JPH02235224A - Projection power control system for optical disk device - Google Patents

Abstract

PURPOSE:To attain stable reading generating no nose at the time of reading and to prevent the generation of damage due to light irradiation to an optical disk by changing the production power of an optical head in accordance with reading time or non-reading time. CONSTITUTION:A projection power control part (laser power control part) 3 controls the optical power of a semiconductor laser in the optical head 2 for projecting a laser beam from the semiconductor laser light source to the optical disk 1 and receiving the reflected light from the optical disk 1 by a 4-divided photodetector based upon a light emitting power setting signal, a read gate signal and a write data/gate signal. At that time, the projection power in reading is set up to a value larger than the projection power of non-reading. Namely, light is emitted by normal reading power only during the period of reading even in the case of on-track on the optical disk, and at the time of non-reading, the reading power is reduced down to a level which does not exert bat influence upon servo (focus/track). Consequently, the generation of damage due to the projection power to the optical disk medium 1 can be prevented and stability at reading can be obtained.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology Problems to be solved by the invention Means for solving the problems (Fig. 1) Working example (a) Description of one example ( Figures 2 to 4) (b)
Description of other embodiments Effects of the invention [Summary] Regarding an output power control method for controlling the output power of an optical head of an optical disk device, it is possible to prevent damage to an optical disk medium due to output power and obtain stability during K read. With the purpose of , an output power control unit was provided to control the output light power of the nod, and the output power during reading was set to be the same as that during non-reading, and the output power was made p larger than that in order to improve the data transfer speed.
Ita.

[Industrial application field]

The present invention relates to an output power control method for controlling the output power of an optical head of an optical disk device.

Devices using optical disks, including magneto-optical disks, are widely used as mass storage devices.

In such optical discs, high-sensitivity media that can record even with low optical power have been developed in recent years, and there is a need to ensure read stability with increased sensitivity.

[Conventional technology]

When using a high-sensitivity medium, the output light power of the optical head (
While the write power (read power) can be reduced, if the power is kept the same as before, even if the rotational speed of the optical disk is increased, reading/writing can be performed and the data transfer speed can be improved.

For this reason, in the past, the read/write power was controlled by the read/write power (a problem to be solved by the present invention). If the track continues, the optical disc medium itself is damaged by the emitted power, causing data failure.

In order to solve this problem, when the output power during reading is lowered, noise increases extremely and read errors are more likely to occur.

Therefore, it is an object of the present invention to provide an output power control system for an optical disc device that prevents damage to an optical disc medium due to output power and provides stability during reading.

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention.

As shown in FIG. 1, the present invention is an optical disc device in which an optical head 2 emits light onto an optical disc 1, and the optical head 2 receives the light from the optical disc 1 to perform a read operation. An output power control section 3 is provided to control the output light power of the optical head 2 using a read gate signal instructing reproduction, and the output power during reading is set higher than the output power during non-reading.

[Effect]

The present invention prevents read errors by emitting light with the normal read power only during reading even while on-track to an optical disk, and when not reading other than that, the servo (servo)
(Focus/Track) The read power has been lowered to a point where no negative effects are desired, preventing negative images on the optical disc and preventing data defects.

Therefore, for example, even if a high-sensitivity medium is used to increase the data transfer rate, stability during reading can be ensured and no damage to the optical disc will occur.

〔Example〕

(a) Description of an Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of a laser bow control section having the structure shown in FIG.

In the figure, the same components as those shown in FIG. 1 are indicated by the same symbols, and 1a is a spindle motor that rotates the optical disk 1tl, and 2 is the aforementioned optical head, which is a semiconductor laser. A light source emits a laser beam to an optical disk 1, and a four-split photodetector receives reflected light from the optical disk 1.

3 is the above-mentioned emission power control section (hereinafter referred to as the laser power control section), which controls the optical power of the semiconductor laser of the optical head 20 by controlling the emission power setting signal, read gate signal, write data/ It is controlled by a gate signal.

4 is a servo circuit that performs focus servo control and track servo control of the optical head 2 from the output of the optical head 204-divided photodetector; 5 is a signal reproducing circuit;
Regenerate the signal from the output of the optical head 204-divided photodetector,
It is output as read data in response to a read gate signal.

6 is a control unit that controls the servo operation of the servo circuit 4 and generates a light emission power setting signal to the laser power control unit 3; 7 is a host controller that outputs the read gate signal to the laser power control unit during reading; 3 and a signal reproducing circuit 5 to obtain read data from the signal reproducing circuit 5, and output write data and a write gate signal at the time of writing to the laser power control section 3 to perform a write operation.

In FIG. 3, 20 is a laser diode (semiconductor laser) in the optical head 2. A monitor diode 21 emits a laser beam, which monitors and receives the light emitted from the laser diode 20 and converts it into a current output.

30 and 31 are inverting amplifiers, each of which inverts and amplifies the output of the monitor diode 21, and 32 is a summing amplifier that subtracts and integrates the output voltage of the inverting amplifier 31 from the set voltage of the power switching circuit, which will be described later. It is something.

33 is a power switching circuit, which includes a voltage dividing resistor '1 * '1
, in parallel with the voltage dividing resistor r1, the read gate signal R
A switch SW that is turned on by the DGT and a resistor r3 are provided, and two power setting voltages V. ,V. This outputs the following.

34 is a drive transistor, laser diode 20
35 is a reference voltage source, which controls the reference voltage +■ of the power switching circuit 330 according to the light emission power setting signal from the control section 6. be.

36 is a light circuit which controls the amount of light emitted from the laser diode 20 in accordance with the write gate and write data from the host controller 7, and causes the laser diode 20 to emit light.

Incidentally, the monitor diode 21, the inverting amplifiers 30, 31, the summing amplifier 32, and the driving transistor 34 and K constitute an automatic power control circuit.

FIG. 4 is an explanatory diagram of the operation of one embodiment of the present invention, and the configurations of FIGS. 2 and 3 will be explained using FIG. 4.

The host controller 7 does not generate any of the gate signals RDGT and WIGT when neither reading nor writing is necessary. Therefore, the power switching circuit 33 of the laser power control unit 3
When the switch SW is off, the voltage dividing resistors rl and r2
The set voltage vo during non-reading, which is the midpoint potential of , is output to the addition amplifier 32 .

Therefore, the light emission amount (output power) of the laser diode 20 is automatically power-controlled to the light emission amount of the low power P0 corresponding to the set voltage vo.

This low power Po is smaller than the read limit power by a factor K, and has sufficient power to stabilize the track/focus servo. Servo.

Next, the upper controller 7 generates a read gate signal RDGTt during a read.

Therefore, the power switching circuit 33 of the laser power control section 3
The switch SW is turned on, and the read setting voltage V1 (Vs>Vo) determined by the resistor r3 is output to the summing amplifier 32.

Therefore, the specified lead power P corresponding to the set potential ■1,
The light emission power of the laser diode 20 is automatically controlled to the light emission amount.

This specified read power P1 is high enough not to generate noise. A read operation is performed using the optical power of the laser diode 20 of the optical head 2, and the signal reproducing circuit 5 reproduces a signal from the reflected light with respect to the emitted light K, and outputs read data to the host controller 7.

Therefore, stable read operation with less noise and fewer read errors is possible.

Furthermore, when writing, the host controller 7 sends the write gate signal WEGT and write data to the laser power control unit 3.
It is output to the write circuit 36 of.

At this time, the automatic power control circuit drives the laser diode 20 through the write circuit 36K, and performs writing and recording on the optical disc 1 with a strong write output power P2 modulated according to the write data.

In this way, when reading, K emits light at the specified read power, ensuring stable read operation without causing read errors, and when not reading, it emits light at a low enough power to stabilize the servo. Therefore, damage caused by laser irradiation to the optical disk is small and data defects do not occur.

This embodiment can be realized by adding a power switching circuit 33t to the conventional automatic power control circuit and changing the power setting potential, so it can be easily realized, and it can also be realized by using the conventional read gate signal. Control is also easy.

(b) Description of other embodiments In the above embodiments, a high-sensitivity medium was explained, but even a medium with normal sensitivity can easily be damaged by the output power and result in data failure. It can be applied without any problem.

Further, it can be applied to magneto-optical disks, and the optical head is not limited to one using a laser light source, but may also be a transmission type optical disk.

Although the present invention has been described above with reference to Examples, the present invention can be modified in various ways according to the spirit of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, since the output power of the optical head is changed between reading and non-reading,
It has the effect of enabling stable reading without noise and preventing damage to the optical disc due to light irradiation, and particularly contributes to improving data transfer speed using high-sensitivity media. Thick.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the present invention. Figure 2 is a configuration diagram of an embodiment of the present invention. Figure 3 is a configuration diagram of the laser power control section configured in Figure 2. FIG. 4 is an explanatory diagram of the operation of an embodiment of the present invention. In the figure, 1... optical disc, 2...optical head, 3... Output power control section. (A)

Claims (1)

[Scope of Claims] An optical disc device in which an optical head (2) emits light onto an optical disc (1), and the optical head (2) receives the light from the optical disc (1) to perform a read operation. An output power control section (3) is provided to control the output light power of the optical head (2) using a read gate signal that instructs data reproduction, and the output power during reading is made larger than the output power during non-reading. An output power control method for an optical disk device characterized by: