Calcolatore Efficienza Quantica CCD
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Photoelectrons per Pixel
6.75 e-
Photoelectrons per Pixel vs Photon Flux
Formula
## CCD Quantum Efficiency and Electron Count Quantum efficiency (QE) is the fraction of incoming photons that produce a detectable photoelectron in the sensor. ### Formula **N_e = F * A * QE * t** - *F* = photon flux (photons per m2 per second) - *A* = pixel area - *QE* = quantum efficiency (0 to 1) - *t* = exposure time Shot noise follows a Poisson distribution: sigma = sqrt(N_e).
Esempio Risolto
3.75 um pixels (A = 1.406e-11 m2), QE = 0.80, flux = 1e10 ph/m2/s, 60 s exposure.
- 01N_e = F * A * QE * t
- 02N_e = 1e10 * 1.406e-11 * 0.8 * 60
- 03N_e = 0.1406 * 0.8 * 60
- 04N_e = 6.749 electrons
- 05Shot noise = sqrt(6.749) = 2.60 e-
Domande Frequenti
What is a good quantum efficiency?
Modern scientific CCDs reach 90% or higher at peak wavelength. Consumer CMOS sensors typically achieve 50-80%.
Does QE vary with wavelength?
Yes, significantly. QE peaks in the visible or near-infrared and drops in the blue and UV. Spectral QE curves are important for filter selection.
What limits detection of faint objects?
Read noise at short exposures and sky background shot noise at long exposures. Higher QE helps in all regimes.