JPH01128237A - tracking adjustment device - Google Patents

Abstract

PURPOSE:To stabilize the adjusting accuracy and to shorten the adjusting time and also to eliminate the need for a particular skill and hence to enable the tracking adjustment by correcting a DC offset amt. of a tracking error signal based on an average tracking error value. CONSTITUTION:The title adjuster is constitutive of an optical device 2 for projecting a beam of light upon an optical disk 1 recorded with an information signal in a prescribed track form, a tracking error detecting means 3 for producing a tracking error signal 8 based on a modulated beam of light modulated by projecting the beam of light upon the optical disk 1, an average tracking error value detecting means 4 for minimizing the influence of a plane waving of the optical disk 1, etc., and detecting the mean value, based on the signal 8, a tracking correcting means 5 for adding the obtained mean value (average tracking error value) 9 in its reverse polarity to the signal 8, a tracking driving means 6 for oscillating the optical device 2 by using a tracking driving signal 10 and a rotating mechanism 7 for rotating the optical disk 1, etc. By this method, the DC offset amt. of the error signal 8 is corrected accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tracking adjustment device for an optical disc on which information signals are recorded in the form of a predetermined trunk.

2. Description of the Related Art When an optical device and a tracking error detection means move to a position on the trunk of an optical disk to read an information signal, the optical device may be deviated from the track due to an error in the tracking error detection means or an offset on the circuit. It was necessary to make tracking adjustments because the information reproduction ability deteriorated due to the spot being hit. Until now, tracking adjustment was done manually by humans. As an example of tracking adjustment, the readout signal from the optical disk is monitored, the tracking adjustment volume is turned, and the point where the jitter of the readout signal is the minimum is judged with the human eye, and the DC offset amount of the tracking error signal is determined. There was a way to adjust it.

Problems to be Solved by the Invention However, in the tracking adjustment configured as described above, since the judgment and adjustment are made using the human eye, the adjustment accuracy is not constant, the adjustment takes time, and special skills are required to make the adjustment. The problem was that it required

In view of the above-mentioned problems, the present invention provides a trunking adjustment device that has stable adjustment accuracy, short adjustment time, and does not require special skills for adjustment.

Means for Solving the Problems In order to solve the above problems, the tracking adjustment device of the present invention includes an optical device that projects light onto an optical disk, and a light beam projected from the optical device that is modulated by hitting the optical disk. tracking error detection means for creating a tracking error signal based on the modulated light; tracking error average value detection means for calculating the average value of the tracking error signals created by the tracking error detection means; and the tracking error average value tracking correction means for adding the tracking error signal to the tracking error signal; tracking drive means for driving the optical device; and a rotation mechanism for rotating the disc-shaped recording medium. D
It is equipped with a configuration for correcting the amount of C offset.

Effect of the Invention With the above-described configuration, the present invention corrects the DC offset amount of the tracking error signal based on the tracking error average value, thereby stabilizing the adjustment accuracy and reducing the adjustment time compared to judgment made by human eyes. Short<, allows for tracking adjustments that do not require special skills for adjustment.

Embodiment Hereinafter, a tracking adjustment device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a tracking adjustment device according to an embodiment of the present invention. In FIG. 1, 1 is an optical disk, 2 is an optical device that projects light onto the optical disk I, and 3 is a tracking device based on modulated light that is modulated when the light projected from the optical device 2 hits the optical disk 1. 4 is a tracking error detection means for creating an error signal 8; 4 is a tracking error average value detection means for calculating the average value of the tracking error signal 8 created by the tracking error detection means 3; 5 is a tracking error average value detection means for calculating the average value of the tracking error signal 8 created by the tracking error detection means 3; It is a tracking correction means that adds to the tracking error signal 8, 6 is a tracking drive means that drives the optical device 2 with the tracking drive signal 1o, and 7 is a rotation mechanism that rotates the optical disc 1. In this embodiment, it is assumed that the tracking error signal is obtained as a digital value.

The tracking adjustment device configured as described above is shown below in Figs. 1, 2(a), (b), and 3(a).
) (bl (C) and Figure 4 (a) (b) and Figure 5
The operation will be explained using FIG. 6, FIG. 7, and FIG. 8.

First, the tracking error detection means 3 will be explained. When a track deviation occurs based on the modulated light that is modulated by the light projected from the optical device 2 hitting the optical disk I, a tracking error signal 8 is generated according to the amount of trunk deviation. It is equipped with a mechanism to generate , such as the far field method and the phase difference method. It should be noted that such a tracking error detection means is already well known and the present invention does not focus on this means, so further explanation will be omitted. FIG. 2 (al (b)) shows a tracking error signal 8 generated when the optical device 2 and the tracking error detection means 3 cross the track due to the eccentricity of the optical disc 1 when the tracking drive means 6 is turned off.
FIG.

FIG. 2(a) shows the tracking error signal 8 when there is no DC offset shift of the tracking error signal, and the amplitude center of the tracking error signal 8 is zero volts. On the other hand, the tracking error signal 8 (see Fig. 2) is caused by the imbalance of the tracking error detection means 3.
This shows that the center of amplitude of is fluctuating. The present invention aims to adjust the amplitude center of this tracking error signal 8 to zero volts.

The first reason for performing such tracking adjustment is that when the optical device 2 and the tracking error detection means 3 move to a position on the track of the optical disc 1 and read out an information signal, errors in the tracking error detection means 3 and circuit errors may occur. As shown in FIG. 4(b), due to the offset, etc., a DC offset shift of the tracking error signal occurs, and the spot of the optical device hits a location deviated from the track, reducing the information reproducing ability. The second problem is the stability of tracking against defects on the optical disk l. During information reproduction, the servo is applied to set the tracking error signal 8 to zero volts, but when a defect occurs, the light projected from the optical device 2 does not return to the tracking error detection means 3, so the tracking error signal 8 Without being detected, the optical device 2 and the tracking error detection means 3 become free and move. Assuming that the range of displacement during the defect is L, when the tracking error signal 8 is detected after the defect, the servo will try to set the trunking error signal 8 to zero volts, but as shown in Fig. 4(a) If there is no DC offset shift in the tracking error signal as shown in Figure 2, the displacement during the defect is covered by the servo pull-in range, and the servo is applied to one point on the original track. However, the fourth
As shown in Figure fb), when there is a DC offset deviation in the tracking error signal, the servo that was originally applied at five points cannot cover the amount of deviation during the defect, and the servo is applied at a point close to the adjacent track ( The possibility of a track jump occurring increases, and the information reproducing ability of the optical disc 1 is significantly reduced.

The above matters directly affect the performance of the rib layer, which causes skipping in the sound of a DC player.

From the above, the tracking adjustment deviation directly affects the information reproducing ability, and it is necessary to perform tracking adjustment. The tracking adjustment means first detects the average value of the tracking error signal generated by the tracking error detection means 3 using the tracking error average value detection means 4. In this case, the average value of the tracking error signal is detected by the tracking error average value detecting means 4 which cumulatively adds the tracking error signal 8. The tracking error signal 8 shown in FIG. 2 is based on the assumption that track crossing is performed at a constant speed in the direction perpendicular to the track direction, ignoring the influence of eccentricity, and there is no surface wobbling of the optical disc 1. Actually, the average value of the tracking error signal when the optical disc 1 is rotated includes various measurement error factors, and the average value of the tracking error signal varies greatly. There are three causes of error in measuring the average value of the tracking error signal, and solutions for each will be described below.

FIG. 3 is a conceptual diagram illustrating error factors in measuring the average value of the tracking error signal. The first factor is shown in Figure 3 (a).
As shown in , this is an average value measurement error that occurs because there are few track crosses due to eccentricity. This can be solved by providing a tracking drive means 6 that increases the track cross by swinging the optical bag W1. For example, as shown in FIG. 5, the tracking drive means 6 is composed of a sine wave oscillator 61 and a driver 62 that receives the output of the sine wave oscillator, and the oscillation frequency is set so as not to synchronize with the rotation period of the optical disc 1 in order to increase track crossing. Furthermore, the gain of the driver is set to be sufficient, and the oscillation amplitude is set so that the track cross frequency is one-half or less of the cumulatively added sampling frequency according to the sampling theorem.

The second factor is the optical disc 1 as shown in Figure 3(b).
This is the amplitude center fluctuation of the tracking error signal due to surface wobbling.

In the case of surface wobbling, the tilt of the optical disc 1 changes, which causes a change in the direction of reflection of the light modulated by the optical disc 1, and modulation errors due to the fact that the depth of focus is not 1/4 wavelength. , which produces a fluctuation in the amplitude center of the tracking error signal. Taking advantage of the fact that surface wobbling is synchronized with the rotation period, if the average value detection time of the tracking error signal is set as one cycle of the optical disc 1, then the tracking error values sampled at various inclinations of the disc will be cumulatively added. Errors caused by local measurements can be reduced. Specifically, as shown in FIG. 6, the rotation period of the optical disk 1 is determined from the radius of the optical disk 1 and the linear velocity of the optical disk 1 at the tracking adjustment measurement point, and the rotation period is divided into N equal parts using a rotation period counter 48. Cumulatively add N times in time. The third factor is shown in Figure 3 (C
), the tracking error signal 8 becomes dull at the peak of the eccentricity of the optical disc 1, so the cumulative addition value becomes large.
This is the average value measurement error caused by having an offset. This problem is solved by the tracking error average value detection means 4 which invalidates the data in the corrupted portion. To explain the third factor in detail, near the peak of eccentricity, the speed at which the truck crosses the track decreases as it approaches the peak of eccentricity, and the trunk crossing speed becomes zero at the peak of eccentricity.

Then, the trunk crossing speed increases toward the center of the eccentricity, the speed reaches its maximum at the center of the eccentricity, and as it approaches the peak of the other eccentricity, the speed of track crossing decreases, and the track crossing speed decreases at the peak of the other eccentricity. becomes zero. The effect of eccentricity referred to here occurs in the same manner when the eccentricity of the optical disc 1 itself is added to the eccentricity of the optical device 2. As shown in Fig. 6, the method of invalidating the data of the actually distorted portion is to set an upper limit value and a lower limit value to the value of the input tracking error signal using the tracking error average value detection means 4, and then continuously When the time during which the tracking error signal exceeds that value exceeds a certain period of time, the tracking error signal is not cumulatively added to subsequent data while the upper and lower limits are exceeded. A specific configuration example of the tracking error average value detection means 4 is shown in FIG. Adder 41 with tracking error signal 8 as one input
, a register 42 that receives the adder output as input, a shift clock 43 that updates the register value, and the output of the register 42 is connected to the other input of the adder 41.The shift clock 43 generates the tracking error signal 8. The basic configuration is cumulative addition. Furthermore, the rounding detection circuit 44 that receives the tracking error signal 8 as input generates a sampling prohibition signal (low) 45 when the value of the input tracking error signal 8 continuously exceeds the upper and lower limits for a certain period of time or more. and sampling signal 4
6 and the sampling prohibition signal 45 using an AND circuit 47, and the output of the AND circuit is used as the shift clock 43 of the register, so that there is a time when the value of the tracking error signal 8 continuously exceeds the upper and lower limits. The tracking error signal 8 is prevented from being cumulatively added after a certain period of time or more.

As shown in FIG. 8, the rounding detection circuit 44 receives the tracking error signal 8 and includes a bypass filter 8o that cuts the DC of the tracking error signal, and an absolute value conversion circuit 81 that converts the DC-canted tracking error signal into an absolute value. is compared with the threshold value using the output of the absolute value conversion circuit 81 as input, and the threshold value 8 is determined.
A magnitude comparison logic 82 that outputs a high signal when the absolute value is greater than 6 and a low signal when the absolute value is smaller than the threshold value 86, and a magnitude comparison logic 82 that outputs a signal that is low when the absolute value is smaller than the threshold value 86; A counter 83 that counts the time exceeded (time when the output of 82 is high), an inverter 84 that inverts the output of the magnitude comparison logic 82 and uses it as a reset signal (resets when high) for the counter 83, and a certain bit data of the counter 83. This is realized by constructing an inverter 85 that inverts the signal and generates the sampling prohibition signal 45. 6th
Returning to the figure, there is a rotation period counter 48 that receives the sampling signal 46 and counts the rotation period, and a register 42 that uses the carry output of the rotation period counter 48 as a clock.
By using the D-flip-flop 49 whose output is the D input and the carry output of the rotation period counter 48 as the clear signal of the register 42, it is possible to make one cycle of the optical disc 1 the tracking error average value detection time. Ru. As shown in FIG. 7, the tracking error average value 9 detected in this way is converted into a reverse polarity by the tracking correction means 5 by the inverter 51 and added to the tracking error signal 8 by the adder 5.
2, the tracking deviation as shown in FIG. 2(b) is corrected so that the amplitude center of the tracking error signal becomes zero volts as shown in FIG. 2(a).

As described above, according to this embodiment, the optical device 2 projects light onto the optical disk 1 on which information signals are recorded in a predetermined track form, and the light projected from the optical device 2 hits the optical disk 1. A tracking error detection means 3 generates a tracking error signal 8 based on the modulated light, and a tracking error detection means 3 generates a tracking error signal 8 based on the modulated light. Tracking error average value detection means 4 for detecting an average tracking error value that reduces the influence caused by the dulling of the tracking error signal 8 at the peak of eccentricity of 1, and the tracking error detected by the average tracking error value detection means 4. In order to reduce the influence of the tracking correction means 5 which adds the average value 9 to the tracking error signal 8 with the opposite polarity and the fact that there are few track crosses (less eccentricity), which is one of the causes of error in measuring the average value of the tracking error signal,
By providing the tracking drive means 6 that swings the optical device 2 using the tracking drive signal 10 and the rotation mechanism 7 that rotates the optical disc 1, the adjustment accuracy is stabilized.
Tracking adjustment can be performed in a short adjustment time and does not require special skills for adjustment. Although the above embodiment is constructed using hardware, it goes without saying that it can also be implemented using a software algorithm for a computer. In addition, in the above embodiment, the tracking correction is configured to be corrected for each rotation period, but once the tracking error average value is measured, that value is stored in a memory etc. and the value is offset. It is also conceivable to continue adding as follows.

Effects of the Invention As described above, the present invention provides an optical device for projecting light onto an optical disk on which information signals are recorded in a predetermined trunk form, and a modulation method in which the light projected from the optical device is modulated by hitting the optical disk. tracking error detection means for creating a tracking error signal based on light;
tracking error average value detection means for calculating a tracking error average value signal based on the tracking error signal created by the tracking error detection means; and tracking correction means for correcting the tracking error signal based on the tracking error average value. By providing a tracking drive means that drives the optical device using a tracking drive signal and a rotation mechanism that rotates the optical disk, the adjustment accuracy is stabilized and the adjustment time is short.
Tracking adjustments can be made that do not require special skills for adjustment.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a tracking adjustment device according to an embodiment of the present invention, FIGS. Figure 3 (a)
(b) (C) are conceptual diagrams explaining the error factors in measuring the average value of the tracking error signal, Figures 4 (a) and (b) are conceptual diagrams showing the necessity of tracking adjustment, and Figure 5 is a conceptual diagram of the tracking drive means. FIG. 6 is a block diagram of the tracking error average value detection means, FIG. 7 is a block diagram of the tracking correction means, and FIG. 8 is a block diagram of the rounding detection circuit. 1... Optical disk, 2... Optical device,
3... Tracking error detection means, 4...
... Tracking error average value detection means, 5...
...Tracking correction means, 6...Tracking drive means, 7...Rotation mechanism, 8...
Tracking error signal, 9... Tracking error average value, 10... Tracking drive signal, 41... Adder, 42... Register, 43... ...Shift clock, 44...
Accenture detection circuit, 45...Sampling prohibition signal, 46...Sampling signal, 47...
...AND circuit, 4 days...Rotation period counter,
49...D-flip-flop, 51...
...Inverter, 52...Adder, 53...
...Corrected tracking error signal, 61...
... Sine wave oscillator, 62 ... Driver, 80
... Bypass filter, 81 ... Absolute value conversion circuit, 82 ... Size comparison logic, 83.
...Counter, 84...Inverter, 8
5...Inverter, 86...Threshold value. Name of agent: Patent attorney Toshio Nakao Haka1 person■
solid

Claims (6)

[Claims] (1) Tracking based on an optical device that projects light onto an optical disk on which information signals are recorded in a predetermined track form, and modulated light that is modulated when the light projected from the optical device hits the optical disk. tracking error detection means for creating an error signal; tracking error average value detection means for calculating the average value of the tracking error signals created by the tracking error detection means; and tracking for adding the tracking error average value to the tracking error signal. A tracking adjustment device comprising a correction means, a tracking drive means for driving the optical device, and a rotation mechanism for rotating the optical disk. (2) The tracking adjustment device according to claim (1), wherein the tracking drive means swings the optical device. (3) The tracking adjustment device according to claim (1), wherein the tracking error average value detection means is provided with a tracking error signal cumulative addition means. (4) The tracking adjustment device according to claim (1), wherein the tracking error average value detection means uses one period of the optical disc as the tracking error average value detection time. (5) The tracking error average value detection means detects the tracking error average value by partially invalidating the tracking error signal.
Tracking adjustment device described in ). (6) The tracking adjustment device according to claim (1), wherein the tracking correction means adds the tracking error average value to the tracking error signal with opposite polarity.