Abstract:
The present invention provides a method of adjusting light diffusing and light focusing capability of an optical element. First, an optical substrate having a first surface area is provided. Then, pluralities of pervious convexes are formed on an optical substrate, wherein the pervious convexes occupy a second surface area on the optical substrate. Diffusing effect of the optical element can be lowered/improved by increasing/decreasing an arrangement regularity of the pervious convexes. Diffusing effect enlarging/reducing the size of the optical element can also be lowered/increased by enlarging/reducing the size of pervious convexes. The focusing effects of the optical element can be improved/lowered by increasing/decreasing the ratio of the second surface area and the first surface area.

Description:
RELATED APPLICATIONS  
       [0001]     The present application is based on, and claims priority from, Taiwan Application Serial Number 94147286, filed Dec. 29, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.  
       BACKGROUND  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to an optical element. More particularly, the present invention relates to a method for adjusting light diffusing and light focusing capability of an optical element.  
         [0004]     2. Description of Related Art  
         [0005]     Planar light sources with uniform brightness are hard to generate because of manufacturing limitations of light sources and light emitting devices such as light emitting diodes (LED), which are point light sources, and cold cathode fluorescent lamps (CCFL), which are linear light sources. When a product requires a planar light source, an optical element that can diffuse light is conventionally present in the product so as to diffuse the light emitted from the light sources. In addition, the product should also comprise another focusing element so that the light can be focused on the front.  
         [0006]     A typical example is a back light module of a liquid crystal display (LCD).  FIG. 1  is a cross-section schematic diagram showing a traditional back light module of a liquid crystal display. In  FIG. 1 , because liquid crystal cannot be self-illuminated, a light source  104  is added to the back of a LCD panel  102  so that the LCD images can be displayed. Generally, a back light module  100  is used in the LCD. First, a light emitted from the light source  104  is guided into a light guide plate  106 . After the light is reflected by a reflector  108 , the light passes through a diffuser plate  110 , which diffuses the light. Then, the light passes through an enhancer plate  112 , which focuses the light. After the light passes through the diffuser plate  110  and the enhancer plate  112 , it would pass through and illuminate the LCD panel  102 .  
         [0007]     When several optical elements are used to homogenize and focus light, partial light is absorbed by the optical elements during light transmission, which results in inefficient utilization of the light. However, if an optical element can both diffuse and focus light, the light absorbed by the optical elements will be reduced, but the light diffusing effect and light focusing capability of the optical element cannot be individually adjusted according to the demands and thus the optical element has poor utilization. The term “light diffusion” means the percentage of scattered light compared to the total transmitted light.  
         [0008]     Therefore, there is a need for reducing the number of optical elements and obtaining light diffusing effect and focusing light effect of an optical element according to demands without decreasing the brightness to resolve the problems mentioned above.  
       SUMMARY  
       [0009]     In one aspect, this present invention provides an optical element that can achieve the effect that conventionally requires two optical elements to achieve.  
         [0010]     In another aspect, this present invention provides methods for adjusting light diffusing and light focusing capability of an optical element by changing the design of the optical element according to demands to obtain desired light diffusing effect and light focusing effect.  
         [0011]     In accordance with the foregoing and other aspects of the present invention, the present invention provides a method for adjusting light diffusing and light focusing capability of an optical element, wherein the optical element design is changed according to the demands of the display device to achieve the desired light diffusing effect and light focusing effect. First, an optical substrate having a first surface area is provided. Then, a plurality of pervious convexes are formed on the optical substrate. The pervious convexes occupy a second surface area on the optical substrate. An arrangement regularity of the pervious convexes can be increased/decreased to lower/improve the diffusing effect of the optical element and the ratio of the second surface area and the first surface area can be increased/decreased to improve/lower the focusing effect of the optical element.  
         [0012]     According to one preferred embodiment of the present invention, the distance between two neighboring pervious convex on the optical substrate can be changed to increase/decrease the diffusing and focusing effects of the optical element.  
         [0013]     According to another preferred embodiment of the present invention, arrangement regularity or the sizes of the pervious convexes can be changed to increase or decrease the diffusing effect of the optical element while the ratio of the second surface area and the first surface area remains unchanged.  
         [0014]     According to yet another preferred embodiment of the present invention, arrangement regularity or the sizes of the pervious convexes can be adjusted to maintain the diffusing effect of the optical element while the ratio of the second surface area and the first surface area is reduced.  
         [0015]     Thus, the present invention provides a method to adjust the diffusing and focusing light capabilities of an optical element, wherein the optical element design is changed according to the demands of the display device to achieve the desired light diffusing effect and light focusing effect. The method for changing the optical element design comprises adjusting sizes, arrangement regularity or areas of the pervious convexes occupied on the optical substrate to obtain the desired light diffusing effect and light focusing effect. Moreover, the optical element of the present invention can achieve the effects that conventionally required two optical elements. That is, the optical element of the present invention has capabilities of both diffusing light and focusing light. Furthermore, the optical element of the present invention not only can turn uneven incident light into planar light sources with uniform brightness, but can also increase the front-side brightness. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention can be more fully understood by reading the following detailed description of the preferred embodiment, with reference made to the accompanying drawings as follows:  
         [0017]      FIG. 1  is a cross-section schematic diagram showing a traditional back light module of a liquid crystal display.  
         [0018]      FIG. 2  is a top view diagram showing an optical element.  
         [0019]      FIG. 3  is a cross-section schematic diagram along the I-I′ line in  FIG. 2 .  
         [0020]      FIG. 4  to  FIG. 9  are top view diagrams showing an optical element according to different embodiments of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     The method of the present invention can reduce the number of required optical elements, and adjust the light diffusing and the light focusing effects of the optical element according to demands. The embodiments provided herein are for description of the use and manufacture of the present invention and should not be used to limit the scope of the claims.  
         [0022]      FIG. 2  is a top view diagram showing an optical element. In  FIG. 2 , an optical element  200  comprises an optical substrate  202  and pervious convexes  204 . The optical substrate  202  has a first surface area and the pervious convexes  204  occupy a second surface area on the optical substrate  202 . The distance between two pervious convexes  204  is a 1 . Preferred materials for the optical element  200  mentioned above are those with high visible light transparency, such as glass, polyester and the like. The scale of the pervious convexes  204  is smaller than micro-scale, preferably 2-20 μm in size. According to the preferred embodiment of the present invention, the pervious convexes  204  are more preferably 3-10 μm in size.  
         [0023]      FIG. 3  is a cross-section schematic diagram along the I-I′ line in  FIG. 2 . In  FIG. 2  and  FIG. 3 , the pervious convexes  204  are pyramid structures having the same size and in a regular arrangement. Each of the pyramid structures has a pointed tip on the top. An angle θ of the pointed tip on the top is preferably between 65° and 115°. Alternatively, the pervious convexes  204  can have tops with a blunted surface according to the demands.  
         [0024]     The scale of the pervious convexes  204  are smaller than micro-scale so that the optical element  200  can diffuse light, and the pervious convexes  204  are pyramid structures so that the optical element  200  can focus light. Thus, the optical element of the present invention can achieve the effect that conventionally required two optical elements to achieve. That is, the optical element of the present invention can both diffuse and focus light. The optical element of the present invention shows light diffusing effect between 17% and 55% preferably, and light focusing effect less than 200% preferably.  
         [0025]     The present invention provides a method to adjust light diffusing and light focusing capability of an optical element, wherein the optical element design is changed according to the demands of the display device to achieve the desired light diffusing effect and/or light focusing light effect. The following description describes different methods for adjusting the optical element design to obtain the desired light diffusing effect and/or light focusing effect according to embodiments of the present invention.  
         [0026]      FIG. 4  is a top view diagram showing an optical element according to one embodiment of the present invention. In  FIG. 2  and  FIG. 4 , the pervious convexes  304  in  FIG. 4  have the same size as the pervious convexes  204  in  FIG. 2 . However, the distance b 1  between two pervious convexes  304  is greater than the distance a 1 , between two neighboring pervious convexes  204 . That is, the surface area on the optical substrate  302  occupied by the pervious convexes  304  in  FIG. 4  is smaller than the surface area on the optical substrate  202  occupied by the pervious convexes  204  in  FIG. 2 . The optical element  200  in  FIG. 2  and the optical element  300  in  FIG. 4  are subjected to the light diffusing test and the light focusing test. The results show that the light diffusing effect and the light focusing effect of the optical element  300  in  FIG. 4  are less than the light diffusing effect and the focusing light effect of the optical element  200  in  FIG. 2 .  
         [0027]      FIG. 5  is a top view diagram showing an optical element according to another embodiment of the present invention. In  FIG. 2  and  FIG. 5 , the pervious convexes  404  in  FIG. 5  have the same size as the pervious convexes  204  in  FIG. 2 , and the distance b 2  between two neighboring pervious convexes  404  is the same as the distance a 1 , between two neighboring pervious convexes  204 . However, the pervious convexes  404  in  FIG. 5  are arranged more irregularly than the pervious convexes  204  in  FIG. 2 . The optical element  200  in  FIG. 2  and the optical element  400  in  FIG. 5  are subjected to the light diffusing test and the light focusing test. The results show that the light diffusing effect of the optical element  400  in  FIG. 5  is greater than the light diffusing effect of the optical element  200  in  FIG. 2 , and the light focusing effect of the optical element  400  in  FIG. 5  is the same as the light focusing effect of the optical element  200  in  FIG. 2 .  
         [0028]     The results of the optical element  200 ,  300  and  400  respectively in  FIG. 2 ,  FIG. 4  and  FIG. 5  are analyzed. The results show that the optical element having the same pervious convex density, such as the optical element  200  in  FIG. 2  and the optical element  400  in  FIG. 5 , have the same light focusing effect. The optical element has lower pervious convex density, such as the optical element  300  in  FIG. 4 , the light focusing effect of the optical element is reduced. In  FIG. 2  and  FIG. 5 , the optical element  400 , having a more irregular arrangement than the optical element  200 , has higher light diffusing effect. Therefore, the arrangement regularity of the optical element can be changed to increase or decrease the light focusing effect of the optical element.  
         [0029]      FIG. 6  is a top view diagram showing an optical element according to one embodiment of the present invention. In  FIG. 6 , an optical substrate  502  comprises first pervious convexes  504  and second pervious convexes  506 . The first pervious convexes  504  are smaller than the second pervious convexes  506 . In  FIG. 2  and  FIG. 6 , the surface area on the optical substrate  502  occupied by the first pervious convexes  504  and the second pervious convexes  506  in  FIG. 6  is the same as the surface area on the optical substrate  202  occupied by the pervious convexes  204  in  FIG. 2 . The distance b 3  between two neighboring pervious convexes  504 ,  506  is the same as the distance a 1  between two neighboring pervious convexes  204 . However, the pervious convexes  504 ,  506  on the optical substrate  502  in  FIG. 6  have different sizes, in comparison with  FIG. 2 . The optical element  200  in  FIG. 2  and the optical element  500  in  FIG. 6  are subjected to the light diffusing test and the light focusing test. The results show that the light diffusing effect of the optical element  500  in  FIG. 6  is greater than the light diffusing effect of the optical element  200  in  FIG. 2 , but the light focusing effect of the optical element  500  in  FIG. 6  is the same as the light focusing effect of the optical element  200  in  FIG. 2 .  
         [0030]     Thus, the results of the optical elements  200 ,  400  and  500  respectively in  FIG. 2 ,  FIG. 5  and  FIG. 6  are analyzed, which show that the light diffusing effect of the optical element can be enhanced or reduced by changing the arrangement regularity or sizes of the pervious convexes while the surface area on the optical substrate occupied by the pervious convexes remains unchanged.  
         [0031]      FIG. 7  is a top view diagram showing an optical element according to one embodiment of the present invention. In  FIG. 2  and  FIG. 7 , the pervious convexes  604  in  FIG. 7  have the same size as the pervious convexes  204  in  FIG. 2 . However, the distance b 4  between two neighboring pervious convexes  604  is larger than the distance a 1 , between two neighboring pervious convexes  204 , and the pervious convexes  604  in  FIG. 7  are arranged more irregularly than the pervious convexes  204  in  FIG. 2 . The optical element  200  in  FIG. 2  and the optical element  600  in  FIG. 7  are subjected to the light diffusing test and the light focusing test. The results show that the light focusing effect of the optical element  600  are smaller than the optical element  200  in  FIG. 2 , but the light diffusing effect of the optical element  600  in  FIG. 7  is the same as the optical element  200  in  FIG. 2 . From the results above, the light focusing effect and light diffusing effect of the optical element are decreased by decreasing the pervious convexes occupy a second surface area on the optical substrate. The arrangement of the pervious convexes can be adjusted to improve the light diffusing effect of the optical element until the light diffusing effect of the optical element  600  is the same as the optical element  200  in  FIG. 2 .  
         [0032]      FIG. 8  is a top view diagram showing an optical element according to another embodiment of the present invention. In  FIG. 8 , an optical substrate  702  comprises a first pervious convexes  704  and a second pervious convexes  706 . The first pervious convexes  704  are smaller than the second pervious convexes  706 . In  FIG. 2  and  FIG. 8 , the distance b 5  between two neighboring pervious convexes  704 ,  706  in  FIG. 8  is greater than the distance a 1 , between two neighboring pervious convexes  204  in  FIG. 2 . That is, the surface area on the optical substrate  702  occupied by the pervious convexes  704 ,  706  in  FIG. 8  is smaller than the surface area on the optical substrate  202  occupied by the pervious convexes  204  in  FIG. 2 . The pervious convexes  704 ,  706  in  FIG. 8  are arranged more irregularly than the pervious convexes  204  in  FIG. 2 . The optical element  200  in  FIG. 2  and the optical element  700  in  FIG. 8  are subjected to the light diffusing test and the light focusing test. The results show that the light focusing effect of the optical element  700  in  FIG. 8  is less than the optical element  200  in  FIG. 2 , but the light diffusing effect of the optical element  700  in  FIG. 8  is the same as the optical element  200  in  FIG. 2 .  
         [0033]     The results of the optical elements  200 ,  300 ,  600  and  700  respectively in  FIG. 2 ,  FIG. 4 ,  FIG. 7  and  FIG. 8  are analyzed. The results show that density of the pervious convexes is lower and surface area on the optical substrate occupied by the pervious convexes is reduced, such as the optical element  200  in  FIG. 2  and the optical element  300  in  FIG. 4 , the light focusing effect and the light diffusing effect of the optical element are reduced. The arrangement regularity of the optical element can be changed, such as in comparison with  FIG. 2  and  FIG. 7 , or the arrangement regularity and sizes of the optical element can be changed simultaneously, such as in comparison with  FIG. 2  and  FIG. 8 , to improve the light diffusing effect of the optical element until the light diffusing effect of the optical element  700  in  FIG. 8  is the same as the optical element  200  in  FIG. 2 .  
         [0034]      FIG. 9  is a top view diagram showing an optical element according to another embodiment of the present invention. In  FIG. 4  and  FIG. 9 , a surface area occupied by the first pervious convexes  804  on the optical substrate  802  in  FIG. 9  is the same as the surface area occupied by the pervious convexes  304  in  FIG. 4  on the optical substrate  302 . The distance b 6  between two neighboring pervious convexes  804  is the same as the distance b 1 , between two neighboring pervious convexes  304  in  FIG. 4 . However, the pervious convexes  804  on the optical substrate  802  in  FIG. 9  have greater sizes than the pervious convexes  304  in  FIG. 4 . The optical element  300  in  FIG. 4  and the optical element  800  in  FIG. 9  are subjected to the light diffusing test and the light focusing test. The results show that the light focusing effect of the optical element  800  in  FIG. 9  is the same as the optical element  300  in  FIG. 4 , but the light diffusing effect of the optical element  800  in  FIG. 9  is less than the optical element  300  in  FIG. 4 .  
         [0035]     The results are listed in Table 1 showing the relation between different sizes of the pervious convexes and the light diffusing effect thereof. From the results of  FIG. 4 ,  FIG. 9  and Table 1, when the surface area occupied by the pervious convexes on the optical substrate is unchanged, the light focusing effect of the optical element is the same. The light focusing effect of the optical element can be increased or decreased by decrease or increase the sizes of the pervious convexes can be increased or reduced to decrease or increase.  
                                   TABLE 1                           Different sizes of pervious convexes and       light diffusing effect of optical element                Light diffusing effect of optical       Sizes of pervious convexes (microns)   element (%)                    2   55       5   29       10   24       20   17                  
 
         [0036]     Thus, the present invention provides a method to adjust the light diffusing and light focusing capabilities of an optical element, wherein the optical element design is changed according to the demands of the display device to achieve the desired light diffusing effect and light focusing effect. The method for changing the optical element design comprises adjusting sizes, arrangement regularity or areas of the pervious convexes occupied on the optical substrate to obtain the desired light diffusing effect and the light focusing effect. Moreover, the optical element of the present invention can achieve the effect that conventionally required two optical elements. That is, the optical element of the present invention has capabilities of both diffusing light and focusing light. Furthermore, the optical element of the present invention cannot turn uneven incident light into planar light sources with uniform brightness, but can also increase the forward brightness.  
         [0037]     The preferred embodiments of the present invention described above should not be regarded as limitations to the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. The scope of the present invention is as defined in the appended claims.