radar equipment

Abstract

To provide a radar device which can effectively suppress attenuation, reflection, and multiple reflection of a radar wave so as to have highly-accurate radar functions such as small noise and a large dynamic range.SOLUTION: A radar device includes: a radar unit 15 having an antenna; and a shielding member 18 which covers at least a part of a front surface of the radar unit 15 having the antenna and which is made of a foamed resin. The shielding member 18 contains carbon of weight ratio of 3% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to radar devices, and more particularly to radar devices mounted on vehicles. [Background technology]

[0002] For driver assistance and autonomous driving, various sensors are used, including accelerometers and GPS sensors, as well as cameras, LiDAR (Light Detection and Ranging), and millimeter-wave sensors.

[0003] In particular, millimeter-wave radar maintains high object detection performance without being affected by environmental factors such as nighttime or backlighting, or adverse weather conditions such as dense fog, rain, and snow. Furthermore, it can directly detect the distance, direction, and relative velocity to an object. Therefore, it has the characteristic of being able to detect even nearby objects quickly and with high accuracy.

[0004] A vehicle lighting fixture has been proposed that incorporates a millimeter-wave radar inside the lighting chamber and includes a light guide member that transmits millimeter waves between the front cover and the millimeter-wave radar (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4842161 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when a light guide is placed in front of a millimeter-wave radar, the electromagnetic waves emitted from the millimeter-wave radar are reflected and absorbed by the light guide due to the dielectric constant and dielectric loss tangent of the light guide, causing a decrease in the radiated power of the electromagnetic waves and significantly reducing the detection performance of the millimeter-wave radar.

[0007] Therefore, while it is possible to improve the appearance of a vehicle by using light guide components (such as light guide rods) typically used in automobile headlights, this can lead to a loss of radar functionality.

[0008] The present invention has been made in view of the above-mentioned points, and aims to provide a radar device that can effectively suppress attenuation, reflection, and multiple reflection of radar waves, has low noise, and possesses high-precision radar functions such as a large dynamic range.

[0009] Furthermore, the objective is to provide a radar device that does not alter the radar wave emission pattern and has an extension that makes the radar unit difficult to see from the outside. [Means for solving the problem]

[0010] One Embodiment of the Present Invention The radar device comprises a radar unit having an antenna and a shielding member covering at least a portion of the front surface of the radar unit on which the antenna is provided, wherein the shielding member is made of a resin selected from polycarbonate resin, acrylic resin, polyimide resin, and epoxy resin, and is a foamed resin having air bubbles in the resin, wherein the foamed resin has a reduced dielectric constant compared to a foamed resin without air bubbles, the air bubble ratio of the foamed resin is 50% or more, the shielding member has a thickness of less than or equal to the power half-depth of the electromagnetic waves radiated by the radar unit, and the power half-depth of the shielding member is longer than the power half-depth of the shielding member without air bubbles.

[0011] Other embodiments of the present invention The lamp device comprises a lamp housing composed of a base, a transparent cover held by the base, a lamp unit built into the lamp housing, a radar unit having an antenna built into the lamp housing, and a shielding member covering the front surface of the radar unit on which the antenna is provided. The shielding member is made of a resin selected from polycarbonate resin, acrylic resin, polyimide resin, and epoxy resin, and is a foamed resin having air bubbles in the resin. The foamed resin has a lower dielectric constant compared to a foamed resin without air bubbles, and the air bubble ratio of the foamed resin is 50% or more. The shielding member has a thickness of less than or equal to the power half-depth of the electromagnetic waves radiated by the radar unit, and the power half-depth of the shielding member is longer than the power half-depth of the shielding member without air bubbles. [Brief explanation of the drawing]

[0012] [Figure 1] This figure schematically shows an example of the internal structure of a lamp device according to one embodiment of the present invention. [Figure 2] This is a perspective view showing the arrangement of the millimeter-wave radar unit 15 and the shielding member 18. [Figure 3A] This figure shows the view of the shielding member 18 from the antenna surface 15S side of the millimeter-wave radar unit 15. [Figure 3B] This diagram schematically shows a cross-section of the millimeter-wave radar unit 15 and the shielding member 18. [Figure 3C] This figure shows a shielding member 18 that covers the entire electromagnetic wave transmission / reception area 15R, which is a part of the front surface of the millimeter-wave radar unit 15. [Figure 4] This is a cross-sectional view showing the case where a shielding member is placed in front of the antenna surface 15S of the millimeter-wave radar 15. [Figure 5] This is a partial enlarged cross-sectional view showing a part of the cross-section of the shielding member 18 of the present embodiment. [Figure 6] This is a perspective view schematically showing the shielding member 18 which is a modification example of the present embodiment. [Figure 7] This is a diagram for explaining the reflection suppression effect by the shielding member 18 of the present embodiment. [Figure 8A] This is a plan view schematically showing the arrangement configuration of the millimeter-wave radar unit 15, the shielding member 18, and the transparent cover 12 in another embodiment of the present invention. [Figure 8B] This is a cross-sectional view schematically showing the arrangement configuration of the millimeter-wave radar unit 15, the shielding member 18, and the transparent cover 12 as seen from the line W-W in FIG. 8A.

Mode for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be described, but these may be appropriately modified or combined and applied. Also, in the following description and the accompanying drawings, substantially the same or equivalent parts will be denoted by the same reference numerals and described.

[0014] FIG. 1 is a diagram schematically showing an example of the internal structure of a lamp device 10 according to an embodiment of the present invention. The lamp device 10 is, for example, a headlamp mounted on a vehicle such as an automobile. FIG. 1 schematically shows a cross-section in a horizontal plane (or a plane parallel to the road surface) when the lamp device 10 (left headlamp) mounted on the left front of the vehicle is viewed from above.

[0015] In the lamp device 10, the lamp housing is composed of a base 11 and a transparent cover 12 held by the base 11. Inside the lamp housing are a headlight unit 14, which is a lamp unit (light source), a millimeter-wave radar unit 15, a light-emitting unit 16, a shielding member 18, and an extension 19. The shielding member 18 is a type of extension member that makes the millimeter-wave radar unit 15 difficult to see from the outside. In this specification, the device consisting of the radar unit 15 and the shielding member 18 is referred to as a radar device.

[0016] In this specification, the term "lamp unit" refers not only to headlights but also to any light source that has the purpose or function of emitting light outwards, such as taillights and backlights.

[0017] The headlight unit 14 has a light source such as an LED (Light Emitting Diode) and a lens or reflector for distributing and illuminating the light from the light source. The headlight unit 14 is arranged along the optical axis AX1 and is configured to emit light LB of low beam (passing beam) and high beam (driving beam) in the forward direction (FRONT in the figure).

[0018] The millimeter-wave radar unit 15 has a transmitting / receiving surface on its front side, which is equipped with a millimeter-wave transmitting and receiving antenna. In this specification, the transmitting / receiving surface of the millimeter-wave radar unit 15 (the front surface of the millimeter-wave radar unit 15) is also referred to as the antenna surface.

[0019] More specifically, the millimeter-wave radar unit 15 has a transmitting antenna and a receiving antenna on its transmitting / receiving surface (electromagnetic wave radiating surface) 15S (see Figure 2). The millimeter-wave radar unit 15 radiates electromagnetic waves (millimeter waves) from the transmitting antenna and receives the reflected waves reflected by the target object with the receiving antenna. The received signal is processed by a control device, for example, an ECU (Electronic Control Unit) (not shown), to detect the distance, angle, and velocity between the unit and the target object. The millimeter-wave radar unit 15 uses millimeter waves in the 76-81 GHz band, particularly in the 79 GHz band, but is not limited to this frequency band. Also, the antenna may have both transmitting and receiving functions.

[0020] The light-emitting unit 16 includes a light source 16A and a light guide 16B which consists of at least one light guide member that guides the light from the light source 16A. The light-emitting unit 16 functions as a DRL (Daytime Running Light) or a turn lamp. The light source 16A is, for example, an LED or an incandescent light bulb, and supplies its light to the light guide 16B.

[0021] The normal direction AX2 of the antenna surface 15S of the millimeter-wave radar unit 15 is positioned such that it is tilted by an angle θ (45° in this embodiment) toward the outward direction of the vehicle (i.e., to the left in the case of the left headlight) with respect to the optical axis AX1 of the headlight unit 14.

[0022] On the antenna surface 15S side of the millimeter-wave radar unit 15, a shielding member 18 is provided, which is positioned with a gap between it and the antenna surface 15S and covers the antenna surface 15S. In addition, at least one extension 19 is provided inside the lamp housing. The extension 19 is a decorative component provided to reflect light, guide light, or make internal structures etc. difficult to see from the outside.

[0023] Figure 2 is a perspective view showing the arrangement of the millimeter-wave radar unit 15 and the shielding member 18. Figure 3A shows the shielding member 18 as viewed from the antenna surface 15S side of the millimeter-wave radar unit 15. Figure 3B is a schematic cross-section of the millimeter-wave radar unit 15 and the shielding member 18.

[0024] In this embodiment, a shielding member 18 is provided on the front side of the millimeter-wave radar unit 15, with a gap between it and the antenna surface 15S of the millimeter-wave radar unit 15, and covering the entire surface of the antenna surface 15S when viewed from the normal direction AX2 of the antenna surface 15S. Preferably, when viewed from the normal direction of the antenna surface 15S, the shielding member 18 is larger than the antenna surface 15S.

[0025] More preferably, the size and position of the shielding member 18 are set such that the entire surface of the antenna surface 15S and electromagnetic waves radiated in a direction inclined from the normal direction of the antenna surface 15S, for example in a direction of 80°, pass through the shielding member 18. By doing so, no phase difference or intensity discrepancy occurs between electromagnetic waves emitted in the direction normal to the antenna surface 15S and electromagnetic waves radiated in, for example, an 80° direction, and information such as the position of the object can be detected with high accuracy. The shielding member 18 may also be provided in contact with the antenna surface 15S.

[0026] The shielding member 18 is configured, for example, as a parallel plate of constant thickness, with its normal vector positioned according to the angular range of the antenna's radiation pattern. Preferably, the parallel plate-shaped shielding member 18 is positioned perpendicular to the central axis or reference axis of the antenna's radiation pattern. Alternatively, it is preferred that it is positioned perpendicular to the antenna's radiation plane.

[0027] The antenna radiation pattern referred to here is the angular distribution of electromagnetic wave intensity transmitted from the antenna surface 15S of the millimeter-wave radar unit 15. Generally, the intensity is greatest in the direction normal to the antenna surface 15S, and the electromagnetic wave intensity decreases as the angle from the normal increases. The angle at which the intensity drops to -3dB from the maximum intensity is called the half-width of the antenna pattern, which is, for example, 80°.

[0028] Furthermore, as shown in Figure 3C, if the antenna of the millimeter-wave radar unit 15 is provided in a portion of the front surface of the millimeter-wave radar unit 15, and millimeter-wave radiation and reception are performed in that portion, then it is sufficient that the shielding member 18 covers at least the entire electromagnetic wave transmission / reception area (hereinafter referred to as the antenna beam area) 15R, which is that portion of the surface.

[0029] In this case, it is preferable to cover the area of ​​the front surface (antenna surface 15S) of the millimeter-wave radar unit 15 other than the antenna beam area 15R (i.e., the area not shielded by the shielding member 18) with other extensions. Alternatively, the area not shielded by the shielding member 18 can be made difficult to see from the outside by the light guide 16B of the light-emitting unit 16 itself, or by utilizing the light emitted from the DRL or turn lamp from the light guide 16B.

[0030] By covering the area other than the antenna beam region 15R on the front of the millimeter-wave radar unit 15 with other extensions, effective shielding and aesthetically pleasing shielding can be achieved.

[0031] Figure 4 is a cross-sectional view showing the case where a shielding member is placed in front of the antenna surface 15S of the millimeter-wave radar 15. More specifically, it schematically shows the case when millimeter-wave MW (wavelength λ) radiated from the millimeter-wave radar unit 15 is transmitted through a shielding member 21 (thickness TG) made of resin or the like. A portion of the millimeter-wave MW is reflected by the shielding member 21 (reflected wave WR), and the millimeter waves passing through the shielding member 21 are absorbed and attenuated by the shielding member 21 and radiated to the outside (transmitted millimeter-wave WA).

[0032] Figure 5 is a partially enlarged cross-sectional view showing an enlarged portion of the cross-section of the shielding member 18 of this embodiment. It schematically shows that the shielding member 18 is made of foamed resin.

[0033] The shielding member 18 is made of foamed resin. The shielding member 18 is formed by sealing carbon dioxide gas or the like in a transparent resin such as polycarbonate, acrylic, polyimide, or epoxy, creating bubbles 18A within the resin. Because gas is sealed in the resin, it is possible to lower the dielectric constant and significantly reduce the influence on electromagnetic waves. If the bubble ratio (the proportion of bubbles in the total volume) of the foamed resin is 50% or more, the influence of the resin can be almost ignored.

[0034] The relative permittivity and dielectric loss of foamed resin can be measured using methods such as waveguide S-parameter method and free-space S-parameter method. While direct measurement is the most accurate method, for simple estimation, the relative permittivity and dielectric loss can be expressed by the following equations. Note that the relative permittivity of air was set to 1 according to ASWindeler's equation. (εr-εa) / (εr-1)=F / 100×3εa / (2εa+1) tanδ' = tanδ × F / 100

[0035] Here, εa is the relative permittivity of the foamed resin, εr is the relative permittivity of the resin, F is the bubble rate (%), tanδ' is the dielectric loss tangent of the foamed resin, and tanδ is the dielectric loss tangent of the resin.

[0036] Electromagnetic waves emitted from millimeter-wave radar are reflected by the shielding material if the dielectric constant difference between the shielding material and the air is large. In addition, due to the dielectric loss of the shielding material, the electromagnetic waves emitted from the millimeter-wave radar are absorbed within the shielding material and converted into heat. As a result, when a shielding material is placed in front of the antenna surface of a millimeter-wave radar, problems arise such as a decrease in the intensity of the emitted electromagnetic waves and a change in the direction of radiation (antenna pattern) of the emitted electromagnetic waves due to the dielectric constant difference between the shielding material and the air.

[0037] Assuming that the frequency of the millimeter wave used in the millimeter wave radar is f (Hz), the wavelength λ (m) in the frequency space is as follows. λ = c / f (where c is the speed of light)

[0038] For example, if the frequency f is 79 GHz, the wavelength λ is 3.8 mm. Assuming that the wavelength in the resin (dielectric) is λd and the relative permittivity of the resin is εr, the wavelength in the resin is expressed as follows. λd = λ / εr 1 / 2

[0039] Also, if the wavelength in space is 3.8 mm and the relative permittivity of the resin is 2.74, the wavelength in the resin is 2.3 mm.

[0040] The distance D (power half - attenuation depth) at which the power density of the electromagnetic wave irradiated on the foamed resin is halved can be simply expressed as follows, assuming that the loss tangent of the foamed resin is tanδ'. D (m) = 3.32×10 7 / (f×εa 1 / 2 ×tanδ')

[0041] For example, when a resin with a relative permittivity of 2.74 and a loss tangent of 0.026 is foamed and the volume ratio of the porosity is 50%, from the above formula, the relative permittivity εa of the foamed resin is 1.73 and the loss tangent tanδ' is 0.013. For example, the power half - attenuation depth of an electromagnetic wave with a frequency of 79 GHz is as follows. D (m) = 3.32×10 7 / (79×10 9 ×1.73 1 / 2 ×0.013) = 24.5 (mm)

[0042] On the other hand, when the resin is not foamed, the thickness at which the power is halved is as follows. D (m) = 3.32×10 7 / (79×10 9 ×2.74 1 / 2 ×0.026) = 9.8 (mm)

[0043] In other words, when resin is foamed with a volume ratio of 50% air bubbles, the power halving depth becomes approximately 2.5 times thicker.

[0044] Furthermore, incorporating carbon-based black pigments such as carbon into the resin increases electromagnetic wave absorption. Therefore, the black pigment used as a shielding material in the shielding member 18 is preferably iron oxide (e.g., magnetite-type triiron tetroxide), a composite oxide of copper and chromium, or a composite oxide of copper, chromium, and zinc. This reduces electromagnetic wave absorption compared to carbon-based black pigments. On the other hand, increasing the carbon content in the extension parts other than the shielding member 18 can increase electromagnetic wave absorption and suppress multiple reflections. If carbon must be used in the shielding member 18 due to design requirements, reducing the carbon content to 3% or less by weight can reduce electromagnetic wave absorption.

[0045] Furthermore, since the shielding member 18 of this embodiment is made of foamed resin and contains air bubbles, it exhibits significant light scattering within the resin, resulting in a greater shielding effect compared to resins without air bubbles. Therefore, by using the shielding material with low electromagnetic wave absorption, a greater shielding effect and electromagnetic wave absorption reduction effect can be obtained with less black pigment.

[0046] Here, the thickness of the dielectric material such as the shielding member 18 is selected as follows. That is, if TG is the thickness of the dielectric material through which the electromagnetic waves pass, then when the reflection loss is greater than or equal to the transmission loss (reflection loss ≥ transmission loss), TG = n × λd / 2 (where n is a natural number) This is preferable. Note that if the thickness TG is an integer multiple of λd / 2, the transmission loss will also increase, so it is preferable to use an integer value that satisfies the condition that reflection loss ≥ transmission loss.

[0047] Furthermore, even if TG is not perfectly matched to n × λd / 2 (where n is a natural number), practical problems do not occur if the thickness is set so that the power reflection loss falls within a frequency band where the power reflection loss is, for example, -10 dB or less (reflected power is 10% or less) for a given frequency f. The range of such thickness TG can be determined, for example, by using the S-parameter method, which determines the reflection loss S 11This can be derived by setting a conditional equation such that the value of is -10dB or less, and solving for the thickness TG.

[0048]

number

[0049]

number

[0050]

number

[0051]

number

[0052]

number

[0053] (c air : Speed ​​of light in air, c vac :Speed ​​of light in a vacuum, ω:Angular frequency of electromagnetic waves (=2×π×f[Hz]), ε r : Complex permittivity of a dielectric, λ c :Cutoff wavelength (the upper limit of the wavelength at which the fundamental mode propagates, which determines the minimum operating frequency of the transmission line. In coaxial lines, λ c =∞))

[0054] Furthermore, the acceptable range of thickness TG may be determined by experimentally evaluating the dependence of reflection loss on thickness TG to determine an appropriate value (for example, a value such that the reflection loss is -10 dB or less). Note that if the reflection loss exceeds -10 dB, it may cause malfunctions in the equipment.

[0055] Furthermore, when the reflection loss is less than the transmission loss (reflection loss < transmission loss), the millimeter-wave radar can be used without problems by setting the dielectric thickness TG to a thickness less than or equal to the power half-depth.

[0056] As explained above, by using foamed resin as a shielding material on the front surface (antenna surface) of the millimeter-wave radar, it becomes possible to make the millimeter-wave radar invisible from the front of the light fixture and to suppress the attenuation of the electromagnetic waves of the millimeter-wave radar.

[0057] [Example of modification] Figure 6 is a schematic perspective view showing a shielding member 18, which is a modified example of this embodiment. A rectangular groove 18G is formed on one surface of the shielding member 18.

[0058] More specifically, the surface (back surface of the shielding member 18) 18R of the shielding member 18 facing the antenna surface 15S of the millimeter-wave radar unit 15 has multiple rectangular grooves 18G arranged at regular intervals and parallel to each other.

[0059] The depth DG of the groove 18G is formed such that DG = k × λ0 / 4 (where k is a natural number), where λ0 is the wavelength of the millimeter waves from the millimeter-wave radar unit 15 (in air). Furthermore, the groove 18G is formed to be parallel to the polarization plane PD of the millimeter waves from the millimeter-wave radar unit 15. Alternatively, the shielding member 18 is positioned parallel to the polarization plane PD of the millimeter waves.

[0060] By configuring the shielding member 18 in this way, the millimeter waves from the millimeter-wave radar unit 15 cancel each other out at the back surface 18R of the shielding member 18, resulting in a significant reduction in reflection. Therefore, according to this modified example, it is possible to further suppress the reflection of radar waves and provide a high-precision lamp device with minimal radar functional loss.

[0061] Figure 7 illustrates that the shielding member 18 of this embodiment and its modifications (hereinafter referred to as "this embodiment") has a significant reflection suppression effect.

[0062] More specifically, millimeter waves emitted from the millimeter-wave radar unit 15 and transmitted through the shielding member 18 are partially reflected by the transparent cover 12. The electromagnetic waves reflected by the transparent cover 12 are then reflected by the shielding member 18, the light guide 16B of the light-emitting unit 16, and other extensions 19, generating multiple reflected waves (MR). Such multiple reflected waves (MR) disturb not only the transmitted signal but also the received signal, generating noise and degrading the dynamic range and accuracy.

[0063] However, because the shielding member 18 of this embodiment has a low relative permittivity, the reflectivity of millimeter waves at the front surface 18F of the shielding member 18 is low, and reflection is suppressed. As a result, the effects of multiple reflections are cumulatively reduced. Furthermore, the absorption loss of the shielding member 18 is also reduced, making it possible to provide a lamp device with low noise, a large dynamic range, and high-precision radar functionality.

[0064] Figure 8A is a schematic diagram showing the arrangement of the millimeter-wave radar unit 15, shielding member 18, and transparent cover 12 in another embodiment of the present invention. Note that this is a view from the front side (vertical direction) of the antenna surface (radar wave radiating surface) 15S of the transmitting and receiving antenna 15A of the millimeter-wave radar unit 15.

[0065] Figure 8B is a schematic cross-sectional view showing the arrangement of the millimeter-wave radar unit 15, shielding member 18, and transparent cover 12 as seen from the WW line in Figure 8A.

[0066] As shown in Figure 8B, parallel plate-shaped shielding members 18 are arranged in front of the antenna surface 15S of the millimeter-wave radar unit 15 at a constant interval C2. The shielding members 18 have a thickness TG.

[0067] For example, the shielding member 18 is configured as a plate-like body with parallel flat plates and a substantially constant layer thickness, and both surfaces are arranged parallel to the antenna surface 15S of the millimeter-wave radar unit 15. The shielding member 18 is formed from a resin such as polycarbonate, acrylic, epoxy, or polyimide in a plate shape.

[0068] Furthermore, the shielding member 18 and the millimeter-wave radar unit 15 are arranged such that the distance between the shielding member 18 and the transparent cover 12 is a constant distance C1. The transparent cover 12 is formed as a light-transmitting cover made of transparent resin or the like. It may be opaque, such as having a color, as long as it is light-transmitting.

[0069] The transparent cover 12 may have a curved shape overall, or it may have parts of different thicknesses. However, when viewed from a direction perpendicular to the antenna surface 15S (hereinafter also referred to as the vertical view), it is preferable that the region of the transparent cover 12 that overlaps with the antenna surface 15S (electromagnetic wave radiating surface) (hereinafter also referred to as the radiating surface corresponding region) 12S has a parallel plate shape with a constant thickness.

[0070] The shielding member 18 is configured to be sized and positioned such that it covers the entire antenna surface 15S when viewed from a direction perpendicular to the antenna surface 15S of the millimeter-wave radar unit 15.

[0071] As shown in Figures 8A and 8B, the front region 12S of the transparent cover 12, the shielding member 18, and the antenna surface 15S are arranged to be parallel to each other.

[0072] Preferably, the transparent cover 12 is configured such that, when viewed from a direction perpendicular to the antenna surface 15S, the area of ​​the transparent cover 12 that overlaps with the antenna surface 15S (radiation surface corresponding area) 12S covers the entire antenna surface 15S in terms of size and arrangement.

[0073] [Spacing and thickness of shielding member 18 and transparent cover 12] As described above, the shielding member 18 and the transparent cover 12 positioned on the front side (antenna surface 15S side) of the millimeter-wave radar unit 15 are made of, for example, resin, and due to the dielectric constants of each, reflection of electromagnetic waves occurs at the interface between the resin and the air due to the difference in dielectric constants between the resin and the air.

[0074] At that time, if the phases of the transmitted electromagnetic wave and the reflected electromagnetic wave are in opposite directions, the transmitted electromagnetic wave will be attenuated due to its combination with the reflected electromagnetic wave.

[0075] More specifically, in this specification, the frequency f (Hz) of the millimeter-wave radar is, for example, 76 GHz to 81 GHz. When the frequency f (Hz) is, for example, 79 GHz, the wavelength λ0 (in air) is 3.8 mm.

[0076] For example, when the relative permittivity εr1 = 2.4 of the transparent cover 12 (dielectric) is 2.45 mm, the wavelength λd in the transparent cover 12 is 2.45 mm, and when the relative permittivity εr2 = 1.73 of the shielding member 18 is 2.89 mm.

[0077] When the thickness of the radiating surface area 12S of the transparent cover 12 is TK, the relative permittivity is εr1, and the wavelength (effective wavelength) in the resin (medium) is λd1, and the thickness of the shielding member 18 is TG, the relative permittivity is εr2, and the effective wavelength in the resin (medium) is λd2, the radiating surface area 12S of the transparent cover 12, the shielding member 18, and the antenna surface 15S of the millimeter-wave radar unit 15 are arranged to satisfy the following relationship. In the following equation, C1 is the distance between the radiating surface area 12S and the shielding member 18, C2 is the distance between the shielding member 18 and the antenna surface 15S (electromagnetic wave radiating surface), and n1, n2, m1, m2 are natural numbers. TK = n1 × λd1 / 2 ... (6) TG = n² × λd² / 2 ···(7) C1 = m1 × λ / 2 ... (8) C2 = m2 × λ / 2 ... (9)

[0078] Therefore, by appropriately selecting the thickness TK of the radiation surface area 12S and the thickness TG of the shielding member 18, the reflection loss of electromagnetic waves occurring at the interface between the transparent cover 12 and the space, and at the interface between the shielding member 18 and the space, can be reduced. In other words, multiple reflections not only between the shielding member 18 and the antenna surface 15S (electromagnetic wave radiation surface), but also between the radiation surface area 12S of the transparent cover 12 and the shielding member 18 can be suppressed. Therefore, these synergistic multiple reflections can be effectively suppressed. In addition, changes in the electromagnetic wave radiation pattern can be reduced.

[0079] That is, as described above, according to the lamp device of the present embodiment, it is possible to solve the problem that the reflected electromagnetic waves between the transparent cover 12 and the shielding member 18 are further multiply reflected between the transparent cover 12 and the shielding member 18 to increase noise.

[0080] In addition, it is possible to solve the problem that the reflected electromagnetic waves that have strayed into the space between the transparent cover 12 and the shielding member 18 are multiply reflected between the transparent cover 12 and the shielding member 18 to increase noise.

[0081] Note that if the thicknesses TK and TG are increased, the transmission loss increases due to the dielectric loss tangent of the resin. Therefore, it is preferable that n1 = 2 to 4 for the thickness TK and n2 = 2 or 3 for the thickness TG.

[0082] In addition, the radiation surface corresponding region 12S of the transparent cover 12 and the shielding member 18 can be slightly deflected due to vibrations and environmental temperatures during the use of the lamp device 10. Although the transmission and reflection characteristics also change slightly due to the deflection, it is preferable that the intervals C1 and C2 are not too small in order to suppress the average characteristic change over the entire surfaces of the radiation surface corresponding region 12S and the shielding member 18. Since both the radiation surface corresponding region 12S and the shielding member 18 can be deflected, it is preferable that the interval C1 is larger than the interval C2 (m1 < m2).

[0083] In addition, since reflected electromagnetic waves from other members (such as extensions) in the lamp device enter the spaces of these intervals C1 and C2 to become noise, it is preferable that the intervals C1 and C2 are not too large.

[0084] Considering the above, it is preferable that m1 ≧ 4 and m2 ≧ 2, and it is more preferable that 4 ≦ m1 ≦ 8 and 2 ≦ m2 ≦ 4.

[0085] Note that even if TK, TG, C1, and C2 do not exactly match the above relational expressions, it is extremely effective to suppress multiple reflections by setting them so as to fall within a frequency band in which the power reflection loss with respect to the frequency f is -10 dB or less (the reflected power is 10% or less).

[0086] The ranges for TK, TG, C1, and C2 can be derived, for example, by using the aforementioned S-parameter method to set a conditional equation such that the reflection loss S11 is -10 dB or less, and then solving for TK, TG, C1, and C2. TK and TG can be calculated by referring to the dielectric constant of each material, and C1 and C2 can be calculated by referring to the dielectric constant of air. Alternatively, the dependence of reflection loss on TK, TG, C1, and C2 can be evaluated experimentally to determine appropriate values ​​(for example, values ​​such that the reflection loss is -10 dB or less). [Explanation of symbols]

[0087] 10: Lamp device 11: Base 12: Transparent cover 14: Lamp Unit 15: Millimeter-wave radar unit 15S: Antenna side 15R: Electromagnetic wave transmission and reception area 16: Light-emitting unit 16A:Light source 16B: Light guide 18: Shielding member 18A: Air bubbles 19: Extension

Claims

1. A radar unit having an antenna, The radar unit on which the antenna is provided has a shielding member made of foamed resin that covers at least a portion of the front surface, The aforementioned foamed resin is a foamed resin in which the dielectric constant is reduced compared to the case without air bubbles. The foamed resin has a bubble rate of 50% or more. The shielding member has a thickness of less than or equal to the power half-depth of the electromagnetic waves radiated by the radar unit. The power halving depth of the shielding member is longer than the power halving depth when the shielding member does not have air bubbles. The shielding member has a plurality of rectangular grooves on the surface of the radar unit facing the front surface, arranged parallel to the polarization plane of the electromagnetic waves emitted by the radar unit, and the depth DG of the plurality of grooves satisfies DG = k × λ0 / 4 (where k is a natural number), where λ0 is the wavelength of the electromagnetic waves emitted by the radar unit in air. Radar device.

2. The radar device according to claim 1, wherein the shielding member is positioned such that the entire antenna surface of the radar unit and electromagnetic waves radiated from the antenna surface pass through the shielding member in a direction inclined at 80° from the normal direction of the antenna surface.

3. The radar device according to claim 1 or claim 2, wherein the shielding member is made of a resin selected from polycarbonate resin, acrylic resin, polyimide resin, and epoxy resin.

4. Substrate and, A lamp housing comprising a transparent cover held by the aforementioned base, The lamp unit built into the lamp housing, A radar unit having an antenna built into the lamp housing, The radar unit on which the antenna is provided has a shielding member made of foamed resin that covers the front surface of the radar unit, The aforementioned foamed resin is a foamed resin in which the dielectric constant is reduced compared to the case without air bubbles. The foamed resin has a bubble rate of 50% or more. The shielding member has a thickness of less than or equal to the power half-depth of the electromagnetic waves radiated by the radar unit. The power halving depth of the shielding member is longer than the power halving depth when the shielding member does not have air bubbles. The shielding member has a plurality of rectangular grooves on the surface of the radar unit facing the front surface, arranged parallel to the polarization plane of the electromagnetic waves emitted by the radar unit, and the depth DG of the plurality of grooves satisfies DG = k × λ0 / 4 (where k is a natural number), where λ0 is the wavelength of the electromagnetic waves emitted by the radar unit in air. Radar device.

5. The lamp device according to claim 4, wherein the shielding member is positioned such that the entire antenna surface of the radar unit and electromagnetic waves radiated from the antenna surface pass through the shielding member in a direction inclined at 80° from the normal direction of the antenna surface.

6. The lamp device according to claim 4 or claim 5, wherein the shielding member is made of a resin selected from polycarbonate resin, acrylic resin, polyimide resin, and epoxy resin.

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