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Image sensor PCB and heavy dark noise

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Jun 5, 2017
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I've designed a video processing system. The camera is based on an On-semi image sensor, plus SER and DES chips, and an FPGA for processing.
There is a problem which I struggle with it for a while. In too dark conditions, there is a very heavy horizontal white line noise on the screen (I know such noise exist in image sensor theory, but the problem is the level of noise is very high.).
- I know the source of noise is not the SER/DES/CSI reader/FPGA... because using the sensor settings, I can make a fully black output which is clearly visible at the display, without any noise.
- using "fade-to-black" and smililar settings, I can make the video darker to "hide" the noise, but can't remove it.
- noise does not exist in light conditions. it is a dark noise.
- I am very suspicious to the sensor PCB itself.
did anyone have such a experience?

Unclear which parts of your system are carrying analog signals and are susceptible to interfering signals respectively generating noise on its own. Where is the video signal digitized?
--- Updated ---

Data sheet should tell if the observed noise level is excessive or just expectable.

Sensor is Onsemi AS0149. Lense is mounted just upon that, and sensor has digital output. All analog part is inside the chip (except external power and AGND pin). We have directly connected DGND to AGND.
Actually, I generated a fixed black video from inside the sensor using some settings in the sensor, and that video is displayed on the screen very clear without any noise. Then I conclude that the path "sensor digital output-> SER -> Cable -> DES -> FPGA -> LCD" is not responsible for the noise.
then, the only remaining noise source can be un-filtered AGND or power (we have already many 100nF capacitors there), or sensor settings.
In datasheet it is called "row-noise", and there is a filter for that. But even after that, the level of noise is very high. I put an image here:
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