| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection optical system at which aberration is sufficiently corrected to project the picture of a display element in which miniaturization and an high density picture element are attained and whose cost is reduced. SOLUTION: This system is orderly composed of a first negative group Gr1, a second positive group Gr2, a third positive group Gr3 and a prism PR from an enlarging side. The first group Gr1 has only a negative lens as a lens and also has an aspherical surface r4*. The second group Gr2 is composed of a positive lens, and has an aperture diaphragm SP at the nearly front side focal position of the third group Gr3. The third group Gr3 has at least, one positive lens consisting of a lens material whose abnormal part dispersibility and Abbe number are regulated.
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