JPH04356736A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a focus servo circuit from erroneously operating based on a transient focus error signal in accordance with a track jump. CONSTITUTION:The track jump signal from a tracking servo circuit 7 is supplied to the focus servo circuit 6, wherein the focus servo operation based on the focus error signal is prohibitted only during the track jump to make it to the hold state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording/reproducing device, and in particular, when an optical head accesses an arbitrary track, continues to follow the same track, or performs a track jump, the focus operation is affected. The present invention relates to a novel optical recording/reproducing device that prevents focus errors from increasing.

0002

2. Description of the Related Art Optical recording and reproducing devices record and reproduce information by irradiating a laser beam through an optical head onto an optical recording and reproducing medium such as a rotating magneto-optical disk. A tracking servo is used so that the light irradiates while accurately following the recording track on the disk, and a focus servo is used so that the laser beam is focused on the recording surface of the disk. Furthermore, the optical head is provided with a condensing lens that condenses the light beam emitted from the laser oscillator onto the disk surface, a focus actuator that adjusts the focus of this condensing lens, and the like. Further, a focus detection signal and a tracking detection signal are output from this optical head.

The focus detection signal is input to a focus servo circuit. The focus servo circuit monitors the focal shift of the beam emitted from the condenser lens using this focus detection signal. If a focus shift is detected, a focus error signal is output to the focus actuator drive circuit. Then, the focus actuator drive circuit drives the focus actuator based on this focus error signal to correct the focal shift of the beam.

On the other hand, the tracking detection signal is input to a tracking servo circuit. The tracking servo circuit monitors whether the emitted beam is following a predetermined track based on this tracking detection signal, and outputs a tracking error signal and a track jump signal if necessary. The tracking actuator drive circuit inputs the tracking error signal and track jump signal, and moves the output beam from the condenser lens in the radial direction of the disk based on these signals. In this way, information written on a desired track can be reproduced.

[0005]

[Problems to be Solved by the Invention] In the above-mentioned optical recording and reproducing apparatus, when an arbitrary other track is accessed from the current track and a recording or reproducing operation is to be performed, the optical recording/reproducing apparatus waits while following the operation starting track. state. If the track is in a spiral shape, the vehicle must jump the track once during tracing one lap in order to follow the same track. In such a case, the tracking error signal changes greatly due to the track jump, but in conventional optical recording/reproducing devices, this change may also be seen in the focus error signal. That is, recording/reproducing tracks are generally formed by guide grooves, etc., and in optical recording/reproducing media having such guide grooves, reflection diffraction from the guide grooves is a method for making the light beam follow the guide grooves. Tracking errors are detected using changes in intensity due to light interference effects, and tracking servo is applied based on this. Further, in focus error detection, since the physically same reflected light as in tracking error detection is used, adjustment errors and the like affect the focus error signal (optical wraparound) as described above. In focus error detection methods that use focused light, such as the knife-edge method, the effect of wraparound is relatively small, but it is Due to variations in assembly accuracy when assembling the optical head, etc.
The effect of track jumps may be significant on the focus error signal.

[0006] As described above, when the tracking error signal wraps around the focus error signal, the focus error signal does not accurately represent the actual physical focus error while the tracking error signal wraps around the focus error signal. However, in conventional optical recording and reproducing devices, the focus actuator drive circuit adjusts the focus of the optical head based on the focus error signal during this time, so the tracking error increases and the focus is out of focus at the end of the track jump. turn into. In such a defocused state, it is difficult to accurately record or reproduce information signals, and errors in recording or reproduction are likely to occur.

In order to accurately record and reproduce information signals,
It is conceivable that the recording/reproducing operation may be interrupted after a track jump until the focus error signal is stabilized. However, in this case, while the operation is interrupted, it is not possible to record or reproduce areas where the light flux moves relative to the optical recording/reproducing medium, so the amount of information that can be recorded on the medium decreases. It has the disadvantage of being

[0008]

[Means for Solving the Problems] An optical recording and reproducing apparatus according to the present invention records and reproduces information signals by irradiating an optical recording and reproducing medium with a beam of light. an optical head including a lens that condenses light, a focus actuator that adjusts the focus of this lens, and a tracking actuator that causes the light beam to follow a track on a medium; a focus servo circuit that drives the focus actuator; and the tracking actuator. It has a tracking servo circuit that drives an optical head, and a focus holding means that freezes the operation of the focus actuator only while the light beam moves from the track being followed to an adjacent track.

[0009]

Embodiment Next, FIG. 1 showing an entire embodiment of the present invention will be described. FIG. 1 shows a magneto-optical disk 1, an optical head 2, a laser diode (LD) drive circuit 3, and a magnetic field generation circuit 4.
, an RF amplifier 5 for amplifying the reproduced RF reproduction signal, a focus servo circuit 6, and a tracking servo circuit 7. When recording information here, the information signal is sent to the LD drive circuit 3, the laser beam is modulated in a predetermined manner, and the signal is recorded on the recording surface of the disk. Furthermore, the optical head 2 includes a laser diode 8, a collimator lens 9, a beam shaping prism 10, and a polarizing beam splitter 1.
1, 12, and an objective lens 13, the laser light emitted from the laser diode 8 passes through the above-mentioned path and is irradiated onto the magneto-optical disk 1. The light from the splitter 12 passes through a quarter-wave plate 14 and a lens 15, and is photoelectrically converted by a reproduced signal detector 16. On the other hand, the light from the beam splitter 11 passes through the lens 17 and the beam splitter 18.
The track error signal is sent to the track error detector 19 via the track error detector 19, where the track error signal is detected. The other light from the beam splitter is sent to a focus error detector 21 via a knife edge 20, where a focus error signal is detected. The outputs of the tracking servo circuit 7 and the focus servo circuit 6 are sent to the lens actuator 22 via drive circuits 7a and 6a, and
Control the position of 3.

The above configuration and operation are the same as those of a conventional optical reproducing device. A feature of the present invention is that the tracking servo circuit 7 supplies the focus servo circuit 6 with a control signal for holding the focus error signal for a tracking jump period.

Next, the tracking servo circuit will be explained in detail with reference to FIG. In the figure, signals Ta and Tb extracted from a detector 19 are sent to a differential amplifier 23 to generate a tracking error signal. The gain of the generated error signal is controlled by the AGC circuit 24 according to the total amount of light. Therefore, the detection signals Ta and Tb are sent to the sum amplifier 25, and an AGC control signal is generated. The track error signal passed through the AGC circuit 24 is supplied to an error amplifier 26 via a gain adjuster. The output of the error amplifier 26 is a lead-lag filter 27, a switch 28, and a mixing amplifier 2.
9 and is supplied to the drive circuit 7a.

When performing a track jump, a control signal is output from the CPU unit 30. The situation at this time will be explained with reference to the waveform diagram of FIG. When performing a track jump, the servo is turned on/off from the CPU unit 30.
The F control signal CT is output, and the switch 28 turns the servo operation ON/OFF based on this signal. The jump pulse generator 31 generates a tracking jump pulse TJP based on the servo ON/OFF control signal CT and the tracking error signal TER from the error amplifier 26, and
X Supplies to AMP29. As shown in FIG. 3, the track jump pulse TJP has a kick pulse part P1 from the servo OFF to the zero-crossing timing of the tracking error signal TER, and in this part the beam moves from the track being followed to the next track. will be started. Track Jump Pulse TJP is Kick Pulse P
1, there is a brake pulse portion P2 having a width of a certain period t1 (approximately 100 uS in this embodiment), and after P2, the servo operation is returned to the ON state. Furthermore, the jump pulse generator 31 outputs to the hold pulse generator 32 a timing signal TS having a width of a certain period t2 (approximately 200 uS in this embodiment) from the timing of switching from the kick pulse P1 to the brake pulse P2. The hold pulse generator 32 generates a signal from the timing signal TS and the servo OFF signal.
A hold control signal HCT as shown in FIG. 3 is generated and output to the focus servo circuit 6. The hold pulse generator is a distinctive part of the invention.

In the tracking servo circuit shown in FIG. 2, a positioner servo circuit 33 is provided, and when accessing a distance longer than a certain distance, data based on the distance to the target point is sent from the CPU unit 30, and the drive is performed based on this data. A drive signal is output to circuit 7b. Drive circuit 7b
drives the positioner motor according to the drive signal to move the optical head. When the target point is almost reached, the CPU
Instead of data from the unit, MIX AMP29
The output is sent to the positioner servo circuit 33, which outputs a drive signal such that the DC component of the tracking error signal becomes zero to 7b.

Next, the hold operation in the focus servo circuit based on the hold control signal HCT output from the tracking servo circuit will be explained. In the focus servo circuit shown in FIG. 4, the detection signals Fa and Fb from the detector 21 are sent to the differential amplifier 34 to generate a focus error signal, and sent to the AGC circuit 35. The AGC circuit 35 controls the gain of the focus error signal based on a control signal corresponding to the total amount of light from the sum amplifier 36. The error signal from the AGC circuit 35 is input to the sample hold circuit 37 via a gain adjuster. The sample and hold circuit 37 includes a tracking servo circuit (
Hold control signal HCT output from Figure 2)
Based on this, the input focus error signal is held for a period specified by this signal.

The focus error signal from the sample hold circuit 37 is sent to the drive circuit 6a (FIG. 1) via an error amplifier 38, a lead-lag filter 39, a switch 40, and a buffer amplifier 41. FIG. 5 is a diagram for explaining the hold operation of the focus error signal, including the tracking error signal TER and the hold control signal HC.
T, focus error output signal FE due to hold operation
R shows the focus error output signal FER' when there is no hold operation. As can be seen from FIG. 5, it can be seen that without the hold operation, the amplitude of the focus error signal fluctuates, and the focus servo operation is not performed normally. In the present invention, the focus actuator is
The state at the start of the track jump is retained. Track jump is completed and hold control signal HC
When T becomes high level, the focus servo circuit again outputs a focus error signal based on the focus detection signal. In this case, since the focus actuator is fixed during the track jump, the focus of the beam remains almost unchanged even after the track jump is completed.

[0016]

Effects of the Invention In the present invention, since a focus holding means is provided that freezes the operation of the focus actuator only while the light beam moves between tracks on the optical disk, the tracking error signal is not changed to the focus error signal. It is possible to avoid fluctuations in the focal position due to wraparound. In the present invention, when the movement between tracks is completed, the focus servo operation is started. At this time, the focal position of the lens remains at the position before movement,
Even after a track jump, the focus shift is extremely small and the focusing operation is quickly resumed. Thereby, information can be stably recorded or reproduced even immediately after the track jump ends.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an optical recording/reproducing apparatus according to the present invention.

FIG. 2 is a block diagram of the tracking servo circuit in FIG. 1.

FIG. 3 is a waveform diagram for explaining the operation of the tracking servo circuit in FIG. 2;

FIG. 4 is a block diagram of the focus servo circuit in FIG. 1.

FIG. 5 is a waveform diagram for explaining a hold operation in the focus servo circuit.

[Explanation of symbols]

1 Magneto-optical disk 2 Optical head 3 Laser diode drive circuit 4 External magnetic field generator 5 RF signal amplifier 6 Focus servo circuit 7 Tracking servo circuit 8 Positioner motor

Claims (2)

[Claims] 1. In an optical recording and reproducing apparatus that records and reproduces information signals by irradiating a light beam onto an optical recording and reproducing medium, a lens that focuses the light beam on the surface of the optical recording and reproducing medium;
and an optical head including a focus actuator that adjusts the focus of this lens, a focus servo circuit that drives and controls the focus actuator, and a tracking servo that drives and controls the optical head to follow a light beam on a track of an optical recording medium. 1. An optical recording/reproducing device comprising: a circuit; and focus position holding means for freezing the operation of the focus actuator only while the light beam moves from the track being followed to another track. 2. The tracking servo circuit includes tracking error signal extraction means and control signal formation means for forming a control signal for freezing the operation of the focus actuator from the tracking error signal. The optical recording/reproducing device described above.