The improvement of highly effective emitters and fast line detectors enables to make new industrial applications for terahertz measurement imaging and tomography.
Terahertz radiation’s wavelength 30 µm bis three mm has low power, is non-ionizing, and transmit most plastic components. Therefore, it is actually of wonderful interest in numerous fields of metrology and top quality management.
For the style of quasi-optical THz-systems classical raytracing and physical optics propagation tools are applied. Difficult tasks for the optical style will be the substantial wavelength, the broad spectral bandwidth plus the readily available lens supplies. The amount of lenses within the setups ought to be as low as you possibly can to prevent absorption losses within the bulk material.
Aspherical lenses are fabricated by ultra-precision (UP) turning. As antireflective remedy with the plastic lenses surfaces shapes like moth-eye structures are employed, that are also fabricated by ultra-precision machining. Mirrors are also made use of especially in off-axis paraboloids.
Foamed polymers are broadly employed in market as packaging and insulating material at the same time as modeling material for lost-foam casting. In particular inside the latter procedure, higher demands are created for the polymer foam good quality.
A homogenous density distribution in the foam model is often a deciding element for the high-quality in the resulting casting. Because the models may perhaps show process-induced density fluctuations, these has to be identified along with the foaming approach should be adjusted accordingly.
Because of the lack of appropriate metrology, the densities have already been determined using the invasive strategies that are slow and are performed with low nearby resolution. Hence, it was not doable to establish a direct comparison amongst the model and casting top quality.
The Fraunhofer IOF in cooperation with Fraunhofer IFAM created a brand new measurement process for the non-destructive determination on the density distribution and fluctuation primarily based around the THz imaging strategy.
Ultrashort terahertz measurement (THz) pulses (? = 0.1 – ten THz, ? = 30 µm – three mm) are electromagnetic pulses with just a single oscillation cycle of your electrical field strength.
The low-energy radiation penetrates paper, plastics, dry wood and also the majority of ceramics, and exhibits a higher sensitivity to water. It truly is feasible to figure out material densities and thicknesses applying time of flight measurements of THz pulses via polymer foam and plastic samples.
Semiconductor elements and photoconductive material exited by a femtosecond fiber laser will be the principal sources in the THz radiation utilized in our laboratories. The fiber lasers essential for the THz generation and detection are also created and created at Fraunhofer IOF.
Through the verification the foam sheet was systematically divided into sections; the density of every single segment was measured by a destructive system and compared with information accomplished in the terahertz measurement.