Patent Publication Number: US-2022240414-A1

Title: Imaging device

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to an imaging device. 
     Description of the Related Art 
     For example, JP 2010-213000 A discloses an imaging device that cools an imaging element by a Peltier element (thermoelectric element). The heat absorbed by the Peltier element from the imaging element is transferred to a heat sink having a plurality of fins. The plurality of fins of the heat sink are cooled by the air blown from the cooling fan. 
     SUMMARY OF THE INVENTION 
     However, in the case of the imaging device described in JP 2010-213000 A, it is necessary to continue to supply electric power to the thermoelectric element while cooling the imaging element. As a result, the battery of the imaging device is consumed faster. 
     Therefore, it is an object of the present disclosure to cool a heat generating source such as an imaging element in an imaging device while suppressing power consumption. 
     In order to solve the above-mentioned problems, according to one aspect of the present disclosure, an imaging device is provided which includes: 
     a heat generating source; 
     a heat radiating plate that cools the heat generating source; 
     a thermoelectric element that includes a heat absorbing surface in contact with the heat radiating plate and a heat radiating surface different from the heat absorbing surface, and receives supply of electric power to discharge the heat absorbed by the heat absorbing surface from the heat radiating surface; 
     a first heat sink that is in contact with the heat radiating surface of the thermoelectric element and is spaced apart from the heat radiating plate; and 
     a second heat sink that is in contact with the heat radiating plate. 
     According to the present disclosure, it is possible to cool a heat generating source such as an imaging element in an imaging device while suppressing power consumption. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an imaging device according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of a cooling system of an imaging element; 
         FIG. 3  is an exploded perspective view of the cooling system of the imaging element; 
         FIG. 4  is a cross-sectional view of the cooling system of the imaging element; 
         FIG. 5  is a cross-sectional view of an imaging device in which a duct is shown; 
         FIG. 6  is a block diagram of a control system of an imaging device that cools the imaging element; and 
         FIG. 7  is a diagram showing an example of a timing chart showing the operation timing of a fan and a thermoelectric element. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, a detailed description of an embodiment will be given with reference to drawings as appropriate. However, a detailed description more than necessary may be omitted in some cases. For example, a detailed description of a well-known item and a duplicate description for a substantially identical component may be omitted in some cases. This is to avoid an unnecessarily redundant description and to allow those skilled in the art to easily understand the following description. 
     In addition, the inventor(s) provides the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and it is not intended to limit the subject matter described in the claims by these. 
     Hereinafter, the imaging device according to the embodiment of the present disclosure will be described with reference to the drawings. 
       FIG. 1  is a perspective view of an imaging device according to an embodiment of the present disclosure. Further,  FIG. 2  is a perspective view of a cooling system of an imaging element. Further,  FIG. 3  is an exploded perspective view of the cooling system of the imaging element.  FIG. 4  is a cross-sectional view of the cooling system of the imaging element. 
     The X-Y-Z orthogonal coordinate system shown in the figure is for facilitating the understanding of the present disclosure, and does not limit the present disclosure. The X-axis direction indicates the front-back direction of the imaging device, the Y-axis direction indicates the left-right direction of the imaging device, and the Z-axis direction indicates the height direction. Further, in the present specification, the side where a subject of the imaging device is present is referred to as a “front side”, and the side where the imaging device is present is referred to as a “rear side”. 
     As shown in  FIG. 1 , in the case of the present embodiment, an imaging device  10  has a casing  12  having a substantially cubic shape and an imaging element  14  arranged therein. The imaging element  14  is, for example, a CCD image sensor, a CMOS image sensor, or the like. An image of the subject is incident on a light receiving surface  14   a  of the imaging element  14  via a lens (not shown) attached to a lens mounting portion  16 . The imaging element  14  outputs an electric signal corresponding to the incident image, that is, takes an image (captures a still image or a moving image). 
     As shown in  FIGS. 2 to 4 , the imaging device  10  also has a substrate  18  on which the imaging element  14  is mounted and a heat radiating plate  20  for cooling the imaging element  14 . 
     As shown in  FIG. 3 , the imaging element  14  is mounted on the substrate  18  via a back surface  14   b  on the side opposite to the light receiving surface  14   a . The substrate  18  is formed with, for example, a circuit that AD-converts an electric signal from the imaging element  14  and outputs the AD-converted electric signal to an image processing circuit. In the case of this embodiment, as shown in  FIG. 4 , a temperature sensor  22  for detecting the temperature of the substrate  18  is provided. 
     The heat radiating plate  20  is a member arranged in the casing  12 , made of a material having high thermal conductivity, for example, a metal material such as aluminum or copper, and supporting the substrate  18 . Further, the heat radiating plate  20  cools the imaging element  14  by absorbing heat from the imaging element  14  which becomes a high temperature state during shooting. 
     As shown in  FIGS. 3 and 4 , in the case of the present embodiment, the substrate  18  exists between the heat radiating plate  20  and the imaging element  14 . Since the heat radiating plate  20  is in direct contact with the back surface  14   b  of the imaging element  14 , the substrate  18  is formed at a position corresponding to the central portion of the back surface  14   b  of the imaging element  14 , which can be the hottest, and includes a through hole  18   a  that penetrates in a thickness direction (X-axis direction). A convex portion  20   b  is formed on a front surface  20   a  of the heat radiating plate  20  so as to enter the through hole  18   a  of the substrate  18  to be in contact with the central portion of the back surface  14   b  of the imaging element  14 . As a result, the heat radiating plate  20  can cool the imaging element  14  with a higher cooling efficiency than the case of indirectly cooling the imaging element  14  via the substrate  18 . 
     In order to cool the heat radiating plate  20 , as shown in  FIGS. 3 and 4 , the imaging device  10  further has a thermoelectric element  24 , a first heat sink  26 , and a second heat sink  28  inside the casing  12 . 
     As shown in  FIG. 4 , the thermoelectric element  24  is, for example, a Peltier element including a heat absorbing surface  24   a  that is in contact with a heat generating source and absorbs heat of the heat generating source, and a heat radiating surface  24   b  that is a surface different from the heat absorbing surface  24   a , is located on the opposite side of the heat absorbing surface  24   a , and discharges the heat absorbed by the heat absorbing surface  24   a . Upon receiving supply of electric power, the thermoelectric element  24  absorbs heat from the heat generating source via the heat absorbing surface  24   a , and discharges the absorbed heat from the heat radiating surface  24   b . Note that, in the case of the present embodiment, the heat generating source is the imaging element  14 . 
     In the case of the present embodiment, as shown in  FIG. 4 , the thermoelectric element  24  comes into contact with a rear surface  20   c  of the heat radiating plate  20  via its heat absorbing surface  24   a . Specifically, the heat absorbing surface  24   a  of the thermoelectric element  24  comes into contact with a bottom surface  20   e  of a concave portion  20   d  formed in the convex portion  20   b . As a result, the thermoelectric element  24  faces the imaging element  14  with the convex portion  20   b  of the heat radiating plate  20  interposed between the imaging element  14  and the thermoelectric element  24 . As a result, the heat absorbing surface  24   a  of the thermoelectric element  24  is thermally connected to the central portion of the back surface  14   b  of the imaging element  14 , which can be the hottest, via the heat radiating plate  20  at the shortest distance. The term “thermally connected” as used herein refers to a state in which two objects are in direct or indirect contact with each other without passing through air and can transfer heat to each other. As a result, the thermoelectric element  24  can efficiently cool the central portion of the imaging element  14 , which can be the hottest. A heat conductive tape or the like that promotes heat transfer between the thermoelectric element  24  and the heat radiating plate  20  may be provided between the heat absorbing surface  24   a  of the thermoelectric element  24  and the heat radiating plate  20 . 
     As shown in  FIG. 4 , the first heat sink  26  is made of a material having high thermal conductivity, for example, a metal material such as aluminum or copper, and includes a base portion  26   a  and a plurality of fins  26   b  that extend from the base portion  26   a  in parallel to each other. In the case of the present embodiment, a convex portion  26   c  that comes into contact with the heat radiating surface  24   b  of the thermoelectric element  24  is provided on the surface of the base portion  26   a  on the side opposite to the surface on which the plurality of fins  26   b  are provided. 
     In the case of the present embodiment, as shown in  FIG. 4 , the first heat sink  26  is in contact with the heat radiating surface  24   b  of the thermoelectric element  24  arranged in the concave portion  20   d  of the heat radiating plate  20  via the convex portion  26   c , As a result, the first heat sink  26  is thermally connected to the thermoelectric element  24 . On the other hand, the first heat sink  26  is not thermally connected to the heat radiating plate  20 . Specifically, in the case of the present embodiment, the base portion  26   a  of the first heat sink  26  is spaced apart from the rear surface  20   c  of the heat radiating plate  20 , and is not in contact with the heat radiating plate  20 . These reasons will be described later. 
     As shown in  FIG. 4 , the second heat sink  28  is made of a material having high thermal conductivity, for example, a metal material such as aluminum or copper, and includes a base portion  28   a  and a plurality of fins  28   b  that extend from the base portion  28   a  in parallel to each other. 
     Unlike the first heat sink  26 , the second heat sink  28  is spaced apart from the thermoelectric element  24  and is not thermally connected. On the other hand, the second heat sink  28  is thermally connected to the heat radiating plate  20 . Specifically, in the case of the present embodiment, the second heat sink  28  is thermally connected by contacting the rear surface  20   c  of the heat radiating plate  20 . These reasons will be described later. 
     Further, in the case of the present embodiment, the first heat sink  26  and the second heat sink  28  are spaced apart from each other so that heat transfer does not substantially occur between them. The reason for this will be described later. 
     In the case of the present embodiment, as shown in  FIG. 2 , the imaging device  10  further includes a fan  30  inside the casing  12  for cooling both the first heat sink  26  and the second heat sink  28 . 
       FIG. 5  is a cross-sectional view of an imaging device in which a duct is shown. 
     As shown in  FIG. 5 , in the case of the present embodiment, the fan  30  is arranged in the duct  32  formed in the casing  12 . As shown in  FIG. 1 , the duct  32  extends inside the casing  12  so as to connect an intake port  12   b  and an exhaust port  12   c  formed on the right side surface  12   a  of the casing  12 . As shown in  FIG. 5 , the fan  30  is provided in a straight line portion extending in the height direction (Z-axis direction) in the duct  32 . As the fan  30  rotates, as shown by the broken line, air flows from the outside into the duct  32  through the intake port  12   b , flows through the duct  32 , and flows out through the exhaust port  12   c.    
     As shown in  FIGS. 4 and 5 , the plurality of fins  26   b  of the first heat sink  26  and the plurality of fins  28   b  of the second heat sink  28  are arranged in the duct  32  so as to be located on the downstream side of the fan  30 . As a result, the air blown by the fan  30  flows between the plurality of fins  26   b  of the first heat sink  26  and between the plurality of fins  28   b  of the second heat sink  28 . As a result, the first heat sink  26  and the second heat sink  28  are cooled by the fan  30 . Note that, in the case of the present embodiment, the plurality of fins  26   b  of the first heat sink  26  and the plurality of fins  28   b  of the second heat sink  28  are arranged equidistant from the fan  30 , that is, are arranged in parallel with respect to the air flow direction in the duct  32 . As a result, the first heat sink  26  and the second heat sink  28  are cooled to the same extent by the fan  30  (compared to the case where the first heat sink  26  and the second heat sink  28  are arranged in series in the air flow direction). 
     Up to this point, the configuration of the imaging device  10 , particularly the configuration for cooling the imaging element  14 , has been described. From here, the control of the imaging device  10  for cooling the imaging element  14  by using the fan  30  and the thermoelectric element  24  will be described. 
       FIG. 6  is a block diagram of a control system of an imaging device that cools an imaging element. 
     As shown in  FIG. 6 , the imaging device  10  includes a controller  50  that executes various controls including cooling control of the imaging element  14 . The controller  50  includes, for example, a CPU and a storage device such as a ROM or RAM that stores a program for causing the CPU to execute various operations. 
     As an example, the controller  50  controls an image processing circuit  52  that processes an electric signal from the imaging element  14 , that is, an image data of an image captured by the imaging element  14 , and acquires the image-processed image from the image processing circuit  52 . For example, the image processing circuit  52  is an image processing chip. Further, as an example, the controller  50  controls a card writer  56 , which is a writing device for recording an image data acquired from the image processing circuit  52  on a memory card  54 , which is a recording medium that can be attached to and detached from the imaging device  10 . For example, the memory card  54  is a CFexpress card. Further, as an example, the controller  50  controls a power supply control circuit  60  that distributes the electric power of the battery  58  to the imaging element  14 , the thermoelectric element  24 , the fan  30 , and the like. Furthermore, as an example, the controller  50  executes, for example, start and stop of moving image shooting, change of image processing conditions, and the like on the basis of user input via an input device  62  such as a plurality of buttons provided on the casing  12 . Note that, the controller  50  also executes various controls on other components of the imaging device  10  (not shown in  FIG. 6 ). 
     In the case of the present embodiment, the controller  50  selectively executes the first cooling mode and the second cooling mode as the control of the fan  30  and the thermoelectric element  24  for cooling the imaging element  14 . 
       FIG. 7  shows an example of a timing chart showing the operation timings of the fan and the thermoelectric element. 
     As shown as an example in  FIG. 7 , when the imaging device  10  starts shooting (timing Ts), the temperature of the imaging element  14  starts to rise. Similarly, the temperature detected by the temperature sensor  22  starts to rise. That is, the temperature of the substrate  18  and the temperature of the heat radiating plate  20  that supports the substrate  18  start to rise. Note that, since there is a correlation between the temperature of the substrate  18  and the temperature of the heat radiating plate  20 , in the case of the present embodiment, the temperature of the heat radiating plate  20  is indirectly detected from the temperature of the substrate  18  detected by the temperature sensor  22 . Further, the reason why the temperature sensor  22  is not provided on the heat radiating plate  20  but is provided on the substrate  18  is that a circuit or the like for supplying electric power to the temperature sensor  22  is formed on the substrate  18 . 
     In the case of the present embodiment, the controller  50  executes a first cooling mode M 1  or a second cooling mode M 2  on the basis of the temperature detected by the temperature sensor  22  while the imaging device  10  is shooting, for example, during moving image shooting, that is, while the imaging element  14  continues to generate heat. 
     As shown in  FIG. 7 , the first cooling mode M 1  is a control mode in which the controller  50  operates only the fan  30  to cool the heat radiating plate  20 . During execution of the first cooling mode M 1 , the controller  50  maintains the thermoelectric element  24  in an unpowered OFF state. During execution of the first cooling mode M 1 , the rotation speed of the fan  30  may change based on the change in the temperature detected by the temperature sensor  22 , or may be maintained at a predetermined constant rotation speed (for example, such a rotation speed that the microphone of the imaging device  10  does not pick up rotation sound of the fan  30 ). 
     During execution of the first cooling mode M 1 , almost all of the heat generated from the imaging element  14  is transferred to the second heat sink  28  via the heat radiating plate  20 . That is, the imaging element  14  is cooled by the second heat sink  28 . Further, in the case of the present embodiment, the second heat sink  28  to which heat is transferred is cooled by the fan  30 . Note that, a small part of the heat is transferred from the heat radiating plate  20  to the first heat sink  26  via the stopped thermoelectric element  24 . 
     As the shooting of the imaging device  10  further continues, the temperature of the imaging element  14  further rises, and thereby the temperature detected by the temperature sensor  22  also further rises. When the temperature detected by the temperature sensor  22  reaches a predetermined temperature tc, the controller  50  switches from the first cooling mode M 1  to the second cooling mode M 2 . The predetermined temperature tc is determined based on the temperature range in which the imaging element  14  can normally operate. 
     As shown in  FIG. 7 , when the first cooling mode M 1  is switched to the second cooling mode M 2 , the controller  50  supplies electric power to operate (turn on) the thermoelectric element  24 . Further, the controller  50  maintains the fan  30  in a rotating state. Note that, during execution of the second cooling mode M 2 , the rotation speed of the fan  30  may change based on the change in the temperature detected by the temperature sensor  22 , or may be maintained at a predetermined constant rotation speed. 
     During execution of the second cooling mode M 2 , a part of the heat generated from the imaging element  14  is transferred from the heat radiating plate  20  to the first heat sink  26  by the thermoelectric element  24  in the ON state. That is, the imaging element  14  is cooled by the combination of the thermoelectric element  24  and the first heat sink  26 . Further, the remaining heat is transferred to the second heat sink  28  via the heat radiating plate  20 . That is, the imaging element  14  is cooled by the second heat sink  28 . The first heat sink  26  and the second heat sink  28  to which heat is transferred are cooled by the fan  30 . By performing such cooling using the thermoelectric element  24  and cooling without the thermoelectric element  24  in combination, the temperature detected by the temperature sensor  22  decreases, that is, the temperature of the imaging element  14  decreases. Thus, the thermoelectric element  24  has a sufficient cooling capacity capable of decreasing the temperature of the imaging element  14  in cooperation with the fan  30 . 
     As shown in  FIG. 4 , the first heat sink  26  is spaced apart from the heat radiating plate  20 , that is, the space between the first heat sink  26  and the heat radiating plate  20  is thermally insulated by an air layer. This is because it suppresses that a part of the heat transferred from the thermoelectric element  24  to the first heat sink  26  during execution of the second cooling mode M 2  returns to the heat radiating plate  20  if the first heat sink  26  and the heat radiating plate  20  are in contact with each other. Otherwise, a thermal loop is generated in which heat is repeatedly transferred to the heat radiating plate  20 , the thermoelectric element  24 , the first heat sink  26 , and the heat radiating plate  20  in sequence, and the cooling efficiency of the second cooling mode M 2  is lowered. Also, during execution of the first cooling mode M 1 , the first heat sink  26  continues to be cooled by the fan  30 . As a result, the first heat sink  26  is in a state of substantially not holding heat because heat is not transferred from the thermoelectric element  24  in the OFF state. Therefore, when the thermoelectric element  24  shifts to the ON state, the first heat sink  26  can quickly absorb the heat held by the heat radiating plate  20 . As a result, the temperature of the imaging element  14  can be quickly lowered. 
     Further, in the case of the present embodiment, as shown in  FIG. 4 , the first heat sink  26  and the second heat sink  28  are spaced apart from each other, that is, the space between the first heat sink  26  and the second heat sink  28  is thermally insulated by an air layer. This is because it suppresses that a part of the heat transferred from the thermoelectric element  24  to the first heat sink  26  during execution of the second cooling mode M 2  returns to the heat radiating plate  20  via the second heat sink  28  if the first heat sink  26  and the second heat sink  28  are in contact with each other. Otherwise, a thermal loop is generated in which heat is repeatedly transferred to the heat radiating plate  20 , the thermoelectric element  24 , the first heat sink  26 , the second heat sink  28 , and the heat radiating plate  20  in sequence, and the cooling efficiency of the second cooling mode M 2  is lowered. 
     Alternatively, if the cooling by the thermoelectric element  24  in the second cooling mode M 2  causes the temperature of the imaging element  14  to decrease in an acceptable time, that is, if the effect of the thermal loop described above is small, then the first heat sink  26  and the second heat sink  28  may be in contact with each other so that heat transfer is possible. As a result, the first heat sink  26  can be used for cooling the heat radiating plate  20  during execution of the first cooling mode M 1 . 
     As shown in  FIG. 7 , the execution of the second cooling mode M 2  decreases the temperature of the imaging element  14 , thereby decreasing the temperature detected by the temperature sensor  22 . When the temperature detected by the temperature sensor  22  returns to the predetermined temperature tc, the controller  50  switches from the second cooling mode M 2  to the first cooling mode M 1 , that is, shifts the thermoelectric element  24  to the OFF state. 
     By alternately repeating the first cooling mode M 1  and the second cooling mode M 2 , the temperature of the imaging element  14  can be maintained constant. Specifically, the temperature of the imaging element  14  can be maintained constant without maintaining the ON state of the thermoelectric element  24 . As a result, the imaging element  14  can be cooled while suppressing the power consumption of the thermoelectric element  24 , that is, without continuously supplying the electric power to the thermoelectric element  24 . 
     As shown in  FIG. 7 , when the shooting of the imaging device  10  is completed (timing Te), the controller  50  stops the fan  30  and shifts the thermoelectric element  24  to the OFF state if it is in the ON state. The fan  30  may rotate from the end timing of shooting until a predetermined time elapses. 
     According to such an embodiment, the imaging element  14  which is a heat generating source can be cooled while suppressing power consumption. 
     Although the embodiment of the present disclosure has been described above with reference to the above-described embodiment, the embodiments of the present disclosure are not limited to the above-described embodiment. 
     In the case of the above embodiment, as shown in  FIG. 5 , the first heat sink  26  and the second heat sink  28  are cooled by a common fan  30 . However, the embodiments of the present disclosure are not limited to this. For example, one part of at least one of the first heat sink  26  and the second heat sink  28  may be cooled by the outside air by being exposed to the outside of the casing  12 . 
     Further, in the case of the above-described embodiment, as shown in  FIG. 7 , the thermoelectric element  24  is controlled based on the temperature detected by the temperature sensor  22 . However, the embodiments of the present disclosure are not limited to this. For example, the thermoelectric element  24  may be controlled based on the elapsed time from the start of moving image shooting, the outside air temperature, and the like. 
     Further, in the case of the above-described embodiment, the imaging element  14  is cooled by the thermoelectric element  24 , the first heat sink  26 , and the second heat sink  28 . However, the embodiments of the present disclosure are not limited to this. As shown in  FIG. 6 , the heat generating source to be cooled may be an imaging element  14 , an image processing circuit  52  (image processing chip) that processes an image data of an image captured by the imaging element  14 , or a card writer  56  that records on the memory card  54  an image data processed by the image processing circuit  52 . Alternatively, each of at least two of these may be provided with a thermoelectric element, a first heat sink, and a second heat sink. 
     That is, in a broad sense, the imaging device according to the embodiment of the present disclosure includes a heat generating source, a heat radiating plate that cools the heat radiating source, a thermoelectric element including a heat absorbing surface in contact with the heat radiating plate and a heat radiating surface different from the heat absorbing surface, and receiving supply of electric power to discharge the heat absorbed by the heat absorbing surface from the heat radiating surface, a first heat sink that is in contact with the heat radiating surface of the thermoelectric element and is spaced apart from the heat radiating plate, and a second heat sink that is in contact with the heat radiating plate. 
     As described above, the embodiment has been described as an example of the technology in the present disclosure. For this purpose, the drawings and detailed description are provided. Accordingly, among the components described in the drawings and the detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem may also be included in order to exemplify the above technology. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the drawings and detailed description. 
     Moreover, since the above-mentioned embodiment is for demonstrating the technology in the present disclosure, various changes, substitutions, additions, omissions, etc. can be performed in a claim or its equivalent range. 
     The present disclosure is applicable to imaging devices that require cooling.