Spectacles have been designed for correcting the double vision associated with various forms of strabismus (`squint'). These correctors consist of light-weight, refracting Fresnel wedge prisms that can bend the optic axis by large deviations, while maintaining a relatively thin profile. Using a special mold structure, compatible with cost-effective production, a continuously variable range of prism angles can be pressed in suitable substrates, such as polycarbonate. The flat surface of the prism is embossed with a binary optics diffraction grating for compensating the prism's inherent color dispersion. Over a wide range of deviation angles, the Fresnel prism combined with the right grating achieves uniformly excellent quality of the perceived image, well suited for ophthalmological applications.
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