Glass fiber defects detection.

Basically communication glass fibers are produced in two types: mono-mode and multi-mode.
Glass fibers graded-index-fiber Mono-mode fiber is used for long distance communication, multi-mode glass fiber is used for short distances e.g. between network servers.
The production of the multi-mode or graded index fiber is relative complex.

The production starts with a hollow tube, the core rod. This hollow tube is internally filled with up to 1000 very thin glass layers with different refractive indexes.
To change the ratio of siliciumtetrachloride and germaniumtetrachloride in the tube filling gas the difference in refractive index is created.

A small disturbance in the fiber core rod during this production process causes a serious loss of light in the fiber and it's not acceptable.

Current situation/illumination

Until now the core rod is manually inspected on these small disturbances.

Im pol 60d Red BL 01 Im pol 60d Red BL 02 Im pol 60d Red BL 03 This manually inspection uses polarized light and on behalf of wave length difference a small colored disturbances of the light is visible.

On the left 3 images shows the results of an polaroid image. The quality of these small disturbances is very poor so no reliable automatically vision detection is possible.

J.A.I.M.S. solution

To improve the image quality a highly sophisticated back light is used. Result shows next image.
Core Rod defect_002 Core Rod defect_133 The created image is processed by several filter operations to get the best image quality as possible.

Based on this image all necessary measurements as length, width, curve and bubble dimensions are possible.

Rotating the core rod, acquiring and subsequently processing the image, a 3D error shape can be created. Images shows the defect during rotation. Core_Rod_Defects_01 Core_Rod_Defects_02

Conclusion: for glass fiber quality inspection, highly sophisticated illumination and an advanced vision algorithm is necessary.