Phase modulation methods for imaging around corners with reflectively scattered light required illumination of the occluded scene with a light source either in the scene or with direct line of sight to the scene. The RM (reflection matrix) allows control and refocusing of light after reflection, which could provide a means of illuminating an occluded scene without access or line of sight. Two optical arrangements, one focal-plane, the other an imaging system, were used to measure the RM of five different rough-surface reflectors. Intensity enhancement values of up to 24 were achieved. Surface roughness, correlation length, and slope were examined for their effect on enhancement. Diffraction-based simulations were used to corroborate experimental results.
Burgi, K. W., Marciniak, M. A., Oxley, M. E., & Nauyoks, S. E. (2017). Measuring the reflection matrix of a rough surface. Applied Sciences, 7(6), 568. https://doi.org/10.3390/app7060568