Thomas S. Villani

Progress toward an uncooled IR imager with 5-mK NETD

The bi-material concept for room-temperature infrared imaging has the potential of reaching an NE(Delta) T approaching the theoretical limit because of its high responsivity and low noise. The approach, which is 100% compatible with silicon IC foundry processing, utilizes a novel combination of surface micromachining and conventional integrated circuits to produce a bimaterial thermally sensitive element that controls the position of a capacitive plate coupled to the input of a low noise MOS amplifier. This approach can achieve the high sensitivity, the low weight, and the low cost necessary for equipment such as helmet-mounted IR viewers and IR rifle sights. The pixel design has the following benefits: (1) an order of magnitude improvement in NE(Delta) T due to extremely high sensitivity and low noise; (2) low cost due to 100% silicon IC compatibility; (3) high image quality and increased yield due to ability to do offset and sensitivity corrections on the imager, pixel-by-pixel; (4) no cryogenic cooler and no high vacuum processing; (5) commercial applications such as law enforcement, home security, and transportation safety.

Construction And Performance Of A 320 X 244-Element IR-CCD Imager With PtSi Schottky-Barrier Detectors

A 320 x 244-element IR-CCD imager was developed with 40μm x 40-μm pixels, 43% fill factor, and a saturation signal of 1.4 x 106 electrons/pixel. Charge-transfer inefficiency of less than 10-4 per transfer was achieved for operation of the imager at 77K with horizontal clock frequency of 6.2 MHz using a 12-μm-wide horizontal output register with a 3-μm-wide trench. The device was operated at temperatures as low as 50K with sufficiently low transfer losses to produce good quality video images. Excellent quality thermal imaging was demonstrated for operation of the 320 x 244 imager at 30 frames/s with 100 mm f/1.4 lens, an f/1.3 cold shield, and 3.4-μm long-pass filter at 77K.

640 x 480 element PtSi IR sensor with low-noise MOS X-Y addressable multiplexer

The design of a 640 by 480 element PtSi IR sensor is presented which includes a low-noise MOS X-Y addressable readout multiplexer and an on-chip correlated double-sampling amplifier. The sensor is designed to load scan data into CMOS horizontal and vertical scanning registers by means of a multiplexed horizontal/vertical input address port and onchip decoding, allowing any element in the focal plane array to be randomly accessed. The FPA is shown to be operable in both the interlaced and noninterlaced formats, with variable exposure control. Enhanced noise performance is shown due to the use of buried channel source follower buffers in the horizontal signal lines. It was shown that 24 micron square pixels with a 1.5 micron double level metal CMOS process provide a fill factor of 38 percent. TTL compatibility and ESD protection diodes are key features of the digital inputs to the sensors chip.

Schottky-barrier image sensor with 100% fill factor

A new concept, the Direct Schottky Injection (DSI), is described for a three-dimensional construction of infrared imagers with a continuous Schottky-barrier-detector surface on one side of a thinned (10 to 25 microns) silicon substrate and p-type buried-channel CCD readout structure on the other side. The DSI structure provides a 100-percent fill factor, a large charge-handling capacity, and a high-density pixel design. The construction and operation are described for DSI imagers with frame-transfer CCD (FT-CCD) and interline-transfer CCD(IT-CCD) readout. The operation of the IT-CCD DSI imager was demonstrated with a 128 x 128 focal plane array (FPA) with 50 x 50-micron pixels.

Performance of generation III 640 x 480 PtSi MOS array

The design and performance of a third generation 640(H) X 480(V) PtSi focal plane array is presented. The 3 to 5 micron MWIR focal plane array supports interlaced, progressive scan, and subframe readout under control of on-chip digital decoders. The new design utilizes 1.25 micrometers design rules to achieve a 50% fill-factor, a noise equivalent delta temperature of <0.07 C (f/1.5, 30 Hz, 300 K), and a saturation level >1.5 X 106e. The power dissipation is less than 110 mW.

High-frame-rate infrared and visible cameras for test range instrumentation

Field deployable, high frame rate camera systems have been developed to support the test and evaluation activities at the White Sands Missile Range. The infrared cameras employ a 640 by 480 format PtSi focal plane array (FPA). The visible cameras employ a 1024 by 1024 format backside illuminated CCD. The monolithic, MOS architecture of the PtSi FPA supports commandable frame rate, frame size, and integration time. The infrared cameras provide 3 - 5 micron thermal imaging in selectable modes from 30 Hz frame rate, 640 by 480 frame size, 33 ms integration time to 300 Hz frame rate, 133 by 142 frame size, 1 ms integration time. The infrared cameras employ a 500 mm, f/1.7 lens. Video outputs are 12-bit digital video and RS170 analog video with histogram-based contrast enhancement. The 1024 by 1024 format CCD has a 32-port, split-frame transfer architecture. The visible cameras exploit this architecture to provide selectable modes from 30 Hz frame rate, 1024 by 1024 frame size, 32 ms integration time to 300 Hz frame rate, 1024 by 1024 frame size (with 2:1 vertical binning), 0.5 ms integration time. The visible cameras employ a 500 mm, f/4 lens, with integration time controlled by an electro-optical shutter. Video outputs are RS170 analog video (512 by 480 pixels), and 12-bit digital video.

1024 X 1024 pixel high-frame-rate digital CCD cameras

Field deployable, high frame rate visible CCD camera systems have been developed to support the Test and Evaluation activities at the White Sands Missile Range. These visible cameras are designed around a Sarnoff 1024 X 1024 pixel, backside illuminated CCD with a 32-port, split-frame transfer architecture. The cameras exploit this architecture to provide selectable modes from a 30 Hz frame rate at 1024 X 1024 pixels to a 300 Hz frame rate with 1024 X 512 pixels (2:1 vertical binning). The cameras are configured with a 500 mm, f/4 lens, and a Ferro-electric liquid crystal electro-optic shutter, to provide variable integration times from 0.5 to 32 msec. Video outputs provided are RS170 analog video in a reduced 512 X 480 pixel format, and 12-bit full resolution digital video data stream provided through a high speed serial/parallel digital coaxial interface. At a frame rate of 300 frames per second, these cameras deliver video data at an average rate of 1.9 Gbits/sec, and a burst rate of 2.8 Gbits/sec, with the capability of reaching an average 12 bit digital data rate of 3.8 Gbits/sec when higher frame rate imagers become available.

Compact high-performance MWIR camera with exposure control and 12-bit video processor

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.

PtSi gimbal-based FLIR for airborne applications

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.

640 x 480 MWIR and LWIR camera system developments

The performance of a 640 x 480 PtSi, 3,5 microns (MWIR), Stirling cooled camera system with a minimum resolvable temperature of 0.03 is considered. A preliminary specification of a full-TV resolution PtSi radiometer was developed using the measured performance characteristics of the Stirling cooled camera. The radiometer is capable of imaging rapid thermal transients from 25 to 250 C with better than 1 percent temperature resolution. This performance is achieved using the electronic exposure control capability of the MOS focal plane array (FPA). A liquid nitrogen cooled camera with an eight-position filter wheel has been developed using the 640 x 480 PtSi FPA. Low thermal mass packaging for the FPA was developed for Joule-Thomson applications.