New-Tech Europe Magazine | December 2018

the direction of polarization can be precisely set. Glass filters are reliable and can be fitted to sensors of any wavelength. The filters are mounted on the sensor permanently and integrated into the vision system. The lifespan of the filters, which are protected from the external environment, is longer than that of external polarizers. The speed of the application remains unchanged because all polarization data can be recorded immediately. However, resolution is lower due to the addition of the filters, and the splitting of the pixels by different polarization angles. Additionally, the 4D polarizers that are fitted directly to the pixel (i.e., on-chip polarizers) have four filters every 45 degrees, but they are mounted directly on each pixel inside the sensor. Therefore, variable data from four polarization angles is recorded simultaneously. Afterward, the polarization can be reconstructed from the different intensities of the four filtered pixel angles. This method enables the amount and the angle of the polarized light in a scene to be accurately identified. Sensors that are currently available on the market, like the SONY IMX250, cover a wavelength range of 400 nm to 850 nm. They are very reliable, easy to use, and have a very long service life. Unlike conventional polarizers, filters inside the sensor reduce reflections from different directions. How Applications Can Benefit from Polarizers Polarizing filters are a simple and fast solution for improving image quality. They eliminate the effects of reflections and glare on surfaces like glass, plastic, and metal in many vision applications. In particular, inspection results can be significantly improved by polarizing filters in industrial quality assurance, traffic and infrastructure systems, and medicine.

Polarizers can eliminate reflections on reflective surfaces or increase the contrast in industrial and automated systems. It allows images to be recorded through transparent but reflecting surfaces. Therefore, products wrapped in film or plastic can be measured and inspected through the packaging. In addition, the filter can suppress the shiny effect of metals by making the surfaces significantly darker. This property of polarizers makes the reliable analysis of even shiny cylindrical or curved objects possible. The increase in contrast described above and the degree of polarization means that shapes and parts can be recognized and clearly distinguished in poor light conditions. Consequently, the degree of polarization can make scratches visible, too. In addition, polarized light enables the analysis of the distribution of stress in transparent plastics. Therefore, material stresses, tensions, and other related problems can be identified more quickly by measuring the internal strains. For example, air bubbles in plastic bottles, defects in films, or in cast or extruded plastics can be reliably detected with implemented in intelligent transport or traffic monitoring system can identify a person behind a window in a vehicle when the glare on the window or windscreen would normally prevent an image from being detected and recorded. The option for determining the direction of light in traffic and transport applications is very useful when there is a need to identify the source of lights in darkness or at dusk, and to prevent reflections. Autonomous cars can benefit from improved road detection functions in all types of light conditions by recording the flat surface of the road with polarization filters. Directpolarizersorthoseinstalledinthe polarizers. Polarizing filters

sensor, offer totally new measurement methods and applications for drones. The simultaneous recording at the aforementioned 4 angles of polarization allows the benefits of polarized light in more compact, fully integrated vision systems. Drones, and in principle, infrastructure applications, can use polarizers to detect objects under water by eliminating the reflections on the surface of the water. One industry that can benefit from this type of implementation is agriculture. The growth and readiness for the harvesting of rice in paddy fields can be assessed cost-effectively from the air with a single camera. Polarization improves the detection of objects in every respect by making additional image data visible. In many applications, it can be easier, quicker, more cost-effective, and more reliable to invest in polarizing filters. Polarization is a superior alternative to struggling with complex lighting solutions or using tactile processes. Special polarizing sensors are slightly more expensive than standard sensors. However, the small additional expense in the initial investment is quickly compensated by the ease of use and the reliability of the solutions. The benefits of polarization compared to tactile sensors are even more obvious. In addition, external polarizers can be retrofitted to existing applications. Users who need images with greater contrast or want to eliminate mirroring or reflections should definitely test a set-up with polarization. The on- chip variants of this technology can be easily used for compact, smart, embedded vision applications. A Quick Method for Improving Images

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