JPH06101126B2 - Positioning control circuit for optical disc player - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing an optical disc, such as a compact disc or a laser disc.
In particular, the tracking control system of this reproducing apparatus constitutes a dual control system consisting of a tracking control loop for driving only the objective lens and a feed control system for driving the entire pickup, and an optical system for performing the control processing by digital calculation. The present invention relates to a positioning control circuit of a disc reproducing device.

The characteristics of conventional optical disc players such as CDs are that high-density recording and high-speed random access are possible. That is, because of the high-density recording, in order to follow the fine track (track pitch is about 1.6 μm), focus control for narrowing the light beam to the convergence limit of the objective lens and high-precision tracking control Need. On the other hand, in order to enable random access, it is necessary to move the reproducing pickup at a high speed in the radial direction of the disc.

It is mechanically extremely difficult to make these two requests with only one movable part. For this reason, it is common to have a dual control system that is divided into two parts, a tracking actuator that follows the light beam on the track and a feed mechanism that moves the entire pickup, and is associated with each other.

As a means for performing random access at high speed, a voice coil type linear motor is used for the feeding mechanism.
As a method for stabilizing the control of the voice coil linear motor, a method of detecting the speed of the feed mechanism and providing a speed feedback loop in the control system of the feed mechanism is generally used.

Now, with the recent progress of digital signal processing technology and LSI technology, it has become general to perform signal processing of control systems by numerical calculation. However, the control band of the tracking actuator control system is
It is a wide band around 1kHz. With conventional semiconductor technology, it has been difficult to obtain a processing speed that allows this control system to be performed by digital processing, so that sufficient efforts have not been made. Therefore, the control system of the actuator of the optical pickup and the pickup feed mechanism is only the reproducing device which is performed by an analog circuit.

However, the control system based on such an analog circuit essentially has an offset and a temperature drift in the DC voltage of the amplifier circuit. Therefore, there is a problem in that the positioning accuracy of the control system easily causes an error due to these offsets and drifts.

In addition, in a control system using analog circuits, processing such as low-pass compensation filters and phase compensation filters is performed using capacitors and resistors, so even if ICs are used in the control circuits, these capacitors and resistors will not be removed. It is necessary as an attachment part. For this reason, there are problems that the cost is increased and the miniaturization is hindered.

In view of the above problems, the present invention provides a positioning control circuit for an optical disc reproducing apparatus, which is suitable for digital operation and is inexpensive.

Means for Solving the Problems In order to solve the above problems, the positioning control circuit of the optical disc reproducing apparatus of the present invention is configured such that information is recorded on a plurality of optically reproducible tracks. Reproducing means for irradiating the record carrier with a radiation beam and receiving a modulated radiation beam generated thereby for photoelectric conversion, and error detecting means for detecting a tracking error signal from the output of the reproducing means. Tracking control means for numerically calculating the output of the error detection means to output tracking operation data and causing the radiation beam and the track to follow the path of the radiation beam, and moving means for moving the reproducing means in the direction traversing the track. And position detecting means for detecting the absolute position of this moving means, and the output of this position detecting means is digitized to output absolute position data. Position digitizing means for applying force, search control means for detecting a positional error between the absolute position data and a predetermined target position, and outputting position correction data and a search command signal for instructing the start of a search operation, Switching means for selecting the position correction data in the search operation and selecting the tracking operation data for other operations in response to the search command signal, and detecting the moving speed of the moving means and performing the search. Speed detecting means for varying the gain according to the command signal, speed digitizing means for digitizing the output of the speed detecting means and converting it into speed data, and adding means for adding the speed data and the output data of the switching means. Calculating means for calculating position control data by processing the output of the adding means, and multiplying the position control data by a predetermined coefficient and responding to the search command signal. Variable coefficient means for varying the lever coefficient, voltage converting means for converting the output of the variable coefficient means into a voltage, and drive for generating a drive signal for influencing the movement of the moving means in accordance with the output of the voltage converting means. And a structure including a means.

Action The present invention, which has the above-described configuration, configures the control system by the digital arithmetic processing, so that it is possible to prevent DC offset and temperature drift from occurring in the control circuit. Further, since the gain of the speed detecting means is switched between the address search and the play at the stage before the digitizing means, it is possible to perform the address search mode requiring the dynamic range and the reproducing mode requiring the resolution. The word length of the digitizing means can be effectively used. Further, also in the variable coefficient means, the gain is switched between the address search and the play as in the digitizing means, so that the stability of the control system can be secured.

Embodiments A positioning control circuit of an optical disk reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a positioning control circuit of an optical disc reproducing apparatus of the present invention. In FIG. 1, reference numeral 100 denotes a disc, and an address for recognizing a reproduction position is recorded on a spiral track. 101
Is a pickup, which has a 4- or 6-divided photodiode for irradiating a light beam on the track of the disc 100 and receiving reflected light wave-optically modulated by the pits on the track. An actuator that moves in the focus direction and the tracking direction is configured. Reference numeral 103 denotes an error detection means, which performs current-voltage conversion on the sum of photocurrents due to the modulated radiation beam received by the photodiode of the pickup 101, and the relative between the radiation beam and the track is determined by the difference in the light intensity or phase of this modulated radiation beam. Detects position error. Reference numeral 104 denotes a tracking control means, which calculates the output of the error detection means 103 and outputs the tracking operation data Dt by calculating the output data of the tracking digitization means 104a and the tracking digitization means 104a and performing phase compensation. The pickup 10 receives the outputs of the tracking calculation means 104b, the tracking voltage conversion means 104c for converting the tracking operation data Dt into a voltage, and the tracking voltage conversion means 104c so that the radiation beam generates a motion that follows the path of the track.
It is composed of tracking drive means 104d for driving 1. Reference numeral 105 denotes a moving means that moves the pickup 101 in a direction crossing the track. Reference numeral 115 denotes a position detecting means, which detects the absolute position of the moving means 105. Reference numeral 116 is a position digitizing means, which digitizes the output of the position detecting means 115 and outputs absolute position data Dp. Reference numeral 106 denotes a search control means, which receives the absolute position data from the position digitizing means 116 and when the value does not match the target value, the address
A search command signal Sa that instructs the start of the search mode is output, and position correction data Da that corrects the positional error is output. A switching unit 107 outputs the position correction data Da when the search command signal Sa is output, and outputs the tracking operation data Dt when the search command signal Sa is not output. Reference numeral 108 denotes a speed detecting means, which detects a moving speed of the moving means 105 and outputs a speed detection signal Sv. 109 is a speed digitizing means, which is a speed detection signal S
v is A / D converted and speed detection data Dv is output. Reference numeral 110 denotes an adding means, which outputs the output of the switching means 107 and the speed detection data Dv.
Is numerically added at a predetermined ratio. Reference numeral 111 denotes a calculation means, which performs a calculation process on the output of the addition means 110 by a digital filter configuration using a difference equation for filtering such as low frequency compensation. 112 is a variable coefficient means, which is a search command signal S
When a is output, the coefficient is set large, and when the search command signal Sa is not output, the coefficient is set small. Reference numeral 113 denotes a voltage converting means, which converts the output data of the variable coefficient means 112 into a voltage signal. Reference numeral 114 denotes a driving means, which applies a driving voltage signal to the moving means 105 to generate acceleration for moving the entire pickup 101.

The operation of the positioning control circuit of the optical disc reproducing apparatus configured as described above will be described.

Moving means 105, speed detecting means 108, digitizing means 109, adding means
A series of loops composed of 110, calculation means 111, variable coefficient means 112, voltage conversion means 113, and drive means 114 constitute a velocity feedback loop having the C terminal of the addition means 110 as a control input, and constitute a velocity control loop of the positioning control circuit. Make up the body. The moving means 105 is moved at a constant speed proportional to the input from the C terminal. Here, the optical disc reproducing apparatus has the following two modes. The (1) address search mode, (2) steady play mode, and first address search mode are modes in which the pickup 101 is moved to a track having a desired address.

The second regular play mode is address search
In this mode, the pickup 101 follows the track after the mode is completed. The purpose of the positioning control circuit at this time is to correct the deviation from the center of operation that occurs when the actuator that constitutes the pickup 101 is following the spiral track of the disk 100, so that the actuator does not deviate from its movable range. Is to

FIG. 2 is a schematic flow chart diagram in the address search mode, showing the state of switching between the above two modes. In the figure, the numbers in the figure indicate the order in which each step is executed. The address search sequence of the optical disc reproducing apparatus in this embodiment will be described below with reference to FIG. 2 by taking a CD player as an example.

Now, for example, a music number or an index to be heard is input from a key board of the reproducing apparatus. These song numbers and indexes are converted into target position data by a microprocessor in charge of the man-machine interface. This target position data is transmitted to the search control means 106. The above corresponds to the first step in FIG.

Upon receiving this target position data, the search control means 106 receives the data of the current position of the moving means 105 from the position digitizing means 116. The above corresponds to the second step in FIG.

The search control means 106 determines whether or not the current position data and the target position data match. The above corresponds to the third step in FIG.

If these two data do not match, the search control means 106 outputs the position correction data Da to the switching means 107. The above corresponds to the fourth step in FIG.

Along with this fourth step, the search control means 106 outputs the search command signal Sa to the switching means 107, the speed detecting means 108 and the variable coefficient means 112. The above corresponds to the fifth step in FIG.

At the time when this fifth step is completed (that is, when the search command signal Sa is output), the reproducing apparatus enters the address search mode. In this address search mode, the switching means 107 is connected to the B terminal side, and the position correction data D from the C terminal of the adding means 110 to the velocity feedback loop of the moving means 105.
a is supplied. The moving means 105 starts a constant velocity motion according to the position correction data Da. Here, the moving means 105 must reach the target position as fast as possible. For this reason, the speed range that the speed detecting means 108 has to detect is about 33 mm, assuming that the track from the innermost track to the outermost track is moved within 1 second.
/ sec or more. Therefore, in the address search mode, the operation dynamic range of the digitizing means 109 is set to be above the speed range. As a result, the digitizing means 10
9 means that the speed of the moving means 105 can be sufficiently converted into the speed data Dv even during the address search. The above corresponds to the sixth step in FIG.

The search control means 106 repeats the above second to sixth steps until the current position data output by the reproducing means 102 matches the target position data. When the current position data matches the target position data, the search control means 106
Cancels the search command signal Sa. The above corresponds to the seventh step in FIG.

After this, the playback device enters the steady play mode. When the search command signal Sa is released, the switching means 107 is connected to the A terminal side and the tracking operation data Dt output from the tracking control means 104 to the speed feedback loop of the moving means 105 is connected to the C terminal of the adding means 110. Is supplied. The moving means 105 starts a constant velocity motion according to the tracking operation data Dt. Further, the gain of the speed detecting means 108 is reduced in response to the cancellation of the search command signal Sa, and the variable coefficient means 1
12 gains are increased.

By the way, the moving speed in the address search mode is 33
While it was more than mm / sec, the moving speed in this steady play mode was 0.015 mm / sec on average, and the digitizing means 109 in this mode is required to have a wider dynamic range. Rather, it is resolution. Therefore, the dead zone due to rounding at the time of digitizing is reduced by lowering the gain of the digitizing means 109 according to the cancellation of the search command signal Sa. At the same time, the gain of the variable coefficient means 112 is increased so that the gain of the entire velocity feedback loop of the moving means 105 is substantially matched with the address search mode. The above corresponds to the eighth step in FIG.

In this way, since a proper gain can be given to the speed detecting means 108 and the variable coefficient means 112 according to the mode required for the reproducing apparatus, the word length of the digitizing means 109 can be effectively used.

Now, the speed detecting means 108 and the variable coefficient means 112 described above can be easily configured. FIG. 3 is a circuit diagram showing an example of the structure of the speed detecting means in the embodiment of FIG.

In the figure, 108a is an operational amplifier, and 108b is a variable resistor, which is attached to the moving means 105 and detects the moving distance of the moving means 105. 108c is a capacitor, 108d, 108e, 108f and 108g are fixed resistors, and 108h is an analog switch.

The operation of one example of the speed detecting means configured as described above will be described below.

In the figure, the inside of the broken line constitutes a high-pass filter determined by the capacitor 108c and the fixed resistor 108d.
As a result, the moving means 105 output from the variable resistor 108b
It is possible to detect the moving speed of the moving means 105 by differentiating the voltage corresponding to the moving distance of. Further, the analog switch 108g and the fixed resistor 108h can be opened and closed according to the search command signal Sa to increase or decrease the gain of this high pass filter.

FIG. 4 is a circuit diagram showing another configuration example of the speed detecting means in the embodiment of FIG.

In the figure, reference numeral 108b is a variable resistor, which is the same as the variable resistor 108b in FIG. 108i
Is a voltage-frequency converter (V / F converter), 108j is a crystal oscillator, 108k is a frequency divider, and 109a is a counter.

The operation of one example of the speed detecting means configured as described above will be described below.

In the figure, moving means output from the variable resistor 108b
The voltage corresponding to the moving distance of 105 is converted into a frequency signal proportional to the moving speed of the moving means 105 by the V / F converter 108i. By counting the pulse width of this frequency signal with the counter 109a using the clock output from the frequency divider 108k, the speed of the moving means 105 can be detected numerically.
Further, by increasing or decreasing the frequency division ratio K of the frequency divider 108k according to the search command signal Sa, it is possible to equivalently increase or decrease the sensitivity of the speed detecting means.

FIG. 5 is a circuit diagram showing still another configuration example of the speed detecting means in the embodiment of FIG.

In the figure, 108l is a frequency divider, where 108b, 108i,
Since 108j and 109a have the same circuit configuration as that shown in FIG.

The operation of one example of the speed detecting means configured as described above will be described below.

In the figure, the moving speed of the moving means 105 converted by the V / F converter 108i is frequency-divided by the frequency divider 108l. The crystal width of the crystal oscillator 10
The speed of the moving means 105 can be numerically detected by counting with the counter 109a using the clock output from 8j. Further, by increasing or decreasing the frequency division ratio L of the frequency divider 108l according to the search command signal Sa, it is possible to equivalently increase or decrease the sensitivity of the speed detecting means.

Further, the variable coefficient means 112 is a bit
This can be done by shifting or multiplication in the ALU. In terms of hardware, it can be easily configured by a shift register or a digital multiplier. Also,
The same effect can be obtained by switching the gain of the voltage converting means.

As described above, the speed detecting means and the variable coefficient means for varying the gain according to the search command signal Sa can be configured by an extremely simple circuit.

Although the positioning control circuit in the CD player has been described in the above embodiment, the present invention can be similarly applied to an LD player and other optical disk reproducing apparatuses. In addition, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the invention.

As described above, according to the present invention, the gain of the speed detecting means is switched between the address search and the play before the digitizing means. Therefore, an address search mode requiring a wide dynamic range. The word length of the digitizing means can be effectively used in the reproduction mode which requires time and resolution. This enables ALUs and Cs that perform digital arithmetic processing.
The scale of hardware such as CU can be minimized. Further, also in the variable coefficient means, the gain is switched between the address search and the play as in the digitizing means, so that the stability of the control system can be secured.

As a result, it is suitable and inexpensive for digital operation.

[Brief description of drawings]

FIG. 1 is a block diagram of a positioning control circuit of an optical disc reproducing apparatus in an embodiment of the present invention, FIG. 2 is a schematic flow chart diagram in an address search mode, and FIG.
FIG. 5 is a circuit diagram showing a configuration example of the speed detecting means in the embodiment of FIG. 1, FIG. 4 is a circuit diagram showing another configuration example of the speed detecting means in the embodiment of FIG. 1, and FIG. FIG. 6 is a circuit diagram showing still another configuration example of the speed detecting means in the embodiment of FIG. 100 ... disk, 103 ... error detecting means, 104 ... tracking control means, 105 ... moving means, 106 ... search control means, 107 ... switching means, 108 ... speed detecting means, 109 ...
... speed digitizing means, 110 ... adding means, 111 ... computing means, 112 ... variable coefficient means, 113 ... voltage converting means, 114 ...
... Driving means, 115 ... Position detecting means, 116 ... Position digitizing means.

Claims (1)

[Claims] 1. An information record carrier in which information is recorded in a plurality of substantially optically reproducible tracks is irradiated with a radiation beam on the tracks and a modulated radiation beam generated thereby is received. Reproduction means for photoelectric conversion, error detection means for detecting a tracking error from the output of the reproduction means, numerical calculation of the output of the error detection means to output tracking operation data, and the path of the radiation beam and the track. Tracking control means for following the above, moving means for moving the reproducing means in the direction traversing the track, position detecting means for detecting the absolute position of this moving means, and output of this position detection is digitized to be absolute. The position digitizing means for outputting the position data and the position correction data are detected by detecting a positional error between the absolute position data and a predetermined target position. Search control means for outputting a search command signal for instructing the start of a search operation and the position correction data in the search operation according to the search command signal, and the tracking operation data for other operations. Switching means for selecting, speed detecting means for detecting the moving speed of the moving means and varying the gain in accordance with the search command signal, and speed for converting the output of the speed detecting means into speed data. The digitizing means, the adding means for adding the speed data and the output data of the switching means, the calculating means for calculating the position control data by processing the output of the adding means, and the position control data are predetermined. Variable coefficient means for multiplying the coefficient and varying the coefficient according to the search command signal, voltage converting means for converting the output of the variable coefficient means into a voltage, and voltage converting Positioning control circuit of the optical disk reproducing apparatus characterized by comprising a driving means for making the driving signals affecting the motion of the moving means in accordance with the output of the stage.