An optical data destruction system using a high power laser beam is introduced. The system exposes data marks on
optical media to a focused high power line beam. The exposure changes the physical and optical properties of the data
marks and surrounding layers, making retrieval of the data impossible. Maintaining the focused laser beam on a data
layer is achieved by a focus servo using a diffractive optical element (DOE). The system performance is evaluated from
a number of destruction experiments on CD-Recordable (CD-R) and CD-ReWritable (CD-RW).
Changes in data marks and groove structures are examined when a high power laser beam (>0.5 W) is focused on compact disk recordable (CD-R) data layers. Observations are recorded as a function of exposure condition and the type of dye used in the recording layer. All samples experience a decrease in the depths of data mark features and the pregroove modulations on exposure. Data marks on cyanine- and azo-dye disks become optically invisible after exposure, while data marks on phthalocyanine-dye disks remain visible, even after high-power exposure. Also, phthalocyanine-dye disks show interesting phenomena, including mixture of the dye and the substrate material during recording and contrast reversal of the marks.
Wavelength-domain tracking (WDT) is a new concept for application in multiple-beam optical storage systems. Tracking errors caused by use of multiple beams on curved tracks are avoided in WDT systems by optimizing separations of focused beam spots. The control of beam spot separations is accomplished by wavelength tuning of individual laser sources. Feasibility of WDT is demonstrated by implementation and testing of a single-beam WDT tracking servo. Also, a novel method of error signal extraction by low-frequency modulation is proposed.
A wavelength-domain tracking scheme is a new concept for application in multiple-beam systems. Track-following is achieved by wavelength tuning. Also, a novel method of error signal extraction by low frequency modulation is proposed.