ABERRATION DETECTION DEVICE, SUBSTRATE THICKNESS DETECTION DEVICE, OPTICAL HEAD AND OPTICAL INFORMATION PROCESSOR, COMPUTER, IMAGE RECORDING DEVICE, IMAGE REPRODUCING DEVICE, AND CAR NAVIGATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To detect spherical aberration signal without lowering S/N ratio for a recording information signal of a recordable optical disk.

SOLUTION: An aberration detection device collects a converging light 1 of a main beam on an information recording medium and a converging light 2 of a sub beam on the information recording medium so that a focal position differs in a direction toward separation and the direction of an optical axis. Magnitude of reflection of the converging light 2 on the information recording medium is detected using a light detector.

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