OPTICAL SYSTEM WITH PINHOLE APERTURE FOR MIDDLE INFRARED RANGE Russian patent published in 2011 - IPC G02B13/14 G02B9/64 

FIELD: physics.

SUBSTANCE: system consists of two components with an intermediate image in between and an aperture diaphragm between the second component and the image plane. The first component is made from two menisci whose concave side faces the image plane, and the second component is made from five lenses. Refracting surfaces of the lenses are spherical. The lenses are made from two materials. Optical power of the first and second menisci of the first component is equal to (1.9-2.7) and (1.8-1.0) of the optical power of the first component. Materials of the said menisci have refraction index not less than 3.4 and 4.0, and average dispersion coefficients differ by not less than 2 times. The following relationships are satisfied: f' f'₂ / f'₁ ≥ p', where f'₁ f'₂, f' are focal distances of the first and second components and the entire system, respectively; p' is the distance from the aperture diaphragm to the image plane.

EFFECT: high image quality within the entire field of vision, high aperture ratio, exclusion of aspherical surfaces, fewer types of materials, high light distribution on the field, wider spectral range, smaller diametre of the first component, providing a flat intermediate image.

17 dwg, 1 tbl