Abstract:
An exemplary lens includes an active part configured for refracting light transmitting therethrough, an inactive part surrounding the active part, and a collar formed on a surface of the inactive part.

Description:
BACKGROUND 
   1. Technical Field 
   The present invention relates to optical imaging devices and, particularly, to a lens with a collar and a lens module using the same. 
   2. Description of Related Art 
   With the development of optical imaging technology, electronic devices, such as digital cameras and mobile phones to name a few, adopting imaging technology has been introduced and marketed. 
   A typical lens module  40  is shown in  FIG. 6 . The lens module  40  includes a barrel  42 , a first lens  44 , a second lens  46 , and a spacer  48  received in the barrel  42 . The spacer  48  is sandwiched between the first lens  44  and the second lens  46 . The first lens  44  includes an active part  442  and an inactive part  444  surrounding the active part  142 . The active part  442  is configured for refracting light transmitting therethrough. The inactive part  444  has a first flat surface (not labeled). Similarly, the second lens  46  includes an active part  462  and an inactive part  464 . The inactive part  464  has a second flat surface (not labeled). A first side of the spacer  48  contacts the first flat surface of the inactive part  444 , and an opposite second side of the spacer  48  contacts the second flat surface of the inactive part  464 . In assembly, the first lens  44 , the spacer  48 , and the second lens  46  are in this order placed into the barrel  42 . 
   In the above lens module  40 , the second lens  46  is engaged with the first lens  44  via the spacer  48 . Due to accumulated errors during assembly of the spacer  48  and the second lens  46 , an optical axis (not labeled) of the second lens  46  may deviate from that of the first lens  44 . Accordingly, imaging quality of such a lens module  10  deteriorates, directly depending on the deviation between the two optical axes. 
   Therefore, a new lens and a new lens module are desired to overcome the above mentioned problems. 
   SUMMARY 
   An exemplary lens includes an active part configured for refracting light transmitting therethrough, an inactive part surrounding the active part, and a collar formed on a surface of the inactive part. 
   An exemplary lens module includes a barrel, a first lens received in the barrel, and a second lens received in the barrel. The first lens includes a first active part configured for refracting light transmitting therethrough, a first inactive part surrounding the first active part, and a first collar formed on a surface of the first inactive part. The first collar includes a first inner surface and a first outer surface. The second lens includes a second active part, a second inactive part surrounding the second active part, and a second collar extending from a surface of the second inactive part. The second collar includes a second inner surface and a second outer surface. The second collar is engaged with the first collar in such a manner that the second inner surface is in contact with the first outer surface. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is a schematic, side cross-sectional view of a lens module, according to a first embodiment. 
       FIG. 2  is a schematic, perspective view of a lens of the lens module of  FIG. 1 . 
       FIG. 3  is a schematic, perspective inverted view of the lens of  FIG. 2 . 
       FIG. 4  is a schematic, side cross-sectional view of a lens module, according to a second embodiment. 
       FIG. 5  is a schematic, side cross-sectional view of a lens module, according to a third embodiment. 
       FIG. 6  is a schematic, side cross-sectional view of a typical lens module. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Embodiments will now be described in detail below with reference to the drawings. 
   Referring to  FIG. 1 , a lens module  10  of a first embodiment is shown. The lens module  10  includes a barrel  11 , a first lens  12 , a second lens  14 , and a light blocking plate  16 . The first lens  12  and the second lens  14  are received in the barrel. The light blocking plate  16  is sandwiched between the first lens  12  and the second lens  14 . 
   Referring to  FIGS. 1-3 , the second lens  14  includes an active part  142 , an inactive part  144  surrounding the active part  142 , and a first collar  146  on a surface (not labeled) of the inactive part  144 . The active part  142  is configured for refracting light traveling through the second lens. The first collar  146  extends outwardly in a direction parallel to an optical axis (not labeled) of the second lens  14  from the inactive part  144 . The first collar  146  defines a receiving space (not labeled) therein. The first collar  146  is configured (i.e., structured and arranged) for engaging with the first lens  12 . In the present embodiment, the first collar  146  is a cylindrical wall. It should be noted that the first collar  146  can also be a discontinuous ring shape. The first collar  146  has an inner surface  1462  and an outer surface  1464 . 
   The first collar  146  has a trapezoid side cross-section. A shorter side of the two parallel sides of the trapezoid is at a distal end of the inactive part  144 . That is, the collar  146  tapers in a direction away from the active part  144 . In addition, the outer surface  1464  also slants obliquely relative to a surface normal of the active part  142  in the present embodiment. The configuration of the second lens  14  allows it to be easily released from an injection molding mold. 
   Referring to  FIG. 1 , similarly to the second lens  14 , the first lens  12  includes a second collar  126 , and the second collar  126  has an inner surface  1264  and an outer surface  1262 . The inner surface  1264  can be oblique relative to an active part (not labeled) of the first lens  12 . 
   During assembly, the second lens  14  is coupled directly onto the first lens  12  and they are positioned relative to each other by the circular walls instead of adopting a spacer sandwiched between the first lens  12  and the second lens  14 . Because the inner surface  1462  of the second lens  14  is in direct contact with the outer surface  1262  of the first lens  12 , the second lens  14  is in a substantially precise optical alignment with the first lens  12 . I.e., an optical axis (not labeled) of the first lens  12  is aligned along the optical axis of the second lens  12 . 
   The inner surface  1462  and the outer surface  1262  are both oblique in the present embodiment. The two oblique surfaces can be obtained using an ultraprecision machine. A slope of the outer surface  1262  is the same as that of the inner surface  1462 . Because the slope of the outer surface  1262  is the same as the inner surface  1462  of the second lens  14 , precise optical alignment of the first and second lenses  12 ,  14  is achieved. Furthermore, the two oblique surfaces  1264 ,  1464  facilitate assembling the second lens  14  to the first lens  12 . 
   A method for assembling the lens module  10  includes the steps of:
         inserting the first lens  12  into the barrel  11 ;   disposing the light blocking plate  16  on the first lens  12 ;   placing the second lens  14  into the barrel  11  in such a manner that the outer surface  1262  contacts the inner surface  1462  and guides/slides the second lens  14  to a precise optical alignment with the first lens  12 ;   applying an adhesive substance between the barrel  11  and the side surface of the second lens  14 , thus securing the first lens  12  and the second lens  14  in the barrel.       

   Referring to  FIG. 4 , a lens module  20  of a second embodiment is shown. Similar to the lens module  10 , the lens module  20  includes a first lens  22 , a second lens  24 , and a third lens. The first lens  22  has a first collar  222 . The second lens  24  has a second collar  244  and a third collar  246  each extending from opposite sides of the  24  at an inactive part  242  correspondingly. The third lens  26  has a fourth collar  262  extending vertically from a surface (not labeled) of the inactive part (not labeled) of the third lens  26 . The second collar  244  is for engaging with the first collar  222 , and the third collar  246  is for engaging with the fourth collar  262 . Due to such a configuration, the first lens  22  and the third lens  26  are in precise optical alignment with the second lens  24 . 
   Referring to  FIG. 5 , a lens module  30  of a third embodiment is shown. The lens module  30  is similar to the lens module  10 , except that an inner surface  3462  of a first collar  346  and an outer surface  3262  of a second collar  326  are both vertically straight. 
   While certain embodiments have been described and exemplified above, various other embodiments from the foregoing disclosure will be apparent to those skilled in the art. 
   The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.