Patent Publication Number: US-2015062962-A1

Title: Lighting apparatus

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwan Application Serial Number 102132039, filed Sep. 5, 2013, which is herein incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of the present invention relates to a lighting apparatus. 
     2. Description of Related Art 
     Because a light emitting diodes (LED) has advantages such as low power-consumption, it has become a popular lighting device and been widely applied in illumination and backlighting of display. In order to increase the lighting range of the LED, a light guide plate is typically employed in which the LED can be disposed on the lateral surface of the light guide plate. When the LED emits light, the light enters the light guide plate through the lateral surface of the light guide plate, and it goes out of the light guide plate through the upper surface of the light guide plate. 
     Although the light can be uniformly distributed in view of the upper surface of the light guide plate, the requirements of exhibiting a particular pattern through the light guide plate is simply not satisfactory. 
     SUMMARY 
     One aspect of the present invention is to provide a lighting apparatus that can control the light to show a particular pattern. 
     In accordance with one embodiment of the present invention, the lighting apparatus includes at least one lighting element and a light guide plate. The lighting element is used for emitting a first light having a first wavelength. The light guide plate includes an optical waveguide zone and a wavelength converting zone. The optical waveguide zone is disposed on the lighting element for allowing the first light traveling within the optical waveguide zone by total reflection. The optical waveguide zone includes an upper total reflection surface, a lower total reflection surface, a light incident surface and a first light outgoing surface. The upper total reflection surface and the lower total reflection surface are parallel to each other and disposed on opposite sides of the optical waveguide zone. The light incident surface is positioned on a partial area of the lower total reflection surface, and positioned on an optical path of the first light emitted by the lighting element, so as to allow the first light to go into the optical waveguide zone through the light incident surface and to travel within the optical waveguide zone by total reflection. The first light outgoing surface is adjoined to the upper total reflection surface and the lower total reflection surface. The wavelength converting zone is adjoined to the first light outgoing surface for receiving the first light from the first light outgoing surface. The wavelength converting zone includes a wavelength converting material therein for converting a portion of the first light to be a second light having a second wavelength that is greater than the first wavelength. The wavelength converting zone has a second light outgoing surface, so as to allow the first light and the second light to go out of the light guide plate and to mix as a third light. 
     In the foregoing embodiment, the light emitted by the lighting element can travel into the wavelength converting zone by total reflection, and can go out of the light guide plate through the wavelength converting zone. In other words, in a top view of the light guide plate, the optical waveguide zone is dark, and the wavelength converting zone is bright. Therefore, the manufacturer can design the pattern of the wavelength converting zone to control the light to show a particular pattern. 
     Further, the wavelength converting material can lengthen the wavelength of the light. When the wavelength is lengthened, the refractive index of the medium (such as the material of the wavelength converting zone) can be reduced, and the critical angle can be therefore reduced, so as to prevent the light traveling within the wavelength converting zone from total reflection when it arrives at the second light outgoing surface, thereby allowing more lights to go out of the light guide plate through the second light outgoing surface, and improving the brightness and the lighting efficiency of the lighting apparatus. 
     Moreover, because the wavelength converting zone can be bright without any lighting element being disposed on the wavelength converting zone, the amount of the lighting elements can be reduced, such that the cost can be reduced as well. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a perspective view of a lighting apparatus in accordance with one embodiment of the present invention; 
         FIG. 2  is a side view of the lighting apparatus in  FIG. 1  illustrating the optical path thereof; 
         FIG. 3  is a side view of the lighting apparatus illustrating the optical path thereof in accordance with another embodiment of the present invention; and 
         FIG. 4  is a perspective view of the lighting apparatus in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       FIG. 1  is a perspective view of a lighting apparatus  10  in accordance with one embodiment of the present invention. As shown in  FIG. 1 , the lighting apparatus  10  includes at least one lighting element  100 , a light guide plate  200  and a circuit board  300 . The lighting element  100  is disposed between the light guide plate  200  and the circuit board  300 . In other words, the light guide plate  200  is disposed above the lighting element  100 , and the circuit board  300  is disposed under the lighting element  100 . 
       FIG. 2  is a side view of the lighting apparatus  10  in  FIG. 1  illustrating the optical path thereof. As shown in  FIG. 2 , the light guide plate  200  includes an optical waveguide zone  210  and a wavelength converting zone  220 . The optical waveguide zone  210  is disposed on the lighting element  100 . The optical waveguide zone  210  includes an upper total reflection surface  212 , a lower total reflection surface  214 , a light incident surface  216  and a first light outgoing surface  218 . The upper total reflection surface  212  and the lower total reflection surface  214  are parallel to each other and disposed on opposite sides of the optical waveguide zone  210 . The upper total reflection surface  212  and the lower total reflection surface  214  can reflect the light, so as to prevent the light from going out of the optical waveguide zone  210  through the upper total reflection surface  212  and the lower total reflection surface  214 . The light incident surface  216  is positioned on a partial area of the lower total reflection surface  214 . The light incident surface  216  is positioned on an optical path of the light emitted by the lighting element  100 , such that the light emitted by the lighting element  100  can go into the optical waveguide zone  210 . The first light outgoing surface  218  is adjoined to the upper total reflection surface  212  and the lower total reflection surface  214 . 
     The wavelength converting zone  220  is adjoined to the first light outgoing surface  218 . The wavelength converting zone  220  includes a second light outgoing surface  224 . The second light outgoing surface  224  is adjoined to the upper total reflection surface  212  of the optical waveguide zone  210 . The wavelength converting zone  220  includes a wavelength converting material  222  therein. The wavelength converting material  222  can scatter the light for facilitating the light to go out of the second light outgoing surface  224 . The wavelength converting material  222  can also lengthen the wavelength of the light. When the wavelength is lengthened, the refractive index of the medium (such as the material of the wavelength converting zone  220 ) can be reduced, and the critical angle can be therefore reduced, so as to prevent the light traveling within the wavelength converting zone  220  from total reflection when it arrives at the second light outgoing surface  224 , thereby allowing more lights to go out of the light guide plate  200  through the second light outgoing surface  224 , and improving the brightness and the lighting efficiency of the lighting apparatus  10 . 
     Because the upper total reflection surface  212  and the lower total reflection surface  214  allow the first light L1 emitted by the lighting element  100  to travel within the optical waveguide zone  210  by total reflection, they can prevent the first light L1 from going out of the optical waveguide zone  210  through the upper total reflection surface  212  or the lower total reflection surface  214 . Therefore, the optical waveguide zone  210  is dark. Further, because the light can go out of the light guide plate  200  through the second light outgoing surface  224 , the wavelength converting zone  220  is bright. In other words, the brightness of the optical waveguide zone  210  is not equal to the brightness of the wavelength converting zone  220 , so that the viewer may visually percept that the wavelength converting zone  220  is lighting, while the optical waveguide zone  210  is not lighting. As such, the pattern of the wavelength converting zone  220  can be designed based on the necessity, so that the lighting apparatus  10  can show various lighting patterns. 
     Moreover, the wavelength converting zone  220  can be bright without any lighting element  100  being disposed thereon, and instead, the lighting element  100  is only disposed on the optical waveguide zone  210 , such as the middle area of the light guide plate  200 . Therefore, the amount of the lighting elements  100  can be reduced, such that the cost can be reduced as well. 
     As shown in  FIG. 2 , during operation, the lighting element  100  emits a first light L1 having a first wavelength. The first light L1 can go into the optical waveguide zone  210  through the light incident surface  216 . The upper total reflection surface  212  and the lower total reflection surface  214  can totally reflect the first light L1 within the optical waveguide zone  210 , so that the first light L1 can travel within the optical waveguide zone  210  by total reflection. When the first light L1 arrives at the first light outgoing surface  218 , the first light L1 can go into the wavelength converting zone  220  through the first light outgoing surface  218 . When the first light L1 travels within the wavelength converting zone  220 , a portion of the first light L1 is converted to be a second light L2 having a second wavelength. The remaining non-converted first light L1 can travel within the wavelength converting zone  220  as well. The wavelength converting material  222  is scatterable for light, so as to facilitate the third light L3 mixed by the first light L1 and the second light L2 to go out of the light guide plate  200 . Moreover, the wavelength of the second light L2 is greater than the wavelength of the first light L1, and because the lengthened wavelength can reduce the critical angle, the third light L3 having the wavelength greater than which of the first light L1 can go out of the light guide plate  200  more easily. 
     In some embodiments, the upper total reflection surface  212  and the lower total reflection surface  214  can be, but are not limited to be, implemented by coating reflective material, such as Argentum, on the upper and lower surfaces of the optical waveguide zone  210 . 
     In some embodiments, the second light outgoing surface  224  is a rough surface. In other words, the second light outgoing surface  224  includes an uneven microstructure thereon. As such, the incident angle of which the light go out of the light guide plate  200  through the second light outgoing surface  224  can be reduced, thereby preventing total reflection occurring at the second light outgoing surface  224 , so as to facilitate the light to go out of the light guide plate  200 . 
     In some embodiments, the wavelength converting zone  220  and the optical waveguide zone  210  are linearly arranged along the same direction. In other words, the wavelength converting zone  220  and the optical waveguide zone  210  are arranged along a straight line. In some embodiments, the second light outgoing surface  224  is not only adjoined to the upper total reflection surface  212 , but also is substantially parallel to the upper total reflection surface  212 . In other words, the second light outgoing surface  224  and the upper total reflection surface  212  are coplanar. 
     In some embodiments, the optical waveguide zone  210  is a linear area having a first end  211  and a second end  213 . The first end  211  and the second end  213  are opposite to each other, and they respectively have the first light outgoing surfaces  218 . The wavelength converting zone  220  is adjoined to the first end  211 , and another wavelength converting zone  220  is adjoined to the second end  213 . Therefore, as shown in  FIG. 1 , when the lighting element  100  is lighting, the lighting apparatus  10  can show the pattern in which the left and right sides are bright, and the middle area is dark. 
     In some embodiments, as shown in  FIG. 2 , the lighting element  100  is disposed on the circuit board  300 , and is electrically connected to the circuit board  300 . As such, the lighting element  100  can be driven by the driving components (not shown) on the circuit board  300  to emit a light. 
     In some embodiments, as shown in  FIG. 2 , the lighting apparatus  10  includes an encapsulant  400 . The encapsulant  400  covers the lighting element  100  for protecting the lighting element  100 . The encapsulant  400  adheres the lighting element  100  to the light incident surface  216  of the optical waveguide zone  210 . In particular, the encapsulant  400  is adhered between the light incident surface  216  of the optical waveguide zone  210  and the circuit board  300 . 
     In some embodiments, the wavelength converting material  222  can be phosphor, dye, pigment or any combination thereof. The wavelength converting material  222  can be excited by the light from the lighting element  100 , so as to lengthen the wavelength of the light. In some embodiments, the lighting element  100  can be an LED. Preferably, the lighting element  100  can be the LED emitting the light having short wavelength, so as to excite the wavelength converting material  222 . For example, the lighting element  100  can be a blue LED or an UV LED. In some embodiments, because the light guide plate  200  has a wavelength converting zone  220 , a wavelength converting material in the lighting element  100  can be omitted. In other words, the lighting element  100  can be an LED die without encapsulated by the wavelength converting material. Moreover, the diameter of particles of the wavelength converting material  222  is scatterable for the incident light, so as to facilitate the light to go out of the light guide plate  200 . 
       FIG. 3  is a side view of the lighting apparatus  10   a  illustrating the optical path thereof in accordance with another embodiment of the present invention. As shown in  FIG. 3 , the main difference between this embodiment and the foregoing embodiment is that: the lighting apparatus  10   a  includes two reflective sheets  510  and  520 . The reflective sheet  510  is disposed on the upper total reflection surface  212 , so as to totally reflect the light arriving at the upper total reflection surface  212 . The reflective sheet  520  is disposed on the lower total reflection surface  214 , so as to totally reflect the light arriving at the lower total reflection surface  214 . The reflective sheets  510  and  520  can further prevent the light from going out of the optical waveguide zone  210  through the upper total reflection surface  212  and the lower total reflection surface  214 . 
     In some embodiments, the reflective sheet  520  has an opening  522 . The light incident surface  216  is exposed on the opening  522 , and a portion of the lighting element  100  is positioned in the opening  522 . In this configuration, the light emitted by the lighting element  100  can go into the optical waveguide zone  210  through the light incident surface  216  without blocking by the reflective sheet  520 . 
       FIG. 4  is a perspective view of the lighting apparatus  10   b  in accordance with another embodiment of the present invention. As shown in  FIG. 4 , the main difference between the lighting apparatus  10   b  and the lighting apparatus  10  in  FIG. 1  is that the wavelength converting zone  220   a  includes the shape different from which of the wavelength converting zone  220  in  FIG. 1 . More particularly, the wavelength converting zone  220   a  is an annular structure, and the optical waveguide zone  210  is surrounded by the wavelength converting zone  220   a.  In other embodiments, the wavelength converting zone  220   a  can be in other shape, such as triangle or hexagon and so on. 
     Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.