Singleé channel, multichannel and imaging types of UV detectors are reviewed. Solid-state detectors are still not well developed for UV work. Single-channel detectors such as vacuum photodiodes (PDs), photomultiplier tubes (PMTs), multichannel PMTs, and imaging detectors are used in the entire UV region. The spectral detective quantum efficiencies for the various detectors depend upon the types of cathodes and electron multipliers chosené, but peak DQEs are as high as 25 percent for PDs, 15 percent for PMTs, 15 percent for multichannel PMTs, and 15 percent for imaging detectors. Response times for these detectors range from impuélse response times of 15é0 ps FWHM for high-speed PMTs to the RS-170 video rate for IDs.
In the past, analysis of flame propagations within a spark ignition engine combustion chamber has been analyzed
with pressure diagrams. These pressure diagrams have helped to develop the geometry within the combustion
chamber. Photographing or electronically imaging the flame propagations are very important in the visualization of
combustion characteristics. Attempts to use intensification with videography have met with limited success. A new
integrated intensified imager is now available which works in conjunction with the KODAK EKTAPRO 1000 Motion
Analyzer. The intensified imager to be discussed uses a two stage intensifier coupled to a solid-state sensor array.
The first stage shutters the image at microsecond rates. The second stage amplifies the light from the first stage
over a short integration period. The coupling of these two stages to Kodak's 1000 frame per second motion analyzer
has significantly extended the use of high speed videography for flame propagation studies. This paper will address
the imaging requirements for flame propagation studies and the methods for performing analysis using an intensified
Imaging multianode microchannel array (MAMA) detector systems with 1024 x 1024 pixel formats have been produced for visible and UV wavelengths; the UV types employ 'solar blind' photocathodes whose detective quantum efficiencies are significantly higher than those of currently available CCDs operating at far-UV and EUV wavelengths. Attention is presently given to the configurations and performance capabilities of state-of-the-art MAMA detectors, with a view to the development requirements of the hybrid electronic circuits needed for forthcoming spacecraft-sensor applications. Gain, dark noise, uniformity, and dynamic range performance data are presented for the curved-channel 'chevron', 'Z-plate', and helical-channel high gain microchannel plate configurations that are currently under evaluation with MAMA detector systems.
In order to track and measure weak, small, multiple and high speed moving targets, a new kind of high speed cinecamera with a gated intensifier has been developed. The techniques of image intensifying, laser illumination, electric shuttering and high speed photography have been used, to obtain high light-gain, good imaging quality, and long measuring distance. The system has a gated intensifier and gating circuit with an adjustable gating time of 1 to 300 microns and adjustable photography frequency of 1 to 100 frames/second. The nonlens coupling method solves the two problems of electrostatic discharge and dynamic friction between the film and the optic fiber faceplate. The resolution has been improved by using a coupling fiber optic plate with low numerical aperture.
For full swing commercially available 1/2" and 2/3" imaging sensors in standard
video cameras call for an illumination density of approximately 0.5 to 1.0 lx at
Improved sensitivities can be achieved by use of image intensifier tubes, coupled
to the CCD either fiberoptically or by relay lens. Such configurations are wellknown
at black and white low light level TV cameras.
Three-channel color cameras with three CCDs have to be equipped with three image
intensifier tubes intensifying each of the color component images (RGB) absolutely
free of geometric distortions. Such 3-channel low light level cameras are complex
in design and expensive.
The paper presents a low light level CCD color camera with only one chip and only
one image intensifier tube with an excellent cost/performance ratio. An absolutely
distortion-free proximity focus image intensifier diode PROXIFIER R of high
resolution with a color stripe filter beneath its photocathode is fiberoptically
coupled to a CCD with such a precision that the position of the filter-stripes
coincides with that of the vertical pixel rows of the CCD.
There is increasing demand for high resolution image sensor for applications
in high definition television, high resolution x-ray imaging in the medical
field. In order to meet the requirements of these applications, a high resolution
Plumbicon camera tube was developed at Philips Components.
A camera tube for high definition imaging is required to have high
sensitivity, good spectral response, high signal to noise ratio, low lag and
retention. The tube is designed with electrostatic deflection to achieve uniform
and high resolution. An additional design feature is the low capacitance target
for highest signal to noise ratio. This is especially important in wide bandwidth
high line rate systems. This feature in combination with new Plumbicon layer
technology provides the benefit of low light level contrast detectability.
As applications are forthcoing in gated image intensifier tubes the selection of the output screens phosphor or these uses becomes less routne The c!assc P-20 green phosphor has some peculiarities that niust be reckoned with in nonCW modes such as a long-term decay tail and a rather slow rise time, At the other extreme is the rare-earth P-6 also green and its cousin, the P-47 (blue), with rise and fail times in the nanosecond range Ethciencies are ower..only about 20% ot the P-20's but. this can usually be compensated by increasing overall gain by other means The integrating time of the ultimate readout device (often CCL's, ton example) may determine the most approprIate phoerhor Data will be presented to aid the systen designer in selecting a phosphor
This paper will describe a high quantum efficiency imaging phosphor diode optimized for 500-700 nm sensitivity. Potential applications for this tube include undersea imaging and detection of 530-nm laser light. The tube is designed to function as a low noise factor optical amplifier. The tube consists of an 18-mm CsO activated GaAs/AlGaAs photocathode and a high resolution P46 phosphor screen enclosed in a Kovar/ceramic vacuum envelope. Measured results for quantum efficiency (QE), MTF, dark current, noise factor, operating life, response time and gain are presented. Finally, the paper discusses the engineering tradeoffs associated with fabricating a GaAs/AlGaAs cathode with high short wavelength QE.
A class of stimulable phosphors, called electron trapping (ETTM) materials, have
been developed that are responsive in the infrared. When the ET materials have been prepumped
with short wavelength visible light and subsequently exposed to infrared, a visible
orange to red wavelength is produced. Such an emission is readily detected by an image
intensifier and offers an inexpensive method for extending the sensitivity range of image
intensifier photocathodes, such as S-25. The infrared sensitivity range is from 0.8 ,um to
1.6gm, and the response time is on the order of tens of nanoseconds. A hand-held infrared
viewer (called a NIRSCOPETM) has been constructed by mating the IR-stimulable
phosphor with an image intensifier.
The specific applications where the NIRSCOPE is useful are those involved with
the imaging of near-JR emitting objects or imaging scenes in a dark environment. These
include the following:
o Imaging the emission output of laser diodes.
o Detection of JR leakage from damaged fiber optic cables.
o Imaging of near-JR laser targeting and ranging.
o Alignment of optical bench components for near-JR propagation.
o Dark room viewer for film processing.
Cathodoluminescent phosphor screens are commonly used in display devices such
as CRT's and image intensifiers. Conventional methods of fabricating such screens involve
the physical deposition of phosphor powder on an appropriate substrate, such as clear
glass. In addition, high resolution display devices are now utilizing thin powder layers on
fiber optic faceplates, greatly enhancing their resolution capabilities. At present, a typical
resolution achievable with powder screens on fiber optic faceplates is approximately 50
lp/mm, or about 10 X 10 micron pixel size, and is primarily limited by the faceplate
resolution. However, as the ultimate resolution of fiber optic faceplates is improved (i.e.,
as the fiber diameters are reduced), phosphor powder particle size and thickness will also
have to be reduced to maintain high overall screen resolution. For example, in order to
achieve a 1 micron resolution, a phosphor screen 1 micron thick would be required with
1 micron diameter or less particle size. However, it is not likely that current screen
manufacturing technologies can readily achieve the desired particle size, thickness, and
uniformity requirements to further improve resolution.
A great deal of effort is presently being focused on developing high resolution, high sensitivity medium wavelength IR (MWIR) imaging systems for a variety of applications. These range from thermal imaging for industrial applications to military applications for detecting vehicles, missiles, etc. The present state-of-the-art method for MWIR imaging consists of fabricating linear and two-dimensional arrays of semiconductor detectors, such as HgCdTe, InSb, etc., and incorporating these into an appropriate optical imaging system. However, such devices are difficult to make and are very expensive. A new detector medium is described which can be fabricated at low cost for use in MWIR imaging. Specifically, the new medium is an electron trapping material capable of up-converting MWIR to visible wavelengths, which can be easily detected with a commercial camera system. This paper will describe the specific performance characteristics of the new phosphor material and its application in MWIR imaging.
The increasing awareness of the full range of detection capabilities of the microchannel plate-based detectors has led to the use of these electron multipliers in an ever increasing range of applications. Recent advances in the state of the art (ultra-small pores and high-output technology) have led to significant increases in dynamic range. This paper focuses on the design considerations for the optimal dynamic range in microchannel plate detectors. Factors such as size, gain, temperature, pulse height resolution and background noise are considered.
The Microchannel-plate Intensified CCD (MIC) photon-counting detector system has been developed as a future replacement for a common user photon counting detector, the IPCS (Image Photon Counting System) on both the Isaac Newton and William Herschel telescopes at the La Palma Observatory and at the Anglo-Australian Observatory. These detectors previously incorporated EMI 4-stage cascade image intensifiers. This paper addresses the technological aspects of the design and optimization of very high gain MCP image intensifiers for such photon counting systems, and particularly the optimization of device detective quantum efficiency.
Microchannel plate (MCP) dynamic range has recently been enhanced for both very low and very high input flux conditions. Improvements in MCP manufacturing technology reported earlier have led to MCPs with substantially reduced radioisotope levels, giving dramatically lower internal background-counting rates. An update is given on the Galileo low noise MCP. Also, new results in increasing the MCP linear counting range for high input flux densities are presented. By bonding the active face of a very low resistance MCP (less than 1 megaohm) to a substrate providing a conductive path for heat transport, the bias current limit (hence, MCP output count rate limit) can be increased up to two orders of magnitude. Normal pulse-counting MCP operation was observed at bias currents of several mA when a curved-channel MCP (80:1) was bonded to a ceramic multianode substrate; the MCP temperature rise above ambient was less than 40 C.
A new type of microchannel plate (MCP) is described which has been optimized for use in generation II and generation III image intensifier tubes. The results of a program focused on improving the SNRs of these generations of image intensification tubes through the optimization of the microchannel plate are presented. The effects of open area ratio (OAR), funneling, secondary emission coefficients, first strike conversion efficiency, gain, enhancement coatings, aging, and filming are discussed.
Development of glasses for production of high numerical aperture (N.A.) fiber optic
faceplates (FOFPs) has historically concentrated on achieving desired refractive indices at the
expense of other physical properties. Consequently, the viscosity and stability of currently
produced FOFP glasses makes production of high quality faceplates difficult and expensive. In
response, a joint program was undertaken to develop a new high N.A. FOFP glass system with
physical properties specifically tailored for optimized FOFP production. This program has
yielded a new, highly stable, glass system which has been demonstrated to produce high n.a.
FOFPs with higher intrinsic transmission than existing materials. In this paper we review the
design process, glass system properties, and properties and performance of FOFPs from pilot
scale production runs.
The use of machine vision equipment to quantify internal optical aberrations
has recently proven to be effective for the inspection of fused fiberoptic
components . The fundamental benefits of this approach to dimensional inspection
are improved accuracy , repeatability and speed , in conjunction with automatic
data collection and statistical analysis . Recently revised specifications and
supporting calculations governing the optical distortion limits of an imaged
straight line across an 18mm clear aperture of a fiberoptic component have made
the current measurement method using an optical comparator both cumbersome and
unreliable. Requirements for inspection and certification of the maximum
deviation , warranting measurement on nunrous axes across the optic , further
illustrate the benefits of the vision inspection system. This discussion will
concentrate on vision equinent , optical techniques and referenced patterns
incorporated in the measurement of S-distortion to the new specifications in
fused fiberoptic inverters.
A commercial Modulation Transfer Function (MTF) measurement system
has been customized to be application specific to spatially
coherent fiber optic coupled imaging systems. Theoretical
considerations, the required mathematical assumptions and the
modified test conditions used to achieve accurate and repeatable
MTF measurements are described. Experimental results on a matrix
of advanced fiber optic materials evaluate for short range order
effects including element size, orientation, shear distortion and
architecture. These results help to emphasize the value of the
MTF curve over limiting resolution or discrete MTF values in
qualifying the imaging performance of fiber optics.
Distortion-free fiber optic faceplates (FOFPs) are required to improve the optical
performance of electronic imaging systems, particularly CCD-based imaging devices. In the
course of determining the intrinsic sources of image distortion in FOFPs we have developed novel
fiber architectures capable of producing ultra-low distortion arrays1. In this paper we review this
analysis, present experimental results on two new FOFP architectures that have been
demonstrated to produce ultra-low distortion FOFPs, and discuss prospects for further work.
This article discusses a number of the major problems confronting the development of
present day semiconducting JR focal plane detectors for large array space based applications,
shows that an entirely new detector technology based on superconductivity may circumvent
many of these difficulties, provides detailed data on the characteristics of these devices and
outlines the development program underway to exploit this new technology.
Thin-film superconductors invite the single-process/single-substrate fabrication of IR detector arrays and their associated processing circuitry. In place of the bolometric thermal-detection principle typical of previous superconductor-employing schemes, the temperature-dependence of the current-voltage relation in a current-biased Josephson tunnel junction is used in the present device; this yields very low intrinsic detector noise, as well as clearly-defined 'on' and 'off' states. Superconducting processing circuitry encompassing addressing and decoding circuits, analog amplifiers, and ADC has been tested for an 8 x 8 prototype array.
One of the key issues in the development of IR focalplane
systems is the need for low-noise and low-power read-
out circuitry which is compatible with the detector technology.
Superconductive circuitry offers several advantages
over more conventional circuitry. These include much lower
power consumption and the possibility of unique circuit
topologies relevant for developing advanced monolithic
detectors. On-chip signal processing through A/D conversion
with digital gamma-ray suppression and digital integration
appears possible. This paper reviews the progress that TRW
has made in developing several of the key components of such
a superconductive read-out system. We have developed a semi-
conductor/Josephson-junction 3-terminal device for direct
interfacing to semiconductor detectors as well as thin-film
superconductive detectors. The 3-terminal device has a current
gain of : 500 and provides an optimum interface to further
superconductive stages. Performance when coupled to a SQUID
read-out will be discussed.
Imaging photon detectors (IPDs) can perform down to light levels of a few photons/sq cm/sec; this is 5-6 orders of magnitude more sensitive than civil and military low-light TV systems, and obviates the use of cryogenically cooled arrays which can destroy the linearity of cooled CCDs. An account is presently given of the characteristics of vacuum-tube IPDs with resistive anode, with centroiding CCD, and with wedge-and-strip readout, in order to evaluate their comparative advantages. All three readout system types are in principle capable of covering the entire EM spectrum, from MeV photons/particles down to less than 1 eV, and share similar limitations in count rate, counting efficiency, and resolution.
The great interest in image converter tubes with a lock system is explained by the fact that they have no competitors among the devices for the registration of ultrafast phenomena under conditions of diffuse scattered light background. A wide range of types of such tubes is being produced nowadays, and an understanding of ways of improving their most important parameters exists. A design for a sidescreen tube with a lock of 'shutter deflector' type is presented.
In the optical channel of picosecond recording system a set of cross-over image
tubes and microchannel intensifiers were used together with either light sensitive
cooled CCD-image sensor (520. JC pixels) or electron-bombarded CCD installed inside
cross-over type image tube, or SIT-vidicon sensor. 4.5±0.5 Ps light pulses from YA1O3
:Nd laser at l.O8jum wavelength, and 2 Ps light pulses from AlGaAs/GaAs semiconductor
laser at 850 nm wavelength were employed for comparative measurements of the
recording system. It is shown that the electron-bombarded CCD matrix placed inside
cross-over type image tube and matched through fibre optics window directly to
pv-oo1 temporal-analysing image converter tube, provides the overall system spatial
resolution of 25 line pairs/mm at 30% MTF, dynamic range of not less than 50 and
input photocathode sensitivity about 2E-1O J/cm**2.