Fr.: filtre de bande
An electric filter that transmits a known band of frequencies but suppresses unwanted frequencies above and below this band.
pâlâye-ye došekastgar, ~ došekasti
Fr.: filtre biréfringent
A type of narrow-band filter that uses the birefringence to produce selective absorption of polarized light.
→ birefringent; → filter.
circular variable filter (CVF)
pâlâye-ye vartande-ye parhuni, ~ ~ dâyereyi
Fr.: filtre circulaire variable
Circular band-pass interference filter whose thickness and central wavelength vary along the perimeter. They are used in low-resolution spectrophotometers mainly in the infra-red.
Fr.: filtre à coupure
Filter rejecting all light with wavelengths on one side of the cutoff wavelength.
pâlâye-ye dofâm (#)
Fr.: filtre dichroïque
An → interference filter used to selectively pass light of a small range of colors while reflecting other colors.
1) General: A device for separating the constituents of a system according to
a physical property. In particular, a device for removing solid matter suspended
in a liquid by forcing the suspension through a material which retains the solid
matter while allowing the liquid to pass.
From M.L. filtrum "felt," which was used to strain impurities from liquid, from W.Gmc. *filtiz.
Pâlâyé, from pâlây present stem of pâludan "to filter, purify;" Mid.Pers. pâludan, pâlây- "to strain, filter, purify," from Proto-Iranian *pari-harz-, from prefix *pari- "around," → peri-, + harz- "to let go, release;" cf. Av. pairi.harəz- "to filter," from pairi- "around, over" (cf. Skt. pari; Gk. peri "around, about, beyond;" L. per "through;" PIE base *per- "through, across, beyond") + harəz- "to release" (especially water, liquid; cf. Chorasmian pžy- "to purify, filter;" Arm. (loanword) parzel "to filter, purify;"
Fr.: filtre de verre
A filter used in → broad-band photometry. The → bandwidth ranges usually between 30 and 100 nm.
Fr.: filtre interférentiel
A filter that uses the phenomenon of optical interferences between plane-parallel semi-transparent reflectors to transmit light selectively over a narrow wavelength band.
→ interference; → filter.
pâlâye-ye Lyot (#)
Fr.: filtre de Lyot
A type of narrow-band filter consisting of a series of birefringent crystals and polarizers invented by the French astronomer Bernard Lyot (1897-1952) for isolating and observing significant wavelengths of solar light.
→ Lyot division; → filter.
neutral density filter
pâlâye-ye cagâli-ye natâr
Fr.: filtre neutre
A filter having a flat response over the range of wavelengths of interest. Also called neutral filter or gray filter.
Fr.: filtre neutre
Same as → neutral density filter.
pâlâye-ye qotbandé (#)
Fr.: filtre polarisant
A filter that polarizes light passing through it.