Abstract:
A backlight unit includes a light source and a lens unit optically coupled to the light source. A surface of the lens unit facing the light source includes areas coated with a reflective material for reflecting light from the light source away from the lens, and a transmissive area for transmitting light from the light source towards ran output surface of the lens. A display device includes a display panel, a light diffuser, the backlight unit and a reflective element, the backlight unit arranged between the light diffuser and the reflective element, and the display panel positioned opposite the backlight unit with respect to the light diffuser.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Korean Patent Application No. 10-2013-0030090, filed on Mar. 21, 2013 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The following description relates to a display device having a backlight unit which radiates light to a display panel. 
     2. Description of the Related Art 
     A display panel using a liquid crystal display (LCD), which is common in display devices, does not emit light directly. Therefore, a backlight unit is provided at the rear of the display panel, and a light diffuser or a light guide plate is installed between the display panel and the backlight unit, so that light radiated from the backlight unit may be diffused through the light diffuser to be uniformly distributed to the entirety of the display panel. 
     Display devices are divided into a direct type and an edge type according to the positions of backlight units. A direct type display device has a structure in which a plurality of light emitting diodes is broadly arranged at the rear of a display panel and thus directly radiate light to the display panel. An edge type display device has a structure in which a plurality of light emitting diodes is arranged at the edge of a display panel and light radiated from the plurality of light emitting diodes is diffused by a light guide plate and then transmitted to the display panel. 
     In the above conventional direct type display device, if a distance between the display panel and the backlight unit is excessively short, light radiated from the respective light emitting diodes may form a hot spot on the display panel. In order to prevent formation of a hot spot, a distance between the display panel and the backlight unit should be sufficient, and thus, the thickness of the display device is increased and slimming of a product is limited. The edge type display device may be advantageous in terms of slimming of the display device, as compared to the direct type display device, but additionally requires the light guide plate to guide light radiated from the light emitting diodes at the edge of the display panel to the central region of the display panel, and may be thus disadvantageous in terms of price competitiveness. 
     SUMMARY 
     Therefore, the following description relates to a display device using a display panel in which a backlight unit to radiate light to the display panel is installed at the central region of the rear surface of the display panel to reduce the number of optical elements of the backlight unit, and the structure of a lens unit of the backlight unit is improved to eliminate a dark region formed on the display panel due to the shadow of the backlight unit. 
     Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     In accordance with an aspect of the present disclosure, a backlight unit of a display device includes a light source installed at a position, separated from the central region of a light diffuser diffusing light by a predetermined distance, to radiate light to the light diffuser, and a lens unit installed between the light diffuser and the light source and having a surface facing the light source, the surface of the lens unit facing the light source including reflective areas which are coated with a reflective material and reflect a part of light radiated from the light source, and a transmissive area which is not coated with a reflective material and transmits the other part of light radiated from the light source. 
     The light source may include a plurality of optical elements, the plurality of optical elements may be arranged in a long strip shape in parallel with the light diffuser, and the lens unit may be arranged in a long strip shape along the arrangement shape of the plurality of optical elements. 
     The plurality of optical elements may be arranged in one of the vertical direction and the horizontal direction of the light diffuser. 
     The plurality of optical elements may be arranged in the shape of two parallel strips in the vertical direction of the light diffuser, and the lens unit may be arranged in the shape of two parallel strips along the arrangement shape of the plurality of optical elements. 
     The plurality of optical elements may be arranged in the shape of two parallel strips in the vertical direction of the light diffuser, and the plurality of optical elements in the shape of the two parallel strips may be arranged in a zigzag pattern. 
     The lens unit may have the surface facing the light source, the transmissive area may be formed along the central axis in the lengthwise direction of the surface of the lens unit facing the light source to have predetermined width and length, and the reflective areas may be formed at both sides of the transmissive area. 
     The reflective areas may include a first reflective area and a second reflective area divided from each other by the transmissive area, and the first reflective area and the second reflective area may be inclined symmetrically to each other. 
     The first reflective area and the second reflective area may be inclined in the direction of the light diffuser. 
     The reflective areas on the surface of the lens unit facing the light source may have a predetermined curvature. 
     The lens unit may have a surface facing the light diffuser, and the surface of the lens unit facing the light diffuser may be flat. 
     The lens unit may have a surface facing the light diffuser, and some parts of the surface of the lens unit facing the light diffuser may be concave. 
     The positions of the concave parts may coincide with the positions of a plurality of optical elements of the light source. 
     The size of the concave parts may coincide with the size of a plurality of optical elements of the light source. 
     The size of the concave parts may be greater than or smaller than the size of a plurality of optical elements of the light source. 
     The lens unit may have a surface facing the light diffuser, and some parts of the surface of the lens unit facing the light diffuser may be convex. 
     The positions of the convex parts may coincide with the positions of a plurality of optical elements of the light source. 
     The size of the convex parts may coincide with the size of a plurality of optical elements of the light source. 
     The size of the convex parts may be greater than or smaller than the size of a plurality of optical elements of the light source. 
     The lens unit may have a surface facing the light diffuser, and the entirety of surface of the lens unit facing the light diffuser may be convex. 
     The lens unit may have a surface facing the light diffuser, and the entirety of surface of the lens unit facing the light diffuser may be concave. 
     The lens unit may have a surface facing the light diffuser, and a long and concave groove may be formed on the surface of the lens unit facing the light diffuser in the lengthwise direction of the lens unit. 
     The lens unit may have a surface facing the light diffuser, and a long and convex groove may be formed on the surface of the lens unit facing the light diffuser. 
     The lens unit may include a plurality of optical elements, and the lens unit may be provided to correspond to the plurality of optical elements. 
     In accordance with an aspect of the present disclosure, a display device includes a display panel to display an image, a light diffuser installed at the rear of the display panel to diffuse light, a bottom chassis installed at the rear of the light diffuser and provided with a reflective surface on a surface of the bottom chassis facing the light diffuser, a light source installed between the light diffuser and the bottom chassis to be separated from the central region of the light diffuser by a predetermined distance, and radiating light to the light diffuser, and a lens unit installed between the light diffuser and the light source and having a surface facing the light source, the surface of the lens unit facing the light source including reflective areas which are coated with a reflective material and reflect a part of light radiated from the light source, and a transmissive area which is not coated with a reflective material and transmits the other part of light radiated from the light source. 
     A part of light radiated from the light source may be reflected by the reflective areas of the lens unit, and then reflected by the reflective surface of the bottom chassis. 
     The light source may include a plurality of optical elements, the plurality of optical elements may be arranged in a long strip shape in parallel with the rear surface of the light diffuser, and the lens unit may be arranged in a long strip shape along the arrangement shape of the plurality of optical elements. 
     The lens unit may have the surface facing the light source, the transmissive area may be formed along the central axis in the lengthwise direction of the surface of the lens unit facing the light source to have predetermined width and length, and the reflective areas may be formed at both sides of the transmissive area. 
     The lens unit may include a plurality of optical elements, and the lens unit may be provided to correspond to the plurality of optical elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a perspective view of a display device in accordance with an embodiment of the present disclosure; 
         FIG. 2  is an exploded perspective view of the display device in accordance with the embodiment of the present disclosure; 
         FIG. 3  is an exploded perspective view of a display module shown in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the display module shown in  FIG. 2 ; 
         FIG. 5  is an exploded perspective view of a backlight unit of the display module in accordance with the embodiment of the present disclosure; 
         FIG. 6  is a view illustrating the detailed shape and configuration of the backlight unit of the display module in accordance with the embodiment of the present disclosure; 
         FIG. 7  is a view illustrating optical characteristics of the backlight unit in accordance with the embodiment of the present disclosure; 
         FIG. 8  is a view illustrating lens units of the backlight unit in accordance with various modified embodiments of the present disclosure; 
         FIG. 9  is a view illustrating a backlight unit in accordance with an embodiment of the present disclosure; 
         FIG. 10  is a view illustrating a backlight unit in accordance with an embodiment of the present disclosure; and 
         FIG. 11  is a view illustrating a backlight unit in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIG. 1  is a perspective view of a display device in accordance with an embodiment of the present disclosure. As exemplarily shown in  FIG. 1 , a display device  100  includes a display module  10 , and a front case  20 F and a rear case  20 R forming the external appearance of the display device  100  and supporting and protecting the display module  10 . 
       FIG. 2  is an exploded perspective view of the display device in accordance with the embodiment of the present disclosure. As exemplarily shown in  FIG. 2 , the display device  100  in accordance with the embodiment of the present disclosure includes the display module  10  displaying an image, the front case  20 F and the rear case  20 R provided in front of and at the rear of the display module  10  and combined with each other, and a control substrate  30  disposed between the display module  10  and the rear case  20 R to supply power and transmit a control signal to the display module  10 . 
       FIG. 3  is an exploded perspective view of the display module  10  shown in  FIG. 2 , and  FIG. 4  is a cross-sectional view of the display module  10  shown in  FIG. 2 . As exemplarily shown in  FIGS. 3 and 4 , the display module  10  of the display device  100  in accordance with the embodiment of the present disclosure includes a display panel  11  including a liquid crystal display and displaying an image, a backlight unit  12  disposed at the rear of the display panel  11  to be separated from the display panel  11  and radiating light to the display panel  11 , a light diffuser  13  to diffuse light radiated from the backlight unit  12 , and a plurality of optical sheets  14 A and  14 B disposed on the rear surface of the display panel  11 . 
     Further, the display module  10  includes a middle mold  15  supporting the display panel  11  and the light diffuser  13 , a top chassis  16  installed in front of the middle mold  15  and maintaining the fixed state of the display panel  11  to the middle mold  15 , and a bottom chassis  17  installed at the rear of the middle mold  15  such that the backlight unit  12  is installed on the bottom chassis  17 . The optical sheets  14 A and  14 B include a prism film  14 A focusing light diffused by the light diffuser  13  in a direction vertical to the display panel  11 , and a protective film  14 B to protect the prism film  14 A. The display panel  11  is disposed in front of the middle mold  15 , the light diffuser  13  is disposed at the rear of the middle mold  15 , and the display panel  11  and the light diffuser  13  are supported by the middle mold  15 . The top chassis  16  includes a bezel part  16   a  covering the edge of the front surface of the display panel  11 , and a top side part  16   b  bent backward from the edge of the bezel part  16   a . The bottom chassis  17  includes a rear surface part  17   a  formed in an about rectangular shape such that the backlight unit  12  is seated on the rear surface part  17   a , and a bottom side part  17   b  extending forward from the edge of the rear surface part  17   a.    
     A reflective surface  408  reflecting light radiated from the backlight unit  12  to proceed toward the light diffuser  13  is formed on the inner surfaces (i.e., the surfaces facing the light diffuser  13 ) of the rear surface part  17   a  and the bottom side part  17   b . For this purpose, the inner surface of the bottom chassis  17  is coated with a reflective material. Otherwise, a reflective plate reflecting light radiated from the backlight unit  12  toward the light diffuser  13  may be additionally installed between the bottom chassis  17  and the backlight unit  12 . The backlight unit  12  includes a light source  402  and a lens unit  404 . The light source  402  serves to radiate light and the lens unit  404  serves to uniformly transmit light radiated from the light source  402  to the entirety of the light diffuser  13 . The structure of such a backlight unit  12  will be described in detail below with reference to  FIGS. 5 and 6 . 
       FIG. 5  is an exploded perspective view of the backlight unit of the display module in accordance with the embodiment of the present disclosure, and  FIG. 6  is a view illustrating the detailed shape and configuration of the backlight unit of the display module in accordance with the embodiment of the present disclosure. 
     First, as exemplarily shown in  FIG. 5 , the light source  402  is installed at a position separated from the rear surface of the light diffuser  13  by a predetermined distance, and the lens unit  404  is installed between the light diffuser  13  and the light source  402 . The light source  402  includes a plurality of optical elements (for example, a plurality of light emitting diodes), and is located at a position separated from the rear surface of the light diffuser  13  by a predetermined distance and corresponding to the central portion of the light diffuser  13 . Further, the light source  402  is arranged in a long strip shape extended in the vertical direction of the light diffuser  13  and having a length equal to the vertical length of the light diffuser  13 . The lens unit  404  is also arranged in a strip shape having a length similar to the length of the light source  402  according to the arrangement shape of the light source  402 . Here, the ‘vertical direction’ refers to the direction of the shorter one of the horizontal length and the vertical length of the light diffuser  13 . 
     The lens unit  404  of the display panel  11  has a surface facing the light diffuser  13  and a surface facing the light source  402 . The surface of the lens unit  404  facing the light source  402  includes reflective areas  406  which are coated with a reflective material to reflect light and a transmissive area  410  which is not coated with a reflective material to transmit light. As exemplarily shown in  FIG. 5 , the transmissive area  410  of the lens unit  404  which is not coated with a reflective material is formed along the central axis in the lengthwise direction of the surface of the lens unit  404  facing the light source  402  to have predetermined width and length, and the reflective areas  406  which are coated with a reflective material are formed at both sides of the transmissive area  410 . The reflective areas  406  may include a first reflective area  406   a  and a second reflective area  406   b  divided by the transmissive area  410 . The first reflective area  406   a  and the second reflective area  406   b  of the reflective areas  406  are inclined symmetrically to each other in the direction of the light diffuser  13 . 
     Further, as exemplarily shown in  FIG. 6 , the light source  402  of the backlight unit  12  includes a printed circuit board  12   a  provided with a conductive pattern forming an electrical circuit and arranged on the bottom chassis  17 , light emitting diodes  12   b  installed on the printed circuit board  12   a  to face the light diffuser  13 , and protective lids  12   c  to protect the light emitting diodes  12   b . One light emitting diode  12   b  and one protective lid  12   c  form one optical element. 
     As exemplarily shown in  FIG. 6 , the cross-section of the lens unit  404  of the backlight unit  12  is formed in a substantially triangular shape that is inverted, if a region where the light source  402  is located is defined as the bottom and a region where the light diffuser  13  is located is defined as the top. In the inverted triangular cross-section of the lens unit  404 , the reflective areas  406  are formed at portions corresponding to inclined sides (inclined planes of a 3D shape). The reflective areas  406  are not formed on the entirety of the inclined sides of the lens unit  404 . That is, the reflective areas  406  are not formed at a central portion of the lens unit  404  close to the light source  402 , i.e., a portion of the lens unit  404  corresponding to the transmissive area  410 . 
     A part of light radiated from the light source  402  is incident upon the lens unit  404  through the transmissive area  410 , and the proceeding path of incident light may be diffused by the action of the lens unit  404 . Further, the remainder of light radiated from the light source  402  is reflected by the reflective areas  406 , is again reflected by the reflective surface  408  formed on the inner surface of the bottom chassis  17  illustrated with reference to  FIGS. 3 and 4 , and then reaches the light diffuser  13 . 
     The reason why the surface of the lens unit  404  facing the light source  402  is divided into the reflective areas  406  and the transmissive area  410  is as follows. If the lens unit  404  is not divided into the reflective areas  406  and the transmissive area  410  and the lens unit  404  is configured such that the entirety of the surface of the lens unit  404  facing the light source  402  is coated with a reflective material, light incident at an angle more than a critical angle is totally reflected, and light incident at an angle under the critical angle is transmitted, an amount of light totally reflected and an amount of light transmitted are determined according to accuracy in cutting of the lens unit  404 , and thus precision machining of the lens unit  404  is required, a product manufacturing process becomes complicated, and manufacturing costs are increased. 
     However, if the reflective areas  406  which are coated with a reflective material and the transmissive area  410  which is not coated with a reflective material are formed on the surface of the lens unit  404  facing the light source  402 , as in the lens unit  404  in accordance with the embodiment of the present disclosure, reflection and transmission of light may be achieved more conveniently, as compared to the precise lens cutting method. This may simplify a manufacturing process and reduce a process time, and thus product manufacturing costs may be greatly reduced. 
     Although  FIGS. 5 and 6  illustrates the surface of the lens unit  404  facing the light source  402  as being formed in a curved shape, the reflective areas  406  may be formed in a spherical shape, an aspherical shape, or a flat surface to acquire light diffusing characteristics of a desired level in consideration of light transmission environments, such as the distance between the backlight unit  12  and the light diffuser  13  and the area of the light diffuser  13 . 
       FIG. 7  is a view illustrating optical characteristics of the backlight unit in accordance with the embodiment of the present disclosure. In  FIG. 7 , in order to describe optical characteristics of the backlight unit  12 , reference numerals of some elements which are the same as those in  FIGS. 3 to 6  are omitted. As exemplarily shown in  FIG. 7 , a part of light radiated from the light source  402  may be transmitted to the light diffuser  13  through various paths through reflection by the reflective areas  406  and reflection by the inner surface  408  of the bottom chassis  17 . Further, the remainder of light radiated from the light source  402  may be incident upon the lens unit  404  through the transmissive area  410  and be transmitted to the light diffuser  13  through various paths by the action of the lens unit  404 . 
     In the backlight unit  12  in accordance with the embodiment of the present disclosure, the reflective areas  406  and the transmissive area  410  of the lens unit  404  may exhibit effects, as follows. 
     First, when the backlight unit  12  is located at the central region of the light diffuser  13 , light diffusion efficiency may be improved and the number of optical elements (for example, LEDs) may be reduced, as compared to when the backlight unit  12  is located at the edge of the light diffuser  13 . However, on the assumption that the entirety of the surface of the lens unit  404  facing the light source  402  forms a reflective area without a transmissive area, the reflective area blocks light radiated from the light source  402  and forms the shadow at the central region of the light diffuser  13 , and a dark region is generated at the central region of the display panel  11  due to the shadow. This goes against the conditions of the display panel requiring uniform light distribution, and may thus be disadvantageous. 
     Therefore, by providing the transmissive area  410  on the lens unit  404  so that light is transmitted through the transmissive area  410  between the reflective areas  406 , as in the backlight unit  12  in accordance with the embodiment of the present disclosure, the shadow which may be formed by the reflective areas  406  is compensated for by light transmitted by the transmissive area  410 , and thus, a dark region generated due to the shadow of the reflective areas  406  may be eliminated. Because the dark region which may be generated when the backlight unit  12  is located at the central region of the light diffuser  13  is eliminated in such a manner, advantages (improvement of light diffusion efficiency and reduction in the number of optical elements) acquired if the backlight unit  12  is located at the central region of the rear surface of the light diffuser  13  may be sufficiently obtained. 
       FIG. 8  is a view illustrating lens units of the backlight unit in accordance with various modified embodiments of the present disclosure. As exemplarily shown in  FIG. 8 , light incident upon the lens unit  404  through the transmissive area  410  may be more widely diffused or more concentrated at some areas by variously modifying the surface of the lens unit  404  facing the light diffuser  13 . Such light diffusion and concentration may serve to uniformly radiate light to the display panel  11 . 
     In the first modified embodiment of  FIG. 8 , some parts of the surface of the lens unit  404  facing the light diffuser  13  are concave to alter the optical path and the light diffusion degree. The positions of the concave parts of the lens unit  404  may correspond to the positions of a plurality of optical elements of the light source  402 . Further, the size of the concave parts of the lens unit  404  may correspond to the size of the plurality of optical elements of the light source  402 , or may be greater than or smaller than the size of the plurality of optical elements of the light source  402 . The curvature of the concave parts of the lens unit  404  may be determined according to a desired light diffusion degree and a desired optical path. 
     In the second modified embodiment of  FIG. 8 , some parts of the surface of the lens unit  404  facing the light diffuser  13  are convex to alter the optical path and the light diffusion degree. The positions of the convex parts of the lens unit  404  may correspond to the positions of the plurality of optical elements of the light source  402 , or be located between two neighboring optical elements of the light source  402 . Further, the size of the convex parts of the lens unit  404  may correspond to the size of the plurality of optical elements of the light source  402 , or may be greater than or smaller than the size of the plurality of optical elements of the light source  402 . The curvature of the convex parts of the lens unit  404  may be determined according to a desired light diffusion degree and a desired optical path. 
     In the third modified embodiment of  FIG. 8 , the entirety of the surface of the lens unit  404  facing the light diffuser  13  is convex to alter the optical path and the light diffusion degree. The curvature of the convex surface of the lens unit  404  facing the light diffuser  13  may be determined according to a desired light diffusion degree and a desired optical path. 
     In the fourth modified embodiment of  FIG. 8 , the entirety of the surface of the lens unit  404  facing the light diffuser  13  is concave to alter the optical path and the light diffusion degree. The curvature of the concave surface of the lens unit  404  facing the light diffuser  13  may be determined according to a desired light diffusion degree and a desired optical path. 
     In the fifth modified embodiment of  FIG. 8 , a long and concave groove is formed on the surface of the lens unit  404  facing the light diffuser  13  in the lengthwise direction of the lens unit  404  to alter the optical path and the light diffusion degree. The position of such a long and concave groove may correspond to the arrangement position of the plurality of optical elements of the light source  402 . Further, the width and length of the long and concave groove may correspond to the size and arrangement length of the light source  402 . The curvature of the inner surface of the concave groove may be determined according to a desired light diffusion degree and a desired optical path. 
     In the sixth modified embodiment of  FIG. 8 , a long and convex groove is formed on the surface of the lens unit  404  facing the light diffuser  13  to alter the optical path and the light diffusion degree. The position of such a long and convex groove may correspond to the arrangement position of the plurality of optical elements of the light source  402 . Further, the width and length of the long and convex groove may correspond to the size and arrangement length of the light source  402 . The curvature of the outer surface of the convex groove may be determined according to a desired light diffusion degree and a desired optical path. 
       FIG. 9  is a view illustrating a backlight unit in accordance with an embodiment of the present disclosure. As exemplarily shown in  FIG. 9 , a plurality of backlight units  102  is arranged at a position separated from the rear surface of a light diffuser  13  by a predetermined distance and corresponding to the central region of the light diffuser  13  in the vertical direction of the light diffuser  13  to have a length equal to the vertical length of the light diffuser  13 . Here, the ‘vertical direction’ refers to the direction of the shorter one of the horizontal length and the vertical length of the light diffuser  13 . If the horizontal length and the vertical length are the same, the vertical direction may be the horizontal direction. 
       FIG. 10  is a view illustrating a backlight unit in accordance with an embodiment of the present disclosure. As exemplarily shown in  FIG. 10 , one backlight unit  12  is arranged at a position separated from the rear surface of a light diffuser  13  by a predetermined distance and corresponding to the central region of the light diffuser  13  in the horizontal direction of the light diffuser  13  to have a length equal to the horizontal length of the light diffuser  13 . Here, the ‘horizontal direction’ refers to the direction of the longer one of the horizontal length and the vertical length of the light diffuser  13 . If the horizontal length and the vertical length are the same, the horizontal direction may be the vertical direction. 
       FIG. 11  is a view illustrating a backlight unit in accordance with a further modified embodiment of the present disclosure. As exemplarily shown in  FIG. 11 , a plurality of optical elements  1102 , each of which includes a light emitting diode  12   b  and a protective lid  12   c , is installed on a printed circuit board  12   a  forming a light source  402  of a backlight unit  12 . Here, the plurality of optical elements  1102  may be arranged in a zigzag pattern. If the optical elements  1102 , provided in number equal to the number of the optical elements  1102  arranged in a line in the backlight unit  12  shown in  FIG. 2 , are arranged in a zigzag pattern, as exemplarily shown in  FIG. 11 , light radiated from the backlight unit  12  may reach more distant positions on the light diffuser  13  in the horizontal direction (the direction of the longer one of the horizontal length and the vertical length) of the light diffuser  13 , and the backlight unit  12  of  FIG. 11  using the same number of the optical elements  1102  may acquire higher light transmission characteristics than the backlight unit  12  of  FIG. 5  in terms of light diffusion. 
     As is apparent from the above description, a display device using a display panel in accordance with an embodiment of the present disclosure includes a backlight unit to radiate light to the display panel installed at the central region of the rear surface of the display panel, and may thus radiate light to the entirety of a light diffuser using only a small number of optical elements without a light guide plate. Further, the display device may eliminate generation of the shadow of the backlight unit through reflective areas and a transmissive area of a lens unit. 
     Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.