PHOTOACOUSTIC REMOTE SENSING (PARS)

• US 20160113507A1
• Filed: 10/21/2015
• Published: 04/28/2016
• Est. Priority Date: 10/22/2014
• Status: Active Grant

• Current Assignee: Illumisonics Inc.
• Original Assignee: Illumisonics Inc.
• Inventors: Zemp, Roger, Reza, Parsin Haji
• Granted Patent: US 10,117,583 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: G01N 2021/1706 in solids
• CPC Class Codes: G01N 2021/1725 Modulation of properties by light, e.g. photoreflectance
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 21/1717 with a modulation of one or more physical properties of the sample during the optical investigation, e.g. electro-reflectance
• CPC Class Codes: G01N 2201/06113 Coherent sources; lasers
• CPC Class Codes: G01N 2201/08 Optical fibres; light guides
• CPC Class Codes: G01N 2201/0846 Fibre interface with sample, e.g. for spatial resolution

Abstract

A photoacoustic remote sensing system (PARS) for imaging a subsurface structure in a sample has an excitation beam configured to generate ultrasonic signals in the sample at an excitation location; an interrogation beam incident on the sample at the excitation location, a portion of the interrogation beam returning from the sample that is indicative of the generated ultrasonic signals; an optical system that focuses at least one of the excitation beam and the interrogation beam with a focal point that is below the surface of the sample; and a detector that detects the returning portion of the interrogation beam.

Claims

1. A photoacoustic remote sensing system (PARS) for imaging a subsurface structure in a sample, comprising:

an excitation beam configured to generate ultrasonic signals in the sample at an excitation location;

an interrogation beam incident on the sample at the excitation location, a portion of the interrogation beam returning from the sample that is indicative of the generated ultrasonic signals;

an optical system that focuses the excitation beam at a first focal point and the interrogation beam at a second focal point, the first and second focal points being below the surface of the sample; and

an interferometer that detects the returning portion of the interrogation beam.

2. The PARS of claim 1, wherein the first and second focal points are within 1 mm of the surface of the sample.

3. The PARS of claim 1, wherein the first and second focal points are greater than 1 μ

m below the surface of the sample.

4. The PARS of claim 1, wherein the focal point is spaced below the surface of the sample at a depth that is greater than a focal zone of the respective at least one of the excitation beam and the interrogation beam.

5. The PARS of claim 1, wherein the excitation beam and the interrogation beam have a lateral separation of less than 1 mm on the sample.

6. The PARS of claim 1, wherein the excitation beam and the interrogation beam have a lateral separation of less than 0.5 mm on the sample.

7. The PARS of claim 1, wherein the excitation beam has a focal point that is laterally within the focal zone of the interrogation beam.

8. The PARS of claim 1, wherein the interrogation beam has a focal point that is laterally within the focal zone of the excitation beam.

9. The PARS of claim 1, further comprising a processor that calculates an image of the sample based on the returning portion of the interrogation beam.

10. The PARS of claim 1, wherein at least one of the first focal point and the second focal point has a focal diameter of less than 30 μ

m.

11. The PARS of claim 1, wherein at least one of the first focal point and the second focal point has a focal diameter of less than 10 μ

m.

12. The PARS of claim 1, wherein at least one of the first focal point and the second focal point has a focal diameter of less than 1 μ

m.

13. The PARS of claim 1, wherein the excitation beam is scanned through the sample while the interrogation beam is stationary.

14. The PARS of claim 1, wherein the interrogation beam is scanned through the sample while the excitation beam is stationary.

15. The PARS of claim 1, wherein each of the interrogation beam and the excitation beam are scanned through the sample concurrently.

16. A photoacoustic remote sensing system (PARS) for imaging a subsurface structure in a sample, comprising:

an excitation beam configured to generate ultrasonic signals in the sample at an excitation location;

an optical system that focuses the excitation beam with a focal point that is below the surface of the sample;

an interrogation beam directed toward an optical element that is responsive to the ultrasonic signals, the optical element being interposed between the sample and the interrogation beam, wherein the generated ultrasonic signals are characterized by a returning portion of the interrogation beam; and

an interferometer that detects the returning portion of the interrogation beam.

17. The PARS system of claim 16, wherein the optical element is a Fabry Perot element.

18. The PARS system of claim 16, wherein the interferometer detects ultrasonic signals to a depth of 7 cm within the sample.

19. The PARS of claim 16, wherein the focal point is within 1 mm of the surface of the sample.

20. The PARS of claim 16, wherein the focal point is greater than 1 μ

m below the surface of the sample.

21. The PARS of claim 16, wherein the focal point is spaced below the surface of the sample at a depth that is greater than a focal zone of the respective at least one of the excitation beam and the interrogation beam.

22. The PARS of claim 16, wherein at least one of the first focal point and the second focal point has a focal diameter of less than 30 μ

m.

23. The PARS of claim 16, wherein at least one of the first focal point and the second focal point has a focal diameter of less than 10 μ

m.

24. The PARS of claim 16, wherein at least one of the first focal point and the second focal point has a focal diameter of less than 1 μ

m.

25. The PARS of claim 16, wherein the interrogation beam has a focal point that is laterally within the focal zone of the excitation beam.

26. The PARS of claim 16, further comprising a processor that calculates an image of the sample based on the returning portion of the interrogation beam.

27. An endoscopic device that uses a photoacoustic remote sensing system (PARS) for imaging a subsurface structure in a sample, the endoscopic device comprising:

a fiber optic cable having an input end and a detection end;

an excitation beam coupled to the input end of the fiber optic cable, wherein in use the excitation beam generates ultrasonic signals in the sample at an excitation location that is adjacent to the detection end of the fiber optic cable, the fiber optic cable focusing the excitation beam at a first focal point that is below the surface of the sample;

an interrogation beam coupled to the input end of the fiber optic cable and incident on the excitation location, the fiber optic cable focusing the excitation beam at a first focal point that is below the surface of the sample, wherein a portion of the interrogation beam that is indicative of the generated ultrasonic signals is received by the detection end of the fiber optic cable and travels to the input end; and

an interferometer that receives the returning portion of the interrogation beam at the input end of the fiber optic cable.