JP2020126071A - Optical coherence tomography device and optical coherence tomography computation program - Google Patents

Abstract

To obtain good motion contrast data.SOLUTION: The present invention comprises: first three-dimensional OCT data acquisition means for acquiring first three-dimensional OCT data having at least a two-frame OCT signal relating to each scan line of a preset two-dimensional scan range; second three-dimensional OCT data acquisition means for acquiring second three-dimensional OCT data having at least a two-frame OCT signal relating to the same scan line as the first three-dimensional OCT data acquisition means, after the first three-dimensional OCT data is acquired by the first three-dimensional OCT data acquisition means; and synthesis processing means for synthesizing first motion contrast data based on the first three-dimensional OCT data and second motion contrast data based on the second three-dimensional OCT data and thereby obtaining composite motion contrast data.SELECTED DRAWING: Figure 7

Description

The present disclosure relates to an optical coherence tomography apparatus and an optical coherence tomography calculation program for obtaining motion contrast data of a subject.

In recent years, a device for obtaining a motion contrast by applying the OCT technology has been proposed (for example, refer to Patent Document 1).

JP, 2005-131107, A

In the conventional OCT motion contrast data, there are cases where good motion contrast data cannot be acquired due to movement of the subject (for example, the eye), weak signals, and the like.

In view of the above problems, an object of the present disclosure is to provide an optical coherence tomography device and an optical coherence tomography calculation program that can obtain good motion contrast data.

In order to solve the above problems, the present disclosure is characterized by having the following configurations.

(1)
An OCT optical system for acquiring an OCT signal by the measurement light and the reference light applied to the eye to be inspected;
First three-dimensional OCT data acquisition means for acquiring first three-dimensional OCT data having OCT signals of at least two frames for each scan line of a preset two-dimensional scanning range,
After the first three-dimensional OCT data acquisition unit acquires the first three-dimensional OCT data, at least two frames of OCT signals are provided for each scan line that is the same as the first three-dimensional OCT data acquisition unit. Second three-dimensional OCT data acquisition means for acquiring second three-dimensional OCT data,
A combining process for obtaining combined motion contrast data by combining the first motion contrast data based on the first three-dimensional OCT data and the second motion contrast data based on the second three-dimensional OCT data Means and
It is characterized by including.
(2)
A first three-dimensional OCT data acquisition step of acquiring first three-dimensional OCT data having OCT signals of at least two frames for each scan line in a preset two-dimensional scanning range;
After the first three-dimensional OCT data is acquired by the first three-dimensional OCT data acquisition step, at least two frames of OCT signals are included for each scan line that is the same as in the first three-dimensional OCT data acquisition step. A second three-dimensional OCT data acquisition step of acquiring second three-dimensional OCT data;
A combining process for obtaining combined motion contrast data by combining the first motion contrast data based on the first three-dimensional OCT data and the second motion contrast data based on the second three-dimensional OCT data Steps,
Causes the computer to execute.

It is a block diagram explaining the composition of the optical coherence tomography device concerning this embodiment. It is a figure which shows the outline of the OCT optical system which concerns on this embodiment. It is an image figure of a fundus for explaining photography of this embodiment. It is a figure explaining the relationship of the acquisition operation of an OCT signal, and the acquisition operation of a front image. The flowchart of a determination process is shown. It is a figure explaining an example of change of a relation of acquisition operation of an OCT signal and acquisition operation of a front image. It is a figure which shows an example at the time of acquiring at least 8 OCT signals.

Hereinafter, one of typical embodiments will be described with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of the optical coherence tomography apparatus according to this embodiment. FIG. 2 is a schematic diagram illustrating the OCT optical system.

An optical coherence tomography apparatus (hereinafter, referred to as an OCT device) 1 processes a detection signal acquired by an OCT optical system (interference optical system) 100. In the present embodiment, the OCT device 1 observes the image captured by the OCT optical system 100 on the display means (for example, monitor) 75. For example, the OCT device 1 includes an OCT optical system, a CPU (control unit) 70, a mouse (operation unit) 76, a memory (storage unit) 72, and a monitor 75, and each unit is connected via a bus or the like. Electrically connected to the CPU 70. In the following description, the case where the fundus of the eye to be inspected is imaged by the OCT device 1 as the subject will be described as an example. Of course, the OCT device 1 can image various living bodies. For example, the ear, nose, various organs, etc. may be mentioned. Further, for example, the OCT device 1 may be a device that images the anterior segment of the eye to be examined.

The control unit 70 controls the operation of each unit based on an arithmetic program and various control programs stored in the memory 72 (details will be described later). As the control unit 70, the operation unit 76, the memory 72, and the monitor 75, an arithmetic processing unit, an input unit, a storage unit, and a display unit of a commercially available PC (personal computer) are used to install various programs on the commercially available PC. You may do it.

In addition, in the present embodiment, the OCT device 1 is described as an example in which the OCT optical system 100 and each unit are integrated, but the present invention is not limited thereto. For example, the OCT device 1 may not have the OCT optical system 100. In this case, the OCT device is connected to a separately provided OCT optical system or the like, receives an OCT signal or OCT image data, and performs various kinds of arithmetic processing based on the received information.

For example, in the present embodiment, the OCT optical system 100 includes the front observation optical system 200. Of course, the OCT optical system and the front observation optical system 200 may not be integrated. The OCT optical system 100 irradiates the fundus Ef with measurement light. The OCT optical system 100 detects the interference state between the measurement light reflected from the fundus Ef and the reference light by the light receiving element (detector 120). The OCT optical system 100 includes an irradiation position changing unit (for example, the optical scanner 108, the fixation target projecting unit 300) that changes the irradiation position of the measurement light on the fundus Ef in order to change the imaging position on the fundus Ef. The control unit 70 controls the operation of the irradiation position changing unit based on the set imaging position information, and acquires a tomographic image based on the light reception signal from the detector 120.

<OCT optical system>
The OCT optical system 100 will be described. The OCT optical system 100 has a device configuration of a so-called optical coherence tomography (OCT) for ophthalmology, and captures a tomographic image of the eye E to be inspected. The OCT optical system 100 splits the light emitted from the measurement light source 102 into measurement light (sample light) and reference light by a coupler (light splitter) 104. Then, the OCT optical system 100 guides the measurement light to the fundus Ef of the eye E by the measurement optical system 106 and guides the reference light to the reference optical system 110. After that, the detector 120 is caused to receive the interference light resulting from the combination of the measurement light reflected by the fundus Ef and the reference light.

The detector 120 detects an interference signal between the measurement light and the reference light. In the case of the Fourier domain OCT, the spectrum intensity (spectral interference signal) of the interference light is detected by the detector 120, and the complex OCT signal is acquired by the Fourier transform on the spectrum intensity data.

For example, in the Fourier domain OCT, the depth profile (A scan signal) in a predetermined range is acquired by calculating the absolute value of the amplitude in the complex OCT signal acquired by the Fourier transform on the spectrum intensity data. OCT image data (tomographic image data) is acquired by arranging the depth profiles of the measurement light scanned by the optical scanner 108 at each scanning position. Furthermore, three-dimensional OCT image data (three-dimensional tomographic image data) may be acquired by scanning the measurement light two-dimensionally. Also, from the three-dimensional OCT image data, an OCT front face (Enface) image (for example, an integrated image integrated in the depth direction, an integrated value of spectrum data at each XY position, and an XY position at a certain depth direction). Brightness data, retinal surface image, etc.) may be acquired.

Also, motion contrast data is acquired from at least two or more OCT signals at the same position (same site) at different times. That is, at least two or more complex OCT signals are analyzed to obtain the motion contrast data. For example, the functional OCT signal is obtained from the complex OCT signal. Functional OCT image data is acquired by arranging the functional OCT signals at each scanning position of the measurement light scanned by the optical scanner 108. Furthermore, three-dimensional functional OCT image data (three-dimensional motion contrast data) is acquired by two-dimensionally scanning the measurement light in the XY directions. Further, an OCT function front face (Enface) image (for example, Doppler front face (Enface) image, signal image data speckle variance front face image) is acquired from the three-dimensional function OCT image data. It should be noted that each image data may be image data or signal data. The details of the motion contrast data will be described later.

Examples of the Fourier domain OCT include Spectral-domain OCT (SD-OCT) and Swept-source OCT (SS-OCT). Further, for example, Time-domain OCT (TD-OCT) may be used. In the case of SD-OCT, a low coherent light source (broadband light source) is used as the light source 102, and the detector 120 is provided with a spectroscopic optical system (spectrometer) that separates the interference light into each frequency component (each wavelength component). .. The spectrometer includes, for example, a diffraction grating and a line sensor. In the case of SS-OCT, a wavelength scanning light source (wavelength variable light source) that changes the emission wavelength at high speed with time is used as the light source 102, and the detector 120 is provided with, for example, a single light receiving element. The light source 102 includes, for example, a light source, a fiber ring resonator, and a wavelength selection filter. Then, as the wavelength selection filter, for example, a combination of a diffraction grating and a polygon mirror and a Fabry-Perot etalon can be used.

The light emitted from the light source 102 is split by the coupler 104 into a measurement light beam and a reference light beam. Then, the measurement light beam is emitted into the air after passing through the optical fiber. The light flux is focused on the fundus Ef via the optical scanner 108 and other optical members of the measurement optical system 106. Then, the light reflected by the fundus Ef is returned to the optical fiber through the same optical path.

The optical scanner 108 scans the measurement light two-dimensionally (XY direction) on the fundus. The optical scanner 108 is arranged at a position substantially conjugate with the pupil. The optical scanner 108 is, for example, two galvanometer mirrors, and the reflection angle thereof is arbitrarily adjusted by the drive mechanism 50.

As a result, the light flux emitted from the light source 102 has its reflection (traveling) direction changed, and is scanned at an arbitrary position on the fundus. As a result, the imaging position on the fundus Ef is changed. The optical scanner 108 may have any configuration that deflects light. For example, in addition to a reflection mirror (galvano mirror, polygon mirror, resonant scanner), an acousto-optic element (AOM) that changes the traveling (deflection) direction of light is used.

The reference optical system 110 produces|generates the reference light combined with the reflected light acquired by reflection of the measurement light in the fundus Ef. The reference optical system 110 may be a Michelson type or a Mach-Zehnder type. The reference optical system 110 is formed by, for example, a reflective optical system (for example, a reference mirror), and reflects light from the coupler 104 back to the coupler 104 by being reflected by the reflective optical system and guides it to the detector 120. As another example, the reference optical system 110 is formed by a transmissive optical system (for example, an optical fiber) and guides the light from the coupler 104 to the detector 120 by transmitting the light without returning it.

The reference optical system 110 has a configuration that changes the optical path length difference between the measurement light and the reference light by moving an optical member in the reference light path. For example, the reference mirror is moved in the optical axis direction. The configuration for changing the optical path length difference may be arranged in the measurement optical path of the measurement optical system 106.

<Frontal observation optical system>
The front observation optical system 200 acquires front image data of an eye to be inspected. The front image data may be image data or signal data. For example, the front observation optical system 200 is provided to obtain a front image of the fundus oculi Ef. The front-viewing optical system 200 includes, for example, an optical scanner that two-dimensionally scans the measurement light (for example, infrared light) emitted from a light source on the fundus, and a confocal aperture that is arranged substantially conjugate with the fundus. And a second light receiving element for receiving the fundus reflected light via the device, and has a so-called ophthalmic scanning laser ophthalmoscope (SLO) device configuration.

The front observation optical system 200 may be of a so-called fundus camera type. In addition, for example, an infrared imaging optical system that images an object using infrared light may be used. Further, for example, the OCT optical system 100 may also serve as the front observation optical system 200. That is, the front image data (hereinafter, referred to as a front image) may be acquired using data forming a two-dimensionally obtained tomographic image (OCT front image).

The front observation optical system 200 may not be integrated with the OCT device or the like. In this case, for example, the front image data acquired by the separately provided front observation optical system 200 is received by the OCT device or the like.

<Fixed target projection unit>
The fixation target projection unit 300 has an optical system for guiding the line-of-sight direction of the eye E. The fixation target projection unit 300 has a fixation target to be presented to the eye E and can guide the eye E in a plurality of directions.

For example, the fixation target projection unit 300 has a visible light source that emits visible light, and changes the presentation position of the target in two dimensions. As a result, the line-of-sight direction is changed, and as a result, the imaging region is changed. For example, when the fixation target is presented in the same direction as the imaging optical axis, the center of the fundus is set as the imaging site. Further, when the fixation target is presented above the imaging optical axis, the upper part of the fundus is set as the imaging site. That is, the imaging region is changed according to the position of the optotype with respect to the imaging optical axis.

As the fixation target projection unit 300, for example, the fixation position is adjusted by the lighting position of the LEDs arranged in a matrix, the light from the light source is scanned by the optical scanner, and the fixation position is controlled by the lighting control of the light source. Various configurations such as a configuration for adjusting are conceivable. The fixation target projection unit 300 may be an internal fixation lamp type or an external fixation lamp type.

<Control part>
The control unit 70 includes a CPU (processor), a RAM, a ROM and the like. The CPU of the control unit 70 controls the entire apparatus such as each member of each configuration 100 to 300. The RAM temporarily stores various information. The ROM of the control unit 70 stores various programs for controlling the operation of the entire apparatus, initial values, and the like. The control unit 70 may be composed of a plurality of control units (that is, a plurality of processors).

A nonvolatile memory (storage unit) 72, an operation unit (control unit) 76, a display unit (monitor) 75, and the like are electrically connected to the control unit 70. The non-volatile memory (memory) 72 is a non-transitory storage medium that can retain stored contents even when power supply is cut off. For example, a hard disk drive, a flash ROM, the OCT device 1, and a USB memory detachably attached to the OCT optical system 100 can be used as the non-volatile memory 72. The memory 72 stores an imaging control program for controlling imaging of a front image and a tomographic image by the OCT optical system 100. In addition, the memory 72 stores a fundus analysis program that enables the OCT device 1 to be used. Further, in the memory 72, tomographic image data (OCT image data) on the scan line, three-dimensional tomographic image data (three-dimensional OCT image data), front image data (front fundus image data), and information on imaging positions of the tomographic image data. Various types of information regarding shooting are stored. Various operation instructions from the examiner are input to the operation unit 76.

The operation unit 76 outputs a signal according to the input operation instruction to the control unit 70. As the operation unit 74, for example, at least one of a mouse, a joystick, a keyboard, a touch panel, etc. may be used.

The monitor 75 may be a display mounted on the apparatus body or a display connected to the body. A display of a personal computer (hereinafter referred to as “PC”) may be used. Multiple displays may be used together. Further, the monitor 75 may be a touch panel. When the monitor 75 is a touch panel, the monitor 75 functions as an operation unit. Various images including tomographic image data and front image data captured by the OCT optical system 100 are displayed on the monitor 75.

<Signal processing method>
In the present embodiment, which describes an arithmetic processing method for obtaining motion contrast data from an OCT signal in the present embodiment, in order to obtain motion contrast data, the control unit 70 has at least two frames at different times at the same position. The interference signal (OCT signal) of is acquired.

In the present embodiment, the control unit 70 acquires motion contrast data (for example, functional OCT image data) from a plurality of OCT signals by performing processing related to the Doppler phase difference method and processing related to the vector difference method. As a method of processing the complex OCT signal, for example, a method of calculating the phase difference of the complex OCT signal, a method of calculating the vector difference of the complex OCT signal, a method of multiplying the phase difference and the vector difference of the complex OCT signal, and the like are considered. To be In this embodiment, a method of multiplying the phase difference and the vector difference will be described as an example.

First, the control unit 70 Fourier transforms the OCT signal acquired by the OCT optical system 100. The control unit 70 obtains a complex OCT signal by Fourier transform. The complex OCT signal includes a real number component and an imaginary number component.

To obtain the blood flow signal, it is necessary to compare images at the same position at different times. Therefore, the control unit 70 preferably aligns the images based on the image information. Image registration is the process of aligning multiple images of the same scene. As a cause of the displacement of the image, for example, the movement of the subject's eye during imaging (for example, involuntary eye movement, fine accommodation movement, pulsation, etc.) can be considered. Even if the positions of the frames are aligned, a phase shift may occur between the A scan lines in the same image. Therefore, it is preferable to perform the phase correction. Note that the registration and phase correction processing are for facilitating the processing of this embodiment and are not essential.

Next, the control unit 70 calculates the phase difference for the complex OCT signals acquired at at least two different times at the same position. The control unit 70 removes the random phase difference existing in the region where the S/N ratio (signal noise ratio) is low.

The control unit 70 removes a portion having a small phase difference. This is to remove a reflection signal from a high reflection part such as NFL (nerve fiber layer). This makes it easy to distinguish whether the signal is from the highly reflective portion or the signal from the blood vessel. In this embodiment, one frame for which the phase difference has been calculated is acquired. When there are a plurality of frames for which the phase difference has been calculated, it is better for the control unit 70 to remove the noise by subjecting the signals of the frames subjected to the above processing to arithmetic mean processing.

Next, the control unit 70 calculates the vector difference of the complex OCT signal. For example, the vector difference of the complex OCT signal detected by the OCT optical system is calculated. For example, the complex OCT signal can be represented as a vector on the complex plane. Therefore, two signals at the same position at different times are detected and the vector difference is calculated to generate contrast image data in the eye to be inspected. When the vector difference is imaged, for example, the image may be imaged based on phase information in addition to the magnitude of the difference. In this embodiment, one frame for which the vector difference is calculated is acquired. When there are a plurality of frames for which the vector difference is calculated, it is better that the control unit 70 removes noise by performing arithmetic mean processing on the signals of the frames subjected to the above processing.

The control unit 70 uses the calculation result of the phase difference as a filter for the calculation result of the vector difference. In the description of the present embodiment, “filtering” means, for example, weighting a certain numerical value. For example, the control unit 70 performs weighting by multiplying the calculation result of the vector difference by the calculation result of the phase difference. That is, the vector difference in the part with a small phase difference is weakened, and the vector difference in the part with a large phase difference is strengthened. As a result, the vector difference calculation result is weighted by the phase difference calculation result.

In the process of this embodiment, the control unit 70 multiplies the calculation result of the vector difference and the calculation result of the phase difference, for example. Thereby, the control unit 70 generates the functional OCT image data weighted by the calculation result of the phase difference.

By multiplying the calculation result of the vector difference and the calculation result of the phase difference, the demerits of the respective measurement methods can be canceled, and the image data of the blood vessel part can be acquired successfully.

The control unit 70 performs the above arithmetic processing for each scanning line and acquires the functional OCT image data for each scanning line. Then, by acquiring the functional OCT image data at these plural positions, it is possible to acquire the three-dimensional functional OCT front image data used as the pseudo angiographic image.

Note that, in the present embodiment, the control unit 70 has been described by taking as an example the configuration in which the calculation result of the vector difference and the calculation result of the phase difference are multiplied in order to acquire the motion contrast data, but the present invention is not limited to this. Not done. For example, the motion contrast data may be acquired using the calculation result of the vector difference. Further, for example, the motion contrast data may be acquired using the calculation result of the phase difference. Further, for example, the motion contrast data may be acquired by an amplitude difference result, Amplitude-decorrelation, Speckle variance, Phase variance, or the like.

It should be noted that in the present embodiment, the control unit 70 has been described as an example of the configuration in which the motion contrast data is acquired using the two OCT signals, but the configuration is not limited to this. The motion contrast data may be configured to be acquired by two or more OCT signals.

<Shooting operation>
Hereinafter, a series of imaging operations using the OCT device 1 will be described. Note that the following description will be given by taking the case of acquiring three-dimensional functional OCT image data as an example. Of course, the technique disclosed in the present invention can be applied when acquiring motion contrast data. For example, it can be applied to the case of acquiring the functional OCT signal, the case of acquiring the functional OCT image data, and the like.

First, the examiner instructs the subject to gaze at the fixation target of the fixation target projection unit 300, and then monitors the anterior segment observation image captured by the anterior segment observation camera (not shown) on the monitor 75. While viewing, the alignment operation is performed using the operation unit 76 (for example, a joystick (not shown)) so that the measurement optical axis comes to the center of the pupil of the eye to be inspected.

For example, when the alignment operation is completed, the control unit 70 controls the OCT optical system 100 to acquire the three-dimensional OCT image data corresponding to the set area, and also controls the front observation optical system 200 to generate the fundus image data. (Ocular fundus image data) is acquired. Then, the control unit 70 acquires three-dimensional OCT image data by the OCT optical system 100 and fundus image data by the front observation optical system 200 as needed. Note that the three-dimensional OCT image data includes image data in which A scan signals are two-dimensionally arranged in the XY directions, a three-dimensional graphic image, and the like.

The examiner uses the front image of the fundus of the front observation optical system 200 to set the scanning position. Then, when the image capturing start signal is output from the operation unit 76, the control unit 70 controls the operation of the optical scanner 108 to two-dimensionally scan the measurement light in the XY directions in the scanning range corresponding to the imaging region. Thus, the acquisition of the three-dimensional functional OCT image data is started. The scanning pattern may be, for example, a raster scan, a plurality of line scans, a circle shape, a refracted shape, a bent shape, or the like.

Hereinafter, the imaging operation using the OCT device 1 will be described. FIG. 3 is a schematic diagram for explaining shooting according to this embodiment. In the present embodiment, for example, when a signal for starting imaging is output, the control unit 70 acquires a plurality of OCT signals by the OCT optical system 100 in the first scanning region on the fundus of the eye to be examined. Further, the control unit 70 acquires the first front image by the front observation optical system 200 when acquiring the plurality of OCT signals by the OCT optical system 100 in the first scanning region. Then, the control unit 70 acquires the second front image by the front observation optical system 200 after the OCT optical system 100 acquires the plurality of OCT signals in the first scanning region. Next, the control unit 70 detects the positional deviation between the first front image and the second front image by image processing, and based on the detection result of the positional deviation, the plurality of OCT signals acquired in the first scanning region. The quality of is judged. The control unit 70 processes the plurality of OCT signals determined to be good and acquires the motion contrast data on the fundus of the eye to be examined.

<OCT signal acquisition>
This will be described in more detail. For example, when a signal to start imaging is output, the control unit 70 controls the driving of the optical scanner 108 to scan the fundus with the measurement light in order to acquire the three-dimensional functional OCT image data. For example, the control unit 70 controls the OCT optical system 100 in order to acquire the OCT signal at the set frame rate in response to the output of the signal for starting imaging. The frame rate for obtaining the OCT signal may or may not be changed before and after the start of the acquisition of the OCT signal.

The control unit 70 acquires a plurality of OCT signals in the same scanning area. The same scanning area does not have to be completely the same scanning area, and may be the same scanning area. Therefore, the control unit 70 repeats scanning in the same scanning region on the fundus. With such a plurality of scans, the control unit 70 can acquire a plurality of OCT signals in the same scan area.

For example, the control unit 70 uses the optical scanner 108 to scan the set first scanning region with the measurement light a plurality of times. In the present embodiment, a case where one scanning position (first scanning position) is set as the first scanning region will be described as an example. Of course, a plurality of scanning positions (for example, two scanning positions of the first scanning position and the second scanning position) may be set as the scanning region (details will be described later).

As shown in FIG. 3, for example, the control unit 70 scans the measurement light in the X direction along the first scanning position (scan line) S1. The scanning of the measurement light in any of the XY directions (for example, the X direction) in this way is called "B scan". Hereinafter, the OCT signal of one frame will be described as an OCT signal obtained by one B scan. The control unit 70 acquires the OCT signal detected by the detector 120 during scanning. In FIG. 3, the direction of the Z axis is the direction of the optical axis of the measurement light. The direction of the X axis is perpendicular to the Z axis and to the left and right. The direction of the Y axis is vertical to the Z axis and is the vertical direction.

When the first scan is completed, the control unit 70 performs the second scan at the same position as the first scan. For example, the control unit 70 scans the measurement light along the first scan line S1 shown in FIG. 3 and then scans the measurement light again. The control unit 70 acquires the OCT signal detected by the detector 120 during the second scanning. As a result, the control unit 70 can acquire OCT signals of two frames at the same scanning position but at different times. For example, the control unit 70 repeatedly acquires OCT signals at the same scanning position and acquires OCT signals of four frames. In addition, in the present embodiment, the configuration in which the OCT signals of four frames are acquired at the same scanning position will be described as an example, but the present invention is not limited to this. It is sufficient that the OCT signals of at least two frames are acquired at the same position. For example, the scanning at the same position may be repeated 8 times to obtain continuous 8 frames of OCT signals at different times, or the scanning at the same position may be repeated twice to obtain OCT signals of 2 frames at different times. May be acquired.

Note that if the OCT signals at the same position at different times can be acquired by one scan, the second scan need not be performed. For example, when scanning two measurement lights whose optical axes are deviated by a predetermined interval at one time, it is not necessary to scan a plurality of times, and it is only necessary to be able to acquire OCT signals at the same position in the subject at different times. That is, the same position does not need to be the completely the same position, and may be scanned at substantially the same position. When the two measuring lights are scanned at one time, an arbitrary blood flow velocity can be detected as a target by the interval between the two measuring lights.

<Front image acquisition>
On the other hand, the control unit 70 controls the front-viewing optical system 200 in order to repeat the front-view image at the set frame rate in response to the output of the signal for starting the shooting. The frame rate for obtaining the front image may be changed before or after the start of capturing, or may not be changed. In the embodiment, the frame rate when obtaining the OCT signal is four times the frame rate when obtaining the front image. That is, the OCT signal of 4 frames can be acquired in the time for acquiring the front image of 1 frame. In the present embodiment, the frame rate for acquiring the OCT signal and the frame rate for acquiring the front image are set so that at least two OCT signals are acquired while the front image of one frame is acquired. Just do it.

Further, for example, in the present embodiment, the relationship between the frame rate when obtaining the OCT signal and the frame rate when obtaining the front image is until the acquisition of a plurality of OCT signals in at least one scanning region is completed. It may be set such that the time required for the acquisition is less than or equal to the time required to complete the acquisition of one front image. For example, a frame rate for obtaining an OCT signal and a frame for obtaining a front image so that an OCT signal having a preset number of frames for obtaining motion contrast data in at least one scanning region is obtained. It is sufficient if the rate is set.

The control unit 70 repeats the front image acquisition operation while a plurality of OCT signals are acquired. With such control, the control unit 70 monitors the movement (movement) of the eye while the OCT signal is being acquired. For example, the control unit 70 receives the reflected light from the front of the fundus by the operation of the front observation optical system 200. The control unit 70 acquires the front image by processing the received reflected light. The control unit 70 causes the memory 72 to store the acquired front images at any time. As described above, the control unit 70 causes the front image and the OCT signal to be acquired in parallel.

<Parallel acquisition of OCT signal acquisition and front image acquisition>
FIG. 4 is a diagram illustrating the relationship between the OCT signal acquisition operation and the front image acquisition operation. In FIG. 4, the horizontal axis is the time axis (T). For example, the control unit 70 starts the acquisition of the first front image F1 in response to the output of the signal for starting shooting. When the acquisition of the first front image F1 is completed, the control unit 70 causes the memory 72 to store the first front image F1. In the present embodiment, the acquisition of the first front image (one-frame front image) F1 is completed when the time T1 has elapsed from the output timing (at the start of acquisition) T0 of the shooting start signal. To do. That is, it indicates that the time T1 has elapsed before the first front image F1 is acquired.

Next, the control unit 70 starts the acquisition of the second front image F2. Further, in parallel with the acquisition of the second front image F2, a plurality of OCT signals in the first scanning line S1 are acquired. In the present embodiment, the frame rate at the time of acquiring the OCT signal is four times the frame rate at the time of acquiring the front image, so that it is 4 before the acquisition of one frame of the front image. It is possible to acquire OCT signals for frames. For example, the control unit 70 controls the plurality of OCT signals O1, O2, O3, O4 in the first scan line S1 during the time T2 for acquiring the second front image F2 (time between the time T1 and the time T2). Can be obtained. When the acquisition of the second front image F2 is completed, the control unit 70 stores it in the memory 72.

<OCT signal quality judgment>
Next, the control unit 70 determines pass/fail (appropriateness) of the plurality of OCT signals O1, O2, O3, O4 acquired in the first scan line S1. FIG. 5 shows a flowchart of the determination process. In this embodiment, the quality of the OCT signal is determined in real time. The determination result is used to process a plurality of OCT signals and acquire motion contrast data.

For example, the control unit 70 performs the determination process each time a front image and a plurality of OCT signals are acquired (A1). For example, the control unit 70 detects the positional deviation between the acquired front images (A2). For example, in positional deviation detection, a front image at the time of acquisition of a plurality of OCT signals and after acquisition of a plurality of OCT signals is used. In this embodiment, the front image acquired before the acquisition of the plurality of OCT signals is used as the front image when the plurality of OCT signals is acquired. Of course, the front image at the time of acquiring the plurality of OCT signals is not limited to the front image acquired before the acquisition of the plurality of OCT. For example, the front image at the time of acquiring a plurality of OCT signals may be a front image acquired during the acquisition of a plurality of OCT. Note that in the present embodiment, the acquisition of a plurality of OCT signals is completed as the front image after the front images at the time of acquiring a plurality of OCT signals are acquired and the front images after the acquisition of the plurality of OCT signals are acquired. At the same time, the front image that has been acquired is used. Of course, the front image after the acquisition of the plurality of OCT signals is not limited to the front image that is acquired at the same time when the acquisition of the plurality of OCT signals is completed. For example, the front image after the acquisition of the plurality of OCT signals may be the front image acquired after the acquisition of the plurality of OCT signals (preferably immediately after the completion of the acquisition of the OCT signals).

For example, when the control unit 70 determines pass/fail of the plurality of OCT signals O1, O2, O3, O4 acquired in the first scan line S1, the control unit 70 may include the plurality of OCT signals O1, O2 in the first scan line S1. The first front image F1 before the acquisition of O3 and O4 and the second front image F2 that has been acquired at the same time as the acquisition of the plurality of OCT signals O1, O2, O3, and O4 are used. The control unit 70 detects the positional deviation between the first front image F1 and the second front image F2 by image processing. This makes it possible to detect the movement of the eye in the first scanning line S1 while the plurality of OCT signals O1, O2, O3, O4 are being acquired. That is, it is possible to detect whether or not the scanning position is deviated when the plurality of OCT signals O1, O2, O3, and O4 are acquired.

Next, for example, the control unit 70 determines pass/fail of the plurality of OCT signals O1, O2, O3, O4 acquired in the first scan line S1 based on the detection result of the positional deviation. For example, the control unit 70 determines whether the positional deviation (deviation amount) satisfies an allowable range (for example, a predetermined threshold value) (A3). For example, the control unit 70 determines that the plurality of OCT signals are good when the deviation amount satisfies the allowable range (YES in FIG. 5). Further, for example, the control unit 70 determines that the plurality of OCT signals are not good when the shift amount does not satisfy the allowable range (NO in FIG. 5 ).

For example, when it is determined that the plurality of OCT signals are good, the control unit 70 stores the plurality of OCT signals O1, O2, O3, O4 acquired in the first scanning line S1 in the memory 72 (A5). ). Next, the control unit 70 determines whether the shooting has been completed up to the final scan line Sn. That is, the control unit 70 determines whether or not the photographing in the entire scanning area (in the present embodiment, all the scanning lines) is completed (A6). When it is determined that the photographing on all scanning lines (all scanning positions) is completed, the control unit 70 ends the photographing (A9). If it is determined that the photographing on all scanning lines is not completed, the photographing is continued. For example, the control unit 70 sets the area for acquiring the plurality of OCT signals O1, O2, O3, O4 to the second scanning area (main scanning area) different from the first scanning area (first scanning line S1 in this embodiment). In the embodiment, the scanning line is changed to the second scanning line S2) (A7). That is, the control unit 70 ends the acquisition of the plurality of OCT signals O1, O2, O3, O4 in the first scanning line S1, and the plurality of OCT signals O1, O2, O3 acquired in the first scanning line S1. , O4 are stored in the memory 72. Then, the control unit 70 starts acquisition of the plurality of OCT signals O1, O2, O3, O4 (for example, refer to FIG. 4) in the second scanning line (second scanning position) S2 (A8).

For example, the control unit 70 changes the sub-scanning position (position in the Y direction) by controlling the optical scanner 108, and scans the measurement light in the main scanning direction (X direction) multiple times on the second scanning line S2. To do. The change of the scanning position is not limited to the Y direction. It may be changed in the X direction. This enables wide-angle shooting in the X direction. Of course, the configuration may be changed to both the X direction and the Y direction. As shown in FIG. 4, when acquiring the plurality of OCT signals O1, O2, O3, O4 in the second scan line S2, the control unit 70 performs the same operation as in the case of the first scan line S1. 3 The front image F3 is acquired. Then, the control unit 70 determines pass/fail of the plurality of OCT signals O1, O2, O3, O4 acquired in the second scanning line S2. In this case, for the determination, the acquisition of the second front image F2 and the acquisition of the plurality of OCT signals O1, O2, O3, O4 before the acquisition of the plurality of OCT signals O1, O2, O3, O4 in the second scan line S2 ( At the time T3), the third front image F3 that has been acquired at the same time is used. The control unit 70 detects the positional deviation between the second front image F2 and the third front image F3 by image processing, and based on the detection result of the positional deviation, the plurality of OCT signals O1 acquired in the second scanning line S2. , O2, O3, O4 is judged.

In addition, in the present embodiment, when determining the quality of a plurality of OCT signals, consecutively acquired front images (for example, the first front image F1 and the second front image F2) are used for the determination process. Although the configuration has been described as an example, the present invention is not limited to this. The front image for performing the OCT determination process is a front image before the acquisition of a plurality of OCT signals in the scan line and a front image acquired after the front image before the acquisition of the plurality of OCT signals. It suffices that the front image acquired after the OCT signal is acquired is used. For example, the first front image acquired at the start of shooting is set as the reference image. Then, at each scanning position, a plurality of OCT signals may be acquired, and the determination process may be performed based on the positional shift between the acquired front image and the reference image. More specifically, for example, a configuration in which the first front image F1 and the third front image F3 are used when determining the plurality of OCT signals O1, O2, O3, O4 in the second scanning line S2 can be mentioned. ..

Similar to the post-judgment operation in the first scan line S1, the control unit 70 obtains the plurality of OCT signals O1, O2, O3, and O4 when it is determined that the plurality of OCT signals are good. To the next scanning position (scan line). Similarly, the control unit 70 performs the determination process while acquiring the OCT signal and the front image, and scans each of the scanning lines up to the final scanning line Sn with the measurement light a plurality of times to scan each scanning line. , A plurality of OCT signals are acquired. That is, as shown in FIG. 3, the control unit 70 raster-scans (scans at the transverse position) the measurement light, and in each scan line (S1 to Sn), at least two frames different in time (in the present embodiment, in the present embodiment). 4 frames) of the OCT signal. Thereby, three-dimensional information of the fundus can be acquired. Even if the image capturing is not completed up to the final scanning position, the image capturing operation may be terminated at that point when the examiner operates to stop the image capturing. In this way, by determining the quality of the acquired plurality of OCT signals and changing the scanning region based on the judgment result, the plurality of OCT signals in each scanning region can be acquired more quickly.

On the other hand, for example, when it is determined that the plurality of OCT signals are not good, the control unit 70 reacquires the plurality of OCT signals in the first scan line S1. For example, the control unit 70 deletes the plurality of OCT signals O1, O2, O3, O4 and the first front image F1 acquired in the first scan line S1 (A11) and starts reacquisition. The control unit 70 controls the optical scanner 108 and corrects the scanning position based on the amount of deviation between the first front image F1 and the second front image F2 (A12). For example, the control unit 70 appropriately drives and controls the two galvanometer mirrors of the optical scanner 108 so that the deviation of the scanning position is corrected. After correcting the scanning position, the control unit 70 starts the acquisition of a plurality of OCT signals again in the first scanning line S1 (A13).

The control unit 70 acquires the front image after the scanning position correction before acquiring the plurality of OCT signals. That is, for example, a front image when reacquiring a plurality of OCT signals is acquired. After reacquiring the plurality of OCT signals, the control unit 70 is based on the front image at the time of reacquiring the plurality of OCT signals, the front image that has been acquired at the same time when the reacquisition of the plurality of OCT signals is completed, and the positional deviation. Then, the quality of the reacquired OCT signals is determined. Then, the control unit 70 determines, based on the determination result, whether to shift to the scan at the next scan position or to execute the scan at the same scan position again. In addition, when the OCT signal is not properly acquired a plurality of times, the control unit 70 displays an error (for example, a display prompting the resetting of the shooting position, a display prompting the readjustment of the shooting conditions), and the shooting ends. It may be allowed to. In this way, when a plurality of OCT signals cannot be acquired satisfactorily, a plurality of OCT signals are acquired again, so that a plurality of OCT signals in each scanning region can be acquired accurately.

<Acquisition of motion contrast data>
The control unit 70 processes the plurality of OCT signals determined to be good and acquires motion contrast data (in the present embodiment, acquires three-dimensional functional OCT image data) in the fundus of the eye to be examined. For example, when the control unit 70 shifts to the acquisition of a plurality of OCT signals in the next scan line, the control unit 70 performs the arithmetic processing of the plurality of OCT signals in each scan line acquired up to that point.

For example, the control unit 70 acquires a plurality of OCT signals in the first scanning line S1 and then scans a plurality of OCT signals (acquisition positions) from the first scanning line S1 to the second scanning line S2. To move. When starting the acquisition of the plurality of OCT signals in the second scan line S2, the control unit 70 starts the arithmetic processing of the acquired OCT signals in the first scan line S1. That is, the control unit 70 starts arithmetic processing of a plurality of OCT signals corresponding to the first scan line S1 while acquiring the OCT signal in the second scan line S2, and performs the first scan. The functional OCT image data in the line S1 is acquired. The control unit 70 performs the above process for each scanning line, and acquires the functional OCT image data for each scanning line while acquiring a plurality of OCT signals for each scanning line. Then, by acquiring the functional OCT image data at these plural positions (scan lines), a three-dimensional functional OCT front image that is a pseudo angiographic image (an image that can be used as an angiographic image for a purpose). Data can be acquired. As described above, by performing the calculation for acquiring the motion contrast data during the acquisition of the plurality of OCT signals, the motion contrast data can be acquired more quickly. In addition, in the present embodiment, when the process moves to the acquisition of a plurality of OCT signals in the next scanning line, the arithmetic processing of the plurality of OCT signals in each scanning line acquired up to that point is performed. But is not limited to this. For example, the control unit 70 may be configured to start the arithmetic processing of the plurality of OCT signals in each scanning line after acquiring the plurality of OCT signals in each scanning line.

As described above, based on the detection result of the positional deviation between the front image at the time of acquiring the plurality of OCT signals and the front image after the acquisition of the plurality of OCT signals in the predetermined scanning region, the image is acquired in the predetermined scanning region. By determining the quality of the plurality of OCT signals, it is possible to collectively determine the quality of the plurality of OCT signals acquired in the same region (the same scanning region). Therefore, it is possible to easily confirm whether or not the acquired plurality of OCT signals have been satisfactorily imaged. This makes it possible to easily and accurately acquire a plurality of OCT signals in the same scanning region.

<Transformation example>
Note that, in the present embodiment, the configuration is such that the acquisition of the plurality of OCT signals in the first scanning line S1 is started after the completion of acquisition of the first front image F1. However, the present invention is not limited to this. The configuration may be such that the acquisition of a plurality of OCT signals is started in parallel with the acquisition of the first front image F1 according to the output of the imaging start signal. In this case, when determining the quality of the plurality of OCT signals, the plurality of OCT signals acquired in parallel with the acquisition of the first front image F1 (acquired together with the start of imaging) are deleted, and the second front image is deleted. The determination process for a plurality of OCT signals is started from the plurality of OCT signals acquired in parallel during the acquisition of F2. For example, in the first scanning line S1, eight frames of OCT signals (four frames of OCT signals when acquiring the first front image F1 and four frames of OCT signals when acquiring the second front image F2) are acquired, The OCT signals for four frames when the first front image F1 is acquired are deleted.

In addition, in the present embodiment, the configuration in which the front image acquisition start timing and the plurality of OCT signal acquisition start timings in the predetermined scanning region are synchronized is taken as an example, but the present invention is not limited to this. The acquisition start operation of the plurality of OCT signals and the acquisition start operation of the front image in the predetermined scanning region may be asynchronous. For example, as shown in FIG. 6, while the first front image F1 is being acquired (for example, after half the time T1 has elapsed), acquisition of a plurality of OCT signals in the first scan line S1 is started. In this case, when acquiring the plurality of OCT signals O1, O2, O3, O4 in the first scanning line S1, the first front image F1 and the second front image F2 are acquired. That is, the determination process for the plurality of OCT signals O1, O2, O3, O4 in the first scanning line S1 is performed by using the positional shift between the first front image F1 and the second front image F2. The acquisition of the plurality of OCT signals O1, O2, O3, O4 in the second scan line S2 is started during the acquisition of the second front image F2 (for example, after half the time T2 has elapsed). The determination processing is performed on the plurality of OCT signals O1, O2, O3, O4 in the second scanning line S2 based on the second front image F2 and the third front image F3.

Note that in the present embodiment, based on the detection result of the positional deviation between the front image of one frame when a plurality of OCT signals are acquired in a predetermined scanning region and the front image of one frame after the acquisition of a plurality of OCT signals, the predetermined displacement is determined. However, the configuration is not limited to this. For example, when using a front observation optical system (for example, an infrared observation optical system) capable of acquiring a plurality of front images while acquiring a plurality of OCT signals, one front is selected from the plurality of front images. The determination process may be performed by selecting an image (for example, the latest front image). Further, for example, all the front images may be used to perform a plurality of OCT signal determination processes.

Note that, in the present embodiment, the case where one scanning position (first scanning position) is set as the first scanning region is taken as an example, but the present invention is not limited to this. A plurality of scanning positions may be set as the scanning area. For example, the measurement light may be set to be scanned at two scanning positions, that is, a first scanning position and a second scanning position, as the first scanning region. In this case, for example, when the frame rate for acquiring the front image and the OCT signal is the frame rate described in the present embodiment (when the frame rate for acquiring the OCT signal is four times the frame rate for acquiring the front image), 1 is set. While acquiring the front image of the frame, two frames of OCT signals are acquired at the first scanning position, and two frames of OCT signals are acquired at the second scanning position. That is, based on the detection result of the positional deviation between the front image of one frame at the time of acquiring a plurality of OCT signals in the predetermined scanning region (for example, the first scanning region) and the front image of one frame after the acquisition of the plurality of OCT signals. In the case of performing the determination by the above, the quality of the plurality of OCT signals at the two scanning positions can be collectively determined. Then, the control unit 70 processes each of the plurality of OCT signals acquired with respect to at least two (two in the present embodiment) scanning positions to obtain motion contrast data at each scanning position on the fundus of the eye to be examined. Get each. In this way, motion contrast data at a plurality of scanning positions is acquired during acquisition of a plurality of OCT signals and during detection of a single positional deviation between front images acquired after the acquisition of a plurality of OCT signals. Therefore, the shooting can be completed more quickly.

When a plurality of scanning positions are set as the scanning region, an arbitrary order can be used as the order of acquiring the plurality of OCT signals at each scanning position. For example, when the measurement light is set to be scanned at two scanning positions, that is, a first scanning position and a second scanning position, as the first scanning region, one frame at the first scanning position After acquiring the OCT signal, one frame of the OCT signal is acquired at the second scanning position. After that, one frame of OCT signal is acquired at the first scanning position, and one frame of OCT signal is acquired at the second scanning position. That is, the OCT signals of two frames are acquired at the respective scanning positions by alternately acquiring the OCT signals at the first scanning position and the second scanning position. Further, for example, when acquiring the OCT signal of one frame at the first scanning position and the second scanning position, the OCT signal at the first scanning position and the second scanning position in one scan are obtained. You may make it acquire the OCT signal in.

Note that, in the present embodiment, when it is determined that the OCT signal is not good, the imaging is performed again in the same scanning region, but the present invention is not limited to this. The configuration may be such that the OCT signal of the scan region determined to have a poor OCT signal is re-photographed after all the scan positions are completed. In addition, the examiner may be notified of the scanning region in which the OCT signal is not properly acquired. In this case, the examiner may execute re-imaging or the like based on the notified information.

In addition, in the present embodiment, the case where the front image of the fundus of the eye is acquired in order to detect the displacement of the fundus of the eye to be examined has been described as an example, but the present invention is not limited to this. For example, the front image of the anterior segment of the eye to be inspected may be captured, and the fundus may be captured based on the positional deviation between the front images of the anterior segment.

<Motion contrast data based on eight or more OCT signals at the same position (for example, see FIG. 7)>
The control unit 70 may acquire motion contrast data (hereinafter, abbreviated as MC data) based on eight or more OCT signals related to the same scanning position. By using eight or more OCT signals, it is possible to acquire high-quality MC data with reduced noise, as compared with the case where MC data is obtained based on four OCT signals. As a result, for example, a fine blood vessel structure of the eye to be examined can be favorably imaged, and a clinically useful image can be obtained. In addition, for example, analysis using MC data can be performed accurately.

When obtaining MC data based on four OCT signals, normally, three MC data are obtained by obtaining MC data between OCT signals that are temporally consecutive. The final MC data is obtained by combining the three MC data (for example, arithmetic mean).

On the other hand, for example, when at least four OCT signals are obtained twice and at least eight OCT signals are obtained, the control unit 70 causes the control unit 70 to obtain at least the first at least by obtaining MC data between the OCT signals that are temporally consecutive. You may acquire 1st at least 3 MC data by 4 OCT signals, and may acquire 2nd at least 3 MC data by 2nd at least 4 OCT signals. Further, the first at least three MC data and the second at least three MC data may be combined to obtain the final MC data. As a result, it is possible to obtain high-quality MC data with reduced noise, as compared with the case of obtaining MC data obtained by combining three MC data. Further, by obtaining at least four OCT signals three or more times and acquiring MC data based on at least twelve or more OCT signals, it is possible to further improve the image quality.

By performing scanning control (signal acquisition) in units of at least four OCT signals, it is faster to acquire at least four OCT signals than in the case of collectively acquiring at least eight OCT signals. As, for example, MC data in a state in which the movement of the subject's eye is stable is obtained in each scan control. Therefore, by acquiring the MC data based on the MC data in each scan control, for example, it is possible to acquire high-quality MC data in which the influence of eye movement is small and noise is reduced.

Further, for example, even when the MC data based on one of the at least four OCT signals could not be acquired well, this can be compensated by the MC data based on the other of the at least four OCT signals, and as a result, Good MC data can be acquired. In this case, since MC data based on the other of at least four OCT signals has at least three MC data, it is possible to secure a good image quality to some extent. In this case, of course, the control is not limited to the case where the scanning control is performed in units of four OCT signals, and as another example, the control unit 70 performs the scanning control in units of five or more OCT signals and performs five or more OCT signals. May be acquired multiple times (for example, twice or three times or more).

Optionally, if the scan control is performed in units of at least four OCT signals, the scan line may be changed in units of at least four OCT signals as a first example. As a second example, the scanning position may be corrected in units of at least four OCT signals. As a third example, the quality of the OCT signal may be determined in units of at least four OCT signals. As a fourth example, one frame of the front image of the observation optical system 200 may be acquired in units of at least four OCT signals, and this may be used to correct the scanning position and determine whether the image is good or bad. Good. As a fifth example, for example, a predetermined scan stop time may be provided every time at least four OCT signals are obtained. Of course, it is not always necessary to perform scanning control (signal acquisition) in units of at least four OCT signals, and eight or more OCT signals may be collectively acquired.

The OCT signal relating to the same scanning position may be, for example, an OCT signal having the same scanning position in B scan units (for example, B scan OCT data having the same scanning line), or a scanning position in A scan units. It may be the same OCT signal (for example, A scan OCT data at the same position as a result, although the scan lines for obtaining B scan are different).

The obtained MC data may be, for example, B-scan MC data obtained based on temporally different B-scan OCT signals. The MC data may be, for example, front MC data (enface MC data) or three-dimensional MC data obtained based on B scan MC data in different scan lines.

The OCT signals relating to the same scanning position do not necessarily have to be the same scanning position exactly, and may be the same scanning position within a range in which MC data can be obtained.

<Scan control>
When performing scanning control in units of four or more OCT signals, the control unit 70, for example, for the same scanning position, the first scanning for obtaining the first OCT signal group including the first at least four OCT signals. The control and the second scanning control for obtaining the second OCT signal group including the second at least four OCT signals may be performed.

In this case, the control unit 70 may perform, for example, first scan control for obtaining a first OCT signal group including at least four OCT signals that are temporally different at the same scan position. In addition, for example, the control unit 70, after acquiring the first OCT signal group by the first scanning control, includes the second OCT signal including at least four OCT signals that are temporally different at the same scanning position as the first OCT signal group. The second scan control may be performed to obtain the OCT signal group.

Further, the control unit 70 may scan each of the plurality of scanning lines with the measurement light at least four times as the first scanning control, for example. In addition, for example, the control unit 70 may scan each of the plurality of scanning lines with the measurement light at least four times as the second scanning control. In this case, for example, at least one of the first scan control and the second scan control may be performed on a plurality of scan lines that satisfy a preset two-dimensional scan range (for example, a rectangular area).

When scanning the plurality of scan lines with the measurement light, the control unit 70 causes the plurality of scan lines to be scanned with the measurement light at least four times respectively as the first scan control, and the plurality of scan lines are scanned in the first scan control. After performing the scanning of the scanning lines of, as the second scanning control, the measuring light may be scanned at least four times for each of the plurality of scanning lines. As a result, when the same scan line is scanned eight times or more, a time difference is provided between the first scan control and the second scan control, so that the first scan is affected by, for example, stagnation of red blood cells. Imaging of capillaries, which was difficult to image only during control, is also possible. In this case, the control unit 70 scans all the scan lines in the first scan control and then performs the second scan control after performing the scan for the plurality of scan lines in the first scan control. Alternatively, the second scan control may be performed after scanning some of the plurality of scan lines in the first scan control.

Further, when the measurement light is scanned with respect to a plurality of scanning lines, for example, the scanning direction and the scanning position of each scanning line may be the same in the first scanning control and the second scanning control. As a result, for example, it is possible to reliably perform alignment between the B scan MC data obtained by the first scan control and the second scan control, and it is possible to improve the image quality of the combined B scan MC data. Becomes

Further, the sub-scanning direction in the first scan control and the sub-scanning direction in the second scan control may be opposite directions. By performing the reciprocal scanning in the sub-scanning direction, the scanning is performed in the adjacent scanning lines after the first scanning control, so that the fluctuation of the OCT signal in the Z direction due to, for example, the curvature of the eye can be suppressed.

When scanning control is performed in units of four or more OCT signals, the time intervals for acquiring at least four OCT signals may be different between the first scanning control and the second scanning control. Thereby, for example, since the motion contrast signal can be detected regardless of the difference in blood flow velocity, it becomes possible to image a blood vessel which was difficult to be imaged only during the first scan control. In addition, by setting the same time interval when acquiring at least four OCT signals between the first scanning control and the second scanning control, it is possible to improve the image quality of images of the same quality.

In this case, the scanning speed, the scanning density, and the optical path lengths of the measurement light and the reference light when acquiring at least four OCT signals are not limited to the above but between the first scanning control and the second scanning control. At least one of the difference and the polarization state of the measurement light may be different.

When the optical path length difference is different, in the first scanning control, the control unit 70 is in a state in which the surface of the subject is placed on the back side from the depth position where the optical path lengths of the measurement light and the reference light match. The OCT signal may be acquired, and in the second scanning control, the OCT signal may be acquired in a state in which the back surface of the subject is arranged in front of the depth position where the optical path lengths of the measurement light and the reference light match. According to the above method, for example, when obtaining the fundus MC data, it is possible to combine the MC data suitable for the retina side and the MC data suitable for the choroid side. Of course, in the first scanning control, the control unit 70 acquires the OCT signal in a state in which the back surface of the subject is placed on the front side with respect to the depth position where the optical path lengths of the measurement light and the reference light match each other, and the second In the scanning control, the OCT signal may be acquired in a state in which the surface of the subject is placed on the back side from the depth position where the optical path lengths of the measurement light and the reference light match.

<Good/bad judgment of OCT signal group>
Optionally, the control unit 70 obtains the first determination for determining the quality of the first OCT signal group obtained in the first scanning control for each scanning line and the second determination for the second scanning control. At least one of the second determinations for determining the quality of the obtained second OCT signal group for each scan line may be performed. This makes it possible to avoid data acquisition by an OCT signal group that is unsuitable for MC data. The determination for each scanning line may be performed in units of one scanning line or in units of a plurality of scanning lines.

Furthermore, as a quality determination method, at least one of the positional deviation between the front images and the positional deviation between the OCT signals may be used. In this case, when the positional deviation satisfies the allowable range, the result is good, and when the positional deviation is outside the allowable range, the result may be negative. Note that the quality is not limited to the position shift determination, and the quality may be determined based on the image quality of the OCT signal or the image quality of MC data based on the OCT signal. The above-described embodiment may be used for the control based on the result of the quality determination in the first scanning control and the second scanning control.

Note that the determination conditions of the first determination and the second determination may be different, and by making the determination conditions different, for example, a desired OCT signal can be acquired. In this case, for example, by relaxing one of the determination conditions for the quality determination condition, the time and effort for re-acquisition can be saved, and the imaging time can be shortened. Even in this case, since at least four OCT signals are secured, a certain image quality can be secured. Of course, the determination conditions of the first determination and the second determination may be the same.

Note that the control unit 70 suspends the second scan control for the scan line for which the first OCT signal group is determined to be good by the first determination, regardless of the result of the second determination, and It may be possible to shift to the scan line of. Thereby, even when the second scanning control is performed, it is possible to reduce the lengthening of the photographing time. For example, in the second scan control, when obtaining the second OCT signal group on a certain scan line, the control unit 70 does not obtain a good result as a determination result, and even if the signal acquisition is not completed, After a lapse of time or a certain number of acquisitions, the next scan line may be started. Even in this case, since at least four OCT signals are secured, a certain image quality can be secured.

<Acquisition of third motion contrast data>
The control unit 70 controls the first MC data based on the first OCT signal group obtained by the first scanning control and the second MC data based on the second OCT signal group obtained by the second scanning control. The third MC data may be obtained based on the MC data of

In this case, the control unit 70 may obtain, as the third MC data, composite MC data based on the first MC data and the second MC data, for example. As the composite MC data, for example, arithmetic mean data may be obtained for each pixel. Further, as a method other than arithmetic averaging, the maximum value or mode value in the first MC data and the second MC data may be used for each pixel.

For example, the control unit 70 may combine the first at least three MC data under the first scanning control and the second at least three MC data under the second scanning control. In this case, the control unit 70 combines the first at least three MC data to obtain the first combined MC data, and at the same time combines the second at least three MC data into the second combined MC data. You may get Then, the control unit 70 may further perform a combining process on the first combined MC data and the second combined MC data to acquire the third MC data. The present invention is not limited to this, and the control unit 70 may integrally combine the first at least three MC data and the second at least three MC data to obtain the third MC data.

When obtaining the third MC data based on the first MC data and the second MC data, the control unit 70 obtains the first MC data, the second MC data, and the third scan control. Third MC data may be obtained based on the MC data. In the third scan control, the control unit 70 includes, for example, a third OCT signal group including at least four OCT signals temporally different at the same scan position as the first OCT signal group and the second OCT signal group. May be performed at least once.

Hereinafter, an example will be described as an example in which MC data is obtained based on eight or more OCT signals related to the same scanning position. It should be noted that the above description can be applied to other portions related to the photographing operation.

<Example>
In the previous stage of the imaging operation, the examiner may operate the operation unit 84 to set the number of frames of the OCT signal for acquiring the MC data. For example, at least 4 or 8 frames may be settable. Of course, 12 frames and 16 frames may also be settable.

<First scanning control>
In the first scanning control, the control unit 70 controls the optical scanner 108 to scan each scanning line with the measurement light at least four times. The control unit 70 acquires an OCT signal of at least 4 frames for each scan line.

For example, the control unit 70 scans the measurement light on the first scan line SL1 at least four times in the main scanning direction. The control unit 70 generates an OCT signal of at least 4 frames corresponding to the first scan line SL1 based on the output signal from the detector 120.

When the first scan line SL1 has been scanned at least four times, the control unit 70 controls the optical scanner 108 to scan the second scan line SL2 with the measurement light at least four times in the main scanning direction. The control unit 70 generates an OCT signal of at least 4 frames corresponding to the second scan line SL2 based on the output signal from the detector 120.

Similarly, the control unit 70 scans each of the third scan line SL3,..., The n−1th scan line SLn−1, and the nth scan line SLn with the measurement light at least four times, so that each scan line SL3. At least four frames of OCT signals corresponding to the scan lines are generated. That is, in the first scan control, each scan line is scanned at least four times.

The controller 70 stores in the memory 72 OCT signals of at least four frames corresponding to the scan lines SLi (i=1 to n) of the preset two-dimensional scan range SA. Each OCT signal may be stored as a still image in association with each scanning line. As a result, the first three-dimensional OCT data having the OCT signal of at least 4 frames is acquired for each scan line.

<Second scanning control>
After the end of the first scan control, the control unit 70 shifts to the second scan control. The transition from the first scan control to the second scan control may be automatically performed or may be performed based on a trigger signal from the operation unit 74. The automatic control is effective, for example, in that the time can be shortened, and the manual control is effective in that the state of the subject can be confirmed before the start of the second scanning control, which requires a relatively long time.

The control unit 70 may temporarily display the front MC data based on the OCT signal obtained by the first scanning control on the display unit 75 so that the examiner can confirm the quality of the image. With this, the examiner can finish the imaging in a short time without performing the second scanning control, and can perform additional control if necessary.

In the second scanning control, the control unit 70 controls the optical scanner 108 to scan each scanning line with the measurement light at least four times. The control unit 70 acquires an OCT signal of at least 4 frames for each scan line.

For example, the control unit 70 scans the measurement light in the main scanning direction at least four times in the nth scan line SLn. The control unit 70 generates the OCT signal of at least 4 frames corresponding to the nth scan line SLn based on the output signal from the detector 120.

When the scanning of the nth scan line SLn is completed at least four times, the control unit 70 controls the optical scanner 108 so that the measurement light is scanned at least 4 times in the main scanning direction in the (n-1)th scan line SLn-1. Scan twice. The control unit 70 generates an OCT signal of at least four frames corresponding to the (n-1)th scan line SLn-1 based on the output signal from the detector 120.

Similarly, the control unit 70 scans the n−th scanning line SLn−2,..., The second scanning line SL2, and the first scanning line SL1 with the measuring light at least four times, respectively. At least four frames of OCT signals corresponding to the scan lines are generated. That is, also in the second scan control, each scan line is scanned at least four times.

The control unit 70 stores the OCT signal corresponding to the scanning line SLi (i=1 to n) in the preset two-dimensional scanning range SA in the memory 72. Each OCT signal may be stored as a still image in association with each scanning line. As a result, the second three-dimensional OCT data having the OCT signal of at least 4 frames is acquired for each scan line.

Here, when the OCT signal of at least 4 frames is obtained a plurality of times with respect to the scanning range SA, as described above, the sub-scanning direction in the first scanning control and the sub-scanning direction in the second scanning control are set to opposite directions. Good. As a result, it is possible to reduce the change of the scanning line and reduce the influence of the displacement of the eye. For example, with respect to the Z position of the OCT signal, it is possible to reduce the influence of the curvature of the eye. Therefore, when adjusting the Z position by adjusting the optical path length, a small amount of adjustment is required. Of course, each sub-scanning direction may be the same direction.

In the above embodiment, the example in which the OCT signal of at least 4 frames is obtained twice with respect to the scanning range SA is shown, but the OCT signal of at least 4 frames may be obtained at least 3 times. For example, the OCT signal of at least 12 frames may be acquired by acquiring the OCT signal of at least 4 frames three times. Furthermore, the OCT signal of at least 16 frames may be acquired by acquiring the OCT signal of at least 4 frames four times. By further increasing the number of frames used for combining the motion contrast data, it is possible to further improve the image quality. For example, it becomes easy to confirm a fine blood vessel structure. The sub-scanning direction in the third acquisition may be opposite to the sub-scanning direction in the second acquisition.

In the above embodiment, the control unit 70 may display the progress statuses of the first scanning control and the second scanning control on the monitor 75, respectively. In this case, for example, the control unit 70 may display the number of scan lines already scanned and the total number of scan lines for each scan control (for example, 1/n). Further, the control unit 70 may display the sub-scanning direction of the measurement light on the monitor 75 (for example, arrow display).

<Acquisition of MC data>
The control unit 70 processes the OCT signals of the first at least four frames obtained by the first scanning control to acquire the MC data of the first at least three frames. Further, the OCT signal of the second at least 4 frames obtained by the second scanning control is processed to obtain the MC data of the second at least 3 frames. Here, the control unit 70 may acquire at least three frames of the first MC data and at least three frames of the second MC data for each scan line. Note that various methods can be adopted as a method of obtaining MC data based on a plurality of OCT signals that are temporally different, and therefore description thereof will be omitted. When at least 4 frames of OCT signals are processed to obtain at least 3 MC data, temporally continuous OCT signals may be processed to obtain 3 MC data, and further, they are not temporally continuous. The OCT signal may be processed to obtain MC data.

Here, the control unit 70 synthesizes the MC data of the first at least three frames and the MC data of the second at least three frames with respect to the same scanning line (for example, arithmetic mean processing, super-resolution processing). Etc.) to obtain the third MC data. As a result, composite MC data is acquired for each scan line. As a result, high-quality MC data is acquired by combining MC data of 6 frames or more. According to the averaging process, noise on the image is reduced and MC data with excellent contrast is acquired. In this case, the maximum value process or the mode value may be used. Moreover, according to the super-resolution processing, the resolution of MC data can be increased.

The control unit 70 may obtain high-quality front MC data or high-quality three-dimensional MC data based on the third MC data obtained in each scan line.

In the above embodiment, when the first OCT signal group and the second OCT signal group are obtained for the same scan line, these are not continuously acquired but each scan line SLi (i=1 to n). ), the second OCT signal group is obtained by obtaining the second OCT signal group in each scan line SLi (i=1 to n) after obtaining the first OCT signal group in It is possible to secure a certain time until the signal group is obtained.

The blood flow in the capillaries may be smooth during a certain period of time, and as a result, the blood vessel structure can be accurately imaged. Note that, of course, when obtaining the first OCT signal group and the second OCT signal group with respect to the same scanning line, the present embodiment can be applied even when these are continuously obtained.

<Tracking>
Optionally, the controller 70 controls the drive of the optical scanner 108 based on, for example, a front image acquired by the observation optical system 200 to obtain OCT signals of 4 frames or more in each scan line. The scanning position may be corrected.

In this case, the control unit 70 corrects the scanning position each time an OCT signal of 4 frames or more is obtained in at least one scanning line in at least one of the first scanning control and the second scanning control. Good. Thereby, the scanning position of the OCT signal group in at least one scanning line can be integrally corrected.

When correcting the scanning position, for example, the control unit 70 detects a position shift between the live moving image of the front image acquired by the observation optical system 200 and the still image (reference image) acquired in advance by image processing. Good. The control unit 70 may correct the scanning position by controlling the driving of the optical scanner 108 based on the detection result. Here, the control unit 70 acquires an OCT signal of 4 frames or more in at least one scanning line while one frame of the front image is acquired in at least one of the first scanning control and the second scanning control. You may.

When correcting the scanning position, the control unit 70 acquires the first front image as the reference image by the observation optical system 200, for example, when acquiring the OCT signal of at least four frames in the first scanning line. The second front image may be acquired by the observation optical system after the acquisition of the OCT signal in one scanning line and after the acquisition of the first front image. The control unit 70 may detect the positional shift between the first front image and the second front image by image processing, and correct the scanning position based on the detected positional shift.

<A scan unit correction>
Optionally, the control unit 70, for example, when performing a combining process between the MC data obtained by the first scan control and the MC data obtained by the second scan control, performs A scan. The positional deviation in the Z direction may be corrected in units of image processing. As a result, the positional deviation between the MC data is accurately corrected and high quality MC data can be obtained. When correcting the shift in units of A scans for the MC data acquired using the above tracking, the shift between the MC data can be corrected more accurately because the shift in the XY directions is corrected in advance.

<Image judgment>
Optionally, the controller 70 may determine pass/fail of at least four OCT signals obtained for at least one scan line based on the eye image acquired by the observation optical system 200.

In this case, for example, in at least one of the first scan control and the second scan control, the control unit 70 determines pass/fail each time an OCT signal of 4 frames or more is obtained in at least one scan line. Good. This makes it possible to integrally determine the quality of the OCT signal group in at least one scanning line.

When performing the quality determination, the control unit 70 may detect the positional deviation between the live moving image acquired by the observation optical system 200 and the still image (reference image) acquired in advance by image processing. The control unit 70 may determine pass/fail of at least four OCT signals based on the detection result of the positional deviation when at least four OCT signals are obtained for at least one scanning line. Regarding the method of detecting the positional deviation, for example, the first front image and the second front image may be acquired as in the case of <Tracking> above. Here, the control unit 70 acquires an OCT signal of 4 frames or more in at least one scanning line while one frame of the front image is acquired in at least one of the first scanning control and the second scanning control. You may.

When performing the pass/fail determination, for example, the control unit 70 may move to the next scan line when it is determined to be good, and may acquire the OCT signal regarding the scan line again when it is determined to be bad. The control unit 70 may combine the control based on the pass/fail judgment result of the OCT signal with the scanning position correction.

<Transformation form>
Hereinafter, a modified form according to the present embodiment will be shown. The control unit 70 may overlap at least a part of the scanning range between the first scanning control and the second scanning control and acquire at least eight OCT signals in the overlapping scanning range.

In this case, it is not limited to the case where the scanning direction and the scanning position of each scanning line are the same. For example, the control unit 70 may perform scan control between the first scan control and the second scan control such that the main scan direction and the sub scan direction are orthogonal to each other. As an example, in the first scanning control, the main scanning direction is the X direction and the sub scanning direction is the Y direction, and in the second scanning control, the main scanning direction is the Y direction and the sub scanning direction is the X direction. May be. In this case, the control unit 70 may combine the MC data under the first scan control and the MC data under the second scan control to obtain the combined MC data. Further, the control unit 70 determines the correlation between the first three-dimensional OCT data obtained by the first scanning control and the second three-dimensional OCT data obtained by the second scanning control. After correcting each three-dimensional OCT data by utilizing it, a combining process for obtaining combined MC data may be performed.

In the above description, a case has been described in which four or more OCT signals are obtained multiple times to obtain eight or more OCT signals, but two or more OCT signals are obtained multiple times (for example, two or three times). Even when the above) is obtained and four or more OCT signals are obtained, the present embodiment can be applied. That is, the control unit 70 performs the first scan control for obtaining the first OCT signal group including the first plurality of OCT signals and the second scan control including the second plurality of OCT signals for the same scanning position. The second scan control for obtaining the OCT signal group may be performed. When two or more OCT signals are obtained a plurality of times, signal acquisition may be stopped at any timing, for example.

It should be noted that each feature (for example, device configuration, control, calculation, etc.) described in the above embodiment can be applied even when two or more OCT signals are obtained a plurality of times (for example, two or three times or more). Needless to say, for example, in the above-described embodiment, the control for obtaining four or more OCT signals a plurality of times, and the point for obtaining the third MC data based on the four or more OCT signals in each scanning control. Each feature can be implemented by substituting a configuration for obtaining two or more OCT signals a plurality of times to obtain the third MC data based on the two OCT signals in each scan control. As an example thereof, (control in the case of performing the first scan control and the second scan control for a plurality of scan lines), (correction of displacement between MC data), (correction of scan position based on front image), (OCT Determining pass/fail of a signal group), (transition of the next scan line after interrupting the second scan control), (a plurality of OCT signals are acquired between the first scan control and the second scan control). The time interval, the scanning speed, the scanning density, and/or the difference in the optical path length between the measurement light and the reference light), the two or more OCT signals are transmitted a plurality of times (for example, twice, Needless to say, the present invention can be applied to the case where it is obtained 3 times or more.

When obtaining two or more OCT signals a plurality of times, for example, the control unit 70 may obtain two OCT signals a plurality of times to obtain four or more OCT signals. In this case, at least the first MC data is acquired based on the first two OCT signals, the second MC data is acquired based on the second two OCT signals, and the third MC data is acquired based on these. MC data may be acquired. By performing the scan control in units of the first two OCT signals, each scan control can be performed in a shorter time than in the case where four or more OCT signals are continuously acquired.

When obtaining two or more OCT signals a plurality of times, for example, the control unit 70 may obtain three OCT signals a plurality of times to obtain six or more OCT signals. In this case, at least the first at least two MC data are acquired based on the first three OCT signals, and the second at least two MC data are acquired based on the second three OCT signals. 3rd MC data may be acquired based on. By performing the scan control in units of the first three OCT signals, each scan control can be performed in a shorter time than in the case where six or more OCT signals are continuously acquired.

Further, the number of OCT signals acquired at the same scanning position may differ between the first scanning control and the second scanning control. For example, one scanning control may obtain four or more OCT signals, and the other scanning control may obtain two or three OCT signals. Of course, the number of acquisitions is not limited to this.

The control unit 70 may perform the third scanning control for obtaining the third OCT signal group at least once, in addition to the first scanning control and the second scanning control. Here, the third OCT signal group may include, for example, at least two OCT signals that are temporally different at the same scanning position as the first OCT signal group and the second OCT signal group. According to the third scan control, new MC data can be acquired in addition to the first MC data and the second MC data, and by combining these, high-quality MC data can be acquired. By obtaining the third OCT signal group a plurality of times, higher image quality can be achieved.

In the present embodiment, the optical coherence tomography apparatus that acquires the OCT signal is described as an example, and the present invention is not limited to this. The technology of the present disclosure can be applied to any device that acquires motion contrast data from a plurality of signals (for example, an imaging signal acquired by a fundus imaging device with a wavefront compensation function).

The present invention is not limited to the device described in this embodiment. For example, the optical coherence tomography calculation software (program) that performs the functions of the above-described embodiments is supplied to the system or device via a network or various storage media. Then, the computer of the system or the apparatus (for example, CPU) can read and execute the program.

1 Optical Coherence Tomography Device 70 Control Unit 72 Memory 75 Monitor 76 Operation Unit 100 Interferometric Optical System (OCT Optical System)
108 Optical Scanner 120 Detector 200 Front Observation Optical System 300 Fixation Target Projection Unit

Claims (5)

An OCT optical system for acquiring an OCT signal by the measurement light and the reference light applied to the eye to be inspected;
First three-dimensional OCT data acquisition means for acquiring first three-dimensional OCT data having OCT signals of at least two frames for each scan line of a preset two-dimensional scanning range,
After the first three-dimensional OCT data acquisition unit acquires the first three-dimensional OCT data, at least two frames of OCT signals are provided for each scan line that is the same as the first three-dimensional OCT data acquisition unit. Second three-dimensional OCT data acquisition means for acquiring second three-dimensional OCT data,
A combining process for obtaining combined motion contrast data by combining the first motion contrast data based on the first three-dimensional OCT data and the second motion contrast data based on the second three-dimensional OCT data Means and
An optical coherence tomography apparatus comprising: The optical coherence according to claim 1, wherein the synthesizing processing unit obtains the synthetic motion contrast data by performing an averaging process on the first motion contrast data and the second motion contrast data. Tomography device. Third third for obtaining third three-dimensional OCT data having OCT signals of at least two frames for each scan line that is the same as the first three-dimensional OCT data obtaining means and the second three-dimensional OCT data obtaining means. Dimensional OCT data acquisition means is provided,
The synthesis processing means includes first motion contrast data based on the first three-dimensional OCT data, second motion contrast data based on the second three-dimensional OCT data, and the third three-dimensional OCT data. 3. The optical coherence tomography apparatus according to claim 1, wherein synthetic motion contrast data is obtained by synthesizing the third motion contrast data based on the above. The optical coherence tomography apparatus according to claim 1, wherein the synthesizing processing unit acquires frontal motion contrast data or three-dimensional motion contrast data based on the synthetic motion contrast data. A first three-dimensional OCT data acquisition step of acquiring first three-dimensional OCT data having OCT signals of at least two frames for each scan line in a preset two-dimensional scanning range;
After the first three-dimensional OCT data is acquired by the first three-dimensional OCT data acquisition step, at least two frames of OCT signals are included for each scan line that is the same as in the first three-dimensional OCT data acquisition step. A second three-dimensional OCT data acquisition step of acquiring second three-dimensional OCT data;
A combining process for obtaining combined motion contrast data by combining the first motion contrast data based on the first three-dimensional OCT data and the second motion contrast data based on the second three-dimensional OCT data Steps,
An optical coherence tomography calculation program that causes a computer to execute.

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