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wavefrontshaping / ALP4lib

Python control module for Vialux DMDs based on ALP4.X API.
MIT License
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Intensity change Inconsistent when input image pixel value around 120 #26

Open Andrew-XQY opened 3 months ago

Andrew-XQY commented 3 months ago

Hi, I'm using the 8-bit DMD image depth to display a single-channel image. I noticed an intensity boost when the input pixel value crossed 120 (I was testing intensity change for an image with the same pixel value from 50 to 255 with each stride of 5, when it goes from 120 to 125, the actual measured average intensity using a CMOS camera changed three times more compared to all the others, like from 115 to 120 or from 125 to 130). All the other settings remain the same. Not sure why this happened.

roflmaostc commented 2 months ago

Are you aware that the 8bit works by displaying different binary patterns for different timings?

So depending on the exposure time of your camera you might observe strange effects. Sometimes it captures a weird amount of binary frames.

Andrew-XQY commented 1 month ago

Hi Felix,

Thanks for pointing out how the 8-bit modulation works with different timing patterns. I'm considering that the DMD might be using Pulse Width Modulation (PWM) for modeling various intensities. My current camera setup has an exposure time of about 80ms. Do you think this duration is sufficient to cover several PWM cycles, such that the PWM effect could be negligible? Thanks!

roflmaostc commented 1 month ago

I think the 8bit framerate is like 290Hz (model dependent) so 3.4ms per frame probably.

I guess 80ms should be fine. Do you observe the effect by also showing a single flat image with different intensities around the questionable one?