Papers by Keyword: DMD

Abstract: Ti-6Al-4V is the most common used titanium alloy in aerospace. Parts are therefore often machined from wrought material with high buy-to-fly ratios. Additive manufacturing, however, allows to build parts rapidly and directly from computer-aided design information, offering better material utilisation and lead time reduction. Despite the high potential for aerospace applications, the reliability of the mechanical properties is still at an early stage. This work should give a first overview by determining and comparing DMLS, EBM and DMD Ti-6Al-4V material. Each process is compared based on standardised post treatments, specimen geometries and test methods.It can be seen that the chemistry, the microstructure, and the defect formation differs between the processes, which leads to a scatter in the experimentally determined static tensile, axial fatigue, and crack growth properties.

Abstract: Polymer MLA is fabricated by used of the DMD-based maskless lithography method. The process flow is described in this paper. The obtained photoresist concave MLA, which is used as a pattern to fabricate PDMS convex MLA, and the resulted PDMS MLA are measured with 3D surface profiler based on scanning white light interferometry. Besides, the transmission and reflection spectrum of PDMS film sample are also measured and used to calculate the refractive index of the PDMS film.

Abstract: Projector calibration can be seen as a special case of the camera calibration. It can establish the relationship of the three dimensional space coordinates for points and projector image coordinates for points DMD by using a projector to project coding pattern. In camera calibration, ZHANG’s self-calibration was conducted in the maximum likelihood linear refinement. Operation process takes the lens distortion factors into account finding out the camera internal and external parameters finally. Using this algorithm to the projector calibration can solve the traditional linear calibration algorithm which is complex and poor robustness. Otherwise, it can improve the practicability of calibration method. This method can both calibrate the internal and external parameters of projector, which can solve the problem of independently inside or outside calibration.

Abstract: Dynamic infrared scene generator is one of the important means to test the detection,track and anti-interference performance of the infrared seeker. The article to a certain type of air-to-air missile seeker loop simulation application object, based on the micro-mirror array (DMD), Vega Prime software and its infrared module for the development of tools,Real-time infrared images with vary objects and backgrounds in different conditions are generated to simulate the infrared radiation at the pupil of the guide system.The radiation of blackbody is reflected and modulated by digital micro mirror device based on infrared video signal,which is used to test and evaluate the performance of infrared seeker.The results indicate that the system has the advantages of compact structure,high real-time performance,high frame frequency,high resolution,and great dynamic range.

Abstract: With FPGA as the host controller, a set of hardware system based on digital micro-mirror device (DMD) for compressive imaging (CI) was developed. This paper studies the principle and characteristic of DMD control. First, the data of PC Screen image is transferred to DMD driver by software using binary pulse width modulation (BPWM) technology. The data is then rewritten into a control single which finally directs the DMD. The test results proved that the digital image received can be loaded onto the micro-mirrors excellently and with optics module installed, the system could successfully implement the CS measurement patterns which satisfy CI system.

Abstract: The simulation of temperature field during laser direct metal deposition(DMD) were researched. The finite element model of single track cladding, multi-track overlapping and multi-layer deposition were established. The temperature field was simulated by ANSYS software basing on life-and-death element and cycle algorithm. Under different process parameters, the temperature and temperature gradient on the cross-section of sample were simulated during single- track scanning, multi-track overlapping and multi-layer deposition. Temperature cycle curves at different position were analyzed and were consistent with actually value. Both simulation and experiment showed that heat accumulation during continuous forming greatly affected the temperature of molten pool.

Abstract: The realization of Hadamard Transform (HT) encoding mask is the key technology to Hadamard Transform Spectroscopy. In order to realize HT mask using DMD, the theory of HT and principle of light modulate of DMD are explained. DMD is controlled by programming to realize cyclic HT mask based on S-matrix. The performance of the mask is also verified by building a spectroscopy experiment system, and higher SNR spectrum information is acquired. The results indicate that the SNR in HT mode is 38.4323 while 11.3446 in scanning mode, the gain of SNR is 3.38. It can be concluded that the HT encoding mask that realized by DMD is feasible, spectrum signal’s intensity and SNR can be improved effectively.

Abstract: A low-cost microfabrication tool based on digital mirror device(DMD) is presented in this paper. The imaging principle of the system is described and the fabrication methods for binary and nonbinary micro optical elements(MOE) are also discussed in detail. It is expected to provide an understanding of MOEs fabrication using DMD-based maskless lithography technique.

Abstract: In order to fabricate micro/meso structures, a novel micro-stereolithography (SL) system with dynamic pattern generator using digital micro-mirror device (DMD) has been investigated. The micro-stereolithography system solidifies photo-sensitive resin with image mask generated by dynamic pattern generator. The micro-stereolithography system is made up of dynamic pattern generator, recoating system and control system. The dynamic pattern generator consists of parabolic concentrator, UV lamp, collimating lens, shutter, DMD and its control, lens and computer. UV light intensity distribution in the imaging plane is investigated. Uniformity UV light intensity distribution is obtained in the imaging plane with changing small area’s gray-scale, and the difference between maximum and minimum value of UV light intensity is 0.4µW/cm2. Small size parts with intricate microstructures have been fabricated with the novel SL system. Compared with laser scanning SL system, the advantage of the novel micro-SL system is that the new SL system can build small objects having micro-structures with low cost in shorter time. The novel micro-SL system provides a solution to the problem that has hampered the progress of SL process into high resolution with low cost.