Electronic light pen system

Abstract

An electronic light pen used in conjunction with a video display permits the position of the light pen to be determined with respect to the video display by the particular color or grey scale value of light emitted by the video display and received by the electronic light pen. The light from the video display is separated into three primary colors for a color display, namely red, blue, and green, and separated into grey scale shades for a monochrome display. Positional information of the light pen is calculated based on the relation of the color measured to the color previously programmed and presently displayed on that area of the screen, at any instant in time. The light pen has a focusing system that focuses light from the display to its optical detectors. The optical detectors have red, green, and blue filters to determine the brightness of each color. A grey scale value may be determined if the display is monochrome. An optional telephoto lens attachment allows the light pen to be aimed at displays from a distance, or to be used with projection displays. A display can be written with color information to preprogrammed locations on the screen. The colors at each area of the display can be unique, at any instant in time. When that color is read by the light pen the position may be accurately determined. A colored arrow, or other pointer, similar to a conventional mouse pointer, may be created by using software and may be continuously re-displayed to follow the light pen as it points to different parts of the screen, by determining the color gradient encountered by the light pen and re-positioning the arrow underneath the tip of the pen.