Patent ID: 6072758
Filing Date: 2000-06-06
Classification: G11B

Abstract:
A disc recording and/or reproduction apparatus, comprising:irradiation means for irradiating a light beam upon a disc;detection means for detecting an amount of energy of said light beam reflected from said disc;comparing means for comparing said value of said detected energy level with a reference level PIR1, said reference level being determined according to the expression:PIR1=(PI(dldisc, dlmode)-PIref).times.(a/b).times.(c/d)+(PI(sldisc, slmode)-PIref).times.(e/f).times.1/2+PIrefwhere PI(dldisc, dlmode) is the expected level of a pull in signal when a double layer disc is reproduced in a double layer mode; PI(sldisc, slmode) is the expected level of a pull in signal when a single layer disc is reproduced in a single layer mode; PIref is a fixed DC component of both PI(dldisc, dlmode) and PI(sldisc, slmode); a and b represent relative values of laser power where a:b=the laser power when reproducing is being performed in single layer mode: the laser power when reproducing is being performed in double layer mode; c and d represent relative values of the gain of a preamplifier where c:d=the gain of the preamplifier when reproducing is being performed in single layer mode: the gain of the preamplifier when reproducing is being performed in double layer mode; e and f represent relative values of the pull in signal where e:f=the level of the pull in signal when focusing is off: the level of the pull in signal when focusing is on; anddetermination means for determining a type of disc based upon the result of said comparison of said comparing means.