Glossary
- Wavelength ( of a light wave ): distance between two consecutive identical states of the electric ( or magnetic ) field
- Quantum efficiency: percentage of photons absorbed by a photodetector and effectively producing a signal
- Signal to noise ratio: (often called by its acronym : SNR) ratio between the signal and the noise; for a photodetector, the signal is the current or voltage generated by the detected light
- Photon noise: intrinsic noise in light caused by its corpuscular nature
- Dark current: electric current flowing through a photosensitive device in complete darkness (in the absence of incident light)
- Readout noise ( image sensor ): noise introduced by the on-chip amplifier during the conversion of the charge of a single pixel ( electrons successfully hit by photons ) into a signal ( current or voltage )
- Full well capacity ( image sensor ): maximum charge that a single pixel can contain before saturating
- Pixel: smallest sensitive element of an imaging sensor
- Transverse magnification: size ratio of an image and an object, the image being conjugated to the object by an optical system; for centered optical systems, the transverse magnification is defined with objects in a plane perpendicular to the optical axis - transverse magnification is then positive if object and image have the same orientation and negative otherwise
- Lambertian light source: light source with a constant radiance (or luminance) whichever the direction
- Radiance ( radiometry ): for a light source or a diffusing/reflecting surface, power emitted per unit of solid angle and per unit of apparent area
- Secondary light source: object diffusing and eventually reflecting / transmitting the light coming from a light source generally called primary light source