Micromirror Device Research Articles

Fast and reliable technique for spatial coherence measurement with a temporally modulated nonredundant slit array.

We propose a method of measuring the spatial coherence of light by means of a temporally modulated nonredundant slit array implemented on a digital micromirror device. We first formulate the theory of the spatial coherence measurement to incorporate a general case when the observation plane is not necessarily placed in the far field of the slit array. We then demonstrate experimentally that a single measurement determines the spatial coherence for 15 different slit separations accurately, even if background light is unavoidable, under the condition that a nonredundant array of six slits is illuminated evenly. These results clearly show that fast and highly reliable spatial coherence measurement is achievable with the proposed method without any difficulties.

Alternating projection-based phase optimization for arbitrary glare suppression through multimode fiber

Wavefront shaping for glare suppression helps to reduce the speckle background through scattering media and enables imaging, sensing, and some speckle-related advanced applications through customizing the speckle light field. For glare suppression in a target region, current methods are either slow or not sufficiently generic. Here, an alternating projection method that fully exploits the transmission matrix of the scattering medium is proposed for fast and arbitrary glare suppression. Parallelly, multiple phase masks corresponding to different target regions can be computationally optimized without iterative hardware feedback. Numerical simulation shows that under phase-only modulation, a suppression factor of ∼10−3 can be realized for a large target region with only 30 iterations. With the use of a graphics processing unit and a digital micromirror device, fast and effective glare suppression for target regions of various shapes and sizes was demonstrated at the distal end of a multimode fiber. This technique could be promising for applications like multimode fiber-based speckle optical tweezer or endoscopy with speckle illumination inside complex environments.

Evaluation of a digital micro-mirror device based near-infrared spectrometer for rapid and accurate prediction of quality attributes in poultry feed

In this study, we proposed and evaluated a digital micro-mirror (DMD) based ELICO near-infrared spectrometer (NIRS) for predicting moisture, protein, and fat content in soya meal for poultry feed at a low cost and compared the results to those of the Bruker NIRS. Preprocessing, partial least squares regression (PLSR) methods, and the wet chemical method were used to develop prediction models on both instruments by using soya samples with moisture variations of 9–16%, protein variations of 41–51%, and fat variations of 0.7–3.0%. We found that the wavelength ranges of 1410–1470 nm, 1470–1560 nm, and 1100–1400 nm are sensitive wavelength ranges for the precise detection of moisture, protein, and fat, respectively. The experiment results of ELICO NIRS showed that the correlation coefficient (R2), root mean square error (RMSE), relative performance determinant (RPD), and range error ratio (RER) were 0.89, 0.77%, 3.2, and 8.5; 0.84, 1.03%, 2.7, and 9.7; and 0.86, 0.29%, 2.7, and 7.8 for moisture, protein, and fat, respectively. The maximum standard deviation was 0.006, 0.005, and 0.006 found for moisture, protein, and fat, respectively. Bruker NIRS showed that the R2, RMSE, RPD, and RER were 0.83, 1.03%, 2.4, and 6.4; 0.89,0.75%, 3.0, and 13.5; and 0.74, 0.31%, 2.7, and 7.6 for moisture, protein, and fat content of soya meal, respectively. Further, the prototype outcomes were compared with the previous studies done with various techniques. As a result, the ELICO NIRS has a good figure of merit that fits within an acceptable range, and the prediction findings were well correlated with the wet chemistry method, performed similarly to Bruker NIRS. The ELICO prototype can reliably estimate a wide range of feed ingredients and has a lot of potential as a field and laboratory instrument, allowing small-to-large industries, retailers, and educational institutions to use it at a low cost.

Generation of structured beams with optional turbulence levels using a digital micromirror device

The dynamic spatial control of light fields, including spatial shaping and turbulence simulation, is essential for applications such as free-space optical communication. We propose a method for generating and rapidly switching structured beams with coherently superposed modes and optional turbulence levels using a digital micromirror device (DMD). The composite holograms encoded by Lee and Superpixel methods are quantitatively analyzed in terms of fidelity and efficiency, and both can generate structured beams under turbulence with high fidelity. The loaded turbulence intensity is verified by measuring the Strehl Ratio of generated beams, and the propagation characteristics is verified by reconstructing the three-dimensional spatial field through a stack of cross-sectional images. A more compact and robust experimental system is adopted, which reduces the power loss than traditional two consecutive modulations and improves the switching speed than phase-only modulators. The measurements consist with theoretical simulations, and the experimental method will promote applications of DMD in structured beam generation.

Single-pixel coherent diffractive imaging based on super-pixel holography

Quantitative phase imaging (QPI) is a powerful approach to study dynamics associated with both thickness and refractive index fluctuations. In this work, we propose a coherent diffractive QPI scheme based on single-pixel imaging structure and coherent modulation imaging. In this scheme, digital micro-mirror device with high refresh rate is employed for structured illumination. Synchronously, a single point detector is used to perform mode selected measurement of diffraction intensity. Based on the illumination structure and point signals, phase imaging is realized using a reweighted amplitude flow phase retrieval algorithm. Non-interference modality omits the reference arm, which simplifies the apparatus and improves the system robustness. This proposed technique is demonstrated by QPI of both digital binary and grayscale objects. The three-dimensional profile measurement of a plano-convex lens shows the possibility of phase retrieval for real objects. Accordingly our technique will promote the application of single-pixel phase imaging to biomedical imaging, x-ray diffraction imaging and three-dimensional profilometry.

3D printing of bioinspired hydrogel microstructures with programmable and complex shape deformations based on a digital micro-mirror device

4D printing, which enables programmable deformation of structures, has broadened the application of 3D printing. Nowadays, 4D printing is usually done by multi-material printing, in which different spatial locations are endowed with different properties. This approach, however, increases the difficulty of 3D printing. Here, we propose a programmable control of single-material hydrogel deformation stimulated by unilateral water absorption. The control scheme includes structure control, gray value control, droplet distribution control, and hydrogel concentration control. Various bionic deformation structures are fabricated. Furthermore, a water-absorbing and swelling powered micro-manipulator is fabricated to achieve controlled grasping and releasing of objects. The materials and stimulation modalities in the proposed programmable control scheme have good cytocompatibility and are easily accessible. This suggests that the control scheme holds great potential for applications in tissue engineering, bionic technology, and micro and nano fabrication.

Long-distance mid-wave infrared super-resolution compressive imaging

Super-resolution imaging (SRI) for mid-wave infrared (MWIR) has attracted increasing attention in recent years due to the expensive price for a large number of pixels MWIR cameras. Investigation of the compressed sensing method can partially improves the resolution. However, the quality of SRI is highly related to the transfer function matrix of the optical system, which is difficult to be accurately measured because of the noise existed in MWIR detection, especially in long-distance systems. In this work, we propose a transfer function matrix calculation method which overcomes the issues of low imaging contrast and signal-to-noise ratio compared with previous studies. And we further establish a long-distance focal plane array-based compressive imaging system with a resolution of two digital micro-mirror device pixels which just satisfies the system diffraction limit. In addition, we achieve the 4 × 4 times super-resolution high-quality reconstruction of long-distance digital and physical objects with only six measurements.

Dual-pixel tracking of the fast-moving target based on window complementary modulation.

Real-time tracking of fast-moving targets has been utilized in various fields. However, the tracking performance of image-based systems for fast-moving targets is still limited by the huge data throughput and computation. In this study, an image-free target tracking system utilizing a digital micromirror device (DMD) is proposed. The proposed system effectively combines the dual-pixel measurement and window complementary modulation, and the alternating interpolation Kalman filter is implemented to fully use the performance of the DMD and maximize the update rate of the system. The accuracy of the proposed system at the maximum update rate of 22.2 kHz can achieve 0.1 pixels according to the experimental results. Meanwhile, we experimentally demonstrated that the accuracy of the proposed image-free target tracking system is within 0.3 pixels at a maximal velocity of 2 × 104 pixel/s at 22.2 kHz by evaluating the performance of the proposed image-free target tracking system when tracking fast-moving targets with different maximal velocity.

Defect corrections for coherent optical information processing of grayscale images in a DMD-based 4f-system using a collimated light source.

Digital micromirror device (DMD)-based 4f-systems, a type of coherent optical information processing system, have become a powerful tool for optical convolutional neural networks taking advantage of their fast modulation speed and high-resolution capability. However, proper high bit-depth image information processing remains challenging due to the optical diffractions that arise from the binary nature of DMD operation. In this paper, we first characterize the diffraction phenomena that cause irradiance defects, namely the nonlinear grayscale and unintended dark lines. Then to resolve the issues, we propose a DMD operation method and a modified structure of the 4f-system based on blazed diffraction grating theory and numerical calculation of the Rayleigh-Sommerfeld propagation model. As a demonstration, we implement high bit-depth image information processing with an optimized optical 4f-system using DMDs and a collimated coherent light source.

54.2: Invited Paper: Flat Liquid Crystal Microlens Based on Spatially‐variant Photoalignment

54.2: <i>Invited Paper:</i> Flat Liquid Crystal Microlens Based on Spatially‐variant Photoalignment

Programmable Aperture Using a Digital Micromirror Device for In-Line Holographic Microscopy

We present the novel use of a digital micromirror device (DMD) as a digitally adjustable and programmable aperture for lens-free digital in-line holographic microscopy (LFDIHMY). The proposed micro-electro-mechanical system (MEMS) based DMD aperture can be used as a compact and inexpensive replacement for existing mechanical based aperture control methods required for many resolution enhancement methods. Simulation of the DMD aperture in an in-line holography setup is presented using a general DMD model from literature. A hardware prototype was successfully implemented and demonstrated. The resolution of both simulated and experimental holograms recorded with a conventional pinhole aperture and the proposed DMD aperture are compared using a 1951 USAF resolution test target. We show that a resolution of 2.46 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm { \mu {\textbf {m}}}$ </tex-math></inline-formula> , close to the sensor pixel limit, can be obtained with each aperture. This demonstrates that a DMD can be used as a programmable replacement for a pinhole aperture.

Technology of static oblique lithography used to improve the fidelity of lithography pattern based on DMD projection lithography

This paper proposes a static oblique lithography (SOL) strategy based on conventional digital micromirror device (DMD) projection lithography. This strategy combines the oblique lithography on oblique scanning lithography with static lithography to ensure that we can produce high fidelity microstructures with very smooth curved edges in all directions and more accurate relative line positions. Not only does the single-axis high-precision micromotion stage of this strategy enable a significant reduction in fabrication cost, but also enables the lithography of subpixel-width curves with smooth edges used our improved sub-pattern quantization strategy. The intensity distribution of the actual diffracted light field at the focal point of the helical zone plate fabricated by the SOL is highly matched with the intensity distribution of the designed simulated light field. This shows that the SOL can play an important role in the field of micro-optical device fabrication.

Consistent pattern printing of the gap structure in femtosecond laser DMD projection lithography.

Maskless lithography technologies have been developed and played an important role in the fabrication of functional micronano devices for microelectronics, biochips and photonics. Optical projection lithography based on digital micromirror device (DMD) is an efficient maskless lithography technology that can rapidly fabricate complex structures. The precise modulation of gap width by DMD maskless optical projection lithography (MOPL) using femtosecond laser becomes important for achieving micronano structures. Herein, we have investigated the relationship between the structure morphology and the light intensity distribution at the image plane by multi-slit diffraction model and Abbe imaging principle, and optimized the gap width more accurately by modulating exposure energy. The aperture diameter of the objective lens has a substantial effect on the pattern consistency. The continuously adjustable structural gap widths of 2144 nm, 2158 nm and 1703 nm corresponding to 6, 12, 24 pixels are obtained by varying the exposure energy in the home-built MOPL system. However, the ideal gap structure cannot be obtained only by adjusting the exposure energy when the gap width is small, such as 1 or 2 pixels. Furthermore, we have proposed an alternative way to achieve fine gap structures through the structural decomposition design and precise control of exposure energy in different regions without changing the MOPL optical system. This study would provide a promising protocol for fabricating gap microstructures with controllable configuration using MOPL technique.

Non-paraxial diffraction analysis for developing DMD-based optical systems.

We propose a non-paraxial diffraction model of the digital micromirror device (DMD) by combining the conventional Fraunhofer diffraction and a simple method of coordinative mapping. It is equivalent to adding aberrations of diffracted wave fields to the aberration-free Fraunhofer diffraction instead of complex integral calculations, allowing the simulated diffraction patterns to be consistent with the actual experimental counterparts. Moreover, it is verified by the experiments and literature that the diffraction angles, orders, and efficiency can all be well predicted for arbitrary incident angles and wavelengths. Especially for diffracted zenith angles within 50°, the predicted values reveal ∼1% error, and in a broader range, the predicted errors of diffracted azimuth angles are less than 4%. To the best of our knowledge, it is the first model capable of describing the non-paraxial diffraction behavior of the DMD. The proposed model with universality and effectiveness will help users to optimally construct DMD-based optical systems by guiding optical layouts, selection of light sources, and utilization and suppression of diffraction effects.

An LED-Based structured illumination microscope using a digital micromirror device and GPU accelerated image reconstruction.

When combined with computational approaches, fluorescence imaging becomes one of the most powerful tools in biomedical research. It is possible to achieve resolution figures beyond the diffraction limit, and improve the performance and flexibility of high-resolution imaging systems with techniques such as structured illumination microscopy (SIM) reconstruction. In this study, the hardware and software implementation of an LED-based super-resolution imaging system using SIM employing GPU accelerated parallel image reconstruction is presented. The sample is illuminated with two-dimensional sinusoidal patterns with various orientations and lateral phase shifts generated using a digital micromirror device (DMD). SIM reconstruction is carried out in frequency space using parallel CUDA kernel functions. Furthermore, a general purpose toolbox for the parallel image reconstruction algorithm and an infrastructure that allows all users to perform parallel operations on images without developing any CUDA kernel code is presented. The developed image reconstruction algorithm was run separately on a CPU and a GPU. Two different SIM reconstruction algorithms have been developed for the CPU as mono-thread CPU algorithm and multi-thread OpenMP CPU algorithm. SIM reconstruction of 1024 × 1024 px images was achieved in 1.49 s using GPU computation, indicating an enhancement by ∼28 and ∼20 in computation time when compared with mono-thread CPU computation and multi-thread OpenMP CPU computation, respectively.

All-MEMS Lidar Using Hybrid Optical Architecture with Digital Micromirror Devices and a 2D-MEMS Mirror.

In a lidar system, replacing moving components with solid-state devices is highly anticipated to make a reliable and compact lidar system, provided that a substantially large beam area with a large angular extent as well as high angular resolution is assured for the lidar transmitter and receiver. A new quasi-solid-state lidar optical architecture employs a transmitter with a two-dimensional MEMS mirror for fine beam steering at a fraction of the degree of the angular resolution and is combined with a digital micromirror device for wide FOV scanning over 37 degree while sustaining a large aperture area of 140 mm squared. In the receiver, a second digital micromirror device is synchronized to the transmitter DMD, which enables a large FOV receiver. An angular resolution of by was achieved with 0.588 fps for scanning 1344 points within the field of view.

Computational model for the nonlinear dynamic response of MEMS-based micromirror

In this study, it is aimed to perform Finite Element Analysis (FEA) of micromirror based on Micro-Electro-Mechanical Systems (MEMS) and to examine the nonlinear and dynamic responses of this system. Micromirror devices are indispensable, especially for optical systems and form the basis of them. In this work, dynamic and nonlinear responses of micromirror with 4 symmetric arms and one reflective surface were investigated. During the design and modeling, it is assumed that the upper and lower layers of the reflective surface have equal tensile and compressive stresses. The analysis of the system was obtained by applying a force of up to 30 GPa Prestressed on the reflective surface. The design and FEA of the micromirror system were made with the Comsol Multiphysics program. The nonlinear response of the analysis was carried out with the MATLAB program. This model, which has the most basic design of micromirror structures used in optical systems, is thought to be a source for a good examination of the nonlinear dynamic model and for understanding more complex structures.

Analysis of Stray Light and Enhancement of SNR in DMD-Based Spectrometers.

Due to advantages such as the high efficiency of light utilization, small volume, and vibration resistance, digital micro-mirror device (DMD)-based spectrometers are widely used in ocean investigations, mountain surveys, and other field science research. In order to eliminate the stray light caused by DMDs, the stray light in DMD-based spectrometers was first measured and analyzed. Then, the stray light was classified into wavelength-related components and wavelength-unrelated components. Moreover, the noise caused by the stray light was analyzed from the perspective of encoding equation, and the de-noising decoding equation was deduced. The results showed that the accuracy range of absorbance was enhanced from [0, 1.9] to [0, 3.1] in single-stripe mode and the accuracy range of absorbance was enhanced from [0, 3.8] to [0, 6.3] in Hadamard transform (HT) multiple-stripe mode. A conclusion can be drawn that the de-noising strategy is feasible and effective for enhancing the SNR in DMD-based spectrometers.

Binary Computer-Generated Holograms by Simulated-Annealing Binary Search

The binary computer-generated hologram (BCGH) has attracted much attention recently because it can address the high-speed binary spatial light modulator (SLM), such as a digital micromirror device (DMD) SLM. In this paper, our concern is the development of an algorithm to produce high-quality BCGHs. In particular, simulated annealing (SA) is an efficient algorithm used to produce a phase-only computer-generated hologram. In the study of SA for the production of a BCGH, we found some inherent shortcomings of SA, and the quality of the produced BCGHs is limited. Accordingly, we have modified SA and propose the simulated-annealing binary search (SABS) algorithm. We have also proposed a method to quickly determine the parameters for SABS. In the comparison with SA, the mean square error of the SABS BCGHs decreases by 32% on average. Therefore, the SABS is a promising technique for a high-quality holographic display by DMD.

Robust site-resolved addressing via dynamically tracking the phase of optical lattices

Single-site-resolved addressing offers an unprecedented capability of manipulating atoms in optical lattices. We demonstrate a robust site-resolved addressing by locking the position of the addressing beam to the optical lattice phase. The addressing beam is modulated by a digital micromirror device (DMD) integrated into a quantum gas microscope (QGM). A typical experiment with ultracold atoms takes several hours to collect hundreds of samples by repeating the sequence of programmed operations, whose duration is 40 seconds. During the collection, the phase of optical lattices can drift over a few lattice sites. According to the phases of the lattice obtained from the current experimental realizations, we correct the addressing beam position for the subsequent realization by shifting the pattern of the activated micromirrors on the DMD. This feedback loop is compiled to an application with a graphical user interface (GUI) for relevant devices, which is synchronized to the experimental sequence. The long-term (5 hours) position deviation between the pointing of the addressing beam and the lattice phase is suppressed to a 0.02(2)/0.02(2) lattice spacing in the X/Y direction, verifying a 10-fold reduction in comparison to that without feedback. With the help of phase-locking, the success rate of site-resolved addressing is improved substantially from 60(7)% to 95(2)%.