Light sensors detect light and come in various types, such as photocells, CCDs, and photomultipliers. They are used in everyday objects like security systems, electronic devices, and barcode scanners. Infrared technology is increasingly used in motion-activated light sensors, saving energy costs. Light sensors are also used in scientific breakthroughs, such as in robotics and fiber optic technology.
A light sensor, as the name suggests, is a device used to detect light. There are many different types of light sensors, each of which work a little differently. A photocell or photoresistor, for example, is a small sensor that changes its resistance when light strikes it; they are used in many consumer products to determine the intensity of light. A charge-coupled device (CCD) carries electrically charged signals and is used as a light sensor in digital cameras and night vision devices. Photomultipliers detect light and multiply it.
Devices that include these sensors have many uses in scientific applications, but are also found in objects that people encounter every day. A simple light sensor can be part of a security or safety device, such as a burglar alarm or garage door opener. These types of devices often work by sending a beam of light from one sensor to another; if the light goes out, an alarm sounds or the garage door doesn’t close.
Many modern electronic devices, such as computers, wireless phones, and televisions, use ambient light sensors to automatically control the brightness of a screen, especially in low- or bright-light situations. They can detect how much light is in a room and turn the brightness up or down to a more comfortable level for the user. Light sensors can also be used to automatically turn on lights inside or outside a home or business in the dark.
The barcode scanners found in most retail outlets work using light sensor technology. The light emitted by the scanner illuminates the barcode, which is read and decoded by a sensor. QR (Quick Response) codes work in much the same way, although they contain more information and can usually be read using a smartphone if the user has downloaded a code reader.
While some products using light sensors have been around for several years, these sensors continue to become more prominent, especially through infrared technology. Warm-blooded animals, including humans, give off heat, which can be seen as infrared light. This energy can be detected by using infrared light sensors to tell when a person is walking, rather than being triggered by another non-human movement.
Motion-activated light sensors that recognize infrared can be found, for example, in grocery stores. When a shopper passes, the sensor in a shop window recognizes the passage of a person and the lights turn on. The lights are dimmed when no customers are in front of the suitcase and the shop saves on energy costs. Many retailers and businesses use similar technology to control lights in rooms that aren’t in constant use, such as conference rooms or restrooms.
Light sensors continue to have many uses in science, from the simplest science experiments to the latest breakthroughs in space, medicine and robotics. Robots, for example, can use light sensors to “see” and navigate a room, sensing objects by sensing how light bounces off them. Improvements in fiber optic technology will likely bring even more breakthroughs, as this technology can measure light and send signals in extreme conditions or in remote locations where electricity is not available.
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