JP2774295B2 - Optical information recording / reproducing device - Google Patents

Description

The present invention relates to an optical information recording / reproducing apparatus for recording, reproducing, or erasing information on an optical recording medium such as an optical disk and a magneto-optical disk. The present invention relates to an automatic correction circuit for tracking offset in tracking control of an objective lens with respect to.

(Prior Art) FIG. 6 shows a known type of automatic tracking offset correction circuit. Here, tracking control is performed by the push-pull method, but an offset occurs in the tracking signal D at a position of the objective lens relative to the optical head. The tracking signal D contains the offset amount and the buffer amplifier 1, AG
When supplied to the drive circuit of the actuator via the C circuit 2 and the buffer 4, when the servo loop is closed, the following problems occur. That is, as shown in FIG. 2, the tracking signal D has an offset on the + side (for example, + F (V)) when the objective lens is moved to the outer periphery, and on the one side (for example, -F (V)) when the objective lens is moved to the inner periphery. Occur. This also occurs in signals A and C, but if the servo loop is closed in this state, the above servo loop is controlled with respect to the reference voltage, so it is stable in the state where an offset is occurring If the margin for operation is reduced, and if there is a slight disturbance or a change in amplitude, the servo may be disconnected.

Therefore, usually, in order to prevent this, a detection signal of the relative position of the objective lens with respect to the optical head is given to the objective lens position sensor amplifier 5 as an offset erasing signal,
As shown in the figure, a voltage (DC voltage component) -F (V), + F having a polarity opposite to the offset amount of the tracking signal D described above.
(V) is output from the correction value determination circuit 6 and added to the tracking signal in the adder 3 to cancel the offset amount. For this reason, the offset amount is removed from the signal C, and the servo loop does not come off.

(Problems to be Solved by the Invention) However, in the above-described method, the offset amount actually included in the tracking signal is slightly different from the offset amount detected by the objective lens position sensor depending on the personality of the recording medium. The differences are not taken into account. Here, the “individuality of the recording medium” is based on a difference in the media such as a difference in a group, for example, and includes a circuit adjustment in a tracking control unit, a numerical change due to a temperature, and the like. For these reasons, a slight correction error must be allowed between the offset amount calculated from the position information of the objective lens and the offset amount actually included in the tracking signal.

(Object of the Invention) The present invention has been made based on the above circumstances, and detects an offset amount that changes depending on the personality of a recording medium,
An object of the present invention is to realize an automatic correction of a tracking offset without a correction error by correcting an offset cancellation signal uniquely determined from a relative position of an objective lens with respect to an optical head.

Therefore, according to the present invention, there is provided an objective lens which is drivably supported by an optical head and forms a light beam spot on a track of a recording medium for recording or reproducing information. Position detecting means for detecting a relative position of the objective lens with respect to the optical head, means for generating a tracking signal indicating a deviation of the light beam spot from the track by a push-pull method, and the objective lens based on the tracking signal And an means for generating an offset signal for correcting an offset amount of the tracking signal generated as the objective lens moves in the tracking direction based on the relative position detected by the position detection means. Before using the recording medium, move the objective lens Move a predetermined amount in the locking direction, detect the offset amount specific to the medium to be used from the DC component of the tracking signal generated at that time, and detect the change in the offset signal based on the comparison between the offset amount and the offset signal Means for correcting the offset signal using the change, and means for applying the corrected offset signal to the tracking signal to remove the offset amount from the tracking signal. And

(Operation) As described above, for example, when the group shape is different,
Since there is provided a means for detecting a change in the offset amount according to the recording medium used and correcting the offset signal using the change, there is no correction error in the push-pull tracking control. Offset correction of the tracking signal can be performed, and more accurate tracking control can be performed.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to the drawings. In the embodiment shown in FIG. 1, the same components as those in the description of the conventional example described above (see FIG. 6) are given the same reference numerals, and description thereof will be omitted. Particularly, in the present invention, the tracking signal D is output to the buffer 4 via the buffer amplifier 1, the AGC circuit 2, and the adder 3 as described above, and the drive of the actuator for driving the objective lens 13 based on the tracking signal D is performed. The tracking coil 12 in the optical head is driven via the circuit 11. Thereby, the objective lens 13 is driven in the outer circumferential or inner circumferential direction.

On the other hand, in the optical system, a laser beam is emitted from the semiconductor laser 14 in the fixed optical system region, passes through the optical system 15 and the objective lens 13, and the light beam spot is focused on the recording medium 18. The light beam reflected from the recording medium 18 is supplied to a tracking signal sensor as position detecting means for detecting the relative position of the objective lens 1 with respect to the optical head via the objective lens 13, the optical system 15, and the optical system 16. Then, the signal is converted into an electric signal by the tracking signal sensor and output as a tracking signal D from the sensor amplifier 17.

In this manner, a tracking servo loop that generates a tracking signal indicating a deviation of the light beam spot from the track is formed by the push-pull method.

Further, there is provided means for generating an offset signal indicating an offset amount of a tracking signal generated as the objective lens 13 moves in the track direction based on a relative position detected by an objective lens position sensor (not shown).

That is, in this embodiment, the objective lens position sensor amplifier 5 is prepared as the above-mentioned generating means. Further, a track count circuit is used as a means for detecting a change in the offset amount according to the recording medium to be used, for example, a recording medium having a personality having a different group shape and the like, and using the change amount to correct the offset amount. 7. Offset detection circuit
10, an A / D converter 9, a D / A converter 19, a control circuit 8, and a correction value determination circuit 6 are provided. The track count circuit 7 detects the required movable range + E μm when the objective lens 13 moves in the outer peripheral direction, and detects the required movable range −E μm when the objective lens moves in the inner peripheral direction.

On the other hand, in the offset detection circuit 10, the offset amounts + F (V) and -F (V) generated with respect to the reference voltage at that time.
Is detected (see FIG. 2). And the DC component is A / D
The digital data is converted by the converter 9 and temporarily stored in a memory of a control circuit described later. In the control circuit 8, the output signal of the track count circuit 7 and the offset amount + F (V),-
The change amount of the offset amount is calculated from F (V) as ΔH (V), and this is converted into an analog via the D / A converter 19,
It is provided to the correction value determination circuit 6. In the correction value determination circuit 6,
As already described, the objective lens position sensor amplifier 5
, Voltages (DC voltage components) -G (V) and + G (V) having polarities opposite to the offset amount of the tracking signal D are received as offset erasure signals.
(V) = − G (V) −ΔH (V) or + F (V) =
+ G (V) + ΔH (V) as error-free correction value −F
(V) and + F (V) are obtained.

Further, in order to remove the above-mentioned offset amount from the tracking signal D, a correction value determination circuit 6 is added to the tracking signal D.
A means for applying the corrected offset signal from is provided. In this embodiment, the application means is an adder 3
The correction value having no error is guided to the adder 3 and added to the tracking signal A to eliminate the offset amount. That is, J (+ F
(V) -G (V)) and K (+
F (V) -F (V)).

In another embodiment shown in FIG. 5, the acquisition signal of the offset detection circuit 10 is obtained from the output signal C of the adder 3.
Although different from the previous embodiment, the others are completely the same,
In the same manner, the offset elimination signal is corrected in the correction value determination circuit 6 by taking out the correction error signal in the control circuit 8, and the correction error is eliminated. In this embodiment, the track count circuit 7 is used as an offset amount detecting means for detecting an offset amount that changes depending on the personality of the recording medium, and the personality of the recording medium is determined from the offset signal detected by the offset amount detecting means. The offset detection circuit 10, the A / D converter 9, the control circuit 8, and the D / A converter 19 are used as means for calculating the amount of change in the offset amount that changes depending on the condition. To achieve similar results with the components of
Without departing from the essence of the present invention, they are included in the technical scope of the present invention.

(Effects of the Invention) As described in detail above, the present invention relates to an objective lens that is drivably supported by an optical head and forms an optical beam spot on a track of a recording medium for recording or reproducing information. Position detecting means for detecting a relative position of the objective lens with respect to the optical head; means for generating a tracking signal indicating deviation of the light beam spot with respect to the track by a push-pull method; An actuator for driving a lens and an offset signal for correcting an offset amount of the tracking signal generated as the objective lens moves in the tracking direction are generated based on the relative position detected by the position detection unit. Means,
Prior to using the recording medium, the objective lens is moved in the tracking direction by a predetermined amount, and the offset amount specific to the medium to be used is detected from the DC component of the tracking signal generated at that time, and the offset amount and the offset signal are used. Means for detecting a change in the offset signal based on the comparison, and means for correcting the offset signal using the change, and the correction to the tracking signal to remove the offset from the tracking signal. Means for applying an offset signal.

Therefore, for example, a means for detecting a change in the offset amount according to the recording medium to be used, such as a different group shape, and correcting the offset signal using the change is provided. In the pull type tracking control, offset correction of a tracking signal without a correction error can be performed, and more accurate tracking control can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an automatic tracking / offset correction circuit showing one embodiment of the present invention, FIG. 2 is a graph showing an offset amount generated depending on the position of an objective lens, and FIG.
FIG. 4 is a graph of an offset correction output by the objective lens position detection circuit, FIG. 4 is a graph showing an output after correction, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIG. 6 shows a conventional example. It is a block diagram. DESCRIPTION OF SYMBOLS 1 ... Buffer amplifier, 2 ... AGC circuit, 3 ... Adder, 4 ... Buffer amplifier, 5 ... Objective lens position sensor amplifier, 6 ... Correction value determination circuit, 7 ... Track count circuit, 8 ... ... Control circuit, 9 A / D converter, 10 ...
Offset detection circuit, 11 Actuator drive circuit, 12 Tracking coil, 13 Objective lens, 14
…… Semiconductor laser, 15, 16… Optical system, 17… Tracking signal sensor amplifier, 18… Recording medium, 19… D / A converter.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/09

Claims (1)

(57) [Claims] 1. An objective lens which is drivably supported by an optical head and forms a light beam spot on a track of a recording medium for recording or reproducing information, and a relative position of the objective lens with respect to the optical head. Position detection means for detecting the position of the light beam spot, means for generating a tracking signal indicating a deviation of the light beam spot from the track by a push-pull method, an actuator for driving the objective lens based on the tracking signal, Means for generating an offset signal for correcting an offset amount of the tracking signal generated in accordance with movement in the tracking direction based on the relative position detected by the position detection means; and Moving the objective lens in the tracking direction by a predetermined amount, Detect the offset amount specific to the medium to be used from the DC component of the generated tracking signal, detect the change amount of the offset signal based on the comparison between the offset amount and the offset signal, using the change amount An optical information recording / reproducing apparatus comprising: means for correcting the offset signal; and means for applying the corrected offset signal to the tracking signal in order to remove the offset amount from the tracking signal. .