About
130
Publications
16,700
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,137
Citations
Introduction
Additional affiliations
March 2019 - present
Self
Position
- Consultant
January 2013 - February 2019
Telops
Position
- Senior Researcher
October 1986 - December 2012
Education
September 1982 - August 1985
Publications
Publications (130)
Efforts are continuously made for improving internal combustion engines (ICEs) efficiency. Lowering fuel consumption and reducing soot formation are among the challenges being addressed when seeking to improve engine designs. In this work, ICEs characterization was carried out on an elongated single-cylinder transparent diesel engine equipped with...
Characterization of ship plumes is very challenging due to the great variety of ships, fuel, and fuel grades, as well as the extent of a gas plume. In this work, imaging of ship plumes from an operating ferry boat was carried out using standoff midwave (3-5 μm) infrared hyperspectral imaging. Quantitative chemical imaging of combustion gases was ac...
Efforts are continuously made to improve internal combustion engines’ (ICEs) efficiency. Lowering fuel consumption and reducing soot formation are among the challenges being addressed when seeking to improve engine designs. In this work, ICE characterization was carried out on an optical engine at Istituto Motori Consiglio Nazionale delle Ricerche...
Characterization of hazardous lands using ground-based techniques can be very challenging. For this reason, airborne surveys are often preferred. The use of thermal infrared imaging represents an interesting approach as surveys can be carried out under various illumination conditions and that the presence of buried objects typically modifies the th...
Thermal infrared imaging is a field of science that evolves rapidly. Scientists have used for years the s implest tool: thermal broadband cameras. Th ese allow to perform target characterization in both the longwave (LWIR) and midwave (MWIR) infrared spectral range. Infrared thermal imaging is used for a wide range of applications, especially in th...
Thermal infrared imaging is a field of science that evolves rapidly. Scientists have used for years the simplest tool: thermal broadband cameras. This allows to perform target characterization in both the longwave (LWIR) and midwave (MWIR) infrared spectral range. Infrared thermal imaging is used for a wide range of applications, especially in the...
Minerals such as silicates, aluminosilicates (feldspar), magnesium silicates (serpentine) and olivines are among the most commonly encountered in the environment. Airborne mineral mapping of these minerals using conventional visible-near infrared (VNIR, 0.4-1.4 µm) and shortwave infrared (SWIR, 1.4-3 µm) sensors can be very challenging since the Si...
Minerals such as silicates, aluminosilicates (feldspar), magnesium silicates (serpentine) and olivines are among the most commonly encountered in the environment. Airborne mineral mapping of these minerals using conventional visible-near infrared (VNIR, 0.4-1.4 µm) and shortwave infrared (SWIR, 1.4-3 µm) sensors can be very challenging since the Si...
Airborne thermal infrared (TIR) imaging is often used to study the problematic of urban heat islands (UHI). However, surface temperature measurement using remote sensing techniques often fail to take into account the spectral emissivity of the investigated materials. This leads to mismatches between the true surface temperature and the measured bri...
For years, scientists have used thermal broadband cameras to perform target characterization in the longwave (LWIR) and midwave (MWIR) infrared spectral bands The analysis of broadband imaging sequences typically provides energy, morphological and/or spatiotemporal information. However, there is very little information about the chemical nature of...
Processing long-wave infrared (LWIR) hyperspectral imagery to surface emissivity or reflectance units via atmospheric
compensation and temperature-emissivity separation (TES) affords the opportunity to remotely classify and identify
solid materials with minimal interference from atmospheric effects. This paper describes an automated atmospheric
com...
One of the biggest and challenging limitations of infrared cameras in surveillance applications is the limited dynamic range. Image blooming and other artifacts may hide important details in the scene when saturation occurs. Many different techniques such as using multiple exposure times have been developed in the past to help overcome these issues...
Characterization of gas clouds are challenging situations to address due to the large and uneven distribution of these fast
moving entities. Whether gas characterization is carried out for gas leaks surveys or environmental monitoring purposes,
explosives and/or toxic chemicals are often involved. In such situations, airborne measurements present d...
This paper presents detection and identification of gases using an infrared imaging Fourier-Transform Spectrometer (iFTS). The company Telops has developed an iFTS instrument, the Hyper-Cam, which is offered as a medium or long wave infrared sensor. The principle of operation of the spectrometer and the methodology for standoff gas detection and id...
There is provided a method for referencing and correcting the beating spectrum generated by the interference of the components of a frequency comb source. The proposed method allows monitoring of variations of a mapping between the source and the beating replica. This can then be used to compensate small variations of the source in Fourier transfor...
Carbone dioxide (CO2) and methane (CH4) are the main gases which originate from the decomposition of organic material. Both of these are considered greenhouse gases due to their high propensity in absorbing and emitting infrared radiation. For this reason, landfill installations are often equipped with wells and pumping systems to collect these gas...
Image uniformity and accurate radiometric calibration are key features
of state-of-the-art infrared cameras. Over the past years several
non-uniformity correction and radiometric calibration techniques have
been developed. In this paper we present and compare different
techniques: 2-point calibration, CNUC™/multipoint's calibration
and Telops' Real...
Laminar and turbulent flow fields found in smokestacks, flames, jet engine exhaust, and rocket plumes are of practical and academic interest and could greatly benefit from spatially resolved spectral measurements. Key physical flow field parameters such as temperature and species concentrations can be extracted from spectral observations. Spectral...
Flares and smokestacks are hard-to-reach structures that might turn out being difficult to characterize once in operation, i.e. in industrial environments. Standoff thermal hyperspectral imaging represents a powerful approach for these challenging installations as it is a non-invasive technique providing valuable information about both the chemical...
Turbulent flow study could benefit from spatially-resolved spectra. We report a method for imaging FTS which minimizes scene-change artifacts due to rapid, stochastic temperature variations and enables recovery of temperature fluctuation statistics.
There is growing interest in measuring gaseous emissions to understand
their environmental impact. It is thus desired to identify and quantify
such emissions, ideally from standoff distances. AFIT and Telops have
performed several field experiments, using the Telops Hyper-Cam infrared
hyperspectral imager to perform identification and quantificatio...
This paper presents a theoretical evaluation of the pumping light intensity transmitted through an inhomogeneously broadened line system submitted to a coherent microwave excitation. A model is developed for the case of rubidium 87 atoms interacting with a buffer gas and optically pumped by all components of the D1 and D2 lines. The light generated...
The Telops Hyper-Cam midwave (InSb 1.5-5.mum) imaging Fourier-transform spectrometer observed the plume from a coal-burning power plant smokestack. From a distance of 600 meters, the plume was captured on a 128×64 pixel sub-window of the focal-plane array with each pixel imaging a 19.5×19.5cm2 region. Asymmetric interferograms were collected with l...
Benefiting from the rich amount of information provided by a hyperspectral imager such as an imaging Fourier-transform spectrometer, we developed a suite of gas quantification algorithms that were applied to identify the gas released by distant stacks, and to quantify their specific mass flow rates. The method successfully performs the gas quantifi...
The midwave and longwave infrared regions of the electromagnetic spectrum contain rich information which can be captured by hyperspectral sensors thus enabling enhanced detection of targets of interest. A continuous hyperspectral imaging measurement capability operated 24/7 over varying seasons and weather conditions permits the evaluation of hyper...
Accurate radiometric calibration is a key feature of modern infrared
cameras. Considering the newly available infrared focal plane arrays
(FPA) exhibiting very high spatial resolution and faster readout speed,
we developed a method to provide a dedicated radiometric calibration of
every pixel. The novel approach is based on detected fluxes rather t...
Many laboratories are presently working on the project of an optically pumped cesium beam frequency standard using semiconductor laser(s). Particularly interesting pumping schemes using two lasers have been proposed by CUTLER [1] and have been tried experimentally [2],[3],[4]. It is expected that these schemes, where one of the lasers must be π-pol...
Jet engine exhaust radiates strongly in the midwave infrared due to line emission from combustion byproducts such as CO2, CO, and H2O. Imaging Fourier-transform spectrometers (IFTS) have the potential to measure spatial variations in plume temperature and density. However, the turbulent flow yields rapid, stochastic fluctuations in radiance during...
We report a thorough analysis of the impact of sampling jitter in imaging Fourier-Transform Spectrometers operating with an externally triggered integrating camera. Through estimation of integrating parameters statistics, we can predict resulting spectral noise.
A new approach is described to compensate the variations induced by laser frequency instabilities in the recently demonstrated Fourier transform spectroscopy that is based on the RF beating spectra of two frequency combs generated by mode-locked lasers. The proposed method extracts the mutual fluctuations of the lasers by monitoring the beating sig...
We report a novel approach to characterize photoconductive detectors. A measurement procedure is set up in order to deduce blackbody responsivity and photoconductive gain, while clearly separating source and background contributions to the shot noise.
We discuss the realisation of an all-fiber spectrometer working on the principle of heterodyne measurement using two high brightness frequency combs exhibiting supercontinua in the NIR (1.2 µm - 1.9 µm).
This presentation will discuss several recent developments that will impact the way we do Fourier-transform spectrometry. Real-time instrument line shape correction, new interferogram sampling techniques, frequency combs and super-continuum MID-IR sources will all be discussed.
Based on a simple variable transformation in the spectral domain, a new method to parametrize any window in the same way as Kaiser–Bessel or Dolph–Chebyshev windows is presented, allowing a very flexible trade-off between the width of the main lobe and the height of the sidelobes. The derivation of the method is a generalization of the procedure us...
A novel matrix inversion approach is proposed to correct several contributions to the instrument line shape (ILS) of a Fourier transform spectrometer. The matrix formalism for the ILS is first quickly reviewed. Formal inversion of the ILS matrix is next discussed, along with its limitations. The stability of the inversion process for large field-of...
The instrument line shape (ILS) of a Fourier-transform spectrometer is expressed in a matrix form. For all line shape effects that scale with wavenumber, the ILS matrix is shown to be transposed in the spectral and interferogram domains. The novel representation of the ILS matrix in the interferogram domain yields an insightful physical interpretat...
1] SCISAT-1, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission for remote sensing of the Earth's atmosphere. It was launched into low Earth circular orbit (altitude 650 km, inclination 74°) on 12 Aug. 2003. The primary ACE instrument is a high spectral resolution (0.02 cm À1) Fourier Transform Spectrometer (F...
The instrument line shape (ILS) of Fourier-transform spectrometers is modeled within a framework that enables us to take into account the partial coherence of optical fields. The cross spectral density and the angular coherence functions are used to develop a global ILS model including all possible geometric defects that can be introduced by a real...
Wavelength meters are instruments designed to measure the wavelength of an electromagnetic wave. Electromagnetic waves are the classic way to represent modifications of the space surrounding a moving electrically charged body. Time-varying electric and magnetic fields are produced and can be sensed.Wavelength is a well-established parameter when co...
Wavelength meters are instruments designed to measure the wavelength of an electromagnetic wave. Electromagnetic waves are the classic way to represent modifications of the space surrounding a moving electrically charged body. Time‐varying electric and magnetic fields are produced and can be sensed.Wavelength is a well‐established parameter when co...
It is well known that the response of semiconductor photodetectors depends on the state of polarization of the incident light. The magnitude of this effect is quantified as the logarithm of the ratio of the maximum and minimum values of the responsivity when the detector is illuminated with completely polarized radiation of different polarization s...
We propose fast algorithms for the integration and removal of instrument line shapes (ILS) where the ILS scaling with wavenumbers and the sinc function are taken into account. Results are applied to correct HBr spectra.
The optical path difference of a Fourier-transform spectrometer is extracted using a Hilbert transform and Kalman filtered prior to the position sampling. An adaptive equalization step reduces the effects of channel mismatch.
The use of instrument line shape characterization to retrieve instrument parameters is investigated.
Divergence contribution to the instrument line-shape is measured using a special high resolution, high divergence interferometer. Presence of a phase inside the ILS is observed and its effect on transmission lines is experimentally demonstrated.
Since 1997, Defence Research and Development Canada - Valcartier (DRDC Valcartier) has been developing a Fourier-transform infrared (FTIR) spectrometer for the passive standoff detection of chemical clouds. This instrument, referred to as the Compact ATtmospheric Sounding Interferometer (CATSI), is a double-beam optically balanced FTIR spectrometer...
Standoff detection of chemical agents may be enhanced with the capability to measure an image of the agent concentration. The use of an imaging Fourier-Transform Spectrometer to perform these measurements is extensively modeled in order to predict its ultimate capabilities. The model developed allows one to determine the optimal configuration of th...
The effect of diffraction on the instrument line shape of a Fourier-transform spectrometer is studied with an analytical line-shape model. The expression for the instrument line shape of a diffracted point source is obtained. A simple condition on the throughput of the instrument is derived under which diffraction is negligible when compared with t...
An Instrument Lineshape model is presented with capabilities to predict various field-of-view geometries, including general illumination. A sensitivity analysis has been performed for various contributors to the lineshape. Measurements made with a gas cell and a laser source are presented.
We propose a new and efficient matrix algorithm for the integration and the inversion of wavelength dependent effects in Fourier transform spectrometers. The proposed algorithm takes into account and overcomes finite resolution difficulties.
Fourier-transform spectrometers using plane mirror interferometers can suffer from residual mirror misalignment. An efficient algorithm has been developed to correct directly, in real-time, the sampled interferogram for signal distortions arising from this residual tilt.
A high resolution, high divergence Fourier transform spectrometer for detailed instrument lineshape study is presented. The instrument will allow better validation of instrument line-shape models.
The impact of optical aberrations in the input collimator on the instrument line shape of a Fourier-transform spectrometer is modeled using an analytic line shape model. Each third-order aberration is considered separately. Design guidelines are obtained stating which aberrations are more important and allowing to choose the sign of some aberration...
This paper reports sensitive measurement of the power spectral density of semiconductor laser frequency fluctuations over a wide frequency range (about 9 decades, starting from 1 Hz and ending over 1 GHz). This broad range allows the observation of flicker and white noise contributions, as well as contributions from the current source driving the l...
A radiometric model of the instrument line shape (ILS) of Fourier-transform spectrometers is presented. We show first that common line-shape models are based on distribution of the radiant intensity in the interferometer. The complete steps between the source and the ILS are exposed as the core of the model. Relationships between the ILS, the spect...
We propose an experimental setup for generating multiple frequency references in the optical telecommunication frequency range. It is based on a comb of equally spaced frequencies, centered at 1550 nm, generated by a passively mode-locked semiconductor laser with a saturable absorber. The repetition rate of the pulse train can be modified using a t...
© 2001 Optical Society of America
© 2001 Optical Society of America
A simple and powerful method for obtaining analytic instrument line shapes (ILS’s) for Fourier transform spectrometers is explained. ILS’s for off-axis circular and rectangular detectors are calculated to illustrate the method. Results match earlier ILS simulations. The contribution of the nonuniformity of light intensity across the detector surfac...
Spaceborne Fourier-transform spectrometers must use a reliable metrology source to replace the conventional HeNe laser acting as the spatial sampling reference in ground instruments. Because of their lifetime and ruggedness, semiconductor lasers appear to be ideal candidates. However the fringe signal resulting from a semiconductor laser exhibits a...
This paper presents a summary of some of the research activities conducted at the Centre d'optique, photonique et laser from Universite Laval that find applications in the field of optical communications. The subjects considered are: absolute frequency control, compensation of dispersion and nonlinear effects within dense wavelength division multip...
The throughput of a tilted Fourier-transform spectrometer (FTS) with collimation is calculated. It is shown that the maximum off-axis angle that is acceptable in the interferometer is inversely proportional to the distance between the detector and the location where the tilt is applied to the wave fronts and is also inversely proportional to the ti...
Some aspects of imaging
Fourier transform
spectrometers are still not generally understood. One particular point leading to confusion concerns the throughput of time-scanning imaging instruments and how it can be compared to the étendue of conventional Fourier transform infrared radiometers
(FTIRs). This paper shows that a scanning imaging
Four...
We present our recent results toward the realization of an absolute frequency standard at 1556 nm based on the two-photon transition in rubidium at 778 nm. A compact transportable absolute frequency standard is described. Emphasis is put on the design of a periodically poled lithium niobate waveguide for efficient second-harmonic generation