JP4333144B2 - Driving method of solid-state imaging device - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は固体撮像素子の駆動方法に関する。詳しくは、デジタルスチールカメラ等に用いられる固体撮像素子の駆動方法に係るものである。
【０００２】
【従来の技術】
２次元イメージセンサを備え、デジタルスチールカメラに用いられる固体撮像素子では、受光部として光電変換を行う受光素子の列方向（縦方向）の配列にそれぞれ隣接対応して、読み出された電荷の垂直方向の転送を行う垂直転送部が配設され、これら複数の垂直転送部には電荷を水平方向に転送する水平転送部が接続して配設されており、受光部から垂直転送部に読み出され、水平転送部に転送された電荷は、水平転送部によって転送され、受光信号として読み出される。
【０００３】
さて、デジタルスチールカメラで撮影を行う場合には、デジタルスチールカメラに取り付けられた液晶画面に被写体を動画として表示し、スチール写真として撮像したい映像を決定した後にスチール写真の撮像を行う。この一連の撮像動作において、動画の撮像時にはスチール写真の撮像時と比較して高速での画像処理が必要とされるために、個々の画素の信号を間引いて画面の表示を行う間引き読み出しモードが用いられることが多く、一方、スチール写真の撮像時には精密な画像を得るために、読み出し時に個々の画素の信号の間引きや混合を行わずに各画素の信号を個々に出力し画面の表示を行う全画素読み出しモードが用いられることが多い。
【０００４】
図４はデジタルスチールカメラにおける間引き読み出しモード及び全画素読み出しモードを説明するための電極構成模式図を示しており、図４中符号（１０１）〜（１４０）は受光部を示し、図４中の「Ｇ」、「Ｒ」及び「Ｂ」の記号はカラーフィルターの「グリーン」、「レッド」及び「ブルー」を示している。
【０００５】
ここで、ＩＳＩＴ方式のデジタルスチールカメラでは、垂直電極（１）１０１に図５中符号Ｖ１で示す駆動パルスを与え、垂直電極（２）１０２に図５中符号Ｖ２で示す駆動パルスを与え、垂直電極（３）１０３に図５中符号Ｖ３で示す駆動パルスを与え、垂直電極（４）１０４に図５中符号Ｖ４で示す駆動パルスを与えることにより、間引き読み出しモード及び全画素読み出しモードを使い分けている。なお、図５では全画素読み出しモードにおいて１フレームを２フィールドで読み出す駆動パルスとしている。
【０００６】
即ち、ＩＳＩＴ方式のデジタルスチールカメラでは、図５中符号Ａで示す間引き読み出しモードから図５中符号Ｂで示す全画素読み出しモードに切り換えた後に、垂直電極（１）のみに読み出し電圧を印加することにより、図５中符号ＳＵＢで示す電子シャッターパルスの最終の立ち上がり時からメカニカルシャッターパルスが閉じるまでの期間である図５中符号Ｃで示す露光期間中に入力光に応じて符号（１０１）〜（１０５）、符号（１１１）〜（１１５）、符号（１２１）〜（１２５）及び符号（１３１）〜（１３５）で示す受光部に蓄積された電荷が垂直転送部に読み出され、垂直転送部に読み出された電荷は水平転送部に転送され、水平転送クロックパルスによって順次水平転送部から出力部へ転送され出力される。その後、垂直電極（３）のみに読み出し電圧を印加することにより符号（１０６）〜（１１０）、符号（１１６）〜（１２０）、符号（１２６）〜（１３０）及び符号（１３６）〜（１４０）で示す受光部に蓄積された電荷が垂直転送部に読み出され、垂直転送部に読み出された電荷は水平転送部に転送され、水平転送クロックパルスによって順次水平転送部から出力部へ転送され出力される。この様にして２回に分けて読み出した信号を重ね合わせることにより固体撮像素子の全画素から電荷を読み出して１つの映像を得ることができる。
【０００７】
ここで、露光中に発生する高輝度の被写体を撮像した時に受光部だけでなく垂直転送部にも電荷が入り込み出力画面上で高輝度の被写体の上下に縦線が発生する現象であるスミアや、通常は受光部から基板へ排出される受光部に蓄積することができない過剰電荷が基板側ではなく垂直転送部へ漏れ込み出力画面上でスミア同様に高輝度被写体の上下に縦線が発生する現象であるブルーミングの成分であるスミア信号やブルーミング信号等の不要電荷は、メカニカルシャッターを閉じた後受光部から電荷を読み出すまでの間に、垂直転送部の高速掃き出し転送による１フィールド以上の空送りを設けることにより掃き出される。
即ち、スミア信号やブルーミング信号等の不要電荷は、図５中符号Ｄで示す期間における高速掃き出し転送によって掃き出される。
【０００８】
【発明が解決しようとする課題】
上記の様に、メカニカルシャッターを閉じた後受光部から電荷を読み出すまでの間に垂直転送部の高速駆動を行うことにより不要電荷を排除することは可能であるものの、低消費電力・高速駆動の固体撮像素子の提供においては垂直転送部の高速駆動を行うことは不都合である。
特に近年の固体撮像素子においてはより一層の高フレームレート化、低消費電力化の要求が高まってきているために、垂直転送部の高速駆動を行うことによる不都合が顕著となる。
【０００９】
本発明は、以上の点に鑑みて創案されたものであって、不要電荷を排除しつつ高フレームレート化及び消費電力の抑制を図ることができる固体撮像素子の駆動方法を提供することを目的とするものである。
【００１０】
【課題を解決するための手段】
上記の目的を達成するために、本発明に係る固体撮像素子の駆動方法は、複数の受光部がマトリクス状に配列され、前記受光部の垂直列毎に設けられた各受光部から電荷を転送する垂直転送部を有する撮像部と、前記垂直転送部より電荷が転送され、転送された電荷を水平方向に転送する水平転送部と、該水平転送部より電荷が転送され、転送された電荷を出力する出力部とを備える固体撮像素子の駆動方法において、露光期間中に、前記垂直転送部に印加する全ての電圧をローレベルにする。
【００１１】
ここで、露光期間中に垂直転送部に印加する全ての電圧をローレベルにすることによって、垂直転送部に対応する部分にポテンシャルの井戸が形成されるのを阻止し、不要電荷が垂直転送部に蓄積することを抑制することができる。
【００１２】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参照しながら説明し、本発明の理解に供する。
【００１３】
図１に本発明を適用した固体撮像素子の駆動方法の一例であるＩＳＩＴ方式のデジタルスチールカメラの駆動方法において固体撮像素子に印加する垂直転送クロックパルスの動作タイミングを示す。
ここで、図１中符号Ｖ１は垂直電極（１）に与える駆動パルスの動作タイミングを示し、図１中符号Ｖ２は垂直電極（２）に与える駆動パルスの動作タイミングを示し、図１中符号Ｖ３は垂直電極（３）に与える駆動パルスの動作タイミングを示し、図１中符号Ｖ４は垂直電極（４）に与える駆動パルスの動作タイミングを示しており、図１中符号ＳＵＢで示す電子シャッターパルスの最終の立ち上がり時からメカニカルシャッターが閉じるまでの期間である図１中符号ａで示す露光期間中に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをローレベル（以下、Ｌレベルと表す）としている。
【００１４】
なお、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスは、間引き読み出しモード時に垂直電極（１）及び垂直電極（３）に読み出し電圧を印加することにより受光部から垂直転送部に読み出された電荷が全て水平転送部に転送され、垂直転送部が空の状態になった直後に一斉にＬレベルとしている。
即ち、読み出し電圧の印加時から垂直転送部に読み出された電荷を全て水平転送部に転送するために必要な図１中符号ｂで示す期間が経過した直後に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスの全てをＬレベルとしている。
【００１５】
また、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスがＬレベルとなった瞬間に露光期間が開始する様に電子シャッターパルスを制御している。
即ち、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスがＬレベルとなった後には電子シャッターパルスはＬレベルに保持している。
【００１６】
ここで、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスを露光期間中にＬレベルとするのは、露光期間中に不要電荷が垂直転送部に蓄積するのを抑制するためであり、露光期間中に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスがＬレベルであれば充分であり、必ずしも垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスの全てを同時にＬレベルとする必要は無いが、固体撮像素子に印加する駆動パルスの制御の容易化という観点を考慮すると、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスの全てを同時にＬレベルとする方が好ましい。
【００１７】
同様に、露光期間中に不要電荷が垂直転送部に蓄積するのを抑制するために、露光期間中に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスがＬレベルであれば充分であり、必ずしも間引き読み出しモード時の読み出し電圧の印加時から、垂直転送部に読み出された電荷を全て水平転送部に転送する期間が経過した直後に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルにする必要は無く、図２で示す様に、間引き読み出しモード時の読み出し電圧印加時から、垂直転送部に読み出された電荷を全て水平転送部に転送する図２中符号ｂで示す期間が経過し、更に図２中符号ｃで示す所定期間が経過した後に、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルにしても良いが、図２中符号ｃで示す期間は垂直転送部の空送りを行っている期間であり、無用の空送り期間を無くすべく、読み出し電圧の印加時から、垂直転送部に読み出された電荷を全て水平転送部に転送する期間が経過した直後に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとする方が好ましい。
【００１８】
更に、上記した様に、露光期間中に不要電荷が垂直転送部に蓄積するのを抑制するために、露光期間中に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスがＬレベルであれば充分であり、必ずしも垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとした瞬間に露光期間を開始する必要は無く、即ち、必ずしも垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとした後、常に電子シャッターパルスをＬレベルに保持する必要は無く、図３で示す様に、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとした後、図３中符号ｄで示す所定期間が経過した後に露光期間を開始しても良い。即ち、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとし、図３中符号ｄで示す所定期間電子シャッターパルスとしてハイレベル及びＬレベルと交互に印加した後に、電子シャッターパルスをＬレベルに保持しても良い。但し、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとし所定期間を経た後に露光期間を開始する必要性は無く、固体撮像素子の駆動シーケンスの容易化の観点を考慮すると、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとした後には電子シャッターパルスをＬレベルに保持し、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルとした瞬間に露光期間を開始する方が好ましい。
【００１９】
さて、本発明を適用したＩＳＩＴ方式のデジタルスチールカメラでは、図１中符号Ａで示す間引き読み出しモードから図１中符号Ｂで示す全画素読み出しモードに切り換えた後に、垂直転送部の高速掃き出し転送を行うこと無く垂直電極（１）のみに読み出し電圧を印加することにより、露光期間中に入力光に応じて符号（１０１）〜（１０５）、符号（１１１）〜（１１５）、符号（１２１）〜（１２５）及び符号（１３１）〜（１３５）で示す受光部に蓄積された電荷が垂直転送部に読み出され、上記した従来のＩＳＩＴ方式のデジタルスチールカメラと同様に、垂直転送部に読み出された電荷は水平転送部を介して出力部へ転送され出力される。
【００２０】
次に、垂直転送部（１）のみに読み出し電圧を印加して受光部から垂直転送部及び水平転送部を介して電荷を出力部へ転送し出力する間に垂直転送部に蓄積した不要電荷の掃き出すために、垂直転送部の高速掃き出し転送を行う。
【００２１】
続いて、垂直電極（３）のみに読み出し電圧を印加することにより符号（１０６）〜（１１０）、符号（１１６）〜（１２０）、符号（１２６）〜（１３０）及び符号（１３６）〜（１４０）で示す受光部に蓄積された電荷が垂直転送部に転送され、上記した従来のＩＳＩＴ方式のデジタルスチールカメラと同様に垂直転送部に読み出された電荷は水平転送部を介して出力部へ転送され出力される。
【００２２】
本発明を適用したＩＳＩＴ方式のデジタルスチールカメラの駆動方法では、露光期間中に垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に印加する駆動パルスをＬレベルにすることにより、垂直電極（１）、垂直電極（２）、垂直電極（３）及び垂直電極（４）に対応する部分にポテンシャルの井戸が形成されるのを阻止し、不要電荷が垂直転送部に蓄積することを抑制することができるために、メカニカルシャッターを閉じた後受光部から電荷を読み出すまでの間に、垂直転送部の高速駆動を行うことにより不要電荷を排除する必要が無く、固体撮像素子の高フレームレート化を図ることができる。
更に、メカニカルシャッターを閉じた後受光部から電荷を読み出すまでの間に行う垂直転送部の高速駆動期間を省略できることにより、垂直転送クロックの各位相のオーバーラップ期間を増やすことができ、垂直転送効率の向上を図ることができると共に、固体撮像素子の消費電力を抑制することができる。
また、消費電力の抑制は固体撮像素子の発熱をも抑制することとなり、熱による不要電荷の発生、即ち、暗電流成分の発生を抑制することができる。
【００２３】
【発明の効果】
以上述べてきた如く、本発明の固体撮像素子の駆動方法では、不要電荷を排除しつつ高フレームレート化及び消費電力の抑制を図ることができる。
【図面の簡単な説明】
【図１】本発明を適用した固体撮像素子の駆動方法の一例であるＩＳＩＴ方式のデジタルスチールカメラの駆動方法において固体撮像素子に印加する垂直転送クロックパルスの動作タイミングである。
【図２】図１に示す垂直転送クロックパルスの動作タイミングの変形例を示す動作タイミングである。
【図３】図１に示す垂直転送クロックパルスの動作タイミングの他の変形例を示す動作タイミングである。
【図４】デジタルスチールカメラにおける高速ドラフトモード及びフレーム読み出しモードを説明するための電極構成模式図である。
【図５】従来のＩＳＩＴ方式のデジタルスチールカメラの固体撮像素子に印加する垂直転送クロックパルスの動作タイミングである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for driving a solid-state imaging device. Specifically, the present invention relates to a method for driving a solid-state imaging device used in a digital still camera or the like.
[0002]
[Prior art]
In a solid-state imaging device that includes a two-dimensional image sensor and is used in a digital still camera, the vertical direction of the read electric charge corresponds to the array in the column direction (vertical direction) of the light receiving elements that perform photoelectric conversion as a light receiving unit. A vertical transfer unit for transferring the direction is arranged, and a horizontal transfer unit for transferring charges in the horizontal direction is connected to the plurality of vertical transfer units, and reading is performed from the light receiving unit to the vertical transfer unit. Then, the charges transferred to the horizontal transfer unit are transferred by the horizontal transfer unit and read as a light reception signal.
[0003]
Now, when shooting with a digital still camera, the subject is displayed as a moving image on a liquid crystal screen attached to the digital still camera, and after determining the video to be captured as a still photo, the still photo is captured. In this series of imaging operations, when moving images are captured, image processing is required at a higher speed than when still images are captured. Therefore, a thinning readout mode for thinning out individual pixel signals and displaying a screen is provided. On the other hand, in order to obtain a precise image when taking still pictures, on the other hand, each pixel signal is output individually and displayed on the screen without thinning out or mixing the individual pixel signals at the time of reading. An all-pixel readout mode is often used.
[0004]
FIG. 4 is a schematic diagram of an electrode configuration for explaining the thinning readout mode and all-pixel readout mode in the digital still camera. Reference numerals (101) to (140) in FIG. The symbols “G”, “R”, and “B” indicate “green”, “red”, and “blue” of the color filter.
[0005]
Here, in the digital still camera ISIT method supplies a drive pulse shown in vertical electrodes (1) 101 in FIG. 5, reference numeral V 1, supplies a drive pulse shown in vertical electrodes (2) 102 in FIG. 5, reference numeral V 2 , the vertical electrodes (3) 103 supplies a drive pulse shown in FIG. 5, reference numeral V 3, by applying a drive pulse shown in vertical electrode (4) 104 in FIG. 5, reference numeral V 4, the thinning readout mode and all pixel readout Different modes are used. In FIG. 5, a driving pulse for reading one frame in two fields in the all-pixel reading mode is shown.
[0006]
That is, in the ISIT digital still camera, after switching from the thinning readout mode indicated by symbol A in FIG. 5 to the all pixel readout mode indicated by symbol B in FIG. 5, a readout voltage is applied only to the vertical electrode (1). Accordingly, reference numerals (101) to (101) to (101) to (101) in accordance with the input light during the exposure period indicated by reference numeral C in FIG. 5, which is a period from the last rise of the electronic shutter pulse indicated by reference numeral SUB in FIG. 5 to the closing of the mechanical shutter pulse. 105), the charges (111) to (115), the signs (121) to (125), and the charges (131) to (135) accumulated in the light receiving unit are read out to the vertical transfer unit, and the vertical transfer unit The charges read out are transferred to the horizontal transfer unit, and sequentially transferred from the horizontal transfer unit to the output unit by the horizontal transfer clock pulse and output. Thereafter, by applying a read voltage only to the vertical electrode (3), reference numerals (106) to (110), reference numerals (116) to (120), reference numerals (126) to (130), and reference numerals (136) to (140). The charge accumulated in the light receiving unit indicated by () is read out to the vertical transfer unit, the charge read out to the vertical transfer unit is transferred to the horizontal transfer unit, and sequentially transferred from the horizontal transfer unit to the output unit by the horizontal transfer clock pulse. And output. In this way, by superimposing the signals read out in two steps, the charge can be read out from all the pixels of the solid-state imaging device to obtain one image.
[0007]
Here, when a high-brightness object that occurs during exposure is imaged, charges enter not only the light receiving unit but also the vertical transfer unit, and vertical lines appear above and below the high-brightness object on the output screen. Normally, excess charges that cannot be accumulated in the light receiving unit discharged from the light receiving unit to the substrate leak into the vertical transfer unit instead of the substrate side, and vertical lines are generated above and below the high-brightness object on the output screen in the same manner as smear. Unwanted charges such as smear signal and blooming signal, which are components of blooming, which is a phenomenon, are fed by one or more fields by high-speed sweep transfer by the vertical transfer unit before the charge is read from the light receiving unit after the mechanical shutter is closed. It is swept out by providing.
That is, unnecessary charges such as a smear signal and a blooming signal are swept out by high-speed sweep transfer during a period indicated by a symbol D in FIG.
[0008]
[Problems to be solved by the invention]
As described above, it is possible to eliminate unnecessary charges by performing high-speed driving of the vertical transfer unit during the period from when the mechanical shutter is closed until the charge is read out from the light-receiving unit, but with low power consumption and high-speed driving. In providing a solid-state image sensor, it is inconvenient to drive the vertical transfer unit at high speed.
In particular, in recent solid-state imaging devices, there is an increasing demand for higher frame rate and lower power consumption, and thus inconvenience due to high-speed driving of the vertical transfer unit becomes significant.
[0009]
The present invention has been made in view of the above points, and an object of the present invention is to provide a driving method of a solid-state imaging device capable of achieving a high frame rate and suppressing power consumption while eliminating unnecessary charges. It is what.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the solid-state imaging device driving method of the present invention, a plurality of light receiving portions are arranged in a matrix and charges are transferred from each light receiving portion provided for each vertical column of the light receiving portions. An image pickup unit having a vertical transfer unit, a charge transferred from the vertical transfer unit, a horizontal transfer unit that transfers the transferred charge in a horizontal direction, a charge transferred from the horizontal transfer unit, and the transferred charge In a solid-state imaging device driving method including an output unit for outputting, all voltages applied to the vertical transfer unit are set to a low level during an exposure period.
[0011]
Here, by setting all the voltages applied to the vertical transfer unit during the exposure period to a low level, formation of a potential well in a portion corresponding to the vertical transfer unit is prevented, and unnecessary charges are generated in the vertical transfer unit. It is possible to suppress accumulation in
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings to provide an understanding of the present invention.
[0013]
FIG. 1 shows an operation timing of a vertical transfer clock pulse applied to a solid-state image sensor in an ISIT digital still camera drive method as an example of a solid-state image sensor drive method to which the present invention is applied.
Here, FIG. 1, reference numeral V 1 was shows the operation timing of the driving pulses applied to the vertical electrodes (1), Figure 1, reference numeral V 2 shows an operation timing of the driving pulses applied to the vertical electrodes (2), in Figure 1 code V 3 shows an operation timing of the driving pulses applied to the vertical electrodes (3), the code V 4 in Fig. 1 shows the operation timing of the driving pulses applied to the vertical electrodes (4), shown in Figure 1 numeral SUB The vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (during the exposure period indicated by symbol a in FIG. 1, which is the period from the last rise of the electronic shutter pulse to the closing of the mechanical shutter. The drive pulse applied to 4) is at a low level (hereinafter referred to as L level).
[0014]
The drive pulses applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) are read voltages to the vertical electrode (1) and the vertical electrode (3) in the thinning-out reading mode. Is applied, all charges read from the light receiving unit to the vertical transfer unit are transferred to the horizontal transfer unit, and immediately after the vertical transfer unit is in an empty state, they are simultaneously set to the L level.
That is, the vertical electrode (1) and the vertical electrode immediately after the period indicated by the symbol b in FIG. 1 necessary for transferring all charges read to the vertical transfer unit from the time of application of the read voltage to the horizontal transfer unit. (2) All the drive pulses applied to the vertical electrode (3) and the vertical electrode (4) are set to L level.
[0015]
Also, the electronic shutter pulse is controlled so that the exposure period starts at the moment when the drive pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3) and the vertical electrode (4) becomes L level. is doing.
That is, after the drive pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) becomes L level, the electronic shutter pulse is held at L level.
[0016]
Here, the drive pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) is set to the L level during the exposure period because unnecessary charges are generated during the exposure period. This is to suppress accumulation in the vertical transfer section, and the drive pulse applied to the vertical electrode (1), vertical electrode (2), vertical electrode (3) and vertical electrode (4) during the exposure period is at the L level. However, all of the drive pulses applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) are not necessarily set to the L level at the same time. Considering the viewpoint of facilitating control of the drive pulse applied to the element, all of the drive pulses applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3) and the vertical electrode (4) are simultaneously set to L. The level is preferred.
[0017]
Similarly, the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) are suppressed during the exposure period in order to prevent unnecessary charges from accumulating in the vertical transfer unit during the exposure period. It is sufficient that the drive pulse to be applied to the L level, and immediately after the period for transferring all the charges read to the vertical transfer unit to the horizontal transfer unit has elapsed since the application of the read voltage in the thinning readout mode. The drive pulses applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) do not need to be at the L level, and as shown in FIG. After the read voltage is applied, a period indicated by a symbol b in FIG. 2 for transferring all charges read to the vertical transfer unit to the horizontal transfer unit elapses, and further after a predetermined period indicated by a symbol c in FIG. Vertical electrode (1), vertical electrode (2) The drive pulse applied to the vertical electrode (3) and the vertical electrode (4) may be set to the L level. However, the period indicated by reference numeral c in FIG. 2 is a period during which the vertical transfer unit is idle, and is unnecessary. In order to eliminate the idle feed period, the vertical electrode (1), the vertical electrode (2), and the vertical electrode are immediately after the period when the charges read to the vertical transfer unit are all transferred to the horizontal transfer unit after the read voltage is applied. It is preferable to set the drive pulse applied to the electrode (3) and the vertical electrode (4) to L level.
[0018]
Furthermore, as described above, the vertical electrode (1), the vertical electrode (2), the vertical electrode (3) and the vertical electrode (1) are suppressed during the exposure period in order to prevent unnecessary charges from accumulating in the vertical transfer unit during the exposure period. It is sufficient if the drive pulse applied to the electrode (4) is L level, and the drive pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) is not necessarily L. It is not necessary to start the exposure period at the moment of setting the level, that is, the drive pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3) and the vertical electrode (4) is always set to the L level. Thereafter, there is no need to always hold the electronic shutter pulse at the L level, and as shown in FIG. 3, driving is applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4). After setting the pulse to the L level, the place indicated by the symbol d in FIG. May be the start of the exposure period after the period has elapsed. That is, the drive pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) is set to the L level, and is set to the high level as the electronic shutter pulse for a predetermined period indicated by d in FIG. The electronic shutter pulse may be held at the L level after being alternately applied to the L level. However, it is not necessary to set the driving pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) to the L level, and then start the exposure period after a predetermined period. Considering the viewpoint of facilitating the drive sequence of the image sensor, the electrons applied after the drive pulses applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) are set to the L level. A method in which the exposure period starts at the moment when the shutter pulse is held at the L level and the driving pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) is set to the L level. Is preferred.
[0019]
Now, in the ISIT digital still camera to which the present invention is applied, after switching from the thinning readout mode indicated by symbol A in FIG. 1 to the all pixel readout mode indicated by symbol B in FIG. By applying a read voltage only to the vertical electrode (1) without performing the steps (101) to (105), (111) to (115), and (121) to (121) according to the input light during the exposure period. Charges accumulated in the light receiving unit indicated by (125) and symbols (131) to (135) are read out to the vertical transfer unit, and read out to the vertical transfer unit in the same manner as the above-described conventional ISIT digital still camera. The charged charges are transferred to the output unit via the horizontal transfer unit and output.
[0020]
Next, the read voltage is applied only to the vertical transfer unit (1), and charges are transferred from the light receiving unit to the output unit via the vertical transfer unit and the horizontal transfer unit and output, and the unnecessary charges accumulated in the vertical transfer unit are output. In order to sweep out, high-speed sweep transfer of the vertical transfer unit is performed.
[0021]
Subsequently, by applying a read voltage only to the vertical electrode (3), reference numerals (106) to (110), reference numerals (116) to (120), reference numerals (126) to (130), and reference numerals (136) to (136) 140) is transferred to the vertical transfer unit, and the charge read to the vertical transfer unit is output to the output unit via the horizontal transfer unit in the same manner as the above-described conventional ISIT digital still camera. To be output.
[0022]
In the driving method of the ISIT digital still camera to which the present invention is applied, a driving pulse applied to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4) is set to L during the exposure period. By setting the level, potential wells are prevented from being formed in portions corresponding to the vertical electrode (1), the vertical electrode (2), the vertical electrode (3), and the vertical electrode (4), and unnecessary charges are vertically generated. Since it is possible to suppress accumulation in the transfer unit, it is not necessary to eliminate unnecessary charges by driving the vertical transfer unit at high speed after the mechanical shutter is closed and before the charge is read from the light receiving unit. Therefore, it is possible to increase the frame rate of the solid-state imaging device.
Furthermore, the overlap period of each phase of the vertical transfer clock can be increased by eliminating the high-speed drive period of the vertical transfer part that is performed after the mechanical shutter is closed and before the charge is read out from the light receiving part. The power consumption of the solid-state image sensor can be suppressed.
Further, suppression of power consumption also suppresses heat generation of the solid-state imaging device, and generation of unnecessary charges due to heat, that is, generation of dark current components can be suppressed.
[0023]
【The invention's effect】
As described above, in the method for driving a solid-state imaging device according to the present invention, it is possible to increase the frame rate and suppress power consumption while eliminating unnecessary charges.
[Brief description of the drawings]
FIG. 1 is an operation timing of a vertical transfer clock pulse applied to a solid-state image sensor in an ISIT digital still camera drive method which is an example of a solid-state image sensor drive method to which the present invention is applied.
FIG. 2 is an operation timing showing a modification of the operation timing of the vertical transfer clock pulse shown in FIG.
FIG. 3 is an operation timing showing another modification of the operation timing of the vertical transfer clock pulse shown in FIG. 1;
FIG. 4 is an electrode configuration schematic diagram for explaining a high-speed draft mode and a frame readout mode in a digital still camera.
FIG. 5 is an operation timing of a vertical transfer clock pulse applied to a solid-state image sensor of a conventional ISIT digital still camera.
Claims (1)
前記垂直転送部より電荷が転送され、転送された電荷を水平方向に転送する水平転送部と、
該水平転送部より電荷が転送され、転送された電荷を出力する出力部とを備える固体撮像素子の駆動方法において、
先のタイミングで前記受光部から前記垂直転送部に読み出された電荷が全て前記水平転送部に転送されたタイミングと略同タイミングで露光期間を開始すると共に、
露光期間中は、前記垂直転送部に印加する全ての電圧をローレベルにする
固体撮像素子の駆動方法。An imaging unit having a plurality of light receiving units arranged in a matrix and having a vertical transfer unit that transfers charges from each light receiving unit provided for each vertical column of the light receiving units;
Charges are transferred from the vertical transfer unit, a horizontal transfer unit for transferring the transferred charge in the horizontal direction,
In a method for driving a solid-state imaging device, the charge is transferred from the horizontal transfer unit, and the output unit outputs the transferred charge.
The exposure period starts at substantially the same timing as the timing at which all the charges read from the light receiving unit to the vertical transfer unit at the previous timing are transferred to the horizontal transfer unit, and
A solid-state imaging device driving method in which all voltages applied to the vertical transfer unit are set to a low level during an exposure period .
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