WO2019082840A1

WO2019082840A1 - Ophthalmological imaging device and control method for same

Info

Publication number: WO2019082840A1
Application number: PCT/JP2018/039174
Authority: WO
Inventors: 航坂川; 稲生　耕久
Original assignee: キヤノン株式会社
Priority date: 2017-10-27
Filing date: 2018-10-22
Publication date: 2019-05-02

Abstract

This ophthalmological imaging device is characterized by comprising a detection unit that detects, as an interference signal, interference light formed between light returning from a subject onto which measurement light was emitted and reference light corresponding to the measurement light, a conversion unit that converts the detected interference signal, and an arithmetic processing unit that generates a tomogram of the subject using the converted interference signal, the arithmetic processing unit generating the tomogram using a plurality of components attained from the converted interference signal, the components including a frequency component higher than a Nyquist frequency of the conversion unit, and a frequency component lower than the Nyquist frequency of the conversion unit.

Description

Ophthalmic imaging apparatus and control method thereof

The present invention relates to an ophthalmologic imaging apparatus and a control method thereof.

At present, as an ophthalmologic apparatus for observing or photographing an eye, for example, an anterior segment photographing apparatus, an eye fundus camera, a confocal laser scanning ophthalmoscope (SLO) apparatus, light using multi-wavelength light wave interference There is an optical coherence tomography (OCT) apparatus and the like. Above all, since an OCT apparatus can obtain a tomographic image of a subject with high resolution, it is becoming an indispensable apparatus especially in a specialized outpatient department of the retina as an ophthalmologic apparatus.

In the case of imaging the fundus of the subject's eye in a wide range, when the curvature of the fundus is large, or when the site to be imaged is long in the depth direction, the ophthalmic OCT apparatus has the optical path length of the reference light and the optical path length of the irradiation light. The difference may be large. Here, the light path length of the irradiation light means the light path length of the light path obtained by combining the light path of the irradiation light and the light path of the reflected light. If the optical path length difference is large, the OCT apparatus causes aliasing or chipping of a tomogram, and can not obtain a tomogram representing the shape of the fundus correctly.

Therefore, Patent Document 1 discloses a technique for inverting a tomogram in which aliasing has occurred and synthesizing the original tomogram and detecting a retina by image analysis. By this technique, it is possible to perform appropriate shape analysis of the fundus in a wide range in the depth direction.

JP, 2014-176566, A

One of the ophthalmologic imaging apparatuses according to the present invention is
A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
A converter for converting the detected interference signal;
An arithmetic processing unit that generates a tomogram of the subject using the converted interference signal;
The arithmetic processing unit is a plurality of components obtained from the converted interference signal, and uses a component of a frequency higher than the Nyquist frequency of the conversion unit and a component of a frequency lower than the Nyquist frequency of the conversion unit. , Generating the tomogram.

Schematic diagram of OCT according to the present embodiment The figure which shows the relationship between the frequency of a signal and a tomogram in this embodiment The figure which shows the relationship between the frequency of a signal and a tomogram in this embodiment The figure which shows the relationship between the frequency of a signal and a tomogram in this embodiment The figure which shows the relationship between the frequency of a signal and a tomogram in this embodiment The figure which shows the relationship between the frequency of a signal and a tomogram in this embodiment The figure which shows the method of acquiring a tomogram wider in the depth direction in this embodiment The figure which shows the method of acquiring a tomogram wider in the depth direction in this embodiment The figure which shows the method of acquiring a tomogram wider in the depth direction in this embodiment The figure which shows the method of acquiring a tomogram wider in the depth direction in this embodiment A diagram showing a flow for acquiring a wider tomographic image in the depth direction in the present embodiment

The conventional technique is a technique for inverting and connecting tomograms after occurrence of aliasing and performing shape analysis. For this reason, it does not remove the aliasing itself from the tomogram. That is, it is not possible to obtain a tomogram suitable for observing the detailed structure of the portion where the aliasing has occurred.

Therefore, one of the objects of the present embodiment is to acquire a tomogram that is wider in the depth direction and in which aliasing is reduced.

For example, one of the ophthalmologic imaging apparatus according to the present embodiment is a plurality of components (for example, information including intensity and phase) obtained from the interference signal converted by the conversion unit, and the Nyquist frequency of the conversion unit A tomogram of the object is generated using the high frequency component and the low frequency component lower than the Nyquist frequency of the conversion unit. As a result, it is possible to acquire a tomogram that is wider in the depth direction and in which aliasing is reduced. The present embodiment will be described below.

(Optical coherence tomography)
FIG. 1 is a view showing a configuration of an OCT (an example of an ophthalmologic imaging apparatus) according to the present embodiment. The wavelength swept light source 101 is a light source in which the wavelength of light to be emitted temporally changes from a short wavelength to a long wavelength, or from a long wavelength to a short wavelength. The light L emitted from the wavelength sweeping light source 101 is demultiplexed into the irradiation light LA (measurement light) and the reference light LB by a branching fiber coupler 102 which is an example of a dividing means. Further, the irradiation light LA is collimated by the collimator lens 103, reflected by the scanning mirror 108, passes through the condenser lens 105, and is irradiated onto the subject 107. Further, the light LA ′ (return light) which is irradiated to and reflected by the object 107 is incident on the coupler 104 via the coupler 102. On the other hand, the reference light LB passes through the collimator lens 109, the

mirrors

110 and 111, and the condenser lens 112, and enters the coupler 104 as light LB ′. The light LA ′ and the light LB ′ are simultaneously multiplexed by the coupler 104 and demultiplexed, and enter the differential detector 120 as an example of the detection unit as interference light.

The differential detector 120 also converts the intensity of the interference light into an analog signal. The analog signal output from the differential detector 120 is branched, one of which becomes only a low frequency component by the low pass filter 121, and is converted into a digital signal by an AD conversion unit 131 which is an example of a conversion unit. The other becomes high frequency components only by the high pass filter 122, and is converted into a digital signal by an AD conversion unit 132 which is an example of another conversion unit. The bands of the low pass filter 121 and the high pass filter 122 are electrically adjustable. The low pass filter 121 and the high pass filter 122 are an example of a filter unit that attenuates the detected interference signal according to a predetermined frequency characteristic. These digital signals are processed by an arithmetic processing unit 114, which is an example of an arithmetic processing unit, in a method described later. The arithmetic processing unit 114 obtains information of the object 107 by performing processing such as Fourier transform on these digital signals. The display unit 115 displays a tomogram of the subject obtained by the arithmetic processing unit 114. The arithmetic processing device may be communicably connected to the ophthalmologic imaging device. The arithmetic processing unit may be incorporated in the inside of the ophthalmologic imaging apparatus.

The above is the process of acquiring a tomogram at a certain point of the subject 107, and thus acquiring information on a cross section in the depth direction of the subject 107 is referred to as an A-scan. Further, information on a tomographic image of the subject in a direction orthogonal to the A-scan, that is, a scan for acquiring a two-dimensional image is referred to as a B-scan. In the present embodiment, B-scan is performed by the scanning mirror 108.

(Tomogram acquisition)
Acquisition of a tomogram will be described with reference to FIG. Here, the case where the band of the low pass filter 121 in FIG. 1 is adjusted sufficiently wide will be described. In this case, since all analog signals output from the differential detector 120 pass through the low pass filter 121, the low pass filter 121 may be ignored.

Here, FIG. 2A shows the appearance of a tomographic image of the fundus of the subject 107. The positions of the

mirrors

110 and 111 are adjusted by the method described later so that the optical path length of the irradiation light matches the optical path length of the reference light when the irradiation light is reflected at the depth position 240.

Further, FIG. 2B shows that the arithmetic processing unit 114 Fourier-transforms the signal obtained by A-scanning the position 201 of FIG. 2A, and shows the signal strength for each frequency component. The horizontal axis represents frequency, and the vertical axis represents the logarithm of signal strength. The DC component 241 represents frequency 0. When the optical path length of the irradiation light and the optical path length of the reference light completely match, the irradiation light and the reference light intensify each other at all the swept wavelengths, so that a signal of a DC component is obtained. When the optical path length of the irradiation light and the optical path length of the reference light are different, interference occurs according to the difference, and the frequency of the signal changes.

Further, at the position 201, since the object 107 is at a position deeper than the depth position 240, an optical path length difference occurs, and a real image 202 is obtained. The Nyquist frequency 242 is half the frequency of the sampling frequency of the AD converter 131, and is the maximum frequency that can be acquired by the AD converter 131. When analog-to-digital conversion is performed by the AD conversion unit 131, aliasing occurs around the Nyquist frequency. The mirror image 203 is an image representing a frequency indistinguishable from the real image 202 when sampled by the AD conversion unit 131.

Further, FIG. 2C shows a tomogram of a certain stage generated by the arithmetic processing unit 114. The upper end 243 of the image represents the DC component 241 and the lower end 244 of the image represents the Nyquist frequency 242. Line 204 is an image of the signal of FIG. 2B. Since the real image 202 is entirely included in the range from the DC component to the Nyquist frequency, a tomographic image is included on the straight line 204 between the upper end and the lower end of the image.

Further, FIG. 2D shows the signal at position 211 in the same manner as FIG. 2B. Since the object 107 is at a deeper position than the position 201 at the position 211, the real image 212 has a frequency higher than that of the real image 202. The real image 212 partially overlaps the folded mirror image 213 because it partially exceeds the Nyquist frequency. Therefore, on the straight line 214, the original tomographic image and the folded tomographic image are partially overlapped.

Further, FIG. 2E shows the signal at position 221 in the same manner as FIG. 2B. Since the object 107 is at a position deeper than the position 211 at the position 221, the real image 222 has a higher frequency and exceeds the Nyquist frequency. Therefore, on the straight line 224, only the mirror image 223, that is, the folded portion is imaged. Such sampling of a signal having a frequency exceeding the Nyquist frequency is generally referred to as undersampling.

As understood from the above, when the sampling frequency of the AD conversion unit 131 is not sufficient for the range in the depth direction of the subject 107, aliasing occurs in the tomogram and a tomogram representing the structure of the subject 107 correctly Can not get.

The position adjustment of the

mirrors

110 and 111 described above is performed as follows. The photographer adjusts the positions of the

mirrors

110 and 111 which are an example of the optical path length changing unit by the input unit (not shown) while looking at the image shown in FIG. 2C or the like displayed on the display unit 115. By appropriately adjusting the positions of the

mirrors

110 and 111, it is possible to obtain a tomogram in which aliasing occurs only at the lower end of the image as shown in FIG. 2B. The adjustment of the positions of the

mirrors

110 and 111 can be performed by, for example, moving the

mirrors

110 and 111 along the optical axis with a common stage, thereby changing the optical path length of the reference light. The optical path length changing unit may change not only the optical path length of the reference light but also the optical path length of the measurement light, or both of the optical path length of the reference light and the optical path length of the measurement light It may be changed. That is, the light length change unit may be anything as long as it can change the difference between the light path length of the reference light and the light path length of the measurement light.

If the positions of the

mirrors

110 and 111 are not appropriate, aliasing may occur at the upper end of the image. This is the case where the depth position 240 and the subject 107 overlap. At this time, the frequency components of the signal are distributed on both sides of the direct current component 241, and the area where the frequency is negative is folded back to the positive area as a mirror image to cause aliasing of the tomographic image. In the conventional OCT apparatus, the expression of aliasing of a tomogram often refers to this aliasing. On the other hand, in the present invention, it is premised that such folding at the upper end 243 of the image is avoided by position adjustment of the

mirrors

110 and 111. As a result, aliasing due to the Nyquist frequency occurs at the lower end 244 of the image, but in the following, the arithmetic processing unit 114 is used to suppress aliasing due to the Nyquist frequency and to image the structure of the object 107 in a wide range in the depth direction. Describes the process that is additionally performed.

In the following description, for the sake of simplicity, it is assumed that there is no phase shift of the filter. Similarly, it is assumed that the signals obtained by A-scan the fundus are in phase at all frequencies. At this time, since the frequency distribution consisting of only real numbers can be obtained by Fourier transforming this signal, only the real numbers will be used in the following description.

(Reduction of aliasing)
FIG. 3 is a diagram showing an additional process for imaging the structure of the object 107 in a wide range in the depth direction. Here, FIG. 3A is a diagram showing the frequency characteristics of the filter. A characteristic 301 is a frequency characteristic of the low pass filter 121, and a characteristic 311 is a frequency characteristic of the high pass filter 122. The abscissa represents the frequency, and the ordinate represents the logarithm of the filter transmittance. In either case, the cutoff frequency is adjusted to be in the vicinity of the Nyquist frequency 242. In addition, it is preferable to store a graph as shown in FIG. 3A, a table showing a graph, or the like in the storage unit as information on the frequency characteristic of the filter.

Further, FIG. 3B shows the frequency characteristic of the low pass filter 121 and the tomographic image 312 acquired from the digital signal obtained by the AD conversion unit 131. The tomogram 312 is an example of a first partial tomogram generated using a component having a frequency lower than the Nyquist frequency of the conversion unit. Here, the signal S _L and the signal S _H indicates a signal output from the differential detector 120 at each frequency. The frequencies of the signal S _L and the signal S _H are symmetrical about the Nyquist frequency 242. The signal S _L and the signal S _H are attenuated by the low pass filter 121. The transmittances P _L and P _H are values indicating the transmittances of the low pass filter 121 at the frequencies of the signal S _L and the signal S _H , respectively. These are values determined during adjustment of the device. When the signal S _L and the signal S _H are attenuated by the low pass filter 121, the signals input to the AD conversion unit 131 are P _L S _L and P _H S _H , respectively. These results one signal S _P which when analog / digital conversion is summed overlap by folding the AD conversion unit 131. Processing unit 114 stores the signal S _P obtained by the Fourier transform, and generates a tomographic image 312 in which the intensity of the signal S _P and brightness simultaneously. On the other hand, the signal S _P consistent with that from the above description, determined by the following equation.

Further, FIG. 3C shows the frequency characteristic of the high pass filter 122 and the tomographic image 322 acquired from the digital signal obtained by the AD conversion unit 132 in the same manner as FIG. 3B. The tomogram 322 is an example of a second partial tomogram generated using a component having a frequency higher than the Nyquist frequency of the conversion unit. As in FIG. 3B, the signal S _Q matches the one determined by the following equation.

If these equations are solved as simultaneous equations, the signal S _L and the signal S _H can be obtained as follows.

Thus, processor 114 uses the signals and the transmittance of the filter used to generate the tomographic image 312 and the tomographic image 322, it is possible to obtain a signal S _L and the signal S _H. That is, the signal S _L below the Nyquist frequency and the signal S _H above the Nyquist frequency, which are overlapped due to the folding, can be separated by the above method. By performing this calculation for all frequencies other than the Nyquist frequency 242, a signal of each frequency can be obtained. The above calculation can not be performed at the Nyquist frequency 242 because P _L and P _H coincide, but by using the signal obtained by analog / digital conversion as it is, the signal S _L (in this case, the same signal as the signal S _H Can be asked).

Further, FIG. 3D shows a tomogram obtained by imaging the intensity of the signal obtained as described above and imaging the object 107 in a deep range. It can be seen that tomographic images in a wide range in the depth direction are obtained as compared to FIGS. 2C, 3B, and 3C.

In the above description, it is assumed that there is no frequency shift of the filter, and the signal obtained by A-scan of the fundus is in phase at all frequencies. However, in an actual frequency filter, phase shift occurs. In addition, signals obtained by actually performing A-scan on the fundus include signals of various phases. Therefore, it is desirable to perform calculations taking these into consideration. Specifically, all of the signals S _{L and} S _{H, the} transmittances P _L , P _H , Q _L and Q _H , and the luminances S _{P and} S _Q used in the above description may be replaced with real numbers and complex numbers. The transmittances P _L , P _H , Q _L and Q _H can be obtained as complex numbers from the gain characteristics and the phase characteristics of the filter. Signal S _P, S _Q can be obtained by Fourier transforming a signal obtained by A-scan the fundus. Since the signals S _{L and} S _H are obtained as complex numbers from the above calculation, their intensities may be used as the luminance of the image. The component in the present embodiment is information including not only intensity but also phase, and is information including not only mounting but also a complex number.

FIG. 4 shows a flow until a tomographic image is generated and displayed based on the above description. In step S401, the arithmetic processing unit 114 acquires the interference signal obtained by the AD conversion unit 131 and the AD conversion unit 132. In step S402, the processing unit 114 performs a Fourier transform of these interference signals to obtain the signal _S P, the _{S Q.} In step S403, the processing unit 114 performs a calculation to separate at the Nyquist frequency signals in the manner described above, to obtain signal S _L, the S _H. In step S404, the processing unit 114 generates a tomographic image shown in FIG. 3D seeking intensity of the signal _{_S} L, _S _H. In step S405, the display unit 115 displays a tomogram.

In this embodiment, short-time shooting is possible. This is because it is not necessary to drive the

mirrors

110 and 111 to change the optical path length of the reference light in order to acquire a plurality of images with different folding strengths, and the scanning performed by the mirror 108 to obtain the tomographic image of FIG. It is because it is good at times.

In addition, the transmittance values of the low pass filter 121 and the high pass filter 122 may be updated after adjustment of the device in consideration of environmental dependency and the like. For example, these transmittances may be calculated from signals obtained by reflecting the irradiation light by a mirror (not shown) inside the apparatus before or during the inspection. Further, the value of the transmittance may be estimated based on the obtained luminance distribution of the tomogram of FIG. 3D, and the tomogram of FIG. 3D may be regenerated.

Further, the formula for obtaining the signal S _L and the signal S _H may be a material other than the above. For example, when the filter is close to the ideal filter and the cutoff frequency is close to the Nyquist frequency, the aliasing portion hardly occurs in the tomogram 312 and only the aliasing portion occurs in the tomogram 322. Therefore, a tomographic image close to a desired tomographic image can be obtained by inverting the tomographic image 322 up and down and simply connecting the tomographic image 312. This and P _H and Q _L in the above formula is 0, the same as the calculation in the case of the 1 P _L and Q _H.

Also, the filter used may not be a combination of a low pass filter and a high pass filter. For example, a combination in which the cutoff frequency is different only by the low pass filter may be used. The value of the above P _L and Q _L may be only the low-pass filter can perform the same calculations for different values of different or or P _H and Q _H. In addition, a band pass filter may be used in consideration of a frequency higher than twice the Nyquist frequency.

Also, three or more filters may be provided. By combining the three or more filters having different frequency bands and performing the same calculation, it is possible to obtain a tomogram in an even deeper range. In addition, the signal intensities obtained by using a plurality of filters in the same band may be averaged to increase the calculation accuracy of the luminance.

Also, there may be one filter. Similar calculations may be made from filtered and non-filtered signals. In that case, since the attenuation in a signal not passed through the filter substantially no, the value of P _L and P _H may be substantially 1. Furthermore, if the only filter is close to the ideal low-pass filter, Q _L should be 1 and Q _H should be 0. In this case, the above equation for S _H corresponds to a simple subtraction of the filtered signal from the unfiltered signal. That is, in such a configuration, a tomogram in a wide range in the depth direction can be obtained by the subtraction processing of signals.

Also, the band may be switched temporally by one filter. By acquiring a plurality of tomograms continuously while switching the band, it is possible to generate a tomogram in a deeper range from the plurality of tomograms. In this case, in order to reduce the influence of the movement of the subject's eye, it is preferable to acquire a plurality of tomograms in a short time. For that purpose, it is preferable that the filter band be electrically changed as in the present embodiment. Note that, as a configuration for switching the filter band, for example, a configuration including a characteristic change unit (for example, variable resistance) provided in the filter to change the frequency characteristic of the filter and a control unit that controls the characteristic change unit is preferable. .

Moreover, in the present embodiment, the attenuation of the signal due to other than the filter is also included in the value of the transmittance of the filter. That is, calculation is performed by regarding the decrease in signal strength due to defocusing and the attenuation due to the filter characteristics inside the AD conversion unit as the attenuation due to the low pass filter 121 and the high pass filter 122. However, these may be treated as separate parameters.

In addition, sampling frequencies of the AD conversion unit 131 and the AD conversion unit 132 may be different from each other. It may be possible to switch whether or not the processing unit 114 performs the above processing.

Alternatively, the final tomogram 3D may be generated from the obtained signals directly using the above equation without generating the tomogram 312 and the tomogram 322. In that case, since the imaging of the

tomograms

312 and 322 is unnecessary, higher speed processing is possible.

Further, in the present embodiment, it is assumed that the wavelength sweep by the wavelength sweep light source 101 is stable and the velocity is constant with respect to the wave number, but the light source may not be a constant velocity. In such a case, a configuration is preferable in which k-clocks for sampling at equal wave number intervals in the light source or in the device are generated and input to the AD conversion unit. Note that k-clock is an example of a clock generation unit that generates a clock at which the conversion unit samples an analog signal. In addition, k-clock is an interferometer in which an optical path through which a part of light from the wavelength swept light source 101 passes is branched into a first optical path and a second optical path having a difference in optical path length with respect to the first optical path. It is preferred to be configured. Here, even if the wavelength sweeping by the wavelength sweeping light source 101 is not at a constant speed, a component of a frequency higher than the Nyquist frequency of the converting unit is a time during which sampling of interference signals (analog signals) is performed twice It can be regarded as a component that vibrates in a shorter time. In addition, even when the wavelength sweeping by the wavelength sweeping light source 101 is not at a constant speed, the component of the frequency lower than the Nyquist frequency of the converting unit is from the time when the sampling of the interference signal (analog signal) by the converting unit is performed twice. It shall be regarded as a component that vibrates for a long time.

In addition, although this embodiment is SS-OCT, it may be applied to other OCTs. For example, in the SD-OCT, an optical low pass filter may be disposed in front of the line sensor to perform the same role as the low pass filter 121 of the present embodiment. Further, the present invention may be applied to the reduction in resolution based on the pixel size of the line sensor, the design of the diffraction grating, the lens and the like as the same effect as the low pass filter.

As described above, according to this embodiment, it is possible to calculate a signal of a frequency higher than the Nyquist frequency and a signal of a frequency lower than the Nyquist frequency. As a result, an area of a frequency higher than the Nyquist frequency, that is, a deeper area of the fundus can be imaged, and a wide tomographic image in the depth direction can be obtained. Furthermore, as compared with the method of changing the optical path length, the signal acquisition can be performed in a short time, and the influence of the involuntary eye movement and fatigue of the eye to be examined can be suppressed.

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

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the following claims are attached to disclose the scope of the present invention.

The present application claims priority based on Japanese Patent Application No. 2017-208428 filed Oct. 27, 2017 and Japanese Patent Application No. 2018-147777 submitted on August 6, 2018, The entire contents of the description are incorporated herein.

Claims

A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
A converter for converting the detected interference signal from an analog signal to a digital signal;
An arithmetic processing unit that generates a tomogram of the subject using the converted interference signal;
The arithmetic processing unit is a plurality of components obtained from the converted interference signal, and uses a component of a frequency higher than the Nyquist frequency of the conversion unit and a component of a frequency lower than the Nyquist frequency of the conversion unit. An ophthalmologic imaging apparatus characterized by generating the tomogram.
The arithmetic processing unit generates a first partial tomogram using the low frequency component, generates a second partial tomogram using the high frequency component, and the first partial tomogram The ophthalmologic imaging apparatus according to claim 1, wherein the tomogram is generated by combining the second partial tomogram.
It further comprises a filter unit for attenuating the detected interference signal according to a predetermined frequency characteristic,
The ophthalmologic imaging apparatus according to claim 1, wherein the conversion unit converts the attenuated interference signal.
A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
A filter unit for attenuating the detected interference signal according to a predetermined frequency characteristic;
A converter for converting the attenuated interference signal from an analog signal to a digital signal;
An arithmetic processing unit that generates a tomogram of the subject using the converted interference signal;
The operation processing unit generates the tomogram by using a plurality of components obtained from the converted interference signal.
Unlike the conversion unit, the processing unit further includes another conversion unit for converting the detected interference signal, and the arithmetic processing unit is configured to use the attenuated interference signal and the interference signal converted by the other conversion unit. The ophthalmic imaging apparatus according to claim 3, wherein the tomographic image is generated using the plurality of components obtained.
The arithmetic processing unit according to claim 5, wherein any one of the plurality of components is acquired by subtracting the attenuated interference signal and the interference signal converted by the another conversion unit. Ophthalmic imaging device.
A characteristic change unit provided in the filter unit to change the frequency characteristic of the filter unit;
A control unit that controls the characteristic change unit;
The arithmetic processing unit uses the plurality of components obtained from the interference signal converted before the frequency characteristic is changed and the interference signal converted after the frequency characteristic is changed, tomograms The ophthalmologic imaging apparatus according to claim 3 or 4, wherein
The arithmetic processing unit acquires the plurality of components using information on the frequency characteristics of the filter unit and the converted interference signal, and generates the tomographic image using the plurality of acquired components. The ophthalmologic photographing apparatus according to any one of claims 3 to 7, characterized in that
The optical system further includes an optical path length change unit that changes at least one of the optical path length of the reference light and the optical path length of the measurement light,
The arithmetic processing unit acquires the plurality of components from which the aliasing component is separated by using the converted interference signal acquired without the change of the optical path length by the optical path length changing unit being performed. The ophthalmologic imaging apparatus according to any one of claims 1 to 8, wherein the tomogram is generated using a plurality of components.
A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
A converter for converting the detected interference signal from an analog signal to a digital signal;
An arithmetic processing unit that generates a tomogram of the subject using the converted interference signal;
An optical path length changing unit configured to change at least one of an optical path length of the reference light and an optical path length of the measurement light;
The arithmetic processing unit acquires a plurality of components in which the aliasing components are separated by using a plurality of the converted interference signals having different aliasing components acquired without changing the optical path length by the optical path length changing unit. An ophthalmologic imaging apparatus, wherein the tomogram is generated using the plurality of acquired components.
Wavelength swept light source,
A dividing means for dividing light from a wavelength swept light source into the measurement light and the reference light;
The conversion unit is configured as an interferometer in which an optical path through which part of the light from the wavelength swept light source passes is branched into a first optical path and a second optical path having a difference in optical path length with respect to the first optical path A clock generation unit that generates a clock for sampling by
The ophthalmic imaging apparatus according to any one of claims 1 to 10, further comprising:
A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
And converting the detected interference signal from an analog signal to a digital signal.
Using a plurality of components obtained from the converted interference signal, a component of a frequency higher than the Nyquist frequency of the conversion unit, and a component of a frequency lower than the Nyquist frequency of the conversion unit, A control method of an ophthalmologic imaging apparatus, comprising the step of generating an image.
A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
A filter unit for attenuating the detected interference signal according to a predetermined frequency characteristic;
A control unit for converting the attenuated interference signal from an analog signal into a digital signal,
A control method of an ophthalmologic imaging apparatus, wherein the tomogram is generated using a plurality of components obtained from the converted interference signal.
A detection unit that detects, as an interference signal, interference light due to return light from an object irradiated with measurement light and reference light corresponding to the measurement light;
A converter for converting the detected interference signal from an analog signal to a digital signal;
A control method of an ophthalmologic imaging apparatus, comprising: an optical path length changing unit that changes at least one of an optical path length of the reference light and an optical path length of the measurement light;
The plurality of components from which the aliasing component is separated are acquired using the plurality of converted interference signals having different intensities of the aliasing component acquired without changing the optical path length by the optical path length changing unit, and the acquisition is performed A control method of an ophthalmologic imaging apparatus, wherein the tomogram is generated using the plurality of components.
A program that causes a computer to execute the control method of the ophthalmologic imaging apparatus according to any one of claims 12 to 14.