The basic function is to produce cold light, which can provide various endoscopes that use fiber-guided light beams as the light source part to provide brightness illumination for observation and inspection of the inner cavity. According to various needs, add corresponding structures to achieve other functions, such as adding air pumps to many medical cold light sources to generate gas, and transmit the gas to the human body through the inner pipe of the endoscope. The human body needs to be checked. Inflate and pressurize the part to achieve the purpose of opening. At the same time, the air pressure is used to squeeze water to the mirror body to flush the mirror surface and the lesion site for observation, diagnosis and treatment. And according to the gas volume adjustment device. In some cases, in order to eliminate the loosening of images due to actions during observation, diagnosis and treatment, the cold light source also adds a high-speed flash.