Overview
ISO 9039:2008 - Optics and photonics - Quality evaluation of optical systems - Determination of distortion - specifies standardized methods to measure and report distortion in optical imaging systems. It applies to systems with rotationally symmetric image geometry over the optical spectral range 100 nm to 15 000 nm, and is also applicable to electro‑optical imaging systems when rotational symmetry is assured. The standard excludes anamorphic and fibre‑optic systems. ISO 9039:2008 focuses on radial distortion and provides procedures, test setups and reporting requirements for quality evaluation.
Key topics and technical requirements
- Scope and definitions: clear definitions of absolute distortion, relative distortion, object/image heights, field angles, lateral/angular magnification and reference planes.
- Classes of application: four practical measurement classes - infinite object/finite image, infinite/infinite, finite/finite, finite/infinite - with the appropriate reference quantities (image distance a′, angular magnification Γ, lateral magnification m, object distance a).
- Test methods: measurement of conjugate pairs of object‑ and image‑side coordinates (object pupil field angle ω or object height h, and image pupil field angle ω′ or image height h′).
- Apparatus and alignment:
- Use of collimators, telescopes, illuminated reticles or narrow slits to represent object positions.
- Axis of rotation should pass through the centre of the entrance/exit pupil to cover full aperture.
- Alignment of reference plane and image/object plane parallelism; autocollimators recommended for precision.
- Accuracy and error assessment: instruments must have accuracies so their influence on calculated distortion is typically 5–10× smaller than the permissible tolerance; measurement stability and swivel bearing precision must be assessed.
- Procedure and evaluation: calculation formulas for absolute and relative distortion are provided per class; direction of radiation affects sign of distortion and must be considered.
- Reporting and annexes: guidance on presentation of results, test reports and informative annexes (e.g., zero‑point shifting, picture‑height distortion).
Applications and practical value
- Ensures consistent, repeatable distortion measurement for camera lenses, microscope objectives, photogrammetric lenses, and electro‑optical imaging systems.
- Useful for optical designers, lens manufacturers, quality engineers, metrology labs and R&D teams who need to verify geometric fidelity and meet acceptance criteria.
- Enables objective comparison of distortion specifications, helps tune production calibration (e.g., calibrated focal length for photogrammetric lenses) and supports system integration where geometric accuracy matters (imaging, surveying, machine vision).
Who should use this standard
- Optical test laboratories, lens manufacturers, system integrators, and quality assurance engineers working in optics, photonics, machine vision, aerospace imaging and photogrammetry.
Related standards
- Prepared by ISO/TC 172 (Optics and photonics, Subcommittee SC 1). Use alongside other ISO optics and photonics quality and test standards for comprehensive optical system characterization.
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