Patent Publication Number: US-2022236538-A1

Title: Optical path folding element, imaging lens module and electronic device

Description:
RELATED APPLICATIONS 
     The present application is a continuation of the application Ser. No. 16/852,581, filed on Apr. 20, 2020, which is a continuation of the application Ser. No. 16/159,828, filed on Oct. 15, 2018, U.S. Pat. No. 10,663,697 issued on May 26, 2020, which is a continuation of the application Ser. No. 15/292,215, filed on Oct. 13, 2016, U.S. Pat. No. 10,133,037 issued on Nov. 20, 2018, and claims priority to Taiwan application serial number 105213079, filed on Aug. 26, 2016, the entire contents of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to an optical path folding element and imaging lens module. More particularly, the present disclosure relates to an optical path folding element and imaging lens module for an electronic device. 
     Description of Related Art 
     Due to the popularity of personal electronic products and mobile communication products having camera functionalities, such as smart phones and tablet personal computers, the demand for compact imaging lens modules has been increasing. However, conventional telephoto lens assembly is limited by surface shapes or materials of lens elements so that the volume cannot be reduced easily and price is too high, and further the application range is limited. Hence, one of the goals in the optical lens industry is to find out how to satisfy market specification and demand under the arrangement of telephoto characteristic, miniaturization and high image quality at the same time, and applicable to portable device, compact electronic device, zoom device, multiple lens assembly device and so on. 
     One of current solutions is favorable to utilize an optical path folding element, such as a prism, to fold and tilt an incident light ray for reducing the volume of the mechanism and an attenuation amount of the light ray efficiently. However, how to stabilize the engagement between the optical path folding element and other elements of the imaging lens module while minimizing the volume and keep a good alignment effect for providing high image quality is very important to date. 
     SUMMARY 
     According to one aspect of the present disclosure, an optical path folding element includes an incident surface, a path folding surface and an exiting surface. The incident surface allows a light ray to pass into the optical path folding element. The path folding surface folds the light ray from the incident surface. The exiting surface allows the light ray to pass through and depart from the optical path folding element. At least one of the incident surface and the exiting surface includes an optical effective portion and at least one engaging structure symmetrically disposed around the optical effective portion. The engaging structure includes an annular surface portion and an inclined surface portion. The annular surface portion surrounds the optical effective portion, and the inclined surface portion is located between the annular surface portion and the optical effective portion. An angle between the annular surface portion and the inclined surface portion is θ1, and the following condition is satisfied: 95 degrees&lt;θ1&lt;130 degrees. 
     According to another aspect of the present disclosure, an imaging lens module includes the abovementioned optical path folding element. 
     According to yet another aspect of the present disclosure, an electronic device includes the abovementioned imaging lens module. 
     According to further another aspect of the present disclosure, an optical path folding element includes an incident surface, a path folding surface and an exiting surface. The incident surface allows a light ray to pass into the optical path folding element. The path folding surface folds the light ray from the incident surface. The exiting surface allows the light ray to pass through and depart from the optical path folding element. At least one of the incident surface and the exiting surface includes an optical effective portion and at least one engaging structure symmetrically disposed around the optical effective portion. The engaging structure includes an annular surface portion and a conical surface. The annular surface portion surrounds the optical effective portion, and the conical surface is located between the annular surface portion and the optical effective portion. An angle between the annular surface portion and the conical surface is θ2, and the following condition is satisfied: 95 degrees&lt;θ2&lt;130 degrees. 
     According to still another aspect of the present disclosure, an imaging lens module includes the abovementioned optical path folding element. 
     According to yet another aspect of the present disclosure, an electronic device includes the abovementioned imaging lens module. 
     According to another aspect of the present disclosure, an imaging lens module includes the plastic barrel according to the foregoing aspect and an optical lens assembly, which is disposed in the plastic barrel and includes at least one lens element. 
     According to another aspect of the present disclosure, an electronic device includes the imaging lens module according to the foregoing aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1A  is a three dimensional view of an optical path folding element according to a 1st example of the present disclosure; 
         FIG. 1B  is a cross-sectional view of the optical path element according to the 1st example of the present disclosure; 
         FIG. 2A  is a three dimensional view of an optical path folding element according to a 2nd example of the present disclosure; 
         FIG. 2B  is a cross-sectional view of the optical path element according to the 2nd example of the present disclosure; 
         FIG. 3A  is a three dimensional view of an optical path folding element according to a 3rd example of the present disclosure; 
         FIG. 3B  is a cross-sectional view of the optical path element according to the 3rd example of the present disclosure; 
         FIG. 4A  is a three dimensional view of an optical path folding element according to a 4th example of the present disclosure; 
         FIG. 4B  is a cross-sectional view of the optical path element according to the 4th example of the present disclosure; 
         FIG. 5A  is a three dimensional view of an optical path folding element according to a 5th example of the present disclosure; 
         FIG. 5B  is a cross-sectional view of the optical path element according to the 5th example of the present disclosure; 
         FIG. 6  is a cross-sectional view of an imaging lens module according to a 6th example of the present disclosure; 
         FIG. 7  is a cross-sectional view of an imaging lens module according to a 7th example of the present disclosure; 
         FIG. 8  is a cross-sectional view of an imaging lens module according to an 8th example of the present disclosure; 
         FIG. 9  is a cross-sectional view of an imaging lens module according to a 9th example of the present disclosure; 
         FIG. 10  is a schematic view of an electronic device according to a 10th example of the present disclosure; 
         FIG. 11  is a schematic view of an electronic device according to an 11th example of the present disclosure; and 
         FIG. 12  is a schematic view of an electronic device according to a 12th example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides an optical path folding element, and the optical path folding element includes an incident surface, a path folding surface and an exiting surface. The incident surface allows a light ray to pass into the optical path folding element. The path folding surface folds the light ray from the incident surface. The exiting surface allows the light ray to pass through and depart from the optical path folding element. 
     At least one of the incident surface and the exiting surface includes an optical effective portion and at least one engaging structure. The engaging structure is symmetrically disposed around the optical effective portion. 
     According to one embodiment of the present disclosure, the engaging structure can include an annular surface portion and an inclined surface portion. The annular surface portion surrounds the optical effective portion, and the inclined surface portion is located between the annular surface portion and the optical effective portion. When an angle between the annular surface portion and the inclined surface portion is θ1, the following condition is satisfied: 95 degrees&lt;θ1&lt;130 degrees. Thus, the engagement effect of the engaging structure and the alignment effect of the optical path folding element can be improved. Preferably, the following condition is satisfied: 100 degrees&lt;θ1&lt;120 degrees. 
     According to another embodiment of the present disclosure, the engaging structure can include an annular surface portion and a conical surface. Preferably, the conical surface is a closed ring for increasing the convenience of the manufacturing process. 
     As mentioned above, the engaging structure is not limited to be disposed on the incident surface or the exiting surface. That is, the engaging structure can be disposed on both of the two surfaces according to the needs of the following application. Furthermore, there is a step between the annular surface portion and the optical effective portion due to the configuration of the inclined surface portion. Thus, the optical path folding element can be engaged with other elements in the imaging lens module by the step for increasing the stability of the whole structure. 
     Moreover, the optical path folding element can be made of a plastic material and is suitable to be applied in the imaging lens module which is non wide-angle and has the demand of compact size. 
     In particular, the optical path folding element can be made of a materiel with a lower Abbe number, such as the EP series of Mitsubishi gas chemical company, Inc (MGC) or the SP series of Teijin. Common optical plastic materials, such as the OKP series of Osaka gas chemical (OGC), also can be used in the present disclosure. 
     In the present disclosure, when the Abbe number of the optical path folding element is V, the following condition is satisfied: V&lt;32.0. Thus, differences between deflection paths of light rays, which have different wavelengths, in visible spectrum can be reduced. Preferably, the following condition is satisfied: V&lt;25.0. 
     In addition, the path folding surface of the present disclosure can include a metallic layer covered thereon for folding the light ray from the incident surface. Preferably, the metallic layer is an aluminum metallic layer suitable for applying to an optical system with imaging demands. The aluminum metallic layer is cheaper so that it is favorable for reducing the cost in the following application. Furthermore, the light ray is folded by 90 degrees when passing through the path folding surface for simplifying the optical structure. Moreover, a distance between a center of the incident surface and a center of the path folding surface can be equal to a distance between the center of the path folding surface and a center of the exiting surface. Accordingly, the optical path folding element can further fit the requests of the optical design, and thus, it will reduce the opportunities of sacrificing the optical specifications under the specific condition. 
     In details, an area occupied by the optical effective portion is equal to or more than 40% of a total area of the incident surface or the exiting surface for expanding the light absorption range and maintaining the requirements for high resolution and image quality of present compact imaging lens modules. In addition, the optical effective portion can be a plane, spherical or aspheric area. Moreover, the appearance of the optical effective portion can be polygon-shaped, such as rectangular or octagonal. 
     When a width of the abovementioned inclined surface portion is L1, the following condition is satisfied: 0.07 mm&lt;L1&lt;0.35 mm. Thus, the stability of the engagement between the optical path folding element and other elements of the imaging lens module can be enhanced while compact size of the optical path folding element is maintained. In another embodiment of the present disclosure, when a width of the conical surface is L2, the following condition is satisfied: 0.07 mm&lt;L2&lt;0.35 mm. 
     The present disclosure further provides an imaging lens module including the optical path folding element according to any one of the two embodiments as mentioned above. The optical path folding element can be engaged with at least one lens element or an opaque member of the imaging lens module through the engaging structure thereof. When the optical path folding element is engaged with the lens element, the optical path folding element can be aligned to an optical axis of the lens element for increasing the optical accuracy and maintaining high image quality. When the optical path folding element is engaged with the opaque member, the stability of the whole imaging lens module can be increased, and image quality of the imaging lens module will not be affected due to the collision in the external environment. In particular, the opaque member can be but not limited to a cover, a base or a barrel of the imaging lens module. Furthermore, the imaging lens module can be applied to 3D (three-dimensional) image capturing applications, in products such as digital cameras, mobile devices, digital tablets, smart TVs, surveillance systems, motion sensing input devices, driving recording systems, rearview camera systems, and wearable devices. 
     Accordingly, an electronic device is further provided in the present disclosure for satisfying the requirements for high resolution and image quality of present compact imaging lens modules. Preferably, the electronic device can further include but not limited to a display, a control unit, a storage unit, a random access memory unit (RAM) or a read-only memory unit (ROM) or a combination thereof. 
     According to the aforementioned embodiments, a plurality of examples are provided in cooperated with figures for details. 
     1st Embodiment 
     Please refer to  FIG. 1A  and  FIG. 1B .  FIG. 1A  is a three dimensional view of an optical path folding element  1000  according to a 1st example of the present disclosure, and  FIG. 1B  is a cross-sectional view of the optical path element  1000  according to the 1st example of the present disclosure. As shown in  FIG. 1A , the optical path folding element  1000  of the 1st example includes an incident surface  1100 , a path folding surface  1200  and an exiting surface  1300 . The light ray I passes through the incident surface  1100  to enter the optical path folding element  1000 . After passing through the path folding surface  1200 , the light ray I has a folding angle of 90 degrees and passes through the exiting surface  1300  to depart from the optical path folding element  1000 . 
     In particular, the optical path folding element  1000  is a triangular prism, and the optical path folding element  1000  is made of a plastic material. Thereby, the optical path folding element  100  can be applied in an imaging lens module which has the demand of compact size. 
     In the 1st example, the exiting surface  1300  of the optical path folding element  1000  includes an optical effective portion  1400  and an engaging structure  1500 . The engaging structure  1500  includes an annular surface portion  1501  and an inclined surface portion  1502 . As shown in  FIG. 1A , the optical effective portion  1400  is a rectangular-shaped portion. The annular surface portion  1501  is symmetrically disposed around the optical effective portion  1400 , that is, the annular surface portion  1501  surrounds the optical effective portion  1400  continuously. The inclined surface portion  1502  is located between the annular surface portion  1501  and the optical effective portion  1400 . More particularly, the inclined surface portion  1502  includes four trapezoidal surfaces corresponding to the optical effective portion  1400  which is the rectangular-shaped portion. Each of the four trapezoidal surfaces is located between each side of the optical effective portion  1400  and the annular surface portion  1501 , respectively. 
     As shown in  FIG. 1B , the annular surface portion  1501  and the exiting surface  1300  are coplanar. The optical effective portion  1400  and the inclined surface portion  1502  protrude from the exiting surface  1300 , that is, there is a step between the optical effective portion  1400  and the annular surface portion  1501  due to the configuration of the inclined surface portion  1502 . Accordingly, as shown in the cross-sectional view of the optical path folding element  1000 , the exiting surface  1300 , the optical effective portion  1400  and the inclined surface portion  1502  form a trapezoid protrusion. A top surface of the trapezoid protrusion is the optical effect portion  1400 , and a sidewall of the trapezoid protrusion is one of the trapezoidal surfaces of the inclined surface portion  1502 . Preferably, an angle between the annular surface portion  1501  and the inclined surface portion  1502  is θ1, and a width of the inclined surface portion  1502  is L1. When the angle θ1 and the width L1 of the inclined surface portion  1502  satisfy a specific condition, the engagement effect of the engaging structure  1500  and the alignment effect of the optical path folding element  1000  can be improved for maintaining high structural stability and image quality under the request of miniaturization. 
     Please refer to Table 1 as follows, the conditions, such as the material and the Abbe number of the optical path folding element  1000 , a ratio between an area occupied by the optical effective portion  1400  and a total area of the exiting surface  1300 , the angle θ1 between the annular surface portion  1501  and the inclined surface portion  1502  and the width L1 of the inclined surface portion  1502 , are listed therein. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 (1st Example) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Abbe number 
                 20.4 
               
               
                   
                 Material 
                 Plastic 
               
               
                   
                 Manufactor/Product series 
                 MGC/EP 
               
               
                   
                 Ratio between an area occupied by optical 
                 50 
               
               
                   
                 effective portion and a total area of exiting 
                   
               
               
                   
                 surface (%) 
                   
               
               
                   
                 θ1 
                 110 
               
               
                   
                 (degrees) 
                   
               
               
                   
                 L1  
                 0.21 
               
               
                   
                 (mm) 
               
               
                   
                   
               
            
           
         
       
     
     The engaging structure  1500  can be manufactured through an injection molding process by a mold, which has an appearance corresponding to the abovementioned features of the engaging structure  1500 , at the same time with the optical path folding element  1000 . The engaging structure  1500  of the optical path folding element  1000  also can be manufactured by pasting a trapezoid protrusion on the exiting surface  1300 , and preferably the materials of the trapezoid protrusion can be the same with the materials of the optical path folding element  1000 . However, the manufacturing process of the optical path folding element  1000  is not the main feature of the present disclosure and will not be further described herein. 
     2nd Example 
     Please refer to  FIG. 2A  and  FIG. 2B .  FIG. 2A  is a three dimensional view of an optical path folding element  2000  according to a 2nd example of the present disclosure, and  FIG. 2B  is a cross-sectional view of the optical path element  2000  according to the 2nd example of the present disclosure. As shown in  FIG. 2A , the optical path folding element  2000  of the 2nd example is a triangular prism and includes an incident surface  2100 , a path folding surface  2200  and an exiting surface  2300 . The light ray I passes through the incident surface  2100  to enter the optical path folding element  2000 . After passing through the path folding surface  2200 , the light ray I has a folding angle of 90 degrees and passes through the exiting surface  2300  to depart from the optical path folding element  2000 . 
     In the 2nd example, the exiting surface  2300  of the optical path folding element  2000  includes an optical effective portion  2400  and an engaging structure  2500 . In particular, the optical effective portion  2400  is a rectangular-shaped portion. The engaging structure  2500  includes an annular surface portion  2501  and an inclined surface portion  2502 . The annular surface portion  2501  is symmetrically disposed around the optical effective portion  2400 , that is, the annular surface portion  2501  surrounds the optical effective portion  2400  continuously. The inclined surface portion  2502  is located between the annular surface portion  2501  and the optical effective portion  2400 . More particularly, the inclined surface portion  2502  includes four trapezoidal surfaces corresponding to the optical effective portion  2400  which is the rectangular-shaped portion. Each of the four trapezoidal surfaces is located between each side of the optical effective portion  2400  and the annular surface portion  2501 , respectively. 
     As shown in  FIG. 2B , the annular surface portion  2501  and the exiting surface  2300  are coplanar. The optical effective portion  2400  and the inclined surface portion  2502  protrude from the exiting surface  2300 , and therefore, there is a step between the optical effective portion  2400  and the annular surface portion  2501  due to the configuration of the inclined surface portion  2502 . Accordingly, as shown in the cross-sectional view of the optical path folding element  2000 , the exiting surface  2300 , the optical effective portion  2400  and the inclined surface portion  2502  form a trapezoid protrusion. A top surface of the trapezoid protrusion is the optical effect portion  2400 , and a sidewall of the trapezoid protrusion is one of the trapezoidal surfaces of the inclined surface portion  2502 . Preferably, an angle between the annular surface portion  2501  and the inclined surface portion  2502  is θ1, and a width of the inclined surface portion  2502  is L1. When the angle θ1 and the width L1 of the inclined surface portion  2502  satisfy a specific condition, the engagement effect of the engaging structure  2500  and the alignment effect of the optical path folding element  2000  can be improved for maintaining high structural stability and image quality under the request of miniaturization. 
     Please refer to Table 2, the conditions, such as the material and the Abbe number of the optical path folding element  2000 , a ratio between an area occupied by the optical effective portion  2400  and a total area of the exiting surface  2300 , the angle θ1 between the annular surface portion  2501  and the inclined surface portion  2502  and the width L1 of the inclined surface portion  2502 , are listed therein. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 (2nd Example) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Abbe number 
                 19.5 
               
               
                   
                 Material 
                 Plastic 
               
               
                   
                 Manufactor/Product series 
                 MGC/EP 
               
               
                   
                 Ratio between an area occupied by optical 
                 82 
               
               
                   
                 effective portion and a total area of exiting 
                   
               
               
                   
                 surface (%) 
                   
               
               
                   
                 θ1 
                 105 
               
               
                   
                 (degrees) 
                   
               
               
                   
                 L1 
                 0.21 
               
               
                   
                 (mm) 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 2, it is different from the 1st example that a ratio between an area occupied by the optical effective portion  2400  and a total area of the exiting surface  2300  is 82% to increase the light absorption range efficiently for satisfying the requirements for high resolution and image quality of present compact optical elements. 
     3rd Example 
     Please refer to  FIG. 3A  and  FIG. 3B .  FIG. 3A  is a three dimensional view of an optical path folding element  3000  according to a 3rd example of the present disclosure, and  FIG. 3B  is a cross-sectional view of the optical path element  3000  according to the 3rd example of the present disclosure. As shown in  FIG. 3A , the optical path folding element  3000  of the 3rd example is a triangular prism and includes an incident surface  3100 , a path folding surface  3200  and an exiting surface  3300 . The light ray I passes through the incident surface  3100  to enter the optical path folding element  3000 . After passing through the path folding surface  3200 , the light ray I has a folding angle of 90 degrees and passes through the exiting surface  3300  to depart from the optical path folding element  3000 . 
     In the 3rd example, the exiting surface  3300  of the optical path folding element  3000  includes an optical effective portion  3400  and an engaging structure  3500 . It is different from the 1st example that the optical effective portion  3400  is an octagonal-shaped portion. The engaging structure  3500  includes an annular surface portion  3501  and an inclined surface portion  3502 . The annular surface portion  3501  is symmetrically disposed around the optical effective portion  3400 , that is, the annular surface portion  3501  surrounds the optical effective portion  3400  continuously. The inclined surface portion  3502  is located between the annular surface portion  3501  and the optical effective portion  3400 . More particularly, the inclined surface portion  3502  includes eight trapezoidal surfaces corresponding to the optical effective portion  3400  which is the octagonal-shaped portion. Each of the eight trapezoidal surfaces is located between each side of the optical effective portion  3400  and the annular surface portion  3501 , respectively. 
     As shown in  FIG. 3B , the annular surface portion  3501  and the exiting surface  3300  are coplanar. The optical effective portion  3400  and the inclined surface portion  3502  protrude from the exiting surface  3300 , and therefore, there is a step between the optical effective portion  3400  and the annular surface portion  3501  due to the configuration of the inclined surface portion  3502 . Preferably, an angle between the annular surface portion  3501  and the inclined surface portion  3502  is θ1, and a width of the inclined surface portion  3502  is L1. When the angle θ1 and the width L1 of the inclined surface portion  3502  satisfy a specific condition, the engagement effect of the engaging structure  3500  and the alignment effect of the optical path folding element  3000  can be improved for maintaining high structural stability and image quality under the request of miniaturization. 
     Please refer to Table 3, the conditions, such as the material and the Abbe number of the optical path folding element  3000 , a ratio between an area occupied by the optical effective portion  3400  and a total area of the exiting surface  3300 , the angle θ1 between the annular surface portion  3501  and the inclined surface portion  3502  and the width L1 of the inclined surface portion  3502 , are listed therein. 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 (3rd Example) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Abbe number 
                 23.4 
               
               
                   
                 Material 
                 Plastic 
               
               
                   
                 Manufactor/Product series 
                 OGC/OKP 
               
               
                   
                 Ratio between an area occupied by optical 
                 79 
               
               
                   
                 effective portion and a total area of exiting 
                   
               
               
                   
                 surface (%) 
                   
               
               
                   
                 θ1 
                 115 
               
               
                   
                 (degrees) 
                   
               
               
                   
                 L1 
                 0.22 
               
               
                   
                 (mm) 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 3, it is different from the 1st example that a ratio between an area occupied by the optical effective portion  3400  and a total area of the exiting surface  3300  is 79% to increase the light absorption range efficiently for satisfying the requirements for high resolution and image quality of present compact optical elements. Moreover, in the 3rd example, the angle θ1 between the annular surface portion  3501  and the inclined surface portion  3502  is larger than that of the 1st example so that the stability of the whole imaging lens module using thereof will be enhanced. 
     4th Example 
     Please refer to  FIG. 4A  and  FIG. 4B .  FIG. 4A  is a three dimensional view of an optical path folding element  4000  according to a 4th example of the present disclosure, and  FIG. 4B  is a cross-sectional view of the optical path element  4000  according to the 4th example of the present disclosure. As shown in  FIG. 4A , the optical path folding element  4000  of the 4th example is a triangular prism and includes an incident surface  4100 , a path folding surface  4200  and an exiting surface  4300 . The light ray I passes through the incident surface  4100  to enter the optical path folding element  4000 . After passing through the path folding surface  4200 , the light ray I has a folding angle of 90 degrees and passes through the exiting surface  4300  to depart from the optical path folding element  4000 . 
     In the 4th example, the exiting surface  4300  of the optical path folding element  4000  includes an optical effective portion  4400  and an engaging structure  4500 . The optical effective portion  4400  of the 4th example is a circular-shaped portion, and further, the engaging structure  4500  includes an annular surface portion  4501  and a conical surface  4502 . The annular surface portion  4501  surrounds the optical effective portion  4400 , and the conical surface  4502  is located between the annular surface portion  4501  and the optical effective portion  4400 . Preferably, the conical surface  4502  is a closed ring for increasing the convenience of the manufacturing process. 
     As shown in  FIG. 4B , the annular surface portion  4501  and the exiting surface  4300  are coplanar. The optical effective portion  4400  and the conical surface  4502  protrude from the exiting surface  4300 , and therefore, there is a step between the optical effective portion  4400  and the annular surface portion  4501  due to the configuration of the conical surface  4502 . Preferably, an angle between the annular surface portion  4501  and the conical surface  4502  is θ2, and a width of the conical surface  4502  is L2. When the angle θ2 and the width L2 of the conical surface  4502  satisfy a specific condition, the engagement effect of the engaging structure  4500  and the alignment effect of the optical path folding element  4000  can be improved for maintaining high structural stability and image quality under the request of miniaturization. 
     Please refer to Table 4, the conditions, such as the material and the Abbe number of the optical path folding element  4000 , a ratio between an area occupied by the optical effective portion  4400  and a total area of the exiting surface  4300 , the angle θ2 between the annular surface portion  4501  and the conical surface  4502  and the width L2 of the conical surface  4502 , are listed therein. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 (4th Example) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Abbe number 
                 23.3 
               
               
                   
                 Material 
                 Plastic 
               
               
                   
                 Manufactor/Product series 
                 Teijin/SP 
               
               
                   
                 Ratio between an area occupied by optical 
                 45 
               
               
                   
                 effective portion and a total area of exiting 
                   
               
               
                   
                 surface (%) 
                   
               
               
                   
                 ⊖2 
                 110 
               
               
                   
                 (degrees) 
                   
               
               
                   
                 L2  
                 0.32 
               
               
                   
                 (mm) 
               
               
                   
                   
               
            
           
         
       
     
     5th Example 
     Please refer to  FIG. 5A  and  FIG. 5B .  FIG. 5A  is a three dimensional view of an optical path folding element  5000  according to a 5th example of the present disclosure, and  FIG. 5B  is a cross-sectional view of the optical path element  5000  according to the 5th example of the present disclosure. As shown in  FIG. 5A , the optical path folding element  5000  of the 5th example is a triangular prism and includes an incident surface  5100 , a path folding surface  5200  and an exiting surface  5300 . The light ray I passes through the incident surface  5100  to enter the optical path folding element  5000 . After passing through the path folding surface  5200 , the light ray I has a folding angle of 90 degrees and passes through the exiting surface  5300  to depart from the optical path folding element  5000 . 
     In the 5th example, the exiting surface  5300  of the optical path folding element  5000  includes an optical effective portion  5400  and an engaging structure  5500 . In particular, the optical effective portion  5400  of the 5th example is a circular-shaped portion. The engaging structure  5500  includes an annular surface portion  5501  and a conical surface  5502 . Moreover, the annular surface portion  5501  surrounds the optical effective portion  5400 , and the conical surface  5502  is located between the annular surface portion  5501  and the optical effective portion  5400 . Preferably, the conical surface  5502  is a closed ring for increasing the convenience of the manufacturing process. 
     As shown in  FIG. 5B , the annular surface portion  5501  and the exiting surface  5300  are also coplanar. However, the optical effective portion  5400  and the conical surface  5502  are recessed into the exiting surface  5300  for further minimizing an occupied space of the optical path folding element  5000  and satisfying the demand of compact size. In details, the optical path folding element  5000  has a circular recess formed on the exiting surface  5300 . A bottom surface of the circular recess is the optical effective portion  5400 , and further, a sidewall of the circular recess is the conical surface  5502 . Preferably, an angle between the annular surface portion  5501  and the conical surface  5502  is θ2, and a width of the conical surface  5502  is L2. When the angle θ2 and the width L2 of the conical surface  5502  satisfy a specific condition, the engagement effect of the engaging structure  5500  and the alignment effect of the optical path folding element  5000  can be improved for maintaining the high structural stability and image quality under the request of miniaturization. 
     Please refer to Table 5, the conditions, such as the material and the Abbe number of the optical path folding element  5000 , a ratio between an area occupied by the optical effective portion  5400  and a total area of the exiting surface  5300 , the angle θ2 between the annular surface portion  5501  and the conical surface  5502  and the width L2 of the conical surface  5502 , are listed therein. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 (5th Example) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Abbe number 
                 21.4 
               
               
                   
                 Material 
                 Plastic 
               
               
                   
                 Manufactor/Product series 
                 OGC/OKP 
               
               
                   
                 Ratio between an area occupied by optical 
                 29 
               
               
                   
                 effective portion and a total area of exiting 
                   
               
               
                   
                 surface (%) 
                   
               
               
                   
                 ⊖2 
                 110 
               
               
                   
                 (degrees) 
                   
               
               
                   
                 L2 
                 0.32 
               
               
                   
                 (mm) 
               
               
                   
                   
               
            
           
         
       
     
     6th Example 
     Please refer to  FIG. 6 , which is a cross-sectional view of an imaging lens module  100  according to a 6th example of the present disclosure. As shown in  FIG. 6 , the imaging lens module  100  includes an opaque member  110 , an optical lens assembly  120  and an optical path folding element  6000 . The optical lens assembly  120  and the optical path folding element  6000  are located inside the opaque member  110 . 
     In the 6th example, the opaque member  110  is a cover of the imaging lens module  100  for protecting the assembled elements from being affected by the external environment. In particular, the opaque member  110  includes an object-end portion  111 , a tube portion  112  and an image-end portion  113 . The object-end portion  111  includes an object-end opening  111   a , and the image-end portion  113  includes an image-end opening  113   a.    
     In details, the object-end portion  111  faces toward an imaged object (not shown herein) and is provided for disposing the optical path folding element  6000  therein. The tube portion  112  is provided for disposing a plurality of lens elements therein, and the image-end portion  113  is closest to an image surface P in the imaging lens module  100 . 
     In the 6th example, the optical lens assembly  120  includes, in order from the object-end portion  111  to the image-end portion  113  along an optical axis, a first lens element  121 , a second lens element  122 , a third lens element  123  and a fourth lens element  124 . 
     In addition, the lens element of the optical lens assembly  120  can be made of plastic or glass materials. When the lens element is made of the plastic material, manufacturing costs can be effectively reduced. When the lens elements are made of glass materials, the distribution of the refractive power of the optical photographing assembly may be more flexible to design. Moreover, the optical lens assembly  120  can include other optical elements (their reference numerals are omitted), such as spacers, light blocking sheets and so on. 
     According to  FIG. 6 , the structure of the optical path folding element  6000  of the 6th example is approximately the same with the 1st example, the 2nd example and the 3rd example. That is, the optical path folding element  6000  is a triangular prism and includes an incident surface  6100 , a path folding surface  6200  and an exiting surface  6300 . Accordingly, the light ray passes through the object-end opening  111   a  and the incident surface  6100  to enter the optical path folding element  6000 , which is located in the object-end portion  111 . After passing through the path folding surface  6200 , the folded light ray departs from the optical path folding element  6000  through the exiting surface  6300  and then enters into the optical lens assembly  120 , which is located in the tube portion  112 . Finally, the light ray departs from the optical lens assembly  120  and passes through the image-end opening  113   a  to image on the image surface P. 
     The difference of the 6th example is that the incident surface  6100  of the optical path folding element  6000  includes an optical effective portion  6400  and an engaging structure  6500 . In particular, the engaging structure  6500  includes an annular surface portion  6501  and an inclined surface portion  6502 . The inclined surface portion  6502  is located between the annular surface portion  6501  and the optical effective portion  6400 . Thus, there is a step between the optical effective portion  6400  and the annular surface portion  6501  due to the configuration of the inclined surface portion  6502 . 
     As shown in a partial enlarged view of  FIG. 6 , the optical path folding element  6000  is engaged with two sides of the object-end opening  111   a  of the opaque member  110  through the step which is between the optical effective portion  6400  and the annular surface portion  6501 . The two sides of the object-end opening  111   a  can further include at least one engaging member (not shown herein) for stabilizing the engagement between the optical path folding element  6000  and the opaque member  110 . Furthermore, an angle θ1 between the annular surface portion  6501  and the inclined surface portion  6502  is 105 degrees, and a width L1 of the inclined surface portion  6502  is 0.11 mm. Thus, the stability of the whole structure can be enhanced by the engagement between the engaging structure  6500  of the optical path folding element  6000  and the opaque member  110 . 
     7th Example 
     Please refer to  FIG. 7 , which is a cross-sectional view of an imaging lens module  200  according to a 7th example of the present disclosure. As shown in  FIG. 7 , the imaging lens module  200  includes an opaque member  210 , an optical lens assembly  220  and an optical path folding element  7000 . The optical lens assembly  220  and the optical path folding element  7000  are located inside the opaque member  210 . 
     In the 7th example, the opaque member  210  is a cover of the imaging lens module  200  for protecting the assembled elements from being affected by the external environment. In particular, the opaque member  210  includes an object-end portion  211 , a tube portion  212  and an image-end portion  213 . 
     In details, the object-end portion  211  faces toward an imaged object (not shown herein) and is provided for disposing the optical path folding element  7000  therein. The tube portion  212  is provided for disposing a plurality of lens elements therein, and the image-end portion  213  is closest to an image surface P in the imaging lens module  200 . 
     In the 7th example, the optical lens assembly  220  includes, in order from the object-end portion  211  to the image-end portion  213  along an optical axis, a first lens element  221 , a second lens element  222 , a third lens element  223  and a fourth lens element  224 . The optical lens assembly  220  can include other optical elements (their reference numerals are omitted), such as spacers, light blocking sheets and so on. 
     As shown in  FIG. 7 , the structure of the optical path folding element  7000  of the 7th example is approximately the same with the 1st example, the 2nd example and the 3rd example. That is, the optical path folding element  7000  is a triangular prism and includes an incident surface  7100 , a path folding surface  7200  and an exiting surface  7300 . Moreover, the exiting surface  7300  of the optical path folding element  7000  includes an optical effective portion  7400  and an engaging structure  7500 . The engaging structure  7500  includes an annular surface portion  7501  and an inclined surface portion  7502 . In particular, the inclined surface portion  7502  is located between the annular surface portion  7501  and the optical effective portion  7400 . Thus, there is a step between the optical effective portion  7400  and the annular surface portion  7501  due to the configuration of the inclined surface portion  7502 . 
     Accordingly, the light ray passes through the incident surface  7100  of the optical path folding element  7000 , which is located in the object-end portion  111 , to enter therein and is folded by 90 degrees using the path folding surface  7200 . Then, the folded light ray departs from the optical path folding element  7000  through the exiting surface  7300  and then enters into the optical lens assembly  220 , which is located in the tube portion  212 . Finally, the light ray departs from the optical lens assembly  220  and passes through the image-end portion  213  to image on the image surface P. 
     The difference of the 7th example is that the central portion of the optical effective portion  6400  is a concave spherical surface. In addition, as shown in a partial enlarged view of  FIG. 7 , there are a plurality of engaging members  212   a  formed at a connection area between the tube portion  212  and the object-end portion  211  of the opaque member  210 . Thus, the optical path folding element  7000  can be engaged with the engaging elements  212   a  through the step which is between the optical effective portion  7400  and the annular surface portion  7501 . In particular, the aforementioned engaging element  212   a  can be but not limited to a protrusion. More particularly, the engaging elements  212   a  also can be an engaging structure having a square opening. Furthermore, the engaging elements  212   a  can be integrated with the opaque member  210 . Preferably, an angle θ1 between the annular surface portion  7501  and the inclined surface portion  7502  is 115 degrees, and a width L1 of the inclined surface portion  7502  is 0.19 mm. Thus, the stability of the whole structure can be improved. 
     8th Example 
     Please refer to  FIG. 8 , which is a cross-sectional view of an imaging lens module  300  according to an 8th example of the present disclosure. As shown in  FIG. 8 , the imaging lens module  300  includes a cover  310 , an optical lens assembly  320  and an optical path folding element  8000 . The optical lens assembly  320  and the optical path folding element  8000  are located inside the cover  310 . In particular, the cover  310  is provided for protecting the assembled elements from being affected by the external environment. 
     In the 8th example, the optical lens assembly  320  includes four lens elements. In particular, the elements covered by the cover  310  of the imaging lens module  300  are, in order from an object side to an image side along an optical axis, the optical path folding element  8000 , a first lens element  321 , a second lens element  322 , a third lens element  323  and a fourth lens element  324  of the optical lens assembly  320 . The optical lens assembly  320  can include other optical elements (their reference numerals are omitted), such as spacers, light blocking sheets and so on. 
     According to  FIG. 8 , the structure of the optical path folding element  8000  of the 8th example is approximately the same with the 4th example. That is, the optical path folding element  8000  is a triangular prism and includes an incident surface  8100 , a path folding surface  8200  and an exiting surface  8300 . Moreover, the exiting surface  8300  of the optical path folding element  8000  includes an optical effective portion  8400  and an engaging structure  8500 . The engaging structure  8500  includes an annular surface portion  8501  and a conical surface  8502 . In particular, the conical surface  8502  is located between the annular surface portion  8501  and the optical effective portion  8400 . Thus, there is a step between the optical effective portion  8400  and the annular surface portion  8501  due to the configuration of the conical surface  8502 . 
     Accordingly, the light ray passes through the incident surface  8100  to enter the optical path folding element  8000  and is folded by 90 degrees using the path folding surface  8200 . Then, the folded light ray departs from the optical path folding element  8000  through the exiting surface  8300  and then enters into the optical lens assembly  320 . Finally, the light ray departs from the optical lens assembly  320  to image on the image surface P. 
     In the 8th example, the optical path folding element  6000  is engaged with the opaque member  110  of the imaging lens module  100 . However, in the 8th example, the optical path folding element  8000  is engaged with the first lens element  321  of the optical lens assembly  320 . In details, another engaging structure (not shown herein) can be further formed in an off-axial region of the first lens element  321  to be engaged with the engaging structure  8500  of the optical path folding element  8000  for fixing the optical path folding element  8000 . 
     As shown in a partial enlarged view of  FIG. 8 , the first lens element  321  is a concave lens element. In addition, the first lens element  321  can be fixed in the cover  310  by the structural design of the cover  310 . Thus, the optical path folding element  8000  leans against two sides of the concave surface of the first lens element  321  by the step, which is between the optical effective  8400  and the annular surface portion  8501 , for fixing. In particular, an angle θ2 between the annular surface portion  8501  and the conical surface  8502  is 105 degrees, and a width L2 of the conical surface  8502  is 0.11 mm. Thus, the stability of the whole structure can be improved. 
     9th Example 
     Please refer to  FIG. 9 , which is a cross-sectional view of an imaging lens module  400  according to a 9th example of the present disclosure. As shown in  FIG. 9 , the imaging lens module  400  can include a cover  410 , an optical lens assembly  420  and an optical path folding element  9000 . The optical lens assembly  420  and the optical path folding element  9000  are located inside the cover  410 . In particular, the cover  410  is provided for protecting the assembled elements from being affected by the external environment. 
     In the 9th example, the optical lens assembly  420  includes four lens elements. In particular, the elements covered by the cover  410  of the imaging lens module  400  are, in order from an object side to an image side along an optical axis, the optical path folding element  9000 , a first lens element  421 , a second lens element  422 , a third lens element  423  and a fourth lens element  424  of the optical lens assembly  420 . The optical lens assembly  420  can include other optical elements (their reference numerals are omitted), such as spacers, light blocking sheets and so on. 
     According to  FIG. 9 , the structure of the optical path folding element  9000  of the 9th example is approximately the same with the 5th example. That is, the optical path folding element  9000  is a triangular prism and includes an incident surface  9100 , a path folding surface  9200  and an exiting surface  9300 . Moreover, the exiting surface  9300  of the optical path folding element  9000  includes an optical effective portion  9400  and an engaging structure  9500 . The engaging structure  9500  includes an annular surface portion  9501  and a conical surface  9502 . It is noted that, in the 9th example, the optical effective portion  9400  and the conical surface  9502  are recessed into the exiting surface  9300 . 
     Accordingly, the light ray passes through the incident surface  9100  to enter the optical path folding element  9000  and is folded by 90 degrees using the path folding surface  9200 . Then, the folded light ray departs from the optical path folding element  9000  through the exiting surface  9300  and then enters into the optical lens assembly  420 . Finally, the light ray departs from the optical lens assembly  420  to image on the image surface P. 
     In the 9th example, the optical path folding element  9000  is engaged with the first lens element  421  of the optical lens assembly  420  as same as the 8th example. However, an annular notch  421   a  is formed in the off-axial region (that is, the two sides of the concave surface) of the lens element although the first lens element  421  is also a concave lens element as same as the 8th example. As shown in a partial enlarged view of  FIG. 9 , the optical path folding element  9000  is engaged with the annular notch  421   a  of the first lens element  421  by the step, which is between the optical effective  9400  and the annular surface portion  9501 , for fixing. In details, the step is able to be cooperated with the annular notch  421   a  because the conical surface  9502  is the closed ring. In particular, an angle θ2 between the annular surface portion  9501  and the conical surface  9502  is 115 degrees, and a width L2 of the conical surface  9502  is 0.19 mm. Thus, the stability of the whole structure can be improved. 
     10th Example 
     Please refer to  FIG. 10 , which is a schematic view of an electronic device  10  according to a 10th example of the present disclosure. The electronic device  10  of the 10th embodiment is a smart phone and includes an imaging lens module  500 . The imaging lens module  500  can be the abovementioned imaging lens module according to any of the 6th example, the 7th example, the 8th example and the 9th example. The imaging lens module  500  includes an optical path folding element (not shown herein) according to the present disclosure. Therefore, it is favorable for enhancing the image quality so as to satisfy the requirements of high-end optical systems with camera functionalities. Furthermore, the electronic device  10  can further include an image sensor (not shown herein), in which the image sensor is disposed on an image surface (not shown herein) of the imaging lens module  500 . Preferably, the electronic device  10  can further include but not limited to a display, a control unit, a storage unit, a random access memory unit (RAM), a read-only memory unit (ROM) or a combination thereof. 
     11th Example 
     Please refer to  FIG. 11 , which is a schematic view of an electronic device  20  according to an 11th example of the present disclosure. The electronic device  20  of the 11th example is a tablet. The electronic device  20  includes an imaging lens module  600 . The imaging lens module  600  can be the abovementioned imaging lens module according to any of the 6th example, the 7th example, the 8th example and the 9th example. The imaging lens module  600  includes an optical path folding element (not shown herein) according to the present disclosure. 
     12th Example 
     Please refer to  FIG. 12 , which is a schematic view of an electronic device  30  according to a 12th example of the present disclosure. The electronic device  30  of the 12th example is a wearable device. The electronic device  30  includes an imaging lens module  700 . The imaging lens module  700  can be the abovementioned imaging lens module according to any of the 6th example, the 7th example, the 8th example and the 9th example. The imaging lens module  700  includes an optical path folding element (not shown herein) according to the present disclosure. 
     Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.