514 research outputs found

    Fast Compressive 3D Single-pixel Imaging

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    In this work, we demonstrate a modified photometric stereo system with perfect pixel registration, capable of reconstructing continuous real-time 3D video at ~8 Hz for 64 x 64 image resolution by employing evolutionary compressed sensing

    Overcoming the Challenges Associated with Image-based Mapping of Small Bodies in Preparation for the OSIRIS-REx Mission to (101955) Bennu

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    The OSIRIS-REx Asteroid Sample Return Mission is the third mission in NASA's New Frontiers Program and is the first U.S. mission to return samples from an asteroid to Earth. The most important decision ahead of the OSIRIS-REx team is the selection of a prime sample-site on the surface of asteroid (101955) Bennu. Mission success hinges on identifying a site that is safe and has regolith that can readily be ingested by the spacecraft's sampling mechanism. To inform this mission-critical decision, the surface of Bennu is mapped using the OSIRIS-REx Camera Suite and the images are used to develop several foundational data products. Acquiring the necessary inputs to these data products requires observational strategies that are defined specifically to overcome the challenges associated with mapping a small irregular body. We present these strategies in the context of assessing candidate sample-sites at Bennu according to a framework of decisions regarding the relative safety, sampleability, and scientific value across the asteroid's surface. To create data products that aid these assessments, we describe the best practices developed by the OSIRIS-REx team for image-based mapping of irregular small bodies. We emphasize the importance of using 3D shape models and the ability to work in body-fixed rectangular coordinates when dealing with planetary surfaces that cannot be uniquely addressed by body-fixed latitude and longitude.Comment: 31 pages, 10 figures, 2 table

    Low-cost single-pixel 3D imaging by using an LED array

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    We propose a method to perform color imaging with a single photodiode by using light structured illumination generated with a low-cost color LED array. The LED array is used to generate a sequence of color Hadamard patterns which are projected onto the object by a simple optical system while the photodiode records the light intensity. A field programmable gate array (FPGA) controls the LED panel allowing us to obtain high refresh rates up to 10 kHz. The system is extended to 3D imaging by simply adding a low number of photodiodes at different locations. The 3D shape of the object is obtained by using a noncalibrated photometric stereo technique. Experimental results are provided for an LED array with 32 × 32 elements

    Innovative Techniques for Digitizing and Restoring Deteriorated Historical Documents

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    Recent large-scale document digitization initiatives have created new modes of access to modern library collections with the development of new hardware and software technologies. Most commonly, these digitization projects focus on accurately scanning bound texts, some reaching an efficiency of more than one million volumes per year. While vast digital collections are changing the way users access texts, current scanning paradigms can not handle many non-standard materials. Documentation forms such as manuscripts, scrolls, codices, deteriorated film, epigraphy, and rock art all hold a wealth of human knowledge in physical forms not accessible by standard book scanning technologies. This great omission motivates the development of new technology, presented by this thesis, that is not-only effective with deteriorated bound works, damaged manuscripts, and disintegrating photonegatives but also easily utilized by non-technical staff. First, a novel point light source calibration technique is presented that can be performed by library staff. Then, a photometric correction technique which uses known illumination and surface properties to remove shading distortions in deteriorated document images can be automatically applied. To complete the restoration process, a geometric correction is applied. Also unique to this work is the development of an image-based uncalibrated document scanner that utilizes the transmissivity of document substrates. This scanner extracts intrinsic document color information from one or both sides of a document. Simultaneously, the document shape is estimated to obtain distortion information. Lastly, this thesis provides a restoration framework for damaged photographic negatives that corrects photometric and geometric distortions. Current restoration techniques for the discussed form of negatives require physical manipulation to the photograph. The novel acquisition and restoration system presented here provides the first known solution to digitize and restore deteriorated photographic negatives without damaging the original negative in any way. This thesis work develops new methods of document scanning and restoration suitable for wide-scale deployment. By creating easy to access technologies, library staff can implement their own scanning initiatives and large-scale scanning projects can expand their current document-sets

    FaceVR: Real-Time Facial Reenactment and Eye Gaze Control in Virtual Reality

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    We introduce FaceVR, a novel method for gaze-aware facial reenactment in the Virtual Reality (VR) context. The key component of FaceVR is a robust algorithm to perform real-time facial motion capture of an actor who is wearing a head-mounted display (HMD), as well as a new data-driven approach for eye tracking from monocular videos. In addition to these face reconstruction components, FaceVR incorporates photo-realistic re-rendering in real time, thus allowing artificial modifications of face and eye appearances. For instance, we can alter facial expressions, change gaze directions, or remove the VR goggles in realistic re-renderings. In a live setup with a source and a target actor, we apply these newly-introduced algorithmic components. We assume that the source actor is wearing a VR device, and we capture his facial expressions and eye movement in real-time. For the target video, we mimic a similar tracking process; however, we use the source input to drive the animations of the target video, thus enabling gaze-aware facial reenactment. To render the modified target video on a stereo display, we augment our capture and reconstruction process with stereo data. In the end, FaceVR produces compelling results for a variety of applications, such as gaze-aware facial reenactment, reenactment in virtual reality, removal of VR goggles, and re-targeting of somebody's gaze direction in a video conferencing call

    Investigations into applications of photometric stereo and single-pixel imaging

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    Computational image reconstruction is generally an inverse procedure which helps to recover the original information in a scene. Various imaging techniques have been developed to extract certain kinds of information for applications in different fields. The focus of this thesis is to improve two elegant and powerful methods among those approaches, namely, photometric stereo and single-pixel imaging, into a more practical and applicable phase. With the advances in modern imaging technology, 3D information is playing an increasingly significant role in real-world applications, from robotic vision, manufacturing, entertainment, and biology to security. While an immense amount of research has been conducted over the last few decades, the requirement of generating a rapid and accurate estimation of scene depth information with a cost-efficient system remains challenging. In the first work, we developed an inexpensive computational camera system allowing fast 3D reconstruction of objects based on the principle of photometric stereo. By analysing the estimated 3D data of various objects, we noticed good quantitative agreement with the known reference object with a wide viewing angle. With a low-cost accessory, our system provides a simplified reconstruction routine alongside a high efficiency, which extends its portability and capability for practical applications. Single-pixel imaging is an emerging paradigm which utilises spatial correlation of light with a single-pixel detector to form an image. It provides an alternative strategy to conventional imaging techniques which reply on a pixelated sensor for spatial resolution. In the second work, we combined photometric stereo with single-pixel imaging to evolve a new 3D imaging system with an efficient realtime sampling scheme. By utilising a high-speed structured illumination and four single-pixel detectors, multiple images of a scene with different shading profiles were able to be reconstructed with perfect pixel registration for depth estimation, empowering 3D imaging of dynamic scene. A compressive strategy, known as evolutionary compressed sensing, was further employed to improve the frame rate of 3D single-pixel video at an expense of only a modest reduction in image quality. This system represents a step-forward towards real-time 3D single-pixel imaging. By using single-pixel imaging technique, it offers a feasible solution for situations that are costly or constrained with conventional pixelated camera sensor, for instance, near-infrared (NIR) imaging and fluorescence imaging through multimode fibres. However, the signal-to-noise ratio (SNR) scales poorly when increasing the single-pixel imaging resolution. In the last work, we developed a NIR single-pixel imaging system with micro-scanning, an optimisation approach that generates a higher-resolution image while maintaining the SNR of the lower-resolution images where it is derived from. With the use of sunlight and an infrared heat lamp as the illumination sources and a set of NIR bandpass filters, our system indicated a well capability of revealing the water absorption underneath the surfaces of plant leaves and fruits compared to an expensive pixelated InGaAs camera. Additional efforts were devoted to further improve the image quality of a modified single-pixel imaging system that allows visible and NIR dual-band detection simultaneously

    An introduction to ghost imaging: quantum and classical

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    Ghost imaging has been a subject of interest to the quantum optics community for the past 20 years. Initially seen as manifestation of quantum spookiness, it is now recognized as being implementable in both single- and many-photon number regimes. Beyond its scientific curiosity, it is now feeding novel imaging modalities potentially offering performance attributes that traditional approaches cannot match
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