Optical coherence tomography apparatus and computer program for displaying tomographic images

Abstract

This invention provides an optical coherence tomography (OCT) apparatus and a computer program for displaying tomographic images. The OCT apparatus is a polarization-sensitive type. It includes an imaging unit and a display unit, wherein the imaging unit captures tomographic images of the examined eye; and the display unit displays the tomographic images captured by the imaging unit. The tomographic images include at least two of the following: an image representing the tissue within the examined eye using scattering intensity; an image representing the distribution of melanin within the examined eye; an image representing the fiber density within the examined eye; an image representing the direction of fiber travel within the examined eye; and an image representing blood flow within the examined eye. The display unit superimposes at least two images from the same location on the same cross-section. Therefore, the state of the examined eye can be readily and comprehensively assessed.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a polarization-sensitive optical coherence tomographic device and a computer program for displaying tomographic images. Background Technology

[0002] Optical coherence tomography (OCT) devices are non-invasive and non-contact, and therefore widely used in ophthalmic devices as a method for acquiring tomographic images of biological tissues. Furthermore, technologies have been developed that allow OCT devices to capture tomographic images that visualize various information within the biological tissue, in addition to capturing tomographic images representing the scattering intensity of the biological tissue. For example, Patent Document 1 discloses a polarization-sensitive OCT device. In the OCT device of Patent Document 1, in addition to acquiring a tomographic brightness image based on the intensity of the returned light from the examined eye, a delay image and a DOPU image representing the polarization state of the examined eye are also acquired. Furthermore, the OCT device of Patent Document 1 displays the acquired tomographic image based on the intensity of the returned light from the examined eye and the tomographic image representing the polarization state of the examined eye side-by-side on a display unit. By simultaneously displaying multiple tomographic images with various characteristics on the display unit, it is easy to evaluate the state of the examined eye from multiple angles.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2013-146445 Summary of the Invention

[0006] [The technical problem that the invention aims to solve]

[0007] In the optical coherence tomography apparatus of Patent Document 1, a tomographic image obtained based on the intensity of the reflected light from the subject and a tomographic image representing the polarization state of the subject are displayed side by side. However, even when the two images are displayed on the same screen, sometimes abnormalities or other conditions in the examined eye that can be observed in one image do not appear in the other image. Therefore, even when multiple different images of the examined eye are displayed, the user must pay attention to both images, making it difficult to evaluate the state of the examined eye from multiple perspectives.

[0008] This specification discloses a technique that allows for comprehensive and easy assessment of the condition of the examined eye.

[0009] [Technical solutions used to solve technical problems]

[0010] The optical coherence tomography (OCT) apparatus disclosed in this specification is a polarization-sensitive OCT apparatus. The OCT apparatus includes an imaging unit and a display unit, wherein the imaging unit captures tomographic images of the examined eye; and the display unit displays the tomographic images captured by the imaging unit. The tomographic images include at least two of the following: an image representing the tissue within the examined eye using scattering intensity; an image representing the distribution of melanin within the examined eye; an image representing the fiber density within the examined eye; an image representing the direction of fiber travel within the examined eye; and an image representing blood flow within the examined eye. The display unit superimposes at least two images from the same location on the same cross-section.

[0011] In the aforementioned optical coherence tomography apparatus, at least two tomographic images that visualize different information about the tissues within the examined eye are superimposed and displayed. This allows for a comprehensive understanding of the state based on various information at different locations (sections) within the tissues of the examined eye. Consequently, it is easier to prevent the omission of characteristic conditions (initial detections) such as diseases appearing in the tomographic images.

[0012] Furthermore, this specification discloses a computer program for displaying tomographic images of an examined eye. The computer program enables a computer to function as both a tomographic image generation unit and a display processing unit, wherein the tomographic image generation unit generates at least two tomographic images of the following types: a tomographic image representing the tissues within the examined eye using scattering intensity; a tomographic image representing the distribution of melanin within the examined eye; a tomographic image representing the fiber density within the examined eye; a tomographic image representing the direction of fiber travel within the examined eye; and a tomographic image representing blood flow within the examined eye; the display processing unit displays at least two tomographic images superimposed at the same location on the same cross-section. Attached Figure Description

[0013] Figure 1 This is a diagram showing a schematic structure of the optical system of the optical coherence tomography apparatus involved in the embodiment.

[0014] Figure 2 This is a block diagram illustrating the control system of the optical coherence tomography apparatus involved in the embodiment.

[0015] Figure 3 This is a block diagram representing the structure of a sampling trigger / clock generator.

[0016] Figure 4 This is a flowchart illustrating an example of a process that overlays tomographic images of the examined eye.

[0017] Figure 5 This is an example of a case where only the tomographic image of the tissues within the examined eye is displayed using scattering intensity (so-called a standard tomographic image).

[0018] Figure 6 This is an example of a case where only a tomographic image representing the entropy within the examined eye is displayed.

[0019] Figure 7 This is an example of a case where only a birefringent tomographic image of the examined eye is displayed.

[0020] Figure 8 This is an example of a case where only a tomographic image showing the direction of fiber travel within the examined eye is displayed.

[0021] Figure 9 The images shown represent an example of a case where only a tomographic image showing blood flow within the examined eye is displayed. (a) shows only a tomographic image showing blood flow within the examined eye, and (b) shows a typical tomographic image corresponding to (a) as a reference.

[0022] Figure 10 An example of an image with multiple tomographic images superimposed is an image on top of a normal tomographic image, showing the entropy within the examined eye.

[0023] Figure 11 Another example is an image with multiple tomographic images superimposed, representing an image on top of a normal tomographic image with a tomographic image representing birefringence within the examined eye.

[0024] Figure 12 Another example of an image with multiple tomographic images superimposed is an image in which a tomographic image representing birefringence within the examined eye is superimposed on a normal tomographic image, and a tomographic image representing entropy within the examined eye is superimposed on top of it.

[0025] Figure 13 Another example of an image with multiple tomographic images superimposed is an image in which a tomographic image representing the entropy within the examined eye is superimposed on a normal tomographic image, and a tomographic image representing birefringence within the examined eye is superimposed on top of that.

[0026] Figure 14 This is a flowchart illustrating an example of the process of overlaying and displaying the En-face image of the examined eye.

[0027] Figure 15 Here are examples of En-face images: (a) shows a typical En-face image within the examined eye; (b) shows an En-face image showing the entropy within the examined eye; and (c) shows an En-face image showing birefringence within the examined eye.

[0028] Figure 16Here are examples of images with multiple En-face images superimposed: (a) shows an image with an En-face image representing the entropy within the examined eye superimposed on a normal En-face image; (b) shows an image with an En-face image representing birefringence within the examined eye superimposed on a normal En-face image; (c) shows an image with an En-face image representing birefringence within the examined eye superimposed on a normal En-face image, and an En-face image representing the entropy within the examined eye superimposed on top of it; and (d) shows an image with an En-face image representing entropy within the examined eye superimposed on a normal En-face image, and an En-face image representing birefringence within the examined eye superimposed on top of it.

[0029] Figure 17 Here are examples of En-face images generated by selecting a range in the depth direction: (a) shows a typical En-face image of the eye near the superficial choroid, (b) shows an En-face image showing the entropy of the eye near the superficial choroid, (c) shows an image of (b) superimposed on the image of (a), (d) shows a typical En-face image of the eye near the deep choroid, (e) shows an En-face image showing the entropy of the eye near the deep choroid, and (f) shows an image of (e) superimposed on the image of (d). Detailed Implementation

[0030] The main features of the embodiments described below are listed first. Furthermore, the technical elements described below are independent technical elements, which exert their technical utility individually or in various combinations, and are not limited to the combinations described in the claims at the time of application.

[0031] (Feature 1) The optical coherence tomography apparatus disclosed in this specification may also include a range indicating mechanism that indicates the numerical range of the indicators displayed in each of the at least two images. The display unit may also display at least two images for the numerical range indicated by the range indicating mechanism. With this structure, the range of each image to be displayed can be selected according to the evaluation characteristics desired by the user.

[0032] (Feature 2) The optical coherence tomography apparatus disclosed in this specification may also have a superposition order indicator mechanism that indicates the order in which at least two images are superimposed. The display unit may also display at least two images superimposed in the order indicated by the superposition order indicator mechanism. According to this structure, the vertical positional relationship of at least two images when superimposing can be selected according to the evaluation characteristics desired by the user.

[0033] (Feature 3) In the optical coherence tomography apparatus disclosed in this specification, an image representing the distribution of melanin in the examined eye can also be generated based on entropy. An image representing the fiber density in the examined eye can also be generated based on birefringence. According to this structure, suitable images that are easy to understand the state of the examined eye can be displayed for both the image representing the distribution of melanin in the examined eye and the image representing the fiber density in the examined eye.

[0034] (Feature 4) In the optical coherence tomography apparatus disclosed in this specification, the imaging unit may also include a light source, a measurement light generation unit, a reference light generation unit, and an interference light detection unit. The measurement light generation unit generates measurement light using light from the light source and illuminates the generated measurement light onto the eye under examination to generate reflected light from the eye under examination. The reference light generation unit generates reference light using light from the light source. The interference light detection unit detects interference light, which is obtained by combining the reflected light from the eye under examination generated by the measurement light generation unit and the reference light generated by the reference light generation unit. The measurement light generation unit can also generate a first polarized measurement light and a second polarized measurement light using light from a light source, and illuminate the tested eye with the first polarized measurement light and the second polarized measurement light, wherein the first polarized measurement light vibrates in a first direction; the second polarized measurement light vibrates in a second direction different from the first direction; the reflected light from the tested eye of the first polarized measurement light generates a first polarized reflected light vibrating in the first direction and a second polarized reflected light vibrating in the second direction; the reflected light from the tested eye of the second polarized measurement light generates a third polarized reflected light vibrating in the first direction and a fourth polarized reflected light vibrating in the second direction. The interference light detection unit can also detect the first, second, third, and fourth interference lights. The first interference light refers to the interference light obtained by combining the reflected light of the first polarized light and the reference light; the second interference light refers to the interference light obtained by combining the reflected light of the second polarized light and the reference light; the third interference light refers to the interference light obtained by combining the reflected light of the third polarized light and the reference light; and the fourth interference light refers to the interference light obtained by combining the reflected light of the fourth polarized light and the reference light. Based on this structure, tomographic images that visualize different information about the tissues within the examined eye (e.g., images representing the tissues within the examined eye using scattering intensity, images representing the distribution of melanin within the examined eye, images representing the fiber density within the examined eye, and images representing the direction of fiber travel within the examined eye, etc.) can be appropriately generated.

[0035] (Feature 5) In the optical coherence tomography apparatus disclosed in this specification, images representing the tissues within the examined eye using scattering intensity can also be generated using at least one of the first, second, third, and fourth interference lights. Images representing the distribution of melanin within the examined eye can also be generated using the first, second, third, and fourth interference lights. Images representing the fiber density within the examined eye can also be generated using the first, second, third, and fourth interference lights. Images representing the direction of fiber travel within the examined eye can also be generated using the first, second, third, and fourth interference lights. Images representing blood flow within the examined eye can also be generated using the first, second, third, and fourth interference lights. Based on this structure, it is possible to appropriately generate images representing the tissues within the examined eye using scattering intensity, images representing the distribution of melanin within the examined eye, images representing the fiber density within the examined eye, images representing the direction of fiber travel within the examined eye, and images representing blood flow within the examined eye.

[0036] (Feature 6) In the optical coherence tomography apparatus disclosed in this specification, the display unit may also be configured to display an En-face image generated from an image captured by the imaging unit, relating to at least two images. The display unit may also superimpose the En-face images relating to at least two images. With this configuration, a larger range of the examined eye can be easily identified.

[0037] [Example] (Example 1)

[0038] The optical coherence tomography apparatus described in this embodiment will now be explained. This optical coherence tomography apparatus is a polarization-sensitive OCT (PS-OCT) device capable of capturing the polarization characteristics of the object under test using a wavelength-scanning Fourier domain method (swept-source optical coherence tomography: SS-OCT) with a wavelength-scanning light source.

[0039] like Figure 1 As shown, the optical coherence tomography apparatus of this embodiment includes: a light source 11; a measurement light generating unit (21-29, 31, 32) that generates measurement light using light from the light source 11; a reference light generating unit (41-46, 51) that generates reference light using light from the light source 11; interference light generating units 60 and 70 that combine reflected light from the examined eye 500 generated by the measurement light generating unit and reference light generated by the reference light generating unit to generate interference light; and interference light detection units 80 and 90 that detect the interference light generated by the interference light generating units 60 and 70.

[0040] (light source)

[0041] Light source 11 is a wavelength sweeping type light source, whose emitted light wavelength (wavenumber) changes at a predetermined period. Because the wavelength of the light irradiating the examined eye 500 changes (sweeps), the intensity distribution of light reflected from various locations along the depth direction of the examined eye 500 can be obtained by performing Fourier analysis on the signal obtained from the interference light, wherein the interference light is the interference between the reflected light from the examined eye 500 and the reference light.

[0042] Additionally, a polarization control device 12 and an optical fiber coupler 13 are connected to the light source 11. A PMFC (polarization-preserving fiber coupler) 14 and a sampling trigger / clock generator 100 are connected to the optical fiber coupler 13. Therefore, the light output from the light source 11 is input to the PMFC 14 and the sampling trigger / clock generator 100 respectively via the polarization control device 12 and the optical fiber coupler 13. The sampling trigger / clock generator 100 uses the light from the light source 11 to generate the sampling trigger and sampling clock for the signal processors 83 and 93, which will be described later.

[0043] (Measuring the light generation unit)

[0044] The measurement light generation unit (21-29, 31, 32) includes: a PMFC21 connected to PMFC14; two measurement optical paths S1 and S2 branching from PMFC21; a polarization beam combiner / splitter 25 connecting the two measurement optical paths S1 and S2; a collimating mirror 26 connected to the polarization beam combiner / splitter 25; and galvanometer mirrors 27 and 28 and a lens 29. An optical path difference generation unit 22 and a circulator 23 are arranged on measurement optical path S1. Only a circulator 24 is arranged on measurement optical path S2. Therefore, the optical path difference ΔL between measurement optical paths S1 and S2 is generated by the optical path difference generation unit 22. The optical path difference ΔL can be set to be longer than the measurement range in the depth direction of the examined eye 500. This prevents the superposition of interference beams with different optical path differences. For example, an optical fiber, a mirror, or a prism can be used in the optical path difference generation unit 22. In this embodiment, the optical path difference generation unit 22 uses a 1m PM optical fiber. Additionally, the measurement light generation unit also includes PMFCs 31 and 32. PMFC 31 is connected to circulator 23. PMFC 32 is connected to circulator 24.

[0045] The light (i.e., the measurement light) branching off from PMFC14 is input into the aforementioned measurement light generation units (21-29, 31, 32). PMFC21 splits the measurement light input from PMFC14 into a first measurement light and a second measurement light. The first measurement light split by PMFC21 is introduced into measurement optical path S1, and the second measurement light is introduced into measurement optical path S2. The first measurement light introduced into measurement optical path S1 is input into polarization beam combiner / splitter 25 through optical path difference generation unit 22 and circulator 23. The second measurement light introduced into measurement optical path S2 is input into polarization beam combiner / splitter 25 through circulator 24. PM fiber 304 is connected to polarization beam combiner / splitter 25 with its circumferential direction rotated 90 degrees relative to PM fiber 302. Accordingly, the second measurement light input into polarization beam combiner / splitter 25 becomes light with a polarization component orthogonal to the first measurement light. An optical path difference generating unit 22 is provided on the measurement optical path S1. Therefore, the first measurement light is delayed by the distance of the optical path difference generating unit 22 relative to the second measurement light (i.e., an optical path difference ΔL is generated). A polarizing beam combiner / splitter 25 superimposes the input first and second measurement lights. The light output from the polarizing beam combiner / splitter 25 (the light obtained by superimposing the first and second measurement lights) is irradiated onto the eye under test 500 via a collimating lens 26, galvanometer lenses 27 and 28, and a lens 29. The light irradiating the eye under test 500 is scanned in the xy direction by galvanometer lenses 27 and 28.

[0046] Light illuminating the eye under examination 500 is reflected by the eye under examination 500. Here, the light reflected by the eye under examination 500 is scattered on or inside the surface of the eye under examination 500. Opposite to the incident path, the reflected light from the eye under examination 500 passes through lens 29, galvanometer lenses 28 and 27, and collimating lens 26, and is input to polarization beam combiner / splitter 25. Polarization beam combiner / splitter 25 splits the input reflected light into two mutually orthogonal polarization components. For ease of explanation, these two polarization components are referred to here as horizontally polarized reflected light (horizontal polarization component) and vertically polarized reflected light (vertical polarization component). Then, the horizontally polarized reflected light is introduced into measurement optical path S1, and the vertically polarized reflected light is introduced into measurement optical path S2.

[0047] The horizontally polarized reflected light has its optical path altered by circulator 23 and is input to PMFC31. PMFC31 branches the input horizontally polarized reflected light, which is then input to PMFC61 and 71 respectively. Therefore, the horizontally polarized reflected light input to PMFC61 and 71 contains a reflected light component based on the first measurement light and a reflected light component based on the second measurement light. The vertically polarized reflected light has its optical path altered by circulator 24 and is input to PMFC32. PMFC32 branches the input vertically polarized reflected light, which is then input to PMFC62 and 72. Therefore, the vertically polarized reflected light input to PMFC62 and 72 contains a reflected light component based on the first measurement light and a reflected light component based on the second measurement light.

[0048] (Refer to the light generation section)

[0049] The reference light generating unit (41-46, 51) includes a circulator 41 connected to PMFC14, reference delay lines (42, 43) connected to circulator 41, PMFC44 connected to circulator 41, two reference optical paths R1 and R2 branching from PMFC44, PMFC46 connected to reference optical path R1, and PMFC51 connected to reference optical path R2. An optical path difference generating unit 45 is disposed on reference optical path R1. No optical path difference generating unit is disposed on reference optical path R2. Therefore, the optical path difference ΔL' between reference optical path R1 and reference optical path R2 is generated by the optical path difference generating unit 45. The optical path difference generating unit 45 may be, for example, an optical fiber. The optical path ΔL' of the optical path difference generating unit 45 may also be the same as the optical path ΔL of the optical path difference generating unit 22. By making the optical path differences ΔL and ΔL' the same, the depth positions of the multi-beam interference light relative to the examined eye 500, as described later, are the same. That is, it is not necessary to align the positions of the acquired multiple tomographic images.

[0050] The light (i.e., reference light) branching off from PMFC14 is input into the aforementioned reference light generating unit (41-46, 51). The reference light input from PMFC14 is fed into reference delay lines (42, 43) via circulator 41. Reference delay lines (42, 43) are composed of collimating lens 42 and reference reflecting mirror 43. The reference light input into reference delay lines (42, 43) is irradiated onto reference reflecting mirror 43 via collimating lens 42. The reference light reflected by reference reflecting mirror 43 is fed into circulator 41 via collimating lens 42. Here, reference reflecting mirror 43 can be moved closer to or further away from collimating lens 42. In this embodiment, before starting the measurement, the position of reference reflecting mirror 43 is adjusted such that the signal from the examined eye 500 is within the measurement range of the depth direction of OCT.

[0051] The reference light reflected by the reference mirror 43 has its optical path altered by the circulator 41 and is input to PMFC44. PMFC44 branches the input reference light into a first reference light and a second reference light. The first reference light is introduced into reference optical path R1, and the second reference light is introduced into reference optical path R2. The first reference light is input to PMFC46 through the optical path difference generator 45. The reference light input to PMFC46 is branched into a first branch reference light and a second branch reference light. The first branch reference light is input to PMFC61 through collimating mirror 47 and lens 48. The second branch reference light is input to PMFC62 through collimating mirror 49 and lens 50. The second reference light is input to PMFC51 and split into a third branch reference light and a fourth branch reference light. The third branch reference light is input to PMFC71 through collimating mirror 52 and lens 53. The fourth branch reference light is input to PMFC72 through collimating mirror 54 and lens 55.

[0052] (Interference light generation section)

[0053] Interference light generation units 60 and 70 include a first interference light generation unit 60 and a second interference light generation unit 70. The first interference light generation unit 60 includes PMFCs 61 and 62. As described above, horizontally polarized reflected light is input to PMFC 61 by the measurement light generation unit, and a first branch reference light (light with optical path difference ΔL') is input to PMFC 61 by the reference light generation unit. Here, the horizontally polarized reflected light includes a reflected light component based on the first measurement light (light with optical path difference ΔL) and a reflected light component based on the second measurement light (light without optical path difference ΔL). Therefore, in PMFC 61, the reflected light component based on the first measurement light (light with optical path difference ΔL) and the first branch reference light in the horizontally polarized reflected light are combined to generate the first interference light (horizontally polarized light component).

[0054] Furthermore, vertically polarized reflected light is input to PMFC62 by the measurement light generation unit, and a second branch reference light (light with an optical path difference ΔL') is input to PMFC62 by the reference light generation unit. Here, the vertically polarized reflected light includes a reflected light component based on the first measurement light (light with an optical path difference ΔL) and a reflected light component based on the second measurement light (light without an optical path difference ΔL). Therefore, in PMFC62, the reflected light component based on the first measurement light (light with an optical path difference ΔL) and the second branch reference light in the vertically polarized reflected light are combined to generate a second interference light (vertically polarized light component).

[0055] The second interference light generation unit 70 includes PMFCs 71 and 72. As described above, horizontally polarized reflected light is input to PMFC 71 from the measurement light generation unit, and a third branch reference light (light without optical path difference ΔL') is input to PMFC 71 from the reference light generation unit. Therefore, in PMFC 71, the reflected light component based on the second measurement light (light without optical path difference ΔL) and the third branch reference light in the horizontally polarized reflected light are combined to generate the third interference light (horizontally polarized light component).

[0056] Additionally, vertically polarized reflected light is input to PMFC72 from the measurement light generation unit, and a fourth branch reference light (light without optical path difference ΔL') is input to PMFC72 from the reference light generation unit. Therefore, in PMFC72, the reflected light component based on the second measurement light (light without optical path difference ΔL) and the fourth branch reference light in the vertically polarized reflected light are combined to generate a fourth interference light (vertically polarized light component). The first and second interference lights correspond to the measurement light via measurement optical path S1, and the third and fourth interference lights correspond to the measurement light via measurement optical path S2.

[0057] (Interference Light Detection Department)

[0058] Interference light detection units 80 and 90 include: a first interference light detection unit 80, which detects interference light (first interference light and second interference light) generated by the first interference light generation unit 60; and a second interference light detection unit 90, which detects interference light (third interference light and fourth interference light) generated by the second interference light generation unit 70.

[0059] The first interference light detection unit 80 includes balanced photodetectors 81 and 82 (hereinafter also referred to as "detectors 81 and 82") and a signal processor 83 connected to detectors 81 and 82. A PMFC 61 is connected to detector 81, and the signal processor 83 is connected to the output terminal of detector 81. PMFC 61 branches the first interference light into two interference beams with a phase difference of 180 degrees and inputs them into detector 81. Detector 81 performs differential amplification and noise reduction processing on the two interference beams with a phase difference of 180 degrees input from PMFC 61, converts them into an electrical signal (the first interference signal), and outputs the first interference signal to signal processor 83. That is, the first interference signal is the interference signal HH of the horizontally polarized reflected light from the tested eye 500 and the reference light based on the horizontally polarized light measurement light. Similarly, PMFC 62 is connected to detector 82, and the signal processor 83 is connected to the output terminal of detector 82. PMFC62 branches the second interference beam into two beams with a 180-degree phase difference and inputs them into detector 82. Detector 82 performs differential amplification and noise reduction processing on the two beams with a 180-degree phase difference, converts them into an electrical signal (the second interference signal), and outputs the second interference signal to signal processor 83. That is, the second interference signal is the interference signal HV of the vertically polarized reflected light from the examined eye 500 and the reference light based on the horizontally polarized measurement light.

[0060] The signal processor 83 includes a first signal processing unit 84 that receives a first interference signal and a second signal processing unit 85 that receives a second interference signal. The first signal processing unit 84 samples the first interference signal based on a sampling trigger and a sampling clock input from the sampling trigger / clock generator 100 to the signal processor 83. Similarly, the second signal processing unit 85 samples the second interference signal based on the sampling trigger and sampling clock input from the sampling trigger / clock generator 100 to the signal processor 83. The first and second interference signals sampled by the first and second signal processing units 84 and 85 are input to the arithmetic unit 202, which will be described later. The signal processor 83 can utilize a known data acquisition device (so-called DAQ).

[0061] The second interference light detection unit 90, like the first interference light detection unit 80, includes balanced photodetectors 91 and 92 (hereinafter also referred to as "detectors 91 and 92") and a signal processor 93 connected to detectors 91 and 92. A PMFC 71 is connected to detector 91, and the signal processor 93 is connected to the output terminal of detector 91. The PMFC 71 branches the third interference light into two interference beams with a 180-degree phase difference and inputs them into detector 91. Detector 91 performs differential amplification and noise reduction processing on the two interference beams with a 180-degree phase difference, converts them into an electrical signal (the third interference signal), and outputs the third interference signal to signal processor 93. That is, the third interference signal is the interference signal VH based on the horizontally polarized reflected light from the tested eye 500 and the reference light of the vertically polarized measurement light. Similarly, a PMFC 72 is connected to detector 92, and the signal processor 93 is connected to the output terminal of detector 92. PMFC72 branches the fourth interference beam into two interference beams with a 180-degree phase difference and inputs them into detector 92. Detector 92 performs differential amplification and noise reduction processing on the two interference beams with a 180-degree phase difference, converts them into an electrical signal (the fourth interference signal), and outputs the fourth interference signal to signal processor 93. That is, the fourth interference signal is the interference signal VV of the vertically polarized reflected light from the tested eye 500 and the reference light based on the vertically polarized light measurement light.

[0062] The signal processor 93 includes a third signal processing unit 94 for receiving a third interference signal and a fourth signal processing unit 95 for receiving a fourth interference signal. The third signal processing unit 94 samples the third interference signal based on a sampling trigger and a sampling clock input from the sampling trigger / clock generator 100 to the signal processor 93. Similarly, the fourth signal processing unit 95 samples the fourth interference signal based on a sampling trigger and a sampling clock input from the sampling trigger / clock generator 100 to the signal processor 93. The third and fourth interference signals obtained by the third and fourth signal processing units 94 and 95 are input to the arithmetic unit 202, which will be described later. The signal processor 93 can also use a known data acquisition device (so-called DAQ). With this structure, interference signals representing the four polarization characteristics of the examined eye 500 can be acquired. Furthermore, in this embodiment, signal processors 83 and 93 with two signal processing units are used, but the structure is not limited to this. For example, one signal processor with four signal processing units can be used, or four signal processors with one signal processing unit can be used.

[0063] Next, the structure of the control system of the optical coherence tomography apparatus involved in this embodiment will be described. For example... Figure 2As shown, the optical coherence tomography apparatus is controlled by a computing unit 200. The computing unit 200 comprises a computing unit 202, a first interference light detection unit 80, and a second interference light detection unit 90. The first interference light detection unit 80, the second interference light detection unit 90, and the computing unit 202 are connected to the measurement unit 10. The computing unit 202 outputs a control signal to the measurement unit 10 to drive the galvanometer mirrors 27 and 28, thereby scanning the position of the measurement light incident on the examined eye 500. The first interference light detection unit 80, triggered by sampling trigger 1, acquires first sampled data based on the sampling clock 1 input from the measurement unit 10 for the interference signals (interference signal HH and interference signal HV) input from the measurement unit 10, and outputs the first sampled data to the computing unit 202. The computing unit 202 performs Fourier transform and other computational processing on the first sampled data to generate HH tomographic images and HV tomographic images. The second interference light detection unit 90, triggered by sampling trigger 2, acquires second sampling data based on the sampling clock 2 input from the measurement unit 10 for the interference signals (interference signal VH and interference signal VV) input from the measurement unit 10, and outputs the second sampling data to the calculation unit 202. The calculation unit 202 performs operations such as Fourier transform processing on the second sampling data to generate VH tomographic images and VV tomographic images. Here, the HH tomographic image, VH tomographic image, HV tomographic image, and VV tomographic image are tomographic images at the same location. Therefore, the calculation unit 202 can generate tomographic images of the examined eye 500 representing the four polarization characteristics (HH, HV, VH, VV) of the Jones matrix.

[0064] like Figure 3 As shown, the sampling trigger / clock generator 100 includes an optical fiber coupler 102, sampling trigger generators (140-152), and sampling clock generators (160-172). Light from the light source 11 is input to the sampling trigger generator 140 and the sampling clock generator 160 via optical fiber coupler 13 and optical fiber coupler 102, respectively.

[0065] (Sampling trigger generator)

[0066] The sampling trigger generator 140 can also use, for example, FBG (Fiber Bragg Grating) 144 to generate sampling triggers. Figure 3As shown, FBG144 reflects only light of a specific wavelength from the light source 11, generating a sampling trigger. The generated sampling trigger is input to distributor 150. Distributor 150 assigns the sampling trigger to sampling trigger 1 and sampling trigger 2. Sampling trigger 1 is input to arithmetic unit 202 via signal delay circuit 152. Sampling trigger 2 is directly input to arithmetic unit 202. Sampling trigger 1 becomes the trigger signal for the interference signals (first interference signal and second interference signal) input to arithmetic unit 202 from first interference light detection unit 80. Sampling trigger 2 becomes the trigger signal for the interference signals (third interference signal and fourth interference signal) input to arithmetic unit 202 from second interference light detection unit 90. Signal delay circuit 152 is designed such that the time delay of sampling trigger 1 relative to sampling trigger 2 corresponds to the optical path difference ΔL of optical path difference generation unit 22. Accordingly, the frequency at which sampling of the interference signal input from first interference light detection unit 80 begins is the same as the frequency at which sampling of the interference signal input from second interference light detection unit 90 begins. Here, only sampling trigger 1 can be generated. Since the optical path difference ΔL is known, when sampling the interference signal input from the second interference light detection unit 90, sampling can begin by delaying the time from sampling trigger 1 by an amount corresponding to the optical path difference ΔL.

[0067] (Sampling clock generator)

[0068] The sampling clock generator can also be constructed, for example, from a Mach-Zehnder interferometer. Figure 3 As shown, the sampling clock generator uses a Mach-Zehnder interferometer to generate sampling clocks of equal frequency. The sampling clocks generated by the Mach-Zehnder interferometer are input to a distributor 172. The distributor 172 distributes the sampling clocks into sampling clock 1 and sampling clock 2. Sampling clock 1 is input to the first interference light detection unit 80 via a signal delay circuit 174. Sampling clock 2 is directly input to the second interference light detection unit 90. The signal delay circuit 174 is designed to delay the time by an amount corresponding to the optical path difference ΔL of the optical path difference generation unit 22. Accordingly, even for interference light delayed by an amount corresponding to the optical path difference generation unit 22, sampling can be performed at the same time. Accordingly, positional shifts in the acquired multiple tomographic images can be prevented. In this embodiment, a Mach-Zehnder interferometer is used to generate the sampling clocks. However, a Michelson interferometer or a circuit can also be used to generate the sampling clocks. Alternatively, a light source with a sampling clock generator can also be used to generate the sampling clocks.

[0069] Next, refer to Figure 4The process of overlaying and displaying the tomographic images of the examined eye 500 on the display 120 will be described. In this embodiment, the process of overlaying and displaying the tomographic images of the fundus of the examined eye 500 will be described as an example. Furthermore, the tomographic images are not limited to images obtained by photographing the fundus of the examined eye 500. The tomographic images may also be images obtained by photographing portions of the examined eye 500 other than the fundus, for example, images obtained by photographing the anterior eye.

[0070] like Figure 4 As shown, firstly, the processing unit 202 acquires a tomographic image of the examined eye 500 (S12). The process of acquiring the tomographic image of the examined eye 500 is performed according to the following steps. First, the examiner operates a control component such as a joystick (not shown) to align the optical coherence tomography device relative to the examined eye 500. That is, in response to the examiner's operation of the control component, the processing unit 202 drives a position adjustment mechanism (not shown). Accordingly, the position of the optical coherence tomography device relative to the examined eye 500 in the xy direction (longitudinal and transverse directions) and the z direction (direction of forward and backward movement) is adjusted.

[0071] Next, the computing unit 202 captures a tomographic image of the fundus of the examined eye 500. In this embodiment, this is performed using a raster scanning method. This allows the acquisition of a tomographic image of the fundus of the examined eye 500 covering the entire area. However, the method for capturing the tomographic image of the fundus of the examined eye 500 is not limited to a raster scanning method. Any method capable of capturing a tomographic image of the fundus of the examined eye 500 covering the entire area can be used; for example, a radial scanning method can also be employed.

[0072] When a tomographic image of the fundus of the examined eye 500 is acquired in step S12, the computation unit 202 generates various tomographic images representing different characteristics based on the tomographic image acquired in step S12 (S14). As described above, the optical coherence tomography apparatus of this embodiment is a polarization-sensitive optical coherence tomography apparatus, therefore, it is possible to simultaneously acquire tomographic images captured by irradiating the examined eye 500 with a vertical wave and tomographic images captured by irradiating the examined eye 500 with a horizontal wave. By using these two types of tomographic images, the computation unit 202 can generate, in addition to generating tomographic images representing the tissue within the examined eye 500 using scattering intensity (so-called ordinary tomographic images, hereinafter simply referred to as "ordinary tomographic images"), tomographic images representing the entropy within the examined eye 500 (hereinafter simply referred to as "tomographic images representing entropy"), tomographic images representing birefringence within the examined eye 500 (hereinafter simply referred to as "tomographic images representing birefringence"), tomographic images representing the fiber direction of travel within the examined eye 500 (hereinafter simply referred to as "tomographic images representing fiber direction of travel"), and tomographic images representing blood flow within the examined eye 500 (hereinafter simply referred to as "tomographic images representing blood flow"), etc. In this embodiment, the ordinary tomographic image, the tomographic image representing entropy, the tomographic image representing birefringence, the tomographic image representing the fiber direction of travel, and the tomographic image representing blood flow are generated using four interference signals HH, HV, VH, and VV. In addition, typical tomographic images can also be generated using any one or more of the four interference signals HH, HV, VH, and VV.

[0073] Tomographic images representing entropy, birefringence, fiber direction of travel, and blood flow can be generated using known methods. For example, a tomographic image representing entropy can be generated by calculating the entropy of the acquired tomographic image. Furthermore, a tomographic image representing birefringence can be obtained by the following method: During tomographic imaging, speckle patterns are generated due to interference between scattered light generated by fine structures below the OCT resolution. The phase difference between the polarized signals of the generated speckle patterns is displayed. Based on this, a tomographic image representing birefringence is obtained. Additionally, a tomographic image representing fiber direction of travel can be generated by calculating the axis of birefringence. Furthermore, a tomographic image representing blood flow can be obtained by the following method: In step S12, a process of taking multiple tomographic images is performed. During this process, speckle patterns are generated due to interference between scattered light generated by fine structures below the OCT resolution. The variance of the scattering intensity signal or phase signal of the generated speckle patterns is displayed. Based on this, a tomographic image representing blood flow is obtained. The various tomographic images described above represent the same location on the same cross-section of the examined eye 500. Furthermore, the generated tomographic images can be those that can be generated using a polarization-sensitive optical coherence tomography apparatus, or tomographic images representing other characteristics besides those described above can be generated.

[0074] Next, the arithmetic unit 202 displays the various tomographic images generated in step S14 on the display 120 (S16). That is, in this embodiment, the arithmetic unit 202 displays the general tomographic image, the tomographic image representing entropy, the tomographic image representing birefringence, the tomographic image representing the fiber's direction of travel, and the tomographic image representing blood flow generated in step S14 side by side on the display 120.

[0075] Each tomographic image is displayed according to an index appropriate to the characteristics shown by that tomographic image. In typical tomographic images, the index is, for example, the intensity (dB) of the scattered light (brightness). Figure 5 In the example shown, the tomographic image appears black at 0 dB, white at 35 dB, and changes gradually between 0 and 35 dB. Furthermore, in tomographic images representing entropy, the index is, for example, a dimensionless quantity. Figure 6 In the example shown, the tomographic image is displayed in yellow when the value is 0, in cyan when the value is 1, and gradually changes from yellow to orange, red, purple, and cyan between 0 and 1. Furthermore, in tomographic images representing birefringence, the index is, for example, the phase retardation (rad) based on birefringence. Figure 7In the example shown, the tomographic image is displayed in yellow at 0 rad, in dark blue at 0.5 rad, and gradually changes from yellow to yellow-green, green, cyan, and dark blue between 0 and 0.5 rad. Additionally, in tomographic images indicating the fiber's direction of travel, the index is, for example, the angle of the polarization axis (in rad). Figure 8 In the example shown, the tomographic image appears black at -π, white at +π, and changes gradually between -π and +π. Furthermore, in tomographic images representing blood flow, the parameters are, for example, dimensionless quantities. Figure 9 In the example shown in (a), the tomographic image appears black when the value is 0, white when the value is 1, and changes gradually between 0 and 1.

[0076] Next, the calculation unit 202 determines whether more than two tomographic images have been selected from the multiple tomographic images displayed (S18). Specifically, the user uses an input mechanism such as a mouse (illustration omitted) to select multiple desired images from the various tomographic images displayed on the monitor 120. Then, when the image selection operation is finished, the user indicates that the image selection operation is complete. For example, a button indicating "complete" is displayed on the monitor 120, and the user clicks the button indicating "complete" using an input mechanism, thereby indicating that the image selection operation is complete. The calculation unit 202 remains on standby until the image selection operation is indicated as complete (no in step S18). The following explanation will take the case where the user selects a normal tomographic image and a tomographic image representing entropy as an example.

[0077] When the image selection operation is indicated as complete (yes in step S18), the calculation unit 202 determines whether the order in which the multiple images are superimposed selected in step S18 has been chosen (S20). Specifically, the user uses an input mechanism such as a mouse (illustration omitted) to select the superimposition order for the tomographic images displayed on the display 120. Then, when the sequential selection operation ends, the user indicates that the sequential selection operation is complete. The calculation unit 202 remains on standby until the sequential selection operation is indicated as complete (no in step S20). For example, the user may instruct the superimposition of the entropy-representing tomographic image on top of the normal tomographic image and the entropy-representing tomographic image selected in step S18.

[0078] When the sequential selection operation is indicated as complete (yes in step S20), the calculation unit 202 determines whether a numerical range (range) of the index has been selected for each of the selected tomographic images (S22). Specifically, the user uses an input mechanism such as a mouse (illustration omitted) to select the range of the index to be displayed for each of the selected tomographic images. For example, when a tomographic image representing entropy is superimposed on a normal tomographic image, the same full range as the image displayed in step S16 is displayed for the normal tomographic image, so the user does not select a range. On the other hand, for the tomographic image representing entropy, the user selects a range of values, for example, 0.3 to 0.7, by removing the vicinity of 0 and 1 in the dimensionless quantity 0 to 1 (full range) displayed in step S16. When the range selection operation is finished, the user indicates that the range selection operation is complete. The calculation unit 202 remains on standby until the range selection operation is indicated as complete (no in step S22).

[0079] When the indication of completion of the value range image selection operation is given (Yes in step S22), the calculation unit 202 overlays the multiple images selected in step S18 and displays them on the display 120 (S24). At this time, the calculation unit 202 determines the order in which the multiple tomographic images are overlaid (i.e., the vertical relationship of the display) according to the order selected in step S20. In addition, the calculation unit 202 only overlays the tomographic image obtained by cropping the value range selected in step S22. For example, in Figure 10 In the example shown, the calculation unit 202 superimposes a tomographic image representing entropy onto the normal tomographic image according to the order selected in step S20. Furthermore, according to the value range selected in step S22, the normal tomographic image displays the entire range, while the tomographic image representing entropy is superimposed only on the normal tomographic image for values ​​in the range of 0.3 to 0.7.

[0080] For example, in Figure 10 In the example shown, a tomographic image representing entropy is overlaid on a regular tomographic image, and this overlaid image is displayed on a monitor 120. By displaying the calculated entropy, the distribution of substances, primarily melanin, within the examined eye 500 can be visualized. Without examining only the image representing entropy, it is impossible to obtain a detailed understanding of the structure within the examined eye 500, and it is sometimes difficult to determine the location of melanin within the examined eye 500. On the other hand, with a regular tomographic image, the location of various tissues within the examined eye 500 can be visually confirmed. Figure 10In the example shown, a tomographic image representing entropy is superimposed on a standard tomographic image for display. Therefore, the user can simultaneously understand the structure within the examined eye 500 using the standard tomographic image and confirm the distribution of melanin within the examined eye 500, thereby easily establishing the correspondence between the structure within the examined eye 500 and the distribution of melanin. Accordingly, for example, diseases involving changes in retinal pigment epithelial cells (RPE cells) can be easily detected, thus being beneficial for diagnosing age-related macular degeneration and retinitis pigmentosa.

[0081] In addition, Figure 10 In the example shown, for a tomographic image representing entropy, the value range of 0 to 1 is reduced to 0.3 to 0.7 and superimposed on the normal tomographic image. This allows only the range the user wants to confirm to be displayed.

[0082] Furthermore, the examples above illustrate the case of superimposing a tomographic image representing entropy onto a regular tomographic image, but the combination of superimposed tomographic images is not limited. For example, such as... Figure 11 As shown, a tomographic image representing birefringence can also be superimposed on a regular tomographic image. In the tomographic image representing birefringence, the distribution of fiber density within the examined eye 500 can be determined. By superimposing a birefringence image on a regular tomographic image, the correspondence between the structure within the examined eye 500 and the distribution of fiber density within the examined eye 500 is easily determined. Accordingly, for example, diseases in which the structure of the examined eye 500 changes due to elongation of the axial length or high intraocular pressure can be easily detected, thus being beneficial for diagnosing high myopia and glaucoma.

[0083] Alternatively, a tomographic image showing the fiber direction can be superimposed on a regular tomographic image. By superimposing a tomographic image showing the fiber direction on a regular tomographic image, the correspondence between the structures within the examined eye 500 and the fiber direction within the examined eye 500 can be easily determined. Accordingly, for example, diseases in which the structure of the examined eye 500 changes due to elongation of the axial length or high intraocular pressure can be easily detected, which is beneficial for the diagnosis of high myopia and glaucoma.

[0084] Alternatively, tomographic images representing blood flow can be superimposed on standard tomographic images. By superimposing these images, the correspondence between the structures within 500 nm of the examined eye and the distribution of blood flow within that area becomes readily apparent. This facilitates the detection of vascular abnormalities and is beneficial for diagnosing diseases involving blood loss, such as glaucoma and myopia, as well as diseases with abnormal blood vessels, such as choroidal neovascularization.

[0085] Furthermore, in the example above, two tomographic images were superimposed, but the number of superimposed tomographic images is not limited; more than three tomographic images can also be superimposed. By superimposing more than three images, it is easier to determine the correspondence between multiple characteristics of the examined eye 500.

[0086] For example, in Figure 12 In the example shown, three images are superimposed: a normal tomographic image, a tomographic image representing entropy, and a tomographic image representing birefringence. In this case, in step S18, the three images are selected: the normal tomographic image, the tomographic image representing entropy, and the tomographic image representing birefringence. Next, in step S20, the calculation unit 202 determines whether the order in which the three tomographic images are superimposed has been selected. For example, the user instructs that the tomographic image representing birefringence be superimposed on the normal tomographic image, and that the tomographic image representing entropy be superimposed on top of it. Next, in step S22, the calculation unit 202 determines whether the displayed value range has been selected for the three selected images. For example, the user does not select a value range for the normal tomographic image. Alternatively, the user selects a dimensionless value range of 0.3 to 0.7 for the tomographic image representing entropy. Additionally, the user selects a phase retardation value range of 0.1 to 0.3 rad from 0 to 0.5 rad for the image representing birefringence. Then, in step S24, the calculation unit 202 displays the three tomographic images superimposed on the display 120. At this time, the calculation unit 202 superimposes the normal tomographic image, the tomographic image representing birefringence, and the tomographic image representing entropy in the order selected in step S20. In addition, according to the value range selected in step S22, the calculation unit 202 displays the entire range for the normal tomographic image, superimposes only the value range of 0.1 to 0.3 rad on the normal tomographic image for the tomographic image representing birefringence, and further superimposes only the value range of 0.3 to 0.7 on the tomographic image representing entropy.

[0087] By superimposing a tomographic image representing entropy and a tomographic image representing birefringence onto a normal tomographic image, it is easy to determine the correspondence between the structure within 500 mm of the examined eye and the distribution of melanin or fiber density, and it is also easy to determine the correspondence between the distribution of melanin and the distribution of fiber density.

[0088] Furthermore, in this embodiment, multiple tomographic images are superimposed and displayed in step S24 according to the order selected in step S20, but this structure is not limited to this. For example, it can be configured such that the superimposed order can be changed after multiple tomographic images are superimposed and displayed in step S24. By changing the order of the superimposed multiple tomographic images after the user has confirmed the displayed images, the tomographic image displayed on the lower side is displayed on the upper side, thereby making it easier for the user to understand the correspondence between the multiple tomographic images. For example, Figure 13This represents an image in which a tomographic image representing entropy is superimposed on a normal tomographic image, and a tomographic image representing birefringence is superimposed on top of that. Figure 12 and Figure 13 Each image is superimposed with three images: a typical tomographic image, a tomographic image representing entropy, and a tomographic image representing birefringence. Figure 12 In the image, the tomographic image representing entropy is displayed at the top. Figure 13 In the center, the birefringence tomographic image is displayed at the top. This allows users to more clearly understand the correspondence between multiple tomographic images, even when the same type of tomographic images are superimposed, by comparing multiple images with different superposition orders.

[0089] In addition, in this embodiment, in step S22, the value range for displaying each tomographic image can be selected. However, in addition to the value range, the color for displaying each tomographic image can also be selected. Specifically, in step S22, after selecting the value range for displaying each tomographic image, the calculation unit 202 can also determine whether a color has been selected for displaying each tomographic image. As described above, each tomographic image is displayed in a gradient manner within the value range of its index. Therefore, when no color is selected, it is displayed in a gradient manner within the selected value range. By displaying in a gradient manner, the user can easily grasp the state of the numerical distribution of the tomographic image within the selected value range. On the other hand, when a color is selected, the tomographic image is displayed in a single color regardless of the numerical value of the tomographic image. When displayed in a single color, the amount of information about the tomographic image is reduced. On the other hand, when displayed in superimposed form, it is easy to determine which tomographic image is displayed based on the color. Therefore, especially in cases where a large number of tomographic images are superimposed, such as when two or more tomographic images are superimposed on a normal tomographic image, it is easy to understand each tomographic image by color when each tomographic image is displayed in a single color.

[0090] Furthermore, in this embodiment, the user selects the displayed value range in step S22, but this structure is not limited to it. The displayed value range can also be determined by the calculation unit 202. For example, the calculation unit 202 may acquire multiple data points obtained from images of a normal eye (i.e., a normal eye) without any abnormalities, and determine a threshold based on the data from the multiple normal eyes. Specifically, the calculation unit 202 can determine the threshold (e.g., average ±1σ to ±3σ) based on the standard deviation of the data from the multiple normal eyes. Additionally, the threshold can also be a value that is clinically relevant. For example, values ​​considered to indicate poor vision or values ​​proven useful for detecting RPE cell rupture can be used as thresholds. Alternatively, the calculation unit 202 may display the value range determined by it, allowing the user to change the value range based on the displayed range.

[0091] Furthermore, in this embodiment, only the value range selected in step S22 is superimposed and displayed for each tomographic image in step S24. However, for example, in addition to the value range, the transmittance of each tomographic image can also be selected. For example, when a tomographic image representing entropy is superimposed on a normal tomographic image, the calculation unit 202 can also determine whether the transmittance has been selected for the upper tomographic image representing entropy, which is in an upper-lower relationship. Accordingly, it is easy to visually confirm the lower normal tomographic image, which is in an upper-lower relationship, by looking at the tomographic image representing entropy superimposed on it. Therefore, even if two or more tomographic images are superimposed, the user can visually confirm both the lower and upper tomographic images. Alternatively, the transmittance can be changed after multiple tomographic images are superimposed and displayed.

[0092] In this embodiment, the image selected in step S18 is overlaid. However, it could also be configured such that, instead of the user selecting the image to be overlaid, an image of the same type as the previously selected image is chosen. Specifically, the types of images selected in step S18 could be stored in a memory (not shown), allowing the selection of images of the types stored in the memory (not shown) in step S18 to be performed again when the process of overlaying and displaying tomographic images is executed. Alternatively, the order of the overlay images selected in step S20 and the value range selected in step S22 could also be stored in a memory (not shown), allowing the selection of the stored order and value range to be performed again when the process of overlaying and displaying tomographic images is executed. Furthermore, if the color and transmittance of each tomographic image are selected, the color and transmittance previously selected by the user could be read from the memory (not shown) and selected.

[0093] (Example 2)

[0094] In Embodiment 1 described above, multiple tomographic images are superimposed, but this structure is not limited to. For example, the superimposed images can also be En-face images. En-face images are obtained by compressing three-dimensional data into a two-dimensional frontal image by calculating the maximum, minimum, or average values ​​in the depth direction for each A-scan. (See also...) Figures 14-17 This describes the process of overlaying the En-face image of the examined eye 500 onto the display 120.

[0095] When generating the En-face image, the user uses an input device such as a mouse (illustration omitted) to input instructions for generating the En-face image. Based on this, the process of generating the En-face image begins. After this, as... Figure 14As shown, firstly, the arithmetic unit 202 acquires the tomographic image of the examined eye 500 (S32). Furthermore, the processing in step S32 is the same as that in step S12 of Embodiment 1 described above, therefore detailed explanation is omitted. Alternatively, it is also possible to select an instruction for generating an En-face image after the processing in step S32.

[0096] Next, the computation unit 202 determines whether the generation conditions for the En-face image have been selected (S34). Specifically, the user selects the range of the depth direction for generating the En-face image. In addition, the user selects whether to calculate the maximum value, minimum value, or average value to generate the En-face image.

[0097] Here, the method for selecting the depth direction range for generating the En-face image will be explained. As the depth direction range for generating the En-face image, it is possible to select the entire depth direction of the tomographic image of the examined eye 500 obtained in step S32, or it is possible to select only the range of a specific depth direction within the tomographic image of the examined eye 500 obtained in step S32. When generating the En-face image only for the specific depth direction range within the tomographic image of the examined eye 500, it can be generated, for example, in the following order. First, the calculation unit 202 determines (segments) the boundaries of the layers within the examined eye 500 for each tomographic image. Furthermore, segmentation can be performed using known methods, therefore, detailed explanation is omitted. Next, the user selects the depth direction range. For example, the user selects the boundaries of two desired segmented layers. In this case, the calculation unit 202 generates the En-face image only between the boundaries of the two selected layers. Alternatively, the user can select the boundary of one layer and the thickness of the generated En-face image. In this case, the computation unit 202 generates an En-face image with a thickness selected only for the boundary of the selected layer. Alternatively, the depth direction range can be changed after being selected by the user. For example, the depth direction range can be shifted along the depth direction while maintaining the thickness selected by the user.

[0098] In step S34, the user uses an input mechanism such as a mouse (illustration omitted) to select whether the depth direction range for generating the En-face image is the entire depth direction or a specific depth direction range. Furthermore, if the depth direction range for generating the En-face image is a specific depth direction range, the user selects either two boundaries of the segmented layer or one boundary and thickness of the segmented layer. The user also selects whether to use the maximum, minimum, or average value when generating the En-face image. The computation unit 202 remains on standby until the selection operation indicating the generation conditions of the En-face image is completed (no in step S34).

[0099] When the selection of the generation conditions for the En-face image is completed (Yes in step S34), the calculation unit 202 generates various En-face images representing different characteristics using the tomographic image obtained in step S32, based on the generation conditions selected in step S36 (S36). That is, En-face images are generated for images representing various characteristics (e.g., an image representing the tissue within the examined eye 500 using scattering intensity, an image representing the entropy within the examined eye 500, an image representing the birefringence within the examined eye 500, an image representing the fiber direction within the examined eye 500, and an image representing the blood flow within the examined eye 500). Then, the calculation unit 202 displays each En-face image generated in step S38 on the display 120 (S38). Next, the calculation unit 202 determines whether multiple images have been selected from the multiple En-face images displayed on the display 120 (S40), and then determines whether the order in which the selected En-face images are superimposed has been selected (S42), and whether the value range displayed for each En-face image has been selected (44). Then, the arithmetic unit 202 displays multiple En-face images superimposed on the display 120 based on the information selected in steps S40 to S44 (S46). Furthermore, the processing in steps S40 to S44 is the same as that in steps S18 to S22 of Embodiment 1 described above, therefore detailed explanation is omitted. Additionally, in this embodiment, the superposition order, the displayed value range, and the transmittance can be changed after the En-face images are superimposed and displayed. Furthermore, the generation conditions for the En-face images in step S34 can also be changed after the En-face images are superimposed and displayed. By superimposing and displaying multiple En-face images, a larger range of the examined eye 500 can be easily confirmed.

[0100] For example, Figure 15 and Figure 16 This example demonstrates how to generate an En-face image by calculating the maximum value of the overall depth direction range of the tomographic image of the examined eye 500. Figure 15(a) in the image is the En-face image generated from a typical tomographic image (hereinafter also referred to as the typical En-face image). Figure 15 (b) in the image is the En-face image generated from the tomographic image representing entropy (hereinafter also referred to as the En-face image representing entropy). Figure 15 (c) in the figure is the En-face image generated from the tomographic image representing birefringence (hereinafter also referred to as the En-face image representing birefringence).

[0101] Figure 16 (a) in Figure 16 (d) in the text indicates overlay display. Figure 15 (a) in Figure 15 Example of an En-face image in (c) of the diagram. Figure 16 In the diagram, (a) represents an image with an entropy-representing En-face image superimposed on the normal En-face image. The normal En-face image is selected to display the full range, while the entropy-representing En-face image uses a value range of 0.4 to 0.5. By superimposing the entropy-representing En-face image on the normal En-face image, a wider range of melanin distribution in the examined eye 500 can be obtained, making it easier to grasp the melanin distribution across the entire surface of the fundus of the examined eye 500.

[0102] Figure 16 (b) in the diagram represents an image with a birefringence En-face image superimposed on the normal En-face image. For the normal En-face image, select to display the full range; for the birefringence En-face image, select a value range of 0.3 to 0.5 rad. By superimposing the birefringence En-face image on the normal En-face image, it is easy to determine the distribution of fiber density across the entire surface of the fundus of the examined eye 500.

[0103] Figure 16 In this context, (c) represents an image where an En-face image representing birefringence is superimposed on a normal En-face image, and an En-face image representing entropy is superimposed on top of that. Additionally, Figure 16 In this context, (d) represents an image where an En-face image representing entropy is superimposed on a regular En-face image, and an En-face image representing birefringence is superimposed on top of that. For example... Figure 16 (c) and Figure 16As shown in (d), by overlaying an En-face image representing entropy and an En-face image representing birefringence onto a normal En-face image, it is easy to grasp the correspondence between the distribution of melanin and the distribution of fiber density on the entire surface of the fundus of the examined eye 500.

[0104] In addition, for example, Figure 17 This example illustrates how to generate an En-face image by calculating the maximum value of a range in a specific depth direction for only 500 tomographic images of the examined eye. Figure 17 In the image (a), a typical En-face image near the superficial layer of the choroid was selected. Figure 17 (b) in the text indicates that... Figure 17 En-face images representing entropy for the same area (i.e., near the superficial layer of the choroid) in (a) of the image. Additionally, Figure 17 (c) in Figure 17 (a) is simply overlaid on the usual En-face image. Figure 17 (b) represents the entropy range of 0.2–0.5 in the En-face image. Furthermore, Figure 17 (d) in the image indicates that a typical En-face image near the deep choroid was selected. Figure 17 (e) in the text indicates that it is related to... Figure 17 En-face images representing entropy for the same region (i.e., near the deep choroid) in (d) of the image. Additionally, Figure 17 (f) in Figure 17 (d) is simply overlaid on the usual En-face image. Figure 17 The (e) in the image represents the entropy range of 0.2 to 0.5 in the En-face image. For example... Figure 17 (c) and Figure 17 As shown in (f), by selecting the depth direction range of the examined eye 500 to generate an En-face image, it is easy to determine the state of the examined eye 500 within a specific range (tissue or layer) desired by the user. Therefore, it can be used more effectively for the diagnosis of diseases of the examined eye 500.

[0105] The above description details specific examples of the technology disclosed in this specification, but these are merely examples and do not limit the technical solution of the present invention. The technology described in the technical solution of the present invention includes variations and modifications to the specific examples described above. Furthermore, the technical elements described in this specification or drawings can exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the technical solution of the present invention at the time of application. In addition, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives is itself technically useful.

Claims

1. A polarization-sensitive optical coherence tomography device, characterized in that, It has a camera unit and a display unit, among which, The imaging unit captures tomographic images of the examined eye; The display unit displays the tomographic image captured by the imaging unit. The tomographic images include at least two of the following: an image representing the tissue within the examined eye using scattering intensity; an image representing the distribution of melanin within the examined eye; an image representing the fiber density within the examined eye; an image representing the direction of fiber travel within the examined eye; and an image representing blood flow within the examined eye. The display unit overlays at least two images from the same location on the same cross-section. It also includes a range indicator mechanism that indicates the numerical range of the indicators displayed by each of the at least two images. The display unit displays the index of the numerical range indicated by the range indicator mechanism within the full range of the index of each of the at least two images, and overlays the at least two images in such a way that the index of the range outside the numerical range is not displayed.

2. The optical coherence tomography apparatus according to claim 1, characterized in that, It also includes a stacking order indicator mechanism that indicates the order in which the at least two images are stacked. The display unit displays the at least two images in the order indicated by the overlay order indicator mechanism.

3. The optical coherence tomography apparatus according to claim 1, characterized in that, The image representing the distribution of melanin within the examined eye is generated based on entropy. The image representing the fiber density within the examined eye is generated based on birefringence.

4. The optical coherence tomography apparatus according to claim 1, characterized in that, The imaging unit includes a light source, a measuring light generating unit, a reference light generating unit, and an interference light detection unit, wherein... The measuring light generating unit uses the light from the light source to generate measuring light, and illuminates the generated measuring light onto the eye under examination to generate reflected light from the eye under examination; The reference light generating unit uses the light from the light source to generate reference light; The interference light detection unit detects interference light, which is obtained by combining the reflected light from the tested eye generated by the measurement light generation unit and the reference light generated by the reference light generation unit. The measurement light generation unit generates a first polarized measurement light and a second polarized measurement light using the light from the light source, and illuminates the tested eye with the first polarized measurement light and the second polarized measurement light, wherein the first polarized measurement light vibrates in a first direction; and the second polarized measurement light vibrates in a second direction different from the first direction. The measurement light generation unit uses the first polarized light to measure the reflected light from the examined eye, and generates a first polarized light reflected light vibrating in the first direction and a second polarized light reflected light vibrating in the second direction. The measurement light generation unit uses the second polarized light to measure the reflected light from the examined eye, and generates a third polarized light reflecting light vibrating in the first direction and a fourth polarized light reflecting light vibrating in the second direction. The interference light detection unit detects the first interference light, the second interference light, the third interference light, and the fourth interference light. The first interference light is the interference light obtained by combining the reflected light of the first polarized light and the reference light; the second interference light is the interference light obtained by combining the reflected light of the second polarized light and the reference light; the third interference light is the interference light obtained by combining the reflected light of the third polarized light and the reference light; and the fourth interference light is the interference light obtained by combining the reflected light of the fourth polarized light and the reference light.

5. The optical coherence tomography apparatus according to claim 4, characterized in that, An image representing the tissue within the examined eye using scattering intensity is generated using at least one of the first interference light, the second interference light, the third interference light, and the fourth interference light. The image representing the distribution of melanin within the examined eye was generated using the first interference light, the second interference light, the third interference light, and the fourth interference light. The image representing the fiber density within the examined eye is generated using the first interference beam, the second interference beam, the third interference beam, and the fourth interference beam. An image representing the direction of fiber travel within the examined eye is generated using the first interference beam, the second interference beam, the third interference beam, and the fourth interference beam. The image representing the blood flow within the examined eye is generated using the first interference light, the second interference light, the third interference light, and the fourth interference light.

6. The optical coherence tomography apparatus according to claim 1, characterized in that, The display unit is configured to display an En-face image relating to the at least two images, the En-face image being generated from images captured by the imaging unit. The display unit overlays the En-face images of the at least two images.

7. A computer-readable storage medium storing a computer program for displaying tomographic images of an examined eye, characterized in that, This computer program enables the computer to function as a tomographic image generation unit, a range acquisition unit, and a display processing unit, wherein... The tomographic image generation unit generates at least two of the following tomographic images: a tomographic image representing the tissue within the examined eye using scattering intensity; a tomographic image representing the distribution of melanin within the examined eye; a tomographic image representing the fiber density within the examined eye; a tomographic image representing the direction of fiber travel within the examined eye; and a tomographic image representing blood flow within the examined eye. The range acquisition unit acquires the numerical range of the indicators displayed by each of the at least two tomographic images; The display processing unit displays the index of the numerical range obtained by the range acquisition unit within the full range of the index of each of the at least two tomographic images at the same position of the same cross section, and superimposes the at least two tomographic images in a manner that does not display the index of the range outside the numerical range.

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