Design of a high-uniformity illumination system based on multi-beam superposition

In biomedical experiments such as in vivo microscopy, to achieve high-uniformity illumination on two differently sized illuminated surfaces within a confined space, a multi-beam superposition illumination system comprising a laser source, multi-channel optical fibers, a square light pipe, and a projection lens was designed. Based on the principle of étendue conservation, the integrating square light pipe was designed; meanwhile, using the edge ray principle, the projection lens was designed in the form of critical illumination, and uniformity was enhanced through the superposition of four symmetrically arranged oblique beams. Based on the principles of étendue and radiometry, the illuminance equation at any point on the illuminated surface was derived, and a multi-slanted-beam superposition illumination model was established. The optical system simulation was completed using LightTools software to analyze the influence of light source luminous flux fluctuation on illumination uniformity, and the optical efficiency of the system was analyzed, with a total optical efficiency simulation value of 72.8%. Finally, the system performance was tested through a physical experiment. The experimental results show that the illumination uniformity on the two illuminated surfaces reached 93.2% and 94.9%, respectively, which closely matches the simulation results, providing a reference for the design of low-cost and high-uniformity illumination systems.