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Blooming of CCD

  1. Aug 8, 2007 #1
    Hi guys
    I was getting into a hobble with my project.my tutor said the aim of my project is to find out the distribution of Bloomed Charge, but i only have several dark images associated with the readout of KODAK KAF-0402. I supposed it was related to Dark current and Dark Noise. Because the rate of Dark current can predict, and the variation rate of Dark current of each pixel is the main point which will affect the distribution of Bloomed Charge.
    SO am I right?:confused::confused::confused: Any body knows a lot about CCD technology can give me a help. thank you!:smile:(I got a lot querys, if you can help i want to use msn for more communication. appreciated for your help.)
     
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  3. Aug 8, 2007 #2

    berkeman

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    I don't think blooming has anything to do with dark current. Isn't blooming from overloading the CCD pixels with too much light?
     
  4. Aug 8, 2007 #3

    mgb_phys

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    Blooming is charge flowing out of a ccd 'pixel' into surrounding areas.
    You can prevent this with anti-blooming drains, electronic structures which carry away overflowing charge but scientific CCDs including the KAF-0402 don't have these beacuse they significantly reduce efficency.

    The only relationship between blooming and dark current is that seriously overexposed CCD pixels can have raised dark current for some time afterwards. This is mainly a problem in cryogenic astronomical cameras.

    The big book of CCDs is by James Janesick.
     
  5. Aug 8, 2007 #4
    thank you for your reply guys! I know the blooming is because of overloaded from light. but the tutor want me to indicate the distribuation of ccd bloomed charge.
    just like MGB said the dark current value will raise, and also the dark current noise can be predicted. so if the CCD just exposure equaly, the pixel contain more dark current noise will possibily blooming first right? so we can indicate the distribution of bloomed charge then, right? i hope i'm right! if not i really don't know how to write my project report.
    BTW the value of the pixel charge i read from the image by MATLAB is what?
    my tutor said it's quantum and he said quantum=52 electrons? I thought it's wrong.because the saturation signal is100000 electrons. but the biggest value i got is 4095,so 4095x52= 212940 electrons, head and shoulders above saturation signal.How could that happened? i thought the maximal value of charge should equal or less saturation signal right? impossible more than it.so what's the unit of the value i got from the image by matlab? ADU? if it's ADU what about gains of ADU? I just want to know how many electrons it contained with each pixels.

    thank you for your answers? appreciate
     
  6. Aug 8, 2007 #5

    mgb_phys

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    The increased rate of dark current can show where blooming occurred, presumably you have before and after blooming dark frames?
    Remember that the dark count has shot noise statistics so has a root(n) uncertainty.

    The 4095 could be due to some scaling in the software or possibly a negative value caused by subtracting two images.
    The gain of the ccd (the 52adu/e) depends on both the chip and the readout electronics, there is a technique to measure it statistically if you have a sequence of dark images with different exposure times.
     
  7. Aug 9, 2007 #6
    Can you tell me more about that technique? Actually I got a sequence of dark images with 100ms,200ms,300ms,500ms,800ms,1800ms,4800ms,9800ms intergration time dark images. so how to measure the gain of it?
     
  8. Aug 9, 2007 #7

    mgb_phys

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