Imaging apparatus

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The cooling structure for image pickup devices addresses the issue of condensation-induced short circuits by using a substrate with a through hole and strategically positioned members to prevent direct contact between condensation and the image sensor, enhancing reliability in high temperature and humidity environments.

JP2025057563APending Publication Date: 2025-04-09CANON KK

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Patent Information

Application Number: JP2023167271
Authority / Receiving Office: JP · JP
Patent Type: Applications
Current Assignee / Owner
Filing Date: 2023-09-28
Publication Date: 2025-04-09

AI Technical Summary

Technical Problem

Conventional cooling structures for image pickup devices are prone to short circuits due to condensation, and existing methods to prevent condensation, such as using sealed cases with moisture absorbers, are not entirely effective, especially in high temperature and humidity environments.

Method used

The proposed cooling structure includes a substrate with a through hole, a cooling element, a first member on which the cooling element is disposed, a second member with a protrusion opposing the image pickup device through the through hole, and a third member between the first and second members, enhancing reliability by preventing direct contact between condensation and the image sensor.

Benefits of technology

This configuration significantly reduces the risk of short circuits from condensation, allowing for longer-term reliable operation of the image pickup device even in harsh environmental conditions.

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Abstract

To provide a cooling structure of an imaging apparatus, of which reliability is improved so as to enable a use for a long period.SOLUTION: An imaging apparatus 1 comprises: an imaging element 250; a sensor substrate 251 to which the imaging element is mounted; a peltier element 271 that is thermally connected to the imaging element 250; a cooling block 240 that is a member arranged between the imaging element 250 and the peltier element 271; and a heat insulation member 260 that is arranged between the cooling block 240 and the bottom cover 210. The cooling block 240 comprises a convex part 240a that is faced to a back surface of the imaging element 250 while passing the penetration hole formed in the sensor substrate 251. The sensor substrate 251 is fixed to the heat insulation member 260.SELECTED DRAWING: Figure 6

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Description

[Technical field]

[0001] The present invention relates to a cooling technique for an imaging element provided in an imaging device. [Background technology]

[0002] Dark current may occur in an image sensor as the temperature rises. For example, noise caused by dark current may cause a decrease in the quality of captured images when capturing images for surveillance purposes at night or in dark places. To address this issue, there are imaging devices that capture images while cooling the image sensor using a cooling means such as a Peltier element.

[0003] Patent Document 1 discloses a technique for simply and effectively cooling a surface-mounted photoelectric conversion element having multiple pins arranged on its back surface. The board is provided with a front-side copper foil pattern to which a fixing terminal that is not connected to the internal wiring of the photoelectric conversion element is connected, and a through-hole via that connects the back-side copper foil pattern. A cooling member fixed to the back-side copper foil pattern dissipates heat from the fixing terminal through the front-side copper foil pattern, the through-hole via, and the back-side copper foil pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6588243 Summary of the Invention [Problem to be solved by the invention]

[0005] In a conventional cooling structure, a cooling member is fixed to a substrate. Therefore, if condensation occurs on the cooling member, the imaging element on the substrate may be shorted out by the condensed water. As a measure to prevent condensation, there is a method of storing the imaging element and the cooling member in a sealed case and placing a moisture absorbent such as silica gel inside the sealed case. However, it is difficult to completely prevent water vapor from entering the sealed case, and the performance (amount of moisture absorption) of the moisture absorbent is also limited. In addition, a case is assumed where a surveillance camera that is used regularly is installed in a hot and humid environment. If water vapor gradually enters the sealed case and condensation occurs on the cooling member, there is a problem that the imaging device cannot withstand long-term use. An object of the present invention is to provide a cooling structure for an imaging device with improved reliability so that the imaging device can be used for a long period of time. [Means for solving the problem]

[0006] An imaging device according to an embodiment of the present invention comprises an imaging element, a substrate on which the imaging element is mounted, a cooling element for cooling the imaging element, a first member on which the cooling element is disposed, a second member disposed between the cooling element and the imaging element and having a convex portion facing the imaging element through a through hole formed in the substrate, and a third member disposed between the first member and the second member and to which the substrate is fixed. Effect of the Invention

[0007] According to the present invention, it is possible to provide a cooling structure for an imaging device with improved reliability so that the imaging device can be used for a long period of time. [Brief description of the drawings]

[0008] [Figure 1] 1 is an external view of an imaging device according to an embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing a schematic configuration of a camera unit in the imaging device. [Diagram 3] FIG. 2 is an external view of an imaging and cooling unit in the imaging device. [Figure 4]FIG. 2 is a front view of the imaging and cooling unit of the imaging device in a normal position. [Diagram 5] FIG. 2 is a cross-sectional view of the imaging and cooling unit of the imaging device in a normal position. [Figure 6] 6 is an enlarged cross-sectional view showing a region in the vicinity of the imaging element in FIG. 5. [Figure 7] FIG. 2 is an exploded perspective view showing a schematic configuration of an imaging and cooling unit. [Figure 8] FIG. 13 is a diagram showing the imaging and cooling unit with some of its components removed. [Figure 9] FIG. 2 is a front view showing a cooling block of the imaging and cooling unit. [Figure 10] FIG. 13 is a side view showing another example of a cooling block of the imaging and cooling unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. An example in which the imaging device of the present embodiment is applied to a surveillance camera will be described. However, imaging devices include various electronic devices with imaging functions, such as digital cameras (still cameras and video cameras), camera-equipped information processing devices (smartphones, tablet computers, etc.), and vehicle-mounted cameras.

[0010] The schematic configuration of the imaging device will be described with reference to Figures 1 and 2. Figure 1 is an external view of the imaging device 1. Figure 2 is an exploded perspective view showing the schematic configuration of a camera unit in the imaging device 1. The imaging device 1 includes a mount unit 100, an imaging and cooling unit 200, a duct unit 300, a rear unit 400, and a plurality of exterior panels 600.

[0011] The mount unit 100 has a mount structure to which a lens device can be attached, and is composed of a metal base member. The lens device is an interchangeable lens, and a user can attach various lens devices to the device body of the imaging device 1 according to the subject and shooting environment. Note that the mount structure of an interchangeable lens is publicly known, so a detailed description thereof will be omitted.

[0012] The imaging and cooling unit 200 includes an imaging element and components of an optical system. The imaging and cooling unit 200 is attached and fixed to the mount unit 100. In FIG. 1, the optical axis of the interchangeable lens is indicated by a dashed line. Light that is incident on the interchangeable lens and mount unit 100 along the optical axis is guided to the imaging element, which will be described later. A signal that is photoelectrically converted by receiving light by the imaging element is converted into data, and the rear unit 400 performs image processing. Details of the internal configuration of the imaging and cooling unit 200 will be described later.

[0013] The duct unit 300 includes at least one fan, and is made of a structural material that supports the fan and a control board. The duct unit 300 is configured to be able to take in and exhaust air through openings in the exterior panel 600 and the rear unit 400. When the duct unit 300 takes in and exhausts air, the imaging and cooling unit 200 is cooled by the air flowing inside the imaging device 1.

[0014] The rear unit 400 includes a metal base member and a substrate. For example, the base member is formed by aluminum die casting, and has sufficient strength to support and fix switches, connectors, etc. The substrate is equipped with a cable connector, a switch, etc., and by connecting an external device to the substrate via the cable connector, it is possible to view and store data of captured images. The device body of the imaging device 1 can be controlled using the external device and the switch connected to the substrate via the cable connector. The rear unit 400 also has an exhaust opening. The rear unit 400 is connected to the duct unit 300, and the air inside the device body of the imaging device 1 can be exhausted to the outside from the exhaust opening.

[0015] The exterior panel 600 is made of flat sheet metal or metal members, and is detachably attached to the mount unit 100 and the rear unit 400. The exterior panel 600 has an intake opening. The exterior panel 600 is connected to the duct unit 300, and can draw outside air into the device body of the imaging device 1 through the intake opening. The entire configuration of the device body of the imaging device 1 is completed by covering the portion between the mount unit 100 and the rear unit 400 with the multiple exterior panels 600.

[0016] Next, the configuration of the imaging and cooling unit 200 will be described with reference to Figs. 3 to 8. Fig. 3 is an external perspective view of the imaging and cooling unit 200. Fig. 4 is a front view of the imaging and cooling unit 200 in the normal posture of the imaging device 1. The normal posture is the posture of the imaging device when the optical axis direction is horizontal. Fig. 5 is a cross-sectional view of the imaging and cooling unit 200 taken along the dashed line A shown in Fig. 4. Fig. 6 is an enlarged cross-sectional view showing the area near the imaging element in Fig. 5. Fig. 7 is an exploded perspective view of the imaging and cooling unit 200. For simplicity of illustration, screws and wiring are omitted. Fig. 8 is a perspective view showing the imaging and cooling unit 200 with the members above the top cover 220 removed.

[0017] The imaging and cooling unit 200 has a hollow sealed structure and is roughly rectangular in shape. A sealed space is formed by the opposing metallic bottom cover 210 and top cover 220, and a front window glass 278 that functions as a lid for the top cover 220. The imaging element 250 and a Peltier element 271 that is a cooling element for the imaging element 250 are arranged in the sealed space.

[0018] The bottom cover 210 is a flat plate-shaped member. The substantially central portion of one surface of the bottom cover 210 is the mounting portion 210a of the Peltier element 271. The mounting portion 210a has a flat surface that contacts the heat dissipation surface of the Peltier element 271. The bottom cover 210 is provided with a heat dissipation fin 212 on the surface opposite to the mounting portion 210a. By exposing the heat dissipation fin 212 to the inside of the duct of the duct unit 300, the heat transferred from the Peltier element 271 to the bottom cover 210 and the heat dissipation fin 212 is dissipated to the outside by the air in the duct. A connection portion insertion hole 210b is provided on the side of the mounting portion 210a of the Peltier element 271, and the signal lines of the Peltier element 271 and the image sensor 250 can be drawn to the outside while maintaining the airtightness of the image sensor and cooling unit 200. The gap between the signal line and the bottom cover 210 can be sealed with an elastic material such as rubber or an adhesive to ensure airtightness.

[0019] A material with high sealing performance and high thermal conductivity, such as a metal material such as an aluminum alloy, is preferably used for the bottom cover 210. Also, the contact surface of the attachment portion 210a with the Peltier element 271 is preferably a surface with high flatness and low surface roughness in order to efficiently transfer heat from the Peltier element 271 to the bottom cover 210.

[0020] The Peltier element 271 is disposed on the mounting portion 210a of the bottom cover 210. The Peltier element 271 is a cooling element having one surface used as a cooling surface and the other surface used as a heat dissipation surface. The heat dissipation surface of the Peltier element 271 contacts the flat surface of the mounting portion 210a. Wiring for supplying power to the Peltier element 271 is connected to a control board (not shown) through a connection portion insertion hole 210b.

[0021] The cooling block 240 is a solid member that is slightly larger than the Peltier element 271. The cooling block 240 is fastened to the bottom cover 210 by a plurality of screws 272 (FIG. 6) arranged around the Peltier element 271, with one side surface of the cooling block 240 being arranged in contact with the cooling surface side of the Peltier element 271. In other words, the Peltier element 271 is sandwiched between the cooling block 240 and the bottom cover 210.

[0022] Cooling block 240 has a protruding portion 240a. Protruding portion 240a protrudes from approximately the center of cooling block 240 on the opposite side to the cooling surface of Peltier element 271. Imaging element 250 and sensor substrate 251 are disposed in a region adjacent to protruding portion 240a. When the temperature of the cooling surface of Peltier element 271 is lowered, heat from imaging element 250 is transferred to Peltier element 271 through cooling block 240, so that the temperature of imaging element 250 can be lowered.

[0023] The cooling structure for the imaging element 250 includes a cooling block 240, a heat insulating member 260, a Peltier element 271, a bottom cover 210, and heat dissipation fins 212. The material of the cooling block 240 is an aluminum alloy or the like having a higher thermal conductivity than the heat insulating member 260, and the heat of the imaging element 250 can be efficiently transferred to the cooling surface of the Peltier element 271. In addition, in order to prevent the heat of the bottom cover 210 from being transferred to the cooling block 240, a heat insulating member 260 made of synthetic resin is disposed between the bottom cover 210 and the cooling block 240. The heat insulating member 260 also serves as a cable holder for the Peltier element 271. Furthermore, a heat insulating member 273 (FIGS. 6 and 7) is disposed between the screw 272 and the cooling block 240. In order to prevent the heat of the bottom cover 210 from being transferred to the cooling block 240 via the screw 272, the heat insulating member 273 is formed of a synthetic resin or the like having a low thermal conductivity.

[0024] The top cover 220 is a hollow member in the shape of a substantially rectangular parallelepiped with openings on two opposing planes. A sealed housing is formed by attaching and fixing the top cover 220 to the bottom cover 210. The material of the top cover 220 is a metal (aluminum alloy, etc.) with high sealing properties and high thermal conductivity. The top cover 220 has a rectangular groove around the opening on the mount unit 100 side. A window seal member 277 (FIG. 7) of approximately the same shape is disposed in the groove. The window seal member 277 is an elastic body such as rubber, and more preferably, butyl rubber or fluororubber, which is less permeable to moisture and has high sealing properties, is used.

[0025] The front window glass 278 is a rectangular optical member made of transparent glass or the like. The front window glass 278 is disposed on the surface of the window seal member 277 opposite to the top cover 220. Light incident from the mount unit 100 passes through the front window glass 278 and reaches the imaging element 250.

[0026] The metal plate 230, which is a pressing member, is fixed to the top cover 220 by screw fastening. As a result, the front window glass 278 and the window seal member 277 are sandwiched between the metal plate 230 and the top cover 220.

[0027] The substantially rectangular seal member 276 is attached to a predetermined location (groove) of the bottom cover 210 so as to surround the mounting portion 210a of the Peltier element 271. In order to keep the imaging and cooling unit 200 in an airtight state, the seal member 276 is an elastic body such as butyl rubber or fluororubber with low gas permeability. The bottom cover 210 and the top cover 220 are attached and fixed so that the seal member 276 is compressed and sandwiched between the two members, and the imaging and cooling unit 200 is assembled in an airtight state.

[0028] As described above, by forming the sealed housing using a metal cover member and an elastic seal member, the amount of water vapor that invades can be significantly reduced, and it is possible to prevent condensation from occurring in the sealed housing for several years after the imaging device is first used. However, water vapor may gradually invade the sealed housing, even if only slightly. In particular, when a security camera is used 24 hours a day, 365 days a year, and used for a long period of time in a high-temperature and high-humidity environment, condensation may occur in the sealed housing. Therefore, a configuration will be described in which the water generated by the condensation is less likely to adhere to the sensor board 251 even if condensation occurs in the sealed housing.

[0029] 6, in this embodiment, the sensor substrate 251 has an opening 251a in the center in order to cool the imaging element 250. The opening 251a of the sensor substrate 251 is a through hole, and the protruding portion 240a of the cooling block 240 is close to the imaging element 250 through the opening 251a. The protruding portion 240a is thermally connected to the imaging element 250 via thermally conductive grease.

[0030] 8(A) shows bottom cover 210, cooling block 240, and heat insulating member 260, and FIG. 8(B) further shows imaging element 250 and sensor board 251. Sensor board 251 is screwed to screw seats 260a of heat insulating member 260 at four points on the four corners, instead of to cooling block 240. Note that the screw fastening points may be two or three of the four corners of sensor board 251. Since sensor board 251 and cooling block 240 do not come into contact with each other, even if condensation occurs on cooling block 240, moisture from the condensation does not directly adhere to sensor board 251.

[0031] In addition, since the cooling block 240 does not have a fixing portion for the sensor board 251, water does not accumulate in the uneven portion formed by the fixing portion. The cooling block 240 is fixed by fastening the Peltier element 271 at four points near the approximate center of the four sides of the Peltier element 271 with screws 272 when viewed from a direction perpendicular to the Peltier element 271, as shown in FIG. 8(A). Since the strength of the four corners of the rectangular parallelepiped of the Peltier element 271 is relatively low, it is preferable to fix the cooling block 240 to the bottom cover 210 near the center of each side, not near the four corners. By fixing the sensor board 251 to the heat insulating member 260 near the four corners of the Peltier element 271 when viewed from a direction perpendicular to the Peltier element 271, the imaging and cooling unit 200 can be made smaller.

[0032] Convex portion 240a of cooling block 240 is inclined so that a lower surface portion (lower side surface portion) 240b (FIG. 6) in the vertical direction slopes downward as it moves away from imaging element 250. Even if condensation occurs on convex portion 240a, the condensed water flows from imaging element 250 toward cooling block 240 along the slope of lower surface portion 240b, so imaging element 250 on sensor substrate 251 does not get wet with water.

[0033] 9 is a front view of cooling block 240. Upper surface portion (upper side surface portion) 240c in the vertical direction of convex portion 240a of cooling block 240 is shaped so that condensed water does not flow toward sensor substrate 251. Upper surface portion 240c is inclined so as to descend from the approximate center to the left and right ends. Water generated by condensation flows along the slope of upper surface portion 240c and does not reach sensor substrate 251.

[0034] 10 is a side view showing another example of the cooling block 240. The upper surface 240d of the convex portion 240a of the cooling block 240 has an inclined surface that is approximately parallel to the inclined surface of the lower surface 240b. The surface of the upper surface 240d is inclined downward as it becomes farther away from the imaging element 250. Water generated by condensation inside the sealed housing flows along the inclined surface of the upper surface 240d and does not reach the sensor board 251.

[0035] When the imaging device 1 is in the normal position, water generated by condensation inside the sealed housing flows downward and may eventually reach the sealing member 276. In that case, measures must be taken to prevent the sealing performance of the sealed housing from decreasing. Therefore, a water-absorbent member that absorbs water droplets is disposed in front of the sealing member 276. For example, the water-absorbent member is a sponge 290 (FIG. 5) that has water absorption properties, and is disposed in the lower area of the sealed housing in the vertical direction.

[0036] According to this embodiment, an imaging device equipped with a cooling structure for an imaging element can be used for a longer period of time even in a high-temperature and high-humidity environment.

[0037] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and changes are possible within the scope of the gist of the present invention. For example, the seal member 276 and the window seal member 277 are not limited to butyl rubber or fluororubber, and other elastic materials (such as silicone rubber) may be used as long as certain conditions are met. The certain conditions are that the airtightness of the sealed housing of the imaging and cooling unit 200 can be sufficiently maintained. Furthermore, various seal members may be omitted as long as the certain conditions are met.

[0038] In order to increase the heat transfer rate, a thermally conductive sheet may be placed or thermally conductive grease may be applied between members where heat transfer occurs, for example, between the Peltier element 271 and the bottom cover 210. Although the Peltier element is shown as an example of a thermoelectric element in the embodiment, the present invention can be applied to cooling structures using various cooling elements.

[0039] Embodiments of the present disclosure include the following configurations. [Configuration 1] An imaging element; A substrate on which the imaging element is mounted; A cooling element for cooling the imaging element; a first member on which the cooling element is disposed; a second member disposed between the cooling element and the imaging element, the second member having a protrusion facing the imaging element through a through hole formed in the substrate; a third member disposed between the first member and the second member and to which the substrate is fixed; 1. An imaging device comprising: [Configuration 2] The second member has a higher thermal conductivity than the third member. 2. The imaging device according to configuration 1, [Configuration 3] A fourth member is fixed to the first member to form a sealed housing having the imaging element and the cooling element. 3. The imaging device according to configuration 1 or 2, [Configuration 4] When viewed from a direction perpendicular to the cooling element, the second member is fixed to the first member with screws at four locations near approximately the centers of the four sides of the cooling element, and the substrate is fixed to the third member with screws at least two locations near the four corners of the cooling element. 4. The imaging device according to any one of configurations 1 to 3. [Configuration 5] When the imaging device is in the normal position, the convex portion is inclined so that the upper or lower surface in the vertical direction is lowered as it moves away from the imaging element. 5. The imaging device according to any one of configurations 1 to 4. [Configuration 6] When the imaging device is in the normal position and viewed from a direction perpendicular to the imaging element, the convex portion has an upper surface in the vertical direction that is inclined so as to descend toward the end, with the upper surface being at the approximate center as the top. 6. The imaging device according to any one of configurations 1 to 5. [Configuration 7] When the imaging device is in the normal position, a water-absorbent member is disposed in the lower area in the vertical direction within the sealed housing. 4. The imaging device according to configuration 3. [Configuration 8] The protrusion is thermally connected to the image sensor via thermally conductive grease. 8. The imaging device according to any one of configurations 1 to 7. [Configuration 9] a seal member surrounding the cooling element; The first member and the fourth member compress and hold the seal member. 4. The imaging device according to configuration 3. [Explanation of symbols]

[0040] 200 imaging and cooling unit, 210 bottom cover, 220 top cover, 240 cooling block, 250 imaging element, 251 sensor board, 260 heat insulating member, 271 Peltier element, 276 sealing member

Claims

1. An imaging element; A substrate on which the imaging element is mounted; A cooling element for cooling the imaging element; a first member on which the cooling element is disposed; a second member disposed between the cooling element and the imaging element, the second member having a protrusion facing the imaging element through a through hole formed in the substrate; a third member disposed between the first member and the second member and to which the substrate is fixed; 1. An imaging device comprising:

2. The second member has a higher thermal conductivity than the third member.