MAY 1998 REPORT FOR

W. CHARLES SYMONS, III

With the acceptance of the paper presentation entitled Electromagnetic Scattering Analysis of Sample Objects Within the Near-Field of a Subwavelength Aperture Utilizing FDTD Methods, developing a generalized near-field to far-field transformation algorithm for the FDTD NSOM model became a greater priority. At this time, this algorithm is currently under development but should allow the current FDTD model to simulate NSOM imaging of variously shaped objects in addition to the current thin wire samples. In addition to enhancing the FDTD model, the Moment Method model's convergence study of the current on the sample wires was nearly finalized. As it turns out, the variation of the steeply sloped excitation vector with increasing basis functions has been the main problem. A new convergence study is currently underway and results should be available soon.

As far as the actual NSOM instrument, a solution to the current LabView driver software problem involving the inability of the Windows 95 version to utilize the 16-bit Melles Griot LabView dll files has been found. With the inability of Melles Griot to provide 32-bit dll files, the two best options involve either thunking the 16-bit dlls or installing the Windows 3.1 version of LabView. Because the process of thunking 16-bit dlls is both difficult and time consuming, both Windows 95 and Windows 3.1 will be installed on the NSOM control computer utilizing a multiple OS boot manager. In this manner, the NSOM LabView program can be written and utilized in the 16-bit environment of Windows 3.1. The NSOM control computer is currently being loaded with the dual OS system such that the NSOM LabView program development can be completed soon.

In addition to the above projects, a preliminary design for the laser dermatome optical feedback circuit was tested. Although this test was performed quickly during a dermatome cutting experiment, a reliable signal was detected such that computer timing issues are now being considered. In order to better protect the dermatome control circuitry during the dermatome cutting experiments, the dermatome control circuitry was mounted in a separate box as seen in Figures 1 and 2 below. As far as the actual dermatome skin grafting experiments are concerned, the modified dermatome does produce better grafts than the previous model but it still tends to sink into soft surfaces thereby displacing the cutting angle of the laser. Currently, several adjustments and modifications are being considered to alleviate this problem.

Figure 1: Mounted Dermatome Control Circuitry.

Figure 2: Dermatome Control Box Connections.