Patent ID: 10983442

Abstract:
A projection objective, used for projecting an object space to an image space. The objective includes, from the object space along an optical axis in sequence: a first lens set (G1) having positive focal power, a second lens set (G2) having negative focal power, a third lens set (G3) having positive focal power, a fourth lens set (G4) having negative focal power, and a fifth lens set (G5) having positive focal power. Aspheric lenses are provided in the first lens set (G1), the second lens set (G2), the third lens set (G3), the fourth lens set (G4), and the fifth lens set (G5). According to the design, the number of lenses is reduced, the structure of the objective is more compact, the transmittance of the objective is improved, the structural design of aspheric lenses is optimized, the asphericity of the aspheric lenses is reduced, the processing difficulty and costs for the aspheric lenses are reduced, and except for the above situations, the objective has a bitelecentric structure, and the sensitivity of the objective for micro irregularity defects on a mask surface is reduced.