Maskless Microscopic Lithography through Shaping Ultraviolet Laser with Digital Micro-mirror Device

Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or quasi-Gaussian distribution will carry the pattern on DMD to etch the resin. It provides a method of precise control of laser beam shapes and?photon-induced curing behavior of resin. This technology provides an accurate micro-fabrication of microstructures used for micro-systems. As a virtual mask generator and a binary-amplitude spatial light modulator, DMD is equivalent to the masks in the conventional exposure system. As the virtual masks and shaped laser beam can be achieved flexibly, it is a good method of precision soft lithography for 2D/3D microstructures.

Three-detector setup for PAL spectrometer based on DRS4 waveform digitizing board

A digital three-detector positron lifetime spectrometer was developed.It consists of a DRS4 waveform digitizing board and three La Br3scintillation detectors coupled to XP2020Q photomultiplier tubes.DRS4 waveform digitizing allows data sampling at up to 5 GSPS with high amplitude resolution,with good time scale linearity and stability.In the triple-coincidence,the new system could reach a 195 ps time resolution,which is better than the conventional analog apparatus with the same detectors.This spectrometer can be applied to the other scintillation timing measurements with picoseconds accuracy.

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).

The Basis for Design and Manufacture of a DSP-Based Coincidence Spectrometer

The coincidence technique and the coincidence spectroscopy have been developed and applied for over 40 years. Most of popular coincidence measurement systems were based on analog electronics techniques such as time to amplitude conversion (TAC) or logic selecting coincidence unit. The above-mentioned systems are relatively cumbersome and complicated to use. With the strong growth of digital electronics techniques and computational science, the coincidence measurement systems will be constructed simpler but more efficient with the sake of application. This article presents the design principle and signal processing of a simple two-channel coincidence system by a technique of digital signal processing (DSP) using Field Programmable Gate Arrays (FPGA) devices at Nuclear Research Institute (NRI), Dalat.

γ射线探测综合实验教学平台开发

针对传统γ射线探测实验装置定位精度不高、搭建麻烦、可开展的实验项目少,不利于实验重复与教学等缺点,该文设计开发了一款γ射线探测与测量综合实验教学平台,完成了平台的机械设计加工以及γ射线探测专用数字化多道分析器研制。基于该平台,可完成多个关于γ射线探测与应用的认知、基础、综合型、探究型实验项目。实践教学效果证明,该平台稳定性好,操作性强,实验结果准确,方便教师教学,能使学生更好地理解与掌握γ射线的性质、γ射线与物质相互作用的机制以及γ射线的应用。

宽波段傅里叶变换太阳光谱仪等光程差采样系统设计

太阳成像光谱探测是诊断太阳大气磁场和热力学参数的主要手段.傅里叶变换太阳光谱仪(Fourier Transform Solar Spectrometer, FTSS)具有宽波段的优势,是当前中红外高分辨率太阳光谱探测的最佳选择.FTSS通过采集目标辐射等光程差干涉图,反演获得光谱图,等光程差采样的间隔决定了反演光谱波长范围.因此从FTSS宽波段光谱观测对不同等光程差采样间隔需求出发,基于现场可编程门阵列(Field Programmable Gate Array, FPGA)技术,采用全数字分频、倍频方案,设计了一套宽波段FTSS等光程差采样系统.采用分布式余数补偿方法,有效解决了在参考激光干涉信号倍频过程中,输出采样信号在输出信号周期间误差累积问题,并降低了输出采样信号的误差及非均匀性;经功能仿真及实验测试,系统在200 Hz–50 kHz频率范围内,频率误差δ <0.04%,可有效满足FTSS的300 nm–25μm宽波段的光谱观测数据采集需求,为后续可见和红外波段FTSS的研制奠定了技术基础.

Dynamic infrared scene simulation using grayscale modulation of digital micro-mirror device

Dynamic infrared scene simulation is for discovering and solving the problems encountered in designing, developing and manufacturing infrared imaging guidance weapons. The infrared scene simulation is explored by using the digital grayscale modulation method. The infrared image modulation model of a digital micro-mirror device （DMD） is established and then the infrared scene simulator prototype which is based on DMD grayscale modulation is developed. To evaluate its main parameters such as resolution, contrast, minimum temperature difference, gray scale, various DMD subsystems such as signal decoding, image normalization, synchronization drive, pulse width modulation （PWM） and DMD chips are designed. The infrared scene simulator is tested on a certain infrared missile seeker. The test results show preliminarily that the infrared scene simulator has high gray scale, small geometrical distortion and highly resolvable imaging resolution and contrast and yields high-fidelity images, thus being able to meet the requirements for the infrared scene simulation inside a laboratory.

System design for precise digitization and readout of the CSNS-WNS BaF2 spectrometer

The BaF2 （barium fluoride） spectrometer is one of the experiment facilities at the CSNS-WNS（White Neutron Source at China Spallation Neutron Source）, currently under construction. It is designed to precisely measure the（n, γ） cross section, with 92 crystal elements and complete 4π steradian coverage. In order to improve the precision of measurement, in this paper, a new precise digitization and readout method is proposed. Waveform digitizing with 1 GSps sampling rate and 12-bit resolution is used to precisely capture the detector signal. To solve the problem of massive data readout and processing, the readout electronics is designed as a distributed architecture with 4 PXIe crates. The digitized signal is concentrated to the PXIe crate controller through a PCIe bus on the backplane and transmitted to the data acquisition system over gigabit Ethernet in parallel. Besides, the clock and trigger can be fanned out synchronously to every electronic channel over a high-precision distribution network. Test results show that the prototype of the readout electronics can achieve good performance and meet the requirements of the CSNS-WNS BaF2 spectrometer.

A new positron annihilation lifetime spectrometer based on DRS4 waveform digitizing board

A new simple digital positron lifetime spectrometer has been developed. It includes a DRS4 waveform digitizing board and two scintillation detectors based on the XP2020Q photomultiplier tubes and LaBr3 scintillators. The DRS4 waveform digitizing can handle small pulses, down to few tens of millivolts, and its time scale linearity and stability are very good. The new system has reached a 206 ps time resolution, which is better than the conventional analog apparatus using the same detectors. These improvements make this spectrometer more simple and convenient in comparison with other spectrometers, and it can be applied to the other scintillation timing measurements with picosecond accuracy.

Compressed sensing reconstruction of sparse spectrum based on digital micro-mirror device platform

A new method which employs compressive sensing(CS) to reconstruct the sparse spectrum is designed and experimentally demonstrated. On the basis of CS theory, the simulation results indicate that the probability of reconstruction is high when the step of the sparsity adaptive matching pursuit algorithm is confirmed as 1. Contrastive analysis for four kinds of commonly used measurement matrices: part Hadamard, Bernoulli, Toeplitz and Circular matrix, has been conducted. The results illustrate that the part Hadamard matrix has better performance of reconstruction than the other matrices. The experimental system of the spectral compression reconstruction is mainly based on the digital micro-mirror device(DMD). The experimental results prove that CS can reconstruct sparse spectrum well under the condition of 50% sampling rate. The system error 0.0781 is obtained, which is defined by the average value of the 2-norm. Furthermore, the proposed method shows a dominant ability to discard redundancy.

数字微镜哈达玛光谱仪谱线弯曲的分析与修正

由于数字微镜（digital micro-mirror device,DMD）哈达玛变换光谱仪其成本低,光能利用率高及无运动部件等优势,逐渐成为光谱仪领域的研究重点。研制了一款基于DMD的哈达玛变换光谱仪。为了解决光谱仪谱线弯曲造成的光谱分辨率下降的问题,对基于DMD的哈达玛变换光谱仪中的谱线弯曲所引起的谱带混叠进行了分析。首先,导出了谱带混叠与谱线弯曲的关系式。然后,提出了两个过程来解决谱带混叠,一是通过调整DMD编码条纹,使DMD所编码的谱带最大限度地与标准谱带重合;二是通过数据处理对谱带混叠进行修正。最后,通过对谱线曲率半径为5.8×10~4,7.8×10~4和9.7×10~4μm等六种情况下谱带混叠进行了分析与修正,拟合出光谱混叠和修正效果与谱线曲率半径的关系。结果表明：对于不同程度的谱线弯曲经过这两个过程修正后,分辨率都会改善到接近光学系统的分辨率,说明这两个过程对修正谱线弯曲具有普适性、并且方法简单、有效。

核磁共振谱仪数字接收机的原理与实现

核磁共振波谱仪射频系统数字化是现代核磁谱仪的发展方向 ,用数字检波技术代替模拟正交检波是数字接收机的一项新技术 .本文在分析模拟正交检波原理与不足的基础上 ,介绍了数字正交检波、过采样和采用中频直接采样的原理 ,及在 40 0MHz核磁谱仪上的实现方案 .

基于IBOB的射电望远镜宽带数字频谱仪系统的设计与测试

简述了基于IBOB和Xilinx System Generator平台的射电望远镜宽带数字频谱仪系统的设计与应用;给出了双路400MHz、2048通道、16IP输出数字频谱仪系统的具体设计方案,并对该数字频谱仪器的性能指标进行了分析和测试,验证了方案的可行性;最后初步讨论了滤波器设备对后端系统的影响。

基于FPGA的数字核信号处理系统的研究

核能谱是核物理研究、射线探测和核技术应用领域中获取的重要信息,对其测量技术的改进一直为热点研究问题。论文基于FPGA设计一套数字核信号处理系统,对高速ADC采样后的数字核信号通过FPGA控制的高速USB接口电路,直接传送给计算机的测试平台以实现核信号的离线处理,同时该数字核信号在FPGA中实现其滤波成形、堆积识别,基线恢复等功能,得到的能谱通过USB接口传送给计算机。通过测试,系统既能实现原始核信号的传输与保存,又能实现数字核信号的在线处理。

大体积NaI(Tl)数字式车载γ能谱仪的研制

车载γ能谱仪主要应用于区域放射性核素活度测量、放射源搜索及核污染检测,而数字化技术是提高车载γ能谱仪灵敏度与快速响应的有效方法。本文研制了可支持1~5个4L大体积NaI（Tl）的数字式车载γ能谱仪系统。该系统采用数字核脉冲处理技术独立获取多个NaI（Tl）晶体的能谱,并通过无线WiFi、快速以太网、RS232等3种方式发送谱线数据给军用计算机。本系统在计算机上实现了实时核素识别、数字成图、色差能谱显示、ROI监控、数据回放等功能。结果表明,本系统采用数字技术后提升了车载γ能谱仪的能量分辨率、低能射线识别度和能量线性度,且具备更加稳定精确的数字稳谱效果。该系统不仅可用于放射性资源勘查,也可用于快速核应急、核污染检测、放射源搜索等。

基于数字微镜器件的中阶梯光栅光谱仪的光学系统设计

研究了一种基于数字微镜器件(DMD)具有新型光路结构的中阶梯光栅光谱仪,并采用新的谱图信息接收方式来降低其使用成本和数据处理过程的复杂程度。将具有单波长选通功能的DMD与一维探测器光电倍增管(PMT)相结合接收中阶梯光栅光谱仪的光谱信息,在降低仪器成本的同时将中阶梯光栅光谱仪谱图还原算法与DMD扫描驱动算法相整合,提高了算法效率。由于DMD的填充因子比CCD稍低,该类光谱仪对成像质量和能量集中度提出了更高的要求。本文根据DMD型中阶梯光栅光谱仪特点,在有限的可挑选的光学材料下,采用多重优化的方式合理设计了中阶梯光栅光谱仪准直镜、中阶梯光栅、棱镜、聚焦镜等各个光学元件的光路结构参数,并且在Czerny-Turner结构中加入校正透镜和场镜,校正了系统所有像差,提高了整个光学系统的成像质量和光谱分辨率。最终设计的光谱仪系统分辨率达0.01nm,单个微反射镜内的光斑能量聚集度达到70%。

光学悬浮沙粒径谱仪

在海岸工程应用中,需要了解悬沙运移规律,由于我国近海河口悬沙浓度很高,尚未有可用的现场测量仪器.在国家863计划的支持下,我们研制成功了可用于现场高浓度悬沙测量的 '光学悬浮沙粒径谱仪'.文章介绍光学悬浮沙粒径谱仪的原理、现场实验结果和高浓度悬沙数字图像分析技术.现场实验表明,该仪器可用于粒径5～100 μm浓度大于10%的悬沙现场测量.文中给出了芦潮港海区悬沙测量结果.

应用两种近地可见光成像传感器估测棉花冠层叶片氮素状况

作物叶片含氮量是作物长势监测、产量及品质估测的重要依据,实时、无损地监测植株体内氮素营养状况有助于棉花氮肥的正确施用。本研究比较2种近地可见光传感器的光谱和颜色信息用于监测棉花氮素营养的能力,确定MSI200成像光谱仪和数码相机监测棉花冠层叶片氮含量最佳的波段、光谱指数和颜色参数并建立估测模型。结果表明,在可见光波段,冠层反射率随着冠层叶片氮素含量的增加而降低,且叶片含氮量的光谱敏感波段主要位于绿光和红光区域;与棉花冠层叶片含氮量的拟合效果最好的2种传感器的光谱指数为差值指数DI(R580,R680)和G-R,而颜色参数则分别为b*和H,同一传感器以光谱指数的拟合效果优于颜色参数,不同传感器以MSI200数据的拟合效果优于数码相机;利用独立试验资料检验所建模型的估测性能表明,差值指数对棉花冠层叶片氮素的预测能力优于比值指数和归一化差值指数,DI(R580,R680)和G-R所建模型的估测精度最高,分别为0.8131和0.7636。因此,利用数码相机和MSI200型成像光谱仪可以定量估测棉花冠层叶片氮素营养状况。

具有快速调制功能NMR发射机的设计与实现

介绍了一种具有快速幅度、相位和频率调制功能的核磁共振射频发射机.数字中频子系统中采用了两个级联的数控振荡器,前一级数控振荡器在FPGA内实现,用于产生基带调制信号;后一级则采用具有正交调制功能的DDS芯片,由它来完成基带信号的采样率转换、中频产生、调制和输出.射频脉冲的相位和频率偏置的设置直接由级联NCO实现,而幅度设置则由步进衰减器和中频幅度调制共同实现.该发射机的基本性能和功能满足常规1D/2DNMR实验需求.

用于低场磁共振成像的直接射频采样数字接收机

提出一种用于低场磁共振成像谱仪的数字接收机的设计.它基于直接射频采样技术,本文详细讨论了其设计过程.实验结果表明,设计的数字接收机具有结构简单、性能优良和实用性较强的特点.