JPH07111783B2 - Semiconductor laser control circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser control circuit used in an optical recording / reproducing apparatus for recording / reproducing information on / from an optical disc.

2. Description of the Related Art FIG. 3 is a block diagram of a semiconductor laser control circuit in a traffic jam. An output light of a semiconductor laser 1 is received by a photodetector 2, and an operational amplifier 3 converts a received light into a current-voltage to obtain a control error voltage. . During recording, the modulation stage 7 performs optical pulse modulation according to the recording signal. The peak value of the received recording pulse light is peak-detected 4, and the peak value of the recording pulse light is kept constant by changing the current source 6 by comparing and outputting with the reference voltage 5. During reproduction, the reference voltage 5 is switched to the reproduction power value and the DC power is kept constant.

However, with the above-mentioned configuration, (1) the bottom value of the recording pulsed light cannot be controlled. (2) Since the peak detection efficiency varies depending on the frequency of the recording signal, the peak value of the recording pulse light changes. (3) A response time for peak detection occurs every time switching from reproduction to recording and the peak value of the recording pulse light rises slowly, resulting in power shortage and the problem that the first data in the recording area cannot be recorded normally. there were.

The present invention stably controls both the peak value and the bottom value of the recording pulse light even when the frequency of the recording signal changes, and further, the head data of the recording area immediately after switching from reproduction to recording / erasing. It is intended for stable and reliable recording.

Means for Solving the Problems In order to achieve the above object, in the semiconductor laser control circuit of the present invention, first, in the optical power servo section, it corresponds to the DC emission power during reproduction, the bottom value of the optical pulse waveform, and the peak value. The optical power value to be set is set by the power servo system. Next, each optical power value set in the optical power hold section is sampled and held. The held optical power values are used to reproduce, record, and erase signals on the optical disk.

In order to perform stable recording and erasing from the first recorded data immediately after switching from playback to recording and erasing, when playing the pre-pit portion while erasing or recording signals in each recording area continuously, The DC emission power of is made to correspond to the bottom value or peak value corresponding to the erased state of the optical pulse waveform.

Further, in order to improve the recording efficiency of the optical disk, it is effective to set the optical power servo section for each group in which several recording areas are collected.

Operation According to the present invention, the DC light emission power at the time of reproduction, the bottom value and the peak value of the recording / erasing pulse light can be set independently and precisely in the optical power servo section. Next, in the optical power hold section,
Since the DC emission power, the optical power value corresponding to the bottom value and the peak value of the recording / erasing pulse light are held, the emission power is stable regardless of the frequency of the recording signal. Further, since the transient response of the power servo does not occur when switching from reproduction to recording / erasing, stable recording can be performed from the first bit data of each recording area.

Further, in some optical discs using a phase-change recording material, the signal characteristics of the data at the beginning of the recording area may deteriorate if the emission power changes drastically, such as when switching from reproduction to recording / erasing. is there. Therefore, the level of the reproduction light when reproducing the address or the servo mark while continuously erasing the recording in each recording area is set to the optical power value corresponding to the erasing of the recording pulse light. By doing so, there is no power difference between the reproduction and the subsequent recording / erasing, and it is possible to prevent the signal deterioration of the head data.

Embodiment 1 FIG. 1 shows the configuration of a semiconductor laser control circuit in an embodiment of the present invention. FIG. 2 is an operation waveform diagram of the same embodiment. The output light of the semiconductor laser 1 is received by the photodetector 2 and the received current is converted into a current-voltage by the operational amplifier 3. The output of the operational amplifier 3 becomes the optical power control error voltage 9 and is input to the operational amplifiers 10, 11 and 12 constituting the servo system. FIG. 2 (a) shows the structure of the pre-pit portion formatted on the optical disc. Reference numeral 13 is a servo mark (SM) composed of wobble pits or the like for performing tracking servo. Servo mark 13 is recorded area 14
Is provided immediately before, and tracking servo is applied while sampling the reproduced signal. Several recording areas 14 are grouped into one group (sector) and a sector address (AD) 15 is given. 16 is the optical power servo section (ALPC)
, And sets each optical power level for reproduction, erasing (bottom value) and recording (peak value). The section other than the optical power servo section 16 is an optical power hold section. FIG. 2 (g) shows the optical output waveform of the semiconductor laser 1.

FIG. 1 shows the reproduced sample gate signal, and the signal waveform is shown in FIG. 2 (d). When the reproduction sample gate signal 17 is at a high level, the reproduction sample hold circuit 19 is set to the sampling state, and the optical power servo section during reproduction is started. At the low level, the hold state is set, which is the optical power hold section during reproduction.

First, when the reproduction sample gate signal 17 is at a high level, the optical power control error voltage 9 and the reproduction reference voltage 18 are compared and output by the operational amplifier 10 which constitutes the servo system during reproduction. Since the sample-hold circuit 19 is in the sample state, the output voltage of the operational amplifier 10 drives the reproduction current source 20 and sets the DC emission power during reproduction of the semiconductor laser (21 in FIG. 2). Next, when the reproduction sample gate signal 17 is at a low level, the output voltage of the operational amplifier 10 is held by the reproduction sample hold circuit 19, so that the reproduction DC light emission power is kept constant (22 in FIG. 2).

FIG. 1 shows the bottom value sample gate signal of the optical pulse waveform, and the signal waveform is shown in FIG. 2 (e). When the bottom value sample gate signal 23 is at a high level, the bottom value sample and hold circuit 24 is set to the sampling state, and the optical power servo section of the bottom value (during erasing) is set. At the low level, the hold state is set and the optical power servo section of the bottom value (at the time of erasing) is set.

First, when the bottom value sample gate signal 23 is at high level,
The optical power control error voltage 9 and the bottom value reference voltage 25 are compared and output by the operational amplifier 11 forming the bottom value servo system. Since the sample hold circuit 19 is in the sample state, the output voltage of the operational amplifier 11 drives the bottom value current source 26 and sets the bottom value power of the optical pulse waveform (2 in FIG. 2).
7). Next, when the bottom value sample gate signal 23 is at a low level, the output voltage of the operational amplifier 11 is held by the bottom value sample hold circuit 24, so that the bottom value power of the optical pulse waveform is held constant (28 in FIG. 2). ).

Reference numeral 29 in FIG. 1 represents a peak value sample gate signal of the optical pulse waveform, and the signal waveform is shown in FIG. 2 (f). When the peak value sample gate signal 29 is at a high level, the peak value sample and hold circuit 30 is set to the sampling state, and the peak value (during recording) becomes the optical power servo section. At the low level, the hold state is set, and the optical power hold section of the peak value (during recording) is set.

First, when the peak value sample gate signal 29 is at high level,
The optical power control error voltage 9 and the peak value reference voltage 31 are compared and output by the operational amplifier 12 that constitutes the peak value servo system. Since the sample-hold circuit 19 is in the sample state, the output voltage of the operational amplifier 12 drives the peak value current source 32 and sets the peak value power of the optical pulse waveform (3 in FIG. 2).
3). Next, when the peak value sample gate signal 29 is at a low level, the output voltage of the operational amplifier 12 is held by the peak value sample hold circuit 30, so that the peak value power of the optical pulse waveform is held constant (34 in FIG. 2). ).

Reference numeral 35 denotes a modulation stage, which modulates the optical pulse of the semiconductor laser 1 with the held peak value power and bottom value power according to the recording signal 36 shown in FIG. Reference numeral 37 denotes a write gate signal, which is set to a high level when the gate 38 of the recording signal 36 to the modulation stage 35 operates and the bottom value current source switch 39 turns on.
The write gate signal 37 is shown in FIG. The write gate signal is set to a high level in the optical power servo section of the bottom value and the peak value and the optical power hold section at the time of pulse modulation.

As described above, in the optical power hold section, the DC emission power at the time of reproduction, the optical power value corresponding to the bottom value and the peak value of the recording / erasing pulsed light are held, and therefore, even if the frequency of the recording signal changes. The emission power is stable. Further, since the transient response of the power servo does not occur when switching from reproduction to recording / erasing, it is possible to stably record with the optical power value set from the first bit data of each recording area.

Further, in an optical disc using a certain phase change recording material, the recording / reproducing characteristics of the data at the beginning of the recording area deteriorates when the emission power changes drastically, such as when switching from reproduction to recording / erasing. There is also. Therefore, the level of the reproduction light when reproducing the sector address 15 and the servo mark 13 while continuously erasing the recording in each recording area is set to the optical power value (for example, the bottom value) corresponding to the erasing of the recording pulse light. . By doing so, there is no power difference between the reproduction and the subsequent recording / erasing, and it is possible to prevent the deterioration of the recording / reproducing characteristics of the head data.
For example, when reproducing the servo mark 13 shown in FIG. 2A while continuously recording and erasing in each recording area 14, the normal reproduction power value held (FIG. 2G 39)
Instead, the bottom value power of the light pulse waveform (39 in FIG. 2 (g)) is used. In order to reproduce with the bottom value power, the write gate signal 37 may be set to the high level in the section of the servo mark 13 as shown in FIG. By doing so, there is no power difference between reproduction and subsequent recording / erasing, and it is possible to prevent signal deterioration of the head data.

EFFECTS OF THE INVENTION As described above, according to the present invention, the DC emission power at the time of reproduction, the bottom value and the peak value of the recording / erasing pulse light can be set independently and precisely in the optical power servo section. In the optical power hold section, the DC emission power at the time of reproduction, the optical power value corresponding to the bottom value and the peak value of the recording / erasing pulsed light are held, so the emission power is stable regardless of the frequency of the recording signal. .

Furthermore, since the transient response of the power servo does not occur when switching from reproduction to recording / erasure, the first 1 of each recording area
Data can be recorded stably from the bit data.

Further, in some optical discs using a phase-change recording material, the signal characteristics of the data at the beginning of the recording area may deteriorate if the emission power changes drastically, such as when switching from reproduction to recording / erasing. is there. Therefore, the level of the reproduction light when reproducing the address or the servo mark while continuously erasing the recording in each recording area is set to the optical power value corresponding to the erasing of the recording pulse light. By doing so, there is no power difference between the reproduction and the subsequent recording / erasing, and it is possible to prevent the signal deterioration of the head data.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a semiconductor laser control circuit according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the same embodiment, and FIG. 3 is a circuit diagram of a conventional semiconductor laser control circuit. 1 ... Semiconductor laser, 2 ... Photodetector, 16 ... Optical power servo section, 17,23,30 ... Sample hold, 35 ... Modulation stage.

Claims (3)

[Claims] 1. An optical power control error voltage generating means for receiving an output light of a semiconductor laser by a photodetector and generating an optical power control error voltage from the photodetection current, and outputting the output light of the semiconductor laser from an optical disk. A first optical power value which is a DC light emission power value when reproducing data, a second optical power value which is a bottom value of an optical pulse waveform modulated by a recording signal when erasing or recording a signal on the optical disk, an optical disk In order to set the third optical power value, which is the peak value of the optical pulse waveform modulated by the recording signal when recording or erasing the signal in the first, first, second and third respective reference voltages are generated. In the optical power servo section, the optical power control error voltage and the first, second and third reference voltages are compared and output to output the respective optical power control voltages. Generate the first
And second and third optical power control voltage generating means, and sample and hold each optical power control voltage at the time when the first, second and third optical power control voltages become stable in the optical power hold section. First, second and third voltage holding means, and first, second and third current source means for supplying a current proportional to the optical power control voltage held by each voltage holding means to the semiconductor laser. An optical pulse modulating means for optically modulating the second optical power value to the bottom value of the optical pulse waveform modulated by the recording signal and the third optical power value to the peak value of the optical pulse waveform modulated by the recording signal. A semiconductor laser control circuit equipped with. 2. An information recording area on an optical disk surface is divided into recording areas such as sectors or segments, and each recording area is continuously recorded on an optical disk having a pre-pit portion such as a sector address or a tracking servo mark. In order to reproduce the signal of the pre-pit portion while erasing or recording the signal in the area, the reproducing light power value emitted by the semiconductor laser was made to correspond to the second light power value or the third light power value. The semiconductor laser control circuit according to claim 1. 3. The semiconductor laser control circuit according to claim 1, wherein the optical power servo section is provided for each group in which the recording areas are collected.