Speckle mitigation

Patent metadata

Field	Value
Publication number	US-10684114-B2
Application number	US-201916290041-A
Country	US
Kind code	B2
Filing date	Mar 1, 2019
Priority date	Mar 1, 2018
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

Described herein is a method and system for mitigating the effects of speckle in a laser Doppler system, and, in particular in a laser Doppler vibrometry/velocimetry system. A scan unit is provided in at least one of: a transmit path for scanning at least one beam from a transmitting antenna over a moving target surface and a receive path for scanning at least one reflected beam received from the moving target surface onto a receiving antenna. An averaging unit is provided prior to post-processing or demodulation to average electrical signals corresponding to the reflected beams. By averaging before demodulation, speckle in the output signal is mitigated.

First claim

What is claimed is:

1. A method of mitigating effects of speckle in a laser-based sensor, the method comprising:
generating at least one light beam from at least one coherent light source;
splitting the at least one light beam into a first component and a second component;
directing the first component of the at least one light beam to a transmitting antenna;
transmitting the first component of the at least one light beam from the transmitting antenna towards a moving target surface, wherein transmitting the first component comprises scanning the at least one light beam over the moving target surface;
receiving at least one reflected light beam from the moving target surface at a receiving antenna, wherein receiving the at least one reflected light beam comprises scanning the at least one reflected light beam onto the receiving antenna;
combining the at least one reflected light beam with the second component of the at least one light beam to form at least one combined beam;
converting the at least one combined light beam into at least one electrical signal; and
processing the at least one electrical signal to derive an output signal indicative of motion of the moving target surface, wherein processing the at least one electrical signal comprises averaging the electrical signals corresponding to reflected beams and demodulating the averaged electrical signals.

2. The method according to claim 1 , wherein receiving the at least one reflected light beam comprises receiving the reflected scanned beams from the moving target surface.

3. The method according to claim 1 , wherein receiving the at least one reflected light beam comprises scanning the at least one reflected beam from the moving target surface ( 190 ) at the receiving antenna, and wherein transmitting the first component comprises transmitting the at least one light beam from the transmitting antenna to the moving target surface.

4. The method according to claim 1 , wherein converting the at least one combined light beam into at least one electrical signal comprises detecting the at least one combined beam using a detector array, the electrical signals corresponding to the output from each detector element in the detector array.

5. The method according to claim 4 , wherein converting the at least one combined light beam into at least one electrical signal further comprises reading out the electrical signals from the detector array.

6. The method according to claim 1 , further comprising focusing at least one of: the transmitted light beam onto the moving target surface and the reflected light beam at the receiving antenna.

7. A laser-based sensor comprising:
at least one coherent light source configured for generating at least one light beam;
at least one splitter configured for splitting the at least one light beam into a first component and a second component;
a transmitting antenna configured for receiving the first component of the at least one light beam from the at least one light source and for transmitting the first component of the at least one light beam to a moving target surface;
a receiving antenna configured for receiving at least one reflected light beam from the moving target surface;
a combiner configured for combining with the at least one reflected beam with the second component of the at least one light beam to form at least one combined beam;
a detector array configured for receiving the at least one combined beam from the combiner and for converting the at least one combined beam into at least one electrical signal;
at least one processor configured for processing the at least one electrical signal to derive an output signal indicative of motion of the moving target surface;
at least one of a transmit scan unit configured for scanning the first component of the at least one light beam over the moving target surface and a receive scan unit configured for scanning the at least one reflected beam onto the receiving antenna; and
an averaging unit configured for averaging electrical signals corresponding to the at least one combined beam and for passing the averaged electrical signals to the at least one processor for demodulation.

8. The sensor according to claim 7 , wherein the at least one coherent light source, the transmitting antenna, the receiving antenna, the detector array, and at least one of the scan transmit unit and the receive scan unit form part of a photonic integrated circuit.

9. The sensor according to claim 8 , further comprising a driver circuit configured for driving the photonic integrated circuit.

10. The sensor according to claim 7 , further comprising a readout electronics circuit configured for reading out the electrical signals from the detector array.

11. The sensor according to claim 7 , further comprising an optical frequency shifter configured for shifting the frequency of at least one of the first component of the at least one light beam and the second component of the at least one light beam prior to combining with the at least one reflected beam.

12. The sensor according to claim 7 , further comprising focusing optics configured for focusing at least one of the transmitted light beam onto the moving target surface and the reflected light beam at the receiving antenna.

13. A laser Doppler system including a sensor, wherein the sensor comprises:
at least one coherent light source configured for generating at least one light beam;
at least one splitter configured for splitting the at least one light beam into a first component and a second component;
a transmitting antenna configured for receiving the first component of the at least one light beam from the at least one light source and for transmitting the first component of the at least one light beam to a moving target surface;
a receiving antenna configured for receiving at least one reflected light beam from the moving target surface;
a combiner configured for combining with the at least one reflected beam with the second component of the at least one light beam to form at least one combined beam;
a detector array configured for receiving the at least one combined beam from the combiner and for converting the at least one combined beam into at least one electrical signal;
at least one processor configured for processing the at least one electrical signal to derive an output signal indicative of motion of the moving target surface;
at least one of a transmit scan unit configured for scanning the first component of the at least one light beam over the moving target surface and a receive scan unit configured for scanning the at least one reflected beam onto the receiving antenna; and
an averaging unit configured for averaging electrical signals corresponding to the at least one combined beam and for passing the averaged electrical signals to the at least one processor for demodulation.

Assignees

• Imec Vzw
• Univ Gent

Inventors

• Li Yanlu
• Baets Roeland
• Ryckeboer Eva
• Zhu Jinghao

Classifications

• G01S17/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01N2021/479

  Speckle · CPC title

• G01B9/02082 Primary

  Caused by speckles · CPC title

• G01N21/4795 Primary

  spatially resolved investigating of object in scattering medium (in vivo A61B) · CPC title

• G01H9/004

  using fibre optic sensors (light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125) · CPC title