NearUV

NearUV, short for near ultraviolet, refers to the portion of the electromagnetic spectrum closest to visible light within the ultraviolet range. In most contexts, nearUV corresponds to the UV-A band, roughly 315 to 400 nanometers, although some fields extend the boundary down to about 300 or 395 nm. Because definitions vary by discipline, nearUV is sometimes described as the border region between visible light and the deeper ultraviolet.

Because UV light carries more energy than visible light, nearUV interacts with materials and biological tissues differently. The atmosphere absorbs much of the shorter ultraviolet wavelengths, but nearUV reaches the surface in significant amounts, with UVA (315–400 nm) being the dominant component. The human eye is not sensitive to nearUV, though some animals can detect portions of it. NearUV can induce fluorescence in certain substances and can contribute to photoaging and other effects in skin, though it is less energetic than UV-B and UV-C.

Applications of nearUV span science and technology. In photography and imaging, nearUV is used in UV photography to reveal materials or features not visible in ordinary light, often requiring specialized UV-transmitting lenses and sensors. In astronomy, nearUV observations enable study of hot stars and interstellar gas, though atmospheric transmission and detector sensitivity present challenges. In industry and research, nearUV light is used for curing coatings, water purification, and various spectroscopy techniques. UV LEDs and lamps operating in the nearUV range (around 360–400 nm) are common in lighting, sensing, and medical applications, benefiting from advances in GaN-based semiconductors.

Technical considerations for nearUV systems include the choice of optics (often quartz or UV-grade glass), coatings to maximize transmission, detectors with UV sensitivity, and calibration to account for atmospheric and instrumental responses.