Liquid crystal display integrated with hall effect pointing device

• US 5,389,951 A
• Filed: 07/21/1993
• Issued: 02/14/1995
• Est. Priority Date: 07/21/1993
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Baker, Robert G.
• Primary Examiner(s): Oberley, Alvin E.
• Assistant Examiner(s): GOON, GIN F
• Application Number:
  US08/095,626
• Time in Patent Office: 573 Days
• Field of Search: 345/104, 345/173, 345/174, 345/175, 345/177, 345/179, 345/180, 345/182, 345/92, 178/18, 178/19
• US Class Current: 345/174
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

A liquid crystal display (LCD) is constructed in layers including an integrated circuit layer containing thin film transistors (TFTs) for controlling activation of individual liquid crystal cells, and selectively actuatable Hall effect elements (HEEs) for controlling operation of the TFTs. The display operates in different modes including operating solely as an output device, or as an input device, or both. Each HEE and TFT is contained in a cell circuit that further includes a switch operable in a plurality of modes in accordance with the settings of mode control signals and cell selection signals. A magnetic actuator produces a magnetic field for selectively actuating cells. Cell circuits produce output signals dependent on the polarity of the actuating magnetic field. An alternate cell circuit allows a cell to be actuated by a field of one polarity and deactuated by a second field of the opposite polarity.

Claims

1. Liquid crystal display apparatus comprising:

a liquid crystal display (LCD) comprising a layer of liquid crystal cells (LCCs) each containing liquid crystal material, said LCCs being arranged in a rectangular array;

a magnetic actuator that is selectively movable adjacent to said LCD and said LCCs for selectively actuating said LCCs; and

a substrate positioned adjacent said layer, said substrate having a plurality of cell circuits, each cell circuit being positioned adjacent a different LCC and comprising

a thin film transistor (TFT) for actuating liquid crystal material adjacent thereto in response to a control signal applied to such TFT,

a Hall sensor cell (HSC) comprising a Hall effect element (HEE) and signal conditioning circuitry coupled to said HEE for generating a first control signal in response to actuation of said HEE by said actuator, and

a switch having a first control signal input coupled to said signal conditioning circuitry for receiving said first control signal therefrom, said switch further having an output coupled to said TFT for transmitting a control signal thereto, said switch having a plurality of modes of operation including a first mode in which control signals generated by said signal conditioning circuitry are propagated through said switch and applied to said TFT to thereby actuate said liquid crystal material when said actuator is adjacent said HEE.

2. Liquid crystal display apparatus in accordance with claim 1 further comprising:

video processing means coupled to said cell circuits for generating and transmitting second control signals; and

in each cell circuit, said switch has a second control signal input for receiving second control signals from said video processing means, said switch having a second mode of operation in which said second control signals from said video processing means are applied to said TFT for actuating liquid crystal material adjacent to said TFT.

3. Liquid crystal display apparatus in accordance with claim 2 comprising:

a computer coupled to said video processing means; and

said switch in each cell circuit has a third mode of operation in which said first control signal from said HSC is inputted into said computer.

4. Liquid crystal display apparatus in accordance with claim 3 comprising:

mode control means for generating mode control signals for controlling operation of said switches; and

each switch comprises mode input means for receiving said mode control signals for selectively setting said switch to operate in accordance with said mode control signals.

5. Liquid crystal display apparatus in accordance with claim 4 comprising:

I/O line means connected to said video processing means for selectively transmitting said second control signals to said TFTs when said switches are set to operate in said second mode and transmitting said first control signals to said computer when said switches are set to operate in said third mode.

6. Liquid crystal display apparatus in accordance with claim 5 wherein said mode control means operates to switch back and forth between said second and third modes to thereby time multiplex transmitting said second and first control signals on said I/O line means thereby concurrently operating said LCD as both an output device in which information from said computer is displayed and an input device in which information can be entered into said computer by manipulation of said actuator.

7. Liquid crystal display apparatus in accordance with claim 5 comprising:

cell selection means coupled to said switches for selectively enabling said switches one-at-a-time to input said first control signals into said computer when said switches are set to said third mode and to selectively actuate said LCCs one-at-a-time when said switches are set to said second mode.

8. Liquid crystal display apparatus in accordance with claim 7 wherein:

said LCCs and said cell circuits are arranged in columns and rows; and

said cell selection means comprises a plurality of row lines, each row line being connected to a plurality of switches in a row, and each column line being connected to a plurality of switches in a column, whereby a given switch is enabled by coincident active signals on said row line and said column line connected thereto.

9. Liquid crystal display apparatus in accordance with claim 8 wherein said I/O line means comprises a plurality of sense lines each connected to a plurality of switches in a different column.

10. Liquid crystal display apparatus in accordance with claim 9 wherein each cell circuit further comprises:

a differential amplifier coupled to said HEE in such cell for receiving said Hall effect voltage therefrom, said differential amplifier producing an output signal proportional to said Hall effect voltage produced by said HEE connected thereto, and

a trigger connected to said differential amplifier for producing a digital output signal indicating when said voltage from said differential amplifier is above a predetermined magnitude.

11. Liquid crystal display apparatus in accordance with claim 10 wherein each cell circuit further comprises:

a second HEE;

a second differential amplifier coupled to said second HEE in such cell for receiving said Hall effect voltage therefrom, said second differential amplifier producing a second output voltage signal proportional to said Hall effect voltage produced by said second HEE connected thereto, and

a second trigger connected to said second differential amplifier for producing a second digital output signal indicating when said second output voltage signal from said second differential amplifier is greater than a second predetermined value when said second HEE is actuated by a magnetic field having a polarity opposite to that which actuates said first mentioned HEE in such cell.

12. Liquid crystal display apparatus comprising:

a liquid crystal display (LCD) comprising a layer of liquid crystal cells (LCCs) each containing liquid crystal material, said LCCs being arranged in a rectangular array;

a magnetic actuator that is selectively movable adjacent to said LCD and said LCCs for selectively actuating said LCCs;

a substrate positioned adjacent said layer, said substrate having a plurality of cell circuits, each cell circuit being positioned adjacent a different LCC and comprising

a thin film transistor (TFT) for actuating liquid crystal material adjacent thereto in response to a control signal applied to such TFT,

a Hall sensor cell (HSC) comprising a Hall effect element (HEE) for generating a Hall effect voltage, a differential amplifier coupled to said HEE for receiving said Hall effect voltage therefrom, said differential amplifier producing an output signal proportional to said Hall effect voltage produced by said HEE connected thereto, and a trigger connected to said differential amplifier for producing a digital output signal indicating when said voltage from said differential amplifier is above a predetermined magnitude and thereby generating a first control signal in response to actuation of said HEE by said actuator,

a switch having a first control signal input coupled to said trigger for receiving said first control signal therefrom, said switch further having an output coupled to said TFT for transmitting a control signal thereto, said switch having a plurality of modes of operation including a first mode in which control signals generated by said trigger are propagated through said switch and applied to said TFT to thereby actuate said liquid crystal material when said actuator is adjacent said HEE;

said LCCs and said cell circuits being arranged in columns and rows;

mode control means for generating mode control signals for controlling operation of said switches comprised in said cell circuits;

video processing means coupled to said cell circuits for generating and transmitting second control signals;

a computer coupled to said video processing means;

said switch in each cell circuit having a second control signal input for receiving second control signals from said video processing means and mode input means for receiving said mode control signals for selectively setting said switch to operate in accordance with said mode control signals, said switch having (a) a second mode of operation in which said second control signals from said video processing means are applied to said TFT for actuating liquid crystal material adjacent to said TFT and (b) a third mode of operation in which said first control signal from said HSC is inputted into said computer;

I/O line means connected to said video processing means for selectively transmitting said second control signals to said TFTs when said switches are set to operate in said second mode and transmitting said first control signals to said computer when said switches are set to operate in said third mode, said I/O line means comprising a plurality of sense lines each connected to a plurality of switches in a different column; and

cell selection means comprising a plurality of row lines, each row line being connected to a plurality of switches in a row, and each column line being connected to a plurality of switches in a column, whereby a given switch is enabled by coincident active signals on said row line and said column line connected thereto for selectively enabling said switches one-at-a-time to input said first control signals into said computer when said switches are set to said third mode and to selectively actuate said LCCs one-at-a-time when said switches are set to said second mode.

13. Liquid crystal display apparatus comprising:

a liquid crystal display (LCD) comprising a layer of liquid crystal cells (LCCs) each containing liquid crystal material, said LCCs being arranged in a rectangular array;

a magnetic actuator that is selectively movable adjacent to said LCD and said LCCs for selectively actuating said LCCs;

a substrate positioned adjacent said layer, said substrate having a plurality of cell circuits, each cell circuit being positioned adjacent a different LCC and comprising

a thin film transistor (TFT) for actuating liquid crystal material adjacent thereto in response to a control signal applied to such TFT,

a first Hall sensor cell (HSC) comprising a first Hall effect element (HEE) actuated by a magnetic field having a first polarity for generating a Hall effect voltage, a first differential amplifier coupled to said HEE for receiving said Hall effect voltage therefrom, said first differential amplifier producing an output signal proportional to said Hall effect voltage produced by said first HEE connected thereto, and a first trigger connected to said differential amplifier for producing a digital output signal indicating when said voltage from said first differential amplifier is above a predetermined magnitude and thereby generating a first control signal in response to actuation of said first HEE by said actuator,

a second Hall sensor cell (HSC) comprising a second Hall effect element (HEE) actuated by a magnetic field having a polarity opposite said first polarity for generating a Hall effect voltage, a second differential amplifier coupled to said HEE for receiving said Hall effect voltage therefrom, said second differential amplifier producing an output signal proportional to said Hall effect voltage produced by said second HEE connected thereto, and a second trigger connected to said differential amplifier for producing a digital output signal indicating when said voltage from said second differential amplifier is above a predetermined magnitude and thereby generating a second control signal in response to actuation of said HEE by said actuator,

a switch having a first control signal input coupled to said first and second triggers for receiving said first and second control signals therefrom, said switch further having an output coupled to said TFT for transmitting a control signal thereto, said switch having a plurality of modes of operation including a first mode in which control signals generated by said triggers are propagated through said switch and applied to said TFT to thereby activate said liquid crystal material when a first polarity of magnetic field is adjacent said HEE and deactivate said liquid crystal material when a second polarity of magnetic field is adjacent said HEE;

said LCCs and said cell circuits being arranged in columns and rows;

mode control means for generating mode control signals for controlling operation of said switches comprised in said cell circuits;

video processing means coupled to said cell circuits for generating and transmitting third control signals;

a computer coupled to said video processing means;

said switch in each cell circuit having a control signal input for receiving third control signals from said video processing means and mode input means for receiving said mode control signals for selectively setting said switch to operate in accordance with said mode control signals, said switch having (a) a second mode of operation in which said third control signals from said video processing means are applied to said TFT for actuating liquid crystal material adjacent to said TFT and (b) a third mode of operation in which said first and second control signals from said HSC is inputted into said computer;

I/O line means connected to said video processing means for selectively transmitting said third control signals to said TFTs when said switches are set to operate in said second mode and transmitting said first and second control signals to said computer when said switches are set to operate in said third mode, said I/O line means comprising a plurality of sense lines each connected to a plurality of switches in a different column; and

cell selection means comprising a plurality of row lines, each row line being connected to a plurality of switches in a row, and each column line being connected to a plurality of switches in a column, whereby a given switch is enabled by coincident active signals on said row line and said column line connected thereto for selectively enabling said switches one-at-a-time to input said first and second control signals into said computer when said switches are set to said third mode and to selectively actuate said LCCs one-at-a-time when said switches are set to said second mode.