JPS6223370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information recording and reproducing apparatus, and more particularly to an apparatus for following (referred to as tracking) an information groove (referred to as a track) recorded on an optical disk by a reproducing pickup.

An optical disk is a disk whose surface is coated with a photoreceptor thin film, and records data by forming a pit-shaped photosensitive area (referred to as a pit) with a convergent laser beam spot modulated on and off by a recording information signal. Reproduction is performed by electrostatically detecting the presence or absence of pits using microelectrodes, or by detecting changes in the intensity of reflected light from a focused laser spot.

The tracks are formed in a spiral or concentric shape, but when the optical disk is replaced, the track eccentricity of about 100 μm with respect to the center of rotation of the optical disk occurs during reproduction. During playback, you must follow this track accurately with the pick-up. This tracking is performed by scanning the optical spot in the radial direction of the optical disk using a carbano mirror, etc., but in order to do so, a signal (referred to as an error signal) indicating the amount and direction of deviation between the optical spot and the track is required.
need to be formed.

Conventionally, one method for detecting this direction of deviation is to meander the track (hereinafter referred to as pre-woveling) and record the track. This pre-wobbling is performed by slightly vibrating the recording light spot in the direction perpendicular to the track. When a light spot passes through this track, the reflected light undergoes intensity modulation in accordance with its meandering. The phase of the modulation depends on whether the optical spot is shifted to the right or left of the track.
Since they differ by 180°, the direction of deviation can be determined by synchronously detecting this modulated signal.

An example of a conventional pre-wobbled track is shown in FIG. In this example, track 1 is pre-wobbled left and right in a rectangular waveform in accordance with the period of synchronization signal 2.

In this figure, the track is drawn as a block of half wavelength of the spatial wavelength of the pre-wave ring.

Light spot 3 moves along such a track as arrow 4
FIG. 2 shows a modulation component (referred to as a pre-wobbling signal) caused by the pre-wobbling of the reproduced signal when the signal passes in the direction of the pre-wobbling signal. This signal is obtained by envelope detection of the reflected light intensity signal (reproduction signal). When the light spot is on the left side of the track, the pre-wobbling signal has a waveform of 5 (shown in Figure 2a), for example, and when it is on the right side, the phase is reversed and becomes 6 (shown in Figure 2c). I get an output like . Also, when the vehicle just passes through the center of the track, the pre-wobbling signal becomes zero as indicated by 7 (as shown in FIG. 2b). When this pre-wobbling signal is synchronously detected using a gate signal 8 (shown in FIG. 2d) which is equal to the pre-wobbling period formed from the synchronizing signal 2 and has a constant phase, an error signal is obtained.

FIG. 3 shows that the light spots (intensity distribution is indicated by 11) are located on track rows 10-1, 10-2, 10-3.
The relationship between the error signal waveform and the track when crossing is shown. FIG. 3a is a sectional view of the optical disk 9 seen from a direction perpendicular to the track. truck, 10
When a light spot having an intensity distribution such as 11 crosses -1, 10-2 and 10-3 in the direction of arrow 12, an error signal waveform 13 shown in FIG. 3b is obtained. That is, zero is crossed at the center of the track and between the tracks, and the signs are different on the left and right sides of the track. Therefore, if you adjust the direction of rotation of the galvano mirror so that when this signal is positive, the light spot moves to the right on the drawing, and when it is negative, it moves to the left, the light spot can always be moved toward the track center by this error signal. and tracking becomes possible.

However, when this signal is used for tracking, there are the following drawbacks. When the light spot is between tracks, for example tracks 10-1 and 1
The sign of the error signal near the middle 14 of 0-2 is different between tracks 10-1 and 10-2. For this reason, both tracks exert an attractive force on the optical spot, but when the track spacing (referred to as track pitch) is narrowed for the purpose of high-density recording, the error signals from these individual tracks interfere to cancel each other out. ,
The peak value 15 of the combined error signal decreases, and the slope 16 becomes gentle (this peak value determines the maximum eccentricity width that can be tracked, and the slope is a factor that suppresses the tracking deviation, so it is desirable that both are as large as possible). That is, as the track pitch narrows, the optical spot tends to deviate from the track, the deviation increases even during tracking, the optical spot tends to meander within the track, and the reproduced signal becomes unstable. Therefore, due to the above-mentioned limitations on tracking, the track pitch has been suppressed, and an increase in the density of optical disk recording has been hindered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording and reproducing apparatus which solves the problems in tracking using conventional pre-wobbling and is capable of stably tracking even tracks recorded at high density.

In the present invention, by inverting the phase of the pre-wobbling for each track, the sign of the error signal from the adjacent track is inverted, and the adjacent track exerts a repulsive force on the optical spot, making it easier to track the target track. achieved its purpose. This phase inversion of the pre-wob ring is achieved by setting the frequency of the pre-wob ring to an integral multiple of the optical disc rotation frequency, and inverting the phase of the vibration of the optical spot for pre-wob ring recording every time the optical disc rotates once. It will be done. Alternatively, the phases of adjacent tracks can be automatically reversed by setting the pre-wobbling frequency to a half-integer multiple of the optical disk rotation frequency.

The present invention will be explained in detail below using examples.

FIG. 4 shows a pre-wobbled track waveform of the first embodiment of the present invention.

In FIG. 4, both tracks 17 and 17' are pre-wobbled in a rectangular waveform at the same frequency as the synchronizing signal 2. Further, the phases of the tracks 17 and 17' are reversed.

Assume that the pre-wobbling signal waveform when the light spot 3 passes on the right side of the track 17 in the direction of the arrow 4 is given as shown in 18 in Fig. 5a (this signal moves the light spot to the right). ). At this time, the pre-wobbling waveform due to the adjacent track 17' is shown in Fig. 5b.
It can be seen that the signal 19 is given as shown in FIG. 1, and is in phase with the signal 18.

These signals 18 and 19 are connected to gate signal 8 (fifth
FIGS. 6a and 6b show the relationship between the output waveform of the error signal and the track when synchronous detection is performed using the method shown in FIG. 6c). The light spot is located on the track 10' shown in Figure 6a.
The error signal when crossing -1, 10'-2 and 10'-3 is given as 20 shown in FIG. 6b.
That is, it crosses zero only at the center of the track,
On the left side of the tracking target track 10'-2, a positive value is taken up to the center of the adjacent track 10'-1, and on the right side, a negative value is taken up to the center of the track 10'-3. Therefore, the optical spot pull-in range extends to the center of the adjacent track, and is twice as large as the error signal 13' caused by conventional pre-wobbling. Also, the track 10'-1 with a narrow track pitch,
10'-2, 10'-3, conventional signal 13'
Due to interference with adjacent tracks, the peak value is low and the slope is gentle. On the other hand, in the case of the signal 20, the narrower the track pitch and the stronger the interference between adjacent tracks, the higher the peak value and the steeper the slope, making stable tracking possible.

FIG. 7 shows a pre-wobbled track recording method and apparatus according to the present invention. In the present invention, the laser beam 22 of the semiconductor laser 21 is transmitted through the lens 23.
24, the light is focused onto the optical disc 9 in the form of a spot 25 for recording. A signal, such as a video signal, generated by the recording information source 26 is digitally encoded by a digital signal converter 29 and then input to a semiconductor laser driver 30. In this way, the output light 22 of the semiconductor laser 21 is on-off modulated according to its digital code, and image information is recorded as pits on the disk.

Next, the pre-wobble ring of the track of the present invention will be explained. First, a rectangular wave signal 32 is generated by a rectangular wave generator 31 driven in synchronization with a synchronizing signal extracted from a signal generated from a signal source 26 by a horizontal synchronizing signal distributor 27 . This signal 32 is input to a voltage controlled oscillator 34 through a phase inverter 33. The oscillation frequency of this oscillator changes depending on the waveform of the rectangular wave 32. When the output 35 of this oscillator is input to an ultrasonic light deflector 36, an ultrasonic wave whose wavelength changes according to the rectangular wave 32 is generated inside the deflector, thereby deflecting the laser light 22. As a result, the optical spot 25 is also slightly vibrated in the direction perpendicular to the track, so that the recording track is pre-wobbled in accordance with the rectangular wave signal 32. While the track width is 0.8 μm, the pre-wobble width is approximately 0.2 μm.

Further, the phase inversion of the pre-wobbling signal for each rotation of the disk is performed as follows. That is, in the case of video signal recording, a signal from a frame pulse generator 28 that generates a frame pulse corresponding to one frame (one screen) using a vertical synchronizing signal and a horizontal periodic pulse is input to the phase inverter 33, The phase of the pre-wobbling signal 32 is inverted.

During playback, phase information of the pre-wobble ring for each track is required. This phase information is written into the vertical synchronization signal by a digital signal generator 37 working with the flip-flop 28 signal. In this embodiment, "0" is written as a signal for even-numbered tracks, and "1" is written for odd-numbered tracks.

Next, a pre-wobbling signal reproducing method and apparatus will be explained using FIG. 8. In this embodiment, a semiconductor laser 38 is used to reproduce recorded information on the optical disc 9.
using reflected light. The semiconductor laser beam 39 is focused onto the optical disk by lenses 40 and 41, and the reflected light from the disk surface is reflected by a beam splitter 42 and focused onto a photodetector 43. In this way, the information written in track 17 is converted into an electrical signal 44. After the signal 44 is amplified,
The signal is input to a demodulator 45 and an envelope detector 50. The demodulator output is input to a horizontal synchronizing signal distributor 46, a vertical signal distributor 47, and a pre-wobbling phase information decoder 48, and is also supplied to a television to reproduce images. The output of the vertical signal distributor 47 is input to a pulse generator 49, which generates a pulse for each vertical synchronization signal, and inputs it to a decoder 48.
Activate. The decoder 48 generates a pulse 52 every time it decodes phase information, and this pulse activates the phase inversion circuit 55. Horizontal synchronization signal 53
is input to a gate circuit for synchronous detection 54 to generate a rectangular wave having the same period as the pre-wobbling signal, and after having its phase inverted by an inverting circuit 55 for each rotation of the disk, it is input to a phase detector 56.

On the other hand, the pre-wobbling signal detected by the envelope detector 50 is input to the phase detector 56 via a bandpass detector 57 and an amplifier 58. Furthermore, the phase detector output passes through a low frequency filter 59,
An error signal 60 is obtained. By using this error signal, the track 17 can be tracked with the optical spot.

Although this embodiment has described pre-wobbling in the case of video signal recording, it may also be a PCM-encoded audio signal, computer digital information, or the like. In this case, a PCM synchronization signal or an address signal is used as the synchronization signal.

In this embodiment, the pre-wobbling waveform is a rectangular wave with a period equal to that of the horizontal synchronizing signal, but it may be an integral multiple of the horizontal synchronizing signal. Alternatively, a sinusoidal waveform may be used. Furthermore, in order to avoid crosstalk with the video signal, it is also possible to pre-wobble only the horizontal synchronization signal portion.

FIG. 9 shows a pre-wound track 61 according to a second embodiment of the present invention. The frequencies of the pre-wob ring and the synchronization signal are half-integer multiples of the rotational frequency of the optical disc, so that the phases of the synchronization signal 2 and the pre-wob ring are shifted by half a cycle between adjacent tracks. Therefore, the phase of the pre-wobble ring will be reversed between adjacent tracks.

Error signals when the light spot traverses this track are shown in FIGS. 10a and 10b. In this case, when passing the center between the tracks, for example, point 62 (shown in FIG. 10b) from track 10'-1 to track 10'-2 shown in FIG. 10a, the gate signal 8 for synchronous detection
is activated by the synchronizing signal of track 10'-2, so error signal 63 is inverted at point 62. However, since the track 10'-2 exerts a repulsive force on the optical spot until it passes this intermediate point 62, an error signal with a steeper slope and a larger peak value than the conventional error signal 13' is obtained, resulting in a stable error signal. Tracking becomes possible.

As described above, according to the present invention, a stable tracking error signal can be obtained even when adjacent tracks are in close proximity. Additionally, the tracking range can be expanded to twice that of the conventional pre-wobbling method.

Furthermore, although the present invention has been described with respect to reproduction using a light spot, it is equally applicable to electrostatic detection using microelectrodes.

Further, although the present invention has been described using an optical disk as an example of application, the present invention is not limited to this in any way, and can also be applied to tracking recording tracks of a magnetic disk.

In the above description, a case has been described in which tracking is performed by inverting the phase for each track, but the present invention is not limited to this, and tracking can also be performed by changing the frequency. This will be explained below with reference to the drawings.

111, 112, 113, 114 in Figure 11,
115 and 116 represent information tracks. The direction of the arrow in the figure is inside. On this information track, a single frequency is recorded so as to be superimposed on the information signal so that it can be distinguished from the tracking signal, for example, the information signal, and the frequency is ensured to be different between adjacent tracks. To do this, a minimum of three different frequencies are required.
If these three frequencies are f ₁ , f ₂ and f ₃ , then
For example, as shown in FIG. 1, f ₁ , f ₂ , and f ₃ may be recorded in sequence. To track a track on which a tracking signal is recorded in this way, the following procedure is performed. For example, consider the case where information is reproduced using a light spot. When reproducing the track 112 in FIG. 11, the frequency f ₁ is determined from the reproduced signal.
Separate the and _f3 signals and apply a tracking servo so that each signal strength is equal. 1st
1a is when the optical spot is above the track 112, and the signal strengths of frequencies f ₁ and f ₃ are equal. b is when the light spot is shifted in the direction of the arrow, and the signal component of frequency _f3 is larger. c is when the light spot is shifted in the opposite direction to the arrow, and the signal component of frequency _f1 is larger. Therefore, if the signal strength at frequency f ₁ is V(f ₁ ), the amount and direction of deviation from the track can be determined by V(f ₃ )-V(f ₁ ). In other words, a tracking servo signal is obtained. FIG. 12a shows a track, and FIG. 12b shows a tracking servo signal. The tracking range is T in FIG. 12. In the conventional well-known method, the tracking retraction range is t in FIG. 12. Therefore, it can be seen that according to the present invention, the tracking retraction range is three times that of the conventional one.

The present invention will be explained in detail by way of examples.

FIG. 13 is a block diagram of an apparatus for optically recording information according to the present invention. The light beam 10A of the laser light source 13-10 is modulated by the optical modulator 13-11, and is then modulated by the auxiliary lens 13-12 and the folding mirror 13-.
13, the light is focused onto a recording medium of a disk 13-15 by a focusing lens 13-14 to a light spot of about 1 μmφ, and a signal is recorded in accordance with the modulation. The laser light source 13-10 is, for example, an Ar ⁺ laser, and the optical modulator 13-11 is an electro-optic crystal. Signal 13-2 that drives optical modulator 13-11
2 is an adder circuit 13-2 which adds the signal 13-23 from the information source 13-16 and the tracking signal 13-27.
17. The tracking signal 13-27 is obtained by sequentially converting signals 13-24, 13-25, and 13-26 from three oscillators 13-19, 13-20, and 13-21, each having a different frequency, by a switch circuit 13-18. It was sent out on a bicycle. Oscillator 13-19, 13
Let the frequencies of -20 and 13-21 be f ₁ , f ₂ , and f ₃ . Timing signal 1 of switch circuit 13-18
3-28 is the rotation motor 1 of the disk 13-15.
The output of encoder 13-30 of 3-29 is designed so that one pulse is output for one revolution of the disk. The configuration of the switch circuits 13-18 is, for example, the first
The structure is as shown in Figure 4. In Fig. 14, 100, 101, 102 are analog switches, 103 is a 3-bit counter, 104, 105
is a monostable multivibrator, and 106 and 107 are nonstable multivibrators.

Analog switches 100, 1 are shown in FIGS. 15a to 15b.
A time chart of a circuit that generates drive signals 01 and 102 is shown. Figure 15a represents signals 13-28. The signal 111' of b is the output of the ternary counter 103 and drives the analog switch 100. The signal 112' at c is the output of monostable multivibrator 104 and is supplied to astable multivibrator 106 and monostable multivibrator 105. d signal 113' is the output of the astable multivibrator 106 and drives the analog switch 101. The e signal 114' is the output of the monostable multivibrator 105, and the f signal 115' is the output of the astable multivibrator 107 driven by the signal 114' and drives the analog switch 102. In this way, different tracking signals can be recorded on the spiral track in adjacent tracks as shown in FIG. 11 together with the information signal.

FIG. 16 shows an information reproducing device according to the present invention. An information track as shown in FIG. 11 is recorded on the surface of the disk 16-15. The laser beam 40A emitted from the laser light source 16-40 passes through the auxiliary lens 16-41, the half mirror 16-42, and the folding mirror 16-43 to the focusing lens 16-43.
44 onto the surface of the disks 16-15. The reflected light from the disk 16-15 is guided to a photodetector 16-45 by a half mirror 16-42, and a reproduced signal 16-53 is obtained. The reproduced signal 16-53 is the information signal 1 which is supplied to the high-pass filter 16-46 and from which the tracking signal has been removed.
6-54, and the reproduction circuit 16-47 performs reproduction. The reproduced signal 16-53 is also supplied to band filters 16-48, 16-49, and 16-50. Band filter 16-48, 16-4
The center frequencies of 9, 16-50 are f ₁ , f ₂ , and
f ₃ , and its output signal 16-56, 16
-57, 16-58, only tracking signals of frequencies f ₁ , f ₂ , f ₃ can be detected. Circuit 16-5
1 is the output signal 16-56, 16-57, 16-
Select two of 58 and output signals 16-59
and 16-60, and the combination is sequentially changed to cyclic by timing signals 16-62. Circuit 16-51
The configuration is as shown in FIG. In Figure 17, 200, 201, 202, 203, 20
4 and 205 are analog switches, 206 is 3
The counters 207 and 208 are monostable multivibrators, and 209 and 210 are nonstable multivibrators. Two analog switches are turned on and off at the same time. Further, the drive signal for the analog switch is given from the timing signal in the same way as explained in the embodiment. Output signals 16-59 and 16-60
is amplified by a differential amplifier 16-52, and its output signal 16-61 drives a folding mirror 16-43 for tracking. Timing signal 16-62 is the same as timing signal 13-28 of FIG. 15a. In this way, a spiral track can be reproduced.

In the above description, the information track is in the form of a spiral, but recording and reproduction of the concentric information track may be performed as follows. That is, in the case of recording, the timing signal 13-28 in FIG.
Instead of taking the timing signal 13 from the output of the encoder 13-30, the timing signal 13 from the information source 13-16
-55 drives the switch circuit 13-18. The information source 13-16 is an information signal 1 for one track round.
3-23, the timing signal 13-
55 should be generated. In the case of reproduction, the signals 16-56 and 16-5 in FIG. 16 are activated in accordance with the frequency of the tracking signal of the information track to be reproduced by the circuit 16-51 in FIG.
The circuit may select two signals from 7 and 16-58. Further, in the above description, the tracking signal is always superimposed on the information signal, but it may be superimposed only on a plurality of parts of the information track. For example, if the information signal is a video signal, the tracking signal can be superimposed only on the horizontal synchronization signal section. In this way, there is no fear that the tracking signal will leak into the video signal, and the
The design of the high-pass filter 16-46 in FIG. 6 becomes easier.

As described above, according to the present invention, accurate tracking is possible even if the track interval is made very narrow, and information can be recorded at high density.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional recorded information track, FIGS. 2 a to d and 3 a to b are diagrams for explaining conventional tracking, and FIG. 4 is a diagram according to the present invention. Figures 5a-c and 6a-b showing recorded information tracking are diagrams illustrating tracking according to the present invention, Figures 7 and 8.
9 is a diagram showing another example of the information track according to the present invention, FIG. 10 is a diagram explaining the tracking, and FIG. 11 is a diagram showing an information recording device and a reproducing device, respectively. FIGS. 12a and 12b are diagrams for explaining the tracking, FIG. 13 is a diagram showing the configuration of an embodiment of the information recording device according to the present invention, and FIG. FIG. 13 is a diagram showing the configuration of the main part, FIG. 15 is a diagram explaining the operation of the present invention, FIG.
FIG. 7 is a diagram showing the configuration of the main part of FIG. 16.

Claims (1)

[Claims] 1. A signal is recorded as a plurality of pits, the plurality of pits form a track, the plurality of pits include meandering pits distributed on both sides of the center line of the track, and the plurality of pits include meandering pits distributed on both sides of the center line of the track, A recording medium characterized in that the meandering of the pits has a phase opposite to that of the adjacent tracks, and the meandering is continuous along the center line of the track. 2. A track is formed on the recording medium, and pits are distributed on both sides of the center line of the track and meander, and the meandering has a phase opposite to that of the adjacent track, and the meandering is along the center line of the track. A plurality of continuously provided pits are scanned to detect an intensity modulated signal whose intensity has been modulated by the meandering pits, and from the intensity modulated signal,
A tracking method characterized in that error signals with different signs are obtained between adjacent tracks and between tracks, and the center of the track is tracked using the error signals. 3. A light source, a focusing means for focusing the light beam emitted from the light source into a spot on a recording medium, and a modulation means for intensity-modulating the light beam emitted from the light source according to the signal to be recorded. and a deflecting means for deflecting a light beam emitted from the light source, and a meandering track distributed on both sides of the center line of the track, the meandering having a phase opposite to that of an adjacent track, and the meandering being a deflection means for deflecting a light beam emitted from the light source. A recording device comprising: a control system that supplies a control signal to the deflection means for forming a plurality of pits on the recording medium according to the signal so as to be continuously provided along a center line. .