A method of wavefronts cross-correlation by means of so-called Second-Harmonic-Generated Hologram (SHG hologram) is considered. According to this method the interference pattern of an object wave and a reference wave is recorded in nonlinear light-sensitive material using its second order. The SHG hologram generates the wave that forms the reconstructed image of the object without time delay in the moment when interfering wavefronts intersect the light-sensitive material, the frequency of the reconstructed wave being doubled in comparison with the frequency of the recorded waves. The expression that describes the electrical field of the reconstructed wave is deduced. Basing on this expression the methods for the construction of the image generated by SHG hologram are developed.

Photonic devices with low insertion loss are important in dense wavelength division multiplexing (DWDM) systems. Currently most of these devices, such as variable optical attenuators (VOA), switches, filters, and dispersion compensators, etc., involve bulk (or micro-optic) components that require conversions between fibers and free-space optical elements leading to high insertion loss. Recently, we have proposed, analyzed, and demonstrated several fiber based devices for DWDM optical communication systems. Here we present an in-line fiber VOA, a 2x2 switchable wavelength add/drop filter, and high performance dispersion compensators. The VOA is built with a side-polished fiber covered with a liquid crystal overlay. By varying the orientation of the liquid crystal molecules using an applied electric field, the loss of the device can be controlled. The 2x2 wavelength switch is designed by recording electrically switchable holographic gratings in a layer of holographic polymer dispersed liquid crystal (H-PDLC) sandwiched between two side-polished fibers. The dispersion compensators are based on high precision fiber Bragg gratings (FBG). A unique method for writing FBGs with arbitrary phase and amplitude distributions is demonstrated. All of these devices are analyzed theoretically and demonstrated experimentally. Both theoretical and experimental results will be presented and discussed. These devices are suitable for DWDM optical information transmission and network management.

In this paper, we will provide a brief review on the progress of a unique all-fiber tunable filter based on the combination of single resonant band long period grating (LPG) and harsh environment electro-optic polymer second cladding layer recently developed at Penn State University. The single resonant band LPG is used to select the resonant wavelength and the tuning of resonant wavelength is realized by changing the refractive index of electro-optic polymer cladding layer via external electric field. Although the basic operational principle and implementation of this unique tunable filter have been previously reported by authors, this paper is focused on recent progress in this project.

The paper considers the neural memory of the human brain from the viewpoint of visual information processing. A model that explains the principle of data recording and storing, memory relaxation, associative remembering and other memory functions is offered. The model of associative memory is based on the methods of holography, "wave biochemistry" and autowaves. Brief consideration is given to the associative properties of holographic neural structures and the memory architecture using running chemical reactions. The paper also outlines the problem of developing artificial memory elements for restoring the brain functions and possible interface devices for coupling neurons to electronic systems.

An ultra-short pulse is very useful as a tool for various applications because of its ultra-short temporal duration, ultra-high bandwidth, and ultra-high peak power. In general, in the pulse measurement by using current methods, the retrieved signal pulse is influenced by properties of a detector used in the measurement system. For example, a noise is added to acquisition data by a dark current of the detector. In current methods, post calculation for acquisition data cannot eliminate all of the deviations caused by the detector absolutely, so that we must retrieve the signal pulse from the deviant data. On the other hand, as a pulse measurement system capable of applying optical signal processing, we have proposed optical spectrogram scope (OSS). OSS is a pulse measurement system based on an optical correlation technique. In the OSS system, processing based on the optical correlation technique is implemented by using an optical filtering technique. Then, by designing the optical filter used in the OSS system, we can promptly implement various processing based on the optical correlation technique. For example, to inhibit the influence of properties of the detector at the minimum, we have proposed a new method using previous analysis before acquisition. In this method, we introduce ideas of optical signal processing into the pulse measurement system. To demonstrate the proposed method of sensitive detection of multi-transitional spectral patterns by using OSS, we executed preliminary experiments. In our experiment, we measured a signal pulse containing two signal components of different transitional spectral patterns.

A virtual-optical based encryption model with the aid of public key infrastructure (PKI) is presented in this paper. The proposed model employs a hybrid architecture in which our previously published encryption method based on virtual-optics scheme (VOS) can be used to encipher and decipher data while an asymmetric algorithm, for example RSA, is applied for enciphering and deciphering the session key(s). The whole information security model is run under the framework of international standard ITU-T X.509 PKI, which is on basis of public-key cryptography and digital signatures. This PKI-based VOS security approach has additional features like confidentiality, authentication, and integrity for the purpose of data encryption under the environment of network. Numerical experiments prove the effectiveness of the method. The security of proposed model is briefly analyzed by examining some possible attacks from the viewpoint of a cryptanalysis.

In order to overcome the resolution limits of the detector array to the spectrometer, the super-resolution algorithms is adopted. On the basis of the study on the integral and sampling property of the detector array, the spectral line adaptability to the super-resolution algorithms was verified. The algorithms were tested respectively by three classic spectral line profiles - Gaussian, Lorentzian and Voigt, and the deviation of the reconstructed spectral line and the original one was analyzed. Consequently, the super-resolution algorithm and its optimal parameter for different spectral line profiles were deduced.

We have developed optically-addressed and electrically-addressed liquid crystal spatial phase-only light modulators without pixelized structures. We obtained a large depth of phase-only modulation based on the electro-optical characteristics of a parallel-aligned nematic liquid crystal. We also confirmed that the satisfactory phase modulation capability and high diffraction efficiency of these spatial light modulators were useful for practical applications such as optical correlation, holographic measurement, optical waveform shaping, and optical wavefront compensation.

We propose a new wavelet transform, which is the differential Haar-Gaussian wavelet transform. This new wavelet transform is applied to the edge detection, which can be processed in both spatial and the frequency domains. The bandwidth-matching algorithm and the telecentric optics are used to achieve fast calculation, and to produce high-precision edge detection results with large depth of focus.

By introducing a method that a hard-edged aperture function can be expanded into an approximate sum of complex Gaussian functions with finite numbers, the analytical expression of Wigner distribution function for a Gaussian beam passing through a cylindrical symmetric and paraxial ABCD optical system with a hard-edged aperture is obtained. Numerical calculations show that the effect of an aperture on the Wigner distribution function is prominent. The analytical results are also compared with the integral calculation results and they show that this method of expanding a hard aperture into Gaussian functions with finite numbers is proper and ascendant. This method could also be extended to studying the Wigner distribution functions of other light beams passing through a paraxial ABCD optical system with a hard-edged aperture.

Phase retrieval algorithms based on 4-f system for optical image encryption are compared in respect of the image retrieval quality and the convergence. Simulation results show that enlarging the searching space can decrypt the image with extremely high quality, while employing the searching strategy of modifying both the phase-distributions in the input and the frequency planes can result in much faster convergence for the algorithm.

In this paper, we present an approach of real-time implementation of multimedia data security based on virtual-optics with the aid of a parallel digital signal processor (DSP). In order to partially compensate the parallelism of optical processing lost by digital implementation, we make full use of parallel hardware architecture and parallel computation structure of the TMS320C6701 DSP, leading to a high-efficiency operation. This approach makes it possible for the virtual-optics imaging methodology (VOIM) to be realized in real-time applications in embedded systems for multimedia data security. Experiments with multimedia data are performed to validate the proposed method, and parameter-sensitivities are quantitatively analyzed and illustrated.

We suggest an effective and simple algorithm providing a polynomial storage capacity of a network of the form M ~ N^2s+1, where N is the dimension of the stored binary patterns. In this problem the value of the free parameter s is restricted by the inequalities N >> slnN ≥ 1. The algorithm allows us to identify a large number of highly distorted similar patterns. The negative influence of correlations of the patterns is suppressed by choosing a sufficiently large value of the parameter s. We show the efficiency of the algorithm by the example of a perceptron identifier, but it also can be used to increase the storage capacity of full connected systems of associative memory.

Fabrication of digital sinusoidal gratings for accurate integration of segmented 3D image data is presented. The main advantages of using digital 2-D fringe patterns for our proposed data fusion scheme include (1) high matching accuracy, (2) improved robustness, (3) reduced computational time, and (4) capability of compensating distortions of the optical system at every pixel location.

The JPEG2000 is new image compression standard, which develop different quantization factors in each sub-band of the wavelet transform, where those factors are attached in image format. In this paper, we develop an algorithm to determine those factors adaptively by using fuzzy logic, therefore it will became more suitable to each image condition, and also provides an effective and better compression ratio. The available low and high frequency image samples are used, and the criteria of output results such as: Peak Signal to Noise Ratio (PSNR), Compression Ratio (CR), Entropy, etc., will be compared. The simulation results indicate that such algorithm can improve image quality as well as the compression performance accordingly.

Photoinduced anisotropic properties of pyrrylfulgide are studied. From measurement of the photoinduced spectrum of dichroism, the birefringence spectrum is evaluated by Kramers-Kronig relations. At optimal exposure of 13 ~ 20J/cm² a maximum photoinduced dichroism (D_{perpendicular} - D_parallel) of about 0.1 and a maximum photoinduced birefringence (n_{perpendicular} - n_parallel) of about 8×10^-4 are achieved. We exploit this photoinduced anisotropy and use a pyrrylfulgide/PMMA film to demonstrate optical image processing such as contrast reversal, image subtraction and summation, low-pass filtering and edge-enhancement. From the spectra of dichroism and birefringence the spectrum of the diffraction efficiency for polarization holography is calculated. We demonstrate that diffracted images with high signal-to-noise-ratio (SNR) can be obtained by holographic recording with orthogonal polarization.

As multiprocessing comes into the mainstream, the board-to-board interconnects become even more critical. In a shared-memory multiprocessing system, the shared bus topology is the preferred interconnect scheme because its broadcast nature can be effectively utilized to reduce communication latency, lessen networking complexity, and support cache coherence. In the electrical domain, however, a major performance bottleneck is anticipated due to the restricted bus bandwidth. In this paper, an innovative architecture, optical centralized shared bus, is proposed for use in the multiprocessing systems. This architecture utilizes the terascale bandwidth capacity of substrate-guided optical interconnects, while at the same time, retaining the essential merits of the shared bus topology. Thus, a smooth migration with substantial multiprocessing performance improvement is expected. A conceptual emulation of the shared-memory multiprocessing scheme is demonstrated on a generic PCI subsystem with an optical centralized shared bus. The objective of this effort is to prove the technical feasibility from the architecture standpoint.

Three-dimensional image recognition is an important issue in the field of information optics. There have been many researches in the 3D object recognition. Recently much attention has been focused on integral imaging, which used to be called integral photography in the past. In this paper, we will discuss our recent works on the 3D image capture, processing and correlation using the integral imaging technique. By using a lens array, we capture different perspectives of a 3D object at one time. Then, the information can be processed to figure out the original 3D image based on multi-baseline stereoscopy techniques. A composite lens array that consists of different-focal-length lenses can be more efficient for this purpose. The captured images can be used for multiple joint transform correlation with reference images. From the results, we can obtain the correlation between the 3D object and the reference object. And also, we can figure out both transverse and longitudinal shift information of the 3D object with respect to the reference 3D object. Both theoretical discussion and experimental proof are provided.

In three-dimensional display based on integral imaging, the resolution of the elemental images is a major factor that determines the resolution of the integrated three-dimensional image. Though the pixel pitch of the display panel imposes fundamental limit on the resolution of the elemental images, it is often not fully utilized due to low resolution of the pickup devices. In this paper, we propose a method to enhance the resolution of the elemental images. The proposed method estimates the sub-pixel disparity of the elemental images and generates high resolution elemental images using multiple low resolution elemental images. We explain the principle and verify it by simulation and experimental results.

We present a novel color pattern recognition technology based on non-zero order joint transform correlator (NOJTC) system in this paper. In this method, each of the color target image is transformed to a grayscale image by using encoding technique. We also use minimum average correlation energy (MACE) approach to design an optimized synthetic reference function. When the input plane is gray-scaled and monochromatic, the function can be displayed in the liquid crystal spatial light modulator (LCSLM) to achieve real-time operation. Furthermore, we apply a joint transform power spectrum (JTPS) subtraction method to remove the zero-order terms and the desired peaks can be easily detected.

Hybrid optoelectronic joint transform correlator (HOJTC), exploiting the Fourier transform property of a lens, implements target detection in real time. Adaptive nonlinear digital filtering in the joint transform power spectrum (JTPS) plane improves the immunity against the noise and clutter. In this paper, electrically addressed liquid crystal devices (EALCD) are used as the space light modulators (SLM), Charge Coupled Device (CCD) matrix camera as the square law detector and Ar⁺ laser as the light source. We develop the hybrid optoelectronic joint transform correlator controlled by computers, which can successfully detect and recognize the target in cluttered scenes in real time. The speed rate of the recognition is 25 frames per second. As the experiment examples, the target recognition of a tank and a car in cluttered scenes is presented. The experiments show that the intensity of cross-correlation peaks after adaptive nonlinear digital filtering is increased greatly, the performance of the joint transform correlator is improved, and it can detect the distorted and noisy targets in cluttered scenes in real time. It was found that using wavelet filter in frequency domain is a very effective way to suppress clutter noise while maintaining high tolerance for distortion.

A method for measuring refractive index of plate glass by joint transform correlative technique is given. In the one of two correlative light beams passing through the two correlative images of certain separation in input plane, a unknown refractive index and known thickness plate glass is inserted with a certainty angle (θ). Joint transform power spectrum (JPS) is recorded separately at the back focal plane of the lens by a CCD detector when Θ = 90° or Θ = 45°, the JPS is sent to the LCD on the input plane by the computer. Then two groups of correlative points will be recorded separately by the CCD detector. On the basis of the interval difference value between two groups of altered correlative points, the refractive index is calculated. Theory analysis and examination result are given.

The use of laser diode in joint transform correlator (JTC) is discussed as an example of potential applications to optical signal processing. Effects of the coherence and astigmatism of laser diode beam are analyzed. Two methods for correcting laser diode beam using a cylindrical lens or a pair of cylindrical lenses are also reviewed. A corrected laser diode can be used in JTC to totally eliminate the effect of astigmatism.

We have applied the diffractive optics and digital holography technologies to the design and fabrication of fiber Bragg gratings (FBG). We studied the phase mask near field diffraction using the numerical simulation. Our new understanding on the phase mask has critical importance for fabrication of complex FBGs, such as the sampled grating DBR laser, multi-channel dispersion compensator, and phase-shift band-pass filters. In the design of the FBGs we introduced the phase-only sampling multi-channel FBGs using the Dammann diffractive grating, such that the maximum reflective index modulation required for N channels is only √N times of that for the single channel. We apply the discrete layer-peeling algorithm directly design the multi-channel FBGs, whose seed grating contains abrupt phase jumps in order to correct the channel distortions in the sampled multi-channel complex gratings. In addition, we introduced the iterative layer-peeling algorithm as a generic approach for the design of the FBGs. Our research provided a foundation of the advanced multichannel complex FBGs technology, which produces FBGs of very high channel count (45 channels and higher).

With the fluctuation of the environmental factors, such as temperature, wind, and atmospheric pressure, the birefringence of a fiber changes along the fiber link and the effects of polarization mode dispersion (PMD) are random and time-varying, which makes it necessary to design a tunable and adaptive Fiber communication; Optical fiber; Fiber Bragg grating; Differential group delay; Dispersion compensation; Polarization mode dispersion compensation; Birefringence; Linearly chirped fiber Bragg grating; Piezoelectric transducer PMD compensator. Such a novel tunable first-order PMD compensator has been proposed and characterized in this paper. The scheme of PMD compensation employs sampled fiber Bragg gratings fabricated with uniform-period phase masks. This all-fiber compensation technique is cost-effective and adjustable in designing the differential group delay (DGD) profile. The numerical simulation results show that the efficiency of this PMD compensator is assessed for 10 Gb/s NRZ transmission systems with large DGD. With the compensator, a significant improvement can be achieved in the bit rate pattern of the received signal.

A new unequal-period radial hollow Bragg fiber structure has been optimum designed to improve the guided flux transmit characteristics. The core of this Bragg fiber is composed of air, and the cladding is formed by a set of alternating layers of up-doped and down-doped silica. The number of the cladding medium layers can be reduced greatly, and some simulation results have been obtained. The simplification of the cladding layers is useful for the fabrication of Bragg fiber.

Two volume holographic storage schemes using random phase multiplexing technique are presented. A ground glass is spatially shifted to multiplex the signals for both storage schemes. The diffraction selectivity of the ground glass is experimental investigated and theoretically analyzed.

A method of numerical reconstruction of hologram recorded on a low resolution CCD with different perspectives is presented. The hologram generated by 3D object at any plane located in the Fresnel diffraction region is magnified by a lens and is then recorded on a low resolution CCD sensor and numerical reconstruction is obtained by using linear interpolation and FFT. The 3D reconstruction of the different perspectives can be gained by the method introducing a window in the digital hologram and moving this window inside the whole digital hologram. The experimental results are also given.

In digital holography, holograms are recorded by a CCD-array, and the complex amplitude of the object wave is numerically reconstructed via computer. For different recording conditions and different properties of objects, different reconstruction algorithms are required. The conventional reconstruction algorithms were conceived directly by replacing the diffraction integral with summation. Each method has its limitation in the valid range for correctly calculating the diffraction integral. The Single Fourier Transform method is valid for far Fresnel zone hologram, whereas the convolution method is appropriate for near Fresnel holograms. Here, we present a general reconstruction model from the perspective of “Generalized sampling theory”. Given that the function space in which the unknown complex amplitude lies, an approximation of the continuous complex amplitude at the CCD can be synthesized from a set of basis functions with the recorded samples as weights. Back-propagation of the approximated complex amplitude to the original object plane yields an expression relating the continuous complex amplitude of the object with the recorded samples. By adopting different basis functions and different formulas for describing the diffraction process, an optimal reconstruction algorithm can be developed for various recording conditions and different diffraction characteristics of the object. Contrary to the conventional algorithms where values are available only at specific grid, complex amplitude at any position of the object can be obtained using this model. In addition, the effect due to the non-zero fill factor of the CCD can also be incorporated into the reconstruction algorithm to be further compensated by over-weighting the high frequency components. Two basis functions: Dirac delta- and Sinc-, are studied in detail.

Digital reconstruction of samples of the object wave front amplitude from samples of its hologram is addressed and is treated as a process of sampling the object wave front. Signal sampling is a linear transformation that is fully specified by its point spread function. Point spread functions of the hologram reconstruction algorithms are derived that explicitly show how the reconstruction results depend on the holographic setups and photographic camera physical parameters such as object-to-camera distance, radiation wave length, camera size, pitch, fill factor and alike. Three reconstruction algorithms are introduced and analyzed: a general algorithm and more commonly known Fourier and Convolution ones extended to enable reconstruction with arbitrary scale factor. For convolution algorithm, it is shown additionally that reconstruction results contain, in general, certain extra distortions as compared to general and Fourier reconstructions.

We propose and characterize nanowire-embedding in photonic crystal. This embedding method becomes a novel fabrication process for photonic crystal line defect, which enhances freedom in waveguide manufacturing. The characteristics of the nanowire defect waveguide are investigated by using a cascaded low pass filter model in circuit theory. We can find that the wave propagation characteristics correspond to the specific case of optical branch phonon vibration in solid crystals, where diatomic vibration occurs with multiple particle interaction. Actually, the dispersion characteristics of the proposed system are similar to the optical branch phonon vibration of the transition metal compounds. There are multiple modes (i.e., different Bloch wave numbers) for an optical frequency with local minimum of frequency at the lower wave number. Waveguide bending ability was confirmed by using FDTD (finite difference time domain) simulations. Nanowire-embedding in photonic crystal is expected to open a new territory to the field of photonic integrated circuit from fabrication process to waveguide and various photonic devices.

In this paper, a MicroPhotonic-based high-Q tunable RF filter architecture is proposed. The architecture uses a Vertical Cavity Surface Emitting Laser (VCSEL) array, a 2D ultra-wideband photo-receiver array and a multi-cavity optical substrate to generate a large number of optical true-time delays thus achieving arbitrary, high-resolution RF filter transfer characteristics. By tuning the responses of the different optical cavities, adaptive high-Q RF filter characteristics can be realized over a wide RF frequency range. Proof-of-concept experimental results demonstrate the adaptability of the MicroPhotonic-based RF filter.

Two control beams (a linearly and a circularly polarized) are used to pump poly(methyl methacrylate) (PMMA) films doped with azobenzene chromophore Disperse Red 1 (DR1), and the all-optical switching effects with low background and high stability are reported. The switching effects are experimentally investigated by changing the pump conditions of two control beams. Experiments show that the circularly polarized pump beam can disorder the oriented chromophores and speed up the relaxation of photo-induced birefringence, consequently decrease the background and increase the stability and the extinction ratio of the switching signals.

We present a simple method to generate a stable high-power (> 30 dBm) multi-wavelength ytterbium/erbium co-doped double-cladding fiber ring laser source at room temperature. This method is based a wavelength-dependent filter through spatial mode beating between the LP₀₁ and LP₁₁ modes within the multimode fiber section. We also investigate the relationship between the lasing wavelengths and the length of the ytterbium/erbium fibers (YEFs), the number of lasing wavelength lines dependent on the total pumping power level and the polarization states, and the characteristics of both the wavelength switching operation and the total output power. Eight simultaneous lasing wavelengths with 0.78 nm spacing were generated at room temperature.

The nature of scanning image acquisition greatly facilitates incorporation of various contrast signals for imaging and integration with techniques in signal processing. In this study, we are reporting imaging modalities and techniques based on nonlinear optical and ultrafast effects that are excited by ultrafast laser. Additionally, the use of signal processing electronics allows signal conditioning techniques, such as dithering, lock-in detection, O etc, to be employed so that better signal to noise ratio can be resulted and special features in imaging can be emphasized.

Integral imaging is a promising way of three-dimensional display because it provides observers with full parallax and continuous view points without the use of glasses. However, the limitation on the viewing angle and the expressible depth should be overcome for integral imaging to be applied to real systems. There have been various methods such as using mechanical movements or polarization switching to improve the viewing angle of integral imaging. In this paper, we propose a viewing angle enhanced integral imaging system without any mechanical movement or polarization control. This new viewing angle enhanced system utilizes lenticular lens sheet to angularly multiplex the information emitted from each pixel. Thus each pixel can affect multiple lenses and the effective area of an elemental image is increased, which brings the enhanced viewing angle. The simulation result of the proposed system and the experimental results are provided.

In this paper, we propose a wide-viewing-angle three-dimensional integral imaging using a curved screen and a curved lens array. Elemental images are projected to the curved screen. Incorporation of the curved screen and the curved lens array instead of a conventional flat display panel and a flat lens array expands the viewing angle remarkably. In addition adopting barriers between a curved lens array and a curved screen eliminates the flipped images effectively without affecting the viewing angle. The principle of the proposed system is explained and the experimental results about the viewing angle of real and virtual images are also presented.

We present an improved design approach for N×N silica-based multimode interference (MMI) devices. By this approach, we could determine a well-defined range of the length of the multimode section that would produce optimal device performance. The range is linked to the propagation constant spacing of fundamental and higher order modes of the multimode waveguide. Related design principles and issues of silica-based MMI devices will be discussed.

We report the first results of self-assembled nanostructures using colloids for antireflection optical coatings. Two-dimensional (2D) periodic nano-structures were made by using self-assembled 2D colloidal crystals on top of a transparent substrate. An atomic force microscope was used to evaluate the quality of the nanostructure. The feature size of the structures was around 105 nm. This sub-wavelength structure is equivalent to an artificial film on top of the substrate. The effective refractive index of the film is found to be around 1.3. Such a low-index materials is desired for anti-reflection coating to reduce Fresnal reflection. We have observed the reduced reflection from glass surfaces as well as enhanced transmission. Our calculated results agree well with experimental measurement.

Some approaches, which include iterative reconstruction-reprojection (IRR), projection space iteration reconstruction-reprojection (PSIRR) and other interpolation methods, have already been proposed for the reconstruction of fields including opaque objects. In the IRR, the interpolation operation is performed in the object space during backprojection-reprojection. The errors associated with the interpolation degrade the reconstructed image and may cause divergence unless a large number of rays and views are adopted. In the research of optical test, the testing views are often limited; therefore, the results are usually poor when using the IRR to reconstruct the fields including opaque objects. To improve the reconstruction precision in this case, a new approach is proposed, which is based on the discrete IRR algorithm and the finite impulse response (FIR) lowpass filer (DIRRLF). This filer is used to process the reprojection data between the iterative reconstruction and the reprojection stages. Different window functions and bandwidths are adopted for the lowpass filter. The compared reconstruction results of discrete IRR algorithm and DIRRLF algorithm for an asymmetrical single-peak simulation field including a circle round opaque object are studied with the numerical simulation of computer. The results show that this algorithm has higher reconstruction precision than the discrete IRR algorithm and has a potential application of reconstructing real three-dimensional fields including opaque objects.

In this paper, a 1-D bar code is used to implement image measurement of object displacement. The bar code is etched or printed on a rod to be a coded scale with bar widths modulated by a sinusoidal function and so the rod has unique phase at each position. During the measurement, an imaging sensor collects image of partial code elements of the whole scale. The displacement can be obtained from phase analysis of collected bars. The phase is calculated via Fourier transform with elimination of windowing effect for the collected image is actually a rectangular windowed signal. If the digital frequency of bar code is high enough and there is enough bars on photosurface, the calculated phase fluctuation caused by noise introduced by bar width detection can be small enough so that the calculated value can be amended to be the ideal one and thus the measuring error is mainly determined by positioning precision of bar center on the photosurface. Under the conditions described in the paper, our experimental results show that the maximum of displacement measuring error is 0.036mm and the standard deviation 0.024mm, which indicates the feasibility of this method and good application prospect of it.

The properties of light scattering from air bubbles in water have recently attracted considerable attention, but in practical applications such as in underwater detection, submarine imaging etc., we must take account of light scattering from various sizes of particles suspended in water. The situation of air bubbles and particles co-exist in water was studied in the first time. It is known that an air bubble in water is an example of a scatterer for which the refractive index of core (gas) is less than that of surroundings, which differs significantly from that for particles in water. Consequently, the forward light scattering characteristics of both air bubbles and typical particulate assemblages in the ocean are estimated with Mie theory, the result are analyzed and compared to validate the influence of particles on forward light scattering of air bubbles in the ocean. A preliminary laboratory experiment is also carried out to investigate the properties of forward light scattering (scattering angle less than 4 degrees) caused by particles and air bubbles and to illustrate the differences of light scattering between them.

The novel remote sensor of the Space Solar Telescope (SST) is scheduled for launch in 2008. It will be uniquely designed to be the world’s first facility capable of observing with γ = 0.1" spatial resolution in vector magnetograms in the photosphere and the chromosphere, and 0.5" in soft X-rays. The high spatial resolution makes the on-orbit automatic focus (AF) the key technique to catch images. The paper brings forward a new method of the minimum entropy (ME) criterion for the astro-observation. Further more, we have applied such technology to the on-orbit AF of SST. The emulational program calculated the image entropies of different off-focus states. Data indicate that the minimum image entropy is corresponding to the optimal image plane; the ME criterion is more suitable for the heavenly bodies of low contrast and the focusing precision is 0.01 mm (δ' = 0.01mm).

A theoretical model for the Laser induced dispersion optical filter (LIDOF) is presented. The filter has a higher transmission and a narrower line width than excited-state Faraday anomalous dispersion optical-filter (ESFADOF). The theoretical treatment is valid for different atoms LIDOF systems.

As monitoring the abrasion of tools becomes more and more important during metal cutting, many research efforts have been made in this aspect. This paper proposed a new method that detect and measure it directly by digital image technology and developed a detecting and measure system based on digital image. It is prone to automatically disposed and to integrate with machining and control information. A new filter method that average many same size images when acquiring images is proposed. At the same time, a new edge detection way by wavelet transform is also proposed. A new wavelet function is given when selection wavelet functions, which describe gray change of images more availably, as well as may avoid the jamming of noise. The rule of three is proposed to calibrate this system in this paper, and calibration precision arrives at application requirement. Functions of the software of this system include acquiring and processing images, edge detecting and segmenting images, and measure and analysis images. Images of tools are acquired by camera and CCD and video card. It can automatically differentiate and pick-up available information of the original image, such as area and perimeter and width and length and the location of the center of the abrasion region, by image processing and segmenting.

The spectra of the optical signals emitted by plasma during laser welding were studied using wavelet analysis. In the presence of the wavelet analysis, the detection of the pool penetration defects in welding process was realized. Comparing optical signals in welding process with and without joint penetration problem, the significant differences can be observed. By continuous wavelet transform, the coefficient lines of some scales have rapid fluctuation at the positions where pool penetration defect occurred, and the maximal coefficient values at the signal breakdown correspond to the length of the defect. In discrete wavelet analysis, the amplitude of low-frequency component of optical signals is fallen down remarkably when the welding defects occur. Correspondingly, the high-frequency component of the signals is almost decline to zero simultaneously. Considering that wavelet analysis can decompose the optical signals, extract the characteristic information of the signals and define the defects location accurately, it can be used to implement process-control of laser welding.

A Dammann grating can generate an array of uniform intensity and equally spaced spots for an incoming monochromatic light beam. But chromatic dispersion will occur when a beam of femtosecond laser pulse, which contains a broad spectral bandwidth, is split by a Dammann grating. Furthermore, the quantity of chromatic dispersion is different in each diffraction order. As a result, diffraction spots of splitting beams are becoming more elliptical as the diffraction order increases. In this paper, we propose a method of using an m time density’s grating to collimate the mth order beam that is split by a Dammann grating. In this way, an array of femtosecond laser beams that are eliminated lateral chromatic dispersion can be obtained by using a Dammann grating and a group of compensation gratings. At the same time, the increased width of the compensated output pulse is briefly discussed with Kirchhoff-Fresnel integral, and in the case of the pulse duration of 100fs, the increased amount of the pulse width at the different diffraction orders and the shape variation of the output diffraction spots are not serious. As a new kind of beam splitter, this splitting and compensation system is high efficiency and material dispersion is avoided if reflection gratings are employed. It should be highly interesting in practical applications of splitting femtosecond laser pulses for pulse-width measurement, pump-probe measurement, and micromachining at multiple points.

We put forward the concept of femtosecond laser speckles and studied twelve speckle patterns produced by four aluminium sheets with different surface roughness under illumination of three laser sources of one continuous wave laser and two other femtosecond pulsed lasers with FWHM widths of 36fs and 12fs, respectively. The femtosecond laser speckles are different from the conventional speckles in that femtosecond pulsed laser contain ultra-wide spectral contents. We explain the reason that makes femtosecond laser speckles different from conventional speckles. The relationship between speckle contrast and bandwidth of femtosecond laser is established, which well explains the experimental speckle contrast of the twelve speckle patterns.

The classical scheme of OBS (Optical Burst Switching) optical wavelength channels uses ITU-T’s DWDM (Dense Wavelength Divided Multiplex) standard wavelength at 1550nm band. BHPs (Burst Header Packet) over control optical wavelength channel and BPs (Burst Packet) over burst packets optical wavelength channels all choose this band. A novel scheme of OBS control optical wavelength channel selects 1310nm wavelength as the control optical wavelength channel, and the other channels are the same with the classical scheme. The key design is to choose broadband 1310/1550 wavelength divided multiplexer and demultiplexer, the band range is from 1270 to 1350nm at 1310nm band, from 1520 to 1610nm at 1550nm band, also its isolation is more than 30dB. The novel scheme has advantages of saving resource of DWDM wavelength channels and reducing cost of OBS system based on assuring the capability and quality of OBS system, comparing with the classical scheme.

Region logical operation is proposed for segmenting the object from the background or noise. Region logical operation is quite different from ordinary pixel logical operation. The entire object is processed region-by-region rather than pixel-by-pixel when regional logical algorithm is used for pattern recognition. The experimental results show object pre-processing based on region logical operation is simple and effective, it can be widely used in optical pattern recognition and image processing.

We synthesized and analyzed the optical transfer function (OTF) of the modified triangular interferometer (MTI) using two-pupil synthesis method. In the case of MTI, we demonstrated that we can obtain bipolar functions and complex hologram without bias by two-pupil synthesis method.

The phase unwrapping is a very difficult problem for profilometry of object containing depth discontinuities. The problem can be resolved with dual-frequency measurement technique. Two measurements with dual different frequencies cannot be contented with real-time demand. A novel profilometry is based on compound grating, generated by computer software, projected by liquid crystal projector, so that the grating with different precision is easily created, conveniently changed. The same purpose is attained as successively capturing two deforming gratings with different frequency. Two phase maps are estimated simultaneously, whose sensitivity to height variation is correlated with the pattern grating frequency. The phase uncertainty of the fine grating can be revised by the phase information coming from the coarse one. Finally, satisfactory experimental results are demonstrated. Meanwhile, it is verified that the new method has such advantages as high speed, accurate unwrapping and extensive measure range.

A new kind of optoelectronic hybrid joint transform correlator is proposed in this paper, it fulfills edge enhancement preprocessing for the input images in the spatial field and subtraction modifying and exponential filtering for the joint power spectrum in frequency field with electronic method. The influence of different edge enhancement operators (Log, Roberts, Sobel and Prewitt) and exponential parameters value on correlation result is studied. When the values of two exponential parameters are matched, the correlator can produce excellent correlation output. Computer simulation results show that the proposed correlator can eliminate the strong zero-order component in the output plane, enhance and sharpen the auto-correlation peak and restrain cross-correlations between each input targets. So the correlation recognition ability of this hybrid system is quite better than the classical joint transform correlator, it can be used for multi-object recognition.

In this paper, a convolute structure optoelectronic hybrid processing system for cruise missile scene matching guidance based on Joint Transform Correlator was proposed. An electrically addressed liquid crystal displays (EALCD) controlled by computer was used as spatial light modulator (SLM) was placed on input plane, on which reference image and target image were juxtaposed to display; in addition, CCD camera as a square law detector was placed in frequently spectrum plane recorded joint transform power spectrum and correlation result. Owing to detected the joint power spectrum and correlation result by CCD camera, the system could achieve sharper correlation peak and location accuracy by using edge detection input image and binaryzation of joint power spectrum. It was very advantageous to meet the demand of further improving performance, speed, strike accuracy of the cruise missile. Computer simulation and optical experiments showed that even in noisy background, the system can achieve excellent recognition and location performances with max speed: 16frames/s, recognition probability greater than 94%, and location accuracy better than a pixel.

Generalization ability of feed-forward neural networks is discussed in this paper. Firstly, presents and certifies two practical methods for improving networks generalization ability based on theory and experiment research. Secondly, gives a measuring model of networks generalization ability with generalization error. The essential is to define a probability input model and regard the expectation error of network upon testing samples as index for measuring networks generalization ability. Computation quantity and complexity are much less compared with traditional method.

In this paper, the contaminants on the substrate surfaces are cleaned using Q-switched pulse laser irradiation, which with pulse duration typically about 20ns and wavelength typically in the 1064nm or 532nm. A new mechanism for laser cleaning is proposed, which based on opto-acoustic effect that breakdown of the air above the target is obtained by a laser beam, and a laser-induced shock wave is produced to remove the various pollutants on the solid substrate surfaces. This method is much more effective than traditional conservative cleaning techniques including the continuous wave laser cleaning, there are many advantages for this new laser cleaning technology, such as the dry treatment, non-contact, non-damage to the substrate, no environmental pollution, and energy-economic, and so on. We make the theoretical analysis for this physical model of cleaning contaminant in detail and provided some experimental results and photographs.

The Moiré method is a well-known technique which can be used to measure in-plane and out-of-plane deformations. The basis of all moiré methods is gratings, which for metrological applications are primarily an array of dark and bright lines or a set of crossed array of lines or dots. Moiré is a process where the intensity distributions of two dissimilar grid patterns are combined, for example by superimposition. The direct approach to generating moiré patterns is utilizing the aliasing phenomenon, which is generally avoided in traditional image processing, now can be used to analyze the deformed specimen grating for deformation studies. An alternate approach, the digital moiré method, is to use logical operations for generating moiré patterns. Accepted as a novel mathematical tool, wavelet transform has a great advantage for image processing. In this pager, we apply it to simulate the aliasing phenomenon. In analysis of moiré fringes, phase shifting is by far the most powerful of fringe analysis techniques. For digital moiré, phase shifting can be achieved simply by translating the software generated gratings by the appropriate fractional steps. An application for large deformation of rubber material is given; the result shows that the method is feasible.

Sparse-aperture imaging systems are desirable for aerospace applications because they can capture the same resolution as a filled aperture while reducing the systems’ size and weight. A novel sparse-aperture model named dual three-sub-aperture is proposed. By comparing with the famous Golay 6, dual three-sub-aperture is regarded as a better configuration for aerospace remote sensing. But the images of sparse-aperture systems become blurry because of the modulation transfer function (MTF) loss. It is necessary to optimize the image quality by image restoration process. In order to achieve ideal images, image filter technique has been studied. First, the imaging simulations of dual three-sub-aperture system and the Golay 6 with different fill factor are generated. The images formed by these systems are recovered by means of proper filters. Then different kinds of noises and different noise levels are added, various filters with different parameters are applied to recover these images. And the optimal deblurred images are gained. Through the quantitative evaluations of its image quality it is shown that the mentioned filter technique can be used to effectively improve the quality of the images degraded by the MTF’s loss, i.e. the details in images can be enhanced and its edges be sharpened.

The purpose of this study is to apply a free-space optical interconnection to a reconfigurable board-to-board connection where the wiring patterns connecting boards are optically formed without electrical-optical conversion. We regard a photorefractive bi-directional connection module (PBCM) based on a mutually pumped phase conjugate mirror as a key device to construct such a connection network and employ PBCMs at input/output interfaces of each board. Although optical behaviors of PBCM are influenced by the exposure conditions, we especially focus on the diameter of beams illuminating photorefractive media placed inside PBCM so as to find some geometrical restrictions in a design of networking system. Through numerical analyses, we show a sample configuration of PBCM for the board-to-board interconnection and present a conceptual design of input/output interface.

Iris, one important biometric feature, has unique advantages: it has complex texture and is almost unchanged for the lifespan. So iris recognition has been widely studied for intelligent personal identification. Most of researchers use wavelets as iris feature extractor. And their systems obtain high accuracy. But wavelet transform is time consuming, so the problem is to enhance the useful information but still keep high processing speed. This is the reason we propose an opto-electronic system for iris recognition because of high parallelism of optics. In this system, we use eigen-images generated corresponding to optimally chosen wavelet packets to compress the iris image bank. After optical correlation between eigen-images and input, the statistic features are extracted. Simulation shows that wavelet packets preprocessing of the input images results in higher identification rate. And this preprocessing can be fulfilled by optical wavelet packet transform (OWPT), a new optical transform introduced by us. To generate the approximations of 2-D wavelet packet basis functions for implementing OWPT, mother wavelet, which has scaling functions, is utilized. Using the cascade algorithm and 2-D separable wavelet transform scheme, an optical wavelet packet filter is constructed based on the selected best bases. Inserting this filter makes the recognition performance better.

Based on the cascade algorithm and the theory of 2-D separable wavelet transform, 2-D approximations of scaling and wavelet basis functions are computed and used in optical wavelet transform. The optical transform using these separable wavelet bases can be called optical separable wavelet transform. And the selection of mother wavelets is extended. Unlike 2-D discrete separable wavelet transform, optical separable wavelet transform does not have limitation on direction selectivity. Linearly combining multiple directional channels as a superposition filter, the transform of these bases can be fulfilled simultaneously and the transform results can be synthesized on the output plane. In this paper, 2-D scaling and wavelet basis functions of a biorthogonal wavelet, bior2.6, are calculated. Four directional channels combine into an oriented optical filter to increase the extracted feature energy in high frequency band. And simulation results are presented.

Conventional current transformer (CT) is based on the principles of electric magnetic induction with copper wire windings and iron cores, it is widely used in power systems. But it emerges more weakness as the applied voltage and power capacity more and more increase. Over the past 20 years optical current sensors have received significant attention by a number of groups around the world as next generation high voltage measurement devices, with a view to replacing iron-corn current transformers in the electric power industry. In the opposite side of conventional current transformer, optical fiber current sensor provides a solution of the existed problems. It brings the significant advantages that they are non-conductive and lightweight, which can allow for much simpler insulation and mounting designs as the application voltage increase to1000kV or more to day. In addition, optical sensors do not exhibit hysteresis and provide a much large dynamic range and frequency response than iron-core CT. Optical fiber Bragg grating current sensor is the most potential important one among the optical current sensors, but its current transferred sensibility and the capability of anti-variance of temperature and stress still in a lower level. In this paper, a copper coated Bragg grating current sensor are described. The sensibility is improved significantly.

Multiple synthetic discriminant function (SDF) filters has been verified to be a better strategy for distortion invariant optical pattern recognition, especially for the in-plane rotation invariant ones. However, how to select the training sets is very crucial for the filter’s validity. In this paper, referring to the Rayleigh criteria, the distortion tolerance of a single matched spatial filter (MSF) has been tested by using a digital-optical hybrid 4f correlation system. Experimental results are ±5° and ±8% for the rotation and scaling distortion tolerance, respectively. According to the results, an equal correlation peak phase-only SDF algorithm has been adopted to synthesize two SDF filters, in which the training set images have been correspondingly selected with 5° and 10° intervals. The SDF filter constructed with 10° interval training sets has demonstrated as good performance as that one with 5° interval, but with the advantage of reduction by half of the number of multiple SDF filters for 360° full-rotation, which indicated that the double of distortion tolerance selected as the interval of training images is more suitable for real-time correlator recognitions.

We have detected the fluorescence characteristics of two aromatic pollution materials - Zyongyuan Crude oil and anthracene by OMA and obtained their fluorescence time. By analyzing their spectra properties, we find that there is a clear order. Long fluorescence wave occurs earlier than short fluorescence wave. This solution is also analyzed and explained by atomic energy levels theory.

A novel multiplexed velocimeter using a proprietary grating is proposed for measuring the velocity of particles in blood vessel. Two orthogonal gratings are multiplexed. The specially designed multiplexed grating is imaged on a microscopic region using a laser diode. The light scattered by the moving particles is collected using the same imaging lens and detected by a detector. The resulting electronic signal contains both two components of velocity, which can be separated using an electronic signal processor.

By means of experimental technique of optical fractional Fourier transform, we have determined the fractal dimension of a regular ordinary fractal pattern to demonstrate the feasibility of this approach. Experimental results show that optical fractional Fourier transform is a practical method to analyze the ordinary fractal patterns.

We propose a new watermarking scheme that can be used to embed multiple bits and also resilient to JPEG compression and geometrical transforms such as scaling, rotation, and cropping, based on holographic watermark that allows multiple watermark recovery without original content (cover image). The holographic watermark is that Fourier transformed digital hologram, embedded into cover image in the spatial domain. The proposed method has not only increased robustness with a stronger embedding but also imperceptibility of the watermark in the evaluation process. To compare with the conventional scheme, the spread spectrum, we embedded and recovered maximum 1,024 bits that consist of binary number over PSNR (peak signal-to-noise ratio) 39dB. And also, we computed robustness with BER (bit-error rate) corresponding the above attacks.

By introducing the converting method from electron-impact ionization cross sections to rate coefficients through using a semi-experiential formula, we try to probe a semi-experiential formula for converting the photo-ionization cross sections into photo-ionization rate coefficient. It’s found that photo-ionization rate coefficient is direct proportion to photo-ionization cross sections, the rate S is related with light resource.

Monitoring of water quality is essential to modern life. Not only is it a major factor in safeguarding public health, high quality freshwater is also a key input in agriculture and many industrial process. A preliminary prototype for hydrogen peroxide content in water is setup and introduced. Based on the detection of beam deviation due to the refractive index changes of the aqueous hydrogen peroxide solution, hydrogen peroxide content can be measured by a position-sensitive detector. Measurement principle is theoretically described. Experimental results indicate the feasibility of the developed system. Not like intensity-modulated refractive index sensor which necessitates a stable light source, this sensor exploits the beam deviation due to optical refraction at the receiving end face of the measurement cell, which is caused by changes in refractive index with different hydrogen peroxide content in water. Hydrogen peroxide content measurement resolution can reach about 0.01% within the measurement range from distilled water to hydrogen peroxide content of 30%.

In this paper, the degradation of signal degree of polarization (DOP) by first and second order polarization mode dispersion (PMD) in 40Gb/s RZ and NRZ optical communication is analyzed by numerical simulation. The simulation results show that the degradation of signal DOP by first order PMD is monotony, but which is fluctuated by second order PMD. The influence of two components of second order PMD on DOP for NRZ code and RZ are also investigated by numerical simulation method. The results also show that the influence of the depolarization component and the PCD component on NRZ and RZ data formats are different. Those results will provide the theory basis for how to select proper compensation arithmetic. A compensation system is founded to compensate the first and high order PMD effectively by DOP as feedback signal and particle swarm optimizer (PSO) as compensation arithmetic. Here, we introduce an intelligent method PSO as a searching algorithm to multi-DOF (degree of freedom) PMD compensation, The PSO algorithm used here is described as: (1) Local neighborhood structure is employed to avoid being trapped into sub-optima. (2) 20 particles are employed. So 20 time units (less than 20 ms) are required in one iteration. (3) The maximum iteration number is set to 50. The experiment result show that the first and second PMD can be compensated at the same times for 10 Gb/s RZ and NRZ by using DOP as feedback signal and PSO as searching algorithm.

Based on the principles of geometry optics and photometry, the light energy propagating through optical fiber and monochromator has been analyzed respectively in the paper. The expressions of the utilization ratio of light energy for coupling between the common extended source and the fiber and the monochromator has been deduced theoretically. The relationships between the utilization ratio and relative aperture of convex lens, numerical aperture of the fiber, relative aperture of the monochromator and object distance are discussed. The experimental results are consistent with the theoretical analyses. The conclusions are useful and helpful for us to conduct optical experiments and utilize and choose extended source and convex lens when we work on the coupling system between the extended sources and optical fiber and monochromator.

A new quick processing method to obtain the statistical properties of the weak laser speckle in free-space diffraction field whose speckle contrast V is less than 1 has been presented in this paper. During the process of experimental work, the conventional hypothesis of the laser speckle statistical regularity of keeping roundness was used. Based on the hypothesis, many images of laser speckle in different detection angles by a CCD sensor on the surface of samples coated with thermal sprayed with ZrO₂8Y₂O₃ have been processed. The density distribution of probability and the contrast of speckles were obtained. Even though the processing experimental data is gray-matrix but the intensity-matrix, the results are the same. The rationality of the process and the density distribution of probability are discussed in this paper. The experimental results accord well with the theoretical analysis and indicate that the method is feasible. This method makes the measurement of the surface roughness by laser speckle more convenient.

By irradiating alternative external light into the system with four-wave mixing in photorefractive polymers, the restriction on the generation of a phase conjugate beam or diffracted light will be demonstrated in this experiment. In addition, in order to verify the use of a two-dimensional array for simultaneous switching, the elimination of only part of diffraction grating recorded will be experimentally conducted.

The fingerprint (FP) provides an optimal foundation for Automatic Personal Identification Systems. Over the last two decades significant progress in Automatic Fingerprint Identification Systems (AFIS) has been achieved. However, the performance of AFIS still suffers from the FP image quality captured by FP sensors, the enhancement techniques for FP images and feature extraction, and the available approaches of feature matching. In this paper, we proposed a fingerprint enhancement algorithm based on Fourier filtering. In our algorithm the fingerprint enhancement were transformed from spatial domain to frequency domain by Fourier transforming. In addition, Fingerprint matching is one of the most important problems in AFIS. We proposed a minutia matching algorithm. In our algorithm, a simpler alignment method is used. We introduced ridge information into the minutia matching process in a simple but effective way and solved the problem of the matching of vector pairs with low computational cost.

In digital holography holograms are recorded by a CCD and image reconstruction is performed by a computer. It is free from tedious photographic processing and delivers three-dimensional distributions of both amplitude and phase quantitatively. Its main limitation that is caused by much lower resolution of CCDs than photographic materials has been substantially overcome by phase-shifting digital holography that reduces the spatial frequency of hologram by employing the in-line setup and directly evaluates complex amplitude at the CCD plane to eliminate the conjugate image appearing in the off-axis setup. In this paper we describe its basic principle and applications with emphasis on image formation and measurements of shape and deformation of diffusely reflecting surfaces in comparison with conventional holographic interferometry and electronic speckle pattern interferometry.