Speckle noise in high-resolution synthetic aperture radar (SAR) images is generated by the coherent processing of radar signals and exists in all types of coherent imaging systems. We study the statistical properties of speckle noise in a four-look SEASAT SAR image concentrating on homogeneous areas of the image. Experimental determination of the signal-to-noise ratio and ofthe probability density of the recorded intensity is performed showing evidence of correlation between underlying looks. Based on a model taking into account the weighting and possible correlation between the underlying looks, a theoretical expression for the effective number of independent looks is proposed and the corresponding probability density function of the intensity is compared to the experimentally extracted histograms of intensity fluctuations.
An automatic system for analyzing specklegrams point by point is described. A new method of evaluating Young's fringes based on making a TV camera scan both horizontally and vertically is proposed. Tracking, filtering, and edge lo cating techniques are developed to acquire fringe data. Experiments show that Young's fringes can be determined with an accuracy of 1% in spacing and 1° in orientation, and the displacement can be found with an accuracy of 1 μm in the range 20 to 100 μm.
This paper presents an improved technique for testing laser beam
collimation using a phase conjugate Twyman-Green interferometer. The
technique is useful for measuring laser beam divergence. It is possible using this technique to detect the defocusing of the order of one micrometer for a well corrected collimating lens. A relation is derived for the defocusing that can be detected by the phase conjugate interferometer.
We describe the basic theory and technique of a collimation testing method based on analysis of the lateral shearing interference fringe. The changed fringe spacing and the orientation after rotation of a single wedge plate through 180 deg. indicate the degree of collimation of the light beam. The preliminary experimental equipment is described, precision analyses are presented, and the usefulness for practical applications is demonstrated.
The exponential gain of two-beam coupling in lnP:Fe crystals under dc fields is a function of the pump beam intensity at a given temperature. We propose two methods to extend the sample volume working under optimum conditions. The first method is based on a negative thermal gradient and the second uses an auxiliary incoherent beam. Theoretical simulations predict an integrated gain of l5cm1 and 10cm1, respectively (for λ = 1.06 μm. Λ = 5 μm and E0 = 10 kV/cm) in thick crystals (L = 5 mm). Preliminary experimental results confirm that high gain performances can be achieved by using these methods.
A coherent optical processor is constructed using two-wave mixing in a BaTiO3 crystal. This system is capable of performing autocorrelation of an input image in two successive steps. Theoretical considerations of the system are successfully compared with the experimental results. Influences of the mixing angle and intensity ratios on the result are discussed.
Segmentation ofvehicles in natural backgrounds using absolute range imagery is considered. The segmentation technique exploits the small-scale planarity of man-made vehicles without explicit use of surface orientation information. A planarity test is used as the initial step in partitioning man-made vehicles from natural backgrounds. The planarity test is based on an estimate of the statistics of the absolute value of the error associated with fitting planes to small regions of the Cartesian coordinates of range image pixels. The planarity test is developed as a function of the standard deviation of the noise associated with range measurements. Heuristics used in conjunction with this algorithm are also presented. This algorithm has been evaluated on a database of 57 real range images, and results are presented. Application of the algorithm to two specific cases is shown in detail.
Time-sequential imagery is difficult to analyze because of its high dimensionality. This paper advances a new algorithm that screens input data in an intelligent way, discards data with negligible information, and uses the remaining images to represent the sequence in an optimal compact form. We present data to illustrate how this algorithm can be used to do novelty filtering, novelty detection, segmentation, background independent modeling, and classification.
The use of moment invariants for the detection of flaws in automated image processing inspection of printed graphic material is investigated. Prior work with moment invariants has concentrated on twodimensional image pattern recognition. A major limitation in pattern recognition applications has been the segmentation of the image from its background. Automated image processing inspection of printed material does not suffer from this limitation because a standard image background exists. The potential for separating flawed and unflawed printed material using moment invariants is demonstrated with formal statistical experiments.
This paper focuses on blur estimation for image restoration. In real-life applications, blur characteristics are usually unknown, and the
point spread function (PSF) must be determined from the degraded image. The identification and restoration procedure uses the fast Kalman filter structure. Processing on columns is decorrelated by first applying fast Fourier transform on the rows. To overcome the boundary problems, a mirror image is used. The 2-D identification and restoration problem is then transformed into a set of N 1-D identification and restoration problems on the columns. If the blur is assumed to be linear and spatially invariant, the problem is to estimate the coefficients of the PSF. This function extends over a large but limited number of pixels, thus leading to a large number of parameters that must be evaluated. The usual procedures for ARMA parameter estimation have failed in image parameter estimation, primarily due to the size of the MA part. The parameters are then constrained to be smooth by assuming that they are on a continuous function such as a Gaussian, polynomial, or wavelet function. The estimation then consists in evaluating hyperparameters computed by optimization of a likelihood function. The global procedure involves recursively estimating the unknown parameters using the maximum likelihood method, and restoring the image using the Kalman filter. Results are presented for an artificially blurred gray-level image.
Size distributions of particles within a binary image can be generated by morphological filtering processes known as granulometries. Granulometries filter the image by structuring elements of ever-increasing size, the result being a distribution whose statistics carry information regarding the shape and size of particles within the image. A granulometric approach to the analysis of the microstructure of electrophotographic images is discussed. The method is applied to both simulated and real images, the former being generated in a manner consistent with existing magnetic brush development and optical density transform models. Size distribution statistics are analyzed in terms of feedback control and copier quality control.
An architectural design of a ground-based antenna (telescope) for receiving optical communications from deep space is presented. A channel capacity of 1 00 kbits/s from Saturn or 5 Mbits/s from Mars requires a 30-cm-diameter transmitter and a 10-m-diameter reception antenna. The f/0.5 primary mirror will be hexagonally segmented and will have a surface roughness tolerance of 2 μm rms to effect a substantial savings relative to the cost of an astronomical optical imaging telescope of the same diameter. The antenna will receive communications even when the deepspace laser source appears to be located within a small angle of the sun (small solar elongation). Instead of a long, unwieldy, conventional sunshade, a sunshade consisting of hexagonal tubes will be mounted in precise alignment with the primary mirror segmentation. The ends of the tubes will be trimmed so that both the sunshade and the antenna will fit within a more-than-hemispherical dome whose diameter clears a sphere only six-fifths the diameter of the primary reflector. This sunshade permits reception when solar elongations are as small as 12°. Additional vanes may be inserted in the hexagonal tubes to permit reception at 6° or 3°. The frequency-doubled output of the Nd:YAG source laser will be tuned dynamically to lie within a Fraunhofer line (a spectral interval of reduced solar emission) to carry the signal with reduced interference from sunlight. The source laser and the Fraunhofer filter (a narrowband predetection optical filter) will be tuned to match the Doppler shifts of the source and background. Typical Doppler shifts are less than 0.05 nm or 53 GHz. A typical Saturn-to-Earth data link can reduce its source power requirement from 8.8 W to 2 W of laser output by employing a Fraunhofer filter instead of a conventional multilayer dielectric filter.
A new method for extracting quantitative information from a double exposure holographic interferogram is presented. Dual reference beams are used to produce continuously variable phase differences between the two images of the object at the recording stage of the hologram. Image reconstruction at three known phase differences, via a CCD camera and digital framestore, allow new automatic image processing methods to calculate the three-dimensional surface deformation.
A method that uses a single algorithm to trace rays in isotropic media and both ordinary and extraordinary rays in uniaxial media is presented. This method is designed to be compatible with conventional raytracing algorithms so that it is easily integrated into existing ray-tracing programs. A discussion of ray doubling in systems containing multiple uniaxial elements is also presented.
A simple design for a double-beam reflectometer to measure absolute values of reflectance and transmittance of specularly reflecting surfaces at normal incidence without requiring any reference standard is discussed.
Chalcohalide glasses are mixtures of chalcogenides and halides. This paper reviews the properties and structure of various glass-forming chalcohalide systems. These materials possess high transmittance in the infrared, which make them candidates for various applications in the area of infrared fiber optics. In general, the packing density, glass transition temperature (Tg), and refractive indices decrease with the addition of a halogen component into binary chalcogenide glasses. It also seems to be theoretically possible that the attenuation loss of the glasses and fibers, especially at 10.6 μm, decreases at the same time. The observed changes in the properties of glasses are in good agreement with the proposed structural model, suggesting degradation of the network connectivity by the addition of network-terminating halogen atoms.
In this paper, the principle and diagram of the two-dimensional automatic straightness measurement system are introduced, an automatic readout method is described, and the calibration results are given. This system has been used in an industrial environment.
This paper describes the electronic design and performance of a small, rugged airborne camera. The camera device is designed into a small package with high reliability linear CCDs and features high-resolution digital processing. The high full-well capacity and low noise floor (<280 electrons rms) yield a dynamic range of more than 70 dB. Some problems regarding choosing the appropriate analog-to-digital converter are discussed.