Large area electronic writing system

• US 5,495,269 A
• Filed: 04/03/1992
• Issued: 02/27/1996
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Steinmetz, David L., Elrod, Scott A.
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US07/863,650
• Time in Patent Office: 1,425 Days
• Field of Search: 340/706, 340/707, 359/443, 359/447, 359/448, 359/449, 359/451, 359/452, 359/453, 359/460, 345/178, 345/179, 178/18
• US Class Current: 345/179
• CPC Class Codes: G06F 3/0386 for light pen
• CPC Class Codes: G06F 3/0425 using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected tracking a projected light spot to determine a position on a display surface G06F3/0386

Abstract

Collaborative work on an interactive system is facilitated by accurately capturing and displaying information on an interactive system, wherein multiple persons may work together for supplying and receiving information with a single large area display. A large area electronic writing system is provided which employs a large area display screen, an image projection system, and an image receiving system including a light emitting pen. The display screen is designed with the imaging surface in front of the substrate, with a thin abrasion resistant layer protecting the imaging surface from the pen tip. The screen is held together with dowel pins pressed through the layers, and is curved to provide pressure for holding the layers together and mechanical rigidity against flexure during writing. The imaging surface disperses light from both the projection system and the light pen. The image receiving system comprises a very large aperture lens for gathering light energy from the light spot created by the light emitting pen. The amount of energy from the light spot which reaches the integrating detector is more critical to accurate pen position sensing than the focus of the light spot, so that the aperture of the lens is more important than its imaging quality. The light emitting pen is modified to additionally disperse light at its tip.

Claims

1. A large area electronic writing system, comprising:

a parallax reducing display screen with a light dispersive imaging surface;

means for projecting a modifiable light spot representing input location information upon one side of said imaging surface;

means for sensing said light spot and for generating output signals representative of said input location information, said means for sensing being located on a second side of said imaging surface and comprising;

a large aperture imaging lens, said aperture corresponding to f1.0 or less; and

a position sensing integrating detector, said large aperture imaging lens focusing energy from substantially the entire imaging surface upon said position sensing integrating detector; and

rear-projection means for displaying information upon said second side of said imaging surface, whereby said displayed information indicates an accurate pixel location corresponding to said light spot input location information.

2. A large area electronic writing system as described in claim 1, wherein said parallax reducing display screen further comprises

a layer of rigid, transparent substrate;

said light dispersive imaging surface; and

a protective layer, said protective layer being significantly thinner than said substrate layer;

said imaging surface being juxtaposed between said substrate and said protective layer, said display screen being positioned with one side of said protective layer being located immediately adjacent to said one side of said imaging surface.

3. A large area electronic writing system as described in claim 2, wherein said display screen further comprises a thin layer of lubricant on a second side of said protective layer.

4. A large area electronic writing system as described in claim 1, wherein said parallax reducing display screen further comprises

a layer of rigid, transparent substrate:

said light dispersive imaging surface, said second side of said imaging surface being adjacent to said substrate; and

a protective layer adjacent to said one side of said imaging surface, said protective layer being significantly thinner than said substrate layer;

whereby parallax is reduced when said light spot source is in contact with said protective layer.

5. A large area electronic writing system as described in claim 1, wherein said projecting means for a modifiable light spot representing location information comprises a light emitting diode with a roughened tip surface.

6. A large area electronic writing system, comprising:

a parallax reducing, highly dispersive display screen with a light dispersive imaging surface;

a widely divergent modifiable light beam representing input location information towards one side of said imaging surface;

a sensor for sensing said light beam and for generating output signals representative of said input location information, said sensor being located on a second side of said imaging surface and comprising;

a large aperture imaging lens, said aperture corresponding to f1.0 or less; and

a position sensing integrating detector, said large aperture imaging lens focusing energy from substantially the entire imaging surface upon said position sensing integrating detector; and

a rear-projector for displaying information upon said second side of said imaging surface, whereby said displayed information indicates an accurate pixel location corresponding to said input location information.

7. A large area electronic writing system as described in claim 6, wherein said position sensing integrating detector is a position sensing photodiode.