METHOD FOR COUPLING NARROW-BAND INTERFERENCE FILTERS TO TWO-MIRROR AND CATADIOPTRIC TELESCOPES

摘要

A monochromator in which the separation of the mirrors of a two-mirror telescope (50) is altered to produce a virtual object (57, 58) for a converging lens (Lf), termed a "forcing lens", the forcing lens being so located between the virtual object and a narrow-band interference filter (70) (typically containing a Fabry-Perot etalon) that the convergent beam of light from the telescope passes through the interference filter at a high focal ratio, relative to the telescope's conventional focal ratio, before it traverses the forcing lens, which forms the optical system's only real image (57f, 58f), at a different, and much lower, focal ratio. Image contrast, relative to the contrast at the telescope's conventional focus, is notably enhanced. By means of a graduated series of entrance pupils, a step-wise-zoom, constant-contrast monochromator may be constructed. Formulas are provided for parfocalizing a series of forcing lenses, thereby allowing real-image height to be adjusted.