Research On Light Focusing Though Scattering Media By Complex Field Modulation Based On Superpixel Method And Digital Micromirror Device

When a beam of light passes through a scattering medium,it loses its directionality due to the influence of multiple scattering,which not only limits optical imaging greatly,but also seriously hinders the development of biomedicine,communication and other optical technologies.The wavefront shaping technology developed in recent years can focus light through scattering media by modulating the incident wavefront,which makes it possible to image the intermal structure of strong scattering media such as living tissues,and has attracted extensive attention.Wavefront shaping technology uses amplitude or phase modulators to control the incident wavefront.Amplitude modulators have fast modulation speed but weak modulation performance,while phase modulators have strong modulation performance but slow modulation speed.Both of them cannot meet the requirements of imaging the intermal structure of living tissues.In this paper,the superpixel method is studied theoretically.The digital micromirror device based on superpixel method can modulate the amplitude and phase of the light field while maintaining the original fast modulation rate.In order to explore the feasibility of this method in experiment,this paper designs an experimental scheme based on four-step phase-shifting method to detect the effect of phase modulation of superpixel method,and confirms that this method can be used to control wavefront through the analysis of the results.On this basis,the experimental scheme of optical focusing is designed by combining superpixel method with genetic algorithm in depth,and the relative enhancement factor of 0.71 is obtained in the experiment,which is the highest value of all wavefront shaping optical focusing experiments based on digital micromirror device so far.To improve the speed of optimization,the multi-frequency parallel optimization algorithm is researched theoretically and simulated in this paper.Based on the experience,an experimental scheme of optical focusing combined with superpixel method is designed.Finally,only 1000 masks are needed to achieve high-quality focusing of the target point.