| 摘要 |
<P>PROBLEM TO BE SOLVED: To realize an inexpensive, compact, and mirror type projection optical system equipped with a small mirror and able to obtain a satisfactory image without degrading a wide angle property. <P>SOLUTION: In a projection optical system for enlarging and projecting an original image, which is on a conjugate surface on the reduction side, onto a screen, which is on a conjugate surface on the enlargement side, the optical system comprises, in order from the reducing side, a first optical group G1 composed of a plurality of lenses and having positive refractive power, and a second optical group G2 having one concave reflecting face. The first optical group includes an aperture diaphragm S. A lens PML of positive refractive power is disposed on the most enlarging side of the first optical group. If the maximum value that is in a distance from one optical axis shared by the most lenses among the lenses composing the first optical group to a beam of light and that is within the display range of the original image is Yi, and the maximum value in the concave reflection face of the second optical group is Ym, Yi and Ym satisfy the following expression (1): 3.5<Ym/Yi<5.0. <P>COPYRIGHT: (C)2013,JPO&INPIT |
