Objective lens moving control method and apparatus
View Patent ↗In a layer jump, a control signal based on a focus error signal is masked in a period based on a moving speed of an objective lens so as not to be influenced by an unnecessary light component. Thereafter, an observation of the control signal based on the focus error signal is restarted, and a brake signal is sent to the objective lens, and a focus servo is switched to the ON status. Thus, accuracy of the layer jump is improved when the unnecessary light component exists in an interlayer portion of the focus error signal.
1. An objective lens moving control method for controlling the movement of an objective lens in its focusing direction on the basis of focus error signal corresponding to a focusing shift of the objective lens from a recording layer of a multilayer recording optical disk, the merhud comprising the steps of:
detecting a changing request of a recording layer to be converged by the laser beam emitted from the objective lens;
starting the approach of the objective lens so the recording layer to be converged by a laser beam;
determining a time T in accordance with a moving speed of said objective lens;
calculating a masking time based on the time T;
not starting braking of said objective lens by masking signals indicating that an absolute value of a focus error signal exceeds a predetermined second reference level during the masking time from a time point at which the absolute value of the focus error signal becomes lower than a predetermined first reference level for a first time after exceeding the first reference level, and
starting braking of the objective lens when the absolute value of the focus error signal exceeds the second reference value after the masking time has passed.
2. An objective lens moving control method according to claim 1 , wherein
said time T is a time until the absolute value of the focus error signal is lower than said first reference level for the first time after the focus error signal exceeds said first reference level.
3. An objective lens moving control method according to claim 1 , further comprising:
focusing onto the recording layer in be converged by the laser beam after the braking of said objective lens is terminated.
4. An objective lens moving control method according to claim 2 , further comprising
focusing onto the recording layer to be converged by the laser beam after the braking of said objective lens is terminated.
5. An objective lens moving controller for controlling the movement of an objective lens in its focusing lens on the basis of a focus error signal corresponding to a focusing shift of the objective lens from a recording layer of a multilayer recording optical disk, the controller comprising:
detecting means which detects a changing request of a recording layer to be converged by the laser beam emitted from the objective lens; and
controlling means; wherein,
when said detecting means detects said changing request, said controlling means starts the approach of the objective lens to the recording layer to be converged by a laser beam, determines a time T in accordance with a moving speed of said objective lens, calculates a masking time based on the time T, does not start braking of the objective lens by masking signals indicating that an absolute value of a focus error signal exceeds a predetermined second reference level during the masking time from a time point at which the absolute value of the focus error signal becomes lower than a predetermined first reference level for a first time after exceeding the first reference level, and starts braking of said objective lens when the absolute value exceeds the second reference value after the masking time has passed.
6. An objective lens moving controller according to claim 5 , wherein
said time T is a time until the obsolete value of the focus error signal is lower than said first reference level for the first time after the focus error signal exceeds said first reference level.
7. An objective lens moving controller according to claim 5 , wherein
the objective lens moving controller further comprises focus leading-in means for moving a focal point of said objective lens onto the recording layer to be converged by the laser beam, and
said control means moves the focal point onto the recording layer to be converged by the laser beam after the braking of said objective lens is terminated.
8. An objective lens moving controller according to claim 6 , wherein
the objective lens moving controller further comprises focus leading-in means for moving a focal point of said objective lens onto the recording layer to be converged by the laser beam, and
said control means moves the focal point onto the recording layer to be converged by the laser beam after the braking of said objective lens is terminated.
9. An optical disk drive unit comprising an objective lens moving controller according to claim 5 .
10. An optical disk drive unit comprising an objective lens moving controller according to claim 6 .
11. An optical disk drive unit comprising an objective lens moving controller according to claim 7 .
12. An optical disk drive unit comprising an objective lens moving controller according to claim 8 .
13. A recording medium recording an executable program which can be executed in an objective lens moving controller which controls the movement of an objective lens in its focusing direction on the basis of a focus error signal corresponding to a focusing shift of the objective lens from a recording layer of a multilayer recording optical disk, the program executing:
processing for receiving a changing request of the recording layer to be converged by the laser beam emitted from the objective lens;
processing for starting the approach of the objective lens to the recording layer to be converged by a laser beam;
processing for determining a time T in accordance with a moving speed of said objective lens;
processing for calculating a masking time based on the time T;
not starting braking at said objective lens by masking signals indicating that an absolute value of a focus error signal exceeds a predetermined second reference level during the masking time from a time point at which the absolute value of the focus error signal becomes lower than a predetermined first reference level for a first time after exceeding the first reference level; and
starting braking of said objective lens when the absolute value exceeds the second reference value after the masking time has passed.