China
Africa
Explore chapters and articles related to this topic
Organic–Inorganic Semiconductor Heterojunctions for Hybrid Light-Emitting Diodes
Published in Ye Zhou, Optoelectronic Organic–Inorganic Semiconductor Heterojunctions, 2021
Radiometry describes the science of the measurement of electromagnetic radiation, which includes visible light. For LED characterization, the radiant flux Φrad(λ) is an important quantity. It describes the total radiant energy per unit time and is measured in Watts (W).
Introduction to Computer Vision and Basic Concepts of Image Formation
Published in Manas Kamal Bhuyan, Computer Vision and Image Processing, 2019
It is important to know the location of a point of a real world scene in the image plane. This can be determined by geometry of image formation process. The physics of light can determine the brightness of a point in the image plane as a function of surface illumination and surface reflectance properties. The visual perception of scenes depends on illumination to visualize objects. The concept of image formation can be clearly understood from the principles of radiometry.Radiometry Radiometry is the science of measuring light in any portion of the electromagnetic spectrum. All light measurements are considered, as radiometry, whereas photometry is a subset of radiometry weighted for a human eye response. Radiometry is the measurement of electromagnetic radiation, primarily optical, whereas Photometry photometry quantifies camera/eye sensitivity. We will now briefly discuss some important radiometric quantities.
Transducers
Published in Anton F. P. van Putten, Electronic Measurement Systems, 2019
In table 6.15 we present an overview of units used in the optical domain. We make a distinction between radiometric and photometric units. Radiometry is the science of electromagnetic radiation. Photometry is the science of electromagnetic radiation in the visible region to which the eye reacts.
Research on method of high-precision 3D scene optical remote sensing imaging simulation
Published in Journal of Modern Optics, 2019
Jun-Feng Wang, Zhen-Ting Chen, Xue-you Hu, Chuan-Wen Lin, Cui-Hua Li, Lei Hong, Chang-Jun Zha
A method of ORSIS for 3D scene is presented in this paper. Key techniques of high-precision remote sensing simulation method for 3D digital scenes were discussed, including simulation process, at-sensor radiance components, radiometry solver, mixed pixel. We have proposed a material texture mapping method to get a higher spatial resolution without increasing the amount of facet. Using ray tracing to calculate the radiance at the entrance, the bidirectional reflection characteristics of the target material and the mixed pixel effect are considered. Multi-sampling method was introduced to solve the pixel mixture issue effectively. Comparing simulated results with GF-2 real images, the spatial similarity is very high and the relative error of at-sensor radiance is less than 10%. The main error sources are atmosphere and material spectrum data. Obtaining accurate atmosphere parameters is very significant for simulation results. Material spectrums are measured at some sample points that cannot characterizes every point of same material, especially for mutable material such as grass, soil and bustling cement road. It’s better to mark one material to more levels to characterize its variance. So, this method can provide reference for the high-precision remote sensing simulation of 3D digital scenes.
Lighting Research Today: The More Things Change, the More They Stay the Same
Published in LEUKOS, 2019
Jennifer A. Veitch, Robert G. Davis
Kevin Houser’s presentation in Copenhagen exemplified this, describing the general research process as a search to relate X (independent or predictor variables) to Y (dependent or outcome variables) while controlling Z (extraneous variables that we want to exclude). His focus was primarily on the many ways in which we can describe our X, the light or lighting conditions that we study, whether we manipulate them (as in a laboratory experiment) or measure them (as in a field investigation). Myriam Aries also emphasized the importance of establishing a strong signal in research by clearly defining the stimulus variables and the lit environment in which it occurs and then taking steps to measure the stimuli with precision. Werner Osterhaus focused specifically on measuring daylight well in a field setting, which is a particularly challenging task even with the advanced devices available today. Peter Blattner provided the pure metrology perspective on lighting measurements, reminding us that physics meets physiology when radiometry becomes photometry and pointing ahead to the development of spectral sensitivity functions other than Vλ, through which we will be able to better understand the effects of our stimuli on the ipRGCs.
Reconfiguration of an Electrothermal-Arc Plasma Source for In Situ PMI Studies
Published in Fusion Science and Technology, 2021
E. G. Lindquist, T. E. Gebhart, D. Elliott, E. W. Garren, Z. He, N. Kafle, C. D. Smith, C. E. Thomas, S. J. Zinkle, T. M. Biewer
A characteristic broadband OES spectra is shown in Fig. 4, and emission lines of interest over the broadband range are labeled. Characteristic lines are from the helium fill gas, tungsten electrode material, boron nitride ablative liner material, and 304 stainless steel target plate. Visible light radiometry can also be done with the cameras equipped with various narrow bandpass transmission filters. Typically, the spectral bandpass FWHM is ~10 nm but filters with ~2-nm bandpass are also available. The bandpass is centered on a wavelength of interest, for example He I light at 667 nm. However, broadband blackbody emission light occurring within this band is measured by the camera in addition to the narrow atomic spectral emission lines.