Combustion processes are characterized by some parameters, including spectroscopic ones. Therefore, it is proposed to use the methods of applied optical spectroscopy to solve the task of diagnosing a combustion process of gaseous hydrocarbon fuel. In this case, the control device is a spectral–selective device that scans optical radiation as a signal carrying spectroscopic information about the combustion process. It can replace most of the control – measuring equipment located at the place of measuring. This device executes spectral measurements in specified areas of the optical range using a set of narrowband interference optical filters tuned to the specific wavelengths. The modernity of the device is confirmed by the Russian Federation patent. In this research, an installation was developed, which includes a burner and a gas supply system. An analysis of the spectroscopic informative properties in the emission spectrum of the flame arising from the combustion of hydrocarbon fuel was carried out. The experiment was accomplished by using the Ocean Optics USB2000 + spectrometer. The results of this experiment provided comprehensive information on the wavelength values of the optical filters are needed. These filters are part of the spectral–selective diagnostic device. Then a prototype of the spectral selective device for a combustion diagnostic was developed and assembled. In this paper, the results of experimental research of this device and a comparative analysis with the Ocean Optics USB2000 + spectrometer within the case of solving the problem of gaseous hydrocarbon fuel combustion diagnostics are also provided.
The possibility of transferring the idea of radio-frequency sequential heterodyne spectrum analysis to the optical range is considered. The similarity of signal processing of the radio and optical ranges by the method of sequential heterodyne analysis is noted. We consider the issue of a panoramic optical local oscillator in the form of a tunable laser, where stochastic phenomena are taken into account in the form of the sum of oscillations with a linear change in the instantaneous frequency and the stochastic component as interference, i.e. the spectrum is considered against the background of the generated interference. In this regard, it is proposed to use the technique of compression of radar signals to reduce the influence of the stochastic component of the oscillations of the laser panoramic local oscillator. It is noted that the main task on the path to realizing the idea put forward is to create a laser panoramic local oscillator with a low level of the stochastic radiation component of a tunable laser.
The role of spectral measurements in science and technology is noted. The measurement of optical spectra by an idealized spectral device based on an acousto-optic tunable filter is considered. It is shown that the acousto-optical methods of spectral measurements can be considered as a manifestation of the bilinear property of acousto-optical interaction. In this context, the transition to linear integral operators describing the measurement of the spectra of radio and optical signals is made. An analysis is given of the procedure for measuring the optical spectrum with a spectral device based on an acousto-optic tunable filter with an abrupt change in the frequency of the control signal. The comprehensive characteristic of such a device, its complex spread function, as well as the result of measuring the optical spectrum in the form of an energy spectrum, has been established.
Subject of the present paper is the application of a multichannel optical spectrometer performing spectral measurements in specified areas of the optical range using a set of narrow-band interference optical filters that are tuned to certain wavelengths. A special construction principle of the developed spectral-selective device allows to the transmission of the analyzed radiation through not only one optical fiber, but a bundle of fibers, which increases the sensitivity of the device without compromising its resolution. Tasks of monitoring and controlling the combustion processes and the prospects of using non-contact optical spectroscopy for their solution are considered. Results of the analysis of informative features in the radiation spectrum of various combustion processes are presented. Recommendations are given both on the choice of materials for infrared and visible filters, and on the parameters of the primary geometric structure that is used for the synthetization. A technique for the evaluation of the manufacturing quality or of the results of the filter structure design is proposed. A visible range filter based on a combination of zirconium oxide and silicon oxide layers has been developed. The results of the influence analysis of the layers number on obtaining the required spectral characteristics are presented.
A mathematical model of the spectral transform implemented in a diffraction grating spectral device based on the principles of radio optics, the system approach and the theory of linear systems is presenter in paper. The model is based on a sequential describing of the optical signal conversion by all elements of the device. The rejection of the principles of geometric optics when describing the operation of the device is argued. The proposed model in a strict mathematical form allows to establish important properties of the spectra in various diffraction orders: a nonlinear relationship of the spatial and frequency scale and a multiple improvement in the spectral resolution with an increase in the number of the diffraction order. In addition, a method has been established for improving the resolution of the device by applying diffraction gratings with a modified topology of the location of the strokes, which makes it possible to increase the intensity of the diffracted light into higher diffraction orders. Changing the topology consist in location of the strokes at not at an equidistant distance, i.e. introduction of spatial modulation. The results of computer simulation of a diffraction grating with the proposed topology and calculations of the theoretically achievable resolution of device with such grating are presented. A comparison is made between ordinary and high-order diffraction gratings according to their efficiency.
KEYWORDS: Combustion, Spectroscopy, Control systems, Optical spectroscopy, Process control, Diffraction gratings, Spectroscopes, Chemical analysis, Signal analyzers, Optical filters
During this article, we have reviewed an application of optical spectroscopy in the control of physical and technological processes, which include: monitoring combustion processes, monitoring a rocket engine state, the monitoring process of melting metals, dyeing textile materials, etc. We have given a solution for contactless optical spectroscopy to control these processes. Contactless spectroscopy means the absence of direct contact between the resolving system of the spectral device and analyzed radiation. This was done by using optical fiber as a transmission system. In this case, spectral devices are the traditional diffraction grating device and a multichannel optical spectrometer. There is giving schemes for creating control devices based on these spectral devices, and their comparison is made. Results of hightemperature process experimental researches of NaCl burning and recording the spectral line of Na in spectrum flame of gas-jet. That researches accomplished via developed laboratory models of control devices based on spectral devices.
This article reflects the application of optical spectroscopy methods in automatic control systems of combustion process in thermal power plants and different transport systems engines. Forming of controlled states and error signals is carried out by means of the multichannel optical spectrometer where the spectral decomposition is based on a resonance phenomenon in the narrow-band optical interference filters on the measurement data of the electromagnetic radiation spectrum as one of the results of the combustion process. This device carries out the contactless spectrum analysis in the predetermined optical ranges using a set of narrow-band interference optical filters tuned to certain wavelengths and fiber-optical system using for analyzed optical radiation transmitting. This radiation carries the spectroscopic information about the controlled combustion process. Using fiber-optical system excludes the negative impact of various extreme factors on the spectrometer operation as part of the error signal forming system. The special principle of the developed multichannel optical spectrometer construction allows applying not only one optical fiber but a fiber bundle. That increases the sensitivity of the device without reducing of its resolution. The novelty of the developed device is confirmed by the patent of the Russian Federation. This paper presents the results of the development of the multichannel optical spectrometer set-up and the results of its experimental research. The experimental research is carried out to determine the spectral line of copper (Cu) when burning copper powder.
Further development of stochastic aspect of the harmonic signal analysis theory is considered in this article. The choice of the analyzed signal model in the form of a harmonized finite random process is reasoned. It allows to receive the estimation of energy realization of a random process.
The energy spectrum estimations of a random process have been obtained basis on an instantaneous spectrum of the harmonized random process processing. These estimations have been received both in the form of convolution with the Bartlett spectral window and in the form of reference values.
These reference values are obtained by detecting CCD structures in acousto-optic spectrum analyzer and a diffraction grating spectral device, as well as by narrow-band filtering in a multichannel optical spectrometer.
Energy spectrum estimation (i.e. evaluation) of optical radiation with the new spectrum analyzer is considered. This device is parallel resonant optical spectrum analyzer; its resolving system is a set of narrow–band optical resonators in the form of interference filters, each of which is equivalent to a system with lumped parameters. This allows us to consider only oscillations of the optical field in the form of scalar functions and adopt as a model of analyzed signal harmonized scalar random process. Photo detector operation and average of photocurrent using an integrator and integrating circuit is considered too. On the basis of the application prolate entire spheroidal wave function theory energy spectrum estimation by the integral of photocurrent is obtained. This estimation of the energy spectrum is consistent and asymptotically unbiased.
The idea of acousto-optic self-tuning deflector, which automatically returns the position of the acoustic line,
corresponding to the mode of Bragg diffraction feedback implementation is proposed. Features of sodium
bismuthate’s double molybdate grown by new technology – low gradient Czochralski process are illustrated.
This paper aims to inform those interested in the scientific work of a large group of scientists: workers of the
Department of Electronics and Optical communications of St. Petersburg State University of Aerospace
Instrumentation in collaboration with workers of the Department of Quantum Electronics of St. Petersburg State
Technical University in the area of researches and development of acousto-optic tunable filters (AOTF).
Paper discusses the important features of the AOTF structure and their parameters that affect its work, such as:
spectral range of optical radiation, spectral resolution, active aperture of the optical radiation, optical transmission
of the working spectral range, optical radiation polarization (linear, circular or arbitrary) , diffraction efficiency,
contrast, distortion of the optical radiation’s front, frequency range of elastic waves, switching time, maximum
electric control power, impedance.
Also the AOTF using is considered: AOTF’s implications for control of laser radiation, AOTF’s application to
determine the counterfeit money. The last part of the report focuses on materials that act as antireflection thin
films.
Spectral characteristics of "clean" and enlightened substrates of ZnSe and Ge are shown. As seen from the
examples in the report, antireflection thin films increase transmittance of optical elements.
Recently spectroscopic methods of diagnostics of the liquid propellant rocket engines for prevention of emergencies
become topical. Such diagnostics is based on tracking appearance of spectral lines of engine’s constructional materials in
spectrum of rocket plume radiation and glow dynamics of these lines. The multichannel optical spectral device
considered in this paper makes the contactless spectrum analysis of optical radiations that allows to use this spectral
device for diagnostics of the liquid propellant rocket engines. The novelty of this spectral device lies in application of the
fiber-optical bundle and N parallel channels of the spectrum analysis [1]. Each channel contains the narrow-band optical
filtration which has been set on the certain wave length. The fiber-optical bundle is used for transmitting analyzed optical
radiation on a safe distance for the device from the rocket engine. This method of the contactless rocket engine
diagnostics allows to except a direct contact of the spectral device with the field of rocket blast radiation and to eliminate
negative influence of the engine on the spectral device, for example the acoustic impact.
Parallel spectrum analyzer including n analyzed channels power optical signals spectrum assessment is examined.
Problem examination is based not on traditional in optics spectrum definition as wavelength function, but on
traditional in harmonic analysis theory definition as frequency functions. Each analyzed channel includes a piece
of optical fiber, optical resonator (filter), photo detector and integrator. Input-output ratio of a spectral device
using parallel analysis is defined by matrix integral operator. Its kernel is matrix complex spectrum spread
function of a spectral device. Spectral measurements are only examined in a single channel because all the
channels have identical working algorithm. Optical signals spectrum measurement is carried out in two phases.
The first phase is to describe the complex spectra of optical signals measurement. Not only the transfer function
of optical resonator is considered on this phase, but frequency attenuation response of optical fiber as well. The
second phase is to define power characteristic of optical radiation, which includes photo detection and electrical
signal integration on the output of the photo detector. Transition from complex matrix integral operator to power
matrix integral operator is carried out. Power spectrum assessment properties for each channel are defined. The
main property of power spectrum assessment is it’s asymptotically consistence.
The parallel spectrum analyzer of optical signals is presented. This device is one of spectral devices which receive
spectroscopic information in an optical range. The method of receiving spectroscopic information based on the resonance
phenomenon is described. The novelty of the method lies in implementing the spectral decomposition by the principle of
the narrow-band optical filtration in n parallel channels of the spectrum analyzer. Furthermore, this device can make
parallel analysis of spectrum of optical radiations which are in places of difficult access, for instance, in unfavorable
conditions of high humidity, high temperature and toxic contamination. The result is achieved due to specific structure of
the analyzer which contains n channels of spectrum analyzer and the group of optical fibers which transmits analyzed
optical radiation on the given distance.
The parallel spectrum analyzer of optical signals is presented. This device is one of spectral devices which receives
spectroscopic information in an optical range. It can be used for research of spectral characteristics of materials, sources
of optical signals, atmosphere, etc. The method of receiving spectroscopic information as a result of processing an
optical signal in n parallel channels of the spectrum analyzer is described. The novelty of the method lies in ability of the
device to make parallel analysis of spectrum of optical radiations which are in places of difficult access, for instance, in
unfavorable conditions of high humidity, high temperature and toxic contamination. The result is achieved due to
specific structure of the analyzer which contains n channels of spectrum analyzer and the group of optical fibers which
transmits analyzed optical radiation on the given distance.
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