Terahertz imaging opens up use in paint analysis

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A new method to measure the thickness of paint layers has been developed based on terahertz reflectometry, which could have uses in quality control when spray-painting car bodies. Unlike conventional methods, the paint remains undamaged, making the technique useful for a variety of applications including art analysis. The researchers will describe their work at CLEO 2014 in San Jose, USA, in a presentation on 11 June at 5:15pm.

‘It's a problem that’s quite challenging,’ said Anis Rahman, founder of Applied Research and Photonics, in Harrisburg, Pennsylvania. ‘None of the current methods are very successful in determining the thickness of individual layers and coatings in a non-destructive fashion.’

The new technique, which was developed by Rahman and his son, Aunik, uses terahertz reflectometry, in which a beam of terahertz radiation is fired onto the paint. The terahertz beam penetrates the paint layers and bounces back at different intensities depending on the thickness of each layer. Measuring the intensities of the reflected beams reveals the thickness of each coat of paint down to a precision of tens of nanometres. This method can also be used to estimate the size of any particles added to the paint as small as 25nm.

In addition to quality control, the method would be useful for testing paints as well, Rahman said. Environmental health applications are also possible, since the method can help detect whether old paint contains lead. Archaeologists and art historians can employ it to analyse the paint on artefacts.

The researchers are also configuring the techniques to analyse the structure of skin as a way to help diagnose early stages of skin cancer such as melanoma and basal cell carcinoma. With the addition of spectroscopy to measure the different wavelengths of reflected beams, this technique can be used to analyse the structure of skin layers and determine if they are healthy or diseased.

The instrument is ready for commercialisation and Rahman says they are currently looking for partners to help bring it to market.