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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 4 — Feb. 13, 2012
  • pp: 4763–4775

Laser lithographic approach to micro-optical freeform elements with extremely large sag heights

Jens Dunkel, Frank Wippermann, Andreas Brückner, Andreas Bräuer, and Andreas Tünnermann  »View Author Affiliations


Optics Express, Vol. 20, Issue 4, pp. 4763-4775 (2012)
http://dx.doi.org/10.1364/OE.20.004763


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Abstract

Artificial compound eye cameras are an attractive approach to generate imaging systems of maximum miniaturization. Their thickness can be reduced by a factor of two in comparison to miniaturized single aperture cameras with the same pixel size and resolution. The imaging performance of these systems can be improved significantly by the use of micro-optical refractive freeform arrays (RFFA). Due to the complexity of these non-symmetric surface profiles with sag heights larger than 50 µm in combination with extreme profile accuracies better than λ/14 (rms), there is no dedicated fabrication technology currently available. In the presented research, significant improvements in the fabrication of these elements with laser lithography were reached. Therefore, a laser lithographic process based on several coating steps in combination with a multiple exposure strategy was developed that is suitable for the fabrication of arbitrary freeform structures with sag heights up to 60 µm. In order to minimize surface deviations caused by unavoidable process nonlinearities, a compensation strategy based on an empirical process model is used. The achievable accuracy of the proposed method and its limitations were investigated by fabricating a spherical micro lens array for demonstration. The fabricated elements possess a shape deviation of less than 1.3 µm (rms) and can be used as master structures for a subsequent replication process in order to realize a cost efficient mass production of artificial compound eye optics on wafer level.

© 2012 OSA

OCIS Codes
(110.0110) Imaging systems : Imaging systems
(220.3740) Optical design and fabrication : Lithography
(220.4000) Optical design and fabrication : Microstructure fabrication
(330.1720) Vision, color, and visual optics : Color vision
(350.3950) Other areas of optics : Micro-optics

ToC Category:
Optical Design and Fabrication

History
Original Manuscript: November 22, 2011
Revised Manuscript: February 3, 2012
Manuscript Accepted: February 3, 2012
Published: February 10, 2012

Virtual Issues
Vol. 7, Iss. 4 Virtual Journal for Biomedical Optics

Citation
Jens Dunkel, Frank Wippermann, Andreas Brückner, Andreas Bräuer, and Andreas Tünnermann, "Laser lithographic approach to micro-optical freeform elements with extremely large sag heights," Opt. Express 20, 4763-4775 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-4-4763


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