Computed laminography technique improves voxel resolution for inspecting flat components.
Nikon Industrial Metrology has released a new x-ray computed laminography (CL) technique to help quality engineers achieve higher resolutions and faster inspection times in nondestructive testing applications. According to the company, its Tilted CT technology can facilitate faster and more reliable inspections of planar, flat or high-aspect-ratio components.
3D computed tomography (CT) is essential in nondestructive testing for quality engineers in many industries. Creating a 3D image of a sample by compiling multiple X-rays from different directions around a rotational axis results in highly detailed representations of both internal and external features. This can reveal otherwise hidden flaws, and is also useful for geometric dimensioning and tolerancing analysis.
However, one of the drawbacks of using CT is that the images it produces can have limited resolution because the axis of rotation must be orthogonal to the x-ray beam. As a result, images of samples with an area of interest at their center may lack the necessary level of magnification to improve resolution because moving the sample closer would cause it to collide with the x-ray source as it turns.
Computed laminography is a subtype of x-ray tomography in which the rotation axis of a sample is titled at an oblique angle to the x-ray beam. It’s sometimes referred to as “2.5D inspection” because it lies between 2D x-ray radioscopy on the one hand and CT on the other. While it’s most commonly applied to flat components, such as printed circuit boards (PCBs) and microchips, CL is useful for any component with a high aspect ratio, with long x-ray path lengths along the object plane or where the size of the component requires the rotation axis to be positioned further from the x-ray source to avoid collision.
Tilted CL gets around this issue with CT by allowing the axis of rotation to be adjusted up to 30 degrees, enabling the sample to rotate fully. This results in both higher magnification and image clarity, as well as faster scanning times. A company press release claims that, “in one comparative test, a scan that took more than seven hours using an X-ray microscope was completed in less than one hour with Tilted CT on a SEMI S2/S8 compliant XT H225 2x system.”
The technology can also eliminate artifacts caused by high-density features that lower x-ray attenuation. Tilting the axis of rotation helps position areas of high-attenuation so that they rotate above or below a lower-density area of interest, rather than in front of it.
As a result, Tilted CT can aid the inspection of additively manufactured metal parts before they are separated from the build plate. Tilting the entire structure, including the plate, ensures that the denser plate is rotating at the same angle as the x-ray cone beam, thereby eliminating it as an obstruction.
In addition to the XT H225 2x system, Tilted CT is also available for Nikon’s XT H225 and large-envelope M2 X-ray CT systems. While it’s technically applicable to any size of component, users are still restricted by cabinet size and the requirements for holding a stationary sample at an oblique angle. As such, samples more than half a meter in length will likely be difficult to hold still during scanning.
Watch the introduction video below for more information:
