JPS6378345A - Servo device in recording disk reproducing device - Google Patents

Abstract

PURPOSE:To contrive the simplification of a circuit constitution and to reduce a cost by applying signal processing of each error signal digitally in time division so as to use a signal processing circuit in common. CONSTITUTION:A changeover circuit 1 applies a switching control to each analog error signal in the order of such as a time base error signal, a tracking error signal, a focusing error signal, a tracking error signal, a time base error signal,..., in time division for the sequential output in response to timing pulses b-d. Each error signal subjected to time division is sampled/held by a sample/ hold circuit 3 synchronously with the timing pulses b-d and A/D converted. Then the processing such as equalizing or the like is executed digitally sequentially and D/A-converted, the result is distributed into each system at every changeover circuit 7 synchronously with the timing pulses b-d and fed respectively to a corresponding section to be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a servo device in a recording disk reproducing device.

BACKGROUND ART In a disc playback device that optically plays back recorded information on a recording disc (hereinafter simply referred to as a disc) such as a digital audio disc or video disc, a spindle servo device controls the rotation of the disc. The recording information is read by a pickup provided movably in the radial direction.

In addition, such a disc reproducing apparatus includes a four-sixth servo device that controls the optical spot for information detection by the pickup to converge correctly on the recording surface of the disc, and a four-sixth servo device that controls the optical spot for information detection by the pickup so that the optical spot is formed, for example, in a spiral shape on the recording surface of the disc. Various servo devices are indispensable, such as a tracking servo device that controls the recording track to be accurately tracked, and a time-base servo device that controls the playback signal to correct time base fluctuations.

In conventional devices equipped with these various servo devices, signal processing such as equalizing for error signals obtained from each servo system was performed by a signal processing circuit provided for each servo system. The disadvantage is that the number of elements becomes enormous, the circuit configuration becomes complicated, and the cost increases.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the drawbacks of the conventional ones as described above, and by digitally processing each error signal in a time-sharing manner, the signal processing circuit is shared and the circuit is integrated. It is an object of the present invention to provide a servo device for a recording disk reproducing device that can simplify the configuration and reduce costs.

The servo device according to the present invention inputs each analog error signal of various servo systems including at least a focus servo system, processes these analog error signals in a time division manner in synchronization with a sampling signal of a predetermined frequency, and sequentially outputs analog error signals. is converted into a digital error signal, and after predetermined arithmetic processing is performed, it is converted back into an analog error signal, and this analog error signal is supplied to each controlled part of various servo systems in synchronization with the sampling signal. The present invention is characterized in that when the focus servo system servo pulls in, priority is given to digital processing of the focus error signal until the focus servo system locks in.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, a switching circuit 1 for selectively outputting a plurality of inputs includes error signals of three types of servo systems, for example, a time-axis servo system, a focus servo system, and a tracking servo system, that is, a time-axis error signal. , a focus error signal, and a tracking error signal are input. The switching circuit 1 is composed of, for example, three analog switches provided corresponding to each servo system.

In a time axis servo system, if the recording disk is a video disk, a signal corresponding to the phase difference between a horizontal synchronization signal separated and extracted from a read RF (high frequency) signal read from the disk and a reference horizontal synchronization signal is generated on the time axis. Used as an error signal. Therefore, a time axis error signal is derived every time a horizontal synchronization signal occurs. On the other hand, the focus error signal is detected by a well-known detection method such as the astigmatism method, the critical angle detection method, or the Knifezi method, and the tracking error signal is detected by a well-known detection method such as the three-beam method, push-pull method, heterodyne method, or time difference detection method. is generated using the detection method.

A switching circuit 1 which receives time axis, focus, and tracking analog error signals sequentially outputs each analog error signal in a time-division manner in synchronization with timing pulses generated from a timing controller 2. for example,
Since the time axis error signal is derived every time a horizontal synchronization signal is generated, the time axis error signal is output every IH (H is a horizontal scanning period), and the focus error signal and tracking signal are output at an appropriate timing within this IH period. Output each error signal. Regarding the tracking error signal, the focus error signal is 1 within the IH period.
For example, instead of being output once, it is generated twice. As a result, the switching circuit 1 outputs each analog error signal in the order of time axis error signal, tracking error signal, focus error signal, tracking error signal, time axis error signal, etc., in the order of, for example, 1/4H period. will be output sequentially in a time-division manner.

These analog error signals are supplied to the sample and hold circuit 3 and sampled and held at each of the above-mentioned timings.

That is, the time axis error signal and the focus error signal are sampled at a period of IH, and the tracking error signal is sampled at a period of 1/2H. This sample hold output is converted into a digital error signal by an A/D (analog/digital) converter 4 and sent to the CPU (
The signal is supplied to an arithmetic processing circuit 5 consisting of a central processing circuit (central processing circuit) and the like. In the arithmetic processing circuit 5, predetermined arithmetic processing such as equalization is performed on each digital error signal. The processed digital error signal is converted into an analog error signal by a D/A (digital/analog) 6 and then supplied to a switching circuit 7. The switching circuit 7 distributes the serially supplied analog error signals at the previous sampling timing and supplies them to the controlled parts of each servo system.

In a time-axis servo system, for example, a COD is a variable delay element that is inserted into the signal line of the read RF signal reproduction processing system and whose delay amount changes depending on the signal level of the time-axis error signal.
(charge-coupled device) In a focus servo system, the focus actuator drives the objective lens, which forms part of the optical system of the pickup, in the direction of its optical axis; in the tracking servo, for example, the focus actuator causes the optical system of the pickup to swing. Each docking actuator becomes a driven part.

On the other hand, a lock-in detection circuit 8 is provided that detects the lock-in state of the focus servo based on the focus error signal, and this lock-in detection circuit 8 has a so-called figure-eight curve characteristic before and after the focus position when the focus servo is pulled in. When the signal level of the focus error signal indicating the focus error signal falls within a predetermined range centered around the zero level (focus position), a lock-in detection signal is generated and supplied to the system controller 9. The system controller 9 generates timing pulses to the timing controller 2 until a lock-in signal is generated when the focus servo is retracted when the system is started up or when the servo is retracted after the servo is unlocked. In addition to controlling the spacing, etc., the switching circuit 7 also controls to select only the signal line of the focus servo system.

In this configuration, in the steady state of the system, as shown in FIG. 2, the timing controller 2 transmits the IH period to each servo system in synchronization with the reproduction horizontal synchronizing pulse (a) with a phase difference of, for example, 1/4H. (b), 1/2
Timing pulses of H period (C·) and IH period (d) are generated, respectively. In response to these timing pulses (b) to (d), the switching circuit 1 outputs, for example, a time axis error signal, a tracking error signal, a focus error signal, a tracking error signal, a time axis error signal, etc.
. . . Switching control is performed to sequentially output each analog error signal in a time-division manner. Each time-divided error signal is sampled and held in the sample and hold circuit 3 in synchronization with each timing pulse (b) to (d).
/D converted. Then, as shown in Figure (e), processing such as equalization is performed digitally and the D/A
After the conversion, the switching circuit 7 distributes the pulses to each system in synchronization with the timing pulses (b') to (d) to the corresponding controlled parts, that is, the tracking actuator, focus actuator, and CCD, respectively. Supplied. In FIG. 2(e), the shaded portion is a blank period, and the other portions are processing periods of each servo system.

On the other hand, during the focus servo pull-in period when starting up the system or the re-pull-in period after the servo is unlocked, a stable playback horizontal synchronization signal cannot be obtained until the focus servo locks in. Since the optical system is also in an unstable state, tracking servo and time axis servo are meaningless. Therefore, during the focus servo pull-in period, under the control of the system controller 9, the timing controller 2 ignores the reproduced horizontal synchronization pulse that is input in an unstable state and generates a timing pulse (d) for the focus servo at a 1/2H cycle, for example. occurs. As a result, during the pull-in period, as shown in Figure (e), the sampling frequency of the focus servo and the processing time of the servo can be increased compared to the steady state, so the focus pull-in process is made more reliable and the time is increased. Division efficiency can be increased.

When the focus servo locks in and the lock-in detection pulse (f) is emitted from the lock-in detection circuit 8, the timing controller 2 is activated by the system controller 9.
control is stopped, and from then on, the system controller 9 synchronizes with the reproduction horizontal synchronization pulse (a) to
Timing pulses (b) to (d) with a phase difference of 4H
occurs, resulting in steady-state control.

The operational flow of the timing pulse generation procedure under the control of the system controller 9 described above is shown in FIG. That is, when a system start command is issued, first it is determined whether or not the focus servo is locked in (step S1), and if it is not locked in, a timing pulse of a predetermined period is generated regardless of the reproduction horizontal synchronization pulse. A command is issued to the timing controller 2 to generate a timing pulse based on the reproduction horizontal synchronization pulse (step S2), and a command is issued to the timing controller 2 to generate a timing pulse based on the reproduction horizontal synchronization pulse (step S3).

In addition, in the above embodiment, the tracking servo system,
Regarding the focus servo system and the time axis servo system, we have explained the case where the signal processing of each error signal is performed digitally in a time-sharing manner, but the case in which the signal processing of each error signal is performed digitally in a time-sharing manner is also applied to the spindle servo system, slider servo system, etc. It is also possible to perform signal processing.

As described in detail, according to the present invention, the signal processing from the A/D converter to the D/A converter is performed by digitally processing each error signal of various servo systems in a time-sharing manner. Since the circuit can be used in common for each servo system, it is possible to reduce the circuit scale and cost by using an IC (integrated circuit), for example.

Furthermore, when the focus servo system's servo is being pulled in, the time and sampling frequency allotted to the focus servo can be increased by digitally processing only the focus error signal until the servo locks in. can be made more reliable and time sharing efficiency can be increased.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart showing the operation timing of the circuit in FIG. 1, and FIG. 3 is a flow chart showing the processing procedure of the system controller in FIG. 1. . Explanation of symbols of main parts 1.7...Switching circuit 2...Timing controller 3...
Sample hold circuit 5... Arithmetic processing circuit

Claims (1)

[Claims] A switching means that inputs each analog error signal of various servo systems including at least a focus servo system and sequentially outputs these analog error signals in a time-sharing manner in synchronization with a sampling signal of a predetermined frequency, and an analog error signal that passes through the switching means. means for converting the digital error signal into a digital error signal; arithmetic processing means for performing predetermined arithmetic processing on the digital error signal; and means for converting the digital error signal processed by the arithmetic processing means into an analog error signal; comprising means for supplying the analog error signal to each controlled part of the various servo systems in synchronization with the sampling signal, and means for detecting a locked state of the focus servo system and generating a lock-in detection signal, A servo device for a recording disk reproducing device, characterized in that when the focus servo system servo pulls in, arithmetic processing of an error signal of the focus servo system is performed with priority until the lock-in detection signal is generated.