Microlens arrays

Microlens arrays have been fabricated by the direct inkjet printing of an UV curable hybrid polymer (17). A periodic pattern of pol3mer drops was inkjet printed on a surface-treated glass substrate and cured by UV light. 

Periodic arrays of almost semispherical microlenses of 50 /im diameter size and a focal distance of 48 jmi could be obtained. The optical characteristics of the microlenses were measured by infrared methods. 

Large numerical aperture and short focal distance make the inkjet printing of microlenses very attractive for applications in optical interconnects and pixelated imagine sensors. This is a simple and a cheap alternative to the conventionally used photolithography (17). 

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S M oiler and SR Forrest, Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays, J. Appl. Phys., 91 3324-3327, 2001. 

Kobayashi, M., Fnjita, K., Kaneko, T., et al. 2002. Second harmonic generation microscope with microlens array scaimer. Opt. Lett. 27 1324. 

M. C. Hutley, Microlens Arrays (Institution of Physics, Teddington, 1991). 

Wu, H., Odom, T.W., Whitesides, G.M., Reduction photolithography using microlens arrays Applications in gray scale photolithography. Anal. Chem. 2002, 74(14), 3267-3273. 

In a somewhat similar fashion, Ishii et alP- have demonstrated inkjet fabrication of polymeric microlenses for optical chip packaging. UV curable epoxy resin is deposited onto optical devices by inkjet printing. When the droplets hit the surface, they form into partial spheres due to their surface tension, and are UV-cured to form the microlens with diameters from 20 to 40 tm with /-numbers of 1.0 to 11.0. Their uniformity in a microlens array was measured to be within 1% in diameter and 3 tm in pitch (total count of 36 lenses). They have also demonstrated hybrid integration of inkjetted microlenses with a wire-bonded vertical-cavity-surface-emitting laser (VCSEL) with coupling efficiencies of 4 dB higher than without the microlens. 

Peng H-, Ho Y.L., Yu X.-J., Wong M. and Kwok H.-S., Coupling Efficiency Enhancement in Organic Light-Emitting Devices Using Microlens Array-Theory and Experiment, /. Display Technol. 1 (2005) 278... 

J.-Y. Huang, Y.-S. Lu and J.A. Yeh, Self-assembled high NA microlens arrays using global dielectrophoretic energy wells. Optics Express, 14, 10779-10784 (2006). 

Kim J, Serpe MJ, Lyon LA (2005b) Photoswitchable microlens arrays. Angew Chem Int Ed 44 1333-1336... 

Aizenberg, J. and Hendler, G. (2004) Designing efficient microlens arrays Lessons from nature, J. Mater, Chem, 14, 2066. This and the earlier papers make fascinating reading. 

Y.H. Kim, H.S. Jeong, J.H. Kim, E.K. Yoon, D.K. Yoon, H.-T. Jung, Fabrication of two-dimensional dimple and conical microlens arrays from a highly periodic toroidal-shaped liquid crystal defect array. J. Mater. Chem. 20, 6557-6561 (2010)... 

Chandra, D., Yang, S., Lin, P.C. Strain responsive concave and convex microlens arrays. Appl. Phys. Lett. 91(25), 251912 (2007)... 

Yang, S., et al Functional biomimetic microlens arrays with integrated pores. Adv. Mater. 17(4), 435-438 (2005)... 

Wang X, Wilkinson TD, Mann M, Teo KBK, Milne WI. Characterization of a liquid crystal microlens array using multiwalled carbon nanotube electrodes. Appl Opt 2010 49 3311-5. 

Multiscale microlens arrays can be directly fabricated on a hydrophobic flat surface by a simple inkjet printing technique (20). Inorganic/organic hybrid precursor polymers based on silicones are used. These structures are modified with organic structures that can be eventually crosslinked (21). 

A microlens array can be inkjet printed by forming all microlenses in a single pass from the printhead or by multiple passes, where a portion of the microlenses in the microlens array are formed during each pass. When multiple passes are used, generally photocuring of the resin is carried out before the second pass is carried out. Also, by using multiple passes, the spacing between the lenses can be minimized (22). 

S. I. Chang, J. B. Yoon, (2004) "Shape-controlled, high fill-factor microlens arrays... 

We show an example of optical component using a plana microlens array and micro-optical-bench (MOB) as in Fig. 33. This is based on vertical cavity surface emitting laser array and alignment free MOB. 

The microlens array is a useful component for optical interconnections, optical fiber switches, shutters of optical super-resolution devices, light deflection devices, and image processing. In 3-D display systems based on integral photography, the microlens array with dynamically... 

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