JP2013244363A - Fundus photographing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fundus photographing apparatus which maintains alignment of an eye and a photographing unit by suppressing the generation of a flare.SOLUTION: A fundus photographing apparatus includes: a photographing unit which comprises a fundus illuminating optical system illuminating the fundus of the eye, a visual target presentation optical system for projecting a fixation target for guiding a visual line and an examination target for performing a visual function examination of the retina onto the fundus of the eye, and a fundus photographing optical system comprising an imaging element for obtaining an fundus photographing image by photographing the fundus of the eye; an alignment means for aligning the photographing unit and the eye on the basis of a predetermined alignment criterion; and a flare extraction means for extracting a flare included in the fundus photographing image taken by the imaging element, by image processing. When the flare is extracted by the flare extraction means, the alignment means moves the photographing unit in an operation distance direction getting away from a patient's eye, and restrains the flare from being generated by displacement between the eye and the photographing unit.

Description

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

  In a fundus imaging device in which fundus observation or imaging is performed with the fundus in focus, a test target is projected onto each measurement point on the fundus (retina), and the visual function test of the eye based on the response of the patient's eye Is known (see, for example, Patent Document 1).

  In addition, in the fundus imaging device, in order to suppress the occurrence of flare caused by eye movement or rotation that occurs during the examination and to suitably perform the visual function examination of the eye, it detects the light amount of a plurality of parts of the fundus image obtained by the imaging device. Thus, there has been proposed one that avoids the occurrence of flare by moving the imaging unit in the vertical and horizontal directions based on the detection result (see Patent Document 2).

Japanese Patent Laid-Open No. 2003-235800 Japanese Patent No. 9-070388

  However, the situation in which flare is likely to occur does not change by simply moving the imaging unit in the direction perpendicular to the optical axis (up, down, left and right) as in Patent Document 2. For this reason, in the case where the examination of the patient requires time like the fundus imaging apparatus shown in Patent Document 1, the flare detection and the movement of the imaging unit accompanying the shift in the positional relationship between the eye and the imaging unit are repeated. There is a risk of affecting the stable operation of the device.

  In view of the above-described problems of the prior art, an object of the present invention is to provide a fundus imaging apparatus in which the alignment between the eye and the imaging unit is suitably maintained.

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

(1) a fundus illumination optical system that illuminates the fundus of a patient's eye, a visual target presenting optical system that projects a fixation target that guides the line of sight of the patient's eye and a test index that performs a visual function test of the retina onto the fundus, An imaging unit including a fundus imaging optical system including an imaging element for imaging the fundus and obtaining a fundus imaging image, and alignment means for aligning the imaging unit and the patient's eye based on a predetermined alignment standard In the fundus imaging apparatus, a flare extraction unit that extracts a flare included in the fundus photographed image captured by the image sensor by image processing, and the alignment unit is configured to extract the flare by the flare extraction unit. Further, by moving the imaging unit a predetermined distance in the working distance direction away from the patient's eye, it is possible to suppress the occurrence of flare due to the positional deviation between the patient's eye and the imaging unit. It is characterized by.
(2) The fundus imaging apparatus according to (1) includes a tracking unit that corrects a shift in the presentation position of the examination target on the fundus caused by rotation of the patient's eye, and the alignment unit includes the tracking unit. When the flare is extracted by the flare extraction means when the flare is extracted by the flare extraction means when the flare is extracted by the flare extraction means Based on the above, the imaging unit is controlled to move in the vertical and horizontal directions perpendicular to the optical axis.
(3) In the fundus imaging apparatus according to (2), the alignment unit further includes a center-of-gravity calculation unit that obtains position information of the center of gravity of the flare region extracted by the flare extraction unit by a calculation process, and the center-of-gravity calculation unit Control means for performing alignment control in the vertical and horizontal directions at the same working distance of the imaging unit with respect to the patient's eye based on the obtained position information of the center of gravity and the alignment reference.
(4) The fundus imaging apparatus according to (3) includes a storage unit that stores a movement amount when the imaging unit is moved in a working distance direction away from the patient's eye.
(5) In the fundus imaging apparatus according to (4), the alignment unit moves the imaging unit in a working distance direction away from the patient's eye in proportion to the area of the flare region extracted by the flare extraction unit. It is characterized by that.

  According to the present invention, it is possible to provide a fundus imaging apparatus in which the alignment between the eye and the imaging unit is suitably maintained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a fundus photographing apparatus capable of performing fundus observation and photographing and visual field inspection of the fundus will be described as an example. FIG. 1 is an external configuration diagram of a fundus imaging apparatus. FIG. 2 is an explanatory diagram of an optical system and a control system of the fundus imaging apparatus.

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 face of the subject.
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 movable table 2 slides on the base 1a in the XZ direction by the sliding mechanism. The 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 is moved 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 imaging / inspection conditions, and a mouse, a keyboard, a touch panel (attached to the monitor 8), or the like is 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 subject side of the imaging unit 3, there are an imaging window 9 for the subject to look inside the apparatus, and a response button 7b for the patient to input a response signal when examining the visual function of the eye (retina). Is provided.

  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 portion, and a visual target presentation optical system 70 that guides the line of sight of the subject (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, A perforated mirror 22 and an objective lens 25 are provided.
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 focusing lens 32 movable in the optical axis direction, an imaging lens 33, and a flip-up mirror 34. 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 photographing optical axis L1 in between, and a finite distance index (patient eye) by a divergent light beam at a predetermined projection angle toward the cornea of the eye E. A rectangular index extending in the vertical direction). 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 the anterior eye portion and the imaging device 38 are in a substantially conjugate relationship when the auxiliary lens 20 is placed on the optical axis L1. 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 the present embodiment, the point light source 27 is provided in the vicinity of the aperture of the perforated mirror (substantially conjugate position of the fundus), and the working light W formed on the fundus is formed by turning on the point light source 27 during fundus observation. Alignment in the working distance direction is performed. The point light source 27 is constituted by the tip of a fiber dot.

<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 light of a predetermined color (for example, red, green, and blue), and a collimator lens that converts each laser light into parallel light. , A dichroic mirror for collimating each laser beam that has been collimated by a collimator lens, a lens that is moved on the optical axis in order to change the irradiation diameter of the collimated laser beam, and passed through the lens And a scanning unit for scanning the laser beam on the screen 72. The control unit 80, which will be 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, not only monochrome but also a color target can be presented by a combination of laser beams irradiated from the laser light source. For example, the Ishihara-style color vision abnormality test table and visual function test targets using colors of specific wavelengths (for example, red, blue, green) are presented, so that the presence or absence of color vision abnormalities in the patient and abnormal cones ( It becomes possible to identify color vision anomalies for a specific color. In addition, various types of visual function tests can be performed using a single test apparatus.

  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. Various indicators may be formed using a known liquid crystal display or the like.

  <Control System> The control unit 80 is connected to the above-described optical system and control system and controls various operations. The control unit 80 is connected to a memory 83 as a storage unit, and various programs are stored in advance. Further, the memory 83 stores luminance threshold information for binarizing the captured image in order to extract the flare area included in the captured image.

Further, the memory 83 stores information (hereinafter referred to as a first threshold value) of the flare area (number of pixels) that serves as a reference when the photographing unit 3 is moved in the working distance direction. In addition, information (hereinafter referred to as a second threshold) of flare area (number of pixels) serving as a reference when moving the photographing unit 3 in a direction perpendicular to the optical axis L1 (up / down / left / right direction) is stored. Further, the memory 83 stores in advance various information such as the amount of movement of the photographing unit 3 in the working distance direction (the driving amount of the driving unit 6).
The first threshold value is set to a value larger than the second threshold value. As a result, when the area of the flare (region) included in the fundus image is large, first, the imaging unit 3 is moved in the working distance direction.

  For example, the control unit 80 detects an alignment index from the anterior segment image captured by the image sensor 38. The control unit 80 displays the fundus image captured by the image sensor 35 on the monitor 8 and adjusts the fundus focus based on the separation state of the focus index. Furthermore, in this embodiment, when performing a fundus visual field inspection, a flare (area) is detected from a fundus image captured by the image sensor 38, and first the imaging unit 3 is moved in the working distance direction. As a result, flare is less likely to occur due to eye movement or rotation that occurs during the visual field inspection, and the alignment between the eye E and the imaging unit 3 is stably maintained.

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. In this state, when the subject looks into the apparatus through the imaging window 9, the anterior eye part 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 targets M1 and M2 appear on the anterior eye image F1, the controller 80 aligns the imaging unit 3 and the eye E based on the light reception results of the alignment targets 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 targets M1 and M2 matches the pupil center obtained from the anterior segment image. In addition, the imaging unit 3 is moved in the front-rear (Z) direction with respect to the eye E so that the distance between the alignment targets M1 and M2 is a predetermined distance, thereby performing alignment in the working distance direction. For details of the alignment operation, refer to International Publication No. 2008/062527.

  When 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, retracts the auxiliary lens 26 from the optical path, and turns on the light source 11. 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.

In addition, when the fundus is observed by the monitor 8, the light source 27 is turned on, so that the working dots W are projected onto the fundus. The control unit 80 detects the position of the working dot W by image processing, and performs alignment so that no flare occurs in the fundus image.
When the fundus image F2 is clearly displayed on the monitor 8, auto-alignment that corrects the positional deviation between the eye E and the imaging unit 3 (optical axis L1) caused by the movement and rotation of the eye E that occurs during visual field measurement, and a presentation target The control unit 80 performs tracking control for correcting the positional deviation.

  By the way, in the visual function test, since the test takes time, if the positional deviation between the eye E and the imaging unit 3 occurs due to the movement of the patient's head placed on the face support unit 5 during the test, the image is captured by the image sensor 35. The fundus photographed image (fundus image) includes flare due to the corneal reflection light (note that the flare is photographed as part of the annular luminous flux because the ring slit 17 for forming the annular luminous flux deviates from the observation field of view. It is caused by entering the luminous flux). If flare is included in the fundus image, the fundus observation image becomes difficult to see, and the accuracy of alignment between the eye and the photographing unit 3 is lowered during tracking based on the fundus image, which adversely affects the examination.

  Therefore, in the prior art, the light amount is detected at a plurality of portions of the fundus image captured by the image sensor 35, and the imaging unit 3 is moved in the vertical and horizontal directions (perpendicular to the imaging optical axis L1) based on the detection result. Thus, the flare is prevented from being included in the fundus image. However, movement in a plane perpendicular to the optical axis L1 (up / down / left / right direction) does not improve the occurrence of flare, and flare repeatedly occurs due to the misalignment between the eye E and the imaging unit 3 that occurs during the examination. If the position correction of the eye E and the imaging unit 3 is repeated, the smooth operation of the apparatus is affected. In addition, the vibration and noise of the device caused by the position correction may adversely affect the examination result of the patient.

  By the way, it is known that flare is likely to occur when the working distance between the eye E and the photographing unit 3 is short. That is, the ring slit 17 placed on the optical axis L1 for the purpose of forming the annular light flux and removing the corneal reflected light is projected onto the eye due to the change in the imaging magnification when the working distance between the eye E and the photographing unit 3 is shortened. As a result, the image of the ring slit 17 is reduced to make it difficult to remove the corneal reflection light, and flare is likely to occur due to the vertical and horizontal misalignment between the eye E and the imaging unit 3 (the amount of generation increases). .

  Therefore, in the present invention, when a predetermined amount of flare occurs during the visual function test of the patient, the flare is removed from the image of the ring slit 17 by first moving the imaging unit 3 in the working distance direction away from the eye E. Make it easier. Accordingly, even if the eye E and the photographing unit 3 are subsequently displaced in the vertical and horizontal directions, flare is less likely to occur. Further, even if flare occurs, the area of the flare can be suppressed, so that the moving amount of the photographing unit 3 in the vertical and horizontal directions can be reduced.

FIG. 5 is a flowchart showing the operation principle of alignment, and FIG. 6 is an explanatory diagram of the alignment principle using a fundus image.
When the focusing is completed, in step S101, the control unit 80 acquires a fundus image (image data) from the image sensor 38 at a predetermined step (time interval). At this time, if there is an influence of the corneal reflection light due to the movement or rotation of the eye E, a white flare is generated around the fundus image.

Next, in step S102, the control unit 80 binarizes each pixel constituting the acquired fundus image (image data) based on the threshold value information of luminance stored in advance in the memory 83 as flare extraction means. As a result, a set of pixels having a luminance value higher than the threshold value is extracted as the flare region R1, and a set of pixels having a luminance value lower than the threshold value is classified as the other region R2.
Here, as shown in FIG. 6A, a flare is generated on the right side of the fundus image, and a flare region R1 is set (extracted) on the right side of the fundus image by binarization of pixels. Note that the luminance threshold value for pixel binarization is determined in advance based on experiments or the like and stored in the memory 83.

  Next, in step S103, the control unit 80 compares the first threshold value stored in advance in the memory 83 with the area (number of pixels) of the flare region R1. If it is determined that the area of the flare region R1 is greater than or equal to the first threshold value regarding the working distance, the process proceeds to step S104. Although illustration is omitted here, it is assumed that the process proceeds to step S104 also when the flare region R1 is first detected after the start of inspection.

  In step S104, the control unit 80 drives the drive unit 6 to move the imaging unit 3 by a predetermined distance in a direction away from the patient (eye E). Note that the movement amount of the photographing unit 3 is stored in advance in the memory 83 based on experimental results and the like. For example, it is assumed that the imaging unit 3 is moved in a direction of retracting 1 mm from the patient (eye E) by driving the driving unit 6.

  After the movement process is completed, whether or not the visual field inspection is completed is determined in step S105. If it is determined in step S105 that the visual field inspection has not been completed, the process returns to step S101, and image data acquisition by the image sensor 38 is repeated. On the other hand, when it is determined in step S105 that the visual field inspection is completed, the alignment process ends. Whether or not the visual field inspection has been completed is determined by setting the number of times of projection of the inspection target on the patient's eye by operating the control unit 7a. Alternatively, the examiner may determine whether or not the visual field inspection is completed.

On the other hand, if it is determined in step S103 that the area of the flare region R1 is smaller than the first threshold value, the process proceeds to step S110.
In step S110, the control unit 80 compares the second threshold value stored in the memory 83 with the area of the flare region R1. If it is determined that the flare area R1 is smaller than the second threshold value, the process proceeds to step S105 to determine whether or not the visual field inspection is completed. On the other hand, if it is determined in step S110 that the area of the flare region R1 is equal to or larger than the second threshold (smaller than the first threshold), the process proceeds to step S111, and the moving direction and moving distance of the photographing unit 3 in the XY directions are set. Desired.

  For example, in step S111, the control unit 80 obtains the center of gravity (position) O1 (x, y) of the extracted image moment of the flare region R1 by image processing. The center of gravity O1 (x, y) shown here is a center of gravity based on the luminance information of the image, and is obtained by a well-known image processing moment calculation. For example, it is calculated by equation (1).

式（１）において、ｆ（ｘ、ｙ）は座標（ｘ、ｙ）に対応する画素の輝度値である。つまり式（１）において、ｘ方向の重心位置と、ｙ方向の重心位置と個別に求めることで、フレア領域Ｒ１の重心Ｏ１（ｘ、ｙ）を決定している。

In equation (1), f (x, y) is the luminance value of the pixel corresponding to the coordinates (x, y). That is, in the equation (1), the center of gravity O1 (x, y) of the flare region R1 is determined by separately obtaining the center of gravity position in the x direction and the center of gravity in the y direction.

  Next, the control unit 80 obtains a difference between the obtained coordinates of the center of gravity O1 of the flare region R1 and the coordinates of the center O2 (optical axis L1) of the image sensor 38 that is the alignment reference position, and moves and moves the photographing unit 3. Find the quantity (vector).

  Then, in step S104, the control unit 80 moves the photographing unit 3 by driving the driving unit 6 so that the center of gravity O1 of the flare region R1 and the center O2 (optical axis L1) of the imaging element 38 approach each other. Note that the center of gravity O1 of the flare region R1 and the center O2 of the image sensor 38 do not necessarily have to coincide with each other, and the movement amount of the photographing unit 3 may be determined so that no flare is included in the fundus image.

  At this time, the moving speed of the photographing unit 3 may be changed according to the difference (the length of the vector V) between the center of gravity O1 and the center O2. That is, the moving speed of the photographing unit 3 is increased as the difference increases and the vector V increases. On the other hand, the moving speed of the photographing unit 3 is decreased as the difference is smaller and the vector V is shorter. In this way, the positional deviation of the eye E and the imaging unit 3 in the X and Y directions can be more suitably suppressed according to the degree of movement or rotation angle of the eye E. In the present embodiment, the center of gravity of the image sensor is described as an example of the alignment reference position, but the present invention is not limited to this. A predetermined position on the light receiving element that is set to match the imaging unit and the patient's eye with a predetermined positional relationship may be set as the alignment reference position.

  When the above steps S101 to S105 are repeated, if in step S103 a large misalignment occurs again between the eye E and the photographing unit 3 and the occurrence of a flare exceeding a predetermined amount is detected. In step S104, the photographing unit 3 is moved in the working distance direction. As a result, a situation in which flare is hardly generated is maintained.

When the movement of the imaging unit 3 in step S104 is completed, it is determined whether or not the visual field inspection is completed in step S105.
As described above, the imaging unit 3 is moved in the working distance direction away from the eye E by the (first) flare detection, and thereafter, the positional deviation in the vertical and horizontal directions between the eye E and the imaging unit 3 occurs. However, flare is less likely to occur. As a result, frequent movement of the imaging unit 3 in the XY directions due to eye rotation or the like occurring during the visual function test can be suppressed, and the visual function test of the patient's eye can be performed stably. Even if flare occurs after the photographing unit 3 is moved in the working distance direction, the amount of flare generated (area) can be suppressed, so that the driving amount of the photographing unit 3 can be reduced.

  As described above, the corneal reflected light is suitably blocked by the ring slit 17 by moving the imaging unit 3 in the direction away from the patient (eye E) based on the detection result of the flare region R1. Therefore, even if the patient and the imaging unit 3 are misaligned during the examination, the corneal reflected light is removed by the ring slit 17, and flare hardly appears on the image sensor 35.

  In the above description, the moving distance in the working distance direction of the photographing unit 3 in step S104 is set to a constant value. In addition to this, the moving distance of the photographing unit 3 may be adjusted according to the area (number of pixels) of the flare region R1 detected in step S103. For example, when the area of the flare region R1 is large (the number of pixels is large), the moving distance in the working distance direction of the photographing unit 3 is increased, and when the area of the flare region R1 is small (the number of pixels is small), The movement distance in the working distance direction may be decreased.

  Further, the processing of step S103 and step S104 may be repeated until the area of the flare region R1 detected in step S103 becomes equal to or smaller than the first threshold value. That is, as a result of comparing the area of the flare region R1 with the first threshold value in step S103, if the area of the flare region R1 is larger than the threshold value, the photographing unit 3 is moved by a predetermined distance in the working distance direction in step S104. Thereafter, the process returns to step S103 again, and the comparison between the area of the flare region R1 and the first threshold value is repeatedly performed. If it is determined that the area of the flare region R1 is equal to or greater than the threshold value, the imaging unit 3 is similarly moved in the working distance direction in step S104, and the area of the flare region R1 is determined to be smaller than the threshold value. In step S105, it is determined whether or not the visual field inspection is completed.

  In the above description, the example in which the movement of the photographing unit 3 in the working distance direction and the movement in the XY direction are separated is shown. In addition to this, the movement of the photographing unit 3 in the working distance direction and the movement in the XY direction may be performed simultaneously. In this case, when the flare area is detected, the photographing unit 3 is moved in the working distance direction by a predetermined amount stored in the memory 83, and at the same time, the center of gravity O1 of the flare area R1 obtained in the above-described step S111. Then, the imaging unit 3 is moved in the XY directions so that the center O2 (optical axis L1) of the image sensor 38 approaches.

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. 7 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 alignment and tracking are 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. 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.
At this time, since the occurrence of flare is suppressed by the alignment process as described above, the movement of the imaging unit 3 accompanying the movement of the patient's eye E is suppressed, and the patient's visual function test can be performed stably.

  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. 8, the attenuation value of the luminance of the presented visual target is used to display 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, as an example of the fundus imaging apparatus, the fundus imaging apparatus capable of performing both fundus imaging of the eye and a visual function test is shown as an example. In addition to this, the configuration of the present invention can be applied to a fundus imaging apparatus that performs alignment between the eye and the imaging unit. For example, the alignment of a well-known fundus camera, the alignment of an optical tomography apparatus that captures a tomographic image of the eye, and further, the configuration of the present invention is applied to a multi-function machine of these fundus imaging apparatuses. The occurrence of flare itself can be suitably suppressed.

It is an external appearance block diagram of a fundus imaging apparatus. It is explanatory drawing of the optical system and control system of a fundus imaging apparatus. 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 a flowchart which shows the operation principle of alignment. It is explanatory drawing of the alignment principle using a fundus image.

DESCRIPTION OF SYMBOLS 3 Image | photographing part 8 Monitor 10 Illumination optical system 30 Observation and imaging | photography optical system 35 Image pick-up element 40 Focus parameter | index projection optical system 70 Target presentation optical system 80 Control part

Claims (5)

A fundus illumination optical system for illuminating the fundus of the patient's eye, a visual target presenting optical system for projecting a fixation target for guiding the line of sight of the patient's eye and a test index for performing a visual function test of the retina, and photographing the fundus An imaging unit including a fundus imaging optical system including an imaging device for obtaining a fundus imaging image, and an alignment unit that aligns the imaging unit and the patient's eye based on a predetermined alignment standard,
A fundus photographing apparatus comprising:
A flare extraction means for extracting flare included in the fundus photographic image captured by the image sensor by image processing;
When the flare is extracted by the flare extraction unit, the alignment unit moves the imaging unit by a predetermined distance in a working distance direction away from the patient's eye, thereby causing a positional deviation between the patient's eye and the imaging unit. A fundus photographing apparatus characterized by suppressing the occurrence of flare caused by the. The fundus imaging apparatus according to claim 1 comprises:
Tracking means for correcting a shift in the presentation position of the test optotype on the fundus caused by rotation of the patient's eye,
When the tracking unit performs tracking, the alignment unit moves the imaging unit in a working distance direction away from a patient's eye when the flare is extracted by the flare extracting unit, and then moves the flare. A fundus imaging apparatus, wherein the imaging unit is controlled to move in the vertical and horizontal directions perpendicular to the optical axis based on the flare extraction result by the extraction unit. The fundus photographing apparatus according to claim 2,
The alignment means further includes
Centroid calculating means for obtaining position information of the centroid of the area of the flare extracted by the flare extracting means by calculation processing;
Control means for performing vertical and horizontal alignment control at the same working distance of the imaging unit with respect to the patient's eye based on the position information of the center of gravity obtained by the center of gravity calculating means and the alignment reference;
A fundus photographing apparatus comprising: The fundus imaging apparatus according to claim 3 comprises:
A fundus imaging apparatus comprising: a storage unit that stores a movement amount when moving the imaging unit in a working distance direction away from the patient's eye. The fundus imaging apparatus according to claim 4,
The fundus imaging apparatus, wherein the alignment unit moves the imaging unit in a working distance direction away from the patient's eye in proportion to the area of the flare region extracted by the flare extraction unit.

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