Matrix display device with write-in facility
First Claim
1. An active matrix liquid crystal display device comprising:
- a display panel having an array of picture elements each comprising a liquid crystal display element and an associated switching means, a set of row address conductors and a set of column address conductors connected to the picture elements, drive means for applying drive signals to the set of row address conductors and to the set of column address conductors for driving the picture elements, said drive means being arranged to apply data signals to the column address conductors and a selection signal to each row address conductor individually in turn so as to operate the switching means of the picture elements associated with the selected row address conductor thereby to apply the data signals to their respective display elements, the display panel further including an array of active addressed sensing elements each comprising a photosensitive element and a switching device, wherein the sensing elements each include a charge storage means which is connected to the switching device, wherein the switching devices of each row of sensing elements are each connected to a said row address conductor and a said column address conductor and are operable by a said selection signal applied to an associated row address conductor of said set of row address conductors so as to charge the charge storage means of the sensing elements according to the level of the data signals, wherein the photosensitive element of each sensing element is connected so as to discharge the charge storage means in response to the illumination thereof, and detection means connected to the sensing elements for periodically detecting the state of charge of their respective charge storage means.
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Abstract
An active matrix liquid crystal display device in which an array of picture elements which include respective switching means, e.g. TFTs, are driven a row at a time by drive signals supplied via a set of row and a set of column address conductors. The device also includes an array of active addressed sensing elements each consisting of a photosensitive element, e.g. a thin film photoresistor or photodiode, a charge storage capacitor and a switching device, e.g. a TFT. The sensing element connected to respective row and column address conductors. The charge storage capacitors are periodically charged through operation of their associated switching devices by the drive signals and are selectively discharged via their associated photosensitive element when illuminated by, for example, a light pen. The states of the charge storage capacitors of all of the sensing elements are determined, one row at a time, by a detection circuit connected to the column address conductors during each display field period in synchronism with the driving of the rows of picture elements.
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Citations
25 Claims
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1. An active matrix liquid crystal display device comprising:
- a display panel having an array of picture elements each comprising a liquid crystal display element and an associated switching means, a set of row address conductors and a set of column address conductors connected to the picture elements, drive means for applying drive signals to the set of row address conductors and to the set of column address conductors for driving the picture elements, said drive means being arranged to apply data signals to the column address conductors and a selection signal to each row address conductor individually in turn so as to operate the switching means of the picture elements associated with the selected row address conductor thereby to apply the data signals to their respective display elements, the display panel further including an array of active addressed sensing elements each comprising a photosensitive element and a switching device, wherein the sensing elements each include a charge storage means which is connected to the switching device, wherein the switching devices of each row of sensing elements are each connected to a said row address conductor and a said column address conductor and are operable by a said selection signal applied to an associated row address conductor of said set of row address conductors so as to charge the charge storage means of the sensing elements according to the level of the data signals, wherein the photosensitive element of each sensing element is connected so as to discharge the charge storage means in response to the illumination thereof, and detection means connected to the sensing elements for periodically detecting the state of charge of their respective charge storage means.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A display device comprising:
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a matrix array of picture elements each of which includes an electro-optical display element connected to a first switching device, a plurality of row and column address conductors coupled to the picture elements, drive means for periodically applying drive selection signals to the row address conductors and data signals to the column address conductors for selectively driving rows of picture elements in turn according to the data signals, an array of sensing elements each comprising a photosensitive element, a second switching device, and a charge storage means coupled to the photosensitive element and to a respective column address conductor via its respective second switching device, said sensing element being coupled to said row and column address conductors so that the second switching devices are operated by said drive selection signals applied to the row address conductors so as to selectively charge the charge storage means according to the level of said data signals on the column address connectors, wherein the photosensitive element of each sensing element is connected so as to discharge its charge storage means in response to illumination of said photosensitive element during a first time interval, and detection means connected to the sensing elements so as to periodically detect the state of charge of the respective charge storage means of the sensing elements during a second time interval. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 24, 25)
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22. An active matrix liquid crystal display device comprising:
- a display panel having an array of picture elements each comprising a liquid crystal display element and an associated switching means, a set of row address conductors and a set of column address conductors connected to the picture elements, drive means for applying drive signals to the set of row address conductors and to the set of column address conductors for driving the picture elements, the display panel further including an array of active addressed sensing elements each comprising a photosensitive element and a switching device, characterised in that the sensing elements each include a charge storage means which is connected to the switching device, in that the switching devices are operable by the drive signals applied to said row and column address conductors so as to charge the charge storage means, in that control electrodes of the switching means and the switching devices in a given row of display elements are connected to a common row address conductor whereby the switching means and the switching devices of said given row are simultaneously activated into conduction by a drive signal applied to said common row address conductor, in that the photosensitive element of each sensing element is connected so as to discharge the charge storage means in response to the illumination thereof, and detection means connected to the sensing elements for periodically detecting the state of charge of their respective charge storage means.
- View Dependent Claims (23)
Specification