Abstract:
A lens module ( 100 ) includes a barrel ( 10 ), a lens ( 20 ), an image sensor module ( 30 ) and a grating ( 22 ). The lens is received in the barrel for focusing optical signals. The image sensor module is installed on an end of the barrel for receiving and transforming the optical signals. The grating is formed on the lens for preventing unnecessary optical signals from being received by the image sensor module.

Description:
1. FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to lens modules and, more particularly, to a lens module for an optical device such as a microscope, a camera module, a digital camera module used in a portable electronic device, or such like. 
       2. DESCRIPTION OF RELATED ART 
       [0002]    With the ongoing development of microcircuitry and multimedia technologies, digital cameras are now in widespread use. High-end portable electronic devices, such as mobile phones and personal digital assistants (PDAs), are being developed to be increasingly multi-functional. Many of these portable electronic devices are now equipped with a digital camera module. These electronic devices enable consumers to enjoy capturing digital pictures anytime and anywhere. At the same time, the need for digital picture quality has become greater and greater. 
         [0003]    In a typical camera module, a lens module is very important to the quality of the pictures captured by the camera module. The lens module typically includes a tubular body and a plurality of lenses. Each lens has a lens portion and a mounting portion. The lens portion is located at a center of the mounting portion. The lenses are coaxially received in the tubular body. The lens portions of the plurality of lenses act together to concentrate a first portion of the image light incident on the lens portions onto an image sensor to capture an image. However, a second portion of image light incident on the mounting portions is also refracted onto the image sensor by the mounting portions. As a result, the second portion of image light interferes with the first portion of image light, thereby reducing the quality of the pictures captured by the image sensor. 
         [0004]    Therefore, a new optical lens is desired in order to overcome the above-described shortcomings. 
       SUMMARY OF THE INVENTION 
       [0005]    In a preferred embodiment thereof, a lens module includes a barrel, a lens, an image sensor module and a grating. The lens is received in the barrel for focusing optical signals. The image sensor module is installed on an end of the barrel for receiving and transforming the optical signals. The grating is formed on the lens for preventing unnecessary optical signals from being received by the image sensor module. 
         [0006]    Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the lens module 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 lens module. Moreover, in the drawings, like reference numerals designate corresponding parts through out the several views. 
           [0008]      FIG. 1  is a cut-away view of a lens module in accordance with a first embodiment of the present lens module with grating; 
           [0009]      FIG. 2  is an enlarged cut-away view of a lens of the lens module in accordance with the first embodiment of the present lens module with grating; 
           [0010]      FIG. 3  is a cut-away view of a lens module in accordance with a second embodiment of the present lens module with grating; and 
           [0011]      FIG. 4  is an enlarged cut-away view of a lens of the lens module in accordance with the second embodiment of the present lens module with grating. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to the drawings in detail,  FIG. 1  shows a lens  20  for use with a lens module  100 . The lens module  100  is taken here as an exemplary application, for the purpose of describing details of the lens  20  of a preferred embodiment of the present lens module with grating. It is to be understood, however, that the lens  20  could be suitably used in other environments (e.g. in a telescope or in a microscope). As such, although proving particularly advantageous when used in the lens module  100 , the lens  20  should not be considered limited in scope solely to an intended use environment of the lens module  100 . The lens module  100  includes a barrel  10 , the lens  20 , and an image sensor module  30 . The lens  20  is received in the barrel  10 . The image sensor module  30  is installed on an end of the barrel  10 . 
         [0013]    The barrel  10  is a hollow cylinder in shape and the barrel  10  includes a inner surface  101 , a screening end  111  and an installing end  12  positioned opposite to the screening end  11 . The barrel  10  defines an opening  13  in a centre of the screening end  11 . The opening  13  has a Y-shaped cross section thereby forming a conical sidewall  131  and a cylindrical sidewall  132 . 
         [0014]    The lens  20  is a substantially round disk in shape. The lens  20  includes an outer surface  201 , a lens portion  21 , a diffractive grating  22  and a mounting portion  23 . The outer surface  201  is shaped corresponding to the shape of the inner surface  101 . A diameter of the lens  20  is substantially equal to an inner diameter of the barrel  10  so that the lens  20  is fully received in the barrel  10 . The lens portion  21  is a spherical portion formed in a centre of the lens  20 . The diffractive grating  22  is formed around the lens portion  21 . The mounting portion  23  is a planar portion formed around the diffractive grating  22 . 
         [0015]    Also referring to  FIG. 2 , the diffractive grating  22  includes an opaque film  220  and a plurality of transmitting slots  221 . The opaque film  220  is an annular film formed on a surface of the lens  20  and covering an area around the lens portion  21 . The diameter of the opaque film  220  is corresponding to the diameter of the cylindrical sidewall  132 . All transmitting slots  221  are equidistantly formed on the lens  20 . Each transmitting slot  221  is an annular slot formed around the lens portion  21  and through the opaque film  220 . 
         [0016]    The image sensor module  30  includes a base  31  and an image sensor  32 . The base  31  is installed on the installing end  12  of the barrel  10 . The image sensor  32  is secured on the base  31  and received in the barrel  10 . 
         [0017]    In assembly, the lens  20  is inserted into the barrel  10  from the installing end  12 . The outer surface  201  cooperates with the inner surface  101 , and the lens  20  is secured in the barrel  10  so that the axis of the lens portion  21  of the lens  20  is perpendicular to a radial direction of the barrel  10 . Additionally, a plurality of lenses  20  can also be inserted and secured in the barrel  10 . The installing end  12  is secured on the base  31 . The image sensor  32  is secured on the base  31  and received in the barrel  10 . Optical signals coming from the lens  20  are transformed into electronic signals by the image sensor  32 . 
         [0018]    In use, the lens portion  21  and the diffractive grating  22  are both exposed in the barrel  10 . Either the lens portion  21  or the diffractive grating  22  receives incident optical signals. Incident optical signals arriving at the lens portion  21  are focused by the lens portion  21  and are received by the image sensor  32 , thus these optical signals are transformed into electronic signals. Incident optical signals that have not been focused (shown as line A) arrive at the diffractive grating  22 , these unnecessary incident optical signals are diffracted by the diffractive grating  22 . Therefore the incident signals that have not been focused are refracted out the periphery of the image sensor  32 , and the image sensor  32  can not receive unnecessary optical signals. In this way quality of the picture captured by the image sensor  32  is improved. 
         [0019]    Referring to  FIG. 3 , a lens module  200  according to a second embodiment is provided. All components of the lens module  200  are similar to the lens module  100  except that the diffractive grating  22  of the lens module  100  is replaced by a reflecting grating  24 . The reflecting grating  24  is an annular film made of reflexible materials installed on a surface of the lens  20 . The reflecting grating  24  covers an area around the lens portion  21 , and the mounting portion  23  is defined around the reflecting grating  24 . The diameter of the reflecting grating  24  corresponds to the diameter of the cylindrical sidewall  132 . The reflecting grating  24  defines a plurality of reflecting slots  241 . All reflecting slots  241  are equidistantly formed on the reflecting grating  24 . Each reflecting slot  241  is an annular slot formed around the lens portion  21  and has a triangular section, thus a serrated surface is formed on the reflecting grating  24 . 
         [0020]    Assembly of the lens module  200  is similar to assembly of the lens module  100 . In use, the lens portion  21  and the reflecting grating  24  are both exposed from the barrel  10 . Either the lens portion  21  or the reflecting grating  24  receives incident optical signals. Also referring to  FIG. 4 , incident optical signals that have not been focused (shown as line B) arrive at the reflecting grating  24 , these unnecessary incident optical signals are reflected by the reflecting grating  24 . Therefore the incident signals that have not been focused are refracted out the periphery of the image sensor  32 , and the image sensor  32  can not receive unnecessary optical signals. In this way quality of the picture captured by the image sensor  32  is improved. 
         [0021]    It is to be understood, however, that even though numerous characteristics and advantages of the present lens module with grating have been set forth in the foregoing description, together with details of the structure and function of the lens module with grating, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the lens module with grating to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.