Patent Publication Number: US-2015065797-A1

Title: Electronic endoscope device, imaging module, and image pick-up lens molding method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2013/061865 filed on Apr. 23, 2013, which claims priority under 35 U.S.C §119(a) to Japanese Patent Application No. 2012-120645 filed on May 28, 2012. Each of the above application is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic endoscope device, an imaging module, and an image pick-up lens molding method. 
     2. Description of the Related Art 
     An imaging module including an imaging element and an objective lens optical system is built in an endoscope tip portion of an electronic endoscope device in such a manner that image light from a part to be observed, which enters through the objective lens optical system, is focused on a light receiving surface of the imaging element. 
     The objective lens optical system is configured by the combination of a plurality of optical elements, for example, as described in the following JP2010-22617A and JP1997-105871A (JP-H09-105871A). An objective lens optical system described in JP2010-22617A is illustrated in  FIG. 6 . 
     A back side of a first optical element G 1  that constitutes a tip lens is formed with a spherical recess S that applies lens power to the first optical element G 1 , and a second optical element G 2  that is a plate-shaped member is attached so as to block the recess S. If a sealed state of a gap formed by the recess S is not maintained, dew formation will occur in the recess S and the quality of a captured image will be degraded. 
     Thus, in the related art, an adhesive layer M is provided on a joining surface between the first optical element G 1  and the second optical element G 2  to tightly bond both of the elements together so as to maintain the sealed state. However, even if the first optical element G 1  and the second optical element G 2  are brought into close contact with each other with the adhesive layer M, there is a concern that moisture may permeate into the gap S if a long period of time passes. This concern becomes greater as the length of the adhesive layer M up to the recess S becomes shorter. 
     As for the present endoscope, the external diameter thereof is about 9 mm and making the diameter smaller is attempted. A light guide through which illumination light is guided, a forceps pipe, and an air/water supply pipe besides the objective lens optical system are provided in an endoscope tip portion. For this reason, the diameter (the diameter D of  FIG. 6 ) of the objective lens optical system becomes about 3 mm to 4 mm, and a bonding margin portion of the adhesive, that is the length of the adhesive layer M will become 1 mm or less, 
     Moreover, it is difficult to uniformly apply the adhesive to such a narrow place, and there is also a problem in that the assembly cost of the imaging module will be increased. If the adhesive is unevenly applied, a concern becomes high that moisture may permeate into the gap S from an uneven portion of the adhesive. If a surplus adhesive is applied in order to avoid this, the surplus adhesive will ooze out in the direction of an optical axis, and the imaging module will become defective. 
     For this reason, the problem of the sealability of the recess S of the tip lens should be solved as the objective lens optical system of the imaging module becomes smaller. Moreover, it is necessary to make the assembly of the objective lens optical system easy. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an electronic endoscope device, an imaging module, and an image pick-up lens molding method that can prevent dew formation and facilitate manufacture. 
     The imaging module of the invention is a lens module including an objective lens optical system; and an imaging element that receives incident light that has entered through the objective lens optical system. The objective lens optical system includes a tip lens in which a tip surface that incident light enters and a back surface opposite to the tip surface are formed in a plane, and a recess that condenses the incident light is formed at a central portion of the back surface; a plane plate that is installed on a back side of the tip lens to block the recess; and a lens barrel that integrally molds and forms the entire outer peripheral surfaces of the tip lens and the plane plate with resin, while a state is maintained where the plane plate is pressed against the tip lens, and the plane plate and the back surface of the tip lens are directly brought into close contact with each other at an entire joining surface therebetween. 
     The electronic endoscope device of the invention has the above imaging module built in an endoscope tip portion. 
     The imaging lens molding method of the invention is a method for molding an imaging lens of a lens barrel that houses a tip lens in which a tip surface that incident light enters and a back surface opposite to the tip surface are formed in a plane, and a recess that condenses the incident light is formed at a central portion of the back surface, and a plane plate that is installed on a back side of the tip lens to block the recess. The method includes integrally molding the entire outer peripheral surfaces of the tip lens and the plane plate with resin, while a state is maintained where the plane plate is pressed against the tip lens, and the plane plate and the back surface of the tip lens are directly brought into close contact with each other at an entire joining surface therebetween. 
     According to the invention, the plane plate and the back surface of the tip lens are directly brought into close contact with each other at the entire surface without providing an adhesive layer therebetween, permeation of moisture into it recess S formed in the tip lens can be prevented, and it is possible to keep the quality of a captured image high. 
     When an adhesive layer is provided between the plane plate and the back surface of the tip lens, an interface is formed between the plane plate and the adhesive layer, and an interface is also formed between the adhesive layer and the back surface of the tip lens. If the plane plate and the rip lens are bonded together with the adhesive, the entire interfaces of the two interfaces are not brought into a close contact state when the interfaces are viewed from the size of a moisture molecule level, and a gap through which moisture molecules pass will be formed. 
     In the invention, since no adhesive layer is provided, the number of interfaces, that is, a permeation path for moisture molecules, decreases, and it is possible to prevent permeation of moisture into the recess space S. This effect becomes greater as the imaging module is smaller. 
     Additionally, since the invention provides the structure in which the adhesive layer is made unnecessary, the assembly of the imaging module becomes easy and it is possible to achieve cost reduction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system configuration view of an electronic endoscope device related to an embodiment of the invention. 
         FIG. 2  is a perspective view of an endoscope tip portion illustrated in  FIG. 1 . 
         FIG. 3  is a cross-sectional schematic view taken along line illustrated in  FIG. 2 . 
         FIG. 4  is a view describing a method for manufacturing it preceding stage lens barrel illustrated in  FIG. 3 . 
         FIG. 5  is a cross-sectional view of the preceding stage lens barrel and a tip lens manufactured by the method described in  FIG. 4 . 
         FIG. 6  is a longitudinal cross-sectional view of an objective lens optical system built in a related-art endoscope tip portion. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the invention will be described with reference to the drawings. 
       FIG. 1  is a system configuration view of an electronic endoscope device related to an embodiment of the invention. The electronic endoscope device (endoscope system)  10  of the present embodiment is constituted of an endoscope  12 , a processor unit  14  and a light source unit  16  that constitute a body device. The endoscope  12  includes a flexible insertion section  20  inserted into a patient&#39;s (subject&#39;s) body cavity, an operation section  22  provided continuously at a base end portion of the insertion section  20 , and a universal cord  24  connected to the processor unit  14  and the light source unit  16 . 
     A tip portion  26  is provided continuously at a tip of the insertion section  20 , and an imaging chip  54  (refer to  FIG. 3 ) that constitutes an imaging module for picking up an image of the inside of the body cavity is built within the tip portion  26 . A bending portion  28  formed by coupling a plurality of bending pieces together is provided behind the tip portion  26 . When an angle knob  30  provided at the operation section  22  is operated, a wire inserted into the insertion section  20  is pushed/pulled and the bending portion  2  makes bending motions in vertical and horizontal directions. Accordingly, the tip portion  26  is directed to a desired direction within the body cavity. 
     A connector  36  is provided at a base end of the universal cord  24 . The connector  36  is a composite type connector, and is not only connected to the processor unit  14  but also connected to the light source unit  16 . 
     The processor unit  14  supplies electric power to the endoscope  12  via a cable  68  (refer to  FIG. 3 ) inserted through the universal cord  24  to control the driving of the imaging chip  54 , receives imaging signals transmitted via the cable  68  from the imaging chip  54 , and performs various signal processing on the received imaging signals to convert the imaging signals to image data. 
     The image data converted by the processor unit  14  is displayed on as monitor  38  cable-connected to the processor unit  14  as an endoscope pick-up image (observation image). Additionally, the processor unit  14  is also electrically connected to the light source unit  16  via the connector  36 , and generally controls the operation of the endoscope system  10  including the light source unit  16 . 
       FIG. 2  is a perspective view of the tip portion  26  of the endoscope  12 . As illustrated in  FIG. 2 , a tip surface  26   a  of the tip portion  26  is provided with an observation window  40 , illumination windows  42 , a forceps outlet  44 , and an air/water supply nozzle  46 . 
     The observation window  40  is arranged so as to be eccentric to one side from center of the tip surface  26   a.  Two illumination windows  42  are disposed at positions symmetrical to the observation window  40  as a center, and irradiate a part to be observed within the body cavity with illumination light from the light source unit  16 . 
     The forceps outlet  44  is connected to a forceps pipe  44   a  (refer to  FIG. 3 ) disposed within the insertion section  20 , and communicates with a forceps inlet  34  (refer to  FIG. 1 ) provided in the operation section  22 . Various treatment tools having an injection needle, a high-frequency knife, and the like disposed at tips thereof are inserted through the forceps inlet  34 , and the tips of the various treatment tools are passed into the body cavity from the forceps outlet  44 . 
     The air/water simply nozzle  46  jets washing air or water supplied from an air/water supply unit built in the light source unit  16  toward the observation window  40  or the inside of the body cavity in response to the operation of an air/water supply button  32  (refer to  FIG. 1 ) provided at the operation section  22 . 
       FIG. 3  is a cross-sectional schematic view taken along line III-III of  FIG. 2 , and is a view illustrating as longitudinal cross-section of the imaging module built in the tip portion  26  of the endoscope  12 . As illustrated in  FIG. 3 , a lens barrel  51  that holds an objective lens optical system  50  for taking in image light of the part to be observed within the body cavity is disposed in the depths of the observation window  40 . 
     The objective lens optical system  50  includes a tip lens  50   a,  a disc-like transparent parallel plane plate (simply referred to as is plane plate)  50   b,  a fixed lens  50   e,  movable lenses  50   d  and  50   e,  and a fixed lens  50   f  from a tip side. Here, the tip side means a tip portion  26  side of the endoscope  12 . 
     An optical axis of the objective lens optical system  50  is provided so as to become parallel to a central axis of the insertion section  20 . A prism  56  that bends the image light of the part to be observed, which has been through the objective lens optical system  50 , substantially at a right angle and guides the bent image light towards the imaging chip  54  is connected to a rear end of the lens barrel  51 . 
     The imaging chip  54  is constituted by a solid-state imaging element  58 , such as a CCD type and a CMOS type, and a monolithic semiconductor with which a peripheral circuit that performs the driving and signal input/output of the signal of the solid-state imaging element  58  are integrally formed. The imaging chip  54  and the peripheral circuit are mounted on a supporting substrate  62 . An imaging surface (light receiving surface) of the solid-state imaging element  58  is arranged so as to face an emission surface of the prism  56 . 
     The objective lens optical system  50  in the illustrated example constitutes a zoom lens, and the solid-state imaging element  58  is enabled to capture an image in which the part to be observed is enlarged with a desired magnification by moving the positions of the movable lenses  50   d  and  50   e  along the optical axis and changing a mutual distance between the movable lenses or distances from the fixed lenses  50   c  and  50   f.    
     For this reason, cylindrical cam members  52   a  and  52   b  are attached to the movable lenses  50   d  and  50   e,  respectively. Inner peripheral surfaces of center holes of the cylindrical cam members  52   a  and  52   b  are respectively provided with projections  52   c  and  52   d,  and a cam shaft  53  is inserted into the center holes. Cam grooves  53   a  and  53   b  that are slidably fitted to the projections  52   c  and  52   d,  respectively, are engraved in a peripheral surface of the cam shaft  53 . 
     As the cam shaft  53  is rotationally driven around an axis, the cylindrical cam members  52   a  and  52   b  move in an axial direction, and the movable lenses  50   d  and  50   e  move along the optical axis of the objective lens optical system  50 . The magnifying power of the objective lens optical system  50 , that is, the focal distance of the objective lens optical system  50 , is adjusted depending on the rotational position of the cam shaft  53 . 
     A power transmission wire  48  is attached to a base end of the cam shaft  53 . The power transmission wire  48  is inserted to the operation section  22  of  FIG. 1 , and is rotationally driven by a motor (not illustrated) provided at the operation section  22 . An endoscope operator operates an enlargement/reduction instruction switch of the motor provided at the operation section  22 , thereby issuing an instruction for enlargement/reduction of a captured image. 
     A plurality of input/output terminals are provided side by side on a surface portion of the supporting substrate  62 , at a rear end of the supporting substrate  62  provided to extend toward a rear end of the insertion section  20 , and signal lines  66  for intermediating exchange of various signals with the processor unit  14  via the universal cord  24  of  FIG. 1  are joined to the input/output terminals. 
     The plurality of signal lines  66  are collectively inserted into the flexible tubular cable  68 . The cable  68  is inserted through the insertion section  20 , the operation section  22 , and the universal cord  24  respectively, and is connected to the connector  36 . 
     Although illustration is omitted in  FIGS. 2 and 3 , an emission end of a light guide that guides illumination light from the light source unit  16  is disposed in the depths of the illumination window  42 . Similar to the cable  68 , the light guide configured by bundling a number of optical fibers is inserted through the insertion section  20 , the operation section  22 , and the universal cord  24 , respectively, and an incident end is connected to the connector  36 . 
     The lens barrel  51  of the present embodiment has a two-stage configuration and is constituted by a preceding stage lens barrel  51   a  and a subsequent stage lens barrel  51   b  having the same optical axis, and the subsequent stage lens barrel  51   b  is provided continuously at a rear portion of the preceding stage lens barrel  51   a.    
     The tip lens  50   a,  the plane plate  50   b,  and the fixed lens  50   c  are housed within the preceding stage lens barrel  51   a.  The movable lenses  50   d  and  50   e  and the fixed lens  50   f  are housed in the subsequent stage lens barrel  51   b.    
     The tip lens  50   a  is a condensing lens in which a tip surface is planar and a spherical recess S is formed on a back side. The recess S is blocked by the plane plate  50   b.  A combination structure of the tip lens  50   a  and the plane plate  50   b  is similar to the objective lens optical system described in JP2010-22617A. 
     However, the present embodiment provides a structure in which the plane plate  50   b  is directly brought into close contact with a back surface of the tip lens  50   a  without providing an adhesive layer between the back surface of the tip lens  50   a  and the plane plate  50   b,  and even a slight gap is not formed between a joining surface between both the tip lens and plane plate. This manufacturing method will be described with reference to  FIG. 4  to be described below. 
     When the back surface of the tip lens  50   a  and the plane plate  50   b  come into close contact with each other, moisture can be prevented from entering the recess S of the tip lens  50   a  through the joining surface. That is, even if a cleaning liquid is jetted from the nozzle  46  of  FIG. 2  to the tip lens  50   a  and the temperature of the tip lens  50   a  falls, a phenomenon in which dew formation occurs within the recess S and the recess space becoming cloudy is prevented. 
       FIG. 4  is a cross-sectional view illustrating a manufacturing method of providing a structure in which the tip lens  50   a  made of glass and the plane plate  50   b  made of glass is molded integrally with the preceding stage lens barrel  51   a,  the back surface of the tip lens  50   a  is directly brought into close contact with the plane plate  50   b,  and even a slight gap is not formed in the joining surface between both the tip lens and the plane plate. 
     A substantially hemispherical recess S centered on the optical axis is formed in the back surface of the tabular cylindrical tip lens  50   a,  and a back surface  71  other than the recess S is polished into a flat plane. Although it is better that the flatness of the back surface  71  is higher and it is ideal that the back surface is a perfect plane in which an irregularity difference (height difference) is zero, at least, it is preferable that the polishing roughness is No. 400 or more at a grinding surface. 
     Although it is better that the flatness of a surface  72  of the plane plate  50   b  that blocks the recess S of the tip lens  50   a  is higher, at least, it is also preferable to grind this surface in a plane having the performance of ten or more Newton rings. 
     Since the external diameters of the tip lens  50   a  and the plane plate  50   b  are about 3 mm, it is easy to grind the back surface  71  and the surface  72  with the flatness as described above. In addition, in the illustrated example, the external diameter or the plane plate  50   b  is made smaller than the external diameter of the tip lens  50   a.    
     A first mold  80  forms a disk shape and a bottomed hole  80   a  into which a planar tip surface side of the tip lens  50   a  is drilled at a center position of the first mold. The hole  80   a  is formed with such an internal diameter that the tip lens  50   a  is insertable thereinto and a gap is not formed between an outer peripheral surface of the tip lens  50   a  and an inner peripheral surface of the hole  80   a.  A central axis of the hole  80   a  is provided so as to coincide with the optical axis of the tip lens  50   a  when the tip lens  50   a  is inserted into the hole  80   a.    
     An annular ring  80   b  that is concentric with the hole  80   a  is provided to protrude from an outer peripheral edge of the first mold  80 . A cylindrical second mold  82  is fitted to and placed on the first mold  80  so as to come into contact with an inner peripheral surface of the annular ring  80   b.  When the second mold  82  is fitted to the first mold  80 , the second mold  82  becomes concentric with the hole  80   a  for a tip lens of the first mold  80 . 
     The internal diameter of the second mold  82  is made greater than the external diameter of the tip lens  50   a,  and is reduced so that the second mold becomes narrow gradually as being away from the hole  80   a.  Accordingly, a resin tilling space  90  is formed between the second mold  82  and the tip lens  50   a.  Additionally, radial through-holes  82   a  and  82   b  are drilled in a peripheral wall of the second mold  82 . 
     When the second mold  82  is fitted and fixed to the first mold  80 , a height position  82   c  of the second mold  82  has a height above a height position of  82   d  when the plane plate  50   b  is placed on the tip lens  50   a  inserted into the hole  80   a.    
     A third mold  84  placed on the second mold  82  is formed in a cylindrical shape that has an internal diameter that is smoothly continuous with the internal diameter of the second mold  82 . A protrusion  82   e  for alignment is provided to protrude from the second mold  82 , and a recess  84   a  is formed at a position where the recess matches the protrusion  82   e,  in the third mold  84 . That is, when the recess  84   a  is fitted to the protrusion  82   c  and the third mold  84  is placed on the second mold  82 , the third mold  84  is aligned concentrically with the second mold  82 . 
     A cylindrical opening surface of the third mold  84  opposite to the first mold  80  is blocked by an end wall portion  84   b,  and a cylindrical through-hole  84   c  that is coaxial with the hole  80   a  is drilled at a center position of the end wall portion  84   b.  The diameter of the through-hole  84   c  is made greater than the recess S of the tip lens  50   a  and is made smaller than the external diameter of the plane plate  50   b.    
     A fourth mold  86  inserted into the through-hole  84   c  of the third mold  84  forms a columnar shape, and a tip surface  86   a  that presses the plane plate  50   b  against the tip lens  50   a  side within the first, second, and third molds  80 ,  82 , and  84 , respectively, is formed in a plane. The external diameter of the fourth mold  86  is made substantially equal to the internal diameter of the through-hole  84   c  in such a manner that a gap is not formed between both the fourth mold and the through hole. A tip portion of the fourth mold  86  is formed at an inclined portion  86   b  in which a columnar corner is chamfered and is reduced in diameter toward a tip surface. The external diameter of the tip surface  86   a  is reduced so as to have a smaller diameter than the diameter of the recess S of the tip lens  50   a.    
     As described with reference to  FIG. 4 , while the tip lens  50   a  is installed in the hole  80   a  of the first mold  80 , the plane plate  50   b  is placed on the tip lens  50   a.  Then, the second mold  82  is placed on the first mold  80  so as to be concentrical with the first mold, the third mold  84  is placed on the second mold so as to be concentrical with the second mold, and finally, the fourth mold  86  is inserted. 
     Since the plane plate  50   b  does not have a condensing action, an optical axis is not present. For this reason, there is no problem even if the central axis of the plane plate  50   b  slightly shifts with respect to the optical axis. Then, the fourth mold  86  is pressed, the plane plate  50   b  is pressed against the back surface of the tip lens  50   a,  and a space  90  inside the dies is filled with molding resin from the lateral wall openings $ 2   a  and  82   b  of the second mold  82  while mechanically keeping the close contact state between both the plane plate and the tip lens. 
     After the molding resin is cured, the first to fourth molds  80 ,  82 ,  84 , and  86 , respectively, are removed, and burrs of the resin and the resin within the openings  82   a  and  82   b  are removed. Accordingly, an integral structural article of the first lens barrel  51   a  and the tip lens  50   a,  and the plane plate  50   b  is completed. A longitudinal cross-sectional view of this integral structural article is illustrated in  FIG. 5 . 
     In  FIG. 5 , molding resin  91  cured in a cylindrical shape constitutes the preceding stage lens barrel  51   a  of  FIG. 3 . A tip portion of the resin  91  covers about ⅔ of the base end side in the outer peripheral surface of the tip lens  51   a.  Since the liquid resin  91  is made to flow into the space  90  (refer to  FIG. 4 ) and is cured, the resin  91  and the peripheral wall surface of the tip lens  50   a  are brought into a close contact state and an anchored state similar to when being bonded with an adhesive. 
     The resin  91  covers the entire surface of the outer peripheral surface of the plane plate  50   b  and is brought into close contact with and anchored to the outer peripheral surface, and covers most of a back-side periphery of the plane plate  50   b  and is brought into close contact with and anchored to the back-side periphery. A flange portion  91   a  provided to protrude in the direction of an inner periphery of the resin  91  that covers the back side of the plane plate  50   b  is a portion formed by the inclined portion  86   b  of the fourth mold  86  of  FIG. 4 . 
     Since a circular tip surface of the fourth mold  86  has a smaller diameter than the diameter of a back surface recess S of the tip lens  50   a  the resin (flange portion)  91  has such a shape that the resin covers all of the joining surface between the back surface  71  of the tip lens  50   a  and the surface  72  of the plane plate  50   b.    
     When the preceding stage lens barrel  51   a  is manufactured, the fourth mold  86  of  FIG. 4  is pressed against the plane plate  50   b  at a predetermined pressure or higher, and the resin  91  is made to flow into the space  90  and cured while maintaining this state. 
     If only the plane plate  50  is pressed down to such a degree that the plane plate does not shift from the tip lens  50   a  without pressing the mold  86  at a predetermined pressure or higher, and the resin  91  is made to flow in and cured, a gap will be formed in the joining surface between the back surface  71  and the surface  72 . This is because, even if the resin  91  does not flow in between the back surface  71  and the surface  72 , a gap of about 1 micron will be formed if the irregularity difference between the respective surfaces  71  and  72  is present at about 1 micron. Although it can be said that this gap is small, it is sufficient for moisture to permeate into the recess S. 
     Thus, in the present embodiment, the method of pressing the mold  86  against the plane plate  50  at a predetermined pressure or higher and making the resin  91  flow into the molds to cure the resin is adopted. The amount of pressure the mold is pressed depends on the material or thickness of the plane plate  50  and the flatness of each of the surfaces  71  and  72  in the joining surface. If the flatness is made high, the plane plate  50  can be only slightly deflected in such a manner that the respective surfaces  71  and  72  in the joining surface are brought into close contact with each other over their entire surfaces with a low pressure, and even a slight gap can be prevented from being formed. With this state maintained, the resin  91  is made to flow into the molds and cured. 
     The resin  91  is cured in a state where the flange  91   a  of the resin  91  covers the entire surface of the joining surface on which the back surface  71  of the tip lens  50   a  and the surface  72  of the plane plate  50  overlap each other and the plane plate  50   b  is pressed against the tip lens  50   a  side. Accordingly, even if the preceding stage lens barrel  51   a  is removed from the molds, the close contact between the plane plate  50   b  and the tip lens  50   a  is held at the joining surface therebetween. 
     In addition, the fixed lens  50   c  of  FIG. 3  is attached within the space  91   b  from which the mold  86  of the preceding stage lens barrel in was removed. Then, the preceding stage lens barrel  51   a  and the subsequent stage lens barrel  51   b  are coupled together so as to have the same optical axis, thereby completing the objective lens optical system  50 . Then, an imaging module for an endoscope is completed as the prism  56  and the imaging chip  54  (and substrate  62 ) are connected to the objective lens optical system  50 . 
     As described above, according to the imaging module related to the embodiment, permeation of moisture into the recess space S formed in the tip lens can be prevented, and it is possible to keep the quality of a captured image high. Additionally, since no adhesive layer is provided between the tip lens  50   a  and the plane plate  50   b,  malfunctions caused by the physical and chemical degradation of the adhesive layer can also be prevented. Moreover, by virtue of the structure in which the adhesive layer is made unnecessary, the assembly of the imaging module becomes easy and it is possible to achieve cost reduction. 
     In addition, although the embodiment illustrated in  FIG. 5  is configured so that the tip of the resin  91  extends up to a mid portion of the peripheral wall of the tip lens  50   a,  for example as in the related art of  FIG. 6 , the tip of the resin may extend to the tip surface of the tip lens and a hook portion may be formed on the tip portion so as to pinch the tip lens  50   a.    
     Additionally, although the imaging module for an endoscope has been described in the above-described embodiment, for example, the invention can also be similarly applied to an imaging module in which the diameter of the objective lens optical system is small, as in an imaging module built in a mobile telephone with a built-in camera or the like. 
     As described above, the imaging module of the embodiment is an imaging molding including an objective lens optical system, and an imaging element that receives incident light that has entered through the objective lens optical system. The objective lens optical system includes a tip lens in which a tip surface that incident light enters and a back surface opposite to the tip surface are formed in a plane, and a recess that condenses the incident light is formed at a central portion of the back surface; a plane plate that is installed on a back side of the tip lens to block the recess, and a lens barrel that integrally molds and forms the entire outer peripheral surfaces of the tip lens and the plane plate with resin, while a state is maintained where the plane plate is pressed against the tip lens, and the plane plate and the back surface of the tip lens are directly brought into close contact with each other at an entire joining surface therebetween. 
     Additionally, in the imaging module of the embodiment, the external diameter of the plane plate is smaller than the external diameter of the tip lens. 
     Additionally, in the imaging module of the embodiment, the entire outer peripheral surfaces of the tip lens and the plane plate and a peripheral region that is a non-passage for the incident light in the back surface of the plane plate are integrally molded with resin. 
     Additionally, in the imaging module of the embodiment, the peripheral region is a region that covers the entire surface of the joining surface. 
     Additionally, the electronic endoscope device of the embodiment has the above imaging module built in an endoscope tip portion. 
     Additionally, the imaging lens molding method of the embodiment is a method for molding an imaging lens of a lens barrel that houses a tip lens in which a tip surface that incident light enters and a back surface opposite to the tip surface are formed in a plane, and a recess that condenses the incident light is formed at a central portion of the back surface, and a plane plate that is installed on a back side of the tip lens to block the recess. The method includes integrally molding the entire outer peripheral surfaces of the tip lens and the plane plate with resin, while a state is maintained where the plane plate is pressed against the tip lens, and the plane plate and the back surface of the tip lens are directly brought into close contact with each other at an entire joining surface therebetween. 
     According to the embodiment described above, since the back surface of the tip lens and the plane plate are mechanically brought into close contact with each other at the entire joining surface therebetween without using an adhesive, it is possible to capture a high-quality image while being resistant to moisture. Additionally, since no adhesive is used, assembly becomes easy. 
     Since the tip lens portion of the imaging module related to the invention is resistant to moisture, the invention is useful when built in an imaging device used under a humid environment, especially an endoscope tip portion.