The recent progress of fiber sensing techniques in Tianjin University is introduced in this paper. Parallel demodulation for Extrinsic Fabry-Perot Interferometer (EFPI) and Fiber Bragg Grating (FBG) sensors is realized based on white light interference, with EFPI measurement precision of 0.81 μm and FBG wavelength measurement precision of 14 pm. Concentration detection of acetylene is realized by using intra-cavity fiber laser with sensitivity less than 100 ppm. Distributed sensing based on polarization maintaining fiber is realized with resolution of 6 cm. FBG demodulation equipment is developed by using edge filter, with wavelength resolution of 1.2 pm and scan rate more than 200 kHz. Two-dimension and three-dimension scanning of tooth model is realized by using all-fiber optical coherence tomography (OCT). And the dynamic characteristics like temperature and oscillation detection of fiber ring are realized for fiber optic gyroscope.

The classical three-loop servo system is researched, and the influences of the four kinds of random noises on the tracking precision are discussed particularly, which come from the processes of measuring current, speed, position and torque disturbance. Then the transfer functions are deduced between these random noises and tracking precision. Based on the transmutation of the transfer functions, the relation among system bandwidth, tuning arithmetic and random noises is deduced, which offers reference for choosing the sensor, processing the measured data and ensuring tuning arithmetic parameter. Moreover, an emulation experiment has been done under these random noises which obey the Gauss-distributing. And a segment linearization method is put forward upon the amplitude-frequency curve of the random noises and tracking precision, by which the influences of four kinds of the random noise on tracking precision are quantized. Comparing the quantized results with the emulated results, it has been proved that this method is correct and feasible. At last, comparing the method with the emulation under the four sorts of noise acting on the servo system at the same time, the same conclusion is gained.

As professional equipment for calibration of space-location vision camera, the static target simulator supplies exact simulated targets in special work environment. The precision of target decides calibration level as a key part of target simulator. The mathematic model of deformed target is built based on special working conditions, and score of deformation h is determined that can meet required precision through analysis of two points position precision Δδ'ij and geometrical relationship between Δδ'ij and h. For final optimum values, by applying Ansys, the target structure is further optimized with h as one of optimized parameters. The correctness of design is proved by reconstructed target with a result that the optimized parameters h=5.5 μm is smaller than theoretical value 14 μm.

The test method of the bullet impact location based on a large area and parallel laser screen was studied. Taking the laser diode line generator as the light source, the parallel laser screen unit was formed by using aplanatic cylindrical Fresnel lens with long focal length. By splicing seamlessly with multiple parallel laser-screen units, the large area laser screen can be constructed. Because of the Gaussian profile of the luminous flux density along the transverse direction in a parallel laser-screen unit when a bullet with certain diameter passes through different transverse location of the unit, the photo detector obtains different signal. Therefore, according to the amplitude of the signal, the bullet impact transverse location can be subdivided within the width of a parallel laser screen unit. The feasibility of such subdivision scheme is verified by live firing experiments of 7.62 mm caliber. Experiment results show that the system has sufficient sensitivity to acquire signals of small objects. For the length of 10 m laser screen, the standard deviation of differences between this system coordinate measured data and bullet holes coordinate ones is 5.16 mm.

A method of tire specification extraction was presented. First, in image pre-processing, iterative least square method was used to fit accurate positioning of the circle center, and coordinate transformation and bilinear interpolation stretching were used to preprocess tire image. Then, window transform was used to reduce image dimensions from two-dimensional to one-dimensional vector, and thus one-dimensional vector was proposed to construct the sawtooth with extreme points. Finally, by using the parameters, the characteristics of the waveform were described to extract character region of tire specifications. Experimental results show that this method can effectively extract the tire specification.

According to the operating principle of one scanning aerial reconnaissance CCD camera, an analysis expression of image motion was derived with collinearity equation, which was about attitude disturbance and image obliquity. Combining the working parameters of imaging obliquity and attitude disturbance, a simulation analysis was given, and the results show that image motion is independent on image obliquity and linearizes relationship of attitude disturbance when image obliquity θ<0.13 rad. Beyond this range, image motion is nonlinear with image obliquity and attitude disturbance. The whole trends will increase coupling with the increase of the disturbance, which can supply a theory basis for the same species of camera and its image motion compensation devices.

The low signal-to-noise ratio of photon counting limited its application in the filed of Optics Time Domain Reflection (OTDR) because of the quantum fluctuation. We presented a method using photon counting modulation spectroscopy in OTDR with single photon detection at 1.55 μm. It is found that the noise amplitude of the quantum fluctuation has a uniform distributing in the frequency domain. The effect from quantum fluctuation has been effectively restrained by using the photon counting modulation and demodulated with lock-in amplifier. The enhancement of signal-to-noise ratio can be achieved by using setting the filter bandwidth via changing the integration time of the lock-in amplifier. Compared with the direct photon counting measurement, the signal-to-noise improvement ratio could reach 28.3 dB.

Defocusing effect on the patterns of microlens array imaging photolithography is analyzed, and tolerance of defocusing range of the system is given. Meanwhile, a novel method with simple structure for zooming is proposed, which is able to be used in microlens array photolithography system for zooming. Then the equipment based on adjustment focus method is applied to microlens array imaging photolithography, and experiments are carried out on the microlens array imaging system. At last, it is proved that the quality of patterns fabricated by this zooming method approaches to the optimized image quality of microlens.

Contrast, signal-to-noise ratio, resolution and sampling are used as an integrated evaluation standard for the imaging quality of the X-ray in-line phase contrast imaging system. The optimization flow of parameters for the proposed optimized method is erected for the object which has the feature of one dimensional step blurred edge distribution widely applied in many fields. The correlative parameters of the imaging systems under the radiation of sub-micrometer sized focus X-ray source, laser-based micrometer sized focus X-ray source and synchrotron radiation X-ray source are optimized by the means of numerical simulation. The outcome shows that the parameter optimization is completed commendably by the optimized flow. It is obvious that the method can be applied to the optimization of each X-ray source based on simple correction if necessary.

The pulse spreading is one of the dominant factors that influence the ranging performance of the airborne laser scanner. Firstly, the dependence of the backscattered pulse width on the flying height and the scanning angle was analyzed, and then the attenuation of the backscattered power due to pulse spreading was investigated. The influence of the pulse spreading on the system’s Signal-to-noise Ratio (SNR) and the ranging accuracy was studied. The maximum flying height of aircraft was analyzed based on the scanning angle and the platform flying height and the system’s parameters. The simulations indicate that the width of the back-scattered laser pulse increases considerably from the centre to the edge of the air strip. The received power and SNR decrease sharply with the increase of the scanning angle. The ranging accuracy is variable, and decreases sharply from the centre to the edge of the air strip.

The output properties of passively Q-switched Nd:YAG/Cr4+:YAG ceramic laser was studied theoretically and experimentally. The repetition rate, the average output power and the single pulse energy were measured for different output coupling transmissions. The experimental results were compared with the theoretical calculation results. It can be shown that the repetition rate of output Q-switched laser decreases with the increasing of the output coupling transmission, whereas the average output power and the single pulse energy firstly increase to maximum and then decrease as the output coupling transmission increases. However, the optimal output coupling transmissions for the maximum average output power and the maximum single-pulse energy are different.

The dimension and configuration of aerial cameras is mainly determined by the optical system. A miniaturization design was made based on the requirement of a 25× aerial zoom lens. In order to decrease total optical length, a design scheme was employed by selecting mechanically compensated zoom lens with a negative compensator, shortening the focus length of variator and compensator, and increasing the distance between front group and variator. An initial configuration was obtained by solving equations of aberrations. According to aberration theory, the aberrations were corrected by using ZEMAX optical design software. The result indicates that the focusing length can vary from 20mm to 500 mm continuously for this system, the optical total length is only 198 mm, and the Modulation Transfer Function (MTF) values are higher than 0.4 at 0 field and 0.2 at 0.7 field respectively.

In-phase/Quadrature-phase (IQ) imbalance can result in severe performance degradation in optical Direct-detection Orthogonal-frequency-division-multiplexing (DD-OFDM) systems. We build two optical back-to-back DD-OFDM systems, which implement Double-sideband (DSB) and Single-sideband (SSB) modulation, respectively. The tolerance to IQ imbalance of these two systems is analyzed and compared by using Error Vector Magnitude (EVM) and Symbol Error Rate (SER). It is found that, in the back-to-back case, the DSB system has stronger robustness to IQ imbalance than the SSB System. We further build two optical DD-OFDM systems each with 40-km transmission, which respectively implement DSB and SSB transmission. Similarly, the tolerance to IQ imbalance of these two systems are analyzed and compared in terms of EVM and SER. It is found that, however, in the case of 40-km transmission, the SSB system has stronger robustness to IQ imbalance than the DSB system. As a result, it is concluded that, in the case of transmission, SSB modulation can enhance the tolerance to IQ imbalance of DD-OFDM systems.

To undertake analysis of CCD noise effect on lossless compression of remote sensing images, ISO/IEC standard images and UK-DMC multispectral images were selected. The ISO/IEC standard test images were encoded with JPEG2000-lossless compression method after being contaminated with different levels of simulated CCD noise based on CCD noise model. Using the encoded noise image, the change of compression ratios of the images with different noise levels was investigated. Furthermore, the analysis of noise effect on data transmission efficiency was undertaken by using noise-contaminated multispectral images. Based on experimental results, it is indicated that the compression ratio and data transmission efficiency will decrease once the image is contaminated by CCD noise. With regard to CCD noise, the shot and readout noise modeled as Poisson noise and thermal and dark current noise modeled as Gaussian noise are principal factors for the decrease of lossless compression efficiency. The impulse noise induced by detector malfunction has the least effect on the decrease of lossless compression efficiency.

A new Content-Based Image Retrieval (CBIR) method based on the high-order moments of multi-scale and multi-direction Gabor filtering coefficients was presented and the algorithm for measuring the features of smoothness and consistency of texture which was extracted by a Gabor filter bank was given by using the variance of filtering coefficients. The feature vector for CBIR is composed of the values of the energy, variance, kurtosis, smoothness and consistency of filtering coefficients in 4 scales and 6 directions. The typical images from Brodatz texture database and Corel images were utilized in the contrast experiments, which show that the proposed method gives better precision than traditional Gabor filtering method.

The current infrared and visible image fusion faces the difficult of obtaining infrared target and extracting the scene of visible image. An infrared and visible image fusion method based on Nonsubsampled Contoutlet Transform (NSCT) is proposed by using the advantage of nonsubsampled Contoutlet transform’s direction and anisotropy. Firstly, the source images were decomposed. Then, low-frequency sub-band establishes new feature energy, and weights it for the fusion. And high-frequency sub-band selects the max variance of the image fusion rules. By using the algorithm for infrared and visible light images in the fusion experiments, the fusion quality assessment is given. The experimental results show that the proposed image fusion algorithm gets more image detail in the information, and the amount of information has be increased significantly.

During the process of transmission and duplication of color images among the digital imaging devices, it is necessary to use color management to ensure the accuracy and the consistency of color restoration. One of the key technologies of color management is colorimetric characterization for digital imaging devices. According to the principle of colorimetric characterization of digital imaging device, the non-linear relationship between the RGB of digital imaging device and the CIE Lab of standard colorimetry value is established by means of polynomial regression method. Meanwhile, under Matlab software programming, a fast modeling software has been designed for colorimetric characterization of digital image processing devices. The experimental result shows that the software could realize a fast and precise conversion from RGB colorimetry value to the CIE Lab standard colorimetry value.

A Synthetic Aperture Radar (SAR) image retrieval algorithm is proposed based on semi-variances and Hu moments with rotation-invariant and flip-invariant. A set of semi-variances with selected lags and directions represents the image spatial continuity information. In order to achieve rotation-invariant and flip-invariant, the semi-variances were re-ordered according to the spatial major direction determined by weighted semi-variances proposed in this paper. The re-ordered semi-variances combined with 12 Hu moments represent SAR image features. Canberra distance was used to measure the similarity of normalized image features. Experiments were conducted on different scenes of rotated and flipped SAR images. Compared with algorithms based on multi-scale decomposition, the experiment results demonstrate that the proposed method is outstanding and more efficient than other algorithms.

Er3+-doped bismuth-based glasses with the composition of Bi2O3-B2O3-Si2O were prepared by conventional high-temperature melting and annealing method. The 1.5 μm band spectroscopic properties of Er3+ were measured and analyzed, and the research focused on the transient response of 1.5 μm band fluorescence under the pulse excitation at 975 nm. The results show that there was a rise- and fall-response process of Er3+ fluorescence corresponding to the up and down-edge of 975 nm pulse, respectively, and the response rate is dependent on the lifetime of Er3+ at 4I13/2 level. With the increase of Bi2O3 component content, the lifetime of Er3+ decreases resulting from the energy transfer aroused by OH groups in the glass, and the response becomes faster accordingly.

The mode field of photonic crystal fiber structured with hexagon symmetry hole cladding was analyzed by multipole method, and the effective indexes of base mode of different wave length were got. The characteristics of this photonic crystal fiber grating were computed and simulated by coupled-mode method and transmission matrix method. Moreover, the differences were compared between conventional fiber grating and photonic crystal fiber grating on their reflection spectrum and delay. The apodization characters of this fiber grating were also researched to get optimal apodization function and corresponding transmission spectra. Compared with the conventional fiber grating, it is found that the refractive index of core mode declines as wavelength rising, and photonic crystal fiber grating show a clear blue shift. When chirp processed, 10 centimeter-long photonic crystal fiber grating can provide 1 200 ps linear delay.

For some iris image capture devices, the same iris texture gotten in different times may shift. This shift may lead to offset of the iris feature encoding, and thus affect the characteristic match of the iris directly. By analyzing the factors of the iris texture shift, the regularity of the shift is found and a matching method of segmentation shift is put forth. Experimental results show that the method proposed in this paper can significantly increase similarity of the same iris which is captured in different times.

Aimed at the human face contour tracking in video image sequences, a contour tracking algorithm is proposed in which an improved level set method is introduced into the particle filtering framework. The face contour is represented by zero level set function and approached by evolution of the level set function. To deal with the partial occlusion, the shape prior is added to the updating process to constrain the curve evolution. This algorithm can simultaneously track the affine motion of the face region and deformation of the face contour in the framework of particle filtering. Experimental results show that the proposed algorithm can track the face contour accurately and be robust to illumination changes, background interference and partial occlusion.

2D Kaiser filters with selective frequencies, selective orientations as well as changeable channels were constructed to extract iris features. The features were divided into several parts based on their amplitudes, and analysis of all the parts show that there is an ‘effective amplitude threshold’ (L) hiding in the iris features. The features with amplitudes bigger than L can achieve effective iris recognition, while those with amplitudes smaller than L are uncorrelated noises. By setting the noise features as “invalid codes”, we optimized Hamming distance and improved the correct matching rate of same pairs of irises. Results show that compared with Gabor method, the optimization method improves the right recognition rate from 98.6% up to 99.9 % and has a null fault acceptance rate with lower fault rejection rate.

The algorithm of iris location is a pivotal step in iris recognition and the speed and accuracy of location is the standard to evaluate the effectiveness of the algorithm. According to the grayscale characteristic of the pupil area, a fast iris location algorithm is presented based on image sub block. Firstly, find an approximate location area of the pupil roughly. Then, locate it accurately by using the methods of morphology and geometry. Finally, locate the outer circle with integral differential operator in the delimited area after pupil location. An experiment on iris location with 756 images in iris image library of version 1.0 of Chinese Academy of Sciences has been completed. The results with 98.80% accuracy and 1.5s average positioning time shows that the algorithm improves recognition speed notably.

A fast recognition algorithm based on tri-encoding method for one-dimension barcode was presented. First, the image was threshold by OTSU method and the barcode area was separated from the background. Then by analyzing projection characters of the binary image, tri-encoding including 0-1 encoding, similar running length encoding and strip-space encoding was established step by step. Finally, barcodes were found and verified by using table look-up technique from the code table. The procedure of the recognition can strongly handle several kinds of drawbacks like noise, irregularity, deficiency and contamination. Application results show that the correct recognition rate is higher than 99% and the average recognition time is about 5 ms.

An effective method for three-dimensional (3D) imaging with kinoform based on reflective phase-only Liquid Crystal Spatial Light Modulator (LC-SLM) was proposed. 3D image actually was reconstructed by the diffraction of kinoform using LC-SLM as a display unit. The calculation of kinoform, the relationships between parameters of LC-SLM with the kinoform, and some influencing factors in the quality of the reconstructed image were discussed in detail. In order to enhance the displaying resolution, a displayed object was decomposed into several sampling groups, and the corresponding kinoforms were calculated. When the kinoforms were inputted into LC-SLM successively within residual time of human eyes, the diffraction light wave may reconstruct the image of the original object, and then an observer can see a 3D image in free space. Experimental results demonstrate the correctness of the proposed approach, which provides an effective way for 3D display in practical application.

In the quick change process of impact or blast, sampling rate of CCD is lower than object move rate, which result in deficiency of CCD’s sampling. A novel method based on Fourier Transform Profilometry (FTP) was proposed, in which a two-frequency sine patterns is projected onto the object and the deformed fringe is captured by CCD. Some problems caused by deficiency of sampling and breaking fringes were solved in 3-D phase unwrapping by using the low-frequency grating unwrapping phase marked fringes. The same rank of high-frequency deformed fringes was tracked by marked fringes, and 3-D phase unwrapping by high-frequency grating fringes was obtained. Computer simulation experiment and glazed tile rupture experiment proves the feasibility of this method.