JP5199008B2 - Fundus camera - Google Patents

Description

  The present invention relates to a fundus camera that photographs the fundus of a subject's eye.

  Conventional fundus cameras generally perform fine adjustment of the shooting position by moving the shooting part using a joystick while referring to corneal bright spots (so-called working dots) that can be observed together with the fundus observation image. is there.

Such an apparatus includes an alignment detection system that detects a relative position between the subject's eye and the imaging unit, and a drive mechanism that moves the imaging unit by electric drive, and is based on a detection result from the alignment detection system. It is known that an alignment error is detected and automatic alignment is activated when the alignment error exceeds a predetermined allowable alignment range (see Patent Document 1). In this case, the imaging position can be finely adjusted by the examiner by setting the alignment allowable range wider. The fundus camera that performs such automatic alignment control is convenient for the examiner because the photographing position is automatically corrected when the subject's eye moves greatly and the working dot disappears.
JP 2005-160550 A

  By the way, when the subject's eye is an intense hyperopic eye, the imaging magnification of the fundus image is reduced in focusing, so that the flare cannot be completely removed by the optical mask (or electronic mask), and the fundus observation is displayed on the display monitor. Flare may occur around the image. However, when taking an image of an intense hyperopic eye using the above automatic alignment control, when the examiner adjusts the shooting position to avoid flare, the alignment deviation exceeds the allowable range and the automatic alignment is activated. Therefore, there are cases where alignment cannot be performed to a good photographing position.

  In view of the above problems, an object of the present invention is to provide a fundus camera that can suitably perform fine adjustment of a photographing position.

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

(1) an observation optical system for observing the fundus of a subject's eye, which has a focus lens movably arranged in the optical axis direction and an image sensor;
A photographing optical system for photographing the fundus;
An imaging unit in which the observation optical system and the imaging optical system are disposed;
A moving mechanism unit that includes an electric motor and moves the imaging unit relative to the subject's eye;
A monitor,
A display control unit for processing an output signal from the image sensor and displaying an observation image of the fundus on the monitor;
An alignment detection optical system having a light receiving element for detecting misalignment of the imaging unit with respect to the subject's eye;
A movement control unit that detects an alignment deviation of the imaging unit with respect to the eye of the subject based on an output signal from the light receiving element, and outputs a drive signal to the moving mechanism unit based on the detection result;
In a fundus camera having
The movement control unit sets a first alignment allowable range when the focus lens is in the 0D position, and movement information of the focus lens when the focus lens is moved in the plus direction from the 0D position. And setting the second alignment tolerance range wider than the first alignment tolerance range, and driving the moving mechanism unit so that the detected alignment deviation falls within the set alignment tolerance range. To do.
(2) In the fundus camera of (1), when the second alignment allowable range is set, the movement control unit sets the second alignment allowable range based on a movement amount of the focus lens with respect to the 0D position. It is characterized by changing the size.
(3) In the fundus camera of (2), when the focus lens is moved in the minus direction from the 0D position, the movement control unit is configured to perform the first alignment allowable range based on movement information of the focus lens. A narrower third alignment allowable range is set.

  According to the present invention, fine adjustment of the photographing position can be suitably performed.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is an external configuration diagram of a fundus camera according to the present embodiment.

  The fundus camera has a base 1, a moving base 2 provided so as to be movable in the left-right direction (X direction) and the front and rear (working distance) direction (Z direction) with respect to the base 1. An imaging unit (device main body) 3 that is provided so as to be movable in the left-right direction, the up-down direction (Y direction), and the front-rear direction and houses an optical system described later, and a base 1 for supporting the face of the subject And a face support unit 5 provided.

  Further, the present apparatus is provided with an automatic movement mechanism that has an electric motor and moves the imaging unit 3 relative to the subject's eye. That is, the imaging unit 3 is moved in the XYZ direction (three-dimensional direction) with respect to the subject's eye by the electric XYZ driving unit 6 provided on the movable table 2.

  Further, the present apparatus is provided with a manual movement mechanism for moving the imaging unit 3 relative to the subject's eye by operating the operation member (joystick 4). That is, when the joystick 4 is tilted, the movable table 2 is slid in the XZ direction on the base 1 by the sliding mechanism. When the rotary knob 4a is rotated, the XYZ driving unit 6 is driven and the photographing unit 3 is moved in the Y direction. Note that a monitor 8 that displays a fundus observation image, a fundus image, an anterior eye observation image, and the like is provided on the examiner side of the imaging unit 3.

  FIG. 2 is a schematic configuration diagram of an optical system and a control system housed in the photographing unit 3. The imaging unit 3 includes an imaging optical system for imaging the fundus of the subject's eye E and a fundus observation optical system for observing the fundus. In FIG. 2, the optical system includes an illumination optical system 10, a fundus observation / photographing optical system 30, an alignment index projection optical system 50, an anterior ocular segment observation optical system 60, and a fixation target presenting optical system 70. , And is divided into major parts.

  <Illumination Optical System> The illumination optical system 10 includes a fundus observation illumination optical system and a photographing illumination optical system. The photographing illumination optical system includes a photographing illumination light source 14 such as a flash lamp, a condenser lens 15, a ring slit 17, a relay lens 18, a total reflection mirror 19, a black spot plate 20 having a black spot at the center, and a relay. A lens 21, a perforated mirror 22, and an objective lens 25 are provided.

  The fundus observation illumination optical system includes a fundus observation illumination light source 11 such as a halogen lamp, an infrared transmission filter 12 that transmits infrared light having a wavelength of 750 nm or more, a condenser lens 13, a condenser lens 13, and a ring slit 17. And the optical system from the ring slit 17 to the objective lens 25. The dichroic mirror 16 has a characteristic of reflecting the light from the light source 11 and transmitting the light from the light source 14.

  <Fundus observation / fundus imaging optical system> The fundus observation / imaging optical system 30 includes an objective lens 25, an imaging diaphragm 31 located near the aperture of the perforated mirror 22, and a focusing lens 32 movable in the optical axis direction. The imaging lens 33 and a total reflection mirror 34 that is moved out and out of the optical path by the insertion / removal mechanism 39 during fundus photographing. The photographing optical system and the fundus observation optical system are connected from the objective lens 25 to the imaging lens 33. Share the optical system. The imaging aperture 31 is disposed at a position substantially conjugate with the pupil of the subject's eye E with respect to the objective lens 25. The focusing lens 32 is moved in the optical axis direction by a moving mechanism 49 including a motor or the like. In the optical path in the passing direction of the mirror 34, a two-dimensional imaging element 35 for imaging having sensitivity in the visible range is arranged. On the optical path in the reflection direction of the mirror 34, a dichroic mirror 37 having infrared light reflection and visible light transmission characteristics, a relay lens 36, and an observation two-dimensional imaging device 38 having sensitivity in the infrared region are arranged. ing.

  In addition, a dichroic mirror (wavelength selection mirror) 24 is disposed between the objective lens 25 and the perforated mirror 22 as an optical path branching member that goes out and out of the optical path by the insertion / removal mechanism 66 during fundus photography. The dichroic mirror 24 has a characteristic of reflecting the light of the alignment index projection optical system 50 and the light of the anterior ocular segment observation illumination light source 58 and transmitting the light of the fundus observation illumination light source 11 that has passed through the filter 12.

  The light beam emitted from the light source 11 is converted into an infrared light beam by the filter 12, passes through the condenser lens 13, is reflected by the dichroic mirror 16, and illuminates the ring slit 17. The light that has passed through the ring slit 17 passes through the relay lens 18, is reflected by the mirror 19, passes through the black spot plate 20 and the relay lens 21, and is reflected by the perforated mirror 22. The light reflected by the perforated mirror 22 is transmitted through the dichroic mirror 24, converged once in the vicinity of the pupil of the subject eye E by the objective lens 25, and then diffused to illuminate the fundus of the subject eye E.

  The reflected light beam from the fundus passes through the objective lens 25, the dichroic mirror 24, the aperture of the perforated mirror 22, the photographing aperture 31, the focusing lens 32, and the imaging lens 33, and is reflected by the flip-up mirror 34 and the dichroic mirror 37. Then, the light passes through the relay lens 36 and forms an image on the image sensor 38. The output of the image sensor 38 is input to the controller 80, and the fundus observation image of the eye E of the subject imaged by the image sensor 38 is displayed on the monitor 8 as shown in FIG.

  The light beam emitted from the light source 14 passes through the condenser lens 15 and the dichroic mirror 16 and illuminates the fundus through the same optical path as the illumination light for fundus observation. The reflected light beam from the fundus 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 forms an image on the image sensor 35.

  <Alignment Index Projection Optical System> The alignment index projection optical system 50 that projects the alignment index beam is 45 degrees concentrically about the photographic optical axis L1 as shown in the diagram within the dotted line A in the upper left of FIG. A plurality of infrared light sources that emit infrared light having a central wavelength of 940 nm are arranged at intervals. The alignment index projection optical system 50 includes a first index projection optical system having an infrared light source 51 and a collimating lens 52 arranged symmetrically with respect to a vertical plane passing through the photographing optical axis L1, and a first index projection optical system. And a second index projection optical system having six infrared light sources 53 arranged at positions different from the system. The first index projection optical system projects an infinite index on the cornea of the subject's eye E from the left and right directions, and the second index projection optical system projects an index of finite distance on the cornea of the subject's eye E in the vertical direction. Or project from an oblique direction. In FIG. 2, only the first index projection optical system and a part of the second index projection optical system are shown for convenience.

  <Anterior Eye Observation Optical System> An anterior eye observation (imaging) optical system 60 that images the anterior eye part of the subject's eye E is provided with a field lens 61 and a total reflection mirror in the optical path in the reflection direction of the dichroic mirror 24. 62, a diaphragm 63, a relay lens 64, and a two-dimensional imaging element (light receiving element) 65 having infrared sensitivity. The imaging element 65 also serves as an imaging means for detecting an alignment index, and an anterior eye image and an alignment index image illuminated by a light source 58 that emits infrared light having a center wavelength of 940 nm are captured. The anterior segment image passes through the objective lens 25, is reflected by the dichroic mirror 24, passes through the field lens 61, is reflected by the mirror 62, passes through the diaphragm 63 and the relay lens 64, and forms an image on the image sensor 65. To do. Further, the light beam emitted from the light source of the alignment index projection optical system 50 is projected onto the cornea, and the cornea reflection image is formed on the image sensor 65 through the objective lens 25 to the relay lens 64. The output of the image sensor 65 is input to the control unit 80, and the anterior eye image captured by the image sensor 65 is displayed on the monitor 8 as shown in FIG. Note that the anterior ocular segment observation optical system 60 also serves as an alignment detection optical system for detecting misalignment of the imaging unit 3 with respect to the subject eye E.

  <Fixation target presentation optical system> A fixation target presentation optical system 70 for presenting a fixation target for fixing the eye E of the subject includes a red light source 74, a light shielding plate 71 having an opening formed therein, A relay lens 75, and shares the optical path of the observation optical system 30 from the flip-up mirror 34 to the objective lens 25 via the dichroic mirror 37. Note that the fixation target presentation optical system 70 has a configuration (not shown) in which the fixation target presentation position is variable (not shown), and can guide the subject's eye E in a predetermined line-of-sight direction (for example, a special feature). (See Kaikai 2005-95450). Therefore, it is possible to perform peripheral shooting.

  In this case, the light shielding plate 71 is illuminated from behind by the light source 74 to become a fixation target (fixation lamp). The light beam from the fixation target passes through the relay lens 75 and the dichroic mirror 37, and is reflected by the flip-up mirror 34, and forms the imaging lens 33, the focusing lens 32, the perforated mirror 22, the dichroic mirror 24, and the objective lens. 25 passes through 25 and is focused on the fundus of the subject's eye, and the subject visually recognizes the light flux from the opening 71 as a fixation target.

  <Control System> The image sensors 65, 38 and 35 are connected to the control unit 80. The control unit 80 detects an alignment index from the anterior segment image captured by the image sensor 65. The control unit 80 is connected to the monitor 8 and controls the display image (for example, the output signal from the image sensor 38 is processed to display the fundus observation image on the monitor 8). In addition, the control unit 80 includes an XYZ driving unit 6, a moving mechanism 49, an insertion / removal mechanism 39, a rotary knob 4a, a photographing switch 4b, a switch unit 84 having various switches, a memory 85 as a storage unit, A light source or the like is connected.

  Here, the control unit 80 detects the misalignment of the imaging unit 3 with respect to the subject's eye E based on the light reception signal output from the imaging element (light receiving element) 65, and based on the detection result, the XYZ driving unit 6. A drive signal is output to.

  Further, in the present embodiment, since a light receiving element (imaging element 65) that can acquire an anterior segment image of the subject's eye E (capable of imaging at least the pupil region of the subject's eye) is used, alignment is possible. The range is set wider than in the case where an alignment shift is detected by capturing a fundus image.

  Further, as shown in the anterior ocular segment observation image of FIG. 3 and the fundus oculi observation image of FIG. 4, the control unit 80 electronically places a reticle (alignment mark) LT serving as an alignment reference at a predetermined position on the screen of the display monitor 8. The alignment index A1 is electronically formed on the screen of the display monitor 8 so that the relative distance between the alignment index A1 and the reticle LT is changed based on the detected alignment deviation in the XY direction. To display. In addition, the control unit 80 displays an indicator G that indicates the misalignment in the Z direction, and increases or decreases the number of the indicators G based on the detected misalignment in the Z direction.

  In the above configuration, the moving position of the focusing lens 32 and the imaging magnification of the fundus image are in a pair relationship. That is, when the position of the focusing lens 32 is changed, the imaging magnification of the fundus image formed on the image sensor 35 (image sensor 38) changes. In this case, when the focusing lens 32 arranged at a position corresponding to 0D is moved in the plus direction, the imaging magnification of the fundus image is reduced as compared to 0D. Further, when the focusing lens 32 arranged at a position corresponding to 0D is moved in the minus direction, the imaging magnification of the fundus image is increased as compared to 0D.

  The operation of the fundus camera having the above configuration will be described. First, the face of the subject is supported by the face support unit 5. In the initial stage, the dichroic mirror 24 is inserted in the optical path of the photographic optical system 30, and the anterior segment image captured by the image sensor 65 is displayed on the monitor 8. The examiner moves the imaging unit 3 left and right and up and down by operating the joystick 4 so that the anterior segment image appears on the monitor 8. When the anterior segment image appears on the monitor 8, as shown in FIG. 3, eight index images Ma to Mh appear.

  As described above, when the alignment index image projected on the cornea is detected by the image sensor 65, the control unit 80 starts automatic alignment control. The control unit 80 detects the alignment deviation amount Δd of the apparatus main body 3 with respect to the subject's eye E based on the imaging signal from the imaging element 65. More specifically, the XY coordinate of the center of the ring shape formed by the index images Ma to Mh projected in a ring shape is detected as the substantially corneal apex position Mo, and is set in the XY direction set on the image sensor 65 in advance. A deviation amount Δd between the alignment reference position O1 (for example, the intersection of the imaging surface of the imaging element 65 and the photographing optical axis L1) and the corneal apex position coordinates is obtained (see FIG. 6).

  Then, the control unit 80 operates automatic alignment by drive control of the XYZ drive unit 6 so that the deviation amount Δd falls within the allowable range A for completion of alignment. Whether or not the alignment amount in the XY direction is appropriate is determined depending on whether or not the deviation amount Δd falls within the allowable range A for completion of alignment and the time continues for a certain time (for example, 10 frames of image processing or 0.3 second). .

  Further, the control unit 80 obtains the alignment deviation amount in the Z direction by comparing the interval between the index images Ma and Me at infinity detected as described above and the interval between the index images Mh and Mf at finite distance. . In this case, when the apparatus main body 3 is displaced in the working distance direction, the control unit 80 changes the interval between the index images Mh and Mf while the interval between the infinity indexes Ma and Me hardly changes. Thus, the amount of alignment deviation in the working distance direction with respect to the subject's eye E is obtained (for details, refer to JP-A-6-46999).

  Similarly, in the Z direction, the control unit 80 obtains a deviation amount with respect to the alignment reference position O1 (z) in the Z direction, and the deviation amount falls within a predetermined alignment allowable range A. The automatic alignment by drive control 6 is activated. The control unit 80 determines whether or not the alignment in the Z direction is appropriate depending on whether or not the amount of deviation in the Z direction is within an allowable range for completion of alignment for a certain period of time.

  When the alignment operation in the XYZ directions satisfies the alignment completion condition by the alignment operation described above, the control unit 80 determines that the alignment in the XYZ directions is matched, and stops the operation of the driving unit 6.

  When it is determined that the predetermined alignment condition is satisfied, the control unit 80 switches the display image on the monitor 8 from the anterior ocular segment image to the fundus oculi observation image (see FIG. 4). When the observation screen switching signal is issued in this way, the control unit 80 switches the alignment allowable range for operating the automatic alignment from the allowable range A to the allowable range C, and whether the alignment deviation amount is within the allowable range C. To determine whether automatic alignment is possible. The allowable range C is set wider than the allowable range A.

  The examiner adjusts the focus of the fundus using a focus adjustment switch provided in the switch unit 84. In this case, the focusing lens 32 is disposed at a position corresponding to 0D (diopter) as an initial position, and when the focus adjustment switch is operated by the examiner, the control unit 80 moves the moving mechanism based on the operation signal. The drive motor 49 is driven to move the focusing lens 32 in the optical axis direction. As an optical system for focus adjustment, an index projection optical system for projecting a focus index on the fundus of the eye to be examined, and an index detection optical system having a light receiving element and detecting the focus index projected on the fundus You may make it provide. For example, the control unit 80 detects a focus state with respect to the fundus based on an output signal from the light receiving element, and controls driving of the moving mechanism 49 so that the fundus is in focus (autofocus control). Further, an output signal from the light receiving element may be displayed on the monitor 8.

  During the focus adjustment as described above, the control unit 80 detects the position of the focusing lens 32 moved in the optical axis direction, and changes the size of the alignment allowable range C based on the detection result.

  As a sensor for detecting the position of the focusing lens 32, for example, a pulse motor is used as the drive motor of the moving mechanism 49, and a drive signal supplied to the pulse motor with reference to an origin position set by a photosensor or the like ( A configuration in which the control unit 80 measures the number of pulses) is conceivable. In this case, in addition to the above configuration, the movement information of the focusing lens 32 may be detected using various position detection mechanisms such as a potentiometer.

  FIG. 5 is a flowchart for explaining the flow of changing the alignment allowable range according to the position of the focusing lens 32. FIG. 6 is a diagram for explaining the change of the alignment allowable range according to the position of the focusing lens 32.

  When the focusing lens 32 is at the 0D position, the control unit 80 sets the allowable alignment range C to the first allowable alignment range C1 (see FIG. 6A). The permissible range C1 is based on a normal eye and allows fine adjustment of the photographing position by the examiner. Further, the allowable range C1 is difficult to finely adjust when the subject's eye E moves greatly or the alignment deviation becomes too large. It is set so that the shooting position can be corrected. For example, the allowable range C1 is set to an area having a radius of 1.5 mm with the alignment reference position O1 as the center.

  In addition, when the focusing lens 32 is moved in the plus direction (the direction corresponding to the hyperopic eye) from the 0D position, the control unit 80 determines the second alignment range wider than the first alignment allowable range C1 based on the movement information of the focusing lens 32. 2 is set (see FIG. 6B).

  In addition, when the focusing lens 32 is moved in the minus direction (direction corresponding to the nearsighted eye) from the 0D position, the control unit 80 determines the third narrower than the first alignment allowable range C1 based on the movement information of the focusing lens 32. An alignment allowable range C3 is set (see FIG. 6C). In this case, it is preferable to change the alignment tolerance in the Z direction as well as change the alignment tolerance in the XY directions.

  More specifically, when the focusing lens 32 is moved from a position corresponding to 0D and the second alignment allowable range C2 or the third alignment allowable range C3 is set, the control unit 80 moves the focus lens with respect to the 0D position. The width of the second alignment allowable range C2 or the third alignment allowable range C3 is changed based on the movement amount.

  FIG. 7 is a diagram when the width of the second allowable alignment range C2 or the allowable third alignment range C3 is changed based on the amount of movement of the focus lens with respect to the 0D position. In this case, the control unit 80 increases the allowable range C2 continuously or stepwise as the position of the focusing lens 32 moves in the plus direction from the position corresponding to 0D. Thereby, in focusing, the range in which fine adjustment of the alignment can be performed by the examiner increases as the distance of the subject's eye E increases.

  Further, the control unit 80 decreases the allowable range C3 continuously or stepwise as the position of the focusing lens 32 moves in the minus direction from the position corresponding to 0D. Thereby, in focusing, the range in which the fine adjustment of the alignment can be performed by the examiner is reduced as the myopia of the subject eye E becomes stronger.

  When the allowable ranges C2 and C3 are set as described above, the degree of occurrence of flare due to the change in the imaging magnification due to the change in the position of the focusing lens 32 is obtained in advance through experiments or the like, and the flare is manually determined by the examiner. It is necessary to set an alignment allowable range so that an image with a small amount can be observed. In this case, the smaller the imaging magnification is, the higher the occurrence rate of flare is. Therefore, it is necessary to secure a wider alignment allowable range. Further, since the flare generation rate decreases as the imaging magnification increases, flare can be avoided even in a narrower alignment tolerance range.

  When the allowable range C (C1, C2, C3) is set as described above, the control unit 80 operates automatic alignment using the alignment allowable range set as described above. That is, when the detected misalignment is outside the predetermined allowable alignment range C (C1, C2, C3), the control unit 80 causes the alignment error to fall within the allowable range C (C1, C2, C3). The drive unit 6 is driven. In addition, when the detected misalignment is within a predetermined alignment allowable range C (C1, C2, C3), the control unit 80 does not drive the XYZ drive unit 6 (drive prohibition). That is, when the focusing lens 32 is in the plus position, the control unit 80 does not drive the XYZ driving unit 6 until the alignment deviation detected exceeds the allowable alignment range C1, but exceeds the allowable alignment range C2.

  When the allowable range is set wide as described above, the examiner performs fine adjustment of the photographing position by manual operation of the joystick 4 while viewing the fundus image displayed on the monitor 8, and the desired fundus image is displayed. Then, the photographing switch 4b is pushed to photograph a visible fundus image.

  With the configuration as described above, when the focusing lens 32 is positioned on the plus side of the reference position, the imaging magnification of the fundus image is reduced, and flare is likely to occur around the fundus image. Since the examiner can perform fine adjustment of manual alignment over a wide range, even if the subject's eye E is an intense hyperopic eye, a good fundus image can be obtained. When the subject's eye E moves greatly, automatic alignment is activated, so that the examiner can concentrate on fine adjustment of the imaging position.

  Further, when the focusing lens 32 is on the negative side of the reference position, the imaging magnification of the fundus image is increased, and when the flare hardly occurs around the fundus image, the allowable alignment range is narrow. Because it is done, unnecessary operations can be reduced. When the subject's eye E moves greatly, automatic alignment is activated, so that the examiner can concentrate on fine adjustment of the imaging position.

  In the above configuration, the size of the allowable alignment range is changed even in the minus direction from the reference position. However, the allowable alignment range may be changed only in the positive direction from the reference position.

  In the above description, the width of the second or third alignment allowable range is changed based on the amount of movement of the focusing lens 32 with respect to the 0D position. However, the present invention is not limited to this. For example, when the focusing lens 32 is placed between the 0D position and a predetermined position on the plus side (for example, + 6D position), the control unit 80 sets the first alignment allowable range C1. When the focusing lens 32 is placed in the plus direction from the predetermined position on the plus side, a second allowable alignment range C2 wider than the allowable range C1 may be set. The same control is possible for the minus direction.

  In the above description, the alignment deviation is detected using the alignment index image formed on the image sensor 65. However, the alignment deviation is detected using the anterior segment image imaged on the image sensor 65. You may make it detect. For example, the pupil center position in the anterior segment image is detected by image processing based on the light reception signal from the image sensor 65, and the alignment deviation is obtained from the positional relationship between the detected pupil center position and the alignment reference position O1. Can be considered.

It is an external appearance block diagram of the fundus camera which concerns on this embodiment. It is a schematic block diagram of the optical system and control system accommodated in an imaging | photography part. It is a figure which shows an example of an anterior ocular segment observation screen. It is a figure which shows an example of a fundus observation screen. It is a flowchart explaining the flow of the alignment allowable range change according to the position of a focusing lens. It is a figure explaining the change of the alignment tolerance | permissible_range according to the position of the focusing lens. It is a figure when changing the width | variety of the 2nd alignment tolerance | permissible_range C2 or the 3rd alignment tolerance | permissible_range based on the moving amount | distance of the focus lens with respect to 0D position.

Explanation of symbols

3 Imaging unit 6 XYZ driving unit 8 Monitor 30 Fundus observation / imaging optical system 32 Focusing lens 35 Two-dimensional imaging device 60 Anterior ocular segment observation optical system 65 Imaging device 80 Control unit

Claims (3)

An observation optical system for observing the fundus of the subject's eye, having a focus lens movably arranged in the optical axis direction and an image sensor;
A photographing optical system for photographing the fundus;
An imaging unit in which the observation optical system and the imaging optical system are disposed;
A moving mechanism unit that includes an electric motor and moves the imaging unit relative to the subject's eye;
A monitor,
A display control unit for processing an output signal from the image sensor and displaying an observation image of the fundus on the monitor;
An alignment detection optical system having a light receiving element for detecting misalignment of the imaging unit with respect to the subject's eye;
A movement control unit that detects an alignment deviation of the imaging unit with respect to the eye of the subject based on an output signal from the light receiving element, and outputs a drive signal to the moving mechanism unit based on the detection result;
In a fundus camera having
The movement control unit sets a first alignment allowable range when the focus lens is in the 0D position, and movement information of the focus lens when the focus lens is moved in the plus direction from the 0D position. And setting the second alignment tolerance range wider than the first alignment tolerance range, and driving the moving mechanism unit so that the detected alignment deviation falls within the set alignment tolerance range. Fundus camera. 2. The fundus camera according to claim 1, wherein when the second alignment allowable range is set, the movement control unit increases the width of the second alignment allowable range based on a movement amount of the focus lens with respect to the 0D position. Fundus camera characterized by changing. 3. The fundus camera according to claim 2, wherein when the focus lens is moved in the minus direction from the 0D position, the movement control unit is configured to have a first narrower range than the first alignment allowable range based on movement information of the focus lens. The fundus camera is characterized in that the alignment allowable range of 3 is set.