ISO 9335:2025

Overview

ISO 9335:2025 - Optics and photonics - Optical transfer function - Principles and procedures of measurement - provides practical guidance for measuring the optical transfer function (OTF) of imaging systems. The standard describes the construction and use of OTF measuring equipment that analyses the radiation distribution in the image plane of an optical system, specifies factors that influence OTF measurement, and defines rules for equipment performance, environmental controls, data correction and presentation. Interferometer-based instruments are outside the scope of this document.

Key topics and technical requirements

• Measuring conditions and I‑state: Identify and fix the imaging state (I‑state) parameters - focus, magnification, aperture, spectral content - so measurements are reproducible.
• Measurement uncertainty: Equipment and environment must support the prescribed measuring conditions to achieve the declared uncertainty of measurement.
• Environmental controls: Requirements and recommendations for temperature, humidity, vibration isolation and electromagnetic disturbances to minimise measurement bias.
• Measuring equipment and system components:
  • Optical mounts and benches, defocusing tolerances, and measuring scales
  • Test target units and mounting of the specimen
  • Image evaluation systems and auxiliary imaging systems
• Measurement procedures: Guidance on setting conditions (spectral characteristics, angular distribution, aperture, image scale, focusing), handling isoplanatic regions, veiling glare, fixed pattern noise, analysed area selection, and signal‑to‑noise considerations.
• Data corrections and presentation:
  • Normalization, frequency‑scale corrections, and modulation corrections
  • Treatment of auxiliary imaging systems and graphical/numerical presentation of OTF data
• Uncertainty checks: Procedures for verifying and documenting uncertainty contributions and measurement repeatability.

Applications and users

ISO 9335:2025 is intended for professionals and organizations involved in objective image‑quality assessment and optical metrology, including:

• Optical engineers designing lenses, camera modules and imaging optics
• Test and calibration laboratories performing OTF characterization
• Manufacturing quality control teams validating imaging performance
• R&D in optics, photonics and electro‑optical systems
• Standards bodies and consultants preparing measurement protocols

Practical applications include lens qualification, sensor and camera module testing, production acceptance tests, benchmarking imaging system performance, and supporting product specifications and compliance.

Related standards

• ISO 9334 - Optics and photonics - Optical transfer function - Definitions and mathematical relationships (normative reference for terminology and definitions)
• ISO/IEC Guides referenced for expressing measurement uncertainty and terms (GUM and VIM concepts are aligned in the 2025 edition)

Keywords: ISO 9335:2025, optical transfer function, OTF measurement, optics and photonics, image quality, measurement uncertainty, test target, image evaluation system.