Performance improvements for VOx microbolometer FPAs

Abstract

Raytheon is producing high-quality 320 x 240 microbolometer FPAs with 25 µm pitch pixels. The 320 x 240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50 µm pixels. Typical NETD values for these FPAs are <50mK with an f/1 aperture and operating at 30 Hz frame rates. Pixel operability is greater than 99.9% on most FPAs, and uncorrected responsivity nonuniformity is less than 4% (sigma/mean). These 25 µm microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. These arrays have produced excellent image quality, and are currently fielded in a variety of demonstration systems.The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased, and also has enabled the development of a large-format 640 x 480 FPA array.Raytheon is producing these arrays with excellent sensitivity and typical NETD values of <50mK with an f/1 aperture and operating at 30 Hz frame rates. These arrays have excellent operability and image quality. Several dual FOV prototype 640 x 480 systems have been delivered under the LCMS and UAV programs.RVS has developed a flexible uncooled front end (UFE) electronics that will serve as the basis for the camera engine systems using 320 x 240 arrays. RVS has developed a 640 x 480 Common Uncooled Engine (CUE) which is intended for small pixel, high performance applications. The CUE is the ideal cornerstone for ground and airborne systems, multi-mode sensor, weapon sight or seeker architectures, and commercial surveillance.

Performance model for uncooled infrared bolometer arrays and performance predictions of bolometers operating at atmospheric pressure

“…Conventional single-level infrared bolometer arrays with small pixel pitches typically have a fill factor between 60% and 70% (b = 0.6 to 0.7) [10,11,18]. Two-layer bolometer designs (umbrella designs) have been reported that reach pixel fill factors of up to 90% (b = 0.9) [12,18].…”

“…Thus, a high fraction of the incident infrared radiation at a specific wavelength k is absorbed in the bolometer membrane [9]. For a targeted wavelength interval of 8-14 lm, the distance between the bolometer membrane and the mirror on the substrate is typically about 2-2.5 lm [9,12]. In such a bolometer design only the upper surface of the bolometer membrane is radiating.…”

“…(1)-(9) correctly predict these contributing NETD parts when the infrared bolometer and system design parameters are set to the values shown in Table 1. All values in Table 1 are typical values for the respective parameters used in uncooled infrared bolometer arrays [4][5][6][7][8][9][10][11][12]20].…”

“…The noise equivalent temperature difference (NETD) is one of the most important performance parameters for infrared imaging systems and is defined as the difference in temperature between two side-by-side blackbodies of large lateral extent which, when viewed by the infrared imaging system, gives rise to a difference in signal-to-noise ratio of 1 in the electrical outputs of the two halves of the array, viewing the two blackbodies. Infrared imaging systems based on uncooled bolometer arrays can today reach NETDs of as low as 25 mK with a F-number of the infrared optics of F = 1 [1,[9][10][11][12]. A NETD of 80 mK-200 mK is sufficient for many commercial infrared imaging applications [2,3].…”

Integrated micro Pirani gauge based hermetical package monitoring for uncooled VO x bolometer FPAs

“…To reduce the noise and enlarge the sensitivity, the heat transfer between the VO x film and the substrate of the cavity should be as low as possible, therefore conventional bolometers operate with vacuum levels \0.01 mbar (Murphy et al 2004). This presents a challenge to the packaging technology since gas leakage usually exists over time.…”