Every laser scanning system combines a variety of optical and electronic components to achieve a particular set of quality, throughput and cost goals. In optimizing such a system there is a vital need to make the best use of the capabilities of each component. This can only be achieved when there is a mutual understanding, among the various members of the design team, of the significant considerations - advantages, limitations and tradeoffs - in each other's field.
The Scophony Light Valve when used in a laser scanner exhibits a coherent imaging response. Because of this coherent response, electronic manipulation of the acoustooptic modulator's drive signal can produce unique optical imaging effects, effects which cannot be achieved with the flying spot scanner architecture. An example of this electronic processing is a shift in the plane of best focus of the scanner which is achieved by passing the modulator's drive signal through a chirp filter. This electronic focus shift can enable a three dimensional television display.
Today, many of the applications that employ lasers require the laser to be modulated and deflected. The dominant devices to perform these tasks are acousto-optic and electro-optic modulators. The principles of operation and the applications of each method are different. This paper will describe the principles of operation and the applications of acousto-optic Bragg cells and electro-optic Pockel's cells.
A number of investigations have been performed at XEOS for the purposes of: (1) characterizing the time-dependent polarization states of the 632.8 nm output beam of internal mirror He-Ne lasers, and (2) evaluating the effect of beam polarization on the Bragg diffraction efficiency of an AO modulator. The results of these two lines of investigation have suggested that, under certain circumstances, extraneous fluctuations or noise can be induced in the diffracted beam by polarization fluctuations of the laser beam. It is the purpose of this report to define the conditions under which polarization induced noise is produced, to evaluate the magnitudes of these effects, and to suggest practical methods by which polarization noise can be eliminated.
Since dry silver film is processed by heat, it may be viewed on a light table only seconds after exposure. On the other hand, wet films require both bulky chemicals and substantial time before an image can be analyzed. Processing of dry silver film, although simple in concept, is not so simple when reduced to practice. The main concern is the effect of film temperature gradients on uniformity of optical film density. RCA has developed two thermal processors, different in implementation but based on the same philosophy. Pressurized air is directed to both sides of the film to support the film and to conduct the heat to the film. Porous graphite is used as the medium through which heat and air are introduced. The initial thermal processor was designed to process 9.5-inch-wide film moving at speeds ranging from 0.0034 to 0.008 inch per second. The processor configuration was curved to match the plane generated by the laser recording beam. The second thermal processor was configured to process 5-inch-wide film moving at a continuously variable rate ranging from 0.15 to 3.5 inches per second. Due to field flattening optics used in this laser recorder, the required film processing area was plane. In addition, this processor was sectioned in the direction of film motion, giving the processor the capability of varying both temperature and effective processing area.
The optical recording characteristics of a silver halide thin film structure were investigated with respect to its possible use as a read-write-erasable medium. Tracks of ~1μm spots were recorded using a polarized He-Ne as the writing source. The recorded tracks were viewed with a GaAs laser between crossed polarizers; the writing energy density was determined to be ~0.2 joules/cm2 in the transmission mode. Erasure was also demonstrated by re-exposing a portion of the recorded tracks with the defocused write laser with its polarization rotates by 45° from the original write polarization direction.
The Harris Corporation has been involved in the independent testing and evaluation of transparent electrophotographic films for application to high performance data recording. Various materials have been evaluated for holographic and spot recording in the past with primary recommendation given to silver halide films, which possess the key characteristics of excellent exposure sensitivity, diffraction efficiency, and signal-to-noise ratio. Transparent electrophotographic film however, has evolved into a close competitor for silver halide's position with respect to high resolution data recording. This competition is the result not only of improvements in the microimaging characteristics of transparent electrophotographic films, but also of their inherently fast in-line processing capability to produce the final archival image within seconds, convenient daylight handling, and updateability. Experimentally however, each transparent electrophotographic film tested operates via an individual mechanism characteristic to its composition. A materials evaluation breadboard was designed to provide basic characterization of image quality and image stability parameters. The design included recommended processing stations which were supplied by each film manufacturer for imagewise deposition of high resolution toner particles. The results of this independent evaluation includes information on the sensitometry, diffraction efficiency and signal-to-noise ratio as a function of spatial frequency, and microimaging characteristics. This paper is an extension of a recent paper presented at the SPIE conference in August 1979 entitled: Tranparent Electrophotographic Film for High Resolution Holographic Recorders.
The complex optical index of refraction for evaporated films of tellurium has been measured using ellipsometry over the wavelength range 439 to 633 nm. Values of n and k. for the index as a function of wavelength and as a function of thickness are presented. The transmittance and reflectance of single layers of tellurium, as well as multilayer structures to be used for optical data recording media, are shown as a function of wavelength. Oxide formation of these films has also been measured, and a model for the role of oxides in altering adhesion of the films is presented.
Amorphous materials can be used in a variety of configurations for optical recording and storing of information. Focused laser beams yield changes in state between crystalline and amorphous giving high quality images without ablation or post processing of the film. Tailoring material compositions to a particular application results in films that can be read in reflection or transmission, and store information in a read-only or erasable form. The materials inherently provide permanence of storage, even in the case of erasable films, due to threshold imaging mechanisms. Films can be coated on a variety of substrates, including flexible plastic, sheet plastic, and glass, depending on reading and writing system requirements.
A detailed discussion of an on-line Laser Beam Recorder/Processor utilizing transparent electrophotography as well as its performance in regard to critical image processing parameters and their impact on sensitometry and image quality is presented. Good sensitometry and high image quality combined with near real time access has been demonstrated. Sensitometric parameters such as D-max, D-min and gamma can be controlled during dynamic processing through electrical parameters.
An Elastomer Storage Device with potential as a temporary frame store in signal processing applications was evaluated. The photometric sensitivity was 50 ergs per square centimeter at 514.5 nm when cycled at 10 frames per second. The resolution showed bandpass characteristics with the center frequency at 80 cycles/mm and 50% MTF response at 20 and 140 cycles/mm. Device lifetimes in excess of 10 million cycles were measured.
The article is meant to provide the digital image recording community with an overview of digital image processing, and recording. The Digital Interactive Image Processing System (DIIPS) was assembled by ESL for Air Force Systems Command under ROME AIR DEVELOPMENT CENTER's guidance. The system provides the capability of mensuration and exploitation of digital imagery with both mono and stereo digital images as inputs. This development provided for system design, basic hardware, software and operational procedures to enable the Air Force's System Command photo analyst to perform digital mensuration and exploitation of stereo digital images as inputs. The engineering model was based on state-of-the-art technology and to the extent possible off-the-shelf hardware and software. A LASER RECORDER was also developed for the DIIPS Systems and is known as the Ultra High Resolution Image Recorder (UHRIR). The UHRIR is a prototype model that will enable the Air Force Systems Command to record computer enhanced digital image data on photographic film at high resolution with geometric and radiometric distortion minimized.
A high resolution laser image recorder/processor for reconnaissance applications has been designed with an integral wet film processor providing rapid access to the imagery. This system operates over a wide range of film velocities with nearly instant film velocity change capability. The laser recorder/processor system is described. Specific details are given on the film and processing against a 5-second development requirement. The method of obtaining consistent density over a 7 to 1 range of film velocities is explained in detail. A linear or definable density over a range of 3 density units is achieved with the equipment. Examples of product output are shown, demonstrating its high resolution, high quality, low grain and large density range.
A recording technique has been developed that allows machine-readable digital information to be encoded within human-readable imagery. Each picture element in the recorded image consists of a square matrix of discrete spots, each spot taking one of several possible optical densities. A specific format consisting of a 2 x 2 spot matrix, with 8 quantization levels per spot, has been investigated in detail. This 2 x 2 x (8) format encodes 12 bits of machine-readable digital information per pixel and can exhibit 330 discrete readable pixel densities. This technique can be used, for example, to record human-readable imagery derived from EO sensors with 10 bits of dynamic range. The full sensor data base could be recovered from the imagery, by use of a suitable reader, without loss of digital information. In addition, collateral information such as height data, annotation, etc., can be encoded within the digital data in machine-retrievable format in a way that does not affect the human-readable information. This paper discusses algorithms developed for mapping the digital data into human-readable pixel densities, some techniques for error correction and pixel identification, and examples of collateral data fusion. Results of a digital data retrieval experiment are presented.
This paper presents operating details and performance specifications for an automatic laser raster scanner that provides an ordered vector (chain) file as an output. Several recent software enhancements to the system will be discussed. In the past, the vectorizing software ran as a post processor to the scanning system. The total systems software (scanner, vectorizer, control program) have now been integrated to provide a significant performance improvement. An entirely new software package will also be discussed. This single program utilizes the same hardware (scanner plus PDP 11/70) and produces the vector output "on the fly" but with performance improvements over the integrated system software. Speeds of over 5000 lineal inches/hour are possible. Quality of vector output and its relationship to DTM are an important topic. Slides of vector/raster output will be shown to illustrate the systems capabilities, and discussed in terms of the system hardware and software.
The design of a digital archival optical mass memory system poses several significant challenges. It must provide high information storage density, allow fast access to the data stored in the memory and provide archival storage of that data. In addition, to be fully responsive to a variety of user needs, the system must be compatible with both the low data rate requirements of computer compatibility and the high data rates of downlink satellite recording. This paper will outline the design approach and detailed subsystem parameters for one such system, the MASTAR archival optical mass memory. The key features of this system include: the use of an acoustic travelling-wave lens system to scan data at rates of up to 50 Mb/s, storage of 109 user bits of information on 148mm X 0.007" fiche, storage of over 1000 fiche in a 17" diameter x 17" high carousel and access to any data block in less than 8 seconds. Experimental results and design considerations for a low cost reader for the system will also be presented.
The optical disk has become a viable candidate for mass digital data storage. Its unique characteristics make it suitable for archival, wideband, high density record and playback applications as well as those requiring fast access to a large data base. RCA has been pursuing the development of such systems for government mass data storage and retrieval requirements. This work is centered around a unique "tri-layer" optical disk structure, which offers high sensitivity and signal-to-noise ratio (SNR) at very high packing densities. The two major areas of pursuit are record and playback at data rates of 200 Mb/s or more and multiple-disk record and playback units for very large on-line capacities. Record and playback at high data rates is achieved through simultaneous multiple, parallel-channel operation. Present day solutions involve splitting the output from a single high-power argon laser into multiple beams, modulating each beam independently, and focusing them onto a rotating optical disk to simultaneously form a closely spaced series of data tracks. Single-channel rates of 50 Mb/s and multiple-channel rates of 150 Mb/s have been demonstrated on laboratory breadboard equipment. Designs for equipments that will operate at 400 Mb/s are being pursued for implementation in an engineering development model. Concept designs for multiple disk record and playback systems are centered around two "jukebox" configurations, which can provide fast automatic access to large on-line data stores. A feasibility design for a reader unit with an access time of three seconds to 1013 bits (100 disks) has been performed. A second concept provides a capability of both record andplayback of 50 Mb/s with an access time of seven seconds to 1013 bits. This unit features an expansion capability for servicing multiple simultaneous user requests. Both "jukebox" configurations have been developed for large archival mass memory systems. These systems require a storage capability of 1013 bits (1014 bits on-line) at record and playback data rates of 50 Mb/s and access times of 3 to 15 seconds.
Acousto-optical Bragg cell advancements during the past few years have resulted in devices and subsystems applicable to a variety of wideband receiver systems. One such application is the direct recording of signal information from a wideband receiver. These receivers currently have intermediate frequency (IF) bandwidths of greater than 100 MHz, which is necessary for detection of a variety of wideband signals. The recorder configuration described in this paper is capable of recording signals with greater than 200 mHz bandwidth centered at base band or directly at the receiver IF.
A real-time digital image simulation facility is described. The facility is memory centered with a large random access memory combined with a pair of 300 megabyte parallel transfer disk drives. The recording rate for the facility will be from DC to 240 megabits/sec. The facility is designed to accept as input a variety of digitized video signals including those from a high speed laser scanner system. A comparison of computer-centered versus memory-centered image processing systems is made. Input from a laser film scanning system and output to a laser printing system is illustrated.
This paper presents some of the reasons that a hybrid RA/VE file may yet be the most ideal type of data structure for use in the Automated Cartographic Systems. There will be a discussion of the various data acquisition techniques available today and the relative merits of each will be reviewed. The systems discussed will cover coherent as well as non-coherent scanning systems, manual digitizers and their place in todays production environment. The final output of the systems will be covered. The data manipulations which are required for producing a manuscript and the necessity to create a data base in a manageable form (whether it be pure vector or a hybrid file) are also addressed.