Solid Microlenses

This chapter focuses on examples of microlenses made of solids whose focal lengths cannot be tuned during their operations. Microlenses with fixed focal lengths whose focal points are shifted by moving their positions are also discussed in this chapter. These non-tunable microlenses include  

Microlens arrays fabricated through molding processes Injection-molded plastic lenses 

Self-assembled supermolecular nanoscale spherical lenses 

Lenses fabricated by direct photo-induced polymerization 

Lens arrays fabricated from melting polystyrene beads 

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Solid microlenses and microlens arrays have been studied and used for more than twenty years [12], Some applications of microlens arrays such as beam shaping [46], focusing light onto CCD arrays [47], and Shack-Hartmann wave-front sensors [10] have been commercialized. Applications of solid microlens arrays are covered extensively in Daly s book [12]. In this book, we will cover some new applications and fabrications of solid microlenses and microlens arrays in Chapter 4, and will focus on tunable microlenses. 

After UV exposure, the third step was to remove the stamper. At this stage, the solid planoconcave microlens arrays were formed on the bottom substrate as in Figure 5.8c. When the sample was heated from the stamper side, the stamper could be easily peeled off without damaging the concave polymer microlens. The final step was to inject the LC-monomer mixture into the recessed portions of the concave polymer microlenses and to seal them with a top ITO glass substrate (Figure 5.8d). 

X. Zeng and H. Jiang, "An endoscope utilizing tunable-focus microlenses actuated through infrared light," in The 15th International Conference on Solid-State Sensors, Actuators and Microsystems Denver, CO, USA, 2009, pp. 1214-1217. 

In the previous chapters, we discussed the importance of microlenses in communications, imaging, lithography, displays, and sensors. Although microlenses have undergone rapid development in recent years, most studies of microlenses, especially tunable types, are still preliminary, and their market applications remain limited. The most common applications are solid microlens arrays, as discussed in Chapter 4. Microlenses with different characteristics such as size, focal length, and fill factor are commercially available. 

The history of microlenses spans more than 400 years. With the development of microscale fabrication methods, microlenses have in the past decades drawn a lot of interest and found many applications, many of which are unique. The intriguing feature of most of these microlenses is that they all involve liquids some are formed directly from liquids some use liquids during operation some are solid but their fabrication involves liquids. Therefore, in this book, we aim to examine the recent progress in the emerging and fascinating field of liquid-based microlenses. 

Saitoh A., Gotoh T, and Tanaka K., Chalcogenide-glass microlenses for optical fibers,/. Non-Cryst. Solids, 299302,983-987 (2002). 

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