GB692617A - Improvements in optical instruments - Google Patents

Abstract

692,617. Optical apparatus. HERRMANN, F. Dec. 12, 1950 [Dec. 12, 1949], No. 31889/49. Classes 97 (i) and 97 (ii). An optical instrument such as a theodolite, level, gun sight, rangefinder, microscope, spectrometer, goniometer or other instrument in which more than one field of view is observed comprises an optical system projecting a first field on to an eye-piece or graticule in front thereof to form a first exit pupil, and at least one further optical system, lying outside but close to the rays of the first system and pro. jecting a second field to form a second exit pupil which lies close to the first exit pupil whereby the fields can be seen separately by merely moving the eye. Fig. 1 shows a theodolite comprising objective 18, eyepiece 11 and graticule 12. The theodolite is rotatable about a vertical axis 10 and about a horizontal axis 15, scales 19, 17 being provided to indicate the respective rotations. Images of two diametrically-opposite portions of the scale 19 are formed at the graticule 12 by prisms 9, 8 and lenses 14 while similar images of the scale 17 are formed by prisms 16 and lenses 13, the exit pupils of the lenses 13 and 14 being separated from each other and, if desired, adjacent that of the theodolite system so that the observer, after sighting through the system 18, 11 must move his eye slightly to observe the scale readings. Fig. 2 shows an instrument for measuring the power of a lens and comprising collimator 25, objective 23, eye-piece 21, rotatable graticule 34 and lens power scale 31 including a linear portion. An image of a portion of the scale 31 is formed at the graticule 34 by prism 32 and lenses 33 having an exit pupil 36 spaced from that of the observing system 35. The image of the scale 31 is read against a circular line on the graticule 34, concentric with its axis of rotation, and the linear portion of the scale image serves as a fiducial mark against which a circular scale on the graticule is read to indicate its angular position. A scale reading system, applied to a spherometer or similar instrument incorporating a measuring microscope consists of a main scale 43, Fig. 3, divided and figured, for example, in mms. and tenths, adjacent an auxiliary scale 46 divided in mms. and tenths but figured in hundredths and thousandths of mms., images of these scales, at a magnification of 12.5, being formed in the graticule 41 of an eye-piece 50 by a lens 44. The graticule bears a zero line 42 against which the image of the scale 43 is read. The scale 46, moved parallel to the scale 43 by a screw 49, bears a fiducial mark 47 an image of which, at a magnification of #, is formed adjacent the image of the scale 43. By adjusting the screw 49 the scale 46 permits accurate measurement of the image of the scale 43.