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This paper introduces the Watermark Imaging System (WImSy) which can be used to photograph, document, and study sheets of paper. The WImSy provides surface images, raking light images, and transmitted light images of the paper, all in perfect alignment. We develop algorithms that exploit this alignment by combining several images together in a process that mimics both the “surface image removal” technique and the method of “high dynamic range” photographs. An improved optimization criterion and an automatic parameter selection procedure streamline the process and make it practical for art historians and conservators to extract the relevant information to study watermarks. The effectiveness of the method is demonstrated in several experiments on images taken with the WImSy at the Metropolitan Museum of Art in New York and at the Getty Museum in Los Angeles, and the results are compared with manually optimized images.

A high resolution Ku-Band Synthetic Aperture Radar (SAR) was recently flown on a hand-launched Unmanned Aerial System (UAS), demonstrating a breakthrough in resolution for small size, weight and power (SWaP). Ku-Band SAR systems are a useful tool in border patrol, agriculture, crops control, petroleum reserve, surveillance missions, particularly when combined with the Coherent Change Detection (CCD) capability of this system. A continuous-wave (CW) transmitter with near 100% duty factor and an innovative wave-form generator were utilized to minimize power consumption to 24 Watts DC while eliminating the need for high power Ku-Band amplifiers. The weight was trimmed by replacing the typical gimbaled narrow-beam antenna with broad-coverage horn antennas designed to accommodate the platform's roll, pitch, and yaw.

The dominant trend with conventional image sensors is toward scaled-down pixel sizes to increase spatial resolution and decrease chip size and cost [1]. While highly capable chips, these monolithic image sensors devote substantial perimeter area to signal acquisition and control circuitry and trade off pixel complexity for fill factor. For applications such as wide-area persistent surveillance, reconnaissance, and astronomical sky surveys it is desirable to have simultaneous near-real-time imagery with fast, wide field-of-view coverage. Since the fabrication of a complex large-format sensor on a single piece of silicon is cost and yield-prohibitive and is limited to the wafer size, for these applications many smaller-sized image sensors are tiled together to realize very large arrays [2,3]. Ideally the tiled image sensor has no missing pixels and the pixel pitch is continuous across the seam to minimize loss of information content. CCD-based imagers have been favored for these large mosaic arrays because of their low noise and high sensitivity, but CMOS-based image sensors bring architectural benefits, including electronic shutters, enhanced radiation tolerance, and higher data-rate digital outputs that are more easily scalable to larger arrays. In [4] we report the first back-illuminated, 1Mpixel, 3D-integrated CMOS image sensor with 8µm-pitch 3D via connections. The chip employs a conventional pixel layout and requires 500µm of perimeter silicon to house the support circuitry and protect the array from saw damage. In this paper we present a back-illuminated 1Mpixel CMOS image sensor tile that includes a 64-channel vertically integrated ADC chip stack, and requires only a few pixels of silicon perimeter to the pixel array. The tile and system connector design support 4-side abuttability and fast burst data rates.