Dual-sided phase conjugating surface techniques for imaging

We describe the principle of operation and study the imaging capabilities of a dual sided phase conjugating lens operating as an imaging sensor in free space or in an environment where significant multipath or scattering may be present. The image formation is based on the wavefront reversal properties of the phase conjugating array. By the means of numerical simulation we show that the characteristic resolution of a single dielectric target in free space is about one wavelength, λ, across the range and 3-4λ along the range for CW illumination and about one centre-wavelength λ₀ when the target is illuminated with a Gaussian packet. For multiple targets in free space resolution across and along the range is ~2λ₀ when illuminated by a Gaussian packet. It is shown that a weakly scattering object can only be detected behind a lossy dielectric wall using CW or UWB phase conjugation techniques when the backscattered field from the wall is eliminated. A procedure for achieving this is proposed. Numerical simulations for through-the-wall imaging using the phase conjugating lens technique with wall backscatter elimination demonstrates the possibility for small target high-resolution imaging.