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.

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.

Contrast Signal to Noise Ratio

2021 ◽  
Vol 2021 (17) ◽  
pp. 186-1-186-6
Author(s):  
Robin Jenkin
Keyword(s):  
Autonomous Vehicles ◽  
Signal To Noise Ratio ◽  
Focal Length ◽  
Signal To Noise ◽  
Quality Metric ◽  
Camera Systems ◽  
Image Quality Metric ◽  
Recognition Of Objects ◽  
Noise Ratio ◽  
Supply Information

The detection and recognition of objects is essential for the operation of autonomous vehicles and robots. Designing and predicting the performance of camera systems intended to supply information to neural networks and vision algorithms is nontrivial. Optimization has to occur across many parameters, such as focal length, f-number, pixel and sensor size, exposure regime and transmission schemes. As such numerous metrics are being explored to assist with these design choices. Detectability index (SNRI) is derived from signal detection theory as applied to imaging systems and is used to estimate the ability of a system to statistically distinguish objects [1], most notably in the medical imaging and defense fields [2]. A new metric is proposed, Contrast Signal to Noise Ratio (CSNR), which is calculated simply as mean contrast divided by the standard deviation of the contrast. This is distinct from contrast to noise ratio which uses the noise of the image as the denominator [3,4]. It is shown mathematically that the metric is proportional to the idealized observer for a cobblestone target and a constant may be calculated to estimate SNRI from CSNR, accounting for target size. Results are further compared to Contrast Detection Probability (CDP), which is a relatively new objective image quality metric proposed within IEEE P2020 to rank the performance of camera systems intended for use in autonomous vehicles [5]. CSNR is shown to generate information in illumination and contrast conditions where CDP saturates and further can be modified to provide CDP-like results.

scholarly journals Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar

2020 ◽  
Author(s):  
Pyry Pentikäinen ◽  
Ewan James O'Connor ◽  
Antti Juhani Manninen ◽  
Pablo Ortiz-Amezcua
Keyword(s):  
Signal To Noise Ratio ◽  
Focal Length ◽  
Quantitative Information ◽  
Absolute Difference ◽  
Beam Diameter ◽  
Doppler Lidar ◽  
Signal To Noise ◽  
Uncertainty Estimates ◽  
Noise Ratio ◽  
Two Parameters

Abstract. Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for Halo Photonics Streamline and XR pulsed heterodyne Doppler lidars. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small.

scholarly journals A scanning strategy optimized for signal-to-noise ratio for the Geostationary Carbon Cycle Observatory (GeoCarb) instrument

2019 ◽  
Vol 12 (6) ◽  
pp. 3317-3334 ◽  
Author(s):  
Jeffrey Nivitanont ◽  
Sean M. R. Crowell ◽  
Berrien Moore III
Keyword(s):  
North America ◽  
South America ◽  
Carbon Cycle ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Scanning Strategy ◽  
Entire Area ◽  
Area Of Interest ◽  
Noise Ratio ◽  
Tropical South America

Abstract. The Geostationary Carbon Cycle Observatory (GeoCarb) will make measurements of greenhouse gases over the contiguous North and South American landmasses at daily temporal resolution. The extreme flexibility of observing from geostationary orbit induces an optimization problem, as operators must choose what to observe and when. The proposed scanning strategy for the GeoCarb mission tracks the sun's path from east to west and covers the entire area of interest in five coherent regions in the order of tropical South America east, tropical South America west, temperate South America, tropical North America, and temperate North America. We express this problem in terms of a geometric set cover problem, and use an incremental optimization (IO) algorithm to create a scanning strategy that minimizes expected error as a function of the signal-to-noise ratio (SNR). The IO algorithm used in this studied is a modified greedy algorithm that selects, incrementally at 5 min intervals, the scanning areas with the highest predicted SNR with respect to air mass factor (AF) and solar zenith angle (SZA) while also considering operational constraints to minimize overlapping scans and observations over water. As a proof of concept, two experiments are performed applying the IO algorithm offline to create an SNR-optimized strategy and compare it to the proposed strategy. The first experiment considers all landmasses with equal importance and the second experiment illustrates a temporary campaign mode that gives major urban areas greater importance weighting. Using a simple instrument model, we found that there is a significant performance increase with respect to overall predicted error when comparing the algorithm-selected scanning strategies to the proposed scanning strategy.

scholarly journals Miniature Broadband NIR Spectrometer Based on FR4 Electromagnetic Scanning Micro-Grating

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 393
Author(s):  
Liangkun Huang ◽  
Quan Wen ◽  
Jian Huang ◽  
Fan Yu ◽  
Hongjie Lei ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Optical System ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Focal Length ◽  
Parabolic Mirror ◽  
Signal To Noise ◽  
Full Spectrum ◽  
Scanning Angle ◽  
Noise Ratio

This paper presents a miniaturized, broadband near-infrared (NIR) spectrometer with a flame-retardant 4 (FR4)-based scanning micrograte. A 90° off-axis parabolic mirror and a crossed Czerny–Turner structure were used for creating an astigmatism-free optical system design. The optical system of the spectrometer consists of a 90° off-axis parabolic mirror, an FR4-based scanning micrograte, and a two-color indium gallium arsenide (InGaAs) diode with a crossed Czerny–Turner structure optical design. We used a wide exit slit and an off-axis parabolic mirror with a short focal length to improve the signal-to-noise ratio (SNR) of the full spectrum. We enabled a miniaturized design for the spectrometer by utilizing a novel FR4 micrograte for spectral dispersion and spatial scanning. The spectrometer can detect the full near-infrared spectrum while only using a two-color InGaAs diode, and thus, the grating scanning angle of this spectrometer is small when compared to a dual-detector-based spectrometer. In addition, the angle signal can be obtained through an angle sensor, which is integrated into the scanning micrograte. The real-time angle signal is used to form a closed-loop control over the scanning micrograte and calibrate the spectral signal. Finally, a series of tests was performed. The experimental results showed that the spectrometer has a working wavelength range of 800–2500 nm. The resolution is 10 nm at a wavelength range of 800–1650 nm and 15 nm at a wavelength range of 1650–2500 nm. Similarly, the stability of these two wavelength ranges is better than ±1 nm and ±2 nm, respectively. The spectrometer’s volume is 80 × 75 × 65 mm3 and its weight is 0.5 kg. The maximum spectral fluctuation does not exceed 1.5% and the signal-to-noise ratio is 284 after only one instance of averaging.

scholarly journals High sensitivity photo receiver design

2004 ◽  
Vol 17 (1) ◽  
pp. 121-131
Author(s):  
Zbigniew Bielecki ◽  
Wladyslaw Kolosowski ◽  
Edward Sedek
Keyword(s):  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Low Noise ◽  
Operating Conditions ◽  
Receiver Design ◽  
Signal To Noise ◽  
Optical Detectors ◽  
Noise Ratio ◽  
Photo Receiver

The paper describes low noise preampliers designed for optical detectors Analysis of operating conditions affecting signal-to-noise ratio has been carried out. Each preamplier was carefully optimized to work with particular type of the detector.

scholarly journals Fluctuations of the number of adsorbed micro/nanoparticles in sensors for measurement of particle concentration in air and liquid environments

2015 ◽  
Vol 21 (1-2) ◽  
pp. 141-147
Author(s):  
Ivana Jokic ◽  
Zoran Djuric ◽  
Katarina Radulovic ◽  
Milos Frantlovic
Keyword(s):  
Mass Transfer ◽  
Signal To Noise Ratio ◽  
Reaction Chamber ◽  
Operating Conditions ◽  
Total Power ◽  
Environmental Sensors ◽  
Signal To Noise ◽  
Particle Detection ◽  
Transfer Processes ◽  
Noise Ratio

A theoretical model of fluctuations of the number of adsorbed micro/nanoparticles in environmental sensors operating in air and liquids is presented, taking into account the effects of the mass transfer processes of the target particles in a sensor reaction chamber. The expressions for the total power of the corresponding adsorption-desorption noise, and for the corresponding signal-to-noise ratio are also derived. The presented analysis shows that the transfer processes can have a significant influence on the sensors limiting performance. The influence on both the fluctuations spectrum and the signal-to-noise ratio is estimated at different values of target particles concentration, functionalization sites surface density, and adsorption and desorption rate constants (the values are chosen from the ranges corresponding to real conditions). The analysis provides the guidelines for optimization of sensor design and operating conditions for the given target substance and sensor functionalization, in order to decrease the influence of the mass transfer, thus improving the ultimate performance (e.g. minimal detectable signal, signal-to-noise ratio) of sensors for particle detection. The calculations we performed show that it is possible to increase the signal-to-noise ratio for as much as two orders of magnitude by using the optimization that eliminates the mass transfer influence.

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 Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar

2020 ◽  
Vol 13 (5) ◽  
pp. 2849-2863
Author(s):  
Pyry Pentikäinen ◽  
Ewan James O'Connor ◽  
Antti Juhani Manninen ◽  
Pablo Ortiz-Amezcua
Keyword(s):  
Signal To Noise Ratio ◽  
Focal Length ◽  
Quantitative Information ◽  
Absolute Difference ◽  
Beam Diameter ◽  
Doppler Lidar ◽  
Signal To Noise ◽  
Uncertainty Estimates ◽  
Noise Ratio ◽  
Two Parameters

Abstract. Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for pulsed heterodyne Doppler lidars. The method was tested with Halo Photonics StreamLine and StreamLine XR Doppler lidars but should also be applicable to other pulsed heterodyne Doppler lidar systems. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

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