The FPS vidicon which is a magnetic focus, electrostatic deflection design has clear advantages over other design combinations. These include high, uniform resolution; low shading and low distortion; low power; small size and ruggedness. New, shorter tubes are described. These include a 1-inch diameter tube with about 3.1 inch length overall, yielding 75% MTF at 400 TV lines; and a 5/8-inch tube with 2.3 inch length with 50% MTF at 400 TV lines. The reasons for the high performance are discussed; the possibility of making still smaller vidicons is considered, indicating that vidicons with image diagonals as small as 0.2 inches are feasible.
"Ebsicon" is the generic name for any camera tube which contains a photoelectron-bombarded silicon diode array target. Following a description of the motivation for and the development of a large-format Ebsicon (one containing an 80 mm photocathode and a 32 mm silicon target), the features of the device are presented. Emphasis is placed on the point-source performance of the tube in terms of the achieved point-source image cell density and the point-source response fall-off away from the center of the scanned area. Photocathode requirements are discussed in the context of the expected performance of the Air Force's up-coming Ground-based Electro-Optical Deep Space Surveillance (GEODSS) system. Then, field measurements for exposure times of 0.6 and 1/30 second, using G-type stars, are described and compared to the projected performance of a GEODSS electro-optical sensor. Finally, a list is presented of additional, important, and measured features of delivered, large-format Ebsicons.
The Digicon, chosen by NASA as the detector for the High Resolution Spectrograph (HRS) and the Faint Object Spectrograph (FOS) is a 512 parallel output channel vacuum ptioto-detector. Where are two HRS Digicons with spectral sensitivity ranges from 1050 Å to 1800 Å and 1150 Å to 3000 Å. A respectively, and two FOS Digicons, which have spectral ranges ex-tending to 7000 Å. The significant requirements for these devices are 0.01 counts per second background count rate per diode, state-of-the-art Digicon pulse height resolution (typical 15%) and a high degree of imaging precision and stability. The results of a manu-facturing and test program to develop the Digicons coupled with extensive prior work has shown that these requirements can be met. The Digicon because of its inherent ruggedness is particularly well suited to space applications.
This paper describes a television camera tube developed for use in aircraft flight simulators. These simulators are used to provide training for low altitude flying using a model board to duplicate the terrain to be encountered. The tube was designed to havc high resolution and low geometric distortion characteristics while operating in an environment providing low input irradiation. This was accomplished by coupling a high performance image i tensifier (WX-31836) to a high resolution two inch vidicon (WX-5168).
The characteristics of the new 18 mm and standard 25 mm pyroelectric vidicons are comioared. The smaller 12 mm target in the new PEV tube results in lower lag, pedestal current and bandwidth thus allowing a camera system based on the new tube to achieve performance com-parable to the standard tube. The 18 mm PEV shows a sensitivity of 2.5 °C in the pan mode with resulting chopper-mode minimum resolvable temperature (MRT) measured at 0.4°C for 2.5 1p/mm spatial frequency.
The Space Telescope Digicons are extremely powerful detectors, each one consisting of 512 parallel photon-counting channels. During testing, each channel of each Digicon must be characterized as to its photon-counting and noise characteristics, resulting in a tre-mendous volume of data. Furthermore, tests must be made at the component and subassembly level to screen parts not suitable for further processing. Adding to this testing task are the additional requirements that the tubes must be tested at high voltage without encapsulation, they must be kept scrupulously clean, and, in some cases, they must be tested in the vacuum ultraviolet portion of the spectrum. This paper describes the design and use of a unique, accurate and efficient test facility now in operation at EVC. Many of the tests are run by computer control, and in some cases the data are preprocessed and evaluated by the computer due to the human incomprehensibility of data consisting of thousands of numbers.
The design and operation of a new high speed family of CCD line imaging devices are pre-sented in this paper. The devices, CCD 133 and CCD 143, contain 1024 and 2048 photosites on 13 μm centers respectively. They are second generation devices having an overall improved performance compared with the first generation devices (CCD 121 and CCD 131) including higher sensitivity, enhanced blue response and lower dark signal. The devices also incorpo-rate on-chip clock driver circuitry so that only two external clocks are required for their operation. Excellent performance has been obtained with up to 20 MHz data rate. The devices are designed for page scanning applications including high speed facsimile, optical character recognition, and other imaging systems which require high resolution, high sensitivity, and high speed.
Charge-Coupled Device (CCD) area image detectors of the interline-transfer type include a design feature which enables analog image data to be electrically inserted into the vertical registers via a horizontal input register and, when the device is adequately cooled, this data can be temporarily stored in the vertical registers. Such analog storage devices have been successfully used in several R & D programs performing functions such as TV scan rate reduction, background cancellation in chopper operated pyroelectric vidicons and precision TV field delay for image processing. The results from these programs, consolidated with other CCD technology advances, form the basis for a new program now in progress at Fairchild Camera and Instrument Corp. sponsored by the Night Vision and E Ilectro Optical Laboratory. This program has as its objective the development of an Analog TV Scan Rate Converter and its primary storage element, a two-dimensional analog storage charge-coupled device containing 640 X 256 storage sites. The scan rate converter is intended to interface with TV data compression systems and other systems which require a large two-dimensional analog memory plane. This paper describes the Analog TV Scan Rate converter and the storage CCD under development. The current status of analog image storage using charge-coupled devices is reviewed and potential applications are explored.
A new "streak" tube has been developed for use in diagnostic applications involving very high-speed optical transients such as the Shiva laser-fusion studies at the University of California's Lawrence Livermore Laboratory. The tube combines the direct read-out characteristics of a CCD (charge-coupled device) with the high-speed deflection system incorporated in the light-shutter image tube to give immediate electronic read-out of information suitable for data processing. The front section of the tube is an image-intensifier stage with an infrared-sensitive photoc thode (S-1) sensitive to the laser wavelength of 1.06 micrometers. When the laser beam is incident on the photocathode, the emitted stream of electrons is accelerated and deflected by a ramp voltage applied to deflecting electrodes. The deflected beam impacts the CCD, producing several thousand electron-hole pairs per photoelectron. The charge pattern is then scanned out providing a time-intensitv profile of the laser beam.
The Charge Injection Device (CID) is a conductor-insulator-semiconductor structure that employs intracell charge transfer and charge injection to achieve an image sensing function. The significant temporal noise sources are Johnson noise in the distributed resistance of array conductor materials (e.g., polysilicon), in the channel resistance of MOS multiplex selection switches, and in the video amplifier. A source of both temporal noise and fixed pattern noise is array dark current and the spatial variation in this dark current, respectively. There are two factors that lead to very low dark current in CID arrays. First, only the charge storage region, which is smaller than the photosensitive region, is depleted and contributing significant dark current. The second factor is that the interface states that result in surface leakage current are continuously quenched under normal imager operat-ing conditions with the result that only the depleted periphery of each charge storage site contributes surface leakage. Since good quality charge transfer structures are normally surface leakage current dominated, this is an important effect. The major sources of fixed pattern noise are different with the various readout techni-ques. Sequential injection is a destructive readout technique that automatically cancels multiplexer interference and array fixed pattern variations. The fixed pattern noise mea-sured on a random access array operating with sequential injection readout was approximately a factor of 1000 below the saturation signal, lower than the temporal noise. With Pre-injection Readout, multiplexer switching noise couples directly into the video signal bus leading to a high level of fixed pattern noise. Since this component of fixed pattern noise repeats during each line of video, it is readily cancelled with the aid of one line of video storage. Fixed pattern noise after this type of cancellation has been measured as a factor of 250 below saturation. Row Readout operates through the driving of one set of array lines to cause signal charge to transfer to the orthogonal set of array lines with the result that switching noise is greatly suppressed. Raw fixed pattern noise levels of approximately three percent of saturation have been measured. In a low video rate device, fixed pattern noise was suppressed to below one part in 30,000 of saturation with this readout method. The extremely low-loss non-destructive readout capability of the CID structure results in the capability to read imager signals repeatedly for summation in external memory. Since the temporal noise that accompanies the signal sums incoherently, the signal-to-noise ratio improves in proportion to the square root of the number of readout operations. Noise levels below 100 carriers per pixel have resulted with this technique. No intrinsic limitation on the dynamic range improvement that can be obtained with this technique has been identified. External limitations, such as the time available to perform repeated non-destructive readout operations, have prevailed to date.
A complete intensified television camera has been developed using an intensified CID in conjunction with a standard camera control. The camera has been made in two versions, one for intermediate to low light levels and one for low light levels. In both cases the camera uses proximity focused tubes. The range of the camera has been extended four orders of magnitude with only a 20% loss in maximum resolution over the unintensified version. These intensifiers have been specially modified for use in these cameras. As a result threshold imaging has been achieved at 10-7 foot candles incident on the faceplate of the tube with the camera operating at standard TV scan rates. The camera head can be kept as small as 3.6 in. x 3.1 in. x 3.0 in. and weigh less than one pound. Selection of the photocathode allows the camera to have sensitivity from the UV to the near IR and allow for fast gating of the camera to less than 5 nsec, if necessary. Both camera designs are discussed with respect to performance and design.
Brief reviews of the structure and normal operating conditions for manufactured versions of 488 by 380 element CCD image sensors are followed by descriptions of the performance available from typical devices and by description of common types of cosmetic blemishes which limit the yield of production sensors. The 488 by 380 element sensors are fabricated by buried channel CCD technology. They utilize an interline transfer technique to achieve a high CTF at Nyquist frequencies, which results in crisp imagery from reasonable die areas. The sensors also offer wide dynamic range, good low light level capability, and compatibility with NTSC quality requirements.
Large area charge coupled device (CCD) imagers with fewer defects are now becoming avail-able in quantity and the demand for small, stable, high resolution standard and specialized cameras is increasing. This demand is for CCD camera systems operating in any one of three different modes: (1) full-frame mode, used for staring applications, (2) frame-store mode,' used for TV applications and (3) time-delay and integration mode, used for scanning applica-tions. The camera designer is challenged to assure commonalty in his circuitry in order to provide rapid reaction to customer system requirements with affordable cameras. This tech-nique will allow for standard building blocks (PC board modules) to be selected and assem-bled together with appropriate housings and wiring harnesses to provide cameras in any of the three modes mentioned above. The modular concept includes various logic modules, video modules, power supply modules, CCD front-end modules and several special purpose modules in-cluding an analog-to-digital converter module, a thermo-electric cooling package and a low light level intensifier tube assembly. These modules are initially to be fabricated using standard off-the-shelf parts, and will be suitable for conversion to large-scale-integrated (LSI) and hybrid packages as volume warrants.
During January 1982 the NASA space transportation system will launch a Galileo spacecraft composed of an orbiting bus and an atmospheric entry probe to arrive at the planet Jupiter in July 1985. A prime element of the orbiter's scientific instrument payload will be a new generation slow-scan planetary imaging system based on a newly developed 800 x 800 charge-coupled device (CCD) image sensor. Following Jupiter orbit insertion, the single, narrow-angle, CCD camera, designated the Solid State Imaging (SSI) Subsystem, will operate for 20 months as the orbiter makes repeated encounters with Jupiter and its Galilean Satellites. During this period the SSI will acquire 40,000 images of Jupiter's atmosphere and the sur-faces of the Galilean Satellites. This paper describes the SSI, its operational modes, and science objectives.
Existing integrated infrared detector array technology is being evaluated under low-background conditions to determine its applicability in orbiting astronomical applications where extended integration times and photometric accuracy are of interest. Preliminary performance results of a 1 x 20 element InSb CCD array under simulated astronomical conditions are presented. Using the findings of these tests, improved linear-and area-array technology will be developed for use in NASA programs such as the Shuttle Infrared Telescope Facility. For wavelengths less than 30 μm, extrinsic silicon and intrinsic arrays with CCD readout will be evaluated and improved as required, while multiplexed arrays of Ge:Ga for wavelengths in the range 30 to 120 μm will be developed as fundamental understanding of this material improves. Future efforts will include development of improved drive and readout circuitry, and consideration of alternate multiplexing schemes.
Deep space surveillance is going through an evolutionary process. The impetus for this evolution stems from the changing threat and the requirement to perform more demanding missions. These requirements have placed severe demands on our existing technology and stimulated the search for new technology developments that will provide higher performance. The emergence of charge coupled device (CCD) technology offers great promise in the area of deep space surveillance. To pursue further the capability of CCD's and to quantify their performance advantages, DARPA sponsored the Teal Amber I program in early 1976. Teal Amber I is designed to develop visible CCD technology and to conduct a focal plane development and demonstration program. This paper presents the reader with a description of the sensor system concept, an overview of the process by which it is derived, and the performance predictions for the sensor in a full-up focal plane configuration. The focal plane processing system is described along with the development and status of the imager charge coupled devices. The paper concludes with a description of the Phase II demonstration program and the perform-ance results that were achieved in Phase II.
A 128 x 128 element CID imager was operated in a simulated stellar tracking environment and ev8luated f8r temporal and pattern noise and spectral response over a temperature range of -40oC to +25oC. The test devices were fabricated on long-lifetime bulk silicon material and utilized very thin upper-level polysilicon electrodes for enhanced spectral response. A standard microcomputer was used to generate all control signals and to collect and process performance data. The results of this program were used to predict the performance of a 400 x 400 CID array designed specifically for stellar-tracking.
Recent advances in large area charge coupled device (CCD) imaging detectors and high speed microprocessors have prompted the development of a new class of electro-optical tracking instruments at the Jet Propulsion Laboratory (JPL). These instruments are designed for standardized NASA-wide usage and are characterized by their extremely high pointing accuracy and stability and performance capabilities which are largely software defined and thus easily adapted to a variety of mission requirements. This paper presents an examination of the methods by which CCD detectors are being incorporated in star tracker instruments and the performance capa-bilities that can be expected from currently available devices. The multi-function sensor concept, in which a single sensor can function in a variety of guidance applications, is described. Software algorithms designed to provide efficient extraction of guidance information from both point and extended images are also presented. CCD star tracker implementations currently underway at JPL are described, and performance data obtained during laboratory testing is presented and discussed.
The demonstration of high charge transfer efficiencies in Schottky barrier GaAs CCEs1 allows the exploration of this technology for optical imagers for star tracking applications. A device concept is described which utilizes this development and illustrates optimization of the device parameters for ionizing radiation environments, high operational temperature and long storage time requirements. Considerations are given to the noise components in relation to the star signal and attention is drawn to the necessity of minimizing the active device volume when designing for operation in a radiation environment. The shot noise multiplier associated with operating the device in a gamma environment has been calculated and is expected to be lower for GaAs based devices than for silicon. The requirements for imaging seventh magnitude stars will be discussed. The technology employs a heterojunction CCD approach consisting of a GaAs absorber layer, a GaAlAs channel layer, and a GaAlAs passivation layer, sealed to glass. The radiation hardness of this device will be discussed for neutron and gamma irradiation.
Anodized Ta203/native oxide/n-type (111)B GaAs MOS devices are evaluated using variable frequency capac-itance and conductance measurements. Total movement of the Fermi level is seen restricted to .42 eV by an interface state distribution having a minimum density of 3.5 X 1012 eV-1 cm-2 at .84 eV from the conduction band. The anomalous frequency dispersion of the accumulation capacitance, lack of strong inversion and loss mechanisms are discussed. Pulsed deep depletion characteristics and long storage times are observed. Due to the chemically stable nature of the anodized Ta overlayer, linear array burried channel GaAs MOS charge transfer devices were fabricated.
This paper describes the factors governing the Performance Efficiency (PE) of Indium Antimonide Charge Injection Devices (CID) arrays. Factors influencing PE in both line and area arrays are considered and compared to experimental results. An important factor re-lates to the signal charge loss of a dual gate array operating in the charge sharing mode (CSM). The chief advantages of the CSM are that it overcomes charge transfer problems that might be present in practical arrays, and it is believed to be radiation damage resistant. The chief limitation is that only the charge residing under the sensing gate of the dual gate site is read out. This loss can be lessened by designing the sensing gate to be a large fraction of the total storage area. Performance data of lx32, lx64 line arrays, 24x16 and 32x32 dual gate area arrays are presented. Line arrays FE up to 56 percent, responsivity variation below 10 percent, and D* of about 3x1011 cm HZ½/watt have been measured.
Requirements for infrared detector array focal planes suitable for a set of prospective planetary missions are developed. Using the Galileo mission to Jupiter as a starting point, objectives and constraints applicable to outer planet missions are developed. The concept for an advanced mapping spectrometer utilizing 128 x 128 element infrared detector arrays is described. Specific implementations for the Saturn Orbiter Dual Probe mission, a Mars Orbiter mission, and a Titan Orbiter mission are defined. The analysis indicates that within the 1 to 5 μm range, broad scientific objectives for these missions can be met using focal plane arrays with detectivities on the order of 101 cm Hz 1/2 W-1. The realization of such high detectivities in a low background application will necessitate careful development of the method by which the detector signals are multiplexed and read out.
Detection of infrared radiation and signal readout has been demonstrated on a monolithic InSb charge coupled infrared imaging device (CCIRID). The device is a 20- element linear imager with MOS detectors coupled to a four-phase, surface channel, charge transfer structure. The charge transfer device is p-channel and has planar ion implanted diode structures for fat zero input and charge readout. Charge transfer efficiency of the present 20-element linear imager is 0.995. Sensitivity measurements on the MOS infrared detectors have yielded a single element D* > 8 x 1011 cm Hz 1/2 /W with an average D* - 5.4 x 1011 cm Hz 1/2 /W over the 20-element array. Data is presented showing the operational characteristics of the 20-element linear imager under various conditions of electrical and optical inputs in both a multiplexed and a time delay and integration (TDI) mode. Plans for a monolithic InSb 100-element linear imager and a 20 x 16 TDI linear imager are discussed.