GB873434A - Improvements in or relating to optical measuring or testing apparatus - Google Patents

Abstract

873,434. Optical testing apparatus. ADAMS, J. R., and KAPELLA Ltd. Oct. 18, 1957 [Oct. 23, 1956], No. 32261/56. Class 97(1) In an optical measuring or testing apparatus of the kind which comprises an alignment telescope which can be sighted on a remote object for investigating positional or like errors, the telescope is provided with a projection fitting including an objective for projecting the telescope image, a projection screen for receiving the projected image, and reflecting means for directing the rays on to the screen and for appropriately erecting the image thereon. As shown, the alignment telescope comprises a spherical boss A from which extends forwardly the main telescope tube A1 containing an objective made up of fixed elements B1, B2, B3 and an element B4, which is axially movable for focusing by means of a micrometer head A4. The telescope tube also contains two lateral deviators Cl, C2 respectively adjustable by rods C3, C4, which are operable by micrometer heads A3 on either side of the boss A. A lamp'house D is attached to the boss and light therefrom is reflected by a half-silvered mirror D2 to illuminate a graticule A2 and a further graticule A5 which is out of focus for direct vision, but the reflection of which may be viewed in a distant mirror. A tube E is rotatably clamped to the boss A opposite the tube A1 by means of a screw-threaded clamping ring E1. This tube E leads to a further inner tube E3 containing a projection objective F and a roof prism G and to which is attached a box-like casing E4 carrying three projection screens H1, H2 and H3. Within this casing is a fixed mirror J4 and a mirror J which is rotatable about a horizontal axis for selectively directing the rays proceeding from the telescope on to any of the screens, according to choice, to form a correctly inverted image of the distant object. The projection objective F is focused by movement along the tube E3 by a hand knob Fl having an eccentric pin F2 engaging a slot in the objective mount F3. The mirror J has three operable positions and is controlled by a hand knob provided with spring detents. In the position J, the beam is directed along the axis a-a on to screen H1; in the position J2 the image passes directly on to the screen H3; and in the position J3 the beam is directed from the mirror J and the mirror J4 on to the screen H2. In a first modification, three mirrors-one fixed and two mounted for rotation about a common axis-are provided in a projection compartment containing two screens. A second modification is described in which a fixed horizontal mirror and a second mirror, rotatable about a horizontal axis, provide images on either of two screens. A third modification is described in which the image is viewed in a plane normal to the telescope axis and image inversion is obtained by a pair of prisms as in prismatic binoculars.