JP2001143281A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To settle a problem where the offset bias injection rate that produces the least value of a C1 error rate cannot be decided and the automation is difficult for the focus balance control since the variation characteristic of the C1 error rate is very broad to the offset bias injection rate in regard to the conventional focus balance control where the C1 error rate is used as a barometer. SOLUTION: In this optical disk device, an RF signal equalizer circuit 2 has a means to perform the switching between the 1st equalizer characteristic that is used for normal reproduction of an RF signal and the 2nd equalizer characteristic that is used focus balance control respectively. The 2nd equalizer characteristic functions to secure the sharp variation of a C1 error rate to the offset bias injection rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device capable of automatically finding an optimum value of an offset bias injection amount for a focus servo constituting an optical pickup.

[0002]

2. Description of the Related Art In recent years, optical disk devices such as CD players and optical disk recording / reproducing devices have become widespread. Such an optical disk device has an optical pickup, irradiates a laser beam along a track on the disk, and detects the intensity of the reflected light to determine the presence or absence of a pit and information. Playing. Here, in order to always keep the spot diameter of the laser beam applied to the track on the disk in the best condition, the optical pickup also needs to slightly move up and down in accordance with the vertical movement of the disk. Therefore, the optical pickup has a focus servo. In order to always irradiate the center of the track with the laser beam, it is necessary to correct the eccentricity of the disk. Therefore, the optical pickup has a tracking servo.

If the optical pickup has large variations, an appropriate amount of offset bias is injected into a focus coil constituting the focus servo, and the spot shape is changed to an optimum shape by deliberately shifting the focal point. The pickup may be used at an operating point having better characteristics. The adjustment performed to obtain the optimum value of the offset bias injection amount is referred to as “focus balance adjustment” in the following description.

Normally, when the focus balance of an optical pickup provided in an optical disk device is adjusted, the C1 error rate, jitter, address signal error rate (for example, The optimum value of the offset bias injection amount must be determined while simultaneously considering a plurality of characteristic barometers, such as an error rate of an ADIP indicating a data storage position and the like, and a tracking error signal.

FIG. 5 is a block diagram showing a configuration of a main part of a conventional optical disk device. The optical disk device mentioned here as an example is one of the plurality of characteristic barometers described above.
The focus balance is adjusted by using, as a characteristic barometer, a C1 error rate that directly affects detection accuracy of a main signal (hereinafter, referred to as an RF signal) such as a recording signal. First, the RF signal output from the optical pickup 20 is adjusted in frequency characteristics and the like by an RF signal equalizer circuit 21, and then the RF signal demodulation circuit 22
Performs demodulation of an RF signal and detection of a flag such as a C1 error. The microcomputer 2 detects the C1 error detected here.
A calculation process is performed in step 5, and the calculation result is displayed on the display unit 26 as a C1 error rate.

On the other hand, a focus error signal output from the optical pickup 20 is subjected to arithmetic processing by a focus balance variable circuit 23, and then is amplified by a focus error signal amplifier 24. The focus error signal is a difference signal of signal strength obtained from each of the plurality of divided light receiving elements. Therefore, the focus balance signal can be intentionally varied by increasing the signal strength of one of the focus balance variable circuits 23 and weakening the signal strength of the other. Here, since the current value applied to a focus servo (not shown) constituting the optical pickup 20 is controlled based on the focus error signal, the offset error is intentionally varied by intentionally varying the focus error signal. It is possible to control the amount of bias injection.

Here, the operator who performs the focus balance adjustment manually adjusts the switch 27 while monitoring the C1 error rate displayed on the display section 26 to perform the focus balance adjustment. The microcomputer 25 varies the focus error signal by issuing an instruction to the focus balance varying circuit 23 according to the input of the switch 27. Hereinafter, a specific method of such manual focus balance adjustment will be described with reference to FIG.

FIG. 6 is a graph showing the variation characteristics of the C1 error rate with respect to the offset bias injection amount. The abscissa indicates the amount of offset bias injection, and the right side indicates the injection amount plus and the left side indicates the injection amount minus. On the other hand, the vertical axis indicates the C1 error rate. A curve 28 shows a variation characteristic of the C1 error rate with respect to the offset bias injection amount. As the focus balance adjustment, it is desirable to determine the offset bias injection amount that provides the minimum value of the C1 error rate, and set the offset bias injection amount to an optimum value. However, since the variation characteristic of the C1 error rate is very broad, it is difficult to determine the minimum value. Therefore, conventionally, the following operation is performed as a suboptimal method.

While monitoring the C1 error rate on the display unit 26, the operator operates the switch 27 to change the offset bias injection amount from 0 to the plus side.
An offset bias injection amount a when the C1 error rate reaches a threshold value x appropriately determined in advance is obtained. Subsequently, the operator shifts the offset bias injection amount from 0 to the negative side, and obtains the offset bias injection amount b when the C1 error rate reaches the threshold value x as before. By calculating the average value c of a and b thus obtained, the optimum value of the offset bias injection amount is obtained.

[0010]

However, as shown in FIG. 6, the offset bias injection amount C
The variation characteristic of one error rate is broad. Therefore, in the method of performing the focus balance adjustment using the C1 error rate as a characteristic barometer as described above, the C1 error rate does not reach the threshold x unless a very large offset bias is injected into the plus side and the minus side. There are many. However, when trying to measure the C1 error rate by increasing the offset bias injection amount unnecessarily, the focus servo drive range may be deviated and adjustment may not be possible. Also, since the focus balance adjustment is performed while reading information from the disk, if the offset bias injection amount is too large, the ADIP error rate described above increases, and the disk cannot be rotated at a constant linear velocity. ,
There is also concern that tracing itself will not be possible. Therefore, even if the microcomputer 25 automatically adjusts the focus balance, it may not be correctly completed.

As described above, when performing the focus balance adjustment, while simultaneously considering a plurality of characteristic barometers such as a C1 error rate, a jitter, an address signal error rate, and a tracking error signal, the optimum amount of the offset bias injection amount is determined. Although it is desirable to determine the value, it is difficult to simultaneously monitor a plurality of characteristic barometers when the operator manually adjusts the focus balance as in the related art. For this reason, at present, only one characteristic barometer is monitored, and focus balance adjustment is performed for the other characteristic barometers so that the characteristic barometer is additionally referred to.

An object of the present invention is to provide an optical disk device capable of automatically adjusting the focus balance without unnecessarily increasing the offset bias injection amount.

[0013]

In order to achieve the above object, an optical disk device according to the present invention comprises: an optical disk device having an equalizer circuit for reproducing a signal read from a disk; Is provided with means for switching between a first equalizer characteristic normally used when reproducing a signal read from a disk and a second equalizer characteristic used when obtaining an optimum value of an offset bias injection amount for an optical pickup. ing. More specifically, the second equalizer characteristic is a characteristic that makes the variation characteristic of the C1 error rate with respect to the offset bias injection amount steep, and when obtaining the optimum value of the offset bias injection amount, The C1 error rate that fluctuates with this is measured, and the offset bias injection amount that provides the minimum C1 error rate is adopted as an optimum value.

Further, when obtaining the optimum value of the offset bias injection amount for the optical pickup, a plurality of characteristic barometers which fluctuate in accordance with the offset bias injection amount are measured simultaneously, and a judgment criterion based on the measured value of each characteristic barometer Means for automatically determining the optimum value of the offset bias injection amount by assigning priorities to. Specifically, the C1 error rate and the tracking error signal are measured as the characteristic barometer.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a main part of an optical disk device according to the present invention. The optical disk device according to the present embodiment performs focus balance adjustment by using a C1 error rate and a tracking error signal as a characteristic barometer. First, with respect to the RF signal output from the optical pickup 1, the RF signal equalizer circuit 2 adjusts the frequency characteristics and the like, and then the RF signal demodulation circuit 3 demodulates the RF signal and detects a flag such as a C1 error. Do. The C1 error detected here is subjected to calculation processing by the microcomputer 7 and used as a C1 error rate for focus balance adjustment. The demodulated signal is sent to a reproduction circuit, a data decompression circuit, and the like (neither is shown), and the signal is reproduced.

On the other hand, the focus error signal output from the optical pickup 1 is subjected to arithmetic processing by a variable focus balance circuit 4 and subsequently amplified by a focus error signal amplifier 5. The focus error signal is a difference signal of signal strength obtained from each of the plurality of divided light receiving elements. Therefore, the focus balance variable circuit 4 increases the signal strength of one of the
By weakening the other signal intensity, the focus error signal can be intentionally varied. Here, since the current value applied to a focus servo (not shown) constituting the optical pickup 1 is controlled based on the focus error signal, the offset error can be controlled by intentionally varying the focus error signal. It is possible to control the amount of bias injection.

The tracking error signal output from the optical pickup 1 is amplified by a tracking error signal amplifier 6 and then passed through a drive circuit (not shown) for driving a tracking servo. This is fed back to the pickup 1. The tracking error signal detected here is sent to the microcomputer 7 to be used for focus balance adjustment.

Here, in the optical disk device according to the present invention, the RF signal equalizer circuit 2 is provided with a first equalizer characteristic (hereinafter, referred to as a "normal use mode") which is normally used when reproducing the RF signal read from the disk. ) And a second equalizer characteristic (hereinafter, referred to as a “focus balance adjustment mode”) used when performing the focus balance adjustment, and the operator starts the focus balance adjustment. Then, the microcomputer 7 automatically starts the focus balance adjustment by issuing an instruction to the RF signal equalizer circuit 2 and the focus balance variable circuit 4. The progress of the focus balance adjustment is displayed on a display unit 8 connected to the microcomputer 7 at appropriate times. Hereinafter, the equalizer characteristics of the RF signal equalizer circuit 2 and switching thereof will be described.

FIG. 2 is a graph showing the equalizer characteristics of the RF signal equalizer circuit 2 provided in the optical disk device according to the present invention. In the figure, the horizontal axis represents frequency, and the vertical axis represents RF signal gain. The equalizer characteristic generally means a frequency characteristic related to the reproduction of an RF signal, but in the following description, it means a characteristic that takes into account not only the frequency characteristic but also the phase characteristic. Here, the curve 9 indicates the equalizer characteristic in the “normal use mode”, that is, the equalizer characteristic normally used when reproducing the RF signal. In any optical disk device, the signal detection sensitivity is lower on the high frequency side than on the low frequency side. To compensate for this, the boost amount on the high frequency side is increased.

On the other hand, a curve 10 is an equalizer characteristic in the "focus balance adjustment mode", that is, an equalizer characteristic used only at the time of focus balance adjustment. In the equalizer characteristic in the “focus balance adjustment mode”, the boost amount on the high frequency side is reduced, and the phase characteristic is also adjusted so that a phase shift does not occur. Such switching of the equalizer characteristics is performed by digital processing, and can be relatively easily realized by configuring the RF signal equalizer circuit 2 with a digital filter or the like.

A specific effect of the above-described switching of the equalizer characteristics will be described. FIG. 3 is a graph showing the variation characteristics of the C1 error rate and the tracking error signal with respect to the offset bias injection amount. The abscissa indicates the amount of offset bias injection, and the right side indicates the injection amount plus and the left side indicates the injection amount minus. On the other hand, the vertical axis indicates the C1 error rate and the tracking error signal. Here, a curve 11 is a variation characteristic of the C1 error rate when the equalizer characteristic of the RF signal equalizer circuit 2 is set to the “normal use mode”. On the other hand, a curve 12 shows a variation characteristic of the C1 error rate when the equalizer characteristic is switched to the “focus balance adjustment mode”. Curve 13 shows the fluctuation characteristics of the tracking error signal.

As shown in the figure, by switching the equalizer characteristics of the RF signal equalizer circuit 2 from the "normal use mode" to the "focus balance adjustment mode", the C1 error rate with respect to the offset bias injection amount is increased as a whole. And the fluctuation characteristics become steep. As described above, only at the time of focus balance adjustment, the equalizer characteristic of the RF signal equalizer circuit 2 is switched to a characteristic optimal for focus balance adjustment, thereby achieving C
The minimum value of one error rate can be determined. Accordingly, it is not necessary to increase the offset bias injection amount to the plus side and the minus side as in the related art, so that the focus balance can be adjusted without lowering the trace performance.

Next, a specific procedure of the automatic focus balance adjustment will be described. FIG. 4 is a flowchart of the automatic focus balance adjustment. When the operator starts focus balance adjustment, the microcomputer 7 switches the equalizer characteristic of the RF signal equalizer circuit 2 to "focus balance adjustment mode" in step # 10. Thereby, C with respect to the offset bias injection amount
The fluctuation characteristic of one error rate shifts from the curve 11 to the curve 12 as shown in FIG.

Subsequently, at step # 15, the microcomputer 7
Is the sum of m points on the minus side and m points on the plus side with the point at which the offset bias injection amount is 0 as the center (2m + 1)
Point a C1 error rate, and sets the measurement point a _n of the tracking error signal. Here, by including a point offset bias injection amount 0 to the measurement point a _n, there is no need to inject the offset bias, which may be realized ideal focus balance adjustment. In the present embodiment, m is set to 3, and a total of seven points a _{1 to} a ₇ with a ₄ (= 0) as the center are set as measurement points. Further, the injection range of the offset bias and the number of measurement points may be appropriately determined according to the characteristics of the optical pickup 1.

[0025] Setting of measurement points a _n at the step # 15 is completed, the said microcomputer 7 at step # 20 n =
By setting 1, the measurement is started in order from the negative side of the offset bias injection amount. First, at step # 25, the values of the C1 error rate (x ₁ ) and the tracking error signal (y ₁ ) at the offset bias injection amount a ₁ are measured, and the measured values are stored. Here, in the check of the C1 error rate in step # 30, the C1 error rate (x _n ) measured this time is _equal to the C1 error rate measured last time.
If it is increasing compared to the error rate (x _n-1 ),
At that point, the process proceeds to step # 45, and the measurement ends. Otherwise, proceed to step # 35, where the count number of n is 1
Are added.

In step # 40, the count is checked. If n is larger than 2m + 1, that is, if the measurement at all the measurement points is completed, the process proceeds to step # 45, and the measurement is completed. Otherwise continue the measurement of the C1 error rate returns to the step # 25 (x _n), and a tracking error signal (y _n). In the present embodiment, since the C1 error rate in a ₄ (x ₄₎ has increased compared to the C1 error rate in a ₃ (x _3), is measured at three points of a ₁ ~a ₃ rows After the measurement, the measurement ends.

When the measurement is completed in step # 45, the flow advances to step # 50 to determine the optimum value of the offset bias injection amount. There are three priorities for the judgment criteria, and the microcomputer 7 adopts, as the optimum value, the offset bias injection amount that satisfies the judgment criteria of higher priority. Hereinafter, each criterion will be described.

First, the first criterion is a measurement point (a _{1 to an -1} ) of the C1 error rate and the tracking error signal.
Among them, the offset bias injection amount providing the minimum C1 error rate is determined as the optimum value. here,
a _n-1 is a measurement point one step before the C1 error rate starts to increase. As described above, since the C1 error rate is an important barometer that directly affects the detection accuracy of the optical pickup 1, a determination criterion in which obtaining the minimum value is given the highest priority is provided. In this embodiment, a ₂
And the C1 error rate (x ₂ ) at a ₃
Since the error rate (x ₃ ) has the same value and the minimum value, the measurement points satisfying the first criterion are _two points a ₂ and a ₃ .

Next, the second criterion is to determine the injection amount of the offset bias providing the maximum tracking error signal as the optimum value when there are a plurality of measurement points satisfying the first criterion. This is because, when the C1 error rate is the same, it can be said that the larger the tracking error signal, the more stable the optical pickup 1 is at the operating point. As described above, it is preferable to use a characteristic barometer to be adjusted with particular emphasis on the determination criterion for the second priority. In the present embodiment, the tracking error signal at the measurement point (a ₂ , a ₃ ) that satisfies the first determination criterion is again the same value (y ₂ , y ₃ ) and becomes the maximum value. The measurement points satisfying the second criterion are 2 of a ₂ and a ₃
Points.

Further, the third criterion is that if there are a plurality of measurement points satisfying the second criterion, the center (=
The offset bias injection amount close to 0) is determined as the optimum value. By providing such a criterion, it is possible to adjust the focus balance with as little an offset bias injection amount as possible. In the present embodiment, among the measurement points (a ₂ , a ₃ ) satisfying the second determination criterion, the measurement point closest to the center is a ₃ , so that the third
Measurement point that meets the criteria is only a _3.

A measurement point that satisfies the above criterion is adopted as the optimum value of the offset bias injection amount in step # 55. Thereafter, in step # 60, the microcomputer 7 returns the equalizer characteristics of the RF signal equalizer circuit 2 to the “normal use mode”. As a result, the variation characteristic of the C1 error rate with respect to the offset bias injection amount shifts from the curve 12 to the curve 11 as shown in FIG. 3, and the focus balance adjustment ends.

According to the above procedure, the focus balance can be automatically adjusted, so that the optimum value of the offset bias injection amount for the optical pickup 1 can be obtained in a very short time. As a result, the work time required for the focus balance adjustment can be reduced, and the work efficiency can be greatly improved. Further, unlike the related art, since the operator does not need to manually perform the focus balance adjustment, there is no variation in the adjustment due to individual differences, and it is possible to perform a highly accurate and stable focus balance adjustment.

In this embodiment, the criterion is 3
As an example, the C1 error rate, the tracking error signal, and the absolute value of the offset bias injection amount are determined. However, the determination criterion is not limited thereto. The characteristic barometer and the like may be changed.

[0034]

The RF signal equalizer circuit provided in the optical disk device according to the present invention has a first equalizer characteristic used for normal reproduction of an RF signal and a second equalizer characteristic used for focus balance adjustment. , Means for switching. Specifically, the second equalizer characteristic is a characteristic that makes the fluctuation characteristic of the C1 error rate with respect to the offset bias injection amount steep, and when obtaining the optimum value of the offset bias injection amount, Then, the C1 error rate fluctuating is measured, and the offset bias injection amount providing the minimum C1 error rate is adopted as an optimum value. This eliminates the necessity of increasing the offset bias injection amount to the plus side and the minus side as in the related art, so that the focus balance can be adjusted without lowering the trace performance.

Further, when obtaining the optimum value of the offset bias injection amount for the optical pickup, a plurality of characteristic barometers that fluctuate according to the offset bias injection amount are measured simultaneously, and a determination criterion based on the measured value of each characteristic barometer Means for automatically determining the optimum value of the offset bias injection amount by assigning priorities to. Specifically, the C1 error rate and the tracking error signal are measured as the characteristic barometer. Accordingly, the focus balance can be automatically adjusted, so that the optimum value of the offset bias injection amount for the optical pickup can be obtained in a very short time, and the work efficiency can be greatly improved. Further, unlike the related art, since the operator does not need to manually perform the focus balance adjustment, there is no variation in the adjustment due to individual differences, and it is possible to perform a stable and accurate focus balance adjustment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of an optical disk device according to the present invention.

FIG. 2 shows an optical disc device according to the present invention;
5 is a graph showing an equalizer characteristic of the F signal equalizer circuit 2.

FIG. 3 is a graph showing a variation characteristic of a C1 error rate and a tracking error signal with respect to an offset bias injection amount.

FIG. 4 is a flowchart of automatic focus balance adjustment.

FIG. 5 is a block diagram showing a configuration of a main part of a conventional optical disk device.

FIG. 6 is a graph showing a variation characteristic of a C1 error rate with respect to an offset bias injection amount.

[Explanation of symbols]

 Reference Signs List 1 optical pickup 2 RF signal equalizer circuit 3 RF signal demodulation circuit 4 variable focus balance circuit 5 focus error signal amplifier 6 tracking error signal amplifier 7 microcomputer 8 display unit

Claims (5)

[Claims] 1. An optical disk device having an equalizer circuit related to reproduction of a signal read from a disk, wherein the equalizer circuit includes a first equalizer characteristic normally used when reproducing a signal read from the disk, and an optical disk. An optical disk device comprising means for switching between a second equalizer characteristic used for obtaining an optimum value of an offset bias injection amount for a pickup. 2. The optical disk device according to claim 1, wherein the second equalizer characteristic is a characteristic that makes the fluctuation characteristic of the C1 error rate with respect to the offset bias injection amount steep. 3. An optimum value of the offset bias injection amount is obtained by measuring a C1 error rate that fluctuates with the offset bias injection amount, and using the offset bias injection amount that provides the minimum C1 error rate as an optimum value. The optical disk device according to claim 2, wherein the optical disk device is employed. 4. An optimum value of an offset bias injection amount for an optical pickup, wherein a plurality of characteristic barometers which fluctuate according to the offset bias injection amount are measured simultaneously, and a criterion based on a measured value of each characteristic barometer. An optical disc device characterized in that the optimum value of the offset bias injection amount is automatically determined by assigning priorities to the optical disk devices. 5. The optical disk device according to claim 4, wherein a C1 error rate and a tracking error signal are measured as the characteristic barometer.