GB197425A - Improvements in rangefinders, heightfinders and inclinometers - Google Patents

Abstract

197,425. Barr & Stroud, Ltd., Barr, A., and Stroud, W. Feb. 16, 1922. Range-finders, height-finders, inclinometers, and like instruments are provided with means for producing a relative motion between the separating line of the eyepiece system and the image of the target when the support of the instrument is rolling or the target is varying its angular elevation. This relative motion is effected, without moving the main tube of the instrument, either by moving the separating line or the target image. If the separating line be produced by a refractory prism, this prism mav be moved through a small distance or the eyepiece prisms may be moved. Alternatively, the inner frame may be bent so that the eyepiece prism is moved relatively to the objectives, or small prisms placed in the converging beams from the negatives may be simultaneously rotated in opposite directions. The eyepiece 5, Fig. 1, comprises a convex lens 6 and a convex lens 7 with a prism 8 on its face to form a separating line, and is mounted on a ring 10 which may be moved slightly in relation to the outer tube 2 of the instrument. Lenses 15, 16, Fig. 5, situated in the path of the rays from the objective to the eyepiece may be rocked up or down by the handle 3 through gearing. Equal refracting prisms 30, 31, Fig. 9, may be displaced longitudinally to positions 32, 33. These constructions, which are examples of many, all provide the relative motion desired. In the case of stereoscope range-finders, relative movement takes place between the measuring marks and the target images. Specification 13507/93 is referred to.