Surface magnetic flux imager using CMOS three-phase lock-in camera

This paper proposes a new method of magneto-optical imaging which can observe the distribution of both amplitude and phase of AC magnetic field using the lock-in detection by means of a three-phase correlation image sensor (3PCIS). We successfully developed 64/spl times/64 and 100/spl times/100 devices using a multi-user CMOS process. We applied the imaging system to the leakage flux inspection of steel plates. It could observe amplitude and phase (direction and delay) of vertical flux components. The imager was also shown to provide rich clues for the horizontal flux components through observing fine movements of domain wall.