Optical Measurement of Narrow Holes

Measuring deep, narrow holes with a ratio of 1:5 (diameter: height) has always been a difficult and largely unsolved problem. It gets worse when we consider that not only the bottom surface needs to be scanned, but also the side walls which are characterized with steep angles that sometimes exceed 75°. This often causes multiple reflections from the side walls, which ruin the signal.

Optical Measurement of Narrow Holes
Optimet has developed a new method which uses an optical filter designed especially for its distance and displacement sensors and the results are amazing!

3D Displacement scan of deep hole: Depth is color-coded

Description of the problem:
Measuring holes with radii of only hundreds of microns with depths of more than 3 millimeters is a complicated mission.

One of the problems which arise while doing this kind of a displacement measurement is the laser reflection off the hole’s side walls which obstructs the measurement. The next challenge is to have the ability of getting the information back from a very small area which is located in very steep angles. These two issues make deep and narrow hole measurement almost unreachable using laser distance sensors.

How we solved it:
Optimet has developed a new optical filter that preserves the advantages of their collinear displacement sensors and enables filtering out all the reflections from the side walls inside the hole. We were even able to reach a 1:7 ratio (hole diameter vs. hole depth). This is by far the most advanced technology for measuring deep holes and the only one which can achieve angular coverage of up to ±85 °

Cross-section profile of deep holes

Find out more about Optimet’s unique displacement sensors.

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2 Comments
  • deba
    Reply

    looking for a laser measuring instrument to measure micro pores in the stainless steel mesh.Thanks

    • Optimet
      Reply

      Hi Deba,

      Stainless steel can be quite challenging to measure with non-contact laser sensors since it’s often a semi-reflective material. It might be even somewhat polished and become very reflective even if not as specular as a mirror. Optimet sensors have the capability of measuring almost all kinds of materials and colors with sub-micron accuracy even very shiny metals as stainless steel.
      Please feel free to contact us directly for more information. We can provide a measurement report on your own sample.
      http://www.optimet.com/technical-service.php

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