Air-coupled ultrasonic interferometry method

Abstract

The invention discloses an air-coupled ultrasonic interferometry method. The method includes the following steps of: taking an air-coupled ultrasonic transducer as a measuring head to face the surfaceof a workpiece, reflecting ultrasonic waves back and forth on the surface of the workpiece, and measuring the phase difference that the first-time reflection echo on the surface of the workpiece reaches the air-coupled ultrasonic transducer; and based on the change of the frequency and wavelength of the ultrasonic waves, converting the measurement of the distance into the change rate of the phaseof acoustic waves relative to the angular frequency of the acoustic waves, wherein the change of the angular frequency of the acoustic waves is equal to the difference between the highest frequency F2 and the lowest frequency F1 in the bandwidth fB of the air-coupled ultrasonic transducer multiplied by 2Pi; and the change of the phase of the acoustic waves is equal to the difference between the integral multiples obtained by dividing the sound path by the wavelength at the frequency F2 and the frequency F1 multiplied by 2Pi. The ultrasonic technology is based on long-term continuous emissionand large-span frequency scanning, and has the advantages of high measurement accuracy and strong anti-interference ability; and the corresponding technology of the ultrasonic technology in laser interference is relatively difficult to achieve.

Description

technical field [0001] The invention relates to the technical field of air-coupled ultrasonic ranging, in particular to an air-coupled ultrasonic interferometry. Background technique [0002] After high-precision nanofabrication of complex structures, high-precision measurement of the free-form surface of the surface is required. However, the high-precision measurement methods and techniques of static free-form surfaces have always been a difficult problem. After ultra-precision machining, ultra-precision measurement of surface profile accuracy is difficult, the cost of measurement is high, and there is no breakthrough in the application of surface characterization theory and measurement methods. [0003] At present, the three-axis coordinate machine technology platform is widely used in the industry for high-precision measurement methods in the free-form surface measurement methods of nano-machined surfaces with complex structures. This technology platform includes high-p...

AI Technical Summary

Problems solved by technology

However, the attenuation of high-frequency ultrasonic waves on the order of 1MHz in the air is so large that it cannot be used for common distance measurements

In addition, the air ultrasonic time-of-flight method is greatly affected by external interference, so the ranging accuracy of the time-of-flight method is greatly reduced in practical applications.

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