Asahi Kogaku Kogyo Kabushiki Kaisha

Tomoyuki Shirai

Tsutomu Fukui

A relative velocity sensing device for sensing an optical beam spot, for example, by using a tracking error difference signal that fluctuates as a sine-wave in accordance with a movement of the beam spot. The tracking error difference signal is converted into a first sawtooth wave signal, and a second sawtooth wave signal, having a phase which is offset from the first sawtooth wave signal by one half of the period thereof. A first differential signal is obtained in accordance with the first sawtooth wave signal, and a second differential signal is obtained in accordance with the second sawtooth wave signal. The level of a tracking error sum signal is shifted to obtain a level-shifted signal, so that a polarity signal is obtained. The first differential signal is selected when the polarity signal is positive, and the second differential signal is selected when the polarity signal is negative and, thus, a velocity signal showing the velocity of the beam spot with a high accuracy may be obtained.

Relative velocity sensing device

An optical head locating mechanism for locating an optical head adapted to be positioned in an optical device at a desired point. The optical head locating mechanism comprises a first location device for floating the optical head and locating it at a desired position along a focusing direction, and a second in a direction orthogonal to a tracking direction. Thus, it becomes possible to smoothly and quickly move the optical head, and further it becomes possible to accurately locate the optical head.

Optical head locating mechanism for magnetically locating an optical head

A color sign inserting circuit for a video signal reproducing system is disclosed, which comprises a the color burst detecting circuit for extracting color burst from a video signal detected from a recording system, a flywheel oscillator locked to the average values of the frequency and phase of a color burst signal extracted from the color burst detecting circuit for detecting time axis variation components, a phase shifter for controlling the phase of the clock output of the flywheel oscillator, and a sign inserting circuit for superimposing the output of the phase shifter and a sign signal on the video signal. Display of an inserted sign in color in the reproduction of video thus can be realized by merely adding an inexpensive color signal shifter to the conventional functions necessary for the video signal processing.

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Saitama, Japan

Tomoyuki Shirai