Contaminant detection using a CZT photon counting detector with TDI image reconstruction

Abstract

Food x-ray inspection systems are designed to detect unwanted physical contaminants in packaged food to maintain a high level of food safety for consumers. Modern day x-ray inspection systems often utilize line scan sensors to detect these physical contaminants but are limited to single or dual energies. However, by using a photon counting detector (PCD), a new generation of food inspection systems capable of acquiring images at more than two energy bins could improve discrimination between low density contaminants. In this work, five type of contaminants were embedded in an acrylic phantom and imaged using a cadmium zinc telluride (CZT) PCD with a pixel pitch of 330 μm. A set of images were acquired while the phantom was stationary, and another set of images were acquired while the phantom was moving to mimic the movement of a conveyor belt. Image quality was assessed by evaluating the contrast-to-noise ratio (CNR) for each set of images. For imaging times larger than 25 ms, the results showed that the moving phantom data set yielded larger CNR values compared to a stationary phantom. While conventional x-ray inspections often utilize line scan sensors, we report that physical contaminant detection is possible with a CZT PCD x-ray imaging system.

Optimization of a CZT photon counting detector for contaminant detection

“…The set-up of the X-ray imaging system used in this work is the same as our previous work as shown in figure 1a and no external filtration was used [6]. Based on our previous work, results showed that for imaging times greater than 25 ms, a moving phantom yielded larger CNR values compared to a stationary phantom.…”

“…Previously, our research group successfully showed that a phantom in constant motion provided superior image quality in comparison to a stationary phantom [6]. Therefore, in this work, all images were acquired while the phantom was moving parallel to the CZT PCD and X-ray tube at a constant speed of 10 mm/s.…”

“…This flat field correction is useful to reduce fixed pattern noise which can significantly degrade the spatial resolution and image quality. Both the flat field and dark field images were acquired for 60 s and scaled down to 1 ms equivalent images as was previously done in our work [6]. These scaled down 60 s images showed less pixel variation compared to acquiring flat field and dark field images at a frame rate of 1000 fps.…”

“…Previously, our research group developed a time delay and integration (TDI) algorithm to reconstruct planar X-ray images while a phantom moving at a constant speed is imaged [6]. This algorithm is useful when the width of the detector is much smaller than the size of the object being imaged and allows a 2-dimensional image of the object to be reconstructed.…”

Vision-based measurement method for geometric dimensions of PVC pipe end faces

“…Numerous researchers have conducted extensive studies on various geometric dimension image measurement techniques for different workpieces, achieving significant breakthroughs [4][5][6][7]. Gong-Y and Seibel [8] utilized three-dimensional optical technology to gauge complex micro-surfaces, such as internal threaded holes, within machined parts.…”