The Art of Precision: Mastering the Laser Interferometer
The world of machine tools and precision engineering is built on the foundation of precise measurement. In this realm, the laser interferometer has emerged as a renowned tool for achieving high-precision standards. In this blog post, we will delve into the intricacies of laser interferometers, exploring their advantages, limitations, and the sources of errors that must be taken into account when measuring with these devices.
The Power of Laser Interferometry
Laser interferometry has revolutionized the field of precision measurement, providing unparalleled accuracy and precision. This revolutionary technology is based on the principle of interference, where a laser beam is split into two or more beams that are coincident and then recombined to produce an interference pattern. The accuracy of the laser interferometer is directly dependent on the laser wavelength, boasting an impressive precision of better than 0.5 ppm (parts per million).
The Five Degrees of Freedom
Laser interferometers can measure five of the six degrees of freedom of a single axis, including linear positioning, rectitude in the horizontal plane, rectitude in the vertical plane, pitch angle, and banking angle. This versatility makes them an invaluable tool for machine tool calibration and quality control.
Sources of Error in Laser Interferometry
While laser interferometers are renowned for their precision, there are several sources of error that must be taken into account when measuring with these devices. These include:
- Environmental Error
Environmental conditions such as temperature, humidity, and air pressure can significantly impact the accuracy of a laser interferometer. Even a 1°C change in ambient temperature can result in a measurement error of approximately 1 ppm. To mitigate this risk, it is crucial to maintain stable environmental conditions during the measurement period.
- Surface Temperature of the Tool-Machine
Temperature changes within the machine tool itself can also introduce errors. For example, the coefficient of thermal expansion of steel lead screws is approximately 10.8 ppm/°C, resulting in an extension of nearly 10.8 microns per meter for each degree Celsius increase in temperature.
- Chemin Dead Error (Strad Error)
This type of error is caused by changes in environmental conditions during measurement, including changes in atmospheric pressure and the temperature of the material fixed with the laser interferometer and target mirror. The dead racing area of a laser measurement refers to the distance between the laser interferometer and the point of measurement at the end of the measurement path.
- Cosinus Error
When the laser beam path is not aligned with the movement axis of the machine tool, an error is generated between the measured length and the actual movement length. This error is proportional to the cosine of the angle between the laser beam and the machine tool axis.
- Aberration Error (ABE)
The ABE principle of error is a fundamental aspect of length and length measurement. The measured axis and the measured axis must be on the same straight line or its extension line. This principle helps to eliminate errors generated by angular movement, with an estimated discrepancy of approximately 5 μm/m per second angle.
Conclusion
In conclusion, laser interferometers have revolutionized the field of precision measurement, offering unparalleled accuracy and precision. While there are sources of error that must be taken into account, these can be mitigated by maintaining stable environmental conditions, ensuring proper machine tool alignment, and employing proper measurement techniques. By understanding the intricacies of laser interferometry, machine tool manufacturers can ensure the delivery of high-quality products that meet the demands of the modern world.
