Polarization beam splitter and optical system using the same, and image displaying apparatus, using the same

A polarization beam splitter having:

• a polarized beam splitting layer having a structure in which a plurality of gratings parallel to a first direction are periodically disposed in a second direction orthogonal to the first direction, each of the gratings having a refractive index;
• and
• two optical members sandwiching therebetween the polarized beam splitting layer, each of the members having a refractive index of which refractive indices are equal to each other,
• wherein said polarized beam splitting layer transmits therethrough, of light incident thereon, chiefly light of a polarized component parallel to said first direction, and reflects light of a polarized component parallel to said second direction when the refractive indices of the optical members is defined as nP, and the refractive index of the gratings is defined as nG, and a value obtained by dividing a width of the gratings by a disposing period is defined as f, and an incident angle of light incident into the polarization beam splitter is defined as θ, the following conditional expression is satisfied
• sin
• ⁢
• ⁢
• θ
• >
• 1
• n
• p
• ⁢
• f
• n
• G
• 2
• +
• 1
• -
• f
• .