Thermal Infrared Imaging: Instrumentation and Method Development

A recently development thermal infrared camera system was improved by designing new components to downsize physical aspect and improve the instrument\u27s performance. A new thermal infrared light source was developed and characterized. It is designed from a custom-made Macor backpiece that holds an alumina screw. High resistance wire is coiled around the screw. The coiled wire is covered with an alumina coating. Most light sources have a spectral emissivity similar to that of a blackbody emitter. This source has a spectral irradiance profile that is not similar to a blackbody source. Thus, the lamp has an improved efficiency in the thermal infrared region. The thermal infrared camera\u27s microbolometer detector was calibrated for its response at specific wavelengths. An infrared camera responds with a single value that is the sum of all detectable wavelengths. This was done by developing a method to determine the spectral response from the camera a given wavelength. At 8 µm, the camera\u27s response is an instant onset; yet at longer wavelengths, the camera\u27s response diminishes at a slower rate. A technique has been discovered that identifies differences on a surface using a thermal infrared camera. This technique exploits differences in polarity and heat capacity by exposing the surface to hot water vapor. We demonstrate this by showing the application of identifying blood on fabrics. Bloodstains that are diluted more than 20x are barely or not visible to the human eye. Our method uses a handheld steamer and a thermal infrared camera to observe the adsorption of water vapor. With sensitive thermal cameras, a small increase in temperature can easily be detected: this leads to visual contrast when observing the thermographic movie. Evidence suggests that the change in temperature is due to differential adsorption of water vapor