| 摘要 |
PROBLEM TO BE SOLVED: To improve the SN characteristics of tracking error signals. SOLUTION: A tracking error detecting circuit is constituted of as a push-pull system employing a quadripartite type photodetector. The circuit is provided with four gain control amplifiers 20, 22, 24 and 26, four bottom envelope circuits 28, 30, 32 and 34, a pair of subtracting circuits 36 and 38, an adding (a subtracting) circuit 40, an offset circuit 42 and a gain control circuit 44. The circuits 28, 30, 32 and 34 are made up by capacitor type peak hold circuits, detect the bottom envelopes of RF signals SA, SB, SC and SD given through the amplifiers 20, 22, 24 and 26 from light receiving regions A, B, C and D of the photodetector and output bottom envelope signals SA<SB>btm</SB>, SB<SB>btm</SB>, SC<SB>btm</SB>and SD<SB>btm</SB>that represent the respective bottom envelope wave forms. COPYRIGHT: (C)2003,JPO
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