JPH03723B2 - - 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 substantially parallel light rays. Figure 1 shows a cross section of such a front lens, and as seen in the figure, the density of light incident from light source C on the Fresnel prism of lens b decreases toward the end of lens b. are doing. 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 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 vehicular 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 the front lens is constituted by a composite lens consisting of an inner lens and an outer lens, and the inner lens is equipped with a prism consisting of a plurality of segments, and a reflective surface is provided on the housing side opposite to the inner lens, the prism of the inner lens is a Fresnel prism that controls incident light into approximately parallel light, and the outer lens is a fish-shaped prism. As an eye prism,
The shape of the reflective surface is such that the amount of light flux incident on the reflective surface is changed according to the planar area of each segment of the prism, and the ratio of the amount of luminous flux incident on each segment to the planar area of each segment is approximately constant. The present invention provides a method for forming a . Hereinafter, details of the method of the present invention will be explained based on embodiments shown in the drawings.

FIG. 3 is a diagram showing one embodiment of the vehicle lamp according to the present invention, in which A is a sectional view and B is a partially cutaway front view.

In the figure, reference numeral 1 denotes a housing made of synthetic resin or the like, and a light source 3 is disposed within a lamp chamber defined by the housing 1 and a front lens 2 disposed in front of the housing. A center line Z passing through the light source 3 is the optical axis of the lamp. The front lens 2 is configured as a compound lens consisting of an inner lens 22 and an outer lens 21.
A Fresnel prism 22a consisting of a plurality of segments is provided on the outer surface of the outer lens 2.
1 has a fisheye lens 21a formed on its inner surface. The inner surface of the housing 1 on the lens side is a reflective surface 1a formed into a mirror-like surface by metal vapor deposition, etc., and is configured so that the light emitted from the light source 3 is reflected on this reflective surface 1a and made to enter the inner lens 22. has been done. The Fresnel prism 22a of the inner lens 22 controls the reflected light from the reflective surface 1a into substantially parallel light and makes it enter the outer lens, and the fisheye prism 21a formed on the outer lens 21 makes the light enter the outer lens from the inner lens 22. The light is controlled and projected forward in a desired light distribution.

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 22a with a constant luminous flux density. Fourth
The figure is an explanatory diagram showing the situation of incident light to a Fresnel prism, but any prism segment
It is assumed that the light emitted from the light source 3 between the optical paths l ₁ and l ₂ enters the light receiving surface of P _o after being reflected by the portion R _o of the reflecting surface, and that the prism is a concentric Fresnel, and the prism The radius of the innermost edge (vertical distance from optical axis Z) where optical path l ₁ of segment P _o enters is
If r ₁ is the radius of the outermost edge where the optical path l ₂ is incident, r ₂ is,
The planar area S _o of the light receiving surface of the prism segment P _o is So ≒ _π (r ² ₂ − r ² ₁ ) ......(1) Also, the optical path l ₁ that the reflective surface portion R _o extends to the light source 3 , l ₂ is the angle between optical path l ₁ with respect to optical axis Z as θ ₁ and the angle of optical path l ₂ with respect to optical axis Z as 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 of the planar area Sn of the light receiving surface to the solid angle ω may be made constant. That is, the following S _o /ω _o S _o /ω _o = (r ² ₂ − ^{r 2} ₁ )/2 (cos θ ₁ − cos θ ₂ ) derived from the above equations (1) and (2).
3) The curved shape of the reflecting surface 1a is set so that the value is constant for each prism segment.

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 vertical distance from the optical axis (Z-axis) of the point P ₀ ' on the lens 22 that is reflected at point P ₀ and enters. is L′, from light source 3 to origin 0
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 3 is the position of the light source, and this point is P _f (0, 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 (0, f) with an X coordinate of 0 and a Z coordinate of 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, 0) 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 Figure 5, the coordinates of the light source P _f (0, f) and the first incident point P ₀ (L, 0) of the reflective 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 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 reduced to such an extent that it can be practically considered as zero.

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 22. 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 Next, by equation (11), the second incident point on the lens is determined.
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≒0, L≠0 L′≒0, L′≠0 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 then 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.

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 provided on the outer surface of the inner lens 22 with a constant luminous flux density. In this way, the light incident on the inner lens 22 enters the outer lens 21 as light substantially parallel to the optical axis Z by the Fresnel prism 22a on the outer surface, and then enters the outer lens 21 as light substantially parallel to the optical axis Z.
1a, the light is emitted while being controlled to have a desired light distribution characteristic.

Note that, without being limited to the above embodiments, the outer lens 21 may be configured as a cover lens, a fisheye prism may be provided on the outer surface of the inner lens 22,
A Fresnel prism may be provided on the inner surface.

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 the surface 1a, it is possible to configure the front lens so 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. Therefore, the molding conditions for the lens are improved, and the lens itself can also be made lighter. 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 the drawing]

Figures 1 and 2 show conventional vehicle lights, respectively. Figure 1 is a partial sectional view of a lamp that uses only direct light, and Figure 2 is a partial cross-sectional view of a lamp that uses direct light and reflected light. FIG. 3 to 6 show a vehicle lamp according to the present invention, FIG. 3A is a front view, FIG. 3B is a cross-sectional view taken from FIG. FIG. 5 is an explanatory diagram showing the state of incident light on the prism, FIG. 5 is an explanatory diagram of the reflective surface according to the method of the present invention, and FIG. 6 is an explanatory diagram of the calculation process for designing the reflective surface in one embodiment of the method of the present invention. be. DESCRIPTION OF SYMBOLS 1...Housing, 1a...Reflection surface, 2...Front lens, 2a...Fresnel prism, 3...Light source, 21...Outer lens, 21a...Fisheye prism, 22...Inner lens, 22a... Fresnel prism.

Claims (1)

[Scope of Claims] 1. A vehicular lamp in which a light source is arranged in a lamp chamber defined by a housing and a front lens, in which the front lens is composed of a composite lens consisting of an inner lens and an outer lens, and the inner lens The prism of the inner lens is a Fresnel prism that controls incident light into approximately parallel light, the outer lens is a fisheye prism, and the prism is opposed to the inner lens and reflected toward the housing side. By providing a surface and setting the reflective surface according to the following procedure, the ratio of the amount of light flux incident on each segment of the prism of the inner lens to the plane area of each segment is all approximately constant. A method for forming a reflective surface of a vehicle lamp, characterized by: Step 1 Value of f at the coordinates P _f (0, f) of the light source, value L at the coordinates P ₀ (L, 0) of the first incident point on the reflective surface,
and the coordinates of the first incident point of the lens P ₀ ′(L′,
Set the value of the X coordinate L' of z ₀ '). 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 Using the coordinates P _f (0, f) and P ₀ (L, 0), find the optical path l ₀ from the light source P _f to the first incident point P ₀ on the reflective surface, and calculate the coordinate P ₀ (L, 0). ) and P ₀ ′(L′, z ₀ ′),
Determine the optical path l _{0 '} from the first incidence point P 0 of the reflective surface to the coordinates P ₀ ' of the first incidence point of the lens. Step ₃ : Determine the neutral line N ₀ from the above-mentioned optical paths l ₀ and l ₀ ', and A tangent line z=a ₁ x+b ₁ at the first incident point P ₀ is determined perpendicularly to the neutral line N ₀ . Step 4 Z for the X coordinate (x ₁ = L + p) of the next incident point P ₁ after the first incident point P ₀ on the reflective surface
The coordinate z 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 Find the X coordinate x ₁ ′ of the next incident point P 1 ′ (x ₁ ′, z ₁ ′) on the lens using _the following equation (11). However, L≠0, L'≠0, L≠L'x' = Optical axis center (Z
Perpendicular _distance (on the X _- axis) from the center of the reflecting surface
Vertical (on the X-axis) distance from the light source L = Vertical (on the X-axis) distance from the optical axis center (Z-axis) of the above point P ₀ f = Focal length (on the Z-axis from the light source to the above point P ₀ x = vertical distance (on the X axis) from the optical axis center (Z axis) of _{the reflection point P 1 on} the reflective surface of the light incident on the above point P 1 z = z coordinate of the above P ₁ point (Distance along the Z-axis from the center of the optical axis) Step 6 Using the above lens equation, find the Z coordinate z ₁ ′ for x ₁ ′ obtained in step 5, and calculate the next incident point P ₁ ′ (x ₁ ′, z ₁ ′). Step 7 P _f (0, f), P ₁ obtained as above
(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 point P ₁
The optical path l ₁ ′ from to point P ₁ ′ is determined, and these steps are repeated sequentially.