The original endoscope was made of rigid tube, which was invented over 100 years ago. Although they have been gradually improved, they are still not widely used. Later, in the 1950s, endoscopes were made of flexible tubes, so they could be easily bent in the corners of the human body. 1965, Harold Hawkins installed a cylindrical lens on the endoscope to make the field of vision clearer. Nowadays, endoscopes usually have two glass fiber tubes, through which light enters the body, and doctors observe through the other tube or through a camera. Some endoscopes even have micro-integrated circuit sensors that feed back the observed information to the computer.
Photo: Early endoscope made in 1870. It uses a hard tube instead of a rubber hose.
Some operations can be done by endoscope and laser. The optical fiber of endoscope can transmit laser beam, cauterize vegetation or tumor, and seal bleeding blood vessels.
Simply put, there are many reflecting surfaces inside the endoscope, and after many reflections, the information in the body can be seen by the doctor.