APPENDIX
iKon-L APPENDIX
Page 161
A1.1.12 - Quantum Efficiency/Spectral Response
The glossary refers to signals as a number of electrons. More strictly speaking these are ‘photoelectrons’,
created when a photon is absorbed. When a UV or visible photon is absorbed by the detector it can at best
produce only one photoelectron. Photons of different wavelengths have different probabilities of producing a
photoelectron and this probability is usually expressed as Quantum Efficiency (QE) or spectral response.
QE is a percentage measure of the probability of a single photon producing a photoelectron, while spectral
response is the number of electrons that will be produced per unit photon energy. Many factors contribute to
the QE of a CCD, but the most significant factor is the absorption coefficient of the silicon that serves as the
bulk material of the device
A1.1.13 - Readout
Readout is the process by which data are taken from the pixels of the CCD
and stored in computer memory.
The pixels, which are arranged in a single row, are read out individually in sequence. Readout involves
amplifying the charge on each pixel into a voltage, performing an A/D conversion, and storing the data in
computer memory. The time taken to perform this operation is known as the ‘read time’.
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