| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zoom lens which enlarges and projects an image from a light valve that forms the image by changing the reflecting direction of light such as a DMD, onto a screen or the other, achieves high performance, a small lens aperture, and reduction of cost, and is optimum for a thin type projection display device. <P>SOLUTION: The zoom lens includes, in order from an enlargement side, a first lens group having positive refractive power as a whole, a second lens group having negative refractive power as a whole, a third lens group having positive refractive power as a whole, a fourth lens group having negative refractive power as a whole, and a fifth lens group having positive refractive power as a whole. The zoom lens is constituted by arranging the light valve such as a DMD after providing a large space on the reduction side of the fifth lens group, and can perform variable power from a wide angle end to a telephoto end. 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 the enlargement side toward the reduction side to perform variable power. <P>COPYRIGHT: (C)2011,JPO&INPIT |
