JPH117648A - Semiconductor laser control device for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium LS control device capable of stably and surely deleting recorded data in an optional range. SOLUTION: Recording and deleting driving current sources 11c and 11b are provided by interpolating switches 12c and 12b for supplying recording and deleting driving currents to a driving current source 11a for supplying a reproducing driving current to an LD 13, and current control circuits 14, 15 and 16 are provided respectively for controlling the current values of the driving current sources 11a, 11c and 11b so as to obtain optical output levels necessary for reproducing, recording and deleting while monitoring the optical output of the LD 13. In a deletion mode, for a driving current obtained from the reproducing driving current source 11a, a deleting driving current obtained from the deleting driving current source 11b is pulse-divided and added by the switch 12b and then supplied to the LD 13 and then substantial DC deletion is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser control apparatus for recording, reproducing, and erasing data on a rewritable optical recording medium using a single semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, DVD (Digital Video Disc) and CD-RW (Co-RW) have been used as rewritable optical recording media.
Optical disks such as mpact Disc-ReWritable) are known. As a recording method of a rewritable optical disk, for example, there are a method using a phase change between a crystalline state and an amorphous state, and a magneto-optical recording method. The data recording, reproducing and erasing modes of these optical disks are controlled by switching the optical output level using one semiconductor laser (LD). Usually, a high light output level is used in the recording mode, a lowest DC light output level is used in the reproduction mode, and a DC light output level intermediate between the recording mode and the reproduction mode is used in the erasing mode.

An LD control circuit for an optical disk which requires such mode control is conventionally configured as shown in FIG. The LD 33 has a drive current source 31a for reproduction and erasure.
Are connected in series, and a switch 32 is connected to the drive current source 31a.
, A driving current source 31b for recording is additionally provided. A read / erase current control circuit 34 is provided to control the drive current source 31a, and a recording current control circuit 35 is provided to control the drive current source 31b. LD33
Is monitored by a photodetector 36 such as a photodiode, and the detection output is amplified by an amplifier 37 and fed back to current control circuits 34 and 35. The loop gain control (servo control) of the current control circuits 34 and 35, respectively. )
Is made. In the recording mode, the recording data pulse circuit 3
8 controls the switch 32 to drive the current source 31b.
Is pulsed, and the LD 33 is driven.

FIG. 4 shows the output light of the LD 33 in each of the recording, reproducing and erasing modes. The light output for recording is
Drive current source 31b controlled by current control circuit 35
Is pulsed by the switch 32 controlled by the recording data pulse circuit 38, as shown in the figure. In the reproduction mode, the drive current source 31a controlled by the current control circuit 34 is used for LD driving, and a DC light output is provided. The light output level I1 in the recording mode is sufficiently higher than the light output level I2 in the reproduction mode. In the erase mode, using the same current control circuit 34 and the drive current source 31a as in the reproduction mode, the light output level I2 in the recording mode is higher than the light output level I2 in the reproduction mode.
The gain control of the current control circuit 34 is performed so that an optical output level I3 lower than 1 is obtained, thereby performing DC erasure.

[0005]

As described above, in the conventional method, the LD drive circuits for the reproducing system and the erasing system are shared, and a DC light output level required for erasing is obtained by servo gain control. However, in this method, stable erasure becomes difficult when erasing a part of the recording surface of the optical disk. As shown in FIG. 5, when trying to rise to a desired erasing light output level in the middle of the reproduction mode, the time constant of the control circuit 34 is large, so that τ = 20 to 30 msec.
This is because a slight delay occurs. For example, considering that a narrow recording area such as one or two frames is instantaneously erased, one subcode frame = 1/75 [sec] ≒ 13
When [msec] is handled at a quadruple speed, one subcode frame is equal to 3.3 [msec], and if there is the above-mentioned time delay τ, erasing is performed in a state where the DC light output level is unstable, and When the output level is stabilized, a situation occurs in which the area to be erased is passed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a rewritable optical recording medium LD capable of stably and reliably erasing recorded data in an arbitrary range.
It is intended to provide a control device.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a semiconductor laser control device for recording, reproducing and erasing a rewritable optical recording medium, comprising: a reproducing drive for supplying a reproducing driving current to the semiconductor laser. A current source, a recording and erasing drive current source provided in parallel with the reproducing drive current source for supplying a recording and erasing drive current to the semiconductor laser, and monitoring the optical output of the semiconductor laser. Meanwhile, reproduction, recording and erasing current control loops provided for controlling the current values of the reproducing, recording and erasing drive current sources so as to obtain the optical output levels necessary for reproduction, recording and erasing, respectively. In the erasing mode, the current obtained from the erasing drive current source is divided into pulses and added to the current obtained from the reproducing drive current source, and added to the semiconductor laser. Is characterized in that an adding means for feeding.

In the present invention, a drive current source for erasing and a current control loop for controlling the drive current source are provided independently of the reproducing system. A large time delay due to gain control does not occur when the mode rises. Further, in the present invention, the erasing drive current is divided into pulses, added to the reproduction drive current, and supplied to the LD. As a result, the light output in the erase mode can rise at a high speed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an optical disk LD control circuit according to an embodiment of the present invention. The optical disk (not shown) is, for example, a CD-RW,
Is mounted on an optical head for recording, reproducing and erasing the optical disk. The LD 13 is provided with a drive current source 11a for reproduction in series, a drive current source 11c for recording is provided in parallel with the drive current source 11a via a switch 12c, and further in parallel with a switch 12b. A drive current source 11b for erasing is provided.

Driving current source 11 for reproduction, erasure and recording
In order to control and drive each of a, 11b and 11c,
Current control circuits 14, 1 each having a loop gain set
5 and 16 are provided separately. That is, a photodetector 17 such as a photodiode for monitoring the output light of the LD 13
Is amplified by an amplifier 18 and fed back to the current control circuits 14, 15, and 16, whereby current control loops for reproduction, erasure, and recording are independently configured.

The switch 12c provided in the recording drive current source 11c is controlled on / off by a recording data pulse circuit 19. That is, the switch 12c has a function of an adding means for pulsating the recording drive current ic and simultaneously adding the pulse to the reproduction drive current ia. The same applies to the switch 12b provided in the erasing drive current source 11b. The switch 12b is turned on / off by the erasing pulse generation circuit 20, and the pulsed erasing drive current ib is added to the reproduction drive current ia. Work.

L driven by drive current ia for reproduction
The output light power I2 of D13 is set to a sufficiently small level necessary to detect the reflected light from the recording pit. This drive current ia for reproduction is added to the pulsed drive current i for recording.
c, the output light power I of the 44LD 13 driven by adding
1 is set to a sufficiently high level necessary for recording. Also, the output light power I3 of the LD 13 driven by adding the pulsed drive current ib for erasing to the drive current ia for reproduction.
Is set between the output light power I2 for reproduction and the output light power I1 for recording (for example, about half the level of the output light power I1 for recording).

In such a configuration, in the reproduction mode,
The current ia of the drive current source 11a controlled by the current control circuit 14 is supplied to the LD 13, and a DC light output of level I2 is applied to the optical disc. As a result, it is possible to reproduce the data of the recording track of the optical disk which is rotationally driven and subjected to tracking control. When high-speed writing is performed, an unrecorded area is searched in the reproduction mode. When the unrecorded area is searched, the current control circuit 16 is turned on (recording mode ON), and the current ic of the drive current source 11c is pulsed. And added to the reproduction current ia. As a result, recording with high output light power I1 is performed. The duty ratio of the recording pulse light is about 50%.

The erasing mode is controlled basically in the same manner as the recording mode. FIG. 2 shows the operation waveforms. When the recording area to be erased is searched in the reproduction mode and the erase mode is turned on, the erase pulse generation circuit 20 generates a pulse having a time width corresponding to the area to be erased. The switch 12b is controlled by this pulse, and the current ib from the servo-controlled drive current source 11b is pulsed and added to the reproduction current ia to perform LD driving. As a result, while the erase mode is ON, the pulsed light output of the level I3 is added to the DC light output of the level I3, and the substantial DC
Erasure is performed. To be said to be a substantial DC cancellation,
The pulsed light output in the erasing mode needs to have a duty ratio greater than a certain level, and is preferably 90% or higher. However, if the duty ratio is 50% or more, substantially substantial DC erasure is possible.

As described above, in this embodiment, the loop gain is set independently of the erasing drive current source 11b and the reproducing current control circuit 14 for controlling the erasing drive current source 11b separately from the reproducing system. And a current control circuit 15 for erasing.
The drive current for erasing is pulsed and added to the drive current for reproduction. That is, the combination of providing a current control circuit having a loop gain independent of the reproduction system and addition by pulsing the erasing drive current makes it possible to use the current control circuit of the reproduction system as it is for the Unlike the conventional method in which switching is performed, a large time delay does not occur in the rise of the optical output in the erase mode, and the rise delay in the erase mode can be reduced to about 200 μsec or less.

The optical disk to which the present invention can be applied uses a small optical output level for reproduction, uses a large optical output level for recording as compared with reproduction, and an optical output intermediate between the reproduction and recording optical output levels for erasure. What is necessary is just to use a level, and the recording principle does not matter.

[0017]

As described above, according to the present invention, an erasing drive current source and a current control loop for controlling the erasing drive current source are provided independently of the reproducing system. By performing LD driving by adding to the driving current, high-speed rise of the optical output in the erasing mode is enabled,
Even when erasing a narrow recording area on an optical disc,
Stable and reliable erasure is possible.

[Brief description of the drawings]

FIG. 1 shows an LD of an optical disk according to an embodiment of the present invention.
2 shows a configuration of a driving circuit.

FIG. 2 shows operation waveforms for explaining an operation in an erase mode according to the embodiment.

FIG. 3 shows a configuration of an LD drive circuit of a conventional optical disc.

FIG. 4 shows operation waveforms for explaining operations in a recording, reproducing and erasing mode by the LD driving circuit.

FIG. 5 shows LD output light power in an erasing mode by the LD driving circuit.

[Explanation of symbols]

11a: drive current source for reproduction, 11b: drive current source for erasure, 11c: drive current source for recording, 12b, 12c: switches (addition means), 13: LD, 14: current control circuit for reproduction, 15: erasure Current control circuit, 16: recording current control circuit, 17: photodetector, 18: amplifier, 19: recording data pulse circuit, 20: erase pulse generation circuit.

Claims (1)

[Claims] An apparatus for controlling a semiconductor laser for recording, reproducing and erasing a rewritable optical recording medium, comprising: a reproducing driving current source for supplying a reproducing driving current to the semiconductor laser; A recording and erasing drive current source provided in parallel with the reproduction drive current source for supplying a recording and erasure drive current, respectively, for reproducing, recording and erasing while monitoring the optical output of the semiconductor laser; A reproducing, recording and erasing current control loop provided for controlling the current values of the reproducing, recording and erasing drive current sources to obtain a required optical output level; and Adding means for dividing the current obtained from the erasing drive current source into pulses and adding the current obtained from the erasing drive current source to the current obtained from the drive current source for supply to the semiconductor laser; The semiconductor laser control apparatus for an optical recording medium characterized by comprising.