Schlieren optics for leak detection

The purpose of this research was to develop an optical method of leak detection. Various modifications of schlieren optics were explored with initial emphasis on leak detection of the plumbing within the orbital maneuvering system of the space shuttle (OMS pod). The schlieren scheme envisioned for OMS pod leak detection was that of a high contrast pattern on flexible reflecting material imaged onto a negative of the same pattern. We find that the OMS pod geometry constrains the characteristic length scale of the pattern to the order of 0.001 inch. Our experiments suggest that optical modulation transfer efficiency will be very low for such patterns, which will limit the sensitivity of the technique. Optical elements which allow a negative of the scene to be reversibly recorded using light from the scene itself were explored for their potential in adaptive single-ended schlieren systems. Elements studied include photochromic glass, bacteriorhodopsin, and a transmissive liquid crystal display. The dynamics of writing and reading patterns were studied using intensity profiles from recorded images. Schlieren detection of index gradients in air was demonstrated

RF signal impact study of an SPT

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76213/1/AIAA-1996-2706-928.pd

Plume characterization of the SPT-100

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76626/1/AIAA-1996-3298-655.pd

An experimental study of diffraction -induced effects on single -cycle terahertz pulses.

This doctoral thesis documents a study of diffraction-induced effects uniquely characteristic of broadband, single-cycle electromagnetic pulses. A general introduction of terahertz (THz) optoelectronics is first presented to properly place this study in context. Models detailing a basic means of generation and detection of THz radiation is also provided. Following this, the spatiotemporal effect on a single-cycle pulse due to the Gouy phase shift is then introduced. This experimental study considers the phase effects imparted on these broadband pulses via transmissive optics (or quadratic phase media), in addition to a direct observation of the predicted on-axis polarity reversal imposed by the Gouy phase shift after passing through a focus. Next, an application exploiting the space-time symmetry of solutions to the wave equation is presented. Here, the transmission function of one and two-dimensional objects is interpreted by time-reversing and back-propagating electric fields diffracted from the object. After deriving a time-reversed form of the Huygens-Fresnel diffraction integral, we demonstrate through simulation and experimentation, the reconstruction of one- and two-dimensional objects by numerically back-propagating measured scattered terahertz transients. The spatial resolution determined by a time-domain adaptation of the Sparrow criterion is found to correspond to approximately 30% of the peak wavelength and 85% of the mean wavelength of the power spectrum associated with the single-cycle waveforms. Finally, the modulation transfer function is simulated and is shown to be nearly diffraction-limited when compared to an ideal imaging system.Ph.D.OpticsPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126388/2/3016947.pd