Abstract:
A lens module for transforming optical signals into electrical signals includes an image sensor provided at a tail of an optical axis to transform optical signals into electrical signals; a first lens provided on the image sensor, wherein the first lens has at least a non-flat lens portion; and a second lens provided on the first lens, wherein the second lens has at least a non-flat lens portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to an optical device, and more particularly to a lens module. 
         [0003]    2. Description of the Related Art 
         [0004]    In recent days, image pick-up apparatus, such as digital camera, video camera, microscope, and scanner, are made as smaller and lighter as possible for user to carry and operate in an easy way so that lens modules, which are mounted on the image pick-up apparatus to catch images, are asked as smaller as possible accordingly. Except for the size and weight, optical performance is asked as higher as possible to catch images with high definition and contrast. Therefore, size and optical performance are the important things in the modern lens modules. 
         [0005]    As shown in  FIG. 1 , a conventional lens module  5  includes an image sensor  100 , a cover glass  110 , and at least a lens  120 . The image sensor  100  transforms the optical signals into electrical signals, the cover glass  100  is attached to the image sensor  100  for protection, and the lens  120  is provided on the cover glass  100  to change the character of light. 
         [0006]    In the conventional lens module  5  the cover glass  110  does nothing but protects the image sensor  100 . However, it increases the thickness of the lens module  5 , and furthermore, it may change the optical character of the light emitting therethrough, such as changing the path of light and decreasing the intensity, and that may affect the optical performance of the conventional lens module  5 . Therefore, the conventional lens module  5  still has some places to be improved. 
       SUMMARY OF THE INVENTION 
       [0007]    The primary objective of the present invention is to provide a lens module with small size and high optical performance. 
         [0008]    According to the objective of the present invention, a lens module for transforming optical signals into electrical signals includes an image sensor provided at a tail of an optical axis to transform optical signals into electrical signals; a first lens provided on the image sensor, wherein the first lens has at least a non-flat lens portion; and a second lens provided on the first lens, wherein the second lens has at least a non-flat lens portion. 
         [0009]    In an embodiment, the lens module further includes an IR cut filter provided on the first lens or on the second lens. 
         [0010]    In an embodiment, the IR cut filter is provided on a side of the first lens proximal to the image sensor. 
         [0011]    In an embodiment, the first lens has a flat lens portion opposite to the non-flat lens portion and attached to the image sensor. 
         [0012]    In an embodiment, the first lens has a lens portion opposite to the non-flat lens portion and a protrusion around the lens portion, whereby the protrusion is attached to the image sensor so that the lens portion keeps a distance away from the image sensor. 
         [0013]    In an embodiment, the lens portion within the protrusion is non-flat. 
         [0014]    In an embodiment, the second lens further has a non-flat lens portion opposite to the non-flat lens portion. 
         [0015]    The present further provides a lens module for transforming optical signals into electrical signals, including an image sensor provided at a tail of an optical axis to transform optical signals into electrical signals; and a lens provided on the image sensor, wherein the lens has at least a convex lens portion. 
         [0016]    In an embodiment, the lens has a flat lens portion opposite to the convex lens portion to be attached to the image sensor. 
         [0017]    In an embodiment, the lens has a protrusion around the convex lens portion to be attached to the image sensor so that the convex lens portion keeps a distance away from the image sensor. 
         [0018]    In an embodiment, the lens has a flat lens portion opposite to the convex lens portion. 
         [0019]    In an embodiment, the lens has a non-flat lens portion opposite to the convex lens portion. 
         [0020]    In an embodiment, a height of the protrusion is greater than a depth of the recess. 
         [0021]    In an embodiment, a depth of the recess is greater than a height of the protrusion. 
         [0022]    In an embodiment, an angle between a sidewall of the protrusion of the first lens and a horizontal plane is in a range between 60 degrees and 90 degrees. 
         [0023]    In an embodiment, an angle between a sidewall of the protrusion of the first lens and a horizontal plane is in a range between 75 degrees and 85 degrees. 
         [0024]    In an embodiment, an angle between a sidewall of the recess of the second lens and a horizontal plane is in a range between 90 degrees and 120 degrees. 
         [0025]    In an embodiment, an angle between a sidewall of the recess of the second lens and a horizontal plane is in a range between 95 degrees and 105 degrees. 
         [0026]    In an embodiment, the first lens portion of the first lens is concave, and the second lens portion of the second lens is concave. 
         [0027]    In an embodiment, the first lens portion of the first lens is convex, and the second lens portion of the second lens is concave. 
         [0028]    In an embodiment, the first lens portion of the first lens is concave, and the second lens portion of the second lens is convex. 
         [0029]    Therefore, the engagement of the protrusion and the recess may fix the first and the second lenses before the glue solidified in an easy and accurate way. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a sketch diagram of the conventional lens module; 
           [0031]      FIG. 2  is a sketch diagram of a first preferred embodiment of the present invention; 
           [0032]      FIG. 3  is a sketch diagram of a second preferred embodiment of the present invention; 
           [0033]      FIG. 4  is a sketch diagram of a third preferred embodiment of the present invention; and 
           [0034]      FIG. 5  is a sketch diagram of a fourth preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    As shown in  FIG. 2 , a lens module  1  of the first preferred embodiment of the present invention includes an image sensor and a lens  20 . 
         [0036]    The image sensor  10  is provided at a tail of an optical axis to transform optical signals into electrical signals. The image sensor  10  may be complementary metal oxide semiconductor (CMOS), charge coupled device (CCD), or other equivalent devices. 
         [0037]    The lens  20  is on the optical axis and covers the image sensor  10 . The lens  20  has a first lens portion  20   a  attached to the image sensor  10  and a second lens portion  20   b  opposite to the first lens portion  20   a . The first lens portion  20   a  is flat, and the second lens portion  20   b  is convex. 
         [0038]    The lens  20  provides both functions of changing light character and protecting the image sensor  10 , in other words, the first lens portion  20   a  changes light character, and the lens  20  is attached to the image sensor  10  to protect it. An IR cut filter  25  is provided on the first lens portion  20   a  of the lens  20  to filter infrared rays out that may increase the optical performance of the lens module  1 . 
         [0039]    In conclusion, it is obvious that no cover glass is needed in the lens module  1  of the present invention because the lens  20  serves both functions of protecting image sensor  10  and changing light character. With the filter  25  and the convex second lens portion  20   b  the lens module  1  of the present invention has a small size and a high optical performance. 
         [0040]    Except for the structure disclosed as above, it may provide two or more lenses to serve the same function. As shown in  FIG. 3 , a lens module  2  of the second preferred embodiment of the present invention includes an image sensor  30 , a first lens  41 , and a second lens  42 . 
         [0041]    The image sensor  30  is provided at a tail of an optical axis to transform optical signals into electrical signals. 
         [0042]    The first lens  41  is on the optical axis and is provided on the image sensor  30 . The first lens  41  has a flat first lens portion  41   a  attached to the image sensor  30  and a concave second lens portion  41   b  opposite to the first lens portion  41   a . An IR cut filter  45  is provided on the first lens portion  41   a  of the first lens  41 . 
         [0043]    The second lens  42  is on the optical axis also and is next to the first lens  41 . The second lens  42  has a concave first lens portion  42   a  facing the second lens portion  41   b  of the first lens  41  and a convex second lens portion  42   b  opposite to the first lens portion  42   a . The character of the first and the second lens portions  42   a ,  42   b  of the second lens  42  are based on the optical requirements of the lens module  2  so that the first and the second lens portions  42   a ,  42   b  of the second lens  42  may be convex, concave, or flat. 
         [0044]    The lens module  2  of the second preferred embodiment provides the first lens  41  to server both functions of protecting the image sensor  30  and changing light character so that no cover glass is needed in the lens module  2 . The second lens  42  and the filter  45  work with the first lens  41  to increase the optical performance of the lens module  2 . 
         [0045]    The lens for protecting the image sensor may be not fully attached to the image sensor. As shown in  FIG. 4 , a lens module  3  of the first preferred embodiment of the present invention includes an image  50  and a lens  60 . 
         [0046]    The image sensor  50  is provided at a tail of an optical axis to transform optical signals into electrical signals. 
         [0047]    The lens  60  is on the optical axis and is above the image sensor  50 . The lens  60  has a convex first lens portion  60   a  and an annular protrusion  602  around the first lens portion  60   a . The lens  60  is provided on the image sensor  50  by attaching the protrusion  602  to the image sensor  50  so that the first lens portion  60   a  is kept a distance away from the image sensor  50 . The lens  60  further has a flat second lens portion  60   b  opposite to the first lens portion  60   a , and an IR cut filter  65  on the first lens portion  60   a . The same as above, the first and second lens portions  60   a ,  60   b  may be flat, convex, or concave based on the optical requirements. 
         [0048]    The lens  60  of the present embodiment serves both functions of protecting image sensor  10  and changing light character, and the first lens portion  60   a  may not be flat to enhance the optical function. 
         [0049]    The idea of the third embodiment may be achieved by two or more lenses as well. As shown in  FIG. 5 , a lens module  4  of the fourth preferred embodiment of the present invention includes an image sensor  70 , a first lens  81 , and a second lens  82 . 
         [0050]    The image sensor  70  is provided at a tail of an optical axis to transform optical signals into electrical signals. 
         [0051]    The first lens  81  is on the optical axis and is above the image sensor  30 . The first lens  81  has a convex first lens portion  81   a  and an annular protrusion  812  around the first lens portion  81   a . The first lens  81  is provided on the image sensor  70  by attaching the protrusion  812  to the image sensor  70  so that the first lens portion  81   a  is kept a distance away from the image sensor  70 . The first lens  81  further has a concave second lens portion  81   b  opposite to the first lens portion  81   a , and an IR cut filter  85  on the first lens portion  81   a . The same as above, the first and second lens portions  81   a ,  81   b  may be flat, convex, or concave based on the optical requirements. 
         [0052]    The second lens  82  is on the optical axis also and next to the first lens  81 . The second lens  82  has a concave first lens portion  82   a  facing the second lens portion  81   b  of the first lens  81  and a convex second lens portion  82   b  opposite to the first lens portion  42   a . The same as above, the first and the second lens portions  82   a ,  82   b  may be convex, concave, or flat based on the optical requirement. 
         [0053]    The lens module  4  of the fourth preferred embodiment provides the first lens  81  to server both functions of protecting the image sensor  70  and changing light character so that no cover glass is needed in the lens module  4 . The second lens  82  and the filter  85  work with the first lens  81  to increase the optical performance of the lens module  4 . 
         [0054]    In above embodiment the IR cut filter is provided on the side of the lens closest to the image sensor. It is easy to understand that the IR cut filter may be provided on any side of the lenses. The description above is a few preferred embodiments of the present invention and the equivalence of the present invention is still in the scope of claim construction of the present invention.