About ten years ago the Army, responding to pointed suggestions of Luis Alvarez, decided that an army that could be effective night and day would be twice as useful and probably twice as effective as an army that could act only while the sun was up. With that decision came concerted efforts to turn the technology of cathodes, electron optics, phosphors and optical coupling into a viable program to give the soldier the ability to see at night.

To begin I must draw your attention to the change of title of this presentation. The new title is "The State of the Art for the Detection of Concealed Handguns and Explosives". You will realize that this is substantially less ambitious than the original. The influence of time has brought about this curtailment -- time available to prepare and time allowed to speak. With such constraints it did not seem possible to do justice to the subject. Fortunately, I need not do more than mention a number of topics for they will be covered by distinguished speakers to follow. Some such topics are microwave holography, photography, television, infrared and low light level image intensifiers. I will only mention these topics and give more emphasis on other techniques.

The feasibility of high resolution milli-meter microwave holographic imaging of metallic objects through optically opaque dielectric barriers is considered in the context of detection and identification of concealed weapons. Reasons for the selection of millimeter wavelengths and for a holographic mode of imaging based on phase information alone as opposed to direct imaging are given. The recording of phasigrams (phase-only holo-grams) of metallic objects such as a toy pistol illuminated by millimeter wave radiation and the retrieval of recognizable visible images of these objects from their phasigrams are described together with the equipment used to demonstrate the imaging process. Results obtained when a complex shaped object such as the toy pistol was concealed behind a layer of clothing or leather are also shown. The prospects of real-time remote holographic imaging which would make personal search unnecessary are discussed. Conclusions regarding application of such imaging techniques to remote screening of individuals at airport boarding gates as a hyjack prevention measure and remote search and surveillance of crowds in political rallies are drawn.

Photographic surveillance of plant, equipment, personnel, locations, etc, yields a unique set of benefits. These benefits have led to the wide use and acceptance of the concept of photographic surveillance. The use of cameras for surveillance commenced in the early 1930s and received a sub-stantial boost during World War II. The advent of faster films has expanded the practicality of photo surveillance and today the availability of high quality - low cost -easy-to-use super 8 materials makes photog-raphic surveillance almost commonplace.

Recent advances in television systems, both in telemetry and closed circuit, have made it possible to utilize TV for law enforcement applications. The development of low light level television cameras, in the visible and the near IR spectrum, have advanced to the point that they are dependable as a means of remotely detecting, verifying and identifying intruders. Systems developed for military applications as well as results from military potential testing will be discussed. Description of technology includes discussion of cameras, motion detection, and remote operation of cameras. Training and reliability considerations are also discussed.

The purpose of this paper is to discuss the concept of thermal imaging, explain the operation of a typical thermal imaging system, and to present a brief overview of the cur-rent state-of-the-art in thermal imaging systems applicable to law enforcement and general security needs.

A passive intrusion detector has been developed which detects personnel, vehicles and other targets by means of the infrared radiation they emit. In its basic form, the in-strument monitors two side-by-side fields of view, and a target-to-background contrast of 0.1°C (or correspondingly more for targets smaller than the full field of view) actuates the system. Intrusion can be indicated by audio and visual alarm outputs. This paper will described several narrow field passive infrared intrusion detectors .

This paper attempts to explain the basic principles of video recording machines and discusses important considerations when selecting these devices for use in a TV system. The recorder can be a crucial element in a TV surveillance system. It can furnish law enforcement with a documented copy of the criminal act which is apparently widely accepted in a court of law as long as the recordings were obtained in an acceptable manner. For good, hard evidence , however, it is important that the pictorial evidence be as clear and distinctive as possible. In some cases, this requires a high performance machine, but in others, a moderate, inexpensive recorder will do. This should give some indication that the total system should be carefully examined and the choices weighed. It is hoped that this paper will make these choices more clear.

In January 1972 the Baltimore County Police Department had the opportunity to work jointly with Westinghouse Electric Corporation in a matter of a criminal investigation concerning a series of burglaries. This cooperative effort represented a breakthrough for local law enforcement in dealing with agencies outside the government for it gave evidence that resources previously unavailable, could be brought to bear on the crime problem and that the scientific community was prepared to lend whatever support was necessary to help stem the spiraling crime rate.

The practice of using closed circuit television systems for surveillance such as, protecting safes, watching for unwarranted intruders, detecting fires, etc., has in recent years become common place. However, the disadvantage of this is that an operator is required to watch one or more monitors at all times. This can be come very tedious or strenuous, depending on the number of monitors and could result in an increase in the number of operators required for this task and hence, a rise in cost.

Since the Santa Barbara and Chevron oil spills, the bulk of the private and government attention in the field of oil pollution has been devoted to developing regulations, methods, and procedures to reduce the probability of oil spillage. In addition efforts have been expended to develop cleanup techniques and equipment to control the oil that is accidentally spilled and then reported to the proper authorities.

The problem of determining the quality of an image produced by a line-scanning system received increased attention in the early 1960's with the advent of low-light-level television and infrared imaging systems for military aircraft. In addition, the interest in manned lunar exploration, with the attendant need for better evaluation of the lunar surface, made necessary the telemetering of image data by such systems as Lunar Orbiter and Surveyor. An understanding of image quality became more critical once it was realized that digitizing of the video signal for transmission introduced a different form of noise (the so-called "striping") into the video signal. As a result of these several more-or-less simultaneous needs, research into the nature of line-scan image quality and its effect upon image interpretability was begun about 1961, and has continued through the present.

Electro-optical sensors can be of significant aid to our law enforcement agencies particularly if their capabilities and limitations are fully understood. In the following, the imaging process is discussed as it applies to the needs and requirements of security, surveillance and law enforcement. Our approach is to associate quantitative signal-to-noise ratios with simple geometric images as developed by electro-optical sensors, to determine the observer's SNR needs through psychophysical experimentation and then, through further psychophysical experimentation, to correlate the detectability of these simple images with the visual discrimination of the images of real objects. The visual discrimination tasks we consider are simple image detection and the higher order tasks of recognition and identification. The concepts developed form a rational basis for the selection of electro-optical equipments which have a reasonable expectation of actually performing a desired function.

Electro-optical systems should be specified or evaluated on the basis of their ability to acquire and to transfer useful information to a human observer, with sufficient detail for the required task, under the scene illumination and scene contrast conditions available in the area under surveillance.

The science of fingerprinting constitutes the only infallible means of positive identification of persons, known to man, since statistics show that the probability of finding two identical fingerprints is stochastically zero. The ridge patterns which can be seen on a newly born infant will remain unchanged throughout the life of an individual unless they are destroyed by accident or disease.

There exists today a widespread demand for secure means of personal identification. Examples of this are to be found in the operation of the current wide range of credit card and bank identification systems, the increased use of the newly introduced money-vending machines, the need for personal identification for recorded entry into restricted locations, the authorization of computer or computer programme use to approved operators, and in the need for simpler forms of passport, visa, and international border control. The logical manner of realizing a secure and reliable general purpose identification system is the provision of a machine readable card carrying information about the holder. This machine readability is essential both from the point of view of use in unattended locations, and from the point of view of accurate capture of card data. A personal photograph, signature, and a secret number held by the card owner, all represent identification features which find application either alone or in combination. The latter is particularly relevant when the point of card-use is unattended.

Police and Federal Security Agencies use of image intensifiers for night time surveillance activities has generated a requirement for positive identification capabilities from photographic imagery. Even with the fastest films available conventional photographic equipment cannot meet this requirement in total darkness. Industry has responded to this need by providing police and federal authorities with photographic cameras incorporating image intensifiers as first fielded by the U.S. Army. We shall refer to these as first generation image intensifier devices.

About twelve years ago, the use of optically encoded signatures was proposed as a way to prevent the fraudulent use of savings bank pass books in branch bank operations.

A basic problem in testing and evaluating night vision devices is the establishment of a low level scene whose radiation characteristics are accurately known and readily reproducible. In regard to the scene being readily reproducible, there is a twofold requirement: (1) that it be reproducible over extended periods of time, i. e. , from one month or year to the next, and (2) that it be readily reproduced in different geographic locations, so that the conditions of evaluation of the device may be duplicated by different organizations, such as the manufacturer and the end user. Requirements for such a scene include the following: the scene should include elements allowing the resolution, the linearity (gray scale), flare, and overload characteristics to be judged; the spectral radiance of various portions of the scene must be accurately known; the radiance levels in the scene should be adjustable so that the device or system under test may be evaluated both at its ultimate sensitivity, where the input noise of the system begins to deteriorate the scene, and at higher levels where the input noise is negligible and other performance characteristics of the system, such as maximum resolution and gray scale linearity, can be evaluated.

The earliest U.S. electro-optical work to remove the cover of darkness centered around the development in the 1950's of an infrared image tube. This infrared image tube detected targets illuminated by covert infrared search-lights and converted their images to visible displays. The best known device using this technology was the "sniperscope" which had the obvious disadvantage of being an active system. That is, the IR search-light was needed to covertly illuminate the target and could be rather easily detected by a sophisticated enemy.

Photographers have long been striving for high performance, low f/number lenses to get that special picture under extremely poor lighting conditions without the aid of flood lights or flash. The image intensifiers heveloped at Ft. Belvoiris Night Vision Laboratory for the infiltration problems of the Vietnam War have the potential of giving the photographer low-light-level capability without imposing unreasonable lens size requirements. This paper is directed toward discussing the photographic systems that can be built around such intensifiers, their advantages and the fundamental limitations encountered.