Profile control technology for high-performance microlens array

A profile formation and control approach has been developed for manufacturing micro-optical elements with continuous profile and deep relief depth. Based on Dill's exposure model, an effective expression for determining the exposure dose function is established by using a supposition of equivalent exposure threshold inside a resist layer. An analytical simplified formula is further deduced by taking absorbance as constant B, and the approximate condition is discussed. For evaluating the simplified formula, the profile error was calculated and analyzed by simulation. With the exposure dose function, the binary mask for manipulating the light distribution by means of a moving-mask lithographic method can be designed. Experimental results are given and show the comparative performance to the required profile and relief depth. A series of refractive microlens arrays with aspherical profiles, a wide range of numerical apertures (0.005 to 0.6), and high fill factors were accomplished in the lab and may be applied to many systems. (C) 2004 society of Photo-Optical Instrumentation Engineers.