Information & Communication

Physical Devices

Technical Applications


Sensors can be divided into categories in different ways. One common distinction is between active and passive sensors, i.e., between sensors which send out a signal and react to the response (like radar) and sensors which simply process information about the ambient environment (like thermometers). Another way to sub-divide sensors is into imaging, i.e., those that produce a "picture" of the physical object they sense, and non-imaging, which do not.


As an example of imaging sensors, charge-coupled devices (CCD) are used in cameras to give high-resolution images limited by the number of pixels used. Sensor arrays containing millions of pixels, each a few microns across, are possible. As pixel size has shrunk and data available to the system has grown, processing has gained importance. Because of their particular importance, imaging, non-imaging, and passive sensors are singled out in this discussion.


A variety of civilian and military applications are dependent on imaging sensors. Imaging sensors are also critical in remote sensing from space, scanning microscopy, and machine vision (an important area of robotics). Imaging sensors contribute to a number of national goals, including healthy and educated citizenry, job creation and economic growth, harnessing information technology, improved environmental quality, and enhanced national security. Passive sensors have a special importance in military applications because they do not reveal their location or characteristics to an adversary. There are several important applications that can be emphasized for passive sensors. For example, they can provide warning of an adversary's active sensors, enhance night vision, or be used for thermal imaging to identify and target military assets and then perform damage assessment. Radar guided missiles, laser designation systems, and laser range finders are a few examples of offensive systems that detectors could search for, and upon detection alert friendly forces to imminent threats. Damage assessment is a vital task to follow-up strikes, and with the advent of new weapon types remains particularly critical.


Europe and Japan have lost their leads in chemical and biosensor technologies over the last several years, although the Japanese are involved in a very broad range of biosensor development for both biomedical and bioprocess control applications. U.S. firms have stepped up R&D efforts as a result of environmental monitoring needs, a rekindled interest in developing better chemical and biological defense detection capability, and the marketing success of some biosensor-based medical diagnostic kits, e.g., "consumer- friendly" home pregnancy and blood sugar tests.