JPH03725B2 - - 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 vehicular lamp in which a light source is disposed within a lamp chamber defined by a housing and a front lens, in which the brightness of the lens surface can be made uniform.

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 entering the lens is projected forward as substantially parallel lines. Figure 1 shows a cross section of such a front lens, and as seen in the figure, the light source C is connected to the Fresnel prism of lens b.
The density of light incident from the lens b decreases toward the end of the lens b. Therefore, there is a large difference in the brightness of the lens surface between the part near the optical axis Z and the end of the lens, 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 a 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 a. The light is made 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.

As described above, the conventional vehicular lamp has a problem in that the brightness in the peripheral area is lower than the brightness in the area close to the optical axis, resulting in non-uniformity in the lens surface brightness. This drawback is more severe 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 light source is disposed within 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, and a plurality of reflective surfaces are provided on the front lens. The Fresnel prism is provided with a Fresnel prism consisting of segments, and the amount of light flux that intersects 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 amount of light flux that enters each segment and each The present invention provides a method for forming the shape of a reflecting surface so that the ratio of the plane area of each segment to the plane area of each segment is substantially 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.
A light source 3 is disposed within a lamp chamber defined by a front lens 2 and a front lens 2 disposed in front of the lamp. A center line Z passing through the light source 3 is the optical axis of the lamp. The front lens 2 is provided with a Fresnel prism 2a consisting of a plurality of segments on its inner surface on the housing side. Further, the inner surface of the housing 1 on the lens side is a reflective surface 1a formed into a mirror surface by metal vapor deposition, etc., and the light emitted from the light source 3 is reflected by the reflective surface 1a.
It is configured such that the light is reflected by a, intersects the optical axis Z, and enters the Fresnel prism 2a of the front lens 2.

In the present invention, the curved shape of the reflective surface 1a is configured so that the reflected light from the reflective surface 1a is incident on each segment of the Fresnel prism 2a, crossing the optical axis Z 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 _radius (optical axis _Z If the radius of the outermost edge where the optical path l ₂ is incident is r ₁ , the planar area S _o of the light receiving surface of the prism segment P _o is S _o ≒ _π (r ² ₂ − ^{r 2} 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. If the angle with respect to the optical axis Z is θ ₂ , then ω _o =2π(cos θ ₁ −cos _{θ 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 light reception 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, the point on the lens 2 that is reflected at the point P ₀ and enters the optical axis and crosses the optical axis.
The vertical distance of P ₀ ' from the optical axis (Z axis) is L', and the distance (focal length) from the light source to the origin O (center point of the reflective surface 1a) is 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, and is the starting point of 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 3 is the position of the light source, and this point is P _f (O, f)
shall be.

Considering this point specifically in relation to the constituent members, it is the light source (filament of the light source bulb) 3,
Analytically speaking, one point P _f in space is a point (O, f) with X coordinate = O and Z coordinate = 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 P _f (O, f) of the light source 3 and the first incident point P ₀ (L,
Once the coordinates of O) are determined, the first incident point P ₀ from the light source P _f
The optical path l ₀ leading to is found.

Similarly, from the first incident point P ₀ to the first
The optical path l ₀ ' leading to the incident point P ₀ ' 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 known method as the tangent method to obtain approximate values, but by making the minute dimension p sufficiently small (0.1 mm in this example), the error can be reduced in practical terms. It can be made small enough to be 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 makes with respect to the light source 3, 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 solid angle ω ₀ from the light source 3 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 3, and the light within the range of the solid angle ω ₁ are reflected by the reflective surface 1a and incident on the lens 2, resulting in a When calculating the plane area S ₁ on lens 2, 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.

As explained above, according to the method for forming a reflective surface according to the present invention, a reflective surface having a curved surface set by an original calculation, instead of a reflective surface having a substantially paraboloid of revolution shape (FIG. 2a) in the prior art. 1a, 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 approximately 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 the brightness is uniform across the front surface of the lens.
A lamp with excellent light distribution performance can be obtained.

In addition, as shown in Figure 3, the direct light from the light source, the reflected light from the reflective surface, and the lens incidence angle are quite close to each other, making it easier to effectively control direct light and increasing the effective light amount of the entire lamp. We can provide lighting equipment with excellent performance.

[Brief explanation of drawings]

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...Reflecting surface, 2...Front lens, 2a...Fresnel prism, 3...Light source.

Claims (1)

[Claims] 1. A vehicle lamp in which a light source is arranged in a light chamber defined by a housing and a front lens, in which a reflective surface is provided on the housing side facing the front lens, and a plurality of reflective surfaces are provided on the front lens. In addition to being equipped with a Fresnel prism consisting of segments,
By setting the reflecting surface according to the following procedure, the ratio of the amount of reflected light flux that intersects the optical axis and enters each segment to the planar area of each segment is all approximately constant. A method for forming a reflective surface of a vehicle lamp, characterized by: 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.