Is webcam shadow noise a random signal?

Question

Electronics

Hello everyone, next question. We take an ordinary cheap webcam, completely close the lens (for example, with black plasticine), shoot a video signal, it is noise from gray dots, you can amplify (multiply the brightness) and then it even looks a bit like a TV screen without a selected channel (although I don’t know whether this remains on current TVs, I don’t have it). Noise has some patterns. First, there is something like "broken pixels", the color of which does not change much. Secondly, there is such a feeling (perhaps it is false) that some periodicity in time can be traced in the noise. There are also oddities: sometimes (about once a minute) there is a powerful short-term burst of noise brightness. As I understand it, the nature of the CCD noise is quantum, i.e. can we say that this signal is truly random? If yes,

Answer 1

Yes, the noise will be random but for the entire matrix as a whole. For each individual pixel, it will depend on its sensitivity obtained during the production of the matrix. So you need to take groups of pixels at least 8x8 and preferably 64x64. The patterns can be related to radio signal sources nearby - such as a mobile phone and wi-fi.