JPS63254779A - Semiconductor-laser driving system - Google Patents
Semiconductor-laser driving systemInfo
- Publication number
- JPS63254779A JPS63254779A JP62090169A JP9016987A JPS63254779A JP S63254779 A JPS63254779 A JP S63254779A JP 62090169 A JP62090169 A JP 62090169A JP 9016987 A JP9016987 A JP 9016987A JP S63254779 A JPS63254779 A JP S63254779A
- Authority
- JP
- Japan
- Prior art keywords
- converter
- optical output
- current
- output
- constant
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 claims abstract description 23
- 239000004065 semiconductor Substances 0.000 claims description 12
- 238000010586 diagram Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 3
- 238000013139 quantization Methods 0.000 description 3
- 239000003990 capacitor Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/06209—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in single-section lasers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
- H05B45/14—Controlling the intensity of the light using electrical feedback from LEDs or from LED modules
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0617—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium using memorised or pre-programmed laser characteristics
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Semiconductor Lasers (AREA)
Abstract
Description
【発明の詳細な説明】
〈産業上の利用分野〉
この発明は、半導体レーザを駆動する方法に関するもの
である。DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for driving a semiconductor laser.
〈従来の技術〉
半導体レーザは、ある種のPN接合に順方向電流IFを
流すことによりレーザ光を得るもので、IFと光出力P
oとの関係はリニアでなく、IFを増加していくと、あ
る電流Ithでレーザ発振が始まり、以後はIFの増加
と共にレーザ洋出力POも増加する。この特性を第2図
に示す。<Prior art> A semiconductor laser obtains laser light by passing a forward current IF through a type of PN junction, and the IF and optical output P are
The relationship with o is not linear; as IF is increased, laser oscillation begins at a certain current Ith, and thereafter, as IF increases, laser output PO also increases. This characteristic is shown in FIG.
ところが、xthや微分効率ηと呼ばれるIFの変化に
対するPOの変化の割合は一定ではなく、周囲温度や個
体によって変化する。However, the ratio of change in PO to change in IF, called xth and differential efficiency η, is not constant and changes depending on the ambient temperature and the individual.
このような半導体レーザを一定光出力で駆動するために
、第3図に示す方式が一般に用いられている。1は半導
体レーザで、増幅器3の出力で制御される電流源4によ
って駆動される。また光出力はホトダイオード2によっ
てモニタされ、第3図では抵抗5によって電圧に変換さ
れる。この電圧は増幅器3に入力され、全体で負帰還ル
ープを構成している◇増幅器3の一方の入力には、基準
電圧V refが印加されており、結局光出力は基準電
圧で規定される一定値になる。In order to drive such a semiconductor laser with a constant optical output, a method shown in FIG. 3 is generally used. 1 is a semiconductor laser, which is driven by a current source 4 controlled by the output of an amplifier 3; The light output is also monitored by a photodiode 2 and converted into a voltage by a resistor 5 in FIG. This voltage is input to the amplifier 3, and the whole constitutes a negative feedback loop. ◇A reference voltage V ref is applied to one input of the amplifier 3, and the optical output is eventually kept constant as defined by the reference voltage. Becomes a value.
第3図は、定常的に一定光出力を得るための構成である
が、ある種の応用においては、一定光出力を高速でオン
・オフする必要が生じる。その場合は例えば、第4図に
示す構成が用いられる。第4図は第3図の構成に、アナ
ログスイッチ7と静電容量8で構成されるサンプルホー
ルド回路と、高速電流スイッチ6、およびバクファアン
グ9を追加したものである。第4図の動作は次のような
ものである。まず、電流スイッチ6を右側に、スィッチ
7をオンにして、基準電圧Vrefで規定される一定光
出力を得る。次に7をオープンにする。Although FIG. 3 shows a configuration for constantly obtaining a constant light output, in certain applications, it becomes necessary to turn on and off the constant light output at high speed. In that case, for example, the configuration shown in FIG. 4 is used. FIG. 4 shows the configuration of FIG. 3 with the addition of a sample and hold circuit composed of an analog switch 7 and a capacitance 8, a high-speed current switch 6, and a buffer ring 9. The operation of FIG. 4 is as follows. First, the current switch 6 is turned on the right side and the switch 7 is turned on to obtain a constant optical output defined by the reference voltage Vref. Next, open 7.
このとき、ホールド容量8で電圧が保持されるので、半
導体レーザを駆動する電流は、変化しない0そうして電
流スイッチ6を高速でオン・オフして、光出力をオン・
オフする。第4図の構成の場合、容量8でホールドされ
る電圧はアナログ量のため、長時間一定値を保持するの
は困難である。長時間にわたって光出力を一定に保つこ
とができるように考えられたのが次の第5図の駆動方法
である。At this time, the voltage is held by the hold capacitor 8, so the current that drives the semiconductor laser does not change.Then, the current switch 6 is turned on and off at high speed to turn on and off the optical output.
Turn off. In the case of the configuration shown in FIG. 4, since the voltage held by the capacitor 8 is an analog quantity, it is difficult to maintain a constant value for a long time. The following driving method shown in FIG. 5 was designed to keep the optical output constant over a long period of time.
第5図は、第4図のサンプルホールド部トバツファアン
プを除いて、アップ/ダウン・カウンタ11とD/A変
換器10と発振器12を導入したもので、増幅器3はコ
ンパレータとして働く。アップ/ダウン・カウンタ11
は、コンパレータ3の出力が’HIGH’の場合、発振
器I2の出力パルスをカウントアツプして、逆に’LO
W’の場合カウントダウンする。カウント結果はD/A
変換器10でIPに変換され、レーザダイオードlを駆
動する。第5図では、電流スイッチ6が右側に倒れた場
合に、全体として負帰還ループを構成して光出力は基準
電圧Vrefで規定される値になる。In FIG. 5, an up/down counter 11, a D/A converter 10, and an oscillator 12 are introduced, except for the buffer amplifier in the sample and hold section of FIG. 4, and the amplifier 3 functions as a comparator. Up/down counter 11
When the output of comparator 3 is 'HIGH', the output pulse of oscillator I2 is counted up, and conversely it is 'LO'.
If W', count down. The count result is D/A
It is converted into IP by a converter 10 and drives a laser diode l. In FIG. 5, when the current switch 6 falls to the right, a negative feedback loop is formed as a whole, and the optical output becomes a value defined by the reference voltage Vref.
第5図の場合1力ウント分の誤差は生じるが、帰還ルー
プ中にディジタルコードとなる部分があるため、長時間
ホールドについても問題ない。但し、前述のように半導
体レーザのIF−Po特性がIJ ニアでないため、高
精度で一定光出力を得るには、高分解能のD/A変換器
が必要になる。In the case of FIG. 5, an error corresponding to one force count occurs, but since there is a portion that becomes a digital code in the feedback loop, there is no problem even when holding for a long time. However, as mentioned above, since the IF-Po characteristics of the semiconductor laser are not near IJ, a high-resolution D/A converter is required to obtain a constant optical output with high precision.
〈発明が解決しようとする問題点〉 第5図の方式において、半導体レーザのfF−P。<Problem that the invention seeks to solve> In the system of FIG. 5, fF-P of the semiconductor laser.
特性で、IFが1thに満たない場合レーザ発損は起こ
らない。よって、IPが1th以下の領域は制御に用い
ることができない。そのために、IFの量子化誤差に比
べてPoの量子化誤差は大きくなる。本発明は上述の問
題点を解決し、Paの制御精度を上げることを目的とし
ている。According to the characteristics, if IF is less than 1th, laser emission loss will not occur. Therefore, an area with an IP of 1th or less cannot be used for control. Therefore, the quantization error of Po becomes larger than the quantization error of IF. The present invention aims to solve the above-mentioned problems and improve the control accuracy of Pa.
く問題点を解決するための手段〉
第5図のD/A変換器を、オフセットを有するものにす
る。Means for Solving the Problems> The D/A converter shown in FIG. 5 is made to have an offset.
〈実施例〉
更に詳しく説明すると、ディジタルコードをD/A変換
器の入力、IFを出力と考えた場合、ディジタルコード
がゼロになっても、IFはあるオフセクト電流IQsが
流れているD△変換システムを用いる。例えば第6図に
示した特性のD/A変換器と同一ビット数で、ディジタ
ルコードとIFの関係が第1図(、)のようなり/A変
換器を用いた場合、Poの量子化幅は、第6図の特性を
有するD/A変換器を用いた場合に比べて小さくするこ
とができ、同一ビット数のD/A変換器を用いてもより
高精度の制御が可能になる。第6図(b)は通常のD/
A変換器を用いた場合の、ディジタルコードと光出力P
Oとの関係であるが、1th以下に対応するディジタル
コード部は光出力に寄与しないため、実際に有効なコー
ドは制限されて、実効的な分解能は下がっている。これ
に対し第1図の場合、ith以下に対応するディジタル
コードはない(Ios > 1th +第1図(b))
か、少ない(tth > Ios +第1図(C))た
め、光出力POの制御に有効に用いることのできるコー
ドの数が多くなる。<Example> To explain in more detail, if we consider the digital code as the input of a D/A converter and the IF as the output, even if the digital code becomes zero, the IF is a D△ conversion in which a certain offset current IQs flows. Use the system. For example, when using a D/A converter with the same number of bits as the D/A converter with the characteristics shown in Fig. 6, and the relationship between the digital code and IF as shown in Fig. 1 (,), the quantization width of Po can be made smaller than when a D/A converter having the characteristics shown in FIG. 6 is used, and even if a D/A converter with the same number of bits is used, more accurate control is possible. Figure 6(b) shows the normal D/
Digital code and optical output P when using A converter
Regarding the relationship with O, since the digital code portion corresponding to 1th or less does not contribute to the optical output, the actually effective codes are limited and the effective resolution is lowered. On the other hand, in the case of Figure 1, there is no digital code corresponding to ith or lower (Ios > 1th + Figure 1 (b))
or less (tth > Ios + FIG. 1(C)), so the number of codes that can be effectively used to control the optical output PO increases.
〈発明の効果〉
同一性能のシステムをより簡単な、また実現しやすい低
分解能のD/A変換器を用いて構成できるため、製品の
低価格化が図れる。また、システムの集積回路化も容易
になる。<Effects of the Invention> Since a system with the same performance can be configured using a simpler and easier to implement low-resolution D/A converter, the cost of the product can be reduced. Furthermore, it becomes easier to integrate the system into an integrated circuit.
第1図は、第5図においてオフセクトを有するD/A変
換器を用いた場合の、ディジタルコードと、頭方向電流
IFおよび光出力POとの関係の一例を示す図、第2図
は、レーザダイオードの頭方向電流IPと光出力Poと
の関係を示す図、第3図は、一定光出力を得るだめの半
導体レーザ駆動回路ブロック例を示す図、第4図は、サ
ンプルホールド回路を用いた一定光出力の高速スイッチ
ングを行うだめの半導体レーザ駆動回路ブロック例を示
す図、第5図は、光出力設定フィードバックルーズにD
/A変換器を挿入した、一定光出力の高速スイッチング
を行うだめの半導体レーザ駆動回路ブロック例を示す図
、第6図は、第5図において通常のD/A変換器を用い
た場合の、ディジタルコ−ドと、順方向電流IFおよび
光出力Poとの関係を示す図である。
符号の説明
l・・・半導体レーザ(レーザダイオード)、2・・・
光出力モニタ用ホトダイオード、3・・・増幅器、4・
・・電流源、5・・・抵抗、6・・・高速電流スイッチ
、7・・・アナログスイッチ、8・・・電圧ホールド用
静電容量、9・・・バッファアンプ、10・・・D/A
変換器、■・・・アップ/ダウン・カウンタ、12・・
・発振器。
代理人 弁理士 杉 山 毅 至(他!名)Oづ)ジク
Lコード
(Q)
第1図
第2図 第3図
:f、4図
i
第5図
イ′4ソタルコード
(Q)
纂
(b)
6!!lFIG. 1 is a diagram showing an example of the relationship between the digital code, the head current IF, and the optical output PO when a D/A converter with an offset is used in FIG. 5, and FIG. A diagram showing the relationship between the head direction current IP of the diode and the optical output Po, FIG. 3 is a diagram showing an example of a semiconductor laser drive circuit block for obtaining a constant optical output, and FIG. Figure 5 is a diagram showing an example of a semiconductor laser drive circuit block for high-speed switching with constant optical output.
FIG. 6 is a diagram showing an example of a semiconductor laser drive circuit block for performing high-speed switching with a constant optical output in which a /A converter is inserted. FIG. 3 is a diagram showing the relationship between a digital code, forward current IF, and optical output Po. Explanation of symbols l... Semiconductor laser (laser diode), 2...
Photodiode for optical output monitor, 3...Amplifier, 4...
...Current source, 5...Resistor, 6...High speed current switch, 7...Analog switch, 8...Capacitance for voltage hold, 9...Buffer amplifier, 10...D/ A
Converter, ■... Up/down counter, 12...
・Oscillator. Agent Patent Attorney Tsuyoshi Sugiyama (and others!) ) 6! ! l
Claims (1)
トを有するD/A変換器を備えたことを特徴とする半導
体レーザ駆動方式。1. A semiconductor laser driving system characterized in that a D/A converter with an offset is provided in a feedback loop for obtaining a constant optical output.
Priority Applications (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP62090169A JPS63254779A (en) | 1987-04-13 | 1987-04-13 | Semiconductor-laser driving system |
DE3854202T DE3854202T2 (en) | 1987-04-13 | 1988-04-13 | Apparatus for operating a semiconductor laser device. |
EP92201060A EP0497431B1 (en) | 1987-04-13 | 1988-04-13 | An apparatus for driving a semiconductor laser device |
DE8888303348T DE3879250T2 (en) | 1987-04-13 | 1988-04-13 | CONTROL DEVICE FOR A SEMICONDUCTOR LASER. |
EP92201061A EP0497432B1 (en) | 1987-04-13 | 1988-04-13 | An apparatus for driving a semiconductor laser device |
EP88303348A EP0287360B1 (en) | 1987-04-13 | 1988-04-13 | An apparatus for driving a semiconductor laser device |
DE3854094T DE3854094T2 (en) | 1987-04-13 | 1988-04-13 | Apparatus for operating a semiconductor laser device. |
US07/368,106 US4912714A (en) | 1987-04-13 | 1989-06-19 | Apparatus for driving a semiconductor laser device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP62090169A JPS63254779A (en) | 1987-04-13 | 1987-04-13 | Semiconductor-laser driving system |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS63254779A true JPS63254779A (en) | 1988-10-21 |
Family
ID=13990984
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP62090169A Pending JPS63254779A (en) | 1987-04-13 | 1987-04-13 | Semiconductor-laser driving system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS63254779A (en) |
-
1987
- 1987-04-13 JP JP62090169A patent/JPS63254779A/en active Pending
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