étendue

A form of etendue — A conserved property of the light in an optical system which characterizes how "spread out" the light is in terms of angle and area: it is the product of its cross-sectional area (normal to the direction of propagation) and the solid angle it subtends.

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Meanings

nounétendue (uncountable)
  1. alternativeuncountableAlternative form of etendue.

    The light power transmitted to the detector is proportional to the product of the solid angle #92;mathit#123;#92;Omega#125; and area A in the central plane, which is imaged by the lens onto the aperture (often called the étendue U).

    2003, Wolfgang Demtröder, “Spectroscopic Instrumentation”, in Laser Spectroscopy: Basic Concepts and Instrumentation (Advanced Texts in Physics), 3rd edition, Berlin: Springer-Verlag, →DOI, →ISBN, →ISSN, page 149
Cite this entry
APA

étendue. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/%C3%A9tendue

MLA

“étendue.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/%C3%A9tendue. Accessed November 5, 2026.

Chicago

WatkinsX Dictionary, s.v. “étendue,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/%C3%A9tendue.

Source: étendue on Wiktionary, CC BY-SA 4.0.