JPS63254779A - Semiconductor-laser driving system - Google Patents

Semiconductor-laser driving system

Info

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
Application number
JP62090169A
Other languages
Japanese (ja)
Inventor
Kazutomi Hatanaka
畠中　一臣
Takashi Ono
隆 大野
Kenji Ogawa
小河　健治
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sharp Corp
Original Assignee
Sharp Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Sharp Corp filed Critical Sharp Corp
Priority to JP62090169A priority Critical patent/JPS63254779A/en
Priority to DE3854202T priority patent/DE3854202T2/en
Priority to EP92201060A priority patent/EP0497431B1/en
Priority to DE8888303348T priority patent/DE3879250T2/en
Priority to EP92201061A priority patent/EP0497432B1/en
Priority to EP88303348A priority patent/EP0287360B1/en
Priority to DE3854094T priority patent/DE3854094T2/en
Publication of JPS63254779A publication Critical patent/JPS63254779A/en
Priority to US07/368,106 priority patent/US4912714A/en
Pending legal-status Critical Current

Links

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

PURPOSE:To improve the control accuracy of an optical output, by providing a D/A converter having an offset function in a feedback loop for obtaining the constant optical output. CONSTITUTION:A D/A converter 10 having an offset function is provided in a feedback loop for obtaining a constant optical output loop. Namely, when it is considered that a digital code is an input into the D/A converter 10 and a forward current IF is an output, the D/A converter system, in which an offset current IOS flows, is used for the current IF. Thus the quantizing width of an optical output PO can be made small. Even if the D/A converter having the same number of bits is used, highly accurate control can be performed.

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.

【図面の簡単な説明】[Brief explanation of drawings]

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)

【特許請求の範囲】[Claims] １、一定光出力を得るための帰還ループ中に、オフセッ
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.
JP62090169A 1987-04-13 1987-04-13 Semiconductor-laser driving system Pending JPS63254779A (en)

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)

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