Fig. 1. Schematic diagram of focusing. (a) Speckles formed as a result of plane waves through a strong scattering medium; (b) a focused spot is formed after amplitude modulation; (c) a focused spot is formed after phase modulation

Fig. 2. Simulation model used for focusing of speckle field

Fig. 3. Processing flow chart of estimation of distribution algorithm

Fig. 4. Results diagram of focusing by amplitude modulation. (a) Random speckle pattern formed from unmodulated incident light; (b) a focusing spot formed by amplitude modulation; (c) relationship between enhancement factor and iterations; (d) amplitude pattern of a focusing spot in (b) formed by loading on SLM

Fig. 5. Single and multiple focusing spots image at the defined target after amplitude modulation. (a) Single spot focusing diagram; (b) two-spot focusing diagram; (c) three-spot focusing diagram

Fig. 6. Results diagram of focusing by phase modulation. (a) Random speckle pattern formed from unmodulated incident light; (b) a focusing spot formed from by phase modulation; (c) change curve of light intensity growth factor with number of iteration at target position; (d) phase pattern of a focusing spot in (b) formed by loading on SLM

Fig. 7. Single and multiple focusing spots image at defined target after phase modulation. (a) Single spot focusing diagram; (b) two-spot focusing diagram; (c) three-spot focusing diagram

Fig. 8. Relationship diagram between light intensity enhancement factor, elapsed time and total number of modulation units

Fig. 9. Relationship diagram between light intensity enhancement factor, elapsed time and number of iteration under phase modulation

Fig. 10. Relationship between enhancement factor of light intensity at target position after phase modulation and noise under different noise levels and algorithms