Patent ID: 7233453

Claim:
A servo track writing device in which each track on a disc medium plane is divided into a plurality of sectors and a format pattern signal containing a servo frame signal is written into each sector, the servo track writing device comprising: at least two non-contact sensors which detect a clock pattern formed on a disc rotated at a constant speed by non-contact and outputs a clock signal of a predetermined frequency; a clock generating unit for generating a clock signal of arbitrary format frequency set up preliminarily based on a clock signal from the non-contact sensors; a writing processing unit for writing a format pattern signal into each track on the disc medium face according to a synchronous signal of a turn of the disc and the clock signal of the format frequency; and a sector correction processing unit which measures an error due to a frequency deflection synchronous with a rotation with respect to a preliminarily determined writing start position for each sector of the disc and corrects a writing start position of a format pattern signal for each sector including a servo frame signal stored in a memory according to the measured error.