US Patent 9664622 Spark sensing device with optical element

The invention relates to the detection of sparks in a channel where material flows. A spark sensing device is positioned in connection with channel where material flows in a flowing direction. The spark sensing device comprises a sensor element and an optical element that transfers a radiation of a spark to the sensor element. The optical element is made of optically transparent material. The optical element is such that it shapes the collection beam of the sensor element to be asymmetrical whereby the viewing angle of the sensor element is wider in a direction transverse to the flowing direction than in the flowing direction.