Whiteboard
Albert Stallion invented whiteboards while working at Alliance in the 1960s. Alliance (now known as PolyVision) produced enameled steel for architectural cladding, but Stallion noted it could also potentially be used as a writing surface. Stallion later left Alliance to form his own whiteboard production company, MagiBoards.
Interactive whiteboard
A few interactive whiteboards can automatically detect projected images during a different type of calibration. The technology was developed by Mitsubishi Electric Research Laboratories Inc and is disclosed in patent 7,001,023. The computer projects a Gray Code sequence of white and black bars on the touch surface and light sensitive sensors behind the touch surface detect the light passing through the touch surface. This sequence allows the computer to align the touch surface with the display; however, it has the disadvantage of having tiny fiber-sized "dead spots" in the resistive touch surface where the light sensors are present. The "dead spots" are so small that touches in that area are still presented to the computer properly.