Overview
ISO/IEC 29158:2025 - Automatic identification and data capture techniques - Bar code symbol quality test specification - Direct part mark (DPM) specifies how to measure and grade the optical quality of bar code symbols that are directly marked on parts (DPM). It defines modifications to the symbol-quality methodology in ISO/IEC 15415, establishes a dedicated symbology specification for DPM, and introduces alternative illumination conditions, new terms/parameters, and modified measurement and grading procedures. The second edition (2025) replaces the 2020 edition and is intended primarily for verifier manufacturers and application specification developers.
Key topics and technical requirements
- Scope and purpose: Tailors ISO/IEC 15415 for the unique optical characteristics of direct part marks (e.g., dot peen, laser mark, ink‑jetting, electro‑chemical etch).
- Lighting and imaging: Defines alternative illumination conditions and camera setups including perpendicular coaxial (“90”), diffuse off‑axis (“D”), and directional lighting modes (Q, T, S), plus tilted coaxial lighting and procedures to evaluate a virtual 90° camera position.
- Image acquisition and calibration: Requirements for camera position, symbol placement, focus, depth of field, system response adjustment and reflectance calibration.
- Image processing steps: Procedures for initializing aperture size, creating histograms, binarization, applying a reference decode algorithm, and final image adjustments.
- Contrast & reflectance parameters: Methods to calculate cell contrast, module modulation, and minimum reflectance.
- Grading methodology: Rules for grading individual parameters (cell contrast, minimum reflectance, cell modulation), identifying fixed pattern damage, and computing the final grade. The standard also revises rounding rules (now always round down) and aligns definitions with ISO/IEC 15415.
- Reporting & communication: Guidelines for communicating grade requirements and results between verifiers and applications, including handling proprietary decodes.
- Normative and informative annexes: Threshold determination, dot‑connecting algorithm, virtual camera position evaluation, and cross‑reference material to ISO/IEC 15415.
Practical applications and users
- Verifier manufacturers: Implement the measurement and grading algorithms and imaging modes required for DPM verification hardware and software.
- Application specification developers: Define acceptance criteria, inspection plans, and verifier settings for industrial traceability programs.
- Quality/traceability teams and system integrators: Use to specify verification requirements for aerospace, automotive, medical device, electronics and other sectors where durable, on‑part marking is used.
- Marking equipment suppliers: Reference for understanding how marks will be evaluated downstream.
Related standards
- ISO/IEC 15415 - Symbol quality test specification for printed 2D symbols (basis for methodology).
- Cross‑references and comparisons to ISO/IEC 15415 are included in ISO/IEC 29158:2025 to clarify differences for DPM contexts.
Keywords: ISO/IEC 29158:2025, Direct Part Marking, DPM, bar code symbol quality, verifier manufacturers, ISO/IEC 15415, illumination conditions, grading, module modulation, cell contrast.
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