Light source (lighting system) is used to introduce light into the body and illuminate the part to be seen. In the early days, a small light bulb was placed at the front end of the endoscope, but in modern times, the light source was placed outside the body and introduced into the body through the optical fiber system. Image transmission: The hard endoscope uses a series of lenses to transmit images to the eyepiece, while the soft endoscope uses optical fiber to transmit images, or a photoelectric coupling element (CCD) is placed at the front end of the endoscope, and then digital image information is transmitted. Some endoscopes are equipped with pipes, which can be washed with water or air to make the field of vision clear. In addition, they can also be used for the operation of surgery or slicing instruments. These pipes are called working channels. Capsule camera is a miniature camera, a light source, a wireless transmitter and a battery. After swallowing, the patient can move with intestinal peristalsis. On the one hand, it flashes regularly and transmits the images in the intestine to the receiver hanging beside the patient. After a day or two, the capsule camera will be discharged from the body through the large intestine, and the doctor will transmit the images received by the receiver to the computer for interpretation and storage.