Improvements in spatial resolution using terahertz time domain spectroscopy (THz-TDS) imaging at 300 GHz are demonstrated for slit diffraction, edge imaging and reflection imaging applied to art and documents. An approach similar to structured illumination with an innovative knife-edge (KE) scan method operating at a distance from the object plane that is shorter than one wavelength is applied to significantly improve upon the resolution limitations due to far-field diffraction with conventional approaches. By this new approach a spatial super resolution better than 1 mm is achieved which effectively violates the Raleigh limit and improves that without the KE by up to 2.1 times.