I learned that one could use a RAM chip as a photosensor. That sounded very interesting and I looked a little deeper into this topic. Obviously, it is not as simple as it sounds, however one could light sensors to detect a pixel brightness.
This was a longer project due to several challenges and summer holidays. I designed a light sensor array that I could move around. The idea was to use a few pixels to measure a relatively large area. The sensor is in a housing with a lens that focuses the light on the light sensors. The whole thing is controlled with a python script and the output is a 64 x 65 pixel image.
Design and arrange a light sensor array PCB
CAD design of the housing
3d printing and assembly
First I was trying to use ItsyBitsy M4 with Arduino, however I was not able to get the SW running stable. I switched to CircuitPython and again had difficulties with the SW. The challenge was the communication between the sensor module and the control PC. After switching to the Arduino board I was able to control everything as planned. I changed the HW a little bit and simplified the build.
Finding a suitable lens was not as easy as hoped since I didn't want to order something just to scrap it or damage it. After some thinking I settled with an old Canon FD lens. The lens is not intended to be used with such a large photosensor and the image corners are very dark. Additionally I think the lens causes some unwanted light loss. Moreover, the lenst is not placed exactly in the middle of the sensor moving area.
The image making process takes more than 20 minutes and that is too much for fast adjustments. In order to improve the image quality I need to use another lens. Since the project took so long I decided to end it. I was able to make an image and I learned a lot - so the basic project objectives were fulfilled.
A little longer journey description: Instructables