Overview
ISO 25178-604:2013 defines the metrological characteristics of non-contact coherence scanning interferometry (CSI) instruments used for areal surface texture measurement and 3D mapping of surface height. As part of the ISO 25178 GPS series, this standard helps users and manufacturers characterize CSI microscopes’ performance, describe key influence quantities, and interpret measurement results consistently across applications.
Key topics
- Scope and purpose: Specifies what metrological parameters are relevant for CSI systems used to capture areal surface topography maps.
- Coordinate systems and measurement loop: Defines the instrument coordinate system (x, y, z) and the measurement loop components that influence uncertainty.
- Sampling and resolution parameters:
- Sampling interval (Dx, Dy) and digitization step (Dz) - spacing and height resolution of captured maps.
- Lateral resolution and lateral period limit (DLIM) - smallest detectable feature and spatial frequency response.
- Width limit for full height transmission - the narrowest groove width where measured height remains faithful.
- Instrument response and transfer:
- Response curve / amplification coefficients - relation between actual and measured quantities.
- Instrument transfer function (ITF) - frequency-dependent amplitude response to surface features.
- Noise and repeatability:
- Instrument noise vs measurement noise - inherent vs operational noise sources.
- Surface topography repeatability - method for assessing reproducibility (standard deviation across repeated maps).
- Influence quantities and uncertainty: Identification and description of factors that affect CSI measurements (optical properties, scanning mechanics, environmental perturbations).
- Informative annexes:
- Annex A: CSI microscope components and overview
- Annex B: CSI theory of operation
- Annex C: Spatial resolution considerations
- Annex D: Example procedure for estimating topography repeatability
- Annex E: Relation to GPS matrix model
Applications
ISO 25178-604 is used by:
- Metrologists and calibration laboratories establishing CSI performance and uncertainty budgets.
- Instrument manufacturers specifying and validating CSI microscopes for areal surface texture measurement.
- Quality engineers and R&D teams in precision manufacturing, optics, semiconductors, tribology, medical-device surfaces, and coatings who require reliable 3D surface topography data.
- Standards bodies and test houses harmonizing measurement practices and data exchange.
Related standards
- ISO 25178 series (Areal surface texture): Parts 1, 2, 3, 6, 70, 71, 601–606, 701 - especially ISO 25178-601 (stylus), -602 (confocal), -603 (phase-shifting interferometry).
- ISO/TR 14638 (GPS masterplan) and ISO 8015 (fundamental GPS rules) for context on specification rules.
Keywords: ISO 25178-604, coherence scanning interferometry, CSI, areal surface texture, 3D mapping, metrological characteristics, instrument noise, lateral resolution, instrument transfer function.