Design method for metalens, metalens, shaping and beam-combination device and display device

A design method for a metalens, when a plurality of Gaussian beams passes through the metalens, the Gaussian beams are shaped into a plurality of flat-topped beams that project to a target position on a target plane, the design method comprising:

• determining an incident parameter, wherein the incident parameter comprises a plurality of wavelengths and a plurality of radius of the plurality of Gaussian beams;
• determining an outgoing parameter, wherein the outgoing parameter comprises a width of the plurality of flat-topped beams;
• setting a plurality of metalens portions on the metalens and determining a position of each metalens portion;
• wherein the plurality of metalens portions and the plurality of Gaussian beams are in one-to-one correspondence,
• calculating a modulation phase distribution of each metalens portion according to the incident parameter, the outgoing parameter and the position of each portion metalens;
• arranging a plurality of unit cells on the metalens portions according to the modulation phase distribution, and obtaining the metalens.