JP7584941B2 - Camera Module - Google Patents

Description

This disclosure relates to a camera module used in security cameras, vehicle-mounted cameras, etc.

As a camera module, for example, as shown in Patent Document 1, an imaging device equipped with a shooting window, a lens, and an imaging element is known. The imaging device disclosed in Patent Document 1 further includes a heater and a fan, and Patent Document 1 discloses that hot air is blown onto the shooting window to prevent condensation in a low-temperature environment. In recent years, there has also been a demand for small, lightweight imaging devices.

JP 2018-14700 A

However, because such imaging devices have a fan for blowing hot air to the shooting window, it is difficult to miniaturize the device. Also, when a small fan is used, the output of the blowing air is reduced, making it difficult to prevent condensation in a low-temperature environment.

The purpose of this disclosure is to provide a camera module that is compact and has high condensation prevention performance even in low-temperature environments.

The camera module of the present disclosure comprises an imaging window, an imaging element, a heater, and a housing that contains the imaging window, the imaging element, and the heater, and the heater is characterized in that the heater has a ceramic base, a heating resistor provided on the ceramic base, and a heat radiation film located on the surface of the ceramic base.

According to the camera module of the present disclosure, the heater has a heat radiation film located on the surface of the ceramic base. This makes it possible to increase the intensity of the radiant heat emitted from the heater surface. Therefore, it is possible to improve the condensation prevention performance in a low-temperature environment without using a fan. As a result, it is possible to miniaturize the camera module while improving the condensation prevention performance in a low-temperature environment.

FIG. 1 is a schematic diagram illustrating an example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. 1 is a schematic diagram showing an example of a heater used in a camera module of the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. 1 is a schematic diagram showing an example of a positional relationship between a heat conductive member and a heater in a camera module according to the present disclosure. FIG. 11A and 11B are schematic diagrams showing other examples of the positional relationship between the heat conductive member and the heater in the camera module of the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure. FIG. 13 is a schematic diagram showing another example of a camera module according to the present disclosure.

The camera module 10 is described in detail below.

Figure 1 is a schematic diagram showing an example of a camera module 10. As shown in Figure 1, the camera module 10 includes an imaging window 1, an imaging element 2, a heater 3, and a housing 4.

The camera module 10 may be used, for example, in a surveillance camera installed in a home or the like for crime prevention purposes, or may be mounted on a mobile communication device such as an automobile or drone.

The camera module 10 is covered by the housing 4, and can capture an image of a subject through a shooting window 1 that is part of the housing 4. The camera module 10 may further include a lens 5 and a camera body 6. The camera module 10 may further include other components for image processing or digital data storage. Furthermore, the camera body 6 may obtain the temperature inside the camera module 10 using a connected temperature sensor, and control the operation of the heater 3 by comparing the internal temperature with a predetermined threshold.

The camera module 10 can form a subject image on the imaging element 2 by using an imaging optical system such as a lens 5. The camera module 10 can capture the subject image using the imaging element 2 to generate an image signal. The camera module 10 can also output the image signal to a display device via a signal connection unit. The display device can display the subject image according to the image signal obtained from the signal connection unit.

When the camera module 10 is placed in a low-temperature environment, the camera body 6 heats up as the electric circuit generates heat when electricity is applied, but the area around the shooting window 1 is easily cooled by the outside air. This can cause condensation on the shooting window 1 or fine moisture like mist to float inside the module. The camera module 10 can remove moisture by having the heater 3. The heater 3 may simply be one that only controls ON/OFF, or one that can control the amount of heat generated. The heater 3 may be one that, for example, is an array of multiple resistors, and the amount of heat generated can be controlled by variably controlling the current or voltage passed through the resistors.

The photographing window 1 in the camera module 10 of the present disclosure is a light-transmitting member through which light from a subject passes. Here, the photographing window 1 may be, for example, a lens 5 or a lens cover that protects the lens 5. The photographing window 1 may form a part of the housing 4. Here, the photographing window 1 is made of, for example, glass, acrylic, plastic, polycarbonate, or other member. The photographing window 1 is a member that is heated by radiation from a heat radiation film 33, which will be described later. The photographing window 1 may have metal particles or the like inside in order to be efficiently heated by radiation from the heat radiation film 33, which will be described later.

As shown in Figures 1 and 6, the heater 3 in the camera module 10 of the present disclosure has a ceramic base 31, a heating resistor 32 provided on the ceramic base 31, and a heat radiation film 33 located on the surface of the ceramic base 31.

The ceramic base 31 is a member for protecting the heating resistor 32. The ceramic base 31 is made of a ceramic material such as alumina, cordierite, mullite, aluminum titanate, β-spodumene, zircon, or titania. The shape of the ceramic base 31 may be, for example, a round bar, plate, or cylinder. The dimensions of the ceramic base 31 can be small enough to fit into the housing 4. For example, when the ceramic base 31 is plate-shaped, the dimensions can be a length of 10 to 160 mm, a thickness of 0.5 to 5.5 mm, and a width of 5 to 160 mm.

The heating resistor 32 is a member that generates heat when electricity is passed through it. The heating resistor 32 may be a member such as gold, silver, tungsten, molybdenum, or silver-palladium. The heating resistor 32 is provided inside or on the surface of a ceramic body. The heating resistor 32 may be a meandering pattern having multiple folded portions.

The heater 3 can transmit heat generated by the heating resistor 32 to the imaging window 1 by radiation. The heater 3 can also heat the imaging window 1 by thermal conduction through the housing 4.

The heat radiation film 33 is a member for enhancing the radiation of the heater 3. The heat radiation film 33 is provided on the surface of the ceramic base 31. The heat radiation film 33 may be a ceramic containing at least one of the metals Mo, W, Ni, Cr, Fe, Co, Mn, and Ti as a blackening component. The heat radiation film 33 may have the same material as the ceramic base 31 as its main component. This can reduce the thermal stress generated between the ceramic base 31 and the heat radiation film 33. The heat radiation film 33 is a ceramic containing a blackening component, which can increase the efficiency of radiation. In particular, the heat radiation film 33 may be a ceramic coat containing molybdenum or tungsten. In this case, the efficiency of radiation can be further increased.

The heat radiation film 33 referred to here may be any material that increases the thermal emissivity when provided on the surface of the ceramic base 31. For example, when the shape, dimensions, and other conditions of the heat radiation film 33 are brought closer to those of the ceramic base 31, the heat radiation film 33 may have a higher thermal emissivity in the infrared region than the ceramic base 31. The heat radiation film 33 may be, for example, a black or gray material. The heat radiation film 33 may also have a rougher surface than the ceramic base 31, for example. This can increase the thermal emissivity.

The heater 3 has a heat radiation film 33, and when the heating resistor 32 is heated by passing electricity through it, electromagnetic waves in the infrared range are radiated from the heat radiation film 33 over a wide area. The radiant heat in the infrared range heats and evaporates mist or condensed moisture inside and outside the housing 4. Furthermore, the amount of moisture present on the optical axis inside the housing 4 can be reduced by simultaneously heating the surrounding glass or plastics.

In addition, as the temperature drops, the saturated water vapor pressure drops, so when the outside air temperature drops and the temperature inside the device drops below 0°C, almost all of the water vapor in the air condenses and appears as frost (frozen). If the heater 3 is operating at this time, the air around the heater 3 is warmed, the temperature rises above 0°C, and the saturated water vapor pressure rises, allowing the frost around the heater 3 to disappear.

When the heated air containing water vapor floats on the photographic window 1, it is cooled on the surface of the photographic window 1, and the saturated water vapor pressure drops. If the temperature near the photographic window 1 is below 0° C. and there is more water vapor than the saturated water vapor pressure at that temperature, the air will condense as frost on the surface of the photographic window 1.

By providing a heat radiation film 33 on the surface of the ceramic base 31, the radiation intensity of the near-infrared to mid-infrared region of the radiant heat in the infrared region can be increased. This can increase the effectiveness of removing minute suspended moisture particles.

Furthermore, since the heater 3 has the heat radiation film 33, the intensity of the radiant heat emitted from the surface of the heater 3 can be increased. Therefore, the condensation prevention performance in a low-temperature environment can be improved without using a fan. As a result, the camera module 10 can be made smaller while improving the condensation prevention performance in a low-temperature environment.

As shown in FIG. 3, the housing 4 may have a trapezoidal cross section, as if a part of a rectangular parallelepiped had been cut off. This allows the shooting window 1 to be tilted, and the snow on the top of the housing 4 to melt without making it difficult for snow to adhere to the shooting window 1 when it snows. It also makes it difficult for water droplets to flow onto the surface of the shooting window 1 when it rains. This provides particularly excellent functionality as an infrared camera that is easily affected by moisture. As shown in FIG. 4, the housing 4 may have a hemispherical portion. By making the hemispherical portion of the housing 4 the shooting window 1, it is possible to reduce the risk of snow adhering to the shooting window 1 when it snows.

At the same time, not only does it prevent condensation on the housing 4 and eliminate fog on the optical axis of the lens 5 with radiant heat, but it also makes use of the fact that water vapor tends to rise, and can eliminate water vapor with the heater 3. In particular, by taking advantage of the excellent straight-line characteristics of infrared light, even if the optical axis of the lens 5 and the shooting window 1 are not perpendicular, the infrared light can go straight without being refracted at the shooting window 1, and this allows the camera to have excellent functions as an infrared camera. At the same time, the radiant heat from the heater 3 is not reflected by the shooting window 1 and does not reach the lens 5, so halation is less likely to occur. By heating the shooting window 1 itself, the risk of the outside of the shooting window 1 freezing can be reduced. In addition, since the intensity of thermal radiation is strongest in the direction perpendicular to the surface of the heater 3, condensation on the shooting window 1 can be further prevented by arranging the shooting window 1 in the direction of irradiation of the surface of the heat radiation film 33.

The heater 3 may also be positioned off the optical axis of the camera lens 5. This is because the heat radiation intensity is strongest in the direction perpendicular to the surface of the heater 3, so by shifting the optical axis of the lens 5 from the optical axis of the infrared radiation of the heater 3, halation during photography can be reduced.

Also, as shown in FIG. 3, the heater 3 may be provided on the inner peripheral surface of the housing 4. This allows the heat generated by the heater 3 to be transferred to the shooting window 1 through the housing 4 by thermal conduction. This allows the shooting window 1 to be heated by both thermal conduction and thermal radiation.

As shown in FIG. 6, the heater 3 may further have an electrode lead-out portion 8, which may be located on the surface of the ceramic base 31 opposite to the surface on which the heat radiation film 33 is provided. This reduces the risk of the electrode lead-out portion 8 being heated by the influence of radiant heat. As a result, heating of the circuit portion connected to the heater 3 can be suppressed, and the long-term reliability of the circuit can be improved.

Also, as shown in FIG. 6, the heater 3 may be plate-shaped, and the heating resistor 32 may be sandwiched between a plurality of sheet-shaped ceramic bases 31. In this case, the heat radiation film 33 may be provided on the entire surface of the ceramic base 31, or may be provided only on one of the main surfaces facing the inside of the housing 4. Compared to when the heat radiation film 33 is provided on the entire surface of the ceramic base 31, the heat capacity of the heater 3 as a whole can be reduced while increasing the radiation intensity partially, thereby making it possible to further increase the temperature rise rate of the imaging window 1.

Also, as shown in FIG. 2, the heater 3 may be cylindrical, and the imaging window 1 may be located inside the heater 3. This allows the imaging window 1 to be heated evenly from the circumferential direction. At this time, the outer peripheral surface of the heater 3 may be in contact with the housing 4.

As shown in FIG. 5, the device may further include a reflector 7 for reflecting radiant heat. This allows the reflector 7 to reflect the radiant heat and heat the imaging window 1. The reflector 7 may be a metal member such as aluminum, copper, or stainless steel. The reflector 7 may be located on the inner peripheral surface of the housing 4, for example. The reflector 7 may be located so as to cover the heater 3. This allows the radiant heat from the heater 3 to be reflected over a wide area.

Also, as shown in Figs. 7 and 8, the heater 3 may be in contact with the photographing window 1. This allows the heat generated by the heater 3 to be transferred to the photographing window 1 by heat transfer. Therefore, the photographing window 1 can be heated more effectively. This further reduces the risk of condensation forming on the photographing window 1.

In this case, as shown in FIG. 7, the heater 3 may be a plate-shaped member with its main surface in contact with the photographing window 1. In this case, heat transfer occurs between the surfaces, and the photographing window 1 can be heated more efficiently. Also, as shown in FIG. 8, the end of the heater 3 may be in contact with the photographing window 1. In this case, the overlap between the photographing window 1 and the heater 3 can be reduced when viewed from the optical axis direction (the direction perpendicular to the lens 5). This allows the field of view of the camera module 10 to be widened.

As shown in FIG. 9, the heater 3 and the imaging window 1 may further include a thermally conductive member 9 in contact with each other. This allows the heat generated by the heater 3 to be transferred to the imaging window 1 via the thermally conductive member 9. This allows the imaging window 1 to be heated more effectively. This further reduces the risk of condensation occurring on the imaging window 1. Here, the thermally conductive member 9 may be any member having a higher thermal conductivity than ceramic. The thermally conductive member 9 is, for example, a metal member such as stainless steel, aluminum, silver, or copper. The heater 3 and the thermally conductive member 9 may be joined by, for example, a resin bonding material. The heater 3 and the thermally conductive member 9 may be bonded by, for example, grease or the like.

In addition, when the heater 3 is in contact with the photographing window 1 as shown in Figs. 7 and 8, or when there is further provided a heat conductive member 9 in contact with the heater 3 and the photographing window 1 as shown in Fig. 9, the photographing window 1 can be heated more effectively than when the photographing window 1 is heated by radiation from the heater 3. Therefore, not only is condensation prevented, but frost or ice adhering to the surface of the photographing window 1 can be removed even in an environment where the outside of the camera freezes. As a result, the subject can be clearly photographed even in harsh external environments such as below freezing.

Also, as shown in FIG. 10, the heat conducting member 9 may be provided so as to surround the photographing window 1. In this case, heat can be evenly transferred to the photographing window 1 in the circumferential direction. Therefore, condensation or freezing that occurs on the photographing window 1 can be evenly eliminated in the circumferential direction.

Also, as shown in FIG. 10, the heat conducting member 9 may be a hollow plate-shaped (disk-shaped) member with multiple heaters 3 provided on its surface. This allows heat to be transferred evenly in the circumferential direction to the shooting window 1. Also, by arranging the multiple heaters 3 evenly in the circumferential direction, stress due to differences in thermal expansion between the heaters 3 and the heat conducting member 9 can be reduced. As a result, the long-term reliability of the camera module 10 can be improved.

Also, as shown in FIG. 11, the heat conducting member 9 may be an annular member with multiple heaters 3 provided on its inner circumferential surface. In this case, the inner circumferential surface of the heat conducting member 9 may have a linear portion when viewed from the optical axis direction, and the heaters 3 may be provided on the linear portion. This increases the contact area between the heaters 3 and the heat conducting member 9, so that the heat generated by the heaters 3 can be transferred to the photographing window 1 via the heat conducting member 9. This allows the photographing window 1 to be heated more effectively. This further reduces the risk of condensation occurring on the photographing window 1.

Also, as shown in FIG. 13, the heat radiation film 33 may be provided on the surface of the heater 3 that contacts the heat conductive member 9. This allows the heat of the heater 3 to be transferred to the imaging window 1 via the heat conductive member 9, while the imaging window 1 can be further heated by radiation from the heat radiation film 33. Therefore, the imaging window 1 can be heated more effectively. This further reduces the risk of condensation occurring on the imaging window 1.

Also, as shown in FIG. 14, the heat radiation film 33 may be provided on the surface of the heater 3 opposite to the surface that contacts the heat conductive member 9. This not only heats the shooting window 1 by thermal conduction and thermal radiation, but also effectively heats the lens 5, image sensor 2, or drive circuit inside the housing 4 with radiant heat. This allows for supplementary heating before operating the camera, for example. As a result, even immediately after operating the camera module 10, it is possible to shoot with a response speed similar to that at room temperature.

The following describes a method of manufacturing the ceramic base 31 and the heat radiation film 33 when they are made of alumina. A conductive paste containing W, Mo, etc. is applied to one main surface of an alumina (Al2O3) raw ceramic sheet by a printing method and patterned, and another paste is applied to the other main surface, that is, a paste containing 0.3 to 12% by weight of at least one of MgO, CaO, SiO2, and ZrO2, and 0.3 to 10% by weight of the blackening component, with the oxide of the component added, and the remainder being Al2O3. Then, this raw ceramic sheet is laminated with a ceramic sheet made of unfired raw ceramic so that the other main surface is on the outside. The raw ceramic for this ceramic sheet is also made of alumina containing 0.3 to 12% by weight of at least one of MgO, CaO, SiO2, and ZrO3. It is then fired at 1400 to 1700°C in a reducing atmosphere. This results in a heater 3 in which the outer peripheral surface of a plate-shaped ceramic base 31 in which a heating resistor 32 pattern 5 is embedded is covered with a black heat radiation film 33 in an integrated sintered state.

According to the above manufacturing method, even if Mo, W, Ni, Cr, Fe, Co, Mn, and Ti are added as oxides, they are insufficiently reduced by firing in a reducing atmosphere to become oxides or simple metals, which become the blackening components.

Thus, according to the heater 3 disclosed herein, by coating the white ceramic base 31 with the blackened heat radiation film 33, it is possible to enhance the heat radiation in the infrared range.

In addition, as disclosed herein, when a blackened heat radiation film 33 is formed on a white ceramic base 31, if the heat radiation film 33 is made significantly thinner, the white ceramic base 31 will be visible, preventing the heater 3 from being blackened. Therefore, by making the thickness of the heat radiation film 33 10 μm or more, preferably 15 μm or more, the white color of the ceramic base 31 will not cause the color of the heater 3 to become lighter, and as a result, a better thermal emissivity can be obtained.

1: Imaging window 2: Imaging element 3: Heater 31: Ceramic base 32: Heat generating resistor 33: Heat radiation film 4: Housing 5: Lens 6: Camera body 7: Reflector 8: Electrode lead-out portion 9: Heat conductive member 10: Camera module

Claims (13)

A shooting window and
An imaging element;
A heater and
a housing that contains the imaging window, the imaging element, and the heater,
The heater includes a ceramic base, a heating resistor provided on the ceramic base, and a heat radiation film located on a surface of the ceramic base,
A camera module , wherein the heat radiation film is a ceramic coating containing molybdenum or tungsten . 2. The camera module according to claim 1 , wherein the imaging window is positioned in a direction perpendicular to a surface of the ceramic base on which the heat radiation film is provided. 3. The camera module according to claim 1 , wherein the heater is provided on an inner circumferential surface of the housing. The heater further has an electrode lead-out portion,
4. The camera module according to claim 1 , wherein the electrode extraction portion is located on a surface of the ceramic base opposite to a surface on which the heat radiation film is provided. The heater is plate-shaped,
5. The camera module according to claim 1 , wherein the heating resistor is provided along the heat radiation film. The heater is cylindrical,
5. The camera module according to claim 1 , wherein the imaging window is positioned inside the heater. 7. The camera module according to claim 1 , further comprising a reflector for reflecting radiant heat. 8. The camera module according to claim 1 , wherein the heater is in contact with the photographing window. 9. The camera module according to claim 1 , further comprising a heat conductive member in contact with the heater and the imaging window. The camera module according to claim 9 , wherein the heat conductive member is provided so as to surround the photographing window. 11. The camera module according to claim 10 , wherein the heat conducting member is a hollow plate-like member, and a plurality of the heaters are provided on a surface thereof. The camera module according to claim 11 , wherein the heat conducting member is an annular member, and a plurality of the heaters are provided on an inner peripheral surface of the annular member. 13. The camera module according to claim 9 , wherein the heat radiation film is provided on a surface of the heater opposite to a surface in contact with the heat conductive member.

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