Abstract:
In an image input apparatus for detecting an image of a fingertip by irradiating the light rays emitted from a light emitting device and transmitting the light rays from the fingertip through an image guide guiding the light rays, the lighting efficiency is improved, power consumption is reduced, and the assembly is facilitated. An image input apparatus according to the present invention includes a main substrate; a lighting module, mounted on the main substrate, including a sub substrate having a light emitting device covered with resin; and an imaging unit, mounted on the main substrate, forming an image based on light rays from an object to be imaged, irradiated by light rays emitted from the light emitting device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to an image input apparatus, and more particularly to an image input apparatus that irradiates light rays emitted by a light emitting device to a fingertip, directs the light image from the fingertip through an image guide guiding the light rays to an imaging device, and detects the image of the fingertip. 
         [0003]    2. Description of the Related Art 
         [0004]    Recently, security in the information communication field has been required to be improved. Under the circumstances, there is a demand for mounting a biometric sensor on an electric device such as a computer and a mobile communication device such a cell phone. As a biometric sensor, a sweep-type fingerprint sensor capable of being downsized has been gathering attention. 
         [0005]    A conventional sweep-type fingerprint sensor generally includes an image guide, made up of a bundle of optical fibers, disposed on a line-type imaging device and is provided so that the light rays emitted from a light emitting device and passed through a fingertip are transmitted into the optical fibers. In this case, some light rays passed through the fingertip are directly transmitted into the fiber where the ridge of the fingerprint is in directly contact with the end surface of the fibers, and the other light rays are also transmitted into the fibers but through air gap due to the valley of the fingertip. In this case, because of the difference in the refractive index between the air gap and the skin (fingertip ridge), as a result, a larger amount of light rays transmitted through the ridge of the fingertip are transmitted down to the imaging device provided at the opposite end of the fibers, thereby forming the image of the fingerprint (see, for example, Patent Document Nos. 1 and 2). 
         [0006]      FIG. 7  shows a cut-open side view of an exemplary fingerprint detection apparatus in the prior art. 
         [0007]    A conventional sweep-type fingerprint detection apparatus  10  generally includes a light emitting device  12 , a light lead block  13 , an image guide  14 , and imaging device  15  mounted on a main substrate  11 , and they are covered with light-blocking resin  16 . 
         [0008]    The light emitting device  12  is made up of, for example, a photodiode and emits light rays. The light rays emitted from the light emitting device  12  are transmitted to the light lead block  13 . The light lead block  13  is fixed on the light emitting device  12  with a light-transparent resin binder and guides the light rays from the light emitting device  12  up to the fingertip  20 . 
         [0009]    The light rays guided to the fingertip  20  are reflected at the fingertip  20  and then guided in the image guide  14 . The image guide  14  is typically arranged so that the light rays from, for example, the valley of a fingerprint or air gap substantially be reflected but the light rays from the skin (the ridge of the fingerprint) substantially be incident on the image guide  14 . The image guide  14  transmits the incident light rays down to the imaging device  15 . The imaging device  15  converts the received light rays transmitted through the image guide  14  into an electronic signal with regard to the each imaging line of the imaging device  15 . 
         [0010]    By the above configuration, a fingerprint image with respect to each line can be formed. Patent Document 1: U.S. Pat. No. 4,932,776 Patent Document 2: Japanese Application Publication No. 2005-118289 
         [0011]    However, in the fingerprint detection apparatus in the related art, the light rays emitted by the light emitting device  12  mounted on the main substrate  11  are guided to the fingertip through the light lead block  13 , the light rays may be attenuated by the light lead block  13  and higher brightness of the light emitting device is required to be increased to compensate the attenuation, thereby disadvantageously causing problems including the increase of power consumption. 
         [0012]    Further, the light lead block  13  is arranged to be fixed on the light emitting device  12  with the light-transparent binder. Because of the structure, when an insufficient light-transparent binder is applied, for example, an air gap may be generated. In this case, when the light-blocking resin is introduced for covering, the light-blocking resin may penetrate into the air gap, thereby blocking light rays so that sufficient light rays may not be transmitted up to the fingertip  20 . Further, when heat is applied, the air gap may be expanded and, as a result, the light emitting device  12  may be damaged. 
         [0013]    Further, in a case where thermoreversible transmissive molded resin is used as the light lead block  13 , since the heat resistance of the resin is low, the light lead block  13  may be deformed upon being heated in, for example, a soldering reflow process. Therefore, any heating process such as the soldering reflow process cannot be performed. As a result, a specific process without heating or heating at lower temperature is to be performed, and the cost is disadvantageously increased. 
         [0014]    The present invention is made in light of the above-mentioned problems, and may provide an image input apparatus capable of increasing the illumination efficiency, reducing power consumption, and facilitating the assembly and a manufacturing method of such an image input apparatus. 
         [0015]    According to one aspect of the present invention, there is provided an image input apparatus including a main substrate ( 111 ); a lighting module ( 112 ), mounted on the main substrate ( 111 ), including a sub substrate ( 121 ) having light emitting devices ( 122 ,  123 ) covered with resin; and imaging unit ( 113 ,  114 ), mounted on the main substrate ( 111 ), forming an image based on light rays from an object to be imaged irradiated by light rays emitted from the light emitting devices ( 122 ,  123 ). 
         [0016]    According to another aspect of the present invention, there is provided an image input apparatus in which the light emitting devices ( 122 ,  123 ) in the lighting module ( 112 ) are electrically connected to the main substrate ( 111 ) through conductive patterns ( 131 - 142 ) formed on the sub substrate ( 121 ), and the light emitting devices ( 122 ,  123 ) in the lighting module ( 112 ) are covered with transparent or translucent resin. 
         [0017]    According to still another aspect of the present invention, there is provided an image input apparatus in which one surface of the main substrate ( 111 ), on which the imaging unit ( 113 ,  114 ) and the lighting module ( 112 ) are mounted, is covered with light-blocking resin ( 116 ). 
         [0018]    According to still another aspect of the present invention, there is provided an image input apparatus in which the imaging unit ( 113 ,  114 ) including an image guide ( 114 ) substantially transmitting or reflecting light rays from a medium depending on the refractive index of the medium; and an imaging device ( 113 ) forming an image from the light rays transmitted through the image guide ( 114 ). 
         [0019]    According to still another aspect of the present invention, there is provided a method of manufacturing an image input apparatus including an imaging unit ( 113 ,  114 ) and light emitting devices ( 122 ,  123 ), wherein an image of an object to be imaged is formed by the light rays from the object irradiated with light rays emitted by the light emitting devices ( 122 ,  123 ), the method including a step of mounting the imaging unit ( 113 ,  114 ) on a main substrate ( 111 ); a step of mounting the light emitting devices ( 122 ,  123 ) on a sub substrate ( 121 ), covering the light emitting device ( 122 ,  123 ) with resin, and mounting a lighting module ( 112 ) including the covered light emitting devices ( 122 ,  123 ) on the main substrate ( 111 ); and a step of covering a surface of the main substrate ( 111 ) on which the imaging unit ( 113 ,  114 ) and the lighting module ( 112 ) are mounted with light-blocking resin ( 116 ). 
         [0020]    According to still another aspect of the present invention, there is provided a method of manufacturing an image input apparatus in which the step of mounting the imaging unit ( 113 ,  114 ) on a main substrate ( 111 ) includes a step of mounting an imaging device ( 113 ) on the main substrate ( 111 ); and a step of placing and fixing an image guide ( 114 ), substantially transmitting or reflecting light rays from a medium depending on the refractive index of the medium, on the imaging device ( 113 ). 
         [0021]    It should be noted that the reference numerals described above are for reference purposes only, and shall not limit the scope and spirit of the present invention. 
         [0022]    According to an embodiment of the present invention, since both a lighting module, in which a light emitting device mounted on a sub substrate is covered with resin, and an imaging device with an image guide placed on the image guide are mounted on a main substrate, the position of the light emitting device can be placed closer to a sweep surface by the thickness of the substrate and accordingly the light rays emitted by the light emitting device can be more efficiently used when an image of the fingertip is formed. 
         [0023]    Further, since the light emitting device is covered with resin, the stress applied to the light emitting device can be reduced and damage to the light emitting device can be accordingly avoided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a perspective view of an exemplary fingerprint detection apparatus according to one embodiment of the present invention; 
           [0025]      FIG. 2  is a partially exploded perspective view of the exemplary fingerprint detection apparatus according to one embodiment of the present invention; 
           [0026]      FIGS. 3A through 3F  are drawings showing the exemplary fingerprint detection apparatus according to one embodiment of the present invention; 
           [0027]      FIG. 4  is a drawing showing an exemplary lighting module according to one embodiment of the present invention; 
           [0028]      FIGS. 5A and 5B  are drawings illustrating a manufacturing method of a fingerprint detection apparatus  100 ; 
           [0029]      FIGS. 6A and 6B  are drawings illustrating a manufacturing method of the fingerprint detection apparatus  100 ; and 
           [0030]      FIG. 7  is a cut-open side view of an exemplary fingerprint detection apparatus in prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]      FIG. 1  is a perspective view of an exemplary fingerprint detection apparatus according to one embodiment of the present invention.  FIG. 2  is an exploded perspective view of a main part of the exemplary fingerprint detection apparatus according to one embodiment of the present invention.  FIGS. 3A through 3F  are drawings showing an exemplary fingerprint detection apparatus according to one embodiment of the present invention. 
         [0032]    A fingerprint detection apparatus  100  according to an embodiment of the present invention is a so-called sweep-type fingerprint detection apparatus that detects the fingerprint of a fingertip by moving the fingertip in the direction substantially perpendicular to the direction of the detection line of the apparatus. The finger print detection apparatus  100  includes a main substrate  111 , a lighting module  112 , an imaging device  113 , an image guide  114 , a system controller  115 , and light-blocking molded resin  116 . 
         [0033]    The main substrate  111  is made up of a printed wiring board on which the lighting module  112 , the imaging device  113 , and the system controller  115  are mounted. The lighting module  112 , the imaging device  113 , and the system controller  115  are electrically connected to each other through wiring patterns formed on the main substrate  111 . 
         [0034]      FIG. 4  shows a configuration of the lighting module  112 . 
         [0035]    The lighting module  112  includes a sub substrate  121 , light emitting devices  122 ,  123 , wires  124 ,  125 , and translucent molded resin  126  and emits light rays toward the fingertip driven by power supplied from the main substrate  111 . 
         [0036]    The sub substrate  121  is made up of, for example, glass epoxy resin. Connection pads  131  through  135  and a connection pattern  139  are formed on the Z1 arrow direction surface of the sub substrate  121 . 
         [0037]    The light emitting device  122  is made up of, for example, a photodiode. The anode of the photodiode is connected to the connection pad  131 . The cathode of the photodiode is connected to the connection pad  133  through the wire  124 . Similarly, the light emitting device  123  includes, for example, a photodiode like that of the light emitting device  122 . The anode of the photodiode is connected to the connection pad  132 . The cathode of the photodiode is connected to the connection pad  134  through the wire  125 . 
         [0038]    The connection pad  131  is connected to the connection pad  136  formed on the Z2 arrow direction surface of the sub substrate  121  by a through hole plug  140 . The connection pad  132  is connected to the connection pad  137  formed on the Z2 arrow direction surface of the sub substrate  121  by a through hole plug  141 . 
         [0039]    The connection pads  133 ,  134  are connected to the connection pad  135  formed on the Z1 arrow direction surface of the sub substrate  121  by the wiring pattern  139 . The connection pad  135  is connected to the connection pad  138  formed on the Z2 arrow direction surface of the sub substrate  121  by the through hole plug  142 . 
         [0040]    The surface of the sub substrate  121  on which the light emitting devices  122 ,  123  are mounted, that is the surface of Z1 arrow direction of the sub substrate  121 , is covered with the translucent molded resin  126 . As the translucent molded resin  126 , for example, heat-hardening resin or translucent white epoxy resin may be used. The translucent molded resin  126  diffuses the light emitted by the light emitting devices  122 ,  123 . 
         [0041]    Due to the sub substrate  121 , the light emitting devices  122 ,  123  can be placed closer to a sweep surface S. Because of this feature, the light emitted by the light emitting devices  122 ,  123  can be effectively transmitted to the fingertip. Further, the translucent molded resin  126  can protect the light emitting devices  122 ,  123  and the wires  124 ,  125 . In this configuration, the thickness D 1  of the sub substrate  121  and the thickness D 2  of the translucent molded resin  126  are appropriately arranged so that the distance between the sweep surface S and the wires  124 ,  125  be a prescribed distance, for example, approximately 0.3 mm through 0.6 mm when the lighting module  112  is mounted on the main substrate  111 . The prescribed distance between the sweep surface S and the wires  124 ,  125  is determined so that the wires  124 ,  125  can be protected against static electricity generated on the sweep surface S. For example, when the distance between the sweep surface S and the wires  124 ,  125  is approximately 0.4 mm, about 20 kV of electrostatic discharge resistance protection can be secured. 
         [0042]    Further, in the lighting module  112 , since the light emitting devices  122 ,  123 , and the wires  124 , 125  are previously covered with the translucent molded resin  126 , for example, an air gap can hardly be formed. Therefore, for example, the penetration of the light-blocking molded resin  116  can be prevented. Further, the expansion of an air gap due to heat, stress on the light emitting devices  122 ,  123  and wires  124 ,  125  and accordingly the damage to the light emitting devices  122 ,  123  and the cutting of wires  124 ,  125  can be prevented. 
         [0043]    As described above, when a lighting part is manufactured as a module to form the lighting module  112 , and the lighting module  112  is mounted on the main substrate  111 , the reliability is improved compared with a case where a light emitting apparatus is mounted on a main substrate and a light lead block is fixed with, for example, a binder. 
         [0044]    In the description, one lighting module  112  is mainly considered and described. However, it should be noted that the lighting module  112  may be formed by mounting the light emitting devices  122 ,  123  on the printed wiring board on which plural connection pads  131  through  135 , a connection pattern  139 , and through hole plugs  140  through  142  are formed; performing wire bonding to provide wires  124 ,  125  to the light emitting devices  122 ,  123 , covering with translucent molded resin  126 , and cutting the printed wiring board. The lighting module  112  is provided as a single electric part when the fingerprint detection apparatus  100  is manufactured. 
         [0045]    The lighting module  112  is mounted on the main substrate  111  with a conductive binder, such as the Ag paste, applied to either the connection pads  136 ,  137 ,  138  or the patterns on the main board  111  opposite to the connection pads  136 ,  137 ,  138  and fixed to the main substrate by heating. 
         [0046]    The imaging device  113  includes, for example, a line-type light-receiving device such as a phototransistor or a phototransistor arranged in one or plural lines and is mounted on the main substrate  111  so that the light-receiving devices are arranged in the X1 and X2 arrow directions. 
         [0047]    The imaging device  113  is die bonded on a prescribed pattern formed on the main substrate  111 , and is electrically connected to the system controller  115 . The imaging device  113  operates based on, for example, a clock and control signals from the system controller  115 , receives the light rays emitted from the other side of the image guide  114 , and converts the received light rays into an electronic signal with respect to each line of the imaging device  113 . The converted signal in the imaging device  113  is transmitted to the system controller  115 . 
         [0048]    The image guide  114  is formed by bundling and fixing plural optical fibers and the fibers on the sweep surface S are typically tilted with respect to the extending direction of the fibers. One surface of the image guide  114  is fixed to the imaging device  113  such that the surface faces the light-receiving part of the imaging device  113 . The opposite end surface of the image guide  114  is formed as a sweep surface S on which a fingertip is swept. It should be noted that the angle of the above tilt is appropriately determined such that light rays from an air gap is substantially reflected on the sweep surface S of the image guide  114  but light rays from skin be substantially entered into the image guide  114  and transmitted down to the surface facing the image device  113 . 
         [0049]    The light emitted from the lighting module  112  is incident on the fingertip. The light rays reflected from the fingertip enter into the surface on the sweep surface S of the image guide  114 . In this case, light rays enter into the sweep surface S of the image guide  114  directly from an air gap or the skin depending on whether the light rays pass through the valley or ridge of the fingerprint, respectively. 
         [0050]    The system controller  115  controls the emission of the light rays from the emitting devices  122 , 123  in the lighting module  112 , and the reading of images by the imaging device  113 . Further, the system controller  115  is connected to a host apparatus and controls the communications with the host apparatus. 
         [0051]    The imaging device  113 , the lighting module  112 , the image guide  114 , and the system controller  115  mounted on the Z1 arrow direction surface of the main substrate  111  are covered with the light-blocking molded resin  116 . The light-blocking molded resin  116  includes black resin and prevents the light rays emitted from the lighting module  112  and surrounding light rays from entering directly into the imaging device  113 . 
         [0052]    According to an embodiment of the present invention, the light emitting devices  122 ,  123  can be placed closer to the sweep surface S by adjusting the thickness of the sub substrate  121 . Therefore, the light rays emitted by the light emitting devices  122 ,  123  can be used efficiently. Further, the influence of static electricity can be reduced by adjusting the thicknesses of the substrate  121  and the translucent molded resin  126 . 
         [0053]    Next, a manufacturing method of the fingerprint detection apparatus  100  is described. 
         [0054]      FIGS. 5A and 5B  and  FIGS. 6A and 6B  are drawings illustrating an exemplary manufacturing method of the fingerprint detection apparatus  100 . 
         [0055]    First, as shown in  FIG. 5A , the imaging device  113  and the system controller  115  are mounted on the main substrate  111 . 
         [0056]    Next, as shown in  FIG. 5B , the image guide  114  is placed on and fixed to the light-receiving device of the imaging device  113 . Further, as shown in  FIG. 6A , the lighting module  112  is mounted on the main substrate  111  with a conductive binder, such as Ag paste, applied to the connection pattern of the main substrate and is fixed to the main substrate  111  by heating. 
         [0057]    Next, as shown in  FIG. 6B , the surface of the main substrate  111  on which the lighting module  112 , the imaging device  113 , the image guide  114 , and the system controller  115  are mounted, that is the Z1 arrow direction surface of the main substrate  111 , is covered with light-blocking resin  116 . 
         [0058]    A manufacturing method featuring one fingerprint detection apparatus is described with reference to  FIGS. 5A and 5B  and  FIGS. 6A and 6B . However, it should be noted that the lighting module  112  may be formed by mounting plural sets of the light modules  112 , the imaging devices  113 , the image guides  114 , and the system controllers  115  on the printed wiring board of the main substrate  111 , covered with the light-blocking resin  116 , and cutting the printed wiring board to cut out one fingerprint detection apparatus  100  as shown in  FIGS. 5A and 5B  and  FIGS. 6A and 6B . 
         [0059]    Though an exemplary embodiment is described in detail above, the present invention is not limited to the specific embodiment described above, and variations and modification may be made without departing from the spirit and scope of the present invention. 
         [0060]    The present invention is based on Japanese Priority Application No. 2006-311936 filed Nov. 17, 2006, the entire contents of which are hereby incorporated herein by reference.