JPH01287785A - Irregular shape detecting device - Google Patents

Abstract

PURPOSE:To obtain the small-sized, lightweight, and thin irregular shape detecting device which is easy to assemble by forming an image forming means integrally with one transparent optical waveguide plate. CONSTITUTION:At least one beam converging means 31 which forms the image of reflected light from the irregular part of a body 10 to be detected on an external image detector on the transparent waveguide plate 11 is assembled integrally in the optical waveguide plate 11. Then reflected light from the irregular part is separated optically when passing in the optical waveguide plate 11 and signal light having irregularity information forms its image on a photodetector 29 by the beam forming means formed integrally in the optical waveguide plate 11. Further, the beam image forming means is formed integrally in the optical waveguide plate 11, so an input part is unitized. Thus, the constitution is made compact to eliminate the need for an extra optical-axis alignment assembling process, thereby simplifying the whole device and reducing its size and thickness.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an uneven shape detection device for detecting an uneven pattern such as a fingerprint, and aims to make the device smaller, thinner, and simpler. When an object is pressed against one plane of the light guide plate and light is irradiated from inside the light guide plate to the object to be tested, the unevenness of the object is detected by optically identifying the scattered signal light from the concave and convex parts of the object surface. In an apparatus for detecting a shape, at least one beam converging means for focusing the reflected light from the uneven portion on an image detector outside the light guide plate is integrally assembled within the light guide plate.

[Industrial application field]

The present invention relates to an uneven shape detection device for detecting an uneven pattern such as a fingerprint.

Fingerprint matching is used as one of the methods for identifying individuals. In this fingerprint verification, since the fingerprint is usually treated as an image, a human-powered device is required to convert the fingerprint into image data.

[Conventional technology]

A fingerprint is a concavo-convex pattern, and the basic principle of detecting concavo-convex patterns conventionally used is shown in FIGS. 17 and 18.

In Fig. 17, when the finger 10 (Fig. 18) is pressed against one plane of the light guide plate (11) made of a transparent material, the convex part P (Fig. 18) of the fingerprint comes into close contact, but the concave part Q (Fig. 18) ) do not touch. A semiconductor laser 15 (LD) irradiates LD light toward the fingerprint contact portion 13 from one surface 11A processed into a prism shape. At this time, if the incident angle of the LD light with respect to the contact surface 13 is selected to cause total reflection, the light r, (Fig. 18) is totally reflected at the concave portion Q and propagates in the X direction, but the convex portion At P, since the light rz (FIG. 18) is scattered, the directivity is weakened and a component propagating in the X direction is generated. Of these, the component element 3 that propagates inside the light guide plate 11 while being totally reflected in the X direction is taken out of the light guide plate by the hologram 17, and is transferred onto the image sensor (CC[l) 29 by the orthogonal cylindrical lens system 21 (21A, 21B). When the image is focused on the fingerprint, an image of the fingerprint convex portion, that is, a fingerprint image can be obtained.

In FIG. 17, 19 is a mirror for bending the direction of light by 90 degrees, and 23 is a spatial filter for extracting a specific spatial frequency component.

FIG. 18 shows an example in which a triangular prism 12 is used as a light guide plate, and the basic principle is exactly the same as that in FIG. 17. In FIG. 18, when the finger 10 is pressed against the oblique side 12A of the triangular prism 12, the raised part P of the fingerprint comes into close contact with the prism, but the recessed part Q does not come into contact with the prism. Another side of the prism 12
The LD 15 illuminates the prism slope from B. When the incident conditions are set so that the irradiated light is totally reflected on the slope, the light r1 is totally reflected at the concave portion 0 and exits from the third surface 12C of the prism with directionality, but the light r2 is scattered at the convex portion P. directionality is weakened. When the light emitted from the prism is imaged on the CCD 29 by the imaging lens 18, the light from the fingerprint concave portion Q with good directivity is strong, and the light from the fingerprint convex portion P is weak. That is, a fingerprint image can be obtained.

[Problem to be solved by the invention]

All of the conventional methods described above include a light source (LBD), a cylindrical lens system 21 (Fig. 17) or an imaging lens system (Fig. 18), and a photodetector (CCD) in addition to the light guide plate.
) must be arranged and configured separately), which not only requires an extra optical axis alignment and assembly process, but also hinders miniaturization of the device).

If the optical system from the light source to the CCD can be made smaller and the fingerprint image can be made smaller, it would be possible to
It can be easily embedded into keyboards, etc., expanding the range of applications for fingerprint verification systems.

The purpose of the present invention is to realize the integration and compactness of the input unit in order to satisfy such requirements.1) It eliminates the need for an extra optical axis alignment assembly process, and also simplifies, miniaturizes, and thins the entire device. It's about trying.

[Means to solve the problem]

To achieve the above object, according to the present invention, at least one beam converging means for focusing the reflected light from the uneven portion of the test object on an image detector outside the transparent light guide plate is integrated within the light guide plate. Its structural feature is that it can be easily assembled.

Preferably, the beam focusing means is formed by a reflection type or transmission type diffraction grating or both.

Most simply, the diffraction grating has a lattice fringe distribution equivalent to a cylindrical, spherical, or aspherical lens.

If the beam converging means is formed by at least two diffraction gratings equivalent to a cylindrical lens, and these diffraction gratings are arranged so that the diffraction gratings are orthogonal to each other, an integrated structure completely equivalent to a conventional orthogonal cylindrical lens system can be obtained. .

The beam converging means can also be constructed by a non-flat surface partially formed on the surface of the light guide plate.

The non-flat surface is preferably a cylindrical surface, a spherical surface, or an aspheric surface.

By arranging two or more cylindrical surfaces at predetermined positions within the light guide plate so that their longitudinal axes are perpendicular to each other, a configuration equivalent to an orthogonal cylindrical lens system can be realized.

A reflective film may be provided on the non-flat surface to reflect light into the light guide plate. The light guide plate is easiest to mold using a plastic mold.

[For production]

The reflected light from the uneven portion is optically separated as it passes through the light guide plate, and the signal light with the unevenness information is imaged on a photodetector by a beam imaging means formed integrally with the light guide plate. be done.

Since the beam imaging means is integrally formed within the light guide plate,
The input section is integrated into a unit, which eliminates the need for an assembly process that involves alignment of the optical axis of the imaging system, and also reduces the size of the entire device.
Contributes to thinning.

If the beam focusing means is made of a diffraction grating (hologram), it can be realized without substantially increasing the thickness of the light guide plate. By combining an appropriate number of reflection holograms and transmission holograms depending on the length of the light guide plate, signal light having unevenness information can be reliably extracted to the outside.

Since the diffraction grating has a function equivalent to that of a cylindrical lens, spherical lens, or aspherical lens, a thin hologram can realize the same focusing function as these sublime lens components.

Even when the focusing means is made of a non-planar material instead of a diffraction grating, the same operation and effect can be obtained in terms of the focusing function.

By forming a reflective film with a high reflectance on a non-planar surface as necessary, it is possible to improve the reflection characteristics of the signal light having unevenness information.

The material of the light guide plate is not particularly limited as long as it is transparent, but if it is made of plastic, it can be easily molded.

〔Example〕

1 and 2 show a first embodiment of the present invention.

Components corresponding to those shown in FIGS. 17 and 18 are indicated by the same component numbers to omit repeated explanation.

At least one reflection type or transmission type hologram (diffraction grating) having a beam focusing function is formed on the upper surface 11A or the lower surface 11B of the light guide plate 11, so that the light guide plate has an imaging function. In the illustrated embodiment, a reflection hologram 31A is formed on the upper surface 11A, and a transmission hologram 31B is formed on the lower surface 11B.

That is, in order to realize an optical system (input system) equivalent to that shown in FIG. 17, two holograms 31A having a cylindrical lens function are used.
, 31B are formed on the upper and lower surfaces of the light guide plate 11 in a positional relationship such that their grating axes are perpendicular to each other. In the same manner as shown in FIG. 17, the light incident on the light guide plate 11 by the semiconductor laser 15, for example, is reflected by the uneven portion of the fingerprint and is totally reflected by the lower surface 11B of the light guide plate 11, and as described above, light is emitted from the concave portions and convex portions. A difference in directivity occurs in the reflected light r3, which is reflected and diffracted (converged) by the first reflection hologram 31A on the top surface, and taken out to the outside by the second transmission hologram 31B on the bottom surface.

The direction of the light taken out to the outside is changed by a predetermined angle (for example, 90 degrees) by a mirror 19 as necessary, and is guided to a CCD 29 via a spatial filter 23 (FIG. 1 shows mirror 1).
(indicates the case where there is no 9).

Further, the second hologram 31B does not necessarily have to be of a transmission type, but may be of a reflection type. In this case, the light is extracted upward from the upper surface 11A of the light guide plate 11, as shown by r' in FIG.

Incidentally, a reflection type hologram is easily created by depositing a metal such as aluminum on a surface relief type (concavo-convex type) hologram (described later). Further, the transmission type hologram may be either a surface uneven type or a volume type.

In addition, in the case where the light extraction position to the outside is far to the right in FIG. It may also be diffracted.

The holograms 31A and 31B having a cylindrical lens function are formed, for example, by forming a lattice stripe distribution on a substrate 32, as shown in FIG. 3, in which the pitch of lattice stripes 33 becomes smaller as they move away from the center. Note that it is also possible to use the surface of the light guide plate 110 as the substrate 32. That is,
Hologram material (photoresist, etc.) on the surface of the light guide plate 11
It is also possible to create a desired hologram by directly applying it (described later).

The first hologram 31A focuses the beam in the X direction, and the second hologram 31B focuses the beam in the X direction.

FIG. 4 shows the structure when considering the specific design of the holograms 31A and 31B. That is, the holograms 31A, 31
For example, when B has a cylindrical lens function, the optical path length from the light scattering point P on the fingerprint image input surface to the first hologram 31A, and from the first hologram 31A to the second hologram 31
The optical path length from the second hologram 31B to the point on the image sensor 29 (FIG. 1.2) is the same as the first one. It is desirable to optimize the focal length of the second holograms 31A and 31B. At that time, the fourth
As shown in the figure, the design is facilitated by partially changing the thicknesses d+ and d2 of the light guide plate 11 (dl < dz) to allow flexibility in the distance between the holograms.

Figure 5 is 1. Reflection within the light guide plate 11 illustrating an embodiment in which the second holograms 31A and 31B' are both reflective types, light is taken out from an output portion 11C obtained by cutting the light guide plate 11 diagonally, and imaged on the CCU 29. As the number of times increases, the light guide plate 11 itself becomes longer in the light propagation direction, but
Since the thickness of the light guide plate itself does not increase in the optical system,
It becomes possible to make it thinner. The spatial filter 23 shown in FIG. 2 can be obtained by closely forming an appropriately shaped light absorber 23' on the total reflection surface of the upper surface 11A of the light guide plate.

That is, in FIG. 5, the spatial filter can also be formed integrally with the light guide plate 11.

FIG. 6 shows a different embodiment from that shown in FIG. 4, in which the second hologram 31B' in FIG. The reflected and diffracted light is again reflected straight toward the second hologram 31B'. An aperture 32 is formed in the center of the second hologram 31B' and also serves as the spatial filter 23 shown in FIG.

FIG. 7 shows yet another embodiment of the present invention, in which the first reflection hologram 31A' has a spherical lens function instead of a cylindrical lens function.

That is, the first reflection hologram 31 as a spherical lens
A' and the second transmission hologram 31 as a cylindrical lens
A case in which B is combined is shown. In order to give the hologram a spherical lens function, the lattice fringes may be distributed concentrically as shown in FIG.

Note that the hologram is not limited to the above-mentioned cylindrical lens function or spherical lens function; for example, a hologram having an aspherical lens function can similarly exhibit a converging lens function.

Hologram 31A having a cylindrical lens function shown in FIG.
In the case of The type hologram 31B also focuses the beam.
.

Figure 8 shows a second method of forming a reflection hologram, which is known per se.
Here are two examples. In the figure (a), a concavo-convex grating 33 is directly formed on the surface of the light guide plate 110 using a stamper or the like, and a metal (
(b) shows a method of vapor-depositing aluminum, etc., in which a reflection hologram is created in advance on a thin substrate 32 in the same manner as in (a), and then turned upside down and attached to the light guide plate 11 with an optical adhesive 40. Show how to glue on top. Same figure (
In b), 42 indicates a layer of vapor-deposited metal (CA1, etc.).

FIG. 9 shows two examples of a method of creating a transmission hologram, which is known per se. As shown in FIG. A method of forming a hologram by coherent copying or mask exposure, or as shown in the same figure (b),
A method in which a hologram (interference fringes) is formed in advance on a hologram dry plate on which a hologram material 45 is formed on a substrate 32 by coherent copying or mask exposure, and then the hologram is turned upside down and adhered onto the light guide plate 11 using an optical adhesive 40. You could think so.

FIG. 10 shows an embodiment in which the beam convergence subactor is formed of a non-flat surface. The embodiment shown in FIG. 10 corresponds to an improved version of the prior art shown in FIG.
One surface 62A of 2 is processed into a prism shape, and light is irradiated with the semiconductor laser 15 in the same manner as shown in FIG. The light from the concave part Q (total reflection) and the convex part P ((dispersion) of the fingerprint propagates through the flat plate by repeating total reflection, but as it is, the light will continue to diverge, so it will be totally reflected. Non-flat surfaces 63A and 63B are formed on the surface portions as light focusing means.In order to take out the light propagating inside the flat plate 62 and make it enter the CCD 29, an extraction surface 62B is cut obliquely to the upper and lower surfaces of the flat plate. form.

In the embodiment shown in FIG. 10, the CCD 29 is directly fixed to the light extraction surface 62B of the light guide plate 62. In addition, basically there should be at least one non-plane, and the first
In Figure 0, for example, the second non-flat surface 62B is not provided, and instead, the CC is placed at the beam convergence position by the first non-flat surface 63A.
If D 29 is arranged, only the first non-flat surface 63A is required.

Specific examples of the non-flat surfaces 63A and 62B include cylindrical surfaces, spherical surfaces,
Possible examples include aspherical surfaces. These non-planar surfaces are completely equivalent to the aforementioned embodiments using holograms from the viewpoint of beam focusing function.

Fig. 11 shows a cylindrical surface 65A as a non-flat surface having a light condensing function.
・The case where 65B is used is shown. In order to enable imaging in both the x and y directions, the two cylindrical surfaces 65A and 165B are formed on the lower surface 62C and the upper surface 62D of the light guide plate 62 so that their central axes are orthogonal to the x and X directions. In order to make the focal length of the cylindrical lenses 65A and 65B long to enable imaging of a wide field of view,
After the light from the subject contact portion 13 is once totally reflected on the bottom surface 62C of the light guide plate 63, the light is focused in the X direction on the first cylindrical surface 65A.

Note that it is possible to cause total reflection on the cylindrical surface 65A, but if the conditions for total reflection are broken, light can be directed into the light guide plate 62 by vapor-depositing a metal such as aluminum on the inner surface. It can be reflected. Next, the light is focused in the X direction on the second cylindrical surface 63B, completely reflected once on the upper surface 62D, and then emitted from the light extraction surface 62B to the CCD 29.
lead to. If the design requires a longer optical path, the number of total reflections at the flat portion of the light guide plate may be increased.

FIG. 12 differs from FIG. 11 only in the direction in which light is taken in, and the other configurations are basically the same as in FIG. 11. That is, in FIG. 11, the light is emitted from the X direction, whereas the
In FIG. 2, light is emitted from the y direction corresponding to FIG. 18, that is, from a direction perpendicular to the propagation direction (X direction) of the fingerprint image, and only the scattered light from the convex portion P is guided to the CCD 21.

A specific example of non-flat surfaces 63A and 63B for condensing light is shown in the first example.
Shown in Figure 3.14. FIG. 13(a) shows a cylindrical lens, when it is made to protrude from the plane of the light guide plate 62, and FIG. 13(b) shows a case where the convex part of the cylindrical surface is flush with the plane of the light guide plate 62, or is embedded inside it. It is. FIG. 14 shows a spherical (or aspherical) convex lens, which, like FIG. 13, can be thought of as a convex type (FIG. 14 (A)) or a recessed type (FIG. 14 (B)). If desired, a highly reflective metal may be deposited on the non-planar surface.

FIG. 15 shows an embodiment in which a spherical surface 63A (FIG. 14) is used as the first non-flat surface and a cylindrical surface 63B (FIG. 13) is used as the second non-flat surface. Since the light beam propagating within the light guide plate 62 is obliquely incident on the spherical lens 63A, aberrations occur. This aberration can be corrected by the cylindrical lens 63B.

FIG. 16 shows the method of assembling the optical system of the present invention.
15 and CCD 29 are respectively incorporated in holders 71 and 73 that are abutted against both ends of the light guide plate 620, and when assembled, the shape is complementary to both ends of the light guide plate 620 so that the entire structure is, for example, a rectangular parallelepiped. .

In the embodiment shown in FIG. 16, the first non-plane is a spherical surface 63.
The A1 second non-plane is formed as a cylindrical surface 63B.

In each of the above embodiments, the material of the light guide plate is not particularly limited as long as it is transparent, but it is generally made of glass or plastic. Note that plastic has the advantage that it is lightweight and can be easily molded into any shape.

〔Effect of the invention〕

As described above, according to the present invention, since the imaging means is integrally formed on one transparent light guide plate, it is simple and easy to assemble, and it is possible to realize a compact, lightweight, and thin uneven shape detection device. .

Moreover, by realizing the imaging means using a hologram or a non-planar image, it can be integrated into the light guide plate without substantially increasing the thickness of the light guide plate.

[Brief explanation of the drawing]

Fig. 1 is an illustrative diagram showing the basic configuration of the detection device according to the present invention, Fig. 2 is a diagram showing the optical system of Fig. 1, and Fig. 3 shows the lattice fringe distribution of the hologram used in the embodiment of the present invention. 4 shows an embodiment different from that in FIG. 2, FIGS. 5, 6, and 7 show three further different embodiments, and FIG. 8(a), (b) is a diagram showing two embodiments of the method for forming a reflection hologram; FIG. 9(a), (
b) is a diagram showing the transmission example, and Figures 11 and 12 are the 10th
FIG. 13(a) is a diagram showing two different embodiments. (b) is 2 when a cylindrical lens is constructed from non-planar surfaces.
Figures 14(a) and 14(b) show two embodiments in which a spherical (or aspherical) lens is constructed from a non-flat surface.
15 is a diagram showing another embodiment using a non-flat surface, FIG. 16 is a diagram showing an example of a simple method of assembling the detection device, and FIGS. 17 and 18 are conventional FIG. 3 is a diagram showing two examples of an uneven shape detection optical system. 10... Test object, 11.62... Light guide plate,
31.63.65... Beam focusing means. Basic configuration of the present invention FIG. 2 FIG. 3 FIG. 11, light guide plate 15, semiconductor lasers 31A, 31B... Hologram embodiment M vapor deposition (b) Reflection type hologram formation method on light guide plate FIG. 8 Exposure ll On light guide plate Transmission type hologram formation method for Figure 9 Example using a non-flat surface Figure 10 Example 1 Example Figure 12 - Convex type Buried type (Q) F, 1□7. : (b) Convex type Recessed type (a) (b) Spherical (aspherical) lens Fig. 14 (Ill JM Example Example of optical system assembly method Fig. 15 Fig. 16) Conventional uneven shape detection optical system (1st example) Figure 7417 Conventional uneven shape detection optical system (2nd example) Figure 18

Claims (1)

[Claims] 1. An object to be detected (10) having an uneven surface shape is pressed against one plane of a transparent light guide plate (11, 62), and light is irradiated from inside the light guide plate to the object to be detected. When the concavities on the surface of an object (
Q) In a device that detects the uneven shape of an object by optically identifying the scattered signal light from the convex part (P), the reflected light from the convex part is detected by an image detector (29) outside the light guide plate.
) at least one beam focusing means (31,
63, 65) are integrally assembled within a light guide plate. 2. The detection device according to claim 1, wherein the beam focusing means is formed by at least one reflection type or transmission type diffraction grating (31A, 31B). 3. The beam converging means is formed by at least one reflection type diffraction grating and at least one transmission type diffraction grating, and extracts the reflected diffraction light by the reflection type diffraction grating to the outside of the transparent polyhedron as diffracted and transmitted light by the transmission type diffraction grating. The detection device according to claim 1, characterized in that: 4. The detection device according to claim 2, wherein the diffraction grating has a lattice fringe distribution equivalent to a cylindrical lens. 5. The detection device according to claim 2, wherein the diffraction grating has a lattice fringe distribution equivalent to a spherical lens. 6. The detection device according to claim 2, wherein the diffraction grating has a lattice fringe distribution equivalent to an aspherical lens. 7. Claim 7, wherein the beam focusing means has at least two diffraction gratings equivalent to cylindrical lenses, and these diffraction gratings are arranged at predetermined positions within the light guide plate so that the diffraction gratings are orthogonal to each other. 1. The detection device according to 1. 8. The beam focusing means includes at least one non-flat surface (63A, 63B, 65A,
65B). Detection device according to claim 1, characterized in that it is formed by: 65B). 9. The detection device according to claim 8, wherein the non-flat surface is a cylindrical surface. 10. The detection device according to claim 8, wherein the non-flat surface is a spherical surface. 11. The detection device according to claim 8, wherein the non-flat surface is an aspherical surface. 12. The beam focusing means is formed by two or more cylindrical surfaces partially formed within the light guide plate, and these cylindrical surfaces are arranged at predetermined positions within the light guide plate such that their longitudinal axes are orthogonal to each other. 9. The detection device according to claim 8. 13. The detection device according to claim 8, wherein the non-flat surface is provided with a reflective film that reflects light into the light guide plate. 14. The detection device according to claim 1, wherein the light guide plate is formed by a plastic mold.