FocusMonitor FM+

The PRIMES FocusMonitor FM+ analyzes and measures laser beam sources in material processing. FM+ determines the beam properties of focused laser beams, in addition to their geometric dimensions, focal position, the beam parameter product and the beam quality factor. The integrated z-axis allows for automatic measuring of entire caustics up to four Rayleigh lengths – facilitating measuring compliance with quality standards.

An update to the original FocusMonitor, the FM+ features new electronics designed to meet current and future requirements for signal processing and a new motherboard with a 16-bit A/D converter. An Ethernet interface allows for fast and secure data exchange with computers or system controllers. The new mechanical design also accommodates upside down installation without additional components.

The FM+ is an opto-mechanically scanning measuring system that scans the laser beam with a special measuring tip. The unit is equipped with a small hole (typically with a diameter of approximately 20 µm) that lets through a small section of the laser beam. Two reflecting mirrors guide this portion of the laser light to a detector selected and configured depending on the laser power and wavelength. This makes it possible to measure the different laser beam sources and systems solely by selecting the optimal measuring tip and corresponding detector. The high orbital velocity of the rotating measuring tip facilitates analysis of high power densities.

A very high signal-to-noise ratio is achieved thanks to the dynamics of the analog-digital converter used. Very low intensities are shown with equal precision next to the high peak intensities. That is one of the requirements for automatically measuring caustics in the area near the focal point over at least four Rayleigh lengths in accordance with ISO 11146.