Eye opener

German researchers develop X-ray camera claimed to provide improved reliability when monitoring components on the production line. Siobhan Wagner reports

an X-ray camera using special optics and claimed to last longer than conventional equipment, could provide manufacturers with improved reliability when monitoring components on the production line.

The developers of the camera at Fraunhofer Institute for Integrated Circuits (IIS) in Erlangen claim the XEye can survive 10 years of X-ray bombardment. In addition, they said, the device, which is available in a range of sizes, is more robust and has a higher resolution than conventional cameras.

While no human could withstand the bombardment of X-rays 24 hours a day, seven days a week, industrial X-ray cameras have to endure those conditions to detect faulty components. The cameras must constantly scrutinise thousands of parts that glide past on the conveyor belt every day and search for dangerous faults, such as fine cracks in car wheels and air bubbles in metal castings.

Most of these special cameras, which cost tens of thousands of pounds, are not capable of tolerating this constant bombardment with damaging radiation for more than a few months before having to be replaced.

The IIS researchers said extensive radiation tests on the XEye indicate an expected service life of up to 10 years, which means massive savings for industry.

X-ray cameras are digital radiation converters. They are mounted opposite the X-ray source in the test apparatus and the components pass between them. The radiation emitted by the source hits the camera’s scintillator, a layer of material that is excited by the X-rays to produce visible light. This light signal is converted into an electrical impulse by a light-sensitive layer, which is divided into pixels and mounted behind the scintillator. The electrical impulses are then digitally processed.

The problem is that the X-rays impinge not only on the scintillator, but also on the light-sensitive layer behind it, thereby damaging it. Some pixels drop out completely, while others become lethargic and only recover slowly from the excitation caused by the scintillator’s light emissions. This results in an afterglow, or ghosting, which makes the camera unusable.

The researchers have increased the service life of the camera by using special optics, which are currently patent pending, to protect the light-sensitive layer from the X-rays.

‘The camera can be produced in virtually any size,’ said Peter Schmitt, head of the Contactless Test and Measuring Systems department at the IIS. ‘The modular construction of the device allows us to simply increase the surface area of the screen,’ he added.

At the moment, said Schmitt, industrial X-ray cameras only produce an image as big as 40 cm2. ‘If you want to inspect a whole wheel, for example, you have to take multiple photographs,’ he said. ‘However, by taking just one you would save a lot of time and money.’

To this end, Schmitt said the IIS is currently planning XEye cameras with a screen size of 60 cm2, which would be capable of producing at least 50 images/sec.

In addition, the XEye could be adjusted to image somewhat awkward components. ‘In many circumstances you just need camera images that are long in one direction, but you don’t need the same size in the other direction, such as cycle handlebars,’ said Schmitt.

The XEye is currently being tested by a German steel tubing manufacturer to monitor weld seams. The device delivers seven images/sec with a screen size of 20 cm2, which is fast enough to monitor all the of the production.

The researchers are currently taking orders for instalments in production plants.

‘We hope to have our first commercial camera installed in January,’ said Schmitt.