Overview
ISO/TS 22247:2022 - "Optics and photonics - Effective numerical aperture of laser lenses - Definition and verification procedure" defines how to characterize a laser lens’s ability to collimate divergent beams or focus collimated beams to small spots. The technical specification gives terms, definitions, coordinate systems and a practical verification procedure that yields a reliable effective numerical aperture (NAeff) for laser lenses used in beam forming.
Key topics and requirements
- Effective numerical aperture (NAeff): Defined as the sine of half the maximum divergence angle for which a nearly diffraction-limited beam can be collimated or focused without unacceptable aberration or more than 0.5 increase in beam propagation ratio.
- Beam characterization metrics: Uses beam propagation ratio (M²), divergence angles and encircled-power/second-moment beam diameters consistent with ISO 11146-1.
- Verification procedures: Provides methods to verify NAeff using:
- Beam propagation ratio method (measures how lens affects M²), and
- Residual divergence method (measures divergence after collimation).
- Lens types covered: Rotationally symmetric lenses and cylindrical lenses (including long cylindrical lenses with sequential and parallel test procedures).
- Probe laser requirements: Specifies acceptable probe beam characteristics (simple astigmatic beams, limits on M²) and orientation rules for cylindrical lenses.
- Test reporting: Specifies mandatory test-report content - lens and probe laser details, measurement results (both methods), and lower limits for NAeff.
Practical applications
ISO/TS 22247:2022 is directly applicable wherever precise laser beam shaping and spot size control are required:
- Lens manufacturers - for specification, production control and conformance statements of laser lenses.
- Optical design and integration engineers - to select lenses for collimation, focusing and beam-forming applications.
- Test and calibration laboratories - to perform reproducible verification of lens performance.
- System integrators in industries such as laser material processing, microscopy, LiDAR, optical metrology and high-precision manufacturing - where reliable lens behavior affects system performance.
Related standards
- ISO 11146-1 - Test methods for laser beam widths, divergence angles and beam propagation ratios; referenced for coordinate systems, M² definitions and beam-measurement foundations.
ISO/TS 22247:2022 provides a practical, standardized way to express and verify the effective numerical aperture of laser lenses, enabling consistent supplier specifications and informed component selection for beam-forming systems.