Depth sensingOne way to do dildo depth sensing is infrared reflection. If IR emitters and receivers are alternated, when there is something in front of an IR emitter, the light will be reflected back- so the receiver will sense a higher amount of light than when nothing is in front of it. This can be used to produce a real-time depth measurement.
The infrared is visible to cameras but not to people. (Common IR wavelengths are 850nm and 920nm. Humans can see a dull glow at 850nm when observed head-on, and nothing at all at 920nm.)
Very sloppily "installed" by pouring silicone around the LED strip. You can see that position was not fixed properly during the pour. I would also expect this to delaminate and fall apart quickly- in future revisions I would cure a silicone shell that the LEDs would go inside, rather than curing the silicone around the LEDs.
The silicone is Dragon Skin 10, and this design works- enough IR passes through the silicone to get a strong reading when the light is reflected.
The final design for this would likely be surface-mount IR LEDs on a flexible circuit.