PROJECTION LENS SYSTEM HAVING MAGNIFICATION CHANGING FUNCTION AND PROJECTOR

摘要

A zoom lens is a projection lens which is composed of a negative first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a fifth lens group, and a positive sixth lens group in order from the enlargement conjugate side, and changes magnification by changing the intervals between the lens groups. At least the second, third, and fifth lens groups move when the magnification is changed, and the third lens group moves from the enlargement conjugate side to the reduction conjugate side when the magnification is changed from a telephoto end to a wide angle end. An aperture stop is disposed between the surface closest to the reduction conjugate side of the third lens group and the surface closest to the enlargement conjugate side of the fifth lens group, and is approximately telecentric on the reduction conjugate side.

主权项

1. A projection lens system, comprising, in order from an enlargement conjugate side:
a first lens group having a negative refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; a fifth lens group; and a sixth lens group having a positive refractive power, the projection lens system achieving zooming by varying a distance between lens groups, wherein at least the second lens group, the third lens group, and the fifth lens group each move during zooming; the third lens group moves from the enlargement conjugate side to a reduction conjugate side during zooming from a telephoto end to a wide-angle end; an aperture stop is disposed between a most reduction-conjugate-side surface of the third lens group and a most enlargement-conjugate-side surface of the fifth lens group; the projection lens system is substantially telecentric on the reduction conjugate side; and the fourth lens group includes, in order from the enlargement conjugate side, two or more negative lens elements and a positive lens element.