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11 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What does CCD stand for? |
Charged Couple Device |
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What are CCDs? |
Silicon integrated chip made up of Metal Oxide Silicon (MOS) capacitors. |
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What is each MOS capacitor made of? |
A photosite= a photodiode so can store charge |
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How does the CCD form a picture? |
1) Light photons fall onto the MOS capacitors. 2) Photons liberate electrons on the capacitors to higher energy levels. 3) Brighter light- more photons hit photosite- more electrons liberated. 4) >electrons mean >charge 5) light levels are represented by charge which builds up over time. |
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What is quantum efficiency? |
% incident photons |
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What level of quantum efficiency is better for low light levels? |
High quantum efficiency. |
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What must quantum efficiency be constant for and why? |
1) Must be constant for all photosites. 2) So relative intensity is the same. |
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What is resolution due to? |
No. photosites |
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How is info from photosites transfered to screen? |
Charge is measured systematically then converted to correct light intensity: 1) CLOCK PULSE shifts charge in each row down. 2) SHIFT REGISTER measures charge on bottom photosites. 3) SERIES OF PULSES represent charge level in each photosite before charge emptied & process repeated. 4) SYSTEM identifies which charge level goes with which pixel on screen & image built up. |
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How are coloured images produced using filters? |
1) R,G & B filters over photosites so only pick up one colour. 2) filters in pairs of colours: e.g B found using R&G filters. 3) the 3 colours put together for final image. |
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How are coloured images produced using separate CCDs? |
1) 3 CCDs with R,G & B filters in front of each CCD. 2) Put together to make final image using mirrors & lenses. |
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