JPH08161471A - Detector for rugged pattern on surface of object - Google Patents

Abstract

PURPOSE: To detect avoid an afocal state and to detect a fingerprint pattern inexpensivly with high compactness by forming the detector with an image pickup element reading a pattern of a surface of an object depressed onto a pressing face and an optical system forming an image of the pattern to the image pickup element. CONSTITUTION: A light emitted from a light emitting body 140 to a pressing face 111 with which projections 102 of a fingerprint are in contact is scattered in every direction basically. A light emission face 114 is arranged to a transparent solid body 110 in parallel with the pressing face 111 and a lens 130 and an image pickup element 120 such as CCD image sensor are arranged on an optical axis being a straight line passing through the center of a fingerprint detection range 111a perpendicular to the pressing face 111 so that an image on the fingerprint detection range 111a is optically formed on the image pickup element 120. Thus, the light made incident into the lens 130 among the scattered lights is collected on the image pickup element 120 and then the pattern of the projections 102 of the fingerprint on the fingerprint detection range 111a is detected brightly by the image pickup element 120.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting uneven patterns on the surface of an object represented by a fingerprint, and more particularly to a structure of an optical detecting section for detecting the uneven patterns.

[0002]

2. Description of the Related Art A typical example of the structure of a conventional optical detecting section is shown in, for example, Japanese Patent Laid-Open No. 2-194485 Fingerprint Data Input Device, but basically it is as shown in FIG. Is.

With the finger placed on the pressing surface 111 of the finger on the prism 110, the pressing surface 111 is irradiated with illumination light from the light source 140, and the reflected light from the pressing surface 111 is reflected by the lens 13.
The image of the fingerprint on the pressing surface 111 is focused on the image pickup element 120 via the light beam 0. Since the manner of reflection from the pressing surface portion with respect to the concave portion 101 of the fingerprint and the reflected light intensity are different from the manner of reflection from the pressing surface portion with which the convex portion 102 of the fingerprint is in contact and the reflected light intensity,
The fingerprint pattern is observed on the image sensor 120.

Further, FIG. 4 shows an optical system in which, when the angle of incidence of the illumination light on the concave portion 101 of the fingerprint exceeds the critical angle at which the illumination light is totally reflected, the totally reflected light enters the image sensor 120. In this case, the convex portion 10 of the fingerprint is shown at this time.
The concave portion 101 of the fingerprint is detected brighter than that of 2. However, in this case, the design is often difficult due to measures against the glare phenomenon.

There is also an optical system in which the incident angle of the illumination light is within the critical angle, but in this case, the convex portion of the fingerprint is detected brighter than the concave portion of the fingerprint. However, in this case, it is often difficult to increase the contrast between the concave and convex portions of the fingerprint of the detected image.

In any case, the first major problem is
When the pressing surface is not perpendicular to the axis of the optical system of the lens 130 and the image pickup element 120 and is parallel to the paper surface of this paper, the depth of field of the optical system at a position distant from the axis of the optical system within the plane. That is, a so-called defocus phenomenon occurs in which the sharpness is deteriorated due to the relationship. Therefore, the fingerprint detection range in which sufficient sharpness can be obtained is inevitably narrowed, information about the fingerprint is insufficient, and there are problems such as an error in fingerprint collation.

The second problem is that it is difficult to obtain a high-contrast detected image of the pattern of the concave and convex portions of the fingerprint.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure of an optical detecting section capable of avoiding the defocus phenomenon.

Another object of the present invention is to provide a novel optical system capable of detecting a fingerprint pattern in a state of higher contrast.

Still another object of the present invention is to provide a structure of an optical detecting section which enables a fingerprint pattern detecting apparatus to be manufactured compactly and at low cost.

Still another object of the present invention is to improve the performance of a fingerprint collation device as an application of a fingerprint pattern detection device, in order to improve its performance, the relative positional relationship between a fingertip and an optical system is
It is an object of the present invention to provide a structure capable of reducing a deviation between a detection time for registering a fingerprint and a detection time for collating a fingerprint.

Still another object of the present invention is to detect the S
To increase the N ratio, to provide a structure for blocking disturbance light to the optical system as much as possible.

[0013]

In order to solve the above first problem, in the present invention, the axis of the optical system for detecting the reflected light from the pressing surface 111 is arranged substantially perpendicular to the pressing surface 111. The image on the pressing surface 111 is optically formed on the image pickup device with sufficient definition.

In order to solve the above second problem, the pressing surface 1
The irradiation angle of most of the illuminating light flux to 11 is set to exceed the critical angle, and most of the illuminating light irradiated to the pressing surface portion of the concave portion 101 of the fingerprint is totally reflected, and the totally reflected light is reflected to the image sensor 120. Do not let it enter, and the convex part 10 of the fingerprint
The diffused reflected light from the pressing surface portion in contact with the image pickup element 120
As a result, the detection image of the concave portion 101 of the fingerprint is made extremely dark as compared with the detection image of the convex portion 102 of the fingerprint, so that the high contrast of the pattern of the concave portion and the convex portion of the fingerprint can be detected.

In order to solve the above-mentioned third problem, in the present invention, a lens portion which is entangled with an optical system of a fingerprint pattern detecting device is integrally provided on a transparent solid forming a pressing surface of a finger.

In order to solve the fourth problem, in the present invention, a guide wall for the fingertip is provided on the pressing surface of the finger.

In order to solve the above-mentioned fifth problem, in the present invention, the pressing surface of the finger is arranged inside the hole into which one finger is inserted.

[0018]

【Example】

(Embodiment 1) This is a basic embodiment of the present invention and will be described with reference to FIG.

FIG. 1 is a diagram showing a relationship between a finger and an optical detecting portion at the time of detecting a fingerprint, in which a finger 100 is pressed against a pressing surface 111. The pressing surface 111 is one surface of the transparent solid 110. Illumination light is emitted from a light emitting body 140 such as a light emitting diode, a fluorescent lamp, or a rare earth lamp, and passes through an optical path length changer 150 such as a lens to pass through a light incident surface 112 of the transparent solid 110 to a fingerprint detection range 111a of a pressing surface 111.
It is irradiated so that it covers.

The irradiation angle of the irradiation light is basically an angle that exceeds the so-called critical angle at which the irradiation light is totally reflected when the pressing surface 111 is in contact with air. Actually, it may be technically or costly to set the irradiation angles of all the irradiation lights to be equal to or more than the critical angle by the optical path length changer 150. From the viewpoint, it is sufficient that a sufficient amount of light flux is greater than or equal to the critical angle. From the viewpoint of energy efficiency, it is desirable that the ratio of the luminous flux exceeding the critical angle and being as close to the critical angle as possible is desirable. The light radiated to the portion of the pressing surface 111 facing the concave portion 101 of the fingerprint is totally reflected and goes out of the detection portion from the surface 113. On the other hand, the light applied to the portion of the pressing surface 111 with which the convex portion 102 of the fingerprint is in contact is basically scattered in all directions.

Therefore, the transparent solid 110 has a pressing surface 111.
A surface 114 (hereinafter referred to as a light emitting surface 114) parallel to the optical axis is a straight line which is perpendicular to the pressing surface 111 and passes through the center of the fingerprint detection range 111a, and the lenses 130 and C are arranged on the optical axis.
The image sensor 120 such as a CD image sensor is arranged so that the image on the fingerprint detection range 111a is optically formed on the image sensor 120. Therefore, of the scattered light, the light incident on the lens 130 is collected on the image sensor 120, and the pattern of the convex portion 102 of the fingerprint on the fingerprint detection range 111a is brightly detected by the image sensor 120.

The image pickup element 120 is generally a photodetection element having two-dimensional matrix-shaped detection pixels, and the information from the image pickup element 120 is sent to a computer and used for processing such as storage, analysis, comparison and the like. .

The shaded portions 160 and 170 are light-shielding walls for reducing the disturbance light to the image sensor 120 as much as possible.

Due to the structure of the optical detecting portion of this embodiment, the image pickup device 120 and the pressing surface 111 are parallel to each other, and the fingerprint detection range 111a and the image pickup device 120 are present near the optical axis of the optical system. Defocusing of the image on the fingerprint detection area 111a does not occur, and the drawbacks of the conventional optical detection unit structure are improved.

Further, the reflected light entering the image pickup element 120 from the pressing surface portion of the fingerprint against the concave portion 101 is extremely reduced, and the contrast of the detected image is improved. Of course, there is no glare phenomenon seen from the image sensor.

The optical axis does not necessarily need to be exactly perpendicular to the pressing surface 111, and may be deviated from the vertical within an allowable range due to the relationship between the subject depth of the optical system and the size of the subject. In connection with this, the light emitting surface 114 does not necessarily have to be exactly parallel to the pressing surface 111.

(Embodiment 2) This is an evolution of the structure shown in FIG. 1. The structure is shown in FIG. 2 and will be described.

The first difference from the first embodiment is that the light emitter 140
The optical path length changer 150 for increasing the ratio of the illumination light (scattering state) from the light exceeding the critical angle is provided with an independent lens, and an incident surface (light incident surface) of the illumination light of the transparent solid 110 is provided.
This is a change to the lens portion 112a integrally provided on the 112.

The second difference is that the lens portion 114a integrally provided on the light emitting surface 114 on the transparent solid 110 plays the role of the lens 130 for forming the image on the fingerprint detection range 111a on the image pickup device 120. That is to share.

Of course, depending on the design method, the lens 1
It is possible to eliminate 30.

The reason why the lens 130 is used together is that the axial length of the optical system can be shortened without deteriorating the image quality, and the effect is that the entire apparatus according to the present invention can be made compact.

In the present embodiment, it is a great effect that the transparent solid 110 is integrated with the lens portion so that it can be made compact and the cost can be reduced. By the way, the transparent solid 110 is a component that can be mass-produced by injection molding, and the cost can be greatly reduced by integrating the lenses.

The shaded portions 160 and 170 are light shielding walls for reducing the disturbance light to the image pickup device 120 as much as possible.

(Embodiment 3) This embodiment relates to a structure which an optical detecting section should have when the device according to the present invention is used for a fingerprint collating device, and its contents are shown in FIG. To do.

The first feature is that a projection 115 having two-sided walls arranged substantially at right angles is provided as a finger positioning guide on the pressing surface 111 on the transparent solid 110. The effect is that regardless of the thickness of the finger, the side surface and the tip of the finger can be pressed against these two walls, so that the finger of the finger with respect to the optical detection unit can be detected no matter when the fingerprint pattern is detected by the same person. Since the position is almost unchanged, the detected images of fingerprints are almost the same. Therefore, the difference between the detected images of the fingerprints at the time of fingerprint registration and the matching is reduced, and it becomes very easy to match the reference points for the comparison of the images at the fingerprint matching. That is, the fingerprint collation algorithm can be simplified and highly accurate, resulting in a reduction in the amount of computer software, an increase in processing speed, a saving in computer memory, an improvement in collation accuracy, and an improvement in the reliability of the collation device. It will be.

The projection 115 can be formed integrally with the transparent solid 110 by injection molding, and its height is shown to the extent that the influence on the finger positioning accuracy due to the change in the length of the fingernail can be eliminated. Although not applied, it is possible to devise a method of holding it low so that it does not come into contact with the nail even partially.
There is no moving part, and there is an effect that low cost and high reliability are obtained.

The second feature is that the pressing surface 111 and the entire fingertip are covered with the light blocking member 180 so that unnecessary disturbance light does not enter the image pickup element 120.

Further, a hole 181 through which the finger passes is provided at the entrance of the finger, and the finger is provided with elasticity so that both the light-shielding property is maintained and the finger is easily taken in and out.

Although the fingerprint has been mainly described as an example of the uneven pattern on the surface of the object, the optical detecting portion according to the present invention has a convex portion in contact with a transparent solid and a surface in contact with the transparent solid. Anything that changes the condition of total internal reflection may be used.

[0040]

As described above, according to the present invention, a defocused image in a conventional optical detecting section of a pattern detecting apparatus for a surface of an object having irregularities, which is represented by fingerprint detection, makes a detected image clear. It has been possible to provide a structure of an optical detection unit capable of avoiding a decrease in detection accuracy due to a decrease in degree or a decrease in reliability due to a lack of information due to a narrow range of a detected part.

As another effect, the contrast of the fingerprint detection pattern could be improved.

Further, as still another effect, it is possible to provide a structure of an optical detecting portion which enables a fingerprint pattern detecting device to be manufactured compactly and at low cost.

Further, as a further effect, it is possible to provide a structure in which the fingerprint collation apparatus can improve the reliability without shifting the position of the finger during fingerprint registration and collation.

Further, as still another effect, it is possible to provide a structure capable of blocking ambient light to the optical system as much as possible and maintaining good operability.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical detection unit which is the basis of the present invention.

FIG. 2 is a diagram showing an example of lens integration and the like of the example shown in FIG.

FIG. 3 is a diagram showing a fingertip positioning structure and a disturbance light blocking structure when the present invention is used in a fingerprint matching device.

FIG. 4 is a diagram showing a typical structure of an optical detection unit used in a conventional fingerprint detector.

[Explanation of symbols]

 100 Finger 101 Fingerprint Depression 102 Fingerprint Convex 110 Transparent Solid (Prism in Conventional Example) 111 Pressing Surface 111a Fingerprint Detection Range 112 Light Incident Surface 112a Lens Part 113 Surface 114 Light Emitting Surface 114a Lens Part 115 Protrusion 120 Imaging Device 130 Lens 140 Light emitter 150 Optical path length changer 160 Shielding wall 170 Shielding wall 180 Shielding member 181 Hole

Claims (8)

[Claims] 1. A transparent solid having a pressing surface on which an object having a concave-convex pattern is pressed, and illumination arranged so that illumination light is emitted from inside the transparent solid to the pressing surface at an angle exceeding a critical angle. An optical system, an image sensor that reads a pattern on the surface of the object pressed against the pressing surface by detecting reflected light other than totally reflected light of the reflected light on the pressing surface of the illumination light, and the pattern An uneven surface pattern detection device for an object surface, which comprises an optical system for forming an image on the image pickup device. 2. The object surface according to claim 1, wherein an optical axis of the optical system is substantially perpendicular to the pressing surface, and the transparent solid has a light emitting surface at a position facing the pressing surface. Uneven pattern detection device. 3. The uneven surface pattern detection device according to claim 2, wherein the light emitting surface is a lens surface. 4. The uneven surface pattern detection device according to claim 1, wherein the illumination optical system includes at least a light emitting body and a lens integrally provided on the transparent solid. 5. The uneven surface pattern detection device according to claim 1, wherein a projection for planar alignment of the object to be pressed is provided on the pressing surface. 6. The uneven surface pattern detection device according to claim 5, wherein the projections are arranged so as to regulate the planar position of the object from two directions. 7. The uneven surface pattern detecting device according to claim 1, wherein at least the pressing surface is covered with a light shielding member except for a hole portion through which the object passes. 8. The uneven surface pattern detecting device according to claim 7, wherein the hole portion has elasticity.