the inventor has developed a novel configuration for acoustic touch detection systems that consists of multiple substrates . it is built on a primary substrate and utilizes one or multiple secondary substrates for wave generation and propagation that are coupled to the primary substrate and have different properties therefrom . this present invention solves or improves three problems historically associated with such systems . the three problems summarized are : first , in a typical prior art arrangement wherein the desired touch region is to correspond to a visual display , the only reasonable choice of substrate material is glass , and typically a lead glass , as is utilized in a cathode ray tube ( crt ) display , soda lime glass , such as an ordinary window glass , or another float glass , as used in plasma display panels ( pdp ) and most optical filter substrates . all of these substrate materials significantly attenuate the acoustic wave amplitude as it propagates along the surface , thus limiting the size of practical touch displays because the acoustic waves must travel not only across the desired touch region but also twice along two edge lengths which comprise the wave redirecting arrays . second , as the acoustic wave redirecting arrays constructed on the glass substrate are almost necessarily for economic and compatibility reasons glass frit fired at high temperature , the manufacturing process thereby is caused to have lowered yields . further , replacement of damaged or defective parts is also correspondingly higher . third , as the acoustic wave redirecting arrays are located on same substrate as the desired touch detection region , and acoustic waves must transverse along the surface , it is difficult to provide a protective seal for the redirecting arrays , coupled transducers , and other associated components because typical sealing materials severely divert and attenuate the acoustic wave . prior art seal systems have difficulty limiting this attenuation to at least − 6 db , as stated in u . s . pat . no . 6 , 236 , 391 , and , even worse , to keep it non - varying which , if varying , causes false touch reports . now it is well known that other materials , such as steel , aluminum , or brass transmit sound more efficiently than glass , but are opaque . indeed , although some glasses are more efficient , they are typically expensive or otherwise unusable with existing display devices . however , if the acoustic wave redirecting arrays could exist on a more efficient surface the first problem listed above would be significantly reduced and larger touch systems could be built . modifying the glass substrate in the array regions , perhaps laminating a thin layer of a material such as brass or aluminum is out of the question , being very impractical because the thermal expansion coefficients are very different . the inventor has determined that just that can be done in a novel arrangement wherein the redirected waves can easily and relatively efficiently be coupled , or transferred , from one substrate of a different material , such as , for example , aluminum to the touch region on a substrate of glass . the inventor has developed an arrangement of two overlapping substrates wherein the acoustic waves are easily transferred between facing surfaces utilizing a coupling material with the property that the wavelength of the longitudinal bulk wavelength is less than the surface wavelength of either substrate . this acoustic coupling means is illustrated in fig3 and described in the following detailed description section of the present invention . the benefits of this coupling means , by allowing the acoustic wave redirecting reflector arrays to be positioned on a secondary substrate with less acoustic energy loss , can now be seen to also provide a sealing method with acceptable and non - varying attenuation . indeed , such seal means can be extended to surround and isolate the reflector arrays and further to seal the entire periphery of the desired touch region . moreover , the construction of the reflector arrays can be of more exacting and less expensive manufacturing methods as is commonly available , such as stamping , etching , electro - plating , anodizing , etc . thermal expansion mismatch can be compensated for by laminating a material , not shown , to the back of the secondary substrates . therefore , all of the three problems listed above are solved or significantly reduced by this novel configuration referring again to the drawings , there is illustrated , for example most basically in fig2 , an acoustic touch detection apparatus that includes components 1 through 23 and that is in accordance with the present invention . components shown in fig2 that are similar to components shown in fig1 have the same numerical identifiers . the apparatus may be part of graphics display apparatus , the first contactable surface corresponding to displayed images being integral to said graphic display . such graphic display typically comprising a graphics controller , not shown , and a display device such as an lcd , crt , or pdp having a touchable display surface 9 . however , it is to be appreciated that the invention is readily applicable to other display devices , e . g ., electroluminescent , led , or even displays as simple as an elevator number display , any of these can be employed . moreover , the controlled apparatus need not necessarily be a display device since the touch control system to be described can , as readily , evoke a response from other types of controllable apparatus . in some applications , a separate panel is disposed over the faceplate of the display device or , if desired , such separate panel can be disposed at a location remote from the controlled device or be a window to a real world view . in the apparatus illustrated in fig2 , the apparatus includes a primary substrate 1 , is typically the faceplate , or panel , commonly designated a “ touch control panel ” or simply “ touch panel ” since graphics , or other information may be ordered up for display from a controller 24 in response to an operator &# 39 ; s command which can take the form of a touching of a particular area of a menu associated with the touch control panel . in the preferred embodiment , the primary substrate is formed from a transparent material , such as a glass that would be utilizes in one of the devices described in the immediately preceding paragraph and also including soda lime glass , leaded glass and emi glass . the display surface corresponds to the touch region 9 , whether it is an actual graphic apparatus faceplate , optical or emi filter , the window of a building or vehicle , or a separate panel , any of these constitutes a primary substrate 1 , the surface of which is capable of propagating surface acoustic waves . it is to be appreciated that the touch panel can adopt the format of a tablet , e . g ., a sheet of glass or other substrate capable of propagating surface acoustic waves which , in the interests of convenience , or to import flexibility to the system , can be positioned at a location remote from the apparatus to be controlled . more particularly , a touch control tablet which is positioned at a location remote from a controlled image display device can be a video monitor or computer display monitor . a touch control panel can be coupled to the monitor by a cable 13 . however , it is recognized that the control effects instituted by the tablet could readily be applied to the monitor by an infrared ( ir ) or other wireless means so as to dispense with cabling . moreover , as noted , the apparatus controlled by the touch control tablet need not be an image display device . it can be , by way of example , a home entertainment center ( radio , stereo , tv , etc . ), actuated by a remotely located touch control tablet . such a touch panel according to this invention works as follows . the act of touching serves to interrupt or reduce wave energy directed along one or more paths that form a grid overlying the panel . detection and analysis of such interruption serves to identify the x , y , or other coordinates of the touched area , and , if desired , a number relating to the amount of wave energy reduction loosely interpreted as a pressure , which information , in turn , is determinative of the graphics to be delivered up for display or other response as intended by a purposefully initiated touch . to this end , the touch control system may further include a computer for the controller 24 for rendering an interface circuit 14 operative in a predetermined sequence so that when a perturbation , or interruption of acoustic wave energy is detected , converted to an electrical signal and fed back to the computer , via said interface circuit , such that the location of the interruption is identifiable by the computer . the computer utilized for the controller 24 , appropriately programmed , can then take any predetermined controlled action as necessary with devices controlled by , or in communication with , said system . such action typically includes the output of appropriate information to a display controller to change the video display to graphics associated with the “ touch panel ” address intentionally activated by the operator . a conventional touch screen interface circuit 14 has input terminals coupled , via a cable 13 a , to receiver transducers 6 a , 6 b and output terminals coupled to transmitter transducers 3 a , 3 b which are positioned as illustrated in fig2 a . it is understood that the interface circuit 14 has additional input and output terminals or cable 13 b that may be coupled to the computer 24 for interacting therewith . preferably , the interface circuit 14 , often in conjunction with timing signals from a computer , outputs firing signals that stimulate transducers 3 a and 3 b in a timed sequence so that the location of a subsequent interruption of a surface wave is identifiable . at least one transmitter transducer 3 which may be of the type particularly described in the adler patent , is coupled to or mounted upon the bottom , or lower , surface of at least one secondary substrate 2 that is carried along an edge of the primary substrate 1 . the transmitter transducer couples acoustic energy to the secondary substrate . for the apparatus shown in fig2 , there are two secondary substrates 2 a and 2 b with transducer 3 a mounted upon one of the secondary substrates 2 a and transducer 3 b mounted upon the other of the secondary substrates 2 b . an energy source ( not shown ) in the interface circuit 14 serves to apply input signals to transmitter , or input , transducers 3 a and 3 b , as shown in fig2 , which transducers , in response thereto , individually launch a burst of acoustic surface waves along first and second paths 11 a , 12 a , respectively on or near the bottom surfaces of substrates 2 a and 2 c which carry wave directing arrays 4 a and 4 c . the arrays 4 a and 4 c derive wave components 5 a , 5 b , and 5 c and 7 a , 7 b , and 7 c directed toward the edge of substrates 2 a and 2 c geometrically positioned near and towards the touch sensitive surface 9 , on the upper , or top , surface of substrate 1 . as illustrated in fig3 , wave components are acoustically coupled via coupling material 10 a and transferred from the bottom surfaces of the secondary substrates 2 a and 2 c to the top surface , or near the top surface , of primary substrate 1 to transverse the touch sensitive region 9 . also as shown in fig2 , the first and second receiver , or output , transducers 6 a and 6 b , are disposed upon and acoustically coupled to the bottom surfaces of their own secondary substrates 2 b and 2 d which are mounted along edges of the primary substrate 1 opposite from corresponding secondary substrates , 2 a and 2 c , respectively . the invention contemplates that , in the preferred embodiment , the secondary substrates 2 a and 2 c are formed from a metallic material , such as , for example , aluminum , brass , steel , nickel , chrome , copper , or combinations and alloys thereof or from a high efficiency tempered glass . the output transducers 6 a and 6 b develop electrical signals in response to acoustic energy received along paths 11 b and 12 b along the bottom surfaces of the substrates 2 b and 2 d . this acoustic energy is collected by the wave component directing arrays 4 b and 4 d , disposed upon the bottom surfaces of substrates 2 b and 2 d , from derived wave components 5 a , 5 b , and 5 c and 7 a , 7 b , and 7 c which are received after propagating across the touch sensitive region 9 on the top surface of the primary substrate 1 and acoustically coupled via coupling material 10 a and transferred to the bottom surfaces of substrates 2 b and 2 d . the invention contemplates that , in the preferred embodiment , the secondary substrates 2 b and 2 d also are formed from a metallic material , such as , for example , aluminum , brass , steel , nickel , chrome , copper , or combinations and alloys thereof or from a high efficiency tempered glass , while the coupling material is selected as one of the group of an acrylic glass such as plexiglass , an acrylic glass such as lucite ( polymethyl methacrylate ( pmma ), poly ( methyl 2 - methylpropenoate ), an elastomer , rubber , latex , silicone , a grease , and combinations thereof . the invention also contemplates that , in the preferred embodiment , the wave component directing arrays 4 a , 4 b , 4 c and 4 d comprise individual reflectors elements created by steps or grooves oriented at an angle in the basic substrate material that are formed by a processes of etching , stamping , molding , plating or screening and firing . receiver transducers 6 a and 6 b , upon receipt of the surface waves launched by their associated input transducers develop respective output signals which , upon analysis , will exhibit a characteristic of the launched surface wave . such characteristic , e . g . a change in amplitude , is attributable to a perturbation of a received surface wave component relating to an intentionally touched probe shown at position 8 in fig2 b , which diverts , or damps , acoustic energy from the wave burst components 5 b and 7 b associated with probe position 8 and the time the wave burst components pass through it relative to the time the bursts were initiated . while the preferred embodiment of the invention has been illustrated and described as utilizing surface acoustic waves , it will be appreciated that the invention also may be practiced with any acoustic waves that propagate through the primary and secondary substrates , preferably near the surfaces thereof . an important difference between the present invention and prior art devices is that prior art , as exemplified by the afore referenced adler patent , specifically and intentionally claimed and specified a single substrate associated with the touch region and wave component generating arrays . indeed , the novelty of arrangement of functions in the present invention is due to a coupling means , specifically a proper choice of material and geometry , to acoustically couple and transfer surface or near surface waves between independent substrates which can be of different physical properties . the general principal of this coupling means is similar to that of wedge transducers commonly used to initiate surface waves for surface analysis and quality testing . referring to fig3 a , an acoustic wave 15 a traveling toward an edge on or near the surface of the secondary substrate 2 is converted into a longitudinal bulk wave 16 a at the junction of the coupling material 10 a just as if it were passing through a wedge transducer . this coupling is quite efficient , having coupling coefficients of typically 60 % to 80 % wave amplitude reduction , or more , and travels at an angle 18 to the surface determined by arc - cos ( longitudinal wavelength in the coupling material 10 a / surface wavelength along surface 2 ). as the bulk wave 16 a travels through to the other , now facing , surface of the substrate 1 to be intentionally touched , it is again converted into a surface wave 17 which then travels on or near the surface of the substrate 1 to be intentionally touched . the second conversion is most efficient at the angle 19 determined by arc - cos ( longitudinal wavelength in the coupling / surface wavelength along surface 1 ). this two - step conversion coupling method transfers acoustic waves most efficiently when the two substrates are at a slight angle to each other in the region of coupling as illustrated in fig3 a . however , coupling materials can be chosen with properties such that the loss is small even when the substrates are parallel , as shown in fig3 b . indeed , as long as there is intimate contact , which can be accomplished by physical bonding , along the entire axis the coupling is non - critical to the dimensions of the coupling material . the following example illustrates this relationship in some detail so that both the elegance and novelty of this invention may be fully appreciated . the following example illustrates the calculation of the angles 18 and 19 of fig3 a for selected materials . selecting lucite as the coupling material 10 , glass for the primary substrate 1 whereupon touches are detected , and aluminum for the secondary substrates 2 , acoustic waves are generated with a frequency of 5 . 53 mhz , which is common in the industry because of compatibility with communication systems . the velocity of acoustic waves in these materials , and several others , are summarized as follows : wave velocities in cm / usec material longitudinal shear surface aluminum 0 . 635 0 . 310 0 . 290 brass x x 0 . 148 glass ( float ) 0 . 679 0 . 343 0 . 310 steel x x 0 . 281 lucite 0 . 268 x x rubber 0 . 149 x x now , if it is assumed that the coupling material 10 is rubber , the results are : now this is a very interesting result . with rubber , there is only about 2 degrees difference between the calculated values for angles 18 and 19 . it is therefore possible to just fill a gap at the edge between two facing parallel substrates , either an ultraviolet or air curing silicone rubber will work well , and a reasonably efficient coupling results , well within the − 6 db design goal . further , the width and thickness of the coupling material 10 are not critical . the bond can be arbitrarily thin . experience teaches that the width of the coupling material seal , although not critical , should be about 5 wavelengths , that is , about 5 × 0 . 022 in ( for glass )= 0 . 11 in . or about ⅛ inch . use of a rubber product , such as rtv silicone is also perfect for forming seals . the realization that this coupling material in this geometrical configuration can also be used as a seal has already been mentioned . there are several embodiments of this invention contemplated which utilize this fact . first , the touch apparatus can be built and sealed modularly as illustrated in fig4 . this is the preferred embodiment for larger size touch systems . here , each wave component deriving or gathering re - directing reflector array 4 a , 4 b , 4 c , and 4 d on substrates 2 a , 2 b , 2 c , and 2 d can be individually attached and sealed to any touch substrate capable of propagating acoustic waves , without modification of that substrate except simple attachment with a common and inexpensive calking method , e . g . rtv silicone , at room temperature . an alternate embodiment of the invention , shown in fig5 , uses a common secondary substrate formed into a protective bezel . another alternate embodiment of the invention , shown in fig6 a includes reflective secondary substrates that reflect the acoustic waves back to the secondary substrate carrying the transmitter transducer . this embodiment also contemplates that the transducer functions as both transmitting and receiving transducers with the propagation of the acoustic waves illustrated by the arrows shown in fig6 a . an alternate embodiment of the screen shown in fig6 a is illustrated in fig6 b that utilizes reflections at an edge of the primary substrate 1 without provision of a secondary substrate . other possible embodiments include , but are not limited to , the acoustic coupling of the transducers external to the secondary arrays as illustrated in fig7 , the bending of the substrates 2 around the sides of a display device to lessen the edge , or bezel border dimension , and lamination of materials to the fronts of the secondary substrates 2 to compensate for temperature induced stress due to differing expansion coefficients . yet another embodiment of the invention is illustrated in fig8 , which includes longer transmitting devices , 3 a and 3 b , that extend along their respective secondary substrates 2 a and 2 c parallel to the edge of the primary substrate 1 . thus , the transmitting devices 3 a and 3 b launch acoustic waves directly across the primary substrate 1 , as illustrated by the arrows labeled 5 a , 5 b , 5 c , 7 a , 7 b and 7 c . still other embodiments and implementations of the present invention are contemplated and are within the spirit and scope of this invention . for example , the long transmitters shown in fig8 may be utilized with the reflective edges of the primary substrate 1 illustrated in fig6 a , in conjunction with a receiving array on the same secondary substrate . in accordance with the provisions of the patent statutes , the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment . however , it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope .