Method of determining operation conditions of a laser-based particle detector

Patent metadata

Field	Value
Publication number	US-10641695-B2
Application number	US-201916558184-A
Country	US
Kind code	B2
Filing date	Sep 2, 2019
Priority date	Mar 2, 2017
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

A method for determining operating conditions of a particle detector that includes a multimode Vertical Cavity Surface Emitting Laser (VCSEL) includes providing an electrical drive current to the multimode VCSEL such that a laser beam is emitted by the multimode VCSEL and varying the electrical drive current within a predefined range of electrical drive currents. The method further includes determining, as a function of the electrical drive current, an intensity signal of an optical wave within a laser cavity of the multimode VCSEL, determining, as a function of the electrical drive current, a noise measure of the intensity signal, determining a range of electrical drive currents for which the noise measure is below a predefined threshold noise measure value, and determining operating conditions of the particle detector by choosing an electrical drive current for particle detection out of the determined low noise range of electrical drive currents.

First claim

The invention claimed is:

1. A method for determining operating conditions of a particle detector for detecting a particle density of particles with a size of less than 20 μm in a fluid, wherein the particle detector include a multimode Vertical Cavity Surface Emitting Laser (VCSEL), the method comprising:
providing an electrical drive current to the multimode VCSEL such that a laser beam is emitted by the multimode VCSEL;
varying the electrical drive current within a predefined range of electrical drive currents;
determining, as a function of the electrical drive current, an intensity signal of an optical wave within a laser cavity of the multimode VCSEL;
determining, as a function of the electrical drive current, a noise measure of the intensity signal;
determining a range of electrical drive currents for which the noise measure is below a predefined threshold noise measure value;
determining at least a part of the operating conditions of the particle detector by choosing an electrical drive current for particle detection out of the determined low noise range of electrical drive currents,
detecting a trigger event during operation of the particle detector;
determining the noise measure of the intensity signal of the optical wave within the laser cavity of the multimode VCSEL during operation of the particle detector;
determining a new range of electrical drive currents if the noise measure of the intensity signal of the optical wave within the laser cavity during operation of the particle detector exceeds an operating threshold,
determining at least a part of the operating conditions of the particle detector by choosing, from the new range of electrical drive currents, a new electrical drive current for particle detection.

2. The method according to claim 1 , wherein the range of electrical drive currents is further determined as a function of ambient temperature, and wherein the electrical drive current for particle detection is chosen depending on an ambient temperature during particle detection.

3. The method according to claim 1 , wherein the range of electrical drive currents is further determined as a function of operating temperature of the particle detector, and wherein the electrical drive current for particle detection is chosen depending on an operating temperature during particle detection.

4. The method according to claim 1 , wherein the trigger event is detection of a signal-to-noise ratio of a self-mixing interference signal in the laser cavity of the optical wave within the laser cavity of the multimode VCSEL during operation of the particle detector below a signal-to-noise ratio threshold.

5. The method according to claim 1 , wherein the trigger event is switching on the particle detector.

6. The method according to claim 1 , wherein the trigger event is expiration of a predetermined time period.

7. The method according to claim 1 , further comprising starting a calibration procedure of the particle detector at the new electrical drive current.

8. A computer program product comprising computer executable code stored on at least one memory device, wherein the computer executable code includes instructions for carrying out the method according to claim 1 .

9. A particle detector for detecting a particle density of particles with a size of less than 20 μm in a fluid, the particle detector comprising:
a laser;
an electrical driver configured to provide a drive current to the laser,
a detector coupled to the laser and configured to determine a self-mixing interference signal of an optical wave within a laser cavity of the laser; and
a controller,
wherein the laser is a multimode Vertical Cavity Surface Emitting Laser (VCSEL),
wherein the particle detector is configured to determine a trigger event,
wherein the controller is configured to provide control signals to control the electrical driver so as to vary a drive current of the laser within a predefined range of drive currents after detection of the trigger event,
wherein the controller is further configured to determine a noise measure of an intensity signal in the laser cavity as a function of the drive current based on detection signals provided by the detector,
wherein the controller is further configured to determine a range of drive currents in which the noise measure is below a predefined threshold value,
wherein the controller is further configured to select a drive current for particle detection out of the determined range of drive currents, and
wherein the controller is further configured to control the electrical driver to provide the drive current during operation of the particle detector.

10. A particle detector according to claim 9 , wherein the controller is configured to determine a signal-to-noise ratio of the self-mixing interference signal determined by the detector during operation of the particle detector, and
wherein the controller is further configured to provide the control signals to control the electrical driver to vary the drive current of the laser if the signal-to-noise ratio during operation of the particle detector is below a signal-to-noise ratio threshold.

11. The particle detector according to claim 9 , wherein the controller is further configured to initiate a calibration procedure after controlling the electrical driver to provide the drive current during operation of the particle detector.

12. The particle detector according to claim 9 , wherein the VCSEL has an aperture with a diameter between 5 μm and 7 μm.

13. The particle detector according to claim 9 , wherein an interface between a semiconductor surface of an outcoupling surface of the VCSEL is out of an anti-node of a standing wave pattern of the laser by at least 20 nm.

14. A mobile communication device comprising the particle detector according to claim 9 .

Assignees

• Philips Photonics Gmbh
• Trumpf Photonic Components Gmbh

Inventors

• Weichmann Ulrich
• Hellmig Joachim Wilhelm
• Van Der Lee Alexander Marc
• Moench Holger Joachim

Classifications

• G01N15/0205 Primary

  by optical means · CPC title

• H01S5/183

  having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] · CPC title

• G01N2015/1493

  Particle size · CPC title

• G01N2015/0003

  Determining electric mobility, velocity profile, average speed or velocity of a plurality of particles · CPC title

• G01N2015/1486

  Counting the particles · CPC title