Surface photoreliefs, forming due to photoreduction of aromatic ketones and photodimerization of substituted anthracenes in poly(methylmethacrylate) layers are investigated. The photorelief is formed in a process of thermally activated structural relaxation of the material exposed extending a layer thickness. The relative photorelief height reaches several percent. Phototdimerization reversibility causes the reversibility of the relaxation relief and opens the prospects to the repeated relief hologram recording.

The mechanism of thermal interference and crowding on amplitude variation of the optical readout in a high density magneto-optical disk is studied. A simple method of eliminating the amplitude variation and achieving uniform amplitude of optical readouts in successive recording pulses is demonstrated. A thermomagnetic switching model is used to explain the mechanism for the thermal interference. A correlation model is also applied to describe how successful the thermal compensation is achieved. Good agreement is reached between the experimental and the simulation results.

The memory capacity of terminal attractor (TA) model associative memory is investigated based on the consistency between the stored pattern x$_i)^(m) and the obtained equilibrium state x_i in statistical thermodynamics. By the computer simulations, we give intuitive estimates of the memory capacity of the TA model associative memory. FOr the feasibility of the optical implementation of the TA associative memory, we impose some approximations to original TA associative memory without loosing the essence of the TA model. The memory capacity of such a modified TA model associative memory is also given by the numerical simulation. In this simulation, a 10 X 10 neuron network model is used and Hamming distances among inputs and the stored patterns are chosen to be equal to 5 or more both in the original and modified TA models. The results indicate that the absolute memory capacity of the TA model is greater than 0.35N, which contrasts with the relative capacity of 0.15N or the theoretical absolute capacity of N/(41nN) for the conventional associative memory.

We propose a novel approach to time-domain storage of serial optical data. In this approach, two identical impulse- equivalent sequences are used as write and read pulses to store and later retrieve optical information. These pulse sequences are both amplitude- and phase-modulated in such a way that their autocorrelations resemble, as closely as theoretically possible, the autocorrelation of a single large brief pulse to ensure faithful data retrieval. Such impulse-equivalent sequences are known to exist for all lengths, permitting the storage of large bandwidth data. In a proof-of-concept experiment, we have successfully stored a 42-microsecond long stream containing 420 bits of data in a 40-MHz spectral channel in a Eu³⁺:Y₂SiO₅ crystal. The stored data was repeatedly recalled for up to eight times with high signal fidelity, showing no measurable sidelobe-induced noise.

High density and high data rate are two key points in the development of ODS (optical data storage) which has advanced remarkably in recent years. The aim of this contribution is to report on the migration from CD-E to DVD-RAM by changing: 1) the recording media from heat-mode material to photo-mode material, 2) the recording laser from near infrared to green or blue wavelength, and 3) the recording methods from CD- format to sectorial format and from PPM-RLL to PWM-RLL, where PPM and PWM are pulse position modulation and pulse width modulation respectively, of which all have a potential to achieve an ultrafast recording rate-60ps/bit.

Digital image compression techniques are reviewed in this paper. To achieve a high compression ratio at a certain image quality, a combination f these techniques is used in practical systems. Factors affecting choice of image compression techniques are discussed in detail. Three international standards on image compression techniques, such as JEPG, MPEG, and H.261 are briefly described.

SmTbFeCO amorphous films were r.f.-magnetron sputtered from a mosaic target onto glass substrate. The magnetic and magneto-optical properties of SmTbFeCo thin films deposited at different argon pressure, sputtering power and negative substrate bias voltage were studied. It is shown that the deposition conditions strongly affect the reflectivity R, the coercivity Hc and Kerr rotation angle (theta) _k. In order to meet the requirement of magneto-optical recording, it is optimal to choose Ar pressure of 0.47 approximately 0.73 Pa, sputtering power of 300 approximately 350W, and negative substrate bias voltage of -80V approximately -110V.

In this paper, computer simulation of 3D object parallel correlation pattern recognition has been done by using a bank of filters, the results show that a bank of filters is essential to pattern recognition. The reason that the experimental results are not satisfactory is analyzed.

The dual-stage actuators are used in the positioning servo system of optical disk drives. The direct single-variable design (DSD) technique is studied for designing the tracking servo system in which there is a sensor to measure the relative displacement between the two stages. The conclusion clearly given is that a servo system using a dual-stage actuator with multi-variable characteristics can be directly designed as two single-variable systems. The tracking servo system can be designed as two independent servo loops. The multivariable problem can be treated as a single-variable problem. The features and forms of the dual-stage-actuator servo systems are also studied. The control accuracy and robust stability of the system by DSD are investigated. The interaction between the loops is studied by use of an equivalent perturbed model. The simulation of tracking control of the system is presented.

Optical disk array improves performance of optical drive in many aspects. The mechanism of separate drive and disk reduce the MTTR (mean time to repaired) of single failure. So data security increases much better than other array system. Parallel structure and reasonable redundant data distribution multiply the I/O speed much more by reducing average distance between different data.

The polymeric cross-linked hydrogel doped with dye 4- nitroaniline was prepared. The nonlinear optical properties of this material has been studied. The optical storage effects and the dynamic lens effects in this dye doped hydrogel under laser radiation have been observed. It is reasonable to show that this dye doped polymer get will find some applications in optical signal processing.

A holographic element for the common CD pick-up to play DVD is designed in this paper. The focus of holographic element is the same as that of the objective lens of CD player. The holographic element is fixed before the objective lens. The focus of DVD player with this holographic element is 8.5 mm, the number aperture is 0.75, and the focusing beam spot is 0.5 um. DVD player with the holographic element is characteristic of compensating the main optical error met in the common CD player well.

Physical properties of In₄₇Sb₁₄Te₃₉ thin films prepared by DC magnetron sputtering method are studied. X- ray diffraction and DSC results indicate that the crystallization compounds include mainly In₃SbTe₂ with small amounts of InTe, In₂Te₃. Optical recording test of the films state clearly that larger reflectivity contrast can be obtained at lower power Argon laser irradiation. The erasing contrast is comparatively lower but can be improved by multi-films match.

Co-Pt alloy films with perpendicular magnetic anisotropy and 100 percent remanence ratio were successfully prepared using e-beam coevaporation. A series of vacuum annealing was done on these alloy samples to study their thermal stability. The experimental results were as follows: a) For annealing temperature at 200 to approximately 300 degrees C, the Kerr rotation angle was almost unchanged or presented a slow decrease with the lasting of annealing, and the increase in coercivity was also small; b) For annealing temperature above 300 degrees C, both coercivity and Kerr rotation angle dropped prominently, and in the mean time magnetization became partly in-plane; c) Thermal stability is also probably a problem that needs to be solved for CoPt alloy films. The change of magnetic and magneto-optical properties of Co-Pt alloy films during annealing was considered to be related to the strength variation of different textures in films.

Several types of metallophthalocyanines have been synthesized to study their optical absorption and recording characteristics. VOPc and TiOPc films, prepared by vacuum sublimation, exhibited excellent thermal stability. The optical spectra of VOPc and TiOPc showed that the absorptive peaks were located at (lambda) equals 726nm and 712nm respectively. Some new recording characteristics of VOPc and TiOPc thin films were found from the measurements of reflectivity contrast (RC) versus different parameters as follows: RC versus film thickness at (lambda) equals 780nm; RC versus laser power at pulse width (tau) equals 500ns, and RC versus recording pulse width at laser power (rho) equals 13mW. THe mechanism of optical recording process in VOPc and TiOPc films was discussed. The dynamic testing result of TiOPc WORM disk showed that its carrier-to-noise ratio (CNR) reached 45 d when disk rotation speed was 1800 rpm, linear velocity was 14.1M/sec, and recording frequency was 4 MHz. Both of VOPc and TiOPC were found good enough for image storing.

Based on nm fabrication technology, a developed player for dual and multilayer disk is proposed in this paper. A multifocus device with focus 8.5 mm is used. The distance between two neighbor focal plane is 0.45 mm. The numeral aperture of the developed player is 0.59, the focusing spot is 0.93 um. The developed player with the multifocus device is not only simple in structure, light in weight, but also can focus automatically at any layer of multilayer disk eve, no mechanical movement. Compared to the common CD player, the developed player is characteristic of only one multifocus device to focus and split beam, where the prism and the grating in common CD player are displaced, but the focusing and the tracing error signals can be obtained conveniently for servo detection.

Ag_1-xCo_x alloy films were prepared by RF magnetron sputtering onto glass substrate. And the samples were annealed at 200 degrees C and 400 degrees C AgCo films with Co contents below 32 at percent are generally superparamagnetic in their as-deposition state. The fraction of Co atoms in the ferromagnetic component increases monotonically with increasing annealing temperature (Ta) and/or at percent Co. The (theta) _k also increase, but for the Co contents above 45 at percent, as the Ta increase, the (theta) _k increase slowly. For Ag₅₅Co₄₅ (theta) _k equals 0.08 degrees, reflection (R) equals 0.90 and Hc equals 2000 Oe, and for Ag₅₀Co₅₀ (theta) _k equals 0.10 degrees, R equals 0.85 and Hc equals 2500 Oe are obtained. We found that most film's magnetic hysteresis loops with applied external field H normal to film surface and in film plane are similar. We analyzed these phenomenon according to the film's structure.

Here we report LD pumped solidified miniature Nd:YAG laser and Nd:YVO₄ laser with KTP crystal as intracavity frequency doubling material. Using 1W LD 70 mW and 80 mW of the green laser output in TEM_oo mode have been measured for Nd:YAG laser and Nd:YVO₄ laser, respectively. The output stability is better than +/- 3 percent and the beam quality coefficient M² is smaller than 1.2. The laser is small is size and very suitable for optical recording and storage.

Room temperature reflectivity measurement over the energy 0.7eV to 7eV has been made on the phase change recording thin film based on Ge-Sb-Te alloy. The reflectivity curves have been obtained by spectrophotometer. An analysis of reflectivity curves for this recording medium has been made by use of Kramers-Kronig (KK) relation. The refraction index n($omaga) have been obtained as a n energy function. The optical gaps of the recording medium are 0.71eV in glassy state and 1.32eV in crystalline state. The research results show that this recording medium can be used as a phase change optical storage material in short wavelength range. This paper provides a research method by use of KK relation to obtain optical properties of recording thin film, and gives a practical application of this phase change recording medium in short wavelength range and high density storage.

A new simple method of producing line beam from thin laser beam by only a spherical lens is proposed and some experiment results are given. The mechanism of the transformation is due to the large astigmatism of the lens. The evaluation to the generated beams and some related problems are discussed. This simple technique may be useful in 3D profile measurement by light-sectioning surface profile measurement of cylinder lens or reflector by laser scanning and other cases requiring line beam illumination.

In this paper, a principle of synthetic aperture microscope based on the synthetic aperture principle and inverse scattering imaging is described. The algorithm of inverse problem is introduced and the results of computer simulation are given.

We have developed an ultra-high-capacity double-sided multi- data-layer ROM that includes additional UV-cured-resin space-layers on two polycarbonate (PC) substrates. This ROM is made using the photo-polymerization (2P) method and has a structure that bonds the two substrates together. In a double-sided dual-data-layer ROM, using the smallest mark size of 0.44 micrometers with a 0.74-micrometer track-pitch for each layer provides a total data capacity of 17 GB using the 8-16 modulation method. Each side of the double-sided dual-sided dual-data-layer ROM consists of a Si-rich silicon nitride semi-reflective layer (layer 0 or 2) on a 570- micrometers-thick PC substrate and an Al reflective layer (layer 1 or 3) on an additional 50-micrometer-thick space layer. We achieved a base jitter of less than 8 percent and a radial tilt margin of 0.7 degree for all four data layers. We also examined the double-sided multi-data-layer ROM disc structure, and demonstrated the feasibility of the double- sided tri-data-layer ROM that includes a total of six layers and has an ultra-high capacity of 25.5 GB.