There is a really neat patent, number 6,343,534, which is titled "Landmine Detector with a High-Power Microwave Illuminator and Infrared Detector." Here is the abstract:
"A hybrid remote-sensing apparatus is based on an active high-power microwave (HPM) illuminator and a passive infrared (IR) detector for the detection of shallow buried landmines. A 2.45 GHz, 5 kW microwave source is used for illumination and the thermal signature at the soil surface is detected in the 8-12 µm region both in near real-time as well as after a brief time-delay following illumination. The thermal signature at the soil surface is primarily made up of two components. A thermal signature occurs at the soil surface in near real-time due to the interference of the incident beam and the beam reflected by buried mines. A second thermal signature is generated when temperature contrasts due to differential microwave absorption by a mine and the surrounding soil are conducted upwards from that mine location to the surface. Both signatures are dependent on the complex dielectric constants of mines and the soil. These signatures can be used to determine the location of different types of metallic and non-metallic mine surrogates, dummy mines without explosives and live mines with explosives."
Basically, it involves using a RF magnetron, like that from a common microwave oven, to "heat" the soil in a particular area. After a few minutes of RF heating, the area is then viewed using a infrared thermal camera to locate any "hot" spots. Presumably, a landmine buried in the soil will retain some heat due to the dielectric absorption by the explosives inside the mine. This would then be visible when viewed through the thermal camera, if it's not buried too far down.
![[mine]](mine.gif)
This device doesn't appear to be too complicated to homebrew. A person controlling the robot would have a little T.V. screen showing the video output from the thermal viewer. If you locate any suspicious objects, you can then throw rocks at them from a safe distance.
The wireless video link and most of the power supplies are trivial to homebrew.
Robot chassis could be a radio controlled riding lawnmower.
![[fig-1]](fig-1.gif)
Example photos from the above patent. Figure 5a, 5b, 5c, and 5d are IR pictures of the sand surface over mine surrogates buried in moist sand at different depths which were taken at different times before and after irradiation with high-power microwaves.
