Estimation of stray-light and fluorescence effects in differential spectroscopy

AbstractUnderstanding stray light (SL) is a crucial aspect in the development of high-end optical instruments, for instance space telescopes. As it drives image quality, SL must be controlled by design and characterized experimentally. However, conventional SL characterization methods are limited as they do not provide information on its origins. The problem is complex due to the diversity of light interaction processes with surfaces, creating various SL contributors. Therefore, when SL level is higher than expected, it can be difficult to determine how to improve the system. We demonstrate a new approach, ultrafast time-of-flight SL characterization, where a pulsed laser source and a streak camera are used to record individually SL contributors which travel with a specific optical path length. Furthermore, the optical path length offers a means of identification to determine its origin. We demonstrate this method in an imaging system, measuring and identifying individual ghosts and scattering components. We then show how it can be used to reverse-engineer the instrument SL origins.

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Microwave Spectroscopy as a Potential Tool for Color Grading Diamonds

Energies ◽

10.3390/en14123507 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3507

Author(s):

Yossi Rabinowitz ◽

Ariel Etinger ◽

Asher Yahalom ◽

Haim Cohen ◽

Yosef Pinhasi

Keyword(s):

Electromagnetic Property ◽

Precise Determination ◽

Visible Spectral Range ◽

Stray Light ◽

Light Transmittance ◽

Structural Defects ◽

Frequency Range ◽

Color Grade ◽

Color Grading ◽

Nitrogen Contamination

A diamond’s color grading is a dominant property that determines its market value. Its color quality is dependent on the light transmittance through the diamond and is largely influenced by nitrogen contamination, which induces a yellow/brown tint within the diamond, as well as by structural defects in the crystal (in rare cases boron contamination results in a blue tint). Generally, spectroscopic instrumentation (in the infrared or UV–visible spectral range) is used in industry to measure polished and rough diamonds, but the results are not accurate enough for precise determination of color grade. Thus, new methods should be developed to determine the color grade of diamonds at longer wavelengths, such as microwave (MV). No difference exists between rough and polished diamonds regarding stray light when the MW frequency is used. Thus, several waveguides that cover a frequency range of 3.95–26.5 GHz, as well as suitable resonator mirrors, have been developed using transmission/reflection and resonator methods. A good correlation between the S12 parameter and the nitrogen contamination content was found using the transmission/reflection method. It was concluded that electromagnetic property measurements of diamonds in the MW frequency range can be used to determine their nitrogen content and color grading. The MW technique results were in good agreement with those obtained from the infrared spectra of diamonds.

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The Improvement on the Performance of DMD Hadamard Transform Near-Infrared Spectrometer by Double Filter Strategy and a New Hadamard Mask

Micromachines ◽

10.3390/mi10020149 ◽

2019 ◽

Vol 10 (2) ◽

pp. 149 ◽

Cited By ~ 1

Author(s):

Zifeng Lu ◽

Jinghang Zhang ◽

Hua Liu ◽

Jialin Xu ◽

Jinhuan Li

Keyword(s):

Near Infrared ◽

Signal To Noise Ratio ◽

Nonuniform Distribution ◽

Stray Light ◽

Spectral Energy ◽

Hadamard Transform ◽

Digital Micromirror Device ◽

Infrared Spectrometer ◽

Near Infrared Spectrometer ◽

The Impact

In the Hadamard transform (HT) near-infrared (NIR) spectrometer, there are defects that can create a nonuniform distribution of spectral energy, significantly influencing the absorbance of the whole spectrum, generating stray light, and making the signal-to-noise ratio (SNR) of the spectrum inconsistent. To address this issue and improve the performance of the digital micromirror device (DMD) Hadamard transform near-infrared spectrometer, a split waveband scan mode is proposed to mitigate the impact of the stray light, and a new Hadamard mask of variable-width stripes is put forward to improve the SNR of the spectrometer. The results of the simulations and experiments indicate that by the new scan mode and Hadamard mask, the influence of stray light is restrained and reduced. In addition, the SNR of the spectrometer also is increased.

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Quantitative Analysis of Raman Spectra in Si/SiGe Nanostructures

MRS Proceedings ◽

10.1557/opl.2013.271 ◽

2013 ◽

Vol 1510 ◽

Author(s):

Selina Mala ◽

Leonid Tsybeskov ◽

Jean-Marc Baribeau ◽

Xiaohua Wu ◽

David J. Lockwood

Keyword(s):

Experimental Data ◽

Thermal Conductivity ◽

Quantitative Analysis ◽

Raman Spectra ◽

Instrumental Response ◽

Sample Surface ◽

Stray Light ◽

Raman Signal ◽

Longitudinal Acoustic ◽

Local Sample

ABSTRACTWe present comprehensive quantitative analysis of Raman spectra in two-(Si/SiGe superlattices) and three-(Si/SiGe cluster multilayers) dimensional nanostructures. We find that the Raman spectra baseline is due to the sample surface imperfection and instrumental response associated with the stray light. The Raman signal intensity is analyzed, and Ge composition is calculated and compared with the experimental data. The local sample temperature and thermal conductivity are calculated, and the spectrum of longitudinal acoustic phonons is explained.

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A Homogeneous Field for Light Adaptation

Perceptual and Motor Skills ◽

10.2466/pms.1968.26.2.521 ◽

1968 ◽

Vol 26 (2) ◽

pp. 521-522

Author(s):

Henry W. Mertens

Keyword(s):

Light Adaptation ◽

Space Perception ◽

Stray Light ◽

Homogeneous Field

A light-adaptation device which creates a homogeneous field is described. It can be used easily between observations in space perception experiments to reduce sensitivity of the eyes to stray light in the experimental display and does not itself introduce extraneous cues.

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