Infrared sensor cover

Abstract

This easily suppresses the decrease in infrared transmittance in the cover body that occurs with increasing incident angle. [Solution] The infrared sensor cover 30 is applied to an infrared sensor 21 which includes a transmitting unit 23 that transmits infrared IR toward the outside of the vehicle 10 and a receiving unit 24 that receives infrared IR reflected after hitting an object. The infrared sensor cover 30 covers the transmitting unit 23 and the receiving unit 24 from the front in the direction of infrared IR transmission. The infrared sensor cover 30 includes a cover body 31 that is transparent to infrared IR. The reflection suppression layer 35 that suppresses the reflection of infrared IR constitutes the rear surface, which is at least one of the two surfaces of the cover body 31 in the transmission direction, and has a uniform thickness. The reflection suppression layer 35 is formed so that the transmittance of infrared IR passing through the cover body 31 is maximized when infrared IR is irradiated at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

Description

Technical Field

[0001] The present invention relates to an infrared sensor cover that covers a transmitter and a receiver of infrared rays in an infrared sensor from the front in the infrared ray transmission direction.

Background Art

[0002] An infrared sensor mounted on a vehicle includes a transmitter and a receiver of infrared rays. The transmitter transmits infrared rays to the outside of the vehicle while changing the transmission direction within a predetermined angular range with respect to each of the vehicle width direction and the vertical direction. The receiver receives infrared rays reflected by an object outside the vehicle, such as a preceding vehicle, a pedestrian, or the like. The transmitted and received infrared rays are used for detecting the position of the object or for detecting the distance, relative speed, etc. between the vehicle and the object.

[0003] When the infrared sensor is attached to the vehicle in an exposed state, the transmitter and the receiver can be directly seen from the front in the infrared ray transmission direction. For this reason, not only the infrared sensor itself but also the appearance around the infrared sensor in the vehicle is impaired. In addition, it is necessary to protect the transmitter and the receiver from impacts and the like. Therefore, the transmitter and the receiver are covered by an infrared sensor cover from the front in the infrared ray transmission direction. The infrared sensor cover includes a cover main body portion having infrared ray transmissivity. As one form of the cover main body portion, it is known that at least one of both surfaces of the cover main body portion in the transmission direction is constituted by a reflection suppression layer that suppresses reflection of infrared rays.

[0004] By the way, in recent infrared sensors, the transmitter tends to transmit infrared rays in a wider angular range with respect to the vehicle width direction, for example, in an angular range of -60 degrees or more and +60 degrees or less. In this case, generally, the infrared sensor cover is designed so that the transmittance of infrared rays that pass through the cover main body portion is maximized when the infrared rays are irradiated on the cover main body portion at an incident angle of 0 degrees. However, as the incident angle increases, the reflectance increases and the transmittance decreases.

[0005] Furthermore, this phenomenon can also occur when infrared light is shone onto the cover body, which is significantly inclined with respect to the vertical and horizontal planes. Therefore, various infrared sensor covers have been proposed that can suppress the decrease in transmittance that occurs with increasing incident angles. For example, in the infrared sensor cover described in Patent Document 1, the reflection suppression layer is formed such that the thickness of the reflection suppression layer at any position where the incident angle is 45 degrees or more and 60 degrees or less is k times the thickness of the reflection suppression layer at the position where the incident angle is 0 degrees. In the above infrared sensor cover, the thickness of the reflection suppression layer gradually increases as the incident angle increases. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-173264 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in the infrared sensor cover described in Patent Document 1, it is difficult to deposit a reflection suppression layer such that the film thickness gradually increases as the incident angle increases. [Means for solving the problem]

[0008] The following describes various embodiments of an infrared sensor cover designed to solve the above problems. [Aspect 1] An infrared sensor cover applied to an infrared sensor comprising a transmitting unit that transmits infrared rays toward the outside of a vehicle and a receiving unit that receives the infrared rays reflected after hitting an object on the outside, and covering the transmitting unit and the receiving unit from the front in the direction of infrared radiation transmission, comprising a cover body that is transparent to infrared rays, the cover body comprising a reflection suppression layer that suppresses the reflection of the irradiated infrared rays, the reflection suppression layer constituting at least one of both sides of the cover body in the direction of transmission and having a uniform thickness, and the reflection suppression layer being formed such that the transmittance of the infrared rays passing through the cover body is maximized when the infrared rays are irradiated onto the reflection suppression layer at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0009] Here, assuming that the reflection suppression layer is formed such that the transmittance of infrared radiation in the cover body is maximized when infrared radiation is irradiated onto the reflection suppression layer at an incident angle of 0 degrees, then the transmittance of infrared radiation irradiated at an incident angle of 0 degrees will be maximized. The transmittance of infrared radiation irradiated at an incident angle greater than 0 degrees decreases as the incident angle increases.

[0010] In contrast, by forming a reflection suppression layer that satisfies the conditions described in [Aspect 1] above, the transmittance of infrared radiation irradiated at any angle of incidence within the range of 30 degrees or more and 60 degrees or less is maximized.

[0011] Furthermore, the transmittance of infrared radiation irradiated at an incident angle within the range of 0 degrees or more and less than 30 degrees is lower than when infrared radiation is irradiated through a reflection suppression layer that is formed to maximize infrared transmittance when irradiated at an incident angle of 0 degrees. However, the degree of decrease in transmittance is only a few percent.

[0012] Furthermore, among infrared radiation irradiated at an incident angle within the range of 30 degrees or more and 60 degrees or less, the transmittance of infrared radiation irradiated at an incident angle where the transmittance is not maximized is as high as the transmittance of infrared radiation irradiated at an incident angle where the transmittance is maximized. The transmittance at this incident angle is higher than when infrared radiation is irradiated at the aforementioned angular range against a reflection suppression layer that is formed so that the transmittance of infrared radiation is maximized when irradiated at an incident angle of 0 degrees.

[0013] Therefore, it is possible to increase the transmittance when infrared light is irradiated onto the reflection suppression layer at any angle of incidence within a wide range of angles from 0 degrees to 60 degrees. Furthermore, the reflection suppression layer exhibits the above-mentioned functions and effects while having a uniform thickness. Therefore, unlike the infrared sensor cover described in Patent Document 1, the reflection suppression layer does not need to be formed so that its thickness gradually increases as the incident angle increases. Compared to the infrared sensor cover described in Patent Document 1, the reflection suppression layer can be formed more easily.

[0014] [Aspect 2] The infrared sensor cover according to [Aspect 1], wherein the reflection suppression layer is located at the rearmost part of the cover body in the transmission direction. According to the above configuration, the rearmost part of the cover body where the reflection suppression layer is provided is the area to which infrared light transmitted from the infrared sensor's transmitter is irradiated. Therefore, the amount of infrared light reflected by the reflection suppression layer after transmission from the transmitter is reduced, and the amount of infrared light transmitted through the cover body forward in the transmission direction is increased. When this reflection suppression layer is formed to satisfy the conditions described in [Aspect 1] above, it is possible to increase the transmittance of the reflection suppression layer when infrared light is irradiated from the rear in the transmission direction at any angle of incidence within the angular range of 0 degrees to 60 degrees.

[0015] [Aspect 3] The infrared sensor cover according to [Aspect 1] or [Aspect 2], wherein the reflection suppression layer is composed of a dielectric multilayer film formed by stacking a plurality of dielectric thin films, each having a uniform thickness, and the thickness of each of the plurality of dielectric thin films is set to a value that maximizes the transmittance of the infrared light that passes through the cover body when the infrared light is irradiated onto the reflection suppression layer at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0016] When a dielectric multilayer film, which is formed by stacking multiple dielectric thin films, each having a uniform thickness, is used as a reflection suppression layer, a correlation is observed between the incident angle at which transmittance is maximized and the film thickness of each dielectric thin film. Furthermore, when the film thickness of each dielectric thin film is set to a value that satisfies the conditions described in [Aspect 3] above, the transmittance is maximized when infrared light is irradiated onto the reflection suppression layer at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0017] Furthermore, since each of the multiple dielectric thin films has a uniform thickness, each dielectric thin film does not need to be formed in such a way that its thickness gradually increases as the angle of incidence increases. Compared to the infrared sensor cover described in Patent Document 1, each dielectric thin film, and consequently the reflection suppression layer, can be formed more easily.

[0018] [Aspect 4] The infrared sensor cover according to any one of [Aspect 1] to [Aspect 3], wherein the reflection suppression layer is formed such that when the infrared light is irradiated onto the reflection suppression layer at an incident angle within the angular range of 0 degrees or more and 60 degrees or less, the transmittance of the infrared light that passes through the cover body is 90% or more.

[0019] According to the above configuration, when infrared light is irradiated onto the reflection suppression layer formed to satisfy the conditions described in [Aspect 4] above at any incident angle within the angular range of 0 degrees to 60 degrees, the transmittance becomes 90% or more. Therefore, it is possible to enable the infrared sensor to perform detection with higher detection accuracy. [Effects of the Invention]

[0020] According to the present invention, it is possible to easily suppress the decrease in the infrared transmittance in the cover main body portion as the incident angle increases.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a partial side cross-sectional view showing an infrared sensor and an infrared sensor cover respectively arranged on the upper part (roof) of a vehicle in one embodiment. [Figure 2] FIG. 2 is a side cross-sectional view schematically showing the infrared sensor in the above embodiment. [Figure 3] FIG. 3 is a plan view showing the vehicle in the above embodiment together with the horizontal angle range of the infrared rays transmitted while changing the transmission direction. [Figure 4] FIG. 4 is an explanatory view showing an enlarged cross-sectional structure of a part of the cover main body portion in the above embodiment and schematically showing the infrared sensor. [Figure 5] FIG. 5 is a graph showing the results of measuring the transmittance for each incident angle of infrared rays. [Figure 6] FIG. 6 is a plan cross-sectional view showing a modification example of an infrared sensor cover separate from the infrared sensor. [Figure 7] FIG. 7 is a plan cross-sectional view showing another modification example of an infrared sensor cover separate from the infrared sensor. [Figure 8] FIG. 8 is a side cross-sectional view schematically showing an infrared sensor having a modified infrared sensor cover as a part of itself. [Figure 9] FIG. 9 is a partial side cross-sectional view showing a modification example of an infrared sensor cover having a glass of a vehicle as a part of its constituent members. [Figure 10] FIG. 10 is also a partial side cross-sectional view showing a modification example of an infrared sensor cover having a glass of a vehicle as a part of its constituent members. [Figure 11] FIG. 11 is a partial side cross-sectional view showing a modification example of an infrared sensor cover formed by being incorporated into a glass of a vehicle. [Modes for carrying out the invention]

[0022] Hereinafter, an embodiment of the present invention applied to an infrared sensor cover for vehicles will be described with reference to Figures 1 to 5. In the following description, the forward direction of vehicle 10 will be referred to as "forward," and the reverse direction as "rear." The vertical direction refers to the vertical direction of vehicle 10. The left-right direction refers to the vehicle width direction and coincides with the left-right direction when vehicle 10 is moving forward.

[0023] <Superstructure of vehicle 10> As shown in Figures 1 and 3, vehicle 10, as an example of a vehicle, is equipped with a plate-shaped roof member 11 on its upper part. The roof member 11 constitutes at least a part of the roof located above the passenger compartment of vehicle 10. The roof member 11 plays a role in protecting the occupants from rain, wind, snow, sunlight, etc.

[0024] In the front part of the roof member 11, a bulge portion 12 is formed in the central part in this embodiment, which bulges upward in the left-right direction. The bulge portion 12 has a space portion 13 inside. The bulge portion 12 has an inclined portion 14 at its front end that is steeply inclined with respect to the vertical plane and the horizontal plane, respectively, so that it is located further forward towards the bottom. The inclined portion 14 has a window portion 15 that connects the space portion 13 inside the bulge portion 12 to the outside of the bulge portion 12, in this case the space portion in front.

[0025] The infrared sensor 21 and infrared sensor cover 30 are located on the upper part (roof) of the vehicle 10, including the bulging portion 12. Next, each part will be described. <Infrared sensor 21> The infrared sensor 21 is a sensor for monitoring the area in front and to the front side. In this embodiment, a LiDAR (Light Detection and Ranging) device is used as the infrared sensor 21. At least a part of the infrared sensor 21, and in this embodiment the whole, is located within the bulge 12 and behind the window 15. In other words, the entire infrared sensor 21 is located above the roof member 11.

[0026] As shown in Figure 2, the rear half of the outer shell of the infrared sensor 21 is made up of a case 22 with an open front end. The front half of the outer shell is made up of a cover 25. Inside the case 22 are the infrared IR transmitter 23 and receiver 24.

[0027] The transmitting unit 23 transmits infrared (IR) light with a wavelength of approximately 900 nm toward the outside of the vehicle 10. In the left-right direction, the transmitting unit 23 transmits while changing the transmission direction within a predetermined angular range R1, as shown in Figure 3. In the up-down direction, the transmitting unit 23 transmits while changing the transmission direction within a predetermined angular range R2, as shown in Figure 1.

[0028] As shown in Figure 2, the receiving unit 24 receives infrared IR reflected from objects outside the vehicle (not shown), including preceding vehicles and pedestrians. The infrared sensor 21 recognizes the object based on the transmitted infrared IR and the received infrared IR, and also detects the distance and relative speed between the vehicle 10 and the object.

[0029] As mentioned above, since the infrared sensor 21 transmits infrared (IR) signals toward the front of the vehicle 10, the direction of transmission of infrared (IR) signals by the infrared sensor 21 is from the rear to the front of the vehicle 10. The front direction in the infrared (IR) transmission direction roughly coincides with the front of the vehicle 10, and the rear direction in the same transmission direction roughly coincides with the rear of the vehicle 10. Therefore, in the following description, the front direction in the infrared (IR) transmission direction will simply be referred to as "front," "front," etc., and the rear direction in the same transmission direction will simply be referred to as "rear," "back," etc.

[0030] The cover 25 is positioned on the front side of the case 22, thereby covering the transmitting unit 23 and the receiving unit 24 from the front. <Infrared sensor cover 30> As shown in Figures 1 and 4, the infrared sensor cover 30 in this embodiment is provided separately from the infrared sensor 21. The infrared sensor cover 30 is attached to the inclined portion 14 with the window portion 15 closed. Therefore, the infrared sensor cover 30 is inclined significantly with respect to the vertical and horizontal planes, so that it is positioned further forward towards the bottom of the infrared sensor 21.

[0031] The skeletal structure of the infrared sensor cover 30 is composed of a cover body 31 that is transparent to infrared rays (IR). The cover body 31 is positioned in front of the infrared sensor 21, thereby indirectly covering the transmitting unit 23 and the receiving unit 24 from the front via the cover 25 (see Figure 2) of the infrared sensor 21.

[0032] The infrared sensor cover 30 is equipped with a mounting portion (not shown) in addition to the cover body portion 31. The infrared sensor cover 30 is attached to the inclined portion 14 of the bulging portion 12 by screw fastening, claw fitting, etc., at the mounting portion.

[0033] The infrared sensor cover 30 not only functions as a garnish to decorate the upper part of the vehicle 10 by covering the transmitter 23 and receiver 24 from the front, but also has the function of protecting the transmitter 23 and receiver 24 from impacts and the like.

[0034] As shown in Figure 4, the cover body 31 comprises a base material 32 that transmits infrared rays (IR), a hard coat layer 33, a protective layer 34, and a reflection suppression layer 35. The cover body 31 is flat and has a uniform thickness. Next, each part will be described.

[0035] The base material 32 is flat and forms the skeletal portion of the cover body 31. The base material 32 is made of PC (polycarbonate) resin, but may also be made of an acrylic resin such as PMMA (polymethyl methacrylate) resin. In this embodiment, the base material 32 is made of a material-coated resin material that is mainly composed of PC and colored black or the like by mixing a coloring agent such as a pigment with the PC.

[0036] The hard coat layer 33 is formed by applying, for example, an acrylic paint to the front surface of the substrate 32. The hard coat layer 33 has a higher hardness than the substrate 32. The front surface of the hard coat layer 33 constitutes the front surface of the cover body 31 and also constitutes the design surface of the infrared sensor cover 30. The hard coat layer 33 may be made of a hard coat film having a higher hardness than the substrate 32.

[0037] The reflection suppression layer 35 constitutes at least one of the two surfaces of the cover body 31 in the transmission direction. In this embodiment, the reflection suppression layer 35 is located at the rearmost part of the cover body 31, so that the rear surface 35r of the reflection suppression layer 35 constitutes the rear surface of the cover body 31. The reflection suppression layer 35 has a uniform thickness. The reflection suppression layer 35 reduces the reflection of infrared IR transmitted from the transmission unit 23 by interference with the same infrared IR, and has the function of suppressing the reduction in the amount of infrared IR transmitted through the cover body 31 due to reflection.

[0038] In this embodiment, the reflection suppression layer 35 is composed of a dielectric multilayer film, but it may be composed of a different film. The dielectric multilayer film is a film formed by alternately stacking a dielectric thin film 36 made of a high refractive index material and a dielectric thin film 37 made of a low refractive index material having a lower refractive index than the dielectric thin film 36 by vacuum deposition, sputtering, wet coating, etc. In this embodiment, the reflection suppression layer 35 is formed by alternately stacking a dielectric thin film 36 made of silica and a dielectric thin film 37 made of niobia, but this is just one example, and the dielectric thin films 36 and 37 may be formed of other materials. The dielectric thin films 36 and 37 each have a uniform thickness.

[0039] Thus, when dielectric thin films 36 and 37 are used as reflection suppression layers 35, a correlation can be observed between the incident angle at which the transmittance of infrared rays (IR) in the cover body portion 31 is maximized and the thickness of each dielectric thin film 36 and 37.

[0040] In other words, when infrared (IR) light is irradiated onto each dielectric thin film 36, 37 of the reflection suppression layer 35, the infrared (IR) light is transmitted through or reflected at one interface in the thickness direction of each dielectric thin film 36, 37, i.e., the irradiated interface. The transmitted infrared (IR) light reaches the other interface of the dielectric thin film 36, 37, i.e., the unirradiated interface, and is transmitted or reflected again. The amount of infrared (IR) light transmitted or reflected at each interface can be quantitatively expressed by Fresnel's equation. When the thickness of each dielectric thin film 36, 37 becomes an odd multiple of 1 / 4 wavelength of the infrared (IR) light, the reflected waves generated at both interfaces interfere and cancel each other out. The reflection of infrared (IR) light in the reflection suppression layer 35 is suppressed. The thickness of each dielectric thin film 36, 37 depends on both the refractive index of the dielectric thin films 36, 37 and the angle of incidence of the infrared (IR) light.

[0041] Furthermore, taking the above points into consideration, in this embodiment, the thickness of each dielectric thin film 36 and 37 is formed such that the following conditions are met in relation to the incident angle of infrared IR and the transmittance of infrared IR in the cover body 31.

[0042] Condition 1: The value must be such that the transmittance is maximized when infrared (IR) light is irradiated onto the reflection suppression layer 35 at an incident angle within the range of 30 degrees or more and 60 degrees or less. Condition 2: The value must be such that the transmittance is 90% or more when infrared (IR) light is irradiated onto the reflection suppression layer 35 at an incident angle within the range of 0 degrees to 60 degrees.

[0043] The protective layer 34 is formed between the substrate 32 and the anti-reflection layer 35. The protective layer 34 has the function of improving the adhesion of the anti-reflection layer 35 to the substrate 32. In this embodiment, the protective layer 34 is formed by applying a UV-curable acrylic resin to the rear surface of the substrate 32.

[0044] <Operation of this embodiment> As shown in Figures 1 to 3, when infrared (IR) is transmitted from the transmitter 23 of the infrared sensor 21, the infrared (IR) is irradiated from the rear onto the cover body 31 of the infrared sensor cover 30 and passes through the cover body 31 toward the front. The infrared (IR) that has passed through the cover body 31 hits an object outside the vehicle 10 and is reflected, and then irradiated again onto the cover body 31 from the front and passes through the cover body 31 toward the rear. The infrared (IR) that has passed through the cover body 31 is received by the receiver 24.

[0045] As shown in Figure 4, in this embodiment, the reflection suppression layer 35 is located at the rearmost part of the cover body 31. This is the part of the cover body 31 that is irradiated with infrared IR transmitted from the infrared sensor 21's transmitting unit 23. As a result, the amount of infrared IR reflected by the reflection suppression layer 35 after transmission from the transmitting unit 23 is reduced, and the amount of infrared IR transmitted forward through the cover body 31 is increased. Compared to a case where the reflection suppression layer 35 is not provided, the amount of infrared IR transmitted forward through the cover body 31 is increased.

[0046] Here, Figure 5 shows the results of measuring the relationship between the incident angle of infrared (IR) on the cover body and the infrared (IR) transmittance in the cover body. Characteristic line L1 in Figure 5 shows the measurement results for measurement target 1. Characteristic line L2 shows the measurement results for measurement target 2. Characteristic line L3 shows the measurement results for measurement target 3.

[0047] Measurement target 1: An infrared sensor cover whose main body is composed solely of a base material 32. For this measurement target 1, infrared IR is irradiated onto the rear surface of the base material 32. Measurement target 2: An infrared sensor cover whose main body is composed of a substrate 32, a hard coat layer 33, a protective layer 34, and a reflection suppression layer 35. The thickness of each of the multiple dielectric thin films 36 and 37 in the reflection suppression layer 35 is set to be uniform. Furthermore, the thickness of each dielectric thin film 36 and 37 is set to the value that maximizes the infrared IR transmittance in the main body of the cover when infrared IR is irradiated onto the reflection suppression layer 35 at an incident angle of 0 degrees.

[0048] Measurement target 3: The infrared sensor cover 30 of the above embodiment. That is, as shown in Figure 4, the infrared sensor cover 30 is composed of a cover body 31 made up of a substrate 32, a hard coat layer 33, a protective layer 34, and a reflection suppression layer 35. The thickness of each of the multiple dielectric thin films 36, 37 in the reflection suppression layer 35 is set to be uniform. Furthermore, the thickness of each dielectric thin film 36, 37 is set to a value that maximizes the transmittance of infrared IR in the cover body 31 when infrared IR is irradiated onto the reflection suppression layer 35 at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0049] In measurement target 3, the film thickness of each dielectric thin film 36, 37 is set to the value that maximizes transmittance when infrared IR is irradiated onto the reflection suppression layer 35 from behind at an incident angle of 60 degrees. Specifically, of the two dielectric thin films 36, the film thickness of the dielectric thin film 36 closer to the substrate 32 is set to 100 nm, and the film thickness of the dielectric thin film 36 further away from the substrate 32 is set to 200 nm. Also, of the two dielectric thin films 37, the film thickness of the dielectric thin film 37 closer to the substrate 32 is set to 30 nm, and the film thickness of the dielectric thin film 37 further away from the substrate 32 is set to 80 nm.

[0050] The characteristic curve L1 reveals the following: The transmittance of infrared (IR) irradiated onto measurement target 1 at an incident angle of 0 degrees is at its maximum (a few percent lower than 90%). The transmittance of infrared (IR) irradiated onto measurement target 1 at an incident angle greater than 0 degrees decreases with increasing incident angle. More specifically, the transmittance of infrared (IR) irradiated onto measurement target 1 at an incident angle greater than 0 degrees but less than 30 degrees decreases gradually with increasing incident angle. The transmittance of infrared (IR) irradiated onto measurement target 1 at an incident angle of 30 degrees or more but less than 70 degrees decreases with increasing incident angle to a greater extent than the transmittance of infrared (IR) irradiated at an incident angle greater than 0 degrees but less than 30 degrees. The transmittance of infrared (IR) irradiated onto measurement target 1 at an incident angle of 70 degrees is less than 70%.

[0051] The following can be observed from characteristic curve L2: Characteristic curve L2 shows a similar trend to characteristic curve L1. That is, the transmittance of infrared (IR) irradiated onto measurement target 2 at an incident angle of 0 degrees is at its maximum (close to 95%). The transmittance of infrared (IR) irradiated onto measurement target 2 at an incident angle greater than 0 degrees decreases as the incident angle increases. More specifically, the transmittance of infrared (IR) irradiated onto measurement target 2 at an incident angle greater than 0 degrees and less than 30 degrees decreases gradually as the incident angle increases. The transmittance of infrared (IR) irradiated onto measurement target 2 at an incident angle of 30 degrees is higher than 90%. The transmittance of infrared (IR) irradiated onto measurement target 2 at an incident angle greater than 30 degrees and less than 70 degrees decreases to a greater extent as the incident angle increases than the transmittance of infrared (IR) irradiated at an incident angle greater than 0 degrees and less than 30 degrees. The transmittance of infrared (IR) irradiated onto measurement target 2 at an incident angle of 70 degrees is close to 70%.

[0052] However, the reflection suppression layer 35 on measurement target 2 targets all infrared IR irradiated onto measurement target 2 at an incident angle of 0 degrees or more and 70 degrees or less, and suppresses the reflection of those infrared IR. The amount of infrared IR transmitted through the cover body of measurement target 2 will be greater than the amount of infrared IR transmitted through measurement target 1, regardless of the incident angle within the above angular range (0 degrees or more and 70 degrees or less). Therefore, when infrared IR is irradiated onto measurement target 1 and measurement target 2 at the same incident angle, the transmittance of infrared IR in measurement target 2 will be higher than the transmittance of infrared IR in measurement target 1.

[0053] The characteristic curve L3 reveals the following: When infrared (IR) light is irradiated onto the reflection suppression layer 35 of measurement object 3 at an incident angle of 0 degrees, the transmittance of the infrared (IR) light is slightly higher than 90%. Furthermore, when infrared (IR) light is irradiated onto measurement object 3 at an incident angle greater than 0 degrees and less than 30 degrees, the transmittance is lower than when infrared (IR) light is irradiated onto the reflection suppression layer 35 of measurement object 2 at the same incident angle. However, within the above angular range (greater than 0 degrees and less than 30 degrees), when infrared (IR) light is irradiated onto the reflection suppression layer 35 of measurement object 3, the deviation from the transmittance of measurement object 2 gradually decreases as the incident angle increases. When irradiated at an incident angle of 30 degrees, the above deviation becomes approximately 0.

[0054] For measurement target 3, the transmittance of infrared (IR) irradiated at an incident angle within the angular range of 30 degrees or more and 60 degrees or less will be maximized. Characteristic line L3 will have a characteristic where the incident angle at which the transmittance is maximized is shifted to the larger incident angle side compared to characteristic line L2.

[0055] Furthermore, among infrared IR irradiated at an incident angle within the angular range of 30 degrees or more and 60 degrees or less, the transmittance of infrared IR irradiated at an incident angle where the transmittance is not maximized is as high as the transmittance of infrared IR irradiated at an incident angle where the transmittance is maximized. The transmittance at this incident angle is higher for the reflection suppression layer 35 of measurement target 2 than when infrared IR is irradiated at the same incident angle as for the reflection suppression layer 35 of measurement target 3 (characteristic line L2).

[0056] Furthermore, characteristic line L3 indicates that when infrared IR is irradiated onto the reflection suppression layer 35 at any incident angle within the angular range of 0 degrees or more and 60 degrees or less, the transmittance of infrared IR passing through the cover body 31 is 90% or more.

[0057] <Effects of this embodiment> (1) As shown in Figure 4, the reflection suppression layer 35 constitutes at least one of the two surfaces of the cover body 31 in the transmission direction.

[0058] Therefore, the transmittance can be increased compared to when the reflection suppression layer 35 is not provided (see characteristic line L1 in Figure 5) (see characteristic lines L2 and L3 in Figure 5). This effect can be obtained when infrared IR is irradiated at any incident angle between 0 degrees and 70 degrees.

[0059] (2) The reflection suppression layer 35 is formed such that the transmittance of infrared IR passing through the cover body 31 is maximized when infrared IR is irradiated at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0060] Therefore, as shown by the characteristic line L3 in Figure 5, the transmittance can be increased regardless of the angle of incidence of the infrared IR irradiated onto the reflection suppression layer 35, within the angular range of 0 degrees or more and 60 degrees or less.

[0061] These effects are obtained when infrared (IR) light is transmitted to the cover body 31 while changing the transmission direction within angular ranges R1 and R2 in the left-right and up-down directions, respectively. Furthermore, as shown in Figure 1, the above effects are similarly obtained when infrared (IR) light is transmitted to the cover body 31 which is significantly inclined with respect to the vertical and horizontal planes.

[0062] (3) Since the reflection suppression layer 35 in Figure 4 has a uniform thickness, it does not need to be formed so that its thickness gradually increases as the angle of incidence increases. Therefore, the reflection suppression layer 35 can be formed more easily than in the infrared sensor cover described in Patent Document 1.

[0063] (4) As shown in Figure 4, the location on the cover body 31 where the reflection suppression layer 35 is provided is the rearmost part of the cover body 31, which is the location where infrared IR transmitted from the infrared sensor 21's transmitting unit 23 is irradiated.

[0064] Therefore, as shown by the characteristic line L3 in Figure 5, the transmittance can be increased even when infrared IR is irradiated from behind at any angle within the angular range of 0 degrees or more and 60 degrees or less to the reflection suppression layer 35 at the rearmost part of the cover body 31.

[0065] (5) As shown in Figure 4, the reflection suppression layer 35 is composed of a dielectric multilayer film made by stacking a plurality of dielectric thin films 36, 37, each having a uniform thickness. In this dielectric multilayer film, a correlation is observed between the incident angle at which the transmittance is maximized and the thickness of each dielectric thin film 36, 37. The thickness of each dielectric thin film 36, 37 is set to a value that maximizes the transmittance of infrared IR when infrared IR is irradiated onto the reflection suppression layer 35 at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0066] Therefore, by setting the film thickness as described above, the transmittance of infrared IR can be increased regardless of the angle of incidence within the above angular range (30 degrees or more and 60 degrees or less) when infrared IR is irradiated onto the reflection suppression layer 35.

[0067] Furthermore, since each of the multiple dielectric thin films 36 and 37 has a uniform thickness, each dielectric thin film 36 and 37 does not need to be formed in such a way that its thickness gradually increases as the angle of incidence increases. Therefore, each dielectric thin film 36 and 37, and consequently the reflection suppression layer 35, can be formed more easily than in the infrared sensor cover described in Patent Document 1.

[0068] (6) The reflection suppression layer 35 is formed such that when infrared IR is irradiated onto the reflection suppression layer 35 at an incident angle within the angular range of 0 degrees or more and 60 degrees or less, the transmittance of infrared IR that passes through the cover body 31 is 90% or more.

[0069] Therefore, infrared IR transmitted from the transmitting unit 23 of the infrared sensor 21 and incident on the reflection suppression layer 35 at any incident angle within the above angular range (0 degrees or more and 60 degrees or less) can be transmitted through the cover body 31 with a transmittance of 90% or more. As a result, the infrared sensor 21 can perform detection with higher detection accuracy.

[0070] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0071] (Matters concerning base material 32) In Figure 4, the substrate 32 is preferably black in terms of aesthetics and noise suppression. However, the substrate 32 may be colored with a color other than black, as long as the impact on the performance of the infrared sensor 21 is within an acceptable range.

[0072] (Matters concerning the reflection suppression layer 35) In the above embodiment, the reflection suppression layer 35 is composed of a dielectric multilayer film formed by stacking multiple dielectric thin films 36, 37. The materials of the dielectric thin films 36, 37, the number of layers, etc., may be changed to something different from those described above.

[0073] The reflection suppression layer 35 in Figure 4 may be located at the very front of the cover body 31 instead of at the very rear, or in addition to at the very front. The same modification may be made to the cover body 31 in the modified example of Figure 11 described later. When the reflection suppression layer 35 is located at the very front of the cover body 31, the front surface of the reflection suppression layer 35 constitutes the front surface of the cover body 31 and also constitutes the design surface of the infrared sensor cover 30.

[0074] In this modified example, the infrared (IR) light that hits the object and is reflected is irradiated from the front onto the front reflection suppression layer 35. The reflection suppression layer 35 reduces the reflection of the infrared (IR) light irradiated from the front by interference with the same infrared (IR) light, thereby suppressing the reduction in the amount of infrared (IR) light that passes through the reflection suppression layer 35 due to reflection. As a result of this suppression, the amount of infrared (IR) light that passes through the reflection suppression layer 35 from front to back increases. Compared to the case where the reflection suppression layer 35 is not located at the very front of the cover body 31, the amount of infrared (IR) light that passes through the cover body 31 from front to back increases.

[0075] In this modified example, as in the above embodiment, it is preferable that the front reflection suppression layer 35 is formed such that its transmittance is maximized when it is irradiated from the front at an incident angle within the range of 30 degrees or more and 60 degrees or less.

[0076] According to this modified example, although the direction in which infrared IR is incident and transmitted is reversed compared to when the reflection suppression layer 35 is located at the rearmost part of the cover body 31, the same effects as in the above embodiment can be obtained. That is, the decrease in infrared IR transmittance that occurs with increasing incidence angle can be easily suppressed.

[0077] If the required transmittance value at the cover body 31 is lower than 90% when infrared IR is irradiated at any incident angle within the angular range of 0 degrees or more and 60 degrees or less, the reflection suppression layer 35 may be formed to have a value lower than 90%, provided that the required value is met.

[0078] (Matters concerning the main body of the cover 31) Unlike the above embodiment in which the cover body 31 is formed in a flat shape, the cover body 31 may be formed in a curved shape that bulges forward, as shown in Figures 6 and 7. The central portion of the cover body 31 is located at the very front. The portion of the cover body 31 surrounding the central portion (hereinafter referred to as the peripheral portion) is located further back than the central portion. Moreover, the peripheral portion is located further back the further it is from the central portion. The base material 32 is also formed in the same shape as the cover body 31.

[0079] The difference between the modified example in Figure 6 and the modified example in Figure 7 is that in the former, the thickness of the cover body 31 is uniform in both the central and peripheral parts, whereas in the latter, the thickness of the peripheral part gradually decreases as it approaches the periphery. The thickness of the base material 32 is the same as the thickness of the cover body 31.

[0080] Note that in Figures 6 and 7, for convenience, the cover body 31 is shown as being composed of a single layer. However, the cover body 31 has the same layer configuration as in the above embodiment (see Figure 4). The reflection suppression layer 35 has a uniform thickness. The reflection suppression layer 35 constitutes at least one of the two surfaces of the cover body 31 in the transmission direction.

[0081] Here, if the cover body 31 is formed in the same shape as the above embodiment, such as a flat plate with uniform thickness, then as the angle of incidence increases, the amount of infrared radiation (IR) reflected at the interface between the reflection suppression layer 35 and the air increases. Consequently, the amount of infrared radiation (IR) transmitted through the reflection suppression layer 35 and, by extension, the cover body 31 decreases.

[0082] However, in the modified examples shown in Figures 6 and 7, where the cover body 31 is curved to bulge forward, the direction of the infrared (IR) radiation irradiated onto the cover body 31 can be brought closer to the normal (NL) even when the angle of incidence is large. This makes it possible to reduce the degree to which the amount of infrared (IR) transmitted decreases as the angle of incidence increases.

[0083] Furthermore, as shown in Figure 7, if the thickness of the peripheral portion of the cover body 31 gradually decreases as it approaches the periphery, the amount of infrared IR absorption in the peripheral portion can be reduced, and the decrease in transmittance can be suppressed. As a result, the detection accuracy of the infrared sensor 21 can be further improved.

[0084] (Other matters) The infrared sensor cover of the present invention is also applicable when the cover body is not inclined and is arranged parallel to the vertical plane, that is, perpendicular to the horizontal plane.

[0085] The cover 25 of the infrared sensor 21 in Figure 2 may be composed of an infrared sensor cover 40, as shown in Figure 8. In this case, the infrared sensor cover 40 comprises a cylindrical peripheral wall portion 41 positioned on the front side of the case 22 and a plate-shaped cover body portion 31 formed at the front end of the peripheral wall portion 41. The infrared sensor cover 40 is sized to cover the open front portion of the case 22 of the infrared sensor 21. The infrared sensor cover 40 covers the transmitting unit 23 and the receiving unit 24 from the front.

[0086] In Figure 8, the cover body portion 31 of the infrared sensor cover 40 is shown as being composed of a single layer for convenience, but it has the same layer configuration as the cover body portion 31 of the infrared sensor cover 30 in the above embodiment (see Figure 4).

[0087] The configuration other than that described above is the same as in the above embodiment. Therefore, in the modified example in Figure 8, the same reference numerals are used for elements similar to those described in the above embodiment, and redundant explanations are omitted.

[0088] Therefore, although the position of the cover body portion 31 of the infrared sensor cover 40 in the modified example of Figure 8 differs from that of the above embodiment, it is similar to the above embodiment in that it covers the transmitting unit 23 and the receiving unit 24 from the front. For this reason, the same operation and effects as the above embodiment can be obtained with this modified example as well.

[0089] In Figure 4, if the anti-reflective layer 35 can be directly laminated to the rear surface of the substrate 32 in close contact, the protective layer 34 may be omitted from the cover body 31. Also, the hard coat layer 33 may be appropriately omitted from the cover body 31 in Figure 4. These omissions may also be made to the cover body 31 in the modified example of Figure 11, which will be described later.

[0090] The cover body 31 may be formed by adding a new layer to the layer configuration shown in Figure 4. The infrared sensor 21 and infrared sensor covers 30, 40 (hereinafter referred to as "infrared sensor 21, etc.") may be placed in locations different from those in the above embodiment, provided that they are on the upper part (roof) of the vehicle 10. For example, the infrared sensor 21, etc. may be placed at the rear, central, or other locations of the roof member 11 in the front-rear direction.

[0091] The infrared sensor 21, etc., may be positioned on the upper part of the vehicle 10 such that a portion of it is located below the roof member 11. The infrared sensor 21, etc., may be placed in a location different from that of the above embodiment, provided that it is lower than the top (roof) of the vehicle 10.

[0092] In this case, the infrared sensor 21, etc., may be located at the front of the vehicle 10, for example, in the front grille, front bumper, etc. Alternatively, the infrared sensor 21, etc., may be located at the rear of the vehicle 10, for example, in the rear bumper, etc.

[0093] When the infrared sensor 21 is located at the rear of the vehicle 10, the transmitting unit 23 of the infrared sensor 21 transmits infrared IR toward the rear of the vehicle 10. The infrared sensor covers 30 and 40 are located in front of the transmitting unit 23 in the direction of infrared IR transmission, in this case, behind the transmitting unit 23 of the vehicle 10.

[0094] Furthermore, the infrared sensor 21 may be positioned inside the vehicle, close to a window glass (hereinafter simply referred to as "glass") 16 such as the windshield (also called the windshield) or the rear window (also called the back door glass). The windshield is inclined with respect to the vertical and horizontal planes such that the lower part is located further forward. The glass 16 is transparent to infrared rays (IR). Therefore, a part of the glass 16 may be used as part of the infrared sensor cover.

[0095] Figures 9 and 10 show examples of modified infrared sensor covers in which a portion of the glass 16 is used as part of the cover body. The modified example in Figure 9 shows an infrared sensor cover 50 in which a portion of the glass 16 is used as a base material 52, and a reflection suppression layer 35 is formed on the rear side of this base material 52 via a protective layer 34. In this case, the cover body 51 is composed of the base material 52, the protective layer 34, and the reflection suppression layer 35. The base material 52 constitutes the front end of the cover body 31. The cover body 51 is transparent to infrared rays (IR). The dashed line in Figure 3 shows the protective layer 34 and the reflection suppression layer 35 when the infrared sensor 21 is positioned close to the upper part of the windshield (glass 16) from the rear.

[0096] In the modified example shown in Figure 9, if the anti-reflective layer 35 can be directly laminated in close contact with the rear surface of the substrate 52, the protective layer 34 may be omitted from the cover body 51. The modified example in Figure 10 shows an infrared sensor cover 60 in which a film body 63 is placed behind the glass substrate 62, with a portion of the glass 16 used as the glass substrate 62 and having a reflection suppression layer 35 at its rearmost end. The film body 63 comprises a film substrate 64, a reflection suppression layer 35 laminated on the rear side of the film substrate 64 via a protective layer 34, and an adhesive layer 65 formed on the front side of the film substrate 64. The film body 63 is bonded to the rear surface of the glass substrate 62 at the adhesive layer 65. The film substrate 64 and the adhesive layer 65, like the protective layer 34 and the reflection suppression layer 35, are each transparent to infrared rays (IR).

[0097] The cover body 61 is composed of a glass substrate 62 and a film body 63. The glass substrate 62 constitutes the front end of the cover body 61. The film substrate 64 is located in the middle of the cover body 61 in the front-rear direction. The cover body 61 is transparent to infrared rays (IR).

[0098] In the modified example shown in Figure 10, if the anti-reflective layer 35 can be directly laminated in close contact with the rear surface of the film substrate 64, the protective layer 34 may be omitted from the cover body 61.

[0099] The modified example in Figure 9 differs from the above embodiment in that the base material 32 is formed from a resin material, in that the base material 52 is composed of a part of the glass 16, and the modified example in Figure 10 differs from the above embodiment in that the glass base material 62 is composed of a part of the glass 16. However, both modified examples are common to the above embodiment in that they satisfy the following requirements 1 to 3.

[0100] Requirement 1: The cover body portions 51 and 61 have a reflection suppression layer 35 with a uniform thickness. Requirement 2: The reflection suppression layer 35 constitutes the rear surface, which is at least one of the two surfaces of the cover body portions 51 and 61 in the transmission direction.

[0101] Requirement 3: The reflection suppression layer 35 is formed such that the transmittance of infrared IR passing through the cover body 51, 61 is maximized when infrared IR is irradiated at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

[0102] Therefore, the infrared sensor covers 50 and 60 can also provide the same functions and effects as the infrared sensor cover 30 in the above embodiment. As another example in which a portion of the glass 16 is used as part of the infrared sensor cover, as shown in Figure 11, a portion of the glass 16 may be cut out to form a through-hole 72 that penetrates the glass 16 in the front-to-back direction. Then, a cover body portion 31 having a base material 32, a hard coat layer 33, a protective layer 34, and an anti-reflection layer 35 may be placed in this through-hole 72, similar to the embodiment described above.

[0103] The through-hole 72 may be formed at a location away from the peripheral edge of the glass 16. In this case, the through-hole 72 will be surrounded by the glass 16. The main part or all of the infrared sensor cover 70 may be composed of the cover body 31 and the glass 16 surrounding it.

[0104] Therefore, this infrared sensor cover 70 can obtain the same functions and effects as the infrared sensor cover 30 of the above embodiment. Furthermore, a portion of the peripheral edge of the through-hole 72 may be made of sheet metal (not shown) placed on the peripheral edge of the glass 16. In this case, the through-hole 72 will be surrounded by the glass 16 and the sheet metal. The main body portion 31 and the surrounding glass 16 and sheet metal constitute the main or entirety of the infrared sensor cover 70.

[0105] The glass 16 in the infrared sensor covers 50, 60, and 70 described above may be made of inorganic glass or organic glass. The infrared sensor 21 and the like may be installed in a vehicle of a different type than the vehicle 10, such as a train, aircraft, or ship. [Explanation of symbols]

[0106] 10…Vehicle (vehicle) 21…Infrared sensor 23...Transmitter 24... Receiver 30, 40, 50, 60, 70… Infrared sensor cover 31, 51, 61... Cover body 35...Reflection suppression layer 35r…Rear side (side) 36, 37… Dielectric thin films IR...Infrared R1...Angle range

Claims

1. This infrared sensor cover is applied to an infrared sensor comprising a transmitting unit that transmits infrared rays toward the outside of a vehicle and a receiving unit that receives the infrared rays reflected after hitting an object on the outside, and covers the transmitting unit and the receiving unit from the front in the direction of infrared radiation transmission. The cover body portion having infrared transparency is provided, The cover body is equipped with a reflection suppression layer that suppresses the reflection of the irradiated infrared rays, The reflection suppression layer constitutes at least one of the two surfaces of the cover body in the transmission direction and has a uniform thickness. An infrared sensor cover in which the reflection suppression layer is formed such that the transmittance of the infrared light passing through the cover body is maximized when the infrared light is irradiated onto the reflection suppression layer at an incident angle within the range of 30 degrees or more and 60 degrees or less.

2. The infrared sensor cover according to claim 1, wherein the reflection suppression layer is located at the rearmost part of the cover body in the transmission direction.

3. The reflection suppression layer is composed of a dielectric multilayer film formed by stacking multiple dielectric thin films, each having a uniform thickness. The infrared sensor cover according to claim 1, wherein the thickness of each of the plurality of dielectric thin films is set to a value that maximizes the transmittance of the infrared light that passes through the cover body when the infrared light is irradiated onto the reflection suppression layer at an incident angle within the angular range of 30 degrees or more and 60 degrees or less.

4. An infrared sensor cover according to any one of claims 1 to 3, wherein the reflection suppression layer is formed such that when the infrared light is irradiated onto the reflection suppression layer at an incident angle within the angular range of 0 degrees or more and 60 degrees or less, the transmittance of the infrared light that passes through the cover body is 90% or more.

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