US Patent 7403348 Lens assembly for projecting image

A lens assembly includes plural lens components. A first lens element of the first lens component is aspherical and plastic, disposed on a side of a screen surface, for adjusting focus in image projection to the screen surface. A first lens barrel holds the first lens component. A second lens barrel holds a second lens component. A stationary barrel movably contains the second lens barrel. The second lens barrel is rotated helically relative to the stationary barrel, to adjust the focus for the plural lens components. Thereafter the first lens barrel is rotated helically relative to the second lens barrel, to correct image distortion for the plural lens components, and also to adjust a rotational position of the first lens element. So a gate mark on an edge portion of the first lens element is offset from an effective projecting region of the image projection.