The philosophy of design in automating image detectors for use in spectroscopy is dictated by the characteristics of the detectors. The broad range of useful detectors forces general purpose spectroscopic systems to be very flexible. A sample application of imaging detectors is used to present an example of how the devices are used. A multiple box approach was selected to match the above contraints. The detector controllers are preprogrammed state sequences. The computer box in the system was designed on the basis of data word size, data rate, computation requirements, and program support. A specially designed Direct Memory Access OW channel is the key item of the floppy disk/RAM memory microcomputer. The design of the DMA is the key to allowing the detector timing to handle asynchronous events.
The Optical Multichannel Analyzer (OMA 2 ) utilizes a microprocessor for detector control and for data acquisition; the same microprocessor is also used for data manipulation. This paper reviews the processing necessary to transform numbers aathered with a typical system into useful data which describe the optical source. Emphasis is on the data manipulation rather then experimental techniques. OMA 2 is a registered trademark of EG&G Princeton Applied Research Corporation. (EG&G PARC)
The basic goal was to design a multipurpose, multifunctional spectral radiometer system having a lifetime longer than present projections of possible future applications. The basic solution was to use a microprocessoras the Fundamental component of system architecture. Maximum potential was achieved by making use of software coupling to operate the microprocessor both as a controller of analog Functions as well as a digital data processor. Analog control functions presently include operation of spectral filter selection systems, scanning mirrors, optical path selectors, and automatic switching of attenuators and bandpass filters. Data processing is both analog and digital and includes data normalization, signal averaging and equation processing. The paper describes the various design considerations and the selected implementations.
Applying a spectral radiometer system to the broadest range of field measurements requires achieving maximum sensitivity and maximum spectral resolution over a broad band of wavelengths. A survey is made of methods of accomplishing this goal by conventional techniques and it is concluded that this requires the use of ponderous methods involving optical-mechanical control of the optical paths of multiple detectors and complex data processing to remove the effects of varying spectral sensitivity. The use of microprocessor control is surveyed and its application to specific radiometric processes is described in detail. Examples include the use of microprocessor control to switch the output of a sandwich radiation detector together with control of a spctral filter so as to use the most favorable detector-filter combinations. Also described is how the microprocessor makes possible automatic gain control, data sample averaging and data normalization to effectively remove the effects of the natural non-uniform spectral response of high-sensitivity detectors. The paper gives examples of the application of the radiometer to a reflectometer, transmissometer and other uses.
This paper describes a unique, state-of-the-art spectral calibration system. SAM2 (Spectral Analysis Microcomputer) automatically calibrates the optical responsivity of detectors and light measuring instruments from 220 nm to 1800 nm. Three pages of data and plot are automatically printed out at the end of each measurement cycle. SAM2 does both radiometric and photometric calibrations and analysis. Self prompting measurement programs, stored in PROM memory, are initiated via simple commands entered on the associated teleprinter.
The reflection properties of opaque fluorescent materials are measured with a 450/00 (illumination-viewing) spectroradiometer system interfaced to a desktop calculator. These measured values are then used to determine the samples' chromaticity coordinates and the fluorescent contribution to the radiance factor. To obtain these parameters, the calculator is used to optimize the design of an illuminant D-65 simulator; accept data for instrument calibration and reflectance measurements; calculate the sample's chromaticity coordinates; and graphically display the sample's non-fluorescent and total radiance factors. The performance requirements and chromaticity coordinates of a sample are displayed on a computer prepared plot to aid in evaluating a material's conformance to desired specifications.
Temperature distributions and species densities can be determined in cylindrical plasmas by using the Abel inversion technique to obtain the volumetric emission coefficient from lateral radiance measurements on optically thin spectral lines. These diagnostics are especially useful for studying arcs and glow discharges. Extensive spectroscopic measurements and data analysis routines are required for each determination, and user-interactive judgements are required at several points in the analysis. We have interfaced a Polymorphic 8813 microprocessor-based computer with our spectroscopic instruments for this task. The computer speaks BASIC and has 56 kbytes of user-available RAM. An S-100 compatible analog interface board is used for control of an optical spectrometer and a translation stage, as well as for digitization of the data in real time. Software was written for filing the data on minifloppy disks, performing data analysis, and printing or plotting the results with a small line printer or with an X-Y recorder. We were able to obtain a reliable and productive facility without large capital equipment outlays because of the modest cost of the microprocessorbased computer and its ability to interact with the expensive equipment that was already on hand.
A system for airborne infrared spectral signature measurements has been developed using a Fourier transform spectrometer interfaced to a microprocessor data acquisition, control and display system. The microprocessor is a DEC LSI-ll with 20KW RAM, 4KW EPROM, DMA spectrometer interface, digital magnetic tape, and dot-matrix video graphic display. A real-time executive tailored to the requirements and resources available allows concurrent data acquisition, recording, reduction and display. Using multiple buffers, acquisition of spectrometer data via DMA is overlapped with magnetic tape output. A background task selects the most recent spectrometer data and processes it using an FFT into a raw spectrum. A reference background spectrum is subtracted to isolate the data component, then a reference instrument response function is applied to obtain a calibrated absolute irradiance spectrum. The irradiance spectrum is displayed on the video graphic display and mixed with boresight camera video to show the target spectrum superimposed on the target image. Extensive selftest facilities are incorporated for testing all system components and compatibility with data reduction systems. System calibration is supported by selection of reference blackbody temperatures, apertures, and distances. The instrument response curve obtained during calibration is displayed for verification of correct spectrometer operation or diagnosis of faults.
The intent of this paper is to develop an understanding of the design considerations for a solid-state image sensing system. The method used is to individually discuss the operational and design factors for the following system components and considerations: solid-state image sensors, illumination sources, common types of lenses, lens and image sensor selection, and the techniques involved in system evaluation. The sensor will be discussed in terms of element resolution and configuration, spectral response, theory of operation, and video processing requirements. Common types of illumination sources and lenses will be outlined as they apply to solid-state imaging systems. The section on lens and image sen-sor selection has an example of how to proceed from an application concept to the selection of an array and lens. System performance is evaluated in terms of the Modulation Transfer Function (MTF). The MTF of each component part (i.e., lens, sensor, and video processing circuit) is considered from the standpoint of how each individual MTF combines to affect the MTF of the entire system. Experimental results are used to reinforce calculated MTF relationships. Careful consideration must be given to how each component part affects the overall performance of a solid-state image sensing system. The Modulation Transfer Function is most commonly used to characterize the performance of an optical or electro-optical system.
With the development of large high-performance self-scanned optical and infrared solid-state imaging devices for military, scientific, and commercial applications, novel techniques for the detailed testing and evaluation of these devices are required. For most military and scientific applications, detailed characterizations of device performance and fairly sophisticated computer-aided measurement facilities are required to fulfill these needs. This is primarily due to the very large number of detectors in each device and the wide dynamic ranges and high data rates involved. This paper is a review of the basic hardware and software requirements for near real-time testing, and evaluation of these advanced technology devices with emphasis on data acquisition, data manipulation and processing, data storage, display of quick-look and processed data, and housekeeping and experimental control. As an example of such a facility, the Mosaic Sensor Test and Calibration (MOSTAC) facility at the Lockheed Palo Alto Research Laboratory will be discussed.
This paper describes the design and engineering of a laser scanning system for production applications. The laser scanning techniques, the timing control, the logic design of the pattern recognition subsystem, the digital computer servo control for the loading and un-loading of parts, and the laser probe rotation and its synchronization will be discussed. The laser inspection machine is designed to automatically inspect the surface of precision-bored holes, such as those in automobile master cylinders, without contacting the machined surface. Although the controls are relatively sophisticated, operation of the laser inspection machine is simple. A laser light beam from a commercially available gas laser, directed through a probe, scans the entire surface of the bore. Reflected light, picked up through optics by photoelectric sensors, generates signals that are fed to a mini-computer for processing. A pattern recognition techniques program in the computer determines acceptance or rejection of the part being inspected. The system's acceptance specifications are adjustable and are set to the user's established tolerances. However, the computer-controlled laser system is capable of defining from 10 to 75 rms surface finish, and voids or flaws from 0.0005 to 0.020 inch. Following the successful demonstration with an engineering prototype, the described laser machine has proved its capability to consistently ensure high-quality master brake cylinders. It thus provides a safety improvement for the automotive braking system. Flawless, smooth cylinder bores eliminate premature wearing of the rubber seals, resulting in a longer-lasting master brake cylinder and a safer and more reliable automobile. The results obtained from use of this system, which has been in operation about a year for replacement of a tedious, manual operation on one of the high-volume lines at the Bendix Hydraulics Division, have been very satisfactory.
The integration of a microprocessor into a detector test console is described. Responsivity and D* measurements are performed as a function of frequency, detector bias voltage, and detector temperature. The system has been designed for use with a photoconductor test console; however, minor modifications will allow it to be used for evaluation of other detector types. Detector tests for a single photoconductor element usually require about 250 data points to fully characterize its optimum operating temperature, bias, and frequency response. The increasing importance of high density detector focal plane arrays with 100 elements or more has stimulated interest in microprocessor control to reduce operator fatigue and other human engineering problems. Therefore, a data collection and analysis scheme using a microprocessor can give test results that are not only more accurate but much less expensive. This system costs about $2500 to integrate into an appropriate existing detector test console.
A microcomputer-based instrument forlimage alignment with respect to a reference image is described which uses the DEFT sensor (Direct Electronic Fourier Transform) for image sensing and preprocessing. The instrument alignment algorithm which uses the two-dimensional Fourier transform as input is also described. It generates signals used to steer the stage carrying the test image into the correct orientation. This algorithm has computational advantages over algorithms which use image intensity data as input and is suitable for a microcomputer-based instrument since the two-dimensional Fourier transform is provided by the DEFT sensor.
A microcomputer control system was developed for an AGA System 680 Thermovision(R) Application of the infrared scanning camera to plume radiance measurements necessitated the development of a technique for achieving very rapid convergence to optimum operating conditions. The microprocessor based programmable controller satisfies this requirement and offers great operational felxibility. The plume radiation measurements system is comprised of an AGA 680 system, a Sangamo Sabre VI recorder, and the microcomputer system. The AGA equipment includes a 680 infrared camera with broadband anti-reflection coatings, a tape recorder adapter, a color monitor, and a remote filter and aperture selector. The Sangamo Sabre VI recorder is an IRIG portable recorder/reproducer configured with wideband group I FM and direct electronics. The control system incorporates an Intel 80/10 single board computer. Real time operator interaction is achieved through keyboard entry and off line through use of eraseable programmable read only memories. The design philosophy included complete retention of the Thermovision(R) manual controls and the use of inexpensive and readily available electronic components. The controller converges on appropriate operating conditions in an iterative manner based on sampling the signal level in a selectable field of view. Modifications of the AGA system were minimal consisting of the addition of three printed circuit boards and minor rewiring of the manual control unit. The remaining hardware required is housed in two companion chassis, one incorporating a single board computer and interface electronics and the other contains the electronics permitting choice of area of convergence. Results obtained in a ground test facility are presented. The results demonstrate both the utility of the microcomputer system in controlling the infrared camera and its capability to provide experiment control.
The data extraction and control functions of the Integrated Imaging Irradiance (0) Sensor have been implemented in software on a Data General Nova 3/12 minicomputer and used for real-time optical wavefront tilt correction. Two combinations of electronic front-end processing and software control, the faster of which can operate at information rates of up to 1 kHz, have been developed and analyzed. Critical timing considerations governing the operation of these programs in conjunction with the Data General DG/DAC analog-digital I/O interface are examined. Custom handlers which make optimal use of the DG/DAC hardware, real-time data collection and storage procedures, and off-line analysis and display software are discussed, and experimental results using the 13 Sensor optical breadboard under closed-loop computer control are presented.
The need for deformable mirror systems, large and mall, has generated the requirement for methods of control. A closed-loop control algorithm contains the means to measure an optical quality criterion, such as the root-mean-squared (rms) wavefront error, compute the appropriate correction signals, and apply those signals to the system. By looping over these steps, a desired optical system quality may be attained and maintained in a changing environment. This paper describes a digital system designed to control active optical systems in a stable environment, such as an in-process test, where a loop time measured in minutes is adequate. A discussion on the host minicomputer as well as the measurement, computation, and control aspects of the system is presented.
Since the development of the microprocessor, instrument designers can take a fresh look at the performance require ments of their system designs. The microprocessor allows the instrument to perform tasks which previously required subjective judgement of a skilled technician. The instrument can adjust its mode of operation dependent upon the nature of the data collected. It can also employ internal calibration techniques and statistical analysis of data to improve its consistency. Data can be stored and processed before being displayed, or a decision can be made to take additional data to improve the accuracy. The output format can be tailored to customary formats which can be easily modified on demand. This paper describes how these approaches have been employed in cwo ophthalmic instruments. The first is the Dioptron8automatic refractor which is used to objectively obtain a preliminary eyeglass prescription. The second is the Perimetron automatic projection perimeter which measures the contrast sensitivity of the retina over the entire field of vision. This instrument. is capable of performing many tasks normally requiring a highly skilled technician.
An instrument has been constructed for real time measurement of particle size in the range of 0.2 to 20 microns in diameter. This unit is designed for use in industrial stationary sources, and employs a helium neon laser source and two modes of light scattering, low angle forward scattering and polarization dependent, 90° scattering. A Z80 micro-processor provides control of the measurement functions. These include control of the synchronization and multiplexing of eight separate detectors, computation of a particle size histogram from the raw data, and control of the data printout through an alpha-numeric printer.
Progress in opto-electronic components combined with the development of the micro-processor made it possible to realize a new family of surveying instruments which can measure angles and distances, combine these readings and yield true three dimensional position information. The paper describes the HP3820A which combines a one arc second tiltmeter and a microprocessor in a single instrument.
A video interferogram processor has been developed that uses a standard television camera interfaced to a Z-80 microcomputer to acquire the coordinates of fringe centers. It features single-frame capture with software control of digitization, editing, data selection, and order assignment. A. PDP 11/03 receives the processor data and performs a Zernike polynomial fit from which graphics output is generated.
In this paper the architecture and measurement capabilities of a new digitally assisted high precision phase measurement interferometer are discussed. A brief discussion of the error sources in the instrument is presented. The capabilities of the instrument are demonstrated with specific examples.
The application of image processing and pattern recognition techniques to object identification and tracking at video rates is a problem of wide interest. Previous attempts have been limited to simple thresholding or correlations within a restricted window. New high-speed algorithms have been implemented using micropro-grammable (bit-slice) processors and specialized digital logic to produce an "intelligent" imaging tracker. Adaptive statistical clustering and projection based classification algorithms are applied in real time to identify and track objects that change in appearance through complex and nonstationary background/foreground situations. The system comprises four pipelined processors which, in turn, separate the target image from the background, locate and describe the target shape, establish an intelligent tracking strategy, and generate control signals which drive the telescope mount and optimize the size and orientation of the output image and the gain of the image tube.
An effective approach to the design of a line scan camera controller is covered in this paper. Primary features of the controller, other than the microprocessor operation, which are covered, include camera data compression and presentation to the microprocessor, mathematical capability for efficient mensuration, real-time capability for machine and process interface, and steps to make the hardware more versatile in order to complement the flexibility of software. A detailed example is given in the application of the controller to the production sizing and grading of spherical bearing rollers under the dual constraints of high thruput (2400 rollers/hour) and high accuracy (50 microinches).