Stray Light Considerations
Common Sources in MLA Systems:
Autofluorescence: See Glossary
Surface Scatter: Caused by micro-scale surface roughness or particulate contamination on lens surfaces.
Diffraction: As the patterned structures approach the wavelength of light used in the optical system, managing this light becomes more critical.
Profile Transitions: Occurs in the blending zones between adjacent microlenses where the curvature is not perfectly continuous or deviates from the design profile.
Edge Effects: Arise near the perimeter of an MLA where lenslets may be incomplete or irregularly shaped.
Internal Reflections: From uncoated or poorly matched interfaces, such as air-polymer boundaries, especially when no anti-reflection (AR) coating is applied.
Defects and Imperfections: Includes voids, bubbles, or surface deformations introduced during replication, molding, or curing processes.
Consequences of Stray Light:
Degraded image contrast or signal-to-noise ratio in imaging systems
Background illumination artifacts in projection or structured light applications
Crosstalk between adjacent pixels or wavefront regions
Misleading metrology results in laser-based or beam shaping setups
Mitigation Strategies:
Specifying low-RMS surface roughness (<10 nm typical)
Optimizing lens profile transitions with high-fidelity grayscale or laser patterning
Application of conformal AR coatings to minimize reflections
Designing with aperture or masking at array edges and transition zones
Using materials with low internal scatter and minimal autofluorescence
In high-performance MLA applications such as AR/VR optics, fluorescence microscopy, or sensor development, stray light control is a critical design parameter and often specified alongside surface roughness, RoC uniformity, and transmission.