Prototype Robotic System for Multimodal Forensics and Failure Analysis

A number of analytical techniques are used in the forensic science field, in failure analyses and inspection. The range of objects that are subjected to these analyses is very wide, from components of industrial technology, through parts of means of transport, including aircraft, to objects of art. One of the main techniques is the X-ray methods, but this is usually supplemented by other analyses depending on the nature of the material or object being examined. X-ray fluorescence, multispectral imaging, industrial CT, X-ray diffraction and other techniques are used. The prototype device for robotic analysis, imaging and mapping of 3D objects is being developed and tested to be used in the aforementioned areas. The system´s principle is integration of imaging and analytical technologies onto six-axis robotic arms which allow wide flexibility range concerning the sample size or shape. The system allows non-destructive examination of wide spectrum of samples with complicated curvatures. Robotic scanners system opens the door to explore new approaches to both 2D and 3D X-ray imaging, especially in combination with photon-counting detectors. Platform allows combining several imaging modalities with any required number of robots. Such modalities range from visible light imaging, UV, IR, to 3D surface profiling, air-coupled ultrasound to 2D X-ray imaging, and CT. Prototype system is based on Radalytica's multi-robot imaging platform, referred to as RadalyX. System measures nearly all conventional 2D and 3D trajectories of X-ray imaging with precisely calibrated and repeatable geometrical accuracy leading to a spatial resolution of up to 50 µm. The imaging modules are operated in continuous, discrete, or combination of modes along the scan path to trigger data acquisition at precise geometry relative to the inspected parts. The stations are positioned arbitrarily and geometrically calibrated to enable different scanning modes such as thru-transmission and reflectance e.g. ultrasound pitch-catch. For X-ray imaging, RadalyX's standard configuration is composed of two robotic stations. One robot carries an X-ray tube, and the other holds a photon-counting imaging, or another detector. RadalyX is equipped with accurate geometrical calibrations that allow positioning both robots precisely yet arbitrarily. Therefore, the robots can be moved to different locations during on-site inspections. The new generation of X-ray imaging detectors provides a high picture quality with a spatial resolution level in the micrometer range in 2D or 3D imaging. The basic version of the robotic scanner allows transmission X-ray imaging and mapping of the individual photons with high sensitivity and resolution detectors. These detectors are the result of an intensive international cooperation led by the CERN laboratory in Geneva. The particular used type of imaging detectors allows to measure X-ray wave lengths. From the changes in the X-rays spectrum after it has gone through the sample, it is possible to presume the elemental composition of the examined object. The key parts of the scanner are two robotic stations. One robot carries an X-ray tube whose emission spot size range is 8–40 µm, and the operating voltage range is 10–130 kV, and the other one holds a photon-counting imaging detector of the Widepix MPX3 family. Robots can move and rotate freely about the sample in a precisely synchronized movement. It provides almost absolute flexibility of viewing angles. The very high sensitivity, spatial resolution, and dynamic range of the used detectors enable us to push the X-ray image quality to its physical limits. System is equipped with accurate geometrical calibrations that allow positioning both robots precisely yet arbitrarily. Therefore, the robots can be moved to different locations during on-site inspections. Differences in spectrum changes then reflect in the resultant image in the form of false colours. The pixel array sizes range from 256×1280 to 1280×1280 pixels depending on the detector version. Each pixel contains analog and digital electronics to process electric pulses generated by radiation in the sensor. These detectors are so-called direct conversion devices where the radiation is converted directly to a signal contrary to scintillator-based imagers where the radiation is converted to light first and then to an electric signal. The direct conversion approach eliminates most sources of noise in the pixels yielding considerably improved contrast and signal-to-noise in images. Moreover, since the electronics process every detected pulse individually, it is possible to compare the pulses with predefined discrimination level(s) (thresholds). Only pulses caused by radiation with energy higher than the threshold are recorded in the digital counter that can be configured to up to 24-bits. This approach first of all eliminates all electronic noise that is below the threshold. The pixel matrix contains therefore zero counts if no radiation is present. Secondly, it allows considerable suppressing for example scattered radiation by setting the threshold to a sufficient level. Finally, it also allows performing absorption spectroscopy imaging that allows recognizing materials present in an examined sample by analyzing changes in the X-ray spectrum caused by different materials of the sample. This approach is used for analysis of art. Another extension modality is XRD phase mapping which exploits properties the Timepix3 spectral imaging detector which records the position and energy of every detected photon as well as the time of detection. Regarding these properties, a monochromator can be left out from the XRD device. The construction fundamentally simplifies the XRD device and allows integration with robots. The robotic scanner further allows scanning and mapping of crystallic properties of the whole examined object on surface. This information is further combined with the XRF elemental mapping of the whole object. There exist many possibilities how to combine the XRF data with transmission maps and X-ray imaging data – a robotic scanner measures all analytical modalities in a common reference system. The system is supplemented with other modalities which allow to obtain more analytical data – VNIR, SWIR and the UV modules. The use of this information is very wide. The individual image layers can be switched on and arbitrarily combined with the obtained maps. In the forensic field, the use is rather extensive –tools and marks examination, forensic defectoscopy and metallography and other security areas [5].