ISO 25178-603:2025

Overview

ISO 25178-603:2025 is the ISO standard that specifies the design and metrological characteristics of non-contact phase shifting interferometry (PSI) instruments used for areal surface topography measurement. The standard covers instrument requirements, metrological characteristics, and design features for PSI systems (commonly implemented as interference microscopes). Because areal data can be reduced to profiles, the methods in this standard are also applicable to profiling measurements.

Key topics and requirements

• Instrument scope and architecture: PSI instruments shall include an interference objective or equivalent interferometer assembly, a controlled phase shifting mechanism, imaging (electronic camera) and data acquisition systems.
• PSI methods supported: Linear PSI, sinusoidal PSI and other time-dependent phase-shifting patterns (parallel/instantaneous polarization or carrier methods are outside the scope).
• Data processing: Use of validated PSI algorithms to convert digitized interference images into areal topography, application of a calculated or calibrated equivalent wavelength, and employment of phase unwrapping algorithms to mitigate fringe-order (2π) errors.
• Metrological characteristics: Design and calibration shall consider the metrological characteristics defined in ISO 25178-600 (reference norm). Annex B of ISO 25178-603:2025 describes common error sources (influence quantities) and their relation to instrument calibration and uncertainty.
• Key definitions referenced: phase shifting interferometry (PSI), interference objective, equivalent wavelength, phase change on reflection (PCOR), fringe-order error.
• Information flow & design guidance: Clause 4 provides an information flow concept for PSI microscopes; Clause 6 and Annex A offer examples of design features and operating principles.

Applications and users

• Practical applications: Non-contact metrology of optically smooth surfaces (e.g., polished parts, optical components, microfabricated surfaces), precision surface characterization in research and production, optical-component testing, and high-resolution surface texture analysis.
• Who uses this standard: Instrument designers and manufacturers, metrology and calibration laboratories, quality engineers in precision manufacturing, standards bodies, and researchers working with areal surface texture and interferometric measurement methods.

Related standards

• ISO 25178-600:2019 (metrological characteristics for areal topography methods)
• ISO 25178-607:2019 (phase shifting mechanism references)
• ISO 14638, ISO 8015, ISO 14253-1 (GPS framework and decision rules)
• ISO/TR 14999-2 and ISO 10934 (interferometry and microscopy guidance)

Keywords: ISO 25178-603:2025, phase shifting interferometry, PSI instruments, areal surface topography, non-contact metrology, interference microscope, equivalent wavelength, phase unwrapping, fringe-order error.