JP2005321562A5 - - Google Patents

Claims (16)

In a polarization separation element in which a polarization separation layer having a structure in which a plurality of layers having structural birefringence are stacked is provided between two optical members, the polarization directions exhibiting a high refractive index of the structural birefringence layer are adjacent to each other. A polarization separation element characterized in that the layers are arranged and stacked in a (substantially) orthogonal direction between layers. 2. The polarization separation element according to claim 1, wherein, among the light rays incident on the polarization separation layer, a polarization component of a light beam that is mainly reflected and a polarization component of a light beam that is mainly transmitted are orthogonal to each other, the two directions, and the structure complex. A polarization separation element, wherein two directions perpendicular to the polarization direction showing a high refractive index of the refractive layer are (almost) equal.   3. The polarization separation element according to claim 2, wherein, of the two optical members, an exit surface from which light transmitted through the polarization separation layer of light incident from an incident surface provided on one optical member exits is the other optical member. The exit surface provided on the member and from which the reflected light in the polarization separation layer exits is provided on the same optical member as the entrance surface, and the direction of the reflected light is different from the incident light. Polarization separation element.   4. The polarization separation element according to claim 3, wherein a polarization component in a direction parallel to an incident plane when incident light is incident on the polarization separation layer is p-polarized light, and a polarization component in a direction orthogonal to the incident plane is s-polarized light. A polarization separation element that transmits p-polarized light and reflects s-polarized light. 5. The polarization separation element according to claim 4, wherein the polarization separation layer has a structure in which a layer having a first structural birefringence and a layer having a second structural birefringence are alternately stacked, and the first structural birefringence is formed. When the effective refractive indexes for the s-polarized light and the p-polarized light of the layer having n are n1s and n1p, respectively, and the effective refractive indexes for the s-polarized light and the p-polarized light of the second structural birefringence are n2s and n2p, respectively, A polarization separation element satisfying the conditional expression:
n1p <n1s
n2p> n2s
| N1s-n2s |> | n1p-n2p |   6. The polarization separating element according to claim 5, wherein each of the layers having the structural structure birefringence includes a one-dimensional grating composed of at least two media, and the grating has a periodic structure shorter than a wavelength to be used. A polarization separation element.   7. The polarization separation element according to claim 6, wherein at least one of the two media constituting the layer having structural birefringence is a dielectric, and at least one of the other is air. 8. The polarization separation element according to claim 7, wherein a refractive index ni of the dielectric satisfies the following expression.
1.5 <ni The polarization separation element according to claim 8, wherein the dielectric is titanium oxide (TiO ₂ ). The polarization separating element according to claim 5, wherein effective refractive indexes n1p and n2p for p-polarized light of the layer having the first structural birefringence and the layer having the second structural birefringence satisfy the following conditional expression: A polarization separation element characterized by this.
0.95 <n1p / n2p <1.2   11. The polarization separating element according to claim 5, comprising a Brewster angle determined by an effective refractive index with respect to p-polarized light of the layer having the first structural birefringence and the layer having the second structural birefringence. A polarization separation element, wherein a light beam is incident on the polarization separation layer in an angle range.   12. The polarization separating element according to claim 5, wherein an angle larger than a critical angle determined by an effective refractive index with respect to s-polarized light of the layer having the first structural birefringence and the layer having the second structural birefringence. In the polarization separation element, at least a part of the light beam is incident. 12. The polarization separating element according to claim 5, wherein the thickness d1 of the layer having the first structural birefringence, the thickness d2 of the layer having the second structural birefringence, and use on the shortest wavelength side. A polarization separation element characterized in that the relationship with the wavelength λ _S satisfies the following conditional expression.
(N _1s d ₁ · cos θ) / λ _S <0.5
0.2 <d ₂ / λ _S <1.0
Where θ is the angle of incidence of the incident light on the polarization separation layer. 14. The polarization separation element according to claim 5, wherein the ratios (filling factors) f1 and f2 of the dielectric medium to the lattice pitch of the dielectric in the one-dimensional grating having the structural birefringence satisfy the following conditional expressions. A polarization separation element.
Where f1 and f2 are the filling factors of the layers having the first and second structural birefringence, respectively.
0.15 <f1 <0.9
0.10 <f2 <0.8 15. The polarization separation element according to claim 1, wherein an absolute value of a photoelastic constant of the optical member is smaller than 0.1 × 10 ⁻⁸ cm ² / N.   The polarization separation element according to any one of claims 1 to 15, wherein the light beam from the light source unit is guided to a modulation unit that modulates based on an image signal, and the light beam modulated by the modulation unit is projected into the projection optical system. A projection type display device that projects onto a predetermined plane.