Abstract:
The purpose of the present invention is to provide a lens unit which can create an effective light shield despite the simple process by which the lens unit is produced. A non-transmissive filler (BD) is filled and solidified in the gap between the outer periphery of a light shielding member (SH 1 ) and the outer peripheries of a first lens (L 1 ) and a second lens (L 2 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a lens unit suitable for imaging lenses and the like. 
       BACKGROUND ART 
       [0002]    Compact and extremely thin type imaging devices (hereafter, also called a camera module) are employed for mobile terminals such as mobile telephones and PDA, which are compact and thin electric devices, such as mobile telephones and PDA (Personal Digital Assistant). As imaging elements used for these imaging devices, solid state imaging elements such as CCD image sensors and CMOS image sensors are known. In recent years, the imaging elements have been improved to increase the number of pixels, and to attain higher image resolution and higher performance. Further, an imaging lens to form an image of an object on these imaging elements is required to become compact more in response to the miniaturization of imaging elements, and such requirement tends to become stronger from year to year. 
         [0003]    As an imaging lens used for the imaging device built in such a mobile terminal, an optical system constituted by resin lenses has been known. Incidentally, in the imaging lens, due to unnecessary reflection, glare, and diffusion in a lens barrel or on a lens end face, ghost and flare may take place. In order to prevent such ghost and flare, there is a technique to dispose between lenses a light shielding member (stop) including an opening to restrict a range to allow light rays to pass through. The positioning of the light shielding member is important, because, if it enters an effective diameter, it itself causes ghost or flare. 
         [0004]    PTL (Patent Literature) 1 discloses a technique to utilize a black metal ring as a light shielding member. The advantages of this conventional technique are to make it easy to obtain the positioning accuracy and dimensional accuracy of a light shielding member, and to make it possible to shield light up to a position as near as the end of an effective diameter. However, since a guide for positioning such as a taper and a light shielding member are not likely to deform, a release portion to avoid interference is needed. Accordingly, there is a defect that it is to be disposed only at a limited portion of a lens. 
       CITATION LIST 
     Patent Literature 
       [0005]    PTL1: Japanese Unexamined Patent Application Publication No. 2006-79073 Official Report 
         [0006]    PTL2: Japanese Unexamined Patent Application Publication No. 2010-217279 Official Report 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    On the other hand, there is also a technique to use a material other than a solid material such as a black adhesive agent as another light shielding member. According to such a technique, since a light shielding member deforms unlike the above technique, there is an advantage that restrictions in arrangement are few. However, it is difficult to control a position and a thickness due to the fluidity of an adhesive agent. Accordingly, such an adhesive agent tends to invade an effective diameter, which cause poor products. There is a defect that the yield tends to become low. 
         [0008]    There is also a technique to avoid such a defect. 
         [0009]    PTL2 discloses a technique to form a groove at a position where a light shielding adhesive agent is filled us and to fill the adhesive agent at the groove, thereby making it possible to control the position of the adhesive agent and preventing the lowering of the yield. Further, the height of the adhesive agent filled in the groove is made lower than a surface to come in contact with a lens, whereby dispersion in the thickness of the adhesive agent is made not to influence the accuracy of a position coming in contact with a lens. 
         [0010]    Then, the present invention has been achieved in view of the problems of the conventional techniques, and an object of the present invention is to provide a lens unit capable of shielding light effectively in spite of having been produced through simple processes. 
       Solution to Problem 
       [0011]    A lens unit described in claim  1  includes a first lens, a second lens, an annular light shielding member disposed between the first lens and the second lens, wherein the outer periphery of the light shielding member is disposed at an inside than the outer periphery of the first lens or the second lens, and a non-transmissive filler material is filled up and solidified over a space (region) between the outer periphery of the light shielding member and the outer periphery of the first lens or the second lens. 
         [0012]      FIG. 1  is a cross sectional view of a lens unit LU′ according to a comparative example, and  FIG. 2  is a cross sectional view of a lens unit LU in this embodiment according to the present invention, which shows a state of being assembled in a not-shown imaging apparatus and in which an object side is an upper side and an image side is a lower side.  FIG. 3  is an illustration in which the constitution shown in  FIG. 2  is cut along line and is viewed from the arrow direction. The lens unit LU′ of the comparative example shown in  FIG. 1  includes a first lens L 1 , a second lens L 2 , and an annular light shielding member SH 1  arranged between the first lens L 1  and the second lens L 2 , but does not include a filler material. Here, the outer periphery of the light shielding member SH 1  is disposed at an inside than the outer periphery of the first lens L 1  or the second lens L 2 , and on the outer periphery of the light shielding member SH 1 , the flange portion FL 1  of the first lens L 1  and the flange portion FL 2  of the second lens L 2  come in contact with each other. 
         [0013]    Here, when external light rays OL have invaded the lens unit LU′ from the outside, the external light rays OL are reflected on the image side surface of the first lens L 1 , then, reflected on the outer periphery of the lens unit LU′, penetrate the flange portions FL 1  and FL 2 , so as to pass through the second lens L 2 , and escape to the image side. Accordingly, there is a fear that these rays may become ghost and may reduce imaging quality. 
         [0014]    On the other hand, in the case of the present invention, a non-transmissive filler material is filled up and solidified over a space between the outer periphery of the light shielding member and the outer periphery of each of the first lens and the second lens. Here, an important thing is that, as shown with hatching in  FIG. 3 , the filler material BD is brought in contact with the outer peripheral entire periphery of the light shielding member SH 1 , and brought in contact with the outer peripheral entire periphery of each of the first lens L 1  and the second lens L 2 . If this condition is satisfied, the filler material BD may protrude from the outer periphery of the light shielding member SH 1  to an inner side. However, the filler material BD does not protrude from the inner periphery of the light shielding member SH 1  to an inner side. It is because there is a fear that if the filler material BD protrudes to an inner side, for example, when the light shielding member SH 1  is used as an aperture stop, the function of the light shielding member SH 1  cannot be exhibited. 
         [0015]    In the case of the present invention, when external light rays OL have invaded from the outside, as shown in  FIG. 2 , the external light rays OL are reflected on the image side surface of the first lens L 1 , reflected on the outer periphery of the lens unit LU′, and then, shielded by the filler material BD filled up over a space between the outer periphery of the light shielding member SH 1  and the outer periphery of each of the first lens L 1  and the second lens L 2 . Accordingly, since the external light rays OL do not pass to the second lens L 2  side, an effect to suppress ghost is high. 
         [0016]      FIG. 4  is an illustration showing an enlarged peripheral portion of a lens unit corresponding to the conventional technique of Patent Document 2. In the example shown in  FIG. 4 , a groove GV is disposed along the entire circumference on the top surface of the flange portion FL 2  of the lens and a fluid A is provided in its inside. However, such an operation to pour the fluid A into the groove GV increase one process in the number of processes, and it is necessary to control a filling amount so as not to make the fluid A overflow. Accordingly, there is a problem that time and effort is needed and production cost increases. On the other hand, according to the present invention, unless the filler material BD protrudes from the inner periphery of the light shielding member SH 1  to the inside, even if the filler material BD is coated more than needed, there is no problem in the point of the yield, and the reduction of the number of processes can be attained. Further, depending on a case, even if the filler material BD protrudes into the outer periphery of a lens, there is no problem in the point of the function. 
         [0017]    Further, in the constitution shown in  FIG. 4 , since the flange portion FL 2  where this groove GV is disposed becomes thinner than other portions, the molding becomes difficult in a lens having been thinned to the limitation. Furthermore, if a groove GV is formed on a lens having been thinned, the strength on the portion of the groove becomes much weaker. Moreover, since the transferring section of the molding die shaped so as to transfer this groove GV becomes a convex, there are problems that the machining to form the convex takes a lot of time and the concentration of the stress on the molding die into the convex shortens the service life of the molding die. On the other hand, according to the present invention, there is no need to dispose a grove to be filled up with a filler material. Accordingly, there are advantages that the production cost of the molding die decreases, the service life of the molding die becomes longer, and the strength of the lens becomes high. 
         [0018]    In addition, in the constitution of  FIG. 4 , since the groove GV cannot be brought in contact with the light shielding member SH 1 , there is a fear that external light rays OL may pass between them. However, in the present invention, since the filler material BD is brought in contact with the outer peripheral entire periphery of the light shielding member SH 1 , there is no fear that external light rays OL pass through. 
         [0019]    The lens unit described in claim  2  in the invention described in claim  1  is characterized in that the filler material is an adhesive agent to bond the first lens and the second lens. 
         [0020]    If a light shielding function can be given to an adhesive agent, the reduction of the number of processes can be attained more. 
         [0021]    The lens unit described in claim  3  in the invention described in claim  2  is characterized in that as the adhesive agent, an adhesive agent in which an energy hardenable adhesive agent serving as a base material and carbon black or a metal powder are mixed is used. 
         [0022]    When an energy hardenable adhesive agent is used, since it becomes unnecessary to care about the hardening time, handling characteristics becomes excellent. Examples of the energy hardenable adhesive agent include a UV hardenable adhesive agent which is solidified by being irradiating with UV light rays and a heat hardenable adhesive agent which hardens by being heated. Here, an adhesive agent in which a UV hardenable adhesive agent is mixed with carbon etc., becomes difficult to be hardened due to its light shielding properties. However, a heat hardenable adhesive agent has no problem that hardening is obstructed by the light shielding properties, which is desirable. Further, at the time of joining three lenses, even if light shielding portions overlap with each other, it becomes possible to harden them by heating the entire body. 
         [0023]    The lens unit described in claim  4  in the invention described in claim  3  is characterized in that the energy hardenable adhesive agent is a UV hardenable adhesive, and when the UV hardenable adhesive is hardened, UV light rays are irradiated from both sides of the optical axis to the UV hardenable adhesive provided between the first lens and the second lens. 
         [0024]    As mentioned above, although an adhesive agent in which a UV hardenable adhesive agent is mixed with carbon etc., becomes difficult to be hardened due to its light shielding properties, when UV light rays are irradiated from both sides of the optical axis, it becomes possible to harden the adhesive agent effectively. 
         [0025]    The lens unit described in claim  5  in the invention described in claim  3  is characterized in that the energy hardenable adhesive agent is a heat hardenable adhesive. In the case where UV light rays are difficult to reach a portion between lenses, the heat hardenable adhesive is effective. 
         [0026]    The lens unit described in claim  5  in the invention described in any one of claims  1  to  4  is characterized in that the first lens and the second lens are bonded each other while a distance between the first lens and the second lens is kept at a predetermined distance. 
         [0027]    Even if a filler material is non-transmissive for light, if its thickness is made thin, light tends to permeate through the filler material. In particular, in the state that the first lens and the second lens comes in contact with each other, the thickness of the filler material between them becomes near zero. Then, a distance between the first lens and the second lens is kept at a predetermined distance, whereby the thickness of the filler material filled up between them can be made to a thickness not to allow light to permeate through. 
         [0028]    The lens unit described in claim  6  in the invention described in any one of claims  1  to  5  is characterized in that a first lens array including a plurality of the first lenses and a second lens array including a plurality of the second lenses are arranged to face each other and pasted to each other while interposing the light shielding member and the filler material between the first lens and the second lens, and thereafter, the pasted first lens array and second lens array are cut out for each pair of the first lens and the second lens. 
         [0029]    With this, a plurality of lens units can be produced in large quantities at low cost. 
         [0030]    The lens unit described in claim  7  in the invention described in any one of claims  1  to  6  is characterized in that the lens unit further includes a third lens and an another annular light shielding member disposed between the second lens and the third lens, the outer periphery of the another light shielding member is disposed at an inside than the outer periphery of the second lens or the third lens, and the filler material is filled and solidified over a space between the outer periphery of the light shielding member and the outer periphery of the second lens or the third lens. 
         [0031]    With this, it becomes possible to provide a lens unit in which three or more lenses are superimposed in the optical axis direction. 
       Advantageous Effects of Invention 
       [0032]    According to the present invention, it becomes possible to provide a lens unit capable of shielding light effectively in spite of having been produced through simple processes. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0033]      FIG. 1  is a cross sectional view of a lens unit LU′ according to a comparative example to the present invention. 
           [0034]      FIG. 2  is a cross sectional view of a lens unit LU according to this embodiment of the present invention. 
           [0035]      FIG. 3  is an illustration in which the constitution shown in  FIG. 2  is cut along III-III line and is viewed from the arrow direction. 
           [0036]      FIG. 4  is an illustration showing an enlarged peripheral portion of a lens unit corresponding to the conventional technique of Patent Document 2. 
           [0037]      FIG. 5  is an illustration showing a process of molding a lens array used in this embodiment by using a molding mold, and (a) shows a state that a glass GL is dropped from a nozzle NZ to a lower molding die  20 , and (b) shows an upper molding die  10 . 
           [0038]      FIG. 6  is an illustration showing a process of molding a lens array used in this embodiment by using a molding mold, and shows a state of molding with molding dies. 
           [0039]      FIG. 7  is an illustration showing a process of molding a lens array used in this embodiment by using a molding mold, and shows a state after the molding dies are released. 
           [0040]      FIG. 8  is a perspective view showing a state after a lens array is released from the molding dies. 
           [0041]      FIG. 9  is a perspective view of the front side of a first glass lens array LA 1 . 
           [0042]      FIG. 10  is a perspective view of the back side of the first glass lens array LA 1 . 
           [0043]      FIG. 11  is a cross sectional view of the first glass lens array LA 1 . 
           [0044]      FIG. 12  is a cross-sectional view showing holders HLD and HLD′ to hold the respective back surfaces of the glass lens arrays LA 1  and LA 1 ′. 
           [0045]      FIG. 13  is a perspective view of the holders HLD and HLD′. 
           [0046]      FIG. 14  is a schematic diagram of an apparatus which maintains a predetermined distance between the holder HLD holding the first glass lens array LA 1  and the holder HLD′ holding the second glass lens array LA 1 ′. 
           [0047]      FIG. 15  is a schematic diagram of processes (a) to (e) by which the first glass lens array LA 1  and the second glass lens array LA 1 ′ are pasted together so as to form a lens unit LU. 
           [0048]      FIG. 16  is an illustration in which a state shown in  FIG. 15(   d ) is cut along a XVI-XVI line and viewed from the optical axis direction. 
           [0049]      FIG. 17  is a perspective view of a lens unit LU. 
           [0050]      FIG. 18  is a schematic diagram of processes (a) to (i) by which the first glass lens array LA 1 , the second glass lens array LA 1 ′, and the third glass lens array LA 1 ″ are pasted together so as to form a lens unit LU. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0051]    Hereafter, the embodiments of the present invention will be described with reference to drawings.  FIGS. 5 to 8  are illustrations showing a process of molding a lens array employed in the present embodiment by using a molding die. On the underside surface (lower surface)  11  of an upper molding die  10 , four optical surface transferring surfaces  12  are formed so as to protrude in an arrangement of two rows and two lines. The periphery of each of the optical surface transferring surfaces  12  is shaped in a circular step portion  13  which protrudes by one step from the underside surface  11 . The upper molding die  10  is made of a hard and brittle material capable of enduring glass molding, such as ultra-hard alloy and silicon carbide. A below-mentioned lower molding die  20  is similar to the upper molding die  10 . 
         [0052]    On the other hand, on the top surface  21  of the lower molding die  20 , an approximately square-shaped land portion  22  is formed, and on the flat top surface  23  of the land portion  22 , four optical surface transferring surfaces  24  are formed so as to become concave in an arrangement of two rows and two lines. On each of the four sides of the land portion  22 , a flat surface portion  25  is formed so as to incline at a predetermined angle relative to the respective optical axes of the optical surface transferring surfaces  24 . The two flat surface portions  25  which neighbor on each other so as to make the respective axes orthogonal to each other are connected via a corner portion  26  (refer to  FIG. 8 ). Such a flat surface portion  25  can be formed with sufficient accuracy by machining with a milling cutter and the like. On the land portion  22 , a concave portion used to transfer a mark to indicate a direction may be disposed. Further, a number used to discriminate each of the optical surface transferring surfaces  24  may be disposed at a position other than the optical surface transferring surfaces  24 . 
         [0053]    The multiple optical surface transferring surfaces of the molding die can be formed through grinding with a grinding stone by using an ultra-precision processing machine. After the grinding, in order to remove grinding traces, the optical surface transferring surfaces are subjected to polishing so that each of them can be finished into a mirror surface. The positional accuracy of each of optical surfaces can be confirmed such that a distance from the flat surface portion  25  to the optical surface transferring surface  24  and a distance between the two optical surface transferring surfaces  24  are measured with the use of a three-dimensional measuring instrument and the resulting measurements are checked whether to fall within a predetermined specification. 
         [0054]    Next, description will be given to the molding of a lens array with reference to  FIGS. 5 to 8 . In the case where a lens array including a plurality of optical surfaces is collectively molded by press-molding between the molding dies, any one of the following two methods may be employed. 
         [0055]    In the first method (1), as with the conventional glass lens molding, a preform is preliminarily prepared so as to be shaped in an approximate form of a lens portion. A plurality of such preforms are separately arranged on the respective molding surfaces of a molding die and molded by heating and cooling. 
         [0056]    In the second method (2), a liquefied molten glass is dropped from an upper portion onto the molding surface and molded by cooling without heating. 
         [0057]    In this embodiment, in view of a constitution configured to mold a glass lens array, it is preferable to employ the second method (2). The reason is that the second method (2) makes it possible to enlarge a difference in thickness between a lens portion and a non-lens portion (a portion between two lenses in a plurality of lenses or a portion forming an end portion of an intermediate fabrication component). Further, according to a preferable method, it is preferable to drop collectively a large glass droplet, i.e., a molten glass droplet with a volume capable of being filled sufficiently into at least two molding surfaces without dropping a glass droplet separately into each molding surface. Furthermore, according to a more preferable method, a dropping position is determined so as to drop a large molten glass droplet at a position located with an equal distance from each of a plurality of molding surfaces expected to be filled with a glass droplet. With the employment of the above methods, it becomes possible to minimize a time difference among the respective time periods of the molding surfaces to take for being filled separately with a glass droplet. Accordingly, it becomes possible to minimize a shape difference among the molded lens shapes and a bad influence to optical performance. Naturally, in consideration of the above time difference, small glass droplets may be dropped separately simultaneously into respective molding surfaces, thereby attaining the similar effects. However, in order to make glass into such small glass droplets, an apparatus becomes large and complicate in terms of constitution. Accordingly, the former is more preferable. 
         [0058]    Namely, in the case of a large droplet in the former, as shown in  FIG. 5(   a ), the lower molding die  20  is located beneath a platinum nozzle NZ which communicates with a storage section (not-shown) which stores heated molten glass, and a liquid droplet of the molten glass GL is dropped collectively from the platinum nozzle NZ toward a position on the top surface  21  which is located with an equal distance from each of the plurality of optical surface transferring surfaces  24 . In this state, since the viscosity of the glass GL is low, the dropped glass GL spreads on the top surface  21  so as to wrap up the land portion  22  so that the shape of the land portion  22  is transferred onto the glass GL. Further, in the case of dropping separately small liquid droplets in the latter, a comparatively-large liquid droplet of the glass GL is made to pass through four small holes so as to be separated into four small liquid droplets while adjusting the quantity of each liquid droplet, and the four small liquid droplets are fed separately approximately simultaneously onto the top surface  21 . When liquefied molten glass is dropped, since an air pocket tends to take place among the respective molding surfaces, it is necessary to consider sufficiently the dropping condition to drop the molten glass such as volume. 
         [0059]    Successively, before the glass GL cools, the lower molding die  20  is made approach a position which is located beneath the upper molding die  10  shown in  FIG. 5  ( b ) and faces the upper molding die  10 , and the lower molding die  20  is aligned with the upper molding die  10 . Further, as shown in  FIG. 6 , molding is performed by making the upper molding die  10  and the lower molding die  20  approach each other with the use of a not-shown guide. With this operation, onto the top surface of the flattened glass GL, the optical surface transferring surfaces  12  and the circular step portions  13  of the upper molding die  10  are transferred, and onto its bottom surface, the shape of the land portion  22  of the lower molding die  20  is transferred. At this time, while the underside surface  11  of the upper molding die  10  and the top surface  21  of the lower molding die  20  are held in parallel to each other and separated from each other with a predetermined distance, the glass GL is made cool. The glass GL solidifies in the state that the glass GL is flattened so as to surround around the periphery and the shape of the flat surface portion  25  is transferred onto the glass GL. 
         [0060]    Subsequently, as shown in  FIGS. 7 and 8 , the upper molding die  10  and the lower molding die  20  is made to separate from each other, and the glass GL is taken out, thereby forming a glass lens array LA 1 .  FIG. 9  is a perspective view of the front side of the glass lens array LA 1 , and  FIG. 10  is a perspective view of its back side. Further,  FIG. 11  is a cross-sectional view of the glass lens array LA 1  at a position including the optical axis. 
         [0061]    As shown in the drawings, the glass lens array LA 1  is shaped in a thin square (or octagon) plate as a whole. The glass lens array LA 1  includes a top surface LA 1   a  which is transferred and molded from the underside surface  11  of the upper molding die  10  and is a highly precise flat surface; four concave optical surfaces LA 1   b  which are transferred from the optical surface transferring surfaces  12  onto the top surface LA 1   a ; and shallow circular grooves LA 1   c  which are transferred from the circular step portions  13  to the respective peripheries of the concave optical surfaces LA 1   b . The circular grooves LA 1   c  are used, for example, to accommodate respective light shielding members SH (refer to  FIG. 2 ). 
         [0062]    Further, the glass lens array LA 1  includes a bottom surface LA 1   d  which is transferred from the top surface  23  of the land portion  22  of the lower molding die  20  and is a highly precise flat surface; four convex optical surfaces LA 1   e  which are transferred and molded from the optical surface transferring surface  24  onto the bottom surface LA 1   d , and first flat surfaces LA 1   f  and corner connecting portions LA 1   g  which are transferred respectively from the flat surface portions  25  and the corner portions  26  of the land portion  22 . A reference symbol LA 1   h  represents a mark which is transferred simultaneously and indicates a direction. The first flat surfaces LA 1   f  and the corner connecting portions LA 1   g  constitute an inner peripheral surface. 
         [0063]    In  FIG. 11 , each of the first flat surfaces LA 1   f  is made incline at an angle of 10° to 60° (here, 45°) with respect to each of the respective optical axes OA of the optical surfaces. 
         [0064]    Next, description will be given to a process of forming an intermediate fabrication component  1 M by pasting a glass lens array molded separately in the similar manner to that of the glass lens array LA 1  onto the glass lens array LA 1 .  FIG. 12  is a cross-sectional view showing holders HLD and HLD′ to hold the respective back surfaces of the glass lens arrays LA 1  and LA 1 ′, and  FIG. 13  is a perspective view. The holders HLD and HLD′ are mounted on a XYZ table TBL (not-shown) capable of moving three dimensionally. Here, it is presupposed that a direction along the optical axis of the optical surface is made a Z direction, and directions orthogonal to the Z direction are made an X direction and a Y direction respectively. 
         [0065]    The holder HLD and HLD′ each shaped in a rectangular barrel includes tapered surfaces HLD 1  on its external periphery at the holding side and end surfaces HLD 2  which intersects with the respective tapered surfaces HLD 1 . The tapered surfaces HLD 1  each of which serves as a second flat surface are provided by four in response to the number of the first flat surfaces LA 1   f  of the glass lens array LA 1 , and each of the tapered surfaces HLD 1  is made incline by 45° with respect to the axis of the central opening HLD 3  of the holder HLD. The central opening HLD 3  has a size capable of surrounding the optical surfaces LA 1   e  of the glass lens array LA 1 . Therefore, the end surfaces HLD 2  are enabled to come in contact with the bottom surface LA 1   d  of the glass lens array LA 1 . The back surface side of the central opening HLD 3  is connected to a negative pressure source P. Here, the two tapered surfaces HLD 1  neighboring on each other are connected via a corner tapered surface HLD 5 . The tapered surfaces HLD 1  and the corner tapered surfaces HLD 5  constitute an outer peripheral surface. It may be preferable to form an escape portion (concave portion) E configured to receive the mark LA 1   h  at a part from one of the end faces HLD 2  to one of the corner tapered surfaces HLD 5 . 
         [0066]    It is preferable that each of the holders HLD and HLD′ is made of a stainless material, and subjected to quenching treatment in order to suppress abrasion and deformation, whereby hardness is made HRC  56  or more. Further with regard to a distance between the two tapered surfaces HLD 1  facing each other, an amount of shrinkage at the time of molding of a lens array is calculated, and then the distance is preferably determined in consideration of the amount of shrinkage as a feedback value. 
         [0067]    From the state shown in  FIGS. 12 and 13 , when the holder HLD is made approach the glass lens array LA 1 , the end surfaces HLD 2  are brought in contact with the bottom surface LA 1   d  of the glass lens array LA 1 . In this state, when the inside of the central opening HLD 3  is made into a negative pressure, the glass lens array LA 1  is adsorbed and held by the holder HLD. In this state, the first flat surfaces LA 1   f  of the glass lens arrays LA 1  face the respective tapered surfaces HLD 1  of the holder HLD with a clearance Δ of 10 μm or less (for example, 2 μm)(refer to  FIG. 10 ), or come in contact with the respective tapered surfaces HLD 1 . Further, the corner connecting portions LA 1   g  face the respective corner tapered surfaces HLD 5  with a clearance equal to or more than the above clearance. 
         [0068]    When the first flat surfaces LA 1   f  come in contact with the respective tapered surfaces HLD 1 , the glass lens array LA 1  cannot rotate more than that for the holder HLD. Meanwhile, since the tapered surfaces HLD 1  are regulated by the respective opposite first flat surface LA 1   f , the glass lens array LA 1  cannot move more than that relatively to the holder HLD. That is, by holding the glass lens array LA 1  with the holder HLD, the glass lens array LA 1  can be positioned with high precision for the holder HLD. Therefore, by positioning the two holders HLD to each other with high precision with the XYZ table TBL, the two glass lens arrays LA 1  held respectively by the two holders HLD can be positioned to each other with high precision while facing each other. As a result, with this positioning, all the four optical surfaces can be aligned with high precision. 
         [0069]      FIG. 14  is a schematic diagram of an apparatus which maintains a predetermined distance between the holder HLD holding the first glass lens array LA 1  and the holder HLD′ holding the second glass lens array LA 1 ′. A bolt BT is screwed into a shifting XYZ table TBL which secures the holder HLD and is movable in the vertical direction. The lower end of the Bolt BT is brought in contact with the top surface of a fixed XYZ table TBL′ which secures the holder HLD′. 
         [0070]    When the bolt BT is rotated relatively to the shifting XYZ table TBL, the lower end of Bolt BT moves vertically, whereby a distance between the holder HLD and the HLD′ changes. Accordingly, a distance between the first glass lens array LA 1  and the second glass lens array LA 1 ′ can be maintained at a predetermined distance. A lock nut NT is used to secure the bolt BT with a set pushed-out length to the shifting XYZ table TBL. With the above constitution, the film thickness of a light-shielding adhesive agent BD (later-mentioned) can be managed. 
         [0071]      FIG. 15  is a schematic diagram of processes (a) to (e) by which the first glass lens array LA 1  and the second glass lens array LA 1 ′ are pasted together with each other so as to form a lens unit LU. Here, the illustration of each of the holders HLD and HLD′ is omitted. A 304 type stainless steel serving as a raw material is colored with black, and then the colored stainless steel is used as the light shielding member SH 1 . 
         [0072]    First, as shown in  FIG. 15(   a ), four light shielding members SH 1  each shaped in a doughnut plate are arranged in conformity with the respective lens sections of the second glass lens array LA 1 ′ held by the holder (not-shown). Here, since four shallow concave portions (LA 1   c  in  FIG. 11)  each having a tapered inner periphery surface are formed on the second glass lens array LA 1 ′, the centering of each of the light shielding members SH 1  can be performed based on them. 
         [0073]    Subsequently, as shown in  FIG. 15(   b ), a proper amount of a UV hardenable light shielding adhesive agent BD (for example, Product Name: “World Lock” manufactured by Kyoritsu Chemical &amp; Co., Ltd.) is coated on the surface SF 2  of the second glass lens array LA 1 ′. Successively, as shown in  FIG. 15(   c ), the surface SF 1  of the first glass lens array LA 1  which is held precisely by the holder (not-shown) mounted on the shifting stage is made to face the surface SF 2  of the second glass lens array LA 1 ′, and is made to approach to the surface SF 2  up to a predetermined distance (a gap of about 5 μm between lenses) by using the apparatus shown in  FIG. 14 . Here, as the light shielding adhesive agent BD, a heat hardenable adhesive agent may be used. 
         [0074]    Subsequently, as shown in  FIG. 15(   d ), UV light rays are irradiated from the underside surface of the second glass lens array LA 1 ′. Here, in addition to this, UV light rays may be irradiated from the top surface side of the first glass lens array LA 1 . With this, the light shielding adhesive agent BD is solidified. 
         [0075]      FIG. 16  is an illustration in which a state shown in  FIG. 15(   d ) is cut along a XVI-XVI line and viewed from the optical axis direction. As shown with hatching in  FIG. 16 , a light shielding filler material BD is brought in contact with the outer peripheral entire periphery of each of the four light shielding members SH 1 . Here, the light shielding filler material BD has not reached the outer periphery of the second glass lens array LA 1 ′. However, as mentioned later, the glass lens arrays LA 1  and LA 1 ′ are cut out along dotted lines ( FIG. 15  ( e )), and separated into lens units. Accordingly, if the light shielding filler material BD is filled up to cut-out positions, the light shielding filler material BD is enough to form the lens units. That is, cut-out positions become respective outer peripheries of the lens units. 
         [0076]    After the adhesive agent was solidified, as shown in  FIG. 15(   e ), the absorption of the upper holder is stopped, and the upper holder is separated away, whereby a lens array body IM 12  held at the lower holder can be taken out. Successively, the lens array body IM 12  is cut out along dotted lines with a not-shown dicing blade, whereby it becomes possible to obtain a lens unit sown in  FIG. 17 . The lens unit LU includes the first lens L 1 , the second lens L 2 , and the light shielding member SH 1  disposed between the first lens L 1  and the second lens L 2 , and, the light shielding filler material BD is filled up at the outer periphery of each of the light shielding member SH 1  and the lens unit LU. In the case where each of the flange portion FL 1  of the first lens L 1  and the flange portion FL 2  of the second lens L 2  is shaped in a rectangular form, since superfluous potions are formed at the four corners, external light rays tend to invade. Accordingly, the effects of the present invention can be exhibited particularly. 
         [0077]      FIG. 18  is a schematic diagram of processes (a) to (i) of pasting the first glass lens array LA 1 , the second glass lens array LA 1 ′, and the third glass lens array LA 1 ″ together so as form lens units LU. 
         [0078]    Since  FIGS. 18(   a ) to  18 ( d ) are equivalent to the processes from  FIGS. 15(   a ) to  15 ( d ), descriptions for them are omitted. Apart from these processes, the third glass lens array LA 1 ″ is produced. Successively, as shown in  FIG. 18(   e ), four light shielding members SH 2  each shaped in a doughnut plate are arranged in conformity with the respective lens sections of the third glass lens array LA 1 ″ held by the holder (not-shown). Here, since four shallow concave portions each having a tapered inner periphery surface are formed on the third glass lens array LA 1 ′, the centering of each of the light shielding members SH 2  can be performed based on them. 
         [0079]    Subsequently, as shown in  FIG. 18(   f ), a proper amount of a UV hardenable light shielding adhesive agent BD is coated on the surface SF 3  of the third glass lens array LA 1 ″. Successively, as shown in  FIG. 18(   g ), the lens array body IM 12  is made to face the surface SF 3  of the third glass lens array LA 3  which is held precisely by the holder (not-shown), and is made to approach to it up to a predetermined distance (a gap of about 5 μm between lenses) by using the apparatus shown in  FIG. 14 . 
         [0080]    Subsequently, as shown in  FIG. 18(   h ), UV light rays are irradiated from the underside surface of the third glass lens array LA 1 ″, and the UV light rays reach the light shielding adhesive agent BD filled up on the surface SF 3  of the third glass lens array LA 1 ″ without being interrupted. With this, the light shielding adhesive agent BD is solidified. 
         [0081]    After the adhesive agent was solidified, as shown in  FIG. 18(   i ), the absorption of the upper holder is stopped, and the upper holder is separated away, whereby the third glass lens array LA 1 ″ held at the lower holder can be taken out. Successively, the third glass lens array LA 1 ″ is cut out along dotted lines with a not-shown dicing blade, whereby it becomes possible to obtain a lens unit with a three lens constitution. 
         [0082]    It is clear for a person skilled in the art from the embodiment and technical concept described in this description that the present invention should not be limited to the embodiments described in the description and includes other modified embodiments. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  Upper Mold 
           11  Underside Surface 
           12  Optical Surface Transferring Surface 
           13  Circular Step Portion 
           20  Lower Mold 
           21  Top Surface 
           22  Land Portion 
           23  Top Surface 
           24  Optical Surface Transferring Surface 
           25  Flat Surface Portion 
           26  Corner Portion 
           40  Mirror Frame 
           40   a  Flange portion 
           40   b  Opening 
           40   c  Inner Peripheral Surface 
         LU Lens unit 
         FL 1  Rectangular Plate-shaped Flange 
         FL 2  Rectangular Plate-shaped Flange 
         LA 1  First Glass Lens Array 
         LA 1 ′ Second Glass Lens Array 
         LA 1 ″ Third Glass Lens Array 
         LA 1   b  Concave Optical Surface 
         LA 1   c  Circular groove 
         LA 1   d  Bottom Surface 
         LA 1   e  Optical Surface 
         LA 1   e  Convex Optical Surface 
         LA 1   f  Flat Surface 
         LA 1   g  Corner Linking Portion 
         IM 12  Lens Array Body 
         HLD, HLD′ Holder 
         HLD 1  Tapered Surface 
         HLD 2  End Face 
         HLD 3  Central Opening 
         HLD 4  Roll-off 
         HLD 5  Corner Tapered Surface 
         NZ Platinum Nozzle 
         SH 1 , SH 2  Light shielding member