4. Experimental results

4.1 Image formation procedure

The experimental basis for imaging an object depends on the nature of the radiation source: wide or narrow spectral bandwidth, coherent or incoherent detection. If the source is sufficiently powerful, work has shown that it is possible to illuminate the entire object with the THz beam and set up a 2D matrix detection system (amplified laser source, cascade source, etc.). In our example, we prefer to use conventional broadband sources as with a femtosecond laser oscillator system. The terahertz optics developed focus the beam at the diffraction limit. We then move the object located at the waist of the beam, and reconstruct the image pixel by pixel. This gives us a huge amount of information, enabling us to adjust contrast to highlight a particular characteristic...