Verfahren und Vorrichtung zur automatischen Scharfeinstellung optischer Systeme

摘要

1,179,815. Automatic focusing. JOS. SCHNEIDER & CO. OPTISCHE WERKE. 16 Feb., 1968 [18 Feb., 1967], No. 7645/68. Addition to 1,170,438. Heading H4D. Specification describes an improvement of the automatic focusing device described in Specification 1,170,438, wherein to overcome the fault of said device, whereupon a change of position of the optical fibre ends from a point in the focal plane 3, Fig. 1, having high contrast to a point having lower contrast causes the focusing lens to hunt even when the image is in sharp focus, the contrast of the image is additionally detected in front of the focal plane (411, 511) and behind the focal plane (41, 51, Fig. 3). Thus when the optical fibre pair ends 4 and 5, Fig. 2, are in the focal plane and detecting maximum contrast, the other two optical fibre pair ends 41, 51 and 411, 511 are detecting contrasts less than said maximum by equal amounts. The optical fibre pair 1 and 2, having ends 4 and 5 produce a contrast output from differential amplifier 8, via photo-electric converters 6 and 7. Differential amplifiers 81 and 811 similarly produce contrast outputs for the infront-of and behind optical fibre pair ends respectively. The outputs from amplifiers 8 and 81 are rectified at 12 and 121 and fed to differential amplifier 13. The output from amplifiers 811 is rectified at 1211 and fed to differential amplifier 14 together with the rectified output of amplifier 8. The outputs of amplifiers 13 and 14 are fed to differential amplifier 15, whose output is negative, Fig. 1, when lens 10 is too far from the focal plane, is zero, Fig. 2, when the image is focused and is positive, Fig. 3, when the lens is too near the focal plane.