Patent Publication Number: US-2009219435-A1

Title: Composite lens and lens module having same

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure relates generally to optical elements, and more particularly to a composite lens with an optical filter embedded therein and a lens module having the composite lens. 
     2. Description of Related Art 
     Currently, portable electronic devices such as personal digital assistants (PDAs), cellular telephones, and others, with image capture capability are becoming increasingly popular, requiring the deployment of an image capture device in the device. 
     An image capture device generally consists of a lens module and an image sensor. Light for image formation passes through the lens module and then converges on the image sensor, such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). The image sensor eventually converts analog signals into digital signals for generating an image. 
     Generally, the image sensor can detect light of spectral range from 380 nm to 1200 nm. However, since the visible light spectrum ranges from 390 nm to 760 nm, the image sensor receives not only visible light but also unwanted infrared light. If the infrared light is not filtered, the final image is flawed thereby. Thus, an infrared (IR) cut filter is usually disposed in front of the image sensor to block infrared light but pass visible light. 
     However, addition of an optical element, such as IR cut filter, to the lens module increases the number of optical elements, complicating assembly of the lens module and negatively affecting precision of lens module function. 
     What is needed, therefore, is an unitary composite lens and a lens module having same providing simplified assembly while maintaining optical precision. 
     SUMMARY 
     A unitary composite lens includes a body and an optical filter embedded therein. 
     Advantages and novel features of the unitary composite lens and the lens module having same will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. 
         FIG. 1  is a cross-section of a lens module incorporating an unitary composite lens in accordance with a first exemplary embodiment. 
         FIG. 2  is a cross-section of a lens module incorporating an unitary composite lens in accordance with a second exemplary embodiment. 
     
    
    
     Corresponding reference characters indicate corresponding parts. The exemplifications set out herein illustrate at least one preferred embodiment of the unitary composite lens and the lens module having same, in one form, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner. 
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     Reference will now be made to the drawings to describe embodiments of the unitary composite lens and the lens module having same in detail. 
     Referring to  FIG. 1 , a lens module  1  in accordance with an illustrated embodiment, includes a lens barrel  10  and a unitary composite lens  11 . In the embodiment, the lens module  1  can be deployed in electronic devices such as notebook computers, personal digital assistants (PDAs), or cellular telephones. 
     The lens barrel  10  has a cylindrical body and a front end joined thereto. An opening P is defined at the front end thereof, through which light enters the body. The cylindrical body defines an inner space accommodating the unitary composite lens  11 . The light passes through the unitary composite lens  11  and converges on a sensor (not shown in  FIG. 1 ). The sensor can be a solid-state sensor such as a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS). 
     The unitary composite lens  11  includes a body  111  and an optical filter  112  embedded therein. In the embodiment, the body  111  is plastic and covers the optical filter  112  entirely, by means of conventional injection-molding practice. The surface of the body  111  can be spherical or non-spherical. 
     The optical filter  112  includes a substrate  112   a  and a first filter film  112   b  disposed on a surface of the substrate  112   a.  The substrate  112   a  is transparent material such as glass. In the embodiment, the first filter film  112   b  is an infrared cut filter, which blocks the transmission of the infrared light while passing the visible light. The first filter film  112   b  consists of alternating stacked high- and low-reflective films. The high-reflective film can be titanium dioxide (TiO 2 ), niobium pentoxide (Nb 2 O 5 ) or tantalum pentaoxide (Ta 2 O 5 ). In addition, the low-reflective film is silicon dioxide (SiO 2 ). 
     In practice, injection molding is utilized to form the unitary composite lens  11 . A mold inversing the contours and features of the product, i.e. the unitary composite lens is firstly provided. The optical filter  112  is fastened to the mold and the mold is closed. Material for body  111  of the unitary composite lens  11 , such as, molten plastic, is injected at high pressure into the mold. As a result, the optical filter  112  is embedded in the body  111 , forming the unitary composite lens  11 . 
     Referring to  FIG. 2 , the optical filter  11  of the illustrated embodiment can further include a second filter film  112   c,  disposed on an opposite surface of the substrate  112   b  from the first filter film  112   a.  Thus, stress between the substrate  112   b  and the filter films  112   a,    112   c  is balanced, and deflection of the optical filter  11  and resulting optical aberration is avoided. In the embodiment, the second filter film  112   c  also can be an infrared cut filter. 
     In conclusion, by integrating the optical filter with the lens to form a unitary composite lens, the number of optical elements are reduced. When the unitary composite lens is to be installed in the lens module, assembly is simplified, as is resulting efficiency of process. 
     Finally, it is to be understood that the described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.