Image projection apparatus

An image projection apparatus comprising:

• a reflective display element configured to modulate illumination light from a light source and to emit the light thus modulated;
• a projection optical system configured to project the light thus modulated onto a projection surface;
• and
• a polarizing beam splitter configured to guide the illumination light to the reflective display element and to guide a predetermined polarization component of the light thus modulated to the projection optical system;
• wherein the polarizing beam splitter is a polarizing beam splitter that blue-band light enters, includes a lead-free glass member, and satisfies conditional expressions below:
• 50<α*E*β*A/κ<300
• A=(1−T̂(L/0.01))+M
• T=(T1+T2)/2
• where α represents a linear expansion coefficient (10−7/K) of the glass member, E represents a Young's modulus (109 Pa) of the glass member, β represents a photoelastic coefficient (10−12/Pa) of the glass member, A represents an absorptivity of the polarizing beam splitter for blue-band light, κ represents a thermal conductivity (W/mK) of the glass member, L represents a distance from an incident surface to a first exit surface of the polarizing beam splitter, M represents an absorptivity of a member other than the glass member on an incident optical path in the polarizing beam splitter for light having a wavelength of 440 nm, T1 represents a transmissivity of the glass member having a thickness of 10 mm for light having a wavelength of 420 nm, and T2 represents a transmissivity of the glass member having a thickness of 10 mm for light having a wavelength of 460 nm,
• wherein the incident surface is a surface of the polarizing beam splitter, which the illumination light entering the polarizing beam splitter from the light source passes through,
• wherein the first exit surface is another surface of the polarizing beam splitter, which the illumination light emitted from the polarizing beam splitter passes through,
• wherein the incident optical path is an optical path on which the illumination light travels from the incident surface to the first exit surface, and
• wherein the distance from the incident surface to the first exit surface is a sum of a length of the glass member from the incident surface to the member other than the glass member on the incident optical path, and a length of the glass member from the member other than the glass member to the first exit surface on the incident optical path.