Overview - ISO 14880-3:2024 (Microlens arrays test methods)
ISO 14880-3:2024 specifies standardized test methods for the optical properties (other than wavefront aberrations) of microlenses in microlens arrays, including very small surface-relief lenses and graded‑index microlenses. The standard focuses on measurable quantities such as effective back/front focal length, chromatic behaviour, focal-spot uniformity, coupling efficiency and imaging quality. It complements ISO 14880-1 (vocabulary) and works with other parts of the series that address wavefront and non‑optical characteristics.
Key topics and technical requirements
- Scope and applicability: Applies to microlens arrays formed on one or more surfaces of a common substrate and to graded‑index microlenses.
- Substrate test: Optical substrate quality contributes to focal‑position accuracy and shall be quantified per ISO 10110-5.
- Microscope technique (primary method):
- Principle: locate lens surface/vertex optically and determine effective back/front focal length from axial displacement to focus on an image of a distant source.
- Test system: microscope with focusing aid (e.g., split‑field), calibrated displacement transducer, suitable light source, test graticule or illuminated fibre, video camera and image analyser.
- Requirement: microscope objective NA must exceed the microlens NA at the focal point.
- Environmental/control: temperature‑controlled, vibration‑free conditions (recommended ~20 °C); clean optical surfaces.
- Interferometry and wavefront‑sensing alternatives: Annex A covers interferometric techniques (e.g., Fizeau, Twyman‑Green) and Annex D describes Shack‑Hartmann methods for focal‑spot mapping.
- Additional methods: Annex B describes confocal measurement of focal length; Annex C discusses coupling efficiency and imaging quality evaluation.
- Calibration and reporting: Use calibration artefacts (known microlens focal length, step‑height standards); report light source properties, measurement uncertainties and test conditions.
Practical applications and users
Who benefits:
- Optical engineers and metrology laboratories validating microlens performance
- Manufacturers of microlens arrays (quality control, acceptance testing)
- System integrators in displays, imaging, 3D displays, VCSEL and detector coupling, and optical parallel processors
- R&D teams developing graded‑index or micro‑optical components
Why use it:
- Ensures repeatable, comparable measurements of focal length, chromatic behavior, focal‑spot uniformity, coupling efficiency and imaging quality
- Improves interchangeability between suppliers and confidence for integration into photonics systems
Related standards