Patent Publication Number: US-11640059-B2

Title: Head-mounted display optical module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of priority to Chinese Patent Application No. 201911359455.1, filed on Dec. 25, 2019, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of head-mounted displays, and in particular, to a head-mounted display optical module. 
     BACKGROUND 
     Both virtual reality technology and augmented reality technology are computer simulation systems that can create and experience virtual worlds and have been widely used in various fields such as games, entertainment, education, medical treatment, and military simulation. 
     In related designs, light emitted by a display panel utilizing the virtual reality technology and the augmented reality technology at a large exit angle has a problem of color shift, that is, large viewing angle color shift, which will affect an image quality observed by a user. In addition, the light emitted by the display panel at the large exit angle has low energy and a low optical efficiency. 
     SUMMARY 
     An embodiment of the present disclosure provides a head-mounted display optical module for imaging a display image of a display panel at a user viewing side. The head-mounted display optical module includes an optical lens group located at a light-emitting display side of the display panel, and at least one protective layer located on an optical path between the display panel and the optical lens group. The at least one protective layer includes at least one first protective layer that has a refractive index continuously changing therein at least along a radial direction that is located in a plane of the first protective layer and points from a center of the first protective layer to an edge of the first protective layer. 
     In an embodiment, the refractive index of the first protective layer satisfies: n=m 0 +m 2 ·r 2 +m 4 ·r 4 +j·z 1 , where n denotes the refractive index of the first protective layer, r denotes a radial distance from the center of the first protective layer, z 1  denotes an axial distance from the center of the first protective layer, the axial direction is perpendicular to a plane of the first protective layer, and m 0 , m 2 , m 4 , and j are real numbers. 
     In the head-mounted display optical module provided by the embodiment of the present disclosure, an image displayed on the display panel is emitted to an outside of the display panel in a form of light of various angles. Since in the embodiment of the present disclosure the refractive index of an interior of the first protective layer continuously changes at least along the radial direction, when the light emitted from the display panel is projected to the first protective layer, different positions of the first protective layer have different refractive indexes, to match with the light emitted from different positions of the display panel at different angles. Due to presence of the first protective layer, the first protective layer can amplify the exit angle of the light emitted by the display panel to a relatively large level at a position where a large exit angle is required, the first protective layer can amplify the exit angle of the light emitted by the display panel to a moderate level at a position where a medium exit angle is required, and the first protective layer can amplify the exit angle of the light emitted by the display panel to a relatively small level at a position where a small exit angle is required. In short, due to the presence of the first protective layer in the protective layer, it is possible to lower design requirements for the display panel, decrease the exit angle of the light emitted by the display panel, reduce or even avoid large viewing angle color shift of the display panel, in order to enable the user to observe the image without color shift at a large field of view and also improve an optical efficiency. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic diagram of a head-mounted display optical module provided by an embodiment of the present disclosure; 
         FIG.  2    is a top view of a first protective layer shown in  FIG.  1   ; 
         FIG.  3    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure; 
         FIG.  4    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure; 
         FIG.  5    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure; and 
         FIG.  6    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present disclosure will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present disclosure, rather than to limit the present disclosure. In addition, it should be noted that, in order to facilitate description, the drawings only show parts related to the present disclosure but not all structures. 
     The head-mounted display optical module is configured to image and project the image displayed on the display panel at the user viewing side. The light emitted from the display panel is finally projected to the user viewing side in parallel light. Since the larger the incidence angle of the light projected to the user viewing side, the larger the field of view at which the user observes the image, the larger the size of the finally imaged image, and the better the user experience. Imaging at large field of view at which the user observes the image requires that the exit angle of the light emitted by the display panel is relatively large, but the light emitted by the display panel at a large exit angle has the problems of color shift and low optical efficiency, that is, the large viewing angle color shift, which will result in low image quality observed by the user, and also relatively low optical efficiency. 
       FIG.  1    is a schematic diagram of a head-mounted display optical module provided by an embodiment of the present disclosure, and  FIG.  2    is a top view of a first protective layer shown in  FIG.  1   . Referring to  FIG.  1    and  FIG.  2   , the head-mounted display optical module includes at least one protective layer  20  and an optical lens group  30 . The optical lens group  30  is located at a light-emitting display side of the display panel  10 . The protective layer  20  is located on an optical path between the display panel  10  and the optical lens group  30 . Light emitted from the display panel  10  is first projected to the protective layer  20  and then projected to a user viewing side  40  via the optical lens group  30 . The at least one protective layer  20  includes at least one first protective layer  21 , a refractive index of the first protective layer  21  continuously changes therein at least along a radial direction, and the radial direction U is located in a plane of the first protective layer  21  and points from a center L 0  of the first protective layer  21  to an edge of the first protective layer  21 . The center L 0  of the first protective layer  21  can be a center of gravity of the first protective layer  21 . 
     Exemplarily, referring to  FIG.  1    and  FIG.  2   , the first protective layer  21  can be made of a material having a gradient refractive index. The refractive index of the first protective layer  21  can continuously change therein along the radial direction U, or the refractive index of the first protective layer  21  can continuously change therein along the radial direction U and an axial direction. The axial direction is a direction perpendicular to the plane of the first protective layer  21 . In  FIG.  1    and  FIG.  2   , the plane of the first protective layer  21  is located is a plane defined by a direction X and a direction Y, and a direction Z is the axial direction of the first protective layer  21 . 
     In the head-mounted display optical module provided by the embodiment of the present disclosure, an image displayed on the display panel is emitted to an outside of the display panel in a form of light with various angles. Since in the embodiment of the present disclosure the refractive index of the interior of the first protective layer continuously changes at least along the radial direction, when the light emitted from the display panel is projected to the first protective layer, different positions of the first protective layer have different refractive indexes, to match with the light emitted from different positions of the display panel at different angles. Due to presence of the first protective layer, the first protective layer can amplify the exit angle of the light emitted by the display panel to a relatively large level at a position where a large exit angle is required, the first protective layer can amplify the exit angle of the light emitted by the display panel to a moderate level at a position where a medium exit angle is required, and the first protective layer can amplify the exit angle of the light emitted by the display panel to a relatively small level at a position where a small exit angle is required. In short, due to the presence of the first protective layer in the protective layer, it is possible to lower design requirements for the display panel, decrease the requirement for an exit angle of the light emitted by the display panel, reduce or even avoid large viewing angle color shift of the display panel, in order to enable the user to observe the image without color shift at a large field of view, and also improve an optical efficiency of light at a large viewing angle to improve an energy utilization rate. 
     It should be noted that in the embodiment of the present disclosure, the first protective layer can use a material having a gradient refractive index, and the first protective layer having the gradient refractive index is used in the field of head-mounted display (including virtual reality and augmented reality), but not in other technical fields. A role of the first protective layer having the gradient refractive index is to match the light emitted from different positions of the display panel at different angles, to refract (diffuse), to different degrees, the light emitted from the different positions at different angles. The first protective layer having the gradient refractive index is different from a gradient index lens in the optical field, and the gradient index lens in the related art often acts like a convex lens to converge light or acts as a concave lens to diverge light. The gradient index lens in the related art is a design in which there is a fixed focus, while in the present disclosure, the first protective layer is not intended to realize the function of the convex lens or the concave lens, that is, a design purpose and a principle of the first protective layer in the present disclosure are different from those of the gradient index lens presented in the related art. 
     Exemplarily, referring to  FIG.  1    and  FIG.  2   , an exit angle of light emitted from a center of the display panel  10  is relatively small, and an exit angle of light emitted from an edge of the display panel  10  is relatively large. The refractive index of the first protective layer  21  can gradually increase therein along the radial direction U. 
     In an embodiment, referring to  FIG.  1    and  FIG.  2   , the refractive index of the first protective layer  21  satisfies: n=m 0 +m 2 ·r 2 +m 4 ·r 4 +j·z 1 , where n denotes the refractive index of the first protective layer, r denotes a radial distance from the center L 0  of the first protective layer  21 , z 1  denotes an axial distance from the center L 0  of the first protective layer  21 , the axial direction is perpendicular to the plane of the first protective layer  21 , and m 0 , m 2 , m 4  and j are real numbers. It should be noted that a formula which the refractive index n of the first protective layer  21  satisfies is a formula suitable for the field of virtual reality or the field of augmented reality display. In other embodiments, the refractive index n of the first protective layer  21  can also be in other forms, and it is not limited to the form of this formula. 
     In an embodiment, n=1.5+0.046r 2 . In the embodiment of the present disclosure, the refractive index n of the first protective layer  21  is mainly related to r 2 , and the refractive index n of the first protective layer  21  conforms to a parabolic form. In the embodiment of the present disclosure, the formula n=1.5+0.046r 2  can be obtained by the formula n=m 0 +m 2 ·r 2 +m 4 ·r 4 +j·z 1  in a case where m 0 =1.5, m 2 =0.046, m 4 =0, and j=0. 
     In an embodiment, n=1.5+0.01r 2 +0.004r 4 . In the embodiment of the present disclosure, the refractive index n of the first protective layer  21  is related to r 4  in addition to being related to r 2 . In the embodiment of the present disclosure, the formula n=1.5+0.01r 2 +0.004r 4  can be obtained by the formula n=m 0 +m 2 ·r 2 +m 4 ·r 4 +j·z 1  in a case where m 0 =1.5, m 2 =0.01, m 4 =0.0004, and j=0. 
     In an embodiment, the refractive index of the first protective layer  21  further continuously changes therein along the axial direction. The refractive index n of the first protective layer  21  satisfies: n=1.5+0.005r 2 +0.0001r 4 +0.003z 1  in the embodiment of the present disclosure, the refractive index n of the first protective layer  21  is related to the axial direction in addition to being related to r 2  and r 4 . In the embodiment of the present disclosure, the formula n=1.5+0.005r 2 +0.0001r 4 +0.003z 1  can be obtained by the formula n=m 0 +m 2 ·r 2 +m 4 ·r 4 +j·z 1  in a case where m 0 =1.5, m 2 =0.005, m 4 =0.0001, and j=0.003. 
       FIG.  3    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure. Referring to  FIG.  3   , the protective layer  20  includes at least two first protective layers  21 . Compared with only one first protective layer  21 , the at least two first protective layers  21  can further reduce requirement of the exit angle of the light emitted by the display panel  10 , to further reduce the large viewing angle color shift of the display panel  10 . In another aspect, in the case where the exit angle of the light emitted by the display panel  10  is fixed, with respect to the case of providing one first protective layer  21 , providing at least two first protective layers  21  can reduce a requirement for a change of the refractive index of the first protective layer  21 , expand a range of materials that can be selected for the first protective layer  21  and reduce design difficulty of the first protective layer  21 . 
       FIG.  4    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure. Referring to  FIG.  4   , the protective layer  20  further includes at least one second protective layer  22 , and any two positions inside of the second protective layer  22  have a same refractive index. In other words, the refractive indexes of the second protective layer  22  are the same at all positions thereof, and does not change gradually. The at least one second protective layer  22  is located between the display panel  10  and the at least one first protective layer  21 . That is, the second protective layer  22  is located between the display panel  10  and the first protective layer  21 . 
     Exemplarily, referring to  FIG.  4   , the second protective layer  22  can be a parallel glass plate, and the second protective layer  22  can be, for example, a protective cover attached to the light emitting side of the display panel  10 . 
     In an embodiment, referring to  FIG.  1   , the optical lens group  30  includes a first convex lens  32 , a curved mirror  31 , and a transflective component  33 . The curved mirror  31  is located at a side of the transflective component  33  facing away from the user viewing side  40 , and the transflective component  33  is located on an optical path between the first convex lens  32  and the curved mirror  31 . The first convex lens  32  is located between the protective layer  20  and the transflective component  33 . 
     Exemplarily, referring to  FIG.  1   , after passing through the protective layer  20 , the light emitted from the display panel passes through the first convex lens  32  and is projected to the transflective component  33 , reflected by the transflective component  33  to the curved mirror  31  and projected to the transflective component  33  again after being reflected by the curved mirror  31 , and then passes through the transflective component  33  and is projected to the user viewing side  40 . 
     Exemplarily, referring to  FIG.  1   , in a feasible embodiment, the curved mirror  31  can be a reflective mirror, and the head-mounted display optical module is a virtual reality module. In another feasible embodiment, the curved mirror  31  can be a transflective lens, and the transflective lens can also transmit ambient light to the user viewing side, and the head-mounted display optical module is an augmented reality module. 
     In an embodiment, referring to  FIG.  1   , the curved mirror  31  includes a first aspherical surface  310 , and the first aspheric surface  310  can be a surface of the curved mirror  31  facing towards the transflective component  33 . The first convex lens  32  includes a second aspherical surface  320 , and the second aspheric surface  320  can be, for example, a surface of the first convex lens  32  facing towards the transflective component  33 . The first aspheric surface  310  and the second aspheric surface  320  satisfy an even-order aspheric surface formula: 
     
       
         
           
             
               
                 z 
                 2 
               
               = 
               
                 
                   
                     cy 
                     2 
                   
                   
                     1 
                     + 
                     
                       
                         1 
                         - 
                         
                           
                             ( 
                             
                               1 
                               + 
                               k 
                             
                             ) 
                           
                           ⁢ 
                           
                             c 
                             2 
                           
                           ⁢ 
                           
                             y 
                             2 
                           
                         
                       
                     
                   
                 
                 + 
                 
                   Ay 
                   4 
                 
                 + 
                 
                   By 
                   6 
                 
                 + 
                 
                   Cy 
                   8 
                 
                 + 
                 
                   Dy 
                   10 
                 
                 + 
                 
                   Ey 
                   12 
                 
                 + 
                 
                   Fy 
                   14 
                 
               
             
             , 
           
         
       
     
     where z 2  denotes an axial sagittal height of an aspheric surface, y denotes a radial distance of the aspheric surface, k denotes a conic coefficient, c denotes a curvature, and A, B, C, D, E, F are aspheric coefficients. 
     And the first aspheric surface  310  and the second aspheric surface  320  can satisfy: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 first aspheric 
                  2.62e−6 
                  3.96e−8 
                 −1.97e−11 
                 1.23e−12 
                 0 
                 0  
               
               
                 surface 
                   
                   
                   
                   
                   
                   
               
               
                 second aspheric 
                 −9.33e−5 
                 −3.12e−7 
                 4.13e−8 
                 7.60e−10 
                 0 
                 0, 
               
               
                 surface 
               
               
                   
               
            
           
         
       
     
     where “e” in each numerical value such as 2.62e-6 represents the power of 10, and for example, 2. 62e-6 is equivalent to 2.62*10 −6 . 
     Exemplarily, referring to  FIG.  1   , for the first aspherical surface  310 , a direction X is an axial direction of the first aspherical surface  310 , and a direction Z is a radial direction of the first aspherical surface  310 . For the second aspheric surface  320 , the direction X is a radial direction of the second aspheric surface  320 , and the direction Z is an axial direction of the second aspheric surface  320 . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Table of design parameters of various optical surfaces of a first type 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                   
                   
                 Machinery 
                 Conic 
                 X 
                 Y 
               
               
                 Number 
                 Shape 
                 Curvature 
                 Thickness 
                 Material 
                 Diameter 
                 Coefficient 
                 tilt 
                 eccentricity 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinity 
                 Infinity 
                   
                 Infinity 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 STO 
                 Spherical 
                 Infinity 
                 16 
                   
                 6 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 2 
                 Coordinate 
                   
                 0 
                   
                   
                   
                 −45 
                   
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 3 
                 Spherical 
                 Infinity 
                 0.5 
                 PMMA 
                 28 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 4 
                 Spherical 
                 Infinity 
                 0 
                   
                   
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 5 
                 Coordinate 
                   
                 11 
                   
                   
                   
                 45 
                   
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 6 
                 Coordinate 
                   
                 0 
                   
                   
                   
                   
                 −0.19 
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 7 
                 Even-Order 
                 −58.31 
                 −11 
                 MIRROR 
                 20 
                 7.85 
                   
                   
               
               
                   
                 Aspheric 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 8 
                 Coordinate 
                   
                 0.13 
                   
                   
                   
                 −45 
                 0.13 
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 9 
                 Spherical 
                 Infinity 
                 0 
                 MIRROR 
                 28 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 10 
                 Coordinate 
                   
                 14.07 
                   
                   
                   
                 −45 
                   
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 11 
                 Coordinate 
                   
                 0 
                   
                   
                   
                   
                 −0.19 
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 12 
                 Even-Order 
                  10.95 
                 4.59 
                 H-K9L 
                 15 
                 0.57 
                   
                   
               
               
                   
                 Aspheric 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 13 
                 Gradient 
                 Infinity 
                 0.7 
                   
                 15 
                 0 
                   
                   
               
               
                   
                 Refractive 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Index Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 IMA 
                 Spherical 
                 Infinity 
                   
                   
                 15 
                 0 
                   
                   
               
               
                   
                 Surface 
               
               
                   
               
            
           
         
       
     
     The design parameters of the corresponding optical surfaces in Table 1 correspond to the head-mounted display optical module shown in  FIG.  1   , and the first aspherical surface  310  and the second aspherical surface  320  satisfy: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 first aspheric 
                  2.62e−6 
                  3.96e−8 
                 −1.97e−11 
                 1.23e−12 
                 0 
                 0 
               
               
                 surface 
                   
                   
                   
                   
                   
                   
               
               
                 second aspheric 
                 −9.33e−5 
                 −3.12e−7 
                 4.13e−8 
                 7.60e−10 
                 0 
                 0. 
               
               
                 surface 
               
               
                   
               
            
           
         
       
     
     In the column of the surface number in Table 1, “OBJ” represents an object plane, and “STO” represents the user viewing side  40 . “2, 5, 6, 8, 10, 11” in the column of the surface number indicate virtual surfaces and all correspond to the “Coordinate Breakpoint” in the column of the surface type, and the “Coordinate Breakpoint” is used to rotate a coordinate system. “3, 4” in the column of the surface number represent two surfaces of the transflective component  33 , “7” in the column of the surface number represents the first aspheric surface  310 , “9” in the column of the surface number represents a surface of the transflective component  33  adjacent to the first aspherical surface  310  where the light reaches after being reflected by the first aspherical surface  310 , “12” in the column of the surface number represents the second aspherical surface  320 , “13” in the column of the surface number represents a surface of the first protective layer  21 , and “IMA” in the column of the surface number represents an image plane, i.e., the light-emitting display surface of the display panel  10 . “Infinity” in Table 1 represents infinity. Along a propagation direction of the light, in the column of the radius of curvature, a positive value represents that a center of curvature is at a side of a surface close to the display panel  10 , and a negative value represents that the center of curvature is at a side of the surface close to the user viewing side  40 . In the column of the material, “PMMA” represents a polymethyl methacrylate, “MIRROR” represents a reflective material, and a space in the column of the material represents air. The value in the column of the thickness is a distance between a current surface and a previous surface. The two columns of the X tilt and the Y eccentricity are parameter columns of the virtual surfaces. The radius of curvature, the thickness, the machinery diameter and the Y eccentricity is of unit of mm. The column of the X tilt is in a unit of degree. 
     In an embodiment, referring to  FIG.  1   , the curved mirror  31  includes a first aspherical surface  310 , and the first aspheric surface  310  can be a surface of the curved mirror  31  facing towards the transflective component  33 . The first convex lens  32  includes a second aspherical surface  320 , and the second aspheric surface  320  can be, for example, a surface of the first convex lens  32  facing towards the transflective component  33 . The first aspheric surface  310  and the second aspheric surface  320  satisfy the even-order aspheric surface formula: 
     
       
         
           
             
               
                 z 
                 2 
               
               = 
               
                 
                   
                     cy 
                     2 
                   
                   
                     1 
                     + 
                     
                       
                         1 
                         - 
                         
                           
                             ( 
                             
                               1 
                               + 
                               k 
                             
                             ) 
                           
                           ⁢ 
                           
                             c 
                             2 
                           
                           ⁢ 
                           
                             y 
                             2 
                           
                         
                       
                     
                   
                 
                 + 
                 
                   Ay 
                   4 
                 
                 + 
                 
                   By 
                   6 
                 
                 + 
                 
                   Cy 
                   8 
                 
                 + 
                 
                   Dy 
                   10 
                 
                 + 
                 
                   Ey 
                   12 
                 
                 + 
                 
                   Fy 
                   14 
                 
               
             
             , 
           
         
       
     
     where z 2  denotes an axial sagittal height of an aspheric surface, y denotes a radial distance of the aspheric surface, k denotes a conic coefficient, c denotes a curvature, and A, B, C, D, E, F are aspheric coefficients. 
     And the first aspheric surface  310  and the second aspheric surface  320  can satisfy: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 first aspheric 
                  2.71e−6 
                  4.01e−8 
                 −1.86e−11 
                 2.13e−12 
                 0 
                 0 
               
               
                 surface 
                   
                   
                   
                   
                   
                   
               
               
                 second aspheric 
                 −9.42e−5 
                 −3.23e−7 
                 4.02e−8 
                 6.55e−10 
                 0 
                 0. 
               
               
                 surface 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Table of design parameters of various optical surfaces of a second type 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                   
                   
                 Machinery 
                 Conic 
                   
                 Y 
               
               
                 Number 
                 Shape 
                 Curvature 
                 Thickness 
                 Material 
                 Diameter 
                 Coefficient 
                 tilt 
                 eccentricity 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinity 
                 Infinity 
                   
                 Infinity 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 STO 
                 Spherical 
                 Infinity 
                 16 
                   
                 6 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 2 
                 Coordinate 
                   
                 0 
                   
                   
                   
                 −45 
                   
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 3 
                 Spherical 
                 Infinity 
                 0.5 
                 PMMA 
                 28 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 4 
                 Spherical 
                 Infinity 
                 0 
                   
                 28 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 5 
                 Coordinate 
                   
                 11 
                   
                   
                   
                 45 
                   
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 6 
                 Coordinate 
                   
                 0 
                   
                   
                   
                   
                 −0.18 
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 7 
                 Even-Order 
                 −58.28 
                 −11 
                 MIRROR 
                 20 
                 7.85 
                   
                   
               
               
                   
                 Aspheric 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 8 
                 Coordinate 
                   
                 0.12 
                   
                   
                   
                 −45 
                 0.12 
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 9 
                 Spherical 
                 Infinity 
                 0 
                 MIRROR 
                 28 
                 0 
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 10 
                 Coordinate 
                   
                 13.49 
                   
                   
                   
                 −45 
                   
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 11 
                 Coordinate 
                   
                 0 
                   
                   
                   
                   
                 −0.18 
               
               
                   
                 Breakpoint 
                   
                   
                   
                   
                   
                   
                   
               
               
                 12 
                 Even-Order 
                  10.84 
                 4.58 
                 H-K9L 
                 15 
                 0.57 
                   
                   
               
               
                   
                 Aspheric 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 13 
                 Gradient 
                 Infinity 
                 0.7 
                   
                 15 
                 0 
                   
                   
               
               
                   
                 Refractive 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Index Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 14 
                 Spherical 
                 Infinity 
                 0.7 
                 N-BK7 
                 15 
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 IMA 
                 Spherical 
                 Infinity 
                   
                   
                 15 
                 0 
                   
                   
               
               
                   
                 Surface 
               
               
                   
               
            
           
         
       
     
     The design parameters of the corresponding optical surface in Table 2 correspond to the head-mounted display optical module shown in  FIG.  4   , and the first aspheric surface  310  and the second aspheric surface  320  satisfy: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 first aspheric 
                  2.62e−6 
                  3.96e−8 
                 −1.97e−11 
                 1.23e−12 
                 0 
                 0 
               
               
                 surface 
                   
                   
                   
                   
                   
                   
               
               
                 second aspheric 
                 −9.33e−5 
                 −3.12e−7 
                 4.13e−8 
                 7.60e−10 
                 0 
                 0. 
               
               
                 surface 
               
               
                   
               
            
           
         
       
     
     The meanings, units of various columns and the meanings of the parameters of the columns in Table 2 are the same as those in Table 1 and will not be repeated herein. 
       FIG.  5    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure. Referring to  FIG.  5   , the optical lens group  30  includes a second convex lens  34  and a first lens group  35 , and the first lens group  35  is located between the second convex lens  34  and the protective layer  20 . The display panel  10 , the protective layer  20 , the first lens group  35 , and the second convex lens  34  are disposed to have a same optical axis. The first lens group  35  can include one or more lenses. 
     In an embodiment, referring to  FIG.  5   , the second convex lens  34  includes a third aspherical surface  330  and a fourth aspherical surface  340 , and the fourth aspherical surface  340  is located between the third aspherical surface  330  and the first lens group  35 . The third aspherical surface  330  and the fourth aspherical surface  340  satisfy the even-order aspherical formula: 
     
       
         
           
             
               
                 z 
                 2 
               
               = 
               
                 
                   
                     cy 
                     2 
                   
                   
                     1 
                     + 
                     
                       
                         1 
                         - 
                         
                           
                             ( 
                             
                               1 
                               + 
                               k 
                             
                             ) 
                           
                           ⁢ 
                           
                             c 
                             2 
                           
                           ⁢ 
                           
                             y 
                             2 
                           
                         
                       
                     
                   
                 
                 + 
                 
                   Ay 
                   4 
                 
                 + 
                 
                   By 
                   6 
                 
                 + 
                 
                   Cy 
                   8 
                 
                 + 
                 
                   Dy 
                   10 
                 
                 + 
                 
                   Ey 
                   12 
                 
                 + 
                 
                   Fy 
                   14 
                 
               
             
             , 
           
         
       
     
     where z 2  denotes an axial sagittal height of an aspheric surface, y denotes a radial distance of the aspheric surface, k denotes a conic coefficient, c denotes a curvature, and A, B, C, D, E, F are aspheric coefficients. 
     And the third aspheric surface and the fourth aspheric surface satisfy: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 third 
                 7.93e−7 
                  4.32e−9 
                 3.38e−10 
                 −1.66e−12 
                 2.01e−15 
                 0 
               
               
                 aspheric 
                   
                   
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
                   
               
               
                 fourth 
                 7.55e−6 
                 −5.18e−8 
                 6.57e−10 
                 −2.12e−12 
                 2.53e−15 
                 0. 
               
               
                 aspheric 
                   
                   
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
         
       
     
       FIG.  6    is a schematic diagram of a head-mounted display optical module provided by another embodiment of the present disclosure. Referring to  FIG.  6   , the first lens group  35  includes a polarizer  351 , a phase retarder  352 , a third convex lens  353  and a selective transflective film  354 . The polarizer  351 , the phase retarder  352 , the third convex lens  353 , and the selective transflective film  354  are sequentially provided along an optical axis from the user viewing side  40  towards the display panel  10 . 
     Exemplarily, referring to  FIG.  6   , the polarizer  351  is a reflective polarizer, and the phase retarder  352  is a quarter wave plate. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Table of design parameters of various optical surfaces of a third type 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Surface 
                 Surface 
                 Radius of 
                   
                   
                 Machinery 
                 Conic 
               
               
                 Number 
                 Shape 
                 Curvature 
                 Thickness 
                 Material 
                 Diameter 
                 Coefficient 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Spherical 
                 Infinity 
                 Infinity 
                   
                 0 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 STO 
                 Spherical 
                 Infinity 
                 15 
                   
                 8 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 2 
                 Even-Order 
                 115.78 
                 4.20 
                 E48R 
                 49 
                 −41.41 
               
               
                   
                 Aspheric 
                   
                   
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 3 
                 Even-Order 
                 −106.61  
                 4.76 
                   
                 49 
                 8.66 
               
               
                   
                 Aspheric 
                   
                   
                   
                   
                   
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 4 
                 Spherical 
                 Infinity 
                 0.11 
                 PMMA 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 5 
                 Spherical 
                 Infinity 
                 7.29 
                 N-BK7 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 6 
                 Spherical 
                 −77.24 
                 0.19 
                 PMMA 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 7 
                 Spherical 
                 −77.24 
                 0.19 
                 MIRROR 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 8 
                 Spherical 
                 −77.24 
                 −7.29 
                 N-BK7 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 9 
                 Spherical 
                 Infinity 
                 −0.11 
                 PMMA 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 10 
                 Spherical 
                 Infinity 
                 0.11 
                 MIRROR 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 11 
                 Spherical 
                 Infinity 
                 7.29 
                 N-BK7 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 12 
                 Spherical 
                 −77.24 
                 0.19 
                 PMMA 
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 13 
                 Spherical 
                 −77.24 
                 8.95 
                   
                 49 
                 0 
               
               
                   
                 Surface 
                   
                   
                   
                   
                   
               
               
                 14 
                 Gradient 
                 Infinity 
                 0.90 
                   
                 28 
                 0 
               
               
                   
                 Refractive 
                   
                   
                   
                   
                   
               
               
                   
                 Index Surface 
                   
                   
                   
                   
                   
               
               
                 IMA 
                 Spherical 
                 Infinity 
                   
                   
                 28 
                 0 
               
               
                   
                 Surface 
               
               
                   
               
            
           
         
       
     
     The corresponding design parameters of the optical surface in Table 3 correspond to the head-mounted display optical module shown in  FIG.  6   , and the third aspheric surface  330  and the fourth aspheric surface  340  satisfy: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 third 
                 7.93e−7 
                  4.32e−9 
                 3.38e−10 
                 −1.66e−12 
                 2.01e−15 
                 0 
               
               
                 aspheric 
                   
                   
                   
                   
                   
                   
               
               
                 surface 
                   
                   
                   
                   
                   
                   
               
               
                 fourth 
                 7.55e−6 
                 −5.18e−8 
                 6.57e−10 
                 −2.12e−12 
                 2.53e−15 
                 0. 
               
               
                 aspheric 
                   
                   
                   
                   
                   
                   
               
               
                 surface 
               
               
                   
               
            
           
         
       
     
     The meanings, units of various columns and the meanings of the parameters of the columns in Table 3 are the same as those in Table 1 and will not be repeated herein. 
     An embodiment of the present disclosure further provides a head-mounted display optical device, and it includes the head-mounted display optical module and the display panel in any of the above embodiments. The head-mounted display optical module is located at the light-emitting display side of the display panel. It can be understood that, for the sake of clarity, the schematic view of the head-mounted display optical module shown in  FIG.  1    to  FIG.  6    also illustrates the display panel  10  and the user viewing side  40 . Since the head-mounted display optical device includes the head-mounted display optical module in any one of the above embodiments, it has the beneficial effects of the above-mentioned head-mounted display optical module, that is, the user can observe the image without color shift at the large field of view, and the optical efficiency can also be improved. 
     Note that the above are only exemplary embodiments of the present disclosure and the applied technical principles. Those skilled in the art will understand that the present disclosure is not limited to the specific embodiments described herein, and various obvious modifications, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of the present disclosure. Therefore, although the present disclosure has been described in more detail through the above embodiments, the present disclosure is not limited to the above embodiments, and other equivalent embodiments can be included without departing from the concept of the present disclosure, while the scope of the present disclosure is determined by the scope of the appended claims.