US 11,692,809 B2
Self-mixing interferometry-based absolute distance measurement with distance reference
Ahmet Fatih Cihan, San Jose, CA (US); and Mehmet Mutlu, San Jose, CA (US)
Assigned to Apple Inc., Cupertino, CA (US)
Filed by Apple Inc., Cupertino, CA (US)
Filed on Jul. 31, 2020, as Appl. No. 16/945,573.
Claims priority of provisional application 62/902,268, filed on Sep. 18, 2019.
Prior Publication US 2021/0080248 A1, Mar. 18, 2021
Int. Cl. G01P 3/36 (2006.01); G01B 9/02 (2022.01); G01P 5/26 (2006.01); G01S 17/58 (2006.01)
CPC G01B 9/02092 (2013.01) [G01P 5/26 (2013.01); G01S 17/58 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A device, comprising:
a frame;
an optical element attached to the frame and having a known optical thickness between a first surface and a second surface of the optical element;
an SMI sensor attached to the frame and configured to,
emit a modulated beam of electromagnetic radiation toward the first surface of the optical element; and
generate an SMI signal containing disturbances caused by reflections or backscatters of the modulated beam of electromagnetic radiation from the first surface and the second surface; and
a processor configured to,
relate the disturbances to the known optical thickness of the optical element; and
determine a distance between two objects using the SMI signal and the relationship of the disturbances to the known optical thickness of the optical element.