JP2006178788A - Image sensor and valuable card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optically detect a contact body with high accuracy in spite of a thin type. <P>SOLUTION: This image sensor has: a fiber plate 11 comprising a plurality of optical fibers 111 densely disposed such that optical axes face a thickness direction; a total internal reflection light guide film 12 having a light injection part (a), disposed on one face of the fiber plate 11; a solid-state imaging device 13 disposed on the other face of the fiber plate 11; and a light source 14 supplying light to the light injection part. The light injected from the light source through the light injection part is totally internally reflected and propagated inside the total internal reflection light guide film. Each the optical fiber makes irregularly reflected light SC of a contacted area of an imaging target contacting with a face opposite to the fiber of the total internal reflection light guide film 12 incident and outputs it to the solid-state imaging device 13, while the solid-state imaging device 13 detects the incident light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image sensor and a valuable card that are thin and capable of optically detecting a contact body with high resolution.

  Conventionally, an image sensor is generally used as an image sensor. For example, an optical image sensor used as a fingerprint sensor is superior in water resistance compared to a pressure-sensitive sensor that uses pressure on a piezo element or an electrostatic sensor that detects the capacitance between the sensor and a detection target. It is difficult to deteriorate and has a low failure rate.

FIG. 9 shows an outline of a conventional optical fingerprint sensor (Patent Document 1) using an optical fiber. In FIG. 9, an optical fingerprint sensor (fingerprint sensor module) 9 enters a light source 91, glass 93 on which light emitted from the light source 91 is incident, and reflected light of a finger placed on the glass 93 surface from the tip. It consists of a group of optical fibers 94 and an image sensor 95 placed at a position where light passing through the optical fibers 94 is incident. The light source 91 is fixed to the support plate 921, the image sensor 95 is fixed to the support plate 922, and the optical fiber 94 is attached to the image sensor 95.
JP 2003-317085 A

  Incidentally, the optical fingerprint sensor 9 shown in FIG. 9 is not easy to manufacture because the light source 91 and the image sensor 95 must be mounted on the inclined support plates 921 and 922. Also, practical resolution cannot be obtained unless the distance between the reflection point (P) of the finger placed on the glass 93 surface and the tip P ′ of the optical fiber 94 is reduced, but the configuration of FIG. 9 has limitations. Yes, this practical resolution cannot be obtained.

  In general, there are two types of optical fingerprint sensors: one that recognizes reflected light from a fingerprint as an image, and the other that utilizes the fact that the fingerprint-pressed part is totally reflected. ing. The optical fingerprint sensor 9 of FIG. 9 employs the former method (recognizing the reflected light from the finger of the light transmitted through the glass 93 as a normal image), so the image recognition accuracy is low.

  An object of the present invention is to provide an image sensor capable of optically detecting a contact body such as a fingerprint with a high resolution while being thin, and a valuable card equipped with the image sensor.

  The image sensor of the present invention comprises a fiber plate composed of a plurality of optical fibers arranged densely so that the optical axis is directed in the thickness direction, and a light injection section, and a total reflection guide disposed on one surface of the fiber plate. An optical film, a solid-state imaging device disposed on the other surface of the fiber plate or a photosensitive element array formed on the other surface of the fiber plate, and a light source that supplies light to the light injection unit, The light injected from the light source through the light injection part is totally reflected and propagated in the total reflection light guide film, and each optical fiber is in contact with the surface of the total reflection light guide film opposite to the optical fiber. The irregularly reflected light of the contacted area of the imaging target is incident and output to the solid-state imaging device or the photosensitive element array, and the solid-state imaging device or the photosensitive element array is And detecting the incident light.

  In the image sensor of the present invention, as described above, light detection can be performed by a solid-state imaging device, or light detection is performed directly on the other surface (lower surface) of the fiber plate by a photosensitive element array formed by a semiconductor process. be able to. The solid-state imaging device is a CCD or the like manufactured separately from the fiber plate. The photosensitive element array is a semiconductor element group formed on the lower surface of the fiber plate by a semiconductor process.

  In the image sensor of the present invention, a light shielding portion can be formed on the side surface of each optical fiber. In this case, the gap between the optical fibers may be filled with a light shielding material.

  In the image sensor of the present invention, the thickness of the total reflection light guide film can be set in a range of 5 to 500 μm (in some cases, a maximum of about 1 mm). The diameter of the optical fiber can be set in the range of 5 to 200 μm.

  The valuable card of the present invention is equipped with the above-described image sensor, and the card function becomes effective when, for example, fingerprint verification is successful (for example, transmission and reception of passwords and IDs are possible. Or can be written into the memory in the card).

  In the present invention, fingerprints and the like are detected by a total reflection method, so that the contact body can be optically detected with high resolution while being thin, and each light source and the like can be easily mounted.

  FIG. 1 is an explanatory view showing an embodiment of the image sensor of the present invention. In FIG. 1, the image sensor 1 includes a fiber plate 11, a total reflection light guide film 12, a solid-state imaging device 13, and a light source 14.

  The fiber plate 11 has a rectangular plate shape and is composed of a plurality of optical fibers 111 arranged densely (usually densely) so that the optical axis faces the thickness direction. The diameter r of the optical fiber 111 (see FIG. 2A) is not limited, and is 50 μm in this embodiment, but can be appropriately set to 20 to 200 μm. As the optical fiber 111, various types such as quartz, glass and plastic can be used.

There is no limitation on the thickness of the fiber plate 11 (the length of the optical fiber 111). In the present embodiment, the thickness is 2 mm, but the thickness can be appropriately set within a range of 100 μm to 5 mm.
Each optical fiber 111 is formed in an integral plate shape by the adhesive C. The optical fiber 111 can have a two-layer structure in which the clad covers the core, and the light passing through each optical fiber 111 can be configured not to leak to the outside (for example, another optical fiber 111).

  A light shielding portion 112 can be formed on the side surface of each optical fiber 111 as shown in FIG. In addition, as illustrated in FIG. 2B, the adhesive C can be made to contain a color pigment so that the adhesive C can function as the light shielding portion 112. In addition, a single-layer structure can be used as each optical fiber 111, and also in this case, the light shielding portion 112 can be formed on the side surface of each optical fiber 111.

  The total reflection light guide film 12 is made of a transparent synthetic resin (for example, a refractive index of 1.3 to 1.7) provided with the light injection part 121, and is disposed on one surface of the fiber plate 11. In this embodiment, although the light injection part 121 was provided in one place of the total reflection light guide film 12, it can also be provided in several places.

  As shown in FIG. 3A, the light injection part 121 has a substantially triangular shape with the light injection part a as a vertex and the opposite side continuing to the side of the total reflection light guide film 12. Further, as shown in FIG. 3B, the side view has a substantially triangular shape in which the light injection portion a is a side and the diagonal continues to the total reflection light guide film 12.

  The solid-state imaging device 13 is disposed on the surface of the fiber plate 11 opposite to the total reflection light guide film 12. In the present embodiment, a CCD is used as the solid-state imaging device 13, but other imaging elements such as a CMOS can also be used.

  Further, the solid-state imaging device 13 and the fiber plate 11 may be joined by an adhesive Y as shown in FIG. 4A, or the solid-state imaging device 13 is protected as shown in FIG. 4B. May be joined via a flexible material 16 for the purpose.

The light source 14 is an LED in this embodiment, and can supply light to the light injection part a.
FIG. 5 is an explanatory diagram showing the behavior of the light emitted from the light source 14. The operation of the image sensor 1 will be described below.

  The light B from the light source 14 (not shown in FIG. 5) is injected into the total reflection light guide film 12 through the light injection part 121. The light B that is totally reflected and propagated inside the total reflection light guide film 12 is irregularly reflected at the portion where the finger is in contact with the surface (the pressing portion P of the convex portion of the fingerprint). The irregularly reflected light SC is incident on the optical fiber 111 just below the pressing portion. If the thickness L of the total reflection light-guiding film 12 is small, most of the irregularly reflected light SC is incident on the optical fiber 111 immediately below the irregularly reflecting portion P. In the present embodiment, as described above, the thickness L of the total reflection light guide film 12 needs to be made small enough not to reduce the resolution of the detection target (for example, fingerprint). In this embodiment of fingerprint detection, as described above, the thickness L of the total reflection light guide film 12 is 50 μm or less. The diameter r of the optical fiber 111 is 10 μm.

The irregularly reflected light SC is sent to the solid-state imaging device 13 via the optical fiber 111. The solid-state imaging device 13 detects this light and sends it to a detection circuit (not shown).
FIG. 6 is an explanatory side view of a valuable card 100 with a fingerprint sensor to which the image sensor 1 described above is applied. The valuable card 100 with a fingerprint sensor includes only the image sensor 1, the circuit unit 2, the substrate unit 3 on which these are mounted, the cover unit 4, and the pressure sensor 5.

  FIG. 7A shows the structure of the valuable card 100, and FIG. 7B shows a surface view. As shown in FIG. 7A, in the valuable card 100, in addition to the image sensor 1 and the circuit unit 2, an antenna 61, a battery 62, a switch 63, an interface 64, and a fingerprint sensor 5 (not shown) are mounted.

  As shown in FIG. 8, the circuit unit 2 includes a CPU 21, an EEPROM 22, a RAM 23, a DSP 24, and a communication circuit 25. The circuit unit 2 includes a pressure sensor 5, an antenna 61, a battery 62, a switch 63, and an interface 64. Is connected.

  The CPU 21 controls the entire circuit unit 2. The EEPROM 22 stores system programs, various setting values, registered fingerprint data, and the like. A work area for the CPU 21 is secured in the RAM 23. The DSP 24 processes the data acquired by the solid-state imaging device 13 (specifically, by performing contrast processing, separation dot connection processing, etc.), and generates a detection image. The valuable card 100 may be configured not to include the DSP 24. In this case, the CPU 21 performs image generation processing using a detection image generation program stored in the EEPROM 22.

  When the switch 53 is operated, power from the battery 62 is supplied to the image sensor 1 and the circuit unit 2 and is controlled to be turned off after a predetermined time has elapsed. When the press sensor 5 detects a finger press, the light source 14 is driven and a fingerprint is detected.

  In this embodiment, the fingerprint collation process can be performed by the DSP 24, and the CPU 21 can perform the fingerprint collation process by a fingerprint collation program in the EEPROM 22. Needless to say, when the valuable card 100 does not include the DSP 24, the CPU 21 performs fingerprint collation processing by the fingerprint collation program in the EEPROM 22.

  The communication circuit 25 can output, for example, information stored in the EEPROM 22 to an external device via the antenna 61, and the communication circuit 25 can write information received from the external device in the EEPROM 22.

  When the image sensor 1 is configured as a part of a mobile phone, a CPU, a ROM, a RAM, a battery, and the like attached to the mobile phone can be used.

  In the embodiment of the present invention, fingerprint detection with a resolution higher than 250 to 500 dpi or 500 dpi is possible.

  In addition, a photosensitive element can be formed on the lower surface of the fiber plate 11 independently of the density of the optical fiber, or one photosensitive element can be formed on the lower surface of the fiber plate 11 for each optical fiber.

It is explanatory drawing which shows one Embodiment of the image sensor of this invention. (A) is a diagram showing an optical fiber in which a light shielding portion is formed, and (B) is a diagram in which a coloring pigment is contained in the adhesive material C so that the adhesive material C can function as the light shielding portion 112. (A) is a plane view explanatory drawing of a light injection part, (B) is a side view explanatory drawing of a light injection part. (A), (B) is side surface expansion explanatory drawing of a fiber plate and a solid-state imaging device. It is explanatory drawing which shows the behavior of the light radiate | emitted from the light source at the time of reading a fingerprint image. It is side surface explanatory drawing of a valuable card with a fingerprint sensor which applied the image sensor. (A) is a figure which shows the structure of a valuable card, (B) is a surface figure. It is a figure which shows the circuit part structure of a valuable card. Optical fiber. It is a figure which shows the outline | summary of the used conventional optical fingerprint sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image sensor 2 Circuit part 3 Board | substrate part 4 Cover part 5 Press sensor 11 Fiber plate 12 Total reflection light guide film 13 Solid-state imaging device 14 Light source 21 CPU
22 EEPROM
23 RAM
24 DSP
25 communication circuit 61 antenna 62 battery 63 switch 64 interface 100 valuable card 111 optical fiber 112 light shielding part 121 light injection part

Claims (5)

A fiber plate composed of a plurality of optical fibers arranged closely so that the optical axis faces the thickness direction;
A light injection part, and a total reflection light guide film disposed on one surface of the fiber plate;
A solid-state imaging device disposed on the other surface of the fiber plate or a photosensitive element array formed on the other surface of the fiber plate;
A light source for supplying light to the light injection part,
The total reflection light-guiding film causes the light injected from the light source through the light injection unit to totally reflect and propagate,
Each of the optical fibers is incident on the solid-state imaging device or the photosensitive element array by entering irregularly reflected light of the contacted area of the imaging target in contact with the surface opposite to the optical fiber of the total reflection light guide film,
The solid-state imaging device or the photosensitive element array detects the incident light;
An image sensor characterized by that.   The image sensor according to claim 1, wherein a light shielding portion is formed on a side surface of each optical fiber.   The image sensor according to claim 1, wherein a thickness of the total reflection light guide film is set in a range of 5 to 500 μm.   The image sensor according to any one of claims 1 to 3, wherein the optical fiber has a diameter in a range of 5 to 200 µm. A valuable card on which the image sensor according to claim 1 is mounted.

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