JPH03724B2 - - 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 incident on the lens is irradiated forward as a substantially parallel light source. Figure 1 shows a cross section of such a front lens, and as seen in Figure A, the density of light incident from light source C on the Fresnel prism of lens b is at the end of lens b. It has decreased by a certain amount. Therefore, there is a large difference in the brightness of the lens surface between the portion near the optical axis Z and the end of the lens, and the light distribution performance of the lamp becomes unfavorable.

In addition, Figure B shows a multi-lamp type lamp with multiple light sources arranged inside the lamp chamber, but in this case as well, the middle part between the optical axes Z and Z becomes a dark part where the amount of light is low, and the brightness of the lens surface decreases. It becomes non-uniform.

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, with this method, the density distribution of the light reflected by the reflective 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 larger light-emitting areas, 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 part of the Fresnel prism facing the light source bulb socket is a reflective Fresnel prism, the other part is a refractive Fresnel prism, and the planar area of each segment of the refractive Fresnel prism is Provided is a method for forming the shape of the reflecting surface so that the ratio of the amount of luminous flux incident on each segment to the planar area of each segment is all substantially constant by changing the amount of luminous flux incident from the reflecting surface accordingly. It is. Hereinafter, details of the method of the present invention will be explained based on embodiments shown in the drawings.

In addition, in the following explanation, the case of a multi-lamp type lighting fixture in which a plurality of light sources are arranged in the lamp chamber will be mainly described, but the present invention is not particularly limited to the case of a multi-lamp type, and can be applied to a single-lamp type. This can be similarly applied to other lighting equipment.

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.
Light sources 3a and 3b are disposed within a lamp chamber defined by a front lens 2 and a front lens 2 disposed in front of the light source. Center lines Z and Z passing through the light sources 3a and 3b are the optical axis of the lamp. The front lens 2 has Fresnel prisms 2a, 2b, 2c, and 2d each consisting of a plurality of segments on its inner surface on the housing side. Further, the lens-side inner surface of the housing 1 has reflective surfaces 1a and 1b formed into mirror-like surfaces by metal vapor deposition, etc., and the light emitted from the light source 3 is reflected by the reflective surfaces 1a and 1b.
It is configured so that the light is reflected by a and 1b and incident on Fresnel prisms 2a and 2c of the front lens 2.

The light source bulbs 3a and 3b are each connected to a socket 31.
It is fixed to the housing 1 by holders 32a and 32b via a and 31b. Front lens 2
Of the Fresnel prisms provided in the , the Fresnel prisms 2a and 2c into which the reflected light from the reflective surfaces 1a and 1b enters are refractive Fresnel prisms, and the reflected light does not enter into the Fresnel prisms and the light sources 3a and 3b
a light source bulb socket 31a into which direct light enters;
Fresnel prism 2a in the part facing 31b,
2b is a reflective Fresnel prism.

In the present invention, the curved shapes of the reflective surfaces 1a and 1b are configured so that the reflected light from the reflective surfaces 1a and 1b is incident on each segment of the Fresnel prism 2a 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 that the prism segment is a concentric Fresnel.
If the radius of the innermost edge (vertical distance from optical axis Z) where optical path l ₁ of P _o enters is r ₁ and the radius of the outermost edge where optical path l ₂ enters is r ₂ , then the light receiving surface of prism segment P _{o is} The plane area _So is _So ≒ 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 _Ro extends to the light source 3 is , the angle of optical path l ₁ with respect to optical axis Z is θ ₁ , and the angle of optical path l ₂ with respect to 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
The vertical distance from the light source 3 to the origin O (the center point of the reflective surface 1a) is f.
shall be.

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 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 is 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, 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 Fig. 5), which is separated from the first reflection point P ₀ by a minute dimension p in the X-ray direction, 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 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.

FIG. 7 is a sectional view showing another embodiment of the vehicle lamp of the present invention. In this embodiment, the light source bulb sockets 31a and 31 of the front lens 2 are
The portion facing b (the portions 2b and 2d in FIG. 3 above) is a compound lens provided with inner lenses 4a and 4b. The direct light from the light sources 3a, 3b is once incident on the reflective Fresnel prisms 41a, 41b of the inner lenses 4a, 4b, and then is projected through the refractive Fresnel prism of the front lens 2. Therefore, according to this example, it is possible to eliminate the sense of discontinuity between the refractive Fresnel prism and the reflective prism of the front lens as in the previous example.

FIG. 8 is a sectional view showing still another embodiment of the vehicle lamp of the present invention. In this example, the front lens 2 is constructed as a composite lens consisting of an outer lens 21 and an inner lens 22 as a whole. The inner lens 22 in this case, like the front lens 2 in the example shown in FIG. is fisheye prism 2
1a. The light is emitted from the light sources 3a and 3b and reflected by the reflecting surfaces 1a and 1b, and the light is emitted from the inner lens 2.
2 and the light that directly enters the inner lens 22 from the light sources 3a and 3b is controlled to be substantially parallel light by the Fresnel prism of the inner lens 22, and enters the outer lens 21, and the light that enters the outer lens 21 through the fisheye prism 21a of the outer lens 21. The light is controlled to obtain a light distribution pattern according to the required light distribution standard, and the light is projected outside the lamp room.

As described in detail above, according to the method for forming a reflective surface according to the present invention, instead of a reflective surface having a substantially paraboloid of revolution shape (FIG. 2a) in the prior art, a reflective surface having a curved surface set by an original calculation is used. Using surfaces 1a and 1b,
It can be configured such that the luminous flux density of the reflected light incident on 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. Furthermore, in the conventional lamps shown in FIGS. 1 and 2, the prism angle of the prism of the front lens is set so as to control the direct light incident from the light source, but according to the method of the present invention, the prism angle is set so as to control the direct light incident from the light source. As is clear from the figure, the prism angle can be set to control the reflected light that enters at a smaller angle of incidence than the former, so the prism angle only needs to be large, and the height of the prism peaks can therefore be reduced. becomes smaller. This has the effect of improving the molding conditions for the lens and reducing the weight of the lens itself. As described above, the method of the present invention can provide a lamp with excellent performance that cannot be obtained with conventional vehicular lamps.

[Brief explanation of drawings]

1A, B and 2 are sectional views schematically illustrating conventional examples of vehicle lamps, and FIG. 3 is a partial sectional view schematically illustrating an embodiment of a method for forming a vehicular 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. 7 is a sectional view of another embodiment of the vehicle lamp according to the present invention, and FIG. 8 is a sectional view of still another embodiment. 1... Housing, 1a, 1b... Reflective surface, 2
...Front lens, 2a, 2b, 2c, 2d...Fresnel prism, 21...Outer lens, 21
a...Fisheye prism, 22...Inner lens,
22a, 22b, 22c, 22d... Fresnel prism, 3, 3a, 3b... light source, 31a, 31
b...Socket, 32a, 32b...Holder,
4a, 4b... Inner lens, 41a, 41
b...Fresnel prism.

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. The part of the Fresnel prism facing the light source bulb socket is provided with a reflective Fresnel prism, and the other part is provided with a refractive Fresnel prism, and the reflective surface is formed in the following manner. Accordingly, the reflective surface of a vehicle lamp is configured such that the ratio between the amount of luminous flux incident on each segment of the refractive Fresnel prism and the planar area of each segment is all approximately constant. How to form. 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 coordinate P _{0 '} of the first point of incidence on 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.