Digital Mirror Device Research Articles

Smartphone-based optical sectioning (SOS) microscopy with a telecentric design for fluorescence imaging.

We propose a smartphone-based optical sectioning (SOS) microscope based on the HiLo technique, with a single smartphone replacing a high-cost illumination source and a camera sensor. We built our SOS with off-the-shelf optical, mechanical cage systems with 3D-printed adapters to seamlessly integrate the smartphone with the SOS main body. The liquid light guide can be integrated with the adapter, guiding the smartphone's LED light to the digital mirror device (DMD) with neglectable loss. We used an electrically tuneable lens (ETL) instead of a mechanical translation stage to realise low-cost axial scanning. The ETL was conjugated to the objective lens's back pupil plane (BPP) to construct a telecentric design by a 4f configuration to maintain the lateral magnification for different axial positions. SOS has a 571.5µm telecentric scanning range and an 11.7µm axial resolution. The broadband smartphone LED torch can effectively excite fluorescent polystyrene (PS) beads. We successfully used SOS for high-contrast fluorescent PS beads imaging with different wavelengths and optical sectioning imaging of multilayer fluorescent PS beads. To our knowledge, the proposed SOS is the first smartphone-based HiLo optical sectioning microscopy (£1965), which can save around £7035 compared with a traditional HiLo system (£9000). It is a powerful tool for biomedical research in resource-limited areas.

Optimizing microlens arrays for incoherent HiLo microscopy

HiLo microscopy is a powerful, low-cost, and easily configurable technique for acquiring high-contrast optically-sectioned images. However, traditional HiLo microscopes are based on coherent light sources with diffusive glass plates or incoherent light sources with digital mirror devices (DMD) and spatial light modulators (SLM), which are more expensive. Here, we propose a new low-cost HiLo microscopy technique using MLAs and incoherent LED light sources. We simulated structured illumination (SI) patterns and HiLo image generation. To observe how MLAs affect HiLo images, we used three common MLAs with specific microlens pitch and numerical aperture (NA) to generate periodic illumination patterns. Our simulations concluded that the MLA's NA does not significantly affect HiLo images, and a larger lens pitch can bring a higher image contrast. However, there is an optimized lens pitch. If the lens pitch is equal to or higher than 140 μm, artifacts are observed in HiLo images. Based on our simulations, employing the cross-type MLA with a 0.01NA and a period of 120 μm yields the optimal HiLo image (94.6 % contrast). In our quantitative analysis with the traditional HiLo, where SI patterns were set with the same period, we calculated the SSIM index between each HiLo-Ground Truth image pair. The cross-type MLA HiLo performed slightly better (SSIM = 0.9554) than the traditional HiLo (SSIM = 0.9396). However, when using the hexagon-type MLA, artifacts were evident in the final HiLo image (SSIM = 0.9054). The cylinder-type MLA HiLo result (SSIM = 0.9366) is similar to the traditional HiLo. To our knowledge, this is the first numerical study about MLA-based HiLo microscopy. This study can benefit researchers using MLAs and incoherent light sources to configure their low-cost HiLo microscopes.

Stiffness-Tunable Substrate Fabrication by DMD-Based Optical Projection Lithography for Cancer Cell Invasion Studies.

Cancer cell invasion is a critical cause of fatality in cancer patients. Physiologically relevant tumor models play a key role in revealing the mechanisms underlying the invasive behavior of cancer cells. However, most existing models only consider interactions between cells and extracellular matrix (ECM) components while neglecting the role of matrix stiffness in tumor invasion. Here, we propose an effective approach that can construct stiffness-tunable substrates using digital mirror device (DMD)-based optical projection lithography to explore the invasion behavior of cancer cells. The printability, mechanical properties, and cell viability of three-dimensional (3D) models can be tuned by the concentration of prepolymer and the exposure time. The invasion trajectories of gastric cancer cells in tumor models of different stiffness were automatically detected and tracked in real-time using a deep learning algorithm. The results show that tumor models of different mechanical stiffness can yield distinct regulatory effects. Moreover, owing to the biophysical characteristics of the 3D in vitro model, different cellular substructures of cancer cells were induced. The proposed tunable substrate construction method can be used to build various microstructures to achieve simulation of cancer invasion and antitumor screening, which has great potential in promoting personalized therapy.

Flexible Optically Rewritable Electronic Paper

In this article, we present the procedure of preparation of flexible electronic paper with a photosensitive azo dye layer as the key element for changing the orientation of the polarization plane. The main steps of the technology for the fabrication of flexible e-paper are reported. The possible production of Digital Mirror Devices and the roll-to-roll process is discussed. Images on flexible e-paper are demonstrated, including bank card options. The advantages of optically rewritable e-paper technology in comparison with the e-ink usually used for this purpose are highlighted. Potential applications of flexible optically rewritable e-paper include price tags for supermarkets, indoor and outdoor advertisements, smart card labels, etc.

High dynamic reflection surface 3D reconstruction with sharing phase demodulation mechanism and multi-indicators guided phase domain fusion.

Accurate and complete 3D measurement of complex high dynamic range (HDR) surfaces has been challenging for structured light projection technique. The behavior of spraying a layer of diffuse reflection material, which will inevitably incur additional thickness. Existing methods based on additional facilities will increase the cost of hardware system. The algorithms-based methods are cost-effective and nondestructive, but they generally require redundant patterns for image fusion and model training, which fail to be suitable for practicing automated 3D measurement for complex HDR surfaces. In this paper, a HDR surface 3D reconstruction method based on sharing demodulation phase unwrapping mechanism and multi-indicators guided phase fusion strategy is proposed. The division of the exposure interval is optimized via the image entropy to generate an optimal exposure sequence. The combination of temporal-spatial binary (TSB) encoding fringe patterns with time-integration strategy and the variable exposure mode of digital mirror device (DMD)-based projector with a minimum projection exposure time of 233μs enables the proposed approach to broadly adapt complex HDR surfaces. We propose an efficient phase analysis solution called sharing mechanism that wrapped phase sequences from captured different intensity fringe images are unwrapped through sharing the same group of misaligned Gray code (MGC) decoding result. Finally, a phase sequences fusion model guided by multi-indicators, including exposure quality, phase gradient smoothness and pixel effectiveness, is established to obtain an optimum phase map for final 3D reconstruction. Comparative experiments indicate that the proposed method can completely restore the 3D topography of HDR surfaces with the images reduction of at least 65% and the measurement integrity is maintained at over 98% while preserving the measurement accuracy and excluding the outliers.

Temporal-spatial binary encoding method based on dynamic threshold optimization for 3D shape measurement.

The binary encoding method has been widely used for three-dimensional (3D) shape measurement due to the high-speed projection characteristics of its digital mirror device (DMD)-based projector. However, traditional binary encoding methods require a larger defocus to achieve a good sinusoidality, leading to a reduction in the measurement depth of field and signal-to-noise ratio (SNR) of captured images, which can adversely affect the accuracy of phase extraction, particularly high-frequency fringes for 3D reconstruction. This paper proposes a spatial-temporal binary encoding method based on dynamic threshold optimization for 3D shape measurement. The proposed method decomposes an 8-bit sinusoidal fringe pattern into multiple(K) binary patterns, which can be outlined into two steps: determining the dynamic threshold and then performing temporal-spatial error diffusion encoding. By using an integral imaging strategy, approximate sinusoidal patterns can be obtained under nearly focused projection, which can then be subjected to absolute phase unwrapping and 3D reconstruction. The experiments show that compared to the three comparative algorithms under the same experimental conditions, this proposed method improves the reconstruction error of measuring a plane and an object by at least 13.66% and 12.57% when K=2. The dynamic experimental result on the palm confirms that the proposed method can reliably reconstruct the 3D shape of the moving object.

Parallel two-photon lithography achieving uniform sub-200 nm features with thousands of individually controlled foci.

The limited throughput of nano-scale laser lithography has been the bottleneck for its industrial applications. Although using multiple laser foci to parallelize the lithography process is an effective and straightforward strategy to improve rate, most conventional multi-focus methods are plagued by non-uniform laser intensity distribution due to the lack of individual control for each focus, which greatly hinders the nano-scale precision. In this paper, we present a highly uniform parallel two-photon lithography method based on a digital mirror device (DMD) and microlens array (MLA), which allows the generation of thousands of femtosecond (fs) laser foci with individual on-off switching and intensity-tuning capability. In the experiments, we generated a 1,600-laser focus array for parallel fabrication. Notably, the intensity uniformity of the focus array reached 97.7%, where the intensity-tuning precision for each focus reached 0.83%. A uniform dot array structure was fabricated to demonstrate parallel fabrication of sub-diffraction limit features, i.e., below 1/4 λ or 200 nm. The multi-focus lithography method has the potential of realizing rapid fabrication of sub-diffraction, arbitrarily complex, and large-scale 3D structures with three orders of magnitude higher fabrication rate.

Spectrometer-based wavelength interrogation SPR imaging via Hadamard transform.

We present spectrometer-based wavelength interrogation surface plasmon resonance imaging (SPRi) without mechanical scanning. A polarized broadband light source illuminates an object via a gold-coated prism; the reflected light is spatially modulated by a digital mirror device (DMD) and then measured with a spectrometer. Reflectance spectral images are reconstructed via the Hadamard transform (HT), and a refractive index (RI) map is visualized from the reflectance spectral images by analyzing the resonance peak shift of the spectrum at each image pixel. We demonstrate the feasibility of our method by evaluating the resolution, sensitivity, and dynamic detection range, experimentally obtained as ∼2.203 × 10-6 RI unit (RIU), ∼3,407 nm/RIU, and ∼0.1403 RIU, respectively. Furthermore, simulations are performed to validate the experimental results.

Multifocal Plane Display Based on Dual Polarity Stereoscopic Metasurface

AbstractStereoscopic 3D display devices have been developed toward integration and compactness. Metasurfaces have immeasurable advantages in the field of 3D display due to their tiny structures and flexible design capabilities. Here, a 3D multifocal display method based on stereoscopic metasurface (SMS) is proposed and demonstrated. Based on Dammann optimization method and Fourier expansion with zone plate to generate phase profile, such SMS can reorganize different planar images projected from Digital Mirror Device to form 3D images with correct depth clues. Thanks to the large Numerical Aperture of nano‐devices, total 20 multi‐focal planes can be independently used for display by considering dual polarization multiplexing. The experimental effects for stereoscopic arrangement of 3D number, letters, and several 3D images are demonstrated. Such compact‐scale SMSs have great potential to the applications of augmented/virtual reality devices, stereoscopic optical engraving, 3D optical manipulation, etc.

Single-Pixel Compressive Digital Holographic Encryption System Based on Circular Harmonic Key and Parallel Phase Shifting Digital Holography

An encryption system that combines compressive sensing (CS) and two-step parallel phase shifting digital holography (PPSDH) using double random phase encoding (DRPE) is presented in this paper. The two-step PPSDH is a linear inline holographic scheme and is much suitable for encrypting the 2D/3D information in a single exposure. The distribution of random phase mask (RPM) in the DRPE is implemented using circular harmonic key which increases the security of the encryption process. In this system, the keys used to encrypt are spatial positions of the planes, wavelength, and rotation of the circular harmonics in RPMs, and CS acts as an additional key that makes the system more secure than the conventional optical encryption methods. At the transmission end, two-step PPSDH is applied to encrypt the object information in single hologram. The digital mirror device (DMD) is placed between the object and a single-pixel detector for acquiring fewer hologram measurements. At the receiver end, the single digital hologram is numerically recovered by using a CS optimization problem. The original complex object field is decrypted from the CS recovered holograms by the inversion of two-step PPSDH process with the help of the correct keys. The numerical simulations are presented for complex 2D and 3D objects to test the feasibility of the proposed encryption and decryption system. The proposed method carried out intensity and phase reconstruction of the original object field using single-pixel compressive imaging. The computer simulation results demonstrated that the encrypted information is highly secured with the rotation of the circular harmonic key. The sensitivity of the decrypted intensity and phase images is also studied with variations of the encrypted keys. The obtained results show that the proposed encryption scheme is feasible and has better security performance and robustness.

Structured light illumination for pressure-sensitive paint measurement under ambient light

We propose a pressure-sensitive paint (PSP) method under ambient light based on structured light illumination. In the PSP method, pressure is obtained by measuring the variation of the emission light intensity from a PSP coating when it is illuminated by a light source. Since the extraction of the emission light from ambient light is difficult in the conventional PSP method, the existence of ambient light induces a noticeable measurement error. While spatially uniform light is used as illumination light in the conventional PSP method, structured light, the spatial intensity of which is actively controlled, is used in the proposed method. By measuring the PSP emission by varying the spatial pattern of the structured light illumination, one can eliminate ambient light, which is not synchronized with the structured light and can measure pressure without the effect of ambient light. In this study, we demonstrate the pressure measurement under ambient light using structured light with a sinusoidal wave generated by a digital mirror device. The measured pressure agrees well with the pressure measured by a pressure transducer connected to a pressure tap. The proposed method is promising under ambient light conditions.

UCsim2: two-dimensionally structured illumination microscopy using UC2.

State-of-the-art microscopy techniques enable the imaging of sub-diffraction barrier biological structures at the price of high costs or a lack of transparency. We try to reduce some of these barriers by presenting a super-resolution upgrade to our recently presented open-source optical toolbox UC2. Our new injection moulded parts allow larger builds with higher precision. The 4× lower manufacturing tolerance compared to three-dimensional printing makes assemblies more reproducible. By adding consumer-grade available open-source hardware such as digital mirror devices and laser projectors, we demonstrate a compact three-dimensional multimodal setup that combines image scanning microscopy and structured illumination microscopy. We demonstrate a gain in resolution and optical sectioning using the two different modes compared to the widefield limit by imaging Alexa Fluor ® 647- and Silicon Rhodamine-stained HeLa cells. We compare different objective lenses and by sharing the designs and manuals of our setup, we make super-resolution imaging available to everyone. This article is part of the Theo Murphy meeting issue 'Super-resolution structured illumination microscopy (part 2)'.

Reconstruction of Hadamard coded spectral data based on diffraction theory

Hardmard transfer imaging spectrometer (HTIS) is a novel computationally optical system. Its characteristic of multi-channel multiplexing increases the luminous flux of the optical system without sacrificing spatial resolution, thereby enabling the system’s signal-to-noise ratio to be significantly higher than traditional spectrometer’s. Encoding with digital mirror devices (DMD) in the system causes a serious diffraction effect that gives rise to the apparent degradation of the imaging formation. For improving the image quality and spectral accuracy of the reconstructed data cube, the Hadamard coded spectral imaging data degradation model is established based on the scalar diffraction theory. A data reconstruction algorithm is proposed based on the Lucy Richardson (L-R) algorithm. Through the simulation experiment, the process of image degradation is revealed. On the one hand, it proves that the degradation of system imaging diffraction is the main reason for the distortion of reconstructed data. On the other hand, it verifies the effectiveness of the correction method adopted in this paper. The evaluation result of the spectral angle distance of the restored data cube after L-R correction is 0.1296, and the image similarity evaluation factor is better than 0.85. Compared with the reconstructed data before being corrected, the corrected data is greatly improved in quality. The experimental results show that the algorithm has a good correction effect on the data cube reconstruction of HTIS.

Single-Cell Image-Based Screening with Integration of Motorized Stages and Digital Mirror Device

Single-Cell Image-Based Screening with Integration of Motorized Stages and Digital Mirror Device

High-Speed RGB+IR Projector Based on Coaxial Optical Design with Two Digital Mirror Devices

High-Speed RGB+IR Projector Based on Coaxial Optical Design with Two Digital Mirror Devices

Spatially Resolved, Multiplexed Digital Characterization of Protein Distribution and Abundance in Formalin-Fixed, Paraffin-Embedded (FFPE) Diffuse Large B Cell Lymphoma Tissue Sections Based on the Nanostring® Digital Spatial Profiling (DSP) Technology

Imaging-based techniques are powerful tools for analyzing protein and mRNA expression and localization within the tumor microenvironment. However, they typically suffer from a number of challenges, including lack of dynamic range, difficult quantitation, and labor intensive workflow for very limited multiplexing. We have developed a novel platform based on the nCounter® barcoding technology that enables spatially resolved, digital characterization of proteins and mRNA in a highly multiplexed assay. The assay relies upon probes coupled to photocleavable oligonucleotide tags which are released from discrete regions of the tissue using focused through-objective UV (~ 365nm) exposure. An automated prototype capable of imaging, selective illumination using a digital mirror device, and sample collection was developed by modifying a standard microscope. Cleaved tags are quantitated in an nCounter assay, and counts are mapped back to tissue location, yielding a spatially-resolved digital profile of analyte abundance.To apply this technology to the characterization of hematological malignancies, we have developed the nCounter Vantage 3D™ Heme RNA panel that characterizes biology known to be relevant for these tumors, including specific profiling of MAPK, MYC signaling, NF-κB, PI3K-AKT, and B cell and T cell receptor signaling. We have also developed the Vantage 3D Heme panel of antibodies that focuses on common signaling pathways, with an emphasis on phosphorylated targets. We have used these panels to characterize differences in protein expression between ABC and GCB subtypes of diffuse large B cell lymphoma.3 ABC and 3 GCB lymphoma samples, previously identified by the NanoString Lymphoma Subtyping Test, were profiled on the DSP platform. 5 um tissue sections were stained with fluorescent antibodies for CD45 (to illuminate tumor and infiltrating immune cells), CD3 (to identify infiltrating T cells) and SYTO-83 (to illuminate nuclei), along with the oligo labeled antibodies from either the heme panel or the ST signaling panel. Regions of interested (ROI) were selected based on abundance of CD45 and CD3 staining from the ST-panel stained tissue section, and the same ROI was selected on the heme panel stained section using image alignment.In this study, we used these two Vantage 3D Heme panels to compare protein expression between the different subtypes of DLBCL and identify proteins that vary between subtype. We also identified heterogeneity of protein expression within the ABC subtype for the key tumor suppressors p53 and individual sample variation of expression in p-AKT within the GCB subtype. Furthermore, we observe strong concordance of signal from antibodies that are included in both antibody panels, suggesting technical reproducibility of the platform.Data are analyzed on software that is being developed in parallel with the technology, which enables visualization of the individual ROI within a sample, comparison of ROI across samples, and comparison of the individual probe counts within and between ROI.ConclusionsNanostring digital spatial profiling provides a quantitative and reproducible digital readout for multiplexed protein expression from the same microscopic regions of individual tissue sections. In this study we demonstrate how DSP technology can help elucidate protein expression profiles within individual lymphoid tumor specimens. First we show how regions of interest with the tumor (ROI) are identified and profiled using two multiplex protein panels simultaneously. Second, we demonstrate high platform concordance between proteins present within different NanoString panel products. Finally, we present methodology and data analysis workflow capable of identifying protein expression differences both within individual tumors, and between ABC and GCB lymphoma subtypes. Application of this technology to the study of hematological malignancies may help to identify novel drug targets and/or characterize response to therapy, thus helping to define novel biology and accelerate the clinical development path. DisclosuresWhite:Nanostring Technologies Inc.: Employment. Elliott:Nanostring Technologies Inc.: Employment. Liang:Nanostring Technologies Inc.: Employment. Warren:NanoString Technologies: Employment, Equity Ownership. Beechem:NanoString Technologies: Employment, Equity Ownership.

Synthesis of vector nonuniformly correlated light beams by a single digital mirror device.

We present a stable and flexible way to generate the vector nonuniformly correlated (NUC) beams with a compact optical system that involves only a single digital mirror device and a common-path interferometer. The system provides near real-time generation and accurate control of the phase difference between the orthogonal field components of the vector NUC beams. We discuss the methodology based on the vectorial pseudo-mode decomposition of the cross-spectral density matrix of the beam. The method is validated by experimentally generating a class of vector NUC beams, named electromagnetic cosh-Gauss NUC beams, which have not been previously synthesized. Such beams display self-focusing feature on propagation and can reduce to different types of scalar NUC beams by selecting out the linearly polarized components at different polarization angles.

Digital light processing stereolithography of hydroxyapatite scaffolds with bone‐like architecture, permeability, and mechanical properties

AbstractThis work deals with the additive manufacturing and characterization of hydroxyapatite scaffolds mimicking the trabecular architecture of cancellous bone. A novel approach was proposed relying on stereolithographic technology, which builds foam‐like ceramic scaffolds by using three‐dimensional (3D) micro‐tomographic reconstructions of polymeric sponges as virtual templates for the manufacturing process. The layer‐by‐layer fabrication process involves the selective polymerization of a photocurable resin in which hydroxyapatite particles are homogeneously dispersed. Irradiation is performed by a dynamic mask that projects blue light onto the slurry. After sintering, highly‐porous hydroxyapatite scaffolds (total porosity ~0.80, pore size 100‐800 µm) replicating the 3D open‐cell architecture of the polymeric template as well as spongy bone were obtained. Intrinsic permeability of scaffolds was determined by measuring laminar airflow alternating pressure wave drops and was found to be within 0.75‐1.74 × 10−9 m2, which is comparable to the range of human cancellous bone. Compressive tests were also carried out in order to determine the strength (~1.60 MPa), elastic modulus (~513 MPa) and Weibull modulus (m = 2.2) of the scaffolds. Overall, the fabrication strategy used to print hydroxyapatite scaffolds (tomographic imaging combined with digital mirror device [DMD]‐based stereolithography) shows great promise for the development of porous bioceramics with bone‐like architecture and mass transport properties.

Autostereoscopic display for multiviewers positioned at different distances using time-multiplexed layered directional backlight.

In this paper, an autostereoscopic display system based on a time-multiplexed directional backlight using a large aperture Fresnel lens is proposed. High-resolution stereoscopy for multiple viewers positioned at different distances from the screen is achieved in the proposed system by layering polymer dispersed liquid crystal screens behind the Fresnel lens. The screens with segmented electrodes are electrically controlled to change the position of light diffusion, while the time-multiplexed backlight is projected by a digital mirror device projector at a high refresh rate. The light is diffused at the conjugate focal points of the observers' eyes to deliver directional light to each eye. The right-eye image and the left-eye image are alternated on the LCD panel in front of the lens to synchronize with the backlight.

Surface-Scanning Raman Characterization of Dark Materials Based on a Digital Mirror Device (DMD)

When Raman spectroscopy is used for material analysis, a laser is focused on the sample by a lens. Dark materials have a stronger ability to absorb light and hence the laser may heat these samples to the ignition point. Thus, Raman spectroscopy of dark materials is a challenging problem. High-frequency surface scanning technology based on a digital mirror device and Lissajous pattern modulation is presented in this study. The scanning was performed according to a given path in the detection process and the sampling area was changed from point source detection to area source detection. In addition, the optical structure of the handheld Raman spectrometer was optimized by changing relevant optical components. In addition, the detection efficiency and detection limit were improved so that its performance was significantly enhanced.