In this paper, we built a free-space scattering-type scanning near-field millimeter wave microscope using two tapered dielectric probes facing each other and a sample in between based on MVNA. Nylon, Teflon and PVC dielectric tapered probes are compared in this system. We adopted a PVC probe and a Teflon probe as incident and receiving probes. The resolution is frequency dependent. In order to increase the resolution and contrast, we additionally positioned a metal probe tip between the dielectric tapered probe and the object under test. First experiment results on this signal improvement concept will be reported for a 2 um tungsten probe, yielding an increased field enhancement and leading to the contrast improvement