The device includes light source module, dividing/merging light system, and projecting lens. The dividing/merging light system includes polarizer, two wave plates with wide waveband, polarized light splitter, plane dichroic mirror coated by two-color spectrum film, analyzer and three reflection type liquid crystals for modulating red, green and blue colors. Polarized light from light source and dividing/merging light system passing through polarizer and first wave plate with wide waveband enters into polarized light splitter. Light beam reflected from polarized light splitter enters into reflection type liquid crystal; and light beam transmitted from polarized light splitter enters into other two reflection type liquid crystals. Reflected light beams modulated by three reflection type liquid crystals returned back along original optical paths passing through polarized light splitter, second wave plate and analyzer are projected to projecting lens.