OCT device

Abstract

To provide an OCT apparatus which is capable of satisfactorily imaging both an anterior eye part OCT and an eyeground OCT and is compact.SOLUTION: The OCT apparatus, which selectively images OCT data of the eyeground and OCT data of the anterior eye part, comprises a spectral optical system which spectrally detects an interference light between a return light of a measurement light applied to a subject eye and a reference light. The spectral optical system comprises: a collimate system for collimating the interference light; a dispersion element for spectrally diffracting the collimated interference light at each spectrum wavelength; an image formation system for image-forming the interference light at each spectrum wavelength on an imaging face; and a photodetection element disposed on the imaging face. An object side focal length of the collimate system is shorter than an image side focal length of the image formation system.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an OCT apparatus.

Background Art

[0002] In the field of ophthalmology, an Optical Coherence Tomography (OCT), which is an apparatus for photographing tomographic images of tissues of an eye to be examined, is known.

[0003] There are several methods for obtaining OCT data. Currently, an apparatus that employs a spectral domain method (SD-OCT; Spectral-domain OCT) is widely used in ophthalmic facilities.

[0004] SD-OCT includes a broadband OCT light source and a spectroscopic optical system as a spectrometer. In SD-OCT, interference light between the return light of the measurement light irradiated to the eye to be examined 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 in the depth direction of the eye to be examined.

[0005] At this time, the spectroscopic optical system includes an optical element called a grating, 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 imaging the interference light from the grating on the light receiving element (see, for example, Patent Document 1).

[0006] In addition, a technique for selectively photographing fundus OCT and anterior segment OCT by switching the optical system is known. For example, Patent Document 2 discloses an SD-OCT that can easily photograph anterior segment OCT by attaching an adapter lens to fundus OCT.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-035949 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-138904 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] In the fundus tissue, for example, the retina, a large number of layer structures are formed within a mere 0.2 to 0.3 millimeters, so a high-resolution imaging device is required. On the other hand, for anterior segment OCT, a device with a wide imaging range, suitable for grasping the shape of each part, is suitable.

[0009] Now In the SD-OCT of each company on a certain day, the depth range is mainly in the range of about 2 mm to 2.3 mm, and 3 mm by "AngioVue" (registered trademark) of Optvue is the longest. However, a sufficient imaging range for the anterior segment has not been ensured. For example, in Patent Document 2, only a single part in the anterior segment, such as corneal scan and gonioscopic scan, is imaged.

[0010] The inventor has considered an optical system of SD-OCT that can image a plurality of parts in the anterior segment in the depth direction in a lump and can ensure the resolution required for fundus OCT. As a result, in SD-OCT, in order to improve each performance of resolution and imaging range in the depth direction, it was effective to increase the focal length of the imaging system along with increasing the number of pixels of the light receiving element. and , and the sensitivity attenuation according to the depth position is caused by the fact that the spot size of the interference light is large with respect to the element size of the light receiving element. That is, the sensitivity decreases more on the high-frequency side (depth position farther from zero delay). The spot size is minimized when the focal length of the collimating system is the same as or longer than the focal length of the imaging system. At this time, the sensitivity performance in the spectroscopic optical system is optimized. with

[0011] By the way, the fact that the spot size of the interference light is large with respect to the element size of the light receiving element causes sensitivity attenuation according to the depth position. That is, the sensitivity decreases more on the high-frequency side (depth position farther from zero delay). The spot size is minimized when the focal length of the collimating system is the same as or longer than the focal length of the imaging system. At this time, the sensitivity performance in the spectroscopic optical system is optimized.

[0012] Therefore, in the above consideration, if the focal length of the collimating system is increased in accordance with the imaging system, it is considered that the overall length of the spectrometer will become extremely large.

[0013] On the other hand, the present disclosure has been made in view of the problems of the prior art, and it is a technical problem to provide an OCT device that can satisfactorily image both the anterior segment OCT and the fundus OCT and is compact.

Means for Solving the Problems

[0014] An OCT device according to a first aspect of the present invention is an OCT device that selectively images OCT data of the fundus and OCT data of the anterior segment of the eye, and includes a spectroscopic optical system that spectroscopically detects interference light between the return light of the measurement light irradiated to the eye to be examined and the reference light. The spectroscopic optical system includes a collimating system that collimates the interference light, an optical element that disperses the collimated interference light for each spectral wavelength, an imaging system that forms an image of the interference light for each spectral wavelength on an imaging surface, and a light receiving element disposed on the imaging surface. The object-side focal length of the collimating system is shorter than the image-side focal length of the imaging system.

Effects of the Invention

[0015] According to the present disclosure, it is possible to satisfactorily image both the anterior segment OCT and the fundus OCT, and a compact OCT device can be provided.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0017] Hereinafter, exemplary embodiments of the OCT apparatus according to the present disclosure will be described with reference to the drawings. The OCT apparatus 1 according to the embodiment is SD-OCT (Spectral-domain OCT). The OCT apparatus 1 acquires OCT data of the eye to be examined. In the OCT apparatus 1 of the present embodiment, fundus OCT data and anterior segment OCT data are selectively captured. As shown in FIG. 1, the OCT apparatus 1 may include a control unit 70, and the control unit 70 may switch the imaging mode between the fundus imaging mode and the anterior segment imaging mode. Fundus OCT is captured in the fundus imaging mode, and anterior segment OCT is captured in the anterior segment imaging mode.

[0018] First, with reference to FIG. 1, the schematic configuration of the optical system of the OCT apparatus 1 according to the present embodiment will be described. As shown in FIG. 1, the OCT apparatus 1 includes an OCT optical system (interference optical system) 100. Additionally, the OCT apparatus 1 may include a light guiding optical system 200 and an optical path length adjusting unit.

[0019] 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, an optical splitter 15, and a reference optical system 30. As shown in FIG. 1, each part is connected by optical fibers 17a to 17d as light guiding paths.

[0020] The OCT optical system 100 detects, by means of the spectroscopic optical system 20, a spectral interference signal between the return light of the measurement light irradiated to the eye to be examined and the reference light. By subjecting the spectral interference signal to arithmetic processing by an image processor, OCT data of the eye to be examined is acquired (generated).

[0021] The OCT light source 11 of the present embodiment emits low-coherent and broadband light. For example, the OCT light source 11 is 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.

[0022] The optical splitter 15 splits the light from the OCT light source 11 into measurement light and reference light. In FIG. 1, the optical splitter 15 is shown as a fiber coupler. As shown in FIG. 1, the measurement light is irradiated to the eye to be examined via a light guiding optical system 40. Further, the return light of the eye to be examined 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 through 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 optical splitter 15 in FIG. 1), and then guided to the spectroscopic optical system 20.

[0023] As shown in FIG. 1, the light guiding optical system 40 may include an optical scanner 41, an objective optical system 45, etc. The optical scanner 41 is used to scan the measurement light on the tissue of the eye to be examined. The measurement light scanned by the optical scanner 41 is scanned on the tissue of the eye to be examined via the objective optical system 45.

[0024] When acquiring fundus OCT, as shown in FIG. 1, the measurement light passing through the objective optical system 45 may be rotated about a single point (referred to as the turning point). By arranging the turning point at the anterior segment of the eye through alignment, fundus OCT is acquired.

[0025] When acquiring anterior segment OCT, as shown in FIG. 2, an anterior segment attachment 50 (attachment lens 50a) may be inserted between the objective optical system 45 and the eye to be examined E. Thereby, the scanning mode of the measurement light may be changed between the case of acquiring fundus OCT and the case of acquiring anterior segment OCT. By inserting the attachment lens 50a, the measurement light is irradiated telecentrically and anterior segment OCT is acquired.

[0026] 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 the individual difference in the axial length of each eye to be examined. Also, when photographing anterior segment OCT, it may be adjusted to a predetermined value. The optical path length adjustment unit changes the optical path length of at least either the measurement optical path or the reference optical path. In FIG. 1, the optical path length is changed by moving the output end of the fiber in the light guiding optical system 40 in the optical axis direction.

[0027] <Spectroscopic optical system> The spectroscopic optical system 20 of the present embodiment is used as a spectrometer. The spectroscopic optical system 20 spectroscopically detects the interference light between the return light of the measurement light and the reference light. That is, the spectroscopic optical system 20 splits the interference light into frequency components and detects the interference signal for each frequency.

[0028] As shown in FIG. 3, in the present embodiment, the spectroscopic optical system 20 includes a collimating system 22, a grating (dispersion element) 24, an imaging system 25, and an imaging element (an example of a light receiving element) 26. Additionally, the spectroscopic optical system 20 of the present embodiment includes a folding mirror 23.

[0029] However, the spectroscopic optical system does not necessarily have to be provided with a mirror for bending the optical path. For example, it is advantageous that the dimension in the direction intersecting the optical axis is such that the optical path is not bent.

[0030] The combined light beam of the return light of the measurement light and the reference light is guided to the spectroscopic optical system 20 through the incident end 21. Here, the incident end 21 is the apparent point light source of the interference light in the spectroscopic optical system 20. For example, the end of the fiber 17b can be used as the incident end 21.

[0031] The collimating system 22 collimates the interference light from the incident end 21. In FIG. 3, the incident end 21 is disposed at the focal position (object-side focal position) of the collimating system 22. In FIG. 3, the collimated interference light is bent by the mirror 23 and irradiated onto the grating 24. In FIG. 3, the collimating system 22 is formed by a lens 22a (collimating lens).

[0032] The mirror 23 bends the interference light at an angle of 90° or more. Thereby, the accommodation dimension of the spectroscopic optical system 20 is reduced. The mirror 23 is disposed between the collimating system 22 and the grating 24. That is, it is disposed in the region where the interference light is collimated.

[0033] The grating 24 disperses the interference light. As shown in FIG. 3, the grating 24 may be a transmissive optical element (for example, a diffraction grating). However, the grating 24 may be replaced with a reflective optical element. The interference light is dispersed by the grating 24 in a direction that coincides with the direction in which the pixels are arranged in the imaging element 26.

[0034] The dispersed interference light is incident on the imaging system 25. As a result, the interference light is imaged on the imaging surface through the imaging system 25. In FIG. 3, the imaging system 25 is constituted by two lenses, i.e., a lens 25a and a lens 25b. However, this is merely an example, and various alternative configurations can be adopted for the imaging system 25.

[0035] The imaging element 26 is a line sensor (one-dimensional imaging element) in which pixels (elements) are arranged in a one-dimensional direction. The imaging element 26 is disposed on the imaging surface, that is, at the position of the focal length (image-side focal length) of the imaging system 25.

[0036] Among the optical paths of the spectroscopic optical system 20, the distance between the collimating system 22 and the grating 24 has no relation to performance and can thus be set to any value. Therefore, the overall length of the spectroscopic optical system 20 is substantially governed by the focal length f1 of the collimating system 22 and the focal length f2 of the imaging system 25. In this embodiment, the apparatus 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. That is, both f1 and f2 are fixed. That is, in this embodiment, the conditions of the spectrometer do not change when acquiring the fundus OCT and the anterior segment OCT, respectively.

[0037] Here, the relationship between the depth direction resolution in SD-OCT and the depth range to be imaged will be described. Unless otherwise specified, the depth range in this embodiment is the depth from one end of the imaging range with zero delay to the other end. That is, in this embodiment, it refers to a value based on an optical system design that does not rely on the full-range technique.

[0038] First, the resolution in the depth direction in OCT can be expressed by the following relational expression.

[0039]

Equation

[0040] However, 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).

[0041] Also, the imaging range in the depth direction (depth range) can be expressed by the relational expressions shown in Equation 2 to Equation 3.

[0042]

Number

[0043]

Number

[0044]

Number

[0045] However, z max represents the depth range, N represents the number of elements in the imaging element, λ0 represents the central wavelength of the measurement light, a represents the grating constant of the grating, dλ represents the sampling wavelength width, Δx represents the width of one element in the imaging element, θ represents the diffraction angle in the grating, m represents the diffraction order, and f2 represents the focal length of the imaging system, respectively. From Numbers 2 to 4, it can be seen that the depth range z max is proportional to the focal length f2 of the imaging system. Also, since the depth range z max is proportional to the number of pixels N and inversely proportional to the width of one element Δx, it can be seen that the depth range z max increases with the increase in the number of high pixels of the imaging element.

[0046] Here, in SD-OCT, on the imaging plane by the imaging system, the spectrum of the interference light is distributed in one direction. The width of the distribution of the interference light derived from the light source performance is called the source bandwidth.

[0047] As shown in Figure 4A, for the source bandwidth, if the signal range detected by the imaging element is narrow, the total light reception width Δλ becomes small and the resolution in the depth direction decreases (δz becomes a large value). On the other hand, since the imaging element samples the signal at a high density, the sampling width dλ becomes small. Therefore, the depth range z max is increased.

[0048] In FIG. 4B, the balance of the signal range detected by the imaging device is achieved with respect to the width of the spectral distribution in the source band. Therefore, although the resolution in the depth direction is improved compared to the case of FIG. 4A, the depth range z max becomes narrow.

[0049] As a result of the above considerations, in order to maintain a resolution suitable for fundus OCT (preferably 7 μm or less) as in the conventional design and at the same time realize a wider depth range than the conventional design suitable for anterior segment OCT, it is necessary to sufficiently increase the focal length f2 of the imaging system together with increasing the number of pixels of the imaging device. At this time, since the corneal thickness and the anterior chamber depth are about 0.5 mm and 2 - 3 mm, respectively, the depth range that can image from the corneal apex to the anterior capsule of the lens is preferably 4 mm or more.

[0050] By the way, in the spectrometer, it can be considered that the interfered light in the spectrally separated state forms an image with a finite spot size on the imaging surface. The larger the spot size with respect to the width of one element Δx, the less the interference signal for each frequency can be decomposed, and as a result, it is considered that sensitivity attenuation occurs. At this time, it is known that the sensitivity decreases more on the high-frequency region side (that is, the position farther 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.

[0051] On the other hand, in the present 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.

[0052] By the way, regarding the sensitivity attenuation, it can be expressed as a relational expression using the following depth range z max as follows.

[0053]

Equation

[0054] However, R(z) represents sensitivity attenuation, z represents the depth position, and ω represents the angular frequency, respectively.

[0055] 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 interval A near the origin, there is almost no change corresponding to z max 2) In interval B with a large value relative to interval A, there is a positive correlation between z and R(z). However, the slope of R(z) turns to a decreasing trend after passing through the pole change point. max 3) In interval C, R(z) asymptotes to a finite value. The change corresponding to z almost disappears. max Therefore, only in a part of the interval (interval B), when the depth range z

[0056] is expanded, the sensitivity attenuation is suppressed. For this reason, in this interval, at least a part of the influence on the sensitivity attenuation caused by the fact that the spot size of the depth range z max is not minimized can be offset by expanding the depth range z max max is considered to be offset by expanding the depth range z max

[0057] Next, FIG. 6 shows the sensitivity attenuation curves, which are the simulation results based on the formula, for two types of depth ranges of 3 mm and 4.2 mm. However, each sensitivity attenuation curve in FIG. 6 is premised on the state where the spot size is minimized.

[0058] From FIG. 6, it can be observed that between the depth ranges of 3 mm and 4.2 mm, the larger the depth range, the gentler the slope of the sensitivity attenuation. For example, in FIG. 6, the performance at 3 mm in the graph of the depth range of 3 mm is equivalent to the performance at 4.2 mm in the graph of the depth range of 4.2 mm.

[0059] From the simulation results, it is confirmed that when the depth range is extended from the range of conventional SD-OCT to the range required for one-shot imaging from the corneal apex to the anterior lens capsule, the effect of suppressing sensitivity attenuation can be enjoyed. Therefore, since a sensitivity margin is created even in the region away from zero delay, the focal length f1 of the collimating system 22 can be shortened accordingly. As a result, both the anterior segment OCT and the fundus OCT can be imaged well, and a compact OCT device can be realized.

[0060] However, the sensitivity attenuation of the actual device cannot be accurately predicted only by the simulation values. Therefore, for the imaging system 25 when the depth resolution δz: is 7 μm or less and the depth range z max : is 4 mm or more, the anterior segment OCT and the fundus OCT were imaged in an optical system where the focal length f1 of the collimating system 22 was made shorter than f2, and verification was performed on the influence of sensitivity attenuation. At this time, f1 is less than half of f2. More specifically, the ratio of f1:f2 is approximately 1:3. In this case, the total length of the spectrometer is shortened by up to about 60% compared to the state where the spot size is minimized.

[0061] Figures 7A and 7B show the fundus OCT and the anterior segment OCT, respectively.

[0062] FIG. 7A shows a B-scan of the fundus when the scanning length (field angle) in the transverse direction is 16 mm (approximate field angle 50°). In fundus OCT, since the fundus is curved, there are height differences in the fundus tissue depicted in the B-scan in the transverse direction. The height differences vary among individuals for each eye examined, and generally, they become more prominent in cases such as high myopia. Also, as the scanning length (field angle) in the B-scan increases, the height differences are more likely to appear. Therefore, in fundus OCT, it is inevitable that a part of the fundus tissue is depicted in the high-frequency side region (region away from the zero delay), and sensitivity attenuation is likely to be a problem. For example, as shown in FIG. 7A, when photographing with central fixation, the central part of the fundus is depicted at the deepest position. In particular, there are concerns about the impact on eyes with long axial lengths such as high myopia. However, as a verification result, as shown in FIG. 7A, even in the case of high myopia of -14D, the shape at the central part of the fundus and the main layer structure from the retinal surface to the choroidal surface can be visually identified, and no problems due to sensitivity attenuation were observed.

[0063] Also, as shown in FIG. 7B, in anterior segment OCT, it is possible to photograph the anterior capsule of the lens and the angle tissue from the corneal apex in one shot.

[0064] As described above, according to the present disclosure, even in a compact spectrometer 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 secure the resolution required for fundus OCT while ensuring a depth-direction imaging range sufficient to photograph a plurality of sites in the anterior segment together.

[0065] Based on the estimation of the present inventors from the imaging results such as FIGS. 7A and 7B, if the ratio of f1:f2 is in the range of approximately 1:4 or less, it is considered that the optical system can be shortened while enjoying the necessary sensitivity.

[0066] <Application of Full-Range Technology> Furthermore, full-range technology may be applied to the OCT data. Various methods for removing virtual images in OCT data are called full-range technology. In this embodiment, any full-range technology may be applied, and thereby, a wider range of OCT data with selectively removed virtual images may be obtained. When using full-range technology, since OCT data can be acquired from a region straddling zero delay, the substantial imaging range in the depth direction can be increased.

[0067] Note that, as an example of full-range technology, techniques for removing virtual images (also called mirror images) with additional hardware, techniques for correction by software without using additional hardware, etc. can be cited. Also, based on a plurality of OCT data with different optical path lengths when detecting spectral interference signals, at least complementary processing is performed on the overlapping region between the real image and the virtual image in the OCT data, and another full-range technology for generating OCT data subjected to the complementary processing has been proposed. Any of these may be applied in this embodiment.

[0068] <Fixing method of optical elements in the spectroscopic optical system> Next, with reference to FIGS. 8 and 9, a configuration for fixedly holding the spectroscopic optical system will be described. As shown in FIG. 8, in this embodiment, the OCT apparatus 1 may include a fixing and holding unit 200 for fixedly holding the spectroscopic optical system 20 on the base 250.

[0069] 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.

[0070] The first and second optical mounts 210 and 220 hold at least two of the plurality of optical elements (input end 21, collimating lens 22a, grading 24, imaging lenses 25a and 25b, light receiving element 26) included in the spectroscopic optical system 20. Specifically, two adjacent optical elements 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 are configured to suppress changes in the holding interval of the optical elements due to their own deformation according to temperature.

[0071] Incidentally, the spot size of the interference light on the imaging surface is enlarged when the interval between each optical element deviates from the designed value. If the interval between the optical elements deviates from the designed value, a decrease in sensitivity may occur. Therefore, when examining the influence 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, it was experimentally confirmed that the influence on the spot size increases in the order of 1) to 5) (descending order).

[0072] 1) Input end 21 and collimating 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 deviation between 1) and 2) is dominant with respect to the spot size. With the deviation of 3), some influence was seen on the spot size. The influence on the spot size due to the deviation of 4) and 5) was hardly seen.

[0073] Therefore, as shown in FIG. 8, in the present embodiment, the input end 21 and the collimating lens 22a are held by the first optical mount 210. Also, the two imaging lenses 25a and 25b are held by the second optical mount 220.

[0074] 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 collimating lens 22a. The third member 213 is fixed to both the first member 211 and the second member 212.

[0075] 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.

[0076] The first and second optical mounts 210 and 220 form a nested structure having folding portions B1 and B2 (see FIG. 9) at a plurality of locations (two locations in this embodiment) by the first to third members 211 to 213 and 221 to 223. As a result, in the first and second optical mounts 210 and 220, the displacement of the holding interval between the two optical elements held by each mount, which is caused by the thermal deformation of the first and second optical mounts 210 and 220, is canceled out among the first to third members 211 to 213 and 221 to 223 due to the thermal deformation of the first to third members 211 to 213 and 221 to 223.

[0077] Also, the surfaces of the first to third members 211 to 213 and 221 to 223 that are adjacent (in contact) to each other may be formed by lathe machining. By using lathe machining with high machining accuracy, in the first and second optical mounts 210 and 220, the first to third members 211 to 213 and 221 to 223 can be arranged closely, and the axial misalignment of the two optical elements held by each of the first and second optical mounts 210 and 220 is suppressed.

[0078] Referring to FIG. 9, the structures of the first and second optical mounts 210 and 220 will be described in detail. In FIG. 9, the first members 211 and 221 and the third members 213 and 223 are formed to extend toward each other along the optical axis from the holding positions of the optical elements. The second members 212 and 222 are arranged so as to overlap at least partially with both the first members 211 and 221 and the third members 213 and 223 in a direction intersecting the optical axis.

[0079] In FIG. 9, reference numeral p11 indicates the holding position of the optical element in the first members 211 and 221, and reference numeral p22 indicates the holding position of the optical element in the second members 212 and 222. Further, reference numeral q13 indicates the fixing position between the first members 211 and 221 and the second members 212 and 222, and reference numeral q23 indicates the fixing position between the first members 211 and 221 and the second members 212 and 222.

[0080] As shown in FIG. 9, the fixing position q13 is arranged on the holding position p22 side of the second members 212 and 222 (downstream side of the spectroscopic optical system 20 in this embodiment) with respect to the fixing position q23. Around the fixing position q13, a folding portion B1 is formed by the first members 211 and 221 and the third members 213 and 223.

[0081] The fixing position q23 is arranged on the holding position p11 side of the first members 211 and 221 (upstream side of the spectroscopic optical system 20 in this embodiment) with respect to the fixing position q13. Around the fixing position q23, a folding portion B2 is formed by the second members 212 and 222 and the third members 213 and 223.

[0082] When looking at the two members forming the folding portion from the folding portion, the directions of thermal deformation of the two members are made to coincide. Therefore, in this embodiment, in the first members 211 and 221 and the second members 212 and 222, even if dimensional changes due to thermal deformation occur, if equivalent dimensional changes occur in the third members 213 and 223, the holding interval between the two optical elements by the first and second optical mounts 210 and 220 is maintained before and after the temperature change.

[0083] Here, the distance from the holding position p11 to the fixing position q13 in the first members 211 and 221 is denoted as Dx, the distance from the holding position p22 to the fixing position q23 in the second members 212 and 222 is denoted as Dy, and the distance between the two fixing positions q13 and q23 in the third members 213 and 223 is denoted as Dz, respectively. According to the present embodiment, the dimensions affecting the thermal deformation in the optical axis direction of the first members 211 and 221, the second members 212 and 222, and the third members 213 and 223 are Dx, Dy, and Dz.

[0084] Also, let the coefficients of thermal expansion of the first members 211 and 221, the second members 212 and 222, and the third members 213 and 223 be β1, β2, and β3, respectively. When the temperature changes from the temperature T to the temperature Ta, if the allowable error in the change of the holding interval of the optical element is E, then by utilizing the difference in thermal expansion of each member, the material of each member and Dx, Dy, and Dz are determined so as to satisfy the following relational expression.

[0085]

Equation

[0086] That is, in the present embodiment, the material of each member and Dx, Dy, and Dz are determined such that the amount of dimensional change due to thermal deformation in the first members 211 and 221 and the second members 212 and 222 is substantially equal to the amount of dimensional change due to thermal deformation in the third members 213 and 223.

[0087] As shown in FIG. 9, if Dx, Dy, and Dz are close, the material of each member is selected such that β1, β2 < β3. For example, the first members 211 and 221 and the second members 212 and 222 may be made of the same material (that is, β1 = β2). As an example, iron may be used for the first members 211 and 221 and the second members 212 and 222, and aluminum may be used for the third members 213 and 223. Of course, each member may also be a combination of different materials having different coefficients of thermal expansion.

[0088] By providing the first and second optical mounts 210 and 220 as described above, it is possible to appropriately suppress changes in the distance between optical elements (changes according to temperature) that have a great influence on the spot size of the interference light on the imaging surface of the spectroscopic optical system 20, and to appropriately maintain the sensitivity performance at each temperature. In particular, as described above, even when an optical design disadvantageous in terms of sensitivity is adopted 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 preferably suppress a decrease in sensitivity performance due to temperature changes.

[0089] Returning to FIG. 8, the description 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. Further, the second optical mount 220 is connected to a fourth optical mount 240 on the downstream side. The third optical mount 230 fixedly holds the mirror 23 and the grating 24. The fourth optical mount 240 fixedly holds the light receiving element 26.

[0090] In the present embodiment, among the fixed holding units 200, each of the third optical mount 230 and the fourth optical mount 240 is directly connected to the base 250 with screws or the like. At least at the connection portion of either the third optical mount 230 or the fourth optical mount 240, deformation when the fixed holding unit 200 is deformed by heat can be absorbed by a washer or the like. Thereby, when the fixed holding unit 200 is deformed by temperature, concentration of mechanical load can be avoided, and deterioration of the optical system can be suppressed.

[0091] The present disclosure has been described based on the embodiments, but the present disclosure is not limited to the above embodiments, and various modifications are possible.

Explanation of reference numerals

[0092] 1 OCT apparatus 20 Spectroscopic optical system 22 Collimating system 24 Dispersion element (grating) 25 Imaging system 26 Light receiving element 210 First optical mount 220 Second optical mount 211, 221 First member 212, 222 Second member 213, 223 Third member

Claims

1. An OCT device that selectively captures OCT data of the fundus and OCT data of the anterior segment of the eye, comprising a spectroscopic optical system that spectroscopically detects the interference light between the return light of the measurement light irradiated on the eye to be examined and the reference light, wherein the spectroscopic optical system comprises a collimating system that collimates the interference light, a dispersion element that disperses the collimated interference light for each spectral wavelength, an imaging system that forms the interference light for each spectral wavelength on an imaging surface, and a light receiving element disposed on the imaging surface, wherein the object-side focal length of the collimating system is shorter than the image-side focal length of the imaging system. The OCT device.

2. The OCT device according to claim 1, wherein the object-side focal length of the collimating system is 1 / 2 or less of the image-side focal length of the imaging system.

3. The OCT device according to claim 2, wherein the object-side focal length of the collimating system is 1 / 4 or more of the image-side focal length of the imaging system.

4. The OCT device according to any one of claims 1 to 3, wherein a mirror that folds back the light beam by 90° or more is disposed between the collimating system and the dispersion element.

5. The collimating system is formed by a collimating lens, and the OCT device according to any one of claims 1 to 4, further comprising an optical mount that holds the collimating lens and the incident end of the interference light in the spectroscopic optical system and suppresses displacement of the holding interval due to thermal deformation.

6. The imaging system has two imaging lenses and the OCT device according to any one of claims 1 to 4, further comprising an optical mount that holds the two imaging lenses and suppresses displacement of the holding interval due to thermal deformation.

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