Abstract: An optical structure is characterized by improving a primary lens of a photovoltaic concentrator system. The optical structure is accomplished by properly dividing the primary lens, determining required optical operational regions, and arranging the optical operational regions basing on an identical location into an annular array, thereby forming the complete optical structure. The optical structure facilitates enhancing uniformity of light distribution throughout the optical operational regions, improving photoelectric conversion efficiency of a solar cell having the optical structure, and reducing operational distance between the primary lens and the solar cell.