Abstract:
1,140,017. Monochromators. BECKMAN INSTRUMENTS Inc. March 2, 1967 [March 10, 1966], No. 9954/67. Heading G2J. A monochrometer having a rotatable diffraction grating 13 is provided adjacent an exit slit 15 with a movable interference filter 23 which passes or reflects radiation of different wavelengths at different location thereof, the filter 23 being moved in accordance with rotation of the grating 13. In Fig. 1, a circular interference filter 23 is mounted in a rotatable wheel 22, and the wavelength passed by the filter 23 varies linearly as a function of angle. The grating 13 and filter 23 are rotated synchronously by means of cams 17 and 27 respectively which are fixed to a motor-driven shaft 18. The circular interference filter may be replaced by a filter wheel carrying a plurality of concentric arcuate filters which may have overlapping passbands. In the embodiment of Fig. 5 (not shown) a reflecting interference filter is used. Radiation from the exit slit 15 is directed between two parallel reflection interference filters (41), (42) towards a focusing region (45) which redirects the radiation between the filters to form an image of the exit slit. The number of reflections between the filters (41), (42) is selected in accordance with the degree of accuracy required.