Shear horizontal wave device for sensing a touch-position

• US 5,886,452 A
• Filed: 08/01/1997
• Issued: 03/23/1999
• Est. Priority Date: 08/01/1997
• Status: Expired due to Term

• Current Assignee: Kohji Toda
• Original Assignee: Kohji Toda
• Inventors: Toda, Kohji
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US08/904,533
• Time in Patent Office: 599 Days
• Field of Search: 310/313 R, 310/313 B, 310/313 D, 367/118, 367/907, 333/193, 73/632, 178/18, 178/19
• US Class Current: 310/313.00R
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G06F 3/043 using propagating acoustic waves

Abstract

An SH wave position-sensing device comprising two SH wave transducing units X and Y, a nonpiezoelectric plate and a signal controller. Each unit contains piezoelectric substrates P_T0, P_R0, P_Ti (i=1, 2, . . . , N) and P_Ri (i=1, 2, . . . , N), interdigital transducers T₀, R₀, T_i (i=1, 2, . . . , N) and R_i (i=1, 2, . . . , N). The interdigital transducers T₀, R₀, T_i and R_i, are formed on an upper- or a lower end surface of the piezoelectric substrates P_T0, P_R0, P_Ti and P_Ri, respectively. The lower end surface of each piezoelectric substrate is cemented on an upper end surface of the nonpiezoelectric plate. The finger direction of each interdigital transducer R_i is slanting to that of each interdigital transducer T_i. When an electric signal is applied to the interdigital transducer T₀, an SH wave is excited in a bilayer zone B_T0 formed by the piezoelectric substrate P_T0 and the nonpiezoelectric plate, transmitted to a bilayer zone B_R0 formed by the piezoelectric substrate P_R0 and the nonpiezoelectric plate, and transduced to an electric signal with a phase θ_base and delivered at the interdigital transducer R₀.

Claims

1. An SH wave position-sensing device comprising:

two SH wave transducing units X and Y, each thereof consisting of

a piezoelectric substrate P_T0,

a piezoelectric substrate P_R0,

piezoelectric substrates P_Ti (i=1, 2, . . . , N),

piezoelectric substrates P_Ri (i=1, 2, . . . , N), each of said piezoelectric substrates P_T0, P_R0, P_Ti and P_Ri, having an upper- and a lower end surfaces running perpendicular to the direction of the thickness d thereof,

an input interdigital transducer T₀ formed on said upper- or said lower end surface of said piezoelectric substrate P_T0,

an output interdigital transducer R₀ opposed to said interdigital transducer T₀ and placed on said upper- or said lower end surface of said piezoelectric substrate P_R0 such that the finger direction of said interdigital transducer R₀ runs parallel with that of said interdigital transducer T₀,

input interdigital transducers T_i (i=1, 2, . . . , N) formed on said upper- or said lower end surface of said piezoelectric substrates P_Ti, respectively, the polarization axis of each of said piezoelectric substrates P_T0, P_R0, P_Ti and P_Ri, being parallel to the finger direction of said interdigital transducers T₀, R₀ and T_i, said thickness d being smaller than an interdigital periodicity P of said interdigital transducers T₀, R₀ and T_i,

output interdigital transducers R_i (i=1, 2, . . . , N) opposed to said interdigital transducers T_i and placed on said upper- or said lower end surface of said piezoelectric substrates P_Ri, respectively, such that the finger direction of each interdigital transducer R_i is slanting to that of each interdigital transducer T_i by an angle α

, an interdigital periodicity P_N along the vertical direction to the finger direction of each interdigital transducer R_i being equal to the product of said interdigital periodicity P and cos α

, an overlap length L_P along the finger direction of each interdigital transducer R_i being equal to the product of an overlap length L of each interdigital transducer T_i and sec α

as well as the product of said interdigital periodicity P and cosec α

,

an amplifier, and

a phase comparator, an output terminal of said interdigital transducer R₀ being connected with an input terminal of said phase comparator and an input terminal of each of said interdigital transducers T₀ and T_i, via said amplifier;

a nonpiezoelectric plate having an upper- and a lower end surfaces, each piezoelectric substrate being mounted on said upper end surface of said nonpiezoelectric plate through said lower end surface of each piezoelectric substrate, the boundary surface of each piezoelectric substrate to said nonpiezoelectric plate being under electrically shorted condition; and

a signal controller, an output terminal of each interdigital transducer R_i being connected with an input terminal of said signal controller via said phase comparator,

a part, adjacent to said piezoelectric substrate P_T0, of said nonpiezoelectric plate, and said piezoelectric substrate P_T0 forming a bilayer zone B_T0,

a part, adjacent to said piezoelectric substrate P_R0, of said nonpiezoelectric plate, and said piezoelectric substrate P_R0 forming a bilayer zone B_R0,

the remaining part, between said bilayer zones B_T0 and B_R0, of said nonpiezoelectric plate consisting of a monolayer zone,

a part, adjacent to said piezoelectric substrate P_Ti, of said nonpiezoelectric plate, and said piezoelectric substrate P_Ti forming a bilayer zone B_Ti (i=1, 2, . . . , N),

a part, adjacent to said piezoelectric substrate P_Ri, of said nonpiezoelectric plate, and said piezoelectric substrate P_Ri forming a bilayer zone B_Ri (i=1, 2, . . . , N),

the remaining part, between said bilayer zones B_Ti and B_Ri, of said nonpiezoelectric plate consisting of a monolayer zone,

said interdigital transducer T₀ receiving an electric signal with a frequency approximately corresponding to said interdigital periodicity P, exciting an SH wave of the zeroth mode and the higher order modes in said bilayer zone B_T0, and transmitting said SH wave, having the wavelength approximately equal to said interdigital periodicity P, to said bilayer zone B_R0 through an upper end surface of said monolayer zone between said bilayer zones B_T0 and B_R0,

said interdigital transducer R₀ transducing said SH wave in said bilayer zone B_R0 to an electric signal with a phase θ

_base and delivering said electric signal,

each interdigital transducer T_i receiving an electric signal with a frequency approximately corresponding to said interdigital periodicity P, exciting an SH wave of the zeroth mode and the higher order modes in said bilayer zone B_Ti, and transmitting said SH wave, having the wavelength approximately equal to said interdigital periodicity P, to said bilayer zone B_Ri through an upper end surface of said monolayer zone between said bilayer zones B_Ti and B_Ri, the phase velocity of said SH wave approximating to the average value between the shear wave velocity traveling on said nonpiezoelectric plate alone and that traveling on each piezoelectric substrate alone,

each interdigital transducer R_i transducing said SH wave in said bilayer zone B_Ri to electric signals E_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x) with phases θ

_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x), respectively, said phases θ

_j corresponding to positions F_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x) on said upper end surface of said monolayer zone between said bilayer zones B_Ti and B_Ri, each electric signal E_j having a frequency approximately corresponding to said interdigital periodicity P, the total phase Σ

θ

_j made by said phases θ

_j being zero, the total electric signal Σ

E_j made by said electric signals E_J being zero and not able to be detected at each interdigital transducer R_i,

said interdigital transducers T_i and R_i forming propagation lanes D_i (i=1, 2, . . . , N) of the SH wave on said upper end surface of said monolayer zone between said bilayer zones B_Ti and B_Ri, each propagation lane D_i consisting of minute propagation lanes Z_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x) corresponding to said positions F_j and said phases θ

_j, a propagation lane Z₀ existing on the line not only vertical to the finger direction of each interdigital transducer T_i but also dividing said overlap length L into two halves,

each interdigital transducer R_i delivering an electric signal E_-j with a phase θ

_-j only when touching with a finger or others on a position F_j,

said phase comparator detecting a difference between said phases θ

_-j and θ

_base,

said signal controller sensing a touched position F_j by finding one, delivering said electric signal E_-j, of said interdigital transducers R_i, and by evaluating said difference between said phases θ

_-j and θ

_base.

2. An SH wave position-sensing device as defined in claim 1, wherein each SH wave transducing unit further comprising

a switch connected with input terminals of said interdigital transducers T_i and supplying said interdigital transducers T_i with said electric signal with a frequency approximately corresponding to said interdigital periodicity P with a fixed period in turn,

output terminals of said interdigital transducers R_i being connected with each other at an output point,

said signal controller sensing a touched position F_j by finding one, supplied with said electric signal just when said electric signal E_-j is detected at said output point, of said interdigital transducers T_i, and by evaluating said difference between said phases θ

_-j and θ

_base.

3. An SH wave position-sensing device as defined in claim 1, wherein two neighbors of said propagation lanes D_i are closed or partially overlapping each other.

4. An SH wave position-sensing device as defined in claim 1, wherein said propagation lanes D_i of said SH wave transducing unit X and those of said SH wave transducing unit Y are vertical to each other.

5. An SH wave position-sensing device as defined in claim 1, wherein the thickness of said nonpiezoelectric plate is larger than said thickness d, said nonpiezoelectric plate being made of a material such that the shear wave velocity traveling on said nonpiezoelectric plate alone is higher than that traveling on each piezoelectric substrate alone.

6. An SH wave position-sensing device as defined in claim 1, wherein each piezoelectric substrate is made of a piezoelectric ceramic.

7. An SH wave position-sensing device comprising:

two SH wave transducing units X and Y, each thereof consisting of

piezoelectric substrates P_Ti (i=1, 2, . . . , N),

piezoelectric substrates P_Ri (i=1, 2, . . . , N), each of said piezoelectric substrates P_Ti and P_Ri, having an upper- and a lower end surfaces running perpendicular to the direction of the thickness d thereof,

input interdigital transducers T_i (i=1, 2, . . . , N) formed on said upper- or said lower end surface of said piezoelectric substrates P_Ti, respectively, the polarization axis of each of said piezoelectric substrates P_Ti and P_Ri, being parallel to the finger direction of each interdigital transducers T_i, said thickness d being smaller than an interdigital periodicity P of each interdigital transducers T_i,

output interdigital transducers R_i (i=1, 2, . . . , N) opposed to said interdigital transducers T_i and placed on said upper- or said lower end surface of said piezoelectric substrates P_Ri, respectively, such that the finger direction of each interdigital transducer R_i is slanting to that of each interdigital transducer T_i by an angle α

, an interdigital periodicity P_N along the vertical direction to the finger direction of each interdigital transducer R_i being equal to the product of said interdigital periodicity P and cos α

, an overlap length L_P along the finger direction of each interdigital transducer R_i being equal to the product of an overlap length L of each interdigital transducer T_i and sec α

as well as the product of N times (N=1, 2, . . . , N) said interdigital periodicity P and cosec α

, and

an amplifier;

a nonpiezoelectric plate having an upper- and a lower end surfaces, each piezoelectric substrate being mounted on said upper end surface of said nonpiezoelectric plate through said lower end surface of each piezoelectric substrate, the boundary surface of each piezoelectric substrate to said nonpiezoelectric plate being under electrically shorted condition; and

a signal controller, output terminals of said interdigital transducers R_i being connected with each other at an output point, said output point being connected with an input terminal of said signal controller and input terminals of said interdigital transducers T_i via said amplifier,

a part, adjacent to said piezoelectric substrate P_Ti, of said nonpiezoelectric plate, and said piezoelectric substrate P_Ti forming a bilayer zone B_Ti (i=1, 2, . . . , N),

a part, adjacent to said piezoelectric substrate P_Ri, of said nonpiezoelectric plate, and said piezoelectric substrate P_Ri forming a bilayer zone B_Ri (i=1, 2, . . . , N),

the remaining part, between said bilayer zones B_Ti and B_Ri, of said nonpiezoelectric plate consisting of a monolayer zone,

each interdigital transducer T_i receiving an electric signal with a frequency approximately corresponding to said interdigital periodicity P, exciting an SH wave of the zeroth mode and the higher order modes in said bilayer zone B_Ti, and transmitting said SH wave, having the wavelength approximately equal to said interdigital periodicity P, to said bilayer zone B_Ri through an upper end surface of said monolayer zone between said bilayer zones B_Ti and B_Ri, the phase velocity of said SH wave approximating to the average value between the shear wave velocity traveling on said nonpiezoelectric plate alone and that traveling on each piezoelectric substrate alone,

each interdigital transducer R_i transducing said SH wave to electric signals E_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x) with frequencies f_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x), respectively, said frequencies f_j corresponding to positions F_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x) on said upper end surface of said monolayer zone between said bilayer zones B_Ti and B_Ri, the total electric signal Σ

E_j made by said electric signals E_j being zero and not able to be detected at each interdigital transducer R_i,

said interdigital transducers T_i and R_i forming propagation lanes D_i (i=1, 2, . . . , N) of the SH wave on said upper end surface of said monolayer zone between said bilayer zones B_Ti and B_Ri, each propagation lane D_i consisting of minute propagation lanes Z_j (j=x, . . . , 2, 1, 0, -1, -2, . . . , -x) corresponding to said positions F_j, a propagation lane Z₀ existing on the line not only vertical to the finger direction of each interdigital transducer T_i but also dividing said overlap length L into two halves,

each interdigital transducer R_i delivering an electric signal E_-j with a frequency f_-j only when touching with a finger or others on a position F_j,

said signal controller sensing a touched position F_j by finding one, delivering said electric signal E_-j, of said interdigital transducers R_i, and by evaluating said frequency f_-j.

8. An SH wave position-sensing device as defined in claim 7, wherein each SH wave transducing unit further comprising

a switch connected with input terminals of said interdigital transducers T_i and supplying said interdigital transducers T_i with said electric signal with a frequency approximately corresponding to said interdigital periodicity P with a fixed period in turn,

said signal controller sensing a touched position F_j by finding one, supplied with said electric signal just when said electric signal E_-j is detected at said output point, of said interdigital transducers T_i, and by evaluating said frequency f_-j.

9. An SH wave position-sensing device as defined in claim 7, wherein two neighbors of said propagation lanes D_i are closed or partially overlapping each other.

10. An SH wave position-sensing device as defined in claim 7, wherein said propagation lanes D_i of said SH wave transducing unit X and those of said SH wave transducing unit Y are vertical to each other.

11. An SH wave position-sensing device as defined in claim 7, wherein the thickness of said nonpiezoelectric plate is larger than said thickness d, said nonpiezoelectric plate being made of a material such that the shear wave velocity traveling on said nonpiezoelectric plate alone is higher than that traveling on each piezoelectric substrate alone.

12. An SH wave position-sensing device as defined in claim 7, wherein each piezoelectric substrate is made of a piezoelectric ceramic.