Paper white direct view display

• US 6,639,572 B1
• Filed: 04/10/2000
• Issued: 10/28/2003
• Est. Priority Date: 10/28/1998
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Lyon, John J., Little, Michael L.
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Nguyen, Jimmy H.
• Application Number:
  US09/546,285
• Time in Patent Office: 1,296 Days
• Field of Search: 345/55, 345/108, 345/109, 345/102, 359/223, 359/234, 359/227, 359/243, 359/290, 359/291
• US Class Current: 345/55
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38

Abstract

A low power, paper white, direct-view display includes an array of hinged micromirrors that are deflected between two states, a first state in which the micromirror covers a portion of the background and a second state in which the micromirror uncovers the background. In one particular configuration, a stability mechanism is incorporated in the display so that the micromirrors switch between stable states and remain in those stable states unless and until an actuating force is applied to the micromirrors that is sufficient to overcome an actuation threshold. The mechanics of the hinge, stiction due to Van der Waals forces or a combination of both can be used to provide bistability. Bistability allows power to be removed from the display between updates but requires active actuation between both states. The drive electronics are similar to those used in multiplexed LCDs.

Claims

1. A direct view display, comprising:

a background;

an array of micromirrors, each micromirror has a top surface that absorbs light and a bottom surface that reflects light; and

an array of hinges that are adapted to rotate and switch the respective micromirrors between two states, a first state in which the micromirror covers a portion of the background thereby exposing the micromirror'"'"'s top surface and a second state in which the micromirror substantially uncovers and exposes the portion of the background, wherein said background reflects ambient light, said micromirrors being configured in pairs that switch together so that, in said first state, their top surfaces absorb ambient light and, in said second state, their top surfaces face each other to reduce the absorption of ambient light and their bottom surfaces are exposed to reflect ambient light to and from the background.

2. The display of claim 1, wherein the micromirrors are electrostatically actuated.

3. The display of claim 2, further comprising a controller that applies a potential to produce electrostatic forces for actuating the micromirrors between their two states.

4. The display of claim 3, wherein the controller applies a first potential to enable selected micromirrors for a period longer than a response time of the micromirrors, and then applies a second potential to actuate the enabled micromirrors between their first and second states, the remaining non-enabled micromirrors remaining in their current state.

5. The display of claim 1, further comprising a stability mechanism that causes said micromirrors to remain in either of the first and second states unless and until an actuating force is applied to the micromirrors that is sufficient to overcome an actuation threshold.

6. The display of claim 5, wherein said array of hinges comprises an array of bistable torsional hinges that provide the stability mechanism, said bistable torsional hinges exhibiting a compressive stress when flat such that the hinge wants to rotate up or down between a pair of stable states to relieve the compressive stress, said torsional hinge rotating between its stable states to actuate the micromirrors between their two states.

7. The display of claim 5, wherein said array of hinges comprises an array of bistable S-hinges that provide the stability mechanism, said bistable S-hinges including a torsional hinge for rotating the micromirror and a compliant strap having two relaxed states corresponding to the mirror'"'"'s first and second states and a compressed state that first resists and then assist the actuation of the micromirror between its first and second states.

8. The display of claim 5, wherein said array of hinges comprises an array of bistable latch hinges that provide the stability mechanism, said bistable latch hinges including a torsional hinge for rotating the mirror, which has a tab extension that extends beyond said torsional hinge, and a latch mechanism that supports the tab extension in the micromirror'"'"'s first stable state thereby preventing it from rotating upward and catches the tab extension in the micromirror'"'"'s second state thereby preventing it from rotating downward.

9. The display of claim 8, wherein said latch mechanism comprises a compliant ribbon and an electrode that actuates the ribbon up and down to catch and release the tab extension.

10. The display of claim 5, wherein said array of hinges comprises an array of bistable stretch hinges that provide the stability mechanism, said bistable stretch hinges having an elastic property such that when the micromirror is rotated to its second state the hinge is stretched causing said hinge to snap back and contact the background where is stays due to stiction forces.

11. The display of claim 5, wherein the stability mechanism comprises first and second stops associated with each of the micromirrors, the first and second stops positioned so that their respective micromirror contacts the first and second stops when the respective micromirror is in the first and second states, respectively, wherein the micromirrors and their respective first and second stops are adapted so that stiction forces are created when the micromirrors contact their respective first or second stops that hold the micromirrors in either state when power is removed from the array of micromirrors.

12. The display of claim 5, wherein each said micromirror has a tab extension that extends beyond said hinge, said stability mechanism comprising a pair of electrodes underneath said micromirror and tab extension on either side of the hinge that actuate the micromirror between its first and second states, bistability being achieved by bringing the tap extension into contact with its underlying electrode.

13. The display of claim 5, wherein said micromirrors have a residual stress that causes them to curl upward into their second states, further comprising an array of electrodes on the background that are separated from the mirrors by a dielectric layer, said electrodes being configured to first receive an actuation voltage that rotates the micromirrors downward and flattens them against the dielectric layer and then receive a holding voltage, which together with the stiction force between the micromirror and dielectric, holds the micromirrors in their first state.

14. A direct-view display, comprising:

a background;

an array of micromirrors, each micromirror has a top surface that absorbs light and a bottom surface that reflects light;

an array of hinges that are adapted to rotate and switch the respective micromirrors between two stable states, a first state in which the micromirror covers a portion of the background thereby exposing the micromirror'"'"'s top surface and a second state in which the micromirror substantially uncovers and exposes the portion of the background, wherein said background reflects ambient light, said micromirrors being configured in pairs that switch together so that, in said first state, their top surfaces absorb ambient light and, in said second state, their top surfaces face each other to reduce the absorption of ambient light and their bottom surfaces are exposed to reflect ambient light to and from the background; and

a stability mechanism that causes said micromirrors to remain in either stable state unless and until the actuating force applied to the micromirrors is sufficient to overcome an actuation threshold.

15. The display of claim 14, wherein said array of hinges comprises an array of bistable torsional hinges that provide the stability mechanism, said bistable torsional hinges exhibiting a compressive stress when flat such that the hinge wants to rotate up or down between a pair of stable states to relieve the compressive stress, said torsional hinge rotating between its stable states to actuate the micromirrors between their two states.

16. The display of claim 14, wherein said array of hinges comprises an array of bistable S-hinges that provide the stability mechanism, said bistable S-hinges including a torsional hinge for rotating the micromirror and a compliant strap having two relaxed states corresponding the mirror'"'"'s first and second states and a compressed state that first resists and then assists the actuation of the micromirror between its first and second states.

17. The display of claim 14, wherein said array of hinges comprises an array of bistable latch hinges that provide the stability mechanism, said bistable latch hinges including a torsional hinge for rotating the mirror, which has a tab extension that extends beyond said torsional hinge, and a latch mechanism that supports the tab extension in the micromirror'"'"'s first stable state thereby preventing it from rotating upward and catches the tab extension in the micromirror'"'"'s second state thereby preventing it from rotating downward.

18. The display of claim 17, wherein said latch mechanism comprises a compliant ribbon and electrode that actuates the ribbon up and down to catch and release the tab extension.

19. The display of claim 14, wherein said array of hinges comprises an array of bistable stretch hinges that provide the stability mechanism, said bistable stretch hinges having an elastic property such that when the micromirror is rotated to its second state the hinge is stretched causing said hinge to snap back and contact the background where is stays due to stiction forces.

20. The display of claim 14, wherein the stability mechanism comprises first and second stops associated with each of the micromirrors, the first and second stops positioned so that their respective micromirror contacts the first and second stops when the respective micromirror is in the first and second states, respectively, wherein the micromirrors and their respective first and second stops are adapted so that stiction forces are created when the micromirrors contact their respective first or second stops that hold the micromirrors in either state when power is removed from the array of micromirrors.

21. The display of claim 14, wherein each said micromirror has a tab extension that extends beyond said hinge, said stability mechanism comprising a pair of electrodes underneath said micromirror and tab extension on either side of the hinge that actuate the micromirror between its first and second states, bistability being achieved by bringing the tap extension into contact with its underlying electrode.

22. The display of claim 14, wherein said micromirrors have a residual stress that causes them to curl upward into their second states, further comprising an array of electrodes on the background that are separated from the mirrors by a dielectric layer, said electrodes being configured to first receive an actuation voltage that rotates the micromirrors downward and flattens them against the dielectric layer and then receive a holding voltage, which together with the stiction force between the micromirror and dielectric, holds the micromirrors in their first state.

23. A bistable direct-view display, comprising:

a background;

an array of micromirrors, each micromirror has a top surface that absorbs light and a bottom surface that reflects light;

an array of hinges that are adapted to rotate and switch the respective micromirrors between two stable states, a first state in which the micromirror covers a portion of the background thereby exposing the micromirror'"'"'s top surface and a second state in which the micromirror substantially uncovers and exposes the portion of the background, wherein said background reflects ambient light, said micromirrors being configured in pairs that switch together so that, in said first state, their top surfaces absorb ambient light and, in said second state, their top surfaces face each other to reduce the absorption of ambient light and their bottom surfaces are exposed to reflect ambient light to and from the background;

a bistable mechanism that causes said micromirrors to remain in either stable state unless and until an actuating force is applied to the micromirrors that is sufficient to overcome an actuation threshold; and

a controller that applies a first potential to the micromirrors a row at a time to enable that row and applies a second potential to each column of micromirrors to produce an actuating force on the micromirrors in the enabled row that exceeds the actuation threshold and actuate the enabled mirrors between their two stable states, the actuating forces on the micromirrors in the remaining non-enabled rows being insufficient to overcome the actuation threshold so that the non-enabled mirrors remain in their current stable state.