JP5701660B2 - Fundus photographing device - Google Patents

Description

  The present invention relates to a fundus imaging apparatus that captures a tomographic image of a subject's fundus.

  An optical tomography (OCT) using low-coherent light is known as an optical tomographic imaging apparatus that captures a tomographic image of the fundus of a subject's eye (see Patent Document 1).

  In such an apparatus, the examiner focuses the fundus tomographic image using the focus state of the fundus front image acquired by the SLO optical system or the fundus camera optical system. Further, after the focus adjustment, the optical path length adjustment and the polarization state adjustment (polarizer adjustment) are performed to optimize the measurement.

  In recent years, an apparatus in which an optical system dedicated to photographing the fundus front such as an SLO optical system or a fundus camera optical system is not mounted has been proposed (see Patent Document 2). This apparatus scans the measurement light beam two-dimensionally and integrates the spectral intensity of the interference signal from the light receiving element at each XY point to form a front image.

JP 2009-291252 A US Patent Registration No. 7301644

  By the way, when adjusting imaging conditions without using an optical system dedicated to frontal fundus imaging such as an SLO optical system or a fundus camera optical system as in Patent Document 2, focus adjustment, optical path length adjustment, and polarization state adjustment are performed as follows: It is necessary to use an OCT optical system. For this reason, when trying to automate these adjustments, it is difficult to adjust the shooting conditions as compared to a dedicated optical system. Therefore, automatic adjustment may end in an insufficient state, and the fundus tomographic image may not be displayed well on the monitor.

  In view of the above problems, an object of the present invention is to provide a fundus imaging apparatus that suitably adjusts imaging conditions and acquires a fundus tomographic image without using an optical system dedicated to fundus frontal imaging.

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

(1) The fundus imaging apparatus according to the first aspect of the present disclosure divides a light beam emitted from a light source into measurement light and reference light, guides the measurement light beam to a subject's eye fundus, and uses the reference light as a reference optical system. After guiding, the interference optical system for detecting the interference state between the measurement light reflected from the fundus and the reference light by a detector , and the measurement light or the reference light for adjusting the optical path length difference between the measurement light and the reference light Driving means for driving an optical member disposed in the optical path of the fundus photographing apparatus for taking a tomographic image of the fundus based on an output signal from the detector, and controlling the driving of the driving means. First optical path length adjusting means for moving the optical member to a position where a fundus tomographic image is acquired based on an output signal output from the detector at each position of the optical member while moving the optical member And by the first optical path length adjusting means A second optical path length adjusting means for readjusting the position of the optical member from the integer positions, during operation of said first optical path length adjusting means and the second optical path length adjusting means, the output signal from the detector And an optical adjusting means for adjusting the interference optical system.
(2) The fundus imaging apparatus according to the second aspect of the present disclosure divides the light beam emitted from the light source into measurement light and reference light, guides the measurement light beam to the eye fundus of the subject, and uses the reference light as a reference optical system. After guiding, the interference optical system for detecting the interference state between the measurement light reflected from the fundus and the reference light by a detector, and the measurement light or the reference light for adjusting the optical path length difference between the measurement light and the reference light Driving means for driving the optical member arranged in the optical path of the subject, and focusing the optical member arranged in the optical path of the measurement light for correcting the diopter for the subject's fundus on the eye fundus of the subject A focus adjusting means for moving the position to a position, and a polarization adjusting means for substantially matching the polarization states of the measurement light and the reference light by driving a polarizing element arranged in the optical path of the measurement light or the optical path of the reference light, Based on the output signal from the detector In a fundus imaging apparatus for capturing a tomographic image, the driving of the driving unit is controlled to move the optical member, and based on output signals output from the detector at each position of the optical member, First optical path length adjusting means for moving the optical member to a position where an image is acquired; and second optical path length adjusting means for readjusting the position of the optical member from the position adjusted by the first optical path length adjusting means; The focus adjusting means is output from the detector through optical path length adjustment by the first optical path length adjusting means during operation of the first optical path length adjusting means and the second optical path length adjusting means. The focusing optical member is moved to a focus position with respect to the fundus of the subject's eye based on the output signal, and the polarization adjusting means is connected to the detector after the optical path length adjustment by the second optical path length adjusting means. Based on the output signal output, the polarizing element is driven, and performs the adjustment of the polarization state.

  According to the present invention, imaging conditions are suitably adjusted without using an optical system dedicated to fundus front imaging, and a fundus tomogram can be acquired.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an optical system and a control system of the optical tomography apparatus according to the present embodiment. In the following description, a fundus photographing apparatus which is one of ophthalmic photographing apparatuses will be described as an example. In this embodiment, the depth direction of the eye to be examined is described as the Z direction (optical axis L1 direction), the horizontal component on the plane perpendicular to the depth direction is defined as the X direction, and the vertical component is described as the Y direction.

  In FIG. 1, the optical system divides a light beam emitted from a light source into measurement light and reference light, guides the measurement light beam to the subject's eye fundus, guides the reference light to the reference optical system, and then from the fundus An interference optical system (OCT optical system) 200 that detects an interference state between the reflected measurement light and the reference light by a detector, and a fixation target projection unit 300 are provided. The interference optical system 200 includes a measurement optical system 200a and a reference light optical system 200b. In addition, the interference optical system 200 splits the interference light generated by the reference light and the measurement light for each frequency (wavelength), and makes the light receiving means (in this embodiment, a one-dimensional light receiving element) receive the split interference light. An optical system 800 is included. Further, the dichroic mirror 40 has a characteristic of reflecting light having a wavelength component used as measurement light of the OCT optical system 200 and transmitting light having a wavelength component used for the fixation target projection unit 300.

  First, the configuration of the OCT optical system 200 provided on the reflection side of the dichroic mirror 40 will be described. Reference numeral 27 denotes an OCT light source that emits low-coherent light used as measurement light and reference light of the OCT optical system 200. For example, an SLD light source is used. For the OCT light source 27, for example, a light source having a center wavelength of 840 nm and a bandwidth of 50 nm is used. Reference numeral 26 denotes a fiber coupler that doubles as a light splitting member and a light coupling member. The light emitted from the OCT light source 27 is split into reference light and measurement light by the fiber coupler 26 via an optical fiber 38a as a light guide. The measurement light goes to the eye E through the optical fiber 38b, and the reference light goes to the reference mirror 31 through the optical fiber 38c (polarizer (polarizing element) 33).

  In the optical path for emitting the measurement light toward the eye E, the focusing optical is movable in the optical axis direction to correct the diopter for the end 39b of the optical fiber 38b for emitting the measurement light and the fundus of the subject. A scanning unit (optical scanner) 23 composed of a combination of two galvanometer mirrors that can scan the measurement light in the XY directions on the fundus by driving the member (focusing lens) 24, the scanning drive mechanism 51, and a relay lens 22 Has been placed. The dichroic mirror 40 and the objective lens 10 serve as a light guide optical system that guides OCT measurement light from the OCT optical system 200 to the fundus of the eye to be examined.

  The measurement light emitted from the end 39b of the optical fiber 38b reaches the scanning unit 23 via the focusing lens 24, and the reflection direction is changed by driving the two galvanometer mirrors. Then, the measurement light reflected by the scanning unit 23 is reflected by the dichroic mirror 40 via the relay lens 22 and then condensed on the fundus of the eye to be examined via the objective lens 10.

  Then, the measurement light reflected from the fundus is reflected by the dichroic mirror 40 through the objective lens 10, travels to the OCT optical system 200, passes through the relay lens 22, the two galvanometer mirrors of the scanning unit 23, and the focusing lens 24. The light enters the end 39b of the optical fiber 38b. The measurement light incident on the end 39b reaches the end 84a of the optical fiber 38d through the optical fiber 38b, the fiber coupler 26, and the optical fiber 38d.

  On the other hand, an optical fiber 38 c, an end portion 39 c of the optical fiber 38 c that emits the reference light, a collimator lens 29, and the reference mirror 31 are arranged in the optical path that emits the reference light toward the reference mirror 31. The optical fiber 38c is rotated by the drive mechanism 34 in order to change the polarization direction of the reference light. That is, the optical fiber 38c and the drive mechanism 34 are used as a polarizer 33 for adjusting the polarization direction. The polarizer is not limited to the above-described configuration, and any polarizer may be used as long as the polarization state of the measurement light and the reference light is substantially matched by driving the polarizer disposed in the optical path of the measurement light or the optical path of the reference light. . For example, a half-wave plate or a quarter-wave plate can be used, or one that changes the polarization state by applying pressure to the fiber to deform it can be applied.

  The polarizer 33 (polarization controller) may be configured to adjust the polarization direction of at least one of the measurement light and the reference light in order to match the polarization directions of the measurement light and the reference light. For example, the polarizer may be arranged in the optical path of the measurement light.

  Further, the reference mirror driving mechanism 50 drives the reference mirror 31 disposed in the optical path of the measurement light or reference light in order to adjust the optical path length with the measurement light or reference light. In this embodiment, the reference mirror 31 is arranged in the optical path of the reference light, and is configured to be movable in the optical axis direction so as to change the optical path length of the reference light.

  The reference light emitted from the end 39c of the optical fiber 38c is converted into a parallel light beam by the collimator lens 29, reflected by the reference mirror 31, collected by the collimator lens 29, and incident on the end 39c of the optical fiber 38c. The reference light incident on the end 39c reaches the fiber coupler 26 via the optical fiber 38c and the optical fiber 38c (polarizer 33).

  Then, the reference light generated as described above by the light emitted from the light source 27 and the fundus reflection light by the measurement light irradiated on the eye fundus to be examined are combined by the fiber coupler 26 to be interference light, The light is emitted from the end portion 84a through the fiber 38d. A spectroscopic optical system 800 (spectrometer unit) that separates interference light into frequency components to obtain an interference signal for each frequency includes a collimator lens 80, a grating mirror (diffraction grating) 81, a condensing lens 82, and a light receiving element 83. . The light receiving element 83 is a one-dimensional element (line sensor) having sensitivity in the infrared region.

  Here, the interference light emitted from the end portion 84 a is collimated by the collimator lens 80, and then is split into frequency components by the grating mirror 81. Then, the interference light split into frequency components is condensed on the light receiving surface of the detector (light receiving element) 83 via the condenser lens 82. Thereby, spectrum information of interference fringes is recorded on the light receiving element 83. Then, a tomographic image of the eye is captured based on the output signal from the light receiving element 83. That is, the spectrum information is input to the control unit 70 and analyzed using Fourier transform, whereby information in the depth direction of the subject's eye can be measured. Here, the control unit 70 can acquire a tomographic image by causing the scanning unit 23 to scan the measurement light on the fundus in a predetermined transverse direction. For example, by scanning in the X direction or the Y direction, a tomographic image (fundus tomographic image) on the XZ plane or YZ plane of the subject's fundus can be acquired (in this embodiment, the measurement light is applied to the fundus in this way. On the other hand, a method of performing one-dimensional scanning and obtaining a tomographic image is referred to as B-scan). The acquired fundus tomographic image is stored in the memory 72 connected to the control unit 70. Furthermore, by controlling the driving of the scanning unit 23 and scanning the measurement light in the XY direction two-dimensionally, based on the output signal from the light receiving element 83, the two-dimensional moving image regarding the XY direction of the subject's eye fundus It is also possible to acquire a three-dimensional image of the fundus of the eye to be examined.

  The reference mirror 31 is moved in the optical axis direction by driving of the drive mechanism 50, and the movable range is set so as to cope with the difference in the axial length of each eye to be examined. In FIG. 1, the reference mirror 31 can move in a range from a movement limit position K1 in the direction in which the optical path length of the reference light is shortened to a movement limit position K2 in the direction in which the optical path length of the reference light is increased.

  The initial position (movement start position) of the reference mirror 31 before starting automatic optical path length adjustment (first automatic optical path length adjustment (details will be described later)) is set to the movement limit position K1 or the movement limit position K2. Of course, an intermediate position before the start of initialization may be set as the initial position. Moreover, it is good also as a setting which can change an initial position arbitrarily.

  The focusing lens 24 is moved in the optical axis direction by driving of the drive mechanism 24a, and the movable range is set. The focusing lens 24 moves from a first movement limit position (for example, a position where the refractive power corresponds to −15D, that is, a position where the focus is achieved by the refractive power of −15D) to a second movement limit position (for example, the refractive power becomes + 15D). The range up to the corresponding position) can be moved.

  The initial position of the focusing lens 24 is a position corresponding to the average eye refractive power of the eye to be examined (for example, a position corresponding to 0D). Of course, the position before moving to the initial position may be set as the initial position. Moreover, it is good also as a setting which can change an initial position arbitrarily. Either the first movement limit position or the second movement limit position may be the initial position.

  The optical fiber 38c is rotationally moved by the drive of the drive mechanism 34, and the movable range is set. The optical fiber 38c is capable of rotational movement from a first movement limit position (for example, 0 °) to a second movement limit position (for example, 180 °).

  The optical fiber 38c is located at a midway position between the first movement limit position and the second movement limit position, and is not moved until after the second automatic optical path length adjustment is completed. Therefore, in the polarizer 33, the midway position becomes the initial position.

  Next, the fixation target projection unit 300 will be described. The fixation target projecting unit 300 includes an optical system for guiding the line-of-sight direction of the eye E. The projection unit 300 has a fixation target presented to the eye E, and can guide the eye E in a plurality of directions.

  For example, the fixation target projection unit 300 has a visible light source that emits visible light, and changes the presentation position of the target two-dimensionally. Thereby, the line-of-sight direction is changed, and as a result, the imaging region is changed. For example, when the fixation target is presented from the same direction as the imaging optical axis, the center of the fundus is set as the imaging site. When the fixation target is presented upward with respect to the imaging optical axis, the upper part of the fundus is set as the imaging region. That is, the imaging region is changed according to the position of the target with respect to the imaging optical axis.

  As the fixation target projection unit 300, for example, a configuration in which the fixation position is adjusted by the lighting positions of LEDs arranged in a matrix, light from a light source is scanned using an optical scanner, and fixation is performed by lighting control of the light source. Various configurations such as a configuration for adjusting the position are conceivable. The projection unit 300 may be an internal fixation lamp type or an external fixation lamp type.

  The control unit 70 is connected to a display monitor 75, a memory 72, a control unit 74, a reference mirror drive mechanism 50, a drive mechanism 24a for moving the focusing lens 24 in the optical axis direction, a drive mechanism 34, and the like. Yes.

  FIG. 2 is a diagram illustrating an example of a tomographic image acquired (formed) by the OCT optical system 200. The image data G of the tomographic image includes first image data G1 corresponding to the near side from the optical path length matching position and second image data G2 corresponding to the back side from the optical path length matching position. The images are symmetrical with respect to the depth position S where the optical path lengths coincide.

  In the above configuration, when the reference mirror 31 is arranged so that the depth position where the optical path lengths of the measurement light and the reference light coincide with each other is formed on the front side of the retina surface, the sensitivity on the retina surface side with respect to the choroid side portion. A fundus tomographic image (normal image) having a high is acquired. In this case, the fundus tomographic images in the first image data G1 and the second image data G2 face each other. In this case, a real image is acquired in the first image data G1, and a virtual image (mirror image) is acquired in the second image data G2.

  On the other hand, when the reference mirror 31 is arranged so that the depth position where the optical path lengths of the measurement light and the reference light coincide with each other is formed on the back side from the retina surface, the fundus is more sensitive on the choroid side portion than the retina surface side. A tomographic image (reverse image) is acquired. In this case, the fundus tomograms in the first image data G1 and the second image data G2 are in opposite directions. In this case, a real image is acquired in the second image data G2, and a virtual image (mirror image) is acquired in the first image data G1.

  For example, the control unit 70 extracts image data of the first image data G1 or the second image data G2 from the image data G of the tomographic image and displays the image data on the screen of the monitor 75. In the present embodiment, the first image data G1 is set to be extracted.

  In the present embodiment, the control unit 70 performs dispersion correction processing by software on the spectrum data output from the light receiving element 83. Then, a depth profile is obtained based on the spectrum data after dispersion correction. For this reason, a difference in image quality occurs between the real image and the virtual image.

  For example, a first dispersion correction value (for normal image) is acquired from the memory 72 as a dispersion correction value for correcting the influence of dispersion on the real image, and the spectrum data output from the light receiving element 83 is used as the first dispersion correction value. And tomographic image data is formed by Fourier transforming the corrected spectral intensity data. Thereby, when a real image is acquired in the first image data G1, the real image is acquired as a high-sensitivity and high-resolution image. When a virtual image is acquired in the first image data G1, the virtual image is Due to the difference in dispersion correction value, a low-resolution blurred image is obtained.

  Of course, the present invention is not limited to this, and software dispersion correction for virtual images may be performed. Moreover, the setting which extracts the 2nd image data G2 may be sufficient, and of course the setting which extracts both the 1st image data G1 and the 2nd image data G2 may be sufficient. Moreover, you may set arbitrarily with a predetermined | prescribed switch.

  The control operation of the apparatus having the above configuration will be described. FIG. 3 is a flowchart showing an operation flow in the present apparatus. The examiner instructs the subject to gaze at the fixation target of the fixation target projection unit 300, and then observes the anterior ocular segment observation image captured by the anterior ocular segment observation camera (not shown) on the monitor 75. The alignment operation is performed using a joystick (not shown) so that the measurement optical axis is at the center of the pupil of the eye to be examined.

  Next, optimization is performed so that the fundus site desired by the examiner can be observed with high sensitivity and high resolution. In the present embodiment, the optimization control is control of optical path length adjustment, focus adjustment, and polarization state adjustment (polarizer adjustment).

  The examiner presses an optimization start switch (Optimize switch) 74 a arranged in the control unit 74. When an operation signal is issued from the optimization start switch 74a, the control unit 70 issues a trigger signal for starting optimization control and starts optimization.

  Here, the controller 70 optimizes the imaging conditions by adjusting the OCT optical system 200 between the first optical path length adjustment and the second optical path length adjustment. As optimization in the present embodiment, for example, the first automatic optical path length adjustment, the focus adjustment, the second automatic optical path length adjustment, and the polarizer adjustment are performed in this order. After the optimization is completed, when an imaging switch (not shown) is pressed by the examiner, a fundus tomographic image is captured and stored in the memory 75.

  In the present embodiment, the first automatic optical path length adjustment, focus adjustment, and polarizer adjustment are performed by detecting the signal intensity of the tomographic image. In the following description, a predetermined evaluation value B is used as an index indicating the signal strength.

  The evaluation value B is obtained from the equation B = ((average maximum luminance value of the image) − (average luminance value of the background area of the image)) / (standard deviation of the luminance value of the background area). The control unit 70 acquires the luminance distribution data of the tomographic image acquired based on the output signal from the light receiving element 83. For example, FIG. 4 is a diagram illustrating an image displayed on the screen of the monitor 75 when the reference mirror, the focusing lens, and the polarizer are arranged at predetermined positions.

  First, the control unit 70 sets a plurality of scanning lines to be scanned in the depth direction (A scanning direction), and obtains luminance distribution data on each scanning line. In FIG. 4, the image is divided into 10 and 10 dividing lines are used as scanning lines. FIG. 5 is a diagram illustrating a change in luminance distribution in the depth direction of an image.

  Here, the control unit 70 calculates the maximum luminance value (hereinafter, abbreviated as the maximum luminance value) from the luminance distribution corresponding to each scanning line. And the control part 70 calculates the average value of the maximum luminance value in each scanning line as the maximum luminance value in a fundus tomographic image. And the control part 70 calculates the average value of the luminance value of the background area | region in each scanning line as an average luminance value of the background area | region in a fundus tomographic image.

  Thus, the calculated evaluation value B is used in the first automatic optical path length adjustment, focus adjustment, and polarizer adjustment. In this case, it is preferable to calculate the evaluation value B in the tomographic image in the image data G1.

<Optimization control>
FIG. 6 is a diagram for explaining optimization control according to the present embodiment. Generally, the control unit 70 sets the positions of the reference mirror 31 and the focusing lens 24 to the initial positions as initialization control. After the initialization is completed, the control unit 70 moves the reference mirror 31 in one direction from the set initial position in a predetermined step, and performs the first optical path length adjustment (first automatic optical path length adjustment). After the completion of the first optical path length adjustment, the control unit 70 acquires in-focus position information, moves the focussing lens 24 to the in-focus position, and performs autofocus adjustment. Then, after the autofocus adjustment is completed, the reference mirror 31 is moved again in the optical axis direction, and second optical path length adjustment is performed to readjust the optical path length (fine adjustment of the optical path length). After completing the second optical path length adjustment, the control unit 70 drives the polarizer 33 for adjusting the polarization state of the reference light, and adjusts the polarization state of the measurement light.

  Hereinafter, an example of optimization control will be described in detail.

<Initialization>
First, the control unit 70 controls initialization. In the initialization control, the positions of the reference mirror 31 and the focusing lens 24 are moved to the initial position (movement start position).

  When the initialization control is started, the control unit 70 selects either the movement limit position K1 or the movement limit position K2 as the initial position of the reference mirror 31. The initial position is determined by selecting a position closer to the movement limit position K1 or the movement limit position K2 than the position of the reference mirror 31 before the initialization control is started. Then, the control unit 70 moves the reference mirror 31 to the initial position of the movement limit position K1 or the movement limit position K2. Of course, the moving direction for setting the initial position may be determined based on different criteria.

  Further, the control unit 70 moves the focusing lens 24 to an initial position (a position corresponding to 0D in the present embodiment).

<First automatic optical path length adjustment (coarse adjustment)>
When the initialization is completed as described above, the control unit 70 then performs the first automatic optical path length adjustment (automatic coarse optical path length adjustment). FIG. 7 is a flowchart showing the flow of the control operation for the first automatic optical path length adjustment.

  The control unit 70 controls the drive of the drive mechanism 50 to move the reference mirror 31 and acquires a fundus tomographic image based on output signals output from the light receiving element 83 at each position of the reference mirror 31. The reference mirror 31 is moved to the position.

  Specifically, after acquiring the tomographic image at the initial position, the control unit 70 moves the reference mirror 31 toward the movement limit position opposite to the initial position. For example, when the limit position K1 is selected (set) as the initial position of the reference mirror 31, it is moved in the direction toward the limit position K2.

  Here, the control unit 70 moves the reference mirror 31 in a predetermined step (for example, 2 mm step as an imaging range), sequentially acquires tomographic images at each moving position, and determines the position at which the fundus tomographic image is acquired. I will explore.

  In this case, the control unit 70 acquires a tomographic image every time the reference mirror 31 is stopped at the discretely set movement positions of the reference mirror 31. Then, the control unit 70 analyzes the tomographic image acquired at each position. For example, the control unit 70 calculates the evaluation value B of the tomographic image acquired at each position. Then, the control unit 70 stores the position of the reference mirror 31 and the evaluation value B of the tomographic image in the memory 75 in association with each other.

  FIG. 8 is a diagram illustrating an example of a calculation result of the evaluation value B for each position of the reference mirror 31. The horizontal axis represents the position of the reference mirror, and the vertical axis represents the evaluation value B at each position of the reference mirror.

  Here, the control unit 70 detects the peak of the evaluation value B from the obtained calculation result of the evaluation value B for each position of the reference mirror 31. Then, the control unit 70 causes the memory 75 to store the position of the reference mirror 31 corresponding to the peak detection position. Then, the control unit 70 moves the reference mirror 31 to a position corresponding to the peak of the evaluation value B. In general, the position of the reference mirror 31 when the real image of the fundus appears in the tomographic image is the position where the peak of the evaluation value B is detected. However, when there is no focus, the position of the reference mirror 31 when the virtual image appears in the tomographic image may be a position where the peak of the evaluation value B is detected.

  When the optical path length is roughly adjusted as described above, at least a part of the fundus tomographic image is displayed at any position on the monitor 72.

  In the present embodiment, when the reference mirror 31 is moved in a predetermined step, the evaluation value B does not increase and the driving of the reference mirror 31 may be stopped at a position where the evaluation starts. Further, the control unit 70 may estimate the position of the reference mirror corresponding to the peak from the calculation result of the evaluation value B for each position of the reference mirror 31. (For example, an approximate curve indicating a change in the evaluation value B is created).

<Auto focus adjustment>
When the first automatic optical path length adjustment is completed, the control unit 70 then performs focus adjustment.

  The control unit 70 moves the focusing lens 24 to the in-focus position with respect to the subject's fundus based on the output signal output from the light receiving element 83 through the first automatic optical path length adjustment.

  Specifically, the control unit 70 controls driving of the driving unit 24a, and moves the lens 24 in a predetermined step from a predetermined initial position. Then, the control unit 70 sequentially acquires tomographic images at each moving position, and searches for an in-focus position (a position where the fundus tomographic image is in focus).

  For example, the control unit 70 moves the lens 24 by 0.5D toward a certain movement limit position, and moves the lens 24 in the opposite direction if the in-focus position is not found. In addition, the movement step of the lens 24 is not limited to this, For example, 1D may be sufficient, 2D may be sufficient, and the structure set arbitrarily may be sufficient.

  In the search for the in-focus position, every time the focusing lens 24 is stopped at a discretely set moving position of the focusing lens 24, an image acquired at that position is analyzed. For example, the control unit 70 calculates the evaluation value B of the tomographic image acquired at each position. Then, the control unit 70 stores the position of the lens 24 and the evaluation value B of the tomographic image in the memory 75 in association with each other.

  Here, the control unit 70 detects the peak of the evaluation value B from the obtained calculation result of the evaluation value B for each position of the focusing lens 24. Then, the controller 70 moves the focusing lens 24 to a position corresponding to the peak detection position. As described above, the focus adjustment is completed.

<Second optical path length adjustment (fine adjustment)>
The controller 70 readjusts the position of the reference mirror 31 from the position adjusted by the first automatic optical path length adjustment based on the output signal output from the light receiving element 83 through the focus adjustment.

  Specifically, when the focus adjustment is completed, the control unit 70 performs the second automatic optical path length adjustment for moving the reference mirror 31 based on the tomographic image acquired by the focus adjustment.

  Here, the control unit 70 determines whether the fundus tomographic image acquired after the focus adjustment is a real image or a virtual image in the image data G1. For example, the control unit 70 determines that the fundus fundus image is a real image when the half-value width with respect to the peak in the luminance distribution in the depth direction is smaller than a predetermined allowable width, and determines that the fundus tomography when the half-value width is larger than the predetermined allowable width. Virtualize the image. Note that the determination of the real / virtual shape of the tomographic image may be any method that uses the difference in image quality between the real image and the virtual image. For example, in addition to the half width, the contrast of the tomographic image, the rising edge of the tomographic image Degree etc. are used. Further, the shape of a fundus tomographic image may be used.

  When the acquired fundus tomographic image is determined to be a virtual image, the control unit 70 moves the reference mirror 31 in the direction in which the real image is acquired (the direction in which the reference light is shortened). At this time, the control unit 70 calculates the amount of movement of the reference mirror 31 that makes the amount of deviation from the optical path length matching position S to the image detection position zero, and further moves the reference mirror 31 by twice the calculated amount of movement. Move. As a result, only the real image is acquired. In this case, the amount of deviation when the reference mirror 31 is moved by a certain amount may be obtained in advance. Accordingly, the control unit 70 can move the reference mirror 31 so that the amount of deviation from the depth position of the optical path length tomographic image to the image detection position becomes a predetermined amount of deviation, and the fundus tomographic image is predetermined. Can be displayed at the display position. The means for moving the reference mirror 31 is not limited to this. For example, when it is determined as a virtual image, a predetermined offset amount for moving the reference mirror 31 in a direction in which the real image is acquired (a direction in which the reference light is shortened) is set in advance. Then, when it is determined that the fundus tomographic image is a virtual image, the control unit 70 moves the reference mirror 31 by a predetermined offset amount.

  When the acquired fundus tomographic image is determined to be a real image, the control unit 70 regards the position where the peak of the luminance distribution in the depth direction is detected as the image position, and sets the optical path length adjustment position and the image set in advance. The amount of displacement with respect to the position is calculated, and the reference mirror 31 is moved so that the amount of displacement is eliminated (see Japanese Patent Application Laid-Open No. 2010-12111).

  As described above, the control unit 70 preferably performs real / virtual determination on the tomographic image of the image data G1, and further determines in parallel whether the real image and the virtual image coexist in the image data G1. For example, the control unit 70 detects the average position of the detection positions of the maximum luminance value in each scanning line calculated as described above as the image position P1 of the fundus tomographic image. Then, the control unit 70 calculates a deviation amount from the depth position S (the upper end position of the first image data) where the optical path lengths of the measurement light and the reference light coincide with each other to the image detection position P1. That is, the control unit 70 detects the image position of the fundus tomogram based on the depth position S where the optical path lengths of the measurement light and the reference light match.

  Then, when the image position P1 of the fundus tomographic image calculated as described above is in the vicinity of the upper end of the tomographic image (for example, an area corresponding to ¼ from the upper end of the tomographic image), the control unit 70 performs a fundus tomographic image. It is determined that the real image and the virtual image of are co-existing. In this case, the control unit 70 moves the reference mirror 31 by a predetermined amount toward the direction in which only the real image is acquired (the direction in which the reference light is shortened). In this case, the moving direction and moving amount of the reference mirror 31 from the state where the real image and the virtual image coexist to the state where only the real image is obtained are obtained in advance by experiment or simulation and stored in the memory 72. That's fine.

  As described above, the optimization control is operated in the procedure of the first automatic optical path length adjustment, the focus adjustment, and the second automatic optical path length adjustment. In the present embodiment, the first automatic optical path length adjustment roughly adjusts the optical path length based on the signal strength of the output signal output from the light receiving element 83 so that the tomographic image includes the fundus tomographic image. It is. On the other hand, in the second automatic optical path length adjustment, position information of the fundus tomographic image in the depth direction is acquired based on the output signal output from the light receiving element 83, and the fundus tomographic image is determined based on the acquired position information. The optical path length is severely adjusted so that the optical path length is acquired at the depth position. The first automatic optical path length adjustment is an optical path length adjustment for enabling focus adjustment, while the second automatic optical path length adjustment is an optical path length adjustment for adjusting to an optimal optical path length during photographing.

  For example, since the focus adjustment is performed based on the luminance value of the fundus tomographic image, the fundus tomographic image needs to be included in the imaging range of the tomographic image. For this reason, since the optical path length is roughly adjusted by the first automatic optical path length adjustment before the focus adjustment, and the fundus tomographic image is acquired in the tomographic image, the focus can be adjusted smoothly.

  In addition, by adjusting the optical path length after focus adjustment based on the tomographic image as described above, the optical path length can be adjusted using a fundus image whose image quality (resolution, contrast, etc.) has been improved by focus adjustment. The fundus image can be reliably guided toward

  That is, in the optical path length adjustment before the focus adjustment, since the luminance detected from the image is weak, the determination of the real image / virtual image and the guidance control of the fundus tomographic image to an appropriate depth position may not be performed properly. Therefore, by performing automatic optical path length adjustment (OPL) control before and after focusing as described above, the optical path length adjustment can be performed smoothly and stably.

  As a result, the optical path length adjustment and the focus adjustment can be smoothly performed even in an optical tomography apparatus that does not use an optical system dedicated to photographing the fundus front such as an SLO optical system or a fundus camera optical system.

<Polarizer adjustment>
The control unit 70 drives the polarizer 33 based on the output signal output from the light receiving element 83 after the second automatic optical path length adjustment, and adjusts the polarization state.

  Specifically, the control unit 70 moves the position of the polarizer 33 from the initial position to the movement start position. The initial position of the polarizer 33 is arranged at a position midway between the first movement limit position and the second movement limit position. Note that the movement start position of the polarizer 33 at the time of polarizer adjustment is the position of the first movement limit position or the second movement limit position.

  The controller 70 selects the movement start position of either the first movement limit position or the second movement limit position from the midway position and moves the polarizer 33. For example, the control unit 70 selects the first movement limit position as the movement start position, and moves the polarizer 33. Then, the control unit 70 moves the polarizer 33 from the first movement limit position toward the second movement limit position. When the movement start position is the second movement limit position, the movement is moved in the direction of the first movement limit position. Then, the image on the screen of the monitor 75 at each moving position is sequentially acquired, and a position where the interference light can be received strongly (a position where the polarization state of the measurement light and the reference light matches) is searched.

  The search for the position where the polarization state matches is performed by analyzing the image acquired at the arrangement position and calculating the evaluation value B every time the polarizer 33 is stopped at the movement position of the polarizer 33 set discretely. .

  The controller 70 moves the polarizer 33 by 5 ° to the movement limit position opposite to the movement start position. In the present embodiment, the polarizer 33 is moved by 5 °, but the present invention is not limited to this. For example, it may be 10 °, 20 °, or a configuration that can be arbitrarily set.

  Here, the control unit 70 detects an evaluation value B (peak value) that is a peak from the obtained calculation result of the evaluation value B for each position of the polarizer 33, and a position corresponding to the position where the peak value is detected. The polarizer 33 is moved. As described above, the polarizer adjustment is completed.

  As described above, when the optimization control is completed, the examiner desires even an optical tomography apparatus that does not include an optical system dedicated to frontal fundus photography such as an SLO optical system or a fundus camera optical system. Can be observed with high sensitivity and high resolution. Of course, the above method can also be applied to an apparatus including an optical system dedicated to photographing the fundus front.

<Transformation example>
Further, as a configuration for changing the optical path length difference between the optical path length of the measurement light and the optical path length of the reference light, the optical path length with the reference light may be adjusted by changing the optical path length of the measurement light. Good. For example, in the optical system of FIG. 1, the reference mirror 31 is fixed, and the relay lens 24 and the fiber end portion 39b are moved together to change the optical path length of the measurement light with respect to the optical path length of the reference light. Can be considered.

  In the above description, in the optimization control operation, it is configured to shift to the next adjustment after the previous adjustment is completed, but is not limited thereto. For example, the control unit 70 may determine whether or not the optimization adjustment is successful based on the luminance information of the tomographic image, and stop the optimization adjustment based on the determination result. In this case, for example, a control operation as shown in the flowchart of FIG. 9 can be considered. The controller 70 determines whether or not the first automatic optical path length is adjusted. The determination may be made, for example, by setting a predetermined threshold and determining whether or not the detected value (for example, the evaluation value B or the luminance value) exceeds the threshold. When the control unit 70 determines that the adjustment has failed, the control unit 70 causes the optimization control to be performed again. At this time, the optimization control may be stopped every time the optimization control fails, or the optimization control may be stopped when the optimization control fails several times. Further, when the optimization fails, a configuration may be adopted in which the examiner selects whether or not to perform the re-optimization by displaying on the monitor 75 a display indicating that the optimization has failed.

  If it is determined that the control unit 70 has failed, the polarizer 33 is rotationally driven, for example, by a predetermined angle (for example, 90 °) at which the polarization state changes before the optimization control is performed again. It may be. In this way, by adjusting the members other than the member for which the success or failure of the adjustment has been adjusted, the state in which the fundus tomographic image is received changes, and the optimization can be controlled when reoptimization is performed. It may become.

  In the above description, the optical path length adjustment, the focus adjustment, and the polarizer adjustment are performed as the optimization control operation. However, the present invention is not limited to this. For example, the polarizer adjustment may be omitted. In this case, the time required for optimization is reduced, but the sensitivity and resolution of the fundus tomographic image are reduced.

  In the above description, the optimization control operation is performed in the order of the first automatic optical path length adjustment, the focus adjustment, the second automatic optical path length adjustment, and the polarizer adjustment, but is not limited thereto. For example, polarizer adjustment may be performed between the first automatic optical path length adjustment and the focus adjustment. Further, the polarizer adjustment may be performed between the focus adjustment and the second automatic optical path length adjustment.

  In the above description, the focus adjustment is performed between the first automatic optical path length adjustment and the second automatic optical path length adjustment, and the focus is matched by one focus adjustment. However, the present invention is not limited to this. . For example, focus adjustment may be performed before and after the second optical path length adjustment. In this case, the control unit 70 performs the first focus adjustment so roughly as to allow fine adjustment of the optical path length by the second optical path length adjustment, and after completing the fine adjustment of the optical path length by the second optical path length adjustment, The focus may be matched by the two focus adjustment.

  Further, even when the first automatic optical path length adjustment is not completed, the focus adjustment may be started when the fundus tomographic image is acquired. That is, the operation timings of the first optical path length adjustment, the focus adjustment, and the second optical path length adjustment may overlap.

  In the above description, the real / virtual image of the fundus tomographic image is determined using the luminance distribution in the tomographic image. However, the cross-sectional shape of the tomographic image when the real image of the fundus tomographic image is acquired The cross-sectional shape in the tomographic image when the virtual image of the fundus tomographic image is acquired may be compared, and a determination condition capable of determining a real image / virtual image may be set in consideration of the comparison result. For example, the fact that the real image and the virtual image are symmetrical in the depth direction is used. More specifically, image processing is performed on the retinal pigment epithelium from the first image data G1 of the fundus tomogram (for example, data having a luminance value exceeding a predetermined threshold value corresponding to the luminance value of the retinal pigment epithelium is extracted. The real image / virtual image may be determined based on the extracted curved shape of the retinal pigment epithelium. Note that the present invention can also be applied to a configuration in which dispersion correction is performed using an optical member. Of course, the present invention can also be applied to a combination of optical dispersion correction and software dispersion correction.

  In the above description, each imaging condition is adjusted based on the depth profile after Fourier transform, but the present invention is not limited to this. That is, each imaging condition may be adjusted based on the output signal output from the detector. For example, spectral data before Fourier transform may be used.

  In the above description, the spectrum domain OCT using a spectrum meter has been described as an example, but the present invention is not limited to this. For example, SS-OCT (Swept source OCT) provided with a wavelength variable light source may be used.

It is a figure which shows the optical system and control system of the optical tomography apparatus which concerns on this embodiment. It is a figure which shows an example of the tomographic image acquired by an OCT optical system. It is a flowchart which shows the flow of operation | movement in this apparatus. It is a figure explaining the scanning line scanned on a tomographic image in order to obtain | require the luminance distribution data of a tomographic image. It is a figure which shows the change of the luminance distribution in the depth direction of an image. It is a figure explaining the optimization control which concerns on this embodiment. It is a flowchart which shows the flow of control operation of 1st automatic optical path length adjustment. It is a figure which shows an example of the calculation result of the evaluation value for every position of a reference mirror. It is a flowchart which shows the control operation of the example of a change.

DESCRIPTION OF SYMBOLS 23 Scan part 24 Focusing lens 24a Drive mechanism 31 Reference mirror 33 Polarizer 34 Drive mechanism 50 Drive mechanism 70 Control part 72 Memory 75 Display monitor 200 OCT optical system 300 Fixation target projection unit

Claims (6)

The light beam emitted from the light source is divided into measurement light and reference light, the measurement light beam is guided to the eye fundus of the subject, the reference light is guided to the reference optical system, and then the measurement light and the reference light reflected from the fundus An interference optical system for detecting the interference state of the
Driving means for driving an optical member disposed in the optical path of the measurement light or the reference light in order to adjust the optical path length difference between the measurement light and the reference light,
In the fundus imaging apparatus for capturing a tomographic image of the fundus based on the output signal from the detector,
The optical member is moved by controlling the drive of the driving means, and the optical member is located at a position where a fundus tomographic image is acquired based on an output signal output from the detector at each position of the optical member. First optical path length adjusting means for moving
Second optical path length adjusting means for readjusting the position of the optical member from the position adjusted by the first optical path length adjusting means;
An optical adjusting means for adjusting the interference optical system based on an output signal from the detector during the operation of the first optical path length adjusting means and the second optical path length adjusting means;
A fundus photographing apparatus comprising: The fundus imaging apparatus according to claim 1,
A focusing optical member disposed in the optical path of the measuring light to correct the diopter for the fundus of the subject,
The optical adjustment means is a focus adjustment means for moving the focus optical member to a focus position with respect to the subject's eye fundus,
The focus adjustment unit moves the focus optical member to a focus position with respect to the fundus of the subject's eye based on an output signal output from the detector through an optical path length adjustment by the first optical path length adjustment unit. ,
The second optical path length adjusting means shifts the position of the optical member from the position adjusted by the first optical path length adjusting means, based on an output signal output from the detector through focus adjustment by the focus adjusting means. A fundus imaging apparatus characterized by readjustment. In the fundus imaging apparatus according to claim 1 or 2 ,
The first optical path length adjusting means is based on the signal strength of the output signal output from the detector,
While adjusting the optical path length roughly so that the tomographic image includes the fundus tomographic image,
The second optical path length adjusting unit acquires position information of the fundus tomographic image in the depth direction based on the output signal output from the detector, and the fundus tomographic image is determined based on the acquired position information. A fundus imaging apparatus characterized by severely adjusting an optical path length so as to be acquired at a depth position. In the fundus imaging apparatus according to any one of claims 1 to 3 ,
The optical adjustment unit includes a polarization adjustment unit that substantially matches the polarization state of the measurement light and the reference light by driving a polarization element disposed in the optical path of the measurement light or the optical path of the reference light.
The polarization adjuster based on the output signal outputted from the detector, the polarizing element is driven, the fundus photographing apparatus characterized by adjusting the polarization state. In the fundus imaging apparatus according to any one of claims 1 to 4 ,
An adjustment determination means for determining whether or not the optimization adjustment is successful based on the luminance information of the tomographic image;
An ocular fundus photographing apparatus comprising: an optimization control unit that stops adjustment of optimization based on a determination result of the adjustment determination unit. The light beam emitted from the light source is divided into measurement light and reference light, the measurement light beam is guided to the eye fundus of the subject, the reference light is guided to the reference optical system, and then the measurement light and the reference light reflected from the fundus An interference optical system for detecting the interference state of the
Drive means for driving an optical member arranged in the optical path of the measurement light or the reference light in order to adjust the optical path length difference between the measurement light and the reference light;
Focus adjusting means for moving a focusing optical member arranged in the optical path of the measurement light to correct the diopter for the subject's fundus to a focus position with respect to the subject's fundus;
A polarization adjusting unit that substantially matches the polarization state of the measurement light and the reference light by driving a polarizing element disposed in the optical path of the measurement light or the optical path of the reference light;
In the fundus imaging apparatus for capturing a tomographic image of the fundus based on the output signal from the detector,
The optical member is moved by controlling the drive of the driving means, and the optical member is located at a position where a fundus tomographic image is acquired based on an output signal output from the detector at each position of the optical member. First optical path length adjusting means for moving
Second optical path length adjusting means for readjusting the position of the optical member from the position adjusted by the first optical path length adjusting means,
The focus adjusting means outputs an output signal output from the detector through optical path length adjustment by the first optical path length adjusting means during operation of the first optical path length adjusting means and the second optical path length adjusting means. Based on the above, the focus optical member is moved to a focus position with respect to the subject's fundus,
The fundus photography is characterized in that the polarization adjustment unit drives the polarization element to adjust the polarization state based on an output signal output from the detector after the optical path length adjustment by the second optical path length adjustment unit. apparatus.