Vehicular lighting fixture

Abstract

To provide a vehicular lighting fixture which includes a projection optical system in which lowering of illuminance in a peripheral region out of an illuminated region is suppressed.SOLUTION: A vehicular lighting fixture includes: a light source (micro LED array) 12 for forming a desired light pattern; and a projection optical system 2 constituted by including a first lens 21 for projecting a light pattern of the light source 12 as a light distribution pattern. The projection optical system 2 includes a second lens 22 for deflecting the light emitted in an optical axis direction from an end part position of the light source 12 deviated from an optical axis of the first lens 21 toward an optical axis position of a light incident surface of the first lens 21, between the first lens 21 and the light source 12. A distance d between the light incident surface of the first lens 21 and a light emission surface of the second lens 22 on the optical axis is set based on a curvature radius r of the second lens 22, a distance x from an optical axis of the end part of the light source 12, and a refraction index n of the second lens 22.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a lighting fixture used in vehicles such as automobiles, and more particularly to a vehicle lighting fixture suitable for use in a projector-type headlamp that projects light from a light source in a required light distribution pattern using a projection optical system. [Background technology]

[0002] Projector-type headlamps have been proposed for automobiles, which project a desired light pattern formed by a light source onto the area ahead of the vehicle using a projection optical system. This type of headlamp is used in headlamps that perform ADB (Adaptive Driving Beam) light distribution control, which can obtain light distribution that prevents dazzling to objects such as vehicles and pedestrians in the area ahead. ADB light distribution control detects objects using a position detection device, reduces the amount of light in the area where the detected object is located, or turns off the light, and brightens the rest of the wide area.

[0003] Patent Document 1 proposes a headlamp that performs ADB light distribution control using a micro LED array, in which a large number of micro LEDs (light emitting diodes) with minute light emitting areas are arranged in a matrix, as a light source. In this headlamp, the light emission of the large number of micro LEDs that make up the micro LED array is selectively controlled to form a required light emission pattern, and this light emission pattern is projected onto the area in front of the vehicle by a projection optical system to illuminate with a light distribution pattern that is ADB light distribution controlled. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-168131 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, free-form projection lenses formed by resin molding have been provided as projection optical systems that perform ADB light distribution control. Furthermore, in response to demands for high-precision ADB light distribution control, large-sized micro LED arrays with increased vertical and horizontal dimensions have been provided, which use an increased number of micro LEDs as light sources. As the size of the micro LED array increases, light emitted from the micro LEDs at the periphery of the micro LED array is incident on the periphery of the projection lens. Typically, in lamps that use a single projection lens as a projection optical system, the brightness of the peripheral region tends to be lower than that of the central region including the optical axis due to the influence of lens aberrations of the projection lens. Therefore, the illuminance of the region illuminated by light emitted from the micro LEDs at the periphery of the micro LED array, i.e., the peripheral region of the light distribution pattern formed by light emitted from the peripheral region of the projection lens, is reduced, making it difficult to perform suitable light distribution control.

[0006] In order to prevent such a decrease in illuminance in the peripheral area, it is conceivable to increase the diameter of the projection lens and project the light distribution pattern using the center of the projection lens. However, this would increase the diameter of the projection lens, which would in turn increase the thickness of the projection lens, resulting in the problem of the projection optical system becoming large and heavy.

[0007] An object of the present invention is to provide a vehicle lamp equipped with a projection optical system that suppresses a decrease in illuminance in a peripheral area of ​​an illuminated area. [Means for solving the problem]

[0008] The vehicle lighting fixture of the present invention comprises a projection optical system including a light source capable of forming a required light pattern and a first lens that projects the light pattern formed on the light source as a light distribution pattern, and the projection optical system comprises a second lens between the first lens and the light source that deflects light emitted in the optical axis direction from an end position of the light source that is off the optical axis of the first lens toward the optical axis position of the light incident surface of the first lens.

[0009] In the present invention, the distance between the light entrance surface of the first lens and the light exit surface of the second lens on the optical axis is set based on the radius of curvature of the second lens, the distance from the optical axis to the end of the light source, and the refractive index of the second lens. In this case, it is preferable that the second lens be a glass plano-convex lens whose light exit surface is formed of a spherical surface facing the first lens. Furthermore, it is preferable that the light source in the present invention be an LED array in which multiple micro LEDs or LEDs are arranged in a matrix. [Effects of the Invention]

[0010] According to the present invention, a small and lightweight vehicle lamp can be obtained that prevents a decrease in illuminance in the peripheral area of ​​the light distribution pattern. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic perspective view of an automobile equipped with a vehicle lamp (headlamp) according to the present invention; [Figure 2] FIG. 1 is a schematic perspective view of a headlamp. [Figure 3] Schematic cross-sectional view of a headlamp. [Figure 4] FIG. [Figure 5] Headlamp light distribution diagram and illuminance characteristics diagram. [Figure 6] Light path diagram of part of the optical system [Figure 7] FIG. [Figure 8] FIG. 10 is a front view of a modified example of the control form of the micro LED array. [Figure 9] Front view of the LED array. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view of an automobile CAR equipped with a vehicle lamp according to the present invention. Front lamps FL are equipped on the left and right sides of the front of the automobile CAR. FIG. 1 shows a partially cutaway perspective view of the left front lamp FL, and the right front lamp FL has a symmetrical configuration. The front lamp FL houses two lamp units CL and HL in a lamp housing 100 composed of a lamp body 101 with an opening at the front and a translucent cover 102 attached to the opening of the lamp body 101. The upper lamp unit CL is configured as a clearance lamp, a turn signal lamp, and a DRL (Daytime Running Lamp) using a light guide. The lower lamp unit HL is configured as a headlamp to which the present invention is applied.

[0013] Figure 2 is an external perspective view of the headlamp (headlamp unit) HL shown in Figure 1. It comprises an integrally assembled heat sink 10 and lens holder 20, with a light source 1 mounted on the heat sink 10 and a projection optical system 2 incorporated within the lens holder 20. When the light source 1 emits light, the light emitted from the light source 1 is projected by the projection optical system 2 toward the area in front of the automobile CAR, providing illumination with a required light distribution pattern.

[0014] In the embodiment, a flange plate 30 is integrally provided with the lens holder 20, and an aiming mechanism 3 is provided on this flange plate 30. This aiming mechanism 3 includes a fulcrum portion 31, a vertical aiming portion 32, and a horizontal aiming portion 33. By rotating the aiming screws 321, 331 of each aiming portion 32, 33, the entire headlamp HL can be tilted up and down and left and right around the fulcrum portion 31, and the illumination optical axis Lx of the headlamp HL can be adjusted to face the reference direction. Since the aiming mechanism 3 has a known configuration, a detailed description thereof will be omitted.

[0015] FIG. 3 is a horizontal schematic cross-sectional view of the headlamp HL shown in FIG. 2 , and FIG. 4 is an exploded perspective view of the main components. The light source 1 includes a micro LED array 12 mounted on a substrate 11 supported by a heat sink 10. The micro LED array 12 is formed by arranging a large number of micro LEDs, each emitting white light, in a matrix and integrally forming a light-emitting surface that is a rectangular shape with a side length of 1 mm or less. Here, the micro LED array 12 is formed into a rectangle whose horizontal dimension 2x is longer than its vertical dimension 2y. When the center position of the light-emitting surface of the micro LED array 12 in the vertical and horizontal directions is defined as the array optical axis Ax, x is the dimension from the array optical axis Ax to both the left and right ends of the micro LED array 12 in the horizontal direction, and y is the dimension from the array optical axis Ax to both the top and bottom ends of the micro LED array 12 in the vertical direction. For example, the horizontal dimension 2x is approximately 10 mm, and the vertical dimension 2y is approximately several mm.

[0016] Although not shown, a light-emitting circuit for emitting light from the micro LED array 12 is formed on the substrate 11, and this light-emitting circuit is connected to a light-emitting control device 4, which is schematically shown in Fig. 3. The light-emitting control device 4 supplies power to the light-emitting circuit while the automobile CAR is running, thereby controlling the light emission of the micro LED array 12. The light-emitting control device 4 is connected to an object detection device that detects objects such as other vehicles and pedestrians, and is configured to perform ADB light distribution control by selectively turning off or dimming the light from the micro LED array 12 when an object is detected.

[0017] The projection optical system 2 is configured as a doublet lens consisting of two lenses, a first lens 21 and a second lens 22, and is fixedly supported within a lens holder 20. The first lens 21 is configured as a biconvex lens with a required diameter, and the second lens 22 is configured as a plano-convex lens with a smaller diameter. As shown in FIG. 3, the lens optical axes of the first lens 21 and the second lens 22 are aligned, and hereinafter, this aligned lens optical axis will be referred to as the lens optical axis Lx. This lens optical axis Lx is aligned with the array optical axis Ax described above. Note that the lens optical axes of the first lens 21 and the second lens 22 are lines connecting the centers of curvature of the lens entrance surface and lens exit surface of each lens.

[0018] The first lens 21 is formed of a light-transmitting resin such as PMMA (acrylic resin) or PC (polycarbonate resin), and the light incident surface facing the second lens 22 is formed as a spherical surface, while the light exit surface on the opposite side is formed as a free-form surface such as an aspherical surface. The second lens 22 is formed of a light-transmitting glass such as crown glass, and the light incident surface on the light source side facing the micro LED array 12 is formed as a flat surface, while the light exit surface facing the first lens 21 is formed as a spherical surface. Here, the second lens 22 is formed to have a diameter dimension or side dimension longer than the long side dimension of the micro LED array 12, which in this example is the horizontal dimension 2x of the micro LED array 12.

[0019] In the headlamp HL configured as described above, when the light-emitting control device 4 is driven by the driver's operation, the light emission of the micro LED array 12 is controlled through the light-emitting circuit. At this time, the ADB light distribution control is set by default, and the light-emitting control device 4 selectively and individually controls the light emission of the micro LED array 12 in response to the object detected by the object detection device. Therefore, a required light emission pattern is formed in the emitted micro LED array 12, and the formed light emission pattern is irradiated toward the area ahead of the automobile by the projection optical system 2. As a result, illumination is performed with a light distribution pattern corresponding to the light emission pattern.

[0020] For example, as shown in Figure 5(a), by turning off or dimming the micro LEDs corresponding to the area where a detected object Ob, such as an oncoming vehicle, is present, the illuminance of the area where the object Ob is present is reduced compared to other areas, preventing dazzling of the object. Meanwhile, ADB light distribution control is implemented, increasing the illuminance of areas where the object Ob is not present, improving visibility of the area ahead of the vehicle. In Figure 5(a), the symbols H and L represent horizontal and vertical lines passing through the lens optical axis Lx of the projection optical system 2, respectively.

[0021] 6 is a schematic diagram showing a part of the optical path in the projection optical system 2. The micro LED array 12 is set at a position closer than the focal position F2 of the second lens 22, and the light from the micro LED array 12 is diverged by the second lens 22, forming a virtual light source of the micro LED array 12. This virtual light source is formed at a position close to the focal position F1 of the first lens 21, so that the light emission pattern formed on the micro LED array 12 by the first lens 21 is projected onto the front area of ​​the automobile CAR, making it possible to project a light distribution pattern under ADB light distribution control as shown in FIG.

[0022] 6, the light of the micro LED array 12 transmitted through the second lens 22 is incident on the light incident surface of the first lens 21. In particular, the light emitted from the peripheral portion of the micro LED array 12 perpendicular to the light emitting surface, i.e., the light incident parallel to the lens optical axis Lx, is refracted at the light exit surface of the second lens 22, and after its path (optical path) is deflected, it is incident on the light incident surface of the first lens 21 at a position on the lens optical axis Lx. By configuring in this way, it is possible to avoid a decrease in the illuminance of the light at the peripheral portion of the micro LED array 12, as will be described later.

[0023] To achieve this, in the present invention, as shown in FIG. 7, the inter-lens distance d between the light incident surface of the first lens 21 and the light exit surface of the second lens 22 on the lens optical axis Lx is set as follows: In FIG. 7, the symbols are as follows: O: Center of curvature of second lens 22 A: Intersection point between the light incident surface of the first lens 21 and the lens optical axis Lx B: Intersection point between the light exit surface of the second lens 22 and the lens optical axis Lx C: Refraction point where light emitted parallel to the optical axis Lx from the end of the micro LED array 11 in the longitudinal direction (x direction) is refracted (deflected) on the light emission surface of the second lens 22 D: Intersection of a line segment extending perpendicularly from point C to the lens optical axis Lx and the lens optical axis Lx r: radius of curvature of the light exit surface of the second lens 22 x: length from the longitudinal end of the micro LED array 12 to the lens optical axis Lx d: Distance between points A and B on the lens optical axis Lx z: The distance between points B and D on the lens optical axis Lx θ: The angle of incidence at which light deflected at point C strikes point A θi: The angle of incidence of light incident on point C parallel to the lens optical axis Lx θo: The angle of light emission at point C n: refractive index of the second lens

[0024] First, find the distance z. From the Pythagorean theorem of △ODC, r 2 =x 2 +(rz) 2 ···(1) Transforming equation (1) with respect to z gives equation (2).

number

[0025] From △ACD and angle θ, tanθ=x / (d+z) (3) Also, the angle θo in FIG. 7 is the sum of the vertical angle θi and the alternate angle θ, so θ=θo-θi (4) About △DOC sinθi=x / r (5) From Snell's law for the second lens 22, n·sinθo=sinθi··(6) From equations (5) and (6), sinθo=nx / r (7)

[0026] From equations (4), (6) and (7), θ=arcsin(nx / r)-arcsin(x / r) ···(8) Note that arcsin is the arc sine. Applying equation (8) to equation (3), tan[arcsin(nx / r)-arcsin(x / r)]=x / (d+z) ···(9)

[0027] Transforming equation (9) gives equation (10).

number

[0028] The inter-lens distance d can be calculated from equations (2) and (10).

number

[0029] Here, x in the formula d is the dimension of the long side of the micro LED array whose light-emitting surface is rectangular. If the side dimension y is longer than the side dimension x of the micro LED array, x should be replaced with y.

[0030] When the inter-lens distance d between the first lens 21 and the second lens 22 is set, as described above, light emitted parallel to the lens optical axis Lx from both ends in the x direction of the micro LED array 12 that is farthest from the lens optical axis Lx among the many micro LEDs that make up the micro LED array 12 is incident on the center (position of the lens optical axis Lx) of the light incident surface of the first lens 21. Therefore, light emitted parallel to the lens optical axis from all micro LEDs that make up the micro LED array 12 is incident on the center of the light incident surface of the first lens 21 or its vicinity.

[0031] In this way, most of the light emitted parallel to the lens optical axis Lx from all the micro LEDs of the micro LED array 12, in other words, most of the light emitted from each micro LED, is incident on or near the center position of the light reflecting surface of the first lens 21. Therefore, even if the first lens 21 has lens characteristics such that the illuminance of projected light transmitted through the peripheral portion is reduced, the light from each micro LED of the micro LED array 12 is projected by transmitting through the central region of the first lens 21, and reduction in the illuminance of the projected light is suppressed.

[0032] Therefore, by adding the second lens 22 as an auxiliary lens to a projection optical system with a single lens configuration consisting only of the first lens 21, it is possible to increase the illuminance in the peripheral area of ​​the projected light distribution pattern. The second lens 22 only needs to have a dimension equal to or greater than the longitudinal dimension of the micro LED array 12 serving as the light source, so a small lens can be used. Therefore, in order to increase the illuminance in the peripheral area of ​​the light distribution pattern in a projection optical system consisting only of the first lens 21, it is not necessary to form the first lens 21 with a large diameter, nor is it necessary to increase the lens thickness of the first lens 21, making it possible to reduce the size and weight of the projection optical system 2.

[0033] Incidentally, Fig. 5(b) shows the illuminance distribution when lighting is performed to form a light distribution pattern in the area in front of an automobile CAR, as shown in Fig. 5(a). In this figure, the vertical axis represents the illuminance distribution on a horizontal line H1 passing through the center of the light distribution pattern (a portion corresponding to the hot zone slightly below the lens optical axis Lx), and represents the ratio based on the illuminance at the center of the light distribution pattern. The dashed line S2 represents the illuminance distribution when the first lens 21 is used alone, and the solid line S1 represents the illuminance distribution of this embodiment equipped with the second lens 22. It can be seen that the embodiment improves the illuminance at both ends of the light distribution pattern.

[0034] Although not shown, the plano-convex lens of second lens 22 may be configured with its spherical surface facing the light source 1 as the light incident surface and its flat surface as the light exit surface. Alternatively, second lens 22 may be a biconvex lens or a meniscus lens. In these cases, the form of light refraction in the second lens will differ from that in the embodiment, and therefore the formula for calculating the inter-lens distance d will be different from that in the embodiment.

[0035] Furthermore, the light of the micro LED array 12 emitted from the second lens 22 is incident on the lens optical axis Lx or a region nearby the lens optical axis Lx on the light incident surface of the first lens 21. This reduces the amount of light transmitted through the peripheral region of the first lens 21, thereby reducing lens aberration in the first lens 21, particularly spherical aberration occurring in the lens peripheral portion. This improves the resolution of the peripheral portion of the light distribution pattern, i.e., the resolution of the light distribution pattern formed on the micro LED array 12.

[0036] In the present invention, when the light emission control device 4 selectively controls the light emission of the micro LED array 12 to form a light emission pattern, the multiple micro LEDs constituting the micro LED array 12 may be unitized into groups of different numbers. In the example of Fig. 8, in the longitudinal direction (x direction) of the micro LED array 12, a region of required dimensions centered on the array optical axis Ax is defined as a central region Ac, and the area outside this central region Ac is defined as a peripheral region As. In the central region Ac, one row of micro LEDs is defined as one unit, and in the peripheral region As, multiple rows of micro LEDs are collectively defined as one unit. For example, as shown by the solid lines in Fig. 8, the central region Ac is defined as one row unit, and the peripheral region As is defined as two or three rows unit.

[0037] When performing ADB light distribution control, the light-emission control device 4 controls light emission for each unit. Therefore, light emission of the micro LEDs in the central area Ac is controlled in units of one row, and light emission of the micro LEDs in the peripheral area As is controlled in units of two or three rows. For example, even if the resolution of the first lens 21 in the peripheral area As is lower than that in the central area Ac, the area of ​​one unit for which light emission is controlled is doubled or tripled, so the effect of the reduced resolution is not noticeable.

[0038] That is, when controlling the light distribution pattern by ADB light distribution control, the resolution of the light distribution pattern in the peripheral area As is initially estimated to be low and the light distribution pattern is controlled accordingly. As a result, even if light emission control is performed on multiple rows of micro LEDs as one unit, the light distribution pattern will be similar to that obtained when the resolution is reduced in the peripheral area As of the first lens 21. Therefore, when designing the free-form surface of the first lens 21, the design burden is reduced in order to improve the resolution in the peripheral area As of the first lens 21, making it easier to design and manufacture the first lens 21 and enabling cost reduction. Although not shown in the drawings, the micro LED array 12 may be unitized into different numbers not only in the longitudinal direction but also in the transverse direction (Y direction).

[0039] The light source in the present invention does not have to be the micro LED array described in the embodiment. As shown in Fig. 9, it may be configured as an LED array 12A in which LEDs 121 having a light-emitting surface larger than that of a micro LED are arranged in a matrix. In this case, the size of the unit pattern of the light distribution pattern formed by ADB light distribution control becomes larger compared to when the light source is configured as a micro LED array, but the basic function is the same as in the embodiment.

[0040] Furthermore, by making the second lens out of glass as in the embodiment, the heat generated by the light source 1 is shielded by the second lens, and it is also possible to mitigate the effect of heat on the first lens made of resin.

[0041] The present invention is not limited to the headlamps described in the embodiments, but can be similarly applied to any lamp that requires improvement in brightness and resolution in the peripheral areas of light distribution. [Explanation of symbols]

[0042] HL Headlamp 1 light source 2 Projection optical system 3 Aiming mechanism 4 Light-emitting control device 10 Heatsink 11 Circuit Board 12 micro LED arrays 12A LED array 21 First lens 22 Second lens 100 Lamp Housing FL front lamp HL Headlamp d Lens distance Lx Optical axis (lens optical axis)

Claims

1. A vehicle lamp having a projection optical system including a light source capable of forming a required light pattern and a first lens that projects the light pattern formed on the light source as a light distribution pattern, wherein the projection optical system has a second lens between the first lens and the light source that deflects light emitted in the optical axis direction from an end position of the light source that is off the optical axis of the first lens toward the optical axis position of the light incident surface of the first lens.

2. 2. The vehicle lamp according to claim 1, wherein the second lens is a lens having a positive refractive power.

3. 3. The vehicle lamp according to claim 2, wherein a lens distance d on the optical axis between the light incident surface of the first lens and the light exit surface of the second lens satisfies the following relational expression: [Equation 4] where r is the radius of curvature of the second lens, x is the distance from the optical axis to the end of the light source, and n is the refractive index of the second lens.

4. 3. The vehicle lamp according to claim 2, wherein the second lens is a glass plano-convex lens having a spherical light-emitting surface facing the first lens.

5. 3. The vehicle lamp according to claim 2, wherein the optical axis of the second lens is aligned with that of the first lens.

6. 3. The vehicle lamp according to claim 2, wherein the second lens forms a virtual image of the light source at or near a focal position of the first lens.

7. 2. The vehicle lamp according to claim 1, wherein the light source is an LED array in which a plurality of micro LEDs or LEDs are arranged in a matrix.

8. 8. The vehicle lamp according to claim 7, further comprising a light emission control device that selectively controls light emission of the micro LEDs or LEDs that constitute the LED array, and performs ADB light distribution control on the light distribution pattern to be projected.

9. 9. A vehicle lamp according to claim 1, which is configured as a headlamp of an automobile.

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