Patent EP0458513A1 successfully refreshed from Google Patents.
EP0458513A1
Expired / Lapsed
EP
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LCD touch screen
Assignee: HP Inc
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Filing: 1991-05-14
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Granted: —
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Expires: 2011-05-14
Abstract
Abstract A touch screen (10) includes a liquid crystal display (LCD) having a viewing surface (23) through which light passes into and out of the display and a back surface comprising a transflector (26) such as transflective film. The transflector (26) reflects some of the light back through the display and viewing surface (23) and transmits some of the light. An array (28) of light dependent resistors (34) or equivalent light detecting devices underlie the transflector (26) and detect a change in the transmitted light caused by a touching of the viewing surface (23). The light detecting array (28) may be integrated into a keyboard interface (42). In such a case, keys are displayed on the viewing surface (23) opposite resistors in the array (28) to indicate where the viewing surface (23) must be touched to actuate the key.
Inventors
- 👤 Gregory J. May
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 15:26
CPC Classifications
G; G06; G06F; G06F3/00; G06F3/01; G06F3/03; G06F3/041; G06F3/042; G06F3/0421; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/1333; G02F1/13338
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
73 words
A touch screen (10) comprising: a liquid crystal display having a viewing surface (23) through which light passes into and out of the display and a back surface comprising a transflector (26) for reflecting some of the light back through the display and for transmitting some of the light; and light detecting means (28) for detecting a change in the light transmitted through the transflector caused by a touching of the viewing surface.
Claim 2
Dependent Claim
28 words
The touch screen of claim 1 in which the light detecting means comprises a light dependent resistor (34) whose resistance varies with the intensity of the light detected.
Claim 3
Dependent Claim
16 words
The touch screen of claim 1 in which the light detecting means comprises a phototransistor (38).
Claim 4
Dependent Claim
16 words
The touch screen of claim 1 in which the light detecting means comprises a photodiode (36).
Claim 5
Dependent Claim
34 words
The touch screen of claim 1 including threshold adjustment means (60-76) for adjusting the threshold level of transmitted light that the light detecting means must detect to indicate a touching of the viewing surface.
Claim 6
Dependent Claim
29 words
The touch screen of claim 5 in which the threshold adjustment means comprises a comparator (60) for comparing output of the light detecting means against an adjustable reference level.
Claim 7
Dependent Claim
30 words
The touch screen of claim 5 in which the threshold adjustment means comprises an analog-to-digital converter (76) for comparing output of the light detecting means against an adjustable reference level.
Claim 8
Dependent Claim
48 words
The touch screen of claim 1 including signaling means (42) coupled to the light detecting means for producing a signal in response to a detection of a change in transmitted light caused by a touching of the viewing surface, the signal produced indicating the location of the touch.
Claim 9
Dependent Claim
60 words
The touch screen of claim 8 in which the signaling means comprises a keyboard interface (42) having a matrix of conductive lines coupled together at intersections by separate light detecting means, each light detecting means being a key that may be actuated by touching the viewing surface at a location that limits the light transmitted to the light detecting means.
Claim 10
Dependent Claim
33 words
The touch screen of claim 1 including means (32) for controlling the liquid crystal display to indicate where the viewing surface must be touched for the light detecting means to detect the touch.
Claim 11
Dependent Claim
21 words
The touch screen of claim 1 in which the light detecting means (28) comprises a plurality of separate light detecting devices.
Claim 12
Dependent Claim
139 words
A touch screen (10) comprising: a liquid crystal display having a viewing surface (23) through which light passes into and out of the display and a back surface comprising a transflector (26) for reflecting some of the light back through the display and for transmitting some of the light; a plurality of separate light detecting means (28) underlying the transflector for detecting a change in the light transmitted through the transflector caused by a touching of the viewing surface; and a keyboard interface (42) comprising a conductive line connected to each separate light detecting means, each such means being a key that may be actuated by touching the viewing surface at a location that limits the light transmitted to the light detecting means sufficiently for the means to change the logic state of a signal on the connected line.
Claim 13
Dependent Claim
37 words
The touch screen of claim 12 in which the light detecting means comprises light dependent switches (44) and the keyboard interface (42) includes a matrix of conductive lines coupled together at intersections by separate light dependent switches.
Claim 14
Dependent Claim
22 words
The touch screen of claim 13 in which the keyboard interface includes lines connected to keys (46) other than light detecting switches.
Claim 15
Dependent Claim
149 words
A touch screen (10) comprising: a liquid crystal display having a viewing surface (23) through which light passes into and out of the display and a back surface comprising a transflector (26) for reflecting some of the light back through the display and for transmitting some of the light; a plurality of separate light detecting means (28) adjacent to the transflector for detecting a change in the light transmitted through the transflector caused by a touching of the viewing surface; signaling means (42) coupled to the separate light detecting means for producing a signal in response to a detection of a change in transmitted light caused by a touching of the viewing surface, the signal produced indicating the location of the touch; and means (32) for controlling the liquid crystal display to indicate where the viewing surface must be touched for a light detecting means to detect the touch.
References Cited (Backward Citations)
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