Laser sensor for particle density detection

Patent metadata

Field	Value
Publication number	US-10866083-B2
Application number	US-201615745144-A
Country	US
Kind code	B2
Filing date	Jul 14, 2016
Priority date	Jul 30, 2015
Publication date	Dec 15, 2020
Grant date	Dec 15, 2020

Abstract

The invention describes a laser sensor module (100) for particle density detection. The laser sensor module (100) comprising at least one first laser (110), at least one first detector (120) and at least one electrical driver (130). The first laser (110) is adapted to emit first laser light in reaction to signals provided by the at least one electrical driver (130). The at least one first detector (120) is adapted to detect a first self-mixing interference signal of an optical wave within a first laser cavity of the first laser (110). The first self-mixing interference signal is caused by first reflected laser light reentering the first laser cavity, the first reflected laser light being reflected by a particle receiving at least a part of the first laser light. The laser sensor module (100) is adapted to reduce multiple counts of the particle. The invention further describes a related method and computer program product.

First claim

The invention claimed is:

1. A laser sensor apparatus comprising:
at least one first laser;
at least one first detector circuit;
at least one electrical driver,
wherein the first laser is arranged to emit a first laser light in reaction to signals provided by the at least one electrical driver,
wherein the at least one first detector circuit is arranged to detect a first self-mixing interference signal of an optical wave within a first laser cavity of the first laser,
wherein the first self-mixing interference signal is caused by first reflected laser light reentering the first laser cavity,
wherein the first reflected laser light is being reflected by a particle receiving at least a part of the first laser light,
wherein the laser sensor-apparatus is arranged to reduce multiple counts of the particle,
wherein the laser sensor-apparatus is arranged to interrupt detection of particles for a predetermined time period,
wherein the predetermined time period is selected such that multiple detection of the particle is reduced; and
a controller circuit,
wherein the controller circuit is arranged to evaluate the first self-mixing interference signal provided by the sensor in order to count the particle,
wherein the controller circuit is arranged to interrupt the detection of particles,
wherein the controller circuit is arranged to interrupt evaluation of the first self-mixing interference signal provided by the sensor for the predetermined time period,
wherein the controller circuit is arranged to generate a control signal upon detection of the particle,
wherein the controller circuit is arranged to interrupt the detection of particles for the predetermined time period after detection of the particle.

2. The laser sensor-apparatus according to claim 1 , wherein the at least one electrical driver is arranged to periodically interrupt the detection of particles by means of the signals.

3. The laser sensor-apparatus according to claim 1 ,
wherein the controller circuit is arranged to transfer the control signal to the electrical driver,
wherein the electrical driver is arranged to interrupt emission of first laser light for the predetermined time period.

4. The laser sensor-apparatus according to claim 1 further comprising at least a first optical device, wherein the first optical device is arranged to focus the first laser light on a first focus region.

5. The laser sensor-apparatus according to claim 1 further comprising a laser array, the laser array comprising at least the first laser and a second laser,
wherein the second laser is arranged to enable independent detection of the particle using a second self-mixing interference signal,
wherein the second self-mixing interference signal is caused by second laser light emitted by the second laser,
wherein the controller circuit is arranged to reduce multiple counts of the particle by evaluation of at least the first self-mixing interference signal and the second self-mixing interference signal.

6. The laser sensor-apparatus according to claim 5 ,
wherein the laser sensor-apparatus comprises at least a first optical device,
wherein the first optical device is arranged to focus at least the first laser light on a first focus region and is arranged to focus the second laser light on a second focus region such that a detection volume for detecting the particle density is increased.

7. The laser sensor-apparatus according to claim 6 ,
wherein the laser sensor-apparatus comprises at least a first movable mirror arranged to reflect at least the first and the second laser light such that at least the first and the second focus regions move,
wherein the first movable mirror is arranged to move at least the first and the second focus regions such that traces of the first and the second focus regions do not overlap.

8. The laser sensor-apparatus according to claim 5 ,
wherein the first detector circuit is arranged to detect the first self-mixing interference signal and the second self-mixing interference signal,
wherein the controller circuit is arranged to switch off at least a portion of the laser array based on the particle density.

9. The laser sensor-apparatus according to claim 5 ,
wherein the controller circuit is arranged to determine a projection of a first velocity of the particle along an optical axis parallel to the first or second laser light based on the first self-mixing interference signal or second self-mixing interference signal,
wherein the controller circuit is arranged to reduce multiple counts of the particle using the first velocity.

10. A method of particle density detection, the method comprising:
emitting a first laser light using a first laser;
receiving a first reflected laser light in a first laser cavity of the first laser, wherein the first reflected laser light is reflected by a particle, the particle receiving at least a part of the first laser light;
determining a first self-mixing interference signal of an optical wave within the first laser cavity, wherein the first self-mixing interference signal is caused by the first reflected first laser light reentering the first laser cavity;
reducing multiple counts of the particle by interrupting detection of particles for a predetermined time period, wherein the predetermined time period is selected such that multiple detection of the particle is reduced;
evaluating the first self-mixing interference signal in order to detect the particle;
generating a control signal upon detection of the particle; and
interrupting the detection of particles for the predetermined time period after detection of the particle.

11. A computer program comprising code arranged to perform all the steps of claim 10 when the program is run on a computer.

12. The method of claim 10 , wherein a first optical device is arranged to focus the first laser light on a first focus region.

13. The method according to claim 10 further comprising,
emitting a second laser light using a second laser;
receiving a second reflected laser light in a second laser cavity of the second laser, wherein the second reflected laser light is reflected by a particle, the particle receiving at least a part of the second laser light;
determining a second self-mixing interference signal of an optical wave within the second laser cavity, wherein the second self-mixing interference signal is caused by the second reflected second laser light reentering second first laser cavity; and
reducing multiple counts of the particle by evaluation of at least the first self-mixing interference signal and the second self-mixing interference signal.

14. The method according to claim 13 further comprising,
focusing at least the first laser light on a first focus region and focusing the second laser light on a second focus region such that a detection volume for detecting the particle density is increased.

15. The method according to claim 14 further comprising, moving a movable mirror such that at least the first and the second focus regions such that traces of the first and the second focus regions do not overlap, wherein the first movable mirror is arranged to reflect at least the first and the second laser light such that at least the first and the second focus regions move.

16. The method according to claim 13 further comprising,
determining a projection of a first velocity of the particle along an optical axis parallel to the first or second laser light based on the first self-mixing interference signal or second self-mixing interference signal; and
reducing multiple counts of the partic

Assignees

• Trumpf Photonic Components Gmbh

Inventors

• Van Der Lee Alexander Marc
• Hellmig Joachim Wilhelm
• Spruit Johannes Hendrikus Maria
• Moench Holger
• Ronda Cornelis Reinder
• Karakaya Koray

Classifications

• G01S7/4916

  using self-mixing in the laser cavity · CPC title

• G01N2015/0046

  in gas, e.g. smoke · CPC title

• G01S17/32

  using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated · CPC title

• G01B9/02092 Primary

  Self-mixing interferometers, i.e. feedback of light from object into laser cavity · CPC title

• G01S7/4817

  relating to scanning · CPC title