An active stereo method for three-dimensional shape measurement is proposed. The proposed method uses epipolar constraint and binary coding structured light to perform dense and accurate stereo matching. The correspondence in horizontal directions is determined by epipolar constraint, and the binary code determines the correspondence in vertical directions. A high redundancy skeleton coding method is proposed to improve the decoding accuracy significantly. And the matching algorithm is achieved sub-pixel accuracy. The point cloud is calculated by triangulation. Spatial re-sampling based on the Delaunay triangulation and inverse distance weighting interpolation is implemented to get a uniform data density for a comfortable visualization. Compared with phase-shift methods, the proposed one is more robust. It preforms reliably even in noisy conditions. The experiment results are presented to demonstrate the effectiveness of the proposed method. The resolution is analyzed and verified by experiment. It achieves 1/1200 by two 2-megapixel cameras and can improve by increasing the image resolution. The robustness is also verified. The experiment demonstrated that our method has great immunity of three main type of noise in the phase-shift method.
A novel optical security technique for safeguarding user passwords based on an optical fractal synthesizer is proposed. A validating experiment has been carried out. In the proposed technique, a user password is protected by being converted to a fractal image. When a user sets up a new password, the password is transformed into a fractal pattern, and the fractal pattern is stored in authority. If the user is online-validated, his or her password is converted to a fractal pattern again to compare with the previous stored fractal pattern. The converting process is called the fractal encoding procedure, which consists of two steps. First, the password is nonlinearly transformed to get the parameters for the optical fractal synthesizer. Then the optical fractal synthesizer is operated to generate the output fractal image. The experimental result proves the validity of our method. The proposed technique bridges the gap between digital security systems and optical security systems and has many advantages, such as high security level, convenience, flexibility, hyper extensibility, etc. This provides an interesting optical security technique for the protection of digital passwords.
An optic-electronic hybrid certificate validation technique based on Fresnel encoding is proposed. A confirming experiment has been carried out. This technique consists of two processes: encoding and decoding. During the encoding process, an original image is encoded by a computer into an encoded image, which is subsequently printed on a certificate. During the decoding process, the encoded image is extracted from the certificate and decoded optically. The experimental result proves the validity and reveals some advantages of our method. Compared with some previous works, more useful original information can be encoded in our method. The security level of our method is also enhanced by importing the Fresnel diffraction range z as another key. This paper also explores practical application of this technique.
In this paper, we propose a new encoding method to make a binary amplitude-based phase-only-encoded barcode in a
security system based on the conventional random phase encoding technique. In this method, the values of the phase
distribution in the system are quantified with a high phase level, and afterwards the result is encoded into a binary matrix
based on the rule of decimal-binary conversion. The binary matrix is arranged specially and printed as the 2-D anti-counterfeit
label which can be printed by standard halftoning technology and read by optical scanning device. It is
obvious that the higher phase level could be chosen to obtain the better reconstruction image in the improved method
and the fabrication is also very convenient. In additions, computer simulations and optical scanning experiments are
illustrated in detail. The tolerance to data loss of the encoded barcode is also studied particularly. The results show that
the presented encoding method has advantage of robustness and high security, and very convenient to be popularized in
This paper proposes the Fuzzy Control Iterative Algorithm (FCIA) for the design of diffractive optical elements for laser
beam shaping. Firstly, to improve the poor uniformity of output laser beam obtained by the G-S algorithm, we put
forward the Profile Smoothing Algorithm (PSA), which is effective in improving beam uniformity but slack in
controlling the Mean Square Error. Then we put forward the Fuzzy Control Iterative Algorithm, which combines PSA
and G-S algorithm by fuzzy control theory. Taking advantages of GS and PSA, FCIA can decrease both Mean Square
Error and nonuniformity of output beam simultaneously. Computer-designed result shows that an extremely ideal output
beam is derived by using FCIA. The Mean Square Error is 0.75%. The nonuniformity is 0.46%. And the energy
converting efficiency is up to 94.91%. This paper affords a novel algorithm for the design of diffractive optical elements
for laser beam shaping.
This paper presents a method for solving main problems in the multi-source data integration of land and sea including the inconsistent horizontal and vertical datum, the differences of data model and format and the discrepancy of a geographical feature derived from different data source,. Firstly, based on the transformation of horizontal coordinate and calibration of vertical datum, spatial data are reconciled. Secondly, DEM of digital coastal zone are established by the combination of topographic and bathymetric data from sampled soundings and simplified contours. Finally, the visualization and multi-scale representation of the DEM is realized. Experimental results demonstrate that the proposed method could seamlessly integrate multi-source land and sea data.
In the last 20 years, x-ray imaging technology has developed to meet the needs of x-ray photoetching, spatial exploration, high-energy physics, and diagnosis of inertial confinement fusion. Because conventional imaging methods are not suitable in the x-ray range, grazing reflective imaging and coded aperture imaging methods have been adopted. In this paper, we describe the design of a noncoaxial grazing incidence KBA microscope. The microscope consists of two sets of spherical mirrors that scatter in orthogonal planes. An optical ray tracing program is used to analyze and evaluate the theoretical aberrations of the microscope. This allows us to optimize the x-ray imaging system. The analytical results provide a reliable foundation for determining the useful range and the manufacturing and assembly tolerances of the microscope.
Minimally invasive surgery (MIS) has contributed significantly to patient care by reducing the morbidity associated with more invasive procedures. MIS procedures have become standard treatment for gallbladder disease and some abdominal malignancies. The imaging system has played a major role in the evolving field of minimally invasive surgery (MIS). The image need to have good resolution, large magnification, especially, the image need to have depth cue at the same time the image have no flicker and suit brightness. The video stereo-laparoscopy system can meet the demand of the doctors. This paper introduces the 3d video laparoscopy has those characteristic, field frequency: 100Hz, the depth space: 150mm, resolution: 10pl/mm. The work principle of the system is introduced in detail, and the optical system and time-division stereo-display system are described briefly in this paper. The system has focusing image lens, it can image on the CCD chip, the optical signal can change the video signal, and through A/D switch of the image processing system become the digital signal, then display the polarized image on the screen of the monitor through the liquid crystal shutters. The doctors with the polarized glasses can watch the 3D image without flicker of the tissue or organ. The 3D video laparoscope system has apply in the MIS field and praised by doctors. Contrast to the traditional 2D video laparoscopy system, it has some merit such as reducing the time of surgery, reducing the problem of surgery and the trained time.
In the latest 20 years, x-ray imaging technology has developed fast in order to meet the need of x-ray photo-etching, spatial exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) etc. But, Since refractive index of materials in the x-ray region is lower than 1, and x-ray is strongly absorbed by the materials, it is very difficult to image objects in the x ray region. Conventional imaging methods are hardly suitable to x-ray range. Generally, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. In this paper, non-coaxial grazing reflective imaging KB and KBA microscope systems are discussed in detail, and an x-ray microscope consisting of four mirrors working at grazing incidence is designed. It is an anastigmatic system, and the oblique angle of the image is evidently decreased. The resolution of 5-7 can be obtained within 2 field of view. And finally we also make analysis of the key problems that are met in the processing of manufacturing this system are analyzed.
The robustness and security of random phase encoding technique are analyzed. We study the tolerance to data loss of the decrypting key for binary text and a grayscale image. To enhance the security, an improved phase coding scheme based on the chaos theory is proposed. The proposed optical setups for image decryption are depicted. The analyses show that the improved scheme can effectively improved the security.
In the processing diagnosis of the inertia confinement fusion (ICF), the ring coded aperture imaging technique is applied in order to gain high space and time resolutions simultaneously. The key of acquiring high spatial resolution is how to obtain a point spread function of an imaging system. The common method is the firsthand projection method which is an approximate one. The x-ray diffraction effect is neglected in the method, so the resolution of reconstructed image is decreased. We have derived the point spread function (PSF) of the ring coded aperture from scalar diffraction theory. And the Wiener filter is fabricated on the basis of the PSF. In National Key Laboratory of Laser Fusion, at China Academy of Engineering Physics, the imaging experiment on the diagnosis of ICF is completed using the ring coded aperture plate with inner diameter <i>d</i><sub>1</sub> = 250μm and outer diameter <i>d</i><sub>2</sub> = 260μm .The obtained coded image is processed by the Wiener filter which diffractive effect is considered. The processed results have shown that resolution and modulation contrast of acquired image are evidently better than the results obtained by the firsthand projection method.
Stereo endoscope has played an important role in video 3-dimensional laparoscopy system. This paper presents the design principle of the stereo endoscope applying in minimal invasive surgery (MIS). Optical imaging technologies and instrument designs are discussed in relation to their current and future use in MIS procedures, then this paper analyses and compares three design methods of optical system, technical limitations in imaging technology are described along
with potential solutions. We put forward to a new optical design methods, namely, the system adopts two optical channels stereoscopic-imaging technique to replicate human binocular vision. A stereoscopic system for video endoscopes includes objective lens system, relay system, eyepiece system and the focused lens between eyepiece and
CCD. This paper present equal-angle pairs from symmetrically disposed object points to the system. This equal-angle property enables accurate object/image mapping onto the final stereo image pair. And the doctors can watch the true stereo image on the screen. This optical system has common characteristic compare to the common laparoscopy with long work distance-300mm and wide field-70 degree, as a result, the optical system have serious aberration related field, especially in distortion, the distortion can reduced from 15% to 5%.
In the latest 20 years, x-ray imaging technology has developed fast in order to meet the need of x-ray photo-etching, spatial exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) et al. Since refractive index of materials in the x-ray region is lower than 1, and x-ray is strongly absorbed by materials, it is very difficult to image objects in the x-ray region. Conventional imaging methods are hardly suitable to x-ray range. In general, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. In this paper, according to user’s requirement, we have designed a non-coaxial grazing KBA microscope. The microscope consists of two sets of perpendicular spherical mirrors, each set includes two parallel mirrors. Taking it as an example, we have compiled an optical computing program for the non-coaxial grazing imaging systems so as to analyze and evaluate aberrations of KBA microscope. Thus it can help us to get an optimal comprehension of KBA x-ray imaging system. In the same time, the analytical results provide reliable foundation for evaluating imaging quality of KBA microscope.
An improved chaotic algorithm for image encryption on the basis of conventional chaotic encryption algorithm is proposed. Two keys are presented in our technique. One is called private key, which is fixed and protected in the system. The other is named assistant key, which is public and transferred with the encrypted image together. For different original image, different assistant key should be chosen so that one could get different encrypted key. The updated encryption algorithm not only can resist a known-plaintext attack, but also offers an effective solution for key management. The analyses and the computer simulations show that the security is improved greatly, and can be easily realized with hardware.
The light deflector is one of the key components in laser scanning and imaging system, such as rotating holographic gratings, galvanometric mirrors, acoustooptical scanners and rotating polygonal scanners, etc. Of these scanning elements the most commonly used scanner is rotating polygonal scanner. This paper will first briefly discuss the operating principle of rotating polygon and two different polygon scanning configurations: a post-objective scanning scheme and a so-called pre-objective scanning scheme using flat-field scan lens (f-theta scan lens). The emphases will be put on the analysis of the relationship between scanning error and some important error factors of polygon used in the pre-objective scanning scheme. A set of formulae are developed to calculate the tolerance of polygonal reflecting surface, divided angle, the degree of malalignment between reflect surface and the axis of rotation and rotating speed error etc. It provides a reliable foundation for the constitution of the tolerance polygon and rotating speed.
In the field of human motion analysis, recovering 3D human postures from image sequence may encounter many difficult issues due to the little understanding of how visual mechanisms works. This topic has motivates increasing interests among image processing researchers. In this paper, a method of recovery of 3D human posture from single view is proposed. The recovery process is as follows: First, the image sequences of human motion are acquired by single camera. The body region is extracted from the image by background subtraction, and body silhouette is represented by FCC(Freeman Chain Code); then each part of the body is labeled, and the coordinates of joints connecting the body parts are retrieved. Thus the sequence of 2D human skeletons is recovered from the image sequence. At last, 3D human skeleton can be recovered by perspective projection model of the camera and knowledge about human structure. This paper gives the tracking results for three different kinds of human motion. The 3D human skeletons can be successfully retrieved in the whole course ofthe complex movement. This proves that the system have certain advantages and fascinating applications. It is a basic and important step toward the recognition of human motion.
Stereo matching is the key problem of depth information measure using the disparity in stereo vision. In this paper, a new stereo matching algorithm, combining both the modified genetic algorithm and the classic feature matching technique, is presented. The chromosome construction and the fitness function for stereo matching are proposed. According to the corresponding constraint of stereo matching, genetic algorithm is applied to this problem. Finally, the experiment using the proposed method is given, and the experiment results show that the proposed algorithm is more applicable and stable.
Stereo matching is an important and necessary technique for stereo vision. It is usually not good practice to try to find corresponding points for all pixels, and feature points are selected so that unambiguous matches might be obtained. Meantime, in order to reduce the computational cost of finding correspondence, multistage matching is often applied. Wavelet transform has good multi-resolution representation. Using zero- crossing points of wavelet transform coefficients as the features, the corresponding features in a pari of images are found by decomposing images into several levels (multi-scale analysis). So disparity estimation and error exclusion can be finished simultaneously. The efficiency of this algorithm is increased. Finally, the given algorithm is tested on stereo image pairs.
In order to acquire high reflectance, how to select the thickness d<SUB>H</SUB> and d<SUB>L</SUB> of the high and low atomic numbers materials should be considered first of all in the design of soft x-ray multi-layer. This paper introduced a simple design method based on matrix method. In the design process of a multi-layer mirror using Mo/Si at (lambda) equals 13.1 nm and normal incidence, its reflectance reaches 67.0 percent when layers are 30. Compared with other method, although its reflectance is a bit lower, it is a simple and practical method.
This paper presents a method for acquiring sine grating pattern of dynamic varying frequency using for measuring the modulation transfer function (MTF) of CCD. The measured results show that the spatial frequencies of grating patterns generated by this method can be continuously changed within the range of 0.2 to 80 lp/mm, the frequent of which is lower than 1 lp/mm. The modulation contrast of patterns is close to one. We have used them to measure the MTF of area array and linear CCD, and the result are satisfactory.
A hybrid digital-optical joint transform correlator has been built for recognition of objects with noise and multiple objects. The correlator uses two optically addressed LCLVs as input transducer and for intensity-recording the joint transform spectrum, two optical lenses for performing a Fourier transform, a CCD camera as active output transducer, and a digital system for postprocessing the output signal and refreshing the reference image through our object library. In our experiment, the spatially separated images are imaged onto one light valve, whose output is written on the second light valve. The output of the second light valve is optically processed to produce a correlation signal at the output transducer. The correlator is supported by a digital system so that the output can be digitized for further processing. Some experimental results for multiple-object recognition are presented and discussed.
In this paper basic principle of range-Doppler imaging in inverse synthetic aperture radar (ISAR) is analyzed. Simulating experiments of ISAR imaging on far-distant rotating multi-point targets are finished. The data films of ISAR in rectangular and polar coordinate formats are generated by microcomputer. Two-dimensional image with high- resolution are obtained by optical processing technology. Possible motion errors are discussed in the paper. Compensating methods and experimental results for some motion errors are given. Finally, feasibility of optoelectronic hybrid real-time processing for ISAR data is investigated.