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

1. A recording/reproducing apparatus of an information-recording medium comprising:

a photo-detecting device for detecting a light beam reflected from the information-recording medium, the photo-detecting device detecting a light amount signal of a region having a large change in a light amount and a light amount signal of a region having a small change in a light amount according to a tilt amount of the information-recording medium;

a processing device for processing signals of the plurality of light beams detected by said photo-detecting device to supply a push-pull value of each region; and

a tilt controller for compensating an influence of a radial shift by using the two push-pull values from the processing device.

2. The apparatus of claim 1 , wherein the photo-detecting device has eight regions that are evenly divided in size, and wherein signals detected in said regions are designated by A 1 , A 2 , B 2 , B 1 , C 1 , C 2 , D 2 and D 1 starting from seventh octant of the eight regions.

3. The apparatus of claim 2 , wherein the processing device produces two push-pull signals P 1 and P 2 , where P 1 =(A 1 +D 1 )−(B 1 +C 1 ) and P 2 =(A 2 +D 2 )−(B 2 +C 2 ); and outputs a tilt information signal T according to a following equation:

T=P 1 − k*P 2

wherein k is a constant to minimize the influence of a radial shift.

4. The apparatus of claim 1 , further comprising:

a hologram means installed on an optical path of the light beam reflected from the information-recording medium.

5. 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 signal of a region having a small change in a light amount according to a tilt amount of the information-recording medium;

calculating a push-pull value of each region; and

removing an influence of a radial shift by using the two push-pull values.

6. The method of claim 5 , wherein, in the step of detecting a light amount signal, the reflected light reflected from the information-recording medium is divided into regions that are left and right sides of vertical lines, and a light amount of a region having a large difference in a light amount and a light amount of a region having a small difference in a light amount.

7. The method of claim 5 , wherein, the step of calculating a push-pull value comprises:

obtaining a difference between the light amount signals that are detected from the left and right sides of vertical lines having a large change in a light amount, to obtain a first push-pull value; and

obtaining a difference between the light amount signals that are detected from the left and right sides of vertical lines having a small change in a light amount variation, to obtain a second push-pull value.

8. The method of claim 5 , further

obtaining a tilt information,

wherein the step of obtaining the tilt information comprises,

multiplying one of the push-pull values by a constant, which minimizes the influence of a radial shift,

subtracting the multiplied push-pull value from the other push-pull value, and

outputting the tilt information from the subtraction result with substituting determined constant into the subtraction.

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

dividing a light reflected from an information-recording medium to left and 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 on a tilt amount; and

subtracting the push-pull value from a tracking error value and detecting a tilt value.

10. The method of claim 9 , wherein the first push-pull signal is obtained from a difference between a light amount of the region having a relatively large change in a light amount in the upper portion or the lower portion of the left region of the reflected light and a light amount of a region having a relatively large change in a light amount in the upper portion or the lower portion of the right region of the reflected light.

11. The method of claim 9 , wherein the second push-pull signal is obtained from a difference between a light amount of the region having a relatively small change in a light amount in the upper portion or the lower portion of the left region of the reflected light and a light amount of a region having a relatively small change in a light amount in the upper portion or the lower portion of the right region of the reflected light.

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

detecting pluralities of light signals received by a photo-detecting device arranged in a light receiving path, wherein signals detected in eight regions are designated by A 1 , A 2 , B 2 , B 1 , C 1 , C 2 , D 2 and D 1 starting from seventh octant of the eight regions;

calculating push-pull signals P 1 and P 2 ,

wherein P 1 =(A 1 +D 1 )−(B 1 +C 1 ) and P 2 =(A 2 +D 2 )−(B 2 +C 2 ); and

outputting a tilt information signal T according to a following equation

T=P 1 k*P 2

wherein k is a constant to minimize the influence of a radial shift.

13. The method of claim 12 , wherein the constant k is a value that satisfies a condition where no variation in the tilt information signal T is found even when there is an intentional radial shift.

14. The method of claim 12 , further comprising a step of compensating a tilt of the information-recording medium according to the tilt information signal T by substituting the constant k in the equation.