Method for setting the loop gain in a focusing servo loop

Claim 2

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of times to cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; determining, after each upward movement and after each downward movement, whether a sampled value of said S-shaped error signal exceeds a predetermined threshold, and setting the loop gain based exclusively upon a maximum sampled value of a plurality of said sampled values obtained from said S-shaped error signal, wherein said plurality of sampled values only includes sample values that exceed said predetermined threshold.

Claim 3

A method according to claim 1, wherein said sample values are differences between positive and negative wave heights, or peak-to-peak values of said S-shaped error signal.

Claim 4

The method as claimed in claim 1, wherein said moving step is repeated a predetermined number of times, such that a predetermined number of sample values are obtained for said loop gain setting step.

Claim 5

The method as claimed in claim 1, wherein said objective lens is repeatedly moved between a point above and a point below said focusing point during each up-down motion.

Claim 6

The method as claimed in claim 1, wherein each of said sample values represent amplitudes of said S-shaped error signal, and wherein samples are measured during multiple up-down passes of the objective lens through said focusing point.

Claim 7

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of times to cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; determining, after each upward movement and after each downward movement of the optical pickup, whether sampled value of said S-shaped error signal exceeds a predetermined threshold to differentiate between sample values that represent noise and sample values that represent a true focusing error signal; and setting the loop gain based only upon a plurality of said sampled values that exceed said predetermined threshold.

Claim 8

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of times to cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; determining, after each upward movement and after each downward movement of the optical pickup, whether sampled value of said S-shaped error signal exceeds a predetermined threshold to differentiate between sample values that represent noise and sample values that represent a true focusing error signal; and setting the loop gain based only upon a plurality of said sampled values that exceed said predetermined threshold.

Claim 9

A method according to claim 6, wherein said loop gain is set on the basis of an average value of a plurality of said sample values.

Claim 11

The method as claimed in claim 8, further comprising detecting the presence of an instruction to eject the disc from said player at a time during the setting of said loop gain; in response to said detecting, generating a reverse rotation driving pulse having one of a pulse height and pulse width dependent upon the pulse width of said forward driving pulse and the elapsed time since the termination of said forward driving pulse, said pulse width W 2 equaling the following equation; ##EQU1## where W 1 equals the pulse width of the forward driving pulse, X equals a constant, and T 2 equals a time elapsed since the forward driving pulse was stopped; and applying said reverse rotation driving pulse as a braking pulse to said spindle motor.

Claim 12

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising the steps of: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of times to cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; and setting the loop gain based exclusively upon a maximum value of a plurality of said sampled values of said S-shaped error signal, wherein said disc is rotated at a speed slower than a disc playing speed while said loop gain setting method is performed.

Claim 13

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising the steps of: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of times to cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; and setting the loop gain based exclusively upon a maximum value of a plurality of said sampled values of said S-shaped error signal, wherein said disc is rotated at a speed slower than a disc playing speed while said loop gain setting method is performed.

Claim 14

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of time stop cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; and setting the loop gain based exclusively upon a maximum value of a plurality of said sampled values of said S-shaped error signal, wherein the step of rotating said disc generates a forward driving pulse of a predetermined width, and applying said forward driving pulse to a spindle motor which rotates said disc in a direction and speed determined by said forward driving pulse, said speed being slower than a normal playing speed.

Claim 15

In a disc player of the type having an objective lens for focusing a reading light on the surface of a disc and a focusing servo loop for adjusting the height of said lens for proper focusing, said loop having a gain controlled amplifier and a focus error signal generator; a method of setting the loop gain of said servo-loop while said servo loop is open, comprising: rotating said disc in said disc player; moving said objective lens repeatedly in an up-down pattern through the focusing point a predetermined number of time stop cause said error signal generator to generate an error signal having an S-shape in the vicinity of said focusing point; sampling the values of said S-shaped error signal during each up-down movement of the objective lens; and setting the loop gain based exclusively upon a maximum value of a plurality of said sampled values of said S-shaped error signal, wherein the step of rotating said disc generates a forward driving pulse of a predetermined width, and applying said forward driving pulse to a spindle motor which rotates said disc in a direction and speed determined by said forward driving pulse, said speed being slower than a normal playing speed.