# US 10,502,544 B2 · Efficient sampling of optical coherence tomography data for explicit ranging over extended depth

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- Number: US 10,502,544 B2
- Document ID: US10502544B2
- Status: Granted
- Kind: B2
- Application number: 16/308,800
- Filed: 2017-06-14
- Published: 2019-05-16
- Granted: 2019-12-10
- Earliest claimed: 2016-06-15
- Assignees: Carl Zeiss Meditec AG
- Applicants: Carl Zeiss Meditec, Inc.; Carl Zeiss Meditec AG
- Inventors: Yuan Liu; Nathan Shemonski; Matthew J. Everett
- Web page: https://patentgrep.com/patent/US10502544B2

## CPC

- G01B 9/02009: {by using two or more low coherence lengths using different or varying spectral width}
- G01B 9/02078: {Caused by ambiguity}
- G01B 9/02087: {Combining two or more images of the same region}
- A61B 3/102: {for optical coherence tomography [OCT]}
- G01B 9/02091: Tomographic interferometers, e.g. based on optical coherence
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

An efficient OCT data collection and processing method for obtaining a high-axial-resolution image with explicit ranging over an extended depth is described. The method includes collecting a first dataset at a transverse location of the sample. The first dataset comprises spectra of a bandwidth (Δk1) sampled at a spectral sampling interval (dk1). A second dataset comprising spectra of a bandwidth (Δk2) sampled at a spectral sampling interval (dk2) is collected. The bandwidth Δk2 is less than Δk1 and spectral sampling interval dk2 is less than dk1. The first and the second datasets are processed to generate at least one A-scan with an axial resolution higher than the axial resolution corresponding to the bandwidth Δk2 and a depth range larger than the depth range provided by sampling interval dk1.

## Claims

### Claim 1

A method of collecting and processing OCT data of a sample using an optical coherence tomography (OCT) system, said method comprising:
collecting a first dataset at a transverse location of the sample, said first dataset comprising spectra of a bandwidth (Δk1) sampled at a spectral sampling interval (dk1);
collecting a second dataset at said a transverse location of the sample, said second dataset comprising spectra of a bandwidth (Δk2) sampled at a spectral sampling interval (dk2), wherein Δk2 is less than Δk1 and dk2 is less than dk1;
processing the first and the second datasets together to generate at least one A-scan, wherein the processed A-scan has an axial resolution greater than the axial resolution corresponding to Δk2 and a depth range greater than the depth range provided by dk1; and
storing or displaying the results of said processing or a further analysis thereof.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein the processed A-scan has an axial resolution corresponding to the bandwidth Δk1, and wherein data from the second dataset is used to determine the axial location of the sample from said at least one A-scan over a range greater than that given by the sampling interval dk1.

### Claim 3 (depends on 1)

The method as recited in claim 1, wherein the first dataset is collected before the second dataset.

### Claim 4 (depends on 1)

The method as recited in claim 1, wherein the first and/or second datasets are complex-valued datasets.

### Claim 5 (depends on 1)

The method as recited in claim 1, wherein the first dataset further comprises a spectral resolution, δk1, that is less than the spectral sampling interval, dk1, (δk1<dk1).

### Claim 6 (depends on 1)

The method as recited in claim 1, wherein processing the first and the second datasets comprises:
combining the first and the second datasets;
detecting a true imaging depth window from the combined or individual datasets; and
using the detected true imaging depth window to generate the at least one A-scan.

### Claim 7 (depends on 1)

The method as recited in claim 1, wherein said processing is performed in one or more of a spatial domain and spectral domain.

### Claim 8 (depends on 6)

The method as recited in claim 6, further comprising:
prior to said combining, filtering one or more of the first dataset and the second dataset.

### Claim 9 (depends on 6)

The method as recited in claim 6, wherein said combining involves multiplying the first dataset by the second dataset.

### Claim 10 (depends on 6)

The method as recited in claim 6, wherein said true imaging depth window detection includes using a maximum-signal approach that comprises comparing corresponding pixels in different imaging windows and detecting an imaging window with the maximum signal as the true imaging depth window.

### Claim 11 (depends on 6)

The method as recited in claim 6, wherein said true imaging depth window detection includes using a center-of-mass approach that comprises computing a center of mass of each A-scan and setting an imaging window of a pre-defined depth extent around it.

### Claim 12 (depends on 1)

The method as recited in claim 1, wherein the number of spectral samples of the first dataset varies at different transverse locations on a sample.

### Claim 13 (depends on 12)

The method as recited in claim 12, wherein the integration time of each spectral sample of the first dataset varies at different transverse locations on a sample.

### Claim 14 (depends on 12)

The method as recited in claim 12, wherein the optical power used to acquire the first dataset varies at different transverse locations on a sample.

### Claim 15 (depends on 1)

The method as recited in claim 1, wherein the OCT system comprises one of a swept-source OCT (SS-OCT) system, a spectral-domain OCT (SD-OCT) system, and a combination of SS-OCT and SD-OCT systems.

### Claim 16 (depends on 1)

The method as recited in claim 1, wherein the processing step generates a plurality of A-scans.

### Claim 17

An optical coherence tomography (OCT) system for collecting and processing OCT data of a sample, said system comprising:
a light source for generating a light beam;
a beam divider for separating the light beam into a sample arm and a reference arm, said sample arm containing the sample to be imaged;
optics for scanning the beam in the sample arm over a set of transverse locations on the sample;
a detector for measuring light returned from both the sample arm and the reference arm and generating signals in response thereto and;
a processor for processing the signals and generating data based on the processed signals,
said OCT system capable of scanning the sample in a first mode and a second mode, wherein:
the sample is scanned in the first mode to obtain a first dataset, wherein the first dataset comprises spectra of a bandwidth (Δk1) sampled at a spectral sampling interval (dk1),
the sample is scanned in the second mode to obtain a second dataset, wherein the second OCT dataset comprises spectra of a bandwidth (Δk2) sampled at a spectral sampling interval (dk2), wherein Δk2 is less than Δk1 and dk2 is less than dk1, and
said processor processes the first dataset and the second dataset to generate at least one A-scan, said A-scan having an axial resolution greater than the axial resolution provided by Δk2 and a depth range greater than the depth range provided by dk1.

### Claim 18 (depends on 17)

The OCT system as recited in claim 17, wherein the processed A-scan has an axial resolution corresponding to the bandwidth Δk1, and wherein data from the second dataset is used to determine the axial location of the sample from said at least one A-scan over a range greater than that given by the sampling interval dk1.

### Claim 19 (depends on 17)

The OCT system as recited in claim 17, wherein the detector is a quadrature detection apparatus for acquiring complex-valued interference signals.

### Claim 20 (depends on 17)

The OCT system as recited in claim 17, wherein the processor performs the following steps to generate the at least one A-scan: combining the first and the second datasets; detecting a true imaging depth window from the combined or individual datasets; and using the detected true imaging depth window to generate the at least one A-scan.

### Claim 21 (depends on 17)

The OCT system as recited in claim 17, wherein the FD-OCT system comprises one of a swept-source OCT (SS-OCT) system, a spectral-domain OCT (SD-OCT) system, and a combination of SS-OCT and SD-OCT systems.