| 摘要 |
PROBLEM TO BE SOLVED: To obtain a surface functioning as a reflection surface having high reflection factor without applying coating processing for reflection by specifying the refractive index of a prism. SOLUTION: An incident surface which is orthogonal to the optical axis of a first lens array 4 and a slanting face crossing to it are formed at a separating part respectively separating plural luminous fluxes split by the first lens array 4 as first and second linearly polarized light beams 6 and 7 whose polarization directions are mutually orthogonal, and the separating part possesses the prism 51 where a polarized light separating plane 5a reflecting the first linearly polarized light beam 6 is formed on the slanting face. The refractive index of the prism 51 is constituted so as to satisfy an expression. In the expression,ϕmeans an incident angle for a parallel plate, and W means the breadth of a first lens, and H means the longitudinal width of the first lens, and F means the focal distance of the first lens and N means the refractive index of the prism. Thus, the rear face of the parallel plate 52 substantially functions as a total reflection surface.
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