Wednesday, May 8, 2013

Why are rigid borescopes better?


Some specialists are interested in rigid borescopes and they want to know their pros and cons.
Rigid borescope with a light source

A rigid optical borescope (can be seen here) is an optical device with a rigid metal tube and eyepiece on one end and an objective lens on the other. Between them we can find a complex relay optical system.  Optical systems in them can be of three main types: Hopkins rod lenses, achromatic doublets and gradient rod lenses. For large diameter the achromatic doublet relays are good, but as the diameter tube gets smaller the rod lenses provide better images. For very small rigid borescopes, the gradient index lens relays are better. The tube contains also glass fibers for illumination. 
The illumination can be provided either by LED light source attached as a handle to the light post of the borescope, or by external powerful Metal Halide, Xenon or Halogen light source. In this case the light is transferred via flexible glass fiber guide. alideAn internal image of the object is formed by the objective lens and magnified by the eyepiece, which presents it to the eye. 
What are advantages of rigid borescopes? They provide a superior image at a lower cost compared to a flexible fiberscopes. The image is exceptionally clear. When an object is located within direct access, rigid borescopes work well. They are recommended for gunsmithing, automobile inspection like observation of automotive cylinders, injectors and hydraulic bodies. It is possible to attach a video camera to the eyepiece, and after that the inspector can record video and still images for further processing.
What then are disadvantages of rigid borescopes? Rigid borescopes are limited to access to a straight line. It is impossible to view hidden objects behind something.  Besides they are fragile instruments and don’t like falling down.
There are many rigid borescopes in the market with diameter from 1.8 mm to 8 mm and length from 10 cm to 90 cm.  As you can see they have more advantages than disadvantages and can be very efficient for inspection work
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