Industrial CT solution takes inspection of large components to the next level

Nikon Introduces “Offset.CT” for X-ray CT system

May 26, 2021

Nikon is pleased to announce a microfocus spot CT system with elevated levels of X-ray flux and magnification to deliver unrivalled acquisition speed and image quality.

An industrial X-ray CT (computed tomography) solution that drastically improves the inspection of large components, even those that are dense, has been introduced by Nikon. The holistic offering, which is not available from any other supplier, incorporates the company's unique rotating target capable of tolerating a highly focused spot of electrons from the filament. This recent innovation has been combined with two other attributes, one being Offset.CT while the other is the ability to vary the distance between the source and flat panel detector. The package is completed by intelligent software that analyses the results.

Product Information

Product Name X-ray CT system software “Offset.CT”
Availability From May 26, 2021

X-ray physics dictates that higher flux, provided the focused electron spot impinging on the target does not increase in size, brings the benefit of raising resolution to reveal more detail in denser objects, or shortening the scanning time, or a combination of the two. Nikon has been able to boost the flux while keeping the microfocus spot size small by spinning its Rotating.Target 2.0. It keeps the tungsten surface cool by raising the efficiency of heat dissipation, avoiding deterioration under conditions of high incident and reflected power.

In a conventional CT system, scanning a component for non-destructive investigation involves the object lying completely within the cone beam so that the entire cross-section is illuminated with X-ray photons at each view angle as it rotates through 360 degrees. To accommodate a larger object, it has to be placed further away from the source and nearer the detector, reducing geometric magnification and hence the resolution of the image.

The resulting radiographs and the tomographic volume derived from them are therefore less sharp. That is exactly what a user does not want, as the lower quality hampers the identification of internal flaws such as voids and cracks for failure analysis and makes inspecting and measuring features in the interior of a component or assembly more difficult.

Two other technological features incorporated into the latest X-ray CT solution from Nikon address this problem by increasing the magnification of the component onto the detector, hence augmenting further the resolution of the resulting images.

First, Offset.CT allows a component to be placed to the side of the source-to-detector centreline such that up to nearly half of the object lies outside the cone beam, widening the field of view by typically 70 percent. A component that just fits into the cone beam near the detector can thus be placed closer to the source to increase the magnification by up to three times.

Alternatively in the same scanner and therefore without taking up more space in a laboratory or factory, by keeping the component position and hence the magnification unaltered, a larger object even wider than the detector itself may be investigated in its entirety, not just a small region of interest.

A high definition voxel model of the complete component is reconstructed from Offset.CT data using a special interpolation and weighting algorithm in the latest version of the manufacturer's Inspect-X software. The feature is available on all Nikon 180 kV, 225 kV, 320 kV and 450 kV X-ray CT systems apart from the XT V range, on which it would be of limited use as the machines are intended mainly for inspecting small, low density electronics.

The second technological feature, shortening the distance between the source and the detector (Focal spot to Imager Distance, or FID), also has the effect of casting a larger image and increasing both magnification and power. Nikon CT cabinets have the option of variable FID with motorised movement of the detector. X-ray intensity drops with increasing distance and shortening the FID boosts the flux by the square of the movement, ie halving the distance quadruples the power. The larger image and the higher flux both serve to improve radiographic resolution and quality (signal-to-noise ratio), or increase scanning speed, or a combination of the two as noted earlier.

The information is current as of the date of publication. It is subject to change without notice.