# Reflective Inverse Diffusion
## 5 Conclusions  
This research demonstrates reflective inverse diffusion. Just as transmissive inverse diffusion seeks to image through scattering media and biological tissues, the goal of reflective inverse diffusion is to investigate the possibility of imaging from reflective scattering media. Mathematical analysis based on diffraction theory was presented and provides propagation-based simulations that corroborate experimental results. In addition to proof-of-concept results, non-mechanical beam steering was demonstrated. Although it was shown that the reflective properties of the sample affect spot enhancement, the exact relationship that material properties, such as surface roughness and correlation length, have on enhancement is left for future work.  
While our transmissive inverse diffusion experiment through white paint produced an enhancement of 56, reflective inverse diffusion using metallic reflectors produced enhancements between 67 and 122 in the specular region. The high specular reflectance and sample stability are factors that contributed to the larger enhancement levels. The more diffuse reflecting materials provided levels of enhancement lower than the transmission case, but produced enhancement over a wider scatter angle than the more specular samples.  
Our continued research seeks to improve the experimental results with better equipment, namely the SLM and CCD, and better optimization algorithms, to expand simulation methods to better model noise and to further examine the relationship between specular and diffuse reflectance to provide a method for predicting enhancement. Better equipment and optimization algorithms are also expected to provide insight into the case of decorrelation observed in these samples. Just as matrix methods have been successfully implemented in transmission to allow near real-time control of the enhanced spot location [22], we are also investigating this for use in reflection. Future work will also include  
Figure 13: Enhancement comparisons of specular and diffuse regions of reflection. Enhancement is plotted after each optimization with the CCD placed in the specular region at 45\({}^{\circ}\) from the reflector surface normal (blue). Specular is defined as a reflection angle of 45\({}^{\circ}\)\(\pm\) 0.5\({}^{\circ}\) from the surface normal. Diffuse is defined as 15\({}^{\circ}\) off specular.  
a polarization study. It is known that some reflectors depolarize light more than others, e.g., bulk versus surface scatterers. It is possible that polarization can be used to improve the reflective inverse diffusion results.  
This work is supported by the Air Force Office of Scientific Research. The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the United States Government. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.  
[PERSON] developed the mathematical model, conducted the MATLAB(r) simulations, and wrote the paper. [PERSON] conducted the measurements the in laboratory, generated figures from the experimental data, and assisted with the interpretation of the experimental results. [PERSON] contributed to the idea, the mathematical model, and organization of the research. [PERSON] contributed to development of the mathematical model.  
The authors declare no conflict of interest.