Photonics Dictionary

A dichroic coating, also known as a dichroic filter or dichroic mirror, is an optical coating designed to selectively transmit or reflect certain wavelengths of light while simultaneously absorbing...

A dichroic mirror, also known as a dichroic beamsplitter or interference filter beamsplitter, is an optical device that selectively reflects or transmits light based on its wavelength. Dichroic...

A color filter that is designed to gradually increase or decrease its absorption with wavelength.

A filter purposely made to be placed before a lens to render the image rather unclear.

A linear computation or algorithm performed on a selected series in the form of an input signal that produces a new series as output. The computational device may be a specifically designed...

Digital signal processing (DSP) refers to the manipulation and analysis of signals, which are representations of physical quantities that vary over time or space. In the context of DSP, these signals...

A complex filter that uses polarization and interference to transmit light that is nearly monochromatic.

In image processing, any operation that strengthens information about the edges of objects displayed. Three types of spatial filtering are used: shift and difference, gradient and Laplacian.

A color filter, generally used in photography, to emphasize certain color tones and to modify others in a picture for a more dramatic image. A blue effect filter, for example, darkens red and yellow,...

An electrostatic device that uses an electric potential barrier to allow the transmittance of electrons at or above a set level of energy while stopping the passage of those below it.

When a block of glass (prism, window, filter, etc.) is placed into a converging light bundle, it increases the physical distance to the point of focus. The equivalent air path for that block of glass...

An etalon is an optical device that consists of two parallel reflecting surfaces separated by a precise and known distance. It operates based on the principle of optical interference and is used to...

In ultraviolet and fluorescence photography, the term applied to the filter used in the photographic system and with the exciting source to screen out ambient radiations and to transmit the exciting...

A nonabsorbing, multireflecting device, similar in design to the Fabry-Perot interferometer, that serves as a multilayer, narrow-bandpass filter.

A fiber Bragg grating (FBG) is a type of optical filter that is inscribed or "written" into the core of an optical fiber. It consists of a periodic modulation of the refractive index along the length...

1. With respect to radiation, a device used to attenuate particular wavelengths or frequencies while passing others with relatively no change. 2. See digital filter.

The necessary increase of a photograph's exposure time as the result of the additional absorption of light by the filter being used.

A grating used as a reflectance filter, particularly in the far-infrared. Small plane gratings, blazed for the wavelength of the unwanted radiation, are produced for this purpose.

A function used in a convolution filtering operation. The image to be filtered is convolved with the filtering kernel to obtain the enhanced image.

A spectrophotometer that makes use of filters to isolate narrow bands of the spectrum.

A device that holds a number of filters and allows the filter with the desired characteristics to be rotated into an optical aperture.

Any of a number of instruments that uses a flame to vaporize a solution of the chemical being analyzed so that light may be passed through the vapor. Monochromation of the transmitted light is...

A filter, partially opaque to near-ultraviolet, visible and infrared radiation, that may be made by exposing and processing photographic film. Such materials are almost equally opaque to radiation of...

The frequency domain is a concept used in signal processing and analysis to represent signals and data in terms of their frequency components. In contrast to the time domain, where signals are...

A technique for measuring the concentration of any gases. Identical infrared beams are alternately chopped, one passing through a reference cell and the other passing through a cell with the gas...

The term half bandwidth (HBW) generally refers to the width of a spectral band or frequency range at half of its maximum amplitude. It is commonly used in the context of signal processing, optics,...

1. The value on either the leading or the trailing edge of a laser pulse at which the power is one-half of its maximum value. 2. The wavelength at which a filter is transmitting one-half of its peak...

A filter, used in photography, that absorbs the ultraviolet and extreme blue violet radiation scattered by atmospheric haze.

A glass filter that transmits visible light while absorbing infrared energy (heat).

A filter that allows heat radiation from an incident beam to pass without absorption or reflection.

A filter possessing one transmission band that extends from a cutoff frequency other than zero to frequency at infinity.

A holographic grating is a type of diffraction grating that is produced using holographic recording techniques. It consists of a periodic structure of alternating transparent and opaque regions,...

A specific type of hologram that will transmit a pure plane wave when the hologram is illuminated by the type of wave it is matched to.

A hyperspectral imaging camera is a sophisticated imaging device capable of capturing and processing data across a wide range of wavelengths within the electromagnetic spectrum, typically from...

Any filter in which the range of frequencies within a chosen radius suffers no attenuation and the range of frequencies outside the radius is entirely attenuated.

Filtering procedures aimed at estimating the original image by removing the blurring and noise suppression that occur during image processing.

An InGaAs (indium gallium arsenide) camera is a type of imaging device that utilizes InGaAs sensors to capture images in the near-infrared (NIR) spectrum. InGaAs is a semiconductor material that is...

In a microscope, a space reserved to accommodate an optical filter or polarizer.

A filter exhibiting transparency, absorption or reflectance characteristics specifically for spectral control of wavelengths longer than 700 µm.

Infrared optics refer to optical components and systems designed to manipulate and control infrared (IR) light, which lies beyond the visible spectrum. These components are crucial for various...

The photographic recording of images on a medium sensitive to infrared radiation, using a source capable of emitting in the infrared and a filter that transmits only infrared radiation.

In a camera, the movement of one or more lenses behind the front lens, rather than of the front lens itself, to bring the subject into focus. Because internal focusing does not require the front lens...