OPTICAL SYSTEM WITH REMOTE APERTURES FOR INFRARED SPECTRUM Russian patent published in 2010 - IPC G02B9/60 G02B13/14 

FIELD: physics.

SUBSTANCE: optical system has an objective lens which constructs real intermediate image, a projection objective lens which inverts the image, and an aperture diaphragm lying between the projection objective lens and the image plane. The objective lens has a positive meniscus whose convex surface faces the object space and a biconcave lens. The projection objective lens has three menisci lying close to each other. The first and third menisci are positive and their convex surfaces face each other. The second meniscus is negative and its concave surface faces the image plane. All refracting surfaces are spherical. Relationships given in the formula of invention hold in the system.

EFFECT: increased technological effectiveness, increased distance of the input aperture from the first surface, and the output aperture from the last surface of the system, increased back focal distance, reduction of possible calculated focal distances to 15 mm while maintaining the aperture ratio, field angle and high image quality within the entire field.

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