GB190325682A - Improvements in Range Finders. - Google Patents

Abstract

25,682. Grubb, Sir H., and Grubb, G. R. Nov. 24. Range-finders.-A telescope, at one end of a base, forms two separate images (one above the other when the base is horizontal), which have a lateral displacement with respect to each other. The images are brought exactly over each other by means of two adjustable prisms, the movement required indicating the range. The object-glass of the telescope is divided along a diameter and the halves k, k<1>, Fig. 7, are placed with their curved edges touching. The rays from a mirror, at the other end of the base, are turned by the reflector c, shown in the vertical section, Fig. 4, to pass through the lower half k of the object-glass, the direct rays from the object passing through the upper half k<1>. The two half-circular pencils of rays are brought together to form one circular pencil by a compound prism, shown in front and back view in Figs. 10 and 11 respectively, which also acts as an inverter. The compound prism consists of five right-angle prisms, three, viz., n, o, p, being arranged one above the other, and the other two, q<1>, r<1>, side by side. The reflected rays pass through the face n<1>, are reflected by the inclined face n<3> to the faces r<2>, r', then to the inclined face 0<3> from which they pass to the lenses of the eyepiece. The direct rays enter the prism p and are similarly reflected. The prism o is divided along the line o* to keep the sets of rays separate, and to produce a decided line of demarcation between the images. The deviation of the direct rays required to bring the two images exactly over each other, is produced by means of two glass discs u, v, Fig. 4, placed in front of the upper half k<1> of the object-glass. These discs are slightly wedgeshaped and may be cut from a long-focus lens of about four times the diameter of the object-glass, parts being selected by trial which can produce half the minimum deviation required. The deviation is adjusted to bring the images over each other, by rotating the discs u, n with respect to each other by means of a pinion 3 gearing with crown-wheels 4, 5 carried by the discs. The pinion 3 is rotated by means of a milled head at the eyepiece end of a shaft 8 geared to the pinion 3. One disc carries a scale and the other an index 12, the position of the index on the scale being read by the microscope 13 provided with reflecting-prisms mounted in a tube carried by the disc v, The opening through which the reflected rays pass to the reflector c is covered by a piece of glass with a curvature twice that of the discs u, v so that the focus of the two halves of the object-glass is the same.