Vehicular lighting fixture

Abstract

Provided is a vehicular lighting fixture capable of suppressing an influence of aberration and heat in a projection lens and projecting a highly accurate light pattern. The vehicular lighting fixture comprises a projection lens (2) for projecting a required light distribution pattern by projecting light emitted from a light source (3). The projection lens (2) comprises, in order from the side opposite to the light source (3), a first lens (21) and a second lens (22) of resin, and a third lens (23) and a fourth lens (24) of glass. A diaphragm (25) for limiting the light diameter of the projected light is disposed between the second lens (resin lens) (22) and the third lens (glass lens). By narrowing down the diaphragm (25), the aberration of the projection lens (2) is reduced. The heat of the light source (3) is suppressed by the diaphragm (25) from being transferred from the third lens (23) side toward the second lens (22) side.

Description

Vehicle lighting fixtures

[0001] The present invention relates to a lamp used in a vehicle such as an automobile, and more particularly to a vehicle lamp suitable for use as a headlamp that performs adaptive driving beam (ADB) light distribution control.

[0002] ADB light distribution control has been proposed as a technology for controlling light distribution in headlamps of vehicles such as automobiles. This ADB light distribution control is a technology for controlling light distribution so as not to dazzle other vehicles, such as oncoming vehicles and preceding vehicles, or pedestrians, as detected from images captured by a camera. As one headlamp that performs this ADB light distribution control, a headlamp that uses a multi-segment light-emitting element (multi-segment LED array) in which micro LEDs on the order of μm are arranged in a matrix as a light source has been proposed.

[0003] For example, Patent Document 1 proposes a technology that uses a multi-segment LED array, also known as a micro LED array, as a light source and projects light emitted from the multi-segment LED array using an optical system to form a light distribution pattern. In this technology, the light-emitting surfaces of the emitted micro LEDs are projected to form unit light patterns, and the light patterns of the multiple micro LEDs are combined to form a desired light distribution pattern. Therefore, by selectively controlling the light emission of the micro LEDs, ADB light distribution control with a desired light distribution pattern is possible.

[0004] Japanese Patent Application Laid-Open No. 2021-068513

[0005] In such ADB light distribution control, it is preferable to project the unit light patterns of the micro LEDs as accurate shapes, i.e., light patterns corresponding to the shape of the light-emitting surface. However, if aberration occurs in the projection lens, the shape of the unit light patterns of the micro LEDs to be projected changes, making it difficult to control the projection of the light distribution pattern synthesized from these, i.e., to achieve high-precision ADB light distribution control. Furthermore, the projection lens is thermally deformed by the heat generated when the light source emits light, which affects the shape of the projected light pattern. This is particularly true for projection lenses that include resin lenses.

[0006] In Patent Document 1, the projection lens is composed of multiple lenses (triplet lenses) and attempts are made to reduce the aberration of the projection lens. However, when illuminating a wide area in front of a vehicle using ADB light distribution control, a significant amount of light emitted from the small LEDs passes through the peripheral area of ​​the projection lens, i.e., the light is incident on the projection lens at a large angle with respect to the optical axis, making it difficult to reduce the coma aberration caused by this light.

[0007] In addition, in Patent Document 1, the lens closer to the light source is made of a glass lens, and the lens opposite the light source is made of a resin lens, making the resin lens less susceptible to the effects of heat. However, it is difficult to prevent heat from being transferred through the glass lens to the resin lens, particularly heat transfer due to radiation, and it is difficult to prevent the shape of the light pattern from being affected by heat.

[0008] An object of the present invention is to provide a vehicle lamp that suppresses the influence of aberration and heat in the projection lens and enables projection of a highly accurate light pattern.

[0009] The vehicle lamp of the present invention is a vehicle lamp including a light source and a projection lens that projects light emitted from the light source to project a required light distribution pattern, the projection lens including a resin lens and a glass lens, the resin lens and the glass lens being arranged on the opposite side of the light source, and an aperture that limits the diameter of the projected light being arranged between the glass lens and the resin lens.

[0010] For example, the projection lens may include, in order from the side opposite the light source, a first lens having positive refractive power, a second lens having negative refractive power, and a third and fourth lens having positive refractive power, the first and second lenses being made of resin, the third and fourth lenses being made of glass, and an aperture being disposed between the second and third lenses. Here, it is preferable that the third and fourth lenses are each made of a plano-convex spherical lens, with the spherical surfaces of the lenses facing each other. It is also preferable that the focal length of the third lens is longer than that of the fourth lens.

[0011] The diaphragm is preferably made of a material having a lower thermal conductivity than glass or resin, and is preferably a variable diaphragm whose aperture diameter is variable so that the aperture value can be changed in accordance with the light distribution pattern to be projected.

[0012] According to the present invention, it is possible to provide a vehicle lamp that can suppress aberration in the projection lens and the influence of heat on the light pattern, and that can particularly realize highly accurate ADB light distribution control.

[0013] 5(c1) shows an enlarged view of a portion c1 in the case of the low beam light distribution pattern PLo, and FIG. 5(c2) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c1) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c2) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c1) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c2) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c1) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c2) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c1) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PLo ... PLo. 5(c2) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PA. 5(c1) shows an enlarged view of a portion c2 in the case of the ADB light distribution pattern PLo. 5(c2) shows an enlarge

[0014] Next, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a schematic configuration of an automobile equipped with a headlamp embodying the present invention, and a schematic perspective view of the headlamp. Left and right headlamps R-HL and L-HL are attached to the left and right front portions of the body of an automobile CAR. Each headlamp R-HL and L-HL is equipped with an ADB lamp unit ALU capable of ADB light distribution control and a clearance lamp unit CLU, which are integrally disposed within a lamp housing 100.

[0015] The left and right headlamps R-HL and L-HL have a symmetrical configuration, and a partially cutaway perspective view of the right headlamp R-HL is shown enlarged in Figure 1. The lamp housing 100 includes a lamp body 101 that opens toward the front of the vehicle and a light-transmitting cover 102 attached to this opening. An ADB lamp unit ALU and a clearance lamp unit CLU are disposed within this lamp housing 100.

[0016] As will be described in detail below, the ADB lamp unit ALU is configured to project an ADB light distribution pattern by irradiating light emitted from a light source onto the area in front of the vehicle using a projection lens. In this configuration, the ADB lamp unit ALU is capable of projecting light distribution patterns including low beam and high beam light distributions. The clearance lamp unit CLU is also configured to function as a turn signal lamp, daytime running lamp, etc. The clearance lamp unit CLU utilizes a light guide, but this is not relevant to the present invention and therefore will not be described in detail.

[0017] Fig. 2 is a perspective view of the schematic configuration of the ADB lamp unit ALU, and Fig. 3 is a longitudinal cross-sectional view thereof. The unit case 1 also serves as a heat sink 10, and a light source unit 3 is disposed within it. The light source unit 3 is equipped with a micro LED (light emitting diode) array 31 as a light source, and this micro LED array 31 is mounted on a light source substrate 30 that is internally supported within the unit case 1. This micro LED array 31 is configured with a large number of micro LEDs 32 that emit white light, arranged vertically and horizontally in a matrix, and any micro LED is selectively made to emit light under the control of an ADB control circuit 41, which will be described later.

[0018] The projection lens 2 has a lens configuration in which multiple lens groups are housed within a lens barrel 20. It is basically configured as a triplet lens, and is composed of, in order from the front of the lamp, a first lens group LG1, a second lens group LG2, and a third lens group LG3. The first lens group LG1 is composed of a first lens 21 which is a biconvex lens with positive refractive power. The second lens group LG2 is composed of a second lens 22 which is a biconcave lens with negative refractive power. The third lens group LG3 is composed of a composite lens (combined lens) of a third lens 23 and a fourth lens 24 which are both plano-convex lenses, and is configured as a lens with positive refractive power overall.

[0019] Of the four lenses 21 to 24 that make up the projection lens 2, the first lens 21 and the second lens 22 are made of a light-transmitting resin. For example, the first lens 21 is made of PMMA (acrylic resin), and the second lens 22 is made of PC (polycarbonate resin). The third lens 23 and the fourth lens 24 are made of light-transmitting glass, for example, N-K9L (borosilicate crown glass).

[0020] Furthermore, the first lens 21 and the second lens 22 are designed with aspherical convex and concave surfaces. The third lens 23 and the fourth lens 24 are each composed of a plano-convex spherical lens, and are arranged with their spherical surfaces facing each other. The positive refractive power (refractive power) of the first lens 21 is set to a value close to the negative refractive power of the second lens 22. The third lens 23 is composed of a lens with a longer focal length than the fourth lens 24, thereby making the refractive power of the fourth lens 24 greater than that of the third lens 23. The third lens group LG3, which includes these lenses, is configured as a lens with positive refractive power in the direction of light emission, as described above. By configuring the lenses 21 to 24 in this way, aberrations in the projection lens 2, namely, chromatic aberration, spherical aberration, astigmatism, and coma, are reduced. The configuration related to coma, among these aberrations, will be described later.

[0021] Furthermore, the projection lens 2 is provided with an aperture 25 between the second lens 22 and the third lens 23. Although not shown in detail, this aperture 25 is configured, for example, such that a plurality of aperture blades are arranged in the circumferential direction on an aperture ring attached to the lens barrel 20, and the aperture ring is rotated by an aperture drive unit to tilt each aperture blade, thereby changing the aperture diameter of the aperture opening formed by these aperture blades. Furthermore, this is configured to change the light diameter (diameter of the light beam) of light transmitted through the projection lens 2. Alternatively, the aperture may be configured such that a plurality of aperture plates are moved radially to change the aperture diameter.

[0022] The diaphragm 25 is made of a material with a lower thermal conductivity than the resin or glass that constitutes the lenses 21 to 24. The diaphragm blades of the diaphragm 25 shield the space between the peripheral edges of the second lens 22 and the third lens 23, and are designed so that when the diaphragm blades are fully open, the F-number of the entire projection lens 2 is at least 0.7 or less. When the diaphragm 25 is driven to reduce the diameter of the diaphragm opening, the peripheral region of the projection lens 2 is shielded, resulting in a so-called stopped-down state, and the F-number of the entire projection lens 2 increases.

[0023] The first lens 21 to fourth lens 24 are internally supported in the lens barrel 20 with their respective lens optical axes aligned, and this optical axis is configured as the lens optical axis Lx of the entire projection lens 2. The lens barrel 20 is attached to the unit case 1 of the ADB lamp unit ALU with the rear focal point of the projection lens 2 positioned extremely close to the light-emitting surface of the micro LED array 31.

[0024] 4 is a block circuit diagram of the ADB control system 4 in the ADB lamp unit ALU. A lighting control switch 43 operated by the driver is connected to the ADB control circuit 41, and the ADB control circuit 41 controls the light emission of the micro LED array 31 by setting and operating this lighting control switch 43. A vehicle ECU (electronic control unit) 42, to which an on-board camera 44 is connected, is connected to the ADB control circuit 41. The vehicle ECU 42 detects a vehicle ahead of the vehicle based on an image of the area ahead of the vehicle captured by the on-board camera 44. The ADB control circuit 41 is configured to control the ADB light emission of the micro LED array 31 so as not to dazzle the vehicle ahead detected by the vehicle ECU 42 when set to ADB control. Furthermore, the ADB control circuit 41 is connected to an aperture drive unit of the aperture 25 provided in the projection lens 2, and is configured to control the aperture opening of the aperture 25 by setting the lighting control switch 43.

[0025] In the headlamp HL of embodiment 1 equipped with the projection lens 2 configured as described above, the light distribution is controlled by the driver's setting of the lighting control switch 43. For example, when set to high beam light distribution, the ADB control circuit 41 causes substantially all of the micro LEDs 32 of the micro LED array 31 to emit light, and as shown schematically in FIG. 5( a), the light patterns Ps of the micro LEDs 32 are combined to project a high beam light distribution pattern PHi. When the lighting control switch 43 is set to low beam light distribution, the light emission of the micro LED array 31 is controlled so that a light pattern Ps below the cutoff line COL in FIG. 5( a) is projected. This results in a low beam light distribution pattern PLo. In FIG. 5( a), V is a vertical line passing through the optical axis Lx of the projection lens, and H is a horizontal line passing through an angular position slightly above the optical axis Lx.

[0026] When the lighting control switch 43 is set to ADB light distribution control, the vehicle ECU 42 detects a preceding vehicle Ob1 and an oncoming vehicle Ob2 as forward vehicles present in the area ahead of the automobile based on images captured by the onboard camera 44. When no forward vehicles are detected, the ADB control circuit 41 controls the light emission of the micro LED array 31 to project the high beam light distribution pattern PHi shown in FIG.

[0027] When a forward vehicle is detected, the ADB control circuit 41 projects an ADB light distribution pattern PA in which the micro LEDs corresponding to the illumination area overlapping the detected forward vehicle are dimmed or turned off. That is, in the ADB light distribution pattern PA, as shown in FIG. 5B, the illumination area to which the forward vehicles Ob1 and Ob2 belong is selectively dimmed or blocked to prevent dazzling of the forward vehicles Ob1 and Ob2. In the illumination area where the forward vehicles Ob1 and Ob2 do not exist, the light pattern Ps of the emitted micro LEDs 32 is projected, illuminating the corresponding area at a predetermined brightness, thereby executing ADB light distribution control with improved visibility.

[0028] Here, when projecting the low-beam light distribution pattern PLo and the high-beam light distribution pattern PHi, there is little need to control the sharpness of the boundaries at the periphery of the light distribution patterns, so the effects of aberration in the light distribution patterns can be ignored. Therefore, in this case, the diaphragm 25 is set to fully open or nearly fully open, and the projection lens 2 is set to a low F-number. This increases the lens brightness of the projection lens 2, i.e., the amount of light transmitted, and enables the projection of a bright light distribution pattern that makes effective use of the light emitted by the micro LED array 31.

[0029] On the other hand, when projecting the ADB light distribution pattern PA, it is necessary to project each light pattern Ps of the numerous micro-LEDs with high accuracy. That is, as shown in FIG. 5B, it is necessary to sharpen the boundary between the shaded or dimmed area where the forward vehicles Ob1 and Ob2 are present and the illuminated area where they are not present. If the boundary is unclear, part of the light pattern may be projected onto the forward vehicles Ob1 and Ob2, potentially dazzling the occupants of the forward vehicles. In this case, the influence of coma aberration occurring in the projection lens 2 cannot be ignored.

[0030] In the projection lens 2 of this embodiment, an aperture 25 is disposed between the second lens 22 and the third lens 23, and by narrowing the aperture diameter of this aperture 25, it is possible to block or reduce the light transmitted through the lens periphery of the projection lens 2. Therefore, the proportion of light transmitted through the lens periphery, where the angle of incidence with respect to the optical axis Lx of the projection lens 2 is relatively large, that contributes to the formation of the light pattern PA is reduced, and coma aberration caused by light transmitted through the lens periphery can be suppressed. This allows the boundary of the light pattern Ps of the micro LEDs to be projected sharply, and enables high-precision ADB light distribution control.

[0031] If it is not possible to completely prevent coma in the projection lens 2, it is preferable to design the projection lens 2 so that inward coma (coma that trails along the optical axis) remains. For example, as described in JP 2017-16928 A, inward coma can be controlled by making the curvature of the principal surface of the projection lens greater than the curvature of the arc that passes through the principal point and has the focal point as its center.

[0032] By applying this design to the projection lens 2, the coma aberration occurring in the light pattern Ps of each micro LED 32 is controlled to inward coma aberration. This makes it possible to sharpen the boundary between the illuminated area and the light-blocking area of ​​the light pattern, where the inner side toward the center of the light distribution pattern is the illuminated area and the outer side is the light-blocking area. For example, in the case of the low-beam light distribution pattern PLo in Figure 5(a), as shown by the enlarged view of portion c1 in Figure 5(c1), the boundary of the light pattern Ps, i.e., the cutoff line COL, can be projected sharply by inward coma aberration.

[0033] 5(c2), even if inward coma aberration occurs at the boundary between the illuminated area and the shaded area, the margin between the front vehicle Ob2, i.e., the margin for preventing the illuminated area from overlapping with the front vehicle, can be reduced. Therefore, the boundary can be moved closer to the front vehicle Ob2, thereby expanding the illuminated area on the host vehicle side, and the safety of the host vehicle when traveling can be improved.

[0034] Considering the environmental temperature of the projection lens 2, when the micro LED array 31 is extinguished, the temperature of the projection lens 2 is approximately equal to the outside air temperature, and is generally between 0°C and 40°C. On the other hand, when the micro LED array 31 is emitting light, the heat generated by the micro LED array 31 causes the temperature of the projection lens 2 to rise to approximately 80°C. As a result, the fourth lens 24 and the third lens 23, which are close to the micro LED array 31, are susceptible to the effects of heat, but these third lens 23 and fourth lens 24 are glass lenses whose thermal expansion coefficients are approximately two orders of magnitude smaller than those of resin, and therefore the effect on the refractive power can be ignored.

[0035] On the other hand, the first lens 21 and the second lens 22 are susceptible to the effects of heat via the third lens 23, and heat is transferred in particular through the lens barrel 20 that supports each lens. An aperture 25 is disposed in the lens barrel 20 between the second lens 22 and the third lens 23, and this aperture 25 suppresses heat transfer through the lens barrel 20. In particular, when the aperture 25 is made of a material with low thermal conductivity, the effect of suppressing heat transfer is enhanced.

[0036] Heat conduction due to radiation from the third lens 23 to the second lens 22 is also possible. In particular, the second lens 22, which is a biconcave lens, and the third lens 23, which is a plano-convex lens, are close to each other at their respective peripheral regions, and heat conduction in these peripheral regions is considered. The diaphragm 25 arranged in the projection lens 2 has diaphragm blades of the second lens 22 and the third lens 23 extending to the peripheral regions, so the conduction of radiant heat in such peripheral regions is suppressed. Therefore, the influence of heat on the refractive power of the first lens 21 and the second lens 22, which are made of resin lenses, is negligible. In this way, the influence of heat on the light distribution pattern, particularly the ADB light distribution pattern, in the projection lens 2 can be suppressed, thereby achieving high-precision ADB light distribution control.

[0037] In the present invention, the third lens group LG3 of the projection lens 2 may be composed of a single lens. That is, as shown in FIG. 6 , the configuration of a projection lens 2A is such that the first lens 21 of the first lens group LG1 and the second lens 22 of the second lens group LG2 have the same configuration, but the third lens group LG3 is composed of a third lens 23A that is a biconvex lens with positive refractive power. When the first lens 21 and the second lens 22 have the same configuration as those in the embodiment, the third lens 23A is configured as a lens equivalent to a composite lens formed by combining the third lens 23 and the fourth lens 24 of the embodiment. Designing the projection lens 2A in this manner provides the same effects as those of the embodiment.

[0038] This projection lens 2A can be expected to simplify its structure because the total number of lenses can be reduced. On the other hand, when controlling coma aberration, this projection lens 2A requires the biconvex surface of the third lens 23A to be designed aspherical, which can make design and manufacturing difficult. In contrast, in the projection lens of the above-described embodiment, the third lens group LG3 is configured as a composite lens of the third lens 23 and the fourth lens 24, so that the lens surfaces of the third lens 23 and the fourth lens 24 can be designed as spherical, which simplifies design and manufacturing. Furthermore, because the spherical surfaces of the third lens 23 and the fourth lens 24 are arranged opposite each other, design to reduce aberrations is also simplified.

[0039] In the ADB lamp unit of the embodiment, an example has been shown in which the light source is configured as a micro LED array, i.e., a multi-segment LED, to form an ADB light distribution, but the present invention can also be applied to a lamp that uses a MEMS (micro electro mechanical systems) mirror array as the light source. Alternatively, the present invention is not limited to lamps that directly project light from a light source using a projection lens, but can also be applied to lamps that use a projection lens that projects light that has been optically scanned using light reflected from a rotating mirror and an oscillating mirror.

[0040] This international application claims priority based on Japanese Patent Application No. 2023-128411, filed on August 7, 2023, the entire contents of which are incorporated herein by reference.

[0041] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

[0042] REFERENCE SIGNS LIST 1 ADB lamp unit 2, 2A Projection lens 3 Light source unit 4 ADB control system 10 Heat sink 20 Lens barrel 21 to 24 First to fourth lenses 25 Aperture 30 Substrate 31 Micro LED array 32 Micro LED 41 ADB control circuit 42 Vehicle ECU 43 Lighting control switch 44 In-vehicle camera L-HL, R-HL Headlamp LG1 to LG3 First to third lens groups PHi High beam light distribution pattern PLo Low beam light distribution pattern PA ADB light distribution pattern Ps Light pattern (micro LED) Ob1, Ob2 Forward vehicle

Claims

1. A vehicle lamp including a light source and a projection lens that projects the light emitted from the light source to project a required light distribution pattern, the projection lens including a resin lens and a glass lens, the resin lens and the glass lens are arranged on the opposite side to the light source, and an aperture that limits the diameter of the projected light is arranged between the glass lens and the resin lens.

2. The vehicle lamp according to claim 1, wherein the projection lens includes, in order from the side opposite the light source, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens and a fourth lens having positive refractive power, the first lens and the second lens being made of resin, the third lens and the fourth lens being made of glass, and the diaphragm is disposed between the second lens and the third lens.

3. A vehicle lamp according to claim 2, wherein the third lens and the fourth lens are each constituted by a plano-convex spherical lens, and the spherical surfaces of the third lens and the fourth lens are disposed opposite to each other.

4. The vehicle lamp according to claim 3, wherein the focal length of the third lens is longer than the focal length of the fourth lens.

5. The vehicle lamp according to claim 1, wherein the projection lens includes, in order from the side opposite the light source, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, the first lens and the second lens being made of resin, and the third lens being made of glass.

6. A vehicle lamp according to claim 1, wherein the aperture is made of a material having a lower thermal conductivity than glass and resin.

7. The vehicle lamp according to claim 1, wherein the diaphragm is configured as a variable diaphragm whose aperture diameter is variable, and the diaphragm value is changed according to the light distribution pattern to be projected.

8. A vehicle lamp according to any one of claims 1 to 7, wherein the light source is composed of a multi-segment light-emitting element in which a large number of minute light-emitting elements are arranged, and ADB light distribution control is performed by controlling the light emission of the minute light-emitting elements.

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