Understanding Indirect Time-of-Flight Depth Sensing

Re:Understanding Indirect Time-of-Flight Depth Sensing by jcims on Tuesday April 20, 2021 @09:55AM (#26874707)

I worked briefly with a company that manufactured surveying equipment back in the mid 2000's and they had a similar setup (single sensor though). They could get sub-millimeter precision as well, but they had to 'chirp' the light power modulation from very long (e.g. 1km) to short (sub millimeter) in order to remove any aliasing that would occur when the distance was a multiple of the measurement baseline.

If these are 90 degrees out of phase I don't know how they eliminate that possibility without doing something similar. (e.g. imagine the modulation is at 30MHz and your measurement interval is 10m, how would you differentiate between 20.034m and 30.034m?

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Re:Understanding Indirect Time-of-Flight Depth Sensing by rzw2 on Tuesday April 20, 2021 @12:44PM (#26877106)

The microsoft kinect does 3 frequency measurements to get the higher distance precision of higher modulation frequencies and to extend the maximum distance so the phase wrapping (aliasing) can be solved.

Based on some Microsoft patent filings and other research papers I wrote a short article on possible phase unwrapping methods on iToF sensors, https://medium.com/chronoptics-time-of-flight/phase-wrapping...

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Re:Understanding Indirect Time-of-Flight Depth Sensing by jcims on Tuesday April 20, 2021 @02:49PM (#26879346)

Fantastic article!!! They definitely need your animations, it's way more intuitive.

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Re:Understanding Indirect Time-of-Flight Depth Sensing by rzw2 on Tuesday April 20, 2021 @07:09PM (#26883188)

Thanks, got any references to how the surveying equipment de-aliasing method worked?

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Re:Understanding Indirect Time-of-Flight Depth Sensing by jcims on Tuesday April 20, 2021 @08:12PM (#26883738)

I don’t unfortunately. I was there doing an information security assessment and the guy I was working with was one of the product engineers. When I wrapped my work we spent another hour or two just talking about their products and how they worked.

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Re:Understanding Indirect Time-of-Flight Depth Sensing by opwieurposiu on Tuesday April 20, 2021 @10:20AM (#26875027)

The kinect does do the "chirp", but this detail is omitted from TFA.

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