Non-contact measurement of central lens thickness

Kunkel, Matthias; Schulze, J.; Kogel‐Hollacher, Markus; Sprentall, Susan

doi:10.2351/1.5060438

Cited by 13 publications

(13 citation statements)

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“…Preliminary experiments by Hillen et al 7 mapped time history profiles of the liquid film thickness beneath the droplet impact cavity (referred to herein as the sub-cavity film thickness) formed by single impinging drops at different radial locations utilizing a commercially available non-contact chromatic optical measuring sensor 9 . The sub-cavity volume was then computed by integration of the profiles.…”

Section: Figure 2 Single Drop Impingement Into An Unheated Initial Lmentioning

confidence: 99%

Droplet impact time histories for a range of Weber numbers and liquid film thicknesses for spray cooling application

Hillen

Taylor

Menchini

et al. 2013

43rd Fluid Dynamics Conference

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Spray cooling is a topic of current interest for its ability to uniformly remove high levels of waste heat for densely packed microelectronics. A Monte-Carlo (MC) spray cooling simulation model is under development that is based on empirical data to be a cost effective design tool that will predict accurate heat fluxes based on nozzle conditions and heater geometry. This work reports spray and single drop experiments with the goal of computing the volume beneath a drop impact cavity (sub-cavity volume) created by a single impinging droplet on an initial liquid layer. A relevant test plan for the single drop experiments in terms of We and Re numbers was created through utilization of Phase Doppler Anemometry to characterize a water spray generated by a nozzle of interest for varying flow conditions. Liquid thickness profiles of the sub-cavity formed by a single impinging drop onto a range of initial liquid film thicknesses were measured versus time via a non-contact optical thickness sensor. Time dependent sub-cavity volumes were computed by integrating these sub-cavity liquid film thickness profiles measured radially outward from the impact centerline. It is found that higher We and lower h 0 * result in a more radially uniform sub-cavity surface contour versus time, except for regions near the outer bottom cavity radius, where the liquid film was thinner. The sub-cavity volume was found to be nearly constant for a majority of the cavity lifetime and increased with We and h 0 * . These results will be incorporated in future work into the MC model to improve its predictive capability. Nomenclatured = Drop diameter Greek Letters D = Arithmetic mean droplet diameter ρ = Density D 32 = Sauter mean droplet diameter η = Index of refraction Fr = Froude number = μ = Dynamic viscosity h = Liquid film thickness σ = Surface tension R = Radial location τ = Dimensionless time (t•V axial /d) Re = Reynolds number = Superscripts T = Temperature * = Dimensionless parameter t = Time Subscripts V = Arithmetic mean velocity 0 = Initial condition Vol = Sub-cavity volume axial = Axial velocity component We = Weber number = c = Cavity z = Axial standoff distance from the nozzle tip r = Radial velocity component s = Spray

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Section: Figure 2 Single Drop Impingement Into An Unheated Initial Lmentioning

confidence: 99%

Droplet impact time histories for a range of Weber numbers and liquid film thicknesses for spray cooling application

Hillen

Taylor

Menchini

et al. 2013

43rd Fluid Dynamics Conference

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“…As we are interested in only one value for the thickness of the sample, it seems appropriate to take an average over all positions z P (α). This is achieved by integrating the correction factor over the full aperture as already discussed in [5]. Furthermore, the actual intensity distribution of the collimated beam in front of the chromatic front lens must be considered as weighting function g(α) if it deviates from the intensity distribution of a plane wave (rectangular distribution).…”

Section: Thickness Determinationmentioning

confidence: 99%

Thickness Determination of Transparent Coatings

Quinten

2019

PhotonicsViews

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Thickness determination of transparent objects or thick transparent layers can be carried out rather simpy using a chromatic confocal sensor. One obtains the thickness as the difference between two distance peaks multiplied with the refractive index of the object's material. A more detailed analysis however reveals that this result should be corrected by a factor that considers the refraction in detail. In this paper we derive and discuss this correction factor and give tabulated values for different refractive indices and aperture angles of the chromatic probe.

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“…Contact measurement can only be utilized when machining and assembling the lenses, which has lower accuracy and even causes damage to the coated lens. The non-contact measurement methods mainly include machine vision method [9], chromatic confocal microscopy [10,11], low coherence interferometry [12], and laser differential confocal technique [13,14]. Machine vision method has advantages of continuous measurement and flexible in production line with an accuracy of less than 0.005 mm.…”

Section: Introductionmentioning

confidence: 99%