| 摘要 |
PROBLEM TO BE SOLVED: To avoid the increase of back focus and to easily and surely compensate astigmatism generated by a dichroic mirror by increasing the amount of the astigmatism of one video light beam or setting the thickness and/or the inclination of the dichroic mirror so that the amount of the astigmatism of one video light beam and that of the other video light beam may coincide with each other. SOLUTION: In this projection type display device, the 1st and the 2nd dichroic mirrors 22 and 23 are arranged so that the astigmatism may be generated in the respective video light beams LG, LR and LB, and the generated amount of the astigmatism is made equal among the respective video light beams LG, LR and LB. At such a time, since the astigmatism of synthesized video light beam is compensated altogether by a compensation lens arranged on the emitting surface side of a polarizing beam splitter after easily and accurately compensating so that the astigmatism may be equal by generating the astigmatism by a plate glass in the video light beams LG, LR and LB, the astigmatism is easily and accurately compensated.
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