Fresnel lens sheet and rear projection screen

• US 20040196562A1
• Filed: 08/29/2003
• Published: 10/07/2004
• Est. Priority Date: 08/30/2002
• Status: Active Grant

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Honda, Makoto, Watanabe, Hitomu
• Granted Patent: US 6,987,624 B2
• Time in Patent Office: Days
• US Class Current: 359/626
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: G02B 5/045 Prism arrays

Abstract

A Fresnel lens sheet has a light-receiving surface and a light-emitting surface. The light-receiving surface is provided with a plurality of prism groups, each including a plurality of straight or circular prisms. Each of the prisms of the prism groups has a total reflection surface that reflects incident light totally toward a viewing side. The height of the prisms formed in a predetermined specific region in the light-receiving surface of the Fresnel lens sheet is bigger than that of the prisms in another region.

Claims

1. A Fresnel lens sheet having a light-receiving surface on which light emitted by a light source falls, and a light-emitting surface from which the light emitted by the light source is emitted, said Fresnel lens sheet comprising:

a plurality of prism groups, each including a plurality of prisms, each having a totally reflecting surface that reflects incident light totally toward the light-emitting surface;

wherein the light-receiving surface on the side of the light source is divided into a predetermined specific region and another region, and

the prisms in the predetermined specific region have a height bigger than that of the prisms in another region.

2. The Fresnel lens sheet according to claim 1, wherein

the prisms in the specific region have a width smaller than that of the prisms in another region.

4. The Fresnel lens sheet according to claim 1, wherein

light rays emitted by the light source fall on the specific region of the light-receiving surface at incidence angles in the range of 35°

to 45°

.

5. The Fresnel lens sheet according to claim 1, wherein

the height of the prisms nearer to the light source among those formed in the specific region is bigger than that of the prisms farther from the light source among those formed in the specific region.

6. The Fresnel lens sheet according to claim 2, wherein

the width of the prisms nearer to the light source among those formed in the specific region is smaller than that of the prisms farther from the light source among those formed in the specific region.

7. The Fresnel lens sheet according to claim 1, wherein

the prisms have the same apex angle.

8. The Fresnel lens sheet according to claim 1, wherein

the prisms have the same width.

10. The Fresnel lens sheet according to claim 2, wherein

the height of the prisms nearer to the light source among those formed in the specific region is bigger than that of the prisms farther from the light source among those formed in the specific region, and the width of the prisms nearer to the light source among those formed in the specific region is smaller than that of the prisms farther from the light source among those formed in the specific region.

3. A Fresnel lens sheet having a light-receiving surface on which light emitted by a light source falls, and a light-emitting surface from which the light emitted by the light source is emitted, said Fresnel lens sheet comprising:

a plurality of prism groups, each including a plurality of prisms, each having a totally reflecting surface that reflects incident light totally toward the light-emitting surface;

wherein the light-receiving surface on the side of the light source is divided into a predetermined specific region and another region, and

the prisms in the predetermined specific region have a width smaller than that of the prisms in another region.

9. The Fresnel lens sheet according to claim 3, wherein

the prisms have the same height.

11. A rear projection screen comprising a Fresnel lens sheet having a light-receiving surface on which light emitted by a light source falls, and a light-emitting surface from which the light emitted by the light source is emitted;

wherein a plurality of prism groups, each including a plurality of prisms, each having a totally reflecting surface that reflects incident light totally toward the light-emitting surface are formed in the light-receiving surface,

the light-receiving surface on the side of the light source is divided into a predetermined specific region and another region, and

the prisms in the predetermined specific region have a height bigger than that of the prisms in another region.

13. The rear projection screen according to claim 11, wherein

the prisms formed in the predetermined specific region have a width smaller than that of the prisms formed in another region.

12. A rear projection screen comprising a Fresnel lens sheet having a light-receiving surface on which light emitted by a light source falls, and a light-emitting surface from which the light emitted by the light source is emitted;

wherein a plurality of prism groups, each including a plurality of prisms each having a totally reflecting surface that reflects incident light totally toward the light-emitting surface are formed in the light-receiving surface,

the light-receiving surface on the side of the light source is divided into a predetermined specific region and another region, and

the prisms in the predetermined specific region have a width smaller than that of the prisms in another region.