JPH02114775A - Automatic focus video camera - Google Patents
Automatic focus video cameraInfo
- Publication number
- JPH02114775A JPH02114775A JP63268985A JP26898588A JPH02114775A JP H02114775 A JPH02114775 A JP H02114775A JP 63268985 A JP63268985 A JP 63268985A JP 26898588 A JP26898588 A JP 26898588A JP H02114775 A JPH02114775 A JP H02114775A
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- Japan
- Prior art keywords
- focus evaluation
- evaluation value
- value
- focus
- threshold
- Prior art date
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Links
- 238000011156 evaluation Methods 0.000 claims abstract description 83
- 230000008859 change Effects 0.000 claims abstract description 12
- 238000001514 detection method Methods 0.000 claims description 7
- 230000007423 decrease Effects 0.000 claims 1
- 230000003247 decreasing effect Effects 0.000 claims 1
- 230000004044 response Effects 0.000 abstract description 3
- 239000006185 dispersion Substances 0.000 abstract 1
- 238000004364 calculation method Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 238000005070 sampling Methods 0.000 description 4
- 230000006870 function Effects 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000007257 malfunction Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 241000251468 Actinopterygii Species 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Landscapes
- Automatic Focus Adjustment (AREA)
Abstract
Description
【発明の詳細な説明】
＝１
（イ） 産業上の利用分野
本発明は、撮像素子から得られる映像信号を基に、焦点
の自動整合を行うビデオカメラのオートフォーカス回路
に関する。DETAILED DESCRIPTION OF THE INVENTION =1 (A) Field of Industrial Application The present invention relates to an autofocus circuit for a video camera that automatically adjusts focus based on a video signal obtained from an image sensor.
（ロ）従来の技術
ビデオカメラのオートフォーカス装置に於て、撮像素子
からの映像信号自体を焦点制御状態の評価に用いる方法
は、木質的にパララ・ソクスが存在ぜず、また被写界・
深度が浅い場合や遠方の被写体に対しても、精度よく焦
点を合わぜられるなど優れた点が多い。しかも、オー
トフォーカス用の特別なセンサも不必要で機構的にも極
めてｕ単である。(b) Conventional technology In the autofocus device of a video camera, the method of using the video signal itself from the image sensor to evaluate the focus control state has no parallax or sox, and
It has many advantages, such as being able to focus accurately even when the depth of field is shallow or for distant subjects. Moreover, O
There is no need for a special sensor for focusing, and the mechanism is extremely simple.
この様なオートフォーカス装置としては、特開昭６３−
１２５９１０号＜Ｇ Ｏ２Ｂ ７／１１）に−例が開示
されている。As such an autofocus device, Japanese Patent Application Laid-open No. 63-
An example is disclosed in No. 125910<G O2B 7/11).
以下にこの従来技術の骨子を第２図、第３図を参照に説
明する。The gist of this prior art will be explained below with reference to FIGS. 2 and 3.
第２図は上記従来技術に関わるオートフォーカス回路の
全体の回路ブロック図である。リンス（１）によって結
像された画像は、撮像素子を含む撮像回路（４）によっ
て映像信号となり、焦点評価値発生回路く焦点評価値検
出手段）（５）に入力される。FIG. 2 is an overall circuit block diagram of an autofocus circuit related to the above-mentioned prior art. The image formed by the rinse (1) is turned into a video signal by an image pickup circuit (4) including an image pickup element, and is input to a focus evaluation value generation circuit (focus evaluation value detection means) (5).
この焦点評価値発生回路（５）は、例えば第３図に示す
ように構成される。撮像映像信号より同期分離回路（５
ａ）によって分離された垂直同期信号及び水平同期信号
は、サンプリングエリアを設定するためにゲート制御回
路（５ｂ）に入力きれる。This focus evaluation value generation circuit (5) is configured as shown in FIG. 3, for example. Synchronization separation circuit (5
The vertical synchronization signal and horizontal synchronization signal separated by a) can be input to a gate control circuit (5b) to set a sampling area.
ゲート制御回路（５ｂ）では、垂直同期信号、水平同期
信号及び固定の発振器出力に基いて、画面中央部分に長
方形のサンプリングエリアを設定し、このサンプリング
エリアの範囲のみの輝度信号の通過を許容するゲート開
閉信号をゲート回路（５Ｃ）に供給する。The gate control circuit (5b) sets a rectangular sampling area in the center of the screen based on the vertical synchronization signal, horizontal synchronization signal, and fixed oscillator output, and allows the luminance signal to pass only within this sampling area. A gate opening/closing signal is supplied to the gate circuit (5C).
ゲート回路（５Ｃ）によってサンプリングエリアの範囲
内に対応する輝度信号が、高域通過フィルタ（ＨＰＦ）
（５ｄ）を通過してその高域成分のみが分離され、次段
の検波回路（５ｅ）にて振幅検波される。この検波出力
はＡ／Ｄ変換回路（５ｆ）にてデシクル値に変換され、
積算回路（５ｇ）でフィールド毎に精算されて、この１
フイ一ルド分の積算値が現フィールドの焦点評価値とし
て出力される。The gate circuit (5C) converts the luminance signal corresponding to the sampling area into a high-pass filter (HPF).
(5d), only its high-frequency components are separated, and the amplitude is detected in the next stage detection circuit (5e). This detection output is converted into a decile value by the A/D conversion circuit (5f),
The integration circuit (5g) calculates this value for each field.
The integrated value for one field is output as the focus evaluation value for the current field.
前述のように構成された焦点評価値発生回路（５）は常
時１フイ一ルド分の焦点評価値を出力する。The focus evaluation value generation circuit (5) configured as described above always outputs the focus evaluation value for one field.
合焦動作開始直後に、最初の焦点評価値は最大値メモリ
く６）と初期値メモリ（７）に保持諮れる。Immediately after the start of the focusing operation, the initial focus evaluation value is stored in the maximum value memory (6) and the initial value memory (7).
その後、フォーカスモータ制御回路（フォーカス制御手
段）（ｌＯ）は、フォーカスモータくフォーカス制御手
段〉（３）を予め決められた方向に回転させて、受光レ
ンズ（１）を支持するフォーカスリング（２）を回動さ
せ、受光レンズ（１）を光軸方向に変位させて撮像素子
との距離を変化きせ第２比較器（９〉出力を監視１−る
。第２比較器（変化認識手段）（９）は、フォーカスモ
ータ駆動後の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、両者が予め第２ｗ４値メ
モリ（１６）に設定跡れた第２ｇ４値（Ｒ２）以上に異
なる時に、その大小を出力する。Thereafter, the focus motor control circuit (focus control means) (lO) rotates the focus motor (focus control means) (3) in a predetermined direction, and rotates the focus ring (2) that supports the light receiving lens (1). The second comparator (9> Monitors the output. The second comparator (change recognition means) 9) compares the focus evaluation value after driving the focus motor with the initial evaluation value held in the initial value memory (7), and calculates the second g4 value ( R2) When the difference is greater than or equal to, output the magnitude.
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
フォーカスモータく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なされた場
合にはそのままの回転方向を保持し、現在の評価値が初
期評価値よりも小才いと判断された場合には、フォーカ
スモータの回転方向を逆にして、第１比較器出力を監視
する。The focus motor control circuit (10) includes a second comparator (9).
) rotates the focus motor 3) in the initial direction until it outputs a large or small output, and if the current focus evaluation value outputs a larger value than the initial evaluation value, the rotation direction remains the same. is held, and if it is determined that the current evaluation value is smaller than the initial evaluation value, the rotation direction of the focus motor is reversed and the output of the first comparator is monitored.
第１比較器（変化認識手段）（８〉は、最大値メモリ（
６）に保持されているこれまでの最大の焦点評価値と現
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）の内容に比べて太きいく第１モード）、予め第１
ＥＲ値メモリ＜１５）に設定した第１閾値（Ｒ１）以上
に減少したく第２モード）の２通りの比較信号（３１）
（Ｓ２）を出力する。ここで最大値メモリ（６〉は第１
比較器（８）の出力に基づいて、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
新詐れ、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 (change recognition means) (8> is the maximum value memory (
The maximum focus evaluation value stored in 6) is compared with the current evaluation value, and the current focus evaluation value is thicker than the contents of the maximum value memory (6). 1st
Two types of comparison signals (31) in which the ER value memory < 15) is set to be lower than the first threshold (R1) (second mode)
(S2) is output. Here, the maximum value memory (6> is the first
Based on the output of the comparator (8), if the current evaluation value is larger than the contents of the maximum value memory (6), the value will be incorrectly updated and the maximum value of the focus evaluation value up to now will always be retained. be done.
（３０）はフォーカスモータ（３）のモータ位置を検出
するモータ位置検出回路で、具体的にはフォーカスモー
フ（３）の回転に応じて出力されるＦＧパルス（例えば
１回転に１００個発生する）をカウントするＵＰ／ＤＯ
ＷＮカウン〃であり、レンズを近点側から遠点側に移動
させる方向にフォーカスモーフく３）が回転する場合（
こは、ＦＧパルスを加算し、逆ブ〕向に回転する場合に
はＦＧパルスを減算する。従って、このカウンタのカウ
ント値自体がモタ位置となり、モータ位置信号として出
力される。(30) is a motor position detection circuit that detects the motor position of the focus motor (3). Specifically, the FG pulse (for example, 100 pulses are generated per rotation) is output according to the rotation of the focus morph (3). UP/DO to count
WN counter〃, and when the focus morph (3) rotates in the direction of moving the lens from the near point side to the far point side (
This adds the FG pulse, and subtracts the FG pulse when rotating in the reverse direction. Therefore, the count value of this counter itself becomes the motor position and is output as a motor position signal.
（１３）はフォーカスレンズ（１）を支持するフォカス
リング（２）を回転駆動するフォーカスモーフ（３）の
回転位置を指示するモータ位置信号を受けて、モータ位
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
値となった場合のモータ（装置を常時保持するように更
新される。尚、フォカスリング（２〉は受光レンズ（１
）を支持し、リング自体の回転により受光レンズ（１）
を光軸方向に進退させることになり、従って、前述のモ
ータ位置は受光レンズ（１）の光軸有向についてのレン
ズ位置に略対応することになる。(13) is a motor position memory that receives a motor position signal instructing the rotational position of a focus morph (3) that rotationally drives a focus ring (2) that supports a focus lens (1), and stores the motor position; Maximum value memory (
6), when the maximum evaluation value is reached based on the output of the first comparator (8), the motor (device is updated to hold the device at all times.The focus ring (2>) is the light receiving lens (1).
), and the receiving lens (1) is rotated by the ring itself.
Therefore, the above-mentioned motor position approximately corresponds to the lens position of the light-receiving lens (1) with respect to the direction of the optical axis.
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フ（
３）を回転きけながら、第１比較器（８）出力を監視し
、焦点評（ｉｌ′Ｉｉ値が最大評価値に比べて予め設定
された第１ｗ！Ｉ値（Ｒ１〉より〕」−さいという第２
モードが指示されると同時にフォーカスモーフく３）を
逆転させる。The focus motor control circuit (10) includes a second comparator (9).
) focus morph in the direction determined based on the output (
3), monitor the output of the first comparator (8) and compare the focus evaluation (il'Ii value with the maximum evaluation value from the preset first w!I value (R1)). The second
At the same time as the mode is instructed, the focus morph (3) is reversed.
このフ１−カスモーク（３）の逆転により、受光レンズ
（１）の移動方向は、例えば撮像素子に接近する功向か
ら離れる方向へ、あるいはその逆に離れる方向から接近
する方向に変わる。Due to this reversal of the lens (3), the moving direction of the light receiving lens (1) changes, for example, from the direction of approaching the imaging element to the direction of moving away from it, or vice versa, from the direction of moving away from it to the direction of approaching it.
この逆転後、モータ位置メモリフ１３）の内容と、現在
のモータ位置信号とが第３比較器（１４）にて比較され
、一致したとき、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ときに、フォーカスモー
フ（３）を停止させるようにフォーカスモータ制御回路
（１０）は機能ｒる。同時にフォーカスモータ制御回路
（１０）は【−ンズ停止信号（ＬＳ）を出力する。尚、
第４区は上述の合焦動作に伴うレンズ位置と焦点評価値
との関係を示ｊ図であり、点（Ｐ）はレンズ（１）の初
期位置を示す。After this reversal, the contents of the motor position memory 13) and the current motor position signal are compared in 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 morph (3) when it returns to the position. At the same time, the focus motor control circuit (10) outputs a lens stop signal (LS). still,
The fourth section is a diagram showing the relationship between the lens position and the focus evaluation value accompanying the above-mentioned focusing operation, and point (P) indicates the initial position of the lens (1).
（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、二の第４
メモリ＜１１〉の保持内容は現在の焦点評価値と比較さ
れ、現在の焦点評価値が第４メモリ（１１）の内容に比
へ、予め第３閾値メモリ（１７）に設定された第３閾値
（Ｒ３”）以上に小きくな−）たときに、被写体が変化
したと判断され、被写体変化信号が出力される。フォー
カスモータ制御回路（１０）はこの信号を受は取ると、
再び合焦動作をやり直して被写体の変化に追随する。(11> is the focus motor control circuit (10>) when the focusing operation is completed and the lens stop signal (LS>) is issued, and at the same time the focus evaluation value at that point is held.
The second fourth comparator (12)
The content held in the memory <11> is compared with the current focus evaluation value, and the current focus evaluation value is compared to the content of the fourth memory (11), and the third threshold value previously set in the third threshold memory (17) is compared. (R3") or more, it is determined that the subject has changed, and a subject change signal is output. When the focus motor control circuit (10) receives this signal,
Repeat the focusing operation to follow changes in the subject.
（ハ〉 発明が解決しようとする課題
前記従来技術にとして示したオートフォーカス装置は、
合焦精度及び広範囲な被写体への対応性には優れでいる
が、以下に示す欠点を有している。(c) Problems to be Solved by the Invention The autofocus device shown in the above prior art is as follows:
Although it has excellent focusing accuracy and adaptability to a wide range of subjects, it has the following drawbacks.
即ち、第１乃至第３閾値（Ｒ１）（Ｒ２＞（Ｒ３）は焦
点評価値の大きさに無関係に予め決められた固定値であ
るため、これらの値を小さく設定すると、焦点評価値が
大きい場合には微少な変動の影響を受け、ピンボケの状
態での合焦動作の終了や煩雑な合焦動作の再開のＷ、囚
となる。また、上述の各個を大きく設定すると、合焦点
を一旦行き過ぎて反転する際の行き過ぎ量の増大や、画
面が変化してもピンボケのままで合焦動作の再起動が為
されないという事態が発生する。That is, since the first to third threshold values (R1) (R2>(R3) are fixed values determined in advance regardless of the magnitude of the focus evaluation value, if these values are set small, the focus evaluation value becomes large. In some cases, the camera may be affected by minute fluctuations, causing the user to end the focusing operation in an out-of-focus state or restart the cumbersome focusing operation.In addition, if each of the above values is set to a large value, the in-focus point may be temporarily This may result in an increase in the amount of overshoot when reversing the focus, or a situation where the focus remains out of focus even if the screen changes and the focusing operation is not restarted.
そこで、各閾値を焦点評価値（Ｆ）を定数（Ｐ）で除し
た値とすることも考えられる。即ち、例えは再起動のた
めの第３閾値（Ｒ３）をＲ３＝ Ｆ／Ｐと指定すると、
この第３閾値（Ｒ３）は第５図の如く右上りの直線（傾
きは１／Ｐ）に沿って焦点評価値に応じて変化すること
になる。Therefore, it is also possible to set each threshold value to a value obtained by dividing the focus evaluation value (F) by a constant (P). That is, for example, if the third threshold (R3) for restarting is specified as R3=F/P,
This third threshold value (R3) changes according to the focus evaluation value along a straight line upward to the right (the slope is 1/P) as shown in FIG.
この様に第３＠値（Ｒ３）を設定すると上述の如く単純
に固定値と設定する場合に比ｌ〜、誤動作を生じにくく
なるが、単純な右上りの直線状の変化では、今度は逆に
焦点評価値が特に高い被写体に一９＝
＝１０＝
関しては第３閾値（Ｒ３）が極端に大きくなり、焦点評
価値が特に低い被写体に関しては極端に小さくなってし
まう。特に焦点評価値がもともと低い被写体ではビンボ
ゲの度合と焦点評価値の直線性が取り難く、通常の被写
体に比べて被写体自体の僅かな動きや、ノイズによるば
らつきにより焦点評価値の変動が大きくなり、極端に小
きい第３閾値（Ｒ３）により誤って再起動がかかってし
まう惧れもある。Setting the third @ value (R3) in this way makes malfunctions less likely to occur compared to simply setting it to a fixed value as described above, but a simple upward-to-the-right linear change will cause the reverse to occur. The third threshold value (R3) becomes extremely large for a subject whose focus evaluation value is particularly high, and becomes extremely small for a subject whose focus evaluation value is particularly low. In particular, for subjects whose focus evaluation value is originally low, it is difficult to maintain linearity between the degree of blurring and the focus evaluation value, and compared to a normal subject, the focus evaluation value will fluctuate more due to slight movements of the subject itself or variations due to noise. There is also a risk that an extremely small third threshold value (R3) may cause an erroneous restart.
（ニ）課題を解決するための手段
本発明は焦点評価値の変化を確認するための閾値を決定
するだめの演算回路を設け、前記従来技術の定数（Ｐ）
をも焦点評価値に応して変化させることを特徴とする。(d) Means for Solving the Problems The present invention provides an arithmetic circuit for determining a threshold value for confirming a change in focus evaluation value, and uses the constant (P) of the prior art.
is also changed according to the focus evaluation value.
（ホ）作用
本発明は上述の如く構成したので焦点評価値が極端に低
い被写体や高い被写体に対しても適切な閾値が得られる
。従って、被写体やその環境によって焦魚評価値の太き
才が異なっても各々に最適な閾値が得られ、常に安定し
たオートフォーカス動作が為される。(E) Function Since the present invention is configured as described above, an appropriate threshold value can be obtained even for subjects with extremely low or high focus evaluation values. Therefore, even if the thickness of the scorched fish evaluation value varies depending on the subject and its environment, the optimal threshold value can be obtained for each, and stable autofocus operation can always be performed.
（へ）実施例
以下、図面に従い本発明の一実施例に一ついて説明する
。(F) Embodiment Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.
尚、図面において第２図及び第３図と同一部分には同一
符号を付して説明を省略する。In the drawings, parts that are the same as those in FIGS. 2 and 3 are designated by the same reference numerals, and explanations thereof will be omitted.
第１図は本実施例におけるオートフォーカス回路の回路
ブロック図である。レンズ〈１〉によって結像された画
像は、撮像素子を含む撮像回路（４）によって撮像映像
信号となり、この中の輝度信号が焦点評価値発生回路（
５〉に入力されて、以下従来例と同様の動作により合焦
動作が実行される。FIG. 1 is a circuit block diagram of an autofocus circuit in this embodiment. The image formed by the lens <1> is turned into a captured video signal by an imaging circuit (4) including an image sensor, and a luminance signal therein is sent to a focus evaluation value generation circuit (
5>, and the focusing operation is thereafter executed in the same manner as in the conventional example.
この時、従来例では予め各メモリ内に設定されテイタ第
１乃至第３ｖＡ値（Ｒ１）（Ｒ２）（Ｒ３）はいずれも
固定値であったが、本実施例では、第ｉＷＡ値（Ｒ１）
は最大値メモリ（６）に格納された最大の焦点評価値よ
り第１演算回路（閾値変更手段）（１５）にて算出され
、同様に第２閾値（Ｒ２）は初期値メモリ（７）に格納
された焦点評価値より第２演算回路（閾値変更手段）（
１６）にて算出され、第３閾値（Ｒ３）は現在の焦点評
価値より第３演算回路（基準値変更手段）（１７）にて
算出される。At this time, in the conventional example, the first to third vA values (R1), (R2, and R3) were set in advance in each memory, and were all fixed values, but in this embodiment, the iWA value (R1)
is calculated by the first calculation circuit (threshold value changing means) (15) from the maximum focus evaluation value stored in the maximum value memory (6), and similarly, the second threshold value (R2) is calculated in the initial value memory (7). The second calculation circuit (threshold value changing means) (
16), and the third threshold value (R3) is calculated by the third calculation circuit (reference value changing means) (17) from the current focus evaluation value.
次に演算回路における演算内容について説明する。現在
の焦点評価値を（Ｆ）とすると第３閾値（Ｒ３）は次の
様に求まる。Next, the contents of the calculation in the calculation circuit will be explained. If the current focus evaluation value is (F), the third threshold (R3) is determined as follows.
焦点評価値（Ｆ）が所定値（Ｃ１）以上の場合、即ち
Ｆ２Ｏ３の時には
Ｒ３−Ｆ／Ｐｔ となり、
焦点評価値（Ｆ）が所定値（Ｃ１）と（Ｃ２）（但し、
ｃｌ ＞Ｃ２）の間の値である場合、即ちＣ２≦Ｆ＜Ｃ
Ｉ の時には
Ｒ３＝Ｆ／Ｐ２ となり、
焦点評価値（Ｆ）が所定値（Ｃ２）より小さい場合であ
る
Ｆ＜Ｃ２の時には
Ｒ３＝ｍａｘ（Ｆ／Ｐ ３ 、 ｂ ）即ち、Ｆ／Ｐ３
か限界値（ｂ）の中の大きい方を第３閾値（Ｒ３）とす
る。When the focus evaluation value (F) is greater than or equal to the predetermined value (C1), that is, when F2O3, it becomes R3-F/Pt, and the focus evaluation value (F) is equal to the predetermined value (C1) and (C2) (however,
cl > C2), that is, C2≦F<C
When I, R3=F/P2, and when F<C2, which is when the focus evaluation value (F) is smaller than the predetermined value (C2), R3=max(F/P3, b), that is, F/P3.
or the limit value (b), whichever is larger is set as the third threshold value (R3).
ここで、所定値（Ｐｉ）（Ｒ２）（Ｒ３）にはＰｔ＞Ｒ
２＞Ｒ３の関係が成り立つため、上述の演算によって決
定された第３閾値（Ｒ３）と焦点評価値（Ｆンとの関係
は第６図に示す様になる。即し、焦点評価値が小さい範
囲では第３閾値（Ｒ３）は傾きが最大の１／Ｐ３の直線
（４０）に沿って中間の範囲では傾きも中間の１／Ｐ２
の直線（４１）に沿って、大きい範囲では傾きが最小の
１／Ｐ１の直線（４２）に沿って変化することになり、
前述の従来例の如く焦点評価値の全ての範囲に亘って固
定値を設定した場合に生じた焦点評価値が大きい（また
は小キレ・）被写体に対して第３閾値（Ｒ３）が４１さ
過ぎる（または大き過ぎる）事態は回避きれる。更に焦
点評価値の全ての範囲に亘って傾きが一定の直線上に変
化する様に設定した場合に生じた、焦点評価値が大きい
くまたは小さい）被写体に対して第３閾値（Ｒ３）が大
き過ぎる（または小き過ぎる）事態は回避される。Here, the predetermined value (Pi) (R2) (R3) is Pt>R
Since the relationship 2>R3 holds true, the relationship between the third threshold (R3) determined by the above calculation and the focus evaluation value (Fn) is as shown in FIG. 6. That is, the focus evaluation value is small. In the range, the third threshold value (R3) is along the straight line (40) with the maximum slope of 1/P3, and in the middle range, the slope is also the middle of 1/P2.
Along the straight line (41), the slope changes along the straight line (42) of 1/P1, which has the minimum slope in a large range,
When a fixed value is set over the entire range of focus evaluation values as in the conventional example described above, the third threshold value (R3) is 41 too high for a subject with a large focus evaluation value (or a small sharpness). (or too big) The situation can be avoided. Furthermore, the third threshold (R3) is large for subjects with large or small focus evaluation values, which occurs when the slope is set to change on a constant straight line over the entire range of focus evaluation values. Too much (or too little) situations are avoided.
尚、定数（Ｐｉ）（Ｒ２）（Ｒ３）は予め実験的に設定
された値であり、限界値（ｂ）は焦点評価値が極端に小
さい時に、これ以上小さくすると誤動作発生率が極めて
大きくなると判断される閾値である。The constants (Pi) (R2) and (R3) are values set experimentally in advance, and the limit value (b) is set when the focus evaluation value is extremely small, and if it is made smaller than this, the malfunction occurrence rate will be extremely high. This is the threshold value for judgment.
第１及び第２閾値（Ｒ１）（Ｒ２＞も前述の第３閾値（
Ｒ３）の算出方法と同様に、最大値メモリ（６）及び初
期値メモリ（７）内に格納された焦点評価値を複数の範
囲に分割し、各範囲に応して傾きが異なる直線に沿って
変化させる様に第１及び第２演算回路（１５）（１６）
にて算出される。The first and second thresholds (R1) (R2> are also the aforementioned third threshold (
Similar to the calculation method of R3), the focus evaluation value stored in the maximum value memory (6) and the initial value memory (7) is divided into multiple ranges, and the calculation is performed along a straight line with a different slope depending on each range. The first and second arithmetic circuits (15) (16)
Calculated by
尚、第１図の回路動作は、マイクロコンピュタによりソ
フトウェア的に容易に処理可能であることは言うまでも
ない。It goes without saying that the circuit operation shown in FIG. 1 can be easily processed by software using a microcomputer.
くト）発明の効果
一ヒ述のごとく本発明によれば、被写体が有する高域成
分の大小によらず、焦点評価値の変化確認のための閾値
や基準値が常に適切な値に設定され、合焦動作途中の合
焦点からの行き過ぎ量のばらつきや合焦動作終了後の被
写体の僅かな動きに応して頻繁に合焦動作が再開きれる
ことが抑えられ、常に安定したオートフォーカス動作が
得られる。H) Effects of the Invention According to the present invention, the threshold and reference value for checking changes in the focus evaluation value are always set to appropriate values, regardless of the magnitude of the high-frequency components of the subject. This prevents frequent restarts of the focusing operation in response to variations in the amount of overshooting from the in-focus point during the focusing operation or slight movements of the subject after the focusing operation has ended, and ensures stable autofocus operation at all times. can get.
第１図、第６図は本発明の一実施例に係り、第１図は回
路ブロック図、第６図は第３＠値の変化を示す図である
。第２図、第３図は従来例の回路ブロック図、第４図は
合焦動作時のレンズ移動に伴う焦点評価値の変化を示す
図、第５図は従来例の第３閾僅の設定方法を示す図であ
る。
（５）・・・焦点評価値発生回路（焦点評価値検出手段
）、（１）・・・リンス゛、（３）・・・フォーカスモ
ーフ（フォーカス制御手段）、＜１０〉・・・フォーカ
スモーフ制御回路（フォーカス制御手段）、（１７）・
・・第３演算回路く基準値変更手段）、く８）、（９）
・・・第１、第２比較器く変化認識手段）、（１５）、
（１６）・・・第１、第２演算回路く閾値変更手段）。1 and 6 relate to an embodiment of the present invention, with FIG. 1 being a circuit block diagram and FIG. 6 being a diagram showing changes in the third @ value. Figures 2 and 3 are circuit block diagrams of the conventional example, Figure 4 is a diagram showing changes in focus evaluation value due to lens movement during focusing operation, and Figure 5 is the setting of the third threshold of the conventional example. FIG. 2 is a diagram illustrating the method. (5)...Focus evaluation value generation circuit (focus evaluation value detection means), (1)...Rinse, (3)...Focus morph (focus control means), <10>...Focus morph control Circuit (focus control means), (17)
...Third arithmetic circuit reference value changing means), 8), (9)
... first and second comparators (change recognition means), (15),
(16)...first and second arithmetic circuit threshold value changing means).
Claims (4)
を焦点評価値として検出する焦点評価値検出手段と、 前記焦点評価値が最大となる位置までレンズを移動させ
て一旦位置固定する合焦動作を実行し、且つ前記合焦動
作完了後に前記焦点評価値が基準値以上変化した場合に
、前記合焦動作を再開するフォーカス制御手段と、 前記基準値を前記焦点評価値の大きさに応じて変化させ
る基準値変更手段とを備え、 該基準値変更手段にて前記基準値を前記焦点評価値の１
／Ｐ倍（Ｐ：実数）に設定し、且つ前記焦点評価値の大
きさによって前記Ｐを変化させることを特徴とするオー
トフォーカスビデオカメラ。(1) Focus evaluation value detection means for detecting the high-frequency component level of a video signal obtained from an image sensor as a focus evaluation value; and a focusing unit for moving a lens to a position where the focus evaluation value is maximum and temporarily fixing the position. a focus control means for executing the focusing operation and restarting the focusing operation when the focus evaluation value changes by a reference value or more after the completion of the focusing operation; and adjusting the reference value according to the magnitude of the focus evaluation value. and a reference value changing means for changing the reference value by one of the focus evaluation values.
/P times (P: real number), and the P is changed depending on the magnitude of the focus evaluation value.
小さくすることを特徴とする請求項１記載のオートフォ
ーカスビデオカメラ。(2) The autofocus video camera according to claim 1, wherein as the focus evaluation value becomes smaller, the P becomes smaller.
を焦点評価値として検出する焦点評価値検出手段と、 前記焦点評価値の変化量が閾値に達した時に、前記焦点
評価値が変化したと認識する変化認識手段と、 該変化認識手段出力に基いて前記焦点評価値が最大とな
る位置にレンズを移動させる合焦動作を実行するフォー
カス制御手段と、 前記閾値を前記焦点評価値の大きさに応じて変化させる
閾値変更手段とを備え、 該閾値変更手段にて前記閾値を前記焦点評価値１／Ｐ倍
（Ｐ：実数）に設定し、且つ前記焦点評価値の大きさに
よって前記Ｐを変化させることを特徴とするオートフォ
ーカスビデオカメラ。(3) a focus evaluation value detection means for detecting a high-frequency component rubel of a video signal obtained from an image sensor as a focus evaluation value; and when the amount of change in the focus evaluation value reaches a threshold, the focus evaluation value changes. a change recognition means for recognizing the change recognition means; a focus control means for performing a focusing operation to move the lens to a position where the focus evaluation value is maximized based on the output of the change recognition means; a threshold value changing means for changing the threshold value according to the magnitude of the focus evaluation value, the threshold value changing means setting the threshold value to 1/P times the focus evaluation value (P: a real number); An autofocus video camera characterized by changing the
小さくすることを特徴とする請求項３記載のオートフォ
ーカスビデオカメラ。(4) The autofocus video camera according to claim 3, wherein the P is decreased as the focus evaluation value decreases.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63268985A JPH0785575B2 (en) | 1988-10-25 | 1988-10-25 | Autofocus video camera |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63268985A JPH0785575B2 (en) | 1988-10-25 | 1988-10-25 | Autofocus video camera |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02114775A true JPH02114775A (en) | 1990-04-26 |
| JPH0785575B2 JPH0785575B2 (en) | 1995-09-13 |
Family
ID=17466055
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63268985A Expired - Lifetime JPH0785575B2 (en) | 1988-10-25 | 1988-10-25 | Autofocus video camera |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0785575B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006215391A (en) * | 2005-02-04 | 2006-08-17 | Fujinon Corp | Autofocus system |
| JP2008197521A (en) * | 2007-02-15 | 2008-08-28 | Sanyo Electric Co Ltd | Video camera |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6086972A (en) * | 1983-10-19 | 1985-05-16 | Hitachi Ltd | Automatic focusing device |
-
1988
- 1988-10-25 JP JP63268985A patent/JPH0785575B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6086972A (en) * | 1983-10-19 | 1985-05-16 | Hitachi Ltd | Automatic focusing device |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006215391A (en) * | 2005-02-04 | 2006-08-17 | Fujinon Corp | Autofocus system |
| JP4573032B2 (en) * | 2005-02-04 | 2010-11-04 | 富士フイルム株式会社 | Auto focus system |
| JP2008197521A (en) * | 2007-02-15 | 2008-08-28 | Sanyo Electric Co Ltd | Video camera |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0785575B2 (en) | 1995-09-13 |
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