JP2005202877A - Photoconducting image guide member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoconducting image guide member which is suitable for a fingerprint sensor capable of acquiring fingerprint information having a high resolution of a width direction of a finger with good contrast, and the size of which can be reduced. <P>SOLUTION: The photoconducting image guide member 60 is a bundle of optical fiber pieces in which countless optical fiber pieces 70 are crowded together and aligned, and has a long shape in an X1-X2 direction as a whole. The optical fiber pieces 70 are inclined in a Y2 direction. The emitting surface of the elliptical shape of the optical fiber piece 70 coincides in its minor axis with the aligning direction of the photodetecting elements of an optical sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light guide image guide member, and more particularly to a light guide image guide member applicable to a line type fingerprint sensor.

  In recent years, from the viewpoint of security, electronic devices such as computers and portable communication devices such as mobile phones have been required to have a fingerprint sensor for identifying the fingerprint of a hand for personal authentication.

  From the viewpoint of light to obtain a fingerprint image, the fingerprint sensor uses light reflected from the finger surface and light scattered inside the finger and emitted from the finger surface. It is roughly divided into

  Also, from the viewpoint of the method of acquiring a fingerprint image that is a surface image, the fingerprint sensor has light receiving elements arranged in a matrix, and an area type fingerprint sensor that can obtain a surface image by pressing the fingertip, and a light receiving device. There is a line-type fingerprint sensor in which elements are arranged in a straight line, and a line image is obtained at each time point by sliding while pressing a fingertip, and a plane image is obtained from the line image.

  Here, the fingerprint sensor is required to be as small as possible so that it can be incorporated into a small device such as a portable communication device, in addition to sufficient reliability and low manufacturing cost.

An intra-finger scattered light type fingerprint sensor is generally configured to include a light source that applies light to the fingertip, an optical sensor, and a light guide image guide member that guides light from the fingertip to the optical sensor. The light guide image guide member has a shape in which the surface on which the fingertip comes into contact has a size corresponding to the entire fingertip, and the direction in which a number of optical fibers constituting the light guide image guide member are inclined is applied to the fingertip Is the longitudinal direction of that finger.
U.S. Pat. No. 4,932,776

  The light guide image guide member has a shape in which the surface on which the fingertip comes into contact has a size corresponding to the entire fingertip, resulting in an increase in size. For this reason, the fingerprint sensor is also increased in size, and it has been difficult to incorporate it into a small device such as a portable communication device.

  Conventionally, there is no light guide image guide member having a small size suitable for a line-type fingerprint sensor, which has a structure in which a large number of optical fiber pieces are gathered in parallel.

  Then, an object of this invention is to provide the light guide image guide member which solved the said subject.

In order to solve the above problems, the present invention is a light guide image guide member having a structure in which a large number of optical fiber pieces are assembled in parallel.
It has an elongated shape,
The optical fiber piece is configured to be inclined in a direction along a short side of the light guide image guide member,
The cross section perpendicular to the longitudinal direction is a parallelogram, and the parallelogram is such that the upper and lower surfaces of the light guide image guide member form one opposing parallel side, and the other opposing parallel side is the light beam. A light guide image guide member characterized by having a configuration that substantially coincides with an inclined direction of a fiber piece.

  According to the present invention, since the light guide image guide member has an elongated shape, the line-type fingerprint sensor can be miniaturized, and the fingerprint sensor can be mounted on a small device such as a mobile phone. Since the cross-section perpendicular to the longitudinal direction of the light guide image guide member is a parallelogram, when a line fingerprint sensor is configured, a space is formed below the inclined side surface of the light guide image guide member. It becomes possible to form, and it is possible to mount electronic components in this space as required. Since the optical fiber piece is inclined in the direction along the short side of the light guide image guide member, when the line type fingerprint sensor is configured, the elliptical shape of the emission surface of the optical fiber piece is the direction in which the light receiving elements are arranged. The direction perpendicular to the long axis is the major axis, and the fingerprint image obtained by sliding the fingertip has a better resolution in the horizontal direction than in the vertical direction.

  Next, an embodiment of the present invention will be described.

  FIG. 1 shows a light guide image guide member 60 according to Embodiment 1 of the present invention. X1-X2 is the longitudinal direction, Y1-Y2 is the width direction, and Z1-Z2 is the height direction. FIG. 2 is an enlarged cross-sectional view of the light guide image guide member 60. In FIG. 2, the height direction is greatly reduced for convenience of illustration. The light guide image guide member 60 absorbs light incident from the air and absorbs light scattered in the finger through the air layer although it is scattered light in the finger, and does not pass through the air layer from the surface of the fingertip. It has the role of guiding the directly scattered light within the finger to the light receiving element 42 described later. The reason why light scattered from within the finger and scattered light within the finger that has entered through the air layer is prevented from reaching the light receiving element is that it is noise. The light guide image guide member 60 is a bundle of optical fiber pieces in which an infinite number of optical fiber pieces 70 are inclined and densely aligned in the Y2 direction, and has a long and narrow shape as a whole in the X1-X2 direction. The optical fiber piece 70 is inclined in the Y1-Y2 direction, which is a direction along the short side of the light guide image guide member 60, and both the upper surface 61 and the lower surface 62 that are horizontal surfaces, and the inclined surface that is an inclined surface. It has side surfaces 63 and 64, and a cross section perpendicular to the longitudinal direction is a parallelogram. The portion where the optical fiber pieces 70-1 on the Y1 end side are arranged in the X1-X2 direction forms the inclined side surface 63, and the portion where the optical fiber pieces 70-n on the Y2 end side are arranged in the X1-X2 direction is inclined. Side surfaces 64 are formed. The parallelogram is formed by the edges of the upper surface 61 and the lower surface 62 forming one opposing parallel side 61a, 62a, and the edges of the inclined side surfaces 63, 64 forming a pair of opposing sides 63a, 64a. ing. The optical fiber piece 70 has dimensions of, for example, a length L2 of about 15 mm, a width W2 of about 2 mm, and a height H2 of about 2 mm.

  In addition, the inclination direction of the inclined side surfaces 63 and 64 (sides 63a and 64a) may be slightly deviated from the inclination direction of the optical fiber pieces 70-1 and 70-n. The inclination direction of 64a) only needs to substantially coincide with the inclination direction of the optical fiber pieces 70-1 and 70-n.

  In the light guide image guide member 60, the point A on the Y1 side of the upper surface 61 is located on the Y2 side from the point B on the Y2 side of the lower surface 62, as shown in FIG. The reason for this will be described later.

  As shown in FIG. 5, the light guide image guide member 60 is incorporated in the fingerprint sensor 20. In FIG. 1, the X1-X2 direction corresponds to the width of the fingertip, and the Y2 direction slides the fingertip. Direction.

  Here, for convenience of explanation, three surfaces orthogonal to each other are defined with reference to the direction in which the fingertip is slid, that is, the direction of the short side of the light guide image guide member 60. Reference numeral 200 denotes an XZ plane, which is a vertical plane orthogonal to the direction in which the fingertip is slid, and is referred to as “fingertip slide direction orthogonal vertical plane”. Reference numeral 201 denotes an XY plane, which is a horizontal plane. Reference numeral 202 denotes a YZ plane, which is a vertical plane in the direction in which the fingertip is slid, and is referred to as a “fingertip slide direction vertical plane”.

  Each optical fiber piece 70 is located in the fingertip slide direction orthogonal vertical plane 200, is inclined at an angle θ1 in the Y2 direction with respect to the Z axis, and is closely arranged in the X1-X2 direction and the Y1-Y2 direction. Yes. Each optical fiber piece 61 has a diameter of 10 to 40 μm, and has a core 71 at the center, a clad 72 around the core 71, as shown in FIG. The structure has a light absorption layer 73 that absorbs light in the periphery, and has an incident surface 75 on which light is incident and an output surface 76 on which light is emitted. The light absorption layer 73 is a material mainly composed of glass and has a thickness of 1 to 5 μm. The refractive index n1 of the core 71 is 1.62, for example, and the refractive index n2 of the clad 72 is 1.52, for example. In addition, the incident surface 75 and the emission surface 76 have an elliptical shape having a major axis in the X1-X2 direction. Reference numeral 74 denotes an interface between the core 71 and the clad 72. Both the entrance surface 75 and the exit surface 76 are horizontal surfaces. The incident surfaces 75 of the optical fiber pieces 70 gather to form the upper surface 61 of the light guide image guide member 60, and the emission surfaces 76 of the optical fiber pieces 70 gather to form the lower surface 62 of the light guide image guide member 60. doing. The angle of the incident surface 75 of the optical fiber piece 70 with respect to the optical axis 77 of the optical fiber piece 70 (equal to the angle θ1 described above) is determined as follows. That is, first, as shown in FIG. 3B, the light that has entered the core 71 from the air through the incident surface 75 is determined not to be totally reflected by the boundary surface 74. That is, the light 90 refracted at the incident surface 75 from a direction perpendicular to the incident surface 75 and incident on the core 71 is of course refracted at the incident surface 75 from the direction substantially parallel to the incident surface 75 to be within the core 71. Is also refracted at the boundary surface 74, enters the cladding 72, reaches the light absorption layer 73, and is absorbed here. Second, since the optical refractive index n of the finger is about 1.5 to 1.7, as shown in FIG. 3 (C), the light exits from the inside of the fingertip 1 and enters without passing through the air layer. It is determined that a part of the finger scattered light 95 incident on the core 71 through the surface 75 is incident at an angle θ6 larger than a critical angle θ2, which will be described later, and totally reflected by the boundary surface 74. is there. The light totally reflected by the boundary surface 74 reaches the emission surface 76 and is emitted from here.

Here, when the refractive index n1 of the core 71 is 1.62 and the refractive index n2 of the clad 72 is 1.52, the angle θ1 is optically calculated. In FIG. 3A, θ2 is a critical angle at the boundary surface between the core 71 and the clad 72.
The angle θ4 is a refraction angle of light that has been refracted by the incident surface 75 and entered into the core 71 from the right side in the air to the incident surface 75 in FIG.
The angles θ3, θ4, θ5, and θ1 are in a relationship of θ3 = 90−θ2, θ5 = θ3 + θ4, and θ1 = 90−θ5.

  The critical angle θ2 is θ2 = sin−1 (1.52 / 1.62) ≈70, and the angle θ4 is θ4 = sin−1 (1 / 1.62) ≈38. θ3 is 20 degrees, θ5 is 58 degrees, and θ1 is about 32 degrees.

  Therefore, theoretically, the angle θ1 needs to be smaller than 32 degrees. However, in this embodiment, the angle θ1 is about 40 degrees. This is because, even when the angle θ1 is greater than 32 degrees, for example, about 40 degrees, it has been confirmed by experiments that a fingerprint image of a finger with good contrast is displayed. The reason is considered that the boundary between the core 71 and the clad 72 is in a gradation state, and irregular reflection occurs in this portion. The inventor has confirmed through experiments that the angle θ1 is not limited to 40 degrees and that there is no practical problem even when the angle θ1 is about 48 degrees. Therefore, the angle θ1 may be 48 degrees or less, for example.

  In addition, mounting of the light guide image guide member 60 becomes more difficult as the angle θ1 of the optical fiber piece 70 becomes an acute angle. However, the angle θ1 is about 40 degrees, and it is not difficult to mount the light guide image guide member 60. Further, the angle θ1 of the optical fiber piece 70 and the length L2 of the light guide image guide member 60 are in a relation that the length L2 becomes shorter as the angle θ1 becomes larger, and the angle θ1 is set to 40 degrees that is larger than 32 degrees. Reduces the width W2 of the light guide image guide member 60 and finally shortens the length W1 of the fingerprint sensor 20.

  As shown in FIG. 4, the light guide image guide member 60 draws a thick material (primary drawing), bundles the drawn optical fibers and bundles them again (secondary drawing), and becomes thin. The optical fiber bundles are bundled and drawn again (tertiary drawing) to obtain a bundle 110 made of an infinite number of extremely thin optical fibers. The optical fiber bundle 110 is cut obliquely and sliced to produce an infinite number of inclined light beams. A plate 111 that is a bundle of fiber pieces is obtained, and the plate 111 is obtained by appropriately dicing.

  5 to 7 show the fingerprint sensor 20 to which the light guide image guide member 60 according to the first embodiment of the present invention is applied. 5A is a perspective view, FIG. 6A is a plan view, and FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6A. FIG. 5A is a perspective view showing the inside of the fingerprint sensor 20 so that the inside structure can be easily understood.

  The fingerprint sensor 20 is a system that uses scattered light within a finger and is configured to collect a fingerprint by sliding the finger, and a light emitting diode chip 30-1 to 30-3, CCD, or CMOS image sensor on the interposer 21. The light sensor chip 40, the capacitor chip 50, the resistance element, the transistor, and the like are mounted, and the light guide image guide member 60 is mounted on the light sensor chip 40 with the adhesive layer 100, and the light emitting diode chip. The illumination guide member 80 is adhered and mounted on the adhesive layer 101 on 30-1 to 30-3, and the light emitting diodes 30-1 to 30-3, the optical sensor chip 40, the capacitor chip 50, the resistance element, the transistor, The light guide image guide member 60 and the illumination guide member 80 are covered with a synthetic resin mold part 90 having a light shielding property and Having are integrated surrounded by structure. The fingerprint sensor 20 has a length L1 of about 17 mm, a width W1 of about 5 mm, and a height H1 of about 3 mm, and is small.

  Since the cross section of the light guide image guide member 60 is a parallelogram and the light guide image guide member 60 is inclined in the Y2 direction, the lower side of the light guide image guide member 60 indicated by reference numeral 135 in FIG. A space is formed in this portion, and this space 135 can be used for mounting electronic components.

  The optical sensor chip 40 includes a linear light receiving element group 42a in which a large number of 256 light receiving elements 42 are formed in a line along the longitudinal direction of the silicon substrate 41 on an elongated silicon substrate 41. It is. The light receiving elements 42 have a size of about 40 μm square, for example, are arranged at a pitch of 43 μm, for example, 600 dots / inch, and the number is, for example, 256. The optical sensor chip 40 is mounted on the Y1 side of the interposer 21, and the light receiving elements 42 are arranged in a line in the X1-X2 direction. The light guide image guide member 60 is mounted in accordance with the linear light receiving element group 42a so that the longitudinal direction thereof coincides with the longitudinal direction of the optical sensor chip 40. As shown in FIG. 6B, the size relationship between the optical fiber piece 70 and the light receiving element 42 is such that the light exiting surfaces 76 of the two optical fiber pieces 70 adjacent in the Y1-Y2 direction have one light receiving element 42. It is the relationship which opposes. Moreover, the light guide image guide member 60 and the light emitting diodes 30-1 to 30-3 are close to each other in the Y1-Y2 direction.

  As shown in FIG. 8, the fingerprint sensor 20 is positioned at the slit 121 portion of the casing 120 of the cellular phone using the flange portion 20b, and the upper surface 20a is exposed on the surface of the casing 120. In addition, the seal member 130 is incorporated so as to be waterproof.

  When collecting a fingerprint, as shown in FIG. 8, the fingertip 1 is pressed against the upper surface 20a of the fingerprint sensor 20 and is slid in the Y2 direction. The light emitting diode chips 30-1 to 30-3 emit light, and the light 10 passes through the adhesive layer 101 and the illumination guide member 80, exits from the upper surface of the fingerprint sensor 20, enters the fingertip 1, and enters the tissue in the fingertip 1. The fingertip 1 becomes brighter.

  As shown in an enlarged view in FIG. 9, among the scattered light within the finger emitted from the surface of the portion of the fingertip 1 that is in contact with the fingerprint sensor 20, the light 13 b emitted from the concave portion 1 b is a light guide image guide member. The light 13a that is absorbed in the light 60 and does not reach the optical sensor chip 40, and is emitted from the convex portion 1a is totally reflected in the light guide image guide member 60 and reaches the light receiving element 42 of the light sensor chip 40, and the optical sensor. By processing information from the chip 40, linear fingerprint information of a portion of the fingertip 1 that is in contact with the light guide image guide member 60 is obtained. By sliding the fingertip 1, the portion of the fingertip 1 that is in contact with the light guide image guide member 60 moves to the fingertip side, and the linear fingerprint information obtained at that time is combined with the fingertip 1. Can be obtained.

  Note that the relationship between the optical fiber piece 70 and the light receiving element 42 is such that, as shown in FIG. 6B, the minor axis of the elliptical entrance surface 75 and exit surface 76 of the optical fiber piece 70 is the X1-X2 direction and the major axis. Are in the Y1-Y2 direction, and the exit surface 76 is arranged more densely in the X1-X2 direction than in the Y1-Y2 direction, and thus the resolution of the fingerprint information is higher than that in the finger length direction. The finger width direction is better. This is because the line that characterizes the fingerprint is mainly in the length direction of the finger, and the lines that characterize the fingerprint are aligned in the width direction of the finger. This is convenient.

  In the light guide image guide member 60, the point A on the Y1 side of the upper surface 61 is located on the Y2 side from the point B on the Y2 side of the lower surface 62, as shown in FIG. Therefore, the light receiving element 42 is not located directly below the upper surface 61 but is located at a position shifted in the Y1 direction from a position directly below the upper surface 61. Therefore, even if light from directly above indicated by reference numeral 150 passes through the absorption layer 73 of the light guide image guide member 60 and enters as indicated by reference numeral 151, the entered light 151 is received by the light receiving element 42. Will not reach. Therefore, the light receiving element 42 is not affected by the incident light 151, and fingerprint information with good contrast can be obtained.

  Further, as shown in FIG. 10, the light guide image guide member 60 formed by surrounding the light guide image guide member 60 with a light shielding resin 140 may be used as an independent light guide image guide member.

  FIG. 11 shows a light guide image guide member 60A according to the second embodiment of the present invention. 12 and 13 show a fingerprint sensor 20A provided with a light guide image guide member 60A. As shown in FIG. 13, the light guide image guide member 60 </ b> A has a configuration in which a portion 150 surrounded by a broken line is added to the light guide image guide member 60, and a cross section perpendicular to the longitudinal direction is a trapezoid. This is different from the light guide image guide member 60 described above. Other portions are the same as those of the light guide image guide member 60 described above, and corresponding portions are denoted by the same reference numerals. The fingerprint sensor 20A is the same as the fingerprint sensor 20 except for the light guide image guide member 60A, and the corresponding parts are denoted by the same reference numerals.

  The light guide image guide member 60A is obtained by appropriately dicing the plate 111, which is a bundle of an infinite number of inclined optical fiber pieces in FIG. The light guide image guide member 60A has an upper surface 61A and a lower surface 62A that are horizontal surfaces, an inclined side surface 63A that is an inclined surface, and a vertical side surface 65 that is a vertical surface, and has a trapezoidal cross section perpendicular to the longitudinal direction. It is a parallelogram. In the trapezoid, the edges of the upper surface 61A and the lower surface 62A form one opposing parallel side 61Aa, 62Aa, the edge of the inclined side surface 63A forms the inclined side 63A, and the edge of the vertical side surface 65 forms the vertical side 65A. It is formed by forming.

  In the light guide image guide member 60A, the resolution of fingerprint information is better in the finger width direction than in the finger length direction.

  Since the light guide image guide member 60A has a wide lower surface 62A, it is stable during mounting and easy to mount.

  Similar to the fingerprint sensor 20 provided with the light guide image guide member 60, the fingerprint sensor 20A provided with the light guide image guide member 60A has high resolution in the width direction of the finger and has high contrast fingerprint information. Can be obtained.

  Further, as shown in FIG. 14, the light guide image guide member 60A formed by surrounding the light guide image guide member 60A with a light shielding resin 160 may be used as an independent light guide image guide member.

  As shown in FIG. 8, for example, it can be incorporated in a mobile phone so as to be exposed from the slit of the housing.

It is a perspective view of the light guide image guide member which becomes Example 1 of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the light guide image guide member of FIG. It is a figure which shows reflection and refraction of the light inside an optical fiber piece while expanding and showing the optical fiber piece which comprises a light guide image guide member. It is a figure which shows the manufacturing process of a light guide image guide member. It is a perspective view of a fingerprint sensor provided with the light guide image guide member of FIG. It is a top view of the fingerprint sensor of FIG. It is sectional drawing which follows VII-VII in FIG. 6 (A). It is a figure which shows the attachment state and fingerprint collection state to the apparatus of the fingerprint sensor of FIG. It is a figure which shows the state of total reflection and refraction of the light which injected into the light guide image guide member from the fingertip in the fingerprint collection state. It is a figure which shows the modification of the light guide image guide member of FIG. It is a perspective view of the light guide image guide member which becomes Example 2 of this invention. It is a perspective view of a fingerprint sensor provided with the light guide image guide member of FIG. It is sectional drawing of the fingerprint sensor of FIG. It is a figure which shows the modification of the light guide image guide member of FIG. 20, 20A Fingerprint sensor 21 Interposer 30-1 to 30-3 Light emitting diode chip 40 Optical sensor chip 42 Light receiving element 60, 60A Light guide image guide member 70 Optical fiber piece 80 Illumination guide member 90 Synthetic resin mold part

Claims (5)

A light guide image guide member having a structure in which a large number of optical fiber pieces are gathered in parallel,
It is an elongated shape,
The optical fiber piece is configured to be inclined in a direction along a short side of the light guide image guide member,
The shape of the cross section perpendicular to the longitudinal direction is a parallelogram,
A light guide image guide member characterized by having an upper surface and a lower surface that are both horizontal, and a pair of inclined surfaces that substantially coincide with the inclined direction of the optical fiber piece. In the light guide image guide member according to claim 1,
The position of the end of the upper surface opposite to the inclined direction is configured to be shifted in the inclined direction from the position of the inclined lower end of the lower surface. A light guide image guide member. A light guide image guide member having a structure in which a large number of optical fiber pieces are gathered in parallel,
It has an elongated shape,
The optical fiber piece is configured to be inclined in a direction along a short side of the light guide image guide member,
The shape of the cross section perpendicular to the longitudinal direction is a trapezoid,
Both the upper and lower surfaces are horizontal, one inclined surface substantially coincides with the inclined direction of the optical fiber piece, and a vertical surface opposite to the inclined surface. A light guide image guide member. In the light guide image guide member according to claim 1 or 3,
A light guide image guide member, wherein an inclination angle of an optical fiber piece with respect to a horizontal plane is larger than a logically obtained angle. On the interposer, an optical line sensor chip having a linear light receiving element group in which light receiving elements are arranged in a straight line and a light source member are mounted close to each other,
The light guide image guide member according to claim 1 or 3 is arranged on the optical line sensor chip in accordance with the linear light receiving element group, and the direction of inclination of the optical fiber piece is incident on the optical fiber piece. A fingerprint sensor characterized in that a surface is set in a direction close to the light source member and mounted.

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