Patent Publication Number: US-2011061799-A1

Title: Miniaturized Lens Assembly and Method for Making the Same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 11/439,117, filed on May 24, 2006. 
     This application claims priority of Taiwanese Application No. 094122900, filed on Jul. 6, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a lens assembly, more particularly to a miniaturized lens assembly. This invention also relates to a method for making the miniaturized lens assembly. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional lens assembly is made by preparing optical lenses  901  and annular spacers  902  separately, and assembling the optical lenses  901  and the annular spacers  902  into a barrel  9  in sequence. However, when it is desired to apply the lens assembly to a camera phone, the lens assembly is required to be minimized in size. The aforesaid method cannot be used to make the miniaturized lens assembly applicable to camera phones in view of very high precision requirements thereof. 
     Referring to  FIGS. 2 and 3 , WO2004027880 discloses a camera device and a method for manufacturing the camera device. As shown in  FIGS. 2 and 3 , in one preferred embodiment of the method for manufacturing the camera device, a silicon wafer  1  having a plurality of image-capturing elements  101 , a first micro-spacer wafer  2  having a plurality of first through holes  201 , a first cover wafer  3  having a plurality of cover plates  301 , a first lens substrate  4  having a plurality of first lenses  401 , a second micro-spacer wafer  5  having a plurality of second through holes  501 , a second lens substrate  6  having a plurality of second lenses  601 , a third micro-spacer wafer (not shown), and a second cover wafer  7  are prepared, stacked, aligned with one another along main optical axes, and bonded to one another by using adhesive layers  8  to form a laminate. The laminate is sawn to obtain a plurality of camera devices, each of which includes one of the image-capturing elements  101 , a first micro-spacer element  202  having the first through hole  201 , the cover plate  301 , the first lens  401 , the second micro-spacer element  502  having the second through hole  501 , the second lens  601 , and the adhesive layers  8 . 
     Although the method disclosed in WO2004027880 can make a plurality of camera devices at the same time, the following disadvantages are encountered: 
     1. The alignment of the wafers and substrates used for making the camera devices is carried out along the optical axes. Such an alignment is troublesome and difficult to control precisely. Moreover, since there is no aligning mark for sawing the laminate, it is difficult to saw the laminate precisely. 
     2. The adhesive layers  8  are required for bonding the wafers and substrates together. That is to say, in addition to the first micro-spacer element  202  and the second micro-spacer element  502 , a plurality of the adhesive layers  8  are required in each of the camera devices to bond the aforesaid components together. The total thickness of the camera device is thus still relatively large. Furthermore, it is required to control the thickness of each of the adhesive layers  8  carefully to obtain a predetermined spacing between two adjacent components of the camera device. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a miniaturized lens assembly in which spacing and bonding of two adjacent components of the miniaturized lens assembly can be achieved simultaneously. 
     An other object of the present invention is to provide a method for making the miniaturized lens assembly. 
     Therefore, in one aspect of this invention, a miniaturized lens assembly includes an image-capturing unit, a lens unit, and a binding layer. The image-capturing unit includes an image-capturing member. The lens unit includes an image-projecting portion for projecting an image along an optical axis to the image-capturing member. The binding layer extends around the optical axis, and binds the image-capturing unit to the lens unit. The binding layer includes a photosensitive polymeric material and spaces apart the lens unit and the image-capturing unit. 
     In another aspect of this invention, a method for making the miniaturized lens assembly includes the steps of: 
     a) preparing an imaging substrate including a plurality of image-capturing members, and a lens substrate including a plurality of image-projecting portions that correspond respectively to the image-capturing members; 
     b) applying a photosensitive polymeric material to the lens substrate; 
     c) irradiating and developing the photosensitive polymeric material to form a binding layer having a plurality of through holes aligned respectively with the image-projecting portions on the lens substrate; 
     d) aligning the image-projecting portions of the lens substrate with the image-capturing members of the imaging substrate, and stacking the lens substrate and the imaging substrate together such that the binding layer is disposed between the lens substrate and the imaging substrate; 
     e) bonding the lens substrate to the imaging substrate by pressing the lens substrate and the binding layer against the imaging substrate while curing the binding layer by heating; and 
     f) separating the image-projecting portions from the lens substrate and separating the image-capturing members from the imaging substrate by cutting the lens substrate and the imaging substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a sectional view of a conventional lens assembly; 
         FIG. 2  is a schematic view illustrating a method for manufacturing a conventional camera device disclosed in WO2004027880; 
         FIG. 3  is a partly sectional view of the conventional camera device disclosed in WO2004027880; 
         FIG. 4  is a sectional view of the preferred embodiment of a miniaturized lens assembly according to this invention mounted on a circuit board; and 
         FIGS. 5-13  are views to illustrate consecutive steps of the preferred embodiment of a method for making the miniaturized lens assembly of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 4 , the preferred embodiment of the miniaturized lens assembly  80  according to this invention includes an image-capturing unit  13 , a first lens unit  23 , a first binding layer  50 , a second lens unit  63 , a second binding layer  70 , a light-shielding member  90 , and a barrel  150 . 
     The image-capturing unit  13  includes an image-capturing member  11 . 
     The first lens unit  23  includes a first image-projecting portion  21  for projecting an image along an optical axis to the image-capturing member  11 . 
     The first binding layer  50  extends annularly around the optical axis, and binds the image-capturing unit  13  to the first lens unit  23 . The first binding layer  50  includes a photosensitive polymeric material, and has a spacing thickness to space apart the first lens unit  23  and the image-capturing unit  13 . In this preferred embodiment, the photosensitive polymeric material is a photoresist. 
     The second lens unit  63  includes a second image-projecting portion  61  for projecting the image along the optical axis to the image-capturing member  11  through the first image-projecting portion  21 . 
     The second binding layer  70  extends annularly around the optical axis, and binds the second lens unit  63  to the first lens unit  23 . The second binding layer  70  includes the photosensitive polymeric material and has a spacing thickness to space apart the first and second lens units  23 , 63 . In this preferred embodiment, the photosensitive polymeric material is a photoresist. 
     The light-shielding member  90  surrounds the first binding layer  50 , the first lens unit  23 , the second binding layer  70 , and the second lens unit  63 , is coaxial with the optical axis, and has an opening  91  to permit projection of light onto the second image-projecting portion  61  of the second lens unit  63  and the first image-projecting portion  21  of the first lens unit  23 . 
     The barrel  150  receives the image-capturing unit  13 , the first binding layer  50 , the first lens unit  23 , the second binding layer  70 , the second lens unit  63 , and the light-shielding member  90 . The barrel  150  has an opening  151  proximate to and aligned with the opening  91  of the light-shielding member  90  to permit projection of light onto the second image-projecting portion  61  of the second lens unit  63  and the first image-projecting portion  21  of the first lens unit  23 . 
     The preferred embodiment of the method for making the miniaturized lens assembly  80  according to this invention includes the steps of: 
     A) Preparing an Imaging Substrate and a First Lens Substrate: 
     Referring to  FIGS. 5 and 6 , an imaging substrate  10  and a first lens substrate  20  are prepared. The imaging substrate  10  includes a plurality of image-capturing members  11  which are arranged in rows and columns along two intersecting cutting directions (X, Y). The imaging substrate  10  is provided with two aligning marks  12  spaced apart from each other along one of the two cutting directions (X). The first lens substrate  20  includes a plurality of first image-projecting portions  21  that correspond respectively to the image-capturing members  11 . The first lens substrate  20  is provided with four first aligning marks  22 . Two of the first aligning marks  22  are formed on a top surface  2200  (see  FIG. 7 ) of the first lens substrate  20 . The other two of the first aligning marks  22  are formed on a bottom surface  2220  of the first lens substrate  20 , and are aligned with the first aligning marks  22  on the top surface  2200  of the first lens substrate  20  and with the aligning marks  12  of the imaging substrate  10 , respectively. In this preferred embodiment, each of the image-capturing members  11  is a charge coupled device or a complementary metal-oxide semiconductor. The first lens substrate  20  is an infra-red filter in this embodiment. 
     B) Applying a Photosensitive Polymeric Material: 
     Referring to  FIG. 7 , a photosensitive polymeric material  30  is applied to the first lens substrate  20 . In this preferred embodiment, the photosensitive polymeric material  30  is a positive photoresist, such as AZ4210 and AZ1500 series of photoresist manufactured by AZ Electronic Materials, or a negative photoresist, such as a photosensitive BCE photoresist manufactured by Dow Chemical. 
     C) Soft Baking: 
     The first lens substrate  20  together with the photosensitive polymeric material  30  is soft baked by heating at a temperature ranging from 60 to 90° C. to remove a solvent contained in the photosensitive polymeric material  30 . 
     D) Irradiating and Developing: 
     The photosensitive polymeric material  30  is irradiated through a photo mask  40 , which includes a plurality of through holes  41  aligned with the first image-projecting portions  21  of the first lens substrate  20  correspondingly, and two aligning holes  42  aligned with the first aligning marks  22  of the first lens substrate  20  correspondingly. In this preferred embodiment, the photosensitive polymeric material  30  is a positive photoresist. If a negative photoresist is used, the photo mask  40  should be changed with a photo mask having a pattern reverse to that of the photo mask  40 . 
     Subsequently, the photosensitive polymeric material  30  is developed using a developing agent to dissolve the irradiated portions of the photosensitive polymeric material  30  to form a first binding layer  50 , which has a plurality of first through holes  51  aligned respectively with the first image-projecting portions  21  on the first lens substrate  20 , and two first aligning holes  52  aligned with the first aligning marks  22  of the first lens substrate  20  correspondingly. 
     E) Aligning and Stacking: 
     Referring to  FIG. 8 , the first image-projecting portions  21  of the first lens substrate  20  are aligned with the image-capturing members  11  of the imaging substrate  10  by aligning the first aligning marks  22  of the first lens substrate  20  with the aligning marks  12  of the imaging substrate  10  correspondingly. The first lens substrate  20  and the imaging substrate  10  are stacked together such that the first binding layer  50  is disposed between the first lens substrate  20  and the imaging substrate  10 . 
     F) Bonding: 
     The first lens substrate  20  is bonded to the imaging substrate  10  by pressing the first lens substrate  20  and the first binding layer  50  against the imaging substrate  10  while curing the first binding layer  50  under vacuum by heating at a temperature ranging from 90 to 300° C. 
     G) Preparing a Second Lens Substrate: 
     Referring to  FIG. 9 , a second lens substrate  60  is prepared, which includes a plurality of second image-projecting portions  61  that correspond respectively to the image-capturing members  11  of the imaging substrate  10 . The second lens substrate  60  further includes four second aligning marks  62 . Two of the second aligning marks  62  are formed on a top surface  620  of the second lens substrate  60 . The other two of the second aligning marks  62  are formed on a bottom surface  622  of the second lens substrate  60 , and are aligned with the second aligning marks  62  on the top surface  620  of the second lens substrate  20  and with the first aligning marks  22  of the first lens substrate  20 , respectively. The second lens substrate  60  is made using an upper mold unit  100  and a lower mold unit  200 . The upper mold unit  100  includes an upper mold plate  110 , an array of upper mold cores  120  mounted in the upper mold plate  110  along the cutting directions (X, Y) two upper mark molding cores  130  mounted in the upper mold plate  110  along one of the cutting directions (X), and an upper fixing plate  140  stacked on the upper mold plate  110 . The lower mold unit  200  includes a lower mold plate  210 , an array of lower mold cores  220  mounted in the lower mold plate  210  and corresponding to the upper mold cores  120 , two lower mark molding cores  230  mounted in the lower mold plate  210  and corresponding to the upper mark molding cores  130 , and a lower fixing plate  240  stacked below the lower mold plate  210 . 
     H) Forming a Second Binding Layer: 
     Referring to  FIG. 10 , the steps similar to the aforesaid steps B), C), and D) are conducted to form a second binding layer  70  on the second lens substrate  60 . The second binding layer  70  has a plurality of second through holes  71  aligned with the second image-projecting portions  61  on the second lens substrate  60 , respectively, and two second aligning holes  72  aligned with the second aligning marks  62  of the second lens substrate  20  correspondingly. 
     I) Aligning and Stacking: 
     Referring to  FIG. 11 , the second image-projecting portions  61  of the second lens substrate  60  are aligned with the first image-projecting portions  21  of the first lens substrate  20  and the image-capturing members  11  of the imaging substrate  10  by aligning the second aligning marks  62  of the second lens substrate  60  with the first aligning marks  22  of the first lens substrate  20  correspondingly. The second lens substrate  60  is stacked on the first lens substrate  20  bonded to the imaging substrate  10  such that the second binding layer  70  is disposed between the first lens substrate  20  and the second lens substrate  60 . 
     J) Bonding: 
     The second lens substrate  60  is bonded to the first lens substrate  20  via the second binding layer  70  using a bonding step similar to the aforesaid step F). Therefore, a laminate  700  is obtained, which includes the imaging substrate  10 , the first binding layer  50 , the first lens substrate  20 , the second binding layer  70 , and the second lens substrate  60  in sequence. 
     K) Cutting: 
     Referring to  FIG. 12 , the laminate  700  is fixed on a work table  400  of a cutting machine (not shown) using a UV tape  300 . The second aligning marks  62  of the second lens substrate  20  are aligned with reference aligning marks by adjusting the work table  400 . The laminate  700  is cut by a cutting tool  500  along the cutting directions (X, Y) so as to separate the second image-projecting portions  61  from the second lens substrate  60 , to separate the first image-projecting portions  21  from the first lens substrate  20 , and to separate the image-capturing members  11  from the imaging substrate  10 . Therefore, a plurality of semi-products  81  are obtained accordingly. Each of the semi-products includes the image-capturing unit  13  having the image-capturing member  11 , the first binding layer  50  having the first through hole  51 , the first lens unit  23  having the first image-projecting portion  21 , the second binding layer  70  having the second through hole  71 , and the second lens unit  63  having the second image-projecting portion  61 . The semi-products  81  can be removed from the work table  400  by exposing the UV-tape  300  to a UV-light. 
     L) Covering Each Semi-Product: 
     Referring to  FIG. 13 , a light-shielding member  90  is provided to cover each of the semi-products  81  so as to avoid reflection of light. In this preferred embodiment, the light-shielding member  90  is made of ink. 
     M) Disposing Each of the Semi-Products in a Corresponding Barrel: 
     Referring again to  FIG. 4 , each of the semi-products  81  covered with the light-shielding member  90  is disposed in a corresponding barrel  150  so as to obtain the miniaturized lens assembly  80 , which can be fastened on a base seat  610  of a circuit board  600  by screwing. 
     It should be noted that, according to specific optical requirements, a plurality of the second lens substrates  60  can be stacked on the first lens substrate  20  so that the miniaturized lens assembly  80  includes a plurality of the second lens units  63 . 
     In view of the aforesaid, the miniaturized lens assembly  80  of this invention has the following advantages: 
     1) A plurality of the miniaturized lens assemblies  80  can be made at the same time. The manufacture of the miniaturized lens assembly  80  is relatively simple. Therefore, the productivity is increased significantly, and the production cost is reduced. 
     2) Since the imaging substrate  10 , the first lens substrate  20 , and the second lens substrate  60  are provided with the aligning marks  12 , the first aligning marks  22 , and the second first aligning marks  62 , the stacking and cutting steps can be carried out simply and precisely. 
     3) In addition to acting as a binder for binding the imaging substrate  10 , the first lens substrate  20 , and the second lens substrate  60  together, the first binding layer  50  and the second binding layer  70  also act as spacers to space the imaging substrate  10  apart from the first lens substrate  20  and to space the first lens substrate  20  apart from the second lens substrate  60 . Therefore, the overall thickness of the miniaturized lens assembly  80  of this invention can be controlled relatively easily and can be reduced as compared to the aforesaid prior art. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.