Instrument for rapidly imaging the fields in magnetic media

An instrument to produce images of the magnetic fields on selected areas of magnetic media is being developed. Although most types of planar media can be imaged, the immediate application is for magnetic tape. Here, it replaces the use of ferrofluids, giving much higher resolution and contrast. The resolution is 1 micron, with a dynamic range of 40 dB. The current instrument can examine an area of 5 cm multiplied by 1 cm, but larger areas could be handled with minor changes. Detailed images of most features of interest, such as stop marks on magnetic tape, can be produced in less than 15 minutes. Lower resolution images of approximately 5 cm lengths of tape for feature identification can be made in significantly less time. Details of the instrument's performance and example images of interest to the forensic community are presented.