JPH0727647B2 - Jumping scanning device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording / reproducing a signal on an optically recordable / reproducible disc having concentric or spiral tracks. In particular, the present invention relates to jumping scanning for instantaneously moving a light beam on a disk for writing or reading a signal from a track to an adjacent track.

2. Description of the Related Art Various types of optical recording / reproducing devices have been proposed. For example, a surface of a substrate having tracks with concentric concavo-convex structures is used to irradiate a light beam generated from a light source such as a semiconductor laser onto a disk on which a material film that is optically recordable / reproducible is formed by a method such as evaporation However, when reproducing the signal, the signal is read from the reflected light from the disc with a relatively weak fixed light quantity, and when the signal is recorded, the light quantity of the light beam is strongly modulated according to the recorded signal to write the signal. There is.

In such an optical recording / reproducing apparatus, focus control is performed so that the light beam is always in a substantially convergent state on the recording material film, and control is performed so that the light beam always scans a predetermined track correctly. Tracking control is being performed. Further, in order to move the light beam to an arbitrary track on the disk, jumping scanning for moving the light beam from a certain track to its adjacent track is performed.

The movement of the light beam to an arbitrary track on the disk is realized by repeating this jumping scan.

This jumping scanning is usually a means for moving the light beam relative to the track in a direction perpendicular to the longitudinal direction of the track and horizontal to the disk surface (that is, the disk radial direction) in order to perform tracking control ( If the tracking moving means) is to be jumping-scanned to, for example, the track on the inner circumference side, the tracking control is disabled and the driving pulse (hereinafter referred to as acceleration pulse) is forcibly accelerated and moved in the inner circumference direction. When the beam arrives near the track on the inner circumference side, the tracking control is operated again to perform the jumping scan.

However, the bandwidth of tracking control is not infinite,
In reality, since it is limited, if the speed of the light beam traversing the target track is high, tracking control pull-in fails and jumping scanning cannot be performed correctly.

Therefore, usually, it is detected that the light beam is positioned between the tracks, and the driving pulse that has been accelerated has almost the same peak value and pulse width, but the driving pulse of the opposite polarity (hereinafter, deceleration pulse This is done so that the relative velocity between the light beam and the track on the adjacent track is decreased so that the tracking control pull-in operation does not fail.

The fact that the light beam is located at the midpoint between the tracks is performed by detecting the zero cross of the tracking error signal by utilizing that the tracking error signal becomes zero at the midpoint between the tracks. There is.

FIG. 2 shows this state.

2a shows a tracking control ON / OFF command signal, b shows an acceleration / deceleration pulse, c shows a tracking error signal, and d shows a zero-cross detection signal.

Further, as shown in FIG. 2, when the jumping operation is started or ended, a large number of zero crosses of the tracking error signal may occur due to eccentricity of the disk, hunting at the time of pulling in the tracking control, and the like. Therefore, the deceleration pulse is applied at the timing of the zero-cross signal after the end of the normal acceleration pulse.

Problems to be Solved by the Invention In the jumping scan, if the jumping scan is intended to be performed in a short time, it is conceivable to lengthen the widths of the acceleration pulse and the deceleration pulse. That is, the proportion of the time during which the acceleration / deceleration pulse is applied during the time required for the jumping scan is increased. In such a case, due to external disturbances such as shock and vibration from the outside, eccentricity of the disk, etc., the tracks pass through the tracks and the midpoint of the tracks during the acceleration pulse application, and the deceleration pulse is not correctly applied and jumping scanning is performed. May fail. This is shown in FIG.

3A shows a tracking control ON / OFF signal, b an acceleration / deceleration pulse, c a tracking error signal, and d a zero cross detection signal.

In FIG. 3, as described above, since the light beam passes through the track and the midpoint of the track during the application of the acceleration pulse, the deceleration pulse is not applied at the midpoint between the track and The zero-cross signal generated at the position of the track causes the deceleration pulse to be applied, so that one jumping scan fails.

The present invention provides a binarizing circuit for a tracking error signal,
After the acceleration pulse, follow the output level of the binarization circuit,
The feature is that a deceleration pulse is applied.

Therefore, in the jumping scan, even if the track crosses the midpoint between tracks while applying the acceleration pulse, that is, even if the zero crossing of the tracking error signal occurs during the application of the acceleration pulse, deceleration is immediately performed after the completion of the acceleration pulse. It is possible to generate a pulse and prevent a jumping scan from failing.

EXAMPLES Examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a tracking control system for performing tracking control and a jumping circuit for performing jumping scanning according to the present invention.

In FIG. 1, a light beam emitted from a light source 1 such as a semiconductor laser passes through a collimator lens 2 for collimating the light beam, is reflected by a polarization beam splitter 3, and
It passes through a 4λ plate 4, is converged by a converging lens 5, and is irradiated onto a disk 7 which is being rotated by a motor 6.
The reflected light from the disk 7 passes through the converging lens 5, the 1 / 4λ plate 4, and the beam splitter 3, and enters the two-divided photodetector 8. The dividing line of the two-divided photodetector 8 is arranged in the longitudinal direction of the track on the light receiving surface.

The output signal of the 2-split photodetector 8 is input to the differential amplifier 9.

The output signal of the differential amplifier 9 configured in this way is
It is known that a tracking error signal as shown in the figure is obtained.

That is, in FIG. 4A, when the light beam 10 is located right above the track 11 on the disk 7, the output signal of the differential amplifier 9 becomes zero level, and when the light beam is deviated left and right with respect to the longitudinal direction of the track, the deviation amount is A signal corresponding to is generated with opposite polarities. Further, the output signal of the differential amplifier 9 becomes zero level even when the light beam is positioned exactly in the middle of the tracks.

The output signal of the differential amplifier 9 turns tracking control ON / OFF.
It is added to the tracking element 15 via a switch 12, an adder circuit 13, and a drive circuit 14 for switching.

The tracking element 15 drives the converging lens 5 in the direction horizontal to the surface of the recording material and perpendicular to the track (disk radial direction) according to the signal from the drive circuit 14 so that the light beam 10 scans the track 7 correctly. Is done. Next, jumping scanning will be described.
Instruct whether to move the light beam to a track on the outer circumference side of the track following (hereinafter referred to as jump down) or to move the light beam to a track on the inner circumference side (hereinafter referred to as jump up). The direction signal 16 and the jumping start signal 17 are input to the command circuit 18. A command signal 22 and a command signal 23 are input from the command circuit 18 to the positive pulse generation circuit 19 and the negative pulse generation circuit 20, respectively. When the positive pulse generating circuit 19 and the negative pulse generating circuit 20 receive the command signal 22 or 23, the positive pulse generating circuit 19 and the negative pulse generating circuit 20 generate positive and negative pulses having substantially the same absolute value of the pulse width and the peak value, respectively. The outputs of the positive pulse generation circuit 19 and the negative pulse generation circuit 20 are input to the above-mentioned addition circuit 13,
It is input to the tracking element 15 via the drive circuit 14, and the converging lens 5 is driven in opposite directions in the disk radial direction, that is, the positive pulse is directed to the inner circumference and the negative pulse is driven to the outer circumference at a constant acceleration for a predetermined time.

The tracking error signal which is the output signal of the differential amplifier 9 is also input to the binarization circuit 21 which binarizes the input signal with a constant threshold value. In this embodiment, the threshold value of the binarization circuit 21 is set to zero level, and a high output is output when the tracking error signal is positive, and a low output is output when the tracking error signal is negative.

The output signal of the binarization circuit 21 is sent to the command circuit 18 as the direction signal 1
6, input with jumping start signal 17.

FIG. 5 shows the signal waveforms of the main parts of FIG. 1 during the jump-up operation as time elapses.

The operation of this embodiment will be described in more detail with reference to FIG.

FIG. 5A is a direction signal 16 for instructing the direction of jumping scanning, b is a tracking ON / OFF command signal, c is a jumping start signal, and d is a command signal to the positive pulse generation circuit 19.
22 and e are command signals 23, f and g to the negative pulse generation circuit 20.
Are output signals of the positive pulse generating circuit 19 and the negative pulse generating circuit 20, h is a tracking error signal output from the differential amplifier 9, and i is an output signal of the binarizing circuit 21.

The direction signal 16 is set to a high level in the case of jump-up and a low level in the case of jump-down prior to the jumping scan, and its value is held at least during the jumping scan. After that, tracking control is disabled at Low level, and the tracking ON / OFF command signal that operates at High level is set to Low to disable tracking control. Then, the jumping start signal 17 is immediately set to the high level.

When the rising edge of the jumping start signal 17 is detected, the command circuit 18 first sets the command signal 22 to the high level if the direction signal 16 is at the high level, and first sets the command signal 23 to the high level if it is at the low level. .

As shown in Fig. 5, when jumping up, the direction signal
Since 16 is set to the high level, the command circuit 18 first sets the command signal 22 to the high level.

Immediately after detecting the rising edge of the command signal 22, the positive pulse generation circuit 19 adds a positive pulse having a constant time width Δt ₁ to the addition circuit.
It outputs to 13 and the tracking element 15 is accelerated toward the inner circumference at a constant acceleration α ₁ for a period of Δt ₁ .

Therefore, when jumping up, the positive pulse generated by the positive pulse generation circuit 19 is the acceleration pulse, and the negative pulse generated by the negative pulse generation circuit 20 is the deceleration pulse, which will be described in detail later.

As the tracking element 15 moves in the inner peripheral direction, the differential amplifier 9 outputs a positive tracking error signal and outputs 2
The output signal of the binarization circuit 21 becomes the high level as described above.

After the acceleration pulse ends, the tracking element 15 moves toward the inner circumference at a substantially constant speed due to inertia, and eventually reaches the midpoint between the tracks. At this time, the tracking error signal changes from positive to zero level and then to negative, and the output signal level of the binarization circuit 21 switches from the high level to the low level.

Command circuit 18 indicates that the acceleration pulse has ended, direction signal 16
, The command signal 23 is output when the three states of being at the High level (that is, jumping up) and the output of the binarization circuit 21 being at the Low level are satisfied. Sixth
The figure shows a more detailed block diagram of the part of the command circuit 18 that performs this operation and the signal waveforms of each part over time.

The jumping start signal 17 is the mono multivibrator 24
Input to the mono multivibrator 24, the command signal 22
A pulse with a constant time width Δt ₁ is generated from the rising edge of. The output signal of the mono multivibrator 24 is input to the flip-flop 25 that operates at the falling edge of the input signal. Therefore, the output of the flip-flop 25 changes from the low level to the high level after a fixed time Δt ₁ from the rising edge of the jumping start signal 17. Therefore, the fact that the output of the flip-flop 25 is at the high level means that the acceleration pulse (in the case of jump-up, the positive pulse) has ended.

On the other hand, the output signal of the binarization circuit 21 is inverted by the inverter 26, and is input to the 3-input AND circuit 27 and the flip-flop 25.
Is input together with the output signal and the direction signal 16.

Therefore, the output of the AND circuit 27 becomes High level
It is when the acceleration pulse is completed, the direction signal 16 is at the high level, and the output of the binarization circuit 21 is at the low level.

The output of the 3-input AND circuit 27 is input to the mono multivibrator 28 that operates at the rising edge of the input signal, and the output of the mono multivibrator 28 is used as the command signal 23.

In FIG. 6, a is a jumping start signal 17,
b is a mono-multivibrator 24, c is a flip-flop
25 and d are output signals of the binarization circuit 21, e is an inverter 26,
f is a 3-input AND circuit 27, g is a mono-multivibrator
28 output signals.

As soon as the negative pulse output circuit 20 detects the rising edge of the command signal 23, it generates a negative pulse having the same time width Δt _{1 as} the positive pulse, and causes the tracking element 15 to have the same absolute value as that of the positive pulse, but with the opposite polarity. The acceleration is decelerated by -α ₁ .
Immediately after the end of the deceleration pulse, the tracking ON / OFF command signal is again set to the high level, the tracking control is activated, and the light beam scans one inner track.

When jumping down, the direction signal 16 is set to the Low level prior to the jumping scan, and when the jumping start signal 17 becomes the High level, the command circuit 18 first raises the command signal 23 to make it negative. A pulse is applied to the tracking element 15 to accelerate it toward the outer circumference.

Therefore, when jumping down, the negative pulse becomes an acceleration pulse.

Command circuit 18, this time, that the acceleration pulse has ended,
When the direction signal 16 is at the low level (jump down) and the output of the binarization circuit 21 is at the high level, the command signal 22 is raised and the positive pulse is tracked. It is applied to 15 and jumping scanning is performed. Therefore, the deceleration pulse at the time of jump down is a positive pulse.

Next, the operation in the case where the light beam passes through the midpoint between the tracks before the acceleration pulse ends due to external disturbances such as vibrations and shocks, or eccentricity of the disk is added to the present embodiment configured as described above. Let us consider the case of jump-up as an example.

Figures 7a-i represent the same signals as Figures 5a-i.

In FIG. 7, the time required from the rise of the command signal 22 until the light beam is positioned at the midpoint between the tracks is indicated by Δt ₂ .

As described above, when the light beam passes through the track and the midpoint of the track before the end of the acceleration pulse due to the disturbance, Δt ₁ > Δt ₂ holds. However, at the end of the acceleration pulse (that is, after Δt ₁ from the rise of the command signal 22), the output of the binarization circuit 21 is at the Low level as shown in FIG. Jumping scanning in which the command signal 23 is raised and a negative pulse (deceleration pulse) is applied to the tracking element 15 is normally completed, and the light beam can scan adjacent tracks.

Therefore, as described in the above "Problems to be solved by the invention", the deceleration pulse is not applied and the jumping scan does not fail.

In the present embodiment, the threshold value of the binarization circuit 21 is set to the zero level, but it does not necessarily have to be the zero level, and it is obvious that the operation as in the above embodiment is performed even in the vicinity of the zero level. Therefore, detailed description is avoided.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to perform a stable and high-speed jumping operation as compared with a conventional device even when there is a disturbance such as vibration or eccentricity, and its practical effect. Is big.

[Brief description of drawings]

FIG. 1 is a block diagram of a tracking control and jumping circuit according to the present invention, FIGS. 2 and 3 are signal diagrams for explaining a jumping scan of a conventional device, and FIG. 4 is a position of a light beam and a track. Relationships and relationship diagrams of tracking error signals, FIGS. 5, 6, and 7 are signal diagrams for explaining the jumping scan in the embodiment of the present invention. 1 ... Semiconductor laser, 2 ... Collimator lens, 3 ...
… Beam splitter, 4 …… λ / 4 plate, 5 …… Convergent lens, 6 …… Disk motor, 7 …… Disk, 8 ……
Photodetector, 9 ... Differential amplifier, 12 ... Switch, 13 ...
Adder circuit, 14 …… Drive circuit, 15 …… Tracking element,
18 ... Command circuit, 19 ... Positive pulse generation circuit, 20 ... Negative pulse generation circuit, 21 ... Binarization circuit.

Claims (2)

[Claims] 1. A conversion unit for recording or reproducing information on or from a record carrier having information or a track on which the information is recorded, and detecting a positional relationship between the conversion unit and the track on the record carrier. Tracking error signal detecting means, transfer means for transferring the converting means in a direction perpendicular to the track on the record carrier, and a target track which is one of adjacent tracks from an arbitrary start track of the tracks, An acceleration signal generating means for outputting an acceleration signal for accelerating the converting means to the transfer means and an acceleration signal generating means for accelerating the converting means, and a deceleration signal having a polarity opposite to that of the acceleration signal for outputting to the transferring means. The output of the deceleration signal generating means for decelerating and the output of the tracking error signal loss means are binarized, and the output is high level or low level. Position detecting means for detecting whether or not the converting means is located on the target track side with respect to the midpoint between the start track and the target track. After acceleration, after the end of acceleration, the conversion means detects that the conversion means is located on the target track side with respect to the midpoint between the start track and the target track, and starts the operation of the deceleration signal generation means, A jumping scanning device which performs a jumping scan by decelerating the conversion means. 2. An instruction means for outputting an instruction signal for instructing which one of the adjacent tracks from the start track is to be the target track is provided, and the position detecting means is provided with a converting means for the start track in response to the instruction signal. 2. The jumping scanning device according to claim 1, wherein the level for detecting that it is located closer to the target track than the midpoint between the target track and the target track is switched.