ISO 25178-606:2015

Overview

ISO 25178-606:2015 - part of the ISO 25178 areal surface texture family - specifies the nominal metrological characteristics of non-contact surface texture measuring instruments that use focus variation (FV) sensors. It defines terminology, measurement coordinate systems, instrument components, and the influence quantities that affect areal topography measurements made with FV microscopes. Informative annexes describe FV microscope components and relate the standard to the GPS matrix model.

Key topics and technical requirements

This standard focuses on the metrological behaviour and characteristics of FV-based areal surface texture instruments. Key technical topics include:

• Scope of measurement: definition of the measuring volume, coordinate system (x, y, z) and the measurement loop connecting probe, positioning, and workholding.
• Terms and definitions: harmonized vocabulary for areal methods and FV-specific concepts (for example, areal reference, surface probe, sampling interval).
• Instrument response and linearity: concepts such as response curve and amplification coefficient used to characterize how measured quantities relate to actual quantities.
• Noise and repeatability: definitions of instrument noise and measurement noise, and surface topography measurement repeatability as a metric for measurement uncertainty.
• Spatial and height resolution: parameters like sampling interval (x, y), digitisation step in z, lateral resolution, and width limit for full height transmission, which influence the ability to detect surface features.
• Influence quantities: identification and description of factors (optical, mechanical, environmental, and processing) that affect FV measurements.
• Informative guidance: Annex A (components of a focus variation microscope) and Annex B (relationship to the GPS matrix model) to aid interpretation and implementation.

The document references and aligns terminology and concepts with other ISO GPS documents and metrology standards (listed in the normative references).

Practical applications and who uses this standard

ISO 25178-606:2015 is used by professionals who specify, develop, validate or interpret areal surface texture measurements made with focus variation instruments:

• Metrology and calibration laboratories establishing instrument performance baselines and uncertainty budgets
• Instrument manufacturers designing and documenting FV microscopes and specifying nominal characteristics
• Quality and process engineers in precision manufacturing (automotive, aerospace, medical devices, optics) who rely on non-contact topography data for part acceptance
• Research organizations and universities studying surface functional performance and measurement method comparison
• Standards bodies and test houses harmonizing surface texture metrology across methods

Related standards

ISO 25178-606 is part of the ISO 25178 series. Closely related documents include:

• ISO 25178-1/-2/-3 (general areal surface texture concepts and parameters)
• ISO 25178-6 (classification of measuring methods)
• ISO 25178-601/602/603/604/605 (nominal characteristics for other probe types)
• ISO 14978 and ISO 17450 (general GPS metrology concepts)

Keywords: ISO 25178-606, focus variation, FV microscope, areal surface texture, non-contact instruments, metrological characteristics, surface topography, measurement noise, sampling interval, lateral resolution.