Asymmetric drive for optical modulator

Abstract

Some embodiments relate to electrophoretic optical modulators with asymmetric electrode drive. An alternating current electrical signal is applied to a plurality of electrodes on at least two substrates, thereby obtaining an electric field between the substrates. The amplitude of the AC electrical signal is modulated thereby causing a low electric field region to move relative to the electrode.

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 glass) are known in the art. Typically, an optically active glass system comprises two parallel plates made of a transparent dielectric material (such as a glass material or a 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 material, a charged material or a chargeable material. The faces of the two plates facing each other carry electrodes facing each other. The electrodes are connected to a power source associated with a control device.

[0003] The electrodes of each plate are formed by pairs of interlaced combs. The electrodes of two interlaced combs can be subjected to voltages of the same polarity or opposite polarity. By applying a suitable voltage to the electrodes, the particles can be concentrated at different locations between the electrodes, giving the system a transparent or opaque appearance.

[0004] There are a number of drawbacks associated with known systems. Although optically active glass can be transformed from one state to another (e.g., from a transparent state to an opaque state), this transformation takes a long time and is often not completely uniform. In addition, the lifespan of existing devices is limited. Summary of the invention

[0005] Embodiments herein address these and other problems. For example, in one embodiment, an electrophoretic optical modulator includes at least a first substrate and a second substrate, the second substrate being arranged opposite to the first substrate. An optical layer is arranged between the first substrate and the second substrate, the optical layer including a fluid, the fluid including particles, the particles being charged or capable of being charged. A plurality of interdigitated electrodes are arranged to span each of the first substrate and the second substrate. A controller is configured to apply an alternating current signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes, thereby providing electrophoretic motion of the particles toward one of the plurality of electrodes or providing electrophoretic motion of the particles from one of the plurality of electrodes to cause modulation of the optical properties of the optical modulator. The controller is configured to modulate the amplitude of the alternating current signal, the alternating current signal being applied to the plurality of electrodes on the substrate to cause a low electric field region to move relative to the electrodes.

[0006] By modulating the amplitude of the signal, the area with low (especially the lowest) electric field is moved in the optical layer. For example, if the signal on one substrate is scaled down, while the signal on the other substrate is not scaled down or is even scaled up, the low electric field area is moved towards the previous substrate. Similarly, by manipulating the signal on the adjacent electrode, the low electric field area can be moved parallel to the substrate. In fact, the movement of particles in the low electric field area can be absent, and the particles are stationary relative to the electrodes. Moving such an area allows stationary particles to escape from it so that they do not slow down the transformation of the panel. In particular, the so-called dead zone (in which the electric field does not exist) can be moved in the optical layer.

[0007] Moving low electric field regions (especially dead zones) has several advantages. Particles in low electric field regions do not respond to the electric field as quickly as particles in high electric field regions. Therefore, those regions transform slowly and the transformation is not uniform. In addition, by moving low electric field regions back and forth, the mixing of particles is increased overall.

[0008] Optical modulators as described herein can be used in a wide range of practical applications. For example, optical modulators with at most one non-transparent substrate can be used as surfaces that can change their optical appearance (such as their reflective state or transmissive state). In particular, optical modulators with all substrates transparent can be used as optically active glass, for example for offices, cars, boxes, etc.

[0009] An embodiment of the control method may be implemented on a computer as a computer-implemented method, or implemented in dedicated hardware, or implemented in a combination of the two. Executable code for an embodiment of the method may be stored on a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, online software, etc. Preferably, the computer program product includes non-transitory program code stored on a computer-readable medium for executing an embodiment of the method when the program product is executed on a computer.

[0010] In one embodiment, the computer program comprises computer program code, which is suitable for performing all or part of the steps of one embodiment of the method when the computer program is run on a computer. Preferably, the computer program is embodied on a computer readable medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further details, aspects and embodiments of the present invention will be described by way of example only and with reference to the accompanying drawings. The elements in the drawings are illustrated for the sake of simplicity and clarity and are not necessarily drawn to scale. In the drawings, elements corresponding to elements already described may have the same reference numerals. In the drawings:

[0012] Figure 1a An example of an embodiment of a substrate is schematically shown,

[0013] Figure 1b schematically illustrates an example of an embodiment of an optical modulator,

[0014] Figure 1c.1 to Figure 1c.4 Schematically illustrating an example of one implementation of a scaling factor,

[0015] Figure 2a.1 shows an example of an electric field in one embodiment of an optical modulator,

[0016] Figure 2a.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0017] Figure 2b.1 shows an example of an electric field in one embodiment of an optical modulator,

[0018] Figure 2b.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0019] Figure 2c.1 shows an example of an electric field in one embodiment of an optical modulator,

[0020] Figure 2c.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0021] 3a to 3c show examples of electric fields in one embodiment of an optical modulator,

[0022] Figure 4a.1 shows an example of an electric field in one embodiment of an optical modulator,

[0023] Figure 4a.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0024] Figure 4b.1 shows an example of an electric field in one embodiment of an optical modulator,

[0025] Figure 4b.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0026] 5a and 5b show examples of electric fields in one embodiment of an optical modulator,

[0027] Figure 6a.1shows an example of an electric field in one embodiment of an optical modulator,

[0028] Figure 6a.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0029] Figure 6b.1 shows an example of an electric field in one embodiment of an optical modulator,

[0030] Figure 6b.2 schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0031] Figures 7a to 7c schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0032] Figure 8a schematically illustrates an example of an embodiment of an optical modulator,

[0033] Figure 8b schematically illustrates an example of an AC signal in one embodiment of an optical modulator,

[0034] Figure 9a schematically illustrates an example of an embodiment of an optical modulator,

[0035] Figure 9b schematically illustrates an example of an embodiment of an optical modulator,

[0036] Fig.9c Schematically shows an example of an embodiment of a motor vehicle,

[0037] Fig.10 One embodiment of a method of controlling an electrophoretic optical modulator with asymmetric electrode drive is schematically shown,

[0038] Fig.11a Schematically shows a computer readable medium according to one embodiment, the computer readable medium having a writable portion, the writable portion comprising a computer program,

[0039] Fig.11b A representation of a processor system according to one embodiment is schematically shown.

[0040] Reference Number List

[0041] 1, 2, 3, 4 electrodes

[0042] 10. Optical Modulator

[0043] 11. First substrate

[0044] 12. Second substrate

[0045] 13, 13a, 13b Electrode

[0046] 14, 14a, 14b Electrode

[0047] 15 Fluid

[0048] 16 Controller

[0049] 30 pcs

[0050] 20 Car

[0051] 21. Optical Modulator

[0052] 40 Optical Modulator

[0053] 41 First substrate

[0054] 42 Second substrate

[0055] 43 Third substrate

[0056] 46 Controller

[0057] 100 substrates

[0058] 101 First Direction

[0059] 102 Second Direction

[0060] 110 first electrode

[0061] 120 second electrode

[0062] 111-113 Main Line

[0063] 121-123 Main Line

[0064] 151 First Substrate

[0065] 152 Optical layer

[0066] 153 Second substrate

[0067] 160 Controller

[0068] 1000, 1001 Computer readable medium

[0069] 1010 Writable part

[0070] 1020 Computer Programs

[0071] 1110 Integrated Circuit

[0072] 1120 Processing Unit

[0073] 1122 Memory

[0074] 1124 ASIC

[0075] 1126 Communication Components

[0076] 1130 Interconnect

[0077] 1140 Processor System DETAILED DESCRIPTION

[0078] While the invention is susceptible of embodiment in many different forms, one or more specific embodiments are shown in the drawings and will be described in detail herein, it being understood that this disclosure is to be considered as illustrative of the principles of the invention and is not intended to limit the invention to the specific embodiments shown and described.

[0079] In the following, for ease of understanding, the elements of the embodiments are described in operation. However, it will be apparent that the corresponding elements are arranged to perform the functions described as being performed by them.

[0080] Furthermore, the invention is not limited to the embodiments, and the invention resides in each and every novel feature or combination of features described herein or recited in mutually different dependent claims.

[0081] Figure 1a Schematically shows an example of an embodiment of a substrate 100 used in an optical modulator according to an embodiment. At least two electrodes are arranged in a pattern across the surface of the substrate 100. Figure 1a Shown in the figure are two electrodes located on the same surface: a first electrode 110 and a second electrode 120. There may be more than two electrodes on the same side of the substrate, for example to facilitate finer-grained control. For example, multiple electrodes may be used to facilitate segmented substrates, such as for segmented optical modulators. For example, in a segmented optical modulator, some regions may have different optical properties, such as different transparencies or reflectivities. Embodiments with two electrodes are shown below, but additional electrodes may be added to them, for example by replicating similar structures adjacent to each other.

[0082] The first electrode 110 and the second electrode 120 are applied to the same side of the substrate. The two electrodes are arranged to cross the substrate in a pattern. There may also be one, two or more electrodes on the other surface of the substrate 100, for example, to facilitate the stacking of three or more substrates. The electrodes may be applied to the substrate in a lithographic manner (e.g., using a mask representing the electrode pattern). The electrodes may also be applied by embedding the electrodes in the substrate.

[0083] The first electrode 110 and the second electrode 120 each include a plurality of main lines. Figure 1a As shown, the first electrode 110 includes main lines 111, 112 and 113, and the second electrode 120 includes main lines 121, 122 and 123. Typically, each electrode will include more than three lines. The main lines extend across the substrate. The multiple main lines of the first electrode and the second electrode are arranged alternately on the substrate relative to each other. The main lines extend across the substrate in a first direction 101. When viewed in a second direction 102, the main lines from different multiple main lines meet alternately, for example, the first multiple main lines from the first electrode and the second multiple main lines from the second electrode meet alternately. The first direction and the second direction are at an angle to each other, and typically the angle is substantially perpendicular. The first direction and the second direction may each be parallel to the side of the substrate, but this is not necessary.

[0084] For example, substrate 100 can be combined with another substrate to form a transparent optical modulator, at least one of which is transparent. Light incident with the optical modulator is modulated in a manner that depends on the particles in the optical layer between the two substrates. In one embodiment, both substrates are transparent to form a light modulator. One exciting application of a substrate such as substrate 100 is smart glass (e.g., a light modulator), which can be used in home housing, offices, greenhouses, automobiles, etc.

[0085] The level of transparency or reflectivity of the light modulator can be electrically adapted. For example, in a light modulator (e.g., in smart glass), two substrates (such as substrate 100) are stacked so that the sides to which the two electrodes are applied face each other. A fluid with particles is enclosed between the two substrates. Smart glass embodiments are discussed further below. In one embodiment, an electrode (e.g., two or more electrodes) is applied to one surface of each substrate. There may also be one, two or more electrodes on the other surface of substrate 100, for example to facilitate stacking of three or more substrates.

[0086] Some of the following embodiments show examples of modulating transparency levels or reflectivity levels. Light modulators can be adapted for other optical effects. For example, if desired, the embodiments can be modified to different translucency levels instead of different transparency levels. If desired, the type of particles used in one embodiment can be changed, for example, to particles that absorb or reflect different wavelengths, and to particles that reflect specularly or diffusely to different degrees. For example, in one embodiment, the light modulator can modulate different reflectance levels. The particles can also emit light. Stacking multiple optical layers further increases the possibilities.

[0087] Two alternating sets of main lines are sufficient to provide an electrically adaptable glass; thanks to the alternating two sets, the electric field at any part of the substrate can be controlled, since two opposing electrodes define the part from two opposing sides.

[0088] Multiple electrodes applied on the substrates are interdigitated to manipulate the electric field between the two substrates. Figure 1a In FIG. 1 , the main electrode is shown as having multiple interdigitated parallel main lines. This is a possible configuration, but in one embodiment, the shape of the electrode can be greatly changed. For example, by adapting the shape of the electrode, the diffraction effect can be modified.

[0089] Figure 1b An example of an embodiment of an electrophoretic optical modulator is schematically shown. A substrate (such as Figure 1a The substrate schematically shown in FIG. 1 may be combined with a similar substrate opposite it (e.g., with its mirror image). Figure 1a The four electrodes schematically intersecting at line AB are Figure 1b is shown in . Figure 1b 1 and 15. The optical layer 152 is disposed between the first substrate 151 and the second substrate 153. The optical layer 152 between the first substrate 151 and the second substrate 153 includes a fluid, and the fluid includes particles (not shown). The particles are charged or can be charged.

[0090] At least two interdigital electrodes are arranged on the first substrate 151 and the second substrate 153, and at least two interdigital electrodes are arranged to be opposite to each other. Shown on the first substrate 151 are two electrodes 1 and electrode 2. For example, electrode 1 can be electrode 111, and electrode 2 can be electrode 121. Shown on the second electrode 153 are two electrodes 4 (opposite to electrode 1) and electrode 3 (opposite to electrode 2). Although not shown, the substrate 151 may continue with electrode 1, electrode 2, electrode 1, electrode 2, ..., and the substrate 153 may continue with electrode 4, electrode 3, electrode 4, electrode 3, ..., and so on.

[0091] The controller 160 is configured to apply an alternating current signal to each of the plurality of electrodes on the two substrates (e.g., to electrode 1, electrode 2, electrode 3, and electrode 4) to obtain an electric field between the plurality of electrodes. The electric field provides electrophoretic motion of particles toward one of the plurality of electrodes, or provides electrophoretic motion of particles from one of the plurality of electrodes to cause modulation of the optical properties of the light modulator. Figure 2a.1 to Figure 6b.2 The numbering of the middle electrodes is the same as that of the electrodes in the cross section.

[0092] The controller 160 is configured to control and / or generate an asymmetric AC signal for the electrophoretic optical modulator.

[0093] The controller 160 is configured to apply an alternating current signal for application to the plurality of electrodes to obtain an electric field between the plurality of electrodes, thereby providing electrophoretic motion of particles toward one of the plurality of electrodes, or providing electrophoretic motion of particles from one of the plurality of electrodes, to cause modulation of the optical properties of the light modulator. For example, the controller 160 may generate an alternating current signal. For example, in the case where each substrate has two electrodes, the controller 160 may be configured to generate a set of four alternating current signals for application to the electrodes. The application may be directly from the controller 160 to the electrodes. The application may be indirectly from the controller 160 to the electrodes, for example, through an intermediate processing device, such as an amplifier and / or a filter, etc.

[0094] Many optical properties can be modulated in an optical modulator; for example, transparency, reflectivity, color, etc. For simplicity, embodiments are described in terms of control of grayscale between fully transparent and fully opaque. However, the skilled person will appreciate that different optical properties can be manipulated by using different particles and / or different substrates. Particles are sometimes referred to as pigments.

[0095] The controller 160 is configured to modulate the amplitude of an alternating current signal applied to the plurality of electrodes on the substrate to cause the low electric field region to move relative to the electrodes.

[0096] In conventional driving of the electrodes of the optical modulator (including during AC driving), the electric field potential shows some areas in the optical layer where the electric field is much lower than the electric field at other areas in the optical layer. Such low electric field areas are disadvantageous because particles in such areas are difficult to control. In particular, due to the low electric field in the low electric field areas, the particles move slower there. Most of the time required to change from one optical state to another is caused by the slow movement of the particles in the low electric field areas.

[0097] For example, the electric field strength in the low electric field region of the optical layer may be only 25% or less of the electric field strength in other locations in the optical layer. For example, compared to the maximum electric field in the optical layer, the electric field strength in some regions of the optical layer may be only 15% or less, 10% or less, 1% or less, etc. For example, the electric field strength in the low electric field region of the optical layer may be less than 2*10^6V / m, less than 1*10^6V / m, less than 1*10^5V / m, etc. For example, the low electric field region may be considered to be a region in the optical layer where the electric field is the smallest. For example, the low electric field region may be considered to be a region in the optical layer where the electric field is the smallest or is a predetermined percentage (e.g., at most 10%, at most 15%, etc.) greater than the minimum electric field.

[0098] The electric field can be measured directly, but computer simulations of the electric field have proven to be accurate enough for practical applications. For example, the well-known COMSOL software can be used to simulate the electric field map. Here, the intensity of the electric field can be generated using an electrostatic study based on the AC / DC module of COMSOL Multiphysics. The electric field maps shown in this article were created using the software mentioned above.

[0099] In particular, there may be regions in the optical layer where the electric field is absent, e.g., where the electric field is zero or substantially zero. Such regions are referred to as dead zones. Particles in the dead zones are substantially nonresponsive to electrophoretic control. Particles may be deflected out of the dead zones by other methods (e.g., slow entropy movement) and become susceptible to controlled movement again. Dead zones are particularly problematic for rapid transitions between optical modes of optical modulators. Dead zones are sometimes referred to as electric field neutral regions, or neutral points. The neutral point may be a point in a 2D intersection as shown; however, in a physical 3D implementation, the neutral point may be a neutral curve or a neutral volume.

[0100] In an embodiment, the problems caused by low electric field regions, especially dead zones, are solved by varying the potential difference between electrodes.This electric field neutral point or neutral volume is moved in the optical layer between the substrates by modulating the relative amplitudes of the signals applied to the electrodes.

[0101] In one embodiment, the overall drive can use an AC signal and maintain current neutrality and balance in multiple electric fields in a timely manner. This is advantageous because it reduces corrosion to the electrodes.

[0102] In one embodiment, the electric field lines are modulated so that the neutral point is shifted into place in the optical layer so that the total volume increases under the influence of the electric field (eg, electrophoretic control).

[0103] In one embodiment, the main parameter that is changed in the signal is the amplitude, e.g., the amplification level of the signal. Other parameters that are changed in an asymmetrical manner between electrodes include frequency, signal shape (square, sinusoidal, etc.), duration, phase.

[0104] The advantage of asymmetric driving of electrodes (as further explained herein) is faster transition between optical states. Asymmetric driving of electrodes further provides the advantage of more uniform transition because the difference between the slow transition position and the fast transition position on the panel is reduced. An additional advantage of asymmetric driving is to reduce the accumulation of particles on the electrodes. In conventional optical modulators (especially in DC drive modulators), particles can accumulate on the electrodes and can be locally tightly bound here. This will cause the particles to interact here and the particles to form irreversible aggregates. Such aggregates of particles are undesirable. The aggregation effect leads to problems such as non-uniformity and gravity effects. However, when in the case of asymmetric driving as in one embodiment, the particles are increasingly active, so gradually cooling to the aggregate is limited. In addition, the particles move more evenly.

[0105] Dead zones (e.g., neutral points or neutral volumes) can also cause optical aberrations as particles accumulate during operation. By increasing particle mobility, aggregation is reduced and particles are less likely to fall due to gravity. Improved particle mobility allows particles to better approach and disperse to achieve a non-transparent state while maintaining a particle distribution that is closer to the initial state dispersed during manufacturing.

[0106] Interestingly, asymmetric drive can be added to existing algorithms for driving the panel to a target grayscale. In addition, the introduction of asymmetric drive can still maintain current neutrality. For example, an algorithm such as that described in PCT / EP2021 / 071346 entitled "Light Modulator, Light Modulator Method And Smart Glazing" can be used, and a scaling of the signal is introduced to move the low electric field areas, especially the dead zones.

[0107] For example, the controller may be configured with a set of algorithms, for example, for one or more of the following functions: increase transparency, reduce transparency, maintain current transparency, etc. There may be more or fewer algorithms. For example, the algorithm may be different depending on the jump size of the desired transparency. For example, the maintenance algorithm may be omitted. For example, in a simplified embodiment, the controller may have an algorithm for driving towards full transparency, and an algorithm for driving to full opacity. For example, a computer program code may be stored in the memory of the controller to implement the algorithm. In one embodiment, the controller is configured to apply a programmed drive algorithm and last for a period of time, which may depend on the current transparency, the target transparency, and the measured sensor value (e.g., as explained in the cited PCT application).

[0108] Existing algorithms can be modified by periodically scaling down or scaling up one or more signals so that the low electric field area, especially the dead zone, moves. For example, by introducing asymmetric scaling and changing the direction of the asymmetric scaling after a predetermined period, the existing drive algorithm can be modified to be asymmetric. When the asymmetry of the drive changes, the low electric field area moves. In one embodiment, the volume in the optical layer is scanned by higher intensity electric field lines to cause all particles in the volume to be susceptible to electrical control at a certain point during the scan. Asymmetric drive can be used advantageously for driving towards target transparency and for maintaining grayscale. The opening drive can also be changed in an asymmetric manner while maintaining grayscale.

[0109] Asymmetric actuation allows for faster transitions, in particular very fast switching off of the device (ie actuation towards opacity), since a larger portion of the particle population is moved independent of the initial position of the particles, which comprises an intermediate position between the electrode and the electrode surface.

[0110] Typically, scaling of the signal is applied to paired 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. Before scaling, the electrode signals typically have the same phase and have the same amplitude; in fact, 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 capture particles. For example, scaling differences can be used to compensate for hardware differences such as substrate magnification, etc. In particular, signal X and signal Y can be conventional AC drive signals for an electrophoretic optical modulator. Signal X and signal Y can be scaled to move low electric field regions in the optical layer. For example, a time-varying scaling factor can be applied to the signal. Figure 1c.1 to Figure 1c.4 An example of one implementation of the scaling factor is schematically shown.

[0111] exist Figure 1c.1 In one embodiment, the scaling factors are selected so that one signal is scaled up (increased) and the other signal is scaled down (decreased). 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.

[0112] exist Figure 1c.2 In the embodiment, the scaling factor is selected so that only one of the two signals is increased while the other remains constant. In the accompanying drawings, the scaling alternates. Note that in these embodiments, instead of scaling up, scaling down can be used. In fact, it is easier to use scaling down because the signals remain within predetermined limits.

[0113] Figure 1c.3 and Figure 1c.2Same, except that zooming is alternated with periods where zooming is not used.

[0114] exist Figure 1c.4 In , only one of the signals is scaled while the other is held constant. Figure 1c.5 In , only one of the signals is scaled while the other is held constant. Figure 1c.5 In the embodiment, the signal is alternately scaled up and scaled down. In this embodiment, periods of scaling and no scaling are combined.

[0115] Many other variations are possible. For example, a scaling with a small amount of noise could be added to slightly randomize the location of the low electric field regions. These embodiments use a triangular transformation scaling factor, but other shapes are possible, such as square wave, sinusoidal, etc.

[0116] Fig. 2a to 2c schematically illustrate examples of alternating current signals in one embodiment of an optical modulator arranged for closing a panel, ie for reducing the transparency of the panel. Figure 2a.1 , Figure 2b.1 and Figure 2c.1 An example of an electric field in one embodiment of an optical modulator is shown. Figure 1b are shown in the same plane as shown. Figure 2a.2 , Figure 2b.2 and Figure 2c.2 An example of an AC signal corresponding to an electric field diagram is schematically shown. Note that Figure 2a.2 , Figure 2b.2 and Figure 2c.2 The signal after scaling is schematically shown, and Figure 1c.1 to Figure 1c.4 The scaling factors are schematically shown.

[0117] The movement of the particles is largely controlled by the electric field and its shape (as indicated by the electric field graph), although some other factors may also have some influence on the movement of the particles, such as Brownian motion, temperature, etc.

[0118] Figure 2a.2 The y-axis in (and similar figures) schematically indicates the voltage of the signal applied to the electrode. The horizontal dashed lines in the four signals indicate a neutral voltage, such as a zero voltage line for each signal. The x-axis schematically indicates time. Note that the four signals are AC signals. FIG. 2 shows a square signal, but other AC type signals (such as triangle, sinusoidal, and combinations thereof) may be used. Figure 2a.2 The drive shown in is configured to turn off the optical modulator, for example to reduce transparency, increase grayscale levels. Figure 2a.2If the drive shown in is continued for a long time, the substrate will eventually approach maximum opacity. Although it is not necessary to continue driving until full opacity; before that time, the drive can be terminated at some desired gray level.

[0119] Note that signal 1 and signal 4 are equal so that there is a dead zone midway between substrate 1 and substrate 4. The same applies to signal 2 and signal 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, such as there is a low electric field region. The particles in the low electric field region respond to the electric field, but respond very slowly.

[0120] In the off operation, as shown in Figures 2a to 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 when driving.

[0121] exist Figure 2a.2 In , the AC signal applied to the relative electrode pair 1 and 4 is equal to the AC signal applied to the relative electrode pair 2 and 3. Figure 2a.2 In the embodiment, the AC signal applied to adjacent electrode pairs 1 and 2 is equal to the AC signal applied to adjacent electrode pairs 4 and 3, except that the phase shift is more than 180 degrees in this example. The relative electrode pairs are two different electrodes opposite to each other on the relative substrates. The adjacent electrode pairs are two different electrodes adjacent to each other on the same substrate. There is a dead zone midway between electrode 1 and electrode 4, and there is a dead zone midway between electrode 2 and electrode 3.

[0122] Figure 2b.2 Figure 2 shows the asymmetry introduced when driving the panel. Figure 2b.2 , the AC signals applied to the opposing electrode pairs 1 and 4 are equal to the AC signals applied to the opposing electrode pairs 2 and 3, except for the scaling. For example, by scaling down the drive on electrode 1 and electrode 2 (e.g., by scaling down the drive on one electrode in a pair of opposing electrodes), Figure 2a.2 Drivers in Figure 2b.2 In this example, the signals of electrode 1 and electrode 2 have been scaled down. Scaling up or down can be done using an amplifier through a variable resistor or by changing parameters in a signal generator, etc. Figure 2b.2 , the AC signal applied to adjacent electrode pairs 1 and 2 is equal to the AC signal applied to adjacent electrode pairs 4 and 3, except that it is phase shifted, in this example by more than 180 degrees.

[0123] Figure 2b.2 The effect of the drive shown in the figure is still to close the panel. Note that Figure 2a.1 The low electric field region in Figure 2b.1in particular, the dead zone has moved upward.

[0124] exist Figure 2c.2 In the embodiment, the direction of scaling is reversed. During the closing operation, the asymmetry introduced in a pair of opposing electrodes is now in opposite directions. This means that the dead zone is now moved downwards, for example towards the bottom substrate. Note that the direction upward is relative to the direction downward. These terms here refer to the panel as shown in the figure and are shorthand for towards the first substrate or towards the second substrate; in one embodiment, the panel can be vertical so that directions like upward and downward can be forward and backward or the like.

[0125] To reduce transparency (e.g., to turn off the panel), the panel may be driven by alternating between the three types of signals. For example, the drive may have a middle dead zone as in FIG. 2a, a top dead zone as in FIG. 2b, or a bottom dead zone as in FIG. 2c. For example, in one embodiment, the drive may repeat a cycle such as middle dead zone drive, top dead zone drive, middle dead zone drive, and bottom dead zone drive.

[0126] Using this type of two-way asymmetric drive to turn off the panel enables dark grey to be reached significantly faster. With conventional symmetric drive, the transition from 10% grey to 1% grey (ie from light grey to full black) can take about ten times longer than in one embodiment.

[0127] Using two-way asymmetric drive is preferred because a larger portion of the volume is scanned, thereby improving the mixing of particles. Although not required; improved drive can be achieved by repeating cycles such as middle dead zone drive, top dead zone drive.

[0128] Figures 3a to 3c show examples of electric fields in one embodiment of an optical modulator. Figure 2a.1 to Figure 2c.1 The electric field diagrams in are the same. Shown in Figures 3a to 3c are low electric field regions schematically indicated by circles. The center of the circle corresponds to a portion of the field where there is no electric field, such as a dead zone. Note that the position of the dead zone moves relative to the electrode. In this example, the dead zone moves substantially orthogonal to the substrate. Orthogonal movement is convenient, although not necessary, and the dead zone can also be moved parallel to the substrate by introducing asymmetry in a pair of adjacent electrodes and in a pair of opposing electrodes. However, orthogonal movement is sufficient for improving mixing.

[0129] Figures 3a to 3c show different stages of using asymmetric drive in a closing operation. The dead zone moves within the optical layer between two opposing substrates, for example toward or away from either of the two substrates. For example, the controller can be configured to apply a scaling operation to a signal that is applied to an electrode. For example, the signals applied to the opposing electrodes can be identical, except that the signals applied to one or both of them are scaled. The amount of scaling depends on the application, for example, on the size of the panel and the thickness of the optical layer. As an embodiment, a first AC signal applied to a first electrode can be scaled relative to a second AC signal applied to a second electrode (e.g., opposite to the first electrode), wherein the lower amplitude of the first AC signal and the second AC signal is at most 70%, 50%, 45%, 40%, 30% of the higher amplitude.

[0130] The signal schematically shown in the figure is a square wave, although in practice this is not at all necessary. Alternatively, the signal may be a sine wave. For example, a low pass filter may be applied to the signal as shown in the figure. The low pass threshold may be chosen to be dependent on the size of the panel, for example 1 kHz for larger panels.

[0131] For example, in one embodiment, the controller may have a signal generator configured for a dead zone in the middle of the optical layer. The asymmetric modulator may modulate the signal to move the dead zone 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 lower scaling factor and a higher scaling factor. The controller may also directly generate the scaled signal.

[0132] Scaling can keep one signal constant while reducing and / or increasing another signal. For example, a first AC signal can have a constant amplitude, and a second AC signal can be scaled relative to the first AC signal. The signal that is kept constant and the signal that is scaled can be switched in time. Scaling can be done on a low voltage signal, but can also be introduced during amplification of the signal. In one embodiment, the scaling of the signal is randomized so that the position of the dead zone is randomized. In one embodiment, the scaling of the signal is controlled so as to move the position of the low electric field region in a controlled manner, such as along a predetermined path through the optical layer.

[0133] Once the target gray level is reached (e.g., as indicated by a sensor associated with the panel (e.g., an optical sensor and / or an electrical sensor), the drive signal may be terminated. The panel will maintain its gray level for some time (although the appearance of the panel may decay over time) so that a conventional maintenance drive may be used. The maintenance drive may include driving the panel slowly and at low power to a gray level close to the target gray level. The maintenance drive may be alternated with no drive at all. During the maintenance period, an asymmetric signal may also be used as this will improve mixing and increase the durability of the panel.

[0134] Figs. 4a-4b schematically illustrate examples of AC signals in one embodiment of an optical modulator arranged for opening a panel, ie increasing the transparency of the panel. Figure 4a.1 and Figure 4b.1 An example of an electric field in an embodiment of an optical modulator is shown. Figure 1b are shown in the same plane as shown. Figure 4a.2 and Figure 4b.2 An example of an AC signal corresponding to an electric field diagram is schematically shown.

[0135] exist Figure 4a.2 In , the AC signal applied to the adjacent electrode pairs 1 and 2 is equal to the AC signal applied to the adjacent electrode pairs 3 and 4. Figure 4a.2 In the example, the AC signal applied to the opposing electrode pair 1 and 4 is equal to the AC signal applied to the opposing electrode pair 2 and 3, except that it is phase shifted, in this example, by more than 180 degrees. There is a low electric field region midway between electrode 1 and electrode 2, and there is a low electric field region midway between electrode 3 and electrode 4, which extends from substrate to substrate. Figure 4a.1 Two dead zones are also shown: the dead zone between electrodes 1 and 2, and the dead zone between electrodes 3 and 4. These two dead zones are located outside the optical layer. These dead zones themselves are not a problem because there are no particles associated with electrodes 1 to 4 shown. However, a low electric field region stretches between the two dead zones. Particles in the low electric field region respond to the electric field faster than particles in the dead zones, but particles in the low electric field region still move slower than those particles at other locations in the optical layer. For example, the electric field in the low electric field region between the two dead zones can be 25% lower than the field directly midway between the electrodes.

[0136] Figure 4b.2 Figure 2 shows the asymmetry introduced when driving the panel. Figure 4b.2In FIG. 1 , the AC signal applied to adjacent electrode pair 1 and 2 is equal to the AC signal applied to adjacent electrode pair 3 and 4, except for scaling. For example, by scaling down the drive on electrode 2 and electrode 3 (e.g., by scaling down the drive on one electrode in a pair of adjacent electrodes), the AC signal applied to adjacent electrode pair 1 and 2 is equal to the AC signal applied to adjacent electrode pair 3 and 4. Figure 4a.2 Drivers in Figure 4b.2 In this example, the signals of electrodes 2 and 3 have been scaled down. Figure 4b.2 In FIG. 1 , the AC signal applied to the opposing electrode pair 1 and 4 is equal to the AC signal applied to the adjacent electrode pair 2 and 3, except that it is phase shifted, in this example by more than 180 degrees.

[0137] Figure 4b.2 The effect of the drive shown is still to open the panel. Figure 4b.1 middle, Figure 4a.1 The low electric field region in has been moved to the right. The size of the low electric field region has also been slightly increased. Figure 4b.2 If drive of the type shown in is used, this would make it more difficult to move particles near electrodes 2 and 3, but because the drive is combined with asymmetric drive in the other direction this is not a problem.

[0138] exist Figure 4b.2 The direction of scaling can also be reversed, for example by scaling down Signal 1 and Signal 4 instead of scaling down Signal 2 and Signal 3. During the opening operation, the asymmetry introduced in a pair of adjacent electrodes will thus be in opposite directions, for example the low electric field region will move to the left.

[0139] In order to increase transparency (e.g., to open the panel), the panel can be driven by alternating between three types of signals. For example, the drive may have a central low electric field area as in Fig. 4a, a right low electric field area as in Fig. 4b, or a left low electric field area (not shown in a separate figure). For example, in one embodiment, the drive may be repeatedly cycled between low electric fields at the following positions: center, left, center, right; or just center, left. The time spent in different stages does not need to be equal. In order to open, the time spent in the center may be more than the time spent driving with a left low electric field or a right low electric field.

[0140] In one embodiment, during the opening operation, the low electric field region may move parallel to the substrate. Similar options for generating the signal as discussed with respect to the closing operation are possible for the opening operation. For example, the signal may be scaled, and the scaling factor may be repeated over a range of scaling factors.

[0141] Figures 5a-5b show examples of electric fields in one embodiment of an optical modulator. Figure 4a.1 to Figure 4b.15a to 5c show a low electric field region schematically indicated by an ellipse. The electric field in the ellipse is about 1.5*10^6 V / m. When comparing FIG. 5a and FIG. 5b, it is noted that the low electric field region is moved 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) is moved to the right, in this example, the movement is parallel to the substrate. It is also noted that the dead zone located outside the optical layer is moved to the right.

[0142] Figures 6a to 6b schematically illustrate an example of an AC signal in an embodiment of an optical modulator, which is arranged for diagonal drive. Diagonal drive can be used to close the panel. Diagonal drive can be used to mix particles in the optical layer. Mixed particles are beneficial to the life of the panel. Mixed particles can also be used as a stage during the closing of the panel. For example, a period of diagonal drive as in Figures 6a and 6b can be followed by a drive as in Figures 2a to 2c. Diagonal drive can also be used to reach a grayscale between closing the panel and opening the panel.

[0143] Figure 6a.1 and Figure 6b.1 An example of an electric field in an embodiment of an optical modulator is shown. Figure 1b are shown in the same plane as shown. Figure 6a.2 and Figure 6b.2 An example of an AC signal corresponding to an electric field diagram is schematically shown.

[0144] exist Figure 6a.2 In , the AC signal applied to the diagonal electrode pair 1 and 3 is equal to the AC signal applied to the diagonal electrode pair 2 and 4. Figure 6a.2 In the example, the AC signal applied to adjacent electrode pairs 1 and 2 is equal to the AC signal applied to adjacent electrode pairs 3 and 4, except that it is phase shifted, in this example by more than 180 degrees. There is a dead zone midway between electrodes 1, 2, 3, and 4. In the dead zone, the electric field is substantially empty.

[0145] Figure 6b.2 Figure 2 shows the asymmetry introduced when driving the panel. Figure 6b.2 , the AC signals applied to the diagonal electrode pair 1 and 3 are equal to the AC signals applied to the diagonal electrode pair 2 and 4, except for scaling. For example, by scaling down the drive on electrode 1 and electrode 2 (e.g., by scaling down the drive on one electrode in a pair of diagonal electrodes), Figure 6a.2 Drivers in Figure 6b.2 In the driver. Figure 6b.2, the AC signal applied to adjacent electrode pairs 1 and 2 is equal to the AC signal applied to adjacent electrode pairs 3 and 4, except that it is phase shifted, in this example by more than 180 degrees. Note that all signals applied to electrodes on one substrate (in this example, the upper substrate) have been scaled down. For example, in one embodiment, the amplitude of the signal applied to one of the two substrates is lower than the amplitude of the signal applied to the other of the two substrates. Therefore, Figure 6a.1 The dead zone in Figure 6b.1 In this example, the dead zone moves orthogonally to the substrate, although non-orthogonal movement is also possible, for example by Figure 6b.2 Signal 1 and Signal 2 in are scaled by different amounts.

[0146] In one embodiment, the controller is configured for a closing operation of the optical modulator, in which the AC signals applied to opposing electrodes on opposing substrates are scaled relative to each other, and the controller modulates the scaling to move 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.

[0147] In one embodiment, the controller is configured for an opening operation of the optical modulator, and in a closing operation, AC signals applied to adjacent electrodes on the same substrate are scaled relative to each other, and the controller modulates the scaling to move the low electric field region. In one embodiment, AC signals applied to opposing electrodes on opposing substrates are phase shifted relative to each other.

[0148] In one embodiment, the asymmetric drive includes applying different amplitude signals to at least some electrodes in the optical modulator. Other asymmetric drive types are also possible, such as asymmetric drives with different frequencies. For example, the same amplitude can be used on all electrodes, but the frequency can be changed between at least some electrode pairs. In addition to the amplitude, the frequency can also be changed.

[0149] In one embodiment, the optical modulator is an electrophoretic modulator, wherein the 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. Using only relatively low frequency signals is sufficient to obtain effective drive of the optical modulator. In one embodiment, at least some of the AC signals include high frequency components. 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 causes the particles to move due to the dielectrophoretic effect as well as the electrophoretic effect.

[0150] When the target gray level is reached, the high frequency components can be removed. This saves energy and reduces the heating 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 to 7c An example of an AC signal in one embodiment of an optical modulator is schematically shown. Figures 7a to 7c Corresponding to a with schematic HF composition Figure 2a.2 , Figure 2b.2 , Figure 2c.2 . Figure 4a.2 , Figure 4b.2 , Figure 6a.2 and Figure 6b.2 It can also be enhanced with HF components.

[0151] Figure 8a An example of an embodiment of an optical modulator is schematically shown. Figure 8b An example of an AC signal in one embodiment of an optical modulator is schematically shown. The optical modulators shown in the other figures use two phases for all signals. However, this is not necessary, and in fact, it may be advantageous to use different phases for more than two signals. For example, Figure 8b A first signal on an electrode is shown. A second signal on adjacent electrode 2 is identical but offset by a first phase shift. A third signal on electrode 3 is identical to the signal on electrode 2 but offset by a second phase shift. The signal of electrode 4 is phase shifted by a third phase shift compared to signal 3. The first signal is identical to the fourth signal offset by a fourth phase shift. The four phase shifts may all be equal to 360 / 4 = 90 degrees, but this is not required. In one embodiment, the phase difference changes over time.

[0152] The advantage of increasing the phase shift of the four signals is that the particles are better held in the cell gap. Thus, a given transparency or no transparency can be maintained with lower power. Figure 8b , the amplitudes of the four signals are shown to be equal, but in one embodiment, the amplitudes may be varied.

[0153] Using different phases for more than two signals can be used to trap particles in the gaps between adjacent electrodes; this is particularly advantageous when the panel is turned off and a grey level is maintained.

[0154] For example, taking the signal on electrode 4 as a reference, signal 1 may have a phase shift and amplitude scaling, signal 2 may have another phase shift and amplitude scaling (possibly the same scaling), and signal 3 may have another phase shift and no amplitude scaling.

[0155] Figure 9aAn embodiment of a light modulator 10 is schematically shown, which may be applied in smart glass. A light modulator is an example of an optical modulator.

[0156] Reference is made to patent application PCT / EP2020 / 052379, which is incorporated herein by reference; this application includes advantageous designs of light modulators, which can be further improved, for example by including electrodes, building blocks and / or substrates as explained herein.

[0157] The optical modulator 10 can be electrically switched between a transparent state and a non-transparent state and between a non-transparent state and a transparent state, or can be electrically switched between a reflective state and a non-reflective state and between a non-reflective state and a reflective state. The optical modulator 10 comprises a first substrate 11 and a second substrate 12 arranged relative to each other. At least two electrodes are applied on the inner side of the first substrate 11: electrodes 13a, 13b are shown. These at least two electrodes are collectively referred to as electrodes 13. At least two electrodes are applied on the inner side of the second substrate 12: electrodes 14a, 14b are shown. These at least two electrodes are collectively referred to as electrodes 14. The configuration of the electrodes is interdigitated, but can be greatly varied in other respects. In particular, it is not necessary for the main lines of the electrodes to extend parallel across the substrates.

[0158] Fluid 15 is disposed between the substrates. The fluid includes particles 30, such as nanoparticles and / or microparticles, wherein the particles are charged or can be charged. For example, the particles can inherently carry a charge on their surface. For example, the particles can be surrounded by charged molecules.

[0159] The electrodes are arranged to drive the particles 30 towards or away from the electrodes depending on the applied electric field. The optical properties of the light modulator, in particular the transparency or reflectivity, depend on the position of the particles 30 in the fluid. For example, the connectors may be provided for applying an electromagnetic field to the electrodes.

[0160] In one embodiment, substrates 11 and 12 may be optically transparent (except for the electrodes), typically >95% transparent at the relevant wavelength, e.g. >99% transparent. Taking the electrodes into account, the transparency may be much lower, e.g. 70%. The term "optical" may relate to wavelengths visible to the human eye (about 380 nm to about 750 nm) (where applicable), and may relate to a wider range of wavelengths (including infrared (about 750 nm to 1 μm) and ultraviolet (about 10 nm to 380 nm) and their sub-options) (where applicable). In an exemplary embodiment of the optical modulator, the substrate material is selected from glass and polymers. Transparent materials may also be used for the electrodes. In one embodiment of the optical modulator, only substrates 11 and 12 are transparent.

[0161] In another embodiment, one substrate (such as the bottom substrate 12) can be reflective or partially reflective, while the top substrate 11 is transparent. The optical properties of the light modulator, especially the reflectivity, depend on the position of the particles 30 in the fluid. When the panel is in the open state (vertical drive), the particles will be mostly located between the opposing electrodes of the two substrates, so that the incident light can travel relatively unimpeded through the transparent top substrate and the optical layer, and be reflected or partially reflected on the bottom substrate.

[0162] 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 light 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, even more preferably less than 50 μm, such as less than 30 μm.

[0163] In one embodiment, the modulator may be disposed in a flexible polymer and the rest of the device may be disposed in glass. The glass may be rigid glass or flexible glass. A protective layer may be disposed on the substrate if desired. If more than one color is provided, more than one layer of flexible polymer may be provided. The polymer may be polyethylene naphthalate (PEN), polyethylene terephthalate (PET) (optionally with a SiN layer), polyethylene (PE), etc. In another embodiment, the device may be disposed in at least one flexible polymer. In this way, the modulator may be attached to any surface, for example by using an adhesive.

[0164] The particles 30 may be adapted to absorb light, thereby preventing certain wavelengths from traveling through. The particles 30 may reflect light; for example, the reflection may be specular, diffuse, or something in between. The particles may absorb some wavelengths and reflect other wavelengths. The particles may additionally or alternatively emit light, for example using phosphorescence, fluorescence, etc. Even the fluid may emit light, the emissivity of the light being modulated by changing the position of the particles.

[0165] In an exemplary embodiment of the light modulator, the size of the nanoparticles is 20nm to 1000nm, preferably 20nm to 300nm, more preferably less than 200nm. In an exemplary embodiment of the light modulator, the nanoparticles / microparticles may include a coating and / or a pigment, and preferably include a core. In an exemplary embodiment of the light modulator, the coating of the particles is made of a material selected from a conductive material and a semiconductive material.

[0166] In an exemplary embodiment of the optical modulator, the particles are suitable for absorbing light with a wavelength of 10nm to 1mm, such as 400nm to 800nm, 700nm to 1μm and 10nm to 400nm, and / or suitable for absorbing a portion of light (filter) in the wavelength range of 10nm to 1mm, and combinations of the above.

[0167] In an exemplary embodiment of the light modulator, the particles are charged or can be charged. For example, the charge on the particles can be 0.1e to 10e (5*10-7 to 0.1 C / m2) per particle.

[0168] In an exemplary embodiment of the light modulator, the amount of fluid present is 1 g / m2 to 1000 g / m2, preferably 2 g / m2 to 75 g / m2, more preferably 20 g / m2 to 50 g / m2, such as 30 g / m2 to 40 g / m2. A great advantage is that with the arrangement of the invention, less fluid can be used, and also less particles can be used.

[0169] In an exemplary embodiment of the light modulator, the particles are present in an amount of 0.01 g / m2 to 70 g / m2, preferably 0.02 g / m2 to 10 g / m2, such as 0.1 g / m2 to 3 g / m2.

[0170] In an exemplary embodiment of the light modulator, the particles have a color selected from cyan, magenta and yellow, and selected from black and white, and selected from combinations of the above colors.

[0171] In an exemplary embodiment of the light modulator, the fluid includes one or more of a surfactant, an emulsifier, a polar compound, and a compound capable of forming hydrogen bonds.

[0172] The fluid 15 may be a non-polar fluid with a dielectric constant less than 15. In an exemplary embodiment of the light modulator, the fluid has a relative dielectric constant r less than 100, preferably less than 10, such as less than 5. In an exemplary embodiment of the light modulator, the fluid 15 has a dynamic viscosity higher than 10 mPa.s.

[0173] Electrodes 13a, 13b and electrodes 14a, 14b are in fluid contact with the fluid. The fluid may be in contact with the electrodes directly or indirectly, for example, the fluid may contact the second medium with the electrodes such as through a porous layer. In one embodiment, the electrodes cover about 1% to 30% of the substrate surface. In one embodiment, the electrodes include a conductive material with a resistivity of less than 100 nm (at 273K; as a comparison, the ITO typically used has 105 nm), which is similar to a conductivity of >1*107 S / m at 20°C.

[0174] In one embodiment of the light modulator, the electrodes include copper, silver, gold, aluminum, graphene, titanium, indium and combinations thereof, preferably copper. The electrodes may be embedded in the polymer substrate in the form of wires (eg, microwires); for example, copper microwires.

[0175] The connector is used to apply an electromagnetic field to the electrode, wherein the electromagnetic field applied to the electrode causes the nanoparticles and microparticles to move from the first electrode to the second electrode, and from the second electrode to the first electrode. A connector for applying an electromagnetic field to the electrode may be provided. For example, in an exemplary embodiment of the optical modulator, the current is between -100μA and +100μA, preferably between -30μA and +30μA, and more preferably between -25μA and +25μA. For example, a power supply may be electrically connected to at least two electrodes. The power supply may be suitable for providing waveform power. At least one of the amplitude, frequency and phase may be suitable for providing different states in the optical modulator. For example, multiple aspects of the power supply may be adapted by a controller.

[0176] The light modulator 10 may comprise one or more segments, a segment being a single optically switchable entity, the size of which may be varied.The substrate at least partially encloses a volume, which may be a segment.

[0177] The device may include a drive circuit that changes the appearance of the (individual) segments by applying an electromagnetic field. Thus, the appearance of the light modulator and one or more parts thereof may also be changed. For example, the segments may have an area of ​​at least 1 mm2. The design allows stacking and thus more colors; for example, for full color applications, a stack of two or three modulators may provide most or all colors, respectively.

[0178] Having one or more segments allows the light modulator to be controlled locally; this is advantageous for some applications, but it is not necessary. For smart glass, the light modulator can be used with or without segments. For example, when applied to smart glass, transparency or reflectivity can be controlled locally, such as blocking sun spots without reducing transparency or reflectivity in the entire window. The segments can be relatively large, such as having a diameter of at least 1 mm or at least 1 cm, etc.

[0179] In an exemplary embodiment of the light modulator, the substrates (11, 12) are aligned, and / or the electrodes (13, 14) are aligned. For example, the electrodes 13a, 13b and the electrodes 14a, 14b may be aligned relative to each other. In the aligned substrates, the electrodes on different substrates are behind each other when viewed from a direction orthogonal to the substrates. When the light modulator is disassembled and both substrates are arranged with the electrodes facing upward, the electrode patterns are mirror images of each other.

[0180] Aligning the substrates can increase the maximum transparency or maximum reflectivity of the light modulator; on the other hand, when the light modulator is selected for more criteria than a transparency range or a reflectivity range, it may be better to not align or not fully align the two substrates. The light modulators can be stacked. For example, two stacked light modulators can be made of three substrates, where the middle substrate has electrodes on both of its surfaces. In one embodiment of the light modulator, optionally at least one substrate 11, 12 of the first light modulator is the same as the substrate 11, 12 of at least one second light modulator. For stacked modulators, alignment can also increase the maximum transparency or maximum reflectivity, but may be detrimental to other considerations (e.g., diffraction).

[0181] Figure 9b An example of an embodiment of an optical modulator 40 is schematically shown. The optical modulator 40 is similar to the optical modulator 10, except that it includes multiple optical layers; in the example shown, two optical layers. There may also be more than two optical layers. Each optical layer is arranged between two substrates. The optical modulator 40 may be viewed as Figure 9a As shown, the light modulator 40 includes three substrates: a first substrate 41, a second substrate 42, and a third substrate 43. Between substrates 41 and 42 is an optical layer, and between substrates 42 and 43 is an optical layer. The optical layer can be similar to the optical layer in the light modulator 10. The controller 46 is configured to control the current on the electrodes of the substrates. For example, Figure 9b , the controller 46 may be electrically connected to at least (4 times 2 equals) 8 electrodes.

[0182] Interestingly, the particles in multiple optical layers can be different, so that multiple 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 different wavelengths, for example, can have different colors. This can be used to create different colors and / or different color intensities on the panel via the controller 46. For example, a four-substrate panel can have three optical layers, each with a different color particle, such as cyan, yellow, and magenta. By controlling the transparency or reflectivity of different colors, a wide color spectrum can be created.

[0183] The surface of one substrate facing the other substrate may be provided with two or more patterns, such as in one embodiment. For example, the outer substrates 41 and 43 may receive electrodes only on the inner side, while the inner substrate (eg, substrate 42) may have electrodes on both sides.

[0184] The substrate 41 and the substrate 42 may be considered together as one embodiment of a light modulator. Similarly, the substrate 42 and the substrate 43 may be considered together as one embodiment of a light modulator.

[0185] Fig.9c An example of an embodiment of a car 20 with a smart glass window 21 is schematically shown. This is a particularly advantageous embodiment because the level of incident light can change frequently and rapidly during driving. Using smart glass in a car has the advantage that the light level can be maintained at a constant level by adjusting the transparency of the window. In a car, a faster and / or more uniform transition between optical states (e.g., a faster transition towards non-transparent) is particularly advantageous because it reduces driver distraction during the transition. The car 20 may include a controller configured to control the transparency or reflectivity of the window 21.

[0186] Smart glass can also be used in other glass applications, especially where the amount of incident light is variable, such as buildings, offices, houses, greenhouses, skylights. Skylights are windows placed in the ceiling to allow sunlight to enter a room.

[0187] The light modulator may have two optical states, such as a transparent state and a non-transparent state, or a reflective state and a non-reflective state. The light modulator (e.g., light modulator 10 or light modulator 40) may be configured as:

[0188] - switching to a second optical state, such as a non-transparent state or a non-reflective state, by creating an alternating voltage on at least one of the first substrate and the second substrate, applying an alternating current between at least a first electrode and a second electrode on the first substrate and / or applying an alternating current between a first electrode and a second electrode on the second substrate, and

[0189] -Switching to a first optical state, such as a transparent state or a reflective state, by creating an alternating voltage between a first substrate and a second substrate, applying an alternating current between a first electrode on the first substrate and a first electrode on the second substrate, and / or applying an alternating current between a second electrode on the first substrate and a second electrode on the second substrate.

[0190] The electrode pattern on the first substrate is at least partially arranged in the same pattern as the second electrodes on the second substrate. Typically, the electrodes are opposite to each other, but the pattern of the first electrode and the pattern of the second electrode may also be offset relative to each other.

[0191] A protective coating may be disposed on at least a portion of an interior surface area of ​​at least one of the first substrate and the second substrate.

[0192] The driving signal applied to the driving electrode typically has a voltage that varies. For example, the power supply can be operated at an alternating frequency to be used to switch to a transparent state or a non-transparent state. This signal can have a frequency such as between 1 Hz and 1000 Hz. By continuously switching the charged electrode of the relative polarity on the first substrate and the second substrate, and / or continuously switching the charged electrode of the relative polarity between the first substrate and the second substrate, a balanced electrolysis current can be obtained.

[0193] In one embodiment, a method of controlling an electrophoretic optical modulator with asymmetric electrode drive comprises:

[0194] - applying an alternating current signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes to provide electrophoretic movement of the particles toward or from one of the plurality of electrodes to cause modulation of an optical property of the light modulator,

[0195] - Modulating the amplitude of an alternating current signal applied to a plurality of electrodes on a substrate to cause a low electric field region (in which the electric field is reduced) to move relative to the electrodes. For example, Fig.10 An embodiment of a method 400 for controlling an electrophoretic optical modulator with asymmetric electrode drive is schematically shown. The method 400 comprises:

[0196] receiving (410) a command to increase or decrease panel transparency,

[0197] Depending on the received command, a set of AC signals is selected (420),

[0198] periodically varying (430) the relative amplitudes of the set of AC signals,

[0199] The signal is applied (440) to electrodes in the panel.

[0200] As will be apparent to those skilled in the art, many different ways of performing a method according to an embodiment are possible. For example, the order of steps may be performed in the order shown, but the order of steps may be changed, or some steps may be performed in parallel. In addition, other method steps may be inserted between steps. The inserted steps may represent a refinement of a method such as described herein, or may be unrelated to the method. For example, step 430 may be performed at least partially in parallel with step 440. In addition, a given step may not be fully completed before starting the next step.

[0201] The embodiments of the method can be performed using software, which includes instructions for causing a processor system to perform method 400. The software may include only those steps taken by a specific sub-entity of the system. The software may be stored in a suitable storage medium (such as a hard disk, a floppy disk, a memory, an optical disk, etc.). The software may be sent as a signal wired or wirelessly or using a data network (e.g., the Internet). The software may be available for download and / or remote use on a server. The embodiments of the method can be performed using a bitstream, which is arranged to configure a programmable logic (e.g., a field programmable gate array (FPGA)) to perform the method.

[0202] It will be appreciated that the present invention also extends to a computer program suitable for putting the present invention into practice, particularly a computer program on or in a carrier. The program may be in the form of source code, object code, code intermediate source, and object code such as a partially compiled form, or any other form suitable for implementing an embodiment of the method. An embodiment related to a computer program product includes computer executable instructions corresponding to each processing step of at least one method described. These instructions may be subdivided into subroutines and / or stored in one or more files, which may be linked statically or dynamically. Another embodiment related to a computer program product includes computer executable instructions corresponding to each device of at least one of the systems and / or products described.

[0203] Fig.11a A computer readable medium 1000 having a writable portion 1010 is shown, as well as a computer readable medium 1001 also 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 example a memory card. The computer readable medium 1000 and 1001 can store data 1020, wherein the data can indicate instructions, which, when executed by a processor system, cause the processor system to perform a method according to an embodiment. The computer program 1020 can be included on the computer readable medium 1000 as a physical mark or by magnetization of the computer readable medium 1000. However, any other suitable embodiment can also be envisioned. In addition, it will be understood that although the computer readable medium 1000 is shown as an optical disk here, the computer readable medium 1000 can be any suitable computer readable medium, such as a hard disk, a solid state memory, a 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 electrophoresis control.

[0204] Fig.11bA schematic representation of a processor system 1140 is shown according to one embodiment. The processor system includes one or more integrated circuits 1110. Fig.11b The architecture of one or more integrated circuits 1110 is schematically shown in FIG. The circuit 1110 includes a processing unit 1120 (e.g., a CPU) for running a computer program component to execute a method according to an embodiment and / or a module or unit implementing it. The circuit 1110 includes a memory 1122 for storing programming codes, data, etc. A portion of the memory 1122 may be read-only. The circuit 1110 may include a communication element 1126, such as an antenna, a connector, or both or the like. The circuit 1110 may include an application specific integrated circuit 1124, which is used to perform some or all of the processing defined in the method. The processor 1120, the memory 1122, the application specific integrated circuit 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 arranged for contact communication and / or contactless communication, using an antenna and / or a connector, respectively.

[0205] 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, wherein the processor is arranged 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., flash memory). The memory circuit may be a volatile memory, such as an SRAM memory. In the latter case, the device may include a non-volatile software interface (e.g., a hard disk, a network interface, etc.), which is arranged to provide software.

[0206] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments.

[0207] In the claims, any reference numerals placed in brackets shall not be interpreted as limiting the claims. The use of the verb "comprise" and its variants does not exclude the presence of elements or steps other than those stated in the claims. The article "a" or "an" before an element does not exclude the presence of multiple such elements. When an expression such as "at least one" is placed before a list of elements, it means selecting all elements or any subset thereof from the 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 can be implemented by a device comprising hardware of several different elements, and by a device of a suitably programmed computer. In a device claim that lists several parts, several of these devices can be implemented by the same hardware item. The mere fact that certain measures are recorded in different dependent claims does not indicate that the combination of these measures cannot be used to advantage.

[0208] In the claims, the signs in parentheses refer to the reference symbols in the drawings of the exemplary embodiments or the formula of the embodiments, thereby improving the intelligibility of the claims. These signs should not be interpreted as limiting the claims.

Claims

1. An electrophoretic optical modulator with asymmetric electrode drive, the optical modulator comprising: at least a first substrate and a second substrate, the second substrate being arranged opposite to the first substrate; an optical layer, the optical layer being arranged between the first substrate and the second substrate, the optical layer comprising a fluid, the fluid comprising particles, the particles being charged or capable of being charged; a plurality of interdigitated electrodes arranged across each of the first substrate and the second substrate; and a controller configured to apply an alternating current signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes to provide electrophoretic motion of particles toward or from one of the plurality of electrodes to cause modulation of an optical property of the light modulator, wherein - the controller is configured to modulate the amplitude of the alternating current signal applied to the plurality of electrodes on the substrate to cause the low electric field region to move relative to the electrodes.

2. An electrophoretic optical modulator, wherein the low electric field region is a region where particle motion is stationary relative to the electrode. 3 . The optical modulator according to claim 2 , wherein the controller is configured for a shut-down operation of the optical modulator, the dead zone moves between two opposing electrodes on opposing substrates. 4 . The optical modulator of claim 1 , wherein the controller is configured for an opening operation of the optical modulator, the low electric field region moves parallel to the substrate.

5. An optical modulator according to any one of the preceding claims, wherein the amplitude is modulated until a target grey level is reached, after which the controller applies an electrical sustain signal to the plurality of electrodes on the substrate, thereby maintaining the grey level of the optical modulator.

6. An optical modulator according to any one of the preceding claims, wherein a first AC signal applied to the first electrode is scaled relative to a second AC signal applied to the second electrode.

7. An optical modulator according to any one of the preceding claims, wherein the scaling between the two AC signals applied to the two electrodes cycles between a lower scaling factor and a higher scaling factor.

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

9. An optical modulator according to any one of the preceding claims, wherein the scaling between two AC signals applied to two electrodes is modulated to randomize the positions of the low electric field regions.

10. An optical modulator according to any one of the preceding claims, wherein the controller is configured to: - a closing operation in which the ratio of the amplitudes of a pair of signals applied to a pair of opposing electrodes on opposing substrates is changed, and / or - An opening operation in which the amplitude ratio of a pair of signals applied to a pair of adjacent electrodes on the same substrate is changed.

11. An optical modulator according to any of the preceding claims, wherein a first AC signal applied to a first electrode is scaled relative to a second AC signal applied to a second electrode, wherein the lower amplitude of the first AC signal and the second AC signal is at most 70%, 50%, 45%, 40%, 30% of the higher amplitude.

12. An optical modulator according to any of the preceding claims, wherein at least one of the AC signals has a high frequency component and a lower frequency component, the high frequency component having a frequency of at least 500 Hz or 750 Hz, preferably at least 1 kHz, and the lower frequency component having a frequency of at most 100 Hz.

13. An optical modulator according to any one of the preceding claims, wherein the high frequency components are removed when a target grey level is reached.

14. An optical modulator according to any preceding claim, wherein a low pass filter is applied to the AC signal.

15. The optical modulator according to any one of claims 12 to 14, wherein particles in the fluid move under the influence of electrophoretic force and dielectrophoretic force.

16. An optical modulator according to any one of the preceding claims, wherein the first substrate includes a first electrode and an adjacent second electrode, and the second substrate includes a third electrode and an adjacent fourth electrode, the first electrode and the fourth electrode are opposite to each other, and the second electrode and the third electrode are opposite to each other, and the controller is configured to use a first phase for the first electrode, an increased phase for the second electrode, another increased phase for the third electrode, and yet another increased phase for the fourth electrode.

17. An electrophoretic optical modulator, wherein the low electric field region is a dead zone where no electric field exists, and the controller is configured to move the dead zone relative to the electrode.

18. A controller, the controller being configured to control an asymmetric alternating current signal of an electrophoretic optical modulator, the optical modulator comprising: at least a first substrate and a second substrate, the second substrate being arranged opposite to the first substrate; an optical layer, the optical layer being arranged between the first substrate and the second substrate, the optical layer comprising a fluid, the fluid comprising particles, the particles being charged or capable of being charged; a plurality of interdigitated electrodes arranged across each of the first substrate and the second substrate; The controller is configured to apply an alternating current signal to the plurality of electrodes to obtain an electric field between the plurality of electrodes, thereby providing electrophoretic motion of particles toward one of the plurality of electrodes, or providing electrophoretic motion of particles from one of the plurality of electrodes to cause modulation of optical properties of the light modulator, wherein the controller is configured to modulate the amplitude of the alternating current signal applied to the plurality of electrodes on the substrate to cause a low electric field region to move relative to the electrodes.

19. A method for controlling an electrophoretic optical modulator with asymmetric electrode drive, the optical modulator comprising: at least a first substrate and a second substrate, the second substrate being arranged opposite to the first substrate; an optical layer, the optical layer being arranged between the first substrate and the second substrate, the optical layer comprising a fluid, the fluid comprising particles, the particles being charged or capable of being charged; a plurality of interdigitated electrodes arranged across each of the first substrate and the second substrate, the method comprising: - causing an alternating current signal to be applied to the plurality of electrodes to obtain an electric field between the plurality of electrodes, thereby providing electrophoretic motion of particles towards or from one of the plurality of electrodes to cause modulation of an optical property of the light modulator, - Modulating the amplitude of the alternating current signal applied to the plurality of electrodes on the substrate to cause low electric field regions to move relative to the electrodes.

20. A transitory or non-transitory computer-readable medium (1000) comprising data (1020) representing instructions which, when executed by a processor system, cause the processor system to perform the method of claim 19.

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