RETROREFLECTIVE ELEMENT Russian patent published in 2011 - IPC G02B5/128 

FIELD: physics.

SUBSTANCE: retroreflective element is in form of a biconvex composite lens comprising two lenses joined to together on a spherical surface with curvature radius R₃. The centres of curvature of the surfaces of the lenses coincide. The curvature radius R₃ is selected based on the condition (R₁-S₁') < R₃ < 0 or 0 < R₃ < R₁, where S₁' is the distance to the Gaussian plane of the first surface of the first lens; R₁ is the curvature radius of the first surface. The thickness of the first lens d₁ is equal to the difference between R₁ and R₃. The thickness of the second lens d₂ is determined by the expression: d₂ = S' ± δ, where δ is correction factor whose value is selected based on the condition of ensuring correction of wave aberration of wide beam radiation. The curvature radius of the second surface of the second lens R₂ is equal to the difference between R₃ and d₂. Refraction indices of materials of the lenses are chosen such that the refraction index of the material of those lenses, whose signs of surface curvature radius coincide, is greater than that of the material of lenses whose signs of surface curvature radius are opposite.

EFFECT: longer operating range of the retroreflective element in a wide range of retroreflection angles owing to increase in axial lighting force and reduced angular divergence of back reflected radiation.

2 cl, 2 dwg, 3 tbl