The material constitution of modern photocathodes (i.e. third generation) has remained a constant for almost two decades. The active GaAs layer is grown by metal organic chemical vapor deposition (MOCVD) and processed to create a negative electron affinity (NEA) surface for photoemission. Thus, these types of cathodes are limited in their spectral response by the band gap energy of the GaAs. There is interest in extending this range past 1000nm while preserving a high quantum efficiency (QE). This would allow taking advantage of an increased luminescence of night sky in the infrared. MOCVD grown InGaAs photocathodes have a photoresponse (PR) in the near infrared. Still, a major drawback to date has been its low QE. We believe that the use of molecular beam epitaxy (MBE) to grow this alloy will permit the fabrication of a higher quality device beyond today's standards, with improved equivalent background illumination and higher QE over a 700nm to 1100nm spectral range. To demonstrate this concept two reflection mode InGaAs photocathode were grown. These cathodes were NEA activated with Cs:O in situ in the MBE reactor after their growth and their PR recorded. Following the activation, optical characterization techniques (i.e. photoluminescence, Raman spectroscopy) were employed to probe electron and phonon energy to relate fundamental material parameters to the observed PR. The collected information is being used to correct and enhance growth characteristics to increase spectral response and QE.

Modern image tube intensifier photocathodes rely on a GaAs active layer, which has traditionally been grown using metallorganic chemical vapor deposition (MOCVD) due to its high throughput and lower cost of operation. Molecular beam epitaxy (MBE) processes have not been thoroughly investigated in that context. The latter technique demonstrates greater structural interface control as well as an improved growth quality for a multitude of applications. Still, at this point it is uncertain, considering actual fabrication techniques for image intensifiers, that the higher growth quality will result in an improvement of devices. Studies are being carried out to compare fundamental optical parameters between GaAs photocathodes grown by both MOCVD and MBE following the same growth and fabrication guidelines. These experiments involve using photoluminescence and Raman spectroscopy to obtain electron and phonon energy information on the materials. An atomic force microscope (AFM) is employed to compare the surface roughness of both methods. In addition, the white light responses of the photocathodes are also evaluated during the creation of a negative electron affinity (NEA) surface to observe any differences between the two growth techniques.

As compared with III generation intensifiers, IV generations have bigger sensitivity and much broader spectral response for low light level imaging detectors. IV generation intensifier properties are improved for NEA photo-cathode sensitivity and spectral response. In this paper, a new method is introduced to increase NEA photo-cathode sensitivity and expand infrared response. In the method, spectral response of GaAs:Cs-O NEA photo-cathode is controlled with automatic survey instrument of dynamic spectral response on photo-electronic materials. During processing NEA photo-cathode, it is observed that sensitivity rises slowly when photo-cathode is illuminated with incident ambient radiation, and infrared sensitivity begins reduction when photo-cathode is measured with automatic survey instrument. The reduction of infrared sensitivity has influenced on spectral matching factor of photo-cathode-object combination and detecting distance and has resulted in the practical use of low light level night vision instrument. During processing NEA photo-cathode with Cs-O layer, we can keep watching spectral response change with automatic survey instrument: when sensitivity rises slowly as photo-cathode is illuminated with incident ambient radiation and infrared sensitivity reaches a highest peak value, we can achieve optimum GaAs:Cs-O photo-cathode for low light level imaging detectors. We studied the thickness of a layer GaAs:Cs-O photo-cathode with take off X-Ray photo-electron spectroscopy, it is clear that the thickness of Cs-O layer is about 0.7~1.0 nm.

In this paper, a large activation and analysis system is introduced , which consists of automatic spectral response recording equipment, x-ray photoelectron spectrometer and ultrahigh vacuum chamber. Then, activation and on-line spectral response measurement are described. For the first time, on-line measured spectral response curves of GaAs:Cs-O NEA photocathodes are presented. These curves indicate the typical variation in spectral response caused by the deposition of cesium and oxygen. By the way of comparing and analyzing those curves, some valuable data obtained which are helpful in investigating the mechanism of the activation.

This paper presents the current status and summary of image intensified night vision system technologies using Northrop Grumman Electro-Optical Systems (NGEOS) advanced image intensifier (I²) tubes and associated NGEOS advanced I² technologies. NGEOS advanced I² technologies is divided into three fully proven and critical I² subtechnologies: Unfilmed microchannel plate (MCP) based I², Autogated power supply technologies, and 16mm halo free I² technology. The initial discussion in this paper will center around the three major NGEOS advanced I² subtechnologies and their respective night vision system performance benefits. Secondly, this paper will present and discuss the laboratory and field (ground and aerial) performance results from these various advanced night vision systems and technologies. Finally, this paper concludes with the extension and application of the previously noted advanced image intensifier technologies in digital imaging system applications such as image fusion systems combining image intensification and uncooled infrared sensors (SWIR/MWIR/LWIR).

Photocathode gating offers the benefits of extending the dynamic range of an image intensifier (I²) tube as well as enabling a digital operating mode for camera and LIDAR applications, and has had applicability in the military, scientific, and industrial fields. Conventional gating applications have been limited to system level solutions, wherein the temporal characteristics of the photocathode gating signal are controlled at the system level. In these systems, the I² and associated power supply act as slaves to the gating control inputs from system control electronics. Recently, Northrop Grumman Electro-Optical Systems (NGEOS) has applied the concepts of photocathode gating to the development of high performance miniature wrap-around power supplies used on 18mm and 25mm Generation III I² filmed and Unfilmed MCP based tubes for military applications. Offering internal stand-alone sensing and control of gating characteristics for the I² (Autogating), these devices provide the user with the advantages of increased dynamic range in a drop-in replacement solution into existing night vision systems.

This paper presents the use of an image intensifier as an astronomical eyepiece for real-time observation of deep sky objects. The optical frequency spectra of observational astronomical objects are reported and compared with the spectral response curve of a Generation 3 intensified optical system. Image intensifier performance on various classes of deep sky objects is also reported along with methods for performing real-time image enhancement.

Image intensifiers (Gen II) have been quoted in the past of having On/Off, or rejection ratios of 10⁷. In this paper we investigate the relationship of the On/Off ratio with incident wavelength. The data shows that the On/Off ratio can vary by as much as 10² with values of only 10⁴ at ~200nm for a given image intensifier. This low On/Off ratio can limit the sensitivity of an intensified CCD camera under certain conditions where there is an abundance of UV, such as combustion. This is particularly true in situations where the CCD exposure and readout times, typically milliseconds, takes longer than the required 'On' time of the photocathode, which is typically nanoseconds. Test data also shows the advantage of switching the MCP on and off simultaneously with the photocathode, which brings the rejection ratios up to >10⁸.

The Image Intensifier Tube (IIT) is the most critical component within a night vision device. Acquisition, production, test and evaluation of image intensifier tubes can be greatly enhanced by the application of machine vision technology. The Navy, Air Force and Army have invested over $2,000,000 in the development of a machine vision-based test set known as the Automated Intensifier Measurement System (AIMS). This paper will describe methodologies employed in the AIMS to measure Modulation Transfer Function (MTF), Dark Spots, Bright Spots, Shear Distortion, and Gross Distortion.

A signal-noise ratio (SNR) testset for image intensifiers is reconstructed. The signal processing module, computer module and measurement software of testset are redeveloped. The frequency spectrum measurement of noise of image intensifiers is achieved by integrating fast Fouier transform (FFT) with hardware filter and infinite impulse response digital filter (IIR DF). The improved testset is used to analyze frequency spectra of noise of image intensifiers. The results are given and analyzed. The measurement method of SNR is discussed basing on the obtained frequency spectra of noise.

The challenging performances requirement placed on the Earth Observing System (EOS) SOLar Stellar Irradiance Comparison Experiment II, part of the SOlar Radiation and Climate Experiment (SORCE), is to measure the solar irradiance from 115 nm - 320 nm to within 5% of its absolute value, with a 0.5% per year relative accuracy for a mission life of 5 years. The integrated flight Photomultiplier Tube (PMT) detector package developed for these instruments contains a PMT, PMT housing, high voltage divider, pulse amplifier discriminator (PAD) and high voltage power supply. This paper summarizes the results of laboratory measurements that were made on the performance characteristics of the detectors systems selected for flight. These measurements include pulse height distribution, quantum efficiency, photocathode uniformity, photocathode temperature response for both Cesium Iodide and Cesium Telluride, as well as, PAD dead-time and light hysteresis.

The Cluster mission comprises four 'identical' satellites devoted to the study of the Earth's magnetosphere. For accurate differential measurements, it is important to maintain a precise understanding of instrument performance. Hence, for Cluster and future multi-spacecraft missions, an effective method of in-orbit monitoring and optimisation of detector behaviour is essential. This is particularly challenging in the case of microchannel plates (MCPs), especially in the situation where, because of lifetime considerations, no scrubbing of the plates was performed prior to launch. This paper explores just this problem in the case of the Cluster-PEACE sensors where the problem is made yet more difficult since mass and power constraints severely limited the amount of diagnostic data available from the instrument - in particular, no pulse height information is directly available. We describe here a technique that lets us evaluate the degradation of the MCPs in space and optimise the operation of the instrument to provide consistent performance. Utilising data from the two sensors on each satellite from various regions of space and coupling with ground characterisation/calibration data, normalised pulse height distributions are indirectly extracted. Although the general behaviour is as expected, the performance shows considerable differences between the different sensors. The results also differ considerably in detail from lifetime tests carried out with a representative MCP on the ground.

A hybrid photodetector based on a Gen 3 photocathode and electron-bombarded silicon, non-pixilated, position sensitive, Avalanche Photo Diode (APD) is being developed. The device promises gains of over 10⁶ and sub-millimeter spatial resolution. Signals read at the output of the device can be used to build up images, integrated over the time scales relevant to the process being studied. This integration as a post-process allows significant flexibility in investigation at very low light levels. A design and fabrication process is being developed that can be readily adapted for fast-turnaround proof-of-concept prototypes using a variety of solid state detectors. This process approach also facilitates the parallel development of high Quantum Efficiency (QE), low dark count III-V based photocathodes with a broad range of spectral response from UV to NIR. The Imaging Hybrid Avalanche Photo Diode (IHAPD) is targeted to bioluminescence, chemoluminescence and other low light level spectral imaging. A discussion of a reflection mode hybrid APD development is included as well.

The Advanced Night Vision Goggle (ANVG) program is developing integrated wide field of view (WFOV) helmet-mounted image intensifier night vision goggle systems. ANVG will provide a FOV of approximately 40° (vertical) × 100° (horizontal) and an integrated heads-up display for overlay of flight symbology and/or FLIR imagery. The added FLIR complements the I² imagery in out of the window or ground applications. ANVG will significantly improve safety, situational awareness, and mission capabilities in differing environments. ANVG achieves the ultra wide FOV using four image intensifier tubes in a head-mounted configuration. Additional features include a miniature flat panel display and a lightweight uncooled FLIR. The integrated design will demonstrate the capability of helmet-mounted I² and FLIR image fusion. Fusion will be accomplished optically and will offer significant opportunities for ground applications. This paper summarizes the basic technologies, lessons learned, and program status.

The Night Vision & Electronic Sensors Directorate (NVESD) has conducted a series of image fusion evaluations under the Head-Tracked Vision System (HTVS) program. The HTVS is a driving system for both wheeled and tracked military vehicles, wherein dual-waveband sensors are directed in a more natural head-slewed imaging mode. The HTVS consists of thermal and image-intensified TV sensors, a high-speed gimbal, a head-mounted display, and a head tracker. A series of NVESD field tests over the past two years has investigated the degree to which additive (A+B) image fusion of these sensors enhances overall driving performance. Additive fusion employs a single (but user adjustable) fractional weighting for all the features of each sensor's image. More recently, NVESD and Sarnoff Corporation have begun a cooperative effort to evaluate and refine Sarnoff's "feature-level" multi-resolution (pyramid) algorithms for image fusion. This approach employs digital processing techniques to select at each image point only the sensor with the strongest features, and to utilize only those features to reconstruct the fused video image. This selection process is performed simultaneously at multiple scales of the image, which are combined to form the reconstructed fused image. All image fusion techniques attempt to combine the "best of both sensors" in a single image. Typically, thermal sensors are better for detecting military threats and targets, while image-intensified sensors provide more natural scene cues and detect cultural lighting. This investigation will address the differences between additive fusion and feature-level image fusion techniques for enhancing the driver's overall situational awareness.

The “night vision” community has developed and refined a series of test and measurement routines for characterization of “green monochrome” tube and system performance. Although these tools could be directly applied to Color Night Vision Systems, a detailed re-examination of these techniques in the context of “Color” provides a more meaningful metric. The creation of a color contrast measure is proposed as the first step in the development of Color Night Vision specific performance characterization.

A novel CCD has been commercially produced by Marconi Applied Technology, UK under the trade name of L3Vision, and by Texas Instruments, USA under the trade name Impactron, both of which incorporate an all solid-state electron multiplying structure based on the Impact Ionisation phenomenon in silicon. This technology combines the single photon detection sensitivity of ICCDs with the inherent advantages of CCDs. Here we compare the electron multiplying CCD (EMCCD) with scientific ICCDs. In particular we look at the effect of the Excess Noise Factors on the respective S/N performances. We compare QEs, spatial resolution, darksignal, EBI and Clock Induced Charge (CIC), with the latter two as the ultimate limitations on sensitivity. We conclude that the electron multiplying CCD is a credible alternative to ICCDs in all non-gated applications.

Two Hamamatsu photodiode array detectors of the type that will be flown in the MASCS instrument on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury were subjected to proton radiation to verify survival in the mission radiation environment and quantify expected levels of radiation-induced degradation of the dark field response during the mission. These same detector types were also evaluated for susceptibility to latch-up due to ionizing radiation.

Although it would seem obvious that object-oriented specification lends itself well to image processing systems, there is almost no research to substantiate this position. In this paper the use of object-oriented techniques in the specification of imaging systems is investigated and compared to a widely used alternative - Structured Analysis and Design - by way of a simple case study. The paper concludes with some recommendations for best practices and future research.

Real-time imaging systems are expected to perform at a rate set by the operating environment. This places additional temporal constraints on the implementation, and has led to advance in parallel processing and optimization. The constraints are also applied, however, to the analysis and design models of the system, an aspect that has received far less consideration, particularly outside of academia. It is well understood that the earlier a bug is discovered the cheaper the fix and this is taken to the extent that, if an error can be found during design or even analysis, the repair can be several orders of magnitude cheaper. It is therefore an economic imperative that the analysis and design models are sufficiently expressive such that the flaws in the models can be discovered before they are implemented, and this applies equally to real-time constraints. To achieve this a change in the modeling languages used is needed. An approach that offers potential in this respect is proposed here. The Unified Modeling Language is used as the basis for a transformation of the design model into a formal description of the system which is amenable to simulation and rigorous proving.

Digital, Interaction Television will be deployed in the next few years, where the key-standard for Europe is DVB/MHP4. Initial experiences are already reported, but for advanced use scenarios, and application areas basic research issues, such as synchronization of MPEG-7 metadata, retrieved either from the broadcast stream, or the feedback channel are still to be done. In this research work we consider, that metadata will be available from multiple sources, especially commercial emerging MPEG-7 extractors, and streamed to a digiTV client over the broadcast- or feedback network. MPEG-7¹ provides asynchronous or synchronous delivery at transport layer, and DVB/MHP standards provide synchronization via a trigger mechanism. As an example we show a simple hyperlinked television show, where we segmented each frame into elements of interest, to which a hyperlink can be added. The key aspects of this paper are as follows: Description and introduction of a Digital Broadcast Item (DBI) for structuring hyperlinked TV to one entity, that is exchanged between several parties in the broadcast chain based on MPEG-21 standards; MPEG-7 metdata extraction models and image segmentation authoring tools for obtaining information about the hyperlinks within a video segment, and within a still frame; Metadata transmission and synchronization models; MPEG-7 Systems compliant software architecture at client side;

The introduction of new, more powerful personal computers and workstations has ushered in a new era of computing. New machines are now capable of supporting full-motion video. The problem of video compression is a difficult and important one, and has inspired a great deal of research and development activity. A number of video compression techniques and standards have been introduced in the past few years, particularly MPEG for interactive multimedia and for digital NTSC and HDTV applications, and H.261/H.263 for video telecommunications. These techniques use motion estimation techniques to reduce the amount of data that is stored and transmitted for each frame of video. This paper is about these motion estimation techniques, their implementations, their complexity, advantages, and drawbacks. An overview of the MPEG video compression standard is first presented with an emphasis on how it utilizes motion compensation to achieve its high compression gains. Then a survey of current motion estimation techniques is presented, including the exhaustive search and a number of fast block-based search algorithms.

This paper presents a hierarchical approach for human eye tracking. The tracking process is accomplished in three steps: head outline tracking, head pose recovery and eye localization. First, active particle filtering is presented to track a head outline. Compared with the traditional particle filtering, the active particle filtering improves the efficiency of every particle and accordingly reduces the number of required particles. In order to recover the head pose, only one view of the head is used to build the shape/texture template including multiple head features, and then the method "combination of views" (Ullman 1996) is applied to model changes of shapes and textures of the head features during head rotation. Based on the result of head pose recovery, the eyes can be localized efficiently in a restricted search space. The algorithm successfully tracks eyes of human heads that undergo translation, scaling and wide-range rotation in the office scene. The non-optimized implementation runs at about 3 frames per second on Pentium III 450MHz PC.

Pellet's position is the key of ICF. The paper introduces an automatic orientation method using two cameras. It based on the 2-D image coordinates resolve the 3-D information. Two steps are considered. Firstly, 3-D orientation is estimated by auto-focus algorithm using pellet edge location to subpixel values in 2-D digital imagery. Secondly, 3-D position is estimated by centroid algorithm and auto-focus algorithm. By this way, it can ignore the forms of pellet edge. In the paper, analytical formulations of the problem are given. It also gives analyse between the centroid algorithm and edge fit algorithm in accuracy. Defocus factors have been compensated in order to obtain accurate estimates of the parameters by the imaged edges. The experiments have shown the accuracy of location pellet can reach 0.2 um, and orientation pellet can reach 3’.

Described is a real-time meat inspection system developed for the beef processing industry by eMerge Interactive. Designed to detect and localize trace amounts of contamination on cattle carcasses in the packing process, the system affords the beef industry an accurate, high speed, passive optical method of inspection. Using a method patented by United States Department of Agriculture and Iowa State University, the system takes advantage of fluorescing chlorophyll found in the animal's diet and therefore the digestive track to allow detection and imaging of contaminated areas that may harbor potentially dangerous microbial pathogens. Featuring real-time image processing and documentation of performance, the system can be easily integrated into a processing facility's Hazard Analysis and Critical Control Point quality assurance program. This paper describes the VerifEYE carcass inspection and removal verification system. Results indicating the feasibility of the method, as well as field data collected using a prototype system during four university trials conducted in 2001 are presented. Two successful demonstrations using the prototype system were held at a major U.S. meat processing facility in early 2002.

We describe current efforts in the development of a CMOS sensor based megapixel camera with acquisition frame rates in excess of 500 per second. The focus in this development is two fold: a low cost, easily adaptable sensor, and secondly, proposed integration with image processing hardware within the camera module. The aim of this sensor is to flexibly support applications of imaging in the presence of turbulence, for which we present such algorithms that might take advantage of processing hardware at the sensor head. Secondary applications of the processing hardware include image analysis and compression.

Several factors make observational astronomy difficult for pre-college students and teachers. (1) not many schools have teachers trained to use and maintain astronomy equipment; (2) school usually happens during the day and observing normally is a night-time activity; (3) the scourge of light pollution has hidden the stars from many students living in or near cities; (4) there is a general lack of access to expertise when needed. In addition, physically disabled students cannot climb ladders, to access the telescope eyepiece. Internet access to computer-controlled telescopes equipped with digital cameras can solve many of these difficulties. This enables students and their teachers to access well-maintained, robust Internet-controllable telescopes in dark-site locations and to consult more readily with experts. We present the results of technical solutions to Internet-control of telescopes, by Software Bisque, the New Mexico Skies Guest Observatory and the Youth Activities Committee of the Astronomical League in collaboration with Denver University Astronomy. We jointly submitted a funding proposal to the Institute for Connecting Science Research to the Classroom, and conducted a pilot program allowing high school students to access a CCD-equipped, accurately-pointing and tracking telescope, controllable over the Web, with a user-friendly skymap browser tool. With suitably placed telescopes worldwide, observing from the classroom in daylight will become feasible, as we have demonstrated with Australian and Eurasian student users of the New Mexico Skies Internet telescope. We report here on a three-month pilot project exploring this solution, conducted Feb-May 2002. User interest proved phenomenal, while user statistics proved diverse and there were distinct lessons learned about how to enhance student participation in the research process. We thank the Institute for Connecting Science Research to the Classroom for a grant to the University of Denver in partial support of this effort, and acknowleedge in-kind support from the estate of William Herschel Womble. Details at website www.du.edu/~rstencel/stn.htm.

CMOS image sensors have several clear advantages over CCD image sensors: selective readout, low power, small size, high frame rate, on-chip functionality, and low cost. However CCD image system still dominates over digital camera market, because the CMOS image system has a poor dynamic range and peak signal-to-noise ratio. In this paper, we propose a new enhanced DR and SNR CMOS image sensor with pixel parallel analog-to-digital converter (ADC) and memory. The proposed reset and time-to-digital converter (TDC) increase the well capacity of the image sensor. Consequently, DR and peak SNR are increased simultaneously while other DR enhancement schemes can't increase peak SNR. The circuit reuse concept is proposed to increase the fill factor. We designed and simulated the proposed circuit and achieved 12bit resolution with 1000frames/sec. Power consumption per each pixel is 50nW. DR is increased by 36dB and peak SNR is enhanced by 18dB.

In Generation III image intensifier (I²) tubes, the input of the microchannel plate (MCP) is typically coated with a thin dielectric film to prevent ions generated in the MCP during operation from migrating back to the cathode and damaging the delicate (Cs:O) activation layer. While dramatically improving operational life, the presence of the film serves as a scattering center for the signal electrons and significantly reduces the signal-to-noise ratio (SNR) of the image tube. To prevent or minimize the impact of the ion barrier film (IBF) on tube performance the night vision industry has focused on reducing the thickness of the IBF or more preferably in developing a process that completely removes the film ("unfilmed") to improve the SNR while maintaining operational life. In this paper, we present an overview of the role of the ion barrier in Generation III image intensifiers and present the results of a Monte Carlo simulation on electron transport through dielectric films with varying stoichiometry, thickness, and accelerating voltage.

An x-ray streak camera operating in accumulation mode was developed for studying ultrafast dynamics at synchrotron facilities. A laser-triggered photoconductive switch was used as a sweeping unit to obtain low timing jitter. The fast rise time of the ramp pulse generated by the switch (90 ps) combined with the fast response of the traveling wave deflection plates (150 ps) significantly reduced the jitter caused by the shot-to-shot laser fluctuation. At ~1% rms (root mean square) laser energy fluctuation, the resolution of the camera is 1.1 ps when over 5000 laser shots were accumulated. This is two times better than that of the previous design with slower response (300 ps) deflection plates.