| 摘要 |
PURPOSE:To improve lens characteristics by varying the quantity or range exposure of resist according to gamma characteristics of the resist and approximating the shape of the stepwise saw-tooth waves of the remaining film of the resist to the ideal curve of a micro Fresnel lens. CONSTITUTION:A figure (a) shows variation in the thickness of the remaining film with the quantity of exposure of the resist and a curve in a figure (b) varies the range of exposure, so its gamma characteristics are used as they are. Then, 13-18 of the same exposure are projected on this curve and shifted onto the phase shift function psi(gamma) of an ideal curve in a figure (c) to determine the exposure range of each time in a radius-(gamma) direction. At this time, the thickness of the remaining film remains according to longitudinal axes 25-30, but the exposure range in the radius-(gamma) direction is corrected by the gamma characteristic curve in the figure (b) as to the phase shift function psi(gamma), so the shape of stepwise saw-tooth waves of the remaining resist film which is formed actually conforms to the phase shift function psi(gamma) of the ideal curve in a figure (d). Consequently, lens characteristics such as primary efficiency of convergence and a beam spot diameter are improved. |
