High voltage equipment that runs for a long time could produce corona discharge phenomenon. The harm of corona discharge is serious, so it’s necessary to detect the corona. As a new technology of detecting high pressure discharge equipment fault, this article used ultraviolet discharge detection that can fuse to corona and visible light images and can locate fault point accurately. The article used the theory of projection pursuit in genetic algorithm, and used the collection of ultraviolet corona figure after processing of the Delphi software as a hierarchical data, and the level model of genetic projection pursuit was set up to study the quantitative classification of corona discharge strength. The experimental results verified the rationality of the model. Test results achieve the desired requirements, and have certain practical significance to discharge fault detection.群体智能与智能电网等。

A step-by-step asymptotic method of image corner detection is proposed in high speed vision detection for quantities of micro two-dimensional workpieces. In this method, the inherent geometric relationship in the single pixel contour is taken as a priori information, based on which, the region where corners exist is separated from full contour. After that, we select suitable algorithm to detect corners and get their positions accurately along with false corners being eliminated in time. Then, we can lock region again ... This process continues circularly, until all the corners have been detected. Experimental results show that, for the same workpiece, whose images are getting in different position and attitude, the standard deviation of distance between points is within 0.5 pixels. Compared with Harris corner detection algorithm and CSS corner detection algorithm, the proposed method is scarcely affected by foreign substance in the field. Due to the accuracy, high speed and high repeatability, this method has obvious advantage in high speed vision detection for quantities of micro two-dimensional workpieces.

Since glare is mixed with imaging rays, the measurement and the evaluation are always difficult research issues on physical optics. This paper describes the physical characteristics of glare by point spread function. Subsequently, a measurement method for scattering glare is proposed. Specifically, a computational processor before image formation is presented as two-arm system. The feedback subsystem is composed of digital micro-mirror device and charge-coupled device. The collection of images and modulation of glare rays is utilized by feedback subsystem to reconstruct the glare distribution. Finally, experimental results show the performance of the proposed approach. The proposed method provides the foundation to evaluate the scattering glare. In addition, the paper suggests a solving way of removing glare in visual measurement.

In microscopic measurement, the image inclination can distort the image. The traditional laser triangulation method is improved by using multi-light beam and a laser triangulation with multi-light spots was proposed to measure the inclination angle. Firstly, the laser beams expanded were separated by a double wedge, and formed four beams approximately parallel. Then, the four beams were projected to the plane mirror, and became four spots in CCD after reflected. The multi-light spot optics system could avoid the effects of translation because the distance between the four spots was only related to the inclination angle and not sensitive to the translation. By calculating the distance between four spots, the inclination angle could be compensated, therefore the image distortion was reduced. Experimental results show that the optical device, based on laser triangulation method with multi-light spot, could measure the inclination of microscopic image accurately and fast. It can be applied wildly, such as solid state nuclear track detectors, topography measurement and so on.

Light screen array is applied to measure firing dispersion in range, and the structure parameters of the array influences the measuring result directly. Based on double-V shaped six-light-screen array, the influence of the structure parameter, the angles of incidence and the impact location to the measurement accuracy of velocity and coordinates are analyzed, and then the error transfer formulas are deduced. The relations between the measurement accuracy of velocity and coordinates to each influence factors are simulated and plotted in MATLAB. The conclusion provided a reference for improving the measuring accuracy and optimizing the engineering design.

To measure the Modulation Transfer Function (MTF) based on the theory of frequency spectrum is one of methods to rapidly evaluate the image quality of near-to-eye display system. However, some parameters during the rapid measurement have an obvious impact on the experiment results. So eliminating and offsetting the dispersion are the mostly factors when the method can be applied to measurement successfully or not. Reasons that may cause the error during measurement are analyzed specifically, and then influence degree of errors and method of discriminating clarity are discussed. Analysis of the main errors affecting the measurement of Contrast Transfer Function (CTF) shows that error value is below 3% when the tilt angle is within ±0.5°, brightness of light changes in the range of 0.6I~I, (I is the maximum value when the CCD works in the linear region) and object length changes within 5 mm, and the errors are all less than 1.5%. The experiment results verify the feasibility and practicability of the method and have the instructive significance on improving measure precision.

For the measurement of five step phase shift optical interferometry, a new quality-guided map is proposed to be used in the region growing algorithm. Firstly, all the residues in the wrapped images are balanced based on the placement of the branch cuts. Then, the wrapped phase image is divided into some regions based on different quality values of the pixels, and the minimum quality value is assigned to pixels that belong to the branch cuts. The new quality-guided map is used to guide the region-growing unwrapping algorithm based on predictions from the highest quality values to the lowest. If the border area is overlapping, adjust the offset to merge. The proposed algorithm works fast and is robust against noise, as demonstrated in experimental and simulated data, compared with the traditional region-growing unwrapping algorithm based on predictions.

A dynamic measuring method for combining the laser light curtains and CCD is proposed to achieve a precise measurement of the vehicles outside dimensions. Rapidly acquisition image of the laser spot light curtain is modulated by vehicles height with CCD cameras mounted gantry vertex, and extract the vehicle distribution data of the edge based on region growing centroid matching algorithm to measure vehicle width. Secondly, a sequence of images with mosaic method is used to get the vehicle panoramic image, and pinpoint the front and rear of vehicle by panoramic image projected first-order differential, then depending on the camera perspective model to measure the length of the vehicle, combined with a width edge distribution data to correct the length accuracy. Obtain infrared light curtain vertically mounted projection data via FPGA processing system to measure vehicle height. The measurement method have the advantages of a space occupied by small, simple installation structure, strong anti-jamming capability and high accuracy measurements compared with traditional measurement methods of laser radar and infrared light curtain. The results of the outer contour of the vehicle size measuring test show that the measurement system error is <1% and the average time-consuming is lower than 50 s. Verify the accuracy and real time of this measurement method, and this measurement method is robust and important applications.

In order to measure the dynamic near infrared laser wavefront, a structure of oblique incidence of reflective shearing point diffraction interferometer is proposed. The point diffraction interferometer is integrated in flat substrate plated with special films. The coherent beams are reflected at the front and rear surfaces of the substrate respectively. The shear of the two beams introduces linear spatial carrier frequency to the point diffraction interferogram. The single shot interferogram is processed by Fourier transform method to retrieve the near infrared wavefront under test automatically. Experiment is carried on to test the transmitted wavefront of a F/10 lenses 1 313 nm wavelength and the result is in agreement with that obtained by Hartmann wavefront sensor. Image alignment method is studied that is used for quick pinhole alignment. As a result, the project can be applied to measure the dynamic near infrared wavefront.

We developed a broadband spectroscopic imaging ellipsometer, which is free of chromatic aberration, by using an all-reflective focusing optical structure with special polarization control. A calibration method by measuring multiple standard samples was employed in the system calibration procedure. By applying the obtained system calibration parameters, we can determine the test sample’s spatial distributions of ellipsometric angles ψ and σ, and the film thickness after the imaging ellipsometric analysis. To test the accuracy of our home-made imaging ellipsometer, we have measured the SiO2/Si samples with the thicknesses of 3 nm~300 nm at multiple wavelengths between 200 nm and 1 000 nm. The experimental result shows that the SiO2 film thickness can be determined within the maximum relative measurement error of 6%.

Terahertz (THz) absorber with dynamically tunable bandwidth possesses huge application value in the field of switches, sensors and THz detection. However, the perfect absorbers based on traditional metamaterials are not intelligent enough to capture the electromagnetic wave in a tunable way. We utilized monolayer graphene and cross-shaped metallic sub-wavelength structure to design broadband absorber with tunable absorption frequency in terahertz regime. The absorption frequency can be turned by changing the chemical potential of graphene which can be easily controlled by the bias voltage supplied to graphene. Simulation results show that 1.3 THz average bandwidth was achieved. And the almost perfect absorption shifted from 2.04 THz~3.53 THz to 3.15 THz~4.24 THz continuously.

Based on the special optical properties of the subwavelength grating, a fabrication method of thiol-ene subwavelength grating is presented. An elastic PDMS subwavelength grating was used as the imprint mold and thiol-ene was the imprint resist. Using the UV-curable soft-lithogaphy, thiol-ene subwavelength grating was fabricated, which included a PMMA film as the waveguide layer. The thiol-ene subwavelength grating with the period of 300 nm was stimulated and fabricated using this method. The experimental results show that the thiol-ene subwavelength grating could reflect the blue light with wavelength ranged from 448 nm～482 nm at a specific angle, which were consistent with the simulation results. The results indicate that the method proposed in this article could effectively fabricate the subwavelength grating structure. Furthermore, the method is simple, low-cost, and easy to high throughput, which has broad application prospects in the preparation of micro and nano structures.

We theoretically utilize bowtie aperture combined with the Metal-insulator-metal (MIM) scheme to obtain sub-30-nm (λ/12) high aspect plasmonic spot. The improvement of the depth profile is attributed to the asymmetry electromagnetic mode excitation in the metal-insulator-metal structure and the decaying compensation of the reflective metal layer. It is demonstrated that the depth profile of the 28 nm hot spot is more than 20 nm, which is about 4 times of the bowtie aperture without the MIM scheme. Futuremore, the spot of 47 nm diameter (FWHM) and 25 nm depth was achieved in photo-resist in the experiment, which demonstrated the advantages of the new structure on reducing the size and improving the depth profile of the spot.structure

A novel method is demonstrated to realize dynamical control of resonant response of terahertz metamaterials. The paper presents a type of structurally tunable terahertz meta-materials (SMM) which consists of double layer Split-ring Resonators (SRRs) with one flexible cantilever sitting along the gap. Based on the difference of expansion coefficient between the double materials (i.e. Al and SiO2), fine tuning of the cantilever angles can be conveniently adjusted by the temperature difference. By changing the radius of curvature of the cantilevers, we obtain a tunable terahertz band-stop filter with a wide tuning range about 0.32 THz. This tunable band-stop filter using deformation MMs shows its great potential in tunable metamaterials applications, such as sensors, switches, modulators and phase shifters.

Recently, light wave band biochemical sensors of single molecule detection are common to be seen. However, because of the light wave’s nano-scale length, the devices of small size are difficult to process and have poor sensing repeatability. Therefore, we proposed a terahertz (Terahertz, THz) sensor chip constituted of simple sub-wavelength metal block arrays. In theory, we established its sensing model based on Fabry-Perot (FP) resonance, combined with the analysis of the influence of the localized surface plasmon resonance of sub-wavelength metal structure of sensitivity in the Finite Element Method (FEM). Based on this, a large area and homogeneous structure was fabricated with the orthogonal lithography. The experimental result indicates that the resonance frequency shift 53 GHz for 0.025 mol/L D(+)-Glucose solution, which possess high sensitivity. Our works can provide theoretical guidance for the design of high sensitive terahertz sensor.

In order to simplify the optical structure of the encryption system and enhance the security, an encryption method based on diffraction imaging principle is proposed by using phase mask removal method. In the proposed optical encryption approach, three random phase masks are placed in the optical path, and a CCD camera in the output plane is used to record the diffraction intensity distribution as ciphertext. In encryption, one of the three random phase masks is removed at a time, and the other two masks are used for optical encryption. Accordingly, three diffraction intensity distributions are recorded in all. Decryption process uses digital method. The original image can be retrieved from the ciphertext and security keys by means of phase retrieval algorithm. The encryption could be achieved without any movement of the optical devices, and only intensity distributions are recorded as ciphertext, thereby facilitating the optical implementation. Simulation results show that the proposal can achieve gray image encryption, and have multiple encryption keys. As a result, high security is gained. Meanwhile, the proposed approach has the ability to resist noise attack and occlusion attack, which makes the proposal suitable for harsh transmission conditions.