Optimizing microscan for radiometry with cooled IR cameras

Optical microscanning is a popular method in infrared imaging, providing a relatively cost-efficient means to increase the spatial resolution of the camera system. Here, we discuss the impact of microscan on parameters relevant for thermography applications. Other than imaging applications, thermography is extremely sensitive to changes of the absolute irradiation power caused by the additional microscan optics. Additional reflectance and stray radiation must be avoided or corrected for. Also, current and future developments in detector technology, such as reduced pixel pitch, will pose new challenges to the feasibility of microscan. As a practical example, we will present a microscan implementation adapted to the specific needs of thermography applications with infrared cameras based on a cooled detector. A fast rotating filter wheel with precisely adjusted deflection windows is used to produce the desired image shift. This allows us to utilize microscan while retaining the high imaging speeds usually required in applications employing cooled infrared detectors. Often, calibrated thermographic cameras are used in applications necessitating a wide range of calibrated temperature measuring ranges reaching from -40 °C to <2000 °C. Optimizing the design of the microscan device for compactness opens the possibility to combine the feature with additional optical filters, allowing wide temperature measurement ranges as well as imaging within different spectral windows.