A conventional grayscale image sensor pixel can be modeled as a "light bucket." Photons arrive on the sensor pixel for a fixed exposure time. The light bucket fills up with photo-electrons linearly proportional to the number of incident photons until its full well capacity is reached. The final readout is a Poisson random variable (shot noise) plus some Gaussian perturbations (due to quantization, dark current and readout noise). This model, although abstracted away from the underlying analog pixel electronics, is a quite useful model of signal and noise in a conventional image sensor pixel.

I am trying to build a similar signal and noise model, abstracted away from the pixel's MOSFET microelectronics, for a logarithmic image sensor (similar to Section 2 in this paper by Hasinoff et al. or Figure 1b of the EMVA 1288 standard.)

  1. Is there any notion of saturation for a log pixel?
  2. How does shot noise come into play in the logarithmic non-linearity?
  3. Is there any notion of "exposure time" or "integration time" to average out shot noise in a log pixel?
  4. Is there an EMVA standard (or some other standard) for log sensors (and more generally, for sensors non-linear photo-response, such as a quanta image sensor)?
  • \$\begingroup\$ Aha, an "is it possible" question..... \$\endgroup\$ – Andy aka May 2 '19 at 15:25
  • \$\begingroup\$ By "is it possible" what I really mean "Have you seen anything like it in literature"? \$\endgroup\$ – Atul Ingle May 2 '19 at 15:26
  • \$\begingroup\$ Take the tour: electronics.stackexchange.com/tour and you'll probably realize that your question is invalid. \$\endgroup\$ – Andy aka May 2 '19 at 15:30
  • 1
    \$\begingroup\$ Thanks Andy. I have edited the question to tighten it up a bit. \$\endgroup\$ – Atul Ingle May 2 '19 at 15:38
  • \$\begingroup\$ Slide #54 here seems to have a simple formula for the SNR at large flux levels. cafe.stanford.edu/~abbas/group/papers_and_pub/… Perhaps there's some intuitive interpretation of saturation in terms of the photodiode's junction capacitance. \$\endgroup\$ – Atul Ingle May 4 '19 at 20:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.