X-Ray Food Inspection System

Overview

An x-ray food inspection system passes packaged or bulk food through a thin x-ray beam and reads how much of the beam each part of the product absorbs, building an image in which dense foreign bodies stand out from the food around them. Where a metal detector finds only metal, an x-ray system finds metal, glass, stone, dense mineral, dense bone, and some dense plastics and rubber, and it sees them even inside metallized film or a foil tray that would blind a metal detector. The same image also supports quality checks: counting items in a pack, measuring fill level, spotting voids or trapped product in a seal, and estimating mass. The flagged pack is then removed by a reject device before it leaves the line.

The system is built around a source and a detector facing each other across a belt, all inside a shielded box. The X-Ray Generator makes the beam, the Line-Scan Detector reads it, the Shielded Cabinet keeps the radiation contained, the Conveyor Section moves product through, the Imaging and Analysis turns the readings into an inspected image, the Reject System removes bad packs, the Controller and HMI runs it, and the Cooling System keeps the tube from overheating.

Making the beam

The X-Ray Generator produces x-rays in a sealed X-Ray Tube. Inside, the Cathode is a heated filament that boils off electrons, the HV Generator accelerates them across tens of kilovolts, and they strike the Tungsten Anode, a tungsten target, where the sudden deceleration emits x-rays. Most of the input energy becomes heat at the anode, which is why cooling is essential. A Collimator of lead shapes the emission into a thin fan beam aimed across the belt at the detector, and the Tube Housing absorbs all radiation except that collimated beam. The Filament Supply sets the beam current by controlling the filament temperature.

Reading the image

As the fan beam crosses the belt, the Line-Scan Detector reads its intensity at hundreds of points along a line. A Scintillator strip converts the arriving x-rays into visible light in proportion to dose, and a Photodiode Array below it turns that light into one row of pixels. A Detector Readout Board digitizes the row, and because the Conveyor Section moves the product through at a steady speed tracked by the Belt Encoder, stacking those rows builds a complete grey-scale image where darker means denser. The Image Acquisition Board uses a Image FPGA to stitch the lines and apply flat-field correction so the image is uniform across the belt.

Finding contaminants and defects

The Analysis Computer runs the analysis on the assembled image. A dense contaminant absorbs more of the beam than the food around it and shows as a dark spot, so detection comes down to separating real contaminants from the natural density variation of the food. The algorithms model the expected product so a folded edge or a bone-in cut is not mistaken for a stone, and multi-level analysis helps where the product itself is dense or uneven. Beyond contaminants, the same image supports mass estimation from total absorption, item counting, fill and headspace checks, and trapped-product detection in seals. Results and the images that produced them are kept on Image Storage for traceability.

Keeping it safe and cool

Because the machine makes ionizing radiation, the Shielded Cabinet is a sealed enclosure. Lead-lined Lead-Lined Panel walls absorb scattered radiation, and overlapping Tunnel Curtain flaps of lead-loaded rubber block the beam at the belt openings while letting product through. An Interlock Switch cuts the source the instant a guard is opened, and a Warning Light shows when the beam is on, so operators can stand beside a running machine safely. The tube dumps most of its input as heat, so the Cooling System loop circulates coolant with a Coolant Pump through a Heat Exchanger to let the source run continuously.

Rejecting, verifying, and use

Flagged packs are removed by the Reject System, which fires a Reject Pusher timed by belt position and uses a Confirm Sensor and a locked Reject Bin so a contaminated pack cannot reach the customer or return to the line. The Controller and HMI holds a recipe per product and logs every event for audit. A scheduled routine passes a Test Card carrying calibrated metal, glass, and stone specks to confirm the system still finds the smallest defect it is set for, and a failed test stops the line. X-ray systems inspect retail packs on belts, and related designs check loose bulk product in a chute, pumped product in a pipe, and tall rigid containers from the side. They cost more than metal detectors and use a radiation source that requires registration and trained handling, so they are chosen where the extra detection of glass, stone, and bone, or the inline quality checks, justify it.