WO2022250065A1 - 光断層画像撮影装置 - Google Patents
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- 238000003384 imaging method Methods 0.000 title claims abstract description 50
- 238000011156 evaluation Methods 0.000 claims abstract description 75
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- 238000007689 inspection Methods 0.000 claims description 19
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- 238000010586 diagram Methods 0.000 description 8
- 238000012014 optical coherence tomography Methods 0.000 description 5
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- 230000004424 eye movement Effects 0.000 description 4
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- 230000001678 irradiating effect Effects 0.000 description 2
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- 238000012790 confirmation Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000193 eyeblink Effects 0.000 description 1
- 210000004220 fundus oculi Anatomy 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/102—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for optical coherence tomography [OCT]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/0008—Apparatus for testing the eyes; Instruments for examining the eyes provided with illuminating means
Definitions
- the technology disclosed in this specification relates to an optical tomography apparatus.
- An optical tomographic imaging device that acquires a tomographic image of the subject's eye has been developed.
- An optical tomography apparatus includes a measurement optical system that irradiates an eye with light from a light source and guides the reflected light, and a reference optical system that generates reference light from the light from the light source.
- a tomographic image of the subject's eye is generated from interference light obtained by combining the reflected light (measurement light) guided by the measurement optical system and the reference light generated by the reference optical system. If the tomographic image of the eye to be inspected is not properly captured, the tomographic image of the eye to be inspected needs to be re-captured.
- an evaluation index indicating whether or not a tomographic image is properly captured may be displayed on the display unit.
- QI Quality Index
- the optical tomography apparatus disclosed in Japanese Patent Application Laid-Open No. 2013-9798 presents to the examiner whether or not the tomographic image is appropriately captured by displaying the evaluation index. If the tomographic image is not captured properly, it must be retaken. become.
- the examiner since the evaluation index is displayed for each tomographic image, the examiner needs to confirm the evaluation index for each of a plurality of tomographic images generated in one imaging. There is Therefore, the time required for the examiner to check the evaluation indices for all of the multiple tomographic images is long, and the time for restraining the examinee for imaging is long.
- This specification discloses a technique for reducing the burden on a subject when capturing a tomographic image.
- the optical tomography apparatus disclosed in the present specification executes an imaging process of scanning light over an imaging range set for an eye to be inspected, thereby obtaining n tomograms (n is an integer of 2 or more) from the imaging range. It includes an imaging unit that captures an image, a generation unit that generates an evaluation index for evaluating image quality of a tomographic image, and a display unit that displays the evaluation index generated by the generation unit.
- the generator generates an evaluation index for each of the n tomographic images.
- the display unit simultaneously displays the evaluation indices of the n tomographic images in one screen.
- the evaluation indexes of a plurality of (n) tomographic images obtained by executing the imaging process are simultaneously displayed on one screen, so that the examiner can perform imaging by the imaging process. It is possible to confirm all evaluation results of a plurality of tomographic images obtained in a short time. Therefore, it is not necessary to check the evaluation results for each tomographic image, and the time required to check the evaluation results for all of the plurality of tomographic images can be shortened.
- FIG. 1 is a diagram showing a schematic configuration of an optical system of an optical tomography apparatus according to an embodiment
- FIG. 1 is a block diagram showing a control system of an optical tomography apparatus according to an embodiment
- FIG. FIG. 2 is a block diagram showing the configuration of a sampling trigger/clock generator
- FIG. 4 is a flowchart showing an example of processing for displaying a preview screen after capturing a tomographic image of an eye to be inspected
- FIG. 4 is a diagram for explaining a formula for calculating QI (Quality Index)
- 4 is a slow chart showing an example of processing for calculating maximum luminance
- FIG. 5 is a diagram for explaining processing for thinning out A-scan information used when calculating maximum luminance
- FIG. 1 is a diagram showing a schematic configuration of an optical system of an optical tomography apparatus according to an embodiment
- FIG. 1 is a block diagram showing a control system of an optical tomography apparatus according to an embodiment
- FIG. 2 is a block
- FIG. 10A is a diagram for explaining processing for limiting the range in the depth direction of A-scan information used when calculating maximum luminance, and FIG. , (b) show the case where the subject's eye is photographed in a displaced state.
- FIG. 10 is a diagram showing QI evaluation results and fixation state evaluation results, in which (a) shows the case where the subject's eye is in an appropriate position, (b) shows the case where the subject's eye blinks, and (c). indicates the case where the subject's eye is at a displaced position.
- FIG. 4 is a diagram showing an example of a preview screen displayed on a monitor; 4A and 4B are views showing an example of a preview screen and a simple report displayed on a monitor; FIG.
- the evaluation index is a luminance evaluation index for evaluating image quality based on the luminance of a tomographic image, and a fixation evaluation index for evaluating the fixation state of the subject's eye. and at least one of.
- the luminance evaluation index it is possible to evaluate, for example, whether the alignment and focus are appropriate, and whether or not the subject's eye is blinking.
- the fixation evaluation index is used, for example, it is possible to evaluate whether the fixation is not properly performed due to involuntary eye movement or the like, whether or not the eye to be inspected is blinking, and the like. Therefore, by including at least one of the luminance evaluation index and the fixation evaluation index as the evaluation index, the image quality of the tomographic image can be appropriately evaluated.
- the generator selects m tomographic images (m is a natural number smaller than n) from n tomographic images, and selects a desired image from the selected tomographic images. may further generate an inspection report showing the inspection results of The display unit may further display the generated inspection report. According to such a configuration, by displaying the inspection report, it is possible to confirm that the imaging for the desired inspection was performed appropriately. Also, when generating an inspection report, only m tomographic images selected from n tomographic images are used instead of all n tomographic images. Therefore, a simple inspection report generated from m tomographic images takes less time to generate than an inspection report generated from n tomographic images. By generating the inspection report as a simple inspection report in this way, it is possible to confirm that the imaging has been properly performed while shortening the time required to generate the inspection report.
- the optical tomographic imaging apparatus can capture the polarization characteristics of a subject by a wavelength sweeping Fourier domain method (swept-source optical coherence tomography: SS-OCT) using a wavelength sweeping light source. It is a possible polarization-sensitive OCT (PS-OCT) device.
- SS-OCT wavelength sweeping Fourier domain method
- PS-OCT polarization-sensitive OCT
- the optical tomography apparatus of this embodiment includes a light source 11, measurement light generation units (21 to 29, 31, 32) that generate measurement light from the light from the light source 11, and the light source 11.
- a reference light generator (41 to 46, 51) that generates reference light from light, and the reflected light from the subject's eye 500 generated by the measurement light generator and the reference light generated by the reference light generator are combined.
- the light source 11 is a wavelength swept light source, and the wavelength (wave number) of emitted light changes at a predetermined cycle. Since the wavelength of the light irradiated to the subject's eye 500 changes (sweeps), the signal obtained from the interference light between the reflected light from the subject's eye 500 and the reference light is subjected to Fourier analysis to obtain the depth direction of the subject's eye 500. It is possible to obtain the intensity distribution of the light reflected from each part of .
- a polarization controller 12 and a fiber coupler 13 are connected to the light source 11 , and a PMFC (Polarization Maintaining Fiber Coupler) 14 and a sampling trigger/clock generator 100 are connected to the fiber coupler 13 . Therefore, the light output from the light source 11 is input to the PMFC 14 and the sample trigger/clock generator 100 via the polarization controller 12 and the fiber coupler 13, respectively.
- the sampling trigger/clock generator 100 uses light from the light source 11 to generate sampling triggers and sampling clocks for signal processors 83 and 93, which will be described later.
- Measurement light generators (21 to 29, 31, 32) include PMFC 21 connected to PMFC 14, two measurement optical paths S1 and S2 branched from PMFC 21, and a polarization beam combiner / It comprises a splitter 25 , a collimator lens 26 connected to the polarization beam combiner/splitter 25 , galvanomirrors 27 , 28 and a lens 29 .
- An optical path length difference generator 22 and a circulator 23 are arranged in the measurement optical path S1. Only the circulator 24 is arranged in the measuring optical path S2. Therefore, the optical path length difference ⁇ L between the measurement optical path S1 and the measurement optical path S2 is generated by the optical path length difference generator 22 .
- the optical path length difference ⁇ L may be set longer than the measurement range of the subject's eye 500 in the depth direction. As a result, it is possible to prevent overlapping of interference lights with different optical path length differences.
- the optical path length difference generator 22 for example, an optical fiber may be used, or an optical system such as a mirror or a prism may be used. In the present embodiment, a 1 m PM fiber is used for the optical path length difference generator 22 .
- the measurement light generator further includes PMFCs 31 and 32 .
- PMFC 31 is connected to circulator 23 .
- PMFC 32 is connected to circulator 24 .
- One light branched by the PMFC 14 (that is, the measurement light) is input to the measurement light generators (21 to 29, 31, 32).
- the PMFC 21 splits the measurement light input from the PMFC 14 into first measurement light and second measurement light.
- the first measurement light split by the PMFC 21 is guided to the measurement optical path S1, and the second measurement light is guided to the measurement optical path S2.
- the first measurement light guided to the measurement optical path S1 is input to the polarization beam combiner/splitter 25 through the optical path length difference generator 22 and the circulator 23 .
- the second measurement light guided to the measurement optical path S2 passes through the circulator 24 and enters the polarization beam combiner/splitter 25 .
- PM fiber 304 is connected to polarizing beam combiner/splitter 25 circumferentially rotated 90 degrees with respect to PM fiber 302 .
- the second measurement light input to the polarization beam combiner/splitter 25 has a polarization component orthogonal to that of the first measurement light. Since the optical path length difference generator 22 is provided in the measurement light path S1, the first measurement light is delayed from the second measurement light by the distance of the optical path length difference generator 22 (that is, the optical path difference ⁇ L is occurring).
- the polarization beam combiner/splitter 25 superimposes the input first measurement light and second measurement light.
- the light output from the polarization beam combiner/splitter 25 (light in which the first measurement light and the second measurement light are superimposed) is applied to the subject's eye 500 via the collimator lens 26, the galvanometer mirrors 27 and 28, and the lens 29. be.
- the light applied to the eye 500 to be examined is scanned in the xy direction by the galvanomirrors 27 and 28 .
- the light irradiated to the subject's eye 500 is reflected by the subject's eye 500 .
- the light reflected by the eye 500 to be examined scatters on the surface and inside the eye 500 to be examined.
- Reflected light from the subject's eye 500 passes through the lens 29 , the galvanomirrors 28 and 27 and the collimator lens 26 in the opposite direction of the incident path, and enters the polarization beam combiner/splitter 25 .
- Polarization beam combiner/splitter 25 splits the incoming reflected light into two mutually orthogonal polarization components.
- they are referred to as horizontally polarized reflected light (horizontal polarized component) and vertically polarized reflected light (vertically polarized component).
- the horizontally polarized reflected light is guided to the measurement optical path S1
- the vertically polarized reflected light is guided to the measurement optical path S2.
- the horizontally polarized reflected light has its optical path changed by the circulator 23 and is input to the PMFC 31 .
- the PMFC 31 splits the input horizontally polarized reflected light and inputs the split light to the PMFCs 61 and 71, respectively. Therefore, the horizontally polarized reflected light input to the PMFCs 61 and 71 contains a reflected light component of the first measurement light and a reflected light component of the second measurement light.
- the vertically polarized reflected light has its optical path changed by the circulator 24 and is input to the PMFC 32 .
- the PMFC 32 splits the input vertically polarized reflected light and inputs the split light to the PMFCs 62 and 72 . Therefore, the vertically polarized reflected light input to the PMFCs 62 and 72 contains a reflected light component of the first measurement light and a reflected light component of the second measurement light.
- the reference light generators (41 to 46, 51) include a circulator 41 connected to the PMFC 14, reference delay lines (42, 43) connected to the circulator 41, a PMFC 44 connected to the circulator 41, and branches from the PMFC 44.
- a PMFC 46 connected to the reference optical path R1 and a PMFC 51 connected to the reference optical path R2 are provided.
- An optical path length difference generator 45 is arranged in the reference optical path R1.
- An optical path length difference generator is not provided in the reference optical path R2. Therefore, the optical path length difference ⁇ L′ between the reference optical path R1 and the reference optical path R2 is generated by the optical path length difference generator 45.
- FIG. for example, an optical fiber is used for the optical path length difference generator 45 .
- the optical path length ⁇ L′ of the optical path length difference generator 45 may be the same as the optical path length ⁇ L of the optical path length difference generator 22 .
- the other light (that is, the reference light) split by the PMFC 14 is input to the reference light generators (41 to 46, 51).
- the reference light input from PMFC 14 passes through circulator 41 and is input to reference delay lines (42, 43).
- a reference delay line (42, 43) is composed of a collimator lens 42 and a reference mirror 43.
- FIG. Reference light input to the reference delay lines ( 42 , 43 ) is applied to the reference mirror 43 via the collimator lens 42 .
- the reference light reflected by the reference mirror 43 is input to the circulator 41 via the collimator lens 42 .
- the reference mirror 43 is movable in a direction to approach or separate from the collimator lens 42 .
- the position of the reference mirror 43 is adjusted so that the signal from the eye 500 to be examined falls within the depth-direction measurement range of OCT.
- the reference light reflected by the reference mirror 43 has its optical path changed by the circulator 41 and is input to the PMFC 44 .
- the PMFC 44 splits the input reference light into a first reference light and a second reference light.
- the first reference light is guided to the reference optical path R1, and the second reference light is guided to the reference optical path R2.
- the first reference light is input to PMFC 46 through optical path length difference generator 45 .
- the reference light input to the PMFC 46 is branched into a first branched reference light and a second branched reference light.
- the first branched reference light is input to PMFC 61 through collimator lens 47 and lens 48 .
- the second branched reference light is input to PMFC 62 through collimator lens 49 and lens 50 .
- the second reference light is input to the PMFC 51 and split into a third branched reference light and a fourth branched reference light.
- the third branched reference light passes through the collimator lens 52 and the lens 53 and is input to the PMFC 71 .
- the fourth branched reference light passes through the collimator lens 54 and the lens 55 and is input to the PMFC 72 .
- the interference light generators 60 and 70 include a first interference light generator 60 and a second interference light generator 70 .
- the first interference light generator 60 has PMFCs 61 and 62 .
- the PMFC 61 receives the horizontally polarized reflected light from the measurement light generator and the first branched reference light (the light having the optical path difference ⁇ L′) from the reference light generator.
- the horizontally polarized reflected light includes a reflected light component of the first measurement light (light having the optical path difference ⁇ L) and a reflected light component of the second measurement light (light having no optical path difference ⁇ L). ing.
- the reflected light component (the light having the optical path difference ⁇ L) from the first measuring light in the horizontally polarized reflected light and the first branched reference light are combined to form the first interference light (horizontally polarized component). is generated.
- the PMFC 62 receives the vertically polarized reflected light from the measurement light generator and the second branched reference light (light having the optical path difference ⁇ L') from the reference light generator.
- the vertically polarized reflected light includes a reflected light component of the first measurement light (light having the optical path difference ⁇ L) and a reflected light component of the second measurement light (light having no optical path difference ⁇ L). ing. Therefore, in the PMFC 62, the reflected light component (light having the optical path difference ⁇ L) of the first measurement light among the vertically polarized reflected light and the second branched reference light are combined to form the second interference light (vertically polarized component). is generated.
- the second interference light generator 70 has PMFCs 71 and 72 .
- the PMFC 71 receives the horizontally polarized reflected light from the measurement light generator and the third branched reference light (light without the optical path difference ⁇ L′) from the reference light generator. Therefore, in the PMFC 71, the reflected light component (light having no optical path difference ⁇ L) of the second measurement light among the horizontally polarized reflected light and the third branched reference light are combined to form the third interference light (horizontal polarized component ) is generated.
- the PMFC 72 receives the vertically polarized reflected light from the measurement light generator and the fourth branched reference light (light without the optical path difference ⁇ L') from the reference light generator. Therefore, in the PMFC 72, the reflected light component of the second measuring light (the light having no optical path difference ⁇ L) among the vertically polarized reflected light and the fourth branched reference light are combined to form the fourth interference light (vertically polarized component ) is generated.
- the first interference light and the second interference light correspond to the measurement light passing through the measurement optical path S1
- the third interference light and the fourth interference light correspond to the measurement light passing through the measurement optical path S2.
- Interference light detection units 80 and 90 include a first interference light detection unit 80 that detects the interference light (first interference light and second interference light) generated by the first interference light generation unit 60, and a second interference light generation unit.
- a second interference light detection section 90 is provided to detect the interference light (the third interference light and the fourth interference light) generated by the section 70 .
- the first interference light detection section 80 includes balanced photodetectors 81 and 82 (hereinafter also simply referred to as “detectors 81 and 82”) and a signal processor 83 connected to the detectors 81 and 82. .
- a PMFC 61 is connected to the detector 81 , and a signal processor 83 is connected to an output terminal of the detector 81 .
- the PMFC 61 splits the first interference light into two interference lights with a phase difference of 180 degrees, and inputs them to the detector 81 .
- the detector 81 performs differential amplification and noise reduction processing on the two interference lights input from the PMFC 61 whose phases differ by 180 degrees, converts them into electrical signals (first interference signals), and converts the first interference signals into electrical signals (first interference signals).
- the first interference signal is the interference signal HH between the horizontally polarized light reflected from the eye 500 by the horizontally polarized measurement light and the reference light.
- PMFC 62 is connected to detector 82
- signal processor 83 is connected to the output terminal of detector 82 .
- the PMFC 62 splits the second interference light into two interference lights with a phase difference of 180 degrees, and inputs them to the detector 82 .
- the detector 82 performs differential amplification and noise reduction processing on the two interfering lights whose phases differ by 180 degrees, converts them into electrical signals (second interference signals), and converts the second interference signals into signal processors 83 output to That is, the second interference signal is the interference signal HV between the vertically polarized light reflected from the eye 500 by the horizontally polarized measurement light and the reference light.
- the signal processor 83 includes a first signal processing section 84 to which the first interference signal is input, and a second signal processing section 85 to which the second interference signal is input.
- the first signal processor 84 samples the first interference signal based on the sampling trigger and sampling clock input from the sampling trigger/clock generator 100 to the signal processor 83 .
- 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 interference signal and the second interference signal sampled by the first signal processing section 84 and the second signal processing section 85 are input to the calculation section 202, which will be described later.
- a known data acquisition device can be used for the signal processor 83 .
- the second interference light detection unit 90 includes balanced photodetectors 91 and 92 (hereinafter also simply referred to as “detectors 91 and 92”) and detectors 91 and 92. It has a connected signal processor 93 .
- a PMFC 71 is connected to the detector 91 , and a signal processor 93 is connected to the output terminal of the detector 91 .
- the PMFC 71 splits the third interference light into two interference lights with a phase difference of 180 degrees, and inputs them to the detector 91 .
- the detector 91 performs differential amplification and noise reduction processing on the two interfering lights whose phases differ by 180 degrees, converts them into electrical signals (third interference signal), and converts the third interference signal into a signal processor 93 output to That is, the third interference signal is the interference signal VH between the horizontally polarized light reflected from the eye 500 by the vertically polarized measurement light and the reference light.
- the PMFC 72 is connected to the detector 92 and the signal processor 93 is connected to the output terminal of the detector 92 .
- the PMFC 72 splits the fourth interference light into two interference lights with a phase difference of 180 degrees, and inputs them to the detector 92 .
- the detector 92 performs differential amplification and noise reduction processing on the two interfering lights whose phases are different by 180 degrees, converts them into electrical signals (fourth interference signals), and converts the fourth interference signals to the signal processor 93. output to That is, the fourth interference signal is the interference signal VV between the vertically polarized light reflected from the subject's eye 500 from the vertically polarized measurement light and the reference light.
- the signal processor 93 includes a third signal processing section 94 to which the third interference signal is input, and a fourth signal processing section 95 to which the fourth interference signal is input.
- the third signal processor 94 samples the third interference signal based on the sampling trigger and sampling clock input from the sampling trigger/clock generator 100 to the signal processor 93 .
- the fourth signal processor 95 samples the fourth interference signal based on the sampling trigger and sampling clock input from the sampling trigger/clock generator 100 to the signal processor 93 .
- the third interference signal and the fourth interference signal sampled by the third signal processing section 94 and the fourth signal processing section 95 are input to the calculation section 202, which will be described later.
- a known data acquisition device can also be used for the signal processor 93 .
- the signal processors 83 and 93 having two signal processors are used, but the configuration is not limited to this.
- one signal processor having four signal processors may be used, or four signal processors each having one signal processor may be used.
- the optical tomography apparatus is controlled by an arithmetic unit 200.
- FIG. The computing device 200 is composed of a computing section 202 , a first interference light detection section 80 and a second interference light detection section 90 .
- the first interference light detection section 80 , the second interference light detection section 90 and the calculation section 202 are connected to the measurement section 10 .
- the calculation unit 202 outputs a control signal to the measurement unit 10 and drives the galvanomirrors 27 and 28 to scan the incident position of the measurement light on the eye 500 to be examined.
- the first interference light detection unit 80 detects the interference signals (interference signal HH and interference signal HV) input from the measurement unit 10 using the sampling trigger 1 as a trigger, and the sampling clock 1 input from the measurement unit 10. Based on this, the first sampling data is acquired and the first sampling data is output to the calculation unit 202 .
- the calculation unit 202 performs calculation processing such as Fourier transform processing on the first sampling data to generate an HH tomographic image and an HV tomographic image.
- the second interference light detection unit 90 responds to the interference signals (interference signal VH and interference signal VV) input from the measurement unit 10 by using the sampling clock 2 input from the measurement unit 10. Based on this, it acquires the second sampling data and outputs the second sampling data to the calculation unit 202 .
- the calculation unit 202 performs calculation processing such as Fourier transform processing on the second sampling data to generate a VH tomographic image and a VV tomographic image.
- the HH tomographic image, the VH tomographic image, the HV tomographic image, and the VV tomographic image are tomographic images of the same position. Therefore, the calculation unit 202 can generate a tomographic image of four polarization characteristics (HH, HV, VH, VV) representing the Jones matrix of the eye 500 to be examined.
- the sampling trigger/clock generator 100 includes a 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 through the fiber couplers 13 and 102, respectively.
- the sampling trigger generator 140 may generate sampling triggers using, for example, an FBG (Fiber Bragg Grating) 144 . As shown in FIG. 3, the FBG 144 reflects only specific wavelengths of light incident from the light source 11 to generate sampling triggers.
- the generated sampling trigger is input to distributor 150 .
- Distributor 150 distributes the sampling triggers to sampling trigger 1 and sampling trigger 2 .
- the sampling trigger 1 is input to the calculation section 202 via the signal delay circuit 152 .
- the sampling trigger 2 is input to the calculation unit 202 as it is.
- the sampling trigger 1 serves as a trigger signal for interference signals (first interference signal and second interference signal) input from the first interference light detector 80 to the calculator 202 .
- Sampling trigger 2 serves as a trigger signal for the interference signals (the third interference signal and the fourth interference signal) input from the second interference light detector 90 to the calculator 202 .
- the signal delay circuit 152 is designed so that the sampling trigger 1 is delayed with respect to the sampling trigger 2 by the optical path length difference ⁇ L of the optical path length difference generator 22 .
- the frequency at which sampling of the interference signal input from the first interference light detection section 80 is started can be the same as the frequency at which sampling of the interference signal input from the second interference light detection section 90 is started.
- only sampling trigger 1 may be generated. Since the optical path difference ⁇ L is known, when sampling the interference input from the second interference light detector 90, sampling may be started with a time delay of the optical path difference ⁇ L from the sampling trigger 1. .
- the sampling clock generator may, for example, consist of a Mach-Zehnder interferometer. As shown in FIG. 3, the sampling clock generator uses a Mach-Zehnder interferometer to generate equal-frequency sampling clocks.
- a sampling clock generated by the Mach-Zehnder interferometer is input to the distributor 172 .
- the distributor 172 distributes the sampling clock to sampling clock 1 and sampling clock 2 .
- the sampling clock 1 is input to the first interference light detection section 80 through the signal delay circuit 174 .
- the sampling clock 2 is directly input to the second interference light detector 90 .
- the signal delay circuit 174 is designed to delay time by the optical path length difference ⁇ L of the optical path length difference generator 22 .
- the interference light delayed by the optical path length difference generator 22 can be sampled at the same timing. Thereby, it is possible to prevent positional deviation of the plurality of tomographic images to be acquired.
- a Mach-Zehnder interferometer is used to generate the sampling clock.
- a Michelson interferometer or an electrical circuit may be used to generate the sampling clock.
- a light source having a sampling clock generator may be used as the light source to generate the sampling clock.
- the optical tomographic imaging apparatus of this embodiment also includes an SLO (Scanning Laser Ophthalmoscope) optical system (not shown) that acquires a front image of the eye 500 to be examined.
- SLO Sccanning Laser Ophthalmoscope
- the SLO optical system one used in a known ophthalmologic apparatus can be used, and therefore the detailed configuration thereof will not be described.
- the preview screen is a screen used by the examiner to determine whether or not the eye 500 to be examined has been photographed appropriately.
- a plurality of tomographic images are acquired within a set range of the eye 500 to be inspected in order to obtain data related to a desired examination of the eye 500 to be inspected (for example, an examination designated by a doctor). to shoot. If, for example, the subject's eye 500 moves or blinks due to involuntary eye movement or the like while a plurality of tomographic images are being captured, all the tomographic images cannot be captured appropriately.
- the monitor 120 displays an evaluation index and an image (preview screen) indicating whether or not each tomographic image is properly captured.
- the examiner uses the preview screen to determine whether or not each tomographic image has been captured appropriately, and decides whether or not to re-capture the subject's eye 500 .
- the calculation unit 202 first determines whether or not the type of examination has been selected (S12).
- the optical tomographic imaging apparatus of this embodiment is a polarization-sensitive optical tomographic imaging apparatus.
- a tomographic image captured by irradiating a horizontal wave on the By using these two types of tomographic images, the calculation unit 202 can generate not only a tomographic image (a so-called normal tomographic image) showing the tissue in the eye 500 to be inspected by scattering intensity, but also a tomographic image showing the entropy in the eye 500 to be inspected.
- An image, a tomographic image showing birefringence in the eye 500 to be examined, a tomographic image showing the running direction of fibers in the eye 500 to be examined, a tomographic image showing blood flow in the eye 500 to be examined, and the like can be generated.
- the calculation unit 202 uses these multiple types of tomographic images, the calculation unit 202 generates an examination report corresponding to the type of examination.
- the examiner selects a desired examination from a plurality of examinations displayed on the monitor 120 using input means (not shown) such as a mouse. Then, when the examination type selection work is completed, the inspector instructs completion of the selection work. For example, the inspector uses the input means to press an "OK" button displayed on the monitor 120, thereby instructing completion of the selection work.
- the calculation unit 202 waits until the inspector instructs completion of the selection work described above (NO in step S12).
- the calculation unit 202 acquires the front image of the subject's eye 500 (S14). Specifically, the examiner operates an operation member such as a joystick (not shown) to align the optical tomography apparatus with respect to the eye 500 to be examined. That is, the calculation unit 202 drives a position adjustment mechanism (not shown) according to the operation of the operation member by the examiner. As a result, the position of the optical tomographic imaging apparatus with respect to the eye 500 to be examined is adjusted in the xy direction (longitudinal and horizontal directions) and in the z direction (forward and backward movement direction).
- the computing unit 202 captures a front image of the subject's eye 500 using the SLO optical system.
- the photographed front image is stored in a memory (not shown) of the calculation unit 202 .
- the front image acquired here is used as a reference image when evaluating the fixation state in the following process (more specifically, the process of step S22).
- the front image obtained in step S14 is also referred to as a "reference front image”.
- the calculation unit 202 acquires a tomographic image of the subject's eye 500 (S16).
- a tomographic image is obtained by irradiating the subject's eye 500 with light using a raster scan method.
- a tomographic image of the fundus of the subject's eye 500 in a square area centered on the set position is obtained.
- the method of capturing a tomographic image of the fundus of the subject's eye 500 is not limited to the raster scan method.
- a tomographic image of the fundus oculi of the subject's eye 500 may be acquired over the entire desired region, and may be captured by, for example, a radial scanning method.
- the calculation unit 202 acquires a front image of the subject's eye 500 (S18). This front image is acquired substantially simultaneously with the tomographic image acquired in step S16.
- the calculation unit 202 calculates QI (Quality Index) for the tomographic image acquired in step S16 (S20).
- QI is a brightness evaluation index for evaluating image quality based on the brightness of a tomographic image. For example, if the subject's eye 500 is out of focus or the positional relationship between the eye to be inspected 500 and the optical tomographic imaging apparatus is not appropriate, the tomographic image may not be captured properly because the luminance of the tomographic image is low. In addition, if some of the captured tomographic images have low brightness, the brightness may vary among the tomographic images, and a desired inspection report may not be created with high accuracy. Therefore, each tomographic image is evaluated based on the brightness.
- Equation 1 an example of the QI calculation method will be described. QI is calculated using the formula represented by Equation 1 below.
- Equation 1 With reference to FIG. 5, the function of the formula represented by Equation 1 above will be described.
- round indicates a function that rounds to an integer.
- maximum indicates the maximum brightness 602 of the interference signal obtained from a particular position on the fundus of the subject's eye 500, which in FIG. 5 is approximately 65 dB, for example. A method of calculating the maximum brightness 602 will be described in detail later.
- noise indicates the luminance (noise floor luminance) 604 of the portion of the subject's eye 500 where there is no image (that is, the portion where scattered light does not occur), and is set to approximately 40 dB or less in FIG. 5, for example.
- "cut” indicates the luminance (cutoff luminance) 606 that does not contribute to image evaluation, for example, the noise floor luminance 604 (approximately 40 dB in FIG. 5) is set to a range of approximately 10 dB (approximately 40 to 50 dB in FIG. 5). It is Therefore, the signal 607 indicating luminance within the range of the cut-off luminance 606 is determined to be an unnecessary signal for QI calculation.
- “range” indicates the luminance range 608 to which 256 gradations are assigned, for example, set to range from the noise floor luminance 604 (approximately 40 dB in FIG. 5) to approximately 35 dB (approximately 40-75 dB in FIG. 5).
- "10" in the above Equation 1 indicates that the QI is evaluated in 10 stages.
- QI is an index that evaluates the luminance in a range 610 obtained by excluding the cut-off luminance 606 from the luminance range 608 in 10 levels.
- the maximum luminance 602 is calculated by the following method.
- the calculation unit 202 selects A-scan information to be used for calculating the maximum luminance 602 from among a plurality of pieces of A-scan information forming the tomographic image (S32). That is, when measuring the subject's eye 500, tomographic information (so-called A-scan information) indicating the relationship between the position in the depth direction along the measurement optical axis and the signal intensity is acquired from the interference light.
- a plurality of pieces of A-scan information are acquired by scanning measurement light, and a tomographic image of the eye 500 to be inspected is generated using the pieces of A-scan information.
- step S32 a plurality of pieces of A-scan information forming the tomographic image are thinned out to reduce the amount of A-scan information used for calculating the maximum luminance 602.
- FIG. 7 schematically shows a tomographic image
- the curve indicates the surface of the retina of the subject's eye 500
- the arrow indicates A-scan information forming the tomographic image.
- the tomographic image is composed of 512 lines of A-scan information.
- the A-scan information is thinned out so that only one out of four of the 512 lines of A-scan information is used. That is, for continuous A-scan information, one line of A-scan information (arrows indicated by solid lines in FIG. 7) is selected for every four lines, and three lines of A-scan information (arrows indicated by broken lines in FIG. 7) in between are selected. Do not choose.
- the calculation unit 202 limits the range in the depth direction of the A-scan information used for calculating the maximum luminance 602 to a preset range (S34). Specifically, as shown in FIG. 8A, the range in the depth direction of the A-scan information used for calculating the maximum luminance 602 is captured by the subject eye 500 when the subject eye 500 is at an appropriate position. 620, which is near the center of the depthwise range to be measured. When a tomographic image is captured with the eye 500 to be inspected at an appropriate position, most of the tomographic image of the eye 500 to be inspected (tissue in which scattered light is generated) is included in the range 620, and a range 622 deeper than the range 620 is included.
- a range 624 that is shallower than the range 620 does not include much of the tomographic image of the subject's eye 500 (tissue that causes scattered light). Therefore, by limiting the range in the depth direction of the A-scan information to the range as described above, the maximum brightness 602 within the range 620 in the depth direction near the center when the subject's eye 500 is in an appropriate position is calculated.
- the imaging range of the subject's eye 500 extends in the depth direction ((b) in FIG. 8(b). ) shifts to a deeper range 622 than the range 620, and the portion captured outside the range 620 increases. If the range in the depth direction is limited to a range 620 near the center when the subject's eye 500 is at an appropriate position, when the subject's eye 500 is photographed in a state deviated from the appropriate position, the subject's eye 500 will be located in the range 620.
- the 500 imaging range (the portion where scattered light occurs) is hardly included.
- a tomographic image captured with the subject's eye 500 displaced from the appropriate position the calculated maximum luminance is low, and the QI evaluation is low.
- a tomographic image captured with the subject's eye 500 displaced becomes an inappropriate image because the position of the tomographic image is shifted in the depth direction from other tomographic images captured at appropriate positions.
- the QI becomes low, no problem occurs. Therefore, by limiting the range of the A-scan information in the depth direction, it is possible to reduce the calculation cost (calculation load) of the maximum brightness 602 without causing problems in the QI evaluation.
- the calculation unit 202 calculates the average value within the range limited in the depth direction in step S34 for each piece of A-scan information obtained by thinning out the number of pieces of A-scan information in step S32 (S36).
- the average value calculated here is used as the luminance value of each piece of A-scan information.
- the calculation unit 202 identifies the maximum luminance 602 from the luminance value (average value) of each piece of A-scan information calculated in step S36 (S38). Specifically, the calculation unit 202 specifies the maximum luminance value (average value) of the A-scan information calculated in step S36 as the maximum luminance 602 . The calculation unit 202 substitutes the maximum luminance 602 calculated in this way into the equation represented by Equation 1 above to calculate the QI. Thereby, the QI can be calculated for the acquired tomographic image.
- the calculation unit 202 evaluates the fixation state (S22).
- the fixation state is evaluated using the front image of the subject's eye 500 acquired in step S18 (that is, the front image acquired substantially simultaneously with the tomographic image of the subject's eye 500 acquired in step S16) as a reference acquired in step S14. by comparing it with the frontal image of the
- FIG. 9A shows a case where the subject's eye 500 does not move due to involuntary eye movement or the like and is in an appropriate position.
- the front image obtained in step S18 substantially matches the reference front image.
- the calculation unit 202 determines that the fixation state is appropriate.
- FIG. 9B if the user is blinking, the front image is not captured in step S18. In this case, the calculation unit 202 determines that the evaluation of the fixation state is inappropriate.
- FIG. 9B shows a case where the subject's eye 500 does not move due to involuntary eye movement or the like and is in an appropriate position.
- the front image obtained in step S18 does not match the reference front image.
- the subject's eye 500 is photographed at a lower position than when it is in the appropriate position (in the case of FIG. 9(a)), and does not match the position of the subject's eye 500 in the reference front image. .
- the calculation unit 202 determines that the fixation state is inappropriate.
- the QI may be determined to be low.
- the maximum luminance 602 is calculated to be large.
- the QI may be determined to be high.
- the fixation state is evaluated by comparing the front image acquired in step S18 with a reference front image.
- the calculation unit 202 determines whether or not all tomographic images have been acquired from the set imaging range (S24). If all tomographic images have not been acquired (NO in step S24), the process returns to step S16, and the processes of steps S16 to S24 are repeated.
- a preview screen 700 includes a front image 702 of an eye 500 to be examined, an evaluation result by QI (bar 706 in FIG. 10), an evaluation result by fixation state (bar 708 in FIG. 10), and A tomographic image 712 of the eye to be examined 500 , a tomographic image 714 indicating entropy in the eye to be examined 500 , a Save button 716 , and a Retake button 718 are provided.
- the front image 702 of the subject's eye 500 is the front image acquired in step S14 (that is, the reference front image). It is shown.
- a tomographic image 712 is a tomographic image (a so-called normal tomographic image) showing tissue in the subject's eye 500 by scattering intensity, and is selected from a plurality of tomographic images.
- a tomographic image 714 showing the entropy within the subject's eye 500 is the center of the imaging range.
- the QI evaluation result is determined based on the QI calculated in step S20.
- the calculation unit 202 is divided into three cases of low QI (eg, 1 to 4), medium QI (eg, 5 to 7), and high QI (eg, 8 to 10). Classify.
- the evaluation results of all the tomographic images are simultaneously displayed in one screen so that the examiner can determine the evaluation results of all the tomographic images at a glance.
- the QI evaluation result is displayed by a bar 706 (hereinafter also referred to as QI bar 706).
- the QI bar 706 shows each of the three categories in a different color.
- the QI bar 706 indicates the evaluation result in green when the QI is high, yellow when the QI is medium, and red when the QI is low. .
- 256 tomographic images are taken, and each tomographic image is numbered 1 to 256 along the cross section.
- a QI bar 706 shows the QI evaluation results of the tomographic images corresponding to the tomographic images Nos. 1 to 256 arranged side by side and color-coded. As a result, the QI evaluation results of all tomographic images can be confirmed at a glance.
- the result of the fixation state evaluation is displayed based on the fixation state evaluation in step S22.
- the evaluation result based on the fixation state is also displayed by a bar 708 (hereinafter also referred to as fixation bar 708).
- fixation bar 708 shows the evaluation result in green when the fixation state is appropriate (that is, when the front image acquired in step S18 substantially matches the reference front image). If the state is inappropriate (that is, if the front image acquired in step S18 does not match the reference front image), the evaluation result is indicated in red. In addition, when the deviation between the front image acquired in step S18 and the reference front image is slight, the evaluation result may be indicated in yellow as moderately appropriate.
- a fixation bar 708 is displayed below the QI bar 706 .
- a fixation bar 708 shows the evaluation results of the fixation state of the tomographic images corresponding to each of the tomographic images Nos. 1 to 256 arranged side by side and color-coded. Thereby, the evaluation results of the fixation states of all the tomographic images can be confirmed at a glance.
- a bar 704 showing each tomographic image (hereinafter also referred to as an image slide bar 704) is displayed in parallel.
- a selection button 710 for selecting each tomographic image is also displayed on the monitor 120 .
- a selection button 710 can be used to move the image slide bar 704 left and right to select a tomographic image.
- a selected tomographic image 712 is displayed on the monitor 120 .
- a QI bar 706 and a fixation bar 708 display evaluation results of the tomographic images at positions corresponding to the respective tomographic images on the image slide bar 704 . This allows the examiner to easily identify the tomographic image that is considered inappropriate in the QI bar 706 and fixation bar 708 .
- the examiner can display a tomographic image that is determined to be inappropriate in the QI bar 706 and the fixation bar 708 and individually check whether or not the tomographic image has been captured appropriately.
- the QI bar 706 and the fixation bar 708 it is possible to easily identify inappropriate tomographic images, thereby reducing the burden of checking work on the examiner.
- the calculation unit 202 determines whether or not the Retake button 718 has been pressed (S28).
- a retake button 718 can be pressed by the examiner using input means (not shown) such as a mouse.
- the examiner confirms the preview screen 700 displayed in step S26, and presses a retake button 718 when it is determined that the imaging of the eye 500 to be examined has not been properly performed. If the Retake button 718 is pressed (YES in step S28), the calculation unit 202 re-photographs the eye 500 to be examined. That is, the process returns to step S14 and repeats the processes of steps S14 to S28.
- the calculation unit 202 determines whether the Save button 716 has been pressed (S30).
- a Save button 716 can be pressed by the examiner using input means (not shown) such as a mouse. The examiner checks the preview screen 700 displayed in step S26, and presses a Save button 716 when it is determined that the image of the eye 500 to be examined has been properly captured.
- the calculation unit 202 stores the tomographic image of the subject's eye 500 acquired in step S16 in the memory (not shown) of the calculation unit 202 (S32). .
- the save (Save) button 716 has not been pressed (NO in step S30)
- the process returns to step S28. The processing of S30 is repeated.
- the computing unit 202 When the tomographic image of the subject's eye 500 is saved, the computing unit 202 creates a simple report (S34).
- the simple report means an examination report corresponding to the desired examination selected in step S12 and created using part of all tomographic images. In this embodiment, a total of 128 tomographic images of the subject's eye 500 are obtained.
- the calculation unit 202 selects 5 tomographic images from the 128 tomographic images, and creates an inspection report of the desired inspection selected in step S12 as a simple report.
- the simple report is created, as shown in FIG. 11, the calculation unit 202 causes the monitor 120 to display the preview screen 700 displayed in step S26 and the simple report 720 created in step S34 (S36).
- the simple report has a limited number of tomographic images used for analysis, so the time required for creation processing is reduced. Since the simple report uses only a part of the tomographic image for analysis, even if it is insufficient as an examination report, the examiner can check the simple report to obtain, for example, a polarization image. By referring to the image that cannot be displayed on the preview screen 700, it is possible to judge whether the diseased part is imaged as intended, and by checking the result of comparison with the normal eye database, the eye 500 to be examined can be properly imaged. It can be used to determine whether or not Note that an inspection report created using all tomographic images (128 tomographic images in this embodiment) is automatically generated after the processing shown in FIG. created.
- the examiner checks the display of the QI evaluation result, the fixation state evaluation result, the simple report, and the like displayed on the monitor 120, and determines whether or not the imaging has been performed appropriately.
- the QI bar 706 and the fixation bar 708 simultaneously display the QI evaluation results and the fixation state evaluation results for all tomographic images on the same screen. Therefore, it is possible to shorten the time required to determine whether or not the tomographic image has been captured appropriately based on the QI and the fixation state.
- the simple report can be used to confirm whether or not the imaging has been performed appropriately so that a desired inspection report can be created.
- a simple report takes less time to create than an examination report created using all tomographic images. Therefore, the time until the preview screen 700 is displayed can be shortened, and the time from the start of shooting to the completion of confirmation by the preview screen 700 can be shortened.
- the examiner determines that the imaging has not been properly performed, the subject's eye 500 is imaged again. On the other hand, if the examiner determines that the imaging has been performed appropriately, the imaging of the subject's eye 500 ends. In the present embodiment, it is possible to shorten the time required to determine whether or not the imaging has been properly performed, so that the time required to restrain the subject for imaging the eye 500 to be examined can be shortened.
- the QI evaluation result and the fixation state evaluation result are displayed using bars, but the present invention is not limited to such a configuration. It is sufficient if the QI evaluation results and the fixation state evaluation results of all tomographic images can be displayed simultaneously on the same screen.
- the QI evaluation results and the fixation state evaluation results may be displayed using graphs. , may be scored and displayed simultaneously on one screen.
- the preview screen 700 is displayed and the simple report 720 is created after saving the tomographic image of the eye 500 to be examined, but the configuration is not limited to this.
- a simple report 720 may be created and the preview screen 700 and the simple report 720 may be displayed on the monitor 120 .
- the examiner can check the preview screen 700 and the simple report 720 at the same time to determine whether the tomographic image of the subject's eye 500 has been properly captured.
- a polarization-sensitive optical tomography apparatus is used, but the configuration is not limited to this.
- the type of optical coherence tomography is not particularly limited, and for example, an optical tomographic imaging apparatus that is not polarization sensitive may be used.
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Abstract
Description
光源11は、波長掃引型の光源であり、出射される光の波長(波数)が所定の周期で変化する。被検眼500に照射される光の波長が変化(掃引)するため、被検眼500からの反射光と参照光との干渉光から得られる信号をフーリエ解析することで、被検眼500の深さ方向の各部位から反射される光の強度分布を得ることができる。
測定光生成部(21~29、31、32)は、PMFC14に接続されたPMFC21と、PMFC21から分岐する2つの測定光路S1、S2と、2つの測定光路S1、S2を接続する偏光ビームコンバイナ/スプリッタ25と、偏光ビームコンバイナ/スプリッタ25に接続されるコリメータレンズ26、ガルバノミラー27、28及びレンズ29を備えている。測定光路S1には、光路長差生成部22とサーキュレータ23が配置されている。測定光路S2には、サーキュレータ24のみが配置されている。したがって、測定光路S1と測定光路S2との光路長差ΔLは、光路長差生成部22によって生成される。光路長差ΔLは、被検眼500の深さ方向の測定範囲よりも長く設定してもよい。これにより、光路長差の異なる干渉光が重なることを防止できる。光路長差生成部22には、例えば、光ファイバが用いられてもよいし、ミラーやプリズム等の光学系が用いられてもよい。本実施例では、光路長差生成部22に、1mのPMファイバを用いている。また、測定光生成部は、PMFC31、32をさらに備えている。PMFC31は、サーキュレータ23に接続されている。PMFC32は、サーキュレータ24に接続されている。
参照光生成部(41~46、51)は、PMFC14に接続されたサーキュレータ41と、サーキュレータ41に接続された参照遅延ライン(42、43)と、サーキュレータ41に接続されたPMFC44と、PMFC44から分岐する2つの参照光路R1、R2と、参照光路R1に接続されるPMFC46と、参照光路R2に接続されるPMFC51を備えている。参照光路R1には、光路長差生成部45が配置されている。参照光路R2には、光路長差生成部は設けられていない。したがって、参照光路R1と参照光路R2との光路長差ΔL’は、光路長差生成部45によって生成される。光路長差生成部45には、例えば、光ファイバが用いられる。光路長差生成部45の光路長ΔL’は、光路長差生成部22の光路長ΔLと同一としてもよい。光路長差ΔLとΔL’を同一にすることで、後述する複数の干渉光の被検眼500に対する深さ位置が同一となる。すなわち、取得される複数の断層像の位置合わせが不要となる。
干渉光生成部60、70は、第1干渉光生成部60と、第2干渉光生成部70を備えている。第1干渉光生成部60は、PMFC61、62を有している。上述したように、PMFC61には、測定光生成部より水平偏光反射光が入力され、参照光生成部より第1分岐参照光(光路長差ΔL’を有する光)が入力される。ここで、水平偏光反射光には、第1測定光による反射光成分(光路長差ΔLを有する光)と、第2測定光による反射光成分(光路長差ΔLを有しない光)が含まれている。したがって、PMFC61では、水平偏光反射光のうち第1測定光による反射光成分(光路長差ΔLを有する光)と、第1分岐参照光とが合波されて第1干渉光(水平偏光成分)が生成される。
干渉光検出部80、90は、第1干渉光生成部60で生成された干渉光(第1干渉光及び第2干渉光)を検出する第1干渉光検出部80と、第2干渉光生成部70で生成された干渉光(第3干渉光及び第4干渉光)を検出する第2干渉光検出部90を備えている。
サンプリングトリガー発生器140は、例えば、FBG(Fiber Bragg Grating)144を用いて、サンプリングトリガーを生成してもよい。図3に示すように、FBG144は、光源11から入射される光の特定の波長のみを反射して、サンプリングトリガーを生成する。生成されたサンプリングトリガーは、分配器150に入力される。分配器150は、サンプリングトリガーを、サンプリングトリガー1とサンプリングトリガー2に分配する。サンプリングトリガー1は、信号遅延回路152を介して、演算部202に入力される。サンプリングトリガー2は、そのまま演算部202に入力される。サンプリングトリガー1は、第1干渉光検出部80から演算部202に入力される干渉信号(第1干渉信号と第2干渉信号)のトリガー信号となる。サンプリングトリガー2は、第2干渉光検出部90から演算部202に入力される干渉信号(第3干渉信号と第4干渉信号)のトリガー信号となる。信号遅延回路152は、サンプリングトリガー1がサンプリングトリガー2に対して、光路長差生成部22の光路長差ΔLの分だけ時間が遅延するように設計されている。これにより、第1干渉光検出部80から入力される干渉信号のサンプリングを開始する周波数と、第2干渉光検出部90から入力される干渉信号のサンプリングを開始する周波数を同じにすることができる。ここで、サンプリングトリガー1だけを生成してもよい。光路長差ΔLが既知であるので、第2干渉光検出部90から入力される干渉をサンプリングする際、サンプリングトリガー1から光路長差ΔLの分だけ時間を遅延するようにサンプリングを開始すればよい。
サンプリングクロック発生器は、例えば、マッハツェンダー干渉計で構成されていてもよい。図3に示すように、サンプリングクロック発生器は、マッハツェンダー干渉計を用いて、等周波数のサンプリングクロックを生成する。マッハツェンダー干渉計で生成されたサンプリングクロックは、分配器172に入力される。分配器172は、サンプリングクロックを、サンプリングクロック1とサンプリングクロック2に分配する。サンプリングクロック1は、信号遅延回路174を通って、第1干渉光検出部80に入力される。サンプリングクロック2は、そのまま第2干渉光検出部90に入力される。信号遅延回路174は、光路長差生成部22の光路長差ΔLの分だけ時間が遅延するように設計されている。これにより、光路長差生成部22の分だけ遅延している干渉光に対しても、同じタイミングでサンプリングすることができる。これにより、取得する複数の断層画像の位置ずれが防止できる。本実施例では、サンプリングクロックを生成するのに、マッハツェンダー干渉計を用いている。しかしながら、サンプリングクロックを生成するのに、マイケルソン干渉計を用いてもよいし、電気回路を用いてもよい。また、光源に、サンプリングクロック発生器を備えた光源を用いて、サンプリングクロックを生成してもよい。
QI = round( (max-noise)-cut)/(range-cut) * 10 )
Claims (3)
- 被検眼に設定された撮影範囲に対し光を走査する撮影処理を実行することで、前記撮影範囲からn枚(nは2以上の整数)の断層画像を撮影する撮影部と、
前記断層画像の画質を評価する評価指標を生成する生成部と、
前記生成部で生成された前記評価指標を表示する表示部と、を備えており、
前記生成部は、前記n枚の断層画像のそれぞれについて前記評価指標を生成し、
前記表示部は、前記n枚の断層画像の前記評価指標のそれぞれを同時に一画面内に表示する、光断層画像撮影装置。 - 前記評価指標は、前記断層画像の輝度に基づいて画質を評価する輝度評価指標と、前記被検眼の固視状態を評価する固視評価指標と、の少なくとも1つを含む、請求項1に記載の光断層画像撮影装置。
- 前記生成部は、n枚の断層画像からm枚(mはnより小さい自然数)の断層画像を選択し、選択した断層画像から所望の検査結果を示す検査レポートをさらに生成し、
前記表示部は、生成された検査レポートをさらに表示する、請求項1又は2に記載の光断層画像撮影装置。
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