Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2000-12-21
2002-11-05
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S239000
Reexamination Certificate
active
06476848
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a display system with a linear array of electromechanical grating devices that is scanned in order to generate a two-dimensional image. More particularly, the invention relates to an electromechanical grating display system that uses a segmented waveplate to select diffracted light beams for projection onto a screen.
BACKGROUND OF THE INVENTION
Spatial light modulators consisting of an array of high-speed electromechanical phase gratings are important for a variety of systems, including display, optical processing, printing, optical data storage and spectroscopy. Each of the devices on the array can be individually controlled to selectively reflect or diffract an incident light beam into a number of light beams of discrete orders. Depending on the application, one or more of the modulated light beams may be collected and used by the optical system.
Electromechanical phase gratings can be formed in metallized elastomer gels. The electrodes below the elastomer are patterned so that the application of a voltage deforms the elastomer producing a nearly sinusoidal phase grating. These types of devices have been successfully used in color projection displays; see
Metallized viscoelastic control layers for light
-valve projection displays, by Brinker et al., Displays 16, 1994, pp. 13-20, and
Full
-
colour diffraction
-
based optical system for light
-
valve projection displays,
by
Roder et al., Displays 16, 1995, pp. 27-34.
An electromechanical phase grating with a much faster response time can be made of suspended micromechanical ribbon elements, as described in U.S. Pat. No. 5,311,360, issued May 10, 1994 to Bloom et al., entitled Method and Apparatus for Modulating a Light Beam. This device, also known as a grating light valve (GLV), can be fabricated with CMOS-like processes on silicon. For display or printing, linear arrays of GLV devices can be used with a scanning Schlieren optical system as described in U.S. Pat. No. 5,982,553, issuedNov. 9, 1999 to Bloom et al., entitled Display Device Incorporating One-Dimensional Grating Light-Valve Array. Alternatively, an interferometric optical system can be used to display an image as disclosed in U.S. Pat. No. 6,088,102, issued Jul. 11, 2000 to Manhart, entitled Display Apparatus Including Grating Light-Valve Array and Interferometric Optical System. In the scanning Schlieren display system of Bloom et al. '553, the plane of diffraction that contains the diffracted light beams is parallel to the axis of the linear GLV array because the grating period is parallel to the axis. This feature increases the cost and complexity of the display system. Specifically, efficient collection of the primary diffracted light beams requires at least one dimension of the optical elements to be significantly larger than the extent of the linear GLV array. Furthermore, the diffracted and reflected light beams overlap spatially throughout most of the optical system. Separation of diffracted light from reflected light is accomplished in close proximity to a Fourier plane of the Schlieren optical system. However, the Fourier plane is also usually the preferred location of a scanning mirror for producing a two-dimensional image.
Recently, a linear array of electromechanical conformal grating devices was disclosed by Kowarz, in U.S. Ser. No. 09/491,354, filed Jan. 26, 2000. For this class of devices, it is preferable to have the grating period perpendicular to the axis of the linear array. The diffracted light beams are then spatially separated throughout most of the optical system. In U.S. Ser. No. 09/491,354, it was mentioned that a simplified display system can be designed based on this type of spatial light modulator. However, no specific description of the display system was given. There is a need therefore for a scanning display system that utilizes a linear array of electromechanical conformal grating devices. Furthermore, there is a need for a display system that is simpler and less costly than other known systems.
SUMMARY OF THE INVENTION
The need is met according to the present invention by providing a display system that includes: a light source providing illumination; a linear array of electromechanical grating devices of at least two individually operable devices receiving the illumination wherein a grating period is oriented at a predetermined angle with respect to an axis of the linear array wherein the angle is large enough to separate diffracted light beams prior to a projection lens system for projecting light onto a screen; a polarization sensitive element that passes diffracted light beams according to their polarization state; a segmented waveplate for altering the polarization state of a discrete number of selected diffracted light beams wherein the segmented waveplate is located between the linear array and the polarization sensitive element; a scanning element for moving the selectively passed diffracted light beams on the screen; and a controller for providing a data stream to the individually operable devices.
The present invention has several advantages, including: 1) improvement in contrast by eliminating reflections from the projection lens, because such reflections are directed away from the screen; 2) reduction in size of the scanning mirror, because now the scanning mirror can be placed directly at the Fourier plane; 3) increase in design flexibility, because now selection and separation of diffracted orders can take place almost anywhere in the system, rather than solely at the Fourier plane; and 4) reduction in size of lenses and other optical elements.
REFERENCES:
patent: 4441791 (1984-04-01), Hornbeck
patent: 4626920 (1986-12-01), Glenn
patent: 4857978 (1989-08-01), Goldburt et al.
patent: 5170283 (1992-12-01), O'Brien et al.
patent: 5311360 (1994-05-01), Bloom et al.
patent: 5459610 (1995-10-01), Bloom et al.
patent: 5661592 (1997-08-01), Bornstein et al.
patent: 5677783 (1997-10-01), Bloom et al.
patent: 5841579 (1998-11-01), Bloom
patent: 5844711 (1998-12-01), Long, Jr.
patent: 5982553 (1999-11-01), Bloom et al.
patent: 6082861 (2000-07-01), Dove et al.
patent: 6088102 (2000-07-01), Manhart
patent: 6323984 (2001-11-01), Trisnadi
W. Brinker et al., “Metallized Viscoelastic Control Layers For Light-Valve Projection Displays,” Feb. 7, 1994, pp. 13-20.
Roder et al., “Full-Colour Diffraction-Based Optical System For Light-Valve Projection Displays,” 1995, pp. 27-34.
Brazas, Jr. John C.
Kowarz Marek W.
Phalen James G.
Eastman Kodak Company
Pham Hai
Shaw Stephen H.
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