Image Sensor Terminology
The definition of most commonly used terms in solid state image sensors is given below
Charge-coupled device (CCD): CCD is a charge transfer device that collects light in pixels and then uses clock pulses to shift the charge along a chain of pixels.
Correlated double sampling (CDS): CDS is the technique of taking two samples of a signal closely spaced in time and subtracting the rst signal from the second to remove the low frequency correlated noise.
Dark current: The signal charge that the pixel collects in the absence of light divided by the integration time.
Dynamic range: It is ratio of the saturation signal to the root mean square (rms) noise floor of the sensor.
Fill factor: It is the ratio of light sensitive area to the pixels total area.
Fixed pattern noise (FPN): It is the noise due to mismatch in the properties – transistor thresholds, gain, parasitic capacitance, pixel geometry – of pixels.
Integration time: It is the time that the sensor is exposed to light to integrate the photo generated signal charge.
Microlens: It is a lens etched directly on the chip’s surface for each pixel to focus the light on to the light sensitive area of the pixel.
Photocurrent/photocharge: It is is current/charge generated due to the exposure of silicon to light.
Photosite: It is the portion of the silicon that functions as a light-sensitive area.
Pixel: It is discrete photosensitive cell that collects and holds a photocharge.
Quantum efficiency: It is the ratio of photon-generated electrons that the pixel captures to the photons incident on the pixel area