Measurement of internal bubbles

[Steved]

Hello: I have an application where we need to measure the internal bubbles of a translucent cylinder. Normally, we would cross section the part - however, for this application, we cannot cut or destroy the part. We were trying to use a microscope but it is hard to get below the surface to see the bubbles. <br>
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Is there a way to measure these bubbles? Aside from the microscope, the other ideas we had were internal illumination, optical comparators and index matching fluids.<br>
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I appreciate any suggestions. Thank you and have a great day.<br>
Steve d

 

[randi]

It appears that some industries that fabricates, glass tubes or transpaent or translucent materials in rod or tube forms like lexan or lucite etc. is using light transmission through the material. 100% transmission would mean no defects of any kind - bubble, knots, stones, streaks etc.

These appear to be applied on-line automated, using light sources, cameras, recorders/ visual scanning devices that are applicable to high speed manufacturing lines. Optical transmissibility measurement appears to be the key solution for a non-destructive and good reliability measurement.

Edmund Scientific might be able to supply some experimental equipement if you look at it this way. High purity glass sample, that is bubble free should have a very high internal transmittence for a given monochromatic light. This can be measured by a refractometer supplid by this company. Can this instrument or a similar device be used in your application. Then you will have to develop your own pass fail criteria as to zero bubble or an acceptable bubble size
with reference to an internal transmittence value.

Hope this is of some help. check with

http://www.edsci.com

 

[IRstuff]

Another possibility is to measure the scatter of the light by illuminating with a collimated laser. The scatter pattern should be able to give you some indication of the size and possible distribution of the bubbles.

If you want to get really fancy, you could use a range-gated camera and a pulsed laser to get pictures at depth.

TTFN

 

[Steved]

Randi: Thank you for the information. Please have a great weekend,
Steved

 

[Steved]

IR stuff: Sorry about the late reply, thanks for the information. take care,
Steved

 

[analogkid2digitalman]

Steved:

You may want to consider distortion effects of cylindrical lensing caused by the material if your measurements need to be precise. Cylinders have the effect of optically 'stretching' one axis more than another. To illustrate, take a glass or clear plastic rod, place ithorizontally on some printed text, and look through the rod at text.

 

[Steved]

Hello analogkid2digitalman:

Thank you also for this information. The person I did the work for has retired. I will see if this work has been picked up by someone else. take care,
Steved

 

[soptic]

A gas bubble detector is available at

http://www.sensoptic.ch

which may suit your application

 

[Steved]

soptic: Thanks, I still need to check if this was picked up by someone else.
Steved