Friday, November 22, 2019

Espros on ToF Camera Calibration

Espros distributors Pacer (UK) and Aprizes (China) publish Espros application notes on ToF camera calibration. Almost everything affects the ToF measurements, some factors have quite a dramatic influence:

The main error sources which affect the accuracy of distance measurement are:
  • Distance response non-uniformity DRNU of the sensor
  • Temperature drift
  • Ambient light
  • The magnitude of the signal amplitude
Under the term DRNU, we treat all factors that lead to a different distance reading between any of the pixels in the pixel-field looking to the inside of a sphere. These factors are sensor/camera related and include:
  • Flat-field error of the pixel-field
  • Column A/D converter differences
  • Row addressing differences
  • Fixed-pattern noise caused by manufacturing tolerances
  • 4th order harmonics distortion of the demodulation algorithm

Another Espros presentation gives more info on ToF error sources:


  1. Hi EPC teams,

    DLL on-chips are good ideal but how to correlation with ground truth objects depth cause by amplitude reducing with distance? This's items should be product offset factor in the calibration, right?


    1. Dear Lucky

      It is correct that received TOF amplitude is reduced with distance. But this is only the signal strength of the received signal. The TOF distance calculation itself is independent of the signal amplitude. So far, this has no further impact beyond an increase of the distance noise (temporal noise, relative accuracy). But the absolute accuracy is related only to the traveling time of the photons - and is independent of the TOF amplitude. If you like to go into more detail, please, refer to the datasheets of our TOF imagers as well as to our application note AN10 Calibration and Compensation.
      More background in detail about this you can learn also by joining the ESPROS TOF Developer Conferences.

      If you have any further questions, please let us know.

      Thank you and best regards
      ESPROS Team


All comments are moderated to avoid spam and personal attacks.