JP2751561B2 - Tracking control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus that optically records a signal on a recording medium using a light source such as a laser and reproduces the recorded signal. More particularly, the present invention relates to a tracking control device that controls a light beam irradiating a recording medium to scan a track correctly.

2. Description of the Related Art Hereinafter, an example of a conventional tracking control device will be described with reference to the drawings.

FIG. 8 is a block diagram of a tracking control device in a conventional example, FIG. 9 is a waveform diagram of a tracking error signal, and FIG.
FIG. 10 is a distribution diagram of reflected light on a tracking detection photodetector when tracking error detection is performed by the far field method. In FIG. 8, 1 is an optical disk,
2 is a light beam, 3 is an objective lens, 4 is an optical head,
The light beam 2 emitted from the optical head 4 is narrowed down to a minute spot by the objective lens 3 and is incident on the optical disk 1 to record and reproduce information. Reference numeral 5 denotes a focus control circuit that performs focus control so that the light beam 2 is focused on the medium surface of the optical disk 1. Reference numeral 6 denotes a tracking error signal detector, and reference numeral 7 denotes a phase compensation circuit that performs phase compensation and the like on the tracking error signal obtained by the tracking error signal detector 6. Reference numeral 8 denotes an actuator drive circuit, and reference numeral 9 denotes a tracking actuator, which performs tracking control for moving the objective lens 3 in a direction substantially perpendicular to the information recording track on the medium surface of the optical disk 1 so that the light beam 2 follows the information recording track.
Reference numeral 10 denotes a transfer device for moving the optical head 4 and the tracking actuator 9 in a direction substantially perpendicular to the information recording track. 12 is an offset generator, and 11 is a subtractor for subtracting the output of the offset generator 12 from the tracking error signal.

In the conventional tracking control device configured as described above, first, after the focus servo is started to operate stably by performing the focus control, the average of the maximum value and the minimum value of the tracking error signal is determined by the target position of the tracking control (hereinafter referred to as the target position). An offset is given by the offset generator 12 so as to obtain a tracking position, and the tracking control is adjusted.

Problems to be Solved by the Invention In the conventional tracking control device, the average value of the maximum value and the minimum value of the tracking error signal is set as the tracking position. However, in the tracking error signal detection by the far field method, an offset occurs in the tracking error signal when the optical axis of the reflected light from the optical disc is shifted. This will be described with reference to FIG. In FIG. 10, 92 is a photodetector for detecting a tracking error signal, 910 is the 0th-order reflected light of the light beam, 911 is the 1st-order reflected light of the light beam, 912 is the -1st-order reflected light of the light beam, and 901 is the 0th-order reflected light. The dividing line of the photodetector 92 when the optical axis of the reflected light coincides with the dividing line, and 902 is the dividing line of the photodetector 92 when the optical axis of the zero-order reflected light does not coincide with the dividing line.
As shown in FIG. 10, on the tracking photodetector 92, there are a 0-order reflected light 910, a first-order reflected light 911, and a -1st-order reflected light 912 of the light beam 2 from the optical disc 1, and the dividing line of the photodiode. The difference between the light amount on the right side of 901 or 902 and the light amount on the left side is detected as a tracking error signal. Here, the dividing lines 901 and 0 of the photodetector 92 are
When the center of the next light 910 is aligned, the tracking position of the tracking error signal TE shown in FIG.
It becomes position of the center P _ave of P ₁ and the minimum point P _2. However, when the dividing line of the photodetector 92 is located at the position of the dividing line 902 and deviated from the center of the zero-order reflected light 910, the tracking position P ₀ of the tracking error signal TE shown in FIG.
P ₁ and not a position of the center P _ave minimum point P _2. Therefore, the conventional tracking control apparatus has a problem that a correct tracking position cannot be detected when an optical axis shift or the like occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-accuracy tracking control device capable of reliably and automatically detecting a correct tracking position.

Means for Solving the Problems In order to achieve the above object, the present invention provides a convergence means for converging a light beam toward a recording medium, and a convergence point of the light beam converged by the convergence means on a track on the recording medium. Means for moving across the recording medium, and a track shift that generates a signal corresponding to the positional relationship between the light beam and the track of the recording medium due to transmitted light transmitted through the recording medium or reflected light reflected from the recording medium. Detecting means, tracking control means for driving the moving means in accordance with a signal from the track deviation detecting means to control the light beam to be positioned on the track, and detecting the sum of the transmitted light amount or the reflected light amount from the recording medium. Light amount detecting means for calculating, a calculating means for obtaining an extreme point of a signal of the light amount detecting means, and an eye of the tracking control means based on a result of the calculating means. Target position adjusting means for changing a target position, wherein the calculating means approximates a signal from the light quantity detecting means to a predetermined function to obtain a pole point.

The present invention also provides a converging means for converging the light beam toward the recording medium, a moving means for moving a convergence point of the light beam converged by the converging means so as to cross a track on the recording medium, A track shift detecting means for generating a signal corresponding to a positional relationship between a light beam of the recording medium and a track by transmitted light transmitted through the recording medium or reflected light reflected from the recording medium; Tracking control means for controlling the light beam to be positioned on a track by driving the moving means;
Light amount detecting means for detecting the sum of the transmitted light amount or the reflected light amount from the recording medium, first function approximating means for approximating a signal of the light amount detecting means to a function, and a signal of the track shift detecting means as a function And a second function approximation means for approximating, wherein the target position of the tracking control means is adjusted according to a result of comparing the respective functions obtained by the first and second function approximation means. It is composed.

Operation In the present invention, the value of the tracking error signal at the extreme point of the sum of the reflected light amounts or the sum of the transmitted light amounts is used as the tracking position. FIG. 2 is a signal waveform diagram showing the relationship between the track position, the tracking error signal, and the reflected light amount sum signal. In FIG. 2, TE is a tracking error signal of a light beam focused on a minute spot with respect to an information recording track, and TS is a reflected light sum signal. For example, when the optical axis of the light beam deviates from the photodetector of the tracking error signal detector, TE at the land center or groove center of the track is not 0 but P0. However, at the center of the land, the TS has a maximum value, and at the center of the groove, the TS has a minimum value. That is, at the center of the information recording track, the sum of the reflected light amounts is an extreme point (a local maximum point in the case of groove recording, and a local minimum point in the case of groove recording). Therefore, a reliable tracking position detection is performed by finding a local maximum point or a local minimum point. be able to.

Example A first example of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a tracking control device according to one embodiment of the present invention. The same parts as those of the conventional tracking control device are denoted by the same reference numerals, and description thereof will be omitted. FIG. 2 is a signal waveform diagram showing the relationship between the track position of the light beam, the tracking error signal TE, and the reflected light amount sum signal TS, as described above.

 Hereinafter, description will be made with reference to these drawings.

The reflected light sum signal detector 21 obtains the sum of the reflected light amounts from the optical disc 1,
22 is entered. The tracking error signal from the tracking error signal detector 6 is also input to the microprocessor 22 via the AD converter 25. As shown in FIG. 2, the input signal is a signal that changes periodically with time. The microprocessor detects the input TS at predetermined time intervals, and obtains a maximum point or a minimum point of the TS from the data.

After detecting the pole of the TS, the TE level at the pole is detected, and the TE is corrected by the DA converter 23 and the subtractor 11 so that the position corresponding to the signal level becomes the tracking position. Then, tracking control is performed using the corrected TE.

Next, a method of detecting a pole of TS in the first embodiment will be described in more detail.

FIG. 3 shows a microprocessor via AD converters 24 and 25
22 is a waveform diagram of discrete values of TS and TE captured by 22 and a function that approximates TS from the discrete values.

After the device is turned on and the focus control is operated, the microprocessor 22 operates the movement signal generator 26 to move or oscillate the tracking actuator 9 or the transfer device 10 to obtain a stable track crossing signal. The microprocessor 22 detects the TS by a predetermined number of samples via the AD converter 24 at a predetermined timing. In this embodiment, a case where the number of samples is five will be described. The approximation accuracy can be improved by increasing the number of samples. Points A, B, C, D, and E in FIG. 3 are points on the TS detected by the microprocessor 22. This point A,
Assuming that the time at which points B, C, D, and E are detected is t and each signal amplitude is y, the phase x of TS is x = 2πt / T (where T is the period of the reflected light sum signal TS). Therefore, the relationship between x and y can be approximated to a predetermined periodic function y = f (x).

The microprocessor 22 calculates the points A, B, C, D,
When the point E is detected, for example, it approximates a predetermined periodic function y = a cos (x−b) + c (1). There are various methods for approximation. For example, the approximation can be performed by applying the least square method. From the above equation (1), a cos (x−b) + cy = 0 (2) is established. In the equation (2), the phase x _j and the signal amplitude y of the signal actually detected by the microprocessor 22 are expressed. _{When j} (where j is a number representing the order of the detected signals) is substituted, it does not become 0 due to the influence of noise, sampling error, or the like, and a cos (x _j −b) + c−y _j = v _j . (2) ′. Where the sum of the squares of v _j (N is a set predetermined number of samples and 5 is set in this embodiment) When the values of a, b, and c are determined so that
Can accurately reproduce the actual TS as shown by the solid line y = f (x) in FIG. This approximated function curve is measured by the microprocessor 22 (points A to E).
Through the approximate average position of point). Therefore, by performing this arithmetic processing, it is possible to calculate a predetermined function y = f (x) that approximates the relationship between the phase x and the reflected light sum y.

Since this function f (x) is a periodic function, the maximum point or the minimum point can be easily calculated by obtaining the points x = 2mπ + b and x = (2m + 1) π + b. The microprocessor 22 obtains the phase value xd of the maximum point of f (x) or the phase value xs of the minimum point, and calculates the time t corresponding thereto,
At that time, that is, the TE at point d or point s is
Capture by Further, the fetched value is compared with the reference value 0, and data corresponding to the difference is output. The output data is converted into an analog value by the DA converter 23, and the TE is corrected by the subtractor 11. And TE after correction
Phase compensation to the tracking actuator 9
Can be controlled at the correct tracking position.

Here, the microprocessor 22 recognizes whether the disc 1 is groove-recorded or land-recorded based on information from a sensing hole of a cartridge in which the disc 1 is stored or information pre-recorded on the disc 1. Is detected, and in the case of land recording, TE at the maximum point of TS is detected and corrected.

This embodiment is also applicable to a case where approximation is made with a real function other than the periodic function. For example, a case of approximation using a cubic function will be described.

Points A, B, C, D, and E in FIG. 4 are reflected light sum signals detected by the microprocessor 22 as in FIG.
It is a point on TS. The vicinity of the maximum point or the minimum point can be approximated by a cubic function. This point A, B
X is the time at which the points, C, D, and E are detected, and y is the cubic function that approximates the relationship between x and y when the signal amplitude is y. Y = ax ³ + bx ² + cx + d (4) Y '= 3ax ² + 2bx + C (5) The intersection of the function with the y-axis, ie, 3ax ² + 2bx + C = 0 (6) is the local maximum and minimum of TS. . The difference xdd-xss of the time x between the local maximum point and the local minimum point is a half cycle of the reflected light sum signal, and this portion is turned back and repeated at a predetermined cycle, whereby the actual detection is performed as shown in L in FIG. Be done
TS can be easily obtained.

Thereafter, by correcting the TE in the same manner as in the case where the periodic function is approximated, the control can be performed at the correct tracking position.

FIG. 5 shows a flow of processing of the microprocessor 22 in the first embodiment.

The average of each TS input to the microprocessor 22 or the TE at the extreme point is obtained twice or more and the average is calculated.
The adjustment accuracy can be improved by adjusting the average value. Further, the accuracy can be improved by performing the TS function approximation twice or more and averaging the extreme points in each function.

Next, a second embodiment of the present invention will be described. The second embodiment can be realized by the configuration shown in FIG. 1 similar to the first embodiment, and is obtained by changing the processing content of the microprocessor 22 in FIG. Therefore, the description will be made with reference to FIGS. 1 and 2 as in the first embodiment.

The reflected light sum signal detector 21 calculates the sum TS of the reflected light amount from the optical disc 1 and inputs the sum TS to the microprocessor 22 via the AD converter 24. The tracking error signal TE from the tracking error signal detector 6 is also input to the microprocessor 22 via the AD converter 25. As shown in FIG. 2, the input signal is a signal that changes periodically with time. The microprocessor 22 detects the input TS and TE at predetermined time intervals, and obtains a maximum point or a minimum point of the TS from the data.

After detecting the pole of TS, the level of TE at the pole is detected, and the tracking error signal is corrected by the DA converter 23 and the subtractor 11 so that the position corresponding to the signal level becomes the tracking position. And the corrected TE
Is used to perform tracking control.

Next, a method of detecting the extreme point of the TS and detecting the level of the TE at the extreme point in the second embodiment will be described in further detail.

FIG. 6 shows a microprocessor via AD converters 24 and 25
22 is a waveform diagram of each signal showing discrete values of TS and TE taken in by 22. FIG.

After the device is turned on and the focus control is operated, the microprocessor 22 operates the movement signal generator 26 to move or oscillate the tracking actuator 9 or the transfer device 10 to obtain a stable track crossing signal. The microprocessor 22 detects the TS through the AD converter 24 and the TE through the AD converter 25 by a predetermined number of samples at a predetermined timing. Point A1, point B1, point C1 in FIG.
The points D1 and E1 are points on the TS detected by the microprocessor 22. Assuming that the detected time of the points A1, B1, C1, D1, and E1 is t, and each signal amplitude is y, the TS phase x
Is represented by x = 2πt / T (where T is the period of the reflected light amount sum signal), and the relationship between x and y is a predetermined periodic function y = f (x)
Can be approximated by

When detecting the points A1, B1, C1, D1, and E1, the microprocessor 22 approximates, for example, a predetermined periodic function y = a cos (x−b) + c (7). Although there are various methods for approximation, as in the first embodiment, the approximation can be performed by applying the least square method. From the above equation (1), a cos (x−b) + cy = 0 (8) is established. In this equation (2), the phase x _j and the signal amplitude y of the signal actually detected by the microprocessor 22 are expressed. _{When j} (where j is a number representing the order of the detected signals) is substituted, it does not become 0 due to the influence of noise, sampling error, or the like, and a cos (x _j −b) + c−y _j = v _j . 9) '. Where the sum of the squares of v _j (N is a set predetermined number of samples and 5 is set in this embodiment) When the values of a, b, and c are determined so that
Can accurately reproduce the actual TS as shown by the solid line y = f (x) in FIG. This approximated function curve is measured by the microprocessor 22 (from point A1 to point E1).
Through the approximate average position of point). Therefore, by performing this arithmetic processing, it is possible to calculate a predetermined function y = f (x) that approximates the relationship between the phase x and the reflected light sum y.

Similarly, the tracking error signal can be approximated to a predetermined function. The microprocessor 22 detects a predetermined number of samples via the AD converter 25 at substantially the same timing as that of the TS. A2 point, B2 point, C2 point, D2 in Fig. 6
The point E2 is a point on the TE detected by the microprocessor 22. Assuming that the detected time of the points A2, B2, C2, D2 and E2 is t and each signal amplitude is y, the phase x of TE is x = 2πt / T (where T is the tracking error signal And the relationship between x and y is a predetermined periodic function y = g (x)
Can be approximated by

When detecting the points A2, B2, C2, D2, and E2, the microprocessor 22 applies a least squares method or the like to approximate a predetermined periodic function y = a cos (x-β) + γ (11). The curve representing the approximated function can accurately reproduce the actual TE as shown by the solid line y = g (x) in FIG. This approximated function curve passes through the position of the average of the actually measured values (points A2 to E2) by the microprocessor 22. Therefore, by performing this arithmetic processing, it is possible to calculate a predetermined function y = g (x) that approximates the relationship between the phase x and the amplitude y of the TE.

The microprocessor 22 calculates an approximate function f of each of TS and TE.
After obtaining (x) and g (x), the two functions f (x) and g (x) are compared. That is, the maximum or minimum point x = 2mπ + b and x = (2m + 1) π + b of the function f (x)
The tracking error signal at that time is calculated from the value of g (x) at that time, and data corresponding to the difference from the reference value 0 is output. Output data is DA converter
The signal is converted into an analog value by 23, and the tracking error signal is corrected by the subtractor 11. Therefore, the corrected tracking error signal can be controlled at a correct tracking position.

As in the first embodiment, the microprocessor 22 recognizes whether the disc 1 is groove-recorded or land-recorded based on information from a sensing hole of a cartridge in which the disc 1 is stored or information recorded in the disc 1 in advance. For groove recording, the minimum point of TS, for land recording,
The tracking error signal at the TE maximum point is detected and corrected.

In the second embodiment as well, a case where approximation with a real function such as a cubic function other than the periodic function is applicable, and the accuracy of adjustment can be improved by increasing the number of samples for function approximation of each signal. Can be raised.

Further, the average of the TS amplitude or the average of the TE amplitude input to the microprocessor 22 is obtained, and an approximate calculation is performed based on the average value, whereby the adjustment accuracy can be improved. Alternatively, the function approximation of TS or TE may be performed twice or more, and the average of the values obtained by each function may be calculated.

As described above, in the present invention, when the reflected light amount sum signal is approximated to a predetermined function, the method of performing the adjustment by approximating the reproduction signal characteristic by the least square method has been described. Even when the approximation method is used, it can be adapted by changing the arithmetic processing executed by the microprocessor 22.

FIG. 7 shows a flow of processing of the microprocessor 22 in the second embodiment.

In the first and second embodiments, the information recorded by the reflected light from the optical disk 1 is reproduced, or an error signal for focus and tracking control is detected. The same effect can be obtained in a device configured to obtain an information signal or an error signal for control by light.

In the first and second embodiments, the tracking position is adjusted immediately after the power is turned on. However, the time measurement function of the microprocessor 22 is used to execute the adjustment every predetermined time after the apparatus is started. Alternatively, the tracking position may be adjusted when a recording / reproducing command is not sent from the host for a predetermined time. Further, when a recording or reproduction command is issued from the host, if the signal recorded on the recording medium cannot be correctly recorded or cannot be reproduced, the tracking position is adjusted so that the tracking position is adjusted. It is possible to perform stable recording and reproduction. If a temperature sensor such as an acceleration sensor or a thermistor using a piezoelectric element is attached to the device, the sensor can detect when vibration or shock is applied to the device or when the temperature inside the device changes. When the device is configured to adjust the tracking position, the temperature change during use of the device,
Even if the adjustment state shifts due to external vibration, impact, or the like, it is possible to quickly respond.

Further, the adjustment of the tracking position in the present apparatus is performed by the first
Although the adjustment is realized by the subtractor 11 shown in the figure, the adjustment can be realized more easily in the digital control system by adding and subtracting the numerical data of the control signal according to the operation result. Thus, the same effect can be obtained even if the present invention is applied to another adjustment method for changing the size of the target position of the tracking control system.

Effect of the Invention As described above, according to the present invention, a correct tracking control target position can be detected, and highly accurate tracking control can be realized. As a result, a high-quality signal can be recorded and reproduced, and a highly reliable device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a tracking control device according to one embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part for explaining the operation of the tracking control device of FIG. 1, FIG.
FIG. 4 is a signal waveform diagram for explaining a method of adjusting a tracking position of the optical recording / reproducing apparatus according to the first embodiment of the present invention, and FIG. 5 is a diagram showing processing of a microprocessor in the first embodiment. FIG. 6 is a flowchart showing the flow, FIG. 6 is a signal waveform diagram for explaining a method of adjusting the tracking position of the optical recording / reproducing apparatus according to the second embodiment of the present invention,
FIG. 7 is a flowchart showing the flow of processing in the microprocessor of the second embodiment, FIG. 8 is a block diagram showing the configuration of a conventional tracking control device, FIG. 9 is a waveform diagram of a tracking error signal, and FIG. FIG. 10 is a distribution diagram of the reflected light on the photodiode for tracking detection. DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Light beam, 3 ... Objective lens, 4 ... Optical head, 5 ... Focus control circuit, 6 ...
... Tracking error detection circuit, 7 ... Phase compensation circuit, 8
... Actuator drive circuit, 9 ... Tracking actuator, 10 ... Transfer device, 11 ... Subtractor, 12 ... Offset generator, 21 ... Reflected light amount sum signal detector, 22 ... Microprocessor, 23 ... DA converter, 24 …… AD converter,
25 AD converter, 26 Moving signal generator, 92 Photodetector, 901 902 Dividing line, 910 Zero-order light, 911
... Primary light, 912.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-211840 (JP, A) JP-A-2-187933 (JP, A) JP-A-61-194646 (JP, A) JP-A 64-64 89034 (JP, A) JP-A-3-178043 (JP, A) JP-A-2-246024 (JP, A)

Claims (11)

(57) [Claims] A converging means for converging a light beam toward a recording medium; a moving means for moving a convergence point of the light beam converged by the converging means so as to cross a track on the recording medium; A track shift detecting means for generating a signal corresponding to a positional relationship between a light beam of the recording medium and a track by transmitted light transmitted through the recording medium or reflected light reflected from the recording medium; Tracking control means for driving the moving means to control the light beam to be positioned on the track, light amount detecting means for detecting the sum of the transmitted light amount or reflected light amount from the recording medium, and the signal of the light amount detecting means. Calculating means for calculating an extreme point; and target position adjusting means for changing a target position of the tracking control means based on a result of the calculating means. Calculating means tracking control apparatus and obtains a pole approximates the signal of the light amount detecting means to a predetermined function. 2. The tracking control device according to claim 1, wherein the calculating means approximates the signal of the light quantity detecting means to a periodic function. 3. The tracking control device according to claim 1, wherein the calculating means approximates the signal of the light quantity detecting means to a cubic function. 4. A converging means for converging a light beam toward a recording medium, a moving means for moving a convergence point of the light beam converged by the converging means so as to cross a track on the recording medium, and A track shift detecting means for generating a signal corresponding to a positional relationship between a light beam of the recording medium and a track by transmitted light transmitted through the recording medium or reflected light reflected from the recording medium; Tracking control means for driving the moving means to control the light beam to be positioned on the track; light quantity detection means for detecting the sum of the transmitted light quantity or reflected light quantity from the recording medium; and a signal of the light quantity detection means. A first function approximation unit for approximating a function, and a second function approximation unit for approximating a signal of the track deviation detection unit to a function, , Depending on the result of comparing the function of each determined by the second function approximation means, tracking control apparatus and adjusting a target position of the tracking control means. 5. A tracking control means for calculating a value of a second function g (x) approximated by a second function approximation means corresponding to a pole of the first function f (x) obtained by the first function approximation means. 5. The tracking control device according to claim 4, wherein the target position is adjusted. 6. The tracking control device according to claim 5, wherein the first and second function approximating means approximate a periodic function. 7. The apparatus according to claim 1, further comprising a time measuring means for adjusting a target position of the tracking control means at predetermined time intervals or when the signal has not been recorded or reproduced for a predetermined time period. 5. The tracking control device according to 1 or 4. 8. The apparatus according to claim 1, wherein when a signal recorded on a recording medium cannot be reproduced, said signal is reproduced again after adjusting a target position of said tracking control means. 5. The tracking control device according to 4. 9. When a signal cannot be correctly recorded on a recording medium, a target position of the tracking control means is adjusted,
5. The tracking control device according to claim 1, wherein the signal is recorded again. 10. An apparatus according to claim 1, further comprising: acceleration detecting means for detecting vibrations and shocks applied to the apparatus from outside, wherein when the acceleration signal of the acceleration detecting means exceeds a predetermined magnitude, the target position of the tracking control means is adjusted. 5. The tracking control device according to claim 1, wherein 11. The apparatus according to claim 1, further comprising a temperature detecting means for detecting a temperature inside the apparatus, wherein a target position of the tracking control means is adjusted when a signal of the temperature detecting means exceeds a predetermined value. 5. The tracking control device according to 1 or 4.