Infrared (IR) light, a component of the electromagnetic spectrum, exists beyond human vision. With wavelengths longer than visible light (typically 700 nanometers to 1 millimeter), IR radiation is invisible. It is a pervasive form of energy, emitted by all objects above absolute zero, from a human body’s warmth to everyday items. While invisible, its presence can be sensed and measured.
Simple Methods for Infrared Detection
Many common electronic devices offer an accessible way to detect infrared light. Digital sensors in smartphones, cameras, and webcams are sensitive to a broader spectrum than human vision. This sensitivity extends into the near-infrared range, allowing them to register IR emissions.
To observe infrared light using a smartphone, point a TV remote’s emitter at your phone’s camera lens and press any button. The screen should display a flickering or steady light, often white or blue, from the remote’s LED. This visible light is the camera’s interpretation of the invisible infrared signal. Most smartphone rear cameras have an infrared filter, but front-facing or older digital cameras are more effective for this test.
Older digital cameras without strong infrared filters can detect these emissions. Pointing an active IR source, like a remote control, at the camera’s lens and observing the viewfinder or screen will reveal the same light. Webcams connected to a computer also display infrared light as a visible glow when an IR source is aimed at their lens.
Dedicated Infrared Detection Devices
Specialized devices detect infrared light for specific purposes. Thermal cameras, or infrared cameras, sense heat or thermal infrared radiation emitted by objects. They convert this invisible heat signature into a visible image, often using colors to represent different temperatures. This makes them valuable for identifying heat loss in buildings or detecting overheating electrical components.
Night vision goggles detect infrared by amplifying faint ambient light, including near-infrared. They collect photons, convert them into electrons, and multiply them using an image intensifier tube. The amplified signal projects onto a phosphor screen, creating the characteristic green-tinted image for vision in very low-light conditions.
Infrared thermometers measure temperature without physical contact by detecting infrared radiation from an object’s surface. A lens focuses this radiation onto a thermopile detector, converting the absorbed infrared energy into an electrical signal. This signal is processed and displayed as a temperature reading, useful for rapid checks.
Infrared sensors detect IR signals or changes in IR levels. Passive infrared (PIR) sensors measure infrared light radiating from objects, detecting changes in heat signatures caused by movement. These sensors are common in motion detectors and security systems, triggering alarms or lights when a warm body enters their detection zone.
Practical Uses of Infrared Detection
Infrared detection is integrated across many practical applications, enhancing daily life and specialized fields. In consumer electronics, infrared technology is used in remote controls for TVs, air conditioners, and other home devices. These remotes transmit coded infrared pulses that communicate commands to receivers, enabling wireless control.
Security and surveillance systems rely on infrared detection. Infrared cameras provide night vision, allowing monitoring and evidence collection in complete darkness by detecting heat signatures. Motion detectors utilize passive infrared sensors to identify intruders by sensing changes in emitted heat, triggering alarms or lights.
In medical applications, infrared detection offers non-invasive diagnostic and monitoring tools. Infrared thermometers provide rapid, non-contact temperature measurements, useful for fever screening. Thermal imaging, or thermography, detects subtle temperature variations on the body’s surface, aiding in assessing inflammation, circulatory disorders, and early detection of certain conditions.
Industrial and scientific sectors benefit from infrared technology. Thermal cameras are employed in predictive maintenance to identify overheating machinery or electrical components, preventing costly failures. In astronomy, infrared telescopes penetrate cosmic dust clouds to reveal celestial objects otherwise obscured from view.
Infrared sensors contribute to everyday convenience and automation. Automatic doors often use infrared beams to detect approaching individuals, facilitating hands-free entry. Hand dryers activate through infrared proximity sensors, providing a hygienic and efficient solution.