Optical design of the N.A. 0.75 plan-apochromatic microscope objective

To improve the common microscope objective with small field of view, poor field curve and chromatic aberration correction, A 20× plan-apochromatic microscope objective is designed in this paper by Code V software. This objective has a large field of view, high N.A., and plan-apochromatic characteristic designed by reasonable structure optimization, focal power distribution and material selection. The result shows that the objective is a plan-apochromatic lens in visible wide band. The plan field number is 0.11 μm and the largest focal shift is 0.5 μm, which meet the specification of the international standard for microscope objectives. The MTF curve is closed to the diffraction limit. The tolerance analysis shows that RMS wavefront error gets worse to 0.24λ and the objective lens can be applied and manufactured actually.