Abstract: A volume-phase optical grating, preferably supported between substrates and prisms, uses large-angle input and output light beams to provide a very high degree of dispersion and improved separation of closely spaced wavelength channels. The average refractive index of the grating medium is also less than that of the supporting substrates and prisms, thereby providing improved uniformity and reduced sensitivity to the state of light polarization. The device therefore finds utility as a wavelength multiplexer, demultiplexer or optical spectrum analyzer in fields such as optical communications and optical signal processing. The grating itself may be constructed by conventional interferometric or holographic techniques, and may be a reflection or transmission device. In a system configuration, optical fibers may be used to carry the multiplexed or demultiplexed optical signals. Optoelectric detectors may also be used to detect different wavelengths and convert the optical signals into electrical counterparts.

Abstract: A holographic diffuser for use in conjunction with a back-lit flat-panel display and a source of illumination in the form of one or more tubular lamp segments is recorded so as to receive light from the lamp segments and scatter it preferentially along a plane perpendicular to the axis of the bulbs. In a back-lit display having vertically oriented tubular lamps, the diffuser scatters substantially more in the horizontal dimension, thus filling in the gaps of light intensity between the bulbs, which would otherwise be viewed by an observer, as with conventional diffusers. The high aspect ratio diffusers of the present invention are preferably formed by projecting coherent radiation through a mask having dimensions functionally related to the desired final aspect ratio, with an optional collimating lens being used to project that mask to infinity. A contact exposure process is also described.