Overview
ISO 11670:2003 - "Lasers and laser-related equipment - Test methods for laser beam parameters - Beam positional stability" specifies standardized methods to measure and characterize the positional and angular stability of laser beams. The standard defines terminology, coordinate systems, measurement principles and procedures, and data evaluation metrics used to quantify beam pointing and wander over short, medium and long time scales.
Key topics and technical requirements
- Scope and definitions: Precise definitions for beam positional movement, beam positional stability (defined as four times the standard deviation of centroid movement at a plane), beam angular stability (twice the standard deviation of measured angular movement), relative stability metrics and the beam stability parameter product S.
- Coordinate systems: Clear description of the laboratory system and the beam-axis system (average propagation direction), plus azimuth angle and coordinate transformation procedures to align measured data to the beam-axis frame.
- Measurement principles:
- Positional stability: centroid movement measured in the image plane with a position-sensitive detector; evaluation via standard deviation over the chosen time interval.
- Angular stability: centroid movement measured in the focal plane of a focusing element; converted to angular variation.
- Time-scale categories: short-term (1 s), medium-term (1 min), long-term (1 h) stability definitions for consistent reporting.
- Test arrangement & equipment: requirements for coaxial alignment of laser and measurement optics, control of environment (thermal equilibration, avoid air turbulence), detection systems, beam-forming optics, and calibration procedures.
- Practical measurement guidance: avoids clipping or diffraction that would add >1% error; rule-of-thumb test for apertures (an aperture that reduces signal by 5% should be
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