Asymmetric drive for optical modulators

Abstract

Some embodiments are directed to electrophoretic optical modulators using asymmetric electrode driving. An electrical AC signal is applied to a plurality of electrodes on at least two substrates to obtain an electric field between the substrates. The amplitude of the electrical AC signal is modulated to move a low electric field region relative to the electrodes.

Description

Technical Field

[0001] The present invention relates to an electrophoretic optical modulator, a controller, a method of controlling an electrophoretic optical modulator, and a computer-readable medium.

Background Art

[0002] Optical modulators such as optically active glazing systems are known in the art. Typically, an optically active glazing system comprises two parallel plates made from a transparent dielectric material such as glass or a plastic material. The internal volume defined between the plates may be subdivided into a plurality of small, independent volumes or individual cells filled with a dielectric fluid. The fluid contains a suspension of particles of a dielectric, charged or chargeable material. Opposing faces of the two plates carry electrodes facing each other. The electrodes are connected to a power supply associated with control means.

[0003] The electrodes of each plate may be formed by combs arranged alternately in pairs with each other. The electrodes of two alternately arranged combs can take voltages of the same or opposite polarities. With a suitable voltage on the electrodes, the particles can be concentrated at different locations between the electrodes, providing the system with either a transparent or an opaque appearance.

[0004] There are various drawbacks associated with known systems. Optically active glazing can transition from one state to another, for example, from a transparent state to an opaque state, but such transitions take a long time and are often not completely uniform. Furthermore, the lifespan of existing devices is limited.

Summary of the Invention

Means for Solving the Problems

[0005] Embodiments herein solve these and other problems. For example, in one embodiment, an electrophoretic optical modulator comprises at least a first substrate and a second substrate positioned opposite at least the first substrate. An optical layer containing a fluid containing particles is positioned between the first and second substrates, the particles being charged or capable of being charged. A plurality of inter-mating electrodes are positioned across each of the first and second substrates. A controller is configured to apply an electric AC signal to the plurality of electrodes to obtain an electric field between them, resulting in electrophoretic motion of particles toward or from one of the plurality of electrodes, and causing modulation of the optical properties of the optical modulator. The controller is configured to modulate the amplitude of the electric AC signal applied to the plurality of electrodes on the substrates to shift a low electric field region relative to the electrodes.

[0006] By modulating the amplitude of the signal, the low-electric-field region, and especially the lowest-electric-field region, moves within the optical layer. For example, if the signal to one substrate is scaled down while the signal to the other substrate is not, or even scaled up, the low-electric-field region will move toward the former substrate. Similarly, by manipulating the signal to neighboring electrodes, the low-electric-field region can be made to move parallel to the substrate. In fact, particle motion may not exist in the low-electric-field region, and the particles may be stationary relative to the electrodes. Moving such a region allows stationary particles to escape so that they do not slow down the panel transition. In particular, the so-called dead region, where there is no electric field, can move within the optical layer.

[0007] Moving through low-electric-field regions, particularly the insulated region, offers several advantages. Particles in low-electric-field regions do not respond to the electric field as quickly as particles in high-electric-field regions. As a result, these regions transition slowly, and the transition is not uniform. Furthermore, moving through low-electric-field regions increases the overall mixing of particles.

[0008] Optical modulators as described herein can be applied in a wide variety of practical applications. For example, an optical modulator having up to one opaque substrate can be used as a surface whose optical appearance, such as its reflection or transmission state, can be altered. In particular, optical modulators that make all substrates transparent can be used for optical active glazing, for example, in offices, automobiles, casings, and the like.

[0009] Embodiments of the control method may be implemented on a computer, in dedicated hardware, or a combination of both, as a method of implementation on a computer. Executable code for embodiments of the method may be stored in a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, and online software. Preferably, the computer program product includes non-temporary program code stored on a computer-readable medium for performing embodiments of the method when the program product is executed on a computer.

[0010] In one embodiment, the computer program includes computer program code adapted to perform all or part of the steps of the embodiment of this method when the computer program is executed on a computer. Preferably, the computer program is embodied in a computer-readable medium.

[0011] Further details, aspects, and embodiments of the present invention are described merely by reference with the drawings. Elements in the drawings are illustrated for simplicity and clarity and are not necessarily depicted to scale. In the drawings, elements corresponding to elements already described may have the same reference numerals. [Brief explanation of the drawing]

[0012] [Figure 1a] This figure schematically shows an example of a substrate embodiment. [Figure 1b] This figure schematically shows an example of an embodiment of an optical modulator. [Figure 1c.1] This figure schematically shows an example of an embodiment of the scaling factor. [Figure 1c.2] This figure schematically shows an example of an embodiment of the scaling factor. [Figure 1c.3] This figure schematically shows an example of an embodiment of the scaling factor. [Figure 1c.4] This figure schematically shows an example of an embodiment of the scaling factor. [Figure 1c.5] This figure schematically shows an example of an embodiment of the scaling factor. [Figure 2a.1] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 2a.2] This figure schematically shows an example of an AC signal in an embodiment of an optical modulator. [Figure 2b.1] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 2b.2] This figure schematically shows an example of an AC signal in an embodiment of an optical modulator. [Figure 2c.1] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 2c.2] This figure schematically shows an example of an AC signal in an embodiment of an optical modulator. [Figure 3a] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 3b] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 3c] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 4a.1] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 4a.2] This figure schematically shows an example of an AC signal in an embodiment of an optical modulator. [Figure 4b.1] This figure shows an example of an electric field in an embodiment of an optical modulator. [Figure 4b.2] This figure schematically shows an example of an AC signal in an embodiment of an optical modulator. [Figure 5a]A diagram showing an example of an electric field in an embodiment of an optical modulator. [Figure 5b] A diagram showing an example of an electric field in an embodiment of an optical modulator. [Figure 6a.1] A diagram showing an example of an electric field in an embodiment of an optical modulator. [Figure 6a.2] A diagram schematically showing an example of an AC signal in an embodiment of an optical modulator. [Figure 6b.1] A diagram showing an example of an electric field in an embodiment of an optical modulator. [Figure 6b.2] A diagram schematically showing an example of an AC signal in an embodiment of an optical modulator. [Figure 7a] A diagram schematically showing an example of an AC signal in an embodiment of an optical modulator. [Figure 7b] A diagram schematically showing an example of an AC signal in an embodiment of an optical modulator. [Figure 7c] A diagram schematically showing an example of an AC signal in an embodiment of an optical modulator. [Figure 8a] A diagram schematically showing an example of an embodiment of an optical modulator. [Figure 8b] A diagram schematically showing an example of an AC signal in an embodiment of an optical modulator. [Figure 9a] A diagram schematically showing an example of an embodiment of an optical modulator. [Figure 9b] A diagram schematically showing an example of an embodiment of an optical modulator. [Figure 9c] A diagram schematically showing an example of an embodiment of an automobile. [Figure 10] A diagram schematically showing an example of a method for controlling an electrophoretic optical modulator using asymmetric electrode driving. [Figure 11a] A diagram schematically showing a computer-readable medium having a writable portion including a computer program according to an embodiment. [Figure 11b] A diagram schematically showing a representation of a processor system according to an embodiment.

Embodiments for Carrying Out the Invention

[0013] List of reference numbers 1,2,3,4 electrode 10 Optical modulator 11. First substrate 12 Second substrate 13,13a,13b electrode 14,14a,14b electrode 15 Fluid 16 Controllers 30 particles 20 Automobiles 21 Optical modulator 40 Optical modulators 41 First substrate 42 Second substrate 43 Third substrate 46 Controllers 100 circuit boards 101 First Direction 102 Second direction 110 First electrode 120 Second electrode 111-113 Main line 121-123 Main line 151 First substrate 152 Optical layer 153 Second substrate 160 controllers 1000,1001 Computer-readable media 1010 Writable portion 1020 Computer Programs 1110 Integrated Circuit 1120 Processing Unit 1122 memory 1124 Dedicated Integrated Circuit 1126 Communication elements 1130 Interconnection section 1140 Processor System

[0014] While the present invention can take many different forms, one or more specific embodiments are shown in the drawings and described in detail herein, with the understanding that this disclosure should be considered an illustration of the principles of the invention and that the invention is not intended to be limited to the specific embodiments shown and described herein.

[0015] In the following, for the purpose of understanding, the elements of the embodiments will be described in terms of their operation. However, it will be obvious that each element is configured to perform the function described as being performed by them.

[0016] Furthermore, the present invention is not limited to embodiments, and the present invention lies in any novel features or combinations of features described herein or enumerated in mutually different dependent claims.

[0017] Figure 1a schematically shows an example of an embodiment of a substrate 100 for use in an optical modulator according to one embodiment. There are at least two electrodes arranged in a pattern across the surface of the substrate 100. Shown in Figure 1a are two electrodes on the same surface: a first electrode 110 and a second electrode 120. For example, to facilitate finer grain control, there may be three or more electrodes on the same side of the substrate. For example, multiple electrodes may be used to facilitate a segmented substrate, for example, for a segmented optical modulator. For example, in a segmented optical modulator, several zones may have different optical properties, such as different transparency or reflectivity. An embodiment with two electrodes is shown below, but additional electrodes may be added to them, for example, by duplicating similar structures side by side.

[0018] The first electrode 110 and the second electrode 120 are applied to the same side of the substrate. The two electrodes are arranged in a pattern across the substrate. Additionally, one, two, or more electrodes may be present on the other surface of the substrate 100, for example, to facilitate the lamination of three or more substrates. Applying the electrodes to the substrate can be done by lithography, for example, using a mask that represents the electrode pattern. Electrodes can also be applied by embedding them in the substrate.

[0019] The first electrode 110 and the second electrode 120 each have a multiple of main lines. As shown in Figure 1a, the first electrode 110 has main lines 111, 112, and 113, and the second electrode 120 has main lines 121, 122, and 123. Typically, each electrode has more than three lines. The main lines extend across the substrate. The multiples of main lines of the first and second electrodes are arranged alternately with respect to each other on the substrate. The main lines extend across the substrate in a first direction 101. When viewed in a second direction 102, the main lines alternately encounter different multiples, for example, from the first and second multiples in the first and second electrodes, respectively. The first and second directions are at an angle to each other, and typically, the angle is substantially perpendicular. The first and second directions may, but are not required to be, parallel to the side of the substrate.

[0020] For example, substrate 100 may be combined with another substrate to form a transparent optical modulator, at least one of which is transparent. Light incident by the optical modulator is modulated in a manner that depends on particles in the optical layer between the two substrates. In one embodiment, both substrates are transparent and form an optical modulator. Motivating applications for substrates such as substrate 100 are smart glazing, e.g., optical modulators, which can be applied to residential buildings, offices, greenhouses, automobiles, and similar applications.

[0021] The level of transparency or reflectivity of the optical modulator can be electrically matched. For example, in an optical modulator, for example in smart glazing, two substrates, such as substrate 100, are stacked such that the sides to which two electrodes are applied face each other. A fluid having particles is surrounded between the two substrates. Embodiments of smart glazing are described further below. In one embodiment, electrodes, for example, two or more electrodes, are applied to one surface of each substrate. Alternatively, for example, one, two, or more electrodes may be present on the other surface of substrate 100 to facilitate the stacking of three or more substrates.

[0022] The following embodiments illustrate examples of modulating transparency or reflectivity levels. The optical modulator may be adapted for other optical effects. For example, if desired, the embodiment may be modified to different levels of light transmission instead of different levels of transparency. If desired, the type of particles used in the embodiment may be varied, for example, to particles that differ in which wavelengths they absorb or reflect, and how specular or diffuse the reflection is. For example, in one embodiment, the optical modulator may modulate different levels of reflection. The particles may also emit light. Laminating multiple optical layers further increases the possibilities.

[0023] To provide electrically compatible glazing, it is sufficient to have two sets of alternating main lines; as a result of these two alternating sets, the electric field in any part of the substrate can be controlled, since the two opposing electrodes border that part from two opposing sides.

[0024] Multiple electrodes applied to a substrate are interdigitated to manipulate the electric field between the two substrates. In Figure 1a, the main electrode is shown having multiple inter-interdigitated parallel mains. While this is a possible configuration, in one embodiment, the shape of the electrodes can vary considerably. For example, the diffraction effect can be altered by adapting the shape of the electrodes.

[0025] Figure 1b schematically shows an example of an embodiment of an electrophoretic optical modulator. A substrate, such as the one schematically shown in Figure 1a, can be combined with a similar substrate facing it, for example, its mirror image. Four electrodes of a schematic intersection of such an optical modulator along line AB in Figure 1a are shown in Figure 1b. Shown in Figure 1b are a first substrate 151 and a second substrate 153 arranged facing each other. An optical layer 152 is placed between the first substrate 151 and the second substrate 153. The optical layer 152 between the first substrate 152 and the second substrate 153 contains a fluid (not shown) containing particles. The particles are charged or can be charged.

[0026] At least two mated electrodes are arranged on the first substrate 151 and substrate 153. At least two mated electrodes are arranged facing each other. On the first substrate 151 are two electrodes 1 and 2. For example, electrode 1 may be electrode 111, and electrode 2 may be electrode 121. On the second substrate 153 are two electrodes 4 (facing electrode 1) and electrode 3 (facing electrode 2). Although not shown, the substrate 151 may have electrodes 1, 2, 1, 2, ... and the substrate 153 may have electrodes 4, 3, 4, 3, ... and so on.

[0027] The controller 160 is configured to apply an electric AC signal to each of the multiple electrodes on the two substrates, for example, electrodes 1, 2, 3, and 4, in order to obtain an electric field between the multiple electrodes. The electric field causes electrophoretic motion of particles toward or from one of the multiple electrodes, thereby causing modulation of the optical properties of the optical modulator. Electrodes with the same numbers in the cross-sectional view are used in Figures 2a.1–6b.2.

[0028] The controller 160 is configured to control and / or generate an asymmetric AC signal for the electrophoretic optical modulator.

[0029] The controller 160 is configured to obtain an electric field between the multiple electrodes and apply an electric AC signal to the multiple electrodes to produce an electrophoretic motion of particles toward or from one of the multiple electrodes, thereby causing modulation of the optical properties of the optical modulator. For example, the controller 160 may generate an electric AC signal. For example, in the case of two electrodes per substrate, the controller 160 may be configured to generate a set of four AC signals for application to the electrodes. The application may be direct from the controller 160 to the electrodes. The application may be indirect from the controller 160 to the electrodes, for example, through an intermediate processing device, such as an amplifier and / or filter.

[0030] For example, there are several optical properties that can be modulated in an optical modulator, such as transparency, reflectivity, and color. For the sake of simplicity, embodiments will be described with respect to the control of a grayscale between completely transparent and completely opaque. However, those skilled in the art will understand that different optical properties can be manipulated by using different particles and / or different substrates. The particles are sometimes referred to as dyes.

[0031] The controller 160 is configured to modulate the amplitude of an electric AC signal applied to multiple electrodes on the substrate, thereby shifting the low electric field region relative to the electrodes.

[0032] In conventional driving of optical modulator electrodes, including AC driving, the electric field potential is lower in regions of the optical layer where the electric field is much lower than in other regions of the optical layer. Such low-electric-field regions are disadvantageous because particles are difficult to control within them. In particular, due to the low electric field within the low-electric-field region, particles move more slowly there. Most of the time required to transition from one optical state to another is caused by the slow motion of particles in the low-electric-field region.

[0033] For example, in a low-electric-field region of an optical layer, the electric field intensity may be less than 25% of that in other parts of the optical layer. For example, in some areas of an optical layer, the electric field intensity may be less than 15%, less than 10%, or less than 1% compared to the maximum electric field in the optical layer. For example, in a low-electric-field region of an optical layer, the electric field intensity may be less than 2*10^6 V / m, less than 1*10^6 V / m, less than 1*10^5 V / m, etc. For example, a low-electric-field region can be considered a region in the optical layer where the electric field is minimal. For example, a low-electric-field region can be considered a region in the optical layer where the electric field is minimal or a predetermined percentage greater than the minimum, e.g., 10% maximum, 15% maximum, etc.

[0034] While electric fields can be measured directly, computer simulations of electric fields have proven to be sufficiently accurate for practical applications. For example, well-known COMSOL software may be used for simulated electric field diagrams. In this specification, the electric field intensity can be generated using the Electrostatic study under the AC / DC module of COMSOL Multiphysics. The electric field diagrams shown herein were produced using the aforementioned software.

[0035] In particular, within the optical layer, there may be regions where there is no electric field, for example, zero or substantially zero. Such regions are called dead zones. Particles within dead zones are essentially unresponsive to electrophoretic control. Through other means, such as slow entropic movement, particles can drift out of the dead zone and become susceptible again to the effects of controlled motion. Dead zones are particularly problematic for rapid transitions between optical modes of an optical modulator. Dead zones are sometimes referred to as neutral regions or neutral points. A neutral point can be a point within a 2D intersection as shown in the figure; however, in a physical 3D embodiment, a neutral point can be a neutral curve or neutral volume.

[0036] In the embodiment, problems caused by low-electric-field regions and especially insensitive regions are solved by variations in the potential difference between electrodes. By modulating the relative magnitude of the signal applied to the electrodes, this electric-field neutral point or volume is moved within the optical layer between the substrates.

[0037] In one embodiment, the overall drive can use an AC signal to maintain the neutrality and equilibrium of the flow in various electric fields over time. This is advantageous because it reduces electrode corrosion.

[0038] In one embodiment, the electric field line is modulated such that the neutral point shifts position within the optical layer, resulting in an increase in the total volume under electric field influence, for example, electrophoretic control.

[0039] In one embodiment, the main parameter that can be varied within the signal is amplitude, for example, the amplification level of the signal. Other parameters that can be varied asymmetrically between electrodes include frequency, signal shape (square, sinusoidal, etc.), duration, and phase.

[0040] Asymmetric driving of electrodes has the advantage of faster transitions between optical states, as will be further described herein. Asymmetric driving of electrodes further provides the advantage of more uniform transitions because the difference between slow and fast transition locations on the panel is reduced. An additional advantage of asymmetric driving is reduced accumulation of particles on the electrodes. In conventional optical modulators, particularly in DC-driven modulators, particles can accumulate on the electrodes and be locally compressed there. This can lead to particle interactions there and the formation of irreversible aggregates of particles. Such aggregation of particles is undesirable. The aggregation effect causes problems such as heterogeneity and gravitational effects. However, in asymmetric driving, as in one embodiment, the particles have increased motion and are therefore limited to annealing to aggregation. Furthermore, the particle motion is more uniform.

[0041] Insensitive regions, such as neutral points or volumes, also lead to optical aberrations due to particle accumulation during operation. By increasing particle mobility, aggregation is reduced, and particles are less likely to fall due to gravity. Improved particle mobility allows for better approach and dispersion of particles to reach an opaque state while maintaining a particle distribution closer to the initial dispersion state at the time of manufacture.

[0042] Interestingly, asymmetric driving can be added to existing algorithms used to drive panels toward a target grayscale. Furthermore, introducing asymmetric driving can still maintain flow neutrality. For example, using the algorithm described in PCT / EP2021 / 071346, titled "Lightmodulator, Lightmodulator Method And Smart Glazing," signal scaling can be introduced to move through low-electric-field regions, particularly the dead zone.

[0043] For example, the controller may consist of a set of algorithms for one or more functions, such as increasing transparency, decreasing transparency, or maintaining current transparency. More or fewer algorithms may exist. For example, the algorithms may vary depending on the magnitude of the increase in desired transparency. For example, the maintenance algorithm may be omitted. For example, in a simplified embodiment, the controller may have an algorithm for driving toward complete transparency and an algorithm for driving toward complete opacity. For example, computer program code may be stored in the controller's memory to implement the algorithms. In one embodiment, the controller is configured to apply a programmed driving algorithm over a specific duration, which may depend, for example, current transparency, target transparency, and measured sensor values, as described in the cited PCT application.

[0044] Existing algorithms can be modified by periodically up- or down-scaling one or more of the signals so that the low-electric-field region, and in particular the dead region, shifts. For example, an existing driving algorithm can be modified to be asymmetric by introducing asymmetric scaling, and then changing the direction of the asymmetric scaling after a predetermined period. As the asymmetry of the driving changes, the low-electric-field region shifts. In one embodiment, a volume within an optical layer is scanned by higher-intensity electric field lines, causing all particles within the volume to become susceptible to electrical control at some point during scanning. Asymmetric driving can be used advantageously for both driving toward a target transparency and maintaining grayscale. Open driving can also be varied in asymmetry while maintaining grayscale.

[0045] Asymmetric driving allows for faster transitions, particularly much faster device closure (i.e., driving towards opacity), because the majority of the particle ensemble moves independently of the particle's initial location, including intermediate positions between the electrode and the electrode surface.

[0046] Typically, signal scaling is applied to pairs of electrode signals. For example, a pair of signals X and Y may be applied to a pair of electrodes. The electrodes may be, for example, a pair of opposing electrodes, a pair of neighboring electrodes, or a pair of diagonally opposing electrodes. The electrode signals before scaling typically have the same phase and the same amplitude; in fact, the pair of signals may be the same signal. However, even before scaling, differences in phase or amplitude may exist. For example, a phase difference may be used to trap particles. For example, a scaling difference may be used to compensate for hardware differences, amplitude, and similar differences, for example, between substrates. In particular, signals X and Y may be conventional AC-driven signals for an electrophoretic optical modulator. Signals X and Y may be scaled to shift low-electric-field regions within the optical layer. For example, a time-varying scaling factor may be applied to the signals. Figures 1c.1–1c.4 schematically show examples of embodiments of scaling factors.

[0047] In Figure 1c.1, the scaling factors are selected such that when one signal is scaled down (de-amplified), the other signal is scaled up (amplified). In one embodiment, the product of the scaling factors may be 1. In one embodiment, the sum of the logarithms of the scaling factors may be 0.

[0048] In Figure 1c.2, the scaling factor is selected such that only one of the two signals is attenuated while the other remains constant. Within the figure, scaling is performed alternately. Note that in these examples, scaling down may be used instead of scaling up. In fact, using scaling down is easier because it keeps the signal within a predetermined range.

[0049] Figure 1c.3 is the same as Figure 1c.2, except that scaling is performed alternately with periods when scaling is not used.

[0050] In Figure 1c.4, only one of the signals is scaled, while the other remains constant. In Figure 1c.5, only one of the signals is scaled, while the other remains constant. In Figure 1c.5, the signals are alternately scaled up and scaled down. In this example, scaling is combined with periods of no scaling.

[0051] Many other variations are possible. For example, a slightly noisy scaling can be added to slightly randomize the location of the low-electric-field region. These examples use a scaling factor that changes in a triangular pattern, but other shapes are also possible, such as square waves and sine waves.

[0052] Figures 2a-2c schematically show examples of AC signals in an embodiment of an optical modulator configured to close a panel, i.e., to reduce the transparency of the panel. Figures 2a.1, 2b.1, and 2c.1 show examples of electric fields in an embodiment of an optical modulator. The electric fields are shown in the same plane as shown in Figure 1b. Figures 2a.2, 2b.2, and 2c.2 schematically show examples of AC signals corresponding to the electric field diagrams. Note that Figures 2a.2, 2b.2, and 2c.2 schematically show the scaled signals, while Figures 1c.1-1c.4 schematically show the scaling factors.

[0053] The motion of a particle is largely determined by the electric field and its shape, as shown in the electric field diagram, but other factors, such as Brownian motion and temperature, can also have some influence on the particle's movement.

[0054] In Figure 2a.2, and in similar figures, the y-axis schematically represents the voltage of the signal applied to the electrodes. The horizontal dashed lines in the four signals represent the neutral voltage of each signal, e.g., the zero voltage line. The x-axis schematically represents time. Note that the four signals are AC signals. Figure 2 shows a square signal, but other AC type signals such as triangular, sine wave, and combinations thereof may be used. The drive shown in Figure 2a.2 is configured to close the optical modulator, e.g., to reduce transparency and increase the gray level. If the drive shown in Figure 2a.2 is continued for a long time, the substrate will gradually approach maximum opacity. That said, the drive does not need to continue until it is completely opaque; the drive may be terminated at some desired gray level before that time.

[0055] Note that signals 1 and 4 are equal, as there is a dead zone between substrates 1 and 4. The same is true for signals 2 and 3. Particles within the dead zone do not respond to the electric field because there is no electric field there. Near the zero electric field point, the electric field is low, for example, a low electric field region exists. Particles within the low electric field region respond to the electric field, but slowly.

[0056] In the closing operation, as shown in Figures 2a-2c, the low-electric-field region includes a dead zone between the substrates, for example, within the optical layer. The dead zone is moved by introducing asymmetry in the drive.

[0057] In Figure 2a.2, the AC signals applied to opposing electrode pairs 1 and 4, and opposing electrode pairs 2 and 3, are equal. In Figure 2a.2, the AC signals applied to neighboring electrode pairs 1 and 2, and neighboring electrode pairs 4 and 3, are equal except for a phase shift, in this case a 180-degree phase shift. Opposing electrode pairs are two different electrodes facing each other on opposing substrates. Neighboring electrode pairs are two different electrodes adjacent to each other on the same substrate. There are dead zones between electrodes 1 and 4, and between electrodes 2 and 3.

[0058] Figure 2b.2 illustrates the asymmetry introduced into the panel drive. In Figure 2b.2, the AC signals applied to opposing electrode pairs 1 and 4, and opposing electrode pairs 2 and 3, are equal except for scaling. For example, the drive in Figure 2b.2 can be obtained from the drive in Figure 2a.2 by scaling down the drive at electrodes 1 and 2, for example, by scaling down the drive of one electrode in a pair of opposing electrodes. In this case, the signals to electrodes 1 and 2 are scaled down. Scaling up or down can be done using an amplifier, by a variable resistor, or by changing a parameter in a signal generator. In Figure 2b.2, the AC signals applied to neighboring electrode pairs 1 and 2, and neighboring electrode pairs 4 and 3, are equal except for a phase shift, in this case a 180-degree phase shift.

[0059] The effect of the drive shown in Figure 2b.2 is still to close the panel. Note that the low-electric-field region in Figure 2a.1 has been moved upward in Figure 2b.1; in particular, the insensitive region has been moved upward.

[0060] In Figure 2c.2, the scaling direction is reversed. The asymmetry introduced to the pair of opposing electrodes during the closing operation is here in the opposite direction. This means that the dead zone is here moved downward, for example, toward the lower substrate. Note that the up and down directions are relative. These terms, in this specification, are abbreviations for toward the first substrate or toward the second substrate in relation to a panel as shown in the figure; in one embodiment, the panel may be perpendicular such that the up and down directions can be forward and backward, or similar.

[0061] To reduce transparency, for example, to close the panel, the panel may be driven by using three types of signals alternately. For example, the drive may have an intermediate dead region as shown in Figure 2a, an upper dead region as shown in Figure 2b, or a lower dead region as shown in Figure 2c. For example, in one embodiment, the drive may repeat a cycle of: intermediate dead region drive, upper dead region drive, intermediate dead region drive, and lower dead region drive.

[0062] Using this type of two-way asymmetric drive to close the panel significantly speeds up the transition to dark gray. With conventional symmetric drives, the transition from 10% gray to 1% gray, i.e., from light gray to complete dark, can take approximately 10 times longer compared to one embodiment.

[0063] Using bidirectional asymmetric drive is preferable because a large portion of the volume is scanned, thereby improving particle mixing. Although not essential, improved drive can be achieved by repeating cycles such as driving in the middle dead zone and driving in the upper dead zone.

[0064] Figures 3a-3c show examples of electric fields in embodiments of optical modulators. The electric field diagrams in Figures 3a-3c are the same as those in Figures 2a.1-2c.1. Figures 3a-3c show low-electric-field regions schematically represented by circles. The centers of the circles coincide with a portion of the field where there is no electric field, for example, a dead region. Note that the position of the dead region shifts relative to the electrodes. In this case, the dead region shifts substantially orthogonally with respect to the substrate. Orthogonal shifting is convenient and not essential, but by introducing asymmetry between neighboring electrode pairs and opposing electrode pairs, the dead region can also be shifted parallel to the substrate. However, for improved mixing, orthogonal shifting is sufficient.

[0065] Figures 3a-3c illustrate different stages in a closed operation using asymmetric drive. The dead region moves within the optical layer between two opposing substrates, for example, toward one of the two substrates and away from one of the two substrates. For example, the controller may be configured to apply a scaling operation to the signal applied to the electrodes. For example, signals applied to opposing electrodes may be the same, except that scaling is applied to one or both of them. The amount of scaling depends on the application, e.g., the size of the panel and the thickness of the optical layer. As an example, a first AC signal applied to a first electrode may be scaled, for example, to a second AC signal applied to a second electrode facing the first electrode, with the lower amplitudes of the first and second AC signals being up to 70%, 50%, 45%, 40%, and 30% of the higher amplitudes.

[0066] The signal schematically shown in the figure is a square wave, but this is not at all necessary in practice. The signal could instead be a sine wave. For example, a low-pass filter can be applied to the signal as shown in the figure. The low-pass threshold can be chosen depending on the size of the panel, for example, 1 kHz for larger panels.

[0067] For example, in one embodiment, the controller may have a signal generator configured for the intermediate dead region of the optical layer. An asymmetric modulator may modulate the signal to move the dead region toward or away from one of the substrates. The asymmetric modulator may cycle through different scalings. For example, the scaling between two AC signals applied to a pair of opposing electrodes may cycle between a low scaling factor and a high scaling factor. The controller may also directly generate the scaled signal.

[0068] Scaling can reduce and / or increase one signal while keeping another signal constant. For example, a first AC signal may have a constant amplitude, and a second AC signal may be scaled relative to the first AC signal. The signal kept constant and the signal scaled may switch over time. Scaling can be performed on low-voltage signals, but it can also be introduced during signal amplification. In one embodiment, signal scaling is randomized to randomize the location of the dead zone. In one embodiment, signal scaling is controlled to move the location of the low-electric-field region in a controlled manner, for example, along a predetermined path through an optical layer.

[0069] Once the target gray level is reached, for example, as indicated by the panel, or by sensors associated with optical and / or electrical sensors, the drive signal may be interrupted. The panel will maintain its gray level for a while, but the panel's appearance may decay over time, and as a result, conventional maintenance drive may be used. Maintenance drive may involve slow, low-power driving of the panel to a gray level close to the target gray level. Maintenance drive may be performed alternately with no drive at all. Asymmetric signals may also be used during maintenance, as this improves mixing and increases the panel's durability.

[0070] Figures 4a-4b schematically show examples of AC signals in an embodiment of an optical modulator configured to open a panel, i.e., to increase the transparency of the panel. Figures 4a.1 and 4b.1 show examples of electric fields in an embodiment of an optical modulator. The electric field is shown in the same plane as shown in Figure 1b. Figures 4a.2 and 4b.2 schematically show examples of AC signals corresponding to the electric field diagrams.

[0071] In Figure 4a.2, the AC signals applied to neighboring electrode pairs 1 and 2, and neighboring electrode pairs 3 and 4, are equal. In Figure 4a.2, the AC signals applied to opposing electrode pairs 1 and 4, and opposing electrode pairs 2 and 3, are equal, except for a phase shift, in this case a 180-degree phase shift. Low-electric-field regions exist between electrodes 1 and 2 and between electrodes 3 and 4, extending from substrate to substrate. Figure 4a.1 also shows two dead regions: a dead region between electrodes 1 and 2 and a dead region between electrodes 3 and 4. These two dead regions are located outside the optical layer. These dead regions are not a problem in themselves, as there are no particles corresponding to the shown electrodes 1-4. However, a low-electric-field region exists extending between these two dead regions. Particles in the low-electric-field region respond to the electric field more quickly than particles in the dead regions, but particles in the low-electric-field region still move slower than particles somewhere within the optical layer. For example, the electric field in the low-electric-field region between two insensitive regions may be 25% lower than the fields in between and directly between the electrodes.

[0072] Figure 4b.2 illustrates the asymmetry introduced into the panel drive. In Figure 4b.2, the AC signals applied to neighboring electrode pairs 1 and 2, and neighboring electrode pairs 3 and 4, are equal except for scaling. For example, the drive in Figure 4b.2 can be obtained from the drive in Figure 4a.2 by scaling down the drive at electrodes 2 and 3, for example by scaling down the drive of one electrode in a pair of neighboring electrodes. In this case, the signals to electrodes 2 and 3 are scaled down. In Figure 4b.2, the AC signals applied to opposing electrode pairs 1 and 4, and neighboring electrode pairs 2 and 3, are equal except for a phase shift, in this case a 180-degree phase shift.

[0073] The effect of the drive shown in Figure 4b.2 is still to open the panel. Note that the low-electric-field region in Figure 4a.1 has been moved to the right in Figure 4b.1. The size of the low-electric-field has also been increased somewhat. If only the type of drive shown in Figure 4b.2 were used, this could make it more difficult to move particles near electrodes 2 and 3, but this is not a problem because the drive is combined with asymmetric drive in other directions.

[0074] In Figure 4b.2, the direction of scaling can also be reversed, for example, by scaling down signals 1 and 4 instead of signals 2 and 3. The asymmetry introduced to the pair of neighboring electrodes during the open operation is then in the opposite direction, for example, the low-electric-field region shifts to the left.

[0075] To increase transparency, for example, to open the panel, the panel can be driven by using three types of signals alternately. For example, the drive may have a central low-electric-field region as shown in Figure 4a, a right low-electric-field region as shown in Figure 4b, or a left low-electric-field region (not shown in a separate figure). For example, in one embodiment, the drive may cycle repeatedly between low electric fields: center, left, center-right; or just center, left. The time spent in different phases does not have to be equal. When open, the time spent in the center may be longer than the time spent driving in the left or right low-electric-field regions.

[0076] In one embodiment, during the opening operation, the low-electric-field region may move parallel to the substrate. Similar options for generating the signal are available for the opening operation as discussed for the closing operation. For example, the signal may be scaled, and the scaling factor may repeatedly pass through a range of the scaling factor.

[0077] Figures 5a and 5b show examples of electric fields in an embodiment of an optical modulator. The electric field diagrams in Figures 5a and 5b are the same as those in Figures 4a.1 and 4b.1. Figures 5a and 5c show a low-electric-field region schematically represented by an ellipse. The electric field within the ellipse is approximately 1.5 * 10^6 V / m. When comparing Figures 5a and 5b, note that the low-electric-field region has shifted to the right. For example, the center of the low-electric-field region, e.g., the center of gravity, or the center weighted by the electric field strength, has shifted to the right, in this case parallel to the substrate. Also note that the insensitive region outside the optical layer has shifted to the right.

[0078] Figures 6a and 6b schematically show an example of an AC signal in an embodiment of an optical modulator arranged for diagonal drive. Diagonal drive can be used for panel closing. Diagonal drive can be used to mix particles in the optical layer. Mixing particles is advantageous for panel life. Mixing particles can also be used as one step during panel closing. For example, a period of diagonal drive as shown in Figures 6a and 6b may be followed by a drive as shown in Figures 2a and 2c. Diagonal drive can also be used to reach the gray between closed and open panels.

[0079] Figures 6a.1 and 6b.1 show examples of electric fields in an embodiment of an optical modulator. The electric field is shown in the same plane as shown in Figure 1b. Figures 6a.2 and 6b.2 schematically show examples of AC signals corresponding to the electric field diagrams.

[0080] In Figure 6a.2, the AC signals applied to diagonal electrode pairs 1 and 3, and diagonal electrode pairs 2 and 4, are equal. In Figure 6a.2, the AC signals applied to neighboring electrode pairs 1 and 2, and neighboring electrode pairs 3 and 4, are equal except for a phase shift, in this case a 180-degree phase shift. A dead region exists between electrodes 1, 2, 3, and 4. In the dead region, the electric field is substantially zero.

[0081] Figure 6b.2 illustrates the asymmetry introduced into the panel drive. In Figure 6b.2, the AC signals applied to diagonal electrode pairs 1 and 3, and diagonal electrode pairs 2 and 4, are equal except for scaling. For example, the drive in Figure 6b.2 can be obtained from the drive in Figure 6a.2 by scaling down the drive at electrodes 1 and 2, for example, by scaling down the drive at one of the electrodes in a pair of diagonal electrodes. In Figure 6b.2, the AC signals applied to neighboring electrode pairs 1 and 2, and neighboring electrode pairs 3 and 4, are equal except for a phase shift, in this case a 180-degree phase shift. Note that all signals applied to the electrodes on one substrate, in this case the upper substrate, are scaled down. For example, in one embodiment, the signal applied to one of the two substrates has a lower amplitude than the signal applied to the other of the two substrates. As a result, the dead region in Figure 6a.1 is shifted upward in Figure 6b.1. In this case, the dead zone moved orthogonally with respect to the substrate, but non-orthogonal movement is also possible, for example, by scaling signals 1 and 2 in Figure 6b.2 by different amounts.

[0082] In one embodiment, the controller is configured for the closing operation of an optical modulator, in which AC signals applied to opposing electrodes on opposing substrates are scaled relative to each other, and the controller modulates the scaling, thus shifting the low-electric-field region. In one embodiment, AC signals applied to neighboring electrodes on the same substrate are phase-shifted relative to each other.

[0083] In one embodiment, the controller is configured for the opening operation of the optical modulator, and in the closing operation, AC signals applied to neighboring electrodes on the same substrate are scaled relative to each other, and the controller modulates the scaling, thus shifting the low-electric-field region. In one embodiment, AC signals applied to opposing electrodes on opposing substrates are phase-shifted relative to each other.

[0084] In one embodiment, asymmetric driving involves applying different amplitude signals to at least some of the electrodes in an optical modulator. Other types of asymmetric driving are also possible, such as asymmetric driving with different frequencies. For example, the same amplitude may be used for all electrodes, but the frequency may be varied among at least some pairs. Frequency may also be varied in addition to amplitude.

[0085] In one embodiment, the optical modulator is an electrophoretic modulator, and particles are moved due to the electrophoretic effect. In one embodiment, a high-frequency component may be added to the signal. For example, in one embodiment, the electrophoretic drive uses a frequency of, for example, up to 100 Hz. To obtain efficient driving of the optical modulator, it is sufficient to use only relatively low-frequency signals. In one embodiment, at least some of the AC signals include a high-frequency component. For example, in one embodiment, the high-frequency component may have a frequency of at least 500 Hz, or at least 750 Hz, preferably at least 1 kHz. The high-frequency component moves the particles due to the dielectrophoretic effect in addition to the electrophoretic effect.

[0086] High-frequency components can be removed when the target gray level is reached. Doing so saves energy and reduces the heat-up of the optical modulator. A low-pass filter can be applied to the AC signal. For example, the low-pass filter can be set to a threshold just above the frequency of the high-frequency components. Figures 7a–7c schematically show examples of AC signals in an embodiment of the optical modulator. Figures 7a–7c correspond to Figures 2a.2, 2b.2, and 2c.2 with schematic HF components. Figures 4a.2, 4b.2, 6a.2, and 6b.2 can similarly be enhanced with HF components.

[0087] Figure 8a schematically shows an example of an optical modulator embodiment. Figure 8b schematically shows an example of an AC signal in an optical modulator embodiment. Optical modulators shown in other figures use two phases for all signals. However, this is not mandatory, and in fact, it may be advantageous to use different phases for three or more signals. For example, Figure 8b shows a first signal for an electrode. A second signal for the neighboring electrode 2 is the same but shifted by the first phase shift. A third signal for electrode 3 is the same as the electrode 2 signal but shifted by the second phase shift. A signal for electrode 4 is phase shifted by the third phase shift compared to signal 3. The first signal is the same as a fourth signal shifted by the fourth phase shift. All four phase shifts may be equal to 360 / 4 = 90 degrees, but this is not mandatory. In one embodiment, the phase difference changes over time.

[0088] The advantage of having an increased phase shift for the four signals is that the particles are better kept within the cell gap. As a result, a given transparency or lack thereof can be maintained at lower power. In Figure 8b, the amplitudes of the four signals shown are equal, although the amplitudes can be varied in one embodiment.

[0089] Using different phases for three or more signals can be used to trap particles within the gaps between neighboring electrodes; this is particularly advantageous when closing the panel and maintaining a gray level.

[0090] For example, with respect to the signal to electrode 4 as the reference, signal 1 may have a phase shift and amplitude scaling, signal 2 may have a further phase shift and amplitude scaling (possibly the same scaling), and signal 3 may have a further phase shift without amplitude scaling.

[0091] Figure 9a schematically shows an embodiment of an optical modulator 10 that can be applied to smart glazing. The optical modulator is an example of an optical modulator.

[0092] References are made herein by reference to patent application PCT / EP2020 / 052379, which includes, for example, advantageous designs for optical modulators that include electrodes, construct blocks, and / or can be further improved by substrates such as those described herein.

[0093] The optical modulator 10 can be electronically switched between a transparent state and an opaque state, and vice versa, or between a reflective state and an antireflective state, and vice versa. The optical modulator 10 comprises a first substrate 11 and a second substrate 12 arranged facing each other. At least two electrodes are applied to the inside of the first substrate 11: shown are electrodes 13a and 13b. These at least two electrodes are collectively referred to as electrode 13. At least two electrodes are applied to the inside of the second substrate 12: shown are electrodes 14a and 14b. These at least two electrodes are collectively referred to as electrode 14. The configuration of the electrodes is mutually mated, but can be significantly modified. In particular, it is not necessary for the main lines of the electrodes to spread parallel across the substrates.

[0094] A fluid 15 is provided between the substrates. The fluid contains particles 30, such as nanoparticles and / or microparticles, which are charged or can be charged. For example, particles can inherently carry an electric charge on their surface. For example, particles can be surrounded by charged molecules.

[0095] The electrodes are positioned to drive the particles 30 so that they move toward or away from the electrodes depending on the applied electric field. The optical properties of the optical modulator, in particular its transparency or reflectivity, depend on the location of the particles 30 in the fluid. For example, a connection may be provided to apply an electromagnetic field to the electrodes.

[0096] In the example, substrates 11 and 12 may be optically transparent outside the electrodes, such as >99% transparency, and typically >95% transparency at the relevant wavelengths. Considering the electrodes, transparency may be much lower, for example, 70%. The term “optical” may refer to wavelengths visible to the human eye (approximately 380 nm–750 nm), and, where applicable, to a broader range of wavelengths including infrared (approximately 750 nm–1 μm) and ultraviolet (approximately 10 nm–380 nm), as well as partial selections thereof. In exemplary embodiments of the optical modulator, the substrate material is selected from glass and polymer. Transparent materials may also be used for the electrodes. In embodiments of the optical modulator, only substrates 11 and 12 are transparent.

[0097] In another example, one substrate, such as the lower substrate 12, may be reflective or partially reflective, while the upper substrate 11 is transparent. The optical properties of the optical modulator, in particular its reflectivity, depend on the location of the particles 30 in the fluid. When the panel is open (vertically driven), most of the particles are located between the opposing electrodes of the two substrates, and as a result, incident light can pass through the transparent upper substrate and the relatively unobstructed optical layer, and is reflected or partially reflected on the lower substrate.

[0098] The distance between the first substrate and the second substrate is typically less than 30 μm, such as 15 μm. In an exemplary embodiment of the optical modulator, the distance between the first substrate and the second substrate is less than 500 μm, preferably less than 200 μm, preferably less than 100 μm, and more preferably less than 30 μm, and less than 50 μm.

[0099] In the example, the modulator may be provided from a flexible polymer, and the remainder of the device may be provided from glass. The glass may be rigid glass or flexible glass. A protective layer may be provided on the substrate if required. If two or more colors are provided, two or more layers of the flexible polymer may be provided. The polymer may be polyethylene naphthalate (PEN), polyethylene terephthalate (PET) (optionally having a SiN layer), polyethylene (PE), etc. In a further example, the device may be provided from at least one flexible polymer. Thus, the modulator may be mounted on any surface, for example, by using an adhesive.

[0100] Particle 30 may be adapted to absorb light, thereby preventing certain wavelengths from passing through. Particle 30 may reflect light; for example, the reflection may be specular, diffuse, or somewhere in between. Particles may absorb some wavelengths and reflect others. Particles may further, or instead, emit light, for example, using phosphorescence, fluorescence, or similar phenomena. Even fluids may emit light, and this emission can be modulated by changing the position of the particles.

[0101] In exemplary embodiments of the optical modulator, the size of the nanoparticles is 20–1000 nm, preferably 20–300 nm, and more preferably less than 200 nm. In exemplary embodiments of the optical modulator, the nanoparticles / microparticles may include a coating and / or dye, and preferably include a core. In exemplary embodiments of the optical modulator, the particle coating is made from a material selected from conductive or semiconductor materials.

[0102] In an exemplary embodiment of the optical modulator, the particles are adapted to absorb light having wavelengths of 10 nm–1 mm, for example, 400–800 nm, 700 nm–1 μm, and 10–400 nm, and / or are configured to absorb a portion of light having a (filtered) wavelength range that falls within 10 nm–1 mm, or a combination thereof.

[0103] In exemplary embodiments of the optical modulator, the particles are charged or can be charged. For example, the charge on the particles may be between 0.1e and 10e per particle (5*10⁻⁷-0.1 C / m²).

[0104] In exemplary embodiments of the optical modulator, the fluid is present in amounts of 20-50 g / m², such as 1-1000 g / m², preferably 2-75 g / m², and more preferably 30-40 g / m². A major advantage of this layout is that much less fluid and much less particles can be used.

[0105] In an exemplary embodiment of the optical modulator, the particles are present in an amount of 0.02–10 g / m², such as 0.01–70 g / m², preferably 0.1–3 g / m².

[0106] In an exemplary embodiment of the optical modulator, the particles have colors selected from cyan, magenta, and yellow, as well as black and white, and combinations thereof.

[0107] In an exemplary embodiment of the optical modulator, the fluid comprises one or more of the following: surfactants, emulsifiers, polar compounds, and compounds capable of forming hydrogen bonds.

[0108] The fluid 15 may be a nonpolar fluid having a dielectric constant of less than 15. In an exemplary embodiment of the optical modulator, the fluid has a relative permittivity □r of less than 10, preferably less than 5. In an exemplary embodiment of the optical modulator, the fluid 15 has a kinematic viscosity coefficient greater than 10 mPa·s.

[0109] Electrodes 13a, 13b and electrodes 14a, 14b are in fluid contact with a fluid. The fluid may be in direct contact with the electrodes or indirectly, for example, the fluid may be in contact with a second medium having electrodes, such as through a porous layer. In one embodiment, the electrodes cover about 1-30% of the substrate surface. In one embodiment, the electrodes include a conductive material having a conductivity of >1*10⁷ S / m at 20°C and a resistance of less than 100 N□m (at 273 K; for comparison, ITO, which is typically used, has 10⁵ N□m).

[0110] In one embodiment of the optical modulator, the electrodes include copper, silver, gold, aluminum, graphene, titanium, indium, and combinations thereof, preferably copper. The electrodes may be in the form of wires, such as microwires, such as copper microwires, embedded in a polymer-based substrate.

[0111] A connection for applying an electromagnetic field to the electrodes is provided. The electromagnetic field applied to the electrodes results in the motion of nano and microparticles from the first electrode to the second electrode and vice versa. For example, in an exemplary embodiment of the optical modulator, the current is -100 to +100 μA, preferably -30 to +30 μA, more preferably -25 to +25 μA. For example, a power supply device may be electrically connected to at least two electrodes. The power supply device may be adapted to provide waveform power. At least one of amplitude, frequency, and phase may be adaptable to provide different states within the optical modulator. For example, the mode of power may be adapted by a controller.

[0112] The optical modulator 10 may include one or more segments, each segment being a single optically switchable entity of varying sizes. The substrate at least partially surrounds the volume that may be a segment.

[0113] This device may include driver circuits for changing the appearance of (individual) segments by applying an electromagnetic field. Therefore, the appearance of the optical modulator, or one or more parts thereof, can also be changed. For example, a segment may have an area of ​​at least 1 mm². This design allows for stacking to enable more colors; for example, in a full-color application, a stack of two or three modulators may each provide most or all of the colors.

[0114] Having one or more segments allows for localized control of the optical modulator; this is advantageous in some applications but not essential. In the case of smart glazing, the optical modulator can be used with or without segments. For example, when applied to smart glazing, transparency or reflectivity can be controlled locally to block sun patches, for example, without reducing transparency or reflectivity across the entire window. The segments may be relatively large, for example, having a diameter of at least 1 mm or at least 1 cm.

[0115] In an exemplary embodiment of the optical modulator, the substrates (11, 12) are aligned, and / or the electrodes (13, 14) are aligned. For example, electrodes 13a, 13b and electrodes 14a, 14b may be aligned so that they face each other. In aligned substrates, electrodes on different substrates are behind each other when viewed in a direction perpendicular to the substrates. When the optical modulator is disassembled and the substrates are arranged with both electrodes facing upward, the electrode patterns are mirror images of each other.

[0116] Aligning substrates can increase the maximum transparency or reflectivity of an optical modulator; on the other hand, when selecting an optical modulator for criteria beyond a range such as transparency or reflectivity, it may be better not to align the two substrates, or not to align them completely. Optical modulators can be stacked. For example, two stacked optical modulators may be fabricated from three substrates, the middle one having electrodes on both of its surfaces. In one embodiment of the optical modulator, at least one substrate 11, 12 of the first optical modulator is optionally the same as the substrate 11, 12 of at least one second optical modulator. In the case of stacked modulators, alignment can also increase maximum transparency or reflectivity, but it may negatively affect other considerations, such as diffraction.

[0117] Figure 9b schematically shows an example of an embodiment of the optical modulator 40. The optical modulator 40 is similar to the optical modulator 10, except that it comprises multiple optical layers; in the shown example, there are two optical layers. Three or more optical layers may be present. Each optical layer is located between two substrates. The optical modulator 40 can be considered a stack of two-substrate optical modulators, as shown in Figure 9a. As shown, the optical modulator 40 comprises three substrates: a first substrate 41, a second substrate 42, and a third substrate 43. There is an optical layer between substrates 41 and 42, and an optical layer between substrates 42 and 43. The optical layers may be similar to those in the optical modulator 10. A controller 46 is configured to control the current on the electrodes of the substrates. For example, in Figure 9b, the controller 46 may be electrically connected to at least 4 × 2 = 8 electrodes.

[0118] Interestingly, the particles in multiple optical layers can be different, so that the multiple layers can be used to control more optical properties of the optical modulator. For example, particles in different optical layers may absorb or reflect at different wavelengths, and may have different colors, for example. This can be used by controller 46 to produce different colors and / or different color intensities on the panel. For example, a 4-substrate panel may have three optical layers, each having different colored particles, for example, cyan, yellow, and magenta. By controlling transparency or reflectivity for different colors, a variety of color spectra can be produced.

[0119] The surface of a substrate facing another substrate may be supplied with two or more patterns, for example, as shown in the embodiment. For example, outer substrates 41 and 43 may receive electrodes only on the inside, while an inner substrate, for example, substrate 42, may have electrodes on both sides.

[0120] Substrates 41 and 42 can be considered collectively as an embodiment of an optical modulator. Similarly, substrates 42 and 43 can be considered collectively as an embodiment of an optical modulator.

[0121] Figure 9c schematically shows an example of an embodiment of a vehicle 20 having smart glazing for a window 21. This is a particularly advantageous embodiment because it allows for frequent and rapid changes in the level of incident illumination while driving. The use of smart glazing in a vehicle has the advantage that the light level can be maintained at a constant level by adjusting the transparency of the vehicle window. Faster and / or more uniform transitions between optical states, e.g., faster transitions toward opacity, are particularly advantageous in a vehicle because they reduce driver distraction during the transition. The vehicle 20 may include a controller configured to control the transparency or reflectivity of the window 21.

[0122] Smart glazing can also be used in other glazing applications, particularly where the amount of incident light is variable, such as in buildings, offices, homes, greenhouses, and skylights. A skylight is a window placed in the ceiling to allow sunlight into a room.

[0123] An optical modulator may have two optical states, for example, a transparent state and an opaque state, or a reflective state and an antireflective state. An optical modulator, for example, optical modulator 10 or optical modulator 40, - By generating an alternating current voltage on at least one of the first and second substrates, and applying an alternating current between the first electrode and the second electrode on at least the first substrate and / or between the first electrode and the second electrode on the second substrate, a switch to a second optical state, for example, an opaque state or an anti-reflective state, and - The system may be configured to switch to a first optical state, such as a transparent state or a reflective state, by generating an alternating current voltage between a first substrate and a second substrate, and applying an alternating current between a first electrode on the first substrate and a first electrode on the second substrate and / or between a second electrode on the first substrate and a second electrode on the second substrate.

[0124] The electrode pattern on the first substrate is arranged in a pattern that is at least partially identical to that of the second electrode on the second substrate. Typically, the electrodes face each other, but the patterns of the first and second electrodes may also be shifted relative to each other.

[0125] A protective coating may be provided on at least a portion of the inner surface area of ​​at least one of the first and second substrates provided.

[0126] The drive signal applied to the drive electrode typically has a fluctuating voltage. For example, a power supply device may operate at an AC frequency for switching between a transparent or opaque state. Such a signal may have a frequency of, for example, 1-1000 Hz. The equilibrium electrolytic current can be obtained by continuously switching the polarity of reverse-charged electrodes on the first and second substrates, and / or between the first and second substrates.

[0127] In one embodiment, a method for controlling an electrophoretic optical modulator using asymmetric electrode drive is: - Applying an electric AC signal to multiple electrodes to obtain an electric field between them, thereby causing electrophoretic motion of particles toward or from one of the electrodes, and thus modulating the optical properties of the optical modulator. - This includes modulating the amplitude of an electrical AC signal applied to multiple electrodes on a substrate to shift a low-electric-field region where the electric field is reduced relative to the electrodes. For example, Figure 10 schematically shows an example of a method 400 for controlling an electrophoretic optical modulator using asymmetric electrode drive. Method 400 is: Receiving commands to increase or decrease panel transparency (410), Select a set of AC signals according to the received command (420), The relative amplitude of a set of AC signals is changed periodically (430). Applying a signal to electrodes within the panel (440) Includes.

[0128] As will be apparent to those skilled in the art, many different ways are possible to carry out the method according to one embodiment. For example, the order of the steps may be as shown, but the order of the steps may be changed, or some steps may be carried out in parallel. Furthermore, other method steps may be inserted between the steps. The inserted steps may represent fine-tuning of the method, such as those described herein, or they may be unrelated to the present method. For example, steps 430 and 440 may be carried out at least partially in parallel. Furthermore, a given step does not have to be completely completed before the next step begins.

[0129] Embodiments of the Method may be executed using software that includes instructions for a processor system to perform Method 400. The software may include only steps taken by a particular subentity of the system. The software may be stored on a suitable storage medium such as a hard disk, floppy disk, memory, or optical disk. The software may be transmitted as a signal along a wire, wirelessly, or using a data network, such as the Internet. The software may be made available for download and / or remote use on a server. Embodiments of the Method may be executed using programmable logic, such as a bitstream configured to constitute a field-programmable gate array (FPGA), in order to perform the Method.

[0130] It should be understood that the present invention also extends to computer programs, in particular computer programs on or within a carrier, adapted to realize the present invention. The program may be in the form of object code, such as source code, object code, code intermediate source, and partially compiled forms, or any other form suitable for use in the implementation of the implementation of the Method. Embodiments relating to a computer program product include computer executable instructions corresponding to each of at least one processing step of the Method described. These instructions may be subdivided into subroutines and / or stored in one or more files that can be linked statically or dynamically. Another embodiment relating to a computer program product includes computer executable instructions corresponding to each of at least one means of the System and / or Product described.

[0131] Figure 11a shows a computer-readable medium 1000 having a writable portion 1010, and a computer-readable medium 1001 having a writable portion. The computer-readable medium 1000 is shown in the form of an optically readable medium. The computer-readable medium 1001 is shown in the form of electronic memory, in this case a memory card. The computer-readable mediums 1000 and 1001 may store data 1020, which, when executed by a processor system, may represent instructions causing the processor system to perform a method according to one embodiment. The computer program 1020 may be embodied on the computer-readable medium 1000 as a physical mark or by using the magnetization of the computer-readable medium 1000. However, any other suitable embodiments can be similarly conceivable. Furthermore, although the computer-readable medium 1000 is shown herein as an optical disc, it should be understood that the computer-readable medium 1000 may be any suitable computer-readable medium such as a hard disk, solid-state memory, or flash memory, and may be non-recordable or recordable. The computer program 1020 includes instructions for causing the processor system to perform the electrophoresis control method.

[0132] Figure 11b shows a schematic diagram of a processor system 1140 according to one embodiment. The processor system comprises one or more integrated circuits 1110. The architecture of one or more integrated circuits 1110 is schematically shown in Figure 11b. Circuit 1110 implements a module or unit thereof that performs the method according to one embodiment, and / or includes a processing unit 1120, e.g., a CPU, for executing computer program components. Circuit 1110 includes a memory 1122 for storing programming code, data, etc. Part of the memory 1122 may be read-only. Circuit 1110 may include communication elements 1126, e.g., an antenna, a connector, or both, and similar. Circuit 1110 may include a dedicated integrated circuit 1124 for performing some or all of the processing defined in this method. The processor 1120, memory 1122, dedicated IC 1124, and communication elements 1126 may be connected to each other via an interconnection unit 1130, e.g., a bus. The processor system 1110 may be configured for contact and / or contactless communication using antennas and / or connectors, respectively.

[0133] For example, in one embodiment, the processor system 1140, for example, an electrophoresis controller or an optical modulator, may comprise a processor circuit and a memory circuit, the processor being configured to execute software stored in the memory circuit. For example, the processor circuit may be an Intel Core i7 processor, an ARM Cortex-R8, or the like. In one embodiment, the processor circuit may be an ARM Cortex-M0. The memory circuit may be a ROM circuit or a non-volatile memory, such as flash memory. The memory circuit may be a volatile memory, such as SRAM memory. In the latter case, the device may comprise a non-volatile software interface, such as a hard drive or a network interface, configured to provide the software.

[0134] It should be noted that the embodiments described above are illustrative rather than limiting, and that those skilled in the art can design many alternative embodiments.

[0135] In a claim, any reference numerals placed between parentheses should not be construed as limiting the claim. The use of the verb “to provide” and its conjugations does not exclude the existence of elements or steps other than those described in the claim. The articles “a” or “an” preceding an element do not exclude the existence of multiple such elements. Expressions such as “at least one of” when following a list of elements represent a selection of all or any subset of the elements from that list. For example, the expression “at least one of A, B, and C” should be understood to include A only, B only, C only, both A and B, both A and C, both B and C, or all of A, B, and C. The present invention can be implemented using hardware comprising several distinct elements and using a suitably programmed computer. In a device claim enumerating several means, some of these means may be embodied by identical items of hardware. The mere fact that certain techniques are enumerated in mutually different dependent claims does not indicate that a combination of these techniques cannot be used to benefit one another.

[0136] In the claims, references in parentheses refer to reference numerals in the drawings illustrating embodiments or formulas of embodiments, thereby enhancing the understanding of the claims. These references should not be construed as limiting the claims.

Claims

1. An electrophoretic optical modulator using asymmetric electrode drive, comprising: at least a first substrate and a second substrate disposed opposite to at least the first substrate; an optical layer disposed between the first substrate and the second substrate containing a fluid containing particles, wherein the particles are charged or can be charged; a plurality of inter-mating electrodes disposed across each of the first and second substrates; and a controller configured to apply an electric AC signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes, thereby causing electrophoretic motion of particles toward or from one of the plurality of electrodes, and thereby causing modulation of the optical properties of the optical modulator. - The controller modulates the amplitude of the AC electrical signal applied to multiple electrodes on the substrate. - Modulating the amplitude shifts the low-electric-field region relative to the electrode, and the low-electric-field region is the region where particle movement relative to the electrode is stationary, or - By modulating the amplitude, the low electric field region is shifted relative to the electrode, and the electric field intensity in the low electric field region of the optical layer is 25% or less of the maximum electric field intensity within the optical layer. An electrophoretic optical modulator configured as follows.

2. The optical modulator according to claim 1, wherein the controller is configured for the closing operation of the optical modulator, and the low electric field region moves orthogonally with respect to the substrate.

3. The optical modulator according to claim 1, wherein the controller is configured for opening the optical modulator, and the low electric field region moves parallel to the substrate.

4. The optical modulator according to claim 1, wherein the amplitude is modulated until it reaches a target gray level, and thereafter the controller applies an electrical maintenance signal to a plurality of electrodes on a substrate to maintain the gray level of the optical modulator.

5. The optical modulator according to claim 1, wherein a first AC signal applied to a first electrode is scaled relative to a second AC signal applied to a second electrode.

6. The optical modulator according to claim 1, wherein the scaling between two AC signals applied to two electrodes cycles between a low scaling factor and a high scaling factor.

7. The optical modulator according to claim 6, wherein the first AC signal has a constant amplitude, and the second AC signal is scaled relative to the first AC signal.

8. The optical modulator according to claim 1, wherein the scaling between two AC signals applied to two electrodes is modulated to randomize the location of the low-electric-field region.

9. The controller, - Configured for a closed operation, in which the amplitude ratio of a pair of signals applied to a pair of opposing electrodes on opposing substrates changes, and / or - An optical modulator according to claim 1, configured for an open operation, wherein the ratio of amplitudes in a pair of signals applied to a pair of neighboring electrodes on the same substrate is changed during the open operation.

10. The optical modulator according to claim 1, wherein a first AC signal applied to a first electrode is scaled relative to a second AC signal applied to a second electrode, and the lower amplitudes of the first and second AC signals are up to 70%, 50%, 45%, 40%, and 30% of the higher amplitudes.

11. The optical modulator according to claim 1, wherein at least one of the AC signals has a high-frequency component having a frequency of at least 500 Hz and a low-frequency component having a frequency of up to 100 Hz.

12. The optical modulator according to claim 1, wherein high-frequency components are removed when they reach a target gray level.

13. The optical modulator according to claim 1, wherein a low-pass filter is applied to the AC signal.

14. The optical modulator according to claim 11, wherein particles in a fluid move under the influence of electrophoretic and dielectrophoretic forces.

15. The optical modulator according to claim 1, wherein the first substrate comprises a first electrode and a neighboring second electrode, the second substrate comprises a third electrode and a neighboring fourth electrode, the first and fourth electrodes facing each other, the second and third electrodes facing each other, and the controller is configured to use a first phase for the first electrode, an increased phase for the second electrode, a further increased phase for the third electrode, and a further increased phase for the fourth electrode.

16. The electrophoretic optical modulator according to claim 1, wherein the low electric field region is a dead region where there is no electric field, and the controller is configured to move the dead region relative to the electrode.

17. - The electric field intensity in the low-electric-field region of the optical layer is 15% or less, or 10% or less, or 1% or less compared to the maximum electric field within the optical layer, and / or - The electric field strength in the low electric field region of the optical layer is less than 2 * 10^6 V / m, less than 1 * 10^6 V / m, or less than 1 * 10^5 V / m, and / or - In the low electric field region, the electric field strength is up to 10% or up to 15% greater than the minimum electric field within the optical layer. The electrophoretic optical modulator according to claim 1.

18. A controller configured to control an asymmetric AC signal for an electrophoretic optical modulator, The optical modulator comprises at least a first substrate and a second substrate positioned opposite at least the first substrate, and an optical layer disposed between the first substrate and the second substrate containing a fluid containing particles, wherein the particles are charged or can be charged, and a plurality of inter-mating electrodes disposed across each of the first and second substrates, wherein the controller is configured to obtain an electric field between the plurality of electrodes and apply an electric AC signal to the plurality of electrodes to cause modulation of the optical properties of the optical modulator by causing electrophoretic motion of particles toward or from one of the plurality of electrodes, and the controller modulates the amplitude of the electric AC signal applied to the plurality of electrodes on the substrate, - Modulating the amplitude shifts the low-electric-field region relative to the electrode, and the low-electric-field region is the region where particle movement relative to the electrode is stationary, or - By modulating the amplitude, the low-electric-field region is shifted relative to the electrode, and the electric field intensity in the low-electric-field region of the optical layer is 25% or less of the maximum electric field intensity within the optical layer. A controller configured in such a way.

19. A method for controlling an electrophoretic optical modulator using asymmetric electrode drive, wherein the optical modulator comprises at least a first substrate and a second substrate positioned opposite at least the first substrate, an optical layer disposed between the first substrate and the second substrate containing a fluid containing particles, the particles being charged or chargeable, and a plurality of interlocking electrodes disposed across each of the first and second substrates, and this method is - Applying an electric AC signal to multiple electrodes to obtain an electric field between them, thereby causing electrophoretic motion of particles toward or from one of the electrodes, and thus modulating the optical properties of the optical modulator. - Modulating the amplitude of an electrical AC signal applied to multiple electrodes on a substrate, - Modulating the amplitude shifts the low-electric-field region relative to the electrode, and the low-electric-field region is the region where particle movement relative to the electrode is stationary, or - By modulating the amplitude, the low electric field region is shifted relative to the electrode, and the electric field intensity in the low electric field region of the optical layer is 25% or less of the maximum electric field intensity within the optical layer. thing Methods that include...

20. A temporary or non-temporary computer-readable medium (1000) containing data (1020) representing instructions that cause the processor system to perform the method according to claim 19 when executed by the processor system.

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