Focus Variation Instruments

Helmli, Franz

doi:10.1007/978-3-642-12012-1_7

Cited by 45 publications

(35 citation statements)

References 3 publications

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“…Although using the maximum value of the focus metric to estimate the surface position has a physical basis, it does not utilize other information of the focus curve, such as the peak width and shape, to improve the depth estimate. Fitting a polynomial or point spread function curve, as applied in FVM [8], could further improve the axial resolution.…”

Section: Discussionmentioning

confidence: 99%

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Sub-millimeter depth-resolved digital holography

Rooij

Kalkman

2017

Appl. Opt.

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We present sub-millimeter full-field depth from focus digital holography of surface topography of rough objects. For each pixel, the depth of the object is calculated from the variance of the intensity image over a set of reconstruction distances. First, we theoretically describe the axial resolution of this method and show that sub-millimeter resolution is feasible. Second, using a digital holography setup without magnifying optics or lateral scanning we experimentally demonstrate 100 μm axial resolution depth ranging and surface topography imaging. This is significantly better than what has previously been reported using digital holography and could make this technique useful for rapid large-area characterization of surface topography of objects.

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Section: Discussionmentioning

confidence: 99%

“…The axial precision of this technique depends on the magnification used; 2.5 × and 100 × magnifications, for example, lead to micrometer and nanometer range precision, respectively [8]. Just like in WLI, the acquisition time is relatively long due to the requirement of axial scanning.…”

Section: Introductionmentioning

confidence: 99%

Sub-millimeter depth-resolved digital holography

Rooij

Kalkman

2017

Appl. Opt.

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“…However, the first modern research works related to the development basis of a new measurement technique, as well as the design and construction of the focus variation instrument, began in the early 1990s. Some of these early experiments were described in one chapter of a work by R. Leach [12], as well as by F. Helmli [13] and F. Helmli, R. Danzl, M. Prantl, M. Grabner and S. Scherer [14,15].…”

Section: Characteristics Of the Focus-variation Microscopymentioning

confidence: 99%

“…In order to obtain a surface microtopography, it is necessary to carry out the scan process in the z axis. For each of the positions in this axis, the focus variation (Fz) calculated as a standard deviation of the grey values of a small local region is measured from the equation proposed by F. Helmli in the work [13] and given below:…”

Section: Characteristics Of the Focus-variation Microscopymentioning

confidence: 99%

The Use of Focus-Variation Microscopy for the Assessment of Active Surfaces of a New Generation of Coated Abrasive Tools

Kapłonek

Nadolny

Królczyk

2016

Measurement Science Review

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In this paper, the selected results of measurements and analysis of the active surfaces of a new generation of coated abrasive tools obtained by the use of focus-variation microscopy (FVM) are presented and discussed. The origin of this technique, as well as its general metrological characteristics is briefly described. Additionally, information regarding the focus variation microscope used in the experiments -InfiniteFocus ® IF G4 produced by Alicona Imaging, is also given. The measurements were carried out on microfinishing films (IMFF), abrasive portable belts with Cubitron™ II grains, and single-layer abrasive discs with Trizact™ grains. The obtained results were processed and analyzed employing TalyMap 4.0 software in the form of maps and profiles, surface microtopographies, AbbottFirestone curves, and calculated values of selected areal parameters. This allowed us to describe the active surfaces of the coated abrasive tools, as well as to assess the possibility of applying the FVM technique in such kinds of measurements.

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“…They include various lens systems that can be equipped with measuring lenses, which allows measurements with different resolutions. The semipermeable mirror directs the beam coming out of the source to the optical path of the system, and the lens focuses it on the measured element (Nayar and Nakagawa, 1994;Helmli, 2011). Depending on the topography of the tested element, the light reflects on the surface of the object when it reaches it.…”

Section: Introductionmentioning

confidence: 99%

The Optical Aspect of Errors in Measurements of Surface Asperities Using the Optical Profilometry Method

et al. 2020

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The paper presents the impact of lighting type and direction on measurements of surface asperities using focus-variation microscopy. Particular attention was paid to the direction of lighting when using a light ring. It was pointed out that the lighting direction directly affects the values of the parameters Rt, Rz, and Rc. The article also presents the impact of a light polarizer on the surface topography parameters. It has been shown that the positioning of a sample with a regular and directed structure relative to the optical axis of the light polarizer affects the accuracy of mapping surface asperities. The largest differences were observed for Rz and Rt parameters. A method of using an external polarizer mounted on a focus variation microscope lens was also presented.

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Focus Variation Instruments

Cited by 45 publications

References 3 publications

Sub-millimeter depth-resolved digital holography

Sub-millimeter depth-resolved digital holography

The Use of Focus-Variation Microscopy for the Assessment of Active Surfaces of a New Generation of Coated Abrasive Tools

The Optical Aspect of Errors in Measurements of Surface Asperities Using the Optical Profilometry Method

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