Complex images for electrostatic problem in parallel-plate conducting structures and three conducting planes

It is well known that the exact images of a point charge in parallel-plate conducting structures are countless. In the Letter, the concept of complex images is introduced to investigate the electrostatic problem in the parallel-plate structures and three conducting planes. It has been shown that only a few complex images which have complex amplitudes and are located at complex positions are used to replace the innumerable exact images, and the error is less than 0.3% when they are used to compute the electrostatic field in the parallel-plate structure and three conducting planes.