Emerging Digital Micromirror Device Based Systems and Applications XIV

The brain is challenging to image because brain tissue scatters light strongly, and out-of-focus sources contribute to unresolved background. Useful signal sources are often sparsely distributed within the tissue. For example, membrane-targeted fluorescent reporters of voltage or soluble signaling molecules are distributed on a sparse two-dimensional manifold in a three-dimensional space. By structuring the incident illumination in space, wave-vector, and polarization, one can maximize the likelihood that incident photons excite useful fluorescence, while minimizing the levels of nonspecific background. I will describe strategies for using structured illumination to image neural activity in vivo.

In this work, we developed a new method for high throughput imaging flow cytometry, using diffractive optics elements to generate linear laser spot array for illumination, and single-pixel detectors for detection. The illumination spots are arranged in a line at equal intervals and form a small angle with the direction of the cell movement. When the cell passes through the illumination area, the two-dimensional information of the cell's fluorescence and scattered intensity profile is encoded into signals detected by the PMTs. Fluorescence and scattering imaging were experimentally demonstrated for beads and cells traveling at a velocity of 4.7 m/s in a microfluidic chip, with a resolution of 1 μm and a maximum throughput of 5000cell/s.

we introduce automated serial OCM toward statistical 3D digital histopathology. Our research is the extension of previous work in order to enhance the process of imaging acquisition. Our approach has three unique features, (1) surface tracking, (2) single body and automated system combined vibratome and microscopic imaging head, and (3) selection of magnification. In validation test, various mouse organs were imaged and quantified at the region of interest which presented less labor and shorten image acquisition time compared to previous works.

We present stem cell detection within whole, unfiltered blood by multiphoton microscopic imaging in-flow. By employing high-speed SLIDE microscopy we capture 16000 frames per second of murine stem cells labelled with harmonic nanoparticles. This permits a highly sensitive and fast detection of meandering stem cells used in myocardic regenerative medicine, where aggregated cells can have a devastating effect. A SLIDE microscopy system with 3.3MHz line-scan rate achieves background-free, high resolution microscopic images of the stem cells in blood flow. We achieve Gigahertz pixel rate by maximizing the pulse rate to the quasi-instantaneous harmonic signal of the BFO nanoparticle labels. The high sensitivity of this system permits high-throughput microscopic imaging in-flow for precise preclinical assessment of regenerative medicine protocols.

Dielectric metasurfaces can be used to control optical wavefronts with capabilities that were not possible before. Making these capabilities dynamic would open a wide range of applications related to LIDAR, ranging, object recognition, etc. Unfortunately, most tuning methods rely on small changes in refractive index, that require metasurface structures with high quality factor resonances that are very sensitive to fabrication imperfections and are hard to control. One method that does not require such high quality resonances is based on nano-electro-mechanics. In this talk I present our recent efforts in developing nano-electro-mechanical metasurfaces based on multi-mode interference. These metasurfaces are used for optical beam deflection and for controlling the chiral properties.

Additive manufacturing of polymer parts via photpolymerization has emerged as versatile production technology. Toolless fabrication of arbitrarily shaped 3D printed parts has shown promise for industrial application, especially when processing high viscosity resins which lead to polymers with enhanced thermomechanical properties. However, until recently these production machines were limited by both field of view and light sources capable of providing sufficient energy density. With the advent of scrolling DLP projectors, high throughput systems could be conceived. By precise signal control and image plane matching, a novel additive manufacturing platform was developed. A pixel pitch of 50 µm is maintained over a printbed of up to 1 m x 0.28 m. It is capable of processing high viscosity resins at a throughput rate increased by over a magnitude compared to conventional Hot Lithography printers, enabling industrial scale production of high performance polymer parts.

Computed axial lithography (CAL) is an emerging volumetric additive manufacturing technology which presents unique opportunities in layerless ultra-rapid fabrication. However, the required process control places particular demands on computing and delivering the appropriate 3D distribution of optical energy, as well as monitoring the solidifying structure within the photo-resin. For example, continued reaction after tomographic exposure is not currently accounted for and could lead to higher degree-of-conversion than designed and consequent feature dilations. Color Schlieren Tomography (CST) is developed as an in-situ metrology tool to monitor volumetrically the internal refractive index and the forming geometry. Major improvements of CST in real-time computation and processing of 3D reconstruction have enabled event-driven patterning control such as auto-termination. With this technique, we monitored the polymerization process in real-time during and after termination of the exposure period signaled by an index-volume termination criterion. Monitoring of continued polymerization after termination (dark polymerization) shows that the refractive index change can rise to 10 times higher than its value at termination. The time-resolved 3D reconstruction data provided by CST can be used for chemical kinetics modeling and development of compensation schemes.

The recent development of the MEMS Phase Light Modulator (PLM) enables fast laser beam steering for lidar applications by displaying Computer Generated Hologram (CGH) on-the-fly without resorting to iterative CGH calculation algorithm. We discuss the application of MEMS PLM (Texas Instruments PLM) for quasi-continuous laser beam steering by deterministically calculated CGH and the importance of phase error on diffraction efficiency. We also address the CGH calculation algorithm and experimental demonstration that steers beam into multiple points with variable beam ratio.

Gradient descent is an efficient algorithm to optimize differentiable functions with continuous variables, yet it is not suitable for computer generated holography (CGH) with binary light modulators. To address this, we replaced binary pixel values with continuous variables that are binarized with a thresholding operation, and we introduced gradients of the sigmoid function as surrogate gradients to ensure the differentiability of the binarization step. We implemented this method both to directly optimize binary holograms, and to train deep learning-based CGH models. Simulations and experimental results show that our method achieves greater speed, and higher accuracy and contrast than existing algorithms.

Laser beam steering is an essential function for LiDAR. Phase Light Modulator (PLM) provides a capability of steering beam in a random-access manner but suffers from limited FOV and side lobes. In this paper, we present a DMD (Digital Micromirror Device)-PLM hybrid beam steering system that features high resolution, large-FOV, and parasitic free. This system can provide a FOV of more than 40 degrees with more than 4 million target points.

In this presentation we show a field of view super-resolution ability while using shifts in time to deal with the diffraction limit as well as the limited density of sampling in space caused due to the stringent size of camera’s pixels/pitch (geometric resolution limit). Using a low-resolution camera, we were able to achieve a high-resolution image by complying with certain conditions that we defined. For that end, we utilized a setup of sub-pixel shifts and grating shifts by time multiplexing, in addition to field of view multiplexing that overcame the diffraction related resolution reduction. The generation of the sub-pixel shifts needed for the operability of the proposed super resolving concept is achieved using DLP device. Improving optical systems resolution is extremely valuable mission in various fields of science and engineering. It helps researchers and industrial companies alike to leap forward the efficiency and ability of their microscopes, telescopes, imaging satellites and aerial photography.

Structured light has become topical of late, allowing custom optical fields to be tailored in all degrees of freedom, and finding applications that include optical trapping and tweezing, microscopy, communications and even quantum protocols. Commonly, the light is tailored in its spatial degrees of freedom for arbitrary polarization, amplitude and phase control, executed on spatial light modulators. This invited talk will outline the role of digital micro-mirror devices (DMDs) in the creation, control and detection of structured light fields, covering fundamentals for “getting started” to the state-of-the-art in real-time control with high speed and fidelity. The talk will cover topics ranging from lasers to single photons, highlighting the versatility of the DMD toolkit.

We developed a novel spectrum simulating light source that uses a high brightness Laser-Driven Light Source (LDLS) and high throughput, spectrally programable light engine to deliver high fidelity spectrum matching between 380 nm and 780 nm. The light source leverages the tunability of a digital micromirror device (DMD) with characterization algorithms to produce open-loop spectral matched light output. A monitoring spectrometer is not necessary for matching preloaded target spectra after an initial characterization of the system transfer function. The reported light source can match spectral lines down to 4.5 nm full-width-half-maximum (FWHM) linewidth and simulate the detailed spectral profiles of compact fluorescent lamps with high fidelity. With a 380 nm to 780 nm wavelength range, the source can be a valuable tool for sensor calibration, hyperspectral imaging, and medical-related research.

Texas Instruments (TI) is developing a phase light modulator (PLM) based on the same processes, equipment sets, and design knowledge as the mature, reliable spatial light modulator (SLM) DMD. This new device operates in a piston mode with each mirror moving up and down instead of rotating left and right as the SLM DMD does. Since the PLM is based on the SLM DMD, TI has a strong foundation for reliability. Early results from various life tests and environmental tests confirm that PLM reliability is comparable to the mature SLM reliability. The paper discusses reliability test results and performance metrics.

Most of smart headlight engines are designed using blue LED or laser light sources for the exciting the phosphor conversion layer producing white light output. The phosphor conversion layers have been fabricated by silicone-based phosphor, glass-based phosphor, ceramic-based phosphor, and single crystal-based phosphor. Among these different phosphor materials, the single crystal phosphor (SCP) exhibits excellent thermal stability, better conversion efficiency, and high transparency to yellow light, but the required high-temperature fabrication process, has been an impediment for widespread commercial production. Recently, the issues of higher fabrication temperature of the SCP have been overcome by using a novel design of single crystal growth to produce SCP with higher yield and better uniformity. In this study, the smart headlight consists of a well-developed, high efficiency, automotive qualified white LED, a TI digit mirror device (DMD), a projection lens, and a LED together with two laser diodes and a SCP plate.

Polymer powder bed additive manufacturing is the most prolific industrial additive manufacturing technology, thanks to Laser Sintering and High Speed Sintering (HSS) technologies. Recent advancements have included adding additional laser systems (with significant costs) and the use of HSS technologies to increase machine throughput. However, polymer powder bed AM technologies are still very limited on processable materials and quality control. Ascend Manufacturing is leveraging high power digital micromirror devices (DMD) to overcome these obstacles and provide a commercial next-generation additive manufacturing solution. This presentation will introduce Ascend Manufacturing's novel Large Area Projection Sintering technology and discuss the additional advantages of area-based processing.

A LIDAR system is built with Digital Micromirror Device (DMD), Micro Electro Mechanical System (MEMS) based resonant mirror, and 905nm nanosecond pulsed laser which contribute to achieving a large product of beam area and throw of beam scan (Etendue) in a solid state lidar implementation which are important aspects for an advanced LIDAR system. We also demonstrate a live lidar image that represents the location and distance of an object in which a micro controller and Matlab is used to control a custom Time of Flight (electronics) with Constant Fraction Discriminator (CFD).

We present a deterministic CGH beam steering method using CUDA-OpenGL interoperability enable to reduce the required time for CGH generation and display. Our proposed approach for CGH calculation and display on GTX 1650Ti, i7-10750H@2.6GHz performs faster than the display upper limit of current PLM, resulting the beam steering speed of 180Hz, and could be further accelerated by either improving the performance of PLM or applying our program on a better GPU. In addition, we successfully combine YOLOv4-tiny model with our GPU-based CGH beam steering, allowing our system to do AI-based dynamic beam tracking in order to trace the object of interest.

We present a 3D electromagnetic diffraction simulation of a digital micromirror device (DMD) from 0.4 μm to 5 μm. The DMD induces wavelength-dependent diffraction effects that impact stray light, optical throughput, and the pupil illumination distribution of a system. To quantify this we perform a finite-difference time-domain simulation and calculate the far-field light distribution. We analyze the DMD's optical efficiency in the specular regime (λ < 1 μm); the diffraction-dominated regime (3 μm < λ < 5 μm); and, uniquely, the transition region, where the specular reflection and diffraction contributions are comparable (1 μm < λ < 3 μm). These results inform system performance parameters, provide optical design constraints, and create a framework of use cases for DMDs.

Periodicity of the Computer Generated Holograms (CGHs) for beam steering makes it possible to utilize the Talbot self-phase-image of the CGH to enhance the diffraction efficiency in the infrared domain. First, the phase CGH pattern is displayed on Texas Instrument Phase Light Modulator (TI-PLM). The Talbot image formed by the periodic phase CGH is superimposed on top of the PLM itself by light recycling optics employing polarization. The architecture doubles phase modulation by a factor of two, which enables using TI-PLM designed for visible wavelength for infrared laser beam steering for lidar applications.