Abstract:
An optical fiber array module is provided. The optical fiber array module includes a light emitting device to emit light having a pre-set convergence angle through a a side surface (having a window or opening) thereof; an optical fiber array including a plurality of optical fibers (each optical fiber being an optical transmission medium); and a concentrator having a first side surface, a second side surface facing the side surface of the light emitting device, and a through-hole extended from the first side surface to the second side surface, wherein the through-hole has a width gradually narrower in a direction from the first side surface to the second side surface, wherein an end portion of the optical fiber array is inserted into the through-hole, thereby enabling concentration of the end portion of the optical fiber array d.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. § 119 to an application entitled “Optical Fiber Array Module, Fabrication Method thereof, and Portable Terminal,” filed in the Korean Intellectual Property Office on Dec. 9, 2005 and assigned Ser. No. 2005-120761, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to an optical fiber array, and in particular, to an optical fiber array module including a light emitting device and an optical fiber array.  
         [0004]     2. Description of the Related Art  
         [0005]     Optical fiber arrays are composed of a plurality of optical fibers arranged in parallel. Each optical fiber is an optical transmission medium and can selectively include a protection layer of a resin substance, which is coated on the outer surface of the plurality of optical fibers. The protection layer is used to fix the plurality of optical fibers. Optical fiber array modules structure aligns an optical fiber array and a light emitting device. A side view light emitting diode (LED) is conventionally used as the light emitting device. Such an optical fiber array module is used as a backlight to illuminate key tops of a portable terminal.  
         [0006]      FIG. 1  is a plan view of a conventional optical fiber array module  100 .  FIG. 2  is a perspective view of a side view LED  110  illustrated in  FIG. 1 . Referring to  FIGS. 1 and 2 , the optical fiber array module  100  includes the side view LED  110  for generating light and an optical fiber array  120  coupling a light beam  116  emitted from the side view LED  110  therein.  
         [0007]     The side view LED  110  includes a rectangular type window  114  on one side surface  112  thereof. The side view LED  110  emits the light beam  116  having a pre-set divergence angle from the window  114 . A horizontal width W 1  (hereinafter, width) of the window  114  is 1.9 mm, and a vertical width (hereinafter, length) of the window  114  is 0.46 mm.  
         [0008]     The optical fiber array  120  is composed of 28-core plastic optical fibers  122 . Each optical fiber is an optical transmission medium and is arranged in parallel. The optical fiber array  120  can also selectively include a protection layer of a resin substance, which is coated on the outer surface of the 28-core plastic optical fibers  122 , to fix the 28-core plastic optical fibers  122 . Each of the 28-core plastic optical fibers  122  includes a core and a clad. The core has a high refractive index in which light travels with total reflection. The clad has a low refractive index and surrounds the core. The width W 3  of the optical fiber array  120  is 7 mm, and the diameter W 2  of each of the 28-core plastic optical fibers  122  is 0.25 mm.  
         [0009]     For efficient optical coupling, it is preferable to minimize the distance between the window  114  of the side view LED  110  and an end portion of the optical fiber array  120 . However, since the width W 1  of the window  114  is narrower than the width W 3  of the optical fiber array  120  and the divergence angle of the side view LED  110  is narrow, reduction of the distance is limited.  
         [0010]     A technique of widening a divergence angle of an LED using a grating has been disclosed. However, luminance distribution of light is not uniform within the widened divergence angle. Thus, in practice, an effective divergence angle for obtaining uniform luminance is not changed. In addition, optical coupling efficiency is low, since the distance between a window of the LED and an end portion of an optical fiber array is still large.  
         [0011]     As described above, in conventional optical fiber array modules, luminance of light coupled to the optical fiber array is low, since the distance between a window of an LED and an end portion of an optical fiber array must be more than several or tens mm.  
         [0012]     Thus, there is a need in the art for an optical fiber array module for maximizing optical coupling efficiency by minimizing the distance between a window of an LED and an end portion of an optical fiber array.  
       SUMMARY OF THE INVENTION  
       [0013]     An object of the present invention is to reduce or overcome at least the above problems and/or disadvantages in the art. Accordingly, an object of the present invention is to provide an optical fiber array module for maximizing optical coupling efficiency by minimizing the distance between a window of a light emitting diode (LED) and an end portion of an optical fiber array, a fabrication method thereof, and a portable terminal.  
         [0014]     According to the principles of the present invention, an optical fiber array module is provided. The optical fiber array module includes a light emitting device to emit light having a pre-set convergence angle through a side surface thereof; an optical fiber array having a plurality of optical fibers; and a concentrator including a first side surface, a second side surface facing the window of the light emitting device, and a through-hole extended from the first side surface to the second side surface, wherein the through-hole has a width gradually narrower in a direction from the first side surface to the second side surface, wherein an end portion of the optical fiber array is inserted into the through-hole, thereby enabling concentration of the end portion of the optical fiber array.  
         [0015]     Further, according to the principles of the present invention, a method of fabricating an optical fiber array module is provided. The method including the steps of: (a) providing an optical fiber array comprising a plurality of optical fibers; (c) concentrating an end portion of the optical fiber array; and (d) aligning a light emitting device and the concentrated optical fiber array so that a side surface of the light emitting device faces the end of the optical fiber array.  
         [0016]     Still further, according to principles of the present invention, a portable terminal is provided. The portable terminal including a light emitting device to emit light having a pre-set convergence angle through a window included on one side surface thereof; an optical fiber array comprising a plurality of optical fibers; and a concentrator having a first side surface, a second side surface facing the window of the light emitting device, and a through-hole extended from the first side surface to the second side surface, wherein the through-hole has a width gradually narrower in a direction from the first side surface to the second side surface, wherein an end portion of the optical fiber array is inserted into the through-hole, thereby enabling concentration of the end portion of the optical fiber array.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawing in which:  
         [0018]      FIG. 1  is a plan view of a conventional optical fiber array module;  
         [0019]      FIG. 2  is a perspective view of a side view LED illustrated in  FIG. 1 ;  
         [0020]      FIG. 3  is a plan view of an optical fiber array module according to a first preferred embodiment of the present invention;  
         [0021]      FIG. 4  is a perspective view of a light emitting device illustrated in  FIG. 3 ;  
         [0022]      FIGS. 5 and 6  are plan views for explaining a method of extending an optical fiber array illustrated in  FIG. 3 ;  
         [0023]      FIG. 7  is a graph illustrating optical loss and light-receiving ratio characteristics according to an extension rate of an optical fiber;  
         [0024]      FIG. 8  is a plan view of an optical fiber array module according to a second preferred embodiment of the present invention;  
         [0025]      FIG. 9  is a perspective view of a concentrator illustrated in  FIG. 8 ;  
         [0026]      FIG. 10  is a plan view of a portion of a portable terminal according to a third preferred embodiment of the present invention; and  
         [0027]      FIG. 11  is a magnified bottom view of a circle A of  FIG. 10 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     Embodiments of the present invention will be described herein below with reference to the accompanying drawings. For the purposes of clarity and simplicity, well-known functions or constructions are not described in detail as they would obscure the invention in unnecessary detail.  
         [0029]      FIG. 3  is a plan view of an optical fiber array module  200  according to a first preferred embodiment of the present invention.  FIG. 4  is a perspective view of a light emitting device  240  illustrated in  FIG. 3 .  FIGS. 5 and 6  are plan views for explaining a method of extending an optical fiber array illustrated in  FIG. 3 . Referring to FIGS.  3  to  6 , the optical fiber array module  200  includes a light emitting device  240  to generate light and an extended optical fiber array  210 ′, to couple a light beam  246  emitted from the light emitting device  240  therein.  
         [0030]     The light emitting device  240  includes a rectangular type window  244  on one side surface  242  thereof. The light emitting device  240  emits the light beam  246  having a pre-set divergence angle from the window  244 . Illustratively, a width W 8  of the window  244  is 1.9 mm, and a length of the window  244  is 0.46 mm. A conventional side view LED can be used as the light emitting device  240 .  
         [0031]     The extended optical fiber array  210 ′ is composed of 28-core extended optical fibers  212 ′, Each optical fiber is an optical transmission medium and the extended optical fiber array  210 ′ can also selectively include a protection layer of a resin substance, which is coated on the outer surface of the extended optical fibers  212 ′, to fix the extended optical fibers  212 ′. If the extended optical fiber array  210 ′ includes the protection layer, a protection layer portion coated on an end portion  214 ′ of the extended optical fiber array  210 ′ is removed for an extension process described later. Each of the extended optical fibers  212 ′ includes a core and a clad. The core has a high refractive index, in which light travels with total reflection. The clad has a low refractive index, surrounding the core. Illustratively, a width W 5  of the extended optical fiber array  210 ′ is 7 mm, and a diameter W 4  of each of the extended optical fibers  212 ′ is 0.25 mm. An end portion  213 ′ of each of the extended optical fibers  212 ′ has a diameter gradually shorter in the end direction, and a diameter W 6  of the end of each of the extended optical fibers  212 ′ is 0.17 mm. The end portion  214 ′ of the extended optical fiber array  210 ′ is concentrated so that the ends of the extended optical fibers  212 ′ are laid in three layers. According, the width of the extended optical fiber array  210 ′ is gradually narrower in the end direction, and a width W 7  of the end of the extended optical fiber array  210 ′ is narrower than 1.9 mm. That is, the width W 7  of the end of the extended optical fiber array  210 ′ is set to be equal to or narrower than the width W 8  of the window  244 . The end of the extended optical fiber array  210 ′ closely faces or adheres to the window  244 .  
         [0032]     The end portion  213 ′ of each of the extended optical fibers  212 ′ is gradually thinner in the end direction by the extension process. The extension process of the extended optical fiber array  210  will now be described.  
         [0033]      FIG. 5  is a plan view of an original optical fiber array  210  before the extension process is performed.  FIG. 6  is a plan view of the extended optical fiber array  210 ′.  
         [0034]     First and second clips  220  and  230  are assembled on an end portion  214  of the original optical fiber array  210 . The original optical fiber array  210  has a uniform width W 5 . The second clip  230  fixes the end of the original optical fiber array  210 . The first clip  220  fixes a portion apart a predetermined distance from the end of the original optical fiber array  210 .  
         [0035]     The end portion  214  of the original optical fiber array  210  is extended by moving the second clip  230  in a farther direction from the first clip  220 ., For example, extending the end of the original optical fiber array  210 , while heating the end portion  214  of the original optical fiber array  210  at 80˜90° C. To make a diameter of the end of each of original optical fibers  212  from 0.25 mm to 0.17 mm, it is preferable that an extension rate of the end portion  214 ′ of the extended optical fiber array  210 ′ be substantially 60%. For example, If the length of the end portion  214  of the original optical fiber array  210  is LO and the length of the end portion  214 ′ of the extended optical fiber array  210 ′ is L, the extension rate is defined as (L−L0)/L0×100.  
         [0036]     As described above, the end portion  214 ′ of the extended optical fiber array  210 ′ is concentrated so that the ends of the extended optical fibers  212 ′ are laid in three layers as illustrated in  FIG. 3 . To maintain a concentrated state of the end portion  214 ′ of the extended optical fiber array  210 ′, a bonding agent may be coated on the end portion  214 ′ of the extended optical fiber array  210 ′.  
         [0037]      FIG. 7  is a graph illustrating optical loss and light-receiving ratio characteristics according to an extension rate of an optical fiber. In  FIG. 7 , the optical fiber has a predetermined length. If the optical fiber is extended, diffusion and distinction characteristics of the optical fiber vary. In this manner, optical loss is varied indicating a power ratio of output light to input light and a light-receiving ratio indicating a power ratio of transmitted light to input light according to the extension rate. As illustrated in  FIG. 7 , when the extension rate is 60%, the light-receiving ratio is reduced to 85%.  
         [0038]     The optical loss and the light-receiving ratio of the extended optical fiber array  210 ′ are inferior than those of the original optical fiber array  210 . However, optical coupling efficiency increases, since the end of the extended optical fiber array  210 ′ closely faces or adheres to the window  244 .  
         [0039]     A concentrator for concentrating an end portion of an extended optical fiber array will be described in a second preferred embodiment of the present invention.  
         [0040]     When an end portion of an optical fiber array is concentrated using the concentrator according to the second preferred embodiment, it will be understood by those skilled in the art that a non-extended optical fiber array can be used. Thus, if the diameter of each of optical fibers included in the non-extended optical fiber array is small enough, the area of the end of the non-extended optical fiber array, which is concentrated using the concentrator, can be equal to or less than an area of a window of a light emitting device. In this case, it is not necessary to extend of the end of the non-extended optical fiber array to align the end of the non-extended optical fiber array and the window of the light emitting device.  
         [0041]      FIG. 8  is a plan view of an optical fiber array module  200 ′ according to the second preferred embodiment of the present invention.  FIG. 9  is a perspective view of a concentrator  300  illustrated in  FIG. 8 . Since the optical fiber array module  200 ′ is the same as the optical fiber array module  200  of  FIG. 3  except that the optical fiber array module  200 ′ further includes the concentrator  300 , the same or similar elements are denoted by the same reference numerals. The description of these elements is omitted.  
         [0042]     Referring to  FIGS. 8 and 9 , the concentrator  300  includes a rectangular type base plate  310  and a through-hole  320  formed to penetrate first and second side surfaces  330  and  335  of the base plate  310  and having a rectangular cross section. The first and second side surfaces  330  and  335  are located opposite to each other. The through-hole  320  is extended from the first side surface  330  to the second side surface  335  and has a width gradually narrower in a direction from the first side surface  330  to the second side surface  335 . The through-hole  320  includes a guiding part  322  having the widest uniform width W 9 , a taper part  324  extended from the guiding part  322  and having a width gradually narrower, and an aligning part  326  extended from the taper part  324  and having the narrowest uniform width W 10 . The width W 10  of the aligning part  326  is equal to or narrower than the width W 8  of the window  244  of the light emitting device  240 . Preferably the width W 10  is set to be a slightly narrower than the width W 8  of the window  244  of the light emitting device  240 .  
         [0043]     The end portion  214 ′ of the extended optical fiber array  210 ′ is inserted into the through-hole  320  of the concentrator  300 . The end portion  214 ′ is concentrated while passing through the taper part  324 . The ends of the extended optical fibers  212 ′ are closely aligned in three layers in the aligning part  326 .  
         [0044]     The second side surface  335  of the concentrator  300  closely faces or adheres to the side surface  242  of the light emitting device  240 . Further, the end of the extended optical fiber array  210 ′ faces the window  244  of the light emitting device  240 .  
         [0045]     A portable terminal using the optical fiber array module  200 ′ will be described in a third preferred embodiment of the present invention. The portable terminal includes a keypad having a plurality of key tops and a printed circuit board (PCB) having a plurality of switches respectively aligned with the plurality of key tops. If a user presses a certain key top, a switch aligned with the pressed key top is activated. The extended optical fiber array  210 ′ of the optical fiber array module  200 ′ illuminates the key tops of the keypad. The extended optical fiber array  210 ′ is disposed between the keypad and the PCB. Moreover, the extended optical fiber array  210 ′ has a pattern to output a portion of light corresponding to each of the key tops toward each of the key tops. The pattern can be formed by scratching the surface of the extended optical fiber array  210 ′. In this case, by scratching cores of the extended optical fiber array  210 ′, light traveling with total reflection in each of the cores is output outside each of the cores resulting from the scratch breaking a total reflection condition.  
         [0046]      FIG. 10  is a plan view of a portion of a portable terminal  400  according to the third preferred embodiment of the present invention.  FIG. 11  is a magnified bottom view of a circle A of  FIG. 10 . The portable terminal  400  illustrated in  FIG. 10  includes the optical fiber array module  200 ′ illustrated in  FIG. 8 . Thus, the same or similar elements are denoted by the same reference numerals. The description of these elements is omitted.  
         [0047]      FIG. 10  shows a PCB  410 . The PCB has a plurality of switches (not shown) thereon. The extended optical fiber array  210 ′ disposed on a top surface  412  of the PCB  410  to cover the plurality of switches. The concentrator  300  and the light emitting device  240  are disposed on a bottom surface  414  of the PCB  410 . The plurality of switches is respectively aligned with a plurality of key tops (not shown). The extended optical fiber array  210 ′ is bent in a pre-set shape on the top surface  412  of the PCB  410  to illuminate the key tops.  
         [0048]     The PCB  410  has a hole  420  penetrating between the top surface  412  and the bottom surface  414  on an edge thereof. The end portion  214 ′ of the extended optical fiber array  210 ′ is extended to the window  244  of the light emitting device  240  disposed on the bottom surface  414  of the PCB  410  by passing through the hole  420 .  
         [0049]     Referring to  FIG. 11 , the window  244  of the light emitting device  240  faces the through-hole  320  of the concentrator  300 . For convenience of understanding, the concentrator  300  is shown as a cross sectional view in  FIG. 11 . The end portion  214 ′ of the extended optical fiber array  210 ′ is inserted into the through-hole  320  of the concentrator  300  and concentrated while passing through the through-hole  320 . The end of the extended optical fiber array  210 ′ is aligned to face the window  244  of the light emitting device  240 .  
         [0050]     As described above, in an optical fiber array module, a fabrication method thereof, and a portable terminal according to the present invention, by extending an end portion of an optical fiber array and aligning it with a light emitting device, the distance between a window of the light emitting device and the end of the optical fiber array is minimized. Thus, the optical coupling efficiency maximized.  
         [0051]     While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.