Abstract:
A lens module includes a lens barrel, two lenses, and a light shielding plate. The lens barrel has a light passing hole and a receiving hole in communication with the light passing hole. The lenses are received in the receiving hole and aligned with the light passing hole and aligned with the light passing hole. The light shielding plate is arranged between the two lenses. The conic section of the light shielding plate prevents unwanted or stray light from reaching the image sensor.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates generally to a lens module and an image pick-up apparatus incorporating the lens module. 
         [0003]    2. Description of Related Art 
         [0004]    Many image pick-up apparatuses are used in a variety of consumer electronic devices, such as notebook computers, personal digital assistants (PDAs), and cellular telephones. There is an increasing demand for better image quality, which essentially depends on the quality of the lens module of the image pick-up apparatus. That is, a lens module with a high image quality is desired. 
         [0005]    Referring now to  FIG. 6 , a lens module  15  used in an image pick-up apparatus includes a light shielding plate  11  and two lenses  151 ,  152 . The two lenses  151  and  152  are aligned with each other, and the light shielding plate  11  is sandwiched between and aligned with the two lenses  151  and  152 . The light shielding plate  11  defines a cylindrical through hole  15 A at the center thereof for allowing the passage of light, and has an inner side face  150  in the through hole  15 A. The light shielding plate  11  is for absorbing light which falls thereon, thereby eliminating the stray light in the lens module  15 . In other words, glare in the lens module  15  is eliminated. When the light through the lens module  15  is very strong, the inner side face  150  of the light shielding plate  11  in the through hole  15 A cannot completely prevent the stray light, and reflects some of the light onto the image sensor of an image pick-up apparatus incorporating the lens module  15 . This will influence the imaging quality of the image pick-up apparatus incorporating the lens module  10 . 
         [0006]    Therefore, there is a need for a lens module and an image pick-up apparatus, to overcome the above mentioned limitations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments can be better understood with reference 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 views. 
           [0008]      FIG. 1  is a sectional view of a light shielding plate according to a first exemplary embodiment. 
           [0009]      FIG. 2  is a sectional view of a light shielding plate according to a second exemplary embodiment. 
           [0010]      FIG. 3  is a sectional view of a light shielding plate according to a third exemplary embodiment. 
           [0011]      FIG. 4  is a sectional view of an image pick-up apparatus comprising the light shielding plates of  FIGS. 1 and 2 , according to a fourth exemplary embodiment. 
           [0012]      FIG. 5  is a sectional view of a lens module comprising the light shielding plate of  FIG. 3 , according to a fifth exemplary embodiment. 
           [0013]      FIG. 6  is a sectional view of a related art of a lens module. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , a light shielding plate  10  in accordance with a first exemplary embodiment is a round disk. The light shielding plate  10  has a first surface  10 A and a second surface  10 B facing away from the first surface  10 A. The light shielding plate  10  defines a through hole  10 C at the center thereof and through the first and second surfaces  10 A and  10 B. The through hole  10 C tapers from the first surface  10 A to the second surface  10 B, thereby forming a small section of a shallow cone (conical surface  101 ) in the through hole  10 C. The conical surface  101  is interconnected between the first surface  10 A and the second surface  10 B. In an alternative embodiment, the light shielding plate  10  can also be rectangular. The thickness of the light shielding plate  10  is in the range from about 0.030 mm to about 0.054 mm. 
         [0015]    Referring to  FIG. 2 , a light shielding plate  20  in accordance with a second exemplary embodiment is also a round disk. The light shielding plate  20  has a third surface  20 A and a fourth surface  20 B facing away from the third surface  20 A. The light shielding plate  20  defines a through hole  20 C at the center thereof and through the third and fourth surfaces  20 A and  20 B. The through hole  20 C tapers from the fourth surface  20 B to the third surface  20 A, thereby forming a conical surface  201  in the through hole  20 C. The conical surface  201  is interconnected between the third surface  20 A and the fourth surface  20 B. The light shielding plate  20  has an outer diameter and a thickness greater than those of the light shielding plate  10 . In an alternative embodiment, the light shielding plate  20  can also be rectangular. 
         [0016]    Referring to  FIG. 3 , a light shielding plate  30  in accordance with a third exemplary embodiment is also a round disk. The light shielding plate  30  has a fifth surface  30 A and a sixth surface  30 B facing away from the fifth surface  30 A. The light shielding plate  30  defines a through hole  30 C at the center thereof and through the fifth surface  30 A and the sixth surface  30 B. The through hole  30 C includes a first hole portion  30 CA adjacent to the fifth surface  30 A, and a second hole portion  30 CB adjacent to the sixth surface  30 B. The first hole portion  30 CA and the second hole portion  30 CB are aligned with and in communication with each other, so as to create (in section) an internal knife edge. An imaginary interface  30 CC between the first hole portion  30 CA and the second hole portion  30 CB is formed between the fifth surface  30 A and the sixth surface  30 B. The first hole portion  30 CA tapers from the fifth surface  30 A to the interface  30 CC, and the second hole portion  30 CB tapers from sixth surface  30 B to the interface  30 CC. Thus, a first conical surface  301  is defined in the first hole portion  30 CA, and the second conical surface  302  is defined in the second hole portion  30 CB. The first conical surface  301  and the second conical surface  302  intersect at a common line in the interface  30 CC. 
         [0017]    Referring to  FIG. 4 , an image pick-up apparatus  100  in accordance with a fourth exemplary embodiment includes the light shielding plate  10 , the light shielding plate  20 , a lens barrel  33 , a first lens  40 , a second lens  50 , a third lens  60 , an infrared filter  70 , a holder  80 , and an image sensor  90 . The lens barrel  33  has a first end face  311  and an opposite second end face  312 . A light passing hole  313  is defined in the first end face  311 , and a receiving hole  314  is defined in the second end face  312 . The light passing hole  313  is conical in section and tapers away from the first end face  311 . The receiving hole  314  is cylindrical. The light passing hole  313  is in communication with the receiving hole  314 , thereby forming an interface  315  between the light passing hole  313  and the receiving hole  314 . The light passing hole  313  at the interface  315  has a diameter less than that of the receiving hole  314 . Thus, the interface  315  faces toward the receiving hole  314 . The light passing hole  313  allows ambient light to enter into the receiving hole  314 . The receiving hole  314  receives the light shielding plate  10 , the light shielding plate  20 , the first lens  40 , the second lens  50 , the third lens  60 , and the Infrared filter  70 . The lens barrel  33  has an outer thread  330  on the surface adjacent to the second end face  312 . 
         [0018]    In this embodiment, the first, second and third lenses  40 ,  50 , and  60  are plastic. The first lens  40  is adjacent to the first end face  311 , the third lens  60  is adjacent to the second face  312 , and the second lens  50  is between the first lens  40  and the third lens  60 . The first, second and third lenses  40 ,  50 , and  60  focus light entering the light passing hole  313  onto the image sensor  90 . 
         [0019]    The first lens  40  includes a central round portion  402  and a peripheral stepped structure  404 . The peripheral stepped structure includes a radially extending portion  406  surrounding the central round portion  402 , and an axially extending portion  408  extending axially from the radially extending portion  406  toward the second lens  50 . The peripheral stepped structure  404  has an inward-facing surface  410  and a conical side face  412 . The inward-facing surface  410  belongs to the radially extending portion  406 , and is adjacent to the central round portion  402 . The conical side face  412  belongs to the axially extending portion  408 , and is adjacent to the inward-facing surface  410 . The conical side face  412  is inclined in a direction away from the central round portion  402 . 
         [0020]    The second lens  50  includes a central round portion  502  and a peripheral portion  504  surrounding the second central round portion  502 . The peripheral portion  504  has an outward-facing surface  506  adjacent to the second central round portion  502 , and a conical side face  508  adjacent to the outward-facing surface  506 . The conical side face  508  extends inwards from the out-facing surface  506 , and is inclined in a direction away from the second central round portion  502 . The inclined angle between the outward-facing surface  506  and the conical side face  508  is the same as that between the inward-facing surface  410  and the conical side face  412 . 
         [0021]    The third lens  60  includes a central round portion  602  and a peripheral portion  604  surrounding the second central round portion  602 . The Infrared filter  70  filters IR light at this point. 
         [0022]    The first lens  40 , the second lens  50 , the third lens  60  and the Infrared filter  70  are received in the receiving hole  314  from the first end face  311  to the second end face  312  in the order described. The second lens  50  engages with the first lens  40  in such a way that the conical side face  508  contacts the conical side face  412 , and the inward-facing surface  410  faces and is parallel with the outward-facing surface  506 . The light shielding plate  10  is arranged between the inward-facing surface  410  and the outward-facing surface  506  in such a manner that the first surface  10 A contacts the inward-facing surface  410  and the second surface  10 B contacts the outward-facing surface  506 . The through hole  10 C is aligned with the central round portions  402  and  502 . The second light shielding plate  20  is arranged between the second lens  50  and the third lens  60  in such a manner that the peripheral portion  504  is in contact with the third surface  20 A and the peripheral portion  604  is in contact with the fourth surface  20 B. The Infrared filter  70  is in contact with the peripheral portion  604  of the third lens  60 . 
         [0023]    The holder  80  includes a cylindrical connection portion  80 A and a receiving portion  80 B. The connection portion  80 A defines a cylindrical through hole  85  and an interior thread  85 A in the through hole  85 . The interior thread  85 A is in threaded engagement with the outer thread  330 . The receiving portion  80 B extends axially from the end of the connection portion  80 A away from the lens barrel  33 . The receiving portion  80 B defines a through hole  87  in communication with the through hole  85 . The image pick-up apparatus  100  further includes a printed circuit board  95  fixed to the end of the receiving portion  80 B away from the connection portion  80 A and capping the through hole  87 . 
         [0024]    The image sensor  90  can be a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS). The image sensor  90  is arranged on and electrically connected with the printed circuit board  95 . The image sensor  90  is received in the through hole  87 , and faces the Infrared filter  70 . The image sensor  90  is optically coupled with the first lens  40 , the second lens  50 , the third lens  60  and the Infrared filter  70 . 
         [0025]    In this embodiment, because the conical surface  101  is inclined toward the first end face  311 , the conical surface  101  can reflect some of the light entering the light passing hole  313  away from the image sensor. Furthermore, the conical surface  201  is inclined away from the first end face  311 , thus any light which does not fall directly through the light passing hole  313  can reach the conical surface  201 . Thus, any glare in the image pick-up apparatus  10  is effectively reduced. 
         [0026]    In alternative embodiments, the locations of the light shielding plates  10  and  20  can be exchanged. The number of the lenses in the image pick-up apparatus  100  may vary. 
         [0027]    Referring to  FIG. 5 , an image pick-up apparatus  200  in accordance with a fifth exemplary embodiment is similar to the image pick-up apparatus  100  of the fourth exemplary embodiment. The distinguishing features are that the light shielding plate  30  is between the second lens  50  and the third lens  60 , instead of the square-edged light shielding plate  11 . The through hole  15 A of the light shielding plate  11  has a diameter greater than that of the interface  30 CC of the light shielding plate  30 . The first conical surface  301  of the light shielding plate  30  has the same function as that of the conical surface  101  in the image pick-up apparatus  100 , and the second conical surface  302  of the light shielding plate  30  has the same function as that of the conical surface  201  in the image pick-up apparatus  100 . 
         [0028]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.