| 摘要 |
330,101. Everett, E. A. May 6, 1929. Optical apparatus. -. A sighting device for locating a light source 11 at a point comprises a lens 12, provided with a diaphragm 13 having apertures 15 at equal distances from its centre and a screen 14 on which the lens and diaphragm form images of the light source 11. When source 11 is at a point conjugate to screen 14 with respect to lens 13 the images formed by the pencils passing through the apertures coincide and are symmetrical with respect to axis x-x. For other positions of source 11 the various apertures produce separate, images offset with respect to axis x-x. The lens 12 may be replaced by prisms of suitable angle placed at each aperture. Fig. 3 shows the apparatus being used to adjust the filament 11 of bulb 33 at the focus of a projecting lens 26. The focal point of lens 26 is arranged to be conjugate to screen 14 with respect to lens 12 and bulb 33 is adjusted on its mounting until the images on screen 14 coincide. |
