| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zoom lens which enlarges and projects an image on a screen or the like, achieves high performance, a small lens aperture, and reduction of cost, and is optimal for a thin type projection display device, and to provide a projection type display device using the zoom lens. <P>SOLUTION: The zoom lens includes, in order from an enlargement side: a first lens group having negative refractive power as a whole or being nearly afocal; a second lens group having positive refractive power as a whole; a third lens group having negative refractive power as a whole; a fourth lens group having positive refractive power as a whole; and a fifth lens group having positive refractive power as a whole. The first lens group, the third lens group and the fifth lens group are fixed during variable power operation, and the second lens group and the fourth lens group are moved integrally along an optical axis from a reduction side toward the enlargement side to perform variable power. Also, the first lens group is divided into a first-a lens group having negative refractive power and a first-b lens group having positive refractive power in order from the enlargement side, wherein the first-a lens group is moved in the direction of the optical axis to perform focus operation. <P>COPYRIGHT: (C)2011,JPO&INPIT |
