This PDF file contains the front matter associated with SPIE Proceedings Volume 12900, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Single-shot high-speed mapping photography is a powerful tool for studying fast dynamics in diverse applications. Despite much recent progress, existing methods are still strained by the trade-off between sequence depth and light throughput, errors induced by parallax, limited imaging dimensionality, and the potential damage by pulsed illumination. To overcome these limitations, we explore time-varying optical diffraction as a new gating mechanism to obtain ultrahigh imaging speed. Inspired by the pulse front tilt-gated imaging and the space-time duality in optics, we embody the proposed paradigm in the developed diffraction-gated real-time ultrahigh-speed mapping (DRUM) photography. The sweeping optical diffraction envelope generated by the inter-pattern transition of a digital micromirror device enables sequential time-gating at the sub-microsecond level. DRUM photography can capture a transient event in a single exposure at 4.8 million frames per second. We apply it to the investigation of femtosecond laser-induced breakdown in liquid and laser ablation in biological samples.

Using a digital micromirror device (DMD) coupled to two array sensors, we have set up a compact modular system that enables a region of interest of an object to be targeted using a quasi-one-dimensional or point-like characterization device. The system acts as an optical compressor, reducing the amount of data needed to analyze a region of interest of the object under test. At the aim of applying this approach for the spectral characterization of the eye, a spectrometer is used to carry out spectral measurements of the selected region of interest. The results presented have enabled us to validate the proof of concept of our system with preliminary tests on ex-vivo corneas. Applications in the field of ophthalmology are foreseen and being studied for early diagnosis of eye diseases.

Traditional methods of manufacturing graded-index (GRIN) lenses, such as chemical vapor deposition, ion exchange processes, and neutron irradiation, are time consuming, labor intensive, and cannot yield custom refractive index profiles. Additive manufacturing (AM) methods provide a potential alternative route to produce polymeric GRIN lenses easier as well as reduce costs. To date, AM approaches for GRIN lens production include inkjet 3D printing and multiphoton direct laser writing, which suffer from difficulty in material formulation and extremely large print times for macro scale lenses. This work seeks to create GRIN lenses using digital light processing (DLP) vat photopolymerization (VPP) AM. The main challenge of DLP VPP AM is related to the uncontrolled light penetration that induces additional curing in previously printed layers, which makes the control of conversion difficult. We adapted a conversion prediction model that was previously developed to predict the conversion profiles in printed parts by DLP VPP based on accumulated light dosage. By studying the index of refraction as a function of polymerization for various resin formulations, in combination with the conversion prediction model, we were able to utilize the grayscale capability of DLP to generate GRIN profiles through partial polymerization. This model was used to generate the 3D printing parameters needed to maintain proper extent of cure throughout the entirety of the print. These prints were then characterized to determine both the accuracy of the print design and the optical performance of the lens.

The use of Digital Light Processing (DLP)-based technologies has driven innovation in industries such as additive manufacturing, metrology, lithography and, increasingly, biomedical research and bioprinting. In addition to image quality parameters (magnification, line contrast, distortion), two key characteristics govern the manufacturing success: intensity on the image plane, and Full On/Full Off (FO:FO) contrast. Both need to be balanced carefully in the illumination design. We discuss detailed considerations for developing an UV DLP projector. Specifically, by choosing TIR prism design rationale, fine tuning the exact geometry, tailoring the other illumination optics and an improved coating design, we achieve an illumination that is both high-contrast and high-intensity.

Electronics of the future—more tightly integrated with freeform 3D design—require rethinking the often bulky, planar design of current circuit boards. Significant size reduction compared to conventional PCBs can be made by working with bare die components over packaged SMDs, and by placing and interconnecting these dies in 3D space. To this end, TNO at Holst Centre has developed a novel multi-material additive manufacturing technique: “3D Additive Lithography for Electronics” (3D-ALE). By combining direct imaging lithography and 3D printing, this system is optimized for the production of electrically interconnected, heterogeneously integrated freeform functional devices. A scanning DMD-based light engine is used to pattern photopolymer and allows printing of electrical features down to 10 µm line spacings. Using industry-standard conductive pastes, electrical components can subsequently be integrated and interconnected within the printed polymer body. A microelectronic demonstrator to enable endoscopic ultrasound imaging via a catheter will be demonstrated. The device features sub-mm sized, bare die ASIC and CMUT chips integrated and interconnected using the 3D-ALE system.

This paper presents an optimized capturing strategy for large depth-of-field (DOF) 3D microscopic structured-light imaging with the focus stacking technique. Different from the conventional focus stacking method that captures fringe images under a series of pre-defined focus settings, the proposed method automatically determines effective focus settings for the measured objects and only captures fringe images under these effective focus settings. Specifically, the proposed method first roughly measures the depths of objects using the focal sweep technique, then calculates the effective focus settings that locate the camera focal plane on the valid depths of the objects. Finally, the focus stacking technique is applied to reconstruct the 3D point cloud using the fringe images captured under the effective focus settings.

In 1985 I joined Texas Instruments’ (TI’s) Deformable Mirror Device (DMD) group to develop applications of the cantilever device in coherent optical signal processing. At that time I witnessed the “aha discovery” that led to the invention of the DLP. It is interesting to consider the many years of effort that led Larry Hornbeck to this commercially successful implementation, not just the technology, but the efforts to sustain the project through sponsored R&D. While TI viewed the only sustainable market as (incoherent) display applications, the DMD group sustained the effort with DoD funding for coherent and incoherent optical signal processing systems, including matched filter correlators, digital optical switches, optical crossbar switches and related neural network processors. For coherent signal processing the need for a 2π phase-only (piston-motion pixel) spatial light modulator (SLM) was readily apparent to the sponsors. While TI saw little commercial justification for the phase-only device, this need inspired me around 1991 to develop a new class of real-time computer-generated holography algorithms referred to a pseudorandom encoding, in which each phase-only pixel is encoded with a desired magnitude and phase. The optical Fourier transforms of the modulation enabled my developments of multi-spot object targeting and laser tweezer systems. Around 2005 I began using Digital Light Processing (DLP) developer kits in place of scanners to time-share images with a small number of detectors. One system using a single, high sensitivity detector together with well-chosen DLP frames quickly forms a “partial image” of a point-like scene objects – arguably, an early version of compressive sensing. This paper concludes with recommendations on optimizing the performance and applications of, and potential markets for TI’s recently demonstrated phase-only DLP.

The High Efficiency Pixel (HEP) is the first new pixel node for Texas Instruments DLP® Products since 2013. It gives DLP Products a high efficiency Digital Micromirror Device (DMD) that has the area and tilt to support high brightness LED illumination with high contrast and a wide color gamut. HEP was designed to provide a cost-effective solution utilizing CMOS yield learning from prior pixel nodes and DMD superstructure designed specifically with high stiction margin operation. This results in a cost effective, high reliability DMD that supports high optical power densities. The pixel node supports a whole product family of the key resolutions: 1080p (or full HD), WUXGA, and 4k UHD. This paper presents the HEP requirements and design methodology and includes testing results and market acceptance.

We present the design, implementation, and verification of high-resolution, diffraction-based augmented reality glasses for assisting persons with visual impairments. Existing systems, both commercially available and under development, provide needed functionality but present problems in terms of weight, size, and bulkiness that can detract from their usefulness. The system described herein addresses these issues while maintaining the capabilities of the other systems. The display component of the glasses employs a single waveguide and dispersion-compensating diffractive elements to maintain image integrity for the viewer while minimizing the size and weight of the overall system. Extensive MATLAB simulation provided precise control over the optical properties of the in-coupling, beam-expansion, and out-coupling optical components. Component parameters were varied systematically, and the performance was evaluated. A conventional lens, 31.9° prism, 2.2 mm waveguide thickness, and two linear diffractive gratings, with appropriate component separation, produced maximum displacement of 0.26 µm, maximum angular difference of 30.76 microdegrees, and output divergence of 12.2°. The output coupler design increased the viewing angle from the original 3.6° to a final 19.7°. Design elements were fabricated and performance of all elements matched well with simulation results. A prototype was constructed and evaluations are ongoing. Small size of all elements, especially the waveguide, allow potential integration into standard eyewear form factors. Although the original design addressed an RGB system, a monochromatic version would further reduce bulkiness and increase wearability while still addressing patient needs. Functions including image configuration, intensity, and magnification control provide utility needed for a variety of visual impairments.

Additive manufacturing (AM) is a digital manufacturing process that can directly convert a computer-aided design model into a physical object layer-by-layer. Due to the additive and discrete nature of the digital manufacturing process, AM needs to find a tradeoff between process resolution, platform size, and production efficiency by tuning the process in the temporal or spatial domains. For the digital-micromirror-device (DMD) based vat photopolymerization (VPP, aka Stereolithography) AM process, I will present two motion-assisted image projection methods recently developed in our lab to improve resolution without sacrificing size and efficiency. First, I will discuss VPP’s energy input in the temporal and spatial domains and present an optimized pixel blending principle. Based on them, a mask image projection method based on subpixel shifting in a split second will be presented to tune the process in both temporal and spatial domains. I will then introduce a hopping light method by adding a complimentary motion of the projection image so the DMD can use a low refresh rate (< 100 Hz) without imaging blurring during the continuous movement of the light projection system. Compared with other AM processes, such as stop-and-go and moving light methods, the hopping light method can resolve the tradeoffs among printing speed, feature resolution, and part size. The challenges in developing the hopping light method and its potential use in metal additive manufacturing will also be discussed. Finally, conclusions will be drawn with thoughts on how the presented spatiotemporal strategy may shed light on future DMD-based AM research.

Automotive Light Detection and Ranging (LiDAR) modules, wearable augmented reality display engines, and field-deployable free-space optical communication systems all require fast and robust solid-state beam and image steering solutions with a wide 2-dimensional field of view, as mechanical laser beam scanning is prone to mechanical failure. Diffractive beam steering with a digital micromirror device provides a robust solid-state beam steering solution to these problems and has been show to increase the field of view in 1-dimension for LiDAR and display systems. By extension, two Digital Micromirror Devices arranged orthogonally can be synchronized with a pulsed laser to diffractively steer a beam arbitrarily in 2-dimensions. This technique enables all-solid-state 2-dimensional beam steering solutions for beam steering and image steering applications.

The Phase-Only Spatial Light Modulator (PLM) is a piston-mode design of the Digital Micromirror Device (DMD) that Texas Instruments DLP® Products has been developing in recent years. While the manufacturing of the PLM shares many of the same process steps of the traditional DMD, the optical system integration of the two devices are fundamentally different. As a result, new optimization is needed to maximize the performance of the PLM based on the device characteristics. This paper covers the optimization of key pixel parameters – array fill factor, mirror flatness, mirror tilt – and generally how the parameters affect a device performance metric we call Zeroth-Order Efficiency. The various improvements are modeled to ascertain expected performance gains and at what point the performance benefits achieve asymptotic behavior. Theoretical and empirical results are shown for the improved key pixel parameters and their corresponding gains made to Zeroth-Order Efficiency.

Suppressing zero order diffraction beam is important to improve the performance of pixelated phase-only spatial light modulator. This issue also impacts the performance of the Texas Instruments Phase Light Modulator (PLM). However, PLM has a unique loading sequence which includes a short fraction of time that the mirrors return to flat resulting in only zero-order diffraction (ZOD) pattern to be generated, followed by the intended computer-generated hologram (CGH) with the ZOD at a less intensity. In this paper, we will show the captured images of ZOD and CGH using a highspeed camera with high dynamic range. We employed a sequence subtraction approach to suppress ZOD using data collected from Texas Instruments 0.67” PLM EVM. This process can be used in conjunction with other ZOD suppression techniques. The experimental results are presented in the paper.

An ideal Near-to-Eye display (NED) requires high-resolution images, a large field of view (FOV) and depth cues. Sometimes, those performances are degraded due to optical aberrations of optics. To correct for aberrations, in this work, we utilize digital phase conjugation (DPC) with a Texas Instruments phase light modulator (TI-PLM) to generate a 3D image with TIR/geometrical image guide. TI-PLM is a type of MEMS device that modulates the phase of the incoming light by moving the micromirrors in a piston motion, thereby modulating the phase. To measure aberration induced by the image guide combiner, we employed an off-axis holography, capturing the off-axis fringes using a camera sensor. Subsequently, image processing on the captured fringes, involving Fourier transform and cropping of +1st order, to extract the final field information while reducing low-frequency noise. Computer-generated hologram (CGH) was generated to negate the phase aberration, which is then displayed on the PLM. Through phase conjugation, we reconstruct the wavefront, resulting in a series of point sources displayed at different depths, and producing a 3D point images. This method allows us to generate multiple point sources with different depths, contributing to the 3D image in our Near-to-Eye display even via aberrated medium.

Texas Instruments has developed a phase light modulator (PLM) based on Micro-Electromechanical System (MEMS). This modulator offers several excellent advantages, including high refresh rate, compact optical path, and high optical efficiency, making it well-suited for applications in laser displays. In this paper, we divide the PLM into three regions and illuminate them with corresponding color laser light. The diffracted image is eventually reproduced and superimposed at the image plane in order to obtain a colorful display. We measured the display indicators such as inherent resolution, coincidence error, contrast ratio, uniformity, optical efficiency and diffraction efficiency of this methodology. The advantages of this methodology lie in its compact optical path and excellent optical efficiency. This work enhances the development of single PLM for color laser display applications in field sequence, including holography and volume display.

Texas Instruments has developed a Phase Light Modulator (PLM) based on Digital Light Processing (DLP) System, which alters the distribution of the light field. This paper explores the fundamental diffraction properties of PLM using the blazed grating model, investigates its capability to steer beams and tests its uniformity as a light field modulator. We selected a typical light field distribution to test the contrast ratio and examined how changing the light field distribution through PLM affects contrast ratio. When there is a single spot area exists in the modulated light field, decreasing the proportion of the individual spot to the entire image area, increases the contrast ratio; When there are multiple spots in the modulated image, increasing their number, decreases the contrast ratio. The feasibility of arbitrarily manipulating light field illumination for display system applications is verified by combining PLM with Digital Micromirror Device (DMD), leading to improved contrast ratios and better realization of High Dynamic Range (HDR) in projected images.