FRESNEL OPTICAL ELEMENT AND PROJECTION TYPE DISPLAY DEVICE

摘要

Among the refraction surfaces (12a) of a Fresnel prism (12), a non-incident surface (12c) blocked by another Fresnel prism (12) so as not to be directly irradiated with light rays from a projector (1) forms an angle (tau') with respect to a reflection surface (12b), such that the angle (tau') differs from a prism front end angle (tau). Thereby, it is possible, for example, to avoid a situation in which light rays reflected without penetrating the refraction surface (12a) are projected as unnecessary light in the direction of the visual field of an observer.