AcWaCo, Acoustic Wavelength Compensation, is a technology that improves the accuracy of length measurement. It revolutionises the laser interferometric measurement by enabling cost effective significant improvement of accuracy and repeatability by practically eliminating all the errors to measurement caused by varying physical properties of air. When compared to present state-of-the-art methods this technology is unique in achieving decrease of measurement error 10-100 fold and it can be applied economically in mass production.

The most prominent application areas are within semiconductors, TFT/LCD monitors and Machine Tools manufacturing industries, enabling considerable productivity and quality improvements.

This new technology for the determination of the refractive index of air along the laser beam path is based on measuring the speed of sound travelling the same path simultaneously with the laser interferometric length measurement beam. The relative effect of change in the temperature of air is about two thousand times stronger on the speed of sound in air than on the refractive index of air. Thus, it is now possible to achieve very precise distance measurements with the laser interferometer using the acoustically defined refractive index.