Overview
ISO 25178-605:2025 specifies the design and metrological characteristics of non-contact point autofocus probe (PAP) instruments used for areal surface topography measurements. The standard covers instrument architecture, required components, measurement data flow and the key metrological parameters that influence accuracy and calibration. It applies to areal measurements and to profile measurements derived from areal data.
Key topics and technical requirements
- Instrument composition: A PAP instrument must include a point autofocus probe (PAP) and a lateral x–y scanning system, and save acquired point cloud data to generate areal topography.
- Core components: objective, autofocus sensor, z-position sensor, autofocus mechanism and scanning stage are defined as essential elements.
- Measurement method: Continuous autofocus-based point acquisition while scanning in x and y; profiles can be extracted from the areal dataset.
- Metrological characteristics (to be considered in design and calibration, in addition to ISO 25178‑600 requirements):
- working distance
- spot size
- focus range
- vertical range
- measurable minimum reflection ratio
- autofocus repeatability
- speckle noise
- temperature drift deviation
- beam offset direction
- Information flow and error sources: The document provides an information-flow concept diagram and informative annexes describing PAP principles (Annex A), common measurement errors and influence quantities (Annex B), and the relation to the GPS matrix model (Annex C).
- Design guidance: Clause additions in the 2025 edition emphasize instrument requirements, metrological characteristics and design features relevant to PAP instruments.
Applications and users
ISO 25178-605:2025 is practical for:
- Metrology laboratories performing areal surface texture calibration and verification.
- Instrument manufacturers and designers developing non-contact PAP systems.
- Quality and process engineers in precision manufacturing (bearing surfaces, optical parts, micro-machined components) who need reliable areal surface characterization.
- R&D and academic researchers studying surface topography measurement methods and uncertainty sources.
Practical benefits include standardized requirements for autofocus-based areal measurement, clearer specification of error contributors (e.g., speckle noise, temperature drift), and guidance to improve repeatability and traceability of topography data.
Related standards
- ISO 25178‑600:2019 - Metrological characteristics for areal topography measuring methods (normative reference).
- ISO 25178 series (general areal surface texture standards).
- ISO 14638, ISO 8015 and ISO 14253‑1 - GPS matrix model and decision rules referenced for contextual GPS requirements.
Open preview (PDF)Geometrical product specifications (GPS) — Surface texture: Areal — Part 605: Design and characteristics of non-contact (point autofocus probe) instruments