Prism-assisted achromatic diffraction system for multi-focus biological microimaging

•Developed a novel aberration-corrected multi-focus microscope based on the principle of the opposite dispersion in refraction and diffraction lenses.•The achromatic method by equilateral triangular prism is more applicable compared with the existing achromatic methods.•The multi-focus microscope can facilitate the rapid acquisition of 3D data and real time observation for live cells in a wide range of depth. Multi-focus microscope, which images multiple object planes of the sample simultaneously with a single shot, can significantly enlarge the observation depth and improve the time resolution of the microscope. Conventional multi-focus microscopes are quite bulky and the achromatic methods can only work for a single multi-focus diffraction lens. To solve this problem, equilateral triangular prisms (ETPs) are employed to correct the chromatic aberration generated by the multi-focus diffraction lens. This achromatic method can cope with a variety of multi-focus lenses with different parameters, which is significant to reduce the system complexity and improve device usability. For the multi-focus lenses with focal length greater than 600 mm, the resolution reduction value can be controlled within 50 nm through the fused silica ETPs. Based on the experimental setup, three sharp images of different object planes can be captured simultaneously by the detector. The resolution and imaging experiments demonstrate that the proposed scheme is reliable and flexible.