Maximizing Data Recovery: Utilizing 3D Digital Laser Microscopy

to Image Damaged Optical Media

“While we haven’t solved all of the challenges regarding data recovery from damaged optical media, we have moved forward in terms of what is possible. The main

instrument we use to gather data is the OLYMPUS LEXT OLS4000, which provides the 3D visualization and measurement aspects critical to obtaining usable

information from damaged optical media.”

Greg Gogolin, Ph.D. Ferris State University

James Jones, Ph.D.George Mason University

Derek Brower, M.S.Ferris State University

Executive Summary

Background

MethodologyFactory-pressed and home-burned optical media use different technologies: factory pressing burns physical pits into the media, while home burning causes color changes on a film layer.

We were able to image both technologies using an OLYMPUS LEXT OLS4000 3D laser scanning confocal microscope. The approach outlined here works regardless of the way the media was initially created.

Figure 1: Image of a damaged home-burned CD. Pits and lands (encoded data) are visible as gray and white dots and dashes. These patterns were converted to 0s and 1s, then decoded to recover the original data.

Once we have a magnified image of the media, a region of consecutive dots and dashes is selected. Although the dots and dashes appear to form concentric circles, they actually form a spiral, so there are no beginnings and endings to the apparent tracks. We measure each dot and dash, then reverse the encoding algorithm used to convert the original data into the dots and dashes that were subsequently written to the media.

Figure 2: A string of dots and dashes selected for decoding.

Media that has been willfully destroyed such as a disc broken into multiple pieces is something that has particularly gained our attention because to a large degree the data often stays intact—it just has a damaged “container.” Here we can visually see that the data appears to have suffered little impact as a result of the trauma. Using the LEXT OLS4000, we can measure the data patterns to confirm whether or not data impact has occurred.

Figure 3: Image of optical disc in multiple pieces.

High magnification allows for precise measurement that can be used to help develop potential ratios for data analysis and recovery. Here is an example of a high-resolution max zoom image of data on an optical disc.

Figure 4: 17120x max zoom image of a damaged DVD.

The main instrument that we utilize to gather information from optical media to evaluate for potential recovery is the OLS4000, which provides the 3D visualization and measurement aspects critical to obtaining usable information from optical media. Here is a 3D data image from an optical disc.

Figure 5: 3D image of data on an optical disc.

Conclusions

Our work has been supported by the National Science Foundation under Grant No. 1116268. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Greg Gogolin, Ph.D. Ferris State University

James Jones, Ph.D.George Mason University

Derek Brower, M.S.Ferris State University