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At least 19 records

Thermal neutron image intensifier tube provides brightly visible radiographic pattern

Vacuum-type neutron image intensifier tube improves image detection in thermal neutron radiographic inspection. This system converts images to an electron image, and with electron acceleration and demagnification between the input target and output screen, produces a bright image viewed through a closed circuit television system.

Berger, H.

Photoelectron counting with an image intensifier tube and a self-scanned photodiode array

A self-scanned photodiode array was fiber-optically coupled to an ITT proximity-focused image intensifier tube. It was determined that a single photoelectron event produces 34,000 charge carriers in a photodiode. This charge is only a factor of 2.8 above the rms noise level of the preamplifier used in the tests, but standard charge-sensitive techniques are at least a factor of 12 better. The image tube and photodiode array combination can be packaged in a disk 5.1 cm in diameter and 2.6 cm thick.

Sandel, B. R.

Interfacing a Two-Stage Image Intensifier Tube to an Echelle Spectrograph

An Echelle spectrograph has been in use at the Marshall Space Flight Center for a number of years. Research has been carried out in the study of the internal motions of ionized gas clouds in the interstellar medium. In order to extend the ability of the spectrograph to allow investigations of the faint outer regions of the gas clouds and to make possible the initiatiion of new research programs dealing with the study of sunspots and the zodiacal light, a two-stage image intensifier tube was incorporated into the instrument. The objective of this work was to interface the image tube with the spectrograph.

Flesch, T. R.

Image intensifier tube observations of the OH airglow during the Space Shuttle simulation

The OH airglow studies discussed have evolved from a lead-sulfide-cell scanning photometer to photographic techniques to, currently, image-tube photography. During the Space Shuttle Simulation, photography (35-mm and 16-mm) and filter-wheel photometry of submicron OH airglow were performed aboard the NASA CV990 Airborne Laboratory. Examples of ground-based and airborne photographs are presented for comparison. Analysis of the aircraft data is described.

Peterson, A. W.

Charge coupled devices for intensified imager applications

Three types of CCD sensors have been successfully incorporated into ICCD (intensified CCD) tubes. Intensifier tubes of varying design and application have been manufactured by three different manufacturers. Typical characteristics of the thinned CCDs incorporated into these ICCD's will be presented. Problems concerning the compatibility of tube processing and CCD performance will be discussed, as well as the procedures used to minimize CCD degradation during tube processing. ICCD tube characteristics will also be presented.

Stubbs, D. P.

Low temperature multi-alkali photocathode processing technique for sealed intensified CCD tubes

A low temperature photocathode process has been used to fabricate an intensified CCD visual photocathode image tube, by incorporating a thinned, backside-illumined CCD as the target anode of a digicon tube of Hubble Space Telescope (HST) design. The CCD digicon tube employs the HST's sodium bialkali photocathode and MgF2 substrate, thereby allowing a direct photocathode quantum efficiency comparison between photocathodes produced by the presently employed low temperature process and those of the conventional high temperature process. Attention is given to the processing chamber used, as well as the details of gas desorption and photocathode processing.

Doliber, D. L.

Real-Time Digital Radiography Upgrade

The objective of the task is to upgrade an existing real-time digital radiography system by replacing an aged image intensifier tube with an amorphous silicon digital x-ray imager. The real-time digital radiography system at GSFC is currently fitted with image intensifier tube with a 4 or 2 inch diameter active area with higher resolution at the smaller area. The image intensifier is exhibiting deterioration in sensitivity associated with extended use and is in need of replacement.

Parker, Bradford H.

Self-scanned Digicon - A digital image tube for astronomical spectroscopy

We have successfully fabricated, tested, and operated a digital image tube consisting of a magnetically focused image intensifier tube in which a self-scanned linear array of 1024 silicon photodiodes operating in the EBS mode serves as the photoelectron image detector, amplifier, and intermediate image storage device. Integral on-chip MOS shift registers driven by an external clock sequentially interrogate the photodiodes through MOS FET multiplex switch arrays. Each output frame is a sequence of 256 analog pulses on each of four video lines. Laboratory and observing tests show that the output signal is photoelectron shot noise limited over at least a range of 1-100,000 detected photoelectrons per picture element, indicating that single photon detection is achieved. High-resolution astronomical spectroscopy has been carried out in the coude spectrograph of the 2.7-m telescope at McDonald Observatory. Examples are shown.

Tull, R. G.

The smoothing dissector.

A technique for adding a form of buffer store to an image dissector is described that increases markedly the photoelectron-detecting ability of the image dissector. The buffer-store function is accomplished in the phosphor screen of an image intensifier tube by the metastable electronic excitation states resulting in the phosphor screen from high-energy photoelectron bombardment. The addition of this image intensifier to an image dissector is shown to cause no nonlinearity in the input/output characteristics of the image dissector.

Eberhardt, E. H.

Monitoring Both Sides Of A Weld In Progress

Proposed remote vision system provides simultaneous viewing of front and back of workpiece while being welded. Enables human or automatic controller to monitor both weld pool on front and weld penetration on back. Nitrogen laser generates ultraviolet light, distributed to both sides of workpiece through two optical fiber cables. Image-intensifier tubes convert reflected ultraviolet light to visible light. Video cameras equipped with high-resolution charge-coupled devices convert visible outputs of image intensifiers into images for viewing on video monitors.

Dickinson, C. B.

Persistence of phosphor glow in microchannel plate image intensifiers

Image intensifier tubes using microchannel plate amplification stages and phosphor output stages are being increasingly used in various detection applications. In this paper, measurements of the decay times of what are attributed to be the P20 phosphors in various image intensifiers are reported. It is found that the long tail on the decay curve of the phosphor following illumination can be a limitation for certain observations. In addition, the background level of phosphor glow (which is seen by the subsequent detection system as a light signal) continues to build with continuing illumination.

Torr, M. R.

Helicopter flights with night-vision goggles: Human factors aspects

Night-vision goggles (NVGs) and, in particular, the advanced, helmet-mounted Aviators Night-Vision-Imaging System (ANVIS) allows helicopter pilots to perform low-level flight at night. It consists of light intensifier tubes which amplify low-intensity ambient illumination (star and moon light) and an optical system which together produce a bright image of the scene. However, these NVGs do not turn night into day, and, while they may often provide significant advantages over unaided night flight, they may also result in visual fatigue, high workload, and safety hazards. These problems reflect both system limitations and human-factors issues. A brief description of the technical characteristics of NVGs and of human night-vision capabilities is followed by a description and analysis of specific perceptual problems which occur with the use of NVGs in flight. Some of the issues addressed include: limitations imposed by a restricted field of view; problems related to binocular rivalry; the consequences of inappropriate focusing of the eye; the effects of ambient illumination levels and of various types of terrain on image quality; difficulties in distance and slope estimation; effects of dazzling; and visual fatigue and superimposed symbology. These issues are described and analyzed in terms of their possible consequences on helicopter pilot performance. The additional influence of individual differences among pilots is emphasized. Thermal imaging systems (forward looking infrared (FLIR)) are described briefly and compared to light intensifier systems (NVGs). Many of the phenomena which are described are not readily understood. More research is required to better understand the human-factors problems created by the use of NVGs and other night-vision aids, to enhance system design, and to improve training methods and simulation techniques.

Brickner, Michael S.

Neutron-image intensifier

Electronic intensifier tube with a demagnification ratio of 9-1 enhances the usefulness of neutron-radiographic techniques. A television signal can be obtained by optical coupling of a small-output phosphor-light image to a television camera.

Berger, H.