Vortex Interferometric Microscopy with Laguerre-Gaussian Beams

In the present research, we discuss the results of analysis of coherent light beams carrying an optical vortex and propagating through the isotropic medium with a complex surface microrelief and its application to super resolution microscopy. It was shown, that phase analysis of singular beam with single charged centered optical vortex allow to retrieve information about sample surface relief. High spatial resolution caused by vortex helical phase sensitivity to disturbances in wave front after reflection or spreading through studying sample, which can be optically transparent or have a reflecting surface. This method applicable for non-destructive testing of live cells and biological tissues in real-time regime with exceeding optical diffraction limit. Vertical resolution of a microscope based on the phase singularity of Laguerre-Gaussian beams of low order can be achieved down to 5,27 nm for helium-neon laser source for optically transparent and reflecting surfaces. Keywords: optical vortex, phase, microscopy, singularit

Применение голографической микроскопии для детектирования взвешенных в воде частиц

In this paper an express method for measuring sea water pollution using digital holographic microscopy is proposed. The theory of the proposed method is described in detail. The experimental setup is described and the advantages of the proposed method are indicated. In addition, the minimum size of the detected particle is evaluated.В данной работе предложен метод для экспрессного детектирования взвешенных частиц. Проведено теоретическое описание метода. Проанализированы его возможности. Приводится подробная схема экспериментальной установки. Проведена оценка минимального размера обнаруживаемой частицы для предложенной экспериментальной установки.Данное исследование было поддержано Программой Крымского федерального университета им. В.И. Вернадского на 2015-2024 (ВГ21/2019) при финансовой поддержке РФФИ и Совета Министров Респуюдики Крым в соответствии с исследовательским проектом №19-42-910010, а также стрипендиальной программмой Президента Российской Федерации для молодых ученых (СП-745.2019.4)

High Quality 3D Shape Reconstruction via Digital Refocusing and Pupil Apodization in Multi-wavelength Holographic Interferometry.

Multi-wavelength holographic interferometry (MWHI) has good potential for evolving into a high quality 3D shape reconstruction technique. There are several remaining challenges, including 1) depth-of-field limitation, leading to axial dimension inaccuracy of out-of-focus objects; and 2) smearing from shiny smooth objects to their dark dull neighbors, generating fake measurements within the dark area. This research is motivated by the goal of developing an advanced optical metrology system that provides accurate 3D profiles for target object or objects of axial dimension larger than the depth-of-field, and for objects with dramatically different surface conditions. The idea of employing digital refocusing in MWHI has been proposed as a solution to the depth-of-field limitation. One the one hand, traditional single wavelength refocusing formula is revised to reduce sensitivity to wavelength error. Investigation over real example demonstrates promising accuracy and repeatability of reconstructed 3D profiles. On the other hand, a phase contrast based focus detection criterion is developed especially for MWHI, which overcomes the problem of phase unwrapping. The combination for these two innovations gives birth to a systematic strategy of acquiring high quality 3D profiles. Following the first phase contrast based focus detection step, interferometric distance measurement by MWHI is implemented as a next step to conduct relative focus detection with high accuracy. This strategy results in ±100mm 3D profile with micron level axial accuracy, which is not available in traditional extended focus image (EFI) solutions. Pupil apodization has been implemented to address the second challenge of smearing. The process of reflective rough surface inspection has been mathematically modeled, which explains the origin of stray light and the necessity of replacing hard-edged pupil with one of gradually attenuating transmission (apodization). Metrics to optimize pupil types and parameters have been chosen especially for MWHI. A Gaussian apodized pupil has been installed and tested. A reduction of smearing in measurement result has been experimentally demonstrated.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91461/1/xulium_1.pd

Design and Development of an Optical Chip Interferometer For High Precision On-Line Surface Measurement

Advances in manufacturing and with the demand of achieving faster throughput at a lower cost in any industrial setting have put forward the need for embedded metrology. Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the workpiece. Providing closer integration of metrology upon the manufacturing platform will improve material processing and reliability of manufacture for high added value products in ultra-high-precision engineering. Currently, almost all available metrology instrumentation is either too bulky, slow, destructive in terms of damaging the surfaces with a contacting stylus or is carried out off-line. One technology that holds promise for improving the current state-of-the-art in the online measurement of surfaces is hybrid photonic integration. This technique provides for the integration of individual optoelectronic components onto silicon daughter boards which are then incorporated on a silica motherboard containing waveguides to produce a complete photonic circuit. This thesis presents first of its kind a novel chip interferometer sensor based on hybrid integration technology for online surface and dimensional metrology applications. The complete metrology sensor system is structured into two parts; hybrid photonic chip and optical probe. The hybrid photonic chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. Optical probe is a separate entity attached to the integrated optic module which serves as optical stylus for surface scanning in two measurement modes a) A single-point for measuring distance and thus form/surface topography through movement of the device or workpiece, b) Profiling (lateral scanning where assessment of 2D surface parameters may be determined in a single shot. Wavelength scanning and phase shifting inteferometry implemented for the retrival of phase information eventually providing the surface height measurement. The signal analysis methodology for the two measurement modes is described as well as a theoretical and experimental appraisal of the metrology capabilities in terms of range and resolution. The incremetal development of various hybrid photonic modules such as wavelength encoder unit, signal detection unit etc. of the chip interferometer are presented. Initial measurement results from various componets of metrology sensor and the surface measurement results in two measurement modes validate the applicability of the described sensor system as a potential metrology tool for online surface measurement applications

Dispersed reference interferometry for on-machine metrology

The reliance of emerging engineering and scientific applications on nanometre scale surfaces has led to the requirement for embedded metrology instrumentation for on-machine measurement in precision and ultra-precision manufacturing processes. In-situ measurement provides reduction in waste, cost and production cycle time of manufactured components however the presence of environmental noise and difficulties of integration make embedded metrology challenging. In this thesis a review of on-machine methods of optical metrology is provided and commercially available instruments are summarised. The requirement for highly miniaturised methods of distance and surface topography measurement for operation within volume limited manufacturing environments is presented and the necessity for smaller, faster probes with increased range, resolution and robustness outlined. The potential for dispersed reference interferometry (DRI) to exceed the capability of existing single-point remote fibre probing instruments is then introduced. DRI as a technique for single-point distance and surface topography measurement is first evaluated in a bulk optics configuration using a short coherence light source and chromatic dispersion within the reference arm. The resulting spectral interferograms have symmetry positions which are directly related to absolute surface position to yield measurement with a 279 nm axial resolution over a 285 μm axial range. Improvement of this resolution results from introduction of template matching, a signal processing technique which correlates a measured interferogram with a set of pre-calculated template interferograms resulting in a relative method of measurement with an axial resolution of 0.6 nm across the 285 μm axial range. Combination of this high resolution, relative measurement method with low resolution but absolute position data is then explored to improve the robustness of DRI to discontinuous and structured surfaces. Determination of high resolution wraparound order using low resolution absolute data is demonstrated over a 30 μm range, with extension to the full range of DRI expected as future improvements increase the measurement rate. Next a DRI topology is introduced which makes use of miniature common-path probes linked by fibre to a remote interrogation interferometer allowing reduction in size of the on-machine metrology apparatus. Modifications to the DRI are described to enable this common-path remote fibre probing, along with changes to the light source, spectrometer and dispersive element which allow extension of the range of DRI to 800 μm while maintaining nanometre axial resolution. Finally, a further work section offers insights into methods to improve miniaturisation of DRI probes as well as providing discussion of methods of hardware and signal processing optimisation to augment the instrument measurement rate

Multi-Wavelength Polarising Interferometer for In-Process Metrology

Micro-scale and nano-scale surfaces are now fabricated to serve in many fields: from optics needed in telescope/microscope imaging to semiconductors integrated in electronic devices such as smart phones and micro sensors. The production of these surfaces is inspiring the development of new metrology instrumentation that can not only ensure the quality but also optimise the manufacturing process. However, the state-of-the-art offline metrology instruments suffer from a main limitation, namely the inability to operate in the manufacture environment. The industry evolution requires in-process and metric metrology instrumentation that can provide rich surface information within harsh manufacture environment. The specification of such instruments has to be non-destructive, fast, and highly accurate; such instruments have to be combined with a production line. Interferometers offer non-destructive and parallel fashion measurement with nanometre accuracy. A well-established phase-shift interferometer (PSI) is widely used for high measurement accuracy; however, it has two limitations. Firstly, the height difference between two adjacent points on the sample should be smaller than quarter of wavelength (Λ/4), and secondly, a PSI is slow and not suitable for in-process measurements, if a mechanical scanning is used for phase shifting. In order to utilise PSI for in-process measurements, data capturing at single exposure should be used to overcome the environmental disturbances and advanced phase unwrapping methods need to be employed to extend the measurement range beyond (Λ/4). This research aimed to develop a multi-wavelength polarising phase-shift interferometer (MPI) for surface measurement and to investigate the possibility of its use for in-process metrology applications. The target specifications of the proposed instrument are as follows: a vertical measurement range greater than (Λ/4) (i.e. greater than 1 μm) with the resolution of a single wavelength interferometer (i.e. less than 10 nm). The MPI requires no mechanical scanning to obtain the phase shift with an extended measurement range using a single shot technique. This represents an improvement over the conventional single wavelength interferometer in terms of the measurement range and speed. The methodology followed to achieve this study’s aims included reviewing the literature and implementing proof-of-concept experiments using mechanical and non-mechanical methods to acquire phase-shifted colour interferograms, hence determining algorithms for fringe analysis. Finally a novel MPI setup using polarisation technique and Red-Green-Blue (RGB) illumination source was developed that can be used for in-process measurement with extended range. An acousto-optics tuneable filter (AOTF) was successfully employed to simultaneously provide RGB wavelengths with approximately 2 nm linewidth. Several fringe analyses and phase unwrapping algorithms, such as fringe order and best-match methods, were explored to retrieve areal surfaces. Colour crosstalk between cameras’ pixels was also investigated. It was found that the crosstalk is significant. A mathematical model and AOTF tuning capability were used to achieve minimum crosstalk. A spatial two dimensional image filtration was used to enhance the interferograms, hence signal-to-noise improvement. The proposed MPI has successfully measured samples (from 40 nm to 4 μm) with few nanometres accuracy and with single exposure (less than 0.3 second). This MPI has the potential for use in the measurement of surfaces produced by ultra-fast manufacturing such as roll-to-roll (R2R) manufacturing process. In the R2R process, structured surfaces are fabricated on large-area substrates (on the scale of several metres squared) at high speed exceeding several meters per minute. As such, MPI can be potentially used to measure moving surfaces within the manufacturing environment at speed limited only to the single exposure of the cameras

백색광 간섭계를 이용한 표면 형상과 박막 두께의 동시 측정에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2017. 2. 박희재.본 논문에서는 백색광 간섭계를 이용하여 시료의 표면 형상과 박막의 두께 분포를 동시에 측정 할 수 있는 방안에 관한 연구를 진행하였다. 반도체와 디스플레이 산업이 발달함에 따라 패턴이 미세화 되고 박막의 두께가 얇아지면서 표면 형상과 박막의 측정에 관한 요구가 증가하고 있다. 투명 박막의 두께가 얇아지면서 간섭계를 이용한 표면 형상 측정이 어려워지고 있으며, 패턴이 미세화 되면서 박막의 두께 측정도 어려워지고 있다. 따라서 기존의 방법으로 측정이 어려운 투명 박막이 있을 때의 표면 형상 측정과 박막의 두께 분포를 동시에 측정 할 수 있는 방법에 관한 연구를 진행하였다. 표면 형상과 박막의 두께를 측정하기 위해 백색광 간섭 신호로부터 단색광 성분을 복원하였으며, 높은 파장 분해능과 짧은 연산 시간을 위해 zoom FFT를 적용하였다. 복원된 파장 별 성분을 이용하여 표면 형상과 박막의 두께를 동시에 체적으로 측정하였다. 박막의 두께를 측정하기 위해 복원된 파장 별 성분의 크기와 위상을 모두 이용하기 때문에 파장 별 성분 중 크기와 위상 중 하나만 사용하는 기존의 두께 측정 방법에 비해 정확하고 안정적인 두께 측정이 가능하다. 또한 기존의 두께 측정 방법과 달리 두께를 직접 계산하기 때문에 빠른 측정이 가능하다. 표면 형상인 높이를 측정하기 위해 복원된 파장 별 성분 중 위상을 이용하였으며, 파장 별 위상으로부터 두께 성분을 제거하였기 때문에 박막의 영향을 받지 않는 참된 높이 측정이 가능하다. 그렇기 때문에 불투명 시료만 측정 가능하던 기존의 방법과 달리 투명 박막이 있는 시료의 표면 형상 측정이 가능하다. 제안한 측정 방법의 성능을 검증하기 위해 다양한 시뮬레이션과 실험을 진행 하였다. 그 결과 높이 측정 오차율은 3 % 이하, 두께 측정 오차율도 3 % 이하, 640 x 480개의 총 307200개 픽셀의 높이와 두께를 측정하는데 약 12초의 시간이 걸리는 것을 확인 하였다.Chapter 1. 서론 1 1.1. 서론 1 1.2. 연구 동향 7 1.3. 연구 내용 11 Chapter 2. 배경 이론 13 2.1. 반사도 이론 13 2.1.1. 복소 굴절 계수 13 2.1.2. 빛의 반사 및 굴절 15 2.1.2.1. 스넬의 법칙 15 2.1.2.2. 프레넬 방정식 15 2.1.3. 단층 막에서의 반사 17 2.1.4. 다층 막에서의 반사 19 2.2. 간섭 신호 이론 21 2.3. 측정 방법 23 2.3.1. 두께 측정 방법 23 2.3.2. 높이 측정 방법 26 2.3.2.1. 위상 천이 간섭계(Phase Shifting Interferometry, PSI) 27 2.3.2.2. 백색광 주사 간섭계(White-light Scanning Interferometry, WSI) 29 2.3.2.3. 백색광 위상 천이 간섭계(White Light Phase Shifting Interferometry, WLPSI) 32 2.3.2.4. 주파수 영역 분석법(Frequency Domain Analysis, FDA) 33 2.3.2.5. 칼라 간섭계(Color interferometry, 3-PSI) 34 2.3.3. 간섭계를 이용한 두께 측정 방법 36 Chapter 3. 투명 박막의 영향 39 3.1. 투명 박막의 영향 39 3.1.1. 단파장 위상에의 영향 41 3.1.2. 백색광 간섭 신호에의 영향 42 3.1.3. 가시도 함수에의 영향 44 3.1.4. 파장 별 위상에의 영향 46 3.2. 박막에 의한 높이 측정 오차 48 Chapter 4. 파장 별 성분 복원 방법 51 4.1. 분광 방법(Spectral resolved method) 51 4.1.1. 시스템 구성 52 4.1.2. 파장 별 성분 복원 방법 53 4.2. 푸리에 변환 방법(Fourier transform method) 55 4.2.1. 시스템 구성 55 4.2.2. 파장 별 성분 복원 방법 56 4.2.3. Zoom FFT 57 4.2.3.1. Zoom FFT 과정 58 4.2.3.2. Zoom FFT의 효과 60 Chapter 5. 두께 측정 방법 63 5.1. 기존 두께 측정 방법 63 5.2. Phase Extraction Method(PEM) 65 5.2.1. 위상 추출 67 5.2.2. 두께 계산 방법 71 5.3. Advanced Phase Extraction Method(APEM) 72 5.3.1. 위상 추출 방법 73 5.3.2. 두께 계산 방법 77 5.3.3. 측정 분해능 78 5.3.4. 측정 가능 범위 80 5.4. APEM과 PEM의 비교 82 5.4.1. 소광 계수의 영향 83 5.4.2. 측정 민감도(measurement sensitivity) 85 Chapter 6. 높이 측정 방법 91 6.1. 반사도만 이용한 두께 측정 94 6.2. 참된 높이 측정 96 6.2.1. 높이 성분의 위상 분리 96 6.2.2. 높이 측정 97 6.3. 복소수를 이용한 두께 측정 방법 98 6.3.1. 두께 성분의 위상 분리 98 6.3.2. 복소수를 이용한 두께 측정 방법 99 6.4. 반복 연산 100 Chapter 7. 시뮬레이션 102 7.1. 높이 측정 시뮬레이션 102 7.1.1. SiO2/Si의 높이 측정 103 7.1.2. PR/Si의 높이 측정 105 7.1.3. SiO2/BK7의 높이 측정 107 7.1.4. 높이 측정 결과 109 7.2. 두께 측정 시뮬레이션 110 7.2.1. SiO2/Si의 두께 측정 110 7.2.2. PR/Si의 두께 측정 112 7.2.3. SiO2/BK7의 두께 측정 114 7.2.4. 두께 측정 결과 116 Chapter 8. 실험 117 8.1. 시스템 구성 118 8.2. 파수 분해능에 관한 실험 120 8.3. 반복 연산에 관한 실험 127 8.4. 시료에 관한 실험 133 8.4.1. 표준 시편 133 8.4.2. 표준 4분할 시편 141 8.5. 연산 시간 148 Chapter 9. 결론 151 References 153 APPENDICES 162 A. 개구수에 의한 영향 162 B. 기존 높이 측정 방법의 노이즈에 대한 강건성 166 B１. 광원에 의한 오차( n1 ) 166 B２. 외부 진동에 의한 오차( n2 ) 167 B３. 검출기에 의한 오차( n3 ) 168Docto

Characterization of a Digital Holography Diagnostic for In Situ Erosion Measurement of Plasma-Facing Components in Fusion Devices

Fusion energy devices, particularly tokamaks, face the challenge of interior surface damage occurring over time from the heat flux of the high-energy plasma they generate. The ability to monitor the rate of surface modification is therefore imperative, but to date no proven technique exists for real-time erosion measurement of planar regions of interest on plasma-facing components in fusion devices. In order to fill this diagnostic gap, a digital holography system has been established at ORNL [Oak Ridge National Laboratory] for the purpose of measuring the erosion effects of plasma-material interaction in situ. The diagnostic has been designed with the goals of measuring both steady-state and off-normal erosion events. It is capable of operating with either one laser for measuring displacements up to 4.5 microns, or two lasers in tandem to extend the measurement range to an upper limit near 2 millimeters. The performance of the digital holography system is characterized in this dissertation. Discussion of the impetus and background of this project is provided in Chapter I, along with a description of the components and technique. Chapter II covers initial characterization of the measurement fidelity regarding surface roughness of stainless steel surfaces, surface displacements in various sizes, and image noise reduction via multi-frame averaging. A threshold roughness average of 300 nanometers was defined for satisfactory correlation between holographic and validation measurements, and dual-laser measurements were accurate for displacements exceeding 100 microns. In Chapter III, improvements for dual-laser resolution, increased image signal, and noise reduction are described. Chapter IV presents an extensive characterization of ex situ erosion measurement on target plates exposed to an electrothermal arc, with a measured average erosion of 150 nanometers per exposure which indicated that erosion would be distinguishable from noise in situ; the holographic results are compared to profilometry and scanning electron microscopy for validation. In Chapter V, measurements of dynamic surface translations simulating material modification are analyzed, and displacement detection is shown to be accurate. A project summary is given in Chapter VI, and initial results are shown of a successful in situ proof-of-concept demonstration of holographic measurement of erosion from the electrothermal arc