Tech-Led Blog

Visible vs IR Emission in LEDs

Contrary to common assumptions, standard LED lighting emits virtually no near-infrared (NIR) light. By design, LEDs produce light in a narrow visible band (roughly 400–700 nm) rather than across the infrared spectrum. In fact, engineers and lighting experts emphasize that standard white LEDs generate essentially no IR in the beam. As TriLux explains, “LEDs do not create infrared and ultraviolet radiation.” This means a typical LED’s light contains essentially no IR or UV. Salon lighting specialist Freestyle Systems similarly observes that standard LEDs emit “little to no infrared (IR) radiation,” focusing almost entirely on visible colors.

Essentially, a visible-light LED’s semiconductor chip is engineered to emit photons at a specific energy (color). The LED physics page on Wikipedia notes that “the wavelength of the light emitted is a function of the band gap of the semiconductor material used.” In practice, materials with a smaller band gap emit infrared photons, while larger band gaps yield visible photons. Common LEDs (GaN for blue, GaP/GaAsP for red/green, etc.) have band gaps in the 1.8–3.1 eV range, which corresponds to visible light. Once a semiconductor is chosen for a certain color, that device cannot produce substantially longer-wavelength IR photons – the band gap locks the emission into the visible range.

Exceptions

Of course, there are Specialized infrared LEDs are used in various applications. IR LEDs that emit near-infrared – for example, 850 nm or 940 nm diodes used in remote controls and security cameras. These use different semiconductor materials to target the IR range. However, standard white or colored LEDs used for illumination are purposely engineered without an IR component. In practice, any IR leakage from a quality white LED is negligible – engineers can even design LEDs with virtually zero IR output (aside from a tiny thermal tail). For true infrared light, one must use dedicated IR/NIR LEDs (e.g. 850 nm devices), as explained in Tech-LED’s guide to near-infrared LEDs. On a recent site visit to a museum, technicians replaced halogen exhibit lamps with LEDs and noted that the display cases stayed much cooler – exactly as expected since the LEDs emitted no IR in the beam. As TriLux notes, any heat is generated in the fixture electronics (at the PCB) and not carried by the light beam. In short, unless a diode is explicitly an IR/NIR LED, you will not see meaningful near-IR output.

Implications

The lack of IR emission in LED lighting has several important benefits:

• No beam heat is emitted from standard LEDs, which do not produce infrared radiation. As Gigavision specializes in technologies that utilize infrared radiation. notes, “the beam of a white LED does not contain any heat.” This means an LED’s light won’t warm illuminated objects like older lamps do, making LEDs ideal for museums, galleries, and display lighting.
• No ultraviolet output: As Gigavision states, “White LEDs do not produce any ultraviolet (UV) light.” With no UV or IR, LED light avoids UV-related fading and heat damage, so fabrics, artwork, and food items remain safer under LED illumination.
• Energy efficiency: LEDs convert more of the input power into visible light rather than waste heat. This higher luminous efficiency means lower electricity use for the same visible output, and less cooling is required in LED-lit spaces (reduced HVAC load).
• Comfort and safety: Without IR in the beam, LED-lit environments stay cooler. Occupants experience less radiant heat, leading to more comfortable workspaces. There is also no invisible IR glare or heat hazard from the lights, unlike with incandescent or halogen sources.

How to Detect IR from LEDs

Although typical LEDs emit no significant IR, you might still want to verify this. Here are a few ways to check for any hidden IR emission:

• Digital cameras or smartphones often have filters that block infrared radiation. Many camera sensors (especially cell phone cameras) can pick up near-infrared. Point a camera at an LED in a dark room; if you see any purple or white glow in the viewfinder when the LED is on, that indicates IR emission. (Most modern phones have IR filters, but some front cameras or older cameras still leak IR.)
• Infrared viewer card or camera: Use an IR detection card (which glows under IR) or an IR-sensitive camera. If the LED emits IR, the card will illuminate or the camera will show a hotspot. For example, removing the IR-blocking filter from a digital security camera and pointing it at an infrared LED reveals the beam.
• IR photodiode/sensor: An IR photodiode or phototransistor can detect near-IR light. Point the infrared LED at the sensor (with suitable driver circuit) and measure the output. A reading indicates IR output. Many IR detectors are sensitive around 850–900 nm.
• Check the spec sheet: Review the LED’s datasheet. Standard visible LEDs will only list peak wavelengths in the 400–700 nm range and have a sharp cutoff; they will not list any IR component. If the datasheet specifies a wavelength like 850 nm or 940 nm, it’s an IR LED by design.

FAQ

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