Recording medium transducing light spot moving velocity detection circuit

Claim 1

A moving velocity detection circuit to detect a moving velocity of a recording medium transducing light spot and a moving direction thereof with first and second sine wave signals having a period varying in inverse proportion to said moving velocity and an advance of phase reversed in accordance with said moving direction, although said first and second sine wave signals have the phase offset by 90 degrees, said moving velocity detection circuit comprising: differential means to provide first and second differential signals obtained by differentiating first and second sine wave signals; signal deforming means to provide a first deformed signal having states of "H" and "L" varying based on a timing when said first sine wave signal traverses a center of its amplitude and a second deformed signal having states of "H" and "L" varying based on a timing when said second sine wave signal traverses a center of its amplitude; half wave signal forming means to provide one and another half wave signals during one period of said first differential based on said second deformed signal and one and another half wave signals during one period of said second differential signal based on said first deformed signal; and adding and subtracting means to provide added and subtracted signals by adding and subtracting said one half wave signals and said another half wave signals with a predetermined combination thereof whereby a polarity of said added and subtracted signals indicates a direction in which said recording medium transducing light spot moves and an absolute value of said added and subtracted signals indicates said moving velocity of said recording medium transducing light spot.