O. Breitenstein, Max Planck Institute of Microstructure Physics, Halle, Germany; F. Altmann, T. Riediger, Fraunhofer Institute for Mechanics of Materials, Halle, Germany; D. Karg, Thermosensorik GmbH, Erlangen, Germany; V. Gottschalk, ELMOS Semiconductor AG, Dortmund, Germany

Summary: A hemispherical silicon solid immersion lens (SIL) was used to improve the spatial resolution of frontside thermal IR imaging in lock-in mode. The bottom of the SIL was cone-shaped to reduce the footprint of the SIL to the size of the imaged region. Thanks to the lock-in operation mode the detection limit improves by 2-3 orders of magnitude, and scattered light does not limit the image contrast. By using this SIL together with an IR camera working in the 3-5 µm wavelength range, a spatial resolution of 1.4 µm was obtained for thermal IR imaging.