JP2012021794A - Method for reading optical interference measurement data, optical interference tomography diagnostic apparatus, and optical interference tomography diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten processing time from measurement up to diagnosis by reducing a data size concerned with processing of optical interference tomography diagnosis without deteriorating measurement accuracy in the processing of optical interference measurement data by an optical interference tomography diagnostic apparatus.SOLUTION: In FD-OCT for acquiring tomographic information from optical spectral information, data to be read out in optical interference measurement data are determined based on measurement depth of measurement light by using the measurement depth of measurement light and the characteristics of interference light to be measured, and only the determined data out of the optical interference measurement data is read out.

Description

  The present invention relates to an optical interference measurement data reading method, an optical coherence tomography diagnosis apparatus, and an optical coherence tomography diagnosis system that acquire a tomographic image using optical interference. In particular, the present invention relates to an optical coherence tomographic imaging apparatus having an interference optical system used for ophthalmic medical treatment and the like, which is suitable for reducing the data size related to optical coherence tomographic diagnosis without degrading the measurement system.

There have been many techniques for improving the image quality (high resolution, high gradation, high dynamic range, etc.) of optical coherence tomographic images acquired in optical coherence tomography (hereinafter referred to as OCT). Proposals have been made.
In particular, OCT has been increasingly applied as an ophthalmic medical device, and is expected to be an indispensable device for diagnosis in specialized retina outpatients.
In particular, in recent years, it has been required to improve the resolution in the surface direction (retinal surface direction) orthogonal to the depth direction as well as the resolution in the depth direction of the eye retina. This is because, by improving the resolution in the direction of the retinal surface, observation of lesions that could not be observed so far, and early detection of further lesions can be expected.
Patent Document 1 discloses an OCT technique that uses an optical system having a high numerical aperture (hereinafter referred to as NA) and has a zone focus function in order to improve the resolution in the retinal plane direction of OCT. According to the technique disclosed in Patent Document 1, it is possible to measure an optical coherence tomographic image of the retina with a zone focus that performs measurement by changing the focus position stepwise using an optical system with a high NA. It is.

In addition, since OCT measures the reflected information of the measurement light from the inside of the eye retina (each layer constituting the retina) as interference light, the intrusion depth of the measurement light increases and the reflected light intensity decreases, and the interference information There is a potential characteristic that it will decrease. This leads to a decrease in the dynamic range of the optical coherence tomographic image.
Patent Document 2 discloses a technique for performing adjustment according to the measurement depth of measurement light in OCT in order to obtain an optical coherence tomographic image with uniform image quality. According to the technique disclosed in Patent Document 2, in Time-Domain OCT that measures a tomographic image by temporally scanning interference light, the tomographic image is controlled by controlling the light intensity of the light source according to the measurement depth. It is possible to obtain an optical coherence tomographic image with uniform brightness.
As described above, many proposals have been made for techniques for realizing high image quality of OCT optical coherence tomographic images.

JP2007-101250A JP-A-2005-083954

However, the prior art described above cannot solve the following problems.
Increasing the image quality of an optical coherence tomographic image, particularly higher resolution and higher gradation, significantly increases measurement data. Further, the expansion of the range to be diagnosed, that is, the request to expand the measurement range of the optical coherence tomographic image also leads to an increase in measurement data.

The increase in measurement data causes an increase in time required for various processes such as measurement, measurement data processing, and image configuration in optical coherence tomographic image diagnosis. As a result, real-time property deterioration from measurement to diagnosis occurs.
That is, it is necessary to take measures for reducing the time required for diagnosis along with the improvement of the image quality of the optical coherence tomographic image, but the conventional technique cannot cope with the above problem.
It should be noted that the measurement accuracy and the image quality deterioration of the optical interference diagnostic image should not be caused so that the time required for the diagnosis is shortened and the accuracy of the optical interference tomographic diagnosis is not lost.

  The present invention has been made in view of the above problems. In the processing of optical interference measurement data, the reading of the optical interference measurement data is controlled based on the measurement depth of the measurement light, so that the optical accuracy is not degraded. It is an object of the present invention to provide an optical interference measurement data reading method, an optical coherence tomography diagnosis apparatus, and an optical coherence tomography diagnosis system that reduce the data size related to coherence tomography diagnosis and shorten the electronic processing time.

In order to solve the above-described problems, the optical interference measurement data reading method according to the present invention has the following configuration.
That is, a method for reading optical interference measurement data in optical coherence tomography diagnosis that measures a tomographic image from optical spectrum information using optical interference, and obtaining an information of measurement depth of optical interference measurement data;
For determining the data to be read out of the optical interference measurement data based on the measurement depth information, a read control step for controlling to read the read data determined in the determination step, and for controlling the read control step And a reading step of reading out the optical interference measurement data based on the data.

In order to solve the above problems, an optical coherence tomographic diagnosis apparatus according to the present invention has the following configuration.
That is, an optical coherence tomographic diagnosis apparatus that measures a tomographic image from optical spectrum information using optical interference, based on the measurement depth information, an acquisition unit that acquires information on the measurement depth of optical interference measurement data, Of the optical interference measurement data, a determination means for determining data to be read, a read control means for controlling to read out the read data determined by the determination means, and reading out the optical interference measurement data based on the control of the read control means And a reading means.

In order to solve the above problems, an optical coherence tomographic diagnosis system according to the present invention has the following configuration.
Optical coherence tomography diagnosis composed of an optical coherence tomography measuring device that measures tomographic information from optical spectrum information using optical interference and an image processing device that constructs an optical coherent tomographic image from the measured tomographic information and presents it to the user The system is an acquisition unit that acquires measurement depth information of optical interference measurement data, a determination unit that determines data to be read out of the optical interference measurement data based on the measurement depth information, and the determination unit. Read control means for controlling the read data to be read, read means for reading the optical interference measurement data based on the control of the read control means, and the optical interference measurement data read by the read means in the image processing An optical coherence tomography measuring device comprising: output means for outputting to the device; input means for inputting output information of the optical coherence tomography measuring device; and the input means. Image producing means for producing an optical interference tomographic image from the input the optical interference measuring data, characterized in that it is composed with the image processing apparatus and a display means for displaying the optical coherent tomography.

  According to the configuration of the present invention, in the processing of optical interference measurement data, the data related to optical coherence tomography diagnosis without degrading the measurement accuracy by controlling the reading of the optical interference measurement data based on the measurement depth of the measurement light. The electronic processing time can be shortened by reducing the size.

Device configuration diagram of optical coherence tomography diagnosis system using OCT in the first embodiment Functional block diagram of the OCT system in the first embodiment The conceptual diagram which shows an example of the internal apparatus structure of OCT in 1st Embodiment The conceptual diagram explaining the measurement depth of OCT in 1st Embodiment Conceptual diagram explaining zone focus in the first embodiment Conceptual diagram for explaining a method of reading optical interference measurement data in the first embodiment The main flowchart which shows the flow of the whole process in 1st Embodiment. The flowchart which shows the flow of the reading process of the optical interference measurement data in 1st Embodiment Conceptual diagram explaining zone focus in the second embodiment Conceptual diagram for explaining a method of reading optical interference measurement data in the second embodiment The flowchart which shows the flow of the reading process of the optical interference measurement data in 2nd Embodiment Conceptual diagram for explaining a method of reading optical interference measurement data in the third embodiment The flowchart which shows the flow of the calibration before measurement in 3rd Embodiment. The flowchart which shows the flow of the reading process of the optical interference measurement data in 4th Embodiment

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
A first embodiment for realizing the present invention will be described with reference to the drawings.
FIG. 1 is an overall view of an apparatus configuration of an optical coherence tomography diagnosis system using OCT according to a first embodiment for explaining features of the present invention.
An image processing system as an optical coherence tomography diagnosis system according to the present embodiment includes an OCT 101 that is an optical coherence tomography diagnosis apparatus, a controller 102, and an image processing apparatus 103.
OCT can measure a tomographic image of a sample with high resolution, and as an optical coherence tomographic diagnosis system using OCT, application to medical equipment such as ophthalmology has been promoted in recent years.
As medical devices for ophthalmology, devices such as an anterior ocular segment photographing machine, a fundus camera, and a confocal laser scanning ophthalmoscope (Scanning Laser Ophthalmoscope: SLO) are known.

In contrast to these conventional devices, OCT can measure tomographic images inside the retina, so it is useful for diagnosing lesions inside the retina, such as macular degeneration and macular hole, which are difficult to appear on the surface of the eye and retina. Very advantageous. In addition, by acquiring a tomographic image of the retina in three dimensions, it is possible to make a diagnosis that cannot be performed with conventional devices, such as enlargement of the lesion and the state of each layer constituting the retina, particularly the observation of the optic nerve cell layer that causes glaucoma. .
It is presumed that medical systems are required to have higher optical coherence tomographic images, higher gradations, and three-dimensionalization for early detection of various lesions and accurate diagnosis. On the other hand, real-time performance from measurement to diagnosis is strongly desired from the viewpoint of reducing the burden on doctors and subjects.

For this reason, the system needs to shorten the processing time while increasing the data by increasing the resolution, gradation, and three-dimensionality of the optical coherence tomographic image.
When paying attention to the measurement time of OCT, several methods based on different measurement principles are known for OCT, and the measurement speed differs for each method.
In OCT, Time-Domain OCT (TD-OCT) that scans interference light temporally to measure in the depth direction of the subject, and Fourier-Domain OCT that performs measurement in the same direction using optical spectrum information of the interference light. It is broadly classified into (FD-OCT).

Further, in FD-OCT, spectral-domain OCT (SD-OCT) that obtains optical spectrum information by dispersing interference light, and Swept- that obtains optical spectrum information by wavelength sweep of measurement light using a wavelength-swept light source. Two methods of Source OCT (SS-OCT) are known.
When comparing each method, in general, FD-OCT that can acquire information in the depth direction of the fault without requiring it is compared with TD-OCT that requires mechanical scanning. It is known to be possible. Note that the measurement speed is comparable between SD-OCT and SS-OCT.

Next, focusing on the method of shortening the processing time in the electronic processing related to diagnosis, a method such as using a high-performance image processing apparatus with excellent computing ability can be considered, but generally the cost increases, New ingenuity is expected.
If the data size related to processing can be reduced using the characteristics of OCT, an optical coherence tomographic image preferable for diagnosis can be obtained without degrading measurement accuracy, the time required for processing can be shortened, and the increase in cost can be suppressed. It becomes possible.

The OCT 101 includes an irradiation unit that irradiates a subject with measurement light, a measurement unit that measures interference light, and an output unit that outputs optical coherence tomographic data to the image processing apparatus 103. In the case of OCT as an ophthalmic medical device, the irradiating means is provided with an eyepiece optical system for observing the eye to be examined, and in the case of SD-OCT, the measuring means is provided with a spectroscope that separates interference light at a wavelength. The OCT 101 has a function of communicating with the controller 102, and exchanges commands and responses such as measurement start and stop from the controller 102.
An image processing apparatus 103 connected to the controller 102 composes an optical coherence tomographic image based on the optical coherence tomographic data input from the OCT 101 and performs various corrections for diagnosis, and an optical coherence tomographic image. Display means for displaying. The image processing apparatus 103 communicates with the OCT 101 via the controller 102. The OCT 101 that has received the measurement start command from the image processing apparatus 103 measures the tomography of the subject using the irradiation unit and the measurement unit.

The controller 102 has functions such as fast Fourier transform (hereinafter referred to as FFT), wave number conversion, optical interference measurement data reading processing, which is a feature of the present embodiment, and transmission format conversion.
In FIG. 1, the image processing apparatus 103 and the controller 102 have separate hardware configurations, but it is also possible to collect the functions of the controller 102 and the image processing apparatus 103 and configure a dedicated image processing apparatus.

In FIG. 1, the OCT 101 and the controller 102 have separate hardware configurations, but a configuration in which all or some of the functions of the OCT 101 and the controller 102 are integrated may be used. In the following description, from a functional viewpoint, a combination of functions of the OCT 101 and the controller 102 will be described as OCT.
In addition, although each device is connected by wire in the drawing, a part or all of them may be connected wirelessly.

FIG. 2 is a functional block diagram of the OCT system in the first embodiment for explaining the features of the present invention.
The OCT 201 has an SD-OCT function. The OCT 201 includes an irradiation unit 203 that irradiates measurement light, a zone focus control unit 204 that controls an optical system of the irradiation unit, a measurement unit 205 that measures interference light, and measurement data of interference light aligned for each wavelength according to the wave number axis. Wavenumber conversion unit 206 that rearranges, optical interference measurement data reading unit 207 that characterizes the present invention, FFT processing unit 208 that converts measurement data of interference light into optical coherence tomographic data, and image processing device 202 as an external processing device I / F 209 for signal transmission to and from. The OCT 201 shown here corresponds to the OCT 101 shown in FIG. 1 and a part of the controller 102.

  The image processing apparatus 202 configures and displays an optical coherence tomographic image based on the optical coherence tomographic data received from the OCT 201. The image processing apparatus 202 includes an I / F 210 for signal transmission with the OCT 201, an image configuration unit 211 that configures an optical coherent tomographic image from optical coherent tomographic data, and a display unit that displays the optical coherent tomographic image. 212. As the image processing apparatus 202, an apparatus having a high-performance arithmetic processing function or graphic display function such as a personal computer or a workstation is generally used. The image processing apparatus 202 shown here corresponds to the image processing apparatus 103 and a part of the controller 102 shown in FIG.

  The irradiation unit 203 corresponding to the irradiation means described in FIG. 1 irradiates the eye to be examined with low coherent light that is measurement light. The irradiation unit 203 includes a light source that emits low-coherent light, an eyepiece optical system that irradiates measurement light onto the retina of the eye to be examined, a scanning unit that scans the measurement light onto the retina, and dispersion compensation that compensates for optical dispersion of the eye to be examined. Has an optical system. Here, the light source constitutes measurement light generation means for generating measurement light to be irradiated to the measurement object, and takes charge of the measurement light generation process. In addition, the eyepiece optical system constitutes a light beam diameter control unit that controls the light beam diameter of the measurement light to obtain an appropriate spot diameter for the measurement, and the scanning unit determines the condensing position of the measurement light by a zone focus control unit described later. Condensing position control means to be controlled is configured. The light beam diameter control means takes the step of controlling the diameter of the light beam that becomes the measurement light, and the light collection position control means takes the step of controlling the light collection position of the measurement light on the fundus. In SD-OCT as an ophthalmic medical device, a super luminescent diode (hereinafter referred to as SLD) that emits light having a central wavelength (for example, 830 nm, 1310 nm, etc.) in the near infrared region is generally used as a low-coherent light source. Is done. However, any other light source that can emit low coherent light, such as Amplified Spontaneous Emission (ASE), may be used.

  The zone focus control unit 204 controls the eyepiece optical system of the irradiation unit 203 for OCT zone focusing. In general, zone focus functions by controlling the NA and focus position in an eyepiece optical system.

A measurement unit 205 corresponding to the measurement unit described in FIG. 1 measures interference light obtained by causing interference between reference light and reflected light from the eye to be examined. The measuring unit 205 includes an interferometer that creates interference light, a spectroscope that splits the interference light, and an imaging device that measures the interference light.
In general, a CCD sensor (Charge Coupled Device) or a CMOS sensor (Complementary Metal Oxide Semiconductor) having sensitivity in the near-infrared region is used as the imaging device.

The wave number conversion unit 206 rearranges the measurement data of the interference light, which is measured and measured by the spectroscope for each wavelength by the measurement unit 205, on the wave number axis. The wave number conversion unit 206 changes the wave number space from the measurement data of the interference light to prepare for the FFT processing for acquiring tomographic information.
The optical interference measurement data reading unit 207 controls reading of the measurement data of the interference light according to the measurement depth of the measurement light. Details will be described later.
The FFT processing unit 208 performs FFT processing on the measurement data of the interference light and converts it into optical coherence tomographic data. By the FFT processing, optical coherence tomographic data constituting measurement information (reflection position and signal intensity) of the eye to be examined is obtained.

  The I / F 209 is used to transmit the optical coherence tomographic data generated by the FFT processing unit 208 to the image processing apparatus 103. The I / F 209 functions as an interface that performs data communication between the OCT 201 and the image processing apparatus 202 together with the I / F 210 of the image processing apparatus 202. As the I / F 210, it is desirable to adopt an I / F 210 that conforms to a communication standard that requires real-time performance and enables large-capacity transmission. The data communication system is a wired system (for example, USB, IEEE 1394, HDMI (registered trademark), optical transmission, etc.) or a wireless system (for example, UWB (Ultra Wide Band), wireless LAN, millimeter wave communication, etc.). Also good.

An I / F 210 is an I / F on the image processing apparatus side. It has the same function as the I / F 209 in the OCT 201, and transmits and receives data in cooperation with the I / F 209. Therefore, the I / F 209 constitutes output means for outputting the optical interference measurement data read by the reading means in the present invention to the image processing apparatus as output information, and the I / F 210 outputs the output information sent from the output means to the image. An input means for inputting to the processing apparatus is configured.
An image constructing unit 211 serving as an image generating unit constructs an optical coherence tomographic image of the retina to be examined from the measurement information (reflection position and signal intensity) of the eye to be examined possessed by the received optical coherent tomographic data. Also, various correction processes such as brightness adjustment, distortion correction, and extraction of a region of interest are applied to the obtained optical coherence tomographic image to reconstruct information that is more preferable for diagnosis.
The display unit 212 serving as a display unit displays the optical coherence tomographic image formed by the image configuration unit 211.

With the OCT system having the above-described configuration, an optical coherence tomographic image of the retina to be examined can be acquired and displayed. In addition, it is possible to reduce the data size related to the processing by utilizing the characteristics of the OCT, and it is possible to obtain an optical coherence tomographic image preferable for diagnosis without degrading the measurement accuracy and to shorten the time related to the processing.
In the form shown in FIG. 2, the FFT processing unit 208 is arranged in the OCT 201 and used as the function of the OCT 201. However, when this is used as the function of the image processing apparatus 202, the data size related to the transfer process can be reduced. Therefore, the transfer time between the I / F 209 and the I / F 210 can be shortened.

In the process of acquiring an optical coherence tomographic image, first, measurement light is irradiated to the eye to be examined by the irradiation unit 203, and wave number conversion processing is performed by the wave number conversion unit 206 on the optical interference measurement data obtained by the measurement unit 205. The optical interference measurement data reading unit 207 outputs valid data to the FFT processing unit 208 of the next process. The FFT processing unit 208 generates tomographic information of the eye retina to be examined based on the optical interference measurement data. The obtained optical coherence tomographic data is transmitted to the image processing apparatus 103 via the I / F 209. The image processing apparatus 103 constructs an optical coherence tomographic image based on the received optical coherence tomographic data, and displays the measurement result of the eye to be examined on the display unit 212.
With the above processing process, it is possible to present a light interference diagnostic image preferable for diagnosis to a user (doctor).

The following configuration can be exemplified as computer hardware applicable to the image processing apparatus 103 (202). That is, the image processing apparatus 103 has a so-called CPU, RAM, ROM, and the like, and these RAMs and ROMs are added by the CPU. The entire computer is controlled using stored programs and data. At the same time, the CPU executes processing performed by the image processing apparatus 103 to which this computer is applied.

The RAM has an area for temporarily storing programs and data loaded from an external storage device or data received from the outside (OCT 201 in this embodiment) via the I / F 307. It also has a work area used when the CPU executes various processes. This RAM can provide various areas for various processes as appropriate.
The ROM stores setting data and a boot program for the computer.
The computer also has an operation unit including a keyboard, a mouse, and the like, and various instructions can be input to the CPU by being operated by an operator of the computer.

The display unit 212 is configured by a CRT, a liquid crystal monitor, or the like, and can display processing results obtained by a CPU or a graphics board (not shown) to the operator using images and characters.
The above-described external storage device is a large-capacity information storage device represented by a hard disk drive device. Here, an OS (Operating System) and programs and data for causing the CPU to execute each process performed by the image processing device 103 are described. Is stored. These programs and data are appropriately loaded into the RAM according to the control by the CPU, and are processed by the CPU.

The I / F in the computer described here corresponds to the I / F 210 shown in FIG. In order to perform data communication with the OCT 201, it mainly functions as a reception interface for receiving optical coherence tomographic data from the OCT 201.
Examples of the hardware configuration arranged in the OCT 201 are as follows.
That is, hardware corresponding to the measurement unit 205, hardware corresponding to the zone focus control unit 204, CPU, RAM, ROM, LSI, and the like can be considered.

The RAM has a work area used for the CPU in the OCT 201 to perform various processes, an area for temporarily storing data received from the image processing apparatus 103 which is an external apparatus via the I / F 209, and the like.
The ROM stores a program for causing the CPU in the OCT 201 to execute processes to be described later performed by the OCT 201, data on optical or electrical settings of the OCT 201, and the like.
Furthermore, hardware corresponding to buttons or the like for directly operating the OCT 201 is also arranged.
The CPU in the OCT 201 executes programs for controlling various devices including the initial setting of the OCT 201.
The I / F as the hardware corresponds to the I / F 209 shown in FIG.

  The LSI is hardware corresponding to the wave number conversion unit 206 and the FFT processing unit 208 shown in FIG. Here, an ASIC that is a dedicated integrated circuit is assumed, but a configuration in which functions are described and implemented in software by a DSP that is a signal processor may be used.

FIG. 3 is a conceptual diagram showing an example of the internal device configuration of the OCT 201 that measures the eye 305 to be examined.
The OCT 201 has a low coherent light source 301. In the case of OCT as an ophthalmic medical device, an SLD that emits light having a central wavelength (for example, 830 nm) in the near-infrared region and a certain wavelength width (for example, 50 nm) is used as the low coherent light source 301. According to the OCT principle, it is known that the wavelength width contributes to the resolution in the optical axis direction of the measurement light, and the wavelength contributes to the resolution in the plane direction perpendicular to the optical axis direction. The center wavelength is determined by the subject, more specifically, by the wavelength-dependent characteristics of scattering and absorption of the subject. It is known that the light absorption of water constituting the living body is minimized near 830 nm. Therefore, for a living body, particularly an eyeball having a vitreous body, deeper immersion of light can be achieved by using light near this wavelength. Can be obtained. In the case of OCT as an ophthalmic medical device, in general, 830 nm is used as a central wavelength, in which high resolution can be easily obtained in order to resolve a dense retinal layer structure with little water absorption.

  The beam splitter 302 separates the light emitted from the low-coherent light source into reference light 312 that irradiates the mirror 306 and measurement light 311 that irradiates the eye 305 to be examined. The beam splitter 302 also has a function as an interferometer that generates interference light 314 by causing interference between the reference light 312 and the return light 313 from the eye to be examined.

  The scanner 303 scans the retina in the plane direction (XY direction) orthogonal to the optical axis with the measurement light 311. The scanner 303 is a device such as a galvanometer mirror or a MEMS scanner, and a device capable of scanning two axes in the X direction and the Y direction alone or in combination with scanning for each axis is used. Note that the center of the measurement light 311 is adjusted to coincide with the rotation center of the scanner 303.

  The eyepiece optical system 304 condenses the measurement light 311 on the retina of the eye to be examined. The zone focus control unit 204 adjusts the NA and focus position of the measurement light 311 by controlling the eyepiece optical system 304, thereby causing zone focusing to function.

The mirror 306 reflects the reference light 312. SD-OCT obtains tomographic information according to the optical path difference between the reference light 312 and the measurement light 311 (and its return light 313). A position on the retina of the eye to be examined where the optical path lengths of the reference light 312 and the measurement light 311 (and the return light 313) coincide with each other is specifically called a coherence gate.
Further, by providing a dispersion compensation optical system (not shown) having a dispersion equivalent to the optical dispersion existing on the optical path of the measurement light 311 (and its return light 313) on the optical path of the reference light 312, the measurement accuracy is improved. Can be improved.

The diffraction grating 307 separates the interference light 314 under the same conditions as the center wavelength and wavelength width of the light source 301.
The imaging optical system 308 forms an image of the interference light dispersed by the diffraction grating 307 on the imaging element 309.
The image sensor 309 measures the interference light. As the image sensor 309, a CCD sensor or a CMOS sensor having sensitivity in the near infrared region is used.
Here, the configuration of the optical coherence tomographic image will be described.

In OCT, in general, scanning in the optical axis direction (z-axis direction) of measurement light is performed by A scan, and A scan is performed a plurality of times in one direction (x or y-axis direction) orthogonal to the optical axis direction of measurement light. Is called B-scan. A single two-dimensional optical coherence tomographic image can be obtained by one B-scan.
One tomographic image is obtained by performing one B-scan on the macula portion of the eye to be examined.
In order to obtain a three-dimensional optical coherence tomographic image, the B scan is also performed in another direction (y or x axis direction) orthogonal to the optical axis direction of the measurement light.
Here, in order to obtain a three-dimensional tomographic image, for example, when the resolution of each of the x, y, and z axes is 1024, 1024, and 2048, and the gradation of one pixel is measured at 10 bits, the measurement is performed. The total data size reaches 2.5 GB (1K = 1024 conversion).

In order to present optical coherence tomographic images that are more suitable for diagnosis as medical devices, the demand for higher resolution and higher gradation will continue to increase, and the size of optical interference measurement data is expected to increase further. The
As described above, the present invention reads optical interference measurement data that reduces the data size related to processing for optical interference measurement data that increases with the demand for higher resolution, higher gradation, and three-dimensionality. One of the methods. Next, the functional configuration for realizing the present invention and the characteristics of the OCT to be used will be described.

Here, the optical interference measurement data reading unit in the first embodiment for explaining the features of the present invention will be described in detail.
The optical interference measurement data reading unit 207 in the first embodiment includes a reading unit that reads optical interference measurement data, and a read control unit that controls reading of the reading unit according to the measurement depth.
The reading unit outputs the optical interference measurement data subjected to the wave number conversion process by the wave number conversion unit 206 to the next process. Further, the reading unit switches presence / absence of output according to an instruction from the reading control unit.

  The reading control unit controls the reading unit based on the measurement depth information from the zone focus control unit 204. The reading control unit calculates a reading interval of the optical interference measurement data from the received measurement depth information, and controls the reading unit based on the calculation result. As described above, the reading control unit functioning as the determining unit in the present embodiment includes the control information of the light beam diameter controlled by the light beam diameter control unit and / or the condensing position controlled by the condensing position control unit. Based on this, the measurement depth is grasped.

  The optical interference measurement data reading unit 207 having the above configuration can control reading of the optical interference measurement data based on the measurement depth of the measurement light. A method for calculating the reading interval of the optical interference measurement data will be described later.

A numerical aperture (NA) and a depth of field (DOF) have a contradictory relationship, and an optical coherence tomography with a high resolution in a plane direction perpendicular to the optical axis is measured by using a lens having a high numerical aperture (NA). An image is obtained.
As one characteristic of OCT, it is known that the resolution in the optical axis direction of measurement light is independent of the NA of the optical system. That is, the resolution in the optical axis direction in OCT is defined by the center wavelength and wavelength width of the low-coherent light source of measurement light.
That is, the use of measurement light having a high NA does not improve the resolution in the optical axis direction, but the interference light can be measured with high sensitivity and the resolution in the plane direction orthogonal to the optical axis. High measurement is possible. Therefore, by dividing and measuring the measurement range in the optical axis direction (zone focus), an optical coherence tomographic image with high resolution and sensitivity can be obtained in both the optical axis direction and the plane direction orthogonal to the optical axis.

Here, the principle of OCT zone focus used in the first embodiment will be described.
For the sake of explanation, in this embodiment, the distance of the measurement light from the coherence gate 901 in the direction of the retinal tomographic depth is called the measurement depth.

In SD-OCT without a zone focus function, using measurement light with a low NA and a deep depth of field, and scanning the measurement light that satisfies the required measurement depth, the maximum measurement depth of the measurement light, An optical coherence tomographic image is acquired.
In zone focus when acquiring an optical coherence tomographic image with measurement light 904 having a high NA and a shallow depth of field, the high NA measurement light is divided into the optical axis direction of the measurement light (the tomographic depth direction of the retina). By performing scanning, an optical coherence tomographic image with high resolution can be obtained in both the optical axis direction and the plane direction orthogonal to the optical axis. In SD-OCT having a zone focus function, measurement light that satisfies the measurement range (range from the minimum measurement depth to the maximum measurement depth) is obtained for each divided area obtained when the measurement light is divided in the optical axis direction. By scanning with, a three-dimensional optical coherence tomographic image with high resolution is acquired.

FIGS. 4A and 4B are conceptual diagrams for explaining the OCT measurement depth in the first embodiment for explaining the features of the present invention.
FIG. 4A shows a Bragg reflection condition that defines light reflection, and FIG. 4B shows a relationship between the Bragg reflection condition and a wavelength region used in SD-OCT.
With reference to FIG. 4 (a), the Bragg reflection condition that defines the reflection of light will be briefly described.

The substance 401 that reflects light corresponds to a subject in OCT. In particular, in the case of OCT as an ophthalmic medical device, it corresponds to each layer of the eye retina to be examined.
The light 402 is reflected from the surface of the subject 401.
The light 403 enters the inside of the subject 401 and is reflected at the next boundary.
When the thickness of the subject 401 is d and the refractive index is n, and the light 402 and the light 403 are perpendicularly incident on the subject 401, the light 402 and the light 403 strengthen each other at the time of reflection according to the following equation. Cause interference.

ここで、ｍは自然数である。この条件を満たす光の波数の間隔を次式で算出することができる。

Here, m is a natural number. The light wave interval satisfying this condition can be calculated by the following equation.

式２によれば、被検体４０１の厚さｄに対して、干渉を起こす光の波数の間隔Δkが一意に決まることを示している。なお、被検体４０１の厚さｄは計測光の計測範囲と置き換えることができる。

According to Equation 2, the wave number interval Δk of light causing interference is uniquely determined with respect to the thickness d of the subject 401. Note that the thickness d of the subject 401 can be replaced with the measurement range of the measurement light.

FIG. 4B illustrates the relationship between the condition of Expression 2 and the wavelength range of the low-coherent light source used in SD-OCT.
Low-coherent light is light having a central wavelength in the near-infrared region and a constant wavelength width as described above, in other words, having a constant wavenumber band ΔK _B (k _{1 to} k ₂ ). ing. In SD-OCT, in the constant frequency band [Delta] K _B, the following equation holds for measuring the light that satisfies the equation 2.

ここで、ｍは自然数（前述のmとは無関係）で、１から撮像素子が計測可能な数までの値を示す。撮像素子が計測可能な波の数は、撮像素子の画素数をＮとすればサンプリング定理に従ってＮ／２になる。

Here, m is a natural number (regardless of the aforementioned m), and represents a value from 1 to a number that can be measured by the image sensor. The number of waves that can be measured by the image sensor is N / 2 according to the sampling theorem, where N is the number of pixels of the image sensor.

From equation 3, it is possible to calculate the measurement depth nd of the measuring light having a wave number band [Delta] K _B, obtained by the following equation.

ここで、δ_Ｋは撮像素子の波数分解能を示す値で、波数帯域ΔＫ_Ｂを撮像素子の画素数Ｎで割ったものである。 The maximum measurement depth nd _max of the measuring light with wave number band [Delta] K _B may be m is obtained by the following equation when N / 2.

Here, [delta] _K a value that indicates the wavenumber resolution of the image pickup device, in which a frequency band [Delta] K _B divided by the number N of pixels of the image sensor.

Here, in the OCT according to the first embodiment of the present invention, the following relationship is established between the measurement depth and the interference light.
That is, as described above, according to Equation 2, the wave number interval Δk of the light causing the interference is uniquely determined according to the measurement depth d, and the wave number interval Δk becomes narrower as the measurement depth d becomes deeper.
Therefore, when the measurement depth d is shallow, the wave number interval Δk is wide, and the measurement data waveform of the interference light is composed of a signal having a low frequency. When the measurement depth d is deep, the wave number interval Δk is narrowed, and the measured interference light is composed of a high-frequency signal.

  By utilizing the relationship between the measurement depth and the interference light, it is possible to perform reading control of optical interference measurement data based on the measurement depth of the measurement light. Next, the zone focus and readout control method in the first embodiment will be described.

5 (a), 5 (b) and 5 (c) are conceptual diagrams for explaining zone focus in the first embodiment for explaining the features of the present invention. In the zone focus in the first embodiment, the measurement region is divided by a width of ²ⁿ with respect to the optical axis direction of the measurement light.
A thick solid line 501 indicates a coherence gate in which the optical path lengths of the reference light and the measurement light coincide with each other, and a thin solid line 502 indicates a necessary measurement depth necessary for diagnosis.
In addition, the measurement lights 503, 504, and 505 indicate lights having different NAs according to the number of divisions.

FIGS. 5 (a) divided by 2 ¹ a required measurement depth with respect to the optical axis of the measuring light, FIG. 5 (b) divided by 2 ^2, zone focusing in the case of division in FIG. 5 (c) 2 ³ An example is shown.
Each measurement area in the zone focusing in order of proximity to the coherence gate 501 and Z _n (n is 2 ^{0-2 (division number))} to be given a convenience XS. Each measurement area in the defined Z _n is the control unit of the reading of the interferometric measurement data in the embodiment in FIG. 5 (a) ~5 (c) .
FIG. 5A shows that an optical coherence tomographic image is obtained by dividing the region into two and scanning the measurement light 503 twice in total. The ranges of the measurement areas Z ₀ and Z ₁ are both 1/2 of the required measurement depth 502.

FIG. 5B shows that the region is divided into four and the optical coherence tomographic image is obtained by scanning the measurement light 504 a total of four times. The range of Z ₀ and Z ₁ is both 1/4 of the required measurement depth 502, and the range of Z ₂ is 1/2 of the required measurement depth 502.

FIG. 5C shows that an optical coherence tomographic image is obtained by dividing the region into eight and scanning the measurement light 505 a total of eight times. The ranges of Z ₀ , Z ₁ , Z ₂ , and Z ₃ are 1/8, 1/8, 1/4, and 1/2 of the required measurement depth 502, respectively.
In the description, while the optical coherence tomographic image is acquired, the same measurement light is scanned as many times as the number of divisions without changing the measurement width (depth of field) of the measurement light. of each measurement region may control the measured width for every measurement region Z _n. As a result, the number of scans equal to the number of divisions is required, whereas the number of scans can be reduced.

For example, by controlling so as to match the measured width to the width of the measurement region Z _n, number of scans can be only the number of Z _n (if the division number is 2 ^2, number of scans 3 times).
By performing zone focusing as described above, it is possible to control reading of optical interference measurement data based on the measurement depth in the first embodiment. Next, details of the optical interference measurement data readout control will be described with reference to the zone focus example of FIG.

FIG. 6 is a conceptual diagram for explaining a method of reading optical interference measurement data in the first embodiment for explaining the features of the present invention.
6A is a method for reading optical interference measurement data at Z ₀ with a shallow measurement depth, FIG. 6B is a method for reading with Z ₁ at an intermediate measurement depth, and FIG. 6C is a measurement method. Each of the reading methods at Z ₂ having a deep depth is shown.
As described above, since the since the measurement according to the equation 2 the depth d is deep becomes the wavenumber spacing Δk narrow, the frequency of the interferometric measurement data become higher at its maximum depth at each measurement region Z _n of zone focusing, an interference signal of the maximum depth of each measurement region Z _n needs to be measured.

When divided by zone focusing where the dividing number 2 ^D required measurement depth, maximum depth nd _n of each layer Z _n is obtained by the following equation. The measurement depth is indicated by Z using 0 to D as parameters.

According to Equation 2, the wave number interval (frequency) of the optical interference measurement data at the maximum depth nd _n of each layer is determined by the following equation.

第１の実施の形態における光干渉計測データの読み出しは式８に基づいて、計測深度に応じて制御を行う。 According to the sampling theorem, the reading interval S of the optical interference measurement data only needs to satisfy the following equation.

The reading of the optical interference measurement data in the first embodiment is controlled according to the measurement depth based on Expression 8.

In (a) of FIG. 6, the division number is 4 (D 2), the measurement position _{Z n} indicates the case of zero. In this case, according to Equation 8, the reading interval S of the optical interference measurement data is four times the wave number resolution δ _k of the image sensor. Therefore, as shown in FIG. 6A, only one of the four pieces of optical interference measurement data needs to be read. Compared to reading all data, the data size can be reduced to ¼.
In (b) of FIG. 6, the division number is 4 (D 2), the measurement position _{Z n} indicates the case 1. In this case, according to Equation 8, the reading interval S of the optical interference measurement data is twice the wave number resolution δ _k of the image sensor. Therefore, as shown in FIG. 6B, only one piece of data needs to be read out of two pieces of optical interference measurement data. Compared to reading all data, the data size can be reduced to ½.

In (c) of FIG. 6, the division number is 4 (D 2), the measurement position _{Z n} indicates the case 2. In this case, according to Equation 8, the reading interval S of the optical interference measurement data matches the wave number resolution δ _k of the image sensor. Therefore, it is necessary to read out all data of the optical interference measurement data as shown in FIG.
As described above, in the example of FIG. 6, the size of the optical interference measurement data can be reduced by 3/8 as a whole compared to the case of reading all data.
Thus, based on the measurement depth in SD-OCT and the characteristics of interference light, by controlling the reading of optical interference measurement data according to the measurement depth, optical interference measurement data related to processing is reduced without impairing measurement accuracy. It is possible to present a light interference diagnostic image that is preferable for diagnosis.

  Next, the flow of optical interference measurement data readout control in the first embodiment will be described.

FIG. 7 is a main flowchart illustrating the overall flow of the optical coherence tomographic image acquisition process according to the first embodiment, illustrating the features of the present invention. The series of processes in this flowchart is for obtaining an optical coherence tomographic image preferable for diagnosis in SD-OCT having a zone focus function.
In step 701, the coherence gate is adjusted near the surface layer of the eye retina to be examined. In general, it is known that in SD-OCT, the closer to the coherence gate, the higher the sensitivity of the interference signal. By adjusting the coherence gate as close as possible to the surface of the retina, it is possible to measure with high sensitivity and obtain an optical coherence tomographic image with a high dynamic range. The coherence gate adjustment method may be a known method. In the SD-OCT in the first embodiment, the coherence gate is adjusted only at the start of diagnosis (start of measurement) and is fixed until at least one B scan is performed. The above process corresponds to one process in the setting process according to the present invention, and is a process of performing reading control of the optical interference measurement data serving as a base before acquiring a tomographic image to be measured.

In step 702, a measurement position is set in SD-OCT having a zone focus function. The optical interference measurement data is acquired by repeating the scan by increasing the measurement depth sequentially from the coherence gate. Note that the application of the present invention is not limited to the example in which the sequential measurement depth is increased and scanning is performed, and the scan may be performed by sequentially decreasing the required measurement depth, or attention is given for reasons such as diagnosis or image recognition processing. When there is a layer, the position may be scanned first. The operations performed in this step correspond to the other steps in the setting process, grasp the necessary measurement depth based on the optical interference measurement data that is the measured tomographic information, and based on the necessary measurement depth, Set the reading control of the optical interference measurement data.
Further, when changing the measurement width (depth of field) of the measurement light in each measurement region, the zone focus control unit 204 adjusts the measurement width of the measurement light 311 by controlling the eyepiece optical system 304.

In step 703, optical interference measurement data is acquired. The irradiation unit 203 of the SD-OCT 201 irradiates the measurement eye with the measurement light, and the measurement unit 205 measures the interference light between the reference light and the measurement light (return light) from the inspection eye.
In step 704, since the optical interference measurement data acquired in step 703 is data that is spectrally separated by the diffraction grating 307 for each wavelength, it is converted into wave number data in preparation for the FFT processing in step 706. The wave number conversion process may be performed by a known method.
In step 705, readout control of optical interference measurement data in the first embodiment is performed. Effective data is read according to the measurement depth, and the data size related to the subsequent processing is reduced. Details will be described later.

In step 706, FFT processing is performed on the optical interference measurement data read in step 705. By performing FFT processing on the optical interference measurement data, optical coherence tomographic data including measurement information (measurement depth and signal intensity), that is, optical tomographic information is obtained.
In step 707, all the measurement areas of the zone focus are measured, and it is determined whether the tomographic image has been measured over the entire area. If the tomographic image measurement has been completed over the entire area, the process proceeds to step 708. If not, the process proceeds to step 702 and the measurement process is repeated.

In step 708, a tomographic image is constructed from the optical coherence tomographic data obtained by the processing so far. The obtained optical coherence tomographic image is subjected to various correction processes such as adjustment of luminance, distortion correction, and extraction of a region of interest to prepare images and information that are more suitable for diagnosis. Regarding the processing of these image configurations, a known method may be used.
In step 709, the optical coherence tomographic image formed in step 708 is presented to the user (mainly a doctor), and the series of optical coherence tomographic image acquisition processing ends.
With the above processing, an optical coherence tomographic image preferable for diagnosis can be obtained.

FIG. 8 is a flowchart for explaining the feature of the present invention and showing the flow of the optical interference measurement data reading process in the first embodiment. The series of processes in this flowchart is intended to realize a reading method according to the measurement depth of the measurement light shown in FIG.
In step 801, the reading control unit in the optical interference measurement data reading unit 207 acquires information on the measurement depth to be measured from the zone focus control unit 204. The zone focus control unit 204 manages measurement depth information in order to control the eyepiece optical system 304 in accordance with the measurement depth. This step corresponds to the acquisition step of acquiring the measurement depth information of the optical interference measurement data in the present invention.

In step 802, the readout control unit calculates the readout interval of the optical interference measurement data shown in Expression 8 and FIG. 6 based on the received measurement depth information.
In step 803, the read control unit determines whether the obtained data is read data based on the read interval calculated in step 802. If it is data to be read, the process proceeds to step 804. If it is not data to be read, the process proceeds to step 805. These steps 803 and 804 correspond to a determination step of determining data to be read out of the optical interference measurement data based on the measurement depth information in the present invention.

In step 804, the reading control unit similarly controls the reading unit arranged in the optical interference measurement data reading unit 207 to output optical interference measurement data. This step corresponds to the read control step for reading the read data determined in the previous determination step, and further corresponds to the read step by performing an operation of actually outputting the optical interference measurement data.
In step 805, it is determined whether reading control has been performed on all the data of the optical interference measurement data. If all data reading control is being performed, the series of optical interference measurement data reading processing ends. If the read control has not been completed yet, the process proceeds to step 803 to repeatedly read data.

  With the above processing, the optical interference measurement data in the first embodiment can be read. Further, the optical interference measurement data reading unit for reading data including the writing process described above includes an acquisition unit, a determination unit, a read control unit, and a reading unit that perform the acquisition step, the determination step, the read control step, and the read step described above. It has a region that functions as a means.

  According to the present embodiment, by using the characteristics of the measurement depth of SD-OCT and the frequency of the interference light waveform to be measured, by providing means for controlling the reading of the optical interference measurement data according to the measurement depth, More specifically, by narrowing the reading interval as the measurement depth increases, the data size related to optical coherence tomographic image processing can be reduced. As a result, the processing time can be shortened, and as a result, real-time performance from tomographic image acquisition to diagnosis can be improved.

Further, the number of divisions of the zone focus measurement area is 2 ^N (N is a natural number), and the measurement position as a data reading control unit is 2 ^N , so that the total number of read data is 2 ^N. The FFT processing unit 208 requires 2 ^N data as an input, and in the past, it was converted into 2 ^N data and input by performing interpolation on all measured data. By performing the read control shown in the form, the processing can be reduced.

(Second Embodiment)
A second embodiment for realizing the present invention will be described with reference to the drawings.
In the first embodiment, the division number of the measurement range of the zone focusing as 2 ^N, the total number of the read data measurement positions also by fixed and 2 ^N as the control unit of the data reading so that 2 ^N Controlled reading of optical interference measurement data. In this case, since the data reading interval is always a natural number multiple of the data interval, the control is easy, but the control depends on the width of each zone focus measurement area.

The feature of the second embodiment resides in performing control independent of the zone focus measurement region. As a result, it is possible to absorb SD-OCT measurement conditions and reduce data related to acquisition of optical coherence tomographic images.
This embodiment will be described focusing on the above features.
Note that the functional blocks of the OCT in the present embodiment are the same as the functional blocks in the first embodiment (FIG. 2), and thus description thereof is omitted.

FIG. 16 is a functional block diagram of the optical interference measurement data reading unit according to the second embodiment, illustrating features of the present invention.
The optical interference measurement data reading unit in the second embodiment (corresponding to the optical interference measurement data reading unit 207 in the first embodiment) is a reading unit that reads optical interference measurement data, and an interpolation processing unit that interpolates read data. And a reading control unit that controls the reading unit and the interpolation processing unit according to the measurement depth.

  An interpolation processing unit, which is an interpolation means that is a characteristic configuration of the present embodiment, interpolates the optical interference measurement data read by the reading unit. Since the other configuration is the same as the configuration exemplified in the first embodiment, the same reference numerals are attached to the same components in the following description. The interpolation processing unit performs an interpolation process in response to an instruction from the read control unit. The interpolation processing in the second embodiment may be a simple configuration that performs two-data weighted interpolation according to the position of data to be generated with two data as inputs.

The reading control unit controls the reading unit based on the measurement depth information from the zone focus control unit 204. The reading interval of the optical interference measurement data is calculated from the measurement depth information received from the zone focus control unit 204, and the reading unit and the interpolation processing unit are controlled based on the calculation result.
The optical interference measurement data reading unit having the above configuration can control the reading of the optical interference measurement data based on the measurement depth of the measurement light. A method for calculating the reading interval of the optical interference measurement data will be described later.

FIGS. 9A to 9C are conceptual diagrams illustrating zone focus in the second embodiment for explaining the features of the present invention. The zone focus in the second embodiment is divided at equal intervals with respect to the optical axis direction of the measurement light (the tomographic depth direction).
In these drawings, a thick solid line 901 indicates a coherence gate in which the optical path lengths of the reference light and the measurement light coincide with each other, and a thin solid line 902 indicates a necessary measurement depth necessary for diagnosis. A broken line indicates a boundary between the measurement areas.
Measurement light 903, 904, and 905 indicate light having different NAs depending on the number of divisions.

9A shows an example of zone focus when the required measurement depth is divided into three in the optical axis direction of the measurement light, FIG. 9B is divided into four, and FIG. 9C is divided into five. Yes.
To be given a Z _n and conveniently names each layer of zone focusing on the order of proximity to the coherence gate 901. Each layer of Z _n defined in FIG 9 (a) ~9 (c) is the reading of the control unit of the optical interferometric measurement data in the second embodiment.
FIG. 9A shows that an optical coherence tomographic image is obtained by dividing the region into three and scanning the measurement light 903 a total of three times. The range of each layer of Z ₁ , Z ₂ , and Z ₃ is 1/3 of the required measurement depth 902.

FIG. 9B shows that an optical coherence tomographic image is obtained by dividing the region into four and scanning the measurement light 904 a total of four times. Z _n is 1/4 of both required measurement depth 902.
FIG. 9C shows that an optical coherence tomographic image is obtained by dividing the region into five and scanning the measurement light 905 a total of five times. Z _n is 1/5 of both required measurement depth 902.
Based on the zone focus as described above, reading of the optical interference measurement data based on the measurement depth in the second embodiment is controlled. Next, details of the optical interference measurement data readout control will be described using the example of zone focus in FIG.

10 (a) and 10 (b) are conceptual diagrams for explaining a method of reading optical interference measurement data in the second embodiment for explaining the features of the present invention.
10 (a) and 10 (b), the number of divisions is 5, and FIG. 10 (a) is a reading method of optical interference measurement data when interpolation processing is performed, and FIG. 10 (b) is a reading without interpolation processing. Shows how.

With equally divided in the zone focusing as the number of divisions D of the required measurement depth, maximum depth nd _n of each layer Z _n is obtained by the following equation. The measurement depth is indicated by Z using 0 to D as parameters.

According to Equation 2, the wave number interval (frequency) of the optical interference measurement data at the maximum depth nd _n of each layer is determined by the following equation.

第２の実施の形態における光干渉計測データの読み出しは、式１１に基づいて計測深度に応じた制御を行う。 According to the sampling theorem, the reading interval S of the optical interference measurement data only needs to satisfy the following equation.

Reading of the optical interference measurement data in the second embodiment performs control according to the measurement depth based on Expression 11.

Figure 10 (a), 10 (b ) both the division number is 5, since the measurement position Z _n is 1 to 5, all the reading interval of the interferometric measurement data is not a natural number, according to equation 11.
When the measurement position Z _n is 1, according to Equation 8, the optical interference measurement data read interval S is five times the wave number resolution δ _k of the image sensor. Therefore, it is only necessary to read out one of five pieces of measurement data as shown in FIG. Compared to reading all data, the data size can be reduced to 1/5.

Next, in the case of the measurement position Z _n is 2 is not a natural number and read interval S becomes 2.5, namely from becoming less of S fraction, it can not be supported by the control of a simple data unit.
In FIG. 10A, reading is performed sequentially at the reading interval S, two adjacent data are read only at a position where the reading position is 2.5 including a decimal, and an optical interference measurement data reading unit ( The position data is interpolated and generated by the interpolation processing unit in the optical interference measurement data reading unit 207 of the first embodiment. That is, when the reading interval S is a value including a small number and the read data position cannot be indicated by a natural number, the interpolation processing unit controls the reading means to read two adjacent data with the read data position interposed therebetween. Then, an interpolation operation using these data is executed. As a result, the data size can be reduced to 3/5 compared with the case of reading all data.

  In FIG. 10B, since it is sufficient to read the optical interference measurement data while satisfying Expression 11, only a single piece of data is read out of two pieces of measurement data by rounding off the decimal number and setting the read interval S to 2. As a result, the data size can be reduced by half compared to the case of reading all data. In this case, the interpolation processing unit described above does not need to perform interpolation processing.

If the measurement position _{Z n} is 3,4, respectively read spacing S, 5/3 (≒ 1.67) , 5/4 (= 1.25) and for the 2 smaller value is, for interpolating When the adjacent two data are read out, all the data are read out as a result. In this case, the interpolation processing unit of the optical interference measurement data reading unit reads all the data without performing the interpolation process, and outputs it to the FFT processing unit 208. That is, when the reading interval S is smaller than 2, the meaning of performing the interpolation processing does not exist, so the reading control unit stops the interpolation processing by the interpolation processing unit and executes the subsequent processing.
As described above, by adding the interpolation process, it is possible to control the reading of the optical interference measurement data according to the measurement depth without depending on the zone focus.

FIG. 11 is a flowchart illustrating the flow of optical interference measurement data reading processing according to the second embodiment, which explains the features of the present invention. The series of processes in this flowchart is intended to realize a reading method according to the measurement depth of the measurement light shown in FIG.
In step 1101, the reading control unit in the optical interference measurement data reading unit 207 described above acquires information on the measurement depth to be measured from the zone focus control unit 204. The zone focus control unit 204 manages measurement depth information in order to control the eyepiece optical system 304 in accordance with the measurement depth.

In step 1102, the readout control unit calculates the readout interval of the optical interference measurement data shown in FIG. 10 based on the received measurement depth information. At this time, whether the reading interval is set to a value including a decimal number as described above with reference to FIG. 10 or a natural number is set by rounding off the decimal number may be arbitrarily set.
In step 1103, the read control unit determines whether the obtained data is read data based on the read interval calculated in step 1102. If it is data to be read, the process proceeds to step 1104. If it is not data to be read, the process proceeds to step 1108.
In step 1104, the reading control unit determines whether or not the reading position is a natural number when reading is performed based on the reading interval calculated in step 1102. If the reading position is a natural number, the process proceeds to step 1105. If the reading position is not a natural number, the process proceeds to step 1106.
In step 1105, the reading control unit controls the reading unit, which is the same configuration of the optical interference measurement data reading unit 207, to output optical interference measurement data.

In step 1106, the reading control unit controls the reading unit to read two data adjacent to the reading position, and further outputs the two data to the interpolation processing unit which is the configuration of the same optical interference measurement data reading unit. At the same time, an interpolation instruction is transmitted to the interpolation processing unit.
In step 1107, the interpolation processing unit performs weighted interpolation on the data position for the two data read in step 1106.
In step 1108, it is determined whether reading control has been performed on all the data of the optical interference measurement data. When all data read control is performed, a series of optical interference measurement data read processing is terminated. If the read control has not been completed yet, the process proceeds to step 1103 to repeatedly read data.
With the above processing, the optical interference measurement data in the second embodiment can be read.

In the zone focus in the present embodiment, the measurement range in the optical axis direction of the measurement light is equally divided as shown in Expression 9 or FIGS. 9A to 9C for simplicity. According to the configuration of the present embodiment, the read control is not limited to the case of equal division, and if the information on the measurement depth can be obtained with respect to the required measurement depth, the same control is performed even in the case of arbitrary division. It can be performed.
According to the present embodiment, by providing the optical interference measurement data reading unit 207 with the interpolation processing unit, it is possible to control the reading of the optical interference measurement data according to the measurement depth without depending on the zone focus. . Further, it is possible to reduce the optical interference measurement data related to the processing without impairing the measurement accuracy.

(Third embodiment)
A third embodiment for realizing the present invention will be described with reference to the drawings.
In the first and second embodiments, in SD-OCT having a zone focus function, data related to optical coherence tomographic image acquisition processing is controlled by controlling the reading of optical interference measurement data according to the measurement depth of measurement light. Reduced size.
The feature of the third embodiment resides in that the optical interference measurement data beyond the required measurement depth is reduced by controlling the reading of the optical interference measurement data. The optical interference measurement data readout control in the third embodiment is also applicable to SD-OCT having no zone focus.
This embodiment will be described focusing on the above features.

FIG. 12 is a conceptual diagram illustrating a method of reading optical interference measurement data in the third embodiment for explaining the features of the present invention.
FIG. 12 shows an SD-OCT scanning method in the case where an optical coherence tomographic image is acquired with measurement light 1204 having a small NA and a deep depth of field. Note that a thick solid line 1201 is a coherence gate in which the optical path lengths of the reference light and the measurement light coincide, a thin solid line 1202 is a necessary measurement depth necessary for diagnosis, and a one-dot chain line 1203 is a maximum measurement that can be measured by the number of pixels of the image sensor. Depth is shown.
The figure also illustrates an optical coherence tomographic image 2005 near the macula in the eye to be examined.

In the case of FIG. 12, the maximum measurement depth of the measurement light 1204 greatly exceeds the necessary measurement depth 1202 required for diagnosis. When scanning is performed as it is, information on a position deeper than the necessary measurement depth 1202 can be obtained. It will be.
If the necessary measurement depth 1202 with respect to the maximum measurement depth 1203 can be known, the effective frequency of the interference light measurement data can be grasped based on the characteristics of the measurement depth and the frequency of the interference light waveform to be measured. By setting the reading interval S of the optical interference measurement data accordingly, information at a position deeper than the required measurement depth can be reduced.
In order to know the necessary measurement depth 1202, pre-scanning may be performed using measurement light having a deep depth of field before scanning for acquiring an actual optical coherence tomographic image.

In the description of FIG. 12, the case of SD-OCT having no zone focus function using measurement light 1204 having a small NA and a deep depth of field is shown. Needless to say, it can be applied.
Further, in the case of SD-OCT having a zone focus function, it is possible to arbitrarily set the necessary number of zone focus divisions and the width of each measurement region with respect to the required measurement depth 1202 by grasping the required measurement depth 1202 in advance. it can.
As described above, by grasping the necessary measurement depth 1202 before the scan for acquiring the optical coherence tomographic image, the reading control of the optical interference measurement data can be applied, and a position deeper than the necessary measurement depth is unnecessary. It is possible to discard such information as data is read out.

Next, the flow of optical interference measurement data readout control in the third embodiment will be described.
In the series of processes in the main flowchart showing the overall flow of the optical coherence tomographic image acquisition process in this embodiment, the necessary measurement depth is acquired and calibration is performed before measurement, so that redundant measurement is performed simultaneously with the reading of the optical interference measurement data. The information is discarded, and an optical coherence tomographic image preferable for diagnosis is obtained.
More specifically, compared with the flowchart of FIG. 7 in the first embodiment, the fourth embodiment includes a step of performing calibration before measurement.

In this step, calibration is performed before the measurement process for acquiring the optical coherence tomographic image (specifically, step 702). Details will be described later.
In step 2102, optical interference measurement data reading control in the third embodiment is performed. Details will be described later.
With the above processing, the optical coherence tomographic image in the third embodiment is acquired.

FIG. 13 is a flowchart illustrating a calibration flow before measurement according to the third embodiment, which explains the features of the present invention. The series of processing in this flowchart is to perform pre-scan to grasp the required measurement depth and scan the basic optical interference measurement data in advance before scanning to obtain the actual optical coherence tomographic image. It is aimed.
In step 1301, pre-scanning is performed using measurement light having a deep depth of field. The prescan may be one A scan.

In the case of OCT as an ophthalmic medical device, the measurement target is generally the retina, and a tomographic image necessary for diagnosis up to the pigment epithelium layer located at the lowest layer of the retina is required. In many cases, the pigment epithelium layer is almost flat on the optical coherence tomographic image, and therefore, the necessary measurement depth can be considered constant during one measurement. Therefore, it is possible to calculate the necessary measurement depth by performing one A scan.
The required measurement depth may be calculated by performing A scan a plurality of times (coarse B scan).

In step 1302, the necessary measurement depth is calculated from the measurement data obtained by the pre-scan in step 1301. In general, in the optical coherence tomographic image of the retina, the pigment epithelium layer exhibits the strongest reflection with respect to the measurement light. Therefore, the necessary measurement depth may be calculated using the position where the signal intensity is strong as an index. Further, when a rough B scan is performed as a pre-scan, the required depth may be calculated using the maximum depth as an index.
In step 1303, in accordance with the required measurement depth obtained in step 1302, the setting for reading control of the optical interference measurement data serving as a base as described in FIG. 12 is performed. Thereby, the information of the fault depth more than the necessary measurement depth can be discarded together with the data reading.

In step 1304, it is determined whether to use the zone focus function. When measurement is performed using zone focus, the process proceeds to step 1305. When the zone focus function is not used or the zone focus function is not provided, a series of calibration processing is ended.
In step 1305, the zone focus is set by dividing the measurement light in the zone focus in the optical axis direction.
With the above processing, the base setting of the optical interference measurement data reading control in the third embodiment can be performed.

  According to the present embodiment, by performing calibration using pre-scanning before acquisition of the optical coherence tomographic image, it is possible to perform presetting that is the basis of optical interference measurement data readout control. Thereby, unnecessary information deeper than the required measurement depth can be discarded at the same time as the data reading, and the size of the optical interference measurement data related to the acquisition of the optical interference tomographic image can be reduced.

(Fourth embodiment)
A fourth embodiment for realizing the present invention will be described with reference to the drawings.
In the first, second, and third embodiments, the data size related to the optical coherence tomographic image acquisition process is reduced on the premise of the optical interference measurement data subjected to the wave number conversion process.
Using the fact that the wavelength and wave number are inversely proportional, the readout control performed on the optical interference measurement data rearranged on the wave number axis is measured for each wavelength before being rearranged on the wave number axis. The present invention can also be applied to measured data.
The feature of the fourth embodiment resides in that readout control is performed on measurement data of interference light that is spectrally separated for each wavelength by the diffraction grating before wave number conversion. This makes it possible to reduce the data size related to the process of acquiring the optical coherence tomographic image before or simultaneously with the wave number conversion process.
This embodiment will be described focusing on the above features.

The functional block of the OCT system in the fourth embodiment does not require the wave number conversion described in the first embodiment, and therefore the wave number conversion unit 206 shown in FIG. The function of the data reading unit 207 is different.
That is, the OCT having the SD-OCT function in this embodiment includes an irradiation unit 203 that irradiates measurement light shown in FIG. 2, a zone focus control unit 204 that controls the optical system of the irradiation unit, a measurement unit 205 that measures interference light, Transmission of signals to and from the optical interference measurement data reading unit (207), the FFT processing unit 208 that converts the measurement data of the interference light into optical coherence tomographic data, and the image processing device 202 as an external processing device in the fourth embodiment. It is comprised from I / F209 used when performing.
The optical interference measurement data reading unit (207) in the present embodiment is a data reading unit that performs optical interference measurement data read control on measurement data that has been spectrally divided for each wavelength according to the measurement depth of the measurement light. Details will be described later.
The OCT system having the above configuration enables control equivalent to the readout control described in the first, second, and third for the optical interference measurement data before wave number conversion.

The optical interference measurement data reading unit (207) in the fourth embodiment reads out according to the reading unit that reads out the optical interference measurement data, the interpolation processing unit that performs interpolation, the reading table that stores the reading control information, and the measurement depth. And a reading control unit that controls the interpolation processing unit.
The reading unit outputs the optical interference measurement data separated for each wavelength to the next processing. Further, the reading unit switches presence / absence of output according to an instruction from the reading control unit.

The interpolation processing unit performs interpolation processing on the data received from the reading unit in accordance with an instruction from the reading control unit. The interpolation processing unit performs interpolation processing considering wave number conversion, and prepares optical interference measurement data that has been subjected to wave number conversion processing.
The read table stores read control information necessary for reading the optical interference measurement data that has been dispersed for each wavelength.

In order to perform FFT processing, optical interference measurement data that has undergone wave number conversion is generally used. In the wave number conversion process, since the wavelength and the wave number are in an inversely proportional relationship, the data is rearranged by calculating the reciprocal of the wavelength with respect to the data measured for each wavelength. Data that is measured at equal intervals for each pixel of the image sensor on the wavelength axis will not be an equally spaced data array when rearranged at the wave number, and therefore, even at the wave number by interpolation processing, Yes.
In this case, a general interpolation method is used, and many methods such as linear interpolation processing and interpolation using a Spline curve are known, and any of them may be used, but interpolation is required by an interpolation algorithm. The number of data is different.
Therefore, the reading control method of the optical interference measurement data dispersed for each wavelength differs depending on the interpolation algorithm used. The above-described readout table stores information on the number of data required for the interpolation processing as well as information on the readout control of the optical interference measurement data corresponding to the measurement depth, as readout control information in association with the interpolation algorithm to be used.
The interpolation algorithm to be used may be arbitrarily set before measurement.

The reading control unit controls the reading unit and the interpolation processing unit with reference to the reading control information stored in the reading table based on the measurement depth information from the zone focus control unit 204.
With the data reading unit having the above-described configuration, it is possible to control data reading based on the measurement depth of the measurement light, even with respect to the optical interference measurement data dispersed for each wavelength. Next, the flow of optical interference measurement data reading control will be described.

A series of processes in the main flowchart showing the overall flow of the optical coherence tomographic image acquisition process in the fourth embodiment is suitable for diagnosis by performing appropriate read control on the optical interference measurement data arranged for each wavelength. The purpose is to obtain optical coherence tomographic images.
Compared with the flowchart of FIG. 7 in the first embodiment, in the fourth embodiment, step 704 for performing wave number conversion is not necessary.
In step 705 for reading optical interference measurement data, reading control of optical interference measurement data arranged for each wavelength is performed in accordance with the elimination of step 704 for wave number conversion in the fourth embodiment. Details will be described later.
Through the above processing, the optical coherence tomographic image in the fourth embodiment is acquired. Subsequently, a flow of control performed in the step of reading optical interference measurement data in the fourth embodiment will be described.

FIG. 14 is a flowchart illustrating the flow of optical interference measurement data reading processing according to the fourth embodiment, which explains the features of the present invention. The series of processes in this flowchart is intended to realize a reading method according to the measurement depth of the measurement light with respect to the optical interference measurement data dispersed for each wavelength.
In step 1401, the reading control unit in the optical interference measurement data reading unit (207) acquires information on the measurement depth to be measured from the zone focus control unit 204. The zone focus control unit 204 manages measurement depth information in order to control the eyepiece optical system 304 in accordance with the measurement depth.

In step 1402, the read control unit similarly obtains read control information with reference to the read table constituting the optical interference measurement data reading unit (207).
In step 1403, the read control unit grasps data to be read out of the optical interference measurement data based on the received measurement depth information and read control information.

In step 1404, the read control unit determines whether the obtained data is read data based on the read information grasped in step 1403. If it is data to be read, the process proceeds to step 1405. If it is not data to be read, the process proceeds to step 1409.
In step 1405, the read control unit determines whether the data to be read is data to be interpolated based on the read data information grasped in step 1403. In the case of interpolation target data, the process proceeds to step 1406. If it is not interpolation target data, the process proceeds to step 1408.
In step 1406, the reading control unit similarly controls the reading unit constituting the optical interference measurement data reading unit to read a plurality of data necessary for interpolation and output the data to the interpolation processing unit. The reading control unit simultaneously transmits an interpolation instruction to the interpolation processing unit.

In step 1407, the interpolation processing unit performs interpolation processing from a plurality of data received from the reading unit in accordance with an instruction from the reading control unit.
In step 1408, the reading control unit controls the reading unit to output optical interference measurement data.
In step 1409, it is determined whether or not reading control has been performed for all data of the optical interference measurement data. When all data read control is performed, a series of optical interference measurement data read processing is terminated. If the read control has not been completed yet, the process proceeds to step 1404 to repeatedly read data.
With the above processing, it is possible to perform read control of optical interference measurement data arranged for each wavelength in the fourth embodiment.

According to the present embodiment, the read control of the present invention is applied to optical interference measurement data arranged for each wavelength by preparing a read table storing interpolation information necessary for wave number conversion. It becomes possible to perform wave number conversion simultaneously with data reading.
In the present embodiment, it may be configured such that only the reading control of the optical interference measurement data is performed without including information necessary for wave number conversion in the read table, and the wave number conversion processing unit separately performs the wave number conversion.
Compared to wave number conversion, which used to interpolate the measurement data arranged for each wavelength and generate and re-arrange the data over the entire wave number band on the wave number axis, it is necessary for data of the required wave number. By reading only the wavelength data and performing interpolation, the processing load related to wave number conversion can be reduced.
Thereby, it is possible to further reduce the processing time related to the optical coherence tomographic image diagnosis.

(Fifth embodiment)
Needless to say, the object of the present invention is achieved by the following. That is, a storage medium (or recording medium) storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or apparatus. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

  Further, by executing the program code read by the computer, an operating system (OS) or the like running on the computer performs part or all of the actual processing based on the instruction of the program code. Needless to say, the process includes the case where the functions of the above-described embodiments are realized.

Furthermore, it is assumed that the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. After that, based on the instruction of the program code, the CPU included in the function expansion card or function expansion unit performs part or all of the actual processing, and the function of the above-described embodiment is realized by the processing. Needless to say.
When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

(Other embodiments)
A person skilled in the art can easily configure a new system by appropriately combining various technologies in the above embodiments, and thus a system based on such various combinations is also within the scope of the present invention. Belongs to.
In the first to fourth embodiments, examples of application in a system using SD-OCT have been described. As described above, according to the present invention, optical interference measurement data readout control is performed by applying the characteristics of measurement depth and interference light in FD-OCT that obtains tomographic information from optical spectrum information. -Not limited to OCT. Even in SS-OCT using a wavelength-swept light source, it is possible to obtain the optical interference measurement data for each measurement depth by dividing the measurement region in the optical axis direction of the measurement light by applying the present invention. Therefore, a system using SS-OCT also belongs to the category of the present invention.
Furthermore, since it is easily possible for those skilled in the art to configure a new system by appropriately combining various technologies in the above-described embodiments, a system based on such various combinations is also included in this system. It belongs to the category of the invention.

801... Acquiring measurement depth information of measurement light 802... Calculating data reading interval 803... Determining whether data is read 804... Reading data 805.・ Step to determine whether or not read control has been performed on all data

Claims (20)

A method for reading optical interference measurement data in an optical coherence tomographic diagnosis that constructs a tomographic image from optical spectrum information using optical interference,
An acquisition step of acquiring information on the measurement depth of the optical interference measurement data;
A determination step for determining data to be read out of the optical interference measurement data based on the measurement depth information;
A read control step for controlling to read the read data determined in the determination step;
A method for reading out optical interference measurement data based on the control in the reading control step.   In the determining step, data not to be read is determined by calculating a read interval for reading the read data based on the measured depth, and the read interval is narrowed as the measured depth increases. Item 4. The optical interference measurement data reading method according to Item 1. A measurement light generation step for generating measurement light to irradiate the measurement target;
A light beam diameter control step for controlling a light beam diameter of the measurement light;
And a condensing position control step for controlling the condensing position of the measurement light,
3. The optical interference measurement data is measured while controlling the condensing position of the measurement light by the condensing position control step during the measurement of the optical interference measurement data. The optical interference measurement data reading method according to the item.   4. The light according to claim 3, wherein the determining step grasps the measurement depth based on a light beam diameter in the light beam diameter control step and / or control information of a light collection position in the light collection position control step. Interference measurement data reading method. The readout control step includes a step of dividing the measurement depth necessary for measuring the tomographic image of the measurement object by a division number ^2D ,
The readout interval S of the optical interference measurement data is set such that the number of divisions is 2 ^D and the measurement depth of each of the divided measurement areas is Z (0 to D).

The optical interference measurement data reading method according to claim 3, wherein the optical interference measurement data reading method is calculated according to: The readout control step includes a step of dividing a measurement depth necessary for measuring the tomographic image of the measurement object by D,
The readout interval S of the optical interference measurement data is defined such that the number of divisions is D and the measurement depth of each of the divided measurement areas is Z (0 to D).

The optical interference measurement data reading method according to claim 3, wherein the optical interference measurement data reading method is calculated according to:   The reading control step, in the dividing step, equally divides a measurement depth necessary for measuring the tomographic image to be measured so that each measurement region has the same width. 7. The optical interference measurement data reading method according to 6.   8. The light according to claim 6, wherein when the reading interval S becomes a value including a decimal, the optical interference measurement data is read out by rounding down the decimal. Interference measurement data reading method. An interpolation step of interpolating the optical interference measurement data read out by the reading step;
When the reading interval S is a value including a decimal number in the reading control step and the reading data position is not a natural number, two adjacent data are read across the reading data position, and the reading data position in the interpolation step The optical interference measurement data reading method according to claim 6, wherein interpolation is performed between the two adjacent data based on the data.   10. The optical interference measurement data reading method according to claim 9, wherein when the reading interval S is smaller than 2, the reading control step stops the interpolation step. Before acquiring a tomographic image to the measurement object, further comprising a setting step for setting the readout control of the optical interference measurement data serving as a base,
The setting step measures at least one tomographic information, grasps a necessary measurement depth based on the measured tomographic information, and based on the grasped necessary measurement depth, the optical interference measurement serving as the basis 2. The optical interference measurement data reading method according to claim 1, wherein data reading control is set.   In the setting step, at least one tomographic information before the tomographic image is measured by controlling the measurement light to light having a deep depth of field by the light beam diameter control unit and the condensing position control unit. The optical interference measurement data reading method according to claim 11, wherein measurement is performed.   2. The readout process according to claim 1, wherein in the readout step, readout is performed on data obtained by subjecting the measurement data of the interference light that has been spectrally divided and measured for each wavelength to the wave number conversion. The optical interference measurement data reading method described.   2. The optical interference measurement data reading method according to claim 1, wherein, in the reading step, reading is performed with respect to measurement data of interference light that is spectrally measured for each wavelength. An optical coherence tomographic diagnosis apparatus that constructs a tomographic image from optical spectrum information using optical interference,
An acquisition means for acquiring measurement depth information of the optical interference measurement data;
Determination means for determining data to be read out of the optical interference measurement data based on the measurement depth information;
Read control means for controlling to read the read data determined by the determination means;
An optical interference diagnostic apparatus comprising: reading means for reading optical interference measurement data based on the control of the reading control means. Measurement light generating means for generating measurement light to be irradiated to the measurement object;
A beam diameter control means for controlling a beam diameter of the measurement light;
A condensing position control means for controlling the condensing position of the measurement light, and
16. The optical coherence tomography according to claim 15, wherein during the measurement of the optical interference measurement data, the optical interference measurement data is measured while controlling the condensing position of the measurement light by the condensing position control means. Measuring device. The readout control unit further includes a dividing unit that divides a measurement depth necessary for measuring the tomographic image to be measured into a predetermined number of divisions,
The readout interval S of the optical interference measurement data set for the readout control means to read out the optical interference measurement data is calculated based on the predetermined number of divisions and the measurement depth of each of the divided measurement areas. The optical coherence tomography diagnosis apparatus according to claim 15. An interpolation means for interpolating the optical interference measurement data read by the reading means;
When the read interval S set by the read control means is a value including a decimal, the interpolation means reads two adjacent data across the position of the data read by the read means, and the interpolation means 18. The optical coherence tomography diagnosis apparatus according to claim 17, wherein interpolation between the two adjacent data is performed based on a data position to be read.   The reading means is either the data obtained by subjecting the optical interference measurement data spectrally measured for each wavelength to wave number conversion processing, or the optical interference measurement data spectrally measured for each wavelength. The optical coherence tomographic diagnosis apparatus according to claim 15, wherein the optical coherence tomographic diagnosis apparatus is read out. Optical coherence tomography diagnosis composed of an optical coherence tomography measuring device that measures tomographic information from optical spectrum information using optical interference and an image processing device that constructs an optical coherent tomographic image from the measured tomographic information and presents it to the user A system,
An optical coherence tomography measurement device according to any one of claims 15 to 19, and an input means for inputting output information of the optical coherence tomography measurement device,
Image generating means for generating an optical coherence tomographic image from the optical interference measurement data input by the input means;
Display means for displaying the optical coherence tomographic image, the image processing apparatus,
An optical coherence tomography diagnosis system comprising:

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