MicrospotMonitor Camera based measuring system for the diagnostics of VIS and NIR-lasers

 

• easurement of foci down to 6 (microns) µm
• Fully automated caustic measurement
• High dynamic up 120 dB

 

 

 

Application

The MicroSpotMonitor is the favorite tool to control and to check very small laser beams for instance used in the laser micro machining.

 

The MicroSpotMonitor measures the power density distribution at different z-positions of your beam within a few minutes.

 

Based on these data are calculated:

 

• dimensions of the laser focus
• focus position in space
• beam propagation ratio M2
• power density distribution

 

The measurements are based on the ISO 11146

 

 

 

Technical description

 

 

The MicroSpotMonitor is a camera based beam diagnostics system. The device measures the spatial power density distribution and determines based on this the beam position and the beam radius of laser beam between 350 nm and 1100 nm. The MicroSpotMonitor works with different sensor elements. Build-in are a CCD sensor and a CMOS - sensor with a logarithmic sensitivity.

 

The main goal of the development was to set-up a system able to detect very small spot even from pulsed laser sources. With a well designed attenuation this is possible even at very high power densities in the range of several hundred MW/cm2.

 

The measurement of the focus is done by an objective. Objective with a magnification between 1:1 to 1:15 are available. This enables the user to measure even highest power densities.The current design can stand an average power of 300 W and pulse power in the multi kW range. The objective is coated for 1064 nm and 532 nm. Between objective and detector a complex attenuation system is integrated.

 

For detection is used a CCD-sensor or a CMOS-sensor with logarithmic sensitivity. The CCD-sensor with a fixed integration time has a dynamic of around 55 dB. With the additional control of the integration time (10 µs to 200 ms) the dynamic range can be expanded to around 80 dB. This leads to a range of more than 130 dB. The logarithmic CMOS-sensor enables a dynamic range of 120 dB. In every case the dynamic is sufficient for a caustic measurement, which requires according to ISO 11146 a range of more than 4 Rayleighlengths. With the integrated z-axis the MicroSpotMonitor can run such measurements within a few minutes.

 

 

Control and presentation

 

For the control of the MicroSpotMonitor and the presentation of the results a user friendly software is available.