Total internal reflection fresnel-lens and devices

Details Total internal reflection fresnel-lens and devices Total internal reflection fresnel-lens and devices

2007-06-12

2007-06-12

Perkey, W. B. (Department: 2851)

Optical: systems and elements

Projection screen

Unitary sheet comprising plural refracting areas

C359S459000, C359S460000

Reexamination Certificate

active

11171070

ABSTRACT:
An off-axis Fresnel lens is disclosed that, when combined with a rear projection screen (comprising, e.g., a lenticular lens, a diffuser, or both), enables construction of rear-projection-type screen devices (e.g., projection television systems) that are thinner and have improved contrast and resolution when compared with conventional projection screen devices. The off-axis Fresnel lens comprises a plurality of concentric, outwardly-extending, total internal reflection-type prism facets. Each facet, in turn, comprises top and bottom sides, one or both of which may be flat or outwardly convex. Embodiments of the invention may also include concentric opaque sections that are disposed between successive prisms, between the prism base and the output surface of the Fresnel lens, and/or between the output surface of the Fresnel lens and the input surface of the projection screen in order to improve contrast. Contrast may also be enhanced by laminating the Fresnel lens to the projection screen.

REFERENCES:
patent: 4531812 (1985-07-01), Oguino
patent: 5870224 (1999-02-01), Saitoh et al.
patent: 6407860 (2002-06-01), Funazaki et al.
patent: 6726859 (2004-04-01), Suzuki et al.
patent: 6989929 (2006-01-01), Watanabe
patent: 2005/0046939 (2005-03-01), Yoshikawa et al.

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