OCT Device

Abstract

To provide an OTC apparatus capable of appropriately suppressing deterioration in the sensitivity performance due to temperature change.SOLUTION: An OCT apparatus comprises: an OCT optical system for acquiring OCT data of a subject's eye; a spectroscopic optical system provided in the OCT optical system, the spectroscopic optical system including a first optical element and a second optical element on an optical path of interference light of return light of measurement light applied to the subject's eye and reference light and spectroscopically detecting the interference light; and an optical mount including a first member for holding the first optical element, a second member for holding the second optical element and a third member to be fixed to both of the first member and the second member. The optical mount offsets displacement of a holding interval of the first optical element and the second optical element caused by thermal deformation of the optical mount among the first member, the second member and the third member in the thermal deformation of the first member, the second member and the third member.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to OCT devices. [Background technology]

[0002] 2. Description of the Related Art In the field of ophthalmology, optical coherence tomography (OCT) is a device that captures a tomographic image of tissue of a subject's eye.

[0003] There are several methods for obtaining OCT data. Currently, devices using the spectral domain method (SD-OCT; Spectral-domain OCT) are widely used in ophthalmology facilities.

[0004] SD-OCT is equipped with a broadband OCT light source and a spectroscopic optical system as a spectrometer. In SD-OCT, the interference light between the return light of the measurement light irradiated to the subject's eye and the reference light is detected as a spectral signal (spectral interference signal) by the spectroscopic optical system. As a result of processing the spectral interference signal, OCT data is acquired as information on the depth direction of the subject's eye.

[0005] In this case, the spectroscopic optical system includes, in addition to an optical element called a grating and a light receiving element such as a linear image sensor, a collimating system for collimating the interference light and guiding it to the grating, and an imaging system for focusing the interference light from the grating on the light receiving element.

[0006] Patent Document 1 also discloses a mechanism for suppressing changes in the optical path length in a spectroscopic optical system due to heat. The spectroscopic optical system disclosed in Patent Document 1 includes a holder for the spectroscopic optical system that suppresses changes in the overall optical path length of the spectroscopic optical system even if the spectroscopic optical system is deformed due to heat. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-035949 A Summary of the Invention [Problem to be solved by the invention]

[0008] When using a photodetector with higher pixel count to expand the imaging range in the depth direction (called the depth range), simply suppressing the change in the overall optical path length in the spectroscopic optical system is not enough to adequately suppress the change in the spot size of the interference light on the imaging plane of the spectroscopic optical system due to temperature, resulting in a decrease in sensitivity performance due to temperature change.

[0009] In contrast, the present disclosure has been made in consideration of the problems of the conventional technology, and has as its technical objective to provide an OCT device that can appropriately suppress deterioration in sensitivity performance due to temperature changes. [Means for solving the problem]

[0010] Books Disclosure The OCT device according to the first aspect of the present invention includes an OCT optical system for acquiring OCT data of a subject's eye, and a spectroscopic optical system provided in the OCT optical system, which generates an interference light between a return light of a measurement light irradiated on the subject's eye and a reference light. an incident end for introducing the interference light from the incident end, a collimating lens for collimating the interference light irradiated from the incident end, a dispersive element for dispersing the collimated interference light into spectral wavelengths, and two imaging lenses for forming an image of the interference light for each spectral wavelength on an imaging plane by the two imaging lenses; The interference light is spectroscopically detected. A light receiving element, A spectroscopic optical system; One of the two imaging lenses in an imaging system A first member for holding the The other of the two imaging lenses in the imaging system and a third member fixed to both the first member and the second member, and the optical mount is configured to suppress deformation of the optical mount due to thermal deformation of the optical mount. The two imaging lenses The displacement of the retention interval is offset between the first member, the second member and the third member due to thermal deformation of the first member, the second member and the third member. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide an OCT device that can appropriately suppress deterioration of sensitivity performance due to temperature changes. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an OCT apparatus. [Diagram 2] FIG. 1 is a diagram showing the overall configuration when photographing anterior segment OCT. [Diagram 3] FIG. 2 is a diagram showing a detailed configuration of a spectroscopic optical system. [Figure 4A] 1 is a diagram showing a case where the light receiving width of an image sensor is narrow with respect to the source bandwidth (the physical width of the spectral distribution originating from a light source). [Figure 4B] This is a diagram showing a case where the light receiving width of the image sensor is balanced with respect to the source bandwidth (the physical width of the spectral distribution originating from the light source). [Diagram 5] 1 is a graph showing the relationship between sensitivity attenuation R(z) and depth range in FD-OCT. [Figure 6] 1 is a graph showing sensitivity attenuation curves for depth ranges of 3 mm and 4.2 mm. [Figure 7A] FIG. 1 shows a fundus OCT image. [Figure 7B] FIG. 1 shows an anterior segment OCT image. [Figure 8] FIG. 2 is a diagram showing a spectroscopic optical system together with a fixing and holding unit. [Figure 9] FIG. 2 is a schematic diagram illustrating the structure of first and second optical mounts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an exemplary embodiment of an OCT device according to the present disclosure will be described with reference to the drawings. An OCT device 1 according to the embodiment is a Spectral-domain OCT (SD-OCT). The OCT device 1 acquires OCT data of a subject's eye. In the OCT device 1 of this embodiment, OCT data of the fundus and OCT data of the anterior segment are selectively photographed. As shown in FIG. 1, the OCT device 1 may have a control unit 70, and the photographing mode may be switched between a fundus photographing mode and an anterior segment photographing mode by the control unit 70. In the fundus photographing mode, a fundus OCT is photographed, and in the anterior segment photographing mode, an anterior segment OCT is photographed.

[0014] First, a schematic configuration of an optical system of an OCT device 1 according to this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the OCT device 1 includes an OCT optical system (interference optical system) 100. Additionally, the OCT device 1 may include a light-guiding optical system 200 and an optical path length adjustment unit.

[0015] The OCT optical system 100 according to the embodiment includes at least a spectroscopic optical system 20. Additionally, the OCT optical system 100 may include an OCT light source 11, a light splitter 15, and a reference optical system 30. As shown in Fig. 1, each part is connected by optical fibers 17a to 17d as a light guide path.

[0016] The OCT optical system 100 detects a spectral interference signal between the return light of the measurement light irradiated to the subject's eye and the reference light by the spectroscopic optical system 20. The spectral interference signal is arithmetically processed by an image processor to obtain (generate) OCT data of the subject's eye.

[0017] The OCT light source 11 of this embodiment emits low-coherent, broadband light. For example, the OCT light source 11 may be an SLD light source, and the light emitted from the OCT light source 11 may be near-infrared light. As an example, light with a central wavelength of 880 nm may be irradiated from the OCT light source 11.

[0018] The light splitter 15 splits the light from the OCT light source 11 into a measurement light and a reference light. In FIG. 1, the light splitter 15 is shown as a fiber coupler. As shown in FIG. 1, the measurement light is irradiated onto the subject's eye via the light guiding optical system 40. Also, the return light from the subject's eye is guided back through the light guiding optical system 40 to the spectroscopic optical system 20. The reference light is guided to the spectroscopic optical system 20 via the reference optical system 30. In FIG. 1, the return light of the measurement light and the reference light are combined by a coupler (for example, the light splitter 15 in FIG. 1) and then guided to the spectroscopic optical system 20.

[0019] 1, the light guiding optical system 40 may include an optical scanner 41 and an objective optical system 45. The optical scanner 41 is used to scan the measurement light on the tissue of the subject's eye. The measurement light scanned by the optical scanner 41 is scanned on the tissue of the subject's eye via the objective optical system 45.

[0020] When obtaining a fundus OCT scan, the measurement light passing through the objective optical system 45 may be rotated around one point (called a pivot point) as shown in Fig. 1. The pivot point is positioned at the anterior segment by alignment, whereby the fundus OCT scan is obtained.

[0021] When acquiring an anterior segment OCT, an anterior segment attachment 50 (attachment lens 50a) may be inserted between the objective optical system 45 and the subject's eye E, as shown in Fig. 2. This allows the scanning mode of the measurement light to be changed between acquiring a fundus OCT and acquiring an anterior segment OCT. By inserting the attachment lens 50a, the measurement light is irradiated telecentrically to acquire an anterior segment OCT.

[0022] The optical path length adjustment unit adjusts the optical path length difference between the measurement light and the reference light. When photographing fundus OCT, the optical path length difference may be corrected according to individual differences in axial length for each subject eye. When photographing anterior segment OCT, the optical path length difference may be adjusted to a predetermined value. The optical path length adjustment unit changes the optical path length of at least one of the measurement optical path and the reference optical path. In FIG. 1, the optical path length is changed by moving the exit end of the fiber in the light guiding optical system 40 in the optical axis direction.

[0023] <Spectroscopic optical system> The spectroscopic optical system 20 of this embodiment is used as a spectrometer. The spectroscopic optical system 20 detects the interference light between the return light of the measurement light and the reference light. That is, the spectroscopic optical system 20 separates the interference light into frequency components and detects the interference signal for each frequency.

[0024] 3, in this embodiment, the spectroscopic optical system 20 includes a collimator system 22, a grating (dispersion element) 24, an imaging system 25, and an image sensor (an example of a light receiving element) 26. Additionally, the spectroscopic optical system 20 of this embodiment includes a folding mirror 23.

[0025] However, the spectroscopic optical system does not necessarily need to include a mirror for bending the optical path. For example, it is more advantageous for the dimensions in the direction intersecting the optical axis not to bend the optical path.

[0026] The combined light beam of the return light of the measurement light and the reference light is guided to the spectroscopic optical system 20 via the incident end 21. The incident end 21 here serves as an apparent point source of interference light in the spectroscopic optical system 20. For example, the end of the fiber 17b can be used as the incident end 21.

[0027] Collimating system 22 collimates the interference light from incident end 21. In Fig. 3, incident end 21 is disposed at the focal position (object side focal position) of collimating system 22. In Fig. 3, the collimated interference light is bent by mirror 23 and irradiated onto grating 24. In Fig. 3, collimating system 22 is formed by lens 22a (collimating lens).

[0028] The mirror 23 bends the interference light at an angle of 90° or more, thereby reducing the storage dimensions of the spectroscopic optical system 20. The mirror 23 is disposed between the collimating system 22 and the grating 24. In other words, the mirror 23 is disposed in a region where the interference light is collimated.

[0029] The grating 24 separates the interference light. As shown in Fig. 3, the grating 24 may be a transmission type optical element (e.g., a diffraction grating). However, the grating 24 may be replaced with a reflection type optical element. The interference light is separated by the grating 24 in a direction that coincides with the direction in which the pixels are arranged in the image sensor 26.

[0030] The dispersed interference light is incident on imaging system 25. As a result, the interference light is imaged on the imaging plane via imaging system 25. In Fig. 3, imaging system 25 is made up of two lenses, lens 25a and lens 25b. However, this is just one example, and various alternative configurations can be adopted for imaging system 25.

[0031] The image sensor 26 is a line sensor (one-dimensional image sensor) in which pixels (elements) are arranged in a one-dimensional direction. The image sensor 26 is disposed on the imaging surface, in other words, at the position of the focal length (image-side focal length) of the imaging system 25.

[0032] In the optical path of the spectroscopic optical system 20, the distance between the collimating system 22 and the grading 24 is not related to performance and can be set to any value. Therefore, the total length of the spectroscopic optical system 20 is substantially dominated by the focal length f1 of the collimating system 22 and the focal length f2 of the imaging system 25. In this embodiment, the device does not include a mechanism for actively changing the focal length f1 of the collimating system 22 and the focal length f2 of the imaging system 25. In other words, f1 and f2 are both fixed. In other words, in this embodiment, the spectrometer conditions do not change when obtaining fundus OCT and anterior segment OCT, respectively.

[0033] Here, the relationship between the depth resolution in SD-OCT and the depth range to be photographed will be described. Unless otherwise specified, the depth range in this embodiment is the depth from one end of the photographing range to the other end when the zero delay is set as one end. In other words, in this embodiment, it refers to a value based on the optical system design that does not rely on the full range technology.

[0034] First, the depth resolution in OCT can be expressed by the following relational expression:

[0035]

number

[0036] Here, Δz represents the resolution in the depth direction, n represents the refractive index, and Δλ represents the total light receiving width (full width at half maximum in the spectral distribution).

[0037] Moreover, the imaging range in the depth direction (depth range) can be expressed by the relational expressions shown in Equations 2 and 3.

[0038]

number

[0039]

number

[0040]

number

[0041] However, z max is the depth range, N is the number of elements in the image sensor, λ0 is the central wavelength of the measurement light, a is the lattice constant of the grating, dλ is the sampling wavelength width, Δx is the width of one element in the image sensor, θ is the diffraction angle in the grating, m is the diffraction order, and f2 is the focal length of the imaging system. From equations 2 to 4, the depth range z max It can be seen that is proportional to the focal length f2 of the imaging system. Also, the depth range z max is proportional to the number of pixels N and inversely proportional to the width of one element Δx, so the depth range z max It can be seen that the increase.

[0042] In SD-OCT, the spectrum of the interference light is distributed in one direction on the imaging plane of the imaging system. The width of the distribution of the interference light resulting from the performance of the light source is called the source bandwidth.

[0043] As shown in FIG. 4A, if the signal range detected by the image sensor is narrow relative to the source bandwidth, the total light receiving width Δλ becomes small and the resolution in the depth direction decreases (δz becomes large). On the other hand, since the image sensor samples the signal at high density, the sampling width dλ becomes small. Therefore, the depth range z max is increased.

[0044] In FIG. 4B, the signal range detected by the image sensor is well balanced with the width of the spectral distribution in the source band. Therefore, the resolution in the depth direction is improved compared to the case of FIG. 4A, but the depth range z max becomes narrower.

[0045] As a result of the above considerations, in order to realize a wider depth range than the conventional design suitable for anterior segment OCT while maintaining a resolution suitable for fundus OCT (preferably 7 μm or less) like the conventional design, it is necessary to increase the number of pixels of the image sensor and to sufficiently increase the focal length f2 of the imaging system. In this case, since the corneal thickness and the anterior chamber depth are about 0.5 mm and 2 to 3 mm, respectively, the depth range capable of imaging from the corneal apex to the anterior lens capsule is preferably 4 mm or more.

[0046] In a spectrometer, the dispersed interference light can be considered to be imaged with a finite spot size on the imaging surface. The larger the spot size is relative to the width of one element Δx, the less likely it is that interference signals of each frequency can be resolved, resulting in attenuation of sensitivity. In this case, it is known that the sensitivity reduction becomes greater toward the high frequency region (i.e., the farther away from the zero delay). The spot size is minimized when the focal length f1 of the collimating system is the same as or longer than the focal length f2 of the imaging system.

[0047] In contrast, in this embodiment, the focal length f1 of the collimating system 22 is shorter than the focal length f2 of the imaging system 25. That is, f1 < f2. Therefore, the spot size is not minimized.

[0048] By the way, regarding the sensitivity attenuation, it can be expressed as a relational expression using the following depth range z max as follows.

[0049]

Equation

[0050] However, R(z) represents sensitivity attenuation, z represents the depth position, and ω represents the angular frequency, respectively.

[0051] As shown in FIG. 5, focusing on the relationship between z max and R(z), the following characteristics 1) to 3) can be observed for each interval. 1) In the interval A near the origin, there is almost no change according to z max . 2) In the interval B with a larger value than the interval A, there is a positive correlation between z max and R(z). However, the slope of R(z) turns to a decreasing trend after passing through the inflection point. 3) In the interval C, R(z) asymptotes to a finite value. The change according to z max becomes almost negligible.

[0052] Therefore, only in some intervals (interval B), the sensitivity attenuation is suppressed when the depth range z max is extended. For this reason, in this interval, at least part of the influence on the sensitivity attenuation caused by the spot size not being minimized in the depth range z max can be offset by extending the depth range z max .

[0053] Next, Fig. 6 shows sensitivity decay curves, which are the results of a simulation based on the above formula, for two depth ranges, 3 mm and 4.2 mm. Note that each sensitivity decay curve in Fig. 6 is based on the premise that the spot size is minimized.

[0054] It can be seen from Fig. 6 that the slope of the sensitivity attenuation becomes gentler as the depth range increases between 3mm and 4.2mm. For example, in Fig. 6, the performance at the position of 3mm in the graph of the depth range of 3mm is equivalent to the performance at the position of 4.2mm in the graph of the depth range of 4.2mm.

[0055] From the simulation results, it is confirmed that the effect of suppressing sensitivity attenuation can be enjoyed when the depth range is expanded from the range of conventional SD-OCT to the range required to capture images from the corneal apex to the anterior lens capsule in one shot. Therefore, since a sensitivity margin is created even in areas away from the zero delay, the focal length f1 of the collimating system 22 can be shortened by that amount. As a result, a compact OCT device can be realized that can capture images of both the anterior segment OCT and the fundus OCT well.

[0056] However, the sensitivity attenuation of the actual device cannot be accurately predicted by the simulation value alone. Therefore, the resolution in the depth direction, δz: 7 μm or less, max In an optical system in which the focal length f1 of the collimating system 22 is shorter than f2, with respect to the focal length f2 of the imaging system 25 when achieving a spot size of 4 mm or more, anterior segment OCT and fundus OCT were photographed to verify the effect of attenuation in sensitivity. In this case, f1 is half or less of f2. More specifically, the ratio of f1:f2 is approximately 1:3. In this case, the overall length of the spectrometer is reduced to a maximum of approximately 60% compared to the state in which the spot size is minimized.

[0057] Figures 7A and B show fundus OCT and anterior segment OCT, respectively.

[0058] FIG. 7A shows a B-scan of the fundus when the transverse scan length (angle of view) is 16 mm (approximately 50° angle of view). In fundus OCT, the fundus is curved, so that the fundus tissue depicted in the B-scan has a height difference in the transverse direction. The height difference varies from one subject's eye to another, and generally, the height difference is more pronounced in severely myopic eyes. In addition, the height difference is more likely to appear as the scan length (angle of view) in the B-scan increases. Therefore, in fundus OCT, it is inevitable that part of the fundus tissue is depicted in the high-frequency region (region far from zero delay), and sensitivity attenuation is likely to be a problem. For example, as shown in FIG. 7A, when photographed with central fixation, the center of the fundus is depicted at the deepest position. In particular, there is concern about the effect on long-axis long eyes such as severely myopic eyes. However, the verification results showed that, even with severe myopia of -14D, as shown in Figure 7A, the shape of the central part of the fundus and the main layer structure from the retinal surface to the choroidal surface could be visually identified, and no problems due to sensitivity attenuation were observed.

[0059] Furthermore, as shown in FIG. 7B, in anterior segment OCT, it is possible to photograph the anterior lens capsule and the tissues of the angle from the corneal apex in one shot.

[0060] As described above, according to the present disclosure, even if a compact spectrometer is used in which the focal length f1 of the collimating system 22 is shorter than the focal length f2 of the imaging system 25, it is possible to ensure the required resolution for fundus OCT while ensuring a depth-direction imaging range sufficient to simultaneously image multiple parts of the anterior segment.

[0061] According to the inventor's estimation based on the photographic results of Figures 7A and 7B, etc., if the ratio of f1:f2 is in the range of approximately 1:4, it is believed that the optical system can be shortened while maintaining the necessary sensitivity.

[0062] <Application of full-range technology> Furthermore, a full-range technique may be applied to the OCT data. Various methods for removing virtual images in OCT data are called full-range techniques. In this embodiment, any of the full-range techniques may be applied, and this may allow acquisition of a wider range of OCT data from which virtual images are selectively removed. When the full-range technique is used, OCT data can be acquired from a region across the zero delay, so that the effective imaging range in the depth direction can be increased.

[0063] Examples of the full-range technique include a technique for removing a virtual image (also called a mirror image) by using additional hardware, and a technique for correcting the image by software without using additional hardware. Another full-range technique has been proposed in which, based on a plurality of OCT data sets having different optical path lengths when detecting a spectral interference signal, at least an interpolation process is performed on an overlapping region between a real image and a virtual image in the OCT data, and the OCT data subjected to the interpolation process is generated. Any of these techniques may be applied to the present embodiment.

[0064] <Method of fixing optical elements in a spectroscopic optical system> Next, a configuration for fixing and holding the spectroscopic optical system will be described with reference to Fig. 8 and Fig. 9. As shown in Fig. 8, in this embodiment, the OCT device 1 may include a fixing and holding unit 200 for fixing and holding the spectroscopic optical system 20 on a base 250.

[0065] In this embodiment, the fixing and holding unit 200 includes at least a first optical mount 210 and a second optical mount 220. The fixing and holding unit 200 may additionally include a third optical mount 230 and a fourth optical mount 240.

[0066] The first and second optical mounts 210 and 220 each hold at least two of the multiple optical elements (incident end 21, collimator lens 22a, grading 24, imaging lenses 25a and 25b, and light receiving element 26) included in the spectroscopic optical system 20. In detail, two optical elements adjacent to each other in the optical axis direction are held by one of the first and second optical mounts 210 and 220. The first and second optical mounts 210 and 220 each have a configuration for suppressing a change in the holding interval of the optical elements due to their own deformation in response to temperature.

[0067] Incidentally, the spot size of the interference light on the imaging plane is enlarged when the interval between each optical element deviates from the design value. When the interval between the optical elements deviates from the design value, a decrease in sensitivity may occur. Therefore, we investigated the effect of the change in the interval between the optical elements on the spot size for each combination of adjacent optical elements in the spectroscopic optical system 20, and experimentally confirmed that the effect on the spot size increases in the order of 1) to 5) (descending order).

[0068] 1) Incident end 21 and collimator lens 22a 2) Imaging lens 25a and imaging lens 25b 3) Imaging lens 25b and light receiving element 26 4) Collimating lens 22a and grading 24 5) Grading 24 and first imaging lens 25a More specifically, the deviations between 1) and 2) are dominant in terms of the spot size. The deviation between 3) has some effect on the spot size. The deviations between 4) and 5) have almost no effect on the spot size.

[0069] 8, in this embodiment, the entrance end 21 and the collimator lens 22a are held by a first optical mount 210. In addition, the second optical mount 220 holds two imaging lenses 25a and 25b.

[0070] The first optical mount 210 includes a first member 211 (first holder), a second member 212 (second holder), and a third member 213 (connecting member). The first member 211 holds the incident end 21 (the end of the fiber 17b). The second member 212 holds the collimator lens 22a. The third member 213 is fixed to both the first member 211 and the second member 212.

[0071] Similarly, the second optical mount 220 includes a first member 221 (first holder), a second member 222 (second holder), and a third member 223 (connecting member). In the second optical mount 220, the first member 221 holds one of the two lenses 25a, 25b included in the imaging system 25, and the second member 222 holds the other. The third member 223 is fixed to both the first member 221 and the second member 222.

[0072] The first and second optical mounts 210, 220 form a nested structure having multiple (two in this embodiment) folded portions B1, B2 (see FIG. 9) by the first to third members 211-213, 221-223. As a result, the first and second optical mounts 210, 220 each have a displacement of the holding interval between two optical elements held by the first and second optical mounts 210, 220, and the displacement caused by thermal deformation of the first and second optical mounts 210, 220 is offset between the first to third members 211-213, 221-223 in the thermal deformation of the first to third members 211-213, 221-223.

[0073] Furthermore, the surfaces of the first to third members 211-213, 221-223 that are adjacent to (in contact with) each other may be formed by lathe processing. By using lathe processing, which has high machining accuracy, the first to third members 211-213, 221-223 can be closely arranged in the first and second optical mounts 210, 220, and axial misalignment of the two optical elements held by each of the first and second optical mounts 210, 220 can be suppressed.

[0074] The structure of the first and second optical mounts 210, 220 will be described in detail with reference to Fig. 9. In Fig. 9, the first members 211, 221 and the third members 213, 223 are formed to extend from the holding positions of the optical elements toward each other along the optical axis. The second members 212, 222 are arranged to overlap at least partially with both the first members 211, 221 and the third members 213, 223 in a direction intersecting the optical axis.

[0075] 9, reference symbol p11 indicates a holding position of the optical element in the first members 211, 221, and reference symbol p22 indicates a holding position of the optical element in the second members 212, 222. Reference symbol q13 indicates a fixing position between the first members 211, 221 and the second members 212, 222, and reference symbol q23 indicates a fixing position between the first members 211, 221 and the second members 212, 222.

[0076] 9, the fixing position q13 is disposed on the holding position p22 side of the second members 212, 222 (in this embodiment, the downstream side of the spectroscopic optical system 20) with respect to the fixing position q23. Around the fixing position q13, a folded portion B1 is formed by the first members 211, 221 and the third members 213, 223.

[0077] The fixed position q23 is disposed on the holding position p11 side of the first members 211, 221 (in this embodiment, the upstream side of the spectroscopic optical system 20) with respect to the fixed position q13. Around the fixed position q23, the second members 212, 222 and the third members 213, 223 form a folded portion B2.

[0078] When the two members forming the folded portion are viewed from the folded portion, the directions of thermal deformation of the two members are aligned. Therefore, in this embodiment, even if dimensional changes due to thermal deformation occur in the first members 211, 221 and the second members 212, 222, if an equivalent dimensional change occurs in the third members 213, 223, the holding distance between the two optical elements by the first and second optical mounts 210, 220 is maintained before and after the temperature change.

[0079] Here, the distance from the holding position p11 to the fixed position q13 in the first member 211, 221 is denoted as Dx, the distance from the holding position p22 to the fixed position q23 in the second member 212, 222 is denoted as Dy, and the distance between the two fixed positions q13, q23 in the third member 213, 223 is denoted as Dz. In this embodiment, the dimensions that affect the thermal deformation in the optical axis direction of the first member 211, 221, the second member 212, 222, and the third member 213, 223 are Dx, Dy, and Dz.

[0080] The thermal expansion coefficients of the first members 211 and 221, the second members 212 and 222, and the third members 213 and 223 are respectively β1, β2, and β3. If the allowable error of the change in the holding interval of the optical element when the temperature changes from temperature T to temperature Ta is E, the material of each member and Dx, Dy, and Dz are determined so as to satisfy the following relational expression by utilizing the difference in thermal expansion of each member.

[0081]

number

[0082] In other words, in this embodiment, the materials of each member and Dx, Dy, and Dz are determined so that the amount of dimensional change due to thermal deformation in the first members 211, 221 and the second members 212, 222 is approximately equal to the amount of dimensional change due to thermal deformation in the third members 213, 223.

[0083] As shown in Fig. 9, if Dx, Dy, and Dz are close to each other, the material of each member is selected so that β1, β2 < β3. For example, the first members 211, 221 and the second members 212, 222 may be made of the same material (i.e., β1 = β2). As an example, the first members 211, 221 and the second members 212, 222 may be made of iron, and the third members 213, 223 may be made of aluminum. Of course, the members may be made of different materials with different thermal expansion coefficients.

[0084] By providing the first and second optical mounts 210, 220 as described above, it is possible to appropriately suppress changes in the spacing between optical elements (changes according to temperature), which have a large effect on the spot size of interference light on the imaging plane of the spectroscopic optical system 20, and to appropriately maintain the sensitivity performance at each temperature. In particular, as described above, even if an optical design that is disadvantageous in terms of sensitivity in which the focal length f1 of the collimating system 22 is shorter than the focal length f2 of the imaging system 25 is adopted, it is possible to suitably suppress deterioration of the sensitivity performance due to temperature changes.

[0085] Returning to Fig. 8, the explanation will be continued. In the example of Fig. 8, the first optical mount 210 and the second optical mount 220 are connected to a third optical mount 230. The second optical mount 220 is connected to a fourth optical mount 240 on the downstream side. The third optical mount 230 fixes and holds the mirror 23 and the grading 24. The fourth optical mount 240 fixes and holds the light receiving element 26.

[0086] In this embodiment, in the fixing and holding unit 200, each of the third optical mount 230 and the fourth optical mount 240 is directly connected to the base 250 by a screw or the like. At least one of the connecting points of the third optical mount 230 and the fourth optical mount 240 can absorb deformation caused by heat in the fixing and holding unit 200 by a washer or the like. This makes it possible to avoid concentration of mechanical load when deformation due to temperature occurs in the fixing and holding unit 200, and to suppress deterioration of the optical system.

[0087] While the present disclosure has been described based on the embodiments, the present disclosure is not limited to the above-described embodiments and various modifications are possible. [Explanation of symbols]

[0088] 1 OCT device 20 Spectroscopic optical system 22 Collimation system 24 Dispersion element (grading) 25 Imaging system 26 Photodetector 210 First Optical Mount 220 Second Optical Mount 211,221 First member 212,222 Second member 213,223 Third member

Claims

1. An OCT optical system for acquiring OCT data of a subject's eye; a spectroscopic optical system provided in the OCT optical system, the spectroscopic optical system including: an incident end that introduces interference light between return light of measurement light irradiated to the subject's eye and reference light; a collimating lens that collimates the interference light irradiated from the incident end; a dispersing element that disperses the collimated interference light for each spectral wavelength; an imaging system having two imaging lenses and that images the interference light for each spectral wavelength on an imaging plane using the two imaging lenses; and a light receiving element that is disposed on the imaging plane and spectrally detects the interference light; an optical mount including a first member that holds one of two imaging lenses included in the imaging system, a second member that holds the other of the two imaging lenses included in the imaging system, and a third member that is fixed to both the first member and the second member; An OCT device in which the optical mount offsets the displacement of the holding distance between the two imaging lenses caused by thermal deformation of the optical mount between the first member, the second member, and the third member through thermal deformation of the first member, the second member, and the third member.

2. a second optical mount formed separately from the optical mount; the second optical mount has a fourth member that holds the incident end, a fifth member that holds the collimator lens, and a sixth member that is fixed to both the fourth member and the fifth member, The OCT device of claim 1, wherein the second optical mount offsets displacement of the holding distance between the incident end and the collimating lens caused by thermal deformation of the second optical mount between the fourth member, the fifth member, and the sixth member in the thermal deformation of the fourth member, the fifth member, and the sixth member.

3. the one imaging lens is located upstream of the other imaging lens in the spectroscopic optical system, 3. The OCT device according to claim 1, wherein the third member is fixed to each of the first member and the second member such that a fixed position between the first member and the third member is located downstream in the spectroscopic optical system relative to a fixed position between the second member and the third member.

4. When the temperature around the device changes from temperature T to temperature Ta, the allowable error of the change in the distance between the two imaging lenses is E, and the dimensions that affect the thermal expansion in the optical axis direction of the first member, the second member, and the third member are Dx, Dy, and Dz, respectively. By utilizing the difference in the thermal expansion coefficient, |Dx・β1(Ta-T)+Dy・β2(Ta-T)−Dz・β3(Ta-T)|<|E| 4. The OCT apparatus according to claim 1, wherein the materials of the first member, the second member, and the third member and the dimensions Dx, Dy, and Dz are determined so as to satisfy the following:

Images