This PDF file contains the front matter associated with SPIE Proceedings Volume 11294, including the Title Page, Copyright Information, Table of Contents, Author and Conference Committee lists.

The development of high throughput three-dimensional (3D) microscopic imaging technique is important for studying cell physiology and early-stage disease diagnoses. Here we propose and demonstrate a digital micromirror device (DMD) based angle-multiplexed high-speed optical diffraction tomography (ODT) technique. Using this ODT technique, we have achieved 3D imaging of cells at over 600 tomogram/second speed, which is 10-100 times faster than current ODTbased 3D cell imaging techniques. We envision that this high-speed ODT system will enable many cutting-edge biomedical applications, such as capturing millisecond scale cell dynamics in 3D space and high throughput 3D imaging of large cell populations.

High speed, high resolution, and large field of view (FOV) are desired for many imaging applications. However, the increase of spatial resolution normally accompanies with a decrease in FOV. Aperture synthesis is often used to improve the spatial resolution, while the requirement of multiple recordings has decreased the temporal resolution. We propose a digital mirror-device (DMD) based synthetic aperture phase microscopy (SAPM) technique to achieve high space bandwidth product (SBP) measurements of sample surface height profiles and quantitative phase maps. Enhanced lateral resolution can be achieved by synthesizing different parts of the sample spatial spectrum, corresponding to different illumination angles, which is experimental demonstrated using resolution targets. The high-speed patterning capability of DMDs and their patterning flexibilities have allowed us to design holograms to generate multiple illumination angles simultaneously to significantly improve the image acquisition speed and reduce data redundancy. With a high-resolution camera and a motorized sample stage, we can extend the sample scanning area to several inches. We envision that the development of this high throughput synthetic aperture phase microscope will enable many potential cutting-edge applications in biomedical imaging and material metrology.

Standard imaging systems provide a spatial resolution that is ultimately dictated by the numerical aperture (NA) of the illumination and collection optics. In biological tissues, the resolution is strongly affected by scattering, which limits the penetration depth to a few tenths of microns. Here we exploit the properties of speckle patterns embedded into a strongly scattering matrix to illuminate the sample at high spatial frequency content. Combining illumination performed through a Digital Micromirror Device(DMD) and a custom deconvolution algorithm, we obtain an increase in the transverse spatial resolution by a factor of 2.5 with respect to the natural diffraction limit.

DMD-based 3D printing is a powerful tool for making high-resolution biomimetic functional tissues and organs with various biomaterials for tissue engineering and regenerative medicine. A plethora of tissues have been fabricated using this technology including liver, heart, lung, kidney, blood vessels, cartilage, and placenta. In this article, we show prevascularization of the artificial tissue constructs using DMD-based 3D printing, which is essential to maintain the long term viability and function of a thick tissue. We also show a 3D printed biomimetic hepatic model that recapitulates the microarchitecture as well as the heterogeneous cell population of various cell types in the native liver tissue. It is important for the biomaterials to mimic the native microenvironment. Finally, we demonstrate that 3D printed tissue-specific decellularized extracellular matrix can improve cell response and behavior.

We demonstrate high-throughput, maskless patterning of biomolecules over centimeter scale areas with a diffraction-unlimited, sub-0.5 µm resolution using beam pen lithography (BPL), a technique employing a massively parallel array of near-field scanning probes. By integrating a digital micromirror device into the light path and aligning the grid of micromirrors to the grid of probes, we achieve independent actuation of >50,000 probes, enabling arbitrary patterning with high uniformity over the entire projection area.

Interest in MEMS fabrication has been growing for the last 50 years; however, the number and quality of tools supporting rapid prototyping in this industry are limited. Laminated resin printing (LRP) combines maskless projector-based lithography with 3D printing techniques to facilitate the rapid production of high-resolution polymer structures in three dimensions with no retooling required. By selectively metalising these structures, high value functional MEMS devices can be rapidly produced, tested and iterated. Microcircuits, enclosed mechanical systems and devices based on cantilevers and membranes have all been demonstrated using this technique.

For polymer 3D printing technologies, there exists a gap between large build volumes, low resolution and small build volumes, high resolution. On the one hand side, classical stereolithographic techniques can be used to build volumes in the range of several cm³ and an accuracy of 10 μm, on the other hand it is possible to cure structures with the size of several nanometers with two-photon polymerization.

Combining both advantages – large building volume and high resolution – in one printing technology would offer a huge variety of applications e.g. printing optical components and adding a functionalization of the surface by a 3D printed micro structure in the same process.

In this presentation, we demonstrate curing of subpixel structures with a standard DLP-projector with an imaged pixel size of around 40 μm. To use this in a printing process, the behavior of the resins under UV radiation must be known and predictable because different parameters are needed depending on the size and shape of the cured area.

Therefore, a parameter study was done to evaluate the dependency of the cured thickness on the shape, the area and the energy of the irradiated pattern. These parameters were used to simulate the cured thickness for a certain irradiance pattern applied by the projector. Based on these simulations a subpixeling technique was applied in order to cure small structures and test simple applications.

Post curing is a common technique in resin based additive manufacturing. With the UV exposure during the print, the polymer might not reach its full polymerization grade. Post curing effects printed optical components as the refractive index depends on the polymerization grade of the material. This talk summarizes some possibilities for printing various diffractive optical elements with a focus on a standard DMD projector. Main object of research is the effects of post curing on the diffractive pattern created by printed samples by evaluating the diffraction contrast. Additionally the refractive index distribution is analyzed with a high-resolution setup.

Complex wavefront manipulation is a promising technique for many applications of optics and photonics. In this report we will present our results on development of DMD wavefront correction experimental setup and discussion of its performance for various parameters of binary fringe pattern and 1^st diffraction order filtration aperture. It was shown that trade-off between spatial resolution and discretisation of the desired amplitude and phase distribution should be achieved. Decrease of the binarized interference fringes width results in higher spatial resolution of the modulated complex wave but increase discretisation of amplitude and phase distributions as well. The correction of wavefront aberrations using digital micromirror device was performed. We observed significant reduction in wavefront phase error by conduction of Zernike polynomials decomposition.

The “Angular Spatial Light Modulator” (ASLM) utilizes digital micromirror device (DMD) as a binary patterned programmable blazed grating to increase number of output pixels of a DMD by merging geometric and diffractive optical capabilities of the DMD. We demonstrate series of capabilities of the ASLM for beam and pattern steering. In particular, a single-chip beam steering lidar, an extended FOV display, a light-field projector, and a multi-view display which can be implemented into AR/VR systems. We also present our metrology results of wavefront distortion of DMD while micro mirrors are transitioning over between on and off states.

Computer Generated Holograms (CGHs) are powerful optical elements used in many fields, such as wavefront shaping, quality testing of complex optics and anti-counterfeiting devices. Lee algorithm is the most used to generate binary amplitude Fourier holograms. Grayscale CGHs are known to give a higher reconstruction quality than binary holograms, but they usually require a cumbersome production process. A very simple and straightforward method of manufacturing rewritable grayscale CGHs is here proposed by taking advantage of two key components: a Digital Micro-mirror Device (DMDs) and a photochromic plate. An innovative algorithm, named Island algorithm, able to generate grayscale amplitude Fourier CGHs, is reported and compared with the standard Lee approach, based on 9 levels. A crucial advantage lies on the fact that the increase or decrease of the quantification does not affect the spatial resolution. In other words, the new coding leads to a higher spatial resolution (for a given CGH size) and a reconstructed image with an order of magnitude higher contrast with respect to the classical Lee-coded hologram. In order to show the large potential of our approach, a 201 levels Island hologram is designed, produced and reconstructed, pushing the contrast to values higher than 10^4. These results reveal the high potential of our process as well as our algorithm for generating programmable grayscale CGHs. Grayscale objects are also studied in order to be produced with our new coding scheme: simulations show a much better reconstruction (resolution, fidelity, contrast) thanks to the quantification of the transparency than the Lee algorithm commonly used.

An approach for recording complex holograms using two beam interference setup incorporating a light modulating device in one of the arms of the holographic setup is proposed. This allows the intensity profile of the beam reflected by the DMD to be adjusted to a pre-determined profile. Using an UV laser, the created interference pattern is recorded into PTR glass plate. The variable light amplitude exposure of the glass is converted to a refractive index change after thermal treatment step. The DMD device makes possible the incorporation of zones in the hologram where there is no interference pattern and therefore there is no hologram. Such custom designed holograms can find applications in laser resonators or as spatially sensitive wavelength filters. In addition, the holograms recorded in the volume of the PTR glass are practically insusceptible to surface damage, changes in the environment and other factors from which holograms recorded in polymers suffer.

Piston‐mode Fourier based optical imaging created using an adaptation of the base DLP® Products torsional, spatial light modulator technology is presented. Technology, advancements and performance metrics such as, actuation speed, efficiency, and pixel coupling are shown for this 10.8 μm pitched pixel array. Device potential includes upwards of 5.7kframes/sec actuation.

In automotive applications of the LiDAR technology, traditionally the LiDAR is mounted atop of the vehicle. This arrangement has been very functional, but produced a very odd-looking vehicle. In addition, this may cause problems like close-range dead angular zones, exposure to dust and precipitation, and hard-to-reach electrical wiring of the LiDAR sensor. In contrast, integrating the LiDAR sensor into the headlight system would solve these issues [1]. Based on a smart algorithm that combines signals from LiDAR and a CCD image, a smart ON/OFF switching of the laser headlights was demonstrated [1]. However, the integration of LiDAR and CCD required many optical components resulting in complicated assembly and high cost. This paper presents a patent pending optical design of a LiDAR system integrated together with an intelligent headlight system using a single DMD. This integrated design uses the capability of the DMD in both the +12° and -12° positions. The micro-mirrors will be switched between +12° and -12° positions without stopping at the 0° position for all its functions. The headlight light source is placed at the -24° position and the LiDAR detector is placed at the +24° position. Pulsed laser will be used for broad area illuminations for LiDAR operations. The targets in front of vehicle will be scanned and the headlight can be programmed to illuminate the selected areas.

In astronomy, multi-object spectrometers (MOS) provide an efficient means to gather large samples of spectral data. Digital Micromirror Devices (DMDs) can be used as programmable slit masks in a MOS. There is strong interest in using DMDs in space-based MOS instruments. Our team has been carrying out an environmental test campaign to qualify eXtended Graphic Array (XGA) DMDs for space deployment. The environmental tests have included mechanical shock and vibration, low temperature, heavy ion radiation, proton radiation, and gamma radiation testing. In each of the tests, the devices were able to withstand the expected conditions of a space mission without adverse effects. Initial gamma radiation testing was performed on fourteen XGA DMDs during June of 2018. Ten of the devices were active and four passive (unbiased) during gamma irradiation. Passive devices accumulated a total ionizing dose (TID) of up to 76 krad(Si) without showing adverse effects. The active devices began to exhibit the appearance of non-latching micromirrors at a TID of 16-19 krad(Si). Non-latching mirrors recovered after annealing at room temperature for as little as 24 hours. The DMDs subjected to the harshest testing conditions were completely recovered after six months. A distinct difference in the pattern of non-latching mirrors was observed between commercial-off-the-shelf (COTS) DMDs with their original windows and re-windowed DMDs. In this work, we present a second round of gamma radiation testing performed on XGA DMDs at the NASA Goddard Space Flight Center in June 2019. One of the main purposes of this testing was to further investigate the differences in TID effects observed between the COTS and re-windowed DMDs. This testing also investigated the use of high temperature annealing to accelerate the recovery of non-latching mirrors. Additionally, DMDs which had previously been irradiated in an unbiased state were tested again while active during gamma irradiation. This work finalizes our efforts to qualify XGA DMDs for use in space and provides a better understanding of the effects of TID on the devices.

This paper presents an industrial augmented reality system that simultaneously measures a component, identifies possible defects and displays the inspection result directly on the component. The processing is done in real time using a single DMD-based projector for both the inspection and augmented reality. The use of a single DMD eliminates the issue of registration between the component being inspected and an auxiliary augmented reality projector. The use of a single projection system also eliminates possible occlusion due to parallax between both projection systems. The system uses an algorithm that computes at video frame rate the temporal sequences of micromirror positions that, when imaged by a high-speed camera, contains a set of structured-light patterns. The temporal sequences are designed such that a human observer sees the desired augmented information. The proposed prototype can acquire 12 range images per second. The range uncertainty at 1-σ is 14 μm and each range image contains approximately one million 3D points.

One of the challenges in high-precision manufacturing is constant inspection as well as efficient communication of the inspection results to the workers. In this context, we are presenting a multi-modal 3D imaging system designed for computer-assisted assembly manufacturing using augmented reality. The three-dimensional measurement subsystem is a structured-light system based on a digital micro-mirror device (DMD). The augmented reality imagery is displayed on the components being manufactured using another DMD-based color projector that uses wavelengths that do not interfere with the 3D measurements. A thermal camera is also part of the system and calibrated with respect to the measurement and projection subsystems. In typical target usage, the system can display localized shape deviation with respect to nominal values, or the surface temperature across the component, or any information obtained or derived from the subsystems. Moreover, it can be used to display assembly instructions and validate the compliance of the final manufactured component.

We develop optical calibration and distortion correction for a recently developed DMD-based volumetric augmented reality display. The display is capable of displaying imagery over a large volume | composed of 280 depth planes over a large depth-range (15 cm to 400 cm) and 40 degrees field-of-view. An unintended property of this display is that the field-of-view of the depth planes changes slightly over depth. This can cause distortions, perceptual errors for the perspective depth cue, and reduce the image quality slightly. To address these issues, we develop an optical calibration method and a distortion correction as a post-processing step to our rendering pipeline.

The state-of-art three-dimensional (3D) shape measurement techniques based on digital fringe projection (DFP) techniques assume that the influence of the shape of projector pixel shape is negligible. However, our research reveals that when the camera pixel size is much smaller (e.g., 1/10 or less) than the projector pixel size in object space, the shape of the projector pixel significantly can impact ultimate measurement quality even when binary defocusing technique is employed. This paper evaluates the performance of two different types of projector pixels: rectangular and diamond shaped. Both simulation and experimental results demonstrated that when, the camera pixel size is significantly smaller than the projector pixel size, it is advantageous to use a projector with rectangular pixels than the projector with a diamond shaped pixels.

This paper presents two structured-light 3D imaging systems that use a quasi-analogue projection subsystem based on a combination of digital micromirror device (DMD), optics, digital processing and calibration procedure. The first system is a high-resolution prototype that acquires 12M 3D point per frame; the second one is a high-speed prototype that generates 150 3D frames per second, with 2M 3D points per frame. The projection subsystem can produce high frame rates, high contrast and high resolution patterns using off-the-shelf components. The structured light patterns used are the same combination of binary and sine wave fringes as those usually encountered in commercial systems. The proposed systems generate the sine wave patterns using a single binary image, thereby exploiting the high frame rate of the DMD.

The paper introduces a new method of digital image correlation by making use of the transitioning state of the digital micro-mirror device (DMD). The projector should be given an OFF time in order to introduce flashing light for dynamic imaging. The dark period between DMD’s ON time is used to solve the saturation problem. Multiple captures are made during each projector cycle. The final unsaturated camera image can be obtained by combining all the images captured during that cycle. Experiments conducted demonstrate the success of the proposed method in performing digital image correlation for highly reflective surface.

In this presentation, we will provide an introduction on how to create a high speed 3D scanner using a TI based DMD and machine vision cameras in order to create a robust 3D imaging system for different applications. Based on over a decade of experience of building industrial scanners for end user applications, we will focus on common pitfalls and provide a framework on how to evaluate the various types of structured light illumination patterns for measurement applications. The speed and flexibility of pattern projection capability offered by digital light processing technology, enables a huge amount of flexibility and options for tailoring different illumination patterns approaches to real world scenarios. In conjunction with the recent advances in imaging sensor technologies and embedded processing, this enables the rapid development of customized solutions. We discuss the trade-offs of various hardware choices. Several example applications are also discussed.

In 3D printed optics based on UV curing resins there is the chance of inhomogeneities within the material with respect to the refractive index. The talk introduces an extension of the previously used Scanning Focused Refractive Index Microscopy with circular focus to a line focus to measure the refractive index distribution. The line focus brings a speed advantage as it enables profile measurements in a single image. Results from 3D printed samples but also GRIN samples are presented. Additionally, the presentation includes a possibility to do live measurements of the refractive index change during curing to characterize resins.