Interactive displays have been developed that receive user input from styluses. In one type of implementation, each stylus is linked by a radio link to the interactive display. Upon activation of the stylus, the radio link is established. Once established, when the stylus is placed near the display the stylus can report its X-Y position to the interactive display via the radio link. To ascertain its X-Y position, the stylus makes electrostatic measurements via an electrode at its tip. This electrode receives signals from or transmits signals to electrodes in the interactive display that are arranged in rows and columns and sequentially driven in cycles. The stylus can detect the precise timing at which a capacitance between the electrode tip and a row (or column) underneath is driven high (or, in some cases, is driven low). Based on this, the stylus can ascertain its row (or column) position. In sequential cycles, the stylus ascertains its row and column position. The stylus can report measurements made by the stylus via the radio link to the interactive display, which, in combination with measurements made by electronics within the interactive display, can be used to ascertain the stylus's row and column position. The interactive display can process the input accordingly to display, for example, a GUI element such as a cursor at the reported location of the stylus.
One drawback with such an approach is that the process of establishing the radio link can take a user perceptible amount of time, which can cause frustration for the user. This delay is caused by the fact that the interactive display typically communicates wirelessly on multiple channels with styluses, and hops between the channels by methods such as frequency hopping spread spectrum techniques. At a 60 Hz clock cycle, hopping over a typical 38 channels can cause up to 0.63 seconds of delay under ideal transmission conditions, and longer delays can result under real world transmission conditions in which radio transmissions are interfered with and transmitted data is lost. Delays of this magnitude are perceptible to users, and can cause frustration, for example, in scenarios, such as brainstorming sessions, presentations, etc., where a premium is placed on quick user interaction with the display.
USPTO Backgrounds
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