2006 Vol. 27, No. 2
In order to comprehend the application of the phaseshift digital interferometry in measurement of optical components, the basic principle of the phaseshift interferometry (PSI) is introduced. The overlapping averaging 4frame algorithm, the configuration of piezoelectric transducer (PZT), the combination method for three PZTs, the correction method for calibration error and nonlinear error of phase shifter, the wave surface phase unwrapping adaptive algorithm, and evaluating specification of wavesurface phase are described. The application of the modern optical interferometry in the measurement of common optical elements, IR optical elements, largeaperture optical elements and aspheric optical components is introduced according to the digital phaseshift wave surface interferometer. It is clearly pointed out that the developing trend of the optical interferometry moves towards high phase resolution, high spatial resolution, wide wave range and highspeed transient measurement, and it will find everincreasing applications in the transient wavefront measurement, microstructure dynamic analysis for micromechanics and so on.
The light which goes through a doubledeck rectangle phase grating with different incidence angles can produce different numbers of beams. Based on the phenomenon, the beam which has high efficiency and uniform distributed light intensity can be obtained by changing and optimizing the grating′s incidence angle. The method of making a new type of splitter by the realtime variational beam feature of the doubledeck rectangle phase grating was investigated theoretically. Two, three or four beams produced by the method were analyzed respectively. Through the simulation with a computer, the optimizing parameters of incidence angle were theoretically derived and the result was discussed. Theoretical analysis shows that the splitter with high diffraction efficiency and uniform distributed light intensity can be designed by incidence angle optimization. The study provides a theoretical basis for making practical and cheap splitting device.
Since there are laminated repeating protection and restoration in an internet laminar model, it makes the realization of the internetwork communication very complex, affects the network transport efficiency and makes the network block. With the wide use of DWDM and the improvement of network sublayer performance, the laminated repeating protection and restoration in internet will never be required. Therefore, the future optical internet threelaminar (application, IP and optical interconnection) protocol model was used and the protection for the optical interconnection lamina was investigated. Based on the investigation, a method of partially shared path protection (PSPP) was put forward. This model can make full use of agile restoration mechanism of the IP lamina and protection restoration mechanism of the optical interconnection lamina to improve network transport efficiency and meet the need of the development at top speed of internet work for the transmission bandwidth.
The holography is a twostep imaging technology which obtains the whole information from an object with the coherent light interference. The development of holography can be roughly divided into four stages: coaxial holography, offaxial holography, white light reconstructing holography, white light holography. The holography has many features, such as three dimension, never tearing, image reconstruction compression and enlargement, and information mass capacity and so on. The holography is an active branch of optics. In recent years, it has penetrated into every field of social life, and been widely applied to the modern scientific research and industrial production. Especially, it has some special superiority in modern test technology, bioengineering, medicine, art, commerce, security as well as modern memory technology. With fast development of the holography, more and more holographic products have already been stepping into the modern life.
The development of sophisticated combat equipments for individual soldiers in the postindustrial era is described. It is proposed that the soldiers′survival and attack capability can be effectively enhanced with better battlefield awareness. In order to decrease the volume and weight of the equipments, and improve the practical applicability, the effective couplings between all the functional modules of certain system was investigated emphatically. The conceptual variation of weapon platforms (individual soldiers have become the important combat platforms) was analyzed. The development techniques, such as relevant information acquisition, transfer, processing, control, display and countermeasure, is elaborated. The feasibility to develop the optoelectronic technology for individual soldiers is revealed. The construction of information platforms, lightweight of optoelectronic systems, improvement of systematic accuracy, decrease of response time, development of "information weapons" and development of light weapon training equipments, etc. are discussed. The priority in the recent development of optoelectronic technology for individual soldiers is put forward in this paper.
To improve the imaging quality of CCD camera and make the lens small in size，compact in structure，the wide field of view (WFOV) optical lens with the standard quadric surface and even aspheric surface was designed．According to the primary aberration theory, the position of aspheric surface and the solution law of initial structure parameters were analyzed. A design example of a lens whose operating wavelength was 0.4-0.7μm，full fieldofview angle was 80°and relative aperture was 1∶1.5 was given on the basis of the theoretical calculation and the optimization of optical design software ZEMAX. The MTF of the lens，which is composed of four spherical lenses and three aspheric lenses，is better than 0.85 at the spatial frequency of 40lp／mm. The full fieldofview distortion of the lens is less than 3％.
The residual stress is an important factor for optic thin film quality，and it has an adverse effect on the optical components. Based on the principle of elasticity and strain misfit, a new calculation method of theoretical model to predict the residual stress distribution on optical thin films is put forward in this paper. The calculated result was compared with the result obtained by an interferometer. The variation of the residual stress of the substrate with parameters of optical thin films was analyzed with the model we set up. The results indicate the model is rational, the total residual stress of the substrate increases when coating temperature rises， intrinsic stress changes little, and the stress of upper and lower surfaces of substrate increases but the stress of thin film decreases when the thickness of the substance is reduced．The central axis of substrate is approximately located at the position of 2／3 below the upper surface of substrate.
Based on the wave aberration theory, the relation between wave surface variance and the number of subapertures is derived when some aberration exists in single subaperture of the optical synthetic aperture imaging system. The derivation result shows that the most sensitive aberration is piston error, and then the defocusing error, tilt error, spherical aberration, coma and astigmatism. To improve the quality of the image, the defocusing error was used to balance the piston error, spherical aberration and astigmatism, and the results were significantly improved, especially the wave surface variance caused by spherical aberration was decreased by 90%. The coefficients of every aberration were decreased with the increase of the number of subapertures (N), but changed slowly when N was greater than 6. The aberration tolerance of synthetic aperture imaging system with N (N≤6) subapertures and Strehl ratio of the system with 3 subapertures were calculated according to Rayleigh criterion.
In order to save the rare iceland crystal and increase the transmittance of polarizing prism, a polarizing prism made of iceland crystal and glass was designed. The design of the prism for superhigh transmittance of e beam with the Brewster incident angle was described. The sample was made of FK2 glass and iceland crystal, between which either glycerine or organic silica gel could be used for gluing. The theoretical analysis and experiment indicate that the transmittance of the prism is more than 96%, and the extinction ratio is better than 10-5. It was proved that the prism could replace the prism which was only made of iceland crystal in general.
With the flexible spatial layout and the degree of design freedom of the free form surface (FFS), the structure of the optical system was simplified and the quality of the image was improved. The method of using user defined surface (UDS) function in CODE V and computer dynamic link library (DLL) technique to design an optical system incorporating with FFS is introduced through a design example. The accuracy and reliability of the approach are verified by the design example of an optical system with spherical and conic surfaces designed by CODE V. An optical system with a FFS prism is also designed with the method, and it made the optical system light in weight and compact in size. The approach expands the functions of CODE V and effectively enlarges its capacity to calculate complicated surface.
There are many optical design softwares, but they are different in forms and expression ways for aberration characteristics, especially between domestic and overseas softwares. The difference is very obvious, for example, the sphere aberration is called “longitudinal aberration”in ZEMAX developed by USA Focus Software Company, but there are some other expressions for it in domestic software including CAOD developed by Beijing Science Technology University, and some other aberration parameters still need to be transferred. In this paper, the beam path of the same cemented double lens was calculated by both ZEMAX and CAOD optical design softwares, and their calculation results of axile aberration, comatic aberration, field curvature, distortion were compared. The purpose of comparison is to build the transforming relationship between the parameters of optical aberration characteristics for the domestic and overseas softwares, and is to provide the way for optical designers to check and recalculate the data with different softwares during designing a lens or optical system.
Mach-Zehnder optical waveguide is an important component unit in electrooptic polymer modulators. By using effective index method (EIM) to calculate the transverse refractive index distribution of polymeric ridge waveguide, 3D light wave field propagation is successfully simplified into 2D propagation. Proceeding from the scalar wave equation observed by the guided modes, the basic computing scheme of the finite difference beam propagation method is obtained by utilizing the transparent boundary condition (TBC) and the CrankNicholson difference scheme. The effect of structure parameters such as ridge width and branch angle on the loss was theoretically studied with the support of the theoretical analysis of the TM mode light wave propagation and loss characteristics in the MZ waveguide structure. The combinational approach of EIM and 2DBPM demonstrates that the design of MZ waveguide can be made effectively by evaluating the influence of the structural parameters on the loss characteristics. The approach has high precision, small calculation complexity and high efficiency, and it provides a theoretical basis for the fabrication of electrooptical polymer modulators.
Fiber grating coupler (FGC) has good wavelength selection characteristic of optical fiber grating as well as multiport advantage of fiber coupler. These features make it easy to realize allfiber optical add/drop multiplex (OADM).Now there are four major types of FGCs: separated structure based on Mach Zehnder interferometer, dissymmetric structure based on 100% coupler, dissymmetric structure based on 0 coupler and symmetric structure based on 100% coupler. The structure, operation principle and present situation of the symmetric structure FGC are introduced emphatically. The test method for the device is proposed. Furthermore, the application of this device used in largescale WDM optical fiber sensor arrays was also investigated.
A fiber Bragg grating (FBG) is inscribed in hydrogensensitized polarization maintaining fiber with a peak wavelength of 1300nm. The temperature sensing characteristics of this polarization maintaining fiber grating were experimentally studied and theoretically analyzed. The result shows that this kind of fiber grating can be used as a temperature sensor for temperature measurement. Since the polarization maintaining fiber grating has a fine linear relationship with temperature, it can replace the singlemode fiber grating and decrease the fabrication cost. This experiment result can be taken as a reference for further study on the polarization maintaining fiber grating.
The Bragg wavelength demodulation technology based on phaseshift fiber grating is proposed. One or more spectral windows with very narrow linewidth can be opened by the phaseshift fiber grating in the reflectance spectrum stopband, and the windows are moved with the variations of the phase shift linearly. In order to implement Bragg wavelength demodulation, the electric current tuning phaseshift technology was utilized in the experiment. The measurement temperature could reach 200℃ and the strain could reach 2000με when the phaseshift fiber grating with maximal wavelength offset of 2nm was used to do the tunable filtering. The experiment shows that the Bragg wavelength demodulation by the phaseshift fiber grating has reached the expected result. A new method is established to solve the demodulation of Bragg wavelength.
Gyro North Finder is widely used in the military and civilian fields. A North Finder system incorporated with a Fiber Optic Gyro (FOG) is introduced in this paper. The system combined computer with DSP, which is used to capture gyro output data and control system. It communicates with computer by RS232 serial port. Data filtering, data resolving and real-time display are executed by computer to find the north. The initial azimuth angle is given by computer when the North is found, and the North is indicated by a beam of laser. The accuracy of the final FOG North Finder system reaches 3to 10 mil. The system can meet the requirements for military and civilian applications.
In order to investigate the feasibility of quantitative analysis with laserinduced breakdown spectroscopy, plasmas were produced by a Qswitched Nd∶YAG laser interacted with the air at atmospheric pressure, then the light of plasmas entered the monochrometer and transferred into an electric signal, and the spectra of these plasmas in the range of 600～800nm were stored and analyzed by the calibrationfree model. Under the condition of delay time of 8μs and gating pulse of 0.4μs, the temperature of plasmas, which was in local thermal equilibrium(LTE), was 1.62×10K which was obtained by means of the twodimensional Boltzmann plane. The 20.75% oxygen content and 79.25% nitrogen content in air were detected on the assumption that there were only oxygen and nitrogen constituents in the air. The results coincide well with the fact. The feasibility was validated by the experiment, and it built a strong basis for the further study and experiment of air pollutant monitoring.
By Comparison with microwave communication, the advantages of the free-space laser communication system, such as big capacity, low power consumption, small volume and light weight, are introduced. The basic principle of the space laser communication is described. The key technologies in highpower light source, antijamming high sensitivity optical signal receiving, fast and precision capture, tracking and aiming of communication link in the space laser communication system, are put forward emphatically. The freespace laser communicationcan find wide applications in military and commercial fields and it has a great potential.
The porous aluminium coating inlaid with copper was obtained by implanting Cu into the pores of anodic oxidation aluminium coating prepared by electroplating. In order to study the influence of sample interval and slit width on the transmission spectra, the transmission spectra of porous aluminium coating with copper in the case of the same sample interval with different slit widths and the same slit width with different sample intervals were measured by UV3101 spectrophotometer respectively. Then the influence of sample interval and slit width on the transmission spectra was analyzed, and the suitable sample interval and slit width for measuring porous aluminium coating with copper were achieved. Experimental results indicate that the slit width of 3 nm and the sample interval of 0.5nm or 1nm are suitable for the visible waveband, and the slit width of 5nm or 8nm and the sample interval of 2nm are suitable for the nearIR waveband.
A fluorescence detecting system Based on the opticalelectrical conversion principle of linear array CCD was designed and it was used to measure the fluorescence spectrum of acetamiprid. The CCD detector was used to take place of the photomultiplier which was widely used as the opticalelectrical converter, and the fast analysis of the spectrum was realized by incorporating a grating. Taking the advantage of the complete different features indicated by noise and signal in the case of wavelet transformation, a method for characteristics extraction of pesticide fluorescence signals and noise elimination based on the wavelet transformation theory was proposed. The experimental result shows that the application of the wavelet denoising technology can keep more information at the peak of fluorescence spectrum, and greatly improve the detecting accuracy of the system.
Compared with selffocusing cylindrical lens, selffocusing cone lens has its unique features. When paraxial collimated beam goes through a cylindrical lens, its amplitude, phase and period remain the same, but for a conelens, all these parameters are changed. Compared with the light equation for cylindrical lens, the equation for conelens is much more complicated. The paper derived a light equation for conelens. With this equation, the light spot size behind conelens can be designed. It can find application in microillumination systems.
The negative effect of the mismatch between time delayed integration (TDI) CCD line scanning velocity and image motion on image quality is fully analyzed with phasemotion modulated transfer function (MTF). In order to verify the effect of the velocity mismatching on the image quality of 96stage TDICCD camera, based on the application environment, the simulative experiment and dynamic testing for the dynamic imaging of the TDICCD camera were conducted by utilizing the target with high contrast characteristic. The results show that within the range of Nyquist frequency, the effect of the synchronization error on the imaging quality can be basically eliminated during the processing of imaging so long as the synchronous error is strictly controlled in the range of ±2% and the imaging clock is in the continuous fourphase operating mode.