Radar Equipment

Abstract

To provide a radar device which can effectively suppress attenuation, reflection, and multiple reflection of a radar wave and offers a high-precision radar function with low noise and a large dynamic range.SOLUTION: A radar device is provided, comprising a radar unit having an antenna, and a shielding member 18 made of a foamed resin at least partially covering a front face of the radar unit equipped with the antenna, the shielding member containing 3% or less carbon by weight.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a radar device, and more particularly to a radar device mounted on a vehicle. [Background technology]

[0002] For driving assistance and autonomous driving, various sensors are used, such as acceleration sensors, GPS sensors, cameras, LiDAR (Light Detection and Ranging), and millimeter wave sensors.

[0003] In particular, millimeter wave radar maintains high target detection performance without being affected by nighttime or backlit environments, or bad weather such as thick fog, rain, and snow. It can also directly detect the distance and direction to a target, as well as the relative speed to the target. Therefore, it has the characteristic of being able to detect targets at close range quickly and with high accuracy.

[0004] There has been proposed a vehicle lamp in which a millimeter wave radar is mounted in a lamp chamber and a light guiding member that transmits millimeter waves is provided between a front cover and the millimeter wave radar (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4842161 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a light-guiding member is placed in front of the millimeter-wave radar, the electromagnetic waves emitted from the millimeter-wave radar are reflected and absorbed by the light-guiding member due to the influence of the dielectric constant and dielectric tangent of the light-guiding member, resulting in a decrease in the radiated power of the radiated electromagnetic waves, which causes a significant decrease in the detection performance of the millimeter-wave radar.

[0007] Therefore, while it is possible to improve the appearance of the millimeter wave radar by making it invisible from the outside, using a light-guiding material (such as a light-guiding rod) that is normally used in automobile headlights, this can cause the radar function to be lost.

[0008] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a radar device having a high-precision radar function, such as being able to effectively suppress attenuation, reflection, and multiple reflection of radar waves, having low noise, and a wide dynamic range.

[0009] Another object of the present invention is to provide a radar device having an extension that makes the radar unit difficult to see from the outside without changing the radiation pattern of the radar waves. [Means for solving the problem]

[0010] A radar device according to one embodiment of the present invention comprises: a radar unit having an antenna; a shielding member made of a foamed resin, the shielding member covering at least a part of a front surface of the radar unit on which the antenna is provided; The shielding member contains 3% or less carbon by weight.

[0011] A radar device according to another embodiment of the present invention comprises: a radar unit having an antenna; a shielding member made of a foamed resin, the shielding member covering at least a part of a front surface of the radar unit on which the antenna is provided; The shielding member contains at least one of an oxide of iron, a composite oxide of copper and chromium, and a composite oxide of copper, chromium, and zinc as a black pigment. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of an internal structure of a lamp device according to an embodiment of the present invention. [Diagram 2]2 is a perspective view showing the arrangement of a millimeter wave radar unit 15 and a shielding member 18. FIG. [Figure 3A] 1 is a diagram showing the shielding member 18 as viewed from the antenna surface 15S side of the millimeter wave radar unit 15. FIG. [Figure 3B] 2 is a diagram showing a cross section of a millimeter wave radar unit 15 and a shielding member 18. FIG. [Figure 3C] 1 is a diagram showing a shielding member 18 that entirely covers an electromagnetic wave transmission / reception region 15R, which is a partial region on the front surface of the millimeter wave radar unit 15. FIG. [Figure 4] 13 is a cross-sectional view showing a case where a shielding member is disposed in front of an antenna surface 15S of a millimeter wave radar 15. FIG. [Diagram 5] 2 is a partially enlarged cross-sectional view showing a part of a cross section of a shielding member 18 of the present embodiment. FIG. [Figure 6] FIG. 13 is a perspective view that shows a schematic diagram of a shielding member 18 that is a modified example of the present embodiment. [Figure 7] 5A to 5C are diagrams illustrating the anti-reflection effect of the shielding member 18 of the present embodiment. [Figure 8A] 13 is a plan view showing a schematic arrangement of a millimeter wave radar unit 15, a shielding member 18, and a transparent cover 12 in another embodiment of the present invention. FIG. [Figure 8B] 8B is a cross-sectional view showing a schematic arrangement of the millimeter wave radar unit 15, the shielding member 18, and the transparent cover 12 as viewed from the line WW in FIG. 8A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following, preferred embodiments of the present invention will be described, but these may be modified or combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

[0014] Fig. 1 is a diagram 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 shows a schematic 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, a lamp housing (housing) is formed by a base 11 and a transparent cover 12 held by the base 11. The lamp housing contains a headlamp unit 14 which is a lamp unit (light source), a millimeter wave radar unit 15 which is a radar unit, 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 lamp unit is not limited to a headlight light source, but refers to a light-emitting source having the purpose and function of emitting light to the outside, such as a tail lamp or backlight.

[0017] The headlamp unit 14 has a light source such as an LED (Light Emitting Diode) and a lens or reflector for distributing and irradiating the light from the light source. The headlamp unit 14 is disposed along an optical axis AX1 and is provided so as to irradiate low beam (passing beam) and high beam (driving beam) light LB in the forward direction (FRONT in the drawing).

[0018] The millimeter wave radar unit 15 has a transmitting / receiving surface on the front of which a millimeter wave transmitting / receiving antenna is provided. In this specification, the transmitting / receiving surface of the millimeter wave radar unit 15 (the surface in front 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 radiation surface) 15S (see FIG. 2). The millimeter wave radar unit 15 emits electromagnetic waves (millimeter waves) from the transmitting antenna, and receives the reflected waves reflected by an object by the receiving antenna. The received signal is processed by a control device, for example, an ECU (Electronic Control Unit) (not shown), and the distance, angle, and speed to the object are detected. The millimeter wave radar unit 15 uses millimeter waves in the 76-81 GHz band, for example, and in particular, millimeter waves in the 79 GHz band, but is not limited to this frequency band. The antenna may have both transmitting and receiving functions.

[0020] The light-emitting unit 16 has a light source 16A and a light guide 16B that is composed 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 Lights) or a turn lamp. The light source 16A has, for example, an LED or an incandescent bulb, and supplies the light to the light guide 16B.

[0021] The normal direction AX2 of the antenna surface 15S of the millimeter-wave radar unit 15 is inclined at an angle θ (45° in this embodiment) toward the outside 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] A shielding member 18 is provided on the antenna surface 15S side of the millimeter wave radar unit 15, 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 design part provided to reflect or guide light, or to make internal structures and the like difficult to see from the outside.

[0023] Fig. 2 is a perspective view showing the arrangement of the millimeter-wave radar unit 15 and the shielding member 18. Fig. 3A is a diagram showing the shielding member 18 as viewed from the antenna surface 15S side of the millimeter-wave radar unit 15. Fig. 3B is a diagram showing 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, the shielding member 18 is larger than the antenna surface 15S when viewed from the normal direction of the antenna surface 15S.

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

[0026] The shielding member 18 is, for example, configured as a parallel plate with a constant thickness, and its normal is arranged according to the angular range of the antenna radiation pattern. The parallel plate-shaped shielding member 18 is preferably arranged so as to be perpendicular to the central axis or reference axis of the antenna radiation pattern. Alternatively, it is preferably arranged so as to be perpendicular to the radiation surface of the antenna.

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

[0028] As shown in FIG. 3C, when the antenna of the millimeter-wave radar unit 15 is provided in a partial area on the front surface of the millimeter-wave radar unit 15 and millimeter waves are emitted and received in that area, it is sufficient that a shielding member 18 is provided so as to cover at least the entire electromagnetic wave transmission / reception area (hereinafter referred to as the antenna beam area) 15R, which is that partial area.

[0029] In this case, it is preferable to cover the area other than the antenna beam area 15R (i.e., the area not shielded by the shielding member 18) on the front surface (antenna surface 15S) of the millimeter wave radar unit 15 with another extension. 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 by the DRL or turn signal lamp from the light guide 16B.

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

[0031] 4 is a cross-sectional view showing a case where a shielding member is arranged in front of the antenna surface 15S of the millimeter wave radar 15. More specifically, the millimeter wave MW (wavelength λ) radiated from the millimeter wave radar unit 15 is shielded by the shielding member made of resin or the like. 18 The figure shows a schematic diagram of the case where the millimeter wave MW passes through a shielding material (thickness TG). 18 A part of the wave is reflected by the shielding material (reflected wave WR). 18 The millimeter waves passing through the shielding material 18The millimeter waves are absorbed and attenuated by the

[0032] 5 is a partially enlarged cross-sectional view showing a part of the cross section of the shielding member 18 of this embodiment, which diagrammatically shows that the shielding member 18 is made of foamed resin.

[0033] The shielding member 18 is made of foamed resin. - Bonnet resin ,acrylic resin , polyimide resin , Epoxy resin It is formed by sealing carbon dioxide gas or the like in a transparent resin such as fluorine, creating bubbles 18A in the resin. Since gas is sealed in the resin, it is possible to lower the dielectric constant and greatly reduce the effect on electromagnetic waves. If the foamed resin's bubble rate (the proportion of bubbles in the total volume) is 50% or more, it is possible to almost ignore the effect of the resin.

[0034] The dielectric constant and dielectric loss of foamed resin can be measured using measurement methods such as the waveguide S-parameter method and the free space S-parameter method. Although it is more accurate to actually measure them, in the case of a simple estimation, the dielectric constant and dielectric loss can be expressed by the following formulas. Note that the dielectric constant of air is set to 1 according to the ASWindeler formula. (εr-εa) / (εr-1)=F / 100×3εa / (2εa+1) tan δ' = tan δ × F / 100

[0035] Here, εa is the relative dielectric constant of the foamed resin, εr is the relative dielectric constant of the resin, F is the air bubble ratio (%), tan δ' is the dielectric tangent of the foamed resin, and tan δ is the dielectric tangent of the resin.

[0036] The electromagnetic waves emitted from the millimeter-wave radar are reflected by the shielding material if there is a large difference in dielectric constant between the shielding material and the air. In addition, due to the influence of the dielectric loss of the shielding material, the electromagnetic waves radiated from the millimeter-wave radar are absorbed within the shielding material and converted into heat. For these reasons, when a shielding material is placed in front of the antenna surface of the millimeter-wave radar, problems occur in that the strength of the radiated electromagnetic waves is reduced and the radiation direction of the radiated electromagnetic waves (antenna pattern) changes due to the difference in dielectric constant between the shielding material and the air.

[0037] If the frequency of the millimeter waves used in millimeter-wave radar is f (Hz), then the wavelength λ (m) in space of that frequency is as follows: λ=c / f (c is the speed of light)

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

[0039] Furthermore, if the wavelength in space is 3.8 mm and the relative dielectric constant of the resin is 2.74, then the wavelength in the resin is 2.3 mm.

[0040] The distance D (power half-depth) at which the power density of the electromagnetic waves irradiated to the foamed resin is reduced to half is simply expressed as follows, where tan δ' is the dielectric tangent of the foamed resin. D(m) = 3.32 × 10 7 / (f×εa 1 / 2 ×tan δ')

[0041] For example, when a resin with a relative dielectric constant of 2.74 and a dielectric loss tangent of 0.026 is foamed and the volume ratio of the air bubbles becomes 50%, the relative dielectric constant εa of the foamed resin is 1.73 and the dielectric loss tangent tanδ' is 0.013 according to the above formula. For example, the half-power 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, if the resin is not foamed, the thickness at which the power consumption is halved is as follows: D(m) = 3.32 × 10 7 / (79×10 9 ×2.74 1 / 2 ×0.026) =9.8(mm)

[0043] That is, when the resin is foamed with a volume ratio of the air bubbles being 50%, the power half-life depth becomes about 2.5 times thicker.

[0044] Furthermore, when carbonaceous black pigments such as carbon are contained in the resin, the absorption of electromagnetic waves is large. Therefore, the black pigments as the shielding material contained in the shielding member 18 are preferably iron oxides (for example, magnetite-type triiron tetroxide), composite oxides of copper and chromium, and composite oxides of copper, chromium, and zinc. These have lower electromagnetic wave absorption than carbonaceous black pigments. On the other hand, by increasing the carbon content of the extension parts other than the shielding member 18, it is possible to increase the absorption of electromagnetic waves and suppress multiple reflections. If it is necessary to use carbon in the shielding member 18 due to design requirements, it is possible to reduce the absorption of electromagnetic waves by setting the carbon content to 3% or less by weight.

[0045] In addition, since the shielding member 18 of this embodiment is a foamed resin and contains bubbles, light scattering is large inside, and the shielding effect is greater than that of a resin that does not contain bubbles. Therefore, by using the above-mentioned shielding material with low electromagnetic wave absorption, a large shielding effect and electromagnetic wave absorption reduction effect can be obtained with a smaller amount of black pigment.

[0046] Here, the thickness of the dielectric material such as the shielding member 18 is selected as follows. That is, if the thickness of the dielectric material through which the electromagnetic wave passes is TG, when the reflection loss is equal to or greater than the transmission loss (reflection loss≧transmission loss), TG=n×λd / 2 (n is a natural number) Note that, since the transmission loss also increases when the thickness TG is an integer multiple of λd / 2, it is preferable to use an integer value that satisfies reflection loss≧transmission loss.

[0047] In addition, even if the TG is not perfectly matched to n×λd / 2 (n is a natural number), no practical problems will occur if the thickness is set so as to fall within a frequency band in which the power reflection loss for frequency f is, for example, -10 dB or less (reflected power is 10% or less). Such a range of thickness TG can be determined by, for example, using the S-parameter method to find the reflection loss S 11 It can be derived by setting a conditional equation such that the value of is -10 dB or less and solving for the thickness TG.

[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053] (c air : speed of light in air, c vac : speed of light in a vacuum, ω: angular frequency of electromagnetic wave (=2×π×f[Hz]), ε r : complex dielectric constant of dielectric, λ cCutoff wavelength (the upper limit of the wavelength at which the fundamental mode propagates, determining the minimum operating frequency of the transmission line. In coaxial lines, it is λ c =∞))

[0054] The allowable range of thickness TG may be determined by experimentally evaluating the dependence of return loss on thickness TG to determine an appropriate value (for example, a value that results in a return loss of -10 dB or less). If the return loss is -10 dB or more, the device may malfunction.

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

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

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

[0058] More specifically, a surface 18R of the shielding member 18 (the back surface 18R of the shielding member 18) facing the antenna surface 15S of the millimeter wave radar unit 15 has a plurality of grooves 18G having a rectangular cross section provided parallel to one another at regular intervals.

[0059] The depth DG of the groove 18G is formed so that DG=k×λ0 / 4 (k is a natural number) where λ0 is the wavelength (in air) of the millimeter waves from the millimeter wave radar unit 15. The groove 18G is formed so as 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 disposed so as to be parallel to the polarization plane PD of the millimeter waves.

[0060] By configuring the shielding member 18 in this manner, the reflected wave and the incident wave of the millimeter wave from the millimeter-wave radar unit 15 cancel each other out at the rear surface 18R of the shielding member 18, greatly reducing reflection. Therefore, according to this modified example, it is possible to further suppress the reflection of the radar wave, and it is possible to provide a high-precision lamp device with little loss of radar function.

[0061] FIG. 7 is a diagram illustrating that the shielding member 18 of this embodiment and its modified example (hereinafter referred to as this embodiment) has a large anti-reflection effect.

[0062] More specifically, the 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 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, since the shielding member 18 of the present embodiment has a small relative dielectric constant, the reflectance of the millimeter wave at the front surface 18F of the shielding member 18 is low and the reflection is suppressed. This reduces the cumulative effect of multiple reflections. In addition, the absorption loss of the shielding member 18 is also reduced, so that a lamp device having low noise, a wide dynamic range, and a highly accurate radar function can be provided.

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

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

[0066] As shown in Fig. 8B, a parallel plate-like shielding member 18 is disposed at a certain distance C2 in front of the antenna surface 15S of the millimeter wave radar unit 15. The shielding member 18 has a thickness TG.

[0067] For example, the shielding member 18 is configured as a parallel flat plate-like body having a substantially uniform 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 made of, for example, polycarbonate. - Bonnet resin ,acrylic resin , Epoxy resin , polyimide resin It is formed into a plate shape from a resin such as the above.

[0068] The shielding member 18 and the millimeter wave radar unit 15 are arranged so 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 such as a transparent resin. Note that as long as it is light-transmitting, it may be semi-transparent, such as colored.

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

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

[0071] As shown in FIGS. 8A and 8B, the front region 12S of the transparent cover 12, the shielding member 18 and the antenna surface 15S are disposed so as to be parallel to one another.

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

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

[0074] At that time, if the phases of the transmitted electromagnetic wave and the reflected electromagnetic wave are in directions that cancel each other out, the transmitted electromagnetic wave is attenuated by being combined 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 the air) is 3.8 mm.

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

[0077] When the thickness of the radiation surface corresponding region 12S of the transparent cover 12 is TK, the relative dielectric constant εr1, the wavelength (effective wavelength) in the resin (medium) is λd1, the thickness of the shielding member 18 is TG, the relative dielectric constant εr2, and the effective wavelength in the resin (medium) is λd2, the radiation surface corresponding region 12S of the transparent cover 12, the shielding member 18, and the antenna surface 15S of the millimeter wave radar unit 15 are provided so as to satisfy the following relationship. In the following formula, C1 is the distance between the radiation surface corresponding region 12S and the shielding member 18, C2 is the distance between the shielding member 18 and the antenna surface 15S (electromagnetic wave radiation surface), and n1, n2, m1, and 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 corresponding region 12S and the thickness TG of the shielding member 18, it is possible to reduce the reflection loss of the electromagnetic wave occurring at the interface between the transparent cover 12 and the space and the interface between the shielding member 18 and the space. In other words, it is possible to suppress not only the multiple reflection between the shielding member 18 and the antenna surface 15S (electromagnetic wave radiation surface), but also the multiple reflection between the radiation surface corresponding region 12S of the transparent cover 12 and the shielding member 18. Therefore, it is possible to effectively suppress these synergistic multiple reflections. In addition, it is possible to reduce the change in the electromagnetic wave radiation pattern.

[0079] In other words, as described above, the lamp device of this embodiment can solve the problem that reflected electromagnetic waves between the transparent cover 12 and the shielding member 18 are further multiple-reflected between the transparent cover 12 and the shielding member 18, thereby increasing noise.

[0080] In addition, the problem of reflected electromagnetic waves that have strayed into the space between the transparent cover 12 and the shielding member 18 being multiple-reflected between the transparent cover 12 and the shielding member 18 and increasing noise can be solved.

[0081] In addition, when the thicknesses TK and TG are increased, the transmission loss increases due to the dielectric 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 may be slightly deflected due to vibrations and ambient temperatures during the use of the lamp device 10. Although the transmission and reflection characteristics also change slightly due to the deflection, in order to suppress the average characteristic change over the entire surfaces of the radiation surface corresponding region 12S and the shielding member 18, it is preferable that the intervals C1 and C2 are not too small. 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] Moreover, in the spaces of these intervals C1 and C2, reflected electromagnetic waves from other members (such as extensions) within the lamp device may enter and become stray noise, so 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 satisfy the above relational expressions, by setting them so as to fall within the frequency band where the reflection loss of power with respect to the frequency f is -10 dB or less (the reflected power is 10% or less), multiple reflections can be extremely effectively suppressed.

[0086] Such ranges of TK, TG, C1, and C2 can be derived, for example, by using the S-parameter method described above to set a conditional expression such that the value of the reflection loss S11 is -10 dB or less, and then solving for TK, TG, C1, and C2. For TK and TG, the relative permittivity of each material can be referred to for calculation, and for C1 and C2, the relative permittivity of air can be referred to for calculation. Also, the dependence of the reflection loss on TK, TG, C1, and C2 may be evaluated experimentally to determine appropriate values (for example, values such that the reflection loss is -10 dB or less).

Explanation of Reference Numerals

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

Claims

1. a radar unit having an antenna; a shielding member that covers at least a portion of a front surface of the radar unit on which the antenna is provided, The shielding member contains 3% or less of carbon by weight, the shielding member is made of a resin selected from a polycarbonate resin, an acrylic resin, a polyimide resin, and an epoxy resin, and is a foamed resin having air bubbles in the resin, The foamed resin has a lower dielectric constant than a foamed resin having no bubbles, The foamed resin has a foaming rate of 50% or more. Radar equipment.

2. the shielding member has a thickness equal to or less than a half-power depth of the electromagnetic wave radiated by the radar unit, The radar device according to claim 1 , wherein the half-power depth of the shielding member is longer than the half-power depth of the shielding member when the shielding member does not have bubbles.

3. 3. The radar device according to claim 1, wherein the shielding member is disposed in a location on the vehicle that is visible from the outside, and the radar unit is disposed in a location that is not visible from the outside due to the shielding member.

4. a radar unit having an antenna; a shielding member that covers at least a portion of a front surface of the radar unit on which the antenna is provided, the shielding member contains at least one of an oxide of iron, a composite oxide of copper and chromium, and a composite oxide of copper, chromium, and zinc as a black pigment; the shielding member is made of a resin selected from a polycarbonate resin, an acrylic resin, a polyimide resin, and an epoxy resin, and is a foamed resin having air bubbles in the resin, The foamed resin has a lower dielectric constant than a foamed resin having no bubbles, The foamed resin has a foaming rate of 50% or more. Radar equipment.

5. the shielding member has a thickness equal to or less than a half-power depth of the electromagnetic wave radiated by the radar unit, The radar device according to claim 4 , wherein the half-power depth of the shielding member is longer than the half-power depth when the shielding member does not have any air bubbles.

6. 6. The radar device according to claim 4, wherein the shielding member is installed in a location on the vehicle that is visible from the outside, and the radar unit is installed in a location that is not visible from the outside due to the shielding member.

7. 7. The radar device according to claim 1, wherein the shielding member and the radar unit are installed inside a lamp device including a lamp housing formed by a base and a transparent cover held by the base.

8. The radar device according to claim 1 , wherein the shielding member has an external color of black.

9. 9. The radar device according to claim 1, wherein the radar unit is a millimeter wave radar unit that uses millimeter waves in a frequency band of 76 to 81 GHz.

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