Optical Measuring Sensor With Nanometer Accuracy

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-11-26 11:39

Small, smaller, very small and much smaller: Precision requirements down to the sub-nanometer range are common in semiconductor manufacturing, product electronics and optics. In fact, mechanical engineering has long been on the way to the “nanoworld”: In precision gear manufacturing, higher pitching accuracy is a suitable means of better distributing the internal forces on the gears. More precisely manufactured tooth geometries lead to lower stress peaks and higher resilience. Even in multi-row rolling bearings, the distribution of the internal forces depends crucially on the smallest manufacturing tolerances, because these systems are statically overdetermined. Precision manufacturing and consequently measurement in the sub-nanometer range are an important prerequisiteto develop existing mechanical systems for even more power density.

Overcome the limits of existing measuring systems

In addition, the miniaturization of products and production processes increases the development pressure from the micro to the nanodimension. This leap in dimensions must be made available on a broad basis and at manageable costs in order to ensure the competitiveness of the products and efficient, future-proof production. On the sensor side, this requires an easily integrable ultra-precision measuring system that overcomes the physical and practical limits of existing measuring systems.

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These measuring systems include glass scales. They are currently considered a benchmark in industry and are used when other measuring systems no longer achieve the required precision. Due to the material measure on the glass scale, this measurement method reaches its limits in the submicrometer range due to the manufacturing process.

Too far from the scene

These and other inductive position measuring systems are attached to the machine bed and are therefore always at a certain distance parallel to the workpiece. The measured position therefore only corresponds to the position of the movable sensor head, but not exactly the position of the workpiece.

Another problem: Systematic errors such as tilting errors caused by guides and bearings (Abbe errors) add up to the workpiece. In addition, there are operational errors, such as: B. different temperature expansions, machine deformations due to process forces, wear and vibrations, etc. These deviations cannot be detected by the known position measuring systems with measuring points. Therefore, further development of these measuring systems down to the sub-micrometer range would not lead to higher positioning accuracy of tools or workpieces.

Distance measurement directly on the target as a solution

The solution to the physical and practical limits of existing measuring systems is to turn away from their measuring principle and use a measuring principle that can directly detect the position of workpieces. In this way, machine and operational measurement errors are excluded from the outset. The interferometric measuring systems known from research offer the possibility of optically measuring distances to “objects” directly on the target and achieve accuracies down to the nanometer range. However, they are extremely expensive, very large, bulky, sensitive and not suitable for integration in machines and manufacturing processes. So far, so-called Michelson interferometers have only been used in the industrial environment for the calibration of machine tools and measuring machines.

Content of the article:

• Page 1: Optical measuring sensor with nanometer accuracy
• Page 2: The Attocube Interferometer

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