Single Digital Micromirror Device Research Articles

Multi-color complex spatial light modulation with a single digital micromirror device.

Spatial light modulators enabling complex light field manipulation has opened up many opportunities in biomedical imaging, holographic display, and adaptive optics. However, traditional spatial light modulators do not allow multi-color operations simultaneously due to their physical constraints, while multi-color modulations are highly desirable in many applications. To overcome this limitation, we demonstrate a multi-color spatial complex light field modulation with a single binary hologram on digital micromirror devices (DMD). This method combines several neighboring micro-mirror pixels into a giant single superpixel, in which the light field's amplitude and phase can be individually determined by internal pixel combinations, and the dynamic range of phase modulation can exceed 2π for the single wavelength. As a result, this extra phase modulation range offers an additional degree of freedom for independent multi-wavelength light modulation. Based on this scheme, multi-color light modulations have been demonstrated in a 2D plane as well as in multiple 3D holographic planes. Moreover, a dual-colored Airy beam has been realized using the same technique. These results bring complex light modulation into a multi-color regime, paving the way for practical applications in information display, imaging, and optical trapping.

Confocal Single-Pixel Imaging

Obtaining depth-selective images requires gating procedures such as spatial, nonlinear, or coherence gating to differentiate light originating from different depths of the volume of interest. Nonlinear gating requires pulsed excitation sources and excitation probes, limiting easy usage. Coherence gating also requires broadband sources and interferometry requiring specialized stable setups. Spatial gating can be used both for fluorescence and reflection geometry and various light sources and thus has the least requirements on hardware, but still requires the use of a pinhole which makes it difficult to use for photography or widefield imaging schemes. Here, we demonstrate that we can utilize a single digital micromirror device (DMD) to simultaneously function as a dynamic illumination modulator and automatically synchronized dynamic pinhole array to obtain depth-sectioned widefield images. Utilizing the multiplexed measurement advantage of single-pixel imaging, we show that the depth and ballistic light gating of the confocal single pixel imaging scheme can be utilized to obtain images through glare and multiple scattering where conventional widefield imaging fails to recover clear images due to saturation or random scattered noise.

In-situ 3D shape measurement system for a high-temperature object in a plasma wind tunnel via DMD-projection laser structured light and adaptive speckle filtering

The evaluation of an object’s 3D shape change during ablation in wind tunnel testing is critical for the optimization of the thermal protection system. However, strong thermal radiation and a harsh environment cause challenges to the traditional measurement methods. A single camera digital micro-mirror device (DMD) projector-structured laser light system is proposed for in-situ 3D shape measurement in a wind tunnel test. A customized DMD combined with a laser source is devised for projecting concentrated full-field high-power structured light stripes. To filter laser speckle noise in projected chessboard images for model calibration, an auto-window Kuwahara adaptive filter is put forward. The 3D shape of a blunt-head cylinder was in-situ measured in a plasma wind tunnel which reached a maximum temperature of 1950 °C. The diameter reconstruction error was within 0.85% (0.17/20.03 mm). With projected laser light and multi-step filters, the ablation process of the front face of a dome-top cylinder at 1950 °C was clearly observed at a long working distance over 1.5 m.

Motionless synthesis and scanning of lattice light sheets with a single digital micromirror device

Lattice light sheet microscopy is uniquely positioned in biomedical imaging modalities due to its superior performance in temporal-spatial resolution and low phototoxicity. However, the imaging system is commonly complicated because producing lattice light sheets involves mechanical scanning and precise alignment. In this Letter, we present an experimental scheme for motionless synthesis and scanning of lattice light sheets using a single digital micromirror device. By fully exploiting its ability of complex amplitude modulation and fast switching, single-shot construction of a uniform lattice light sheet can be achieved by digital dithering. In particular, fast scanning of the lattice light sheet in the depth direction is also realized without any mechanical motion. As a proof of concept, various lattice light sheets are generated and characterized in the experiments. Our work is expected to benefit the development of a compact and low-price lattice light-sheet microscope for biomedical imaging.

Dynamic full-color digital holographic 3D display on single DMD

Digital holography has high potentials for future 3D imaging and display technology. We present a method for a dynamic full-color digital holographic 3D display on single digital micro-mirror device (DMD) with full-color, high-speed and high-fidelity characteristics. We combine the square regions of adjacent micro-mirrors into super-pixels that can modulate amplitude and phase independently. Gray images are achieved by amplitude modulation and precise positioning of each color is achieved by phase modulation. The proposed method realizes a full-color imaging based on the three primary colors and achieves measured structural similarity of more than 88% and color similarity of more than 98%, while retaining the high switch speed of 9 kHz, thus achieving dynamic full-color 3D display on charge-coupled device (CCD).

A hyperspectral projector for simultaneous 3D spatial and hyperspectral imaging via structured illumination.

Both 3D imaging and hyperspectral imaging provide important information of the scene and combining them is beneficial in helping us perceive and understand real-world structures. Previous hyperspectral 3D imaging systems typically require a hyperspectral imaging system as the detector suffers from complicated hardware design, high cost, and high acquisition and reconstruction time. Here, we report a low-cost, high-frame rate, simple-design, and compact hyperspectral stripe projector (HSP) system based on a single digital micro-mirror device, capable of producing hyperspectral patterns where each row of pixels has an independently programmable spectrum. We demonstrate two example applications using the HSP via hyperspectral structured illumination: hyperspectral 3D surface imaging and spectrum-dependent hyperspectral compressive imaging of volume density of participating medium. The hyperspectral patterns simultaneously encode the 3D spatial and spectral information of the target, requiring only a grayscale sensor as the detector. The reported HSP and its applications provide a solution for combining structured illumination techniques with hyperspectral imaging in a simple, efficient, and low-cost manner. The work presented here represents a novel structured illumination technique that provides the basis and inspiration of future variations of hardware systems and software encoding schemes.

Fast laser beam steering into multiple diffraction orders with a single digital micromirror device for time-of-flight lidar

The sampling rate and angular resolution of diffraction-based beam steering employing a digital micromirror device (DMD) can be simultaneously enhanced by at least an order of magnitude by synchronizing multiple nanosecond laser sources and pulses during each DMD actuation. A time-of-flight single-chip DMD lidar with three sources measures a range at a 3.34 kHz sampling rate and a 3.4° angular resolution across a 48° field of view. Employing multiple diffraction orders of the DMD improves the sampling rate at least by a factor of 2 and up to the number of diffraction orders supported by the DMD. An improved sampling rate of 6.68 kHz with a 9.6° angular resolution is experimentally demonstrated by illuminating micromirrors multiple times within a single transition period of the micromirrors.

Occlusion-capable optical-see-through near-eye display using a single digital micromirror device.

Occlusion of a real scene by displayed virtual images mitigates incorrect depth cues and enhances image visibility in augmented reality applications. In this Letter, we propose a novel optical scheme for the occlusion-capable optical-see-through near-eye display. The proposed scheme uses only a single spatial light modulator, as the real-scene mask and virtual image display simultaneously. A polarization-based double-pass configuration is also combined, enabling a compact implementation. The proposed scheme is verified by optical experiments which demonstrate a 60 Hz red-green-blue video display with a 4-bit depth for each color channel and per-pixel dynamic occlusion of a 90.6% maximum occlusion ratio.

Aberration-free 3D imaging via DMD-based two-photon microscopy and sensorless adaptive optics.

In this Letter, we present a new, to our knowledge, aberration-free 3D imaging technique based on digital micromirror device (DMD)-based two-photon microscopy and sensorless adaptive optics (AO), where 3D random-access scanning and modal wavefront correction are realized using a single DMD chip at 22.7 kHz. Specifically, the DMD is simultaneously used as a deformable mirror to modulate a distorted wavefront and a fast scanner to maneuver the laser focus in a 3D space by designed binary holograms. As such, aberration-free 3D imaging is realized by superposing the wavefront correction and 3D scanning holograms. Compared with conventional AO devices and methods, the DMD system can apply optimal wavefront correction information to different imaging regions or even individual pixels without compromising the scanning speed and device resolution. In the experiments, we first focus the laser through a diffuser and apply sensorless AO to retrieve a corrected focus. After that, the DMD performs 3D scanning on a Drosophila brain labeled with green fluorescent protein. The two-photon imaging results, where optimal wavefront correction information is applied to 3×3 separate regions, demonstrate significantly improved resolution and image quality. The new DMD-based imaging solution presents a compact, low-cost, and effective solution for aberration-free two-photon deep tissue imaging, which may find important applications in the field of biophotonics.

Snapshot spatial-temporal compressive imaging.

We build a compressive imaging system that can reconstruct high-speed videos of two fields-of-view by capturing a single frame. A single digital micromirror device is employed to implement high-speed modulation simultaneously on both scenes in a manner that does not compromise spatial resolution. We utilize deep denoising priors in the plug-and-play framework for efficient reconstruction. Two spatial-temporal data cubes, each with the size $ 650 \times 650 \times 20 $650×650×20, are reconstructed from a single two-dimensional spatial measurement.

Factored Occlusion: Single Spatial Light Modulator Occlusion-capable Optical See-through Augmented Reality Display.

Occlusion is a powerful visual cue that is crucial for depth perception and realism in optical see-through augmented reality (OST-AR). However, existing OST-AR systems additively overlay physical and digital content with beam combiners - an approach that does not easily support mutual occlusion, resulting in virtual objects that appear semi-transparent and unrealistic. In this work, we propose a new type of occlusion-capable OST-AR system. Rather than additively combining the real and virtual worlds, we employ a single digital micromirror device (DMD) to merge the respective light paths in a multiplicative manner. This unique approach allows us to simultaneously block light incident from the physical scene on a pixel-by-pixel basis while also modulating the light emitted by a light-emitting diode (LED) to display digital content. Our technique builds on mixed binary/continuous factorization algorithms to optimize time-multiplexed binary DMD patterns and their corresponding LED colors to approximate a target augmented reality (AR) scene. In simulations and with a prototype benchtop display, we demonstrate hard-edge occlusions, plausible shadows, and also gaze-contingent optimization of this novel display mode, which only requires a single spatial light modulator.

Angular and spatial light modulation by single digital micromirror device for multi-image output and nearly-doubled étendue

The "Angular Spatial Light Modulator" (ASLM) achieves simultaneous angular and spatial light modulation at a plane by combining Digital Micromirror Device (DMD) based programmable blazed grating beam steering and binary pattern sequencing. The ASLM system multiplies the number of effective output pixels of the DMD for increased spatial and/or angular degrees of freedom, and nearly-doubles the étendue output of the DMD. We implement multiple illumination and projection schemes to demonstrate ASLM-based extended FOV display, light-field projection, and multi-view display. We also implement time-multiplexed pupil segmented illumination to extend the pattern steering to two dimensions.

Digital micromirror device (DMD)-based high-cycle tensile fatigue testing of 1D nanomaterials

Fatigue behavior of nanomaterials could be critical for numerous nanomechanical applications involving dynamic deformation processes, such as in flexible electronics devices. Despite that substantial research efforts have been made on mechanical characterization of various one-dimensional (1-D) nanomaterials under quasi-static loading, very few works have been done so far on the challenging fatigue testing of individual 1-D nanostructures, in particular for their high-cycle fatigue behavior. Here, instead of designing a new device, commercially available digital micromirror device (DMD) has been adopted to develop a cost-effective platform for investigating the high-cycle fatigue responses of individual nanowires/nanotubes, due to its ultra-high actuation frequency (up to 32,000 Hz), under cyclic tensile straining. We further demonstrated that, due to the small footprint of this MEMS-type device and its remote controlling mechanism, desired in situ tensile fatigue testing of individual nanowire can be achieved inside a scanning electron microscope (SEM). In addition, the millions of independent movable micromirrors on a single DMD chip make our platform particularly suitable for high-throughput testing of various 1-D nanomaterial samples for the statistical analysis of their fatigue characteristics.

High-speed spatial control of the intensity, phase and polarisation of vector beams using a digital micro-mirror device.

The dynamic spatial control of light fields is essential to a range of applications, from microscopy to optical micro-manipulation and communications. Here we describe the use of a single digital micro-mirror device (DMD) to generate and rapidly switch vector beams with spatially controllable intensity, phase and polarisation. We demonstrate local spatial control over linear, elliptical and circular polarisation, allowing the generation of radially and azimuthally polarised beams and Poincaré beams. All of these can be switched at rates of up to 4kHz (limited only by our DMD model), a rate ∼2 orders of magnitude faster than the switching speeds of typical phase-only spatial light modulators. The polarisation state of the generated beams is characterised with spatially resolved Stokes measurements. We also describe detail of technical considerations when using a DMD, and quantify the mode capacity and efficiency of the beam generation. The high-speed switching capabilities of this method will be particularly useful for the control of light propagation through complex media such as multimode fibers, where rapid spatial modulation of intensity, phase and polarisation is required.

Embedded optics and electronics single digital micromirror device-based agile pixel broadband imager and spectrum analyzer for laser beam hotspot detection

To the best of the authors’ knowledge, proposed is the first embedded optics and electronics-based agile pixel broadband optical imager and spectrum analyzer using a single digital micromirror device (DMD) for laser beam hotspot detection. Specifically, the novel design engages both the wavelength-dependent grating structure of the DMD optical chip and its three-tilt-state micromirror programmability to form both an optical spectrum analyzer (OSA) and an agile pixel imager within one basic instrument. Also, to our knowledge, presented for the first time for a DMD chip is a complete mathematical analysis for incident laser beam operations via diffraction theory. Using off-the-shelf components and the Texas Instruments (TI) Lightcrafter DLP chip and drive electronics, embedded engineering of the proposed instrument is implemented for the visible laser wavelength band. Experimental OSA operation of the instrument is demonstrated using classic laser wavelengths of 633 and 532 nm with beam power levels of 20 and 180 mW, respectively. Experimental imaging operation of the instrument compared with a commercial scanning slit-based laser beam profiler is successfully conducted for a 633 nm test laser beam having a hotspot with ∼68% peak-to-null power drop near its center. Applications for the proposed imager-OSA instrument include laser beam testing during laser assembly and manufacturing operations.

Demonstration of multi-wavelength tunable fiber lasers based on a digital micromirror device processor.

Based on a digital micromirror device (DMD) processor as the multi-wavelength narrow-band tunable filter, we demonstrate a multi-port tunable fiber laser through experiments. The key property of this laser is that any lasing wavelength channel from any arbitrary output port can be switched independently over the whole C-band, which is only driven by single DMD chip flexibly. All outputs display an excellent tuning capacity and high consistency in the whole C-band with a 0.02nm linewidth, 0.055nm wavelength tuning step, and side-mode suppression ratio greater than 60dB. Due to the automatic power control and polarization design, the power uniformity of output lasers is less than 0.008dB and the wavelength fluctuation is below 0.02nm within 2h at room temperature.

Nonlinear structured-illumination enhanced temporal focusing multiphoton excitation microscopy with a digital micromirror device.

In this study, the light diffraction of temporal focusing multiphoton excitation microscopy (TFMPEM) and the excitation patterning of nonlinear structured-illumination microscopy (NSIM) can be simultaneously and accurately implemented via a single high-resolution digital micromirror device. The lateral and axial spatial resolutions of the TFMPEM are remarkably improved through the second-order NSIM and projected structured light, respectively. The experimental results demonstrate that the lateral and axial resolutions are enhanced from 397 nm to 168 nm (2.4-fold) and from 2.33 μm to 1.22 μm (1.9-fold), respectively, in full width at the half maximum. Furthermore, a three-dimensionally rendered image of a cytoskeleton cell featuring ~25 nm microtubules is improved, with other microtubules at a distance near the lateral resolution of 168 nm also able to be distinguished.

Rapid generation of light beams carrying orbital angular momentum

We report a technique for encoding both amplitude and phase variations onto a laser beam using a single digital micro-mirror device (DMD). Using this technique, we generate Laguerre-Gaussian and vortex orbital-angular-momentum (OAM) modes, along with modes in a set that is mutually unbiased with respect to the OAM basis. Additionally, we have demonstrated rapid switching among the generated modes at a speed of 4 kHz, which is much faster than the speed regularly achieved by phase-only spatial light modulators (SLMs). The dynamic control of both phase and amplitude of a laser beam is an enabling technology for classical communication and quantum key distribution (QKD) systems that employ spatial mode encoding.

Grayscale laser image formation using a programmable binary mask

We present grayscale laser image formation from a programmable binary mask using a digital micromirror device (DMD) followed by a telescope with an adjustable pinhole low-pass filter. System performance was measured by comparing the intensity conformity with respect to the target image and by the energy conversion efficiency. A theoretical analysis of image precision proved high-precision image formation and inspired the iterative pattern refinement process based on the point spread function of a single DMD pixel to seek optimized image quality. We derived the diffraction efficiency formula of the DMD and discussed the overall system energy efficiency with operation wavelengths. Actual image precision performance was evaluated by measuring the root-mean-square (RMS) error of a series of sinusoidal-flattop profiles with different system bandwidths. We produced grayscale laser images with different spatial spectral content using intensity profiles of Laguerre-Gaussian, Hermite-Gaussian, and Lena-flattop beams. Measured RMS errors of all examples of various bandwidths were consistent with the image precision of the sinusoidal reference patterns. The ripple effect caused by the sharp-edged pinhole was the major contributor to the residual error in the output images. Error histograms had a zero-mean Gaussian distribution with standard deviation equal to the value of the RMS error.

Design of illumination and projection optics for projectors with single digital micromirror devices

We present a new optical system design for a projector with a single digital micromirror device (Texas Instruments Digital Micromirror Device) that improves on previous designs in terms of optical efficiency, uniformity, and contrast while yielding a low-profile and compact system. A rod integrator is incorporated with a compact relay system to maximize light efficiency and to increase illumination uniformity. The uniformity achieved by the optimized optical system was calculated to be 94%. In addition, this unique light-separator design has dual output channels to increase the image contrast by steering the off-state light away from the projection lens. This projector design provides very efficient light utilization, and we discuss how the geometrical optical efficiency of the system can be boosted to approach the theoretical maximum.