There were few imaging or vision tools in the 19th century beyond human sight. The microscope allowed visibility of tiny things and telescopes allowed views of the heavens. Photography was well in hand but it recorded in black and white what the human eye saw in color. It was engineering in the 20th century that introduced color to photography, movies, and television.
It was also 20th century engineering that changed this narrow view for everyone by creating a new class of sensors and precision instruments. They brought a range of vision beyond anything humans could have imagined. This range allows us unprecedented scrutiny: from tiny atomic particles to vast galaxies in the universe. Consequently, this class of engineering has greatly expanded our depth of knowledge by unfolding some of the mysteries of the physical world. These modern tools allow us to see inside the human body, to monitor its life forces, and to identify and treat diseases. Others let us track weather patterns, map ocean floors, and observe brain waves.
Ultrasound presents images formed by the echoes of inaudible sound waves beamed into the body. These images can be of an unborn child or of blood flowing through a beating heart. Ultrasound can diagnose various medical conditions by enabling doctors to "see" diseased tissue that needs repair or removal. Sensors can measure brain waves, the color of blood, heart rates, blood pressure, oxygen levels, and body temperature, and give out instant warnings. They are the very basis of an intensive care unit.
The entire microelectronics revolution is based upon imaging. Without it, we would never have gotten enough transistors on one piece of silicon to make a microprocessor. The key fabrication process for integrated circuits is done by imaging pictures of circuit patterns on photoresist (a light-sensitive material). The development of better cameras and the use of shorter and shorter wavelengths can resolve ever smaller patterns in the photoresist.
Electron microscopes can magnify objects 1 million times (equivalent to magnifying a postage stamp to the size of a small country). Because its power lies in its resolution capabilities as much as its magnifying potential, it is capable of viewing individual molecules. Atomic force and tunneling microscopes can view atoms, and are making nanotechnology (engineering on the scale of billionths of a meter) able to yield machines assembled from single atoms. Another class of microscope is engineered with many different glass elements that cancel out each other's distortions. They produce highly magnified images free of aberrations. Zoom lenses on high-quality cameras work the same way. These are invaluable tools for researchers, geologists, archeologists, and others. X-ray crystallography can investigate the structure of a solid by illuminating it with electrons - a process that helped reveal the structure of a DNA molecule.
Telescopes probe ever deeper into space because of huge mirrors that can grasp up to 10 billion times more light than the naked eye. Their range can extend from the invisible radio and infrared frequencies to the ultraviolet and X-rays, allowing them to observe everything from stellar explosions to dark matter in the universe. Precision engineering shaped them into sensitive instruments that can reveal the detailed structure of stars and galaxies.
The basis for many of these technologies was the discovery of X-rays in 1895 by Wilhelm Konrad Roentgen. Today, while X-rays remain a major diagnostic tool, they are enhanced by computer-aided tomography (CAT scans), magnetic resonance imaging (MRI), and ultrasonic imaging. The four of these, along with endoscopy, which inserts an imaging device into the body, have almost eliminated exploratory surgery as a medical diagnostic tool.
Sonar (sound, navigation, and ranging), invented as a system for underwater detection and location of objects during World War I, helps naval fleets locate submarines and icebergs. Ultrasonic imaging, which utilizes very high frequency sound waves, has found both medical applications and major industrial applications, such as finding flaws hidden within materials. It is also used for microscopy, which can look into opaque materials well beyond their surface.
Radar (radio detection and ranging) was developed to identify and track airplanes and naval warships, and is an especially vital tool for pilots. The radar network NEXRAD is now replacing aging conventional radar units. Computers take in data, display it on a monitor, and run algorithms, that, in conjunction with other meteorological data, detect severe weather phenomena, such as storm cells, hail, cyclones, and tornadoes.
Satellites flying over the Earth have been extensive users of imaging technology, with uses from intelligence gathering to weather tracking. Weather satellites, supplemented with terrestrial radar, have allowed us to improve our prediction capabilities.
