Abstract:
An aspect of the present invention provides a compact light guide device and a light guide apparatus having high productivity and an even light emission property. A light guide device is made of a translucent material, and LED is disposed in a notch step portion formed by cutting at least a part of an inner peripheral surface, thereby guiding light from LED to emit the light to the outside. Particularly, in a surface and a backside of a sidewall portion of the notch step portion, the sidewall portion facing a light-emitting portion of the light-emitting element, at least an inward surface constitutes a reflecting surface diffusing the light, and a pair of facing surface adjacent to each other on both sides of the sidewall portion constitutes a light acceptance surface receiving the light reflected from the reflecting surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light guide device, particularly to a light guide device utilizing LED light having strong optical directivity and a light guide apparatus into which the light guide device is incorporated. 
     2. Description of the Related Art 
     Conventionally, for example, a ring illuminator is known as the light guide device. In the ring illuminator, plural light guide paths are projected outward from an outer peripheral portion of a ring light guide body, and an illuminator portion is disposed in a free end face of the light guide path (refer to, for example, Japanese Patent Application Laid-Open No. 2006-236974). 
     However, in the ring illuminator, downsizing is hardly achieved because of the need for providing the plural light guide paths projected from outer peripheral portion. 
     Therefore, there is proposed a light guide plate, wherein light from a light-emitting element is reflected once by a substantially-chevron reflecting surface formed by partially cutting a light guide device, and the reflected light is received by facing surfaces formed on both sides of the reflecting surface (refer to, for example, Japanese Patent Application Laid-Open No. 2006-228635). 
     However, because the reflecting surface is formed in the substantially-chevron shape, uneven brightness is easily generated to hardly obtain the light guide device evenly emitting the light in the case of low dimensional accuracy of the reflecting surface or low alignment accuracy of the light-emitting element. Particularly, the improved dimensional accuracy and alignment accuracy are required with downsizing the apparatus, which results in problems of low productivity and difficulty of even light emission. 
     In view of the foregoing, an object of the present invention is to provide compact light guide device and light guide apparatus having the high productivity and an even light emission property. 
     SUMMARY OF THE INVENTION 
     In order to solve the above problems, in accordance with a first aspect of the present invention, a light guide device made of a translucent material, a light-emitting element being disposed in a notch step portion formed by cutting at least a part of an inner peripheral surface in the light guide device, thereby guiding light from the light-emitting element to emit the light to an outside, wherein at least an inward surface constitutes a reflecting surface diffusing the light in a surface and a backside of a sidewall portion of the notch step portion, the sidewall portion facing a light-emitting portion of the light-emitting element, and a pair of facing surfaces adjacent to each other on both sides of the sidewall portion constitutes a light acceptance surface receiving the light reflected from the reflecting surface. 
     In the first aspect of the present invention, because the light from the light-emitting element is diffused and reflected by the reflecting surface, even if the light-emitting element has the low alignment accuracy, there is the little unevenness of the brightness in the light received by the light acceptance surface. This enables the light guide device to emit the light having the even brightness. Particularly, the high dimensional accuracy and alignment accuracy are not required because the uneven brightness is hardly generated in the light received by the light acceptance surface. Accordingly, the compact, high-productivity light guide device is obtained. 
     In the light guide device according to first aspect of the present invention, preferably at least an outward surface constitutes the reflecting surface reflecting the light in the light acceptance surface in the surface and backside of the sidewall portion of the notch step portion, the sidewall portion facing the light-emitting portion of the light-emitting element. Accordingly, the reflecting surface is formed in the outer peripheral surface of the light guide device, which facilitates the production to further improve the productivity. 
     In the light guide device according to first aspect of the present invention, preferably a whole of at least an outer peripheral surface facing the light-emitting portion of the light-emitting element constitutes the reflecting surface. Accordingly, in addition to the above-described effect, leakage of the light received by the light acceptance surface from the outer peripheral surface is eliminated to obtain the efficient light guide device. 
     In the light guide device according to first aspect of the present invention, preferably the light guide device is formed in an annular shape or a square frame body. Accordingly, a degree of freedom of design is conveniently increased. 
     In the light guide device according to first aspect of the present invention, preferably the light acceptance surfaces face each other in parallel. The light acceptance surface is not limited to a smooth surface, but the light acceptance surface may be formed in a tapered surface or an arc surface. Accordingly, the efficient light guide device which is easily produced by selecting the optimum light acceptance surface according to a status of use. 
     In accordance with a second aspect of the present invention, a light guide apparatus, wherein a part of the light-emitting element projected from the notch step portion is coated with a coating sheet in the light-emitting element disposed in the notch step portion of the light guide device. 
     Accordingly, the unevenness of the brightness caused by the variation in alignment position is hardly generated because the light from the light-emitting element is hardly directly incident to the light guide device. 
     In accordance with a second aspect of the present invention, a light guide apparatus, wherein a hole through which light of a light-emitting element can directly be emitted outward from a light guide portion is made in a housing jointed to cover the light guide portion of the light guide device. 
     Accordingly, because not only the light of the light guide device is directly emitted to the outside but also the light is emitted from the housing, a wide variety of expressions can be realized to obtain the user-friendly light guide apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are a perspective view and a front view showing the case in which a light guide device according to an embodiment of the present invention is incorporated into a portable music player, respectively; 
         FIG. 2  is a sectional view taken on a line II-II of  FIG. 1B ; 
         FIG. 3  is a partially enlarged view of  FIG. 2 ; 
         FIG. 4  is an exploded perspective view showing the light guide device of the embodiment of  FIG. 1A ; 
         FIG. 5  is an exploded perspective view showing the light guide device of the embodiment when viewed from an angle different from that of  FIG. 4 ; 
         FIGS. 6A ,  6 B, and  6 C are a rear side view, a left side view, and a perspective view showing a light guide ring when viewed from different angles; 
         FIG. 7A  is a rear side view showing a light guide ring,  FIG. 7B  is a left side view showing a light guide ring, and  FIG. 7C  is a sectional view taken on a line C-C of  FIG. 7A ; 
         FIG. 8A  is a rear side view showing a light guide ring, and  FIG. 8B  is a partially enlarged view of a circle B in  FIG. 8A ; and 
         FIG. 9A  is a graph showing a directivity property of LED which is of a light-emitting element,  FIG. 9B  is a plan view showing a measuring position of Example, and  FIG. 9C  is a table showing measurement result. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. As shown in  FIG. 1 , the embodiment is applied to a portable music player, and a manipulation input device  5  and a ring light guide device  50  are integrally built into an attaching hole  4  of a housing  3  including a base  1  and a cover  2 . The manipulation input device  5  is used when a scroll bar in a monitor  7  is scrolled to make selection and direction. A manipulation directing hole  8  is made in an opening edge portion of the attaching hole  4 . 
     As shown in  FIGS. 4 and 5 , the manipulation input device  5  includes a metal base  10  and a flexible resin film, a printed board  20 , four LEDs  24 , a manipulation tool  30 , a shielding sheet  35 , and a manipulation dial  40 . The printed board  20  is covered with an insulating sheet  23   a . The LEDs  24  are light-emitting elements surface-mounted on the printed board. A push button  43  is fitted in the center of the manipulation dial  40 . 
     As shown in  FIGS. 4 and 5 , the metal base  10  is formed in a substantially-square shape, and can be fixed in the housing  3 . In the metal base  10 , elastic engaging portions  11  are raised in substantially-central portions of sides thereof. 
     As shown in  FIGS. 2 to 5 , the printed board  20  is formed by a flexible resin film having the substantially same planar shape as the metal base  10 . A center switch  21  is disposed in the center of the printed board  20 , and switches  22  are arranged around the center switch  21  at equal intervals. A pair of Hall elements  23  and  23  and the four LEDs  24  are mounted at predetermined positions in the printed board  20 . As shown in  FIGS. 2 and 4 , insulating sheet  23   a  adheres integrally to a surface of the printed board  20  except for a portion to be exposed. 
     The manipulation tool  30  has a planar shape with which the printed board  20  can be covered. A fitting hole  31  is made in a central portion of manipulation tool  30 , and engaging pawls  32  are projected in an outer peripheral edge portion to engage the elastic engaging portion  11  of metal base  10 . In order to cause a magnetic flux of the permanent magnet  41  to pass easily, through-holes  33  are made in the manipulation tool  30  so as to surround the fitting hole  31 . As shown in  FIGS. 3 and 5 , manipulating projections  34  are projected in the backside of the manipulation tool  30  to press down the switch  22 . 
     The shielding sheet  35  is used to shield the light of the LED  24  such that the light is not directly incident to the light guide device  50 , and has a planar shape with which the four LEDs  24  mounted on the printed board  20  can be coated. 
     As shown in  FIGS. 4 and 5 , an annular permanent magnet  41  in which N poles and S poles are alternately arranged is fixed to the backside of the manipulation dial  40 , and the push button  43  is fitted in a center hole  42  of the permanent magnet  41  while being able to be pressed down. A manipulating projection  44  is projected in a central portion of a bottom surface of the push button  43 . An annular rib  45  is projected in an edge portion of the backside of the center hole  42 . The bottom surface of the manipulation dial  40  is coated with a sliding sheet  46  having the substantially same planar shape as the manipulation tool  30 . However, as shown in  FIG. 5 , a part of the permanent magnet  41  can be seen from a through-hole  47  made in the sliding sheet  46 . Alternatively, the sliding sheet  46  may be used as the shielding sheet to reduce the number of component and assembling man-hour. 
     As shown in  FIGS. 6 to 8 , the light guide device  50  is made of a translucent material, and is formed in a ring shape which can be fitted in the outer peripheral portion of the manipulation dial  40 . The light guide device  50  includes an annular light-emitting portion  51  projected toward an inner peripheral edge portion on the surface side and an annular light guide portion  55  projected toward an outer peripheral edge portion on the backside. The light is emitted outward from an annular upper end face  52  of the light-emitting portion  51 . A diffusion material is added to the annular upper end face  52  or a diffusion pattern is disposed in the annular upper end face  52 , which allows the light-emitting portion  51  to emit the light more evenly. On the other hand, notch step portions  56  are formed at predetermined intervals in an inner peripheral surface of the light guide portion  55 . As shown in  FIG. 7C , a sidewall portion  57  constituting the notch step portion  56  and the sidewall portion  57  is located in a front face. The sidewall portion  57  has a reflecting surface by performing satin-like forming or dimple forming to an inward surface  57   a . Both side faces constituting the notch step portion  56  are formed in light acceptance surfaces  58  which receive the light reflected from the reflecting surface. A pair of positioning projections  59  is provided in the outer peripheral surface of the light guide portion  55 . 
     Alternatively, and as shown in  FIG. 3 , in the sidewall portion  57 , the satin-like forming or dimple forming may be performed to the outward surface to form the reflecting surface. A reflecting member and a reflecting sheet may separately be provided to reflect the light in an outward surface  57   b  and/or an inward surface  57   a.  The satin-like forming or dimple forming may be performed to the light-emitting portion  51 , the whole outer peripheral surface of the light guide portion  55 , and/or the upper and lower end faces, and the reflecting member and the reflecting sheet may separately be provided. The light acceptance surfaces  58  are not limited to the flat surfaces facing each other in parallel, but a tapered surface, an arc surface, and a combination thereof may be used as the shape of light acceptance surface  58 . 
     A process of assembling the components will be described below. A pair of positioning pins which is a jig (not shown) is inserted in jig holes of the metal base  10  to establish the alignment. On the other hand, after the Hall element  23  is mounted at a predetermined position of the printed board  20 , the printed board  20  adheres integrally to the metal base  10 . The switches  21  and  22  are disposed at predetermined positions of the printed board  20 , and the insulating sheet  23   a  is integrally bonded to the printed board  20 . 
     As shown in  FIGS. 2 to 5  on the other hand, the annular magnet  41  is rigidly bonded in a concentric manner to the backside of the manipulation dial  40 , and the sliding sheet  46  is assembled. The annular rib  45  provided in the backside of the manipulation dial  40  is assembled into the fitting hole  31  of the manipulation tool  30  while the sliding sheet  46  and the shielding sheet  35  are interposed, and a fixing ring  39  ( FIGS. 2 and 3 ) is caulked to the annular rib  45  to prevent drop-off. Therefore, the manipulation dial  40  is rotatably supported by the manipulation tool  30  while the sliding sheet  46  and the shielding sheet  35  are interposed. Then, the elastic engaging portion  11  of the metal base  10  engages the engaging pawl  32  of the manipulation tool  30  to integrate the manipulation dial  40  with the metal base  10 . As a result, the manipulating projection  34  of the manipulation tool  30  abuts on the center switch  22  of the printed board  20  in a manipulatable manner while the manipulating projection  44  of the push button  43  abuts on the center switch  21  of the printed board  20  in a manipulatable manner. 
     Then, the manipulation input device  5  is fixed to the base  1  of the portable music player, and the cover  2  is assembled to the base  1  while the ring light guide device  50  is aligned with the manipulation dial  40 . Therefore, the manipulation dial  5 , the push button  43 , and the light-emitting portion  51  of the ring light guide device  50  are exposed from the fitting hole  4  of the cover  2 . As shown in  FIGS. 2 and 3 , LEDs  24  are positioned to the notch step portions  56  of the ring light guide device  50 , whereby the light-emitting portion  51  of the LED  24  faces the sidewall portion  57  constituting the notch step portion  56 . The light guide portion  55  of the ring light guide device  50  is located immediately below the manipulation directing hole  8  made around the fitting hole  4  of the cover  2 . The manipulation directing hole  8  of the cover  2  may be a simple through-hole, and the manipulation directing hole  8  may be filled with a resin material containing diffusion particles diffusing the light. 
     An example of a method manipulating the portable music player into which the manipulation input device  5  is incorporated will be described below. When the manipulation dial  40  incorporated into the portable music player is turned to integrally turn the annular permanent magnet  41 , the pair of Hall elements  23  and  23  senses a change in permanent magnet  41 , and the a turning direction and a turning amount are detected based on the change in permanent magnet  41 . The detection result is reflected as movement of a scroll bar (not shown) on screen display of the monitor  7  of the portable music player. When the scroll bar reaches a desired position, the push button  43  is pressed to turn on the center switch  21 , thereby outputting the selecting direction. In the peripheral portion of the manipulation dial  40 , a predetermined position is pressed down to turn on the switch  22  located immediately below the manipulating projection  34  of the manipulation tool  30 , thereby outputting the manipulation signal. 
     In reference to  FIGS. 2 and 3 , when the LED  24  is lit on during the manipulation, the light emitted from the light-emitting portion of LED  24  is randomly reflected and diffused by the reflecting surface  57   a  of the sidewall portion  57  of the ring light guide device  50 , and the reflected light is received by the light acceptance surfaces  58  and  58 . Then, the light guided from the light guide portion  55  to the light-emitting portion  51  is emitted outward from the annular upper end face  52  of the light-emitting portion  51 . 
     The light emitted, reflected, and diffused by the reflecting surface  57   a  is emitted outward not only from the annular upper end face  52  of the light-emitting portion  51  but also from the light guide portion  55  through the manipulation directing hole  8 . Alternatively, the light emitted from the light guide portion  55  through the manipulation directing hole  8  may differ from the light emitted from the annular upper end face  52  of the light-emitting portion  51  in a color by providing a colored light diffusion agent in the manipulation directing through-hole  8 . Therefore, advantageously various expressions is enabled to expand a selection range, and a degree of freedom of design is increased. 
     Example 
       FIG. 9A  shows a graph when a light directivity property of LED  24  used in the embodiment is measured. The light directivity property of LED  24  is shown by an elliptical solid line in a semi-circular graph. It is found that the brightness is decreased as an optical axis of LED  24  is inclined from the center. 
     The unevenness of the brightness is measured to specify an allowable range of a light-emitting element attaching tolerance. In the measuring method, as shown in  FIG. 9B , the notch step portion  56  is provided in the center of a straight-shape test piece  9  having the same sectional shape as the embodiment. LED  24  is disposed such that the optical axis of the LED  24  is orthogonal to the sidewall portion  57 . The reflecting surface  57   a  is formed by performing the satin-like forming to the inward surface of the sidewall portion  57  constituting the notch step portion  56 . Then, measurement positions (five points) are provided at equal intervals on both sides about the central portion of the test piece  9 , and the brightness is measured in the lower surface (backside of the paper) of the measurement position, and the unevenness of the brightness is visually observed. 
     The brightness is measured at each measurement position in the case where LED  24  disposed in the notch step portion  56  of the test piece  9  is inclined by 2.5 degrees from the optical axis toward one side. The unevenness of the brightness is computed from the brightness values obtained from the five measurement positions based on the following equation. The  FIG. 9C  shows the measurement results.
 
unevenness of brightness=minimum brightness/maximum brightness×100(%)
 
     Accordingly, the larger value is preferable in the uneven brightness, and 100% is the most preferable value. 
     As is clear from  FIG. 9C , even if the LED attaching angle is inclined within a rage of +10 degrees to −10 degrees with respect to the optical axis, the uneven brightness is small and there is no practical problem. Then, intersection points with the LED brightness curve are determined by writing inavailable incident angles (+10 degrees and −10 degrees) in the graph of  FIG. 9A  by dotted lines. As a result, it can be confirmed that the unevenness of the brightness which becomes actually troublesome is not generated even if the light having the brightness ranging 0 to 35% of the maximum brightness is directly incident from LED to the test piece  9 . In other words, it is found that the unevenness of the brightness is not generated when LED is attached such that the light emitted from LED except for the light having the brightness ranging 0 to 35% of the maximum brightness, i.e., the strong light is not directly incident to the light guide device. Accordingly, the inavailable incident angle shall mean the allowable range of the light-emitting element attaching angle, where the unevenness of the brightness is not generated. Because the light directivity property depends on LED, obviously the inavailable incident angle is changed in each LED used. 
     According to the embodiment, the unevenness of the brightness is not generated, when LED is attached such that the light except for the light having the brightness ranging 0 to 35% of the maximum brightness, i.e., the strong light is not directly incident to the light guide device. Therefore, unlike the conventional technique, the high dimensional accuracy and alignment accuracy are not required, so that the production is easily performed to improve the productivity. Particularly, even if the component becomes reduced in size with downsizing the device, the compact light guide device evenly emitting the light can be obtained. 
     The light guide device of the present invention is not limited to the embodiment, but the light guide device may be formed in various shapes such as a rod shape and a square frame body. 
     In the embodiment, the light guide device of the present invention is applied to the portable music player. However, obviously the light guide device of the present invention can be applied to other electronic devices such as a mobile telephone and a notebook personal computer.