Patent GB-1121724-A (GB)
Title: Arrangements for photoelectric scanning
IPC: G01B11/30
Filed: 1966-04-15
Abstract: 1,121,724. Photo-electric scanning apparatus. ERNST LEITZ G.m.b.H. April 15, 1966 [April 17, 1965], No. 16489/66. Heading G1A. [Also in Division G2] Photo-electric scanning apparatus for scanning a light distribution, index marks, scale divisions &c., comprises reflecting means, deviating a light beam through 90 degrees and having rigidly associated with it an apertured diaphragm or coating, means being provided to oscillate the reflecting means and associated aperture member parallel to the plane of the aperture member. In one arrangement, Fig. 1, the reflecting means is the internal surface of a prism 13 having an apertured diaphragm 12 attached to it. The prism and diaphragm are oscillated in the direction of the beam incident on the prism by an electromagnet oscillator arrangement 14. Light focused from source 10 on to the slit of diaphragm 12 is focused on to a scale 16, arranged on the other side of which is a photo-cell 17, which produces a signal varying with the incident light intensity. In another arrangement, Fig. 2 (not shown), the beam emerging from the oscillating prismdiaphragm arrangement is arranged to be aligned with the beam from the source (20) by having a stationary prism (22) positioned in front of the oscillating prism and shaped to deflect the beam through 90 degrees. In an arrangement for measuring the angle of inclination of an autocollimator mirror, Fig. 3 (not shown), light from a source (30) is focused on to an oscillating diaphragm (33a) attached to a five-sided prism (33) after passage through a fixed prism(32). The oscillation mechanism is an electromagnet causing movement of a flat spring carrying the diaphragm-prism. Light emerging from the diaphragm (33a) passes through a beam divider (36) and is collimated by a lens (36) from which it passes through the scale (41) being scanned, to a photo-cell (39). The markings on the scale (41) indicate values of angle and thus the photo-cell output may be used to determine the angular disposition of the autocollimator mirror (38) with respect to the light axis. A second beam divider (42) and an eyepiece (43) allow a rough determination of the angle to be made before a fine measurement is obtained with the photo-cell (39). The autocollimator mirror angle may also be determined by omitting the eyepiece and by using an array of photo-cells, one corresponding to each scale marking, these being made different to one another in form or separation, in dependence on a code. A further arrangement, for investigating the lines of a spectrum, Fig. 4 (not shown) includes a monochromator (46) before the scanning device, which in this case is simply a carrier for a diaphragm plate (48) and a plane mirror (49), the carrier being oscillated perpendicularly with respect to the incident light. In this arrangement, light of continuously varying wavelength passes through the aperture and is reflected from the mirror always on to the same point of the photo-cell surface. In the arrangements of Figs. 1, 2 and 3 the diaphragm may be replaced by an apertured coating on the prism. Any slight modulation effects in the cell output due to the oscillations of the aperture at the focal point of the lenses 11, 21, 31 are filtered out electronically.