JP3168710B2 - Laser array with power control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser array is a device that integrates a plurality of semiconductor lasers in the first element.

[0002]

2. Description of the Related Art A laser array is a device in which a plurality of semiconductor lasers are integrated in one element, and has been actively developed in recent years with the aim of increasing the speed of recording, reproducing, and erasing and increasing the functions of an optical disk device. (For example, Journal of the Japan Society of Applied Magnetics, 11 (2) p. 217 (1987)). In general, the light output of a semiconductor laser greatly changes due to fluctuations in the ambient temperature and power supply voltage, so a power control circuit is required to keep the light output constant. This power control circuit is provided before the data area of each sector of the optical disk. The operation is performed in a region for setting the laser output.

An example of a laser array having a conventional power control circuit will be described below with reference to the drawings.

FIG. 5 is a perspective view showing the structure of a general laser array. 51a and 51b are laser chips.
52a and 52b are PIN diodes. 59 is a heat sink. The laser beam emitted from the rear end face of the laser chip 51a is received by the PIN diode 52a,
The laser beam emitted from the rear end face of the laser chip 51b is received by the PIN diode 52b.

FIG. 6 is a circuit diagram of a laser array having a conventional power control circuit. 51a and 51b are laser chips. 52a and 52b are PIN diodes. 63a and 63b are current-voltage converters. 6
4a and 64b are comparators for comparing voltages. 6
7a and 67b are set voltages. Switches 66a and 66b are operated by the setting signal LDON68.

The operation will be described below. Signal LD
When the switches 66a and 66b are turned on by the ON 68, both the laser chips 51a and 51b emit light. The laser beam emitted from the laser chip 51a enters the PIN diode 52a and outputs a current corresponding to the intensity of the light. After the current is converted into a voltage by the current-voltage converter 63a, the set voltage 67a is output by the comparator 64a. The comparison is made, and the difference voltage is fed back to the optical output of the laser chip 51a again.
Similarly, the laser beam emitted from the laser chip 51b enters the PIN diode 52b and outputs a current corresponding to the intensity of the light. After the current is converted into a voltage by the current-voltage converter 63b, the current is set by the comparator 64b. The voltage is compared with the voltage 67b, and the difference voltage is fed back to the optical output of the laser chip 51b again. Thus, power control is performed independently for each laser chip.

[0007]

However, in the above-described configuration, stray light of another laser chip enters the PIN diode, for example, when light from the laser chip 51a leaks into the PIN diode 52b, and each laser chip has There is a problem that the output power is affected by the output power of another laser chip and causes an error in the output power. Further, there is a problem that current-voltage converters for the number of laser chips in the laser array are required and the circuit becomes complicated.

The present invention has been made in view of the above problems, and provides a laser array capable of realizing accurate power control of each laser chip of the laser array with a simple circuit configuration.

[0009]

In order to solve the above-mentioned problems, a laser array having a power control circuit according to the present invention comprises:
In a laser array which is a device in which a plurality of semiconductor lasers are integrated in an element, a plurality of laser chips,
A plurality of PIN diodes for receiving a laser beam emitted from a rear end face of the plurality of laser chips; a plurality of PIN diodes comprising the plurality of laser chips, the plurality of PIN diodes and one or more set voltages; Laser chip selecting means for selecting one set of one laser chip for controlling power, one PIN diode, and one set voltage from the set, and a PIN diode selected by the laser chip selecting means and one of the current-to-voltage converter for converting the current to a voltage flowing in the ratio of the voltage converted by the current-voltage converter by a power number is compared with the set voltage selected by the laser chip selection means < and a servo system for feeding back the output voltage of the comparator to the optical output of the laser chip selected by the laser chip selecting means. A hold circuit for holding a voltage, and a light emitting means for emitting a laser chip which is the selected in the held voltage to said hold circuit, one laser by switching between the light emitting means and said laser chip selection means A laser array having a power control circuit characterized in that emission of another laser chip is stopped during power control of the chip, and power control of a plurality of laser chips is performed in a time-division manner.

[0010]

According to the above configuration, while power control of one laser chip is performed, light emission of all other laser chips can be stopped.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser array provided with a power control circuit for use in a read-only optical disk drive according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a laser array having a power control circuit used in a read-only optical disk device according to an embodiment of the present invention.

Reference numerals 11a and 11b are laser chips. 1
2a and 12b are PIN diodes. 14 is a current-voltage converter. Reference numeral 15 denotes a comparator. 16a, 16b
Is a hold circuit. Reference numerals 22a and 22b are reproduction power setting voltages.

Laser chip selecting means 13a, 20
a and 21a are switches operated by the setting signal SLCT18a. Laser chip selection means 13b,
Switches 20b and 21b are operated by the setting signal SLCT18b.

A light emitting means 17a is a setting signal LDON.
A switch operated by 19a. Reference numeral 17b, which is a light emitting means, is a switch operated by the setting signal LDON19b.

Each switch is turned on when the setting signal is HIGH and turned off when the setting signal is LOW.

[0017] Figure 2 is set in the Le <br/> Zaarei having the reproducing power control circuit signal SLCT18a, SLCT
18b, LDON19a, HIGH of LDON19b,
It is a time chart showing a LOW state and a light emitting state of the laser chips 11a and 11b. The operation will be described below.

At time t ₀ , as shown in FIG. 2, the laser chips 11a and 11b
a) Light emission is being performed at a power near the reproducing power according to the voltage held by the hold circuit 16b.

[0019] In time t _1, setting signal LDON19
b, the switch 17b is turned off and the laser chip 1
When the light emission of the laser chip 11a is stopped and the switches 13a, 20a, and 21a are turned on by the setting signal SLCT18a, the laser beam emitted from the rear end face of the laser chip 11a becomes PI
A current corresponding to the intensity of light is incident on the N diode 12a, and the current is output. The current is converted into a voltage by the current-voltage converter 14. Then, the current is converted by the comparator 15 to the reproduction power setting voltage 22a. The light is returned to the optical output of the laser chip 11a again. When this series of servos with respect to the reproduction power setting voltage is stabilized, the feedback voltage is held by the hold circuit 16a.

[0020] setting signal at time t ₂ SLCT18a
The switches 13a, 20a, 21a are turned off to terminate the power control operation, the switch 17a is turned off by the setting signal LDON19a, the light emission of the laser chip 11a is stopped, and the switch 13 is turned off by the setting signal SLCT18b.
b, 20b, and 21b are turned on, and the setting signal LDON19
When the switch 17b is turned on by b, the laser chip 11b emits light, and the laser beam emitted from the end face thereafter enters the PIN diode 12b and outputs a current corresponding to the intensity of the light. Is converted into a voltage, and is compared with the reproduction power setting voltage 22b by the comparator 15, and the difference voltage is fed back to the optical output of the laser chip 11b again. When this series of servos with respect to the reproduction power setting voltage is stabilized, the feedback voltage is held by the hold circuit 16b.

At time t ₃ , setting signal SLCT18
b, the switches 13b, 20b, and 21b are turned off, the reproduction power control operation ends, and the setting signal LDON19a
When the switch 17a is turned on by the
Light is emitted at the reproduction power set by 1a and 11b.

Except for the times t _{1 to} t _{3 in which the} power control is performed, both lasers emit light at the reproduction power, and
Time t _{1 to} t ₂ or t when _one laser is off
_{Since 2 to} t ₃ is as short as about several tens of microseconds, the focus servo and tracking servo operating in the frequency band of several kilohertz do not come off during this period. The power control is performed at regular time intervals when the reproducing operation is not performed.

As described above, according to the present embodiment, while the power of one laser chip is being controlled, the emission of the other laser chip is O
Because it is FF, the influence of stray light from other laser chips is eliminated, accurate power control can be performed, and the set power is held in the hold circuit, so only one current-to-voltage converter and comparator are required. The circuit configuration is simplified.

In this embodiment, a laser array having two laser chips used in a read-only optical disk device has been described. However, a laser array having three or more laser chips has the same effect.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a circuit diagram of a laser array having a power control circuit used in a rewritable phase-change optical disc device according to a second embodiment of the present invention.

Reference numerals 31a and 31b are laser chips. 3
2a and 32b are PIN diodes. 34 is a current-voltage converter. 36, 312, and 318 are comparators. 38a, 38b, 314a, 314b, 320a,
320b is a hold circuit. 310a and 310b are reproduction power setting voltages. 316a and 316b are bias power setting voltages. 322a and 322b are peak power setting voltages. 323a and 323b are print data output units.

Laser chip selecting means 33a, 33
6a, 337a, 338a, 339a, 340a, 34
1a is a switch operated by the setting signal SLCT326a. 33b, 33 as laser chip selecting means
6b, 337b, 338b, 339b, 340b, 34
1b is a switch operated by the setting signal SLCT326b.

The light emitting means 39a has a setting signal LDON.
327a. The light emitting unit 39b is a switch operated by the setting signal LDON327b. 315a and 321a which are light emitting means
Is a switch operated by the setting signal BSON328a. The switches 315b and 321b, which are light emitting units, are operated by the setting signal BSON328b.

Switches 35 and 37, which are set power selection means, are operated by a set signal BSGT329. Switches 311 and 313 as setting power selection means are switches operated by the setting signal BSSV330. Setting power selection means 317 and 319 are setting signals PK
A switch operated by the SV332.

A switch 324a is operated by a setting signal WTDT334a. 324b is a setting signal WT
The switch is operated by the DT 334b. 343
a and 343b are switches operated by the setting signal DTST342.

The switch is turned on when the setting signal is HIGH and turned off when the setting signal is LOW.

FIG. 4 shows a laser array having a power control circuit used in the rewritable phase-change optical disk device.
Setting signals SLCT326a, SLCT326b, LDO
N327a, LDON327b, BSON328a, B
SON328b, BSGT329, BSSV330, P
KSV332, WTDT334a, WTDT334b,
It shows a time chart of the HIGH and LOW states of the DTST 342 and the light emitting states of the laser chips 31a and 31b.

The power control method for the reproduction power, bias power, and peak power of each laser will be described separately for reproduction and recording. First, a method of controlling the reproduction power of each laser during reproduction will be described.

At the time t ₀ , as shown in FIG.
a) Light is being emitted with power near the reproduction power according to the voltage held by the hold circuit 38b.

[0035] In time t _1, setting signal LDON32
The switch 39b is turned off by 7b, the light emission of the laser chip 31b is stopped, and the switches 33a, 336a, 337a, 338 are set by the setting signal SLCT326a.
a, 339a, 340a, and 341a are turned on, and the switches 35 and 37 are turned off by the setting signal BSGT329.
Then, the laser beam emitted from the rear end face of the laser chip 31a enters the PIN diode 32a and outputs a current corresponding to the light intensity. After the current is converted into a voltage by the current / voltage converter 34, the current is converted to a reproduction power setting voltage 310a by the comparator 36, and the difference voltage is fed back to the optical output of the laser chip 31a again. When this series of servos with respect to the reproduction power setting voltage is stabilized, the feedback voltage is held by the hold circuit 38a.

At time t ₂ , setting signal SLCT32
The switches 33a, 336a, 337a, 3
38a, 339a, 340a and 341a are turned off,
When the power control operation of the reproduction power is completed, the setting signal LDO
The switch 39a is turned off by N327a, the light emission of the laser chip 31a stops, and the setting signal SLCT32
6b switches 33b, 336b, 337b, 3
38b, 339b, 340b, and 341b are turned on, and L
When the switch 39b is turned on by the DON 327b, the laser chip 31b emits light, and the laser beam emitted from the end face thereafter enters the PIN diode 32b and outputs a current corresponding to the light intensity. Current-voltage converter 3
After the current is converted into a voltage at 4, the comparator 36 compares the current with the reproduction power setting voltage 310b, and the difference voltage is fed back to the optical output of the laser chip 31b again. When this series of servos for the reproduction power setting voltage is stabilized, the feedback voltage is held by the hold circuit 38b.

At time t ₃ , the setting signal BSGT 32
9, the switches 35 and 37 are turned on, and the setting signal S
The switches 33b, 336b, and 3 are controlled by the LCT 326b.
37b, 338b, 339b, 340b and 341b are O
When the flip-flop is performed, the power control operation of the reproduction power is completed, and the switch 39a is turned on by the setting signal LDON327a, the laser chips 31a and 31b emit light at the set reproduction power.

[0038] than time t ₁ ~t ₃ power control is performed, the two laser is emitted together and, one laser is OFF and The times t ₁ ~t ₂ or t ₂ ~t ₃ number 1
Since it is as short as about 0 microsecond, the focus servo and tracking servo operating in the frequency band of several kilohertz do not come off during this period. Here, the power control of the reproducing power is performed at regular time intervals as in the first embodiment when the recording / reproducing operation is not performed, and the laser output provided before the data area of each sector is performed at the time of reproducing. This is an area for setting and is performed for each sector to be reproduced.

Next, a method of controlling the bias power and peak power of each laser during recording will be described. Laser chip 31 at time t ₄ in FIG. 4
a and 31b are emitting light with the reproduction power according to the voltage held in the hold circuits 38a and 38b, respectively.

[0040] In time t _5, setting signal LDON32
The switch 39b is turned off by 7b, the light emission of the laser chip 31b is stopped, and the switches 33a, 336a, 337a, 338 are set by the setting signal SLCT326a.
a, 339a, 340a, and 341a are turned on, and the switches 315a and 321 are turned on by the setting signal BSON328a.
is turned on and the switches 311 and 313 are turned on by the setting signal BSSV330, the laser chip 31a
The laser beam emitted from the rear end face is incident on the PIN diode 32a, the PIN current is converted into a voltage by the current-voltage converter 34, and then compared with the bias power setting voltage 316a by the comparator 312. The light is returned to the optical output of the laser chip 31a. When this series of servos for the bias power setting voltage is stabilized, the feedback voltage is held by the hold circuit 314a.

At time t ₆ , the setting signal BSSV33
When 0, the switches 311 and 313 are turned off, the power control operation of the bias power ends, and the setting signal PKS is set.
Switches 317 and 319 are turned on by V332,
When the switch 324a is turned on by the setting signal WTDT334a, the laser beam emitted from the rear end face of the laser chip 31a enters the PIN diode 32a, and after the PIN current is converted into the voltage by the current-voltage converter 34,
It is compared with the peak power voltage 322a by the comparator 318,
The difference voltage is fed back to the optical output of the laser chip 31a. When this series of servos with respect to the peak power setting voltage is stabilized, the feedback voltage is held by the hold circuit 320a.

At time t ₇ , the setting signal PKSV33
2, the switches 317 and 319 are turned off, the power control operation of the peak power ends, and the setting signal WTDT is set.
The switch 324a is turned off by the switch 334a, and the switches 315a and 321 are set by the setting signal LDON328a.
a is turned off, the switch 39a is turned off by the setting signal LDON327a, the light emission of the laser chip 31a is stopped, and the switches 33a, 336a, 337a, 338a, 339a, and 339a are set by the setting signal SLCT326a.
40a and 341a are turned off, and the setting signal SLCT32
6b switches 33b, 336b, 337b, 3
38b, 339b, 340b and 341b are turned on, and the switch 39b is turned on by the setting signal LDON327b.
The switch 31 is set by the setting signal BSON328b.
5b and 321b are turned on and the switch 311 is turned on by the setting signal BSSV330, the laser chip 3
1b emits light, and the laser beam emitted from the end face thereafter enters the PIN diode 32b,
After the PIN current is converted into a voltage, the comparator 312 compares the PIN current with the bias power setting voltage 316b, and the difference voltage is fed back to the optical output of the laser chip 31b again. When this series of servos for the bias power setting voltage is stabilized, the feedback voltage is held by the hold circuit 314b.

At time t ₈ , the setting signal BSSV33
When 0, the switches 311 and 313 are turned off, the power control operation of the bias power ends, and the setting signal PKS is set.
Switches 317 and 319 are turned on by V332,
When the switch 324b is turned on by the setting signal WTDT334b, the laser beam emitted from the rear end face of the laser chip 31b is incident on the PIN diode 32b, and the PIN voltage is converted by the current-voltage converter 34 into a voltage.
It is compared with the peak power voltage 322b by the comparator 318,
The difference voltage is fed back to the optical output of the laser chip 31b. When this series of servos with respect to the peak power setting voltage is stabilized, the feedback voltage is held by the hold circuit 320b.

[0044] In time t _9, setting signal PKSV33
2, the switches 317 and 319 are turned off, the power control operation of the peak power ends, and the setting signal SLCT
326b allows switches 33b, 336b, 337
b, 338b, 339b, 340b, 341b are OFF
The switch 39 is set by the setting signal LDON327a.
a is turned on, the switches 315a and 321a are turned on by the setting signal BSON328a, and the setting signal WTDT
When the switch 324a is turned on by the switch 334a, the laser chip 31a emits light at the peak power held by the hold circuit 320a.

[0045] In time t _10, setting signal DTST34
2, when the switches 343a and 343b are turned on, the laser chip 31a switches the recording data output unit 323a.
, And emits light between the two values of the bias power and the peak power held by the hold circuits 314a and 320a, and the laser chip 31b receives the modulation by the recording data output unit 323b.
Light is emitted between the two values of the bias power and the peak power held at 320b.

[0046] In time t _11, setting signal DTST34
2, the switches 343a and 343b are turned off, and the setting signal WTDT334a switches the switches 324a and 343b.
is turned off, the switch 324b is turned off by the setting signal WTDT334b, and the setting signal BSON328 is turned off.
The switches 315a and 321a are turned off by a,
The switch 315b is set by the setting signal BSON328b,
When 321b is turned off, the laser chips 31a, 31
b emits light at the reproduction power.

[0047] than time t ₅ ~t the power control is _{performed. 9,} the two laser is emitted together and, one laser is OFF and The times t ₅ ~t ₇ or t ₇ ~t ₉ Number 1
Since it is as short as about 0 microsecond, the focus servo and tracking servo operating in the frequency band of several kilohertz do not come off during this period. Wherein the power control of the bias power and peak power are provided in front of the data area of each sector in the region for setting the laser output is performed for each sector to be recorded.

As described above, according to the present embodiment, while the power of one laser chip is being controlled, the emission of the other laser chip is O
Because it is FFed, the influence of stray light from other laser chips is eliminated, and the power of the reproduction power, bias power, and peak power of each laser can be accurately controlled.
Since only one current-voltage converter is required and only the number of powers set by the comparator (three in the case of ternary control), the circuit configuration of the device is simplified.

In this embodiment, a laser array having two laser chips used for a rewritable phase-change optical disk apparatus has been described. However, the same effect can be obtained with a laser array having three or more laser chips. Having.

Next, a third embodiment of the present invention will be described. In the third embodiment, an area for setting a laser output provided in front of a data area of each sector is not provided for each sector, and a specific sector, for example, for each track as shown in FIG. Using the optical disk provided at one place, power control similar to that of the second embodiment is performed at regular intervals. According to the present embodiment, the area for setting the laser output for each sector can be reduced, and the recording density is improved.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment uses an optical disc in which a specific track is set as an area for setting a laser output as shown in FIG. 8 without providing an area for setting a laser output for each sector. Power control similar to that of the second embodiment is performed at regular intervals. According to this embodiment, the recording density is improved as much as the area for setting the laser output for each sector can be reduced.

[0052]

As described above, the power control circuit of the present invention
The provided laser array has a configuration in which light emission of all other laser chips is stopped while power control of one laser chip is performed. The effect of stray light from the laser chip is eliminated, and accurate power control can be performed. Even if the number of laser chips in the laser array increases, only one current-voltage converter and the number of powers set by the comparator are required. Therefore, the circuit configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a laser array including a power control circuit used in a read-only optical disc device according to an embodiment of the present invention.

FIG. 2 shows HIGH and LO of each setting signal in the embodiment.
Time chart of W state and light emitting state of each laser chip

FIG. 3 is a circuit diagram of a laser array having a power control circuit used in a rewritable phase-change optical disc device according to a second embodiment of the present invention;

FIG. 4 shows HIGH and LO of each setting signal in the embodiment.
Time chart of W state and light emitting state of each laser chip

FIG. 5 is a perspective view of a laser array.

FIG. 6 is a circuit diagram of a conventional laser array.

FIG. 7 is a plan view showing an optical disc substrate provided with an area for setting a laser output in a specific sector.

FIG. 8 is a plan view showing an optical disk substrate provided with an area for setting a laser output on a specific track.

[Explanation of symbols]

 11a, 11b Laser chip 12a, 12b PIN diode 13a, 13b Switch 14 Current-voltage converter 15 Comparator 16a, 16b Hold circuit 17a, 17b Switch 20a, 20b Switch 21a, 21b Switch 22a, 22b Set voltage

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunji Ohara 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP 4-176176 (JP, A) JP 5-A 308168 (JP, A) JP-A-2-31343 (JP, A) JP-A-63-244334 (JP, A) JP-A-4-141837 (JP, A) JP-A-62-200541 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 12-7/22 H01S 5/0683

Claims (1)

(57) [Claims] 1. A laser array as a device in which a plurality of semiconductor lasers are integrated in one element, a plurality of laser chips, and a plurality of laser chips for receiving a laser beam emitted from rear end surfaces of the plurality of laser chips. PIN diodes, the plurality of laser chips and the plurality of PIs
One set of one laser chip, one PIN diode, and one set voltage for power control from a plurality of sets of N diodes and one or more set voltages.
Laser chip selecting means for selecting a set, one current-voltage converter for converting a current flowing through the PIN diode selected by the laser chip selecting means into a voltage,
Pas for comparing the set voltage selected by the laser chip selection means the voltage converted by the current-voltage converter
And a hold circuit that holds a feedback voltage of a servo system that feeds back the output voltage of the comparator to the optical output of the laser chip selected by the laser chip selecting means; Light emitting means for causing the selected laser chip to emit light at an applied voltage, and switching between the laser chip selecting means and the light emitting means, thereby controlling another laser chip during power control of one laser chip. A laser array comprising a power control circuit, wherein light emission of a chip is stopped and power control of a plurality of laser chips is performed in a time-division manner.