JPS63184935A - Light source device - Google Patents

Abstract

PURPOSE:To simplify the constitution of an optical system and to reduce the size by inputting an output obtained by superposing signals of mutually different frequencies to a laser element which emits plural laser light beams with one-chip or one-package constitution, and controlling the output of laser light. CONSTITUTION:Monitor pilot signals S5 and S6 which differ in frequency are superposed on the driving signals S3 and S4 of plural laser elements LD3 and LD4 and plural monitor laser light beams LA7 and LA8 are converted photoelectrically by a photoelectric converting means PD3 into a monitor detection signal S9. Then a signal component S15 corresponding to the monitor pilot signals S5 and S6 is separated from the signal S9 to generate automatic output control signals S7 and S8 for the corresponding laser elements LD3 and LD4. Consequently, the constitution around the laser elements LD3 and LD4 is simplified more and reduced in size.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Use The present invention relates to a light source device, and is suitable for application to, for example, a light source device of an optical information processing device.

B Summary of the Invention The present invention provides a laser element that emits a plurality of laser beams in one chip or one package, by inputting an output in which muscle frequencies of different frequencies are superimposed on each laser element.
By making it possible to control the output of the laser beam with one monitor, there is no need to provide an output control circuit for each laser element, and the optical system mechanism becomes simple.

C. Conventional technology Conventionally, as an optical information processing device consisting of an optical information recording and/or reproducing device, one that generates a single laser beam from a light source to record and reproduce optical information on an optical disk has been used, for example, in a compact disc. It has been commercialized as discs, laser discs, etc.

In addition to this, a system has recently been proposed in which optical information is recorded and reproduced using several laser beams simultaneously, as described below.

First, D RAW (direct read af
In the optical information processing device of the ter wrHe) method,
As shown in FIG. 3, after optical information is written by irradiating a writing laser spot 1 onto a recording track 3 formed on an optical disk traveling in the direction shown by arrow a, the written light is The information is immediately reproduced by the successive laser spot 2, so that the written optical information can be recognized 1+i at any time.

Secondly, in erasable optical discs,
As shown in FIG. 4, three laser spots, that is, an erasing laser spot 4, a writing laser spot 5, and a reproducing laser spot 6, are irradiated onto the optical disk traveling in the direction of the arrow. After erasing the optical information written on it using the erasing laser spot 4,
New optical information is written using the writing laser spot 5, and immediately after that, the newly recorded optical information is reproduced and confirmed using the reproducing laser spot 6.

Thirdly, HD VS (high definition
tion video system),
As shown in FIG. 5, three reproduction laser spots 8,9,10 are irradiated onto an optical disk traveling in the direction of arrow C, and three recording tracks 1 are formed parallel to each other.
1.12.13, optical information distributed and recorded at high density on recording tracks 11.12.13 is simultaneously reproduced.

In this way, the light forms multiple laser spots.

By configuring a plurality of semiconductor laser elements as a single chip or l-package structure as a source, and controlling the excitation conditions of each semiconductor laser element, the semiconductor laser elements can be placed close to each other and have arbitrary light intensity as required. Like automatic output side? I
II (APC, auto power cont.
It has been considered to generate multiple laser beams stabilized by a rol) circuit.

D Problems to be Solved by the Invention However, in practice, when attempting to configure a plurality of semiconductor laser elements into one chip or one package structure that occupies a small space, it is necessary to detect the intensity of each laser beam generated. It is difficult to make the monitor compact and highly sensitive.

For example, as shown in FIG. 6, two semiconductor laser elements LDI and LD2 are arranged in one package 21,
From this, the laser beam L for recording and reproducing is placed on the optical disk side.
In addition to emitting AI and LA2, it also ejects monitoring laser beams LA3 and LA4, contrary to the optical disc.

Here, the laser beams LA3 and LA4 for monitoring are used for recording,
By irradiating the monitoring photoelectric detection elements PDI and PD2, which are provided correspondingly inside the package 21, with a light intensity corresponding to that of the reproduction laser beams LAI and LA2, respectively, This monitor photoelectric detection element PDi
Detection signals S+ and St representing the light intensity of recording and reproducing laser beams LAI and LA2 are obtained from the PD2.

Thus, by controlling the excitation conditions of the semiconductor laser elements LDI and LD2 using the detection signals S1 and S2, it is possible to control the light intensities of the recording and reproducing laser beams LAI and LA2 to a predetermined level.

By the way, in the case of the configuration as shown in FIG. 6, it is necessary to irradiate the monitoring laser beams LA3 and LA4 to the corresponding photoelectric detection elements PDI and PD2 while blocking each other, and in practice, it is necessary to obtain the light blocking means. It is difficult to do so.

In fact, in practice, between the recording and reproducing laser beams LAI and LA2 emitted from the semiconductor laser elements LDl and LD2 (
Therefore, the distance R between the monitoring laser beams LA3 and LA4 is about 50 to 80 [μm], and it is difficult to provide a light shielding plate 22 as a light shielding means between them in terms of processing accuracy.

In addition, even if light can be blocked, the light-receiving areas of the photoelectric detection elements PDI and PD2 will be smaller as the monitoring laser beams LA3 and LA4 are blocked by the light-shielding plate 22, so the detection signals S and It is unavoidable that the detection sensitivity of S2 becomes low.

The present invention has been made in consideration of the above points, and it is an object of the present invention to reliably obtain a detection signal representing the intensity of each monitor laser and light without providing a light blocking means between a plurality of monitor laser beams. The purpose of this paper is to propose a light source device that enables the following.

E Means for Solving the Problem In order to solve this problem, in the present invention, a plurality of monitoring lasers are emitted together with a plurality of output laser beams LA5 and LA6 emitted from the plurality of laser elements LD3 and LD4, respectively. A monitor detection signal S is obtained by photoelectrically converting the lights LA7 and LA8, and a drive signal S for the plurality of laser elements LD3 and LD4 is generated based on this monitor detection signal S.
In a light source device configured to form automatic output control signals S and S for controlling laser elements LD3 and S4, monitoring pilot signals having different frequencies are added to drive signals S3 and S4 for a plurality of laser elements LD3 and LD4, respectively. S, and S6 are superimposed to produce multiple monitor laser beams LA7 and LA.
8 is photoelectrically converted by a common photoelectric conversion means PD3 to obtain a monitor detection signal S, and a signal component St corresponding to the monitor pilot signal S and S is obtained from the monitor detection signal s9.
S is separated into a plurality of laser elements LD3 and LD.
4, automatic output control signal S? for corresponding laser elements LD3 and LD4? and Ss.

F action multiple monitor laser beam LA? and LA8 are photoelectrically converted by a common photoelectric conversion means PD3 to produce a monitor detection signal S.
, and separate the signal components SIS corresponding to the monitor pilot signals S and S from the monitor detection signal S, respectively, and perform automatic output control on the corresponding laser elements LD3 and LD4 among the plurality of laser elements LD3 and LD4. Signals S and Ss are formed.

In this way, the plurality of monitoring laser beams LA7 and LA8 can be irradiated onto the common photoelectric conversion means PD3 without blocking each other and in such a manner that they overlap with each other.
The configuration around the laser elements LD3 and LD4 can be further simplified and miniaturized.

Embodiment G An embodiment in which the present invention is applied to an optical disk device will be described in detail below with reference to the drawings.

FIG. 1 shows, for example, two semiconductor laser elements LD3 and L.
This shows an embodiment in which D4 is configured in one package. In the same way as in the case of FIG. 6, two-chip half-door laser elements LD3 and LD4 are provided in one package 30. The monitor laser beams LA7 and LA8 are configured to irradiate the photoelectric detection element PD3, which serves as a common photoelectric conversion means, so as to overlap with each other.

Semiconductor laser elements LD3 and LD4 are excited by drive outputs S1 and St sent out from drive control circuits 33 and 34 of automatic output control circuits (APC circuits) 31 and 32, respectively. The drive control circuits 33 and 34 internally generate drive signals S and S4 that determine the intensity of the output laser beams LA5 and LA6 emitted from the corresponding semiconductor laser elements LD3 and LD4, respectively, and also generate a monitoring pilot signal. Monitoring pilot signals S and S given from generation circuits 35 and 36.

is superimposed on the drive signals S and S4 to obtain the drive output S.

and S2.

The drive control circuits 33 and 34 are APC-controlled by automatic output control signals S7 and S, respectively, so that output laser beams LA5 and LA6 having predetermined light intensities are emitted from the semiconductor laser elements LD3 and LD4. Generates drive outputs S1 and S2.

Thus, the semiconductor laser elements LD3 and LD4 receive drive signals S3 and S4, respectively, and a monitoring pilot signal SS.
, &: and Sh, the output laser beams LA5 and LA6 and the monitoring laser beam LA? and LA8 include monitoring pilot signals S and optical components corresponding to S.

In this embodiment, the monitor pilot signals S and S
As shown in FIG.
2, and as a result, the output laser beams LA5 and LA
When the video signal VD is recorded and reproduced on the optical recording medium using the optical recording medium 6, the influence of the monitor pilot signal S and S6 is prevented from occurring.

On the other hand, the photoelectric detection element PD3 receives a monitor detection signal S9 having a frequency spectrum similar to that described above with reference to FIG. This signal is generated and applied to a separation circuit 37 having a bypass filter configuration. The separation circuit 37 receives monitor pilot signals S and S6.
The signal component SI5 corresponding to
0 to the detection circuits 41 and 42, respectively.

The cutoff frequency of the low-pass filter 39 is selected to be a value that allows the frequency component of the monitor pilot signal S to pass, and the cutoff frequency of the bypass filter 40 is selected to be a value that allows the frequency component of the monitor pilot signal S to pass.

The value is selected to allow the frequency components of .

Of the monitor detection signals S9 from the detection circuits 41 and 42,
A detection output SI consisting of a DC voltage representing the magnitude of the monitoring pilot signal S and S, respectively.

and S1□ are obtained, and the detected outputs S11 and SI□ are compared with reference voltages 9,1 and V□,2 of power supplies 50 and 51 in comparison circuits 43 and 44, respectively.

As a result, feedback control signals S7 and S having DC voltage values corresponding to the detection output 311 and SIZ are obtained at the output terminals of the comparison circuits 43 and 44, and are sent to the drive control circuit 33 via the trap circuits 45 and 46. and 34
will be given feedback.

Here, the trap circuits 45 and 46 are connected to the drive control circuit 33.
and 34 are provided to prevent adverse effects on the comparison circuits 43 and 44.

In the above configuration, the semiconductor laser elements LD3 and LD
4 is a drive output Sl obtained by superimposing monitor pilot signals SS and S on the drive signal S and S4, respectively.
and S2, the drive output S1
When S2 is changed by being changed and controlled by the automatic output control signals S and Sll, the change occurs in the same way in the light components contained in the laser beams emitted from the semiconductor laser elements LD3 and LD4.

Therefore, the same change in the light intensity of the video signal light component contained in the output laser beams LA5 and LA6 currently emitted from the semiconductor laser elements LD3 and LD4 is included in the monitoring laser beams LA7 and LA8. This also occurs in the monitor signal light component. Therefore, APC circuits 31 and 32
are respectively APC semiconductor laser devices LD3 and LD4.
In the state of itd[I, the excitation state of each of the semiconductor laser elements LD3 and LD4 is reliably determined by the detection outputs S11 and SIt of the detection circuits 41 and 42, respectively.

According to the above configuration, the monitoring laser beams LA'7 and LA8 incident on the photoelectric detection element PD3 can be irradiated so as to overlap each other without blocking each other.
The configuration of the optical system can be simplified and miniaturized. Incidentally, even when the semiconductor laser elements LD3 and LD4 are housed in one package as described above with reference to FIG. 6, there is no need for a light-shielding structure, which simplifies and downsizes the overall structure of the optical head. obtain.

In the above embodiment, a chip or a package that generates two laser beams is described, but the present invention is not limited to this, and the present invention is not limited to this. It can also be applied to the case where the output of a plurality of laser beams is controlled by superimposing the frequencies of .

H Effects of the Invention As described above, according to the present invention, a common photoelectric conversion element is irradiated with a plurality of monitor laser beams, a monitor detection signal is obtained through photoelectric conversion, and the monitor detection is performed in correspondence with the plurality of laser elements. By separating the signals and forming automatic output control signals that correspond to multiple laser elements, the monitoring laser beams can be irradiated so that they overlap each other without blocking each other, simplifying the configuration of the optical system. Can be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a light source device in an embodiment of the present invention, Fig. 2 is a curve diagram showing frequency components of a signal detected by a photoelectric detector, and Fig. 3 shows a laser spot on a DRAW optical disc. A route map showing the irradiation of a track, Figure 4 is a route map showing the irradiation of the laser spot on an erasable optical disc, Figure 5 is a route map showing the irradiation of the laser spot in the HDVS system, and Figure 6 is a route map showing the irradiation of the laser spot in the HDVS system. It is a route map showing an example of photoelectric detection in one package irradiated with the present laser light. LD3, LD4... Semiconductor laser element, LA5
, LA6...Output laser beam, LA7, LA8...
...Monitoring laser light, PD3...Photoelectric conversion element, 31.32...Automatic output control circuit,
33.34... Drive control circuit, 35.36...
...Monitor pilot signal generation circuit, 37...
...Separation circuit, 39...Low pass filter,
40...Bypass filter.

Claims (1)

[Claims] A monitor detection signal is obtained by photoelectrically converting a plurality of monitor laser beams emitted together with a plurality of output laser beams respectively emitted from a plurality of laser elements, and a monitor detection signal is obtained based on the monitor detection signal. In a light source device configured to form an automatic output control signal for controlling drive signals of the plurality of laser elements, monitor pilot signals having different frequencies are superimposed on the drive signals of the plurality of laser elements, The monitor laser beam is photoelectrically converted by a common photoelectric conversion means to obtain a monitor detection signal, and the signal components corresponding to the monitor pilot signal are separated from the monitor detection signal to select one of the plurality of laser elements. Form an automatic output control signal to the corresponding laser element