CN-119768731-B - Asymmetric driving for optical modulators

Abstract

Some embodiments relate to electrophoretic optical modulators with asymmetric electrode driving. An alternating current 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 alternating current signal is modulated, resulting in a movement of the low electric field region relative to the electrode.

Inventors

• A. Mitiogru
• A. J. Slake

Assignees

• 埃尔斯达动力专利私人有限公司

Dates

Publication Date

20260512

Application Date

20230609

Priority Date

20220628

Claims (20)

1. 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 the first substrate, an optical layer arranged between the first substrate and the second substrate, the optical layer comprising a fluid comprising particles, the particles being charged or chargeable, a plurality of interdigitated electrodes arranged across each of the first substrate and the second substrate, and a controller configured to apply an alternating electrical signal to the plurality of electrodes to obtain an electrical field between the plurality of electrodes to provide electrophoretic movement of the particles towards or from one of the plurality of electrodes to cause modulation of an optical property of the optical modulator, wherein The controller is configured to modulate the amplitude of alternating electrical signals applied to the plurality of electrodes on the substrate, and the asymmetric electrode driving includes applying different amplitude signals to at least some of the electrodes in the optical modulator, Wherein: -modulating the amplitude to cause a low electric field region to move relative to the electrode, wherein the low electric field region is a region where particle movement is stationary relative to the electrode, or -Modulating the amplitude to cause a movement of a low electric field region relative to the electrode, wherein the electric field strength in the low electric field region of the optical layer is 25% or less of the maximum electric field strength in the optical layer.
2. 2. The optical modulator of claim 1, wherein the controller is configured for a closing operation of the optical modulator, the low electric field region moving between two opposing electrodes on an opposing substrate.
3. 3. The optical modulator of claim 1, wherein the controller is configured for an on operation of the optical modulator, the low electric field region moving parallel to the substrate.
4. 4. An optical modulator according to any one of claims 1 to 3, 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.
5. 5. An optical modulator according to any one of claims 1 to 3, wherein the first ac signal applied to the first electrode is scaled relative to the second ac signal applied to the second electrode.
6. 6. An optical modulator according to any one of claims 1 to 3, wherein the scaling between the two ac signals applied to the two electrodes is cycled between a lower scaling factor and a higher scaling factor.
7. 7. The optical modulator of claim 6, wherein a first alternating current signal has a constant amplitude and a second alternating current signal is scaled relative to the first alternating current signal.
8. 8. The optical modulator of claim 1, wherein scaling between two ac signals applied to two electrodes is modulated to randomize the position of the low electric field region.
9. 9. The optical modulator of any of claims 1-3, wherein the controller is configured to: -a closing operation in which the amplitude ratio of a pair of signals applied to a pair of counter electrodes on a counter substrate is changed, and/or -An opening operation, wherein the amplitude ratio of a pair of signals applied to a pair of adjacent electrodes on the same substrate is changed.
10. 10. An optical modulator according to any one of claims 1 to 3, 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.
11. 11. An optical modulator according to any one of claims 1 to 3, wherein at least one of the ac signals has a high frequency component having a frequency of at least 500 Hz or 750Hz and a lower frequency component having a frequency of at most 100 Hz.
12. 12. The optical modulator of claim 11, wherein the high frequency component has a frequency of at least 1 kHz.
13. 13. The optical modulator of claim 11, wherein the high frequency component is removed when a target gray level is reached.
14. 14. The optical modulator of claim 11, wherein a low pass filter is applied to the alternating current signal.
15. 15. The optical modulator of claim 11, wherein particles in the fluid are moved by an electrophoretic force and a dielectrophoretic force.
16. 16. An optical modulator according to any one of claims 1 to 3, wherein the first substrate comprises a first electrode and an adjacent second electrode, and the second substrate comprises a third electrode and an adjacent fourth electrode, the first electrode and the fourth electrode being opposite each other, and the second electrode and the third electrode being opposite each other, the controller being 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. 17. The electrophoretic optical modulator of claim 1 wherein the low electric field region is a dead zone where no electric field is present, the controller configured to move the dead zone relative to the electrode.
18. 18. The electrophoretic optical modulator of claim 1, wherein: The electric field strength in the low electric field region of the optical layer is 15% or less, 10% or less, or 1% or less, or -The electric field strength in the low electric field region of the optical layer is less than 2 10-6V/m less than 1 10-6V/m or less than 1 10A 5V/m, or -The electric field strength in the low electric field region is at most 15%, or at most 10% greater than the minimum electric field strength in the optical layer.
19. 19. A controller 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 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 chargeable, a plurality of interdigitated electrodes arranged across each of the first substrate and the second substrate, the controller being 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 movement of particles towards one of the plurality of electrodes, or to provide electrophoretic movement of particles from one of the plurality of electrodes to cause modulation of optical properties of the optical modulator, wherein the controller is configured to modulate the amplitude of the alternating current signal applied to the plurality of electrodes on the substrate, Wherein: -modulating the amplitude to cause a low electric field region to move relative to the electrode, wherein the low electric field region is a region where particle movement is stationary relative to the electrode, or -Modulating the amplitude to cause a movement of a low electric field region relative to the electrode, wherein the electric field strength in the low electric field region of the optical layer is 25% or less of the maximum electric field strength in the optical layer.
20. 20. A method of controlling an electrophoretic optical modulator having asymmetric electrode drive, the optical modulator comprising at least a first substrate and a second substrate disposed opposite the first substrate, an optical layer disposed between the first substrate and the second substrate, the optical layer comprising a fluid comprising particles, the particles being charged or chargeable, a plurality of interdigitated electrodes disposed 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 to provide electrophoretic movement of particles towards one of the plurality of electrodes or to provide electrophoretic movement of particles from one of the plurality of electrodes to cause modulation of optical properties of the light modulator, -Modulating the amplitude of the alternating current signal applied to the plurality of electrodes on the substrate, wherein: -modulating the amplitude to cause a low electric field region to move relative to the electrode, wherein the low electric field region is a region where particle movement is stationary relative to the electrode, or -Modulating the amplitude to cause a movement of a low electric field region relative to the electrode, wherein the electric field strength in the low electric field region of the optical layer is 25% or less of the maximum electric field strength in the optical layer.

Description

Asymmetric driving for optical modulators Technical Field The invention relates to an electrophoretic optical modulator, a controller, a method of controlling an electrophoretic optical modulator, and a computer readable medium. Background 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 may be subdivided into a plurality of small individual volumes or individual cells filled with a dielectric fluid. The fluid comprises a dielectric material, a charged material, or a suspension of particles of 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 the control device. The electrodes of each plate are formed of pairs of combs that are interleaved with each other. The electrodes of the two interleaved combs are capable of withstanding voltages of the same polarity or opposite polarity. By applying a suitable voltage across the electrodes, the particles can be concentrated at different locations between the electrodes, giving the system a transparent or opaque appearance. There are a number of drawbacks associated with known systems. Although optically active glasses may transition from one state to another (e.g., from a transparent state to an opaque state), such transitions take a long time and are typically not completely uniform. Furthermore, the lifetime of existing devices is limited. Disclosure of Invention Embodiments herein address these and other issues. For example, in one embodiment, an electrophoretic optical modulator includes at least a first substrate and a second substrate disposed opposite the first substrate. An optical layer is disposed between the first substrate and the second substrate, the optical layer comprising a fluid comprising particles that are charged or chargeable. A plurality of interdigital electrodes are 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 to provide electrophoretic movement of the particles towards or from one of the plurality of electrodes to cause modulation of the optical properties of the light modulator. The controller is configured to modulate the amplitude of an alternating current signal applied to a plurality of electrodes on the substrate to cause the low electric field region to move relative to the electrodes. By modulating the amplitude of the signal, the region of low electric field (especially the lowest) moves 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 even scaled up, the low electric field region moves toward the previous substrate. Likewise, by manipulating the signals on adjacent electrodes, the low electric field region can be moved parallel to the substrate. In fact, particle movement in the low electric field region may not exist and the particles are stationary with respect to the electrode. Moving such regions allows stationary particles to escape therefrom so that they do not slow down the transition of the panel. In particular, so-called dead zones (in which no electric field is present) can be moved in the optical layer. Moving the low electric field region (especially the dead region) has several advantages. Particles in the low electric field region do not respond to the electric field as fast as particles in the high electric field region. Thus, those regions transition slowly and the transition is non-uniform. Furthermore, by moving the low electric field region back and forth, mixing of particles is generally increased. The optical modulator as described herein may be used in a wide range of practical applications. For example, an optical modulator having at most one non-transparent substrate may be used as a surface capable of changing its optical appearance (such as its reflective state or transmissive state). In particular, light modulators in which all substrates are transparent can be used as optically active glass, for example for offices, automobiles, cabinets and the like. One embodiment of the control method may be implemented on a computer as a computer-implemented method, or in dedicated hardware, or in a combination of both. Executable code for one embodiment of the method may be stored on a computer program product. Embodiments of the computer program product include memory devices, optical storage devices, integrated circuits, servers, online software, and the like. Preferably, the computer program product comprises non-transitory program code stored on a computer readable medium for performin