Edge-Difference Coding--A New, Efficient Redundancy Reduction Technique for Facsimile Signals

This paper describes an efficient redundancy reduction coding scheme for bi-level facsimile signals and field test results of a Group 3 facsimile machine applying this technique. The bi-level signal obtained by scanning documents is characterized by white-to-black or black-to-white edges. These edges cross successive scan lines smoothly in most cases. This scheme makes use of two-dimensional correlation by coding the difference in positions where an edge crosses successive scan lines. The performance of this scheme has been evaluated by computer simualtions for eight CCITT SG.XIV test documents scanned at an 8 lines/mm rate. This scheme reduces the entropy by 24 to 60 percent over the conventional run-length coding scheme and 2 to 10 percent over one of the currently proposed two-dimensional coding schemes, respectively. In a newly fabricated prototype model of a Group 3 machine using this technique, a run-length coded line is inserted everyKlines to prevent error propagation. In accordance with subjective test results,Kis set equal to two in that machine for the case of 3.85 lines/mm resolution and equal to four for the case of 7.7 lines/mm resolution. For these two levels of resolution, the average transmission times for the eight CCITT test documents are roughly equal to 49 s and 70 s, respectively, at a transmission rate of 4800 bits/s.     

Early schemes for television

More than a dozen schemes for sending visual images by electricity appeared from 1877 to 1884. Some used multiwire lines and mosaic arrays; others used single lines and a scanning method?autographic, spiral, linear. Selenium cells and incandescent filaments were common elements. Basic ideas on scanning speed, repetition frequency, synchronism, picture elements, and beam modulation evolved during these years. Some schemes employed magnetooptic effects, others used polarized light, and an optical equivalent of the cathode-ray tube was proposed for one receiver. Mechanical problems were finally solved by the scanning disk, which, 40 years later, with the aid of electronic techniques, became the foundation for practical mechanical television. Both facsimile and television proposals were covered, partly because they were inseparable during this era and partly to show the continuity of developments.     

Comparison of Redundancy Reducing Codes for Facsimile Transmission of Documents

A comparison and a valuation of different redundancy reducing coding techniques for the digital transmission of facsimile documents on telephone lines is presented. Especially taken into account are those codes which have been submitted to the International Telegraph and Telephone Consultative Committee (CCITT) for standardization of digital group 3 facsimile machines. The reduction factor and the sensitivity of channel errors of these one- and two- dimensional codes have been investigated by computer simulations using the CCITT test documents and burst error patterns of real telephone lines. For a resolution of 1728 picture elements per line and 3.85 lines per mm one-dimensional run length coding proves to be the most economical solution. Using a higher vertical resolution of 7.7 lines per mm the effects of transmission errors are less visible in the received document and two-dimensional codes become more efficient. To achieve a transmission time of 1 min or less for a size A4 document a transmission bit rate of 4800 bits/s is required. For the higher vertical resolution a transmission time of 1 min cannot be guaranteed for all types of documents with this bit rate even if two-dimensional coding is used.     

Electrostatic gray-scale facsimile recording

Gray-scale facsimile recording is achieved by using a special electrode arrangement together with the common electrostatic printing technique. The original optical density of a document is reconstructed on an electrostatic recording medium by varying size and charge density of small charged dots. Thus, the developed charged dots allow a continuous gray scale with optical densities in the limits of 0.05 and 1.6 according to the developing procedure. The resolution of this recording technique may be increased up to 10 dots/mm depending on the geometry of the printing device and the scan mode. A recording speed of several pictures per second of size A4 is possible.     

An Analysis of Test Pattern Signals: The Vertical Wedges

A Fourier analysis of the signal generated by scanning the vertical wedges used in television and facsimile test patterns is presented. This reveals narrow concentrations of signal energy at certain points in the spectrum. When these concentrations of signal energy fall in regions of transmission distortion, such as the cutoff regions of transmission lines, the familiar ringing impairment results.     

Techniques for Reducing the Visibility of Transmission Errors in Digitally Encoded Video Signals

This paper is concerned with the problem of transmission errors in digitally encoded television signals. Various techniques for reducing the visibility of transmission error effects in the reconstructed signals have been evaluated using computer-produced film sequences. It is found that the visibility of errors in element difference coders is sharply reduced if an erroneous line is replaced by an average of adjacent lines. It is shown that the visibility of errors in two coders that use spatial prediction is low and can be further reduced by using a "leaky" predictor. The implications of these results for in-frame, interframe, and facsimile encoders are discussed.     

Facsimile today

Over the past few years, facsimile has become the most popular form of business text communication. The paper gives a brief outline of the way in which a facsimile terminal operates and explains the various scanning and printing technologies in use today. The use of facsimile on the integrated services digital network (ISDN) is also considered     

Internet facsimile as an Internet office appliance

The Internet's emergence as a worldwide digital infrastructure has dramatically encouraged a market for communications-oriented appliances, such as mobile phones, personal assistants, network-enabled games, interactive television, Internet telephony, and Internet facsimile. The marketplace is developing rapidly, along with specialized Internet-based “linking” services to connect these devices. Generally two different technical approaches are being explored for these services. One uses classic Internet technology, such as e-mail or the World Wide Web; the other incorporates unique standards, often derived from earlier non-Internet specifications. This article explores efforts to create Internet facsimile appliances, contrasting them with devices for Internet telephony. Efforts at Internet facsimile have produced two different sets of standards. Store-and-forward Internet facsimile is specialized as a profile of classic Internet mail. Real-time Internet facsimile uses a specialized protocol     

A scan-conversion tube utilizing fiber-optics photon transfer

Scan-conversion tubes utilizing fiber-optics photon transfer (FOPT) are currently being developed by the Westinghouse Electric Corporation under contract from the United States Army Electronics Research and Development Laboratory. The tubes consist of three major components: a reading electron gun, a writing electron gun and an interjacent scan-conversion target. The targets consist of a fiber-optics disc coated on one side with a phosphor and on the other with a photoconductor, the reading gun is similar to the low velocity gun of a vidicon and the writing gun is a high velocity cathode-ray tube gun. The majority of targets tested have incorporated a long storage Permachon type photoconductor and a short persistence phosphor; however, other photoconductors and phosphors can be used to perform a variety of video conversions and/or signal enhancements. Operation of these scan-conversion tubes requires only the circuitry normally associated with the driving of a cathode-ray tube and a vidicon; no RF or other type of cancelling circuitry is required to separate the written and read-out signals.     

Personal computer image communications using facsimile

A prototype terminal is described whereby image application services are obtained by combining the personal computer (PC) and facsimile, in which image input/output and the communication functions are integrated in a single unit. An architecture is suggested which combines the functions of the PC and facsimile, such as display, scanning, printing, storage, and communications. The basic concept of the architecture is as follows: (1) to divide the functional resources of the PC an facsimile, and to call each of them a process; (2) to introduce a unified protocol into the image transfer between the processes; and (3) to introduce a transfer environment in which protocol elements are transferred regardless of the state of the process. It has been confirmed that complex image application services with unified processing can be realized with the architecture     

Design and performance evaluation of 1-by-64 multimode interferencepower splitter for optical communications

A 1-by-64 multimode interference power splitter in SiO₂ has been designed for use in fiber-optics communication systems. The splitter exhibits a minimum loss of 0.5 db and a uniformity of 1.7 dB at a wavelength of 1.55 μm. The polarization sensitivity is below 0.14 dB, the reflection level below -55 dB, and the optical bandwidth 30 nm. The fabrication tolerances are ±0.1 mm on the length and ±3.5 μm on the width of the multimode section of the splitter. In comparison with a branching-type splitter it is found that the designed device is approximately 30% shorter than the branching-type device for comparable losses     

影响高精细丝网印刷质量的因素

丝网印刷已成为微电子封装厚膜电路生产中的关键工艺技术。为满足微电子封装高精度、高密度的要求,从网版和印刷工艺参数两方面分析了影响高精细丝网印刷质量的因素。通过选用一定规格的不锈钢丝网,涂覆适当厚度的感光膜,开发出适合印刷50μm线宽和线间距的精密印刷网版;优化印刷工艺参数,将其中的刮刀压力、刮刀速度、离网间距分别控制在一定范围内,使印刷图形的变形量减少到200mm±30μm,实现线宽和间距为50μm、边缘清晰的精细印刷。     

Direct gravure printing (DGP) method for printing fine-line electrical circuits on ceramics

The tendency toward higher packing densities and higher frequencies for telecommunication devices based on ceramic technology requires smaller dimensions for electrical wiring. Electrical thick-film circuits for ceramic and LTCC-substrates have, up to now, been printed with screen printing, where the printing lines width limit is about 125 /spl mu/m in mass production. A silicone polymer direct gravure printing (Si-DGP) process has been developed to perform smaller dimensions, down to 20 /spl mu/m lines width, for electrical circuitry. In the DGP process, the conductor paste is doctored to the grooves of the gravure and then it is pressed against the substrate. The paste is, thus, printed directly onto the substrate from the patterned gravure. The results showed that, using the DGP process, it was possible to print conductor lines down to 20 /spl mu/m in width. It was also noted that a 100% transfer of paste from the grooves of the gravure could be obtained with commercial pastes using the silicone polymer gravure. A dried thickness of up to 28 /spl mu/m was measured for the narrowest lines. Also conductor lines printed by the Si-DGP method were embedded inside LTCC-module.     

Trends in digital communication by wire

The introduction and rapid spread of pulse code modulation must be examined in the framework of overall capability, efficiency, and cost. However, apart from television, the only field of application that can presently justify a massive investment in a new transmission system is telephony, because it represents the dominant communication market. Other communication services?such as data and facsimile transmission, telegraphy, broadcast sound, and closed-circuit television?must in general travel as passengers on telephony networks if they are to be economically feasible. Hence, the most fruitful approach to an examination of digital communication is to begin by studying PCM telephony and then to see how other services can be coordinated with it.     

The VIDEOGRAPH®electrostatic printing process

An electrostatic printing process called VIDEOGRAPH makes use of a special cathode-ray tube for the generation of latent electrostatic images. Television-like signals produce these images on the surface of dielectrically coated paper by means of a special face plate. This face plate contains a large array of finely spaced electrical conductors which permit the transfer of the electrostatic image produced by the electron beam from the vacuum side of the face plate to the dielectric paper in contact with the atmospheric side of the face plate. These images may be developed and fixed in much the same manner as other electrostatic images. Equipment based on the VIDEOGRAPH process has been principally applied to the production of magazine address labels. The developed equipment produces address labels from digital input data at rates up to 14 000 lines per minute. This results in over 1 000 000 labels per 8 hour operational periods. Other equipments include facsimile, digital line printer, and high-speed point plotters. Printers using the process tend to be quiet in operation, have relatively few reciprocating parts, and provide relatively troublefree high-speed operations. The output is limited to a single copy and, to achieve high resolution, rather expensive precision circuits are required.     

基于无铅SMT焊膏印刷参数优化控制研究

无铅表面组装制程是以模板印刷、表面贴装元件放置、回流焊或波峰焊为主要步骤.其中模板印刷制程在生产线中扮演第一个重要的步骤.文章设计了"印刷结果观测数字化实验"方法,并找出模板印刷工艺无铅化生产的最优化工作参数,得出NP-04LP丝网印刷机,0.127mm厚的不锈钢模板在使用Loetite LF320无铅焊膏时,考虑SM...     

The absorption ink transfer mechanism of gravure offset printing for electronic circuitry

The gravure offset method has been developed toward an industrially viable printing technique for electronic circuitry. In order to obtain the optimum ink resin for printing lines of required thickness (>5 /spl mu/m) of narrow lines (down to 25 /spl mu/m), several ink resin systems have been assessed in previous studies by the authors. The best printed results were obtained with a novel ink using a hydrocarbon resin. This ink did not comply with the traditional ink transfer mechanism based on evaporation of the solvent, but with a postulated new "absorption mechanism.".     

1-Inch Saticon for high-definition color television cameras

A high-resolution 1-in TV camera tube with the Saticon photoconductive layer has been developed for live color image pickup in the high-definition television system based on 2:1 interlaced 1125 scanning lines and 60 fields per second. The inherent high-resolution capability of the Saticon photoconductive target is fully demonstrated by the use of a diode-operation electron gun having no beam crossover point. The electrons emitted from a flat barium-impregnated tungsten cathode are formed into a narrow and laminar electron beam of high current density and low beam temperature using a fine beam-defining aperture about 12 µm in diameter in the positively biased G1disc electrode. The tube has an outstanding resolving power and a low lag characteristic as well as sufficient beam current margin to handle the standard peak signal current of 0.5 µA required for a reasonably highS/Nratio in the wide-band video signal system. The applicability of the design concept to the tubes for standard TV systems is also discussed.     

全光纤相干多普勒连续激光多普勒风速仪研究

介绍了一套全光纤相干连续激光多普勒风速仪,该激光风速仪使用了1.5um光纤激光器作为激光光源,其输出能量为~1W,利用保偏环形器、耦合器等器件搭建了一套同轴收发的风速仪系统。利用距离望远镜~5m的转盘对系统进行了校准实验,实验结果表明系统的速度分辨率和测量与转盘实际速度的线性拟合系数分别为0.021m/s和0.99。该系统还成功实现大气风速的测量（~25m处的大气）。