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Microlens Arrays

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Microlens arrays (MLAs)—sometimes called lenslet arrays—are planar optical components made up of hundreds to millions of miniature lenses arranged on a common substrate.[1] Typical lenslet diameters range from ≈10 µm to a few millimetres, and array pitches can be as small as 3 µm.[2]

Key characteristics

  • Materials – Glasses (e.g. BK7, fused silica), semiconductor wafers (Si), and polymers (PMMA, PC) are common. UV-grade fused-silica transmits from 193 nm up to ≈2.6 µm.[3]
  • Lenslet geometry – Circular, square or hexagonal footprints with spherical, aspheric or freeform surfaces.[4]
  • Fill factor – Hexagonal packing offers ≈91 % theoretical maximum for circular lenses; sub-100 nm border designs push practical values beyond 95 %.[2]
  • Focal length & NA – From sub-mm to >100 mm; NAs up to 0.9 have been demonstrated for high-index Si MLAs.[5]
  • Coatings – Broadband anti-reflection and IR-pass filters are routinely deposited to raise transmission above 98 %.[6]

Fabrication

| Method | Notes | |-|-| | Photolithography + (grey-scale or binary) etching | Wafer-level, sub-µm alignment.[4] | | Photoresist reflow | Low-cost, high fill-factor hemispheres.[2] | | Two-photon polymerisation | True free-form masters.[5] | | Nano-imprint / hot embossing | High-volume plastic replication.[1] | | Precision glass moulding (PGM) | Direct glass MLAs with <0.3 µm form error.[7] |

VR / AR relevance

  • Near-eye light-field displays – A micro-display covered by an MLA recreates angular light-rays, enabling vergence-accommodation cues.[8]
  • Heterogeneous curved eyepieces – Combining freeform lenslets of varying power yields 180° FOV while staying <15 mm thick.[9]
  • Efficiency vs. pancake optics – A single-pass MLA eyepiece avoids the ≈12 % transmission ceiling measured in holographic pancake stacks.[10]
  • Tunable focus – Electrowetting and liquid-crystal MLAs provide millisecond focal sweep for gaze-contingent blur.[11]
  • Pixel-level collimation for µLED waveguides – Lithographically-formed microlenses atop each emitter triple the usable luminous flux at 20° cone angles.[12]
  • Depth sensing / ToF – VCSEL arrays paired with diffusing MLAs produce uniform spots for Face-ID-class modules.[13]
  • Wavefront sensing & adaptive optics – Shack–Hartmann sensors rely on MLAs to subdivide the pupil; metasurface replacements are under study but classic MLAs remain dominant.[14]

Commercial status – As of April 2025 no major consumer headset maker has publicly confirmed shipping an MLA-based eyepiece or light-field module, although multiple prototypes (NVIDIA NELD, ThinVR, Limbak-Meta collaboration) have been demonstrated at academic or industry conferences.[8][9]

See also

References

  1. ↑ 1.0 1.1 Hutley M. C., Stevens R. F., Daly D. & Davies N. (1994). Microlens arrays. IOP Publishing.
  2. ↑ 2.0 2.1 2.2 Wong S. Y. et al. (2018). “High-fill-factor cylindrical microlens arrays via thermal reflow.” Applied Optics, 57 (25) 7296–7303.
  3. ↑ Thorlabs, “UV-grade fused-silica optics datasheet,” 2025.
  4. ↑ 4.0 4.1 Hao Y. et al. (2020). “Large-scale curved microlens arrays on flexible substrates.” Nature Scientific Reports, 10 (1) 11328.
  5. ↑ 5.0 5.1 Gissibl T. et al. (2016). “Two-photon direct laser writing of ultracompact multi-lens objectives.” Nature Photonics, 10 (8) 554–560.
  6. ↑ Jain C. (2023). “High-accuracy precision microlens arrays.” Physik in Unserer Zeit, 54 (2) 66–71.
  7. ↑ Liu Z. et al. (2024). “Alignment error control of double-sided glass MLAs.” Microsystems & Nanoengineering, 10 7.
  8. ↑ 8.0 8.1 Lanman D. & Luebke D. (2013). “Near-eye light-field displays.” ACM TOG, 32 (6) 220.
  9. ↑ 9.0 9.1 Azuma R. et al. (2020). ThinVR project, retrieved 2025-04-25.
  10. ↑ Lee J-H. et al. (2022). “Holographic pancake optics for thin see-through displays.” Optics Express, 29 (22) 35206.
  11. ↑ Kim J. et al. (2020). “Electrowetting liquid MLA for AR integral imaging.” Optics Letters, 45 (2) 511–514.
  12. ↑ Jade Bird Display, “Pixel-Optics for microLED,” White-paper 2022.
  13. ↑ Apple Patent US11571039 B2, 2022.
  14. ↑ Smith T. et al. (2024). “Meta-lens array Shack–Hartmann sensor.” Light: Science & Applications, 13 37.
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