JP7267392B2 - vehicle lamp - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting fixture used in a vehicle such as an automobile, and more particularly to a vehicle lighting fixture suitable for application to a headlamp capable of ADB (Adaptive Driving Beam) light distribution control.

As an automobile headlamp, while enhancing the lighting effect in the front area of the own vehicle, it is effective against vehicles (hereinafter referred to as front vehicles) in the front area of the own vehicle such as preceding vehicles and oncoming vehicles existing in the front area. ADB light distribution control has been proposed as one method for obtaining light distribution that prevents glare. In this ADB light distribution control, the vehicle position detection device detects a forward vehicle, reduces or turns off the amount of light in the area where the detected forward vehicle exists, and brightly illuminates the other wide area.

In recent years, this ADB light distribution control has also been applied to headlamps that use light-emitting elements such as LEDs as light sources. It forms a light distribution for illuminating the area in front of the vehicle. Then, when a forward vehicle is detected, the LED in the illumination area corresponding to the detected forward vehicle is dimmed or extinguished.

In such ADB light distribution control, white light emitted from a plurality of LEDs is projected onto a front area of the host vehicle by a projection lens to form a plurality of illumination areas, and these illumination areas are appropriately combined and synthesized. Thus, a required illumination area is formed. However, due to spherical aberration, such as chromatic aberration, caused by the projection lens, light dispersion occurs at the periphery of each illumination area, and visibility in the illumination area may be reduced.

Patent Document 1 proposes a projection lens that employs a doublet lens consisting of a convex lens and a concave lens and provides a gap between the convex lens and the concave lens in order to improve spherical aberration, particularly chromatic aberration, of the projection lens. . A projection lens has also been proposed in which each surface of a convex lens and a concave lens is aspherical.

JP 2015-222687 A

Although the projection lens of Patent Document 1 is effective in improving chromatic aberration, it is not necessarily sufficient in terms of astigmatism and coma. The sharpness of the peripheral edge of the area is reduced, blurring the boundary of the illuminated area. Therefore, when the ADB control is executed, the light at the boundary of the illumination area adjacent to the dimmed or extinguished area may be radiated toward the forward vehicle, which may dazzle the forward vehicle.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicular lamp having a projection lens with high sharpness capable of clarifying the boundary of an illumination area.

A vehicle lamp according to the present invention includes a light source and a projection lens for projecting light emitted from the light source, wherein the projection lens is a first lens made of a biconvex lens having a positive refractive power; and a triplet lens including a second lens made of a biconcave lens having a refractive power of , and a third lens made of a biconvex lens having a positive refractive power. The first lens and the third lens are lower than the second lens. The distance t1 between the first lens and the second lens, the distance t2 between the second lens and the third lens, and the total lens thickness T of the projection lens are: , 0.03<t1/T<0.1, and 0.03<t2/T<0.1.

As a preferred embodiment of the vehicle lamp of the present invention, the light source is composed of a plurality of light emitting elements, and the light emitted from each light emitting element is projected by the projection lens to form a plurality of corresponding illumination areas. In addition, ADB light distribution control is performed by individually controlling light emission of the plurality of light emitting elements.

According to the present invention, the distance t1 between the first lens and the second lens, the distance t2 between the second lens and the third lens, and the projection lens of the projection lens composed of triplet lenses By designing the total lens thickness T on the optical axis of the lens so as to satisfy a predetermined relational expression, the spherical aberration of the projection lens can be suppressed and the sharpness can be enhanced.

1 is a schematic longitudinal sectional view of a headlamp to which the present invention is applied; FIG. Fig. 3 is a schematic perspective view of the projection lens as seen from the front; Sectional drawing of a projection lens. Design formulas and design values for each surface of convex and concave lenses. The light distribution pattern figure which combined the light radiate|emitted from the LED chip. 4A and 4B are conceptual diagrams for explaining the dimensions of each part of the projection lens, and graphs showing measured values of the spot radius of the lens of the embodiment.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a conceptual configuration in which the present invention is applied to an automobile headlamp HL to which ADB light distribution control is applied. In the following description, regarding the front or rear, the light source side of the headlamp HL is called the rear, and the front side of the headlamp HL is called the front.

The headlamp HL includes a lamp unit 2 inside a lamp housing 1 formed of a lamp body 11 and a front cover 12 made of a translucent material. This lamp unit 2 has a light source 3 and a projection lens 4 which are mounted inside and supported by a unit casing 21 whose inner surface is formed as a light reflecting surface. It is configured to illuminate an area to obtain a desired light distribution.

FIG. 2 is a schematic perspective view of the projection lens 4 as viewed from the front. As shown in FIG. 30, in which nine LED (light emitting diode) chips 301 to 309 that emit white light are mounted. These LED chips 301 to 309 are mounted in two stages, that is, four LED chips 301 to 304 are arranged in the upper stage and five LED chips 305 to 309 are arranged in the lower stage in a horizontal direction. It is When these LED chips 301 to 309 emit light, the light emitted from each of them is directed to the projection lens 4 either directly or after being reflected on the inner surface of the unit casing 21 .

As shown in FIG. 1, the LED chips 301 to 309 are connected to the light emitting circuit 5 through the substrate 31, and are individually controlled by the light emitting circuit 5 so as to emit light, extinguish, and change the light emission intensity. . A lighting switch 51 operated by the driver is connected to the light emitting circuit 5. The lighting switch 51 is configured to switch between low beam light distribution, high beam light distribution, and ADB light distribution. The light emitting circuit 5 is connected to an in-vehicle camera 52 for executing ADB control, detects the forward vehicle from the front image of the automobile captured by the in-vehicle camera 52, and controls the light distribution so as not to dazzle the forward vehicle. is configured to run

As shown in FIG. 3, the projection lens 4 is composed of a triplet lens. In order from the front side of the lamp, a first lens 41 made of a biconvex lens having positive refractive power and a double concave lens having negative refractive power. and a third lens 43 which is a biconvex lens having positive refractive power. In addition, the first lens 41 to the third lens 43 are coaxially arranged, and between the first lens 41 and the second lens 42 and between the second lens 42 and the third lens 43, A gap is secured in the direction along the lens optical axis Lx. The light source 3, that is, the LED chips 301 to 309 are arranged in the vicinity of the focal point Fo of the projection lens 4 on the rear side of the lamp.

Here, as will be described later with reference to FIG. 6, the inter-lens distance t1 between the first lens 41 and the second lens 42 on the lens optical axis is defined as the first inter-lens distance t1, and the second lens 42 and the third lens 43 A second inter-lens distance t2 is defined as the inter-lens distance on the lens optical axis Lx. The total lens thickness T of the projection lens 4 is defined as the distance (dimension) from the first surface S1 of the first lens 41 to the sixth surface S6 of the third lens 43 on the lens optical axis Lx.

The first lens 41 to the third lens 43 constituting the projection lens 4 are made of a translucent material such as resin or glass. It is made of a translucent material with a low refractive index and low dispersion (high Abbe number). For example, the first lens 41 and the third lens 43 are made of crown glass, and the second lens 42 is made of flint glass. Alternatively, the first lens and the third lens are made of PMMA (acrylic resin), and the second lens 42 is made of polycarbonate resin.

In order to reduce chromatic aberration, astigmatism, and coma aberration, the projection lens 4 includes a front surface (first surface) S1 and a rear surface (second surface) S2 of the first lens 41, and a front surface (third surface) of the second lens 42 (third surface). At least the first surface S1 to the fifth surface S5 are designed to be aspheric It is In this embodiment, all of the first to sixth surfaces S1 to S6 are designed as aspherical surfaces based on the aspherical surface definition formula (1) shown in FIG. Here, z is the amount of sag, r is the radial dimension from the optical axis, R is the radius of curvature, k is the conic constant, and α ₁ to α ₂ are aspheric coefficients.

The headlamp HL of the embodiment having the projection lens 4 configured as described above is set to low beam light distribution control or high beam light distribution control by switching the lamp switch 51 by the driver or the like. During low beam light distribution control, the light emitting circuit 5 controls the four LED chips 301 to 304 in the upper stage to emit light. The white light emitted from these LED chips 301 to 304 is projected onto the front area of the automobile by the projection lens 4. In FIG. A low beam light distribution is formed that illuminates the area below the cutoff line approximately along H.

At the time of high beam light distribution control, the lower five LED chips 305 to 309 emit light under the control of the light emitting circuit 5 . The white light from these LED chips 305 to 309 is projected onto the front area of the automobile by the projection lens 4, and the illumination areas P5 to P9 are combined to form a light distribution. This light distribution is combined with the low beam light distributions P1 to P4 to form a high beam light distribution that illuminates a wide area.

On the other hand, when the ADB light distribution control is set by the driver, the light emitting circuit 5 basically controls the high beam light distribution, and based on the image picked up by the vehicle-mounted camera 52, the forward vehicle existing in the front area of the vehicle is detected. To detect. Then, control is performed so as to dim or extinguish the LED chips corresponding to the illumination areas overlapping the detected front vehicle, especially the areas overlapping the illumination areas P5 to P9. As a result, the illumination region to which the forward vehicle belongs is selectively shaded to prevent the forward vehicle from being dazzled, while the ADB light distribution is performed with improved visibility in other illumination regions.

Here, in order to brightly illuminate a wide area in front of the automobile with the light emitted from each of the LED chips 301 to 309, the focal length of the projection lens 4 should be as short as possible and the F number (=f/D) is preferred to be small. Therefore, in this embodiment, as shown in FIG. 6A, the focal length f is designed to be 57 mm, and the lens diameter D is designed to be 67 mm. As a result, the F-number is approximately 0.84, and the illuminance of the illumination area can be increased.

On the other hand, in order to shorten the focal length f of the projection lens 4 as much as possible, the positive refractive powers of the first lens 41 and the third lens 43 should be increased, and the first inter-lens distance t1 and the second inter-lens distance It is necessary to increase t2. However, if the first lens-to-lens distance t1 and the second lens-to-lens distance t2 are increased in this way, it becomes necessary to increase the negative refractive power of the second lens 42. Alternatively, high-order coma tends to become conspicuous, and the sharpness of the projection lens 4 deteriorates.

When chromatic aberration, astigmatism, or coma aberration in the projection lens becomes noticeable, the image of the light source emitted from the light source and projected in front of the vehicle becomes so-called "bokeh," and the spot diameter of the condensed light becomes large. . Therefore, in the case of the lamp unit 2 of the present invention, the sharpness is lowered in the shaded peripheral portions of the illumination regions P1 to P9 shown in FIG. 5, particularly in the side portions away from the lens optical axis Lx. , the boundaries between the illumination areas become ambiguous, resulting in conspicuous deterioration in visibility and light distribution quality, and there is a risk of dazzling vehicles ahead.

Therefore, after designing the first surface S1 to the sixth surface S6 of the projection lens 4 as described above, changes in sharpness are measured while changing the first inter-lens distance t1 and the second inter-lens distance t2. bottom. Here, light with a predetermined luminous flux diameter was incident from the front side of the projection lens 4, that is, from the left side of FIG. This is because the smaller the spot radius, the higher the sharpness. Here, the first lens-to-lens distance t1 and the second lens-to-lens distance t2 are made equal, and both are measured as the lens-to-lens distance t.

According to the measurement, as shown in FIG. 6(b), the ratio of the inter-lens distance t to the total lens thickness T, that is, t/T is in the range of 0.03<t/T<0.1, the spot radius is approximately 25 μm. It turns out that you can do the following. That is, a projection lens with high sharpness can be obtained.

If t/T is made larger than this, the spot radius increases and the sharpness of the projection lens 4 decreases. On the other hand, when t/T becomes smaller than 0.03, the adjacent lenses approach each other and interfere with each other, so that light outside the optical axis of the lens and at the pupil edge does not pass through and is not condensed into a spot. Therefore, the sharpness of the projection lens 4 is lowered for this reason as well.

Although not shown, even when t1 and t2 are different, t1/T and t2/T are set to 0.03<t1/T<0.1 and 0.03<t2/ By setting T<0.1, it is possible to suppress the spot radius and obtain a projection lens with high sharpness.

By designing the projection lens 4 so as to satisfy the above-described relationship between the first inter-lens distance t1 and the second inter-lens distance t2, the illumination regions P1 to P9 shown in FIG. The sharpness of the periphery is improved, and the boundaries of each illumination area become clear. As a result, the visibility in the illuminated area is improved, and dazzling of the preceding vehicle existing in the boundary area of the illuminated area can be reliably prevented.

In the above-described embodiment, an example in which the projection lens has an F-number of 0.84 has been described. By applying it, the sharpness can be improved without increasing the size of the projection lens, that is, without extremely increasing the total lens thickness and the lens diameter.

In the present embodiment, an example in which all of the first to sixth surfaces are designed to be aspheric has been described. The surface may be spherical. The present invention can also be applied to a meniscus lens in which the convex lenses of the first lens and the third lens and the concave lens of the second lens are both curved in the same direction.

Although this embodiment shows an example in which the light source is composed of nine LED chips to form an ADB light distribution, the present invention is not limited to this ADB light distribution. The pattern shape of each illumination area can be set arbitrarily. It can also be applied to a headlamp using a MEMS (micro electromechanical systems) mirror array as a light source.

HL headlamp 1 lamp housing 2 lamp unit 3 light source 4 projection lens 5 light emitting circuit 41 convex lens (first lens)
42 concave lens (second lens)
43 convex lens (third lens)
301-309 LED chips (light-emitting elements)
S1 to S6 1st to 6th surfaces t1, t2 Inter-lens distance T Total lens thickness

Claims (5)

A vehicle lamp including a light source and a projection lens for projecting light emitted from the light source, wherein the projection lens comprises a first lens comprising a biconvex lens having positive refractive power and a biconcave lens having negative refractive power. and a third lens made of a biconvex lens having positive refractive power, wherein the first lens and the third lens are made of a translucent material with a lower dispersion than the second lens. A first inter-lens distance t1 between the first lens and the second lens, a second inter-lens distance t2 between the second lens and the third lens, and a total lens thickness T of the projection lens are A vehicular lamp characterized by having relationships of 0.03<t1/T<0.1 and 0.03<t2/T<0.1. The vehicle lamp according to claim 1 , wherein the first inter-lens distance t1 and the second inter-lens distance t2 are different. 3. The vehicle lamp according to claim 1, wherein the projection lens has an F-number smaller than 1.0. 4. The vehicle according to any one of claims 1 to 3 , wherein the light source comprises a plurality of light emitting elements, and the light emitted from each light emitting element is projected by the projection lens to form a plurality of corresponding illumination areas. lamp. 5. The vehicle lamp according to claim 4 , wherein ADB light distribution control is performed by individually controlling light emission of the plurality of light emitting elements.

Images