JP3540752B2 - Imaging device - Google Patents

Description

上記表１について若干の注釈を加えると、
(1) スチル撮影時のケース１は従来の電子スチルカメラにおける機能順位で、合焦動作が完了しないと記録できないようになっている。これに対しケース２は、合焦動作完了前でも記録され得るものである。
【００３０】
(2) ムービ撮影については後記図３による動作説明で詳述するが、ケース２はムービ撮影なので、記録動作中にときどき第１モードになっても画質に大きな問題を生じないとする。また、ケース３は上記ケース２より若干画質を優先する。更に、ケース４は画質を最優先とするが、非記録時（ＥＶＦ）では若干の画質低下を許容する。
【００３１】
そこで本発明の基本思想は、上記表１に示す記録、ＡＦ等カメラの各動作状態の優先度に応じて、カメラの走査モードを適宜コントロールしようとするものである。次に、実施形態を説明する。
【００３２】
図１は、本発明の一実施形態を示す撮像装置のブロック構成図である。
【００３３】
これは、切換えによりムービ記録可能な電子スチルカメラの要部で、イメージャとしては、インターライン転送ＣＣＤをフィールド蓄積方式で用いることとする。
【００３４】
撮影レンズ１を透過した被写体像は、インターライン転送型ＣＣＤ２の受光部を形成する各フォトダイオード面上に結像されて光電変換される。同ＣＣＤ２は、このＣＣＤ２を駆動するドライバ回路を含むＳＳＧ（同期信号発生器）４から供給される各種のパルス信号により、その蓄積電荷をインターレース読出しあるいはノンインターレース読出しされる。同ＳＳＧ４の動作は、この処理装置全体の動作シーケンスを司るシステムコントローラ５により制御される。
【００３５】
ＣＣＤ２からの出力信号は、電気信号処理回路であるプロセス回路３に入力されて信号処理され、被写体像を記録する記録系８、被写体像をモニタするＥＶＦ７、イメージャＡＦのためのコントラスト情報を検出するＡＦコントラスト検出回路６、およびＴＶモニタ，プリンタ等の外部機器に信号を出力する外部出力端９等に供給される。この記録系８としては、電子スチルカメラの場合にはスチルビデオフロッピを使った静止画記録装置であるが、デジタル記録のときは固体メモリカードが用いられる。また、ビデオムービーの場合にはＶＴＲのデッキ部が対応する。
【００３６】
上記外部出力端９には、システムコントローラ５からフレーム記録可能信号（以下、ＦＲ可能信号と呼称する）が送出されるようになっていて、このＦＲ可能信号は、後述するようにプロセス回路３から出力されている信号がフレーム記録が可能か否かを論理レベルのＨ／Ｌの組合せで出力するものである。
【００３７】
さて、インターレース読出しとノンインターレース読出しを切換える際、このプロセス系の処理方式によっては、単純に上記ＳＳＧ４からＣＣＤ２へ供給される駆動パルスを切換えるだけでは色分離回路等の動作が正常に行われない場合もある。このような場合、当然それに対応してＳＳＧ４からこのプロセス回路３に供給されている制御パルスも各事情に合わせて切換える必要があるが、これについては本発明の本質ではないのでここでの詳細な説明を省略する。
【００３８】
上記プロセス回路３から出力されたビデオ信号が入力されるＡＦコントラスト検出回路６では、例えば電気的なフィルタ等を用いてビデオ信号中からコントラスト情報を抽出し、画像中のどの範囲からコントラスト情報をとってくるかというフォーカスエリアの処理を行って、システムコントローラ５に供給する。すると、システムコントローラ５はこのようなフィールド毎のコントラスト情報に基づき、レンズドライバ１０を介して撮影レンズ１を繰り出しまたは繰り込みし、これに対応して得られるコントラスト情報の変化を見ながら撮影レンズ１を合焦点に駆動する所謂山登り動作を行う。
【００３９】
このように構成された本実施形態の動作を図２，図３のタイムチャートに基づいて以下に説明する。
【００４０】
図２は、電子スチルカメラにおけるスチルモードの典型的なタイムチャートで、インターレースモードとノンインターレースモードとがどのように切換えられるかを示している。なお、ここで用いられるトリガスイッチは、その半押し操作で１段目レリーズスイッチがオンするとＡＦ，ＡＥ動作が行われると共に、記録のためのスタンバイ動作、つまりフロッピディスクを用いたスチルカメラにおけるスピンドルモータの立上げ等が行われる。次に、トリガスイッチを全押し操作すると、２段目レリーズスイッチがオンして実際の記録動作が開始される。なお、この実施形態では、レリーズ釦の半押し操作を２回、従って１段目レリーズスイッチのオンが１１と２１と２回行われ、これに応動してＡＦ動作も１２と２２と２回行われるとしている。
【００４１】
時刻ｔ０でスタートする１段目レリーズスイッチのオン１１に応じて、ＡＦ動作１２が時刻ｔ１で開始される。これと共にＥＶＦ表示１３および外部出力オン１４が同時に行われるが、これら両動作は一連の撮影動作が終了するまで続行される。この場合前記基本概念で説明したように、上記ＡＦ，ＥＶＦ，外部出力の各動作のうちではＡＦ動作が一番重要なので、このＡＦ動作を確実に行えるような走査モード、つまりノンインターレースモード１５が選択され、また、ＦＲ可能信号は“Ｌ”レベル１６に設定される。
【００４２】
ここで、ＦＲ可能信号について説明すると、この信号が外部出力端９（図１参照）を介して外部機器に向け送出されると、外部機器側では、このＦＲ可能信号を受信してその論理レベルを選べることにより“Ｈ”レベルならインターレースモードであると、また“Ｌ”レベルならノンインターレースモードであるとそれぞれ認識する。これによって専用の外部機器の表示モードや記録モードを直接コントロールできる。あるいは、専用機器でない例えばプリンタ等を用いる場合でも、プリンタは通常リモコン端子を有しているので、そのリモコン端子を使って記録する場合に、そのリモコン信号に対してこの信号でゲートをかける等により、実質的にその外部機器での記録動作をインターレース時だけに限定することができる。これは、必ずしも自動的である必要はなく、例えばこの信号に従って表示を行い、人間がそれを監視して記録のタイミングを決定するようにしてもよい。
【００４３】
時刻ｔ２でＡＦ動作１２が終了すると、ＥＶＦ表示１３と外部出力１４のみが引続いて行われることになるが、これら両動作は、本来インターレースモードが望ましい。そこで、走査モードをノンインターレースモード１５からインターレースモード１７に戻すと共に、ＦＲ可能信号を“Ｌ”レベル１６から“Ｈ”レベル１８に変更する。従って、外部機器側でこのＦＲ可能信号が“Ｈ”レベルになったことを検出すると、例えばプリンタ等の外部機器の場合、高精度なフレーム記録を行うことができる。
【００４４】
時刻ｔ３でレリーズ釦の２回目の半押し操作に応動して、２回目の１段目レリーズスイッチのオン２１が行われると、時刻ｔ４でＡＦ動作２２が再び実行される。このとき、ＥＶＦと外部出力は共にオンされているが前述したようにＡＦ動作が優先するので、走査モードをノンインターレースモード２３に設定すると共に、ＦＲ可能信号を“Ｌ”レベル２４にする。この走査モードとＦＲ可能信号とは、時刻ｔ５でＡＦ動作２２が終了すれば、上記１回目のときと同じように、インターレースモード２５と“Ｈ”レベル２６とにそれぞれ戻される。
【００４５】
時刻ｔ６でレリーズ釦が全押し操作され２段目レリーズスイッチのオン２７が行われると、時刻ｔ７で記録動作２８が行われる。この記録動作は実線２５で示すように通常インターレースモードで行われ、特にフレーム記録の場合には、必ずインターレース走査にしなければならない。
【００４６】
しかしながら、連写で被写体の微妙な動きを追尾する、あるいは画像処理上の特殊目的で記録する場合、インターレース読出しでは連続して記録されたフィールドが奇数フィールドから偶数フィールドへ、あるいはこの逆に偶数フィールドから奇数フィールドに切換わるので、走査線のズレが現実には生じて問題になるケースがある。このような場合には、図の波線２９，３０に示すように、記録のためにノンインターレースモードを選択する必要があるが、これは、前記基本概念で説明したように、記録は他の如何なる動作よりも優先するからで、ＥＶＦ表示や外部出力中でもノンインターレース読出しに切換える。しかしながら、上記記録動作２８が終了すれば、上述したようにＥＶＦ動作や外部出力にとってはインターレースモードで走査するのが望ましいのでインターレースモードに復帰することになる。
【００４７】
以上はスチルモードにおける本実施形態の動作である。次にムービモードにおける本実施形態の動作を図３のタイムチャートを参照しながら３つのケースに分けて説明する。
【００４８】
先ず、第１のムービモードを説明する。一般に、ムービモードにおいては、長時間の録画が目的なので、僅かな時間の画質劣化は問題にならない。従ってＡＦ動作はそれ程高速に合焦させる必要はないと考えて、前記基本概念で説明した表１中のムービモードにおけるケース（１）に示したように、高画質のフレーム記録対応のインターレース読出しモードである第１モードのみにし、ＡＦ動作を間欠的サンプリングとする。
【００４９】
この理由を説明すると、インターレースモードで毎フィールドＡＦ情報をとろうとするから、ＡＦにおいてフィールドフリッカが問題になるので、偶数フィールド例えば２フィールド、４フィールド、６フィールド毎に、間欠的にサンプリングしてＡＦするとすれば、インターレースモードでもＡＦ動作にとって何ら妨害にならないからである。
【００５０】
次に、第２のムービモードを説明すると、これはムービモードと雖も合焦動作は少しでも高速に且つ高精度に行いたいという考え方に基づいている。従って、図３に示すように、ＡＦ動作３１が実行されていると、走査モードをノンインターレースモード３２に、またＦＲ可能信号を“Ｌ”レベル３３に設定する。
【００５１】
このように設定しても支障を生じない理由を説明すると、通常行われているＡＦ動作の開始時には、多くは被写体が合焦ポイントから大きく逸脱した大ボケ状態にあるので、高速に且つ連続的にＡＦ動作する必要がある。このためにはノンインターレース走査３２が必要になるが、一度合焦点に達してしまえば、以後のＡＦ動作３４，３５は、可成り間欠的にしか行わない。
【００５２】
従って、通常はインターレースモードで走査しＡＦ時だけノンインターレースモードで走査するようにしても、上述したようにムービでは長時間記録が目的なので、僅かな時間の画質劣化は問題にならないからである。
【００５３】
更に第３のムードモードを説明する。これは上記第１と第２のムードモードを組み合わせたもので、上記図３に示す大ボケ状態からの高速合焦動作３１ではノンインターレースモードと同じである。しかしながら、高速合焦動作３１が終了して待機状態に入れば、以後の間欠的なＡＦ動作３４，３５に対しては、上記第１のムードモードと同じように、走査モードを破線で示すインターレースモード３６，３７に、またＦＲ可能信号をフレーム記録可能な”Ｈ”レベル３８，３９に設定している。即ち、この第３のムービモードではＡＦ動作を高速合焦動作と待機中の間欠動作との２つに分け、高速合焦動作時のみノンインターレースモードで走査するようにしている。
【００５４】
上述の説明は、フィールド蓄積方式のインターライン転送ＣＣＤで実施する場合であるが、本実施形態はこれに限定されることなく、あらゆる種類のイメージャ、例えば撮像管でもビームアパーチャが狭いときには有効な技術思想である。
【００５５】
また、上記実施形態で説明した、カメラにおけるそれぞれの機能の優先度に応じてその走査モードを適宜コントロールしようという概念は、あらゆる種類のイメージャに関して有効であって、例えば固体撮像素子ならＸ−Ｙアドレス方式であれ、あるいはフレームトランスファタイプであれ全てに適用可能である。
【００５６】
更に、上記実施形態では、通常モードとしてフィールド蓄積モードを例にして説明したが、フレーム蓄積モードで動作する系でもフレーム蓄積モードのときと同様の画素（フォトダイオード）だけを使って蓄積時間を半分つまりフィールド単位にする。そして、使わない画素に含まれる余分な電荷を例えばオーバーフロードレイン等に排出する等の特殊な駆動法を用いれば、通常フレーム蓄積モードでインターレース駆動されているものを、感度は半分になるが、ＡＦ動作のためのノンインターレース駆動に切換えることもできる。
【００５７】
【発明の効果】
以上説明したように本発明によれば、撮像素子の出力画像信号を解析して合焦情報を取得するいわゆるイメージャＡＦを有した撮像装置において、撮像素子からの信号読出し方法として、光電変換部の画面の一端から他端への１回の読出し走査に対応する単位読出しを毎回同一方法で繰り返し実行するいわゆるノンインターレース方式を用いることができるようにしたので、イメージャＡＦのコントラスト信号に重畳されるノイズ成分のうち、２フィールド周期成分（フィールドフリッカ）の影響をなくすことができるという顕著な効果が発揮される。
【００５８】
またその際、特に請求項２の発明によれば、光電変換部の全ての画素電荷を出力信号として読み出すように構成したので、感度の低下を生じることが無い。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す撮像装置のブロック構成図である。
【図２】上記図１におけるスチルモードでのタイムチャートである。
【図３】上記図１におけるムービモードでのタイムチャートである。
【図４】インターライン転送ＣＣＤの垂直１列の要部拡大図である。
【図５】上記図４における垂直転送ＣＣＤに印加される各部信号のタイムチャートである。
【図６】走査モードの説明図である。
【図７】基準被写体をインターライン転送ＣＣＤによってフィールド蓄積モードでインターレース読出しするときの説明図である。
【図８】上記図７におけるインターレース読出しとノンインターレース読出しのそれぞれに対するコントラスト情報出力の線図である。
【符号の説明】
４…ＳＳＧ（動作モード自動切換手段）
５…システムコントローラ（動作モード自動切換手段）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an imaging apparatus, and more particularly, to an imaging apparatus that converts a subject image into an electric signal using an imager such as a CCD, processes the signal, and performs AF (autofocus), image recording, and the like.
[0002]
[Prior art]
2. Description of the Related Art Various types of AF devices have been conventionally provided for an AF device for calculating a video signal obtained from a subject image formed on a photoelectric conversion unit such as an imager to obtain a focal point. One type of this type of AF device is a so-called hill-climbing system in which a photographing lens is moved in a direction in which the value indicating the degree of focusing becomes large, and stops when a peak position is detected. There is. This hill-climbing method focuses on the fact that when the image comes into focus, contrast information, which is a high-frequency component in the video signal, increases, and the high-frequency component extracted from the video signal by a band-pass filter or the like is focused on. It is detected as a signal indicating the degree.
[0003]
In order to extract a one-dimensional electric signal from a two-dimensional subject image formed on the imager as the photoelectric conversion means by such an imager AF, for example, in the case of the NTSC system, 525 horizontal scanning lines are extracted by an odd number. An image signal is obtained by interlacing the field and the even field.
[0004]
The actual operation of interlaced reading of the subject image on the imager will be described with reference to FIGS. 4 to 6 taking the field accumulation mode of the interline transfer CCD as an example.
[0005]
FIG. 4 is an enlarged view of the main part of one vertical line of the interline transfer CCD. A four-phase drive vertical transfer CCD 43 is arranged in parallel with the photodiodes 40a, 40b,. Gates XSG1 and XSG2 are connected as shown. Each of the photodiodes 40a, 40b,... Forms a unit pixel on the imager, and is provided one by one corresponding to a horizontal scanning line, and two sections of the vertical transfer CCD 43 are provided for one diode. It is provided correspondingly.
[0006]
In this vertical transfer CCD 43, a fine electrode is adhered on each of the sections numbered 1, 2, 3, and 4 so that the electrode potentials of the sections of the same number can be simultaneously controlled. The electrodes are connected to each other by a vapor-deposited aluminum wiring. When the potential of the fine electrode is set to the “L” level, a potential well is formed below the electrode to accumulate charges.
[0007]
The transfer gate for shifting the signal charges stored in the photodiodes 40a, 40b,... To the respective sections 1, 2, 3, 4, of the vertical transfer CCD 43 is a first gate hatched in FIG. XSG1 and a second gate XSG2 indicated by a white background. When the logic levels of these gates XSG1 and XSG2 are set to "L", the signal charges accumulated in the odd-numbered photodiodes 40a, 41a,... The signal charges accumulated in 41b,... Are respectively transferred to the section 3 of the vertical transfer CCD 43.
[0008]
Then, in the CCD 43, the potential of each section in the CCD channel is sequentially controlled as described later with reference to FIG. 5, so that the odd-numbered fields are accumulated in the odd-numbered photodiodes 40a, 41a,. The signal charges transferred to the section 1 are added to the signal charges transferred to the section 3 after being accumulated in the next even-numbered photodiodes 40b, 41b,... And taken out as an imager output via a horizontal transfer CCD (not shown). It is. On the other hand, in the even field, the signal charges stored in the even-numbered photodiodes 40b, 41b,... And transferred to the section 3 are stored in the next odd-numbered photodiodes 41a, 42a,. And is taken out. The combination of such addition of signal charges is shown in FIG. 4 as 0 for odd fields and E for even fields.
[0009]
Therefore, in interlaced reading in the field accumulation mode of the interline transfer CCD, a combination shift of one horizontal scanning line occurs depending on whether the field is odd or even. This point will be described in detail later in the problem to be solved by the invention.
[0010]
FIG. 5 is a time chart of the signals applied to the vertical transfer CCD 43. Below the horizontal blanking signal HD, the pulse signals XV1 to XV4 applied to the sections 1 to 4 of the CCD 43 are divided into odd and even fields. Are shown separately. If the logic level of the first and second transfer gates XSG1 and XSG2 described below XV4 in the drawing is set to “L” between the times t1 and t2, the data is accumulated by the photodiode during one field period. The transferred charges are transferred to the vertical transfer CCD 43.
[0011]
In the CCD 43, when any one of the logic levels of the pulses XV1, XV2, XV3, and XV4 applied to the sections 1 to 4 is set to "L", as described above, the potential of the area drops, and the charges are accumulated there. Is done. Therefore, for example, in a state where XV1 and XV3 are set to the “L” level to accumulate electric charges, if the potential of XV2 is also set to the “L” level, both electric charges can be mixed.
[0012]
That is, after the signal charge is transferred from the photodiode to the vertical transfer CCD during the charge transfer period from t1 to t2, the applied pulses XV1 to XV4 in the charge mixing period from time t3 to t4 are set to the “L” level. The addition of the accumulated charges can be performed. As a result, the image information of the odd field and the even field can be obtained, so that the interlaced reading can be performed by alternately performing the information, and the non-interlaced reading can be performed by fixing only one of them.
[0013]
FIG. 6 is a diagram for explaining the scanning mode. The interlace driving shown in FIG. 6A is also called normal driving, and odd fields 0 and even fields E forming one frame are alternately shown. On the other hand, in the non-interlace drive of (B), only the odd-numbered field 0 or only the even-numbered field E is continuously displayed. That is, in a mode in which only one of the odd and even read fields is allowed, this may be intermittent rather than continuous. According to the interlace driving, the number of scanning lines is doubled as compared with the non-interlace driving, so that a remarkable improvement in image quality can be expected.
[0014]
[Problems to be solved by the invention]
However, when the interline transfer CCD is interlaced and read in the field accumulation mode, as described with reference to FIG. 4, the odd-numbered signal and the next even-numbered signal are used in the odd-numbered field, and the even-numbered signal is used in the even-numbered field. Since the next odd-numbered signal is added to and read by the transfer unit, a combination shift of one horizontal scanning line occurs depending on the oddness or evenness of the field. Therefore, if this is used for the imager AF, sufficient distance measurement accuracy cannot be obtained. This point will be described in detail with reference to FIGS.
[0015]
FIG. 7 is an explanatory diagram when an image of the reference subject 51 is formed on the imaging surface of the interline transfer CCD and converted into an electric signal, and this is interlaced and read in the field accumulation mode. A3 and areas B1, B2 and B3 of the even field are sequentially read out, respectively. In this case, it is only possible to extract the area, that is, from where to which information is to be taken, only to what extent of the line that comes out in order. The areas B1, B2, and B3 of the even fields are shifted downward by one scanning line from the areas A1, A2, and A3 of the odd fields.
[0016]
Therefore, assuming that the contrast information of the reference subject 51 is KO per scanning line, the contrast information KA and KB in the odd field and the even field are as follows.
[0017]
KA = 3K0
KB = 2K0
That is, when the same subject 51 is imaged by the interline transfer CCD and read out in the field accumulation mode through the interline, the contrast information changes as KA, KB, KA,... As shown in FIG. Field flicker will occur. Note that the normal flicker is a case where the brightness changes periodically, and the above case is also referred to as a flicker as an equivalent. On the other hand, if the non-interlaced readout is performed only on the odd-numbered fields repeatedly, the same contrast information KA can always be obtained as shown in FIG. 8B, so that the field flicker does not occur.
[0018]
Next, the reason why such a field flicker causes a problem in the AF operation will be described. The imager AF referred to as the hill-climbing method operates according to how contrast information changes due to defocusing. When observing a change in contrast information, a periodic component that is not directly related to the movement of the photographing lens is used. If there is, noise will occur and the distance measurement accuracy will decrease. Therefore, in order to obtain contrast information, a constant output without flicker as shown in FIG. 8B is desirable.
[0019]
However, the imager output is supplied to an EVF (Electronic View Finder) display or an external device in addition to the AF operation as well as the recording operation, and is used. In these cases, interlace driving is naturally desirable.
[0020]
Accordingly, an object of the present invention is to provide an imaging apparatus which solves the above-described problem and eliminates the influence of interlace reading which is considered to be a main cause of a two-field periodic component among noise components superimposed on contrast information of an imager AF. It is in.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, a first imaging apparatus according to the present invention includes an imaging device having a two-dimensional photoelectric conversion unit, and a signal reading unit that executes signal reading from the photoelectric conversion unit of the imaging device. An imaging device having: The signal reading means includes: In particular, when the imaging apparatus performs continuous shooting, as a different imaging element driving method when performing normal shooting, The signal reading is performed by repeatedly executing unit reading corresponding to one reading scan from one end to the other end of the screen of the photoelectric conversion unit by the same method each time. I do.
[0022]
In order to achieve the above object, a second imaging device of the present invention is the first imaging device, wherein the imaging device is a charge transfer type solid-state imaging device having a charge transfer path, and the signal reading means is In the above-described unit reading, each pixel charge of the photoelectric conversion unit is added in the charge transfer path, and all pixel charges of the photoelectric conversion unit are read as an output signal. Features.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0024]
First, prior to describing an embodiment of the present invention, a basic concept of the present invention will be described below.
[0025]
In an electronic still camera, a video movie, or the like having a built-in image pickup device, an AF operation, a recording operation (including field recording and frame recording), an EVF display, a video signal output to an external device connected to an external output terminal, and the like are performed. Degrees and properties of requirements for both operation modes of a first mode for obtaining an image signal by interlacing reading of an imager and a second mode for obtaining an image signal by non-interlacing reading of the imager. Are different.
[0026]
That is, the AF operation requires the second mode, the frame recording requires the first mode, and the EVF display and the external output require the first mode, respectively. The second mode may be required only for the purpose.
[0027]
As described above, the requirements for the readout mode possessed by each function are different, but the priority of each function in the camera operation is determined independently. That is, recording in the camera is usually the highest priority, and AF also has a higher priority. On the other hand, in the case of an EVF in which image information is simply monitored, even if the image quality is slightly lowered, the priority may be lowered for a certain time. In addition, the external output is used in various ways, so that the priority becomes higher or lower.
[0028]
This is divided into still photography and movie photography, and the priority of each function is specifically represented by an inequality sign as shown in Table 1 below.
[0029]
[Table 1]

With some remarks about Table 1 above,
(1) Case 1 at the time of still photography is a functional order in a conventional electronic still camera, and cannot be recorded unless a focusing operation is completed. In contrast, Case 2 can be recorded even before the focusing operation is completed.
[0030]
(2) Movie shooting will be described in detail later in the description of the operation with reference to FIG. 3. However, since case 2 is movie shooting, it is assumed that there is no major problem in image quality even if the first mode is occasionally entered during the recording operation. In case 3, image quality is slightly prioritized over case 2. Further, in case 4, the image quality is given the highest priority, but a slight decrease in the image quality is allowed during non-recording (EVF).
[0031]
Therefore, the basic idea of the present invention is to appropriately control the scanning mode of the camera according to the priority of each operation state of the camera such as recording and AF shown in Table 1 above. Next, an embodiment will be described.
[0032]
FIG. 1 is a block diagram of an imaging apparatus according to an embodiment of the present invention.
[0033]
This is a main part of an electronic still camera capable of movie recording by switching, and an interline transfer CCD is used as an imager by a field accumulation method.
[0034]
The subject image transmitted through the photographing lens 1 is formed on each photodiode surface forming a light receiving portion of the interline transfer type CCD 2 and photoelectrically converted. The CCD 2 performs interlaced or non-interlaced reading of its accumulated charge by various pulse signals supplied from an SSG (synchronous signal generator) 4 including a driver circuit for driving the CCD 2. The operation of the SSG 4 is controlled by a system controller 5 that controls the operation sequence of the entire processing apparatus.
[0035]
An output signal from the CCD 2 is input to a process circuit 3 which is an electric signal processing circuit and subjected to signal processing, and a recording system 8 for recording a subject image, an EVF 7 for monitoring a subject image, and contrast information for an imager AF are detected. The signal is supplied to an AF contrast detection circuit 6 and an external output terminal 9 for outputting a signal to an external device such as a TV monitor or a printer. The recording system 8 is a still image recording device using a still video floppy in the case of an electronic still camera, but a solid-state memory card is used in digital recording. In the case of a video movie, the deck of the VTR corresponds to the video movie.
[0036]
A frame recording enable signal (hereinafter, referred to as an FR enable signal) is sent from the system controller 5 to the external output terminal 9, and the FR enable signal is sent from the process circuit 3 as described later. The output signal indicates whether frame recording is possible or not by a combination of logical levels of H / L.
[0037]
When switching between interlaced reading and non-interlaced reading, depending on the processing method of this process system, the operation of the color separation circuit or the like is not normally performed by simply switching the driving pulse supplied from the SSG 4 to the CCD 2. There is also. In such a case, the control pulse supplied from the SSG 4 to the process circuit 3 must be switched in accordance with each situation. However, since this is not the essence of the present invention, the detailed description here will be omitted. Description is omitted.
[0038]
The AF contrast detection circuit 6, to which the video signal output from the process circuit 3 is input, extracts contrast information from the video signal using, for example, an electric filter or the like, and obtains the contrast information from any range in the image. The processing of the focus area of whether or not to come is performed and supplied to the system controller 5. Then, based on such contrast information for each field, the system controller 5 extends or retracts the photographing lens 1 via the lens driver 10 and moves the photographing lens 1 while observing a change in the contrast information obtained corresponding thereto. A so-called hill-climbing operation for driving to a focal point is performed.
[0039]
The operation of the present embodiment thus configured will be described below with reference to the time charts of FIGS.
[0040]
FIG. 2 is a typical time chart of a still mode in an electronic still camera, and shows how an interlace mode and a non-interlace mode are switched. The trigger switch used here performs AF and AE operations when the first-stage release switch is turned on by half-pressing, and also performs a standby operation for recording, that is, a spindle motor in a still camera using a floppy disk. And so on. Next, when the trigger switch is fully pressed, the second-stage release switch is turned on and the actual recording operation is started. In this embodiment, the release button is half-pressed twice, and therefore the first-stage release switch is turned on twice, 11 and 21, and in response to this, the AF operation is also performed twice, 22 and 22 times. It is said to be.
[0041]
The AF operation 12 is started at time t1 in response to the first-stage release switch ON 11 started at time t0. At the same time, the EVF display 13 and the external output ON 14 are simultaneously performed, and both of these operations are continued until a series of photographing operations is completed. In this case, as described in the basic concept, the AF operation is the most important of the AF, EVF, and external output operations. Therefore, the scanning mode in which the AF operation can be reliably performed, that is, the non-interlace mode 15 is used. The selected and the FR enable signal is set to “L” level 16.
[0042]
Here, the FR enable signal will be described. When this signal is sent to an external device via the external output terminal 9 (see FIG. 1), the external device receives the FR enable signal and outputs the logical level of the signal. Can be selected to recognize that the mode is the interlace mode if the level is “H”, and that the mode is the non-interlace mode if the level is “L”. This allows direct control of the display mode and recording mode of the dedicated external device. Alternatively, even when using a non-dedicated device such as a printer, the printer usually has a remote control terminal, and when recording using the remote control terminal, a gate is applied to the remote control signal using this signal. In addition, the recording operation of the external device can be substantially limited to only the time of the interlace. This does not necessarily have to be automatic. For example, display may be performed according to this signal, and a person may monitor the display to determine the timing of recording.
[0043]
When the AF operation 12 is completed at the time t2, only the EVF display 13 and the external output 14 are continuously performed, and both of these operations are originally desirably performed in the interlace mode. Therefore, the scanning mode is returned from the non-interlace mode 15 to the interlace mode 17, and the FR enable signal is changed from the "L" level 16 to the "H" level 18. Therefore, when the external device detects that the FR enable signal has become “H” level, for example, in the case of an external device such as a printer, high-precision frame recording can be performed.
[0044]
At time t3, in response to the second half-press operation of the release button, the second ON operation of the first-stage release switch is performed, and the AF operation 22 is executed again at time t4. At this time, the EVF and the external output are both turned on, but the AF operation has priority as described above. Therefore, the scanning mode is set to the non-interlace mode 23 and the FR enable signal is set to the “L” level 24. When the AF operation 22 ends at time t5, the scanning mode and the FR enable signal are returned to the interlace mode 25 and the “H” level 26, respectively, as in the first time.
[0045]
When the release button is fully pressed at time t6 and the second-stage release switch is turned on 27, a recording operation 28 is performed at time t7. This recording operation is normally performed in the interlaced mode as shown by the solid line 25. In particular, in the case of frame recording, interlaced scanning must be performed.
[0046]
However, when tracking subtle movements of a subject in continuous shooting, or when recording for special purposes in image processing, interlaced readout switches the continuously recorded fields from odd fields to even fields, and vice versa. To the odd field, there is a case where the deviation of the scanning line actually occurs and becomes a problem. In such a case, it is necessary to select the non-interlace mode for recording as shown by the dashed lines 29 and 30 in the figure. This is because recording is performed in any other manner as described in the basic concept. Since the priority is given to the operation, non-interlaced reading is switched even during EVF display or external output. However, when the recording operation 28 is completed, it is desirable to perform the scanning in the interlace mode for the EVF operation and the external output as described above, so that the operation returns to the interlace mode.
[0047]
The above is the operation of the present embodiment in the still mode. Next, the operation of the present embodiment in the movie mode will be described in three cases with reference to the time chart of FIG.
[0048]
First, the first movie mode will be described. In general, in the movie mode, the purpose is to record for a long time, so that the image quality degradation for a short time is not a problem. Therefore, it is considered that the AF operation does not need to be focused at a high speed, and as shown in the case (1) in the movie mode in Table 1 described in the basic concept, the interlaced read mode corresponding to the high-quality frame recording is performed. And the AF operation is intermittent sampling.
[0049]
The reason for this is as follows. Since field AF information is obtained in the interlace mode, field flicker becomes a problem in AF. Therefore, sampling is performed intermittently every even field, for example, every two, four, or six fields. This is because the interfering mode does not hinder the AF operation.
[0050]
Next, the second movie mode will be described. This is based on the idea that the focusing operation is desired to be performed at a high speed and with high accuracy even in the movie mode. Therefore, as shown in FIG. 3, when the AF operation 31 is executed, the scanning mode is set to the non-interlace mode 32 and the FR enable signal is set to the “L” level 33.
[0051]
The reason why such setting does not cause a problem will be explained. At the start of the normal AF operation, since the subject is largely in a large blur state largely deviating from the in-focus point, high-speed and continuous Need to perform the AF operation. For this purpose, non-interlaced scanning 32 is required, but once the focal point is reached, the subsequent AF operations 34 and 35 are performed only intermittently.
[0052]
Therefore, even if scanning is normally performed in the interlaced mode and scanning is performed in the non-interlaced mode only during AF, as described above, the purpose of the movie is to record for a long time, so that slight image quality deterioration does not matter.
[0053]
Further, the third mood mode will be described. This is a combination of the first and second mood modes. The high-speed focusing operation 31 from the large blur state shown in FIG. 3 is the same as the non-interlace mode. However, if the high-speed focusing operation 31 is completed and the camera enters the standby state, the intermittent AF operations 34 and 35 will be interlaced as indicated by the broken line in the scanning mode in the same manner as the first mood mode. The modes 36 and 37 are set, and the FR enable signal is set to "H" levels 38 and 39 at which frame recording is possible. That is, in the third movie mode, the AF operation is divided into a high-speed focusing operation and an intermittent operation during standby, and scanning is performed in the non-interlace mode only during the high-speed focusing operation.
[0054]
Although the above description has been made on the case where the field accumulation type interline transfer CCD is used, the present embodiment is not limited to this, and is effective when any type of imager, for example, an image pickup tube has a narrow beam aperture. It is an idea.
[0055]
Further, the concept of appropriately controlling the scanning mode according to the priority of each function in the camera described in the above embodiment is effective for all types of imagers. It is applicable to all types, whether it is a system or a frame transfer type.
[0056]
Furthermore, in the above embodiment, the field accumulation mode has been described as an example of the normal mode. However, even in a system operating in the frame accumulation mode, the accumulation time is reduced by half using only the same pixels (photodiodes) as in the frame accumulation mode. In other words, it is in field units. Then, if a special driving method such as discharging extra charges included in unused pixels to an overflow drain or the like is used, the sensitivity of half the interlaced driving in the normal frame accumulation mode is reduced. Switching to non-interlace driving for operation is also possible.
[0057]
【The invention's effect】
As described above, according to the present invention, in an imaging apparatus having a so-called imager AF that analyzes an output image signal of an imaging element and obtains focus information, a method of reading out signals from the imaging element includes a photoelectric conversion unit. Since a so-called non-interlace method in which unit reading corresponding to one reading scan from one end to the other end of the screen is repeatedly executed by the same method every time can be used, noise superimposed on the contrast signal of the imager AF can be used. Among the components, a remarkable effect that the influence of a two-field periodic component (field flicker) can be eliminated is exhibited.
[0058]
In this case, in particular, according to the second aspect of the invention, since all the pixel charges of the photoelectric conversion unit are read out as output signals, the sensitivity does not decrease.
[Brief description of the drawings]
FIG. 1 is a block diagram of an imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a time chart in the still mode in FIG. 1;
FIG. 3 is a time chart in the movie mode in FIG. 1;
FIG. 4 is an enlarged view of a main part of one vertical column of an interline transfer CCD.
FIG. 5 is a time chart of various signals applied to the vertical transfer CCD in FIG. 4;
FIG. 6 is an explanatory diagram of a scanning mode.
FIG. 7 is an explanatory diagram when interlaced reading of a reference subject is performed in a field accumulation mode by an interline transfer CCD.
FIG. 8 is a diagram of contrast information output for each of interlaced reading and non-interlaced reading in FIG. 7;
[Explanation of symbols]
4: SSG (operation mode automatic switching means)
5. System controller (operation mode automatic switching means)

Claims (2)

An imaging device comprising: an imaging element having a two-dimensional photoelectric conversion unit; and signal reading means for executing signal reading from the photoelectric conversion unit of the imaging element .
The signal readout unit may perform one-time operation from one end of the screen to the other end of the screen of the photoelectric conversion unit as a method of driving the image sensor different from that during the normal imaging when the imaging apparatus particularly performs continuous imaging . An image pickup apparatus characterized in that the signal readout is performed by repeatedly executing unit readout corresponding to readout scanning every time by the same method. The image pickup device is a charge transfer type solid-state image pickup device having a charge transfer path, and the signal readout unit, at the time of each unit readout, adds pixel charges of the photoelectric conversion unit in the charge transfer path, 2. The imaging device according to claim 1, wherein all the pixel charges of the photoelectric conversion unit are read out as output signals.

Images