Measurement Principle

Laser-Doppler based Length and Speed Measurement

ELOVIS gauges use a special form of dual-beam laser interferometer technology to measure product velocity, with extremely high accuracy. The velocity is integrated over time to measure length. The laser beams intersect in a certain angle and form a pattern of equally spaced bright and dark fringes (fringe distance is a function of laser wavelength and beam angle). Laser light, which is reflected from the moving surface is scattered through this fringe pattern and thus cause an intensity modulation with a frequency which is proportional to the speed of the moving surface, the so-called doppler frequency. There is no need for any markings on the moving surface. The reflected light is collected and converted into an electrical signal by a photo detector. Sophisticated algorithms in combination with a high performance DSP compute the actual speed and length with an accuracy up to 0,01% and better.

Most important:

ELOVIS interferometer technology is not affected by any kind of surface (structure, colour, gloss level, reflectivity, light absorption, unevenness, ...). ELOVIS systems, in more than 95% of all applications, will run without a application specific parametration. ELOVIS systems set standards in lifetime, reliability, size, variability and ease of operation. Please contact us to get more details!