what causes noise in CCDs?
- Thread starter FatBird19
- Start date
pheboglobi
Well-known member
"dark" current - heat, cosmic rays, and electrical resistance can alter the analog signal. It happens to all CCDs regardless, and when you amplify its signal - aka gain, it will amplify the dark current signal distortions as well. Some of it can be random and some of it can be fixed (due to manufacturing imperfections, or imperfections caused by physical abrasions, heat, cosmic rays, etc).
That's a simple and generalized explanation anyway.
Garrett
That's a simple and generalized explanation anyway.
Garrett
BobDiaz
The Professor
FatBird19 said:
NO, we don't run a higher voltage through the CCD, that would burn up the chip. Higher ASA raitings (gain) is performed by increasing the amplification in the pre-amp curcuits. The good news is that the weaker video signal is greater. Bad news, the noise is now higher.
Heat helps to generate a lot of noise. If a CCD is cooled, it will generate less noise. Even the circuits that connvet to the CCD add their own noise to the signal.
Bob Diaz
MarcusX
Well-known member
Ok, I have a question:
Lets say I have a CCD which can record 10.000 frames/sec. I program the CCD to take 5 samples in a row (5/10000 sec.) every 1/24 second. Then I calculate the average of the 5 values for each pixel and record the frame.
Would'nt that give me a superior SNR?
Lets say I have a CCD which can record 10.000 frames/sec. I program the CCD to take 5 samples in a row (5/10000 sec.) every 1/24 second. Then I calculate the average of the 5 values for each pixel and record the frame.
Would'nt that give me a superior SNR?
BobDiaz
The Professor
FYI to all: USA uses "," Germany uses "." in large numbers...
Yes, say you took 1 single frame and looked at the image noise.
Now take 100 frames added together and divided by 100, the signal is the same in all the frames, BUT the noise changes and is averaged out. Thus, there will be less noise in this image.
OK, There is fixed pattern noise in the CCD that would not be removed, but given that fixed pattern noise is roughly the same, one could create an image of the noise and remove (reduce) this noise.
Bob Diaz
Yes, say you took 1 single frame and looked at the image noise.
Now take 100 frames added together and divided by 100, the signal is the same in all the frames, BUT the noise changes and is averaged out. Thus, there will be less noise in this image.
OK, There is fixed pattern noise in the CCD that would not be removed, but given that fixed pattern noise is roughly the same, one could create an image of the noise and remove (reduce) this noise.
Bob Diaz