JPH06342526A - Light spot positioning control device - Google Patents

Abstract

PURPOSE:To stop a light spot at high moving speed on a track by calculating the moving direction and speed of the light spot based on a difference of a digital dislocation signal obtained by sampling a dislocation signal of the light spot with a high speed clock. CONSTITUTION:A dislocation signal of the light spot by an optical head 2 is detected by a track error amplifier 21, etc., and is digital-converted by a multiplexer 51 and an A/D converter 52, etc., in an A/D converter 15, and is then stored in a register part 53. At this time, the multiplexer 51, the converter circuit 52 and the register part 53 are sampled with the high speed conversion clock from a conversion clock generator 55. Then, when the digital dislocation signal is largely changed, the moving direction and the changing speed of the dislocation signal are calculated by a digital signal processor 17 based on a difference of the digital dislocation signal, and even when the movement of the light spot is fast, the light spot is stopped on the track and good focusing, etc., can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling a light beam spot position of an optical disk device for optically recording and reproducing information.

[0002]

2. Description of the Related Art An optical disk device focuses a laser beam and irradiates the information recording surface of a record carrier (optical disk) to optically record and reproduce information. In this type of optical disk device, it is necessary to move the light spot with respect to an extremely narrow information track, align it with a target track, hold it at the center, and focus the light spot.

For this reason, an optical lens for focusing the light beam or a movable mirror for deflecting the beam is arranged in the direction perpendicular to the track so as to optically detect the positional deviation of the light spot with respect to the information track and correct the deviation. Positioning control such as tracking control for moving in the track crossing direction, track access control, and focusing control for focusing the light spot on the target track is performed.

Conventionally, in the positioning control of the light spot, an analog control circuit for converting a position deviation signal optically detected into an electric signal and processing it by an analog electric circuit to generate a drive control signal for moving the light spot ( Device) has been used. In recent years, digital position control devices that perform position control operation (control signal generation process) by digital signal processing have been adopted for the purpose of reducing the circuit scale, improving the function, and reducing the price.

An optical spot position control device based on such a digital system is disclosed in, for example, Japanese Patent Laid-Open No. 2-42630, "Optical Spot Positioning Device". In this prior art, the position shift signals for tracking control and track access control are sampled and held, and those signals are selected by a selector and then A / D converted (analog → digital conversion) and taken into a digital signal processing means. It is shown that a control signal for driving is generated by digital processing, and the output of the digital signal processing means is D / A converted (digital → analog conversion) and supplied to the light spot driving means (actuator etc.). ing.

[0006] As another conventional example, Japanese Patent Laid-Open No. 64-49
There is a technique disclosed in Japanese Patent No. 131. In this example, a focus signal for focus control of a light spot and a track signal and a track access signal for positioning control with respect to a track are time-divided and digitally converted by the same A / D converter, and are converted into digital signal processing means. After importing and performing signal processing (control signal generation for driving),
It is described that the output is time-divisionally output to the corresponding driving means.

In any of these examples, the positional deviation signal is taken into the A / D converter at the sample timing having a constant time interval, and the digital signal processing means processes the signal taken in at the constant sample interval. It is configured to perform (calculation).

[0008]

It is a general method in digital signal processing to sample and capture a signal at a constant time interval as described above, but a change in the position deviation signal in a shorter time than the sampling time interval is promoted. It has the fundamental drawback that it cannot be obtained.

For example, in the case of track access control, when the light spot is moving in the direction traversing the track, it is necessary to detect the moving direction and speed (or movement amount) to stop it on the track. But,
When the track position deviation signal (track error signal) greatly changes at one sample time interval, it becomes difficult to accurately promote the moving direction and moving speed. In particular, the track error signal generally changes in a sinusoidal manner with a cycle of one track pitch with respect to the movement of the light spot in the cross-track direction. Therefore, when the light spot moves more than half a track at one sample time interval, it moves. It becomes impossible to detect the quantity at all.

As described above, the positioning control of the light spot by the digital signal processing is effective for downsizing, high performance and low cost, but the position shift signal is taken in at discrete sampling intervals, A / D conversion, signal Since the processing is performed, it is inevitable that a high-speed change of the signal is hard to catch. Especially when the light spot crosses the information track at a relatively high speed, it becomes difficult to accurately grasp the crossing speed and the crossing direction.

The present invention solves the above problems.
An object of the present invention is to provide a positioning control device capable of accurately detecting a change in a positional deviation signal in a shorter time than a sampling interval and reliably detecting a moving direction, a speed, etc. even when a moving speed of a light spot is relatively high.

[0012]

A light spot positioning control apparatus of the present invention takes in a light spot position shift signal at every sample timing of a fixed time period and converts it into a first digital position shift signal, and at the same time, the fixed time period. An A / D converter that delays a position shift signal by a second time shorter than the cycle and converts the position shift signal into a second position shift signal, and first and second digital position shift signals from the A / D converter And a digital signal processing means for digitally generating the position of the light spot.

[0013]

Operation: Obtaining the amount of change in the positional deviation signal within a short time from the difference between the two digital positional deviation signals that are captured twice at the timing when the optical spot positional deviation signal is shifted by a time shorter than the time period of the sample timing. Thus, even when the moving speed of the light spot is relatively high, the instantaneous moving speed and moving direction of the light spot can be accurately captured.

As a result, the light spot deviates from the track following state, and the light spot can be stably and promptly stopped on the track from the state of moving in the track crossing direction, and the inter-track movement or the tracking deviated. The runaway of the light spot in the can be suppressed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a light spot positioning control device of the present invention, and FIG. 2 is a waveform diagram schematically showing signal states of essential parts for explaining the operation of the device of FIG. FIG. 3 shows the digital signal processor 17 in FIG.
3 is a block diagram schematically showing the processing operation of FIG.

In FIG. 1, the light spot positioning control device has an optical head 2 for irradiating a focused light beam onto an information track on a record carrier 1. The optical head 2 is
An optical means for detecting the positional deviation of the light spot with respect to the information track, a track error detector 12 for converting the positional deviation into an electric signal, an optical means for detecting the focal deviation of the light beam spot with respect to the information recording surface, and A focus error detector 13 for converting defocus into an electric signal is provided. An optical system for optically recording and reproducing information is omitted for simplicity.

The track error detector 12 is composed of, for example, a photodetector divided into two, and a current (photocurrent) that changes in response to a change in reflected light caused by the displacement of the light spot with respect to the information track. ) Occurs. The two current signals output from the track error detector 12 are supplied to the track error amplifier 21. The track error amplifier 21 takes the difference between these current signals, amplifies the difference signal, and outputs a track error signal 101. The track sum amplifier 22 takes the sum of two current signals of the track error detector 12 and amplifies the sum signal to show the total amount of light received by the track error detector 12 (corresponding to the amount of reflected light from the record carrier). The track sum signal 102 is output.

The focus error detector 13 generates a current that changes in accordance with the defocus of the light spot on the recording surface. The focus error amplifier 23 takes the difference between the two current signals from the focus error detector 13 and amplifies the difference signal to output a focus error signal 103.
These signals 101, 102 and 103 are supplied to an A / D converter 15 having a plurality of analog signal input terminals.

In the A / D converter 15, the multiplexer 51 selects the analog signal input input to the plurality of input terminals I1 to I8. The A / D conversion circuit 52 converts the analog signal selected by the multiplexer 51 into a digital signal. The register block 53 includes a plurality of transistors corresponding to the plurality of analog input terminals I1 to I8, and stores the digital signal output from the A / D conversion circuit 52 in the corresponding registers R1 to R8. The conversion clock generator 55 is the sample clock generation circuit 1
4 receives the sample clock 110 designating the start timing of the A / D conversion operation and generates an A / D conversion clock for sequentially converting a plurality of analog input signals input to the multiplexer 51 into digital signals. The selector circuit 54 receives the register selection signal 112 from the digital signal processor 17 and receives the register block 5
The contents (data) of the designated register 3 are output as detection signal data 114. As an A / D converter having such a function and configuration, there is, for example, MC141610 type A / D conversion IC manufactured by Nippon Motorola Co., Ltd.

The digital signal processor 17 is a processor (generally a DSP) for digitally performing input / output and arithmetic processing of digital signals in accordance with a built-in program.
Is abbreviated). The processor 17 sends a register selection signal 112 to the A / D converter 15 to specify a desired register in the register block 53,
The A / D-converted signals are individually fetched, and arithmetic processing is performed based on the fetched signals to generate some drive control signals for moving the optical head 2. As these drive control signals, a tracking control signal generated based on the track error signal 101 for moving the track actuator 11, a head drive control signal for moving the entire optical head 2 at the time of track access, and a focus error signal 103. And a focus control signal for moving a focus actuator (not shown) for controlling the focus of the light spot. These signals are time-divided and output from the digital signal processor 17. Here, for the sake of simplicity, only the tracking control signal 116 is shown for the sake of simplicity.

The digital signal processor 17 performs arithmetic processing based on the data obtained by digitally converting the track error signal 101 and the track sum signal 102 at each sample timing designated by the sample clock 110, and a tracking control signal for moving the track actuator. 116 is output to the D / A converter 18.

The D / A converter 18 converts the tracking control signal, which is digital data, into an analog electric signal (voltage level) and inputs the analog control signal 117 to the power amplifier 19. The power amplifier 19 amplifies the input analog control signal, and the track actuator 11
The drive current 118 for driving is output.

With such a configuration, the track actuator 11 is driven in response to the track error signal, and the displacement of the light spot with respect to the center line of the information track is suppressed to a small level, or the light spot is moved to a desired track. The control for making it performed is performed.

In the present invention, the track error signal 101 is taken in the A / D converter 15 a plurality of times at different timings during one sampling period. That is, the track error signal 101 is connected to the two input terminals I1 and I8 of the multiplexer 51 in the A / D converter 15, and the A / D conversion is performed twice at different timings within one sample period defined by the sample clock 110. To be done. The track sum signal 102 is connected to another input terminal I2 of the multiplexer 51, and the focus error signal 10
3 is connected to the input terminal I3. Here, the terminals (I1 to I8) connecting these signals may be arbitrarily selected.

A plurality of analog signal inputs of the multiplexer 51 are sequentially (serially) converted into digital signals from I1 to I8 according to the A / D conversion clock from the conversion clock generator 55. Therefore, there is a time lag (delay) in the timing at which the input signal of the input terminal I1 and the input signal of I8 are fetched and A / D converted. That is, the track error signal 101 is shifted twice by a time required for the A / D conversion to proceed from I1 to I8 (this is referred to as Ta), and the track error signal 101 is captured and converted twice within one sample period to register R1 of the register unit 53. And stored in R8 as different digital data.

The digital signal processor 17 takes in these data stored in the register section, and when the change amount of the track error signal 101 during one sample period is large, the track error stored in the register R8 which is taken in at a different time is taken in. A control signal 1 for determining the moving direction of the light spot using the signal data, calculating the instantaneous moving speed, and stopping the light spot with respect to the information track.
16 is generated.

The operation of the digital signal processor 17 will be described in more detail with reference to FIGS. 2 and 3. It should be noted that FIG. 2 schematically shows signal states of main parts for explaining the operation of the apparatus, and does not necessarily mean that such a signal is generated. Further, FIG. 3 schematically shows a signal processing system of the digital signal processor, and such hardware is not provided inside the processor. The processor 17 realizes the same function as that shown in FIG. 3 by sequential processing according to the program.

In FIG. 2, the waveform (A) is the change of the track error signal 101, and the waveform (B) is the sample clock 1
10 and waveform (C) show changes in the track sum signal 102, respectively.

The track error signal 101 input to the input terminal I1 of the A / D converter 15 is the sample clock 110.
Is taken into the A / D converter 15 every period Tb of and is converted into a digital signal. Here, if the moving speed of the light spot in the cross-track direction is high, the track error signal 101 changes greatly during one sampling period Tb, and it is not possible to accurately capture the change with one sampling of one sample. Therefore, in the embodiment, the sample clock 110
The track error signal 101 is fetched again at a timing delayed by a certain time Ta.

The track sum signal 102 indicates the amount of reflected light from the optical disk 1 due to the irradiation of the light spot. For example, when the light spot is near the center of the information track, the level of the track sum signal 102 is high (the reflected light is large) and adjacent to it. Near the middle of the track, the track sum signal 102 has a low level (less reflection). Therefore, by comparing the track sum signal 102 with a constant reference level Vs, it is possible to determine whether the light spot is near the center of the track or is out of the center of the track (between tracks). The change direction of the track error signal 101 with respect to the movement of the light spot is reversed depending on whether the track error signal 101 is near the center of the track or between tracks. Therefore, the product of the change direction of the track error signal and the polarity of High / Low of the track sum signal (logical EXOR) can be used to determine the moving direction of the light spot across the track. For example, the track sum signal 102 is at a high level, and the change in the track error signal is increasing (from negative to positive).
In this case, it can be determined that the light spot is moving in the positive direction (from the inner circumference of the disc to the outer circumference).

The waveform (D) is the amount of change in the track error signal 101 calculated based only on the track error signal taken in from the input terminal I1 of the A / D converter 15 (taken only once in one sampling period Tb). Is schematically shown. When the change of the track error signal 101 is gradual, the change can be captured relatively accurately even with a rough sample, but when the change is fast (the state at the left end in the figure), the change of the track error signal 101 is hardly captured. . In this example, the difference (TE (n) -TE (n-1)) of the sampled track error signal 101 is almost 0 at a fast change location.

On the other hand, the difference between the track error signal (denoted by TA) from the input terminal I8 which is fetched and A / D converted after being delayed by a fixed time Ta and the track error signal (denoted by TE) fetched from the input terminal I1 is calculated. Then, as shown in the waveform (E), the rapid change of the track error signal 101 can be detected relatively accurately. When the product of the change amount of the track error signal calculated as in the waveform (E) and the High / Low polarity of the track sum signal is calculated, the moving speed and moving direction of the light spot as shown in the waveform (F) are calculated. The signals V1 to V12 shown are obtained. The light spot can be quickly stopped on the track by controlling the movement of the lens actuator 11 based on this signal.

In FIG. 3, the digital data of the track error signal TE fetched from the input terminal I1 of the A / D converter 15 is the digitized data of the track error signal TA fetched from the input terminal I8 via the register R1. The digitized data of the track sum signal TSM fetched from the input terminal I2 is supplied to the digital signal processor 17 via the register R8 and the register R2.

The digital signal processor 17 takes in the track error signal TE, stores the value in the internal register 71, and performs the phase compensation calculation for tracking control by the loop filter 81. The output of the loop filter 81 is amplified by the gain adjustment block 90 by an appropriate gain KA and supplied to the selector 97. When the optical spot follows the track (during tracking control), the selector 97 allows the output of the gain adjustment block 90 (track error signal whose phase is compensated) to pass therethrough, and the digital signal processor 1 outputs the tracking control signal 116.
Output from 7. This state (tracking control state)
It is not necessary to judge the moving direction of the light spot, but it is necessary to detect the moving direction and speed in order to stably stop the light spot when the light spot is moving off the track and crossing the track. Becomes The track error signal fetched by the digital signal processor 17 is delayed by one delay period Tb by the delay element 72 and stored in the register 73. (Actually, a new track error signal TE (n) is taken into the register 71, and at the same time, the previous sample value TE (n-1) is transferred to the register 73.) Of the new track error data TE (n) stored in the register 73 and the old track error data TE (n-1) stored in the register 73. A signal corresponding to the speed is obtained by dividing the output of the difference calculation block 83 by the sampling time Tb in the division block 87. However, as described above, when the change speed of the track error signal 101 is fast, such a difference cannot capture an accurate change.

On the other hand, the track error signal TA fetched with a time shift is stored in the register 74. This data TA does not need to store a delayed value in the subsequent processing. The instantaneous difference calculation block 84 uses the track error data TA (n) stored in the register 74 and the register 71.
The difference from the track error data TE (n) is calculated. The difference value obtained by the instantaneous difference calculation block is the A / D converter 1
Conversion delay time T for I1 input and I8 input in 5
The instantaneous change of the track error signal 101 at a is shown, and this value is divided by the delay time Ta in the division block 88 to obtain a signal corresponding to the track crossing speed of the light spot. Amount of change in track error signal (TA (n) -TE (n)) obtained from this instantaneous difference
Indicates a change in the track error signal relatively accurately even when the change speed of the track error signal is high.

The absolute value level comparison block 89 compares the result of the instantaneous difference calculation with a predetermined value, and when the value of the instantaneous difference is smaller than the specified value, the change amount of the track error signal is small and the result of the instantaneous difference is dare to be obtained. When it is judged that it is not necessary to use, the selector block 92 is moved so as to select the signal based on the simple difference output from the divider 87. On the contrary, when the value of the instantaneous difference of the track error signal is larger than the specified value, it is determined that the change amount of the track error is too large to be calculated by the mere difference, and the output of the division block 88 (the speed calculated from the instantaneous difference signal). The selector 92 is moved so as to select (corresponding signal). The data TSM indicating the track sum signal is fetched in the register 75 and compared with the reference level by the level comparison block 85 to be high.
It is determined whether (1) or Low (0).

As a result, the high / low of the track sum signal
The polarity signal indicating Low is transmitted to the multiplier 93, and the multiplier 93 multiplies the output signal of the selector 92 (the speed equivalent signal obtained from the difference between the track error signals). The output (product) of the multiplier 93 becomes a signal that indicates the speed of the light spot almost accurately along with the moving direction.

It is to be noted that the difference between the track error signals shows the speed of the light spot almost accurately in the range where the track error signal changes in a substantially linear manner with respect to the positional deviation. The difference between the maximum positive and negative points (peak point and bottom point) becomes inaccurate even if the difference is obtained. The level comparator 82 monitors whether or not the value of the track error data TE exceeds the linear range of the track error signal, and if it exceeds the linear range, the above-mentioned difference calculation (the same applies to the instantaneous difference calculation) is stopped for that moment. Let The register 86 holds a value (VF) that specifies the speed of the light spot across the track. This speed reference value (V
The value of F) generally changes according to the movement of the light spot.
When stopping the light spot, V is set in this register 86.
0 is set as F.

The speed error calculation block 91 has a register 86.
The difference between the value VF held by and the output (speed signal) of the multiplier 93 is obtained. The output of the speed error calculation block 91 is amplified by Kv times by the gain adjustment block 94 so as to have a gain suitable for speed control, and is transmitted to the selector 97. When the light spot is out of the track following state, the selector 97 uses the signal from the mode switching control block to output a signal for speed control (gain adjustment block 9
4 output). The mode switching control block 95 monitors the output (speed signal) of the multiplier 93, and when the value (absolute value) becomes sufficiently small, it judges that the light spot is almost stopped with respect to the information track, and the speed control state. To set the selector 97 to perform the track following operation (that is, to select the output of the gain adjustment block 90).

The signal selected by the selector 97 is sent from the digital signal processor to the tracking control signal 116.
Is output as a signal for driving the track actuator so as to stop the light spot or follow the track.

[0042]

As described above, according to the present invention, the signal indicating the positional deviation of the light spot (track error signal) is captured twice at a timing shifted by a constant time shorter than the period (cycle) of the sample timing. By calculating the amount of change in the track error signal within a short time from the difference between the two digital data (tracking error data), the moving direction and moving speed of the light spot can be increased even when the moving speed of the light spot is relatively large. Can be accurately captured. This has an effect that the light spot can be stopped on the track stably and promptly from the state where the light spot is moving fast in the track crossing direction.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a light spot positioning control device of the present invention.

FIG. 2 is a waveform diagram schematically showing signal states of main parts for explaining the operation of the device shown in one embodiment of the present invention.

FIG. 3 is a block diagram schematically showing the processing operation of a digital signal processor 17.

[Explanation of symbols]

 1 record carrier 2 optical head 11 track actuator 12 track error detector 13 focus error detector 14 sample clock generation circuit 15 A / D converter 17 digital signal processor 18 D / A converter 19 power amplifier 21 track error amplifier 22 track sum Amplifier 23 Focus error amplifier 51 Multiplexer 52 A / D conversion circuit 53 Register block 54 Selector circuit 55 Conversion clock generator

Claims (5)

[Claims] 1. A light beam irradiating means for irradiating a focused light beam spot onto an information track formed in a substantially concentric or spiral shape on a rotating disk-shaped record carrier; Means for optically detecting a relative displacement with respect to the target track to generate a displacement signal; and receiving a reference sample signal of a first time period and delaying it by a second time shorter than the first time. A means for generating a converted sample signal, which takes in the position shift signal at each sample timing of the reference sample signal and converts the position shift signal into a first digital position shift signal, and the position at each sample timing of the one converted sample signal. An analog-to-digital converter that takes in the shift signal and converts it into a second digital position shift signal; Digital signal processing means for digitally processing the first and second digital position shift signals from the digital converter to generate a drive control signal for controlling the position of the light beam spot and supplying the drive control signal to the light beam irradiation means. An optical spot positioning control device comprising: 2. The reference of the light beam spot and the information track based on the first digital position shift signal and the second digital position shift signal from the analog-digital converter. And a means for calculating a signal indicating an instantaneous relative speed near the sample timing, and a means for generating a control signal for causing the speed of the light beam spot with respect to the target track to approach 0 and stop. The optical spot positioning control device according to claim 1. 3. The digital signal processing means compares a difference between the first digital position shift signal and the second digital position shift signal with a predetermined value, and the difference is determined in advance. When it is smaller than a value, the drive control signal is generated only by the first digital displacement signal, and when the difference exceeds the predetermined value, both the first and second displacement signals are used. The optical spot positioning control device according to claim 1, wherein the drive control signal is generated. 4. The analog-to-digital converter inputs a plurality of types of positional deviation signals for controlling the position of the light beam spot, sequentially converts them into digital signals at regular time intervals, and a plurality of digitally converted types are inputted. 2. The light spot positioning control device according to claim 1, wherein the light beam irradiating means is caused to perform a plurality of operations by digitally calculating the signal of FIG. 5. The at least one of the plurality of types of signals is a signal indicating the amount of reflected light from the record carrier due to the irradiation of the light beam spot, and the digital signal processing means includes the first and second digital signals. 5. The optical spot positioning control device for recording according to claim 4, further comprising means for detecting a moving direction of the light beam spot with respect to the information track based on a position shift signal and a signal indicating the reflected light amount.