Nouvelle Méthode de Mesure de la Cohérence Spatiale en Lumière Pseudo-Thermique par Comptage des Photoélectrons

1971 ◽  
Vol 49 (14) ◽  
pp. 1940-1949 ◽  
Author(s):  
Claude Delisle ◽  
Jacques Bures
Keyword(s):  
Light Intensity ◽  
Probability Density ◽  
Spatial Coherence ◽  
Experimental Distribution ◽  
Observation Plane ◽  
Theoretical Probability ◽  
Exact Theory ◽  
Cohérence Spatiale

The light from a pseudothermal source is simultaneously detected in two points of the observation plane with a single photodetector. The degree of spatial coherence between the two points is determined from a comparison between one of the moments of the theoretical probability density P(i) of the light intensity at the photocathode and the corresponding moment of the experimental distribution of the photoelectrons. The moments of the probability density P(i) are derived from an exact theory which takes into account the degree of spatial coherence between the two points of the observation plane.

Light intensity and spatial coherence characteristics of laser coherent detection in a turbulent atmosphere

2020 ◽  
Vol 13 (4) ◽  
pp. 728-736
Author(s):  
REN Jian-ying ◽  
◽  
◽  
SUN Hua-yan ◽  
ZHAO Yan-zhong ◽  
...  
Keyword(s):  
Light Intensity ◽  
Turbulent Atmosphere ◽  
Spatial Coherence ◽  
Coherent Detection

1/f Noise in Optical Output and Non-Gaussianity in Voltage Noise of GaAs Nanoscale Light-Emitting Structures

2017 ◽  
Vol 16 (03) ◽  
pp. 1750030 ◽  
Author(s):  
Alexander V. Belyakov ◽  
Alexey V. Klyuev ◽  
Arkady V. Yakimov
Keyword(s):  
Probability Density Function ◽  
Light Intensity ◽  
Probability Density ◽  
Density Function ◽  
Leakage Current ◽  
Solid Solutions ◽  
Voltage Noise ◽  
Output Intensity ◽  
Light Emitting ◽  
Optical Output

The 1/[Formula: see text] noise investigation in nanoscale light-emitting diodes (LEDs) and lasers, based on GaAs and its solid solutions, is presented here. Spectra of 1/[Formula: see text] noise [Formula: see text] in the voltage across terminals of device, and [Formula: see text] in emitted light intensity, as well as the cross-spectrum [Formula: see text], were measured. It was found that the noise in the leakage current, and in the additional nonlinear current, of devices is transformed into the noise in optical output intensity in spontaneous emission regime. We measured the histogram as the estimate of the probability density function of the voltage noise. The obtained data in lasers characterize the non-Gaussianity and/or nonstationarity of the noise in the regime of induced radiation. In contrast, in LEDs the deviation of noise from Gaussianity practically was not observed.

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

Effect of light intensity on the ultrastructure of the filamentous cyanobacterium, Anabaena variabilis

1988 ◽  
Vol 46 ◽  
pp. 300-301
Author(s):  
C. S. Bricker ◽  
S. R. Barnum ◽  
B. Huang ◽  
J. G. Jaworskl
Keyword(s):  
Fatty Acid ◽  
Light Intensity ◽  
Acid Content ◽  
Fatty Acid Content ◽  
Anabaena Variabilis ◽  
Chloroplast Envelope ◽  
Major Constituent ◽  
Filamentous Cyanobacterium ◽  
Photosynthetic Membrane ◽  
Effect Of Light

Cyanobacteria are Gram negative prokaryotes that are capable of oxygenic photosynthesis. Although there are many similarities between eukaryotes and cyanobacteria in electron transfer and phosphorylation during photosynthesis, there are two features of the photosynthetic apparatus in cyanobacteria which distinguishes them from plants. Cyanobacteria contain phycobiliproteins organized in phycobilisomes on the surface of photosynthetic membrane. Another difference is in the organization of the photosynthetic membranes. Instead of stacked thylakolds within a chloroplast envelope membrane, as seen In eukaryotes, IntracytopIasmlc membranes generally are arranged in three to six concentric layers. Environmental factors such as temperature, nutrition and light fluency can significantly affect the physiology and morphology of cells. The effect of light Intensity shifts on the ultrastructure of Internal membrane in Anabaena variabilis grown under controlled environmental conditions was examined. Since a major constituent of cyanobacterial thylakolds are lipids, the fatty acid content also was measured and correlated with uItrastructural changes. The regulation of fatty acid synthesis in cyanobacteria ultimately can be studied if the fatty acid content can be manipulated.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

Inter-Method Reliability of Pulse Volume Related Measures Derived Using Finger-Photoplethysmography

2018 ◽  
Vol 32 (4) ◽  
pp. 182-190 ◽  
Author(s):  
Kenta Matsumura ◽  
Koichi Shimizu ◽  
Peter Rolfe ◽  
Masanori Kakimoto ◽  
Takehiro Yamakoshi
Keyword(s):  
Light Intensity ◽  
Adverse Effects ◽  
Light Source ◽  
Direct Current ◽  
Resting State ◽  
Current Component ◽  
Psychophysiological Measures ◽  
Pulse Volume ◽  
Optical Paths ◽  
Sensor Positions

Abstract. Pulse volume (PV) and its related measures, such as modified normalized pulse volume (mNPV), direct-current component (DC), and pulse rate (PR), derived from the finger-photoplethysmogram (FPPG), are useful psychophysiological measures. Although considerable uncertainties exist in finger-photoplethysmography, little is known about the extent of the adverse effects on the measures. In this study, we therefore examined the inter-method reliability of each index across sensor positions and light intensities, which are major disturbance factors of FPPG. From the tips of the index fingers of 12 participants in a resting state, three simultaneous FPPGs having overlapping optical paths were recorded, with their light intensity being changed in three steps. The analysis revealed that the minimum values of three coefficients of Cronbach’s α for ln PV, ln mNPV, ln DC, and PR across positions were .948, .850, .922, and 1.000, respectively, and that those across intensities were .774, .985, .485, and .998, respectively. These findings suggest that ln mNPV and PR can be used for psychophysiological studies irrespective of minor differences in sensor attachment positions and light source intensity, whereas and ln DC can also be used for such studies but under the condition of light intensity being fixed.

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