Fresnel lens and lighting apparatus provided with the fresnel lens

Abstract

In a Fresnel lens which is made of a lens material whose refraction index is n, and focuses light beam from a light source at a specified radiation view angle phi, and has plural N pieces of circular lens surfaces arranged concentrically around a common optical axis, and plural circular rise surfaces arranged adjacent alternately between these lens surfaces, and two lens surfaces adjacent via at least one of the rise surfaces are concave surfaces, and tangent lines and at the intersecting point with the rise surfaces of the shape of a cross section passing through the optical axis of those lens surfaces intersect at the outside with respect to the optical axis, and when the angle formed between these tangent lines is defined as theta, a relational equation theta>=phi / (2 n N) stands.

Description

[0001] References to related applications [0002] This application is based on and claims priority from prior Japanese Patent Application No. 2004-269226 filed on September 16, 2004. The entire content of this application is incorporated into this application by reference. technical field [0003] The present invention relates to a Fresnel lens and a lighting device having a Fresnel lens, and more particularly to a lighting device using a Fresnel lens used as a lighting spotlight for a stage and a studio, and a Fresnel lens used therein. Background technique [0004] Lighting fixtures used in stage lighting and studio lighting are often suspended from the ceiling. From a safety point of view, it is desirable that the lighting equipment be light in weight, taking into account the possibility of falling. Typically, lighting fixtures are equipped with high-intensity light sources. Therefore, the lighting equipment is heated to a high temperature due to the heat radiation of...

AI Technical Summary

Problems solved by technology

Due to these spikes, conventional Fresnel lenses have the characteristic of uneven brightness in the illumination beam

[0011] In addition, even if the Fresnel lens is designed so that its lens area does not form an overlap between the illumination distribution components, due to manufacturing errors, etc., the lens surface of the lens area will be slightly shifted, and as a result, the illumination distribution components will still occur. overlap, resulting in uneven illumination

[0012] As mentioned above, in lighting equipment using conventional Fresnel lenses, no effective method has been proposed to solve the problem of uneven illumination, so the emergence of improved Fresnel lenses is expected

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