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OPT8241-CDK-EVM: Calibration issue

Peter Tsai 57
Prodigy 70 points

Part Number: OPT8241-CDK-EVM

Hi,

I have watched the video "2.5 3D Time of Flight system offset calibration" in TI training website.

I can understand the whole calibration step very soon by watching these detailed videos.

But there are some issues bothering me anyway, hope i could find the answers here.

1, What's the difference between "Non-linearity calibration" and "Common phase offset calibration" ?

     For Non-linearity calibration, i measure the actual distance and Phase 1, Phase 2 which i measured in this distance. Calibration Wizard will build a LUT.

     This LUT means the relationship between the distance and the true phase in this distance.

     For Common phase offset calibration, it do the same thing. Measure the actual distance and phase and calculate the offset between the ideal phase and the measured phase.

     I really don't understand what's the difference between these two calibrations.

2, When i do the Common phase offset calibration, for example at 3 meters, i can get the relationship between distance and phase at 3 meters.

    But if my target move to 5 meters, the calibration doesn't work out, does it?

    Should i do the calibration once at 5 meters?

3, How could i combine those calibration LUTs or parameters into a merged LUTs or camera file?

4, In real case, i have to change different camera file or calibration LUT when i change my scenes. Right?

    I have to do lots of times of calibration to prepare lots of camera file for each scenes. Is that right? 

    What's TI's suggestion?

Looking forward to your answers.

Thanks & Regards.

Peter

  • 0
    TI__Expert 3495 points
    1. LUT is using actual raw-phase to lookup 'ideal' phase. Ideal phase is back-computed from actual distance.

    2. If phase relationship is linearized, calibrating at 3m will extend correctly to 5m. One can think of linearity calibration is to ensure the "slope" of a line is constant, and common phase offset is to establish one point on that line. With slope and a point on the line, the phase-to-distance function is fully defined.

    3. TI calibration tool all calibration to *.conf file and *.bin file in the .Voxel/conf directory.

    4. It is not scene change, but rather distance to target change, may require illumination and integration time change, such as long- vs. short-range, may require you to operate in profile at different calibration point.
  • 0 in reply to Larry Li
    Prodigy 70 points
    Hi Larry,

    I got it. Thanks for your reply.

    Peter