Low Light Level TV Camera Research Articles

Current and Future Trends in Military Night Vision Applications

The Army's grand sensor challenges for night vision operations are presented as well as the focused technology quests that offer solutions to the challenges. The technology quests include all solid state low light level TV cameras, mercury cadmium telluride IR detectors on silicon substrates, uncooled thermal imaging, eyesafe laser imaging and aided target recognition. The operational applications, current systems approaches, and technical goals are discussed and the potential breakthroughs are identified. Research opportunities are suggested that could enable new system capabilities, including areas of advanced active thin film research.

A novel type epithermal neutron radiography detecting and imaging system

The transfer technique is widely used for epithermal neutron radiography (ENR) for making images upon the object to be investigated. We propose to use instead of the photosensitive film a gamma sensitive scintillation screen (NaCe single crystal), that is monitored by a computer controlled low light level TV camera. The exposure time has been reduced to a duration of only a short fraction of that needed for the conventional transfer process. The presented ENR images consist of electronic signals that are handled by an advanced image processing and analyzing program, the Iman 1.4 version, using a task oriented video grabber.

Excitation of Earth‐ionosphere cavity resonances by sprite‐associated lightning flashes

Simultaneously recorded discrete excitations of Earth‐ionosphere cavity resonances at Silberborn, Germany, and Hollister, California, ∼9.1 Mm apart, are used to triangulate source locations of lightning flashes in the continental United States with an accuracy of ∼0.8 Mm, as verified by the National Lightning Detection Network. The identified lightning flashes are mainly associated with positive cloud‐to‐ground discharges with first return stroke peak currents ∼20–70 kA. 80% of these particular lightning flashes are associated with sprites, as verified by simultaneous low‐light level TV camera observations at Yucca Ridge, Colorado. This high probability of sprite detection is attributed to particularly large cloud‐to‐ground lightning currents, simultaneously exciting both Earth‐ionosphere cavity resonances and sprites.

Positioning of auroral arcs in all-sky TV images as an inverse problem

Positioning of auroras in all-sky images taken by instruments such as low-light level TV cameras has long been important in understanding how an ambiguity of luminous positions is removed with appropriate models which take into account specific altitude profiles of auroras in the ionosphere. We have developed a method to estimate locations of auroral columns along the earth's magnetic lines of force by an inversion procedure. Two-dimensional luminosity distribution in raw data is considerably large in the data size to be processed at a given time and we show that the problem can be reduced into a simple one-dimensional problem. Models of auroral arcs with simple altitude profile are used. Locations of reconstructed image profiles show decomposing arcs well concentrated only around the lower border of the arcs in the original image data. The method is shown to be effective when it is applied to observed data including a simple auroral arc.

Optical and radar observations of auroral arcs with emphasis on small-scale structures

During a campaign in January 1988 we observed auroral arcs with the EISCAT UHF radar system and a low light level TV camera. The aim was to compare apparent motions of the arc and its small scale structures with plasma motions in the adjacent F-region. It was found (1) that there was a relative motion between arc and plasma of the order of 100–200 m/s southward and (2), in confirmation of earlier findings, that folds and curls, i.e. auroral rays seen edge-on, with wavelengths ranging from 2 to 20 km, moved along the are with average velocities of 10 to 20 km/s. At the same time, the tangential plasma velocity at 300 km height varied between −0.3 and 0.8 km/s westward. Most importantly, for all luminous bands exhibiting fast motions of small-scale structures, the direction of this motion was westward on the equatorward edge, and on most occasions, an eastward directed counterflow could be observed on the poleward edge. The existence of such a counterflow appears to be a fundamental property and may even be used for a physical definition of an auroral arc. We support the interpretation of Davis (1978) that auroral ray, fold, or curl motion is a visible expression of a physical motion of small-scale structures in the local plasma. environment of the auroral acceleration region at about 1 R E altitude. The attendant electric fields are shorted out by parallel potential drops. The counterflow pattern is consistent with the existence of a U-shaped potential at that altitude. The observed asymmetry in brightness, definition, and speed of the countertiowing folds or curls is attributed to their location at the leading or trailing edges of the arc propagating relative to the plasma frame.

Stereo Imaging System for High-Voltage Electron Microscopy

An analysis of three-dimensional ultrastructure is especially efficient when performed on stereo images. The high voltage electron microscope (HVEM) providing high beam penetration and low radiation damage to specimens has been shown to be the most effective instrument for such studies. The successive HVEM stereo images recorded on films are subsequently photoprinted or stored in an image processor memory can be observed on an RGB monitor. Successful stereo imaging must meet several requirements regarding magnification, specimen thickness, tilt axis and angle. In particular, the optimal tilt for stereo perception depends on the thickness and microscopical magnification. Ultramicrotome settings can provide only approximate information on section thickness; however, their sectioning compression, procedural etching or beam induced shrinkage has to be considered. The situation becomes even more difficult when extractable media are used because an amount of extracted material may seriously affect final thickness. An estimation of an exact thickness of whole cell mounts is practically impossible, and therefore, optimal tilt difficult to predict. Then the most reliable way is the laborious recording of series of images at different tilt angles and selection of the most effective. To overcome this constraint, I designed a very reliable system for AEI HVEM 7MkII allowing exact prediction of the perfect tilt angle. The diagram of the system is presented on Fig. 1 and a photograph of the assembly on Fig. 2. It consists of a low light level TV camera with two independent outputs-SIT/TVC/, image processor-Quantex/QIP/, two high resolution flat square monitors-Hitachi/H1 & H2/ and stereo viewer-Nikon/SN/. A signal from the first TV camera output goes to the QIP, after processing is displayed on monitor H1. A signal from the second output goes directly to the second monitor, H2. Prerequisites for using this system are axis-centered or eucentric goniometer and a rotation-free imaging system of HVEM. The recording procedure happens as follows. The specimen is tilted 1/2 of the value of the roughly predicted optimal angle and the resulting image is stored in the Quantex memory followed by recording on the film sheet. The left monitor displays the stored image from QIP, while the right monitor provides the live image. Then the specimen is tilted while being observed with a stereo viewer. When the strongest stereo effect is noticed, then tilting is stopped and an image recorded. If + and − tilt values differ, then perfectly symmetrical values can be calculated followed by image recording. Figs. 3 and 4 represent the stereo images of a human melanoma cell grown on a film grid. An optimal stereo perception was obtained for different magnifications, at different tilt angles determined using the system I have designed.

High-resolution hot-stage experiments

High resolution electron microscopy provides a powerful method for studying controlled dynamic reaction sequences and the development of microstructures on the atomic scale. Temperatures can be controlled with reasonable accuracy using a standard hot-stage, but at elevated temperatures there is some reduction in the contrast, and stability, of images. It is, of course, essential to minimise the effects, including additional heating, of irradiating the sample with a high voltage electron beam in a high vacuum environment, and to take into account the close proximity of two specimen surfaces in designing experiments. TV imaging techniques, in-situ, relocatable ex-situ and environmental methods are being developed for use with two medium voltage side-entry high resolution TEMs, equipped with complementary chemical and structural microanalytical STEM facilities.TV imaging techniques Dynamic reaction sequences are now mostly viewed with a low-light level TV camera (LLTV) using a thin YAG or YAP pickup screen and recorded on U-matic videotape to facilitate subsequent processing. The results can be improved substantially by using a digital framestore based image processor to enhance the signal to noise ratio of the video signal in realtime. A major element in the SNR is the shot noise statistics of the TEM electron beam.

Coordinated photometer and incoherent scatter radar measurement of pulsating arcs with high time resolution

Coordinated photometer and incoherent scatter radar measurements with high time resolution (0.1 s) were made on 1 February 1987 in order to investigate auroral pulsations. Also a low light level TV-camera operated in real speed mode during the experiment. The total energy flux and characteristic energy of Maxwellian energy distribution were measured with a field-aligned multichannel photometer. The radar beam crossed the photometer beam at an altitude of 110 km, where the electron density was modelled successfully using a characteristic energy of ~ 2 keV. With the time resolution of 1.0 s also electron density pulsations were seen, showing correlation with the optical pulsations. Furthermore, during the observed pulsating arcs enhanced electron densities were found in the altitude range of 85–100 km. This indicates a hardening of the precipitating electrons. This change has been modelled by double-Maxwellian distribution with characteristic energies of about 1.3 and 7 keV.

Software pattern recognition applied to nanodiffraction patterns from a STEM instrument

In recent developments, the ASU HB5 has been modified so that the timing, positioning, and scanning of the finely focused electron probe can be entirely controlled by a host computer. This made the asynchronized handshake possible between the HB5 STEM and the image processing system which consists of host computer (PDP 11/34), DeAnza image processor (IP 5000) which is interfaced with a low-light level TV camera, array processor (AP 400) and various peripheral devices. This greatly facilitates the pattern recognition technique initiated by Monosmith and Cowley. Software called NANHB5 is under development which, instead of employing a set of photo-diodes to detect strong spots on a TV screen, uses various software techniques including on-line fast Fourier transform (FFT) to recognize patterns of greater complexity, taking advantage of the sophistication of our image processing system and the flexibility of computer software.

Study on the flute-type hollow cathode discharge by using a low-light-level TV camera

The ignition process of the hollow cathode discharge (HCD) of flute-type is studied by using a low light level TV camera of the SEM (Silicon Electron Multiplication) type. On the basis of the observation, a theoretical explanation of the mechanism of the ligh development is given. It is clarified that there are two stages in the development of discharges: The stage of sustained dark discharge is between the anode and the outer-cylinder and the stage of discharge goes through the hole into the cylinder. Corresponding to these two stages, there exist two γ-processes, i.e., one is occurring at the metal surface surrounding the hole and the other is occurring at the inner surface of the cathode cylinder.

On the crystal structure of small gold crystals and large gold clusters

A large gold cluster with the formula Au 55[(C 6H 5) 3P] 12Cl 6, was imaged with a high-resolution transmission electron microscope (HRTEM) and a proposed model was confirmed. Growth of gold crystals of approximately 4.0 nm size could be followed, row by row of atoms, with the use of a low light level TV camera and on-line image processing.

The effect of atmospheric screening on the visible border of noctilucent clouds

The noctiiucent cloud display of 10/11th July 1979 was observed from two sites in Scotland: Clinterty near Aberdeen, using a low light level TV camera, and Milngavie near Glasgow, using a photographic camera. Coincident observations of the display were made from 23.55 UT until 00.50 UT. By projecting the image of the noctilucent cloud structure as seen by one camera into the field of view of the other camera, the height of the clouds was found to be 82 ± 1 km. Using this result, the effect of atmospheric screening on the visible border of the noctilucent clouds was determined. Taking account of the refraction on the solar grazing rays illuminating the clouds at the visible border and the finite angular diameter of the sun's disc, the altitude of the screening layer was determined to be 7 ± 1 km. Thus, on this occasion, the screening effect of the atmosphere was confined to the troposphere and was probably caused by atmospheric haze and/or tropospheric cloud. This result contrasts markedly with the high values of screening height, ~ 30 km, deduced from measurements made earlier this century, also using the visible boundary of the clouds. The analysis presented herein indicates that these large values were probably in error, due to the poor dynamic range of the photographic films employed.

Direct digitization system for quantification in ion microscopy

Abstract : A system for the quantification of secondary ion mass spectrometric images produced by an ion microscope is presented. The Microscopic Image Digital Acquisition System (MIDAS) developed in this laboratory by coupling a CAMECA IMS-300 ion microscope, a low light level TV camera, a video color graphics system and digital image processing techniques, is described. Ion images detected by the television camera are converted in real time into matrices of point intensities, maintaining the spatial resolution of the original image. These image matrices may then be converted to ion intensity space, or by the use of standards, to concentration. The use of ion implantation to fabricate image standards is presented as an evaluation of MIDAS. Applications of color display as a means of conveying compositional morphological information are demonstrated. (Author)

Utility of low light level television cameras for the fluorescein angiography of the retina (author's transl)

A survey of the major proportion of low-light level TV cameras available on the German market is described. A comparison and an assessment of the applicability of televised fluorescein angiography were carried out with the aid of technical data and measured results. It became evident that some systems were practicable for clinical use. With those it was possible to record angiograms at minimal illumination levels and patient inconvenience was reduced significantly. Measurements of blood flow parameters were possible with good temporal and geometrical resolution and full reproducibility.

Interference Effects in Shadow Image Electron Microscopy (SIEM) and in STEM and CTEM of Surfaces

It has been reported previously (1,2) that, as a result of the high degree of coherence of the incident beam a number of novel interference effects have been seen in shadow images and convergent beam diffraction patterns formed in the HB-S STEM instrument and observed by means of the optical analyser system which incorporates an image intensifier and a low light level TV camera. In this paper we report further new interference phenomena and the results of more detailed analysis of previously reported effects.

A gas proportional scintillation counter for use in large area detector systems without photomultipliers

The properties of a prototype gas proportional scintillation (GPS) detector module are described. The module (25 × 25 × 14 cm 3) is intended to form the basic unit of large area (up to ≈ 100 m 2) calorimetric cosmic ray burst detector. Ionisation from particle tracks in the module is collected onto a point electrode where the GPS signal is generated. A concave mirror focusses this point source onto the end of a fibre optic light guide. In the proposed large area detector these fibres are brought together onto a low light level TV camera which performs the readout. The prototype module has demonstrated an adequate light output for the detection of single muons by such a readout system and also permitted the the investigation of the main operating parameters (gas mixture, EHT, pressure, etc) and operational requirements such as proportionally and long term stability.

Computerized Tomograpy Using Video Techniques

A review of a series of qualitative and quantitative investigations of the capabilities of fluoroscopic systems to produce images having a sufficiently high quality to be used as the input for producing computerized transaxial tomograms is given. Examples of tomographic sections obtained from fluoroscopic image inputs are presented. In addition a quantitative comparison of computerized tomograms of a specially constructed phantom was made between reconstructions made with the EMI head scanner and those made from images provided by a large screen low light level TV camera fluoroscopic system. A phantom made from Lucite containing rods of various materials and sizes was used. The computer printout of each was analyzed and a high degree of correlation (r = 0.98) was noted between the results of both systems. The differential attenuation detectability of the fluoroscopic system was found to be comparable to or better than the EMI unit. As expected from a consideration of the quantum statistics for each system, the noise in the obtained reconstructions was also comparable. It is concluded that such a fluoroscopic system performs favorably when compared to the presently available commercial systems.

Development of deep-ocean work system

The Navy is developing a deep-ocean work system comprised of manipulators and a variety of hydraulic tools integrated to accomplish meaningful work tasks to ocean depths of 20,000 ft. The system can readily adapted to the manned submersibles ALVIN, SEACLIFF, and TURTLE, and the robot vehicles CURV III and RUWS, to extend their work capability. In addition, it can be positioned and controlled by divers or operated by itself from a surface support ship. The system was designed to perform a complete work operation on the sea floor without the necessity of resurfacing for tool interchange. Potential tasks include recovery, construction, installation, and repair operations. Low-light level TV cameras, with quartz-iodide flood lights, augment the vehicle operator's vision for tool exchange and work operations.

Advances in Celestial Navigation

ABSTRACTThe traditional celestial navigation, position fixing with the sextant and stars, has not been displaced by the development of the accurate and all‐weather inertial and radio navigation (LORAN, OMEGA, Satellite) systems. The limitations of these electronic navigation systems require celestial navigation as the back‐up on major naval and commercial vessels. Also it is the prime navigation method on many small Navy, Coast Guard, commercial, and pleasure craft. However, marine celestial navigation is not all‐weather, requiring sufficiently clear weather and illumination to see the celestial body and sea horizon simultaneously. In addition sight reduction from the sextant data to obtain line of positions for plotting is a tedious and time‐consuming procedure. Presently potential exists to extend the operating period of sextants to nighttime, and to assist general navigation, as well, with night vision telescopes and low light level TV (LLLTV) cameras. The state‐of‐the‐art in microelectronics indicates it is feasible to develop a relatively inexpensive, small, hand‐held, portable sextant‐computer system that will alleviate the tedium and blunders of sight reduction, and increase navigation accuracy.This paper describes the new day/night digital readout marine sextant, the concepts of the portable sextant‐computer system, the development of the sight reduction computer program, and the remote‐controlled LLLTV camera‐sextant system, which the navigator can operate within the ship to obtain celestial body sightings.