Fourier tabanlı optik modülasyon ile tek çekimde alt-pozlama görüntülerinin çıkarılması

Through pixel-wise optical coding of images during exposure time, it is possible to extract sub-exposure images from a single capture. Such a capability can be used for different purposes, including high-speed imaging, high-dynamic-range imaging and compressed sensing. Here, we demonstrate a sub-exposure image extraction method, where the exposure coding pattern is inspired from frequency division multiplexing idea of communication systems. The coding masks modulate subexposure images in such a way that they are placed in non-overlapping regions in Fourier domain. The sub-exposure image extraction process involves digital filtering of the captured signal with proper band-pass filters. The prototype imaging system incorporates a Liquid Crystal over Silicon (LCoS) based spatial light modulator synchronized with a camera for pixel-wise exposure coding.Pozlama süresinde piksellerin optik olarak kodlanması vasıtasıyla, tek bir görüntü kaydından birden çok alt-pozlama görüntüsünün elde edilmesi mümkündür. Böyle bir kabiliyet; yüksek hızlı görüntüleme, yüksek dinamik aralıklı görüntüleme ve sıkıştırılmış görüntüleme gibi çeşitli amaçlar için kullanılabilir. Bu tezde, kodlama örüntüsünün haberleşme sistemlerinde kullanılan "frekans bölüşümlü çoğullama" fikrinden esinlenildiği bir alt-pozlama görüntüsü elde etme metodu sunulmaktadır. Bu metodda; optik maskeler, alt-pozlama görüntülerini Fourier uzayında örtüşmeyecek şekilde yerleştirilmesini sağlayacak şekilde tasarlanmıştır. Alt-pozlama görüntüleri, kaydedilmiş sinyalin uygun şekilde bant-geçiren filtrelerden geçirilmesiyle elde edilmektedir. Prototip görüntüleme sistemi; piksel bazlı kodlama için Liquid Crystal over Silicon (LCoS) teknolojisine dayalı bir uzamsal ışık modülatörü ile senkronize edilmiş bir kamera vasıtasıya gerçekleştirilmiştir

Single-shot nanosecond-resolution multiframe passive imaging by multiplexed structured image capture

The Multiplexed Structured Image Capture (MUSIC) technique is used to demonstrate single-shot multiframe passive imaging, with a nanosecond difference between the resulting images. This technique uses modulation of light from a scene before imaging, in order to encode the target’s temporal evolution into spatial frequency shifts, each of which corresponds to a unique time and results in individual and distinct snapshots. The resulting images correspond to different effective imaging gate times, because of the optical path delays. Computer processing of the multiplexed single-shot image recovers the nanosecond-resolution evolution. The MUSIC technique is used to demonstrate imaging of a laser-induced plasma. Simultaneous single-shot measurements of electron numbers by coherent microwave scattering were obtained and showed good agreement with MUSIC characterization. The MUSIC technique demonstrates spatial modulation of images used for passive imaging. This allows multiple frames to be stacked into a single image. This method could also pave the way for real-time imaging and characterization of ultrafast processes and visualization, as well as general tracking of fast objects

Overlapped Fourier coding for optical aberration removal

We present an imaging procedure that simultaneously optimizes a camera’s resolution and retrieves a sample’s phase over a sequence of snapshots. The technique, termed overlapped Fourier coding (OFC), first digitally pans a small aperture across a camera’s pupil plane with a spatial light modulator. At each aperture location, a unique image is acquired. The OFC algorithm then fuses these low-resolution images into a full-resolution estimate of the complex optical field incident upon the detector. Simultaneously, the algorithm utilizes redundancies within the acquired dataset to computationally estimate and remove unknown optical aberrations and system misalignments via simulated annealing. The result is an imaging system that can computationally overcome its optical imperfections to offer enhanced resolution, at the expense of taking multiple snapshots over time

Low-cost,stand-off, 2D+3D face imaging for biometric identification using Fourier transform profilometry –Update

Lockheed Martin Coherent Technologies is developing laser-based technologies for stand-off 2D+3D face imaging for biometric identification. Among other potential industrial, commercial, and governmental users, the Department of Homeland Security (DHS) and the Department of Defense (DoD) desire the ability to capture biometric data from minimally cooperative subjects with a minimally invasive system at stand-off distances. The initial applications are fixed installations for relatively large volume access points such as security check points and transportation gateways for which minimal cooperation, stand-off operation, and real-time operation are desired so that the biometric identification process will have little impact on traffic flow. Last year we presented a paper on the development and testing of a 2D+3D face imager breadboard based on th

Low-cost, stand-off, 2D+3D face imaging for biometric identification using Fourier transform profilometry

EDU meets the goals for the 2D+3D face imager of Class 1M eye-safe operation, 2D+3D face capture at \u3e20-m stand-off distance, ~1-mm lateral resolution, ~1-mm rang

Roadmap on optical security

Postprint (author's final draft

Image Processing Applications in Real Life: 2D Fragmented Image and Document Reassembly and Frequency Division Multiplexed Imaging

In this era of modern technology, image processing is one the most studied disciplines of signal processing and its applications can be found in every aspect of our daily life. In this work three main applications for image processing has been studied. In chapter 1, frequency division multiplexed imaging (FDMI), a novel idea in the field of computational photography, has been introduced. Using FDMI, multiple images are captured simultaneously in a single shot and can later be extracted from the multiplexed image. This is achieved by spatially modulating the images so that they are placed at different locations in the Fourier domain. Finally, a Texas Instruments digital micromirror device (DMD) based implementation of FDMI is presented and results are shown. Chapter 2 discusses the problem of image reassembly which is to restore an image back to its original form from its pieces after it has been fragmented due to different destructive reasons. We propose an efficient algorithm for 2D image fragment reassembly problem based on solving a variation of Longest Common Subsequence (LCS) problem. Our processing pipeline has three steps. First, the boundary of each fragment is extracted automatically; second, a novel boundary matching is performed by solving LCS to identify the best possible adjacency relationship among image fragment pairs; finally, a multi-piece global alignment is used to filter out incorrect pairwise matches and compose the final image. We perform experiments on complicated image fragment datasets and compare our results with existing methods to show the improved efficiency and robustness of our method. The problem of reassembling a hand-torn or machine-shredded document back to its original form is another useful version of the image reassembly problem. Reassembling a shredded document is different from reassembling an ordinary image because the geometric shape of fragments do not carry a lot of valuable information if the document has been machine-shredded rather than hand-torn. On the other hand, matching words and context can be used as an additional tool to help improve the task of reassembly. In the final chapter, document reassembly problem has been addressed through solving a graph optimization problem