Patent Grant
9507464
Embodiments discussed herein are related to, in general, touch sensors using Lamb waves to detect a touch event and a location of a touch.
Touch sensor systems, such as those used with display screens to form touch displays, may act as input devices for interactive computer systems. Such systems may also be used for applications such as information kiosks, computers, order entry systems for restaurants, video displays or signage, mobile devices, etc. By integrating a touch sensor system into a computing device, the computer may provide a user an intuitive, interactive human-machine-interface.
Commercially, the cosmetic look and industrial design of touch devices as well as the cost, robustness, and reliability of such devices is becoming increasingly important. However, the components, physics, and other scientific principles that are leveraged to provide such functionality often inhibit or even degrade certain features and combinations of features that are desirable.
Through applied effort, ingenuity, and innovation taking advantage of an unexpected result, many identified problems of existing touch sensor systems have been solved by developing solutions that are included in embodiments of the present invention, some examples of which are described herein.
Systems, apparatus and related methods are provided to, in general, enable touch sensors using high sensitivity Lamb waves. In one exemplary example, a transmitting transducer mounted on the back of a substrate may be excited to generate a (transmit) surface acoustic wave signal coupled to the back surface of the substrate. A mode conversion array on the back of the substrate may be configured to coherently scatter the surface acoustic wave into a near-longitudinal-resonance Lamb wave that propagates through a touch region (e.g., of the front surface) of the substrate where a user may touch the substrate and, thereby interact with the touch sensor system and impact change in a connected computer system. A second mode conversion array on the back of the substrate may be configured to convert the near-longitudinal-resonance Lamb wave, or the resulting near-longitudinal-resonance Lamb wave in the event of a touch event, into a (return) surface acoustic wave that is coupled to the back of the substrate and may be detected by a receiving transducer mounted on the back of the substrate. The signal received by the receiving transducer may be provided to a processing device for detection of a touch event and a location of a touch, which information may be used by the connected computer system.
For example, some embodiments may include a touch apparatus comprising a substrate. The substrate may have a front surface with a touch region and a back surface. The touch apparatus may be configured to propagate surface acoustic waves on at least a portion of the back surface and near-longitudinal-resonance Lamb waves in at least a portion of the touch region of the substrate.
In some embodiments, the near-longitudinal-resonance Lamb waves may propagate through the touch region with a phase velocity VP, the surface acoustic waves may propagate on the back surface with a velocity VSAW, and VP may be at least about three times VSAW. In some embodiments, the near-longitudinal-resonance Lamb waves may propagate through the touch region at an operating frequency f; the substrate may have a bulk pressure wave velocity VLONG and a thickness d, and d may be greater than (m/2)*(VLONG/f) and less than (5/4)·(m/2)·(VLONG/f), where m is a positive integer.
Some embodiments may provide for a touch apparatus that includes one or more mode conversion arrays. For example, a mode conversion array may be disposed on the back surface of the substrate outside of the touch region. The mode conversion array may be configured to coherently scatter a surface acoustic wave that propagates in a first direction along a length of the mode conversion array into a near-longitudinal-resonance Lamb wave that propagates in a second direction through the touch region.
In some embodiments, the mode conversion array may include multiple reflector elements disposed along the first direction. The multiple reflector elements may be formed from at least one of the group of glass frit, ceramic, loaded polymer, and etched grooves. In some embodiments, the near-longitudinal-resonance Lamb waves may propagate through the touch region with a phase velocity VP; the surface acoustic waves may propagate on the back surface with velocity VSAW; the first direction and the second direction may define a scattering angle Φ; the mode conversion array may include multiple reflector elements disposed along the first direction, each reflector element of the multiple reflector elements disposed at a reflector angle θ relative to the first direction; and cos(θ)/VSAW=cos(θ−Φ)/VP. In some embodiments, the near-longitudinal-resonance Lamb waves may propagate through the touch region at an operating frequency f; and a distance S along the first direction between two consecutive reflector elements of the multiple reflector elements may be given by S=n*(VSAW/f)/(1−(VSAW/Vp)*cos(Φ)), where n is an integer. For example, the scattering angle Φ may be 90°.
In some embodiments, the mode conversion array may be coupled to the back surface of the substrate via an acoustically beneficial layer configured to decrease surface acoustic wave oscillation from the back surface to the front surface of the substrate.
Some embodiments may provide for a touch sensor configured to minimize dispersion. For example, a touch sensor may include one or more transducers and a controller. The transducer be disposed on the back surface of the substrate and configured to generate surface acoustic waves. The controller may be configured generate an excitation signal having an operating frequency f that drives the transducer. The excitation signal may include a frequency spread Δf around the operating frequency f. The near-longitudinal-resonance Lamb waves may propagate through the touch region of the substrate at the operating frequency f with the frequency spread Δf.
In some embodiments, the controller may be further configured to anti-disperse the excitation signal with a frequency dependent phase error configured to compensate for dispersion of the near-longitudinal-resonance Lamb waves caused by propagation of the near-longitudinal-resonance Lamb waves through the substrate with the frequency spread Δf. For example, the near-longitudinal-resonance Lamb waves may propagate through the substrate with a group velocity VGLAMB that varies with varying operating frequencies; and the operating frequency f may be near an inflection point of the group velocity VGLAMB as a function of the varying frequencies. Additionally and/or alternatively, the group velocity VGLAMB may have a low frequency dependence within the frequency spread Δf.
In some embodiments, the near-longitudinal-resonance Lamb waves may propagate a distance L through the touch region; the near-longitudinal-resonance Lamb waves may propagate with a group velocity VGLAMB; the surface acoustic waves may propagate on the back surface with velocity VSAW; a touch on the front surface of the substrate in the touch region may define a distance ΔX; and (VSAW/VGLAMB)*|d(ln(VGLAMB)/d(ln(f))| may be less than or equal to 2*(ΔX/L)/(f/Δf). In some embodiments, the near-longitudinal-resonance Lamb waves may propagate a distance L through the touch region; the near-longitudinal-resonance Lamb waves may propagate with a group velocity VGLAMB; the surface acoustic waves may propagate on the back surface with velocity VSAW; and (VSAW/VGLAMB)*|d(ln(VGLAMB)/d(ln(f))| may be less than 4 or equal to 4.
In some embodiments, the substrate may have a thickness d; the touch apparatus may have an operating frequency f; and the substrate may be configured to propagate the near-longitudinal-resonance Lamb waves at a frequency-thickness product f*d greater than 9.00 MegaHertz-millimeter and less than (5/4)*9.00 MegaHertz-millimeter.
Some embodiments may provide for a touch apparatus configured to facilitate bezel-less designs and other cosmetic advantages. For example, the touch apparatus may include mounting tape disposed on the back surface of the substrate that defines a mounting tape periphery region of the back surface of the substrate outside of the touch region of the front surface of the substrate. The mounting tape may be configured to protect at least one transducer and at least one mode conversion array disposed on the back surface within the mounting tape peripheral region from contaminants when the mounting tape is attached to a display device.
In some embodiments, a connecting portion of the substrate between the front surface and the back surface may be substantially planar. For example, the connecting portion may be flat. In other examples, the connecting portion may be virtually any shape and may be substantially non-planar.
In some embodiments, the touch apparatus may include a coversheet. The coversheet may be disposed at the front surface of the substrate and configured to receive a touch that attenuates the near-longitudinal-resonance lamb waves in at least the portion of the touch region of the substrate. In some embodiments, the coversheet may include a front surface, back surface, and an opaque coating disposed on the back surface, the opaque coating defining an opaque periphery region of the back surface of the coversheet; and a perimeter adhesive bonding material disposed between the front surface of the substrate and the opaque coating, the perimeter adhesive bonding configured to adhere the coversheet to the substrate.
In some embodiments, a perimeter edge of the substrate may be non-linear. For example, the perimeter edge may be curved, angled, or the like. In some embodiments, the touch apparatus may further include a graphic disposed on the back surface and/or front surface of the substrate outside of the touch region.
Some embodiments of the touch apparatus may provide redundant touch determination and/or characteristics of touch determination using high sensitivity Lamb waves. For example, the touch apparatus may be configured to propagate near-sheer-resonance Lamb waves in the touch region of the substrate. In some embodiments, the touch apparatus may further include a controller configured to redundantly determine a location of a touch within the touch region based on an electrical return signal that represents a first attenuation of the near-longitudinal-resonance Lamb waves and a second attenuation of the near-sheer-resonance Lamb waves in the touch region caused by the touch. For example, the controller may be configured to compare to compare a magnitude of the first attenuation with a magnitude of the second attenuation.
Some embodiments may provide for a method of detecting a location of touch on an acoustic touch apparatus. For example, the method may include: generating an electrical excitation signal; sending the electrical excitation signal to a transmitting transducer disposed on a back surface of a substrate, the transmitting transducer configured to transform the electrical excitation signal to an acoustic wave that couples to the substrate as a surface acoustic wave; receiving an electrical return signal from a receiving transducer disposed on the back surface of the substrate, the receiving transducer configured to transform the acoustic wave into the electrical return signal, wherein the electrical return signal represents the acoustic wave including an attenuation that occurs from a touch on a front surface of the substrate while propagating through a touch region of the substrate as a near-longitudinal-resonance Lamb wave; and determining a location of the touch based on the electrical return signal.
In some embodiments, the near-longitudinal-resonance Lamb wave may propagate through the touch region with a phase velocity VP; the surface acoustic wave may propagate on the back surface with a velocity VSAW; and VP may be at least about three times VSAW. In some embodiments, generating the electrical excitation signal may include generating the electrical excitation signal with an operating frequency f; the near-longitudinal-resonance Lamb wave may propagate through the touch region at the operating frequency f; the substrate may have a bulk pressure wave velocity VLONG; the back surface and the front surface of the substrate may be separated by a thickness d; and d may be greater than (m/2)*(VLONG/f) and less than (5/4)·(m/2)·(VLONG/f), where m is a positive integer.
In some embodiments, the substrate may include a mode conversion array on the back surface of the substrate outside of the touch region. The mode conversion array may be configured to coherently scatter the surface acoustic wave as the surface acoustic wave propagates in a first direction along a length of the mode conversion array into a near-longitudinal-resonance Lamb wave that propagates in a second direction through the touch region. In some embodiments, the mode conversion array may include multiple reflector elements disposed along the first direction. The multiple reflector elements may be formed from at least one of the group of glass frit, ceramic, loaded polymer, or etched grooves. In some embodiments, the near-longitudinal-resonance Lamb wave may propagate through the touch region with a phase velocity VP; the surface acoustic wave may propagate on the back surface with velocity VSAW; the first direction and the second direction may define a scattering angle Φ; the mode conversion array may include multiple reflector elements disposed along the first direction, each reflector element of the multiple reflector elements disposed at a reflector angle θ relative to the first direction; and cos(θ)/VSAW=cos(θ−Φ)/VP. In some embodiments, a distance S along the first direction between two consecutive reflector elements of the multiple reflector elements is given by S=n*(VSAW/f)/(1−(VSAW/VP)*cos(Φ)), where n is a positive integer.
Some embodiments of the method may provide for minimizing dispersion for a touch apparatus. For example, generating the electrical excitation signal may include generating the electrical excitation signal with a frequency spread Δf around an operating frequency f. The near-longitudinal-resonance Lamb wave may propagate through the touch region of the substrate at the operating frequency f with the frequency spread Δf.
In some embodiments, the method may further include anti-dispersing the electrical excitation signal with a frequency dependent phase error before sending the electrical excitation signal to the transmitting transducer. The frequency dependent phase error may be configured to compensate for dispersion of the near-longitudinal-resonance Lamb wave caused by propagation of the near-longitudinal-resonance Lamb wave through the substrate with the frequency spread Δf.
In some embodiments, the near-longitudinal-resonance Lamb wave propagates through the substrate with a group velocity VGLAMB that varies with varying operating frequencies; and generating the electrical excitation signal may include generating the electrical excitation with the operating frequency f near an inflection point of the group velocity VGLAMB as a function of the varying operating frequencies. Additionally and/or alternatively, generating the electrical excitation signal may include generating the electrical excitation with the operating frequency f such that the group velocity VGLAMB has a low operating frequency dependence within the frequency spread Δf. In some embodiments, the near-longitudinal-resonance Lamb wave may propagate a distance L through the touch region; the near-longitudinal-resonance Lamb wave may propagate with a group velocity VGLAMB; the surface acoustic wave may propagate on the back surface with velocity VSAW; the touch on the front surface of the substrate in the touch region may define a distance ΔX; and (VSAW/VGLAMB)*|d(ln(VGLAMB)/d(ln(f))| may be less than or equal to 2*(ΔX/L)/(f/Δf). In some embodiments, the near-longitudinal-resonance Lamb wave may propagate a distance L through the touch region; the near-longitudinal-resonance Lamb wave may propagate with a group velocity VGLAMB; the surface acoustic wave may propagate on the back surface with velocity VSAW; and (VSAW/VGLAMB)*|d(ln(VGLAMB)/d(ln(f))| may be less than or equal to 2*(ΔX/L)/(f/Δf).
Some embodiments of the method may provide redundant touch determination and/or characteristics of touch determination using high sensitivity Lamb waves. For example, the electrical return signal may represent the acoustic wave including a second attenuation that occurred from the touch on a front surface of the substrate while propagating through a touch region of the substrate as a near-sheer-resonance Lamb wave. The method may further include redundantly determining the location of the touch based on the electrical return signal that represents the acoustic wave including the attenuation of the near-longitudinal-resonance Lamb wave and the second attenuation of the near-sheer-resonance Lamb waves in the touch region caused by the touch. The method may further include comparing a magnitude of the attenuation represented by the electrical return signal with a magnitude of the second attenuation represented by the electrical return signal.
Some embodiments may include one or more machines, such as an apparatus and/or system, configured to implement the methods and/or other functionality discussed herein. For example, the machine may include circuitry and/or one or more processors and/or other machine components configured to implement the functionality discussed herein based on instructions and/or other data stored in memory and/or other non-transitory computer readable media.
These characteristics as well as additional features, functions, and details of various embodiments are described below. Similarly, corresponding and additional embodiments are also described below.
Having thus described some embodiments in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments contemplated herein are shown. Indeed, various embodiments may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
Some embodiments may provide for touch sensors that use high sensitivity Lamb waves in the touch region, such as near-longitudinal-resonance Lamb waves or near-Lamé waves. Typically, particle motion at the surface of a substrate propagating a Lamb wave of a given power is substantially lower than for a surface acoustic wave (SAW or Rayleigh) wave of the same power, resulting in Lamb wave touch sensitivity being much less than touch sensitivity for SAW. Conventional wisdom is that desired touch sensitivity is difficult to achieve without using SAW in the desired touch area. As such, some bezel-less SAW touchscreen designs (e.g., using only surface acoustic waves) may place transducers and reflective arrays on the back side of the substrate and provide for precisely rounded substrate edges that enable transfer of SAW between back (where the SAWs are generated and collected) and front surface (e.g., where the SAWs traverse in between generation and collection to be attenuated by a touch event), as described in further detail in U.S. Patent Application No. 2011/0234545, titled “Bezel-less Acoustic Touch Apparatus.” Such bezel-less SAW touchscreen products have been met with commercial success, but are costly to manufacture because the precisely rounded substrate edges must be carefully controlled. Further, because a surface acoustic waves transfer from the back surface to the front surface of a substrate and from the front surface to the back surface of a substrate by following the precisely rounded substrate edges, other elements, such as graphics and mounting tapes, can inhibit or degrade use of this type of surface acoustic wave touch systems, and embodiments of the present invention may be used instead.
Under specific conditions described herein, Lamb waves may have much higher touch sensitivities than would normally be expected. Furthermore, some embodiments may provide for low-dispersion and/or reduced susceptibility to parasitic signals. Because Lamb wave are touch sensitive on both sides of the substrate (e.g., unlike surface acoustic waves), bezel-less touch sensor designs may be achieved (e.g., where transducers and reflective arrays are placed on the back surface of the substrate) without requiring that the substrate include precisely rounded substrate connecting edges, or connecting portions.
Other example, but non-exhaustive, advantages that may be realized by various embodiments using high sensitivity Lamb waves, may include anti-dispersion for more accurate touch sensing, larger touch sensor sizes, multi-touch detection (e.g., XYU sensors), smaller touch sensor thickness, flexibility in touch sensor profile shapes and/or industrial design, redundant touch sensing, nature of touch differentiation.
Front surface 120 may include touch-sensitive region 205 (or touch region 205) on which an object 135 (as shown in
Substrate 105 may serve as a propagation medium that supports propagation of surface acoustic waves (SAW) and Lamb waves. Surface acoustic waves and Lamb waves, as discussed in greater detail below, are different types of acoustic waves. In some embodiments, substrate 105 may be transparent and isotropic. Substrate 105 may comprise any suitable glass (e.g., soda lime glass; boron-containing glass, e.g., borosilicate glass; barium-, strontium-, zirconium- or lead-containing glass; crown glass), and/or other suitable material(s). For example, a material capable of propagating surface acoustic waves and Lamb waves with a relatively low loss, thereby resulting in better signals, may be preferred according to some embodiments. In some embodiments of touch sensors that are not intended to be used as touch screens (for example, those intended to be used as a peripheral touchpad or integrated trackpad), one or more opaque substrate materials, having acceptable acoustic losses (such as aluminum and/or steel), may be used in touch sensitive region 205.
One or more acoustic wave transducers 110 may be positioned on, or otherwise coupled to, back surface 125 of substrate 105. Various types of transducers may be used in accordance with some embodiments. As referred to herein, a “transducer” includes a physical element or set of elements that transforms energy from one form to another, such as between electrical energy and a desired form of acoustic energy. For example, transducers 110 may include one or more piezoelectric elements that function as acoustically emissive and/or sensitive structures. Any device that may be configured to transform electrical energy to acoustic energy or acoustic energy to electrical energy may be a transducer or transducing means, in accordance with some embodiments.
Transducers 110 may be disposed on back surface 125 for transmitting and/or receiving acoustic waves. A “transmitting transducer,” as used herein, refers to at least one of transducers 110 that is configured to transform electrical energy into a desired form of acoustic energy. For example, a transmitting transducer may include one or more electrodes that are coupled to a controller. The controller may be configured to generate one or more electrical signals, such as pseudo sinusoidal wave tone bursts at one or more desired frequencies. These electrical signals, which are generated by the controller and provided to the transmitting transducer, are sometimes referred to herein as “excitation signals.” The excitations signals may be applied to the electrodes of the transmitting transducer to cause the piezoelectric element therein to vibrate, thereby transforming electrical signals into acoustic waves having one or more controllable and configurable characteristics (e.g., operating frequency, phase velocity, etc.).
A “receiving transducer,” as used herein, refers to at least one of transducers 110 that is configured to transform acoustic energy into a desired form of electrical energy. A receiving transducer may include, for example, electrodes coupled to the controller, a piezoelectric element, a wedge shaped coupling block, and/or any other suitable component(s). As such, surface acoustic waves traveling through the substrate may cause vibrations in the piezoelectric element (e.g., via the coupling block), which in turn causes an oscillation voltage to appear on the electrodes. In some embodiments, a single physical transducer may serve as both receiving transducer and a transmitting transducer.
At the receiving transducer, the oscillation voltage on the electrodes may include amplitudes that correspond with amplitudes of return surface acoustic waves received at the receiving transducer. Thus, when perturbations, such as those caused by a touch event, attenuate acoustic waves propagating on the substrate between a transmitting transducer and receiving transducer, the attenuation also appears at the electrodes of the receiving transducer in the form of a voltage perturbation, such as attenuation 1380 of return signal 1302 shown in
One or more reflective arrays 115 may be placed on back surface 125 of substrate 105. Each reflective array 115 may include a plurality of reflector elements. In some embodiments, one or more of the reflector elements may be configured to purposefully function as inefficient reflectors that (1) allow a substantial portion of an acoustic wave to pass un-scattered as the acoustic wave propagates along the reflective array, and (2) cause the coherent scattering of a relatively small portion of the acoustic wave. In some embodiments, one or more of the reflective arrays 115 may be mode conversion arrays. A mode conversion array, as used herein, refers to a reflective array that is also configured to transform (e.g., via coherent scattering) acoustic energy from a first acoustic mode to a second acoustic mode, such as from surface acoustic wave mode into a Lamb wave mode and/or vice versa.
Reflective arrays 115 may be formed in any suitable manner. For example, reflective arrays 115 may be formed from glass frit, ceramic, loaded polymer, and/or etched grooves. Reflective arrays 115 may be manufactured by printing, etching, stamping a metal substrate, and/or shaping a mold for a polymer substrate. In one example, reflective arrays 115 may be formed of a glass frit and/or UV curable ink that is silk-screened onto a glass sheet and/or other substrate material, such as formed by a float process, and cured in an oven to form a chevron pattern of raised glass interruptions, which may thereby function as the reflector elements discussed above. In some embodiments, the reflector elements may be configured to have heights and/or depths on the order of 1% of the surface acoustic wave wavelength within substrate 105 and, therefore, only partially couple and reflect the acoustic wave's energy as discussed above.
To detect a touch event, a transducer 115 may generate a surface acoustic wave that is propagated along a first mode conversion array. Referring to
In some embodiments, the Lamb wave propagating along path segment 150 may be sensitive to touch on both front surface 120 and back surface 125 of substrate 105. In most applications, the touch sensitivity of only one surface (typically referred to as the front surface) is used while the other surface (typically referred to as the back surface) is inaccessible to touches and is facing a display device a short distance away (e.g., as shown in
In various embodiments, different types of acoustic waves may be propagated along path segments 140, 150, and 160. If SAW is propagated along path segments 140 and 160 and Lamb waves are propagated along path segment 150, then touch sensor 100 may be referred to as a SAW-LAMB-SAW sensor. If LAMB waves are propagated along path segments 140, 150, and 160, then touch sensor 100 may be referred to as a LAMB-LAMB-LAMB sensor. Similarly, if surface acoustic waves are propagated along path segments 140, 150, and 160, then the touch sensor may be referred to as a SAW-SAW-SAW sensor. Similar comments may apply to acoustic paths from transmitting transducer 110c to receiving transducer 110d (e.g., using reflective arrays 110d and 110c), which may be used to determine another touch coordinate (e.g., the Y-coordinate) of the touch event.
In some embodiments, the operating frequency f (e.g., of the excitation signal) and the thickness d of substrate 105 may be selected to support a particular Lamb wave mode of desired properties, as discussed in further detail below. The reflector elements in reflective arrays 115 may be oriented to support coherent scattering in the desired direction and between desired acoustic modes (e.g., as mode conversion arrays). For example, if it is desired that a surface acoustic wave along path segment 140 be scattered at 90° and mode converted to a Lamb wave along path segment 150, then a reflector angle θ between the reflector element (e.g., as shown for reflector element 116) and the direction of the acoustic path 140 may be chosen to satisfy the relation:
tan(θ)=VP/VSAW Equation 1,
where VP and VSAW are respectively the phase velocity of the Lamb wave of path segment 150 and the phase velocity of the of path segment 140.
In
In some embodiments, touch sensor 100 may support a bezel-less touch/display design (such as shown in
In some embodiments, touch sensor 100 may further include mounting material 225 at the outer perimeter of substrate 105 on back surface 125. Mounting material 225 may be, for example, foam mounting tape (such as 3M VHB). In many bezel-less applications, it may be desirable to not only protect transducers 110 and reflective arrays 115, but also to visually hide them for cosmetic reasons. For this reason, touch sensor 100 may include acoustically benign layer 270 as illustrated in
Display device 310 may be, for example, a liquid crystal display (LCD), organic light emitting device (OLED) display, electrophoretic display (EPD), vacuum fluorescent, cathode ray tube, and/or any other display component. In some embodiments, display device 310 may provide a graphical user interface compatible with touch inputs. Display device 310 may be positioned such that it is visible through substrate 105, thereby enabling a person viewing front surface 120 of substrate 105 to see display device 310 through substrate 105. In some embodiments, display device 310 may be optically bonded to back surface 125. For example, display device 310 may be bonded to back surface 125 via acoustically benign layer 270 and mounting tape 225. Touch controller 315 may be configured to control transducers 110 and to determine touch coordinates.
Housing 320 may contain and protect display device 310, transducers 110, reflective arrays 115, touch controller 315, as well as other components of the device that are not shown to avoid unnecessarily overcomplicating the drawings. One or more of the components of touch sensor device 300 may be attached via housing 320. In some embodiments, touch sensor 105 may be flush mounted within housing 320 such that front surface 120 is flush with (e.g., at the same height) as the top of housing 320. Furthermore, in some embodiments, substrate 105 may be separate from housing 320 by an air gap 302.
For cosmetic reasons, it is often desirable that acoustically benign layer 270 extend all the way to the edge of substrate 105 at connecting surface 130, as is shown in
In addition to holding substrate 105 in place, mounting tape 225 may also provide a seal that protects reflective arrays 115 and transducers 110 from dust, water, and other contaminants in the environment. In bezel-less designs using precisely rounded connecting surfaces 130, mounting tape 225 must be inside the reflective arrays 115 (e.g., in an inactive region) to prevent unwanted attenuation of surface acoustic waves caused by mounting tape 225. As such, a separate outer seal is required to protect reflective arrays 115 and transducers 110 from contaminants. For touch sensor 300, because mounting tape 225 may be in an acoustically inactive region of substrate 105 that also serves as a seal, the complexities of designing and manufacturing the outer seal (e.g., to properly interface with rounded connecting surfaces) is avoided. Furthermore, by avoiding the need of the outer seal and by eliminating the added substrate width of rounded connecting surfaces, touch sensor 300 may include decreased border widths relative to conventional bezel-less touchscreen designs.
By avoiding the need of a seal in addition to the mounting tape, and by eliminating the width in plan view of a rounded glass edge, the design of
The term “Lamb wave” covers a wide variety of possible waves with widely varying properties depending on choices of substrate thickness d, operating frequency f, and specific choice of Lamb wave mode. As is expected because acoustic power of a Lamb wave is distributed throughout the substrate thickness d rather than bound to one surface like surface acoustic waves, Lamb waves generally have dramatically less sensitivity to touches than surface acoustic waves. However, the inventors have appreciated that under exceptional circumstances Lamb waves may have touch sensitivity approaching surface acoustic wave touch sensitivity. A “high sensitivity Lamb wave,” as used herein, refers to Lamb waves of such exceptional circumstances.
One type of high sensitivity Lamb wave is referred to herein as “near-thickness-resonance Lamb wave” or “near-resonance Lamb wave.” Near-resonance Lamb waves may be defined with reference to
Two alternate and unitless horizontal axes 408 and 410 are also included in
With reference to
However, not all Lamb modes close to cut-off are high sensitivity Lamb waves. All cut-off values correspond to an integer or half-integer value on one of the two unitless horizontal axes 408 and 410 of
dCUT-OFF=(k/2)·(VSHEAR/f)=(k/2)·λSHEAR Equation 2,
dCUT-OFF=(m/2)·(VLONG/f)·(m/2)·λLONG Equation 3a,
where k and m are any integers. In
At the longitudinal thickness resonance, Lamb waves having zero group velocity are of little use for propagation across a touch area. Thus for a near-longitudinal-resonance Lamb wave corresponding to integer m, a substrate thickness greater than the cut-off thickness is desired. However it is not desired to have a substrate thickness too much thicker than the cut-off thickness. The thickness is too much thicker if it no longer meets the near-longitudinal-resonance condition of a phase velocity more than three times the SAW velocity. Inspection of
d>(m/2)·(VLONG/f)=(m/2)·λLONG Equation 3b,
d≦(5/4)·(m/2)·(VLONG/f)=(5/4)·(m/2)·λLONG Equation 3c.
Lamb modes near their cut-off are not “high sensitivity” if their cut-off thickness is an integer multiple of half the shear wavelength λSHEAR. Such lamb modes are also referred to herein as “near-shear-resonance Lamb waves.” As stated above, not all Lamb modes close to cut-off are high sensitivity Lamb waves.
The dot-dashed curves in
Table 550 shown in
To gain insight into the source of the relatively high touch sensitivity of near-longitudinal-resonance Lamb waves of
In the cut-off limit, this S4 Lamb wave becomes the thickness resonance illustrated in
Large vertical or perpendicular surface motion may be associated with higher touch sensitivity. The high sensitivity of surface acoustic wave touchscreens (e.g., that use surface acoustic waves in the touch region) to touches is due to the radiation damping mechanism (e.g., emission of pressure waves into finger flesh) which depends on perpendicular surface motion. The much lower touch sensitivity (in units of dB signal reduction) of shear touchscreens (e.g., that use shear waves in the touch region) is due to the fact that its surface motion is only in the plane of the surface and hence touch induced attenuation depends on a viscous damping mechanisms that are much weaker than the radiation damping mechanism. As such, high sensitivity Lamb waves or near-longitudinal-resonance Lamb waves may have relatively large perpendicular surface motion compared with surface motion within the plane of the surface.
Returning to
As discussed above, the values in Tables 500 and 550 are for a nominal operating frequency f of 5.53 MHz and can be scaled for other operating frequencies. For examples, the entries may be multiplied by 5.53 MHz and then divided by the desired operating frequency (e.g., so as to keep the frequency-thickness product constant). Tables 500 and 550 correspond to two specific choices of Poisson's ratio (0.2638 and 0.2100, respectively) and can be recomputed for other values of Poisson's ratio. Table 570 corresponds to the same Poisson's ratio of 0.2638 as Table 500.
Tables of this sort are of value not only for selecting a desired high sensitivity Lamb mode, but also gaining insights on the threat of parasitic or spurious signals from other modes. For example, Table 500 identifies S4 as a potentially interesting high sensitivity Lamb mode in soda-lime glass.
In contrast, the A4 Lamb wave and SH5 shear wave will propagate in 1.8 mm glass at 5.53 MHz as will other modes in Table 500 to the left of S4. If, for example, the acoustic path segment 150 of sensor 100 is desired to be the S4 Lamb mode at 5.53 MHz in 1.8 mm soda-lime glass while the acoustic path segments 140 and 160 along the arrays to be surface acoustic waves, then the reflector elements in reflective arrays 115 may be not an angle of 45° (e.g., as seen in touch sensors without acoustic mode conversion, such as SAW-SAW-SAW sensors) but rather oriented at the reflector angle θ (e.g., the angle θ between the reflector element 116 and the direction of the acoustic path 140 shown in
tan(θ)=VS4/VSAW Equation 4,
where VS4 is the phase velocity Vp of the S4 Lamb wave mode.
In some embodiments, the reflector angle θ may be configured to satisfy the high sensitivity Lamb condition (e.g., when VS4/VSAW>3). Here, reflector angle θ is greater than 71°, such as shown in
Unlike S4 that is near the thickness resonance with vertical motion as illustrated in
The detailed mechanism of scattering of acoustic waves between acoustic path segments 140 and 150, and between acoustic path segments 150 and 160 may depend strongly on the polarizations of the waves involved as well as the materials used in the construction of reflective arrays 115. In various embodiments, the reflective arrays 115 may be fabricated by sintering of a ceramic material such as glass frit, or by UV curing, thermally curing or chemically curing a polymer material loaded with an inorganic materials, or by forming grooves via chemical etching or laser ablation. These different reflective array material options may affect the amplitudes of the desired and parasitic waves differently. By using different reflector material options, it may be possible to further suppress undesired parasitic modes. In various embodiments, for example, the reflector elements of reflective arrays 115 may be formed of glass frit, ceramic material, a loaded polymer material and etched grooves.
As discussed above, touch event detection may be performed by a controller (e.g., touch controller 315 shown in
In some embodiments, touch controller 315 may include ant-dispersion electronics configured to compensate for dispersion. One “anti-dispersion” approach to address Lamb wave dispersion is to use digital signal processing of the received signal to make corrections to compensate or eliminate the effects of dispersion. This approach may use electronics that digitize not only the magnitude of the received signal, but also digitizes its phase, or equivalently digitizes the complete RF waveform and not just its envelop. Examples of processing the received signal, applicable to some embodiments, are discussed in greater detail in U.S. Pat. No. 5,854,450, titled “Acoustic Condition Sensor Employing a Plurality of Mutually Non-orthogonal Waves,” which is incorporated by reference in its entirety herein.
In some embodiments, touch controller 315 may be configured to anti-disperse the electrical excitation signal that drives a transmitting transducer (e.g., transducer 110a shown in
ST(t)={1/√(2π)}·∫ST(ω)·eiωtdω
For a specific SAW-Lamb-SAW acoustic path such as illustrated in
SR(t)={1/√(2π)}·∫SR(ω)·eiωtdω
If the Lamb wave along acoustic path segment 150 (and the surface acoustic wave or other wave along acoustic path segments 140 and 160) are completely non-dispersive, then the received signal SR(t) would have exactly the same time dependence of the transmitted signal ST(t) except for a time delay TDELAY and an attenuation A. Stated mathematically we have the following equation for the no-dispersion condition:
SR(t)=A·ST(t−TDELAY)
With further mathematical manipulation, we have the following:
{1/√(2π)}·∫SR(ω)·eiωtdω=SR(t)=A·ST(t−TDELAY)=A·{1/√(2π)}·∫ST(ω)·eiω(t-Tdelay)dω={1/√(2π)}·∫{A·ST(ω)·e−iωTdelay}·eiωtdω
The equality of the extreme right and left sides of the equation above provides the no-dispersion condition in the frequency domain:
SR(ω)=A·ST(ω)·e−iωTdelay
When there is dispersion, frequency dependent phase errors δφ(ω) may be introduced so that the no-dispersion condition fails, that is SR(t)≠A·ST(t−TDELAY) or:
SR(ω)=A·ST(ω)·eiδφ(ω)·e−iωTdelay
where δφ(ω)≠0.
Referring to
In various embodiments, δφ(ω) may be pre-determined by experiment or theoretically from design. Next, an “anti-dispersed” electrical excitation signal S′T(ω) may be defined such that:
S′T(ω)=e−iδφ(ω)·ST(ω) Equation 5,
where ST(ω) is the Fourier transform of the non-anti-dispersed electrical excitation signal ST(t). In other, in some embodiments, controller 315 may be configured to generate the anti-dispersed electrical excitation signal S′T(ω) to correct for dispersion.
If the received signal is defined as S′R(t), if follows from Equation 5 that:
S′T(t)={1/√(2π)}·∫S′T(ω)·eiωtdω={1/√(2π)}·∫e−iδφ(ω)·ST(ω)·eiωtdω
S′R(ω)=A·S′T(ω)·eiδφ(ω)·e−iωTdelay=A·ST(ω)·e−iδφ(ω)·eiδφ(ω)·eiωTdelay=A·ST(ω)·e−iωTdelay
S′R(ω) is equal to A·ST(ω)·e−iωTdelay which is exactly that value of SR(ω) in the non-dispersion case. Hence by using the anti-dispersed excitation signal, the received signal at the receiving transducer will be dispersion corrected as shown by:
S′R(t)={1/√(2π)}·∫S′R(ω)·eiωtdω={1/√(2π)}·∫A·ST(ω)·e−iωTdelay·eiωtdω=A·ST(t−TDELAY)
In some embodiments, where acoustic path segments 140 and 160 of touch sensor 300 are also dispersive, then the phase error becomes dependent on the touch coordinate and delay time of the acoustic path. The delay time independent phase error δφ(ω) in Equation may be replaced by a delay time dependent phase error δφ(ω,TDELAY). To correct for this delay time dependence of the phase error, two excitation signals may be used to accurately measure a touch coordinate, such as using a first excitation pulse without anti-dispersion to approximately determine a location of a touch and hence an approximate value of TDELAY with which to determine δφ(ω,TDELAY) for use in a second excitation pulse that is anti-dispersed. As such, the anti-dispersed electrical excitation signal S′T(ω) may be defined such that:
S′T(ω)=e−iδφ(ω,T
where ST(ω) is the Fourier transform of the non-anti-dispersed electrical excitation signal ST(t). Alternately and/or additionally, the anti-dispersed excitation bursts may be repeated for a set of values for TDELAY so that every possible touch location is probed with at least one signal that is approximately corrected for dispersion.
In some embodiments, generation of anti-dispersed excitation signal S′T(t) may be accomplished with the aid of a Digital-to-Analog-Converter (DAC) with a conversion rate significantly higher that the touchscreen operating frequency f, preferably higher than about four times the touchscreen operating frequency f. For example, for a touchscreen operating frequency f of 5.53 MHz, a DAC conversation rate of 22 MHz or higher may be used.
In some embodiments, high sensitivity Lamb waves with sufficiently little dispersion may be used instead of, or in addition to, anti-dispersed excitation signals. For example, it may be desirable to minimize the demands on anti-dispersion features added to either the transmit excitation circuit or the receive signal circuit. Furthermore, in some embodiments, it may be desirable to avoid entirely the added complexity of such anti-dispersion correction technology. For example, it may be desirable to use controllers that are the same as or similar to present day commercial controller products that do not digitize received signal phase information or enable anti-dispersion modifications of excitation signals. For such embodiments, it may desirable to select a high sensitivity Lamb wave with sufficiently little dispersion.
A nominal operating frequency f is represented by the heavy vertical dashed line at 706, which in
As discussed above, touch coordinates may be determined by measuring time delays that are determined in part by wave velocities. Referring to
T=2*X/VSAW+L/VGLAMB
If a touch has a width ΔX, then the touch's finite width will correspond to a spread in delay times given by:
ΔTTOUCH=2*ΔX/VSAW
When the Lamb wave group velocity VGLAMB varies over the frequency range Δf, there may be another contribution to delay time spread whose absolute magnitude is given by the following formula:
ΔTDISPERSION=(L/VGLAMB)*|d(ln(VGLAMB)/d(ln(f))|*(Δf/f)
where (L/VGLAMB) is the propagation time for acoustic path segment 150, |d(ln(VGLAMB)/d(ln(f)| is the magnitude of a unit-less derivative involving natural logarithms that may be interpreted as the percent change in Lamb wave group velocity per percent change in frequency.
If delay time spread caused by Lamb wave dispersion ΔTDISPERSION is small compared to the time spread caused by the width of the touch ΔTTOUCH, then dispersion may have little practical effect on touch sensor operation. This small dispersion condition may be expressed in the following inequality:
ΔTTOUCH/ΔTDISPERSION≦1, or equivalently,
(½)·(L/ΔX)·(VSAW/VGLAMB)·|d(ln(VGLAMB)/d(ln(f))|·(Δf/f)≦1 Equation 7.
This small dispersion condition can also be expressed as follows:
(VSAW/VGLAMB)·|d(ln(VGLAMB)/d(ln(f))|≦2·(ΔX/L)/(f/Δf) Equation 8.
In a numerical example applicable to some embodiments, ΔX=12 mm (e.g., the size of a typical touch), L=200 mm and Δf/f=3%, the small dispersion condition of Equations 7 and 8 becomes:
(VSAW/VGLAMB)·|d(ln(VGLAMB)/d(ln(f))|≦4 Equation 9.
The small dispersion condition of Equations 7, 8 and 9 involve not the Lamb wave phase velocity VP, but rather the Lamb wave group velocity VGLAMB. While it is the phase velocity VP that is relevant for coherent scattering analysis such as the choice of orientation of the reflectors of arrays 115, it is the group velocity VGLAMB that determines propagation delay times for acoustic paths such as path segment 150.
The dotted curve in
For example, as shown in
In some embodiments, touch sensor 300 may be configured to utilize near-Lamé waves, or Lamb wave modes that are Lamé waves or are close to being Lamé waves. Similar to Lamb waves at longitudinal-resonance (e.g., as shown in
Lamé waves may be defined as a special case of Lamb waves. As illustrated in
VP=(√2)·VSHEAR
where VSHEAR is the bulk shear wave velocity. A horizontal solid line 906 corresponding to the phase velocity (√2)·VSHEAR is shown in
In other words, Lamé modes may exist when the substrate thickness dLAME is related to shear wavelength λSHEAR as follows:
dLAME=p·λSHEAR/√2 Equation 10,
where p is an integer. This Lamé mode condition can be reexpressed in terms of the operating frequency f and the bulk shear wave velocity VSHEAR as follows:
f·dLAME=p·VSHEAR/√2 Equation 11,
where p is an integer. In some embodiments, a “near-Lamé” wave may be defined as a Lamb mode that would become a Lamé mode if either the operating frequency f or the substrate thickness d were increased or decreased by 20%, or less, from their Lamé mode condition values as expressed in Equations 10 and 11, respectively.
In some embodiments, the touch sensor may use near-Lamé waves with low dispersion.
Table 1000 in
As discussed above,
In some embodiments, acoustically benign layer 270 (e.g., on which reflective arrays 115 and transducers 110 may be disposed, and as shown in
At first glance one might assume that the minimum acceptable substrate thickness d for SAW-LAMB-SAW sensors would be the same as for SAW-SAW-SAW sensors, after all, both must be thick enough to support surface acoustic waves. However, this may not be the case when acoustically beneficial layer 1202, as shown in
In
In some embodiments, acoustically beneficial layer 1270 and/or reflective arrays 115, via suppressing of beat effects, may allow for reduced substrate thicknesses d in SAW-LAMB-SAW sensors. This is because surface acoustic waves may be only propagated in regions of substrate with acoustically beneficial layer 1270 and/or reflective arrays 115. Hence it is possible to construct SAW-LAMB-SAW sensors using substrates that are too thin for SAW-SAW-SAW sensors. For example, 1.75 mm thick soda-lime is too thin to be a substrate for a SAW-SAW-SAW sensor operating at 5.53 MHz, but not too thin for a SAW-Lamb-SAW sensor operating at the same operating frequency f.
In some embodiments, near-shear-resonance Lamb waves may be used with near-longitudinal-resonance Lamb waves to provide redundant information to confirm a location of a touch and/or to determine information about the nature of the touch.
In the construction of the SAW-LAMB-SAW sensor, illustrated in
In some embodiments, the SAW-A7-SAW component of the signal received at transducer 1310b may be considered an undesired parasitic signal and touch sensor 1300 may be designed to suppress it. However, in other embodiments, the SAW-A7-SAW signal may be considered a desired secondary signal that provides additional redundant information to confirm a location of a touch and with which to determine information about the nature of the touch.
In some embodiments, the touch sensor may be designed so that the superposed signals due to SAW-S7-SAW and SAW-A7-SAW are in phase. In this case, the return signal perturbations 1380 and 1390 may take the form of attenuation dips as shown in
In some examples, differences in the acoustical properties of a bare fingertip and a covered fingertip (e.g., with a latex glove) may be used to determine whether a user is properly gloved when operating a touch interface of a device located in a biohazard area. In another example, a touch sensor may be disposed at the bottom of a drip pan that is placed under a leaking engine of an automobile, where “touches” of interest are caused by liquid drops. If the leaking liquid drops are of low viscosity, such as water from a radiator, then the ratio of touch perturbations 1390 and 1380 will be relatively smaller due to lack of viscous damping. In contrast, higher viscosity motor oils will results in larger ratios of touch perturbations 1390 and 1380.
In some embodiments, the touch sensor may include a phase sensitive controller configured to fully capture the information in the signal resulting from interfering SAW-S7-SAW and SAW-A7-SAW components of the return signal being that may well not be in phase. The phase sensitive controller may be configured to measure touch perturbations as changes in complex received amplitudes of the form:
|amplitude|*ei*phase Equation 12
This is in contrast to conventional measurement of touch perturbations as changes in the absolute magnitude (or envelope) of the received signal. Additional details regarding phase sensitive controllers, applicable to some embodiments, are discussed in U.S. Pat. No. 7,683,894, titled “Acoustic Condition Sensor Employing a Plurality of Mutually Non-orthgonal Waves,” which is incorporated by reference in its entirety herein.
In some embodiments, the touch sensor may have a curved or otherwise non-linear profile.
Furthermore, as illustrated by graphic items 1480a, 1480b and 1480c, decals, paint and all sorts to cosmetic additions can be added to the substrate at areas outside the acoustically active area with no effect on touchscreen function. In some embodiments, material may also be added over the reflective arrays, which may be less sensitive than touch region 1405 to the added material, as shown by graphic item 1482. As such, one or more graphics may be added outside of touch region 1405.
In some embodiments, touches may be sensed not only by Lamb waves propagating in the X and Y directions in the touch region (e.g., as shown in
Touch sensor 1500 may also include transmitting transducers 1512a and 1512d, receiving transducers 1512b and 1512c, reflective arrays 1517a, 1517b, 1517c and 1517d for determining U coordinates of touches. For example, transmitting transducer 1512a may be configured to generate a surface acoustic wave along path segment 1542, which via reflective array 1517a is scattered and mode converted to a Lamb wave propagating along path segment 1552, which in turn via reflective array 1517c is mode converted back to a surface acoustic wave propagating along path segment 1562 to receiving transducer 1512c. Acoustic paths from transmitting transducer 1512a to receiving transducer 1512c, may cover the half of the touch region below diagonal 1530. U coordinate measurement for the other half of the touch area above diagonal 1350 may be provided by acoustic paths from transmitting transducer 1512d, along reflective array 1517d, across the touch region, and along reflective array 1517b to receiving transducer 1512b. As such, the entire touch region may be provided with U coordinate measurement in addition to X and Y coordinate measurements of touches, providing touch sensor 1500 with enhanced multi-touch capabilities relative to touch sensor 100.
In some embodiments, reflective arrays 1517a, 1517b, 1517c and 1517d may include reflector elements having reflector angles θ and reflector spacing S (e.g., between two reflector elements) to support coherent scattering at a desired scattering angle Φ (e.g., including, but not necessarily, at 90°).
As shown in
L·cos(θ−Φ)
where L is the length of reflector 1580. In units of cycles, this corresponds to a phase delay of L·cos(θ−Φ)/λLAMB, where λLAMB is the wavelength of the Lamb wave propagating along acoustic path segment 1552. SAW rays 1562a and 1562b are shown as beginning at a common SAW front 1596 which may be aligned with the end of reflector 1580. Between the near end of reflector 1580 and the beginning of SAW ray 1562a is the SAW ray 1586 with length L·cos(θ) and corresponding phase delay of L·cos(θ)/λSAW, where λSAW is the SAW wavelength. The condition that reflector angle θ provides coherent scattering may be satisfied when phase delays from rays 1585 and 1586 are equal as expressed mathematically as (where the reflector length L drops out):
cos(θ)/λSAW=cos(θ−Φ)/λL Equation 13.
Dividing both sides of Equation 13 by the operating frequency f gives the following equivalent form of the coherent scattering condition for the reflector angle θ in terms of SAW and Lamb phase velocities VSAW and VP, respectively:
cos(θ)/VSAW=cos(θ−Φ)/VP Equation 14.
Equations 13 and 14 may be applicable not only to XYU sensor embodiments, but also to other touch sensor embodiments using any desired scattering angle Φ. For example, where desired scattering angle Φ is 90°, Equations 13 and 14 reduces to the same result as that given by Equation 1 above.
S/λSAW−S·cos(Φ)/λL=n Equation 15,
where n is a positive integer. Equation 15 (e.g., the spacing coherence condition) may also be re-expressed as:
S=n·λSAW/(1−(λSAW/λL)·cos(Φ)) Equation 16, or
S=n·(VSAW/f)/(1−(VSAW/VP)*cos(Φ)) Equation 17,
where n is a positive integer.
Equations 15, 16 and 17 may be applicable not only to XYU sensor embodiments, but also to other touch sensor embodiments using any desired scattering angle Φ. For example, where desired scattering angle Φ is 90°, Equations 15, 16 and 17 reduce to:
S=n·λSAW=n·(VSAW/f) Equation 18.
Mounting material 1530 may be placed around the perimeter of substrate 1505 to provide support as well as sealing the transducers and reflective arrays from the external environment.
U coordinate measurement for the other half of the touch region may be provided by acoustic paths between transmitting transducer 1610d and receiving transducer 1610b that include beam splitters 1627d and 1627b. Mounting material 1630 may be placed around the perimeter of substrate 1605 to provide support as well as sealing the transducers and reflective arrays from the external environment. The transducers, beam splitters and reflective arrays may be placed on the back surface 1626 of substrate 1605 and not on the front surface. As such, touch sensor 1600 may be utilized in a bezel-less touch sensor. In some embodiments, an acoustically benign coating and/or acoustically beneficial coating may be added between substrate 1605 and the transducers 1610, beam splitters 1627, and reflective arrays 1615.
In some embodiments, touch sensor 1655 may be configured to provide nature of touch information and/or redundant touch location determination using the detection of two touch types from each of the SAW-LAMB-SAW sub-system and the SAW-SAW-SAW sub-system. For example, a touch in the touch region may be sensed (e.g., simultaneously) by more than one type of wave, namely a high-sensitivity Lamb wave and a surface acoustic wave.
In some embodiments, a touch sensor may include a cover sheet. The coversheet may provide various benefits including response to any stylus and touch operation immunity to water and other contaminants.
As shown, adhesive bonding material 1730 may be disposed around the perimeter of front surface 1720 of touch sensor 1700. Adhesive bonding material 1725 may have no effect on the desired received signals as it is located away from the acoustically active portions of touch sensor 1700. Adhesive bonding material 1625 may be used to adhere, i.e., attach, a coversheet 1740, as is shown in
In some embodiments, coversheet 1740 may include a layered structure to enhance touch sensitivity and increase robustness. An exterior layer (e.g., at the top of coversheet 1740) may be a scratch and wear resistant hardcoat. A load spreading layer (e.g., structural layer of PET (polyethylene terephthalate)) may be disposed under the exterior layer. Under the relatively stiff load spreading layer may be a soft elastomer layer to provide conformability and hence good acoustic contact between coversheet 1740 and substrate 1705 at a touch location. In some embodiments, an additional non-stick layer (e.g., of hard, non-tacky polymer) may be added at the bottom of coversheet 1740 to avoid sticking. More details regarding coversheets applicable to some embodiments are discussed in U.S. Patent Application Publication No. 2011/0291996, titled “Multi-layer Coversheet for SAW Touch Panel,” which is incorporated by reference in its entirety herein.
In some embodiments, a touch sensor using one or more of the Lamb waves discussed herein may not include any reflective arrays.
For clarity, transducers 1820, 1830 and 1840 are shown in
In various embodiments, transducers 1820, 1830 and 1840, as well as the other transducers discussed herein, may be wedge transducers, interdigital transducers, or any other type of transducer capable of generating and/or received the desired wave modes.
In some embodiments, Lamb wave reflection by a substrate edge (e.g., edge 1880 shown in
As shown in
In one example, substrate 1905 of touch sensor 1900 may have a thickness d of 2 mm and may be composed of a glass with low acoustic attenuation. Examples of suitable low acoustic loss substrates, applicable to various embodiments, are described in U.S. Pat. Nos. 5,708,461, 6,236,391 and 6,441,809, each titled “Acoustic Touch Position Sensor Using a Low-loss Transparent Substrate,” and each hereby incorporated by reference in their entirety. Furthermore, operating frequency f may be chosen to support an S0/Lamé mode in a substrate of this material and thickness (e.g. as discussed above in connection with
If frequency dependence of viscosity is neglected, then wave attenuation rates may approximately scale as the square of operating frequency f, implying that a factor four drop in operating frequency f gives a factor 16 drop in attenuation, a factor of 16 increase in maximum possible acoustic path distance, and hence a factor 16 increase in maximum touchscreen size. Accounting for frequency dependent glass viscosity (e.g., decreasing with increasing operating frequency f for most suitable substrates), attenuation typically scales faster than linearly with frequency f but slower than the square of frequency f. As such, the advantage of S0/Lamé to operate at a factor of four lower frequency f than surface acoustic wave (e.g., for the same substrate thickness d) enables an increase in maximum touchscreen size relative to SAW by a factor about between 4 and 16.
In some embodiments, even larger touch sensors may be possible with the addition of additional transducers and/or reflective arrays. Touch sensor design that may be applicable in some embodiments (e.g., including eight transducer designs), are discussed in greater detail in U.S. Pat. No. 5,854,450, incorporated by reference above.
In some embodiments, a substrate (e.g., substrate 1905 or any of the other substrates discussed herein) may be made of aluminum. Acoustic attenuation in aluminum may be similar to that of low-loss glasses. Hence embodiments of touch sensor 1900 in which substrate 1905 is composed of aluminum may also support large touch sensor sizes (e.g., least 100 inches (2½ meters) diagonally in some embodiments).
In some embodiments, a thin white acoustically benign coating may be disposed on the front surface of aluminum substrate 1905. The coating may provide a touch region that serves as an electronic whiteboard, a projection screen which users can touch to interact with the displayed image, or the like.
In some embodiments, substrate 1905 (e.g., whether aluminum, glass, or otherwise) may be cylindrically curved about a vertical axis so that left edge 1970 is brought into contact to right edge 1972, resulting in a cylindrical shell with reflective arrays 1915 and transducers 1910 inside the cylindrical shell and the touch surface on the exterior of the cylindrical shell. In some embodiments, left edge 1970 and right edge 1972 may be welded or otherwise attached such that the cylindrical touch surface is smooth and uninterrupted.
A cylindrical shell is just one of many possible geometrical touch sensor configurations. Other example, but non-exhaustive, touch sensor geometries that may be used with the Lamb waves discussed herein are shown in U.S. Pat. No. 5,854,450, incorporated by reference above. Non-planar geometries may have application in robotics where touch and collision detection on exterior robot surfaces may be desirable. Furthermore, the techniques discussed herein may be leveraged in creating interactive environments in which normally passive surfaces such as table tops and wall surfaces become touch sensitive surfaces and are not limited to touch sensors placed in front of displays.
In some embodiments, method 2000 may be performed by touch controller 315. For clarity, method 2000 is described with reference to touch sensor 100 shown in
In some embodiments, the operating frequency f may be selected to support near-longitudinal-resonance Lamb waves (e.g., or near-Lamé waves for a LAME-LAME-LAME touch sensor) or other high-sensitivity Lamb wave suitable for touch sensing. For example, the properties of the substrate material (e.g., Poisson's ration, VSAW, VSHEAR, VLONG, etc.) may be determined. The thickness d of the substrate may be determined, cut, or otherwise manufactured. Based on the thickness d and the substrate material, the relationship between Lamb wave phase velocity Vp and frequency f may be determined (e.g., as shown in
In some embodiments, the operating frequency f may have a frequency spread Δf which can result in unwanted dispersion. As such, generating the electrical excitation signal may include anti-dispersing the electrical excitation signal with a frequency dependent phase error (e.g., δφ(ω)) before sending the electrical excitation signal to a transmitting transducer, where the frequency dependent phase error may be configured to compensate for dispersion of the acoustic wave (e.g., of near-longitudinal-resonance Lamb waves caused by propagation through the substrate with the frequency spread Δf).
In some embodiments, the operating frequency f may be selected for low dispersion. For example, generating the operating frequency f may include generating the operating frequency f such that the group velocity VGLamb has a low operating frequency dependence and/or where operating frequency f is near an inflection point of the group velocity VGLamb as a function of varying operating frequencies, as discussed above in connecting with
In some embodiments, the operating frequency f and/or thickness d can also be selected to facilitate redundant touch sensing and/or nature of touch determination (e.g., using near-shear-resonance and near-longitudinal-resonance Lamb waves), as discussed above in connection with
At 2006, the circuitry may be configured to transmit the electrical excitation signal to a transmitting transducer that is configured to transform the electrical excitation signal in an acoustic wave. As discussed above, the acoustic wave may vary depending on the type of touch sensor being used. If the sensor is a SAW-LAMB-SAW sensor, for example, then the acoustic wave may be surface acoustic wave. Similarly, if the sensor is LAME-LAME-LAME, then the acoustic wave may be a near-Lamé wave. In some embodiments, the acoustic wave may have the operating frequency f and the frequency spread Δf of the electrical excitation signal.
With reference to
At 2008, the circuitry may be configured to receive an electrical return signal from a receiving transducer (e.g., transducer 110b) that is configured to transform the acoustic wave into the electrical return signal. The electrical return signal may represent the acoustic wave subsequent to its propagation through the sensor. Thus, an attenuation in the acoustic wave, as may be caused by a touch event (e.g., in touch region 205 of front surface 120 of substrate 105 as shown in
At 2010, the circuitry may be configured to process the electrical return signal. Processing the electric return signal may include determining the location of the touch (e.g., a touch coordinate of the touch location) based on the electrical return signal. For example, the touch coordinate may partially represent (i.e., along one sensing axis) a physical location on the touch sensor where the attenuation occurred. The touch coordinate may be determined based on the timing of the attenuation in the electrical return signal. Details regarding techniques for determining touch coordinates based on the electrical return signal are discussed in greater detail in U.S. Provisional Patent Application No. 61/714,187, incorporated by reference above, and U.S. patent application Ser. No. 13/682,621, titled “Segmented Waveguide Core Touch sensor Systems and Methods,” which is hereby incorporated by reference in its entirety.
In some embodiments, processing the electrical return signal may include anti-dispersing the electrical return signal before determining the location of the touch. For example, anti-dispersing the electrical return signal may be performed if anti-dispersing was not performed on the electrical excitation signal at 2004. As discussed above, this approach may use electronics that digitize not only the magnitude of the electrical return signal, but also digitizes its phase. Method 2000 may then end at 2012.
Touch controller 2102 may include one or more processors 2102a configured to execute firmware and/or software programs stored in one or more memory devices 2102b to perform the functionality described herein. For example, touch controller 2102 may be coupled via wires, leads, and/or by any other suitable manner to transducers 2110 to control the transmission (e.g., at a desired operating frequency f) and reception of acoustic waves. Touch controller 2102 may further be configured to determine touch locations, anti-disperse signals, etc.
In some embodiments, touch controller 2102 may be configured to interface with a computer system, such as a personal computer, embedded system, kiosk, user terminal, and/or other machine as a human-to-machine interface device. The computer system may include main controller 2104 with one or more processors 2104a configured to execute firmware and/or software programs stored in one or more memory devices 2104b. Main controller 2104 may generate a visual component (and/or display element) that is sent to display device 2130 for display. The visual component may include or comprise a user interface that is operable using the touch sensor.
The computing system may further include other display devices, audio input and/or output capability, keyboard, electronic camera, other pointing input device, or the like (not shown). The computer system may operate using custom software, but more typically may use a standard and/or other type of operating system. In examples where the computing system is configured to enable use of other user input devices, the touch sensor may be employed as a primary or secondary input device.
Main controller 2104 may be communicatively connected with touch controller 2102. In some embodiments, touch locations may and/or other position information may be sent from touch controller 2102 to main controller 2104, allowing a user to interact with a program executing on main controller 2104 via the touch sensor. In some embodiments, touch controller 2102 may be further configured to map the touch coordinates to appropriate control actions that are sent to main controller 2104. For example, a multi-dimensional dataset (such as a two dimensional table) may be used to associate timing information of an acoustic wave attenuation with one or more coordinates representing a physical location of the sensor. In some embodiments, touch controller 2102 may transmit touch coordinates (e.g., XY or XYU) to main controller 2104.
While
In some embodiments, each processing/controlling component (e.g., processor 2102a and/or processor 2104a) of control system 2100 may be embodied as, for example, circuitry or other type of hardware elements (e.g., a suitably programmed processor, combinational logic circuit, and/or the like). The processing/controlling components may be configured by a computer program product comprising computer-readable program instructions stored on a non-transitory computer-readable medium (e.g., memory 2102b and/or memory 2104b) that is executable by a suitably configured processing, or some combination thereof.
Processor 2102a and/or processor 2104a may, for example, be embodied as various means including one or more microprocessors with accompanying digital signal processor(s), one or more processor(s) without an accompanying digital signal processor, one or more coprocessors, one or more multi-core processors, one or more controllers, processing circuitry, one or more computers, various other processing elements including integrated circuits such as, for example, an ASIC (application specific integrated circuit) or FPGA (field programmable gate array), or some combination thereof. Accordingly, although illustrated in
Whether configured by hardware, firmware/software methods, or by a combination thereof, processor 2102a and/or processor 2104a may comprise an entity capable of performing operations according to various embodiments while configured accordingly. Thus, for example, when processor 2102a and/or processor 2104a are embodied as an ASIC, FPGA or the like, processor 2102a and/or processor 2104a may comprise specifically configured hardware for conducting one or more operations described herein. Alternatively, as another example, when processor 2102a and/or processor 2104a are embodied as an executor of instructions, such as may be stored in memory 2102b and/or memory 2104a, the instructions may specifically configure processor 2102a and/or processor 2104a to perform one or more algorithms and/or operations described herein.
Memory 2102b and/or memory 2104b may comprise, for example, volatile memory, non-volatile memory, or some combination thereof. Although illustrated in
Embodiments have been described above with reference to a block diagram of circuitry and example process flowcharts describing functionality that may be implemented by one or more components of circuitry, such as those discussed above in connection with control system 2100 in combination with a touch sensor. Each block of the circuit diagrams and process flowchart, and combinations of blocks in the circuit diagrams and process flowchart, respectively, may be implemented by various means including computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus, such as processor 2102a and/or processor 2104a, to produce a machine, such that the computer program product includes the instructions which execute on the computer or other programmable data processing apparatus create a means for implementing the functions specified in the flowchart block or blocks.
These computer program instructions may also be stored in a computer-readable storage device (e.g., memory 2102b and/or memory 2104b) that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage device produce an article of manufacture including computer-readable instructions for implementing the function discussed herein. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions discussed herein.
Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the circuit diagrams and process flowcharts, and combinations of blocks in the circuit diagrams and process flowcharts, may be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions.
Many modifications of the embodiments set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
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