This PDF file contains the front matter associated with SPIE Proceedings Volume 8979, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

A hyperspectral imaging system (HsI), described previously, was utilized to evaluate and monitor wounds and their healing surgery and post-operatively. Briefly, the system consists of a DLP® based spectral light modulator providing active spectral illumination that is synchronized with a digital focal plan array for collecting spectroscopic images that are processed for mapping the percentage of oxyhemoglobin at each detector pixel non-invasively and at near video rates ~8 chemically encode images per second.

In this paper we present a novel sensing system, robust Near-infrared Structured Light Scanning (NIRSL) for three-dimensional human model scanning application. Human model scanning due to its nature of various hair and dress appearance and body motion has long been a challenging task. Previous structured light scanning methods typically emitted visible coded light patterns onto static and opaque objects to establish correspondence between a projector and a camera for triangulation. In the success of these methods rely on scanning objects with proper reflective surface for visible light, such as plaster, light colored cloth. Whereas for human model scanning application, conventional methods suffer from low signal to noise ratio caused by low contrast of visible light over the human body. The proposed robust NIRSL, as implemented with the near infrared light, is capable of recovering those dark surfaces, such as hair, dark jeans and black shoes under visible illumination. Moreover, successful structured light scan relies on the assumption that the subject is static during scanning. Due to the nature of body motion, it is very time sensitive to keep this assumption in the case of human model scan. The proposed sensing system, by utilizing the new near-infrared capable high speed LightCrafter DLP projector, is robust to motion, provides accurate and high resolution three-dimensional point cloud, making our system more efficient and robust for human model reconstruction. Experimental results demonstrate that our system is effective and efficient to scan real human models with various dark hair, jeans and shoes, robust to human body motion and produces accurate and high resolution 3D point cloud.

The holy grail of biomedical optical imaging is to perform microscopy deep inside living tissue. Unfortunately, biological tissue scatters light, which prevents the formation of a sharp focus. However, recently it was shown that wavefront shaping can be used to focus light through and inside turbid materials. So far, most experiments used liquid crystal devices, which are too slow to match the dynamics of perfused tissue. Since DMD technology is approximately 1000 times faster, it may bring wavefront shaping to in-vivo applications. We will compare analytically the performance of different methods for focusing light through scattering media with an intensity-only light modulator.

This paper summarizes our decade-long research efforts towards superfast 3D shape measurement leveraging the digital micromirror device (DMD) platforms. Specifically, we will present the following technologies: (1) high-resolution real-time 3D shape measurement technology that achieves 30 Hz simultaneous 3D shape acquisition, reconstruction and display with more than 300,000 points per frame; (2) Superfast 3D optical metrology technology that achieves 3D measurement at a rate of tens of kHz utilizing the binary defocusing method we invented; and (3) the improvement of the binary defocusing technology for superfast and high-accuracy 3D optical metrology using the DMD platforms. This paper will present both principles and experimental results.

We present a quantitative comparison of a fixed-pattern structured light system and a multi-pattern structured light system under varying capture environments. Several factors affect the performance of these systems, which makes the task of a fair comparison a very challenging aspect of this study. We conducted our experiments under controlled environment to enable us to control various system parameters for a fair comparison of these two techniques. We describe our methodology in choosing the system parameters for our study. For this analysis, we used two ground truth models with various depth and spatial variations as well as some smooth regions. These models are representative of two extremes of depth measurement scenarios. We show that multi-pattern approaches can be very accurate in controlled environment in stationary scenes due to high SNR, whereas fixed pattern methods are robust to ambient lighting changes but they have lesser accuracy. Further, in practical applications, we show that the multi-pattern approach has higher spatial and depth resolution when compared to a fixed pattern system.

Much work has been devoted to the calibration of optical cameras, and accurate and simple methods are now available which require only a small number of calibration targets. The problem of obtaining these parameters for light projectors has not been studied as extensively and most current methods require a camera and involve feature extraction from a known projected pattern. In this work we present a novel calibration technique for DLP Projector systems based on phase shifting profilometry projection onto a printed calibration target. In contrast to most current methods, the one presented here does not rely on an initial camera calibration, and so does not carry over the error into projector calibration. A radial interpolation scheme is used to convert features coordinates into projector space, thereby allowing for a very accurate procedure. This allows for highly accurate determination of parameters including lens distortion. Our implementation acquires printed planar calibration scenes in less than 1s. This makes our method both fast and convenient. We evaluate our method in terms of reprojection errors and structured light image reconstruction quality.

In this paper we present a novel sensing system, robust Near-infrared Structured Light Scanning (NIRSL) for three-dimensional human model scanning application. Human model scanning due to its nature of various hair and dress appearance and body motion has long been a challenging task. Previous structured light scanning methods typically emitted visible coded light patterns onto static and opaque objects to establish correspondence between a projector and a camera for triangulation. In the success of these methods rely on scanning objects with proper reflective surface for visible light, such as plaster, light colored cloth. Whereas for human model scanning application, conventional methods suffer from low signal to noise ratio caused by low contrast of visible light over the human body. The proposed robust NIRSL, as implemented with the near infrared light, is capable of recovering those dark surfaces, such as hair, dark jeans and black shoes under visible illumination. Moreover, successful structured light scan relies on the assumption that the subject is static during scanning. Due to the nature of body motion, it is very time sensitive to keep this assumption in the case of human model scan. The proposed sensing system, by utilizing the new near-infrared capable high speed LightCrafter DLP projector, is robust to motion, provides accurate and high resolution three-dimensional point cloud, making our system more efficient and robust for human model reconstruction. Experimental results demonstrate that our system is effective and efficient to scan real human models with various dark hair, jeans and shoes, robust to human body motion and produces accurate and high resolution 3D point cloud.

We report on the development of a highly scalable head-tracking system capable of tracking many users. Throughout the operating area, a series of high-speed (4 kHz) near-infrared LED-based Digital Light Processor (DLP) picoprojectors provide overlapping illumination of the volume. Each projector outputs a sequence of binary images which encode the position of each pixel within the projected image as well as an identifier sequence for the projector. Overlapping projectors use differing temporal multiplexing to allow sensor discrimination and background rejection. Pixel positions from multiple projectors received by each sensor are triangulated to obtain position and orientation.

We present here the use the DMD as a diffraction-based optical switch, where Fourier diffraction patterns are used to steer the incoming beams to any output configuration. We have implemented a single-mode fiber coupled N X N switch and demonstrated its ability to operate over the entire telecommunication C-band centered at 1550 nm. The all-optical switch was built primarily with off-the-shelf components and a Texas Instruments DLP7000™with an array of 1024 X 768 micromirrors. This DMD is capable of switching 100 times faster than currently available technology (3D MOEMS). The switch is robust to typical failure modes, protocol and bit-rate agnostic, and permits full reconfigurable optical add drop multiplexing (ROADM). The switch demonstrator was inserted into a networking testbed for the majority of the measurements. The testbed assembled under the Center for Integrated Access Networks (ClAN), a National Science Foundation (NSF) Engineering Research Center (ERC), provided an environment in which to simulate and test the data routing functionality of the switch. A Fujitsu Flashwave 9500 PS was used to provide the data signal, which was sent through the switch and received by a second Flashwave node. We successfully transmitted an HD video stream through a switched channel without any measurable data loss.

Our objective is precise wavefront reconstruction using complex modulation of light. A high precision amplitude beam shaper based on a digital micromirror device is used to image a shaped beam onto a phase-only spatial light modulator. To achieve our goal, a significant first step is deriving an efficient backwards propagation algorithm for hologram design that does not degrade the image by truncating high spatial frequencies or by aliasing. In addition, we show that reconstruction fidelity also depends on spatial bandwidth of the amplitude modulation. Thus, a minimum in error is found by considering both factors. Simulation verifies that the target image can be successfully reconstructed by using the proposed method.

Visible and Near Infrared (NIR) spectroscopy finds use in a number of applications including security, biomedicine, military, materials science, and materials processing areas to name a few. Visible red and NIR ranges are particularly valuable for in vivo studies because photons in this range have very low potential energy and are hence usually considered noninvasive. Integrated spectrometers operating in the NIR spectral range can have high resolution and transmission, low cost, and can exhibit low noise depending on detection properties and light throughput. Optical and NIR spectrometers in this and other work have been shown to operate under normal environmental conditions (such as temperature, atmospheric gases, and humidity) and do not generally require vacuum operation. In this research, the “spectral analysis” sections of a micro-mirror based Reflective Adaptive Slit (RAS) with single InGaAs photodiode spectrometer has been studied and compared to a conventional InGaAs array detector based spectrometer. It should be noted that in both approach, either RAS with single photodiode or Conventional Array Detector (CAD) based spectrometry, the spectrometer system requires a dispersive element (prism or grating) or filter to separate the polychromatic light beam under analysis. If the system is a so called “active” system, a light source is also needed. In this work we test, model, and compare a Reflective Adaptive Slit micro-mirror based single element photodiode system to a commercial array detector based spectrometer. Within the context of the Reflective single photodiode micro-mirror Slit spectrometer, we are establishing a set of optical requirements to ideally cover a number of applications. In addition to experimental performance comparisons between the spectrometer approaches, we will report on the performance requirements and environmental issues for these NIR spectrometers.

The primary goal of a vehicular headlight is to improve safety in low-light and poor weather conditions. The typical headlight however has very limited flexibility - switching between high and low beams, turning off beams toward the opposing lane or rotating the beam as the vehicle turns - and is not designed for all driving environments. Thus, despite decades of innovation in light source technology, more than half of the vehicular accidents still happen at night even with much less traffic on the road. We will describe a new DMD-based design for a headlight that can be programmed to perform several tasks simultaneously and that can sense, react and adapt quickly to any environment with the goal of increasing safety for all drivers on the road. For example, we will be able to drive with high-beams without glaring any other driver and we will be able to see better during rain and snowstorms when the road is most treacherous to drive. The headlight can also increase contrast of lanes, markings and sidewalks and can alert drivers to sudden obstacles. In this talk, we will lay out the engineering challenges in building this headlight and share our experiences with the prototypes developed over the past two years.

In this paper, we describe a novel super resolution method with variable pinholes arrays. The imaging system is based on super resolved time multiplexing method using variable and moving pinholes arrays. The improved resolution and signal to noise ratio are achieved with improved light intensity in the same exposure time, compared to imaging done with a single pinhole system. This new configuration preserves the advantages of pinhole optics while solving the resolution limitation problem and the low energetic efficiency of such system. The changeable and moving pinholes array can be realized using a DLP matrix. The system can also be used as an addition to several of existing optical systems which use visible, invisible light or even x-ray radiation.

Recently we proposed frequency division multiplexed imaging (FDMI), which allows capturing multiple images in a single shot through spatial modulation and frequency domain filtering. This is achieved by spatially modulating the images so that different images or sub-exposures are placed at different locations in the Fourier domain. As long as there is no overlap of the individual bands, we can recover different components by band-pass filtering the multiplexed image. In this paper, we present a Texas Instruments DMD based implementation of FDMI. An image is formed on the DMD chip; pixels are modulated by the micro-mirrors; and the modulated image is captured by a camera. By applying modulation during a sub-exposure period, the corresponding sub-exposure image is at the end recovered from the fullexposure image. Such a system could be used in a variety of applications, such as motion analysis and image deblurring. We will provide experimental results with the setup, and discuss possible applications as well as limitations.

The field of application of industrial projectors is growing day by day. New Digital Micromirror Device (DMD) - based applications like 3D printing, 3D scanning, Printed Circuit Board (PCB) board printing and others are getting more and more sophisticated. The technical demands for the projection system are rising as new and more stringent requirements appear. The specification for industrial projection systems differ substantially from the ones of business and home beamers. Beamers are designed to please the human eye. Bright colors and image enhancement are far more important than uniformity of the illumination or image distortion. The human eye, followed by the processing of the brain can live with quite high intensity variations on the screen and image distortion. On the other hand, a projector designed for use in a specialized field has to be tailored regarding its unique requirements in order to make no quality compromises. For instance, when the image is projected onto a light sensitive resin, a good uniformity of the illumination is crucial for good material hardening (curing) results. The demands on the hardware and software are often very challenging. In the following we will review some parameters that have to be considered carefully for the design of industrial projectors in order to get the optimum result without compromises.

We have developed the Pixel-level Visible Light Communication (PVLC) projector based on the DLP (Digital Light Processing) system. The projector can embed invisible data pixel by pixel into a visible image to realize augmented reality applications. However, it cannot update either invisible or visible contents in real time. In order to solve the problem, we improve the projector so that a PC can dynamically control the system and enable us to achieve a high-frame-rate feature by resolution conversion. This paper proposes the system framework and the design method for the dynamically reconfigurable PVLC projector.

Multiview three-dimensional (3D) display is able to provide horizontal parallax to viewers with high-resolution and fullcolor images being presented to each view. Most multiview 3D display systems are designed and implemented using multiple projectors, each generating images for one view. Although this multi-projector design strategy is conceptually straightforward, implementation of such multi-projector design often leads to a very expensive system and complicated calibration procedures. Even for a multiview system with a moderate number of projectors (e.g., 32 or 64 projectors), the cost of a multi-projector 3D display system may become prohibitive due to the cost and complexity of integrating multiple projectors. In this article, we describe an optical design technique for a class of multiview 3D display systems that use only a single projector. In this single projector multiview (SPM) system design, multiple views for the 3D display are generated in a time-multiplex fashion by the single high speed projector with specially designed optical components, a scanning mirror, and a reflective mirror array. Images of all views are generated sequentially and projected via the specially design optical system from different viewing directions towards a 3D display screen. Therefore, the single projector is able to generate equivalent number of multiview images from multiple viewing directions, thus fulfilling the tasks of multiple projectors. An obvious advantage of the proposed SPM technique is the significant reduction of cost, size, and complexity, especially when the number of views is high. The SPM strategy also alleviates the time-consuming procedures for multi-projector calibration. The design method is flexible and scalable and can accommodate systems with different number of views.

Digital micromirror devices (DMDs) are used in a variety of display and projection applications to produce high resolution images, both static and animated. A common obstacle to working with DMDs in research and development applications is the steep learning curve required to obtain proficiency in programming the boards that control the behavior of the DMDs. This can discourage developers who wish to use DMDs in new or novel research and development applications which might benefit from their light-control properties. A new software package called Light Animator has been developed that provides a user friendly and more intuitive interface for controlling the DMD. The software allows users to address the micromirror array by the drawing and animation of objects in a style similar to that of commercial drawing programs. Sequences and animation are controlled by dividing the sequence into frames which the user can draw individually or the software can fill in for the user. Examples and descriptions of the software operation are described and operational performance measures are provided. Potential applications include 3D volumetric displays, a 3D scanner when combining the DMD with a CCD camera, and most any 2D application for which DMDs are currently used. The software’s capabilities allow scientists to develop applications more easily and effectively.

Virtual Reality (VR) environments can offer immersion, interaction and realistic images to users. A VR system is usually expensive and requires special equipment in a complex setup. One approach is to use Commodity-Off-The-Shelf (COTS) desktop multi-projectors manually or camera based calibrated to reduce the cost of VR systems without significant decrease of the visual experience. Additionally, for non-planar screen shapes, special optics such as lenses and mirrors are required thus increasing costs. We propose a low-cost, scalable, flexible and mobile solution that allows building complex VR systems that projects images onto a variety of arbitrary surfaces such as planar, cylindrical and spherical surfaces. This approach combines three key aspects: 1) clusters of DLP-picoprojectors to provide homogeneous and continuous pixel density upon arbitrary surfaces without additional optics; 2) LED lighting technology for energy efficiency and light control; 3) smaller physical footprint for flexibility purposes. Therefore, the proposed system is scalable in terms of pixel density, energy and physical space. To achieve these goals, we developed a multi-projector software library called FastFusion that calibrates all projectors in a uniform image that is presented to viewers. FastFusion uses a camera to automatically calibrate geometric and photometric correction of projected images from ad-hoc positioned projectors, the only requirement is some few pixels overlapping amongst them. We present results with eight Pico-projectors, with 7 lumens (LED) and DLP 0.17 HVGA Chipset.

Seamless integration of 3D acquisition and 3D display systems offers enhanced experience in 3D visualization of the real world objects or scenes. The vivid representation of captured 3D objects displayed on a glasses-free 3D display screen could bring the realistic viewing experience to viewers as if they are viewing real-world scene. Although the technologies in 3D acquisition and 3D display have advanced rapidly in recent years, effort is lacking in studying the seamless integration of these two different aspects of 3D technologies. In this paper, we describe our recent progress on integrating a light-field 3D acquisition system and an autostereoscopic multiview 3D display for real-time light field capture and display. This paper focuses on both the architecture design and the implementation of the hardware and the software of this integrated 3D system. A prototype of the integrated 3D system is built to demonstrate the real-time 3D acquisition and 3D display capability of our proposed system.