CMOS sensor features on-pixel polariser for object detection

28th March 2018
Lanna Cooper


Sony Semiconductor has released its new Preguis IMX250 sensor with a four-directional polarisation square pixel array, providing higher contrast for more detailed pictures in less time. The 5.07MP sensor, with a 2/3" optical format, has a 2448x2048 pixel array utilising a 3.45µm pixel size. The IMX250 reaches a frame rate of 144fps at 10 bits.

With global shutter and variable charge-integration time, this sensor is a suitable fit for factory automation as well as for ITS applications and imaging in infrastructure. The sensor, along with additional support services, is available from global imaging expert FRAMOS.

Polarising filters are probably the most useful filters for object detection in imaging. It removes polarised light from the image, thus reducing reflections and glare, while at the same time increasing colour saturation. Most vision systems are using polarisation filters on top of the lens or sometime on a sensor level as on-glass polariser. Sony's IMX250 is the first sensor with an on-chip polariser to minimise system complexity and improve extinction ratio and incident angle dependence. 

Sibel Yorulmaz-Cokugur, Line Manager and Sensor Expert at FRAMOS, explained the IMX250 benefits: "Conventional cameras has to shoot three times while rotating a polariser in front of the camera to filter the light.

Sony's new IMX250 CMOS sensor with its four-directional polarisation only needs one shoot and senses polarisation in any direction. This increases the vision systems speed by increasing the possible throughput and reduces post-processing efforts - both very important factors for automation applications and detection of fast moving objects."

In Factory Automation the form recognition of low contrast or transparent objects can be improved by using direction of polarisation, more details are visible for image analysis leading to a lower fail rate and higher product quality. ITS applications can get use of the IMX250 polariser sensor to remove reflection on car windows, distinguish direct light from reflection and to achieve better shape-recognition in low contrast or HDR conditions.

Self-driving cars benefit from driveway recognition with detecting the flat road surface by direction of polarisation. In infrastructure applications it can recognise objects under water by removing the reflection of the water surface.

Sony's new on-chip polarisation sensor IMX250 improves recognition in any sense by new information of lights from the real world.

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