The present disclosure relates to ultrasonic transducers and more particularly to transparent ultrasonic transducers.
Ultrasonic transducers are widely used to clean surfaces from contamination. Moreover such transducers would be very useful for cleaning transparent surfaces like vehicle windshields, windows and sunroofs, and of course building windows. The requirements of any window device include high transparency and unobstructed view.
The concept of ultrasonic wiperless windshield cleaners can be traced back to the early 1960s. U.S. Pat. No. 3,171,683 (filed in 1963) covers Arthur Ludwig's concept for a “Windshield assembly for motor vehicles and the like.”
In essence, the transducers shake the glass, so that rain, snow, mud, etc. do not stick. However, there appears to be no evidence that the concept was ever demonstrated.
The next significant advance in ultrasonic windshield cleaners was made by Kenro Motoda. His approach, as recorded in U.S. Pat. No. 4,768,256 (filed in 1986), looks rather like Ludwig's, in that there are a set of ultrasonic transducers fixed onto the windshield.
However, his transducers are actually launchers for surface acoustic waves. Unlike conventional vibrations, which generally produce a pattern of standing (stationary) waves on the surface of the glass, surface acoustic waves move the surface of the glass in an elliptical pattern that propagates across the glass, hopefully carrying along with it water, dirt, and other muck obscuring the driver's view. While the progressive motion of the surface acoustic waves should be more effective than the simple shaking of the Ludwig design, it appears that Motoda's design was never produced.
A number of modifications of Motoda's basic design were patented over the years, including one that involved the piezoelectric polymer polyvinylidine fluoride being sandwiched between transparent conducting electrodes to generate the surface acoustic waves, (Broussoux et al, U.S. Pat. No. 5,172,024 (1990)); as well as applications to cleaning semiconductor wafers (Akatsu et al., U.S. Pat. No. 6,021,789 (1998)), and for shaking dust from camera optics (Urakami et al., U.S. Pat. No. 8,063,536 (2009).
The most recent patent activity in this field is described in International Patent Application Publication WO2012095643, filed in 2011 by a small UK engineering firm, Echovista Systems Ltd. While the basic technique is still that of Motoda, the Echovista publication has expanded the possible modes of usage to include ultrasonic vaporization of precipitation from the windshield, the use of other vibrational modes which may be more effective in removing precipitation, using the heating of the windshield caused by the ultrasonic vibration to melt ice and snow and de-fog the windshield, and the use of a windshield washing liquid nozzle, having an effect similar to plunging the windshield into an ultrasonic cleaner. Echovista also appears to have done significant testing on its ultrasonic washer, identifying maximum effectiveness is obtained with an ultrasonic frequency of about 2 MHz, corresponding to an ultrasonic wavelength of about 2.5 mm (0.1 in).
Obviously, all prior art had to position their “macro” ultrasonic transducers 1, 2, 3, 4, 5, 6, 7, 8, on the periphery 9 of the window/windshield 10 to be cleaned (not to obstruct a view) which is shown on
Similar ultrasonic devices could be used to clean solar panels and architectural windows from contamination. Prior art (Vasiliev, 2013) used macro-ultrasonic device located outside of the working area of the solar panel. Ultrasonic cleaning is a very important and economically efficient solution, since allows to significantly boost efficiency of energy generation, avoid using manual labor or expensive robotics.
Efficiency of cleaning could be much higher and power requirements much lower if US transducers could be positioned in a very close proximity/or even right at the point of contamination within a viewing/exposure area of a windshield, window, sunroof or solar panel. But for this to happen such transducer must be not only very transparent, but in case of a windshield, absolutely invisible to the human eye from a short distance of viewing within a vehicle.
Another wide-spread ultrasonic transducer's application is in sensing. Again, most devices have used macro-transducers and could not be implemented on optical devices, displays, windows and windshields. For example, gesture recognition system of Boser (US20140253435) uses an array of microelectromechanical (MEMS) ultrasonic transducers fabricated on Si substrate for emitting acoustic signal and sensing it after reflecting from a moving object. Yet another example is the application of Lee (US20130127783), where ultrasonic transducers (emitters and receivers) located on the periphery of display window. Obviously, such non-transparent obstructive devices cannot be integrated in a transparent object like window or display. Providing such an array is made transparent it could be integrated on the display window to provide non-optical (without cameras) gesture recognition or 3D image caption, which could use 20× less power than camera-based gesture recognition systems, and be more private.
It is within this context that aspects of the present disclosure arise.
Various aspects of the present disclosure will become apparent upon reading the following detailed description and upon reference to the accompanying drawings in which:
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.
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.
Aspects of the present disclosure include transparent ultrasonic devices and methods of manufacturing. Such transducer devices may include a micro- or nano-structured mesh (12) as in
A micro- or nano-structured ultrasonic transducer could be made of a piezoelectric material sandwiched between 2 electrodes, e.g., as shown in
For applications involving surface cleaning of, e.g., windshields, windows, displays and solar panels, ultrasonic transducers could be used in tandem with surface modification techniques, such as making substrate surface hydrophobic, superhydrophobic, or superhydropholic, or photoactive (for example, containing a titanium dioxide (TiO2) composition).
Aspects of the present disclosure include, but are not limited to, the following embodiments.
The following thin film stack can be deposited on a glass or plastic film surface in the viewing area of the device (for example, windshield): thin metal film (for example, silver), piezoelectric material (for example, lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT), barium titanate, ammonium dihydrogen phosphate (ADP), etc.), and thin metal film again (for example, silver). Those materials could be deposited from the vapor phase using sputtering or evaporation, or in the liquid form of suspension particles (nanoink) or in the Sol-Gel form by spinning, dip-coating, slot-die coating, xerography, gravure, screen printing, inkjet printing, microcontact printing, aerosol deposition or others).
The substrate could be additionally pre-patterned with hydrophobic (superhydrophobic) and hydrophilic (superhydrophilic) areas to enhance resolution or control adhesion or structure of deposited materials.
In order to reduce visibility of piezoelectric or conductive features to the human eye, e.g., from a distance of a couple of feet (for a car windshield, for example) the pattern preferably has features with a linewidth of less than 5 micron, more preferably less than 3 micron linewidth, and ideally less than 2 micron linewidth.
The deposition may be done according to any desired pattern (for example, a one-dimensional grating of straight or curved lines or a two-dimensional mesh or an array of small islands, etc.).
The pattern could be uniform/continuous over the surface or divided to multiple areas individually addressable by application of ultrasonic power in order to be able to forward power only to the area where cleaning is necessary.
A substrate, for example glass, is coated with the following thin film stack using, for example, sputtering technique: a thin metal film (for example, silver), a layer of piezoelectric material (for example, PZT), and another thin metal film (for example, silver). Then this stack is then patterned using a suitable patterning technique, for example, laser ablation. Alternatively one can use any of the following patterning techniques followed by material etching: electron-beam lithography, ultraviolet (UV) lithography, nanoimprint lithography, optical lithography, interference lithography, laser scanning lithography, self-assembly, etc. The type of lithography may be chose based on considerations of cost, scalability, and resolution of patterning required for achieving a specific optical, mechanical and cosmetic performance of the device being fabricated.
As shown in
The substrate (11) may be any suitable transparent material, e.g., glass, plastic, etc. The PZT layer stack (piezoelectric material 15 sandwiched between metal films 14) may be formed directly on a surface of the substrate (11). In alternative implementations, the PZT layer stack may be formed on a layer of soft material (16) between the PZT layer stack and the substrate (11), as shown in
In this embodiment, a substrate is coated with a polymer layer, which is then patterned, e.g., using a nanoimprint method. Then, the following materials stack is deposited in protrusions formed as a result of nanoimprint patterning: a metal layer, a piezoelectric material layer, and finally another metal layer. Alternatively, just metal and piezo-electric material if an interdigitated design is used.
In this embodiment, a substrate with conductive layer is patterned with superhydrophobic material (e.g., a self-assembled monolayer) using lithography and lift-off, laser ablation or direct microcontact printing. Then piezoelectric material (PZT) is deposited and annealed; PZT on top of superhydrophobic material can't be crystalized and remains amorphous, thus could be removed during lift-off process.
As shown in
In this embodiment, a substrate is coated with a photosensitive layer, e.g., a photoresist (or multiple layers of photoresist). Then the photosensitive layer is patterned using an optical lithography that assures a reentrant profile of the patterned photoresist features. The pattern includes interdigitated lines or trenches. The substrate is then coated with metal material. Then a lift-off process is done by dissolving photosensitive layer (or layers) to yield a microstructured metal stack on the substrate surface. Finally, a transparent piezoelectric film, for example polyvinylidine fluoride—PVDF films (Kynar® Film & Solef® Film or others), is laminated to the substrate over the patterned electrodes on the substrate surface with an impedance matching material sandwiched between the piezoelectric film and the electrode pattern.
As shown in
As seen in
There are a number of ways to implement Embodiments VIII and IX.
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.
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 At 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=cΔt, where c is a known or estimated speed of sound.
Aspects of the present disclosure allow for ultrasonic transducers to be integrated directly into transparent structures such as vehicle windshields, architectural glass, solar panels, and video displays in a manner that is invisible to the human eye. Integrating ultrasonic transducers into such structures opens up possibilities for implementing self-cleaning, acoustic range finding, gesture recognition and other capabilities in transparent structures.
Applications of transparent ultrasonic transducers include many other applications in addition to those described above. Another possible application of transparent ultrasonic transducer array is glass/window/display-integrated speaker. This may be implemented, e.g., by modifying the system shown in
Another potential application is distance sensing or proximity tooling for medical testing or operations, where a microscope or camera lens or other optics must be in a very close proximity to the tissue, but not touching it. For example, intraocular pressure measurements. A transparent range-finder integrated in an optical fiber or optical lens could be very useful in such applications.
Yet another application depicted in
A variation on the application illustrated in
Aspects of the present disclosure are not limited to the above embodiments. Numerous other embodiments are within the scope of the present disclosure.
By way of example, and not by way of limitation, transparent ultrasonic transducers may be integrated into a display, such as a flat screen television, computer monitor, smart phone display or tablet computer display. For example, as seen in
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.”
This Application claims the priority benefit of International Patent Application Number PCT/US2016/021836, filed Mar. 10, 2016, the entire disclosures of which are incorporated herein by reference. International Patent Application Number PCT/US2016/021836 claims the priority benefit of International Patent Application Number PCT/US2016/015448, filed Jan. 28, 2016, the entire contents of which are incorporated herein by reference. International Patent Application Number PCT/US2016/021836 also claims the priority benefit of U.S. Provisional Patent Application No. 62/117,906 filed Mar. 16, 2015, the entire disclosures of which are incorporated herein by reference.
Number | Date | Country | |
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62117906 | Mar 2015 | US |
Number | Date | Country | |
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Parent | PCT/US2016/021836 | Mar 2016 | US |
Child | 15645991 | US | |
Parent | PCT/US2016/015448 | Jan 2016 | US |
Child | PCT/US2016/021836 | US |