JP2021037088A - Optical interference tomographic apparatus, operation method of optical interference tomographic apparatus, and program - Google Patents

Abstract

To reduce noise in a tomographic image acquired by using SS-OCT.SOLUTION: An optical interference tomographic imaging apparatus includes: detection means for detecting interference light obtained by multiplexing return light based on measurement light obtained by dividing light emitted from a wavelength variable light source and radiated onto an object to be examined, and reference light obtained by dividing the emitted light; an A/D conversion part for converting the interference signal obtained by detecting the interference light from an analog signal to a digital signal on the basis of a clock signal obtained by using part of the emitted light; and changing means for changing at least one piece of data determined to be abnormal of a plurality of pieces of data included in spectrum information corresponding to A scan of an interference signal obtained by the conversion.SELECTED DRAWING: Figure 4

Description

The present invention relates to an optical interference tomographic imaging device, an operation method of the optical interference tomographic imaging device, and a program.

Optical coherence tomography (hereinafter referred to as OCT) has been put into practical use as a method for non-destructively and non-invasively acquiring a tomographic image of a measurement target such as a living body. The OCT apparatus used for carrying out OCT is widely used in ophthalmic diagnosis of the retina, such as being used for acquiring a tomographic image of the retina at the fundus of the eye to be inspected, especially in the ophthalmic field.

In OCT, a tomographic image is obtained by interfering the light reflected from an object to be inspected such as the retina with the reference light and analyzing the time dependence or wave number dependence of the intensity of the interfering light. As such an OCT apparatus, a wavelength sweep optical coherence tomography (SS-OCT: Swept Source Optical Coherence Tomography) apparatus using a wavelength variable light source capable of changing the oscillation wavelength is known.

The tunable light source has a tunable filter inside or outside the light source, and changes the wavelength of the emitted light by temporally changing the voids and the refractive index of the elements inside the filter. In the field of ophthalmology, 100 kHz or higher is often used as a tunable frequency. In order to obtain a tomographic image based on wavenumber dependence analysis, it is necessary to acquire interference signal data at equal wavenumber intervals and perform Fourier transform on this. In SS-OCT, a method of rescaling by interpolating data after sampling at equal time intervals, or a method of sampling interference signals at equal wave number intervals using a signal called k-clock generated from light of a tunable light source. There is. Compared with rescaling, when k-clock is used, it is possible to save the trouble of acquiring extra data and performing interpolation calculation.

Here, it is known that in the OCT apparatus, fixed pattern noise (hereinafter referred to as FPN: Fixed Pattern Noise), which is a lateral streak-shaped artifact, is generated in the acquired tomographic image regardless of the object to be inspected. Some FPNs are generated by multiple reflections of reflected light from optical members (for example, optical fiber end faces and lenses) used for OCT and interference. Patent Document 1 discloses a method for reducing FPN caused by such multiple reflections. Specifically, as a background signal including FPN caused by an optical member, spectrum data obtained without passing through an object to be inspected is acquired. Then, the spectrum data as the background signal corresponding to the noise component is subtracted from the spectrum data as the measurement signal obtained based on the return light obtained by irradiating the object to be inspected with the measurement light. As a result, FPN is removed from the spectral data obtained from the inspected object.

JP-A-2018-89055

Here, the inventor of the present application has found that, for example, in a tomographic image of the retina obtained by SS-OCT, a vertical streak-shaped emission line running in the depth direction of the retina (depth direction of the eye to be inspected) may occur. .. Then, the inventor of the present application generates a noise pattern showing the form of such a vertical streak-shaped emission line due to sudden disturbance of the time interval of k-clock obtained at equal wave number intervals, for example. I found out that there is a possibility. Unlike the FPN caused by the optical member, the vertical streak-shaped emission line is caused by k-clock and does not depend on the acquisition position of the spectrum data. Therefore, it is not easy to reduce the emission line by the conventional method.

One of the objects of the present invention is in view of such a situation, and is to reduce noise in a tomographic image obtained by using SS-OCT.

In order to solve the above problems, the optical interference tomographic imaging apparatus according to one aspect of the present invention is used.
The measurement light obtained by dividing the emission light from the tunable light source, and the return light based on the measurement light irradiated to the object to be inspected and the reference light obtained by dividing the emission light are combined. A detection means for detecting the interference light obtained
An A / D conversion unit that converts an interference signal obtained by detecting the interference light from an analog signal to a digital signal based on a clock signal obtained by using a part of the emitted light.
A changing means for changing at least one data determined to be abnormal among a plurality of data included in the spectrum information corresponding to the A scan of the interference signal obtained by the conversion is provided.

According to one aspect of the present invention, noise in a tomographic image obtained by using SS-OCT can be reduced.

It is the schematic of the whole structure of the SS-OCT apparatus used in the 1st Embodiment. It is a figure which shows the schematic structure of the signal processing part which concerns on 1st Embodiment. It is the schematic which shows the k-clock signal. It is the schematic which shows the acquired interference signal. It is a flowchart which shows the procedure of the signal processing in 1st Embodiment. It is a figure which shows typically the example of the tomographic image obtained in 1st Embodiment. It is the schematic which shows the acquired interference signal. It is a flowchart which shows the signal processing procedure in 2nd Embodiment.

Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the following description is merely explanatory and exemplary in nature and is not intended to limit this disclosure and its use or use in any way. The relative configurations of the components shown in the embodiments, as well as the steps, numerical representations and numerical values, do not limit the scope of the present disclosure unless otherwise specified. Techniques, methods and devices well known to those of skill in the art may not be discussed in detail as those of skill in the art do not need to know these details to enable the embodiments discussed below.

In SS-OCT, when acquiring an interference signal, k-clock may be used as an external clock accepted by the A / D converter (analog-digital converter) used for this acquisition as described above. The k-clock is a signal based on the interference light obtained by branching the light emitted from the tunable light source into two optical paths having an optical path length difference and interfering with these lights. This k-clock is a sine wave-like signal whose period changes according to the sweeping of the wavelength of the emitted light by the tunable light source, and crosses the zero point at equal wavenumber intervals (zero cross). When focusing on a signal in a narrow range such as 5 cycles, the k-clock crosses the zero point at approximately equal intervals in terms of time (zero cross). However, in k-clock, the time interval is suddenly disturbed, and the zero cross interval may change. In particular, when the zero-cross interval is narrowed, the allowable frequency of the external clock accepted by the A / D converter may be exceeded, in which case the data becomes undefined. As a result, the interference signal is not acquired correctly because a large absolute value is recorded. The tomographic image obtained by Fourier transforming the interference signal that is not correctly acquired in this way becomes a noise pattern such as a bright line of constant brightness running in the depth direction (longitudinal direction) of the retina corresponding to the irradiation direction of the interference light. Such vertical streaky bright lines are conspicuous in the tomographic image showing the cross section of the retina, and there is a possibility that the diagnostic efficiency using the tomographic image may be reduced or a false diagnosis may occur. In the following, a device or method for reducing the vertical streak-shaped noise pattern devised by the inventor of the present application will be described in detail.

[First Embodiment]
Hereinafter, the information processing apparatus according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. Further, the signal processing executed in the information processing apparatus according to the first embodiment will be described with reference to FIGS. 3 to 6. The SS-OCT device whose schematic configuration is shown in FIG. 1 and the like is an example, and its form is not limited to the example shown in the figure as long as it can acquire an interference signal or the like described later.

In the present embodiment, the object to be inspected is the human eye (fundus Er of the eye to be inspected 118), but the present invention is not limited to this. The emission line running in the vertical direction, which the present invention intends to reduce, is generated by an abnormality of the external clock used by the A / D converter when receiving a signal, regardless of the mode of the object to be inspected. Therefore, the object to be inspected may be the anterior segment of the eye to be inspected 118. Further, in the SS-OCT apparatus, for example, it is necessary to reduce the emission lines running in the vertical direction generated in the above-mentioned tomographic image even in the skin or organ of the subject to be inspected. Therefore, for example, the operation method according to one aspect of the present invention can be applied even when a tomographic image is acquired by an optical interference tomographic imaging device used in a medical device such as an endoscope other than an ophthalmic device. ..

(Overall configuration of SS-OCT device)
FIG. 1 shows a schematic configuration of the SS-OCT apparatus used in the present embodiment. The SS-OCT apparatus includes an interference signal generation unit 100 and a control unit 143 that generate an interference signal. The control unit 143 is further composed of a signal processing unit 144, a device control unit 145, a display control unit 149, and a display unit 146. The details of the signal processing unit 144 will be described later with reference to FIG.

(Interference signal generation unit 100)
The interference signal generation unit 100 includes a light source 101, optical branching elements 110 and 128, a measurement arm, a reference arm, and a detector 141. The light source 101 is a wavelength sweep (Swept Source: SS) light source, and emits light in a range centered on 1050 nm having a sweep wavelength of 1000 nm to 1100 nm, for example. The light source 101 has a resonator, and the resonator length has a length of, for example, 50 mm. Further, in the present embodiment, k-clock is generated by using the light emitted from the light source 101. Specifically, the light emitted from the light source 101 is guided and divided by the optical branching element 152 via the fiber 151, and is guided to the fiber 102 and the fiber 153, respectively. The light guided to the fiber 153 is guided to the k-clock generator 154 via the fiber 153. The k-clock generation unit 154 is a signal based on the interference light obtained by branching the light emitted from the light source 101 into two optical paths having an optical path length difference and interfering with the light.

The light emitted from the light source 101 is guided to the optical branching element 110 via the fiber 102, and is divided into measurement light and reference light. The division ratio at this time was 30 (measurement light): 70 (reference light). The measurement light obtained by the division is guided to the measurement arm via the fiber 111, and similarly, the reference light is guided to the reference arm via the fiber 119a or the like described later.

A collimator 112, a galvano scanner 114, a scan lens 115, and a focus lens 116 are arranged on the measurement arm in order from the fiber end 111a. The measurement light emitted from the fiber end 111a becomes parallel light by the collimator 112. The measured light that becomes parallel light is applied to the fundus Er of the eye to be inspected 118 via the galvano scanner 114, the scan lens 115, and the focus lens 116. The galvano scanner 114 is used to scan the fundus Er with measurement light.

Although the galvano scanner 114 is shown as a single mirror, it is actually composed of two galvano scanners (X-axis scanner and Y-axis scanner) (not shown) so as to raster-scan the fundus Er of the eye 118 to be inspected. .. Further, the focus lens 116 is fixed on the stage 117, and by moving in the optical axis direction, the focus of the measurement light can be adjusted with respect to the fundus Er. The galvano scanner 114 and the stage 117 are controlled by the device control unit 145, which will be described later, in a desired range of the fundus Er of the eye to be inspected 118 (also referred to as a tomographic image acquisition range, a tomographic image acquisition position, and a measurement light irradiation position). The measurement light can be scanned.

Although detailed description will not be given in this embodiment, a tracking function for detecting the movement of the fundus Er and scanning the measurement light while making the mirror of the galvano scanner 114 follow the movement of the fundus Er is provided. desirable. As for the tracking method, it is possible to use a general technique. As a specific example, there is a method using a scanning laser ophthalmoscope (Scanning Laser Ophthalmoscope: SLO). In this method, a two-dimensional image of the fundus Er is acquired over time using SLO, and characteristic parts such as blood vessels in the image are extracted. Real-time tracking is performed by calculating the amount of movement of the fundus Er from the movement of the extracted feature portion and feeding back the result to the galvano scanner 114. Of course, it is possible to use other tracking methods, and the tracking method is not limited to this.

The measurement light enters the eye 118 to be inspected through the focus lens 116 mounted on the stage 117, and is focused on the fundus Er. The measurement light irradiated to the fundus Er is reflected and scattered by each retinal layer, passes through the above-mentioned optical system path in the reverse direction, and returns to the optical branching element 110. The return light of the measurement light incident on the optical branching element 110 passes through the fiber 126 and is incident on the optical branching element 128.

On the other hand, the reference light branched by the optical branching element 110 is guided to the reference arm via the fiber 119a, the polarization controller 150, and the fiber 119b. A collimator 120, a dispersion compensation glass 122, an ND filter 123, and a collimator 124 are arranged on the reference arm in order from the end portion 119c of the fiber 119b. The reference light emitted from the end 119c is collimated by the collimator 120. The polarization controller 150 is used to change the polarization of the reference light to a desired polarization state. The reference light, which is regarded as parallel light, is guided to the fiber end 127a of the fiber 127 via the dispersion compensation glass 122, the ND filter 123, and the collimator 124.

One end of the collimator lens 124 and the fiber 127 is fixed on the coherence gate stage 125, and the device control unit 145 drives the collimator lens 124 in the optical axis direction in response to a difference in the axial length of the subject. Be controlled. As a result, the optical path length of the reference light can be changed, and the optical path length difference between the optical path length of the measurement light and the optical path length of the reference light can be changed in order to obtain the interference light. Although the case where the optical path length of the reference light is changed is illustrated here, the optical path length of the measurement light may be changed as long as the optical path length difference between the optical path of the measurement light and the optical path of the reference light can be changed. Further, although the example in which the optical axis of the fiber 119b and the optical axis of the fiber 127 face each other in a straight line has been described, a mirror may be arranged in the optical path to bend the optical path.

The reference light that has passed through the fiber 127 is incident on the optical branching element 128. In the optical branching element 128, the return light of the measurement light and the reference light are divided again. The time-divisioned light has a phase inversion to each other. The return light and the reference light of the divided measurement light are incident on one input port of the detector 141 through the fiber 129. Further, the return light and the reference light of the other divided measurement light are incident on the other input port of the detector 141 through the fiber 130. At this time, the return lights of the measurement lights incident on the different input ports of the detector 141 are out of phase with each other. Further, similarly to the return light of the measurement light, the phases of the reference lights incident on the different input ports of the detector 141 are also inverted from each other. As a result, in the interference light observed by the detector 141, the phases of the interference fringes (signals in which the signal strength appears in strength along the wavelength direction) are inverted by different input ports.

The detector 141 is a differential detector, and when two interference signals having inverted phases are input, the DC component can be removed and only the interference component can be output. The interference signal, which is an electric signal from which the DC component detected by the detector 141 has been removed, is input to the signal processing unit 144, which will be described later.

(Control unit 143)
As described above, the control unit 143 includes a signal processing unit 144, a device control unit 145, a display unit 146, and a display control unit 149. As described above, the device control unit 145 controls the operation of each unit of the interference signal generation unit 100 such as the stage 117 and the coherence gate stage 125. The display control unit 149 receives the images and analysis results generated by the signal processing unit 144, and displays these images and the like on the display screen of the display unit 146. Here, the display unit 146 is, for example, a liquid crystal display.

The image data generated by the signal processing unit 144 may be transmitted to the display control unit 149 and then to the display unit 146 by wire or wirelessly. Further, in the present embodiment, the display unit 146 and the like are included in the control unit 143, but the present invention is not limited to this, and the display unit 146 and the like may be provided separately from the control unit 143, for example, an example of a device that can be carried by the user. You may use the tablet which is. In this case, it is preferable that the display unit 146 is equipped with a touch panel function so that the display position of the image can be moved, enlarged / reduced, and the displayed image can be changed on the touch panel. Further, the hatch panel function of the display unit 146 may be used as an input device to enable input operations such as changing a threshold value and specifying an alternative value, which will be described later. Further, the control unit 143 can be configured integrally with the interference signal generation unit 100, or can be partially configured as a separate body. In addition, other functions such as SLO described above that can perform imaging and examination of the eye to be inspected may be added.

Here, the configuration of the signal processing unit 144 according to the present embodiment will be described with reference to FIG. The signal processing unit 144 includes a signal acquisition unit 147 and an image processing unit 148. The signal acquisition unit 147 acquires an interference signal from the detector 141, and performs correction processing described later on the acquired interference signal. An image generation unit 221 and an analysis unit 222 are arranged in the image processing unit 148. The image generation unit 221 has a function of generating a luminance image from an electric signal sent from the signal acquisition unit 147. The analysis unit 222 has an analysis function such as generating layer information (segmentation of the retina) from a luminance image, and a function of generating information for visualizing the analysis result.

The signal acquisition unit 147 includes an acquisition unit 211, a storage unit 212, a threshold value setting unit 213, an abnormality determination unit 214, and a correction unit 215. The acquisition unit 211 acquires the interference signal output from the detector 141 according to the k-clock obtained from the k-clock generation unit 154. In the present embodiment, the interference signal obtained by the detector 141 detecting the interference light is converted from an analog signal to a digital signal based on the k-clock by the acquisition unit 211 that functions as an A / D conversion unit. The interference signal acquired by the acquisition unit 211 may be digital or analog, and when an analog signal is acquired, it may be converted into a digital signal by, for example, the correction unit 215. Further, in the present embodiment, the acquisition unit 211 interferes at equal light frequency (equal wave number) intervals based on the k-block synchronized with the sweep of the wave number of the emitted light generated based on the emitted light of the light source 101. I'm getting a signal. It should be noted that this k-clock can be generated by using a configuration provided in the light source 101 instead of the illustrated configuration.

The storage unit 212 stores the interference signal acquired by the acquisition unit 211. The threshold value setting unit 213 sets the threshold value used for the threshold value processing described later. The threshold value can be appropriately read and set from, for example, a table created in correspondence with the model number of the light source 101, shooting conditions, and the like and stored in the storage unit 212. The storage unit 212 stores the interference signal acquired by the acquisition unit 211. For example, in the present embodiment, the abnormality determination unit 214 compares the interference signal acquired by the acquisition unit 211 with the threshold value set by the threshold value setting unit 213, and whether the obtained interference signal includes an abnormal value. Judge whether or not. When the abnormality determination unit 214 determines that the interference signal includes an abnormal value, the correction unit 215 changes the interference signal to an appropriate value and generates an interference signal with reduced noise.

In addition, the acquisition unit 211 can acquire various images such as tomographic data generated by the image generation unit 221, a two-dimensional tomographic image, a three-dimensional tomographic image, a motion contrast image, and an En-Face image. Here, the tomographic data is data including information on the tomography of the object to be inspected, a signal obtained by subjecting the interference signal by OCT to Fourier transform, a signal obtained by subjecting the signal to arbitrary processing, and a tomographic image based on these. Etc. are included.

Further, the acquisition unit 211 includes a group of shooting conditions (for example, shooting date / time, shooting part name, shooting area, shooting angle of view, shooting method, image resolution and gradation, image pixel size, and image filter) of the image to be image-processed. , And information about the image data format, etc.). The imaging condition group is not limited to the illustrated one. Further, the imaging condition group does not have to include all of the illustrated ones, and may include some of them. Specifically, the acquisition unit 211 acquires the imaging conditions of the SS-OCT device when the image is captured. In addition, the acquisition unit 211 can also acquire a group of shooting conditions stored in the data structure constituting the image according to the data format of the image. When the shooting conditions are not stored in the image data structure, the acquisition unit 211 can also acquire the shooting information group including the shooting condition group from a storage device or the like that separately stores the shooting conditions. In addition, the acquisition unit 211 can also acquire information for identifying the eye to be inspected, such as the subject identification number, from an input unit (not shown) or the like. The acquisition unit 211 may acquire various data, various images, and various information from the storage unit 212 and other devices (not shown) connected to the control unit 143. The acquisition unit 211 can store various acquired data and images in the storage unit 212.

The storage unit 212 stores the information, conditions, etc. acquired by the acquisition unit 211 described above, the image obtained by the image processing unit 148, the shooting conditions at the time of image shooting, and the like. In addition, the storage unit 212 contains information, imaging parameters, images related to the eye to be inspected, such as the attributes of the subject (name, age, etc.) and measurement results (axial length, intraocular pressure, etc.) acquired using other inspection equipment. Analysis parameters and parameters set by the operator can be stored. Note that these images and information may be stored in an external storage device (not shown). Further, the storage unit 212 can also store a program or the like for fulfilling the functions of each component of the control unit 143 by being executed by the processor.

The control unit 143 may be configured by using, for example, a general-purpose computer. The control unit 143 may be configured by using a dedicated computer of the SS-OCT apparatus. The control unit 143 includes a storage medium including a CPU (Central Processing Unit) and an MPU (Micro Processing Unit) (not shown), and a memory such as an optical disk and a ROM (Read Only Memory). Each component of the control unit 143 other than the storage unit 212 may be configured by a software module executed by a processor such as a CPU or MPU. In addition, each component may be composed of a circuit that performs a specific function such as an ASIC, an independent device, or the like. The storage unit 212 may be configured by any storage medium such as an optical disk or a memory.

The control unit 143 may have one processor such as a CPU and a plurality of storage media such as a ROM. Therefore, each component of the control unit 143 functions when at least one or more processors and at least one storage medium are connected and at least one or more processors execute a program stored in at least one storage medium. It may be configured to do so. The processor is not limited to the CPU and MPU, and may be a GPU (Graphics Processing Unit) or the like.

(Scanning of measurement light)
In the following description, the process of acquiring information in the depth direction (information about a tomography, A scan data) of an arbitrary point in the fundus Er of the eye to be inspected 118 is referred to as A scan. For example, by scanning the fundus Er with the measurement light in the arbitrary direction with the galvano scanner 114 so that this one point is continuous in an arbitrary direction, the two-dimensional tomography of the fundus Er is performed in the direction orthogonal to the A scan. Information is available. The process of acquiring such two-dimensional information is referred to as B scan, and the scanning direction of the measurement light is referred to as B scan direction. Further, the obtained image is referred to as a B-scan image. Further, a process of scanning the measurement light in a direction orthogonal to both the A scan direction (depth direction) and the B scan direction to acquire three-dimensional tomographic information is referred to as C scan. Further, the obtained image is referred to as a C-scan image.

When a two-dimensional raster scan is performed in the bottom surface of the eye when acquiring a three-dimensional tomographic image from such three-dimensional tom information, the high-speed scanning direction is generally regarded as the B scan direction, and the B scan is the orthogonal direction thereof. The low-speed scanning direction in which scanning is performed so as to line up with each other is referred to as a C scanning direction. A two-dimensional tomographic image can be obtained by performing A scan and B scan, and a three-dimensional tomographic image can be obtained by performing A scan, B scan and C scan.

The galvano scanner 114 is composed of the above-mentioned pair of deflection mirrors in which the axes of rotation are arranged so as to be orthogonal to each other. In the present embodiment, one deflection mirror scans the measurement light in the X-axis direction, and the other deflection mirror scans the measurement light in the Y-axis direction. Further, the line-shaped scanning directions such as the B scan and the C scan do not have to coincide with the X-axis and the Y-axis of the galvano scanner 114. The scanning directions of the B scan and the C scan can be appropriately determined according to the two-dimensional tomographic image or the three-dimensional tomographic image to be imaged. However, in general, when performing raster scanning, raster scanning is often performed in the direction of the nasal ear and in the direction orthogonal to it.

(Generation of bright lines)
Next, the method of signal acquisition in the present embodiment and the possible causes of emission lines will be described with reference to FIGS. 3 and 4. The k-clock generation unit 154 generates a k-clock signal based on the light guided through the fiber 153. In this embodiment, a Mach-Zehnder interferometer was used to generate the k-clock signal. By adjusting the optical path length difference between the two arms of the Mach-Zehnder interferometer, it is possible to adjust the wavenumber interval of the k-clock. The larger the optical path length difference, the narrower the wavenumber interval of the k-clock, and the tomographic image up to a deeper position can be acquired. The k-clock can be generated not only by the Mach-Zehnder interferometer, but also by using an interferometer such as a Fabry-Perot interferometer that can generate an interferometer at equal wavenumber intervals.

The acquisition unit 211 receives the k-clock signal from the k-clock generation unit 154 via the signal line 160. FIG. 3 schematically shows the relationship between the time and the change in signal strength in the received k-clock. FIG. 3A shows an example of k-clock for 5 cycles, which is normally received when the signal processing unit 144 is operating without disturbance. The acquisition unit 211 samples the data in the interference signal at points 302-1 to 302-5 where the k-clock signal 301 crosses upward to zero. In this case, the interference signal is composed of a data string acquired from the interference light at the timing corresponding to the zero cross of the k-clock. That is, one wavelength sweep is performed from one zero cross to the next zero cross, and acquisition of interference signals (plurality of data) constituting spectral information corresponding to 1A scan is started from one zero cross. The sampled interference signal is subjected to threshold processing and window function processing by the image processing unit 148, and then Fourier transformed. The details of the processing flow will be described later.

In k-clock, the time interval is suddenly disturbed, and the zero cross interval may be narrowed or widened. FIG. 3B is an example in which such a k-clock signal 311 is suddenly disturbed. Each of the data sequences constituting the interference signal is sampled at the upward zero crossing points 312-13-12-5. However, in the illustrated example, the interval between the zero cross points 312-2 and 312-3 is narrow, and a high frequency clock signal is input in this time zone.

Normally, the input band of the clock signal of the A / D converter is selected so as to be used with a margin. In this embodiment, an A / D converter having a band 1.4 times that of the input clock signal is used. However, as illustrated in FIG. 3B, when a clock signal exceeding the upper limit of the input band is input due to sudden disturbance of k-clock, the sampled signal becomes an indefinite value. As a result, in the present embodiment, a large absolute value (abnormal value) such as −20488 is output from the acquisition unit 211 in the 12-bit digital data. In this embodiment, an A / D converter is used to acquire the interference signal. For example, the A / D converter is arranged on the substrate and is configured to be inserted into a PC or the like, so-called A / D conversion. A board may be used. Further, the A / D converter may be configured as one module included in the control unit 143, and it is desirable that the A / D converter is grasped as the A / D converter in the present invention.

Next, in the data string constituting the actually acquired interference signal, what kind of mode the abnormal value shows will be described with reference to the figure. FIG. 4 shows a part of the interference signal (spectral information) acquired by the acquisition unit 211 in the 1A scan. In the figure, the horizontal axis shows the order of acquisition (data number) of the data included in the spectral information acquired in the 1A scan, and the vertical axis shows the intensity (signal intensity) of each data. In reality, each data is indicated by a point, but in order to make it easier to understand the change in intensity, the individual points are connected by a straight line and shown as one interference signal indicating a specific waveform.

The interference signal 401 shown in FIG. 4 includes data 402 indicating an abnormal value whose value has changed significantly due to the disturbance of k-clock. Data 402 exemplifies the above-mentioned output value of 2048, which greatly exceeds the threshold value 403 described later as an absolute value. When the interference signal 401 is Fourier transformed, the data 402 acts like a delta function, and the interference signal 401 is converted into a data string (spectral information) having a substantially uniform large value. That is, the signal intensities indicated at each position in the depth direction of the eye to be inspected all have the same value indicating a large absolute value. Therefore, when a tomographic image is generated from a B scan including an A scan in which such an interference signal 401 is obtained, the data sequence has a noise pattern appearing as a emission line running in the vertical direction (depth direction) in the tomographic image. (See the emission line 611 in FIG. 6 (a)). In the present embodiment, by detecting the existence of data indicating an abnormal value included in the acquired spectral information and changing the abnormal value to an alternative value, noise appearing as such a bright line running in the vertical direction in the tomographic image. Reduce patterns.

(Signal processing)
Next, the method of processing the interference signal in the present invention will be described with reference to the flowchart shown in FIG. In the actual image generation, first, the acquisition unit 211 acquires the interference signal obtained from the detector 141 via the fundus Er (step S501). Further, for example, the device control unit 145 controls the galvano scanner 114 to obtain a state in which the return light of the measurement light from the eye to be inspected 118 does not occur, and in that state, the interference signal obtained from the detector 141 is transmitted to the background. The acquisition unit 211 acquires the signal as a signal (step S502).

In the next step S503, the abnormality determination unit 214 determines whether or not there is an abnormality based on the threshold value 403 (see FIG. 4) stored in advance in the storage unit 212. That is, the abnormality determination unit 214 determines whether or not the data exceeding the threshold value 403 is included in each of the interference signal and the background signal. When it is determined that there is an abnormality (including data exceeding the threshold value), the correction unit 215 changes the data with an alternative value. In the present embodiment, the threshold value is set to 1000, and the data in which the absolute value of the interference signal exceeds the threshold value is determined to be an abnormal value. Further, by using 0 as the alternative value, the abnormal value is changed to 0. By performing the threshold value processing not only on the interference signal but also on the background signal, it is possible to preferably perform the FPN removal processing described later.

After the interference signal and the background signal whose abnormal values have been corrected by the above processing, the image processing unit 148 performs an image generation process. After the threshold value processing, the image generation unit 221 applies a window function to the interference signal and the background signal (step S504). In this embodiment, a cosine taper window is used as the window function.

Next, the image generation unit 221 performs a Fourier transform on the interference signal and the background signal (step S505). The image generation unit 221 uses the phase information calculated from the background signal after the Fourier transform to correct the phase of the interference signal after the Fourier transform. Further, the image generation unit 221 further subtracts the background signal after the Fourier transform from the interference signal after the Fourier transform and the phase correction, for example, and performs a so-called FPN (fixed pattern noise) removal process (step). S506). As the FPN removal method, various known methods such as subtracting the interference signals from each other, such as subtracting the background signal after the abnormal value correction from the interference signal after the abnormal value correction, can also be applied. .. In step S507, the absolute value of the converted data obtained by the image generation unit 221 is calculated, and in step S508, the folded image is removed. By the above processing, it is possible to obtain a tomographic image in which the emission lines running in the vertical direction are reduced as described above.

FIG. 6A shows an example of a tomographic image in which the fundus Er of the eye to be inspected 118 is the subject of imaging and the tomographic image is obtained when the present invention is not applied and when the present invention is applied. The tomographic image 601 shown in FIG. 6A is an example in which the above-mentioned k-clock disorder occurs but the present invention is not applied. In addition to the image of the retina 610, a streak-shaped emission line 611 running in the vertical direction is provided. It is happening. The vertical streak-shaped emission line 611 shows an absolute value in which the signal intensities at each position in the depth direction of the eye to be inspected are all large by Fourier transform due to the existence of data showing an abnormal value such as the spectral information shown in FIG. It occurs when it is converted to the same value. On the other hand, the tomographic image 602 shown in FIG. 6B is a tomographic image generated by using the same interference signal as the tomographic image 601. However, in the case where the present invention is applied, the emission line is removed and the retina is removed. Only 610 images are displayed.

The image generation unit 221 may execute further processing using a tomographic image in which the emission lines running vertically in the tomographic image are reduced, or data constituting the tomographic image. For example, the image generation unit 221 executes a process of aligning each of a plurality of B-scan images obtained from the same scanning line, adding and averaging these B-scan images to generate a tomographic image with better image quality. May be good. In this case, for example, a reference tomographic image is determined from a plurality of tomographic images, and a characteristic site in the tomographic image is extracted as a region of interest. Then, information on the displacement of the region of interest between the different tomographic images to be aligned and the reference tomographic image in the XZ direction, the rotation direction, and the enlargement / reduction is acquired. Then, based on the acquired information on the misalignment, the tomographic image to be aligned is converted in the XZ direction, the rotation direction, and the enlargement / reduction, and the alignment with the reference tomographic image is executed. However, various other known methods can also be used for this alignment. Further, the image generation unit 221 uses a three-dimensional C-scan image, for example, a so-called EnFace image obtained by integrating image data in the depth direction of the retina in an arbitrary range defined by two reference planes. You may execute the process generated by. By generating an averaging image or an EnFace image using the tomographic image after the reduction of the emission line or the tomographic data thereof, an image that is easier to see than before and suitable for diagnosis can be obtained.

Further, the image generation unit 221 can also generate an OCTA image by using a tomographic image with reduced emission lines. OCTA is an angiography method that uses OCT and does not use a contrast medium. The OCTA image integrates three-dimensional motion contrast data acquired based on the depth information of the object to be inspected in the depth direction, and 2 It is generated by projecting onto a dimensional plane. The three-dimensional motion contrast data is data obtained by repeatedly photographing substantially the same portion of an object to be inspected and detecting a temporal change of the subject between the images. In addition, substantially the same place means the position which is the same to the extent that it is permissible to generate the motion contrast data, and includes the place which is slightly deviated from the place which is exactly the same. The motion contrast data can be obtained by calculating, for example, the temporal change of the phase, vector, and intensity of the complex OCT signal from the difference, the ratio, the correlation, etc. between the B-scan images at substantially the same location after the alignment. .. In this case, the method used for obtaining the tomographic image by the above-mentioned addition averaging can be similarly used for the alignment. The image generation unit 221 can also generate an OCTA EnFace image by integrating the three-dimensional data used for generating the OCTA image in an arbitrary range defined by the two reference planes.

The display control unit 149 causes the display unit 146 to display the image or the like generated by the image generation unit 221 as described above. At that time, it is also possible to perform a so-called preview display in which tomographic images with reduced emission lines are continuously generated in chronological order and displayed as a moving image on the display unit 146. It is also possible to generate and acquire a tomographic image in which the random noise floor is reduced at the time of so-called main shooting for storage in the storage unit 212. Further, the reduction process of the emission line described above may not be performed at the time of preview display, and this reduction process may be performed only at the time of main shooting.

In the present embodiment, the image processing unit 148 performs processing up to image generation, but the analysis unit 222 further analyzes the fundus Er of the eye to be inspected 118 using the generated image. Can also be done. Specifically, for example, a B-scan image can be used to extract each layer in the retina. In this case, each layer contained in the retina is specified, for example, based on the brightness profile in the depth direction. Further, in the case of generating an OCTA image, it is also possible to analyze the blood vessels in the retina based on the image or the data used for the image generation. Information obtained by this analysis includes, for example, diagnosis of blood vessel density, length of blood vessel of interest, existence of avascular region (NPA) such as FAZ (Faveal Avascular Zone), calculation of its area and circularity, and the like. Information is illustrated.

As described above, according to the present invention, even when the spectral information constituting the interference signal due to the sudden disturbance of k-clock includes data showing an abnormal value, a tomographic image It is possible to reduce the noise pattern running in the vertical direction inside. It should be noted that the cause of the abnormal value is not limited to the disturbance of the k-clock, but it is also conceivable that the cause is, for example, electromagnetic noise from the outside environment. Even in such a case, by applying the present invention, the effect of reducing the emission line can be similarly obtained.

[Second Embodiment]
In the first embodiment, it is determined whether or not there is data indicating an abnormal value in the acquired spectral information using a fixed threshold value set in advance. On the other hand, in this embodiment, a variable threshold value is used. By changing the threshold value according to the interference signal, for example, even if an emission line due to data that does not exceed the upper limit value of the input band and is difficult to determine as an abnormal value with a fixed threshold value occurs, the said. It is possible to reduce the emission line. Since the basic device configuration is the same as that of the first embodiment described above, the description thereof is omitted here.

FIG. 7 shows a plurality of data included in the spectral information in the same manner as in FIG. FIG. 7 (a) shows an interference signal obtained from, for example, an A scan performed near the center of the macula in the fundus Er, and FIG. 7 (b) is obtained from an A scan performed, for example, at a position away from the macula. It shows the interference signal. Since the degree of reflection / scattering with respect to the measured light differs depending on the part of the fundus, the interference signal 711 shown in FIG. 7 (b) has a small amplitude as a whole with respect to the interference signal 701 shown in FIG. 7 (a). ing. It is assumed that the scales of the strengths of the interference signals (scales on the vertical axis) in FIGS. 7 (a) and 7 (b) are the same here.

FIG. 7A is a diagram showing the same interference signal as in FIG. 4, and the data 702 showing the abnormal value in the interference signal 701 exceeds the threshold value 703 which is the upper limit value of the input band. On the other hand, the interference signal shown in FIG. 7B includes data 712 showing an abnormal value due to the disturbance of k-clock. This data 712 does not exceed the upper limit value (threshold value 703) shown in FIG. 7 (a). In such a case, if the same threshold value 703 as in the case of FIG. 7A is used, the interference signal including the data 712 is determined by the abnormality determination unit 214 as having no abnormality. On the contrary, when the threshold value 713 of FIG. 7B is used as the threshold value, the interference signal 701 shown in FIG. 7A contains data indicating a value exceeding the threshold value 713. In addition to 702, a plurality of them are included.

For example, it is conceivable that the data of the 1B scan or the data of the 1C scan includes a portion where the interference signal shown in FIG. 7A is obtained and a portion where the interference signal shown in FIG. 7B is obtained. In such a case, for example, by using the threshold value 713, the data 712 can be changed as an abnormal value, but at the same time, a plurality of data of the interference message 701 that should not be originally determined as an abnormal value are abnormal values. Is determined and the value is changed to an alternative value. In this case, an image suitable for diagnosis cannot be obtained. Further, when the threshold value 703 is used, the data 712 indicating the abnormal value is determined not to be an abnormal value. In the obtained tomographic image, a vertically running bright line remains at a position corresponding to the A scan shown in FIG. 7 (b).

An object of the present embodiment is to reduce the emission lines running vertically in the tomographic image when scanning the parts having different degrees of reflection / scattering with the measurement light to obtain a tomographic image. Hereinafter, a method of setting a threshold value that can suitably remove an abnormal value even in the above-mentioned situation will be described with reference to the flowchart shown in FIG. The flowchart shown in FIG. 8 is a process when the data acquired in one A scan is used.

First, the threshold value setting unit 213 statistically processes the interference signal data and acquires the peak value of the interference signal (step S801). At the same time, the acquisition of the rms (root mean square) value (step S802) is performed. Here, the peak value is a numerical value in which the absolute value of the amplitude of the interference signal is the maximum value, and when the data value exceeds the upper limit value of the input band as in the above-mentioned data 702, this upper limit value is regarded as the peak value. Become. Next, in step S803, the threshold value D is calculated by the threshold value setting unit 213. The threshold value D is a numerical value calculated based on the peak value or the rms value. For example, in the present embodiment, the threshold value D is a value obtained by multiplying the peak value by 0.5 and further adding the rms value. The coefficient 0.5 and the rms value used as the added value are examples used in this embodiment, and may be appropriately changed according to the degree of variation in the interference signal obtained from the eye to be inspected, the peak value, and the like. .. In this case, a numerical value input screen or the like for change may be displayed on the display screen of the display unit 146 so that the user can change the mathematical expression via the screen.

In the following step S804 and subsequent steps, the threshold value setting unit 213 sequentially compares the i-th data (index i) of the data in the interference signal with the threshold value. First, the data of the index i is acquired (step S804), and then the amplitude (signal strength) of the data and the threshold value D are compared by the abnormality determination unit 214 (step S805). When it is determined that the amplitude is larger than the threshold value D (yes), the threshold value setting unit 213 advances the flow to step S806, and stores the index i and the amplitude value in the storage unit 212. On the other hand, when the abnormality determination unit 214 determines that the peak value is smaller than the threshold value D, the threshold value setting unit 213 advances the flow to step S807.

In step S807, the abnormality determination unit 214 determines whether or not the comparison is completed for all the data included in the interference signal obtained in one A scan. If it is determined that the process is incomplete, the threshold value setting unit 213 advances the flow to step S808, adds 1 to the index i, and returns the flow to step S804. When it is determined that the comparison of all the data is completed, the threshold value setting unit 213 advances the flow to step S809.

The amplitude of the interference signal may change significantly even within one A scan. In this case, the value of the data that should not be abnormal in step S804 may be determined as an abnormal value. In order to avoid this, in the present embodiment, the abnormality determination unit 214 obtains the number of data n of the interference signal data having a large amplitude from the number of indexes of the data stored in the storage unit 212 which is considered to be an abnormality. Step S809). In the following step S810, the abnormality determination unit 214 further compares the predetermined threshold number N with the data number n.

In the present embodiment, 2048 data are acquired (as one interference signal) in 1A scan, and one B scan consists of 1024 A scans. Here, the occurrence rate of the abnormal value obtained empirically is such that one data showing the abnormal value is generated for about 140,000 A scans. This corresponds to the ratio of one vertical emission line to 130 tomographic images generated from the B scan. That is, it is unlikely that a plurality of data indicating an abnormal value is generated in one A scan, and if it is determined that a plurality of such data are generated, an interference signal having a large amplitude is an abnormal value. It is considered that there is no problem even if it is judged that the judgment is erroneous. Therefore, in the present embodiment, by setting the threshold number N = 2, it is possible to prevent data included in the interference signal that should not be determined as an abnormal value from being erroneously determined as an abnormal value. Can be done.

In step S810, when the abnormality determination unit 214 determines that the number of data n is less than the threshold number N, it can be determined that all the stored interference signal data (one data) are abnormal values. Therefore, the correction unit 215 advances the flow to step S811, and the correction unit 215 changes the value of the data indicating the abnormal value to an alternative value. On the other hand, when the abnormality determination unit 214 determines that the number of data n is equal to or greater than the threshold number N, the abnormality determination unit 214 rearranges the stored data in descending order of amplitude, and the data up to the threshold number N. (Only one data) is determined as an abnormal value. After that, the flow is advanced to step S812 by the correction unit 215, and the value of the data indicating an abnormal value is changed by the correction unit 215. By executing such processing, it is possible to prevent data that should be originally processed as a normal value from being erroneously determined as data indicating an abnormal value. Since the procedure leading to the subsequent tomographic image generation is the same as that of the first embodiment, detailed description here will be omitted.

The occurrence rate of abnormal values depends on the operating conditions of SS-OCT. For example, if the wavelength sweep speed of the light source 101 is increased or the wave number interval of the k-clock is narrowed, the probability of sudden k-clock disturbance increases. In this case, the abnormal value can be removed by setting the number N to a value larger than the threshold value 2. The faster the wavelength sweep speed, the stronger the resistance to movements such as fixation tremors of the eye 118 to be inspected, and the narrower the wave number interval, the deeper the tomographic image can be obtained.

Further, in the previous embodiments, 0 is substituted as the alternative value, but it is also possible to use the average value of the data adjacent to the alternative value. It is also possible to exclude only the value of the data for which an abnormal value is determined from all the data, obtain the average value of other data, and use this as an alternative value. Alternatively, the average value of the same number of data values before and after is obtained with the data showing the abnormal value sandwiched between them, and this can be used as an alternative value. This makes it possible to obtain a good tomographic image while removing the noise pattern.

Further, in the present embodiment, the peak value and the rms value are used for calculating the threshold value used when determining the abnormal value, but the method for calculating the threshold value is not limited to the above-mentioned method. For example, the median filter processing may be performed on the interference signal, and the data in which the difference between the filtered data and the original data is large may be determined as an abnormal value. Alternatively, an abnormal value is determined by a method of separating values that are far apart by known statistical processing, such as generating a histogram from the data contained in one interference signal and setting a threshold value using the histogram. You can also do it.

Further, in the case of the present embodiment, for example, in step S809, the number of data showing an abnormal value can be known. For example, when the threshold value 703 of FIG. 7 is set as the second threshold value and the number of data indicating a value exceeding the second threshold value is N or more, the inspector It is also possible to notify that there are more data showing abnormal values than in the normal state. Since the number of abnormal values is larger than the state, the user can know that the tomographic image has not been properly acquired, and that, for example, the existence of a disturbance factor that disturbs k-clock. Various formats such as sound of a buzzer, voice, or alarm display are assumed as the notification format, and the inspector can retake the tomographic image by performing this notification.

As described above, in the mode of occurrence of the abnormal value, data 702 and data 712 as abnormal values having different magnitudes are mixed when the amplitude of the abnormal value and the interference signal does not differ significantly or as shown in FIG. Such cases are also assumed. According to this embodiment, in any case, it is possible to reduce the emission line-like noise pattern running in the vertical direction in the tomographic image.

As described above, the optical interference tomographic imaging apparatus (SS-OCT apparatus) according to one aspect of the present invention includes a tunable light source (light source 101), a detection means (detector 141), and an A / D conversion unit (acquisition unit). 211) and a changing means (correction unit 215). The light emitted from the light source 101 is divided into a measurement light and a reference light. The measurement light is applied to the object to be inspected (fundus Er of the eye to be inspected 118), and the return light from the object to be inspected based on the measurement light is combined with the reference light to generate interference light. The detector 131 detects this interference light as a detection means. The A / D conversion unit analogizes the interference signal obtained from the interference light detected by the detector 141 based on the data acquisition clock signal (k-clock) obtained by using a part of the emitted light of the light source 101. Converts a signal to a digital signal. As a result, a plurality of data (1A scan data) constituting the spectrum information corresponding to the A scan of the inspected object can be obtained corresponding to one wavelength sweep of the light source 101. The changing means changes at least one of the data determined to be abnormal among the plurality of data included in the acquired spectrum information. More specifically, the value of the data determined to be abnormal is changed to another value. By arranging these configurations, the possibility that this interference signal constitutes a emission line is reduced, and in the tomographic image generated by using the interference signal, a emission line-like noise pattern (vertical streak-like artifact) running in the vertical direction is reduced. ) Can be reduced. The existence of abnormal data in a plurality of data can be determined by arranging a determination means (abnormality determination unit 214). The determination means determines whether or not there is data indicating an abnormal value (whether or not there is an abnormality) in the plurality of data included in the acquired spectrum information. In addition, the processing by each of the above-mentioned means corresponds to each step in the operation method of the optical interference tomographic imaging apparatus, which is executed by a computer or the like arranged in the optical interference tomographic imaging apparatus.

The above-mentioned determination means (abnormality determination unit 214) determines whether or not there is an abnormality based on the comparison between each value of the data included in the plurality of data and the threshold value. For the threshold value used by the determination means, for example, the upper limit value of the digital signal obtained from the value of the analog signal that can be converted by the A / D conversion unit (acquisition unit 211) is used. Although this threshold value may be a fixed value, it may be a moving value that is appropriately changed according to the interference signal. That is, the threshold value may be obtained by using each value of the data included in the plurality of data. Alternatively, the threshold value may be set statistically, for example, based on a histogram obtained from a plurality of data, or may be set using a peak value indicated by the data included in the plurality of data. Alternatively, the median filter processing may be performed on a plurality of data, and the value of the difference between the value after the median filter processing and the value before the processing may be used as the threshold value.

Also, as described in the second embodiment, the changing means can determine at least one data to be changed based on the number of data exceeding the threshold value. In addition, if there is a lot of data that exceeds the threshold value, it is possible that the interference signal has been acquired in an inappropriate state. In this case, for example, realignment or adjustment of the light source, etc. It is appropriate to improve the condition and acquire the interference signal. Therefore, a second threshold for reacquisition of the interference signal may be set for the number of thresholds. Then, when the number of data exceeding the threshold value exceeds the second threshold value, it is preferable to notify the examiner of the abnormality, and the optical interference tomographic imaging device is provided with a notification means for this purpose. It is desirable to prepare.

For example, 0 (zero) can be used as an alternative value used by the changing means to change the abnormal value (value of the data determined to be abnormal). Alternatively, as the alternative value, the average value of the values of the data before and after the data determined to be abnormal in the array of a plurality of data including the data determined to be abnormal can be used. Further, as the alternative value, the average value of the values of the remaining data obtained by excluding the data determined to be abnormal from a plurality of data including the data determined to be abnormal can also be used.

Further, the optical interference tomographic imaging apparatus according to one aspect of the present invention can be provided with an image generation means (image generation unit 221) for generating a tomographic image. The image generation unit can generate a tomographic image using the spectral information corresponding to a predetermined number of A scans obtained from the scan range (B scan line) of the measurement light on the object to be inspected. Alternatively, the image generation unit can generate a tomographic image using the spectrum information corresponding to a predetermined number of A scan data including the spectrum information in which at least one data is changed by the changing means.

In the actual image generation, the first spectrum information which is a measurement signal and the second spectrum information which is a background signal can be used. The first spectral information is obtained based on the interference light obtained by combining the return light obtained by irradiating the fundus Er with the measurement light and the reference light. Further, the second spectral information is obtained based on the interference light obtained by combining the return light and the reference light obtained without irradiating the fundus Er with the measurement light. In this case, the determination means determines whether or not there is an abnormality in each of the first spectrum information and the second spectrum information. The image generation means subtracts the amplitude signal obtained from the second spectral information from the amplitude signal obtained from the first spectral information, and generates a tomographic image using the obtained result (signal). When obtaining an amplitude signal based on the first spectrum information, the first spectrum information determined by the determination means to be normal, or at least one data determined to be abnormal is changed to the first spectrum. Any of the data will be used. Further, when obtaining an amplitude signal based on the second spectrum information, the second spectrum information determined by the determination means to be normal, or at least one data determined to be abnormal is changed. Any of the spectral information of is used. The subtraction process described above is not limited to the case where the amplitude signals are performed with each other, and the subtraction process may be performed between the spectral information. In this case, an amplitude signal is generated from the spectral information that is the result of the subtraction, and a tomographic image is generated based on the amplitude signal.

The image generation means is not limited to the generation of the tomographic image, and the generated tomographic image can be used for further processing such as generation of an image. The image generation means can generate, for example, a so-called additive average image. The averaging image is generated by aligning each of a plurality of tomographic images obtained from substantially the same location of the fundus Er and using the plurality of aligned tomographic images. A tomographic image with reduced noise and the like can be obtained by obtaining an added average value of the values of each pixel for a plurality of tomographic images and generating a tomographic image using the added average value. The image generation means can also generate an EnFace image from tomographic data constituting a plurality of tomographic images obtained from a predetermined region of the fundus Er. The Enface image is generated using the tomographic data included in a predetermined depth range of a sequence of tomographic data along the depth direction of the fundus Er. Further, the optical interference tomography apparatus according to one aspect of the present invention includes an analysis unit 222. The analysis unit 222 can analyze the obtained tomographic image and generate diagnostic data used by, for example, a doctor. For example, the analysis unit 222 extracts each layer of the retina of the fundus Er displayed on the generated tomographic image as an extraction means based on the tomographic data constituting the tomographic image.

[Other Embodiments]
In the above-described embodiment, the imaging target is the fundus of the eye, but the imaging target of the present invention is not limited to this, and for example, the anterior segment of the eye to be inspected may be the measurement target. In this case, by arranging a so-called adapter lens or the like that changes the focal position of the measurement light between the interference signal generation unit 100 and the eye to be inspected 118, a tomographic image of the anterior eye portion can be obtained without changing the above-described configuration. Can be done. Further, in the above-described embodiment, the case where the object to be inspected is an eye is described, but since the problem of the present invention can occur in SS-OCT in general, the present invention is applied to an object to be inspected such as skin and organs other than the eye. It is also possible to apply. In this case, the SS-OCT device has an aspect as a medical device such as an endoscope, other than as an imaging device for ophthalmology. Therefore, it is preferable that the present invention is grasped as one aspect of various SS-OCT devices (optical coherence tomography device), and the eye to be inspected is grasped as one aspect of the object to be inspected. Further, since the interference signal acquired by the SS-OCT device is processed, it can be grasped as an information processing device that processes the interference signal obtained from the SS-OCT device.

The present invention can also be achieved by configuring the device as follows. That is, a recording medium (or storage medium) on which a software program code (computer program) that realizes the functions of the above-described embodiment is recorded may be supplied to the system or device. Further, not only the mode of the recording medium but also a computer-readable recording medium may be used. Then, the computer (or CPU or MPU) of the system or device reads and executes the program code stored in the recording medium. In this case, the program code itself read from the recording medium realizes the function of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention. The embodiment can also be realized by a circuit (for example, an ASIC) that realizes one or more functions.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications are made within the scope of the gist of the present invention described in the claims.・ Can be changed.

100: Interference signal generation unit, 143: Control unit, 144: Signal processing unit, 147: Signal acquisition unit, 148: Image processing unit, 211: Acquisition unit, 212: Storage unit, 213: Threshold setting unit, 214: Abnormality judgment unit, 215: Correction unit

Claims (16)

The measurement light obtained by dividing the emission light from the tunable light source, and the return light based on the measurement light irradiated to the object to be inspected and the reference light obtained by dividing the emission light are combined. A detection means for detecting the interference light obtained
An A / D conversion unit that converts an interference signal obtained by detecting the interference light from an analog signal to a digital signal based on a clock signal obtained by using a part of the emitted light.
A changing means for changing at least one data determined to be abnormal among a plurality of data included in the spectrum information corresponding to the A scan of the interference signal obtained by the conversion.
An optical interference tomographic imaging apparatus characterized by comprising. The optical interference tomographic imaging apparatus according to claim 1, further comprising a determination means for determining whether or not abnormal data exists in a plurality of data included in the spectrum information. The second aspect of the present invention is characterized in that the determination means determines whether or not the abnormal data exists based on the comparison between the respective values of the data included in the plurality of data and the threshold value. The optical interference tomographic imaging apparatus described. The threshold value is characterized by being an upper limit value of a digital signal obtained from the values of analog signals that can be converted by the A / D converter, or a value obtained by using the values of each of the plurality of data. The optical interference tomographic imaging apparatus according to claim 3. The threshold value is a histogram obtained from the plurality of data, a peak value indicated by the plurality of data, or a value obtained by performing median filtering on the plurality of data, and a value after the median filter processing and a value before the processing. The optical interference tomographic imaging apparatus according to claim 3, wherein the difference is obtained. The optical interference fault according to any one of claims 3 to 5, wherein the changing means determines at least one data to be changed based on the number of data exceeding the threshold value. Imaging device. The optical interference tomographic imaging according to claim 6, further comprising a notification means for notifying the examiner of an abnormality when the number of data exceeding the threshold value exceeds the second threshold value. apparatus. The changing means sets the value of at least one data determined to be abnormal to zero, averaging the values of data before and after the at least one data determined to be abnormal in the array of the plurality of data. Claims 1 to 7, wherein the value or at least one data determined to be abnormal is changed to any one of the average value of the values of the remaining data excluded from the plurality of data. The optical interference tomographic imaging apparatus according to any one of the above items. The predetermined spectrum information including the spectrum information corresponding to a predetermined number of A scans obtained from the scanning range of the measurement light on the object to be inspected, or the spectrum information in which at least one of the data has been changed by the changing means. The optical interference tomographic imaging apparatus according to any one of claims 1 to 8, further comprising an image generation means for generating a tomographic image using spectral information corresponding to a number of A scan data. The spectrum information includes first spectrum information based on interference light obtained by combining the return light obtained by irradiating the object to be inspected with the measurement light and the reference light, and the measurement light. It includes the second spectral information based on the interference light obtained by combining the return light obtained without irradiating the object to be inspected with the reference light and the reference light.
From the first spectrum information or the amplitude signal obtained from the modified first spectrum information of at least one data determined to be abnormal, it is determined that the second spectrum information or abnormality is present. Any of claims 1 to 8, further comprising an image generating means for generating a tomographic image using the result of subtracting the amplitude signal obtained from the modified second spectral information of at least one data. The optical interference tomographic imaging apparatus according to item 1. The spectrum information includes first spectrum information based on interference light obtained by combining the return light obtained by irradiating the object to be inspected with the measurement light and the reference light, and the measurement light. It includes the second spectral information based on the interference light obtained by combining the return light obtained without irradiating the object to be inspected with the reference light and the reference light.
From the first spectral information in which at least one data determined to be abnormal is changed from the first spectral information or at least one data determined to be abnormal, the second spectral information or at least one data determined to be abnormal is obtained. The optical interference tomographic imaging apparatus according to any one of claims 1 to 8, further comprising an image generating means for generating a tomographic image using the result of subtracting the changed second spectral information. The image generation means aligns each of the plurality of generated tomographic images obtained from substantially the same location of the object to be inspected, and generates an averaging image using the plurality of aligned tomographic images. The optical interference tomographic imaging apparatus according to any one of claims 9 to 11. The image generating means is tomographic data constituting a plurality of generated tomographic images obtained from a predetermined region of the inspected object, and is a sequence of tomographic data along the depth direction of the inspected object. The optical interference tomographic imaging apparatus according to any one of claims 9 to 12, wherein an EnFace image is generated using tomographic data included in a predetermined depth range. The object to be inspected is an eye to be inspected.
Any of claims 9 to 13, further comprising an extraction means for extracting each layer of the retina of the eye to be inspected displayed on the generated tomographic image based on the tomographic data constituting the tomographic image. The optical interference tomographic imaging apparatus according to item 1. The measurement light obtained by dividing the emission light from the variable wavelength light source, and the return light based on the measurement light irradiated to the object to be inspected and the reference light obtained by dividing the emission light are combined. The detection means for detecting the interference light obtained above and the interference signal obtained by detecting the interference light are converted from an analog signal to a digital signal based on a clock signal obtained by using a part of the emitted light. A method of operating an optical coherence tomographic imaging device including an A / D conversion unit.
An optical interference fault including a step of changing at least one data determined to be abnormal among a plurality of data included in the spectral information corresponding to the A scan of the interference signal obtained by the conversion. How to operate the image pickup device. A program comprising causing a computer to execute each step of the operation method according to claim 15.

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