Precise Profilometry

The laser ultrasonic method can be useful to measuring the surface profile or the internal structure of objects with a non-planar surface. The focused transducer (PLU-6F-01) excite a short acoustic pulse (duration about 50 ns). The surface profile can be obtained by moving the transducer in the plane above the object and measuring the distance to it. Precision measurements of the profile of the surface of the investigated objects are performed by the immersion method.

Laser-ultrasonic technology makes it possible to measure the surface profile of not only smooth but also highly rough surfaces. High sensitivity and dynamic range of the method provide high resolution at a level of several microns.

A method of laser ultrasound tomography for the solids profilometry has been developed. It can be used to obtain surface profiles of solids in opaque liquids (for example, cooling oils, oil, etc.) unlike mechanical and optical profilometry methods. Tomographic approach to recording ultrasound signals significantly improves the speed of surface control.

The developed profilometer allows to obtain a profile image of a section with a length of up to 20 mm with a refresh rate of 20 Hz (the profile control rate is more than 100 mm/s). The longitudinal resolution of laser ultrasonic profilometry is up to 15 μm, and the transverse resolution is up to 150 μm. The method is good for a problems which needs high control rate and high longitudinal resolution of images, for example, high-precision control of pipe diameters, projectiles.

The height of the profile is determined with an accuracy not worse than 5 μm for laser ultrasonic profilometry of thermal-protective coatings. The second coating "smoothes" the surface, the height of the irregularities decreases 3 times.

For the precise surface profile evaluation of the investigated object it is possible to create complex diagnostic systems based on the laser ultrasound method.