Endoscopes originated 100 years ago and have undergone four main stages of development, each of which is marked by the main characteristics of the instruments used at that time.

Hard endoscopy stage (1806-1932): Hard endoscopy was first developed by German Philipp Bozzini. It consists of a vase-shaped light source, candles and a series of lenses. It is mainly used for bladder and urethral examination. The rigid endoscope developed by Rosenhein in 1895 consists of three tubes arranged in concentric circles. The central tube is an optical structure. The second layer of tube cavity is equipped with a bulb made of platinum wire and a water-cooled structure. A scale is engraved on the outer wall to reflect the depth of entry. In 1911, Elsner made improvements to the Rosenhein gastroscope, adding a rubber tip to the front end for guidance, but the inability to observe after the lens was dirty became the main defect. Nevertheless, the Elsner gastroscope was still in command until 1932.

Semi-flexion endoscopy stage (1932-1957): Schindler cooperated with Georgwolf, an excellent instrument maker, to develop a gastroscope in 1928. It was finally successful in 1932 and named Wolf-Schinder gastroscope. After that, many people have transformed it to make it more functional and practical.

Optical fiber endoscopy stage (1957 to present): In 1954, British Hopkins and Kapany invented optical fiber technology. In 1957, Hirschowitz and his assistants demonstrated their self-developed optical fiber endoscopy at the American Society of Gastroscopy. In the early 1960s, the Japanese Olympas factory installed a biopsy device and a camera on the basis of optical fiber gastroscopy, which effectively showed gastroscopy. In 1966, the Olympas factory pioneered the front-end angling mechanism, and in 1967, the Machida factory adopted an external cold light source, which greatly increased the amount of light. Small lesions can be found, and the field of vision is further expanded, and the duodenum can be observed. In the past 10 years, with the continuous improvement of ancillary devices, such as the development of surgical instruments and photographic systems, fiber endoscopy can be used not only for diagnosis, but also for surgical treatment.

The era of television endoscopes (after 1983): In 1983, Welch Allyn successfully developed an electronic camera endoscope. The front end of the mirror is equipped with a high-sensitivity miniature video camera, which transmits the recorded image to the television information processing system by means of a telecommunications signal, and then converts the signal into an image that can be seen on the TELEVISION camera. Soon the Japanese Olympas factory launched corresponding models of gastroscopes and occupied most of the market.

In the past 200 years, the structure of endoscopes has undergone four major improvements, from the original hard tube endoscope, semi-curved endoscope to fiber endoscope, to today’s electronic endoscope. With the advancement of science and technology, image quality has also undergone qualitative leaps over and over again. The first hard tube endoscope developed by Bozzine originally used candlelight as the light source, but later changed to a light bulb as the light source. Today, color photos or color TV images are obtained from the endoscope. This image is no longer an ordinary image of tissues and organs, but is like a microscopic image observed under a microscope. The tiny lesions are clearly legible, and it can be seen that the image quality has reached a high level.

Classification of medical endoscopes:

Classified according to its development and imaging structure: it can be roughly divided into three categories: hard tube endoscopes, optical fiber (hose type) endoscopes, and electronic endoscopes.

Classification by medical endoscope function:

1. Endoscopy for the digestive tract: hard tube esophagoscopy; fibroesophagoscopy; electronic esophagoscopy; ultrasound electronic esophagoscopy, fibroesophagoscopy, electronic gastroscopy, ultrasound electronic gastroscopy, fibroduodenoscopy, electronic duodenoscopy, fibrodegenoscopy, electronic colonoscopy, fibrodegenoscopy, electronic colonoscopy, fibrodegenoscopy and rectoscopy.

2. Endoscopy for the respiratory system: hard tube laryngoscope, fiber laryngoscope, electronic laryngoscope, fiber bronchoscope, electronic bronchoscope, thoracoscope and mediastinal mirror.

3. Endoscopy for the peritoneal cavity: there are hard tube type, optical fiber type, and electronic surgical type laparoscopy.

4. Endoscopy for the biliary tract: hard tube biliary mirrors, fibrous biliary mirrors, electronic biliary mirrors, and maternal and child biliary mirrors.

5. Endoscopy for urology:

(1) Cystoscopy: it can be divided into cystoscopes for examination, cystoscopes for ureteral intubation, cystoscopes for surgery, cystoscopes for teaching, cystoscopes for photography, cystoscopes for children, and cystoscopes for women.

(2) Ureteroscopy.

(3) Nephroscopy.

6. Endoscopy for gynecology: colposcopy and hysteroscopy.

7. Endoscopy for blood vessels: endoscopy for blood vessels.

8. Endoscopy for joints: arthroscopy.

Since the application of fiber optics in clinical medicine in the late 1950s, due to the continuous improvement and improvement of the optical system, fiber endoscopes have reached the level of clear images, large viewing field, fine-diameter endoscope body, easy operation, and complete varieties and specifications.

Medical endoscope structure:

Taking the optical fiber gastroscope, which is currently used more commonly, as an example, it consists of:

①the apex part of the endoscope

② the curved part

③ the image guide tube

④the operating part

⑤the light guide tube

⑥the light guide tube joint.

Principles of medical endoscopic imaging:

The principle of fiber endoscopic imaging is to pass the light from a cold light source into the guide beam. A concave lens is installed at the head end of the guide beam (the apex of the endoscope). The light from the guide beam passes through the concave lens and is irradiated on the mucosal surface of the internal cavity of the organ. The light that is irradiated on the mucosal surface of the internal cavity of the organ is reflected, and these reflected rays are imaged light. These reflected light are then reflected back into the observation system, and after a series of optical reactions such as right-angle roof prisms, imaging objective lenses, glass fiber guide beams, and eyepieces, the image of the internal cavity and mucosa of the inspected organ can be observed on the eyepiece in order of sequence. The image of the mucosa of the internal cavity of the inspected organ can be observed on the eyepiece.

Electronic endoscopes are the third generation of endoscopes after the first generation of hard gastroscopes and the second generation of optical fiber endoscopes. The electronic endoscope is mainly composed of three main parts: endoscopy, video information system center, and televisio monitor. Its imaging mainly depends on a miniature image sensor (chargecoupled device, CCD) equipped at the front end of the lens body. The CCD is like a miniature camera that processes the image through an image processor and displays it on the screen of a TV monitor. The image is clearer than ordinary optical fiber endoscopes, the color is realistic, the resolution is higher, and it can be viewed by multiple people at the same time.

The first generation of electronic endoscopes has been used in clinical practice since 1983, and the third generation of electronic endoscopes has been produced for clinical use.  The more famous companies in the world that produce electronic endoscopes include Welchallyn in the United States and Olympus in Japan.  Due to the advent of electronic endoscopy, it has created a new chapter in the history of diagnosis and treatment of endoscopy for more than 100 years. I believe that electronic endoscopy will play a huge role in clinical, teaching and scientific research.

Imaging principle of medical electronic endoscope:

The imaging principle of electronic endoscopes is to use the light emitted by the light source equipped with the television information center, and the light is introduced into the cavity of the subject through the optical fiber guide in the endoscope. The CCD image sensor receives the light reflected from the mucosal surface of the body cavity, converts the light into an electrical signal, and then transmits the signal to the television information center through a wire. The information center stores and processes these electrical signals, and finally transmits them to a TV monitor to display a color mucosal image of the inspected organ on the screen. There are currently two types of CCD image sensors used in the world, and the specific ways in which color images are formed are slightly different.

Advantages of electronic endoscopy in clinical application:

1. Simple, flexible and convenient to operate

Due to the application of electronic technology, when diagnosing and treating diseases, operators, assistants, and other staff can perform various operations under the direct gaze of monitors, so that operators in all aspects can cooperate tacitly and safely.  Therefore, it is easy to operate,lively, convenient and easy to master.
2. The patient’s discomfort is minimized
Due to the fineness of the endoscope body, the discomfort of the patient is minimized when the body is inserted into the body cavity.
3. Greatly improved diagnostic capabilities
Due to the application of CCD, the pixel ratio of fiber endoscopes has been greatly increased, the image is clearer and more realistic, and it has a magnification function. Therefore, it has a high ability to distinguish. It can observe the fine structure of the gastric mucosa, which means that it can observe the smallest anatomical unit of the gastric mucosa-the stomach cell and the small sulcus. Therefore, minor lesions can be found, and the ultimate goal of early detection, early diagnosis, and early treatment can be achieved. In addition, due to the wide field of view of the electronic endoscope and the large bending angle of the front end of the endoscope, blind spots are avoided. Therefore, this is also one of the main factors in the ability of the manuscript to diagnose and avoid missed diagnosis.
4. Facilitate teaching and clinical case discussion
Since the images are observed on the monitor screen, it can be used for more people to observe and learn together and discuss cases. At the same time, it also provides good conditions for improving the level of diagnosis.