POLARIZED LIGHT SEPARATING ELEMENT AND PROJECTION TYPE DISPLAY DEVICE USING THE SAME

PROBLEM TO BE SOLVED: To easily obtain a thin-shaped high-efficiency polarized light separating element by constituting the polarized light separating element of a diffraction grating and an optical anisotropic layer formed adjacent to the diffraction grating. SOLUTION: This polarized light separating element 101 is constituted of the diffraction grating 102 and a double refraction layer 103. The diffraction grating 102 is formed by using an isotropic transparent substrate whose refractive index is N0. The double refraction layer 103 is constituted by orienting the positive uniaxial optical anisotropic body so that the optical axis may be aligned with the (z)-axis direction. As for the double refraction layer 103, the refractive index is N1 in the (z)-axis direction and the refractive index is N2 in an (y)-axis direction, and N1>N2 is established. In the case of selecting so that N0 N1 may be satisfied, the first-order polarized light 104A out of the incident light 104 goes straight through the polarized light separating element 101 as it is, then, the light 104A is emitted. Since N0>N2 is established, the diffraction grating 102 works on the second-order polarized light 104B, then, the second order polarized light 104B is diffracted and emitted.