It is known that the all-fiber self-organizing laser cavity can be formed through inserting an unpumped erbium-doped fiber into an erbium-doped fiber ring cavity. The steady state model of this self-organizing laser cavity is established through introducing the nonlinear coupling equations of the saturable absorption grating into the standby equations of the multimode ring laser, and the single-longitudinal-mode solution with flat side mode spectrum is obtained. The influences of the position of the output coupler, output ratio and pump power on the characteristics of the saturable absorption grating are numerically analyzed. The numerical results show that the grating in the prepositive output coupler structure has a higher longitudinal-mode side mode suppression ratio (LM-SMSR) than in the postpositive output coupler structure with the same pump level and output ratio; and in both structures, the LM-SMSRs of the gratings increase with the output ratio but decrease with the pump power. The optimal range of the output ratio for the prepositive coupler structure is 60%~80%. The numerical results are confirmed by the measured stability maps of the lasers with both structures.

A novel combination of panoramic and long focal length optical system with single sensor based on panoramic annular lens (PAL) is introduced. The proposed system consists of rotating mirror unit, coaxial long focal length unit and PAL unit. The long focal length unit images on the imaging plane of PAL unit by secondary imaging using the blind area of PAL unit′s imaging plane. A mirror is above the long focal length unit which can rotate round about the optical axis and horizontal axis. The object in the ring imaging plane can be amplified 10 times. This system can get panoramic image and amplify image at the same time with the same sensor. The pixels in the inevitable blind area are used. Besides, the distance of the object in the ring imaging can be calculated. The system′s length is about 300 mm and diameter is 160 mm. The field of PAL unit is 360°×(30°~100°). The field of the long focal length unit is ±3°. The modulation transfer function (MTF) of both units is higher than 0.55 at 100 lp/mm in all fields.

Based on the fracture mechanics analysis, the glass thickness of the optical window of an airborne multi-spectral camera is designed in detail. Correlation analyses solve the engineering design problems of the optical window thickness and ensure the design more reasonable and reliable. Considering the complex environment, steady-state temperature field is calculated by means of finite element method. Linking temperature load to generalized force load, the deformation of optical window under the structure-thermal coupling condition is calculated. Optical window surface after deformation are derived by fitting the final deformation value using Zernike polynomial fitting. Fitting coefficients as the input of Zemax, the impact of the deformation of the optical window on the optical performance of multi-spectral camera is analyzed by means of wavefront error and modulaiton transfer function (MTF) as a measurement of imaging quality. The result shows that based on the known operational environment, the impact on imaging quality of optical system is negligible.

Three-dimensional (3D) display has attracted widespread attention all over the world for its intuitive and natural performance. At the same time, three-dimensional interactive technology is also developed fast. A real-time interactive system based on infrared structured light and single-camera is carried out. Infrared structured light is projected onto interactive gesture as encoded procedure, and then infrared images of user′s hand are captured by the camera in real time. An image processing algorithm implemented by OpenCV compares the difference between two consecutive images to obtain the movement information of structured light on user′s hand. Therefore, user′s interactive gestures including movement in three dimensions, zooming and rotating, can be recognized and then transported to three-dimensional display devices in real time. A prototype-equipment is proposed using off-the-shelf CMOS camera and infrared LED. Experimental results show that three-dimensional freehanded interaction can be realized by this approach in low cost.

Aimed at studying the influence of flight parameters on the infrared radiation of a liquid rocket exhaust plume, the FLUENT software is used to calculate the flow field of an exhaust plume under several different flight parameters, then the HITEMP database is adopted to calculate the radiation parameters and the finite volume method (FVM) is used to calculate the infrared radiation between 2 μm and 5 μm. Based on this work, the influences of the altitude and velocity on the spectral radiation intensity as well as 2.5~3.0 μm and 4.2~4.7 μm band radiation intensity are studied. It is found that, the influences of flight parameters on the infrared radiation are exerted by changing the temperature and size of the exhaust plume flow field. At the same velocity, as the altitude increases from 0 to 40 km, the infrared radiation intensities increase gradually, and the band radiation of 4.2~4.7 μm increases faster. At the same altitude, as the Mach number increases, the infrared radiation intensity decreases at first and then becomes stable, and the band radiation of 2.5~3.0 μm decreases faster.

Different from the commercial applications, the avionic wavelength division multiplexing (WDM) network lays much emphasis on hard real-time characteristics. The real-time scheduling algorithm is a key issue to ensure the message transmission performance. According to the real-time communication requirement of avionic WDM network and the traffic characteristics of the avionic network, a weighted round robin scheduling algorithm is proposed based on the periodic task model of real-time communication to guarantee hard real-time transmission in an airborne WDM network, which is comprised of the rotation cycle selection, weights assignment scheme and multi-channel allocation method. Among them, multi-channel allocation method efficiently reduces the splitting times of the message; combined with examples, message weights assignment scheme is determined and it is pointed out that the optimal rotation cycle cannot guarantee the minimum message delay ratio. Research results are meaningful for the design of real-time scheduling parameters and the current practice of avionic WDM network.

In coherent optical transmission system, the inaccurate bit synchronization induced by chromatic dispersion (CD) and local oscillation (LO)frequency modulation (FM) noise reduces the performance of the digital receiver system. To tolerate CD and time jitter, a modified Gardner phase detector for coherent optical differential quadrature phase keying (DQPSK) signal is presented. The proposed scheme, utilizing the features of the signal and inter-symbol interference (ISI), also combining the information both time and frequency domain of the signal, relieves the impairments to the timing recovery caused by CD and noise. A 40 Gb/s polarization division multiplexed DQPSK (PM-DQPSK) signal transmission and coherent detection digital communication system is experimentally demonstrated. The result shows that the scheme is efficient in resisting CD and has a good performance on time jitter.

Based on the sensitivity of long-period fiber grating (LPFG) resonant transmission spectrum to transverse load change, a sensing theory which combines volume expansion status and LPFG spectral characteristics is proposed. The design of a miniaturized resonant peak modulation-based LPFG rebar corrosion sensor is described by combining the spectral characteristics of LPFG with the expansion state monitoring of rebar corrosion. LPFG spectral curves corresponded with different rebar corrosion states under the environment test are captured by the monitoring technique of LPFG transmission spectra. The relation between the resonance peak amplitude change and the state of rebar corrosion is obtained, which shows that the variation of LPFG resonance peak amplitude increases with the intensifying of the degree of rebar corrosion. The method can be used to achieve the accurate monitoring of full volumes of rebars by directly monitoring rebar corrosion states.

A photonic approach to generating a phase-coded microwave signal is proposed and demonstrated. The main principle is to beat the encoded coherent optical sideband to obtain high-frequency, high-coding rate, low-noise encoded microwave signals. The proposed technique, which is simple and conducive to integration, can adapt to different coding rates, generate phase-coded microwave signals with tunable frequency, and solve the bottleneck problem of traditional electronic approaches. The principle is discussed in detail. Mathematical models are developed to consider perturbation on the generated coded signal caused by the phase fluctuations of the microwave driving signal and the optical carrier. The required fiber Bragg grating notch filter is fabricated, and 20 GHz and 25 GHz phase-coded microwave signals are experimentally generated, respectively. The experimental results agree well with theoretical values, and it is proved that the proposed method improves the pulse compression capability.

A novel type of photonic bandgap fiber (PBG-PCF) applied to pulse and slow light is proposed. The designed PBG-PCF is composed of a hollow core and seven cladding layers with air hole arranged by triangular lattice. Its band structure, group index and group velocity dispersion are analyzed in detail by using plane wave expansion method. The simulation results show that slow light property can be improved effectively by microfluid infiltration for the air holes of the inner cladding of PBG-PCF, and an ultra-wide-band photonic crystal slow light optical fiber with a group index of 6, a wide band more than 100 nm, which can transmit flat slow light, is realized. The designed PBG-PCF has promising and potential applications in communication networks, signal processing, optical sensors and nonlinear interactions.

The noises affecting the performance of a repeaterless long-haul fiber hydrophone system are investigated. For the noise due to pre-amplifier, distributed Raman amplifier (DFRA) and erbium-doped fiber amplifier (EDFA) are combined to decrease the noise and the experimental results in noise reduction agree well with the simulated results. The suppression of double-Rayleigh-scattering (DRS) inducing coherent noise by employing the phase generated carrier (PGC) modulation/demodulation technique is demonstrated and the suppression of DRS in systems with different fiber lengths is also discussed. The experimental results show that PGC technique scheme can suppress the DRS noise by 19 dB and the DFRA/EDFA hybrid scheme can decrease the pre-amplifier noise by 7.2 dB. In the end, the phase noise level of a hydrophone system with 100 km long-haul fiber reduces to -113.2 dB (namely 2.2 μrad/Hz1/2), which is identical to the level of a short-haul system. In the system with 200 km fiber, the noise level decreases to -104 dB (namely 6.3 μrad/Hz1/2) and the little increase of the noise is mainly due to the DRS which has not been completely suppressed.

A new method is proposed for calculating the energy-flux-density distribution on focal plane of trough solar concentrators. According to the geometric optical properties of parabolic trough concentrator (PTC), the calculation formulae for incident point coordinate (along the width direction) of incident ray on the focal plane is derived. The sun′s disk model (Buie model) is developed to a linear model of axis symmetry. The energy flux density distribution on linear focal plane is characterized by using frequency statistics function of Origin software, and finally the test is performed with a CCD camera. This calculation method is simple and clear in the function relation, which requires no programming and less calculation, and is applicable for arbitrary surface contour of concentrators and linear receivers. It can offer useful reference for design and optimization of the trough solar concentrating systems.

Since the state-of-the-art methods barely have the capability of super-resolving the closely spaced objects (CSOs) using only single frame data, a super-resolution method based on the sparse reconstruction technique is proposed. The proposed method combines the sparsity of the distribution of CSOs on the focal plane array (FPA) and the structure characteristic of the point spread function (PSF) to construct a sparsely represented measurement model by discretizing the image plane with sampling grids. Then the 1-norm regularization problem is efficiently solved by a second order cone programming framework. For the overestimated sparsity after reconstruction, the Bayesian information criterion (BIC) is utilized for the model selection. The estimated number and positions of CSOs are precisely ascertained at last. Several scenes are set to inspect the efficiency and the super-resolution capability of the proposed method. It indicates that the sparse reconstruction-based method outperforms the existing methods in the ratio of correct detection, the precision of position estimation and the computation load.

We theoretically prove that the point spread function (PSF) of a photoacoustic imaging system is the first derivative of the edge response function, and a step method for measurement of the photoacoustic PSF is proposed. The proposed method is experimentally verified using dyed agarose gel phantom, and the results of theoretical calculations and experimental measurement are in good agreement. The method provides a simple and practical way to measure the PSF of a complex photoacoustic imaging system.

During optical designing, ghost images of optical system should be avoided, so fast and precise analysis of ghost images appears to be very important. The way of first-order ghost-image analysis of imaging system based on Code V and Tracepro is proposed. The surfaces which can cause serious ghost image are found out. The optical system model is established in Tracepro. The image is separated into several parts. Different parts are setted as different spot sources, then, the spot sources are analyzed one by one. During analysis, the order of the ghost is controlled by threshold and ghost-surface is controlled by the surface property. Through analysis, the position of ghost image, and power distribution of ghost image can be obtained.

The invariance of modulation transfer function (MTF invariance) is defined to be the evaluating criterion of the wavefront coding system. The rapid optimization of wavefront coding system based on the MTF invariance is proposed by means of introducing the mathematical program to normal optical design process. The interface called dynamic data exchange (DDE) interface, between mathematical program and optical design program is applied to realize the fast data exchanging and merit function calculating. The MTF invariance of the optimized system decreases to 0.0119, compared with 0.0187 of the original system. Results show that the optimization of special optical systems can be executed more conveniently and fleetly with the help of external program and dynamic data exchange.

In order to improve the optical encoder′s resolution and reduce its volume, an optical pattern rotary encoder based on the image processing technology with an array image sensor is studied. Optical pattern code disc is designed according to the required performance of the optical encoder. The pattern of the spinning disc is acquired by the complementary metal oxide semiconductor (CMOS) image sensor. The processing circuit composed by complex program mable logic device (CPLD) and digital signal processor (DSP) receives the image data, gets the coarse code by the pattern recognition algorithm, and calculates the precision code with sub-pixel size by the improved baseline centroid algorithm. The optical encoder′s angular output is made up of the coarse code and the precision code. In the experiment, this method in an optical pattern rotary encoder whose diameter is 45 mm is applied. Without any additional optical lens, the results show that the encoder′s angular resolution reaches 5″ and the number of subdivision is up to 4096. The peak to peak value of the angle measurement error is 51″. The improved centroid algorithm can suppress the noise and improve the measurement accuracy. The optical pattern rotary encoder can get high resolution, reduce the volume and weight using this pattern code and electronic subdivision technology. It can be used in space flight.

Ellipsometry is an important measurement tool for thin films. A novel calibration method is described for single wavelength ellipsometry, both theoretically (with simulation) and experimentally. The basic idea is as follows: if the relevant information (refractive index n, absorption coefficient k, thickness d) of samples is given prior to measurements, the system calibrating parameters (angle of polarizer P, angle of analyzer A, offset angle of compensator Cs, phase shift of compensator δ, and angel of incidence θ0) can be deduced from the comparison of the measured and calculated Fourier coefficients, with the least square method. These calibrated system parameters can then be used to measure unknown samples. This method is easy to implement and cost-saving. 2~6 samples have been tested in the calibrations, and the errors are analyzed with simulation. Finally, this method is applied to a realistic 632.8 nm laser ellipsometer, and the results obtained with the new calibration method prove the validity of the method and show a maximum error of 0.26 nm.

A method is proposed to compensate intrinsic error in mirror symmetry absolute measurement. Because of the limitation of rotation times in mirror symmetry absolute measurement, intrinsic error of cNθ terms occurs in reconstructed wavefronts of three flats. By adding a rotation with a different angle, the wavefront difference between two measurements before and after rotation is calculated, and the Zernike coefficients of cNθ terms can be obtained by coefficient equations due to rotation invariability of the form of Zernike polynomials in polar coordinates. Therefore the intrinsic error of cNθ terms may be compensated. Because the amount of cNθ terms is infinite, the compensated terms are decided in terms of the balance between accuracy and computing capacity. Computer simulation proves the validity of the proposed method.

By comparing the two images recorded in different configurations on the same object surface, two-dimensional digital image correlation (2D-DIC) method produces full-field displacement with sub-pixel accuracy and full-field strains in the recorded images. In a practical measurement, however, various deteriorative factors, such as small out-of-plane motion of the test object surface, small out-of-plane motion of the sensor target and geometric distortion of the imaging lens may seriously impair the originally assumed linear correspondence between images displacement and object motions. In certain cases, these disadvantages may lead to significant errors in measuring displacements and strains. The measurement errors of 2D-DIC due to the above three unavoidable deteriorative factors are first described briefly. Then, the performances of three typical imaging lenses, including a standard lens, an object-side telecentric lens and a bilateral telecentric lens, against these three deteriorative factors are investigated experimentally using easy-to-implement static, out-of-plane and in-plane rigid body translation tests. A detailed examination reveals that a high-quality bilateral telecentric lens is not only insensitive to out-of-plane motions of the test object and the self-heating of a camera being used, but also demonstrates negligible lens distortion. So the bilateral lens is highly recommended for high accuracy 2D-DIC measurement.

Docking ring is a typical component on space vehicle, which can provide a single circle feature. But monocular vision pose estimation based on single circle with two solutions, which can not be applied to practical engineering application. In order to exclude the interference of false solution, a new method of removing the false solution using Euclidean distance invariance as a constraint is proposed to solve the pose ambiguity, and the paper gives the proof of a unique solution under the constraint. The error simulation analyses of the method are done, and feasible strategies to improve the measurement accuracy are given. According to the projection of the circle on the image, two pose solutions of the circle are calculated. Then a reference point on the circle supporting plane outside the circle is selected. The distance between the reference point and circle center is Euclidean invariant and prior knowledge, which can be used for a constraint to exclude the false solution to get the uniquely correct solution. The effectiveness and superiority of the method are verified by numerical simulation and experiments. Experimental results indicate that the method is robust to the noise, can get the right solution, requires least constraint conditions for the circle, and the calculation process is simple. Pose results are stable and reliable, and more accurate. The relative error of the circle center is less than 0.5%, and the absolute error of pose angle is less than 0.8°.

The displacement measurement theory, the optical path construct and the signal processing method of the sinusoidal phase-modulating self-mixing interferometer are proposed in detail. Phase modulation is introduced by electro-optic crystals in the external cavity and modulated self-mixing interference signal demodulation is achieved by Fourier analysis method. This technique has been used in micro-displacement measurement with nanometer accuracy, which is applied to large range displacement measurement. Agilent 5529A calibrator is included in the displacement measurement both in small and large ranges to evaluate the performance of the interferometer during the experiment. Experimental results show that the range of millimeters displacement is measured at sub-micrometer accuracy and the range of micrometers and nanometer displacement measurement can reach accuracy of 18 nm and 7 nm respectively in the common laboratorial environment. The error source in the measuring process is analyzed, and the results obtained are conformed to that of the experiments.

Camera sensor plane unavoidably contains position installation error and pointing installation error because of the limitation of technologic level. In order to eliminate the influence of installation error, the installation error of target is analyzed qualitatively. It is found that the installation error model and imaging model which explicitly contain pointing installation error of the camera sensor plane. The full aberration model which includes pointing installation error and lens distortion is obtained through a series of transformation. The real image points are corrected based on the calibration results. Numerical simulation and experimental results of half practicality show the correctness and feasibility of the model, and corrected real image points based on calibration results proves that the full aberration model works more effectively than traditional aberration model.

There are two types of apertures, hexagonal and circular, to fabricate planar GRIN microlens arrays with hexagonal aperture and high fill factor by ion-exchange and photolithography. By the designed photomasks of hexagonal and circular aperture, ion-exchange, photolithography and time sampling, the characteristics of ion-diffusion during fabricating the two types of planar GRIN microlens arrays with high fill factor are tested and analyzed. Then we obtain the features of ion-diffusion in such two types of apertures, which are helpful to fabricate planar GRIN microlens arrays with high fill factor when the aperture size and aperture spacing are given.

Increasing dense sampling of the illumination and detection offers an effective way of improving the image reconstruction performances of diffuse optical tomography (DOT). We describe a fast tomographic image reconstruction scheme for a transmission measurement on a slab in the non-contact spatial light DOT providing large measurement data. The proposed method is carried out with the spatial-frequency encoding in both the measurement (source, detection) and the image spaces, and involves a strategy for selecting the useful spatial frequency based on the tissue transfer function. The method is expected to considerably reduce the calculation time for reconstruction whilst retain the quality of the reconstructed images. Additionally, the procedure of the spatial-frequency transform alleviates the ill-posedness of the inverse problem. Results from the simulated data show that it takes only 10 s to reconstruct one absorption image with the proposed method and the speed is more than 400 times faster than that with the conventional one for 81×81 source-detector pairs. Moreover, the proposed method shows a higher quantitativeness ratio and a superior anti-noise capability than the conventional one.

Based on an optical transmission model with nonlinear self-focusing (self-defocusing) effects, a (2+1)-dimensional nonlinear Schrdinger equation is obtained under nondimensionalization. The (2+1)-dimensional variable coefficient nonlinear Schrdinger equation is transformed into the standard (2+1)-dimensional nonlinear Schrdinger equation by using similarity transformation. Interactions between two optical vortex solitons, among four, five and six optical vortex solitons in the waveguides are discussed with different vortex-core spacing and initial phase difference, respectively, by numerical simulation. Some new conclusions are obtained through analyzing the above results. 1) The shape of vortex soliton with selfsimilar charcteristics sustain during the propagation along z-axis. 2) Multiple vortex solitons interact with each other during the propagation along z-axis especially when the distance within them is smaller than a definite value, meanwhile the energy flow among them. Some are strengthened, and some are weakened.

Four-wave mixing (FWM) effect in metal-insulator-metal (MIM) waveguide filled with a Kerr nonlinear medium is investigated, followed by the study about polarization-dependent FWM in such nanoplasmonic structures due to the local enhancement effect of surface plasmons (SP) and birefringent characteristics. When the pumps with the polarization parallel to each other are launched into the waveguide with 250-nm thickness, the FWM efficiency reaches -33 dB. However, when the pumps are perpendicularly polarized, idler waves can not be obtained. For the waveguide with 50-nm thickness, when the pumps are both TM polarized, the FWM efficiency reaches -30 dB. While under other polarization states of pumps, idler waves can not be observed due to the cut off of TE modes. Such FWM-based mechanisms are utilized to construct all-optical logical gates.

Space atmosphere remote sensing urgently requires ultraviolet (UV) panoramic imager. An optical design method of UV panoramic imagers is proposed. The uniformity of image illumination is improved by using barrel distortion and pupil aberration. Based on the requirements of application, an optical system of UV panoramic imagers is designed. The central wavelength is 360 nm, the bandwidth is 10 nm, the field of view is 360°×(70.9°～73.3°), the focal length is 5 mm, and the relative aperture is 13.3. The modulation transfer function (MTF) is more than 0.72 at the Nyquist spatial frequency of 38.5 lp/mm. The root-mean-square (RMS) radius of spot diagram is less than half of the pixel. 80% of the energy is enclosed in a pixel, the f-θ distortion is less than 0.05%, and the uniformity of image illumination is 89%. The design requirements are satisfied. The configuration of this system is compact and is suitable for the application in space atmosphere remote sensing. It is indicated that the optical design idea of UV panoramic imager is feasible, and the design method can be used in other wavelength ranges, which is instructional for designing panoramic imagers.

Based on the wavefront aberration theory and the coordinates transform, the influence of surface-profile error of large mirror on aberration characteristic of optical system is analysed. The optical wavefront aberration and surface-profile error of mirror can be expressed as Fringe Zernike polynomial. The surface profile error on the surface of the system aperture diaphragm (exit pupil or entrance pupil) will introduce constant wavefront aberration coefficient in the full field by analysing the transformation matrix. The error on a surface not at pupil will lead lower order wavefront aberration coefficient in the optical system, the relation between different wavefront aberrations coefficient and fields is different, and the location zero for the lower aberration coefficient always resides at the center of the field of view. The result shows that it′s possible to analyse the wavefront aberration caused by surface-profile error of the reflective mirror using coordinate transformation matrix for improving the efficiency of the alignment.

It is proposed and demonstrated that a method to realize the fiber Bragg grating (FBG) demodulation based on virtually-imaged phased array (VIPA) and infrared imaging system. Two-dimensional (2D) spectral imaging can be realized by using VIPA and diffraction grating. The wavelength of the gratings can be integrated by analyzing the imaging of the infrared camera. It has no moving parts. The reproducibility, stability and reliability of the system is perfect and its resolution is higher than the traditional charge-coupled device (CCD) method by using VIPA as dispersive device instead of volume diffraction grating. The resolution of the system is better than 2 pm.

Considering that the irradiance distribution obtained by using optical fiber and fly-eye lens is of poor uniformity, methods of adding integrator rods and frosted glasses to improve the uniformity of optical fiber irradiation device are proposed. The measurement results indicate that the effect is very remarkable. The ultraviolet A (UVA) band of ultraviolet radiation is measured. The uniformity is raised from ±8.9% to ±3.5% in the irradiated area of 80 mm×80 mm after an integrator rod is added at the input end of the optical fiber. And the uniformity of the central area of 30 mm×30 mm is raised from ±3.3% to ±0.7%. On that basis, after the frosted glass is added at the input end of the fly-eye lens, its uniformity can reach ±0.6% in the central area of 30 mm×30 mm, and the UV irradiance which is eccentrically distributed becomes axially symmetrically distributed. The multiple light sources superposing methods are also put forward to improve uniformity of light source while higher irradiance is obtained at the same time. The results indicate that the irradiance and the uniformity can reach about 30 mW/cm2 and ±3.9% respectively in the irradiated area of 80 mm×80 mm by using two optical fiber irradiation devices to superpose irradiation. Using the methods of superposition of three light sources and casted by the fly-eye lens, the irradiance and the uniformity are about 60 mW/cm2 and ±2.4% respectively in the irradiated area whose diameter is 80 mm.

For a cool 320 pixel×256 pixel detector with staring focal plane array, an infrared continuous zoom optical system using mechanical compensation and folding beam path for middle wavelength infrared (MWIR) is designed. The system is composed of a zoom system and a secondary imaging system, including seven lenses, two reflectors and three even aspheres. The computing process is introduced to obtain structural parameters of the optical system, and then optimization is applied by Zemax. Image evaluation, cam curve and cold reflection are listed. The design results show that the system which works at 3.7~4.8 μm has achieved the zoom of 18~360 mm, and satisfied 100% cold shield efficiency. The modulation transfer function is always bigger than 0.5 at the spatial frequency of 16 lp/mm. The system can be used for airborne optical-electronic detection.

The light collection power and the relative aperture of weak-light spectrometers, such as Raman and hyperspectral spectrometers, are expected as high or big as possible, in order to improve their signal-to-noise ratio (SNR). Littrow-Offner spectroscopic mount has the advantages of both Offner and Littrow mounts, including its simplicity and compactness, concentricity of all spherical elements, low inherent aberration, realizable big relative aperture and high light collection. Such combined mount structure and principle are briefly introduced and then its imaging performance is investigated. Its astigmatic characteristic then is investigated, through application of the sagittal and meridian imaging formulas of spherical mirror and diffractive grating. The means to eliminate astigmatism in the wavelength range is suggested. Furthermore, the inherent astigmatism is corrected by introducing a meniscus singlet with negative astigmatism. In the case of Raman spectrometer, a compact spectroscopic optics with big relative aperture and resolution and excellent imaging quality is optimally designed.

In order to study the depolarization performance for monochromatic light of improved Lyot depolarizer, the method of superposition of multiple beam is proposed. The formula for depolarization degree D that is the function of vibration azimuth angle (VAA) and total retardation is deduced. It is shown by theoretical analysis that D is ideal for any VAA when retardation δ=（N+ 1/2）π (N is integer) on the basis of large enough wedge angle. And when δ=Nπ, VAA makes greatest impact on D. When δ is assigned to the other values, the impact on D made by VAA is between the former two. Using 405 nm diode laser whose beam is expanded and collimated, experiments to measure D of sample whose wedge angle is 6° are conducted. The theoretical results are well verified by experiments. D is over 98.8% when total retardation δ is nearly (N+ 1/2)π by changing incident angle.

A 1×3 splitter based on self-collimation in a two-dimensional square-lattice photonic crystal is presented. The frequency and the direction of propagation of the self-collimated beams in square-lattice photonic crystal composed of elliptical dielectric rods are obtained by the equal-frequency contours (EFC) which are calculated by plane-wave expansion (PWE) method. Then the elliptical rods are rotated counterclockwise and the EFC is caculated employing PWE method. Based on the above, a 1×3 splitter is realized by photonic crystals composed of elliptical rods with different orientation angles. The transmission characteristics of light in the splitter are analyzed via the finite-difference time-domain (FDTD) method, and the resulting electric fields are also given. It is concluded from the electric fields that a 1×3 beam splitter is realized. The proposed splitter is expected to promote the application of photonic crystals in optical integrated circuits.

Using heat conduction equation, the temperature distributions around pits on multi-crystalline silicon surface are calculated under different boundary conditions during etching reaction. The simulation results show that the solution temperature of 15 ℃ controlled by cooling measures can result in an obvious temperature difference between the pits bottoms and multi-crystalline silicon surfaces. This difference is helpful to reduce the pits opening size as well as increase the pits depth. On the other hand, etching the multi-crystalline silicon surface without temperature control will make little temperature difference between the pits bottoms and multi-crystalline silicon surfaces, which produces the trap pits with the shallow and large opening. Silicon surfaces are textured under different temperature conditions in the experiment. Scanning electron microscope (SEM) image of experimental sample surface etched under the low-temperature condition shows the high-density distributions of trap pits with large pits depth and small opening. The experimental results can match the theoretical prediction well.

The atomic coherence effect is investigated experimentally in the thermal strontium atomic beam by means of fluorescence observing, based on the V-type Zeeman-sublevel system of intercombination line of Sr. A theoretical calculation of the V-type electromagnetically induced transparency (EIT) has been elaborated, taking into account the effect of detuning, linewidth and Rabi frequency of the coupling laser on intercombination transition EIT. The V-type electromagnetically induced transparency of intercombination is measured experimentally under different condition of detuning and with different powers of the coupling laser.

In order to evaluate the point spread function (PSF) of optical remote sensors well and truly, a fast multichannel blind deconvolution (MBD)-based estimation method which does not need any ground target is proposed. Multiple sub-images with uniform local background are extracted from a remote sensor image and alternate minimization algorithm is used to implement the blind deconvolution. It only takes 0.4917 s to achieve a percentage mean square error of 1.1% with two noise-free sub-images on a Matlab platform. While the error is 5.9% for two sub-images with the signal-to-noise ratio of 45 dB. By applying the estimated PSF to image restoration, it can bring gray mean gradient from 5.7 to 7.1 and energy of Laplacian from 29 to 46. This method performs more accurately and efficiently than the frequently used slanted-edge method.

Low frequency oscillation of pointing mirrors used for field scanning or image motion compensation induces push length difference between adjacent frames. Local distortion occurs when constant pixel interval between frames is used to output image. The image distortion is modeled based on a space remote sensor image motion model to investigate reasons and features of distortion caused by angle oscillation, as well as to correct it. Orbit parameters, satellite attitude and pointing mirror position are introduced into the model precisely. Distortion patterns are figured out with specified necessary parameters, and image motion of feature point is used to correct the image output. For corrected images with and without mirror oscillations, least square fittings are made. Simulation shows that distortion magnitude relates not only with orbit and vibration parameters, but also with target′s direction. Under ideal condition, distortion rectification accuracy is better than one pixel by the proposed method. Experiments also verify the preferable effects.

In order to improve multi-spectral (MS) image fusion quality, a new pan-sharpening method based on sparse representation is proposed. A linear regression model between the MS image and its intensity component is established. The sparse coefficients of both panchromatic image and MS image are obtained by two dictionaries which are trained to have the same sparse representations for each high-resolution and low-resolution image patch pair. The coefficient of intensity can also be obtained via the linear regression model and the coefficients of MS bands. Then, the sparse coefficients are fused in the general component substitution (GCOS) fusion framework. The fused sparse coefficients are used to reconstruct a high-resolution MS image. As the inherent characteristics and structure of signals are by via sparse representation more efficiently, the proposed method can preserve spectral and spatial details of the source images well. Experimental results on IKONOS satellite images demonstrate the superiority of the proposed method in both spatial resolution improvement and spectral information preservation.

Based on the laser absorption spectroscopy technique and algebraic tomography reconstruction, two-dimensional temperature distribution is reconstructed by using an irregular beam array. The grid weight factor which represents the number of lines across the grid is put forward and used to evaluate the distribution of the line. An improvement of reconstruction is obtained by optimal line distribution. The reconstructed quality with error of less than 15% compares with the non-optimal beam and parallel beam distribution reconstructed results. The reconstructed quality increases with number of emitters increasing. Time division multiplexing technology is adopted to scan two H2O absorption transitions (7205.25 cm -1 and 7416.05 cm-1) simultaneously at 1 kHz repetition rate. Additionally, the numerical results agree well with the experimental results.

The results of HONO trace detection using mid-infrared tunable laser absorption spectroscopy technology based on the 8 μm room-temperature continuous wave quantum cascade laser are reported. The characteristics of the device are estimated and described with pure methane gas. Direct absorption spectroscopy is applied to trace gaseous HONO detection via a 125 m long multi-pass cell. The sensitivity of the instrument is evaluated using HONO sample generated by chemical reaction of H2SO4 and NaNO2. The generated HONO concentration is quantified by means of a denuder system associated with a conventional NOx analyzer, and the minimum detectable HONO concentration is found to be about 7.3 μg/m3 in 1 s integrated time. HONO losses resulting from the optical cell wall are experimentally investigated. The rate constant of HONO determined in the present work might be helpful for future field measurements of HONO, especially when an absorption cell is used.

A 1.6 cm long argon plasma jet torch is generated by using hollow needle to plate discharge device working in atmosphere. Rotational temperature, vibration temperature and electron excitation temperature are studied by using optical emission spectrum. Optical emission spectrum is collected from 300~800 nm, which consists of strong Ar I lines, N2 second positive band system, weak OH－ around 309 nm and N+2 lines. Rotational temperature is obtained by simulating the spectrum shape of OH－radical band with program of “LIFBASE”. Gas temperature is 500 K and keeps a constant number at different positions along the plasma. Vibration temperature is calculated using N2 second positive band system, electron excitation temperature is obtained using spectral line intensity ratio. Spatial distributions of the above two kinds of temperatures are similar; they decrease firstly and then increase with the increase of the distance from the arc root.

Plasma temperature and electron number density are important factors of the laser-induced breakdown spectroscopy (LIBS) measurements. The plasmas are generated using two 532 nm NdYAG pulsed lasers to ablate the plasma breakdown liquid jet of CaCl2 solution. We get the spectrum of 300~450 nm band and analyze the Ca II emission lines. It is assumed that the plasmas produced in the experiment are in local thermodynamic equilibrium(LTE), according to LIBS formula the Ca plasma temperature of 104 K is determined by using the Boltzmann plot method with 6 Ca II lines while the electron density of 1017 cm-3 is obtained from the Stark broadening of Ca II 393.366 nm line. The variations of plasma temperature and electron density with delay time and the time between two pulses are discussed based on experimental results. The advantage of double-pulse LIBS over single-pulse LIBS is proved. Experimental results show that the laser induced Ca plasma is in local thermodynamic equilibrium.

Optical emission spectroscopy is an effective tool to measure plasma parameters and species distribution in plasma. Optical emission spectroscopy is used to measure the microwave plasma of CH4/H2 in situ. The internal radicals, the influence of methane volume fraction on radical emission intensity, and spatial distribution of the radicals and the influence of methane volume fraction on the spatial distribution in MPCVD plasma are investigated. The results show that the optical emission intensity of C2 in plasma increases with the methane volume fraction increasing obviously. Intensity ratios of CH, Hβ, Hγ to C2 reduce with increasing methane volume fraction. The spatial distributions of the radicals especially of C2 become inhomogeneous with the methane volume fraction increasing.

A background elimination method based on harmonic detection in no absorption spectral region (HDINASR) is proposed. It can be used in open and closed gas detection based on tunable diode laser absorption spectroscopy (TDLAS). Background signal component is discussed, background signal searching and spectral line selection principle are designed, and the minimum wavelength spacing formula between adjacent absorption spectral lines is given. The experiment is designed to detect hydrogen fluoride (HF) using TDLAS experimental system. The HF target absorption spectral line, laser working temperature and temperature range of background searching are determined. Experimental results show that with the application of HDINASR background elimination, the curve correlation is increased by 3.4% and the relative amplitude of volume fraction accuracy improving is increased by 5.8%. HDINASR provides an effective background elimination method for open and closed gas detection.

Spatial beam method is explored to eliminate the backside reflection in ellipsometric measurement. The main concept of this program is to focus the beam on the of sample surface, diverge on the bottom, and then the back reflection light will not reach the detector. The quartz glass and niobium oxide monolayer film are chosen as the experimental sample. Quartz glass samples are divided into 3 groups, which are measured directly, after backside grinding, and after the spatial splitting, respectively. For the untreated sample testing, the refractive index values at three incident angles are obviously different. In backside grinding case, the refractive index of the quartz glass appears consistent for three incident angles. After the spatial splitting, the refractive index of the quartz glass appears the same. The spatial splitting method is used for ellipsometric test of anti-niobium oxide monolayer, and good fitting of the experimental data is got.