Beam dividing elements permitting projection of an image with high contrast

摘要

An optical element useful in optical systems such as liquid crystal optical display devices which is capable of projecting images having a high degree of contrast is provided. The optical element comprises a set of prisms whose coatings are designed to cancel one component of the depolarization in the light the prisms deliver. The other depolarization component is removed by returning the light to the projection lens through the same sequence of color-dividing coatings in reverse order. Hence, the optical element eliminates the depolarization components by employing double-pass propagation of polarized light therethrough.