Optical filter

An optical device that selectively transmits, reflects, or absorbs light according to properties such as wavelength, polarization, or intensity. Its selectivity shapes which light reaches a detector, observer, or other optical component.

Interference filter: An optical filter that uses interference in thin films to transmit or reject selected wavelengths. Alternating thin-film layers create wavelength-selective transmission through constructive and destructive interference.
Band-pass filter: A filter that transmits a wavelength interval while attenuating wavelengths on both sides. It isolates a chosen spectral window for detection or illumination.
Transmittance: The fraction of incident light that passes through a material or optical element. A filter's transmission spectrum quantifies which wavelengths it passes.
Monochromator: An optical instrument that selects a narrow wavelength range, typically using a dispersive element and slits. Unlike a fixed filter, it can tune the selected wavelength across a spectrum.
Absorption filter: A filter that removes selected wavelengths by absorbing them in a material. Dyes and colored glass suppress wavelengths through material absorption rather than reflection.
Long-pass filter: A filter that transmits wavelengths above a cutoff and attenuates shorter wavelengths. It blocks shorter-wavelength excitation light while passing longer-wavelength emission.
Reflectance: The fraction of incident light reflected by a surface or optical element. Many filters reject unwanted wavelengths by reflecting them rather than absorbing them.
Prism: A transparent optical element that bends and separates light by wavelength through refraction. A prism spatially disperses colors instead of selectively transmitting a fixed band.
Polarizer: An optical device that transmits light with a selected polarization and attenuates other polarization states. Polarizing filters select light by oscillation direction instead of wavelength.
Short-pass filter: A filter that transmits wavelengths below a cutoff and attenuates longer wavelengths. It selects the short-wavelength side of a spectrum for optical systems.

Linked from 6 pages