JP2845569B2 - Optical disk drive - Google Patents

Description

The present invention relates to an optical disk of a sample servo system and an optical disk device for recording and reproducing information using the optical disk, and more particularly, to a track cross direction and a track cross direction. The present invention relates to an optical disc device capable of stably determining a track cross speed.

(Prior Art) As a sample servo type optical disk, a clock pit located at the center of a track on a concentric or spiral track and a clock pit located at the center of the track and distributed left and right with respect to the center of the track There is known an optical disc in which a servo pattern including first and second wobbled pits is formed intermittently in advance along a track direction.

FIG. 5 shows an example of an optical disk of a sample servo system, wherein 501 is a track, 502 is a data area for recording or reproducing an information signal, and 503 is a servo area in which clock pits and wobbled pits are formed in advance. Show.

FIG. 6 (a) is an enlarged view of a part of FIG. 5. In the servo area 503, a clock pit 602 is arranged at a track center 601. First and second wobbled pits 603 and 604 are arranged in a distributed manner. The light beam 605 relatively moves on the optical disk from left to right on the paper. At this time, the output signal of the photodetector for detecting the reflected light from the optical disk is as shown in FIG.

In an optical disk device, generally, in order to perform track access and eccentricity correction with high accuracy, the direction in which a light beam for recording and reproduction crosses a track and the relative speed at that time (hereinafter referred to as the track cross direction and the track cross speed, respectively) ) Is essential. In a conventional sample servo type optical disk apparatus, a track cross direction and a track cross speed are determined as follows by detecting a reflected signal from an optical disk.

First, a track following error signal indicating a following error of a light beam with respect to a track center 601 is generated by detecting a difference in intensity of reflected light from the first and second wobbled pits 603 and 604, and a signal from the clock pit 602 is generated. A clock pit detection signal is generated by detecting a change in the intensity of the reflected light. The track following error signal and the track pit detection signal are shaped into a binary track following error signal and a binary track pit detection signal.

By performing the level determination of one of the binary track following error signal and the binary track pit detection signal at the level change point of the other signal, a track cross determination output is obtained. By taking the exclusive or (XOR) of these binarized track following error signals and binarized track pit detection signals, measuring the pulse width of the XOR circuit output, and calculating the reciprocal of the pulse width, Track cross speed is required. In this case, the condition is that the duty ratio of the pulse output from the XOR circuit is constant at 50%.

FIG. 7 is a waveform diagram for explaining the generation process of the binarized clock pit detection signal. In the process of moving the light beam on the optical disk, as shown in FIG. 7 (a), if a reflected signal 701 is obtained from the clock pit 502 during on-track and a reflected signal 702 is obtained during off-track, the track pit is detected. The signal 703 is a signal obtained by sampling and holding the peak values from the reflection signal 701 to the reflection signal 702. By binarizing this track pit detection signal 703 with a threshold value 704 set in the middle of the level change range, a binarized track pit detection signal 705 is obtained.
Ideally, the duty ratio of the binary track pit detection signal 705 is 50% when the light beam moves at a constant speed relative to the optical disk.

However, when the level of the reflected signal 701 during on-track and the level of the reflected signal 702 during off-track change as shown in FIG. Track pit detection signal
When 703 is binarized with the same threshold 704, the duty ratio of the binarized track pit signal 705 does not become 50%. Therefore X
Since the duty ratio of the pulse of the OR circuit output does not become 50%, the pulse width of the XOR circuit output does not correctly reflect the track cross speed, and the track cross speed cannot be determined correctly.

Also, if the level of the reflected signals 701 and 702 greatly changes due to a change in the light amount of the light beam or a difference in the modulation degree of the reflected signal,
In an extreme case, as shown in FIG. 7 (c), the track pit detection signal 703 does not intersect with the threshold value 704, so that a binarized track pit detection signal cannot be obtained, and it is impossible to determine the track cross direction and the track cross speed. Become.

(Problems to be Solved by the Invention) As described above, in the conventional optical disk drive using the sample servo type optical disk, when the level of the reflected signal changes due to a change in the light amount of the light beam or a difference in the degree of modulation of the reflected signal, There has been a problem that the track pit detection signal cannot be correctly binarized, and the determination of the track cross direction and the track cross speed based on the binarized track pit signal cannot be performed stably.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disc apparatus capable of stably determining a track cross direction and a track cross speed irrespective of a variation in the light amount of a light beam or a difference in the modulation degree of a reflected signal.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a clock pit located at the center of a track and a first clock pit located on the left and right of the track. And a servo pattern having second wobbled pits intermittently formed along the track direction in a sample servo type optical disc, a track between tracks arranged at an intermediate position between adjacent tracks in the servo pattern. A new pit is formed.

The present invention detects an intensity difference between reflected light from the first and second wobbled pits in an optical disk apparatus that performs at least one of recording and reproduction of information by irradiating a light beam onto such an optical disk. Means for obtaining a first detection signal; and detecting a difference between peak values of the intensities of reflected light from the clock pit and the inter-track pit.
Means for obtaining a second detection signal having a phase difference of 90 ° with respect to the detection signal, and using the first and second detection signals, the direction in which the light beam traverses the track on the optical disk and the light beam Means for determining at least one of the relative movement speeds.

(Operation) In the second detection signal obtained by detecting the difference between the intensity of the reflected light from the pit between tracks newly formed in the servo area of the optical disk and the peak value of the intensity of the reflected light from the clock pit, , The fluctuation of the peak value which is a DC component is canceled. Since the second detection signal surely intersects the threshold value for binarization and has a waveform symmetrical with respect to the threshold value, the second detection signal is surely binarized, and the duty ratio of the binarized waveform is always 50. % Is constant.

Therefore, by using the binarized waveform of the second detection signal and the first detection signal indicating the track following error, the track cross direction and the track cross speed can be changed in the light amount of the light beam and the modulation degree of the reflection signal. It is performed stably without being affected by the difference.

(Example) Hereinafter, an example of the present invention is described with reference to drawings.

FIGS. 1 (a) and 1 (b) are diagrams showing a configuration of a servo area of an optical disc and a waveform of a reflected signal from the servo area according to an embodiment of the present invention. As shown in FIG. 1A, a clock pit 102 is disposed at a track center 101, and the first clock pit 102 is divided left and right with respect to the track center 101.
And second wobbled pits 103 and 104 are formed.

Further, an inter-track pit 105 according to the present invention is formed at an intermediate position between the tracks.
The light beam spot 106 relatively moves on the optical disk from left to right on the plane of the drawing when the track is accessed.
In this case, a reflected signal shown in FIG. 1B is obtained from a photodetector (not shown).

In the example of FIG. 1A, the inter-track pit 105 is formed between the area where the wobbled pits 103 and 104 are formed and the area where the clock pit 102 is formed in the track direction. 2 As shown in FIG. 2A, a clock pit 102 may be formed between a region where the wobbled pits 103 and 104 are formed and a region where the inter-track pit 105 is formed. In other words, the configuration shown in FIG. 2 is a pattern in which the wobbled pits 104 and 105 are shifted by 1/4 track pitch in a direction perpendicular to the track direction (clock pit 102 and pit 105 between tracks).
Is formed. In this case, the reflection signal obtained from the photodetector is as shown in FIG.

FIG. 3 is a block diagram showing a configuration of a main part of an optical disk device using the above-described optical disk. In the figure,
The optical disk 11 is a sample servo type optical disk having the servo area shown in FIG. 1, and a light beam from a laser light source 12 is collimated by a collimating lens 13 during recording and reproduction.
The light is irradiated as a minute spot through the beam splitter 14, the objective lens 15, and the like. At the time of reproduction, the reflected light from the optical disk 11 passes through the objective lens 15 in the opposite direction to the irradiation light, and is guided to the photodetector 16 via the beam splitter 14.

Output signal of the photodetector 16 (hereinafter referred to as a reflected signal) 17
Is binarized by the waveform shaper 18 and then input to the clock regenerator 19. The clock regenerator 19 is the optical disk 11
The clock signal is reproduced with reference to the clock pit in the upper servo area. The timing generator 20 uses the clock signal to generate the first and second wobbled pits 103 and 104,
Timing signals 21, 22, for detecting peak values of reflected light from the clock pit 102 and the inter-track pit 105
Generates 23,24.

The reflection signal 17 output from the photodetector 16 is also input to the track following error signal generation circuit 25. The track following error signal generation circuit 25 includes two sampling circuits 26 and 27 and a differential amplifier 28. The sample and hold circuits 26 and 27 detect the peak values of the reflected light from the first and second wobbled pits 103 and 104 in accordance with the timing signals 21 and 22, and the difference between these peak values is determined by the differential amplifier 28.
, A track following error signal 29 (first detection signal) indicating the following error of the light beam with respect to the track center is generated. The track following error signal 29 is guided to a tracking servo circuit (not shown),
The waveform is shaped into a binary signal by the waveform shaper 30, and becomes a binary track following error signal 31.

The reflected signal 17 output from the photodetector 16 is further input to the sample and hold circuits 32 and 33. In the sample and hold circuit 32, the clock pit is
The peak value of the reflected light intensity from 102 is detected, and the sample hold circuit 33 detects the peak value of the reflected light intensity from the inter-track pit 105 according to the timing signal 24. When the difference between these peak values is detected by the differential amplifier 34, a clock pit detection signal (second detection signal) 35 is generated. This clock pit detection signal 35
Is a signal having a 90 ° phase difference from the track following error signal 29.

The clock pit detection signal 35 obtained in this manner includes, as described later, a change in the light amount of the light beam incident on the optical disc 11 or the reflected light from the optical disc 11,
The effects of the 17 modulation depth differences have been removed. The waveform of the clock pit detection signal 35 is shaped into a binary signal by a waveform shaper 36, and becomes a binary clock pit detection signal 37.

The binarized track following error signal 31 and the binarized clock pit detection signal 35 are input to a clock (CK) input terminal and a D input terminal of a D-type flip-flop 38 for determining a track cross direction. The flip-flop 38 determines the logical level of the binarized clock pit detection signal 37 at the falling edge of the binarized track following error signal 31 to obtain a track cross direction determination output 39.

Similarly, by using a D-type flip-flop to determine the logical level of the binarized track following error signal 31 at the timing of the falling edge of the binarized clock pit detection signal 37, the track cross direction determination output can also be obtained. It is possible to get.

On the other hand, the binarized track following error signal 31 and the binarized clock pit detection signal 35 are also input to the track cross speed determination circuit 40. This track cross speed judgment circuit
40 is an exclusive OR circuit (XOR circuit) 41,
It comprises a pulse width measuring circuit 43 and a speed calculating circuit 45. The XOR circuit 41 takes an exclusive OR of the binarized track following error signal 31 and the binarized clock pit detection signal 35.

Here, when the wobbled amount of the wobbled pits 103 and 104 is 1/4 track pitch with respect to the track center 101, the phase difference between the binary track following error signal 31 and the binary clock pit detection signal 37 is 360 °. / 4 = 90 °. Therefore, the output 42 of the XOR circuit 41, which is the exclusive OR result of these signals 31, 37, is inverted every time the light beam moves by a 1/4 track pitch. Hereinafter, the output 42 of the XOR circuit 41 is referred to as a 1/4 track pitch pulse.

The pulse width measurement circuit 43 is configured using a counter,
The pulse width of the 4-track pitch pulse 42, that is, the time required for the light beam to move by 1/4 track pitch, is measured, and an output 44 of a digital value corresponding to the pulse width is output. If the digital value (pulse width of the 1/4 track pitch pulse) of the output 44 of the pulse width measuring circuit 43 is W and the length of the 1/4 track pitch is L, the speed calculation circuit 45 calculates v = L / By performing the calculation of W, the optical disk 1
The relative movement speed v of the light beam with respect to 1 is obtained, and a track cross speed judgment output 46 is obtained.

According to the above configuration, the track cross direction and the track cross speed can be stably determined. This effect will be described with reference to FIG.

In FIG. 4, reference numerals 401 and 402 denote reflected signals from the clock pit 102 during on-track and off-track, and reference numeral 403 denotes the sample and hold circuit 32 in FIG.
Is the output signal. This signal 403 is a sampled and held peak value of the reflected light intensity from the reflected signal 401 to the reflected signal 402, and the level changes from a negative peak value 408 to a positive peak value 409 with respect to the reference potential 407. .

404 and 405 in FIG. 4 are reflection signals from the inter-track pit 105 during on-track and off-track, and 406 is the sample-and-hold circuit 32 in FIG.
Is the output signal. This signal 406 is obtained by sampling and holding the peak value of the reflected light intensity from the reflected signal 404 to the reflected signal 405. The level of the signal 406 is changed from the negative peak value 408 to the positive peak value 408 with respect to the reference potential 407 similarly to the signal 403. Value409
To change.

The output signals 403, 406 of these sample and hold circuits 32, 33
Is detected by the differential amplifier 34, the clock pit detection signal 35, which is the output signal of the differential amplifier 34, becomes 41 in FIG.
It will be like 0. This clock pit detection signal 410 is a signal in which the DC components of the output signals 403 and 406 of the sample and hold circuits 32 and 33, that is, the changes of the peak values 408 and 409 are canceled, and changes symmetrically with respect to the reference potential 407. Therefore, if the clock pit detection signal 410 is binarized using the reference potential 407 as a threshold, the sample and hold circuit 3
Even if the peak values 408, 409 of the output signals 403, 406 of the 2,33 change, the duty ratio of the binarized clock pit detection signal 37 is kept constant at 50% as shown at 411 in FIG.

Thus, the output signal 4 of the sample and hold circuits 32 and 33 depends on the variation of the light amount of the light beam and the difference in the modulation of the reflected signal.
Even if the peak value 408,409 of 03,406 greatly changes,
By detecting the difference with the differential amplifier 34 and obtaining the track pit detection signal 35 (410) from which the DC component has been removed, the track pit detection signal 35 reliably crosses the threshold value (reference potential) 407. Moreover, the waveform becomes symmetrical with respect to the threshold value 407. Thereby, the binarized clock pit detection signal
37 (411) can be generated reliably, and the duty ratio can be always kept constant at 50%.

Therefore, by using the binarized clock pit detection signal 37 and the binarized track following error signal 31 obtained in this way, the determination of the track cross direction and the track cross speed required at the time of track access or the like can be stably performed. Can be performed.

[Effects of the Invention] As described above in detail, according to the present invention, an inter-track pit is newly added to a servo area of an optical disk, and a track pit detection signal is obtained by using a reflection signal from the inter-track pit. Thus, by using this and the track following error signal together, it is possible to stably determine the track cross direction and the track cross speed irrespective of the fluctuation of the light amount of the light beam or the difference of the modulation degree of the reflection signal.

[Brief description of the drawings]

1 (a) and 1 (b) are views showing the configuration of a servo area of an optical disk and a waveform of a reflected signal from the servo area according to an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are the same. FIG. 3 is a diagram showing a configuration of a servo area of an optical disc and a waveform of a reflected signal from the servo area according to another embodiment. FIG. 3 is a block diagram showing a configuration of a main part of an optical disc apparatus according to an embodiment of the present invention. FIG. 4 is a waveform diagram for explaining the operation of the embodiment, FIG. 5 is a diagram showing an example of an optical disk of a sample servo system, FIG. 6 is a diagram showing an enlarged part of FIG. 7
FIG. 1 is a diagram showing a change in the intensity of a reflected signal and changes in a clock pit detection signal and a binarized clock pit detection signal during track access in the related art. 11 ... Sample servo format optical disk,
12 ... laser light source, 16 ... photodetector, 25 ... track following error signal generation circuit, 29 ... track following error signal (first detection signal), 30 ... binarized track following error signal,
32 …… Sample hold circuit for track pit detection, 33
…… Sample hold circuit for pit detection between tracks, 34
…… Differential amplifier, 35 …… Track pit detection signal (second
Detection signal), 37 ... binarized track pit detection signal,
38 D flip-flop (track cross direction determination circuit), 39 track cross determination output, 40 track cross speed determination circuit, 46 track cross speed determination output, 101 track center, 102 Clock pit,
103,104... First and second wobbled pits, 105.
... pits between tracks, 106 ... light beam spots, 501 ...
... track, 502 ... data area, 503 ... servo area (servo pattern).

Claims (1)

(57) [Claims] 1. A clock pit located at the center of a track, first and second wobbled pits distributed to the left and right of the track, and a center located between adjacent tracks. Means for irradiating a light beam to an optical disc on which a servo pattern having inter-track pits are formed intermittently along the track direction to perform at least one of recording and reproduction of information; and the first and second wobbles. Means for detecting a difference in intensity of light reflected from the pits to obtain a first detection signal; and detecting a difference between peak values of the intensity of light reflected from the clock pit and the inter-track pit to obtain a second detection signal. Using the first and second detection signals, the direction in which the light beam crosses tracks on the optical disk and the relative position of the light beam to the optical disk. Optical disk apparatus characterized by comprising a means for determining at least one of the moving speed.