Paul L. Corredoura

Millimeter-wave imaging system for personnel screening: scanning 10^7 points a second and using no moving parts

In this talk we describe the second version of our novel millimeter wave imaging system. This system is an active coherent system, working at 24GHz, and using planar programmable RF-lens. The system is capable of producing realtime movies without processing latency. Moreover, due to the planar nature of the lens, and its compact form, the footprint of the system is very small. The fact that it is monochromatic assures minimal spectral occupancy resulting in an imaging system well suited to personnel screening. The RF-lens, which lies at the heart of the proposed system, is a passive RF element, capable of focusing RF energy into small volumes within its field of view through a mechanism that changes the phase of the impinging wave on the lens-surface. This enables one to scan image voxels (volume pixels) in front of the lens. Since the phase change can be rapidly switched electronically, more than 10^7 voxels are scanned per second. We will discuss the reasons that lead us to develop this second system, the improvements that were made, and the overall enhancements to the system performance. For example, we will discuss the changes that enable us to go to higher frame rate.

Reducing Brownian motion in an electrostatically tunable MEMS laser

Brownian motion of a tunable vertical-cavity surface-emitting lasers (VCSEL) movable microelectromechanical systems (MEMS) mirror is shown to broaden the spectral width of the laser emission line. A low-noise wavelength feedback system is presented and evaluated. This feedback system is employed to reduce measured linewidth from 1050 to 400 MHz fullwidth at half-maximum (FWHM), an improvement of 62%. The effects of device design parameters on closed-loop Brownian motion levels are analyzed. The potential increases in performance resulting from vacuum packaging and advanced controller design are discussed.