LARGE APERTURE RATIO PROJECTION LENS Russian patent published in 2011 - IPC G02B9/64 G02B13/24 

FIELD: physics.

SUBSTANCE: projection lens has a first group of lenses, an aperture diaphragm and a second group of lenses, all lying in series on the path of optical radiation from the object to the image. The first group of lenses has a negative meniscus whose convex side faces the object, and a biconvex lens with another biconvex lens in between. The first lens of the second group is biconcave. The second lens of the second group is convergent and its convex side faces the image. The third lens of the second group faces the image with its concave side and comprises a biconvex and a biconcave lens glued together. A biconvex lens is placed between the second and third lenses of the second group. All lenses are spherical. The lenses are made from colourless optical glass.

EFFECT: operation of the lens with objects lying at a finite distance, high aperture ratio and illumination on the edge of the image field, providing the value and sign of distortion which is sufficient for correcting X-ray image converter distortion, high manufacturability.

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