Microwave Holography Using Point-Spread Functions Measured With Calibration Objects

Sub-Diffraction Holographic Imaging With Resonant Scatterers

“…The position vectors r P and r Q give the locations of the observation and object's scattering points, respectively. It has been shown in [7] that PSF of the microwave measurement system (assuming that the imaging system is linear space-invariant) can be approximated by recording the scattered field in (1) through measurement of a small object, termed a calibration object (CO), placed at the same image distance of interest. With reference to Fig.…”

“…1(b) (currently we ignore the use of scatterer), the measured scattered field by the antenna over the scanned line for a CO placed at the origin is denoted by E sc,co j (x). The measured scattered field by the antenna over the scanned line for any unknown object on z = 0 line can then be approximated as [7] …”

“…Inspired by the hardware implementation in [6] and the holographic imaging technique in [7], we propose a subdiffraction holographic imaging technique with the measurement of point-spread function (PSF) of the system. Although we propose using a scatterer in the close proximity of the imaged object as in [6], the image reconstruction is performed via processing instead of the use of hardware components such as phase conjugating lens in [6].…”

“…Although we propose using a scatterer in the close proximity of the imaged object as in [6], the image reconstruction is performed via processing instead of the use of hardware components such as phase conjugating lens in [6]. Also, collection of the PSF of the imaging system via the measurement of a small object (the so called calibration object (CO) as in [7]) eliminates the need for providing the incident field and the Green's function for the combination of the antenna and the scatterer in the holographic imaging. This is important since any small and inevitable modeling error in the simulation of the incident field and the Green's function leads to large inaccuracies in the imaging results due to the delicacy of the evanescent waves.…”

Three‐dimensional holographic imaging using data collected over cylindrical apertures

“…To resolve this issue, a method has been proposed in Ref. to acquire the incident field and Green's function specific to the particular acquisition system via measurements of a known calibration object (CO). The method exploits the concept of point‐spread function (PSF) of a linear imaging system where the response due to an arbitrary object is the convolution of the response due to a point‐wise scatterer (called CO) with the spatial variation of that object.…”