Various types of light source, including those in use in pixel based display devices, may be used for light-simulated bar codes. Liquid crystal displays (“LCD”) which utilize a backlight for screen brightness may, for example, be very effective for producing light-simulated bar codes because the entire backlight may be modulated to provide the desired light/dark sequence. Even displays which have no backlight, for example but not limited to OLED and LED displays, may be used for light-simulated bar codes. While the entire display may be used, single pixels or pixel groups of the displays of such displays may be used.