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This paper addresses a near-field imaging problem utilizing extremelylarge-scale multiple-input multiple-output (XL-MIMO) antennas andreconfigurable intelligent surfaces (RISs) already in place for wirelesscommunications. To this end, we consider a system with a fixed transmittingantenna array illuminating a region of interest (ROI) and a fixed receivingantenna array inferring the ROI's scattering coefficients. Leveraging XL-MIMOand high frequencies, the ROI is situated in the radiating near-field region ofboth antenna arrays, thus enhancing the degrees of freedom (DoF) of theilluminating and sensing channels available for imaging, here referred to asholographic imaging. To further boost the imaging performance, we optimize theilluminating waveform by solving a min-max optimization problem having theupper bound of the mean squared error (MSE) of the image estimate as theobjective function. Additionally, we address the challenge of non-line-of-sight(NLOS) scenarios by considering the presence of a RIS and deriving its optimalreflection coefficients. Numerical results investigate the interplay betweenillumination optimization, geometric configuration (monostatic and bistatic),the DoF of the illuminating and sensing channels, image estimation accuracy,and image complexity.

Holographic Imaging with XL-MIMO and RIS: Illumination and Reflection Design