Patent ID: 7745770

Claim:
A light intensity control device, comprising: a light source for outputting a plurality of types of light beams having different wavelengths; a light receiving section for receiving the light beams and converting the light beams into an electric signal in accordance with an intensity of the respective light beam; and a polarization separation section provided between the light source and the light receiving section; wherein: the plurality of types of light beams include a first light beam and a second light beam having a longer wavelength than that of the first light beam; the polarization separation section guides both a light component in a first polarization direction of the second light beam and a light component in a second polarization direction, which is perpendicular to the first polarization direction, of the second light beam to the light receiving section; and the polarization separation section guides a light component in a first polarization direction of the first light beam to the light receiving section, and suppresses a light component in a second polarization direction, which is perpendicular to the first polarization direction, of the first light beam from advancing to the light receiving section.