JPH0454769A - Picture reader having focus detecting means - Google Patents
Picture reader having focus detecting meansInfo
- Publication number
- JPH0454769A JPH0454769A JP2164542A JP16454290A JPH0454769A JP H0454769 A JPH0454769 A JP H0454769A JP 2164542 A JP2164542 A JP 2164542A JP 16454290 A JP16454290 A JP 16454290A JP H0454769 A JPH0454769 A JP H0454769A
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- image
- video signal
- imaging lens
- pattern
- imaging
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- 238000001514 detection method Methods 0.000 claims abstract description 27
- 238000003384 imaging method Methods 0.000 claims description 52
- 238000005286 illumination Methods 0.000 claims description 8
- 238000000034 method Methods 0.000 description 13
- 230000003287 optical effect Effects 0.000 description 6
- 238000005259 measurement Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
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Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は焦点検出手段を栃した画像読取装置に関し、特
に原稿台に載置した画像を結像レンズで撮像手段面上に
結像させて読取る際に画像にコントラストがない場合等
に投影手段から原稿台（画像面）上に所定形状のパター
ンを投影し、該パターン像を利用して結像レンズの合焦
状態を検出するようにした焦点検出手段を有した画像読
取装置に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image reading device equipped with a focus detection means, and in particular, an image reading device that focuses an image placed on a document table onto the surface of the image pickup means using an imaging lens. When there is no contrast in the image during reading, a pattern of a predetermined shape is projected from the projection means onto the document table (image surface), and the focused state of the imaging lens is detected using the pattern image. The present invention relates to an image reading device having a focus detection means.
（従来の技術）
従来より原稿台上に載置した画像を照明系で照明し、該
画像を結像レンズにより撮像手段面上に結像させて、こ
のときの撮像手段からの映像信号を利用して該画像情報
を読取るようにした画像読取装置が種々と捷案されてい
る。(Prior art) Conventionally, an illumination system illuminates an image placed on a document table, the image is formed on the surface of an imaging means by an imaging lens, and the video signal from the imaging means at this time is used. Various image reading devices have been devised to read the image information.
このとき結像レンズの結像状態、即ち合焦状態の良否の
一方法として例えば裸像手段から得られる画像情報を表
示装置に表示して観察しながら行う方法がとられている
。At this time, one method for determining the quality of the imaging state of the imaging lens, that is, the focusing state, is to display image information obtained from a naked image means on a display device and perform observation while observing the image information.
この他、結像レンズの合焦状態の良否を判断するのに原
稿台面と結像レンズとの間の距離を三角測距方式を利用
して測距して行う方法がある。この方法は最近写真用カ
メラやビデオカメラ等において使用されている自動焦点
検出装置に多く用いられている。In addition, there is a method of determining whether the focusing state of the imaging lens is good or bad by measuring the distance between the document table surface and the imaging lens using a triangular distance measuring method. This method has recently been widely used in automatic focus detection devices used in photographic cameras, video cameras, and the like.
又、原稿台上の画像情報を読取るようにした画像読取装
置では特に結像レンズによりＣＣＤ等の撮像手段面上に
結像した画像より得られる映像信号の周波数成分を解析
して行う方法、所謂パッシブ方式が用いられている。In addition, in an image reading device that reads image information on a document table, there is a method in which the frequency components of a video signal obtained from an image formed by an imaging lens on the surface of an imaging means such as a CCD are analyzed. A passive method is used.
この方式では一般に映像信号の周波数成分が結像レンズ
が合焦位置より外れているときは低周波成分が多くなり
、合焦位置に近くなる程高周波成分が多くなってくると
いう性質を利用して映像信号の高周波成分が最大値にな
る点を検知して結像レンズの合焦状態を検出している。This method generally takes advantage of the property that the frequency components of the video signal include more low frequency components when the imaging lens is out of focus position, and higher frequency components increase as the imaging lens approaches the focus position. The in-focus state of the imaging lens is detected by detecting the point where the high frequency component of the video signal reaches its maximum value.
（発明が解決しようとする問題点）
原稿台上に載置した画像を結像レンズで撮像手段面上に
結像させる際の結像レンズの合焦状態を検出する方法と
しての前述のパッシブ方式は画像のコントラストが高い
場合は大変有効である。(Problems to be Solved by the Invention) The above-mentioned passive method is a method for detecting the focused state of the imaging lens when the imaging lens forms an image placed on the document table on the surface of the imaging means. is very effective when the contrast of the image is high.
しかしながらこの方式は画像が白紙等のコントラストが
ない場合やコントラストが低い場合等には高周波成分の
解析動作が精度良く作動せず検出精度が低下してくると
いう問題点がある。However, this method has a problem in that when the image has no contrast, such as a blank sheet of paper, or when the contrast is low, the high-frequency component analysis operation does not work accurately and the detection accuracy decreases.
これに対しては画像読取装置側から一定横様のパターン
を原稿台（画像面）上に投影して、結像レンズによるパ
ターン像を解析して合焦状態を検出する方法がある。To solve this problem, there is a method of projecting a constant horizontal pattern onto a document table (image plane) from the image reading device side and analyzing the pattern image by an imaging lens to detect the in-focus state.
しかしながらこの方法は原稿台上の画像が明るい（輝度
が高い）場合には投影パターン像のコントラストが低下
してくる為、高精度な検出が難しいという問題点があっ
た。However, this method has the problem that when the image on the document table is bright (high luminance), the contrast of the projected pattern image decreases, making it difficult to perform highly accurate detection.
本発明は原稿台上に載置した画像を読取る為の結像レン
ズの合焦状態を検出する際、画像のコントラストがなく
、又低い場合でも更に画像が明るい場合であっても、結
像レンズの合焦状態を高精度に検出することができる焦
点検出手段を有した画像読取装置の提供を目的とする。When detecting the focusing state of an imaging lens for reading an image placed on a document table, the present invention detects whether the imaging lens has no contrast, is low, or is even brighter. An object of the present invention is to provide an image reading device having a focus detection means capable of detecting a focus state with high precision.
（問題点を解決するための手段）
本発明の焦点検出手段を有した画像読取装置は照明手段
で照明された原稿台上の画像を結像レンズで撮像手段面
上に結像させて該画像を読取る際、該原稿台面上に線幅
を異にするストライプ状のパターンを投影する投影手段
と、該投影手段により投影されたパターンを該結像レン
ズにより該撮像手段面上に結像させ、該撮像手段で得ら
れる映像信号を利用して該結像レンズの合焦状態を検出
する焦点検出手段と該画像面上の照度を検出する照度検
出手段、そして註照度検出手段からの信号に応じて該投
影手段により該原稿台面上に投影するパターンの明るさ
を！ＩＩ！！する調整手段とを設けたことを特徴として
いる。(Means for Solving the Problems) An image reading device having a focus detection means of the present invention focuses an image on a document table illuminated by an illumination means onto the surface of an imaging means using an imaging lens. a projection means for projecting a striped pattern having different line widths onto the document table surface, and an image of the pattern projected by the projection means on the imaging means surface by the imaging lens; a focus detection means for detecting a focusing state of the imaging lens using a video signal obtained by the imaging means; an illuminance detection means for detecting illuminance on the image plane; The brightness of the pattern projected onto the document table by the projection means! II! ! The present invention is characterized in that it is provided with an adjustment means for adjusting.
（実施例） 第１図は本発明の第１実施例の要部概略図である。(Example) FIG. 1 is a schematic diagram of main parts of a first embodiment of the present invention.
同図において１は原稿台であり、その面上には読取り用
の画像１ａが載置されている０画像１ａはハロゲンラン
プや蛍光灯等の照明手段（不図示）により照明されてい
る。２はアームであり、原稿台ｌの略中心上方部に配置
する投影手段１０１、照度検出手段１０２、そして撮影
手段１０３等を保持している。３は結像レンズであり、
原稿台ｌ上の画像１ａを撮像手段４面上に結像している
。In the figure, reference numeral 1 denotes a document table, and an image 1a on which an image 1a for reading is placed is illuminated by illumination means (not shown) such as a halogen lamp or a fluorescent lamp. Reference numeral 2 denotes an arm that holds a projection means 101, an illumination detection means 102, a photographing means 103, etc., which are arranged substantially above the center of the document table l. 3 is an imaging lens;
The image 1a on the document table l is focused on the surface of the imaging means 4.
撮像手段４は例えばＣＯＤ等から成っている。The imaging means 4 is composed of, for example, a COD or the like.
１０１は投影手段であり、後述する判別手段１６からの
信号に基づいて照明系７により照明された線幅を異にす
るストライイブ状のパターン６を投影レンズ５により原
稿台１面上に投影している。Reference numeral 101 denotes a projection means, which projects a striped pattern 6 of different line widths illuminated by the illumination system 7 onto the document table 1 using the projection lens 5 based on a signal from the discriminating means 16 to be described later. There is.
１０２は照度検出手段であり、受光レンズ８により原稿
台１上の画像１ａからの反射光を受光素子９に集光し、
画像１ａの明るさ（照度）を測定している。Reference numeral 102 denotes an illuminance detection means, which focuses reflected light from the image 1a on the document table 1 onto a light receiving element 9 using a light receiving lens 8;
The brightness (illuminance) of image 1a is being measured.
１０は調整手段であり、照度検出手段１０２からの出力
信号に基づいて投影手段１０１から投影されるパターン
の明るさを調整している。Reference numeral 10 denotes an adjustment means, which adjusts the brightness of the pattern projected from the projection means 101 based on the output signal from the illuminance detection means 102.
本実施例では結像レンズ３の合焦位置の検出は前述した
ように撮像手段４で得られる映像信号の周波数成分を解
析することにより行っている。即ち映像信号の周波数成
分は結像レンズ３が合焦位置から外れていると高周波成
分は少なく、合焦位置近くになると高周波成分が多く現
われてくる。In this embodiment, the focusing position of the imaging lens 3 is detected by analyzing the frequency components of the video signal obtained by the imaging means 4, as described above. That is, when the imaging lens 3 is out of focus position, there are few high frequency components of the video signal, and as the imaging lens 3 approaches the focus position, many high frequency components appear.
そこで例えば結像レンズ３のフォーカスレンズ３ａを光
軸上移動させたとき又は撮像手段４を光軸上移動させた
ときに映像信号の高周波成分が最大となる点を検知する
ことにより合焦位置を求めている。Therefore, for example, when the focus lens 3a of the imaging lens 3 is moved on the optical axis or when the imaging means 4 is moved on the optical axis, the in-focus position is determined by detecting the point where the high frequency component of the video signal is maximum. I'm looking for it.
具体的にはまず入力手段（不図示）より測距動作命令が
指示されると映像信号処理回路１１は撮影手段１０３で
得られた画像情報より映像信号を得て高周波成分検出回
路１２に入力する。高周波成分検出回路１２は映像信号
の高周波成分を検出し合焦方向判別回路１３に入力する
０合焦方向判別回路１３は高周波成分検出回路１２から
の高周波成分の時間的変化より、合焦の為のフォーカス
駆動信号をフォーカス駆動回路１４に入力する。Specifically, when a distance measurement operation command is first instructed from an input means (not shown), the video signal processing circuit 11 obtains a video signal from the image information obtained by the photographing means 103 and inputs it to the high frequency component detection circuit 12. . The high frequency component detection circuit 12 detects the high frequency component of the video signal and inputs it to the focusing direction determining circuit 13.The focusing direction determining circuit 13 detects the high frequency component of the video signal and inputs it to the focusing direction determining circuit 13. The focus drive signal is input to the focus drive circuit 14.
フォーカス駆動回路１４はこのときの入力信号に基づい
て結像レンズ３のフォーカスレンズ３ａを光軸上移動さ
せて映像信号の高周波成分が最大となる位置を検知し、
これにより結像レンズ３の合焦位置を検出している。The focus drive circuit 14 moves the focus lens 3a of the imaging lens 3 along the optical axis based on the input signal at this time, detects the position where the high frequency component of the video signal is maximum,
This detects the focal position of the imaging lens 3.
尚、このとき表示装置１５に映像信号処理回路１１から
の映像信号を表示して観察するようにしている。At this time, the video signal from the video signal processing circuit 11 is displayed on the display device 15 for observation.
次に本実施例において映像信号処理回路１１で得られる
映像信号を判別手段１６で判別した結果、画像１ａに白
紙等のコントラストがないと判別されたとき又はコント
ラストが低いと判別されたときは投影手段１０１よりパ
ターン６を原稿台１上の画像１ａ面上に投影する。そし
て該画像ｌａ画面上投影されたパターンを結像レンズ３
で撮像手段４面上に結像して、該撮像手段４より得られ
る映像信号を用いて前述した方法により結像レンズ３の
合焦状態を検出するわけであるがこのとき本実施例では
、まず照度検出手段１０２により原稿台ｌ上の画像１ａ
の明るさ（照度）を測定する。そして画像１ａの明るさ
に応じて調整手段１０は投影手段１０１より投影される
パターンの明るさ（強さ）を照明系７の光源の強さを変
える等をして調整している。Next, in this embodiment, as a result of determining the video signal obtained by the video signal processing circuit 11 by the determining means 16, when it is determined that the image 1a has no contrast such as a blank page, or when it is determined that the contrast is low, the projection The pattern 6 is projected onto the image 1a surface on the document table 1 by means 101. Then, the pattern projected on the image la screen is transferred to the imaging lens 3.
An image is formed on the surface of the imaging means 4, and the in-focus state of the imaging lens 3 is detected by the method described above using the video signal obtained from the imaging means 4. At this time, in this embodiment, First, the illuminance detection means 102 detects the image 1a on the document table l.
Measure the brightness (illuminance) of Then, depending on the brightness of the image 1a, the adjusting means 10 adjusts the brightness (intensity) of the pattern projected by the projecting means 101 by changing the intensity of the light source of the illumination system 7, etc.
即ち画像１ａが暗い場合には投影されるパターンの明る
さを低く６１画像１ａが明るい場合は投影されるパター
ンの明るさを強くして画像ｌａ画面上投影されるパター
ンが常に所定のコントラストを有するように調整してい
る。That is, when the image 1a is dark, the brightness of the projected pattern is lowered.61 When the image 1a is bright, the brightness of the projected pattern is increased so that the pattern projected on the image la screen always has a predetermined contrast. It is adjusted as follows.
これにより結像レンズ３の合焦状態の検出精度の向上を
図っている。This improves the accuracy of detecting the focused state of the imaging lens 3.
尚１本実施例においてフォーカス駆動回路１４により結
像レンズ３のフォーカスレンズ３ａを光軸上移動させる
代わりに撮像手段４を光軸上移動させても同様の効果が
得られる。In this embodiment, the same effect can be obtained by moving the imaging means 4 along the optical axis instead of using the focus drive circuit 14 to move the focus lens 3a of the imaging lens 3 along the optical axis.
投影手段１０１より投影されるパターン゛６の横様は線
幅の興なるストライプ状のパターンに限らずパターン像
より所定の映像信号が映像信号処理回路で得られるよう
なパターンであれば例えば２次元的なパターン等どのよ
うな横様であっても良い。The horizontal aspect of the pattern 6 projected by the projection means 101 is not limited to a striped pattern with varying line widths, but can be a two-dimensional pattern as long as a predetermined video signal can be obtained from the pattern image by a video signal processing circuit. It may be any horizontal pattern, such as a horizontal pattern.
本実施例では画像読取装置の性質上、常に測距動作をす
る必要はなく画像の種類を変えた場合等測距条件が変化
した場合のみ測距動作を開始させて、合焦状態が得られ
た後は測距動作を停止するようにしても良い。In this embodiment, due to the nature of the image reading device, it is not necessary to always perform distance measurement operation, and the distance measurement operation is started only when the type of image is changed or the distance measurement conditions change, and the in-focus state can be obtained. After that, the distance measuring operation may be stopped.
照度検出は撮影用光学系の絞り値をセンサーで読み取っ
て、計算で求める事も可能である。Illuminance detection can also be calculated by reading the aperture value of the photographic optical system with a sensor.
（発明の効果）
本発明によれば原稿台上の画像を撮影手段で読取る際画
像にコントラストがなく又コントラストが低い場合でも
更に画像の明るさが種々と変化した場合であっても前述
したような投影手段と照度検出手段を設けることにより
、結像レンズの合焦状態を高精度に検出することができ
、良好なる画像の読取りが出来る焦点検出手段を有した
画像読取装置を達成することができる。(Effects of the Invention) According to the present invention, even when the image on the document table is read by the photographing means, even when the image has no contrast or low contrast, and even when the brightness of the image varies variously, the same effect can be achieved as described above. By providing a projection means and an illuminance detection means, it is possible to detect the focusing state of the imaging lens with high precision, and to achieve an image reading device having a focus detection means that can read an image well. can.
第１図は本発明の第１実施例の要部概略図である。
図中、ｌｏｔは投影手段、１０２は照度検出手段、１０
３は撮影手段、ｌは原稿台、ｌａは画像、２はアーム、
３は結像レンズ、４は撮像手段、５は投影レンズ、６は
ノ（ターン、７は照明系、８は受光レンズ、９は受光素
子、１０は調整手段、１１は映像信号処理回路、１２は
高周波成分検出回路、１３は合焦方向判別回路、１４は
フォーカス駆動回路、１６は１１ｇ！Ｉ手段、である。FIG. 1 is a schematic diagram of main parts of a first embodiment of the present invention. In the figure, lot is a projection means, 102 is an illuminance detection means, and 10
3 is the photographing means, l is the manuscript table, la is the image, 2 is the arm,
3 is an imaging lens, 4 is an imaging means, 5 is a projection lens, 6 is a turn, 7 is an illumination system, 8 is a light receiving lens, 9 is a light receiving element, 10 is an adjusting means, 11 is a video signal processing circuit, 12 1 is a high frequency component detection circuit, 13 is a focusing direction determining circuit, 14 is a focus drive circuit, and 16 is 11g!I means.
Claims (1)
ズで撮影手段面上に結像させて該画像を読取る際、該原
稿台面上に線幅を異にするストライプ状のパターンを投
影する投影手段と、該投影手段により投影されたパター
ンを該結像レンズにより該撮像手段面上に結像させ、該
撮像手段で得られる映像信号を利用して該結像レンズの
合焦状態を検出する焦点検出手段と該画像面上の照度を
検出する照度検出手段、そして該照度検出手段からの信
号に応じて該投影手段により該原稿台面上に投影するパ
ターンの明るさを調整する調整手段とを設けたことを特
徴とする焦点検出手段を有した画像読取装置。(1) When the image on the document table illuminated by the illumination means is formed on the plane of the photographing means by the imaging lens and the image is read, a striped pattern with different line widths is formed on the document table surface. A projection means for projecting, a pattern projected by the projection means is imaged on the surface of the imaging means by the imaging lens, and the focusing state of the imaging lens is determined using a video signal obtained by the imaging means. a focus detection means for detecting the illuminance on the image plane, an illuminance detection means for detecting the illuminance on the image surface, and an adjustment for adjusting the brightness of the pattern projected by the projection means on the document table surface in accordance with a signal from the illuminance detection means. What is claimed is: 1. An image reading device comprising focus detection means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2164542A JPH0454769A (en) | 1990-06-22 | 1990-06-22 | Picture reader having focus detecting means |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2164542A JPH0454769A (en) | 1990-06-22 | 1990-06-22 | Picture reader having focus detecting means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0454769A true JPH0454769A (en) | 1992-02-21 |
Family
ID=15795141
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2164542A Pending JPH0454769A (en) | 1990-06-22 | 1990-06-22 | Picture reader having focus detecting means |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0454769A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007322177A (en) * | 2006-05-30 | 2007-12-13 | Pulstec Industrial Co Ltd | Laser light irradiation measuring device |
| US8266980B2 (en) | 2008-06-30 | 2012-09-18 | Jtekt Corporation | Steering apparatus |
-
1990
- 1990-06-22 JP JP2164542A patent/JPH0454769A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007322177A (en) * | 2006-05-30 | 2007-12-13 | Pulstec Industrial Co Ltd | Laser light irradiation measuring device |
| US8266980B2 (en) | 2008-06-30 | 2012-09-18 | Jtekt Corporation | Steering apparatus |
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