IMAGING TECHNIQUES
Over the last century, successive break throughs in imaging technology have transformed the way we see the objects that surround us. From medicine to engineering to weather forecasting, worlds invisible to the naked eye can now be observed. There are microscopes that can take pictures of individual atoms, the building blocks of matter. These are so small that they have to be magnified 100 million times to become visible. At the other end of the scale, the almost perfect mirrors inside the Hubble Space Telescope capture images of dying stars in distant galaxy.
MACROPHOTOGRAPHY
Macrophotography makes a small subject, such as this image of a human eye on a liquid crystal display (LCD) screen, appear life-size or greater. A special camera lens with powerful magnification lets the
photographer focus from just a few centimetres away. Macrophotography can reveal details that are very difficult, or impossible, to make out with the naked eye. It is often used to make extreme close-up pictures of plants and insects. Scientists can also attach cameras to microscopes to capture objects in even greater detail. This technique is called photomicrography.
DOPPLER RADAR
Doppler radar helps meteorologists to track storms, tornadoes and, as pictured here, hurricanes. Doppler radar measures an object’s speed and direction of movement. A transmitter sends out radio waves into the sky. These travel at the speed of light until they reach their target usually water droplets in clouds –
then they bounce back. By calculating the time it takes for the echoes to bounce back, a computer can work out where clouds are. It can also work out how much water a cloud contains from the strength of the reflected echo beam. In this way, a detailed picture of weather events can be made.
ULTRASOUND
Ultrasound is a medical imaging technique often used to check a baby’s development in its mother’s womb. A probe sends out millions of pulses of high-frequency sound waves at least 100 times greater than those within the range of human hearing – into the body each second. By measuring the time it takes for the echoes to return to the probe, a detailed image is produced on the screen of the ultrasound machine. To produce three-dimensional (3D) images, such as this one, many scans are taken and combined by a computer.
X-RAY MACHINE
This X-ray of a guitar’s components has been enhanced with colour. Images like this are called false-colour X-rays. X-ray machines work like cameras, but instead of visible light they use X-rays, which can penetrate soft materials to reveal the hard structures inside an object. They are most commonly used to diagnose broken bones, but high doses can damage living tissue, so they must be used sparingly.
They are also used by engineers to detect tiny flaws in metal structures, by astronomers to observe distant stars, and by airport security to scan luggage.
MAGNETIC
RESONANCE IMAGING
Magnetic Resonance Imaging, (MRI), allows doctors to explore the body’s structures, such as the brain’s network of nerve connections, shown here. An MRI scanner bombards the body with radio waves that cause vibrations in atoms held in position by the scanner’s powerful magnets. These tiny movements produce the information for a computer to build up a very detailed three-dimensional image. MRI helps doctors diagnose serious conditions, and provides clues about the workings of the brain
SCANNING ELECTRON MICROSCOPE
A Scanning Electron Microscope (SEM) reveals tiny organisms and viruses that are invisible to the naked eye. It can also make images of objects that are difficult to see, such as these tiny hairs on an electric shaver. An SEM works by focusing a stream of electrons into a narrow beam that sweeps the object. The electrons bounce off the object and are converted into an electrical signal by a detector. The signal is used to create a photograph-like image on a TV screen that has a very high resolution, or level of detail. The image is photographed to make a black and white image, but can be coloured digitally – false-coloured – by a computer.
INFRARED THERMOGRAPHY
Infrared thermography is a technique that uses a special camera to see heat. Every object, even very cold ones such as ice cubes, releases infrared, or heat, radiation. In a heat picture, or thermogram, higher temperatures show up as brighter areas. Although the images are black and white, they can be coloured to provide as much information as possible. Thermography has many uses including medical diagnosis, search and rescue operations, and monitoring the energy efficiency of buildings.
CUTAWAY
A cutaway is an illustration technique that reveals the internal parts of an object. This technique is often used to show how something works, usually in 3D, for example the cushioning technology in a high-tech trainer, or the position of an engine in a car. Cutaways were originally drawn on paper by hand, and were very time consuming. Today, technical illustrators are more likely to create cutaways on a computer screen. With digital imaging software and 3D graphic tools, an artist can create a realistic illustration of an object by superimposing some layers on an image and making others transparent.
SCHLIEREN PHOTOGRAPHY
Schlieren photography is used to photograph the flow of air around an object, for example, an aircraft in a wind tunnel. In this image the technique has been used to capture the shockwaves caused by an exploding firecracker. Schlieren photography works because a fast moving object disturbs the air, squashing it in some places and stretching it in others. This causes changes in air pressure and density. When light passes through the air, the differences in density make it refract (bend), causing the image to become lighter or darker where this happens. Colour is added to the image with the use of filters.
EXPLODED VIEW
An exploded view is a type of illustration that separates out the parts of an object, for example the different layers of this smart card. A computer uses separate images of each different element of the object and superimposes them on a main image so that they are depicted in their correct order. This allows us to see how the parts fit together and also the way that they relate to one another. Exploded views are often found in technical manuals to show the order in which the different elements need to be assembled.
