| 摘要 |
1510807 Photoelectric focus detection ERNST LEITZ WETZLAR GmbH 9 Oct 1975 [21 Dec 1974] 41378/75 Addition to 1472454 Heading H4D Apparatus for determining the position of a focal plane of an image within an optical device comprises a pair of optical deflecting systems 19, 20 so arranged in front of an optical imaging system 10 that each half pupil thereof receives light exclusively from a respective deflecting system, an optical grating 11 of a spatial frequency filter disposed at least in the vicinity of the focal plane of the imaging system, means 15, Fig. 1 (not shown) for effecting relative motion between the image and the grating, photo-electric receivers 14-17 to provide output signals in response to respective partial light fluxes from the spatial frequency filter, and means (not shown) to process these signals to provide further signals indicative of the required position. This apparatus is stated to be an improvement in or modification of that of Parent Specification. In order to detect and counteract or compensate for changes in transmission characteristics of any of the paths affecting the image position, there are provided means 22 to generate a reference beam, a mark carrier 23, and means such as 21, Fig. 2, or 25 and 26, Fig. 3, to cause the beam to pass through the apparatus to grating 11 (or another mark carrier), thence to a photo-electric receiver 24 whose output indicates the position of mark carrier 23 relative to grating 11. The spacing of the lens and the image plane may be altered by means of a double wedge 30-33. Wedge elements 30, 32 are movable, and their positions are controllable by signals derived from the reference and the image beams respectively. As well as providing compensation for changes in optical characteristics, this arrangement may be used for automatic focusing. |
