The Need for Laser Beam Diagnostics
Authors: Farnworth C 
Published: March 2009

Lasers are dynamic sources of energy which are ever changing. The laser is prepared for the application through a series of optics varying in quality and complexity. Fluctuations in the laser and the imperfections in the optical train will affect, to some degree of significance, the performance of the beam at the work site. Measuring these variables and their effects on the laser performance has been very inconsistent. Many measurement techniques are based on the perception of the person making the measurement. Inconsistencies in perception affect the results and performance quality of the system.

A method for beam diagnostics has been developed that removes the human perception and offers consistency in measurements of laser beams. The Laser Beam Analyzer (LBA 100) manufactured by Spiricon, is a portable, self contained beam diagnostic instrument that provides numerical and visual analysis of laser characteristics. Data is taken using CCD and vidicon cameras, each chosen for the wavelength of interest. The signal is then digitized for analytical analysis. The system offers algorithms for numerical comparison of beam quality and performance. This user friendly system provides real time measurements, calculations on the fly, and the ability to manipulate and compare data. Accurate analysis of uniformity, distribution, shape, and many other characteristics can be monitored consistently and with a high degree of confidence.

Analysis of the laser source is simplistic. Information pertaining to the laser beam is accurate, comprehensive and consistent for both CW and pulsed laser sources. Variables within the system can be understood and monitored for significant changes, enabling the system to operate at optimal parameters.

The utilization of lasers has increased significantly in a short period of time. Incorporated into many of these new applications are very complex optical trains and light delivery systems. The large increase in laser volume and the multiple variables designed into systems have presented problems in: 1) Beam consistency. 2) Optical uniformity, distortion, and degradation. 3) Monitoring and analysis of critical beam characteristics and performance features.

Laser manufacturers are producing large volumes of lasers to meet the demands of the market. They have restructured their manufacturing process to facilitate mass production of laser technology. Quality control has been set into place to monitor the outgoing product for workmanship and operational characteristics. Data relating to this QC inspection is usually based on a power reading and a visual inspection of the beam to detect any flaws. Information pertaining to the performance of the laser beam based on this criteria may be misleading. Power measurements are based on the total energy that strikes the photodetector. No information is obtained regarding the uniformity or distribution of this energy. Visual examination of the beam for flaws and inconsistencies is distorted by reflection interference and the ability of the human eye to discern intensities and related pattern variances. Also incorporated into this data is the individual perception for interpreting data.