Patent Publication Number: US-2013253272-A1

Title: Endoscope

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to an endoscope comprising a heat dissipation mechanism of an image sensor. 
     2. Description Related to the Prior Art 
     Diagnoses and operations using endoscopes have been widely performed in medical field. The endoscope is provided with an insert section to be inserted into a body cavity of a patient and a handling section provided at a proximal end of the insert section. A distal portion of the insert section incorporates an image sensor for imaging a region of interest in the body cavity. 
     In the distal portion of the insert section, heat generated in the image sensor and the like accumulates and raises the temperature of the insert section. Recently, pixel number and speed of reading image signals have been increased due to a demand to improve image quality of endoscopic images. As a result, heat from the image sensor is increased. An excessive increase in the temperature of the distal portion due to the heat from the image sensor makes the operation of the image sensor unstable. This causes noise in an image signal from the image sensor, resulting in deterioration of the image quality. To prevent the temperature rise, the image sensor is provided with a heat dissipation mechanism. Various types of heat dissipation mechanisms are known. 
     For example, in an endoscope disclosed in Japanese Patent Laid-Open Publication No. 2009-296542, a large-sized heat dissipation member is provided to an image sensor through an insulating member. In an endoscope disclosed in Japanese Patent Laid-Open Publication No. 2011-200401, a heat dissipation member that is fixed to a forceps channel is provided to an image sensor through an insulating member. In an endoscope disclosed in U. S. Patent Application Publication No. 2010/0033559 (corresponding to Japanese Patent Laid-Open Publication No. 2010-035815), an image sensor is provided with a cooling element disposed parallel with the image sensor. In an endoscope disclosed in Japanese Patent Laid-Open Publication No. 2009-066118, piping for flowing cooling fluid is provided close to an image sensor. In an endoscope disclosed in Japanese Patent Laid-Open Publication No. 2010-279527, an image sensor contacts with high thermal conductive ceramic. In an endoscope disclosed in Japanese Patent Laid-Open Publication No. 2010-201023, a heat storage material is disposed close to an image sensor. The heat storage material absorbs heat due to latent heat of a phase change. 
     In the above-described endoscopes, the heat dissipation mechanisms are composed of the large-sized members, which increase material cost. The large-sized heat dissipation mechanism makes the insert section of the endoscope large in diameter and heavy. To reduce physical stress on a patient, it is necessary to downsize and reduce weight of the heat dissipation mechanism while good heat dissipation performance is maintained. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an endoscope provided with a lightweight, downsized, and inexpensive heat dissipation mechanism. 
     To achieve the above and other objects, an endoscope of the present invention is provided with a heat dissipation substrate, a multi-core cable, and a connection member. The heat dissipation substrate is attached to the image sensor such that the heat dissipation substrate is parallel with an imaging surface of the image sensor. The heat dissipation substrate transmits heat from the image sensor. The multi-core cable is composed of signal lines for transmitting signals to and from the image sensor, first shield members covering the respective signal lines, and a second shield member for covering and holding the signal lines together. The second shield member has an electrically conductive layer. The connection member connects the heat dissipation substrate and the electrically conductive layer. The connection member transmits the heat, from the image sensor, from the heat dissipation substrate to the electrically conductive layer. 
     It is preferable that the endoscope further comprises a circuit board. The image sensor is attached to a surface of the circuit board, and the heat dissipation substrate is attached to the back of the circuit board. 
     It is preferable that the connection member is formed using one of paste containing metal particles, soldering, wire bonding, and tape bonding. 
     It is preferable that the heat dissipation substrate is a flexible heat dissipation substrate having a film base made from polymer and a metal layer formed on the film base. It is preferable that the metal layer is formed on each surface of the film base. 
     It is preferable that the circuit board and the heat dissipation substrate are bonded using paste containing metal particles or soldering. 
     It is preferable that the heat dissipation substrate is a ceramic heat dissipation substrate having high thermal conductive ceramic and a metal layer formed on the high thermal conductive ceramic. It is preferable that the metal layer is formed on each surface of the high thermal conductive ceramic. 
     It is preferable that the heat dissipation substrate includes the high thermal conductive layers of different types, and the heat dissipation substrate is adhered to the circuit board using an adhesive. 
     It is preferable that the high thermal conductive layers of different types are a first high thermal conductive layer having thermal conductivity and electrically insulating properties and a second high thermal conductive layer having thermal conductivity higher than the thermal conductivity of the first high thermal conductive layer. 
     It is preferable that the first high thermal conductive layer is attached to the back of the circuit board. 
     According to the present invention, the connection member connects the heat dissipation substrate provided to the image sensor and the electrically conductive layer of the second shield member of the multi-core cable. Thereby, the heat from the image sensor is dissipated to the outside of the endoscope through the heat dissipation substrate and the second shield member of the multi-core cable that extends to the outside of the endoscope. 
     Because the heat dissipation mechanism does not employ a large-sized heavy member, the heat dissipation mechanism is lightweight and downsized, and produced with low manufacture cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and advantages of the present invention will be more apparent from the following detailed description of the preferred embodiments when read in connection with the accompanied drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, and wherein: 
         FIG. 1  is a perspective view illustrating an endoscope system employing an endoscope according to the present invention; 
         FIG. 2  is a front view illustrating an end cover of a distal portion of an insert section of the endoscope; 
         FIG. 3  is a cross-sectional view illustrating a flexible tube portion of the insert section of the endoscope; 
         FIG. 4  is a cross-sectional view of the distal portion of the endoscope according to a first embodiment of the present invention; 
         FIG. 5  is a cross-sectional view of the distal portion of the endoscope according to a modified example of the first embodiment; and 
         FIG. 6  is a cross-sectional view of the distal portion of the endoscope according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIGS. 1 and 2 , an endoscope system  2  is composed of an endoscope  10 , a processor device  11 , a light source device  12 , a monitor  29 , and the like. The endoscope  10  is provided with an insert section  14  to be inserted into a body cavity of a patient, a handling section  15  connected to a basal (proximal) end portion of the insert section  14 , and a universal cord  16  connected to the processor device  11  and the light source device  12 . A connector  28  is connected to an end of the universal cord  16 . The connector  28  is of a multi-connection type. The connector  28  is connected to each of the processor device  11  and the light source device  12 . 
     An air/water feeding device  13  is incorporated in the light source device  12 . The air/water feeding device  13  is composed of a well-known air-supply pump  13 A and a water tank  13 B. The air-supply pump  13 A generates pressure to feed gas such as air and liquid such as cleaning water. The water tank  13 B holds the cleaning water and is provided externally to the light source device  12 . 
     The insert section  14  has a distal portion  14 A, a bending portion  14 B, and a flexible tube portion  14 C. The distal portion  14 A is provided with an imaging section for imaging the inside of the body cavity. The bending portion  14 B is bendable. The flexible tube portion  14 C has flexibility. Hereinafter, a distal end side of the insert section  14  is simply referred to as “the distal end side”. A proximal end side of the insert section  14  is simply referred to as “the proximal end side”. 
     An end cover  20  of the distal portion  14 A is provided with a capture window  21 , lighting windows  22 A and  22 B, a forceps outlet  23  from which forceps or the like are projected into the body cavity, and a jet nozzle  24 . Behind the capture window  21 , the imaging section is attached. The imaging section images the inside of the body cavity of the patient. The two lighting windows  22 A and  22 B are disposed symmetrically with respect to the capture window  21 . The lighting windows  22 A and  22 B apply illumination light from the light source device  12  to a region of interest in the body cavity. The forceps outlet  23  is connected to a forceps inlet  26  provided to the handling section  15 . A treatment tool such as forceps, an injection needle, or a high frequency surgical knife is inserted into the forceps inlet  26 . The jet nozzle  24  ejects the air and the cleaning water, supplied from the air/water feeding device  13 , to the capture window  21  to wash off dirt from the capture window  21  with the cleaning water and dry the capture window  21  with the air. 
     The processor device  11  performs various image processes on an image signal, inputted from the imaging section through the universal cord  16  and the connector  28 , to produce an endoscopic image. The endoscopic image is displayed on the monitor  29  through a cable . The processor device  11  is connected to the light source device  12  through a communication cable, and communicates various types of control data with the light source device  12 . 
     As shown in  FIG. 3 , light guides  31 A and  31 B, a forceps channel  32 , an air/water channel  33 , and a multi-core cable  34  run through the flexible tube portion  14 C. The light guides  31 A and  31 B deliver the light from the light source device  12  to the lighting windows  22 A and  22 B. The forceps channel  32  is a flexible metal pipe and connects the forceps inlet  26  and the forceps outlet  23 . The air/water channel  33  feeds the air and the cleaning water from the air/water feeding device  13  to the jet nozzle  24 . The multi-core cable  34  electrically connects the processor device  11  and the imaging section. 
     The flexible tube portion  14 C is composed of three layers, a helical tubular layer (flex)  36 , a mesh tubular layer (blade)  37 , and a resin (silicon rubber) layer  38  in this order from the inside. The helical tubular layer  36  is made from helically wound steel coils. The mesh tubular layer  37  covers the helical tubular layer  36  to prevent the helical tubular layer  36  from being stretched. The resin layer  38  has flexibility and covers the mesh tubular layer  37 . 
     As shown in  FIG. 4 , a metal stationary tube  41  and the end cover  20  are provided inside the distal portion  14 A. The stationary tube  41  has thermal conductivity and houses the forceps channel  32  and the imaging section. The end cover  20  fills gaps in an opening on the distal end side of the stationary tube  41 . The stationary tube  41  and the end cover  20  are covered with the resin layer  38 . 
     The light guides  31 A and  31 B, the forceps channel  32 , the air/water channel  33 , and the multi-core cable  34  run inside the stationary tube  41 . 
     The forceps channel  32  is connected to the forceps outlet  23  provided through the end cover  20 . Note that lighting lenses (not shown) are disposed behind the respective lighting windows  22 A and  22 B. Exits of the light guides  31 A and  31 B face the respective lighting lenses. The air/water channel  33  is connected to the jet nozzle  24 . An end of each of the forceps channel  32 , the light guides  31 A and  31 B, and the air/water channel  33  is fixed to the end cover  20 . The other end of the forceps channel  32  is connected to the forceps inlet  26 , and the other ends of the light guides  31 A and  31 B are connected to the light source device  12 , and the other end of the air/water channel  33  is connected to the air/water feeding device  13 , through the bending portion  14 B, the flexible tube portion  14 C, the handling section  15 , and the like. 
     As shown in  FIG. 3 , the multi-core cable  34  is composed of signal lines  34 A, first shield members  34 B that cover the respective signal lines  34 A, and a second shield member  34 C. The second shield member  34 C covers and holds the signal lines  34 A, each covered with the first shield member  34 B, together. Each of the first shield member  34 B and the second shield member  34 C functions as an electric shield layer and an electromagnetic shield layer. As shown in  FIG. 4 , the second shield member  34 C is provided with an innermost layer  34 C 1 , a middle layer  34 C 2 , being an electrically conductive layer, and an outermost layer  34 C 3 . Each of the innermost and outermost layers  34 C 1  and  34 C 3  is made from electrically insulating material. The middle layer  34 C 2  is made from electrically conductive material. 
     The distal portion of the endoscope  10  according to a first embodiment of the present invention incorporates the imaging section. As shown in  FIG. 4 , the imaging section is provided with an objective optical system  51 , a prism  52 , and an image sensor  54 . Image light of the region of interest captured through the capture window  21  is incident on the prism  52  through the objective optical system  51 . The prism  52  refracts the image light from the objective optical system  51  in a substantially vertical direction, and thereby forms an image of the region of interest on an imaging surface of the image sensor  54 . The image sensor  54  is a CCD image sensor, a CMOS image sensor, or the like, and generates an image signal into which an image is converted photoelectrically. The image signal is outputted through a circuit board  55  provided on the opposite side of the imaging surface that is parallel (or substantially parallel) with a direction of insertion of the insert section  14 . The circuit board  55  is electrically connected to each of the signal lines  34 A of the multi-core cable  34 . The image signal is sent to the processor device  11  through the multi-core cable  34 . It is preferable that the size of the circuit board  55  is greater than or equal to the size of the image sensor  54 . Transparent glass  56  protects an imaging surface side of the image sensor  54 . 
     To dissipate the heat generated in the image sensor  54  to prevent malfunction of the image sensor  54 , a heat dissipation substrate (thermal conductive substrate)  57  is overlaid onto the back of the circuit board  55 . Note that, alternatively, the heat dissipation substrate  57  maybe overlaid onto the back of the image sensor  54 . The heat dissipation substrate  57  is provided with first and second high thermal conductive layers  57 A and  57 B so as to maintain electrical insulation with the circuit board  55  while having good thermal conductivity. In this embodiment, the first high thermal conductive layer  57 A is made from electrically insulating material with relatively high thermal conductivity. The second high thermal conductive layer  57 B is made from material with thermal conductivity higher than that of the first high thermal conductive layer  57 A. The first and second high thermal conductive layers  57 A and  57 B are adhered to each other using an adhesive with good thermal conductivity. Note that the heat dissipation substrate  57  may be composed only of the first high thermal conductive layer  57 A. When the electrically insulating properties are not necessary, the heat dissipation substrate  57  may be composed only of the second high thermal conductive layer  57 B. 
     The first high thermal conductive layer  57 A is adhered to the circuit board  55  disposed on and parallel (or substantially parallel) with the opposite side of the imaging surface of the image sensor  54  (the back of the image sensor  54 ) with the use of an electrically insulating adhesive. The adhesive preferably has high thermal conductivity in view of heat dissipation performance. It is preferable that a distal end side of the heat dissipation substrate  57  is flush with or protrudes relative to the circuit board  55 . The proximal end side of the heat dissipation substrate  57  preferably protrudes relative to the circuit board  55 . The proximal end side of the second high thermal conductive layer  57 B preferably protrudes relative to the first high thermal conductive layer  57 A. 
     A flexible heat dissipation substrate is used as the heat dissipation substrate  57 . The flexible heat dissipation substrate is composed of a base layer and a metal layer formed on the base layer. The base layer is made from electrically insulating polymer with relatively high thermal conductivity, for example, polyimide. The metal layer is made from metal with high electrical conductivity. The base layer functions as the first high thermal conductive layer  57 A. The metal layer functions as the second high thermal conductive layer  57 B. For example, the base layer is made from polyimide. The metal layer is made from copper. A known product such as DIA-FINE (Japanese registered trademark No. 4901676) is a specific example of the flexible heat dissipation substrate. 
     A ceramic heat dissipation substrate may be used as the heat dissipation substrate  57 . The ceramic heat dissipation substrate is composed of a base layer and a metal layer formed on the base layer. The base layer is made from electrically insulating ceramic with relatively high thermal conductivity. The metal layer is made from metal such as copper or aluminum. The base layer functions as the first high thermal conductive layer  57 A. The metal layer functions as the second high thermal conductive layer  57 B. For example, the base layer is made from alumina, aluminum nitride, or silicon nitride. Specific examples of the ceramic heat dissipation substrates include known products such as the above-mentioned ceramic metallized with the metal layer, DBC (direct-bond-copper, ceramic on which copper is bonded) (Japanese registered trademark No. 1877649), and DBA (direct-bond-aluminum, ceramic on which aluminum is bonded) (Japanese registered trademark No. 2011-082326). 
     Operation of the endoscope according to the first embodiment of the present invention is described. To perform an endoscopic examination, the insert section  14  of the endoscope  10  is inserted into the body cavity. During observation, the image sensor  54  is driven by a signal sent from the processor device  11  through the signal lines  34 A. The signal lines  34 A extend through the connector  28 , the universal cord  16 , the handling section  15 , the flexible tube portion  140 , and the bending portion  14 B to the image sensor  54 . The image light of the region of interest is incident on the imaging surface of the image sensor  54  through the objective optical system  51  and the prism  52 , and the image sensor  54  outputs the image signal. The image signal is transmitted to the processor device  11  in the reverse direction of the above-described transmission path of the signal from the processor device  11 . 
     The image sensor  54  generates heat during operation. The heat is transmitted to the second high thermal conductive layer  57 B with high thermal conductivity, through the first high thermal conductive layer  57 A with relatively high thermal conductivity. The heat is transmitted from the distal end side to the proximal end side of the second high thermal conductive layer  57 B. The heat is then transmitted to the middle layer  34 C 2  of the second shield member  34 C of the multi-core cable  34  through a connection member  72 . The heat transmitted to the middle layer  34 C 2  is transmitted through the multi-core cable  34 , in the same direction as the image signal outputted from the image sensor  54 . Eventually, the heat is released to the outside of the endoscope  10  through the universal cord  16 . 
     It is preferable that the distal end side of the heat dissipation substrate  57  is flush with or protrudes relative to the image sensor  54  or the circuit board  55 . It is preferable that the proximal end side of the heat dissipation substrate  57  protrudes relative to the image sensor  54  or the circuit board  55 . Thereby, the capacity of the heat dissipation substrate  57  to receive the heat from the image sensor  54  increases. The second high thermal conductive layer  57 B is preferably made from metal with high heat capacity, for example, copper. Thereby, the second high thermal conductive layer  57 B can receive most of the heat generated by the image sensor  54  and transmitted through the first high thermal conductive layer  57 A. 
     In a modified example of the first embodiment of the present invention, as shown in  FIG. 5 , the arrangement of the first high thermal conductive layer  57 A and the second high thermal conductive layer  57 B can be reversed only when an electrically insulating adhesive is used. Like reference numerals designate like or corresponding parts in  FIGS. 4 and 5 , and descriptions thereof are omitted. 
     In the modified example of the first embodiment, it is necessary to prevent electrical connection between the signal lines  34 A and the second high thermal conductive layer  57 B made from the electrically conductive material. In the modified example, on the other hand, there is an advantage that the second high thermal conductive layer  57 B made from the electrically conductive material is not electrically connected to the forceps channel  32  and the like because the first high thermal conductive layer  57 A made from the electrically insulating material faces the forceps channel  32  and the like. Note that, also in this modified example, the heat dissipation substrate  57  is provided to the image sensor  54  through the circuit board  55  in a manner similar to the first embodiment. Alternatively, the heat dissipation substrate  57  may be adhered directly to the opposite side of the imaging surface of the image sensor  54  (the back of the image sensor  54 ) only using the electrically insulating adhesive. 
     As shown in  FIGS. 4 and 5 , the connection member  72  thermally connects a proximal end portion of the second high thermal conductive layer  57 B and a part of the middle layer  34 C 2  of the second shield member  34 C. To improve the thermal conductivity, it is preferable that the connection member  72  has good electrical conductivity. The connection member  72  is formed using metal paste, such as silver paste, soldering, wire bonding, or tape bonding, for example. Note that, the proximal end side of the second high thermal conductive layer  57 B preferably protrudes relative to the first high thermal conductive layer  57 A. Thereby, the connection member  72  is formed easily. 
     Next, referring to  FIG. 6 , an endoscope according to a second embodiment of the present invention is described. A heat dissipation substrate  75  is disposed on the opposite side of the imaging surface of the image sensor  54  through the circuit board  55  such that a plane direction of the heat dissipation substrate  75  is parallel with (or substantially parallel with) the image sensor  54 . The heat dissipation substrate  75  is provided with first to third high thermal conductive layers  75 A,  75 B, and  75 C. The first high thermal conductive layer  75 A is sandwiched by the second and third high thermal conductive layers  75 B and  75 C. In this embodiment, the first high thermal conductive layer  75 A is made from electrically insulating and thermally conductive material. Each of the second and third high thermal conductive layers  75 B and  75 C is made from material with good thermal conductivity. The first to third high thermal conductive layers  75 A,  75 B, and  75 C are adhered together with an adhesive. Note that, like reference numerals designate like or corresponding parts in  FIGS. 4 and 6 , and descriptions thereof are omitted. 
     The third high thermal conductive layer  75 C is adhered to the circuit board  55  using an electrically insulating and thermally conductive adhesive, for example. When the surface of the circuit board  55 , on the opposite side of the image sensor  54 , is metallized, electrically conductive material such as solder or paste containing metal particles is preferably used for bonding the metallized surface of the circuit board  55  and the third high thermal conductive layer  75 C in view of adhesive strength and adhesive reliability. Thereby, the heat is transmitted without using the adhesive layer. This is preferable in view of thermal conductivity, and thus the third high thermal conductive layer  75 C receives the heat more effectively. 
     Similar to the heat dissipation substrate  57  of the first embodiment, it is preferable that the distal end side of the heat dissipation substrate  75  is in flush with or protrudes relative to the circuit board  55 . It is preferable that the proximal end side of the heat dissipation substrate  75  protrudes relative to the circuit board  55 . The proximal end side of the second high thermal conductive layer  75 B preferably protrudes relative to the first high thermal conductive layer  75 A. The proximal end side of the third high thermal conductive layer  75 C is preferably shorter than the first high thermal conductive layer  75 A. 
     As described in the first embodiment, a flexible heat dissipation substrate may be used as the heat dissipation substrate  75 . The flexible heat dissipation substrate is provided with a base layer and two metal layers formed on respective surfaces of the base layer. The base layer and the two metal layers function as the first to third high thermal conductive layers  75 A,  75 B, and  75 C, respectively. A ceramic heat dissipation substrate may be used as the heat dissipation substrate  75 . The ceramic heat dissipation substrate is provided with a base layer and two metal layers formed on respective surfaces of the base layer. The base laser and the two metal layers function as the first to third high thermal conductive layers  75 A,  75 B, and  75 C, respectively. 
     Similar to the first embodiment, the connection member  72  thermally connects a proximal end portion of the second high thermal conductive layer  75 B and a part of the middle layer  34 C 2  of the second shield member  34 C. The proximal end side of the third high thermal conductive layer  75 C is preferably shorter than the first high thermal conductive layer  75 A. Thereby, the connection member  72  is formed more easily. In this case, it is necessary to prevent the third high thermal conductive layer  75 C from being electrically connected to the second high thermal conductive layer  75 B and the signal lines  34 A. 
     In the second embodiment, the third high thermal conductive layer  75 C, in addition to the first and second high thermal conductive layers  75 A and  75 B, receives the heat from the image sensor  54 . Thereby, higher heat dissipation performance is achieved. 
     The embodiments of the present invention are not limited to those described above. Embodiments with design changes within the technical idea of the present invention are also included.