An analog recording technique is described where an acousto-optic Bragg cell is driven by an amplitude-modulated carrier and strobed with a pulsed laser. The acoustic column of the Bragg cell is imaged onto film using the zero order diffracted light to maximize system efficiency. Performance characteristics of system components are examined relative to their impact on system bandwidth, dynamic range, and frequency resolution. A breadboard recorder was used to demonstrate the technique and results from system tests are presented. The breadboard recorder achieved a bandwidth extending from 10 to 190 MHz with a dynamic range peak to RMS exceeding 22 dB. A two-dimensional, optical processing technique is described where time-bandwidth products exceeding 106 can be achieved.
A brief summary is given of the principles of operation of a laser image recorder used for spectrum analysis. A special purpose acousto-optic modulator is an essential element of the image recorder. Remarks are made on inhouse efforts in this area. A discussion is presented on some design considerations for extending operation of the recorder to cover bandwidths of 500 MHz.
An optical disc mass memory system is being developed which will provide automatic access to any data in a store of 1013 bits within five seconds. This system contains a library of 128 optical discs with mechanisms for retrieving any disc, loading it onto a turntable, and recording or playing digital data at a rate of 50 Mb/s. The optical discs are housed in protective cartridges to facilitate handling by the operating personnel and automatic disc handling mechanisms. Cartridges are moved from the store to a load station by a belt-driven X-Y transport mechanism. The load station then mounts the discs onto a precision turntable, and they are spun up to speed while housed within their protective cartridges. A window in the cartridge wall provides access for the record and play laser beams to operate on the disc media. The disc handling mechanisms were designed to minimize mechanical shock and vibration while providing a rapid, smooth operation. A special centering hub design, for the turntable minimizes disc eccentricities during multiple load/unload cycles and allows easy inter-changeability among machines. This paper will describe the cartridge, turntable, and disc handling mechanisms designs. Test results from an engineering model implementing these designs will also be presented.
Techniques for testing laser scanning subsystems play an important role in their development. Testing determines how well the design was implemented, indicates whether all pertinent factors were taken into consideration during the design and error analysis, and most importantly, demonstrates system performance. This paper will discuss typical test methods for scanner subsystems designed and fabricated by the Optical Systems Department of Harris Government Communications Systems Division. Specifications for one Harris scanner are given in Table 1, and a method to test each parameter is discussed below.
Multifaceted polygon mirror scanners have been limited in application over the years due to the high cost of fabrication. Recent advances in fabrication technology have permitted costs to be reduced to the extent that these devices can now be considered for new applications.
A simple, polygon-type flying spot scanner with high light throughput, well controlled spot size and good linearity is described. This compact underfilled, double pass optical system, with axial input provides a large scan angle with few optical elements and thus lends itself to a cost-effective design. Since the included scan angle is symmetrical with respect to the optical axis of all active components, a high degree of spot energy uniformity can be achieved. In addition, the spot size can be easily changed to accommodate a wide range of scan line densities. Several successful applications have proven that the system works equally well with gas or solid state lasers, and it can be applied both for raster input and output scanning, including color printing.
A novel way to achieve a flat field large format plotter is described. The system makes use of two spherical mirrors and a small spherical aberration correcting element and can be made achromatic. The field flattening is dynamically obtained, making use of a polygonal scanner reflecting a non-collimated laser beam. An implementation example is given in which diffraction limited performance is achieved over a 436 mm wide format (17") with a spot measuring 17.5 μm at FWHM, employing a HeCd laser as the light source. A systematic way for the system's design is described.
Laser scanning systems are finding increasing applications in commercial products, therefore new methods of generating high resolution scans at moderate frequencies and large amplitudes are constantly being researched. One at the most promising technologies to emerge employs low wobble-resonant scanners. Resonant scanners display all of the above performance characteristics and are available at a reasonable cost. There are two important types of low-wobble resonant scanners. The first has cross-flexure pivots and is designed for large mirrors (up to 40 mm diameter). The other uses two torsion bars, a smaller mirror (10 mm), and is intended for high volume applications. Principal applications, theories of operation, and performance of these scanners are discussed in this paper.
This paper discussed the application of resonant mechanical scanners to bar code readers. Presented are some of the design parameters and trade-offs for the torsion rod and taut band scanner types. Included are the drive requirements and a generalized description of several driver circuits. In addition, examples of a single and two-axis bar code scanner application employing resonant scanners is presented.
Using a laser beam and galvanometer scanners with mirrors in an orthogonal configuration is a simple, low cost way to scan an X-Y flat field in a raster or vector mode. The major drawback in the method has been the geometric distortions inherent in two-axis, flat-field scanning, primarily pincushion, tangent, and focus errors of the imaged beam on the field. Until now the problem has been resolved by pre-objective scanning in which a corrective lens is placed between the scanners and the field. Use has been limited, however, to small fields (20 cm) where corrective lenses are practical. Accurate corrections with multiple wavelengths are difficult, if not impossible. Small fields with large radii also have been used to minimize geometric errors, but long focus distances create a number of optical problems. General Scanning now has a post-objective scanning system which solves these problems in virtually any field size or scan radius configuration. By positioning simple lenses and dynamic focusing before the scanners, a post-objective scanning system is created. In this system, the scanning and focus servos are under precise control of a digital correction computer. This paper discusses the theory of correction and the hardware available, as well as the implementation and performance, of a post-objective scanning system.
The last ten years has seen the commercial introduction of many laser printing systems. These systems have generally been aimed at the very high end of the printer market, where high throughput and high image quality are necessary to justify an equally high price. The optical system of such a printer is typically required to provide the highest resolution and printing speed possible consistent with the properties of the remainder of the system. I would like to describe in this paper some of the trade offs involved in the design of one such optical system, that of the Hewlett Packard 2680.
Electrophotographic technology allows for the simple incorporation of document scanning. This function is accomplished by monitoring the specular reflection of the toned image on the copier's photoconductor drum. Documents can be scanned at a rate and resolution comparable to normal electrophotographic printers. Scanning in this way takes advantage of the panchromatic response of the photoconductor, avoids the color-blindness issue of lasers, and prevents exposure of the user to laser radiation. Our experiments show that the principle source of noise in the scanned signal is due to an interference effect in the photoconductor and a detailed description of this effect will be presented.
When high performance is demanded of an acousto-optic device, certain effects that are usually considered negligible become evident. Fresnel near field effects frequently become important when high efficiency and/or high bandwidth is demanded of a modulator. Large aperture and high resolution deflectors are also effected by acoustic field variations. The design of the transducer and the electrode can be used to alleviate many of these effects.
Over several hundred years of refinement, the graphic arts industry has become skilled in producing images, in the form of printed pages, that maximize both esthetics and information content. Skills of graphic arts practitioners include typeface design; selection of proper combinations of typefaces with proper character spacing for maximum readability; balancing of page components and layout for best economical information transfer; and optimizing picture reproduction techniques consistent with mechanical printing processes.
A general view is given to show todays possibilities of increasing speed of image recording and scanning by using laser technologies. This is based on the products of Dr.-Ing. Rudolf Hell GmbH, a leading manufacturer of laser equipment for the Graphic Arts. A more detailed description follows for flatbed systems and a new recorder for color proofs.
This paper reports on a large-formt (41- by -59 inches), high-resolution (1 x 106 pixels/in2) and high-speed (2.8 x 106pixels/sec) Digital Laser Platemaker (DLPM) that is under development at the US Army Engineer Topographic Laboratories. The development is a stationary drum system with semi-automatic interior media loading. Significant reductions in the through-put-time to produce lithographic copies of digital products produced by the Defense Mapping Agency (DMA) is expected. The primary savings are expected to be derived from the ability to completely by-pass all conventional photographic processes. Plate exposure in the DLPM is accomplished by the modulation of an Argon-Ion UV laser that exposes presensitized or wipe-on press plates.
In view of the continuing improvements in the He Cd technology, a case can be made to support the claim that the He Cd laser is close to being an ideal source for high speed, high resolution recording. Current He-Cd technology will be examined in relation to recording media, modulators, scanners & recording requirements.
The spectral sensitivity of several common photosensitive materials used in high speed writing applications is described along with response characteristics at specific emission wavelengths of common commercial lasers. A comparison is presented of the design and performance characteristics of helium-cadmium versus air cooled argon-ion lasers used for writing on orthochromatic materials. The laser design simplification opportunities are discussed for helium-cadmium lasers because of the high efficiency and low power density inherent in helium-cadmium lasers. New hard sealed coaxial plasma tube construction emulating helium-neon plasma tube construction has dramatically improved the reliability and shelf lifetime of helium-cadmium lasers.
A new type of laser capable of delivering multicolor beams is presented. This laser can emit red, green, and blue colors either independently or simultaneously under cw operating conditions with a wide range of output power levels ,suitable for many information processing applications, especially color scanning and image processing. The basic operating principle of the laser is reviewed, and design features are discussed. General laser operating characteristics and key performance parameters such as spectral power output, noise and stability, and laser beam characteristics are described. Potential applications of this laser are illustrated.
An image scanner/digitizer has been developed which utilizes solid state array sensors to achieve high-speed, high-resolution scanning of black and white images. The internal 68000 microprocessor-controlled unit is desk-top sized, easy to interface, and simple to operate. It incorporates the following features:
o Flat bed input platen o Two selectable input scan widths
o Cursor cropping of scanned area to minimize digital data storage requirements o Eight bit per pixel digitization of imagery
o One bit per pixel digitization of line art
o Reflected or transmitted white light scanning
o Automatic pre-scan sensor calibration
The scanner provides high fidelity digitization of imagery for a variety of applications, including CAD/CAM and medical image enhancement. It is currently being used to input line graphics and photographs to an all-electronic image assembly subsystem. Proprietary software provides a powerful, user-friendly menu of the image processing and page layout functions required for electronic page composition. Simple operator interactions with a data tablet invoke and control the operations of:
o Contrast/brightness enhancements
o Image placement and rotation
o Software-interpolated image sizing
o Cropping and stripping
o Edge enhancement
o Small area modifications o Graphic creation and modification o Application of spot colors from a user-defined color palette
This paper describes the changes in morphology of microscopically textured germanium as a function of the fabrication parameters. A technique of sputtering aluminum from the upper electrode to provide uniform mask formation over the surface is described. This process allows fabrication of much larger area textured surfaces than was possible using previous techniques.
Proc. SPIE 0390, Performance Comparisons Of Electrophotographic, Dry Silver, And Wet Processed Recording Media Exposed With Gas Laser And Laser Diode Light Sources For Image Recording, 0000 (20 September 1982); doi: 10.1117/12.935055
The characteristics of electrophotographic film are particularly useful in Tactical, (transportable) Laser Beam Image Recording (TLBR) where high image quality is desired without the supply and storage problems associated with silver halide or wet film processing. Since electrophotographic and dry silver film can be sensitized to infra red BUR) a directly modulated injection laser diode light source can be used to replace gas lasers in the TLBR. This makes possible a compact and rugged laser recorder. Comparisons of system performance are given for electrophotographic, dry silver, and wet processed media exposed with laser diode and gas laser light sources.
A series of lenses for focusing and collimating the output of semiconductor lasers is described. The description of an anamorphic prism pair to convert the beam cross-section from elliptical to circular is also given. Designs which perform to diffraction limitation, yet lend themselves to low cost manufacturing are specifically considered. Correction for the aberrative effects of diode windows, a situation commonly encountered, is analyzed in detail.
A novel holographic laser beam deflector is described which is invariant with regard to deflector wobble and centration errors, has high radiometric efficiency and provides a bow free scan. The deflector's insensitivity to mechanical error and absence of facet pyramidal error enables a flat field, linearized, high resolution image to be generated utilizing only a simple spherical optical system. In addition to the cost benefits derived from using spherical optical elements, the inherent symmetry they provide readily enables the deflector system to be extended to two dimensional scanning applications. Performance data for a hologon deflector system operating at 633 nm will be presented. Also, a procedure for determining what parameters must be incorporated into the hologon deflector element for nonimpact printing applications will be outlined.
A holographic scanner for laser printing has been developed. The scanner includes a multiple facet disc provided with holographically produced simple linear gratings. The bow correction of a scanning line is carried out with the use of the anamorphic optics. The holographic recording material used is a surface relief phase grating which is fabricated with photoresist. The present holographic scanner allows to obtain the diffraction efficiency of up to 84% and to produce a printed copy having the resolution of 300 pixels per inch, and it has the capability of scanning 12 pages per minute with the print quality equal to that obtained by the scanner employing a polygonal mirror.