| 摘要 |
PROBLEM TO BE SOLVED: To stably obtain a tracking error signal and a land/group detecting signal. SOLUTION: This land/group detector is provided with an optical head 10 utilizing three beams system for obtaining reflected lights from an optical disk which is irradiated with +1st order, zeroth order, -1st order lights L+1 , L0 , L-1 , a hexapartite optical sensor 14 arranging a quadripartite optical sensor 12 at the center and two optical sensor elements (e), (f) at both sides of the optical sensor 12, and a signal processing part 16 for calculating the tracking error signal TE and the land/group detecting signal L/G from an output signal of the hexapartite optical sensor 14. each output signal of the quadripartite optical sensor 12 is expressed as A, B, C, D, and each output signal of the optical sensor elements (e), (f) is expressed as E, F, the signals are calculated from expressions TE=E-F and L/G=2×(A+B+C+D)-(E+F) by the signal processing part 16.
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