US Patent No. 9,557,013

ILLUMINATION OPTICAL SYSTEM AND PROJECTION DISPLAY APPARATUS


Patent No. 9,557,013
Issue Date January 31, 2017
Title Illumination Optical System And Projection Display Apparatus
Inventorship Noriko Nagase, Tokyo (JP)
Assignee NEC DISPLAY SOLUTIONS, LTD., Tokyo (JP)

Claim of US Patent No. 9,557,013

1. An illumination optical system, comprising:
a first light source configured to emit coherent light having a first peak wavelength that belongs to a wavelength region
of visible light;

a second light source configured to emit incoherent light having a second peak wavelength that belongs to a wavelength region
of visible light; and

a dichroic mirror configured to mainly reflect one of the coherent light and the incoherent light while mainly transmitting
another one of the coherent light and the incoherent light, and synthesize optical paths of the coherent light and the incoherent
light,

wherein the dichroic mirror has characteristics in which a first separation wavelength having transmittance of 50% with respect
to S-polarized light is smaller than a second separation wavelength having transmittance of 50% with respect to unpolarized
light,

wherein the first peak wavelength is larger than the first separation wavelength, and
wherein the second peak wavelength is smaller than the second separation wavelength.