POLARISATION


Seeing beneath the surface


Matthew Dale discovers that polarised imaging could soon see a surge in uptake in industrial inspection, thanks to a new sensor from Sony


D


emand for polarised imaging in industry is on the rise, thanks to Sony’s recent release of a set of relatively


low-cost polarised monochrome and colour imaging sensors, the IMX250MZR and IMX250MYR. Built upon the Sony Pregius five-megapixel IMX250 CMOS sensor, the IMX250MZR/ MYR incorporates a layer of nanowire micro- polariser arrays above the sensor’s photodiodes. Each array in the layer comprises four different


angled polarisers – 0°, 45°, 90° and 135° – that are placed over one of four pixels in a 2 x 2 block on the sensor. An array of micro lenses is also positioned on top of the polariser layer of the sensor to reduce crosstalk between pixels. By linearly interpolating the light passing


through the four polarisers, a single intensity pixel value with an associated angle of linear polarisation (AoLP) and degree of linear polarisation (DoLP) can be calculated. Tese values can then be used to produce false colour images, which can reveal scratches, surface defects, and even the internal stresses of materials that would otherwise be undetectable using conventional imaging techniques. Arnaud Destruels, European visual


communication product manager at Sony Europe, said that despite it still being early days for the new sensor, Sony is already seeing


20 Imaging and Machine Vision Europe • August/September 2018


Fraunhofer IIS demonstrated Lucid Imaging’s Phoenix camera being used to inspect carbon fibres at Automatica 2018


strong demand for the technology, and expects this to continue in the future. ‘Intelligent transport systems and security will be key, but similarly, factory automation is also showing strong demand,’ he said. Sony forecasts that the sensor’s uptake


around the globe will mirror existing technology trends, with a strong element of factory automation in Asia, and robotics and intelligent transport systems in Europe.


Removing glare Reflections or glare can make it difficult for machine vision systems to pick up defects, especially on shiny or transparent materials. Tese effects are caused by polarisation,


@imveurope www.imveurope.com


Fraunhofer IIS


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