JPH03726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lamp for a vehicle such as an automobile. More specifically, the present invention relates to a vehicle light that is capable of uniformizing the brightness of the lens surface in a vehicle light that has a plurality of bulbs arranged horizontally in a light chamber defined by a housing and a front lens. be.

Conventionally, in the above-mentioned vehicle lamp, a Fresnel prism consisting of a plurality of segments is installed on the front lens, of which the part near the center of the optical axis is a refractive Fresnel prism, and the surrounding part is a reflective Fresnel prism, which is used to act as a light source. Generally, the lens is constructed so that the light incident on the lens is irradiated forward as substantially parallel light rays. Figure 1 shows a cross section of such a vehicle lamp. As seen in the figure, the light chamber for the stop and table lamp of the rear combination lamp for an automobile is formed into an elongated shape, and the length of the light chamber is Two bulbs a ₁ and a ₂ are placed horizontally along the direction, and the light source C (filament)
are arranged facing each other, and when bulbs a ₁ and a ₂ are lit, the density of light incident from each light source C on the Fresnel prism of elongated lens b becomes the end of lens b. It has decreased by a certain amount. That is, the portions of each bulb a ₁ and a ₂ that are close to the optical axes Z and Z have the highest amount of light, and the ends and middle portions that are farthest from the optical axes Z and Z are dark portions that have less amount of light, and the lens b The brightness of the surface becomes non-uniform, and the light distribution performance of the lamp becomes unfavorable.

Therefore, in order to improve this drawback, a method is taken in which a reflective surface is provided opposite the portion of the front lens where the light density decreases, and the reflected light is made to enter the lens. FIG. 2 is a sectional view schematically showing the structure of such a lamp. That is, a substantially paraboloid-shaped reflecting surface d is provided opposite to a lens portion where the density of light incident on the front lens b from the light source C is significantly reduced, and the light from the light source C is reflected by the reflecting surface d. The light is incident on a portion of the front lens b where the luminous flux density is low. However, as is clear from the figure, in this method, the density distribution of the reflected light by the reflecting surface a also decreases as the distance from the optical axis Z increases, so a decrease in brightness near the lens end is inevitable, and the improvement effect is not sufficient. Even if the reflected light is incident on the lens by the parabolic reflecting surface, the amount of light incident on each part of the lens is not uniform, and the amount of light is large in the part near the optical axis Z. The situation still remains that the further away from , the smaller the amount. In particular, in a lamp in which a plurality of bulbs are arranged in a long and narrow lamp chamber as described above, such a difference in brightness on the lens surface becomes even more remarkable.

In this way, conventional vehicle lights have the problem that the brightness of the peripheral area and the intermediate area between the multiple optical axes is lower than the brightness of the area close to the optical axis, resulting in uneven lens surface brightness. It was hot. This drawback is particularly prevalent in lamps with relatively large light emitting areas, such as tail lamps, and has become a serious problem in vehicular lamps.

The present invention has been made with attention to the problems in the prior art as described above, and is intended to solve these problems. That is, the present invention provides a vehicle lamp in which a plurality of bulbs are arranged horizontally in a lamp chamber defined by a housing and a front lens as described above, in which a reflective surface is provided on the housing side opposite to the front lens, The front lens is provided with a Fresnel prism consisting of a plurality of segments, and the amount of light that crosses the optical axis and enters from the reflective surface is changed according to the planar area of each segment of the Fresnel prism, and The present invention provides a method for forming the shape of a reflecting surface so that the ratio between the amount of incident light flux and the planar area of each segment is all approximately constant. Hereinafter, details of the method of the present invention will be explained based on embodiments shown in the drawings.

FIG. 3 is a partial sectional view showing one embodiment of the vehicle lamp according to the present invention. In the figure, 1 is a housing made of synthetic resin or the like.
Two bulbs A and B are placed horizontally in a lamp chamber defined by a lamp and a front lens 2 disposed in front of the lamp. Further, the light sources (filament portions) 3a and 3b of the bulbs A and B are arranged in opposite directions and are fixed to the housing 1 by holders 32a and 32b via sockets 31a and 31b, respectively. Center lines Z and Z passing through the light sources 3a and 3b are optical axes. The front lens 2 is provided with Fresnel prisms 2a and 2b consisting of a plurality of segments on its inner surface on the housing side. Also, reflective surfaces 1a and 1b are provided on the housing 1 side corresponding to the light sources 3a and 3b, and the light emitted from the light sources 3a and 3b is reflected by these reflective surfaces 1a and 1b to intersect with the optical axes Z and Z. It is configured such that the light is incident on the Fresnel prisms 2a and 2b of the front lens 2.

In the present invention, each segment of the Fresnel prisms 2a, 2b has reflective surfaces 1a, 1b.
The curved surfaces of the reflecting surfaces 1a and 1b are configured so that the reflected light from the reflecting surfaces 1a and 1b is incident with a constant luminous flux density. FIG. 4 is an explanatory diagram illustrating the state of incident light to a Fresnel prism, in which light emitted from the light source 3 between optical paths l ₁ and l ₂ is reflected on the light receiving surface of an arbitrary prism segment P _o . It is assumed that the prism is a concentric Fresnel, and the _radius of the innermost _edge (optical axis _Z If ^r ₁ is _the radius of the outermost edge where _the optical _{path l 2} enters ( _{perpendicular} distance ^from ₁ ) ...(1) Also, the solid angle ω between the optical paths l ₁ and l ₂ that the reflective surface portion R _o extends with respect to the light source 3 is as follows: θ 1 is the angle of the optical path l ₁ with respect to the optical axis Z, and θ ₁ is the angle of the optical path l ₁ with respect to the optical axis Z. The angle with respect to the optical axis Z is θ ₂
Then, ω _o =2π(cosθ ₁ −cosθ ₂ ) ...(2). It is clear that the amount of luminous flux incident on the light-receiving surface of the prism segment P _o is directly proportional to the solid angle ω, so the luminous flux density of the reflected light incident on each prism segment (the amount of luminous flux per unit plane area of the light-receiving surface) is In order to make it constant, the ratio between the planar area S _o of the light receiving surface and the solid angle ω may be made constant. In other words, the following S _o /ω _o S _o /ω _o = (r ² ₂ − ^{r 2} ₁ )/2 (cos θ ₁ − cos θ ₂ )……(3) derived from the above equations (1) and (2) is The curved shape of the reflecting surface 1a is set so that the prism segment has a constant value.

The curved shape of this reflective surface may be set as follows. In other words, in Fig. 5, the center of the optical axis of the lamp is the Z axis, and the Z axis passes through the innermost point _P0 of the reflective surface.
Set the axis perpendicular to the axis as the X axis. The vertical distance (X coordinate) from the optical axis (Z axis _{) of the above point P 0 is} L, and _the optical axis (Z
L' is the vertical distance from the light source 3a to the origin O
Distance (focal length) to (center point of reflective surface 1a)
Let be f.

When designing a vehicle lamp, these f, L,
The value of L' is usually given as a design condition or can be set based on the designer's judgment, so to speak, as a starting point for the design procedure.

Next, an embodiment of the design procedure according to the method of the present invention will be described with reference to FIGS. 5 and 6.

Step 1 3a is the position of the light source, and this point is defined as P _f (O,
f).

If we consider this point specifically in relation to the constituent members, it is the light source (filament of the light source valve) 3a, and if we consider it analytically as one point P _f in space, then the point with X coordinate = O and Z coordinate = f (O, f).

As mentioned above, the above value f can be given as a design condition or can be set as appropriate.

Next, a first incident point P ₀ (L, O) on the reflective surface and a first incident point P ₀ '(L', z ₀ ') on the lens are set. In this case, the values of L and L' can be given as design conditions or can be set arbitrarily.

Here, the value of z ₀ ' may be determined by applying a known method using a separately determined lens equation.

Step 2 As can be easily understood from Fig. 5, the coordinates of the light source P _f (O, f) and the first incident point P ₀ (L, O) of the reflecting surface
Once the coordinates of are determined, the optical path l ₀ from the light source P _f to the first incident point P ₀ is determined.

Similarly, the optical path l ₀ ' from the first incident point P ₀ to the first incident point P ₀ ' of the lens is determined.

Step 3 Find the neutral line N ₀ as the bisector of l ₀ and l ₀ ' (see Figure 6), and find the line perpendicular to this neutral line N ₀ at point P ₀ (this is the line on the reflecting surface 1a). Corresponding to the tangent equation) Find z=a ₁ x+b ₁ .

Step 4: Set the second incident point P 1 (x ₁ , _{z 1 )} on the reflecting surface 1a (see Figure 5), which is a minute distance p in the X-axis direction from the first reflection point P ₀ , as described above. Tangent line z=a ₁ x+
b Find above ₁ .

This method applies a method known as the tangent method to obtain an approximate value, but the above-mentioned minute dimension p
By making it sufficiently small (0.1 mm in this example), the error can be made small enough to be practically considered as O.

Steps 1 to 4 above are the application of publicly known techniques regarding lamp design, but in order to achieve the purpose of the present invention (uniform brightness on the lens surface), step 5 described below is the most important.

This step 5 is a procedure for finding a point P ₁ ' at which the reflected light at the second reflection point P ₁ enters the lens 2. This is because once this second incident point P ₁ ' is determined, the optical path l ₁ ' is determined by calculating backwards from this, and once the optical path l ₁ ' is determined, the shape of the reflecting surface is determined.

Since this second incident point P ₁ ′ (x ₁ ′, z ₁ ′) is naturally located at two points of the lens, the second incident point P ₁ ′ (x ₁ ′, z ₁ ′) ) is most important to find the value x ₁ ' of the X coordinate.

Step 5 Use the following equation (11) to determine the second incident point on the lens.
Find the X coordinate X ₁ ′ of P ₁ ′ (x ₁ ′, z ₁ ′). This formula (11)
is derived as follows.

That is, to find the solid angle ω ₀ that the space between the Z axis (optical axis) and the optical path l ₀ extends to the light source 3a,
If the angle that the optical path l ₀ makes with the Z axis is θ ₀ , then In other words, the solid angle ω ₀ to be found is becomes.

Next, when light within the range of the solid angle ω ₀ from the light source 3a is reflected by the reflecting surface 1a and enters the lens 2, the planar area S ₀ of the light receiving part on the lens 2 is the optical path.
It is determined by the distance L' of the incident point P ₀ ' through l ₀ ', and S ₀ = πL' ² ...(6).

From the above, the ratio of ω ₀ and S ₀ is becomes.

Similarly, the solid angle ω ₁ between the optical paths l ₀ and l ₁ with respect to the light source 3a, and the light within the range of the solid angle ω ₁ is reflected by the reflecting surface 1a and enters the lens 2. When we calculate the plane area S ₁ on lens 2, we get S ₁ = π(x′ ² −L′ ² ) ……(9).

Therefore, the ratio of ω ₁ and S ₁ is becomes.

As mentioned above, in order for the density of the amount of light flux incident on each part of the lens 2 to be constant, S ₀ /ω ₀ =S ₁ /ω ₁ , so from equations (7) and (10), sort this out get.

however, L≒O, L≠O L′≒O, L′≠O L≠L′ It is.

Step 6: Obtained in step 5 using the lens formula above.
Find the Z coordinate z ₁ ′ for x ₁ ′, and
Determine the incident point P ₁ ′ (x ₁ ′, z ₁ ′).

Step 7 Using the coordinate values of each point P _f , P ₁ , P ₁ ' obtained as above, calculate the optical path l ₁ from the light source P _f to the second reflection point P ₁ and the second reflection point. Optical path from P ₁ to second incident point P ₁ ′
Find l ₁ ′, and repeat these steps in the same way to obtain the third reflection point P ₂ (x ₂ , z ₂ ), the third incident point P ₂ ′ (x ₂ ′, z ₂ ′), and so on. , points P ₂ and P ₃ on the reflective surface (not shown)
All you have to do is calculate the coordinates and tangents of ... and set the curved surface of the reflective surface according to the obtained coordinate values. However, in order to improve the calculation accuracy, it is preferable to make the pitch p of the calculation points as small as possible (for example, a value of 1/10 mm or less), and since the amount of calculation will be quite large, it is better to use a computer to calculate it. Not even. By setting the reflective surface 1a based on such calculations, the reflected light from the reflective surface can be made to enter each Fresnel prism segment of the front lens 2 with a constant luminous flux density.

The curved surface of the reflective surface 1b is also set in exactly the same way as the curved surface of the reflective surface 1a is set as described above.

Furthermore, the present invention further reduces the amount of light incident on the vicinity of the end of the front lens 2 and the vicinity of the intermediate part of both optical axes Z by arranging a plurality of bulbs spaced apart in opposite directions. This facilitates configuration.
That is, as shown in FIG. 3, the light sources 3a and 3b are both directed toward the left and right ends K and K of the front lens 2,
Also, by placing it close to both ends K and K, the rising portion e in the direction of the sockets 31a and 31b on the reflective surfaces 1a and 1b is
Although it is restricted by the above, it is possible to make it sufficiently incident near both ends K and K. Further, since there is no restriction on one rising portion h of the reflective surfaces 1a and 1b up to the height of the light sources 3a and 3b, the intermediate portion M of the front lens 2
can be made sufficiently incident.

Furthermore, a fisheye prism 2 is placed on the outside of the front lens 2.
By arranging the outer lens 21a subjected to the above-described method 1, it becomes easy to obtain a light distribution pattern in accordance with a required light distribution standard for the light incident from the light sources 3a and 3b.

Note that the bottom of the housing 1 may be a back cover.

As described in detail above, according to the method for forming a reflective surface according to the present invention, instead of the substantially paraboloid-shaped reflective surface (FIG. 2 d) in the prior art, a reflective surface having a curved surface set by original calculation is used. Using surfaces 1a and 1b,
It can be configured such that the luminous flux density of the reflected light that crosses the optical axis and enters the front lens is substantially constant for each prism segment of the lens. Therefore, the method of the present invention solves the problem of conventional lamps in which the brightness of the lens decreases as the distance from the optical axis increases, and a lamp with uniform brightness across the front surface of the lens and excellent light distribution performance can be obtained. can get. Additionally, as shown in Figure 3, the angle of incidence on the lens between the direct light from the light source and the light reflected from the reflective surface is quite close, making it easier to effectively control direct light and increasing the effective light amount of the entire lamp. It is possible to provide lamps with excellent performance such as.

[Brief explanation of the drawing]

1 and 2 are partial cross-sectional views schematically showing two examples of conventional vehicle lamps, and FIG. 3 is a partial cross-sectional view schematically showing one embodiment of a method for forming a vehicle lamp according to the present invention. FIG. 4 is an explanatory diagram showing the state of incident light on the lens prism in a vehicle lamp according to the method of the present invention, FIG. 5 is an explanatory diagram of a reflective surface according to the method of the present invention, and FIG. FIG. 3 is an explanatory diagram of the calculation process of reflective surface design in one embodiment. 1... Housing, 1a, 1b... Reflective surface, 2
...Front lens, 3a, 3b...Light source.

Claims (1)

[Scope of Claims] 1. In a vehicular lamp in which a light source is disposed within a lamp chamber defined by a housing and a front lens, the plurality of bulbs are spaced apart from each other in opposite directions along the longitudinal direction of the lamp chamber. A reflective surface is provided corresponding to each bulb on the housing side facing the front lens, and the front lens is provided with a Fresnel prism consisting of a plurality of segments, and each of the reflective surfaces is as follows. For a vehicle, the ratio of the amount of luminous flux that crosses the optical axis and enters each segment to the flat area of each segment is all approximately constant by setting according to the procedure of How to form the reflective surface of a lamp. Step 1: The value of f in the coordinates P _f (O, f) of the light source, the value of L in the coordinates P ₀ (L, O) of the first incident point on the reflecting surface, and
X coordinate of the coordinate P ₀ ′ (L′, z ₀ ′) of the first incident point of the lens
Set the value of L′. Here, the value of the Z coordinate z ₀ ' is obtained by substituting the X coordinate L' into a separately determined lens equation. Step 2 The light source is determined by the coordinates P _f (O, f) and P ₀ (L, O).
Find the optical path l ₀ from P _f to the first incident point P ₀ on the reflective surface, and use the coordinates P ₀ (L, O) and P ₀ ′ (L′, z ₀ ′) to find the first incident point P 0 on the reflective surface. Find the optical path l 0 ' from the point P ₀ to the coordinates P _{0 '} of the first incident point of the lens. Step 3: Find the neutral line N 0 from the above optical paths l ₀ and l ₀ ', and find the neutral line N ₀ perpendicular to the neutral line N ₀ . Then, find the tangent line z=a ₁ x+b ₁ at the first incident point P ₀ . Step 4 Next incident point after the first incident point P ₀ on the reflective surface
The Z coordinate z ₁ with respect to the X coordinate (x ₁ =L+p) of P ₁ is determined as an approximate value on the tangent line z=a ₁ x+b ₁ by setting a value p for a minute increase in x. Step 5 Use the following equation (11) to find the next incident point on the lens.
Find the X coordinate x ₁ ′ of P ₁ ′ (x ₁ ′, z ₁ ′). However, L≠O, L'≠O, L≠L'
Perpendicular _distance (on _the (on the axis) Distance L = Vertical (on the X-axis) distance from the optical axis center (Z-axis) of the above point P ₀ = Focal length (distance on the Z-axis from the light source to the above point P ₀ ) x = Reflection point on the reflective surface of the light incident on the above P ₁ ' point
Vertical from the optical axis center (Z axis) of P ₁ (on the X axis)
Distance z = Z coordinate of _one point of the above P (distance along the optical axis center Z axis) Step 6 Obtained in step 5 using the above lens formula
Find the Z coordinate z ₁ ' with respect to x ₁ ' and determine the next incident point P ₁ ' (x ₁ ', z ₁ ') on the lens. Step 7 P _f (O, f), P ₁ (x ₁ ,
z ₁ ), P ₁ ′ (x ₁ ′, z ₁ ′), the optical path l ₁ from the light source P _f to point P ₁ and the optical path l ₁ ′ from point P ₁ to point P ₁ ′ are Then, repeat these steps sequentially.