JPH03154233A - Focus control device and tracking control device for optical disc devices - Google Patents

Abstract

PURPOSE:To always obtain the objective servo performance by applying the cancellation of an offset in a focus error signal and the adjustment of detection gain automatically with an arithmetic processing of a digital signal processor DSP. CONSTITUTION:When a DSP 6 detects the loading of an optical disk 1, a current commanding value moving a lens actuator 2 in a direction (a) is changed to read a peak value of a focus error signal generated before and behind a focal position. Then a conversion constant converted from a prescribed detection gain and an offset of a signal are calculated from the peak value. Then the DSP 6 cancels the offset of the read signal and converts the detection gain by using the conversion constant to apply the detection of a focal position and the compensation characteristic at servo operation. Thus, the offset of the signal and the detection gain are not influenced. The operation is implemented automatically every time a disk is loaded to obtain the servo characteristic being always an object.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a focus control device and a tracking control device for an optical disc device.

(Prior Art) A conventional focus control device for an optical disc device will be described with reference to FIGS. 3 to 5.

In FIG. 3, a light spot S irradiated onto the optical disc 1 is moved in the focus direction (
It can be moved in the thickness direction of the optical disc 1, that is, in the direction of arrow a). The focus shift at this time is determined by the optical system 3 containing a photodiode and the like and the focus error detection circuit 9. The output (focus error signal) of this focus error detection circuit 9 is transmitted to a compensation circuit 10.
The output of the compensation circuit 10 is given as a current command value to the power amplifier 8 via the switch 12 when the focus servo is on. The power amplifier 8 controls the focus by causing a current proportional to the current command value to flow through the lens actuator 2, thereby moving the lens actuator 2 in the direction a.

Incidentally, the offset component and detection gain of the focus error signal generally differ due to variations between optical disc devices (mainly variations in the optical system 3) and variations in the characteristics of the optical disc 1.

Therefore, in order to stably obtain the target focus setting accuracy, it is necessary to perform offset correction of the focus error signal and adjustment of the detection gain using an optical disk having standard characteristics for each optical disk device. FIG. 4 shows a specific example of the error detection circuit 9 having these adjustment functions, and the adjustment procedure is as follows.

First, in the focus servo off state (switch 12 in FIG. 3 is off), a current command value is given to the power amplifier 8 from the test signal generation circuit 11 in FIG. 3 via the switch 13. In response to this current command value, the lens actuator 2 repeats slow reciprocating motion in the focus direction. At this time, the focus error signal output from the focus error detection circuit 9 is observed using a synchroscope or the like.

As shown in FIG. 5(a), the offset that exists before adjustment (arrow b in the figure) is reduced to zero after adjustment as shown in FIG. 5(b), and the error detection gain is adjusted to a predetermined value ( This adjustment amount is indicated by arrow C in FIG. 2(b)).

In addition, in the error detection circuit 9 shown in FIG.
,,op2 is Oheamp, PD,,PD,! ! Optical system 3
photodiode provided in , R1 to RG are resistors, VR
l is a variable resistor for offset adjustment, VR, is gain t
This is a variable resistor for A adjustment.

On the other hand, tracking control is to control the lens actuator 2 in the radial direction of the optical disc 1 (in the direction of arrow a' in FIG. 3), and this case can also be explained in substantially the same way as the focus control described above. That is, in the above description, "focus" may be replaced with "track". However, focus control must already be completed prior to tracking control, and since the optical spot S can cross the track due to eccentricity when the optical disc 1 is rotating, the test signal shown in FIG. 3 is generated. The circuit 11 and switch 13 may be omitted.

(Problems to be Solved by the Invention) As mentioned above, in conventional focus control devices and tracking control devices, in order to stably obtain target setting accuracy, it is necessary to offset the focus error signal for each optical disk device. It is necessary to manually perform correction and detection gain adjustment or offset correction of the track error signal and detection gain adjustment, which is extremely troublesome.

Furthermore, even if the optical disk device has been adjusted for a while,
Depending on the characteristics of the optical disk used, the offset components and detection gains of each error signal may differ, so it is conceivable that the target servo performance may not be obtained. In other words, there is a problem in that the allowable variation range of optical disc characteristics is narrow and the compatibility of optical discs is poor.

The present invention has been made to solve the above problems,
Its purpose is offset correction of focus error signals and track error signals.

Detection gain adjustment can be performed automatically, and
It is an object of the present invention to provide a focus control device and a tracking control device that allow variations in characteristics of optical disks and improve compatibility of optical disks by performing these correction and adjustment operations each time an optical disk is loaded.

(Means for Solving the Problems) In order to achieve the above object, a focus control device according to the present invention includes an optical system for detecting a focus shift of a light spot irradiated onto an optical disk, and a focus control device connected to the output side of the optical system. An error detection circuit and a focus error signal output from this focus error detection circuit are A/D
an A/D converter to convert, and periodically reading the focus error signal via the A/D converter;
Each time the optical disc is loaded, the offset and a conversion constant for converting the focus error signal into a predetermined error detection gain are calculated based on the focus error signal, and the offset is calculated using the offset and conversion constant. Canceled.

and a digital signal processor configured to calculate a compensation characteristic for a focus search operation and a focus servo operation using the focus error signal whose detection gain has been converted, and output a drive command value for controlling the position of the light spot; D to D/A convert the drive command value
/A converter, and a lens actuator that moves the position of the optical spot in the thickness direction of the optical disc based on the drive command value via the D/A converter.

Further, the tracking control device according to the present invention includes an optical system for detecting a track deviation of a light spot irradiated onto an optical disk, a track error detection circuit connected to the output side of the optical system, and an output from the track error detection circuit. an A/D converter that A/D converts a track error signal, and a device that periodically reads the track error signal via the A/D converter, and after the optical disc is loaded and focus control is completed, the track error signal is The track whose offset is calculated based on the error signal and a conversion constant for converting it into a predetermined error detection gain, and whose offset is canceled and whose detection gain is converted using the offset and conversion constant. a digital signal processor that calculates compensation characteristics for track servo operation based on the error signal and outputs a drive command value for controlling the position of the optical spot; and a D/A converter that converts the drive command value from D/A to analog. and a lens actuator that moves the position of the optical spot in the radial direction of the optical disc based on the drive command value via the D/A converter.

(effect) According to the focus control device according to the present invention.

When an optical disc is loaded, a digital signal processor (DSP) detects this and changes the drive command value for moving the lens actuator in the thickness direction of the optical disc to determine the peak value of the focus error signal before and after the in-focus point. read.

Based on this peak value, the DSP calculates an offset of the focus error signal and a conversion constant for converting it into a predetermined error conversion gain.

Next, a focus search operation is performed and a focus servo operation is started near the in-focus point, but the focus error signal read by the DSP is converted using the offset and the conversion constant, and then the in-focus point is detected during the focus search operation. Since the compensating characteristic calculation is performed during the focus servo operation, there is no influence from the offset of the focus error signal or the difference in detection gain.

Since the above operation is automatically executed every time an optical disk is loaded, the target servo performance can always be obtained even if the optical disks have different characteristics.

Furthermore, according to the tracking control device according to the present invention,
After the focus control is completed, the DSP causes the lens actuator to reciprocate in the radial direction of the optical disk, and the peak value of the track error signal generated as the light spot crosses the track is read. Based on this peak value, the DSP calculates a conversion constant for converting the track error signal into an offset and a predetermined error conversion gain.

During track servo operation, the track error signal read by the DSP is converted using the offset and conversion constant, and then the compensation characteristics are calculated. Therefore, the difference in the offset and detection gain of the track error signal may affect the track error signal read by the DSP. The target servo performance can be obtained without suffering.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of a focus control device, and a tracking control device can also be realized with the same configuration as this focus control device.

First, in FIG. 1, the position of the light spot S irradiated onto the optical disc 1 in the focus direction (arrow a direction) can be moved by controlling the lens actuator 2 in the same direction as in the conventional art. The focus shift at this time is determined by the optical system 3 and error detection circuit 4. However, the focus error signal as the output of the error detection circuit 4 has an offset, and the error detection gain also differs depending on the individual optical disk device or disk cassette used.

The focus error signal output from the error detection circuit 4 is periodically read by a digital signal processor (hereinafter referred to as DSP) 6 via an A/D converter 5. In addition.

The sampling frequency at this time is set to a value that is sufficiently large compared to the focus servo frequency band, and is generally set to a value that is 10 times or more the focus servo frequency.

The DSP 6 gives a current command value to the power amplifier 8 via the D/A converter 7 in response to the focus error signal, and the power amplifier 8 drives the lens actuator 2 by passing a current according to the current command value to the lens actuator 2. It is configured as follows.

Next, the focus control function in this example will be explained using DS.
The process performed at P6 will be explained with reference to FIG. 2.

First, when the disk cassette containing the optical disk 1 is inserted, the DSP 6 detects this (21st!! Step S1).Then, with the focus servo off, the lens actuator 2 is moved from the position farthest from the optical disk 1 to the optical disk. The current command value for the power amplifier 8 is changed so as to slowly and forcibly move it in the direction approaching 1.

Then, the DSP 6 reads the peak value of the focus error signal that occurs before and after the first in-focus point (S2) 6 After that,
DSP6 is from the above peak value.

Focus error signal offset F E offs
et and a conversion constant KFg for converting into a predetermined error detection gain according to the following equation (s3).

here.

FE◆p: +peak value of the focus error signal as a read value by the DSP6 FE -p: -peak value of the focus error signal FE p-p: The value of the focus error signal when assuming a predetermined error detection gain It is a peak-to-peak value.

Next, a focus search operation is performed and a focus servo operation is started near the first in-focus point. At this time, the offset of the focus error signal read by the DSP 6 is canceled by the following formula, and the detection gain becomes a predetermined value. is converted to

FEN=(FE−FEoffset)XKFi−
...(2) Here, FEN: Focus error signal converted to a predetermined detection gain with zero offset FE: Focus error signal read by the DSP 6 Focus error signal FEN converted in this way
is used to detect the in-focus point during focus search operation and to calculate compensation characteristics during focus servo operation (S4
), so that focus control is not actually affected by the offset or detection gain of the focus error signal.

By automatically performing the above processing (Sl-S4) each time a disk cassette is loaded, the target servo performance can always be obtained.

Next, the case of the tracking control device can be explained in substantially the same way as the case of the focus control device described above.

However, the difference is that the lens actuator 2 can be moved in the radial direction of the optical disc 1 (in the direction of arrow a' in FIG.
that the processing by the DSP 6 is performed using equations (3) and (4) described later instead of the above equations (1) and (2), and that it is performed after the focus servo operation has already been completed. It is the 1st prize.

That is, in tracking control, the lens actuator 2 is slowly reciprocated in the radial direction of the optical disc 1 by the DSP 6. Then, the peak value of the track error signal generated as the light spot S crosses the track is read, and based on these, the offset numerator E offset of the track error signal and a conversion constant for converting into a predetermined error detection gain are determined. KTII is determined by the following formula.

here.

TE, p: +peak value of the track error signal as a value read by the DSP 6 T E -p: One peak value of the track error signal T E P -P: The peak value of the track error signal when assuming a predetermined error detection gain It is a peak-to-peak value.

Next, the track servo operation begins, but at this time.

After the offset of the track error signal read by the DSP 6 is canceled using the following equation and the detection gain is converted to a predetermined value, a compensation characteristic calculation is performed.

TEN: (TE-TEoffset)XKrg”
(4) Here, TEN: Track error signal converted to a predetermined detection gain with zero offset TE: Track error signal read by the DSP6.

It should be noted that the present invention can be applied to either a so-called write-once type or a rewritable type optical disc device.

(Effects of the Invention) As described above, according to the present invention, the cancellation of the offset of the focus error signal and the track error signal and the detection gain adjustment are automatically performed by arithmetic processing by the DSP. This eliminates the need for complicated manual volume adjustments.

Furthermore, since the offset of each error signal is canceled and the detection gain is adjusted each time a new disk cassette or optical disk is loaded, even if there are variations in the characteristics of the optical disks used, this variation can be compensated for. This has the effect of contributing to improved compatibility of optical discs.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the main parts of an embodiment of the present invention, and FIG.
The figure is a flowchart showing processing in the DSP, Figure 3 is a block diagram showing the main parts of a conventional focus control device, Figure 4 is a block diagram of an error detection circuit, and Figures 5 (a) and (b).
2A and 2B are explanatory diagrams of waveforms of offset and gain before and after SU. 1... Optical disk 2... Lens actuator 3... Optical system 4... Error detection circuit 5...
・A/D converter 6...Digital signal processor (DSP) 7・
...D/A converter 8...Power amplifier S...
・Light spot

Claims (2)

[Claims] (1) An optical system that detects a focus shift of a light spot irradiated onto an optical disc, a focus error detection circuit connected to its output side, and A/D conversion of the focus error signal output from this focus error detection circuit. an A/D converter that periodically reads the focus error signal via the A/D converter, and detects the offset and a predetermined error based on the focus error signal each time the optical disc is loaded. A conversion constant for converting to a gain is calculated, and the offset is canceled using the offset and the conversion constant, and the detection gain is converted using the focus error signal to perform a focus search operation and a focus servo operation. a digital signal processor that performs compensation characteristic calculations and outputs a drive command value for controlling the position of the light spot; a D/A converter that converts the drive command value from D/A to analog; A focus control device for an optical disc device, comprising: a lens actuator that moves the position of the optical spot in the thickness direction of the optical disc based on the drive command value. (2) An optical system that detects the track deviation of the light spot irradiated onto the optical disk, a track error detection circuit connected to its output side, and A/D conversion of the track error signal output from the track error detection circuit. an A/D converter that periodically reads the track error signal via the A/D converter, and calculates the offset amount based on the track error signal after the optical disc is loaded and focus control is completed. and a conversion constant for converting to a predetermined error detection gain, the offset is canceled using the offset and the conversion constant, and the track servo operation is performed using the track error signal with the detection gain converted. a digital signal processor that performs compensation characteristic calculations and outputs a drive command value for controlling the position of the light spot; a D/A converter that converts the drive command value from D/A; and the D/A converter. A tracking control device for an optical disc device, comprising: a lens actuator that moves the position of the optical spot in a radial direction of the optical disc based on the drive command value transmitted through the optical disc.