Definition: Transparent material coated with a reflective layer e.g. film of metal so that it transmits half of the incident light and reflects the other half. * The proportion of light transmitted can be controlled by the thickness of the layer, depending on material used and properties of the substrate. * Used to split beam of light into two parts e.g. in main mirror of auto-focus SLR viewfinders, for front-projection, holography, etc. * Also known as semi-reflective, semi-transparent mirror. But compare with dichroic mirror.

Related Terms: dichroic

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