# US 10,866,083 B2 · Laser sensor for particle density detection

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- Number: US 10,866,083 B2
- Document ID: US10866083B2
- Status: Granted
- Kind: B2
- Application number: 15/745,144
- Filed: 2016-07-14
- Published: 2018-07-26
- Granted: 2020-12-15
- Earliest claimed: 2015-07-30
- Assignees: Trumpf Photonic Components GmbH
- Applicants: Trumpf Photonic Components GmbH
- Inventors: Alexander Marc Van Der Lee; Joachim Wilhelm Hellmig; Johannes Hendrikus Maria Spruit; Holger Moench; Cornelis Reinder Ronda; Koray Karakaya
- Web page: https://patentgrep.com/patent/US10866083B2

## CPC

- G01B 9/02092: {Self-mixing interferometers, i.e. feedback of light from object into laser cavity}
- G01N 15/06: Investigating concentration of particle suspensions (by weighing G01N5/00; investigating sedimentation of particle suspensions G01N15/04; investigating individual particles G01N15/10)
- G01N 15/1434: Optical arrangements
- G01N 15/1456: {without spatial resolution of the texture or inner structure of the particle, e.g. processing of pulse signals}
- G01S 7/4802: {using analysis of echo signal for target characterisation; Target signature; Target cross-section}
- G01S 7/4817: {relating to scanning}
- G01S 7/4916: {using self-mixing in the laser cavity}
- G01S 17/32: using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S 17/58: Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S 17/87: Combinations of systems using electromagnetic waves other than radio waves
- G01S 17/95: for meteorological use
- G01N 15/075: by optical means
- G01N 2015/0046: {in gas, e.g. smoke}
- G01N 2015/1027: {Determining speed or velocity of a particle}
- G01N 2015/1454: {using phase shift or interference, e.g. for improving contrast}
- Y02A 90/10: Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 5)

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.

### Claim 7 (depends on 6)

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.

### Claim 8 (depends on 5)

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.

### Claim 9 (depends on 5)

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.

### Claim 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.

### Claim 11 (depends on 10)

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

### Claim 12 (depends on 10)

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

### Claim 13 (depends on 10)

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.

### Claim 14 (depends on 13)

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.

### Claim 15 (depends on 14)

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.

### Claim 16 (depends on 13)

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 particle using the first velocity.