Holograms have been recorded on an photoconductor-thermoplastic device at 1.15 μm. Diffraction efficiencies of 1–5% were obtained with exposures of 400–800 mJ/cm2. Holograms were formed in situ with rapid processing and at spatial frequencies as high as 1000 lines/mm.
The experimental evaluation of a transparent electrophotographic (TEP) film is reported. The objective of the evaluation was to determine the suitability of TEP films for optical data storage applications, especially those using holography. The characteristics of TEP films that motivated the evaluation are good sensitometric and holographic recording responses, relatively high resolution, and a number of attractive applications properties, e.g., long shelf life, good environmental integrity, and exceptional image permanence. In addition, TEP films have an add-on capability. A general description of TEP films is given, and sensitometric and holographic data are summarized for an experimental TEP film.
Because of the growing number of digital data sources -from satellites such as the LANDSAT series to the increasing use of all-digital information distribution networks in the publishing industries -there has been a corresponding explosion in the need to store that data permanently at very high densities such that it can be retrieved conveniently and quickly. In parallel with these developments, the capability of high density optical data storage and retrieval techniques such as holography and optical spot recording to meet these needs has improved as well. Offering data transfer rates of up to 100 Mb /sec (spot recording) to over 1 Gb /sec (holographic) and information storage densities in excess of 100 Mb /in2, these technologies have now made it possible to configure complete systems for a wide range of mass storage requirements. The basic technologies and building blocks required for such systems, the general criteria for converting a mass memory specification to an optical storage system based on it, and examples of both holographic and direct spot systems are described. The present status of the Wideband Holographic Recorder System, with data transfer rates of over 1 Gb /sec, and the MASTAR 1015 bit archival mass memory with information storage densities of over 100Mb /in2, are also reviewed.The last two decades have brought with them an ever -accelerating growth in the amount of information which is accumulated and processed daily throughout the world. This includes such straightforward types of data as conventional text, which can be digitized as ASCII -coded alphanumeric data, and more complex information such as the digitized imagery gathered from satellites such as NASA's LANDSAT series. Data are growing at such a rate that one user has estimated that single facilities storing as much as 1016 bits of information each will be common before the end of the coming decade.' To meet the challenge posed by this incredible data -gathering problem, a number of corporations have built on parallel developments in the area of laser recording to produce specialized high-density data storage and retrieval systems for a wide range of applications. It is the purpose of this paper to outline some of the key concepts behind the many digital optical data storage and retrieval systems available today, and to make some predictions on the direction this field will take in the next few years.HOLOGRAPHIC DIGITAL DATA STORAGE AND RETRIEVAL One of the first types of high density storage systems developed was the holographic data recorder. The initial appeal of holographic recording for permanent data storage was very simple: in the standard Fourier transform holographic recording technique utilized in almost every system of this type, there was a built -in redundancy of the data as recorded on the data record. To illustrate this basic principle, consider Figure 1. On the left side of the figure is an array of spots which are mutually coherent. As the Gaussian
The experimental evaluation of a photochromic material and a photodichroic material for use in wideband digital disc recording.Photochromics and photodichroics have the capability of high resolution recording at high data rates and are in addition erasable. A general description of the recording mechanisms are given, and the sensitometry, frequency response, and image stability are summarized.
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