Software and digital signal processing algorithms for a novel quantum well hall effect (QWHE) transducer based magnetic field camera

Among various non-destructive testing (NDT) techniques, Magnetic field mapping is one of the most promising in terms of applicability. Depending on the specific structural properties (i.e. conductive or magnetic) of the materials investigated, numerous techniques (such as Magnetic particle inspection-MPI or Magnetic flux leakage-MFL, etc.) which rely on the detection of magnetic field have been developed. In recent years, coils, which are traditional magnetic field detection sensors, have been replaced by solid state Hall Effect sensors. The main motivation under this transformation is the ultraminiature size of the Hall Effect sensors, which enables them to be densely packaged. Furthermore, Hall Effect sensors can also pick-up DC magnetic fields, which make them the suitable transducer for applications like DC MFL. Thanks to advances in semiconductor technology, the dynamic range and sensitivity of the Hall Effect sensors have gradually been enhanced. The newly introduced Quantum Well Hall Effect (QWHE) sensors offer superb dynamic range and sensitivity compared to conventional Si or GaAs Hall Effect transducer technology. In this work, we demonstrate a PC software and digital signal processing (DSP) algorithms developed for a novel hand held QWHE transducer based Magnetic Field Camera. The designed camera consists of a 16x16 QWHE sensor array on a 5mm sensor pitch. The connection between the camera and PC running the software and DSP algorithms is accomplished using a 100BASE-T Ethernet connection. Display update rates (i.e. frames per second - FPS) can go up to 240. The developed software and algorithms allow the visualisation of DC and AC magnetic fields, as well as their spectral content. Furthermore, image processing and enhancement techniques have been deployed for further image and visual quality.