JPH04354478A - Automatic focus video camera - Google Patents
Automatic focus video cameraInfo
- Publication number
- JPH04354478A JPH04354478A JP3129957A JP12995791A JPH04354478A JP H04354478 A JPH04354478 A JP H04354478A JP 3129957 A JP3129957 A JP 3129957A JP 12995791 A JP12995791 A JP 12995791A JP H04354478 A JPH04354478 A JP H04354478A
- Authority
- JP
- Japan
- Prior art keywords
- focus
- relative ratio
- focusing
- evaluation value
- focusing operation
- 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
- 238000011156 evaluation Methods 0.000 claims description 56
- 230000003247 decreasing effect Effects 0.000 claims description 6
- 230000007423 decrease Effects 0.000 claims description 2
- 238000004091 panning Methods 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 230000015654 memory Effects 0.000 description 26
- 238000000034 method Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 230000010354 integration Effects 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 4
- 230000009194 climbing Effects 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 238000003384 imaging method Methods 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Landscapes
- Automatic Focus Adjustment (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は、撮像素子から得られる
撮像映像信号を基に、焦点の自動整合を行うビデオカメ
ラに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera that automatically adjusts focus based on a captured video signal obtained from an image sensor.
【０００２】0002
【従来の技術】ビデオカメラのオートフォーカス装置に
おいて、撮像素子からの撮像映像信号自体を焦点制御状
態の評価に用いる方法は、本質的にパララックスが存在
せず、また被写体深度が浅い場合や遠方の被写体に対し
ても、精度よく焦点を合わせられる等優れた点が多い。
しかも、オートフォーカス用の特別なセンサも不要で機
構的にも極めて簡単である。特開昭６４−８７７１号公
報（Ｈ０４Ｎ５／２３２）には、上述の方式のオートフ
ォーカス装置の一例が開示されている。この従来技術は
、撮像輝度信号をカットオフ周波数の異なる２つのＨＰ
Ｆに入力して、カットオフ周波数が高いＨＰＦ出力の１
フィールド分のディジタル積分値を第１焦点評価値Ｖ１
とし、カットオフ周波数がより低いＨＰＦ出力の１フィ
ールド分のディジタル積分値を第２焦点評価値Ｖ２とし
て検出し、いずれか一方の焦点評価値が最大となる位置
にレンズを移動させて停止させ合焦動作を一旦終了し、
この終了時点での各焦点評価値及び両焦点評価値の相対
比（Ｖ１／Ｖ２）を最大焦点評価値及び最大相対比とし
て保持し、これ以降も、焦点評価値及び相対比を検出し
て焦点評価値が最大焦点評価値から所定幅以上変動する
か、あるいは相対比が最大相対比から所定幅以上変動し
たときに、合焦動作の対象としていた被写体が移動して
、実質的に被写体が変化したとして再びレンズを動かし
て合焦動作を再開するように構成されている。ここで、
各焦点評価値及び相対比は、共にレンズが合焦位置にあ
れば最大値をとる特性を利用している。[Prior Art] In an autofocus device for a video camera, the method of using the imaged image signal itself from the image sensor to evaluate the focus control state is essentially parallax-free, and also when the depth of field is shallow or when shooting at a far distance. It has many excellent features such as being able to focus accurately even on subjects such as Furthermore, there is no need for a special sensor for autofocus, and the mechanism is extremely simple. Japanese Unexamined Patent Publication No. 64-8771 (H04N5/232) discloses an example of an autofocus device of the above-mentioned type. In this conventional technology, the imaging luminance signal is divided into two HPs with different cutoff frequencies.
1 of the HPF output with the higher cutoff frequency.
The digital integral value for the field is the first focus evaluation value V1
Then, the digital integral value for one field of the HPF output with the lower cutoff frequency is detected as the second focus evaluation value V2, and the lens is moved to the position where one of the focus evaluation values is maximum and then stopped. End the focusing operation once,
The relative ratio (V1/V2) of each focus evaluation value and both focus evaluation values at this end is held as the maximum focus evaluation value and the maximum relative ratio, and from now on, the focus evaluation value and relative ratio are detected and the focus is When the evaluation value fluctuates by more than a predetermined width from the maximum focus evaluation value, or when the relative ratio fluctuates by more than a predetermined width from the maximum relative ratio, the subject that was the target of the focusing operation moves and the subject actually changes. The camera is configured to move the lens again and restart the focusing operation. here,
Each focus evaluation value and relative ratio both utilize the characteristic that they take the maximum value when the lens is at the in-focus position.
【０００３】0003
【発明が解決しようとする課題】前述の従来例は、被写
体の種類に応じて絶対量が変化する焦点評価値にのみ依
存するのでなく、被写体の種類に関係ない正規化された
相対比によっても被写体の変化を監視しているので、誤
動作を抑えることに有効である。[Problems to be Solved by the Invention] The conventional example described above does not rely only on the focus evaluation value whose absolute value changes depending on the type of subject, but also relies on a normalized relative ratio that is independent of the type of subject. Since changes in the subject are monitored, it is effective in suppressing malfunctions.
【０００４】ところで、近年は迅速な合焦動作を実現す
るために、変倍作用の機能を持ち、焦点距離に応じて結
像位置が変化するレンズ系において、焦点距離を司るレ
ンズ群を移動させて倍率を可変する焦点距離可変手段と
被写体像の撮像素子上への合焦を司るレンズ群を移動さ
せて合焦状態を得る合焦手段から成る所謂インナーフォ
ーカス方式が賞用されている。この方式はピントが大き
くずれていてもレンズの僅かな移動ストロークにより迅
速に合焦状態に到らしめることができる。By the way, in recent years, in order to achieve quick focusing, the lens group that controls the focal length of a lens system that has a variable magnification function and whose imaging position changes depending on the focal length has been moved. A so-called inner focus system is widely used, which is comprised of a focal length variable means for varying the magnification and a focusing means for obtaining a focused state by moving a lens group that focuses the subject image on the image sensor. With this method, even if the focus is largely out of focus, it is possible to quickly bring the lens into focus with a small movement stroke of the lens.
【０００５】従って、このインナーフォーカス方式のよ
うに追従性の良いオートフォーカス装置に、前述の相対
比を用いた被写体変化監視技術を採用すると、被写体の
僅かな移動あるいはカメラ自身の迅速な復帰を伴うパン
ニング等、新たな合焦動作が不要な瞬間的な被写体の変
化に対しても、相対比が急激に落ち込み、結果として停
止状態にあったレンズは再起動して不要な合焦動作が実
行されることになる。Therefore, if the subject change monitoring technology using the above-mentioned relative ratio is adopted in an autofocus device with good followability such as this inner focus method, it will be difficult to detect a change in the subject due to a slight movement of the subject or a quick return of the camera itself. Even when there is a momentary change in the subject that does not require a new focusing operation, such as panning, the relative ratio suddenly drops, and as a result, the lens that was in a stopped state restarts and performs an unnecessary focusing operation. That will happen.
【０００６】[0006]
【課題を解決するための手段】本発明は、撮像素子より
得られる撮像輝度信号の一定期間Ｔにわたる第１高域成
分レベル及び該第１高域成分よりも低域成分をも含む第
２高域成分レベルを夫々第１及び第２焦点評価値として
順次出力する焦点評価値発生手段と、フォーカスレンズ
の撮像素子に対する相対位置を少なくとも該両焦点評価
値のいずれか一方が最大となる位置に到らしめるフォー
カス制御手段と、合焦動作終了直後の相対比を最大相対
値として保持する保持手段と、一定期間Ｔ毎に最新の相
対比と該最大相対比を比較し、該相対比が最大相対比に
比べ所定幅以上に減少したときに減少状態にあると判断
する比較手段と、減少状態が一定期間Ｔよりも長い時間
にわたって継続する場合に合焦動作を再開することを特
徴とする。[Means for Solving the Problems] The present invention provides a first high-frequency component level over a certain period T of an imaging luminance signal obtained from an image sensor, and a second high-frequency component level that also includes a lower frequency component than the first high-frequency component. a focus evaluation value generating means for sequentially outputting the area component levels as first and second focus evaluation values, respectively; and a focus evaluation value generating means that adjusts the relative position of the focus lens with respect to the image sensor until at least one of the two focus evaluation values reaches a maximum. and a holding means that holds the relative ratio immediately after the completion of the focusing operation as the maximum relative value. The present invention is characterized by a comparison means that determines that the lens is in a decreasing state when the ratio decreases by more than a predetermined width, and restarts the focusing operation when the decreasing condition continues for a time longer than a certain period T.
【０００７】[0007]
【作用】本発明は上述の如く構成したので、瞬間的な相
対比の変化は無視され、不要なレンズ駆動が防止される
。[Operation] Since the present invention is constructed as described above, instantaneous changes in relative ratio are ignored, and unnecessary lens driving is prevented.
【０００８】[0008]
【実施例】以下、図面に従い本発明の一実施例について
説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.
【０００９】図１はインナーフォーカス方式のビデオカ
メラに採用されたオートフォーカス回路の回路ブロック
図である。尚、インナーフォーカス方式は、撮像素子か
ら最も離れた最前部のレンズ群を光軸方向に変位させて
合焦動作を為す前玉方式とは異なり、最前部よりも後段
のレンズ群を変位させて合焦動作を為すもので、前玉方
式に比べて僅かな変位量にて迅速な合焦動作が可能とな
る。FIG. 1 is a circuit block diagram of an autofocus circuit employed in an inner focus type video camera. Note that the inner focus method differs from the front lens method, which performs focusing by displacing the frontmost lens group, which is farthest from the image sensor, in the optical axis direction; It performs focusing operations, and enables quick focusing operations with a small amount of displacement compared to the front lens system.
【００１０】図中、レンズ１によって結像された画像は
、固体撮像素子（ＣＣＤ）を含む撮像回路４によって映
像信号になり、この中の輝度信号がエリア抽出回路３０
を経て第１及び第２フィルタ回路１５、１６に入力され
る。エリア抽出回路３０は、図２に示すように輝度信号
より垂直及び水平同期信号を分離する同期分離回路３０
ａと、両同期信号及び固定の発振器出力に基づいて、画
面中央部分に長方形のフォーカスエリアを設定し、この
エリア内の輝度信号のみの通過を許容するゲート開閉信
号を発するゲート制御回路３０ｂと、前記ゲート開閉信
号を受けて輝度信号のフォーカスエリア内に対応する部
分を時分割的に抜き出すゲート回路３０ｃから成る。
従って、エリア抽出回路３０からはフォーカスエリア内
の輝度信号のみが取り出されることになる。In the figure, an image formed by a lens 1 is converted into a video signal by an image pickup circuit 4 including a solid-state image pickup device (CCD), and a luminance signal therein is converted into a video signal by an area extraction circuit 30.
The signal is input to the first and second filter circuits 15 and 16 via the filter circuit 15 and 16. The area extraction circuit 30 includes a sync separation circuit 30 that separates vertical and horizontal sync signals from the luminance signal, as shown in FIG.
a, a gate control circuit 30b that sets a rectangular focus area in the center of the screen based on both synchronization signals and a fixed oscillator output, and issues a gate opening/closing signal that allows only the luminance signal within this area to pass; It consists of a gate circuit 30c that receives the gate opening/closing signal and extracts a portion of the luminance signal corresponding to the focus area in a time-divisional manner. Therefore, only the luminance signal within the focus area is extracted from the area extraction circuit 30.
【００１１】両フィルタ回路１５、１６はどちらも輝度
信号の高周波成分のみを抜き出すハイパスフィルタ（Ｈ
．Ｐ．Ｆ）であるが、第１フィルタ回路１５は第２フィ
ルタ回路１６に比してより高いカットオフ周波数を有し
ている。具体的には、第１フィルタ回路１５のカットオ
フ周波数は６００ＫＨｚ、第２フィルタ回路１６のそれ
は２００ＫＨｚに設定されている。フィルタ回路１５及
び１６の出力は、フォーカスモータ制御回路１０によっ
て制御されるスイッチ回路１７に入力されて、交互に積
算回路１８に入力される。Both filter circuits 15 and 16 are high-pass filters (H
．． P. F) However, the first filter circuit 15 has a higher cutoff frequency than the second filter circuit 16. Specifically, the cutoff frequency of the first filter circuit 15 is set to 600 KHz, and that of the second filter circuit 16 is set to 200 KHz. The outputs of the filter circuits 15 and 16 are input to a switch circuit 17 controlled by a focus motor control circuit 10, and alternately input to an integration circuit 18.
【００１２】積算回路１８は、具体的にはＡ／Ｄ変換器
、加算器、メモリー回路にて構成されるディジタル積分
器であり、入力される第１または第２フィルタ回路１５
、１６出力を順次Ａ／Ｄ変換器にてメモリー回路に保持
される値と加算して、この加算結果にてメモリー回路の
値を更新する様に動作し、１フィールド毎にリセットす
ることにより、１フィールド分の積分値が出力されるこ
とになる。The integration circuit 18 is specifically a digital integrator constituted by an A/D converter, an adder, and a memory circuit.
, 16 outputs are sequentially added to the value held in the memory circuit by the A/D converter, and the value of the memory circuit is updated with the result of this addition, and is reset for each field. The integral value for one field will be output.
【００１３】積算回路１８出力はスイッチ回路１９を経
ることにより、第１、第２メモリ回路２０、２１に夫々
選択的に出力される。即ち、スイッチ回路１９の切換え
は、スイッチ回路１７に同期する様にフォーカスモータ
制御回路１０からの切換信号にて１フィールド毎に為さ
れるので、第１フィルタ回路１５出力を１フィールド分
積分した積分値は第１焦点評価値Ｐ１として第１メモリ
回路２０に、第２フィルタ回路１６出力を１フィールド
分積分した積分値は第２焦点評価値Ｐ２として第２メモ
リ回路２１に記憶される。従って、第１メモリ回路２０
は、奇数フィールドの積分値により１フレーム毎に更新
され、第２メモリ回路２１は、偶数フィールドの積分値
により１フレーム毎に更新される。こうして得られた両
焦点評価値Ｐ１、Ｐ２は、共に演算回路２３に入力され
る。また、同時に第１焦点評価値Ｐ１は、最大値メモリ
６、第１比較器８等に供給され、山登り合焦動作に用い
られる。The output of the integration circuit 18 is selectively outputted to the first and second memory circuits 20 and 21 through a switch circuit 19, respectively. That is, since switching of the switch circuit 19 is performed for each field by a switching signal from the focus motor control circuit 10 in synchronization with the switch circuit 17, the integral obtained by integrating the output of the first filter circuit 15 for one field is The value is stored in the first memory circuit 20 as the first focus evaluation value P1, and the integral value obtained by integrating the output of the second filter circuit 16 for one field is stored in the second memory circuit 21 as the second focus evaluation value P2. Therefore, the first memory circuit 20
is updated every frame by the integral value of the odd field, and the second memory circuit 21 is updated every frame by the integral value of the even field. The bifocal evaluation values P1 and P2 thus obtained are both input to the calculation circuit 23. At the same time, the first focus evaluation value P1 is supplied to the maximum value memory 6, the first comparator 8, etc., and is used for hill climbing focusing operation.
【００１４】次に第１焦点評価値Ｐ１を用いた合焦動作
について説明する。Next, a focusing operation using the first focus evaluation value P1 will be explained.
【００１５】まず合焦動作開始直後に、最初の第１焦点
評価値は最大値メモリ６と初期値メモリ７に保持される
。その後、フォカースモータ制御回路１０は、フォーカ
スモータ３を予め決められた方向に回転させて、レンズ
１を支持するフォーカスリング２を回動させ、レンズ１
を光軸の一方向に変位させ、即ちレンズ１のＣＣＤに対
する相対位置を変化させて第２比較器９出力を監視する
。第２比較器９は、フォーカスモータ駆動後の第１焦点
評価値と初期値メモリ７に保持されている初期評価値を
比較し、その大小を出力する。Immediately after the start of the focusing operation, the initial first focus evaluation value is held in the maximum value memory 6 and the initial value memory 7. Thereafter, the focus motor control circuit 10 rotates the focus motor 3 in a predetermined direction, rotates the focus ring 2 that supports the lens 1, and rotates the focus ring 2 that supports the lens 1.
is displaced in one direction of the optical axis, that is, the relative position of the lens 1 with respect to the CCD is changed, and the output of the second comparator 9 is monitored. The second comparator 9 compares the first focus evaluation value after driving the focus motor with the initial evaluation value held in the initial value memory 7, and outputs the magnitude thereof.
【００１６】フォーカスモータ制御回路１０は、第２比
較器９が大または小という出力を発するまで、最初の方
向にフォーカスモータ３を回転せしめ、現在の焦点評価
値が初期評価値に比べ大であるという出力が為された場
合にはそのままの回動方向を保持し、現在の評価値が初
期評価値よりも所定変動幅以上に小さいと判断された場
合には、フォーカスモータ３の回転方向を逆にして、第
１比較器８出力を監視する。The focus motor control circuit 10 rotates the focus motor 3 in the initial direction until the second comparator 9 outputs a large or small output, and the current focus evaluation value is larger than the initial evaluation value. When this output is made, the rotation direction is maintained as it is, and when it is determined that the current evaluation value is smaller than the initial evaluation value by more than a predetermined fluctuation range, the rotation direction of the focus motor 3 is reversed. and monitors the output of the first comparator 8.
【００１７】第１比較器８は、最大値メモリ６に保持さ
れている今までの最大の第１焦点評価値と現在の評価値
を比較し、現在の焦点評価値が最大値メモリ６の内容に
比べて大きい（第１モード）、予め設定した第１の閾値
幅Ｌ以上に減少した（第２モード）の２通りの比較信号
Ｓ１、Ｓ２を出力する。ここで最大値メモリ６は第１比
較器８出力に基づいて、現在の評価値が最大値メモリ６
の内容よりも大きい場合には、その値が更新され、常に
現在までの焦点評価値の最大値が保持される。The first comparator 8 compares the maximum first focus evaluation value stored in the maximum value memory 6 with the current evaluation value, and determines whether the current focus evaluation value is the content of the maximum value memory 6. Two types of comparison signals S1 and S2 are output: one is larger than the first threshold width L (first mode), and the other is reduced to a preset first threshold width L or more (second mode). Here, the maximum value memory 6 is based on the output of the first comparator 8, and the current evaluation value is the maximum value memory 6.
If the value is larger than the content of , the value is updated and the maximum value of the focus evaluation value up to now is always held.
【００１８】１３はフォーカスレンズ１を支持するフォ
ーカスリング２の位置を指示するフォーカスモータ回転
位置信号を受けて、フォーカスリング位置を記憶するモ
ータ位置メモリであり、最大値メモリ６と同様に第１比
較器８出力に基づいて最大評価値となった場合のフォー
カスリング位置を常時保持する様に更新される。Reference numeral 13 denotes a motor position memory that receives a focus motor rotation position signal indicating the position of the focus ring 2 that supports the focus lens 1 and stores the focus ring position. The focus ring position is updated so as to always maintain the focus ring position when the maximum evaluation value is reached based on the output of the device 8.
【００１９】フォーカスモータ制御回路１０は、第２比
較器９出力に基づいて決定された方向にフォーカスモー
タ３を回転させながら、第１比較器８出力を監視し、焦
点評価値が最大評価値に比べて予め設定された第１の閾
値幅Ｌより小さいという第２モードが指示されると同時
に図５に示す様にフォーカスモータ３は逆転される。こ
のフォーカスモータ３の逆転により、レンズ１の移動方
向は、例えば撮像素子に接近する方向から離間する方向
へ、あるいはその逆に離間する方向から接近する方向に
変わる。The focus motor control circuit 10 monitors the output of the first comparator 8 while rotating the focus motor 3 in the direction determined based on the output of the second comparator 9, and monitors the output of the first comparator 8 until the focus evaluation value reaches the maximum evaluation value. At the same time as the second mode in which the width is smaller than the preset first threshold width L is instructed, the focus motor 3 is reversed as shown in FIG. By reversing the focus motor 3, the direction of movement of the lens 1 changes, for example, from a direction approaching the image sensor to a direction away from it, or vice versa, from a direction away from it to a direction toward it.
【００２０】この逆転後、モータ位置メモリ１３の内容
と、現在のフォーカスモータ回転位置信号とが第３比較
器１４にて比較され、一致した時、即ちフォーカスリン
グ２が焦点評価値が最大となる位置に戻った時に、フォ
ーカスモータ３を停止させる様にフォーカスモータ制御
回路１０は機能する。同時にフォーカスモータ制御回路
１０はレンズ停止信号ＬＳを出力して、合焦動作が終了
する。After this reversal, the contents of the motor position memory 13 and the current focus motor rotational position signal are compared by the third comparator 14, and when they match, that is, the focus ring 2 has the maximum focus evaluation value. The focus motor control circuit 10 functions to stop the focus motor 3 when the focus motor 3 returns to the position. At the same time, the focus motor control circuit 10 outputs a lens stop signal LS, and the focusing operation ends.
【００２１】次に被写体の変化監視動作について説明す
る。Next, the operation of monitoring changes in the subject will be explained.
【００２２】１１はフォーカスモータ制御回路１０によ
る合焦動作が終了して、レンズ停止信号ＬＳが発せられ
ると同時に、その時点での焦点評価値が保持される第４
メモリであり、後段の第４比較器１２でこの第４メモリ
１１の保持内容は最新の焦点評価値と比較され、最新の
焦点評価値が第４メモリ１１の保持内容に比べ、予め設
定された第２の閾値幅以上に小さくなった時に、被写体
が変化したと判断され、Ｈレベルの第１被写体変化信号
Ｙ１がフォーカスモータ制御回路１０に入力される。Reference numeral 11 denotes a fourth point where the focus evaluation value at that point is held when the focusing operation by the focus motor control circuit 10 is completed and the lens stop signal LS is issued.
The contents held in this fourth memory 11 are compared with the latest focus evaluation value in a fourth comparator 12 at the subsequent stage, and the latest focus evaluation value is compared with the contents held in the fourth memory 11 and set in advance. When the width becomes smaller than the second threshold width, it is determined that the subject has changed, and the first subject change signal Y1 at H level is input to the focus motor control circuit 10.
【００２３】演算回路２３は第１、第２メモリ回路２０
、２１における両焦点評価値Ｐ１、Ｐ２の相対比Ｒ、即
ちＲ＝第１焦点評価値Ｐ１／第２焦点評価値Ｐ２を算出
する。この相対比Ｒと被写体のボケ度合（合焦時のレン
ズ位置よりの移動量あるいはズレ量）との関係をグラフ
に示すと、図４に示す様な単調減少特性曲線となる。
尚、図３には同一被写体を撮像している状態でのレンズ
位置と両焦点評価値との関係を示され、第１フィルタ回
路１５はカットオフ周波数が高いために、第１焦点評価
値Ｐ１はレンズ位置に対して急峻な変化を示し、逆に第
２フィルタ回路１６のカットオフ周波数が前者より低い
ために、第２焦点評価値Ｐ２はレンズ位置に対して緩や
かな変化を示す。The arithmetic circuit 23 includes the first and second memory circuits 20
, 21, the relative ratio R of both focus evaluation values P1 and P2, ie, R=first focus evaluation value P1/second focus evaluation value P2, is calculated. If the relationship between this relative ratio R and the degree of blur of the object (the amount of movement or deviation from the lens position at the time of focusing) is shown in a graph, it will be a monotonically decreasing characteristic curve as shown in FIG. Incidentally, FIG. 3 shows the relationship between the lens position and the bifocal evaluation value when the same subject is imaged, and since the first filter circuit 15 has a high cutoff frequency, the first focus evaluation value P1 shows a steep change with respect to the lens position, and conversely, since the cutoff frequency of the second filter circuit 16 is lower than the former, the second focus evaluation value P2 shows a gradual change with respect to the lens position.
【００２４】図４に示す様な単調減少曲線となるのは、
前記相対比Ｒなる状態量が、焦点評価値と同じ様に被写
体の合焦状態（ボケ度合）を表現できる関数値であり、
比率で表現されているため一種の正規化された状態量で
あり、被写体のおかれている環境の影響をあまり受けに
くい性質を有している。例えば、被写体の照度が変化し
た場合に、焦点評価値の絶対値は変化するが、相対比と
しては大きな変化はない。通常、上記の性質は被写体の
種類を問わぬものである故に、この相対比をボケ度合の
パラメータとして使用することが可能となる。[0024] The monotonically decreasing curve as shown in FIG.
The state quantity of the relative ratio R is a function value that can express the in-focus state (degree of blur) of the subject in the same way as the focus evaluation value,
Since it is expressed as a ratio, it is a kind of normalized state quantity, and has the property of being less affected by the environment in which the subject is placed. For example, when the illuminance of the subject changes, the absolute value of the focus evaluation value changes, but the relative ratio does not change significantly. Normally, the above properties are independent of the type of subject, so this relative ratio can be used as a parameter for the degree of blur.
【００２５】演算回路２３から１フィールド毎に得られ
る相対比Ｒの内、モータ停止信号ＬＳが発せられた時点
での値が最大相対比ＲＭＡＸとして第３メモリ２４に保
持され、これ以降はこの最大相対比ＲＭＡＸが第６比較
器２５に供給される。Of the relative ratios R obtained from the arithmetic circuit 23 for each field, the value at the time the motor stop signal LS is issued is held in the third memory 24 as the maximum relative ratio RMAX. The relative ratio RMAX is supplied to a sixth comparator 25.
【００２６】この第６比較器２５は、合焦動作が一旦終
了したことを示すレンズ停止ＬＳが発せられると同時に
比較動作を開始し、演算回路２３にて算出される相対比
Ｒは、上述の様に両焦点評価値Ｐ１、Ｐ２のいずれか一
方が更新される毎に変化するので、１フィールド毎に更
新され、これに応じて第６比較器２５の比較動作も相対
比Ｒが更新される毎に為される。具体的に第６比較器２
５では、順次入力される相対比Ｒに対して｜ＲＭＡＸ−
Ｒ｜＞ＲＭＡＸ／２の条件式が成立するか否か、即ち最
新の相対比Ｒが最大相対比ＲＭＡＸに対してＲＭＡＸの
１／２以上変化したか否かを判別し、上述の条件式が成
り立つ程に相対比Ｒが最大相対比ＲＭＡＸから大きく変
化した場合にのみＨレベルの比較出力を１フィールド間
、変化判定回路２６に発する。The sixth comparator 25 starts the comparison operation at the same time when the lens stop signal LS indicating that the focusing operation is once completed is issued, and the relative ratio R calculated by the arithmetic circuit 23 is calculated by the above-mentioned Since the bifocal evaluation values P1 and P2 change each time either one of them is updated, it is updated every field, and the comparison operation of the sixth comparator 25 also updates the relative ratio R accordingly. It is done every time. Specifically, the sixth comparator 2
5, |RMAX-
It is determined whether the conditional expression R|>RMAX/2 holds true, that is, whether the latest relative ratio R has changed from the maximum relative ratio RMAX by 1/2 or more of RMAX, and the above conditional expression is determined. Only when the relative ratio R changes significantly from the maximum relative ratio RMAX to the extent that it holds true, an H level comparison output is issued to the change determination circuit 26 for one field.
【００２７】変化判定回路２６は、被写体が極く僅かに
移動したり、あるいはカメラ自身を瞬間的にパンニング
させて再び元の位置に戻した場合の様に、一旦合焦位置
に停止させているレンズ１を再起動させて合焦動作を改
めて再開する必要のない場合か、完全に被写体が移動し
て一連の合焦動作を再開させる必要のある場合かを判別
するために、第６比較器２５のＨレベルの出力が少なく
とも１０フィールド間（約１６０ｍｓｅｃ）連続して発
せられるか監視し、被写体が完全に変化して比較出力が
１０フィールド間にわたって連続的にＨレベルになった
時にＨレベルの第２被写体変化信号Ｙ２をフォーカスモ
ータ制御回路１０に発する。The change determination circuit 26 temporarily stops the camera at the in-focus position when the subject moves very slightly or when the camera itself momentarily pans and returns to its original position. In order to determine whether there is no need to restart the lens 1 and restart the focusing operation, or whether the subject has completely moved and it is necessary to restart the series of focusing operations, the sixth comparator is used. Monitor whether the H level output of 25 is continuously emitted for at least 10 fields (approximately 160 msec), and when the subject changes completely and the comparison output becomes H level continuously for 10 fields, the H level output is determined. A second object change signal Y2 is issued to the focus motor control circuit 10.
【００２８】フォーカスモータ制御回路１０はＨレベル
の第１及び第２被写体変化信号Ｙ１、Ｙ２が共に入力さ
れた場合に、再び一連の合焦動作を行う必要がある程に
被写体が変化したと判断し、最大値メモリ６、初期値メ
モリ７、モータ位置メモリ１３、第３及び第４メモリ２
４、１１をリセットした上で、再びフォーカスモータ３
を初期方向に起動して一連の合焦動作を再開する。When the first and second subject change signals Y1 and Y2 at H level are both input, the focus motor control circuit 10 determines that the subject has changed to the extent that it is necessary to perform a series of focusing operations again. Maximum value memory 6, initial value memory 7, motor position memory 13, third and fourth memories 2
After resetting 4 and 11, focus motor 3 again.
is started in the initial direction to restart the series of focusing operations.
【００２９】尚、前述の合焦動作では、第１焦点評価値
Ｐ１を用いて山登り動作を実行したが、これに代えて第
２焦点評価値Ｐ２あるいは両評価値の和を用いてもよい
。また、フォーカスモータ３によりレンズ２を光軸方向
に進退させることに代えてＣＣＤ自体の光軸方向に進退
させてレンズのＣＣＤに対する相対位置を変化させるこ
とも可能である。また、本オートフォーカス回路をイン
ナーフォーカス方式以外のフォーカス方式に採用しても
同様の効果が得られる。更に、前述の合焦動作及び被写
体変化監視動作は、マイクロコンピュータを用いてソフ
トウェア的に処理可能であることは言うまでもない。In the above-mentioned focusing operation, the mountain climbing operation was performed using the first focus evaluation value P1, but the second focus evaluation value P2 or the sum of both evaluation values may be used instead. Further, instead of moving the lens 2 forward and backward in the optical axis direction by the focus motor 3, it is also possible to move the lens 2 forward and backward in the optical axis direction of the CCD itself to change the relative position of the lens with respect to the CCD. Further, the same effect can be obtained even if the present autofocus circuit is employed in a focus method other than the inner focus method. Furthermore, it goes without saying that the above-described focusing operation and object change monitoring operation can be processed by software using a microcomputer.
【００３０】[0030]
【発明の効果】上述の如く本発明によると、合焦動作が
一旦終了した後の被写体の極く僅かな移動や迅速な復帰
を伴うカメラのパンニングの様に、新たな合焦動作を必
要としない撮影状況下において、被写体の移動及び変化
が確実に把握し、合焦動作による不要なレンズ駆動に伴
うハンチングの発生が防止可能となる。[Effects of the Invention] As described above, according to the present invention, a new focusing operation is not required, such as panning of a camera that involves a very slight movement of the subject or a quick return after the focusing operation has been completed. This makes it possible to reliably grasp the movement and changes of the subject under shooting conditions in which the subject is not being photographed, and to prevent the occurrence of hunting due to unnecessary lens driving due to focusing operations.
【図１】本発明の一実施例の回路ブロック図である。FIG. 1 is a circuit block diagram of an embodiment of the present invention.
【図２】要部回路ブロック図である。FIG. 2 is a main circuit block diagram.
【図３】レンズ位置と焦点評価値の関係を示す図である
。FIG. 3 is a diagram showing the relationship between lens position and focus evaluation value.
【図４】ボケ度合と相対比の関係を示す図である。FIG. 4 is a diagram showing the relationship between blur degree and relative ratio.
【図５】山登り合焦動作を説明する図である。FIG. 5 is a diagram illustrating a mountain climbing focusing operation.
１５ 第１フィルタ回路 １６ 第２フィルタ回路 １８ 積算回路 ２３ 演算回路 ２５ 第６比較回路 ２６ 変化判定回路 １０ フォーカスモータ制御回路 15 First filter circuit 16 Second filter circuit 18 Integration circuit 23 Arithmetic circuit 25 Sixth comparison circuit 26 Change determination circuit 10 Focus motor control circuit
Claims (1)
一定期間Ｔにわたる第１高域成分レベル及び該第１高域
成分よりも低域成分をも含む第２高域成分レベルを夫々
第１及び第２焦点評価値として順次出力する焦点評価値
発生手段と、フォーカスレンズの前記撮像素子に対する
相対位置を一旦合焦位置に到らしめる合焦動作を行うフ
ォーカス制御手段と、前記第２焦点評価値に対する前記
第１焦点評価値の相対比を算出する相対比算出手段と、
前記合焦動作終了直後の相対比を最大相対値として保持
する保持手段と、前記一定期間Ｔ毎に最新の相対比と該
最大相対比を比較し、該相対比が該最大相対比に比べ所
定幅以上に減少したときに減少状態にあると判断する比
較手段と、前記減少状態が前記一定期間Ｔよりも長い時
間にわたって継続する場合に前記合焦動作を再開するこ
とを特徴とするオートフォーカスビデオカメラ。1. A first high-frequency component level and a second high-frequency component level that also includes a lower frequency component than the first high-frequency component over a certain period T of an image pickup luminance signal obtained from an image sensor, respectively. a focus evaluation value generation unit that sequentially outputs a second focus evaluation value; a focus control unit that performs a focusing operation to temporarily bring the relative position of the focus lens to the image pickup device to an in-focus position; and the second focus evaluation value. Relative ratio calculation means for calculating a relative ratio of the first focus evaluation value to
a holding means that holds the relative ratio immediately after the completion of the focusing operation as a maximum relative value; and a holding means that compares the latest relative ratio and the maximum relative ratio every certain period T, and determines that the relative ratio is a predetermined value compared to the maximum relative ratio. The autofocus video is characterized in that: a comparing means determines that the focusing operation is in a decreasing state when the decrease is more than a width, and restarting the focusing operation when the decreasing condition continues for a time longer than the certain period T. camera.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3129957A JPH04354478A (en) | 1991-05-31 | 1991-05-31 | Automatic focus video camera |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3129957A JPH04354478A (en) | 1991-05-31 | 1991-05-31 | Automatic focus video camera |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04354478A true JPH04354478A (en) | 1992-12-08 |
Family
ID=15022618
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3129957A Pending JPH04354478A (en) | 1991-05-31 | 1991-05-31 | Automatic focus video camera |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04354478A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002014278A (en) * | 2000-06-30 | 2002-01-18 | Kyocera Corp | Af system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63203069A (en) * | 1987-02-18 | 1988-08-22 | Sanyo Electric Co Ltd | Automatic focusing circuit |
| JPH01284182A (en) * | 1988-05-11 | 1989-11-15 | Sanyo Electric Co Ltd | Automatic focusing video camera |
| JPH03101381A (en) * | 1989-06-13 | 1991-04-26 | Sanyo Electric Co Ltd | Auto-focusing video camera |
-
1991
- 1991-05-31 JP JP3129957A patent/JPH04354478A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63203069A (en) * | 1987-02-18 | 1988-08-22 | Sanyo Electric Co Ltd | Automatic focusing circuit |
| JPH01284182A (en) * | 1988-05-11 | 1989-11-15 | Sanyo Electric Co Ltd | Automatic focusing video camera |
| JPH03101381A (en) * | 1989-06-13 | 1991-04-26 | Sanyo Electric Co Ltd | Auto-focusing video camera |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002014278A (en) * | 2000-06-30 | 2002-01-18 | Kyocera Corp | Af system |
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