラー展開すると作動距離ＷＤについて、式（２）に示される線形な関数を得る。ここで基準となるディオプターＤ０、基準となる角膜曲率半径ｒ０とする。

... Formula (1)
When the equation (1) is Taylor-expanded, the linear function shown in the equation (2) is obtained for the working distance WD. Here, a reference diopter D0 and a reference corneal curvature radius r0 are used.

・・・式（２）
一方、式（２）で決定される点光源像２７ａと撮像素子３８が共役となる作動距離ＷＤにおける像倍率βは、式（３）で示される。なおβは像倍率（点光源２７に対する点光源像２７ａの撮像素子３８上での倍率）、βiniは撮影光学系の倍率（点光源像２７ａが対物レンズ２５を通過して一旦結像したときの倍率）、ｆcameraは撮影光学系の焦点距離である。

... Formula (2)
On the other hand, the image magnification β at the working distance WD at which the point light source image 27a and the image sensor 38 determined by Expression (2) are conjugate is expressed by Expression (3). Β is an image magnification (magnification of the point light source image 27a on the image sensor 38 with respect to the point light source 27), βini is a magnification of the photographing optical system (when the point light source image 27a is once formed through the objective lens 25). (Magnification), fcamera is the focal length of the photographic optical system.

・・・式（３）
つまり式（３）から像倍率βは角膜曲率半径ｒに依存した関数（単項式）であることが分かる。

... Formula (3)
That is, it can be seen from the equation (3) that the image magnification β is a function (mononomial) depending on the corneal curvature radius r.

  Next, a correction value for obtaining an appropriate working distance is obtained. From the equation (2), the working distance WD at which the point light source image 27a is conjugate with the image sensor 38 can be determined. Therefore, the correction value ΔWD can be written as shown in Equation (4). Here, WD0 is an appropriate working distance for the reference eye (diopter D0, corneal curvature radius r0), and WD is an appropriate working distance for the patient's eye.

・・・式（４）
ここで角膜曲率半径ｒは式（３）の結像倍率βから求められる。またディオプターＤは視度補正検出で得られる。これらを用いて式（４）で求められた補正値ΔＷＤだけ、予め設定された輝点像２７ａの共役位置から作動距離を補正することで、眼底撮影及び視野検査に適切な作動距離となる。

... Formula (4)
Here, the corneal curvature radius r is obtained from the imaging magnification β in Expression (3). The diopter D is obtained by diopter correction detection. Using these, the working distance is corrected from the preset conjugate position of the bright spot image 27a by the correction value ΔWD obtained by the equation (4), so that the working distance is appropriate for fundus photographing and visual field inspection.

  Through the above processing, the corrected working distance between the patient's eye and the imaging unit 3 (objective lens 25) is determined. Further, when the patient's eye is displaced in the working distance direction during the visual field examination, the control unit 80 controls the driving unit 6 so that the working distance takes into account the above-described correction value ΔWD based on the detection result of the working dot W. To move the photographing unit 3. This makes it possible to perform visual function tests and the like while maintaining an appropriate working distance.

Next, the operation principle of tracking for correcting the position of the inspection target presented by the target presentation optical system 70 following the movement or rotation of the eyeball will be described. FIG. 6 is an explanatory diagram of the tracking operation principle, in which a fundus image F2 and a fixation target presentation position T are displayed.
First, the examiner designates feature points (regions) such as the nipple and blood vessels on the fundus image F2 by operating the control unit 7a while confirming the fundus image F2 displayed on the monitor 8. The feature portion may be automatically extracted by image processing.

  The control unit 80 stores the coordinates of the feature points and a predetermined range centered on the feature points in the memory 83 as a reference area S based on the input signal from the control unit 7a, and a frame indicating the reference area S on the monitor 8. Is displayed. Then, the control unit 80 obtains information (feature information for determining the feature portion by image processing) such as the shape of the feature portion and the luminance distribution by image processing in the reference area S, and stores it in the memory 83.

  When the movement amount of the feature point (reference area S) on the monitor 8 is detected by the control unit 80, the target (inspection target) projected on the fundus following the movement (movement) of the eye E is detected. Correction for making the presentation position coincide with the selected position of the monitor 8 is performed. As a result, the influence of the rotation of the eye E that occurs during the examination is suppressed, the examination target is correctly projected at the intended position of the fundus, and the visual function examination can be performed with high accuracy.

In a state where the tracking is performed as described above, the control unit 80 causes a predetermined examination target to be presented at each measurement point of the fundus according to the visual field measurement program stored in the memory 83 in advance.
In this embodiment, the control unit 80 temporarily stops the tracking process at a predetermined time interval and switches to the alignment process using the working dots W in order to correct the working distance change that occurs during the visual field inspection. This makes it possible to continue the inspection while maintaining an appropriate working distance in the visual function inspection that takes time.

  Note that switching between tracking and alignment by working dots W (correction of the working distance) may be controlled in conjunction with the presentation of the inspection target. For example, the tracking process may be temporarily stopped every time the patient's response to the test target is input (or every time the response is input a predetermined number of times), and the alignment using the working dots W may be executed. In addition to this, when a wavelength having a band different from the wavelength of the infrared light source 11 or the visual target presenting optical system 70 is used as the point light source 27 (however, a wavelength band detectable by the image sensor 38), tracking and alignment are performed. Processing can be performed simultaneously.

  The control unit 80 controls the projector 71 to change the presentation position of the test target at random and adjusts the output of the light source of the projector 71 to change the brightness of the target. Further, correction is made for changes in the working distance of the apparatus at a predetermined timing.

  In a state where an appropriate working distance is maintained as described above, the control unit 80 causes a predetermined examination target to be presented at each measurement point of the fundus according to the visual field measurement program stored in the memory 83 in advance. The control unit 80 switches the presentation position of the inspection target at random by driving the projector 71 and adjusts the output of the light source of the projector 71 to change the luminance of the target.

  On the other hand, the patient presses the response button 7b when the test target can be recognized while maintaining fixation. Based on the input signal, the control unit 80 stores the luminance of the examination target in the memory 83 as response information of sensitivity that can be recognized by the patient at the measurement point. When there is no response from the patient, the control unit 80 stores the luminance of the test target in the memory 83 as response information of sensitivity that the patient cannot recognize at the measurement point.

  When the sensitivity measurement at all measurement points is completed, the control unit 80 causes the monitor 8 to display the inspection result of the visual function of the eye, as shown in the example of the distribution diagram of the visual function sensitivity of the eye in FIG. The control unit 80 causes the monitor 8 to display sensitivity distribution states for all measurement points as a schematic diagram. In FIG. 7, the luminance attenuation value of the presented visual target is used for displaying the sensitivity distribution, and the sensitivity distribution is displayed by the difference from the highest luminance. That is, the larger the numerical value displayed on the monitor 8, the higher is the sensitivity at that part.

  When the perimeter side is completed, the control unit 80 turns off the infrared light source 11 and turns on the visible light source 14. Then, the flip-up mirror 34 is retracted from the optical path by driving the insertion / removal mechanism 39. Reflected light from the fundus that is illuminated by the visible light is received by the image sensor 35 through the fundus photographing optical system.

  In the above description, an example in which the configuration of the present invention is applied to a fundus imaging apparatus that projects a test target on each measurement point on the fundus (retina) and performs a visual function test of the eye based on the response of the patient's eye has been described. . In addition to this, the fundus observation and photographing can be performed more suitably by applying the configuration of the present invention to a well-known fundus photographing apparatus for observing or photographing the fundus of a patient such as a fundus camera.

1 is a schematic external view of a fundus photographing apparatus. It is explanatory drawing of an optical system and a control system. It is an example of the anterior segment image displayed on a monitor. It is an example of the fundus oculi image displayed on the monitor. It is explanatory drawing about the correction value calculation of a suitable working distance. It is explanatory drawing of the operation | movement principle of tracking. It is an example of the test result of the visual function sensitivity of eyes.

DESCRIPTION OF SYMBOLS 1 Fundus photographing apparatus 8 Monitor 10 Illumination optical system 25 Objective lens 27 Light source 30 Observation / photographing optical system 32 Diopter correction lens 35 Imaging element 40 Focus index projection optical system 70 Visual target presentation optical system 80 Control unit

Claims (3)

In a fundus imaging apparatus comprising an imaging unit that images the fundus of a patient's eye and a drive unit that moves the imaging unit relative to the patient's eye,
The photographing unit
An illumination optical system for illuminating the fundus;
An alignment means having a light source for projecting an alignment index onto the cornea of the patient's eye via an objective lens;
A focusing means having a diopter correction lens and focusing the fundus;
An imaging optical system including an imaging element that images the reflected image of the alignment index and the reflected image of the fundus illuminated by the illumination optical system via the objective lens;
An eye information acquisition unit having at least one of a corneal shape acquisition unit for obtaining a corneal curvature of a patient's eye from a reflection image of the alignment index and a diopter information acquisition unit for obtaining a spherical power based on diopter correction by the diopter correction lens;
Working distance acquisition means for obtaining a correction value for an appropriate working distance of the imaging unit with respect to the patient's eye based on at least one of corneal curvature and spherical power obtained by the eye information acquisition unit;
The fundus imaging apparatus, wherein the driving unit moves the imaging unit with respect to the patient's eye based on the correction value acquired by the working distance acquisition unit. The fundus imaging apparatus according to claim 1,
The fundus imaging apparatus, wherein the corneal shape acquisition unit obtains the corneal curvature based on an imaging magnification of a reflection image of the alignment index imaged by the imaging element. The fundus photographing apparatus according to claim 2,
The alignment means has a plurality of light sources arranged symmetrically with respect to the optical axis,
The fundus imaging apparatus, wherein the corneal shape acquisition unit obtains an imaging magnification of a reflected image of the alignment index from an interval between the plurality of alignment indexes captured by the imaging element.

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