| abstract |
(57) [Summary] [Structure] The beam combining prism 6 is an isosceles triangular prism 11 having an apex angle of 90 ° + θ or 90 ° −θ with respect to the elevation angle θ of the principal ray of the optical system, and this isosceles triangular prism. Parallelogram prisms 12 and 13 having the same apex angle as the base angle and one side having the same length as the base of the above-mentioned isosceles triangular prism. Are formed by joining, and the dichroic mirror surfaces 14 B and 14 G are formed on the joining surfaces of the prisms 11 and 12 and the joining surfaces of the prisms 11 and 12, respectively, and the mirror surface 14 M is formed on the prism 13. The liquid crystal display element 4 is adjusted so that the images of the three primary colors are accurately overlapped on the composite prism 6. R , 4 G and 4 B are provided. [Effect] The number of parts is reduced, and the device can be downsized. |