Polarization conversion device, polarization conversion unit, and projection type video apparatus

A polarization conversion device, comprising:

• a transmissive substrate that is disposed to form a predetermined angle with respect to incident light;
• a polarization separation portion that is disposed on an incidence-side surface of the transmissive substrate, separates the incident light into first linearly polarized light and second linearly polarized light that are orthogonal to each other, transmits the first linearly polarized light, and reflects the second linearly polarized light;
• and
• a reflective element that is disposed substantially in parallel with the transmissive substrate, and that reflects the second linearly polarized light reflected by the polarization separation portion in a direction that is substantially parallel with an optical path of the first linearly polarized light that is transmitted through the polarization separation portion,
• wherein the transmissive substrate is formed of a crystalline material that has a birefringent property and an optical rotatory property, and a crystal optical axis that is an optical axis of the crystalline material that is not linear birefringent to light passing through the crystalline material,
• the first linearly polarized light, which is transmitted through the polarization separation portion and is incident to the transmissive substrate, is emitted from an emission-side surface of the transmissive substrate while maintaining a polarization plane of the first linearly polarized light,
• a phase difference plate opposing the emission-side of the transmissive substrate, converts the polarization plane of the first linearly polarized light that is transmitted through the transmissive substrate so as to be parallel with the polarization plane of the second linearly polarized light, and emits this light as second linearly polarized light,
• wherein the second linearly polarized light does not propagate in the transmissive substrate and does not enter in the transmissive substrate;
• and
• when an angle made by a projection optical axis in which the crystal optical axis of the transmissive substrate is projected onto a plane orthogonal to an optical axis of the incident light, and the polarization plane of the first linearly polarized light is set as an azimuthal angle θ, θ is 0 (deg).