IP6 - Infinitely adjustable attenuation cell for infrared radiation to fit the metering capacity to different object temperatures

SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
Proceedings OPTO 2009 & IRS² 2009
IRS² Poster Session
H. Rademacher - Technische Universität Dortmund, Dortmund, Germany
301 - 305


In this work a method is described, which allows the extension of measurement prospects of the metering capacity of an infrared camera system. In the following examples a high-speed infrared camera with a MCT-sensor (3-5μm spectral response) and a frame rate of 885 pictures per seconds is used. This type of camera is not equipped with temperature measurement like standard thermography cameras. Its major task is to detect small changes in the radiation intensity. To match the measurement-range of the camera to the amount of emitted radiation by the inspected object, the only parameter needed to change is the exposure time. The few possible discrete steps of changing this time constant, which most cameras contain, can extend the measurement range only to a maximal object temperature, which corresponds to a maximal intensity that can be measured. If the temperature increases the detector will overcharge. This also affects neighbouring pixels (blooming effect). Furthermore the used camera has a limitation when changing the exposure time. After each change, a sensitivity calibration and a homogenizing of the MCTSensor is necessary. This could be difficult if the camera is attached in a complicated assembling and makes a comparison of different measurements very difficult. Another disadvantage is the decreasing sensitivity when using short exposure times. The camera is in fact able to detect higher changes in temperature, but concurrently it is less sensitive to objects at lower temperatures. The measuring of two objects with a great difference in temperature, which appears for example at cutting processes, is difficult or not possible. As well, focusing the object under test is difficult at room temperature, as the contours cannot be seen.