Overhead projector for flat panel display capability

• US 5,593,221 A
• Filed: 06/27/1995
• Issued: 01/14/1997
• Est. Priority Date: 06/27/1995
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Keely, Leroy B., Siefert, Steven, Evanicky, Daniel E.
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US08/495,081
• Time in Patent Office: 567 Days
• Field of Search: 353/122, 353/DIG. 3, 353/119, 353/DIG. 5, 353/120, 353/57, 353/60, 353/61
• US Class Current: 353/122
• CPC Class Codes: G03B 21/132 Overhead projectors, i.e. capable of projecting hand-writing or drawing during action epidiascopic projectors G03B21/08
• CPC Class Codes: Y10S 353/03 Transparent

Abstract

An overhead projector for use with a flat panel display assembly. The specialized overhead projector provides cooling for the LCD flat panel when used in an overhead projection configuration. The projector contains a rail on which the flat panel display is positioned for alignment and to provide air passage there through for cooling. A clamping mechanism is also described for securing the flat panel display to the projector. The flat panel display is a back-lit flat panel display subsystem for direct viewing as a monitor and also has overhead projection capability. The display subsystem contains a removable door assembly which provides for back-lighting for direct viewing. When the door assembly is removed, the active matrix LCD is semi-transparent and can be placed over the imaging screen of the overhead projector such that the LCD color image can be thus projected. The lamps that provide the back-lighting remain within the display subsystem when the door is removed and a unique optical coupling is provided between the lamps and a light pipe within the door. The display subsystem contains a sensor detecting door presence and simultaneously shuts off the lamps and reverses the display image upon door removal for overhead projection capability.

Claims

1. An overhead projector for displaying an image within a flat panel display matrix of a display assembly, said overhead projector comprising:

an illuminated display screen for radiating light through a flat panel display matrix to project said image on a receiving surface;

a pair of tracks positioned on opposite sides of said illuminated display screen for supporting said display assembly thereon;

an air inlet vent positioned adjacent to said illuminated display screen for providing passage to an air current to flow within a channel formed by a top surface of said display screen, side walls of said pair of tracks, and a surface of said display assembly facing said illuminated display screen when said display assembly is positioned on said pair of tracks; and

a fan for causing said air current to flow through said air inlet vent, wherein said air current is for cooling said flat panel display matrix, and wherein said display assembly comprises;

said flat panel display matrix having a first surface for viewing during direct monitoring and an opposite surface for viewing during overhead projection monitoring, wherein said first surface is for facing said illuminated display screen during overhead projection monitoring; and

a pair of permanently secured light sources positioned along two opposite edges of said flat panel display matrix for providing back-light for said flat panel display matrix.

2. An overhead projector as described in claim 1 further comprising a pair of clamps positioned adjacent to said illuminated display screen for mating with receiving holes within said display assembly for positioning and securing said display assembly with respect to said illuminated display screen.

3. An overhead projector as described in claim 1 wherein said illuminated display screen radiates approximately 8000 lumens or more.

4. An overhead projector for displaying an image within a flat panel display matrix of a display assembly, said overhead projector comprising:

an illuminated display screen for radiating light through said flat panel display matrix to project said image on a receiving surface;

a pair of tracks positioned on opposite sides of said illuminated display screen for supporting said display assembly thereon;

an air inlet vent positioned adjacent to said illuminated display screen for providing passage to an air current to flow within a channel formed by a top surface of said display screen, side walls of said pair of tracks, and a surface of said display assembly facing said illuminated display screen when said display assembly is positioned on said pair of tracks;

a fan for causing said air current to flow through said air inlet vent, wherein said air current is for cooling said flat panel display matrix; and

a pair of clamps positioned adjacent to said illuminated display screen for mating with receiving holes within said display assembly for positioning and securing said display assembly with respect to said illuminated display screen.

5. An overhead projector as described in claim 4 wherein said illuminated display screen radiates approximately 8000 lumens.

6. An overhead projector as described in claim 4 wherein said display assembly comprises:

said flat panel display matrix having a first surface for viewing during direct monitoring and an opposite surface for viewing during overhead projection monitoring, wherein said first surface is for facing said illuminated display screen during overhead projection monitoring; and

a pair of permanently secured light sources positioned along two opposite edges of said flat panel display matrix for providing back-light for said flat panel display matrix.

7. A display system comprising:

(a) a flat panel display subsystem, said flat panel display subsystem comprising

(i) a flat panel display matrix having a first surface for viewing during direct monitoring and an opposite surface for viewing during overhead projection monitoring;

(ii) a light source positioned along two opposite edges of said flat panel display matrix for providing back-light for said flat panel display matrix; and

(iii) a removable door assembly, adapted for insertion into and removal from said display subsystem, said removable door assembly comprising a light pipe for optically coupling with said light source to uniformly illuminate said flat panel display matrix with said back-light when said removable door assembly is inserted into said display subsystem; and

(b) an overhead projector for displaying an image within said flat panel display matrix of said flat panel display subsystem, said overhead projector comprising;

(i) an illuminated display screen for radiating light through said flat panel display matrix to project said image on a receiving surface;

(ii) a pair of tracks positioned on opposite sides of said illuminated display screen for supporting said display assembly thereon; and

(iii) an air inlet vent positioned adjacent to said illuminated display screen for providing passage to an air current to flow within a channel formed by a top surface of said display screen, side walls of said pair of tracks, and a surface of said display assembly facing said illuminated display screen when said display assembly is positioned on said pair of tracks.

8. A system as described in claim 7 further comprising a pair of clamps positioned adjacent to said illuminated display screen for mating with receiving holes within said display assembly for positioning and securing said display subsystem with respect to said illuminated display screen.

9. A system as described in claim 7 wherein said illuminated display screen radiates approximately 8000 lumens.

10. A system as described in claim 7 further comprising a fan for causing said air current to flow through said air inlet vent, wherein said air current is for cooling said flat panel display matrix.

11. A system as described in claim 7 wherein said light source comprises a pair of light sets and wherein each light set comprises a pair of high voltage cold cathode fluorescent tubes.

12. A system as described in claim 7 further comprising a base assembly rotatably attached to said display subsystem via a hinge, said base assembly and said display system for supporting said flat panel display matrix for direct monitoring when said base assembly is rotated at a first angle with respect to said display subsystem.

13. A system as described in claim 7 wherein said base assembly further comprises a video input for receiving digital video information.

14. A system as described in claim 7 wherein said removable door assembly further comprises a bi-directional light extraction pattern of dots disposed on one surface of said light pipe for extracting light from said light pipe to illuminate said flat panel display matrix, each dot of said extraction pattern varying in size depending on its position with respect to said light source along a first dimension and varying in size differently, depending on its position with respect to said light source along a second dimension.

15. A method of displaying an image onto a receiving surface using an overhead projector and a flat panel display matrix, said method comprising the steps of:

radiating light through a display screen of said overhead projector to illuminate said a flat panel display matrix to project said image on said receiving surface;

supporting and aligning said flat panel display matrix with a pair of tracks positioned on opposite sides of said display screen of said overhead projector;

forming an air passage channel out of a top surface of said display screen of said overhead projector, side walls of said pair of tracks, and a surface of said display matrix facing said display screen when said display matrix is positioned on said pair of tracks;

causing an air current to flow through said air passage and through an air inlet vent of said overhead projector by using a fan, wherein said air current is for cooling said flat panel display matrix;

sensing whether or not a removable back-lighting assembly is present within a display assembly and generating a first signal indicative thereof, said display assembly containing said flat panel display matrix and a pair of light sources mounted on opposite sides of said flat panel display matrix; and

in response to said first signal being at a first state, automatically turning off said pair of light sources and also displaying said image on said viewing surface from right to left, said first state indicative of said removable back-lighting assembly removed from said display assembly.

16. A method as described in claim 15 further comprising the step of

positioning and securing said display matrix with respect to said display screen by mating a pair of clamps disposed adjacent to said display screen to a pair of receiving holes disposed with said display matrix.

17. A method as described in claim 15 wherein said display screen radiates approximately 8000 lumens.

18. A method as described in claim 15 further comprising the step of:

removing said removable back-lighting assembly from said display assembly for said overhead projection viewing.