JP5242473B2 - Ophthalmic photographing apparatus and calibration method for ophthalmic photographing apparatus - Google Patents

Description

  The present invention relates to an ophthalmologic imaging apparatus that measures optical tomographic imaging and an optical surface profile of a subject's eye using optical coherence tomography (OCT).

  2. Description of the Related Art Conventionally, an ophthalmologic photographing apparatus that measures an optical tomographic image of an eye to be examined and an optical surface profile by optical coherence tomography (OCT) using spectral interference by a spectroscopic optical system is known. In the case of such an ophthalmologic photographing apparatus using spectral interference, the positional relationship between the light receiving element and the interference light dispersed into each wavelength component incident on the light receiving element is important. An ophthalmologic photographing apparatus having a mechanism for adjusting a relative positional relationship between a light receiving element and another optical member is known (see Patent Document 1 and Patent Document 2).

JP 2008-203246 A JP 2007-151622 A

  In such an ophthalmologic photographing apparatus, in order to obtain a more suitable photographed image, it is necessary to precisely match the correspondence between the interference light dispersed into each wavelength component and each pixel of the light receiving element to increase sensitivity. However, with the adjustment mechanism described in Patent Document 1 or Patent Document 2, it is difficult to precisely associate each pixel of the light receiving element with each wavelength with respect to the distribution of wavelength components on the light receiving surface of such a light receiving element. There is a limit to the formation of a more suitable photographed image.

  In view of the above-described problems, the present invention suppresses the deterioration of the image quality of a photographed image based on the positional deviation of the interference light on the light receiving surface of the light receiving element, and performs sensitivity adjustment at a level that cannot be solved by the conventional adjustment mechanism. It is an object of the present invention to provide an ophthalmologic photographing apparatus capable of obtaining a suitable and highly reliable tomographic image and optical surface profile, and a calibration method for the ophthalmic photographing apparatus.

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

(1) Interferometric optics in which a part of the low coherent length light is used as measurement light and a part of the low coherent length light is used as reference light, and the reference light and the reflected light of the measurement light are combined and interfered with each other. A system, a spectroscopic optical system that splits the interference light obtained by the interference optical system into each wavelength component, and that the received interference light is received by the light receiving means, and a light of the eye to be inspected based on the light reception signal from the light receiving means In an ophthalmologic photographing apparatus that acquires image information, a light guiding unit that guides a calibration beam to the spectroscopic optical system, an optical member that causes the calibration beam to interfere, and the calibration beam Based on spectral information obtained by causing the light receiving means to receive light, the relative positional relationship between the emission position of the calibration light beam from the light guiding means and the light receiving means is adjusted. And each pixel of the light receiving means based on spectral information of the interfered light beam for calibration obtained by the light receiving means after the relative positional relationship is adjusted by the adjusting means Calculating means for calculating correction information for correcting the distribution state of each wavelength component with respect to.
(2) In the ophthalmologic photographing apparatus according to (1), an optical member for causing the calibration light beam to interfere is placed in an optical path of an optical system positioned in front of the spectral optical system with respect to the light receiving means. It is characterized by that.
(3) In the ophthalmologic photographing apparatus according to (2), the optical member for causing the calibration light beam to interfere is a cover glass having a predetermined thickness, and the calibration light beam passes through the cover glass. The light beam interferes with the light beam reflected twice inside the cover glass.
(4) In the ophthalmologic photographing apparatus according to (3), the light guiding means is an optical fiber, and the adjusting means is configured to change the light receiving means and the light guiding means by changing a light emitting end of the optical fiber or a position of the light receiving means. The relative positional relationship with the emission position of the calibration light beam from the light means is adjusted.
(5) The received light obtained by synthesizing the reflected light of the measurement light irradiated toward the eye to be examined and the reference light to make interference light, and then splitting the interference light into each wavelength component and receiving it by the light receiving means A method for calibrating an ophthalmologic photographing apparatus that obtains image information based on a result, wherein the light receiving means and the light guiding means are based on spectral information obtained by causing the light receiving means to receive a calibration light beam. A first step of adjusting a relative positional relationship with the emission position of the calibration light beam using a driving unit; and a light receiving unit after the relative positional relationship is adjusted by the first step. And a second step of calculating correction information for correcting the distribution state of each wavelength component for each pixel of the light receiving means based on the obtained spectral information. To do.

  According to the present invention, it is possible to suppress the deterioration of the image quality of the captured image based on the positional deviation of the interference light on the light receiving surface of the light receiving element, and to perform sensitivity adjustment at a level that could not be solved by the conventional adjustment mechanism. A tomographic image and an optical surface profile with high reliability can be obtained.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an optical system and a control system of the ophthalmologic photographing apparatus according to the present embodiment. In this embodiment, the depth direction of the eye to be examined is the Z direction (optical axis L1 direction), the horizontal component on the plane perpendicular to the depth direction (the same plane as the face of the subject) is the X direction, and the vertical direction. The component is described as the Y direction.

  In FIG. 1, the optical system uses a part of the low coherent length light as the measurement light and a part of the low coherent length light as the reference light, and combines the reference light and the reflected light of the measurement light to generate interference. Interference optical system (OCT optical system) 100 to be interfered, and interference light obtained by the interference optical system is dispersed for each frequency (wavelength), and the dispersed interference light is received by light receiving means (in the present embodiment, a one-dimensional light receiving element) ), A fundus observation optical system 300 capable of acquiring a fundus image for fundus observation by photographing the fundus oculi illuminated by infrared light with a two-dimensional light receiving element, Is provided. The interference optical system 100 includes a measurement optical system 100a and a reference light optical system 100b. Further, the dichroic mirror 40 has a characteristic of reflecting light having a wavelength component used as measurement light of the OCT optical system 100 and transmitting light having a wavelength component used as observation light of the fundus observation optical system 300.

  First, the configuration of the OCT optical system 100 will be described. Reference numeral 27 denotes an OCT light source that emits low-coherent light used as measurement light and reference light of the OCT optical system 100. 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 28 denotes an isolator for cutting light from an optical fiber 31 (to be described later) in order to prevent the light source 27 from being broken due to a strong amount of light entering the light source 27. Reference numeral 26 denotes a fiber coupler that doubles as a light splitting member and a light coupling member. The light emitted from the light source 27 passes through the optical fiber 30 serving as a light guide path, is emitted from the end 30a, and passes through an isolator 28 disposed between the two collimator lenses, thereby the end 31a of the optical fiber 31. To the fiber coupler 26. Then, it is divided into reference light and measurement light by the fiber coupler 26, the measurement light is directed to the measurement light optical system 100 a via the optical fiber 32, and the reference light is directed to the reference light optical system 100 b via the optical fiber 33.

  The measurement optical system 100a that emits the measurement light toward the eye E and obtains the reflected light can be moved in the optical axis direction according to the refractive error of the end 32a of the optical fiber 32 that emits the measurement light and the eye to be examined. A relay lens 24, an optical path length correction glass 41 for adjusting the optical path length of the measurement light, and a pair of galvanometer mirrors that can scan the measurement light in the XY directions at high speed on the fundus by driving the galvano drive mechanism 51. The scanning unit 23, the relay lens 22, the dichroic mirror 40, and the objective lens 10 are arranged. Note that the end 32a of the optical fiber 32 is disposed so as to be conjugate with the fundus of the eye to be examined. Further, the reflection surface of the galvanometer mirror of the scanning unit 23 is disposed at a position substantially conjugate with the eye pupil so that measurement light scanned in the XY directions on the fundus is not scattered by the eye pupil. In this embodiment, by disposing the galvanometer mirror so that the intermediate position of the pair of galvanometer mirrors and the eye pupil to be examined are in a conjugate relationship, the reflecting surfaces of both the pair of galvanometer mirrors at a position substantially conjugate with the eye pupil to be examined. Is arranged at a position substantially conjugate with the eye pupil to be examined. The optical arrangement may be such that both reflection surfaces of the pair of galvanometer mirrors have a conjugate relationship with the eye pupil to be examined.

  The measurement light emitted from the end 32a of the optical fiber 32 reaches the galvanometer mirror of the scanning unit 23 via the relay lens 24 and the optical path length correction glass 41, and the reflection direction is changed by driving the pair of galvanometer mirrors. Then, the measurement light reflected by the galvanometer mirror 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 via the objective lens 10 and condensed by the relay lens 24 via the relay lens 22, the galvanometer mirror of the scanning unit 23, and the optical path length correction glass 41. After that, the light enters the end 32 a of the optical fiber 32. The measurement light incident on the end portion 32 a reaches the fiber coupler 34 via the optical fiber 32, the fiber coupler 26, and the optical fiber 35.

  On the other hand, in the reference optical system 100b that can change the optical path length of the reference light in the depth direction (optical axis direction) of the eye to be examined, the end portion 33a of the optical fiber 33 that emits the reference light, the collimator lens 60, and the reference An optical path length correction glass 61 for adjusting the optical path length of the light, an attenuation filter 62 for setting the light intensity of the measurement light when reaching the fiber coupler 34 and the light intensity of the entire reference light to substantially the same level, A focusing lens 63 and an end 36a of the optical fiber 36 are disposed. The optical path length correction glass 61 is referred to according to the change in the optical path length of the measurement light caused by the measurement light having a plurality of wavelength components passing through the objective lens 10, the relay lens 22, and the relay lens 24 of the measurement optical system 100a. Used to correct the optical path length of light. The optical path length correction glass 41 disposed in the measurement optical system 100a corrects the optical path length of the measurement light in accordance with the change in the optical path length of the reference light by inserting the attenuation filter 62 into the reference light optical system 100b. Used for.

  The focusing lens 63 and the end 36a of the optical fiber 36 are configured to be integrally movable in the optical axis direction by the drive mechanism 50 in order to change the optical path length of the reference light. As a result, the configuration can be simplified as compared with the conventional method of moving the reference mirror in the optical axis direction.

  The reference light emitted from the end portion 33 a of the optical fiber 33 is converted into a parallel light beam by the collimator lens 60, condensed by the focusing lens 63 through the optical path length correction glass 61 and the attenuation filter 62, and the end portion 36 a of the optical fiber 36. Is incident on. The reference light incident on the end 36 a reaches the fiber coupler 34 via the optical fiber 36.

  Here, the reflected light of the measurement light and the reference light are combined by the fiber coupler 34 to become interference light, and then travel to the spectroscopic optical system 200 through the optical fiber 39.

  The spectroscopic optical system 200 includes a collimator lens 80, a diffraction grating 81 (dispersing prism or the like may be used) that acts to split interference light emitted from the end 39a of the optical fiber 39 into each wavelength component, and a diffraction grating. A condensing lens 82 that condenses the interference light dispersed by 81 and a light receiving element 83 (in this embodiment, a one-dimensional light receiving element) that receives the interference light dispersed into each wavelength component are disposed as light receiving means. . Interference light (reference light combined with measurement light) emitted from the end 39a of the optical fiber 39 is converted into parallel light by the collimator lens 80, and is split into each wavelength component by the diffraction grating 81, and passes through the condenser lens 82. The light is condensed on the light receiving element 83. Thereby, a spectrum interference fringe (power spectrum) is recorded on the light receiving element 83. A light reception signal from the light receiving element 83 is input to the control unit 70. Here, there is a Fourier transform relationship between the power spectrum received by the light receiving element 83 and the correlation function. Therefore, the control unit 70 obtains a cross-correlation function between the measurement light and the reference light by Fourier transforming the spectral interference fringes measured by the light receiving element 83, and this becomes an OCT signal. Thereby, the shape in the depth direction of the eye to be examined can be measured. A cover glass 400 having a predetermined thickness is disposed in the optical path between the collimator lens 80 and the end 39a of the optical fiber 39. The front surface and the rear surface of the cover glass 400 are planes that intersect perpendicularly to the optical axis L2, and the cover glass 400 has a role for causing a calibration light beam to be described later to interfere. In the present embodiment, the cover glass 400 is disposed between the collimator lens 80 and the end 39a of the optical fiber 39, but is not limited thereto. The cover glass 400 only needs to be disposed in the optical path of the optical system formed before the spectroscopic optical system 200 and through which the calibration light flux passes. In the present embodiment, the cover glass 400 is fixedly disposed in the optical path of a predetermined optical system. However, the present invention is not limited to this. The cover glass 400 can be inserted into and removed from the optical path, and is inserted into the optical path as necessary. It can also be set as a structure.

  Next, the configuration of the position adjustment mechanism 90 that adjusts the position of the light receiving element 83 with respect to other members of the spectroscopic optical system 200 will be described (see FIG. 2). The position adjustment mechanism 90 has a stage surface 91 to which the light receiving element 83 is attached, and the light receiving element 83 is moved in a three-dimensional manner by driving a drive mechanism 92 that moves the stage surface in three linear (xyz) directions. Can be made. The drive mechanism 92 is preferably adjustable in position on the order of several microns or nanometers in consideration of the size per pixel of the light receiving element 83. For example, the minimum unit of the linear movement amount is 1 μm, and the rotational movement is The minimum unit of quantity is 2 minutes. Further, as a drive mechanism used for the position adjustment mechanism 90, one using a piezoelectric (piezo) element or a stepping motor can be considered so that precise position adjustment can be performed. In the present embodiment, the light receiving element 83 can be moved three-dimensionally by the drive mechanism 92, but the light receiving element 83 only needs to be movable at least in the y-axis direction on the paper surface. If there is sufficient space for placing the position adjustment mechanism 90 in the housing, in addition to the three-dimensional direction (xyz direction) described above, the rotation direction of the two axes (rotation on the xy plane and the xz plane) You may provide the rotational drive mechanism to rotate. In the present embodiment, the light receiving element 83 is moved (including rotational movement). However, the present invention is not limited to this, and the light receiving element can be moved relative to other optical members. I just need it. For example, a position adjusting mechanism may be provided at the exit end 39a of the optical fiber 39 that guides a predetermined light beam toward the spectroscopic optical system 200 so that the position and orientation of the exit end 39a can be changed.

  Next, returning to FIG. 1, the fundus oculi observation optical system 300 will be described. In the fundus oculi observation optical system 300, an objective lens 10, an imaging lens 12, and a two-dimensional imaging element 13 are arranged. Here, the reflected light from the fundus illuminated by the fundus observation illumination optical system (not shown) forms an image on the two-dimensional image sensor 13 through the objective lens 10, the dichroic mirror 40, and the imaging lens 12. The image signal output from the two-dimensional image sensor 13 is input to the control unit 70. Then, the control unit 70 displays the fundus image captured by the image sensor 13 on the screen of the display monitor 75. The fundus image captured by the image sensor 13 is used for observing the fundus of the subject's eye and for alignment with the eye when acquiring a tomographic image. Reference numeral 72 denotes a memory which stores the acquired tomographic image, reference spectral information serving as calibration information for adjusting the position of the light receiving element 83, and the like.

  In addition, a switch unit 74 is connected to the control unit 70. The switch unit 74 is provided with, for example, a measurement start switch, a measurement position setting switch, an autocoherence switch, and the like.

  The operation of the apparatus having the above configuration will be described. First, the position adjustment (calibration) of the light receiving element 83 with respect to the interference light will be described. FIG. 5 is a flowchart showing the flow of calibration in the ophthalmologic photographing apparatus according to the present embodiment.

  In the present embodiment, the reference light is used as a calibration light beam, and only the reference light is incident on the light receiving element 83. In this case, the light shielding plate 99 for restricting the reference light and the reflected light of the measurement light from being combined is installed in the optical path through which the measurement light passes (in this embodiment, in front of the inspection window). The reflected light is prevented from reaching the end of the optical fiber 32. In this case, the light shielding plate 99 placed outside the optical path may be moved into the optical path by controlling a driving mechanism (not shown) by the control unit 70.

  Here, when the power source of the apparatus is turned on by the examiner, the control unit 70 turns on the light source 27. At this time, the measurement light emitted from the light source 27 is emitted from the end portion 32 a of the optical fiber 32, but the light shielding plate is disposed with an inclination so that the reflected light does not reach the end portion of the optical fiber 32. By the action of 99, the reflected light does not enter the end portion 32a. Accordingly, as a result, the reference light and the measurement light are not combined, and only the reference light is received by the one-dimensional light receiving element 83.

  The controller 70 performs calibration based on the spectral information obtained by causing the light receiving element 83 to receive the reference light as described above and the standard spectral information stored in the memory 72 in advance. In the present embodiment, the reference spectral information used as a reference for calibration is spectral information when the correspondence between the pixel of the light receiving element 83 and each wavelength component is a predetermined correspondence, The spectral information received by the light receiving element 83 is used when the arrangement of the optical members provided in the system 200 is in an appropriate position. More specifically, it is spectral information in the case where light of a wavelength component pre-assigned to each pixel of the light receiving element 83 is detected, and when appropriate light intensity is obtained for each pixel of the light receiving element 83. Spectral information is used. In this case, information equivalent to the spectral information of the coherent light emitted from the light source 27 can also be used as the reference spectral information.

  Hereinafter, a basic concept for adjusting the position of the light receiving element 83 will be described. In the following description, as shown in FIG. 4, the optical axis L2 direction component in FIG. 1 is on a plane perpendicular to the z direction and the optical axis L2 direction (reference calibration information). A position where the direction component perpendicular to the longitudinal direction of the light receiving element 83 arranged at the position after the completion of the operation is on a plane perpendicular to the y (vertical) direction and the optical axis L2 direction and where the reference spectral information can be detected A description will be made assuming that the longitudinal component of the light receiving element 83 arranged at (position after completion of calibration) is the x (left and right) direction. The light receiving element 83 is mounted on the stage surface 91 of the position adjusting mechanism 90 so that the light receiving surface thereof faces the condenser lens 82.

  Here, with respect to the reference spectral information stored in the memory 72 (see FIG. 3), the waveform of the spectral information detected by the light receiving element 83 is not changed and the entire light amount level of the spectral information is attenuated. If it is, the control unit 70 drives the linear drive mechanism 92 to move the light receiving element 83 in one of the y directions. When the light receiving element 83 is moved in the y direction, the light amount level of the entire spectral information is increased or attenuated, so that the control unit 70 responds to the change in the spectral information detected by the light receiving element 83 and the light amount level of the entire spectral information. The light receiving element 83 is moved in the y direction so as to approach the waveform of the reference spectral information. In this case, for example, the peak of the spectral information may be set to a predetermined light amount level. When the spectroscopic optical system 200 forms a telecentric optical system in which the light beam that has passed through the condenser lens 82 is parallel to the optical axis, the above-described state is due to a shift in the z direction. There are cases. Therefore, in such a case, the movement of the light receiving element 83 takes into account the z direction in addition to the y direction.

  Further, an optical design is made so that the light beam that has passed through the condenser lens 82 is not parallel to the optical axis (a design that does not become a telecentric optical system), and for the reference spectral information (see FIG. 3) stored in the memory 72. Thus, when the waveform of the spectral information detected by the light receiving element 83 is in a gentle state, the light amount level in the central portion is attenuated and the light amount level in the peripheral portion is increased, the control unit 70 Then, the drive mechanism 92 is driven to move the light receiving element 83 in any of the z directions. When the light receiving element 83 is moved in the z direction, the waveform of the spectral information changes, so that the control unit 70 approaches the waveform of the reference spectral information according to the change in the spectral information detected by the light receiving element 83. The light receiving element 83 is moved in the z direction.

  In addition, the pixel position of the light receiving element 83 that detects the peak of the spectral information detected by the light receiving element 83 is shifted with respect to the reference spectral information (see FIG. 3) stored in the memory 72. First, the control unit 70 drives the linear drive mechanism 92 to move the light receiving element 83 in any of the x directions. When the light receiving element 83 is moved in the x direction, the detection position of the peak of spectral information in the light receiving element 83 shifts, so that the control unit 70 changes the light receiving element according to the change in the spectral information detected by the light receiving element 83. The light receiving element 83 is moved in the x direction so that the peak detection position at 83 approaches the peak detection position in the reference spectral information (so that a peak is detected at a preset pixel in the light receiving element 83). Let

  Note that the positional deviation of the optical members (the diffraction grating 81, the light receiving element 83, etc.) in the spectroscopic optical system 200 is not limited to one direction. Therefore, the movement of the xyz in the three directions of the light receiving element 83 is taken into consideration in the memory 72. Position adjustment is performed so as to be as close as possible to the stored reference spectral information. As shown in FIG. 5, the control unit 70 compares the spectral information detected by the light receiving element 83 with the reference spectral information, and drives the drive mechanism 92 to adjust the position of the light receiving element 83. The adjustment of the peak detection position, the adjustment of the waveform, and the adjustment of the light quantity level of the peak in the spectral information obtained by the light receiving element 83 are performed. Since it is difficult to completely match the spectral information obtained by the light receiving element 83 with the reference spectral information, the spectral information obtained by the light receiving element 83 is given a certain allowable range with respect to the reference spectral information. Adjustment may be made so that the information falls within the allowable range set for the reference spectral information. The control unit 70 compares the spectral information after the movement of the light receiving element 83 (after position adjustment) with the reference spectral information, and adjusts the position of the light receiving element 83 again if not within the allowable range. If it is within the allowable range, proceed to the next step. As described above, the position adjustment may be performed by adjusting the position of the emission end 39a of the optical fiber 39, as long as the relative positional deviation between the light receiving element and the other optical member is corrected.

  In the next step, the distribution state of each wavelength component for each pixel on the light receiving element 38 (hereinafter referred to as the wavelength of the spectrometer) based on the spectral information of the calibration light beam obtained by the light receiving element 38 after position adjustment. Correction information for correcting (referred to as mapping) is obtained by calculation.

As shown in FIG. 6, when passing through the cover glass 400, the calibration light beam is reflected twice by the first component E ₁ (transmitted light beam) transmitted through the cover glass 400 and the inside of the cover glass 400. The second component E ₂ (the light beam reflected once at the rear surface and reflected once at the front surface) is combined and received as interference light by the light receiving element. Therefore, the spectral information obtained by the light receiving element 83 has information on the calibration light beam interfered by the cover glass 400. Note that the refractive index n and the thickness d of the cover glass are known in advance. Note that the thickness d is narrower than the measurement range of the OCT optical system 100 of the ophthalmic measurement apparatus according to this embodiment.

  The wavelength λ of the light beam received by the light receiving element 83 by the calibration light beam is expressed by the following equation (1).

ここで、第１近似としてＣ＝Ｄ＝０と考え、Ａ＝λ₀（光源の中心波長）とする。また、想定された波長幅（例えば設計値）を充足するようにＢの値が決定される。ここに、ｐは受光素子８３のピクセル数（画素数）であり、受光素子の中心ピクセルを０とおく。例えば本実施形態で使用する受光素子８３の全画素数が2048画素であったとすると、ｐは-1024〜1023までの値をとることとなる。

Here, it is assumed that C = D = 0 as the first approximation, and A = λ ₀ (center wavelength of the light source). Further, the value of B is determined so as to satisfy an assumed wavelength width (for example, a design value). Here, p is the number of pixels (number of pixels) of the light receiving element 83, and the center pixel of the light receiving element is set to zero. For example, assuming that the total number of pixels of the light receiving element 83 used in this embodiment is 2048 pixels, p takes a value from −1024 to 1023.

  Next, based on even padding (4 times in this embodiment) zero-padding data, the interference intensity I (k) is linearly arranged so as to be equally spaced in the k space (k is the wave number). Ask for. By applying FFT (Fast Fourier Transform) relating to k to I (k), 2nd≡z (peak) is obtained from a peak corresponding to twice the optical thickness nd of the cover glass. Next, after taking out only the real image, the mirror image is discarded (the peak is not moved at the origin), and IFFT (Inverse Fast Fourier Transform) is performed, and the phase φ (k) is obtained from the real part and the imaginary part.

The interference light received by the light receiving element 83 is reflected by the first component E ₁ = E ₀ exp (ikz) transmitted through the cover glass 400 and the cover glass 400 twice, and the second component E 2 delayed in phase. = RE ₀ exp (ik (z + 2nd)) interference (r is the total reflectance of the cover glass), and its intensity distribution I (k) is expressed by the following equation (2)

と表され、前述した位相φ（ｋ）は、式（２）からexp（ik２nd）を取り出し、その位相を求めることを意味する。仮にスペクトロメータの波長マッピングが完璧であるなら、以下の式（３）

The phase φ (k) described above means that exp (ik2nd) is extracted from Equation (2) and its phase is obtained. If the spectrometer wavelength mapping is perfect, the following equation (3)

に示されるような直線になるはずであるが、波長マッピングが不完全なら直線とはならない。

However, if wavelength mapping is incomplete, it will not be a straight line.

  Here, z (peak) is obtained as follows. The interference component can be generalized as exp (ikz), and k and z have a relationship of kz = 2π. From this, it is assumed that z is the number of pixels of the light receiving element, and kmax and kmin are the maximum and minimum values of the k value detected by the light receiving element,

として、表すことができる。なお、ｉ＝０，１，２，・・・，Ｎ／２
ここで、ｚ（peak）に相当する干渉信号が、ｉ（peak）番目の画素で検出されたとすると、ｚ（peak）は以下の式（５）

Can be expressed as: I = 0, 1, 2,..., N / 2
If an interference signal corresponding to z (peak) is detected at the i (peak) th pixel, z (peak) is expressed by the following equation (5).

と表すことができる。

It can be expressed as.

  Since φ (k) should ideally be a straight line with slope z (peak) and intercept 0, assuming that the second-order and third-order nonlinear terms are σ, k is expressed by the following equation (6):

と補正される。これから補正された波長λ´がλ´＝２π／ｋ´と決まる。ここでσは以下の式（７）

It is corrected. The corrected wavelength λ ′ is determined as λ ′ = 2π / k ′. Where σ is the following equation (7)

と展開したときの非線形項σ＝ｂ₂ｋ²+ｂ₃ｋ³である。

And the nonlinear term σ = b ₂ k ² + b ₃ k ³ when expanded.

FIG. 7 is a diagram schematically showing the wavelength mapping of the spectrometer to be corrected by performing the above calculation. Further, the corrected values of φ (kmin) and φ (kmax) are within a predetermined allowable range (for example, about 1E- ⁵ ) from the ideal values z (peak) · kmin and z (peak) · kmax. If so, it is determined that it has converged. If this condition is not satisfied, the same calculation is repeated again using the above-mentioned corrected λ ′.

  Thus, the control unit 70 obtains correction information from the spectral information obtained by the light receiving element 83 by calculation, and stores the obtained correction information in the memory 72. As a result, the correspondence between each wavelength component received by the light receiving element 83 and each pixel is obtained more accurately.

  Thus, when the control unit 70 determines that the relative position adjustment of the light receiving element 83 and the correspondence between each pixel of the light receiving element and each wavelength component are appropriate, the control unit 70 The process proceeds to the step of acquiring the tomographic image of

  Below, operation | movement of the apparatus at the time of acquiring the tomographic image of a to-be-tested eye is demonstrated easily. First, the examiner aligns the measurement optical axis at the center of the pupil on the screen imaged by the anterior eye observation camera (not shown), causes the subject to gaze at the movable fixation lamp (not shown), and Guide to the desired measurement site. The examiner focuses on the fundus based on the infrared fundus image on the display monitor 75. Next, when the autocoherence switch is pressed, the control unit 70 automatically moves the end 36a of the fiber 36 and the focusing lens 63 until the OCT signal is detected by driving the drive mechanism 50.

  Here, when there is an input signal from the measurement start switch, the control unit 70 moves the measurement light two-dimensionally by driving the scanning unit 23 in the XY directions. In this case, the control unit 70 performs a correction process using the correction information stored in the memory 72 on the interference (light reception) signal from the light receiving element 83 obtained in synchronization with the scanning of the measurement light in the XY directions, By acquiring information in the depth direction of the optometry, three-dimensional OCT information can be acquired.

  Note that a calibration mode that is independent of the original measurement (image acquisition) is provided by inputting a specific mode setting switch for setting the calibration mode by providing a dedicated mode for performing calibration as described above. May be performed.

  In the present embodiment, the reference spectral information is acquired in a state where the optical system used in the ophthalmologic photographing apparatus is placed at an appropriate position. The arrangement does not necessarily mean the best state, and it is only necessary to secure an optical arrangement position (state) at which highly reliable image information can be reproduced by calibration.

  Further, in the above description, the reference light emitted from the light source 27 is used as the calibration light beam. However, the present invention is not limited to this. That is, a calibration light beam is guided from a predetermined light source (or a dedicated light source) to the spectroscopic optical system 200, and the guided calibration light beam is received through the spectroscopic optical system 200. It is good also as a structure which performs the above calibrations by making it light-receive.

It is the figure which showed the optical system and control system of the ophthalmologic imaging device in this embodiment. It is the figure which showed the structure of the position adjustment mechanism in this embodiment. It is the figure which showed the example of reference | standard spectral information. It is a figure which shows the basic idea at the time of adjusting the position of a light receiving element. It is the flowchart which showed the flow of the calibration in this embodiment. It is the figure which showed the interference of the light beam which injected into the cover glass used for a calibration. It is the figure which showed typically the wavelength mapping of the spectrometer which is correct | amended.

27 Light source 34 Fiber coupler 39 Optical fiber 70 Control unit 72 Memory 80 Collimator lens 81 Diffraction grating 82 Condensing lens 83 Light receiving element 100 OCT optical system 200 Spectroscopic optical system 300 Fundus observation optical system 400 Cover glass

Claims (5)

An interference optical system that uses a part of the low-coherent length light as the measurement light and a part of the low-coherent length light as the reference light, and combines and interferes with the reference light and the reflected light of the measurement light; A spectral optical system that separates the interference light obtained by the interference optical system into each wavelength component and causes the light receiving means to receive the split interference light, and image information of the eye to be inspected based on a light reception signal from the light receiving means. In the ophthalmic imaging device to be acquired,
It is obtained by guiding a light beam for calibration to the spectroscopic optical system, an optical member for causing the calibration light beam to interfere, and causing the light receiving unit to receive the light beam for calibration. Adjustment means for adjusting the relative positional relationship between the light emission means and the light receiving means from the light guide means based on the spectral information, and the relative positional relationship is adjusted by the adjustment means Correction information for correcting the distribution state of each wavelength component for each pixel of the light receiving means is calculated based on the spectral information of the interfering light flux for calibration obtained by the light receiving means after An ophthalmologic photographing apparatus comprising: a calculating means obtained by: 2. The ophthalmologic photographing apparatus according to claim 1, wherein the optical member for causing the calibration light beam to interfere is placed in an optical path of an optical system positioned in front of the spectral optical system with respect to the light receiving means. Ophthalmic imaging device. 3. The ophthalmologic photographing apparatus according to claim 2, wherein the optical member for causing the calibration light beam to interfere is a cover glass having a predetermined thickness, and the calibration light beam is transmitted through the cover glass and the light beam. An ophthalmologic photographing apparatus characterized by interfering with a light beam reflected twice inside a cover glass. 4. The ophthalmologic photographing apparatus according to claim 3, wherein the light guiding unit is an optical fiber, and the adjusting unit is configured to change the position of the light emitting unit or the light receiving unit from the light receiving unit and the light guiding unit. An ophthalmologic photographing apparatus characterized by adjusting a relative positional relationship with an emission position of the calibration light beam. Based on the light reception result obtained by combining the reflected light of the measurement light irradiated toward the eye to be examined and the reference light to make interference light, then splitting the interference light into each wavelength component and receiving it by the light receiving means A method for calibrating an ophthalmologic photographing apparatus for obtaining image information
Based on the spectral information obtained by causing the light receiving means to receive the calibration light beam, the relative positional relationship between the light receiving means and the emission position of the calibration light beam from the light guiding means is driven. A first step of adjusting using
Correction information for correcting the distribution state of each wavelength component for each pixel of the light receiving means based on the spectral information obtained by the light receiving means after the relative positional relationship has been adjusted by the first step. A second step for calculating
A method for calibrating an ophthalmologic photographing apparatus, comprising:

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