Overview
ISO 17901-2:2015 - Optics and photonics - Holography - Part 2 provides standardized terms and measurement methods for determining the exposure characteristics of holograms recorded by double‑beam interference. It defines how to derive quantitative parameters such as the exposure characteristic curve, exposure at half‑maximum, R‑value (diffraction efficiency at a given spatial frequency) and the amplitude of refractive index modulation (Δn). The standard applies to holographic recording materials broadly and does not restrict manufacturing processes.
Key technical topics and requirements
- Measurement basis: All exposure characteristics are derived from measured diffraction efficiency as specified in ISO 17901‑1.
- Defined parameters:
- Exposure characteristic (η–E) curve - diffraction efficiency vs. exposure.
- Exposure at half‑maximum - exposure producing 50% of peak diffraction efficiency (indicator of material sensitivity).
- R‑value - diffraction efficiency for interference fringes of a specified spatial frequency (indicator of resolution).
- Amplitude of refractive index modulation (Δn) - phase modulation capacity of recording material.
- Measurement environment and setup:
- Recordings must be made in a stable, vibration‑free darkroom (air turbulence and mechanical vibration controlled).
- Optical system for double‑beam interference is specified, with coordinate system conventions and wave‑angle definitions.
- Equipment recommendations include a temporally stable laser (example tolerance: ±5% output fluctuation over 30 min), beam‑expanding objective, pinhole and collimation optics.
- Measurement methods:
- Procedures for obtaining the η–E curve, exposure at half‑maximum and R‑value by recording multiple holograms under controlled exposure or spatial‑frequency conditions.
- Methods for obtaining Δn for both transmission and reflection (volume) holograms, including use of the diffraction efficiency and substitution into provided formulas.
- Documentation: Guidance on reporting results and descriptive metadata for reproducible measurements. Informative annexes cover assembly, recording procedures and fringe spacing relations.
Practical applications and users
ISO 17901‑2 is useful to:
- Optical engineers and R&D teams developing recording materials and holographic optical elements (HOEs).
- Quality‑control and test laboratories performing material sensitivity and resolution characterization.
- Manufacturers of holographic security features, data‑storage media, diffractive optics, AR/VR components and imaging systems.
- Researchers comparing recording performance (sensitivity, resolution, Δn) across materials and processes.
Practical uses include material selection, process optimization, acceptance testing and comparative benchmarking of holographic recording media.
Related standards
- ISO 17901‑1:2015 - Methods for measuring diffraction efficiency and associated optical characteristics of holograms.
- ISO 15902 - Diffractive optics vocabulary and related terminology.