JPH0215432A - Optical disk device - Google Patents

Abstract

PURPOSE:To stably decide an optical beam crossing direction in an optical disk by phase-comparing a track tracing error signal with a clock pit detecting signal which are obtained with detecting the intensity difference of the reflected light from two wobble pits. CONSTITUTION:A track tracing error signal 21 and a clock pit detecting signal 25 are respectively shown in figures (b) and (c), and signals 23 and 27 obtained by binarizing them are shown in figures (d) and (e). When the logical level of a binarized clock pit detecting signal 27 is detected in an FF 28 at the time of the rise edge of the binarized track tracing error signal 23, a signal in a figure (f) whose level is inverted when the track crossing direction is inverted, that is, when a period A shifts to a period B, can be obtained as a track crossing direction deciding output 29. On the contrary, when the logical level of the binarized track tracing error signal 23 is detected by the fall edge of the signal 27, a signal shown in a figure (g) having the level corresponding to the track crossing direction can be obtained as the output 29 in the same way. Thus, the crossing direction of the beams in the optical disk can be accurately decided.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an optical disk device, and particularly to a clock pit located at the center of a concentric or spiral track. A so-called sample servo format optical disk is used, in which a pattern consisting of first and second bulldog bits arranged left and right with respect to the center of the track is formed intermittently along the track direction. The present invention relates to a device for recording and reproducing information.

(Prior Art) Recently, a clock pit placed on a concentric or spiral track and located at the center of the track,
A light beam is irradiated onto an optical disc on which a pattern consisting of first and second wobbled pits arranged left and right with respect to the center of the track is formed intermittently along the track direction. Optical disc devices that record and reproduce information have been developed. This type of optical disc format is called the sample servo format method.

FIG. 4 shows an example of an optical disc using the sample servo format, where 41 is a track, 42 is a data area for recording or reproducing information signals, and 43 is a servo area in which clock pits and wobbled pits are formed in advance. Each is shown below.

5(a) is an enlarged view of a part of FIG. 4, and in the servo area 43, a clock pit 52 is arranged at the track center 51, and
First and second wobbled pits 53 and 54 are arranged so as to be distributed to the left and right. The light beam spot 55 relatively moves on the optical disk from the paper surface to the right. At this time, the output signal of the photodetector that detects the reflected light from the optical disk is as shown in FIG. 5(b).

Incidentally, in an optical disk device, it is generally essential to determine the direction in which a light beam for recording and reproduction crosses a track (hereinafter referred to as the "track cross direction") in order to perform track access, eccentricity correction, etc.

When using an optical disc with a guide groove, which has been conventionally used in optical disc devices, the light beam is guided by the track (guide groove).
The phase relationship between the sum signal and difference signal of the two outputs of the two-split photodetector is different when crossing from the inner circumferential side to the outer circumferential side and when crossing from the outer circumferential side to the inner circumferential side, so this phase relationship is detected. By doing so, it is possible to easily determine the track cross direction.

However, with sample servo format optical discs, it is not possible to stably obtain a sum signal because there are no guide grooves, so depending on the system, such as an optical disc device using an optical disc with guide grooves, it is difficult to determine the cross-track direction. I can't.

(Problems to be Solved by the Invention) I-As mentioned above, in the conventional technology, there is a problem in that the track crossing direction cannot be determined in an optical disk device using a sample servo format optical disk.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc device that can determine the cross-track direction while using a sample servo format optical disc.

[Structure of the Invention] (Means for Solving the Problems) The present invention detects a difference in the intensity of reflected light from a first and second wobbled pit to detect a track following error indicating a tracking error of a light beam with respect to a track. Along with generating a signal,
Detects changes in the intensity of reflected light from clock pits and generates clock pit detection signals corresponding to the changes in intensity,
By comparing the phases of these clock pit detection signals and track following error signals, the direction in which the light beam crosses the tracks on the optical disc is determined.

Specifically, for example, the track following error signal is converted into a binary signal waveform by the waveform shaping means, and the clock pit detection signal is also generated as a binary signal waveform.

In this case, the cross-track direction is determined by, for example, using a flip-flop to detect the level of one of the clock pit detection signal and the output signal of the waveform shaping means at a predetermined edge timing of the other signal. be done.

(Function) Track following error signal generation means are well known, but in the present invention, a clock pit detection signal generation means corresponding to changes in the intensity of reflected light from clock pits is newly provided, and these clock pit detection signals and track following error signal generation means are newly provided. By comparing the phases of the tracking error signals, the cross-track direction is determined as a level change as a result of the phase comparison. Also,
This determination of the cross-track direction is performed when the light beam passes through a servo area in which a pattern including clock pits and wobbled pits is formed. The determination of the cross direction will not become unstable.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an optical disc device according to an embodiment of the present invention. In the same figure, optical disc 1
is a sample servo format optical disk as shown in FIG. 4, for example, and during recording and recording, the light beam from the laser light source 2 passes through the collimating lens 3. It is irradiated as a minute spot via the beam splitter 4, objective lens 5, etc. During reproduction, the reflected light from the optical DIG 1 passes through the objective lens 5 in the opposite direction to the irradiated light and is guided to the photodetector 6 via the beam splitter 4.

The output signal (hereinafter referred to as reflected signal) 7 of the photodetector 6 is
The signal is guided to a reproduced signal processing circuit (not shown) and is also input to a track crossing direction determination circuit 10 based on the present invention. The cross-track direction determining circuit 10 is configured as follows.

First, the reflected signal 7 is binarized by the waveform shaper 11 and then input to the clock regenerator 12 .

The clock regenerator 12 regenerates a clock signal based on the clock pit in the servo area on the optical disc 1.

The timing generator 13 uses this clock signal to generate the first . Timing signal 14 for detecting the peak value of reflected light from the second wobbled pit and clock pit
．． Generate 15.16.

The reflected signal 7 is also input to the track following error signal generation circuit 17, and the peak values of the reflected light from the first and second wobbled pits are determined by two sample and hold circuits 18 and 19 based on the timing signal 14 and 15. detected,
Furthermore, by inputting these peak values to the differential amplifier 20, a track following error signal 21 indicating a tracking error of the light beam with respect to the track is generated. This track following error signal 21 is shaped into a binary signal waveform by a waveform shaper 22, and becomes a binary track following error signal 23.

The reflected signal 7 is further input to a sample hold circuit 24, and a change in the intensity of the reflected light from the clock pit is detected based on the timing signal 16, thereby obtaining a clock pit detection signal 25. This clock pit signal 25 is shaped into a binary signal waveform by a waveform shaper 26, and becomes a binary clock pit detection signal 27.

The binarized track following error signal 23 and clock pit detection signal 27 are respectively input to a CK (clock) input terminal and a D input terminal of a D-type flip-flop 28 which is a track crossing direction determining means. The flip-flop 28 detects the logic level of the clock pit signal 27 at the timing of, for example, a rising edge of the track following error signal 23, thereby obtaining a track crossing direction determination output 29.

Next, the operation will be explained using FIG. 2. In FIG. 2, (a) represents the relative movement of the light beam spot 55 with respect to the track 41 on the optical disc 1. In FIG. Let A be the period in which the spot 55 moves from the inner circumferential side to the outer circumferential side of the optical disc 1, and B be the period in which the spot 55 moves from the outer circumferential side to the inner circumferential side.The track following error signal 21 and the clock pit detection signal 25 are respectively Figures (b) and (c) become,
Signals 23 and 27 obtained by converting these into binary data are shown in the same figure (d
), (e). Note that the state shown in FIG. 2(a) is, for example, a case where the optical disc 1 has eccentricity and track access and tracking are performed on the optical disc 1 with such eccentricity, and in particular, the speed of the eccentricity is This appears at approximately the same speed as the linear motor in the actuator that moves the optical head in the radial direction of the optical disk 1. When the present invention determines the cross-track direction and performs eccentricity correction based on the determination in such a situation,
Particularly effective.

Here, when the flip-flop 28 detects the logic level of the binarized clock pit detection signal 27 at the timing of the rising edge of the binarized track following error signal 23, for example, as the track crossing direction determination output 29,
When the cross-track direction is reversed, that is, as shown in Fig. 1 (
In a), when transitioning from period A to period B, a signal shown in FIG. 2(f) whose level is inverted is obtained. Also,
Conversely, when the logic level of the binarized track following error signal 23 is detected by the falling edge of the binarized clock pit detection signal 27, the track-crossing direction determination output 29 similarly has a level corresponding to the track-crossing direction. A signal shown in FIG. 2(g) is obtained.

FIG. 4 shows the configuration of a cross-track direction determining circuit according to another embodiment of the present invention, in which the sample-hold circuit 24 and waveform shaper 26 as clock pit detection signal generation means in FIG. , level comparator 21
and a D-type flip-flop 32.

That is, the level comparator 31 binarizes the reflected signal 7 from the photodetector 6' of FIG. 1, which is input to the input terminal 30, by comparing it with a predetermined reference level V ref'.

The output signal of this level comparator 31 is applied to the flip-flop 3
A clock pit detection signal is generated by detecting the logic level of the timing signal 16 inputted to the D input terminal of 2 and supplied from the timing generator 13 for detecting the peak value of the reflected light from the clock pit. 27 is generated. As in the case of FIG.
8, and a track-crossing direction determination output 29 is obtained.

Note that the present invention is not limited to the above embodiments, and can be implemented with various modifications. For example, in the embodiment, a signal obtained by converting the track following error signal into a binary value and a binary clock pit signal are phase-compared by the flip-flop 28 to obtain a track-crossing direction determination output. The track-crossing direction determination output may be obtained by comparing the phase of the track pit signal as an analog signal.

[Effects of the Invention] According to the present invention, the track following error signal generated by detecting the difference in the intensity of the reflected light from the first and second wobbled pits and the change in the intensity of the reflected light from the clock pit can be handled. By comparing the phase with the detected clock pit detection signal, it is possible to determine the cross-track direction of the light beam on a sample servo format optical disc, which was previously impossible.

Furthermore, in the present invention, since the cross-track direction is determined using a reflected signal from a servo area in which a pattern consisting of clock pits and wobbled pits on an optical disk is arranged, the recorded state of information pits in the data area is, in principle, Since the determination result is not affected by the above-described method, more stable determination can be made than in the conventional cross-track direction detection method for optical discs with guide grooves.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the main parts of an optical disk device according to an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of the same embodiment, and FIG. FIG. 4 is a block diagram showing the configuration of the cross-track direction determining circuit in the embodiment, FIG. 4 is a diagram showing an example of an optical disc of the sample servo format type, and FIG. 5 is an enlarged view of a part of FIG. 4. DESCRIPTION OF SYMBOLS 1... Optical disk of sample servo format system, 2... Laser light source, 6... Photodetector, 10...
Track crossing direction determination circuit, 17... Track following error signal generation circuit, 21... Track following error signal,
22... Waveform shaper, 23... Binarized track following error signal, 24... Sample hold circuit (clock pit detection signal generation means), 25... Clock pit detection signal, 26...・Waveform shaper, 27...2
Valued clock pit detection signal, 28... Flip-flop (track crossing direction determining means), 29...
- Track crossing direction determination output, 31... Level comparator, 32... Flip-flop (clock pit detection signal generation means) 41... Track, 42... Data area, 43... Servo area, 51 ... Tofuku 11 hearts, Kukupito... 1st and 1st Wobbled Pito 5... Light beam spot.

Claims (2)

[Claims] (1) A clock pit located at the center of the track on a concentric or spiral track;
An optical disc in which information is recorded and reproduced by irradiating a light beam onto an optical disc on which a pattern consisting of first and second wobbled pits distributed on the left and right sides of the track is formed intermittently along the track direction. In the apparatus, means for detecting the difference in intensity of reflected light from the first and second wobbled pits to generate a track following error signal indicating a tracking error of the light beam with respect to the track; A means for detecting a change in the intensity of light and generating a clock pit detection signal corresponding to the change in intensity, and a phase comparison between the clock pit detection signal obtained by this means and the track following error signal, and means for determining a direction in which the light beam crosses the track. (2) A clock pit located at the center of the track on a concentric or spiral track;
An optical disc in which information is recorded and reproduced by irradiating a light beam onto an optical disc on which a pattern consisting of first and second wobbled pits distributed on the left and right sides of the track is formed intermittently along the track direction. In the apparatus, means for detecting the difference in intensity of reflected light from the first and second wobbled pits to generate a track following error signal indicating a tracking error of the light beam with respect to the track; waveform shaping means for converting into a binary signal waveform; means for detecting a change in the intensity of the reflected light from the clock pit and generating a clock pit detection signal having a binary signal waveform corresponding to the intensity change; The direction in which the light beam crosses the track on the optical disk is determined by detecting the level of one of the clock pit detection signal and the output signal of the waveform shaping means at a predetermined edge timing of the other signal. An optical disc device characterized by comprising: means for determining.