Dual-flexure light valve

• US 6,301,000 B1
• Filed: 01/11/2000
• Issued: 10/09/2001
• Est. Priority Date: 01/11/1999
• Status: Expired due to Fees

• Current Assignee: Kenneth Carlisle Johnson
• Original Assignee: Kenneth Carlisle Johnson
• Inventors: Johnson, Kenneth Carlisle
• Primary Examiner(s): Adams, Russell
• Assistant Examiner(s): NGUYEN, HUNG
• Application Number:
  US09/480,426
• Time in Patent Office: 637 Days
• Field of Search: 355/67-68, 355/71, 355/53, 355/44-45, 359/290-291, 359/572
• US Class Current: 355/67
• CPC Class Codes: G03F 7/70275 Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging
• CPC Class Codes: G03F 7/70383 Direct write, i.e. pattern is written directly without the use of a mask by one or multiple beams maskless lithography using a programmable mask G03F7/70291

Abstract

A spatial light modulator pixel includes a flexible reflective surface that is electrostatically actuated to control the surface shape and thereby phase-modulate reflected light. The reflected light is filtered by a projection aperture, wherein the phase modulation controls the amount of light from the pixel that is filtered through the aperture. The spatial light modulator includes and array of such pixels, which are imaged onto a conjugate image plane, and each pixel controls the image brightness at a corresponding conjugate image point. High image contrast is achieved by using a dual-flexure pixel design in which two flexure elements operate conjunctively to maintain well-defined diffraction nodes at or near the projection aperture edges over the full modulation range.

Claims

1. A spatial light modulator comprising an array of radiation-modulating pixel elements, wherein

each pixel comprises a flexible reflective surface supported over a substrate,

the space between each pixel surface and the substrate is partitioned into two cells by means of cell walls that support the surface along two opposite sides of the pixel and along a center line between the two sides,

the portion of the surface over each cell forms a flexure element that is electrostatically actuated to control its surface shape,

illuminating radiation originating from an illumination source reflects off of the pixel array and is focused onto a focal plane conjugate to the source,

a portion of the reflected radiation is filtered by a projection aperture proximate to the focal plane, and

each pixel'"'"'s flexure elements control the reflected radiation'"'"'s phase distribution across the pixel, thereby controlling the amount of radiation energy from that pixel that is filtered by the projection aperture.

2. The spatial light modulator of claim 1, wherein each pixel'"'"'s reflective surface is bordered by phase shifters along two opposite sides of the pixel, wherein the phase shifters are configured to maximize a “

contrast ratio”

defined as the ratio of the maximum to minimum achievable aperture-filtered energy.

3. The spatial light modulator of claim 1, wherein the filtered radiation from each pixel is focused onto a corresponding image point on an image plane conjugate to the spatial light modulator, the projection aperture is disposed in the light path between the spatial light modulator and the image plane, and each pixel controls the image intensity at its corresponding image point.

4. The spatial light modulator of claim 3, wherein a printing surface is disposed proximate to the image plane and is exposed by the filtered radiation.

5. The spatial light modulator of claim 3, wherein a microlens array is disposed proximate to the image plane, the filtered radiation from each pixel is focused by a corresponding microlens element onto a focal point proximate to a printing surface, and the printing surface is scanned relative to the focal points as the pixels are actuated to form a digitally-synthesized, high-resolution exposure image on the printing surface.