JP3270460B2 - Image reading device - Google Patents
Image reading deviceInfo
- Publication number
- JP3270460B2 JP3270460B2 JP23640790A JP23640790A JP3270460B2 JP 3270460 B2 JP3270460 B2 JP 3270460B2 JP 23640790 A JP23640790 A JP 23640790A JP 23640790 A JP23640790 A JP 23640790A JP 3270460 B2 JP3270460 B2 JP 3270460B2
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- Prior art keywords
- illumination light
- illuminance
- original image
- light source
- main illumination
- Prior art date
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Description
【０００１】[0001]
本発明は、原像面の照度を均一化して読取画像を得る
画像読取装置に関する。The present invention relates to an image reading apparatus that obtains a read image by equalizing the illuminance of an original image surface.
【０００２】[0002]
一般に、照明光源から照射される照明光で原像面を照
射し、この原像面で反射した照明光の光路をミラーで反
射して曲折し、結像光学系により光電変換素子などで構
成されて結像面となる撮像面に結像して読取画像を得る
画像読取装置が用いられているが、原像面に照度むらが
生じやすいので、撮像面に結像される読取画像の照度を
均一化するように、拡散板を使用したり、照明光源の輝
度調節などをしている。In general, an original image plane is illuminated with illumination light emitted from an illumination light source, and the optical path of the illumination light reflected on the original image plane is reflected by a mirror and bent, and is constituted by a photoelectric conversion element or the like by an imaging optical system. Although an image reading apparatus that obtains a read image by forming an image on an imaging surface that forms an image forming surface is used, uneven illuminance tends to occur on the original image surface, so that the illuminance of the read image formed on the imaging surface is reduced. In order to achieve uniformity, a diffuser is used and the brightness of an illumination light source is adjusted.
【０００３】 また、周知のように、撮像面に結像する読取画像の照
度むらは、射影変換する一般的な結像光学系のCOS4乗則
に起因した照度むらと、照明光の照度分布がその中心程
照度が高くなるいわゆるガウス関数型に似た照度分布で
あることに起因する照明光自身の照度むらとが原因であ
る。Further, as is well known, the illuminance unevenness of a read image formed on an imaging surface is caused by the illuminance unevenness caused by the COS4 power law of a general imaging optical system that performs projection conversion, and the illuminance distribution of the illumination light. This is due to uneven illuminance of the illumination light itself due to an illuminance distribution similar to a so-called Gaussian function type in which the illuminance increases toward the center.
【０００４】 そして、一般に、画像読取装置の照明光源としては、
安価なことから、複数の発光ダイオードをマトリクス状
に配置した照明光源が使用される。このような照明光源
を備えた画像読取装置の読取画像の照度の均一化につい
て説明する。[0004] Generally, as an illumination light source of an image reading apparatus,
Because of the low cost, an illumination light source in which a plurality of light emitting diodes are arranged in a matrix is used. The uniformity of the illuminance of an image read by an image reading apparatus having such an illumination light source will be described.
【０００５】 図４（ａ）は、18個の発光ダイオードを図４（ｂ）に
示すように３×６のマトリクス状に配置した照明光源11
を備えた画像読取装置を示すもので、照明光源11が照射
した照明光は原像面Ｐを照明し、この原像面Ｐで反射
し、さらに、照明光の光路をミラーＭで曲折し、結像光
学系12を経て撮像面13に読取画像として結像される。FIG. 4A shows an illumination light source 11 in which 18 light emitting diodes are arranged in a 3 × 6 matrix as shown in FIG. 4B.
Illumination light emitted by the illumination light source 11 illuminates the original image plane P, is reflected by the original image plane P, and further bends the optical path of the illumination light with the mirror M. The image is formed as a read image on the imaging surface 13 via the imaging optical system 12.
【０００６】 また、図５（ａ）は、図４に示した画像読取装置の撮
像面13における読取画像の照度分布を概略的に示したも
ので、図５（ｂ）（ｃ）も同様で、本来は平面上に照度
が三次元的に示されるべきものであるが、簡単のため、
線上に照度を二次元的に示したものである。そして、図
５（ｃ）は、照明光源11を構成する発光ダイオードの照
射する各々の照明光の原像面Ｐにおける照度分布を概略
的に示したもので、この照度分布は中心程照度が高くな
るいわゆるガウス関数型の照度分布である。また、図５
（ｂ）は、照明光源11から照射される照明光の原像面Ｐ
における照度分布を概略的に示したもので、この照明光
は照明光源11を構成する各々の発光ダイオードが照射す
る照度が均一でないガウス関数型の照度分布の照明光が
合成されたもので、合成された照明光、すなわち照明光
源11から照射された照明光はこの照明光自身に照度むら
を有している。FIG. 5A schematically shows an illuminance distribution of a read image on the imaging surface 13 of the image reading apparatus shown in FIG. 4, and the same applies to FIGS. 5B and 5C. , The illuminance should be shown three-dimensionally on a plane, but for simplicity,
Illuminance is shown two-dimensionally on a line. FIG. 5C schematically shows the illuminance distribution on the original image plane P of each illuminating light emitted from the light emitting diode constituting the illuminating light source 11, and the illuminance distribution becomes higher toward the center. This is a so-called Gaussian function type illuminance distribution. FIG.
(B) shows the original image plane P of the illumination light emitted from the illumination light source 11.
The illumination light is schematically shown, and this illumination light is a combination of illumination light of a Gaussian function type illumination distribution in which the illumination emitted by each light emitting diode constituting the illumination light source 11 is not uniform. The illumination light thus emitted, that is, the illumination light emitted from the illumination light source 11, has illuminance unevenness in the illumination light itself.
【０００７】 そして、図５（ａ）に示されるように、読取画像は照
明光自身の照度むらと、結像光学系12のCOS4乗則に起因
して読取画像の周辺部程照度が低下した低照度部分によ
る照度むらとを有する。特に、原像面Ｐの周辺部におけ
る照明光自身の照度むらの低照度部分は、読取画像にお
いて照度が著しく低い低照度部分となる。Then, as shown in FIG. 5A, the read image has a lower illuminance in the peripheral portion of the read image due to the uneven illuminance of the illumination light itself and the COS4 law of the imaging optical system 12. It has illuminance unevenness due to a low illuminance portion. In particular, the low illuminance portion of the illuminance unevenness of the illumination light itself in the peripheral portion of the original image plane P is a low illuminance portion in which the illuminance is extremely low in the read image.
【０００８】 そこで、従来は、図４（ａ）中の鎖線で示されるよう
に、照明光源11と原像面Ｐとの間に拡散板14を設け、発
光ダイオードの照射する照明光を拡散させることによ
り、照明光自身の照度むらを低減させるとともに、撮像
面13におけるCOS4乗則に起因する低照度部分に対応した
照明光源11の部分、すなわち図４（ｂ）の発光ダイオー
ド1,2,5,6,13,14,17,18の輝度を上げている。しかし、C
OS4乗則に起因する読取画像周辺部の低照度部分の照度
を上げることはできるものの、拡散板14によっては照明
光自身の照度むらを良好に低減することはできず、原像
面Ｐの周辺部の照明光自身の照度むらの低照度部分は、
読取画像において照度が著しく低い低照度部分になって
しまい、照度むらは10％程度までにしか低減できない。Therefore, conventionally, as shown by a chain line in FIG. 4A, a diffusion plate 14 is provided between the illumination light source 11 and the original image plane P to diffuse the illumination light emitted from the light emitting diode. Thereby, the illuminance unevenness of the illuminating light itself is reduced, and the portion of the illuminating light source 11 corresponding to the low illuminance portion caused by the COS4 law on the imaging surface 13, that is, the light emitting diodes 1, 2, and 5 in FIG. , 6,13,14,17,18 are increased. But C
Although it is possible to increase the illuminance of the low illuminance portion around the read image due to the OS4 power law, the illuminance unevenness of the illumination light itself cannot be reduced satisfactorily by the diffusion plate 14, and the periphery of the original image plane P The low-illumination part of the illumination unevenness of the illumination light itself
A low illuminance portion where the illuminance is extremely low in the read image, and the illuminance unevenness can be reduced only to about 10%.
【０００９】 また、画像読取装置の照明光自身の照度むらを良好に
低減する手段として、発光ダイオードの個数を増すこと
が考えられるが、たくさんの発光ダイオードが必要であ
り、好ましくない。As a means for satisfactorily reducing the illuminance unevenness of the illumination light itself of the image reading apparatus, it is conceivable to increase the number of light emitting diodes. However, many light emitting diodes are required, which is not preferable.
【００１０】 また、反射板を用いて、照明光自身の照度むらを低減
することも考えられるが、照度むらを良好に低減するこ
とはできず、装置も大型化する。Although it is conceivable to reduce the illuminance unevenness of the illumination light itself by using a reflecting plate, the illuminance unevenness cannot be satisfactorily reduced, and the device becomes large.
【００１１】[0011]
前述のように、画像読取装置においては、読取画像の
照度むらの問題の解決が課題となるが、照明光源と原像
面との間に拡散板を設けるとともに、照明光源の周辺部
の発光ダイオードの輝度を上げても照度むらを十分に低
減できない。また、照度むらの低減のために、発光ダイ
オードの個数を増したり、反射板を用いたりすることも
考えられるが、あまり有効ではない。As described above, in the image reading apparatus, the problem of the uneven illuminance of the read image is a problem. However, a diffusion plate is provided between the illumination light source and the original image plane, and the light emitting diodes around the illumination light source are provided. However, even if the brightness is increased, the uneven illuminance cannot be sufficiently reduced. In order to reduce uneven illuminance, it is conceivable to increase the number of light emitting diodes or use a reflector, but this is not very effective.
【００１２】 ところで、画像読取装置における読取画像の照度むら
を低減するには、高照度部と低照度部の照度の絶対的な
差を小さくすること、または、高照度部と低照度部の照
度の相対的な比を小さくすることが考えられる。Meanwhile, in order to reduce uneven illuminance of a read image in the image reading apparatus, the absolute difference between the illuminance of the high illuminance section and the low illuminance section is reduced, or the illuminance of the high illuminance section and the low illuminance section is reduced. It is conceivable to reduce the relative ratio of.
【００１３】 本発明は、上記問題点に鑑みなされたもので、照度む
らを良好に低減し、読取画像の照度の均一化を図った画
像読取装置を提供することを目的とする。The present invention has been made in view of the above-described problems, and has as its object to provide an image reading apparatus capable of favorably reducing uneven illuminance and achieving uniform illuminance of a read image.
【００１４】[0014]
請求項１記載の画像読取装置は、複数の発光素子で構
成され主照明光を照射する主照明光源と、この主照明光
源で照射された主照明光を拡散する第１の拡散板と、こ
の第１の拡散板で拡散された主照明光が照射される原像
面と、この原像面で反射された主照明光の光路を曲折す
るミラーと、このミラーで反射された前記主照明光を結
像する結像光学系と、この結像光学系で結像された画像
を形成し読取画像を得る結像面と、前記結像光学系およ
びミラー間の主照明光の光路の近傍に位置して設けられ
前記ミラーを介した前記原像面までの距離が前記主照明
光源と前記原像面の距離より長い位置に配設された前記
結像面の主照明光の低照度部分の照度を補い前記ミラー
で反射して前記原像面に補助照射光を照射する補助照明
光源と、この補助照明光源で照射された補助照明光を拡
散する第２の拡散板とを具備したものである。The image reading apparatus according to claim 1 includes a main illumination light source configured of a plurality of light emitting elements and configured to emit main illumination light, a first diffusion plate configured to diffuse the main illumination light emitted by the main illumination light source, An original image surface irradiated with the main illumination light diffused by the first diffusion plate, a mirror that bends an optical path of the main illumination light reflected by the original image surface, and the main illumination light reflected by the mirror An imaging optical system that forms an image formed by the imaging optical system, an imaging surface that forms a read image, and an optical path of main illumination light between the imaging optical system and the mirror. The distance between the main illumination light source and the original image plane, where the distance to the original image plane via the mirror is longer than the distance between the main illumination light source and the original image plane. An auxiliary illumination light source that supplements illuminance and reflects the mirror to irradiate the original image surface with auxiliary illumination light; An auxiliary illumination light emitted by the light source is obtained and a second diffusion plate that diffuses.
【００１５】 請求項２記載の画像読取装置は、請求項１記載の画像
読取装置において、原像面およびミラーは、それぞれ三
角プリズムの一面に形成されるものである。According to a second aspect of the present invention, in the image reading apparatus of the first aspect, the original image surface and the mirror are each formed on one surface of the triangular prism.
【００１６】[0016]
請求項１記載の画像読取装置は、主照明光源が照射す
る主照明光は、第１の拡散板を介して原像面を照明し、
この原像面で反射された後、ミラーで結像光学系へ向け
て反射され、この結像光学系により結像面に結像する
が、周縁部に結像光学系のCOS4乗則に起因した低照度部
分と、第１の拡散板を介しても解消し得ずに残存する主
照明光自身の照度むらと、原像面の周辺部における主照
明光自身の照度むらの低照度部分が結像面において照度
を著しく低下した低照度部分とを生じ、補助照明光源が
照射する補助照明光は、第２の拡散板で拡散され、ミラ
ーで反射されて原像面を照射し、補助照明光源からミラ
ーを介した原像面までの距離が主照明光源から原像面ま
での距離より照明距離が長く設定されることにより、発
散が増大して照明範囲が広くなり、原像面のほぼ全範囲
を照明でき、原像面の照度を全体的に上げるとともに、
結像面の主照明光源からの照度が低い低照度部分を補っ
て補助照明光源からの補助照明光を照射するようにして
原像面を照明することにより、COS4乗則に起因する低照
度部分の照度を補い、照度むらを良好に低減して、照度
を均一化した読取画像となるとともに、補助照明光源を
結像光学系およびミラー間の主照明光の光路の近傍に位
置して設け、装置の大型化を防止する。The image reading apparatus according to claim 1, wherein the main illumination light emitted by the main illumination light source illuminates the original image surface via the first diffusion plate,
After being reflected on the original image surface, it is reflected by the mirror toward the imaging optical system, and forms an image on the imaging surface with this imaging optical system. The low illuminance portion, the illuminance unevenness of the main illumination light itself that remains unresolved even through the first diffusion plate, and the low illuminance portion of the illuminance unevenness of the main illumination light itself around the original image surface. A low illuminance portion having significantly reduced illuminance on the imaging surface is generated, and auxiliary illumination light emitted by the auxiliary illumination light source is diffused by the second diffuser, reflected by the mirror, and illuminates the original image surface. By setting the distance from the light source to the original image plane via the mirror longer than the distance from the main illumination light source to the original image plane, the divergence increases and the illumination range becomes wider, and almost the original image plane The entire area can be illuminated, and the illuminance on the original image surface is raised overall,
By illuminating the original image surface by illuminating the auxiliary illumination light from the auxiliary illumination light source to compensate for the low illuminance portion with low illuminance from the main illumination light source on the imaging surface, the low illuminance portion caused by the COS4 power law The illuminance is supplemented, the illuminance unevenness is reduced favorably, and a read image with uniform illuminance is obtained, and the auxiliary illumination light source is provided near the optical path of the main illumination light between the imaging optical system and the mirror, Prevent the equipment from becoming larger.
【００１７】 請求項２記載の画像読取装置は、請求項１記載の画像
読取装置において、原像面およびミラーをそれぞれ三角
プリズムの一面に形成することにより、簡単かつ小型化
が図れる。According to the image reading apparatus of the second aspect, the original image surface and the mirror are formed on one surface of the triangular prism, respectively.
【００１８】[0018]
以下、本発明の一実施例を、画像読取装置の中でも特
に読取画像の照度の均一さが厳しく要求される指紋検出
照合装置について図１を参照して説明する。Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 for a fingerprint detection and collation device that requires strict uniformity of illuminance of a read image among image reading devices.
【００１９】 まず、この種の指紋検出照合装置の原理を簡単に説明
する。First, the principle of this type of fingerprint detection and collation device will be briefly described.
【００２０】 この指紋検出照合装置は、透明平板に指紋を圧着する
と、指紋の凹部により形成される空気層との境界面と、
指紋の凸部が前記透明平板に密着した密着面とが形成さ
れる。そして、指紋が圧着された面を照明すると、空気
層と接する境界面と指が密着した密着面とでは、反射率
の違いから、反射する光量に差を生じる。そして、境界
面で臨界角を越えるように照明すると、境界面を照明し
た照明光はほぼ全反射の状態となり、密着面を照明した
照明光は密着面でほぼ拡散の状態となり、境界面と密着
面の反射量の違いが大きくなる。このように境界面と密
着面とで反射する光量に差を生じて、圧着面で反射した
照明光を結像光学系により結像面に結像して指紋の凹凸
パターンを読み取る。This fingerprint detection and collation device, when a fingerprint is pressed on a transparent flat plate, a boundary surface between the fingerprint and the air layer formed by the concave portion of the fingerprint,
A contact surface where the convex portion of the fingerprint is in close contact with the transparent flat plate is formed. When the surface on which the fingerprint is pressed is illuminated, there is a difference in the amount of reflected light between the boundary surface in contact with the air layer and the contact surface in which the finger is in close contact due to the difference in reflectance. When the light is illuminated so as to exceed the critical angle at the boundary surface, the illumination light illuminating the boundary surface is almost totally reflected, and the illumination light illuminating the contact surface is almost diffused at the contact surface, and is in close contact with the boundary surface. The difference in the amount of reflection on the surface increases. As described above, a difference occurs in the amount of light reflected on the boundary surface and the contact surface, and the illumination light reflected on the compression surface is imaged on the image forming surface by the image forming optical system to read the concave and convex pattern of the fingerprint.
【００２１】 以下、図１、図２および図３を参照しながら、構成と
その作用とについて説明をする。Hereinafter, the configuration and its operation will be described with reference to FIGS. 1, 2 and 3.
【００２２】 図１（ａ）に示すように、１は三角プリズムで、この
三角プリズム１は細長い形状である指紋の原画像に合わ
せて底面部分を長方形状とし、この底面部分を原像面Ｐ
とし、他の２面のいずれか一面は反射膜を施してミラー
であるミラー面Ｍとし、残る一面は透光面Ｔとする。As shown in FIG. 1A, reference numeral 1 denotes a triangular prism. The triangular prism 1 has a rectangular bottom surface in accordance with an elongated fingerprint original image.
One of the other two surfaces is provided with a reflective film to be a mirror surface M which is a mirror, and the other surface is a light transmitting surface T.
【００２３】 また、原像面Ｐの形状に対応して長方形状に、複数の
発光素子としての発光ダイオードLEDをマトリクス状に
配設した主照明光源２を有し、図１（ｂ）に示すよう
に、３×６のマトリクス状の配置である。Further, a main illumination light source 2 having a plurality of light emitting diodes LED as a light emitting element arranged in a matrix in a rectangular shape corresponding to the shape of the original image plane P is shown in FIG. As described above, the arrangement is in a 3 × 6 matrix.
【００２４】 さらに、主照明光源２の前面、すなわち主照明光源２
と透光面Ｔとの間には、第１の拡散板３が設けられ、透
光面Ｔ側には結像光学系４が配設され、さらに、結像光
学系４の結像面となる撮像面５には、原像面Ｐの形状に
対応して長方形状の光電変換素子が設けられている。Further, the front of the main illumination light source 2, that is, the main illumination light source 2
A first diffusing plate 3 is provided between the light-transmitting surface T and the light-transmitting surface T, and an imaging optical system 4 is provided on the light-transmitting surface T side. The imaging surface 5 is provided with a rectangular photoelectric conversion element corresponding to the shape of the original image plane P.
【００２５】 また、６は補助照明光源で、この補助照明光源６は４
つの発光素子としての発光ダイオードLEDを有し、各発
光ダイオードLEDの前面、すなわち補助照明光源６と透
光面Ｔとの間には第２の拡散板７がそれぞれ設けられて
いる。Reference numeral 6 denotes an auxiliary illumination light source.
There are light emitting diodes LED as one light emitting element, and second diffusion plates 7 are respectively provided on the front surface of each light emitting diode LED, that is, between the auxiliary illumination light source 6 and the light transmitting surface T.
【００２６】 なお、Ｆは指で、この指Ｆは指紋面を原像面Ｐに圧着
され、P1は原像面Ｐにおいて指紋の凹部により形成され
る空気層との境界面、P2は、指紋の凸部が原像面Ｐに密
着した密着面である。Note that F is a finger, and the finger F has a fingerprint surface pressed against the original image surface P, P 1 is a boundary surface between the original image surface P and the air layer formed by the concave portion of the fingerprint, and P 2 is a finger. The convex portion of the fingerprint is a contact surface that is in close contact with the original image surface P.
【００２７】 また、主照明光源２から照射された主照明光は、第１
の拡散板３を介して、指Ｆを圧着した原像面Ｐを、指紋
の凹部により形成される空気層との境界面P1で全反射す
る光量が最大になるように照明し、この原像面Ｐで反射
され、ミラー面Ｍに至り、このミラー面Ｍで透光面Ｔへ
向けて反射され、この透光面Ｔから射出し、結像光学系
４を経て、この結像光学系４によって撮像面５に結像さ
れる。The main illumination light emitted from the main illumination light source 2 is the first illumination light.
Through the diffusion plate 3, the original image surface P which crimp the finger F, the amount of light totally reflected at the boundary surface P 1 of an air layer formed by the recess of the fingerprint illuminated to maximize, the original The light is reflected by the image plane P, reaches the mirror surface M, is reflected by the mirror surface M toward the light-transmitting surface T, exits from the light-transmitting surface T, passes through the imaging optical system 4, and passes through the imaging optical system. 4 forms an image on an imaging surface 5.
【００２８】 さらに、主照明光源２から照射される主照明光は、主
照明光源２を構成する各発光ダイオードLEDが照射する
照明光が合成されたもので、各発光ダイオードLEDの照
射する照明光はそれぞれ照度が均一でないガウス関数型
の照度分布を呈するものであるから、主照明光は、この
主照明光自身に照度むらを有している。そして、主照明
光源２から照射された主照明光を、第１の拡散板３を介
すことにより、各発光ダイオードLEDが照射する照明光
を拡散して、主照明光自身の照度むらを低減する。Further, the main illumination light emitted from the main illumination light source 2 is a combination of the illumination light emitted from each light emitting diode LED constituting the main illumination light source 2, and the illumination light emitted from each light emitting diode LED Since each has a Gaussian function type illuminance distribution in which the illuminance is not uniform, the main illumination light itself has uneven illuminance. Then, the main illumination light emitted from the main illumination light source 2 is diffused through the first diffusion plate 3 to diffuse the illumination light emitted by each light emitting diode LED, thereby reducing the illuminance unevenness of the main illumination light itself. I do.
【００２９】 また、図２（ｃ）は、主照明光の撮像面５における結
像の照度分布を概略的に示したものである。すなわち、
主照明光の照度分布は、本来は、平面上に照度が三次元
的に示されるべきものであるが、簡単のため、線上に照
度を二次元的に示したものである。図２（ａ）（ｂ）も
同様である。そして、主照明光の撮像面５における結像
の照度分布は、第１の拡散板３により低減されても残存
する主照明光自身の照度むら、たとえば低照度部１と高
照度部ｈと、結像光学系４のCOS4乗則に起因して結像の
周辺部程照度が低下する照度むらとを有する。特に、原
像面Ｐの周辺部の照明光自身の照度むらの低照度部分
は、撮像面５において照度が著しく低下した低照度部分
Ｌとなる。FIG. 2C schematically shows the illuminance distribution of an image formed on the imaging surface 5 by the main illumination light. That is,
The illuminance distribution of the main illumination light should originally show the illuminance three-dimensionally on a plane, but for simplicity, it shows the illuminance two-dimensionally on a line. 2 (a) and 2 (b) are the same. The illuminance distribution of an image of the main illumination light on the imaging surface 5 is such that the illuminance unevenness of the main illumination light itself remaining even after being reduced by the first diffusion plate 3, for example, the low illuminance section 1 and the high illuminance section h, There is illuminance unevenness in which the illuminance decreases at the periphery of the image due to the COS4 law of the imaging optical system 4. In particular, the low illuminance portion of the illuminance unevenness of the illumination light itself in the peripheral portion of the original image plane P is a low illuminance portion L on the imaging surface 5 where the illuminance is significantly reduced.
【００３０】 図３は、主照明光の撮像面５における照度の明暗を模
式的に示したもので、四隅に平行斜線で示される結像光
学系４のCOS4乗則に起因する低照度部分と、黒塗部で示
される照度が著しく低下した低照度部分Ｌとがある。FIG. 3 schematically shows the brightness of the illuminance of the main illumination light on the imaging surface 5. The low illuminance portion caused by the COS4 power law of the imaging optical system 4 indicated by oblique parallel lines at the four corners is shown in FIG. And a low illuminance portion L in which the illuminance is markedly reduced as indicated by a black portion.
【００３１】 補助照明光源６は、結像光学系４と透光面Ｔとの間に
主照明光の光路の近傍に位置して設けられ、補助照明光
源６の各発光ダイオードLEDから照射された補助照明光
は、第２の拡散板７を介して、透光面Ｔからプリズム１
内に入射し、ミラー面Ｍで原像面Ｐへ向けて反射され
て、この原像面Ｐを照明し、この原像面Ｐで反射され
て、再びミラー面Ｍに至り、このミラー面Ｍで透光面Ｔ
へ向けて反射され、この透光面Ｔから射出し、結像光学
系４を経て、この結像光学系４によって撮像面５に結像
される。The auxiliary illumination light source 6 is provided between the imaging optical system 4 and the light transmitting surface T in the vicinity of the optical path of the main illumination light, and is emitted from each light emitting diode LED of the auxiliary illumination light source 6. The auxiliary illumination light is transmitted from the light transmitting surface T to the prism 1 through the second diffusion plate 7.
And is reflected by the mirror surface M toward the original image surface P to illuminate the original image surface P, is reflected by the original image surface P, and reaches the mirror surface M again. With translucent surface T
The light is reflected from the light transmitting surface T, exits from the light transmitting surface T, passes through the imaging optical system 4, and is imaged on the imaging surface 5 by the imaging optical system 4.
【００３２】 このとき、補助照明光源６を構成する４つの発光ダイ
オードLED各々から照射された各々の補助照明光は、第
２の拡散板７を介すことにより拡散させられる。しか
も、補助照明光は、ミラー面Ｍに至るまでの距離に加え
て、ミラー面Ｍで反射して原像面Ｐを照明するため、照
明距離が長くなり、各々の補助照明光は発散させられる
ことにより、照明範囲が広くなる。これとともに、各々
の補助照明光は、その照度のピークを図３図示の黒塗部
で示される照度が著しく低下した低照度部分Ｌに対応し
た原像面Ｐの部分のいずれか１つに一致させ、１つの低
照度部分Ｌに補助照明光が重複しないようにしている。At this time, each auxiliary illumination light emitted from each of the four light emitting diodes LED constituting the auxiliary illumination light source 6 is diffused through the second diffusion plate 7. Moreover, since the auxiliary illumination light is reflected on the mirror surface M and illuminates the original image plane P, in addition to the distance to the mirror surface M, the illumination distance becomes longer, and each auxiliary illumination light is diverged. Thereby, the illumination range is widened. At the same time, each auxiliary illumination light has its illuminance peak coincident with any one of the portions of the original image plane P corresponding to the low illuminance portion L where the illuminance is markedly reduced as shown by the black portion in FIG. The auxiliary illumination light is prevented from overlapping one low illuminance portion L.
【００３３】 なお、補助照明光源６は、透光面Ｔから射出する照明
光すなわち主照明光と補助照明光の光路をいずれをも妨
げないように、結像光学系４と透光面Ｔとの間に設けら
れる。It should be noted that the auxiliary illumination light source 6 is provided between the imaging optical system 4 and the translucent surface T so that the illumination light emitted from the translucent surface T, that is, the main illumination light and the auxiliary illumination light do not impede any optical path. It is provided between.
【００３４】 図２（ｂ）は、補助照明光の撮像面５における結像の
照度分布を概略的に示したものである。前述の如く補助
照明光が原像面Ｐを照明することにより、図２（ｃ）で
示される主照明光の結像の照度分布の著しく照度の低下
した低照度部分Ｌに、補助照明光の結像の照度のピーク
Ｈが一致している。また、各々の補助照明光は、照度の
高い部分が、原像面Ｐの周辺部に位置するCOS4乗則に起
因する低照度部分と対応した原像面Ｐの部分にも一致し
ているため、各々の補助照明光はその照明範囲のほぼ半
分で原像面Ｐを照明するものであるが、第２の拡散板７
を介し、しかも、照明距離を長くすることによって、補
助照明光の照明範囲を広範囲のものとし、原像面Ｐのほ
ぼ全範囲を照明する。FIG. 2B schematically shows an illuminance distribution of an image formed on the imaging surface 5 by the auxiliary illumination light. By illuminating the original image plane P with the auxiliary illumination light as described above, the auxiliary illumination light is applied to the low illuminance portion L where the illuminance distribution of the image of the main illumination light shown in FIG. The peaks H of the illuminance of the image coincide. Also, in each auxiliary illumination light, the high illuminance portion also matches the portion of the original image plane P corresponding to the low illuminance portion caused by the COS4 power rule located in the peripheral portion of the original image surface P. , Each auxiliary illumination light illuminates the original image plane P in almost half of its illumination range.
, And by extending the illumination distance, the illumination range of the auxiliary illumination light is widened, and almost the entire range of the original image plane P is illuminated.
【００３５】 また、撮像面５で得られる読取画像は、主照明光と補
助照明光のそれぞれの結像の合成であって、読取画像の
照度分布を示したものが、図２（ａ）である。The read image obtained on the imaging surface 5 is a composite of the respective images of the main illumination light and the auxiliary illumination light, and the illuminance distribution of the read image is shown in FIG. is there.
【００３６】 すなわち、補助照明光源６を構成するそれぞれの発光
ダイオードLEDが照射する補助照明光は、主照明光源２
が原像面Ｐを照明して得られた結像の著しく照度の低い
低照度部分Ｌに対応する原像面Ｐの部分に、照度のピー
クＨが一致するようにして照明することにより、COS4乗
則に起因する低照度部分Ｌの照度を補い、しかも、それ
ぞれの発光ダイオードLEDが原像面Ｐのほぼ全範囲を照
明することにより、原像面Ｐの照度を全体的に上げて、
照度むらの相対的な比を小さくする。これにより、照度
むらが良好に低減されて、照度が均一化された読取画像
が得られる。That is, the auxiliary illumination light emitted from each light emitting diode LED constituting the auxiliary illumination light source 6 is
Is illuminated such that the peak H of the illuminance coincides with the portion of the original image plane P corresponding to the low illuminance portion L of the image formed by illuminating the original image plane P, which has extremely low illuminance. By compensating for the illuminance of the low illuminance portion L due to the power law, and furthermore, each light emitting diode LED illuminates almost the entire range of the original image plane P, thereby increasing the illuminance of the original image plane P as a whole.
Reduce the relative ratio of uneven illumination. Thereby, illuminance unevenness is favorably reduced, and a read image with uniform illuminance is obtained.
【００３７】 本実施例の場合、実験によれば、照度むらを３％程度
まで低減することができ、指紋の凹凸パターンの読み取
り精度が向上した。In the case of the present embodiment, according to the experiment, the illuminance unevenness could be reduced to about 3%, and the reading accuracy of the concave and convex pattern of the fingerprint was improved.
【００３８】 また、補助照明光源６を構成する発光ダイオードLED
は４つのみ設ければよく、しかも、補助照明光源６は結
像光学系４と透光面Ｔとの間に設けられるから、補助照
明光源６を設けたにもかかわらず、画像読取装置の大型
化を招くことはなく、しかも、安価にできる。すなわ
ち、補助照明光源６は、主照明光による結像の著しく照
度が低下した部分の個数だけ備えればよく、さらに、備
える位置も主照明光の光路の近傍なので、安価にしかも
装置を大型化することなく、照度むらが低減され照度が
均一化された読取画像にできる。A light emitting diode LED constituting the auxiliary illumination light source 6
Need only be provided, and the auxiliary illumination light source 6 is provided between the imaging optical system 4 and the translucent surface T. Therefore, despite the provision of the auxiliary illumination light source 6, There is no increase in size, and the cost can be reduced. That is, the auxiliary illumination light source 6 only needs to be provided by the number of portions where the illuminance of the image formed by the main illumination light is significantly reduced, and the auxiliary illumination light source 6 is provided near the optical path of the main illumination light. Without reading, unevenness in illuminance is reduced, and a read image with uniform illuminance can be obtained.
【００３９】 なお、本実施例は、指紋検出照合装置に限って記載し
たが、その他の画像読取装置、たとえば複写機、ファク
シミリ、スキャナなどにも適用できる。Although the present embodiment has been described only for the fingerprint detection and collation device, it can be applied to other image reading devices, for example, a copying machine, a facsimile, a scanner, and the like.
【００４０】[0040]
請求項１記載の画像読取装置によれば、主照明光源が
照射する主照明光は、第１の拡散板を介して原像面を照
明し、この原像面で反射された後、ミラーで結像光学系
へ向けて反射され、この結像光学系により結像面に結像
するが、周縁部に結像光学系のCOS4乗則に起因した低照
度部分と、第１の拡散板を介しても解消し得ずに残存す
る主照明光自身の照度むらと、原像面の周辺部における
主照明光自身の照度むらの低照度部分が結像面において
照度を著しく低下した低照度部分とを生じ、補助照明光
源が照射する補助照明光は、第２の拡散板で拡散され、
ミラーで反射されて原像面を照射し、補助照明光源から
ミラーを介した原像面までの距離が主照明光源から原像
面までの距離より照明距離が長く設定されることによ
り、発散が増大して照明範囲が広くなり、原像面のほぼ
全範囲を照明でき、原像面の照度を全体的に上げるとと
もに、結像面の主照明光源からの照度が低い低照度部分
を補って補助照明光源からの補助照明光を照射するよう
にして原像面を照明することにより、COS4乗則に起因す
る低照度部分の照度を補い、照度むらを良好に低減し
て、照度を均一化した読取画像にできるとともに、補助
照明光源を結像光学系およびミラー間の主照明光の光路
の近傍に位置して設けることにより、装置の大型化も防
止できる。According to the image reading device of the first aspect, the main illumination light emitted by the main illumination light source illuminates the original image surface via the first diffusion plate, and after being reflected by the original image surface, is reflected by the mirror. The light is reflected toward the imaging optical system, and the image is formed on the imaging surface by the imaging optical system. The low illuminance portion caused by the COS4 power law of the imaging optical system and the first diffusion plate are arranged on the periphery. The low illuminance part where the illuminance unevenness of the main illumination light itself that remains unresolved even after passing through and the low illuminance part of the illuminance unevenness of the main illumination light itself around the original image surface has significantly reduced the illuminance on the imaging surface The auxiliary illumination light emitted by the auxiliary illumination light source is diffused by the second diffusion plate,
The light is reflected by the mirror and illuminates the original image plane, and the divergence is set by setting the distance from the auxiliary illumination light source to the original image plane via the mirror longer than the distance from the main illumination light source to the original image plane. Increasing the illumination range, it can illuminate almost the entire area of the original image plane, increase the illuminance of the original image plane as a whole, and supplement the low illuminance part where the illuminance from the main illumination light source on the imaging plane is low. By illuminating the original image surface by illuminating the auxiliary illumination light from the auxiliary illumination light source, the illuminance in the low illuminance area caused by the COS4 power law is compensated, the illuminance unevenness is reduced, and the illuminance is made uniform. In addition to providing the read image, the auxiliary illumination light source is provided near the optical path of the main illumination light between the imaging optical system and the mirror, thereby preventing the apparatus from being enlarged.
【００４１】 請求項２記載の画像読取装置によれば、請求項１記載
の画像読取装置に加え、原像面およびミラーをそれぞれ
三角プリズムの一面に形成することにより、簡単かつ小
型化できる。According to the image reading device of the second aspect, in addition to the image reading device of the first aspect, by forming the original image surface and the mirror on one surface of the triangular prism, the size and the size can be simplified and reduced.
【図１】 （ａ）は本発明の画像読取装置の一実施例を示す全体
図、（ｂ）はその主照明光源を示す正面図である。FIG. 1A is an overall view showing an embodiment of an image reading apparatus of the present invention, and FIG. 1B is a front view showing a main illumination light source thereof.
【図２】 （ａ）（ｂ）（ｃ）は照度分布を示すグラフである。FIGS. 2A, 2B and 2C are graphs showing illuminance distributions.
【図３】 主照明光の結像面における照度の明暗を模式的に示した
ものである。FIG. 3 schematically shows the brightness of the illuminance on the image forming plane of the main illumination light.
【図４】 （ａ）は従来例の画像読取装置の一例を示す全体図、
（ｂ）はその主照明光源を示す正面図である。FIG. 4A is an overall view showing an example of a conventional image reading apparatus;
(B) is a front view showing the main illumination light source.
【図５】 （ａ）（ｂ）（ｃ）は従来例の照度分布を示すグラフで
ある。FIGS. 5A, 5B and 5C are graphs showing the illuminance distribution of a conventional example.
２……主照明光源 ３……第１の拡散板 ４……結像光学系 ５……結像面となる撮像面 ６……補助照明光源 ７……第２の拡散板 Ｌ……低照度部分 LED……発光素子としての発光ダイオード Ｍ……ミラーであるミラー面 Ｐ……原像面 2 Main illumination light source 3 First diffusion plate 4 Imaging optical system 5 Imaging surface serving as an imaging surface 6 Auxiliary illumination light source 7 Second diffusion plate L Low illuminance Partial LED: Light-emitting diode as light-emitting element M: Mirror surface that is a mirror P: Original image surface
Claims (2)
する主照明光源と、 この主照明光源で照射された主照明光を拡散する第１の
拡散板と、 この第１の拡散板で拡散された主照明光が照射される原
像面と、 この原像面で反射された主照明光の光路を曲折するミラ
ーと、 このミラーで反射された前記主照明光を結像する結像光
学系と、 この結像光学系で結像された画像を形成し読取画像を得
る結像面と、 前記結合光学系およびミラー間の主照明光の光路の近傍
に位置して設けられ前記ミラーを介した前記原像面まで
の距離が前記主照明光源と前記原像面の距離より長い位
置に配設された前記結像面の主照明光の低照度部分の照
度を補い前記ミラーで反射して前記原像面に補助照明光
を照射する補助照明光源と、 この補助照明光源で照射された補助照明光を拡散する第
２の拡散板と を具備したことを特徴とする画像読取装置。1. A main illumination light source comprising a plurality of light emitting elements for irradiating main illumination light, a first diffusion plate for diffusing the main illumination light emitted by the main illumination light source, and a first diffusion plate An original image surface irradiated with the main illumination light diffused by the above, a mirror that bends an optical path of the main illumination light reflected by the original image surface, and an image forming device that forms an image of the main illumination light reflected by the mirror. An image optical system, an image forming surface that forms an image formed by the image forming optical system and obtains a read image, and is provided near the optical path of main illumination light between the coupling optical system and the mirror. The distance to the original image plane via a mirror supplements the illuminance of the low illuminance portion of the main illumination light on the imaging plane, which is disposed at a position longer than the distance between the main illumination light source and the original image plane. An auxiliary illumination light source for reflecting and irradiating the original image surface with auxiliary illumination light; And a second diffusing plate for diffusing the auxiliary illumination light.
ズムの一面に形成される ことを特徴とする請求項１記載の画像読取装置。2. The image reading device according to claim 1, wherein the original image surface and the mirror are formed on one surface of the triangular prism, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23640790A JP3270460B2 (en) | 1990-09-06 | 1990-09-06 | Image reading device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23640790A JP3270460B2 (en) | 1990-09-06 | 1990-09-06 | Image reading device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04117761A JPH04117761A (en) | 1992-04-17 |
| JP3270460B2 true JP3270460B2 (en) | 2002-04-02 |
Family
ID=17000300
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23640790A Expired - Lifetime JP3270460B2 (en) | 1990-09-06 | 1990-09-06 | Image reading device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3270460B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5359207A (en) * | 1993-11-29 | 1994-10-25 | Xerox Corporation | Wedge scanner utilizing two dimensional sensing arrays |
| JP2007201826A (en) * | 2006-01-26 | 2007-08-09 | Ricoh Co Ltd | Image reading apparatus and image forming apparatus |
-
1990
- 1990-09-06 JP JP23640790A patent/JP3270460B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04117761A (en) | 1992-04-17 |
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