This paper studies the microscopic mechanisms of H2 adsorption on the rutile TiO2 (110) surface by the first-principle plane-wave ultrasoft pseudopotential method based on density functional theory. The changes in the adsorption energy, density of states, distribution of charges, and optical properties on the TiO2 surface are calculated. The experimental results indicate that the rutile TiO2 (110) surfaces doped with C, Mo, and C-Mo separately can easily adsorb H2 in the way of chemical adsorption. After doping, the impurity level formed in the forbidden band can induce the separation of photogenerated electrons and holes. This provides a "step" for electron transitions in the forbidden band and improves the optical properties of the TiO2 surface. In the visible light range of 380-780 nm, the optical performance of C-Mo co-doping,Mo doping, and C doping materials decreases in turn. The absorption coefficient and reflectance peak of the TiO2 surface doped with C-Mo are increased by about 5 times and 6 times, respectively, compared with those of the undoped one. This study deepens the understanding of the microscopic mechanism of H2 adsorption on the TiO2 surface and improves the optical properties of the material by using the doping method, which provides theoretical support for the application of TiO2 in hydrogen sensors.

The high-performance and low-cost ultraviolet photodetectors are promising for wide applications in many important fields. In this paper, well-aligned zinc oxide nanowire arrays (ZNWAs) were first grown on an indium tin oxide (ITO) coated glass substrate by a facile chemical bath deposition method at low temperature. The ZnO nanowires were 30-60 nm in diameter and 600-900 nm in length. Then poly (9-vinayl carbazole) (PVK) thin films were deposited on the ZNWAs, and a ZNWAs/PVK heterojunction ultraviolet photodetector was built. The results show that the ultraviolet photodetector displays good response to 365 nm light. By calculation, its sensitivity, responsivity, detectivity, response time, and decay time at a wavelength of 365 nm were 15.33 (voltage of 0.05 V), 37.72 A/W (voltage of 2 V), 1.29×1012 Jones, 12.6 s, and 34.2 s, respectively.

A vortex fiber with a new structure is designed to solve the problems of small numbers, low orders, and poor transmission quality of the orbital angular momentum modes supported by the general vortex fiber. On the basis of the fabrication of the amethyst-doped tube ring and quartz tube ring, the fiber improves the air filling rate through the nested structure of tube rings. The designed vortex fiber is modeled by the software COMSOL Multiphysics based on the finite element method, and the transmission characteristic parameters are analyzed and calculated. The results reveal that the vortex fiber stably supports certain orders of orbital angular momentum modes in different incident light bands in a "jumping" manner. In the wavelength range of 1500–1600 nm, it can support 44 higher-order orbital angular momentum modes for stable transmission, including the 31st-order mode. Moreover, the detailed analysis of the 44 higher-order modes demonstrates that the effective refractive index difference remains in the order of magnitude of 10-3, the dispersion is relatively flat, the dispersion variation is less than 4.2 ps?km-1?nm-1, the mode purity is greater than 94.5%, the minimum effective mode field area is 122.78 μm2, the maximum nonlinear coefficient is 0.89 km-1·W-1, and the confinement loss is maintained in the order of magnitude between 10-13 dB?m-1 and 10-8 dB?m-1. When the bending radius is greater than 8 mm, the bending has no effect on the number of orbital angular momentum modes that the fiber can support. When the bending radius is less than 8 mm, the number of supported modes decreases as the bending radius decreases.

In the optical fiber transmission system, various physical damage effects seriously affect transmission performance. Therefore, it is necessary to monitor the optical performance of the transmission signals to ensure the normal operation of the high-speed optical transmission network. A multi-task optical performance monitoring scheme based on convolutional neural networks (CNNs) is proposed. The intensity profile and intensity fluctuation features are used as the input of the CNN model for the joint monitoring of the modulation format and optical signal-to-noise ratio (OSNR). The results indicate that all the modulation formats (28-GBaud PDM-QPSK/-8QAM/-16QAM/-32QAM/-64QAM) can be accurately identified (identification accuracy is 100%) under OSNR corresponding to the threshold condition of 20% forward error correction (FEC) (bit error rate is 2.4×10-2). When the intensity profile, the intensity fluctuation, and combination of the two features are used as the model input separately, the mean absolute error of OSNR monitoring is 0.282 dB, 0.245 dB, and 0.165 dB, respectively, and the root mean square error is 0.352 dB, 0.311 dB, and 0.218 dB, respectively. Subsequently, the influence of residual dispersion on the monitoring performance of the proposed scheme is further analyzed.

Optical synthetic aperture is a feasible method for high angular resolution imaging. Due to the existence of multiple apertures, the co-phasing error of the aperture surface caused by vibration reduces imaging quality. Based on the existing imaging principle of optical synthetic apertures, a model for the effect of vibration on the point spread function (PSF) is designed by using an optical synthetic aperture structure, which couples the piston error and tilt error. The time-integrated Strehl ratio (TISR) is proposed, and compared with the traditional evaluation index, TISR can be used to analyze the influence of the coupling co-phasing error on PSF under the time-integrated effect. The results reveal that the PSF imaging performance declines significantly under the continuous effect of vibration, and the TISR curve shows obvious cyclical fluctuations under the time-integrated effect, which eventually converges over time.

This paper proposes a computational ghost imaging (CGI) denoising method based on mean filtering to reduce noise interference from complex environments and improve the imaging quality of CGI. With a 3×3 template mean filter as an example, the paper designs nine groups of Hadamard shifted speckles related to the mean filter, illuminates the measured object by these shifted speckles successively, and obtains corresponding results by a bucket detector. After performing a second-order correlation on the speckles and the sum of the nine groups of values by the bucket detector, the denoised image of the measured object can be obtained. The simulation and experimental results show that compared with traditional CGI, the proposed method has better performance in improving the imaging quality under the same Gaussian and salt and pepper noises. Furthermore, it has a positive denoising effect and can be well applied in varying complex environments. In addition, the proposed method introduces the concept of mean filtering in image denoising to ghost imaging and provides a new idea for applying the signal processing method in CGI.

The atmospheric polarization pattern provides an orientation reference for bionic polarized light navigation. Solar meridian bending can be observed in the distribution of the polarization angle in the atmospheric polarization pattern measured when a deviation angle occurs between the initial orientation of the transmission axis of the polarizer and the polarization reference axis of the camera in the measurement system for the atmospheric polarization pattern. To overcome the influence of the deviation angle on the measurement of the atmospheric polarization pattern, this paper presents a model of the deviation angle error and analyzes the influence of the deviation angle on the measurement accuracy of the atmospheric polarization pattern in detail. Then, it proposes a method of correcting the deviation angle by the characteristics of the atmospheric polarization pattern, that is, utilizing the neutral points and symmetry of the atmospheric polarization pattern to obtain the optimal symmetry axis for the distribution of the polarization angle and thereby correct the deviation angle. The experimental results show that the measurement accuracy of the atmospheric polarization pattern can be improved by correcting the deviation angle.

In low-energy X-ray imaging, fluorescence crosstalk is the most important factor affecting the spatial resolution of fiber-coupled high-resolution charge-coupled device (CCD)/complementary metal-oxide-semiconductor (CMOS) flat-panel detectors. In this paper, a high-resolution scintillation screen with a double-layer structure is proposed on the basis of the suppression effect of interface total reflection on fluorescence crosstalk. The two scintillation layers are coupled by a coupling medium with a small refractive index. The refractive index of the coupling medium can be adjusted to control the output angle of fluorescence on the interface between the upper scintillation screen and the coupling medium, thereby achieving the purpose of suppressing fluorescence crosstalk and improving the spatial resolution detected by scintillation screen. The simulation results based on the point spread function theory show that compared with the single-layer scintillation screen with the same thickness, the proposed scintillation screen with a double-layer structure can achieve higher spatial resolution. The experimental results of X-ray imaging further verify the effectiveness of the proposed scintillation screen in improving the spatial resolution of the detector.

This study is conducted to solve the problem of large measurement errors in the critical oscillation region by the surface light scattering method and explore the ways to apply this method to measure the viscosity of Newtonian fluids in the full viscosity range. To this end, we correct the instrumental broadening effect of small angles in surface light scattering and establish the frequency-domain dispersion equation of surface waves that can precisely describe the full viscosity range of Newtonian fluids considering the dissipation effect of the bulk phases of surface waves at the gas-liquid interface in the near-critical oscillation region. The discrete fast Fourier transform is adopted to transform the time-domain correlation data into the frequency-domain data. A multivariate frequency-domain-based fitting algorithm is developed to ensure the accurate determination of the viscosity and surface tension in any viscosity range and give the uncertainty of statistical significance. This study provides the absolute viscosity measurement theory, method, and system of surface light scattering for full-viscosity-range Newtonian fluids.

Considering the problem of the reduced fringe contrast and measured depth of field when the defocused projection of binary fringes is used to generate sinusoidal fringes for measurement, a structured light measurement method based on the focused projection of binary-coded fringes is proposed. Taking the intensity value of sinusoidal fringes in a single cycle as the law, the binary fringes are encoded, and the encoded binary fringes are processed in a specific way to generate sinusoidal phase-shift fringes that can be used for the actual measurement. Meanwhile, with the two-plus-one phase shift algorithm, the background gray image required for the measurement generated by the binary fringes is reused, which reduces the projection of a uniform plane pattern and improves the measurement speed and accuracy. The experimental results indicate that by taking the standard sphere as the research object, the proposed method can achieve a measured root-mean-square error of 0.0425 mm. When the projector is in focus all the time, binary fringes are employed for measurement, which can avoid the influence of nonlinearity, reduce the influence on the contrast of sinusoidal fringes and the measured depth of field, and yield high-precision reconstruction results.

An N×N optical switch array, which uses a 2×2 optofluidic switch as the switch unit, is proposed in this paper. This switch array adopts a waveguide structure and utilizes the microfluidic pneumatic actuation and piezoelectric ceramic valves to control the relative positions of gas and liquid in each microchannel and thus achieve the optical path selection and switching function. Meanwhile, two topologies of partial blocking and complete non-blocking optical N×N switch arrays are also presented. The optimal path and optical transmission characteristics of the N×N optical switch array are researched and discussed, and the structure is optimized. The research results reveal that the insertion loss and crosstalk are much lower than those of general optical switch arrays. For the wavelength of 1550 nm, the insertion loss of the 4×4 optical switch array is 0.28 dB-0.54 dB, and the maximum crosstalk is -43.5 dB--23.2 dB. This paper implements the optofluidic switch array and solves the common problems of large insertion loss and crosstalk in general optical switch arrays. Moreover, the proposed array has the advantages of good array controllability, negligible polarization-dependent loss, and a broad band (from visible light to near-infrared bands).

As a basic component of signal transmission and data exchange, the optical router is widely used in the on-chip optical interconnection network. The two-dimensional optical router can effectively reduce the complexity of the system and meet the routing requirements of on-chip optical interconnection networks with various topologies. Therefore, a small-size and low-loss two-dimensional optical router based on a single micro-ring resonator is proposed. The proposed scheme can realize two-dimensional routing switching by using only one micro-ring resonator. The two-dimensional optical router has a maximum crosstalk of -11.65 dB and a size of only 100 μm×65 μm. It has the advantages of simple structure and small size, and can be widely used in signal processing systems, communication systems, and interconnection systems.

This paper proposes and numerically studies a scheme of chaos generation in semiconductor lasers with random-digital-phase-modulated optical injection. The simulation results demonstrate that as the modulation rate or modulation depth increases, the laser state changes from injection-locking to chaotic through a quasi-periodic route due to the excitation of undamped relaxation oscillation by the phase change. Chaotic laser with an effective bandwidth over 10 GHz can be generated by random-digital-phase-modulated optical injection. Given the anti-interference capability of digital signals in long-distance transmission, the proposed scheme provides a new approach for long-distance chaos synchronization and key distribution.

Based on the metal organic chemical vapor deposition (MOCVD) technology, we designed a mid-wave infrared quantum cascade laser (QCL) with continuous-wave (CW) and watt-level output powers at room temperature. By optimizing MOCVD growth conditions, we obtained double-phonon resonance (DPR) materials with a high-quality interface and prepared a 4.6 μm QCL with a maximum CW output power of 1.21 W at room temperature. Furthermore, we specifically studied the performance of devices made of materials grown in 30-stage and 40-stage active regions and explored the effect of different active region stages on the device performance. Compared with that of the device in the 30-stage active region, the equivalent output power per unit area of the device in the 40-stage active region is not significantly improved. Instead, the 40-stage device performance drops rapidly as temperature increases, which can be attributed to outstanding heat accumulation and quality deterioration caused by thick epitaxial materials. Therefore, it is necessary to fully consider the balance among factors such as the number of active stages, heat accumulation, and material growth quality when the output power of QCL is improved by increasing the number of active region stages. MOCVD is a technology commonly used in the semiconductor material industry. This research is of great significance for promoting efficient production of QCL materials and expanding applications of QCL technologies in industries.

A broadband metamaterial absorber based on a resonant structure made of conductive plastic film is proposed. The absorber adopts a three-layer structure model of dielectric layer-film unit array-dielectric layer, in which the upper dielectric layer performs the functions of impedance matching and protection of the resistive film resonant structure. Compared with the resistive film structure based on conductive ink, the conductive plastic film adopted not only overcomes the influence of uneven ink thickness on sheet resistance during processing,but also is compatible with the laser etching process, resulting in higher processing accuracy of the resonant structure. The simulation results show that the proposed absorber can maintain an incident wave absorptivity of more than 90% in the frequency range of 6.9-22.7 GHz, with a relative absorption bandwidth of 106.8%. In addition, the proposed structure is insensitive to the polarization characteristics of incident waves, and it can still achieve efficient absorption of electromagnetic waves with wide incident angles in a wide frequency band. More importantly, its resistive film resonant structure and dielectric substrate can be processed independently. Not only saving preparation time, but also removing the restriction of resistive film processing on the choice of substrate material, such a building block type of processing scheme provides a new approach for the development of broadband metamaterial absorbers.

In this paper, the ultrafast transient nonlinear optical response and broadband dynamics mechanisms of carriers based on Fe defects in Fe-doped gallium nitride (GaN∶Fe) crystals were investigated with multi-dimensional pump-probe techniques. The results of the phase object (PO) pump-probe experiment show that the refraction dynamics curve of the carriers exhibits an obvious recovery compared with their absorption curve, and the recovery is due to the broadband absorption of Fe defect states according to the ultrafast transient absorption spectroscopy experiment. Furthermore, both the transient absorption response and the carrier trapping rate can be tuned over a wide range by the Fe content, and the absorption amplitude enlarges and the lifetime of trapped carriers shortens as the Fe content increases. On the basis of the transient optical nonlinearity results, this paper proposes an excitation and trapping model based on the different charge states of the Fe defects. The carrier trapping mechanisms in GaN∶Fe and the important parameters of Fe defect-related trapping rate and optical absorption cross-section are obtained by global analysis and rate equations. The tunable carrier lifetime and ultra-broadband absorption spectra in GaN∶Fe are of great significance for the design and development of optoelectronic devices, such as optical switches, optical limiters, and optoelectronic detectors.

The Laguerre-Gaussian rotating cavity system is a special device for obtaining optomechanically induced transparency (OMIT). This paper further proposes performing nonlinear coupling and orbital angular momentum (OAM) exchange in this cavity to achieve the modulation for the third-order Kerr nonlinear effect. The analytical expressions of Kerr nonlinearities are obtained with the Hamiltonian model of the system. Numerical simulation reveals that when the system is modulated to be in the vicinity of the OMIT windows, the OAM-carrying optical field undergoes slight absorption and intense dispersion, which leads to the generation of giant Kerr nonlinear effects. In contrast to the conventional electromagnetically induced transparency (EIT) and OMIT, the proposed system can be modulated by OAM and other parameters to achieve giant Kerr nonlinearities. In addition, the orbital angular quantum number can also be used to control the group velocity of light propagation and achieve fast- and slow-light effects.

The nonlinear absorption properties of eosin Y (EY), zinc phthalocyanine (ZnPc), and EY/ZnPc composite films are investigated by the Z-scan technique using laser with a pulse energy of 130 μJ, a pulse width of 4 ns, and a wavelength of 532 nm. The experimental results show that EY has intense saturable absorption (SA) while ZnPc has strong reverse saturable absorption (RSA). The absorption properties enhance with the rising mass concentration, and both EY and ZnPc exhibit good stability in repeated tests. EY/ZnPc composite polyvinyl alcohol (PVA) films possess both SA and RSA characteristics. The transmittance of composite films can be adjusted by the mass fraction ratio change of EY and ZnPc. Moreover, the nonlinear absorption coefficient of the material can be adjusted, and the "addition" of material limiting properties is achieved. The composite materials can be used in new types of optical devices, such as optical limiters and optical switches.

In terms of the problems of the traditional rigid industrial endoscope, such as small monitoring field, low resolution, and short working distance in the furnace, a high-definition industrial endoscope with large optical format and long working distance is designed. The integrated design is adopted, and it includes an image telecentric objective system with wide angle and a symmetric aberration elimination relay system with the rod lens. The high-definition industrial endoscope is designed as follows. Its optical F-number is 6, the field of view is 103°, the optical length is 1040 mm, the optical outside diameter is not more than 26 mm, the target diagonal is 16 mm, the system image telecentricity is not more than 1.8° and the modulation transfer function is not more than 0.2@160 lp/mm. Experimental results show that the designed industrial endoscope can obtain a clear image in the range from 40 cm to infinity and can resolve the line pair width of 10 mm at a distance of 5 m, with an angular resolution of 8.73 C/(°). The endoscope has advantages in view of design. Specifically, its receiver target surface is large, and the object resolution is high. The symmetric aberration elimination relay system with the rod lens has good ductility and high luminous flux. Objects and images are connected in telecentric form, with smooth light transmission and uniform illumination on the image surface.

To study the polarization characteristics of light reflection from coated surfaces, this paper proposed a modeling method based on the Monte Carlo method for the polarized bidirectional reflectance distribution function (PBRDF). Specifically, Fourier transform was performed for the three-dimensional reconstruction of a coating-substrate double-layer rough surface. Then, the microfacet theory and the Fresnel equation were employed to solve the processes of stochastic reflection and refraction from a single facet, and the process of polarized light scattering on the reconstructed surface was statistically summated by the polarization ray tracing technique and the Monte Carlo method to obtain the PBRDF of the coated surface. Experimental results show that the PBRDF built by the proposed method is correct and the proposed model outperforms the existing models in accuracy. Finally, the effects of the incident angle, surface roughness, substrate material, and optical thickness of the coating on the polarization characteristics of light reflection from the coated surface are analyzed to provide a theoretical basis for the detection and measurement of coated surfaces.

Optoelectronic oscillator (OEO), a microwave signal source, is a popular research topic in microwave photonics. A quintuple OEO with tunable frequency and phase is proposed and theoretically analyzed, which is based on the stimulated Brillouin scattering (SBS) effect and carrier phase-shifted single-sideband modulation. In this structure, a cascade modulator structure is used to generate five lights with the same power and frequency interval as the pump lights, and then the quintuple OEO is obtained by the Brillouin gain-loss compensation principle. The frequency-tunable microwave signal is obtained by using the Brillouin wavelength-dependent property, and phase-tunable output microwave signal is obtained by adjusting the dual-parallel Mach-Zehnder modulator. The designed OEO can output high-frequency microwave signals with a frequency tuning range of 44.00-47.25 GHz, and on this basis, it can achieve a tunable phase range of 0°-360°.

The cylindrical vector vortex beam presents a cylindrically symmetrical polarization state distribution and has a helical phase wavefront, which can be described by a hybrid-order Poincaré sphere. In this paper, based on the deduction of Jones matrix, we propose and demonstrate a method for generating arbitrary cylindrical vector vortex beams on a hybrid-order Poincaré sphere using vortex half-wave plates. By using the combination of vortex half-wave plate, half-wave plate, and quarter-wave plate, it is feasible to generate cylindrical vector vortex beams at different positions on the hybrid-order Poincaré sphere. The range of orders of hybrid-order Poincaré sphere beams can be further expanded by cascading multiple vortex half-wave plates. In experiments, we have measured the polarization state distribution of various beams at different positions on the hybrid-order Poincaré sphere, and verified their polarization order and topological charge. This simple and flexible method can realize the independent manipulation of topological charge and polarization order, and has potential value for applications including optical micro-manipulation, optical detection and sensing, and design of novel vector vortex laser sources.

This paper investigates the tight focusing properties of the partially coherent radially polarized rotationally-symmetric power-exponent-phase vortex (RPEPV) beam, namely, the radially polarized multi-Gaussian Schell-model RPEPV beam. Specifically, a theoretical model of the partially coherent radially polarized RPEPV beam is built. The Richards-Wolf vectorial diffraction integral theory is applied to study the tight focusing model of the partially coherent radially polarized RPEPV beam passing through a high numerical aperture objective, and the cross-spectral density function of the beam at the focal plane is deduced. Then, the distribution characteristics of the spot intensity, coherence degree, and polarization degree of the focused field are numerically analyzed. The research results show that the parameters, such as beam order, topological charge, power exponent, and coherence width, can be changed to obtain various focal spot distributions, including Gaussian, flat-topped, and polygonal distributions.

A high-resolution scheme for identifying amino acid species on the basis of the quantum weak measurement system is proposed and experimentally demonstrated, and the improvement laws of resolution are explored. In this system, the optical rotation angle of the amino acid solution is taken as the post-selection angle, and the amplified optical spin Hall shifts act as a probe to identify the amino acid species. The resolution of the system for the optical rotation angle can be improved by incident angle adjustment. The proper design of the BK7-dielectric structure interface can make the resolution reach 9.7×10-6 (°)/μm, with an improvement of two orders of magnitude over that of the pure BK7 glass interface. These studies can provide a theoretical basis for the high-precision identification of the amino acid species and expand the application range of quantum weak measurement.

Compared with traditional Raman spectroscopy, ultra-violet (UV) Raman spectroscopy has been used in many fields, with many advantages such as high sensitivity, solar blindness, and high safety for human eyes. When a 266 nm UV laser is used as the light source, the Raman spectrum and fluorescence spectrum may partially overlap, which affects the accurate acquisition of Raman spectrum characteristics. Considering this problem, the morphology and polynomial fitting algorithms are combined to subtract the fluorescence backgrounds of UV Raman spectra. This method integrates the morphology that preserves the spectral features and the simple and effective polynomial fitting algorithm to realize accurate subtraction of fluorescence backgrounds in UV Raman spectra. To verify the effectiveness of the method, we perform baseline corrections on the simulated spectra of four different backgrounds and compare this method with the traditional methods. The results reveal that the proposed method has obvious advantages in accuracy and obtains a better baseline correction effect compared with existing baseline correction algorithms. Furthermore, this method is used to perform baseline corrections on the measured spectra of potassium nitrate samples with different substrates obtained by the UV Raman spectroscopy setup. The results indicate that this method can obtain pure Raman spectra for different substrate backgrounds, which can provide more accurate spectral information for subsequent spectral analysis.

In order to predict the content of iron oxide in soil accurately and quickly, 135 soil samples are collected from the southern edge of Lufeng Dinosaur Valley, and soil spectral data and iron oxide content are measured in the laboratory. The original spectrum is smoothed by the Savitzky-Golay filter, and then conventional spectral transform and continuous wavelet transform are performed. The correlation coefficient (CC) method is used to analyze the correlation between the transform spectrum and iron oxide content. The wavelengths that pass the 0.01 significance test in each scale are selected as the coarse wavelengths, and the wavelengths selected by the competitive adaptive reweighted sampling (CARS) are further used as the characteristic wavelengths. Finally, the support vector regression (SVR) optimized by the genetic algorithm is used for modeling. The results reveal that continuous wavelet transform can improve the correlation between the soil spectral reflectance and iron oxide content. The number of independent variables for modeling can be effectively reduced by the CC-CARS wavelength selection method. The model constructed by the fourth-scale continuous wavelet decomposition (L4-CC-CARS-SVR) has the best effect. The coefficient of determination R2 and root-mean-square error ERMSE of its calibration set is 0.760 and 5.236 g·kg-1,respectively. The R2, ERMSE and performance to interquartile range ratio RPIQ of its validation set is 0.663, 7.798 g·kg-1 and 2.598, respectively, which indicates that the model has good stability and predictive ability.

In order to check the accuracy of color calculation and correction based on CIE1931 2° color matching functions (CMFs) in the existing chromaticity management system, this paper selected an LED panel with three channels (636 nm, 524 nm, and 452 nm) as the target device to display five colors (gray, red, yellow, green, and blue) recommended by CIE and took an LED panel with six channels (672 nm, 636 nm, 524 nm, 508 nm, 472 nm, and 452 nm) for comparison. In total, there were eight primary sets. Furthermore, the paper calculated and adjusted the target color and compared color by CIE1931 2° CMFs to make them have similar XYZ chromaticity values, and forty color samples were obtained. In addition, forty observers with normal color vision were organized for color difference evaluation under fields of view (FOV) of 2.9° and 8.6°, respectively, and then 6400 groups of visual color difference data were collected in the experiments. The results indicate that when the compared color and the reference color stimuli are L1 (the same as the primary set used in the reference panel) and L2 primary sets (with the shift of red primary), CIE1931 2° CMFs are applicable for calculation while in other sets, they work poorly. As the FOV increases, the visual color difference from different FOVs is insignificant.

The rod-anode X-ray source can stick into an object for nondestructive inspection, which is preferred for reliability inspection of the metal tube wall parts with of small cavity. A focusing system with a good electron-optical design is one of the keys to the high-resolution inspection of rod-anode X-ray sources. The focusing system is modeled in terms of the electron-optical theory and the structural characteristics of the rod-anode X-ray source. The electron-optical parameters of this model are then optimized, and the prototype is built for the resolution tests. Both the simulation and experimental results indicate that the resolution of the prototype is better than 50 μm under the acceleration voltage of 50-130 kV.