ISO 25178-604:2025

Overview

ISO 25178-604:2025 - "Geometrical product specifications (GPS) - Surface texture: Areal - Part 604" defines the design and metrological characteristics of coherence scanning interferometry (CSI) instruments used for non‑contact areal surface topography measurement. This second edition (2025) updates terminology, adds requirements for instrument design, and clarifies metrological characteristics and influence quantities. Because areal topography data can be used to extract surface profiles, the guidance is also applicable to profiling measurements.

Key topics and requirements

• Instrument requirements and information flow: summarized normative features and an information‑flow concept for CSI measurement systems (Clause 4).
• Metrological characteristics: definitions and characteristics relevant to repeatability, uncertainty sources and measurement performance (Clause 5, Annex B).
• Design features: classification and design aspects of CSI instruments including scan mechanics and optics (Clause 6).
• CSI signal fundamentals and terminology: formal definitions of CSI scan, CSI signal (correlogram), interference fringes, modulation envelope, equivalent wavelength, scan length/increment and scanning rate (Clause 3, Annex A).
• Common error sources: informative treatment of influence quantities and uncertainty contributors specific to CSI (Annex B).
• Relation to GPS system: placement within the ISO GPS matrix model and applicability of GPS decision rules (Introduction, Annex C).

Keywords covered naturally in this standard: ISO 25178-604:2025, coherence scanning interferometry, CSI instruments, areal surface topography, non‑contact interferometry, white light interferometry, metrological characteristics.

Practical applications and users

• Who uses it:

  • Metrology labs and calibration facilities
  • Instrument designers and manufacturers of optical profilometers and white light interferometers
  • Quality and process engineers in precision manufacturing, optics, semiconductors and tribology research
  • Standards bodies and testing organizations defining acceptance criteria

• Typical applications:

  • Non‑contact measurement of surface texture and roughness using CSI / white light interferometry
  • Areal topography mapping for functional surface assessment (wear, coating, sealing)
  • Extraction of profile data from areal measurements for legacy specifications
  • Instrument specification, validation and uncertainty analysis during procurement, calibration and reporting

Related standards

• ISO 25178-600 (metrological characteristics for areal methods) - normative reference
• ISO 25178 series (surface texture: areal) and ISO 25178-607 (related optical alignment/geometry)
• ISO 10934, ISO 14638, ISO 8015, ISO 14253-1, ISO/TR 14999-2, ISO 11145 - referenced for coherence, optical and GPS principles

Use ISO 25178-604:2025 when specifying, designing, validating or procuring CSI-based areal measurement systems to ensure consistent, traceable and fit‑for‑purpose surface texture measurement.