Shadow Technique Improves Measurement of Micro Holes

June 2, 2005
Shadow Technique Improves Measurement of Micro Holes

Sometimes seeing a shadow can be as good or better than seeing the real thing. A new measurement method* developed by researchers working at the National Institute of Standards and Technology (NIST) is a case in point. The method uses the shadow cast by a small glass probe to infer the dimensions of tiny, microscale holes or other micrometer-sized components. The technique may provide an improved quality control method for measuring the interior dimensions of fuel nozzles, fiber optic connectors, biomedical stents, ink jet cartridges and other precision-engineered products.

Image: NIST researchers and collaborators have developed a new method for measuring the interior dimensions of small holes with an uncertainty of only 35 nanometers. Here, a glass probe is inserted into an optical "ferrule," a device for connecting optical fibers used in communications systems. NIST Photo

Designed to be implemented with the type of coordinate measuring machine (CMM) routinely used in precision manufacturing settings, the method uses a flexible glass fiber with a microsphere attached on one end. The glass probe is attached to the CMM's positioning system, inserted into the part to be measured, and systematically touched to the part's interior walls in multiple locations. A light-emitting diode is used to illuminate the glass fiber.

While the microsphere inside the part is not visible, the shadow of the attached fiber—with a bright band of light at its center—shows the amount of deflection in the probe each time the part's interior is touched. A camera records the shadow positions. Based on prior calibration of the force required to bend the probe a specific distance, the part's dimensions can be determined with an uncertainty of about 35 nanometers (nm). The method can be used for holes as small as 100 micrometers in diameter.

"Our probe has a much smaller measurement uncertainty than other available methods and it is very cost effective to make," says Bala Muralikrishnan, a NIST guest researcher from the University of North Carolina at Charlotte.

The thin, glass fiber is about 20 millimeters long and 50 micrometers in diameter, making it especially useful for measuring relatively deep holes not easily measured with other methods. Replacement probes cost about $100 compared to about $1,000 for those manufactured using silicon micromachining techniques.

*B. Muralikrishnan, J.A. Stone and J. R. Stoup. Measuring internal geometry of fiber ferrules. Presented at the SME MicroManufacturing Conference, Minneapolis, Minn., May 4-5, 2005.

Source: NIST

Explore further: New methods reveal the biomechanics of blood clotting

Related Stories

New methods reveal the biomechanics of blood clotting

December 19, 2017

Platelets are cells in the blood whose job is to stop bleeding by sticking together to form clots and plug up a wound. Now, for the first time, scientists have measured and mapped the key molecular forces on platelets that ...

Lab unlocks secrets of nanoscale 3-D printing

January 4, 2018

Lawrence Livermore National Laboratory (LLNL) researchers have discovered novel ways to extend the capabilities of two-photon lithography (TPL), a high-resolution 3-D printing technique capable of producing nanoscale features ...

Imaging probe printed onto tip of optical fiber

October 26, 2017

Combining speed with incredible precision, a team of Molecular Foundry scientists and industry users developed a way to print extremely small devices on the tip of a glass fiber as thin as a human hair. These tiny devices ...

Getting quicker – more quickly

October 30, 2017

A new procedure simplifies wind tunnel tests and makes the results visible immediately. Athletes have gone up against the wind at ETH to test the new method.

From thin silicate films to the atomic structure of glass

June 5, 2014

Glass ranks as one of the most important materials of our age. You have only to think about smartphones, or drinking glasses, or look out of the window to realise that glass in its various forms is omnipresent. Fibre-optic ...

Recommended for you

Fast computer control for molecular machines

January 19, 2018

Scientists at the Technical University of Munich (TUM) have developed a novel electric propulsion technology for nanorobots. It allows molecular machines to move a hundred thousand times faster than with the biochemical processes ...

Simulations show how atoms behave inside self-healing cement

January 19, 2018

Researchers at Pacific Northwest National Laboratory (PNNL) have developed a self-healing cement that could repair itself in as little as a few hours. Wellbore cement for geothermal applications has a life-span of only 30 ...

How the Elwha dam removals changed the river's mouth

January 19, 2018

For decades, resource managers agreed that removing the two dams on the Elwha River would be a big win for the watershed as a whole and, in particular, for its anadromous trout and salmon. The dams sat on the river for more ...

More genes are active in high-performance maize

January 19, 2018

When two maize inbred lines are crossed with each other, an interesting effect occurs: The hybrid offspring have a significantly higher yield than either of the two parent plants. Scientists at the University of Bonn have ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.