A new and basic approach for the analysis of cell patterns of some specific contact screens and the reproduced halftone images is presented. Optimum parameters for high fidelity tone reproduction by screens of line, square, circular, and concentric ring cell patterns possessing optical transmittance linearly varying with position have been obtained. These parameters can be used for the design of contact screens, the selection of high-gamma films, and film exposure and development process to achieve optimum

This article describes a method of pseudo-color enhancement of aerial infrared thermography. A continuous grey tone thermographic picture has been encoded into a pseudo-color image by means of the technique of half-tone screens preprocessing and spatial filtering. Our results have been compared with the results obtained by digital method, and the discussion of the comparison is given.

An optical method of pseudocolor equidensity encoding of photographic image is described. Frequency modulating of input image is made through! a four grey-levels halftone screen and the pseudocolor encoding is performed in a spatial filtering system where the white light source is used with the color filter placing at the plane of the source slit. The halftone screen is made by means of the Talbot eifect which incorporates the equivalent of low-pass spatial filtering. The spatial frequency of the screen is up to 12.51p/mm. The one-dimensional space-banswidth product is up to 750. The remote sensing image processed by using this method is available.

In this paper results of measurement on dichroism, birefringence and transmrt-tance of silver-chloride emulsions are given. A method of turning the areas of equal grey levels of the multi-grey level black and white images to equal diohroism is provided. The theory, specialities and practical application of equal-density pseudocolor are presented. The anisotropic plate placed between crossed polarizers is illuminated by a parallel beam of white light, equal-density pseudocolor can be observed. Slightly turning the analyzer pseudocolor may be changed. Therefore a complex black and white photographic image transparency can be changed to an observable pseudocolor pattern. The method only needs a high resolusion photographic plate and is characterized by considerable simplicity, stability and flexibility.

A model of laser oscillation is suggested and in the light of the quantization procedure of Dekker s dissipative systems, the laser equations of motion are derived through both density operator and Langevin methods respectively. They have been compared with Lamb s results of the reservoir theory. It can be seen that Lamb s results are the zero-order approximation of the results presented in this article.

The back-reflected laser produced from the laser irradiating targets has been measured. There are following results: 1. the width of spectrum of the back-reflected laser is broadened from 2 A to 66 A; 2. the distribution of near field is homogeneous; 3. the aberrations of wave front are small; 4. the efficiency of the back-reflected laser is in the range of 10-20%.

Laser fusion research has promoted the development of high power lasers. In order to evaluate the beam quality of high power Nd: glass laser system, we have measured some optical characteristics of laser beam, such as energy distribution of near-field, characteristic of far-field and divergence, wavefront distortion and coherence, spectrum of laser beam. The diagnostic instruments we used include a near-field camera for photographing the laser output energy distribution, an array camera for recording the far-field of laser beam, a radial shearing interferometer and lateral shearing interferometer with two plates for measuring the laser beam wavefront. Measurement results are obtained under the conditions of the laser output power of 1010W and l0^{11} W.

Recently the screened effect of resonance excitons absorption in GaAs has been applied to develop some kinds of optical bistability devices, therefore to measure the ultra-fast excitons screened process induced by photoexcited hot carriers is of importance not only for semiconductor physics but also for its applications. We measured the time-resolved spectrum of some GaAs samples at 5 K by means of the exciteing-probing method of picosecond spectroscopy. In our experiment the single laser pulse with duration time of 25 ps at 1.06 jim was used as exciting beam, and the probing beam was from a synchronously pumping optical parametric oscillator whose output wavelength was tuned by temperature. The main results are as following: (1) The screened time of excitons in GaAs is about 600 ps at 5 K. (2) Another transparent peak which comes from the scattering of excitons emerges at 1 ns after the excitation. (3) The transition from eleotron-hole-plasma to the excitonic state (Mott transition) has not seen to be abrupt.

Polarization intermodulated excitation (POLINEX) spectroscopy is a new developing Doppler-free spectroscopic technique which combines the advantages of the polarization spectroscopy and the intermodulated fluorescence speotroscopy. In this technique, a tunable laser beam is circular polarized first and then divided into two parts of nearly same intensities. Two rotating polarizers of different modulated frequencies are used to change the directions of these linear polarized beams periodically with time. When they interact with the atoms, the fluorescence signal are detected via a lock-in amplifier. The POLINEX spectroscopy can effectively eliminate the Doppler-broadened pedestal due to the velocity-changing collisions among atoms as the polarization-modulation is used instead of the amplitude modulation. And that pedestal is a problem in the original saturated spectroscopy and the intermodulated fluorescence spectroscopy. Meanwhile, there is no asymmetry of the line-shape in the polarization spectroscopy, because only the fluorescent or opto-galvanic signal are detected in this new method. In this paper a study of velocity-changing collisions in POLINEX spectroscopy using the rate equation approach is presented. A kernel function is introduced to describe the probability of atom moving out or in the state v (velocity) and m (magnetic quantum number) and the related terms additional to the rate equations. We calculate the total absorption rate and pick out the term concerning the mutual absorption (intermodulated signal). The amplitude of signal is proportional to the difference of the absorption rate when the senses of polarization of two counter-propagating laser beams are same or perpendicular to each other. We obtain the results which show the term related with the Doppler-broadened pedestal being cancelled after the operation of Clebsch-Gordon coefficients. These results coincide with the experiments performed before. Using the density matrix approach we can obtain the same results.

In this article, propagation characteristics of light rays in glass plates with parabolic distributions of refractive index on the thickness are discussed. The central refractive index higher than that of the two big surfaces and the central refractive index lower than that of the two big surfaces are discussed respectively. The former is called glass plates with positively directional distribution of refractive index and the latter is called glass plates with negatively directional distribution of refractive index, and also, propagation of light rays in two perpendicularly intersected glass plates with positively direotional parabolic distribution of refractive index is discussed. Glass plates with positively directional parabolic distribution of refractive index are obtained by using Tl+ ions from the thallium lead silicate glasses is exchanged by K+ ions from the melt. And also, the interference ring is observed by double light ray interferometer. It is obtained from the above discussion that two perpendicularly intersected glass plates with positively directional distribution of refractive index are provided with an imaging property, and a glass plate with negatively directional parabolic distribution of refractive index is provided with a divergent property. In this article, their applications are considered.

A method for density slicing of a photogram and iso-density maping by using the BC002 facsimiler is described. It has the advantages of high-processing rate simple device and acceptable pricision. The reformed equipment is valuable in practical use.

Using the third harmonic radiation of a YAG: Nd laser Radiation as excited light, we have observed the ultraviolet stimulated Raman scattering in optical fiber. The peak-wavelengths of stimulated Raman scattering were identified which distributed at 361.0, 372.2 and 379.1 nm. The corresponding scattering elements of separate peak of stimulated Raman scattering spectrum were analysised.

A method of optimization using statistical tests has been used to investigate the refractive index profiles for graded optical waveguides. A rational merit function and a practical computation procedure have been developed. Calculation was done to determine the index profiles of Ti in-diffused LiNbO3 waveguides produced in our laboratory. Comparisons with the methods reported so far reveal some advantage of our method.

In. the target experiment by multi-beam irradiation time-synchronization is very important. Using a method of two-photon fluorescence (TPF), we have measured the time-synchronization of six beams Nd3+ glass high power laser system (6 X 1011 W). The active-passive mode-locked Nd3+: YAG oscillator of the time-synchronization was used as the light source for the time-synohronization measurement. The pulse width was 20 ps. Time-synohronization for two opposite beams was measured using a TPF cell capable of four beam transmission on the position of target. Time-synohronization for two crossed beams was measured by placing a half-transparent film on the target position and a TPF apparatus. The measurement is simple and perceivable. The error in the measurement of the time-synohronization by two-photon fluorescenoe is presented. The error is about 4ps for two opposite beams and 5ps for two crossed beams. The total error of the time-synchronization for six beams is about 10 ps.

Academician of the Soviet Union Langdsberg (Jlaimcoepr) introduced a dielectric constant ellipsoid in this book "Optics". He condsidered that the total values of the dieleotric oonstants in crystals can be represented by a dielectric constant ellipsoid. The three semi-axes of this ellipsoid are respectively of lengths &1} ea, e3, i. e. the principle oomponents of the dieleotric constant tensor, and the length of any radius veotor of this ellipsoid is equal to the dielectric constant in that direction. In other words, Langd-sberg's dielectric constant ellipsoid corresponds to the dielectric constant tensor. It is pointed out in this paper that the dieleotric constant tensor corresponds to Fresnel's ellipsoid rather than Langdsberg <3 dielectric constant ellipsoid. This correspondence relation is unique. Dielectric constant tensor is a symmetrical second rank tensor, its six independent components are just equal to the six coefficients of Fresnel's ellipsoid equation respectively. Mathmatical derivation indicates that the length of any radius vector of Langdsberg's ellipsoid in not equal to the dielectric constant in that direction. Conversely, the surface whose length of radius vector in a given direotion is equal to the dielectric constant in that direction, is an ovaloid of six degrees. Besides, in this paper, confusing terms, such as dielectric constant ellipsoid, dielectric ellipsoid Fresnel's ellipsoid and index ellipsoid, and their respective corresponding tensors are clearly defined.