Freeform lens arrays for off-axis illumination in an optical lithography system

Abstract

We propose a method of designing a freeform lens array for off-axis illumination (OAI) in optical lithography to produce desired OAI patterns and improve efficiency. Based on the Snell law and the conservation law of energy, a set of first-order partial differential equations are derived and the coordinate relations for each OAI pattern are established. The contours of the freeform lens unit are calculated numerically by solving the partial differential equations, and the freeform lens array is obtained by arraying the lens units. Moreover, the optical performance for each OAI pattern is simulated and analyzed by software. Simulation results show that the irradiance distribution of each OAI pattern can be well controlled with a maximum uniformity of 92.45% and a maximum efficiency of 99.35%. Also, analysis indicates that this method has the advantages of reducing the complexity of the exposure system and having good tolerance to the input intensity variations of the laser beam.

Design of an optical lens combined with a total internal reflection (TIR) freeform surface for a LED front fog lamp

“…Total internal reflection (TIR) lenses are often used in circle and rectangular uniform illumination because of the low light loss and compactness [16][17][18][19]. However, there are still great challenge of applying TIR system for automobile and motorcycle lamps, because the light distribution on the target is required non-symmetrically, and having a clear cut-off line under the horizontal line, such as motorcycle headlight and front fog lamp for automobile.…”

Simultaneous control on the intensity and phase profile of laser beam with Monge-Ampère equation method

“…(6). Based on the analyses presented above, we can find the key to achieving the prescribed beam shaping is to design the first freeform surface.…”

“…This, of course, ensures high degrees of design freedom for laser beam shaping. Being different from some other ray mapping methods [2][3][4][5][6] , for the MA method, it is not necessary to predefine an integrable ray mapping to solve the design model given in Eq. (11), smooth freeform surfaces can be easily obtained.…”

“…There are some traditional methods that can be used to shape the laser beam, which usually utilize some symmetries. Recently, freeform optics becomes very popular in illumination optics [2][3][4][5][6][7][8] due to its high degrees of design freedom. The distinguished features of freeform optics may provide an effective tool to tackle the problem of laser beam shaping.…”

Design of zoom homogenizer to control size of illumination field

“…Researchers have tried to realize the zoom function by modifying the conventional beam homogenizer itself 9 or by adding the lenses to condenser lens part. [10][11][12][13] Several researchers have added a zoom lens to the beam homogenizer and called it a zoom homogenizer. 11,12 In general, zoom lens systems produce a clear image with a fixed image plane at all zoom positions.…”