JPH10104444A - Fiber optical device, photodetection component, and pattern acquisition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to transmit and output the uneven pattern of the surface of a body, which is brought into contact with an input end surface, with high contrast by providing a core and a light absorber, and slanting the input end surface to the axis of the core. SOLUTION: The end surface 25a of each core 32 does not cross the axis at right angles, but slants at a specific angle to the axis. Light beams 72a and 73a which are transmitted through a finger 80 and projected from a recessed part 82 to travel in a gap 83 as to the light 87 from a light source 86 are transmitted through an end surface 35a to enter the core 32. Refracted light beams 72b and 73b of those light beams 72a and 73a travel in the core 32 in directions off the axial direction of the core 32 and are attenuated or removed by the light absorber 34. In the area where a projection part 81 of a fingerprint and the end surface 35a of the core are close to each other, the refractive index of the finger 80 is larger than that of air, so the relation between the incidence angle and refraction angle of the light reaching the end surface 35a by passing through the projection part 81 of the finger 80 as to the light from 87 from the finger 86 changes from the relation in a noncontact area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber optical device used for a pattern acquisition device such as a fingerprint detection device.

[0002]

2. Description of the Related Art A fiber optical device in which a plurality of unit fibers are bundled in parallel has been conventionally known. In particular, Japanese Patent Application Laid-Open No. 4-313737 discloses a fiber optical device in which each unit fiber does not have a clad and is composed of only a core and a light absorber surrounding the core. Both end faces of this device are formed by assembling the end faces of each unit fiber perpendicular to the axis of the core so as to be flush with each other. These end surfaces are surfaces for inputting and outputting an optical image, respectively.

According to such a fiber optical device, light incident on the core at an incident angle equal to or greater than a certain value is absorbed by the light absorber, so that only light incident almost perpendicularly on the input end face is extracted and input. Unnecessary light (in the example of the above publication, light scattered by the liquid crystal layer) obliquely incident on the end face can be blocked. Therefore, the fiber optic device has the effect of outputting a high-contrast image when the image to be transmitted is set to be incident parallel to the axis of the core, that is, perpendicular to the input end face of the device. I do.

[0004]

However, the above fiber optical device is not always suitable for use in an apparatus for acquiring a concavo-convex pattern on an object surface, for example, a fingerprint detection apparatus. In a general concavo-convex pattern acquisition device,
A pattern is obtained by irradiating light from around the object in a state where the object is brought into close contact with the input end face of the fiber optical device. By this light irradiation, light passing through the concave and convex portions of the object is incident on the input end face of the device at various angles. Therefore, using the above fiber optic device that only extracts light that is perpendicularly incident on the input end face,
Since the light emitted from the concave portion and the light emitted from the convex portion are blocked in the same manner, it is not possible to obtain an uneven pattern image having such a high contrast.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to provide a fiber optical device capable of outputting a high-contrast image of an uneven pattern on an object surface in close contact with an input end face.

[0006]

In order to solve the above-mentioned problems, a fiber optic device according to the present invention includes a plurality of substantially parallel cores extending in a predetermined direction, and a plurality of cores surrounding each of the cores. And a light absorber having an absorption coefficient larger than these cores for at least one light wavelength. Both end surfaces of the core and the light absorber are substantially flush with each other to form an input end surface and an output end surface of the device. This input end face
It is inclined at a predetermined angle α with respect to the axis of the core.

[0007] The inclination angle α is obtained by changing the refractive index of air to n _a ,
When the refractive index of the _core is n _cores , α ≦ 90 ° −sin ⁻¹
(N _a / n _core ) is preferably satisfied. In this case, light incident on the core from the air travels in a direction deviated from the axial direction of the core, and is absorbed by the light absorber and attenuated or removed. Therefore, according to the fiber optical device of the present invention, it is possible to transmit and output, with a high contrast, the concavo-convex pattern on the surface of the object brought into close contact with the input end face.

[0008] The output end face of the fiber optic device of the present invention may be substantially perpendicular to the axis of the core.
In this case, light traveling in the core along the axis of the core,
Light is emitted from the output end face perpendicular to the output end face. Therefore, when the output end face of the fiber optical device according to the present invention is opposed to the light receiving surface of the photodetector, light emitted from the output end face can be surely incident on the light receiving range of the photodetector. As a result, a high-resolution pattern can be detected by increasing the S / N of the output of the photodetector. Further, since light is emitted from the output end face perpendicular to the output end face, light can be emitted from the output end face regardless of the medium adjacent to the output end face. Thereby, the application range of the device can be widened.

[0009] The input end face and the output end face of the fiber optic device of the present invention may be substantially parallel. In this case, it is possible to output the optical image incident on the input end face from the output end face without distortion. It is also possible to make the device compact.

According to another aspect of the present invention, there is provided a light receiving component including the above-described fiber optical device and a photodetector that converts an optical image incident on its own light receiving surface into an electric signal and outputs the electric signal. Here, the photodetector is arranged such that the optical image output from the output end face of the fiber optical device is incident on the light receiving surface.

According to still another aspect of the present invention, there is provided a pattern acquiring apparatus including the light receiving component and a light source for illuminating an input end face of the fiber optical device provided in the light receiving component.

[0012]

1 to 3 are views showing the configuration of a fiber optical device according to one embodiment of the present invention.
FIG. 1 is an overall perspective view of the fiber optical device of the present embodiment, and FIG.
3 is a partial cross-sectional view of the fiber optical device according to the present embodiment along a line III-III in FIG. FIG. 1 shows an XYZ orthogonal coordinate system for convenience of explanation.

As shown in FIG. 1, a fiber optical device 10 according to the present embodiment has square side surfaces 22, 24,
It is a hexahedron provided with 25 and 26 and trapezoidal side surfaces 21 and 23, and has a trapezoidal column shape extending in the Y-axis direction in FIG. 1 with the side surfaces 21 and 23 in the ZX plane as the upper surface and the lower surface, respectively.

The structure of the fiber optic device 10 will be described with reference to FIGS. The fiber optical device 10 includes a plurality of rod-shaped cores 32 which are optical waveguides. These cores 32 extend such that their axes 38 are substantially parallel. In addition, these cores 32
Are arranged such that the spacing between the axes 38 is substantially uniform. Each core 32 has a circular cross-section perpendicular to its axis 38. As shown in FIG. 2, the end face 35a of each core 32 is not orthogonal to the axis 38,
At an angle α. The inclination angle α is an angle taken clockwise from the orthogonal projection of the axis 38 of the core onto the core end surface 35a in FIG. On the other hand, an end surface 35 b located opposite to the end surface 35 a of each core 32 is orthogonal to the axis 38.

The side surface of the core 32 is tightly surrounded by a light absorber 34. The light absorber 34 is made of a material having a larger absorption coefficient than the material of the core 32 over the entire visible light region. The light absorber 34 is interposed between the cores 32 while extending in the same direction as the cores 32.
Similarly to the end face 35 a of the core 32, the end face 3 of the light absorber 34
7a is also inclined at an angle α with respect to the axis 38 of the core. The end face 37b of the light absorber 34 opposite to the end face 37a is, like the end face 35b of the core 32, the axis 3
It is orthogonal to 8. The end face 35a of the core and the end face 37a of the light absorber, and the end face 35b of the core and the end face 37b of the light absorber are substantially flush with each other to form the side faces 22, 24 of the device 10.

As described above, the fiber optical device 10
Is a structure in which the core 32 and the light absorber 34 extend in a specific direction, and the side surfaces 22 and 24 are both end surfaces of this structure. When the fiber optical device 10 is used as an optical image transmitting unit, these end surfaces 22 and 24 are surfaces on which an optical image is input and output, respectively. Input end face,
Surface 24 is referred to as the output end surface of fiber optic device 10.

The core 32 and the light absorber 34 can be formed using any material conventionally used to form a general fiber optical device. An example of the composition of the light absorber is disclosed in, for example, US Pat. No. 3,797,910. Commonly used glass-based light absorbers include NiO, Co ₂ O ₃ , CuO, Fe ₂ O ₃ , and Mn.
Various colored oxides such as O ₂ are included. The compositions of the core 32 and the light absorber 34 according to the present embodiment are shown in the following table.

[0018]

[Table 1]

As shown in this table, the core 32
It is made of a transparent glass made of iO ₂ , Al ₂ O ₃ , K ₂ O, and PbO, and has a refractive index of 1.92.
The light absorber 34 is made of SiO ₂ , K ₂ O, PbO, Mn.
It is a black glass made of O ₂ and Cr ₂ O ₃ . FIG. 4 shows the spectrum of the spectral transmittance when the black glass has a thickness of 222 μm.

As best shown in FIG.
Are inclined at an angle α with respect to the axis 38 of the core, the input end face 2 including these end faces 35a
2 is also inclined at an angle α with respect to the axis 38. In the present embodiment, the inclination angle alpha is such that light incident from air into the core 32 travels in a direction deviating from the axis 38 of the core 32, is set below a predetermined maximum inclination angle alpha _m. The maximum inclination angle α _m is an inclination angle at which light incident on the core 32 at an incident angle of 90 ° travels in the same direction as the axis 38 of the core. Hereinafter, with reference to FIG. 5, the maximum inclination angle α _m
Will be described.

FIG. 5 is a partially enlarged longitudinal sectional view of the fiber optical device 10 when the inclination angle α is equal to the maximum inclination angle α _m . In FIG. 5, the refractive index of the _n-core core 32, n _a
Is the refractive index of air. Reference numeral 70a denotes a light beam incident on the end surface 35a of the core 32 from the air at an incident angle of 90 °,
0b is a refracted light ray in the core 32 of the incident light ray 70a, and β is an angle between the refracted light ray 70b and the normal 28 of the end face 35a, that is, a refraction angle. In Figure 5, it represents a refraction angle beta corresponding to the maximum angle of inclination alpha _m and beta _m.

As shown in FIG. 5, the end face 3 of the core 32
Maximum inclination angle alpha _m of 5a, the light incident on the core 32 at an incident angle of 90 ° is angle of inclination so as to proceed the middle core 32 in the axial 38 the same direction. This maximum inclination angle α _m is given by the following 2
It can be obtained from the equation.

[0023] n _a · sin90 ° = n _{core · sinβ m ... (1) α} m + β m = 90 ° ... (2) Solving this two _{formulas, α m = 90 ° -β m} = 90 ° -sin ( (n _a / n _core ) (3) Assuming that n _a = 1, α _m = 90 ° -sin (1 / n _core ) (4)

FIG. 6 is a diagram showing the core 32 based on the above equation (4).
Is a graph showing the relationship between the refractive index n _core and a maximum inclination angle alpha _m of. As shown in this figure, the maximum tilt angle increases as the refractive index of the core 32 increases.

When the inclination angle α of the end face 35a is equal to the maximum inclination angle α _m , the refraction angle of light incident on the core 32 from the air at an incident angle of less than 90 ° is less than β _m . The refracted light beam having such a refraction angle travels in a direction deviated from the axial direction of the core 32, travels to the boundary surface between the core 32 and the light absorber 34, is absorbed by the light absorber 34, and is attenuated or removed. . When the inclination angle α is smaller than the maximum inclination angle α _m , the refraction angles of all light incident within the incident angle of 90 ° become less than β _m, and the light travels in a direction shifted from the axial direction of the core 32. Therefore, light that enters the core 32 from the air at an arbitrary incident angle is absorbed by the light absorber 34 and is attenuated or removed. As a result, if the inclination angle α of the end face 35a is equal to or less than the maximum inclination angle α _m, it is possible to substantially prevent the propagation of light that enters the core 32 from the air via the end face 35a in the core.

In the present embodiment, the refractive index of the core 32 is 1.
The value of the maximum inclination angle α _m corresponding to this value is 5
8.6 °. The inclination angle α of the input end face 22 is set to the value of the maximum inclination angle α _m (= 58.6 °).

FIG. 7 shows a state in which a finger 80, which is an example of a detection target, is brought into close contact with the input end face 22 of the fiber optical device 10,
FIG. 3 is a partial vertical cross-sectional view showing, on an enlarged scale, an internal structure of the device 10 in a state where light 87 is emitted from behind a finger 80 using a light source 86. A region where the end face 35a of the core and the convex portion 81 of the finger 80 are in close contact with each other, and a region where the end face 35a and the concave portion 82 of the finger are not in close contact with each other with the gap 83 therebetween are formed corresponding to the fingerprint uneven structure. . Of the light 87 from the light source 86, the light beams 72 a and 73 a that pass through the finger 80, exit from the concave portion 82, and travel through the gap 83 pass through the end surface 35 a and enter the core 32. The refracted rays 72b, 73b of these rays 72a, 73a travel in the core 32 in a direction deviated from the axial direction of the core 32, as described above,
Attenuated or removed by the light absorber 34. On the other hand, in a region where the convex portion 81 of the fingerprint and the end surface 35a of the core are in close contact with each other, the refractive index of the finger 80 is larger than the refractive index of air. Part 81
The relationship between the angle of incidence and the angle of refraction of the light that passes through and reaches the end face 35a changes from the relationship in the non-contact area. For this reason, among the light that has passed through the contact region from the convex portion 81 of the fingerprint and has entered the core 32, there is also a light ray (for example, the light ray 71 in FIG. 7) that travels in the axial direction of the core 32. .
Such a light beam propagates through the core 32 without being absorbed by the light absorber 34, and reaches an end face 35 b on the opposite side of the end face 35 a of the core 32.

As described above, in the fiber optical device 10, only light that enters the core 32 from the convex portion of the object surface that is in close contact with the input end face 22 reaches the output end face 24. Light that enters the core 32 through the gap from the concave portion on the object surface is attenuated during the propagation process by the absorption of the light absorber 34 and substantially disappears. Therefore, according to the fiber optical device 10, a bright and dark image corresponding to the unevenness of the object surface,
That is, the uneven pattern image can be transmitted with high contrast and output to the outside. In addition, since the fiber optical device 10 can emit only light traveling in the core 32 along the axis, the light flux emitted from each core 32 hardly diffuses. Therefore, the fiber optical device 10 according to the present embodiment has a high positional resolution.

FIG. 8 shows a fiber optic device 10 according to the present embodiment in which a CCD image sensor 90 is an example of a photodetector.
FIG. 3 is a schematic view showing a light receiving component 100 attached to the light receiving device 100. The CCD imaging device 90 is provided with a concave portion 95 of the housing 94.
The CCD chip 92 is provided in the inside.
Is converted into an electric signal by photoelectric conversion. This electric signal is output via a lead terminal 96 extending to the outside through the housing 94. The output end face 24 of the fiber optic device 10
It is joined to the light receiving surface 93 of the CD imaging device 90 via an optical adhesive 98. As the optical adhesive 98, a balsam, an epoxy resin adhesive, an ultraviolet curable resin, or the like can be arbitrarily used. In the present embodiment, Cemedine-1565, which is one of the epoxy resin adhesives, is used as the optical adhesive 98.

The light receiving component 100 can be used in an apparatus for acquiring an uneven pattern on the surface of an object, for example, a fingerprint. FIG. 9 is a schematic diagram showing the configuration of a fingerprint acquisition device using the light receiving component 100. This fingerprint acquisition device includes a light source 86 for illuminating the input end face 22 of the light receiving component 100, a signal processing device 110 electrically connected to a lead terminal 96 of the light receiving component 100, a signal processing device, in addition to the light receiving component 100. A display device 112 electrically connected to 110 is provided. The finger 80 is pressed against and brought into close contact with the input end face 22, and when light 87 is emitted from the light source 86 to the finger 80, a fingerprint pattern optical image of the finger 80 is input to the fiber optical device 10 via the input end face 22. . This fingerprint pattern image is transmitted to the output end face 24, emitted therefrom, and made incident on the light receiving surface 93 of the CCD chip 92. Thus, the fingerprint pattern image of the finger 80 is converted into an electric signal and sent to the signal processing device 110. Signal processing device 11
0 performs an appropriate process based on the output from the CCD image sensor 90 and displays the resulting image signal on the display device 11.
2 to display a fingerprint pattern image on the screen of the display device 112.

The fiber optical device 1 according to the present embodiment
At 0, the output end face 24 is perpendicular to the axis of the core 32, so that the core propagating light traveling inside the core 32 along the axis of the core 32 is emitted perpendicularly to the end face 24 from the output end face 24. Therefore, the light emitted from the output end face 24 is
The light surely enters the light receiving range of the CCD image sensor 90. Further, as described above, the fiber optical device 10 according to the present embodiment has a high positional resolution. Therefore, by attaching the device 10 to the CCD image pickup device 90, the S / N of the output of the CCD image pickup device 90 can be increased, and an uneven pattern with high resolution can be detected.

The fiber optical device 1 according to the present embodiment
0 is configured so that light is emitted perpendicularly to the output end face 24, so that light can be emitted from the output end face 24 regardless of the medium adjacent to the output end face 24. Therefore, the fiber optic device 10 has a wide range of applications. In the above, the example in which the fiber optical device 10 is fixed to the CCD chip 92 with an optical adhesive has been described.
Alternatively, for example, the fiber optical device 10 and the photodetector may be separated from each other with air interposed therebetween, and a lens may be arranged between the two to optically couple them.

FIGS. 10 and 11 show a fiber optical device according to another embodiment of the present invention.
FIG. 1 is an overall perspective view of the fiber optical device 12, and FIG.
1 is a line of the fiber optical device 12 shown in FIG.
It is a partial longitudinal section along XI-XI. As shown in FIG. 10, the fiber optic device 12 has square sides 42, 44, 45 and 46, and parallelogram sides 4
It is a parallelepiped having 1 and 43, and has a quadrangular prism shape extending in the Y-axis direction in FIG. 10 with the side surfaces 41 and 43 in the ZX plane as the upper surface and the lower surface, respectively. Sides 42 and 44
Are in the XY plane, parallel to each other, and have substantially the same area.

Referring to FIG. 11, the fiber optical device 12 includes a plurality of rod-shaped cores 52 as optical waveguides, similarly to the device 10 described above. Extend substantially parallel to each other. These cores 52 are arranged such that the distance between the axes 58 is substantially uniform. Unlike the fiber optic device 10 described above, the end faces 55a and 55b of each core 52 are substantially parallel and both are inclined at an angle α with respect to the axis 58. This inclination angle α is
In FIG. 11, the angle is taken clockwise toward the axis 58 from the orthogonal projection of the axis 58 of the core onto the core end face.

As in the device 10 described above, the side surfaces of the cores 52 are tightly surrounded by a light absorber 54, and the light absorbers 54 extend in the same direction as the core 52 and are located between the cores 52. Intervening. Like the end faces of the core 52, the end faces 57a and 57b of the light absorber 54 are also substantially parallel and have an angle α with respect to the axis 58 of the core.
It is inclined. The core 52 and the light absorber 54 are made of the same material as the core 32 and the light absorber 34 of the fiber optical device 10 described above, respectively. The end face 55a of the core and the end face 57a of the light absorber, and the end face 55b of the core and the end face 57b of the light absorber are substantially flush with each other to form the side faces 42 and 44 of the device 12. As with device 10, these sides 42, 4
4 is an input end face and an output end face of the device 12, respectively.

Similarly to the input end face 22 of the device 10 described above, the inclination angle α of the input and output end faces of the fiber optic device 12 is such that light incident on the core 52 from the air
, Ie, the maximum inclination angle α _m represented by the above equation (3). Therefore, this fiber optic device 12
Also, it is possible to transmit an uneven pattern image on the object surface with high contrast and output the image to the outside. In addition, since the input end face 42 and the output end face 44 are parallel in the fiber optical device 12, according to the device 12, the optical image incident on the input end face can be output from the output end face without distortion. Further, as can be easily understood by comparing FIGS. 1 and 10, the device 12 has an input end face 42.
And the output end face 44 are parallel to each other, so that it is compact.

In the fiber optical device 12, the input and output end faces 42, 45 at an angle such that light incident on the core 52 from the air travels in a direction deviated from the axial direction of the core 52.
44 are both inclined. Therefore, conversely, the output end face 4
When the medium adjacent to 4 is air, only light traveling inside the core 52 in a direction deviated from the axis can be emitted from the output end face 44. That is, if the medium adjacent to the output end face 44 is air, the light propagating along the axis in the core 52 is totally reflected by the end face 55b and cannot be emitted. Therefore, when the fiber optical device 12 is attached to a photodetector, for example, the CCD image pickup device 90 shown in FIG. 8, the output end surface 44 of the device 12 and the light receiving surface 93 of the CCD chip 92 are used.
It is preferable to interpose a sealing material between the output end face 44 and the light receiving face 93 so that air does not enter between them.
As the sealing material, any material having a light-transmitting property and capable of preventing air from being interposed between the output end face 44 and the light receiving face 93, for example, a refractive index matching material such as a matching oil, or the above-described optical adhesive Agents can be used.

[0038]

As described in detail above, the fiber optical device according to the present invention is composed of the core and the light absorber, and the input end face is inclined with respect to the axis of the core. The light incident on the core can be attenuated or removed, so that the concavo-convex pattern on the object surface adhered to the input end face can be transmitted and output with high contrast.

[Brief description of the drawings]

FIG. 1 is an overall perspective view showing a fiber optical device according to an embodiment of the present invention.

FIG. 2 is a partial longitudinal sectional view of the fiber optic device of FIG. 1 along line II-II.

FIG. 3 is a line III-III of the fiber optic device of FIG. 2;
FIG.

FIG. 4 is a spectrum of spectral transmittance of black glass constituting a light absorber in the device of FIG. 1;

FIG. 5 is a partially enlarged longitudinal sectional view of the fiber optical device of FIG. 1 when the inclination angle of the input end face is equal to the maximum inclination angle.

FIG. 6 is a graph showing a relationship between a refractive index of a core and a maximum inclination angle α _m of an input end face.

7 is a partially enlarged longitudinal sectional view of the fiber optical device of FIG. 1 in a state where a finger is brought into close contact with the input end face.

FIG. 8 shows a case where a fiber optical device according to the embodiment is a CCD.
It is a figure which shows schematically the light receiving component attached to an imaging element.

FIG. 9 is a schematic diagram illustrating a configuration of a fingerprint acquisition device including the light receiving component of FIG.

FIG. 10 is an overall perspective view showing a fiber optical device according to another embodiment of the present invention.

11 is a line XI- of the fiber optic device of FIG.
FIG. 11 is a partial longitudinal sectional view along XI.

[Explanation of symbols]

10: Fiber optical device, 22: Input end face, 24:
Output end face, 32 ... core, 34 ... light absorber.

Claims (6)

[Claims] 1. A plurality of substantially parallel cores extending in a predetermined direction, and a light absorber surrounding a side surface of each of the cores and having a larger absorption coefficient for at least one light wavelength than the cores; Wherein both end faces of the core and the light absorber are respectively substantially flush with each other to form an input end face and an output end face of the device, and the input end face is arranged with respect to the axis of the core. Characterized by being inclined at a predetermined angle α. Wherein said inclination angle alpha, when the refractive index of air n _a, the refractive index of the core is n _core, that are satisfied _{α ≦ 90 ° -sin (n a} / n _core) The fiber optic device according to claim 1, wherein: 3. The fiber optic device according to claim 1, wherein said output end face is substantially perpendicular to an axis of said core. 4. The fiber optic device according to claim 1, wherein said input end face and said output end face are substantially parallel. 5. A light receiving component comprising: the fiber optical device according to claim 1; and a photodetector that converts an optical image incident on a light receiving surface into an electric signal and outputs the electric signal, wherein the photodetector includes: A light receiving component arranged so that an optical image output from an output end face of the fiber optical device is incident on a light receiving surface of the photodetector. 6. A pattern acquisition apparatus comprising: the light receiving component according to claim 5; and a light source that illuminates an input end face of the fiber optical device provided in the light receiving component.