MEASUREMENT OF PARAMETERS OF BROADBAND EMISSION USING MINI-SPECTROMETERS

On the basis of mini-spectrometers, a reference lamp of the SIRSH type with a known color temperature, and line spectrum sources, an inexpensive hardware complex has been created for measuring the emission parameters of heterodiodes and interference filters. Examples of recording the emission of heterodiodes (full width at half maximum is 17–30 nm) with a maximum of emission in the region of 659 and 764 nm and measurement of an interference filter (FWHM of the bandwidth is 12 nm) with a maximum transmission of 727 nm are given. The emission parameters of the SIRSH standard lamp are introduced into the program for measuring and processing data, due to which it is possible to significantly refine the value of the wavelength of the maximum emission and transmission.

Testing Evolutionary Models with Red Supergiant and Wolf–Rayet Populations

Despite the many successes that modern massive star evolutionary theory has enjoyed, reproducing the apparent trend in the relative number of red supergiants (RSGs) and Wolf–Rayet (WR) stars has remained elusive. Previous estimates show the RSG/WR ratio decreasing strongly with increasing metallicity. However, the evolutionary models have always predicted a relatively flat distribution for the RSG/WR ratio. In this paper we reexamine this issue, drawing on recent surveys for RSGs and WRs in the Magellanic Clouds, M31, and M33. The RSG surveys have used Gaia astrometry to eliminate foreground contamination and have separated RSGs from asymptotic giant branch stars using near-infrared colors. The surveys for WRs have utilized interference-filter imaging, photometry, and image subtraction techniques to identify candidates, which have then been confirmed spectroscopically. After carefully matching the observational criteria to the models, we now find good agreement in both the single-star Geneva and binary BPASS models with the new observations. The agreement is better when we shift the RSG effective temperatures derived from J − Ks photometry downwards by 200 K in order to agree with the Levesque TiO effective temperature scale. In an appendix we also present a source list of RSGs for the SMC which includes effective temperatures and luminosities derived from near-infrared 2MASS photometry, in the same manner as used for the other galaxies.

Realisation of the ITS-90 and thermodynamic temperature measurements above 960 °C using a monochromator-based radiance comparator

At LNE-Cnam, the International Temperature Scale of 1990 (ITS-90) and thermodynamic temperature measurements above the silver point, are carried out with a radiance comparator. This instrument is, more generally, devoted to any radiance comparison in temperature range from the ambient to 3000 °C. The instrument developed in the early 1990s at LNE-Cnam has the advantage of being completely adjustable. Compared to compact radiation thermometers based on lenses and a narrow-band interference filter, the radiance comparator is only made of gold coated mirrors and a Czerny-Turner monochromator to select the spectral bandwidth. The instrument offers the possibility to tune the geometric extent and the slit scattering function. In return, the radiance comparator is a complex instrument that requires a complete and a regular characterisation at the highest level of accuracy. In the first part, this paper describes the instrument and its operating principle. In a second part, a complete study of the wavelength calibration, the slit scattering function, size of source effect, out-of-band transmittance, linearity and other main sources of uncertainty are presented and discussed. Their associated uncertainties are estimated separately and are grouped together to give an example of propagation of uncertainties when performing the ITS-90.

Water and nitrogen in-situ imaging detection in live corn leaves using near-infrared camera and interference filter

Background Realizing imaging detection of water and nitrogen content in different regions of plant leaves in-site and real-time can provide an efficient new technology for determining crop drought resistance and nutrient regulation mechanisms, or for use in precision agriculture. Near-infrared imaging is the preferred technology for in-situ real-time detection owing to its non-destructive nature; moreover, it provides rich information. However, the use of hyperspectral imaging technology is limited as it is difficult to use it in field because of its high weight and power. Results We developed a smart imaging device using a near-infrared camera and an interference filter; it has a low weight, requires low power, and has a multi-wavelength resolution. The characteristic wavelengths of the filter that realize leaf moisture measurement are 1150 and 1400 nm, respectively, the characteristic wavelength of the filter that realizes nitrogen measurement is 1500 nm, and all filter bandwidths are 25 nm. The prediction result of the average leaf water content model obtained with the device was R2 = 0.930, RMSE = 1.030%; the prediction result of the average nitrogen content model was R2 = 0.750, RMSE = 0.263 g. Conclusions Using the average water and nitrogen content model, an image of distribution of water and nitrogen in different areas of corn leaf was obtained, and its distribution characteristics were consistent with the actual leaf conditions. The experimental materials used in this research were fresh leaves in the field, and the test was completed indoors. Further verification of applying the device and model to the field is underway.