JP2587058B2 - Tracking sensor gain compensation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking sensor gain compensation method for compensating for a gain variation of a sensor for tracking a recording medium.

[Prior Art] FIG. 6 shows, for example, Japanese Patent Application No.
FIG. 1 is a block diagram of a servo system of an optical disk drive using an analog-to-digital converter disclosed in JP 61-8265A. In the figure, (1a) and (1b) correspond to the first and second
(2a) and (2b) are current-voltage converters for converting the detection currents of the first and second photodetectors (1a) and (1b) into voltages, and (3) is a difference signal An arithmetic unit having one input side connected to the first photodetector (2a) and the other input side connected to the second photodetector (2b); A difference signal between the output signal of (2a) and the output signal of the second photodetector (2b) is obtained. (4) is a sum signal calculator, one input side of which is a first photodetector (2)
a) and the other input side is a second photodetector (2b),
Each of them is connected to obtain a sum signal of an output signal of the first photodetector (2a) and an output signal of the second photodetector (2b). (6) is an analog-to-digital converter (hereinafter referred to as an A / D converter), which uses the difference signal from the difference signal calculator (3) as a conversion input signal and outputs the sum from the sum signal calculator (4). The analog input signal is converted to a digital signal using the signal as a reference input signal. (6) is a logic circuit, (7) is a digital-analog converter (hereinafter, referred to as a D / A converter),
(8) is a phase compensator for compensating the phase characteristics of the servo system,
(9) is a driver, and (10) is a tracking actuator for controlling tracking of a light spot.

The servo system of the conventional optical disk drive is configured as described above, and constitutes a part of a sensor optical system for detecting a positional deviation between a guide groove for tracking and a converging spot by a converging optical system. The first and second photodetectors (1a) and (1b) convert the received light into a current. The converted current signal is further converted into a voltage signal by the first and second current-voltage converters (2a) and (2b).
The converted signals are used as a difference signal calculator (3)
In taking the difference, sums the sum signal calculator (4), the difference signal is an analog - as digital conversion input (I _n), the sum signal is an analog - a digital reference input (R), A / D converter ( Input to 5). The A / D converter (5) converts a result obtained by normalizing the difference signal with a sum signal into a digital code.

Here, the difference signal is a signal proportional to the displacement between the guide groove and the condensing spot, and is also proportional to the reflectance of the recording medium and the intensity of the light source. Therefore, by normalizing the difference signal using the sum signal, which is a signal proportional to the reflectance of the recording medium and the intensity of the light source, a signal proportional to only the displacement between the guide groove and the condensing spot can be obtained. Can be.

The converted digital code is supplied to a logic circuit (6).
After performing real-time processing to improve the reliability of the servo system, such as offset adjustment and compensation for a pseudo signal generated in a difference signal due to a defect on a recording medium, the D / A converter (7) performs analog signal processing. Is converted to

The converted analog signal is transmitted to a driver (9) through a phase compensator (8) for compensating a phase characteristic so that a servo loop does not become unstable, and drives a tracking actuator (10) to generate a focused spot. Is moved in the direction of the guide groove.

[Problems to be Solved by the Invention] In the conventional servo circuit as described above, the proportionality constant for the positional deviation between the guide groove for the difference signal and the condensed spot depends on the groove shape of the guide groove and the inclination of the recording medium. If the change is caused by the change, the change cannot be neutralized even by the normalization by the sum signal, so that the servo loop gain fluctuates and the servo system becomes unstable or the processing circuit for improving reliability malfunctions. There were problems such as.

The present invention has been made to solve such a problem, and even if a change in the position error detection sensitivity of a difference signal that cannot be neutralized by normalization by a sum signal occurs, the servo system becomes unstable, It is an object of the present invention to provide a tracking sensor / gain compensation method in a servo system of a recording medium driving device in which a processing circuit does not malfunction.

[Means for Solving the Problems] The tracking sensor / gain compensation method according to the first aspect of the present invention provides a recording medium having a track for tracking in advance, and a light condensing spot formed by condensing light on the recording medium. A condensing optical system to be formed, a sensor optical system for detecting a signal for detecting a positional deviation of the track and the condensed spot, and a drive in a direction in which the positional deviation is reduced from an output signal of the sensor optical system In a servo system of a recording medium driving device having a feedback servo system,
Means for taking the difference between at least two output signals of the sensor optical system, means for taking the sum, gain control means for controlling the gain of the means for taking the difference, an analog-digital conversion input for the difference signal, and a sum signal. And a microcomputer for processing an output signal of the analog-to-digital conversion means. The microcomputer includes a recording medium driving device for tracking sensor / gain compensation. A first sine wave signal applied to the servo system is transferred to the analog-to-digital conversion means, and the sensor is transferred from the analog-to-digital conversion means for one cycle in synchronization with the first sine wave signal. The first sine wave signal is obtained by fetching and averaging the output signal of the optical system to approximate the sine wave signal. After taking out the synchronization component, the first sine wave signal to be applied to the servo system of the recording medium driving device is corrected based on the synchronization component to generate a corrected sine wave signal, and the synchronization of the first sine wave signal is performed. The gain control means is controlled such that the ratio between the amplitude of the component and the amplitude of the corrected sine wave signal falls within an allowable value to keep the tracking sensor sensitivity constant.

The tracking sensor / gain compensation method according to the second aspect of the present invention includes a recording medium having a track for tracking in advance, a condensing optical system for condensing light on the recording medium to form a converging spot, A recording system comprising: a sensor optical system for detecting a signal for detecting a positional deviation between a track and the condensed spot; and a feedback servo system for driving the output signal of the sensor optical system in a direction in which the positional deviation is reduced. In a servo system of a medium driving device, a means for taking a difference between at least two output signals of the sensor optical system, a means for taking a sum, a gain control means for controlling a gain of the means for taking the difference, and an analog signal −
An analog-to-digital converter that uses the sum signal as an analog-to-digital conversion reference input as a digital conversion input, and a microcomputer that processes an output signal of the analog-to-digital converter; and the microcomputer drives an actuator. At this time, the microcomputer transfers a first sine wave signal to be applied to a servo system of the recording medium driving device for tracking sensor gain compensation to the analog-digital conversion means, and synchronizes with the first sine wave signal. Then, after taking in the output signal of the sensor optical system transferred from the analog-digital conversion means for one period, averaging the output signal to approximate a sine wave signal and extracting a synchronous component of the first sine wave signal. Is applied to the servo system of the recording medium drive based on the synchronization component. The first sine wave signal is corrected to generate a corrected sine wave signal, and the gain control means is controlled so that the ratio of the synchronous component of the first sine wave signal to the amplitude of the corrected sine wave signal falls within an allowable value. I do. It is like that.

[Operation] In the first and second aspects of the present invention, the standardized displacement detection is a digital signal which is easily input to the microcomputer because it has already been digitized, and is a periodic signal having the pitch of the guide groove as a cycle. By utilizing this fact, the misregistration detection sensitivity is calculated, and the gain of the means for taking the difference is controlled based on the calculation result. By adjusting the gain of only the difference signal detected by the microcomputer, the change in the position detection sensitivity is neutralized. Therefore, the loop gain of the servo system does not fluctuate, and the servo system does not become unstable, and the processing circuit for improving the reliability does not malfunction due to the reverse operation, thereby deteriorating the reliability.

FIG. 1 is a block diagram showing a tracking sensor gain compensation method for a servo system of an optical disk drive according to an embodiment of the present invention. In the figure, the description of the same or corresponding parts as those of the conventional example of FIG. 6 is omitted. (11)
Is a microcomputer whose input side is the output side of the logic circuit (6), whose output side is one input side of the up-down type gain programmable amplifier (12),
Each is connected. The other input side of the up-down type gain programmable amplifier (12) is connected to the output side of the difference signal calculator (3), and the output side is
Analog-to-digital conversion input (I
_n ) and connected.

FIG. 2 is a diagram showing an operation flowchart of the microcomputer of FIG.

In the tracking sensor gain compensation method configured as described above, the tracking servo system sensor signal converted into a digital code by the A / D converter (5) is relied on as a sensor signal by the logic circuit (6). After being subjected to processing for improving the performance, for example, removal of impulse-like noise, it is transferred to the microcomputer (11).

The microcomputer (11) is a tracking sensor
When performing gain compensation, the amplitude of a periodic waveform (sensor waveform) whose period is the pitch of the guide groove without tracking is detected, and the amplitude is compared with the amplitude of a standard gain. This is done by raising or lowering the gain of the up-down type gain programmable amplifier (12).

For this purpose, the microcomputer (11)
As shown in the figure, in step (S ₁ ), first register MI
N, clears the MAX, all digital coded sensor signal while the disk rotates one step (S ₂₎
And DATA. Next, in step (S ₃ ), the value of DATA is compared with the value of the register MAX. If the value of DATA is larger than the value of the register MAX, the process proceeds to the next step (S ₈ ), and the value of the register MAX is determined by the value of DATA. Update the value of. DATA value is register MAX
If it is smaller than the value of, go to the next step (S ₄ )
Is compared with the value of register MIX, and the value of DATA is
If it is larger than the value of MIX, go to step (S ₉ )
Update the value of register MIX with the value of ATA. If the value of the DATA is less than the value of the register MIX, the process proceeds to step (S _5),
It is determined whether the disk has made one revolution. If there is at least one disk eccentricity, the amplitude of the sensor waveform can be detected by calculating the value of (MAX-MIX).

The (MAX-MIX) value and step amplitude in a standard gain (S ₆₎ (TYP) + is compared to 1dB, (TYP) +1
If dB) or more, the flow advances to step (S _10), the gain of the up-down gain programmable amplifier (12) 1d
B down, if (TYP + 1dB) or less, step (S
Proceed to ₁₁ ). In this step _{(S 11), (MAX-} MIX) value and (TYP-1 dB) are compared, if the value of (MAX-MIX) is smaller, the process proceeds to the next step (S _12), up-down gain The flow is set so that the gain of the programmable amplifier (12) is increased and the process returns to the process of detecting the amplitude of the sensor waveform again. By going around this loop several times,
Ultimately, the amplitude of the sensor waveform falls within ± 1 dB of the amplitude at standard gain. So tracking sensor
It is only necessary to end the gain compensation and start tracking.

FIG. 3 is a diagram showing a tracking sensor gain compensation method for a servo system of an optical disk drive according to another embodiment of the present invention. In the figure, the logic circuit (6) and the microcomputer (11) are the same as the previously described embodiment of FIG. 1 except that the transfer of digitally encoded data is bidirectional.

4 and 5 are operation flowcharts of the microcomputer shown in FIG.

Next, the operation of FIG. 3 will be described with reference to FIG. 4 and FIG.

The tracking servo sensor signal converted into the digital code by the A / D converter (5) is subjected to processing for improving the reliability as the sensor signal in the logic circuit (6), for example, removal of impulse noise. After that, it is transferred to the microcomputer (11).

Also, the microcomputer (11) transfers an applied signal to the tracking actuator (10) to the logic circuit (6) in the form of a digital code. The logic circuit (6) adds the sensor signal transferred to the microcomputer (11) and the transferred applied signal, and transfers the added signal to the D / A converter (7) where it is converted to an analog signal. You.

The microcomputer (11) is a tracking sensor
When performing gain compensation, a servo is applied by applying a sine wave to the tracking actuator (10) with tracking applied, and comparing the amplitude of the applied signal with the amplitude of the tracking sensor signal immediately before the applied point in the applied state. Measure the open-loop gain characteristic of the loop, compare the gain characteristic at a specific frequency or the gain characteristic at a specific frequency band with a standard gain or gain characteristic, and raise or lower the gain of the up-down type gain programmable amplifier (12). Do.

For this purpose, the microcomputer (11)
As shown, first, to start the subroutine SWEEP at step (S _13), the sine wave Asin frequency f (2 [pi
ft) and transfers it to the logic circuit (6). To start the subroutine DATA simultaneously in step (S _14),
In synchronization with the sine wave, the tracking sensor signal transferred from the logic circuit (6) for one cycle is fetched.
Averaging the subroutine AVE at step (S _15).
Then, the program proceeds to a step (S _16), determines whether the averaging number of times is equal to N. If the number of times of averaging N is made sufficiently large, it becomes possible to extract only the synchronous component with respect to the applied sine wave.

Next, the sensor signal averaged for N times is calculated by the step (S
₁₇ ) In subroutine ARX, Bsin (2πf · t +
_Ｂ Approximate the function of _B ). By this approximation, a complete synchronization component has been extracted.

Therefore, the applied signal for the tracking actuator (10) is, Asin (2 [pi f · in step (S ₁₈₎
t) + Bsin (2π f · t + ψ B) = Csin (2π f · t +
ψ _C ). The sensor signal at that time is Bsin (2π f ·
t + ψ _B ), the open loop gain of the servo system can be obtained by calculating B / C.

Therefore, if the frequency is selected as the gain crossover frequency of the servo system, B / C may be 0 dB.

Therefore, tracking sensor gain compensation accuracy is ± 1d
If B / C, B / C is compared with +1 dB in step (S ₁₉ ). If B / C is +1 dB or more, the next step (S ₂₀ )
Then, the gain down command is sent to the up / down type gain programmable amplifier (12). For example, the gain is reduced from the difference signal gain by -1 dB, and the process returns to the subroutine DATA again, and loops until the B / C becomes +1 dB or less. . vice versa,
In step (S _21), B / C is compared to -1dB, B / C is -1dB
In the following cases, the flow advances to step (S _22), sends a gain increase command to the up-down gain programmable amplifier (12), for example + 1 dB, and the gain up from the difference signal gain, again returns to the subroutine DATA, B / C Loop until -1dB or more. When B / C falls within the range of +1 dB or less and -1 dB or more, tracking sensor gain compensation ends.

In the above embodiment, the addition of the sensor signal and the actuator application signal is performed by the logic circuit (6). However, as long as the dead time due to the addition time does not impair the servo stability, the addition is performed by the microcomputer (11). May be. In this case, if the sensor signal transferred from the logic circuit (6) is DATA (t ₀ ) in the algorithm of FIG. 4, the code data transferred to the logic circuit (6) is not Asin (2π ft ₀ ), Asin (2π ft ₀ ) + DA
If the subroutine SWEEP is changed so as to become TA (t ₀ ), the microcomputer (11) performs the addition processing.

Also, in the above embodiment, after calculating the B / C, the gain of the up-down type gain programmable amplifier (12) was increased or decreased only by ± 1 dB.
The gain may be increased or decreased at a time so that it is within dB. In that case, the destination in the algorithm shown in FIG. 4 may be stopped.

In the above embodiment, the tracking sensor gain compensation is terminated when the B / C falls within ± 1 dB.
The amount of displacement of the focused spot due to the applied signal is
If the applied signal is small in a range where no problem occurs when recording, reproducing, or erasing information, the tracking sensor gain compensation may be always performed.

Also, in the above embodiment, the sensor signal averaged in order to extract a component completely synchronized with the applied signal is converted to a Bsin signal.
(2πf · t + ψ _B ), but the time required for this approximation algorithm becomes a problem, and if a practically synchronized component is extracted from the averaged sensor signal in practical use, FIG. subroutine APX step (S ₁₇₎ may be omitted. The algorithm in this case is shown in FIG.

In FIG. 5, first, B is looking for the maximum and minimum values of the sensor signal averaged by the subroutine CUL-B at step (S _23), obtained by taking the difference. Also, C
It is looking and data of the sensor signals averaged by the subroutine CUL-C in step (S _24), the maximum and minimum values of the synchronous addition data example data example Asin (2π f · t), that Gain by taking the difference. The following steps are the same as those described with reference to FIG.

In the above embodiment, the track for tracking is a guide groove, but this may be between the guide grooves. Instead of the guide grooves, for example, servo byte information in the sample servo method may be discrete.

Further, the recording medium is not limited to the optical disk, but may be a magneto-optical disk. The shape may be any of a card shape, a disk shape, a drum shape, and a tape shape as long as it has a track.

In the above embodiment, the difference signal calculator and the up / down type gain programmable amplifier are used for the gain switching of the means for taking the difference. However, if the expected gain change is small, for example, instead of the up / down type gain programmable amplifier, 2 The gain of the stage may be switched.

In the above embodiment, the gain is switched by the analog signal processing circuit. However, the signal digitally coded by the A / D converter may be digitally multiplied by a constant.

[Effects of the Invention] As described above, the present invention provides a recording medium having a track for tracking in advance, a converging optical system for condensing light on the recording medium to form a converging spot, A sensor optical system for detecting a signal for detecting a position shift of the condensing spot, and the position shift is detected from an output signal of the sensor optical system, and a movable portion of the condensing optical system is reduced in the position shift. A means for obtaining a difference between at least two output signals of the sensor optical system, a means for obtaining a sum, and a means for obtaining the difference Gain control means for controlling the gain of
An analog-to-digital conversion means using the difference signal as an analog-to-digital conversion input and a sum signal as an analog-to-digital conversion reference input, and a microcomputer for processing an output signal of the analog-to-digital conversion means. A first sine wave signal to be applied to a servo system of a recording medium driving device for tracking sensor gain compensation is transferred to the analog-digital conversion means, and the analog signal is synchronized with the first sine wave signal for one cycle. Taking in the output signal of the sensor optical system transferred from the digital conversion means, averaging it, approximating it to a sine wave signal, and taking out the synchronization component of the first sine wave signal, The first sine wave signal applied to the servo system of the recording medium drive is corrected to generate a corrected sine wave signal The tracking sensor is compensated by controlling the gain control means so that the ratio between the synchronous component of the first sine wave signal and the amplitude of the corrected sine wave signal falls within an allowable value. There is an effect that compensation for the tracking sensor gain in the frequency band can be performed with high accuracy and high reliability.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a tracking sensor gain compensation method for a servo system of an optical disk drive according to an embodiment of the present invention, FIG. 2 is an operation flowchart of the microcomputer shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing a tracking sensor gain compensation method for a servo system of an optical disk drive according to another embodiment of the present invention. FIGS. 4 and 5 are flowcharts showing the operation of the microcomputer shown in FIG. 3, and FIG. FIG. 10 is a block diagram showing a servo system of a conventional optical disk drive. In the figure, (1a) and (1b) ... first and second photodetectors, (2a) and (2b) ... first and second current-voltage converters, (3) ... difference signal Arithmetic unit, (4) ...
Sum signal arithmetic unit, (5) A / D converter, (6) Logic circuit, (7) D / A converter, (8) Phase compensator, (9) Driver , (10) tracking actuator, (11) microcomputer, (1
2) An up-down type gain programmable amplifier. The same reference numerals in the drawings indicate the same or corresponding parts.

Continuation of the front page (56) References JP-A-60-138740 (JP, A) JP-A-61-280032 (JP, A) JP-A-62-145538 (JP, A) JP-A-62-137781 (JP) JP-A-62-33341 (JP, A) JP-A-60-154336 (JP, A)

Claims (2)

(57) [Claims] 1. A recording medium having a track for tracking in advance, a condensing optical system for condensing light on the recording medium to form a condensed spot, and a displacement of the track and the condensed spot. A sensor optical system for detecting a signal for detection, and a servo system of a recording medium driving device including a feedback servo system for driving the output signal of the sensor optical system in a direction in which the displacement decreases. Means for taking the difference between at least two output signals of the optical system, means for taking the sum, gain control means for controlling the gain of the means for taking the difference, the difference signal as an analog-digital conversion input, and the sum signal as an analog signal. An analog-to-digital converter as a digital conversion reference input, and a microcomputer for processing an output signal of the analog-to-digital converter. A microcomputer which transfers a first sine wave signal to be applied to a servo system of a recording medium driving device for compensating a tracking sensor gain to the analog-digital conversion means. The output signal of the sensor optical system transferred by the analog-digital conversion means for one cycle in synchronization with the signal is taken, averaged, and approximated to a sine wave signal to obtain a synchronous component of the first sine wave signal. After taking out,
Based on the synchronization component, the first sine wave signal applied to the servo system of the recording medium drive is corrected to generate a corrected sine wave signal, and the synchronization component of the first sine wave signal and the corrected sine wave signal are corrected. A tracking sensor gain compensation method, characterized in that the gain control means is controlled so that the amplitude ratio falls within an allowable value to keep the tracking sensor sensitivity constant. 2. A recording medium having a track for tracking in advance, a condensing optical system for condensing light on the recording medium to form a condensed spot, and a displacement of the track and the condensed spot. A sensor optical system for detecting a signal for detection, and a servo system of a recording medium driving device including a feedback servo system for driving the output signal of the sensor optical system in a direction in which the displacement decreases. Means for taking the difference between at least two output signals of the optical system, means for taking the sum, gain control means for controlling the gain of the means for taking the difference, the difference signal as an analog-digital conversion input, and the sum signal as an analog signal. An analog-to-digital converter as a digital conversion reference input, and a microcomputer for processing an output signal of the analog-to-digital converter. And a microcomputer, wherein when the actuator is driven by the microcomputer, the microcomputer converts the first sine wave signal applied to the servo system of the recording medium driving device for the compensation of the tracking sensor gain into the analog-digital conversion. The output signal of the sensor optical system transferred from the analog-to-digital conversion means for one cycle in synchronization with the first sine wave signal is fetched and averaged to approximate the sine wave signal. After taking out the synchronization component of the first sine wave signal, the first sine wave signal applied to the servo system of the recording medium drive is corrected based on the synchronization component to generate a corrected sine wave signal, Controlling the gain control means so that the ratio of the amplitude of the synchronous component of the first sine wave signal to the amplitude of the corrected sine wave signal falls within an allowable value; A tracking sensor gain compensation method characterized in that the detection sensitivity constant.