| 摘要 |
1296070 Electro-optical levelling instruments JUNGNER INSTRUMENT A B 30 Dec 1969 [13 Jan 1969] 63337/69 Heading G1A An optical device for use in a levelling instrument comprises a laser light source 1 whose beam is split in unit 7 to fall on two photo-cells 4, 5 housed in detector 6. One of the split beams is given an additional reflection so that for a small angular deflection of the beam leaving laser 1 the oplit beams are deflected up and down respectively so that the balance of illumination on the two photo-cells is not disturbed. As shown the beam is reflected in prism 2 and split in prism 3 with the beam for photo-cell 4 being subjected to an extra reflection. In alternative embodiments different kinds of prisms may be used, e.g. a divided pentagon prism, Fig. 4 (not shown) and by use of a lens or prism system only a single photocell need be used, Figs. 2 and 3 (not shown). The apparatus can be modified to act as an autocollimator and define a plane by providing one photo-cell in the support for the laser and a second in the position detector together with a prism for reflecting light on to the one photo-cell, Fig. 6 (not shown). |
