Patent ID: 7061840

Claim:
A defect detection apparatus characterized by: maximum value detection means for obtaining a detection maximum value by detecting a maximum value of an RF signal obtained by an operation of reading out a signal from a recording medium; minimum value detection means for obtaining a detection minimum value by detecting a minimum value of said RF signal; maximum value output means for obtaining a subtraction results value for subtracting a required subtraction value from said detection maximum value when said detection maximum value obtained by said maximum value detection means is taken to be in a reducing direction, and outputting said subtraction results value as a maximum value of said RF signal; minimum value output means for obtaining an addition results value for adding a required addition value to said detection minimum value when said detection minimum value obtained by said minimum value detection means is taken to be in an increasing direction, and outputting said addition results value as a minimum value of said RF signal; amplitude level calculating means for calculating an RF amplitude value indicating an amplitude level of said RF signal by subtracting a minimum value outputted by said minimum value output means from a maximum value outputted by said maximum value output means; defect detection means for detecting a defect status by comparing an RF amplitude value calculated by said amplitude level calculating means with a prescribed threshold value; center value calculating means for calculating a center value of an amplitude of said RF signal based on a detection maximum value obtained by said maximum value detection means and a detection minimum value obtained by said minimum value detection means; and variable value setting means for variably setting said subtraction value occurring at said maximum value output means and said addition value occurring at said minimum value output means according to the level of said center value calculated by said center value calculating means.