JPH0529644A - Semiconductor image sensor - Google Patents
Semiconductor image sensorInfo
- Publication number
- JPH0529644A JPH0529644A JP3181247A JP18124791A JPH0529644A JP H0529644 A JPH0529644 A JP H0529644A JP 3181247 A JP3181247 A JP 3181247A JP 18124791 A JP18124791 A JP 18124791A JP H0529644 A JPH0529644 A JP H0529644A
- Authority
- JP
- Japan
- Prior art keywords
- bias voltage
- voltage
- input light
- gate electrode
- emitter
- 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
Landscapes
- Solid State Image Pick-Up Elements (AREA)
- Facsimile Heads (AREA)
- Light Receiving Elements (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、光照射された原稿から
の反射光を受けて電気信号に変換する、半導体イメージ
センサ装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor image sensor device which receives reflected light from a document illuminated with light and converts it into an electric signal.
【０００２】[0002]
【従来の技術】従来のバイポーラ型フォトトランジスタ
を図５に示す。反射光９がフォトトランジスタに入射す
ると、ベース・コレクタ間に電荷が蓄積され、ベース２
からエミッタ１に向かうベース電流が流れる。ベース電
流を直流電流増幅率（以下、ｈFEと称する）倍されたコ
レクタ電流ＩＣがコレクタ５からエミッタ１に向かって
流れる。2. Description of the Related Art FIG. 5 shows a conventional bipolar phototransistor. When the reflected light 9 enters the phototransistor, electric charge is accumulated between the base and the collector, and the base 2
A base current flows from the emitter to the emitter 1. A collector current IC obtained by multiplying the base current by a direct current amplification factor (hereinafter referred to as hFE) flows from the collector 5 toward the emitter 1.
【０００３】半導体イメージセンサ装置の等価回路を図
２に示す。図２においてバイポーラ型フォトトランジス
タＰ１〜Ｐｎは図５のＡ，Ｂを接続端子として組み込ま
れている。アナログスイッチＳ１〜Ｓｎ及びＳＣ１で時
分割された時点で、前記コレクタ電流ＩＣはコンデンサ
Ｃ１に電流として出力される。外部出力としては、コン
デンサＣ１にたまった電荷を出力電圧ＶO1として取り出
す。An equivalent circuit of the semiconductor image sensor device is shown in FIG. In FIG. 2, the bipolar phototransistors P1 to Pn are incorporated with A and B of FIG. 5 as connection terminals. The collector current IC is output as a current to the capacitor C1 when the analog switches S1 to Sn and SC1 are time-divided. As an external output, the electric charge accumulated in the capacitor C1 is taken out as the output voltage VO1.
【０００４】[0004]
【発明が解決しようとする課題】本イメージセンサ装置
で多階調原稿を読み取る場合、入力光量と出力電圧の間
には直線性が要求される。図６に従来のバイポーラトラ
ンジスタのコレクタ電流ーｈFE特性を示す。ｈFEにコレ
クタ電流依存性があり、コレクタ電流の低い領域では、
ｈFEが低く、コレクタ電流が高くなるにしたがって、ｈ
FEが高くなる。図７にこのバイポーラトランジスタをフ
ォトトランジスタとして用いた場合の光電変換特性を示
す。入力光量の低い領域、すなわち、原稿が黒に近い領
域の場合は、増幅率が低く、分解能が低くなり、入力光
量が多くなる、すなわち原稿が白くなるにしたがって、
分解能が高くなってしまうという課題があった。また出
力されたものを人が読み取る場合、反射光量と人の視覚
との関係は直線的ではない。人の目は、黒に近い領域で
は比較認知能力が高く色の違いを感じるが、白くなるに
つれて、区別がつきにくくなる。つまり、黒の領域で多
階分解能を要求されるが、従来のバイポーラフォトトラ
ンジスタでは、黒の領域で分解能が低くなるため、人の
視覚にそぐわないという課題があった。When reading a multi-grayscale original with this image sensor device, linearity is required between the input light quantity and the output voltage. FIG. 6 shows the collector current-hFE characteristics of the conventional bipolar transistor. hFE has collector current dependence, and in the region where the collector current is low,
As hFE decreases and collector current increases, h
FE becomes high. FIG. 7 shows the photoelectric conversion characteristics when this bipolar transistor is used as a phototransistor. In the area where the input light amount is low, that is, in the case where the original is close to black, the amplification factor is low, the resolution is low, and the input light amount is large, that is, the original becomes whiter,
There is a problem that the resolution becomes high. Also, when a person reads the output, the relationship between the amount of reflected light and human vision is not linear. Human eyes have high comparative cognitive ability in a region close to black and feel a difference in color, but as the color becomes whiter, it becomes more difficult to distinguish. That is, multi-level resolution is required in the black region, but the conventional bipolar phototransistor has a problem that the resolution is low in the black region, which is not suitable for human vision.
【０００５】[0005]
【課題を解決するための手段】前記課題を解決するため
に、本発明では、フォトトランジスタのｈFEのコレクタ
（ベース）電流依存性を変化できるようにするため、エ
ミッタ１とベース２との表面接合部にゲート電極を設
け、このゲート電極の電圧を可変電圧発生器に接続する
構成とした。In order to solve the above-mentioned problems, in the present invention, in order to change the collector (base) current dependency of hFE of the phototransistor, the surface junction between the emitter 1 and the base 2 is changed. A gate electrode is provided in the portion and the voltage of the gate electrode is connected to the variable voltage generator.
【０００６】[0006]
【作用】可変電圧発生器の電圧を変えることで、ゲート
電極の電圧を変えることにより、フォトトランジスタの
ｈFE・コレクタ（ベース）電流依存性が変わり、入力光
量と、出力電圧の直線性が制御される。[Function] By changing the voltage of the variable voltage generator, by changing the voltage of the gate electrode, the hFE / collector (base) current dependency of the phototransistor is changed, and the linearity of the input light quantity and the output voltage is controlled. It
【０００７】[0007]
【実施例】以下、本発明を図面に基づいて詳細に説明す
る。図１は本発明によるバイポーラ型フォトトランジス
タの構造を示す断面図である。エミッタ１とベース２の
表面接合部には、ゲート電極３が設けられている。ゲー
ト電極３は可変電圧発生器に接続されバイアス電圧ＶG
がかけられている。図３に本発明によるバイポーラ型フ
ォトトランジスタを用い、バイアス電圧ＶG を変化させ
た場合のコレクタ電流・ｈFE特性を示す。バイアス電圧
ＶG が０の場合、５０のごとく特性を示すが、バイアス
電圧を上げるにしたがって、５１から５３へと特性が変
わってくる。図３における５２の特性を示すバイアス電
圧の場合、ｈFEがコレクタ電流に依存せずに一定の特性
を示している。このバイアス電圧の場合、光電変換特性
は図４の６２に示すように入力光は、微少出力領域から
最大出力領域まで、一定に増幅され、入力光量と出力電
圧の関係は直線となる。また図３の５３の特性を示すバ
イアス電圧の場合、光電変換特性は図４の６３に示すよ
うに微少出力領域では増幅率が高く、最大出力領域では
増幅率が低くなるため、微少出力領域（黒領域）の分解
能が高く、高出力領域（白領域）の分解能が低くなる。The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a bipolar phototransistor according to the present invention. A gate electrode 3 is provided at the surface junction between the emitter 1 and the base 2. The gate electrode 3 is connected to the variable voltage generator, and the bias voltage VG
Is being applied. FIG. 3 shows collector current / hFE characteristics when the bias voltage VG is changed using the bipolar phototransistor according to the present invention. When the bias voltage VG is 0, the characteristic is shown as 50, but the characteristic changes from 51 to 53 as the bias voltage is increased. In the case of the bias voltage having the characteristic of 52 in FIG. 3, hFE shows a constant characteristic without depending on the collector current. In the case of this bias voltage, as shown by 62 in FIG. 4, the photoelectric conversion characteristics are such that the input light is constantly amplified from the minute output region to the maximum output region, and the relationship between the input light amount and the output voltage becomes a straight line. Further, in the case of the bias voltage having the characteristic of 53 in FIG. 3, the photoelectric conversion characteristic has a high amplification factor in the minute output region and a low amplification factor in the maximum output region as indicated by 63 in FIG. The resolution of the black area) is high, and the resolution of the high output area (white area) is low.
【０００８】[0008]
【発明の効果】上記のように、本発明によれば、ｈFEが
コレクタ電流によらず一定のバイアス電圧を選ぶことに
より、直線的光電変換特性が得られ、低コレクタ電流領
域でｈFEの低くならないバイアス電圧を選ぶことにより
黒領域での分解能が低くならない特性が得られる。又、
バイアス電圧の選び方により、所望の光電変換特性が得
られ、必要によって黒領域での分解能がさらに高いフォ
トトランジスタを得ることができる。As described above, according to the present invention, by selecting a constant bias voltage for hFE regardless of the collector current, linear photoelectric conversion characteristics can be obtained, and hFE does not decrease in the low collector current region. By selecting the bias voltage, the characteristic that the resolution in the black region does not decrease can be obtained. or,
A desired photoelectric conversion characteristic can be obtained by selecting a bias voltage, and a phototransistor having a higher resolution in a black region can be obtained if necessary.
【図１】本発明による半導体イメージセンサ装置用フォ
トトランジスタの断面図である。FIG. 1 is a cross-sectional view of a phototransistor for a semiconductor image sensor device according to the present invention.
【図２】半導体イメージセンサ装置の等価回路である。FIG. 2 is an equivalent circuit of a semiconductor image sensor device.
【図３】本発明のフォトトランジスタのｈFEーコレクタ
電流特性を示す図である。FIG. 3 is a diagram showing hFE-collector current characteristics of the phototransistor of the present invention.
【図４】本発明のフォトトランジスタを用いた場合の光
電変換特性を示す図である。FIG. 4 is a diagram showing photoelectric conversion characteristics when the phototransistor of the present invention is used.
【図５】従来の半導体イメージセンサ装置用フォトトラ
ンジスタの断面図である。FIG. 5 is a cross-sectional view of a conventional phototransistor for a semiconductor image sensor device.
【図６】従来のフォトトランジスタのｈFE−コレクタ電
流特性を示す図である。FIG. 6 is a diagram showing hFE-collector current characteristics of a conventional phototransistor.
【図７】従来のフォトトランジスタを用いた場合の光電
変換特性を示す図である。FIG. 7 is a diagram showing photoelectric conversion characteristics when a conventional phototransistor is used.
【符号の説明】 １ エミッタ ２ ベース ３ ゲート ４ バイアス電圧 ５ コレクタ ５０〜５３ ｈFE特性 ６０〜６３ 光電変換特性[Explanation of symbols] 1 emitter 2 base 3 gates 4 Bias voltage 5 collector 50-53 hFE characteristics 60-63 photoelectric conversion characteristics
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 ＦＩ 技術表示箇所 8422−4Ｍ Ｈ０１Ｌ 31/10 Ｅ ─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. 5 Identification code Office reference number FI technical display location 8422-4M H01L 31/10 E
Claims (2)
圧をかけるためのゲート電極を設けたバイポーラ型フォ
トトランジスタを用いることを特徴とする半導体イメー
ジセンサ装置。1. A semiconductor image sensor device comprising a bipolar phototransistor having a gate electrode for applying a bias voltage to a surface of an emitter / base junction.
せることにより直流電流増幅率のコレクタ電流依存性を
変化させ、光電変換特性の直線性を変化させることを特
徴とする請求項１記載の半導体イメージセンサ装置。2. The semiconductor image according to claim 1, wherein the collector current dependency of the direct current amplification factor is changed by changing the bias voltage applied to the gate electrode, and the linearity of the photoelectric conversion characteristic is changed. Sensor device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3181247A JPH0529644A (en) | 1991-07-22 | 1991-07-22 | Semiconductor image sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3181247A JPH0529644A (en) | 1991-07-22 | 1991-07-22 | Semiconductor image sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0529644A true JPH0529644A (en) | 1993-02-05 |
Family
ID=16097370
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3181247A Pending JPH0529644A (en) | 1991-07-22 | 1991-07-22 | Semiconductor image sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0529644A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013187527A (en) * | 2012-03-12 | 2013-09-19 | National Institute Of Advanced Industrial & Technology | Semiconductor device and imaging apparatus |
| US9762822B2 (en) | 2013-09-10 | 2017-09-12 | Ricoh Company, Ltd. | Imaging device including a phototransistor, method of driving the imaging device, and camera including the imaging device |
-
1991
- 1991-07-22 JP JP3181247A patent/JPH0529644A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013187527A (en) * | 2012-03-12 | 2013-09-19 | National Institute Of Advanced Industrial & Technology | Semiconductor device and imaging apparatus |
| US9762822B2 (en) | 2013-09-10 | 2017-09-12 | Ricoh Company, Ltd. | Imaging device including a phototransistor, method of driving the imaging device, and camera including the imaging device |
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