Filter

Filter, filtering or filters may refer to:

Science and technology

Device

• Filter (chemistry), a device which separates solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass
  • Filter (aquarium), critical components of both freshwater and marine aquaria
  • Filter paper, a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solids from liquids or air
  • Air filter, a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air
  • Oil filter, a filter to remove contaminants from engine oil, transmission oil, lubricating oil, or hydraulic oil
  • Pneumatic filter, a device which removes contaminants from a compressed air stream
  • Water filter, removes impurities from water by means of a fine physical barrier, a chemical process or a biological process
  • Cigarette filter, a part of a cigarette intended to filter the smoke inhaled by a smoker
  • Coffee filter, a utensil used to separate coffee grounds from liquid coffee
  • Fuel filter, found in most internal combustion engines
  • Filtration (wine)
• Sieve or macroscopic filter, a device for separating wanted elements from unwanted material

Optics

• Optical filter, selectively transmits light of different wavelengths
  • Interference filter, reflects one or more spectral bands or lines and transmits others, while maintaining a nearly zero coefficient of absorption for all wavelengths of interest
  • Dichroic filter, a very accurate color filter used to selectively pass light of a small range of colors while reflecting other colors
  • Hydrogen-alpha filter, an optical filter that transmits a narrow bandwidth of light centred on the H-alpha wavelength
  • Photographic filter, a camera accessory consisting of an optical filter that can be inserted in the optical path
  • Infrared cut-off filter, designed to reflect or block mid-infrared wavelengths while passing visible light
  • Chelsea filter, a dichromatic optical filter used for identifying coloured stones
  • Astronomical filter, a telescope accessory used to enhance the details of celestial objects

Signal processing

• Filter (signal processing)
  • Electronic filter, an electronic circuit which processes signals, for example to remove unwanted frequency components
  • Digital filter, a system that performs mathematical operations to reduce or enhance certain aspects of a signal
  • Analogue filter, a basic building block of signal processing much used in electronics

Computing

• Filter (higher-order function), in functional programming
• Filter (software), a computer program to process a data stream
• Filter (video), a software component that performs some operation on a multimedia stream
• Email filtering, the processing of email to organize it according to specified criteria
• Content-control software also known as an Internet filter
• Wordfilter, a script typically used on Internet forums or chat rooms
• Berkeley Packet Filter, filter expression used in the qualification of network data
• DSL filter, a low-pass filter installed between analog devices and a telephone line
• Helicon Filter, a raster graphics editor
• Filter (large eddy simulation), a mathematical operation intended to remove a range of small scales from the solution to the Navier-Stokes equations
• Kalman filter, an approximating algorithm in optimal control applications and problems

Mathematics

• Filter (mathematics), a special subset of a partially ordered set.
• Filters in topology, the use of collections of subsets to describe convergence.
• Filtering problem (stochastic processes), a mathematical model for a number of filtering problems in signal processing and the like.
• Filtration (mathematics), an indexed set of subobjects of a given algebraic structure S.

Arts and entertainment

• Filter (TV series), a show on the G4 channel
• Filter (magazine), an off-beat indie music magazine
• Filter Theatre, a British theatre company
• The Filter, a digital content services company based in England
• Filter (band), an American rock band
• "Filter", a song from the album Bend by 8stops7
• "Filter", a song from the album Map of the Soul: 7 by BTS

Other uses

• Category-based filtering of perception, according to (objectivist interpretations of), Kant; See Category
  • Affective filter, an impediment to learning or acquisition caused by negative emotional ("affective") responses to one's environment
• Lane splitting, a practice that cyclists use to pass slow or stopped congested traffic

See also

• Filter coffee, a method for preparing coffee
• Filter feeder, an animal that strains food particles from water
• Philtre (disambiguation)
• Lifter (signal processing)
• Separation process