Design of non-symmetrical projection lens for digital lithography

For the digital micromirror device (DMD) digital lithography, a ten-lenses projection objective was designed for DMD of model 0.7XGA by using Zemax optical design software. The projection objective uses the non-symmetrical structure, which has improved air-spaced triplet as front group and Petzval objective with flat field lens as back group, making it own higher resolution with 2 m. Its paraxial magnification is -0.15,the image-side numerical aperture (NA) is 0.158, the wavefront aberration is less than /20,the distortion is less than 0.014% and focal depth is 20 m. Through using Zemax to simulate, the system reaches diffraction limit theoretically. After tolerance analysis, by using Monte Carlo method, 100 groups of lenses were simulated for fabricating and assembling,results show that 90% of them could realize MTF＞0.46 and 50% could realize MTF＞0.51, which proves the possibility of fabricating and assembling such a non-symmetrical structure.