Patent ID: 7372798

Claim:
An optical element having a rectangular shape viewed from plane, comprising: a dichroic film held between transparent materials, the dichroic film transmitting one of first light included in a wavelength range of 390 to 425 nm and second light included in a wavelength range of 630 to 820 nm and reflecting the other light, a first surface having a first anti-reflection film for preventing reflection of the first light; a second surface having a second anti-reflection film for preventing reflection of the second light, perpendicular to the first surface; a third surface from which the incident light of the first surface and the second surface is emitted, having a third anti-reflection film for preventing the reflection of the first and the second lights; and a fourth surface, the first, second, third and fourth surfaces tilting with respect to the dichroic film, adjacent surfaces being perpendicular to each other, wherein, in the third anti-reflection film, reflectance of the second light is larger than that of the first light.