Conoscopic holography-based long-standoff profilometer for surface inspection in adverse environment

Enguita, J.M.; Álvarez, Ignacio; Fraga, César G.; Marina, Jorge; Fenández, Yolanda; Sirat, Gabriel Y.

doi:10.1117/1.2219097

Cited by 10 publications

(10 citation statements)

References 5 publications

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“…In this configuration, the phase of the signal can be used giving a much higher resolution than the frequency [5] ( figure 4). The problem of the phase is that it wraps around 2π, so measurements of surfaces with discontinuities can not be unambiguously recovered; work is being done to eliminate or reduce this limitation by means of double wavelength illumination [6].…”

Section: Conoscopic Holography Long Stand-off Profilometermentioning

confidence: 97%

Industrial online surface defects detection in continuous casting hot slabs

Álvarez

Marina²,

Enguita

et al. 2009

SPIE Proceedings

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Early surface defects inspection in hot steel products is a difficult task, but can help to reduce significantly production costs. This is the case of steel slabs when they are produced in the continuous casting line. Conoscopic holography phase-based long stand-off profilometers have shown to be a great tool for this kind of inspection, and a breakthrough system based on them is being used for more than 2 years in production conditions with high reliability and economical impact. This paper presents the results of this system and the challenges it has overcome: hot material up to 900ºC, dust, scale over the inspected surface, …

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Section: Conoscopic Holography Long Stand-off Profilometermentioning

confidence: 97%

Industrial online surface defects detection in continuous casting hot slabs

Álvarez

Marina²,

Enguita

et al. 2009

SPIE Proceedings

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“…Processing considerations using this method have already been reported. 12,13,15 It is possible to speed up the processing task using Phase Shifting algorithms applied just to a few rows of the fringe pattern, 16 the pattern can be seen as spatial carrier fringes with the same information coded in every row. If the processed row corresponds with the optical axis of the system, the obtained phase is ϕ 0 , otherwise the changes in the OPD due to the added distance in the vertical coordinate of the fringe pattern must be considered.…”

Section: Profilometer Working Principlementioning

confidence: 99%

“…By measuring the phase instead of the fringe frequency, precision is increased in, at least, one order of magnitude. 12 In order to extract the distance information z from the fringe pattern to the detection plane, both frequency and phase signals can be used. Usual processing methods are based on Fourier Transform methods 9 or Spatial Carrier Phase Shifting.…”

Section: Profilometer Working Principlementioning

confidence: 99%

“…Achievable precisions with this system range from less than one micron for standoffs of 100 mm to 0.2 mm for standoffs beyond one meter. 12,13 Although these systems have been successfully used for surface inspection and defect detection, we have experimented behaviors which cannot be explained by the simple model for fringe formation we have been using, which amongst other things, considers normal incidence of the incoming rays into the Savart plate. These deviations from the ideal case are more noticeable when dealing with high precisions from short distances, and include variations in the density of the fringes which do not relate to profile depth changes and variations in the frequency and phase signals for small defects which are either outside the system's theoretical precision or with a magnitude that does not correspond to the defect size.…”

Section: Introductionmentioning

confidence: 99%

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Fringe pattern characterization by OPD analysis in a lateral shearing interferometric profilometer

et al. 2011

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A common-path interferometric profilometer using a Savart plate as a lateral shearer has been successfully tested under harsh environmental conditions to measure the shape of a surface, detecting defects and characterizing surface properties. The whole profile is obtained from a single image and its depth sensitivity is easily scalable, making this technique suitable for many different applications. Although this system has been successfully used for surface inspection and defect detection, some behaviors cannot be explained by the usual simple model for fringe formation, which, amongst other things, considers normal incidence of the incoming rays into the Savart plate. These deviations from the ideal case are more noticeable for high resolutions from short distances. This paper studies the formation of the fringe pattern, which is crucial for understanding the behavior of the system and proper calibration.

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“…Optical metrology possesses the advantages of being a non-contact method and having high resolution and efficiency for workpiece contour measurement and surface quality inspection. Several methods exist for measuring optical topography, including the stereoscopic method, structured light, laser triangulation, conoscopic holography, the moiré method, and heterodyne interferometry [1,2,3,4,5,6,7,8,9,10,11,12,13].…”

Section: Introductionmentioning

confidence: 99%

Optical Inspection System for Gear Tooth Surfaces Using a Projection Moiré Method

Chen

2019

Sensors

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The demand for rapid online optical inspection of gear tooth surfaces is increasing, especially for precision gears. In this study, a non-contact optical measurement method was established for the inspection of gear tooth surfaces. For the system architecture, a halogen lamp was selected as the light source, and a collimated beam was produced by an autocollimator. Subsequently, moiré fringes were formed as the collimated beam went through the two linear gratings. The moiré fringes projected on the gear tooth surface were recorded with a charge-coupled device (CCD) camera, and the contour of the gear tooth surface was estimated and reconstructed from the phase information of the fringes by our developed computer codes. To verify the accuracy of the system, a spur gear tooth surface measured by a commercial coordinate measuring machine (CMM) was defined as the reference tooth profile. The tooth topography, involute profile deviation, and axial-direction deviation were successfully calculated by measuring the deviation of the optically measured surface based on the reference gear tooth profiles measured using the CMM.

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Conoscopic holography-based long-standoff profilometer for surface inspection in adverse environment

Cited by 10 publications

References 5 publications

Industrial online surface defects detection in continuous casting hot slabs

Industrial online surface defects detection in continuous casting hot slabs

Fringe pattern characterization by OPD analysis in a lateral shearing interferometric profilometer

Optical Inspection System for Gear Tooth Surfaces Using a Projection Moiré Method

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