Digital Micromirror Device Research Articles

Rapid focusing of light through turbid water based on a digital micromirror device

The strong scattering and time variability of dynamic scattering media pose a major challenge to optical focusing and imaging applications. In this paper, a feedback wavefront shaping technology based on digital micromirror devices is proposed, which combines the hardware design and algorithm optimization. Through a new hardware-triggered image acquisition system and dynamic subgroup genetic algorithm, the image acquisition rate and focusing efficiency are significantly improved, and the light is quickly focused in dynamic turbid water. The imaging speed is about 34.89 times that of the traditional method based on a software-triggered image acquisition system and genetic algorithm. The experimental results of focusing through a milk solution show that this technique has a remarkable effect in improving the efficiency of dynamic focusing and the light intensity of focusing region, which provides an effective optimization strategy for optical imaging technology through a dynamic scattering medium in the future.

Programmable scanning diffuse speckle contrast imaging of cerebral blood flow.

Cerebral blood flow (CBF) imaging is crucial for diagnosing cerebrovascular diseases. However, existing large neuroimaging techniques with high cost, low sampling rate, and poor mobility make them unsuitable for continuous and longitudinal CBF monitoring at the bedside. We aimed to develop a low-cost, portable, programmable scanning diffuse speckle contrast imaging (PS-DSCI) technology for fast, high-density, and depth-sensitive imaging of CBF in rodents. The PS-DSCI employed a programmable digital micromirror device (DMD) for remote line-shaped laser (785nm) scanning on tissue surface and synchronized a 2D camera for capturing boundary diffuse laser speckle contrasts. New algorithms were developed to address deformations of line-shaped scanning, thus minimizing CBF reconstruction artifacts. The PS-DSCI was examined in head-simulating phantoms and adult mice. The PS-DSCI enables resolving intralipid particle flow contrasts at different tissue depths. In vivo experiments in adult mice demonstrated the capability of PS-DSCI to image global/regional CBF variations induced by 8% inhalation and transient carotid artery ligations. Compared with conventional point scanning, line scanning in PS-DSCI significantly increases spatiotemporal resolution. The high sampling rate of PS-DSCI is crucial for capturing rapid CBF changes while high spatial resolution is important for visualizing brain vasculature.

Orthonormalization of phase-only basis functions.

Generation of orthonormal optical fields using phase-only spatial light modulators (SLM) or amplitude-only digital micromirror devices (DMD) is an active and diverse research field, with a wide variety of applications. However, these approaches typically come with limited accuracy, and a significant loss in resolution and intensity. We present a different approach: we construct orthonormal fields that can be generated exactly on phase-only hardware without loss of resolution or intensity. Our method can use any set of fields as a starting point and orthonormalize them. Our approach allows control over application-specific requirements such as smoothness, symmetry and overall shape. In many use cases, sets of orthonormal fields can be used as a 'drop-in replacement' for other sets of fields. We demonstrate the practical benefit of our approach in a wavefront shaping experiment, achieving a factor 1.5 increase in performance over a non-orthonormal phase-only basis.

Direct object recovery from the Fraunhofer diffraction integral.

In this Letter, we present a novel, to the best of our knowledge, approach for recovering objects directly from the Fraunhofer diffraction integral, where the diffraction field of an object is approximated by the Fourier transform of this object augmented by an additional phase factor. This phase factor at the observation plane is universal for the diffraction fields generated by objects located at the same plane and illuminated by the same monochromatic plane wave. It can be first extracted from dividing the Fraunhofer diffraction field by the Fourier transform of an object reference. Rapid recovery for unknown objects is then enabled after applying a two-dimensional inverse Fourier transform to the ratio of the Fraunhofer diffraction fields to the phase factor. This approach is verified experimentally by constructing a modified Mach-Zehnder interferometer, with a digital micromirror device (DMD) generating the objects of desired structures. To record the Fraunhofer diffraction and interference patterns on a finite-size CCD camera, a convex lens is introduced with the CCD sensing surface positioned at the focal plane of the lens. The strategy described in [Nat. Commun.7, 10820 (2016)10.1038/ncomms10820] is applied to extract the phase of the diffraction field from the interference pattern. The results demonstrate the efficiency of our approach in swiftly and accurately recovering small objects with elimination of zero-order and conjugate images.

Light Field Modulation Algorithms for Spatial Light Modulators: A Review

The coding method of spatial light modulator is the core key of spatial light field modulation technology, and the needs of the modulation algorithm are different under the specified mode and application requirements. This paper first reviews the progress made in recent years in light field control algorithms for digital micromirror devices (DMDs) and liquid crystal spatial light modulators (LC-SLM). Based on existing algorithms, the impact of optimization methods is analyzed. Then, the application areas of the different algorithms are summarized, and the characteristics of the control algorithms are analyzed. In addition, this review highlights innovative breakthroughs achieved by using various coding schemes and spatial light modulators (SLM) to manipulate the light field. Finally, critical future challenges facing emerging control algorithm technologies are outlined, while prospects for developing SLM control algorithms are proposed.

High-Resolution Single-Pixel Imaging of Spatially Sparse Objects: Real-Time Imaging in the Near-Infrared and Visible Wavelength Ranges Enhanced with Iterative Processing or Deep Learning.

We demonstrate high-resolution single-pixel imaging (SPI) in the visible and near-infrared wavelength ranges using an SPI framework that incorporates a novel, dedicated sampling scheme and a reconstruction algorithm optimized for the rapid imaging of highly sparse scenes at the native digital micromirror device (DMD) resolution of 1024 × 768. The reconstruction algorithm consists of two stages. In the first stage, the vector of SPI measurements is multiplied by the generalized inverse of the measurement matrix. In the second stage, we compare two reconstruction approaches: one based on an iterative algorithm and the other on a trained neural network. The neural network outperforms the iterative method when the object resembles the training set, though it lacks the generality of the iterative approach. For images captured at a compression of 0.41 percent, corresponding to a measurement rate of 6.8 Hz with a DMD operating at 22 kHz, the typical reconstruction time on a desktop with a medium-performance GPU is comparable to the image acquisition rate. This allows the proposed SPI method to support high-resolution dynamic SPI in a variety of applications, using a standard SPI architecture with a DMD modulator operating at its native resolution and bandwidth, and enabling the real-time processing of the measured data with no additional delay on a standard desktop PC.

Modeling the generation and control of Bessel-like beams generated by annular patterns on a digital micromirror device

Bessel beams have been generated using different methods, such as Axicon lens, digital micromirror device (DMD), etc. Due to the infinite energy requirement of ideal Bessel beams in all space, the generated Bessel beams are more appropriately called Bessel-like beams in practice, which are approximations of the ideal Bessel beams. In this work, we theoretically investigated the generation of Bessel-like beams using annular patterns loaded on a DMD based on the scalar diffraction theory. The model predictions were compared and verified with our previous experimental results. For the first time, the theoretical study shows that the DMD-generated Bessel-like beams have an additional amplitude term depending on the annular radius, ring thickness, and incident angle compared with ideal Bessel beams. Furthermore, we modeled the superposition of two Generated Bessel-like beams using two coaxial annular patterns on a DMD, which revealed the periodic intensity distribution along the z axis as predicted previously based on the superposition of two ideal coaxial Bessel beams. Both the simulations and experiments give a similar periodic length that is close to the theoretical values. The modeling results show that the DMD-based method could not only generate a reasonable approximation of the ideal Bessel beams with good controllability and engineering applications but more importantly, provide explicit formulas to guide the design of the annular patterns on the DMD in order to generate and control Bessel-like beams for practical applications.

Matching for realizing high-speed reading in holographic data storage system

In the era of big data, data storage density, and reading speed are becoming increasingly important. Therefore, achieving high-speed data reading in the holographic data storage system is particularly crucial. The key to realizing high-speed data reading in the holographic data storage system is to ensure frame rate matching among key devices. In this paper, we research the frame rate matching of the digital micro-mirror device (DMD), the acousto-optic modulator (AOM), the high-speed camera, and the electric displacement table loaded with materials. We have determined the maximum matching frame rate of the system with respect to changes in the exposure time and resolution of the camera, as well as the phase difference between the AOM and DMD. By finely adjusting the parameters of key devices in the system, we can ultimately achieve a matching frame rate of 18kHz. Under conditions where the electric displacement table speed is 40 mm/s, and the light intensity of the incident materials is 0.6 mW, the holographic data storage system can attain a reading frame rate of up to 8kHz, resulting in a data transfer rate of 5.8GB/s.

High space-bandwidth product DMD holographic display using gradient descent optimization.

Digital micromirror devices (DMDs), owing to their rapid refresh rates and ability to shape particular optical patterns, are key tools for holographic 3D near-eye displays. However, relying on a single-sideband (SSB) filter to eliminate crosstalk from zero-order and conjugate noise leads to an enormous decrease in the utilization of spatial bandwidth product (SBP). In this paper, we develop a new strategy for the binary hologram optimization framework to enable the full utilization of SBP of DMD holographic display by minimizing conjugate noise. Meanwhile, we design a binary operator to estimate the binarization process during the hologram optimization procedure. The experimental results demonstrate our approach can achieve higher SBP and competitive reconstruction quality compared with the conventional single-sideband filtering method.

Spatial Optical Simulator for Classical Statistical Models.

Optical simulators for the Ising model have demonstrated great promise for solving challenging problems in physics and beyond. Here, we develop a spatial optical simulator for a variety of classical statistical systems, including the clock, XY, Potts, and Heisenberg models, utilizing a digital micromirror device composed of a large number of tiny mirrors. Spins, with desired amplitudes or phases of the statistical models, are precisely encoded by a patch of mirrors with a superpixel approach. Then, by modulating the light field in a sequence of designed patterns, the spin-spin interaction is realized in such a way that the Hamiltonian symmetries are preserved. We successfully simulate statistical systems on a fully connected network, with ferromagnetic or Mattis-type random interactions, and observe the corresponding phase transitions between the paramagnetic and the ferromagnetic or spin-glass phases. Our results largely extend the research scope of spatial optical simulators and their versatile applications.

Fiber-integrated hybrid achromatic microlenses by combined femtosecond laser 3D printing

Compact achromats for visible wavelengths are crucial for miniaturized and lightweight full-color endoscopes. Emerging femtosecond laser 3D printing technology offers new possibilities for enhancing the optical performance of miniature imaging lenses on fibers. In this work, we combine refractive and diffractive elements with complementary dispersive properties to create thin, high-performance hybrid achromatic lenses within the visible spectrum, avoiding the use of different optical materials. Using a fiber-integrated hybrid achromatic lens array, clear images are captured across different wavelengths. The fabrication process is carried out using femtosecond laser direct writing (DLW) assisted by femtosecond projection lithography based on a digital micromirror device (DMD). Our work is expected to significantly contribute to the advancement of integrated and miniaturized biomedical imaging devices.

(Invited) Light-Guided Electrodeposition for Functional Integration of Catalyst Pattern on Semiconductor for Efficient Oxygen Evolution Reaction

Photoelectrochemical cells (PECs) for water splitting typically rely on catalysts deposited on the semiconductor due to its lack of intrinsic electrocatalytic activity. However, the placement of catalysts within the light path between the source and semiconductor in artificial leaf-based architectures can hinder the semiconductor's light absorption, diminishing photoelectrochemical activity, especially at high catalyst loading. To address this challenge, we propose a strategy involving the controlled formation of patterned catalysts on the semiconductor surface. This approach, utilizing light-guided electrodeposition facilitated by a digital micromirror device (DMD), enables the direct, localized deposition of transition metal-based catalysts. The resulting patterned catalysts correspond to the light pattern, allowing for optimized photoelectrochemical performance. We demonstrate the efficacy of this strategy on a hematite (α-Fe2O3)-based photoanode, achieving enhanced performance with grid-patterned CoPi catalysts. This approach not only facilitates high catalyst loading but also ensures sufficient light penetration through the exposed intrinsic surface of α-Fe2O3. Our findings suggest that this technique holds promise for advancing the commercialization of PECs, particularly for self-biased water splitting devices aimed at green H2 production.

Automated Grayscale Modulation to Enhance Digital Light Processing Fabrication Accuracy by Correcting Non-uniform Illumination

Abstract In this study, we addressed the challenge of non-uniform illumination in custom Digital Light Processing (DLP) systems, often caused by imperfections in the Digital Micromirror Device (DMD) or misalignments in the optical assembly. These issues lead to dimensional inconsistencies across the fabrication area. To overcome this, we developed an automated system for generating a “grayscale” mask that compensates for non-uniform illumination. This system serves as a pre-printing calibration procedure, enhancing the precision of 3D printed features. Our approach involves dividing the fabrication area into a mesh grid where in-situ light intensities are measured. The system then calculates and acquires grayscale values that correspond to the minimum light intensity, thereby creating a grayscale mask that levels light distribution across the printing area. Additionally, we outline a method to generate grayscale masks for various LED Excitation Powers (LEPs) based on initial data from three predefined powers. We evaluated the effectiveness of this method by comparing features printed with standard “full white” images to those adjusted with our grayscale-modulated images. The results show significant enhancements in both uniformity and dimensional accuracy, confirming the efficacy of our approach. This study demonstrates the potential of grayscale modulation to resolve illumination issue in DLP manufacturing to ensure higher precision in printed features.

High-Throughput Multiplexed Plasmonic Color Encryption of Microgel Architectures via Programmable Dithering-Mask Flow Microlithography.

Silver nanoparticles (AgNPs) are known for their unique plasmonic colors and interaction with light, making them ideal for color printing and data encoding. Traditional methods like electron beam lithography (EBL) and focused ion beam (FIB) milling, however, suffer from low throughput and high costs. In this paper, a scalable and cost-efficient method is introduced for producing multiplexed plasmonic colors by in situ photoreducing AgNPs within microgel architectures with controlled porosity. Utilizing a digital micro-mirror device (DMD)-based flow microlithography system combined with a programmable dithering-mask technique, the high-throughput synthesis of shape or barcoded microparticles is facilitated, along with large-scale, high-resolution images embedded with hidden multiplexed plasmonic colors. This approach allows for a hidden multiplexed plasmonic color code library, significant enhancing the encoding capacity of barcode microparticles from 33 to 303 (a 1000-fold increase). Additionally, quantitative agreement is achieved between chemically encrypted and optically decrypted plasmonic colors using a deep learning classifier. Moreover, the method also supports the production of large scale (>5.6 × 5.6cm2), high-resolution (>300 dpi) microgel arrays encrypted with multiple plasmonic colors in under 30min. The multiplexed plasmonic coloration strategy in microgel architectures paves a new way for hidden data storage, secure optical labeling, and anti-counterfeiting technologies.

Fast and light-efficient wavefront shaping with a MEMS phase-only light modulator

Over the last two decades, spatial light modulators (SLMs) have revolutionized our ability to shape optical fields. They grant independent dynamic control over thousands of degrees-of-freedom within a single light beam. In this work we test a new type of SLM, known as a phase-only light modulator (PLM), that blends the high efficiency of liquid crystal SLMs with the fast switching rates of binary digital micro-mirror devices (DMDs). A PLM has a 2D mega-pixel array of micro-mirrors. The vertical height of each micro-mirror can be independently adjusted with 4-bit precision. Here we provide a concise tutorial on the operation and calibration of a PLM. We demonstrate arbitrary pattern projection, aberration correction, and control of light transport through complex media. We show high-speed wavefront shaping through a multimode optical fiber – scanning over 2000 points at 1.44 kHz. We make available our custom high-speed PLM control software library developed in C++. As PLMs are based upon micro-electromechanical system (MEMS) technology, they are polarization agnostic, and possess fundamental switching rate limitations equivalent to that of DMDs – with operation at up to 10 kHz anticipated in the near future. We expect PLMs will find high-speed light shaping applications across a range of fields including adaptive optics, microscopy, optogenetics and quantum optics.

Stabilization of light sources with digital micromirror devices for calibration of high-precision photometric instruments

Stabilization of light sources with digital micromirror devices for calibration of high-precision photometric instruments

Computational temporal ghost imaging based on complementary modulation

Abstract We report an experimental demonstration of temporal ghost imaging in which a digital micromirror device (DMD) and +1/−1 binary modulation have been combined to give an accurate reconstruction of a nonperiodic time object. Compared to the 0/1 modulation, the reconstruction signal can be improved greatly by +1/−1 binary modulation even with half of the measurements. Experimental results show that 0/1 binary temporal objects up to 4 kHz and sinusoidal time objects up to 1 kHz can be reconstructed by this method. The influences of modulation speed and array detector gray levels are also discussed.

A Scalable Digital Light Processing 3D Printing Method.

The 3D printing method based on digital light processing (DLP) technology can transform liquid resin materials into complex 3D models. However, due to the limitations of digital micromirror device (DMD) specifications, the normal DLP 3D printing method (NDPM) cannot simultaneously process large-size and small-feature parts. Therefore, a scalable DLP 3D printing method (SDPM) was proposed. Different printing resolutions for a part were designed by changing the distance between the projector and the molding liquid level. A scalable DLP printer was built to realize the printing resolution requirements at different sizes. A series of experiments were performed. Firstly, the orthogonal experimental method was used, and the minimum and maximum projection distances were obtained as 20.5 cm and 30.5 cm, respectively. Accordingly, the layer thickness, exposure time, and waiting leveling time were 0.08 mm, 3 s, and 6 s and 0.08 mm, 7 s, and 10 s. Secondly, single-layer column feature printing was finished, which was shown to have two minimum printing resolutions of 101 μm and 157 μm at a projection distance of 20.5 cm and 30.5 cm. Thirdly, a shape accuracy test was conducted by using the SDPM. Compared with the NDPM, the shape accuracy of the small-feature round, diamond, and square parts was improved by 49%, 42%, and 2%, respectively. This study verified that the SDPM can build models with features demonstrating high local shape accuracy.

Generation of partially coherent full Poincaré beam arrays and their Stokes scintillations in turbulent media

A type of vector beam arrays, called partially coherent full Poincaré (PCFP) beam arrays, is introduced and experimentally synthesized using modal-vector-decomposition method. Our experimental system involves a digital micro-mirror device, which can generate such beam arrays with controllable spatial coherence and array structure in almost real-time, enabling to test the impact of atmospheric turbulence on them. Furthermore, we experimentally examine the scintillations of four Stokes parameters (denoted as S0, S1, S2, and S3) of PCFP beam arrays propagating through lab-simulated turbulence. The results indicate that the Stokes scintillations decrease as the number of beamlets increase or spatial coherence decreases. In contrast to S0 scintillation (intensity scintillation), S1, S2, or S3 scintillation is less affected by the turbulence under the same conditions. Our experimental results show that S2 and S3 scintillations could reduce by 67.2% and 52.4% compared to the intensity scintillation in strong turbulence. Our findings have potential applications in free-space optical communication when the Stokes parameter S2 or S3 is served as an information carrier.

High-fidelity metasurface holography illuminated by an ultra-uniform flat-top beam generated through active wavefront shaping.

We present the first, to our knowledge, metasurface holographic display method with exceptional fidelity and minimal edge noise, based on highly uniform flat-top light generated by a digital micromirror device (DMD). Based on the error-diffusion algorithm and iterative refinement process, the amplitude distribution of the initial Gaussian light was dynamically closed-loop modulated, and the standard difference of the intensity of the 3 mm diameter center flat-top beam was reduced to less than 3.4%. The holographic image generated by a flat-top beam illuminated metasurface using this method exhibited a reduction in the brightness coefficient of variation (CV) from 0.82 to 0.58 and a reduction in the contrast difference (CD) of an image pixel intensity from 240 to 160. This method can efficiently improve the quality and uniformity of flat-top light, developing a new perspective for high resolution and fidelity metasurface holographic display by modulating a light source.