JPH054762B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a vehicle lamp having a Fresnel lens in which a Fresnel step consisting of a refractive prism and a reflective prism is formed continuously in the circumferential direction on a non-planar plate. This relates to lenses for use in

[Conventional technology]

Conventionally, a Fresnel step consisting of a refractive prism and a reflective prism formed in the lens member of a Fresnel lens has a lens plate material that is generally flat or curved and spherical, and the lens axis is the optical axis. It is limited to those that form a coincident rotational shape. In such a structure, each Fresnel step could be easily formed by a radial quadratic design.

However, in recent years, lens devices such as outer lenses and inner lenses used in automobile taillights and other vehicle lights have been designed with complex curved shapes that follow the outer shape of the vehicle in order to reduce the aerodynamic drag of the outer shape of the vehicle. A vehicle lens has been proposed in which a Fresnel lens is constructed by providing a mosaic of a large number of Fresnel steps on the lens surface of the lens.

[Problem to be solved by the invention]

However, in the structure of the Fresnel lens described above, the Fresnel steps are designed and configured for each design section, so the ridgeline direction of the Fresnel steps with respect to the circumferential direction is different, and the diffusely reflected light at the boundary is noticeable and is not visible on the lens surface. This has the problem of detracting from the aesthetic appearance of the Fresnel pattern.

The present invention was devised in view of the above problems, and an object of the present invention is to provide a lens for a vehicle lamp having a Fresnel lens in which continuous Fresnel steps are carved in the circumferential direction on a lens member having an arbitrary curved surface. That is.

[Means to solve the problem]

In order to achieve the above object, a lens for a vehicle lamp having a Fresnel lens according to the present invention has a concentric circular partition line drawn on a lens member forming a flat or desired curved surface, and A radial dividing line passing through the center divides the lens member surface into a large number of arcuate Fresnel step design sections, and in each Fresnel step design section, transmitted light from the focal point of the lens passes through a refractive prism or a reflective prism. In a prism lens having a refractive prism surface and a reflective prism surface in which the angle of the peak of each Fresnel step and the slope of the ridgeline of the peak are designed and shaped so as to emit a substantially parallel beam of light, the radiation dividing line is The main idea is to construct a Fresnel step as a minute surface by increasing the number of steps, and to make the structural lines and structural surfaces at the joints of circumferentially adjacent Fresnel steps meander and continue with each other.

[Effect]

The lens for a vehicle lamp having a Fresnel lens according to the present invention has arcuate Fresnel step design sections individually partitioned as described above arranged concentrically in parallel along the partition line on the lens surface, By ultimately increasing the radial division line within the designable range and making the Fresnel step design area constituting the Fresnel step into a microscopic surface, the mountain angle of each Fresnel step and the slope of the ridgeline of the mountain can be determined. The refractive prism surface and the reflective prism surface obtained by engraving can constitute a Fresnel lens having Fresnel steps continuous in the circumferential direction.

〔Example〕

Hereinafter, a specific design principle of engraving Fresnel steps in a lens for a vehicle lamp having a Fresnel lens according to the present invention will be explained.

As shown in Fig. 1, a lens member 1 is placed concentrically at equal pitches (pitch width P) from the center O of the lens on a lens member 1 consisting of a quadratic curved surface with a curvature of r1 on one side and a curvature of r2 in the direction perpendicular to the curvature of the quadratic curved surface. A large number of arcuate Fresnel steps are designed by drawing a circular concentric partition line C and dividing the concentric circular partition line C equally into a number of radial partition lines R in the circumferential direction passing through the center O. Section 2.

FIG. 2 is an enlarged view of one of the arcuate Fresnel step design sections 2, and the arcuate Fresnel step design section 2 has a concentric circular section line C.
1, C2 and radiation division lines R1, R2. The Fresnel step 3 designed and constructed in the arcuate Fresnel step design section 2 will be explained with reference to FIGS. 3 and 4.

First, as shown in FIG. 3, the lens member 1
A refraction system that controls so that a ray l1 from a focal point F on the optical axis L of the Fresnel step 3 is transmitted through the center of the Fresnel step 3 and exits as a ray l2 parallel to the optical axis L within the radiation cross section SR. The apex angle γ of the Fresnel step 3 is determined by designing the inclination angle α of the inner slope 4 and the inclination angle β of the outer slope 5 so as to constitute a prism and a reflective prism.

Next, as shown in Fig. 4, while maintaining this apex angle γ, within the tangential plane SC in the direction of the concentric circular partition line C,
The angle of inclination (θ) of the top ridge line 6 with respect to the lens member 1 is designed so that the transmitted light beam l2 is parallel to the optical axis L.

At this time, a plane lens portion 8 is provided between the outer valley line 7 formed at the valley position of the outer slope 5 and the concentric circular partition line C2.

Since the above inclination angles α and β are the inclination angles with respect to the orthographic projection line, the apex angle γ is γ = α + β, and since α, β and γ are fixed, it is not possible to cut with a 3-axis milling machine. It becomes possible.

In the above Fresnel step design method,
Since each Fresnel step 3 is constructed discontinuously with respect to a three-dimensional curved surface, in the arc-shaped Fresnel step design section divided in the radial direction and concentric circle direction on the lens member surface, the light flux is separated from each Fresnel step. A two-dimensional design can be performed by dividing the cross section 3 into two directions: the transverse direction and the tangential direction.

The present invention is based on the above engraving design principle, and by increasing the number of radial division lines R to the limit that can be engraved, the arcuate Fresnel step design division 2 is created until the flat lens portion 8 is structurally eliminated. In addition to being miniaturized, the structural lines and structural surfaces of the Fresnel steps 3 adjacent in the circumferential direction are continuous with each other, and the Fresnel steps 3 adjacent in the circumferential direction are constructed so as to meander continuously.

When forming the Fresnel step 3 by engraving based on the above three-dimensional Fresnel step engraving design principle, each arcuate Fresnel step design section 2 is
The radial division line α of the inner slope of Fresnel step 3 of
Since the inclination angle β of the outer slope 5 changes continuously, the so-called 5-axis cutting tool is moved in the circumferential direction while being controlled according to the design value, and the cutting is formed by scanning in the surface direction. can do.

〔Effect of the invention〕

Since the lens for a vehicle lamp having a Fresnel lens according to the present invention is configured as described above, even if the lens member has a curved surface with different curvatures in two directions,
The lens structure on the quadratic curve makes it possible to easily obtain the desired transmission control light, and since the structure is continuous in the circumferential direction, diffused reflection of the lens can be reduced, and the Fresnel step is Since it is continuous in the direction, it has characteristics such as excellent moldability when forming a mold.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view a of a lens member showing a design section of a Fresnel step in a lens for a vehicle lamp having a Fresnel lens according to the present invention.
FIG. 2 is an enlarged perspective view showing the three-dimensional Fresnel step, and FIG. 3 is an explanatory view a showing the radial design direction of the Fresnel step. An enlarged sectional view b and FIG. 4 are an explanatory view a showing the circumferential design direction of the Fresnel step and an enlarged sectional view b thereof. DESCRIPTION OF SYMBOLS 1... Lens member, 2... Arc-shaped Fresnel step design section, 3... Fresnel step, 4...
Inner slope, 5...Outer slope, 6...Top ridgeline, 7
...Outer valley line, 8...Plane lens part.

Claims (1)

[Claims] 1. The lens member surface is divided into a large number of arcuate Fresnel step design sections using concentric circular partition lines drawn on a lens member forming a plane or a desired curved surface and radial partition lines passing through the center of the concentric circular partition lines. Along with dividing
In each Fresnel step design section, the angle of the ridge of each Fresnel step and the slope of the ridgeline of the ridge are shaped so that the transmitted light from the focal position of the lens passes through the refractive prism or the reflective prism and exits as a substantially parallel beam. In a Fresnel lens with a refractive prism surface and a reflective prism surface,
By ultimately increasing the radial division line, a Fresnel step is constructed with as small a surface as possible, and the structural lines at the joints of circumferentially adjacent Fresnel steps make the structural surfaces meander and continue. A lens for vehicle lighting that uses a Fresnel lens.