scholarly journals Extension and Limits of Depolarization-Fringe Contrast Roughness Method in Sub-Micron Domain

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5572
Author(s):  
Franziska Pöller ◽  
Félix Salazar Bloise ◽  
Martin Jakobi ◽  
Jie Dong ◽  
Alexander W. Koch
Keyword(s):  
Scattered Light ◽  
Measurement Techniques ◽  
Michelson Interferometer ◽  
Measurement Range ◽  
Quarter Wave Plate ◽  
Contact Method ◽  
Reference Mirror ◽  
Fringe Contrast ◽  
Contrast Technique ◽  
Quarter Wave

To guarantee quality standards for the industry, surface properties, particularly those of roughness, must be considered in many areas of application. Today, several methods are available on the market, but some damage the surface to be tested as they measure it by contact. A non-contact method for the precise estimation of sub-micron roughness values is presented, which can be used as an extension of existing roughness measurement techniques to improve them further considering the depolarized light reflected by the sample. This setup is based on a Michelson interferometer, and by introducing a quarter-wave plate on a half part of the reference mirror, the surface roughness can be directly derived by measuring the fringe contrasts. This article introduces a simple model describing the intensity distortions resulting from the microscopic roughness in divided interferograms when considering depolarization. This work aimed to extend the measurement range of the technique developed in a previous work, in which depolarization effects are taken into account. For verification, the experimental results were compared with the fringe contrast technique, which does not consider the depolarization of the scattered light, especially regarding the extended wavelength interval, highlighting the limits of the technique. In addition, simulations of the experiments are presented. For comparison, the reference values of the sample roughness were also generated by measurements with a stylus profiler.

scholarly journals Non-Contact Roughness Measurement in Sub-Micron Range by Considering Depolarization Effects

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2215
Author(s):  
Franziska Pöller ◽  
Félix Salazar Bloise ◽  
Martin Jakobi ◽  
Shengjia Wang ◽  
Jie Dong ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Michelson Interferometer ◽  
Experimental Results ◽  
Quarter Wave Plate ◽  
Contact Method ◽  
Reference Mirror ◽  
Small Surface ◽  
Measuring Surface ◽  
Quarter Wave

The characteristics of a surface, particularly the roughness, play an important role in different fields of the industry and have to be considered to ensure quality standards. Currently, there are numerous sophisticated methods for measuring surface roughness but plenty of them cause long-term damage because they are in contact with the sample. This article presents a non-contact method to accurately determine small surface roughnesses resulting from the consideration of the depolarization effects caused by the rough surface. This technique can be applied as an extension in various roughness measurements and improves the approach of Chandley’s technique, which does not take into account the depolarization of the light scattered by the sample. The experimental setup and the measurements are easy to perform. The essential component is a quarter wave plate, which is incorporated into a Michelson interferometer. With the resulting two different contrasts and the recorded intensities of the sample and the reference mirror, the surface roughness can be estimated straightforwardly. This article details the theoretical approach, followed by the experimental results and the corresponding uncertainties. The experimental results are compared with Chandley’s method. In order to have reference roughness values of the samples, measurements with a stylus profilometer and with a confocal microscope are performed and compared.

Mobile Optical Coherence Tomography Sensor for Surface Layers Testing

2012 ◽  
Vol 518 ◽  
pp. 201-210
Author(s):  
Sławomir Tomczewski ◽  
Leszek Salbut
Keyword(s):  
Optical Coherence Tomography ◽  
Measurement Range ◽  
Optical Coherence ◽  
Surface Layers ◽  
Reference Mirror ◽  
Fringe Contrast ◽  
Contrast Analysis ◽  
Smart Pixel ◽  
Compact Design ◽  
Axial Scanning

In the paper the new type of mobile sensor based on optical coherence tomography is presented. For increasing the measurement range the special dynamic focusing system which moves imaging plane during axial scanning process is used. Therefore developed system allows focusing on measured layer. Additionally, for image analysis the special type of CMOS matrix (called smart-pixel camera), synchronized with a reference mirror transducer, is applied. Due to hardware realization of a fringe contrast analysis simultaneously in each pixel with high frequency, the time of measurement decreases significantly. These advantages together with a compact design allow the sensor to be used as the mobile device for measurements of surface topography, thickness of surface layers and subsurface defects detection in laboratory, workshop and out-door conditions. Calibration of the designed sensor and its application to the technological measurements of the sticker label layers are presented and discussed.

Investigation of particulate systems using optical pathlength spectroscopy

2000 ◽  
Vol 627 ◽  
Author(s):  
Gabriel Popescu ◽  
Aristide Dogariu
Keyword(s):  
Path Length ◽  
Random Media ◽  
Michelson Interferometer ◽  
Industrial Process ◽  
Optical Path Length ◽  
Industrial Applications ◽  
Optical Path ◽  
Interference Signal ◽  
Optical Length ◽  
Reference Mirror

ABSTRACTIn many industrial applications involving granular media, knowledge about the structural transformations suffered during the industrial process is desirable. Optical techniques are noninvasive, fast, and versatile tools for monitoring such transformations. We have recently introduced optical path-length spectroscopy as a new technique for random media investigation. The principle of the method is to use a partially coherent source in a Michelson interferometer, where the fields from a reference mirror and the sample are combined to obtain an interference signal. When the system under investigation is a multiple-scattering medium, by tuning the optical length of the reference arm, the optical path-length probability density of light backscattered from the sample is obtained. This distribution carries information about the structural details of the medium. In the present paper, we apply the technique of optical path-length spectroscopy to investigate inhomogeneous distributions of particulate dielectrics such as ceramics and powders. The experiments are performed on suspensions of systems with different solid loads, as well as on powders and suspensions of particles with different sizes. We show that the methodology is highly sensitive to changes in volume concentration and particle size and, therefore, it can be successfully used for real-time monitoring. In addition, the technique is fiber optic-based and has all the advantages associated with the inherent versatility.

scholarly journals In-Process Diameter Measurement Technique for Micro-Optical Fiber with Standing Wave Illumination

2021 ◽  
Author(s):  
Masaki Michihata ◽  
Zhao Zheng ◽  
Daiki Funaiwa ◽  
Sojiro Murakami ◽  
Shotaro Kadoya ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Standing Wave ◽  
Dynamic Range ◽  
Scattered Light ◽  
High Dynamic Range ◽  
Measurement Range ◽  
Diameter Distribution ◽  
Process Measurement ◽  
Air Turbulence ◽  
Tapered Optical Fiber

AbstractIn this paper, we propose an in-process measurement method of the diameter of micro-optical fiber such as a tapered optical fiber. The proposed technique is based on analyzing optically scattered light generated by standing wave illumination. The proposed method is significant in that it requires an only limited measurement range and does not require a high dynamic range sensor. These properties are suitable for in-process measurement. This experiment verified that the proposed method could measure a fiber diameter as stable as ± 0.01 μm under an air turbulence environment. As a result of comparing the measured diameter distribution with those by scanning electron microscopy, it was confirmed that the proposed method has a measurement accuracy better than several hundred nanometers.

scholarly journals None sharp corner localized surface plasmons resonance based ultrathin metasurface single layer quarter wave plate

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Qinyu Qian ◽  
Pengfei Liu ◽  
Li Fan ◽  
Liang Zhao ◽  
Chinhua Wang
Keyword(s):  
Surface Plasmons ◽  
Amplitude Ratio ◽  
Single Layer ◽  
Quarter Wave Plate ◽  
Localized Surface Plasmons ◽  
Sharp Corner ◽  
Wave Plate ◽  
Nanophotonic Devices ◽  
Elliptical Ring ◽  
Quarter Wave

AbstractWe report on a non-sharp-corner quarter wave plate (NCQW) within the single layer of only 8 nm thickness structured by the Ag hollow elliptical ring array, where the strong localized surface plasmons (LSP) resonances are excited. By manipulating the parameters of the hollow elliptical ring, the transmitted amplitude and phase of the two orthogonal components are well controlled. The phase difference of π/2 and amplitude ratio of 1 is realized simultaneously at the wavelength of 834 nm with the transmission of 0.46. The proposed NCQW also works well in an ultrawide wavelength band of 110 nm, which suggests an efficient way of exciting LSP resonances and designing wave plates, and provides a great potential for advanced nanophotonic devices and integrated photonic systems.

scholarly journals High-Contrast and Scattering-Type Transflective Liquid Crystal Displays Based on Polymer-Network Liquid Crystals

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 739 ◽  
Author(s):  
Cheng-Kai Liu ◽  
Wei-Hsuan Chen ◽  
Chung-Yu Li ◽  
Ko-Ting Cheng
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Liquid Crystal Displays ◽  
Quarter Wave Plate ◽  
High Contrast ◽  
Trade Off ◽  
Twisted Nematic ◽  
Quarter Wave ◽  
The Common ◽  
Linear Polarizer

The methods to enhance contrast ratios (CRs) in scattering-type transflective liquid crystal displays (ST-TRLCDs) based on polymer-network liquid crystal (PNLC) cells are investigated. Two configurations of ST-TRLCDs are studied and are compared with the common ST-TRLCDs. According to the comparisons, CRs are effectively enhanced by assembling a linear polarizer at the suitable position to achieve better dark states in the transmissive and reflective modes of the reported ST-TRLCDs with the optimized configuration, and its main trade-off is the loss of brightness in the reflective modes. The PNLC cell, which works as an electrically switchable polarizer herein, can be a PN-90° twisted nematic LC (PN-90° TNLC) cell or a homogeneous PNLC (H-PNLC) cell. The optoelectric properties of PN-90° TNLC and those of H-PNLC cells are compared in detail, and the results determine that the ST-TRLCD with the optimized configuration using an H-PNLC cell can achieve the highest CR. Moreover, no quarter-wave plate is used in the ST-TRLCD with the optimized configuration, so a parallax problem caused by QWPs can be solved. Other methods for enhancing the CRs of the ST-TRLCDs are also discussed.

scholarly journals Switchable Ultrathin Quarter-wave Plate in Terahertz Using Active Phase-change Metasurface

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Dacheng Wang ◽  
Lingchao Zhang ◽  
Yinghong Gu ◽  
M. Q. Mehmood ◽  
Yandong Gong ◽  
...  
Keyword(s):  
Phase Change ◽  
Active Phase ◽  
Quarter Wave Plate ◽  
Wave Plate ◽  
Quarter Wave
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