System and method for detecting surface vibrations

• US 10,352,762 B2
• Filed: 12/27/2015
• Issued: 07/16/2019
• Est. Priority Date: 12/27/2014
• Status: Active Grant

• Current Assignee: Gentex Corporation
• Original Assignee: Guardian Optical Technologies Ltd. (Gentex Corporation)
• Inventors: Carmon, Gideon
• Primary Examiner(s): Saint Surin, Jacques M
• Application Number:
  US15/540,049
• Publication Number:
  US 20180266876A1
• Time in Patent Office: 1,297 Days
• Field of Search: 73655
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: G01H 9/00 Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
• CPC Class Codes: G01N 2021/479 Speckle
• CPC Class Codes: G01N 21/4788 Diffraction for sizing particles G01N15/0205
• CPC Class Codes: G02B 27/106 for splitting or combining a plurality of identical beams or images, e.g. image replication
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51

Abstract

A system for detecting vibrations from a surface is provided. The system includes a coherent light source for projecting a multi-beam pattern onto the surface and an imaging device for mapping a speckle field generated by each spot formed on the surface by the multi-beam pattern to a unique region of an imaging sensor. The system further includes a processor for processing speckle field information received by the imaging sensor and deriving surface vibration information.

Claims

1. A system for detecting vibrations from a surface comprising:

(a) a coherent light source for projecting a multi-beam pattern onto the surface, said light source operating in an eye-safe power and frequency levels, wherein the multi-beam pattern forms a plurality of spots on the surface;

(b) an imaging device for mapping a speckle field image generated by each of said plurality of spots formed on the surface and reflected from the surface to a unique region of an imaging sensor through a collecting lens; and

(c) a processor for processing speckle field information received by said imaging sensor, deriving surface vibration information by analyzing speckle pattern variation with time from said speckle field information and analyzing the derived surface vibration information to identify when an amplitude of said derived surface vibration is above a predefined threshold, to detect when the derived surface vibration information is indicative of physiological vibration;

wherein an aperture of said collecting lens and a diameter of said projected multi-beam is adjusted to optimize speckles dynamics detection for a vibration amplitude range of physiological vibrations.

2. The system of claim 1, wherein said imaging device is configured for in-focus mapping of each speckle field formed on the surface by said multi-beam pattern.

3. The system of claim 1, wherein said light source is configured for projecting a single beam and the system further includes a beam splitter.

4. The system of claim 1, wherein said multi-beam pattern is formed from a plurality of non-overlapping non-collimated beams focused onto the surface.

5. The system of claim 1, wherein said light source is configured for projecting a plurality of beams at a light wavelength longer than 650 nm.

6. The system of claim 1, wherein said multi-beam pattern forms a grid on the surface.

7. The system of claim 6, wherein said grid is formed by more than 2 beams.

8. The system of claim 6, wherein said grid covers a field-of-view of up to 180 degrees.

9. The system of claim 1, wherein said processor analyzes a light intensity at each unique region of said imaging sensor to thereby detect speckle dynamics.

10. The system of claim 1, wherein said imaging device includes an optical filter for filtering out ambient light.

11. The system of claim 1, wherein said imaging sensor includes a photodiode or photodiode array and each speckles field is mapped to 1-100 pixels of said imaging sensor.

12. The system of claim 1, wherein said light source is configured for projecting said multi-beam pattern using an optical power of less than 1 milliwatt per beam.

13. The system of claim 1, wherein said collecting lens aperture of said imaging device is selected according to a tradeoff between a large aperture which maximizes a Signal to Noise Ratio (SNR) at large amplitudes and a small aperture for small amplitudes regime, the SNR is calculated using a respective equation selected from:

14. The system of claim 1, wherein said light source is configured for projecting said multi-beam pattern to a surface 0.1-15 m away.

15. The system of claim 1, wherein said processor is further configured for qualifying the surface based on said surface vibration information.

16. The system of claim 15, being capable of identifying a human based on said surface vibration information.

17. The system of claim 1, configured for mounting inside a vehicle.

18. The system of claim 17, being capable of communicating a vehicle occupant count to an onboard system of the vehicle.

21. The system of claim 1, wherein said physiological vibration is at least one of heart beat and breathing.

19. A system for detecting vibrations from a surface comprising:

(a) a coherent light source, operating in an eye-safe power and frequency levels, for projecting a non-collimated beam onto the surface;

(b) an imaging device for mapping a speckle field image generated by a spot formed on the surface by said non-collimated beam and reflected from the surface, to a unique region of an imaging sensor through a collecting lens; and

(c) a processor for processing speckle field information received by said imaging sensor and deriving surface vibration information, by analyzing speckle pattern variation with time from said speckle field information and analyzing the derived surface vibration information to identify when an amplitude of said derived surface vibration is above a predefined threshold, to detect when the derived surface vibration information is indicative of physiological vibration;

wherein an aperture of said collecting lens and a diameter of said projected non-collimated beam is adjusted to optimize speckles dynamics detection for a vibration amplitude range of physiological vibrations.

20. A system for detecting vibrations from a surface comprising:

(a) a coherent light source, operating in an eye-safe power and frequency levels, for projecting a single collimated beam onto the surface;

(b) a photodiode for capturing a speckle field image generated by a spot formed on the surface by said collimated beam and reflected from the surface; and

(c) a processor for processing speckle field information received by said photodiode and deriving surface vibration information from speckle vibrations at an amplitude of 1 μ

m to 50 cm and a frequency of 1Hz-100KHz, by analyzing speckle pattern variation with time from said speckle field information and analyzing the derived surface vibration information to identify when an amplitude of said derived surface vibration is above a predefined threshold, to detect when the derived surface vibration information is indicative of physiological vibration;

wherein an aperture of a collecting lens and a diameter of said projected single collimated beam is adjusted to optimize speckles dynamics detection for a vibration amplitude range of physiological vibrations.