The structure and operation of a new uncooled thermal infrared imaging detector is described which is composed of bimaterial, thermally sensitive microcantilever structures that are the moving elements of variable plate capacitors. The heat sensing microcantilever structures are integrated with CMOS control and amplification electronics to produce a low cost imager that is compatible with silicon IC foundry processing and materials. The bimorph sensor structure is fabricated using amorphous hydrogenated silicon carbide (a-SiC:H) as the low thermal expansion coefficient material, and gold as the high thermal expansion coefficient bimaterial (14 x 10-6/K). Amorphous hydrogenated silicon carbide is an ideal material in this application due to its very low thermal conductivity (0.34 W/m-K) and low thermal expansion coefficient (4x10-6/K). High resistivity (200-400 Ω/sq) thin Ti/W films are used as the infrared resonant cavity absorber and low thermal loss electrical interconnect to the substrate electrical contacts. A temperature coefficient of capacitance, ΔC/C, (equivalent to TCR for microbolometers) above 20% has been measured for these structures, and modeling of the performance of these devices indicates sensor performance in the range NETD < 5 mK and thermal time constants in the 5 -10 msec range are feasible with this technique. Our development efforts have focused on the fabrication of 320 x 240 imaging arrays with 50 micron pitch pixels. A number of these arrays have been fabricated with performance characteristics that are predicted by a detailed thermo-electro-optical-mechanical model of the sensor. The sensor design and the results from measurements of the thermo-electromechanical and optical properties of the detector arrays will be discussed.
New applications for ultra-violet imaging are emerging in the fields of drug discovery and industrial inspection. High throughput is critical for these applications where millions of drug combinations are analyzed in secondary screenings or high rate inspection of small feature sizes over large areas is required. Sarnoff demonstrated in1990 a back illuminated, 1024 X 1024, 18 um pixel, split-frame-transfer device running at > 150 frames per second with high sensitivity in the visible spectrum. Sarnoff designed, fabricated and delivered cameras based on these CCDs and is now extending this technology to devices with higher pixel counts and higher frame rates through CCD architectural enhancements. The high sensitivities obtained in the visible spectrum are being pushed into the deep UV to support these new medical and industrial inspection applications. Sarnoff has achieved measured quantum efficiencies > 55% at 193 nm, rising to 65% at 300 nm, and remaining almost constant out to 750 nm. Optimization of the sensitivity is being pursued to tailor the quantum efficiency for particular wavelengths. Characteristics of these high frame rate CCDs and cameras will be described and results will be presented demonstrating high UV sensitivity down to 150 nm.
The design and performance of a compact infrared camera system is presented. The 3 - 5 micron MWIR imaging system consists of a Stirling-cooled 640 X 480 staring PtSi infrared focal plane array (IRFPA) with a compact, high-performance 12-bit digital image processor. The low-noise CMOS IRFPA is X-Y addressable, utilizes on-chip-scanning registers and has electronic exposure control. The digital image processor uses 16-frame averaged, 2-point non-uniformity compensation and defective pixel substitution circuitry. There are separate 12- bit digital and analog I/O ports for display control and video output. The versatile camera system can be configured in NTSC, CCIR, and progressive scan readout formats and the exposure control settings are digitally programmable.
A new gimbal-based, FLIR camera for several types of airborne platforms has been developed. The FLIR is based on a PtSi on silicon technology: developed for high volume and minimum cost. The gimbal scans an area of 360 degrees in azimuth and an elevation range of plus 15 degrees to minus 105 degrees. It is stabilized to 25 (mu) Rad-rms. A combination of uniformity correction, defect substitution, and compact optics results in a long range, low cost FLIR for all low-speed airborne platforms.