US Patent 7118222 Optical device and protector

An optical device (24) includes: three optical modulators (24A) for modulating respective color lights in accordance with image information; a cross dichroic prism (244) for combining the respective color lights modulated by the optical modulators (24A); a base (247) made of heat-conductive material and fixed to upper and lower faces of the cross dichroic prism (244); an irradiation-side polarization plate (243) having polarization films (243A2 and 243B2) as optical conversion films for converting an optical property of a light beam irradiated by the optical modulators (24A) and substrates (243A1 and 243B1) made of heat-conductive material and provided with the polarization films (243A2 and 243B2) attached thereto; and an irradiation-side retaining plate (246) made of heat-conductive material for supporting and fixing the irradiation-side polarization plate (243). The irradiation-side retaining plate (246) is fixed to a lateral face of the base (247).