An improved device for determining the polar coordinates of points in a plane surface, and a radial triangulator in which this device is employed

摘要

756,994. Measuring apparatus. ROELOFS, R. May 27, 1954 [May 29, 1953], No. 15753/54. Classes 97 (2) and 97 (3). Polar co-ordinates are determined by a rectilinear graduated scale, rotatable about the pole, and which can be moved lengthwise through a short accurately measured distance, and a circular graduated scale which indicates the angular position of the rectilinear scale. Preferably, the rectilinear scale 7, Fig. 1, is mounted in a frame 5 in a bracket 4 which is rotatably mounted on a fixed vertical spindle and plate 12 is non-rotatably movable along the spindle so that it may be lowered for a photograph 11, for example, to be inserted between the scale 7 and the plate 12. As shown in Fig. 1, a radial triangulator comprises the apparatus in duplicate and a stereoscope for the observation of a stereoscopic pair of photographs 11, 11SP1/SP. The circular scales, made of glass, are fixed to the lower ends of the brackets 4, 41 within the casings 2, 2SP1/SP, and their images are projected on to translucent screens 21, 21SP1/SP. Scales 7, 7SP1/SP are provided with measuring marks 8, 8SP1/SP consisting of an accurately spaced line of dots or circles and micrometer screws 6, 61 measure the displacements required for coincidence of a point on the photograph with that mark which is nearest it. Vernier movements actuated by knobs 9, 9SP1/SP allow the vector angle to be finely adjusted. Brackets 4, 4SP1/SP may house lamps below the plates 12, 12SP1/SP to illuminate the photographs. Dove prisms in the stereoscope 22, 22SP1/SP make it possible, when passing from the pair of photographs a, b to the pair b, c, to substitute the photograph c for the photograph a, while the photograph b remains in position. The length of the stereoscopic base can be varied by adjusting the height of prisms 25, 251.