Light irradiation device

A light irradiation device, comprising:

• a light source unit emitting a light to a skin area to be treated;
• and
• a controller operable to control the light source unit;
• the light source unit comprising:
• a substrate:
• first light sources disposed on the substrate and emitting a first light in a blue wavelength band;
• and
• second light sources disposed on the substrate and emitting a second light in a red wavelength band to a near-infrared wavelength band, wherein the first light has a first skin penetration depth and the second light has a second skin penetration depth, the first skin penetration depth and the second skin penetration depth differing depending on a wavelength and the first skin penetration depth being smaller than the second skin penetration depth;
• wherein a first group of first light sources is disposed in a first region corresponding to a first portion of a surface of the substrate, and a group of the second light sources is disposed in a second region surrounding the first region and corresponding to a second portion of the surface of the substrate, wherein the first portion of the surface of the substrate is disposed at a center portion of the substrate and concaved relative to the second portion of the surface of the substrate such that the first group of first light sources is disposed on the first portion concaved from the second portion and the first group of second light sources is disposed on the second portion protruding from the first portion;
• wherein a second group of first light sources is disposed in a third region located between the first region and the second region and corresponding to a third portion of the surface of the substrate and wherein the first portion, the third portion, and the second portion are sequentially arranged in a direction away from the center portion of the substrate such that all of second light sources in the group of second light sources are disposed along an edge of the substrate and located in the second region entirely surrounding the third region;
• the first region is spaced apart from the skin area to be treated farther than the second region is;
• wherein in the first region, direct application of the first light with a first predetermined dose, to the skin area to be treated, causes the first light to penetrate through the skin area to be treated and reactive oxygen species (ROS) to be produced and accumulated in cells of bacteria within the first skin penetration depth, thereby resulting in demise of the bacteria;
• in the second region, direct application of the second light with a second predetermined dose, to an area wider than the skin area to be treated by the first light and in an open state, causes the second light to penetrate through the skin area to be treated and blood vessels to be dilated and promote a blood circulation in the second skin penetration depth, thereby improving a blood flow and promoting immune response,
• wherein the third portion of the surface has an inclined surface connecting the first region and the second region.