2013 Vol. 6, No. 1
The advent of the laser has placed stringent requirements for the fabrication, performance and quality of optical elements employed in systems for most practical applications. Their high power performance is generally governed by three distinct steps. Firstly, the absorption of incident optical radiation(governed primarily by various absorption mechanisms); secondly, a temperature increase and response governed primarily by thermal properties and finally the elements thermo-optical and thermomechanical response, e.g., distortion, stress birefringenous fracture, etc. All of which needs to be understood in the design of efficient, compact, reliable and useful for high power systems with many applications, under a variety of operating conditions such as pulsed, continuous wave, rep-rated or burst mode of varying duty cycles.
This paper reviewed the well-known limit performance of a new generation of high-resolution small satellite Pleiades. The technical characteristics of this satellite were described and its key technical indicators were also given. The advanced technology and design concepts of the Pleiades in the multi-satellite network orbit design, integration super-resolution focal plane design, integrated and comprehensive electronics design and agile attitude control system design were analyzed. On this basis, it also puts forward the development directions of new small satellite technologies to adapt to our national conditions, which included CMOS Time Delay Integration(CMOS TDI) mode imaging, high dynamic range video imaging, flexibility technology based on reconfiguable modules, on-board software design based on software bus, satellite integrated design, etc. All above could provide new ideas for us to research and develop new generation of high performance small satellites with higher ground resolution, higher in-orbit imaging efficiency and higher image quality in the future.
Laser-produced Plasma(LPP) Extreme Ultraviolet Lithography(EUVL) light source, one of the core technologies of next generation lithography, is discussed. A brief review to the development situation of lithography technology in Europe, America and Japan is given. Being a newly arisen research direction, the status of next generation 13.5 nm EUVL source is analyzed, and especially the research on EUVL source based upon LPP at home and abroad is described and analyzed in detail. It points out that the main problems for the EUVL are how to improve the conversion efficiency of EUV light and how to reduce the light debris. Furthermore, the latest research status on the EUVL source at 6.7 nm is also presented. Finally, it introduces the research work of the author's group on EUVL light sources and the detection of mask defect for EUVL.
This paper overviews the research situation and development prospects of artificial compound eye optical systems on the basis of their advantages of small volumes, light weights, large field-of-view and high sensitivity. It introduces the structures and classification of insects' compound eyes, and describes the research development of artificial compound eyes according to the design of artificial imaging systems with curved and plane surfaces. Then, it gives structures, models and imaging abilities of typical compound eye imaging systems at home and abroad, and summarizes their usages and merits in different fields. Finally, the preparing techniques of artificial compound eyes are analyzed. Analyzed results point out that the functions of compound eye optical systems are dependent on the fabrication of the microelements, the super fine machining is a fine and effective micromachining method and it has the potentials to fabricate higher accuracy lens arrays and improve application abilities.
Zoom lens design with liquid lenses is a novel method to greatly reduce the complication of the whole system. This paper reviews the research situation and applications of the technology. Firstly, the principles and characteristics of the some types of liquid lenses are introduced according to the lens classifications on gradient refractive index lenses and variable curvature lenses. The specifications and advantages of several typical lens series such as ARCTIC lens series and Optotune lens series are given. Then, applications of liquid lens in zoom systems are analyzed, and their advantages in focus-tunable glasses, cell phone camera lenses, endoscopes and several types of microscopies are described. Finally, based on a liquid lens, a long focus zoom system with a high zoom ratio of 2.5 is designed for visible light.
To design the mounting structure of a lithographic object lens, the influence model of mounting stress on the lens wavefront distortion was built. The relation between mounting stress and refractivity and the influence of mounting stress on the wavefront distortion of the lens were studied. First, based on the crystal theory, the relationship of lens mounting stress and wavefront distortion of a fused silica lens was established. Then, the influence of different lens mounting structures on the lens wavefront distortion was analyzed. Finally, the properties of lens mounting wavefront distortion were researched, and the fitted lens mounting structure was selected. Analysis results indicate that the lens mounting stress has a great influence on the lens wavefront distortion. The wavefront distortion of a 3-point mounting structure is 3.69 nm. However, the wavefront distortion induced by mounting stress decreases with the increasing mounting points. The above 9-point mounting structure is fitted to the lithographic object lens.
Particle Swarm Optimization(PSO) technique is applied to design a three-lens system in this paper. Merit functions in an optical system are employed as fitness functions, which include the structure parameters of radiuses of curvature, the distances between lens surfaces, refractive indices, the total length of a system and so on. An automatic searching for the optimal design by using these functions is carried out. The results show that the three-lens optical system with small spherical aberrations, meridional field curvatures, dispersions of meridional rays can be designed by using PSO algorithms. Not depending on the definite initial structure of the system, the optical design using PSO algorithms can overcome the shortcomings of modern optical design software which highly depends on an initial structure input by the user. It can create arbitrarily search ranges of structure parameters, and is an important step towards automatic design with artificial intelligence.
A photon imaging system with single photon detecting and imaging capabilities is constructed and a detection method based on pipeline filtering is proposed to detect the stationary point target under a photon limited condition. The stationary point target detection method based on pipeline filtering is studied on the characteristics of position and noise for stationary point targets in photon images. The diameter of pipeline filter is optimized to reduce the false alarm rate. The relationships of detection performance with the number of signal photons and noise photons, the pipeline length and the detection threshold are explored through photon image sequences. For the image sequence with the average incidences of signal and noise of 0.4 and 5.215 respectively, the detection rate can be more than 0.9 and the false alarm rate less than 0.08 when the pipeline length is 9 and detection threshold is 2. The conclusion from experimental results is that the detection rate is mainly affected by the number of signal photons and the false alarm rate is dependent on the number of noise photons.
This article introduces a new comprehensive information processing system for the helicopter anticollision laser radar. Based on the acquirement and correction of helicopter attitude, extraction and identification of a target, and the three-dimensional transformation of data, the processing and display abilities of the system for comprehensive information are improved. Detection experiments of the scan imaging laser radar are designed to verify the effects of these methods. The experimental results indicate that the distortion of detection image is reduced effectively when the helicopter flies for emergency. Even though the roll angle is up to 30?, the correction is still effective. The high-risk targets such as a power line are extracted quickly at the distance of 600 m. Furthermore, the three-dimensional high efficiency integrated display becomes true, and the time of comprehensive processing is less than 10 ms. The new methods of comprehensive information processing of the helicopter anticollision laser radar improves the man-machine interface greatly.
For the purpose to decrease the misalignment error from a testing aspheric surface by Subaperture Stitching Interferometry(SSI), a translated error compensation method is proposed to subtract the misalignment error from each phase detum and to stitch multi-subapertures precisely. The basic principle and process of the method are researched, and a compensation mode is established based on the mode search algorithm. The experiment is carried on for an off-axis SiC aspheric mirror with a clear aperture of 230 mm?141 mm, the phase data of the whole aperture are stitched precisely and the figure error is compensated by eliminating the misalignment error. For the comparison and validation, the asphere mirror is also tested by null compensation method, and the relative errors of PV and RMS are 0.57% and 2.74%, respectively.
The disturbing and damage effects of a femtosecond laser on the CCD camera were researched. A laser pulse with a wavelength of 800 nm, pulse width of 100 fs and a single pulse energy of 500 J was used to radiate an interline CCD solid-state image sensor and the damage threshold was measured in the experiment. The phenomenon of the point damage, line damage and the whole target surface damage were observed while increasing the energy of reaching CCD target surface, and the corresponding damage thresholds were 151.2 mJ/cm2, 508.2 mJ/cm2 and 5.91 J/cm2, respectively. In the different damage situations of the CCD, the resistance values between the clock signal lines, and between the clock signal line and the ground were measured. By contrasting the resistance values of the CCD before and after the damage, it was found that the resistance values between the vertical transfer clock signal lines decreased significantly, and the same results were achieved between the vertical transfer clock signal line and the ground. At last, the damage position and the damage mechanism were discussed.
An irreversible adherence method is proposed to bond the microfluidic channel of a waveguide biosensor to orercome the liquid leaks from the traditional reversible adherence. Several methods on irreversible adherence between Polydimethylsiloxane(PDMS) and Silicon-on-Insulator(SOI) waveguide in the micro-fluidic channel of bio-sensor are illustrated, that is, irradiation with ultraviolet light, activation surface by oxygen plasma, oxidizing surfaces into SiO2 and ultraviolet glue. Firstly, the PDMS and SOI waveguide surfaces are treated with the four methods. Secondly, the bonding capacities are tested and the adherence effect is analysed in quantity. Finally, the activation surface by oxygen plasma is selected as the most effective method for irreversible adherence and other factors probably affecting the adherent effect in the experiment are also discussed.
Mn-doped ZnS nanoparticles were prepared by the Sol-Gel process in this paper, and the influence of doping ion concentration on crystal structures and luminescent properties of ZnS: Mn nanoparticles was discussed. The structures of the samples were characterized by an X-ray diffractometer(XRD). The results show that the as-prepared ZnS: Mn nanoparticles belong to the cubic sphalerite structure. The parvafacies do not occur when Mn2+-doping concentration reaches 6% and the average particle sizes of nanoparticles decrease with the increase of doping concentration. Photoluminescence(PL) spectroscopy and fluorescence spectrum results show that the emission wavelengths of ZnS: Mn nanoparticles around 590 nm can be adjusted by changing the concentration of the ions. In addition, the influence of temperature on morphology and luminescent properties of nanoparticles was studied. The result observed from a high resolution transmission electron microscopy(HRTEM) shows that the average particle sizes of ZnS: Mn samples increase to about 20 nm after ageing for 1 h at the temperature of 50℃. The heating ageing is beneficial to Mn2+ fluorescence produced at 590 nm for ZnS:Mn nanoparticles.