Rapid Reflective Facet Characterization Using Fringe Reflection Techniques

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Charles E. Andraka ◽  
Scott Sadlon ◽  
Brian Myer ◽  
Kirill Trapeznikov ◽  
Christina Liebner
Keyword(s):  
Automotive Industry ◽  
Target Location ◽  
Complete Analysis ◽  
Surface Slope ◽  
Fringe Analysis ◽  
Reflective Mirror ◽  
Facet Analysis ◽  
Shape Determination ◽  
Fringe Patterns ◽  
Rapid Characterization

Reflective mirror facets for concentrating solar power (CSP) systems have stringent requirements on the surface slope accuracy in order to provide adequate system performance. This paper presents a tool that can fully characterize facets quickly enough for 100% inspection on a production line. A facet for a CSP system, specifically a dish concentrator has a parabolic design shape. This shape will concentrate near-parallel rays from the sun to a point (or a line for trough systems). Deviations of surface slope from the design shape impact the performance of the system, either losing power that misses the target or increasing peak fluxes to undesirable levels. During development or production, accurate knowledge of facet defects can lead to improvements to lower cost or improve performance. The reported characterization system, SOFAST (Sandia Optical Fringe Analysis Slope Tool), has a computer-connected camera that images the reflective surface, which is positioned so that it reflects an active target, such as an LCD screen, to the camera. A series of fringe patterns are displayed on the screen while images are captured. Using the captured information, the reflected target location of each pixel of mirror viewed can be determined, and thus through a mathematical transformation, a surface normal map can be developed. This is then fitted to the selected model equation, and the errors from design are characterized. While similar approaches have been explored, several key developments are presented here. The combination of the display, capture, and data reduction in one system allows rapid characterization. An “electronic boresight” approach is utilized to accommodate physical equipment positioning deviations, making the system insensitive to setup errors. Up to 1.5 × 106 points are characterized on each facet. Finally, while prior automotive industry commercial systems resolve the data to shape determination, SOFAST concentrates on slope characterization and reporting, which is tailored to solar applications. SOFAST can be used for facet analysis during development. However, the real payoff is in production, where complete analysis is performed in about 10 s. With optimized coding, this could be further reduced.

Rapid Reflective Facet Characterization Using Fringe Reflection Techniques

2009 ◽  
Author(s):  
Charles E. Andraka ◽  
Scott Sadlon ◽  
Brian Myer ◽  
Kirill Trapeznikov ◽  
Christina Liebner
Keyword(s):  
Data Reduction ◽  
Target Location ◽  
Focal Length ◽  
Complete Analysis ◽  
Small Scale ◽  
Shape Error ◽  
Fringe Analysis ◽  
Forming Process ◽  
Impact Performance ◽  
Slope Error

Mirror facets for Concentrating Solar Power (CSP) systems have stringent requirements on slope accuracy in order to provide adequate system performance. This paper presents a newly developed tool that can characterize facets quickly enough for 100% inspection on a production line. A facet for a CSP system, specifically a dish concentrator, has a parabolic design shape. This shape will concentrate near-parallel rays from the sun to a point (or a line for trough systems). Deviations of surface slope from the design shape impact the performance of the system, either losing power that misses the target, or increasing peak fluxes to undesirable levels. Three types of facet slope errors can impact performance. The first is a focal length error, typically caused by springback in the facet forming process. In this case, the wavelength of the error exceeds the size of the facet, resulting in a parabola, but with the wrong focal length. The results in a slope error that is largely systematic across the facet when the measured slope is compared to the design slope. A second shape error, in which the period of the error is on the order of the length of the facet, manifests also as a systematic slope error. In this case, the facet deviates from a parabolic shape, but can be modeled with a higher order curve. Finally, the residual errors after a model is proposed are usually lumped through a Root Mean Square (RMS) process and characterized as the 1-sigma variation of a normal distribution. This usually characterizes the small-scale imperfections in the facet, and is usually called “slope error”. However, all of these deviations from design are in facet errors in the slope of the manufactured facet. The reported characterization system, named SOFAST (Sandia Optical Fringe Analysis Slope Tool) has a computer-connected camera that images the reflective surface, which is positioned so that it views the reflection of an active target, such as an LCD screen. A series of fringe patterns are displayed on the screen while images are captured. Using the captured information, the reflected target location of each pixel of mirror viewed can be determined, and thus through a mathematical transformation, the surface normal map can be developed. This is then fitted to the selected model equation, and the errors from design are characterized. The reported system currently characterizes point focus mirrors (for dish systems), but extensions to line focus facets are planned. While similar approaches have been explored, several key developments are presented here. The combination of the display, capture, and data reduction in one system allows rapid capture and data reduction. An “electronic boresight” approach is developed accommodating physical equipment positioning errors, making the system insensitive to setup errors. A very large number of points are determined on each facet, providing significant detail as to the location and character of the errors. The system is developed in MatLab, providing intimate interactions with the data as techniques and applications are developed. Finally, while commercial systems typically resolve the data to shape determination, this system concentrates on slope characterization and reporting, which is tailored to the solar applications. This system can be used for facet analysis during development. However, the real payoff is in production, where complete analysis is performed in about 10 seconds. With optimized coding, this could be further reduced.

Nonlinear Optical Properties of PBT in Nematic Solutions

1990 ◽  
Vol 214 ◽  
Author(s):  
Hedi Mattoussi ◽  
Philip G. Kaatz ◽  
Gary D. Patterson ◽  
Guy C. Berry
Keyword(s):  
Optical Properties ◽  
Nonlinear Optical ◽  
Nonlinear Optical Properties ◽  
Lyotropic Liquid Crystal ◽  
Fringe Analysis ◽  
Third Order ◽  
Third Harmonic ◽  
Nematic Director ◽  
Fringe Patterns ◽  
Maker Fringe

ABSTRACTThird-order nonlinear optical properties of lyotropic liquid crystal poly(1,4-phenylene-2,6-benzobisthiazole), PBT, solutions are studied by third harmonic generation measurements. Besides the enhancement observed for this coefficient with respect to the pure PBT, coupling is observed between the mean filed nematic director n and the incident fundamental polarization B0. Different geometries, with respect to the relative orientation of B0 and n, provided different harmonic Maker Fringe Patterns. These data are compared using refractive index measurements, independently achieved on these materials, and necessary for Maker Fringe analysis.

Theoretical fringe analysis for a coherent optics method of residual stress measurement

1988 ◽  
Vol 23 (4) ◽  
pp. 169-178 ◽  
Author(s):  
G Nicoletto
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Hole Drilling ◽  
Fringe Analysis ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
Coherent Optics ◽  
Experimental Response ◽  
Fringe Patterns ◽  
Stress Term

In this paper, the theoretical relationships between relieved in-plane displacements and residual stresses, which are needed for data reduction in a moiré interferometric version of hole drilling method, are obtained. The analysis includes the case of linearly varying biaxial stresses. The theoretical relationships are then used for generating on a computer the corresponding moiré interferometric fringe patterns thus simulating the experimental response under known loading conditions. Various effects due to the degree of residual stress biaxiality, the strength of the linear stress term, the direction of sensitivity of the moiré grid, and the value of the Poisson's ratio are illustrated.

Complete analysis of photoelastic fringe patterns using two wavelengths

2002 ◽  
Author(s):  
Terry Y. Chen ◽  
S. H. Tsao ◽  
H. L. Lee
Keyword(s):  
Complete Analysis ◽  
Fringe Patterns

An Improved Two-Load Method for Whole-Field Complete Photoelastic Fringe Analysis

2005 ◽  
Vol 21 (3) ◽  
pp. 199-203 ◽  
Author(s):  
T. Y. Chen ◽  
H. L. Lee ◽  
Y. C. Chou
Keyword(s):  
Least Squares ◽  
Light Field ◽  
Dark Field ◽  
Fringe Analysis ◽  
Complete Determination ◽  
Fringe Patterns

AbstractAn improved two-load method for whole-field complete determination of photoelastic parameters is presented. The dark-field isoclinic images are used to determine the isoclinic angles. Using two isoclinic maps obtained from two different loads effectively compensates the indeterminable points. The use of dark-field and light-field photoelastic images for normalization extends the two-load method to analyze dark-field photoelastic fringe patterns and avoids model movement. Larger errors on the determined fringe orders are further reduced by a least-squares quadric fitting. The results are compared well to the theoretical ones. Further comparison of the improved two-load method and the two-wavelength method are given.

Microstructure of an extruded rapidly solidified Al-8Fe-2Mo alloy

1986 ◽  
Vol 44 ◽  
pp. 548-549
Author(s):  
W. T. Donlon ◽  
J. E. Allison ◽  
S. Shinozaki
Keyword(s):  
Electron Microscopy ◽  
Automotive Industry ◽  
Fuel Economy ◽  
High Strength ◽  
Al Alloys ◽  
Light Weight ◽  
Thin Sections ◽  
Strength And Durability ◽  
Rapidly Solidified ◽  
Whitney Aircraft

Light weight materials which possess high strength and durability are being utilized by the automotive industry to increase fuel economy. Rapidly solidified (RS) Al alloys are currently being extensively studied for this purpose. In this investigation the microstructure of an extruded Al-8Fe-2Mo alloy, produced by Pratt & Whitney Aircraft, Goverment Products Div. was examined in a JE0L 2000FX AEM. Both electropolished thin sections, and extraction replicas were examined to characterize this material. The consolidation procedure for producing this material included a 9:1 extrusion at 340°C followed by a 16:1 extrusion at 400°C, utilizing RS powders which have also been characterized utilizing electron microscopy.

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