SELF-CLEANING USING TRANSPARENT ULTRASONIC ARRAY

Abstract

An active self-cleaning device for transparent substrates includes a transparent substrate, a piezoelectric transducer array formed on essentially entire transparent substrate surface, including a central area of the transparent device, and an electronic system configured to actuate the piezoelectric transducer array to clean a surface of the substrate. Such a device may be used for applications such as LIDAR, radar and camera enclosures, solar cell panel cover glasses, vehicle windshields, windows, sunroofs and headlamps, street lighting and information displays.

Claims

1. A self-cleaning device, comprising: a transparent substrate; a piezoelectric transducer array formed on essentially entire transparent substrate surface; including a central area of the transparent device; and an electronic system configured to actuate the piezoelectric transducer array to clean a surface of the substrate.

2. The device of claim 1 wherein the piezoelectric transducer array is a combination of patterned layers of metal electrodes and piezoelectric material.

3. The device of claim 1 wherein the piezoelectric transducer array includes a number of piezoelectric transducer chips attached to such substrate at specific places and connected to a transparent conductor lines fabricated on the substrate.

4. The device of claim 1 wherein the piezoelectric transducer array has features of less than 100 microns.

5. The device of claim 1 wherein the piezoelectric transducer array has features of less than 10 microns.

6. The device of claim 1 wherein the piezoelectric transducer array has features of less than 5 microns.

7. The device of claim 1 wherein the piezoelectric transducer array includes one or more transducers that are formed on transparent polymer film, which is laminated onto a substrate.

8. The device of claim 1 wherein the piezoelectric transducer array includes transducers formed on transparent glass film, which is laminated onto a substrate or embedded into product glazing structure.

9. The device of claim 1 wherein the piezoelectric transducer array includes transducers that are encapsulated with a thin transparent polymer film or glass.

10. The device of claim 1 wherein the piezoelectric transducer array includes a patterned piezoelectric material, wherein the patterned piezoelectric material includes an array of individually-addressable piezoelectric transducers.

11. The device of claim 1 wherein some transducers in the piezoelectric transducer array are configured to emit ultrasonic energy and some transducers in the piezoelectric transducer array are configured to detect ultrasonic energy (sensors), so that the control system can obtain information about location of contamination on the substrate surface and direct ultrasonic energy only to contaminated area.

12. The device of claim 1 wherein the substrate is an enclosure of a LIDAR.

13. The device of claim 1 wherein the substrate is an enclosure of a radar.

14. The device of claim 1 wherein the substrate is an enclosure or lens of light detector or camera.

15. The device of claim 1 wherein the substrate is an enclosure of lighting device in a vehicle.

16. The device of claim 1 wherein the substrate is an enclosure of street lighting.

17. The device of claim 1 wherein the substrate is an enclosure of solar panel.

18. The device of claim 1 wherein the substrate is a windshield or window, or sunroof of a car, plane, ship, drone or other transportation vehicle.

19. The device of claim 1 wherein the substrate is a prescription or sunglasses, visors or helmets.

20. The device of claim 1 wherein the substrate is a window of a building.

21. The device of claim 1, wherein the substrate is a surface of an appliance.

22. The device of claim 22, wherein the appliance includes a glass cooktop, oven window, refrigerator shelf, or microwave oven window.

23. The device of claim 1 wherein the piezoelectric transducer array is aperiodic to avoid light diffraction.

24. The device of claim 1, wherein the piezoelectric transducer array includes a microstructure, wherein microstructure is periodic and pitch is chosen to create one or multiple diffraction orders.

25. A method of fabricating a self-cleaning transparent surface, comprising: fabricating an ultrasonic transducers array on a flexible on essentially an entire surface of a transparent substrate, including a central area; attaching such substrate to a transparent surface to be cleaned; and actuating such transducers in order to emit ultrasonic energy towards the surface.

26. A method according to 23 wherein the transducers are configured to remove contamination from the surface when activated.

27. A method according to 23 wherein the transducers are configured to remove water in any phase of water, including liquid, water drops, fog or ice, when activated.

28. A method according to 23 wherein such transparent substrate is LIDAR enclosure.

29. A method according to 23 wherein such transparent substrate is windshield of a transportation vehicle.

30. A method according to 23 wherein such transparent substrate is a window of transportation vehicle or architectural building.

31. A method according to 23 wherein such transparent substrate is enclosure of solar panel.

32. A method according to 23 wherein such transparent substrate is visor, goggle, helmet or glasses.

Description

4. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various aspects of the present disclosure will become apparent upon reading the following detailed description and upon reference to the accompanying drawings in which:

[0024] FIG. 1 is a schematic diagram illustrating an example of a prior art ultrasonic windshield cleaning system in which ultrasonic transducers are attached to glass substrates on the periphery.

[0025] FIG. 2 is a schematic diagram illustrating an example of a prior art LIDAR cleaning system in which the cover glass dome is cleaned by movable wipers.

[0026] FIG. 3 is a schematic diagram illustrating an example of a prior art solar panel cleaning system in which transducers are attached to the backside of the panel

[0027] FIGS. 4A-4C are schematic diagrams illustrating examples of transparent microstructured (patterned) piezoelectric transducers array in accordance with various aspects of the author's previous patent.

[0028] FIG. 5 depicts an embodiment of a microstructured (patterned) piezoelectric ultrasonic transducer design, where a patterned piezoelectric stack (with 2 electrode layers) is shown in cross-section view.

[0029] FIG. 6 is a schematic diagram illustrating example of a transparent piezoelectric transducer array according to aspects of the present disclosure.

[0030] FIG. 7 is a schematic diagram depicting a self-cleaning device for windshield based on transparent piezoelectric transducer array fabricated on essentially entire surface of the windshield, including viewable area

[0031] FIG. 8 Embodiment of self-cleaning device for LIDAR dome based on transparent piezoelectric transducer array fabricated on the surface of the dome.

[0032] FIG. 9 is a cross-sectional schematic diagram of a self-cleaning device for solar panel based on microstructured piezoelectric transducer array fabricated on the surface of the panel, where the microstructure has a triangular shape, which also reflects the light onto the panel surface

[0033] FIG. 10 is a schematic diagram showing an example of a system having two or more arrays of transparent transducers fabricated on a transparent substrate and coupled to a controller.

5. DETAILED DESCRIPTION

[0034] Although the following detailed description contains many specific details for the purposes of illustration, anyone of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the aspects of the disclosure described below are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.

[0035] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as top, bottom, front, back, first, second, etc., is used with reference to the orientation of the figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0036] Aspects of the present disclosure include use of transparent ultrasonic devices in optical components and devices for self-cleaning purposes. Ultrasonic energy emitted by a large array of piezoelectric transducers scattered across an entire glass or film surface to be cleaned in operation of the device (car, plane, solar panel, LIDAR, etc.) is used to dislodge contamination from the surface, or even prevent contamination from sticking to the surface in the first place. The same technology could be used to remove water droplets from the surface by moving them on the surface in the direction out of viewable area, or alternatively, evaporating them using ultrasonic energy. Thus the same technology could be effectively used also to de-ice or de-fog surface.

[0037] Such transducer, and method of their fabrication, have been proposed by authors earlier in PCT/US2016/015448, 991, U.S. Ser. No. 15/645,991, and U.S. 62/470,293, and may include a micro- or nano-structured mesh (12) as in FIG. 4A or a grating (12), as in FIG. 4B, or an array (12), as in FIG. 4C on the surface of a substrate (11), for example glass or polymer film. The criteria of transparency for such transducers could be met by optimizing a ratio of microstructure to an open area of the substrate. The criteria of visibility (unobstructed view) can be met by optimizing the feature size of the structure to be below recognition of a human eye at the required distances. That minimum feature size is usually less than 100 micron, sometimes less than 10 micron, though for the most demanding applications and good human vision, it could be less than 2.5 micron.

[0038] A micro- or nano-structured ultrasonic transducer could be made of a piezoelectric material sandwiched between 2 electrodes, e.g., as shown in FIG. 5. Moreover, both, a piezoelectric thin film (15) and electrodes (14), could be patterned on the substrate surface to yield a very transparent and invisible-to-the-eye device. In an alternative implementation, one or both electrodes could be deposited as a continuous layer of transparent conductive material, and only piezoelectric material would be patterned. Such transparent conduct material could be, e.g., Indium-Tin Oxide (ITO) or another transparent conductive oxide (TCO), or transparent organic conductors, or graphene, or silver nanowires or nanoparticles. Piezoelectric stack could be fabricated on Silicon or other high-temperature tolerant substrate, and then transfer-printed onto glass or polymer film, or other substrate.

[0039] Alternatively, piezoelectric transducer array could be fabricated from individual piezoelectric micro-chips, which are mass-transferred onto target substrate using pick-and-place or mass-transfer equipment, and subsequently attached to the prefabricated transparent conductor lines for powering up the circuit, as shown in FIG. 6. In the example shown schematically in FIG. 6, a transparent piezoelectric transducer array is fabricated from a number of piezoelectric micro-transducers 602 transferred onto a target substrate 601 and bonded to transparent conductor lines (not shown). As an example, for a display application, micro-LED chips 604 may be mass-transferred onto the same substrate. As an alternative example, micro-LED chips may be transferred onto the same substrate and attached to transparent conductor (not shown) for micro-LED display self-cleaning application.

[0040] Aspects of the present disclosure include, but are not limited to, the following embodiments.

Embodiment-I

[0041] Essentially the entire viewable surface of the windshield of a car, plane, ship and other transportation vehicle may be covered with ultrasonic transducer array in a manner that is unobtrusive, transparent and invisible to the human eye (see FIG. 7). Such an array 702 of micro-piezoelectric transducers could be implemented as a continuous array of piezoelectric elements or as an array of separate micro-piezoelectric elements with an individual addressing capability.

[0042] Integrating ultrasonic transducers into the windshield enables to clean it on-demand without using movable parts. Wipers moving in front of the driver's eyes present a severe safety problem, especially with the heavy pouring rain, when one has to move them fast to clean the windshield from water. Wipers cannot do the proper cleaning of some bird's deposits, especially ones, which are cooked by the sun.

[0043] There are many advantages of the proposed technology for cleaning transparent devices. These include: [0044] High efficiency of cleaning and energy savings due to ultrasonic transducers positioned in a very close proximity/right at the place of contaminationon the viewing area of a windshield [0045] Integrating transparent ultrasonic emitting array with sensor array would allow to detect contamination and forward all energy to a specific spot to further optimize cleaning and reduce energy waste [0046] Such devices could be integrated with superhydrophobic or superhydrophilic or photoactive surface treatment for better efficiency. [0047] No mechanical movable fixtures are required. [0048] High transparency; no tint

[0049] The integration of a self-cleaning ultrasonic device with the windshield glass can be done by laminating on windshield glass a piezoelectric array fabricated on the thin flexible glass or polymer film. The array may then be encapsulated with a transparent material (optically clear adhesive or similar) to provide environmental protection. Alternatively, the microstructure could be fabricated on thin transparent glass or polymer film and then laminated or bonded to glass product with microstructure side down, so the thin transparent substrate would act as protection layer against environment.

Embodiment-II

[0050] An ultrasonic transducer array may be fabricated on a LIDAR dome. As illustrated in FIG. 8 the surface of a LIDAR dome 801 (enclosure/lens) may be covered with a piezoelectric transducer array 802. Alternatively, a transparent film or flexible glass substrate with such array may be laminated onto the dome surface. Part of an individually-addressable ultrasonic transducer array could be configured to emit ultrasonic signal, and another partto detect ultrasonic signal. Detector array would sense contamination on the surface and software algorithm will trigger ultrasonic actuation or pulse directed to the place of contamination. Such ultrasonic transducer array can clean the surface of LIDAR dome on-demand and only contaminated surface, which would improve safety (immediate cleaning of contamination as soon as it appears on the surface), and with energy saving (cleaning only small portion of the dome surface). The laser scanning algorithm is optimized to avoid loss of signal due to blockage of light by piezoelectric transducers elements.

Embodiment-III

[0051] An ultrasonic transducer array for cleaning LIDAR may have an aperiodic structure of piezoelectric features, so that light diffraction is avoided for the laser beam at specific wavelength of operation

Embodiment-IV

[0052] An ultrasonic transducer array for cleaning LIDAR may have a periodic, 1D or 2D, structure of piezoelectric features, and the geometry of the microstructure (grating) is optimized to have one or multiple beams (diffractive orders), so that laser beam is diverted to larger angles, or multiple beams are used to scan the space simultaneously to build a 3D map of the area faster or more accurate.

Embodiment-IV

[0053] An ultrasonic transducer array may be fabricated on a solar panel surface, such as a surface of a cover glass or polymer encapsulating film. Alternatively, the transparent film with such an array may be laminated on solar panel surface. Part of an individually-addressable ultrasonic transducer array could be configured to emit ultrasonic signals, and another partto detect ultrasonic signals. The detector array would sense contamination on the surface and software algorithm trigger ultrasonic actuation or pulse directed to the place of contamination. Such an ultrasonic transducer array can clean the surface of solar panel on-demand and only contaminated surface, which would improve efficiency (cleaning of contamination as soon as it appears on the surface), and with energy saving (cleaning only small portion of the dome surface).

Embodiment-V

[0054] A microstructured ultrasonic transducer array 902 for cleaning solar panel 901 may have a transduces with a piezoelectric thin film (15) and electrodes (14) in a triangular cross-sectional shape so that light would reflect from its surface onto the solar panel, as shown in FIG. 9. This would concentrate more light on solar cell surface and increase absorption efficiency of the solar panel.

Embodiment-VI

[0055] An entire transparent substrate, e.g., a-windshield or window, may be divided into multiple areas with an array of individually powered ultrasonic transducers to save energy for forwarding ultrasonic power only to the area where contamination should be removed. Also, the individually addressable ultrasonic transducers or arrays of transducers allow creating an ultrasonic wave to dislodge and move contamination or water droplets on the surface in required direction.

Embodiment-VII

[0056] An ultrasonic transducer array may be fabricated on a lighting fixture, for example, the headlight of a car or lighting enclosure of a street lighting, providing self-cleaning capability.

Embodiment-VIII

[0057] An ultrasonic transducer array may be fabricated on the display cover glass or other encapsulation (environmental protection) layer of display, providing self-cleaning capability.

Embodiment-IX

[0058] There are a number of ways to implement above Embodiments. FIG. 10 illustrates a system having two or more arrays of transparent transducers 82 fabricated on a transparent substrate 81 and coupled to a controller 90. The controller may include a processor 92 coupled to a transmit circuit 94 and a receive circuit 96. In the illustrated example, the arrays of transparent transducers 82 are operatively coupled to the controller 90 via a multiplexer 84. The multiplexer allows the transmit circuit 94 or the receive circuit 96 to be selectively coupled to individual arrays on the substrate 81. The processor 92 may be a programmable microprocessor, a microcontroller, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other suitable device. It is noted that in some implementations, the multiplexer 84, processor 92, transmit circuit 94, and receive circuit 96 may be implemented in a common integrated circuit, such as a system on chip (SOC).

[0059] The transmit circuit 94 provides drive signals that drive the transducers 82 in response to drive instructions from the processor 92. Providing the drive instructions may involve interpretation of digital drive instructions and generation of corresponding analog output signals having sufficient amplitude to generate a desired ultrasound signal with a particular transducer. The drive signals may include switching signals that direct the multiplexer 84 to selectively couple the analog output signals to the particular transducer. By way of example and not by way of limitation, the processor 92 may send drive instructions to the transmit circuit 94 that direct the transmit circuit to couple drive signals to selected arrays in a sequence that sends transverse waves of ultrasound across the substrate from one end to the other.

[0060] The receive circuit receives 96 input signals from the transducers 82 and converts the received signals into a suitable form for signal processing by the processor. Conversion of the received signals may involve amplification of the received signals and conversion of the resulting amplified received signals from analog to digital form. The processor may be programmed or otherwise configured to perform digital signal processing on the resulting digital signals. Such digital signal processing may include time of flight analysis to determine a distance d to an object. Such time of flight analysis may involve determining an elapsed time t between the transmitting of acoustic pulses with one or more of the transducers 82 and detecting an echo of such pulses from the object with the same or different transducers 82. The processor 92 can calculate the distance d from the equation d=ct, where c is a known or estimated speed of sound.

ADDITIONAL EMBODIMENTS

[0061] Aspects of the present disclosure are not limited to the above embodiments. For example, a transducer array for self-cleaning may be fabricated into or onto appliance surfaces (e.g., glass cooktops, oven windows, refrigerator shelves, microwave oven windows) during operation of these devices. In some implementations, the ultrasonic transducer may be engineered to also shield the device against radiofrequency (RF) radiation. Such engineering may include selection of thickness, linewidth and pitch of the patterned conductive electrodes in the ultrasonic transducers that make up the array.

[0062] Numerous other embodiments are within the scope of the present disclosure.

[0063] While the above is a complete description of the preferred embodiment of the present invention, it is possible to use various alternatives, modifications and equivalents. Therefore, the scope of the present invention should be determined not with reference to the above description but should, instead, be determined with reference to the appended claims, along with their full scope of equivalents. Any feature, whether preferred or not, may be combined with any other feature, whether preferred or not. In the claims that follow, the indefinite article A, or An refers to a quantity of one or more of the item following the article, except where expressly stated otherwise. The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase means for.