Abstract:
There is provided an imaging lens including: a transparent substrate; an upper lens disposed on a top of the transparent substrate; and a lower lens disposed on a bottom of the transparent substrate to correspond to the upper lens, wherein one of the upper and lower lenses includes a lens element and a partition wall formed higher than the lens element to surround the lens element. Also, there is provided a method of manufacturing the same. In the imaging lens, the partition wall is replicated together with the lens element on one or both surfaces of the transparent substrate. The partition wall is formed higher than the lens element and has a flat top surface. Therefore, when another lens element is replicated on an opposite surface of the transparent substrate, the previously replicated lens element is prevented from deformation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 2007-0039391 filed on Apr. 23, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an imaging lens and a method of manufacturing the same, and more particularly, to an imaging lens manufactured by eliminating a problem of a dicing process and preventing a lens element from deformation, and a method of manufacturing the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Increasingly smaller pixels of an image sensor for recent use have also led to a smaller size of an optical device installed in an optical apparatus utilizing such an image sensor. The smaller size of the optical device renders it very difficult to assemble the optical apparatus. To overcome this problem, the optical device has been manufactured by a replication method such as hot embossing or ultraviolet (UV) embossing which ensures wafer-scale mass production. 
         [0006]    A replica method is a known art for manufacturing a data storage device such as a compact disc (CD) and a digital versatile disc (DVD), or a micro lens. Usually, glass or plastic is utilized as a substrate to have various replication layers formed thereon. 
         [0007]    Conventionally, to ensure optical properties of a lens, the lens elements are replicated on one surface of the substrate and then the plurality of substrates are deposited. 
         [0008]    However, this conventional configuration where the plurality of substrates are deposited disadvantageously increases height of the lens elements. 
         [0009]    To overcome this problem, as shown in  FIG. 1 , the lens elements are formed by the replica method on both surfaces of the substrate  200 . However, when a replication layer  210  is formed on one surface and another replication layer  220  is formed on an opposite surface, the lens elements may be impaired due to the replication process. 
         [0010]    Moreover, after the replication process, when the substrate is diced into individual lens units along a line  300 , a dicing tape (not shown) needs to be bonded onto the substrate. This requires the lens element on one of the surfaces of the substrate to have negative refractive power or an additional structure for dicing to be installed on the substrate where the replication layers are formed. 
       SUMMARY OF THE INVENTION 
       [0011]    An aspect of the present invention provides a method of manufacturing an imaging lens in which a dicing tape is easily adhered to overcome a problem of a dicing process, thereby preventing lens elements from deformation during replication process. 
         [0012]    Another aspect of the present invention provides an imaging lens manufactured to prevent lens elements from deformation during replication process. 
         [0013]    According to an aspect of the present invention, there is provided an imaging lens including: a transparent substrate; an upper lens disposed on a top of the transparent substrate; and a lower lens disposed on a bottom of the transparent substrate to correspond to the upper lens, wherein one of the upper and lower lenses includes a lens element and a partition wall formed higher than the lens element to surround the lens element. 
         [0014]    The transparent substrate may include an infra-red blocking layer. The transparent substrate may include a stop. 
         [0015]    The upper lens may include an anti-reflective coating layer formed of one of a metallic material and an amorphous carbon-based organic anti-reflective coating material, wherein the metallic material is one selected from a group consisting of Ti, TiN, MoSi, SiNO, SiC, MoO 3 , Si 3 N 4 , AlGaAs, GaAs, CdSe and Inp. 
         [0016]    The lens element may be formed of an aspherical lens having one of positive and negative refractive powers. The lens element may be formed of a diffractive lens having one of positive and negative refractive powers. 
         [0017]    According to another aspect of the present invention, there is provided a method of manufacturing an imaging lens, the method including: forming a plurality of upper lenses on a transparent substrate, the upper lenses each having an upper lens element and an upper partition wall formed higher than the upper lens element to surround the upper lens element; replicating a plurality of lower lenses on a bottom of the transparent substrate to correspond to the upper lenses; and dicing the transparent substrate along a trimming line passing through the upper partition wall. 
         [0018]    The forming a plurality of upper lenses on a transparent substrate may include: forming a stamp on a first substrate to replicate the plurality of upper lenses, and forming the plurality of upper lenses on the transparent substrate using the stamp. 
         [0019]    In the replicating a plurality of lower lenses, the lower lenses each may include a lower partition wall corresponding to the upper partition wall of each of the upper lenses. 
         [0020]    The dicing the transparent substrate may include: adhering a dicing tape on one of the upper and lower partition walls. 
         [0021]    The forming a plurality of upper lenses on a transparent substrate may include forming an anti-reflective coating layer formed of one of a metallic material and an amorphous carbon-based organic anti-reflective coating material, wherein the metallic material is one selected from a group consisting of Ti, TiN, MoSi, SiNO, SiC, MoO 3 , Si 3 N 4 , AlGaAs, GaAs, CdSe and Inp. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0023]      FIG. 1  is an exemplary view for explaining a conventional process of dicing a replica lens; 
           [0024]      FIG. 2A  to  FIG. 2E  are cross-sectional views illustrating a method of manufacturing an imaging lens according to an exemplary embodiment of the invention; 
           [0025]      FIG. 3  is a cross-sectional view illustrating an imaging lens obtained by a method of manufacturing an imaging lens according to an exemplary embodiment of the invention; 
           [0026]      FIG. 4A  to  FIG. 4E  are cross-sectional views illustrating a method of manufacturing an imaging lens according to another exemplary embodiment of the invention; and 
           [0027]      FIG. 5  is across-sectional view illustrating an imaging lens obtained by a method of manufacturing an imaging lens according to another exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0029]      FIG. 2A  to  FIG. 2E  are cross-sectional views illustrating a method of manufacturing an imaging lens according to an exemplary embodiment of the invention.  FIG. 3  is a cross-sectional view illustrating an imaging lens obtained by a method of manufacturing an imaging lens according to an exemplary embodiment of the invention. Regarding the method of manufacturing the imaging lens according to the present embodiment, a description will be given of a dicing process for which a partition wall is formed to surround each of lens elements. In the following description, well-known functions and constructions are not described in detail since they would obscure the intention in unnecessary detail. 
         [0030]    As shown in  FIG. 2A , in manufacturing the imaging lens according to the present embodiment, a master is formed by bonding a plurality of master molds on one surface, e.g., a bottom of a base  400 . Each of the master molds includes a lens mold  402  formed in an identical shape to the imaging lens to replicate the imaging lens, and a partition wall mold  401 . 
         [0031]    The partition wall mold  401  of the master mold is protruded at a height greater than a height of the lens mold  402  to surround the lens mold  402 . Also, the partition wall mold  401  has a flat top surface. The partition wall mold  401  may be formed at a distance of “D” from the lens mold  402  according to size of a desired final imaging lens. Here, the lens mold  402  of the master mold is of a hemispherical convex shape but not limited thereto. The lens mold  402  may be formed of a concave lens, an aspherical lens having positive or, negative refractive power or a diffractive lens. 
         [0032]    Thereafter, as shown in  FIG. 2B , the master including the plurality of master molds with the partition wall molds  401  are turned upside down, and a polymer  403  is applied to cover the master mold including the partition wall mold  401 . The polymer  403  may utilize ultra-violet (UV)-curable polymer, photopolymer epoxy, polycarbonate, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) resin. 
         [0033]    After the polymer  403  is applied to cover the master mold having the partition wall mold  401 , the polymer  403  is compressed from above by a first substrate  410 . Then, the polymer  403  is cured to be bonded to a bottom of the first substrate  410 . Here, according to type of the polymer used, the polymer  403  may be cured by UV embossing where UV is irradiated or hot embossing where heat is applied. 
         [0034]    Particularly, in a case where the first substrate  410  shown in  FIG. 2B  is a transparent substrate, the first substrate  410  is formed of glass, fused silica, quartz, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) or polyethylene terephthalate (PET). Then, the polymer  403  is cured by UV embossing. 
         [0035]    After the polymer  403  is cured, the master including the partition wall mold  401  and the lens mold  402  is removed, thereby allowing a stamp mold  403 - 1  made of the polymer  403  to be formed on the bottom of the first substrate  410 , as shown in  FIG. 2C . 
         [0036]    Meanwhile, a metal film or a photosensitive polymer film made of e.g. Al or Cr may be applied on a transparent substrate  420  to form a stop  430 . Also, an infra-red (IR) filter  440  may be formed on a bottom of the transparent substrate  420 . 
         [0037]    Particularly, in a case where the stop  430  is formed of the metal film made of e.g., Al or Cr, the stop  430  is less bonded to a lens transparent polymer  450  applied thereon due to high hydrophobic characteristics of the metal film. This requires an additional layer to be formed on the metal film. 
         [0038]    Meanwhile, in a case where the stop  430  is formed of the photosensitive polymer, the stop  430  is superbly bonded to the lens transparent polymer  450  due to high hydrophilic characteristics of the photosensitive polymer. This advantageously precludes a need for forming a bonding layer additionally on the photosensitive resin layer. 
         [0039]    Furthermore, in a case where the stop  430  is formed of the metal film, other sequential processes such as exposure, and deposition and removal of the metal film should follow. Meanwhile, in a case where the stop  430  is formed of the photosensitive polymer, the stop  430  can be formed only by exposure due to characteristics of the photosensitive polymer, thereby reducing manufacturing costs and time. 
         [0040]    Meanwhile, the metal film made of e.g., Al or Cr has high reflectivity and thus light passed through the stop  430  is reflected again on the transparent substrate  420  or other lens elements, thereby deteriorating image quality. On the other hand, the photosensitive resin film having a high light absorption rate in a visible light region, when adopted, can prevent degrade in image quality resulting from such internal total reflection. Here, the photosensitive polymer for the stop  430  may have a light absorption rate of at least 90% in a visible light region. 
         [0041]    As described above, the transparent substrate  420  has the stop  430  formed on the top thereof and the IR blocking filter  440  formed on the bottom thereof. Thereafter, as shown in  FIG. 2C , the lens transparent polymer  450  is applied on the transparent substrate  420  having the stop  430  thereon. After the lens transparent polymer  450  is applied on the transparent substrate  420 , the lens transparent polymer  450  is compressed from above by the first substrate  410  having the stamp mold  403 - 1  thereon, and then cured. Here, when the lens transparent polymer  450  on the transparent substrate  420  is compressed by the stamp mold  403 - 1  of the first substrate  410 , optionally, a release agent may be sufficiently applied on an inner surface of the stamp mold  403 - 1  to prevent the stamp mold  403 - 1  from directly contacting the lens transparent polymer  450 . This allows the stamp mold  403 - 1  from being easily separated from the lens transparent polymer  450 . Therefore, when the lens transparent polymer  450  is compressed and cured by virtue of the stamp mold  403 - 1  and separated from each other, as shown in  FIG. 2D , upper lenses can be replicated on the transparent substrate  420  according to an inner shape of the stamp mold  403 - 1 . Each of the upper lenses includes an upper lens element  452  and an upper partition wall  451  formed higher than the lens element  452  to surround the upper lens element  452  and having a flat top surface. 
         [0042]    Subsequently, other lens transparent polymer is applied on a bottom of the IR blocking filter  440 , and then compressed by another stamp mold (not shown) similar to the stamp mold  403 - 1 , cured and separated. This allows lower lens elements  453  to be formed in correspondence with the lens elements  452  of the upper lenses as shown in  FIG. 2D . 
         [0043]    When the lower lens elements  453  are formed to correspond to the upper lens elements  452 , the upper partition wall  451  of the upper lens can prevent the upper lens element  452  from being impaired during the compression process. 
         [0044]    Moreover, one of the lower lens element  453  and the upper lens element  452  may include an anti-reflective coating layer. The anti-reflective coating layer may be formed of one of a metallic material and an amorphous carbon-based organic anti-reflective coating material. Here, the metallic material is one selected from a group consisting of Ti, TiN, MoSi, SiNO, SiC, MoO 3 , Si 3 N 4 , AlGaAs, GaAs, CdSe and Inp. 
         [0045]    As described above, the transparent substrate  420  has the upper partition wall  451  formed on the top thereof and the lower lens element  453  formed on the bottom thereof. Thereafter, as shown in  FIG. 2E , a dicing tape  460  may be adhered to the upper partition wall  451 . 
         [0046]    As shown in  FIG. 2E , the upper partition wall  451  of the upper lens is formed higher than the upper lens element  452  and has a flat top surface, thereby ensuring the dicing tape  460  for the dicing process to be easily adhered to the upper partition wall  451 . 
         [0047]    Afterwards, with the dicing tape  460  adhered to the upper partition wall  451 , as shown in  FIG. 2E , to separate the upper lens elements  452  and the lower lens elements  453  integrally with each other, the transparent substrate  420  is diced along a trimming line  470  passing through the upper partition wall  451 . 
         [0048]    Here, when the dicing process is performed along the trimming line  470 , to prevent the upper lens elements  452  from being damaged by a blade used, the top surface of the upper partition wall  451  should have a width greater than a width of the blade. 
         [0049]    Therefore, with the dicing performed along the trimming line  470 , as shown in  FIG. 3 , an imaging lens is produced. The imaging lens includes the stop  430 , the upper partition wall  451  and the upper lens element  452  formed on the top of the transparent substrate  420 , and the IR blocking filter  440  and the lower lens element  453  formed on the bottom of the transparent substrate  420 . 
         [0050]    Hereinafter, a description will be given of a method of manufacturing an imaging lens according to another exemplary embodiment of the invention. 
         [0051]      FIGS. 4A to 4E  are cross-sectional views illustrating a method of manufacturing an imaging lens according to another exemplary embodiment of the present invention.  FIG. 5  is a cross-sectional view illustrating an imaging lens obtained by a method of manufacturing an imaging lens according to another exemplary embodiment of the invention. 
         [0052]    First, as shown in  FIG. 4A , in manufacturing the imaging lens according to the present embodiment, a master is formed by bonding a plurality of master molds  510  on one surface, e.g., a bottom of base  500  to replicate the imaging lens. 
         [0053]    Each of the master molds  510  includes a partition wall  511  formed in an identical shape to a lens element which is to be formed later. The partition wall  511  is protruded at a height greater than a height of the lens element to surround the lens element and has a flat top surface. Here, the master mold  510  is of a hemispherical convex shape but not limited thereto. The master mold  510  may be formed of a concave lens, an aspherical lens having positive or negative refractive power or a diffractive lens. 
         [0054]    Thereafter, as shown in  FIG. 4B , the master including the plurality of master molds  510  with the partition walls  511  are turned upside down, and a polymer  600  is applied to cover the master mold  510  including the partition wall  511 . The polymer  600  may utilize ultra-violet (UV)-curable polymer, photopolymer epoxy, polycarbonate, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) resin. 
         [0055]    After the polymer  600  is applied to cover the master mold  510  having the partition wall  511 , the polymer  600  is compressed from above by a first substrate  700 . Then, the polymer  600  is bonded to a bottom of the first substrate  700  and UV is irradiated onto the polymer  600  from above the first substrate  700  to cure the polymer  600  by UV embossing. Of course, according to type of the polymer used, the polymer  600  may be cured by UV embossing where UV is irradiated or hot embossing where heat is applied. 
         [0056]    The first substrate  700  shown in  FIG. 4B  may be a transparent substrate formed of glass, fused silica, quartz, polydimethylsiloxane (PDMS), polymethymethacrylate (PMMA) or polyethylene terephthalate (PET). In a case where the first substrate  700  is such a transparent substrate, the polymer  600  can be cured by UV embossing. 
         [0057]    After the polymer  600  is cured, the master including the partition wall  511  is separated, thereby allowing a stamp mold  610  made of the polymer  600  to be formed on the bottom of the first substrate  700 , as shown in  FIG. 4C . Meanwhile, a metal film or a photosensitive polymer film made of e.g. Al or Cr may be applied on a transparent substrate  800  to form a stop  820 . Also, an infra-red (IR) filter  810  is provided on a bottom of the transparent substrate  800 . 
         [0058]    Particularly, in a case where the stop  820  is formed of the metal film made of e.g., Al or Cr, the stop  820  is less bonded to a lens transparent polymer  830  applied thereon due to high hydrophobic characteristics of the metal film. This requires an additional layer to be formed on the metal film. 
         [0059]    Meanwhile, in a case where the stop  820  is formed of the photosensitive polymer, the stop  820  is superbly bonded to the lens transparent polymer  830  due to high hydrophilic characteristics of the photosensitive polymer. This advantageously precludes a need for forming a bonding layer additionally on the photosensitive resin layer. 
         [0060]    Furthermore, in a case where the stop  820  is formed of the metal film, other sequential processes such as exposure, and deposition and removal of the metal film should follow. On the other hand, in a case where the stop  820  is formed of the photosensitive polymer, the stop  820  can be formed only by exposure due to characteristics of the photosensitive polymer, thereby reducing manufacturing costs and time. 
         [0061]    Meanwhile, the metal film made of e.g., Al or Cr has high reflectivity and thus light passed through the stop  820  is reflected again on the transparent substrate  800  or other lens elements, thereby deteriorating image quality. On the other hand, the photosensitive resin film having a high light absorption rate in a visible light region, when adopted, can prevent degrade in image quality resulting from such internal total reflection. Here, the photosensitive polymer for the stop  820  may have a light absorption rate of at least 90% in a visible light region. 
         [0062]    As described above, the transparent substrate has the stop  820  formed on the top thereof and the IR blocking filter  810  formed on the bottom thereof. Thereafter, as shown in  FIG. 4D , the lens transparent polymer  830  is applied on the transparent substrate  800  having the stop  820  thereon. 
         [0063]    After the lens transparent polymer  830  is applied on the transparent substrate  800 , the lens transparent polymer  830  is compressed from above by the first substrate  700  having the stamp mold  610  thereon, and then UV is irradiated from above the transparent substrate  800  to cure the lens transparent polymer  830  by TV embossing. Here, when the lens transparent polymer  830  on the transparent substrate  800  is compressed by the stamp mold  610  of the first substrate  700 , optionally, a release agent may be sufficiently applied on an inner surface of the stamp mold  610  to prevent the stamp mold  610  from directly contacting the lens transparent polymer  830 . This allows the stamp mold  610  from being easily separated from the lens transparent polymer  830 . 
         [0064]    Therefore, when the lens transparent polymer  830  is compressed and cured by virtue of the stamp mold  610  and separated from each other, as shown in  FIG. 4E , upper lenses can be replicated on the transparent substrate  800  according to an inner shape of the stamp mold  610 . Each of the upper lenses includes a lens element  833  and an upper partition wall  832  formed higher than the lens element  833  to surround the lens element  833  and having a flat top surface. 
         [0065]    Subsequently, other lens transparent polymer is applied on a bottom of the IR blocking filter  810 , and then compressed by another stamp mold (not shown) similar to the stamp mold  610 , cured and separated. This allows lower lenses  841  to be replicated corresponding to the upper lenses  831 . Each of the lower lenses includes a lens element  843  and a lower partition wall  842  formed higher than the lens element  843  to surround the lens element and having a flat top surface. 
         [0066]    When the lower lens  841  is replicated corresponding to the upper lens  831 , the upper partition wall  832  can prevent the lens element of the upper lens  831  from being impaired during the compression process. 
         [0067]    Moreover, one of the lower lens element  453  and the upper lens element  452  may include an anti-reflective coating layer. The anti-reflective coating layer may be formed of one of a metallic material and an amorphous carbon-based organic anti-reflective coating material. Here, the metallic material is one selected from a group consisting of Ti, TiN, MoSi, SiNO, SiC, MoO 3 , Si 3 N 4 , AlGaAs, GaAs, CdSe and Inp. 
         [0068]    As described above, the transparent substrate  800  has the upper lenses  831  and the lower lenses  841  formed on the top and bottom thereof, respectively. Thereafter, as shown in  FIG. 4F , a dicing tape  460  may be adhered to one of the upper partition wall  832  and the lower partition wall  842 . The dicing tape  460  may be adhered to the lower partition wall  842  of the lower lens  841  as shown in  FIG. 4F . 
         [0069]    As shown in  FIG. 4F , the upper partition wall  832  of the upper lens  831  and the lower partition wall  842  of the lower lens  841 , respectively, are formed higher than a corresponding one of the upper and lower lens elements and have a flat top surface. This ensures the dicing tape  460  for the dicing process to be easily adhered. 
         [0070]    Afterwards, with the dicing tape  460  adhered to the lower partition wall  842  of the lower lens  841 , as shown in  FIG. 4F , to separate the upper lens  831  and the lower lens  841  integrally with each other, dicing is performed along trimming lines  900  each passing through the upper and lower partition walls  832  and  842 . 
         [0071]    Here, when the dicing process is performed along the trimming lines  900 , to prevent the lens elements from being damaged by a blade used, the respective top surfaces of the upper and lower partition walls  832  and  842  should have a width greater than a width of the blade. 
         [0072]    Therefore, with the dicing performed along the trimming lines  900 , as shown in  FIG. 5 , an imaging lens is produced. The imaging lens includes the upper lens  831  having the stop  820  and the upper partition wall  832  formed on the top of the transparent substrate  800 , and the lower lens  841  having the IR blocking filter  810  and the lower partition wall  842  formed on the bottom of the transparent substrate  800 . 
         [0073]    As set forth above, according to exemplary embodiments of the invention, in a method of manufacturing an imaging lens of the present embodiment, a partition wall formed higher than the lens element and having a flat top surface is replicated together with the lens element on at least one surface of the transparent substrate. This partition wall prevents the previously replicated lens element from being deformed when another lens element is replicated on an opposite surface of the transparent substrate. Also, a dicing tape for a dicing process can be adhered to the partition wall regardless of the shape of the lens element, thereby facilitating the dicing process. 
         [0074]    While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.