Standoff Detection of Oil and Powder Mixtures at 12 Meters Using a Tunable Quantum Cascade Laser-Based System with a Close Focus Telescope and Uncooled Infrared Detector

We have designed and demonstrated a quantum cascade laser (QCL) based standoff system that utilizes an uncooled mercury cadmium telluride (MCT) detector with lock-in signal processing for chemical identification at a distance of 12.5 meters in indoor ambient light conditions. In the system, a tunable quad-QCL operating (1 MHz) in quasi-continuous wave mode between 8.45 and 10.03 μm (∼1182 to 1000 cm−1) serves as the active mid-infrared source for remotely interrogating mineral, powder, and thin film oil samples including powder mixtures (6, 12.5, 25, and 50%) of crystalline quartz (SiO2) in KBr. Light as reflected from a given sample is collected using a 10-inch (25.4 cm) Dall Kirkham telescope and coupled with ZnSe optics to an uncooled MCT detector. The mixture dependence of the highly transparent KBr and strongly absorbing quartz was found to fit a modified version of the Schatz reflectance model for compacted powder mixtures. All reflectance spectra reported are relative to an Au-coated diffuse reflector. A NIST traceable polystyrene standard reflector was also used to determine the QCL wavelength tuning range and calibration.

Middle- and far-infrared detector based on the plane collection of graphene strips

A concept of a middle- and far-infrared detector has been proposed. The detector is built as a planar collection of parallel graphene strips of different length and width. The feature of the detector scheme is the concurrent utilization of two different detection mechanisms: excitation in the given frequency range of low-frequency interband transitions inherent in armchair graphene strips and antenna resonances of strongly slowed-down surface waves (plasmon polaritons). It has been shown that matching these two resonances results in the essential detector signal amplification, thus providing an alternative way how to solve the problem of the low efficiency of resonant graphene antennas. An approach is proposed to analyze the design of such detectors, as well as to discuss the ways of tuning the both mechanisms.

Radiation Model of a Housing of Cooled Infrared Detector Array

The infrared camera detects infrared radiation from the observed objects, Its main element is the array of infrared detectors, which converts the received radiation into an electrical signal. The radiation sources recorded by the detector can be divided as useful, received from the observed scene, and useless received from such objects as the detector housing and lens elements. These unusable radiation sources have a significant impact on the design of the detector itself. The article presents a model of the detector housing and a quantitative analysis of the influence of various radiation sources on the effectiveness of radiation detection from the observed scene.

The heat leakage measurement of dewars for infrared detector arrays

Consideration is given to the analysis of a number of implementation of calorimetry method of infrared detector array dewar’s heat leakage measurements. The heat leakage measurements were made both with and without nitrogen vapor heat capacity consideration. The heat exchange process between nitrogen vapor and Dewar’s well walls was analyzed. The most reliable results were achieved by means of approach with calibration.

Quantification and mitigation of the airborne limb imaging FTIR GLORIA instrument effects and uncertainties

The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an infrared imaging FTS spectrometer with a 2-D infrared detector operated on two high flying research aircrafts. It has flown on eight campaigns and measured along more than 300 000 km of flight track. This paper details our instrument calibration and characterization efforts, which in particular leverage almost exclusively in-flight data. First, we present the framework of our new calibration scheme, which uses information from all three available calibration measurements (two blackbodies and upward pointing deep space measurements). Part of this scheme is a new correction algorithm correcting the erratically changing non-linearity of a subset of detector pixels and the identification of remaining bad pixels. Using this new calibration, we derive a 1-σ bound of 1 % on the instrumental gain error and a bound of 30 nW cm−2 sr−1 cm on the instrumental offset error. We show how we can examine the noise and spectral accuracy for all measured atmospheric spectra and derive a spectral accuracy of 5 ppm, on average. All these errors are compliant with the initial instrument requirements. We also discuss, for the first time, the pointing system of the GLORIA instrument. Combining laboratory calibration efforts with the measurement of astronomical bodies during the flight, we can derive a pointing accuracy of 0.032°, which corresponds to one detector pixel. The paper concludes with a brief study on how these newly characterised instrumental parameters affect temperature and ozone retrievals. We find that, first, the pointing uncertainty and, second, the instrumental gain uncertainty introduce the largest error in the result.