Optical Device for Online Assessment of Magnetic Tape Surface Quality
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
An optical device for online assessment of magnetic tape surface quality uses a cylindrical lens and quadrant detector in a schlieren arrangement. The device provides extremely fast and reliable on-the- spool assessment of acceptable quality for the magnetic tape. In Fig. 1, a gallium arsenide laser 1 is located at the focus of a lens 2. A shutter 3 and polarizer 4 is located immediately after 2. An optional half-wave plate 5 can be included after the polarizer 4. The beam emanating from laser 1 is now collimated and enters a polarizing cube beam-splitter 6. Since the beam is of the appropriate polarization, it traverses splitter 6 without losses. Upon exiting from splitter 6, the beam which was linearly polarized goes through a suitably oriented quarter-wave plate 7 and becomes circularly polarized.