Patent ID: 7236434
Filing Date: 2007-06-26
Classification: G11B

Abstract:
1. An exposure apparatus of an optical disk master having a laser source, a deflector for deflecting a recording laser beam based on the laser beam of said laser source and an objective lens for focusing said recording laser beam on an optical disk master, comprising: a liquid crystal plate provided between said laser source and said deflector; a parallel flat plate provided between said deflector and said objective lens for branching said recording laser beam; the parallel flat plate is configured for branching said recording laser beam into two overlapping beams forming interference patterns; a photodetector that detects reflected light from said parallel flat plate; the photodetector is configured for detecting the interference patterns; adjusting means of adjusting a voltage applied to said liquid crystal plate based on information on wavefront fluctuation of said recording laser beam detected by said photodetector; and the adjusting means comprises means of providing a signal applied to said liquid crystal plate based on the interference patterns detected by said photodetector, to straighten the interference pattern and thereby reduce wavefront fluctuation of said recording laser beam.