Patent ID: 6961176

Claim:
A Fresnel lens sheet having an entrance surface and an exit surface, the entrance surface being provided with a plurality of total reflection Fresnel lens elements; wherein each of the total reflection Fresnel lens elements has a light-receiving facet on which image light falls, and a total-reflection facet that totally reflects the image light fallen on the light-receiving facet toward the exit surface, and horizontal length L 1 (mm) of the Fresnel lens sheet, thickness T 1 (mm) of the Fresnel lens sheet and maximum elongation percentage A 1 (%) of the Fresnel lens sheet at which the Fresnel lens sheet lengthens due to moisture absorption of the Fresnel lens sheet, meet a requisite condition expressed by a relational expression: A 1 ≦0.6T 1 /L 1 .