JPS62187818A - Detecting device for projection and recess surface information - Google Patents

Abstract

PURPOSE:To obtain a sharp image which is not affected by totally reflected illumination light by arranging a guiding-out hologram off the optical path of totally reflected light. CONSTITUTION:When a finger 10, etc., is pressed against a recess and projection surface information input part 1a, the totally reflected light 17 after illuminating a projection and recess surface by total reflection travels by repetitive total reflection. Light scattered by a projection part 6, on the other hand, is propagated radially in every direction. Consequently, only the light which is scattered by projection parts 6 is propagated by repetitive total reflection to the hologram 3 arranged off the optical path of the totally reflected illumination light 17 and then guided out of a transparent flat plate 1, but none of the totally reflected illumination light 17 is propagated to the hologram 3. Thus, there is not such a problem that the totally reflected light 17 is incident on the hologram 3 to make its image brighter and the image decreases in contrast. Further, the totally reflected light 17 is only reflected totally in the transparent flat plate 1 and never reaches human eyes when the finger is placed on the projection and recess surface information input part 1a.

Description

[Detailed Description of the Invention] [Summary] In a device for illuminating a concavo-convex surface information input section with total reflection light when guiding convexity information totally reflected in a transparent flat plate to the outside using a hologram and detecting the convexity information. By arranging the extraction hologram at a position out of the optical path of the total reflection light, a clear image that is not affected by the total reflection illumination light is obtained.

[Industrial application field]

In today's highly information-oriented society, the establishment of security technology for computer systems has become an urgent need. In particular, strict control of entry into the computer room is an important issue in maintaining the confidentiality of information, in order to correctly identify the people handling this system. Currently, for this purpose, passwords, ID cards, and the like are being put into practical use, and personal verification systems using fingerprints and the like are beginning to be introduced.

Up until now, the methods of inputting information on uneven surfaces such as fingerprints have been to apply ink and press it once on paper and then input it using an image sensor, and to use optical elements such as prisms to input information on the glass/air interface. Another method was to instantly obtain a concavo-convex pattern by making a light beam incident at an angle greater than the critical angle.

The present invention is intended to enable uneven surface information to be clearly obtained in a device such as the latter that uses an optical element to immediately detect uneven surface information.

[Conventional technology]

The conventional method of applying ink to a finger, stamping it on paper, and inputting using an imaging system has the problem of staining the finger with ink every time, and also making it difficult to input due to uneven application, blurring, etc. was.

In order to solve this problem, an optical real-time input means using a prism 1) as shown in FIG. 6 has been proposed, as also proposed in Japanese Patent Laid-Open No. 55-81321. This is done by pressing the fingerprint (uneven pattern) on the surface of the finger 10 onto the oblique side of the prism 1), and applying the illumination light 1 to the oblique side.
2 is incident at a critical angle or more. The incident light is scattered by the raised portions 6 of the fingerprint, is totally reflected at the interface 13 with air in the recessed portions 7, and enters the detector 4 such as an image sensor, so that the uneven pattern can be detected.

However, due to leakage light due to multiple reflections, the recess 7
There was a drawback that scattered light from the wafer reaches the detector 4, reducing the contrast of the concave-convex pattern. Furthermore, since a prism is used, it is not possible to reduce the thickness. In particular, when detecting a pattern of protrusions and recesses on the entire surface of the palm, the prism must be made larger, resulting in a large loss of equipment.

Therefore, the applicant of the present invention proposed a device as shown in FIG. 7(b) in Japanese Patent Application No. 60-41437. Reference numeral 1 denotes a flat plate that is transparent to the light of the light source 2 used, and an uneven surface 5 such as a fingerprint is pressed against the uneven surface information input section 1a. A light source 2 for illuminating this uneven surface 5 is arranged directly below. A hologram 3 that takes out the light 9 that is totally reflected in the transparent flat plate 1 to the outside is arranged at a position away from the uneven surface information input section 1a, and a TV camera or the like that detects the light taken out by the hologram 3. A detector 4 is provided.

Fingerprints can also be photographed by placing a film in place of the TV camera.

With the uneven surface 5 such as a fingerprint pressed against the transparent flat plate 1,
When the uneven surface 5 is illuminated by the light source 2, the subsequent paths of light scattered by the convex portions 6 of the uneven surface 5 and light scattered by the concave portions 7 are completely different. That is, the light 8 scattered by the recess 7 enters the transparent flat plate 1, is refracted, and then exits to the outside of the transparent flat plate 1 again.

At this time, according to Snell's law, all the light is emitted from the transparent flat plate 1 parallel to the angle of incidence on the transparent flat plate 1. On the other hand, the components of the light 9c; i, ff, smaller than the boundary angle scattered by the convex portion 6, are emitted to the lower part of the transparent flat plate, but the components larger than the critical angle are
It undergoes repeated total reflection at the transparent flat plate/air interface and propagates within the transparent flat plate 1. That is, in a concavo-convex pattern pressed onto a transparent flat plate, concave portions and convex portions are optically discriminated based on the difference in the scattering angle range of scattered light to the transparent flat plate depending on the presence or absence of an air layer at the interface of the transparent flat plate. The light 8 scattered by the recess 7 as described above
are all emitted outside the transparent flat plate 1, so the light ray 9 propagating inside the transparent flat plate 1 is information only from the convex part 6, so if this is detected, it will be possible to detect only the ridges of the fingerprint. Pattern information can be obtained.

When the light that has been totally reflected and propagated within the transparent flat plate 1 reaches the position of the hologram 3, it is guided into the hologram 3, diffracted by the hologram 3, and guided to the outside.
Photographed with camera 4. In other words, pattern information from only the convex portions 6 can be observed as a fingerprint.

As shown in FIG. 6(a), among the scattered light at the convex portion 6,
It is also possible to make the light scattered at the critical angle or more directly enter the hologram 3 and take it out.

Note that the transparent flat plate 1 may be made of glass, plastic, or the like. Since the hologram 3 extracts the light arriving from the uneven surface information input section 1a to the detector 4 side,
The diffraction grating fringes 3s are at an angle perpendicular to the optical path from the uneven surface information input section 1a.

[Problem that the invention seeks to solve]

However, since the light source 2 is located directly below the transparent flat plate 1, when the computer operator places his or her finger on the uneven surface information input section 1a upon entering the room, the light from the light source 2 enters the eyes 18, which adversely affects the eyes. This is a serious problem because a laser beam is normally used as the light source 2.

As shown by the chain line 14, it is conceivable to provide a light-shielding cover and insert the finger 10 into it, but since the position of the fingertip cannot be confirmed, it is not possible to insert the finger 10 into the light-shielding cover. It is not possible to position the fingertips, and there is a risk that the fingertips may be misaligned. Furthermore, the uneven surface information input section 1a is easily soiled by sweat, oil components, etc., but the soiling is difficult to detect and cleaning is also difficult.

It is also possible to arrange a structure in which a tuff-shaped inlet for detecting finger contact is provided on the transparent flat plate 1, and the laser light source 2 is turned on only when it is detected that the finger is pressed against the uneven surface information input section 1a. However, it is not perfect because a special control circuit is required and light leaking from around the old O enters the eye.

By combining the method of detecting uneven surface information using total internal reflection illumination as shown in FIG. 6 and the concept of the transparent flat plate 1 shown in FIG. 7, it is also possible to create a configuration as shown in FIG. 8.

In other words, the end face of the transparent flat plate 1 is cut diagonally as in (al), and the laser beam 16 is made to enter from the slope 15.

Then, the laser beam is totally reflected in the regions aa', bb', . . . where the laser beam is reflected at the transparent plate/air interface on the surface of the transparent flat plate 1, and total internal reflection illumination is performed. That is, by selecting the angle α of the slope 15 and the critical angle C of the surface of the transparent flat plate as in (bl), total reflection is repeated and the light is guided to the position of the hologram 3 without escaping into the air.

Then, a-a', bb'... on the front side of the transparent flat plate 1.
Assuming that the area is the uneven surface information input section 1a, scattering occurs at the convex portions 6 of the uneven surface, and the scattered light 19 propagates to the position of the hologram 3 in the same manner as in the case of FIG.

Since the light is totally reflected at the transparent flat plate/air interface in the recess 7 , the totally reflected light also reaches the hologram 3 .

When this totally reflected light is detected by the hologram 3, the convex portions 6 are dark and the concave portions 7 are bright, resulting in a negative appearance. Therefore,
By setting the incident angle i to the hologram 3 to be different from the critical angle C, the totally reflected light 17 does not enter the hologram 3, and only the scattered light °19 from the convex portion 6 can enter.

According to this configuration, since all of the laser light is totally reflected within the transparent flat plate 1, the danger of entering the human eye can be avoided. However, even if the incident angle i is different from the critical angle C in this way, the totally reflected light 17 cannot be completely blocked, so a problem arises in that the contrast is degraded by the totally reflected light.

The technical problem of the present invention is to provide an uneven surface information detection device that prevents laser light from entering the human eye by causing total reflection light to enter a transparent flat plate and illuminating the uneven surface information input section by total reflection. The object of the present invention is to solve the above problems and to make it possible to detect uneven surface information with excellent contrast without being affected by total internal reflection illumination light.

[Means for solving problems]

FIG. 1 is a diagram explaining the basic principle of the uneven surface information detection device according to the present invention, in which (a) is a plan view, and (b) is a
-b' sectional view. Reference numeral 1 denotes a flat plate that is transparent to the light from the light source 2, and the uneven surface information input section 1a is illuminated by total internal reflection illumination. The uneven surface information input section 1 a is provided in the middle of the optical path of the totally reflected light 17 and on the front surface side of the transparent flat plate 1 .

3 is a hologram that takes out an image from the inside of the transparent flat plate 1 to the outside, and is arranged at a position away from the optical path of the totally reflected light 17;
An image taken out by this hologram 3 is detected by an image sensor 4 or the like.

Note that in order to introduce the totally reflected light into the transparent flat plate 1, the end face of the transparent flat plate l may be formed obliquely, and the laser beam may be incident from the slope 15 (this is also proposed in Japanese Utility Model Application Publication No. 55-81321). As shown in the figure, the effect of the image extraction hologram 3 can be used in reverse to provide a hologram on the back surface of the transparent flat plate 1, and the laser beam can be introduced into the transparent flat plate 1 by making the hologram incident on the hologram.

[Effect]

As in the case of FIG. 8, touch the finger 10 on the uneven surface information input section la.
etc., the totally reflected light 17 illuminates the uneven surface by total reflection, and then repeats total reflection and travels. One side convex part 6
The scattered light propagates radially in all directions, as shown by 19... Only the light scattered by the portion 6 propagates through repeated total reflections and is taken out of the transparent flat plate 1, but the totally reflected illumination light 17 does not propagate to the hologram 3 position. The incident illumination light 17 brightens the image and does not cause problems such as a decrease in image contrast.Furthermore, the totally reflected light 17 is only totally reflected in the transparent flat plate 1 and is not directed to the uneven surface information manual section 1a. It will not come into contact with the human eye when it is placed.

〔Example〕

Next, how the uneven surface information detecting device according to the present invention is actually implemented will be explained using an example.

FIG. 2 is a perspective view showing the first embodiment of the uneven surface information detection device according to the present invention, and the transparent flat plate 1 is cut along the chain line in FIG. Therefore, when the laser beam is incident from the slope 15 at the end so that the totally reflected illumination light can be totally reflected inside the transparent flat plate 1, the total reflected light 17 will be totally reflected inside the transparent flat plate 1. ,proceed.

Light 1 illuminated by this total reflection light and scattered by the convex parts of the uneven surface
9 is a hologram 3 provided on the back side of the other end of the L-shaped part.
It is totally reflected at the position, taken out to the outside of the transparent flat plate 1, and detected by the image sensor 4. - As an example, an L-shaped transparent flat plate is shown, but FIG.
The transparent flat plate 1 can have any shape as long as the extraction hologram 3 is placed at a position out of the optical path.

FIG. 3 shows an example in which the embodiment shown in FIG. 2 is further improved. The image taken out from the hologram 3 is reflected by a reflecting mirror 20,
The configuration is such that the light enters the image sensor 4 through a set of two cylindrical lenses 21 and a set of two spatial filters 22. Note that it is also possible to omit the reflecting mirror 20 and arrange the cylindrical lens 21, the spatial filter 22, and the image sensor 4 directly below the hologram 3.

The cylindrical lens 21 consists of a vertical cylindrical lens CLv and a horizontal cylindrical lens CLh, which are orthogonal to each other.

Due to the astigmatism of the hologram 3, the focal point in the vertical direction (the optical path direction from the uneven surface information input section 1a to the hologram 3) and the lateral direction (direction perpendicular to the optical path from the uneven surface information input section 1a to the hologram 3). Because the position with the focal point shifts and the image becomes blurry,
In order to correct this blur, two cylindrical lenses CLv and CLh are arranged. Moreover, the spatial filter 22 includes a vertical cylindrical lens CL.
It consists of a spatial filter Fv having a slit 71-5v parallel to the axis of the cylindrical lens CLh, and a spatial filter Fh having a slit Sh parallel to the axis of the horizontal cylindrical lens CLh.

FIG. 4 is a perspective view illustrating that the vertical focus and the horizontal focus are shifted. Point 6 on the finger in Figure 7
When the optical path from to the hologram 3 is developed, it becomes as shown in Fig. 4. In FIG. 7, a single line 9 represents the light scattered at this single point 6, but in reality, as shown in FIG. 4, it propagates from the single point 6 while spreading out in a diffuse spherical wave shape.
Reach hologram 3. Therefore, when the light extracted by the hologram 3 is imaged on the screen 24 by the imaging lens 23 and viewed by an observer, a virtual image 6a will be seen on the extension line of the diffracted light 25.

If the light that enters the hologram 3 from one point 6 is only light that is parallel to the object wave at the time of creating the hologram, no aberration will occur. However, in reality, a plurality of scattered lights such as 91, 92, and 93 are generated and enter the hologram 3. Assuming that only the light ray 92 is parallel to the object wave at the time of creation, the other light rays 91 and 93 cause aberrations and the image appears blurred.

In other words, the light scattered at one point 6 on the finger is the hologram 3
For example, the 3 points above pass through H3 and reach the observer's eye 18. The point where this diffracted light beam 25 is extended in the opposite direction and intersects is a point 6a on the finger observed by the observer. However, no matter where the screen 24 is placed, these light rays do not intersect at one point, but at three points S1...S3.

In other words, this is an aberration. No matter what kind of object light is used to create the hologram 3 from which information light is extracted, the wavefront created for the hologram is different from the wavefront reproduced from the fingerprint, so aberrations occur in the observed fingerprint image. Resulting in.

Aberrations in the hologram 3 can be divided into vertical aberrations and horizontal aberrations, assuming that the direction parallel to the optical path is the vertical direction (2) and the direction perpendicular to the optical path is the lateral direction. Due to astigmatism, at the vertical focus position f6b, a point on the finger is clearly imaged in the vertical direction, but blurred in the horizontal direction. Conversely, at the horizontal focus position 6c, a point on the finger is clearly imaged in the horizontal direction, but blurred in the vertical direction.

Therefore, in Fig. 3, the vertical cylindrical
The lens CLν focuses the image spread in the lateral direction into the slit Sv of the spatial filter Fv arranged at the focal position. Further, the image spread in the vertical direction is focused by the horizontal cylindrical lens CLh into the slit sh of the spatial filter Fh arranged at the focal position. By narrowing down the direction of blur in this way, a clear image with high contrast can be obtained.

Note that if 6b is a vertical focal point and 6c is a horizontal focal point, the distance between the two is called an astigmatism difference. Two cylindrical lenses CL
The interval between ν and CLh is the same as the astigmatism difference.

Since a hologram can also provide the same effect as a cylindrical lens, in the present invention, all optical elements capable of such a cylindrical lens effect are included in the concept of a cylindrical lens.

FIG. 5 is a side view showing the function of the spatial filter 22, and an example of vertical focus will be described. A spatial filter Fv for vertical focus is placed at the focal position of the cylindrical lens CLv.
is placed, the horizontally enlarged and blurred image 6b
is focused by a cylindrical lens CLv into a slit Sv of a spatial filter Fv, and appears on the screen 24,
Image 6d appears. Among the lights 25 between the virtual image 6b and the spatial filter Fv, the image caused by the light 25n that does not pass through the focal position of the cylindrical lens CLv becomes a cause of blur. Therefore, by arranging a spatial filter Fv having a slit Sv at the focal position of the cylindrical lens CLv and allowing only light near the focal position to pass through, an image with good contrast can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, in the uneven surface information detection device that illuminates the uneven surface information input section La with total internal reflection illumination and prevents laser light from entering the human eye, Since the hologram 3 for extraction is placed at the position where the hologram 3 is located, the total reflected light does not reach the hologram 3. As a result, the conventional problem of a part of the total reflection light reaching the hologram 3 and reducing the contrast of the image of uneven surface information is solved.

[Brief explanation of drawings]

Fig. 1 is a plan view and a sectional view showing the basic principle of the uneven surface information detection device according to the present invention, Fig. 2 is a perspective view showing the first embodiment of the present invention, and Fig. 3 is a further improvement of the first embodiment. FIG. 4 is a perspective view showing the effect of generating astigmatism, FIG. 5 is a side view showing the effect of the spatial filter, and FIG. 6 is a perspective view of the uneven surface information using a conventional prism. Fig. 7 is a side view of the detection device; Fig. 7 is a side view of the uneven surface information detection device using a transparent flat plate; Fig. 8 is a side view of the uneven surface information detection device using a transparent flat plate, and Fig. 8 shows that total internal reflection illumination is performed on the transparent flat plate to prevent laser light from entering the human eye. FIG. 3 is a side view of the device. In the figure, 1 is a transparent flat plate, 1a is an uneven surface information input section,
2 is a laser light source, 3 is a hologram, 5 is an uneven surface, 6 is a convex part (one point on the convex part), 6a, 6b, 6c are images of one point on the convex part, 15 is a slope, 17 is total internal reflection (illumination) light , 19 . . . indicate scattered light at the convex portions, respectively. Patent Applicant: Fujitsu Co., Ltd. Agent, Patent Attorney: Minoru Aoyagi

Claims (2)

[Claims] (1), uneven surface information input section (1a) where the uneven surface is crimped;
A transparent flat plate (1) having a transparent flat plate (1) having a transparent flat plate (1), and a transparent flat plate (1) that makes the total reflected light enter the transparent flat plate (1) so that the total reflected light that is totally reflected at the transparent flat plate/air interface reaches the uneven surface information input section (1a). The reflected illumination means, among the light scattered by the uneven surface information input section (1a) and incident on the transparent flat plate (1) at an angle equal to or greater than the critical angle, among the scattered light from the convex parts such as fingerprints, is In an uneven surface information detection device that is equipped with a hologram (3) that is guided to the outside by breaking the reflection conditions and a means for detecting the light that has been guided to the outside, a hologram (3) that is emitted to the outside by disabling the reflection conditions is used. An uneven surface information detection device characterized in that the above-mentioned extracting hologram (3) is disposed to prevent total internal reflection illumination light (17) from entering the hologram (3). (2) The total internal reflection illumination means is characterized in that the end face of the transparent flat plate (1) is formed obliquely, and the laser light is incident from the slope (15). 1
The uneven surface information detection device described in ).