Spectral Radiant Exitance Research Articles

A study of flames with millimeter-wave radiation

It is a valuable issue to explore whether a flame can radiate microwaves, in spite of the electric field formed in the flame. Presented herein is an experimental study on a series of flames with millimeter-wave radiation in the combustion of pyrotechnic films. The pyrotechnic films were composed of ultra-fine red phosphorus (P), sodium nitrate (NaNO3), Polyvinyl Alcohol (PVA) and some additives such as chopped carbon fibers (CFs) and aluminized glass fibers (GFs). The combustion temperatures and millimeter-wave radiation signals of the flames were measured, the millimeter-wave emissivity and spectral radiant exitance were calculated to describe the millimeter-wave radiation intensity. The results demonstrate that the flame of the pyrotechnic films based on P/NaNO3/CFs can radiate millimeter waves, and different materials and their proportion have a great effect on the millimeter-wave radiation intensity.

Compensation method of broadband illuminant fluctuation based on spectrum linear fitting

The intensity of broadband illuminant fluctuates when its' power supply output power changes. Spectral intensities at each wavelength within the band of broadband illuminant fluctuate at different levels. A method based on spectrum linear fitting is proposed to compensate the illuminant spectral intensity in its band when its intensity fluctuates. The spectral intensity fluctuation at each wavelength could be compensated simply by measuring the band intensity with this method. The linear relationship between spectral radiant exitance and whole radiant exitance of ideal blackbody was analysed by researching the radiant exitance at different temperatures. The linear model of broadband illuminant band intensity and spectral intensity was built. Experimental system is composed of a halogen light, a power supply, an aperture, a spectrometer, and a computer mainly. By adjusting the power output of the power supply, we obtained a set of halogen light relative spectral intensities at different power inputs. The spectral intensity of halogen light at different input powers was measured to test the compensation effect of this method. The relationship between spectral intensity and band intensity of halogen light was fitted with linear relation and the fitting errors were analysed. The experimental result shows a linear relationship between spectral intensity and band intensity of halogen light, so the spectral intensity fluctuation can be compensated using the band intensity according to their linear relation. The relative error absolute value of compensated spectral intensity decreases as the halogen light input power increases. Within the range of halogen light input power, the relative error absolute values of spectral intensity compensated with this method are within 5% at vast majority (92%) of the wavelengths.

Calibration of a mid-IR optical emission spectrometer with a 256-array PbSe detector and an absolute spectral analysis of IR signatures

A mid-IR (MWIR) optical emission spectrometer (OES) was designed and constructed to detect the absolute spectral radiant exitance of IR signatures. A 256-array PbSe detector was adopted to analyze the MWIR emission spectrum. Various IR signatures from two flame sources were examined in order to evaluate the performance of the OES and verify its usefulness for low observable technology. The absolute emissions of their IR signatures were calculated and the amount of each emission was compared. The spectral response of the OES in the MWIR range was calibrated using a directly heated graphite blackbody; in addition, the total uncertainty of the OES was determined to be 5.24%.

Calibration and Uncertainty Analysis of an Optical Emission Spectrometer Measuring the Absolute Spectral Radiant Exitance of UV Signatures

AbstractAn optical emission spectrometer (OES) was designed and constructed to detect the absolute spectral radiant exitance of UV signatures for a wavelength range of 240 nm to 440 nm. Using a directly heated graphite black body furnace operating at a temperature of 3000 K, the spectral response of the OES in the UV range was calibrated. To evaluate the performance of the OES system, the emission spectra of molecules were measured in a butane flame and the absolute emissions of the UV signatures were calculated. The uncertainty of the absolute measurement of the UV signature was analyzed by considering various uncertainty budgets, and the total uncertainty of the OES was found to be 1.66 %.

Metal/Fluorocarbon Pyrolants: VI. Combustion Behaviour and Radiation Properties of Magnesium/Poly(Carbon Monofluoride) Pyrolant

AbstractThe performance of poly(carbon monofluoride) (PMF) (synonym: graphite fluoride) (CFx)n, (1) as oxidizer in a fuel rich Mg based pyrolant (ξ(Mg)=0.45) is investigated. The radiance [W sr−1] under both static and dynamic conditions, the spectral radiant exitance [W cm−2 μm−1], the linear burn rate [mm s−1] and the mass consumption rate [g s−1 cm−2] have been determined. Calculations for enthalpy of anaerobic and aerobic combustion [kJ g−1] and for the equilibrium composition of the combustion products as well as combustion temperature are given. A mechanism for the reaction is discussed. The combustion product from Mg/(CFx)n surprisingly reveals the formation of single walled carbon nanotubes (SWCNT) and “carbon nano carpet rolls” (CNCR). For part V see Ref. [1].

Evaluation of Tungsten Cluster Radiation Dependent on Various Metal Halides

Tungsten cluster lamps are expected to yield high efficiency and excellent color rendering. However, a regenerative halogen cycle is required to form and maintain the small clusters within the microwave-excited high-pressure discharge. Metal halides play an important role in building the halogen cycle, but we still do not know how the metal halides affect the radiation characteristics of the tungsten clusters. We investigated the spectral radiant exitance, the luminous flux, and the color temperature of the tungsten cluster radiation in various metal halides, such as NaCl, KCl, CsCl, NaBr, KBr, CsBr, NaI and KI. The radiation from the tungsten clusters yielded a continuous spectrum with a maximum between 650 and 700 nm, although the spectra were dependent on the type of metal halide used. The luminous fluxes in the metal alkali bromides were twice as large as those in the metal alkali chlorides and iodides. Also, the luminous fluxes in the sodium halides were twice as large as those in the potassium halides, and four times as large as those in the cesium halides. From those results, we confirm that NaBr is suitable as a metal halide in tungsten cluster lamps.

MCSによる室内照明空間における3次元色彩分布表示の試み

This paper describes an attempt to represent three-dimensional color distribution in lighting rooms using Monte Carlo simulation (MCS).Generally speaking, the lighting space is usually expected to have different spectral radiant exitances and color distributions in various positions throughout it, since lighting rooms have many types of light sources and room surface walls with various spectral properties.Because the human being perceives a color stimulus with his eyes from a wide visual field, it is important to discuss three dimensional color distribution with regard to human vision at any point in the lighting space.A formulation for the Monte Carlo simulation technique is performed to estimate three dimensional color distribution as quantitively as possible. Firstly, the model room is composed of imaginary 1, 000-unit subdivisions formed by uniformly dividing the lighting room into many single unit spaces. Next, the three-dimensional color distribution on six specified surfaces of a single unit space in the lighting room is investigated by using MCSIt was found that spectral radiant exitance distributions on both sides of the imaginary partitions are quite variable according to their positions and human perceptual location, so three-dimensional color distribution is also complicated by variations in these factors.

モンテカルロ法を用いた相互反射光による色彩変化のシミュレーション

Computer graphics is a useful simulation method for estimation or evaluation of lighting environments. Ray tracing is a common computer graphics method and this method has often been used for various lighting systems. However, in a conventional ray tracing method, it has been difficult to deal with diffusely reflected light. Therefore, synthesized images have been more or less unnatunal. On the other hand, radiosity method can treat diffusely reflected light, but it is difficult to deal with specularly reflected light and transmitted/refracted light by this method.If we trace a beam of light from a source, it is easy to deal with both diffusely reflected and transmitted/refracted light. In a Monte Carlo simulation method, a radiation or a reflection angle is determined statistically by random number. Therefore, we can trace a beam of light from the source.In the previouse paper, we studied the color change caused by inter-reflected light in the interior of a model room with infinite length, with attention to the spectral radiant exitance. In the present paper, luminous exitance was calculated in a model three dimensional space. In addition, calculated results are shown graphically. It was found that the color change caused by inter-reflection light can be handled accurately by using a Monte Carlo method.

CRT colorimetry. part I: Theory and practice

AbstractThe relationship was derived for computer‐controlled color CRT displays between spectral radiant exitance emitted and digital counts. The derivation was historical and could be traced to pioneering work in photographic sensitometry, vacuum tube physics, and broadcast television. By performing radiometric measurements relative to a display's maximum exitance, the model simplified to a two‐stage model. The first stage was a nonlinear transformation relating normalized digital‐to‐analog converter values to device‐dependent monitor tristimulus values using model parameters of gain, offset, and γ. The second stage was a linear transformation where the device‐dependent monitor tristimulus values were transformed to device‐independent CIE tristimulus values. By using the model, colorimetric characterization accuracy of better than 0.5 CIELAB color‐difference units for 125 colors sampling the display color gamut was achieved by measuring the CIE tristimulus values of only eight colors. The model had equivalent performance to methods using extensive measurements and table lookup. © 1993 John Wiley & Sons, Inc.

CRT colorimetry. Part II: Metrology

AbstractThe colorimetric characterization of computer‐controlled CRT displays require radiometric measurements with high precision and accuracy in order to achieve acceptable colorimetric accuracy in defining stimuli generated with this type of imaging modality. Precision and accuracy requirements for photometers, colorimeters, and spectroradiometers were evaluated. When models are used to relate digital counts defining a stimulus and resulting spectral radiant exitance, displays are assumed to exhibit channel and spatial independence. A variety of tests and the results of evaluating four imaging systems are described. From these analyses, measurement accuracy is mainly limited by wavelength scale in the case of spectro‐radiometers and filter fit in the case of colorimeters. Measurement precision is limited by the number of significant figures for fixed‐range devices and signal‐to‐noise limitations for low‐luminance stimuli. Display accuracy is limited by a lack of channel and spatial independence. Display precision is mainly limited by the electronic design of the display and the stability and load independence of the gun amplifiers. © 1993 John Wiley & Sons, Inc.

Spectral radiant exitance of a nonisothermal cavity radiator

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text James M. Palmer, "Spectral radiant exitance of a nonisothermal cavity radiator," Appl. Opt. 18, 758-760 (1979) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article