Direct view display based on a micromechanical modulation

• US 5,636,052 A
• Filed: 07/29/1994
• Issued: 06/03/1997
• Est. Priority Date: 07/29/1994
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Walker, James A., Goossen, Keith W., Arney, Susanne C.
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): BEY, DAWN MARIE
• Application Number:
  US08/283,106
• Time in Patent Office: 1,040 Days
• Field of Search: 359/291, 359/290, 359/248
• US Class Current: 359/291
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

A direct-view display comprising an array of micro-mechanical modulators is disclosed, he modulator used to form the display comprises a suspended, vertically moving membrane and a substrate. The device functions based on optical interference effects between the membrane and the substrate which cause the modulator to either substantially reflect or absorb an optical signal. The interference effects are a function of the size of the air gap between the membrane and substrate, which varies as the membrane moves. The membrane moves in response to a data signal, representative of an image, delivered to the modulator. The display generates an image based on the pattern of light and dark sections of the display corresponding to the reflectivity of each modulator at a given point in time.

Claims

1. A direct-view display comprising:

a plurality of micromechanical modulators which have a variable and controllable reflectivity to an incident optical signal wherein the micromechanical modulators are organized in an array characterized by rows and columns, each micromechanical modulator comprising;

a substrate having a refractive index; and

an optically transparent membrane in spaced and superposed relation to the substrate defining a gap therebetween, the membrane comprising at least a first layer of material, the first layer having a refractive index which is approximately equal to the square root of the refractive index of the substrate, wherein,

the membrane is movable between a first position and a second position in response to a data signal, changing the gap resulting in a change in modulator reflectivity;

drive electronics for individually controlling the reflectivity of each of the micromechanical by selective application of the data signal; and

a light source for generating the optical signal.

2. The direct-view display of claim 1 wherein the substrate is p-doped silicon.

3. The direct-view display of claim 1 wherein the optical membrane is selected from the group consisting of polysilicon, silicon nitride and polyimide.

4. The direct-view display of claim 1 further comprising a flexible support that spaces the membrane from the substrate, wherein the flexible support is located substantially beneath the membrane from the perspective of the substrate.

5. The direct-view display of claim 4 wherein the flexible support comprises a plurality of pedestals positioned over a plurality of trenches.

6. The direct-view display of claim 1 wherein the flexible support comprises a plurality of flexible beams fixed to a support.

7. The direct-view display of claim 1 wherein the gap is an integer multiple of one-quarter of a wavelength of the optical signal when the membrane is in the first position.

8. The direct-view display of claim 1 wherein each modulator further comprises an address electrode for receiving the data signal from the drive electronics.

9. The direct-view display of claim 8 wherein the drive electronics comprise:

an address transistor, one for each modulator of the display, which is in electrical contact with the address electrode of the modulator, the address transistor having a gate and a drain, wherein the gate is electrically connected to a gate line, each row of modulators in the array having its own gate line, and the drain is electrically connected to a data line, each column of modulators in the array having its own data line;

a gate decoder which is in electrical contact with each address transistor in a row of modulators through the gate line;

shift registers for receiving the data signal, which shift registers are in electrical contact with a serial-to-parallel converter to parallel shift the data signal received by the shift registers; and

a driver amplifier electrically connected to the data line, each data line having its own driver amplifier, which receive the parallel shifted data signal,

wherein once a data signal has been received by the shift registers and parallel shifted, the gate decoder activates one row of address transistors by sending a signal along the gate line that is electrically connected to the one row, biasing the gate of each address transistor in the one row, which allows the data signal from the data line to be delivered to the address electrode of the modulator which is located at that particular row and column address.