VARIOSYSTEM FOR INFRARED REGION Russian patent published in 2018 - IPC G02B15/17 G02B13/14 

FIELD: optics.

SUBSTANCE: variosystem consists of a focusing lens comprising a sequentially arranged fixed first component in the form of a positive convex-concave lens, movable second and third components arranged to move along the optical axis, a projection lens and a radiation receiver with a cooled diaphragm. In the focusing lens, the second movable component is a negative convex-concave lens, the third is a biconcave lens and a fourth fixed component is introduced containing two positive and one negative convex-concave lenses. Projection lens is a single positive convex-concave lens. Following ratios are met: 0.25<f'_I/f'_max<0.33; 0.15<|f'_II/f'_max|<0.25; 0.02<|f'_III/f'_max|<0.04; 0.03<f'_IV/f'_max<0.05; 0.07f'_max<d₄<0.15f'_max; 1.2<|β_PL|<1.5, where f'_I, f'_II, f'_III, f'_IV – focal lengths of the first, second, third and fourth components; f'_max – maximum focal length; d₄ – the distance between the last lens of the fourth component and the lens of the projection lens; β_PL – an increase in the projection lens.

EFFECT: reduction of the telecoating ratio and the displacement of mobile components while providing a high multiplicity of the change in the focal length and simplifying the design.

1 cl, 2 dwg, 4 tbl