A Photodiode-Array-Based Near-Infrared Spectrophotometer for the 600–1100 nm Wavelength Region

1989 ◽  
Vol 43 (1) ◽  
pp. 27-32 ◽  
Author(s):  
David M. Mayes ◽  
James B. Callis
Keyword(s):  
Spectral Resolution ◽  
Near Infrared ◽  
Dynamic Range ◽  
Wavelength Region ◽  
Stray Light ◽  
Silicon Photodiode ◽  
Baseline Noise ◽  
Array Detectors ◽  
Infrared Spectrophotometer ◽  
Photodiode Array

We describe a silicon photodiode-array (PDA)-based near-infrared spectrophotometer for making molecular absorption/diffuse reflectance measurements in the 600–1100 nm wavelength range. Absorptions in this spectral region arise from both low-lying electronic states and vibrational overtones of CH, NH, and OH functional groups and combination bands. One disadvantage of silicon-based array detectors is their decreasing quantum efficiency at wavelengths longer than 950 nm. For transmission measurements, this can be compensated for by the technique of spectral plane masking, which markedly improves the consistency and overall level of baseline noise as well as the dynamic range. The instrument's performance is evaluated in the areas of spectral resolution, baseline noise, stray light, and dynamic range, and a comparison is made with a state-of-the-art mechanically scanned instrument. In the study, the PDA spectrometer attained a signal-to-noise ratio two times better than that of the commercial instrument with a time efficiency advantage of twelve, while achieving a spectral resolution three times greater. Finally, the application of analyzing caustic brine solutions by rapid-scanning NIR spectroscopy is illustrated.

scholarly journals 3-D Spectroscopy with a Fourier Transform Spectrometer

1995 ◽  
Vol 149 ◽  
pp. 316-327 ◽  
Author(s):  
J.P. Maillard
Keyword(s):  
Fourier Transform ◽  
Spectral Resolution ◽  
Near Infrared ◽  
Field Of View ◽  
Dark Side ◽  
Fourier Transform Spectrometer ◽  
Array Detectors ◽  
New Type ◽  
Nicmos 3 ◽  
Spectro Imaging

AbstractWith the advent of bidimensional array detectors the throughput advantage of a Fourier Transform Spectrometer (FTS) can be used to create a new type of 3-D spectrometer. The classical multiplex property in the spectral domain of a FTS is multiplied by the number of pixel of the array. The points of the entrance field are all observed in parallel. After discussing the properties of this instrument, the coupling of the FTS of the CFH Telescope to a camera equipped with a NICMOS 3 array is described. With this combination, spectro-imaging in any bandpass between 1 and 2.5 µm is possible within a circular 24” field of view, with a scale of 0.33”/pixel, at seeing-limited spatial resolution. Any spectral resolution is choosable up to 30,000. Illustrations are given by a study of the dark side of Venus at 1.27 µm and of planetary nebulae at 2 µm. Many other objects can benefit from this observing mode in the near infrared. Further developments of this 3-D technique are discussed.

Spatially Encoded Fourier Transform Spectroscopy in the Ultraviolet to Near-Infrared

1989 ◽  
Vol 43 (8) ◽  
pp. 1378-1384 ◽  
Author(s):  
Jonathan V. Sweedler ◽  
M. Bonner Denton
Keyword(s):  
Fourier Transform ◽  
Optical System ◽  
Near Infrared ◽  
Dynamic Range ◽  
Wavelength Region ◽  
Atomic Emission ◽  
Fourier Transform Spectroscopy ◽  
Common Path ◽  
Linear Ccd ◽  
Absorbance Spectra

A spatial (Sagnac triangular common path) interferometer is described and evaluated for obtaining spectra in the 200–950 nm wavelength region. The interferometer has no moving parts, requires no entrance or exit slits, and is easy to align. A linear CCD is employed as the detector, allowing spectra to be simultaneously acquired. The performance of the interferometer is demonstrated for atomic emission and solution absorbance spectra. A method to remove the fixed-pattern response of the detector and optical system is demonstrated which effectively increases the dynamic range of the resulting spectra.

scholarly journals Near Infrared Imaging Magnetometry

1994 ◽  
Vol 154 ◽  
pp. 449-457 ◽  
Author(s):  
Douglas Rabin
Keyword(s):  
Magnetic Field ◽  
Spatial Organization ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Wavelength Region ◽  
Spectral Lines ◽  
Solar Photosphere ◽  
Promising Tool ◽  
Array Measurements ◽  
Array Detectors

Infrared array detectors are a new and promising tool for investigating the properties of magnetic field concentrations in the solar photosphere. Array measurements provide large statistical samples of polarized line profiles and display the spatial organization of the magnetic field. The wavelength region near 1.6 μm has important advantages for magnetometry: spectral lines with magnetic sensitivites ranging from low to very high; low continuum opacity; high continuum flux; and the possibility of sub-arcsecond angular resolution with existing telescopes. Initial results have extended earlier work on the distribution of field strength and flux in plages and revealed new properties specifically connected with spatial structure. The quality and flexibility of near infrared magnetographs can be expected to improve rapidly.

scholarly journals Characteristics of compact spectrometers with diffraction gratings of different typ

2019 ◽  
Vol 85 (1II)) ◽  
pp. 117-121 ◽  
Author(s):  
I. A. Zarubin ◽  
V. A. Labusov ◽  
S. A. Babin
Keyword(s):  
Spectral Range ◽  
Spectral Resolution ◽  
Diffraction Grating ◽  
Atomic Emission ◽  
Light Level ◽  
Stray Light ◽  
Experimental Comparison ◽  
Cover Glass ◽  
Flat Field ◽  
Photodiode Array

Modern small-sized spectrometers are designed mainly by Czerny – Turner scheme with a flat diffraction grating, and with the goal of the maximum aperture at the expense of resolution — by the scheme with a concave diffraction grating with a flat field. Spectrum registration in such spectrometers is carried out by linear photodiode array. The aim of the work is to inform professionals about the characteristics of the compact spectrometers developed by the authors. These spectrometers use unpackaged linear photodiode arrays for spectrum registration that eliminate the reflection of radiation from the cover glass of the photodiode array and reduce stray-light. The tightness of the spectrometer housing increases their service life. The modification parameters of the spectrometer designed according to Czerny – Turner scheme are given. The main advantage of the spectrometer is the low stray-light inside the device and the same spectral resolution throughout the spectral range. The working aperture in Czerny – Turner scheme is limited by aberrations to 1/6. The scheme with a flat field allows operation with a larger working aperture. Three modifications of the spectrometer are developed according to this scheme (description of their main parameters is given). The results of experimental comparison of the spectrometers with different optical schemes in the light intensity and spectral resolution are presented, along with the examples of their application. Devices designed according to Czerny – Turner scheme are used in atomic emission, atomic absorption spectral analysis, and in spectrophotometry for registration of absorption spectra of condensed media. Luminescence and Raman spectra of minerals are recorded on a flat-field spectrometer. The developed compact spectrometers have an operating spectral range 190 – 1100 nm with the possibility of registering spectral regions from 70 to 1000 nm, the best resolution being 0.1 nm and the stray-light level less than 0.05% with the minimum recorded optical density of more than 3. Flat field spectrometers have an increased aperture due to the large working aperture 1/2.1.

Analysis of electron-diffraction intensity profiles using a photodiode-array detection system

1983 ◽  
Vol 41 ◽  
pp. 322-323
Author(s):  
J. B. Warren
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Detection System ◽  
High Energy ◽  
Photographic Emulsion ◽  
Diffraction Intensity ◽  
Silicon Photodiode ◽  
Photodiode Array Detection ◽  
Analog To Digital ◽  
Photodiode Array

Electron diffraction intensity profiles have been used extensively in studies of polycrystalline and amorphous thin films. In previous work, diffraction intensity profiles were quantitized either by mechanically scanning the photographic emulsion with a densitometer or by using deflection coils to scan the diffraction pattern over a stationary detector. Such methods tend to be slow, and the intensities must still be converted from analog to digital form for quantitative analysis. The Instrumentation Division at Brookhaven has designed and constructed a electron diffractometer, based on a silicon photodiode array, that overcomes these disadvantages. The instrument is compact (Fig. 1), can be used with any unmodified electron microscope, and acquires the data in a form immediately accessible by microcomputer.Major components include a RETICON 1024 element photodiode array for the de tector, an Analog Devices MAS-1202 analog digital converter and a Digital Equipment LSI 11/2 microcomputer. The photodiode array cannot detect high energy electrons without damage so an f/1.4 lens is used to focus the phosphor screen image of the diffraction pattern on to the photodiode array.

scholarly journals Comprehensive modeling of bloodstain aging by multivariate Raman spectral resolution with kinetics

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Ayari Takamura ◽  
Daisuke Watanabe ◽  
Rintaro Shimada ◽  
Takeaki Ozawa
Keyword(s):  
Spectral Resolution ◽  
Aging Process ◽  
Near Infrared ◽  
Biochemical Characterization ◽  
Forensic Analysis ◽  
Chemical Mechanism ◽  
Experimental Conditions ◽  
Spectral Components ◽  
Different Temperatures ◽  
Analytical Approaches

Abstract Blood, as a cardinal biological system, is a challenging target for biochemical characterization because of sample complexity and a lack of analytical approaches. To reveal and evaluate aging process of blood compositions is an unexplored issue in forensic analysis, which is useful to elucidate the details of a crime. Here we demonstrate a spectral deconvolution model of near-infrared Raman spectra of bloodstain to comprehensively describe the aging process based on the chemical mechanism, particularly the kinetics. The bloodstain spectra monitored over several months at different temperatures are decomposed into significant spectral components by multivariate calculation. The kinetic schemes of the spectral components are explored and subsequently incorporated into the developed algorithm for the optimal spectral resolution. Consequently, the index of bloodstain aging is proposed, which can be used under different experimental conditions. This work provides a novel perspective on the chemical mechanisms in bloodstain aging and facilitates forensic applications.

scholarly journals A coma-free super-high resolution optical spectrometer using 44 high dispersion sub-gratings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hua-Tian Tu ◽  
An-Qing Jiang ◽  
Jian-Ke Chen ◽  
Wei-Jie Lu ◽  
Kai-Yan Zang ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
Wavelength Region ◽  
Ultra Violet ◽  
High Spectral Resolution ◽  
Visible Range ◽  
High Dispersion ◽  
Charge Coupled Device ◽  
Wide Range ◽  
High Resolution Spectrometer

AbstractUnlike the single grating Czerny–Turner configuration spectrometers, a super-high spectral resolution optical spectrometer with zero coma aberration is first experimentally demonstrated by using a compound integrated diffraction grating module consisting of 44 high dispersion sub-gratings and a two-dimensional backside-illuminated charge-coupled device array photodetector. The demonstrated super-high resolution spectrometer gives 0.005 nm (5 pm) spectral resolution in ultra-violet range and 0.01 nm spectral resolution in the visible range, as well as a uniform efficiency of diffraction in a broad 200 nm to 1000 nm wavelength region. Our new zero-off-axis spectrometer configuration has the unique merit that enables it to be used for a wide range of spectral sensing and measurement applications.

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

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 149 ◽  
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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