JPH0727649B2 - 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 a jumping scanning device 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 disc having an optically recordable and reproducible material film formed on the surface of a substrate having a concentric circular concavo-convex structure by vapor deposition or the like is irradiated with a light beam generated from a light source such as a semiconductor laser. 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, a jumping scan 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, for example, jumping-scanned to the track on the inner circumference side, the tracking control is disabled and the driving pulse (acceleration pulse) is forcibly accelerated and moved in the inner circumference direction. When it arrives in the vicinity of the track on the 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 located at the midpoint between the tracks, and a drive pulse (deceleration pulse) having the same crest value and pulse width as the accelerated drive pulse but the polarity is opposite is detected. In addition, the relative speed between the light beam and the track on the adjacent track is reduced so that the pulling-in of the tracking control 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. 5 shows this state.

FIG. 5a 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 of the tracking error signal c.

Problems to be Solved by the Invention In the jumping scan, the light beam moves at a substantially constant velocity due to inertia until the deceleration pulse is applied after the end of the acceleration pulse. Due to the load, the light beam is not perfectly constant in velocity, but undergoes changes due to external forces.

Therefore, the energy applied to the light beam by the deceleration pulse applied thereafter is not exactly the same as the energy applied by the acceleration pulse, and it is desirable to change it slightly.

Means for Solving the Problems Therefore, the present invention is provided with the crest value adjusting means for the acceleration pulse and the deceleration pulse in order to adjust the energy applied by the acceleration pulse and the deceleration pulse. Further, the crest values of the acceleration pulse and the deceleration pulse can be adjusted independently depending on the direction in which the jumping scan is performed.

Action Stable jumping scanning can be realized because the energy applied to the light beam by the acceleration pulse and the deceleration pulse can be independently adjusted by the peak value adjusting means for the acceleration pulse and the deceleration pulse.

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 the / 4 plate 4, is converged by the converging lens 5, and is irradiated onto the disk 7 being rotated by the motor 6. The reflected light from the disk 7 passes through the converging lens 5, the λ / 4 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.
When located directly above the upper track 11, the output signal of the differential amplifier 9 becomes zero level, and when the light beam shifts to the left and right with respect to the longitudinal direction of the track, a signal corresponding to the shift amount 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 the switch 12, the subtraction circuit 22, the addition circuit 13, and the drive circuit 14 for switching.

The tracking element 15 drives the converging lens 5 in the direction horizontal to the recording material surface and perpendicular to the track (disk radial direction) in accordance with the signal from the drive circuit 14 so that the light beam 10 scans the track 11 correctly. Control is performed.

Next, jumping scanning will be described.

Whether the light beam is moved to the track on the outer circumference side of the track being followed (hereinafter referred to as jump down),
Alternatively, a direction signal 16 for instructing whether to move the light beam to a track on the inner circumference side (hereinafter referred to as jump-up) and a start signal 17 for instructing the start of the jumping operation
Is input to the command circuit 24.

Command signals 28, 29 and 30 are input from the command circuit 24 to the pulse generation circuits 25, 26 and 27, respectively. Pulse generator circuit 25, 26,
27 When receiving the command signals 28, 29 and 30, respectively, pulses having the same pulse width, peak value and polarity are generated.

The output of the pulse generation circuit 27 is input to the tracking element 15 via the subtraction circuit 22, the addition circuit 13, and the drive circuit 14 to drive the converging lens 5 in a fixed direction, for example, the outer peripheral direction, at a fixed acceleration for a fixed time.

On the other hand, the outputs of the pulse generation circuits 25 and 26 are variable resistors 31 and 32.
Is input to the adder circuit 13 via the drive circuit 14,
It is input to the tracking element 15 and accelerates the converging lens 5 in the opposite direction to the pulse generating circuit 27, that is, in the inner peripheral direction for a predetermined time.

The tracking error signal, which is the output signal of the differential amplifier 9, is input to a zero-crossing detection circuit 21 that detects a zero-crossing of the tracking error signal. The output of the zero-crossing detection circuit 21 is
The direction signal 16 and the start signal 17 are input to the command circuit 24.

FIG. 3 shows the signal waveforms of the main parts of FIG. 1 during the jump-down operation, which are displayed over time. Third
The operation of this embodiment will be described in more detail with reference to the drawings.

In FIG. 3, a is a direction sign 16 for instructing a jumping scanning direction, b is a tracking control ON / OFF command signal, and c is a tracking control ON / OFF command signal.
Is the jumping start signal 17, d, e, f are the command signals 29, 28, 30, g, h, i for the pulse generation circuits 26, 25, 27, respectively, and the output of the pulse generation circuits 26, 25, 27, respectively. The signal, j is the tracking error signal output from the differential amplifier 9, and k is the output signal of the zero-crossing detection circuit.

Prior to the jumping scan, the direction signal 16 is set to a low level in the case of jump down, and its value is held at least during the jumping scan. Then Lo
Tracking control is disabled at w level and tracking ON / OFF command signal that operates at High level is set to Low to disable tracking control. Immediately thereafter, the start signal 17 is set to the high level.

When the command circuit 24 detects the rising edge of the start signal, the command circuit 24 follows the direction signal 16 at that time and outputs the pulse generation circuit 2
The command signal is issued to 5,26,27.

When jumping down, the command circuit 24
The pulse generator 27 generates a pulse having a constant time width Δt and a constant amplitude in response to the command signal 30. As described above, the tracking element 15 is directed toward the outer periphery to obtain a constant time acceleration a _{1 of} Δt.
Accelerate with.

As the tracking element 15 moves to the outer circumference, the differential amplifier 9 issues a negative tracking error signal, but when the light beam is positioned at the track and the midpoint of the track, the tracking error signal becomes zero level, and the zero crossing detection circuit 21
Outputs an output signal to the command circuit 24.

The command circuit 24, upon receiving the output of the zero-crossing detection circuit 21, issues a command signal 28, and the pulse generation circuit 25 causes the pulse generation circuit 25 to have a constant time width Δt,
It emits a pulse with a constant amplitude.

The pulse generated by the pulse generation circuit 25 passes through the variable resistor 31, the adder circuit 13, and the drive circuit 14 and is decelerated by the constant acceleration a ₂ in the inner circumferential direction of the tracking element 15 for a certain period of time Δt. When the beam is positioned on the inner track, the tracking control ON / OFF command signal is set to High, the tracking control is activated, and the light beam starts to scan one outer track and jumps down. The operation ends.

The light beam is decelerated by the pulse generated by the pulse generation circuit 25 as described above, and the amount of energy added at that time is changed by changing the peak value of the pulse by the variable resistor 31 during acceleration. It becomes possible to adjust relative to the amount of energy, and stable jump-down operation is realized.

Further, FIG. 4 shows the output signals of the main constituent parts of FIG. 1 at the time of jump-up with the lapse of time.

Figures 4a-k show the same signals as in Figure 3.

When jumping up, the direction signal 16 is set to a high level prior to the start signal 17. Tracking control ON / O
As soon as the FF command signal becomes low level and tracking control becomes inoperative, the start signal 17 is set to high level.

In response to the start signal 17, the command circuit 24 first issues a command signal 29, and the command signal 29 causes the pulse generation circuit 26 to generate a pulse having a constant time width Δt ₁ and a constant amplitude. The pulse generated by the pulse generation circuit 26 has its crest value changed by the variable resistor 32, and passes through the adder circuit 13 and the drive circuit 14 to move the tracking element 15 in the inner circumferential direction at a constant acceleration for a predetermined time Δt.
A ₃ accelerates.

The tracking element moves in the inner circumferential direction, and the differential amplifier 9
Emits a positive tracking error signal, but after that, when the light beam is positioned at the track and the midpoint of the track, the tracking error signal becomes zero level, and the zero crossing detection circuit
21 issues an output signal to the command circuit 24. The command circuit 24 is
When it receives the output of the zero-crossing detection circuit 21, it issues a command signal 30,
The pulse generation circuit 27 emits a pulse having a constant time width Δt and a constant amplitude, and decelerates the tracking element 15 at an acceleration a ₁ for a constant time Δt through the subtraction circuit 22 and the drive circuit 14. After that, when the light beam is positioned on the inner track, the tracking control ON / OFF command signal is set to High and the tracking control is operated so that the light beam scans one inner track. The jump-up operation ends.

Therefore, when jumping up, the amount of energy added during acceleration is changed relative to the energy added during deceleration by changing the peak value of the pulse with the variable resistor 32. A stable jumping operation is possible.

EFFECTS OF THE INVENTION With this configuration, when the jumping operation in the outer peripheral direction is performed, the outer peripheral jumping operation of the second pulse generating circuit is stably operated with respect to the acceleration caused by the first pulse generating means. The deceleration acceleration can be adjusted by changing the crest value of the output pulse, and the deceleration acceleration caused by the first pulse generating means stabilizes the inner circumference jumping operation during the inner circumference jumping operation. Since the crest value of the pulse output from the second pulse generating circuit can be changed so as to operate, the acceleration acceleration can be adjusted, so that the inner jumping operation and the outer jumping operation can be optimally adjusted. A stable jumping operation that does not depend on the jumping direction can be realized.

That is, according to the present invention, three pulse generating circuits are provided,
Only by configuring the peak value of the output of the two pulse generation circuits to be changeable, stable jumping operation that does not depend on the jumping direction can be realized, and the scale of the hardware required to realize the jumping operation can be increased. It can be greatly reduced. Further, as used in this embodiment, all of the pulse generating means emit substantially the same pulse, so that it can be relatively easily constructed with a digital circuit configuration, and the IC can be easily constructed by digital IC technology. It can be made smaller and smaller, and the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a jumping scanning device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a positional relationship between a light beam and a track and a tracking error signal at that time, and FIG. 3 is a jump. FIG. 4 is a signal diagram of the main components in FIG. 1 when down, FIG. 4 is a signal diagram of the main components in FIG. 1 during jump up, and FIG. 5 is an explanatory diagram of a conventional jumping operation. 1 ... Semiconductor laser, 2 ... Collimator lens, 3 ...
Beam splitter, 4 ... λ / 4 plate, 5 ... Converging lens, 7 ... Disk, 8 ... Photodetector, 9 ... Differential amplifier, 12 ... Switch, 13 ... Addition circuit, 14 ... Drive circuit, 15 …… Tracking element, 21 …… Zero crossing detection circuit,
22 ... Subtraction circuit, 24 ... Command circuit, 25, 26, 27 ... Pulse generation circuit, 31, 32 ... Variable resistor.

Claims (1)

[Claims] 1. A converting means for recording or reproducing information optically from an information carrier having information or a plurality of tracks on which the information is recorded, and positions of the converting means and the track on the information carrier. Track deviation detecting means for detecting a relationship, and moving means for transferring the converting means in a direction crossing the tracks on the information carrier substantially vertically.
Tracking control means for driving the moving means according to the output of the track deviation detecting means so that the converting means always follows the track, and one direction of a direction crossing the track substantially vertically. A first pulse generating means for outputting to the moving means a drive pulse for accelerating the converting means in a first direction with a predetermined acceleration, and the converting into a second direction opposite to the first direction. Second pulse generating means and third pulse generating means for outputting a driving pulse for accelerating the means to the moving means and independently setting accelerations for accelerating the converting means, and outputs of the track deviation detecting means Is provided, and the conversion means is provided with a middle point detection means for detecting that the conversion means has reached the middle point of the track and the track, and the jumping scanning in the first direction is performed by the tracking control. After the operation of the stage is interrupted and the converting means is accelerated by the drive pulse output from the first pulse generating means, the drive pulse output from the second pulse generating means is output according to the output of the midpoint detecting means. After decelerating the conversion means, the operation of the tracking control means is restarted, and the jumping scan in the second direction interrupts the operation of the tracking control means and outputs the drive pulse output from the third pulse generation means. After accelerating the converting means, the speed of the converting means is reduced by the drive pulse output from the first pulse generating means in response to the output of the midpoint detecting means, and then the operation of the tracking control means is restarted. A jumping scanning device characterized by the above.