Optical Coherence Tomography Goes Mainstream in Nondestructive Testing

Posted: 2017-10-23

Source: Novus Light

http://www.novu...-oct_N7346.html

Optical coherence tomography (OCT), the most widely used optical medical imaging technology, has finally made its move into the non-destructive testing (NDT) and inspection arena, much as ultrasound did in the 1960’s. Valued for its ability to provide non-contact imaging of surface morphology and subsurface structure with micron-level resolution, the technique can provide quantitative analysis of structure, features, and defects for a wide range of materials. It is also rapid; 3D images may be captured in within few seconds, or a cross-section can be monitored at faster than video rates for real-time manufacturing or process control feedback. It is an interesting time for OCT in nondestructive testing; while it has been qualified as a viable candidate for several NDT applications, it remains to be seen in which markets it will become the technology of choice. We discuss a number of possible applications below.

Based on low-coherence interferometry, OCT uses infrared light to probe the sample and rapidly create a 3D image from a series of cross-sections. It may be used with any dielectric material, including paints, glasses, foils, coatings, polymers, silicone, and rubber, as well as plastics, and for surface features of metals.

While ultrasonic inspection has been the manufacturing industry’s standard in subsurface imaging for simple cross-sections, the technique is limited in its speed and resolution, and requires the use of a coupling medium.

OCT vs Confocal

Confocal imaging offers submicron resolution, but is very expensive, and limited to depths of less than 1 mm. OCT bridges the cost gap, retaining ultrasound’s flexibility in taking the probe to the sample, while offering 2-10 µm resolution and eliminating the need for contact. Its ability to compete with other inspection and process monitoring techniques depends not only on these factors, but also on the unique needs of each industry.

Read the full Article at NovusLight.com.