The main structural components of the new NIST micrometer--a device for measuring the thickness of fine wire, narrow fibers and similar objects—are made of Invar, a nickel-iron alloy that does not react to small changes in temperature. As a result, the measuring device is less prone to error than other state-of-the-art instruments. A laser beam enters from the left side of the drawing and enters a beam splitter cube (1), which divides the beam into two parts. One part remains in the cube, is reflected from a side mirror back towards the center and serves as the reference beam. The other part hits the retroreflector (2). As the floating carriage (3) moves away from the splitter cube and toward the back end of the anvil (4), the distance between the retroreflector and the cube splitter varies (5 When the two beam are brought back together, the laser reports the change in distance.
Credit: NIST
Researchers at the National Institute of Standards and Technology (NIST) have developed a dramatically improved laser-based instrument that measures the diameter of fine-gauge wires, fibers and other objects only about three times the thickness of a human hair. Known as a laser micrometer, the device’s accuracy equals that of its state-of-the-art counterparts but is cheaper, simpler to operate and easier to maintain.
NIST scientists John Stoup and Ted Doiron reported their findings in the December 15, 2020 issue of Metrologia.
The new micrometer uses an advanced laser displacement interferometer, which relies on light to measure the thickness of objects held between two metal contacts. With the new system, researchers can measure the diameter of any object less than 50 millimeters wide, including fine-gauge wires and fibers, with an uncertainty of just 2 nanometers. That’s better than twice the accuracy of previous laser micrometers develo ..
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