Systems and methods for variable-range fourier domain imaging

• US 10,502,546 B2
• Filed: 11/07/2017
• Issued: 12/10/2019
• Est. Priority Date: 11/07/2017
• Status: Active Grant

• Current Assignee: Santec Holdings Corp.
• Original Assignee: Santec Incorporated
• Inventors: Chong, Changho
• Primary Examiner(s): Chowdhury, Tarifur R
• Assistant Examiner(s): Cook, Jonathon
• Application Number:
  US15/806,022
• Publication Number:
  US 20190137255A1
• Time in Patent Office: 763 Days
• Field of Search: 356479, 356497
• CPC Class Codes: G01B 9/0203 With imaging systems
• CPC Class Codes: G01B 9/02034 characterised by particularly shaped beams or wavefronts
• CPC Class Codes: G01B 9/02049 characterised by particular mechanical design details
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G02B 15/144109 arranged +--+
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 7/023 permitting adjustment

Abstract

An optical system includes a light source, an interferometer, and a detector. The interferometer includes a scanner and a lens system disposed downstream of the scanner. The scanner is configured to direct a portion of the optical beam along one of a plurality of different directions within a scanning range. The lens system is configured to project the portion of optical beam to an imaging area defined by a field of view of the optical system, the lens system comprising a first lens, wherein an aspect of the first lens is adjustable so as to render the field of view adjustable without adjusting the scanning range of the scanner. The detector is configured to receive a reflected portion of the optical beam that reflects from an object placed within the imaging area.

Claims

1. An optical system comprising:

a light source configured to generate an optical beam and project the optical beam along an optical path;

an interferometer comprising;

a scanner disposed on the optical path, the scanner being configured to direct a sample component of the optical beam along one of a plurality of different directions within a scanning range; and

a lens system disposed downstream of the scanner, the lens system configured to project the sample component to an imaging area defined by a field of view of the optical system, the lens system comprising a first lens, wherein an aspect of the first lens is adjustable so as to render the field of view adjustable without adjusting the scanning range of the scanner; and

a detector configured to receive a reflected portion of the sample component that reflects from an object placed within the imaging area.

2. The optical system of claim 1, wherein the scanner and the lens system form a sample arm of the interferometer, wherein the interferometer further includes an optical element upstream of the scanner, and wherein the optical element is configured to:

split the optical beam into the sample component and a reference component,

direct the reference component along a reference arm of the interferometer,

direct the sample component to the sample arm, and

guide the reflected portion and the reference component to the detector to generate an interference signal.

3. The optical system of claim 1, wherein the sample arm further includes a beam expander configured to expand the sample component to a desired size prior to the sample component reaching the lens system.

4. The optical system of claim 3, wherein the beam expander includes a first tunable lens, a second tunable lens, and a controller configured to adjust the focal lengths of the first and second lenses.

5. The optical system of claim 4, wherein the controller is configured to:

receive an indication that a desired imaging distance of the OCT system is below a first threshold value; and

in response to receiving the indication that the desired imaging distance is below the first threshold value, provide control signals to the first and second tunable lenses such that focal lengths of the first and second tunable lenses both equal a value, wherein the value equals one half of a distance separating the first and second tunable lenses.

6. The optical system of claim 5, wherein the controller is configured to:

receive an indication that a desired imaging distance is above a second threshold value; and

in response to receiving the indication that the desired imaging distance is above the second threshold value, provide control signals to the first and second tunable lenses such that the focal length of the first tunable lens decreases from the value by an amount and the focal length of the second tunable lens increases from the value by the amount so as to increase the size of the sample component beam.

7. The optical system of claim 1, wherein the lens system includes a camera zoom lens including an additional lens to the first lens, and wherein the adjustable aspect of the first lens includes a relative distance between the first lens and the additional lens.

8. The optical system of claim 1, wherein the first lens comprises a tunable lens having an electrically adjustable radius of curvature.

9. The optical system of claim 1, wherein the light source includes a tunable vertical cavity surface emitting laser.

10. The OCT system of claim 1, wherein the lens system includes at least one of a camera zoom lens and a tunable lens having an electrically variable radius of curvature, wherein the instructions further cause the processing circuit to provide control signals to the lens system to adjust an effective focal length of the lens system so as to change the field of view of the OCT system.

11. The OCT system of claim 10, wherein the instructions cause the processor to:

receive an indication that the OCT system requires an increased field of view; and

in response to receiving the indication that the OCT system requires the increased field of view, provide control signals to the lens system to increase the focal length of the lens system based on the increased field of view.

12. An OCT system comprising:

a light source configured to generate an optical beam;

an interferometer comprising;

an optical element configured to direct a reference component of the optical beam along a reference arm of the interferometer and a sample component of the optical beam along a sample arm of the interferometer, wherein the sample arm comprises;

a scanner configured to direct the sample component along one of a plurality of different directions within a scanning range; and

a lens system disposed downstream of the scanner configured to project the sample beam to an imaging area defined by a field of view of the OCT system, the lens system comprising a first lens, wherein an aspect of the first lens is adjustable so as render the field of view adjustable without adjusting the scanning range of the scanner, and wherein the optical element is further configured to combine the reference component with a reflected portion of the sample component that reflects off an object placed in the imaging area to produce an interference pattern;

a detector configured to receive the interference pattern; and

a computing system including a processing circuit, the processing circuit including a processor and a memory, the memory being structured to store instructions that are executable by the processor to cause the processor to receive an image signal from the detector and generate an OCT image or depth information based on the image signal.

13. The OCT system of claim 12, wherein the sample arm further includes a beam expander configured to adjust the size of the sample component prior to the sample component reaching the lens system.

14. The OCT system of claim 13, wherein the beam expander includes a first tunable lens disposed proximate to a collimating lens disposed upstream of the scanner and a second tunable lens disposed between the first tunable lens and the scanner, wherein the instructions further cause to processor to provide control signals to the first and second tunable lenses to adjust the focal lengths of the first and second lenses adjust the size of the sample beam.

15. The OCT system of claim 14, wherein the instructions further cause the processor to:

receive an indication that a desired imaging distance of the OCT system is below a first threshold value; and

in response to receiving the indication that the desired imaging distance is below the first threshold value, provide control signals to the first and second tunable lenses such that focal lengths of the first and second tunable lenses both equal a value, wherein the value equals one half of a distance separating the first and second tunable lenses.

16. The OCT system of claim 15, wherein the instructions further cause the processor to:

receive an indication that a desired imaging distance of the OCT system is above a second threshold value; and

in response to receiving the indication that the desired imaging distance is above the second threshold value, provide control signals to the first and second tunable lenses such that the focal length of the first tunable lens decreases from the value by an amount and the focal length of the second tunable lens increases from the value by the amount so as to increase the size of the sample component beam.

17. A method of operating an OCT system,

the OCT system comprising:

a light source configured to generate an optical beam;

an interferometer comprising;

an optical element configured to direct a reference component of the optical beam along a reference arm of the interferometer and a sample component of the optical beam along a sample arm of the interferometer, wherein the sample arm comprises;

a scanner configured to direct the sample component along one of a plurality of different directions within a scanning range; and

a lens system disposed downstream of the scanner configured to project the sample beam to an imaging area defined by a field of view of the OCT system, the lens system comprising a first lens, wherein an aspect of the first lens is adjustable so as render the field of view adjustable without adjusting the scanning range of the scanner, and wherein the optical element is further configured to combine the reference component with a reflected portion of the sample component that reflects off an object placed in the imaging area to produce an interference pattern;

a detector configured to receive the interference pattern; and

a computing system including a processing circuit, the processing circuit including a processor and a memory, the memory being structured to store instructions that are executable by the processor to cause the processor to receive an image signal from the detector and generate an OCT image or depth information based on the image signal;

the method comprising;

receiving, by the computing device, an indication of a desired imaging distance; and

in response to receiving the indication, adjusting, by the computing device, an effective focal length of the lens system disposed downstream of the scanner in the sample arm of the interferometer to simultaneously adjust the field of view and the angular resolution of the OCT system based on the desired imaging distance.

18. The method of claim 17, further comprising:

emitting an optical beam from the light source;

splitting the optical beam via the optical element into the sample beam and the reference beam such that the sample beam is directed to the sample arm;

collimating, by the first lens, the sample beam such that the sample beam is of a first diameter;

directing, by the scanner and the lens system, the sample optical beam to an object placed in the imaging area to generate a reflected beam that reflects off the object;

combining, by the optical element, the reference beam and the reflected beam to generate the interference pattern; and

directing, by an optical fiber, the interference pattern to the detector to generate the image signal of the object.

19. The method of claim 18, further comprising:

in response to receiving the indication, adjusting, by the computing device, the focal lengths of a first tunable lens and a second tunable lens of a beam expander disposed downstream of the first lens and upstream of the scanner to adjust a Rayleigh length of the sample beam based on the desired imaging distance.

20. The method of claim 19, further comprising:

determining, by the computing device, that the desired imaging distance is above a threshold; and

in response to the determination, adjusting the effective focal length of the lens system to a maximum value so as to maximize the Rayleigh distance of the sample beam.