This PDF file contains the front matter associated with SPIE Proceedings Volume 10932, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Hyperspectral chemical imaging (HCI) refers to the acquisition of both spatial and spectral information in a single acquisition time frame. HCI is a parallel scheme that allows the collection of spatially-resolved chemical/compositional data at much higher rate compared to traditional chemical imaging which is serial in nature. Recent advances in spatial light modulators (SLM) have enabled many novel HCI imaging schemes. We have implemented several HCI systems using reflective and diffractive SLMs. Their design and performance characterization will be discussed in this talk.

Digital micro-mirror devices (DMDs) have recently emerged as practical spatial light modulators (SLMs) for applications in photonics, primarily due to their modulation rates, which exceed by several orders of magnitude those of the already well-established nematic liquid crystal (LC)-based SLMs. This, however, comes at the expense of limited modulation depth and diffraction efficiency. Here we compare the beam-shaping fidelity of both technologies when applied to light control in complex environments, including an aberrated optical system, a highly scattering layer and a multimode optical fibre. We show that, despite their binary amplitudeonly modulation, DMDs are capable of higher beam-shaping fidelity compared to LC-SLMs in all considered regimes.

Optical wavefront shaping is one of the most effective techniques in focusing light inside a scattering medium. Unfortunately, most of these techniques require direct access to the scattering medium or need to know the scattering properties of the medium beforehand. Through our scheme we develop a novel concept in which both the illumination and the detection is on the same side of the inspected object and the imaging process is a real time fast converging operation that does not require to capture large plurality of images. We model the scattering medium being a biological tissue as a Matrix having mathematical properties matched to the physical and biological aspects of the sample. In our adaptive optics scheme, we aim to estimate the scattering function and thus to encode the intensity of the illuminating laser light source using DMD (Digital Micromirror Device) with an inverse scattering function of the scattering medium, such that after passing its scattering function a focused beam is obtained. We optimize the pattern to be displayed on the DMD using Particle Swarm Algorithm (PSO). As first proof of concept we show validation via numerical MATLAB simulations where we obtain a focused spot behind a scattering medium in amplitude modulation scheme.

The high data bandwidth of Raman imaging precludes high-speed spectroscopic imaging. Conversely, emerging compressive sensing hyperspectroscopy techniques could, in principle, address this issue by using undersampling methodologies with computational reconstructions. However, compressive spectrometer layouts have prohibitive losses for low-light levels applications, such as in the spontaneous Raman imaging of dynamic biological specimens. These losses are due to the fact that high-sensitivity light detectors (photo-counters) have too small active area (typically 100 um) compared to the size of digital micromirror devices (DMD) (~10 mm) used in most compressive layouts. Inspired by pulse shaping techniques of ultrafast spectroscopy, we present a new programmable spectrometer layout with high-throughput and large spectral coupling bandwidths. Exploiting amplitude spectral modulation with DMD allows conventional and compressive Raman imaging and spectroscopy acquisitions with shot-noise-limited sensitivity. With this spectrometer, we demonstrate compressed hyperspectroscopy at faster speeds and at lower costs than traditional cameras used in Raman imaging applications. We showcase imaging of biological specimens at high spatial resolution (250 nm).

We demonstrate a high-speed and high-resolution quantitative phase imaging method by implementing a synthetic aperture technique through using digital micromirror devices (DMDs). DMDs provide high speed steering of the illumination beam angle upon the sample that induces sample frequency shift, which is the basis of achieving high resolution in the quantitative phase imaging (QPI) system. With a high-speed camera for image acquisition, our QPI system achieves synthetic aperture imaging at >25 frame per second (fps). The high-speed imaging capability of the system allows for better observation of samples dynamics, especially in live biological structures, where motions could result in degraded imaging quality. In experiments, our synthetic aperture-based QPI system has resolved sub-diffraction limited structures of 220 nm periods and quantified red blood cell membrane fluctuations, which opens new avenues in material metrology and biological imaging applications.

While there is great interest in 3D printing for microfluidic device fabrication, the challenge has been to achieve feature sizes that are in the truly microfluidic regime (<100 μm). The fundamental problem is that commercial tools and materials, which excel in many other application areas, have not been developed to address the unique needs of microfluidic device fabrication. Consequently, we have created our own stereolithographic 3D printer and materials that are specifically tailored to meet these needs. We review our recent work and show that flow channels as small as 18 µm x 20 µm can be reliably fabricated, as well as compact active elements such as valves and pumps. With these capabilities, we demonstrate highly integrated 3D printed microfluidic devices that measure only a few millimeters on a side, and that integrate separate chip-to-world interfaces through high density interconnects (up to 88 interconnects per square mm) that are directly 3D printed as part of a device chip. These advances open the door to 3D printing as a replacement for expensive cleanroom fabrication processes, with the additional advantage of fast (30 minute), parallel fabrication of many devices in a single print run due to their small size.

Predictive visualisation for laser-processing of materials can be challenging, as the nonlinear interaction of light and matter is complicated to model, particularly when scaling up from atom-level to bulk material. Here, we demonstrate a predictive visualisation approach that uses a pair of neural networks (NNs) that are trained using data obtained from laser machining using a digital micromirror device (DMD) acting as an intensity spatial light modulator. The DMD enables laser machining using many beam shapes, and hence can be used to produce significant amounts of training data for NNs. Here, the training data corresponds to hundreds of DMD patterns (i.e. beam shapes) and their associated images and 3D depth profiles. The trained NNs are able to generate a surface image and 3D depth profile, showing what the ablated surface would look like, for a wide range of ablating beam shapes. The predicted visualisations are remarkably effective and almost indistinguishable from real experimental data in appearance. Such a NN approach has considerable advantages over modelling techniques that start from first-principles (i.e. light-atom interaction), since zero understanding of the underlying physical processes is needed, as instead the NN learns directly via observation of labelled experimental data. We will show that the NN learns key optical properties such as diffraction, the nonlinear interaction of light and matter, and the statistical distribution of debris and burring of material, all with zero human assistance. This offers a new paradigm in predictive capabilities, which could be applied to almost any manufacturing process.

We are developing photopolymer resins with a toughness exceeding 25 MJ/m3, with a strain capacity of >200%, which are low odor, and which can be additively manufactured into a mesh of effective density <50 kg/m3 with individual strut thickness of <250 µm. We are optimizing placement of individual Digital Micromirror Device (DMD) chips (visual field overlap, optics train, staggering, rotation) in LightBars™, which consist of arrays of up to 64 DMDs with sufficient overlap to cure part layers at an anticipated 10 mm/sec to cover 500 mm wide at a voxel resolution of <200 µm such that each voxel is “patterned” by >1,000 different mirrors. Different resins have been tailored with different additive cocktails for rapid manufacturing at different wavelengths ranging from 355 nm to 385 nm to 405 nm.

Recent development of high-resolution micro-Continuous Liquid Interface Production (microCLIP, continuous projection microstereolithography) process has enabled 3D printing of biomedical devices with 10 micron-scale precision. 3D bioresorbable vascular scaffolds (BVS) were printed using an antioxidant, photopolymerizable citric acid-based material (B-InkTM). Despite demonstrating BVS fabrication feasibility, challenges remained. According to literature, a vascular stent when placed in the body must be able to sustain a pressure loading between 10.67kPa and 13.34kPa of pressure loading. To be clinically relevant, struts for vascular scaffolds need to possess very small thickness, 100um or below. Specifically, to improve our material strength/stiffness of our 3D printed BVSs, a dissolved PLLA nanophase (10%, wt./vol in Tetrahydrofuran) and secondary temperature-sensitive initiators (V70, 1wt.%) were added to the photopolymer resin. Through temperature-induced phase separation and solvent exchange, fibrous networks were incorporated through the B-Ink 3D matrix. Secondary initiators allowed for further crosslinkage of the matrix material. Introduction of PLLA nanophase/secondary initiators greatly improved bulk stiffness and yielded BVSs with 100um strut thickness that could sustain the necessary biological radial pressure loadings. This technology and photopolymerizable material is a large step forward toward on-the-spot and on-demand fabrication of patient specific BVSs.

We report, both in theory and experiment, on a novel kind of vortex symmetric Airy beam (VSAB) that exhibits elegant symmetric structure and autofocusing property. A general expression of the symmetric Airy beam (SAB) is derived first, and then VSAB is created by imposing a spiral phase into the initial SAB. Notably, we can tailor the structure and autofocusing behavior of VASB by embedding the vortex or vortices in an on or off-axis mode. Besides, multiple off-axis vortices projected into SAB are also investigated. This proposed VSAB will provide flexibility for optical manipulation and quantum communication.

Single-pixel imaging employs structured illumination to record images with very simple light detectors. It can be an alternative to conventional imaging in certain applications such as imaging with radiation in exotic spectral regions, multidimensional imaging, imaging with low light levels, 3D imaging or imaging through scattering media. In most cases, the measurement process is just a basis transformation which depends on the functions used to codify the light patterns. Sampling the object with a different basis of functions allows us to transform the object directly onto a different space. The more common functions used in single-pixel imaging belong to the Hadamard basis or the Fourier basis, although random patterns are also frequently used, particularly in ghost imaging techniques. In this work we compare the performance of different alternative sampling functions for single pixel imaging, all of them codified with a digital micromirror device (DMD). In particular, we analyze the performance of the system with Hadamard, cosine, Fourier and noiselet patterns. Some of these functions are binary, some others real and other complex functions. However, all of them are codified with the same DMD by using different approaches. We perform both numerical and experimental tests with the different sampling functions and we compare the performance in terms of the efficiency and the signal-to-noise ratio (SNR) of the final images.

Unit cell orientation information is encoded in electron diffraction patterns of crystalline materials. Traditional transmission electron detectors implemented in the scanning electron microscope are highly symmetric and are insensitive to in-plane unit cell orientation information. Herein we detail the implementation of a transmission electron detector that utilizes a digital micromirror array to select anisotropic portions of a diffraction pattern for imaging purposes. We demonstrate that this detector can be used to map the in-plane orientation of grains in two-dimensional materials. The described detector has the potential to replace and/or supplement conventional transmission electron detectors.

Digital fringe projection technique is widely used for high-accuracy three-dimensional (3D) shape measurements. However, when the measured object is moving, there will be severe artifacts and phase errors induced by the movement even though a high-speed fringe projection system is used. Meanwhile, there are different kinds of motion such as uniform and non-uniform motion, which makes the problem even harder to address. To this end, this paper proposes a generic motion error compensation algorithm to deal with different motion artifacts. Both simulation and experiments demonstrated the proposed method can substantially reduce motion-induced measurement error.

The paper proposes a new method for measuring the 3D shape of fast-moving highly reflective surfaces by using the transitioning state of the digital micro-mirror device (DMD). 1-bit binary patterns are used to achieve kHz measurement speeds and to overcome the rigid camera-projection synchronization requirement. More than one captures of the fringes are made during each cycle of the pattern projection. The dark period between DMD’s ON time is used to alleviate saturation problem of highly reflective surfaces. Experiments conducted demonstrate the success of the proposed method for measuring fast-moving shiny surfaces with an image acquisition speed of 1,000 Hz

Using DLP^® projection for 3D surface measurement is well established and very high-speed recording has been reported using binary structured light patterns. Advanced 3D measuring solution adopt phase shifting technology that yields higher data quality and increases the robustness of the inspection systems. Phase shifting requires the projection of precise sinusoidal patters. DLP chips produce native binary intensity modulation patterns and the grayscale output is typically realized by time averaging of the binary bit planes using pulse width modulation. That way, very precise grayscale line profiles can be projected but the pattern rates do not exceed 1200 fps substantially. This paper describes a novel methodology for precise grayscale line projection with up to 10-bit gray values and pattern frequencies that correspond to the maximum DLP pattern refresh rate. The basic principle of this new approach has been verified analyzing phase shifting pattern sequences recorded by an integrated camera. Precise 8-bit line profiles have been generated and the maximum of 50,000 profiles per second can be achieved with partial use of the DLP micro-mirror array. Experimental results are presented that are not only promising for future use in 3D surface inspection but have potential for other areas of industrial DLP applications as well.

Structured Light Imaging (SLI) is a means of digital reconstruction, or Three-Dimensional (3D) scanning, and has uses that span many disciplines. A projector, camera and Personal Computer (PC) are required to perform such 3D scans. Slight variances in synchronization between these three devices can cause malfunctions in the process due to the limitations of PC graphics processors as real-time systems. Previous work used a Field Programmable Gate Array (FPGA) to both drive the projector and trigger the camera, eliminating these timing issues, but still needing an external camera. This work proposes the incorporation of the camera with the FPGA SLI controller by means of a custom printed circuit board (PCB) design. Featuring a high speed image sensor as well as High Definition Multimedia Interface (HDMI) input and output, this PCB enables the FPGA to perform SLI scans as well as pass through HDMI video to the projector for Spatial Augmented Reality (SAR) purposes. Minimizing ripple noise on the power supply by means of effective circuit design and PCB layout, creates a compact and cost effective machine vision sensing solution.

We propose a bandwidth-limited imaging system based on a digital micromirror device (DMD) for three-dimensional (3D) structured light profilometry. By using an error diffusion algorithm with optical low-pass filtering, we obtain high-quality sinusoidal fringe patterns without mirror dithering. An N-step phase-shifting algorithm is then used to recover depth information from objects. Using our bandwidth-limited projector, we demonstrate 3D profilometry of a static object.

Many applications of 3D imaging must deal with objects that are highly specularly reflective and have multiple interreflections, resulting in missing and erroneous points. We use a single camera with multiple DMD projectors, resulting in multiple incident lighting angles to deal with both specular and interreflections. At each camera pixel, multiple 3D point estimates are computed from each of the camera-projector pairs. These multiple estimates are fused together with an expectation maximization (EM) clustering algorithm and the maximum likelihood estimate for each point is obtained. A novel noise filtering algorithm is also presented which makes use of the EM algorithm covariance to suppress spurious points caused by reflections. Results show that our multi-projector approach and EM estimator increase 3D measurement accuracy and recoverable points for complex reflective objects, while reducing error.

This paper introduces a dual-projector phase measuring profiler that adds a second projector to a traditional structured light illumination system to improve the overall quality of 3D scanning. With this method, two projectors are synchronized to a single camera, but each one projects structured light patterns of a unique frequency. The system performance benefits from a wider projection angle and doubled light intensity. In particular, a detailed system implementation in hardware is described. Moreover, the major difference between the phase unwrapping of our dual-projector system versus a single-projector system is discussed with a LUTbased phase unwrapping scheme proposed.

We have developed a high-speed and low-latency projector DynaFlash that can display 8bit black and white images at up to 1,000fps with 3ms delay. Recently we have also developed a high-speed projector DynaFlash v2 that can display 8bit color images at 947fps. These projectors use DMDs and time domain modulation of high-brightness LEDs. In addition, a newly designed communication interface module is installed in a computer for transferring images at high speed. This reduced the delay from image generation to projection to 3ms at best. On the other hand, we developed 1,000fps highspeed image processing that can recognize three dimensional shape and center position of moving objects every 1ms. A combination of the high-speed projector and a high-speed visual tracking system based on the high-speed vision realizes a dynamic projection mapping (DPM) system that can make a realistic projection mapping onto a moving object by using usual 60fps projector. As the high-speed vision can recognize three dimensional shapes of flexible objects every 1ms, so we can calculate appropriate projection images from photos or movies based on the three dimensional shape and position of objects. The high-speed projector displays them onto deformable objects such as T-shirts, even if the shape of objects changes quickly. In this paper, basic architectures of those systems and devices will be explained. In addition, application systems of highspeed projectors including DPM will be also shown.

Matrix-LED systems offer different functionalities to increase road safety, e.g. glare-free high beam and marking light. Shortly after their introduction, efforts have been made to increase the amount of pixels. One of the results is the EVIYOS LED consisting of 1024 individually controllable pixels, which practically set the stage for pixel light systems. Current efforts to implement high-resolution pixel light systems are focused towards the exploration of an efficient light source in combination with the use of spatial light modulators. One approach to implement high-resolution pixel light systems is the use of LED arrays as a light source to illuminate a DLP. Unlike video projectors which require a homogeneous illumination of the DLP in order to obtain a homogeneous projection, headlamps require an inhomogeneous light distribution with high illuminance in the center. In order to receive a high system efficiency preforming the desired illuminance onto the active area of the modulator is advantageous. To further increase the systems efficiency an imaging illumination of the DLP, where the images of the emission surfaces of the LEDs are superposed onto the active area of the DLP, is worthwhile. In this paper, concepts for imaging and non-imaging illumination strategies of a DLP for high resolution headlamps will be introduced. For both illumination strategies the most promising concept will be selected to set up an optical system to illuminate a DLP. The paper concludes with a comparative analysis of the imaging and non-imaging optical system with regards to the system architecture and system efficiency.

Adaptive headlamps with innovative lighting functionalities can increase traffic safety. Subtractive light modulators such as Digital-Micromirror-Devices (DMD), liquid crystal displays (LCD) or liquid crystal on silicon devices (LCoS) are considered to be used as an implementation with a high resolution. In order to realize the regulated light distribution as well as to improve the optical efficiency and on-road projection quality of such headlamp systems, an inhomogeneous illumination on the modulator and whereafter low distortion projection optics are considered. In this paper we present simulation results of an optical concept of inhomogeneous illumination for headlamps.

Texas Instruments’ digital mirror device (DMD) uses thousands to millions of individual micromirrors to direct light as a Spatial Light Modulator (SLM). The Tilt-Roll-Pixel (TRP) is currently the smallest DLP Products pixel node at 5.4μm pitch. The small micromirror size, which enables fast switching speed, and precise tilt angles, exploits this speed on a system level to double or quadruple the resolution by using super-resolution projection. Super-resolution projection overlays multiple sub-sampled images, each shifted on the screen by a fraction of a pixel, and as long as the shifting occurs at a rate faster than the critical flicker fusion threshold, the human visual system will act as a temporal low pass filter and naturally integrate all low-resolution SLM images into a single super-resolution result. This paper will discuss the operation of the TRP node, how this node can be operated more quickly, how super-resolution projection works, and how we modified the optical architecture to leverage the switching speed for super-resolution projection.

A prototype of a Phase Spatial Light Modulator (PLM) device has been developed and demonstrated using DLP Micro-ElectroMechanical System (MEMS) based technology. Designed for a visible (405nm to 632nm) laser, this device uses an array of individually-addressable, digitally-controlled PLM micromirrors that can be addressed to multiple discrete vertical positions. The MEMS superstructure process flow used for DMD micromirrors was adapted to enable manufacturing this device on top of an existing DLP technology CMOS device. The prototype has demonstrated good uniformity across the array and the ability to steer light using phase light modulation. A discussion of some initial performance metrics as well as potential applications will be presented.

In many space-borne surveillance missions, hyperspectral imaging (HSI) sensors are essential to enhance the ability to analyze and classify oceanic and terrestrial parameters and objects/areas of interest. A significant technical challenge is that the amount of raw data acquired by these sensors will begin to exceed the data transmission bandwidths between the spacecraft and the ground station using classical approaches such as imaging onto a detector array. To address such an issue, the compressive line sensing (CLS) imaging concept, originally developed for energy-efficient active laser imaging, is adopted in the design of a hyperspectral imaging sensor. CLS HSI imaging is achieved using a digital micromirror device (DMD) spatial light modulator. A DMD generates a series of 2D binary sensing patterns from a codebook that can be used to encode cross-track spatial-spectral slices in a push-broom type imaging device. In this paper, the development of a testbed using the TI DLP NIRscan™ Nano Evaluation Module to investigate the CLS HSI concept is presented. Initial test results are discussed.

Digital micromirror devices (DMDs) are well suited for highly multiplexed spectroscopy applications. In astronomy, DMDs can be used as a programmable slit mask in a multi-object spectrometer (MOS). There is strong interest in utilizing DMDs for space-based MOS instruments. Over the past several years, we have carried out a program to evaluate the viability of XGA DMDs for operation in space, including their ability to survive the launch environment. The DMDs we tested did not show any failures or adverse effects after mechanical vibration and shock testing. Using heavy ion irradiation, we found that DMDs are susceptible to single event upsets (SEUs), though all SEUs are non-destructive and can be cleared by loading a new pattern. The estimated SEU rate for ”worst week” conditions in interplanetary space was 5.6 upset micromirrors (out of 786,432) per 24 hours. Using high energy protons, we found that DMDs started to show failures at a total ionizing dose of 30 krad(Si) (which is well above the estimated total-dose for a 4 year mission). In this work, we present the total ionizing dose testing performed using gamma rays from a Co-60 source at NASA GSFC. We tested 14 XGA devices and found that individual micromirrors began failing after the devices accumulated a total dose of 16-19 krad(Si). Devices recovered after annealing at room temperature in as little as 24 hours. Devices subjected to the most severe radiation testing conditions were completely recovered after 18 weeks of annealing at room temperature. We also tested unbiased (powered off) devices, which showed no effects up to a dose of 76 krad(Si) (which is the highest TID we achieved during our testing). This work concludes our efforts to space-qualify XGA DMDs, and shows that these devices are well-suited for deployment in space, except in the harshest radiation environments.