JPH02249144A - Optical disk driving device - Google Patents

Abstract

PURPOSE:To reduce the erroneous extraction of a pre-pit and to improve stability in tracking and the reading capability of an address by sampling and holding an output voltage for certain constant time immediately after switching a power to a reproducing power at a pre-pit part, and using the voltage as a reference voltage for a comparator. CONSTITUTION:The reference voltage is set variably, and a ground level immediately after switching the power from recording and erasure to the reproducing power is used as the reference voltage by sampling and holding the level. Therefore, even when the ground level of a pre-pit signal 24 is fluctuated by plane wobbling, etc., the reference voltage is also fluctuated corresponding to that fluctuation, and the reference voltage can be always set at the optimum state, which reduces the erroneous extraction of the pre-pit 22. In such a way, it is possible to improve the stability in the tracking and the reading capability of the address.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disk drive device that records, reproduces, and erases signals on a recording film using a laser beam.

BACKGROUND OF THE INVENTION In recent years, with the rapid increase in the amount of information processed in information processing systems, recording media with a large amount of recording film, especially optical disks, have been attracting attention, particularly in the fields of data processing systems and office automation.

A conventional optical disc drive device will be explained below. An example of an optical disk is a magneto-optical disk. Continuous servo and sampled servo are attracting attention. Sampled servo obtains synchronization signals from clock pits embedded in the magneto-optical disk, so extraction of pre-pits is an important point. In continuous servo, the sector mark and synchronization pull-in signal (hereinafter referred to as VFO) are extracted, the address part is determined, and a synchronization signal is obtained. For this reason, extraction of pre-pits is important for continuous servo as well.

Here, a conventional method for extracting sampled servo wobble and clock pit signals will be described.

FIG. 4 is a block diagram of a pre-pit extraction circuit of a conventional optical disc drive device. 41 is an input signal, 42 is an amplifier, 43 is a constant voltage source, 44 is a bypass filter, 4
5 is a comparator signal and 146 is an output signal. FIG. 5 shows signals during recording of each block configured in FIG. 4.

51 is a part of the trunk of the magneto-optical disk where the sample is held, and 52 is a prepit, which is composed of 53 wobble pins and 54 clock pits. 55 is a laser beam during recording, 56 is an input signal, 57 is a constant voltage source, 58 is a signal after passing through a bypass filter, and 59 is an output signal of a comparator.

First, the laser beam 55 modulated during recording is reflected on the magneto-optical disk and converted into voltage by a photodetector. This signal becomes the input signal 56. During recording, the ground level of the input signal and the amplitude of the pre-pits fluctuate due to the laser intensity being lowered to the reproduction power in the pre-pit portion, or due to surface runout of the magneto-optical disk or defects in the pre-pits. After amplification, the signal passes through a bypass filter 58 and is input to a comparator. Then, a reference voltage for the comparator is supplied from a constant power source 57.

Only signals higher than the comparator reference voltage are output signal 5
It becomes 9. The period of the clock bit is 22.4 μsec, and the interval between the rises of the clock signal 510 was measured by a time interval analyzer (hereinafter referred to as TIA). It is shown in FIG.

105 pieces were measured. Clock chic is 1OOnse
It is c.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, wobble occurs due to changes in the amount of light due to surface wobbling of the optical disk, etc.

The voltage level of the pre-focus signal of the clock bit signal e t c fluctuates, but since the reference voltage of the comparator is constant, the reference voltage deviates from the optimum value, causing an extraction error, causing the synchronization signal to be lost and tracking to become unstable. This makes recording and erasing impossible. Additionally, there is a problem in that the address can be read incorrectly.

The present invention solves the above-mentioned conventional problems, and aims to provide an optical disk drive device which reduces the number of errors in extracting pre-pits and has excellent tracking stability and address reading ability.

Means for Solving the Problem In order to achieve this object, the optical disc drive device of the present invention samples and holds the output voltage for a certain period of time immediately after switching to the playback power in the pre-pit section, and uses this voltage as a reference for the comparator. It consists of being used as a voltage.

action With this configuration, the reference voltage is not constant but recorded.

The ground level immediately after switching from erase to playback power is sampled and held and used as the reference voltage. Therefore, even if the ground level of the prepit signal fluctuates due to surface runout, etc., the reference voltage will also change accordingly, making it possible to always set the reference voltage to the optimal state, thereby preventing prepit extraction errors. can be reduced. Therefore, tracking stability and address reading ability can be improved.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a part of a block diagram for extracting a prepit signal of a magneto-optical disk drive device compatible with sampled servo according to an embodiment of the present invention.

In FIG. 1, 11 is an input signal, 12 is an amplifier, 13 is a bypass filter, 14 is a sample and hold circuit, 1
5 is a sample hold signal generation circuit, 16 is a comparator, and 17 is an output signal. The operation of the magneto-optical disk drive device configured as described above will be described below.

FIG. 2 shows signals during recording in each block of the present embodiment shown in FIG. Reference numeral 21 in FIG. 2 shows a part of a track of a magneto-optical disk compatible with sampled servo, and a pre-pit 22 is composed of a wobble pit 211 and a clock pit 212. Input signal 23
corresponds to FIG. 11. This is a signal obtained by detecting the light reflected on the magneto-optical disk with a photodetector and converting it into a voltage. Since the reproduction power of the laser beam decreases at the pre-pit portion, the signal level fluctuates sharply at the pre-pit portion.

26 is a signal that determines the timing of sampling the input signal 23. 27 is a signal sampled and held by the sample and hold circuit 14; 28 is a signal after passing through the bypass filter 13. 29 is the output signal of the comparator. 210 is the output of laser light.

First, an input signal is amplified by an amplifier 12 and input to a bypass filter 13 and a sample-and-hold circuit 14. At the pre-pit area, the laser beam's recording power decreases from the reproducing power, which may also cause surface runout or groove shape defects on the magneto-optical disk.
tc, the amount of laser light incident on the photodetector also changes.

For this reason, fluctuations in the ground level and fluctuations in the amplitude of the pre-pit between the pre-pit section and the recording section are reflected in the input signal 2 in Figure 2.
It happens like 3. This input signal 23 is amplified by the amplifier 12 and passed through a bypass filter. FIG. 2 shows the signal 28 after passing through. On the other hand, the amplified signal also flows to the sample and hold circuit 14, and the signal that samples and holds the amplitude of the input signal 25 at the timing when the sample timing signal 26 is ON is the comparator 16. The signal that has passed through the sample hold circuit 14 is inputted to the converter 16. Then, among the signals that have passed through the bypass filter, only those signals having an amplitude equal to or higher than the voltage level of the sample-and-hold signal 27 are output to the comparator 16.

Clock signal 2 generated by clock via +-212
Table 3 shows the 105 rise intervals of 13 measured using a time interval analyzer (hereinafter referred to as TIA).
Shown in times. The period of the clock signal is 22.4 μsec, and if the clock is extracted incorrectly, the number will be written at a point on the horizontal axis other than 22.4 μsec. Extraction errors are reduced compared to the conventional example. Further, in the conventional example, the jitter in the clock pit was 0.1 μsec, but in the present embodiment, the jitter was suppressed to 10 nsec or less, and the stability of clock pit extraction was increased.

As described above, according to this embodiment, since the reference voltage of the comparator during pre-focus extraction is used, and the signal sampled and held for a certain period of time immediately after switching to the reproduction power in the pre-pit section is used, surface runout, groove defects, etc. , the reference voltage changes in response to changes in the voltage level of the input signal, so it can always be set to the optimal reference voltage, reducing clock pit extraction errors and suppressing jitter to less than 1/10 of the conventional one. This makes it possible to realize an optical disc drive device with the following features.

Effects of the Invention The present invention samples and holds the output voltage for a certain period of time immediately after switching to the reproduction power in the pre-pit section, and uses it as the reference voltage of the comparator. The reference voltage also changes accordingly, making it possible to always extract pre-pits at the optimal point, providing accurate and stable synchronization signals, improving tracking stability, and providing optical discs with excellent address readability. It is possible to realize a drive.

[Brief explanation of drawings]

FIG. 1 is a block diagram of pre-pit extraction in an optical disc drive device according to an embodiment of the present invention, FIG. 2 is a diagram showing signals in each block of FIG. 1, and FIG. 3 is a clock diagram according to an embodiment of the present invention. The rising interval of the signal is TI
Fig. 4 is a block diagram of pre-pit extraction in a conventional optical disc drive, Fig. 5 is a diagram showing signals in each block of Fig. 4, and Fig. 6 is extraction in a conventional optical disc drive. FIG. 3 is a diagram obtained by measuring the rising interval of a clock signal using a TIA. 11...Input signal, 12...Amplifier,
13... Bypass filter, 14...
- Sample bold circuit, 15... Sample timing signal generation circuit, 16... Comparator, 17... Output signal. Name of agent: Patent attorney Shigetaka Awano (1 person)

Claims (1)

[Claims] When recording or erasing an optical disc, only the pre-pit section is irradiated with the laser intensity reduced to the playback power, and when comparing and extracting the pre-pit signal from the reflected light, the output voltage is sampled and held for a certain period of time immediately after switching to the playback power at the pre-pit section. An optical disk drive device characterized in that this voltage is used as a reference voltage of a comparator.