Automatic focussing device for video camera

Abstract

Abstract PURPOSE:To enable to perform automatic focussing in excellent way independently of the number of longitudinal line components in a picture, by changing the sensitivity of a detector with the number of longitudinal line components having greater difference of contrast included in picked up picture. CONSTITUTION:High band components only are picked up at a high pass filter 4 from a video signal being an electric signal at a camera circuit 2 incident to a lens 1. Positive/negative pulses among the outputs are converted into positive pulses at a full wave rectifying circuit 10, the number of pulses, i.e., number of longitudinal lines is counted at a counter 12, the result is converted into a DC voltage at a D/A converter 13, and this is fed to a control terminal of a variable gain control amplifier 14. Since the gain of the variable gain control amplifier 14 is small when the control voltage is high, a detector 5 is not saturated even if pictures having many longitudianal line components are picked up. Further, focussing is matched by moving the helicoid position of the lens 1 with a motor 8 so that the voltage across a terminal 51 is maximum.

Inventors

• 👤 Kentaro Hanma
• 👤 Michio Masuda
• 👤 Kaoru Yanagawa
• 👤 Michio Ogimoto

Bibliographic Details