Asymmetric Driving for an Optical Modulator

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 for 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 of a transparent dielectric material such as glass or plastic material. The internal volume defined between the plates can 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 surfaces 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 can 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 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 within this specification solve these and other problems. For example, in one embodiment, an electro-optical modulator comprises at least a first substrate and a second substrate disposed opposite the at least first substrate. An optical layer containing a fluid containing particles is disposed between the first substrate and the second substrate, and the particles are charged or chargeable. A plurality of interlocking electrodes are disposed across each of the first substrate and the second substrate. A controller is configured to obtain an electric field between the plurality of electrodes to effect electrophoretic movement of the particles towards or from one of the plurality of electrodes and to cause modulation of the optical properties of the optical modulator by applying an electrical AC signal to the plurality of electrodes. The controller is configured to modulate the amplitude of the electrical AC signal applied to the plurality of electrodes on the substrate to move the low electric field region relative to the electrodes.

[0006] By modulating the amplitude of the signal, the regions where the electric field is low, and especially the lowest, move 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 moves towards the former substrate. Similarly, by manipulating the signals to adjacent electrodes, the low electric field region can be made to move parallel to the substrate. In fact, there can be no particle movement in the low electric field region and the particles are stationary relative to the electrodes. Moving such regions allows the stationary particles to escape therefrom so that they do not slow down the transition of the panel. In particular, the so-called dead region where there is no electric field can be moved within the optical layer.

[0007] Moving the low electric field region, especially the dead region, has several advantages. Particles within the low electric field region do not respond to the electric field as quickly as particles within the high electric field region. As a result, those regions transition slowly and the transition is not uniform. Furthermore, by moving the low electric field region around, the overall mixing of the particles is increased.

[0008] An optical modulator as described in this specification can be applied in a wide variety of practical applications. For example, an optical modulator having at most one opaque substrate can be used as a surface that can change its optical appearance, such as its reflection or transmission state. In particular, an optical modulator that makes all substrates transparent can be used, for example, for optical active glazing for offices, automobiles, casings, and the like.

[0009] Embodiments of the control method can be implemented on a computer as a computer-implemented method, or in dedicated hardware, or in a combination of both. Executable code for embodiments of the method can be stored in a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, online software, and the like. Preferably, the computer program product includes non-transitory program code stored in 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 some of the steps of embodiments of the 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 by way of example only with reference to the drawings. The elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. In the figures, elements corresponding to those already described may have the same reference numerals.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] List of reference numbers 1, 2, 3, 4 electrodes 10 optical modulator 11 first substrate 12 second substrate 13, 13a, 13b electrodes 14, 14a, 14b electrodes 15 fluid 16 controller 30 particles 20 automobile 21 optical modulator 40 optical modulator 41 first substrate 42 second substrate 43 third substrate 46 controller 100 substrate 101 first direction 102 second direction 110 first electrode 120 second electrode 111 - 113 main lines 121 - 123 main lines 151 first substrate 152 optical layer 153 second substrate 160 controller 1000, 1001 computer - readable media 1010 writable part 1020 computer program 1110 integrated circuit 1120 processing device 1122 memory 1124 application - specific integrated circuit 1126 communication element 1130 interconnecting part 1140 processor system

[0014] Although the present invention can have embodiments in many different forms, it is to be understood that one or more specific embodiments are shown in the drawings and described in detail herein under the understanding that the present disclosure should be regarded as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments shown and described.

[0015] In the following, for purposes of understanding, the elements of the embodiments are described in terms of their operations. However, it should be understood that each element is configured to perform the functions described as being performed by them.

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

[0017] FIG. 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 FIG. 1a are two electrodes on the same surface: a first electrode 110 and a second electrode 120. For example, in order to facilitate more fine-grained control, there may be three or more electrodes on the same side of the substrate. For example, the plurality of electrodes can be used to facilitate a segmented substrate, for example, for a segmented optical modulator. For example, in a segmented optical modulator, some zones can have different optical properties, such as different transparency or reflectivity. Although embodiments having two electrodes are shown below, additional electrodes may be added to them, for example, by replicating similar structures adjacent to each other.

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

[0019] The first electrode 110 and the second electrode 120 each comprise multiple main lines. As shown in FIG. 1a, the first electrode 110 comprises main lines 111, 112, and 113, and the second electrode 120 comprises main lines 121, 122, and 123. Typically, each electrode comprises more than three lines. The main lines extend across the substrate. The multiple 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 encounter alternately from different multiples, for example, from the first and second multiples in the first and second electrodes, respectively. The first and second directions are angled with respect to each other, and typically, the angle is substantially perpendicular. The first and second directions can each be parallel to the side surface of the substrate, but this is not essential.

[0020] For example, the substrate 100 can be combined with another substrate to form a transparent optical modulator, at least one of which is transparent. The light incidence by the optical modulator is modulated in a manner depending on the 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 the substrate 100 can be smart glazing, for example, in optical modulators, which can be applied to residential homes, offices, greenhouses, automobiles, and the like.

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

[0022] Some of the following embodiments show examples of modulating the transparency or reflectivity level. The optical modulator can be adapted for other optical effects. For example, if desired, embodiments can be modified to different levels of light transmissivity instead of different levels of transparency. If desired, the type of particles used in the embodiments can be changed to different particles, for example, in terms of which wavelengths they absorb or reflect and how reflective the reflection is, whether specular or diffuse. For example, in one embodiment, the optical modulator can modulate different levels of reflection. The particles can also emit light. Stacking multiple optical layers further increases the possibilities.

[0023] To provide electrically adaptable glazing, it is sufficient to have two sets of alternating main lines; due to the two alternating sets, the electric field at any part of the substrate can be controlled because two opposing electrodes border that part from two opposing sides.

[0024] The plurality of electrodes applied on the substrate are interdigitated to manipulate the electric field between the two substrates. In FIG. 1a, the main electrodes are shown as having a plurality of interdigitated parallel main lines. This is a possible configuration, but in one embodiment, the shape of the electrodes can vary greatly. For example, by adapting the shape of the electrodes, the diffraction effect can be changed.

[0025] Figure 1b schematically shows an example of an embodiment of an electrophoretic optical modulator. A substrate such as that 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 at 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 arranged 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 chargeable.

[0026] At least two interlocking electrodes are arranged on the first substrate 151 and the substrate 153. At least two interlocking electrodes are arranged facing them. Shown on the first substrate 151 are two electrodes 1 and electrode 2. For example, electrode 1 may be electrode 111, and electrode 2 may be electrode 121. Shown 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 continue with electrodes 1, 2, 1, 2,... and the substrate 153 may continue with electrodes 4, 3, 4, 3,... etc.

[0027] The controller 160 is configured to apply an electrical AC signal to each of the plurality of electrodes on the two substrates, for example, to electrodes 1, 2, 3, and 4, to obtain an electric field between the plurality of electrodes. The electric field causes an electrophoretic movement of particles towards or from one of the plurality of electrodes, 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 apply an electrical AC signal for application to a plurality of electrodes to obtain an electric field between the plurality of electrodes and to cause electrophoretic movement of particles towards or from one of the plurality of electrodes, which causes modulation of the optical properties of the modulator. For example, the controller 160 may generate the electrical 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 a filter, etc.

[0030] For example, there are several optical properties that can be modulated in an optical modulator, such as transparency, reflectivity, color, etc. For the purpose of simplicity, the embodiments are described with respect to the control of a gray scale 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. Particles are sometimes referred to as dyes.

[0031] The controller 160 is configured to modulate the amplitude of the electrical AC signal applied to the plurality of electrodes on the substrate to move the low electric field region relative to the electrodes.

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

[0033] For example, in the low electric field region of the optical layer, the electric field strength may be 25% or less than that in other places within the optical layer. For example, in some regions of the optical layer, the electric field strength may be 15% or less, 10% or less, 1% or less compared to the maximum electric field within the optical layer. For example, in the low electric field region of the optical layer, the electric field strength 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, the low electric field region can be regarded as the region within the optical layer where the electric field is minimum. For example, the low electric field region can be regarded as the region within the optical layer where the electric field is minimum or a given percentage greater than the minimum, for example, up to 10%, up to 15%, etc.

[0034] The electric field can be measured directly, but it has been found that computer simulations of the electric field are accurate enough for practical applications. For example, well-known COMSOL software may be used for simulation electric field diagrams. In this specification, the strength of the electric field can be generated using Electrostatic study under the AC / DC module of COMSOL Multiphysics. The electric field diagrams shown in this specification were created using the above-mentioned software.

[0035] In particular, within the optical layer, there may be regions where the electric field is absent, for example, zero or substantially zero. Such regions are called insensitive regions. Particles within the insensitive region essentially do not respond to electrophoretic control. Through other means, such as slow entropic movement, the particles can drift out of the insensitive region and become susceptible again to the influence of controlled movement. The insensitive region is particularly problematic for the rapid transition between optical modes of the optical modulator. The insensitive region is sometimes referred to as the electric field neutral region or neutral point. The neutral point can be a point within a 2D intersection as shown in the figure; however, in a physical 3D embodiment, the neutral point can be a neutral curve or neutral volume.

[0036] In an embodiment, problems caused by the low electric field region and especially the insensitive region are solved by fluctuations in the potential difference between the 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, global driving uses an AC signal and can maintain the neutrality and balance of the flow in various electric fields over time. This is advantageous since it reduces the corrosion of the electrodes.

[0038] In one embodiment, the electric field lines are modulated such that the neutral point shifts its position within the optical layer, and as a result, the total volume under the influence of the electric field, for example, the electrophoretic control, increases.

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

[0040] Asymmetric driving of the electrodes has the advantage of faster transitions between optical states, as further described herein. Asymmetric driving of the electrodes further provides the advantage of more uniform transitions since the difference in slow and fast transition locations on the panel is reduced. An additional advantage of asymmetric driving is the reduced accumulation of particles on the electrodes. In conventional optical modulators, especially in DC-driven modulators, particles can accumulate on the electrodes where they can be locally compressed. This can lead to particle interactions there and to particles forming irreversible agglomerates. Such agglomeration of particles is undesirable. The agglomeration effect causes problems such as inhomogeneity and gravitational effects. However, with asymmetric driving as in one embodiment, the particles are more motile and thus annealing to agglomeration is limited. Furthermore, the particle motion is more uniform.

[0041] The insensitive region, e.g., the neutral point or volume, leads to optical aberrations due to particle accumulation during operation. By increasing the particle mobility, there is less aggregation and the particles are less likely to fall due to gravity. The improved particle mobility enables better approach and dispersion of the particles to reach the opaque state while maintaining a particle distribution closer to the initial state of dispersion during manufacturing.

[0042] Interestingly, the asymmetric drive can be added to existing algorithms used to drive the panel to a target gray scale. Furthermore, introducing the asymmetric drive can still maintain the neutrality of the current. For example, using the algorithm described in PCT / EP2021 / 071346 entitled "Lightmodulator, Lightmodulator Method And Smart Glazing", signal scaling can be introduced to move the low electric field region, especially the insensitive region.

[0043] For example, the controller can be composed of a set of algorithms for one or more of functions such as: increasing transparency, decreasing transparency, maintaining the current transparency, etc. There can be more or fewer algorithms. For example, the algorithms can vary according to the size of the sharp increase in the desired transparency. For example, the algorithm for maintaining can be omitted. For example, in a simplified embodiment, the controller can have an algorithm for driving towards full transparency and an algorithm for driving towards full opacity. For example, the computer program code can be stored in the memory of the controller to implement the algorithms. In one embodiment, the controller is configured to apply a programmed drive algorithm over a specific duration, which can depend on, for example, the current transparency, the target transparency, and the measured sensor values, as described in the cited PCT application.

[0044] Existing algorithms can be modified by periodically up or downscaling one or more of the signals so that the low electric field region, and especially the insensitive region, moves. For example, an existing drive algorithm can be modified to be asymmetric by introducing an asymmetric scaling and to change the direction of the asymmetric scaling after a given period. When the drive asymmetry changes, the low electric field region moves. In one embodiment, the volume within the optical layer is scanned by higher intensity electric field lines, causing all particles within the volume to be susceptible to the effects of electrical control at some point during the scan. Asymmetric driving can advantageously be used both for driving towards the target transparency and for maintaining the gray scale. The open drive can also vary in asymmetry while maintaining the gray scale.

[0045] Asymmetric driving enables faster transitions, especially much faster closing of the device (i.e., driving towards opacity), because most of the particle population is moved regardless of the initial location of the particles, including the intermediate position between the electrodes and the electrode surface.

[0046] Typically, the scaling of the signals is applied to a pair of electrode signals. For example, a pair of signals X and Y can be applied to a pair of electrodes. The electrodes can be, for example, a pair of opposing electrodes, a pair of adjacent electrodes, a pair of diagonally opposing electrodes. The electrode signals before scaling typically have the same phase and the same amplitude; indeed, the pair of signals can be the same signal. However, even before scaling, there can be differences in phase or amplitude. For example, a phase difference can be used to trap particles. For example, a scaling difference can be used to compensate for, for example, hardware differences, amplitude, and the like between substrates. In particular, signals X and Y can be conventional AC drive signals for an electro-optic modulator. Signals X and Y can be scaled to move the low electric field region within the optical layer. For example, a time-varying scaling factor can be applied to the signals. FIGS. 1c.1 - 1c.4 schematically show examples of embodiments of the scaling factor.

[0047] In FIG. 1c.1, the scaling factor is selected such that when one signal is scaled up (amplified), the other is scaled down (de - 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 FIG. 1c.2, the scaling factor is selected such that only one of the two signals is attenuated and the other is kept constant. In the figure, the scaling is done alternately. Note that in these examples, scaling down may be used instead of scaling up. In fact, using scaling down is easier because the signal remains within a given range.

[0049] FIG. 1c.3 is the same as FIG. 1c.2 except that the scaling is done alternately with periods where no scaling is used.

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

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

[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 the optical modulator. The electric fields are shown in the same plane as shown in Fig. 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 movement of the particles is generally determined by the electric field and its shape as shown by the electric field diagram, but some other factors such as, for example, Brownian motion, temperature, etc. can also have some influence on the movement of the particles.

[0054] The y - axis in Fig. 2a.2 and in similar figures schematically shows the voltage of the signal applied to the electrodes. The horizontal dashed lines in the four signals indicate the neutral voltage of each signal, e.g., the zero - voltage line. The x - axis schematically shows time. Note that the four signals are AC signals. Fig. 2 shows a square signal, but other AC - type signals such as triangles, sine waves, and combinations thereof can be used. The drive shown in Fig. 2a.2 is configured to close the optical modulator, e.g., to reduce transparency and increase the gray level. If the drive shown in Fig. 2a.2 is continued for a long time, the substrate gradually approaches maximum opacity. That being said, the drive does not have to continue to full opacity; the drive can end at some desired gray level before that time.

[0055] Note that signals 1 and 4 are equal such that there is a dead zone in the middle between substrates 1 and 4. The same can be said for signals 2 and 3. The particles in 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, e.g., there is a low - electric - field region. The particles in the low - electric - field region respond to the electric field but respond slowly.

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

[0057] In FIG. 2a.2, the AC signals applied to the opposing electrode pairs 1 and 4, and the opposing electrode pairs 2 and 3 are equal. In FIG. 2a.2, the AC signals applied to the adjacent electrode pairs 1 and 2, and the adjacent electrode pairs 4 and 3 are equal except for a phase shift, in this case, a 180 - degree phase shift. The opposing electrode pairs are two different electrodes facing each other on opposing substrates. The adjacent electrode pairs are two different electrodes adjacent to each other on the same substrate. There is an insensitive region in the middle between electrode 1 and 4, and in the middle between electrode 2 and 3.

[0058] FIG. 2b.2 shows the asymmetry introduced in the driving of the panel. In FIG. 2b.2, the AC signals applied to the opposing electrode pairs 1 and 4, and the opposing electrode pairs 2 and 3 are equal except for scaling. For example, the driving in FIG. 2b.2 can be obtained from the driving in FIG. 2a.2 by scaling down the driving at electrodes 1 and 2, for example, by scaling down the driving of one of the electrodes 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 parameters in a signal generator, etc. In FIG. 2b.2, the AC signals applied to the adjacent electrode pairs 1 and 2, and the adjacent 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 driving shown in FIG. 2b.2 is still to close the panel. Note that the low - electric - field region in FIG. 2a.1 has been moved upward in FIG. 2b.1; in particular, the insensitive region has been moved upward.

[0060] In FIG. 2c.2, the scaling direction is reversed. During the closing operation, the asymmetry introduced into the pair of opposing electrodes is now in the opposite direction here. This means that the dead zone is now moved downwards here, for example, towards the lower substrate. Note that the up and down directions are relative. These terms are related to the panel as shown in the figures herein and are abbreviations for going towards the first substrate or towards the second substrate; in one embodiment, the panel can be vertical such that directions such as up and down can be front and back, or the like.

[0061] To reduce transparency, for example, to close the panel, the panel can be driven by alternately using three types of signals. For example, the drive can have a middle dead zone as in FIG. 2a, an upper dead zone as in FIG. 2b, or a lower dead zone as in FIG. 2c. For example, in one embodiment, the drive can repeat a cycle such as middle dead zone drive, upper dead zone drive, middle dead zone drive, and lower dead zone drive.

[0062] Closing the panel using this type of two - directional asymmetric drive significantly speeds up the reach to dark gray. In conventional symmetric drive, the transition from 10% gray to 1% gray, i.e., from bright gray to complete darkness, can take about 10 times longer compared to one embodiment.

[0063] Using two - directional asymmetric drive is preferred because most of the volume is scanned, thereby improving the mixing of particles. Although not essential; the improved drive can be achieved by repeating cycles such as middle dead zone drive, upper dead zone drive, etc.

[0064] Figures 3a - 3c show examples of electric fields in an embodiment of an optical modulator. The electric field diagrams in FIGS. 3a - 3c are the same as those in FIGS. 2a.1 - 2c.1. What is shown in FIGS. 3a - 3c is the low electric field region schematically indicated by a circle. The center of the circle coincides with a portion of the field where there is no electric field, for example, the insensitive region. Note that the position of the insensitive region moves with respect to the electrodes. In this case, the insensitive region moves substantially orthogonally to the substrate. Orthogonal movement is convenient but not essential, and the insensitive region can also be moved parallel to the substrate by introducing asymmetry to adjacent electrode pairs as well as opposite electrode pairs. However, for improved mixing, orthogonal movement is sufficient.

[0065] Figures 3a - 3c show different stages in a closed operation using asymmetric drive. The insensitive region moves within the optical layer between two opposite substrates, for example, towards and away from either of the two substrates. For example, the controller can be configured to apply a scaling operation to the signals applied to the electrodes. For example, the signals applied to opposite electrodes can be the same except for the scaling applied to one or both of them. The amount of scaling depends on the application, for example, the size of the panel and the thickness of the optical layer. As an example, the first AC signal applied to the first electrode can be scaled with respect to the second AC signal applied to the second electrode opposite the first electrode, and the low amplitudes of the first and second AC signals are up to 70%, 50%, 45%, 40%, 30% of the high amplitude.

[0066] The signals schematically shown in the figures are square waves, but in reality, this is not at all essential. The signals can instead be sine waves. For example, a low - pass filter can be applied to the signals as shown in the figures. The low - pass threshold can be selected depending on the size of the panel, for example, 1 kHz for a larger panel.

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

[0068] Scaling may decrease and / or increase one signal while keeping the other signal constant. For example, the first AC signal may have a constant amplitude, and the second AC signal may be scaled with respect to the first AC signal. The signal kept constant and the signal being scaled may switch within time. Scaling may be done for low voltage signals but may also be introduced during signal amplification. In one embodiment, the scaling of the signal is randomized to randomize the position of the insensitive region. In one embodiment, the scaling of the signal is controlled to move the position of the low electric field region in a controlled manner, e.g., along a predefined path through the optical layer.

[0069] Once the target gray level is reached, e.g., as indicated by a sensor associated with a panel, e.g., an optical and / or electrical sensor. The drive signal may be interrupted. The panel holds its gray level for a while, but the appearance of the panel may decay over time, and as a result, conventional sustain driving may be used. Sustain driving may include slow low-power driving of the panel to a gray level near the target gray level. Sustain driving may be alternated with no driving at all. During sustain, asymmetric signals may also be used, as this improves the mixture and increases the durability of the panel.

[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 the optical modulator. The electric fields are 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 adjacent electrode pairs 1 and 2, and adjacent 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. There are low - electric - field regions in the middle between electrode 1 and 2 and in the middle between electrode 3 and 4 that extend from substrate to substrate. Figure 4a.1 also shows two insensitive regions: the insensitive region between electrode 1 and 2 and the insensitive region between electrode 3 and 4. These two insensitive regions are located outside the optical layer. Since there are no particles corresponding to the shown electrodes 1 - 4, these insensitive regions themselves are not a problem. However, there is a low - electric - field region that extends between these two insensitive regions. Particles in the low - electric - field region respond to the electric field faster than particles in the insensitive regions, but particles in the low - electric - field region still move slower than particles somewhere in the optical layer. For example, the electric field in the low - electric - field region between the two insensitive regions can be 25% lower than the field midway and directly between the electrodes.

[0072] Figure 4b.2 shows the asymmetry introduced into the driving of the panel. In Figure 4b.2, the AC signals applied to adjacent electrode pairs 1 and 2, and adjacent electrode pairs 3 and 4 are equal except for scaling. For example, the driving in Figure 4b.2 can be obtained from the driving in Figure 4a.2 by scaling down the driving at electrodes 2 and 3, for example, by scaling down the driving of one of the electrodes in a pair of adjacent electrodes. In this case, the signals to electrodes 2 and 3 are scaled down. In Figure 4b.2, the AC signals applied to opposite electrode pairs 1 and 4, and adjacent 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 driving 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 increased somewhat. If only the type of driving shown in Figure 4b.2 were used, this could make it more difficult to move the particles near electrodes 2 and 3, but this is not a problem because the driving is combined with asymmetric driving 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 into a pair of adjacent electrodes during the opening operation is then in the opposite direction, for example, the low electric field region moves to the left.

[0075] To increase transparency, for example, to open the panel, the panel can be driven by alternately using three types of signals. For example, the driving can have a central low electric field region as shown in FIG. 4a, a right low electric field region as shown in FIG. 4b, or a left low electric field region (not shown in a separate figure). For example, in one embodiment, the driving can repeat the circulation between low electric fields: central, left, central right; or just between central and left. The time spent on different phases does not have to be equal. In the case of opening, the time spent in the center can be longer than the time spent driving with a left or right low electric field.

[0076] In one embodiment, during the opening operation, the low electric field region can move parallel to the substrate. As discussed for the closing operation, similar options for generating the signal are also possible for the opening operation. For example, the signal can be scaled, and the scaling factor can repeatedly pass through the range of the scaling factor.

[0077] FIGS. 5a - 5b show examples of electric fields in an embodiment of an optical modulator. The electric field diagrams in FIGS. 5a - 5b are the same as those in FIGS. 4a.1 - 4b.1. Shown in FIGS. 5a - 5c are low electric field regions schematically indicated by ellipses. The electric field within the ellipse is about 1.5 * 10^6 V / m. Note that when comparing FIGS. 5a and 5b, the low electric field region has moved to the right. For example, the center of the low electric field region, for example, the center of gravity, or the center weighted by the electric field strength, has moved to the right, in this case parallel to the substrate. Note also that the insensitive region outside the optical layer has moved to the right.

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

[0079] Figures 6a.1 and 6b.1 show an example of an electric field 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 an example of an AC signal corresponding to the electric field diagram.

[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 adjacent electrode pairs 1 and 2, and adjacent electrode pairs 3 and 4 are equal except for a phase shift, in this case a 180-degree phase shift. There is a dead zone in the middle between electrodes 1, 2, 3, and 4. In the dead zone, the electric field is substantially zero.

[0081] Figure 6b.2 shows the asymmetry introduced into the driving of the panel. In Figure 6b.2, the AC signals applied to the diagonal electrode pairs 1 and 3, and the diagonal electrode pairs 2 and 4 are equal except for scaling. For example, the driving in Figure 6b.2 can be obtained from the driving in Figure 6a.2 by scaling down the driving at electrodes 1 and 2, for example, by scaling down the driving of one of the electrodes at a pair of diagonal electrodes. In Figure 6b.2, the AC signals applied to the adjacent electrode pairs 1 and 2, and the adjacent electrode pairs 3 and 4 are equal except for a phase shift, in this case, a 180-degree phase shift. Note that all the signals applied to the electrodes on one substrate, in this case the upper substrate, are scaled down. For example, in one embodiment, the signals applied to one of the two substrates have a lower amplitude than the signals applied to the other of the two substrates. As a result, the dead zone in Figure 6a.1 has been moved upward in Figure 6b.1. In this case, the dead zone has moved orthogonally 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 closed operation of the optical modulator, and in the closed operation, the AC signals applied to the opposing electrodes on the opposing substrates are scaled relative to each other, and the controller modulates the scaling and thus moves the low electric field region. In one embodiment, the AC signals applied to adjacent electrodes on the same substrate are phase-shifted relative to each other.

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

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

[0085] In one embodiment, the optical modulator is an electrophoretic modulator, and the particles are moved due to the electrophoretic effect. In one embodiment, a high-frequency component can be added to the signal. For example, in one embodiment, the electrophoretic driving uses a frequency of up to 100 Hz, for example. 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 can 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] The high-frequency component can be removed when the target gray level is reached. By doing so, energy is saved and the heat-up of the optical modulator is reduced. 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 component. FIGS. 7a-7c schematically show examples of AC signals in an embodiment of the optical modulator. FIGS. 7a-7c correspond to FIGS. 2a.2, 2b.2, 2c.2 with a schematic HF component. FIGS. 4a.2, 4b.2, 6a.2, and 6b.2 can likewise be enhanced with an HF component.

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

[0088] The advantage of having increasing phase shifts for four signals is that the particles are better retained within the cell gap. As a result, a given transparency or its absence can be maintained at lower power. In FIG. 8b, the amplitudes of the four signals as shown are equal, but 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 gap between adjacent electrodes; this is particularly advantageous when closing the panel and in maintaining gray levels.

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

[0091] FIG. 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] Reference is made to patent application PCT / EP2020 / 052379, which is incorporated herein by reference; this application includes, for example, advantages such as including electrodes, constructing blocks, and / or a favorable design for an optical modulator that can be further improved by a substrate as 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 a non-reflective state and vice versa. The optical modulator 10 comprises a first substrate 11 and a second substrate 12 arranged facing each other. Inside the first substrate 11, at least two electrodes are applied: shown are electrodes 13a, 13b. These at least two electrodes are collectively referred to as electrode 13. Inside the second substrate 12, at least two electrodes are applied: shown are electrodes 14a, 14b. These at least two electrodes are collectively referred to as electrode 14. The configuration of the electrodes is interlocking but can be changed separately to a large extent. In particular, it is not essential for the main lines of the electrodes to extend parallel across the substrate.

[0094] A fluid 15 is provided between the substrates. The fluid contains particles 30, for example, nanoparticles and / or microparticles, and the particles are charged or chargeable. For example, the particles can essentially carry a charge on their surface. For example, the particles can be surrounded by charged molecules.

[0095] The electrodes are arranged to drive the particles 30 to move towards or away from the electrodes in response to the applied electric field. The optical properties of the optical modulator, in particular, transparency or reflectivity, depend on the location of the particles 30 in the fluid. For example, a connection can be provided to apply an electromagnetic field to the electrodes.

[0096] In an example, substrates 11 and 12 are optically transparent outside the electrodes, can be typically >95% transparent at relevant wavelengths, such as >99% transparent. Considering the electrodes, the transparency can be much lower, for example, 70%. The term "optical" can relate to wavelengths visible to the human eye (from about 380 nm to about 750 nm), and, where applicable, broader wavelengths including infrared (from about 750 nm to 1 μm) and ultraviolet (from about 10 nm to 380 nm), and, where applicable, can relate to partial selections thereof. In an exemplary embodiment of the optical modulator, the substrate material is selected from glass and polymers. The transparent material can also be used for the electrodes. In an embodiment of the optical modulator, only substrates 11 and 12 are transparent.

[0097] In another example, one substrate, such as the lower substrate 12, can be reflective or partially reflective, while the upper substrate 11 is transparent. The optical properties of the optical modulator, particularly the reflectivity, depend on the location of the particles 30 in the fluid. When the panel is in the open state (vertical drive), most of the particles are located between the opposing electrodes of the two substrates, and as a result, the incident light can pass through the transparent upper substrate and the relatively unobstructed optical layer and be 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 even more preferably less than 50 μm, such as less than 30 μm.

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

[0100] The particles 30 can be adapted to absorb light, thereby preventing a specific wavelength from passing through. The particles 30 can reflect light; for example, the reflection can be specular, diffuse, or in between. The particles can absorb some wavelengths and reflect others. The particles can further or alternatively emit light, for example, using phosphorescence, fluorescence, or the like. Even a fluid can emit light, and this emission is modulated by changing the position of the particles.

[0101] In an exemplary embodiment of the optical modulator, the size of the nanoparticles is 20 - 1000 nm, preferably 20 - 300 nm, more preferably less than 200 nm. In an exemplary embodiment of the optical modulator, the nanoparticles / microparticles can include a coating and / or a dye, and preferably, a core. In an exemplary embodiment of the optical modulator, the coating of the particles is made of a material selected from conductor or semiconductor materials.

[0102] In an exemplary embodiment of the optical modulator, the particles are adapted to absorb light having wavelengths in the range 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 the light having a wavelength range falling within 10 nm - 1 mm (filter), and combinations thereof.

[0103] In an exemplary embodiment of the optical modulator, the particles are charged or chargeable. For example, the charge on the particles may be from 0.1e to 10e (5*10-7-0.1 C / m2) per particle.

[0104] In an exemplary embodiment of the optical modulator, the fluid is present in an amount of 20-50 g / m2, such as 1-1000 g / m2, preferably 2-75 g / m2, more preferably 30-40 g / m2. A great advantage in this layout is that much less fluid and much fewer 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 contains one or more of a surfactant, an emulsifier, a polar compound, and a compound capable of forming a hydrogen bond.

[0108] Fluid 15 may be a non-polar fluid having a dielectric constant of less than 15. In an exemplary embodiment of the optical modulator, the fluid has a relative dielectric constant εr of less than 100, preferably less than 5, etc. In an exemplary embodiment of the optical modulator, fluid 15 has a kinematic viscosity coefficient greater than 10 mPa·s.

[0109] The electrodes 13a, 13b, and the electrodes 14a, 14b are in a fluid contact state with the fluid. The fluid can be in direct contact with the electrodes or indirectly, for example, the fluid can contact a second medium having the 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 resistance of less than 100 nΩm (at 273K; for comparison, typically used ITO has 105 nΩm) similar to a conductivity of >1×107 S / m at 20°C.

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

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

[0112] The optical modulator 10 can include one or more segments, and the segments are single optically switchable entities that can have various sizes. The substrate can at least partially surround the volume that can be a segment.

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

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

[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 to face each other. In an aligned substrate, electrodes on different substrates are behind each other when viewed in a direction perpendicular to the substrate. When the optical modulator is disassembled and the substrates are both arranged with the electrodes facing up, the electrode patterns are mirror images of each other.

[0116] Aligning the substrates can increase the maximum transparency or reflectivity of the optical modulator; while, when selecting an optical modulator for criteria more than a range such as transparency or reflectivity, it may be better not to align or not to fully align the two substrates. The optical modulators can be stacked. For example, two stacked optical modulators can be made from three substrates, with the middle one having electrodes on both of its surfaces. In one embodiment of the optical modulator, optionally, at least one substrate 11, 12 of the first optical modulator is the same as the substrate 11, 12 of at least one second optical modulator. In the case of stacked modulators, alignment can also increase the maximum transparency or reflectivity, but there are other considerations, such as it may have an adverse effect on diffraction.

[0117] FIG. 9b schematically shows an example of an embodiment of an optical modulator 40. The optical modulator 40 is similar to the optical modulator 10, except that it comprises a plurality of optical layers; two optical layers in the example shown. There can be three or more optical layers. Each optical layer is disposed between two substrates. The optical modulator 40 can be regarded as a stack of two-substrate optical modulators as in FIG. 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 there is an optical layer between substrates 42 and 43. The optical layer can be the same as that in the optical modulator 10. The controller 46 is configured to control the current on the electrodes of the substrates. For example, in FIG. 9b, the controller 46 can be electrically connected to at least 4×2 = 8 electrodes.

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

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

[0120] Substrates 41 and 42 can be regarded as an embodiment of a light modulator together. Similarly, substrates 42 and 43 can be regarded as an embodiment of a light modulator together.

[0121] FIG. 9c schematically shows an example of an embodiment of an automobile 20 having smart glazing for a window 21. This is a particularly advantageous embodiment because the level of incident illumination can be changed frequently and rapidly during driving. Using smart glazing in an automobile has the advantage that the light level can be maintained at a constant level by adjusting the transparency of the automobile window. A faster and / or more uniform transition between optical states, for example, a faster transition towards opacity, is particularly advantageous in an automobile because it reduces driver distraction during the transition. The automobile 20 can 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, for example, in buildings, offices, homes, greenhouses, skylights. A skylight is a window placed on the ceiling so that sunlight can enter the room.

[0123] The optical modulator can have two optical states, for example, a transparent state and an opaque state, or a reflective state and a non-reflective state. The optical modulator, for example, optical modulator 10 or optical modulator 40, - creating an alternating voltage in 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, so as to switch to a second optical state, for example, an opaque state or a non-reflective state, and - creating an alternating voltage between the first substrate and the second substrate and applying an alternating current between the first electrode on the first substrate and the first electrode on the second substrate and / or between the second electrode on the first substrate and the second electrode on the second substrate, so as to be configured to switch to a first optical state, for example, a transparent state or a reflective state.

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

[0125] A protective coating can be provided on at least a part 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 varying voltage. For example, the power supply device can be operated at an AC frequency for switching between a transparent state and an opaque state. Such a signal can have a frequency of, for example, 1 - 1000 Hz. A balanced electrolytic current can be obtained by continuously switching the polarities of the oppositely charged electrodes on the first and second substrates and / or between the first substrate and the second substrate.

[0127] In one embodiment, a method for controlling an electrophoretic optical modulator using asymmetric electrode driving is - Applying an electrical AC signal to a plurality of electrodes to obtain an electric field between the plurality of electrodes, causing electrophoretic movement of particles towards or from one of the plurality of electrodes, and causing modulation of the optical properties of the light modulator. - Modulating the amplitude of the electrical AC signal applied to the plurality of electrodes on the substrate to move a low electric field region where the electric field is reduced relative to the electrodes. For example, FIG. 10 schematically shows an example of a method 400 for controlling an electrophoretic optical modulator using asymmetric electrode driving. Method 400 includes: Receiving a command to increase or decrease panel transparency (410), Selecting a set of AC signals according to the received command (420), Periodically changing the relative amplitudes in the set of AC signals (430), Applying a signal to the electrodes in the panel (440) including.

[0128] As will be apparent to those skilled in the art, many different ways of performing the method according to an embodiment are possible. For example, the steps may be performed in the order shown, but the order of the steps may be changed, or some steps may be performed 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 may be unrelated to the method. For example, steps 430 and 440 may be performed at least partially in parallel. Furthermore, a given step need not be completely finished before the next step is started.

[0129] Embodiments of the method may be implemented using software that includes instructions for causing a processor system to perform method 400. The software may include only the steps taken by a particular sub-entity of the system. The software may be stored on a suitable storage medium such as a hard disk, floppy disk, memory, optical disk, etc. 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 implemented using a bitstream configured to configure programmable logic, such as a field programmable gate array (FPGA), to perform the method.

[0130] It should also be understood that the present invention extends to a computer program, particularly a computer program carried on or in a carrier wave, adapted to implement the 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 in any other form suitable for use in the implementation of the implementation form of the method. Embodiments related to computer program products include computer-executable instructions corresponding to each of at least one of the processing steps of the described methods. These instructions may be subdivided into subroutines and / or stored in one or more files that may be linked statically or dynamically. Another embodiment related to computer program products includes computer-executable instructions corresponding to each of at least one of the means of the described systems and / or products.

[0131] FIG. 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 an electronic memory, in this case a memory card. The computer-readable media 1000 and 1001 can store data 1020, which, when executed by a processor system, can represent instructions that cause the processor system to perform a method according to one embodiment. The computer program 1020 can be embodied on the computer-readable medium 1000 as a physical mark or using the magnetization of the computer-readable medium 1000. However, any other suitable embodiment is equally conceivable. Furthermore, although the computer-readable medium 1000 is shown herein as an optical disk, it should be understood that the computer-readable medium 1000 can be any suitable computer-readable medium such as a hard disk, solid-state memory, flash memory, etc., and can be non-recordable or recordable. The computer program 1020 includes instructions for causing the processor system to perform the method of electrophoretic control.

[0132] FIG. 11b shows a schematic diagram of a processor system 1140 according to an embodiment. The processor system includes one or more integrated circuits 1110. The architecture of the one or more integrated circuits 1110 is schematically shown in FIG. 11b. Circuit 1110 includes a processing device 1120, e.g., a CPU, for executing computer program components, executing a method according to an embodiment, and / or implementing its modules or units. Circuit 1110 includes a memory 1122 for storing programming code, data, etc. A part of the memory 1122 may be read-only. Circuit 1110 may include a communication element 1126, e.g., an antenna, a connector, or both, and the like. Circuit 1110 may include an application specific integrated circuit 1124 for performing some or all of the processing defined in the present method. The processor 1120, the memory 1122, the application specific IC 1124, and the communication element 1126 may be connected to each other via an interconnect 1130, e.g., a bus. The processor system 1110 may be configured for contact and / or contact-less communication using an antenna and / or a connector respectively.

[0133] For example, in one embodiment, the processor system 1140, e.g., an electrophoresis controller or an optical modulator, may include a processor circuit and a memory circuit, and the processor is 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, etc. 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, e.g., a flash memory. The memory circuit may be a volatile memory, e.g., an SRAM memory. In the latter case, the device may include a non-volatile software interface, e.g., a hard drive, a network interface, etc., configured to provide software.

[0134] The above embodiments are illustrative rather than limiting of the present invention, and it should be noted that those skilled in the art can design many alternative embodiments.

[0135] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those recited in the claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of 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 only A, only B, only C, both A and B, both A and C, both B and C, or all of A, B, and C. The present invention may be implemented using hardware comprising several distinct elements and, preferably, a computer programmed suitably. In device claims enumerating several means, several of these means may be embodied by exactly the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

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

Claims

**Claim 1** An electrophoretic optical modulator using asymmetric electrode driving, comprising at least a first substrate and a second substrate arranged opposite to the first substrate, and an optical layer disposed between the first substrate and the second substrate and containing a fluid with particles, where the particles are charged or chargeable, the optical layer, a plurality of mutually engaging electrodes disposed across each of the first substrate and the second substrate, and a controller configured to apply an electrical AC signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes, causing electrophoretic movement of the particles towards or from one of the plurality of electrodes and causing modulation of the optical characteristics of the optical modulator. - An electrophoretic optical modulator, wherein the controller is configured to modulate the amplitude of the electrical AC signal applied to the plurality of electrodes on the substrate to move the low electric field region relative to the electrodes. **Claim 2** An electrophoretic optical modulator, wherein the low electric field region is a region where the particle movement relative to the electrodes is stationary. **Claim 3** The optical modulator according to claim 2, wherein the controller is configured for the closing operation of the optical modulator and the dead zone moves between two opposing electrodes on the opposing substrates. **Claim 4** The optical modulator according to claim 1, wherein the controller is configured for the opening operation of the optical modulator and the low electric field region moves parallel to the substrate. **Claim 5** The optical modulator according to any one of claims 1 to 4, wherein the amplitude is modulated until the target gray level is reached, and then the controller applies an electrical holding signal to the plurality of electrodes on the substrate to maintain the gray level of the optical modulator. **Claim 6** The optical modulator according to any one of claims 1 to 5, wherein the first AC signal applied to the first electrode is scaled relative to the second AC signal applied to the second electrode. **Claim 7** The optical modulator according to any one of claims 1 to 6, wherein the scaling between the two AC signals applied to the two electrodes circulates between a low scaling factor and a high scaling factor. **Claim 8** The optical modulator according to claim 7, wherein the first AC signal has a constant amplitude and the second AC signal is scaled relative to the first AC signal. **Claim 9** The optical modulator according to any one of claims 1 to 8, wherein the scaling between the two AC signals applied to the two electrodes is modulated to randomize the position of the low electric field region. **Claim 10** The controller is - configured for a closing operation, where the ratio of the amplitudes in a pair of signals applied to a pair of opposing electrodes on opposing substrates changes, and / or - configured for an opening operation, where the ratio of the amplitudes in a pair of signals applied to a pair of adjacent electrodes on the same substrate changes, the optical modulator according to any one of claims 1 to 9. **Claim 11** The first AC signal applied to the first electrode is scaled with respect to the second AC signal applied to the second electrode, and the lower amplitudes of the first and second AC signals are 70%, 50%, 45%, 40%, 30% of the higher amplitude, the optical modulator according to any one of claims 1 to 10. **Claim 12** At least one of the AC signals has a high-frequency component having a frequency of at least 500 Hz, or 750 Hz, preferably at least 1 kHz, and a low-frequency component having a frequency of at most 100 Hz, the optical modulator according to any one of claims 1 to 11. **Claim 13** The high-frequency component is removed when the target gray level is reached, the optical modulator according to any one of claims 1 to 12. **Claim 14** A low-pass filter is applied to the AC signal, the optical modulator according to any one of claims 1 to 13. **Claim 15** Particles in the fluid move under the influence of electrophoresis and dielectrophoresis forces, the optical modulator according to any one of claims 12 to 14. **Claim 16** The first substrate includes a first electrode and an adjacent second electrode, the second substrate includes a third electrode and an adjacent fourth electrode, the first and fourth electrodes face each other, the second and third face 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 still further increased phase for the fourth electrode, the optical modulator according to any one of claims 1 to 15. **Claim 17** A controller configured to control an asymmetric AC signal for an electrokinetic optical modulator, where **Claim 18** a controller configured to control an asymmetric AC signal for an electrokinetic optical modulator, An optical modulator includes at least a first substrate and a second substrate disposed opposite to the at least first substrate, and an optical layer disposed between the first substrate and the second substrate and including a fluid containing particles, wherein the particles are charged or chargeable, and a plurality of mutually engaged electrodes disposed across each of the first substrate and the second substrate. A controller is configured to apply an electrical AC signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes, causing electrophoretic movement of the particles toward or from one of the plurality of electrodes, thereby causing modulation of the optical characteristics of the optical modulator. The controller is configured to modulate the amplitude of the electrical AC signal applied to the plurality of electrodes on the substrate to move the low electric field region relative to the electrodes.

19. A method for controlling an electrophoretic optical modulator using asymmetric electrode driving, the optical modulator including at least a first substrate and a second substrate disposed opposite to the at least first substrate, and an optical layer disposed between the first substrate and the second substrate and including a fluid containing particles, wherein the particles are charged or chargeable, and a plurality of mutually engaged electrodes disposed across each of the first substrate and the second substrate, the method comprising: - obtaining an electric field between the plurality of electrodes, applying an electrical AC signal to the plurality of electrodes to cause electrophoretic movement of the particles toward or from one of the plurality of electrodes, thereby causing modulation of the optical characteristics of the optical modulator; - modulating the amplitude of the electrical AC signal applied to the plurality of electrodes on the substrate to move the low electric field region relative to the electrodes comprising the method.

20. A transient or non-transient computer-readable medium (1000) including data (1020) representing instructions that, when executed by a processor system, cause the processor system to perform the method according to Claim 19.

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