I am working on a project where I have a projector and a camera working together. The camera will record what a person does in front of a projector. Ideally the camera would also record what the projector is showing, but at minimum it just has to record the person and some objects. I am having a hard time with color artifacts however.

First I tried a high end webcam (see3cu55). That displayed horizontal lines of color, I am guessing from the rolling shutter. Second I tried a global shutter webcam, but that just flickers the whole image, showing me one color at a time. Messing with opencv2 settings and shutter speed on that one, I was able to increase the flicker speed to like 7 hz and then average it out. But it is just barely useable. Third I tried to use my coolpix p100. But the camera doesnt work well with linux when connected over usb (in fact it turns off while charging). I tried connecting to it via the hdmi, but the camera will not show me live footage, only recorded footage in that mode. In theory that camera should work since the recorded footage does not have the horizontal line issue, though the live preview does.

One thing I havent tried yet is putting a vertical polarizer over the projector and a horizontal polarizer over the camera, but I am not sure what percent of the reflected light stays polarized.

The projector I am using is DLP. If possible I would like to keep using that projector. At the same time, if there is a type of projector guaranteed to not have artifacts when used with a webcam, I am willing to try it out.

Is the only solution a high end camera that can do everything? or is there something more specialized for this?


1 Answer 1


The main problem is your projector.

A DLP projector does not project the whole picture at the same time, it uses mirrors to steer laser beams across the image. Some do only one color at a time. (See https://www.cnet.com/tech/home-entertainment/dlp-vs-lcd-vs-lcos-projector-tech-pros-and-cons/ for an overview of technologies.)

For pictures, you have to increase the exposure time accordingly. Live video, on the other hand, records at a similar refresh rate and will only get a small part of the projected picture.

For live video, you need another projector, e.g. based on LCD technology. I'd suggest to test the setup with you camera(s) before buying.


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