Analytical 4D Infrared Tomography Using an InSb Focal Plane Array Sensor. 1. 3D Infrared Tomography (Single-Wavelength Approach)

A focal plane array InSb image detector has been used for noninvasive spectroscopic infrared tomography of visually turbid polymer bodies. Tomographic images from a rotating sample, illuminated by infrared light, were taken under distinct, equidistant angular views. Several IR wavelengths were used simultaneously for illumination. This provided for each analyzed sample a four-dimensional data set consisting of three geometric dimensions (x, y, z) and the wavelength axis (λ). Concealed or secret parts inside the turbid hollow polymer body were visualized by three-dimensional numerical computer-assisted tomographic reconstruction using the back-projection algorithm. IR tomography at different wavelengths provided the possibility of differentiation between distinctly absorbing materials inside a visually turbid material. The name 4D IR tomography or spectroscopic infrared tomography is proposed for this new analytical method.