Patent Publication Number: US-2023140383-A1

Title: Lens barrel and optical recognition device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Taiwan Patent Application No. 110140066, filed on Oct. 28, 2021, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a lens barrel and an optical recognition device, and in particular, to a lens barrel and an optical recognition device, wherein an annular groove of the lens barrel can reduce the reflection of non-imaging light projected onto an object-side surface of the lens barrel, so as to reduce the stray light. 
     Related Art 
     With the popularization of electronic products equipped with imaging devices (such as mobile phones, tablet computers, and the like), the rise of miniaturized optical lens module has also been driven, and the demand for the miniaturized optical lens module having a high resolution and excellent imaging quality has also risen sharply. 
     The lens barrel is usually used to carry optical lenses in the optical lens module and provide a distance between any two optical lenses. The surface properties of the lens barrel are critical to the effect of suppressing the stray light. Therefore, the surface properties of the lens barrel jointly affect the imaging quality of the optical lens module. A conventional lens barrel is usually manufactured by means of plastic injection moulding, and has a smooth and bright surface and high reflectivity. Therefore, the stray light cannot be effectively suppressed. 
     Moreover, in the current mobile phone, an image sensor of the optical lens module is no longer disposed on the back side of the mobile phone. Instead, the image sensor of the optical lens module is disposed under the screen of the mobile phone (i.e., the screen of the display), and is sensed by means of the optical recognition technology. However, when the light L passes through a non-optical portion (for example, the light path is a lens barrel  91 →a transparent plate  92  (i.e., a display panel)→an image sensor  93 , as shown in  FIG.  1   ), it is easy for a flat object-side surface  911  of the lens barrel  91  to form the stray light, to affect the recognition accuracy of the image sensor  93 , and to cause the misjudgement or failure of fingerprint recognition. 
     Therefore, it is necessary to provide a lens barrel and an optical recognition device, so as to resolve the foregoing problems. 
     SUMMARY 
     An objective of the present disclosure is to provide a lens barrel and an optical recognition device. In this way, an annular groove of the lens barrel can reduce the reflection of non-imaging light projected onto an object-side surface of the lens barrel, so as to reduce the stray light. 
     To achieve the above objective, the present disclosure provides a lens barrel, defining a central axis, having an accommodating space, and comprising: an object-side opening and an object-side end portion, both located at one end of the central axis, wherein the object-side end portion surrounds the object-side opening and has an object-side surface, the object-side surface comprises an annular groove, a radial cross-section of the annular groove has a first line segment and a second line segment, the first line segment is farther away from the central axis than the second line segment, the first line segment and the second line segment intersect at a first point, and a straight line parallel to the central axis is defined to pass through the first point, a first included angle is formed between the first line segment and the straight line, a second included angle is formed between the second line segment and the straight line, and a third included angle is formed between the first line segment and the second line segment; and an image-side opening, located at the other end of the central axis; wherein 15 degrees≤the third included angle≤90 degrees, and an opening direction of the radial cross-section of the annular groove is away from the central axis. 
     The present disclosure further provides an optical recognition device, in order from an object side to an image side, comprising: a flat plate; a lens module; and an image sensor; wherein the lens module comprises the above-mentioned lens barrel and an optical lens assembly disposed in the lens barrel. 
     According to the optical recognition device of the present disclosure, the annular groove of the lens barrel has zigzag structure, in particular, the included angle (that is, the third included angle) of the radial cross-section of the annular groove is between 15 degrees and 90 degrees, and the opening direction of the radial cross-section of the annular groove is far away from the central axis, whereby the reflection of non-imaging light during projection onto the object-side surface of the lens barrel can be effectively reduced to reduce stray light, reducing non-imaging light entering the lens module, and improving the optical imaging quality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic cross-sectional view of an optical recognition device in the prior art, showing a path of a non-imaging light. 
         FIG.  2    is a schematic cross-sectional assembly view of an optical recognition device according to an embodiment of the present disclosure. 
         FIG.  3    is a schematic cross-sectional assembly view of a lens module according to an embodiment of the present disclosure. 
         FIG.  4    is a schematic cross-sectional view of a lens barrel according to an embodiment of the present disclosure. 
         FIG.  5    is a schematic cross-sectional view I of an enlarged part A of the lens barrel in  FIG.  4   . 
         FIG.  6   a    is a schematic cross-sectional view of a lens barrel according to another embodiment of the present disclosure. 
         FIG.  6   b    is a schematic cross-sectional view of an enlarged part B of the lens barrel in  FIG.  6     a.    
         FIG.  7    is a schematic cross-sectional view of a radial cross-section of an annular groove according to an embodiment of the present disclosure. 
         FIG.  8    is a schematic cross-sectional view II of an enlarged part A of the lens barrel in  FIG.  4   . 
         FIG.  9    is a schematic cross-sectional view III of an enlarged part A of the lens barrel in  FIG.  4   . 
         FIG.  10   a    to  FIG.  10   d    are design diagrams of an annular groove on an object-side surface of the lens barrel of the first to fourth embodiments of the present disclosure, respectively. 
         FIG.  11   a    to  FIG.  11   e    are simulation pictures of stray light according to the first to fourth embodiments of the present disclosure and the comparative example, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     In order to make the foregoing objectives, features and characteristics of the present disclosure clearer and more comprehensive, the related embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. 
       FIG.  2    is a schematic cross-sectional assembly view of an optical recognition device according to an embodiment of the present disclosure. An optical recognition device  1  may be an optical fingerprint-on-display (FOD) recognition device.  FIG.  3    is a schematic cross-sectional assembly view of a lens module according to an embodiment of the present disclosure.  FIG.  4    is a schematic cross-sectional view of a lens barrel according to an embodiment of the present disclosure. Referring to  FIG.  2   ,  FIG.  3   , and  FIG.  4   , the optical recognition device  1  includes, in order from an object side OS to an image side IS: a flat plate  12 , a lens module  11 , and an image sensor  13 . The flat plate  12  may be a display panel and has a display screen. The lens module  11  includes a lens barrel  111  and an optical lens assembly  112 . The optical lens assembly  112  is disposed in an accommodating space  1110  of the lens barrel  111 . The optical lens assembly  112  may include a plurality of optical lenses and may be made of plastic material or glass material. The lens barrel  111  may be an integrated lens barrel and may be made of the plastic material. The accommodating space  1110  of the lens barrel  111  accommodates the optical lenses or other optical elements. The optical element may include a spacer ring, an optical filter (for example, an infrared optical filter, an infrared bandpass optical filter, or other optical band filters), a light-shielding element (for example, an aperture stop or a stop configured to correct edge light), or the like. 
     Referring to  FIG.  4    again, in this embodiment, the lens barrel  111  defines a central axis  110  (that is, an optical axis). The lens barrel  111  has an accommodating space  1110 , and includes an object-side opening  1111 , an object-side end portion  1112 , an image-side opening  1113 , and an image-side end portion  1114 . The object-side opening  1111  and the object-side end portion  1112  are both located at one end of the central axis  110  (close to the object side OS), and the object-side end portion  1112  surrounds the object-side opening  1111 . The image-side opening  1113  and the image-side end portion  1114  are both located at the other end of the central axis  110  (close to the image side IS), and the image-side end portion  1114  surrounds the image-side opening  1113 . 
       FIG.  5    is a schematic cross-sectional view I of an enlarged part A of the lens barrel in  FIG.  4   . The object-side end portion  1112  has an object-side surface  1115 . In this embodiment, the object-side surface  1115  includes a plurality of annular grooves  1116 . The annular grooves  1116  are sequentially arranged in a radial direction  102  and surround the object-side opening  1111 . A cross-section of the plurality of annular grooves  1116  on the object-side surface  1115  may be regarded as the zigzag structure.  FIG.  6   a    is a schematic cross-sectional view of a lens barrel according to another embodiment of the present disclosure.  FIG.  6   b    is a schematic cross-sectional view of an enlarged part B of the lens barrel in  FIG.  6   a   . In another embodiment, the object-side end portion  1112  may include the zigzag structure of only one annular groove  1116 . The annular groove  116  surrounds the object-side opening  1111 . The zigzag structure of the annular groove  1116  can effectively reduce the reflection of non-imaging light during the projection onto the object-side surface  1115  of the lens barrel  111 , so as to reduce the stray light and reduce non-imaging light entering the lens module  11 , thereby improving the optical imaging quality. 
     Referring to  FIG.  5    again, an opening direction  103  of the radial cross-section of the annular groove  1116  is far away from the central axis  110 , and the radial cross-section of the annular groove  1116  has a first line segment a 1  and a second line segment b 1 . The first line segment a 1  is farther away from the central axis  110  than the second line segment b 1 , and the first line segment a 1  and the second line segment b 1  intersect at a first point t 1 . Referring to  FIG.  7   , a straight line O parallel to the central axis  110  is defined to pass through the first point t 1 . A first included angle ∠C is formed between the first line segment a 1  and the straight line O, a second included angle ∠D is formed between the second line segment b 1  and the straight line O, and a third included angle ∠E is formed between the first line segment a 1  and the second line segment b 1 . The third included angle ∠E is required to be between 15 degrees and 90 degrees. That is to say, 15 degrees≤the third included angle ∠E≤90 degrees. The second line segment b 1  and the first line segment a 1  are respectively located on two sides of the straight line O, and the first included angle ∠C is greater than the second included angle ∠D, whereby the opening direction  103  of the radial cross-section of the annular groove  1116  is away from the central axis  110  (as shown in  FIG.  5   ). Preferably, the second line segment b 1  may be parallel to the central axis  110  (that is, parallel to the straight line O). The annular groove  1116  is easier to manufacture, and the stray light can also be reduced. 
       FIG.  8    is a schematic cross-sectional view II of an enlarged part A of the lens barrel in  FIG.  4   . The object-side surface  1115  further includes an annular surface  1117  surrounding the annular groove  1116 , and the annular surface  1117  is closer to the object side OS than the annular groove  1116 . The radial cross-section of the annular groove  1116  has a second point s 1  at a position closest to the object side OS, and a distance D from the annular surface  1117  to the second point s 1  of the radial cross-section of the annular groove  1116  along the central axis  110  is greater than 0.01 mm. When the annular surface  1117  is used as a support during assembling of the optical lens, the distance D can be used as a buffer distance for protecting the annular groove  1116 . The object-side end portion  1112  further includes an image-side surface  1118  in contact with an optical lens (not shown). A distance from the image-side surface  1118  to the first point t 1  of the radial cross-section of the annular groove  1116  along the central axis  110  is defined as a first distance d1, and 0.1 mm≤the first distance d1≤1.0 mm. The first distance d1 should not be too small, so as to avoid insufficient structural strength between the object-side surface  1115  and the image-side surface  1118 . Furthermore, a distance from the image-side surface  1118  to the annular surface  1117  along the central axis  110  is defined as a second distance d2, and 5/10≤a ratio of the first distance d1 to the second distance d2≤9/10, whereby the insufficient structural strength between the object-side surface  1115  and the image-side surface  1118  can also be avoided. 
       FIG.  9    is a schematic cross-sectional view III of an enlarged part A of the lens barrel in  FIG.  4   . The radial length of the annular surface  1117  is defined as a first length R 1 . The first length R 1  is greater than or equal to 0.01 mm. The annular surface  1117  needs to have a sufficient radial length (the first length R 1 ) as a support during assembling of the optical lenses, but the light reflection may be affected. Therefore, the radial length of the annular surface  1117  (the first length R 1 ) needs to be as small as possible. Furthermore, a maximum radial length of the object-side end portion  1112  is defined as a second length R 2 . When 1/100≤a ratio of the first length to the second length≤11/100, the annular surface  1117  has the enough radial length as a support during assembling of the lens, and the influence of light reflection is reduced. 
     The following is a table of differences between optical simulation results of the first to fourth embodiments of the present disclosure (the design with the annular grooves) and the comparative example of the prior art (the design without the annular grooves). 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                   
                   
                   
                 Comparative 
               
               
                   
                 First 
                 Second 
                 Third 
                 Fourth 
                 example of 
               
               
                   
                 embodiment 
                 embodiment 
                 embodiment 
                 embodiment 
                 the prior art 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Design diagrams of the 
                 FIG. 10a 
                 FIG. 10b 
                 FIG. 10c 
                 FIG. 10d 
                 Design 
               
               
                 annular grooves on the 
                   
                   
                   
                   
                 without the 
               
               
                 object-side surface of 
                   
                   
                   
                   
                 annular 
               
               
                 the lens barrel 
                   
                   
                   
                   
                 grooves 
               
               
                 Stray light simulation 
                 FIG. 11a 
                 FIG. 11b 
                 FIG. 11c 
                 FIG. 11d 
                 FIG. 11e 
               
               
                 picture (shown by arrows) 
               
            
           
           
               
               
            
               
                 Light simulation path 
                 Lens barrel → transparent flat plate (e.g., display panel) → image sensor 
               
            
           
           
               
               
               
               
               
               
            
               
                 Energy (illuminance) 
                 3.38E+04 
                 2.48E+04 
                 4.24E+04 
                 8.03E+04 
                 1.72E+5 
               
               
                 simulation value 
               
               
                   
               
            
           
         
       
     
     In the first embodiment of the present disclosure, the object-side surface includes a plurality of annular grooves  1116 , and the third included angle ∠E is 60 degrees. In the second embodiment of the present disclosure, the object-side surface includes a plurality of annular grooves  1116 , and the third included angle ∠E is 15 degrees. In the third embodiment of the present disclosure, the object-side surface includes a plurality of annular grooves  1116 . The second included angle ∠D is 30 degrees, and the third included angle LE is 90 degrees. In the fourth embodiment of the present disclosure, the object-side surface includes one annular groove  1116 . The second included angle ∠D is 10 degrees, and the third included angle ∠E is 90 degrees. It can be known from the above stray light simulation picture that, the stray light simulation picture (pointed by the arrow in  FIG.  11   a    to  FIG.  11   d   ) of the first to fourth embodiments of the present disclosure is more slight than the stray light simulation picture (pointed by the arrow in  FIG.  11   e   ) of the comparative example of the related art. In particular, the stray light simulation picture (pointed by the arrow in  FIG.  11   b   ) of the second embodiment of the present disclosure is the most slight, greatly reducing the influence of the stray light. In addition, it can be known from the above energy (e.g., illuminance) simulation value that the illuminance of the first to fourth embodiments of the present disclosure is indeed less than the illuminance of the comparative example (the design without annular grooves). In particular, the simulation value 2.48 E+04 of the illuminance of the second embodiment of the present disclosure is the minimum value, greatly reducing the influence of the stray light. 
     According to the optical recognition device of the present disclosure, the annular groove of the lens barrel has zigzag structure, in particular, the included angle (that is, the third included angle) of the radial cross-section of the annular groove is between 15 degrees and 90 degrees, and the opening direction of the radial cross-section of the annular groove is far away from the central axis, whereby the reflection of non-imaging light during projection onto the object-side surface of the lens barrel can be effectively reduced to reduce stray light, reducing non-imaging light entering the lens module, and improving the optical imaging quality. 
     The above is merely the preferred implementations or embodiments of the technical means adopted by the present disclosure for solving problems, and is not intended to limit the patent implementation scope of the present disclosure. That is, all the equivalent variations and modifications that correspond to the context and meaning of the patent application scope of the present disclosure or that are made according to the patent scope of the present disclosure shall fall within the protection scope of the patent scope of the present disclosure.