US 11,680,788 B2
Handling obstructions and transmission element contamination for self-mixing particulate matter sensors
Mehmet Mutlu, San Jose, CA (US); and Miaolei Yan, Santa Clara, CA (US)
Assigned to Apple Inc., Cupertino, CA (US)
Filed by Apple Inc., Cupertino, CA (US)
Filed on Aug. 3, 2021, as Appl. No. 17/393,278.
Application 17/393,278 is a division of application No. 16/833,271, filed on Mar. 27, 2020, granted, now 11,112,235.
Claims priority of provisional application 62/830,120, filed on Apr. 5, 2019.
Prior Publication US 2021/0364273 A1, Nov. 25, 2021
This patent is subject to a terminal disclaimer.
Int. Cl. G01B 9/02 (2022.01); G01N 15/06 (2006.01); G01N 15/10 (2006.01); G01S 7/4912 (2020.01); G01S 17/58 (2006.01)
CPC G01B 9/02092 (2013.01) [G01B 9/02045 (2013.01); G01N 15/06 (2013.01); G01N 15/10 (2013.01); G01S 7/4916 (2013.01); G01S 17/58 (2013.01); G01N 2015/0693 (2013.01); G01N 2015/1075 (2013.01)] 20 Claims
OG exemplary drawing
 
8. A method, comprising:
emitting a beam of coherent light from an optical resonant cavity of a self-mixing interferometry sensor through at least one optically transparent material via at least one optical element to illuminate an object;
receiving a reflection or a backscatter of the beam of coherent light into the optical resonant cavity;
producing a self-mixing signal resulting from self-mixing of the beam of coherent light within the optical resonant cavity;
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:
determining a particle velocity using the self-mixing signal; and
determining a particulate matter concentration using the particle velocity and a particle count.