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Exploded view of the NIRST camera module (left) and engineering prototype for the TIR1 and TIR2 bands (right).
Source publication
Along the years INO has been involved in development of various uncooled infrared devices. Todays, the infrared imagers exhibit good resolutions and find their niche in numerous applications. Nevertheless, there is still a trend toward high resolution imaging for demanding applications. At the same time, low-resolution for mass market applications...
Citations
For a normal microbolometric focal plane array, the microbolometric infrared responsivity varies with its substrate temperature fluctuations because of the semiconductor characteristics of the microbolometer array. The relationship between the microbolometric infrared responsivity and substrate temperature is theoretically discussed in this paper. Above the discussion, a new substrate temperature compensation method is proposed for microbolometric focal plane array without TEC. The microbolometric focal plane array is based on a kind of high-speed CMOS readout integrated circuit, of which the microbolometric infrared response voltage signal can be directly read out without infrared response current integration. The bias current for the microbolometer with the proposed substrate temperature compensation method can be adjusted according to the substrate temperature change to achieve a steady microbolometric infrared responsivity. This kind of substrate temperature compensation method is theoretically strict and has been experimentally verified in our laboratory, which is potential for future high-speed, lower-power and small-pixel microbolometric focal plane array.
Over the past decade, INO has leveraged its expertise in the development of uncooled microbolometer detectors for infrared imaging to produce terahertz (THz) imaging systems. By modifying its microbolometer-based focal plane arrays to enhance absorption in the THz bands and by developing custom THz imaging lenses, INO has developed a leading-edge THz imaging system, the IRXCAM-THz-384 camera, capable of exploring novel applications in the emerging field of terahertz imaging and sensing. Using appropriate THz sources, results show that the IRXCAM-THz-384 camera is able to image a variety of concealed objects of interest for applications such as non-destructive testing and weapons detections. By using a longer wavelength (94 GHz) source, it is also capable of sensing the signatures of various objects hidden behind a drywall panel. This article, written as a review of THz research at INO over the past decade, describes the technical components that form the IRXCAM-THz-384 camera and the experimental setup used for active THz imaging. Image results for concealed weapons detection experiments, an exploration of wavelength choice on image quality, and the detection of hidden objects behind drywall are also presented.
In this paper, a low-cost and modularized test bench for microbolometric focal plane array is proposed. Based on the analysis of driving microbolometric focal plane array, we have set up the simple test bench. The test bench consists of four major modules: optical part, driving sequence timer, power supply and signal processing board, and data analyzer. Each module in the test bench is reconfigurable and the driving sequence timer is programmable in system. The proposed test bench is low-cost and has been applied to practical microbolometric focal plane arrays in our laboratory.
INO has developed a hermetic vacuum packaging technology for uncooled
bolometric detectors based on ceramic leadless chip carriers (LCC).
Cavity pressures less than 3 mTorr are obtained. Processes are performed
in a state-of-the art semi-automated vacuum furnace that allows for
independent activation of non-evaporable thin film getters. The getter
activation temperature is limited by both the anti-reflection coated
silicon or germanium window and the MEMS device built on CMOS circuits.
Temperature profiles used to achieve getter activation and vacuum
sealing were optimized to meet lifetime and reliability requirements of
packaged devices. Internal package components were carefully selected
with respect to their outgassing behavior so that a good vacuum
performance was obtained. In this paper, INO's packaging process is
described. The influence of various package internal components, in
particular the CMOS circuits, on vacuum performance is presented. The
package cavity pressure was monitored using INO's pressure microsensors
and the gas composition was determined by internal vapor analysis.
Lifetime was derived from accelerated testing after storage of packaged
detectors at various temperatures from room temperature to 120°C. A
hermeticity yield over 80% was obtained for batches of twelve devices
packaged simultaneously. Packaged FPAs submitted to standard MIL-STD-810
reliability testing (vibration, shock and temperature cycling) exhibited
no change in IR response. Results show that vacuum performance strongly
depends on CMOS circuit chips. Detectors packaged using a thin film
getter show no change in cavity pressure after storage for more than 30
days at 120°C. Moreover, INO's vacuum sealing process is such that
even without a thin film getter, a base pressure of less than 10 mTorr
is obtained and no pressure change is observed after 40 days at
85°C.
