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This paper proposed a new method for reference position detection with high precision for linear encoders by using a home designed scale grating and a coherence function algorithm. Differing from the traditional methods, in which the reference position alignment and calibration of reference position was achieved by detecting the peak of the signal with a negative pulse at the reference position, the method in this paper no longer detects the single peak of the signal, but matching and aligning the integral shape of reference position signal through the algorithm based on the coherence function. The proposed method does not require a complex design and precision manufacturing of reference position. Due to the coherence function algorithm, a multi-pulse reference position signals design is available, which not only reduces the difficulty of reference position design and manufacturing, but also shortens the length of reference position area so that the negative effect on the grating diffraction efficiency is limited. What is more, robustness of the reference detection method introduced here is greatly enhanced. Experimental results show that the accuracy of reference detection can still achieve 2 times of resolution even under the low signal to noise ratio (SNR) of 2dB.

A three-DOF surface encoder can be used to measure the three translational degree of freedom (DOF) displacement of a moving table. A measurement uncertainty of the developed three-DOF surface encoder was systematically investigated to confirm its feasibility on the precision positioning of planar motion stage. An expanded uncertainty of 124.4 nm has been calculated in the measurement results of testing three-axis translational motions over a range of 2.5 μm. Among those error sources, cross-talk errors caused by misalignment existing in experimental setup were identified to be the largest error source.

In this paper, an underwater ranging system based on photoacoustic effect occurring on target surface is proposed. In this proposal, laser pulse generated by blue-green laser is directly incident on target surface, where the photoacoustic effect occurs and a sound source is formed. And then the sound wave which is also called photoacoustic signal is received by the ultrasonic receiver after passing through water. According to the time delay between transmitting laser and receiving photoacoustic signal, and sound velocity in water, the distance between the target and the ultrasonic receiver can be calculated. Differing from underwater range finding by only laser, this approach can avoid backscattering of laser beam, so easier to implement. Experimental system according to this principle has been constructed to verify the feasibility of this technology. The experimental results showed that a ranging accuracy of 1 mm can be effectively achieved when the target is close to the ultrasonic receiver.

Ion Mobility Spectrometry (IMS), having an advantage in real-time and on-line detection, is an atmospheric pressure detecting technique. LA-IMS (Laser Ablation Ion Mobility Spectrometry) uses Nd-YAG laser as ionization source, whose energy is high enough to ionize metal. In this work, we tested the signal in different electric field intensity by a home-made ion mobility spectrometer, using silicon wafers the sample. The transportation of metal ions was match with the formula: Td = d/K • 1/E, when the electric field intensity is greater than 350v/cm. The relationship between signal intensity and collection angle (the angle between drift tube and the surface of the sample) was studied. With the increasing of the collection angle, signal intensity had a significant increase; while the variation of incident angle of the laser had no significant influence. The signal intensity had a 140% increase when the collection angle varied from 0 to 45 degree, while the angle between the drift tube and incident laser beam keeping the same as 90 degree. The position of ion gate in LA-IMS(Laser Ablation Ion Mobility Spectrometry) is different from the traditional ones for the kinetic energy of the ions is too big, if the distance between ion gate and sampling points less than 2.5cm the ion gate will not work, the ions could go through ion gate when it closed. The SNR had been improved by define the signal when the ion gate is closed as background signal, the signal noise including shock wave and electrical field perturbation produced during the interaction between laser beam and samples is eliminated when the signal that the ion gate opened minus the background signal.

The paper presents a dual-beam interference lithography technology for fabrication of diffraction gratings for surface encoders by using cost-effective 405 nm blu-ray laser diodes. In this system, an amplitude division interferometer system is employed. A laser beam raying from a blu-ray laser diode is collimated and then divided into two beams by a beam splitter. These two beams are changed their propagation directions and interfere with each other. Generated interference fringes are exposed on the photoresist coated substrate. Grating line spacing d can be adjusted by changing the incident angle between these two beams. Grating width Wc that determines the measurement of the surface encoder is decided by the coherence length Lc of the laser diode and the grating line spacing d. Calculation and simulation were carried out to decide the grating width. Lc was experimentally obtained. A fabrication system was constructed to verify the feasibility of this technology. Diffraction gratings with a 2.5 micron line spacing and a 2.5 mm width was obtained.

The real-time distance measurement system with dual femtosecond comb lasers combines time-of–flight and interferometric measurement. It has advantages of wide-range, high-accuracy and fast speed at the rate about 10000 pts/s. Such a distance measurement system needs dedicated higher performance of the data acquisition and processing hardware platform to support. This paper introduces the dedicated platform of the developed absolute distance measurement system. This platform is divided into three parts according to their respective functions. First part is the data acquisition module, which function is mainly to realize the A/D conversion. In this part we designed a sampling clock adjustment module to assist the A/D conversion module to sample accurately. The sampling clock adjustment module accept a 250MHz maximum reference clock input, which from the same femtosecond laser source as the optical measurement system, then generate an output clock for the A/D converter that can be delayed up to 20ns with a resolution of 714ps. This data acquisition module can convert the analog laser pulse signal to digital signal with a 14 bits resolution and a 250 MSPS maximum sample rate. Second is the data processing and storage module consists of FPGA and DDR3 modules. The FPGA module calculates the test distance by the 16 bits digital sampling signal from the front data acquisition module. The DDR3 module implements sampling data caching. Finally part is the data transmission and peripheral interfaces module based on three DB9 and USB2.0. We can easily debug the platform in the PC and implement communication with upper machine. We tested our system used dedicate test bench in real-time. The scope of the measurement system range is 0 to 3 meters and the measurement deviation is less than 10um.

Fabrication of a new type hybrid plane optics, Grating-Fresnel (G-Fresnel) lens for miniature spectrometer is presented in this research. A polydimethylsiloxane (PDMS) based soft lithography technology is employed. In this method, the grating surface and Fresnel surface of the G-Fresnel lens are formed simultaneously by sandwiching the PDMS layer between a reverse Fresnel mold and a grating. Surface anti-adhesive treatment method has been proposed to solve the innate adhesion of PDMS layers. A fabrication system is constructed and a G-Fresnel with grating line spacing of 1.11μm (900 lines/mm) and Fresnel lens with a diameter of 25.4 mm and a focal length of 25 mm was successfully fabricated. Three-dimensional surface profilometry has been performed to examine the device quality. Measured results show that replicas remain high fidelity to its primary master mold. A miniature spectrometer system was constructed to evaluate the performances of this fabricated G-Fresnel lens. Experimental results show that the spectrometer can provide about 2 nm resolutions at wavelengths of 450nm, 532 nm, and 650 nm, which verified the effectiveness of this fabrication method.

Ion mobility spectrometry (IMS) is a key trace detection technique for toxic pollutants and explosives in the atmosphere. Ultraviolet radiation photoionization source is widely used as an ionization source for IMS due to its advantages of high selectivity and non-radioactivity. However, UV-IMS bring problems that UV rays will be launched into the drift tube which will cause secondary ionization and lead to the photoelectric effect of the Faraday disk. So air is often used as working gas to reduce the effective distance of UV rays, but it will limit the application areas of UV-IMS. In this paper, we propose a new structure of curved drift tube, which can avoid abnormally incident UV rays. Furthermore, using curved drift tube may increase the length of drift tube and then improve the resolution of UV-IMS according to previous research. We studied the homogeneity of electric field in the curved drift tube, which determined the performance of UV-IMS. Numerical simulation of electric field in curved drift tube was conducted by SIMION in our study. In addition, modeling method and homogeneity standard for electric field were also presented. The influences of key parameters include radius of gyration, gap between electrode as well as inner diameter of curved drift tube, on the homogeneity of electric field were researched and some useful laws were summarized. Finally, an optimized curved drift tube is designed to achieve homogenous drift electric field. There is more than 98.75% of the region inside the curved drift tube where the fluctuation of the electric field strength along the radial direction is less than 0.2% of that along the axial direction.

Laser-induced breakdown spectroscopy (LIBS) is characterized as a powerful tool in in-situ online analysis with its fast and multiple detecting abilities. But in the area of detecting trace sample in aqueous solution of low concentration, the turbulence, scattering, absorbance and cooling effect of liquid medium limits its performance. Traditional method includes liquid jet, liquid-solid transformation and pre-concentration on other medium, yet the procedure of sample preparation is complicated and time consuming. In this work, we propose a new method to achieve pre-concentration, in which filter paper and electro-spray ionization (ESI) are used. In our experiment, we choose MnSO 4 as sample. The surface of filter paper is sprayed with MnSO 4 aqueous solution of different concentration by an ESI. The pulsed laser is focused on the surface of filter paper and the plasma is formed in the focusing area. Through an optical fiber the spectrum of plasma is detected by a spectrometer. The ESI system, pulses generator system and the UI on PC are home-made. The spectra lines of Mn at 257.6nm, 259.4nm and 260.6nm are analyzed. Results show that the limit of detection at 257.6nm is sub-ppb and the R 2 of calibration curve is more than 0.93. Compared with traditional method, like soak and drip processing, our method can increase the concentration of the sample by simply expanding spraying time, achieving a higher signal-to-noise ratio (SNR) and a lower limit of detection (LOD). In addition, the consumption of sample solution is as low as several hundred μl in each detection.

Ion mobility spectrometry (IMS) is widely used in the field of chemical composition analysis. Faraday cup is the most classical method to detect ions for IMS in the atmospheric pressure. However, the performance of Faraday plate was limited by many kinds of factors, including interfering electromagnetic waves, thermal(Johnson) noise, induced current , gain bandwidth product, etc. There is a theoretical limit in detection of ions at ambient condition which is approximately 106 ions per second. In this paper, we introduced a novel way using laser-induced fluorescence (LIF) to bypass the limitation of Faraday plate. Fluorescent ions which were selected by IMS get excited when they fly through the laser excitation area. The fluorescence emitted by the excited ions was captured exponentially and amplified through proper optoelectronic system. Rhodamine 6G (R6G) was selected as the fluorochrome for the reason that excitation wavelength, emission wavelength, and fluorescence quantum yield were more appropriate than others. An orthometric light path is designed to eliminate the adverse impact which was caused by induced laser. The experiment result shows that a fluorescence signal from the sample ions of the IMS could be observed. Compared with Faraday plate, the LIF-IMS may find a potential application in more system at the atmosphere condition.

Ion mobility spectrometry (IMS) is an attractive material analysis technology for developing a miniaturized volatile organic compounds (VOCs) on-site monitoring sensor. Having simple instrumentation, IMS is especially suitable when portability and sensitivity are required. In this work, we designed an ion mobility spectrometer with UV ionization. The geometric parameters of the UV-IMS were optimized based on a numerical simulation. The simulation results demonstrated that the drift electric field in the drift region was approximately homogenous and in the reaction region had an ion focusing effect, which could improve the sensitivity and resolving power of the IMS. The UV-IMS has been constructed and used to detect VOCs, such as acetone, benzene, toluene and m-xylene (BTX). The resolution of these substance measured from the UV-IMS in the atmospheric conditions are about 30 and the limit of detection (LOD) is low to ppmv. The ion mobility module and electric circuit are integrated in a main PCB, which can facilitate mass production and miniaturization. The present UV-IMS is expected to become a tool of choice for the on-site monitoring for VOCs.

After more than ten years' research efforts on the Micro Aerial Vehicle (MAV) since it was proposed in 1990s, the stable flying platform has been matured. The next reasonable goal is to implement more practical applications for MAVs. Equipped with a micro radio-localizer, MAVs have the ability of localizing a target that transmitting radio signals, and further can be a novel promising Anti-Radiation device. A micro radio-localizer prototype and its localization principle and localization algorithm are proposed. The error analysis of the algorithm is also discussed. On the basis of the comparison of the often-used radio localization method, considering the MAVs' inherent limitation on the dimension of the antennas, a signal intensity and guidance information based localization method is proposed. Under the assumption that the electromagnetic wave obeys the free-space spreading model and the signal's power keeps unchanged, the measuring equations under different target motions are established. Localization algorithm is derived. The determination of several factors such as the number of measuring positions, numerical solving method and initial solution is discussed. Error analysis of the localization algorithm is also proposed by utilizing error analysis theory. A radio-localizer prototype is developed and experiment results are shown as well.

Micro machine vision system is an important part of a micromanipulating system which has been used widely in many fields. As the research activities on the micromanipulating system go deeper, micro machine vision system catches more attention. In this paper, micro machine vision system is treated as a kind of machine vision system with constrains and characteristics introduced by specific application environment. Unlike the traditional machine vision system, a micro machine vision system usually does not aim at the reconstruction of the scene. It is introduced to obtain expected position information so that the manipulation can be accomplished accurately. The architecture of the micro machine vision system is proposed. The key issues related to a micro machine vision system such as system layout, optical imaging device and vision system calibration are discussed to explain the proposed architecture further. A task-oriented micro machine vision system for biological micromanipulating system is shown as an example, which is in compliance with the proposed architecture.

The synchronization control technique is one of the most key techniques in the laser range gated (LRG) imaging system. Conventional control circuits are composed of discrete components and Medium Scale Integration (MSI) and Small Scale Integration (SSI), which have bad reliability and poor ability of anti-interference. The idea of using the Complex Programmable Logic Device (CPLD) to realize the monostable trigger circuit is introduced. On the basis of analyzing the performance requirement to the synchronization control of the laser range gated imaging system, a new synchronization control circuit based on CPLD is presented. The circuit based on CPLD is very compact and flexible and has high reliability and strong ability of anti-interference. The synchronization control circuit based on CPLD can provide a wide selection of gate widths, pulse widths and delays. The synchronization control circuit is successfully used in our experiment and the expected result is obtained.

A MEMS based micro colloid thruster (including an source emitter array and an extractor) is designed, fabricated and tested. Source emitter array of the thruster is silicon column etched by ICP. The negative electrode on the extractor can be controlled separately. After bonding together, a single emitter and extractor works on an electrical colloid propulsion principle, and produce µN order thrust. Such a small and controllable thrust is the urgent requirement for a micro-satellite. Thrust test for the micro colloid thruster is made in high vacuum box. Thrust is acted on a cantilever beam, and the displacement of cantilever beam is detected by a current vortex sensor. Analysis to the recording data shows that the maxim thrust produced by a single emitter is about 2 µN, which is agreement with theory estimate.