Showing papers in "Optical Technique in 2009"

Color edge detection based on HSI color space

Abstract: Because it is difficulty to evaluate the similarity of two colors from their distance in RGB color space,color image processing is implemented in Hue Saturation Intensity(HSI) space which reflects the features of human vision.A new method of color distance measurement is presented.A novel color edge detection method is designed.The edge information of hue,saturation and intensity are calculated,and the color edge information is obtained combining the component edge information.The color edge detection is accomplished by non-max suppression and thresholding selection.Experimental results show that the proposed color edge detection method utilizes the hue,saturation and intensity information adequately,and the color edge can be detected effectively.

Image reconstruction for CT based on compressed sensing and ART

Abstract: Algebraic reconstruction technique(ART) is an important method for the image reconstruction of computed tomography(CT),which can recover the image from incomplete projection data.However,ART suffers slow reconstruction speed.An algorithm based on ART is proposed to improve the quality of the recovered image and the speed of reconstruction,making use of the theory of compressed sensing.The algorithm,which combines the gradient sparsity of CT images and ART,performs the projection on the corresponding hyperplane in each iteration, and then adjusts the total variation with the gradient descend method to reduce the l1 norm of the image gradient.The experimental results show the effectiveness of the algorithm.

Research of contrast sensitivity characteristics and model of human vision system

Abstract: The characteristics of human vision system(HVS) are the basis for image technology of displaying,processing and understanding.Studying the visual characteristics through experimental test and theoretical analysis to cause the visual characteristics simulation promotes the development and application of photoelectricity imagery technology.In this measurement,goal gratings are displayed on CRT monitor.Contrast sensitivity to luminance gratings with three kinds of average brightness under the dark environment is measured.According to the experience of former fitting CSFs and distilling mathematical model theoretically, CSFs of three kinds of average brightness are fitted and a new CSF mathematical model are put forward with the exponential form of the linear modulation function.Comparing the results with ones fitted by Nadenau,it shows that this model of human vision sensitivity characteristics is better.

The development and analysis of target detection research based on polarization imaging technology

Abstract: The physical characteristic of target detection based on polarization imaging technology is introduced.Application advantages of polarization imaging technology are outlined.The domestic development of target detection research based on polarization imaging technology is concisely summarized and some problems are pointed out.Then the main achievements in this domain for other countries are specified.The research progress is summed up,some issues are put forward and the prospect in this field is predicted.

An algorithm of digital image encryption based on Arnold transformation

Abstract: A digital image encryption algorithm is presented based on Arnold transformation.The traditional Arnold transformation is improved by adding two parameters a and b,furthermore the Logistic map is used to generate the parameter sequences.The digital image is blocked and the Arnold transformation with different parameters is carried out on each image block of the digital image,thus image location scrambling is achieved.In addition the Arnold transformation is extended to multi-dimensional then used on the image gray scrambling,so as to construct an algorithm combine both the position scrambling and the gray scrambling. The results of simulation show that this algorithm can achieve good image encryption effect.And it has a large key space,key sensitivity and many other advantages such as withstand statistical and known expressly attack.It basically meets the effectiveness and security requirements of image encryption.

Mathematical modeling and software design for screen performance measuring system

Abstract: The Screen Performance Measuring System is mainly for studying a larger screen target and intensity of target to provide the necessary data and theoretical basis.A testing equipment for detecting screen's light distribution(light intensity,consistency,uniformity) is developed,such as screen target and intensity of target.The setting of screen light energy mathematical model and screen performance Measuring software is an important part.In order to achieve their functions,using Visual C + + 6.0 development tool,the collection and processing of the energy distribution are achieved.The system design process from the mathematical modeling and software design is introduced.The testing results show that they are consistent with theoretical analysis of the light energy formula,the quality and level of the Screen Performance Measuring System are improved.

Progress of beam control based on metal surface plasmon polaritons

Abstract: Surface plasmon polaritons(SPPs) is a kind of electromagnetic oscillation coupled with the undulation of charge intensity,which is excited at the interface between metal and dielectric.With the properties of near-field enhancement,surface confinement and short wavelength,SPPs play an important role in nanophotonics.Recently the researches of surface plasmon optics and nano-photonic devices based on SPPs have drawn great attention of international scientists.The principles of SPPs and their optical properties in subwavelength structures are discussed.The applications of SPPs based on subwavelength metal structures in beaming,focusing,guiding and control of near-field beam are introduced, and the potential applications in nano-photonic devices are reviewed.

New algorithm for image de-noising using node threshold wavelet packet transform

Abstract: Wavelet packet transform,which is derived from wavelet transform,can be considered as a linear combination of general wavelet functions and has flexible time-frequency analysis ability.With decomposition level increases,wavelet packet decomposition can focus in range of all frequency.A new algorithm is proposed for image de-noising using node threshold wavelet packet transform.Wavelet packet transform is used for noisy image decomposition.This method operates threshold at sub-band of image signal,uses soft threshold to deal with wavelet packet transform coefficients with different thresholds,and spectral entropy method is applied to estimate the node noise.Finally,the quality of image after de-noising is evaluated using PSNR(Point Signal Noise Ratio).Experiments show that this algorithm has better image de-noising performance,compared with algorithms for wavelet packet image de-noising using other threshold methods.

An improved wavelet thresholding method for image denoising

Abstract: A new thresholding function is proposed,which has the similar function with the traditional thresholding function except high-order derivative.It is continuous at the threshold compared with the hard thresholding function and it can reduce constant bias between the original wavelet coefficient and the estimated wavelet coefficients compared with the soft thresholding function,so the new function can remain the image edges better.Translation-invariant wavelet transform and the new thresholding function can give a new method for removing the Gaussian white noise.The result of the experiment shows the excellent performance of the proposed method.

One method for mirror surface figure treatment in optical instrument

Abstract: The distortion of optical mirror surface includes rigid-body motion and aberration.The aberration is main factor which affects image quality.A new theory mirror surface is built by coordinate transformation.Deformation mirror surface is fit by theory mirror surface.The RMS value and PV value of aberration are calculated using axial direction difference which comes from fitting and deformation mirror surface.The numerical result shows that the algorithms has high accuracy and can be well used in paraboloid and sphere mirror surface figure accuracy analyse when mirror in support and clamping condition.

Orthogonal experiment and analysis on polishing parameters of bonnet polishing

Abstract: For the plane optical work-pieces,the influence to the removal efficiency and surface roughness by the processing parameters,such as the bonnet decrement,rotational speed of the bonnet,puffed pressure,concentration of polishing fluid and the work's radius of curvature is discussed and analyzed according to bonnet polishing mechanism and material removal mechanism.Synthesized with the fore-parameters,the optimized technological parameter for bonnet polishing optical glass is got.By the experiments integrated process parameters,it is shown that the ultra-precision surface texture can be obtained by the bonnet polishing method.This research establishes the foundation for bonnet polishing technology in optical machining field.

Progress of high dynamic range liquid crystal display based on LED backlight with area control technology

Abstract: The unceasing flat light source is used in the conventional Liquid Crystal Display(LCD) as the backlight,the dynamic contrast ratio of LCD is limited due to light leakageThe implementation of High Dynamic Range(HDR) LCD is introduced based on LED backlight with area control technology,which can not only acquire high contrast ratio and large color gamut but also save power efficientlyAccording to practical algorithm flow,there are three important aspects described individually: driving value of LED,distribution of backlight and compensation of LCD panelThe development of display device is summarized based on LED backlight

The research on the fast photograph system with two sequence laser sparking

Abstract: The fast photograph system with two sequence laser sparking source is supposed the first timeDuring the exposure time of the CCD camera,the laser source sparked twice in sequence to emit ultra-short pulsed laser and the two images of the moving object at two different positions is captured in one image frame so one photograph station achieved the function of the two photograph stationsThis technology has great application values in modern ballistic measurement

Defects on-line detection of tire textures based on statistical features

Abstract: According to the abnormality of gray mean and gray distribution of defect region in tire X-ray texture images,an approach based on analysis of statistical features is proposed to implement on-line detection of texture defects.Based on the gray distribution model of tire X-ray texture,the background noise of image is eliminated by normalization preprocessing.Image is divided into blocks,and then gray mean and variance of each block are computed.The mean image and variance images are formed by bilinear interpolation operation.At last,defect detection is achieved by binary processing of mean image and variance image.Compared to traditional manual detecting,experimental results show that lower rate of mis-detection,higher precision and speed are achieved by this method to meet the demand of on-line detection.

Image segmentation of cucumbers based on color and textural features

Abstract: For the cucumber harvesting robot,the recognition is the important steps.First of all,segmentation of cucumber image is required.A new segmentation method combined with color features and texture features is presented.Based on CIE-XYZ photo of chroma,the irrelevant object is filtered,entropy and energy which can distinguish the fruit and the background are got by using of the gray level co-occurrence matrix.Integrating the color and texture features,the recognition problem with little difference between the target and the background is solved.

Study of effect of temperature change on the image shifting of the optical system in star sensor

Abstract: The temperature change of the optical system causes the image shifting.First,the optical materials of the drawtube and lens are determined by lens material characteristic formula,and the study shows that it is better to choose aluminum alloys and bigger ψ as the materials of the drawtube and lens respectively.The above conclusion is further validated by the I-DEAS software.Based on this,according to the matrix optics theory,the star sensor's image shifting formula is deduced for the change of temperature of the system.The image shifting of a special optical system in star sensor is calculated by the formula.The results show image shifting increases with the increase in the temperature difference when the uniform temperature distribution state of the system changes to another one.The 4th to 6th lens cause much more effects on the precision of the star sensor than another lens,and the image shifting decreases obviously on thermal compensation.

Illuminative uniformity design of a LED illumination system

Abstract: With the increasing of emission intensity of high power LED,illumination system with a single LED light source can meet requirements in many fields.The illumination uniformity of such kind of illumination system with a single LED light source is studied.According to nonimaging reflector design method,a method of designing surface profile of the reflector which can let irradiance of the desired area on the target plane be constant is presented.A differential equation is established with this method based on the radiance distribution function of the target plane,and the function of surface profile of the reflector is obtained by solving the differential equation.Model of the illumination system is constructed by rays tracing with ASAP software.Illumination uniformity of the system is obtained,and data of the surface profile for NC manufacture is obtained finally.

Study of NEA GaN photocathode surface model

Abstract: Aimming at the problem that the forming process of the surface state after Cs activation or Cs/O activation is still unknown during NEA GaN photocathode study at present,encircling the photoemission mechanism of NEA GaN photocathode,combining the experiment phenomena during the activation and the successful activation results,the GaN photocathode surface model [GaN(Mg):Cs]:O-Cs after activation with cesium and oxygen is given.Using this model,the reasons that about-1.0 eV effective electron affinity can be achieved after activation only with Cs and about-1.2 eV effective electron affinity can be achieved after activation with Cs/O can be explained well.The surface atom formation can also be explained well,namely the chemical construction of dipole layer after Cs/O activation should be formed by Cs2O2 and CsO2.

Aberrations effect on position accuracy of star sensor

Abstract: Position accuracy of star is an important parameter of star sensor's performance,and it is restricted by the aberrations of the optical system.A new compensatory scheme of aberrations' effects is described in optical systems of star sensors.The star position errors,which are caused by aberrations,are calculated in an optical system of middle-accuracy star sensor.And a star position compensatory scheme is proposed.The results show that the star position errors,which are caused by aberrations,are important in high-accuracy star sensor, such as arcsecond level.And after implementing the star position error compensation scheme,the error components are reduced to 0.38″,0.38″,5.77″ about the X,Y,Z axes respectively,which are about 1/17 of the original.

Fast calibration method for a 3D shape measurement system based on 2D color images

Abstract: System calibration is one of the key technologies for optical 3D shape measurement system based on structured illumination,and it is always complicated and time-consuming.A fast calibration method is proposed based on the color images.This method projects a color chessboard pattern(white and magenta) onto a color chessboard plane(blue and red).The former occupies the green channel of the captured image and it only needs one captured color image at each position to simultaneously calibrate the camera and the projector.Compared with the traditional methods,it has a simple process and an equivalent calibration accuracy. It needs less data to calibrate the system just like the binocular stereo vision needs.A 3D shape measurement system has been calibrated by this method and a plane and a semi-cylinder are measured.In the measurement results,the maximum distance between the points and the polynomial surface is 0.8039mm and the average error is 0.1693mm.The reconstructed shape of semi-cylinder is almost the same as that of the traditional method.Experiments show that this calibration method is practicable and the calibration process is fast.

Laser velocimetry for vehicle based on Janus configuration

Abstract: The error of laser velocimetry system for single beam is analyzed as vehicle's pitching and rolling,and a system based on Janus configuration which is composed of a couple of reference beam system is presented.it is mounted at vehicle's bottom side and transmits laser beam toward the ground in direction of the head and stern of vehicle respectively.Simultaneously the Doppler frequencies in scattered echo signals are detected and vehicle's pitch angle is calculated by Doppler frequencies and inclination angle,and then vehicle's velocity is obtained.Theoretical analysis and simulations indicate that the precision of single beam system is much affected by transmitted inclination angle,pitch angle and the roll velocity.Whereas the Janus system is susceptible to the error by vehicle's pitch and roll,and be able to get the higher precision of speed measurement.The error is lower than 0.5% when roll velocity is 0.3m/s and pitch angle is 16°.

Analysis of active laser detection distance for "cat's eye" target

Abstract: The principle of the active laser detection for electro-optic sensor is based on the cat's eye effect of optical system.Distance is one of the most important parameter for active laser detection system.The mathematical model of maximal detection distance is given by the analysis of several factors including the angle of transmit laser beam,CCD sensitivity and atmospheric visibility,which are the main factors affecting the maximal detection distance.The analysis results show that the maximal detection distance increases with the decrease of laser angle and the advance of CCD sensitivity and the enhancement of atmospheric visibility.

A new method of convex aspheric surface compensation tests

Abstract: The testing of convex aspheric surface is really a trouble in the area of optical test.Based on analyzing several traditional methods,a new method of convex aspheric surface using lens for compensational tests is discussed with the diameter of 110mm lens in details.Assuming the spherical aberration coefficient ∑S1=0,the initial configuration of the optical system is solved based on the third-order aberration theory,and optimize it by Zemax optical design software.The result shows that the system aberration is well revised and the precision of the testing is really high.

Error analysis on the linear CCD crossing measurement system

Abstract: The spatial coordinates error distributed over all the linear CCD target is analyzed by Matlab when the image processing precision is ±0.5 pixel,based on the new error analysis model of the linear CCD crossing measurement system.The spatial coordinates of the vertically indicating steel ball is measured by the linear CCD crossing measurement system in which the distance of the two linear CCD cameras is 1664mm.The experiments results show that the error of Z coordinate is about 0.5mm and the error of Y coordinate is about 0.8mm,which is consistent well with the theory analysis result.The error of Z coordinate is not more than 0.5mm and the error of Y coordinate is not more than 1.1mm.

Analysis of the object detection and survey system based on the fish-eye lens

Abstract: A novel object detection and survey system is designed based on the fish-eyes lens which has an ultra wide range.The fish-eye lens and CCD is used as the image gathering system,the high speed DSP is as the control and processing center.The system uses the algorithm of auto-adapted renewal background subtraction to pick-up the moving object from the image,and uses the algorithm of image processing to survey the azimuth.The experiment indicates that the system has high monitoring ability under each kind of environment.The dynamic background subtraction method has the strong anti-jamming and can distinguish the object accurately,as well as calculates the parameter like azimuth.Compared with the traditional system,this system has wide monitoring space,simple structure and can work stably and reliably.It has widespread application in each safe monitoring domain.

Multi-level interactive image enhancement algorithm based on fuzzy relaxation iterative procedure

Abstract: The study of mapping function is the key of image enhancement algorithms,such as fuzzy relaxation technique establishes mapping function by using fuzzy function and iterative procedure,so the controlled image enhancement processing can be achieved by setting the feasible fuzzy relaxation parameters.In order to enhance different hierarchical image content at the same time and realize controllable image enhancement,multi-level interactive iterative fuzzy relaxation image enhancement algorithm is proposed.The fuzzy relaxation parameters of sub-level are chosen by analyzing the image histogram of sub-level.Fuzzy relaxation iterative function is established.Each sub-level image is enhanced with fuzzy relaxation iterative function,until when iterative processing reach suitable times and the results perform well.The experimental results demonstrate that this algorithm is feasible and valid and can receive better enhancement results in many situations.

Study on the optical properties of amorphous silicon film by simulated annealing algorithm

Abstract: A-Si:H film is deposited on glass by plasma enhanced chemical vapor deposition(PECVD).Transmission spectra of the film are measured by the UV-VIS-NIR spectrophotometer.Thickness,reflection index,absorption coefficient and optical band gap of the film are obtained by studying the transmission spectra using simulated annealing algorithm,the advantages of this method are discussed.

Designing of a novel quasi-static topology of LEO/MEO two-layered optical satellite network

Abstract: A novel two-layered optical satellite network of LEO/MEO with global coverage is designed,which has the quality of quasi-static connectivity of MESH.It satisfies the demand of ATP(acquisition,tracking and pointing)in optical satellite communication and simplifies processing,switching on board satellite,reducing routing overhead.Spacing position expressions of inter-satellite links between the same and different layers are deduced.Simulation results show ranges of distance,azimuth and elevation between two neighboring satellites are small.It's very fit for optical inter-satellite links and can be considered as the reference of building up future optical satellite networks.

Wind disturbance study on large astronomical telescopes

Abstract: Wind loading on mirrors and structures of large optical astronomical telescopes is inevitably to degrade figure accuracy of mirrors and to cause trancking and pointing error of the telescope.It is even more problematic for future giant telescopes that are potentially to implement segmented mirror active optics because wind loading will be the critical influencial issue for the control of the segment mirrors and will finally degrade the overall performance of the telescope.First reviewed are the nature of random wind and usually-used analysis methods of wind loading on large astronomical telescopes.Afterwards,discussed in detail is the analysis method based on Power Spectrum Density(PSD) of wind velocity from the Finite Element Method(FEM) point of view.To demonstrate the discussion,a telescope using segmented active optics is modeled to investigate its responses to both static and dynamic wind loading.Wind response of a segmented mirror is calculated before that performed on the overall telescope.The wind induced degradation of mirror figures is estimated,and further,the tracking and pointing accuracy are given.

Design of LED optical engine for micro-projection display of DMD

Abstract: A light uniformazing algorithm based on rectangular CPC is presented for micro-projection displayThe designed optical engine with rectangular CPC consists of LED,fly's-eye lens and micro-display panel DMDThe light uniformity on the micro-display panel and energy efficiency of the optical engine with rectangular CPC is analyzed by means of softwareExperimental results show that the proposed light uniformazing algorithm and system compared with other uniformazing light algorithm and system have advantages such as lesser capacity,lesser etendue,higher light uniformity more than 92% and higher energy efficiency of 43% to meet the needs of micro-projection display