Ultraviolet has been used in the treatment of psoriasis and other skin diseases for more than half a century. UVA and UVB are mainly used in clinic. Uvb-304 is a special type of UVB, which can be used to treat psoriasis. In the 1980s, researchers found that a kind of UVB with wavelength of 311-313 nm can be particularly effective in the treatment of psoriasis. Later, it was called narrow-band ultraviolet B (NB-UVB). NB-UVB has achieved good curative effect in the treatment of psoriasis, and has become one of the most effective, simplest and safest treatment methods for psoriasis.

UVB light source was originally used to cover the whole spectrum of psoriasis. Studies have shown that 304 nm to 313 nm is the most effective wavelength range for the treatment of psoriasis, and the ultraviolet light with the emission wavelength of 290 nm to 300 nm has no therapeutic effect, but will cause sunburn reaction. These findings make the research of narrow-band UVB light source (the peak value is 311 ± 2 nm) more and more important.

UVB phototherapy system developed by American allux medical company uses UV-LED technology to generate local UVB radiation, which directly irradiates psoriasis plaque. The therapeutic instrument consists of two different modules: the patient connection module (PAU) providing therapeutic radiation and the power module providing medical grade DC power. The size of Pau is 128x90x38 mm. The therapeutic ray in the Pau module is realized by a module light source. The light source is composed of 72 UV-LEDs and 9x8 hexagonal array. The UV-B radiation spectrum emitted is typical Gaussian type, with a luminous wavelength of 310 nm and a FWHM of 15 nm. In order to achieve the uniformity of the light emission wavelength of the whole array, each LED chip is driven by an independent driving current to compensate for each LED chip.