Projection zoom lens

Abstract

When at least two resin lenses having oppositely signed power factors are disposed in positions that are not relatively far away from each other in a lens group disposed on a high magnification side with respect to an aperture stop, the difference in temperature between the two resin lenses can be reduced, whereby the amount of change in the focal point of an overall projection zoom lens can be reduced. The lens groups on the high magnification side with respect to the aperture stop, which are close to the atmosphere, experience a relatively small increase in temperature when in use. The focus shift due to variation in temperature can therefore be reliably reduced by disposing the resin lenses, which are readily affected by an increase in temperature, on the high magnification side with respect to the aperture stop.

Dependencies are inferred from the claim text.