JP2018038468A - Tomographic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tomographic imaging apparatus capable of capturing an anterior eye part tomographic image excellently.SOLUTION: A tomographic imaging apparatus for taking a tomographic image of an eye to be examined includes: an OCT optical system for acquiring a tomographic image of the eye to be examined based on an interference light of a measurement light emitted from a light source and reflected by the eye to be examined, and a reference light corresponding to the measurement light; a scanning optical system 108 for scanning the measurement light to the eye to be examined; light path length correction means (110, for example) for correcting the light path length of at least one of the measurement light and the reference light according to a distance between the eye to be examined and an objective lens; and control means 108 for controlling a swing angle when the measurement light is scanned by the scanning optical system based on a correction amount of the light path length.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a tomographic image capturing apparatus for capturing a tomographic image of an eye to be examined.

  The light beam emitted from the light source is divided into the measurement light beam and the reference light beam, the measurement light beam is guided to a predetermined part of the eye to be examined, the reference light beam is guided to the reference optical system, and then reflected by the predetermined part of the eye to be examined and the reference light beam 2. Description of the Related Art A tomographic imaging apparatus (Optical Coherence Tomography: OCT) that has an interference optical system that causes a light receiving element to receive interference light obtained by combining with a light beam and that captures a tomographic image of the fundus of a subject's eye is known. In such an apparatus, in order to change the photographing position in the optical axis direction, the optical path difference between the measurement light and the reference light can be adjusted by moving a predetermined optical path length changing member in the optical axis direction. (See Patent Document 1).

  Japanese Patent Application Laid-Open No. 2004-228561 discloses an apparatus capable of capturing an anterior ocular segment tomographic image of an eye to be examined by mounting an adapter lens for anterior ocular segment imaging in the tomographic imaging apparatus as described above.

JP 2008-029467 A JP 2011-147612 A

  By the way, in the apparatus as described above, when it is attempted to photograph the anterior segment without using the adapter lens, the optical path between the objective lens and the eye to be examined can be non-telecentric. In this case, since the variation in working distance depends on the optical performance of the anterior ocular segment observation optical system, if the working distance deviates from the design value, the scanning distance of the measurement light in the direction perpendicular to the optical axis changes. As a result, it may not be possible to capture a tomographic image within a desired imaging range.

  In view of the conventional problems, it is an object of the present disclosure to provide a tomographic imaging apparatus that can appropriately shoot an anterior segment tomographic image.

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

  (1) A tomographic imaging apparatus for capturing a tomographic image of an eye to be inspected, based on interference light between measurement light emitted from a light source and reflected by the eye to be examined and reference light corresponding to the measurement light The OCT optical system for acquiring a tomographic image of the eye to be examined, a scanning optical system for scanning the measurement light with respect to the eye to be examined, and the measurement light according to the distance between the eye to be examined and the objective lens And an optical path length correction unit that corrects at least one optical path length of the reference light, and a control unit that controls a swing angle when scanning the measurement light by the scanning optical system based on the correction amount of the optical path length. It is characterized by providing.

It is an external appearance block diagram of the ophthalmic imaging device which comprises an ophthalmic imaging device. It is a figure which shows the optical system of an ophthalmologic imaging apparatus. It is a figure which shows an example of an anterior eye part image. It is a figure which shows an example of an anterior ocular segment tomographic image.

<Embodiment>
Embodiments will be described. The tomographic imaging apparatus of this embodiment captures a tomographic image of the eye to be examined. The tomographic imaging apparatus includes, for example, an OCT optical system (for example, the OCT optical system 100), a scanning optical system (for example, the scanning unit 108), an optical path length correction unit (for example, the reference optical system 110), and a control unit ( For example, a control unit 70) is provided.

  The OCT optical system is a so-called optical coherence tomography (OCT). For example, the OCT optical system captures a tomographic image of the eye to be examined.

  The scanning optical system scans the measurement eye with the measurement light. The scanning optical system includes, for example, an optical member (for example, a galvano mirror 108a) and a first driving unit (for example, a driving unit 108b) that drives the optical member, and the angle of the optical member is changed by the first driving unit. The measuring light is scanned by. The scanning optical system may include an X scanning unit that scans the measurement light in the left-right direction (X-axis direction) of the eye to be examined and a Y scanning unit that scans the measurement light in the vertical direction (Y-axis direction) of the eye to be examined. .

  The optical path length correction unit corrects the optical path length of at least one of the measurement light and the reference light according to the working distance (the distance between the eye to be examined and the objective lens), and changes the optical path difference between the measurement light and the reference light. The optical path length correction unit includes, for example, an optical path length changing member (for example, the reference mirror 31) and a second driving unit (for example, the driving unit 50) that moves the optical path length changing member in the optical axis direction. The optical path length of the reference light is changed by moving the optical path length correction member in the optical axis direction by the second drive unit.

  For example, the control unit controls the tomographic imaging apparatus. For example, the control unit controls the swing angle when the measurement light is scanned by the scanning optical system. The swing angle is, for example, an angle at which the galvanometer mirror is tilted.

  In addition, the control unit controls the optical path length correction unit to correct the optical path length according to the working distance. For example, the control unit corrects the optical path length in accordance with the position of the eye to be examined that appears in the tomographic image. For example, the control unit corrects the optical path length so that the eye to be examined appears at a predetermined position in the tomographic image. When the optical path length is corrected, the control unit controls the swing angle of the scanning optical system according to the correction amount of the optical path length correction unit. For example, when the optical path length is corrected (that is, when the working distance is different from a predetermined value), the size of the shooting range with respect to a predetermined swing angle changes. For example, when the working distance is increased, the photographing range for a predetermined swing angle is widened, and when the working distance is close, the photographing range for a predetermined swing angle is narrowed. Therefore, the control unit can suppress the change in the photographing range even when the working distance is deviated from the predetermined value by controlling the swing angle of the scanning optical system according to the correction amount of the optical path length. .

  If the eye to be examined is not captured at a predetermined position in the tomographic image even if the optical path length is corrected by the optical path length correcting unit, the control unit shifts the predetermined position on the image and the position of the eye to be examined (for example, pixel And the swing angle of the scanning optical system may be controlled according to the correction amount of the optical path length. Also in this case, it is possible to suppress a change in the photographing range due to a shift in the working distance.

  Note that the control unit may correct the optical path length as needed so that the position of the eye to be examined in the tomographic image is constant. In this case, the swing angle of the scanning optical system may be adjusted as needed based on the correction amount of the optical path length so that the tomographic image capturing range is constant regardless of the correction of the optical path length. Thereby, a good tomographic image can be taken even when the eye to be examined moves.

  The apparatus may include a focus adjustment unit. The focus adjustment unit adjusts the collection position of the measurement light of the OCT optical system. The focus adjustment unit includes, for example, a focusing lens (for example, the focusing lens 124) and a third driving unit (for example, the driving unit 125) that moves the focusing lens in the optical axis direction.

  The control unit may control the focus adjustment unit and adjust the collection position of the measurement light based on the correction amount of the optical path length by the optical path length correction unit. For example, the control unit may calculate the working distance based on the correction amount of the optical path length, and may control the focus optical system so that the measurement light is condensed at a position corresponding to the calculated working distance. Thereby, the control unit can easily capture a clear image. Further, the control unit can smoothly shoot a clear image by adjusting the focus in conjunction with the correction of the optical path length.

<Example>
Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is an external configuration diagram of an ophthalmologic photographing apparatus constituting the ophthalmic photographing apparatus according to the present embodiment.

  The ophthalmologic photographing apparatus includes a base 1, a movable base 2 that can move in the left and right direction (X direction) and the front and rear (working distance) direction (Z direction) with respect to the base 1, and a three-dimensional view relative to the movable base 2. An imaging unit (apparatus main body) 3 that is provided so as to be movable in the direction and accommodates an optical system, which will be described later, and a face support unit 5 fixed to the base 1 for supporting the face of the subject. Further, the present apparatus is provided with an automatic movement mechanism that has an actuator and moves the imaging unit 3 relative to the eye of the subject. More specifically, the imaging unit 3 is moved in the left-right direction, the up-down direction (Y direction), and the front-rear direction with respect to the subject's eye E by an electrically driven XYZ drive unit 6 provided on the moving table 2. The

  In addition, the apparatus is provided with a manual movement mechanism that moves the imaging unit 3 relative to the eye of the subject by operating the operation member (joystick 4). More specifically, a sliding mechanism (not shown) that slides the movable table 2 in the XZ direction on the base 1 is provided. When the joystick 4 is operated, the movable table 2 moves on the base 1 in the XZ direction. Is slid in the direction. Further, by rotating a rotary knob provided on the joystick, the XYZ driving unit 6 is driven in Y and the photographing unit 3 is moved in the Y direction. Note that a monitor 8 that displays a fundus observation image, a fundus photographing image, a fundus tomographic image, an anterior ocular segment observation image, and the like is provided on the examiner side of the photographing unit 3.

  FIG. 2 is a schematic configuration diagram of an optical system and a control system housed (incorporated) in the photographing unit 3. In the present embodiment, the axial direction of the subject's eye (eye E) will be described as the Z direction, the horizontal direction as the X direction, and the vertical direction as the Y direction. The surface direction of the fundus may be considered as the XY direction.

  An outline of the apparatus configuration will be described. This apparatus is an optical coherence tomography device (OCT device) 10 for taking a tomographic image of the fundus oculi Ef of the subject's eye E. The OCT device 10 includes an alignment index projection optical system 60, an anterior ocular segment observation optical system 80, an interference optical system (OCT optical system) 100, a front observation optical system 200, a fixation target projection unit 300, and an arithmetic control unit. (CPU) 70.

  The OCT optical system 100 irradiates the fundus with measurement light. The OCT optical system 100 detects the interference state between the measurement light reflected from the fundus and the reference light by the light receiving element (detector 120). The OCT optical system 100 includes a scanning unit (also referred to as an optical scanner) 108 that scans measurement light on the fundus oculi Ef in order to change the imaging position on the fundus oculi Ef. The control unit 70 controls the operation of the scanning unit 108 based on the set scan pattern, and acquires a tomographic image based on the light reception signal from the detector 120.

<OCT optical system>
The OCT optical system 100 has a device configuration of a so-called ophthalmic optical tomography (OCT: Optical coherence tomography) and captures a tomographic image of a patient's eye. The OCT optical system 100 splits the light emitted from the measurement light source 102 into measurement light (sample light) and reference light by a coupler (light splitter) 104. The OCT optical system 100 guides the measurement light to the fundus oculi Ef of the eye E by the measurement optical system 106 and guides the reference light to the reference optical system 110. Thereafter, the detector (light receiving element) 120 receives the interference light obtained by combining the measurement light reflected by the fundus oculi Ef and the reference light.

  The detector 120 detects an interference state between the measurement light and the reference light. In the case of Fourier domain OCT, the spectral intensity of the interference light is detected by the detector 120, and a depth profile (A scan signal) in a predetermined range is obtained by Fourier transform on the spectral intensity data. Examples include Spectral-domain OCT (SD-OCT) and Swept-source OCT (SS-OCT). Moreover, Time-domain OCT (TD-OCT) may be used.

  In the case of SD-OCT, a low-coherent light source (broadband light source) is used as the light source 102, and the detector 120 is provided with a spectroscopic optical system (spectrum meter) that separates interference light into each frequency component (each wavelength component). . The spectrum meter includes, for example, a diffraction grating and a line sensor.

  In the case of SS-OCT, a wavelength scanning light source (wavelength variable light source) that changes the emission wavelength at a high speed in time is used as the light source 102, and a single light receiving element is provided as the detector 120, for example. The light source 102 includes, for example, a light source, a fiber ring resonator, and a wavelength selection filter. Examples of the wavelength selection filter include a combination of a diffraction grating and a polygon mirror, and a filter using a Fabry-Perot etalon.

  The light emitted from the light source 102 is split into a measurement light beam and a reference light beam by the coupler 104. Then, the measurement light flux passes through the optical fiber and is then emitted into the air. The luminous flux is condensed on the fundus oculi Ef via the collimating lens 122, the focusing lens 124, the optical scanner 108, and other optical members of the measurement optical system 106. Then, the light reflected by the fundus oculi Ef is returned to the optical fiber through a similar optical path.

  The optical scanner 108 scans the measurement light in the XY direction (transverse direction) on the fundus. The optical scanner 108 is arranged at a position substantially conjugate with the pupil. The optical scanner 108 is, for example, two galvanometer mirrors 108a, and the reflection angle thereof is arbitrarily adjusted by the drive unit 108b.

  Thereby, the reflection (advance) direction of the light beam emitted from the light source 102 is changed, and is scanned in an arbitrary direction on the fundus. Thereby, the imaging position on the fundus oculi Ef is changed. The optical scanner 108 may be configured to deflect light. For example, in addition to a reflective mirror (galvano mirror, polygon mirror, resonant scanner), an acousto-optic device (AOM) that changes the traveling (deflection) direction of light is used.

  The reference optical system 110 generates reference light that is combined with reflected light acquired by reflection of measurement light at the fundus oculi Ef. The reference optical system 110 may be a Michelson type or a Mach-Zehnder type. The reference optical system 110 is formed by, for example, a reflection optical system (for example, a reference mirror), and reflects light from the coupler 104 back to the coupler 104 by being reflected by the reflection optical system and guides it to the detector 120. As another example, the reference optical system 110 is formed by a transmission optical system (for example, an optical fiber), and guides the light from the coupler 104 to the detector 120 by transmitting the light without returning.

  The reference optical system 110 has a configuration in which the optical path length difference between the measurement light and the reference light is changed by moving an optical member in the reference optical path. For example, the reference mirror 31 is moved in the optical axis direction by the drive unit 50. In this embodiment, the reference optical system 110 functions as an optical path length correction optical system. The configuration for changing the optical path length difference may be arranged in the measurement optical path of the measurement optical system 106.

<Front observation optical system>
The front observation optical system 200 is provided to obtain a front image of the fundus oculi Ef. The observation optical system 200 includes, for example, an optical scanner that two-dimensionally scans the fundus of measurement light (for example, infrared light) emitted from a light source, and a confocal aperture that is disposed at a position substantially conjugate with the fundus. And a second light receiving element for receiving the fundus reflection light, and has a so-called ophthalmic scanning laser ophthalmoscope (SLO) device configuration.

  Note that the configuration of the observation optical system 200 may be a so-called fundus camera type configuration. The OCT optical system 100 may also serve as the observation optical system 200. That is, the front image may be acquired using data forming a tomographic image obtained two-dimensionally (for example, an integrated image in the depth direction of the three-dimensional tomographic image, at each XY position). The integrated value of the spectrum data.

<Fixation target projection unit>
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, the fixation position is adjusted by the lighting positions of the LEDs arranged in a matrix, the light from the light source is scanned using an optical scanner, and the fixation is performed by controlling the lighting 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.

<Alignment index>
The alignment index projection optical system 60 that projects the alignment index light beam includes a plurality of infrared light sources at 45 degree intervals on a concentric circle centered on the photographing optical axis L1 as shown in the diagram in the dotted line A in the upper left of FIG. A first index projection optical system (0 degrees and 180) having an infrared light source 61 and a collimating lens 62 arranged symmetrically with respect to a vertical plane passing through the photographing optical axis L1. A second index projection optical system having six infrared light sources 63 arranged at a position different from that of the first index projection optical system. In this case, the first index projection optical system projects an infinite distance index on the cornea of the subject's eye E from the left and right directions, and the second index projection optical system moves the finite distance index on the cornea of the subject's eye E up and down. Projection is performed from a direction or an oblique direction. In FIG. 2, for convenience, the first index projection optical system (0 degrees and 180 degrees) and only a part of the second index projection optical system (45 degrees and 135 degrees) are shown. .

<Anterior segment observation optical system>
An anterior ocular segment observation (imaging) optical system 80 that images the anterior segment of the subject's eye has a relay lens 84 and a two-dimensional imaging element (light receiving element) 85 having infrared sensitivity on the reflection side of the dichroic mirror 24. Is provided. A two-dimensional image sensor 85 (hereinafter, referred to as an image sensor 85) also serves as an imaging means for detecting an alignment index, and includes an anterior segment illuminated by an anterior segment illumination light source 68 that emits infrared light having a center wavelength of 940 nm. An alignment index is imaged. The anterior segment illuminated by the anterior segment illumination light source 68 is received by the image sensor 85 via the optical system of the dichroic mirror 24 and the relay lens 84. An alignment beam emitted from the light source of the alignment index projection optical system 60 is projected onto the subject's eye cornea, and the cornea reflection image is received by the image sensor 85 via the optical system of the dichroic mirror 24 and the relay lens 84. (Projected). The output of the image sensor 85 is input to the control unit 70, and the anterior segment image captured by the image sensor 85 is displayed on the monitor 8.

<Control unit>
The control unit 70 controls each member of the apparatus. The control unit 70 is also used as an image processing unit that processes the acquired image, an image analysis unit that analyzes the acquired image, and the like. The control unit 70 is realized by a general CPU (Central Processing Unit) or the like.

  The control unit 70 acquires a tomographic image (OCT image) by image processing based on the light reception signal output from the detector 120 of the OCT optical system 100, and receives the light reception signal output from the light receiving element of the front observation optical system 200. A front image (SLO image) is acquired based on the above.

  Further, the control unit 70 detects the misalignment of the imaging unit 3 with respect to the eye E based on the light reception result of the image sensor 85, and drives the driving unit 6 based on the detection result to perform automatic alignment. In this case, for example, the control unit 70 detects the alignment index from the anterior segment image captured by the anterior segment observation optical system 80. Further, the control unit 70 controls the fixation target projection unit 300 to change the fixation position.

  The control unit 70 is electrically connected to the joystick 4, the XYZ drive unit 6, the memory (storage unit) 72, the monitor (display unit) 8, and the operation unit 76. The control unit 70 controls the display screen of the monitor 8. The acquired fundus image is output to the monitor 8 as a still image or a moving image and stored in the memory 72. The memory 72 records, for example, the captured tomographic image, the front image, and various types of information related to imaging (for example, imaging position information of the tomographic image, identification number, etc.). The control unit 70 controls each member of the OCT optical system 100, the front observation optical system 200, and the fixation target projection unit 300 based on the operation signal output from the operation unit 76. Further, a touch panel is used as the monitor 75. For the detailed configuration of the OCT device 10, refer to, for example, Japanese Patent Application Laid-Open No. 2008-29467.

  FIG. 3 is a simplified diagram showing a part of the optical path of the OCT optical system. This apparatus is a non-telecentric system (the optical axis and the principal ray are not parallel) between the objective lens 21 and the eye E to be examined. In this case, if the working distance WD is shifted due to an alignment error or the like, the scanning distance SW changes. For example, FIG. 3A shows a state when alignment is performed at a proper working distance, and FIG. 3B shows a state when alignment is performed at a position farther than the proper working distance. Show. As shown in FIGS. 3A and 3B, when the working distance WD is different, the scanning distance SW when the measurement light is swung at a predetermined swing angle θ changes. That is, when the working distance WD deviates from a predetermined value, the eye to be examined can be shown on the tomographic image by correcting the optical path length, but the imaging range changes.

  For example, FIG. 4A shows a tomographic image taken at an appropriate working distance, and FIG. 4B shows a tomographic image taken at a position away from the appropriate working distance. . As shown in FIGS. 4 (a) and 4 (b), the tomographic image capturing range and the best focus position shift as the working distance fluctuates, so that accurate measurement cannot be performed and an image with low contrast may be obtained. is there.

  Therefore, the tomographic imaging apparatus of the present embodiment realizes a desired scanning distance by setting the swing angle of the galvanometer mirror according to the working distance even when the working distance is deviated.

<Control action>
Hereinafter, the setting of the swing angle according to the working distance will be described together with the control operation of this apparatus. As an example, a case will be described in which a tomographic image of the fundus mode is taken and then a tomographic image of the anterior segment is taken in the anterior segment mode.

<Fundus mode>
First, the control unit 70 captures a tomographic image of the fundus in the fundus mode. The control unit 70 detects the alignment bright spot from the anterior segment image captured by the anterior segment observation optical system 80 and performs alignment with the fundus. When the alignment is completed, the control unit 70 controls the driving of the driving unit 50 based on the light reception signal output from the detector 120, and sets the optical path difference between the measurement light and the reference light so that a fundus tomographic image is acquired. adjust. In this case, the reference mirror 31 is moved within a predetermined movement range corresponding to the difference in the axial length of the eye to be examined.

  Thereafter, when a scanning position / pattern desired by the examiner is set and a predetermined trigger signal is output, the control unit 70 acquires a tomographic image based on the set scanning position / pattern, and the acquired image Data is stored in the memory 72. In accordance with this, the control unit 70 stores a fundus front image acquired by the SLO optical system 200 in the memory 72.

<Anterior segment mode>
When the fundus tomographic image is captured, the control unit 70 switches the imaging mode from the fundus mode to the anterior segment mode. When the mode is switched to the anterior segment mode, the control unit 70 drives the drive unit 6 by a predetermined drive amount (for example, an average eye axis length) and moves the photographing unit 3 backward, for example. As a result, the photographing unit 3 is roughly aligned with the anterior segment. Needless to say, rough alignment may be performed by detecting bright spots in the anterior segment image taken by the anterior segment observation optical system 80.

  The control unit 70 arbitrarily moves the reference mirror 31 in the optical axis direction in a state in which the anterior eye part is roughly aligned, and the optical path length is such that the cornea Ec appears in the tomographic image obtained by the detector 120. Adjust. When the cornea Ec appears in the tomographic image, the control unit 70 calculates the working distance based on the position of the cornea Ec on the tomographic image and the position (or movement amount) of the reference mirror 31. For example, the control unit obtains a deviation amount of the cornea Ec from a predetermined position on the tomographic image and a movement amount (correction amount) of the reference mirror 31 from the predetermined position.

  For example, the position of the cornea Ec is obtained by edge detection of a tomographic image or the like. The amount of deviation of the cornea Ec from the predetermined position is obtained as the distance (number of pixels) between the pixel corresponding to the position of the cornea Ec and the pixel at the predetermined position. Further, the position of the reference mirror 31 is acquired by a sensor (an encoder, a potentiometer, or the like) that detects the position of the reference mirror 31 or a drive amount (for example, the number of pulses) of the drive unit 50. Since the working distance deviation amount according to the deviation amount of the cornea Ec and the working distance deviation amount according to the correction amount of the reference mirror 31 are determined by the design value of the apparatus, for example, the control unit 70 is set to an appropriate value. The true value of the working distance is calculated by adding the amount of deviation of these working distances from the working distance.

  Next, the control unit 70 causes the scanning unit 108 to scan the measurement light in the X direction and the Y direction. Then, XY alignment is performed based on the acquired two tomographic images in the X direction and the Y direction. For example, when a corneal bright spot is detected in the tomographic image in both the X scan and the Y scan, the control unit 70 continues to maintain the alignment state at that position. Here, the corneal bright spot in the tomographic image indicates noise when the reflected light from the cornea is detected and saturated by the detector 120 with high intensity.

  Next, the control unit 70 acquires an appropriate swing angle of the galvanometer mirror 108a based on the calculated working distance. For example, the control unit 70 reads the function of the swing angle with the working distance as a variable, or a table in which the swing angle at which the shooting distance is constant is set for each numerical value of the working distance from the memory 72 and operates. The swing angle of the galvanometer mirror 108a according to the distance is obtained. For example, the swing angle of the galvanometer mirror 108a becomes smaller as the working distance becomes larger than a predetermined value.

  The control unit 70 controls the drive unit 108b based on the calculated result, automatically adjusts the swing angle of the galvano mirror 108a, and acquires a tomographic image using the detector 120.

  As described above, the tomographic imaging apparatus of the present embodiment adjusts the swing angle of the galvanometer mirror 108a based on the working distance calculated from the optical path length correction amount (for example, the movement amount of the reference mirror). Even a non-telecentric optical system can automatically capture an anterior segment tomographic image with little change in scanning distance.

  Note that the control unit 70 may control the position of the focusing lens 124 based on the working distance, similarly to the swing angle of the galvanometer mirror 108a. For example, the control unit 70 reads from the memory 72 a function of the driving amount of the focusing lens 124 using the working distance as a variable, or a table in which the driving amount of the focusing lens 124 corresponding to each numerical value of the working distance is set. Then, the driving amount of the focusing lens 124 corresponding to the working distance is obtained. Accordingly, the control unit 70 can adjust the focus position so that the measurement light is condensed at a position corresponding to the calculated working distance. In this way, by automatically controlling the position of the focusing lens 124 according to the working distance, a clear image can be acquired smoothly.

  Although the optical path difference between the measurement light and the reference light is adjusted by moving the reference mirror, the optical path length of the measurement light may be adjusted. For example, the optical path length of the measurement light may be adjusted by moving the end 139 of the fiber on the measurement light side and the collimator lens 122 integrally in the optical axis direction by a drive mechanism (not shown). Further, the optical path length of the measurement light may be adjusted by moving the photographing unit 3 by the driving unit 6.

  Note that for the tomographic image, image processing for correcting image distortion may be performed according to the working distance. In this embodiment, since the change in the scanning distance is small, the accuracy of distortion correction can be increased, leading to an improvement in the reliability of analysis results such as shape analysis.

60 alignment index projection optical system 70 control unit 72 memory 75 monitor 76 operation unit 80 anterior ocular segment observation optical system 100 interference optical system (OCT optical system)
108 Optical Scanner 200 Front Observation Optical System 300 Fixation Target Projection Unit

Claims (6)

A tomographic imaging apparatus for imaging a tomographic image of an eye to be examined,
An OCT optical system that acquires a tomographic image of the eye to be inspected based on interference light between measurement light emitted from a light source and reflected by the eye to be examined and reference light corresponding to the measurement light;
A scanning optical system for scanning the measurement light with respect to the eye to be examined;
An optical path length correction means for correcting an optical path length of at least one of the measurement light and the reference light according to a distance between the eye to be examined and the objective lens;
A tomographic imaging apparatus comprising: control means for controlling a swing angle when scanning the measurement light by the scanning optical system based on the correction amount of the optical path length.   The tomographic imaging apparatus according to claim 1, wherein the control unit controls the optical path length correction unit to correct the optical path length according to a position of an eye to be inspected in the tomographic image.   The tomographic imaging apparatus according to claim 1, wherein the control unit controls the swing angle based on a position of an eye to be inspected in the tomographic image and a correction amount of the optical path length.   The control means controls the optical path length correction means to correct the optical path length as needed so that the position of the eye to be examined reflected in the tomographic image is constant, and to adjust the tomographic image regardless of the correction of the optical path length. The tomographic imaging apparatus according to claim 1, wherein the swing angle is controlled as needed based on the correction amount so that the imaging range is constant. A focus adjusting means for adjusting the condensing position of the measurement light;
The tomographic imaging apparatus according to claim 1, wherein the control unit controls the focus adjustment unit to adjust the condensing position based on the correction amount.   The tomographic image photographing apparatus according to claim 5, wherein the control unit adjusts the condensing position based on a position of an eye to be inspected in the tomographic image and a correction amount of the optical path length.