GB560325A - Improved optical instrument for testing and gauging - Google Patents

Abstract

560,325. Optical apparatus. HILGER, Ltd., A., and DOWELL, J. H. Sept. 23, 1942, No. 13403. [Class 97 (i)] In apparatus for angle testing and gauging comprising a scale of angles, or other marking, in the focal plane of a collimating lens through which a light beam is directed on to a reflecting surface under test, the reflected beam being also received by the collimating lens, the resultant images are projected on to a screen for observation ; prism and scale combinations, means for locating the reflected beam, and means for facilitating viewing of the screen image, are also described. As shown, the instrument comprises a casing 9 carrying a collimating lens 10, a scale-bearing plate 6 in the focal plane of the lens, and a lamp 1, condenser 3, mirror 4, and prism 5 directing light through the lens 10. A scale 7, Fig. 4, is provided on the plate 6 at a position covered by the exit face of the prism 5, and a second scale 11 is provided thereon in a position such that the image of the scale 7 may cross it or lie near to it. A lens 12 and mirror 13 produce an image of the scales on a screen 14, and the screen may be observed through an aperture 18 and lens 15 by reflection in a mirror 17, or through an aperture 16 and the lens 15 only, the mirror 17 being tilted out of the position shown. The scales 7, 11 may consist of black or coloured lines on a light ground which may be coloured by the use of a filter. Alternatively, the scales may consist of bright lines on a dark ground, and the prism 6 and scales 7, 11, are then replaced by a prism combination 30, 34, 35, Fig. 5, and scales 38, 32. Light passes through the scale 38 to the collimating lens &c., and the reflected beam, forming an image above the scale 38, passes directly through a transparent reflecting surface 37 to the projection lens 12. A second beam from the lamp passes directly through the scale 32 and is reflected by the surface 37 into the lens 12. The background of one or both scales may be coloured; alternatively, gold or other substance reflecting a colour different from -that which it transmits may be provided on the surface 37. To facilitate location of the reflected beam, when the instrument is being set up, a matt white surface 28, Fig. 1, may be provided bearing lines between which the light patch is first caused to fall, adjustments being then made so that the reflected beam is received by the lens 10. Alternatively, a reflecting and imaging system may be provided to produce on the screen 14 a small scale image of the front of the scales 7, 11, and their surroundings, the screen 14 being observed, and adjustments made until the light spot is central thereon. Adjustments may be effected with the aid of a split bearing 21 for the collimator and a nut 22, the bearing being part of a support angularly and slidably adjustable on a slotted bar clamped to a base-plate at an adjustable angle.