Multispot projection, tracking, and calibration

Yalla, Veera Ganesh; Su, Wei Hung; Hassebrook, Laurence G.

doi:10.1117/12.487442

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…In order to estimate the position of the spots of a grid with features different from the calibration ones, we adopted a 2-D second-order parametric model 39 that describes the mapping of the SLM plane onto the sample plane. This model allows us to retrieve the spots position without applying the BDA each time we change the grid shape.…”

Section: Prediction Of Spots Positionmentioning

confidence: 99%

Adaptive optics microspectrometer for cross-correlation measurement of microfluidic flows

et al. 2019

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Mapping flows in vivo is essential for the investigation of cardiovascular pathologies in animal models.The limitation of optical-based methods, such as space-time cross correlation, is the scattering of light by the connective and fat components and the direct wave front distortion by large inhomogeneities in the tissue. Nonlinear excitation of the sample fluorescence helps us by reducing light scattering in excitation. However, there is still a limitation on the signal-background due to the wave front distortion. We develop a diffractive optical microscope based on a single spatial light modulator (SLM) with no movable parts. We combine the correction of wave front distortions to the cross-correlation analysis of the flow dynamics. We use the SLM to shine arbitrary patterns of spots on the sample, to correct their optical aberrations, to shift the aberration corrected spot array on the sample for the collection of fluorescence images, and to measure flow velocities from the cross-correlation functions computed between couples of spots. The setup and the algorithms are tested on various microfluidic devices. By applying the adaptive optics correction algorithm, it is possible to increase up to 5 times the signalto-background ratio and to reduce approximately of the same ratio the uncertainty of the flow speed measurement. By working on grids of spots, we can correct different aberrations in different portions of the field of view, a feature that allows for anisoplanatic aberrations correction. Finally, being more efficient in the excitation, we increase the accuracy of the speed measurement by employing a larger number of spots in the grid despite the fact that the two-photon excitation efficiency scales as the fourth power of this number: we achieve a twofold decrease of the uncertainty and a threefold increase of the accuracy in the evaluation of the flow speed. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Prediction Of Spots Positionmentioning

confidence: 99%

Adaptive optics microspectrometer for cross-correlation measurement of microfluidic flows

et al. 2019

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“…There are various calibration techniques [10][11][12][13][14] for calibrating the 3D scanning systems. The most commonly used technique is the SVD based calibration technique.…”

Section: D System Calibrationmentioning

confidence: 99%

Very high resolution 3D surface scanning using multi-frequency phase measuring profilometry

Yalla

Hassebrook

2005

SPIE Proceedings

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Structured light projection is one of the most accurate non-contact methods for scanning surface topologies. The field of view of such a scan may range from millimeters to several meters. One of the most precise and robust methods of structured light is Phase Measuring Profilometry. This method utilizes a sinusoidal pattern that is laterally shifted across a surface. An image is captured at uniform intervals and the "phase" is recovered for each pixel position by correlating across the shifted patterns. In general, the more pattern shifts and the higher the spatial frequency, the more accurate the depth measurement becomes, at each pixel location. However, with a high frequency, ambiguity errors can occur, so a dual frequency approach is commonly used where a low frequency pattern is used for non-ambiguous depth, followed by high frequency pattern. The low frequency result is used to unwrap the high frequency to yield a nonambiguous and precise phase. If the high frequency is too high, then ambiguity errors will occur. The solution is a multi-frequency method. We present experimental results for several variations of the multi-frequency approach yielding accuracies of 0.127mm standard deviation in depth with 0.92 mm pixel spacing. With consumer camera mega pixel technology this equates to a 0.127mm deviation over a field of view of 2 to 3 meters. To achieve this level of accuracy also requires calibration for radial and perspective distortions. Applications for this technology include noncontact surface measurement and robotic and computer vision.

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Multispot projection, tracking, and calibration

Cited by 2 publications

References 2 publications

Adaptive optics microspectrometer for cross-correlation measurement of microfluidic flows

Adaptive optics microspectrometer for cross-correlation measurement of microfluidic flows

Very high resolution 3D surface scanning using multi-frequency phase measuring profilometry

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