WO1998034152A1 - Temperature compensation of a wedge-shaped liquid-crystal cell - Google Patents
Temperature compensation of a wedge-shaped liquid-crystal cell Download PDFInfo
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- WO1998034152A1 WO1998034152A1 PCT/US1998/000413 US9800413W WO9834152A1 WO 1998034152 A1 WO1998034152 A1 WO 1998034152A1 US 9800413 W US9800413 W US 9800413W WO 9834152 A1 WO9834152 A1 WO 9834152A1
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- liquid
- crystal
- crystal cell
- cell
- temperature
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/133382—Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/133371—Cells with varying thickness of the liquid crystal layer
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
- G02F1/31—Digital deflection, i.e. optical switching
Definitions
- the invention generally relates to liquid-crystal optical devices.
- the invention relates to the temperature compensation of such devices.
- Liquid-crystal modulators are well known. They are most prevalently used in displays ranging in size from wrist watches to flat-panel displays on lap top computers. In such displays, the bias applied to the pixel of the multi-element cell, when used in combination with polarizers, determines whether the pixel absorbs or passes light. Since the output is directly viewed, the ratio of the light passed in the transmissive mode to the light passed in the absorptive mode need not be very high for the contrast between the two states to be readily discernible. This ratio of intensities or similar characteristics is referred to as the extinction ratio for a liquid-crystal cell.
- ⁇ n is the birefringence, that is, the difference between the extraordinary and ordinary refractive indices n e , n beau, and ⁇ is the free-space wavelength of the light with the previously defined quantities.
- the nematic liquid crystal is twisted by 90° when no electrical bias is applied across the cell.
- the transmissivity when a strong electrical bias is applied across the cell is equal to unity when the parallel-polarizer transmissivity / is defined as in Equation (1).
- the ratio of the biased transmissivity to the parallel-polarizer transmissivity / is often called the extinction coefficient although there is some ambiguity in the usage of the latter term.
- the parallel-polarizer transmissivity I needs to be minimized, and it depends upon the thickness d with the dependence defined in Equation (1).
- the transmissivity I is relatively small for values of u greater than 1, it assumes a zero (minimum) value only for a discrete set of parameters dependent upon the positive even integers
- Equation (3) The values stated in either Equation (3) or (4) are known as the first, second, and third minimum conditions respectively and represent conditions for which exact polarization conversion occurs.
- Patel discloses that the gap size can be precisely controlled in a wedge-shaped liquid-crystal cell 10 illustrated in partial cross section in FIG. 1.
- the cell 10 includes two assemblies of respective glass substrates 12, 14 coated with respective electrodes 16, 18 and alignment layers 20, 22, as is common for most liquid-crystal devices.
- two different sizes of spacers are used so that gap 24 assumes the shape of a wedge, that is, of varying gap from the top to the bottom.
- a typical variation in the size of the gap 24 is between 6 and 8 ⁇ m for the infra-red optical switches contemplated by Patel.
- the angle of the wedge is exaggerated in FIG. 1.
- a nematic liquid crystal 26 is filled into the so defined wedge-shaped gap 24.
- This wedge-shaped liquid-crystal cell 10 is usable with an optical beam 28 having a vertical dimension small compared to the size of the cell 10 along the wedge direction.
- the cell 10 is supported on a vertically movable support 30, and an adjustment means 32 vertically moves the support 30 and hence the wedge-shaped liquid-crystal cell 10 up or down until the beam 28 strikes the cell 10 at a position having an optimally sized gap.
- the optimal size can be determined by several optical means, as is explained in the parent application.
- the wedge-shaped liquid-crystal cell allows the operational gap to be established to accuracies virtually unobtainable in planar cells because manufacturing introduces variations in thickness much larger than the required accuracy in gap thickness.
- the refractive index of nematic liquid crystals generally follows the dependence shown in FIG. 2. Above an isotropic transition temperature T shall also known as the clearing temperature, the refractive index is isotropic and the useful nematic qualities are absent. Below the clearing temperature 7 1 , the refractive index is represented by an upper curve 40 for extraordinarily polarized light, that is, n e , and by a lower curve 42 for ordinarily polarized light, that is, n (> .
- the difference between the two refractive indices 40, 42 is the refractive index difference or birefringence ⁇ n appearing in Equation (2).
- the value of the parameter u which depends upon ⁇ n, needs to be precisely controlled for zero transmissivity I.
- the temperature dependence of FIG. 2 shows that the refractive index difference is dependent upon the operating temperature. That is, the birefringence should be represented as ⁇ n(T').
- a liquid-crystal optical system that is compensated for thermal variations in the liquid crystal.
- the temperature of the liquid crystal is monitored by direct or indirect methods to produce a feedback signal that is used to physically change the path length through the liquid crystal of the light being polarization modulated by the liquid crystal.
- the beam path length is effected by relatively moving the cell and the beam along the direction of the wedge.
- FIG. 1 is cross-sectional view of a wedge-shaped liquid-crystal cell.
- FIG. 2 is a graph of the temperature dependence of the refractive index of a typical nematic liquid crystal.
- FIG. 3 is schematic representation of a temperature-sensing embodiment of a temperature-compensating liquid-crystal system.
- FIG. 4 is a graph of the dependence of the optimum cell gap size upon temperature.
- FIG. 5 is a semi-logarithmic graph of the transmitted optical intensities for both a data signal and a probe signal of differing wavelengths as they depend upon the gap size.
- FIG. 6 is a linear graph of the transmitted intensity of the probe signal as function of the gap size.
- FIG. 7 is a schematic representation of a intensity-sensing embodiment of the temperature-compensating liquid-crystal system of the invention.
- FIG. 8 is a circuit schematic of a servo control circuit usable in the embodiment of FIG. 7.
- FIG. 9 is a schematic cross-sectional view of a liquid-crystal cell whose gap is piezoelectrically varied.
- FIG. 10 is a schematic view, partially in cross section, of a liquid-crystal cell whose gap is varied by the application of mechanical force.
- FIG. 11 is a cross-sectional view of a micromechanical embodiment of an adjustable liquid-crystal cell of the invention.
- FIG. 12 is a plan view of the micromechnical embodiment of FIG. 11 taken along the view line 12-12.
- FIG. 13 is a schematic block diagram of a variation of the control system of the invention incorporating an optical performance monitor.
- the invention exploits the fact that thermal variations in the refractive index difference or birefringence ⁇ n can be compensated by a controlled change in the effective cell thickness d.
- the parameter u the only variable in Equation (1), is proportional to the product d- ⁇ n so a thermally induced increase (decrease) in ⁇ n can be compensated by a decrease (increase) in d.
- the effective thickness d can be changed by a simple translation of the cell along the direction of the wedge.
- thermometric embodiment for temperature compensation of a wedge-shaped liquid-crystal cell includes an electronic temperature sensor 50, such as a thermocouple or varistor thermally contacted to the wedge-shaped cell 10. More than one temperature sensor can be placed at different positions of the cell if thermal gradients are expected.
- the output of the temperature sensor 50 is monitored by a control circuit 52, such as a microprocessor or other logic circuitry.
- a look-up table 54 contains optimum vertical positions for the liquid-crystal cell 10 as a function of its temperature.
- the look-up table 54 could be implemented as non-volatile memory with locations storing positions accessed by an address determined by temperature. Plot 62 in FIG.
- An actuator 56 such as a stepper motor, can move the platform 30 supporting the wedge-shaped cell 10 up and down, for instance, through a threaded motor shaft 58 engaging a nut-box 60 fixed to the platform 30.
- the control circuit 52 uses the detected temperature to access the look-up table 54 for a vertical position and issues forward and reverse rotation commands to the motor 56 to bring the vertical position of the platform 30 and hence that of the wedge-shaped cell 10 into conformance with the new desired position.
- An alternative and preferred approach uses active control of the vertical position of the wedge-shaped cell through a feedback circuit, which is preferably servoed to an optical signal traversing the wedge-shaped cell 10.
- a particularly preferred approach is based upon the following observations.
- the extinction ratio or more precisely the parallel-polarizer transmissivity I for the 1550nm data signal of interest is given by plot 70 in FIG. 5 as a function of the effective gap size d.
- ⁇ n s (T) is the birefringence of the liquid crystal at the signal wavelength and at the operating temperature T.
- u is a fixed number, the preferred thickness value d s varies with temperature.
- Plot 72 on FIG. 5 shows the transmissivity L for a probe signal at a significantly different wavelength, here 800nm, as a function of the same cell thickness d.
- the probe wavelength is chosen so that the probe signal is operating far away from any of the minimum conditions u, so that its transmissivity is only slightly below unity (below zero on a logarithmic scale). Nonetheless, the probe signal is operating on one of the tails of its transmissivity curve (it does not really matter which tail) when it traverses a cell with the optimum signal gap d s or even a gap of nearly the same size.
- a representation on a linear scale of the dependence of the probe transmissivity I P on the gap size d is shown by plot 74 in FIG. 6, which is equivalent to plot 72 of FIG. 5. This dependence is nearly but not quite linear.
- the probe transmissivity has a value I P S , here slightly above 0.4.
- the probe signal is monitored and the gap size d s is adjusted to keep the probe intensity at the value I P S .
- the probe intensity may be measured by the probe transmissivity I P or other proportional quantity, such as the detected probe intensity. If the detected probe intensity I P is too high, the gap size d should be increased; if is too low, the gap size d should be decreased. The amount of deviation is a measure of the amount of correction required.
- FIG. 7 A schematic representation is shown in FIG. 7 of a feedback control system that relies upon sensing the intensity of light transmitted through the wedge-shaped cell 10, the taper of which is greatly exaggerated in the figure.
- the wedge-shaped liquid-crystal 10 includes multiple segmented electrodes 80 on one face and an unillustrated electrode on the opposing face to define segments of a multi-wavelength liquid-crystal cell.
- the segments receive respective optical data signals, here assumed to be in the neighborhood of 1550nm, along respective beam paths 28.
- Four electrodes segments 80 and beam paths 28 are illustrated.
- the invention can be used with any number, from one up to a much larger number. Eight to twenty optical channels are being planned for WDM networks with which the invention can be advantageously used.
- the electrodes 80 of the segments can be separately biased to selectively convert the polarization states of the respective optical data signals.
- Unillustrated polarizing elements on the input and output sides are generally required to provide switching or filtering of the optical signals according to the electrical bias applied across the respective liquid-crystal segments.
- the wedge-shaped cell 10 is moved up or down along the wedge direction by the motor 56 and worm drive 58 engaging a worm box 60 or by other type of positional actuator so that the optical signals following the beam paths 28 strike the wedge-shaped cell at an optimal position along the wedge, that is, the position having the optimal gap size d s .
- a light source such as a laser 82 outputs a probe beam 84 which strikes the wedge-shaped liquid-crystal cell 10 at a horizontal position away from the data beams 28 and the segmented electrodes 80 but at a vertical position relatively close to that of the data beams 28.
- the same polarization elements may be used for the probe beam 82 as for the data beams 28, but other polarization schemes may be employed.
- the probe beam 28 is not modulated but is exposed to the same state of the liquid crystal as an unbiased data beam 28.
- the unbiased state for a data signal is the one exhibiting a very high extinction ratio (low transmissivity) for the wavelength of the data signal.
- the wavelength of the probe signal from the laser 82 is significantly different from that of the data signals and does not exhibit absorption resonances at the same gap thickness d.
- the probe intensity varies smoothly with the gap size, as illustrated in FIG. 6, over the desired range of operation.
- An exemplary probe wavelength is around 800nm, a wavelength region for which GaAs-based semiconductor lasers are available.
- An optical detector 86 detects the intensity of the probe beam 84 traversing the liquid-crystal cell 10 and associated polarizers and provides an electrical signal over a detection line 88 to a servo control circuit 90.
- the electrical signal is generally proportional to the intensity of the transmitted probe signal, but strict linearity is not required.
- the servo control circuit 90 processes the probe intensity signal and issues an electrical correction signal over a correction line 92 to the motor 56 to move specified amount in a specified direction (up or down) so as to reduce and eventually zero out any difference between the detected intensity of the probe signal and the desired value. Because the control is included in a feedback loop, the correction does not need to be immediately accurate but may slowly approach the desired state.
- a simple example of the servo control circuit 90 is given in the circuit schematic of FIG. 8.
- the probe intensity signal is connected to one differential input of an analog comparator 94, such as a bipolar differential operational amplifier.
- the other differential input of the comparator 94 is connected to a reference voltage source 96 that has been set to a optimum value V PS , of the probe intensity signal.
- the output of the comparator 94 which is proportional to the difference between its inputs, is input to a PID servo signal circuit 98.
- the PID circuit 98 takes a linear combination of the comparator output signal, its time integral and its time differential to produce a servo signal with quick response, but without excessive overshoot or the possibility of unstable oscillation.
- the servo signal indicating both the direction and the amount of correction for the position of the wedge-shaped cell, is input to a motor controller 100 which converts the correction signals into a form appropriate for the motor 56 controlling the cell position. For example, if the motor 56 is a stepper motor, the motor controller 100 samples the analog servo signal at fixed periods, and converts it to a number of digital pulses (or motor steps) and a second digital signal indicating the direction of rotation for the motor.
- the reference voltage source 96 is a variable voltage source which is calibrated by changing its voltage value until the optical performance of one or more of the data signals is optimized, for example, according to the characterizations described in the parent patent application.
- the slope of the dependence 74 may be opposite to that illustrated.
- the slope is reversed by switching the inputs to the comparator 94 or by changing the sign of the terms in the PID servo circuit 98.
- the magnitude of the slope can be compensated by adjusting the gain of the comparator 94 or by changing the magnitude of the terms in the PID servo circuit 98.
- Equation (7) has been generalized to allow d s to be different from d P . That is, the probe and data signals may be aligned to strike at different vertical positions of the wedge. Any deviations between the birefringence thermal coefficients in Equation (7) will tend to pull the data signals somewhat off the minimum condition of maximum extinction coefficient at temperatures away from the calibration temperature, but the thermal compensation will be good to first order.
- a partial correction for non-equal birefringence thermal coefficients can be effected by vertically offsetting the data and probe beams 28, 84 so as to create a larger thermal effect in one or the other of the beams.
- the translation of the liquid-crystal cell may be effected by any controllable means, whether electrical, mechanical, or a combination thereof.
- the temperature of the liquid-crystal cell may be measured or monitored by any means known in the art.
- the embodiments described above used translation of a wedge-shape liquid- crystal cell to effect the thermal compensation.
- optics controlling the vertical positions of the beams could be used to achieve the same relative movement to accomplish a change in the effective cell gap across which the data beam propagates.
- the effective gap size can be changed in a number of different ways. In a first alternative approach for varying the gap, as illustrated in cross section in FIG.
- the gap of a liquid-crystal cell 110 is determined by one or more spacers 112 composed of a piezoelectric material, such as lead zirconate titanate (PZT).
- Two electrodes 114, 116 sandwich the piezoelectric spacers 112 so that a selected voltage applied across the electrodes 114, 116 causes the piezoelectric spacers 112 to be elastically compressed or extended depending upon the in the direction of the applied field relative to the polarization direction of the materials polarization direction.
- the magnitude of the mechanical deformation is generally proportional to the magnitude of the applied voltage.
- the gap size of the liquid-crystal cell can be electrically controlled.
- the gap-varying electrodes may assume several forms.
- the planar liquid-crystal electrode may be used as one of the gap-varying electrode.
- Another gap- varying electrode is patterned over the piezoelectric spacers 110 and in areas removed from the segmented liquid-crystal electrodes.
- the illustrated liquid-crystal cell is planar, the same concept can be applied to a wedge-shaped cell.
- the glass plates 12, 14 providing the principal mechanical strength of the cell are separated by sets of spacers 120, 122 on the top and bottom of the cell.
- the liquid crystal 26 is filled into the gap between the glass plates 12, 14.
- the liquid-crystal electrodes and the alignment layers between the glass plates 12, 14 and the liquid crystal 26 are not illustrated here.
- At least the spacers 124 on one side of the cell are elastic.
- An actuator 126 for example a pneumatic cylinder applies a controlled force or displacement to an actuating rod 128 pressed against one glass plate 14 in the area of the elastic spacers 124.
- the corresponding area of the other glass plate 12 butts up to a wall 130 of a support 124 to which the actuator 126 is fixed.
- Selective application of force by the actuator 126 will cause the elastic spacers to compress, thereby reducing the size of the cell gap. If such force is applied to all the elastic spacers 124, 126, then the gap is uniformly reduced.
- a selectively tapered wedge is formed with the effective gap at the midpoint being reduced by one-half the reduction of the spacers 124.
- the beams need to be lined up in the direction perpendicular to the wedge direction for them to experience a uniform variation in gap size.
- an adjustable gap in a liquid-crystal cell relies upon a micro electro mechanical system (MEMS).
- MEMS micro electro mechanical system
- This recently developed technology uses the fabrication techniques of silicon integrated circuits to build miniature mechnical system. As illustrated in cross section in FIG. 11 and in plan view in FIG. 12, the top surfaces of two silicon wafers 140, 142 are coated with respective layers 146, 148 of silicon oxynitride (SiO x N y ) to thicknesses of the order of micrometers. The exact thicknesses are chosen so that at least one of the layers 146, 148 is deformable, as will be described later. A series of electrodes are deposited and defined over the silicon oxynitride layers 146.
- segmented liquid-crystal electrodes 150 include segmented liquid-crystal electrodes 150, a matching planar liquid-crystal electrode 152, and two opposed deformation electrodes 154, 156.
- Matching apertures of size of about lOO ⁇ mx lOO ⁇ m are etched from the bottom surface of the silicon wafers 142, 144 in the areas of the electrodes 150, 152, 154, 156 all the way to the silicon oxynitride layers 146, 148.
- the two wafers 142, 144 are bonded together to form a cavity 158 that is filled with a liquid crystal.
- a multi-wavelength liquid-crystal switch is a complex system with many important performance characteristics when used in an extended communication network.
- optical performance monitor 160 as illustrated in the schematic block diagram of FIG. 13, to monitor the optical performance of the optical signals being switched.
- Optical signals are input to the switching system on two optical input paths 162, such as optical fibers.
- Optical couplers 164 are disposed on the optical paths 162 prior to optics 166, such as wavelength-dispersive elements and lenses, distributing the optical input signals to the wedge-shaped liquid-crystal cell 10.
- the optical couplers 164 tap a small fraction of the optical input signals to a 1 ⁇ 4 optical time multiplexer 168.
- output optical couplers 170 are disposed on output optical paths 172 on the output side of switch output optics 174 to tap a portion of the optical output signals to the time multiplexer 168.
- the 1 x4 time multiplexer 168 sequentially couples each of its four inputs to the performance monitor 160.
- the performance monitor 160 which includes additionally optics, measures the intensities and the wavelengths of the four multi-wavelength signals as well as noise levels.
- the controller 52 thus is informed of the signal-to-noise levels of the optical signals and can derive values of cross talk.
- Sufficient intelligence is incorporated into the controller 52 to trade off the thermal signal provided by the thermocouple 50 with the optical performance of the switch to allow an optimized correction signal for the motor 56.
- the thermal monitoring signal may be provided by the out-of-band extinction coefficient, as in FIG. 7, or by other means, and the liquid-crystal gap size may be adjusted by other means than the motor, for example, as shown in FIGS. 8 through 12.
- the performance monitor 140 is also useful for compensating for thermal effects in the switching system other than the thermal coefficient of the liquid crystal. If the optics 146, 150 are affected by temperature, an additional motorized stage can be included to selectively translate the liquid-crystal cell 10 in a direction along which the liquid-crystal segments 80 are arranged so as to align the passbands of the wedge- shaped cell with the multi- wavelength bands.
- the invention thus provides the thermal compensation required of a high- performance liquid-crystal modulator or switch without the necessity of maintaining the temperature within a narrow range.
- the embodiment involving the translation of the wedge-shaped cell involves inexpensive, straightforward technology.
- thermal compensation is the most useful application of the invention, the same inventive features can be applied to compensating for other temporally varying effects, for example, humidity or drifting optical carrier wavelengths, which may affect the optical characteristics of the liquid crystal or the mechanical structure defining and supporting the cell and directly or indirectly affecting its optical characteristics.
Abstract
Description
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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EP98902459A EP0958523A1 (en) | 1997-02-05 | 1998-01-08 | Temperature compensation of a wedge-shaped liquid-crystal cell |
CA002279518A CA2279518A1 (en) | 1997-02-05 | 1998-01-08 | Temperature compensation of a wedge-shaped liquid-crystal cell |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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US3721697P | 1997-02-05 | 1997-02-05 | |
US60/037,216 | 1997-02-05 | ||
US08/891,093 US6075512A (en) | 1997-02-05 | 1997-07-10 | Temperature compensation of a wedge-shaped liquid-crystal cell |
US08/891,093 | 1997-07-10 |
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WO1998034152A1 true WO1998034152A1 (en) | 1998-08-06 |
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PCT/US1998/000413 WO1998034152A1 (en) | 1997-02-05 | 1998-01-08 | Temperature compensation of a wedge-shaped liquid-crystal cell |
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US (1) | US6075512A (en) |
EP (1) | EP0958523A1 (en) |
CA (1) | CA2279518A1 (en) |
WO (1) | WO1998034152A1 (en) |
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US10254542B2 (en) | 2016-11-01 | 2019-04-09 | Microsoft Technology Licensing, Llc | Holographic projector for a waveguide display |
US11022939B2 (en) | 2017-01-03 | 2021-06-01 | Microsoft Technology Licensing, Llc | Reduced bandwidth holographic near-eye display |
US10712567B2 (en) | 2017-06-15 | 2020-07-14 | Microsoft Technology Licensing, Llc | Holographic display system |
CN107632427A (en) * | 2017-11-06 | 2018-01-26 | 南京华日触控显示科技有限公司 | Test liquid crystal photoelectric parameter wedge of glass box and preparation method |
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GB2163864A (en) * | 1984-08-31 | 1986-03-05 | Olympus Optical Co | Spectacle lens |
US4840461A (en) * | 1986-10-07 | 1989-06-20 | British Telecommunications Public Limited Company | Optical switching devices having liquid crystal with splayed molecular orientation |
US5113275A (en) * | 1991-07-03 | 1992-05-12 | Bell Communications Research, Inc. | Temperature compensation of liquid-crystal etalon filters |
US5615029A (en) * | 1995-03-08 | 1997-03-25 | Electronics & Space Corp. | Electro-optic wedge structure for beam steering and method of manufacture |
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US4952032A (en) * | 1987-03-31 | 1990-08-28 | Canon Kabushiki Kaisha | Display device |
US5841500A (en) * | 1997-01-09 | 1998-11-24 | Tellium, Inc. | Wedge-shaped liquid crystal cell |
-
1997
- 1997-07-10 US US08/891,093 patent/US6075512A/en not_active Expired - Fee Related
-
1998
- 1998-01-08 WO PCT/US1998/000413 patent/WO1998034152A1/en not_active Application Discontinuation
- 1998-01-08 EP EP98902459A patent/EP0958523A1/en not_active Withdrawn
- 1998-01-08 CA CA002279518A patent/CA2279518A1/en not_active Abandoned
Patent Citations (4)
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GB2163864A (en) * | 1984-08-31 | 1986-03-05 | Olympus Optical Co | Spectacle lens |
US4840461A (en) * | 1986-10-07 | 1989-06-20 | British Telecommunications Public Limited Company | Optical switching devices having liquid crystal with splayed molecular orientation |
US5113275A (en) * | 1991-07-03 | 1992-05-12 | Bell Communications Research, Inc. | Temperature compensation of liquid-crystal etalon filters |
US5615029A (en) * | 1995-03-08 | 1997-03-25 | Electronics & Space Corp. | Electro-optic wedge structure for beam steering and method of manufacture |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1181620A1 (en) * | 1999-04-16 | 2002-02-27 | Corning Incorporated | Wavelength compensation in a wsxc using off-voltage control |
EP1181620A4 (en) * | 1999-04-16 | 2002-10-16 | Corning Inc | Wavelength compensation in a wsxc using off-voltage control |
US6567202B2 (en) | 1999-04-16 | 2003-05-20 | Corning Incorporated | Wavelength compensation in a WSXC using off-voltage control |
US6775044B2 (en) | 1999-04-16 | 2004-08-10 | Corning Incorporated | Wavelength compensation in a WSXC using off-voltage control |
Also Published As
Publication number | Publication date |
---|---|
US6075512A (en) | 2000-06-13 |
EP0958523A1 (en) | 1999-11-24 |
CA2279518A1 (en) | 1998-08-06 |
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