Method for gradually closing down a focus control loop of an optical drive system

An apparatus for operating an optical drive system capable of reproducing/recording information from/to an associated optical carrier, wherein the apparatus comprises:

• a radiation source for generating a radiation beam,
• a focusing means for focussing the radiation beam,
• an optical receiver means for generating an electric read, signal in response to radiation reflected from the optical carrier,
• a focus tracking system for tracking the carrier with said focussed radiation beam,
• wherein said focus tracking system comprises
• a focus error generating means for generating a focus error signal,
• a focus actuator means for changing a focus position of said focussed radiation beam relative to the optical carrier, said focus actuator means being driven by a supplied correction signal, and
• a correction signal generating means comprising
• a focus controller means for controlling said focus actuator, and, said focus controller means being supplied with said focus error signal, and
• a focus memory loop for applying a stored correction signal to said focus actuator,
• and the apparatus further comprises:
• a) event detection means for generating a signal indicative of the occurrence of an event that requires at least a gradual stop of said focus tracking system,
• b) switching means for disabling the focus controller means by opening the control loop,
• c) adjusting means for gradually reducing, over a period of time, at least one of:
• a memory loop parameter of said focus memory loop, said parameter corresponding to an amplitude of said stored correction signal, and
• a controller parameter of an integrating means of said focus controller means, said controller parameter corresponding to a focus offset position, wherein the period of time is determined based on a natural frequency of the focus actuator means.

A non-transitory computer program product being adapted to enable a computer system comprising at least one computer having data storage means associated therewith to control an optical drive system comprising a radiation source, a focusing means, an optical receiver means and a focus tracking system comprising a focus error generating means, a focus actuator means and a correction signal generating means comprising a focus controller means for controlling said focus actuator, and, said focus controller means being supplied with said focus error signal, and a focus memory loop for applying a stored correction signal to said focus actuator, said computer system executing the steps of:

• a) determining if an event has occurred that requires at least a gradual stop of said focus tracking system, and if positive then,
• b) disabling the focus controller means by opening the control loop, and
• c) gradually reducing, over a period of time, at least one of:
• a memory loop parameter of said focus memory loop, said parameter corresponding to an amplitude of said stored correction signal, and a controller parameter of an integrating means of said focus controller means, said controller parameter corresponding to a focus offset position, wherein the period of time is determined based on a natural frequency of the focus actuator means.

A method for operating an optical drive system capable of reproducing/recording information from/to an optical carrier, wherein the optical drive system comprises:

• a radiation source for generating a radiation beam,
• a focusing means for focussing the radiation beam,
• an optical receiver means for generating an electric read signal in response to radiation reflected from the optical carrier,
• a focus tracking system for tracking the carrier with said focussed radiation beam,
• wherein said focus tracking system comprises
• a focus error generating means for generating a focus error signal,
• a focus actuator means for changing a focus position of said focussed radiation beam relative to the optical carrier, said focus actuator means being driven by a supplied correction signal, and
• a correction signal generating means comprising
• a focus controller means for controlling said focus actuator, and, said focus controller means being supplied with said focus error signal, and
• a focus memory loop for applying a stored correction signal to said focus actuator,
• the method comprises the steps of:
• a) determine if an event has occurred that requires at least a gradual stop of said focus tracking system, and if positive then,
• b) disable the focus controller means by opening the control loop, and
• c) gradually reducing at least one of:
• a memory loop parameter of said focus memory loop, said memory loop parameter corresponding to an amplitude of said stored correction signal, and a controller parameter of an integrating means of said focus controller means, the controller parameter being gradually reduced by leaking away electric charge of an integrator part of the focus controller means, said integrator part having a value corresponding to a focus offset position.

A method for operating an optical drive system capable of reproducing/recording information from/to an optical carrier, wherein the optical drive system comprises:

• a radiation source for generating a radiation beam,
• a focusing means for focussing the radiation beam,
• an optical receiver means for generating an electric read signal in response to radiation reflected from the optical carrier,
• a focus tracking system for tracking the carrier with said focussed radiation beam,
• wherein said focus tracking system comprises
• a focus error generating means for generating a focus error signal,
• a focus actuator means for changing a focus position of said focussed radiation beam relative to the optical carrier, said focus actuator means being driven by a supplied correction signal, and
• a correction signal generating means comprising
• a focus controller means for controlling said focus actuator, and, said focus controller means being supplied with said focus error signal, and
• a focus memory loop for applying a stored correction signal to said focus actuator,
• the method comprises the steps of:
• a) determine if an event has occurred that requires at least a gradual stop of said focus tracking system, and if positive then,
• b) disable the focus controller means by opening the control loop, and
• c) gradually reducing at least one of:
• a memory loop parameter of said focus memory loop, said memory loop parameter corresponding to an amplitude of said stored correction signal, and a controller parameter of an integrating means of said focus controller means, the controller parameter being gradually reduced by reducing a digitally controlled parameter of an integrator part of the focus controller means, said digitally controlled parameter having a value corresponding to a focus offset position.