JONES MATRIX OCT SYSTEM AND PROGRAM FOR CARRYING OUT IMAGE PROCESSING ON MEASURED DATA OBTAINED BY SAID OCT

• US 20160106319A1
• Filed: 05/15/2014
• Published: 04/21/2016
• Est. Priority Date: 05/24/2013
• Status: Active Grant

• Current Assignee: University of Tsukuba
• Original Assignee: University of Tsukuba
• Inventors: YASUNO, Yoshiaki, JU, Myeong Jin, ITOH, Masahide
• Granted Patent: US 10,470,663 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 2576/00 Medical imaging apparatus involving image processing or analysis A61B1/00009, A61B6/52 and A61B8/52 take precedence; image processing per se G06T; details of algorithms for analysing medical images G06T7/0012
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: G01B 2290/35 Mechanical variable delay line
• CPC Class Codes: G01B 2290/45 Multiple detectors for detecting interferometer signals
• CPC Class Codes: G01B 2290/70 Using polarization in the interferometer
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

A Jones matrix OCT offers improved image stability, image quality, and depth range of image, wherein light from a wavelength-scanning light source is split into two optical paths, and a reference arm is provided along one optical path, while a probe arm that irradiates and reflects light onto the measuring target to generate object light is provided along the other optical path. The probe arm has a polarization delay unit that linearly polarizes the light and then splits it into S-wave component and P-wave component, where the S-wave component and P-wave component are superimposed through optical paths of different optical path lengths, respectively, after which optical detectors are used to detect different spectral interference beams in the depth direction of the measuring target corresponding to the vertically polarized component and horizontally polarized component, which respectively correspond to the S-wave component and P-wave component, to obtain four spectral interference signals.

Claims

1. A Jones matrix OCT system having:

a wavelength-scanning light source;

a coupler that splits a light from the wavelength-scanning light source into two optical paths;

a reference arm provided along one of the two optical paths, to reflect one split light using a reference mirror and thus generate reference light;

a probe arm provided along the other of the two optical paths, to irradiate and reflect the other split light onto the measuring target and thus generate object light;

a polarization-separation detection unit that superimposes the reference light and object light to generate spectral interference beams and then detects the spectral interference beams using optical detectors; and

a computer that generates tomographic images of the measuring target based on the spectral interference beams detected by the polarization-separation detection unit;

the Jones matrix OCT system characterized in that;

the probe arm has a polarization delay unit that linearly polarizes the other light and then splits it into S-wave component and P-wave component, where the S-wave component and P-wave component are superimposed with each other through optical paths of different optical path lengths, respectively;

wherein the polarization-separation detection unit can obtain four spectral interference signals by using the optical detectors to detect the different spectral interference beams in a depth direction of the measuring target that correspond to the S-wave component and P-wave component, respectively, among the vertically polarized components of the spectral interference beams, as well as the different spectral interference beams in the depth direction of the measuring target that correspond to the S-wave component and P-wave component, respectively, among the horizontally polarized components; and

the computer can generate tomographic images in the depth z direction of the measuring target, while being constituted in such a way that it will generate tomographic images of higher resolution by obtaining coherent coupling from a matrix of the four spectral interference signals and by further combining the four spectral interference signals after de-randomizing their phases to obtain matrix coherent elements.

2. A Jones matrix OCT system according to claim 1, characterized in that the computer is constituted in such a way that it can display a Doppler image by calculating a formula indicating a square intensity of Doppler phase shift, based on a definition that a Doppler shift between an A-line in a jth B-scan and an A-line in a j+1th B-scan is represented by mutually conjugating coherent components,

where a same point is measured with multiple (m number of) B-scans to obtain the Doppler shift, which is then applied to Doppler measurement to improve a sensitivity of Doppler measurement.

3. A Jones matrix OCT system according to claim 1, characterized in that the computer is constituted in such a way that it can obtain OCT images based on a scattered and reflected light from the measuring target, and can also obtain high-quality scattered OCT images by calculating a coherent average of data from multiple B-scans.

4. A Jones matrix OCT system according to claim 1, characterized in that:

a phase calibration unit having a calibration mirror is provided in an optical path branching from an optical path leading to the measuring target via the coupler;

the calibration mirror reflects interference beams entering the calibration unit, which have been generated at the polarization delay unit due to interference caused by a differential optical path length with respect to the P waves or S waves themselves, and sends the interference beams to the polarization-separation detection unit via the coupler to be superimposed with the reference light into interference beams that function as calibration signals;

a horizontal-balancing polarization detector and a vertical-balancing polarization detector respectively detect the interference beams that function as calibration signals; and

the computer uses these calibration signals to compensate a jitter generating in a synchronization between scanning of a wavelength of the light source and A-scan.

8. A Jones matrix OCT system according to claim 2, characterized in that:

a phase calibration unit having a calibration mirror is provided in an optical path branching from an optical path leading to the measuring target via the coupler;

the calibration mirror reflects interference beams entering the calibration unit, which have been generated at the polarization delay unit due to interference caused by a differential optical path length with respect to the P waves or S waves themselves, and sends the interference beams to the polarization-separation detection unit via the coupler to be superimposed with the reference light into interference beams that function as calibration signals;

a horizontal-balancing polarization detector and a vertical-balancing polarization detector respectively detect the interference beams that function as calibration signals; and

the computer uses these calibration signals to compensate a jitter generating in a synchronization between scanning of a wavelength of the light source and A-scan.

9. A Jones matrix OCT system according to claim 3, characterized in that:

a phase calibration unit having a calibration mirror is provided in an optical path branching from an optical path leading to the measuring target via the coupler;

the calibration mirror reflects interference beams entering the calibration unit, which have been generated at the polarization delay unit due to interference caused by a differential optical path length with respect to the P waves or S waves themselves, and sends the interference beams to the polarization-separation detection unit via the coupler to be superimposed with the reference light into interference beams that function as calibration signals;

a horizontal-balancing polarization detector and a vertical-balancing polarization detector respectively detect the interference beams that function as calibration signals; and

the computer uses these calibration signals to compensate a jitter generating in a synchronization between scanning of a wavelength of the light source and A-scan.

5. A computer readable no-transitory medium storing a program installed in a computer of a Jones matrix OCT system to generate tomographic images of a measuring target based on spectral interference beams detected by an optical detector, where the Jones matrix OCT system has:

a wavelength-scanning light source;

a coupler that splits a light from the wavelength-scanning light source into two optical paths;

a reference arm provided along one of the two optical paths, to reflect one split light using a reference mirror and thus generate reference light;

a probe arm provided along the other of the two optical paths, to irradiate and reflect the other split light onto the measuring target and thus generate object light;

a polarization-separation detection unit that superimposes the reference light and object light to generate spectral interference beams and then detects the spectral interference beams using optical detectors; and

a computer;

wherein the probe arm has a polarization delay unit that linearly polarizes the other light and then splits it into S-wave component and P-wave component, where the S-wave component and P-wave component are superimposed with each other through optical paths of different optical path lengths, respectively;

the polarization-separation detection unit can obtain four spectral interference signals by using the optical detectors to detect the different spectral interference beams in a depth direction of the measuring target that correspond to the S-wave component and P-wave component, respectively, among the vertically polarized components of the spectral interference beams, as well as the different spectral interference beams in the depth direction of the measuring target that correspond to the S-wave component and P-wave component, respectively, among the horizontally polarized components; and

the program is characterized in that it allows the computer to function as an image-processing means that can generate different tomographic images in the depth z direction of the measuring target from the four spectral interference signals, and can also generate tomographic images of higher resolution by obtaining coherent coupling from a matrix of the four spectral interference signals and by also obtaining coherent elements that have been combined after de-randomizing phases of the four spectral interference signals.

6. A computer readable no-transitory medium storing a program according to claim 5, characterized in that it allows the computer to function as an image-processing means that can display a Doppler image by calculating a formula indicating a square intensity of Doppler phase shift, based on a definition that a Doppler shift between an A-line in a jth B-scan and an A-line in a j+1th B-scan is represented by mutually conjugating coherent components, and also improves a sensitivity of Doppler measurement by measuring a same point with multiple (m number of) B-scans to obtain the Doppler shift which is then applied to Doppler measurement.

7. A computer readable no-transitory medium storing a program according to claim 5, characterized in that it allows the computer to function as an image-processing means that can obtain OCT images based on a scattered and reflected light from the measuring target using coherent matrix components, and can also obtain high-quality scattered OCT images by calculating a coherent average of data from multiple B-scans.