JP2005310234A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device which realizes focus pull-in so as to accurately fix a focal point position on a recording surface of an optical disk even if a pseudo S-shaped wave is generated in a focus error signal. <P>SOLUTION: In an optical disk device, a first error signal becomes maximum when the focal point position is located in a condensing means 3 side rather than the recording surface of an optical disk 1, and a 2nd error signal becomes maximum when the focal point position is located at an opposite side of the condensing means 3 rather than recording surface of the optical disk 1. Focus pull-in which fixes the focal point position correctly on the recording surface of the optical disk 1 is realized by starting the driving of the condensing means 3 by a focus driving means 4 based on the focus error signal, when a condition in which the 1st error signal becomes equal to or more than an arbitrary threshold and a condition in which the 2nd error signal becomes equal to or more than an arbitrary threshold are both fulfilled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus capable of recording / reproducing / erasing information.

  In recent years, optical disc-related products that record and reproduce information using light have become popular in the market. In general, in order to read information recorded on an optical disk in a spiral shape from the inner circumference to the outer circumference, the optical disc apparatus keeps the focal point of the light by the condensing means at a predetermined information recording position on the recording surface, and stores the information. Optical servo technology is used to make it readable and writable. The optical servo described above includes a focus servo that moves the condensing means in the optical axis direction and focuses the light on the recording surface of the optical disc, and information recorded on the recording surface by moving the condensing means in the radial direction of the optical disc. There is a tracking servo that adjusts the focal position to the pit row. Hereinafter, the focus servo pull-in control according to the above-described prior art will be described with reference to the drawings.

  FIG. 3 is a configuration diagram of focus pull-in control in a conventional optical disc apparatus. In FIG. 3, 1 is an optical disk which is an information recording medium, 2 is a spindle motor for rotating the optical disk, 3 is a condensing means, 4 is a focus driving means for driving the condensing means 3 in the optical axis direction, and 5 is an alignment for the optical disk. First error detection means for detecting an error signal according to the shift of the focal position, 6 is a second error detection means for detecting an error signal according to the shift of the focus position with respect to the optical disc, and 9 is a first error detection means. Subtracting means 10 for generating a focus error signal by subtracting the first error signal and the second error signal, 10 is a third comparing means for detecting that the focus error signal is equal to or greater than an arbitrary threshold value. .

  The operation principle of the focus servo control in the optical disk apparatus configured as described above will be described below. FIG. 4 schematically shows a focus pull-in operation in a conventional optical disc apparatus. The first error signal is set to have a maximum value when the in-focus position by the light condensing means 3 is located on the light condensing means 3 side with respect to the recording surface of the optical disc 1, and the second error signal is condensing. The focal point is set to a maximum value when the in-focus position by the means 3 is located on the opposite side of the light collecting means 3 from the recording surface of the optical disc 1. As a result, an S-shaped waveform is generated in the focus error signal when the in-focus position by the light condensing means 3 is located in the vicinity of the recording surface of the optical disc 1.

When the in-focus position by the light condensing means 3 is within the range of points A and B in FIG. 4, the focus error signal is zero when it is on the recording surface of the optical disk 1, and the light converging means 3 is removed from the optical disk 1 on the basis of the position. The focus error signal fluctuates in the positive direction when moving away, and the focus error signal fluctuates in the negative direction when the condensing means 3 approaches the optical disc 1.
When it is within this range, the focusing means 3 is driven by the focus driving means 4 in the direction in which the focus error signal is directed toward zero, so that the focal position by the focusing means 3 remains on the recording surface of the optical disc 1. can do.

Next, the operation of pulling in the focus from a state in which the in-focus position by the light collecting means 3 is outside the range of the points A and B in FIG. 4 will be described. The point that the third comparison means 10 detects that the focus error signal has reached the predetermined level H is the first stage, and the third comparison means 10 indicates that the focus error signal has reached the predetermined level L. When the detected point is the second stage, when the focusing means 3 is moved in a direction approaching from a position away from the optical disc 1 by the focus driving means 4 in order to draw the focus, the first stage is detected first. When the second stage is detected, the focus drive unit 4 starts driving the light collecting unit 3 based on the focus error signal, thereby achieving focus pull-in. In addition, there exist the following as a prior art relevant to this (for example, refer patent document 1).
JP 2001-202632 A

  However, in the conventional focus pull-in control described above, when a pseudo S-shaped waveform as shown in FIG. 2 is generated in the focus error signal due to an optical factor, it is not on the recording surface of the optical disc by the pseudo first stage and the pseudo second stage. There is a problem that the in-focus position remains at the position.

  In consideration of such a problem of the conventional focus pull-in device, the present invention accurately sets the in-focus position on the recording surface of the optical disc even when a pseudo-S waveform due to an optical factor is generated in the focus error signal. An object of the present invention is to provide an optical disc apparatus that realizes the focus pull-in so as to stay.

  The present invention detects a light collecting means for focusing on a recording surface of an optical disk, a focus driving means for driving the light collecting means in the direction of the optical axis, and an error signal corresponding to a deviation of a focus position with respect to an optical disk. First error detecting means and second error detecting means, and first comparing means for detecting that the first error signal output from the first error detecting means is equal to or greater than an arbitrary threshold value. A second comparison means for detecting that the second error signal output from the second error detection means is greater than or equal to an arbitrary threshold value, and the first error signal and the second error signal. Subtracting means for generating a focus error signal by performing subtraction, and the first error signal becomes the maximum value when the in-focus position is located closer to the light condensing means than the recording surface of the optical disc, and the in-focus position is More than the recording surface of the optical disc In the optical disc apparatus set so that the second error signal becomes the maximum value when positioned on the opposite side of the means, the condition that the first error signal is equal to or greater than an arbitrary threshold and the second error signal is an arbitrary threshold The optical disc apparatus is characterized in that the focus driving unit starts driving the condensing unit based on the focus error signal when both of the above conditions are satisfied.

  As described above, according to the present invention, the focus error signal is not used for controlling the timing to start the focus pull-in, and the condition that the first error signal is greater than or equal to the arbitrary threshold A and the second error signal is arbitrary. When both the conditions equal to or greater than the threshold value B are satisfied, the focus driving unit starts driving the condensing unit based on the focus error signal. Therefore, when a pseudo S-shaped waveform due to an optical factor is generated in the focus error signal, In addition, it is possible to provide an optical disk device that realizes focus pull-in so that the focal point position can be accurately kept on the recording surface of the optical disk.

  According to the first aspect of the present invention, since the focus error signal is not used to control the timing for starting the focus pull-in, even when a pseudo S-shaped waveform due to an optical factor is generated in the focus error signal, the technique is accurate. In addition, it has the effect of realizing the focus pull-in so as to keep the focal position on the recording surface of the optical disk.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a configuration diagram of focus pull-in control in the optical disc apparatus of the present invention. In FIG. 1, 1 is an optical disk which is an information recording medium, 2 is a spindle motor for rotating the optical disk, 3 is a condensing means, 4 is a focus driving means for driving the condensing means 3 in the optical axis direction, and 5 is an alignment for the optical disk. First error detection means for detecting an error signal corresponding to the shift of the focal position, 6 is a second error detection means for detecting an error signal corresponding to the shift of the focus position with respect to the optical disc, and 7 is a first error detection means. First comparison means for detecting that one error signal is greater than or equal to an arbitrary threshold, 8 is second comparison means for detecting that a second error signal is greater than or equal to an arbitrary threshold, and 9 is first Subtracting means for generating a focus error signal by subtracting the error signal and the second error signal.

  The operation principle of the focus servo control in the optical disk apparatus configured as described above will be described below. FIG. 2 is a schematic diagram of the focus pull-in operation in the optical disc apparatus of the present invention when a pseudo S-shaped waveform is generated in the focus error signal due to an optical factor. The first error signal is set to have a maximum value when the in-focus position by the light condensing means 3 is located on the light condensing means 3 side with respect to the recording surface of the optical disc 1, and the second error signal is condensing. The in-focus position by the means 3 is set to the maximum value when it is located on the opposite side of the light-collecting means 3 from the recording surface of the optical disc 1, but the in-focus position is set to the recording surface of the optical disc 1 due to optical factors. The local maximum value and the local minimum value are generated at points far enough away from the light condensing means 3. As a result, in addition to the occurrence of an S-shaped waveform in the focus error signal when the in-focus position by the condensing means 3 is located in the vicinity of the recording surface of the optical disc 1, the in-focus position is closer to the condensing means than the recording surface of the optical disc 1. A pseudo S-shaped waveform is generated at a position sufficiently away from the third side. When the timing for starting focus pull-in is controlled based on the S-shaped waveform of the focus error signal in a state where such a pseudo-S-shaped waveform is generated in the focus error signal, a normal S-shaped waveform and a pseudo S-shaped waveform are obtained. And the in-focus position remains at a position not on the recording surface of the optical disc. However, the present invention does not use the focus error signal to control the timing for starting the focus pull-in, and the condition that the first error signal is equal to or greater than the arbitrary threshold A and the second error signal is equal to or greater than the arbitrary threshold B. Since the focus driving means starts driving the light collecting means based on the focus error signal when both of the conditions are satisfied, the optical disc can be accurately detected even when a pseudo S-shaped waveform due to an optical factor is generated in the focus error signal. Focus pull-in that keeps the in-focus position on the recording surface is realized.

  The present invention can also be applied to the use of an optical disc apparatus capable of recording / reproducing / erasing information.

Configuration diagram of focus pull-in control in optical disc apparatus of the present invention Schematic diagram of focus pull-in operation in the optical disc apparatus of the present invention Configuration diagram of focus pull-in control in a conventional optical disc apparatus Schematic diagram of focus pull-in operation in a conventional optical disc apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Spindle motor 3 Condensing means 4 Focus drive means 5 1st error detection means 6 2nd error detection means 7 1st comparison means 8 2nd comparison means 9 Subtraction means 10 3rd comparison means

Claims (1)

Condensing means for focusing on the recording surface of the optical disk, focus driving means for driving the condensing means in the direction of the optical axis, and an error signal corresponding to the deviation of the in-focus position with respect to the optical disc. A first error detecting means, a second error detecting means, and a first comparing means for detecting that the first error signal output from the first error detecting means is equal to or greater than an arbitrary threshold value; , Second comparison means for detecting that the second error signal output from the second error detection means is not less than an arbitrary threshold value, the first error signal, and the second error signal. It is composed of subtracting means for generating a focus error signal by subtracting the signal, and the first error signal becomes the maximum value when the in-focus position is located on the light collecting means side with respect to the recording surface of the optical disc, Focus position is optical In the optical disc apparatus in which the second error signal has a maximum value when positioned on the opposite side of the light condensing means with respect to the recording surface of the disk, the first error signal is greater than an arbitrary threshold and the first An optical disc apparatus, wherein the focus driving unit starts driving the condensing unit on the basis of the focus error signal when both of the two error signals satisfy an arbitrary threshold value or more.

Images