CHROMATIC FOCAL PENCIL BEAM-GENERATING APPARATUS

摘要

An optical system (12) is disclosed which focuses a polychromatic source to an extended focal pencil (16). The implementation makes use of two (15, 17) holographic optical elements (HOEs) fabricated and aligned to form a deliberate longitudinal color dispersion (16), but to alleviate lateral chromatic effects. Consequently, the HOE doublet focuses different wavelengths of the source to different locations along the optical axis. The strong intensity of the focused wavelengths dominate at each location, so that the overall beam has a near-diffraction-limited 1/e2 spot size and suffers only relatively weak background illumination. An alternative optical system using bulk lenses (80, 82) and several possible applications for the device are also described.