An optical fixing device (200) comprises light source fixing parts (210) used for fixing a plurality of solid state light sources, second light combination element fixing parts (240) used for fixing at least one second light combination element, a condensing lens fixing part (250) used for fixing a condensing lens, and second reflecting mirror fixing parts (230). The second reflecting mirror fixing parts (230) are arranged corresponding to at least part of the plurality of solid state light sources, and the second reflecting mirror fixing parts (230) are used for fixing second reflecting mirrors. The second light combination elements are used for transmitting light which is emitted by part of the solid state light sources and is not reflected and/or are used for reflecting light reflected by the second reflecting mirrors; and the condensing lens is used for converging the light which passes through the second light combination elements. The optical fixing device (200) is compact in outline dimension and low i
