Current input apparatus available for information systems includes keyboard, mouse, trackball, light pen, and touch panel. The trackball is not suitable to be used for writing on an upright screen. The light pen is only available for the inputs on a scanning screen such as Cathode-Ray Tube (CRT) screen, but not for the inputs on a high resolution screen. The touch panel is disadvantageous to alignment and portability for larger-scale screens. Due to the significant barrel or pincushion distortion of the optical lens, the input systems using conventional sensors may often suffer the alignment degradation caused by the mistakes or unintentional touches to the equipment, and even have to be suspended during its use accordingly. Therefore, single keyboard and/or single mouse installed on a computer system is still relied on currently for the inputs to an information system using an upright large-scale screen. However, single input apparatus is inconvenient for use in the situation where multiple inputs from several persons or opinion exchanges between several persons are required.
Therefore, it is desired a pointing input system and method easy for alignment, capable of precise positioning, and available for high resolution applications.