Abstract:
A method of manufacturing a lens array includes the steps of feeding a first curable resin between a first array mold and a plate member and curing the first resin; separating the plate member from the first array mold; feeding a second curable resin between the first array mold and a second array mold while leaving the cured first resin on the first array mold, and curing the second resin; and removing the first array mold and the second array mold.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method of manufacturing a lens array and a method of manufacturing a stacked lens array. 
       BACKGROUND ART 
       [0002]    In order to reduce a manufacturing cost of imaging lenses or image capturing devices including imaging lenses, a method is known which involves production of lens arrays each consisting of multiple lenses, stacking the lens arrays one another or stacking the lens array and a sensor array consisting of multiple sensors (the number and the locations of the sensors corresponding to the number and the locations of the lens units in the lens array), and cutting (separating) the resultant stack into pieces each including a lens unit. 
         [0003]    According to such a method, two array molds  100  and  110  with multiple recesses (or projections), respectively, corresponding to the shape of lenses are firstly prepared as shown in  FIG. 5A , and the mold  100  is coated with a photocurable or thermally curable resin  120 . Then, as shown in  FIG. 5B , one of the array molds  100  and  110  is moved onto the other such that the space between molds  100  and  110  is filled with the curable resin  120 , and the resin  120  is cured by light or heat. Then, the array molds  100  and  110  are removed as shown in  FIG. 5C  to yield a lens array  122  composed of the cured resin  120  (Refer to Patent Literature 1). 
       CITATION LIST 
     Patent Literature  
       [0004]    Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 2009-279774 (refer to, for example, paragraphs [0031], [0071]-[0072], and [0074]-[0078]) 
       SUMMARY OF THE INVENTION 
     Technical Problem 
       [0005]    Unfortunately, removing the array molds  100  and  110  just after the curing of the resin  120  may cause the cured resin  120  to be deformed after the molds are removed, resulting a variation in pitches of the lenses (distances between the lenses) within a single lens array  122 . This may lead to misalignment between lenses when lens arrays  122  are stacked one another, or between a lens array and a sensor array when a lens array  122  and a sensor array are stacked together. 
         [0006]    Accordingly the main object of the current invention is to provide a method of manufacturing a lens array and a method of manufacturing a stacked lens array which can suppress a variation in lens pitches. 
       Solution to Problem 
       [0007]    According to a first aspect of the present invention, there is provided a method of manufacturing a lens array, the method includes the steps of: 
         [0008]    feeding a first curable resin between a first array mold and a plate member and curing the first resin; 
         [0009]    separating the plate member from the first array mold; 
         [0010]    feeding a second curable resin between the first array mold and a second array mold while leaving the cured first resin on the first array mold, and curing the second resin; and 
         [0011]    removing the first array mold and the second array mold. 
         [0012]    Preferably, the method further includes the step of forming diaphragms on the cured first resin remaining on the first array mold, after separating the plate member and before feeding the second curable resin and curing the second resin. 
         [0013]    According to a second aspect of the present invention, there is provided a method of manufacturing a stacked lens array, the method includes the steps of; 
         [0014]    feeding a first curable resin between a first array mold and a second array mold, and curing the first resin; 
         [0015]    removing the second array mold; 
         [0016]    feeding a second curable resin between a third array mold and a fourth array mold, and curing the second resin; 
         [0017]    removing the fourth array mold; 
         [0018]    bonding the cured first resin remaining on the first array mold and the cured second resin remaining on the third array mold; and 
         [0019]    removing the first array mold and the third array mold. 
         [0020]    Preferably, the method further includes a step of forming a diaphragm on the cured first resin remaining on the first array mold after removing the second array mold. 
       Advantageous Effect of Invention 
       [0021]    According to the first aspect of the present invention, the step of feeding and curing the second curable resin is performed while the first curable resin is left on the first array mold after curing. This can prevent a variation in lens pitches in the first curable resin at least during the step of feeding and curing of the second curable resin. Moreover the first aspect of the present invention can eliminate the use of an adhesive, and thus reduce the manufacturing cost and steps. 
         [0022]    More importantly, the diaphragm is formed in the step between the first curable resin molding and the second curable resin molding. This means that the diaphragm is formed inside the structure of an imaging lens. Thus a separate installation step of a diaphragm on the exterior of an imaging lens is not necessary, and also misalignment between the lens and the diaphragm can be prevented. Additionally, the diaphragm is provided in the area shaped by the plate member of the resin. As a result, the diaphragm resides on a planar surface and can be formed precisely. A further advantage of this case is application of patterning techniques, such as photolithography and screen printing, which are rather inappropriate to delineate patterns on a curved surface. 
         [0023]    According to the second aspect of the present invention, the step of bonding the cured first resin and the cured second resin is performed while the first resin is left on the first array mold after curing and the second resin is left on the third array mold after curing. This can reduce variations in distances between lens components both in the cured first resin and the cured second resin, at least during the bonding step of the cured first resin and the cured second resin. 
         [0024]    More importantly, the diaphragm is formed before the steps of bonding between the cured first resin and the cured second resin. This means that the diaphragm is formed inside the structure of a stacked imaging lens. Thus a separate installation step of a diaphragm on the exterior of a stacked imaging lens is not necessary, and also misalignment between the lens and the diaphragm can be prevented. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0025]      FIG. 1  is a schematic cross sectional view of an imaging lens. 
           [0026]      FIG. 2A  schematically shows a method of manufacturing the imaging lens of  FIG. 1 . 
           [0027]      FIG. 2B  schematically shows a manufacturing step following the step of  FIG. 2A . 
           [0028]      FIG. 2C  schematically shows a manufacturing step following the step of  FIG. 2B . 
           [0029]      FIG. 2D  schematically shows a manufacturing step following the step of  FIG. 2C . 
           [0030]      FIG. 2E  schematically shows a manufacturing step following the step of  FIG. 2D . 
           [0031]      FIG. 2F  schematically shows a manufacturing step following the step of  FIG. 2E . 
           [0032]      FIG. 2G  schematically shows a manufacturing step following the step of  FIG. 2F . 
           [0033]      FIG. 3  is a schematic cross sectional view of a stacked imaging lens. 
           [0034]      FIG. 4A  schematically shows a method of manufacturing the stacked imaging lens of  FIG. 3 . 
           [0035]      FIG. 4B  schematically shows a manufacturing step following the step of  FIG. 4A . 
           [0036]      FIG. 4C  schematically shows a manufacturing step following the step of  FIG. 4B . 
           [0037]      FIG. 4D  schematically shows a manufacturing step following the step of  FIG. 4C . 
           [0038]      FIG. 4E  schematically shows a manufacturing step following the step of  FIG. 4D . 
           [0039]      FIG. 4F  schematically shows a manufacturing step following the step of  FIG. 4E . 
           [0040]      FIG. 5A  schematically shows a method of manufacturing a conventional stacked lens array. 
           [0041]      FIG. 5B  schematically shows a manufacturing step following the step of  FIG. 5A . 
           [0042]      FIG. 5C  schematically shows a manufacturing step following the step of  FIG. 5B . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0043]    Embodiments of the present invention will now be described with reference to the accompanying drawings. 
       First Embodiment  
       [0044]    As shown in  FIG. 1 , an imaging lens  2  is an optical lens including a combination of a resin component  4  and a resin component  6 . 
         [0045]    The resin component  4  has a convex lens portion  4   a . The convex lens portion  4   a  is surrounded by a non-lens portion  4   b  or flange. The resin component  6  also has a convex lens portion  6   a . The convex lens portion  6   a  is surrounded by a non-lens portion  6   b or flange. 
         [0046]    The convex lens portion  4   a  of the resin component  4  and the convex lens portion  6   a  of the resin component  6  are aligned with each other. An optical axis runs through the centers of the convex lens portions  4   a  and  6   a . A diaphragm  8  is provided between the non-lens portion  4   b  of the resin component  4  and the non-lens portion  6   b of the resin component  6  in the interface of the resin components  4  and  6 . 
         [0047]    The resin component  4  is composed of a resin  4 A, and the resin component  6  is composed of a resin  6 A. 
         [0048]    The resin  4 A and  6 A are of photocurable or thermally curable types. 
         [0049]    The resin  4 A and  6 A are different materials with different optical dispersions (Abbe&#39;s numbers), and in particular a low dispersion material for the resin  4 A while a high dispersion material for the resin  6 A. 
         [0050]    The resin  4 A and  6 A may be of the same type. 
         [0051]    Next, a method of manufacturing the imaging lens  2  will now be described. 
         [0052]    As shown in  FIG. 2A , a lens array mold  10  is coated with a resin  4 A. The lens array mold  10  has an array of multiple recess portions  12 . The shape of each recess portion  12  corresponds to the shape of the convex lens portion  4   a  of the imaging lens  2 . 
         [0053]    Then, as shown in  FIG. 2B , one of the lens array mold  10  and a plate member  20  is moved toward the other such that the space between the lens array mold  10  and the plate member  20  is filled with the resin  4 A, and the resin  4 A is cured by light or heat. 
         [0054]    Then, as shown in  FIG. 2C , the plate member  20  is removed. 
         [0055]    Then, as shown in  FIG. 2D , the diaphragm  8  is formed on the cured resin  4 A. 
         [0056]    The diaphragm  8  may be formed with a photoresist including black pigments through photolithography or with a metal film such as a chromium film through etching. An inkjet or screen printing process can also be applied to form the diaphragm  8 . Alternatively, a dimensionally stable black diaphragm member with a similar shape to the lens array, having a light-transmission hole at a region corresponding to the convex lens portion  4   a , can be sandwiched between the resins  4 A and  6 A to form a diaphragm  8 . This prevents a change in distances between the convex lens portions  4   a  and  6   a  after demolding. 
         [0057]    Then, as shown in  FIG. 2E , a lens array mold  30  is coated with the resin  6 A. The lens array mold  30  has an array of multiple recess portions  32 . The shape of each recess portion  32  corresponds to the shape of the convex lens portion  6   a  of the imaging lens  2 . 
         [0058]    Then, as shown in  FIG. 2F , while the cured resin  4 A and the diaphragm  8  are left on the lens array mold  10 , one of the lens array mold  30  and  10  is moved onto the other such that the space between the lens array molds  30  and  10  is filled with the resin  6 A, and then the resin  6 A is cured by light or heat. 
         [0059]    Preferably, the lens array molds  10  and  30  are provided with alignment marks preliminarily formed, so that alignment between these lens array molds  10  and  30  can be achieved through matching of the alignment marks. Alternatively, the lens array molds  10  and  30  are provided with alignment guides preliminarily formed, so that the alignment between the lens array molds  10  and  30  can be achieved by abutting the guides mutually. 
         [0060]    Then, as shown in  FIG. 2G , the lens array molds  10  and  30  are detached from the cured resins  4 A and  6 A to give a lens array  34  composed of the resins  4 A and  6 A. The lens array  34  including convex lens portions  4   a  and  6   a  is cut into multiple imaging lenses  2 . Alternatively, the lens array  34  can also be delivered from the factory as it is. 
         [0061]    According to the above embodiment, from the curing step of the resin  4 A on the lens array mold  10  (see  FIG. 2B ) to the removal step of the lens array molds  10  and  30  (see  FIG. 2G ), the process is carried out with the cured resin  4 A remaining on the lens array mold  10 . This keeps the cured resin  4 A fixed to the recess portions  12  and thus can prevent a change in distance between convex lens portions  4   a  caused by the resin  4 A at least during those steps. 
         [0062]    Moreover, the resin components  4  and  6  are composed of the resins  4 A and  6 A, respectively, which are different resins. The combination of different resins can achieve higher optical performance and more flexible designing compared to a case of manufacturing an imaging lens with a single resin material. 
         [0063]    In addition, the curing of the resin  4 A with the plate member  20  enables the corresponding face of the cured resin  4 A to be planarized, thus facilitating the formation of the diaphragm  8  inside the imaging lens  2 . Such a process does not require a diaphragm structure  36  such as a housing having an opening corresponding to the convex lens portion  4   a  (see  FIG. 1 ) over the exterior of an imaging lens  2 , and alignment between the imaging lens  2  and the diaphragm  36  or an aperture position. This can improve handling performance or versatility of the imaging lens  2 . 
         [0064]    Here, the convex lens portion  4   a  of the resin component  4  and the convex lens portion  6   a  of the resin component  6  may have any profile and can be produced with appropriate lens array molds  10  and  30  having corresponding profiles. 
       Second Embodiment  
       [0065]    As shown in  FIG. 3 , a stacked imaging lens  40  is a combination lens including two lenses, namely a lens  42  and a lens  44 . 
         [0066]    The lens  42  has a convex lens portion  42   a  and a concave lens portion  42   b . The convex lens portion  42   a  and the concave lens portion  42   b  are surrounded by a non-lens portion  42   c  or flange. 
         [0067]    The lens  44  also has a convex lens portion  44   a  and a concave lens portion  44   b . The convex lens portion  44   a  and the concave lens portion  44   b  are surrounded by a non-lens portion  44   c  or flange. 
         [0068]    The convex lens portion  42   a  and the concave lens portion  42   b  of the lens  42  and the convex lens portion  44   a  and the concave lens portion  44   b  of the lens  44  are all arranged in corresponding positions. The concave lens portion  42   b  of the lens  42  faces the concave lens portion  44   b  of the lens  44 . The centers of the convex lens portion  42   a , the concave lens portion  42   b , the convex lens portion  44   a , and the concave lens portion  44   b  are aligned to a common optical axis. A diaphragm  46  is provided between the non-lens portions  42   c  and  44   b  of the lens  42  and  44 , respectively. Instead of such a configuration, the convex lens portion  42   a  may be a concave lens portion, the concave lens portion  42   b  may be a convex lens portion, the convex lens portion  44   a  may be a concave lens portion, and/or the concave lens portion  44   b  may be a convex lens portion. 
         [0069]    The lens  42  is composed of a resin  42 A, and the lens  44  is composed of a resin  44 A. 
         [0070]    The resin  42 A and  44 A are photocurable or thermally curable resins. 
         [0071]    The resin  42 A and  44 A are composed of different materials with different optical dispersions (Abbe&#39;s numbers), and in particular one of the resins  42 A and  44 A is composed of a low dispersion material and the other a high dispersion material. 
         [0072]    In the case of the stacked imaging lens  40 , which is a combination lens, and has an air layer between the lens  42  and  44 , the resin  42 A and  44 A may have the same refractive index. 
         [0073]    The resin  42 A and  46 A may be the same resin. 
         [0074]    Next, a method of manufacturing the stacked imaging lens  40  will now be described. 
         [0075]    As shown in  FIG. 4A , the lens array mold  50  is coated with the resin  42 A. The lens array mold  50  has an array of multiple recess portions  52 . The shape of each recess portion  52  corresponds to the shape of the convex lens portion  42   a  of the lens  42 . 
         [0076]    Then, as shown in  FIG. 4B , one of the lens array molds  50  and  60  is moved onto the other such that the space between the lens array molds  50  and  60  is filled with the resin  42 A, and the resin is cured by light or heat. The lens array mold  60  has an array of multiple projection portions  62 . The shape of each projection portion  62  corresponds to the shape of a concave lens portion  42   b  of the lens  42 . 
         [0077]    Preferably, the lens array molds  50  and  60  are provided with alignment marks preliminarily formed, so that the lens array molds  50  and  60  are aligned with each other by matching the alignment marks. 
         [0078]    Then, as shown in  FIG. 4C , the lens array mold  60  is removed. 
         [0079]    A diaphragm  46  is then formed on the cured resin  42 A. 
         [0080]    The diaphragm  46  can be formed by the same process for the diaphragm  8  in the first embodiment. The diaphragm  46  may extend over a part of the concave lens portion  42   b . A surface covered by the diaphragm  46  is curved in this case, then the diaphragm  46  is preferably formed by an inkjet printing technique. 
         [0081]    In this case, at least an area of the lens array mold  60  corresponding to the area covered by the diaphragm  46  is preferably planar. This has an advantage in that the planar surface can allow for use of patterning techniques, such as photolithography and screen printing, which are rather inappropriate to delineate high precision patterns on a curved surface. 
         [0082]    As shown in  FIG. 4D , a cured resin  44 A on a lens array mold  70  is formed aside from the cured resin  42 A by a similar process shown in  FIG. 4A through 4C . 
         [0083]    Then, as shown in  FIG. 4E , while the cured resin  42 A and the diaphragm  46  remain on the lens array mold  50  and the cured resin  44 A remains on the lens array mold  70 , one of the lens array molds  50  and  70  is moved onto the other to bond the cured resin  42 A, the diaphragm  46 , and the cured resin  44 A. 
         [0084]    The lens array molds  50  and  70  are preferably provided with alignment marks preliminarily formed, then the lens array molds  50  and  70  are aligned with each other through matching the alignment marks, and are mutually bonded with an adhesive or any other means. 
         [0085]    Then, as shown in  FIG. 4F , the lens array molds  50  and  70  are detached from the cured resins  42 A and  44 A to give a stacked lens array  72  including the cured resins  42 A and  44 A. The stacked lens array  72  including the convex lens portions  42   a  (or the concave lens portion  42   b , or the convex lens portions  44   a , or the concave lens portion  44   b ) is cut into multiple stacked imaging lenses  40 . Alternatively, the lens array  72  can also be delivered from the factory as it is. 
         [0086]    According to the above embodiment, from the step of curing the resin  42 A in the lens array mold  50  and curing the resin  44 A in the lens array mold  70  (see  FIG.4B and 4D ) through the step of removing the lens array molds  50  and  70  (see  FIG. 4F ), the process is carried out with the cured resins  42 A and  44 A remaining on the lens array molds  50  and  70 , respectively. Accordingly, the cured resins  42 A and  44 A are maintained in the recess portions  52  and  72 , respectively, at least during those process steps. This enables variations in distances to be reduced between the convex lens portions  42   a  and between the convex lens portions  44   a  caused by the resins  42 A and  44 A. 
         [0087]    Moreover, the lenses  42  and  44  are formed with different resins  42 A and  44 A. The combination of different resins can achieve higher optical performance and more flexible designing of the lens compared to a case of manufacturing a stacked imaging lens with a single resin material. 
         [0088]    In addition, the cured resin  42 A is bonded with the cured resin  44 A after the diaphragm  46  is formed on the cured resin  42 A. This indicates that the diaphragm  46  is formed inside the stacked imaging lens  40 . This does not require a diaphragm structure  74  such as a housing having an opening corresponding to the convex lens portion  42   a  (see  FIG. 3 ) over the exterior of a stacked imaging lens  40 , and alignment between the stacked imaging lens  40  and the diaphragm  74  or an aperture position. This can improve handling performance or versatility of the stacked imaging lens  40 . 
         [0089]    Here, the convex lens portion  42   a  and the concave lens portion  42   b  of the lens  42  and the convex lens portion  44   a  and the concave lens portion  44   b  of the lens  44  may have any profile and can be produced with appropriate lens array molds  50 ,  60 , and  70  having corresponding profiles. 
       INDUSTRIAL APPLICABILITY 
       [0090]    The present invention can be suitably applied to an imaging lens and an image capturing device including such an imaging lens. 
       LIST OF REFERENCE NUMERALS 
       [0091]      2  imaging lens 
         [0092]      4  resin component 
         [0093]      4 A resin 
         [0094]      4   a  convex lens portion 
         [0095]      4   b  non-lens portion (flange) 
         [0096]      6  resin component 
         [0097]      6 A resin 
         [0098]      6   a  convex lens portion 
         [0099]      6   b non-lens portion (flange) 
         [0100]      8  diaphragm 
         [0101]      10  lens array mold 
         [0102]      12  recess portion 
         [0103]      20  plate 
         [0104]      30  lens array mold 
         [0105]      32  recess portion 
         [0106]      34  lens array 
         [0107]      36  diaphragm 
         [0108]      40  stacked imaging lens 
         [0109]      42  lens 
         [0110]      42 A resin 
         [0111]      42   a  convex lens portion 
         [0112]      42   b  concave lens portion 
         [0113]      42   c  non-lens portion (flange) 
         [0114]      44  lens 
         [0115]      44 A resin 
         [0116]      44   a  convex lens portion 
         [0117]      44   b  concave lens portion 
         [0118]      44   c  non-lens portion (flange) 
         [0119]      46  diaphragm 
         [0120]      50  lens array mold 
         [0121]      52  recess portion 
         [0122]      60  lens array mold 
         [0123]      62  projection portion 
         [0124]      70  lens array mold 
         [0125]      72  stacked lens array 
         [0126]      74  diaphragm 
         [0127]      100 ,  110  array mold 
         [0128]      120  curable resin 
         [0129]      122  lens array