APPARATUS FOR OBTAINING ENHANCED CONTRAST IN PROJECTED IMAGES USING DIGITAL MICROMIRROR DEVICES

• US 20140327885A1
• Filed: 05/01/2013
• Published: 11/06/2014
• Est. Priority Date: 05/01/2013
• Status: Abandoned Application

• Current Assignee: David Joseph Mansur
• Original Assignee: David Joseph Mansur
• Inventors: Mansur, David Joseph
• Application Number:
  US13/874,847
• Publication Number:
  US 20140327885A1
• Time in Patent Office: Days
• US Class Current: 353/31
• CPC Class Codes: H04N 9/3126 for spatial light modulators in series

Abstract

A system for projecting digital images of ultraviolet, visible, and infrared scenes in which two or more digital micromirror devices (DMDs) are employed to create projected images which have greater contrast and bit depth than can be achieved with comparable prior art devices. A source DMD creates an image of the digital scene which is used to illuminate a projector DMD, so that the projector DMD is illuminated to an extent proportionate to the corresponding scene brightness, thereby reducing the amount of undesired radiation which would otherwise illuminate the projected scene via scattering, diffraction, and/or spurious reflections from within the projection system. By including dichroic beam-splitters and additional projector DMDs it is possible to project multi-spectral-band images having enhanced contrast and bit depth relative to prior art digital projection systems.

Claims

1. A DMD-based digital projection system for ultraviolet, visible, and/or infrared radiation in which enhanced contrast is achieved by using a first or source DMD, in combination with a series of lenses, to create an image of the desired scene in the plane of a second, or projection DMD which, when optically projected, creates an image of the desired scene, which image exhibits enhanced contrast and dynamic range by virtue of the selective illumination of the second DMD, which selective illumination serves to illuminate only those portions of the micromirror array which are intended to illuminate corresponding elements of the projected scene;

by thus avoiding the illumination of those portions of the projection micromirror array corresponding to dark regions of the projected image, those same portions of the micromirror array are unable to contribute undesired illumination of the projected scene due to scattered, diffracted, or reflected radiation.

2. The system of claim 1 in which infrared images may be projected using standard DMDs, intended for use at visible wavelengths, whose windows have been replaced by windows made from an infrared-transmitting material, which replacement windows have been attached in such a manner as to prevent contamination by particulate materials or by chemicals which might adversely affect the subsequent performance of the DMD.

3. The system of claim 1 in which imaging at two or more different wavelengths or spectral bands may be accomplished by utilizing a single source DMD in combination with separate projection DMDs for each wavelength or spectral band, and by using a first dichroic beam-splitter to separately illuminate the two projection DMDs, and by combining the separate projected images through the use of a second dichroic component.

4. The system of claim 1 in which uniform illumination of the first DMD is provided by Koehler telecentric illumination optics.

5. The system of claim 3 in which separate source DMDs are used for each spectral band.

6. The system of claim 1 in which the image of the source DMD is slightly de-focused to avoid the need for highly precise registration of the source DMD micromirror array on the projection DMD micromirror array.