Patent Number: 7,133,335

Title: Wobble signal reproducing circuit

Abstract: The present invention has an object to stably reproduce wobble signals of all disks of CD-R/RW, DVD-R/RW and DVD-RAM by one wobble signal reproducing circuit. In the wobble signal reproducing circuit, an AGC (AUTOMATIC GAIN CONTROL) circuit for equating a push-pull circuit output of a wide range and an RF amplitude of an optical detector output of two systems obtained by push-pull, and an AGC (AUTOMATIC GAIN CONTROL) circuit for making a wobble amplitude uniform are provided with a function to hold a gain or to change over a response time constant, and at the time of reproduction of the DVD-R/RW, a land pre-pit region is detected by the push-pull output to hold AGC (AUTOMATIC GAIN CONTROL) or change over a response time constant. Besides, in an address information recording region (PID region) at the time of reproduction of the DVD-RAM, the AGC (AUTOMATIC GAIN CONTROL) is held or the response time constant is changed over.

Inventors: Nishimura; Kouichirou (Ebina, JP), Hirose; Kouichi (Yokohama, JP), Katsuki; Manabu (Yokohama, JP), Takeuchi; Toshifumi (Yokohama, JP)

Assignee: Hitachi, Ltd.

International Classification: G11B 20/10 (20060101); G11B 19/02 (20060101)

Expiration Date: 2019-11-07 0:00:00