Image display device and Fresnel lens sheet used therefor

摘要

A Fresnel lens sheet used for an image display device is disclosed. The Fresnel lens sheet is provided with a first prism group in an area of a light entrance plane of the Fresnel lens sheet where the incident angle of light is equal to or more than a predetermined incident angle and a second prism group in an area of a light entrance plane of the Fresnel lens sheet where the incident angle of light is less than the predetermined value.