WO2003069384A1 - Fiber optical plate and irregular pattern detection device - Google Patents

Abstract

A fiber optical plate (1), comprising detection areas (12) where light absorbers are disposed around optical paths and illumination areas (14) where the light adsorber is not installed between the adjacent optical paths, wherein an irregular pattern output surface (124) and an imaging element (4) and an illumination light incident surface (142) and a LED array (5) are joined to each other with a transparent adhesive agent, whereby the axis of the optical paths and an irregular pattern input surface (122) are tilted at a slant angle set so that light incident from the air is not totally reflected on a core/clad boundary surface.

Description

 Akitoda

 Fiber optic plate and uneven pattern detector

Technical field

 The present invention relates to a fiber optical plate and an uneven pattern detecting device to which the fiber optical plate is applied.

Background art

 In recent years, there has been a demand for a smaller and thinner authentication device, such as the realization of a card-shaped uneven pattern (fingerprint) detection device. In order to realize such a concavo-convex pattern detecting device, a method for detecting a concavo-convex pattern on the surface of the measurement target using scattered light inside the measurement target (finger) is suitable.

 A conventional concavo-convex pattern detection device using scattered light inside the object to be measured is disclosed in, for example, Japanese Patent No. 3045629, in which illuminating light enters the inside of the object to be measured from the side, and In some cases, light scattered inside the target is incident on the concave / convex pattern transmission means arranged below the target object. Further, as disclosed in Japanese Patent Application Laid-Open No. 2000-217803, there has been an apparatus in which an illuminating unit arranged on a side of a light receiving element illuminates an object to be measured placed on a light receiving surface of the light receiving element.

Disclosure of the invention,.

However, Japanese Patent No. ³ 04 562 ⁹ No. irregular pattern detector publications, for illuminating means which is separated from the concave-convex patterns transmission means, the side of the object to be measured, that is, disposed obliquely Me above the detection surface However, there is a problem in that the size or thickness of the device is limited. Further, the uneven pattern detection device disclosed in Japanese Patent Application Laid-Open No. 2000-217803 has a problem that the illumination means cannot efficiently illuminate the object to be measured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In an uneven pattern detection device using scattered light inside an object to be measured, the device is reduced in size or thickness, and illumination means is efficiently measured. A fiber optic plate and a fiber optic plate that can illuminate an object The purpose is to provide.

 In order to achieve the above object, a fiber optical plate of the present invention is applied to an uneven pattern detecting device for detecting an uneven pattern of a measured object, and each axis crosses both end surfaces obliquely, and a plurality of fibers are formed in a clad. A plurality of optical fibers are aggregated and arranged so that the cores are arranged at predetermined intervals. The molded optical fiber plate is a fiber optical plate, and a detection area facing an imaging means for imaging an uneven pattern is provided. And an illumination area facing illumination means for illuminating the object to be measured, and a light absorber for absorbing light is provided in the cladding in the detection area.

 In the detection region functioning as the uneven pattern transmission means, the light absorber is provided in the clad, so that the uneven pattern of the measured object is transmitted to the imaging means with high accuracy. On the other hand, in the illumination area, since no light absorber is provided in the cladding, the illumination light emitted by the illumination means is efficiently guided to the object to be measured. In addition, since the fiber optical plate of the present invention is provided with such an illumination area, in manufacturing an uneven pattern detection device, an illumination means is attached to the illumination light incident surface of the fiber optical plate to reduce the size or thickness of the device. It becomes possible to do.

In the fiber optical plate of the present invention, it is preferable that the refractive index of the cladding in the illumination region is lower than the refractive index of the cladding in the detection region. -'.. Fiber optic plate whose axis obliquely intersects the surface of the fiber optic plate at a predetermined angle (slant angle) so that even if disturbance light in the air enters the core, it will not be totally reflected at the core' cladding interface. Can be emitted only at a portion of the exit surface where an object having a higher refractive index than air is in contact. However, by making the refractive index of the cladding in the illumination region lower than the refractive index of the cladding in the detection region, the critical angle at the core-cladding interface in the illumination region becomes smaller. Therefore, even in the case of a fiber optic plate with a slant angle set so that disturbance light in the air is not guided in the detection area, in the illumination area, total reflection is performed at the core / cladding interface at a small angle (incident angle). The illumination light traveling through the core while The light can be emitted to the outside even at the part of the emission surface that is in contact with the air. As a result, the measured object is illuminated more efficiently.

 In the fiber optic plate of the present invention, the refractive index of the core in the illumination region is preferably lower than the refractive index of the core in the detection region.

 By making the refractive index of the core in the illumination region lower than the refractive index of the core in the detection region, the critical angle at the air-core interface in the illumination region increases. Therefore, even in the case of a fiber optical plate in which the axis line and the emission surface obliquely intersect, in the illumination area, the illumination light is easily emitted to the outside even in the portion of the emission surface that is in contact with air. As a result, the measured object is illuminated more efficiently.

 In the fiber optic plate of the present invention, it is preferable that the interval at which the plurality of cores are arranged in the illumination area is longer than the interval at which the plurality of cores are arranged in the detection area.

 By making the interval at which a plurality of cores are arranged in the illumination area longer than the interval at which a plurality of cores are arranged in the detection area, the thickness of the clad interposed between the cores is not changed. The area ratio of the core on the incident surface of the illumination light can be increased, and the incidence efficiency of the illumination light on the illumination region is improved. On the other hand, by relatively shortening the interval at which multiple cores are arranged in the detection area, the number of cores per unit area on the surface of the detection area increases, and the accuracy of the concavo-convex pattern transmitted in the detection area improves. I do.

 The uneven pattern detection device of the present invention includes any one of the fiber optical plates, wherein the imaging means is mounted so as to face one surface of the detection area, and the illumination means is arranged with the imaging means of the illumination area. It is attached so as to face the surface on the side to be cut.

Since the uneven pattern detection device of the present invention includes the above-described fiber optical plate, efficient illumination of the object to be measured can be realized, and the device can be mounted by attaching illumination means to the illumination light incident surface in the illumination area. The size or thickness is reduced. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a plan view of an uneven pattern detecting device 2 to which a fiber optical plate 1 is applied.

 FIG. 2 is a cross-sectional view taken along the line II-II of the uneven pattern detecting device 2 shown in FIG.

 FIG. 3 is a sectional view taken along the line III-III of the uneven pattern detecting device 2 shown in FIG. FIG. 4 is a front view of the LED array 5.

 FIG. 5 is a cross-sectional view of the LED array 5 shown in FIG. 4 along the line VV.

 FIG. 6 is a front view of the fiber optic plate 1 shown in FIG.

 FIG. 7 is a partially enlarged cross-sectional view of the fiber optic plate 1 in the detection area 12.

 FIG. 8 is a diagram showing a state where a finger 6 to be measured is placed on the fiber optical plate 1.

 FIG. 9 is a view showing a mode in which the illumination light is emitted or reflected on the illumination light exit surface 144. As shown in FIG.

 FIG. 10 is a diagram illustrating a mode in which the detection light that has entered the detection region 12 from the finger 6 is guided by the optical transmission line in the detection region 12.

 FIG. 11 is a diagram showing a state in which the illumination light is emitted or reflected on the illumination light exit surface 744.

 FIG. 12 is a diagram illustrating a mode in which the illumination light is emitted or reflected on the illumination light emission surface 844.

 FIG. 13 is a conceptual diagram showing a state in which the LED array 20 is attached to the fiber optical plate 10.

 FIG. 14 is a conceptual diagram showing a mode in which the LED array 60 and the intermediate fiber optical plate 70 are disposed below the illumination light incidence surface 542 with the intermediate fiber optical plate 70 interposed therebetween.

FIG. 15 is a conceptual diagram showing a mode in which an intermediate fiber optical plate 70 is interposed between the LED array 60 and the light receiving surface 80 and the fiber optical plate 50. FIG. 16 is a front view of the embedded LED array 9.

 FIG. 17 is a cross-sectional view of the embedded LED array 9 shown in FIG. 13 taken along the line XIV-XIV.

BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, preferred embodiments of a fiber optical plate and an uneven pattern detection device to which the fiber optical plate according to the present invention is applied will be described in detail with reference to the accompanying drawings.

 [First Embodiment]

 The structure of the fiber optical plate 1 and the uneven pattern detecting device 2 to which the fiber optical plate 1 according to the first embodiment of the present invention is applied will be described.

 FIG. 1 is a plan view of an uneven pattern detecting device 2 to which a fiber optical plate 1 is applied. FIG. 2 is a cross-sectional view taken along the line II-II of the uneven pattern detecting device 2 shown in FIG. FIG. 3 is a sectional view taken along line III-III of the uneven pattern detection device 2 shown in FIG. The frame 3 has a rectangular bottom surface 32, and four wire terminals 34 on two opposite sides of the bottom surface 32 in the short side direction. The image sensor 4 is installed at the center on the bottom surface 32. The imaging device 4 has a flat plate shape, and the upper portion of the imaging device 4 (hereinafter, the direction in which the imaging device 4 is installed as viewed from the bottom surface 32 is the upper direction, and the opposite direction is the lower portion). The image sensor 4 has a rectangular light receiving surface 42, and an outer frame 44 around the light receiving surface 42 on the upper surface of the image sensor 4. The thickness of the imaging element 4 matches the thickness of the LED array 5 described later. Here, the image pickup device 4 is disposed such that the longitudinal direction of the light receiving surface 42 and the longitudinal direction of the bottom surface 32 match. 2 and 3, a portion corresponding to the light receiving surface 42 of the surface of the image sensor 4 is indicated by a thick line. The image sensor 4 includes four wire terminals 46 on two opposing sides (on the outer frame 44) of the light receiving surface 42 on the outer side in the lateral direction. The image sensor 4 is wired by connecting the wire terminals 46 and the wire terminals 34 of the frame 3 with bonding wires 36.

The bottom surface 3 2 of the frame 3 should be adjacent to the image sensor 4 on two opposite sides in the longitudinal direction. LED array 5 is installed. The LED array 5 functioning as an illuminating means has a thin long plate shape, and by applying such a thin illuminating means, the uneven pattern detecting device 2 can be made thin. The LED array 5 is installed such that the length direction coincides with the short direction of the bottom surface 32. FIG. 4 is a front view of the LED array 5. FIG. 5 is a cross-sectional view of the LED array 5 shown in FIG. 4 along the line VV. The LED array 5 includes a long printed board 502 on the bottom surface. A plurality of LEDs 504 are arranged on the printed circuit board 502 along the longitudinal direction of the printed circuit board 502, and a resistor 506 is provided at the end. LED 504 and resistor 506 are wired with lead 508. The entire surface of the printed circuit board 502 on which the LED 504 and the resistor 506 are installed is covered with an epoxy-based transparent resin 510.

The fiber optic plate 1 is set on the image sensor 4 and the LED array 5. The surface of the fiber optic plate 1 is rectangular and its length in the short direction matches the length in the long direction of the LED array 5 and is longer than the length in the short direction of the light receiving surface 42 of the image sensor 4 . The fiber optical plate 1 coincides with the longitudinal direction of its surface and the longitudinal direction of the bottom surface 32 of the frame 3, and its surface covers the entire upper surface of the LED array 5 and the entire light receiving surface 42 of the image sensor 4. The terminal 46 is in contact with the terminal 46 and is not installed. As shown in FIG. 3, the fiber optic plate 1 is composed of a plurality of optical fibers bundled together so that their axes are parallel to each other, and a plurality of cores in a clad. Are arranged at predetermined intervals. The fiber optical plate 1 is sliced so that the axis (center axis) and the surface (end face) of the fiber optical plate 1 obliquely intersect at an angle (slant angle) α °. In the present embodiment, both end faces of the fiber optical plate 1 are parallel. The fiber optic plate 1 has a detection area 12 in the center of the surface in the longitudinal direction where the light absorber is arranged in the clad, and an illumination area 14 in which the light absorber is not arranged in the clad at both ends. Is provided. In FIG. 3, the portion of the fiber optical plate 1 corresponding to the detection area 12 is double oblique. The portion corresponding to the illumination area 14 is indicated by a solid line. On the upper surface of the detection area 12, an uneven pattern input surface 122 for taking in the scattered light inside the object to be measured is formed, and on the lower surface of the detection area 12, the scattered light (detection light) guided is provided. A projection pattern output surface 124 to be emitted is formed. On the lower surface of the illumination area 14, there is formed an illumination light entrance surface 142 on which the illumination light emitted by the illumination means is incident, and on the upper surface of the illumination area 14, the illumination light emission from which the guided illumination light exits Surfaces 144 are formed.

 FIG. 6 is a front view of the fiber optic plate 1 shown in FIG. The dotted area in FIG. 6 indicates the concave / convex pattern input surface 122 of the surface of the fiber optical plate 1, and the portion other than the dotted area indicates the illumination light emitting surface 144.

 The fiber optical plate 1 is installed such that the entire light receiving surface 42 of the image sensor 4 contacts the concave / convex pattern output surface 124, and the LED array 5 contacts the illumination light incident surface 142. The fiber optic plate 1 and the image sensor 4 and the LED array 5 are joined with a transparent adhesive (epoxy or silicone resin).

FIG. 7 is a partially enlarged cross-sectional view of the fiber optic plate 1 in the detection area 12. Each optical transmission line (hereinafter, a portion of the fiber optical plate 1 that is constituted by a core and a clad surrounding the core is referred to as an “optical transmission line”) has a core 160 as a center, and Rad 16 1 closely surrounds core 160. Further, the light absorber 16 2 closely surrounds the clad 16 1. Both ends 16 5 of each optical transmission line are angled (slant angle) with respect to axis 16 4. Incline. This slant angle. The angle is set such that, even when light enters the core 160 from the air, the incident light is not totally reflected at the interface between the core 160 and the clad 161. That is, a predetermined slant angle. Below, the light incident on the core 160 from the air is refracted at the air / core interface at a refraction angle of 3 ° when passing through the end face 1650 of the optical transmission line, and then the core's cladding boundary It reaches the core-cladding interface at an angle (incident angle) smaller than the critical angle on the surface. Slant angle α. The specific angle _c . By using ≤ h. . It can be expressed as. Here, _ac ° is an angle that satisfies the following equations (1) to (3). Where n. Is core 1 6 Refractive index of _0, ηι the refractive index of the cladding 1 6 1, n _a is the refractive index of air. 6 _C ° is the critical angle at the core-cladding interface. . Is the refraction angle of the light incident from the air to the end face 1 65 of the optical transmission line at an incident angle of about 90 °.

n ₀ -si ηθ. ° = η sin 90 ° (core's law of refraction at the clad interface) ··· (1)

η ₀ · sin ^ _c ° = n _a · sin 90. (The law of refraction at the air-core interface) · · (2) a ₀ ° + (i3 ₀ ° + 90 °) + (90 °-6 ° _C ) = 180 ° (3)

O; _c obtained from equations (1) to (3). Considering the above slant angle ο; Is expressed by equation (4).

n₀) 一 s i n"¹ 、 n _&/ n。リ · · · (4) ° ≤ a

n ₀ ) one sin " ¹ , n _& / n. (4)

 In the illumination area 14, no light absorber intervenes between adjacent light transmission paths. The core and the clad constituting the optical transmission line of the illumination region 14 are of the same quality as the core 160 and the cladding 161 constituting the optical transmission line of the detection region 12.

 Next, a method for manufacturing the fiber optical plate 1 will be described.

Fabricated for multi-fiber (MF) or multi-multi-fiber (MMF) sensing areas by assembling an optical fiber whose cladding is coated with a light absorber. Also, by assembling an optical fiber whose cladding is not covered with a light absorber,-Multi-fiber (MF) or Multi-multi-fiber (MMF) is manufactured for the illumination area. However, the optical fiber used to manufacture the multi-fiber (MF) or multi-multi-fiber (MMF) for the detection area and the optical fiber used to manufacture the multi-fiber (MF) or multi-multi-fiber (MMF) for the illumination area Phino has the same outer diameter. The multi-fiber (MF) or multi-multi fiber (MMF) for the detection area and the multi-fiber (MF) or multi-multi fiber (MMF) for the illumination area are aligned in the mold by the required height. At this time, the optical fiber used to manufacture the multi-fiber (MF) or multi-multi fiber (MMF) for the detection area and the multi-fiber (MF) or multi-multi fiber for the illumination area Since the outer diameter of the optical fiber used in the manufacture of Aiva (MM F) is the same as that of the optical fiber, disturbance at the interface is eliminated.

 The aligned multi-fiber (M F) or multi-multi-fiber (MM F) is fused in a hot pressing process.

 The fiber optic plate 1 is completed by slicing and polishing the fused body.

 Next, an operation in which the uneven pattern detecting device 2 detects the uneven pattern on the surface of the measured object will be described.

 FIG. 8 is a diagram showing a state where a finger 6 to be measured is placed on the fiber optical plate 1. As shown in FIG. 8, the finger 6 is placed on the fiber optical plate 1 such that the belly of the finger 6 covers the uneven pattern input surface 122 and the illumination light emission surface 144.

 The illumination light emitted from the LED array 5 enters the illumination area 14 from the illumination light incident surface 14 2. The illumination light that has entered the illumination area 14 is guided by the optical transmission path of the illumination area 14 and reaches the illumination light exit surface 144. The illumination light that has reached the illumination light exit surface 144 enters the inside of the finger 6 at the portion of the illumination light exit surface 144 that contacts the convex part of the finger 6, and becomes scattered light. On the other hand, the illuminating light that has reached the illuminating light exit surface 1 '44 is a portion of the illuminating light exit surface 144 that is located in the concave portion of the belly of the finger 6, i.e., the air comes into contact with the illuminating light exit surface 144. In the portion, the light is totally reflected by the illumination light exit surface 144.

 FIG. 9 is a view showing a mode in which the illumination light is emitted or reflected on the illumination light exit surface 144. As shown in FIG. The end surface 165 a of the optical transmission line shown in FIG. 9 indicates the end surface of the optical transmission line in contact with air, and the end surface 165 b of the optical transmission line indicates the end surface of the optical transmission line in contact with the finger 6.

With reference to FIG. 9, a process of emitting or reflecting the illumination light on the illumination light exit surface 144 will be described in detail. The illumination light guided by the optical transmission path in the illumination area 14 has a critical angle θ _ε of the core-cladding interface. At a larger angle (incident angle), the light travels through the core 160 with total reflection at the core / cladding interface, and reaches the illumination light exit surface 144. As shown in FIG. 9, the illumination light angle phi ° cores in _{(, Φ 2 ° ···.)} - After traveling through the core 1 6 0 while being totally reflected at the clad surface, the incident angle gamma ° (γΛγ ₂ ° ···) reaches the illumination light exit surface 144. Incident angle γ. Is represented by equation (5).

γ ° = φ ° — a ° φ ^ϋ ^ θ ₀ °

Where incident angle y. The angle of refraction of the light incident on the end face of the optical transmission line from the air at an incident angle of about 90 ° (the critical angle at the air-core interface (end face of the optical transmission path)) is 3 _C °. Equation (6) is derived from Equations (3) and (5) for the relationship

_{β 0 ° = θ 0 ° -} α 0 ° ^ θ 0 ° - Fei. φ. One (¾. = Γ. · · · (6)

 Therefore, on the end surface 1 65a of the optical transmission line, the illumination light traveling in the core 160 is totally reflected.

 On the other hand, since the index of refraction of the finger 6 is higher than the index of refraction of the core 160, the illumination light reaching the end face 1 65 b of the optical transmission line exits from the core 160 and enters the inside of the finger 6. can do.

 The light incident on the finger 6 becomes scattered light inside the finger 6, and a part of the scattered light reaches the uneven pattern input surface 122. In the portion of the concave / convex pattern input surface 1 2 2 which is located in the concave portion of the belly of the finger 6, that is, in the portion where the air contacts the concave / convex pattern input surface 1 2 2, the scattered light of the finger 6 After passing through the air layer between the concave and convex pattern input surface 122 and the core 160, the light enters the core 160. The light incident on the core 160 in this manner is not totally reflected at the core-cladding interface, passes through the cladding 161, and is absorbed by the light absorber 162. On the other hand, the detection light incident on the core 160 from the finger 6 at the portion where the convex part of the belly of the finger 6 contacts the uneven pattern input surface 122 of the uneven pattern input surface 122 is The light travels through the core 160 while undergoing total internal reflection, and reaches the convex pattern output surface 124.

FIG. 10 is a diagram illustrating a mode in which the detection light that has entered the detection region 12 from the finger 6 is guided by the optical transmission line in the detection region 12. As in FIG. 9, the end face 16 5 a of the optical transmission path contacts the end face of the optical transmission path in contact with air, and the end face 16 5 b of the optical transmission path contacts the finger 6. 2 shows an end surface of an optical transmission line.

 With reference to FIG. 10, the process in which the detection light that has entered the detection region 12 from the finger 6 is guided by the optical transmission line of the detection region 12 will be described in detail.

 In the concave / convex pattern input surface 1 2 2, the scattered light inside the finger 6 passes through the air layer between the finger 6 and the end surface 1 65 a of the optical transmission path in the portion located in the concave portion of the belly of the finger 6. Then, the end face of the optical transmission line reaches 1 65 a. As described above, in the optical transmission line of the detection region 12, the axis is the slant angle in the angle range shown in Expression (4) with respect to the end surface 165 a of the optical transmission line. The light that has passed through the air layer and entered the core 160 from the end face 16 a of the optical transmission line has a critical angle of 界面 at the core-cladding interface. . At a smaller angle (the angle of incidence), it reaches the core-cladding interface and leaks into the cladding 161, without total internal reflection at the core-cladding interface. Light that has passed through the clad 16 1 and reached the light absorber 16 2 is absorbed by the light absorber 16 2 and attenuated. Therefore, the light that has entered the portion of the concave / convex pattern input surface 122 located in the concave portion of the finger 6 (the end surface 165 a of the optical transmission path) does not reach the concave / convex pattern output surface 124.

Since the refractive index of the finger 6 is higher than the refractive index of the core 160 at the portion of the concave / convex pattern input surface 122 that comes into contact with the convex part of the belly of the finger 6, the angle of refraction is. There is no limit on the angle range of. · Therefore, the part of the detection light incident on the end face 1 65 b of the optical transmission line from the finger 6 is partly a critical angle 6 _{C at the} core-cladding interface. At a larger angle (incident angle) than it reaches the core interface. This detection light travels through the core 160 while being totally reflected at the core-cladding interface, and reaches the uneven pattern output surface 124. Critical angle e _{c at the} core-cladding interface of the detected light. Anything that reaches the core-cladding interface at a smaller angle (angle of incidence) leaks into the cladding 161. However, since the light absorber 161 is disposed around the clad 161, the detection light leaked to the clad 161 does not leak to the adjacent optical transmission line.

Due to the operation of the detection region 12 for guiding the detection light as described above, the light / dark pattern of the detection light corresponding to the concave / convex pattern of the antinode of the finger 6 is present on the convex pattern output surface 124. It is.

 囬 The convex pattern output surface 124 is joined to the light receiving surface 42 of the image sensor 4, and the image sensor 4 detects a light / dark pattern of detection light corresponding to the uneven pattern of the antinode of the finger 6.

 In the present embodiment, by joining the LED array 5 to the illumination light incidence surface 142, the unevenness pattern detection device 2 is reduced in size and thickness. Also, the illumination light is guided to the illumination light exit surface 144 by the optical transmission path of the illumination area 14, and efficiently illuminates the finger 6 to be measured.

 [Second embodiment]

In the fiber optical plate 7 according to the second embodiment of the present invention, the refractive index n ₂ of the clad in the illumination area 74 is lower than the refractive index of the clad in the fiber optical plate 1. The structure of the fiber optical plate 7 is otherwise the same as the structure of the fiber optical plate 1.

Since the refractive index η ₂ of the cladding in the illumination region 74 is lower than the refractive index of the cladding in the fiber optic plate 1, as shown in equation (7), in the illumination region 74, at the core-cladding interface, Critical angle. Is the critical angle at the core-cladding interface of the fiber optic plate 1. . Smaller than.

η ₀ ° = sin " ¹ (n ₉ η ₀ ) <θ ₀ ° = sin— ¹ (n _x / n ₀ )… (7),

 FIG. 11 is a diagram showing a state in which the illumination light is emitted or reflected on the illumination light exit surface 744.

Part of the illuminating light guided by the optical transmission path in the illuminating region 74 has a critical angle of 6 _{C at} the core-cladding interface of the fiber optic plate 1. At a smaller angle (incident angle), the light travels through the core with total reflection at the core / cladding interface, and reaches the illumination light exit surface 7444.

At an angle satisfying the formula (8) (incident angle) η °, the illuminating light totally reflected at the core-cladding interface is the critical angle at the air-core interface] 3 _c . Illumination at a smaller angle (incident angle) The light exit surface 744 is reached.

° ≤; il. < _6c . + α °)

 Therefore, of the illumination light guided by the optical transmission path in the illumination area 74, the one that is totally reflected at the core / cladding interface at an angle (incident angle) that satisfies Equation (8) is the air out of the illumination light exit surface 744 The light can also be emitted to the outside even at the portion in contact with. Therefore, the illumination unit can more efficiently illuminate the measured object.

 [Third embodiment]

In the fiber optical plate 8 according to the third embodiment of the present invention, the refractive index η ₃ of the core and the refractive index η _{4 of the} clad in the illumination area 84 are respectively the same as the refractive index η of the core in the fiber optical plate 1. . And the refractive index _ηι of the cladding. The structure of the fiber optical plate 8 is otherwise the same as the structure of the fiber optical plate 1.

The refractive index η ₃ of the core in the illumination region 84 is the refractive index of the core in the detection region 82 (the refractive index of the core in the fiber optic plate 1) η. Lower than. Therefore, in the illumination area 84, the critical angle at the air-core interface. Is larger than the critical angle at the air-core interface of the detection region 82 (the critical angle at the air ′ core interface of the fiber optic plate 1) _c °. Further, the cladding refractive index n ₄ of the illumination region 8 4, the illumination region 8 4 cores 'critical Sumo detection region 82 of the core at the cladding interface - critical angle at the cladding interface (fiber optics 1 Core' cladding the critical angle at the interface) 6 _C. Is set to be equal to That is, the refractive index n ₄ of the clad in the illumination region 8 4 is expressed by Equation (9).

n ₄ = n ₃ -si ηθ. . , Η ₃ <η _0. (9)

 FIG. 12 is a diagram showing a state in which the illumination light is emitted or reflected on the illumination light emission surface 844.

Illumination area 84 Core 'Illumination light that travels through the core while undergoing total reflection at the cladding interface has an incident angle of ζ. Reaches the illumination light emitting surface 844. Illumination area 8 4 core .cladding The critical angle at the interface is the critical angle e _{c at} the core 'cladding interface of the fiber optic plate 1. Therefore, the relationship expressed by the above-described expression (6) is established even in the illumination area 84. That is, the following equation (10) is derived.

β _ο ° ≤ζ °. · (10)

However, in the illumination area 84, the air 臨界 critical angle at the core interface ■. . But the critical angle 3 _C in air ■ core interface of the fiber-optic plate 1. , The angle of incidence of some of the illumination light on the illumination light exit surface 84 4. Is the critical angle at the air-core interface in the illumination area 84. Smaller than. Such illumination light can also be emitted outside at a portion of the illumination light exit surface 844 that comes into contact with air. Therefore, the illumination means can more efficiently illuminate the measured object.

 In the first to third embodiments, the interval at which the plurality of cores are arranged in the illumination area (the interval at which the center axis of the core is arranged) is set at the interval at which the plurality of cores are arranged at the detection area (the center axis of the core). It is preferable that the core area in the illumination area is larger than the core area in the detection area. The thickness of the cladding of the optical fiber used to manufacture the multi-fiber (MF) or multi-multi-fiber (MM F) for the illumination area and the multi-fiber for the detection area. (MF) or multi-multi-fiber (MM) When the thickness of the cladding and the light absorber of the optical fiber used in the production of F) are the same, the diameter of the core in the illumination area must be larger than the diameter of the core in the detection area, that is, the illumination area By relatively increasing the interval at which the cores are arranged in the above, the area ratio of the core on the illumination light incident surface is increased, and the incidence efficiency of the illumination light in the illumination region is improved. On the other hand, by relatively shortening the interval at which the cores are arranged in the detection area, the number of cores per unit area on the concavo-convex pattern input surface and the concavo-convex pattern output surface increases, and the concavo-convex pattern transmitted in the detection area is increased. Accuracy is improved.

In the first to third embodiments, the illumination direction of the LED array and the illumination area The LED array may be attached to the fiber optic plate so that the direction of the light transmission path matches. FIG. 13 is a conceptual diagram showing a mode in which the LED array 20 is attached to the fiber optic plate 10. The LED array 20 is arranged below the illumination light incident surface 1042 such that the illumination direction matches the direction of the light transmission path in the illumination area 104. The LED array 20 and the illumination light incident surface 1042 are joined by the transparent resin 30. The light receiving surface 40 is bonded to the concave / convex pattern output surface 1024 of the detection region 102. When the illumination direction of the LED array matches the direction of the light transmission path in the illumination area, the efficiency with which the illumination light enters the illumination area 54 is improved.

 In the first to third embodiments, at least one of the refractive index of the core, the refractive index of the clad, the cross-sectional area perpendicular to the central axis of the core, and the interval at which the core is arranged between the illumination light incident surface and the LED array Another fiber optic plate (intermediate fiber optic plate) may be sandwiched. FIG. 14 is a conceptual diagram showing a mode in which the LED array 60 is disposed below the illumination light incident surface 542 with the intermediate fiber optical plate 70 interposed therebetween. The same slant angle as the fiber optic plate 50 is set in the intermediate fiber optic plate 70. By adjusting the refractive index of the core and the cladding of the intermediate fiber optical plate 70, the efficiency of the illumination light entering the illumination area 54 can be improved. Further, an intermediate fiber optical plate 70 may be interposed between the concave / convex pattern output surface 524 and the light receiving surface 80. FIG. 15 is a conceptual diagram showing a mode in which an intermediate fiber optical plate 70 is interposed between the LED array 60 and the light receiving surface 80 and the fiber optical plate 50. By adjusting the refractive indices of the core and the clad constituting the intermediate fiber optical plate 70, it is possible to improve the efficiency with which the illumination light enters the illumination area 54 and the efficiency with which the uneven pattern is output to the light receiving surface 80. .

It is preferable to use an embedded LED array 9 that is thinner than the LED array 5 as the illumination means. FIG. 16 is a front view of the embedded LED array 9. Figure 17 shows the XVII-XVII line of the embedded LED array 9 shown in Figure 16. FIG. A plurality of embedding holes 906 for embedding the LEDs 904 are formed in the long board-shaped printed board 902 along the length direction of the printed board 902. A bottom plate 908 constituting the bottom surface of the embedding hole 906 is attached to the printed circuit board 902 by soldering. An LED 904 is installed on the bottom plate 908 and wired with lead wires 910. By using the LED array 9, a thinner uneven pattern detecting device can be manufactured.

Industrial applicability

 The present invention is applicable to, for example, a fingerprint detector.

Claims

The scope of the claims  1. Applied to a concavo-convex pattern detection device that detects a concavo-convex pattern of an object to be measured, a plurality of cores are arranged at predetermined intervals so that each axis crosses both end faces at an angle and a plurality of cores are arranged at predetermined intervals in the clad. A fiber optic plate formed by assembling and forming optical fibers,  A detection area facing an imaging means for imaging the concavo-convex pattern, and an illumination area adjacent to the detection area and facing illumination means for illuminating the object to be measured,  A fiber optical plate, wherein a light absorber for absorbing light is provided in the cladding in the detection region.  2. The fiber optic plate according to claim 1, wherein a refractive index of the cladding in the illumination region is lower than a refractive index of the cladding in the detection region.  3. The fiber optic plate according to claim 1, wherein a refractive index of the core in the illumination region is lower than a refractive index of the core in the detection region.  4. The interval according to any one of claims 1 to 3, wherein an interval at which the plurality of cores are arranged in the illumination area is longer than an interval at which the plurality of cores are arranged in the detection area. Fiber optical plate.  5. The interval in which the central axes of the plurality of cores are arranged in the illumination area is longer than the interval in which the central axes of the plurality of cores are arranged in the detection area. A fiber optic plate according to any one of the preceding claims.  6. The cross-sectional area perpendicular to the central axis of the plurality of cores in the illumination area is larger than the cross-sectional area perpendicular to the central axis of the plurality of cores in the detection area. Fiber optic plate. 7. The illumination area is perpendicular to the refractive index of the core, the refractive index of the clad, and the central axis of the core. The fiber optics according to any one of claims 1 to 6, wherein a plurality of fiber optic plates differing in at least one of a straight cross-sectional area and an interval at which cores are arranged are stacked. plate.  8. A plurality of fiber optic plates, each having a different refractive index of the core, the refractive index of the clad, the cross-sectional area perpendicular to the central axis of the core, and the interval at which the core is disposed, are stacked. The fiber optic plate according to any one of claims 1 to 7, wherein the fiber optic plate is configured as follows.  9. A fiber optic plate according to any one of claims 1 to 8, wherein the imaging means is attached so as to face one surface of the detection area, and the illumination means is the imaging means in the illumination area. Is mounted so that it faces the surface on which the  An uneven pattern detecting device, characterized in that: