2011 Vol. 4, No. 6
This paper overviews the development of the single diamond machines used in weapons and commercial fields, and introduces nowadays widely-used commercial ultra-precision diamond turning machines. Then, it analyzes the key techniques to achieve nanometer-level precision machining, such as air bearing work spindles, oil hydrostatic bearing X/Z slides, work piece measurement error compensation, optical tool setters, Linear Variable Differential Transformer(LVDT) tool setters and adaptive control systems. Finally, it summarizes the materials suitable for diamond turning, and introduces the fast tool servo and slow slide servo used in the manufacturing of opto-mechanical components. By taking drop-in assembly of a Cassegrain telescope and an fine optical system for examples, this paper shows the important effort of the ultra-precision diamond turning in photoelectric products.
The paper presents the development process of greenhouse gas remote sensing technology. It introduces the design priciples, work modes, spectral band setting and main specifications of foreign advance high spectral resolution remote sensors for greenhouse gases. Furthermore, It is also specified that greenhouse gas remote sensing technology evolves from synthetical instruments to special instruments. Based on the overview about greenhouse gas remote sensing technology, it discusses the future development trend of this kind of instrument and points out that the main emphasis of the research will be some instruments with higher spectral resolution, higher spatial resolution, wider coverages, shorter periods and higher signal to noise ratios.
The present situation of Three-dimensional(3D) display technology is introduced and applications of parallax barriers and lenticular lens arrays to 3D display technology are overviewed. The structures and principles of several kinds of parallax barriers and lenticular lens arrays are given. Then, it describes how to add the different gratings into the traditional stereoscopic display systems to form a combined structure to improve stereoscopic display function of the system, and emphasizes the effects of these gratings on reducing cross-talk and moir fringes, enlarging viewing-angles, and providing full 3D information. Finally, it points out that it is significant to combine two lenticular lens sheets to form a new lens array with a large area, low cost and uniform parameters for researching free stereoscopic display technology.
To meet the high precision requirement of complex space optical systems, and to overcome the limitations of traditional benchmark pass method and computer-aided adjustment technique individually for the complex reflection optical systems with three or more mirrors, a new alignment technique by combining above two methods is proposed. An alignment experiment is performed on the optical system with multiple mirrors by the proposed method. The results show that the alignment technique of combined two methods is effective and reasonable. The misalignments of the mirror in the Y and Z directions have been decreased from 18.651 mm and 9.879 mm to 1.036 mm and 0.102 mm, respectively, and the system wavefront aberration has reached the average value of 1/14(RMS) in a full field. The method is proved to be guidance capability and practical reference for complicated optical systems with multimirrors, which can effectively reduce the alignment time and achieve higher system accuracy.
Based on analysis of properties of SiCp/Al composites, the advantages and disadvantages of common connecting methods for space optical sensors such as fore-imbedding, welding and bonding were demonstrated. A new method of machining threads directly on high volume fraction SiCp/Al composites and mounting steel wire thread sleeves to improve the thread connection was proposed. The tensile test for M4 and M5 threads on high volume fraction SiCp/Al composites were performed. Obtained results suggest that some of them are pulled out before mounting the steel wire thread sleeve. However, M4 and M5 screws are pulled off under 3 000-4 000 N and 8 000-9 000 N, respectively, after mounting the steel wire thread sleeve. The M4 and M5 threads show good shapes, which means that machining threads directly on high volume fraction SiCp/Al composites and mounting the steel wire can meet the requirements of the engineering for tensile strength and it is already used in some projects.
To precisely and effectively complete the heading calibration of a theodolite, this paper analyzes the effect of single error on the heading calibration, and builds a correct model of the heading calibration when the collimating and orientation errors are involved at the same time according to the heading calibration principle. It provides the specific correction and verification methods. Experimental and measurement results indicate that the orientation error measured by positive and inverse pointing methods is equivalent to the error between orientation error and collimating error. The research in this paper proves the feasibility and effectiveness of the correction method and disciplines the method of heading calibration at the dock, which will make sure TTC complete mission successfully.
To meet the testing requirements of high-precision cameras in the outer environment, an off-axis collimator with lightweight, high accuracy, and high temperature stability is designed. Silicon carbide and carbon fiber/epoxy resin matrix composite are adopted to make a reflector and a shading tube respectively for the off-axis aspherical collimator. The collimator can keep accuracy stability in their linear expansion coefficients in a twice at a certain temperature range. After testing, the wavefront aberration of the off-axis collimagor with a diameter of 400 mm and a focal length of 8 m is 1/5(P-V, =632.8 nm) and 1/27(RMS) at a temperature range of (2010) ℃. The collimator can be used in the outer environment.
A high-flux solar simulator capable of delivering a radiative power over 5 kW at peak radiative fluxes exceeding 1 800 suns(AM1.5∶1 sun=1 kW/m2) is studied in this paper. It comprises an array of ten Xe arcs, and each of them is coupled closely with ellipsoidal specular reflectors of common focus. Its optical design, main engineering features, and operating performance are described. The Monte Carlo ray-tracing technique is applied to optimization of the geometrical configuration for maximizing the source-to-target transfer efficiency of radiative power. Calorimeter measurements indicate an average flux over 1 000 kW/m2 at a circular target with 20 mm diameter, which corresponds to radiation uniformity of below 6%. This research facility is used to simulate the radiation characteristics of highly concentrating solar systems and serves as an experimental platform for investigating the thermo chemical processing of solar fuels and for testing advanced high-temperature materials.
As for the larger random walk noise of a piezoelectric gyro in the stabilized platform, the Kalman filtering technology based on a linear accelerometer is proposed to perform the signal filtering. Based on Kalman filtering theory, the observation equation of an angle rate for the piezoelectric gyro is established, and the linear accelerometer is used to measure the inertial angle accelaration of the platform. Then, the signal filtering of piezoelectric gyro is achieved. Experimental results show that the random walk noise level is reduced from 0.005()s-1/ Hz to 0.001 25()s-1/ Hz by using linear accelerometers and without affecting the bandwidth of piezoelectric gyro, which improves the stability precision of the optoelectronic platform.
An external borner for the vehicle opto-electronic stabilized platform was optimized to improve its system accuracy under a dynamic loading mode. The material choice principle and structure mode of the external bordon were introduced. Then, the external border was molded by using UG software, and its structure was analyzed and designed with the finite element method combined with a theoretical analysis. Based on the MSC software, the model was checked and verified. Experimental results demonstrate that the designed border can achieve a smaller rotation inertia with better rigidity and strength and its maximum distortion is 2.6 m in a static state. The result means that this structure can satisfy the operating request.
In order to overcome the crosstalk of a high speed CCD imaging circuit, the reasons of the crosstalk are analyzed and the crosstalk models of CCD imaging circuit are established. The striplines instead of microstrips are used for the multi-channel CCD video signals and the guard lines are used for the striplines to isolate further. To reduce the crosstalk caused by the common impedance of a power supply, the isolated multi-channel power supplies are designed and the effective routing method for decoupling capacitors is used to lower parasitic inductances. The analog and digital parts are layout separately and a whole ground plane is used to reduce the ground bounce. Experiments for a CCD imaging circuit with much severe crosstalk problems are performed by these techniques, results show that the channel isolation is large than 60 dB. The crosstalk is reduced efficiently and the image quality is improved.
Effects of the tilt of a phase mask on wavefront coding systems are analyzed and the generalized pupil function is derived by a coordinate transformation in this paper. The approximate expression shows that the tilt of the phase mask brings a magnification effect on the cubic phase mask coefficient. The effect is independent on the sign of the angle, however, it will get larger with the absolute value of the angle increases. Moreover, the tilt of the phase mask extends both the sides of the Point Spread Function(PSF) envelope and causes a decrease of Modulation Transfer Function(MTF). When the tilt is in the meridian, the magnification effect of cubic phase mask coefficient in the meridian plane is larger than that in sagittal direction, which results in larger extension of PSF and lower MTF in the sagittal direction. All above conclusions are proved by the simulation with MATLAB and optical software.
To keep an inertial navigation system to correct its course errors continuously, a detection method is presented to solve the problem that few stars can be detected in daylight by the shipboard optical measuring equipment. The detecting method for the star body in daytime with strong background is studied. The median filter technology is used to improve the Signal to Noise Ratio(SNR) of an image, and the fuzzy entropy threshold method is used to creat its membership function and select the threshold of a gray-level image to detect star objects in daytime. The experimental result shows that the optical measuring equipment can improve the detecting ability from 3 MV to 4.5 MV and the amount of stars from 5 to 250 or more by this method. It meets the requirement of the inertial navigation system for correcting its course errors continuously. The method can be popularized and can be applied to the fields of dark and small target detection by televisions.
Bar code technology is a widely used photoelectric data entry technology, including encoding, optical sensing, barcode printing and computer recognitions. The article summarizes the function of the bar code technology in the fields of local history library catalog, collection and circulation. It also disscusses the revolutionary influence of the applications of the two-dimensional code technology on the automatic management and the digital construction of the local history library.
An aerosol concentration measurement method based on two channels of transmission and scattering was proposed and a detection device was designed in this paper. The intensities of light scattering at the 90 and transmitting light were measured by two detection ways in periodic, which eliminates the inaccuracy because of light source aging and the difference of detector sensitivity. By choosing MSP430 to be the controller, optical signals were modulated by an exerting pulse signal to LD, and the signals detected were amplified and filtered in the receiver. The system can effectively eliminate environmental interference with the measurement results. The experiment results show that the linear correlation coefficient of the system is 0.976 5 with good linearity, and it is operated stably and reliably.
The differences between Free Space Optical(FSO) communication and traditional communications are investigated, and a physical layer transceiving protocol is built. A field Programmable Gate Array(FPGA) is introduced to achieve the data communication of both the transceiver and outer circuits, and a First in First out(FIFO) memory is utilized to implement the interface of protocol and outer systems. The protocol mainly achieves coding and serializing of the transmitting data and deserializing and decoding of the received data. The result of simulation experiment proves that the transceiving protocol is feasible, which can work reliably at a speed of 40 Mbps.
A new way of extinction ratio compensation for optical modules is proposed. According to the driver current with different temperatures, combined with the calculating methods for the optical power and extinction ratio, the curves of the laser power with current and voltage changings are simulated. And then the modulation current on principle is adjusted to keep the stability of extinction ratio. The compensation way solves the problem of bad laser efficiency uniformity and extends the value of slope efficiency about ten percent. The proposed method improves utilization and yield products, and reduces product costs.
Based on a Nd∶KGW laser, a beam-scanning widening technique and a mask micro-imaging method, a laser mask micromachining system is developed to applied to the micro-marking, carving and forming of miniature workpieces. The plastic film printed by a computer or the liquid crystal are used as masks in the system, and the beam-scanning area(effective mask area) is determined as 30 mm30 mm. The focal lengths of micro-imaging system are selected as 100 mm and 50 mm, which scale down 8~10 and 15~20 times, respectively. The processing size and precision of the system are analyzed, and results indicate that both the minimum marking width and graphic precision of the micromachining system are 10 m, which is consistent with the analysis results. The processing depth of a single laser pulse is 0.07~0.1 m, and the maximum processing depth is 200 m. The micromachining system satisfies the basic requirements of industrial micromachining technology.
-GaSe crystals are grown with the stoichiometric GaSe of 0.05%, 0.1%, 0.5%, 1% and 2%(mass percent) Te and are characterized by GaSe∶Te(0.01%, 0.07%, 0.38%, 0.67% and 2.07%(mass percent)) crystals. The transformation of the rigid layer phonon modes with doping is studied for the first time. The absorption peak of the rigid mode E'(2) centered at ~0.59 THz is rising up in the intensity till reaching a maximal value on the first stage of the doping concentration less than 0.38%(mass percent). This process correlates well with the improvement in the optical property. Further doping is resulting in the decrease of the intensity till vanishing the E'(2) absorption peak at 1%(mass percent) Te. Simultaneously with the E'(2) absorption peak decreasing, the absorption peak of the rigid mode E'(2) centered at 1.78 THz is rising up in the intensity. The two processes correlate well with the degradation in the optical quality of GaSe∶Te crystal. The doping level that results in the highest intensity of the absorption peak of the rigid layer mode E'(2) is proposed as a criterion in the identification of the optimal Te-doping in GaSe crystal that is confirmed by THz generation via optical rectification.
Yb3+∶Y2O3 ultrafine powders were prepared by using the low-temperature combustion synthesis(LCS) with the solutions of mixed nitrates and urea in mol concentration ratio of 3∶1 and at a ignition temperature about 600 ℃. The Yb3+∶Y2O3 ultrafine powders were measured by using a X-ray Diffractometer(XRD), a Scanning Electron Microscope(SEM) and a Fluorescence Spectrometer(FS). The influences of ignition temperature, fuel content and calcination temperature on the characteristics of the powders were investigated. The experimental result shows that the grain diameter of as-prepared powders is about 15-30 nm, and the grain dispersion is good without obvious agglomeration. Moreover the fluorescence performace of the powders is well, and the emission peaks are located at 976, 1 030 and 1 075 nm. As a result, the Yb3+∶Y2O3 ultrafine powders can be propitious to the preparation of Yb3+∶Y2O3 transparent ceramics.
Yb3+/Er3+-codoped oxyfluoride glass ceramics were prepared by the high temperature melting method, and a suitable fusing temperature(1 100 ℃) and annealing temperatures(440 ℃, 480 ℃) of the rare-earth-doped glass ceramics were determined. Experiments show that the transmittance of the host glass is 85%, but the transmittance drops evidently and there are characteristic absorption peaks of rare-earth ions when the host glass is doped with Yb3+/Er3+ ions. With 980 nm laser diode(LD) excitation, the purple emission peak at 410 nm, green emission peak at 532 nm and 546 nm and red emission peak at 656 nm corresponding to 2H9/24I15/2, 2H11/24I15/2, 4S3/24I15/2 and 4F9/24I15/2 transitions of Er3+, respectively, were simultaneously observed at room temperature. The effects of Yb3+/Er3+ in mol concentration ratio and different concentrations of Er3+ ion on the intensity of up-conversion luminescence was studied. The experiments show that the up-conversion luminescence intensity is up to maximum value when the concentration ratio of Yb3+/Er3+ is 4∶1 and concentration of Er3+ ion is 1.5% in mol concentration. According to the relationship between the pump power and luminous intensity, the four up-conversion luminescences are verified to be the two-photon process. Energy transfer was used in discussing the up-conversion mechanism and the pertinent up-conversion mechanism was proposed.