# US 10,312,656 B1 · Wavelength tuning for diffractive optical elements of structured light projectors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,312,656 B1 - Document ID: US10312656B1 - Status: Granted - Kind: B1 - Application number: 15/623,633 - Filed: 2017-06-15 - Granted: 2019-06-04 - Earliest claimed: 2017-06-15 - Assignees: Facebook Technologies, LLC - Applicants: Facebook Technologies, LLC - Inventors: Andrew Matthew Bardagjy; Joseph Duggan; Cina Hazegh; Fei Liu; Mark Timothy Sullivan; Simon Morris Shand Weiss - Web page: https://patentgrep.com/patent/US10312656B1 ## CPC - H01S 3/08009: {using a diffraction grating} - A61B 5/0059: {using light, e.g. diagnosis by transillumination, diascopy, fluorescence (photoacoustic A61B5/0093; optical measurement of heart rate A61B5/02416; optical measurement of blood flow A61B5/0261; optical measurement of analytes A61B5/1455)} - G01B 9/02091: Tomographic interferometers, e.g. based on optical coherence - G01J 1/0252: {Constructional arrangements for compensating for fluctuations caused by, e.g. temperature, or using cooling or temperature stabilization of parts of the device; Controlling the atmosphere inside a photometer; Purge systems, cleaning devices (protection against electromagnetic interferences G01J2001/0276)} - G01J 1/4257: {applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam (monitoring arrangements for lasers in general H01S3/0014)} - G01J 3/10: Arrangements of light sources specially adapted for spectrometry or colorimetry - G01J 3/1838: {Holographic gratings} - G01N 21/4795: {spatially resolved investigating of object in scattering medium (in vivo A61B)} - G02B 5/1866: {Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials (G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence)} - G02B 5/1871: {Transmissive phase gratings} - G02B 7/008: {with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation} - G02B 27/0172: {characterised by optical features} - G02F 1/33: Acousto-optical deflection devices {(circuit or control arrangements therefor G02F1/113)} - G03F 7/2024: {of the already developed image} - G06T 7/90: Determination of colour characteristics - G06T 7/97: {Determining parameters from multiple pictures (depth or shape recovery from multiple images G06T7/55; stereo camera calibration G06T7/85)} - H01S 5/0612: {controlled by temperature} - H01S 5/06837: {Stabilising otherwise than by an applied electric field or current, e.g. by controlling the temperature} - H01S 5/0687: Stabilising the frequency of the laser - G01J 2001/4247: {for testing lamps or other light sources} - G02B 2027/0116: {comprising devices for correcting chromatic aberration} - G02B 2027/0138: {comprising image capture systems, e.g. camera} - G06T 7/521: from laser ranging, e.g. using interferometry; from the projection of structured light - G06T 2207/10016: Video; Image sequence - G06T 2207/10152: Varying illumination - G06T 2207/30168: Image quality inspection - H01S 5/02415: {by using a thermo-electric cooler [TEC], e.g. Peltier element} - H01S 5/06808: {by monitoring the electrical laser parameters, e.g. voltage or current} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - 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) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract A wavelength tuning system determines a temperature calibrated to a DOE of a structured light (SL) projector. The wavelength tuning system includes a camera and controller. The camera captures images of a SL pattern projected by the SL projector. The controller generates tuning instruction. The tuning instructions cause a wavelength regulator of the SL projector to set a light source of the SL projector to different temperatures. The tuning instruction also cause the camera to capture images of the structured light pattern at each of the different temperatures. Using at least some of the captured images, the controller determines the temperature calibrated to the DOE. In one embodiment, the temperature calibrated to the DOE corresponds to a wavelength of light emitted by the light source that result in an estimated minimum power of a zeroth order diffracted beam of the SL pattern. ## Claims ### Claim 1 A wavelength tuning system comprising: a camera configured to capture, in accordance with tuning instructions, images of one or more structured light patterns projected by a structured light projector in accordance with the tuning instructions, the structured light projector comprising a laser light source, a wavelength regulator that regulates temperature of the laser light source, and a diffractive optical element (DOE) that generates structured light patterns using light from the laser light source, and the captured images include images of structured light patterns captured at different temperature values of the light laser source; and a controller configured to: generate the tuning instructions that cause the wavelength regulator to set the laser light source to different temperatures of a set of temperatures, and the camera to capture images of the structured light pattern generated by the structured light projector at each of the different temperatures, and determine a temperature calibrated to the DOE using one or more of the captured images, wherein the temperature calibrated to the DOE corresponds to a wavelength of light emitted by the laser light source that results in an estimated minimum power of a zeroth order diffracted beam of the structured light pattern. ### Claim 2 (depends on 1) The system of claim 1, wherein the controller is further configured to: determine a power of a zeroth order diffracted beam of the structured light pattern for some of the captured images, wherein each determined power value corresponds to a different temperature in the set of temperatures. ### Claim 3 (depends on 2) The system of claim 2, wherein the controller is further configured to: determine a function describing power of the zeroth order diffracted beam as a function of temperature using each of the determined power values; and identify a temperature that corresponds to a minimum power of the zeroth order diffracted beam using the function, wherein the identified temperature is the temperature calibrated to the DOE. ### Claim 4 (depends on 2) The system of claim 2, the controller is further configured to: determine a brightness of a zeroth order diffracted beam of the structured light pattern in one of the captured images; and determine a power of the zeroth order diffracted beam based on the determined brightness value. ### Claim 5 (depends on 1) The system of claim 1, wherein the controller is further configured to: determine a power of a zeroth order diffracted beam of the structured light pattern for some of the captured images, wherein each determined power value corresponds to a different temperature in the set of temperatures; rank the different temperatures in accordance with their corresponding power of the zeroth order diffracted beam; and select a temperature from the ranked temperatures as the temperature calibrated to the DOE, the selected temperature having a lowest power of power of the zeroth order diffracted beam. ### Claim 6 (depends on 1) The system of claim 1, wherein the wavelength regulator is a thermal electric cooler that is coupled directly to the laser light source, and the thermal electric cooler regulates a temperature of the laser light source in accordance with the tuning instructions. ### Claim 7 (depends on 1) The system of claim 1, wherein the wavelength regulator is a resistive heater that is coupled directly to the laser light source, and the resistive heater regulates a temperature of the laser light source in accordance with the tuning instructions. ### Claim 8 (depends on 1) The system of claim 1, wherein the controller is further configured to: determine a range of temperatures in the set of temperatures, wherein an increment between a temperature adjacent to a predicted temperature value for the temperature calibrated to the DOE is smaller than an increment between a temperature adjacent to a maximum temperature in the set of temperatures. ### Claim 9 (depends on 1) The system of claim 1, wherein the controller is further configured to: determine a range of temperatures in the set of temperatures, wherein an increment between adjacent temperature values in the set of temperature values is constant. ### Claim 10 A method comprising: capturing, in accordance with tuning instructions, images of one or more structured light patterns projected by a structured light projector in accordance with the tuning instructions, the structured light projector comprising a laser light source, a wavelength regulator that regulates temperature of the laser light source, and a diffractive optical element (DOE) that generates structured light patterns using light from the laser light source, and the captured images include images of structured light patterns captured at different temperature values of the light laser source; generating the tuning instructions that cause the wavelength regulator to set the laser light source to different temperatures of a set of temperatures, and the camera to capture images of the structured light pattern generated by the structured light projector at each of the different temperatures; and determining a temperature calibrated to the DOE using one or more of the captured images, wherein the temperature calibrated to the DOE corresponds to a wavelength of light emitted by the laser light source that results in an estimated minimum power of a zeroth order diffracted beam of the structured light pattern. ### Claim 11 (depends on 10) The method of claim 10, wherein determining the temperature calibrated to the DOE using one or more of the captured images comprises: determining a power of a zeroth order diffracted beam of the structured light pattern for some of the captured images, wherein each determined power value corresponds to a different temperature in the set of temperatures. ### Claim 12 (depends on 11) The method of claim 11, wherein determining the temperature calibrated to the DOE using one or more of the captured images, further comprises: determining, using each of the determined power values, a function describing power of the zeroth order diffracted beam as a function of temperature; and identifying a temperature that correspond to a minimum power of the zeroth order diffracted beam using the function, wherein the identified temperature is the temperature calibrated to the DOE. ### Claim 13 (depends on 11) The method of claim 11, wherein determining the temperature calibrated to the DOE using one or more of the captured images, further comprises: determining a brightness of a zeroth order diffracted beam of the structured light pattern in one of the captured images; and determining a power of the zeroth order diffracted beam based on the determined brightness value. ### Claim 14 (depends on 10) The method of claim 10, wherein determining the temperature calibrated to the DOE using one or more of the captured images, further comprises: determining a power of a zeroth order diffracted beam of the structured light pattern for some of the captured images, wherein each determined power value corresponds to a different temperature in the set of temperatures; ranking the different temperatures in accordance with their corresponding power of the zeroth order diffracted beam; and selecting a temperature from the ranked temperatures as the temperature calibrated to the DOE, the selected temperature having a lowest power of power of the zeroth order diffracted beam. ### Claim 15 (depends on 10) The method of claim 10, wherein generating the tuning instructions that cause the wavelength regulator to set the laser light source to different temperatures of a set of temperatures, and the camera to capture images of the structured light pattern generated by the structured light projector at each of the different temperatures comprises: determining a range of temperatures in the set of temperatures, wherein an increment between a temperature adjacent to a predicted temperature value for the temperature calibrated to the DOE is smaller than an increment between a temperature adjacent to a maximum temperature in the set of temperatures. ### Claim 16 (depends on 10) The method of claim 10, wherein generating the tuning instructions that cause the wavelength regulator to set the laser light source to different temperatures of a set of temperatures, and the camera to capture images of the structured light pattern generated by the structured light projector at each of the different temperatures comprises: determining a range of temperatures in the set of temperatures, wherein an increment between adjacent temperature values in the set of temperature values is constant. ### Claim 17 A wavelength tuning system comprising: a camera configured to capture, in accordance with tuning instructions, images of one or more structured light patterns projected by a structured light projector in accordance with the tuning instructions, the structured light projector comprising a laser light source, a wavelength regulator that regulates temperature of the laser light source, and a diffractive optical element (DOE) that generates structured light patterns using light from the laser light source, and the captured images include images of structured light patterns captured at different temperature values of the light laser source; and a controller configured to: generate the tuning instructions that cause the wavelength regulator to set the laser light source to different temperatures of a set of temperatures, and the camera to capture images of the structured light pattern generated by the structured light projector at each of the different temperatures, determine a temperature calibrated to the DOE using one or more of the captured images, wherein the temperature calibrated to the DOE corresponds to a wavelength of light emitted by the laser light source that results in at least one performance metric meeting a corresponding threshold value. ### Claim 18 (depends on 17) The system of claim 17, wherein the wavelength regulator is a thermal electric cooler that is coupled directly to the laser light source, and the thermal electric cooler regulates a temperature of the laser light source in accordance with the tuning instructions. ### Claim 19 (depends on 17) The system of claim 17, wherein the wavelength regulator is a resistive heater that is coupled directly to the laser light source, and the resistive heater regulates a temperature of the laser light source in accordance with the tuning instructions. ### Claim 20 (depends on 17) The system of claim 17, wherein the controller is further configured to: determine a range of temperatures in the set of temperatures, wherein an increment between a temperature adjacent to a predicted temperature value for the temperature calibrated to the DOE is smaller than an increment between a temperature adjacent to a maximum temperature in the set of temperatures.