A solid state light source device for generating a constant broad band light useful in multiple SLM projectors. The light source device includes a blue or UV/near UV excitation light and a moving plate carrying wavelength conversion materials to convert the excitation light into a broad band light. The wavelength conversion materials include red, green, yellow and/or blue phosphors, and may pass some of the blue excitation light. The broad band light outputted by the phosphor plate includes at least two primary color components and has a constant intensity and spectrum as a function of time. The solid state light source device further includes a second light source such as a blue light source, and a light combination device which combines the output light of the moving phosphor plate and the light from the second light source into one beam of constant, broad band light.