Imaging module

Abstract

To provide an imaging module capable of preventing peeling of adhesion between an imaging device on a circuit board and a prism at the time of operation of an endoscope or the like.SOLUTION: An imaging module comprises an imaging device, a lens, and an optical component disposed between the imaging device and the lens. A light receiving surface of the imaging device and the optical component are entirely bonded and fixed. A first layer, whose thermal expansion coefficient is larger than that of the imaging device, is bonded to a surface of the imaging device on a side opposite to the light receiving surface. A curing temperature of an adhesive for bonding the imaging device and the optical component is lower than a temperature at the time of operation of the imaging device.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an imaging module. [Background technology]

[0002] An imaging module having an imaging element, a lens barrel, etc. is disposed at the tip of the endoscope. The imaging element is mounted on a circuit board.

[0003] An optical member such as a prism is disposed between the image sensor and the lens barrel to guide the light that has passed through the lens to the imaging surface of the image sensor. The image sensor and the optical member are fixed with adhesive to prevent misalignment.

[0004] For example, Patent Document 1 describes an imaging unit for an endoscope that includes an objective lens placed at the tip of the insertion portion of an endoscope, a lens barrel that holds the objective lens, a prism with a light entrance surface connected to one end of the lens barrel and a light exit surface that is perpendicular to the light entrance surface, a cover glass having one surface bonded to the light exit surface of the prism via an adhesive, and an image sensor substrate that is positioned opposite the light exit surface of the prism, wherein one of the lens barrel, prism, and cover glass has a protrusion provided in a position that covers one side of the interface between the prism and the cover glass on the lens barrel side, and the protrusion has a recess facing one side that forms a closed space between the prism and at least one side of the cover glass. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-030421 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when operating an endoscope, a load is placed on the cable connected to the circuit board, and when the circuit board is pulled, the imaging element on the circuit board is also pulled, causing the adhesion between the imaging element and the prism to come off, which can be a problem.

[0007] The present invention has an object to provide an imaging module that solves the problems of the conventional technology described above and can prevent the adhesion between the imaging element and the prism on the circuit board from coming apart when, for example, operating an endoscope. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention has the following configuration.

[0009] [1] An imaging module including an image sensor, a lens, and an optical component disposed between the image sensor and the lens, The light receiving surface of the image sensor and the optical components are fully bonded and fixed. A first layer having a thermal expansion coefficient larger than that of the image sensor is bonded to a surface of the image sensor opposite to the light receiving surface thereof, An imaging module in which the hardening temperature of an adhesive for bonding an imaging element and an optical component is lower than the operating temperature of the imaging element. [2] The imaging module according to [1], wherein the first layer is a circuit board. [3] The imaging module according to [2], wherein the circuit board is a flexible board. [4] The imaging module according to [2] or [3], wherein the imaging element and the first layer are connected via solder balls. [5] The imaging module according to any one of [1] to [4], wherein a space between the imaging element and the first layer is filled with an adhesive. [6] The imaging module according to any one of [1] to [5], further comprising a third layer, the third layer having a lower thermal expansion coefficient than the first layer, on a surface of the first layer opposite the imaging element. [7] The imaging element has a sensor chip and a cover glass placed on an imaging surface of the sensor chip; The imaging module according to any one of [1] to [6], wherein the sensor chip and the cover glass are bonded and fixed over their entire surfaces. Effect of the Invention

[0010] According to the present invention, it is possible to provide an imaging module that can prevent the adhesion between the imaging element and the prism on the circuit board from coming apart when, for example, an endoscope of the imaging module is operated. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing an example of the configuration of an endoscope system using an endoscope having an imaging module according to the present invention. [Diagram 2] FIG. 1 is a perspective view illustrating an example of an imaging module of the present invention. [Diagram 3] 3 is a side view of the imaging module shown in FIG. 2 with an anchor and a cover member removed. [Figure 4] 4 is an enlarged side view showing a part of the imaging module of FIG. 3. [Diagram 5] 11 is a partially enlarged side view of another example of the imaging module of the present invention. FIG. [Figure 6] FIG. 2 is an enlarged side view of a portion of the imaging module. [Figure 7] FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. [Figure 8] FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. [Figure 9] FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of an imaging module of the present invention will be described with reference to the drawings. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In the drawings of this specification, the scale of each part is appropriately changed for ease of viewing. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] [Imaging module] The imaging module of the present invention comprises: An imaging module including an imaging element, a lens, and an optical component disposed between the imaging element and the lens, The light receiving surface of the image sensor and the optical components are fully bonded and fixed. A first layer having a thermal expansion coefficient larger than that of the image sensor is bonded to a surface of the image sensor opposite to the light receiving surface thereof, In this imaging module, the hardening temperature of the adhesive that bonds the imaging element and the optical components is lower than the operating temperature of the imaging element.

[0014] FIG. 1 conceptually illustrates an example of an endoscope system including an endoscope having an imaging module of the present invention.

[0015] The endoscope system 1 includes an endoscope 2, a light source unit 3, and a processor unit 4. The endoscope 2 has the same configuration as a general endoscope, except for an imaging module 10, which will be described later.

[0016] The endoscope 2 has an insertion section that is inserted into the subject, an operating section connected to the insertion section, and a universal cord extending from the operating section. The insertion section is composed of a tip section, a bending section connected to the tip section, and a flexible section connecting the bending section and the operating section.

[0017] The tip is provided with an imaging module (camera head) having an illumination optical system that emits illumination light to illuminate the observation site, an imaging element that images the observation site, and an imaging optical system. The bending section is configured to be bendable in a direction perpendicular to the longitudinal axis of the insertion section, and the bending operation of the bending section is operated by the operation section. In addition, the flexible section is configured to be relatively flexible so as to be deformable according to the shape of the insertion path of the insertion section.

[0018] The operation unit is provided with buttons for operating the imaging operation of the imaging module at the tip, knobs for operating the bending operation of the bending section, etc. The operation unit is also provided with an introduction port through which a treatment tool such as an electric scalpel is introduced, and a treatment tool channel is provided inside the insertion section, which extends from the introduction port to the tip and through which a treatment tool such as forceps is inserted.

[0019] A connector is provided at the end of the universal cord, and the endoscope 2 is connected via the connector to a light source unit 3 that generates illumination light emitted from the illumination optical system at the tip, and a processor unit 4 that processes video signals acquired by the imaging device at the tip.

[0020] The processor unit 4 processes the input video signal to generate video data of the observed region, and displays and records the generated video data on a monitor. The processor unit 4 may be configured by a processor such as a PC (personal computer).

[0021] The light source unit 3 generates illumination light such as white light or light of a specific wavelength composed of three primary colors, i.e., red (R), green (G), and blue (B), and supplies the light to the endoscope 2, where it propagates through a light guide or the like within the endoscope 2 and is emitted from an illumination optical system at the tip of the insertion portion of the endoscope 2 to illuminate the area to be observed within the body cavity, in order to capture an image of the area to be observed within the body cavity using the imaging device of the endoscope 2 and obtain an image signal.

[0022] A light guide and a group of electric wires (signal cables) are housed inside the insertion section, the operation section, and the universal cord. Illumination light generated by the light source unit 3 is guided to the illumination optical system at the tip via the light guide, and signals and / or power are transmitted between the imaging device at the tip and the processor unit 4 via the group of electric wires.

[0023] The endoscope system 1 may further include a water tank for storing cleaning water, a suction pump for sucking the aspirate (including the supplied cleaning water) from within the body cavity, etc. Furthermore, the endoscope system 1 may further include a supply pump for supplying cleaning water in the water tank or gas such as external air to a duct (not shown) within the endoscope.

[0024] Fig. 2 is a perspective view showing a schematic example of an imaging module of the present invention. Fig. 3 is a side view of Fig. 2. Fig. 3 is also a side view of the imaging module of Fig. 2 with the anchor 24 and the cover member 42 removed.

[0025] The imaging module 10 shown in Figures 2 and 3 has a lens 12, a lens barrel 14 that holds the lens 12, an imaging element 15, an optical member 18, an optical member holder 20, a second layer 19, a circuit board 22, an anchor 24, a cover member 42, and a cable 26.

[0026] 2 and 3 is an example in which the optical member 18 is a prism, and the imaging surface of the sensor chip 16 is disposed parallel to the optical axis of the lens 12. In the following description, the optical member 18 will also be referred to as a prism 18.

[0027] The lens 12 is an optical system that forms an image of incident light on an imaging surface of a sensor chip 16. The lens 12 is held by a lens barrel .

[0028] The lens barrel 14 is a cylindrical member that holds one or more lenses 12. The lens barrel 14 holds the lens 12 so that the optical axis of the lens 12 is perpendicular to the surface of the prism 18 that faces the lens 12.

[0029] There are no particular limitations on the configuration of the lens 12 and the lens barrel 14. For example, the configuration may include one lens 12, or may include two, or four or more lenses 12. Furthermore, each lens 12 may be a convex lens or a concave lens.

[0030] The imaging element 15 has a sensor chip 16 and a cover glass 17 . The sensor chip 16 is an element that captures an image by converting light focused on the imaging surface of the sensor chip 16 by the lens 12 into an electrical signal through photoelectric conversion. The sensor chip 16 is a conventionally known element such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary MOS) sensor.

[0031] The cover glass 17 is disposed on the imaging surface of the sensor chip 16 to protect the imaging surface. The size of the cover glass 17 in a plan view is approximately the same as the size of the imaging surface of the sensor chip 16. The cover glass 17 is adhesively fixed to the entire imaging surface of the sensor chip 16. In the case where the imaging element 15 is configured to have the cover glass 17, the incident surface of the cover glass 17 (the surface opposite to the sensor chip 16) can be said to be the light receiving surface of the imaging element 15.

[0032] A prism 18 is disposed on the cover glass 17 (on the entrance surface).

[0033] The imaging element 15 is disposed closer to the base end than the lens barrel 14. In addition, the imaging element 15 is mounted on a circuit board 22 so that the light receiving surface is parallel to the optical axis of the lens 12, as shown in FIG.

[0034] Circuit board 22 is the first layer in the present invention, and is a board on which imaging element 15 is mounted. Electronic components other than imaging element 15 may also be mounted on circuit board 22. Circuit board 22 is provided with a plurality of connection terminals through which signals or power are input and output to and from imaging element 15 and the electronic components. Signal lines of cable 26 are electrically connected to the connection terminals (see FIG. 3).

[0035] In the illustrated example, the circuit board 22 has a shape in which a plate-like member having a substantially L-shape is curved at two points. Specifically, the circuit board 22 has a first curved portion 22b curved around an axis perpendicular to the optical axis direction of the lens (hereinafter also referred to as the axial direction), and a second curved portion 22c curved around an axis in the axial direction, and the imaging element 15, electronic components, and connection terminals are mounted on three plate-like portions connected by these two curved portions. In the illustrated example, the imaging element 15 is mounted on the upper surface side of the plate-like portion on the lower side in FIG. 3.

[0036] The circuit board 22 is a conventionally known circuit board used in an imaging module of an endoscope. The circuit board 22 may be a flexible board having flexibility. There is no particular limitation on the flexible board 22, and a conventionally known flexible board can be used. As an example, the flexible board is formed by forming a circuit made of copper foil or the like on a base film made of a resin material such as polyimide or polyethylene terephthalate (PET).

[0037] The circuit board 22 may be bent at one point or at three or more points. The arrangement of the imaging element 15, electronic components, connection terminals, and the like on the circuit board 22 is not particularly limited.

[0038] The imaging element 15 and the cable 26 are connected to the circuit on the circuit board 22. Light is converted into an electrical signal by the imaging element 15 (sensor chip 16), and this electrical signal is transmitted and transmitted to the cable 26 via the circuit on the circuit board 22. The cable 26 is inserted through the insertion portion, operation portion, universal cord, etc. of the endoscope, and is connected to the processor unit 4. The cable 26 includes one or more signal wires such as a coaxial cable or a single-axial cable, a shield wire covering the outer periphery of the one or more signal wires, and a protective coating (sheath) covering the outer periphery of the signal wires and the shield wire.

[0039] The circuit board 22 and the imaging element 15 (sensor chip 16) may be electrically connected by the second layer 19. Fig. 6 shows an enlarged view of the vicinity of the imaging element 15. In the example shown in Fig. 6, the second layer 19 has a plurality of solder balls 19a, and the solder balls 19a electrically connect the circuit of the circuit board 22 and the sensor chip 16. In the example shown in Fig. 6, as a preferred embodiment, an underfill 19b is filled in the portion of the space between the imaging element 15 and the circuit board 22 where there are no solder balls 19a. The underfill 19b is an adhesive that fills the space between the imaging element and the first layer in the present invention.

[0040] As the solder ball 19a, a conventionally known solder ball used for electrically connecting a sensor and a substrate in an imaging module of an endoscope can be appropriately used. For example, a Sn-Ag-Cu alloy can be used as the material of the solder ball.

[0041] The underfill 19b may be any known underfill used in an imaging module of an endoscope, for example, a resin material such as an epoxy resin.

[0042] The second layer 19 is not limited to the configuration having the solder balls 19a and the underfill 19b. For example, the second layer 19 may have only the solder balls 19a. Alternatively, the second layer 19 may be an anisotropic conductive film (ACF).

[0043] The second layer 19 has a configuration including solder balls 19a and underfill 19b, so that the amount of warping of the imaging element, which will be described later, can be increased.

[0044] Prism 18 is disposed between lens barrel 14 and image sensor 15 (cover glass 17). Prism 18 bends light that has passed through lens 12 held in lens barrel 14 by 90 degrees to change the optical path and guides it to the light receiving surface of image sensor 15. In the illustrated example, prism 18 is a right-angle prism whose entrance surface and exit surface are perpendicular to each other. Prism 18 is disposed so that its entrance surface faces the base end side surface of lens barrel 14, and its exit surface faces the light receiving surface of image sensor 15 (cover glass 17). Prism 18 is adhesively fixed to image sensor 15 (cover glass 17) over its entire surface.

[0045] Optical member holder 20 is a member that holds lens barrel 14 and prism 18. Optical member holder 20 is a substantially cylindrical member, and lens barrel 14 is fitted into the inside of the cylindrical portion to hold lens barrel 14. The inner surface of optical member holder 20 and the outer peripheral surface of lens barrel 14 are fixed by adhesive.

[0046] Various known adhesives used in conventional endoscopes can be used as the adhesive for bonding the optical member holder 20 and the lens barrel 14. The same applies to adhesives for bonding other members together.

[0047] Optical element holder 20 has a polygonal flange portion 20a on the end face on the base end side of the cylindrical portion, against which the entrance surface of prism 18 abuts, thereby positioning prism 18. Optical element holder 20 holds lens barrel 14 and prism 18 in predetermined positions, thereby fixing the relative positions of lens barrel 14 and prism 18, i.e., the relative positions of lens barrel 14 and image sensor 15.

[0048] Here, the lens barrel 14 is adhesively fixed to the optical element holder 20 with its relative position in the optical axis direction (hereinafter also referred to as the axial direction) of the lens 12 adjusted so that the imaging surface of the sensor chip 16 is in focus.

[0049] The anchor 24 holds the cable 26 relative to the optical element holder 20. In the illustrated example, the anchor 24 has two plate-like portions 24c extending in the optical axis direction, and an arm portion 24a is provided at the tip side of each plate-like portion 24c. The arm portion 24a engages with the flange portion 20a of the optical element holder 20. As shown in FIG. 2, the two plate-like portions 24c are disposed such that their main surfaces are perpendicular to the surface of the circuit board 22 (the surface on which the imaging element 15 is disposed). The two plate-like portions 24c are disposed so as to face each other across a connection portion with the cable 26 on the circuit board 22.

[0050] The anchor 24 also has a holding portion 24b that connects two plate-like portions 24c on the base end side and holds the cable 26. The holding portion 24b is crimped so as to press the cable 26 and holds the cable 26. That is, the holding portion 24b is bent along the outer sheath of the cable 26.

[0051] The arm portion 24a of the anchor 24 and the flange portion 20a of the optical component holder 20, as well as the holding portion 24b of the anchor 24 and the outer cover of the cable 26, may be bonded and fixed with an adhesive.

[0052] In this way, by connecting anchor 24 to optical element holder 20 and cable 26, it is possible to prevent the connection between the connection terminal on circuit board 22 and the signal line from being pulled when cable 26 is pulled, for example, and thus prevent the connection between the connection terminal and the signal line from being broken.

[0053] The cover member 42 is a plate-like member disposed on the opposite side of the anchor 24 from the circuit board 22. The cover member 42, together with the anchor 24, covers and protects the connection points between the connection terminals on the circuit board 22 and the signal lines.

[0054] There is no particular limitation on the material for forming the anchor 24 and the cover member 42, and various resin materials and metal materials used as components for composing the imaging module of an endoscope can be used. Metal materials are preferable from the viewpoint of heat dissipation. In consideration of processability, availability, strength, etc., stainless steel and copper alloys are preferable for the anchor 24 and the cover member 42.

[0055] The cover member 42 may be formed integrally with the anchor 24. Alternatively, the cover member 42 may not be provided.

[0056] In such an imaging module 10, the observation image captured by the imaging element 15 through the lens 12 is focused on the imaging surface of the sensor chip 16 and converted into an electrical signal. This electrical signal is output to the processor unit 4 via the cable 26, converted into a video signal, and the observation image is displayed on a monitor connected to the processor unit 4.

[0057] Here, as described above, when the endoscope is operated, a load is applied to the cable 26 connected to the circuit board 22, and the circuit board 22 is pulled, which causes the imaging element 15 on the circuit board 22 to be pulled as well, resulting in a problem that the adhesion between the imaging element 15 and the prism (optical member) 18 is peeled off. In addition, the inside of the anchor 24 is filled with adhesive, and the load of the cable 26 is applied to the imaging element 15 and the prism 18 via this adhesive, so that the adhesion between the imaging element 15 and the prism 18 is peeled off. In addition, environmental factors such as sterilizing gas when cleaning the endoscope and repeated temperature changes can cause the adhesive that bonds the imaging element 15 and the prism 18 to deteriorate and become more fragile.

[0058] In contrast, the photography module of the present invention has a first layer having a larger thermal expansion coefficient than that of image sensor 15 bonded to the surface opposite the light receiving surface of image sensor 15, and is configured such that the hardening temperature of the adhesive bonding image sensor 15 and optical member 18 is lower than the operating temperature of image sensor 15.

[0059] When the endoscope is operated, the temperature of each component of the imaging module 10 rises due to heat generated by the imaging element 15, the light guide, etc. Therefore, each component of the imaging module 10 expands due to heat. At that time, if the thermal expansion coefficient of the first layer (circuit board) 22 is larger than that of the imaging element 15, the first layer 22 tends to expand in the planar direction more than the imaging element 15, so that the imaging element 15 is subjected to a force that deforms it in a concave shape toward the optical member 18 side. Basically, the temperature at which the adhesive is cured is such that the stress applied to the adhesive layer is approximately zero. Therefore, if the curing temperature of the adhesive is lower than the operating temperature, a pulling force is applied between the imaging element 15 and the optical member 18 in the direction away from each other at the center, and a compressive force is applied at the end, as shown by the arrows in FIG. 4. In this way, during operation of the endoscope which places a load on cable 26, heat generated by imaging element 15 and other components is used to deform the light receiving surface side of imaging element 15 in a concave direction, thereby applying a compressive force to the outer periphery of the adhesive surface between imaging element 15 and optical member 18, thereby tightly adhering imaging element 15 and optical member 18 together, thereby preventing imaging element 15 and optical member 18 from peeling off even if cable 26 is pulled.

[0060] In the present invention, the temperature during operation of the imaging device is defined as follows. An endoscope having an imaging module is placed in an atmosphere of 37°C, the imaging element of the imaging module is driven, and half the maximum amount of light is incident on the light guide of the endoscope, after which an equilibrium state is reached and the temperature is the temperature at the center of the side of the imaging element.

[0061] Generally, a CMOS sensor and a CCD sensor used as the sensor chip 16 have a configuration in which an electrode layer, an insulating film, etc. are formed on a silicon wafer. Therefore, the thermal expansion coefficient of the sensor chip 16 is about 2.5 ppm / °C to 4 ppm / °C. In addition, when the imaging element 15 has a cover glass 17, the thermal expansion coefficient of the imaging element 15 in which the sensor chip 16 and the cover glass 17 are laminated is about 2.5 ppm / °C to 5 ppm / °C.

[0062] Examples of the circuit board 22 having a thermal expansion coefficient larger than that of the imaging element 15 include flexible boards and rigid boards made of resin materials such as polyimide and polyethylene terephthalate. For example, the thermal expansion coefficient of a flexible board is about 20 ppm / °C to 100 ppm / °C.

[0063] The method for measuring the thermal expansion coefficient of each member is as follows. The thermal expansion coefficient is determined by measuring the length between measurement points on a test piece at multiple temperatures and calculating the rate of change in length per unit temperature change. The elastic modulus is determined by applying a load to a test piece in a tensile test, measuring the change in length between the measurement points on the test piece, and calculating the stress and strain. Alternatively, the Young's modulus of each material can be determined by the nanoindentation method, and the composite elastic modulus can be determined from the volume ratio.

[0064] The adhesive for bonding the imaging element 15 and the optical member 18 may be any adhesive that can suitably bond the imaging element 15 and the optical member 18 and has a hardening temperature that is lower than the operating temperature of the imaging element 15. In general, the operating temperature of the imaging element 15 is about 50°C to 85°C. Therefore, the adhesive for bonding the imaging element 15 and the optical member 18 is preferably one that has a hardening temperature of 50°C or less, more preferably one that has a hardening temperature of 40°C or less, and even more preferably one that hardens at room temperature.

[0065] Examples of adhesives whose curing temperature satisfies this range include UV (ultraviolet) curing adhesives, UV + heat curing adhesives, and epoxy adhesives that can be cured at room temperature.

[0066] 4, the imaging element 15 has a configuration including the sensor chip 16 and the cover glass 17, but is not limited to this. As in the example shown in FIG. 5, the imaging element 15 may have a configuration including the sensor chip 16 without the cover glass 17. In this case, the imaging surface of the sensor chip 16 is the light receiving surface of the imaging element 15. In addition, in the case of this configuration, the exit surface of the optical member 18 is adhesively fixed to the imaging surface of the sensor chip 16.

[0067] 4 and 5, the second layer 19 between the imaging element 15 and the circuit board 22 is omitted.

[0068] Moreover, the imaging module of the present invention preferably has a third layer, the third layer having a lower thermal expansion coefficient than the first layer, on the surface of the first layer opposite the imaging element.

[0069] Fig. 7 is a side view conceptually showing another example of the imaging module of the present invention, in which lenses and the like are omitted. The imaging module shown in FIG. 7 includes an optical member 18, an imaging element 15 having a cover glass 17 and a sensor chip 16, a circuit board 22, and a third layer 40.

[0070] The optical member 18, the cover glass 17, the sensor chip 16, and the circuit board 22 have the same configuration as in the above-mentioned example.

[0071] The third layer 40 is disposed on the surface (back surface) of the circuit board 22, which is the first layer, opposite to the imaging element 15. The third layer 40 is made of a material having a lower thermal expansion coefficient than the circuit board 22.

[0072] By disposing the third layer 40, which has a lower coefficient of thermal expansion than the circuit board 22, on the back surface of the circuit board 22, a force acts to restrict the thermal expansion of the circuit board 22. In other words, the imaging element 15 is prevented from warping concavely toward the optical member 18. By disposing such a third layer 40, which has a low coefficient of thermal expansion, on the back surface of the circuit board 22, the amount of warping of the imaging element 15 concavely toward the optical member 18 can be adjusted, and the imaging element 15 can be prevented from being damaged due to excessive warping.

[0073] Materials for the third layer 40 include Invar, Kovar, glass, silicon, stainless steel, and ceramics such as aluminum nitride and silicon nitride.

[0074] Moreover, the thickness of the third layer 40 may be appropriately set according to the amount of adjustment of the amount of warping of the imaging element 15 .

[0075] Moreover, the size of the third layer 40 in a plan view is preferably equal to or larger than the size of the imaging element 15, and the third layer 40 is preferably disposed so as to encompass the imaging element 15 in a plan view.

[0076] 7, the third layer 40 is disposed so that the size (length) of the lens 12 in the optical axis direction is greater than that of the imaging element 15, and so as to encompass the imaging element 15 in the optical axis direction. That is, the side surface of the third layer 40 protrudes beyond the side surface of the imaging element 15.

[0077] A circuit may be formed on the third layer 40. The circuit formed on the third layer 40 may be connected to a circuit on the first layer (flexible substrate) 22 to form a multi-layer circuit board. When a circuit is formed on the third layer 40, the third layer may be made of an insulating material such as ceramic.

[0078] Here, in the example shown in FIG. 3, the imaging surface of the sensor chip 16 (the light receiving surface of the imaging element 15) is arranged parallel to the optical axis of the lens 12, and the optical member 18 arranged between the lens 12 and the imaging element 15 is a prism that bends light by 90 degrees, but this is not limited to the above configuration.

[0079] FIG. 8 is a side view showing another example of the imaging module of the present invention. The imaging module shown in Figure 8 has a lens barrel 14 that holds a lens 12, an optical member holder 20, an optical member 18, an imaging element 15 having a cover glass 17 and a sensor chip 16, a second layer 19, a circuit board 22, and an adhesive layer 44.

[0080] 8, circuit board 22 has a curved portion that is curved at approximately 90°, and has a flat portion parallel to the optical axis of lens 12 and a flat portion perpendicular to the optical axis. A second layer 19, sensor chip 16, and cover glass 17 are laminated on the surface of the portion perpendicular to the optical axis of circuit board 22 (the surface on the lens 12 side). Therefore, the imaging surface of sensor chip 16 (light receiving surface of image sensor 15) is disposed perpendicular to the optical axis of lens 12.

[0081] The optical member 18 guides the light that has passed through the lens 12 to the imaging surface of the sensor chip 16. The optical member 18 has a light entrance surface and an exit surface that are arranged perpendicular to the optical axis. The optical member 18 may simply transmit light, or may have the effect of concentrating light. By having the optical member 18 have the effect of concentrating light, the distance between the lens 12 and the sensor chip 16 can be made closer, and the sensor chip 16 can be made smaller.

[0082] The lens barrel 14 that holds the lens 12, the optical member holder 20, the image sensor 15 having the cover glass 17 and the sensor chip 16, and the second layer 19 are the same as those in the image sensor module shown in FIG. 3, and therefore their description will be omitted.

[0083] The optical member 18 is held by an optical member holder 20 and is positioned relative to the lens barrel 14 which is held by the optical member holder 20 .

[0084] Thus, even when the imaging surface of the sensor chip 16 is arranged perpendicular to the optical axis of the lens 12, the imaging module of the present invention has a configuration in which a first layer (circuit board 22) having a larger thermal expansion coefficient than that of the imaging element 15 is bonded to the surface opposite the light receiving surface of the imaging element 15, and the hardening temperature of the adhesive that bonds the imaging element 15 and the optical member 18 is lower than the operating temperature of the imaging element 15. This makes it possible to prevent the imaging element 15 and the optical member 18 from peeling off from each other even if the cable is pulled during operation of the endoscope.

[0085] Here, in the example shown in Fig. 8, as a preferred embodiment, the adhesive layer 44 is disposed so as to cover at least a part of the side surface of the sensor chip 16. In the example shown in Fig. 8, the adhesive layer 44 is disposed at a position so as to cover the side surface on the curved portion side of the circuit board 22 (the lower side surface in Fig. 8) and the side surface opposite to this side surface (the upper side surface in Fig. 8).

[0086] Damage to the imaging element due to warping can be suppressed by providing the adhesive layer 44 that covers at least a part of the side surface of the sensor chip 16. The adhesive layer 44 may also have functions such as light blocking, gas barrier (sterilizing gas, etc.), and moisture resistance.

[0087] The adhesive layer 44 preferably covers the entire periphery of the sensor chip 16 .

[0088] The adhesive layer 44 may be made of an adhesive or a sealant.

[0089] As the adhesive, various adhesives used in endoscopes can be used. For example, an epoxy resin adhesive can be used. In addition, black epoxy is preferable because of its light blocking properties.

[0090] As the sealing agent, various sealing agents used in endoscopes can be used. The adhesive and sealant should have a high thermal conductivity, but it is preferable that they have insulating properties.

[0091] Even in the case of a configuration in which the imaging surface of sensor chip 16 is arranged parallel to the optical axis of lens 12, as shown in Figure 3 and the like described above, it is preferable to have adhesive layer 44 arranged so as to cover at least a portion of the side surface of sensor chip 16, and it is more preferable that it is applied so as to cover the entire circumference.

[0092] In addition, in the example shown in FIG. 8, adhesive layer 44 is filled between circuit board 22 and prism 18, but this is not limited to this, and adhesive layer 44 may be filled between circuit board 22 and optical element holder 20, as in the example shown in FIG. 9.

[0093] 8, even in the case where the imaging surface of the sensor chip 16 is arranged perpendicular to the optical axis of the lens 12, a third layer made of a material having a lower thermal expansion coefficient than the circuit board 22 may be provided on the rear surface of the circuit board 22. This makes it possible to adjust the amount of warping of the imaging element 15.

[0094] In the above example, the first layer is a circuit board, but is not limited thereto. The first layer may be a member that does not have a circuit and has a thermal expansion coefficient larger than that of the imaging element. From the viewpoint of space efficiency, it is preferable to use a circuit board as the first layer. Furthermore, from the viewpoints of assembly, cost, etc., it is preferable to use a flexible board as the first layer.

[0095] The imaging module according to the present invention has been described in detail above using various embodiments. However, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the gist of the present invention. [Explanation of symbols]

[0096] 1 Endoscope system 2 Endoscope 3 Light source unit 4 Processor Unit 10 Imaging module 12 Lenses 14 Lens barrel 15 Image sensor 16 Sensor chip 17 Coverslip 18 Optical components (prisms) 19 Second Layer 19a Solder ball 19b Underfill 20 Optical component holder 20a Flange part 22 Circuit Board (First Layer) 22a Back 22b First curved section 22c Second curved section 24 Anchor 24a Arm section 24b Holding part 24c Plate-shaped part 26 Cable 40 Third Layer 42 Cover member 44 Adhesive layer

Claims

1. An imaging module including an imaging element, a lens, and an optical component disposed between the imaging element and the lens, The light receiving surface of the imaging element and the optical component are fixed by adhesive over their entire surfaces, a first layer having a thermal expansion coefficient larger than that of the image sensor is bonded to a surface of the image sensor opposite to the light receiving surface, the adhesive for bonding the imaging element and the optical component is any one of an ultraviolet curing adhesive, an ultraviolet and heat curing adhesive, and an epoxy adhesive, and the curing temperature is 50° C. or less; the imaging element and the first layer are connected via solder balls; An imaging module, wherein a space between the imaging element and the first layer is filled with an adhesive.

2. The imaging module of claim 1 , wherein the first layer is a circuit board.

3. The imaging module according to claim 2 , wherein the circuit board is a flexible board.

4. 4. The imaging module according to claim 1, further comprising a third layer on a surface of the first layer opposite the imaging element, the third layer having a thermal expansion coefficient lower than that of the first layer.

5. The imaging module according to claim 4 , wherein a size of the third layer in a plan view is equal to or larger than a size of the imaging element.

6. 6. The imaging module according to claim 4, wherein the material of the third layer is any one of an invar material, a kovar material, glass, silicon, stainless steel, and ceramic.

7. the imaging element includes a sensor chip and a cover glass disposed on an imaging surface of the sensor chip; 7. The imaging module according to claim 1, wherein the sensor chip and the cover glass are bonded and fixed over their entire surfaces.

Images