The disclosed optical projection system comprises: a light source for parallel beam, a first color spectroscope to separate the beam into a first primary color beam and a mixed beam with a second/third primary color beam; a first bilateral telecentric group set after the first spectroscope just at the first light path of the first primary color beam to convert it into a first beam; a second bilateral telecentric group set after the first spectroscope just at the second light path of the mixed beam; a second color spectroscope set at some position to separate the mixed beam into a second and third beam, and a beam-joining projection unit to receive and compose last three beams. |