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OPT9221: Details of sub-frame and quad timing

Rick Marron
Prodigy 10 points
Part Number: OPT9221

Hi,

I am considering using the OPT9221 in a product, and I have some questions related to the sub-frame and quad timing. Specifically:

  1. When the quad components are integrated, are all four (or 6) integrated within a single period of the demodulation signal? The alternative being to integrate the quads each over subsequent periods of demodulation and assuming there is not much variation between the periods.
  2. Similarly, should I be thinking about the sub-frames as a single demodulation period? Meaning, if the demodulation frequency is 50Mhz, then the subframe is only covering 20ns - which is further split into the 4 or 6 quads. Or does a sub-frame contain many demodulation periods?
  3. Are there limitations to how quickly demodulation frequencies can be updated? Can they be changed intra-frame or even intra sub-frame?

Thanks!

Rick

  • 0
    TI__Expert 3495 points
    1. When the quad components are integrated, are all four (or 6) integrated within a single period of the demodulation signal? The alternative being to integrate the quads each over subsequent periods of demodulation and assuming there is not much variation between the periods.

    >> The latter.  Each quad integration window has a different phase step.  If 4-quad mode is used, the integration window of first quad will have 0 degree offset, second quad will have 90 degree offset, third quad will have 180 deg offset, and fourth will have 270 degree offset.

    1. Similarly, should I be thinking about the sub-frames as a single demodulation period? Meaning, if the demodulation frequency is 50Mhz, then the subframe is only covering 20ns - which is further split into the 4 or 6 quads. Or does a sub-frame contain many demodulation periods?

    >> A sub frame is a full-fledged depth frame, made of 4 or 6 quads.  Sub-frames are averaged to make a reported frame. Reported frame is what gets outputted.

    1. Are there limitations to how quickly demodulation frequencies can be updated? Can they be changed intra-frame or even intra sub-frame?

    >> In deliasing mode, the integration window is split half between two modulation frequencies.  Otherwise, customer can change modulation frequency programmatically.

    This tutorial video might help explain pixel operation more.