Spectral Method for Multiplexed Phase Retrieval and Application in Optical Imaging in Complex Media

We introduce a generalized version of phase retrieval called multiplexed phase retrieval. We want to recover the phase of amplitude-only measurements from linear combinations of them. This corresponds to the case in which multiple incoherent sources are sampled jointly, and one would like to recover their individual contributions. We show that a recent spectral method developed for phase retrieval can be generalized to this setting, and that its performance follows a phase transition behavior. We apply this new technique to light focusing at depth in a complex medium. Experimentally, although we only have access to the sum of the intensities on multiple targets, we are able to separately focus on each ones, thus opening potential applications in deep fluorescence imaging and light deliver

Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications

Orbital angular momentum (OAM) has aroused a widespread interest in many fields, especially in telecommunications due to its potential for unleashing new capacity in the severely congested spectrum of commercial communication systems. Beams carrying OAM have a helical phase front and a field strength with a singularity along the axial center, which can be used for information transmission, imaging and particle manipulation. The number of orthogonal OAM modes in a single beam is theoretically infinite and each mode is an element of a complete orthogonal basis that can be employed for multiplexing different signals, thus greatly improving the spectrum efficiency. In this paper, we comprehensively summarize and compare the methods for generation and detection of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications and technical challenges of OAM in communications, including free-space optical communications, optical fiber communications, radio communications and acoustic communications. To complete our survey, we also discuss the state of art of particle manipulation and target imaging with OAM beams

Development of Microscopy Systems for Super-Resolution, Whole-Slide, Hyperspectral, and Confocal Imaging

Optical microscope is an important tool for researchers to study small objects. In this thesis, we will focus on the improvement of traditional microscope systems from several aspects including resolution, field of view, speed, cost, compactness, multimodality. In particular, we will investigate computational imaging methods that bypass the limitations with traditional microscope systems by combining the optical hardware design and image processing algorithm. Examples will include optimizing illumination strategy for the Fourier ptychography (FP), developing field-portable high-resolution microscope using a cellphone lens, investigating pattern-illuminated FP for fluorescence microscopy, demonstrating multimodal microscopic imaging with the use of liquid crystal display, achieving fast and accurate autofocusing for whole slide imaging system

Computational temporal ghost imaging

Ghost imaging is a fascinating process, where light interacting with an object is recorded without resolution, but the shape of the object is nevertheless retrieved, thanks to quantum or classical correlations of this interacting light with either a computed or detected random signal. Recently, ghost imaging has been extended to a time object, by using several thousands copies of this periodic object. Here, we present a very simple device, inspired by computational ghost imaging, that allows the retrieval of a single non-reproducible, periodic or non-periodic, temporal signal. The reconstruction is performed by a single shot, spatially multiplexed, measurement of the spatial intensity correlations between computer-generated random images and the images, modulated by a temporal signal, recorded and summed on a chip CMOS camera used with no temporal resolution. Our device allows the reconstruction of either a single temporal signal with monochrome images or wavelength-multiplexed signals with color images

높은 공간 대역폭을 위한 복소 진폭 이미징 및 디스플레이 시스템

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2021. 2. 이병호.빛을 파동으로 이해하면 간섭과 회절을 포함한 다양한 광학 현상을 해석 할 수 있다. 미래 기술이라 불리는 홀로그램, 3차원 이미징 및 3차원 디스플레이 시스템들은 파동의 복소진폭을 이해하고 변조함으로써 구현될 수 있다. 현존하는 광공학 장치를 넘어서는 파동 광학에 기반한 광공학 장치들을 상용화 및 발전시키기 위해 많은 연구가 진행되어왔지만, 지금껏 구현된 장치들은 공간 대역폭 (space-bandwidth product)의 제한으로 인해 그 성능이 대중의 기대에 부합하기 어려움을 겪고있다. 본 논문은 복소 진폭 이미징 및 디스플레이 시스템에서 공간 대역폭을 향상 시키는 방법을 제안한다. 복소 진폭 변조 시스템의 성능은 광학 시스템의 정보량을 나타내는 공간 대역폭에 의해 제한된다. 이 공간 대역폭을 향상시키기 위하여 저자는 다양한 다중화 기술을 적용하며, 동시에 다중화된 정보를 분리하는 알고리즘과 장치를 고안한다. 첫번째로 디지털 홀로그래피 기술에 공간 주파수를 다중화해 대역폭을 효율적으로 활용하는 방법을 고안하여 획득된 홀로그램의 촬영 영역을 증가시킨다. 두번째로, 단일 촬영 푸리에 타이코그래피 (single-shot Fourier ptychography) 기술에서는 광 조사 다중화를 사용하여 이미지 센서에 기록되는 정보의 양을 확장시킨다. 다중화 된 정보를 분해하고 복소 진폭을 획득하기 위하여 새로운 광학 시스템과 전산 알고리즘을 고안하여 해상도가 향상된 복소 진폭을 획득한다. 세번째로, 저자는 홀로그램 디스플레이에 조명 다중화 및 시분할 기술을 적용한다. 다중화 된 정보는 인간의 인지적 시간 대역폭과 제안된 시스템의 공간 필터링의 결합으로 분해된다. 구현된 홀로그래픽 디스플레이는 공간 대역폭이 확장되어 더 넓은 시야각에 삼차원 홀로그램을 제공한다. 본 논문은 작은 공간대역폭이라는 공통된 문제를 공유하는 이미징 및 디스플레이 분야의 발전에 기여할 것으로 기대된다. 저자는 본 연구에서 제안된 방법이 다양한 복소 진폭 변조 시스템의 성능 향상에 영감을 주며, 나아가 삼차원 계측, 홀로그래피, 가상 및 증강현실을 포함한 다양한 미래 산업에 발전에 기여할 수 있기를 기대한다.Understanding light as a wave makes it possible to interpret a variety of phenomena, including interference and diffraction. By modulating the complex amplitude of the wave, hologram, three-dimensional imaging, and three-dimensional display system, called future technologies, can be implemented that surpass the currently commercialized optical engineering devices. Although a lot of research has been conducted to develop and commercialize the wave optical system, state-of-the-art devices are still far from the performance expected by the public due to the limited space-bandwidth product (SBP). This dissertation presents the studies on high SBP for complex amplitude imaging and display systems. The performance of a complex amplitude modulating system is limited by the SBP, which represents the amount of information in the optical system. To improve the SBP of the complex amplitude in a limited amount of information, the author applies various multiplexing techniques suitable for the implemented system. In practice, the spatial frequency multiplexed digital holography is devised by efficiently allocating frequency bandwidth with dual-wavelength light sources. The author also applies illumination multiplexing to the single-shot Fourier ptychography to expand the amount of information recorded in the image sensor. Computational reconstruction algorithm combined with novel optical design allows the acquired multiplexed information to be decomposed in the imaging system, leading to improvement of size of the image or resolution. Furthermore, the author applied illumination multiplexing and temporal multiplexing techniques to holographic displays. The multiplexed information is decomposed by a combination of human perceptual temporal bandwidth and spatial filtering. The SBP enhanced holographic display is implemented, providing a more wide viewing angle. It is expected that this thesis will contribute to the development of the imaging and display fields, which share a common problem of small SBP. The author hopes that the proposed methods will inspire various researchers to approach the implementation of complex amplitude modulating systems, and various future industries, including 3-D inspection, holography, virtual reality, and augmented reality will be realized with high-performance.Abstract i Contents iii List of Tables vi List of Figures vii 1 Introduction 1 1.1 Complex Amplitude of Wave 1 1.2 Complex Amplitude Optical System 3 1.3 Motivation and Purpose of the Dissertation 5 1.4 Scope and Organization 8 2 Space-Bandwidth Product 10 2.1 Overview of Space-Bandwidth Product 10 2.2 Space-Bandwidth Product of Complex Amplitude Imaging Systems 11 2.3 Space-Bandwidth Product of Complex Amplitude Display Systems 13 3 Double Size Complex Amplitude Imaging via Digital Holography 15 3.1 Introduction 15 3.1.1 Digital Holography 16 3.1.2 Frequency Multiplexed Digital Holography 22 3.1.3 Adaptation of Diffractive Grating for Simple Interferometer 24 3.2 Principle 26 3.2.1 Single Diffraction Grating Off-Axis Digital Holography 26 3.2.2 Double Size Implementation with Multiplexed Illumination 29 3.3 Implementation 32 3.4 Experimental Results 34 3.4.1 Resolution Assessment 34 3.4.2 Imaging Result 36 3.4.3 Quantitative 3-D Measurement 38 3.5 Conclusion 42 4 High-Resolution Complex Amplitude Imaging via Fourier Ptychographic Microscopy 43 4.1 Introduction 43 4.1.1 Phase Retrieval 45 4.1.2 Fourier Ptychographic Microscopy 47 4.2 Principle 52 4.2.1 Imaging System for Single-Shot Fourier Ptychographic Microscopy 52 4.2.2 Multiplexed Illumination 55 4.2.3 Reconstruction Algorithm 58 4.3 Implementation 60 4.3.1 Numerical Simulation 60 4.3.2 System Design 64 4.4 Results and Assessment 65 4.4.1 Resolution 65 4.4.2 Phase Retrieval of Biological Specimen 68 4.5 Discussion 71 4.6 Conclusion 73 5 Viewing Angle Enhancement for Holographic Display 74 5.1 Introduction 74 5.1.1 Complex Amplitude Representation 76 5.1.2 DMD Holographic Displays 79 5.2 Principle 81 5.2.1 Structured Illumination 81 5.2.2 TM with Array System 83 5.2.3 Time Domain Design 84 5.3 Implementation 85 5.3.1 Hardware Design 85 5.3.2 Frequency Domain Design 85 5.3.3 Aberration Correction 87 5.4 Results 88 5.5 Discussion 92 5.5.1 Speckle 92 5.5.2 Applications for Near-eye Displays 94 5.6 Conclusion 99 6 Conclusion 100 Appendix 116 Abstract (In Korean) 117Docto

Ptychographic amplitude and phase reconstruction of bichromatic vortex beams

We experimentally demonstrate that ptychographic coherent diffractive imaging can be used to simultaneously characterize the amplitude and phase of bichromatic orbital angular momenta-shaped vortex beams, which consist of a fundamental field, together with its copropagating second-harmonic field. In contrast to most other orbital angular momentum characterization methods, this approach solves for the complex field of a hyperspectral beam. This technique can also be used to characterize other phase-structured illumination beams, and, in the future, will be able to be extended to other complex fields in the extreme ultraviolet or X-ray spectral regions, as well as to matter waves.The NSF STROBE STC (DMR-1548924); DOE BES AMOS grant (DE-FG02-99ER14982); the NSF GRFP (DGE 1650115); 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation; Junta de Castilla y León (SA046U16); Ministerio de Economía y Competitividad (FIS2016-75652-P)

Optical image compression and encryption methods

International audienceOver the years extensive studies have been carried out to apply coherent optics methods in real-time communications and image transmission. This is especially true when a large amount of information needs to be processed, e.g., in high-resolution imaging. The recent progress in data-processing networks and communication systems has considerably increased the capacity of information exchange. However, the transmitted data can be intercepted by nonauthorized people. This explains why considerable effort is being devoted at the current time to data encryption and secure transmission. In addition, only a small part of the overall information is really useful for many applications. Consequently, applications can tolerate information compression that requires important processing when the transmission bit rate is taken into account. To enable efficient and secure information exchange, it is often necessary to reduce the amount of transmitted information. In this context, much work has been undertaken using the principle of coherent optics filtering for selecting relevant information and encrypting it. Compression and encryption operations are often carried out separately, although they are strongly related and can influence each other. Optical processing methodologies, based on filtering, are described that are applicable to transmission and/or data storage. Finally, the advantages and limitations of a set of optical compression and encryption methods are discussed

Fourier ptychography: current applications and future promises

Traditional imaging systems exhibit a well-known trade-off between the resolution and the field of view of their captured images. Typical cameras and microscopes can either “zoom in” and image at high-resolution, or they can “zoom out” to see a larger area at lower resolution, but can rarely achieve both effects simultaneously. In this review, we present details about a relatively new procedure termed Fourier ptychography (FP), which addresses the above trade-off to produce gigapixel-scale images without requiring any moving parts. To accomplish this, FP captures multiple low-resolution, large field-of-view images and computationally combines them in the Fourier domain into a high-resolution, large field-of-view result. Here, we present details about the various implementations of FP and highlight its demonstrated advantages to date, such as aberration recovery, phase imaging, and 3D tomographic reconstruction, to name a few. After providing some basics about FP, we list important details for successful experimental implementation, discuss its relationship with other computational imaging techniques, and point to the latest advances in the field while highlighting persisting challenges