| 摘要 |
504,845. Range - finders &c. BARR & STROUD, Ltd., and MACGILL, C. D. Dec. 1, 1937, No. 33171. [Class 97 (i)] Sighting-apparatus for estimating the range or base length of a target from the size of its image is provided with means for producing, in the line of sight, two images formed from markings comprised in the apparatus to form reference images, and means for varying the distance apart of the reference images to coincide with the length of the target image, the adjusting- means comprising setting movements corresponding to two of the three related factors, range, length of target base, and subtended angle, and means for mechanically combining these to indicate the third factor. The invention is particularly applicable to apparatus in which the target is observed through a transparent screen which also serves as a reflector for presenting the reference images to the observer. The means for producing and setting the reference images comprises a lamp 3 for illuminating a pair of graticules 5, 6 and a collimator 4 for projecting the rays on to the refiecting screen. The graticule 5 is fixed and the graticule 6 is carried by a rotatable mounting 7 provided with spindles 8 extending through slots in the casing. Each spindle carries a pinion 9 engaging toothed rings on operating heads 10, 12 so that the resultant of the rotations of the heads is applied to the mounting 7. The heads are set in accordance with scales graduated logarithmically to correspond to target base and range. The lower face of the graticule 5 carries two separated diametrical markings 13 and the upper face of the graticule 6 has opaque masking wings 15 on a transparent background, so that by rotation of the graticule 6 the distance between the inner extremities of the unmasked portions of the markings 13 can be varied, Fig. 5. Preferably the graticule 5 also includes a circular mark 14 to assist in sighting, and in this case the wings 15 are provided with transparent arcs 16 so that the image of the circle 14 is complete in all positions of the graticule 6.
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