Digital Micromirror Device Chip Research Articles

Ultraviolet Beam Lithography System for Digital Fabrication of Roller Molds

This article presents a digital ultraviolet (UV) beam lithography system for fabricating microstructures of arbitrary patterns on a roller mold. This roller mold can then be used in roller imprinting for fast and large-area replication of microstructures on substrates. This digital optomechanical system consists of a UV light source, a digital micromirror device (DMD) and its electronic controller, a high-precision image lens, a fiber array integrated with microlenses on both ends, and a two-axis ( x – θ ) servo-controlled motion stage. It exposes a photoresist (PR) layer coated on the cylindrical surface of a roller with a linear array of 192 small UV spots focused by a microlens/fiber array. On the other end of the fibers, UV light is fed by DMD's micromirrors so that the UV light can be dynamically modulated. Finally, by synchronizing the electronics of DMD chip and the mechanical movement (rotation and translation) of the roller, one can achieve arbitrary UV patterning on the roller's PR layer in a digital and maskless manner. This system can successfully achieve UV patterning with a smallest linewidth of 8 μ m, a pattern resolution of 2.5 μ m, and a total patterning width of 192 mm on a roller with a diameter of 100 mm.

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.

16-Port tunable fiber laser based on a digital micromirror device in C-band

A 16-port tunable fiber laser is experimentally demonstrated based on a digital micromirror device (DMD). This laser has the capacity of tuning wavelength from 16 ports flexibly and independently in the whole C-band by only one 0.55-in. DMD chip, a blazed grating for waveband de-multiplexing and a zoom optics system for beam mapping. The results show the outputs from all fiber rings exhibit high uniformity, stability and reliability. The 3-dB linewidth of laser output is less than 0.02 nm, the SMSR exceeds 50 dB and the crosstalk between wavelength channels from adjacent ports is up to 45 dB. The wavelength shift is below 0.02 nm and the output power fluctuation is better than 0.13 dB within 1 h. This multi-port tunable fiber laser is expected to play the role of 16 or even more independent tunable lasers in network application.

Tunable Fiber Laser with High Tuning Resolution in C-band Based on Echelle Grating and DMD Chip.

The tunable fiber laser with high tuning resolution in the C-band is proposed and demonstrated based on a digital micromirror device (DMD) chip and an echelle grating. The laser employs a DMD as a programmable wavelength filter and an echelle grating with high-resolution features to design a cross-dispersion optical path to achieve high-precision tuning. Experimental results show that wavelength channels with 3 dB-linewidth less than 0.02 nm can be tuned flexibly in the C-band and the wavelength tuning resolution is as small as 0.036 nm. The output power fluctuation is better than 0.07 dB, and the wavelength shift is below 0.013 nm in 1 h at room temperature.

Adaptive spatiotemporal optical pulse front tilt using a digital micromirror device and its terahertz application.

We report a new method to temporally and spatially manipulate the pulse front tilt (PFT) intensity profile of an ultrashort optical pulse using a commercial microelectromechanical system, also known as a digital micromirror device (DMD). For our demonstration, we show terahertz generation in a lithium niobate crystal using the PFT pumping scheme derived from a DMD chip. The adaptive functionality of the DMD could be a convenient alternative to the more conventional grating required to generate a laser beam with a PFT intensity profile that is typically used for efficient optical rectification in noncollinear phase-matching conditions. In contrast to a grating, PFT using DMD does not suffer from wavelength dispersion, and exhibits overlap properties between grating and a stair-step echelon mirror.

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.

Digital Micromirror Device (DMD)-Based High-Cycle Torsional Fatigue Testing Micromachine for 1D Nanomaterials

Fatigue behavior of nanomaterials could ultimately limit their applications in variable nano-devices and flexible nanoelectronics. However, very few existing nanoscale mechanical testing instruments were designed for dedicated fatigue experiments, especially for the challenging torsional cyclic loading. In this work, a novel high-cycle torsion straining micromachine, based on the digital micromirror device (DMD), has been developed for the torsional fatigue study on various one-dimensional (1D) nanostructures, such as metallic and semiconductor nanowires. Due to the small footprint of the DMD chip itself and its cable-remote controlling mechanisms, it can be further used for the desired in situ testing under high-resolution optical or electron microscopes (e.g., scanning electron microscope (SEM)), which allows real-time monitoring of the fatigue testing status and construction of useful structure-property relationships for the nanomaterials. We have then demonstrated its applications for testing nanowire samples with diameters about 100 nm and 500 nm, up to 1000 nm, and some of them experienced over hundreds of thousands of loading cycles before fatigue failure. Due to the commercial availability of the DMD and millions of micromirrors available on a single chip, this platform could offer a low-cost and high-throughput nanomechanical solution for the uncovered torsional fatigue behavior of various 1D nanostructures.

Recent progress in direct exposure of interconnects on PCBs

Purpose – This paper aims to use a survey of techniques to present the patterning of electric circuitry on printed circuit boards (PCBs). Second, a proposal of a new technology for direct exposure of interconnects on PCBs, using a digital micromirror device (DMD) is presented. Design/methodology/approach – In this proposal, the DMD chip was incorporated into a prototype system for exposure of soldermask pattern for a mass scale production. As a light source, 52 semiconductor UV lasers were combined together to deliver UV powerful beam onto the DMD chip area. Findings – A laser beam power of around 9 W was achieved from a single exposure head. With five exposure heads installed into a single machine, it is possible to expose 1,400 PCB panels per day. Such a production rate from a single exposure machine satisfies the demands of biggest PCB factories. Research limitations/implications – The Gaussian energy distribution of the laser beam from the 52-lasers head on the PCB surface was experimentally found. Because the exposure image needs to be highly uniform, this made a problem when the printed circuitry quality is considered. This problem was solved by using a software algorithm. Practical implications – The use of UV lasers exposure heads brings economical advantages over conventional bulb UV lamps. The power consumption drops down ten times for lasers source. Social implications – Because the exposure processing can be made with lower electric costs and higher yield, it will make the PCBs cheaper. Originality/value – At present, the idea of collecting a great number of lasers as a UV source for exposure head is attractive solution.

Digital micromirror device (DMD)-based 3D printing of poly(propylene fumarate) scaffolds

Our recent investigations into the 3D printing of poly(propylene fumarate) (PPF), a linear polyester, using a DMD-based system brought us to a resin that used titanium dioxide (TiO2) as an ultraviolet (UV) filter for controlling cure depth. However, this material hindered the 3D printing process due to undesirable lateral or “dark” curing (i.e., in areas not exposed to light from the DMD chip). Well known from its use in sunscreen, another UV filter, oxybenzone, has previously been used in conjunction with TiO2. In this study we hypothesize that combining these two UV filters will result in a synergistic effect that controls cure depth and avoids dark cure. A resin mixture (i.e., polymer, initiator, UV filters) was identified that worked well. The resin was then further characterized through mechanical testing, cure testing, and cytotoxicity testing to investigate its use as a material for bone tissue engineering scaffolds. Results show that the final resin eliminated dark cure as shown through image analysis. Mechanically the new scaffolds proved to be far weaker than those printed from previous resins, with compressive strengths of 7.8±0.5MPa vs. 36.5±1.6MPa, respectively. The new scaffolds showed a 90% reduction in elastic modulus and a 74% increase in max strain. These properties may be useful in tissue engineering applications where resorption is required. Initial cytotoxicity evaluation was negative. As hypothesized, the use of TiO2 and oxybenzone showed synergistic effects in the 3D printing of PPF tissue engineering scaffolds.

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.

Design of a high-numerical-aperture digital micromirror device camera with high dynamic range.

A high-NA imaging system with high dynamic range is presented based on a digital micromirror device (DMD). The DMD camera consists of an objective imaging system and a relay imaging system, connected by a DMD chip. With the introduction of a total internal reflection prism system, the objective imaging system is designed with a working F/# of 1.97, breaking through the F/2.45 limitation of conventional DMD projection lenses. As for the relay imaging system, an off-axis design that could correct off-axis aberrations of the tilt relay imaging system is developed. This structure has the advantage of increasing the NA of the imaging system while maintaining a compact size. Investigation revealed that the dynamic range of a DMD camera could be greatly increased, by 2.41 times. We built one prototype DMD camera with a working F/# of 1.23, and the field experiments proved the validity and reliability our work.

Microlens array fabricated by a low-cost grayscale lithography maskless system

This work presents the fabrication of a contiguous f/#=f/15 Fresnel microlens array (MLA) by employing a low-cost home-built maskless exposure lithographic system based on a digital light projector technology by using Texas Instruments’ digital micromirror device chip. A continuous diffractive phase relief structure was generated on a photoresist-coated silicon wafer, replicated in polydimethylsiloxane (PDMS) and electrostatically bonded to a glass substrate. The whole exposure time takes 10.8 min to expose a 2.4×2.4 mm MLA, with a resolution of 2.5 μm. This exposure time is relatively short, enabling high throughput or fast prototyping. Optical characterization was carried out using a He-Ne laser source (λ=633 nm ), by evaluating the maximum intensity of each spot generated at the MLA focal plane, Imax, as well as its sharpness by measuring their full width at half maximum (FWHM) intensity values. The resulting FWHM and maximum intensity spot average values were FWHM AVG =20±8% μm and Imax AVG =0.71±7% a.u. , respectively. The quality of replication was evaluated by profile characterization of the resulting mold and replica based on step height measurement along 180 μm. The maximum obtained difference was 32 nm, corresponding to 2.5% of the total mold height or λ/20 . AFM measurements were also carried out to quantify the roughness quality between mold and replica. The resulting RMS roughness was 4.73 nm (λ/130 ) and 6.66 nm (λ/95 ) for mold and replica, respectively. A comparison between theoretical and measured intensity profiles at the MLA focal plane was also carried out. A good correspondence between the results was found. Such an MLA can be applied as a Shack–Hartmann wavefront sensor in optical interconnects and to enhance the efficiency of detector arrays.

Holographic display based on a spatial DMD array

The image space of the reconstructed image from the hologram displayed on a digital micromirror device (DMD) is defined by the diffraction pattern induced by the 2D pixel pattern of the DMD, which works as a 2D blazed grating. Within this space, a reconstructed image of 100 mm × 20 mm is spatially multiplexed by a 2 × 5 DMD array that is aligned on a board, without using any extra optics. Each DMD chip reconstructs an image piece of the size 20 mm (width) × 10 mm (height). The reconstructed image looks somewhat noisy but regenerates the original object image faithfully.

Automatic Full-Field 3-D Profilometry Using White Light Confocal Microscopy with DMD-Based Fringe Projection

A new full-field 3-D micro surface profilometer using digital micromirror device (DMD)-based fringe projection strategy and confocal principle is presented in the article. In viewing the fact that conventional laser confocal measurement method not only easily encounters undesired irregular scattering problems, but also lack scanning efficiency due to its single-point type measurement, the newly developed automatic surface profilometer deploys a DMD chip to project spatially encoded digital fringe patterns with dynamic light intensity, onto the object to obtain excellent measurement performance. A novel digital fringe pattern design with adaptive sinusoidal intensity modulation was developed for active fringe projection, to obtain optimized depth resolution with a micrometer lateral resolution in confocal measurement. Some of semiconductor components have been measured to attest the feasibility of the developed approach. The depth measurement resolution can reach better than 0.1μm and the maximal measured error was verified to be less than less than 0.5 % of the measured step size.

P-211: Vibration System Design of Smooth Picture Actuator for DLP Projection TV

Smooth picture module is operated by vibration to tilt the light from the DMD (digital micro mirror device) of DLP projection TV, which makes the screen of the TV smoother and DMD chip cost lower. To satisfy the vibration characteristics of smooth picture module, it is designed by optimizing moment of inertia, spring constant and damping coefficient, using structural and fluid dynamic simulation that showed a good agreement with experimental data. To reduce the material cost and moment of inertia, engineering plastic is used and the reliability is estimated. A VCM (voice coil motor) type actuator for smooth picture has to satisfy performance requirements such as higher driving force, lower power consumption, and lower cost. The initial design and optimization for VCM was performed using FE analysis. It allowed us to optimize the design of magnetic circuit of the proposed actuator to obtain higher force while maintaining a lower cost.

Investigation of nanotribological and nanomechanical properties of the digital micromirror device by atomic force microscopy

The digital micromirror device (DMD) is one of the successfully commercialized devices in the emerging field of microelectromechanical systems. In this study, an atomic force microscope (AFM) was used to characterize the surface roughness and the adhesive forces of landing sites. Micromirror tilting measurements on the DMD chip were made using an AFM to obtain the force required to tilt the micromirror. An asperity contact model was used to analyze the contact area and contact stresses between the spring tip and the landing site. Nanoscale bending tests were conducted on the hinge to measure elastic modulus which was needed in the analysis. These data were used to understand the potential mechanisms for “soft” stuck micromirror occurrences.

Development of a Digital Micromirror Spectrometer for Analytical Atomic Spectrometry

A digital micromirror device (DMD) has been incorporated into a novel spectrometer for use in analytical atomic spectrometry. The device can be taken from a commercial computer projector. A protective glass window covering the DMD chip limits the viewable wavelengths to the visible range. The DMD is used to project an image of the light source onto the exit plane of a flat-field spectrograph. A single photomultiplier tube is used for detection. The high switching rate of the micromirrors (15 μs) enables rapid full-spectrum capture, wavelength-modulation, source-modulation, fast narrow-wavelength window scans, and rapid-wavelength "jumping." Calcium, sodium, and potassium have been determined in several standard reference materials (tomato leaves, bovine liver, rice flour, total diet) by flame atomic absorption and emission spectrometry. Absorption sensitivities for each element are near the 0.02 μg/mL level, and detection limits for both absorption and emission are near the 0.01 μg/mL level. Elemental recoveries were within 10% of certified values for most reference materials.