The working principle of rigid endoscopes Rigid endoscopes generally include two parts: imaging system and lighting transmission system. The imaging system consists of an objective lens group, a rod-shaped lens and an eyepiece. The principle is: the inverted image of the observed object through the objective lens is converted into a positive image through the imaging system, and transmitted to the eyepiece, and then magnified by the eyepiece for observation by the human eye. The lighting transmission system is composed of optical fibers. The working principle is: the light from the cold light source is transmitted through the optical fibers to the front end of the endoscope to illuminate the observed object.
Common faults of rigid endoscopes：
1. No image
Cause analysis：
No image is the most common failure of endoscopes. Damage to the objective lens, water ingress, and fragmentation of the rod-shaped lens in the inner tube will cause no image, and the inner tube lens as long as one of the columnar permeable bodies is broken, it will cause no image.
Exclusion method：
First, use a magnifying glass to check the mirror body for dents or bends;
secondly, to see if the objective lens end is broken; and finally, to check whether the mirror has water due to poor sealing performance.
2. The image is dimmed
Cause analysis：
The darkening of the image is usually caused by the light source. Dirt on the objective lens and optical fiber and moisture entering the hard lens tube will also darken the image.
Exclusion method：
3. Image yellowing
Cause analysis:
Most of the yellowing of the image is due to the failure of the objective lens group.
Exclusion method：
First, check whether the color parameters on the machine are set correctly;
secondly, check whether moisture enters the endoscope; and finally, observe whether the adhesive on the objective lens group has yellowing caused by aging.
4. Dust was found in the image
Cause analysis：
There is dust in the image. One is that there is dirt outside the objective lens and eyepiece, or the entire optical system is dirty. The other is that the columnar permeable body and the spacer column have friction during use, which will also produce fine powder. It is reflected in the image as dust for a long time.
Exclusion method:
Check the objective lens and eyepiece for dirt, dust and scratches.
5. Foggy image
Cause analysis:
The foggy image is mainly caused by the entry of water vapor, especially by aging, water vapor enters the lens body from the objective lens end, the eyepiece end and the optical fiber seal.
Exclusion method:
Check the sealing of the objective lens and the eyepiece end, and check the sealing of the optical fiber interface.
6. The image is deformed and shaded
Cause analysis：
The shading of the image deformation is mostly caused by the bending and deformation of the working tube caused by human factors, and it may also be caused by loosening in the imaging system.
Exclusion method：
Turn the mirror to check whether the mirror body is distorted or bent.