Light in primary colors RGB modulated in a first modulation optical system is transmitted through a relay lens (36) and further divided into a P-polarized light and an S-polarized light by a PS separation wire grid (37). The S-polarized light is transmitted through a wavelength spectral filter (39) to select red/green/blue light components R1, G1, B1 of 615, 515, 450 nm in wavelength, which are then modulated by a Y1 device (44). The P-polarized light is transmitted through a wavelength spectral filter (46) to select red/green/blue light components R2, G2, B2 of 650, 550, 475 nm in wavelength, which are then modulated by a Y2 device (51). The 3 -primary color lights modulated by the Y1/Y2 devices (44), (51) are combined with each other at a PS composite wire grid (55) to project a synthetic light on a screen.