Patent ID: 7518803

Claim:
A prism unit that separates white light into light of different wavelength bands and that integrates light of different wavelength bands into light traveling along a same optical path, the prism unit comprising: a TIR prism having a side surface for totally reflecting input light, and a color separation/integration optical system for separating input light, reflected by the TIR prism, and traveling along an input optical path, into light of three different colors, then integrating the separated light of the three different colors into light traveling along a same output optical path, and then outputting the integrated light as output light toward the TIR prism, the input optical path being different from the output optical path; the color separation/integration optical system including: a first prism having a first prism base member and a first dichroic film formed on the first prism base member, a second prism having a second prism base member and a second dichroic film formed on the second prism base member, and a third prism having a third prism base member, the first dichroic film being disposed to face the second prism, the second dichroic film being disposed to face the third prism, at least one of the first and second dichroic films containing 10% by volume or more of a high-thermal-conductivity substance having a thermal conductivity of 20 W/mK or more at a temperature of 300 K, and the prism unit permitting a luminous flux of 15 000 lumens or more to pass therethrough.