Method and apparatus for reducing microlens surface reflection

Abstract

A microlens has a surface with an effective index of refraction close to the index of air to reduce reflection caused by change in indices of refraction from microlens to air. The microlens having an index of refraction approximately the same as that of air is obtained by providing a rough or bumpy lens-air surface on the microlens. Features protrude from the surface of a microlens to create the rough surface and preferably have a length of greater or equal to a wavelength of light and a width of less than a sub-wavelength of light, from about 1/10 to ¼ of the wavelength of light. The features may be of any suitable shape, including but not limited to triangular, cylindrical, rectangular, trapezoidal, or spherical and may be formed by a variety of suitable processes, including but not limited to mask and etching, lithography, spray-on beads, sputtering, and growing.

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