CCD Quantum Efficiency Calculator Formula

Understand the math behind the ccd quantum efficiency calculator. Each variable explained with a worked example.

Use the CCD Quantum Efficiency Calculator

Formulas Used

Photoelectrons per Pixel

electrons = photon_flux * pixel_area * quantum_efficiency * exposure

Shot Noise

shot_noise = sqrt(photon_flux * pixel_area * quantum_efficiency * exposure)

Variables

VariableDescriptionDefault
photon_fluxPhoton Flux(photons/m2/s)10000000000
pixel_areaPixel Area(m2)1.406e-11
quantum_efficiencyQuantum Efficiency0.8
exposureExposure Time(s)60

How It Works

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).

    Worked Example

    3.75 um pixels (A = 1.406e-11 m2), QE = 0.80, flux = 1e10 ph/m2/s, 60 s exposure.

    photon_flux = 10000000000pixel_area = 1.406e-11quantum_efficiency = 0.8exposure = 60
    1. 01N_e = F * A * QE * t
    2. 02N_e = 1e10 * 1.406e-11 * 0.8 * 60
    3. 03N_e = 0.1406 * 0.8 * 60
    4. 04N_e = 6.749 electrons
    5. 05Shot noise = sqrt(6.749) = 2.60 e-

    Ready to run the numbers?

    Open CCD Quantum Efficiency Calculator