JP2018102789A - Optical coherence tomography apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a favorable OCT image relating to a specific site without necessarily complicating an apparatus configuration.SOLUTION: An optical coherence tomography apparatus includes: an OCT optical system that splits a light flux exited from a light source into measurement light and reference light, guides the measurement light to an analyte and the reference light to a reference optical system, and then detects an interference state between the measurement light reflected from the analyte and the reference light by a detector; and polarization adjustment means for adjusting a polarization state of at least any of the measurement light and the reference light. The optical coherence tomography apparatus acquiring an OCT image on the basis of an output signal from the detector, further includes image acquisition means that controls the polarization adjustment means to adjust the polarization state of a specific site of the analyte included on the OCT image and acquires the OCT image relating to the specific site.SELECTED DRAWING: Figure 9

Description

  The present disclosure relates to an optical coherence tomography apparatus for obtaining an OCT image of a subject.

Optical coherence tomographic imaging apparatuses for obtaining an OCT image of a subject (for example, an eye) are known. Alignment adjustment for aligning the subject, focus adjustment for adjusting the focus on the subject, measurement light and reference Various adjustments such as polarization adjustment for adjusting the polarization state of light are performed (see, for example, Patent Document 1).

JP 2012-213489 A

  Conventionally, since the polarization adjustment is performed based on the signal of the entire OCT image, the entire image is adjusted to a bright state on average. However, since the polarization characteristics differ depending on each tissue of the subject, it may be difficult to obtain an image of a specific part desired by the examiner with an appropriate image quality.

  On the other hand, PS-OCT (Polarization Sensitive OCT) is known as an optical coherence tomography apparatus, but the apparatus configuration becomes complicated, such as preparing a plurality of detectors or multiplexing signals in the depth direction.

  In view of the above problems, it is an object of the present disclosure to provide an optical coherence tomographic imaging apparatus that can acquire a good OCT image related to a specific part without necessarily complicating the apparatus configuration.

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

The light beam emitted from the light source is divided into measurement light and reference light, the measurement light is guided to the subject, the reference light is guided to the reference optical system, and then interference between the measurement light reflected from the subject and the reference light An OCT optical system for detecting the state by a detector;
Polarization adjusting means for adjusting the polarization state of at least one of the measurement light and the reference light;
In an optical coherence tomography apparatus that acquires an OCT image based on an output signal from the detector,
It comprises image acquisition means for controlling the polarization adjusting means to adjust the polarization state with respect to a specific part of the subject included on the OCT image and acquiring the OCT image related to the specific part. .

  According to the present disclosure, a good OCT image regarding a specific part can be acquired without necessarily complicating the apparatus configuration.

  Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

<Overview>
<OCT optical system>
The optical coherence tomography apparatus according to the present embodiment may be, for example, an OCT optical system (optical coherence tomography) for obtaining an OCT image of a subject based on an interference signal between measurement light and reference light. The OCT image acquired by the OCT optical system may be, for example, a morphological tomographic image of a subject or a motion contrast image (OCT angio image). In this case, the OCT image may be an OCT front image (OCT interface image) or a three-dimensional OCT image.

  As an OCT optical system, for example, a light beam emitted from a light source is divided into measurement light and reference light, the measurement light is guided to the subject, the reference light is guided to the reference optical system, and then the measurement is reflected from the subject. The structure which detects the interference state of light and reference light with a detector may be sufficient. The OCT image may be acquired based on an output signal from the detector. Note that the measurement light may be scanned by an optical scanner.

<Polarization adjuster>
For example, a polarization adjustment unit (polarizer) may be provided in the optical path of the OCT optical system, and the polarization adjustment unit may be provided to adjust the polarization state of at least one of the measurement light and the reference light. . The polarization adjusting unit may be arranged in at least one of the optical path of the measurement light and the optical path of the reference light. Note that the polarization adjustment unit may be disposed in the optical path after the optical path of the measurement light and the optical path of the reference light are branched, and may be used to match the polarization states of the measurement light and the reference light.

  For example, the polarization adjustment unit may adjust the polarization direction by rotating an optical fiber in the optical path or applying pressure. In addition, the polarization adjusting unit may adjust the polarization direction using a half-wave plate or a quarter-wave plate. The polarization adjustment unit may be realized by combining a prism (for example, Fresnel ROM) having the same effect as that of the half-wave plate or the quarter-wave plate. The polarization adjustment unit may be configured to be capable of adjusting the polarization direction between at least S-polarized linearly polarized light, P-polarized linearly polarized light, and circularly polarized light.

<Polarization adjustment for specific parts>
For example, the image acquisition unit may control the polarization adjustment unit, adjust the polarization state with respect to the specific part of the subject included in the OCT image, and acquire the OCT image related to the specific part. The image acquisition unit may be a control unit that controls the polarization adjustment unit, for example.

  When acquiring an OCT image related to a specific part, for example, the image acquisition unit may control the polarization adjustment unit so that an OCT image in which the specific part is appropriately imaged is acquired. In this case, the image acquisition unit may control the polarization adjustment unit based on an image signal at a specific part in the OCT image acquired by the OCT optical system. According to such a configuration, it is possible to easily adjust to a polarization state capable of acquiring a good OCT image related to a specific part.

  Without being limited to the above configuration, for example, the image acquisition unit controls the polarization adjusting unit, and the specific part is appropriately imaged by performing adjustment to the polarization state set in advance corresponding to the specific part. An OCT image may be acquired. When the adjustment to the polarization state set in advance is performed, the drive parameter (for example, the rotation position) of the polarization adjustment unit may be stored in advance in the storage unit according to the specific part. The drive parameter corresponding to the specific part can be obtained in advance by experiments, simulations, or the like.

  When acquiring an OCT image related to a specific part, for example, the image acquisition unit controls the polarization adjustment unit, acquires a plurality of OCT images having different polarization states, and selects an OCT image in which the specific part is appropriately imaged. Also good. In this case, the image acquisition unit may select an OCT image in which the specific part is appropriately imaged based on the image signal at the specific part in the OCT image acquired by the OCT optical system. Of course, the present invention is not limited to this, and an OCT image in a polarization state set in advance corresponding to a specific part may be selected from a plurality of OCT images.

  In addition, as an OCT image in which a specific part is appropriately imaged, an OCT image in which a specific part is appropriately imaged relative to an OCT image acquired in another polarization state (for example, luminance of the specific part) Evaluation values such as value and contrast may be relatively high, or a specific part may be rendered relatively better, or an OCT image in which the image quality of the specific part satisfies a predetermined threshold (for example, The evaluation value such as the luminance value and contrast of the specific part may satisfy a predetermined threshold value, or the boundary between the specific part and another part may be clearly detected).

  In addition, when acquiring the OCT image regarding a specific part based on the image signal in the specific part in an OCT image, for example, an image acquisition part detects the specific part of the subject contained on an OCT image by image processing, and detects The image signal at the specified specific part may be evaluated. The image acquisition unit may acquire an OCT image in which the specific part is appropriately imaged by performing a process of evaluating an image signal in the detected specific part. According to such a configuration, since the specific part can be detected by image processing, an OCT image in which the specific part is appropriately imaged can be acquired more reliably. In this case, the image acquisition unit may acquire an evaluation value related to the image quality of the specific part and acquire an OCT image in which the acquired evaluation value satisfies a certain condition.

  The specific part of the subject is not limited to the configuration for detecting the specific part of the subject by image processing, and the specific part of the subject is detected by receiving a selection instruction from the examiner for the specific part in the OCT image displayed on the display unit. You may do it.

  The specific part of the subject may be set in advance based on a scanning signal from an operation unit operated by the examiner. Thereby, the OCT image of the specific part which an examiner desires can be acquired smoothly. The configuration is not limited to this, and the specific part of the subject may be configured to be a predetermined specific part as a default. Moreover, the structure which sets a specific site | part based on the acquired OCT image may be sufficient (For example, the selection instruction | indication on an OCT image is received, a lesion site | part is detected by image processing, and it sets as a specific site | part etc.) .

  Note that the subject may be, for example, an eye to be examined, and the present embodiment can be applied to an ophthalmic OCT apparatus capable of acquiring an OCT image of the eye to be examined. In this case, the fundus or anterior segment of the eye to be examined may be used, or a vitreous body may be used. As a specific part of the fundus, for example, a retina, a choroid, or a lesion part of the fundus may be used, or a characteristic part such as a macula or a papilla may be used. In this case, a specific part of the fundus may be further subdivided, and may be subdivided, for example, as a surface layer portion, a middle layer portion, or a deep layer portion of the retina. Further, the specific part of the anterior segment may be, for example, the cornea, sclera, lens, corner, lesion part of the anterior segment, or may be a characteristic part such as a Syurem tube or a trabecular meshwork. Good. In this case, the specific part of the anterior segment may be further subdivided, for example, it may be subdivided like the corneal epithelium or endothelium, or may be subdivided like the front of the lens or the back of the lens . Further, when an OCT image including the cornea and the retina is acquired, either the cornea or the fundus may be set as the specific part. In this case, the lower sensitivity of the cornea and the fundus may be set as the specific part, and the polarization adjustment may be performed on the set specific part. The OCT image including the cornea and the retina may be used for measuring the axial length.

  Further, the subject is not limited to the eye, and may be another part of the living body (for example, ear, skin) or a subject other than the living body, and the region of interest in the subject is specified. It may be set as a part.

  In the above embodiment, the specific part of the subject may be tracked based on the OCT image including the specific part acquired by the OCT optical system, and the polarization adjustment for the specific part may be performed. By such tracking control, polarization adjustment can be performed reliably even when the subject moves.

  In this case, for example, the image acquisition unit stores the image region of the specific part in the first OCT image as a reference image, performs matching processing with the second OCT image acquired later, Polarization adjustment may be performed based on the image signal of the image region of the specific part. In addition, the present invention is not limited to this, the OCT image acquired at any time is processed, processing for detecting the image region of the specific part is performed, and polarization adjustment is performed based on the detected image signal of the image region of the specific part. You may make it perform.

  In this case, for example, the image acquisition unit may perform tracking control for tracking the specific part by controlling the optical scanner based on the imaging signal from the imaging optical system from the front observation optical system. Even if moves up, down, left and right, it is possible to reliably image a specific part. Further, the image acquisition unit performs tracking control for tracking a specific part by controlling the optical path length difference adjusting unit that adjusts the optical path length difference between the measurement light and the reference light based on an output signal from the OCT optical system, for example. Thus, even if the specific part moves in the front-rear direction (depth direction), the specific part can be reliably imaged.

  In addition, when performing polarization adjustment with respect to a specific site | part, you may make it the control part 70 perform polarization adjustment with respect to a specific site | part based on the information obtained by the test | inspection system different from an OCT optical system. The other inspection system may be, for example, an SLO (scanning laser ophthalmoscope), a fundus camera, a perimeter, or the like, and may be mounted on the apparatus according to the present embodiment together with the OCT optical system. It may be mounted on. In this case, for example, the control unit 70 may set a specific part to be acquired by the OCT optical system based on information obtained by another inspection system, and perform polarization adjustment on the set specific part. Also good. The polarization adjustment for the specified specific part may be adjusted based on an image signal at the specific part, or may be adjusted to a polarization state set in advance corresponding to the specific part. According to this, for example, regarding a disease that is difficult to identify with only an OCT optical system, it is possible to effectively acquire an OCT image of a specific part related to the disease using another examination system, and a complex diagnosis is possible It becomes.

  More specifically, the image acquisition unit may perform polarization adjustment on the specific part so that an appropriate OCT image can be obtained with respect to the specific part set based on information obtained by another inspection system. Good. For example, the technique can be used to obtain an OCT image related to a specific site (for example, a phloem plate) that is a lesion site (for example, the nipple at the time of occurrence of glaucoma) specified by another device and clinically related to the lesion site. Can be used to obtain.

  The OCT apparatus used in the present embodiment may be used as a diagnostic OCT or as a surgical OCT. In the case of diagnostic OCT, it may be a stationary type or a handy type. In the case of the surgical OCT, for example, a probe type OCT or an OCT mounted on a surgical microscope may be used.

<Example>
An embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram illustrating an optical system and a control system of the optical coherence tomography apparatus according to the present embodiment. In the following description, an ophthalmologic imaging apparatus will be described as an example. In addition, although the case where the fundus is imaged is taken as an example, the anterior eye segment may be imaged. In the present embodiment, the depth direction of the eye to be examined is described as the Z direction (optical axis L1 direction), the horizontal direction component on the plane perpendicular to the depth direction is defined as the X direction, and the vertical direction component is defined 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. The OCT optical system 200 may be, for example, a spectral domain OCT (SD-OCT), a swept source OCT (SS-OCT), or a time domain OCT (TD-OCT). There may be.

  First, the configuration of the OCT optical system 200 provided on the reflection side of the dichroic mirror 40 will be described. The OCT light source 27 is 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 or the like 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, in the first automatic optical path length adjustment and focus adjustment, a predetermined evaluation value B is used as an index indicating the signal intensity, and in the polarizer adjustment, an evaluation value C is used as an index indicating the signal intensity of a specific part. (Refer to <Polarizer adjustment> for details.) The evaluation value C may also be used in the first automatic optical path length adjustment and focus adjustment.

  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 and the focus 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 the fundus tomographic image as 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 the fundus tomographic image 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.

  For example, the control unit 70 may move the polarizer 33 by 5 degrees 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.

  Hereinafter, an example in the case of adjusting the polarization state with respect to a specific part is shown. In this case, a specific part desired by the examiner may be set in advance. For example, a plurality of specific parts (for example, retina, choroid, lesion part, anterior eye corner or Sillem tube, etc.) are displayed on the monitor. 75 may be displayed so as to be selectable, and may be selected by the examiner via the control unit 74.

  As the timing for setting the specific part, it is set smoothly through the control unit 74 operated by the examiner at the same time as setting of the imaging part etc. in the stage before the alignment, focus etc. are performed. And shooting is possible. Of course, it may be set at another timing.

  When performing polarization adjustment on a predetermined specific part, for example, the control unit 70 sequentially acquires tomographic images at each movement position of the polarizer 33 and detects the signal intensity at the predetermined specific part more strongly. The optimum position to be searched may be searched.

  The optimum position is, for example, a position where the signal intensity at the specific part is detected more strongly as a result, and is a position where the reflected light and the reference light interfere with each other from the specific part due to the measurement light. The reflected light from a specific part may be either P-polarized light or S-polarized linearly polarized light, or circularly polarized light, and the polarization characteristic of incident light to the specific part, the polarization characteristic of the specific part, the specific part Depending on the polarization characteristics in the optical path. For this reason, when the polarization characteristic of the polarizer 33 does not match the polarization characteristic of the reflected light from the specific part, there is a possibility that the image quality of the specific part is not good or the specific part is not imaged.

  Therefore, by adjusting the polarization characteristics of the polarizer 33 to match the reflected light from the specific part, a tomographic image at a position (optimal position) where the reflected light from the specific part and the reference light more interfere with each other is obtained. As a result, a good tomographic image can be obtained for a specific part. For example, even when the image quality of a specific part is not good at a position with low coherence, a tomographic image in which the specific part is imaged more clearly is obtained by adjusting the polarization of the specific part. In addition, even when the specific part is not imaged at a position where the coherence is low, a tomographic image in which the specific part is imaged can be obtained by adjusting the polarization of the specific part.

  The optimum position is not limited to the peak position where the signal intensity at the specific part is detected most strongly, and may be in the vicinity of the peak position. A tomographic image with high signal intensity can be obtained. Further, the optimum position may be a position where a signal having a certain intensity that can be tolerated in a specific part is detected. According to this, the polarization adjustment can be completed in a shorter time.

  When searching for the optimal position, the control unit 70 analyzes the image acquired at the movement position every time the polarizer 33 is stopped at the movement position of the polarizer 33 set discretely, and evaluates at a specific part. The value C may be calculated.

  When obtaining the evaluation value C at the specific part at each moving position, the control unit 70 may detect the specific part by performing image processing on the tomographic image. When detecting layers such as the retina surface layer and the choroid, the control unit 70 may detect a predetermined layer by, for example, separating a tomographic image for each layer by image processing (segmentation). FIG. 9 is a diagram showing an example when a retinal surface layer is detected as a specific part (see hatching).

  When specifying the lesion site, the control unit 70 may detect the lesion site by image processing from the shape, size, luminance value, and the like of the lesion site, for example. When detecting other feature parts (for example, macular, nipple, corner, Schlemm's canal), the control unit 70 may detect a predetermined feature part by image processing from the brightness, position, etc. of the feature part, for example. .

  When the specific part is detected, the control unit 70 may calculate the evaluation value C at the specific part based on the signal intensity in the image region corresponding to the specific part (see FIG. 10). The evaluation value C may be, for example, the cumulative value, average value, contrast, and sharpness of the luminance values in the image area corresponding to the specific part. Further, the evaluation value C may be a change in the signal intensity in the depth direction. For example, the evaluation value C may be a spread degree of a region having a luminance value greater than or equal to a predetermined threshold value in the depth direction. Moreover, when obtaining the evaluation value in the specific part, the evaluation value C in the specific part detected by the image processing may be used, or the evaluation value C in a certain range including the specific part detected by the image processing. It may be.

  The control unit 70 calculates the movement position corresponding to the optimum position (for example, the position where the evaluation value C reaches a peak, the vicinity of the peak position, the evaluation from the calculation result of the evaluation value C of the specific part for each acquired position of the polarizer 33 A position where the value C satisfies a predetermined threshold value) is detected, and the polarizer 33 is moved to the movement position corresponding to the optimum position. As described above, the polarizer adjustment is completed.

  When the trigger signal for starting imaging is automatically or manually issued after the polarizer adjustment is completed, the control unit 70 controls driving of the scanning drive mechanism 51 and captures a tomographic image with respect to the set scanning region. May be. The captured tomographic image is stored in a storage unit (not shown). In this case, the control unit 70 may acquire a plurality of tomographic images in the set scanning region, and obtain a composite image (for example, an addition average image, a super-resolution image) based on the acquired plurality of tomographic images. You may get it.

  Based on the above, by automatically adjusting the position of the polarizer 33 with respect to a specific part, a tomographic image of the specific part desired by the examiner can be easily acquired. Furthermore, by obtaining a composite image of tomographic images, a clearer tomographic image is acquired for a specific part desired by the examiner.

  FIG. 11 is an example of an OCT image when the retinal surface layer is set as the specific part, and FIG. 12 is an example of an OCT image when the choroid is set as the specific part.

  In the above description, a tomographic image related to one specific part is acquired. However, the present invention is not limited to this, and polarization adjustment for acquiring tomographic images related to a plurality of specific parts may be performed. In this case, the control unit 70 acquires a tomographic image related to the first specific part by adjusting the polarization state with respect to the first specific part (for example, the retina surface layer), and then acquires the second specific part ( For example, a tomographic image related to the second specific part may be acquired by adjusting the polarization state with respect to the choroid.

  Furthermore, the control unit 70 acquires a composite image (for example, an addition average image, a super-resolution image) obtained by synthesizing the first tomographic image related to the first specific part and the second tomographic image related to the second specific part. May be. In addition, the composite image may be a composite image obtained by connecting the image region of the first specific part in the first tomographic image and the image region of the second specific part in the second tomographic image.

  In the above description, the specific part is automatically detected. However, the present invention is not limited to this, and the specific part may be detected manually. For example, the examiner may operate the control unit 74 and specify an area corresponding to a specific part on the tomographic image displayed on the display monitor 75. The control unit 70 may perform polarization adjustment for the designated region. As a result, it is possible to easily acquire a tomographic image with good image quality of a specific part designated on the tomographic image.

  In the above description, the specific part is set in advance by the examiner. However, the present invention is not limited to this. The specific part as a default is set in advance, and the polarization adjustment for the predetermined specific part is performed. May be performed. In this case, the specific part may be changed by parameter setting. When a lesion site is detected, the lesion site may be set as a specific site.

  In the above description, the polarization characteristic of the polarizer 33 arranged in the optical path of the reference light is adjusted to match the reflected light from the specific part. However, the present invention is not limited to this, and the polarizer arranged in the optical path of the measurement light As a result, a tomographic image in which a specific part is well imaged may be acquired. Further, the polarizer 33 may be arranged in both the optical path of the measurement light and the optical path of the reference light, and the polarization of the specific part may be adjusted by adjusting the polarizer of each optical path.

  In addition, the optimal position of the polarizer 33 corresponding to the specific site | part of the eye to be examined may be memorize | stored in a memory | storage part, and may be used for follow-up observation (follow-up). That is, the control unit 70 may call position information of the polarizer 33 corresponding to the specific part from the storage unit and reproduce it at the next imaging. In this case, position information of the polarizer 33 may be stored according to each specific part.

  In the case of follow-up shooting, the control unit 70 may cope with fluctuations due to passage of time by searching within a certain range (for example, ± 10 degrees) with reference to the position information. In addition, follow-up may be performed between different apparatuses. In this case, the polarizer 33 is arranged at a position in which a polarization characteristic change specific to each apparatus when the polarizer 33 is driven is considered with respect to the past optimum position. May be. Alternatively, the position of the polarizer 33 in the follow-up may be obtained by estimating the shift amount from the previous polarizer position based on the age, the turbidity of the crystalline lens, or the like.

  Further, for example, the control unit 70 may perform the apparatus calibration process in a state where the polarizer 33 is arranged at the optimum position corresponding to the specific part of the eye to be examined. For example, the control unit 70 may perform a dispersion correction process by software so that the evaluation value C at the specific part shows a peak. As a result, a better OCT image can be obtained for the specific part.

  Note that the control unit 70 may calculate information (for example, birefringence amount) regarding polarization characteristics at a specific part of the subject based on the OCT images before and after the polarizer 33 is driven and the drive amount of the polarizer 33. For example, the control unit 70 drives the polarizer 33 on the basis of the state in which the polarizer 33 is arranged at the optimum position (for example, the evaluation value C is the position of the luminance peak), and the distance (thickness) in the depth direction of the specific part. ) And the driving amount of the polarizer 33, the birefringence amount may be calculated. In this case, since the polarization characteristic change per unit drive amount of the polarizer 33 × polarizer drive amount = birefringence amount × distance in the depth direction can be regarded, the birefringence amount is the polarization per unit drive amount of the polarizer 33. It is obtained by the characteristic change × the driving amount of the polarizer 33 / the distance (thickness) in the depth direction. Note that the polarization characteristic change per unit driving amount of the polarizer 33 is obtained in advance by experiments and simulations. Further, the polarizer drive amount may be, for example, a drive amount from an optimal position. The distance in the depth direction may be acquired, for example, by obtaining the thickness of the specific part by image processing. According to the above method, it is possible to easily measure the polarization characteristics of a specific part. The above technique can be used, for example, to measure the amount of birefringence of the retinal surface layer (eg, nerve fiber layer).

  In addition, regarding the above-described method, the optimal position of the polarizer 33 regarding the specific part may be calculated by calculating the birefringence of the specific part in advance. In this case, an average value from a plurality of subjects may be obtained, or actual birefringence of the subject acquired in the past may be used.

It is a figure which shows the optical system and control system of the optical tomography apparatus concerning a present Example. 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 figure which shows an example when a specific site | part is set. It is a figure which shows an example of the calculation result of the evaluation value for every position of a polarizer. It is an example of an OCT image when a retina surface layer is set as a specific part. It is an example of an OCT image when a choroid is set as a specific part.

33 Polarizer 70 Control Unit 75 Display Monitor 200 OCT Optical System

Claims (5)

The light beam emitted from the light source is divided into measurement light and reference light, the measurement light is guided to the subject, the reference light is guided to the reference optical system, and then interference between the measurement light reflected from the subject and the reference light An OCT optical system for detecting the state by a detector;
In an optical coherence tomographic imaging apparatus that acquires an OCT image based on a polarization adjustment unit that adjusts a polarization state of at least one of measurement light and reference light, and an output signal from the detector,
It comprises image acquisition means for controlling the polarization adjusting means to adjust the polarization state with respect to a specific part of the subject included on the OCT image and acquiring the OCT image related to the specific part. Optical coherence tomography device.   The optical coherence tomography apparatus according to claim 1, wherein the image acquisition unit controls the polarization adjustment unit so that an OCT image in which the specific part is appropriately imaged is acquired.   The said image acquisition means detects the specific site | part of the subject contained on the said OCT image by image processing, and evaluates the image signal in the detected specific site | part, The any one of Claims 1-2 Optical coherence tomography device.   The image acquisition means performs tracking for a specific part of a subject based on an OCT image including the specific part acquired by the OCT optical system, and performs polarization adjustment for the specific part. Any one of the optical coherence tomography apparatus. The optical coherence tomographic imaging apparatus according to claim 1, wherein the subject is an eye to be examined.