Testing Audio/Video Tapes

Our magneto-optical techniques provide the ability to forensically examine the information stored magnetically on data tapes.

Magnetic tapes are storage media that store magnetic information on a magnetizable, plastic-bonded tape. The information is written onto the tape by an electromagnetic read/write head. Magnetic tapes can be divided into video, audio, and data tapes depending on their intended use. Magneto-optical systems, such as our cmos-magview, offer a wide range of analysis capabilities and have the resolution required to detect even the smallest changes, especially for the forensic examination of magnetic tapes.

Our cmos-magview makes it possible to detect defective or even manipulated spots. The figure clearly shows a manipulated section, which can be documented. The read/write head leaves magnetic traces when it touches the tape. Even minimal positioning errors leave magneto-optically detectable magnetizations on the manipulated spot during the write process. In some cases, these spots can be discerned acoustically, but in most cases, magneto-optical testing is required- These spots can be visualized and analyzed technically with the help of our systems and sensors. Another equally important aspect is the reconstruction of damaged magnetic tapes. Whether the magnetic tape is readable or rewritable is highly dependent on the quality of the individual magnetizations. The lifetime of magnetic tapes decreases significantly, especially when used very frequently. What is known as "sticky-shed syndrome," i.e., the tape tends to stick when stored for long periods of time, is also a well-known problem with magnetic tapes.

Other factors also play a role in addition to the usual forms of tape wear. Magnetic tapes are often used in harsh environments where damage cannot be avoided. For example, if we think of their use in flight/voice recorders in aircraft or space, it is clear that the magnetic structures on the tapes are exposed to a wide range of damaging influences. Magnetic tapes that have been exposed to these types of conditions have to be handled with special care in order to preserve the information stored on them in the best possible quality. Magneto-optical analysis, as a very gentle static method, is ideally suited for this purpose.