JPS6378374A - Servo device in reproducing device for recorded disk - Google Patents

Abstract

PURPOSE:To use a signal processing circuit from an A/D converter up to a D/A converter for each servo system in common by processing each error signal of various servo systems digitally in time division. CONSTITUTION:A switching circuit 1 responds to timing pulses b-d to apply switching control to output each analog error signal in time division sequentially in the order such as a time axis error signal, a tracking error signal, a focus error signal, a tracking error signal, a time base error signal .... Each error signal subject to time division is sampled and held synchronously with each timing pulse by a sample-hold circuit 3 and A/D-converted. The processing such as equalizing is applied digitally sequentially and the result is D/A- converted, then the result is fed respectively to a tracking actuator, a focus actuator and a CCD respectively synchronously with each timing pulse by a changeover circuit 7.

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 focus servo device that controls the information detection optical spot of the pickup to be properly focused on the recording surface of the disc, and 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 equalization for error signals obtained from each servo system is performed by a signal processing circuit provided for each servo system, so the circuit elements are This has the disadvantage of complicating the circuit configuration and increasing costs.

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, processes these analog error signals in a time division manner in synchronization with a sampling signal of a predetermined frequency, and converts the sequentially output analog error signals into digital error signals. After performing predetermined arithmetic processing, it is converted into an analog error signal again, and this analog error signal is supplied to each controlled section of various servo systems in synchronization with the sampling signal, and the sampling signal is characterized in that the frequency is set based on the frequency of the reference signal included in the read signal from the recording disk.

Embodiments 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. , the focus error signal and the tracking error signal are manually generated. 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 can be detected using a well-known detection method such as the astigmatism method, critical angle detection method, or Knifezi method, and the tracking error signal can be detected using a well-known detection method such as the three-beam method, push-pull method, heterogain 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 focus error signal have a period of IH, and the tracking error signal has a period of 1/2H.
It will be sampled at a period of . This sample and hold output is converted into a digital error signal by an A/D (analog/digital) converter 4 and sent to the CPU.
(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.

In this configuration, as shown in FIG. 2, the timing controller 2 outputs IH signals of the same period b), 1 with a phase difference of, for example, 1/4H, for each servo system in synchronization with the reproduction horizontal synchronization pulse (a). Timing pulses with a /2H period (c) and an 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. in this order. 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 synchronization with each timing pulse (b) to (d) in the sample and hold circuit 3, and A/D converted. and,
After digital equalization and other processing and D/A conversion are performed as shown in FIG.
In synchronization with each of the timing pulses (b) to (d), the signals are distributed to each system and supplied to the corresponding controlled parts, that is, the tracking actuator, focus actuator, and CCD described above. In addition, the second
In Figure (e), the shaded portion is a blank period, and the other portions are processing periods for each servo system.

Here, the sampling period of the focus error signal was twice that of the tracking error signal, but this is because the mass of the actuator to be controlled is larger in the focus servo system than in the tracking servo system. Since the accuracy is poor and the tolerance for residual error is large,
This is because sufficient control can be achieved even if the sampling period is set large. In other words, by increasing the sampling period of the focus error signal, the sampling period of the tracking error signal can be conversely reduced, and tracking accuracy can be improved accordingly.

Although this sampling period is not limited to twice, a preferable value is an integral multiple of twice or more.

In this way, by synchronizing the sampling period with the horizontal synchronizing pulse and setting it to an integral multiple thereof, the calculation processing of each servo system can be performed regularly, so that the calculation processing circuit 5 etc. can be used efficiently. become.

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.

Here, in a time axis servo system or a spindle servo system, an oscillator that generates a reference horizontal synchronizing pulse for generating an error signal is essential. It can also be used as Thereby, the circuit configuration of the timing controller 2 can be simplified.

As described in detail, according to the present invention, signal processing of each error signal of various servo systems is performed digitally in a time-sharing manner, thereby converting signals from an A/D converter to a D/A converter. Since the signal processing 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.

In addition, by setting the sampling frequency based on the frequency of the reference signal included in the signal read from the disk, if a servo system that generates an error signal based on the reference signal is included, the error signal will be detected at the timing when the error signal is generated. Since the signal can be reliably sampled,
Even with time-division signal processing, it is possible to reliably control each servo system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a timing chart showing the operation timing of the circuit shown in FIG. 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 and sequentially outputs these analog error signals in a time division manner in synchronization with a sampling signal of a predetermined frequency, and converts the analog error signal passed through the switching means into a digital error signal. means for performing predetermined arithmetic processing on the digital error signal; means for converting the digital error signal processed by the arithmetic processing means into an analog error signal; and means for supplying the sampling signal to each controlled part of the various servo systems in synchronization with the sampling signal, the frequency of the sampling signal being set based on the frequency of the reference signal included in the signal read from the recording disk. A servo device in a recording disk playback device.