JPH0877579A - Method and device for adjusting focus bias - Google Patents

Abstract

PURPOSE: To easily calculate a suitable focus bias voltage value as its central value even for either optical disk or magneto-optical disk and to attain automatic adjustment by detecting error rate limit values in a near side and a far side. CONSTITUTION: A focus bias(FB) is changed in the direction where an objective lens 3a is moved to the far side parting from the disk 1 by variably controlling an electronic volume 22 while executing reproducing operation. At this time, a group error rate(GE) and a block error rate (BE) are monitored by information from an encoder/decoder part 8 whenever the FB is changed. Then, the FB is changed to the far side until either one of the GE and the BE arrives at a read limit error rate(LER). When the GE or the BE arrives at the LER, the resistance value of the volume 22 is stored, and the optimum FB is calculated by prescribed operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus bias adjusting method and a focus bias adjusting device for a recording device and a reproducing device corresponding to a recording medium such as an optical disc and a magneto-optical disc.

[0002]

2. Description of the Related Art In a recording device and a reproducing device corresponding to a disc-shaped recording medium such as an optical disc and a magneto-optical disc, a light beam output from an optical head is controlled so as to have an appropriate focus state on a disc recording surface. For this reason, a focus servo system for driving focus control by driving the objective lens in the optical head toward and away from the disk recording surface is provided. The focus error signal is generated by calculating reflected light information obtained by the optical head, but a bias voltage is added to the focus error signal.

[0003]

In the case of a CD (Compact Disc) player, the bias voltage value for the focus error signal is generally adjusted to the best RF jitter point. FIG. 4 shows the RF reproduction signal error rate BE (hereinafter, referred to as a block error rate) with respect to the focus bias voltage value. Here, when the bias voltage is changed to the near side (the direction in which the objective lens approaches the disk) and the far side (the direction in which the objective lens moves away from the disk), the block error rate BE increases, and at a certain point. Is the reading limit error rate.

The best jitter point is the center point between the two points which are the read limit error rates on the near side and far side, and in the figure, focus bias voltage value =
This is the point that is V _B1 . The voltage value of the focus bias is the voltage value V that is the best point of this jitter.
It will be adjusted to _B1 . As the actual adjustment work,
The operator varied the focus bias voltage while observing the eye pattern of the RF signal, and adjusted the voltage value so that the diamond in the center of the eye pattern was most visible.

Also in the mini disk system, the disk is a reproduction-only premastered disk (optical disk).
If so, the focus bias value may be adjusted as in the case of CD. However, when a recordable magneto-optical disk is used in the mini disk system, the best jitter point does not match the best focus bias point.

In the magneto-optical area of the mini disk, a groove is formed on the disk, and absolute position information (groove address) is obtained by this groove. Further, the disk rotation servo is applied by the sync information of the groove address. Then, when the objective lens moves toward the far side with respect to the disc,
This is because the reproduction error rate GE of the groove address (hereinafter referred to as the groove error rate) starts to deteriorate earlier than the block error rate BE. Further, when the objective lens moves toward the near side with respect to the disc, the block error rate BE first deteriorates.

When the groove error rate GE exceeds the reading limit error rate, the rotary servo becomes unstable and the data reproducing operation is hindered. Therefore, the best point of the focus bias voltage is as shown in FIG. Bias voltage value V _B4 at which the groove error rate GE on the side reaches the read limit error rate and block error rate B on the near side
Bias voltage value V _{B3 at which} E reaches the reading limit error rate
And the central voltage value V _B0 between the two. That is, it is a point different from the bias voltage value V _B1 when the jitter best point is reached.

It is difficult to adjust the focus bias voltage to such a point by a method of varying the voltage while observing the eye pattern, and there is a problem that the adjustment work becomes very inefficient. .

[0009]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an adjusting method for simplifying focus bias adjustment, and an adjusting device for automating the focus bias adjustment. To do.

The focus bias adjusting method of the present invention is performed in the following procedure. The procedure of may be reversed. The error rate is monitored while changing the focus bias voltage so that the focus point moves toward the disk proximity side, and the focus bias voltage value when the error rate reaches a predetermined limit value is detected. In this case, the focus bias voltage value detected becomes the value of V _B3 at which the block error rate BE of FIG. 4 or 5 reaches the limit value as the error rate. The error rate is monitored while changing the focus bias voltage so that the focus point moves toward the far side of the disc, and the focus bias voltage value when the error rate reaches a predetermined limit value is detected. The focus bias voltage value detected in this case is the value of V _B2 at which the block error rate BE of FIG. 4 reaches the limit value as the error rate in the case of an optical disc, and the reproduction error rate in the case of a magneto-optical disc. Is the value of V _B4 at which the groove error rate GE of FIG. 5 reaches the limit value. A focus bias voltage value that is an intermediate value between the two detected focus bias voltage values is calculated and used as the focus bias voltage value to be adjusted. Therefore, in the case of an optical disc, the focus bias voltage value V _B1 is obtained by the calculation of (V _B2 + V _B3 ) / 2. In the case of a magneto-optical disk, the focus bias voltage value V _B0 is obtained by calculating (V _B4 + V _B3 ) / 2.

Next, as a focus bias adjusting device, a focus bias means for applying a focus bias voltage to a focus error signal generated using reflected light information from a disk-shaped recording medium, and a focus bias voltage value in the focus bias means. Bias voltage changing means capable of variably setting
There is provided an error rate monitoring means capable of monitoring the error rate of the F signal and the error rate of the address information reproduced from the groove of the disc-shaped recording medium. Further, focus bias adjustment control means for adjusting the focus bias by the above method is provided. That is, the focus bias adjustment control means controls the bias voltage varying means to vary the focus bias voltage so that the focus points are on the disk proximity side and the disk distant side, and the error rate on the disk proximity side and the disk distant side respectively. The focus bias voltage value at which is a predetermined limit value is detected. Then, a voltage value intermediate between the detected two focus bias voltage values is calculated,
The bias voltage varying means can be controlled so that the calculated voltage value is given to the focus error signal by the focus bias means.

[0012]

By detecting the error rate limit value on the near side and the far side, it is possible to easily calculate the optimum focus bias voltage value as the median value of either the optical disk or the magneto-optical disk. Also, automatic adjustment is possible.

[0013]

Embodiments of the present invention will be described below. FIG. 2 is a block diagram of a magneto-optical disk recording / reproducing apparatus (mini disk recording / reproducing apparatus) in which the embodiment is adopted.

In FIG. 2, reference numeral 1 is a magneto-optical disk or optical disk, and the disk 1 is rotationally driven by a spindle motor 2. An optical head 3 irradiates the disk 1 with laser light during recording / reproduction, and provides a high level laser output for heating the recording track to the Curie temperature during recording on the magneto-optical disk, and during reproduction. The magnetic Kerr effect provides a relatively low level of laser power for detecting data from reflected light.

When the disc 1 is an optical disc in which data is recorded in the form of pits like a CD, the optical head 3 does not have the magnetic Kerr effect but the reflected light level depending on the presence or absence of pits as in the case of a CD player. The reproduction RF signal is extracted according to the change. Of course, the magnetic field recording operation described later is not executed on the optical disc.

In order to perform the data read operation from the disk 1 as described above, the optical head 3 detects the laser diode as the laser output means, the optical system including the deflecting beam splitter and the objective lens, and the reflected light. A detector is installed. The objective lens 3a is held by a biaxial mechanism 4 so as to be displaceable in the disc radial direction and the direction in which it comes in and out of contact with the disc, and the entire optical head 3 is movable in the disc radial direction by a sled mechanism 5.

As a detector for detecting the reflected light, a four-division detector (A, B, C, D) as shown in FIG.
And side spot detectors (E, F), and R
The detector (I, J) for F detection is mounted. These detectors are irradiated with the reflected light from the disc 1 via the Wollaston prism 3b.

Reference numeral 6a denotes a magnetic head for applying a magnetic field modulated by the supplied data to the magneto-optical disk, and is arranged at a position facing the optical head 3 with the disk 1 in between. The magnetic head 6a is moved in the disk radial direction by the sled mechanism 5 together with the optical head 3.

Information detected from the disk 1 by the optical head 3 by the reproducing operation, that is, the detectors A, B,
The outputs of C, D, E, F, I and J are supplied to the RF amplifier 7. The RF amplifier 7 calculates the supplied information by reproducing RF signals, tracking error signals, focus error signals, and absolute position information (absolute position information recorded as pregrooves (wobbling grooves) on the magneto-optical disk 1). Address information, subcode information, focus information (FOK signal), etc. are extracted. Then, the extracted reproduction RF signal is supplied to the encoder / decoder unit 8. Further, the tracking error signal and the focus error signal are supplied to the servo circuit 9. Further FOK
The signal is supplied to the system controller 11.

The RF signal is generated in the RF amplifier 7 by using the output of the detector (I, J). That is, I-J for magneto-optical data, and I + for pit data.
The data by the process of J is extracted. Further, the focus error signal is processed by the RF amplifier 7 by the arithmetic processing (A + C)-(B of the output of the four-division detector (A, B, C, D).
+ D) is executed and generated. The output of the detector (E, F) is used as the tracking error signal and is generated by the calculation of E−F. Furthermore, (A + D)-(B +
The push-pull signal of C) is supplied to the address decoder 10 as groove information.

The servo circuit 9 generates various servo drive signals according to the supplied tracking error signal, focus error signal, track jump command, seek command, rotational speed detection information from the system controller 11, etc., and the biaxial mechanism 4 and The sled mechanism 5 is controlled to perform focus and tracking control, and the spindle motor 2 is controlled to a constant linear velocity (CLV).

The reproduced RF signal is supplied to the encoder / decoder section 8
Then, the EFM demodulation and the decoding process such as CIRC are performed, and the memory controller 12 once writes the data in the buffer RAM 13. The reading of data from the magneto-optical disk 1 by the optical head 3 and the reproduction data transfer from the optical head 3 to the buffer RAM 13 are performed at 1.41 Mbit / sec (intermittently).

The data written in the buffer RAM 13 is read out at the timing when the reproduction data is transferred at 0.3 Mbit / sec, and is supplied to the encoder / decoder section 14. Then, a reproduction signal process such as a decoding process for the audio compression process is performed, an analog signal is formed by the D / A converter 15, and the analog signal is supplied from a terminal 16 to a predetermined amplification circuit section and reproduced and output. For example, it is output as L and R audio signals.

As described above, the data read from the disk 1 is once written into the buffer RAM 13 intermittently at a high speed rate, and then read at a low speed rate to output audio, so that, for example, the tracking servo is temporarily lost and the disk 1 is read. A so-called shock proof function is realized in which the voice output is continued without interruption even if the data reading from the device becomes impossible.

The address decoder 10 performs FM demodulation and biphase decoding on the groove information supplied from the RF amplifier 7 and outputs a groove address (absolute position information). The groove address and the address information decoded by the encoder / decoder unit 8 are transmitted via the encoder / decoder unit 8 to the system controller 1
1 and is used for various control operations. For the magneto-optical disk, the groove address synchronization signal is used for spindle servo control. For the optical disc, the spindle servo control is executed by the EFM sync as in the CD system. In addition, encoder /
The decoder unit 8 supplies the information of the block error rate BE for the RF signal and the groove error rate GE for the groove address to the system controller 11.

When a recording operation is performed on the disk (magneto-optical disk) 1, the recording signal (analog audio signal) supplied to the terminal 17 is converted into an A / D converter 18
After being converted into digital data by, the data is supplied to the encoder / decoder unit 14 and subjected to audio compression encoding processing. The recording data compressed by the encoder / decoder unit 14 is once written in the buffer RAM 13 by the memory controller 12, is also read at a predetermined timing, and is sent to the encoder / decoder unit 8. Then, the encoder / decoder unit 8 performs CIRC encoding, E
It is supplied to the magnetic head drive circuit 6 after being subjected to encoding processing such as FM modulation.

The magnetic head drive circuit 6 supplies a magnetic head drive signal to the magnetic head 6a according to the encoded recording data. That is, the magnetic head 6a applies an N or S magnetic field to the magneto-optical disk 1. Further, at this time, the system controller 11 supplies a control signal to the optical head 3 so as to output a laser beam of a recording level.

Reference numeral 19 denotes an operation input section provided with keys used for user operation, and 20 denotes a display section composed of, for example, a liquid crystal display. Reference numeral 21 denotes a non-volatile RAM. The nonvolatile RAM 21 can store the adjustment value of the focus bias as described later. 22
Shows an electronic volume as a focus bias changing means. The resistance value of the electronic volume 22 sets the offset bias voltage value given to the focus error signal.

In such a recording / reproducing apparatus, the focus bias adjusting apparatus of this embodiment is configured as a circuit in the RF amplifier 7, the encoder / decoder section 8, the system controller 11, and the electronic volume 22.

For automatic adjustment of the focus bias,
The system controller 11 will perform the processing of FIG. First, while performing the reproducing operation, the electronic volume 22 is variably controlled, and the focus bias voltage is changed in the direction in which the objective lens 3a moves to the near side close to the disc 1 (F101). At this time, every time the focus bias voltage is changed, the encoder /
The block error rate B according to the information from the decoder unit 8
Monitor E (F102). Then, the block error rate B
The focus bias voltage is changed until E reaches the reading limit error rate.

At the time when the focus bias voltage reaches V _B3 in FIG. 4 or 5, the block error rate B
E will reach the read limit error rate. Here, the process proceeds to step F103, and the focus bias voltage V _B3 at that time is stored in the internal register. Actually, the resistance value of the electronic volume 22 at this time (the resistance value for setting the focus bias voltage to V _B3 ) may be stored.

Next, while executing the reproducing operation in the same manner,
By variably controlling the electronic volume 22, the focus bias voltage is changed in the direction in which the objective lens 3a moves to the far side away from the disc 1 (F104).
At this time, every time the focus bias voltage is changed, the groove error rate GB and the block error rate BE are monitored by the information from the encoder / decoder unit 8 (F105). Then, the focus bias voltage is changed to the far side until either the groove error rate GB or the block error rate BE reaches the read limit error rate.

When the disk 1 is a magneto-optical disk, the groove error rate GE reaches the read limit error rate when the focus bias voltage becomes V _B4 in FIG. Therefore, the process proceeds to step F106, and the focus bias voltage V _B4 at that time is stored in the internal register. In addition, the resistance value of the electronic volume 22 at this time may be actually stored. When the disc 1 is an optical disc, the block error rate BE reaches the read limit error rate when the focus bias voltage becomes V _B2 in FIG. There step
In step F106, the focus bias voltage V _B2 at that time (the resistance value of the electronic volume 22 for obtaining the focus bias voltage V _B2 ) is stored in the internal register.

Then, in step F107, the median value of the two focus bias voltage values stored in the register is calculated. That is, when the disk 1 is a magneto-optical disk, (V _B3 + V _B4 ) / 2 is calculated to calculate the optimum focus bias voltage V _B0 . When the disc 1 is an optical disc, (V _B3 + V _B2 ) / 2 is calculated, and the optimum focus bias voltage V _B1 is calculated. Of course, when stored as the resistance value of the electronic volume 22, the resistance value of the electronic volume 22 for setting the optimum focus bias voltage V _B0 or V _B1 is calculated.

Then, in step F108, by controlling the electronic volume 22 to the calculated resistance value, the focus bias voltage is controlled to V _B0 or V _B1 as the optimum value, and the adjusting operation ends. By the above adjustment operation, for example, it becomes unnecessary for the operator to make a difficult adjustment while looking at the eye pattern, and the adjustment process is very efficient. Particularly, in the case of the magneto-optical disk, the adjustment, which was very difficult, can be easily completed in a short time. It is also possible to make adjustments during the actual playback operation.

In step F109, the values of V _B0 and V _B1 (the resistance value at that time) calculated by the adjusting operation are stored in the nonvolatile R
You may make it memorize | store in AM21. For example, by executing the focus bias voltage adjusting operation as described above for each of the optical disk and the magneto-optical disk when the recording / reproducing apparatus is shipped from the factory, the nonvolatile R
The AM 21 stores adjustment values for the optical disc and the magneto-optical disc. Thereby, for example, at the time of reproduction operation, the stored adjustment value can be read out and the electronic volume 22 can be set according to the disc to be reproduced (whether it is a premastered disc or a recordable disc), and the focus bias voltage is It will be set to the proper state according to the disc.

Further, the point where the error rate deteriorates may be narrowed or deviated toward the center on the far side and the near side due to changes with time. However, an adjustment operation is performed during use to determine the best value of the focus bias voltage at that time. It is also possible to judge the occurrence of a defect by comparing with the value initially stored in the nonvolatile RAM 21, for example.

By the way, although the focus bias is changed by the electronic volume 22, for example, a PWM signal corresponding to the focus bias value set by the system controller 11 is output, and this is subjected to frequency / voltage conversion by a filter circuit, and is then used as it is. It may be applied to the focus error signal as a bias value.

[0039]

As described above, according to the present invention, the reproduction error rate is monitored while changing the focus bias voltage in the direction in which the focus point is on the near side and the far side, and the reproduction error rate is a predetermined limit value. The focus bias voltage value at the time of reaching is detected. And
A voltage value intermediate between the two detected focus bias voltage values is calculated and used as the focus bias voltage value. Therefore, the optimum bias value can be easily calculated not only for the optical disc and the magneto-optical disc, but also the focus bias adjustment can be automated, so that the efficiency of the adjustment process can be realized.

[Brief description of drawings]

FIG. 1 is a flowchart of a focus bias adjustment operation according to an embodiment.

FIG. 2 is a block diagram of a recording / reproducing apparatus to which the embodiment is adopted.

FIG. 3 is an explanatory diagram of a detector of the recording / reproducing apparatus of the embodiment.

FIG. 4 is an explanatory diagram of a change in error rate with respect to a facus bias value on an optical disc.

FIG. 5 is an explanatory diagram of a change in error rate with respect to a facus bias value in a magneto-optical disk.

[Explanation of symbols]

 1 disk 3 optical head 3a objective lens 4 two-axis mechanism 7 RF amplifier 9 servo circuit 8, 14 encoder / decoder section 11 system controller 12 memory controller 13 buffer RAM 21 non-volatile RAM 22 electronic volume

Claims (2)

[Claims] 1. A method for adjusting a focus bias in a focus servo system of a recording or reproducing apparatus corresponding to a disk-shaped recording medium, wherein an error rate is monitored while changing a focus bias voltage so that a focus point moves toward a disk proximity side. Then, the focus bias voltage value when the error rate reaches a predetermined limit value is detected, and the error rate is monitored while changing the focus bias voltage so that the focus point goes to the far side of the disc. When the focus bias voltage value reaches a predetermined limit value, a focus bias voltage value intermediate between the two detected focus bias voltage values is calculated, and the focus bias voltage value is set as the focus bias voltage value. Focus bias adjustment method 2. A focus bias unit for applying a focus bias voltage to a focus error signal generated using reflected light information from a disk-shaped recording medium, and a focus bias voltage value in the focus bias unit can be variably set. Bias voltage varying means, error rate monitoring means capable of monitoring the error rate of the reproduction RF signal and the error rate of the address information reproduced from the groove of the disk-shaped recording medium, and controlling the bias voltage varying means, The focus bias voltage is varied so that the focus point is on the disk proximity side and the disk distant side, and the focus bias voltage value at which the error rate becomes a predetermined limit value on each of the disk proximity side and the disk distant side is detected,
Focus capable of controlling the bias voltage varying means so that a voltage value intermediate between the two detected focus bias voltage values is calculated and the calculated voltage value is given to the focus error signal by the focus bias means. A focus bias adjustment device comprising: bias adjustment control means.