A polarization conversion system comprises a glass substrate; reflection type polarization plates, formed between top and bottom surfaces of the glass substrate and inclined at a predetermined angle, separating unpolarized incident light into two polarization directions where two directions are at a right angle to each other; polarization conversion plates coupled to the reflection type polarization plates, converting a polarization direction of polarization light by the reflection type polarization plates; and reflection plates positioned in parallel with the reflection type polarization plates, reflecting incident light from the reflection type polarization plates.