SATICON: A new photoconductive camera tube with Se-As-Te target

In order to decrease lag and after-images in blocking-contact photoconductive camera tubes, sufficient electron mobility is required as well as hole mobility, even if a p-type photoconductor is used. In this connection, a new photoconductive target of selenium doped with arsenic and tellurium has been developed. Arsenic doping is used to prevent selenium crystallization. Tellurium doping is used near the signal electrode to increase red sensitivity. Along with the hole blocking contact at the signal electrode, a blocking structure is formed on the beam-scanned surface of the target to prevent injection of the beam electrons. The SATICON tube, employing this target, demonstrates the following characteristics. The sensitivity is 300-450 µA/1m, the gamma is nearly unity, and the spectral response covers the entire visible region. A 2/3-in tube shows a modulation transfer curve as high as 30 percent at 400 TV lines, Its lag is 3 percent at a signal current of 200 nA. Applications to TV broadcasting are expected.     

A camera tube with NEA cold cathode

The GaP NEA cold cathode was used in a noncrossover type of electron gun mounted in a camera tube with a photoconductive amorphous selenium target. Sufficient beam current to operate the camera tube was obtained by passing a forward-bias current of several milliamperes in through the p-n junction. The equivalent beam temperature measured from the beam acceptance curve was about 600 K. This resulted in a considerably reduced capacitive lag at low light levels. At a signal current of 25 nA, the rise and decay lags of a 1-in tube were 90 and 12 percent, respectively, at the third field after turning on or off of the fight. Using a cold cathode with an electron-emitting area 50 µm in diameter, a horizontal limiting resolution of 800 TV lines was obtained at the center and high-quality images with good gradation were reproduced.     

An amorphous silicon imaging tube using high-velocity beam scanning

An imaging tube using hydrogenated amorphous silicon as the photoconductive target with a blocking-type structure and a high secondary electron emission yield surface is successfully operated using a high-velocity electron-beam scanning mode. The internal electric field in the photoconductor is the opposite of those used in conventional tubes in that the secondary electron current is obtained as a video signal. This imaging tube overcomes a lot of the disadvantages of conventional imagers, especially very small decay lag at both high- and low-illumination levels, a high uniform resolution of more than 700 TV lines, and no burning or blooming.     

The IRicon: A passive infrared camera tube

The IRicon is an IR-sensitive photoconductive TV camera tube. Recently declassified, it was developed for the military to whom many tubes were supplied in direct-readout or return-beam form with magnetic or electrostatic focus and deflection. Passive imaging of low-temperature objects such as humans or vehicles was observed with a normal TV speed of response. Resolution varied from about 100 TV lines at very low radiation levels to about 500 at higher levels. Scene temperatures denoting less than 1° C from ambient have been detected using f/1.2 optics.     

The mirror-matrix tube: A novel light valve for projection displays

A completely sealed-off electron beam-addressed light valve offering high reliability, low thermal impedance, and low-voltage operation is described. It is suitable for projection displays and is capable of producing bright high-contrast images with full gray-scale range and long-term storage. The light valve is contained as the faceplate in an otherwise standard, sealed-off 1½-in diameter vidicon tube and utilizes conventional focusing and deflection components. The target, which is fabricated of refractory materials using high-yield semiconductor-processing techniques, is composed of a dense matrix (500 elements/in) of aluminized silicon-dioxide membranes (~ 3000-Å thickness) which are supported centrally on small silicon posts (4-5 µm high) above a transparent sapphire faceplate. These flat, stress-free oxide membranes can be deflected electrostatically (up to 4°) when addressed with the electron beam. Thus an intensity-modulated display of the deposited charge pattern on the "mirror matrix" is produced when this type of light valve is used in conjunction with reflective schlieren optical arrangement, Mechanical and optical considerations have led to a special 4-leaf geometry of the mirror elements, enabling operation at low-voltage levels (175 V) and a high optical gating efficiency (~ 50 percent) to be achieved. Large-screen (2½-by 3½-ft) displays with up to 35-fL highlight brightness ( ×5 screen gain), 15:1 contrast ratio, and 400 TV lines resolution have been demonstrated. In addition, single-frame displays (1/30-s writetime) with full gray scale storage (of many hours) have been achieved. Preliminary studies using higher density mirror matrices (1000 elements/in) show that the display resolution can be extended to 600 TV lines/picture height.     

An HDTV high performance HARP camera-one inch HDTV HARP camera

A high-performance high-definition television camera is described. This camera, which employs a recently developed 1-in HARP pickup tube, provides high-quality pictures and provides 32 times maximum sensitivity compared with an HDTV camera using Saticon tubes. This camera's amplitude response is more than 40% at 800 TV lines. Some unique techniques are developed to correct misregistration precisely and provide fine focusing     

A cathode-ray switch tube with 11 channels of electron multiplication

An 11-channel switch tube with 5 stages of electron multiplication has been developed. In some applications the switch tube will replace the camera-oscilloscope system for recording the rise times of electrical signals. This tube will be used to convert wide-band information from a single channel into eleven channels of lower bandwidth information which can be transmitted over standard telephone cables for telemetering operations. Venetian-blind dynodes are used for the multiplier structure. Each channel is defined by a pair of louvers on the dynode disk. U-shaped shields, which just straddle the louver edge of the preceding dynode, are used to minimize crosstalk. The channel width is 0.120 inch or a total length of 1.32 in for the 11 channels. The collector system provides a method for equalizing the gain of all the channels. The switch tube is 3 in in diameter and 24 in in length. Operating at a 4-kv beam potential with 2-µa beam current, the tube provides 20 ma of output current, with less than 5 per cent crosstalk to adjacent channels. The electron optics and the performance of the tube are described.     

Large-signal transient analysis and effects of lateral charge spreading in television camera tubes

The transient response of television camera tubes to changing levels of illumination is examined. When the entire transient occurs within the exponential retarding potential region of the electron beamI-Vcharacteristic and photoconductive lag can be neglected, exact analytical expressions describing the rise and decay of video signal levels are established. The author present separate solutions to the problem based on the assumptions of electron beam scanning and charging by a hypothetical defocused beam (uniform charging case). The results support arguments in favor of target current biasing to minimize lag and turn-on time. We also show the effects of scanning as opposed to continuous dwelling by a flood beam. The decay transient is shown to be universial in the sense that it is independent of the initial signal strength and depends only on physical tube parameters. The validity of the expression describing signal decay is confirmed experimentally for a silicon diode array vidicon and a return beam silicon diode array vidicon. The effect on the resolution of target surface conductivity in conjunction with a finite electron beam impedance is treated for a steady-state per pattern and isolated circular spot illumination. In particular, the strong dependance of resolution, as limited by a conducting target surface, on operating current level is described. Lateral target leakage is shown to offer little advantage in decreasing lag.     

Characteristics of experimental CdSe vidicons

A high sensitivity vidicon using a CdSe photoconductive target was successfully developed. A new CdSe target with junction-type structure was employed to realize the improved characteristics as given below. The sensitivity is about 20 times higher than that of conventional vidicons, which makes it possible to operate the tube with low levels of faceplate illumination of 0.1-1 lx. A typical sensitivity is 200 nA/0.5 lx with scanning areas of 9.5 × 12.7 mm². The gamma of the light transfer characteristic is 0.9. The tube provides a wide spectral response over the whole range of visible wavelengths. The dark current is less than 1 nA. The lag is 10 percent for a 200-nA signal current. High resolution is achieved. Afterimage and burn-in are hardly observed under normal operational conditions. The life of the tube extends to more than 1000 hours. With these characteristics, the CdSe vidicon can produce suitable pictures with good quality both for industrial use and for broadcasting use. The detailed structure of the target is also discussed.     

A high luminance high-resolution cathode-ray tube for special purposes

For those applications where light sources of high radiance or displays of high resolution are necessary, miniature cathode-ray tubes have been developed with monocrystalline luminescent screens. These newly developed screens consist of cerium-doped yttrium-aluminum garnet (YAG), epitaxially grown on commercially available YAG substrates; they have an excellent heat conductivity and are optically clear. The construction of the tube and its performance in two modes of operation are described. When the tube is operated with a continuous undeflected beam, the luminance of the spot is limited by thermal quenching of the phosphor material. Under these circumstances, the maximum luminance of 1.9 × 10⁸cd/m²(0.55 × 10⁸FTL or 4 × 10⁵W/m²sr) is reached at a power of 70 mW in a 3.5-µA 20-kV beam, focussed to a spot of 9 µm diameter. Equipped with appropriate deflection coils and scanned with an interlaced field of 575 active lines and 25-Hz repetition frequency, the tube can handle up to 20 W of beam power in a 12 × 16 mm²image area. In this mode, the luminance is limited by the design of the electron gun and the desired resolution. At 20 kV and 100 µA (i.e., at 7500 cd/m²) the tube has a half-intensity linewidth of 60 µm, which is equivalent to 500-TV limiting response lines in the same 12 × 16 mm²area.     

A solid-state infrared image converter

A photoconductor-electroluminescent type infrared image converter panel has been studied through the application of doped CdSe photoconductive powder layers of different thickness to the earlier type of image converter and through temperature operation. The spectral sensitivity extended from 0.7 to 1.2 µm with sensitivity peak at 0.9 µm and the minimum detectable input power density reached approximately 2×10^-10W/cm²for 0.9 µm at 0°C. Projected infrared images are converted to visible electroluminescent images with a resolution of 3 to 8 TV lines/mm and a response time of an order of 1 to 10^-2s, depending upon the photoconductor thickness and the operating temperature. The converter panel may be used as a night vision panel with an additional infrared source. This paper describes a preparation of doped CdSe photoconductor suitable for a photoconductor-electroluminescent device, some of its properties, and the effect of the photoconductor thickness and of the operating temperature on the performance of the solid-state infrared image converter. Converted visible images using experimental panels are also shown.     

Electric field distributions in planar transferred-electron devices measured with picosecond optical pulses

The internal static electric field distribution in InP planar transferred-electron devices at subthreshold biases has been measured with a spatial resolution of 1.5 µm by observing the photoconductive current response to picosecond optical pulses. The technique is extremely sensitive to fields in the vicinity of electron velocity saturation values.     

An electron beam activated switch and associated memory

A new type of electron beam activated switch (EBAS) is described which utilizes electron beam induced charge storage in the metal-oxide-semiconductor (MOS) system. The state of the EBAS is determined by monitoring the surface conductance of the semiconductor. After discussing the basic charge-storage phenomena, memory arrays that use the electron beam for storing and reading information are described. A matrix array of EBASs in which information is stored using the electron beam and read by row-column access circuits is discussed in detail. The time to store a bit of information is a function of the current density of the electron beam; an approximate dosage of 10^-5C/cm²is required for storage. A memory design using Schlesinger's microspot tube for the electron optics is discussed. It is shown that storage of 1.0 × 10⁷bits per tube should be possible with presently available electron optical design and semiconductor technology.     

A microspot tube with very high resolution

A 5-inch microspot tube with a spot size of 8 to 9 microns and a beam current of 1.5 µa is described. The neck of this tube uses an accelerating spiral anode, in combination with a decelerating prefocus lens. This combination stretches the 6-inch neck structure to an effective length of 13 to 16 inches. The resulting demagnification of 0.6 permits realizing the above spot size as an electron image of a 1/2 mil object-aperture. The latter is illuminated with a current density of 20a/cm²by a microgun, which uses an impregnated cathode at 2a/cm². The microgun operates by the FRM principle ("Focus Reflex Modulation"). An improved vapor-reacted screen is employed, whose light output is more than tripled from previous types of transparent phosphors.     

A cyclotron resonance frequency multiplier

The current density available from known thermionic cathodes imposes a serious limitation on the power output obtainable from electron tubes operating at frequencies above about 10 Gc. This paper describes a proposal for a frequency multiplier which has the interesting property that the RF energy imparted to the electron beam by the signal source may be one or two orders of magnitude greater than the dc energy supplied by the battery. Thus it is expected that the power output at a particular frequency will be much higher for a given cathode current density than that obtained from conventional types of electron-beam oscillators and amplifiers. The multiplier operates by converting the input energy at one radio frequency into rotational energy of an electron beam by means of a Cuccia coupler. The beam then couples power to the output load via a multicavity circuit containing2ncavities wherenis the frequency multiplication to be obtained. The paper includes details of experimental work on a low-power tube multiplying from 600 Mc to 3600 Mc. In this tube 1.3 watts of RF input power is coupled on to a 50 volt, 260-µa beam and the power at 3600 Mc is coupled out via a 12-cavity magnetron anode structure. Photographs are given of the trace of the rotating beam impinging on a fluorescent screen and these demonstrate the degree of focussing achieved along the length of the tube. The paper concludes with a study of the feasibility of a tube multiplying from 10 Gc to 100 Gc with an output of tens of watts.     

Beam transmission in electron guns having a single-apertured control grid

The ratio of target current to cathode current (beam transmission) has been studied for a number of vidicons and scan converters. These are high-resolution electron tubes that characteristically have a control grid with a single aperture. The results, as anticipated, show that beam transmission is affected much more than total cathode emission by tube aging processes. The transmission was determined by direct beam current measurement and the cathode condition recorded by the cathode imaging technique. Because of the centralized area in which the loss of emission occurred, beam transmission was reduced much more than total cathode current. In vidicons, the decreasing beam transmission was correlated with increasing residual signal after erasure and with saturation of the gamma transfer characteristics at lower light levels. In practice, beam current rather than cathode current, should be monitored.     

A design of triode electron gun

A theoretical study has been made of the focusing of high-current electron beams by means of the aperture effect. The aperture effect is obtained by a triode electron optical system. An equation for describing the beam profile in the system has been described. Both the condition for obtaining the minimum radius of the beam and the condition for optimum focus have also been worked out. Two numerical examples are treated to illustrate the triode focusing of electron beams with two different total current magnitudes of 50 and 250 µa. It is found that by using this triode system the final energy of the electrons and the total current of the electron beam may be adjusted separately.     

Electron beam direct writing technology applied to 512 kbit ROM with 1 µm geometry

A 512 kbit read-only memory (ROM) to store Chinese ideographs has been fabricated using variable-shaped electron beam and dry-etching lithography. 1.0-µm minimum line width was used to delineate device area spacings smaller than those obtained with conventional design rules using photoimaging techniques. SiO2, Si3N4, and polysilicon etchings were accomplished by reactive sputter techniques with CF4+ H2and CCl3F gases using negative electron beam resist PGMA and positive resist AZ-2400. Al etching was carried out by plasma with CCl4gas using negative electron beam resist NER-1. The alignment marks detectability and their locating accuracy were improved by properly using the basis arithmetic operations, subtraction and summation, in backscatter signal processings. 6.6 mm × 8.9 mm chip-by-chip alignment yielded about 0.2-µm level-to-level registration accuracy. Memory cell size and chip size are 5.2 µm × 8.4 µm and 6.6 mm × 8.9 mm, respectively; access time and power dissipation are 400 ns and 800 mW, respectively.     

Photodetectors for optical communication systems

The characteristics of high-sensitivity photodetectors suitable for wide bandwidth optical communication systems are summarized. Photodiodes, photomultipliers, and photoconductive detectors for wavelengths from 0.3 µm to 10.6 µm are covered. The use of internal current gain by means of avalanche and electron multiplication and by means of optical heterodyne detection to increase sensitivity of high speed photodetectors is discussed. The application to visible and infrared laser communication systems is reviewed.     

The transient response of photoconductive camera tubes employing low-velocity scanning

The transient signal which results from the characteristics of a low-velocity electron beam and the capacitance of the scanned surface has been calculated. A very slow transient of the hyperbolic type can result if the scanned surface is stabilized at a retarding field potential. The calculations have been verified by tests on a 6198 Vidicon, which was taken as an example. For this tube, the relative contributions of the "electronic transient" and the photoconductive decay to the observed transient response were determined. They make comparable contributions to the total transient.