Off-axis Non-rotationally Symmetric Superposition Square Spot Uniform Concentration Fresnel Lens

Aiming at the defects of the poor uniformity of concentration distribution and the focused spotshape does not match with solar cells in the traditional point focus Fresnel lens, square spot uniformconcentration Fresnel lens was designed by using the method of off-axis non-rotationally Symmetric Superposition. The square non-rotating symmetry structure was adopted in the lens, a square hole was intercepted in the center of the lens when the lens was designed, which can reduce the center peak irradiance of the focal spot and improve the concentrated distribution on the receiving surface in order to improve the uniformity of the spot light. The ray tracing method has been used to simulate and analyze the influence on the condensing performance caused by structure parameter of lens such as off-axis offset, the length of hole and the off-axis focus length. The results show that the shape of the focus spot of the lens designed by this method is square, and the concentration uniformity is up to 90%.