There are two principal methods of producing correspondence quality copy from a laser printer. One method employs a polygonal mirror spinner as the scanning element and the other method uses an acousto-optic laser beam deflector. The operation and experimental characterization of two breadboard scanner systems, one of each type, are discussed. The performance characteristics are then compared and cost considerations presented.
An electrophotographic film utilizing particle migration phenomena has been under investigation at XEROX for some time. Photographic migration imaging produces visible images by positioning particles imagewise in depth in a softenable layer. The images are formed by a three step process of : 1- Electrostatic charging 2- Imagewise exposure 3- Development by viscocity reduction
A process and materials have been developed for the transfer of electrostatic charge from a photoconductor to clear film. Such a process has applications in high resolution imaging systems. In operation a photoconductive layer coated on a metallic plate is charged by corona and imaged with visual radiation to form a latent image. The photoconductor is then placed in contact with the electrographic film consisting of an active insulating layer on a conductive layer all on a clear film base. While in virtual contact the image charge transfers from the photoconductor to the insulation layer of the film with no external grounding or applied voltage while maintaining 100 1p/mm resolution. A model based on a simple electrical circuit has been developed. The model predicts the division of charge during contact of the photoconductor and film with air gap breakdown on approach. Although many complex charge transfer and air gap breakdown mechanisms may be also be occurring near and during contact, the predominant one can be explained using this model. The experimental apparatus and measurement technique is described. The charge transferred was found to be directly related to the dielectric characteristics of the photoconductor and insulating layer of the electrographic film. The measured surface charge after transfer supports the model developed. The toned image density can also be related to the surface charge on the electrographic film. By variation of these parameters the optimum photoconductor and film configuration can be determined.
New high resolution electrophotographic materials hold promise of adding on-line processing capability to an existing high data rate holographic recording system, for read-after-write applications. Electrostatic and optical density sensitometric data for James River Graphics and Eastman Kodak materials are presented. Processing conditions which yield visibly resolvable line structures at 800 1p/mm spatial frequencies are discussed. The resolution capabilities of these materials also make them candidates for digital spot recording applications.
The photodichroic silicate glass surface is a direct-read-after-write laser recording material which permits instant optical recording without processing of any kind. The required writing energy density at wega Hz rate and higher is 40 mj/cm2. An even, better writing sensitivity is expected for a preconditioned glass surface which is yet to be demonstrated at mega Hz rates. The inherent resolution. capability of this material is better than 2000 cycles/mm, which is consistent with the fine grain structure of the photodichroic silicate glass surface (grain size <0.02μm). The photodichroic silicate glass surface can be pre-recorded. with tracks of width fpm or less. It is potentially a pin-hole-free recording material due to the inherent homogeneity of the silicate glasses, and to the very small sizes of the photosensitive crystals, relative to the wavelength of light and the thickness of the pkotosensitive.glass surface layer. The physical effect of recording is irreversible, yet the recorded spots or bits are erasable. The erased 1-bit can be distinguished easily from the o-bit of course, not distinguishable in the normal read mode), when necessary. There is also a mechanism. to prevent erasing after recording and error corrections are completed. The writing is done with a polarized red light, and non-destructive read is done using a near infrared beam, with the recorded bits between crossed polarizers. The erasure is to re-expose with the wrice beam whose polarization direction has been rotated 45° with respect to the initial polarization exposure direction. In this manuscript, the physical effect of recording is discussed in detail, including the intensity dependent writing sensitivity, the threshold, effect, and the relationships among observed spot size, contrast and the writing energy iliensity. Recording in mega Hz rates as well as write-erase cycling are demonstrated. The read contrast of the recorded image is studied using video microscopy, and the transmission spectra of 1-bits between. crossed polarizers are measured. The origin. of the read contrast is discussed, and the experimental data on the spectra of dichroic absorption difference together with the associated birefringence are presented.
The optical properties of a silver-halide based thin film material are described in terms of its possible use as a high-density, read-write-erasable, optical recording medium. Exposure of the initially optically isotropic film to polarized light in the wavelength region, 0.5-0.7μm induces dichroism and birefringence over a broad wavelength regime, 0.4-1.0μm. The film is essentially insensitive to exposure wavelength beyond 0.8μm. The optic axis of the induced anisotropy coincides with the polarization direction of the incident beam. The optic axis can be rotated to any new direction by re-exposure to a new polarization direction of the incident beam. The use of this material as a read-write-erasable recording medium is shown to be possible utilizing a polarized He-Ne laser as the write source and a GaAs (λ-0.82μm) laser as the read source. The reading mode is accomplished through the induced birefringence at 0.82pm where the film is insensitive to further bleaching. The erase mode is accomplished by re-exposing the recorded spot to a 45 or 90° rotation of the polarization direction of the write beam. Specific sensitivity data will be presented.
The information explosion has created a need for a more effective and versatile mode of storing, accessing and displaying the information. This paper concerns itself with the display of information. To be effective the display device must be portable and useable with low power consumption and sufficient resolution, brightness and contrast for continuous use. The development to produce thin, flat electronic displays combines the patented distributed optics technology with electronically addressed dot matrix display devices, such as liquid crystals. Specifically, to achieve a total display device depth of the order of 15cm (6inches) the system makes use of multiple micro-lenses operating in parallel each with a projection distance of 11.8cm (4.5 inches). Between each parallel micro-lens and its fiber illumination module is placed a 2.5cm (1") square liquid crystal module (LCM) which contains a transmissive liquid crystal cell. Each cell displays its, portion of the desired image. This image when projected with its neighboring module (s)/cell (s) creates a complete nonsegmented image for viewing at the screen. This paper presents the design and performance of a breadboard demonstration unit of the concept using four 2.5cm x 2.5cm(1"x1"),32 by 32 dot matrix liquid crystals producing a 25cm by 25cm (10" by 10") display area. This is followed by the presentation of the design of a developmental model of the concept using seven 5.08mm by 5.08mm (0.2" by 0.2"), 100 by 100 dot matrix crystals. The 5cm by 35.5cm (2" by 14") display area permits the display of 8 lines of 80 characters per line.
This paper describes a wideband optical disc, digital recorder/playback system, the disc itself, test results, applications and future improvements. Recording is accomplished with a modulated laser beam, positioned on the disc by a track mirror and a focus lens. Playback is done at a reduced constant light level. A servo maintains precision focus of the laser spot on the microscopically uneven disc surface. Fine tracking is obtained by a dither track servo. A trilayer antireflection disc structure provides high optical and thermal efficiency, very high sensitivity and signal to noise ratio, and has the potential for low fabrication cost. Record/playback data rates of 50 Mb/s and data densities of 1011 bits per disc side have been demonstrated. Optical disc configurations have been developed for three applications: a 400 Mb/s recorder/reproducer (using eight 50 Mb/s channels), and a 1013 bit jukebox reader, and a 1014 bit mass memory system (with a 3-second access time to any data record). Future systems will use laser diodes for both record and playback, allowing more compact designs with greater reliability and lower cost.
One of the most distinctive features of the optical disk mass storage technology which has been under development at Xerox Electro-Optical Systems is the extremely high numerical aperture (NA) of the objective lenses used for writing and playback. A disk system with a 0.90 NA lens has over five times the data capacity of a comparable disk system with a 0.40 NA lens. This increased data capacity comes at the price of a reduced depth of focus and significantly increased sensitivity to aberrations. The subject of this paper is the performance of the "skew beam" and the "Foucault knife-edge" techniques for sensing focus errors. Specific topics include: (1) An analysis for optimizing the sensitivity of the skew beam configuration, (2) An observation of the close similarity between the skew beam and the Foucault knife-edge techniques, and (3) A partial list of sources of aberrations unique to high numerical aperture optics, and their impact upon the performance of the focus error sensing detector.
SlideStore is an improved optical memory concept that uses metalized glass slides 4 by 4 inches by 60 mils thick as the recording medium. Digital information. is recorded onto these glass slides by ablation of the metal film with a laser beam. Each slide will hold 2.9 x l09 user bits. The information recorded in the present system is digitized pictorial information that has been run-length encoded to increase the packing density. Each slide will hold approximately 12,000 correspondence type documents. A SlideStore is configured to hold 2000 slides in one read write module. The data rate is 5 megabits per second and the error rate is less than 1 in 1011 bits. The engineering prototype is now undergoing systems tests.
A new concept is presented involving the use of dynamic preheating to aid in the laser recording of information on thin metal films. Two beams are used to record a single track of holes in the film. A conventional modulated write beam is preceded by another unmodulated preheat beam. The energy supplied by the preheat beam raises the temperature of the metal film to just below the hole formation threshold. The write beam need only supply the additional energy necessary to actually form the hole. The results of analytic and experimental studies of the preheat aided write process are presented. A proposed application involving multi-channel semiconductor laser recording is described. The use of preheat allows a 50% reduction in the power required of the semiconductor laser and provides for a 55% improvement in the packing density of the written information.
The Image Processing Facility (IPF) of the NASA/Goddard Space Flight Center is required to provide image recording support for several missions incorporating a variety of sensors with widely differing characteristics. In many cases, the general sensor parameters are specified, but detailed information such as the exact image array size and the desired transfer function are not finalized until near the launch of the spacecraft. Economic and scheduling constraints preclude the development of a different film recording device for each sensor; therefore, the approach chosen by NASA was to develop a versatile film recording system capable of meeting the requirements of all of the imaging sensors for which film production responsibilities were envisioned. The recording system developed was designated the high-resolution film recorder (HRFR). A competitive procurement resulted in the selection of the Radio Corporation of America (RCA) for development of the HRFR. This paper addresses the technical requirements imposed by sensor constraints and end users of the film product, and the implementation techniques used to satisfy those requirements. The ability to produce annotated imagery with array sizes ranging from 1 to 400 million picture elements and a programmable radiometric transfer function are among the many capabilities of the recorder. Innovative design and engineering approaches were required to provide the desired versatility without sacrificing performance. Performance of the system will be addressed, with examples of space acquired imagery.
The High Resolution Film Recording System (HRFRS) recently delivered to NASA/Goddard Space Flight Center by RCA, is uniquely characterized by full flexibility in: Resolution (1,000 to 20,000 pixels/scan). Line Rate (15-350 lines/sec), Data Rate (0.5 to 20 MBit/sec), Optical Spot Size (10μm to 200μm), Pixel Aspect Ratio (0.5 to 1.5), and Frame Aspect Ratio (0.5 to 1.5). This flexibility is desinged to accommodate the specific characteristics of all NASA's satellite imaging sensors of the '70's and '80's. RCA renamed this system "Operational Laser Beam Recorder" (OLBR) to reflect the production evnironment in which this versatile, high performance image recorder must operate. Design techniques and objectives are presented which meet the required flexibilities while maintaining simplicity of design, repeatability, quality of performance, and operabil ity in an image production environment. Human factors, careful partitioning of sub-systems and innovative design techniques are successfully employed to yield a versatile film recording system with a minimum of operational complexity.
The Earth Resources Observation Systems (EROS) Data Center is responsible for processing, archiving, reproducing, and distributing satellite and aircraft remotely-sensed Earth imagery data in both film and digital format. Landsat Multispectral Scanner (MSS) and Return Beam Vidicon (RBV) sensor data alone represents a daily recording requirement of 23 billion pixels on 1000 feet of film. New satellites and sensors may double this amount of data within two years. To handle these requirements, the EROS Data Center installed an operational, multi-mode, programmable, high throughput, high resolution laser-beam film recording system directly on-line to the primary digital image processing computer. This system employs an Argon-Ion laser light source, electro-optic modulator, and rotating mirror to expose film in a flat-field line-scanned format at rates up to 400 lines per second. Laboratory-type requirements, such as a geometric fidelity of ± 0.05% and density repeatability within ± 0.05D, are maintained in a high-throughput production environment. To provide for future sensor formats, the scan rate, scanning spot size, film velocity, laser power, and number of overscans are firmware programmable for up to 16 on-line, auto-matically selectable configurations.
Much has been written and discussed on increasing reconnaissance information flow time for imaging systems. Recently, some very high performance, high resolution sensors have been tested or are about to be tested with a Tactical Laser Beam Recorder as the image generator, which significantly improves the reconnaissance information flow rate. A report will be given on the performance and several interesting and novel design features of the laser beam recorder in the reconnaissance applications of the Quick Strike Reconnaissance (QSR), Electronic Solid-State Wide-Angle Camera System (ESSWACS) and Long Range ELECTRO-OPTICAL RECONNAISSANCE SYSTEM (LOREORS). Other laser beam recorders have been designed to provide for a maximum of flexibility and control by the operator. They were also designed physically for a laboratory type of environment where all mechanical and environmental controls are well maintained. This paper describes a laser beam image recorder, which has been designed and fielded for exactly the opposite characteristic. That is, a minimum amount of flexibility for the operator, and a maximum of amount of control by a remote sensor minimizing the operator duties and requirements. It is also designed for the shelter environment of a tactical and field operation, where the environment is not so benign.
Linear arrays of extremely small, individually addressable Light Emitting Diodes (LEDs) are being developed at Perkin-Elmer for use in high bandwidth, high resolution optical recorders. These essentially monolithic arrays offer an attractive alternative to systems now using lasers and scanners. They will be compatible with existing CCD arrays currently being used in various optical sensors, and will make possible a fast, relatively efficient, all solid state optical recorder with very high spatial resolution capabilities. GaAs0.6P 0.4 was selected as the source material for the LEDs because it emits in the red portion of the visible spectrum (i.e. near 6600Å), which is well within the sensitivity range for a number of different recording films. Operating characteristics for arrays of surface-emitting LEDs fabricated on 12-13 μm centers will be discussed in this paper. Included will be data on the radiant intensity as a function of current, and the current-voltage characteristics for individual elements, as well as the results of measurements of both the near-field and the far-field emission patterns. Recent measurements of the radiant intensity indicate that operation in the 1-3 μwatt/steradian range can readily be achieved using LEDs having rectangular emitting areas as small as 9 μm x 14 μm. Output power levels of this magnitude will permit data recording rates in excess of 100 Mpixel/sec.
The use of the Universal Product Code (UPC) in conjunction with the laser-scanner-equipped electronic checkout system has made it technologically possible for supermarket stores to operate more efficiently and accurately. At present, more than 90% of the packages in grocery stores have been marked by the manufacturer with laser-scannable UPC symbols and the installation of laser scanning systems is expected to expand into all major chain stores. Areas to be discussed are: system design features, laser-scanning pattern generation, signal-processing logical considerations, UPC characteristics and encodation.
A flexible image digitizing system is under development to provide for digitization of stereo photographs and graphic materials in an automatic feature extraction system. The digitizing system employs two servo-controlled photograph stages and linear CCD array cameras to scan stereo photographs for image digitization. Raster scanning is accomplished by moving the photograph in a direction approximately normal to the array while reading out successive lines of video from the array. The photograph scanner optics contain zoom magnification and rotation capabilities, providing variable resolution and an ability to correct first order geometric image distortions. Graphic input materials are scanned by a separate line array camera mounted on the plotting head of an XY plotter. The digitizer system employs a hardware digital video processing unit to correct for dark signal and gain variations of the linear arrays. This processor also corrects for geometric distortions of the lens systems and arrays. Control of the overall system is implemented with a minicomputer, which provides scanning, data transfer, calibration, and setup functions of the system. Peripherals of the minicomputer include a large dual access disk storage unit for image data storage and transfer to the main computer of the automatic feature extraction system.
An ever increasing need to have geographic information available in some type of digital data base has prompted a search for methods to automate the process of converting existing cartographic information -(usually in the form of maps, charts and map separates) - into digital form. The information "map" must be digitized and it's contents must be stored or handled in a manner that makes it a useful adjunct to the cartographer in the performance of his map making duties, as well as being an aid to those requiring the digitized information. Automatic digitization by means of a laser scanner in conjunction with sophisticated data handling and data storage techniques have been combined to provide systems which can be used in a production environment for the successful transformation of information contained on line drawings into the digital domain. The system to be described has proven to be both cost effective and efficient to a degree that is pleasing to both the manufacturer and users.
An ultra-high resolution multicolor graphic data terminal is being developed for use in acquisition and exploitation of high density graphical data. The system consists of three storage mode smectic liquid crystal data cells with laser addressing and projection readout. The projected graphical data is superimposed by rear projection onto a common 24 x 32 inch viewing/working surface. A multicolor format is achieved by projecting data from the three cells in three primary colors, thereby producing seven distinguishable composite colors. Each data cell contains 6000 x 8000 addressable pixels for a total memory capacity of 48 x 106 memory locations per cell. The total data capacity of the system is 144 x 106 pixels. A galvanometer mirror deflection system controlled by a beam position sensing feedback loop is used to position the focused 1.06 μm laser writing beam to an accuracy of .006%. The beam position sensing system is relatively insensitive to variations in signal levels and can sense the deflected beam position with a 20 MHz bandwidth. The laser scanning focus lens is an f/8 telecentric design and produces a 4 inch diagonal format with 10,000 TV line resolution and lateral color distortion of less than 0.0002 inches for both the writing laser wavelength at 1.06 μm and the position sensing wavelength at .6328 μm. The three 10X projection lenses have a distortion less than 10,000:1 and can accurately superimpose the images on the viewing screen from the three liquid crystal cells to produce a color graphic display in six colors plus black and white. The imagery can be reversed to produce either a dark field or a bright field display.
Current technology has established laser scanning systems capable of writing high resolution, large-format images. Recent developments have extended this capability to computer-synthesized images. A system known as a Laser Pattern Generator (LPG) has been manufactured using this technology to precisely image printed circuit board (PCB) masters. Exposure time for an image area of eighteen by twenty-four inches is reduced to two minutes from about five hours for the present vectorized plotter method.
The AAIPS Cartographic EBR is a high performance, computer controlled, large format (8" X 5") electron beam recorder developed for the production. of computer generated master recordings on film which are subsequently used to produce a variety of Flight Information Products (FLIP) such as: • Approach and Departure Procedure Books • High and Low Altitude Enroute Charts • IFR and VFR Supplements • General Planning Books • Area Planning Books • Special Use Airspace Books
A laser printhead is described that uses an 18 facet rotating mirror to produce a scanning spot of red light from a 5 milliwatt, HeNe laser. The scan has a high duty-cycle in a direction parallel to the irtruni axis of a conventional ellectrophotog.raphic processing system. The beam is modulated by an 80-megahertz, acoustooptic modulator that allows dot-switching times of 100 nanoseconds. The dot matrix is 240 x 240 per inch over an 8½- x 14-inch document area. Positional timing of the scanning spot is determined by a reference beam scanning a Ronchi grating. This beam is split from the fixed laser b a thin Wedge prism and passes through the same optical system as the scanning beam,. The reference beam is at a slightly different angle than the Bragg angle as it goes into the acoustooptic crystal, so is not affected by the acoustic waves that are transduced. The laser printhead has been designed as a hand-carried, compact, modular-component assembly that allows field replacement of several of its components including the laser.
The sound diffraction profile due to the rectangular electrode of an acousto-optic cell has been computer modeled, with specific attention to the sound profile in the direction orthogonal to light and sound propagation. The profile is uniform only immediately adjacent to the transducer, which is too close for effective light interaction. Effective interaction can occur only when the light beam is at least 1 or 2 millimeters away from the transducer, where the sound field exhibits Fresnel near field fluctuations in sound intensity, corresponding to regions of constructive and destructive interference. The light beam should fit within a region of constructive acoustic interference to optimize the acousto-optic coupling. A deflector requires changing acoustic carrier frequency and therefore changing near-field acoustic profile. The light beam must be located in a region of reasonably uniform sound intensity for all carrier frequencies. A simple experimental method has been developed to test these results, consisting of Schlieren imaging onto a CCD linear array.