Collimator for parallel light beam from semiconductor diode laser - uses coiled glass fibre wave guide with transparent plastics outer skin

摘要

A semiconductor diode laser (1) emits a beam of light (11) which, although bunched but not particularly sharp, passes through a converginglens (L1) placed in its path, the rays meeting at the focal point (f) which is also the end surface (S) of a monomode light wave conductor (2). This is formed by a core-sheath-glass fibre, having sufficient length, and an outer coat of transparent material of suitable refractive index. The light travels along this waveguide (2) which is wound in a coil, and emerges from the other end surface (S1) as a pencil of light having almost the quality of an ideal point light source. This pencil of light (12), then passes through another converging lens (L2). The rays emerging from it as an ideal parallel beam (13). This is an improvement over the usual opaque screen with a minute hole in it, since very little useful light is lost.