Fresnel lens and lighting apparatus provided with the Fresnel lens
First Claim
1. A lighting apparatus comprising:
- a light source which emits light rays;
a Fresnel lens acting as a convex lens having a convergent function of converting the light rays to a spotlight and projecting the spotlight on an illumination area, which is made of a lens material whose refraction index is n, and projects light rays from the light source at a specified radiation view angle φ
to the illumination area, and has an optical axis, the Fresnel lens comprising;
a plurality of Fresnel lens segments which are arranged concentrically around a common optical axis, and are made into ridge shapes respectively, whereineach Fresnel lens segment includes;
a segment lens surface which has a peak and a bottom corresponding to one and the other end of the segment lens surface, respectively, and is curved into a concave surface toward the illumination area in respect to a reference plane connecting the peak and the bottom,a rise surface which is arranged between adjacent lens surfaces, and extended between the peak and the bottom, the light rays projected from adjacent lens surfaces irradiating circular band areas having widths, respectively, which mutually overlap at least half of the width of the circular band area.
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Accused Products
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 φ, 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 θ, a relational equation θ≧φ/(2 n N) stands.
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Citations
9 Claims
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1. A lighting apparatus comprising:
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a light source which emits light rays; a Fresnel lens acting as a convex lens having a convergent function of converting the light rays to a spotlight and projecting the spotlight on an illumination area, which is made of a lens material whose refraction index is n, and projects light rays from the light source at a specified radiation view angle φ
to the illumination area, and has an optical axis, the Fresnel lens comprising;a plurality of Fresnel lens segments which are arranged concentrically around a common optical axis, and are made into ridge shapes respectively, wherein each Fresnel lens segment includes; a segment lens surface which has a peak and a bottom corresponding to one and the other end of the segment lens surface, respectively, and is curved into a concave surface toward the illumination area in respect to a reference plane connecting the peak and the bottom, a rise surface which is arranged between adjacent lens surfaces, and extended between the peak and the bottom, the light rays projected from adjacent lens surfaces irradiating circular band areas having widths, respectively, which mutually overlap at least half of the width of the circular band area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification