Design of wide-band high numerical aperture flat field apochromatic microscope objective

In the field of microscopic imaging, such as gene detection of cancer cells and fluorescence microscopic imaging, wider spectral coverage, high numerical aperture and precise chromatic aberration correction are required for microscopic objectives. In this paper, optical software ZEMAX is used to design a flat-field apochromatic microscopic objective with a magnification of 40× and a numerical aperture of 0.8. The objective lens has the characteristics of wide spectral coverage, high numerical aperture and strict color correction. The results of design and analysis show that the flat field number of the objective is 1.15um and the maximum focal shift is less than 0.5um, which conforms to the international standard of microscopic objective. The modulation transfer function (MTF) approaches the diffraction limit at the frequency up to 208lp/mm, and the objective achieves a flat-field apochromatic design in the range of 400-1000nm. The tolerance analysis results show that the MTF value at 208lp/mm has an 80% probability of being better than 0.5974, and machining and assembly can be carried out according to this tolerance allocation.