6 µm microbolometers for uncooled thermal imaging

Michel, Marvin; Blaeser, Sebastian; Zakizade, Elahe; Weyers, Sascha; Weiler, Dirk

doi:10.1117/12.2597969

Cited by 2 publications

(2 citation statements)

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“…Following the trend of cooled thermal imager technologies, uncooled thermal imagers also aim for smaller pixel pitches to enable higher optical resolutions. [4][5][6] In consequence, this trend led to the development of uncooled thermal imagers based on microbolometers demonstrating their electro-optical functionality down to pixel sizes of only 6 µm in case of Fraunhofer IMS's scalable nanotube-microbolometer technology [1][2][3] and in parallel, to further uncooled thermal imagers with pixel pitches below 10 µm manufactured by InfiRay 7 and Lynred 8 . Since the detector size of those microbolometers continously approaches the optical detection limit in the long wavelength infrared (LWIR), 9 it seems to be only a matter of time when this physical limit will finally be reached.…”

Section: Introductionmentioning

confidence: 99%

Capabilities of scaled microbolometers for uncooled thermal imaging below 10µm pixel pitch

Michel

Blaeser

Litke

et al. 2023

Infrared Technology and Applications XLIX

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The reduction of the pixel pitch of uncooled thermal imagers is still ongoing and by the end of 2021, reached a size of only 8µm within commercially available products. In case of those small pixel sizes, design and manufacturing requirements become more challenging by facing the main technological objectives of maximizing the temperature rise within the microbolometer membrane and simultaneously, being sensitive towards the latter. Tackling these challenges, Fraunhofer IMS provides a manufacturing process for uncooled thermal imagers optimized for the LWIR regime based on a scalable microbolometer technology incorporating vertical nanotubes. Based on this technological concept, we already demonstrated microbolometers with full electro-optical functionality for pixel sizes ranging from 17µm down to 6µm. A comprehensive study of our measurements regarding the scalable microbolometer technology will be presented here. This includes a discussion about design requirements in correlation to the achieved electro-optical results covering electrical noise, NETD, thermal time constant and spectral absorption characteristics. Those key parameters will be summarized and evaluated with respect to the reduction of the active microbolometer area in case of a shrinked pixel size.

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Section: Introductionmentioning

confidence: 99%

Capabilities of scaled microbolometers for uncooled thermal imaging below 10µm pixel pitch

Michel

Blaeser

Litke

et al. 2023

Infrared Technology and Applications XLIX

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show abstract

“…Because of their low cost, integration ease, and wide resistance change range with radiation absorption, microbolometers are the most popular type of infrared radiation detector used in uncooled thermal cameras [4]. Assembling a set of microbolometers into an array at the focal plane of a thermal camera lens forms a focal plane array (FPA), which can be heated by the infrared radiation focused through the lens [5,6]. The electrical Drones 2022, 6, 394 2 of 20 resistance of each individual microbolometer is dependent on its temperature [7] and varies proportionally to the incident infrared radiation.…”

Section: Introductionmentioning

confidence: 99%

A Case Study of Vignetting Nonuniformity in UAV-Based Uncooled Thermal Cameras

Yuan¹,

Hua

2022

Drones

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Uncooled thermal cameras have been employed as common UAV payloads for aerial temperature surveillance in recent years. Due to the lack of internal cooling systems, such cameras often suffer from thermal-drift-induced nonuniformity or vignetting despite having built-in mechanisms to minimize the noise. The current study examined a UAV-based uncooled thermal camera vignetting regarding camera warmup time, ambient temperature, and wind speed and direction, and proposed a simple calibration-based vignetting migration method. The experiments suggested that the camera needed to undergo a warmup period to achieve stabilized performance. The required warmup duration ranged from 20 to 40 min depending on ambient temperature. Camera vignetting severity increased with camera warmup time, decreasing ambient temperature, and wind presence, while wind speed and direction did not make a difference to camera vignetting during the experiments. Utilizing a single image of a customized calibration target, we were able to mitigate vignetting of outdoor images captured in a 30 min duration by approximately 70% to 80% in terms of the intra-image pixel standard deviation (IISD) and 75% in terms of the pixel-wise mean (PWMN) range. The results indicated that outdoor environmental conditions such as air temperature and wind speed during short UAV flights might only minimally influence the thermal camera vignetting severity and pattern. Nonetheless, frequent external shutter-based corrections and considering the camera nonlinear temperature response in future studies have the potential to further improve vignetting correction efficacy for large scene temperature ranges.

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6 µm microbolometers for uncooled thermal imaging

Cited by 2 publications

References 1 publication

Capabilities of scaled microbolometers for uncooled thermal imaging below 10µm pixel pitch

Capabilities of scaled microbolometers for uncooled thermal imaging below 10µm pixel pitch

A Case Study of Vignetting Nonuniformity in UAV-Based Uncooled Thermal Cameras

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