Patent Publication Number: US-2022236512-A1

Title: Optical sensor module

Description:
TECHNICAL FIELD 
     The present disclosure relates to an optical sensor module. 
     BACKGROUND ART 
     Conventionally, an optical sensor module has been known which includes an infrared detector, a lens holding member storing the infrared detector, and a lens fixed to the lens holding member so as to be located forward of the infrared detector with the focal point of the lens overlapping a light receiving portion of the infrared detector. 
     In the optical sensor module, for example, the lens holding member fixing and holding the lens is positioned relative to the infrared detector joined onto an insulating substrate such that the focal point of the lens overlaps the light receiving portion of the infrared detector. For this purpose, an adhesive agent (ultraviolet (UV) curable adhesive agent) is pasted in advance at a position where the bottom surface of the positioned lens holding member comes into contact with the insulating substrate, and then the lens holding member is mounted at the positioned location. Thereafter, ultraviolet rays are applied to the adhesive agent pasted part, to cure the adhesive agent, so that the relative positions of the infrared detector and the lens fixed to the lens holding member will not change. 
     When the adhesive agent is cured, the lens holding member to which the lens is fixed and the insulating substrate to which the infrared detector is joined are adhered to each other, and thus the relative positions of the light receiving portion of the infrared detector and the focal point of the lens are no longer changed. However, in the conventional optical sensor module, the adhesive agent thickness between the lens holding member and the substrate after the lens holding member is mounted thereon cannot be controlled. Therefore, in a case of performing adhesion using an apparatus not having an active alignment function that enables the lens holding member to be mounted while viewing an image acquired by operating the infrared detector, the lens holding member might be mounted in an inclined state with respect to the substrate, due to thickness variation of the adhesive agent, smallness of a load for mounting the lens holding member, imbalance of the position where the lens holding member is adhered, and the like. As a result, there is a possibility that the focal point of the lens deviates from the light receiving portion of the infrared detector and thus the optical sensor module becomes unable to receive light correctly. 
     The optical sensor module is assembled such that the position of the lens is set with the focal point thereof overlapping the light receiving portion of the infrared detector, in order to enable correct imaging by the infrared detector. However, in particular, in a case where the lens is formed integrally with the lens holding member, if the lens holding member is inclined with respect to the infrared detector, there is a possibility that the focal point of the lens deviates from the light receiving portion of the infrared detector and thus light reception cannot be performed correctly. In addition, when the lens holding member is mounted, a wiring member and the like for operating the infrared detector are present on the substrate positioned inside the lens holding member. Therefore, when the lens holding member is mounted on the adhesive agent, if the amount of the pasted adhesive agent is large or the load for mounting the lens holding member is great, the adhesive agent compressed by the lens holding member and thus wetting and spreading to the inner side of the lens holding member comes into contact with the wiring member on the inner side of the lens holding member. The wiring member in contact with the adhesive agent is deformed to come into contact with the wiring member therearound or lead to breakage of a wire, thus causing such a risk that the infrared detector becomes unable to operate, for example. 
     In addition, in a general optical sensor module, the lens holding member and the lens are separate members. Therefore, after the lens holding member is adhered onto the substrate, before the lens is attached to the lens holding member, it is possible to inspect whether or not the adhesive agent protruding to the inner side of the lens holding member is in contact with the wiring member or whether or not the lens holding member is inclined. Accordingly, if there is any problem, the position of the wiring member can be corrected, the lens can be attached so as to cancel out the inclination of the lens holding member, or at worst, this unit can be discarded on the spot. However, in an optical sensor module having the lens and the lens holding member integrated with each other so as to reduce the size as compared to the general optical sensor module, the cost required for members can be reduced but it is impossible to correct the inclination of the lens after the lens holding member is adhered onto the substrate. Moreover, operation failure due to contact between the adhesive agent and the wiring member cannot be inspected until the sensor is actually operated. Therefore, the loss cost when failure occurs is greater than in the case of the general optical sensor module. 
     In order to solve such problems, as an optical sensor module that can prevent the adhesive agent from entering the inner side of the lens holding member and can also suppress inclination of the lens holding member, a structure is proposed in which the lens holding member and the substrate are in contact with each other, a filling space for the adhesive agent is formed on the outer peripheral side of the lens holding member at the contact part, and the lens holding member is adhered to the substrate (see Patent Document 1). 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: JP2006-86671A 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the optical sensor module described in Patent Document 1, since the lens holding member and the substrate are in contact with each other at the contact surface of the lens holding member, inclination of the lens holding member is suppressed, and the adhesive agent is less likely to enter the inner side of the lens holding member. However, in order to bring the lens holding member and the substrate into contact with each other without gaps, working of the contact surface of the lens holding member is required to be accurate, and it is necessary to fill the filling space formed at the outer periphery of the lens holding member with a predetermined amount of adhesive agent while keeping the lens holding member and the substrate in contact with each other. Thus, the process for filling with the adhesive agent is complicated. 
     The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide an optical sensor module that enables an adhesive agent to be easily pasted and suppresses inclination of the lens holding member. 
     Solution to the Problems 
     An optical sensor module according to the present disclosure includes: a substrate having an electrode pattern formed on a surface thereof; a photodetector for detecting light, the photodetector being electrically connected to the electrode pattern and being fixed to the substrate; and a lens holding member to which a lens is fixed, the lens holding member being adhered to the substrate by an adhesive agent at such a position as to surround the photodetector, wherein a bottom surface of the lens holding member adhered to the substrate has projections located in a distributed manner, and distal ends of the projections are in contact with the substrate. 
     Effect of the Invention 
     The optical sensor module according to the present disclosure makes it possible to provide an optical sensor module that enables an adhesive agent to be easily pasted and suppresses inclination of the lens holding member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing the structure of an optical sensor module according to embodiment 1. 
         FIG. 2  is a sectional view along line A-A in  FIG. 1 , showing the structure of the optical sensor module according to embodiment 1. 
         FIG. 3  is an enlarged sectional view showing the structure of a specific part of an optical sensor module in a comparative example. 
         FIG. 4  is an enlarged sectional view showing the structure of a specific part of the optical sensor module according to embodiment 1. 
         FIG. 5  shows a photograph of the cross-section of the specific part of the optical sensor module according to embodiment 1. 
         FIG. 6  is a plan view showing another structure of the optical sensor module according to embodiment 1. 
         FIG. 7  is a sectional view along line A-A in  FIG. 6 , showing the other structure of the optical sensor module according to embodiment 1. 
         FIG. 8  is a plan view showing still another structure of the optical sensor module according to embodiment 1. 
         FIG. 9  is a sectional view along line A-A in  FIG. 8 , showing the still other structure of the optical sensor module according to embodiment 1. 
         FIG. 10  is an enlarged sectional view showing further another structure of the specific part of the optical sensor module according to embodiment 1. 
         FIG. 11  is a plan view showing the structure of an optical sensor module according to embodiment 2. 
         FIG. 12  is a sectional view along line A-A in  FIG. 11 , showing the structure of the optical sensor module according to embodiment 2. 
         FIG. 13  is a plan view showing the structure of an optical sensor module according to embodiment 3. 
         FIG. 14  is a sectional view along line A-A in  FIG. 13 , showing the structure of the optical sensor module according to embodiment 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of an optical sensor module according to the present disclosure will be described with reference to the drawings. In the drawings, the same or similar constituent parts are denoted by the same reference characters. For the purpose of avoiding unnecessary redundant description and facilitating the understanding for a person skilled in the art, description of well-known matters and repetitive description of substantially the same configuration may be omitted. 
     In the drawings, the sizes or the scales of the corresponding constituent parts are independent of each other. For example, between a drawing in which the structure is partially changed and a drawing without such a change, the size or the scale of the same constituent part may be different. In the structure of the optical sensor module, although more other members are actually provided, only parts necessary for explanation of the present disclosure are described and description of the other parts is omitted. In the following description, as an example of the optical sensor module, an optical sensor module for detecting infrared rays is described. However, the embodiments are applicable to various types of optical sensor modules such as a visible-light optical sensor module having the same problems, as well as the infrared optical sensor module. 
     Embodiment 1 
       FIG. 1  is a plan view showing the schematic structure of an optical sensor module  101  according to embodiment 1, and  FIG. 2  is a sectional view along line A-A in  FIG. 1 . The optical sensor module  101  includes, as basic components, an infrared detector  10  as a photodetector, a glass epoxy substrate  20  as a substrate, and a lens holding member  80  integrated with a lens  90  by inserting the lens  90  after molding and then caulking the periphery of the lens  90  with resin. The infrared detector  10  is adhered to one surface of the glass epoxy substrate  20  by Ag paste  60 , and thus fixed and stored inside the lens holding member  80 . The lens  90  for transmitting infrared rays therethrough and focusing the infrared rays is integrally fixed to the lens holding member  80 , and a bottom surface  84  of the lens holding member  80  is adhered to the glass epoxy substrate  20  by an adhesive agent  70 . 
     In  FIG. 1  and  FIG. 2 , only basic constituent parts in the optical sensor module  101  are shown, and components that are not directly relevant to the present disclosure, such as a dedicated IC, wires, capacitors, and connectors, which are other components joined onto the glass epoxy substrate  20 , are not shown. 
     The infrared detector  10  is a thermal-type infrared sensor, e.g., a resistance bolometer type sensor typically using vanadium oxide (VOx) or a silicon-on-insulator (SOI) diode bolometer type sensor using temperature characteristic of a P—N diode, and is made of Si. 
     The glass epoxy substrate  20  is a substrate including a circuit having various functions. The glass epoxy substrate  20  has a plate-shaped glass epoxy base  20   a , and an electrode pattern  20   b  and an electrode pattern  20   c  formed on both surfaces of the glass epoxy base  20   a . The electrode pattern  20   b  and the electrode pattern  20   c  electrically connect the infrared detector  10  fixed on the glass epoxy substrate  20  and another electronic device (not shown), and provide, for example, an interface for making connection to another circuit board, an external power supply, and the like. The glass epoxy base  20   a  is an electrically insulating material, and suffers stress caused by temperature increase during operation of the optical sensor module  101 , due to linear expansion coefficient difference from the lens holding member  80  adhered to the glass epoxy substrate  20  by the adhesive agent  70 , the infrared detector  10  joined to the electrode patterns  20   b ,  20   c  by the Ag paste  60 , the other electronic device joined thereto, and the like. Preferably, the glass epoxy base  20   a  is made of a material having a great thickness so that deformation such as warp due to the stress is less likely to occur, and in general, the glass epoxy base  20   a  having a thickness of 0.8 mm to 1.0 mm is used, for example. 
       FIG. 1  and  FIG. 2  show the example in which only one infrared detector  10  is provided to the glass epoxy substrate  20 . However, a plurality of infrared detectors  10  may be provided to one glass epoxy substrate  20 . Further, although the number of the glass epoxy substrates  20  is one here, the number of the glass epoxy substrates  20  is not limited to one. For example, the following structure may be employed: in one glass epoxy substrate  20 , a plurality of identical electrode patterns  20   b ,  20   c  are provided, the infrared detectors  10  and other electronic devices are arranged and joined one by one onto the individual electrode patterns  20   b ,  20   c , the area of each infrared detector  10  is covered by the lens holding member  80  and thus is sealed, and then cutting and division are performed for the individual electrode patterns  20   b ,  20   c.    
     In general, the electrode pattern  20   b  and the electrode pattern  20   c  are made of the same material. The infrared detector  10  is joined to one electrode pattern  20   b  by the Ag paste  60 , and the electrode pattern  20   b  has a connection portion formed thereon using an Au wire or the like, thereby electrically connecting another electronic device and the infrared detector  10 . Such an electrode pattern  20   b  is a wiring member for electrically connecting the infrared detector  10  and an external circuit, and therefore is preferably made of metal having a small electric resistance. Therefore, in general, the electrode patterns  20   b ,  20   c  are made of a Cu foil having a thickness of about 10 to 40 μm, for example. 
     The infrared detector  10  and the electrode pattern  20   b  formed on the glass epoxy substrate  20  are joined by the Ag paste  60  which is a joining material. When the infrared detector  10  is to be joined by the Ag paste  60 , other electronic components have been already joined onto the glass epoxy substrate  20  by solder. Therefore, preferably, the curing temperature of the Ag paste  60  is lower than the melting point of the solder so that the surrounding solder will not be melted again when the infrared detector  10  is joined. In addition, preferably, the joining material having high thermal conductivity is used in order to prevent temperature increase of the infrared detector  10 . Therefore, the joining material is not limited to the Ag paste and may be another conductive adhesive agent or a sintered joining material of Ag nanoparticle paste or the like, but it is preferable to use the Ag paste in terms of adhesion temperature, thermal conductivity, cost, and the like. 
     The adhesive agent  70  adheres the bottom surface  84  of the lens holding member  80  and the surface of the glass epoxy substrate  20  on the side where the infrared detector  10  is joined. When the lens holding member  80  is to be adhered by the adhesive agent  70 , the infrared detector  10  has been adhered to the surface of the glass epoxy substrate  20  by the Ag paste  60 , the other electronic components have been joined by solder, and Au wires and the like which are members for electrically connecting these have been arranged. Therefore, preferably, the curing temperature of the adhesive agent  70  is lower than the heat-resistant temperatures of the infrared detector  10 , the other electronic components, and the lens holding member  80 , and the melting point of the solder, so that the other members mounted on the glass epoxy substrate  20  will not be broken or the solder will not be melted again when the adhesive agent  70  is cured. 
     Since the above members are stored on the inner side of the lens holding member  80 , it is preferable to prevent the adhesive agent  70  from wetting and spreading to the inner side of the lens holding member  80 , so that a wire will not be detached or adjacent wires will not come into contact with each other. After the adhesive agent  70  is pasted on the glass epoxy substrate  20  and the lens holding member  80  is mounted on the pasted adhesive agent  70 , if a worker performs a conveyance process before the adhesive agent  70  is cured, the lens holding member  80  might be peeled or moved due to vibration during conveyance, impact upon dropping, or the like. This might cause such a problem that infrared rays cannot be focused on the infrared detector  10  so that imaging cannot be performed, an image is partially lost, or an image becomes out of focus, for example. Therefore, preferably, the adhesive agent  70  can be cured in the same apparatus as used for mounting the lens holding member  80  on the pasted adhesive agent  70  and the adhesive agent  70  can be cured without damaging the surrounding members. Therefore, preferably, the adhesive agent  70  is a UV curable adhesive agent which is cured by being irradiated with UV rays or a UV-thermosetting adhesive agent which is cured with combination of UV irradiation and heating at a temperature lower than the melting point of the solder or the heat-resistant temperatures of the surrounding members. 
     Similarly, when the lens holding member  80  is to be mounted on the pasted adhesive agent  70 , if the load for mounting the lens holding member  80  is small or the amount of the pasted adhesive agent  70  is excessively large, the lens holding member  80  might be inclined with respect to the glass epoxy substrate  20 , so that infrared rays cannot be focused on the infrared detector  10 . Conversely, if the load for mounting the lens holding member  80  is excessively great, the adhesive agent  70  might be deformed so as to wet and spread to the inner/outer side of the bottom surface  84  of the lens holding member  80  beyond the design value. The adhesive agent  70  wetting and spreading to the outer side of the lens holding member  80  might hamper attachment of the optical sensor module  101  to a product. In addition, the adhesive agent  70  wetting and spreading to the inner side of the lens holding member  80  might come into contact with the wiring member such as a wire so that the joining part between the wire and the glass epoxy substrate  20  is detached or the wire collapses to come into contact with an adjacent wire. On the other hand, if the amount of the pasted adhesive agent  70  is excessively small, the adhesive agent  70  might not sufficiently wet and spread on the bottom surface  84  of the lens holding member  80 , so that the adhesion strength is weakened and thus reliability of the optical sensor module  101  is reduced. 
     The lens holding member  80  is a box made of thermoplastic resin, thermosetting resin, metal, or the like and having an upper surface portion having a flat-plate shape, a side portion contiguous to the outer edge of the upper surface portion, and an opening surrounded by the side portion. The shape of the upper surface portion is a square shape in the present embodiment 1, but may be a rectangular shape, a circle shape, an elliptic shape, or the like. The lens  90  is integrally fixed in the upper surface portion of the lens holding member  80 , and the entire periphery of the bottom surface  84  is adhered to the glass epoxy substrate  20  by the adhesive agent  70  at such a position that infrared rays having transmitted through the lens  90  are focused on the light receiving portion of the infrared detector  10 . The inside of the lens holding member  80  is evacuated to seal the infrared detector  10 . In order to increase the adhesion area of the bottom surface  84  which is the adhesion surface of the lens holding member  80  and thus enhance the adhesion strength, an edge  81  is formed such that the sides of the square protrude outward as shown in  FIG. 1  and  FIG. 2 . In addition, at the parts corresponding to the four corners of the square, projections  82  having a truncated cone shape with a bottom diameter equal to or smaller than the width of the bottom surface  84  of the lens holding member  80  are formed from the bottom surface  84  of the lens holding member  80  toward the glass epoxy substrate  20  side opposed to the lens holding member  80 . The bottom surface  84  of the lens holding member  80  and the glass epoxy substrate  20  are adhered to each other such that the distal ends of the projections  82  are in contact with the glass epoxy substrate  20 . 
     In a case of using thermoplastic resin for the lens holding member  80 , polycarbonate (PC) is generally used. Other than PC, PA66 (NYLON66), polybutylene terephthalate (PBT), poly phenylene sulfide (PPS), or the like may be used. These resins are high in heat-resisting property and therefore are preferable because, even in a case where heating is needed for curing the adhesive agent  70 , the heating temperature can be set to be high. Since the bottom surface  84  of the lens holding member  80  and the glass epoxy substrate  20  are adhered with the adhesive agent  70  interposed therebetween, the height of the projections  82  becomes the thickness of the adhesive agent. It is desirable to set the height of the projections  82  to be great to such a degree that can absorb the warp amount of the glass epoxy substrate  20  or stress caused by linear expansion coefficient difference between the lens holding member  80  and the glass epoxy substrate  20 , and to be smaller than the thickness of the pasted adhesive agent  70 . Specifically, it is preferable that the height of the projections  82  is about 10 to 200 μm. 
     In the present embodiment 1, the lens  90  is a silicon lens having convex spherical surfaces on both sides, and the outer periphery thereof is covered by the lens holding member  80  so as to be integrated therewith, and thus is fixed to the upper surface portion of the lens holding member  80 . Therefore, when the lens holding member  80  is moved, the lens  90  is also moved together with the lens holding member  80 . Accordingly, the relative position with respect to the infrared detector  10  is changed due to movement of the lens holding member  80 . In addition, the lens  90  allows transmission of infrared rays but does not allow transmission of visible light, and therefore it is impossible to observe the inside of the lens holding member  80  through the lens  90 . 
     In order to perform correct imaging by the infrared detector  10 , assembling is made such that the position of the lens  90  is set with the focal point thereof overlapping the light receiving portion of the infrared detector  10 . However, in particular, in the case where the lens  90  and the lens holding member  80  are formed integrally, if the lens holding member  80  is inclined with respect to the infrared detector  10 , there is a possibility that the focal point of the lens  90  deviates from the light receiving portion of the infrared detector  10  and thus the infrared detector  10  becomes unable to receive light correctly. As a result, there is such a risk that the infrared detector  10  becomes unable to perform imaging, or even if the displacement is slight, an image is partially lost or becomes out of focus, for example. 
     When the lens holding member  80  is mounted, wiring members and the like for operating the infrared detector  10  are present on the electrode pattern  20   b  of the glass epoxy substrate  20  in the area stored in the lens holding member  80 . Therefore, when the lens holding member  80  is mounted on the adhesive agent  70 , if the amount of the pasted adhesive agent  70  is large or the load of a nozzle for mounting the lens holding member  80  is great, the adhesive agent  70  compressed by the lens holding member  80  and thus wetting and spreading to the inner side of the lens holding member  80  comes into contact with the wiring member on the inner side of the lens holding member  80 . The wiring member in contact with the adhesive agent  70  is deformed to come into contact with the wiring member therearound or lead to breakage of a wire, thus causing a risk of such failure that the optical sensor module  101  does not operate, for example. 
     In a case where the lens holding member and the lens in the optical sensor module are separate members, if the displacement is slight, it is possible to adjust the position of the lens again so that the focal point thereof overlaps the light receiving portion of the infrared detector after the adhesive agent adhering the lens holding member to the substrate is cured. However, in the optical sensor module according to the present disclosure, for the purpose of reducing the number of components to reduce the cost, the lens holding member  80  and the lens  90  are formed integrally, and therefore it is impossible to adjust the position of the lens  90  again after the lens holding member  80  is mounted on the adhesive agent  70 . Thus, even before the adhesive agent  70  is cured, a risk of causing failure due to deviation of the relative positions of the light receiving portion of the infrared detector  10  and the focal point of the lens  90  is higher as compared to the optical sensor module in which the lens holding member  80  and the lens  90  are separate members. 
     In order to prevent this, it is important to mount the lens holding member  80  such that the bottom surface  84  of the lens holding member  80  is parallel to the glass epoxy substrate  20  irrespective of the amount of the pasted adhesive agent  70  or the mounting load of the lens holding member  80 . Therefore, in the optical sensor module according to the present embodiment 1, the projections  82  having the same height are provided on the bottom surface  84  at four corners of the lens holding member  80  to which the lens  90  is fixed, as shown in  FIG. 1  and  FIG. 2 . 
     Thus, a space corresponding to the height of the projections  82  is formed between the glass epoxy substrate  20  and the bottom surface  84  of the lens holding member  80 . Therefore, as compared to a case where the bottom surface of the lens holding member is a flat surface without the projections  82 , it is possible to reduce the volume of the adhesive agent  70  that protrudes from under the bottom surface  84  of the lens holding member  80  by being compressed by the lens holding member  80  and wets and spreads to the inner side of the lens holding member  80 . In the optical sensor module having no projections as a comparative example shown in  FIG. 3 , the adhesive agent  70  wetting and spreading to the inner side of the lens holding member  80  has a shape close to a semicircle. On the other hand, in the optical sensor module  101  according to the present embodiment 1, as shown in  FIG. 4 , the adhesive agent  70  wetting and spreading to the inner side has a shape close to a sector shape, so that a distance A over which the adhesive agent  70  wets and spreads on the surface of the glass epoxy substrate  20  can be reduced. Therefore, the adhesive agent  70  compressed by the lens holding member  80  and thus wetting and spreading to the inner side of the lens holding member  80  can be inhibited from coming into contact with the wiring member on the inner side of the lens holding member  80 . 
     In addition, since the projections  82  formed at four locations are set to the same height and the distal ends of the projections  82  are in contact with the glass epoxy substrate  20 , the lens holding member  80  can be prevented from being inclined with respect to the glass epoxy substrate  20 . Thus, the lens  90  integrally formed and fixed to the lens holding member  80  can be prevented from being inclined with respect to the infrared detector  10  joined onto the glass epoxy substrate  20 . Here, the shape of each projection  82  is formed to be a truncated cone with the bottom surface diameter smaller than the width of the bottom surface  84  of the lens holding member  80 , whereby, when the lens holding member  80  is mounted on the adhesive agent  70 , even with an extremely small mounting load, the distal ends of the projections  82  come into contact with the adhesive agent  70  and then can push out the adhesive agent  70  to come into contact with the surface of the glass epoxy substrate  20 .  FIG. 5  shows a cross-section when the lens holding member  80  with the projections  82  provided on the bottom surface  84  is adhered to the glass epoxy substrate  20  by the adhesive agent  70 . 
     Further, since glass epoxy which is a main material of the glass epoxy substrate  20  and thermoplastic resin which is a main material of the lens holding member  80  are different in linear expansion coefficient, stress occurs at the adhesion part due to driving of the infrared detector or change in the ambient temperature. This stress repeatedly occurs as the usage time of the optical sensor module increases, and thus there is a possibility that the adhesion part is broken or peeled due to fatigue. Also by this, the position of the lens holding member  80  might be changed, so that the relative positions of the light receiving portion of the infrared detector  10  and the focal point of the lens  90  are changed, thus causing such a risk that the infrared detector  10  becomes unable to perform imaging, or an image is partially lost or becomes out of focus, for example. 
     In the optical sensor module according to the present embodiment 1, the adhesive agent  70  wets and spreads in the space corresponding to the height of the projections  82  and formed between the glass epoxy substrate  20  and the bottom surface  84  of the lens holding member  80 , whereby the adhesive agent  70  becomes thicker as compared to the optical sensor module without projections. Thus, shear strain occurring in the adhesive agent  70  due to linear expansion coefficient difference between the glass epoxy substrate  20  and the lens holding member  80  can be reduced as compared to the optical sensor module without projections, whereby the life of the adhesion part by the adhesive agent  70  can be prolonged. 
     Any number of the projections  82  may be formed in any shape at any locations on the bottom surface  84  which is the adhesion surface of the lens holding member  80  to be adhered with the adhesive agent  70 . For example, as shown in a plan view in  FIG. 6  and a sectional view in  FIG. 7  along line A-A in  FIG. 6 , projections having a columnar shape may be provided at a total of eight locations at the corners and the centers of the sides of the lens holding member  80 . Alternatively, projections having a prism shape may be provided. Alternatively, as shown in a plan view in  FIG. 8  and a sectional view in  FIG. 9  along line A-A in  FIG. 8 , projections having a triangular pyramid shape may be provided at a total of four locations at the centers of the sides of the lens holding member  80 . Alternatively, projections having a quadrangular pyramid shape may be provided. 
     In the case where the projections  82  are formed at such locations that the distal ends thereof come into contact with the adhesive agent  70  when the lens holding member  80  is mounted on the adhesive agent  70 , it is preferable that each projection  82  has such a shape that the area of the distal end thereof is sufficiently smaller as compared to the bottom surface  84  of the lens holding member  80  so that, even with an extremely small mounting load, the projection  82  can push out the adhesive agent  70  to come into contact with the surface of the glass epoxy substrate  20 . For example, it is preferable that the projections  82  has a pillar shape such as a columnar shape or a prism shape having an area not larger than a square with the length of one side equal to the width of the bottom surface  84 , a conical/pyramidal shape such as a cone or a pyramid, or a frustum shape such as a truncated cone or a truncated pyramid. A conical/pyramidal shape or a frustum shape of which the sectional area reduces from the bottom surface  84  toward the distal end, i.e., the sectional area is smaller at the distal end than at the bottom, is such a shape that, in a case where the lens holding member  80  is formed by injection molding, extraction from a mold can be easily performed, and the adhesive agent  70  can be easily pushed out. Therefore, a conical/pyramidal shape or a frustum shape is particularly preferable. Alternatively, projections having a curved surface, e.g., a hemisphere shape, may be used. 
     In addition, it is necessary to provide three or more projections  82  having the same height so that the lens  90  formed integrally with the lens holding member  80  becomes parallel to the glass epoxy substrate  20  when the lens holding member  80  is mounted on the adhesive agent  70  pasted on the glass epoxy substrate  20 . 
     In addition, as shown in an enlarged sectional view in  FIG. 10 , if each projection  82  is formed such that a corner of the distal end thereof in contact with the adhesive agent  70  and the glass epoxy substrate  20  is rounded, stress caused by temperature change in the optical sensor module  101  does not concentrate on the corner of the distal end of the projection  82 . Thus, the adhesive agent is prevented from peeling from the inner periphery of the lens holding member due to stress concentration by thermal stress, whereby the life of the optical sensor module  101  can be more prolonged. In addition, this configuration can prevent positional displacement of the lens holding member  80  in the height direction and therefore is more preferable. 
     In addition, if the surface roughness of the bottom surface  84  of the lens holding member  80  is made greater as compared to the other parts of the lens holding member  80 , the adhesion strength between the lens holding member  80  and the adhesive agent  70  is increased. Thus, joining reliability can be improved and therefore this configuration is more preferable. 
     Further, if the surface roughness of the distal end of each projection  82  that is in contact with the glass epoxy substrate  20  is made greater as compared to the other surfaces of the lens holding member  80 , the frictional force between the glass epoxy substrate  20  and the lens holding member  80  increases. Thus, positional displacement between the light receiving portion of the infrared detector  10  and the optical center of the lens  90  by positional displacement of the lens holding member  80  due to curing contraction of the adhesive agent  70  or the like can be suppressed and therefore this configuration is more preferable. 
     As described above, in the optical sensor module  101  according to embodiment 1, the projections  82  are provided on the bottom surface  84  which is the adhesion surface of the lens holding member  80  to be adhered by the adhesive agent  70 , whereby a space corresponding to the height of the projections  82  is formed between the glass epoxy substrate  20  and the bottom surface  84  of the lens holding member  80 . Thus, the volume of the adhesive agent  70  wetting and spreading to the inner side of the lens holding member  80  can be reduced. In addition, even if the adhesive agent  70  wets and spreads to the inner side of the lens holding member  80 , the wetting and spreading adhesive agent  70  has a shape close to a sector shape, so that the distance A over which the adhesive agent  70  wets and spreads on the surface of the glass epoxy substrate  20  can be reduced. Therefore, the adhesive agent  70  wetting and spreading to the inner side of the lens holding member  80  can be prevented from coming into contact with the wiring member on the inner side of the lens holding member  80 . In addition, since the plurality of projections  82  are formed to have the same height and the distal ends of the projections  82  are in contact with the glass epoxy substrate  20 , it is possible to prevent such a phenomenon that the lens  90  formed integrally with the lens holding member  80  is inclined with respect to the infrared detector  10  so that the infrared detector  10  becomes unable to perform imaging or an image is partially lost or becomes out of focus. Further, since the adhesive agent  70  is thicker as compared to the optical sensor module without projections, shear strain occurring in the adhesive agent  70  due to linear expansion coefficient difference between the glass epoxy substrate  20  and the lens holding member  80  can be reduced, whereby the life of the adhesion part by the adhesive agent  70  can be prolonged and thus the optical sensor module  101  having high quality can be obtained. 
     Embodiment 2 
       FIG. 11  is a plan view showing the schematic structure of an optical sensor module  102  according to embodiment 2, and  FIG. 12  is a sectional view along line A-A in  FIG. 11 . The optical sensor module  102  according to the present embodiment 2 basically has the same structure as the optical sensor module  101  according to embodiment 1, but has difference as described below. Here, the difference will be mainly described and description of the same constituent parts is omitted.  FIG. 11  and  FIG. 12  are schematic views showing only basic constituent parts in the optical sensor module  102 , and description of the other constituent parts is omitted. 
     In embodiment 1, the infrared detector  10  is sealed by making the inside of the lens holding member  80  into a vacuum state after the entire periphery of the bottom surface  84  of the lens holding member  80  is adhered by the adhesive agent  70 . On the other hand, in the present embodiment 2, as shown in  FIG. 11  and  FIG. 12 , a light transmitting plate  15  which is a light transmitting member is joined onto the infrared detector  10  via a frame  151  so as to be spaced from the surface of the infrared detector  10 . Embodiment 2 is different from embodiment 1 in that the infrared detector  10  is sealed by making the internal space formed between the infrared detector  10  and the light transmitting plate  15  into a vacuum state, and the inside of the lens holding member  80  is not sealed into a vacuum state. 
     The light transmitting plate  15  made of silicon which is a material that allows transmission of infrared rays as with the lens  90  is coated with metal at a part to be joined to the frame  151 , and is joined by solder to the frame  151  joined to the surface of the infrared detector  10 . Thus, the light transmitting plate  15  is fixed to the light incidence side of the light receiving portion of the infrared detector  10  so as to be integrated with the infrared detector  10 , thereby covering the light receiving portion of the infrared detector  10 . The inside enclosed by the infrared detector  10 , the frame  151 , and the light transmitting plate  15  is sealed into a vacuum state. In addition, the light transmitting plate  15  allows transmission of infrared rays but does not allow transmission of visible light, and therefore it is impossible to observe the light receiving portion of the infrared detector  10  through the light transmitting plate  15 . 
     In the present embodiment 2, the positions where the bottom surface  84  of the lens holding member  80  and the glass epoxy substrate  20  are adhered by the adhesive agent  70  are only four corners of the lens holding member  80 , and the projections  82  having the same height are provided on the bottom surface  84  of the lens holding member  80  at a total of four locations at the centers of the sides of the lens holding member  80 . 
     Since the infrared detector  10  is sealed into a vacuum state by the light transmitting plate  15 , it is not necessary to seal the inside of the lens holding member  80  into a vacuum state, and therefore it is not necessary to adhere the entire periphery of the bottom surface  84  of the lens holding member  80  by the adhesive agent  70 . The adhesive agent  70  has only to be pasted in such an amount that the adhesion part will not be broken or peeled due to fatigue, and for example, as shown in  FIG. 11  and  FIG. 12 , the adhesive agent  70  may be pasted at only four corners of the lens holding member  80 . In this case, brims  81  are provided at only the four corners of the lens holding member  80  to be adhered by the adhesive agent  70 , so that the area of the bottom surface  84  can be reduced by an amount of decrease in the adhesion area of the lens holding member  80 , and thus the entire optical sensor module  102  can be downsized. In addition, since the adhesion area of the adhesive agent  70  is reduced as compared to the case of adhering the entire periphery by the adhesive agent  70 , shear strain occurring in the adhesive agent  70  due to linear expansion coefficient difference between the glass epoxy substrate  20  and the lens holding member  80  is reduced. Thus, the effect of the optical sensor module according to the present disclosure that the life of the adhesion part by the adhesive agent  70  can be prolonged is further enhanced. 
     Further, as shown in  FIG. 11  and  FIG. 12 , the projections  82  can be provided at, for example, a total of four locations at the centers of the sides of the lens holding member  80 , and in this way, it becomes easy to provide the projections  82  at such locations where the adhesive agent  70  is not pasted. Thus, the shapes of the projections  82  can be more freely selected. Moreover, since the adhesive agent does not enter between the distal end of each projection  82  and the glass epoxy substrate  20 , the distal end of the projection  82  can be assuredly brought into contact with the surface of the glass epoxy substrate  20 . Thus, the effect of preventing such a phenomenon that the lens  90  formed integrally with the lens holding member  80  is inclined with respect to the infrared detector  10  joined onto the glass epoxy substrate  20  so that imaging cannot be performed or an image is partially lost or becomes out of focus, is obtained more assuredly. 
     In the above description, adhesion is made at only four corners instead of the entire periphery of the bottom surface  84  of the lens holding member  80 . However, in the structure in which vacuum sealing is made by the light transmitting plate  15  and the frame  151 , the entire periphery of the bottom surface  84  of the lens holding member  80  may be adhered by the adhesive agent  70  in the same manner as described in embodiment 1. Also in this case, it is not necessary to seal the inside of the lens holding member  80  into a vacuum state, and therefore the adhesion need not be made in an airtight state. 
     Embodiment 3 
       FIG. 13  is a plan view showing the schematic structure of an optical sensor module  103  according to embodiment 3, and  FIG. 14  is a sectional view along line A-A in  FIG. 13 . Also the optical sensor module  103  according to the present embodiment 3 basically has the same structure as the optical sensor module  101  according to embodiment 1, but has difference as described below. Here, the difference will be mainly described and description of the same constituent parts is omitted.  FIG. 13  and  FIG. 14  are schematic views showing only basic constituent parts in the optical sensor module  103 , and description of the other constituent parts is omitted. 
     In the present embodiment 3, as shown in  FIG. 13  and  FIG. 14 , at the distal end of each projection  82  provided on the bottom surface  84  of the lens holding member  80 , a positioning projection  82   a  extending in a truncated cone shape from the distal end of the projection  82  is formed integrally with the projection  82 . A positioning hole  21  is formed in the glass epoxy substrate  20  at a position corresponding to each positioning projection  82   a , and the bottom surface  84  of the lens holding member  80  and the glass epoxy substrate  20  are adhered in a state in which the positioning projections  82   a  are inserted into the positioning holes  21 . 
     When the lens holding member  80  is to be mounted on the adhesive agent  70  pasted on the glass epoxy substrate  20 , the positioning projections  82   a  are inserted into the positioning holes  21  and then the distal ends of the projections  82  come into contact with the glass epoxy substrate  20 , whereby the glass epoxy substrate  20  and the lens holding member  80  are adhered by the adhesive agent  70 . Thus, for example, when the lens holding member  80  is mounted on the adhesive agent  70  pasted on the glass epoxy substrate  20 , even if the position of the lens holding member  80  attempts to slightly move or rotate due to deformation of the adhesive agent  70 , the lens holding member  80  can be adhered without being displaced, because the positioning projections  82   a  are inserted into the positioning holes  21 . 
     In addition, in a case where the diameter of the bottom surface of the positioning projection  82   a  and the diameter of the positioning hole  21  are made equal to each other, even if contraction of the adhesive agent  70  at the time of adhering the lens holding member  80 , deformation of the adhesive agent  70  due to driving of the optical sensor module  103  or change in the ambient temperature, or the like occurs, the positioning projection  82   a  inserted into the positioning hole  21  is in contact with the entrance of the positioning hole  21  at the bottom surface part and therefore the relative positions of the positioning projection  82   a  and the positioning hole  21  are not changed. Thus, it is possible to prevent such failure that, due to change in the position of the lens holding member  80 , the relative positions of the light receiving portion of the infrared detector  10  and the focal point of the lens  90  are changed so that imaging cannot be performed or an image is partially lost or becomes out of focus, for example. 
     As described above, the positioning projections  82   a  are formed on the distal ends of the projections  82 , the positioning holes  21  are formed in the glass epoxy substrate  20 , and the positioning projections  82   a  are inserted into the positioning holes  21 , whereby positioning of the lens holding member  80  on the glass epoxy substrate  20  can be made assuredly. Further, the position of the lens holding member  80  is not displaced even by deformation of the adhesive agent  70  or thermal stress occurring due to temperature change at the time of or after adhesion, and therefore positional displacement between the light receiving portion of the infrared detector  10  and the optical center of the lens  90  can be prevented. 
     In the present embodiment 3, the projections  82  are formed at four corners of the lens holding member  80 , the positioning projection  82   a  is formed on each projection  82 , and the positioning hole  21  is formed in the glass epoxy substrate at a position corresponding to the positioning projection  82   a . Without limitation thereto, the projections  82  having the positioning projections  82   a  may be provided at a total of eight locations at the corners and the centers of the sides of the lens holding member  80 , or may be provided at a total of four locations at the centers of the sides of the lens holding member  80 . Alternatively, the positioning projections  82   a  may be provided on not all the projections  82  but on only some of the projections  82 . However, in order to obtain the effect of positioning the lens holding member  80  on the glass epoxy substrate  20  and preventing positional displacement of the lens holding member  80  at the time of or after adhesion, it is necessary to provide the positioning projections  82   a  and the positioning holes  21  at mutually corresponding positions in at least two locations. 
     Further, as in the above embodiment 2, the structure may be made such that the light transmitting plate  15  which is the light transmitting member is joined by solder onto the infrared detector  10 , the infrared detector  10  is sealed by making the internal space formed between the infrared detector  10  and the light transmitting plate  15  into a vacuum state, and the inside of the lens holding member  80  is not sealed into a vacuum state. Since the inside of the lens holding member  80  need not be sealed into a vacuum state, it is not necessary to paste the adhesive agent  70  over the entire periphery of the bottom surface  84  of the lens holding member  80 , and therefore it becomes easy to provide the projections  82  at locations where the adhesive agent  70  is not pasted. Moreover, the adhesive agent  70  can be prevented from leaking out through the positioning hole  21  to the back surface of the glass epoxy substrate  20 , and the effect of the present embodiment 3 that the lens holding member  80  is positioned on the glass epoxy substrate  20  and positional displacement of the lens holding member  80  at the time of or after adhesion can be prevented, is obtained more assuredly. 
     Although the disclosure is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects, and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations to one or more of the embodiments of the disclosure. It is therefore understood that numerous modifications which have not been exemplified can be devised without departing from the scope of the present disclosure. For example, at least one of the constituent components may be modified, added, or eliminated. At least one of the constituent components mentioned in at least one of the preferred embodiments may be selected and combined with the constituent components mentioned in another preferred embodiment. 
     DESCRIPTION OF THE REFERENCE CHARACTERS 
     
         
         
           
               10  infrared detector (photodetector) 
               15  light transmitting plate (light transmitting member) 
               20  glass epoxy substrate (substrate) 
               20   a  glass epoxy base 
               20   b ,  20   c  electrode pattern 
               21  positioning hole 
               60  Ag paste 
               70  adhesive agent 
               80  lens holding member 
               82  projection 
               82   a  positioning projection 
               84  bottom surface 
               90  lens 
               101 ,  102 ,  103  optical sensor module