| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical disk drive which has a high reading accuracy for an information recorded on the optical disk by avoiding a problem wherein the focus control becomes impossible because of an error in a focus control signal generated due to lens shift of an objective lens, and to provide its focus control method. SOLUTION: A tetrameric detector 205 includes four photodetecting areas divided by lines parallel to a radial direction of the optical disk and parallel to a tangential direction of the optical disk, and when output values from the respective photodetecting areas are expressed as I<SB>a</SB>, I<SB>b</SB>, I<SB>c</SB>, I<SB>d</SB>continuously around an optical axis of the reflection light and correction factors are expressed as k<SB>1</SB>, k<SB>2</SB>, a servo processing section calculates the focus control signal FE based on an equation FE=k<SB>1</SB>(I<SB>a</SB>-I<SB>d</SB>) + k<SB>2</SB>(I<SB>c</SB>-I<SB>b</SB>), and a control means calculates the correction factors k<SB>1</SB>, k<SB>2</SB>based on an equation k<SB>1</SB>(I<SB>a</SB>+I<SB>d</SB>)<SP>n</SP>=k<SB>2</SB>(I<SB>b</SB>+I<SB>c</SB>)<SP>n</SP>, and n satisfies 0.57<n<1. COPYRIGHT: (C)2009,JPO&INPIT
|
