Micro-CT (computer tomography) is an established method for the non-destructive recording three-dimensional data of the internal structure of objects. It is similar to the methods used in radiology, but is designed for smaller objects and enables a considerably higher resolution.

In principle, X-ray images of an object are recorded in various orientations and then transformed into a three-dimensional data object, which enables any sections and views of the object to be visualised. The advantage of the micro-CT method in comparison with other methods (e.g. tomography in an electron microscope) is the fact that usually considerably less effort is required for preparation.

For more than 25 years, Skyscan has specialised in the development and manufacture of equipment for the three-dimensional measurement and imaging of microscopic objects. The manufacturer's systems now achieve resolutions down to the sub-μm range. As the heart of its High Resolution Micro-CT scanner, the company uses an xiRay11 Ximea X-ray camera. The main reasons for this choice were the special characteristics of the camera. The camera system has an optical 11 megapixel sensor (Kodak KAI-11002), which is cooled in order to effectively suppress noise signals.

In the xiRay11, the X-rays fall in a phosphor layer. This so-called X-ray scintillator converts the X-rays into light frequencies which can be used by the sensor. A fibre-optic system which is hardened against the high-energy radiation is firmly adhered to the glass plate which carries the phosphor coating and to the photo-sensor. This complex structure guarantees the high resolution and highly robust operation.

Compact and fast

The xiRay11 is equipped with the proprietary Ximea Cleanpath sensor driver technology, which delivers excellent images with a resolution of 14 Bit from the 24 x 36 mm full-format sensor surface. At maximum resolution, the camera provides four images per second for the micro-CT. At a higher image rate of 12 images per second, groups of 4 x 4 pixels are combined. The camera system therefore supports a very wide range of exposure times from 12 µsec to 500 seconds.

In addition to this performance data, the xiRay11 is especially suited for the micro-CT due to its very small housing dimensions of only 63 x 63 x 39.2 mm.

The decision to use the X-ray camera was made from direct comparison with other available products. In the course of extensive testing, the xiRay11 delivered considerably higher resolution images with the same exposure times. It was considerably faster and was therefore selected by Skyscan as the system camera.

The use of the new, large-format, cooled digital X-ray camera enables the Skyscan micro-CT systems to produce 3D layer and section views of samples with 8,000 x 8,000 pixels with a detail resolution of down to 0.7 µm In order to process the large amounts of data as rapidly as possible, the manufacturer offers the option of using a cluster of parallel computers.

Wide range of applications

As well as the xiRay11, the camera manufacturer also offer the xiRay16 with 16 megapixel resolution on the basis of the Kodak KAI-1600 sensor, which rounds off the top end of the range of X-ray cameras. The phosphor coating of the scintillator surface can be individually tailored according to requirements. This opens up a wide range of scientific applications.

As well as this, the company offers a wide spectrum of CCD, CMOS and PC cameras with FireWire, Gigabit-Ethernet, USB 2.0 and USB 3.0 interfaces, which are used in many areas of industry, such as motion control, robotics, production and quality control. Miniature and special cameras for medical, research, surveillance and defence applications are also available.

Vision 2012 Stand 1C51