Two sensors are currently in development by NASA that appear to meet the requirements. The first is an extension of conventional TV techniques called the return beam vidicon, which shows promise of a 3500-TV line limiting resolution in the next year with improvement to more than 5000 lines foreseen for the future.
В зависимости от материала и типа мишени В. разделяются на кремниконы, плюмбиконы, кадмиконы, сатиконы и ньювиконы. В. создают сигнал изображения при освещённости мишени от долей до нескольких десятков люксов, обеспечивая разрешающую способность от 400 до 10 000 линий; обладают, как правило, высокой спектральной чувствительностью, малой инерционностью, малыми темновыми токами, линейной характеристикой «свет – сигнал».
> ВИДИКОН • Большая российская энциклопедия - электронная версия
The 4½-in. return-beam vidicon (RBV) can be operated in either a slow-scan, single-frame readout mode or a fast-scan, multiple-frame readout mode. The fast-scan readout mode provides a high-quality, flickerless readout for display to a human observer in a manner similar to that employed in commercial television. This mode can be enhanced by selective electronic magnification of the information by underscanning the target. Typical display monitor parameters would include 2000 × 2000 tv line resolution. With 3:1 electronic magnification, an equivalent of 6000 × 6000 tv lines would be displayed.. The high image-sensor performance and the display flexibilityl-6 a-chieved with the return-beam vidicon have made it attractive for use as an electrical write/read storage tube. Feasibility has been established recently at RCA Aerospace Systems Division for use of this device in various electro-static storage modes. Performance achieved is essentially as good as normal-ly obtained with optical input. The excellent storage characteristics of this tube make it particularly adaptable to many display problems that require alternative and/or simul-taneous display of data available in a variety of optical and electrical formats. The high-resolution return-beam vidicon has a number of characteristics which can be used effectively for design of high-performance sensing, storage, and display systems. The basic characteristics can be examined both in absolute terms and in relation to other electron-beam image tubes (see Fig. 1).
> The High-Resolution Return-Beam Vidicon with Electrical Input | SpringerLink
The Return Beam Vidicon (RBV) operated on Landsat satellites 1 and 2, and acquired approximately 1,600 sub-scenes at 80 meter resolution. The initial RBV sensor configuration used three independent cameras, each sensing a different spectral wavelength such as (0.48 to 0.83, 0.48 to 0.57, 0.58 to 0.68, and 0.70 to 0.83 micrometer). Landsat 1 and 2 RBV data were recorded to 70 millimeter (mm) black and white film rolls at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center and delivered to the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center for archiving and user distribution.
The RBV sensor utilized vidicon tube instruments containing an electron gun that read images from a photoconductive faceplate similar to television cameras The data stream received from the satellite was analog-to-digital preprocessed to correct for radiometric and geometric errors. The RBV system was redesigned for Landsat 3 to use a two-camera configuration mounted side by side that acquired four sub-scenes within the field of view of a Multispectral Scanner (MSS) scene. The Landsat 3 RBV spatial resolution is 40 meters with a spectral wavelength of 0.505 to 0.75 micrometer. Landsat 3 data were also recorded to 70 mm film until the EROS Digital Imagery Processing System (EDIPS) became operational in 1979. EROS Laser Beam Recorders (LBRs) recorded MSS and RBV data at 28 microns to 9-inch film rolls and the imagery was chipped up for archival storage and remains a viable archive backup to the digital MSS archive. However, all of the RBV digital archive data were purged for lack of computer compatible reasons. The last known collection of RBV tapes were disposed of in 2003.
Today, the RBV 70 mm and 9-inch film sources are maintained in the USGS EROS archive and are accessible through EarthExplorer as an on-demand film scanning product. RBV images that are scanned and the black and white images faithfully represent the Landsat RBV film archive as it exists today.
> USGS EROS Archive - Landsat Legacy - Return Beam Vidicon (RBV) Film Only
The Return Beam Vidicon (RBV) camera system features a recently developed sensor which is capable of producing images with a resolution of 4500 TV lines. Discussed here are the operation of RCA's 2-in RBV and how its primary assets are compatible with the system requirements of programs such as the Earth Resources Observation Satellite. The RBV combines the advantages of the conventional storage vidicon ASOS photoconductor and the orthicon electron multiplier. The sensor operates in a slow-scan mode and utilizes the modulated return beam as a signal path to decrease the signal noise. The primary assets of this device are an improved lowlight sensitivity, with higher signal-to-noise ratios than can be obtained with a conventional vidicon, coupled with extremely high resolution. The 4500-line video signal generated in the 1-in format is converted into a high-quality hard copy print by the Laser Beam Image Reproducer (LBIR). — The high image retention characteristic of the photoconductor makes possible the slow-scan readout of a high-definition (100-ft ground resolution from satellite altitudes), nonsmeared image in limited bandwidth. Thus, a three-camera electronically shuttered system can be used to simultaneously photograph a given section of the Earth's surface in three different spectral bands. Data produced by the sequential readout of the three cameras, when superimposed, can be used to generate a sharp multispectral image. The high-resolution, low image distortion (geometric integrity, shading, etc.), characteristic of the RBV, results from the integration of the vidicon with a carefully controlled electron optic and deflection system. Distributed focus coils are used to obtain minimum spot size and proper beam landing over the full format. The image quality of the RBV/LBIR's high-resolution, low-noise picture is comparable with ground reproduction of present-day film and data transfer techniques used in unmanned surveillance satellites.
Published in: Journal of the SMPTE ( Volume: 79 , Issue: 1 , Jan. 1970 )
> A High-Resolution Image Sensor - SMPTE Journals & Magazine