# US 11,112,235 B2 · Handling obstructions and transmission element contamination for self-mixing particulate matter sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,112,235 B2 - Document ID: US11112235B2 - Status: Granted - Kind: B2 - Application number: 16/833,271 - Filed: 2020-03-27 - Published: 2020-10-08 - Granted: 2021-09-07 - Earliest claimed: 2019-04-05 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Mehmet Mutlu; Miaolei Yan - Web page: https://patentgrep.com/patent/US11112235B2 ## CPC - G01B 9/02092: {Self-mixing interferometers, i.e. feedback of light from object into laser cavity} - G01B 9/02004: using frequency scans - G01B 9/02045: {using the Doppler effect} - 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 15/10: Investigating individual particles - G01P 5/001: {Full-field flow measurement, e.g. determining flow velocity and direction in a whole region at the same time, flow visualisation} - G01P 5/20: using particles entrained by a fluid stream (G01P5/22 takes precedence) - G01P 5/26: by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave - G01S 7/4916: {using self-mixing in the laser cavity} - G01S 17/34: using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal - G01S 17/58: Velocity or trajectory determination systems; Sense-of-movement determination systems - G01N 15/075: by optical means - G01N 2015/003: {in liquids, e.g. emulsion} - G01N 2015/0046: {in gas, e.g. smoke} - G01N 2015/1027: {Determining speed or velocity of a particle} - 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) - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - 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 ## Abstract A portable electronic device is operable in a particulate matter concentration mode where the portable electronic device uses a self-mixing interferometry sensor to emit a beam of coherent light from an optical resonant cavity, receive a reflection or backscatter of the beam into the optical resonant cavity, produce a self-mixing signal resulting from a reflection or backscatter of the beam of coherent light, and determine a particle velocity and/or particulate matter concentration using the self-mixing signal. The portable electronic device is also operable in an absolute distance mode where the portable electronic device determines whether or not an absolute distance determined using the self-mixing signal is outside or within a particulate sensing volume associated with the beam of coherent light. If not, the portable electronic device may determine a contamination and/or obstruction is present that may result in inaccurate particle velocity and/or particulate matter concentration determination. ## Claims ### Claim 1 A portable electronic device that senses particulate matter, comprising: at least one optically transparent material; at least one optical element; a self-mixing interferometry sensor configured to emit a beam of coherent light from an optical resonant cavity through the at least one optically transparent material via the at least one optical element to illuminate an object, receive a reflection or a backscatter of the beam of coherent light into the optical resonant cavity, and produce a self-mixing signal resulting from self-mixing of the beam of coherent light within the optical resonant cavity; and a processor configured to: operate in an absolute distance mode by: determining an absolute distance to the object using the self-mixing signal; and upon determining that the absolute distance corresponds to an area inside of a sensing volume associated with the beam of coherent light, switching to a particulate matter concentration determination mode; and operate in the particulate matter concentration determination mode by: determining a particle velocity using the self-mixing signal; and determining a particulate matter concentration using the particle velocity and a particle count. ### Claim 2 (depends on 1) The portable electronic device of claim 1, wherein the processor determines the particle velocity using: a first self-mixing signal measured from a first beam of coherent light; and a second self-mixing signal measured from a second beam of coherent light. ### Claim 3 (depends on 2) The portable electronic device of claim 2, wherein the processor determines the particle velocity using a known angle between the first beam of coherent light and the second beam of coherent light. ### Claim 4 (depends on 2) The portable electronic device of claim 2, wherein: the self-mixing interferometry sensor comprises a first vertical-cavity surface-emitting laser and a second vertical-cavity surface-emitting laser; the first vertical-cavity surface-emitting laser emits the first beam of coherent light; and the second vertical-cavity surface-emitting laser emits the second beam of coherent light. ### Claim 5 (depends on 2) The portable electronic device of claim 2, wherein: the self-mixing interferometry sensor is a single vertical-cavity surface-emitting laser; and the at least one optical element splits the beam of coherent light into the first beam of coherent light and the second beam of coherent light. ### Claim 6 (depends on 1) The portable electronic device of claim 1, wherein the at least one optical element focuses the beam of coherent light at a location corresponding to the sensing volume. ### Claim 7 (depends on 1) The portable electronic device of claim 1, wherein the processor switches from the particulate matter concentration determination mode to the absolute distance mode upon determining the particulate matter concentration discards the particulate matter concentration upon determining the particulate matter concentration is inaccurate.