EP0491436A2
Expired / Lapsed
EP
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Matrix display device with write-in facility
Assignee: Philips Electronics UK Ltd
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Filing: 1991-12-12
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Granted: —
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Expires: 2011-12-12
Abstract
Abstract An active matrix liquid crystal display device comprising an array of picture elements (12) which include respective switching means (20), e.g. TFTs, and which are driven a row at a time by drive signals supplied via sets of row and column address conductors (14,16) further includes an array of active addressed sensing elements (18) each consisting of a photosensitive element (26), e.g. a thin film photoresistor or photodiode, charge storage means (25) and a switching device (24), e.g. a TFT, connected to respective row and column address conductors (14,16). The charge storage means are periodically charged through operation of their associated switching devices by said drive signals and are selectively discharged upon their associated photosensitive element being illuminated by, for example, a light pen (41). The states of the charge storage means of all the sensing elements are determined, one row at a time, by a detection circuit (40) connected to the column address conductors (16) during each display field period in synchronism with the driving of the rows of picture elements. <IMAGE>
Inventors
- 👤 John Martin Shannon
- 👤 Alan George Knapp
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 21:06
CPC Classifications
G; G06; G06F; G06F3/00; G06F3/01; G06F3/03; G06F3/041; G06F3/0412; G06F3/042
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
174 words
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, sets of row and column address conductors connected to the picture elements and drive means for applying drive signals to the sets of conductors for driving the picture elements, the display panel further including an array of active addressed sensing elements each comprising a photo-sensitive 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 the row and column address conductors so as to charge the charge storage means, in that the photo-sensitive element of each sensing element is arranged so as to discharge the charge storage means in response the illumination thereof, and in that the device includes detection means connected to the sensing elements for detecting periodically the state of charge of their charge storage means.
Claim 2
Dependent Claim
108 words
An active matrix liquid crystal display device according to Claim 1, characterised in that the drive means is arranged to apply data signals to the column address conductors and a selection signal to each row address conductor in turn so as to operate the switching means of the picture elements associated with the row address conductor to apply the data signals to their respective display elements, and in that the switching devices of each row of sensing elements are operable by a selection signal applied to an associated row address conductor so as to charge the charge storage means of the sensing elements according to the data signals.
Claim 3
Dependent Claim
53 words
An active matrix liquid crystal display device according to Claim 1 or Claim 2, characterised in that the charge storage means of each sensing element comprises a capacitor connected between the switching device of the sensing element and a row address conductor adjacent that associated with the switching means of the sensing element.
Claim 4
Dependent Claim
56 words
An active matrix liquid crystal display device according to Claim 1 or Claim 2, characterised in that the charge storage means of each sensing element comprises a capacitor connected between the switching device of the sensing element and a source of predetermined potential comprising an auxiliary row conductor common to all sensing elements in a row.
Claim 5
Dependent Claim
38 words
An active matrix liquid crystal display device according to any one of the preceding claims, characterised in that the detection means is arranged to determine the state of the sensing element charge storage means during a display field.
Claim 6
Dependent Claim
64 words
An active matrix liquid crystal display device according to Claim 5, characterised in that the detection means is operable to determine the state of the charge storage means of a row of sensing elements associated with a row address conductor each time a drive signal is applied by the drive means to that row address conductor for driving the associated row of picture elements.
Claim 7
Dependent Claim
118 words
An active matrix liquid crystal display device according to Claim 5 or Claim 6, characterised in that the drive means is arranged to apply a selection signal to each row address conductor and data signals to the column address conductors to drive the picture elements with each row address period, defined by the duration of the selection signal applied to a row address conductor, being divided into a detection interval during which the detection means is operable to detect the state of a sensing element associated with that row address conductor followed by a drive interval during which the drive means is operable to apply data signals for the row of picture elements to the column address conductors.
Claim 8
Dependent Claim
58 words
An active matrix liquid crystal display device according to any one of Claims 5 to 7, characterised in that the detection means is arranged to detect the state of charge of the storage means of a sensing element by measuring the charging characteristic of the charge storage means in response to the application thereto of a predetermined potential.
Claim 9
Dependent Claim
79 words
An active matrix liquid crystal display device according to any one of the preceding claims, characterised in that the device further comprises a light emitting means which is movable over the array of sensing elements so as to illuminate the photo-sensitive elements thereof, and in that the photo-sensitive elements are formed so as to have a wavelength dependent photosensitivity which peaks substantially in the region of the spectrum at which the output of the light emitting means is concentrated.
References Cited (Backward Citations)
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