POLARISATION
to Teledyne Dalsa’s TurboDrive technology – a mode of operation that speeds up the line and frame rates of GigE Vision cameras beyond the nominal link capacity of Gigabit Ethernet without affecting image quality. Manufacturer Flir also plans to release a
camera incorporating Sony’s new sensor. In addition to being available in a GigE Vision format, the upcoming Blackfly S polarised camera will also be offered with a faster USB3 interface, which will enable frame rates of up to 75fps. Jennifer Yeung, director of marketing for
Flir’s Integrated Imaging Solutions division, commented that this faster format will be especially useful for non-industrial polarised imaging applications, such as unmanned aerial surveillance (UAS). Tis will complement the IMX250MZR’s ability to adjust polarisation parameters quickly and automatically when compensating for changing lighting conditions, movement and orientation. Lastly, Sony Europe’s own Image Sensing
Solutions division will be unveiling a new polarised camera incorporating the IMX250MZR at Vision 2018 in Stuttgart, Germany, this November.
Polarisation in practice Potential uses of polarised imaging include inspecting products wrapped in film or plastic through packaging, or inspecting shiny cylindrical or curved objects – both instances where reflections are in abundance. ‘We’ve seen a high demand for technology detecting surface defects – not just in metal,
Sony’s new IMX250MZR sensor incorporates a layer of nanowire micro-polariser arrays and an array of micro lenses above the photodiodes of the Pregius five megapixel IMX250 CMOS sensor
but also for glass and clear plastics, as these are hard to detect with standard imaging cameras,’ said Chang. ‘Even when inspecting opaque materials there are still flaws that are hard to see – especially small ones – with standard imaging cameras. However, these become much more obvious with polarised imaging.’ Polarised imaging can be used to
determine the internal stress, birefringence, surface roughness, film thickness and alloy
composition of materials. According to Chang, the edges of objects can also be detected using the technique, as the corners of an object exhibit different polarisation properties than its flat surfaces. Tis makes polarised imaging a viable tool for object detection and segmentation – an application that has sparked interest in some of Lucid Vision’s customers. Chang described how the company has
also received a lot of queries about whether polarisation can be used to improve existing 3D imaging methods, such as stereo imaging or time of flight. Tis is indeed the case, according to MIT researchers who, in 2015, demonstrated that by exploiting the properties of polarisation, the resolution of conventional 3D imaging devices such as the Microsoſt Kinect – a time- of-flight camera – can be increased by as much as 1,000 times. At Control 2018 in Stuttgart, the Fraunhofer
Institute for Integrated Circuits IIS showed that Lucid Vision’s Phoenix camera could be used to inspect carbon fibres. Polarised imaging is particularly suited to this application because one of the unique properties of carbon fibres is that they polarise incidental unpolarised light parallel to the direction of the fibre. Te Phoenix camera – in combination
Surface defects can be difficult to identify on mobile phone cases using conventional imaging (left). Polarised imaging (right) can therefore be used to help identify scratches and imperfections
22 Imaging and Machine Vision Europe • August/September 2018
with Fraunhofer IIS’ own Polka imaging soſtware – can therefore be used to capture the angle of linear polarisation, calculating the orientation and position of carbon fibres in
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www.imveurope.com
Lucid Vision Labs
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