method and device for the spectral decomposition of the light and the spectral components of light.

摘要

1332304 Optical systems BARR & STROUD Ltd 18 Nov 1970 [27 Nov 1969] 58178/69 Heading G2J [Also in Division H4] A method of splitting a light-beam into spectrally distinct components comprises the steps of linearly polarizing the light-beam by its incidence with a beam-splitter at an angle of incidence of 30 degrees - 50 degrees for the axial ray, rotating the plane of polarization of a spectrally selected component of the linearly polarized beam, and separating the spectrally selected component from the remainder of the beam by a polarization-sensitive device. As shown, light beam 20 is incident on beam-splitter 15 resulting in reflection of a beam 21 with one plane of polarization, and transmission of another beam with a perpendicular plane of polarization. The first beam passes a filter to provide the blue output. The second beam is then passed through plate 14 which acts as a half-wave plate for green radiation, rotating the plane of polarization of the green by 90 degrees, and then reflected from beamsplitter 16, which allows the remainder of the light to pass. Green filter 18 and red filter 19 are provided. A single beam-splitter may be used, when plate 14 is replaced by a quarter-wave plate and a dichroic mirror Figs.8 and 9 (not shown). More complicated arrangements are described which may be used in television or still photography. The beam-splitters may be of birefringent material and are preferably chromatically neutral. The polarization-sensitive device may be a beam-splitter, as above, a Kerr cell or may utilize optically active materials or the Faraday effect. By passing light in the reverse directions, these arrangements may be used to combine lightbeams.