JP5893248B2 - Optical tomographic imaging method and optical tomographic imaging apparatus - Google Patents

Description

  The present invention relates to an optical tomographic image capturing method and an optical tomographic image capturing apparatus, and more particularly to an optical tomographic image capturing method and an optical tomographic image capturing apparatus used for ophthalmic medical care and the like.

  Currently, various types of ophthalmic equipment using optical equipment are used. For example, an anterior ocular segment photographing machine, a fundus camera, a confocal laser scanning ophthalmoscope (SLO), or the like. Among them, an optical tomographic imaging apparatus based on optical coherence tomography (OCT) using low-coherence light is an apparatus that can obtain a tomographic image of an eye to be examined with high resolution. It is becoming an indispensable device for specialized outpatients. Hereinafter, this is referred to as an OCT apparatus.

  The fundus oculi observation device of Patent Document 1 includes a fundus camera unit, an OCT unit, and an arithmetic control device. The fundus camera unit acquires a two-dimensional image of the fundus, and the OCT unit acquires a tomographic image of the fundus. Furthermore, the characteristic part of the fundus can be specified, and measurement can be performed by changing the irradiation position of the measurement light. Then, a fundus tomographic image or a three-dimensional image can be formed.

JP 2009-279031 A

  Until now, tomographic images and three-dimensional images have been acquired in the OCT apparatus. Among them, there is a demand for quantitatively measuring the shape of the eye such as the curvature of the retina. However, since the tomographic image of a general OCT apparatus does not correctly display the spatial shape, it is not suitable for measuring the curvature from the tomographic image.

In order to solve the above-described problem, an optical tomographic imaging method according to the present invention adjusts the distance between an eye to be examined and an objective lens, and returns light from the eye to be obtained that is obtained by irradiating the eye with measurement light. An optical tomographic imaging method for acquiring a tomographic image of an eye to be inspected by a combined light with a reference light, a first step of measuring a distance between the eye to be examined and an objective lens, and acquiring a tomographic image of the eye to be inspected a second step, using a third step of setting a region for calculating the curvature in the tomographic image, the distance measured, possess a fourth step of calculating the curvature of the set area, a curvature The calculation is performed using the distance from the rotation center of the scan of the measurement light to the retina, the scan angle, the coherence gate position determined by the optical path length of the reference light, the coordinates on the tomographic image, and the pixel resolution in the depth direction of the tomographic image. We characterized the Rukoto.

  According to the present invention, the shape of the eye such as the curvature of the retina can be measured quantitatively.

Diagram explaining the OCT apparatus Illustration explaining working distance and scanning radius A diagram showing the relationship between working distance and rotation center-retinal distance Diagram showing changes in tomographic images and two-dimensional images due to changes in working distance Diagram showing changes in anterior segment observation due to changes in working distance The figure which shows the procedure of the signal processing in Example 1. Diagram explaining coordinate transformation The figure explaining calculation of the curvature in Example 2.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[Example 1]
FIG. 1 is a diagram illustrating a configuration of an optical tomographic imaging apparatus according to the first embodiment.

(Optical system)
The optical tomographic imaging apparatus is configured by a Michelson interference system. The outgoing light 102 of the light source 101 is guided to the single mode fiber 107 and enters the optical coupler 108, and is split into the reference light 103 and the measuring light 104 by the optical coupler 108. Then, the measurement light 104 is reflected or scattered by the measurement portion of the retina 125 to be observed, and returns to the optical coupler 108 as return light 105. Then, the optical coupler 108 combines with the reference light 103 that has passed through the reference optical path to become the combined light 106 and reaches the spectroscope 119.

  The light source 101 is a SLD light source (Super Luminescent Diode) which is a typical low-coherent light source. In consideration of measuring the eye, near-infrared light is suitable for the wavelength. Furthermore, since the wavelength affects the resolution in the lateral direction of the obtained tomographic image, it is desirable that the wavelength be as short as possible. Here, the center wavelength is 840 nm and the wavelength width is 50 nm. Of course, other wavelengths may be selected depending on the measurement site to be observed. Note that although the SLD light source is selected here as the type of light source, it is only necessary to emit low-coherent light, and an ASE light source (Amplified Spontaneous Emission) or the like can also be used.

  Next, the reference light path of the reference light 103 will be described. The reference light 103 divided by the optical coupler 108 is emitted as substantially parallel light by the lens 109-1. Thereafter, the reference light 103 passes through the dispersion compensation glass 110 and changes its direction at the mirror 111. Then, the light is again guided to the spectroscope 119 via the optical coupler 108. The dispersion compensation glass 110 compensates the reference light 103 for dispersion when the measurement light 104 reciprocates between the eye to be examined 124 and the scanning optical system. Here, the length is assumed to be 24 mm assuming a representative value as the average eyeball diameter of Japanese. The optical path length of the reference light can be adjusted in the direction of the arrow by the electric stage 112 to adjust the position of the coherence gate. The coherence gate is a position on the optical path of the measurement light that is equidistant from the length of the optical path of the reference light. The electric stage 112 is controlled by the computer 120.

  Next, the measurement optical path of the measurement light 104 will be described. The measurement light 104 divided by the optical coupler 108 is emitted as substantially parallel light by the lens 109-2, and is incident on the mirror of the XY scanner 113 constituting the scanning optical system. In FIG. 1, the XY scanner 113 is a single mirror, but actually two mirrors, an X scan mirror and a Y scan mirror, are arranged close to each other. The measurement light reaches the eye to be examined 124 via the lens 114, the dichroic mirror 115, and the objective lens 128.

  Here, observation of the anterior segment, that is, the cornea 122 will be described. A ring-shaped light source (not shown) outside the objective lens is used as proof light for observing the anterior segment. The illumination light is reflected by the cornea 122, the reflected light passes through the objective lens 128 again, is reflected by the dichroic mirror 115, and reaches the observation system 118 via the split prism 116 and the optical system 117. The split prism 116 is disposed at a position conjugate with the cornea 122.

  Further, the objective lens 128 is disposed so as to face the eye to be examined 124, and shapes the shape when the measurement light is guided to the eye to be examined 124.

(Working distance)
Next, working distance will be described. Here, the working distance 126 is the length of the cornea 122 surface and the objective lens 128 surface. This length corresponds to the distance between the eye to be examined and the objective lens in the present invention. First, the optical system of a general OCT apparatus is designed so that the pupil 129 of the eye to be examined 124 becomes the rotation center of scanning of the measurement light 104. Therefore, it is desirable to perform OCT measurement by adjusting the distance between the objective lens 128 and the eye 124 so that the working distance becomes a design value. However, since the OCT apparatus has a small NA of the optical system, the depth of focus is deep, and as a result, even if the working distance deviates from the design value, imaging can be performed without any problem. If the design value deviates greatly, the light 127 is blocked or the focal point is blurred.

  Here, the relationship between the working distance, the rotation center 202 of the scanning of the measurement light, and the locus 205 of the coherence gate will be described using the schematic diagram of the eye of FIG. In these figures, the horizontal axis is the fast scan x-axis, and the vertical axis is the depth z-axis. Then, the origin of the rotation center is set as the pupil position which is a design value. In this figure, the center of rotation 202 is a point where light rays incident on the retina 201 are extended as they are, and is not a point where light refracted by the cornea or the crystalline lens 123 is connected.

  The rotation center 202 of the measurement light scan moves as the working distance 126 changes. Further, the scanning radius 204 and the scanning angle 206 when the measurement light 104 is scanned also change as the working distance 126 changes. The xy scanner 113 is often composed of two mirrors. For example, it is assumed that the rotation center of the y axis is on the 1 mm objective lens side, for example. In such a case, movement in the y-axis direction by 3D measurement needs to be separately corrected. Here, the discussion is made assuming that the rotation centers of the x-axis and y-axis are the same.

  FIG. 2A shows a case where the center of rotation 202 is closer to the retina 201 than the pupil 129 because the working distance 126 is shorter than the design value. Naturally, the distance between the rotation center 202 and the retina 201 is shorter than the design value. In the OCT measurement, the coherence gate is arranged on the vitreous body side so that the retina 201 can be observed. The position of the locus 205 of the coherence gate can be changed by the reference mirror 111. FIG. 2B shows a time when the working distance 126 substantially matches the design value. The distance between the rotation center 202 and the retina 201 is a design value. FIG. 2C shows a case where the working distance 126 is longer than the design value and the center of rotation 202 is on the objective lens 128 side with respect to the pupil 129.

  As shown in FIGS. 2A to 2C, the locus becomes flat as the scanning radius 204 becomes longer. That is, in the OCT apparatus, the difference between the retina 201 and the locus 205 of the coherence gate is displayed as an image. Therefore, the apparent curvature becomes larger as the scanning radius 204 becomes longer. However, even if the working distance 126 changes, the light that is incident at the same angle with respect to the optical axis is focused on the same part of the eyeball, so the scanning range 207 does not change significantly.

Here, the relationship between the distance change of the working distance 126 and the position of the rotation center 202 will be further described. The difference 210 from the design value of the working distance 126 is expressed as a variable g by a spatial distance. Since the origin is the pupil 129, the value of the variable g is the value of the z axis. The spatial distance from the rotation center 202 to the retina 201 is expressed as f (g) using the variable g. The coherence gate is based on the standard eye retinal position, and is specifically 24 mm from the pupil. A difference 203 on the z-axis from the reference is expressed as a variable s by a spatial distance. Using these, the scanning radius 204L (g) is expressed as Equation 1.

Movement of the coherence gate can be expressed by Equation 2 using the refractive index n _h of the eye in terms of movement amount ΔM of the reference mirror 111.

  Incidentally, the change in the spatial distance f (g) from the rotation center 202 to the retina 201 is not proportional to the change in the working distance 126. This is because the light is refracted by the cornea 122 or the crystalline lens 123. FIG. 3 shows a simulation result of the spatial distance f (g) from the rotation center 202 to the retina 201. The horizontal axis is a change g from the design value of the working distance 126. The vertical axis represents the spatial distance from the rotation center 202 to the retina 201. When the working distance 126 is on the minus side, it can be seen that the movement of the rotation center is smaller than the amount of change of the working distance 126. On the contrary, when it is on the plus side, it can be seen that the movement of the rotation center is larger than the amount of change of the working distance 126. In this simulation, a model with an axial length of 24 mm was used, but f (g) naturally changes when the axial length changes. In this case, a simulation is required for each eye axis length model. Further, when the rotation center is different between the x axis and the y axis, further simulation is required.

  Here, the example which imaged the model eye with the OCT apparatus is demonstrated using FIG. In the model eye, radial and circular patterns are arranged in a portion corresponding to the retina. The portion corresponding to the retina is the surface of the glass. These images were measured by changing the working distance 126 and adjusting the tomographic image so that the vertex of the retina position of the model eye was equidistant from the coherence gate. 4A is a tomographic image when the working distance 126 is 4 mm shorter than the design value, FIG. 4B is a two-dimensional projection image thereof, and FIG. 4C is a tomographic image when the working distance 126 is the design value. FIG. 4D shows the two-dimensional projection image, FIG. 4E shows the tomographic image when the working distance 126 is 4 mm longer than the design value, and FIG. 4F shows the two-dimensional projection image. In each tomographic image, the retina of the model eye is captured as an arc of different curvature. Moreover, the concentric circle and the radiation of the projected image are picked up and projected from the concentric circle and the radiation recorded at the retina position of the model eye. Focusing on the intersection 404 of the circle and the straight line, if the auxiliary line 405 is drawn on the corresponding tomographic image, the image of the retina moves to the lower side of the auxiliary line in FIG. 4A and to the upper side of FIG. You can see that However, as shown in FIGS. 4B, 4D, and 4F, the measurement range has almost no change.

  Next, working distance measurement will be described with reference to FIG. FIG. 5 is an image of the cornea by the anterior ocular segment observation system 118, in which the pupil 501 and the iris 502 are observed. The image of the pupil 501 is designed such that a positive region and a negative region in the y direction are separated from each other by the beam split prism and formed on the observation system 118 with the x axis as a boundary. 5A shows a case where the working distance 126 is shorter than the design value, FIG. 5B shows a case where the working distance 126 substantially matches the design value, and FIG. 5C shows a case where the working distance 126 is longer than the design value. is there. When the working distance 126 substantially matches the design value, the pupil 501 is an unseparated image. On the other hand, when the working distance 126 is shorter than the design value, the image above the pupil moves to the right side, and when it is longer, the image above the pupil moves to the left side. By measuring the difference 503 between the images of the upper and lower pupils 501, the length of the working distance 126 can be known.

  The working distance 126 corresponds to the distance between the eye to be examined and the objective lens in the present invention described above, and the configuration for knowing the length of the working distance 126 described above measures the distance between the eye to be examined and the objective lens in the present invention. Corresponds to the measurement means. The configuration also corresponds to an acquisition unit that acquires the distance between the eye to be examined and the objective lens in the present invention.

  Incidentally, the distance from the center of rotation to the retina can be determined by measuring the moving distance of the working distance 126 and the mirror 111. That is, when the coherence gate is arranged at the design value and coincides with the retina, it can be seen that the axial length is 24 mm as designed. If they do not match, move the coherence gate and look for a location that matches the retina. The true eye axis length can be known from the amount of movement. Although the retina is thick, for example, the boundary between the vitreous body and the nerve fiber layer is considered as a design value.

(Signal processing)
Here, the signal processing of the OCT measurement will be described with reference to FIG.
In step A1, measurement is started. In this state, the OCT apparatus is activated and the eye to be examined is placed at the measurement position.

  In the step A2 corresponding to the first step of the present invention, the working distance (WD) 126 is adjusted and measured. First, the OCT apparatus and the eye to be examined are aligned while observing the cornea 122 by the anterior segment observation system 118. The working distance 126 is adjusted so as to be within about ± 5 mm with respect to the design value. However, when the curvature is large, the measurement light may be brought closer to the eye to be examined in a range where the measurement light is not blocked by the glow. Naturally, the coherence gate and focus position are adjusted along with the adjustment of the working distance. The axial length can be measured by another device, but if necessary, it is measured using an OCT device at this stage. That is, the coherence gate is moved in a state where the working distance 126 is measured, and the boundary between the vitreous body and the nerve fiber layer is searched. Then, the position of the coherence gate at that time is stored. The position of the coherence gate may be measured by an encoder (not shown). As described above, the OCT apparatus corresponds to the image acquisition means for acquiring a tomographic image of the eye to be examined in the present invention.

  In step A3 corresponding to the second step of the present invention, OCT measurement is performed to obtain a tomographic image of the eye to be examined. The scanning range 207 is, for example, 6 mm for imaging the macula, 10 mm for imaging the macula and the nipple. Here, assuming that a range of 6 mm is imaged, 512 lines of data are acquired in the x direction and 512 lines are acquired in the y direction. One-dimensional array data (1024 pixels) is acquired for each line from the spectroscope 119 and sequentially sent to the computer 120. Then, 512 lines in the x direction are stored in units of two-dimensional array data. The data size is 1024 × 512 × 12 bits. This can be 512 sheets in the y direction.

  A tomographic image (B-Scan image) can be obtained from the measured two-dimensional array data by performing removal of fixed noise, wavelength wave number conversion, Fourier transform, and the like. If this tomographic image is confirmed and it is determined that a desired measurement has been made, the eye to be examined is removed from the measurement position.

  In step A4, coordinate conversion from a tomographic image to spatial coordinates is performed in order to calculate the curvature. At that time, an area or a part for which the curvature is desired is set in advance. The operation for making this setting corresponds to the third step of the present invention. This will be described with reference to FIG. FIG. 7A is a tomographic image of the eye to be examined, and the size is 500 (depth) × 512 (horizontal) × 12 bits. In a general tomographic image, the coherence gate 701 is displayed in a straight line. However, the position of the coherence gate is a fan-shaped arc as shown in FIG. That is, if the tomographic image is converted into spatial coordinates, it must be arranged on the fan surface 702 as shown in FIG. Therefore, this coordinate conversion is required to calculate the curvature. First, consider the coordinate transformation for the point in the i-th row and j-th column in the tomographic image. i and j are integers from 0 to 511.

Since the position of the i-th row is a position equidistant from the coherence gate, it can be expressed by a circle formula. Therefore, the curve is expressed as follows using the pixel resolution h and the refractive index n _h . The 0th row 704 is the position of the coherence gate.

Since the scanner is symmetric with respect to the z axis and the scanning angle is sampled at equal intervals and the z axis is symmetric, the equation of the straight line represented by the jth line is expressed by Equation 4 using N. Here, N is 512.

走査範囲Ｗは例えば６ｍｍである。ｆ（ｇ）はシミュレーションなどであらかじめ求めておくのでθ（ｇ）を求めることができる。当然、シミュレーションによってθ（ｇ）を求めてもよい。 Note that the scanning radius 204 and the scanning angle 206 viewed from the retina 201 change due to the change of the working distance 126, but the scanning range 207 (W) does not substantially change, so the scanning angle θ (g) viewed from the retina 201 is expressed by a mathematical formula. There is a relationship like 5.

The scanning range W is 6 mm, for example. Since f (g) is obtained in advance by simulation or the like, θ (g) can be obtained. Of course, you may obtain | require (theta) (g) by simulation.

Using these, the position in the space coordinates can be expressed as Equations 6 and 7.

Next, a part or a region for which the curvature is to be calculated is extracted, and each is coordinate-transformed. Here, the radius of curvature is obtained from three points on the retinal pigment epithelium. Let each point be A ₁ (x ₁ , z ₁ ), A ₂ (x ₂ , z ₂ ), A ₃ (x ₃ , z ₃ ). The points to be extracted may be automatically selected, or may be selected by an operator specifying on the displayed tomographic image. Of course, such a region is a predetermined region in the retina, or the choroid, retinal pigment epithelial layer (RPE) IS / OS (inner and outer joint interface), outer boundary membrane (ELM), Outer granular layer (ONL), outer reticulated layer (OPL), inner granular layer (INL), inner reticulated layer (IPL), nerve cell layer (GCL), nerve fiber layer (NFL), etc. Also good. The setting of the area or portion where the curvature is calculated is executed via setting means for setting the area to be calculated corresponding to the computer 120 that controls various configurations of the present invention.

In step A5, the curvature is calculated. This results in finding the radius of a circle that passes through points A ₁ , A ₂ , A ₃ . In this case, the intersection of the perpendicular bisector of the sides A ₁ A ₂ and A ₂ A ₃ is the center. The perpendicular bisector of the side A ₁ A ₂ is expressed as in Equation 8.

Further, the vertical bisector of the side A ₂ A ₃ is expressed as Equation 9.

Accordingly, the center (x _c , z _c ) of the circle is expressed by Equation 10 and Equation 11 by solving these.

As a result, the radius of curvature 208 (r) is the distance between any _one of the points A ₁ , A ₂ , and A ₃ and the center of the circle, and therefore can be obtained as in Expression 12.

  The curve calculated using the above formula is displayed so as to be superimposed on the tomographic image. The operation for executing the calculation of the curve corresponds to the fourth step of the present invention. In addition, the computer 120 that performs these calculations corresponds to a calculation unit that calculates the curvature of the region set using the measured working distance in the present invention. The display superimposed on the tomographic image of the curve based on the calculated curvature is performed by the computer 120 and a display device (not shown), and these configurations correspond to the display means in the present invention.

  Note that this equation shows a circle passing through three points, and it may deviate from the RPE when displayed superimposed on a tomographic image. If there is a problem, narrow the range and set 3 points again to calculate.

Of course, the local curvature may be obtained by dividing into several regions. Further, the curvature in each region may be obtained from the 3D tomographic image, and the two-dimensional map may be displayed (map display). This map display is performed by the computer 120 and a display device (not shown), and these configurations correspond to map display means for displaying the curvature as a map in the present invention. Further, the calculated curvature may be compared with a standard curvature.
The process ends in step A6. After confirming that the desired data has been obtained, the process ends.

  As described above, according to the present embodiment, it is possible to accurately measure the shape of the eye, particularly the curvature of the retina, by measuring the moving distance of the working distance and the reference mirror.

[Example 2]
Embodiment 2 of the present invention will be described below with reference to the drawings. Here, a method for obtaining the curvature simply will be described.

FIG. 8A schematically shows the spatial distance between the eye to be examined and the measurement system. Here, the region where the radius of curvature is desired to be calculated is the retinal pigment epithelium 802. FIG. 8B is a tomographic image of the eye to be examined obtained by this arrangement, and schematically shows the surface 801 of the nerve fiber layer and the retinal pigment epithelium 802. Points A and B are points where the depth of the retinal pigment epithelium 802 is the same. Point C is the intersection of the vertical bisector of side AB and line AB, and point D is the intersection of the side AB vertical bisector and retinal pigment epithelium 802. Point F is the intersection of the coherence gate and a perpendicular bisector of side AB, and point G is the intersection of a point B on the coherence gate and a straight line that forms the center of rotation. That is, the curvature is calculated by calculating the coherence gate position determined by the base and height of a triangle composed of at least two points having the same depth in the tomographic image and one point on the perpendicular bisector, and the optical path length of the reference light. This is done using information. A corresponding point is shown as A ′ in FIG. Here, when BC = u, CD = v, and BE = r, the relationship is expressed by Equation 13.

When this is solved for the radius of curvature r, Equation 14 is obtained.

In order to obtain the curvature radius r, it is necessary to know u and v. Since u corresponds to the side B′C ′, it may be measured. If it is calibrated beforehand with a model eye or the like, u can be easily found by counting the number of pixels. Next, with respect to v, since the position of the coherence gate is a straight line in the tomographic image as shown in FIG. 7A, correction is required in the z direction. That is, a difference from F occurs when G is projected onto the z axis. Assuming that the correction amount is d, the relationship of Formula 15 is obtained assuming that the side F′C ′ is the optical distance p and B ′ is the q-th column.

これらの関係を用いることによって曲率半径ｒの近似値を求めることができる。 When the optical distance of the side C′D ′ is T, the relationship of Expression 16 is established. T is the product of the pixel resolution of the tomographic image and the number of pixels.

By using these relationships, an approximate value of the curvature radius r can be obtained.

As described above, the measurement light is operated on the retina by two x scanners and y scanners each having different rotation axes, that is, rotation centers. Therefore, it is necessary to correct the tomographic image in consideration of the difference in the position of the rotation center of these scanners. In the present invention, in the fourth step, a tomographic image in which such a difference in the rotation center is reflected in the working distance may be generated. As a result, a more appropriate tomographic image can be obtained in an actual OCT apparatus.
As described above, according to the present embodiment, the curvature of the eye to be examined can be easily obtained.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (14)

A tomographic image of the eye to be examined is obtained by adjusting the distance between the eye to be examined and the objective lens and combining the return light from the eye to be examined and the reference light obtained by irradiating the eye to be examined with measurement light. An optical tomographic imaging method comprising:
A first step of measuring the distance between the eye to be examined and the objective lens;
A second step of acquiring a tomographic image of the eye to be examined;
A third step of setting a region for calculating a curvature in the tomographic image;
A fourth step of calculating a curvature of the set region using the measured distance, and
The curvature is calculated by calculating the distance from the rotation center of the scanning of the measurement light to the retina, the scanning angle, the coherence gate position determined by the optical path length of the reference light, the coordinates on the tomographic image, and the depth direction of the tomographic image. An optical tomographic imaging method characterized by being performed using pixel resolution.   The region is choroid, pigment epithelium layer, inner and outer joint interface, outer boundary membrane, outer granule layer, outer reticulated layer, inner granular layer, inner reticulated layer, nerve cell layer, nerve fiber layer layer, and The optical tomographic image capturing method according to claim 1, wherein the optical tomographic image capturing method is a boundary. Two scanners each having a different center of rotation for scanning the measuring light,
The optical tomographic image according to claim 1, wherein the fourth step further includes a step of correcting a difference in position of the rotation center of each of the scanners when calculating the curvature. Imaging method. A tomographic image of the eye to be examined is obtained by adjusting the distance between the eye to be examined and the objective lens and combining the return light from the eye to be examined and the reference light obtained by irradiating the eye to be examined with measurement light. An optical tomographic imaging method comprising:
A first step of measuring the distance between the eye to be examined and the objective lens;
A second step of acquiring a tomographic image of the eye to be examined;
A third step of setting a region for calculating a curvature in the tomographic image;
A fourth step of calculating the curvature of the set region using the measured distance;
Have
The curvature is calculated by information on the coherence gate position determined by the base and height of a triangle composed of at least two points having the same depth in the tomographic image and one point on the perpendicular bisector, and the optical path length of the reference light. An optical tomographic imaging method characterized by being performed using   5. The optical tomographic imaging method according to claim 1, wherein a curve based on the calculated curvature is displayed so as to be superimposed on the tomographic image. 6.   The optical tomographic imaging method according to claim 1, wherein the curvature is calculated in a plurality of regions, and the curvature is displayed as a map. A tomographic image of the subject eye is obtained by adjusting the working distance between the subject eye and the objective lens and combining the return light from the subject eye and the reference light obtained by irradiating the subject eye with measurement light. An optical tomographic imaging method for
A first step of measuring the working distance between the eye to be examined and the objective lens;
A second step of acquiring a tomographic image of the eye to be examined;
The tomographic image acquired in the second step, the measured optical tomographic imaging method characterized by having a third step of coordinate transformation based on the coordinates determined based on the distance. The optical tomographic imaging method according to claim 7, further comprising a fourth step of calculating a curvature of a predetermined layer or layer boundary of the tomographic image whose coordinates are converted in the third step .   A program that causes a computer to execute each step of the optical tomographic imaging method according to any one of claims 1 to 8. Optical tomographic image for acquiring a tomographic image of the retina of the subject eye based on the combined light obtained by combining the return light from the subject eye irradiated with the measurement light via the objective lens and the reference light corresponding to the measurement light An imaging device,
Obtaining means for obtaining a distance between the eye to be examined and the objective lens;
Detecting means for detecting a predetermined layer or layer boundary of the retina from the tomographic image;
Calculating means for calculating a curvature of a predetermined layer or layer boundary of the retina detected by the detecting means based on the distance;
An optical tomographic imaging apparatus characterized by comprising:   The optical tomographic imaging apparatus according to claim 10, further comprising display means for displaying a curve based on the calculated curvature so as to overlap the tomographic image.   The optical tomographic imaging apparatus according to claim 10 or 11, further comprising map means for calculating the curvature in a plurality of regions and displaying the curvature as a map. Optical tomographic image for acquiring a tomographic image of the retina of the subject eye based on the combined light obtained by combining the return light from the subject eye irradiated with the measurement light via the objective lens and the reference light corresponding to the measurement light An imaging device,
Obtaining means for obtaining a distance between the eye to be examined and the objective lens;
Calculating means for calculating the curvature of the retina in the tomographic image based on the distance;
An optical tomographic imaging apparatus comprising: map means for performing calculation of the curvature in a plurality of regions and displaying the curvature as a map. A tomographic image of the eye to be examined is obtained by adjusting the distance between the eye to be examined and the objective lens and combining the return light from the eye to be examined and the reference light obtained by irradiating the eye to be examined with measurement light. An optical tomographic imaging method comprising:
A first step of measuring the distance between the eye to be examined and the objective lens;
A second step of acquiring a tomographic image of the eye to be examined;
A third step of calculating a curvature of a layer or a layer boundary of the tomographic image using the measured distance,
The curvature is calculated by calculating the distance from the rotation center of the scanning of the measurement light to the retina, the scanning angle, the coherence gate position determined by the optical path length of the reference light, the coordinates on the tomographic image, and the depth direction of the tomographic image. An optical tomographic imaging method characterized by being performed using pixel resolution.

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