Study on off-axis illumination
Zhou C., Lin D., Feng B., Fan J., Cui Z.
The principle of off-axis illumination for improving photolithographic resolution and increasing the depth of focus was presented. The Hopkings imaging theory for calculating the intensity distribution of space image was used, and some results of quadrupole illumination and annular illumination were given. The results showed that the resolution was improved and the depth of focus was increased by off-axis illumination.