JPS62209923A - Light receiving circuit - Google Patents
Light receiving circuitInfo
- Publication number
- JPS62209923A JPS62209923A JP5228486A JP5228486A JPS62209923A JP S62209923 A JPS62209923 A JP S62209923A JP 5228486 A JP5228486 A JP 5228486A JP 5228486 A JP5228486 A JP 5228486A JP S62209923 A JPS62209923 A JP S62209923A
- Authority
- JP
- Japan
- Prior art keywords
- light
- fly
- high frequency
- frequency
- receiving element
- 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
- 239000003990 capacitor Substances 0.000 abstract description 7
- 230000000694 effects Effects 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000009429 electrical wiring Methods 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 230000005693 optoelectronics Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000005674 electromagnetic induction Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Landscapes
- Electronic Switches (AREA)
Abstract
Description
【発明の詳細な説明】
〈産業上の利用分野〉
本発明は、例えば自動開閉ドアを作動する物体検知用電
子スイッチの受光回路に関するものである。DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a light receiving circuit for an electronic switch for detecting an object that operates, for example, an automatically opening/closing door.
〈従来の技術〉
この種の光電子スイッチの受光回路において最も問題と
なるのは、目的とする信号光よりも強い外乱光、例えば
太陽光や一般照明光などの妨害である。通常、光電子ス
イッチにおいて外乱光の妨害が予想される場合には、光
電子スイッチの投光器から断続した光線つまり変調信号
光を投射するようにし、外乱光と信号光との分離を計っ
ている。<Prior Art> The biggest problem in the light receiving circuit of this type of optoelectronic switch is disturbance from external light that is stronger than the intended signal light, such as sunlight or general illumination light. Normally, when interference by disturbance light is expected in a photoelectronic switch, an intermittent light beam, that is, a modulated signal light, is projected from the light projector of the optoelectronic switch in order to separate the disturbance light and the signal light.
この場合、一般照明光等の外乱光に含まれる変調周波数
に対し信号光の変調周波数との間に差をもうけて外乱光
の影響を除去するようにしている。In this case, a difference is created between the modulation frequency of the signal light and the modulation frequency included in the disturbance light such as general illumination light to remove the influence of the disturbance light.
〈発明が解決しようとする問題点〉
しかしながら、受光素子に強力な外乱光が入射すること
によって、受光素子の負荷を含めた受光回路が電流的に
飽和してしまうと、信号光による信号出力が殆ど得られ
ず、受光回路以後に接続される電気回路において外乱光
と信号光による信号を分離することが不可能となる。<Problems to be Solved by the Invention> However, if the light receiving circuit including the load of the light receiving element becomes saturated due to strong disturbance light entering the light receiving element, the signal output by the signal light will decrease. This makes it impossible to separate the signal due to the disturbance light and the signal light in an electric circuit connected after the light receiving circuit.
そしで、前述の問題を解決する手段として、受”光器の
視野を狭くして信号光以外の外乱光ができるだけ受光素
子に入射しないようにする光学的方法や、低周波トラン
スを受光素子の負荷として使用する方法が用いられてい
る。しかし、前者の方法では広い視野を要求される受光
器の場合には適用できず、後者の方法は、低周波トラン
スの低インピーダンス側に受光素子を接続するとともに
高インピーダンス側を出力側としたもので、受光素子の
負荷インピーダンスは略一定であるが、やはり強力な外
乱光が受光素子に入射しすると、トランス鉄心が磁気飽
和して信号出力が得られなくなる他に、衝撃によって鉄
心が振動し、その振動が電気出力となって出力側にあら
れれたり、他の電磁機器から電磁誘導を受けたりする欠
点がある。As a means to solve the above-mentioned problems, there are optical methods that narrow the field of view of the photodetector to prevent as much disturbance light other than signal light from entering the photodetector, and a low-frequency transformer that can be used as a shield for the photodetector. However, the former method cannot be applied to photodetectors that require a wide field of view, and the latter method connects the photodetector to the low-impedance side of a low-frequency transformer. At the same time, the high impedance side is the output side, and the load impedance of the light receiving element is approximately constant, but when strong disturbance light enters the light receiving element, the transformer core becomes magnetically saturated and a signal output is obtained. Another drawback is that the iron core vibrates due to impact, and the vibrations become electrical output and are transmitted to the output side, or receive electromagnetic induction from other electromagnetic devices.
〈発明の目的〉
本発明は、このような問題点に鑑みなされたもので、外
乱光の強い妨害を受けてもその影響が殆ど現れず、目的
とする信号光による信号のみを出力することのできる受
光回路を提供することを目的とするものである。<Purpose of the Invention> The present invention has been made in view of the above-mentioned problems, and it is possible to output only a signal based on the target signal light, with almost no effect even when receiving strong interference from external light. The purpose of this invention is to provide a light receiving circuit that can be used.
く問題点を解決する為の手段〉
本発明の受光回路は、前記目的を達成するために、高周
波の変調信号光を受光して電気信号に変換する受光素子
と、この受光素子の出力電流の電圧への変換用且つ増幅
用であって仮想接地点を前記受光素子に接続して受光素
子の負荷インピーダンスを小さくした増幅器と、この増
幅器の帰還回路に設けられ直流若しくは低周波に対する
帰還量を高周波に対する帰還量よりも大きくなるよう設
定した時定数回路とを備えた構成を要旨とするものであ
る。Means for Solving the Problems> In order to achieve the above object, the light receiving circuit of the present invention includes a light receiving element that receives high frequency modulated signal light and converts it into an electric signal, and an output current of the light receiving element. An amplifier for converting to voltage and for amplification, whose virtual ground point is connected to the light-receiving element to reduce the load impedance of the light-receiving element, and a feedback circuit of this amplifier that converts the amount of feedback for direct current or low frequency into high frequency. The gist of the present invention is to include a time constant circuit that is set to be larger than the amount of feedback for.
く作用〉
前記構成としたことにより、目的とする高周波の変調信
号光と直流若しくは低周波の外乱光とが受光素子により
同時に受光された場合、外乱光による直流または低周波
の光電流が増幅器に入力することにより、この光電流の
強度に応じて増幅器の帰還量が増減し、この外乱光によ
る光電流の出力レベル(VO=−IX (rl+r2)
)が略一定となる。これに対し高周波変調の信号光が増
幅器で増幅される場合、帰還回路の時定数回路により殆
ど帰還されず、そのまま増幅して出力(VO=−I −
r f)される。従って、信号光による出力信号のみを
得ることができ、受光素子の負荷インピーダンスが小さ
いことによって受光素子の内部抵抗の影響を無視できる
。但し、前述の■oは出力レベル、■は光電流、rl、
r2は帰還回路の各抵抗の抵抗値、rfは帰還用抵抗の
抵抗値をそれぞれ示す。Effect> With the above configuration, when the target high-frequency modulated signal light and the DC or low-frequency disturbance light are simultaneously received by the light receiving element, the DC or low-frequency photocurrent due to the disturbance light is transmitted to the amplifier. By inputting the input, the feedback amount of the amplifier increases or decreases according to the intensity of this photocurrent, and the output level of the photocurrent due to this disturbance light (VO=-IX (rl+r2)
) becomes approximately constant. On the other hand, when high-frequency modulated signal light is amplified by an amplifier, it is hardly fed back by the time constant circuit of the feedback circuit, and is directly amplified and output (VO = -I -
r f) be done. Therefore, only the output signal from the signal light can be obtained, and since the load impedance of the light receiving element is small, the influence of the internal resistance of the light receiving element can be ignored. However, the aforementioned ■o is the output level, ■ is the photocurrent, rl,
r2 indicates the resistance value of each resistor in the feedback circuit, and rf indicates the resistance value of the feedback resistor.
〈実施例〉
以下、本発明の実施例を図面に基づいて詳細に説明する
。<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.
一実施例を示した第1図において、ホトダイオードから
成る受光素子PDは、第1の抵抗R1とコンデンサCと
から成る時定数回路TCおよび演算増幅器opの反転入
力端一に接続され、また、演算増幅器OPの非反転入力
端子が接地されていることにより、反転入力端一も非反
転入力端子と同様に接地したのと等価になっている。つ
まり仮想接地されており、この仮想接地点Bが受光素子
PDに接続されている。また、演算増幅器OPの出力端
が信号出力端子VOとして導出されているとともに、第
2の抵抗R2を介して時定数回路TCの第1の抵抗R1
とコンデンサCの直列接続点に接続され、帰還回路が構
成されている。演算増幅器OPの帰還用抵抗Rfとして
は、第1および第2の抵抗R1,R2の抵抗値の和より
も大きな抵抗値のものが用いられている。In FIG. 1 showing one embodiment, a light receiving element PD consisting of a photodiode is connected to a time constant circuit TC consisting of a first resistor R1 and a capacitor C and an inverting input terminal of an operational amplifier op. Since the non-inverting input terminal of the amplifier OP is grounded, it is equivalent to grounding the inverting input terminal 1 as well as the non-inverting input terminal. That is, it is virtually grounded, and this virtual ground point B is connected to the light receiving element PD. Further, the output terminal of the operational amplifier OP is led out as the signal output terminal VO, and the output terminal is connected to the first resistor R1 of the time constant circuit TC via the second resistor R2.
It is connected to the series connection point of capacitor C and capacitor C, forming a feedback circuit. As the feedback resistor Rf of the operational amplifier OP, one having a resistance value greater than the sum of the resistance values of the first and second resistors R1 and R2 is used.
次に、前記構成とした実施例回路の動作を、第2図を参
照しながら説明する。Next, the operation of the embodiment circuit configured as described above will be explained with reference to FIG.
受光素子PDに、低周波数の外乱光と高周波数の変調信
号光とが同時に入射した場合、この受光素子PDには、
第2図(a)図に示すように、外乱光による低周波の光
電流イと変調信号光による高周波の光電流口とが重畳し
た光電流が流れる。この光電流が演算増幅器OPに入力
すると、低周波の光電流イは帰還抵抗Rf、第1および
第2の抵抗R1,R2をそれぞれ通じて帰還され、その
帰還量は、同(b)図に示すように、光電流イとほぼ相
似の電流波形となる。従って、この光電流イによる出力
はほぼ一定となって信号としては出力されない。一方変
調信号光による高周波の光電流の場合には、コンデンサ
Cが高周波数の電圧に対して低いインピーダンスを示す
ので、時定数回路TCの時定数を適当に設定することに
より、このコンデンサCによって高周波の帰還電圧がバ
イパスされ、第1抵抗R1を通じての帰還がかからない
。即ち、時定数回路TCが恰もハイカットフィルタとし
て作用する。従って、この高周波の光電流においては、
帰還用抵抗Rfを通じてのみ帰還される。ここで、帰還
用抵抗Rfの抵抗値は、前述のように第1および第2の
抵抗R1,R2の各抵抗値の和よりも大きいため、低周
波の光電流に対する帰還量が高周波の光電流に対する帰
還量よりも大きくなり、同(C1図に示すように、外乱
光等による低周波の光電流に影響されることなく目的と
する高周波変調信号のみが出力され、しかも、外乱光に
よる飽和を防止することができる。また、受光素子PD
が演算増幅器OPの仮想接地点Aに接続されているので
、帰還用抵抗Rfの抵抗値が第1.第2の抵抗R1,R
2の各抵抗値の和よりも大きくても、高周波の光電流に
対する受光素子PDの負荷インピーダンスZは、帰還用
抵抗Rfの抵抗値をrf、演算増幅器OPのオープン・
ループ・ゲインをAとした場合に、Z=rf/Aで表わ
され、このインピーダンスZは、第1の抵抗R1の抵抗
値よりもはるかに小さくなり、受光素子PDの内部抵抗
の影響を無視できる。When low-frequency disturbance light and high-frequency modulated signal light simultaneously enter the light-receiving element PD, the light-receiving element PD
As shown in FIG. 2(a), a photocurrent flows in which a low-frequency photocurrent A due to disturbance light and a high-frequency photocurrent aperture due to modulated signal light are superimposed. When this photocurrent is input to the operational amplifier OP, the low-frequency photocurrent A is fed back through the feedback resistor Rf and the first and second resistors R1 and R2, respectively, and the amount of feedback is shown in Fig. 3(b). As shown, the current waveform is almost similar to photocurrent A. Therefore, the output due to this photocurrent A remains almost constant and is not output as a signal. On the other hand, in the case of a high-frequency photocurrent caused by modulated signal light, the capacitor C shows a low impedance with respect to the high-frequency voltage. The feedback voltage is bypassed, and no feedback is applied through the first resistor R1. That is, the time constant circuit TC functions as a high-cut filter. Therefore, in this high frequency photocurrent,
It is fed back only through the feedback resistor Rf. Here, since the resistance value of the feedback resistor Rf is larger than the sum of the respective resistance values of the first and second resistors R1 and R2 as described above, the amount of feedback for the low frequency photocurrent is greater than the high frequency photocurrent. (As shown in Figure C1, only the desired high-frequency modulation signal is output without being affected by low-frequency photocurrent caused by disturbance light, etc., and moreover, it is possible to avoid saturation caused by disturbance light. In addition, the light receiving element PD
is connected to the virtual ground point A of the operational amplifier OP, so the resistance value of the feedback resistor Rf is the first. Second resistor R1,R
Even if the resistance value of the feedback resistor Rf is larger than the sum of the resistance values of the operational amplifier OP, the load impedance Z of the photodetector PD against the high-frequency photocurrent can be
When the loop gain is A, it is expressed as Z=rf/A, and this impedance Z is much smaller than the resistance value of the first resistor R1, ignoring the influence of the internal resistance of the photodetector PD. can.
第3図は本発明の他の実施例を示し、この第3図におい
て、第1図と同−若しくは同等のものには同一の符号を
付しである。そして、時定数回路TCを帰還用抵抗Rf
に対し並列接続し、この時定数回路TCに、トランジス
タQと第2の抵抗R2の直列回路を並列接続するととも
に、トランジスタQのベースを、時定数回路TCの第1
の抵抗R1とコンデンサCの直列接続点に接続した構成
において第1図のものと相違する。FIG. 3 shows another embodiment of the present invention, and in FIG. 3, the same or equivalent parts as in FIG. 1 are given the same reference numerals. Then, the time constant circuit TC is connected to the feedback resistor Rf.
A series circuit of a transistor Q and a second resistor R2 is connected in parallel to this time constant circuit TC, and the base of the transistor Q is connected to the first resistor R2 of the time constant circuit TC.
It differs from the one shown in FIG. 1 in that it is connected to the series connection point of resistor R1 and capacitor C.
次に、この実施例の動作について説明する。外乱光によ
る直流若しくは低周波の光電流が増大すると、演算増幅
器OPが逆相アンプであって入出力が逆極性になるので
、出力端子v□の出力信号レベルがグランドレベルより
負側レベルに移行し、それに伴っ゛てトランジスタQの
エミッタも負側レベルとなり、第1の抵抗R1を通じて
トランジスタQのベース電流が増大し、且つコレクタ電
流が増大する。即ち、外乱光による光電流の増減に対応
してコレクタ電流が増減することによって、出力端子V
oの出力信号レベルが一定となる。一方、高周波の変調
信号光による光電流が増大すると、やはり出力端子vo
の出力信号レベルが負側レベルとなってトランジスタQ
のエミッタも負側レベルとなるが、同時に、高周波に対
し低インピーダンスとなるコンデンサCを通じてトラン
ジスタQのベースも負側レベルとなる。そのため、高周
波信号光による光電流が増大してもトランジスタQのベ
ース電流並びにコレクタ電流は何れも増大しない。つま
り、時定数回路TCによって帰還がかからないようにな
っている。従って、前記実施例と同様に外乱光に影響さ
れることなく目的とする高周波変調信号のみを取り出す
ことができる。Next, the operation of this embodiment will be explained. When the DC or low-frequency photocurrent due to disturbance light increases, the operational amplifier OP is a reverse phase amplifier and the input and output have opposite polarities, so the output signal level of the output terminal v□ shifts to a negative level from the ground level. Accordingly, the emitter of the transistor Q also becomes a negative level, the base current of the transistor Q increases through the first resistor R1, and the collector current increases. That is, as the collector current increases or decreases in response to the increase or decrease in photocurrent due to disturbance light, the output terminal V
The output signal level of o becomes constant. On the other hand, when the photocurrent due to the high frequency modulated signal light increases, the output terminal vo
The output signal level of transistor Q becomes negative level and
The emitter of the transistor Q also becomes a negative level, but at the same time, the base of the transistor Q also becomes a negative level through the capacitor C, which has a low impedance to high frequencies. Therefore, even if the photocurrent due to the high-frequency signal light increases, neither the base current nor the collector current of the transistor Q increases. In other words, feedback is not applied by the time constant circuit TC. Therefore, as in the embodiment described above, only the desired high frequency modulation signal can be extracted without being affected by disturbance light.
尚、本発明は、前記実施例に限定されるものではなく、
請求の範囲に基づいて種々の実施態様が考えられのは勿
論である。例えば、受光素子PDとしてホトダイオード
を用いた場合について説明したが、半導体装置検出素子
、ホトトランジスタ等の他の受光素子を使用しても同様
の効果が得られることは言うまでもない。Note that the present invention is not limited to the above embodiments,
Of course, various embodiments are possible based on the scope of the claims. For example, although a case has been described in which a photodiode is used as the light receiving element PD, it goes without saying that similar effects can be obtained by using other light receiving elements such as a semiconductor device detection element or a phototransistor.
〈発明の効果〉
以上詳述したように本発明の受光回路によると、受光素
子を、増幅器の仮想接地点に接続するとともに、この増
幅器の帰還回路に、直流若しくは低周波に対する帰還量
を高周波に対する帰還量よりも大きくなるよう設定した
時定数回路を設けた構成としたので、外乱光の強い妨害
を受けても、飽和したり高周波信号に影響が現われるこ
とが殆どなく、目的とする高周波の変調信号光のみを確
実に検知することができる。また、受光素子の負荷イン
ピーダンスが小さいので、受光素子の内部抵抗の影響を
無視でき、良好な応答性を得られる利点がある。<Effects of the Invention> As detailed above, according to the light receiving circuit of the present invention, the light receiving element is connected to the virtual ground point of the amplifier, and the feedback circuit of the amplifier is connected to the feedback amount for direct current or low frequency waves. The configuration includes a time constant circuit that is set to be larger than the amount of feedback, so even if there is strong interference from external light, there is little saturation or effect on the high frequency signal, and the desired high frequency modulation can be achieved. Only the signal light can be reliably detected. Further, since the load impedance of the light receiving element is small, the influence of the internal resistance of the light receiving element can be ignored, and there is an advantage that good responsiveness can be obtained.
第1図は本発明の受光回路の一実施例の電気結線図、第
2図(a)〜(C1図はそれぞれ第1図の動作波形図、
第3図は本発明の他の実施例の電気結線図である。
PD−・・受光素子 OP−増幅器TC一時定数
回路FIG. 1 is an electrical wiring diagram of an embodiment of the light receiving circuit of the present invention, FIGS. 2(a) to (C1 are respectively operational waveform diagrams of FIG. 1,
FIG. 3 is an electrical wiring diagram of another embodiment of the present invention. PD - Light receiving element OP - Amplifier TC temporary constant circuit
Claims (1)
る受光素子と、この受光素子の出力電流の電圧への変換
用且つ増幅用であって仮想接地点を前記受光素子に接続
して受光素子の負荷インピーダンスを小さくした増幅器
と、この増幅器の帰還回路に設けられ直流若しくは低周
波に対する帰還量を高周波に対する帰還量よりも大きく
なるよう設定した時定数回路とを備えて成ることを特徴
とする受光回路。(1) A light-receiving element that receives high-frequency modulated signal light and converts it into an electrical signal, and a virtual ground point connected to the light-receiving element for converting and amplifying the output current of this light-receiving element to voltage. It is characterized by comprising an amplifier with a reduced load impedance of the light-receiving element, and a time constant circuit provided in the feedback circuit of the amplifier and set so that the amount of feedback for direct current or low frequencies is larger than the amount of feedback for high frequencies. light receiving circuit.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5228486A JPS62209923A (en) | 1986-03-10 | 1986-03-10 | Light receiving circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5228486A JPS62209923A (en) | 1986-03-10 | 1986-03-10 | Light receiving circuit |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS62209923A true JPS62209923A (en) | 1987-09-16 |
Family
ID=12910495
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP5228486A Pending JPS62209923A (en) | 1986-03-10 | 1986-03-10 | Light receiving circuit |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS62209923A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH05299999A (en) * | 1992-04-24 | 1993-11-12 | Opt Kk | Light receiving circuit |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5314303A (en) * | 1976-05-14 | 1978-02-08 | Umufuorumutekunitsuku Heruberu | Method of manufacturing motor blank and cutter therefor |
JPS5422589A (en) * | 1977-07-21 | 1979-02-20 | Hitachi Cable Ltd | Ultra-high voltage power cable |
-
1986
- 1986-03-10 JP JP5228486A patent/JPS62209923A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5314303A (en) * | 1976-05-14 | 1978-02-08 | Umufuorumutekunitsuku Heruberu | Method of manufacturing motor blank and cutter therefor |
JPS5422589A (en) * | 1977-07-21 | 1979-02-20 | Hitachi Cable Ltd | Ultra-high voltage power cable |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH05299999A (en) * | 1992-04-24 | 1993-11-12 | Opt Kk | Light receiving circuit |
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