Patent Publication Number: US-2022229268-A1

Title: Projection lens

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan applications serial no. 110101963, filed on Jan. 19, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a lens, particularly to a fixed-focus projection lens. 
     Description of Related Art 
     Optical lenses are usually used for capturing or projecting images, so the adopted wavelength band is usually that of visible light or infrared light. However, with the advancement of technology, there are a growing number of products applying ultraviolet light, such as a 3D printer that uses an ultraviolet light source. Therefore, there is a need to develop an optical lens that provides good imaging or image-capture effects with less distortion. 
     SUMMARY 
     The present disclosure provides a projection lens capable of providing good optical effects in the ultraviolet wavelength band. 
     The projection lens according to an embodiment of the present disclosure includes a first lens set and a second lens set disposed in sequence from a magnified side to a reduced side. The first lens set and the second lens set are separated by a minimum inner diameter of a lens barrel. The first lens set includes 4 to 6 spherical lenses, and a refractive power of the first lens set is negative. The second lens set includes 4 to 6 lenses, where one of the lenses is an aspheric lens, and a refractive power of the second lens set is positive. A transmittance of the projection lens at a wavelength of 365 nm is greater than or equal to 75%. 
     The projection lens according to an embodiment of the present disclosure includes a first lens set and a second lens set disposed in sequence from a magnified side to a reduced side. The first lens set includes 3 to 5 spherical lenses, a refractive power of the first lens set is negative, and the first lens set is disposed in a first lens barrel. The second lens set includes an aspheric lens, and includes 5 to 7 lenses. A refractive power of the second lens set is positive, and the second lens set is disposed in a second lens barrel. A transmittance of the projection lens at a wavelength of 365 nm is greater than or equal to 75%. 
     Based on the above, since the transmittance of the projection lens of an embodiment of the present disclosure is greater than or equal to 75% at a wavelength of 365 nm, the projection lens is suitable for the ultraviolet wavelength band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a projection lens according to a first embodiment of the disclosure. 
         FIG. 2  is a schematic cross-sectional view of the projection lens of a second embodiment of the disclosure. 
         FIG. 3  is a schematic cross-sectional view of a projection lens according to a third embodiment of the disclosure. 
         FIG. 4  is a schematic cross-sectional view of a projection lens according to a fourth embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a schematic cross-sectional view of a projection lens according to a first embodiment of the disclosure. Referring to  FIG. 1 , in this embodiment, a projection lens  100  includes a lens set G 1  and a lens set G 2  disposed in sequence from a magnified side A 1  to a reduced side A 2 . 
     In this embodiment, the lens set G 1  (which may be referred to as a first lens set) includes 4 to 6 spherical lenses, and a refractive power of the lens set G 1  is negative. Specifically speaking, the lens set G 1  includes a lens L 1  (which may be referred to as a first lens), a lens L 2  (which may be referred to as a second lens), a lens L 3  (which may be referred to as a third lens), a lens L 4  (which may be referred to as a fourth lens), a lens L 5  (which may be referred to as a fifth lens), and a lens L 6  (which may be referred to as a sixth lens) disposed in sequence from the magnified side A 1  to the reduced side A 2  along an optical axis I. The lenses L 1  to L 6  of the lens set G 1  are all glass spherical lenses. In addition, the refractive powers of the lenses L 1  to L 6  are respectively positive, negative, negative, negative, positive, and positive. 
     In another embodiment, the lens set G 1  may also include 3 to 5 spherical lenses, such as a projection lens  400  in  FIG. 4 . 
     In this embodiment, the lens set G 2  (which may be referred to as a second lens set) includes 4 to 6 lenses. A refractive power of the lens set G 2  is positive, and one of the lenses of the lens set G 2  is an aspheric lens. Specifically speaking, the lens set G 2  includes a lens L 7  (which may be referred to as a seventh lens), a lens L 8  (which may be referred to as an eighth lens), a lens L 9  (which may be referred to as a ninth lens), and a lens L 10  (which may be referred to as a tenth lens) disposed from the magnified side A 1  to the reduced side A 2  along the optical axis I. The lens L 7  to the lens L 9  of the lens set G 2  are all glass spherical lenses. The lens L 10  is configured as a glass aspheric lens to eliminate optical distortion. In addition, the refractive powers of the lens L 7  to the lens L 10  are respectively negative, positive, positive, and positive. 
     In another embodiment, the lens set G 2  may also include 5 to 7 lenses, such as the projection lens  400  in  FIG. 4 . 
     In this embodiment, the lens set G 1  is provided in a lens barrel B 1  (which may be referred to as a first lens barrel), and the lens set G 2  is provided in a lens barrel B 2  (which may be referred to as a second lens barrel). The projection lens  100  further includes a main lens barrel MB, and the lens barrel B 1  and the lens barrel B 2  are disposed in the main lens barrel MB. Among the above configuration, the lens barrel B 1  covers the lens barrel B 2 , and the main lens barrel MB covers the lens barrel B 1  and the lens barrel B 2 . In addition, the lens set G 1  and the lens set G 2  are separated by a minimum inner diameter of a lens barrel. The minimum inner diameter of the lens barrel is, for example, the position of an aperture S between the lens L 6  and the lens L 7 . 
     In one embodiment, the projection lens  100  includes ten lenses, whose refractive powers are positive, negative, negative, negative, positive, positive, negative, positive, positive, and positive in sequence from the magnified side A 1  to the reduced side A 2 . 
     In this embodiment, since the projection lens  100  is configured to have a good optical effect in the ultraviolet wavelength band, the projection lens  100  preferably does not have a cemented lens. In other words, the distance between the lenses of the projection lens  100  is preferably maintained by mechanical components. 
     In this embodiment, a transmittance of the projection lens  100  at a wavelength of 365 nm is greater than or equal to 75%. Moreover, the material of each lens of the projection lens  100  has a transmittance greater than or equal to 80% at a wavelength of 365 nm and a thickness of 10 mm, such that the projection lens  100  is suitable for the ultraviolet wavelength band. 
     In this embodiment, the projection lens  100  satisfies the following conditional formula: 13≤TTL/H≤21, where TTL is the total length of the projection lens  100 , H is the image height of an imaging surface of the projection lens  100  on the reduced side A 2 , and the imaging surface is, for example, the position of the digital micromirror device (DMD)  150 . 
     In this embodiment, the throw ratio of the projection lens  100 , that is, the ratio of the distance (projection distance) between the projection lens  100  and the projection screen on the magnified side A 1  to the width of the projection screen, is 1.0. 
     In this embodiment, the F-number (Fno) of the projection lens  100  is 2.2. 
     In this embodiment, the respective distances of the lens set G 1  and the lens set G 2  relative to an imaging surface on the reduced side A 2  is variable. 
     In this embodiment, the optical distortion of the projection lens  100  is less than 0.25%. 
     In this embodiment, the effective focal length (EFL) of the projection lens  100  is greater than or equal to 8 and less than or equal to 14. 
     In this embodiment, the actual configuration of the aforementioned components is shown in Table 1 below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Radius of 
                   
                 Refractive 
                 Abbe 
               
               
                   
                 Sur- 
                 curvature 
                 Distance 
                 index 
                 number 
               
               
                 Device 
                 face 
                 (mm) 
                 (mm) 
                 (nd) 
                 (vd) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 object 
                   
                 0.00E+00 
                 1.23E+02 
                   
                   
               
               
                 cover glass 110 
                 S1 
                 0.00E+00 
                 4.35E+00 
                 1.52 
                 64.14 
               
               
                   
                 S2 
                 0.00E+00 
                 2.00E+00 
               
               
                 lens L1 
                 S3 
                 5.34E+01 
                 2.96E+00 
                 1.65 
                 39.68 
               
               
                   
                 S4 
                 Infinite 
                 1.00E−01 
               
               
                 lens L2 
                 S5 
                 2.63E+02 
                 1.37E+00 
                 1.50 
                 81.55 
               
               
                   
                 S6 
                 1.69E+01 
                 3.36E+00 
               
               
                 lens L3 
                 S7 
                 1.64E+02 
                 1.18E+00 
                 1.50 
                 81.55 
               
               
                   
                 S8 
                 1.96E+01 
                 4.60E+00 
               
               
                 lens L4 
                 S9 
                 Infinite 
                 1.08E+00 
                 1.50 
                 81.55 
               
               
                   
                 S10 
                 2.38E+01 
                 5.84E+00 
               
               
                 lens L5 
                 S11 
                 −1.86E+02  
                 3.04E+00 
                 1.73 
                 51.47 
               
               
                   
                 S12 
                 −2.63E+01  
                 1.26E+01 
               
               
                 lens L6 
                 S13 
                 −2.20E+01  
                 2.04E+00 
                 1.50 
                 81.55 
               
               
                   
                 S14 
                 −1.67E+01  
                 1.75E+01 
               
               
                 aperture S 
                 S15 
                 Infinite 
                 7.61E+00 
               
               
                 lens L7 
                 S16 
                 −8.99E+00  
                 1.50E+00 
                 1.65 
                 39.68 
               
               
                   
                 S17 
                 Infinite 
                 1.00E−03 
               
               
                 lens L8 
                 S18 
                 Infinite 
                 3.87E+00 
                 1.50 
                 81.55 
               
               
                   
                 S19 
                 −1.25E+01  
                 1.00E−01 
               
               
                 lens L9 
                 S20 
                 3.29E+01 
                 5.29E+00 
                 1.49 
                 70.24 
               
               
                   
                 S21 
                 −2.18E+01  
                 1.00E−01 
               
               
                 lens L10 
                 S22 
                 6.85E+01 
                 2.90E+00 
                 1.51 
                 64.03 
               
               
                   
                 S23 
                 −2.84E+01  
                 8.81E+00 
               
               
                 TSP device 120 
                 S24 
                 Infinite 
                 2.00E+00 
                 1.52 
                 58.59 
               
               
                   
                 S25 
                 Infinite 
                 1.60E+00 
               
               
                 prism 130 
                 S26 
                 Infinite 
                 1.20E+01 
                 1.52 
                 64.17 
               
               
                   
                 S27 
                 Infinite 
                 2.00E+00 
               
               
                 cover glass 140 
                 S28 
                 Infinite 
                 1.10E+00 
                 1.52 
                 64.17 
               
               
                   
                 S29 
                 Infinite 
                 3.03E−01 
               
               
                 DMD 150 
                 S30 
                 Infinite 
               
               
                   
               
            
           
         
       
     
     Please refer to  FIG. 1  and Table 1 at the same time. Specifically speaking, in the projection lens  100  of this embodiment, the lens L 1  has a surface S 3  and a surface S 4  from the magnified side A 1  to the reduced side A 2  in sequence, the lens L 2  has a surface S 5  and a surface S 6  from the magnified side A 1  to the reduced side A 2  in sequence. And the rest may be deduced by analogy, so that the description of the surfaces corresponding to each device will not be repeated. Among the above configuration, a display surface of the aperture S and the DMD  150  are respectively represented by a surface S 15  and a surface S 30 , and its radius of curvature is infinite (that is, a plane perpendicular to the optical axis I). 
     In addition, the distance in Table 1 is the distance between the surface to the next surface measured from the magnified side A 1  to the reduced side A 2 . For example, the thickness of the lens L 1  is 2.96E+00 mm, the distance between the lens L 1  and the lens L 2  is 1.00E-01 mm, the thickness of the lens L 2  is 1.37E+00 mm, and the distance between the lens L 2  and the lens L 3  is 3.36E+00 mm, and so on. 
     Among them, the radius of the surface S 3  of the lens L 1  is positive, and the radius of the surface S 4  of the lens L 1  is 0, so the lens L 1  is a plano-convex lens, where a positive radius means that the center of the representative surface shifts toward the magnified side A 1 , as the surface S 3  do, and a negative radius means the center of the representative surface shifts toward the reduced side A 2 , as in the surface S 11 . And the radius of the surface S 5  of the lens L 2  is positive, the radius of the surface S 6  of the lens L 2  is positive, and the absolute value of the radius of the surface S 5  of the lens L 2  is smaller than the absolute value of the radius of the surface S 6  of the lens L 2 . Therefore, the lens L 2  is a negative meniscus lens having a concave surface facing the reduced side A 2 . By analogy, the lens L 3  is a negative meniscus lens having a concave surface facing the reduced side A 2 ; the lens L 4  is a plano-concave lens; the lens L 5  is a positive meniscus lens having a concave surface facing the magnified side A 1 ; the lens L 6  is a negative meniscus lens having a concave surface facing the magnified side A 1 ; lens L 7  is a plano-concave lens; lens L 8  is a plano-convex lens; lens L 9  is a double convex lens; and the lens L 10  is a double convex lens. 
     In this embodiment, the total length of the projection lens  100  (TTL, the distance from the surface S 3  of the lens L 1  to the surface S 23  of the lens L 10 ) is 76.98 mm. The Field of View (FOV) of the projection lens  100  is 50.38 degrees, and the effective focal length (EFL) of the projection lens  100  is 8.37 mm. 
     In this embodiment, the distance between two lenses of the projection lens  100  is less than or equal to 0.01 mm, and the two lenses are non-cemented lenses. For example, the distance between the lens L 7  and the lens L 8  is 0.001 mm. Since the projection lens  100  is configured to have a good optical effect in the ultraviolet band, the two lenses with a distance of less than or equal to 0.01 mm between the projection lens  100  are non-cemented lenses, and it is preferable to maintain the distance between the two lenses with mechanical components. 
     Furthermore, in this embodiment, a digital micromirror device  150  with a smaller size may be selected, cooperating with a transmissive smooth picture (TSP) device  120  to replace the existing products of a higher specification to reduce the costs. The TSP device  120  is a flat plate, which makes the pixel points of the projected image bleed to a small extent through vibration, so as to prevent the graininess of the pixels from being observed by the user. 
     Table 2 below shows a quadric coefficient value K and various aspheric coefficients of the surface S 22  and the surface S 23  of the lens L 10 . The aspheric polynomial may be expressed by the following formula: 
     
       
         
           
             
               
                 
                   x 
                   = 
                   
                     
                       
                         
                           c 
                           ′ 
                         
                         ⁢ 
                         
                           y 
                           2 
                         
                       
                       
                         1 
                         + 
                         
                           
                             1 
                             - 
                             
                               
                                 ( 
                                 
                                   1 
                                   + 
                                   K 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 c 
                                 ′2 
                               
                               ⁢ 
                               
                                 y 
                                 2 
                               
                             
                           
                         
                       
                     
                     + 
                     
                       Ay 
                       4 
                     
                     + 
                     
                       By 
                       6 
                     
                     + 
                     
                       Cy 
                       8 
                     
                     + 
                     
                       Dy 
                       10 
                     
                     + 
                     
                       Ey 
                       12 
                     
                     + 
                     
                       Fy 
                       14 
                     
                     + 
                     
                       Gy 
                       16 
                     
                     + 
                     … 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     Among the above formula, x is the sag in the direction of the optical axis I, and c′ is the reciprocal of the radius of the osculating sphere, that is, the reciprocal of the radius of curvature close to the optical axis, k is the quadric coefficient, y is the height of the aspheric surface, which is the height measured from the center of the lens to the edge of the lens. A to G respectively represent the aspheric coefficients of each order of the aspheric polynomial. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Aspheric coefficient 
               
            
           
           
               
               
               
            
               
                   
                 Surface S22 
                 Surface S23 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 K 
                 −2.25E+01 
                  3.26E+00 
               
               
                   
                 A 
                 −1.42E−05 
                  3.92E−05 
               
               
                   
                 B 
                 −2.05E−07 
                 −1.41E−07 
               
               
                   
                 C 
                  2.45E−09 
                  3.83E−09 
               
               
                   
                 D 
                 −2.24E−12 
                 −1.25E−11 
               
               
                   
                 E 
                 −6.05E−14 
                 −1.21E−14 
               
               
                   
                   
               
            
           
         
       
     
     Based on the above, since the transmittance of the projection lens  100  at a wavelength of 365 nm is greater than or equal to 75% in an embodiment of the present disclosure, the projection lens  100  is suitable for the ultraviolet wavelength band. Furthermore, the lens set G 2  includes an aspheric lens for eliminating optical distortion, so that the projection lens  100  provides good optical effects. 
     The projection lens of the second embodiment of the present disclosure is described below, and the actual configuration of each component is shown in Table 3 below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 Radius of 
                   
                 Refractive 
                 Abbe 
               
               
                   
                 Sur- 
                 curvature 
                 Distance 
                 index 
                 number 
               
               
                 Device 
                 face 
                 (mm) 
                 (mm) 
                 (nd) 
                 (vd) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 object 
                   
                 Infinite 
                 1.26E+02 
                   
                   
               
               
                 cover glass 110 
                 S1 
                 Infinite 
                 4.10E+00 
                 1.52 
                 64.14 
               
               
                   
                 S2 
                 Infinite 
                 2.00E+00 
               
               
                 lens L1 
                 S3 
                  4.91E+01 
                 2.19E+00 
                 1.52 
                 64.14 
               
               
                   
                 S4 
                  9.47E+02 
                 1.00E−01 
               
               
                 lens L2 
                 S5 
                  5.82E+01 
                 1.22E+00 
                 1.71 
                 53.87 
               
               
                   
                 S6 
                  1.55E+01 
                 4.48E+00 
               
               
                 lens L3 
                 S7 
                 −4.44E+01 
                 1.09E+00 
                 1.50 
                 81.55 
               
               
                   
                 S8 
                  1.80E+01 
                 9.21E+00 
               
               
                 lens L4 
                 S9 
                 −1.21E+02 
                 2.47E+00 
                 1.73 
                 51.47 
               
               
                   
                 S10 
                 −2.51E+01 
                 1.42E+01 
               
               
                 lens L5 
                 S11 
                 −2.30E+01 
                 1.41E+00 
                 1.52 
                 58.90 
               
               
                   
                 S12 
                 −1.68E+01 
                 1.72E+01 
               
               
                 aperture S 
                 S13 
                 Infinite 
                 7.62E+00 
               
               
                 lens L6 
                 S14 
                 −8.69E+00 
                 2.68E+00 
                 1.52 
                 64.14 
               
               
                   
                 S15 
                 −5.66E+02 
                 0.01 
               
               
                 lens L7 
                 S16 
                 −6.49E+02 
                 2.77E+00 
                 1.50 
                 81.55 
               
               
                   
                 S17 
                 −1.53E+01 
                 1.00E−01 
               
               
                 lens L8 
                 S18 
                  3.48E+01 
                 4.65E+00 
                 1.50 
                 81.55 
               
               
                   
                 S19 
                 −1.82E+01 
                 1.00E−01 
               
               
                 lens L9 
                 S20 
                  7.74E+01 
                 2.87E+00 
                 1.51 
                 64.03 
               
               
                   
                 S21 
                 −2.46E+01 
                 9.30E+00 
               
               
                 TSP device 120 
                 S22 
                 Infinite 
                 2.00E+00 
                 1.52 
                 58.59 
               
               
                   
                 S23 
                 Infinite 
                 1.60E+00 
               
               
                 prism 130 
                 S24 
                 Infinite 
                 1.20E+01 
                 1.52 
                 64.17 
               
               
                   
                 S25 
                 Infinite 
                 2.00E+00 
               
               
                 cover glass 140 
                 S26 
                 Infinite 
                 1.10E+00 
                 1.52 
                 64.17 
               
               
                   
                 S27 
                 Infinite 
                 3.03E−01 
               
               
                 DMD 150 
                 S28 
                 Infinite 
               
               
                   
               
            
           
         
       
     
       FIG. 2  is a schematic cross-sectional view of the projection lens of a second embodiment of the disclosure. Please refer to  FIG. 2  and Table 3 at the same time. In this embodiment, a projection lens  200  includes nine lenses, whose refractive powers are positive, negative, negative, positive, positive, negative, positive, positive, and positive in sequence from a magnified side A 1  to a reduced side A 2 . In addition, an aperture S is provided between a lens L 5  and a lens L 6 . 
     In this embodiment, a lens L 1  is a positive meniscus lens with a concave surface facing the reduced side A 2 ; a lens L 2  is a negative meniscus lens with a concave surface facing the reduced side A 2 ; a lens L 3  is a biconcave lens; a lens L 4  is a positive meniscus lens with a concave surface facing the magnified side A 1 ; the lens L 5  is a positive meniscus lens with a concave surface facing the magnified side A 1 ; the lens L 6  is a negative meniscus lens with a concave surface facing the magnified side A 1 ; a lens L 7  is a positive meniscus lens with a concave surface facing the magnified side A 1 ; a lens L 8  is a double convex lens; and a lens L 9  is a double convex lens. 
     It is worth mentioning that, in the embodiment in Table 3, the total length of the projection lens  200  is 74.47 mm (which is the sum of the distances from a surface S 3  to a surface S 21  in Table 3). The viewing angle of the projection lens  200  is 50.37 degrees, and the effective focal length of the projection lens  200  is 8.37 mm. 
     Table 4 below shows the quadric coefficient value K and various aspheric coefficients of a surface S 20  and the surface S 21  of the lens L 9 . Please refer to the above formula (1) for the aspheric equation. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Aspheric coefficient 
               
            
           
           
               
               
               
            
               
                   
                 Surface S20 
                 Surface S21 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 K 
                 −1.74E+01 
                  1.02E+00 
               
               
                   
                 A 
                 −1.61E−06 
                  6.34E−05 
               
               
                   
                 B 
                 −7.19E−08 
                 −5.31E−08 
               
               
                   
                 C 
                  3.77E−09 
                  5.21E−09 
               
               
                   
                 D 
                  2.34E−12 
                 −7.23E−12 
               
               
                   
                 E 
                 −6.74E−14 
                 −1.90E−14 
               
               
                   
                   
               
            
           
         
       
     
     The projection lens of the third embodiment of the present disclosure is described below, and the actual configuration of each component is shown in Table 5 below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 Radius of 
                   
                 Refractive 
                 Abbe 
               
               
                   
                 Sur- 
                 curvature 
                 Distance 
                 index 
                 number 
               
               
                 Device 
                 face 
                 (mm) 
                 (mm) 
                 (nd) 
                 (vd) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 object 
                   
                 Infinite 
                 1.14E+02 
                   
                   
               
               
                 cover glass 110 
                 S1 
                 Infinite 
                 4.45E+00 
                 1.52 
                 58.59 
               
               
                   
                 S2 
                 Infinite 
                 9.02E+00 
               
               
                 lens L1 
                 S3 
                 6.21E+01 
                 7.00E+00 
                 1.80 
                 46.53 
               
               
                   
                 S4 
                 4.40E+02 
                 1.00E−01 
               
               
                 lens L2 
                 S5 
                 7.60E+01 
                 6.52E+00 
                 1.73 
                 54.68 
               
               
                   
                 S6 
                 1.63E+01 
                 3.78E+00 
               
               
                 lens L3 
                 S7 
                 −5.31E+01  
                 1.00E+00 
                 1.73 
                 54.68 
               
               
                   
                 S8 
                 2.21E+01 
                 1.04E+01 
               
               
                 lens L4 
                 S9 
                 1.44E+02 
                 3.28E+00 
                 1.77 
                 49.60 
               
               
                   
                 S10 
                 −3.45E+01  
                 1.44E+01 
               
               
                 lens L5 
                 S11 
                 4.85E+01 
                 2.45E+00 
                 1.50 
                 81.61 
               
               
                   
                 S12 
                 −3.27E+01  
                 6.32E+00 
               
               
                 aperture S 
                 S13 
                 Infinite 
                 6.93E+00 
               
               
                 lens L6 
                 S14 
                 −5.28E+01  
                 8.00E−01 
                 1.61 
                 44.27 
               
               
                   
                 S15 
                 8.09E+01 
                 2.37E+00 
               
               
                 lens L7 
                 S16 
                 −1.00E+01  
                 8.50E−01 
                 1.67 
                 38.15 
               
               
                   
                 S17 
                 Infinite 
                 1.00E−03 
               
               
                 lens L8 
                 S18 
                 Infinite 
                 3.84E+00 
                 1.50 
                 81.61 
               
               
                   
                 S19 
                 −1.52E+01  
                 1.00E−01 
               
               
                 lens L9 
                 S20 
                 5.82E+01 
                 4.76E+00 
                 1.50 
                 81.61 
               
               
                   
                 S21 
                 −2.35E+01  
                 1.00E−01 
               
               
                 lens L10 
                 S22 
                 4.54E+01 
                 5.22E+00 
                 1.51 
                 63.75 
               
               
                   
                 S23 
                 −2.25E+01  
                 9.21E+00 
               
               
                 TSP device 120 
                 S24 
                 Infinite 
                 2.00E+00 
                 1.52 
                 58.59 
               
               
                   
                 S25 
                 Infinite 
                 1.60E+00 
               
               
                 prism 130 
                 S26 
                 Infinite 
                 1.20E+01 
                 1.52 
                 64.17 
               
               
                   
                 S27 
                 Infinite 
                 2.00E+00 
               
               
                 cover glass 140 
                 S28 
                 Infinite 
                 1.10E+00 
                 1.52 
                 64.17 
               
               
                   
                 S29 
                 Infinite 
                 3.03E−01 
               
               
                 DMD 150 
                 S30 
                 Infinite 
               
               
                   
               
            
           
         
       
     
       FIG. 3  is a schematic cross-sectional view of a projection lens according to a third embodiment of the disclosure. Please refer to  FIG. 3  and Table 5 at the same time. In this embodiment, a projection lens  300  includes ten lenses, whose refractive powers are positive, negative, negative, positive, positive, negative, negative, positive, positive, and positive in sequence from a magnified side A 1  to a reduced side A 2 . In addition, an aperture S is provided between a lens L 5  and a lens L 6 . The distance between a lens L 7  and a lens L 8  is 0.001 mm. 
     In this embodiment, a lens L 1  is a positive meniscus lens on the concave reduced side A 2 ; a lens L 2  is a negative meniscus lens having a concave surface facing the reduced side A 2 ; a lens L 3  is a biconcave lens; a lens L 4  is a double convex lens; the lens L 5  is a double convex lens; the lens L 6  is a biconcave lens; the lens L 7  is a plano-concave lens; the lens L 8  is a plano-convex lens; a lens L 9  is a double convex lens; a lens L 10  is a double convex lens. 
     It is worth mentioning that, in the embodiment of Table 5, the total length of the projection lens  300  is 80.26 mm (which is the sum of the distances from the surface S 3  to the surface S 23  in Table 5). The angle of view of the projection lens  300  is 48.00 degrees, and the effective focal length of the projection lens  300  is 13.00 mm. 
     Table 6 below shows the quadric coefficient value K and various aspheric coefficients of a surface S 22  and the surface S 23  of the lens L 10 . Please refer to the above formula (1) for the aspheric equation. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Aspheric coefficient 
               
            
           
           
               
               
               
            
               
                   
                 Surface S20 
                 Surface S21 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 K 
                 −7.09E+00 
                 −3.95E+00 
               
               
                   
                 A 
                 −7.13E−06 
                 −1.44E−05 
               
               
                   
                 B 
                 −1.52E−07 
                 −1.23E−07 
               
               
                   
                 C 
                  5.53E−09 
                  6.76E−09 
               
               
                   
                 D 
                 −1.05E−10 
                 −1.27E−10 
               
               
                   
                 E 
                  1.12E−12 
                  1.30E−12 
               
               
                   
                 F 
                 −5.94E−15 
                 −6.74E−15 
               
               
                   
                 G 
                  1.27E−17 
                  1.41E−17 
               
               
                   
                   
               
            
           
         
       
     
     The projection lens of the fourth embodiment of the present disclosure is described below, and the actual configuration of each component is shown in Table 7 below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 7 
               
               
                   
               
               
                   
                   
                 Radius of 
                   
                 Refractive 
                 Abbe 
               
               
                   
                 Sur- 
                 curvature 
                 Distance 
                 index 
                 number 
               
               
                 Device 
                 face 
                 (mm) 
                 (mm) 
                 (nd) 
                 (vd) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 object 
                   
                 Infinite 
                 3.37E+01 
                   
                   
               
               
                 cover glass 110 
                 S1 
                 Infinite 
                 7.12E+00 
                 1.52 
                 58.59 
               
               
                   
                 S2 
                 Infinite 
                 6.35E+00 
               
               
                 lens L1 
                 S3 
                 7.32E+01 
                 7.00E+00 
                 1.80 
                 46.53 
               
               
                   
                 S4 
                 Infinite 
                 1.00E−01 
               
               
                 lens L2 
                 S5 
                 9.56E+01 
                 5.69E+00 
                 1.73 
                 54.68 
               
               
                   
                 S6 
                 1.53E+01 
                 4.46E+00 
               
               
                 lens L3 
                 S7 
                 −6.34E+01  
                 1.28E+00 
                 1.73 
                 54.68 
               
               
                   
                 S8 
                 1.94E+01 
                 1.09E+01 
               
               
                 lens L4 
                 S9 
                 9.80E+01 
                 3.41E+00 
                 1.77 
                 49.60 
               
               
                   
                 S10 
                 −3.51E+01  
                 8.02E+00 
               
               
                 lens L5 
                 S11 
                 8.13E+01 
                 2.70E+00 
                 1.50 
                 81.61 
               
               
                   
                 S12 
                 −2.94E+01  
                 7.65E+00 
               
               
                 aperture S 
                 S13 
                 Infinite 
                 5.60E+00 
               
               
                 lens L6 
                 S14 
                 −7.41E+01  
                 8.00E−01 
                 1.61 
                 44.27 
               
               
                   
                 S15 
                 7.41E+01 
                 3.28E+00 
               
               
                 lens L7 
                 S16 
                 −9.91E+00  
                 8.76E−01 
                 1.67 
                 38.15 
               
               
                   
                 S17 
                 Infinite 
                 1.00E−03 
               
               
                 lens L8 
                 S18 
                 Infinite 
                 4.05E+00 
                 1.50 
                 81.61 
               
               
                   
                 S19 
                 −1.51E+01  
                 1.50E−01 
               
               
                 lens L9 
                 S20 
                 4.09E+01 
                 5.70E+00 
                 1.50 
                 81.61 
               
               
                   
                 S21 
                 −2.30E+01  
                 2.00E−01 
               
               
                 lens L10 
                 S22 
                 5.91E+01 
                 4.61E+00 
                 1.51 
                 63.75 
               
               
                   
                 S23 
                 −2.46E+01  
                 1.05E+01 
               
               
                 TSP device 120 
                 S24 
                 Infinite 
                 2.00E+00 
                 1.52 
                 58.59 
               
               
                   
                 S25 
                 Infinite 
                 1.60E+00 
               
               
                 prism 130 
                 S26 
                 Infinite 
                 1.20E+01 
                 1.52 
                 64.17 
               
               
                   
                 S27 
                 Infinite 
                 2.00E+00 
               
               
                 cover glass 140 
                 S28 
                 Infinite 
                 1.10E+00 
                 1.52 
                 64.17 
               
               
                   
                 S29 
                 Infinite 
                 3.03E−01 
               
               
                 DMD 150 
                 S30 
                 Infinite 
               
               
                   
               
            
           
         
       
     
       FIG. 4  is a schematic cross-sectional view of a projection lens according to a fourth embodiment of the disclosure. Pease refer to  FIG. 4  and Table 7 at the same time. In this embodiment, a projection lens  400  includes ten lenses, whose refractive powers are positive, negative, negative, positive, positive, negative, negative, positive, positive, and positive in sequence from a magnified side A 1  to a reduced side A 2 . In addition, an aperture S is provided between a lens L 5  and a lens L 6 . The distance between a lens L 7  and a lens L 8  is 0.001 mm. 
     In this embodiment, a lens L 1  is a plano-convex lens; a lens L 2  is a negative meniscus lens having a concave surface facing the reduced side A 2 ; a lens L 3  is a biconcave lens; a lens L 4  is a double convex lens; the lens L 5  is a double convex lens; the lens L 6  is a biconcave lens; the lens L 7  is a plano-concave lens; the lens L 8  is a plano-convex lens; a lens L 9  is a double convex lens; a lens L 10  is a double convex lens. 
     In the embodiment of Table 7, the total length of the projection lens  400  is 76.51 mm (which is the sum of the distances from a surface S 3  to a surface S 23  in Table 7). The viewing angle of the projection lens  400  is 50.08 degrees, and the effective focal length of the projection lens  400  is 12.7 mm. 
     Table 8 below shows the quadric coefficient value K and various aspheric coefficients of a surface S 22  and the surface S 23  of the lens L 10 . Please refer to the above formula (1) for the aspheric equation. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Aspheric coefficient 
               
            
           
           
               
               
               
            
               
                   
                 Surface S20 
                 Surface S21 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 K 
                 −2.41E+01 
                 −5.03E+00 
               
               
                   
                 A 
                 −5.25E−06 
                 −1.53E−05 
               
               
                   
                 B 
                 −2.11E−07 
                 −2.05E−07 
               
               
                   
                 C 
                  5.05E−09 
                  8.45E−09 
               
               
                   
                 D 
                 −7.27E−11 
                 −1.29E−10 
               
               
                   
                 E 
                  4.55E−13 
                  9.61E−13 
               
               
                   
                 F 
                 −2.28E−16 
                 −2.64E−15 
               
               
                   
                 G 
                 −5.61E−18 
                 −7.70E−19 
               
               
                   
                   
               
            
           
         
       
     
     In some embodiments of the present disclosure, the F-number of the projection lens is &gt;2.2, and the optical distortion is &lt;0.25%, preferably. In the lens structure, a single lens has a transmittance of &gt;80% under the irradiation of light at a wavelength of 365 nm, the lens has no cemented lens, and the distance of the first lens set and the second lens set relative to the imaging surface on the reduced side of the lens is variable. 
     In sum, since the transmittance of the projection lens of an embodiment of the present disclosure is greater than or equal to 75% at a wavelength of 365 nm, the projection lens is suitable for the ultraviolet wavelength band. Furthermore, as the second lens set includes an aspheric lens for eliminating optical distortion, the projection lens provides good optical effects. 
     Although the present disclosure is described with the above embodiments, it is possible for a person with ordinary knowledge in this technical field to make modifications without changing the essential conditions. For example, replace one lens with high curvature and large thickness with two lenses to increase the feasibility of manufacturing, or reduce the two lenses to one lens to reduce the size and costs. Therefore, those skilled in the art can adjust the number of lenses in the present disclosure in general without changing the essential conditions, and the number is not limited to the number of lenses shown in the embodiments. The number of lenses mentioned in the claims may be modified or replaced by those with general, common knowledge in the art with equivalent alternatives or obvious modifications that can be reasonably anticipated from the embodiments of the specification to have the same performances or purposes. The scope of protection of the disclosure shall still depend on the content of the claims.