JPS6350728Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Technical Field) The present invention relates to an automotive lamp having an elongated rectangular radiation surface. (Prior art) Automotive lamps with elongated emitting surfaces combine a front lens formed with a fisheye prism for diffusion and an inner lens for condensing light to equalize the brightness of the emitting surface (radiating surface). There is. In this type of lamp, the luminous flux from the light source is collimated by the inner lens and enters the front lens, but at this time, the luminous flux density becomes large between the center and the end of the lens, and the luminance of the light emitting surface differs markedly. In particular, the difference becomes more significant as the width of the lamp increases. For example, when the inner lens 1 with a height H and a width W and a light source are arranged at a distance of a focal length F as shown in FIG. The incident ray of light between the upper end an and the lower end bn of the lens end forms an angle αn, and the second
As shown in FIG. 3, the light is converted into parallel light by the inner lens 1 and enters the front lens 2. In that case, center luminous flux density: edge luminous flux density becomes. When H=40, W=400, and F=30, the ratio becomes 0.588 (rad):0.014 (rad), which results in a luminance difference of approximately 40:1, resulting in poor visibility. (Purpose of the invention) An object of the invention is to provide an automotive lamp in which the difference in brightness between the center and the ends of the elongated radiation surface is small. (Summary of the invention) This invention places a light condensing inner lens formed with a linear Fresnel prism orthogonal to the longitudinal direction of this front lens, inside an elongated front lens formed with a diffusion prism such as a fisheye cut. In this automotive lamp in which a light source is arranged at the focal point of the inner lens, an auxiliary inner lens having a semi-cylindrical shape and having a straight Fresnel prism with a cut groove in the circumferential direction formed on the circumferential surface is combined with the inner lens and the light source. The lens is characterized by being arranged so that its central axis passes through the center of the light source and its straight Fresnel prism is parallel to the longitudinal direction of the front lens. (Embodiment) FIGS. 4 to 12 show an embodiment of the present invention, in which 1 is an inner lens for condensing light, 2 is an elongated front lens formed with a diffusion prism such as a fisheye cut, A straight Fresnel prism is formed in the inner lens 1 and is perpendicular to the longitudinal direction of the front lens 2. A housing 3 has a front lens 2 disposed in its front opening, and an inner lens 1 disposed inside the housing. 4 is a light source placed at the focal point of the inner lens 1, and 5 is an auxiliary inner lens placed between the inner lens 1 and the light source 4. This auxiliary inner lens 5 has a semi-cylindrical shape with an inner radius R, and a straight Fresnel prism with circumferential cut grooves is formed on its circumferential surface, and its central axis passes through the center o of the light source 4.
The straight Fresnel prism is arranged parallel to the longitudinal direction of the front lens 2. Note that since the auxiliary inner lens 5 is disposed close to the light source 4, it is preferably formed of heat-resistant resin (such as polycarbonate). With the above structure, the light from the light source 4 becomes a horizontal parallel ray when passing through the auxiliary inner lens 5, and becomes a perfectly parallel ray parallel to the reference axis when passing through the inner lens 1, so that the light from the light source 4 becomes a completely parallel ray parallel to the reference axis when passing through the inner lens 1. The light enters lens 2. In that case, as shown in FIGS. 10 and 11, the angles αo and αn at the center and end portions of the lens are equal. Therefore, tan _-1 (H/2F) in the above equation

The terms in [Formula] are equal, height H = 40, width W = 400,
When focal length F=30, center luminous flux density: edge luminous flux density

[Formula], and the brightness difference is approximately 6.7:1. That is, the difference in brightness is significantly reduced compared to the prior art, and visibility is significantly improved. Moreover, as a result, the brightness also increases compared to the conventional system (dotted line) as shown in FIG. 12, which can contribute to improved safety. Note that by making the auxiliary inner lens have a color equivalent to the color of the lamp light, the flat inner lens and the front lens can be made colorless, thereby preventing a decrease in visibility due to false reflections and the like. Further, although the above embodiment is a case of a horizontally long lamp, the present invention can be similarly implemented with a vertically long lamp. (Effect of the invention) As described above, according to the invention, an auxiliary inner lens having a semi-cylindrical shape and a straight Fresnel prism formed on the cylindrical surface is disposed between the flat inner lens and the light source, so that the end luminous flux The density increases and the difference in brightness between the light emitting surfaces decreases, resulting in improved visibility. Furthermore, since the brightness increases over the entire surface, the brightness becomes sufficient and can contribute to improving safety.

[Brief explanation of the drawing]

FIGS. 1 to 3 are optical explanatory diagrams of a conventional example of an automobile lamp having an elongated radiation surface; FIG. 4 is a plan view showing an embodiment of an automobile lamp according to the present invention; and FIG.
The figure is a front view of the same, FIG. 6 is a side view of the same, FIG. 7 is a longitudinal sectional view of the same, FIG. 8 is a perspective view of the auxiliary inner lens in the same embodiment, and FIGS. The optical explanatory diagram, FIG. 12, is a luminance distribution diagram of the radiation surface of the same embodiment. 1...Flat inner lens, 2...Front lens, 3...Housing, 4...Light source, 5...Auxiliary inner lens.

Claims (1)

[Scope of utility model registration request] A light condensing inner lens formed with a linear Fresnel prism orthogonal to the longitudinal direction of this front lens is placed inside a long and thin front lens formed with a diffusion prism such as a fisheye cut, and a light source is placed at the focal point of this inner lens. In the installed automobile lamp, an auxiliary inner lens having a semi-cylindrical shape and having a straight Fresnel prism with circumferential cut grooves formed on its circumferential surface is placed between the inner lens and the light source so that its central axis is aligned with the center of the light source. An automotive lamp characterized in that the straight Fresnel prism is arranged parallel to the longitudinal direction of the front lens.