Patent Application
20130058200
1. Field of the Invention
The present invention relates to an optical disc drive, and more particularly, to a method for calibrating a tilt of an actuator in a pick-up head of an optical disc drive, where the actuator is used to move an objective lens.
2. Description of the Prior Art
With the trend toward the compact and light-weight consumer electronic products, an error of a driving signal of an actuator is magnified due to a light pick-up head of an optical disc drive, resulting in a larger tilt amount of an objective lens. This may further affect the read/write accuracy of the optical disc drive.
Please refer to
However, as the control voltage outputted from the DSP 14 is transmitted through the analog driving circuit 15 to drive the actuator 16, there is an error in the output level of the control voltage due to the electrical characteristics (e.g., the impedance) of the analog driving circuit 15. As a result, the control voltage fails to move the objective lens 17 to the desired location precisely, which affects the read/write quality of the optical disc drive. In addition, the objective lens 17 may move even beyond the maximum allowable range to crash the pick-up head. Therefore, regarding the actuator motion error, the conventional design has a calibration problem remained unsolved.
It is one objective of the present invention to provide a method for calibrating a tilt of an actuator. A tilt curve is fitted through tilt motions of the actuator driven by a plurality of control voltages. A bias voltage is acquired from the tilt curve according to a standard displacement signal that is not obtained through an analog driving circuit, and then is used to calibrate the tilt of the actuator.
It is another objective of the present invention to provide a method for calibrating a tilt of an actuator. By offsetting a control voltage outputted from a digital signal processor according to a bias voltage, the actuator is driven precisely and thus the read/write quality is improved.
In order to achieve the above objectives, the present invention provides a method for calibrating a tilt of an actuator. The method for calibrating the tilt error of the actuator includes the following steps: focusing a light beam onto a data layer; outputting a plurality of control voltages through an analog driving circuit for driving the actuator to tilt an objective lens, and accordingly recording corresponding displacement signals (e.g., central error signals) of the objective lens; fitting a tilt curve (e.g., a linear curve); outputting a zero control voltage, not through the analog driving circuit, for tilting the objective lens, and accordingly measuring a standard displacement signal; acquiring a bias voltage from the tilt curve according to the standard displacement signal; and offsetting the plurality of control voltages to calibrate the tilt of the actuator.
In the present invention, the digital signal processor outputs the zero control voltage that is not transmitted through the analog driving circuit by turning off the analog driving circuit or setting the analog driving circuit in a high impedance mode. A difference value between the standard displacement signal and a displacement signal corresponding to the zero control voltage on the tilt curve is a tilt error generated from tilting an objective lens. The standard displacement signal is substituted into the tilt curve to obtain a correspondent standard control voltage, which is an error voltage outputted through the analog driving circuit when the digital signal processor outputs the zero control voltage, and the standard control voltage is used as the bias voltage.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
With regard to technical means and utilities thereof used to achieve the above objectives of the present invention, preferred embodiments are described as follows by way of examples and with reference to the accompanying diagrams.
Please refer to
When the digital signal processor 24 outputs the control voltage V, an error is generated in the tilt amount of the objective lens 21 because the control voltage V is fed through the analog driving circuit 25 for driving the actuator 20 to tilt the objective lens 21. No standard tilt amount of the objective lens 21 may be referenced to obtain a corrected tilt amount of the objective lens 21. Therefore, as shown in
Considering a case where the digital signal processor 24 outputs a zero control voltage (i.e., V=0), if the zero control voltage does not pass through the analog driving circuit 25, the tilt amount of the objective lens 21 is not affected by the analog driving circuit 25, and thus there is no error generated therein. As a result, the present invention utilizes the digital signal processor 24 to output the zero control voltage, not through the analog drive circuit, by turning off the analog driving circuit 25 or setting the analog driving circuit in a high impedance mode, thus avoiding the generated error of the tilt amount. Next, a standard central error signal A is measured. A difference value ΔCE between the standard central error signal A and a central error signal corresponding to the zero control voltage on the tilt curve L is a tilt error generated from tilting the objective lens 21 by the actuator 20. A standard control voltage V0 corresponding to the standard central error signal A may be acquired from the tilt curve L by substituting the standard central error signal A into the tilt curve L, wherein the standard central error signal A is generated without being effected by the analog driving circuit 25. The standard control voltage V0 is regarded as a control voltage corrected by the difference value ΔCE, and is an error voltage outputted through the analog driving circuit 25 when the digital signal processor 24 outputs the zero control voltage. As the standard control voltage V0 may be regarded as an average error voltage outputted through the analog driving circuit 25, the standard control voltage V0 is used as a bias voltage outputted from the digital signal processor through the analog driving circuit 25. For example, in a case where a value of the CE signal is measured as 914 by setting the analog driving circuit 25 in a high impedance mode, the standard control voltage V0 acquired from the tilt curve L is −22, which is taken as an offset value of the control voltage outputted from the digital signal processor 24. Therefore, the present invention calibrates the tilt of the actuator 20 by offsetting the control voltage outputted from the analog driving circuit 25 according to the standard control voltage V0.
Therefore, the exemplary method for calibrating a tilt of an actuator first fits a tilt curve of the actuator through tilt motions of the actuator and corresponding displacement signals, wherein the actuator is driven by a plurality of control voltages outputted from a digital signal processor. Next, a standard displacement signal is measured under a condition where an analog driving circuit is turned off or set in a high impedance mode. The standard displacement signal is substituted into the tilt curve to obtain a correspondent standard control voltage, and the standard control voltage is used as a bias voltage to offset the control voltage outputted from the digital signal processor. Therefore, the actuator is driven precisely, and the objective of calibrating the tilt of the actuator is achieved.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 100132353 | Sep 2011 | TW | national |
