Lens heating device

Abstract

The present invention provides a lens heating device that uniformly heats the entire lens of an optical device. [Solution] The present invention provides a lens heating device comprising a metal or metal-plated heat transfer body (4) having a support plate (2) and a heat dissipation ring (3) connected to the support plate (2), and a heating element (1) attached to the support plate (2) of the heat transfer body (4). The heat dissipation ring (3) of the heat transfer body (4) has a connecting portion (31) connected to the support plate (2) and a distal portion (32) connected to the connecting portion (31) on the opposite side of the support plate (2). The heat dissipation ring (3) of the heat transfer body (4) is positioned in contact with the outer circumferential surface of the lens (120) which is placed in the housing (110) of the optical device (100). A gap (33) is provided at the connecting portion (31) of the heat dissipation ring (3) of the heat transfer body (4) that does not directly contact the lens (120), thereby heating the entire lens (120) evenly.

Description

Technical Field

[0001] The present invention relates to a lens heating device that uniformly and efficiently heats a lens in an optical device by means of a heat dissipation ring.

Background Art

[0002] A PTC heater that utilizes the positive temperature characteristics of a PTC thermistor, characterized by automatic temperature control and low power consumption, is used in heating devices such as hot air generators, fluid heaters, planar heaters, anti-freezing devices, or anti-fogging devices. Different from additional temperature adjustment means such as a thermostat including a nichrome heater, when a voltage is applied to a PTC heater that produces an automatic temperature control function without worry about abnormal temperature overheating or wire breakage, etc., and current flows through the PTC heater, it generates heat. However, when it reaches a certain temperature (Curie point), the electrical resistance value rapidly increases and the current amount decreases, and it is maintained at a predetermined temperature. Also, a PTC heater with a small size, light weight, and simple configuration is used in various applications as a highly reliable general-purpose heater.

[0003] On the outer surface of a lens of an in-vehicle or surveillance camera exposed outdoors, ice and snow may adhere during snowfall or rainfall. At sub-zero outside air temperatures, dew condensation or ice of water droplets adhering to the front surface of the lens makes the imaging image of the camera unclear. Therefore, it is necessary to heat the lens with a heating device attached around the lens to melt or evaporate the ice deposits adhering to the lens.

[0004] The following Patent Documents 1 to 4 all disclose a lens device including a cylindrical lens barrel, a plurality of lenses juxtaposed along the axial direction of the lens barrel within the lens barrel, and a heating device having a flexible printed wiring board and a PTC thermistor. The annular heating device heats the outer peripheral portion of the uppermost lens or cover glass to prevent freezing or dew condensation of the lens or cover glass. Also, Patent Documents 5 to 7 all disclose modified examples of lens devices in which a power supply unit for supplying power to the heating device is formed of a metal plate.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 7312164 [Patent Document 2] Patent No. 7339023 [Patent Document 3] Patent No. 7343334 [Patent Document 4] Patent No. 7343359 [Patent Document 5] Japanese Patent Publication No. 2023-128223 [Patent Document 6] Japanese Patent Publication No. 2023-023904 [Patent Document 7] Japanese Patent Publication No. 2022-131077 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, there is a desire for the development of an inexpensive and simple lens heating device that does not use flexible printed circuit boards. The proposed lens heating device is formed from a metal plate having a metal support plate to which a heating element is attached, and a heat dissipation ring connected to the support plate. The heat dissipation ring is positioned adjacent to the outer circumference of the lens, and the lens is heated through the metal plate by the heat generated by the heating element. A lens heating device that does not use flexible printed circuit boards has the advantage of being inexpensive to manufacture and providing stable heating of the lens over a long period of time.

[0007] However, in lens heating devices made of metal plates, the support plate to which the heating element is attached is heated to a high temperature, while the heat from the heating element is not sufficiently and uniformly transferred to the distal portion of the heat dissipation ring, which is connected to the support plate but positioned away from the heating element on the opposite side. Therefore, the connection portion of the heat dissipation ring near the support plate is heated to a high temperature, while the distal portion of the heat dissipation ring on the opposite side of the support plate is not heated sufficiently. As a result, the connection portion near the support plate is heated to a higher temperature than the distal portion of the heat dissipation ring on the opposite side of the support plate, leading to uneven thermal expansion of the lens due to the uneven heating of the heat dissipation ring, which causes distortion in the camera's captured image.

[0008] Therefore, the present invention aims to provide a lens heating device that does not use a flexible printed circuit board. The present invention aims to provide a lens heating device that heats the entire lens uniformly. The present invention aims to provide a lens heating device that avoids the generation of camera image distortion caused by uneven thermal expansion of the lens due to uneven heating. [Means for solving the problem]

[0009] The lens heating device according to the present invention comprises a heat transfer body (4) made of metal or having a metal-plated layer, having a support plate (2) and a heat dissipation ring (3) connected to the support plate (2), and a heating element (1) attached to the support plate (2) of the heat transfer body (4). The heat dissipation ring (3) of the heat transfer body (4) has a connecting portion (31) connected to the support plate (2) and a distal portion (32) connected to the connecting portion (31) on the opposite side of the support plate (2). The heat dissipation ring (3) of the heat transfer body (4) is positioned in contact with the outer circumferential surface of a lens (120) arranged in the housing (110) of an optical device (100), and a gap (33) is provided in the connecting portion (31) of the heat dissipation ring (3) of the heat transfer body (4) that does not directly contact the lens (120).

[0010] The gap (33) provided in the connecting portion (31) of the heat dissipation ring (3) reduces the amount of heat transferred from the connecting portion (31) of the heat dissipation ring (3) to the lens (120), bringing it closer to the amount of heat transferred from the distal portion (32) of the heat dissipation ring (3) to the lens (120). As a result, the heating temperature to the lens (120) is made uniform, preventing distortion of the image captured by the optical device (100) due to uneven temperature distribution across the lens (120). [Brief explanation of the drawing]

[0011] Embodiments of the present invention will be described below with reference to the attached drawings. [Figure 1] Exploded perspective view of the optical device to which the lens heating device of the present invention is attached. [Figure 2] Exploded perspective view showing another embodiment of the lens heating device of the present invention. [Figure 3] Side view of the heat transfer element and lens in Figure 1. [Figure 4]Side view of the heat transfer body and the lens in FIG. 2 [Figure 5] Bottom view showing the bottom surface of the optical device in FIGS. 1 and 2 with the lens attached [Figure 6] Exploded perspective view of the optical device in which a heating element is arranged inside the housing [Figure 7] Perspective view showing the bottom surface of the optical device in FIG. 6 with the lens attached [Figure 8] Side view of the heat transfer body and the lens provided with a protrusion at the connecting part [Figure 9] Perspective view of the heat dissipation ring divided around the connecting part provided with a recess and the distal part [Figure 10] Perspective view of the heat dissipation ring provided with an intermittent part [Figure 11] Perspective view of the heat dissipation ring provided with a notch [Figure 12] Table showing the measured values of the surface temperatures of the heat transfer body and the lens

Embodiments for Carrying Out the Invention

[0012] The embodiments shown in FIGS. 1 to 12 of the lens heating device of the present invention applied to an in-vehicle camera used for functions such as automatic driving, automatic braking, electronic door mirrors, rear monitors, or drive recorders will be described below.

[0013] The optical device (100) shown in FIGS. 1 and 2 includes a cylindrical or rectangular tubular housing (lens barrel, lens body) (110), a lens (120) attached to the opening (111) of the housing (110), and a lens heating device (referred to as a "heating device") (10) that heats the lens (120). A plurality of lenses (120) made of glass or resin are stacked and arranged on the optical path along the central axis inside the housing (110). Although not shown, an image sensor (imaging device) that converts image photons captured through the lens (120) of the optical device (100) into an electronic signal to create a digital image of an object, an electronic substrate on which the image sensor is mounted, the optical device (100), and a camera case that houses these are provided in the in-vehicle camera.

[0014] The heating device (10) shown in Figures 1 and 2 comprises a heat transfer body (4) having an integrally formed support plate (2) and an annular heat dissipation ring (3) connected to the support plate (2), and a heating element (1) attached to the support plate (2) of the heat transfer body (4). The heating element (1) can be any known heating element (heater) that generates heat when energized, for example, a heat-generating resistor such as a PTC thermistor is preferred. The characteristics and manufacturing method of PTC thermistors are known, for example, from Japanese Patent Application Publication No. 2010-3814 by the applicant of this patent, so the details are omitted. In the heating device (10) shown in Figures 1 and 2, a pair of lead terminals (16, 17) leading out from the heating element (1) are connected to a power supply (not shown).

[0015] The heat transfer element (4) is formed in a flat plate shape from a heat-conductive metal such as an aluminum alloy, copper alloy, pure copper, or iron-based metal, or from a resin material that has been metal-plated. The heat dissipation ring (3) of the heat transfer element (4) is formed in an annular or donut shape with a circular hole (13) in the center. The heat dissipation ring (3) also has a connecting portion (31) that is close to the support plate (2) and a distal portion (32) that is separated from the support plate (2). The heat transfer element (4) is provided with a bent portion (4a) formed between the support plate (2) and the heat dissipation ring (3), and the bent portion (4a) shown in Figures 3 and 4 bends the heat dissipation ring (3) at a right angle to the support plate (2). The bent portion (4a) can be formed on the heat transfer element (4) before or after the heating element (1) is fixed to the heat transfer element (4).

[0016] In the optical device (100) shown in Figures 1 and 2, an opening (111) is formed in the cylindrical housing (110), and the heat dissipation ring (3) of the heating device (10) is mounted inside the housing (110) through the opening (111). Subsequently, the lens (120) is inserted into the opening (111) of the housing (110), and the outer edge of the lens (120) is in close contact with the upper surface (3a) of the heat dissipation ring (3), so that the lens (120) is installed inside the housing (110). In the optical device (100) shown in Figures 1 and 2, the heating element (1) is located outside the housing (110), and the heat dissipation ring (3) of the heat transfer element (4) is in contact with the flange (112) of the housing (110). The light rays focused through the lens (120) are taken into the housing (110) through the round hole (13) of the heat dissipation ring (3) and the central hole (112a) of the flange (112) of the housing (110).

[0017] The heat from the heat-generating element (1) transferred to the heat dissipation ring (3) is directly transferred to the lens (120) in contact with the surface of the heat dissipation ring (3), and the lens (120) is also heated by the radiant heat emitted from the heat dissipation ring (3). In addition, the heat on the back surface of the heat dissipation ring (3) is blocked or reflected by the flange (112), and ultimately the lens (120) is effectively heated by conductive heat, radiant heat, and reflected heat. In order to effectively utilize the heat on the bottom surface (3b) of the heat dissipation ring (3), a thin metal film with insulating or heat-reflective properties may be attached to the bottom surface (3b) of the heat dissipation ring (3) or placed between the bottom surface (3b) of the heat dissipation ring (3) and the flange (112) of the housing (110).

[0018] The lens (120), which is attached to the opening (111) of the housing (110), has an upper surface (120a) that is exposed to the outside of the housing (110) and a flat bottom surface (120b) that is located inside the housing (110). The heat dissipation ring (3) of the heating device (10) is adjacent to or in contact with the outer circumference of the bottom surface (120b) of the lens (120). The heating device (10) is fixed to the optical device (100) by sandwiching the heat dissipation ring (3) of the heating device (10) between the flange (112) of the housing (110) and the lens (120) of the optical device (100). The heat transferred from the support plate (2) to the heat dissipation ring (3) via the bent portion (4a) of the heat transfer element (4) heats the lens (120) of the optical device (100) to prevent deterioration of the optical properties due to condensation, freezing, or ice deposits on the lens (120).

[0019] The heat transfer ring (3) of the heat transfer element (4) has a gap (33) between the connecting portion (31) and the lens (120) to prevent direct contact between the connecting portion (31) and the lens (120). The gap (33) to prevent direct contact between the connecting portion (31) and the lens (120) is formed by (i) one or more linear or annular grooves or depressions in a recess (34) (Figure 3) or (ii) a spacer (35) (Figure 4) attached to the distal portion (32) of the heat transfer ring (3). In the heating device (10) of Figure 1, the heat transfer element (4) has a recess (34) in the connecting portion (31) of the heat transfer ring (3), and the recess (34) forms a gap (33) between the connecting portion (31) of the heat transfer ring (3) and the lens (120). For example, regarding a recess (34) having a depth of 1 / 5 to 1 / 2 of the thickness of the heat dissipation ring (3), even a recess (34) with a step of less than 1 / 2 the thickness has the effect of reducing the amount of heat transferred. For example, a recess (34) with a depth of 0.1 mm is formed in a heat dissipation ring (3) with a thickness of 0.4 mm.

[0020] Furthermore, the heat transfer element (4) of the heating device (10) shown in Figure 2 is equipped with a spacer (35) that is bonded to the distal part (32) of the heat dissipation ring (3), and the spacer (35) forms a gap (33) between the connecting part (31) of the heat dissipation ring (3) and the lens (120). For example, a spacer (35) having a thickness of 1 / 5 to 1 / 2 of the thickness of the heat dissipation ring (3) is effective in reducing the amount of heat transferred, and even a spacer (35) with a step of less than 1 / 2 is effective in reducing the amount of heat transferred. For example, a spacer (35) with a thickness of 0.1 mm is bonded to a heat dissipation ring (3) with a thickness of 0.4 mm. The spacer (35) is formed in the form of a thin film of a heat-conductive resin material, which is composed of a silicone resin containing a heat-conductive additive selected from aluminum oxide, aluminum nitride, and silicon carbide or a mixture thereof. Alternatively, a polyimide film may be attached.

[0021] When a heat dissipation ring (3) is positioned adjacent to the outer circumference of the bottom surface (120b) of a lens (120) incorporated into a cylindrical housing (110) of an optical device (100), the distal part (32) of the heat dissipation ring (3) is in close contact with the lens (120), while the connecting part (31) of the heat dissipation ring (3) is separated from the lens (120) via a gap (33). When a recess (34) with a depth of 0.1 mm is formed in the connecting part (31) of the heat dissipation ring (3), or when a spacer (35) with a thickness of 0.1 mm is bonded to the distal part (32) of the heat dissipation ring (3), a gap (33) with a height of 0.1 mm is formed between the connecting part (31) of the heat dissipation ring (3) and the bottom surface (120b) of the lens (120).

[0022] By separating a portion of the connecting portion (31) of the heat dissipation ring (3) from the lens (120) through the gap (33), the contact area of ​​the connecting portion (31) of the heat dissipation ring (3) with respect to the lens (120) can be reduced compared to the contact area of ​​the distal portion (32) with respect to the lens (120). That is, the contact area of ​​the distal portion (32) of the heat dissipation ring (3) with respect to the lens (120) is larger than the contact area of ​​the connecting portion (31) with respect to the lens (120). However, by changing the thickness and shape of the distal portion (32) and the connecting portion (31) of the heat dissipation ring (3), the contact area of ​​the distal portion (32) of the heat dissipation ring (3) with respect to the lens (120) may be made smaller than or equal to the contact area of ​​the connecting portion (31) with respect to the lens (120). When a voltage is applied, the heat generated from the heating element (1) is transferred from the connecting portion (31) to the distal portion (32) of the heat dissipation ring (3) via the support plate (2) of the heat transfer element (4). The connecting portion (31) adjacent to the heating element (1) and the support plate (2) is heated more than the distal portion (32) which is separated from the heating element (1) and the support plate (2). However, since the connecting portion (31) of the heat dissipation ring (3) is separated from the lens (120) via the air gap (33), heat transfer from the connecting portion (31) of the heat dissipation ring (3) to the lens (120) is reduced.

[0023] The bottom surface (120b) of the distal part of the lens (120) that faces and contacts the distal part (32) of the heat dissipation ring (3) is directly heated by the heat dissipation ring (3), while the bottom surface (120b) of the proximal part of the lens (120) that faces and is separated from the connecting part (31) of the heat dissipation ring (3) is indirectly heated by the radiant heat of the heat dissipation ring (3). The gap (33) forms an air layer between the lens (120) and the connecting part (31) of the heat dissipation ring (3), and the inside of the gap (33) is heated by the heat transferred from the connecting part (31) of the heat dissipation ring (3). Furthermore, when the heat dissipation ring (3) of the heat transfer element (4) is positioned adjacent to the outer circumference of the lens (120), the distal part (32) of the heat dissipation ring (3) is in close contact with the lens (120), while the connecting part (31) of the heat dissipation ring (3) is separated from the lens (120) via an air gap (33). As a result, the amount of heat transferred from the connecting part (31) of the heat dissipation ring (3) to the lens (120) decreases and approaches the amount of heat transferred from the distal part (32) of the heat dissipation ring (3) to the lens (120). Therefore, the heating temperature to the lens (120) is made uniform, and distortion of the image captured by the optical device (100) due to uneven temperature distribution across the entire lens (120) can be prevented.

[0024] In the optical device (100) shown in Figures 1 and 2, by placing the heating element (1) outside the housing (110), sufficient space is maintained inside the housing (110) to install the lens (120), and a relatively large heating element (1) that generates sufficient heat can be used. Light that has passed through the multiple lenses (120) and an infrared cut filter (not shown) inside the housing (110) is received by an image sensor (not shown) through a small-diameter circular hole (115a) of an aperture plate (115) attached to the lower part (110b) of the housing (110) shown in Figure 5.

[0025] When attaching the lens heating device (10) according to an embodiment of the present invention to an optical device (100), first, a heating element (1) to be fixed to the support plate (2) of the heat transfer element (4) is prepared, and the support plate (2) and the heat transfer element (4) having a heat dissipation ring (3) are integrally press-molded. In the heating device (10) shown in Figure 1, the heat dissipation ring (3) having a recess (34) is integrally formed with the support plate (2) by press molding. Compared to conventional flexible printed circuit boards, the heat transfer element (4) having the support plate (2) and heat dissipation ring (3) can be integrally formed inexpensively by press molding.

[0026] The heating element (1) is attached to a support plate (2) of a heat transfer element (4) which is made of a heat-conductive metal such as an aluminum alloy, copper alloy, pure copper, or iron-based metal, or a resin material with a metal plating layer. In this case, before or after fixing the heating element (1) to the support plate (2) of the heat transfer element (4), the heat dissipation ring (3) is bent at a right angle to the support plate (2) to form a bent portion (4a) between the support plate (2) and the heat dissipation ring (3). In the heat transfer element (4) of Figure 1, a recess (34) is formed in the connecting portion (31) of the heat dissipation ring (3) during the press molding of the heat transfer element (4). In the heat transfer element (4) of Figure 2, a spacer (35) is bonded to the distal portion (32) of the heat dissipation ring (3) after the press molding of the heat transfer element (4). The spacer (35), formed as a thin film from a heat-conducting resin material consisting of a silicone resin containing a heat-conducting additive, is adhered to the distal portion (32) of the heat dissipation ring (3) by its own adhesive force or by applying another adhesive. Alternatively, a polyimide film may be attached.

[0027] Next, the heat dissipation ring (3), which is integrally formed with the support plate (2) of the heat transfer element (4), is placed inside the cylindrical housing (110) of the optical device (100). At the same time, the bent portion (4a) of the heat transfer element (4) is fitted into the notch (114) of the ring seat (113), and the heat dissipation ring (3) of the heat transfer element (4) is placed on the flange (112) of the housing (110), thereby mounting the heat transfer element (4) to the housing (110). Although not shown in the figures, when placing the heat dissipation ring (3) of the heat transfer element (4) on the flange (112) of the housing (110), a heat reflective material such as metal foil or a thin aluminum film may be attached to the bottom surface (3b) of the heat dissipation ring (3), or a heat reflective material or heat insulating material may be placed between the bottom surface (3b) of the heat dissipation ring (3) and the flange (112) of the housing (110). The heat reflective material reflects the radiant heat from the heat-generating heat dissipation ring (3) toward the lens (120), allowing the lens (120) to be heated more efficiently.

[0028] As shown in Figures 1 and 2, the housing (110) of the optical device (100) is provided with an opening (111) in the upper part (110a) of the housing (110), a ring seat (113) protruding from the flange (112) of the opening (111) of the housing (110), a flange (112) formed on the inside of the ring seat (113), and a notch (114) formed radially in the ring seat (113). The heat dissipation ring (3) of the heat transfer body (4) is placed on the flange (112) on the inside of the ring seat (113), and the lens (120) of the optical device (100) can be placed inside the ring seat (113) in close contact with the heat dissipation ring (3) of the heat transfer body (4). A heat dissipation ring (3) is installed inside the casing (110) through an opening (111) in the cylindrical casing (110) of the optical device (100), and the bent portion (4a) of the heat transfer element (4) is brought into contact with the flange (112) of the casing (110), so that a support plate (2) is positioned outside the casing (110).

[0029] Subsequently, the outer circumference of the lens (120), which is placed inside the opening (111) of the housing (110), is positioned on the upper surface (3a) of the heat dissipation ring (3) of the heat transfer element (4), thereby attaching the lens (120) to the opening (111) of the housing (110). The optical device (100) is completed by attaching the lens (120) to the opening (111) of the housing (110) by crimping, welding, or using adhesive.

[0030] Embodiments of the present invention are modifiable. Some in-vehicle cameras have a structure that prevents the optical device (100) from being housed in the camera case of the in-vehicle camera if the heating element (1) is placed outside the housing (110) of the optical device (100). In this case, as shown in Figure 6, the heating element (1) may be placed inside the housing (110) of the optical device (100). A housing hole (116) is provided in the flange (112) of the housing (110) of the optical device (100), and the heating element (1) is housed in the housing hole (116). As shown in Figure 7, a pair of lead terminals (16, 17) of the heating element (1) are led out to the outside through a pair of small holes (115b) provided in the aperture plate (115) at the lower part (110b) of the housing (110). The pair of lead terminals (16, 17) are connected to a power supply (not shown).

[0031] As shown in Figure 8, one or more protrusions (36) supporting the lens (120) may be provided in the recess (34) of the heat dissipation ring (3). Protrusions (36) that protrude at the same height as the distal portion (32) are provided in a part of the recess (34) of the heat dissipation ring (3) to support the lens (120), and the gap (33) formed between the connecting portion (31) of the heat dissipation ring (3) and the lens (120) prevents the lens (120) from tilting and becoming unstable on the heat dissipation ring (3). Although not shown, multiple recesses (34) may be provided in the connecting portion (31) of the heat dissipation ring (3). Similarly, multiple spacers (35) may be provided in the distal portion (32) of the heat dissipation ring (3). In addition, the positions of the recesses (34) or spacers (35) of the heat dissipation ring (3) can be changed as appropriate. The heating device (10) in Figure 9 has a recess (34) that extends to the center of the circular hole (13) of the heat dissipation ring (3). As shown in Figures 10 and 11, the heat transfer range from the heat dissipation ring (3) to the lens (120) may be changed by providing an intermittent section (6) or notch (7) in a part of the heat dissipation ring (3) of the heat transfer body (4). [Examples]

[0032] The measurement results 1 to 3 obtained by measuring the surface temperature of the heat transfer element and lens using the lens heating device of the present invention are described below. A heat transfer body having a support plate and a heat dissipation ring of a constant thickness of 0.4 mm was formed from an aluminum plate, and a PTC thermistor with a resistance of 2.31 Ω was fixed to the support plate of the heat transfer body. Next, a DC voltage of 5 V was applied to the PTC thermistor at room temperature of 25 °C, and the temperatures of the PTC thermistor and the heat transfer body were measured using a surface temperature measuring device (thermoviewer). As shown in Measurement Results 1 of Figure 12, the temperature of the PTC thermistor, the temperature of the connection part of the heat dissipation ring, the temperature of the distal part of the heat dissipation ring, and the temperature difference between the connection part and the distal part of the heat dissipation ring were 100.8 °C, 84.8 °C, 80.7 °C, and 4.1 °C.

[0033] Next, a heat transfer ring was placed adjacent to the outer circumference of a glass lens with a diameter of 11.9 mm and a thickness of 2.96 mm, and the temperatures of the PTC thermistor and the lens were measured under the same conditions as in Measurement Result 1. In Measurement Result 2, where the connection part of the heat transfer ring and the lens were in close contact without any gaps, the temperatures of the PTC thermistor, the lens adjacent to the connection part of the heat transfer ring, the lens adjacent to the distal part of the heat transfer ring, and the temperature difference between the lens adjacent to the connection part and the lens adjacent to the distal part of the heat transfer ring were 102.2°C, 71.9°C, 68.4°C, and 3.5°C.

[0034] Next, similar to the heat transfer device in Figure 1, a recess with a depth of 0.1 mm was created in the connection part of the heat dissipation ring up to the position in contact with the circular hole in the heat dissipation ring, and the temperature of the PTC thermistor and lens was measured under the same conditions as in Measurement Result 2. In Measurement Result 3, where a gap was created between the connection part of the heat dissipation ring of the heat transfer device and the lens, the temperature of the PTC thermistor, the temperature of the lens adjacent to the connection part of the heat dissipation ring, the temperature of the lens adjacent to the distal part of the heat dissipation ring, and the temperature difference between the lens adjacent to the connection part and the lens adjacent to the distal part of the heat dissipation ring were 100.5°C, 66.5°C, 66.3°C, and 0.2°C. When a thin film of silicone resin with a thickness of 0.1 mm was applied from the distal part of the heat dissipation ring to the connection part between the circular hole and the connection part, and the temperature of the PTC thermistor and lens was measured, the measurement results were the same as in Measurement Result 3.

[0035] Measurement results 1-3 show that measurement result 3, in which a gap is provided between the heat transfer ring connection and the lens, equalizes the temperature difference of the lens to 0.2°C, preventing distortion in the camera's captured image. Although the display of the measurement results is omitted, it was found that even if the position, shape, and depth of the recess in the heat transfer ring connection or the position, shape, and thickness of the resin thin film at the distal end of the heat transfer ring are changed, the gap between the heat transfer ring connection and the lens can suppress uneven heating of the entire lens. [Industrial applicability]

[0036] This invention can be applied to a lens heating device for heating the lens of a camera installed in a low-temperature environment, such as an in-vehicle camera or a surveillance camera. [Explanation of Symbols]

[0037] (1) Heating element, (2) Support plate, (3) Heat dissipation ring, (3a) Top surface, (3b) Bottom surface, (4) Heat transfer element, (4a) Bent section, (10) Lens heating device, (13) Round hole, (16,17) Lead terminals, (31) Connecting section, (32) Distal section, (33) Gap, (34) Recess, (35) Spacer, (100) Optical device, (110) Housing, (111) Opening, (112) Flange, (113) Ring seat, (114) Notch, (120) Lens

Claims

1. The device comprises a heat transfer element made of metal or having a metal-plated layer, having a support plate and a heat dissipation ring connected to the support plate, and a heating element attached to the support plate of the heat transfer element. The heat dissipation ring of the heat transfer element has a connecting portion that is connected to the support plate and a distal portion that is connected to the connecting portion on the opposite side of the support plate. The heat dissipation ring of the heat transfer element is positioned in contact with the outer surface of the lens that is placed in the housing of the optical device. A lens heating device characterized in that a gap is provided at the connection point of the heat dissipation ring of the heat transfer element, preventing direct contact with the lens.

2. The gap that avoids direct contact between the connecting part and the lens is, (i) A recess having one or more straight or annular grooves or depressions or (ii) Spacers attached to the distal part of the heat dissipation ring, A lens heating device according to claim 1, formed by the above.

3. The lens heating device according to claim 2, wherein the heat dissipation ring having a recess is integrally formed with the support plate from the same metal material.

Images