Patent ID: 7760612

Claim:
An optical element, comprising: a dichroic polarization separation film for passing a first light beam of wavelength λ 1 , reflecting linearly polarized light of a second light beam of wavelength)λ 2 that is polarized in a first polarizing direction, and passing linearly polarized light of the second light beam that is polarized in a direction perpendicular to the first polarizing direction; a first ¼ wavelength plate for converting the linearly polarized light of the second light beam that is polarized in the first polarizing direction and reflected by the dichroic polarization separation film, into substantially circularly polarized light; a first reflecting surface for reflecting the second light beam that is converted to circularly polarized light by the first ¼ wavelength plate; a second ¼ wavelength plate for converting again the second light beam that is reflected at the first reflecting surface, that is converted to linearly polarized light with a polarizing direction perpendicular to the first polarizing direction by the first ¼ wavelength plate and passed by the dichroic polarization separation film, into substantially circularly polarized light; and a second reflecting surface for reflecting the second light beam that is converted to substantially circularly polarized light by the second ¼ wavelength plate; wherein the optical element reflects by the dichroic polarization separation film the second light beam that is reflected by the second reflecting surface and converted to linearly polarized light polarized in the first polarizing direction by the second ¼ wavelength plate; and wherein the optical element converts the wave front of the second light beam.