Abstract:
A display module includes a bottom substrate, a display device having a plurality of display pixels, and a diffusion module. The display pixels are disposed between the bottom substrate and the diffusion module. The diffusion module has a thickness and a haze, wherein the haze of the diffusion module satisfies: 
     
       
         
           
             
               A 
               &lt; 
               
                 Haze 
                  
                 
                   ( 
                   % 
                   ) 
                 
               
               &lt; 
               B 
             
             ; 
             wherein 
           
         
       
       
         
           
             
               A 
               = 
               
                 0.642 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.35 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.32 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               B 
               = 
               
                 0.821 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.45 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.60 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               NP 
               = 
               
                 
                   25400 
                   / 
                   PPI 
                 
                 
                   63 
                    
                   
                       
                   
                    
                   µm 
                 
               
             
             ; 
             and 
           
         
       
       
         
           
             
               NT 
               = 
               
                 T 
                 
                   500 
                    
                   
                       
                   
                    
                   µm 
                 
               
             
             ; 
           
         
       
       
         
           
             wherein PPI is a resolution of the display module, T is the thickness of the diffusion module, and Haze is the haze of the diffusion module.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to Taiwan Application Serial Number 105101897, filed Jan. 21, 2016, which is herein incorporated by reference. 
       BACKGROUND 
       [0002]    Field of Disclosure 
         [0003]    The present disclosure relates to a display module. More particularly, the present disclosure relates to a head mounted display applied to virtual reality technology. 
         [0004]    Description of Related Art 
         [0005]    Virtual Reality (VR) is a technology that generates virtual images and provides a virtual space by using computer technologies. With virtual reality glasses, a display device can be disposed adjacent to a user to project images to the user within a short distance. The display device provides the virtual images to the user with an optical design, such that the user can have a virtual experience. The user can also experience senses of sound and touch in cooperated with other devices. The virtual reality, which combines technologies such as computer technology, artificial intelligence, display, and processes, is a high-tech simulation system. 
       SUMMARY 
       [0006]    An aspect of the present disclosure provides a display module includes a bottom substrate, a display device having a plurality of display pixels, and a diffusion module. The display device is disposed between the bottom substrate and the diffusion module. The diffusion module has a thickness and a haze, wherein the haze of the diffusion module satisfies: 
         [0000]    
       
         
           
             
               A 
               &lt; 
               
                 Haze 
                  
                 
                   ( 
                   % 
                   ) 
                 
               
               &lt; 
               B 
             
             ; 
             wherein 
           
         
       
       
         
           
             
               A 
               = 
               
                 0.642 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.35 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.32 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               B 
               = 
               
                 0.821 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.45 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.60 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               NP 
               = 
               
                 
                   25400 
                   / 
                   PPI 
                 
                 
                   63 
                    
                   
                       
                   
                    
                   µm 
                 
               
             
             ; 
             and 
           
         
       
       
         
           
             
               NT 
               = 
               
                 T 
                 
                   500 
                    
                   
                       
                   
                    
                   µm 
                 
               
             
             ; 
           
         
       
     
         [0000]    wherein PPI is a resolution of the display module, T is the thickness of the diffusion module, and Haze is the haze of the diffusion module. 
         [0007]    In one or more embodiments, the diffusion module comprises a diffusion plate including a diffusion layer and a base. The base is disposed between the diffusion layer and the bottom substrate. 
         [0008]    In one or more embodiments, the diffusion module further includes a supporting element disposed between the diffusion plate and the bottom substrate. 
         [0009]    In one or more embodiments, the diffusion layer of the diffusion plate includes a coating layer and a plurality of microstructures. The coating layer is disposed on the base. The microstructures are distributed in the coating layer. 
         [0010]    In one or more embodiments, diameters of the microstructures are about 2 μm to about 20 μm. 
         [0011]    In one or more embodiments, a thickness of the diffusion layer is about 8 μm to about 20 μm. 
         [0012]    In one or more embodiments, each of the display pixels includes an active element and a light emitting device electrically connected to the active element. 
         [0013]    In one or more embodiments, the light emitting devices of the display pixels are organic light emitting diodes. 
         [0014]    In one or more embodiments, 0.6≦NP≦1.46. 
         [0015]    In one or more embodiments, 0.4≦NT≦2.6. 
         [0016]    Another aspect of the present disclosure provides a head mounted display includes the aforementioned display module and at least one magnifying element. The diffusion module of the display module is disposed between the magnifying element and the bottom substrate of the display module. 
         [0017]    In one or more embodiments, a magnification factor of the magnifying element is about 2. 
         [0018]    In one or more embodiments, a distance between the magnifying element and the display module is about 0.5 cm to about 3 cm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a schematic diagram of a head mounted display and eyes of an observer according to one embodiment of the present disclosure; 
           [0020]      FIG. 2  is a schematic diagram of the diffusion plate of  FIG. 1 ; 
           [0021]      FIG. 3  is a schematic diagram of a head mounted display and eyes of an observer according to another embodiment of the present disclosure; 
           [0022]      FIG. 4  is an enlarged diagram of area M of  FIG. 1 ; 
           [0023]      FIGS. 5-7  are top views of the display module of  FIG. 1  according to different embodiments; 
           [0024]      FIG. 8  is a graph of normalized gray scale vs. position of the display module according to one example of the present disclosure; 
           [0025]      FIGS. 9 and 10  are graphs of the sense of grain and the sense of blur of the display module vs. the haze of the diffusion module according to two examples of the present disclosure; 
           [0026]      FIG. 11  is a graph of the sense of grain, the sense of blur, and the haze of the diffusion module with respect to the thickness of the diffusion module according to one example of the present disclosure; and 
           [0027]      FIGS. 12 and 13  are graphs of the haze vs. the thickness of the diffusion module according to two examples of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Reference will now be made in detail to the present embodiments of the disclosure, 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. Further, the term “connect” or “electrically connected,” as used herein, refers to the direct or indirect physical or electrical contact between or among two or more components, or the mutual operation or action of two or more components. 
         [0029]      FIG. 1  is a schematic diagram of a head mounted display  10  and eyes  20  of an observer according to one embodiment of the present disclosure. The head mounted display  10  includes a display module  100  and at least one magnifying element  300 . For example, in  FIG. 1 , the head mounted display  10  includes two magnifying elements  300 , which respectively correspond to the left- and right-eyes  20  of the observer. The display module  100  includes a bottom substrate  110 , a display device  120  having a plurality of display pixels, and a diffusion module  210 . The display module  100  has a resolution. The display device  120  is disposed between the bottom substrate  110  and the diffusion module  210 . The diffusion module  210  has a thickness T and a haze, and the haze of the diffusion module  210  satisfies: 
         [0000]    
       
         
           
             
               A 
               &lt; 
               
                 Haze 
                  
                 
                   ( 
                   % 
                   ) 
                 
               
               &lt; 
               B 
             
             ; 
             wherein 
           
         
       
       
         
           
             
               A 
               = 
               
                 0.642 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.35 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.32 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               B 
               = 
               
                 0.821 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.45 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.60 
                   
                 
               
             
             ; 
           
         
       
       
         
           
             
               NP 
               = 
               
                 
                   25400 
                   / 
                   PPI 
                 
                 
                   63 
                    
                   
                       
                   
                    
                   µm 
                 
               
             
             ; 
             and 
           
         
       
       
         
           
             
               NT 
               = 
               
                 T 
                 
                   500 
                    
                   
                       
                   
                    
                   µm 
                 
               
             
             ; 
           
         
       
     
         [0000]    wherein Haze is the haze of the diffusion module  210 , PPI is a resolution of the display module  100 , NP is a pitch (the unit is μm, and the pitch is calculated from the resolution of the display module  100 ) of the display pixels of the display device  120  divided by 63 μm, and NT is the thickness T (unit is μm) of the diffusion module  210  divided by 500 μm. In the present embodiment, the haze was measured in accordance with Japanese Industrial Standards (JIS) K7105. That is, the haze is a ratio of an amount of the transmission light having an angle greater than 2.5 degrees (relative to the normal line of a measured surface  224   s  of the diffusion module  210 ) to the total amount of the transmission light. 
         [0030]    The head mounted display  10  of the present embodiment provides good display quality by adjusting the relationship between the resolution of the display module  100 , the thickness T of the diffusion module  210 , and the haze of the diffusion module  210 . More specifically, the observer can watch images displayed by the display module  100  through the magnifying elements  300  when he or she wears the head mounted display  10 . However, since the magnifying elements  300  magnify the displayed images, the observer may experience pixelized images if the resolution is low. The pixelized images can be improved by adjusting the haze of the diffusion module  210 , which is disposed on the bottom substrate  110  and the display device  120  (i.e., disposed between the magnifying elements  300  and the bottom substrate  110 ). The diffusion module  210  can diffuse the displayed image of the display device  120 , such that the pixelized images can be improved. However, the image may be over diffused when the haze and/or the thickness T of the diffusion module  210  is increased, presenting the observer with an experience of diffuseness image. Therefore, the display module  100  of the present embodiment can balance the sense of grain and sense of blur by satisfying the aforementioned formulas to provide good display quality. 
         [0031]    In the present embodiment, the diffusion module  210  includes a diffusion plate  220  and a supporting element  230  disposed between the diffusion plate  220  and the bottom substrate  110 . The supporting element  230  may be a glass substrate or a plastic substrate, and the bottom substrate  110  may be a glass substrate or a plastic substrate. The diffusion plate  220  includes a diffusion layer  222  and a base  224 . The haze of the diffusion module  210  mainly depends on the design of the diffusion layer  222 . The base  224  is disposed between the diffusion layer  222  and the supporting element  230 , and the base  224  has the surface  224   s.    
         [0032]      FIG. 2  is a schematic diagram of the diffusion plate  220  of  FIG. 1 . The diffusion layer  222  of the diffusion plate  220  includes a coating layer  225  and a plurality of microstructures  226 . The coating layer  225  is disposed on the base  224 , and the microstructures  226  are distributed in the coating layer  225 . The microstructures  226  can be micro-sized particles, which have diameters of about 2 μm to about 20 μm. These microstructures  226  may have substantially the same diameters D as shown in  FIG. 2 , or the microstructures  226  may have different diameters D. An embodiment falls within the claimed scope as long as the diameters D of the microstructures  226  are in the range of about 2 μm to about 20 μm. The microstructures  226  may be made of organic material or other suitable materials. The microstructures  226  can be particles with regular or irregular profiles. 
         [0033]    The coating layer  225  can be a transparent material, and the coating layer  225  is configured to fix the microstructures  226  onto the base  224 . The haze of the diffusion layer  222  can be changed by adjusting the density of the microstructures  226  in the coating layer  225  (or the distribution density of the microstructures  226  on the surface  224   s  of the base  224 ), the sizes of the microstructures  226 , the surface undulation of the diffusion layer  222 , or the materials of the diffusion layer  222 . For example, the haze of the diffusion layer  222  increases when the density of the microstructures  226  increases, and vice versa. The microstructures  226  can be randomly distributed in the coating layer  225 . That is, the distances among the microstructures  226  can be different, and can be arranged non-periodically. Moreover, the base  224  can be made of low haze and transparent materials, such as plastic (for example, Polyethylene terephthalate (PET), Polycarbonates (PC), Triacetate Cellulose (TAC)), adhesive, glass, or stacks of layers thereof, and the claimed scope is not limited in this respect. 
         [0034]    In some embodiments, the thickness T 1  of the base  224  can be about 50 μm to about 100 μm, and the thickness T 2  of the diffusion layer  222  can be about 8 μm to about 20 μm, and the claimed scope is not limited in this respect. In some embodiments, the thickness T 1  of the base  224  is much greater than the thickness T 2  of the diffusion layer  222 , such that the thickness T 2  of the diffusion layer  222  can be omitted in the calculation of the thickness T 1 ′ of the diffusion plate  220 . That is, the thickness T 1  of the base  224  is substantially equal to the thickness T 1 ′ of the diffusion plate  220 . 
         [0035]    Reference is made to  FIG. 1 . The supporting element  230  is disposed between the diffusion plate  220  and the bottom substrate  110 . The supporting element  230  is configured to increase the thickness T of the diffusion module  210 , making the diffusion module  210  have a desired thickness. In some embodiments, the supporting element  230  can be a low haze and transparent material, such as glass or plastic, and the claimed scope is not limited in this respect. Since the supporting element  230  and the base  224  of the diffusion plate  220  are transparent materials, the transmission of the diffusion module  210  is substantially not reduced. The supporting element  230  has a thickness T 3 . The thickness T of the diffusion module  210 , which is a sum of the thickness T 3  of the supporting element  230  and the thickness T 1 ′ of the diffusion plate  220 , can be adjusted by adjusting the thickness T 3 . In some other embodiments, a plurality of the supporting elements  230  can be added to increase the thickness T of the diffusion module  210 . 
         [0036]    However, the configuration of the diffusion module  210  is not limited to  FIG. 1 .  FIG. 3  is a schematic diagram of a head mounted display  10  and eyes  20  of an observer according to another embodiment of the present disclosure. The difference between  FIGS. 3 and 1  pertains to the configuration of the diffusion module  210 . In  FIG. 3 , the diffusion module  210  includes the diffusion plate  220 . Or, the base  224  and the supporting element  230  of  FIG. 1  are integrally formed. Hence, the thickness of the diffusion plate  220  is the thickness T of the diffusion module  210 . Basically, whether the thickness of the base  224  is adjusted, or the supporting element  230  is added beneath the diffusion plate  220  to thicken the diffusion module  210 , an embodiment falls within the claimed scope as long as the thickness T of the diffusion module  210  can be adjusted. Other relevant details of  FIG. 3  are similar to  FIG. 1 , and, therefore, a description in this regard will not be repeated hereinafter. 
         [0037]      FIG. 4  is an enlarged diagram of area M of  FIG. 1 . Reference is made to  FIGS. 1 and 4 . In the present embodiment, a display sub-pixel  122  includes an active element  132  and a light emitting device. The active element  132  can be a transistor, which is electrically connected to the light emitting device to control the light emitting of the display sub-pixel  122 . The light emitting device can be a light emitting diode, such as an organic light emitting diode, and the claimed scope is not limited in this respect. The display panel made of an organic light emitting diode is self-luminous and has properties like high contrast, low power consumption, fast response time, and high color saturation, being able to provide good display images. In  FIG. 4 , the light emitting device includes a bottom electrode  136 , a light emitting material  134 , and a top electrode  138 . The bottom electrode  136  is electrically connected to the active element  132 , and the light emitting material  134  is disposed between the bottom electrode  136  and the top electrode  138 . In some embodiments, the display device  120  has a plurality of sub-pixels including red sub-pixels  122 , green sub-pixels  124 , and blue sub-pixels  126 . The red sub-pixels  122 , the green sub-pixels  124 , and the blue sub-pixels  126  are disposed between the bottom substrate  110  and the diffusion module  210 . The display module  100  can further includes a sealing  140  surrounding the display device  120  and connected to the bottom substrate  110  and the supporting element  230  as shown in  FIG. 1 , or connected to the bottom substrate  110  and the base  224  of the diffusion plate  220  as shown in  FIG. 3 . As such, the supporting element  230  as shown in  FIG. 1  or the base  224  as shown in  FIG. 3  can be a packaging cover to protect the display device  120 , and the claimed scope is not limited in this respect. In some embodiments, the display device  120  can be thin-film encapsulated, which is an encapsulation process using organic or inorganic material stacking above the light emitting device to protect the display device  120 . In some embodiments, the display device  120  can be white organic light emitting diodes with color filters to form the red sub-pixels  122 , the green sub-pixels  124 , and the blue sub-pixels  126 . In some other embodiments, the red sub-pixels  122 , the green sub-pixels  124 , and the blue sub-pixels  126  can individually be red, green, and blue light emitting materials, such as organic light emitting materials, to respectively emit red, green, and blue lights. Although there are only three types of sub-pixels, i.e., the red sub-pixels  122 , the green sub-pixels  124 , and the blue sub-pixels  126  in  FIG. 1 , other color sub-pixels can be added into the display device  120  to increase the color saturation of the display frames in some other embodiments. 
         [0038]    In  FIG. 1 , the red sub-pixels  122 , the green sub-pixels  124 , and the blue sub-pixels  126  are alternately arranged along a fixed direction. The red sub-pixel  122 , the green sub-pixel  124 , and the blue sub-pixel  126  form a pixel, and each pixel has a pitch p. The resolution (PPI, pixel per inch, i.e., the amount of the pixels in per inch) of the display module  100  can be calculated from the pitch p. The resolution is 25400/p if the unit of the pitch is micrometer. 
         [0039]    However, the arrangement manner of the sub-pixels is not limited in  FIG. 1 .  FIGS. 5-7  are top views of the display module  100  of  FIG. 1  according to different embodiments. In  FIGS. 5-7 , the centers of three sub-pixels of one of the pixels are connected by dashed lines. As shown in  FIGS. 5-7 , the sub-pixels of each pixel are arranged to form a triangle. In  FIG. 5 , two adjacent pixels share a red sub-pixel  122 , a green sub-pixel  124 , or a blue pixel  126 . Such configuration can achieve high-resolution frames with fewer amounts of the sub-pixels. The pitch p of the pixels along a vertical direction is the distance pH (about 63 μm), and the pitch p of the pixels along a lateral direction is the distance pL/4 (about 63 μm). That is, in  FIG. 5 , the resolution of the display module  100  is about 25400/63=403, i.e., there are about 403 pixels per inch. In  FIG. 6 , the pitch p of the pixels along a vertical direction is the distance pH/4 (about 92 μm), and the pitch p of the pixels along a lateral direction is the distance pL (about 92 μm). That is, in  FIG. 6 , the resolution of the display module  100  is about 25400/92=276, i.e., there are about 276 pixels per inch. Moreover, in  FIG. 7 , two adjacent pixels share a red sub-pixel  122  and a blue pixel  126 . Such configuration can achieve high-resolution frames with fewer amounts of the sub-pixels. The pitch p of the pixels along a vertical direction is the distance pH (about 39 μm), and the pitch p of the pixels along a lateral direction is the distance pL/4 (about 39 μm). That is, in  FIG. 7 , the resolution of the display module  100  is about 25400/39=652, i.e., there are about 652 pixels per inch. 
         [0040]    The aforementioned arrangements of the sub-pixels are illustrative only, and should not limit the claimed scope. A person having ordinary skill in the art may select a suitable arrangement for the sub-pixels according to actual requirements. Basically, the display module  100  has a pitch (a+b)/2 if the display module  100  has a pitch a along the lateral direction and a pitch b along the horizontal direction. Moreover, the resolution in  FIG. 6  is referred to as a real resolution since the display module  100  in  FIG. 6  has no shared sub-pixels. The resolutions in  FIGS. 5 and 7  are referred to as virtual resolutions since the red sub-pixels  122 , the green sub-pixels  124 , and the blue sub-pixels  126  in  FIG. 5  and the red sub-pixels  122  and the blue sub-pixels  126  in  FIG. 7  are shared sub-pixels. Furthermore, the diffusion module  210  does not affect the resolution of the display module  100 . The diffusion module  210  can be omitted or only the base  224  or the supporting element  230  of the diffusion module  210  is added in the resolution calculation. 
         [0041]    Reference is made to  FIG. 1 . In the present embodiment, the magnifying element  300  can be a lens, such as a combination of a convex lens(es) or a concave lens(es). The magnification factor of the magnifying element  300  can be about 2. That is, the magnifying element  300  can magnify the display frames of the display module  100  about twice. Moreover, a distance d between the magnifying element  300  and the display module  100  is about 0.5 cm to about 3 cm, and the claimed scope of the present disclosure is not limited in the aforementioned magnification factor and the distance d. 
         [0042]    To obtain the balance between the sense of grain and the sense of blur of the frames, the present disclosure provides an analysis method of the intensity distribution of the frames to obtain the relationship of the sense of grain and the sense of blur of the frames with respect to the haze of the diffusion module.  FIG. 8  is a graph of normalized gray scale vs. position of the display module according to one example of the present disclosure.  FIG. 8  was obtained by measuring the intensity distribution of a line, which was displayed by the display module, along the positions. The normalized gray scale along vertical axis was the values normalized from the measured intensity distribution. The line was located about in the area C of  FIG. 8 , i.e., about 1800 μm to about 4200 μm. The definition of the sense of grain is the standard deviation of the normalized gray scale of the line, the definition of a diffusion distance is the distance of the normalized gray scale from about 80% to about 20% at the edges of the line, and the definition of the sense of blur is the diffusion distance divided by NP. In this example, NP=1 and NT=1. Moreover, the curve  901  represents the normalized gray scale distribution when the haze was about 0%, the curve  902  represents the normalized gray scale distribution when the haze was about 46%, the curve  903  represents the normalized gray scale distribution when the haze was about 67%, the curve  904  represents the normalized gray scale distribution when the haze was about 74%, the curve  905  represents the normalized gray scale distribution when the haze was about 84%, and the curve  906  represents the normalized gray scale distribution when the haze was about 92%. As shown in  FIG. 8 , when the haze was decreased, along the position axis, the variation of the normalized gray scale was increased, the standard deviation of the normalized gray scale was high, and the sense of grain was significant. When the haze was increased, along the position axis, the variation of the normalized gray scale was decreased, the standard deviation of the normalized gray scale was low, and the sense of grain was insignificant. Moreover, when the haze was decreased, the diffusion distance was short and the sense of blur was low. When the haze was increased, the diffusion distance was long and the sense of blur was high. 
         [0043]      FIGS. 9 and 10  are graphs of the sense of grain and the sense of blur of the display module  100  vs. the haze of the diffusion module  210  according to two examples of the present disclosure. In these two examples, the thicknesses of the diffusion module  210  were about 500 μm, i.e., NT=1. The measurement method and the definitions of the terms were the same as  FIG. 8 . 
         [0044]    In the example of  FIG. 9 , the pitch p of the display module was about 63 μm, i.e., NP=1. The curve  912  represented the sense of grain and the curve  914  represented the sense of blur. Table 1 is values of the sense of grain, the sense of blur, and the haze of  FIG. 9 . 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Haze  
                 Sense of  
                 Diffusion 
                 Sense of Blur 
               
               
                   
                 Sample 
                 (%) 
                 Grain 
                 Distance (μm) 
                 (μm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 0 
                 0.2300 
                 38.6 
                 39 
               
               
                   
                 2 
                 46 
                 0.0827 
                 60.7 
                 61 
               
               
                   
                 3 
                 67 
                 0.0248 
                 102.1 
                 102 
               
               
                   
                 4 
                 74 
                 0.0201 
                 114.1 
                 114 
               
               
                   
                 5 
                 84 
                 0.0155 
                 121.6 
                 122 
               
               
                   
                 6 
                 87 
                 0.0129 
                 138.3 
                 138 
               
               
                   
                 7 
                 92 
                 0.0125 
                 286.1 
                 286 
               
               
                   
                   
               
             
          
         
       
     
         [0045]    The results of human factors experiments showed that observers experienced balance feelings between the sense of grain and the sense of blur when the haze was 67%-84%. The human factors experiments were experiments that provided the samples to the observers, and the observers then visually analyzed the sense of grain and the sense of blur of the 7 samples. 
         [0046]    Moreover, in  FIG. 10 , the pitch p of the display module was about 92 μm, i.e., NP=1.46. The curve  922  represented the sense of grain, and the curve  924  represented the sense of blur. Table 2 is values of the sense of grain, the sense of blur, and the haze of  FIG. 10 . 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Haze  
                 Sense of  
                 Diffusion 
                 Sense of Blur 
               
               
                   
                 Sample 
                 (%) 
                 Grain 
                 Distance (μm) 
                 (μm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 0 
                 0.1661 
                 49.3 
                 34 
               
               
                   
                 2 
                 46 
                 0.0783 
                 90.5 
                 62 
               
               
                   
                 3 
                 67 
                 0.0362 
                 113.0 
                 77 
               
               
                   
                 4 
                 74 
                 0.0242 
                 129.9 
                 89 
               
               
                   
                 5 
                 84 
                 0.0176 
                 145.9 
                 100 
               
               
                   
                 6 
                 87 
                 0.0132 
                 162.0 
                 111 
               
               
                   
                 7 
                 92 
                 0.0094 
                 221.6 
                 152 
               
               
                   
                   
               
             
          
         
       
     
         [0047]    The results of human factors experiments showed that observers experienced balance feelings between the sense of grain and the sense of blur when the haze was 74%˜87%. The abovementioned two examples showed the display module has better display qualities when the sense of grain was less than about 0.025 and the sense of blur was less than about 130 μm. In one or more embodiments, 0.6≦NP≦1.46, or 1≦NP≦1.46. 
         [0048]      FIG. 11  is a graph of the sense of grain, the sense of blur, and the haze of the diffusion module with respect to the thickness of the diffusion module according to one example of the present disclosure. The measurement method and the definitions of the terms were the same as  FIG. 8 . In  FIG. 11 , the pitch p of the display module was about 63 μm, i.e., NP=1. The curve  932  represented the sense of grain when the haze was 46%, the curve  934  represented the sense of blur when the haze was 46%, the curve  942  represented the sense of grain when the haze was 67%, the curve  944  represented the sense of blur when the haze was 67%, the curve  952  represented the sense of grain when the haze was 74%, the curve  954  represented the sense of blur when the haze was 74%, the curve  962  represented the sense of grain when the haze was 84%, and the curve  964  represented the sense of blur when the haze was 84%. Table 3 is values of the sense of grain, the sense of blur, the haze, and the thickness of the diffusion module of  FIG. 10 . 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Sense of 
                 Diffusion 
                 Sense of 
               
               
                 Sample 
                 Haze 
                 NT 
                 Grain 
                 Distance (μm) 
                 Blur (μm) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 84 
                 0.97 
                 0.0155 
                 121.6 
                 122 
               
               
                 2 
                 74 
                 0.97 
                 0.0201 
                 114.1 
                 114 
               
               
                 3 
                 74 
                 1.97 
                 0.0085 
                 197.6 
                 198 
               
               
                 4 
                 74 
                 2.97 
                 0.0086 
                 271.6 
                 272 
               
               
                 5 
                 67 
                 1.02 
                 0.0248 
                 102.1 
                 102 
               
               
                 6 
                 67 
                 2.02 
                 0.0106 
                 168.3 
                 168 
               
               
                 7 
                 67 
                 3.02 
                 0.0099 
                 246.9 
                 247 
               
               
                 8 
                 46 
                 1.01 
                 0.0827 
                 60.7 
                 61 
               
               
                 9 
                 46 
                 2.01 
                 0.0376 
                 113.0 
                 113 
               
               
                 10 
                 46 
                 3.01 
                 0.0301 
                 180.7 
                 181 
               
               
                   
               
             
          
         
       
     
         [0049]      FIGS. 12 and 13  are graphs of the haze vs. the thickness of the diffusion module according to two examples of the present disclosure. In  FIG. 12 , the pitch p of the display module was about 63 μm, i.e., NP=1. In  FIG. 13 , the pitch p of the display module was about 92 μm, i.e., NP=1.46. In these two examples, the head mounted displays with different thicknesses and different hazes were proceeded human factors experiments and the obtained display qualities were made as  FIGS. 12 and 13 . In  FIGS. 12 and 13 , the triangle marks (▴) represented good display qualities, the circle marks () represented the display qualities with excessive sense of grain, and the diamond marks (♦) represented the display qualities with excessive sense of blur. Curves A and B were obtained from these data (or marks). The curve A was an interface between the triangle marks and the circle marks with the formula: 
         [0000]    
       
         
           
             
               A 
               = 
               
                 0.642 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.35 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.32 
                   
                 
               
             
             ; 
           
         
       
     
         [0000]    and the curve B was an interface between the triangle marks and the diamond marks with the formula: 
         [0000]    
       
         
           
             
               B 
               = 
               
                 0.821 
                 × 
                 
                   
                     
                       ( 
                       NP 
                       ) 
                     
                     0.45 
                   
                   
                     
                       ( 
                       NT 
                       ) 
                     
                     0.60 
                   
                 
               
             
             ; 
           
         
       
     
         [0000]    and good display qualities could be obtained when A&lt;Haze (%)&lt;B, where B was smaller than or equal to 100%. Moreover,  FIGS. 12 and 13  also showed that the good display qualities were located in the range of 0.4≦NP≦2.6, and the claimed scope of the present disclosure is not limited in this respect. 
         [0050]    Although the present disclosure 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. 
         [0051]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure covers modifications and variations of this disclosure provided they fall within the scope of the following claims.