Method and apparatus for tilt detection in an information-recording medium

A tilt detecting method of an information-recording medium comprising the steps of:

• detecting a light amount signal of a region having a large change in a light amount and a light amount of a region having a small change in a light amount according to a tilt amount of the information-recording medium, by means of a photo-detecting device;
• calculating a push-pull value of each region;
• and
• removing an influence of a radial shift by using the two push-pull values and obtaining a tilt information;
• wherein the photo-detecting device is divided into pluralities of regions which are defined by a vertical, horizontal and diagonal lines centering on the central position of the photo-detecting device and wherein the vertical line is parallel to a track of the information medium.

A tilt detecting method of an information-recording medium comprising the steps of:

• dividing a light reflected from an information-recording medium to a left and a right regions, dividing the left and the right regions to a region having a large change in a light amount and a region having a small change in a light amount;
• obtaining a difference between a sum of the left light amount of the region and the sum of the right light amount of the region having the large change in a light amount, and obtaining a first push-pull value;
• obtaining a difference between a sum of the left light amount of the region and the sum of the right light amount of the region having the small change in a light amount, and obtaining a second push-pull value;
• multiplying the second push-pull value by a constant, subtracting the result value from the first push-pull value, and obtaining a push-pull value depending only on a tilt amount;
• and
• subtracting the push-pull value from a tracking error value and detecting a tilt value;
• wherein the photo-detecting device is divided into pluralities of regions which are defined by a vertical, horizontal and diagonal lines centering on the central position of the photo-detecting device and wherein the vertical line is parallel to a track of the information medium.

A tilt detecting method of an information-recording medium comprising the steps of:

• detecting pluralities of light signals received a photo-detecting device arranged in a light receiving path;
• wherein the photo-detecting device is divided into eight regions which are defined by a vertical, horizontal and diagonal lines centering on the central position of the photo-detecting device and wherein the vertical line is parallel to a track of a information medium;
• and wherein signals detected in said regions are designated by A1, A2, B1, B2, C1, C2, D1 and D2 starting from seventh octant of the eight regions;
• calculating push-pull signals P1 and P2;
• wherein P1=(A1+D1)−(B1+C1) and P2=(A2+D2)−(B2+C2);
• and
• outputting a tilt information signal T according to a following equation:
• T=P1−k*P2
• wherein k is a constant to minimize the influence of a radial shift.