Information entry and display

• US 5,243,332 A
• Filed: 10/31/1991
• Issued: 09/07/1993
• Est. Priority Date: 10/31/1991
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Jacobson, Joseph M.
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): Liang, Regina
• Application Number:
  US07/786,073
• Time in Patent Office: 677 Days
• Field of Search: 340/781, 340/766, 340/760, 340/758, 340/707, 340/706, 340/708, 340/712, 313/507, 313/506, 315/169.3, 382/68, 382/65, 358/479, 358/494, 358/497, 178/18, 178/19, 359/202, 250/208.1
• US Class Current: 345/44
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

Display panels are provided which enable effective document scanning, information display, and entry of information using a stylus. The panels include (in the same panel) light emitting and light detecting functions which are arranged to permit effective scanning, display, and stylus reading techniques. In one aspect there is a two-dimensional panel for scanning information at a scanning surface. The panel has a light emitting layer and a light detecting layer. The light emitting layer is configured to emit light onto the scanning surface at selected pixel locations in response to electrical signals, each electrical signal being impressed at a selected pixel location, the layer having optical apertures defining corresponding optical paths at the pixel locations for light to exit the opposite side of the layer from the scanning surface. The light detecting layer is configured to detect light exiting the layer at pixel locations. The light emitting layer is between the light detecting layer and the scanning surface.

Claims

1. A two-dimensional panel for scanning information at a scanning surface, comprising

a light emitting layer configured to emit light onto said scanning surface at selected pixel locations of said light emitting layer in response to electrical signals, each electrical signal being impressed at one of said selected pixel locations of said light emitting layer, said layer having optical apertures defining corresponding optical paths at said pixel locations for light to exit said layer from a side of said layer opposite from said scanning surface, and

a light detecting layer configured to detect light which has been generated by said light emitting layer, reflected from an object being scanned, passed via said apertures, and exited said light emitting layer from said opposite side at said pixel locations, said light detecting layer being positioned such that said light emitting layer is between said light detecting layer and said scanning surface.

2. The panel of claim 1 wherein

said light emitting layer comprises a non-luminescent transmissive display sublayer, and an electroluminescent sublayer, and

said optical apertures comprise pinholes in said electroluminescent sublayer.

3. The panel of claim 1 wherein said light emitting layer comprises an electroluminescent or gas plasma layer.

4. The panel of claim 1 further comprising

circuitry for scanning successive pixel locations of said light emitting layer and scanning corresponding pixel locations of said light detecting layer to detect light which has been emitted from said light emitting layer, reflected from an object being scanned, and passed via said optical apertures to said light detecting layer.

5. The panel of claim 1 further comprising

an actuator for shifting said relative positions of said light emitting layer and said light detecting layer by a fraction of a pixel location.

6. The panel of claim 1 further comprising circuitry for

a. causing a random subset comprising half of said pixel locations on said light emitting layer to be in an active state in which light generated by or reflected from a stylus at said scanning surface may be received at light detecting layer,

b. causing said subset comprising said remaining half of said pixel locations on said light emitting layer to be in an opposite, passive state in which light generated by or reflected from said stylus may not be received at said detecting layer,

c. detecting whether corresponding light is received at said light detecting layer,

d. if step c is true, replacing said active subset with a random subset of said active subset, or if step c is not true, replacing said active subset with a random subset of said passive subset, and

e. repeating steps a through c a number of times until said random subset generated in step d contains only a single pixel location.

7. The panel of claim 1 wherein said light detecting layer comprises a photoconductor.

8. The panel of claim 1 wherein said light detecting layer comprises a charge coupled device or a charge injection device and an optic array for directing light from pixel locations on said light emitting layer to pixel locations on said charge coupled or charge injection device.

9. The panel of claim 1 further comprising

circuitry for advancing said display from one stored image to a subsequent stored image upon detection of light impinging on said panel.

10. The panel of claim 1 wherein said panel is adapted to serve as an active matrix display.

11. The panel of claim 1 wherein,

in said light emitting layer, each electrical signal is impressed at a signal level higher than a present threshold value associated with said selected location,

said layer exhibiting a hysteresis effect such that when light is not being emitted from a pixel location, said present threshold value at that pixel location is higher than the present threshold value when light is being emitted from said pixel location, and when light is being emitted from a pixel location, said present threshold value at that pixel location is lower than the present threshold value when light is not being emitted from said pixel location, and

circuitry configured to impress an electrical signal at a pixel location and at a selected signal level sufficient

to cause light to begin to be emitted from that location if light is not then being emitted, or

to cause light to continue to be emitted if light is then being emitted.

12. The panel of claim 11 wherein said threshold value defines a value of impedance and said electrical signal comprises a voltage.

13. The panel of claim 11 wherein said layer configured to emit light comprises an electroluminescent material which emits light in response to said electrical signal and a photoconductive material which generates carrier electrons in response to light.

14. The panel of claim 13 wherein said electroluminescent material is arranged in an electroluminescent sublayer of said panel and said photoconductive material is arranged in a separate, photoconductive sublayer of said panel positioned to receive light emitted from said electroluminescent sublayer.

15. The panel of claim 13 wherein said electroluminescent material and said photoconductive material are mixed and arranged in a sublayer of said panel.

16. The panel of claim 13 wherein said layer configured to emit light comprises a material which is both electroluminescent and photoconductive.

17. The panel of claim 11 wherein said circuitry comprises a pattern of conductive rows arranged on a surface of said layer and a pattern of conductive columns arranged on another surface of said layer, said intersection region of a given row conductor with a given column conductor defining a pixel, and a driver circuit for applying said electrical signal between a selected row and column conductors.

18. The panel of claim 17 further comprising

circuitry for measuring impedance, capacitance, or resistance between any row conductor and column conductor for detecting the state of the pixel located at said row and column.

19. The panel of claim 11 wherein said optical apertures define corresponding optical paths for light to enter said layer at said pixel locations, each optical path permitting only light impinging on said layer within a predetermined angle of incidence to enter said layer at said pixel location.

20. Said panel of claim 11 wherein said circuitry comprises a driver circuit connected to

apply said electrical signal at a level above said present threshold and at only a subset of said pixel locations at a level above said present threshold value, and

at a different time, apply said electrical signal above said present threshold and at only another, different subset of said pixel locations.

21. Said panel of claim 20 wherein said subset and said different subset comprise disjoint subsets which together include all pixel locations on said panel.

22. The panel of claim 21 wherein said disjoint subsets are arranged in interleaved checkerboard patterns.

23. The panel of claim 22 wherein said circuitry comprises a driver circuit connected to

apply said electrical signal simultaneously at all of said pixel locations on said panel and at a level above said present threshold value.

24. A two-dimensional panel for displaying information at a surface, comprising

a layer having

an electroluminescent material which emits light from selected pixel locations of said layer in response to a voltage, said voltage being impressed at one of said selected pixel locations of said layer and at a voltage level higher than a present threshold value determined by an impedance associated with said selected location, and

a photoconductive material which generates carrier electrons in response to light,

said layer exhibiting a hysteresis effect such that when light is not being emitted from a pixel location, said present threshold value at that pixel location is higher than the present threshold value when light is being emitted from said pixel location, and when light is being emitted from a pixel location, said present threshold value at that pixel location is lower than the present threshold value when light is not being emitted from said pixel location,

said layer further comprising optical apertures defining corresponding optical paths for light to enter said layer at said pixel locations, each optical path permitting only light impinging on said layer within a predetermined angle of incidence to enter said layer at said pixel location, and

circuitry comprising

a pattern of conductive rows arranged on a surface of said layer and a pattern of conductive columns arranged on another surface of said layer, said intersection region of a given row conductor with a given column conductor defining a pixel location, and

a driver circuit for applying said electrical signal between a selected row and column conductors,

said circuitry being configured to impress a voltage at a pixel location and at a selected voltage level sufficient

to cause light to begin to be emitted from that location if light is not then being emitted, or

to cause light to continue to be emitted if light is then being emitted.

25. A method for scanning a document using a light emitting layer having an array of pixel locations, comprising

a. generating light at a first subset of fewer than all of said pixel locations of said light emitting layer, while generating no light at a second subset of fewer than all of said pixel locations, said first and second subsets being arranged so light generating pixel locations have non-light generating pixels adjacent them,

b. placing said document in a position to reflect said light generated from said first subset of pixel locations in the direction of adjacent said non-light generating pixel locations,

c. permitting light reflected in said direction of said adjacent non-light generating pixel locations to pass through apertures in said light emitting layer, and

d. detecting said passed through light at pixel locations of a light detecting layer.

26. The method of claim 25 further comprising performing steps a, b, c, and d with said roles of said first and second subsets reversed.

27. The method of claim 26 wherein said first and second subsets comprise disjoint subsets which together include all pixel locations on said layer.

28. The method of claim 27 wherein said disjoint subsets are arranged in interleaved checkerboard patterns.

29. A method of deriving free-form information indicated by a computer user using a light emitting stylus at a surface of a two-dimensional panel, comprising

electrically preconditioning said panel to

emit light at pixel locations of said panel which receive light from said stylus when an electrical condition of said panel at said location falls below a threshold, and

thereafter to continue to emit light at said pixel locations even after said light is no longer being received from said stylus,

causing said electrical condition of said panel to fall below said threshold at pixel locations which receive light from said stylus, and

detecting light emitted from said pixel locations.

30. A two-dimensional panel for displaying information at a surface, comprising

an image storage unit having

a layer configured to emit light from selected pixel locations of said layer in response to electrical signals, each electrical signal being impressed at one of said selected pixel locations of said light emitting layer and at a signal level higher than a present threshold value associated with said selected location,

said layer exhibiting a hysteresis effect such that when light is not being emitted from a pixel location, said present threshold value at that pixel location is higher than the present threshold value when light is being emitted from said pixel location, and when light is being emitted from a pixel location, said present threshold value at that pixel location is lower than the present threshold value when light is not being emitted from said pixel location,

an optical write unit comprising

a pixel addressable electroluminescent display, and

circuitry configured to impress an electrical signal at a pixel location and at a selected signal level sufficient to cause light to begin to be emitted from that location if light is not then being emitted or to cause light to continue to be emitted if light is then being emitted.

31. A two-dimensional panel for locating the pixel position of a stylus at a scanning surface, comprising

a nonluminescent transmissive display layer adjacent said scanning surface,

a light emitting layer configured to emit light through said transmissive display layer and onto said scanning surface, said light emitting layer having optical apertures defining corresponding optical paths at said pixel locations for light to exit said light emitting layer from a side of said light emitting layer opposite from said scanning surface, and

a photoconductive layer, said light emitting layer being positioned between said photoconductive layer and said scanning surface, said photoconductive layer being arranged to receive light which has been generated by said stylus or generated by said light emitting layer and reflected from said stylus, passed via said apertures, and exited said light emitting layer from said opposite side, and to close a circuit at a pixel location upon which said light impinges, and

circuitry for measuring the impedances along X and Y axes to a location on the photoconductive layer where a circuit has been closed, in order to identify the pixel location of the stylus.