Patent GB-551688-A (GB)
Title: Improvements in or relating to optical apparatus for measuring, gauging, and the like
IPC: G02B21/00
Filed: 1941-08-25
Abstract: 551,688. Optical gauging-apparatus. BATY, J. E. Aug. 25, 1941, No. 10818. [Class 106 (ii)] [Also in Group XX] In optical-projection gauging apparatus, supports are provided for pairs of parallel reflecting surfaces which are situated between the object to be gauged and a lens, and are arranged to receive and emit two beams in parallel planes, the beams, both as received and emitted, being closer together than twice the intercept between one pair of parallel reflecting surfaces. Fig. 1 shows optical elements of a projector comprising a lamp 20, condenser 21, beam-dividing mirrors 22, 23, and reflecting surfaces on prisms between the objects 25 and a single undivided projection lens 46. The prisms comprise rhomboids 29, 38, and internally-reflecting triangular prisms 32, 33 and 41, 42, the prism combination providing four pairs of parallel reflecting surfaces. The beams from the mirrors 22, 23 pass in parallel planes over opposite edges of the object and are closer together than twice the intercepts between the parallel reflecting surfaces, thus permitting gauging of small objects ; the emergent beams are similarly closely spaced and pass through the central portion of the lens 46. The prism's may be separated, as shown in Fig. 3, to be suitable for larger objects, and the prisms 29, 38, may then be emitted. The close spacing may also be obtained by two pairs of prisms arranged as shown in Fig. 4. Fig. 7 shows an embodyment of the apparatus in plan and Fig. 8 shows details of the prism supports. An additional mirror 78 is interposed between the condenser 75 and the beam-dividing mirrors 80, 81 ; the mirrors 80, 81 may be supported in the manner described in Specification 551,712, so that their separation may be varied and so that their tilts may be adjusted to the helix angle when the object 25 is a screw. The prisms are mounted in a casing 100 and the emergent beams pass to a projection lens 150, to a prism 151 reflecting them vertically, and to a reflector directing them downwardly on to a projection screw. The prisms 41, 42, 33, 32, are respectively carried on bars 101-104, Fig. 8, by bands 106. The bars 102, 103, are angularly adjustable about trunnions 108-111, by levers 112, 113 operable by screws, to move the screen images towards or away from one another and the bars 101, 104 are carried by supports 117, 118 separately adjustable along a bar 1.19 by screws 122, 123. The bar 104 is rigidly secured to the support 118 but the bar 101 is pivoted to the support 117 so that its tilt may be varied by rotation of a knob 135 carrying a long pinion 134 engaging a pinion 133 on a spindle carrying an eccentric pin 131 entering an aperture in the bar 101 ; variation of the tilt affects the parallelism of the projected images. The prisms 29. 38, are carried by separate holders rigidly and detachably securable to the supports 117, 118. The prism arrangement shown in Fig. 4 may be obtained by removing the prisms from the bars 101, 102 and mounting them on other bars replacing these bars. Additional prisms may be used to produce parallelism in the projected images or to bring them into proximity. According to the Provisional Specification, imagereversing prisms may also be provided in front of the projection lens, the means for adjusting the separation of the prisms 32, 33 may be coupled with that for the prisms 41, 42 and the beam-dividing mirrors may be replaced by two mirrors in one part of the beam. Specification 375,820 also is referred to.