Tektronix, Inc.

Philip J Bos

Philip A Johnson

Scott H Rumbaugh

Michael D Jones

Dennis W Prince

Friedrich Scheu

Jolly A Rahman

A switchable color filter (11) includes three polarizing filters (12, 14, and 16) and two zero to substantially half-wave optical retarders (36 and 38) and is incorporated in a field sequential display system (10) to provide output states of light of three different colors to form an image in full color. Each one of four preferred embodiments (11, 11a, 11b, and 11c) of the switchable color filter provides the output states of three colors. The third and fourth preferred embodiments (11b and 11c) provide a fourth additional output state of, respectively, white light and light of a color which is a combination of two of the other output state colors. The optical retarders comprise nematic liquid crystal cells (100) having fast relaxation times to operate the display system at video rates.

Switchable color filter using electrically controllable optical retarders

A photocurable polymer precursor added to a liquid crystal material polymerizes to form a mixture that significantly lowers the threshold and saturation voltages of a standard twisted nematic cell. The performance characteristics of the resulting display device resembles those of a device with a very high pretilt, thereby providing an economical method of fabricating liquid crystal cells of a type that require a high pretilt alignment. The presence of the polymer substantially reduces adverse ion-related effects such as optical droop and charge retention in the liquid crystal display device.

Low electro-optic threshold liquid crystal cell and method of

A color liquid crystal display (LCD) includes many ones of a color cell triad (150) of liquid crystal cells (80R, 80G, 80B) and a negative birefringence compensator plate (110). The color cell triads are positioned between a pair of linear polarizers (112, 114), and each color cell triad is in optical association with colored filters (152R, 152G, 152B). Each of the liquid crystal cells has a symmetrical director field (82, 82') that produces a symmetrical but nonuniform color viewing circle curve (100) from the liquid crystal cell. The negative birefringence plate restores the color viewing angle uniformity. When graphed on a polar plot, the measured light transmission percentage curves (120, 122, 124) characterizing the LCD are substantially concentric circles surrounding the optical axis (18) for all azimuthal angles (28) and viewing angles (24) up to 30 degrees. Thus, the color LCD provides a multi-color display having colors that are perceptibly uniform over a wide range of azimuthal and viewing angles.

Color liquid crystal display having a wide viewing angle

A gray scale LCD cell device (116) combines a liquid crystal cell (80) having a symmetrical director field (82, 82') with a negative birefringence compensator plate (110) and interposes them between a pair of linear polarizers (112, 114). The symmetrical director field produces a symmetrical but nonuniform gray scale or color viewing circle curve (100) from the liquid crystal cell. The negative birefringence plate restores the gray scale or color viewing angle uniformity. When graphed on a polar plot, the measured light transmission percentage curves (120, 122, 124) characterizing the LCD are substantially concentric circles surrounding the optical axis (18) for all azimuthal angles (28) and viewing angles (24) up to 30 degrees. Adding colored filters (152) to a color cell triad (150) provides a basis for a multi-color display having uniformly perceived colors over a wide range of azimuthal and viewing angles.

Gray scale liquid crystal display having a wide viewing angle

Switchable color filter and field sequential full color display system

A light shutter system (10) incorporates a liquid crystal cell (12) operating as a variable optical retarder to selectively produce opaque and transmissive optical states corresponding to the respective first and second amounts of optical retardation of the variable optical retarder. The cell switches between a residual amount of retardation and an increased amount that equals the sum of half-wave retardation and the amount of residual retardation to provide a shutter system whose system retardation switches between zero retardation and half-wave retardation and thereby produces opaque and transmissive states with an optimal contrast ratio. The cell is positioned between a linear polarizing filter (14) and an elliptical analyzer (16), the latter including a linear polarizing filter (20) and an optical retarder (18) of fixed value. The transmission axis of the linear polarizing filters are angularly displaced relative to a projection of the optic axes of the cell by an amount that provides maximum light extinction in the opaque state. Maximum output light transmissive in the transmission state is achieved by establishing for the cell an optical thickness that exceeds half-wave retardation by an additional amount equal to the residual retardation. Other preferred embodiments that provide equivalent performance are described.

High contrast light shutter system

A polarization insensitive optical attenuator (10,40) uses a polymer-dispersed liquid crystal (PDLC) film (14,56) to provide attenuation control over a wide range of attenuation values. The attenuator has a relatively low minimum attenuation and reliable light transmission with minimal insertion loss. The present invention is also adaptable for use with a temperature controller (200) that stabilizes the PDLC film, which promotes more uniform, predictable attenuation values.

Liquid crystal fiber optic attenuator and process for making same

A state-of-polarization (SOP) control system (10) uses a SOP controller (28) that is responsive to a CPU (24) to perform endless and complete polarization signal detection for a fiber optic communication system. The SOP controller (28) comprises liquid crystal variable optical retarders (40, 42 and 44) that adjust the polarization state of local optical signal (36) in response to voltages provided by the CPU (24). The CPU (24) adjusts the voltage applied to the retarders (40, 42, and 44) separately in response to the magnitude of an interference signal (70), which corresponds to the degree to which the polarization of the local optical signal (36) and an input optical signal (12) are different.

Polarization controller for use in optical fiber communication system

A liquid crystal cell (10) includes a chiral liquid crystal material (16) captured between a pair of electrode structures (12 and 14). The liquid crystal material is of a type that exhibits in consecutive order chiral semitic nematic, smectic A, and chiral phases at successively lower temperatures. In a preferred embodiment, the chiral phase is of the smectic C type. The electrode structures have director alignment layers (22 and 22') deposited on their inner surfaces. The directors (28 and 30) of the liquid crystal material in the nematic phase in contact the alignment layers align at relatively large tilt bias angles relative to the alignment layer. The tilt bias angles of the directors in contact with one of the electrode structures are defined in a rotational sense which is opposite that of the tilt bias angles of the directors in contact with the other electrode structure. The liquid crystal cell of the present invention is substantially free from smectic plane alignment defects and exhibits substantially uniform director alignment properties. As a consequence, a display device (36) using the liquid crystal cell has an essentially contaminant-free viewing surface and good light extinction properties. Such a display device also has a relatively large off-axis viewing angle.

Chiral liquid crystal cell

A ferroelectric liquid crystal matrix display drive waveform scheme and circuit are disclosed which produce a resultant waveform at each pixel defined by the intersections of row and column electrodes that varies among three levels during each strobe interval. In a matrix of N rows and M columns, the rows are serially strobed with a strobe waveform that varies through three levels to provide select and non-select strobe signals. During each strobe interval, the column driver circuitry generates three-level and three-phase, time-variant drive waveforms. The circuit can provide up (write) and down (erase) pulses selectively to each pixel of the display using standard twisted-nematic type liquid crystal display drivers. A complex waveform generator provides three-level, three-phase control signals to the supply voltage inputs of the drivers. Timing and synchronizing signals are extracted from the graphics data and timing source outputs to enable the multilevel, multiphase signals to produce the three-phase resultant waveforms at each pixel in a sequence that correctly switches the display state of each pixel in accordance with the data without flicker and with uniform high contrast.

Drive waveform for ferroelectric displays

A stereoscopic imaging system employs an image encoder that comprises a variable optical retarder which is positioned face-to-face with an image source and an image decoder that comprises only passive optical elements. In a first embodiment, the imaging system (50) uses a single variable optical retarder (22) to encode perspective view images by selectively developing zero and half-wave retardation. A passive viewing apparatus (52 and 54) employs retardation plates (56, 58, and 64) to decode the images. In a second embodiment, the imaging system (100) uses a pair of variable optical retarders (101 and 102) to encode perspective view images in left- and right-circularly polarized light. A passive viewing apparatus (106 and 108) employs quarter-wave plates (110 and 114) to decode the images. Each of the preferred embodiments is suitable for use with broadband image source phosphors and in processing perspective view images in full color.

Stereoscopic imaging system with passive viewing apparatus

A field sequential color display system (10) employs a liquid crystal device operating as a variable optical retarder (12) which is positioned in front of the screen (40) of a raster scanned cathode ray tube (38) to develop a high quality multicolored image. The liquid crystal device is divided into upper and lower cell segments (34 and 36) to decrease the time between successive color fields. Each cell segment has a separate electrode structure (30 and 32) and a common electrode structure (22) and is separately commanded by a switching circuit (46) to a predetermined optical retardation state when the electron beam scans the portion of the screen covered by the cell segment. The switching circuit provides signals in a predetermined time sequence to the cell segments to minimize the optical cross talk between them and thereby minimize the spurious transmission of colored light from the display system.

Method and apparatus for reducing optical cross talk in a liquid crystal

A high-speed electro-optical light gate (40) includes a pair of matched variable optical retarders (54 and 56) positioned between a pair of light polarizing filters (42 and 44) to promote rapid switching between optical transmission states for light rays of the wavelength to which the variable optical retarders are tuned. The projections (62 and 66) of the optic axes of the variable optical retarders are orthogonally aligned so that the response time characteristics of the transitions between optical transmission states of the light gate reflect only the turn-on time response characteristic of the variable optical retarders. A field sequential color display system (78) incorporates a switchable color filter (80) which utilizes the alignment configuration of the variable optical retarders of the light gate to provide light output states of white light and light of three different colors to form an image in full color.

High-speed electro-optical light gate and field sequential full color

A field sequential color display system incorporates a color switch which includes a zero to half-wave optical retarder and pleochroic filters to provide an image with high color contrast and resolution over a broad range of display sizes. In a preferred embodiment, a liquid crystal cell which operates between two states of optical retardation comprises the variable retarder to provide a color switch with substantially reduced optical response times.

Field sequential color display system using optical retardation

A liquid crystal cell (100) includes a chiral additive in the liquid crystal material (106) to operate the cell as a rapid starting, high-speed variable optical retarder. The cell is fabricated so that the surface noncontacting directors (116 and 118) of the opposed surfaces of the director alignment layers (112 and 112') of the electrode structures (102 and 104) are tilt-biased in opposite directions. This surface contacting director configuration induces rapid surface noncontacting director (120a, 120b, 120c, 120d, 120e) relaxation without optical bounce when the cell is switched from the field aligned ('ON') state to the partly relaxed ('OFF') state. The chiral additive prevents an inactive cell from relaxing to the splayed topological state, thereby enabling switching operation without a warm-up delay and preventing the surface of the cell from having a mottled appearance when it remains unused.

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Beaverton, OR, United States of America

Philip J Bos