JPS6142094Y2 - - Google Patents
Info
- Publication number
- JPS6142094Y2 JPS6142094Y2 JP9774881U JP9774881U JPS6142094Y2 JP S6142094 Y2 JPS6142094 Y2 JP S6142094Y2 JP 9774881 U JP9774881 U JP 9774881U JP 9774881 U JP9774881 U JP 9774881U JP S6142094 Y2 JPS6142094 Y2 JP S6142094Y2
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- photovoltaic
- logarithmic conversion
- connection point
- current
- 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.)
- Expired
Links
- 239000004065 semiconductor Substances 0.000 claims description 21
- 238000006243 chemical reaction Methods 0.000 claims description 17
- 238000005375 photometry Methods 0.000 description 19
- 239000003990 capacitor Substances 0.000 description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- 230000005669 field effect Effects 0.000 description 3
- 230000004044 response Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000007257 malfunction Effects 0.000 description 1
- 230000011514 reflex Effects 0.000 description 1
Landscapes
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
- Exposure Control For Cameras (AREA)
Description
【考案の詳細な説明】
本考案は、カメラの測光回路、詳しくは、演算
増幅器に測光用光起電力素子および対数変換素子
を接続して構成されるカメラの測光回路に関す
る。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photometric circuit for a camera, and more particularly, to a photometric circuit for a camera that is constructed by connecting a photovoltaic element for photometry and a logarithmic conversion element to an operational amplifier.
この種の測光回路においては、一般に、入力段
にMOS型電界効果トランジスタを使用した高入
力インピーダンスの演算増幅器が用いられてい
る。そして、この演算増幅器の反転入力端子と非
反転入力端子間にシリコンホトセルなどの測光用
光起電力素子が接続され、さらに、この光起電力
素子に流れる光電流を対数圧縮した電圧値に変換
するためのシリコンダイオードなどの対数変換素
子が上記演算増幅器の反転入力端子と出力端子間
に接続されてカメラの測光回路が構成されてい
て、上記対数圧縮した電圧値を基に露出制御や露
出情報表示が行なわれるようになつている。 This type of photometric circuit generally uses a high input impedance operational amplifier using a MOS field effect transistor in its input stage. A photovoltaic device such as a silicon photocell is connected between the inverting input terminal and the non-inverting input terminal of this operational amplifier, and the photocurrent flowing through this photovoltaic device is converted into a logarithmically compressed voltage value. A logarithmic conversion element such as a silicon diode is connected between the inverting input terminal and the output terminal of the operational amplifier to configure the camera photometry circuit, and the exposure control and exposure information are performed based on the logarithmically compressed voltage value. Display is now taking place.
しかし、上記MOS型電界効果トランジスタ、
シリコンホトセル、シリコンダイオード等の素子
には周知のように等価的に接合容量等の容量成分
が存在し、このため、測光回路は電源投入後、上
記素子自体が完全な動作状態に達するまでに時間
を要していた。また、この等価容量のために、演
算増幅器はラツチアツプ現象を起し、電源投入後
安定状態に至るまで時間がかかつていた。この応
答遅れは、被写体が暗い程、即ち光電流の値が小
さい程著しくなる。特に、カメラにおいては、連
写性が要求されているため、上記応答遅れは測光
回路の誤動作の原因となつていた。 However, the above MOS field effect transistor,
As is well known, devices such as silicon photocells and silicon diodes have equivalent capacitance components such as junction capacitance, and for this reason, the photometry circuit has a long delay after the power is turned on until the device itself reaches a fully operational state. It took time. Furthermore, due to this equivalent capacitance, the operational amplifier causes a latch-up phenomenon, and it takes a long time to reach a stable state after the power is turned on. This response delay becomes more significant as the object becomes darker, that is, the value of the photocurrent becomes smaller. In particular, since cameras are required to be capable of continuous shooting, the above-mentioned response delay has been a cause of malfunction of the photometry circuit.
そこで、上記測光回路における応答遅れの改善
に関して、従来、数多くの提案がなされている。
これら従来の手段は、いずれも、上記等価容量を
有する半導体素子に、電源投入時に強制的に急速
に電流を流し込むようにして、これら半導体素子
の動作立上り時点を早めるようにしたものであ
る。しかし、上記従来の手段においては、上記等
価容量の充電完了後に、電流供給源より流れ込む
電流のために、逆に正常な測光が行なわれなくな
るという新たな問題を生じている。即ち、特に、
被写体が暗く光電流が微弱なものとなる場合に
は、上記電流供給源から流れる電流が上記測光に
関する微弱電流に影響を及ぼし、正確な測光出力
が得られなくなる。 Therefore, many proposals have been made to improve the response delay in the photometric circuit.
In all of these conventional means, current is forced to rapidly flow into semiconductor elements having the above-mentioned equivalent capacitance when the power is turned on, so that the operation start-up time of these semiconductor elements is brought forward. However, in the conventional means described above, a new problem arises in that normal photometry cannot be performed due to the current flowing from the current supply source after the completion of charging the equivalent capacitance. That is, in particular,
When the subject is dark and the photocurrent is weak, the current flowing from the current supply source affects the weak current related to photometry, making it impossible to obtain accurate photometry output.
本考案の目的は、上記従来の問題点に鑑み、測
光用光起電力素子と対数変換素子との接続点に、
半導体素子を介して電流供給源を接続すると共
に、電流供給源からの電流の供給が断たれたとき
に、上記半導体素子の両端子間を等電位にして微
小電流をも確実に遮断するようにした、カメラの
測光回路を提供するにある。 In view of the above-mentioned conventional problems, the purpose of the present invention is to provide a
A current supply source is connected through the semiconductor element, and when the current supply from the current supply source is cut off, the potential between both terminals of the semiconductor element is made equal to ensure that even minute currents are cut off. The goal is to provide photometric circuits for cameras.
以下、本考案を図示の実施例に基いて説明す
る。 Hereinafter, the present invention will be explained based on the illustrated embodiments.
図は、本考案の一実施例を示す測光回路の電気
回路図である。測光回路は、カメラの撮影レンズ
を透過した被写体光を受光できる位置に配置され
た測光用光起電力素子1と、この光起電力素子1
に流れる電流を対数圧縮して電圧値に変換するた
めの対数変換素子2と、演算増幅器3と、電流供
給回路4と、この電流供給回路4の出力段に設け
れたスイツチング素子5と、電流供給回路4から
供給される電流を上記光起電力素子1と対数変換
素子2の接続点aに流すための半導体素子6と、
この半導体素子6の両端を上記スイツチング素子
5のオフ時に等電位にするための等電位回路7と
により構成されている。 The figure is an electrical circuit diagram of a photometric circuit showing an embodiment of the present invention. The photometry circuit includes a photovoltaic element 1 for photometry, which is placed at a position where it can receive the subject light that has passed through the photographic lens of the camera, and this photovoltaic element 1.
A logarithmic conversion element 2 for logarithmically compressing the current flowing through the circuit and converting it into a voltage value, an operational amplifier 3, a current supply circuit 4, a switching element 5 provided at the output stage of this current supply circuit 4, and a current a semiconductor element 6 for causing the current supplied from the supply circuit 4 to flow through the connection point a between the photovoltaic element 1 and the logarithmic conversion element 2;
It is constituted by an equipotential circuit 7 for making both ends of the semiconductor element 6 equal potential when the switching element 5 is off.
上記光起電力素子1は、例えばシリコンホトセ
ル等によつて形成されたものであつて、MOS型
電界効果トランジスタを入力段に用いた演算増幅
器3の両入力端子間に、アノードを反転入力端子
に、カソードを非反転入力端子にそれぞれ接続さ
れて配設されている。光起電力素子1は被写体光
を受光することにより、受光量に応じた光電流が
カソードからアノードに向けて流れる。演算増幅
器3の非反転入力端子は基準電圧Vsが印加され
る端子8に接続されている。演算増幅器3の反転
入力端子と出力端子間には、NPN型トランジス
タをダイオードとして利用させるように、そのコ
レクタとベースを共通に接続した対数変換素子2
がコレクタを反転入力端子に、エミツタを出力端
子にそれぞれ接続されて設けられている。 The photovoltaic element 1 is formed of, for example, a silicon photocell, and has an anode connected to an inverting input terminal between both input terminals of an operational amplifier 3 using a MOS field effect transistor at the input stage. and the cathodes are respectively connected to the non-inverting input terminals. When the photovoltaic element 1 receives subject light, a photocurrent flows from the cathode to the anode in accordance with the amount of received light. A non-inverting input terminal of the operational amplifier 3 is connected to a terminal 8 to which a reference voltage Vs is applied. Between the inverting input terminal and the output terminal of the operational amplifier 3, there is a logarithmic conversion element 2 whose collector and base are commonly connected so that the NPN transistor can be used as a diode.
is provided with the collector connected to the inverting input terminal and the emitter connected to the output terminal.
上記電流供給回路4は、その電源9にカメラに
内蔵された電池電源が用いられており、同電源9
の一端に接地され、他端は例えば、一眼レフレツ
クスカメラの可動ミラーに連動して開閉する電源
スイツチ10の一端に接続されている。電源スイ
ツチ10の他端には抵抗11と12の直列回路が
接続され、同回路の他端は接地されている。上記
抵抗11と12の接続点にはコンデンサ13の一
端が接続されている。上記電源スイツチ10と抵
抗11との接続点と、上記コンデンサ13の他端
との間には抵抗14が接続されている。このコン
デンサ13と抵抗14との接続点には抵抗15の
一端が接続されており、抵抗15の他端は、PNP
型トランジスタ16のベースに接続されている。
このトランジスタ16はダイオードとして作用す
るようにコレクタとベースが共通に接続されてお
り、エミツタは上記電源スイツチ10と抵抗11
との接続点に接続されている。また、このトラン
ジスタ16のエミツタは同トランジスタ16と特
性の等しいPNP型トランジスタからなる上記スイ
ツチング素子5のエミツタに接続され、同スイツ
チング素子5のベースは上記トランジスタ16の
ベース、コレクタに接続されている。即ち、トラ
ンジスタ16とスイツチング素子5とはカレント
ミラー回路を形成するように接続されている。 The current supply circuit 4 uses a battery power supply built in the camera as its power supply 9.
One end of the switch is grounded, and the other end is connected to one end of a power switch 10 that opens and closes in conjunction with a movable mirror of a single-lens reflex camera, for example. A series circuit of resistors 11 and 12 is connected to the other end of the power switch 10, and the other end of the circuit is grounded. One end of a capacitor 13 is connected to the connection point between the resistors 11 and 12. A resistor 14 is connected between the connection point between the power switch 10 and the resistor 11 and the other end of the capacitor 13. One end of a resistor 15 is connected to the connection point between the capacitor 13 and the resistor 14, and the other end of the resistor 15 is a PNP
type transistor 16.
The collector and base of this transistor 16 are commonly connected so that it acts as a diode, and the emitter is connected to the power switch 10 and the resistor 11.
connected to the connection point. The emitter of the transistor 16 is connected to the emitter of the switching element 5, which is a PNP transistor having the same characteristics as the transistor 16, and the base of the switching element 5 is connected to the base and collector of the transistor 16. That is, the transistor 16 and the switching element 5 are connected to form a current mirror circuit.
上記スイツチング素子5のコレクタは、ダイオ
ードとして作用するようにコレクタとベースを共
通に接続したNPN型トランジスタからなる半導
体素子6のコレクタに接続され、同半導体素子6
のエミツタは、上記光起電力素子1と対数変換素
子2との接続点aに接続されている。 The collector of the switching element 5 is connected to the collector of a semiconductor element 6 consisting of an NPN transistor whose collector and base are commonly connected so as to act as a diode.
The emitter is connected to the connection point a between the photovoltaic element 1 and the logarithmic conversion element 2.
また、上記スイツチング素子5と半導体素子6
との接続点bには等電位回路7の抵抗17の一端
が接続され、同抵抗17の他端はボルテージホロ
ワ回路を形成している演算増幅器18の反転入力
端子および出力端子に接続されている。この演算
増幅器18の非反転入力端子は上記対数変換素子
2のコレクタに接続されている。なお、この対数
変換素子2のエミツタと接続した前記演算増幅器
3の出力端子は、この測光回路の出力端子となつ
ており、同出力端子には同端子より送出される測
光出力により作動する、カメラの表示回路19お
よび露出制御回路20が接続される。 Further, the switching element 5 and the semiconductor element 6
One end of the resistor 17 of the equipotential circuit 7 is connected to the connection point b, and the other end of the resistor 17 is connected to the inverting input terminal and output terminal of the operational amplifier 18 forming the voltage follower circuit. There is. A non-inverting input terminal of the operational amplifier 18 is connected to the collector of the logarithmic conversion element 2. The output terminal of the operational amplifier 3 connected to the emitter of the logarithmic conversion element 2 is the output terminal of this photometric circuit, and the output terminal is connected to a camera which is operated by the photometric output sent from the same terminal. A display circuit 19 and an exposure control circuit 20 are connected thereto.
次に上記のように構成されたカメラの測光回路
の動作を説明する。 Next, the operation of the photometry circuit of the camera configured as described above will be explained.
カメラのレリーズボタンが押下げられて可動ミ
ラーが上昇すると、これに連動して電源スイツチ
10が閉成し、カメラ内の全電気回路に電源9が
供給され、測光回路にも動作電圧が与えられる。
また電源スイツチ10が閉成すると、電源スイツ
チ10→抵抗14→コンデンサ13→抵抗12の
経路および抵抗14と並列なトランジスタ16→
抵抗15の経路を通じて電流が流れ、コンデンサ
13が充電される。コンデンサ13が充電される
に従つて、同コンデンサ13と抵抗14との接続
点の電位が次第に上昇していく。このコンデンサ
13と抵抗14との接続点の電位が低いうちは、
トランジスタ16が導通し、このトランジスタ1
6に流れるコレクタ電流と等しいコレクタ電流が
カレントミラー効果によりスイツチング素子5に
も流れる。従つて、上記電源スイツチ10を閉成
した時点で、スイツチング素子5から一定の電流
が半導体素子6を通じて上記光起電力素子1と対
数変換素子2との接続点aに流れ込む。このと
き、半導体素子6のコレクタ、エミツタ間の電位
差は、高抵抗17の両端間の電位差に等しい。半
導体素子6を通じて上記接続点aに電流が流れ込
むことにより、演算増幅器3の入力段に存在する
等価容量は瞬時に充電され、安定状態に達すると
共に、演算増幅器3のラツチアツプ現象も解消さ
れる。 When the camera's release button is pressed down and the movable mirror rises, the power switch 10 is closed in conjunction with this, supplying power 9 to all electrical circuits in the camera, and also providing operating voltage to the photometry circuit. .
When the power switch 10 is closed, the power switch 10 → resistor 14 → capacitor 13 → resistor 12 and the transistor 16 in parallel with the resistor 14 →
Current flows through the path of resistor 15 and capacitor 13 is charged. As the capacitor 13 is charged, the potential at the connection point between the capacitor 13 and the resistor 14 gradually increases. As long as the potential at the connection point between capacitor 13 and resistor 14 is low,
Transistor 16 becomes conductive, and this transistor 1
A collector current equal to the collector current flowing through the switching element 6 also flows through the switching element 5 due to the current mirror effect. Therefore, when the power switch 10 is closed, a constant current flows from the switching element 5 through the semiconductor element 6 to the connection point a between the photovoltaic element 1 and the logarithmic conversion element 2. At this time, the potential difference between the collector and emitter of the semiconductor element 6 is equal to the potential difference between both ends of the high resistance 17. As a current flows into the connection point a through the semiconductor element 6, the equivalent capacitance present at the input stage of the operational amplifier 3 is instantly charged and reaches a stable state, and the latch-up phenomenon of the operational amplifier 3 is also eliminated.
上記電源スイツチ10が閉成されてから、ある
短い期間で上記コンデンサ13の充電が行なわれ
て、同コンデンサ13と抵抗14との接続点の電
位が上昇し、ほゞ電源9の電位に達すると、この
時点でトランジスタ16が非導通の状態になり、
これに伴つてスイツチング素子5もオフの状態に
なる。スイツチング素子5がオフになると、同ス
イツチング素子5に接続した高抵抗17の一端の
電位はその他端の電位に等しくなる。高抵抗17
の他端の電位は、演算増幅器18によるボルテー
ジホロワ回路のためにその非反転入力端子に等し
いため、結局、半導体素子6のコレクタとエミツ
タ間の電位は等しくなる。従つて、上記スイツチ
ング素子5がオフになることにより、上記半導体
素子6のコレクタの電位がエミツタの電位に等し
くなると、上記半導体素子6を通じて上記光起電
力素子1と対数変換素子2との接続点aに流れ込
んでいた電流はこのとき完全に零となる。 After the power switch 10 is closed, the capacitor 13 is charged in a short period of time, and the potential at the connection point between the capacitor 13 and the resistor 14 increases until it almost reaches the potential of the power source 9. , at this point the transistor 16 becomes non-conductive,
Along with this, the switching element 5 is also turned off. When the switching element 5 is turned off, the potential at one end of the high resistance 17 connected to the switching element 5 becomes equal to the potential at the other end. High resistance 17
Since the potential at the other end is equal to the non-inverting input terminal of the operational amplifier 18 due to the voltage follower circuit, the potentials between the collector and emitter of the semiconductor element 6 become equal after all. Therefore, when the switching element 5 is turned off and the collector potential of the semiconductor element 6 becomes equal to the emitter potential, the connection point between the photovoltaic element 1 and the logarithmic conversion element 2 is connected through the semiconductor element 6. At this time, the current flowing into a becomes completely zero.
従つて、このあと、可動ミラーが上昇を完了し
て上記光起電力素子1が撮影レンズを透過した被
写体光を受光すると、この受光開始時点で、既
に、上記光起電力素子1、対数変換素子2および
演算増幅器3は安定状態になつており、しかも上
記電流供給回路4からの電流が完全に断たれてい
るので、受光開始と同時に正確な測光動作が行な
われる。そして演算増幅器3の測光出力が正確な
ものとなるので、表示回路19からの表示出力お
よび露出制御回路20の露出制御出力も正確なも
のとなる。特に被写体が暗いために、上記光起電
力素子1の光電流が微弱になる場合でも、この光
起電力素子1の受光開始の時点では、上記等価容
量をチヤージするための電流供給が完全に断たれ
ており、上記微弱電流は被写体の明るさに相応し
たものとなり、高精度の測光出力が得られる。 Therefore, after this, when the movable mirror completes its ascent and the photovoltaic element 1 receives the subject light that has passed through the photographic lens, the photovoltaic element 1 and the logarithmic conversion element have already 2 and the operational amplifier 3 are in a stable state, and the current from the current supply circuit 4 is completely cut off, so that accurate photometry is performed at the same time as light reception begins. Since the photometric output of the operational amplifier 3 becomes accurate, the display output from the display circuit 19 and the exposure control output from the exposure control circuit 20 also become accurate. Even if the photocurrent of the photovoltaic element 1 becomes weak because the subject is particularly dark, the current supply for charging the equivalent capacitance is completely cut off at the time the photovoltaic element 1 starts receiving light. The weak current corresponds to the brightness of the subject, and highly accurate photometric output can be obtained.
なお、スイツチング素子5のオン時間およびそ
のコレクタ電流の大きさは、電流供給回路4のコ
ンデンサ13、抵抗11,12,14,15等の
値を適当に選ぶことにより最適値に設定される。 The on-time of the switching element 5 and the magnitude of its collector current are set to optimal values by appropriately selecting the values of the capacitor 13, resistors 11, 12, 14, 15, etc. of the current supply circuit 4.
以上述べたように、本考案によれば、光起電力
素子と対数変換素子との接続点に半導体素子を通
じて電流を流し、所定時間のあと測光開始前に、
上記電流の供給をスイツチング素子により遮断す
ると共に、このスイツチング素子のオフ時に上記
半導体素子の両端子間を同電位になるようにして
いるので、測光開始後は測光に関する電流の他
は、いかなる微弱電流も測光回路の入力側に流れ
ることなく、測光動作の立上りが早く行なわれる
と共に、被写体光に相応した正確な測光が行なわ
れて高精度の測光出力を得ることができる等の優
れた効果を発揮する。 As described above, according to the present invention, a current is caused to flow through the semiconductor element at the connection point between the photovoltaic element and the logarithmic conversion element, and after a predetermined period of time, before starting photometry,
The supply of the above-mentioned current is cut off by the switching element, and when the switching element is turned off, both terminals of the above-mentioned semiconductor element are made to have the same potential, so that after the start of photometry, there is no weak current other than the current related to photometry. The light does not flow to the input side of the photometry circuit, and the photometry operation starts up quickly, and the photometry is performed accurately according to the subject light, resulting in excellent effects such as being able to obtain highly accurate photometry output. do.
図は、本考案の一実施例を示す、カメラの測光
回路の電気回路図である。
1……光起電力素子、2……対数変換素子、3
……演算増幅器、4……電流供給回路(電流供給
手段)、5……スイツチング素子、6……半導体
素子、7……等電位回路(等電位手段)。
The figure is an electrical circuit diagram of a photometric circuit of a camera, showing an embodiment of the present invention. 1... Photovoltaic element, 2... Logarithmic conversion element, 3
... operational amplifier, 4 ... current supply circuit (current supply means), 5 ... switching element, 6 ... semiconductor element, 7 ... equipotential circuit (equal potential means).
Claims (1)
を発生する光起電力素子と、この光起電力素子に
流れる光電流を対数圧縮して電圧値に変換する対
数変換素子とを演算増幅器に接続したカメラの測
光回路において、 上記光起電力素子と対数変換素子との接続点に
一端が接続された半導体素子と、 この半導体素子の他端に接続されたスイツチン
グ素子と、 このスイツチング素子がオン状態のとき、同ス
イツチング素子および上記半導体素子を通じて上
記光起電力素子と対数変換素子との接続点に電流
を供給する電流供給手段と、 上記スイツチング素子がオフ状態のとき、上記
半導体素子の他端の電位を上記光起電力素子と対
数変換素子との接続点の電位に等しくする等電位
手段と、 を具備してなるカメラの測光回路。[Claims for Utility Model Registration] A photovoltaic element that receives subject light and generates a photocurrent according to its brightness, and a photovoltaic element that logarithmically compresses the photocurrent flowing through the photovoltaic element and converts it into a voltage value. A photometric circuit for a camera in which a logarithmic conversion element is connected to an operational amplifier includes a semiconductor element whose one end is connected to the connection point between the photovoltaic element and the logarithmic conversion element, and a switching element connected to the other end of the semiconductor element. a current supply means for supplying current to a connection point between the photovoltaic element and the logarithmic conversion element through the switching element and the semiconductor element when the switching element is in the on state; and equipotential means for making the potential at the other end of the semiconductor element equal to the potential at the connection point between the photovoltaic element and the logarithmic conversion element.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9774881U JPS584036U (en) | 1981-07-01 | 1981-07-01 | Camera photometry circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9774881U JPS584036U (en) | 1981-07-01 | 1981-07-01 | Camera photometry circuit |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS584036U JPS584036U (en) | 1983-01-11 |
JPS6142094Y2 true JPS6142094Y2 (en) | 1986-11-29 |
Family
ID=29892532
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP9774881U Granted JPS584036U (en) | 1981-07-01 | 1981-07-01 | Camera photometry circuit |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS584036U (en) |
-
1981
- 1981-07-01 JP JP9774881U patent/JPS584036U/en active Granted
Also Published As
Publication number | Publication date |
---|---|
JPS584036U (en) | 1983-01-11 |
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