Patent ID: 11857298
Assignee: APPLE INC.
Field: Medical technology (Instruments)
Classification: CPC A  G | IPC A  G

Claim 5:
6. The wearable device of claim 5, wherein the photodetector is a first photodetector, the wearable device further comprising:
a third emitter positioned within the housing and configured to emit, through the back cover, a third beam of electromagnetic radiation having the first IR wavelength;
a fourth emitter positioned within the housing and configured to emit, through the back cover, a fourth beam of electromagnetic radiation having the second IR wavelength; and
a second photodetector positioned within the housing and filtered to detect a set of wavelengths including the first IR wavelength and the second IR wavelength; wherein:
the first photodetector is grouped with the first and second emitters;
the second photodetector is grouped with the third and fourth emitters, with each of the third emitter, the fourth emitter, and the second photodetector positioned off-axis with respect to the center axis of the back cover; and
the matter differentiation circuit is further configured to indicate whether the back of the housing is likely proximate to the human tissue at least partly in response to signals indicating amounts of the first IR wavelength and the second IR wavelength received by the second photodetector.