Texas Instruments Corporation

Raytheon Company

Claude E Tew

Adam J Lewis, Jr

Walter Marvin Duncan

Frank Joseph Poradish

Benjamin Lowell Lee

Henry C Chu

Hiep V Tran

Richard O Gale, Jr

Joseph H Neal

James L Conner

Dana Dudley

Kevin L Kornher

Scott D Heimbuch

Keith Harold Elliott

Mark L Burton

Carl W Davis

Harlan Paul Cleveland

Fred E Ellis

Christopher L Bohler

Ngai Hung Hong

Randall S Lawson

A method for assuring a blazed condition in a DMD device used in telecommunications applications. By meeting certain conditions in the fabrication and operation of the DMD, the device can achieve a blazed condition and be very effective in switching near monochromatic spatially coherent light, thereby opening up a whole new application field for such devices. This method determines the optimal pixel pitch and mirror tilt angle for a given incident angle and wavelength of near monochromatic spatially coherent light to assure blazed operating conditions. The Fraunhofer envelope is determined by convolving the Fourier transforms of the mirror aperture and the delta function at the center of each mirror and then aligning the center of this envelope with a diffraction order to provide a blazed condition. The method of the present invention presents a formula for precisely determining the mirror pitch and tilt angle to assure that a blazed condition exists for a given incident angle and wavelength of near monochromatic spatially coherent light. Considerations for the special case, know as Littrow conditions, where the incident and the reflected light transverse the same path, are also given. This case is particularly attractive for fiber optic/telecommunication applications since the same optics can be used for incoming and outgoing (reflected) light.

Two-dimensional blazed MEMS granting

Two-dimensional blazed MEMS grating

An optical switch ideally suited for use as an optical add drop multiplexer (OADM). A light beam entering the OADM through a first input fiber ( ) is separated by wavelength to yield multiple light beams ( ). One light beam ( ) is reflected by one or more of the mirrors in mirror array ( ). Depending on the position of the mirrors struck by light beam ( ), the beam is reflected to a first region of a retro-reflector ( ) or a second region ( ). When light beam ( ) is reflected by the second region ( ) of the retro-reflector, it again travels to the mirror array ( ) and is then reflected to a wavelength combiner ( ) and output on the second (&ldquo;drop&rdquo;) output fiber ( ). While a first wavelength light beam ( ) is reflected to the drop output ( ), other wavelengths of light from the first input ( ), for example light beam ( ), are directed to the &ldquo;out&rdquo; optical fiber ( ). A first group of mirrors ( ) in the array ( ) are thus used selectively to switch various wavelengths of the input optical signal to either the &ldquo;out&rdquo; optical fiber ( ) or the &ldquo;drop&rdquo; optical fiber ( ). Another group of mirrors ( ) works cooperatively with the first group to direct light beams destined for the &ldquo;drop&rdquo; output fiber ( ) to the wavelength combiner associated with the &ldquo;drop&rdquo; output. Other groups of mirrors operate to switch various wavelengths from the second input ( ), the &ldquo;add&rdquo; fiber, to the first output &ldquo;out.&rdquo;

Optical add drop multiplexer

A dichroic spiral color wheel ( ) having many spiral-shaped color filters ( ). The boundary between adjacent color filters follows the spiral of Archimedes, defined as r&equals;a&thgr;, where r is the radius of the boundary at a given point, a is a constant, and &thgr; is the angle between a radial line through the given point and a reference radial. Using the spiral of Archimedes provides a boundary between adjacent color filters that is nearly parallel to the rows or columns of the modulator and moves across the light path at a constant speed. These two features make the spiral color wheel much more efficient than color wheels having pie shaped segments. The use of dichroic filters, which reflect out of band light is crucial to the operation of a sequential color recycling display system. When used in a sequential color recycling display system, small filter segments are used to enable on entire filter segment of each of the primary colors, and a clear segment if used, to be simultaneously imaged on the face of the light valve.

Color wheel for a falling raster scan

A family of optical switches. Each switch ( ) includes a holder block ( ) to hold optical fibers ( ) and ferrules ( ) in alignment with a micromirror array ( ). The holder block has a reflective bottom surface ( ). The bottom surface ( ) functions as a retro-reflector when the optical switch ( ) is assembled. The micromirror array ( ) has a substrate on which rows of micromirrors have been fabricated. The ferrules ( ) are held at an angle relative to the micromirror array ( ). This angle allows the light emitted from the input fiber ( ) to traverse the array of micromirrors ( ) to the output fiber ( ). Light from the input fiber ( ) is reflected between a series of mirrors ( ) and the retro-reflective surface ( ) until reaching the output fiber ( ). The rotation of the mirrors determines the path of light across the mirror array ( ) and which output fiber ( ) the light reaches.

Micromirror optical switch

An optical switch using an array of mirrors ( ) to selectively reflect light from an input fiber ( ) to either of a first output fiber ( ) or a second output fiber ( ). Each fiber is held in a ferrule ( ) that aligns the fiber with a focusing device ( ). The focusing device associated with the input fiber causes the beam of light to either collimate, diverge, or converge. The focusing device associated with each output fiber collects the beam of light for input into the output fibers. Light from the input fiber ( ) strikes a first mirror, or group of mirrors, in the array ( ) and is selectively deflected to a second mirror, or group of mirrors, associated with an output fiber ( ), by reflecting the beam of light from a retro-reflector ( ) between the fibers. The second mirror receives the beam from the retro-reflector ( ) and reflects it to the output fiber associated with the second mirror.

A frame-addressed bistable micromirror array and method of operation. An analog input signal representing the desired intensity of an image pixel is applied to input An address signal synchronized to the analog input signal is applied to input of a given micromirror cell to store the pixel intensity information on input capacitor After intensity information for each pixel in the video frame or field, or a portion of the frame of field, is stored on the input capacitor of the appropriate micromirror cell, a frame signal is applied to input to enable the transfer of charge between capacitors and and to turn on transistor allowing a voltage applied to input to charge capacitor The pre-charge voltage is chosen to ensure the biased micromirrors are fully deflected to a first state. A ramp voltage is applied to input A ramp voltage is applied to input When the difference between the voltage across capacitor which is applied to the gate of transistor and the ramp voltage, which is applied to the drain of transistor exceeds the threshold voltage required to turn on transistor transistor is turned on, and the voltage across capacitor follows the ramp voltage applied to The range of the ramp voltage is chosen so that, when any ramp voltage in the range is applied to the deflectable element of the micromirror, the deflectable element will assume the second state.

Analog pulse width modulation cell for digital micromechanical device

In an SLM-type display system, a solid state light source can be used to augment a lamp light source in a least two different ways. First, a solid state source can be used to augment deficiencies in a particular spectral region. Typically, lamps are deficient in red, and a red solid state source would be used. However, the same concept applies to augmenting any color region. Multiple solid state sources could be used to augment more than one region. Second, when the SLM system uses a color wheel, a solid state source can be used to eliminate &ldquo;spoke loss&rdquo;. Multiple solid state sources can be used for providing different colors during the spokes.

Solid state light source augmentation for SLM display systems

Methods of controlling the illumination source (,) of an SLM-based display system (,). It is assumed that the system (,) displays pixel data formatted into a bit-plane format so that all bits of the same bit-weight can be displayed simultaneously. To provide greyscale, the amplitude of the source (,) may be modulated so that bit-planes having greater bit-weights are displayed with more intense illumination than bit-planes having smaller bit-weights (FIGS.,and,). To avoid visual artifacts, the duty cycle of the bit-plane display times may be shortened relative to the frame period. (FIG.,A). The latter method can be accompanied by a shortening of the duty time of the illumination on SLM (,). (FIG.,B). The short duty cycle method may be used together with illumination amplitude modulation, or it may be used with the PWM method of providing greyscale.

Modulated-amplitude illumination for spatial light modulator

A forward looking infrared (FLIR) device implemented using complementary metal oxide semiconductor (CMOS) techniques is disclosed. The device includes optics (10) for focusing infrared energy onto a scanner (12) for scanning across a detector array 16; a signal conditioning integrated circuit 18 for producing television compatible video signals from the detector array outputs which are electrical signals representative of the infrared energy impinging thereon; and a monitor (2) for displaying the video signals. The detector array and signal conditioning IC are mounted on a metallized ceramic chip affixed within a DEWAR (19). Electronics (20) ancillary to the signal conditioning IC is located outside the DEWAR. The signal conditioning IC includes an array of preamplifiers (24) d-c coupled to the detector array for amplifying the detector array outputs, a-c coupled into band limiters (26) for limiting noise, an array of circuits (28) including d-c restoration circuits for restoring the d-c level to the a-c signals, offset circuits for partially correcting the d-c restored signals for MOSFET losses and a multiplexer. The multiplexer multiplexes the partially corrected signals as video signals to a multiplexer post amplifier 36A. The multiplexer post amplifier output goes to a multiplying digital to analog converter (MDAC) 30. The MDAC completes correcting the video signals for offset, and corrects the gain thereof for post amplification in a post amplifier 36 to provide 525 line video for television display.

Forward looking infrared device

An array of individual elements (10) having reduced control circuitry as compared to existing devices. Sets of elements (11) share a memory cell (12), such that each memory cell (12) has the same fanout as other memory cells (12). Each element (11) in a set is switched to an on or off state via a reset line (13) that is separate from that of the other elements (11) in that set. Data is loaded in split bit-frames during a set time period, such that each split bit-frame contains only the data for elements (11) on one reset line (13). Thus, the same memory cell (12) can be used to deliver data to all elements (11) in its fanout because only one element (11) in the fanout is switched at a time.

Time multiplexed addressing circuitry

An improved reticle (20) and method of using it to expose layers of wafers for large integrated circuits (10). The integrated circuit (10) is designed so that nonrepeating patterns are laid out in perimeter areas, distinct from the center area containing contiguous repeating patterns. The reticle (20) is patterned with multiple masks (21-23), with different masks representing the repeating and nonrepeating patterns. The mask (22) representing the repeating pattern may then be stepped and illuminated separately from any mask (21, 23) representing a nonrepeating pattern.

Large die photolithography

A brightness sensing circuit for providing a binary electrical signal for indicating whether incident light exceeds a certain brightness. The circuit's light detector is a photodiode, whose output is amplified by a first current mirror. The circuit has a reference current source, whose output is amplified by a second current mirror. Both currents are delivered to a common node, whose voltage level transitions from low to high when the amplified input current exceeds the amplified reference current. This node is connected to the gate input of a CMOS inverter, which provides a binary output.

On-chip light sensor

A method for controlling a digital micromirror device 40 resulting in decreased mechanical stress, longer device lifetimes, decreased incidence of spontaneous bit reset, and increased pulse-width modulation accuracy. To reduce the device stress, the bias voltage 142 applied to the mirror 50 may be reduced after the mirror 50 has been latched. To prevent premature mirror changes, the address electrode bias voltage 140 may be reduced after the mirror is driven to the desired position. To ensure that the mirror 50 returns to the neutral position during reset, the mirror bias voltage 142 may be raised from ground potential to approximately halfway between the two addressing voltages during the reset period 152. To reduce the effects of hinge memory and to ensure that the mirror 50 rotates toward the proper address electrode, the mirror bias voltage 142 may be gradually increased to allow the mirror 50 time to rotate towards the proper address electrode.

Optimized electronic operation of digital micromirror devices

A circuit primarily for use in conjunction with focal plane arrays which rejects input reset noise without adding power and complexity to the circuit. The circuit includes a preamplifier having input and output terminals, a first capacitor coupled between the input terminal and a source of reference potential, a second capacitor coupled between the output terminal and the source of reference potential, a switch coupled between the output terminal and the second capacitor coupling the output terminal to the second capacitor in response to a first predetermined signal, a third capacitor coupled between the junction of the switch and the second capacitor and a circuit output terminal and a plurality of fourth capacitors, each of the fourth capacitors coupled to a photodetector and having a switch responsive to a second predetermined signal controlling coupling of the fourth capacitor in parallel with the first capacitor. The values of the first, second, third and fourth capacitors are substantially in accordance with the relation C.sub.p /(C.sub.p +C.sub.DN)=C.sub.X /(C.sub.X +C.sub.c), where C.sub.P is the first capacitor, C.sub.X is the second capacitor, C.sub.C is the third capacitor and C.sub.DN is the fourth capacitor.

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Dallas, TX, United States of America

Claude E Tew