Patent ID: 7224539

Claim:
An image improving lens for providing an improved intermediate field of view image of an object, wherein: (a) said image improving lens comprises a lens element having a positive focal length disposed adjacent to a lens element having a negative focal length; (b) said image improving lens has a specified nominal correctable focal length; (c) the image improvement becomes effective when said image improving lens is disposed in optical cooperation with an achromatic doublet, the achromatic doublet having a primary focal length, said image improving lens comprising means for correcting a field aberration of the achromatic doublet, and wherein said optical cooperation fulfills the following conditions: (d) said primary focal length lies within an effective range of said specified nominal correctable focal length; (e) a first image of said object is formed by the achromatic doublet, said first image being disposed at an image distance from the achromatic doublet; (f) said first image is magnified by said image improving lens to form an improved second image; (g) the magnification of said second image with respect to said first image lies between 0.25 and 0.90; and (h) a distance between said image improving lens and the achromatic doublet is smaller than said image distance.