Research On The Rapid Optical Focusing Of Laser After The Wavefront Shaping Based On The Genetic Algorithm Penetrating Scattering Medium

When the laser without modulated is incident to the strong scattering medium,it can’t penetrate the strong scattering medium to realize the light focusing because of the influence of multiple scattering.Three methods,including iterative optimization,phase conjugation and transfer matrix method,are introduced to realize laser focusing through strong scattering media or focusing in scattering media.Genetic algorithm has superior adaptability and high robustness.It is easy to achieve optical focusing based on genetic algorithm,and its noise immunity is excellent.It is possible to imaging in vivo tissue when the focusing speed is fast enough.Therefore,it is important and meaningful to study the faster light focusing method based on genetic algorithm.This paper studies the theory of genetic algorithm and applies genetic algorithm to laser wavefront shaping to realize light focusing.Modulating the phase or amplitude of incident laser can achieve light focusing.The modulation speed of Digital Micromirror Device for laser amplitude is faster than that of liquid crystal spatial light modulator for laser phase modulation.In this paper,we have studied the binary amplitude modulation of the incident light field with Digital Micromirror Device,thus improving the speed of light focusing.The iteration time of genetic algorithm is an important factor that affects the speed of light focusing.There are delays in the two processes of mask matrix transfer from computer to Digital Micromirror Device and CCD camera to record the output light field and send images back to the computer.In this paper,the CCD camera’s lost frame is located.The iterative timing of misalignment is proposed and realized experimentally,which accelerates the speed of wavefront shaping.The parallel operation genetic algorithm is used in the computer to make it run at a faster frame rate,thus improving the speed of optical focusing.In FPGA,the GigE interface and the HDMI interface are implemented,so as to use FPGA to receive and parse the images returned by the CCD camera and to directly output the mask matrix in the FPGA into the digital mirror.The random number is generated.in FPGA and the operation of selection operator,crossover operator,mutation operator and genetic algorithm is implemented to reduce the delay and improve the arithmetic speed,thus improving the speed of light focusing.The genetic algorithm is studied and combined with wavefront shaping to realize the optical focusing of laser through strong scattering medium experimentally.The iterative timing of misalignment is proposed and realized,which avoids the accumulation of iterative delay,and the wave front shaping speed is increased by 4 times from 5Hz to 25 Hz.In experiment,FPGA chip is used instead of computer to operate genetic algorithm to realize optical focusing.The wavefront shaping speed is increased from 5Hz to 60 Hz,which is 11 times higher.