OPTICAL HEAD DEVICE AND OPTICAL INFORMATION PROCESSOR

摘要

PROBLEM TO BE SOLVED: To provide an optical head device which detects a signal by using a detecting light beam passing through a half-mirror, which device realizes an information processor with a low cost and high reliability, which excellently detects signal by giving an satigmatism in a direction different from that of the astigmatism arising in the half-mirror. SOLUTION: A parallel flat plate 11 is so arranged between the half-mirror 2 and an optical detector 9 that the normal line of the parallel flat plate 11 is not included in the meridional plane which is formed by a collimate lens 3 and the half-mirror 2, and the direction and the magnitude of the astigmatism are set in a direction other than 45 degrees.