Overview
IEC 62906-5-4:2018 - “Laser display devices - Part 5-4: Optical measuring methods of colour speckle” defines how to characterize and measure colour speckle produced by laser display devices (LDDs). The standard specifies the fundamental colour speckle distribution in CIE colour systems and provides both calculation-based and direct optical measurement methods. This edition (1.0, 2018-01) includes the corrigendum of June 2022.
Key technical topics and requirements
The document is structured to guide repeatable, traceable measurement and analysis of colour speckle. Major topics include:
- Theory of colour speckle: mechanisms that generate colour speckle and its representation in CIE colour systems.
- Calculation methods: procedures for estimating colour speckle from component (B/G/R) behaviour, including:
- Spectral behaviour measurement of BGR laser sources.
- Target chromaticity and BGR power-ratio adjustment.
- Two calculation approaches: (a) using monochromatic speckle contrasts (Cs‑B, Cs‑G, Cs‑R) and (b) using measured spatial distributions of monochromatic speckles.
- Evaluation metrics, background‑effect elimination, and error analysis (including data‑size effects).
- Direct measuring methods: instrument design and measurement geometries using laser measuring devices (LMDs) with XYZ or BGR filter sets, plus flow charts and example setups.
- Spatial variation measurements: angular colour speckle variation, photometric speckle-contrast uniformity/non‑uniformity, and variance/covariance assessments.
- Calibration and annexes: procedures for calibrating XYZ mismatches, example distributions, and informative explanations to support interpretation.
The standard includes illustrative figures, flow charts and tables to support implementation (measurement geometries, sample distributions, and metric examples).
Practical applications and users
IEC 62906-5-4 is intended for professionals who design, test or certify laser-based displays and projection systems, including:
- Laser display manufacturers - to quantify speckle performance during R&D and production.
- Optical engineers and systems integrators - to optimize B/G/R balance, optics, and speckle mitigation strategies.
- Test and calibration laboratories - to implement standardized measurement procedures and report comparable metrics.
- Standards bodies and certification agencies - to assess compliance and consistency across devices.
- Academic researchers studying speckle phenomena and visual quality in laser displays.
Using the standard helps assess visual quality (speckle perceptibility), compare devices objectively, support product specifications, and guide speckle-reduction design choices.
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