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CCD Cameras - 01 questions with complete solutions
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CCD Cameras - 01 questions well answered to pass
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CCD Cameras - 01CCD - correct answer ✔✔Charged Coupled Device - integrated circuit with a certain number of coupled
condensers (able to hold charges) used to record images.
CCD's invented - correct answer ✔✔1969 by Boyle and Smith of Bell Labs got Nobel Prize in Physics in
2009
CCD's in astronomy - correct answer ✔✔First used in 1979 a liquid N cooled CCD was used in the 1m at
Kitt Peak.
Revolutionized astronomy in the 80's and replaced conventional photograph
CCD advantages - correct answer ✔✔high sensitivity
immediate viewing
ease in processing
indefinite copies without deterioration
CCD disadvantages - correct answer ✔✔small size
solution: chip mosaic
CCD's - correct answer ✔✔are electronic units composed of physical entities called pixels that detect
light
photoelectric effect - correct answer ✔✔CCDs work based on this effect which converts light to an
electric current
Direct Proportion - correct answer ✔✔The numbers of electrons produced is proportional to the
quantity of light received
, CCD basic tasks - correct answer ✔✔1) Generate charge (photoelectric effect)
2) Store charge in each pixel
3) transfer charge to reader
4) Measure the charge (amplify and digitize)
1. Generate the Charge - correct answer ✔✔photoelectric effect - electron absorbs energy from light or
heat, gets excited and transfer from the valence level to the conduction level (BV to BC) by overcoming
gap energy.
An electric potential is applied to prevent recombination of charges if excited electron tries to go back to
valence level
2. Store the Charge - correct answer ✔✔each pixel stores charge in addition to detecting photons
Pixel (name meaning) - correct answer ✔✔Picture element
Pixel (structure) - correct answer ✔✔Photo site (converts photon to electron) and three electrodes of
different voltages to generate a potential well.
Photons are trapped in the closest pixel in the potential well.
Bigger pixels, store more charge (more e-)
CCD resolution (grain) - correct answer ✔✔determined by pixel size and pixel separation
Photon E - correct answer ✔✔blue photons more E than red photons.
longer wavelength photons have less E
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