Charge-coupled devices: Technology and applications

178 zyxwvutsrqponmlk zyx IEEE TRANSACTIONS ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, VOL. ASSP-26, NO. 2 , APRIL 1978 zyxwvutsrqp Charge-Coupled Devices: ‘Fechnology and ApplicationsR. Melen and D. Buss (New York: IEEE Press, 1976,414 pp., $19.95 cloth, $9.95 paper). Reviewed by Allen Gevsho. Much of the current interest in digital signal processing is motivated by the need to achieve discrete-time (sampled-data) signal processing operations on analog signal samples. It just happensthatthe principalmeans forimplementingthese operations is via digital circuitry so that signals are not only sampled, but are also quantized for compatibility with digital hardware.Therecentdevelopment of the charge-coupled device (CCD) opened the way to the possibility of economically implementing discrete-time signal processors without the need for analog-to -digital conversion. The CCD is based on the metal-oxide-semiconductor (MOS) technologyfor fabricating integrated circuits. In its basic form, the CCDis a monolithic array of closely spaced MQS capacitors whichcan store and transferpackets of charge under control of a clock signal. Charge packets can be created with sizes proportional to an applied voltage and an output voltage can becreated proportional to anextracted charge packet. Thus, the CCD can operate as an analog delay line or, inotherwords, as an analog shift register.Additional techniques makeit possible to implementanentire transversal filterwithhundreds of tap weights ona single integrated circuit chip. With its high packing density, the CCD can also be used as a digital memory, recirculating binary valued charge packetsand periodicallyregenerating thebitsbefore excessive noise corruption occurs. Another application of the CCDis image sensing: by convertingabsorbed photons into charge packets, a two-dimensional CCD array can function as a self-scanning image sensor. Linear signal processing with CCD’s is being widely explored now for a variety of specialized applications. In particular, analogdelayandlinearfiltering are two areas of particular importance. Another application of CCD’s that could become of practical importance is real-time spectral analysis. CCD’s are also being explored fortheimplementation of digital signal processors using charge-coupling to realize logical operations. Clearly, there is good reason why many specialists in signal processing arebecoming interested in CCD’s. Melen and Buss have collected 45 papers out of the over 1000 CCD papers that have appeared since 1970. In general, the papers have been well chosen to present the principles of CCD operation and a cross section of the activity in the field. In their introduction, the editors say: “This book is primarily applications-orientedand,apartfromtheintroduction,the papers are selected to represent the state of the art in such a way that the reader can quickly appreciate the current status of any aspect of CCD technology. Since this volume overviews all aspects of CCD’s, it includespapers of a review nature emphasizing the current stateof the art.” The book begins with a basic tutorial paper by Kosonocky and Sauer and is followed by three pioneering papers: the first conceptionofthe CCD reportedby Boyle and Smith,the first implementationby Amelio, Tompsett,andSmith,and Sangster’s 1970 paperdescribing thebucket brigade device (BBD), a sister technology to the CCD. The remaining papers cover the major areas of CCD activity. There are nine papers on device physics and technology, 11 papers on memory, 11 papers on image sensing, and 10 on analog signal processing. Some familiarity withsemiconductor physics is needed lo understand the morebasic papers, but most of the applicationsoriented papers require very little familiarity with device technology. The papers on analog signal processing will be of greatest 10 papersconsist of the interest to ASSP readers.These following: 1) a survey of analog signal processing, 2) a description of a time-delay chip, 3) applications of CCD’s to radar and electronic countermeasures, 4) an ultrasonic imaging lens, 5) transversalfilter design and performance, 6) a very brief survey of communications applications, 7) transversal filtering for spectral analysis via the chirp z-transform, 8) a comparison between the CCD chirp z-transform and the digital FFT, 9) a surfacecharge correlator, andfinally 10) infrared detection and imaging. These 10 papers do give a reasonable representation of the range of activity and the state of the art in analog signal processing. The paper on transversalfilter design (by Baertch et al.) will be of particular interest t o filter designers. Thetwo papers on spectral analysis could be of significant interest to researchers in speech processing. Some specialized applications which are not represented by the selectedpapersincludeHilbert transform filters, tunable bandpass filters and simulators of reverberation, vibrato, and other audio effects. Adaptive filtering and multiplexed filteringmake only a brief appearance inthebook. One notable omission by the editors is the absence of a paper on digital signal processing using CCD logic circuitry. Although the importance of this approach is perhaps not yet established, it is a very distinctive and interesting applicationof the chargecoupling concept. Many of the papers have definite tutorial value and several papers provide comprehensive reviews of the state of the art (as of early 1976). Overall this collection of reprints provides a convenient way “to get on board” for anyone with a serious interest in learning about CCD’s. Thebook serves as an effective documentortime capsule representing the first six years of CCD technology. Allen Gersho (S’58-M’64)received the B.S. degreeinelectrical engineering from Massachusetts Institute of Technology, Cambridge, and NY, in the M.S. and Ph.D. degrees fromCornellUniversity,Ithaca, 1960,1961, and 1963, respectively. Bell Since 1963 he has been amemberoftheTechnicalStaffat Laboratorieswherehe is currently in the Mathematics and Statistics Research Center at Murray Hill, NJ. His recent research activities have included adaptive quantization, modeling of muscle contraction, and filtering with charge-coupleddevices. Digital Image Restoration-H. C. Andrewsand B. R.Hunt (Englewood Cliffs, NJ: Prentice-Hall, 1977, 256 pp., $24.95). Reviewed by Man Mohan Sondhi. This is the fourth book in the Prentice-Hall series on signal processing. Regrettably, it doesnot measureup totheexpectations set by its predecessors (the book on fast Fourier transforms by Brigham, and the books on digital signal processing by Oppenheim and Schafer and by Rabiner and Gold). The book is in three parts. Part I introducesthe basic concepts of image formation, image recording, and the representation of images in terms of orthogonal bases, statistical distributions,and the like. Part I1 deals with the types of image degradations one might encounter inpractice-blurring by the point-spread-function of the imaging system, introduction of noise, etc. It also discusses possibilities of estimating some parameters of the degradation process from the degraded image itself. Part III presents a number of digital restoration methods. zyxwv