Microprismatic Fresnel lens for formation of uniform light circle

The traditional Fresnel lens concentrates the light intensity on the center of the formed image. We present a microprismatic Fresnel lens that transforms a circular incident parallel light beam into a homogeneous light circle with the necessary diameter at a certain distance from the lens. These transforming Fresnel concentrators can be successfully used, for example, in monitoring devices to automatically adjust the output signal from four-quadrant photodetectors. Traditional focusing Fresnel structures are manufactured by photolithographic methods or adjustable direct laser recording with photoresists. These methods enable the formation of stepped optical structures, which have inherent surface defects, resulting in the formation of images that are not high in quality. The proposed specialized Fresnel concentrators can be easily fabricated via the diamond cutting method, which enables the manufacturing of flat working surfaces with exceedingly high optical quality. We also develop a method for simulating the Fresnel transforming lenses as flat conical working facets and calculate the geometric parameters of the circular concentrators. We then feed the simulation results to the diamond cutting method and fabricate the microprismatic light transforming samples. These samples are then investigated experimentally with a collimated laser beam. The obtained data agree with the theoretical predictions.