Hybrid achromatic spectacle lens

Spectacle lens is a very particular optical imaging element of great practical importance. Although its construction is very simple, some demands are specific (in particular, remarkable shift of an output pupil). A number of classic spectacle lens designs have been known for a long time, however some new possibilities of aberration correction appear if we use a hybrid (diffractive-refractive). Hybrid lens is an optical system composed of a classic refractive (“glass”) lens and a diffractive microstructure deposited on one of its surfaces. Imaging properties of such lens can be expressed in terms of dimensionless parameters: z = -r1/r2 (describing the shape of a refractive part), b = za/zb (describing the geometry of diffraction fringes) and h = FD/FR (describing the distribution of focusing power between a diffractive and refractive part). By a proper choice of the parameter h we can compensate chromatic aberration. Thanks to the other free parameters astigmatism can also be corrected. In this contribution the possibilities of particular Seidel aberration correction of a hybrid lens are presented. As an illustration some examples of spectacle hybrid lenses are shown and their imaging characteristics are compared with imaging characteristics of commercially available refractive lenses.