Display device based on grating electromechanical shutter

• US 6,288,824 B1
• Filed: 03/17/1999
• Issued: 09/11/2001
• Est. Priority Date: 11/03/1998
• Status: Expired due to Fees

• Current Assignee: Alex Kastalsky
• Original Assignee: Alex Kastalsky
• Inventors: Kastalsky, Alex
• Primary Examiner(s): Ben, Loha
• Application Number:
  US09/270,614
• Time in Patent Office: 909 Days
• Field of Search: 359/254, 359/259, 359/320, 359/298, 359/290, 359/291, 359/233, 359/295
• US Class Current: 359/254
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955

Abstract

Electrostatic optical shutter is disclosed in which a resilient electrode in the shape of a membrane made from optically transparent and electrically insulating film is disposed over an optically transparent and electrically insulating substrate and supported by one or several flexible tether beams which are attached to the substrate through the conductive pillars. Both the membrane and the substrate contain a grating with periodically repeated parallel stripes made from electrically conductive and opaque material. The stripes are connected at one or both ends to form continuous electrodes, while the grating structures on the electrodes are shifted from each other by a half a period to block the light transmission through the shutter in the unbiased state. Under electrical bias, the membrane is moved both laterally and normally to the substrate, which results in a spatial alignment of the conductive stripes in both grating structures and formation of the openings in the shutter for the light transmission. A flat panel display having video and color capabilities and comprising two-dimensional matrix of such shutters is disclosed. To implement passive matrix driving architecture, each pixel of the display contains a thin-film diode and a thin-film resistor to eliminate cross talk between the pixels. Both the transmissive and reflective modes of the display operation are proposed. A sequential pulsed illumination with the light emitting diodes of three major colors is used to produce the color in the display. Another approach in making a flat panel display, capable of operating in both transmissive and reflective mode, is disclosed in which two-terminal electrical control of the pixels produces effect of bistability in positioning of the membrane relative to the substrate and thereby provides a memory effect, which allows one to hold the “on”-state of each pixel for almost the entire frame time and thus increase the display brightness.

Claims

1. An electrostatic optical shutter having a resilient electrode in the shape of a membrane made from optically transparent and electrically insulating film, wherein said membrane is parallel to and separated by an air gap from an optically transparent and electrically insulating substrate and supported by one flexible tether beam which is attached to said substrate through a conductive pillar;

active areas of both said membrane and substrate contain electrically conductive and opaque film in the shape of a grating with periodically repeating opaque stripes, said stripes being connected at one or both ends to form continuous grating electrodes;

the substrate continuous grating electrode constitutes first shutter electrode, while the grating electrode on said membrane is connected through the conductive film on said tether beam to said conductive pillar to provide second shutter electrode;

said grating electrodes on said substrate and said membrane are shifted from each other by a half a period to block light transmission through the shutter when no voltage is applied between said electrodes and pass the light when appropriate voltage is applied between said grating electrodes, and said membrane is moved to said substrate both normally and laterally, which results in a spatial alignment of said stripes on both said membrane and substrate and formation of openings for light transmission and reflection thereby providing “

on”

-state of the shutter.

2. The shutter of claim 1, wherein said opaque and electrically conducting stripes in said first and second shutter electrodes are wider than said openings, to provide a complete light blocking in an “

off”

-state of the shutter in which no voltage is applied and the shutter does not transmit light.

3. The shutter of claim 2, wherein two tether beams support said membrane to enhance its mechanical strength.

4. The shutter of claim 3 wherein an additional grating electrode, aligned with said second shutter electrode, is deposited on top of the membrane and separated from said second shutter electrode with a layer of transparent and insulating material thereby forming third shutter electrode;

said third shutter electrode and said second shutter electrode on said membrane are electrically connected through two different tether beams to separate controlling circuits, thereby providing a three-terminal shutter with the memory mode based on a voltage controlled bi-stable membrane positioning relative to the substrate.

5. The shutter of claim 4, in which both insulating films on said membrane are etched away within said openings in said second and third shutter electrodes to minimize air drag.

6. The shutter of claim 5 in which an optically reflective film is deposited first on said substrate, prior to said grating electrode on said substrate, and separated from said grating electrode with an optically transparent and insulating film, to reflect light in said “

on”

-state of said shutter and thus produce the reflective optical shutter operating in the memory mode.

7. A reflective passive matrix flat panel display operating in a memory mode which comprises:

a two-dimensional array of the shutters of claim 6 placed in rows and columns, wherein each shutter is located at the intersection of one column and one row;

electrical connections of said first shutter electrodes of said shutters in each row;

conducting lines located next to each column of said shutters for formation of column connections;

thin-film resistors connected in parallel to each shutter;

thin-film diodes connected between said second shutter electrode of each shutter in one column and respective conducting line, thereby forming connections in each column;

conductive lines connecting said third shutter electrodes of all shutters in the array;

a back panel of light emitting diodes to provide illumination with three main colors; and

electronic means to drive the display.

8. A transmissive passive matrix flat panel display operating in the memory mode which comprises:

a two-dimensional array of the shutters of claim 5 placed in rows and columns, wherein each shutter is located at the intersection of one column and one row;

electrical connections of said first shutter electrodes of said shutters in each row;

conducting lines located next to each column of said shutters for formation of column connections;

thin-film resistors connected in parallel to each shutter;

thin-film diodes connected between said second shutter electrode of each shutter in one column and respective conducting line thereby forming connections in each column;

conductive lines connecting said third shutter electrodes of all shutters in the array;

a back panel of light emitting diodes to provide illumination with three main colors; and

electronic means to drive the display.

9. The display of claim 8, in which color is produced by sequential Illumination during the frame time with three main colors, which are provided by periodic pulsed electro-luminescence of light emitting diodes of three different colors.

10. The display of claim 8, in which gray levels are produced by switching the pixel during the frame time to said “

on”

-state, the duration of said “

on”

-state controlling the gray level.

11. The shutter of claim 2, wherein small and electrically isolated pillars, shorter than the gap between said membrane and substrate, are deposited on said substrate to protect said membrane from sticking to said substrate in the “

on”

-state of the shutter in which a voltage is applied between said grating electrodes and said shutter transmits light.

12. The shutter of claim 2, in which the insulating film of said membrane is etched away within said openings in said second shutter electrode to minimize air drag.

13. The shutter of claim 12 in which an optically reflective film is deposited first on said substrate and coated with an optically transparent and insulating film, prior to deposition of a grating film, to reflect light in said “

on”

-state of the shutter and thus produce a reflective mode of optical modulation.

14. A reflective passive matrix flat panel display which comprises:

a two-dimensional array of shutters of claim 13 placed in rows and columns, wherein each shutter is located at the intersection of one column and one row;

electrical connections of said first shutter electrodes of said shutters in each row;

conducting lines located next to each column of said shutters for formation of column connections;

thin-film resistors connected in parallel to each shutter;

thin-film diodes connected between said second shutter electrode of each shutter in one column and respective conducting line thereby forming connections in each column;

a back panel of light emitting diodes to provide illumination with three main colors; and

electronic means to drive the display.

15. A transmissive passive matrix flat panel display which comprises:

a two-dimensional array of the shutters of claim 12 placed in rows and columns, wherein each shutter is located at the intersection of one column and one row;

electrical connections of said first shutter electrodes of said shutters in each row;

conducting lines located next to each column of said shutters for formation of column connections;

thin-film resistors connected in parallel to each shutter;

thin-film diodes connected between said second shutter electrode of each shutter in one column and respective conducting line thereby forming connections in each column;

a back panel of light emitting diodes to provide illumination with three main colors; and

electronic means to drive the display.

16. The display of claim 15, in which color is produced by sequential Illumination during a frame time with three main colors, which are provided by a periodic pulsed electroluminescence of light emitting diodes of three different colors.

17. The display of claim 15, in which gray levels are produced by applying within a row addressing time of one or several pulses having duration shorter than the row addressing time.