Comparison between two methods of optical profilometry on micro-PTC

Marotta, Gianluca; Fontani, D.; Francini, F.; Jafrancesco, D.; Sansoni, P.; Messeri, Matteo; Pierucci, Giacomo; Lucia, Maurizio De

doi:10.1063/1.5117629

Cited by 3 publications

(7 citation statements)

References 12 publications

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“…For each x-position, a scan along the y-position was performed, and the z position and the slope were iteratively calculated. This laser scanning technique was discussed with additional detail in [17].…”

Section: Validationmentioning

confidence: 99%

“…In fact, considering a defect of the same size on the surface of a micro-PTC collector and on a conventional PTC mirror will result in a greater loss of energy on the smaller concentrator, because it affects a larger fraction of the total area of the receiver. In the current testing phase for this technology [14][15][16][17], a fundamental parameter to be experimentally determined and calculated is the optical efficiency of the system. It represents the upper limit that overall efficiency can be reached in the absence of thermal losses.…”

Section: Introductionmentioning

confidence: 99%

“…In the current testing phase for this technology [14][15][16][17], a fundamental parameter to be experimentally determined and calculated is the optical efficiency of the system. It represents the upper limit that overall efficiency can be reached in the absence of thermal losses.…”

Section: Introductionmentioning

confidence: 99%

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Structured Light Profilometry on m-PTC

et al. 2020

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In concentrating solar systems, it is essential to study the optical losses of the collectors. A fundamental parameter is the intercept factor, namely, the fraction of sunrays reflected by the concentrator that reaches the receiver. Optical profilometry studies the relationship between the collector profile and the intercept factor, which influences the collection efficiency. Profilometric analyses were performed on a micro-parabolic trough collector (m-PTC), with reduced sizes and greater mirror curvature than a usual PTC. The proposed technique projects a luminous pattern (structured light) both on the collector with an opaque covering and on a flat reference plane. Measurement set-up and calibration technique were developed for m-PTC. A program coded in Python analyzed the images and reconstructs the mirror profile. The tilted reference plane was reconstructed using an original geometric model and a calibration procedure. The focal length of each parabolic section was calculated, providing information on surface defects in the mirror. An important parameter obtained was the displacement of the focus of the parabola with respect to the ideal position. Using this value, the intercept factor was estimated to be 0.89. The proposed technique was validated by comparing the results with an independent profilometric study applied to the same m-PTC.

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Section: Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structured Light Profilometry on m-PTC

et al. 2020

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“…During the past decades, the Solar Collector Laboratory of CNR-INO has studied [27] and experimented [28] several optical techniques that employ this approach to assess the surface quality on solar mirrors. A method based on color-coded patterns was applied to deformable heliostats [26], reconstructing the shape of the reflecting surface.…”

Section: Introductionmentioning

confidence: 99%

“…In Ref. [28], two methods were briefly introduced without details, then the authors proposed to use structured light profilometry (SLP) [33], adapting the fringe projection for this m-PTC. The SLP technique is fast and allows to examine the entire m-PTC in a unique measurement.…”

Section: Introductionmentioning

confidence: 99%

Laser Profilometry on Micro-PTC

et al. 2022

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Profilometry is useful in detecting surface faults on solar concentrators, which can be imperfectly manufactured, thus affecting system performance. Profilometric analyses are performed on a micro-parabolic trough collector (m-PTC), with reduced sizes and greater mirror curvature than a usual PTC. The peculiar dimensions and shape of this micro-PTC request to develop a specific configuration of laser profilometry. It includes a laser diode with a converging lens placed in front of it, ensuring that the mirror curvature does not affect the beam reflection. A new method to calculate the spot position furnishes the reflected beam center even if it lies outside the target, giving it a virtual expansion. The profile is assessed with an iterative calculation, starting from a first point, physically measured. The results are the 3D profile reconstruction of the parabolic mirror and a map of the slope error for each mirror point. It also estimates the intercept factor, a parameter fundamental to optimize the m-PTC system, whose value is in agreement with a structured light measurement on the same object. This intercept factor was obtained averaging the local intercept factor calculated for each mirror point, which individuates the mirror portions not focusing the sunrays on the tube.

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Deflectometry for specular surfaces: an overview

et al. 2023

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Deflectometry as a technique to assess reflective surfaces has now existed for some 40 years. Its different aspects and variations have been studied in multiple theses and research articles; reviews are available for certain subtopics. Still a field of active development with many unsolved problems, deflectometry now encompasses a large variety of application domains, hardware setup types, and processing workflows for different purposes, and spans a range from qualitative defect inspection of large vehicles to precision measurements of microscopic optics. Over these years, many exciting developments have accumulated in the underlying theory, in the systems design, and in the implementation specifics. This diversity of topics is difficult to grasp for experts and non-experts alike and may present an obstacle to a wider acceptance of deflectometry as a useful tool for research and industrial applications. This paper presents an attempt to summarize the status of deflectometry and to map relations between its notable branches. Its aim is to provide a communication basis for experienced practitioners and also to offer a convenient entry point for those interested in learning about the method. The list of references introduces some prominent trends and established research groups in order to facilitate further self-directed exploration.

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Comparison between two methods of optical profilometry on micro-PTC

Cited by 3 publications

References 12 publications

Structured Light Profilometry on m-PTC

Structured Light Profilometry on m-PTC

Laser Profilometry on Micro-PTC

Deflectometry for specular surfaces: an overview

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