2010 Vol. 31, No. 3
Based on the system design cooncept of acousto-optic tunable filter(AOTF) imaging spectrometer, optomechanical design for an acousto-optic tunable filter(AOTF) imaging spectrometer was presented. It consisted of three group optic lenses. The fore-optical system included objective and collimating lens and the imaging lens collected the +1 and -1 orthogonally polarized orders produced by the AOTF at the same time. The whole system is achromatized from 0.4～0.9 microns and imaging resolution is better than 32lp/mm when MTF reach 0.7.
A low F number long-wavelength infrared optical system with wide field of view is designed. It consists of three aspherical germanium lenses with a reversed telephoto telecentric structure. The effective focal length is 6mm, the relative aperture is 1:0.8, the full field of view is 160, and the total optical length is 86.13mm. The result shows that the modulation transformation function is greater than 0.7 at the spatial frequency of 20lp/mm. The system inherits the advantages of the reversed telephoto telecentric structure, it is simple in structure and small in volume, light in weight, uniform in illumination, and also has large field of view.
A combination of passive optical athermalisation and mechanical-electrical athermalisation is proposed to overcome thermal effect, which may otherwise cause the drift of image plane. Optical athermalisation is used to obtain feasible athermalised lens group, which control the error in a small range. Then mechanical-electrical athermalisation is used to eliminate the remaining error. An infrared system operating at wavelength (7.5～10.5)m with two field of view was designed, and it functions properly at -40℃ to 60℃.
The partial dispersion of some typical glasses working on near infrared band was calculated with the formulas in which P and V were modified. The apochromatism of a wide band system was designed and analyzed. The result shows that the combination of the heavy crown glasses ZK8, ZK4 and special flint type TF3 is effective to correct secondary spectrum. Zonal chromatic aberration of the optical system is decreased from theoretic 0.18mm to 0.084mm in wide spectrum. The rear cut-off length of optical system is long enough for the reflector to image shifting compensation.
A thin aspheric lens group for mobile phone comprises three lens elements with refractive power, from the object side to the image side, a first lens element with positive refractive power, a second lens element with negative refractive power, and the third lens element with negative refractive power, and an aperture stop located between the first lens and the second lens. The plastic lens APL5014DO、POLYSTYR and ARTOND4531 are chosen. The Fnumber is 2.4 and FOV is 58.The length of the total lens group of this optical system is 2.19mm. The MTF at 295lp/mm is higher than 0.2.
From Maxwells equations, with material constitutive relation of optically active crystal and boundary conditions of electric field on the boundary between isotropic media and crystal, through coordinate transformation, the formula of the direction of refracted wave for arbitrary direction incident monochromic plane wave was derived. Furthermore, based on the unit vector of direction of refracted wave, eigen waves of electric field, electric displacement vectors and direction of energy flow can be easily obtained. Based on wave optics and physical properties of crystal, its derivation involved no approximation, and the result is applicable for dual axes, single axis and isotropic crystal with or without optically active property.
We present a method for zoom lens based on reflective phase-only liquid crystal spatial light modulator (LC-SLM). According to the principle of the phase modulation of LC-SLM, incident light waves are controlled by Kinoform, which is writen to LC-SLM. The wavefront of lens is achieved with diffraction. Therefore, the variable focal-length phase Fresnel lens is achieved by changing diffraction distance of calculated Kinoform. Some parameters, such as the diffraction aperture, the diffraction distance and phase levels of Kinoform, are discussed. They are key factors to the variable focallength phase Fresnel lens. Experimental results and the Kinoform of a point light are given. Compared to traditional methods, this method features controllability and accuracy. It will provide a feasible approach for realizing 3D scan display.
The design of optical window on a spherical shell in electro-optical systems is introduced. The comparison between conventional design and solid modeling by UG is made by an example of IR window. The former adopts the method of iterative trying, and the latter acquires the correct size and location of the optical window from UG solid modeling and space geometry transform, the latter is more visualized and theoretical sound. According to the optical features and engineering limitations, the installation of the optical window is determined.
The main stray light of three-mirror system is the light directly comes from the object to the tertiary mirror without hitting on the primary and secondary mirror. The designing of baffles to suppress the stray light is discussed, the formula is deduced, and an auto-design CodeV macro is programmed. An example of baffle design for a three mirror system is cited, moreover the image performance is analyzed and confirmed by ray tracing simulation and imaging experiments.
Due to its superior performances such as energy saving and environmental protection，LED is widely used in automotive lighting. As a key technique on automotive lighting system，light distribution design of LED automotive headlamp is a challenging research subject. LED sources were chosen according to the standard，and Light distribution was analyzed by using parabolic reflector under moving and rotating conditions. Each light source has its selfcontained optical system and arranges the irradiance of different area on distribute-screen, 8 LED sources were used in low-beam system，and 10 LED sources were used in high-beam system. Combined reflector model was drawn in CATIA software. The final results were achieved by using Tracepro after calling different lens model iteratively. Baffle board and complex calculation program were not required in this design process. This method has short design period and high distribution efficiency. The final illumination results completely conform to the revised standard of GB4599-2007.
The terahertz (THz) radiation properties of photoconductive antenna (PCA) were studied. The radiation characteristics of photoconductive antenna were simulated using FDTD; the results calculated were displayed on a computer in pseudo-color graphical. Using electric dipole antenna model and taking 0.1THz as an example, equatorial plane and the meridian plane of the antenna pattern were obtained, the antenna radiation resistance is 790 ohm, and directivity factor is 1.5. The results show that photoconductive antenna can be calculated with dipole antenna theory. Radiation resistance is increased by increasing the electrical length, and the power of terahertz radiation is increased as well.
A 3 axes compass module is calibrated in ideal magnetic environment, and standard calibration parameters are put forward. The output of compass module is measured and compared in ideal magnetic environments of single, two and three alternating magnetic fields. Real-time alternating magnetic density about compass module in two representative states was measured and the result was given. The result shows that the precision of compass module decreases with the increase of the magnetic density, especially at heading direction, which agrees with specific sensitivity theory of compass. The reason of this phenomenon is given and the method of improvement is suggested.
Previous research results show that threshold obtained by maximum between-class variance method (i.e. Otsu method) is biased when the area of object and background differs significantly and may lead to failure segmentation. A new image segmentation method based on maximum scatter difference is proposed. Maximum scatter difference uses generalized scatter difference, i.e., the difference of between-class scatter difference and C times of withinclass scatter difference, as the discriminant measure. Maximum scatter difference considers simultaneously the function of discrimination of betweenclass scatter difference within-class scatter difference. The proposed method can prevents the threshold biasing from maximum between-class variance method. Experimental results show that the proposed method can obtain better segmentation result than otsu method by appropriately selecting parameter C.
The key to apply CCD to implement mammography is to improve the coupled efficiency of light from scintillation screen to CCD, and it is necessary that the image system has a large relative aperture and adopts close imaging, which makes the CCD image seriously distorted. This paper presents an efficient preprocessing method to compensate image distortion. According to the conjugate relation between the object and its image, the object plane was divided into many micro object elements that have one-to-one correspondence with the pixels of image sensor; Monte Carlo method was used to simulate the light distribution on image plane made by the light from each object element, namely point spread function. A point spread array was constructed from all point spread functions of all elements; each row of the array corresponds to the point spread of function an object element. A linear system of equations to describe the relation between all object elements and all image pixels was built on the basis of the point spread array, and a lifelike image was obtained by solving the linear system of equations. The calculation results for an actual optical system verified the validity of the method.
Salt and pepper noise often appears in the acquisition of QR code image. In order to reduce salt and pepper noise as well as maintain image details, median filtering is fequently used in two-dimensional code image pre-processing. However, the typical median filtering algorithm requires a lot of time. Several median filtering methods were applied to the QR code image preprocessing, then the results were compared and QR code image median filtering rules were obtained, the new median filtering method was proposed, which used the window coefficients. Binarization is the first step, then the binary image is processed by median filtering based on filtering window coefficients, and a group of data is obtained through the experimental comparison. The experimental results show the decoding efficiency and accuracy are greatly improved when this coefficients' median fitering is adopted in the QR code image preprocessing.
The approach of inferring the grating profile from its reflection spectrum is referred to as fiber Bragg grating (FBG) synthesis algorithm. Synthesis of FBG is of great significance for the design of special FBG to have desired characteristics. A simple and efficient method based on the coupled-mode theory and transfer matrix method for the design of complex FBG was proposed. The method takes into account only the first reflection, exploiting the approximate Fourier transform relation that exists between the filter spectral response and the coupling function. Its low algorithmic complexity enables the fast synthesis of weak reflection FBG. The method is illustrated by designing two types of dispersion compensators for the applications of optical fiber communication systems, constant dispersion coefficient with 17ps/nm in its 3dB passband and linear dispersion slope coefficient compensators. Numerical simulation results show that the method is very effective for parameter reconstruction of fiber gratings according to desired reflectivity characteristics and can be applied in the design of complex filter based on the reflectivity characteristics of fiber gratings.
The OCDMA system is briefly introduced. The code pattern and code capacity, the role of sequence spread spectrum to the security of OCDMA are analyzed, the expectations of the frequency of the correct address code detection is given with complete error-free detection probability and the address code detection to the security of OCDMA is analyzed. The relationship between OCDMA technology and modern fiber-optic secure communication technology is compared. Some measures to increase security of the OCDMA system are put forward.
Based on the latest development and technical characteristics of FPD technology, a method for producing seamless tiled FPD panels using optical image-shifting technology was put forward. Two image sections were displayed near the border of FPD panels by means of interlace frame display. The image sections were separated using polarizing rotation apparatus and polarizing beam splitter. The separated image section was moved by imageshifting prism to cover the border. The tiled seam width was reduced from 36 millimeters to three pieces of 0.5 millimeter wide prism seam. The seamless tiling of FPD panels was realized successfully with this technology.
In three-dimensional testing systems based on line-structured light, extracting the center of a line-structured light stripe quickly and accurately is a key problem. To extract the center of line-structured light with a length of 2 meter in a large field of view and strong noise background, an exaction method based on region of interest (ROI) is proposed. Firstly, ROI for image processing is defined by using statistic method, then Otsu method is used for threshold segmentation and barycenter method is used to exact the center within ROI. Experiments showed that the extracting time of a 12801024 sized picture of a line-structured light was about 47ms in Visual C ++6.0 by the proposed method and the extraction was proved accurate. The proposed method reduces the interference of strong background noise in large field of view and improves the extraction speed of line-structured light.
This paper investigates a stereo vision based method for model attitude measurement in wind tunnel test. A cooperative object, which can generate two bidirectional collimated laser beams, is firstly mounted on the shell of an aircraft model, and then the aircraft model is placed between two screens. The laser beams, which are projected onto the screen surfaces, generate four laser spots. Once the 3D coordinates of the laser spots are measured accurately by means of stereo vision technique, the attitude of the aircraft model can be determined by the principle of coordinate transformation. The analytical expressions for determining the attitude of an aircraft model in wind tunnel are presented in the paper. In addition, the proposed method was validated in a controlled laboratory condition. The preliminary experimental results show that the maximal error of attitude measurement is less than 0.05 on condition that the distance between two screens is about 6m.
At present, it is a difficulty to achieve rapid and accurate detection of pesticide residues. In the paper, an overlapped spectrum in fluorescence spectroscopy measurements of acetamiprid residues was separated using artificial neural networks,and a fluorescence spectrum measaring system of solid surface acetamiprid residues was designed. By means of artificial neural network principle and back-propagation training algorithm, acetamiprid concentration was determined in mixed components of residues and filter paper with overlapped fluorescence spectrum. In the range of 340nm～400nm, the fluorescence intensities corresponding to 20 wavelengths were used as character parameters, and the neural network was trained and tested. The mean recoveries of 40mg/kg and 90mg/kg acetamiprid were 102% and 97% respectively. The RSDs of the results were 1.4% and 1.9%. The results have shown that the method to using BP network in fluorescence spectral analysis of acetamiprid residue has some advangtages such as shorter measurement cycle, faster training speed and higher accuracy.
Fingerprint minutiae extraction is the key to fingerprint identification technology. To overcome the deficiency of conventional fingerprint minutiae extraction algorithm, an efficient fingerprint minutiae extraction algorithm is proposed, which extracts the original minutiae points directly from the thinned image and gets the results of the preliminary feature extraction. The pseudo-feature points are removed and the true set of points is retained according to the rule of the pseudo-feature points. Experimental results show that this method can effectively eliminate all kinds of pseudo-feature points and reduce the computation time.
To ensure the location accuracy of edge and minimize false edge points produced by noise and uneven gray scale in image is a difficult problem for edge detection. A new multi-scale tensor algorithm is presented to detect image edge. This method could obtain richer partial structure information in different scales. It is proved to be efficient in precision edge detection and noise suppression by experiments.
Since sky-light radiation luminance is a critical parameter of atmospheric optics, it is very important for space target detection and identification. In order to acquire sky-light radiation luminance and evaluate the detection and tracking capability of optoelectronic systems for space target, a measurement system of sky-light luminance was designed and implemented. The work principles of optical signal collection and signal detection，and key techniques such as low-radiation signal detection and metrology of optical radiation used by the system were introduced. The system was applied to measure sky-light radiation luminance and the test result was analyzed. The result indicated that sky-light spectra(380nm～1100nm) could be acquired by the measurement system and more information was provided.
Since the signals were obtained by line CCD in digital level measurement, field range and resolution was restricted because of great changes in viewing distance. It is very difficult for level meter to code and decode. A new coding and decoding method is proposed. Based on area-array CCD, this solution uses mixed coding technology and takes advantage of two-dimensional signal. The tradeoff between a lack of barcode samples when distance is too short and low resolution of image when distance is too long was overcome, and the key technical problem was completely resolved. By optimizing the algorithm, we also achieved real-time online measurement. The results show that measurement of absolute error is between -1mm and 1mm when measuring range is between 2m and 10m, which proved that the proposed method is correct and feasible.
In order to detect the quality of the cartridge precisely in real-time, it is needed to acquire the X ray photo of the cartridge by Non Destructive Testing(NDT) method, then some preprocess algorithms are used to enhance the signal to noise ratio (SNR) of the image. The local average minimum algorithm and the local smoothness minimum algorithm are proposed to extract the feature parameters of the cartridge, which are compared with the normal cartridge parameter, and an identification report about the cartridge quality will be given. The method is fast, precise and efficient.
A hybrid Er3+-doped/Er3+/Yb3+ co-doped double-cladding fiber amplifier is developed. It comprises an Er3+-doped fiber amplifier as a pre-amplifier and a Er3+/Yb3+ co-doped double-cladding fiber amplifier as a post-amplifier. In the Er3+-doped fiber amplifier, the active fiber is a 20m Er3+-doped fiber and is pumped by a single mode semiconductor laser diode with maximum output power of 318mW. The maximum output powr of the pre-amplifier is 113mW. In the Er3+/Yb3+ co-doped double-cladding fiber amplifier, the active fiber is 14m Er3+/Yb3+ co-doped double-cladding fiber and is pumped by two multimode semiconductor laser diode at the wavelength of 915nm. When the input signal power is 10mW and the signal wavelength is 1555nm, the maximum output power of the hybrid fiber amplifier is 32.04dBm or 1.6W, corresponding light-light transfer efficiency is 18.5%.
Comprehensive researches of the spectral characteristics on the domestic Tm-doped double cladding fiber with hexagon inner cladding cross section are presented. When the fiber is pumped by 1064nm laser, the bright blue light is observed. The up-conversion spectra are measured and the mechanism is analyzed. The fluorescent spectra and the laser spectra are also measured when the fiber is pumped by a 785nm LD. The fiber lasers operated at ～2m wavelength are obtained with three different output coupler mirrors and with two fiber lengths of 4.5m and 2.2m, respectively. The maximum output power is 5.1W and the slope efficiency is 41.9%. The experiment results are analyzed.
Dispersion properties, field distribution and propagation loss of symmetric and asymmetric metal clad waveguide at 1500nm were analyzed with effective index method. Simulation was given for Au, Ag and Cu cladding. In asymmetric clad guide simulation, properties of TE modes are the same as those of dielectric waveguide, TM0 mode is the surface mode at metal-dielectric interface with no cut-off. In symmetric clad guide simulation, TM0 mode is even mode which is coupling between surface modes at two metal-dielectric interface, and its effective index is beyond the index range of guide modes. The range of the effective index of TE mode and TM1 mode is larger than guide modes and TM1 mode is odd mode which is coupling between surface modes at two metal-dielectric interface.
We fabricated an organic light emitting diode (OLED) with MoO3 inserting in m-MTDATA/NPB interface as hole injection buffer layer, incorporating an ndoping transport layer which comprises 8-hydroxy-quinolinato lithium (Liq) doped into 4,7-diphyenyl-1, 10-phenanthroline (Bphen) aseolectron injection layer(ETL) By comparing the J-V curves of only devices, the doping rate was set as w(Bphen)∶w(Liq)=65∶35. The device performance was enhanced significantly after using Liq and MoO3. However, the performance was saturated when the thickness was over 1Its the use of MoO3 and n-doping in ETL that facilitated the hole injection and electron injection and transport respectively, reached effective carrier balance in emission zone and improved the device luminance efficiency greatly. The current efficiency, power efficiency and luminance of the devices were improved by about 62%, about 98% and about 60%，with the voltage reduced by about 28%.
A novel system of parallel double-ring temperature sensor is designed and numerical simulated, which is based on the relationship between the temperature and the refractive index of polymer. With the output of the simulation spectrum, the conclusion is achieved that the resonance peaks have distinct displacement as the temperature changes, and the higher thermo-optic coefficient of the polymer is, the more obvious resonance peaks shift. When the temperature increases by 1℃, the resonant peaks shift 32nm. The temperature changes can also be calculated with the resonant peak shift, which provide the feasibility to improve the measurement accuracy of temperature.
Top-emitting white organic light-emitting device was fabricated by optimizing the thickness of MoOx layer with high refractive index and low absorption in the visible region, which is used as out-coupling layer. The structure of the device is Si/Ag(60nm)/MoOx(2nm)/NPB(50nm)/DPVBi(7nm)/rubrene(0.2nm)/Alq3(43nm)/LiF(1nm)/Al(1nm)/Ag(20nm)/MoOx (xnm). We analyzed the influence of out-coupling layers growth on devicesperformance. We researched the influence of the MoOxs thicknesses on EL spectrum. With the increase of MoOx thickness, the transmittance was enhanced for blue light region and the spectrum covered visible light region. CIE was changed from (0.30, 0.49) to (0.33, 0.42) when we added 30nm MoOx as out-coupling layer. When the outcoupling layer was 40nm MoOx, CIE was (0.30, 0.38). It is found that the CIE moved to the equal energy point.
A new physical model for forward scattering of a polarized light beam in atmosphere transmission was established. Based on incoherent light assumption, double and multiple forward scattering theories were derived. To the symmetrical system, the effective Mueller matrix of the forward scattering of polarized light was obtained. It is shown that only seven matrix elements are independent, nine matrix elements are obtained by rotating independent elements. To validate the scattering model, the effective Mueller matrix of the forward scattering of polarized light in 10km atmosphere transmission were simulated with Monte Carlo method, it is proved that theatrical and numerical results are in good agreement.
A triple-passed non-collinear optical parametric chirped pulse amplifier is presented. The signal was triple-passed amplified in a single nonlinear crystal by a long pump pulse, in which the signal and pump pulses of each pass were completely phase matched in the plane to have the maximum of the effective nonlinearity. The total net gain higher than 3.7107, single pulse energy exceeding 3.7mJ with fluctuations less than 3%rms, 30nm amplified signal spectrum and recompressed pulse duration of 82fs were achieved. With this system, the parametric fluorescence is less than 1% of the total output pulse energy when the pump intensity is 350MW/cm2.
Through establishing mathematical relation model of laser, photo-sensitizer and oxygen, photodynamic dose (PDD) in tissue was simulated and its distribution was studied. The change of PDD under the different laser doses of 50mW/cm2，100mW/cm2 and 150mW/cm2 and the photo-sensitizer concentrations of 10mg/kg，20mg/kg and 40mg/kg were simulated. It is concluded that the PDD, an inhomogeneous value in the tissue, changes with many factors such as laser dose, photo-sensitizer and oxygen, and it is obviously effected by the variation of photo-sensitizer concentration.