Miniaturization of an interferometric distance sensor employing diffractive optics

2014 ◽  
Vol 3 (4) ◽  
Author(s):  
Nektarios Koukourakis ◽  
Robert Kuschmierz ◽  
Michael Bohling ◽  
Jürgen Jahns ◽  
Andreas Fischer ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Techniques ◽  
Turbine Blades ◽  
Numerical Aperture ◽  
Optical Element ◽  
Systematic Measurement ◽  
Position Measurement ◽  
Common Path ◽  
The Common ◽  
Path Detection

AbstractIn order to improve safety, lifetime and energy efficiency of turbo machines, the behavior of the turbine blades has to be monitored during operation. This is a great challenge for metrology, since small, robust and non-contact position measurement techniques are required that offer both micrometer accuracy and microsecond temporal resolution. The Laser-Doppler-Distance (LDD) -Sensor proved to be an adequate technique to perform such measurements. However, the usage in turbo machines requires a miniaturized and temperature-stable sensor-head. In this paper we introduce a miniaturized design of the LDD-sensor that is based on common-path detection. First results indicated that the numerical aperture of the common-path detection is small in comparison to former implementations that used separate paths for illumination and detection. We find that decreasing the numerical aperture strongly increases the systematic measurement uncertainty. For this purpose a novel diffractive optical element containing a diffracting-lens was designed and used to increase the numerical aperture of the common-path detection without affecting the sensor size. Experiments prove that the new element reduces the relative systematic measurement uncertainty by a factor of ten. The mean systematic position measurement uncertainty amounts to Δ

scholarly journals Limiting Uncertainty Relations in Laser-Based Measurements of Position and Velocity Due to Quantum Shot Noise

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 264 ◽  
Author(s):  
Andreas Fischer
Keyword(s):  
Measurement Uncertainty ◽  
Wave Vector ◽  
Shot Noise ◽  
Measurement Techniques ◽  
Time Of Flight ◽  
Wave Number ◽  
Uncertainty Relations ◽  
Position Measurement ◽  
Information Theoretic ◽  
Measurement Systems

With the ongoing progress of optoelectronic components, laser-based measurement systems allow measurements of position as well as displacement, strain and velocity with unbeatable speed and low measurement uncertainty. The performance limit is often studied for a single measurement setup, but a fundamental comparison of different measurement principles with respect to the ultimate limit due to quantum shot noise is rare. For this purpose, the Cramér-Rao bound is described as a universal information theoretic tool to calculate the minimal achievable measurement uncertainty for different measurement techniques, and a review of the respective lower bounds for laser-based measurements of position, displacement, strain and velocity at particles and surfaces is presented. As a result, the calculated Cramér-Rao bounds of different measurement principles have similar forms for each measurand including an indirect proportionality with respect to the number of photons and, in case of the position measurement for instance, the wave number squared. Furthermore, an uncertainty principle between the position uncertainty and the wave vector uncertainty was identified, i.e., the measurement uncertainty is minimized by maximizing the wave vector uncertainty. Additionally, physically complementary measurement approaches such as interferometry and time-of-flight positions measurements as well as time-of-flight and Doppler particle velocity measurements are shown to attain the same fundamental limit. Since most of the laser-based measurements perform similar with respect to the quantum shot noise, the realized measurement systems behave differently only due to the available optoelectronic components for the concrete measurement task.

Monitoring High Temperature Steam Pipes Using Optical Strain Measurement Techniques

2006 ◽  
Vol 5-6 ◽  
pp. 145-152 ◽  
Author(s):  
Andrew Morris ◽  
John P. Dear ◽  
Miltiadis Kourmpetis
Keyword(s):  
Wind Turbine ◽  
Strain Measurement ◽  
Measurement Techniques ◽  
Turbine Blades ◽  
Monitoring Methods ◽  
Wind Turbine Blades ◽  
Optical Strain Measurement ◽  
Optical Strain ◽  
High Temperature Steam ◽  
Steam Pipes

Optical strain measurement techniques have been extensively developed in recent years in order to cope in various environments. Power stations and wind turbine blades can provide challenging environments for the use of a measurement technique. There are, however, many installation problems to be overcome. For example, there is the need to have regard for the hostile environment in steam generating plant and the demanding conditions to which wind turbine blades are subjected. Ideally the outputs from individual sensors would be used for continuous remote monitoring. However, measurements can also be useful each time the plant is shut down during a plant outage; which would be used to complement data from existing proven rugged monitoring methods. This paper addresses the monitoring of pressurized steam pipes as to their micro-strain growth related to time in service. This paper presents the progress made in the developing of a ruggedised digital speckle ‘sensor’ and associated image capture system. The effect of subsurface defects in the strain distribution is examined.

scholarly journals The AIV strategy of the common path of Son Of X-Shooter

2020 ◽  
Author(s):  
Federico Biondi ◽  
Kalyan Kumar Radhakrishnan Santhakumari ◽  
Riccardo Claudi ◽  
Matteo Aliverti ◽  
Luca Marafatto ◽  
...  
Keyword(s):  
Common Path ◽  
The Common

scholarly journals Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

2017 ◽  
Vol 10 (1) ◽  
pp. 247-264 ◽  
Author(s):  
Aditya Choukulkar ◽  
W. Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann Weickmann ◽  
Timothy A. Bonin ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Techniques ◽  
Vertical Plane ◽  
Complex Flow ◽  
Field Campaign ◽  
Velocity Statistics ◽  
Spatial Coverage ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Measurement Uncertainties

Abstract. Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO, from 2 March to 31 May 2015 brought together a large suite of in situ and remote sensing measurement platforms to evaluate complex flow measurement strategies. In this paper, measurement uncertainties for different single and multi-Doppler strategies using simple scan geometries (conical, vertical plane and staring) are investigated. The tradeoffs (such as time–space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single-/multi-Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty. It was found that with an increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity along with horizontal homogeneity and less representative line-of-sight velocity statistics. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.

scholarly journals Strongly Focused Circularly Polarized Optical Vortices Regulated by a Fractal Conical Lens

2019 ◽  
Vol 10 (1) ◽  
pp. 28
Author(s):  
Zhirong Liu ◽  
Kelin Huang ◽  
Anlian Yang ◽  
Xun Wang ◽  
Philip H. Jones
Keyword(s):  
Angular Momentum ◽  
Optical Tweezers ◽  
Numerical Aperture ◽  
Optical Element ◽  
Optical Vortex ◽  
Optical Vortices ◽  
Circularly Polarized ◽  
Strong Focusing ◽  
New Type ◽  
Vortex Beams

In this paper, a recently-proposed pure-phase optical element, the fractal conical lens (FCL), is introduced for the regulation of strongly-focused circularly-polarized optical vortices in a high numerical aperture (NA) optical system. Strong focusing characteristics of circularly polarized optical vortices through a high NA system in cases with and without a FCL are investigated comparatively. Moreover, the conversion between spin angular momentum (SAM) and orbital angular momentum (OAM) of the focused optical vortex in the focal vicinity is also analyzed. Results revealed that a FCL of different stage S could significantly regulate the distributions of tight focusing intensity and angular momentum of the circularly polarized optical vortex. The interesting results obtained here may be advantageous when using a FCL to shape vortex beams or utilizing circularly polarized vortex beams to exploit new-type optical tweezers.

A Critical Examination of the Hysteresis in Wells Turbines Using CFD and Lumped Parameter Models

2019 ◽  
Author(s):  
T. Ghisu ◽  
F. Cambuli ◽  
P. Puddu ◽  
I. Virdis ◽  
M. Carta ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Unsteady Aerodynamics ◽  
Lumped Parameter Model ◽  
Hysteretic Behavior ◽  
Critical Examination ◽  
Wells Turbine ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Acceleration And Deceleration ◽  
The Common

Abstract The hysteretic behavior of OWC-installed Wells turbines has been known for decades. The common explanation invokes the presence of unsteady aerodynamics due to the continuously varying incidence of the flow on the turbine blades. This phenomenon is neither new nor unique to Wells turbines, as an aerodynamic hysteresis is present in rapidly oscillating airfoils and wings, as well as in different types of turbomachinery, such as wind turbines and helicopter rotors, which share significant similarities with a Wells turbine. An important difference is the non-dimensional frequency: the hysteresis appears in oscillating airfoils only at frequencies orders of magnitude larger than the ones Wells turbines operate at. This work contains a reexamination of the phenomenon, using both CFD and a lumped parameter model, and shows how the aerodynamic hysteresis in Wells turbines is negligible, and how the often measured differences in performance between acceleration and deceleration are caused by the capacitive behavior of the OWC system.

scholarly journals Optical Measurement Techniques of Recombination Lifetime Based on the Free Carriers Absorption Effect

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Martina De Laurentis ◽  
Andrea Irace
Keyword(s):  
Optical Measurement ◽  
Semiconductor Devices ◽  
Measurement Techniques ◽  
Free Carrier Absorption ◽  
Power Devices ◽  
Electron Hole ◽  
Recombination Lifetime ◽  
Carrier Absorption ◽  
The Common ◽  
Successful Measurement

We review successful measurement techniques for the evaluation of the recombination properties in semiconductor materials based on the optically induced free carrier absorption. All the methodologies presented share the common feature of exploiting a laser beam to excite electron-hole pairs within the volume of the sample under investigation, while the probing methods can vary according to the different methodology analyzed. As recombination properties are of paramount importance in determining the properties of semiconductor devices (i.e, bipolar transistor gain, power devices switching features, and solar cells efficiency), their knowledge allows for better understanding of experimental results and robust TCAD simulator calibration. Being contactless and applicable without any particular preparation of the sample under investigation, they have been considered attractive to monitor these parameters inline or just after production of many different semiconductor devices.

scholarly journals A Priori Approach Of Real-Time Ridesharing Problem With Intermediate Meeting Locations

2014 ◽  
Vol 4 (4) ◽  
pp. 287-299 ◽  
Author(s):  
Kamel Aissat ◽  
Ammar Oulamara
Keyword(s):  
A Priori ◽  
Cost Savings ◽  
Travel Cost ◽  
Cost Rate ◽  
Common Path ◽  
The Core ◽  
New Strategy ◽  
Empirical Performance ◽  
The Common ◽  
Starting Location

Abstract Ridesharing is a mobility concept in which a trip is shared by a vehicle’s driver and one or more passengers called riders. Ridesharing is considered as a more environmentally friendly alternative to single driver commutes in pollution-creating vehicles on overcrowded streets. In this paper, we present the core of a new strategy of the ridesharing system, making it more flexible and competitive than the recurring system. More precisely, we allow the driver and the rider to meet each other at an intermediate starting location and to separate at another intermediate ending location not necessarily their origins and destinations, respectively. This allows to reduce both the driver’s detour and the total travel cost. The term “A priori approach” means that the driver sets the sharing cost rate on the common path with rider in advance. An exact and heuristic approaches to identify meeting locations, while minimizing the total travel cost of both driver and rider are proposed. Finally, we analyze their empirical performance on a set of real road networks consisting of up to 3,5 million nodes and 8,7 million edges. Our experimental results show that our heuristics provide efficient performances within short CPU times and improves the recurring ridesharing approach in terms of cost-savings.

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