Review of post-process optical form metrology for industrial-grade metal additive manufactured parts

The scope of this review is to investigate the main post-process optical form measurement technologies available in industry today and to determine whether they are applicable to industrial-grade metal additive manufactured parts. An in-depth review of the operation of optical three-dimensional form measurement technologies applicable to metal additive manufacturing is presented, with a focus on their fundamental limitations. Looking into the future, some alternative candidate measurement technologies potentially applicable to metal additive manufacturing will be discussed, which either provide higher accuracy than currently available techniques but lack measurement volume, or inversely, which operate in the appropriate measurement volume but are not currently accurate enough to be used for industrial measurement

State-of-The-Art and Applications of 3D Imaging Sensors in Industry, Cultural Heritage, Medicine, and Criminal Investigation

3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a crucial role in the achievement of compactness, robustness and flexibility of the sensors. Today, several 3D sensors are available on the market, even in combination with other sensors in a “sensor fusion” approach. An importance equal to that of physical miniaturization has the portability of the measurements, via suitable interfaces, into software environments designed for their elaboration, e.g., CAD-CAM systems, virtual renders, and rapid prototyping tools. In this paper, following an overview of the state-of-art of 3D imaging sensors, a number of significant examples of their use are presented, with particular reference to industry, heritage, medicine, and criminal investigation applications

Analyses of stone surfaces by optical methods

Ornamental stone products are generally used for decorative cladding. A major quality parameter is their aesthetical appearance, which directly impacts their commercial value. The surface quality of stone products depends on the presence of defects both due to the unpredictability of natural materials and to the actual manufacturing process. This work starts reviewing the literature about optical methods for stone surface inspection. A classification is then proposed focusing on their industrial applicability in order to provide a guideline for future investigations. Three innovative systems are proposed and described in details: a vision system, an optical profilometer and a reflectometer for the inspection of polished, bush-hammered, sand-blasted, flame-finished, waterjet processed, and laser engraved surfaces

Investigation of vibrations of elements of packages with supplementary stiffness elements

The paper analyzes the eigenmodes of bending vibrations of ecological paperboard as of a plate by taking into account the additional effect of bending vibrations of a string included in the paperboard. The tension of the string can be used to control the eigenmodes of the analyzed paperboard. Experimental investigations were conducted using time-averaged projection moiré techniques on a specially developed experimental setup. The performed experimental and numerical studies demonstrated that the first eigenmodes of vibrations of the paperboard with supplementary stiffness elements occur at higher frequencies when compared with the conventional paperboard. The obtained eigenmodes enable to determine not only the vibration characteristics of the wall of the package by nondestructive methods, but also the strength parameters of the material of the package. The obtained results are used in the process of design of package elements

적외선 산란형 근접장 주사 광학 현미경을 이용한 그래핀 표면 위 화학반응 연구

학위논문 (박사) -- 서울대학교 대학원 : 자연과학대학 화학부, 2021. 2. 김지환.This thesis focuses on chemical reaction on graphene surface using atomic force microscopy (AFM) based infrared-scattering type scanning near field optical microscopy (IR-sSNOM). Various studies have been conducted for the unique physical and chemical properties of graphene surface. Accompanied by such advancements, particularly, multi-layer graphene was spotlighted for its facile tunability of bandgap that can be controlled by stacking angles, external electric field, or chemical doping. However, the general technique used to analyze graphene surface, such as Infrared spectroscopy, has fatal limitation. It is impossible to study nanoscopic chemical reactions on graphene surface due to Abbe’s diffraction limit. Regretfully, Raman spectroscopy, which is most commonly used for graphene analysis, also has many limitations. Moreover, this tool only perceives changes of the D, G and 2D band spectra hence fails to capture direct chemical reaction product information. From this point of view, I have two main reasons to pursue this study. First, as a technical point of view, IR-sSNOM is known for its high sensitive nano resolution. It is possible to get IR spectrum of graphene domain less than 10 μm. Additionally, there is no big limitation in sample condition unlike scanning tunneling microscope. In this respect, this technique is ideal tool to analyze graphene surface reaction. Secondly, graphene surface reaction study is worth to investigate as application of electronic graphene as well as prototypical model for organic chemistry. Form this model system study, it is possible to understand pi-pi interactive mechanisms but also catalytic mechanisms of graphene. I believe studying graphene surface reaction will bring new insight to chemistry field본 논문은 주사탐침현미경 기반의 적외선 산란형 근접장 주사 광학 현미경 (IR-sSNOM)을 사용하여 그래핀 표면 위 화학반응에 중점을 둔다. 그래핀 표면의 물리적 및 화학적 고유한 특성에 대해 다양한 연구가 수행되어 왔다. 이러한 발전과 함께, 특히 손쉽게 다층 그래핀의 겹쳐진 각도나 외부에서 인가되는 전기장 또는 화학적 불순물 추가를 통해 띠 간격 조절이 가능해 각광을 받아왔다. 그러나 이런 그래핀의 특성을 분석하는데 사용되는 일반적인 적외선 분광 기법에는 치명적인 한계가 있다. 아베 회절 한계로 인해 그래핀 표면의 나노 화학 반응을 연구하는 것이 불가능하다. 유감스럽게도 그래핀분석에 가장 많이 활용되는 라만 분광 기법에도 동일한 문제가 있다. 또한 이 라만 분광 기법은 D, G 및 2D 대역 스펙트럼의 변화만 감지하므로 직접적인 화학 분자의 정보를 알지 못한다. 이러한 관점에서 저는 두가지의 목표로 이 연구를 진행하고자 한다. 첫째, 분광학적 시각에서 적외선 산란형 근접장 주사 광학 현미경은 고감도의 나노 해상도를 가지는 것으로 잘 알려져 있다. 이 분광 기기를 이용하면 그래핀 10um 미만의 영역의 IR 스펙트럼을 얻을 수 있다. 또한 주사 터널 현미경과 달리 시료 조건에 큰 제한이 없다. 이러한 점에서 이 적외선 산란형 근접장 주사 광학 현미경은 그래핀 표면 위 반응을 분석하는데 이상적인 도구이다. 둘째, 이러한 그래핀 표면 반응 연구는 유기 화학의 원형 모델이 될 뿐만 아니라 그래핀의 전자 응용으로 연구 할 가치가 있다. 이 유기 화학의 원형 모델 시스템 연구를 통해 pi-pi 상호 작용의 메커니즘뿐만 아니라 그래핀 촉매 메커니즘에 대해 이해할 수 있을 것이다. 이러한 그래핀 표면 반응을 연구를 통해 화학 분야에 새로운 통찰력을 가져올 것이라고 확신한다- Table of contents - Chapter 1: Introduction to scattering-type scanning near-field optical microscopy 1.1 Diffraction limit in classical optical microscopy - 7 page 1.2 Nanoscale imaging - 8 page 1.3 Scattering-type near-field optical microscopy - 12 page 1.4 Point-dipole Modeling for IR s-SNOM - 13 page 1.5 Interferometric detection 1.5.1 Homodyne interferometric detection - 17 page 1.5.2 Pseudo-heterodyne detection - 20 page 1.6 References - 24 page Chapter 2: Introduction to graphene surface chemistry 2.1 Graphene Raman spectroscopy - 27 page 2.2 Graphene surface chemistry - 29 page 2.3 Moiré-patterned graphene - 31 page 2.4 Reference - 33 page Chapter 3: Nanoscale visualization of multilayer graphene Mapping of Bernal and non-Bernal stacking domains in bilayer graphene using infrared nanoscopy 3.1.1 Introduction - 39 page 3.1.2 Experiment - 42 page 3.1.3 Results and discussion - 44 page 3.1.4 Conclusion - 53 page 3.1.5 Reference - 54 page Narrow infrared resonance of commensurate-incommensurate transition for tetramer graphene on hexagonal boron nitride 4.1.1 Introduction - 57 page 4.1.2 Experiment - 60 page 4.1.3 Results and discussion - 61 page 4.1.4 Conclusion - 72 page Chapter 4: Studies of selective chemical reaction on graphene surface Stacking-specific reversible oxidation of bilayer graphene 5.1.1 Introduction - 77 page 5.1.2 Experiment - 79 page 5.1.3 Results and discussion - 83 page 5.1.4 Conclusion - 97 page 5.1.5 Reference - 98 page Infrared nano-spectroscopy study on oxidized graphene surface 6.1.1 Introduction - 102 page 6.1.2 Experiment - 104 page 6.1.3 Results and discussion - 106 page 6.1.4 Conclusion - 111 page 7.1.5 Reference - 112 page Reversible multilayer CO2 loading in bilayer graphene 7.1.1 Introduction - 113 page 7.1.2 Experiment - 115 page 7.1.3 Results and discussion - 116 page 7.1.4 Conclusion - 134 page 7.1.5 Reference - 135 pageDocto

3D Shape Measurement of Objects in Motion and Objects with Complex Surfaces

This thesis aims to address the issues caused by high reflective surface and object with motion in the three dimensional (3D) shape measurement based on phase shifting profilometry (PSP). Firstly, the influence of the reflectivity of the object surface on the fringe patterns is analysed. One of the essential factors related to phase precision is modulation index, which has a direct relationship with the surface reflectivity. A comparative study focusing on the modulation index of different materials is presented. The distribution of modulation index for different material samples is statistically analysed, which leads to the conclusion that the modulation index is determined by the diffuse reflectivity. Then the method based on optimized combination of multiple reflected image patterns is proposed to address the saturation issue and improve the accuracy for the reconstruction of object with high reflectivity.A set of phase shifted sinusoidal fringe patterns with different exposure time are projected to the object and then captured by camera. Then a set of masks are generated to select the data for the compositing. Maximalsignal-to-noise ratio combining model is employed to form the composite images pattern. The composite images are then used to phase mapping.Comparing to the method only using the highest intensity of pixels for compositing image, the signal noise ratio (SNR) of composite image is increased due to more efficient use of information carried by the images

Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry

Quick mass production of homogeneous thin film material is required in paper, plastic, fabric, and thin film industries. Due to the high feed rates and small thicknesses, machine vision and other nondestructive evaluation techniques are used to ensure consistent, defect-free material by continuously assessing post-production quality. One of the fastest growing inspection areas is for 0.5-500 micrometer thick thin films, which are used for semiconductor wafers, amorphous photovoltaics, optical films, plastics, and organic and inorganic membranes. As a demonstration application, a prototype roll-feed imaging system has been designed to inspect high-temperature polymer electrolyte membrane (PEM), used for fuel cells, after being die cast onto a moving transparent substrate. The inspection system continuously detects thin film defects and classifies them with a neural network into categories of holes, bubbles, thinning, and gels, with a 1.2% false alarm rate, 7.1% escape rate, and classification accuracy of 96.1%. In slot die casting processes, defect types are indicative of a misbalance in the mass flow rate and web speed; so, based on the classified defects, the inspection system informs the operator of corrective adjustments to these manufacturing parameters. Thickness uniformity is also critical to membrane functionality, so a real-time, full-field transmission densitometer has been created to measure the bi-directional thickness profile of the semi-transparent PEM between 25-400 micrometers. The local thickness of the 75 mm x 100 mm imaged area is determined by converting the optical density of the sample to thickness with the Beer-Lambert law. The PEM extinction coefficient is determined to be 1.4 D/mm and the average thickness error is found to be 4.7%. Finally, the defect inspection and thickness profilometry systems are compiled into a specially-designed graphical user interface for intuitive real-time operation and visualization.M.S.Committee Chair: Tequila Harris; Committee Member: Levent Degertekin; Committee Member: Wayne Dale

Vibrations of elements of packages with supplementary stiffening bio-degradable strips

This paper analyzes the eigenmodes of bending vibrations of a paperboard, which is treated as a plate, taking into account the additional effect of bending vibrations of a supplementary bio-degradable strip included in the paperboard. Results of experimental investigations by means of method of time-averaged projection moiré are presented in the paper and comparisons between the experimental and numerical results are performed. The study revealed that the paperboard with supplementary stiffness elements of bio-degradable strip is more ecological: the introduction of additional stiffness elements to the composition of the paperboard in the packaging material has an effect of additional rigidity of the structure and thus reduces the amplitudes of resonance vibrations. The obtained results are applied in the process of design of elements of packages

Non-contact free-form shape measurement for coordinate measuring machines

Precision measurement of manufactured parts commonly uses contact measurement methods. A Coordinate Measuring Machine (CMM) mounted probe touches the surface of the part, recording the probe’s tip position at each contact. Recently, devices have been developed that continuously scan the probe tip across the surface, allowing points to be measured more quickly. Contact measurement is accurate and fast for shapes that are easily parameterized such as a sphere or a plane, but is slow and requires considerable user input for more general objects such as those with free-form surfaces. Phase stepping fringe projection and photogrammetry are common non-contact shape measurement methods. Photogrammetry builds a 3D model of feature points from images of an object taken from multiple perspectives. In phase stepping fringe projection a series of sinusoidal patterns, with a phase shift between each, is projected towards an object. A camera records a corresponding series of images. The phase of the pattern at each imaged point is calculated and converted to a 3D representation of the object’s surface. Techniques combining phase stepping fringe projection and photogrammetry were developed and are described here. The eventual aim is to develop an optical probe for a CMM to enable non-contact measurement of objects in an industrial setting. For the CMM to accurately report its position the probe must be small, light, and robust. The methods currently used to provide a phase shift require either an accurately calibrated translation stage to move an internal component, or a programmable projector. Neither of these implementations can be practically mounted on a CMM due to size and weight limits or the delicate parts required. A CMM probe consisting of a single camera and a fringe projector was developed. The fringe projector projects a fixed fringe pattern. Phase steps are created by moving the CMM mounted probe, taking advantage of the geometry of the fringe projection system. New techniques to calculate phase from phase stepped images created by relative motion of probe and object are proposed, mathematically modelled, and tested experimentally. Novel techniques for absolute measurement of surfaces by viewing an object from different perspectives are developed. A prototype probe is used to demonstrate measurements of a variety of objects.Engineering and Physical Sciences Research Council (EPSRC) Grant No. GR/T11289/0

Optical Fiber Interferometric Sensors

The contributions presented in this book series portray the advances of the research in the field of interferometric photonic technology and its novel applications. The wide scope explored by the range of different contributions intends to provide a synopsis of the current research trends and the state of the art in this field, covering recent technological improvements, new production methodologies and emerging applications, for researchers coming from different fields of science and industry. The manuscripts published in the Special issue, and re-printed in this book series, report on topics that range from interferometric sensors for thickness and dynamic displacement measurement, up to pulse wave and spirometry applications