The Fourier Self-Deconvolution of Raman Spectra

1985 ◽  
Vol 39 (6) ◽  
pp. 1004-1009 ◽  
Author(s):  
H. J. Bowley ◽  
S. M. H. Collin ◽  
D. L. Gerrard ◽  
D. I. James ◽  
W. F. Maddams ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Signal To Noise Ratio ◽  
Resolution Enhancement ◽  
Operating Conditions ◽  
Array Detector ◽  
Diode Array ◽  
Diode Array Detector ◽  
Signal To Noise ◽  
K Value ◽  
Noise Ratio

Resolution enhancement by the use of Fourier self-deconvolution has been achieved with Raman spectra obtained from an instrument with an intensified diode array detector. A minimum signal-to-noise ratio of about 500:1 is acceptable and this is readily attainable, by spectral accumulation, in the case of relatively strong peaks such as those of carbon tetrachloride at 549 cm−1 and tetrahydrofuran at 915 cm−1. Resolution enhancement factors, K, of about 2.7 are then achieved. Weaker peaks, typified by the v (C-Cl) modes of polyvinyl chloride) require more extensive spectral accumulation, but a K value of 2.2 has proved feasible. The finite resolution imposed by the diode array detector is not a significant limitation. In order to obtain consistently good results it is necessary to optimize the signal-to-noise ratio, by choosing instrumental operating conditions best suited to specific samples.

scholarly journals CMUT-Based Sensor for Acoustic Emission Application: Experimental and Theoretical Contributions to Sensitivity Optimization

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2042
Author(s):  
Redha Boubenia ◽  
Patrice Le Moal ◽  
Gilles Bourbon ◽  
Emmanuel Ramasso ◽  
Eric Joseph
Keyword(s):  
Signal Processing ◽  
Signal To Noise Ratio ◽  
Ultrasonic Transducer ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Signal To Noise ◽  
Coupling Conditions ◽  
Sensor Structure ◽  
Noise Ratio ◽  
Electrical Connections

The paper deals with a capacitive micromachined ultrasonic transducer (CMUT)-based sensor dedicated to the detection of acoustic emissions from damaged structures. This work aims to explore different ways to improve the signal-to-noise ratio and the sensitivity of such sensors focusing on the design and packaging of the sensor, electrical connections, signal processing, coupling conditions, design of the elementary cells and operating conditions. In the first part, the CMUT-R100 sensor prototype is presented and electromechanically characterized. It is mainly composed of a CMUT-chip manufactured using the MUMPS process, including 40 circular 100 µm radius cells and covering a frequency band from 310 kHz to 420 kHz, and work on the packaging, electrical connections and signal processing allowed the signal-to-noise ratio to be increased from 17 dB to 37 dB. In the second part, the sensitivity of the sensor is studied by considering two contributions: the acoustic-mechanical one is dependent on the coupling conditions of the layered sensor structure and the mechanical-electrical one is dependent on the conversion of the mechanical vibration to electrical charges. The acoustic-mechanical sensitivity is experimentally and numerically addressed highlighting the care to be taken in implementation of the silicon chip in the brass housing. Insertion losses of about 50% are experimentally observed on an acoustic test between unpackaged and packaged silicon chip configurations. The mechanical-electrical sensitivity is analytically described leading to a closed-form amplitude of the detected signal under dynamic excitation. Thus, the influence of geometrical parameters, material properties and operating conditions on sensitivity enhancement is clearly established: such as smaller electrostatic air gap, and larger thickness, Young’s modulus and DC bias voltage.

scholarly journals Convolution Network with Custom Loss Function for the Denoising of Low SNR Raman Spectra

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4623
Author(s):  
Sinead Barton ◽  
Salaheddin Alakkari ◽  
Kevin O’Dwyer ◽  
Tomas Ward ◽  
Bryan Hennelly
Keyword(s):  
Raman Spectra ◽  
Loss Function ◽  
Signal To Noise Ratio ◽  
Biomedical Science ◽  
Clinical Tool ◽  
Signal To Noise ◽  
Low Snr ◽  
Low Intensity ◽  
Spectral Peaks ◽  
Noise Ratio

Raman spectroscopy is a powerful diagnostic tool in biomedical science, whereby different disease groups can be classified based on subtle differences in the cell or tissue spectra. A key component in the classification of Raman spectra is the application of multi-variate statistical models. However, Raman scattering is a weak process, resulting in a trade-off between acquisition times and signal-to-noise ratios, which has limited its more widespread adoption as a clinical tool. Typically denoising is applied to the Raman spectrum from a biological sample to improve the signal-to-noise ratio before application of statistical modeling. A popular method for performing this is Savitsky–Golay filtering. Such an algorithm is difficult to tailor so that it can strike a balance between denoising and excessive smoothing of spectral peaks, the characteristics of which are critically important for classification purposes. In this paper, we demonstrate how Convolutional Neural Networks may be enhanced with a non-standard loss function in order to improve the overall signal-to-noise ratio of spectra while limiting corruption of the spectral peaks. Simulated Raman spectra and experimental data are used to train and evaluate the performance of the algorithm in terms of the signal to noise ratio and peak fidelity. The proposed method is demonstrated to effectively smooth noise while preserving spectral features in low intensity spectra which is advantageous when compared with Savitzky–Golay filtering. For low intensity spectra the proposed algorithm was shown to improve the signal to noise ratios by up to 100% in terms of both local and overall signal to noise ratios, indicating that this method would be most suitable for low light or high throughput applications.

scholarly journals Recovery of Raman spectra with low signal-to-noise ratio using Wiener estimation

2014 ◽  
Vol 22 (10) ◽  
pp. 12102 ◽  
Author(s):  
Shuo Chen ◽  
Xiaoqian Lin ◽  
Clement Yuen ◽  
Saraswathi Padmanabhan ◽  
Roger W. Beuerman ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Wiener Estimation ◽  
Noise Ratio

Occurrence of Naphthalene in Honey Consumed in Turkey as Determined by High-Pressure Liquid Chromatography

2007 ◽  
Vol 70 (7) ◽  
pp. 1735-1738 ◽  
Author(s):  
DİREN BEYOĞLU ◽  
GÜLDEN Z. OMURTAG
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
High Performance ◽  
Limit Of Detection ◽  
Array Detector ◽  
Diode Array ◽  
Diode Array Detector ◽  
Signal To Noise ◽  
Limit Of Quantification ◽  
Naphthalene Concentration

This study is the first report on an investigation of the naphthalene concentration in samples of contaminated honey consumed in Turkey. Naphthalene was detected using high-performance liquid chromatography with a diode array detector at 220 nm. In one suspected contaminated specimen, the presence of naphthalene was confirmed by gas chromatography with mass spectrometry (GC-MS) at a concentration of 1.13 μg/kg. The limit of detection was 0.023 μg/g and the limit of quantification was 0.078 μg/g with signal-to-noise ratios of 3 and 10, respectively. A total of 100 samples of commercially available honey obtained from markets (53 samples) and street bazaars (47 samples) were analyzed. Mean naphthalene recovery from honey known to be contaminated with 1 μg/g was 80.4% (SD = 4.84%, n = 7).

A New Accessory for Infrared Emission Spectroscopy Measurements

1986 ◽  
Vol 40 (3) ◽  
pp. 401-405 ◽  
Author(s):  
M. Handke ◽  
N. J. Harrick
Keyword(s):  
Background Radiation ◽  
Signal To Noise Ratio ◽  
Focal Length ◽  
Infrared Emission ◽  
Operating Conditions ◽  
Signal To Noise ◽  
Small Areas ◽  
Area Of Interest ◽  
Ellipsoidal Mirror ◽  
Noise Ratio

The principal problem in measurement of emission IR spectra is the low signal-to-noise ratio resulting from the large background radiation relative to sample emission. One method of increasing the signal is to collect the emitted radiation over a very large solid angle using an ellipsoidal mirror. In this method, placing the sample at the short focal length of the ellipsoid both increases the amount of radiation collected for an improved signal-to-noise ratio as well as facilitates sampling of small areas. For locating the area of interest, a microscope is mounted on the emission accessory. The results of testing this emission accessory under different operating conditions such as different samples, emission angles, temperatures, etc., are presented.

A Design of Raman Spectrograph for Optical Activity and Normal Raman Measurements

1983 ◽  
Vol 37 (5) ◽  
pp. 447-449 ◽  
Author(s):  
P. L. Polavarapu
Keyword(s):  
Raman Spectra ◽  
Optical Activity ◽  
Scattered Light ◽  
Array Detector ◽  
Diode Array ◽  
Diode Array Detector

A multipurpose Raman spectrograph employing a diode array detector and optics for collecting scattered light in two orthogonal scattering planes is described. Raman spectra representing the performance of the instrument are presented.

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