Elastic wave position-sensing device

• US 5,852,433 A
• Filed: 08/09/1996
• Issued: 12/22/1998
• Est. Priority Date: 08/09/1996
• Status: Expired due to Term

• Current Assignee: Toda, Kohji
• Original Assignee: Toda, Kohji
• Inventors: Toda, Kohji
• Primary Examiner(s): CHOW, DOON Y
• Application Number:
  US08/694,987
• Time in Patent Office: 865 Days
• Field of Search: 345/177, 345/173, 345/174, 345/175, 345/176, 345/179, 345/156, 345/157, 341/22, 178/18, 178/19
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate

Abstract

An elastic wave position-sensing device comprising at least two elastic wave transducing units X and Y having N propagation lanes U_Xi (i=1, 2, . . . , N) and U_Yi (i=1, 2, . . . , N), respectively, a nonpiezoelectric plate, a display panel mounted on one end surface of the nonpiezoelectric plate, and a controlling system connected with the units X and Y. Each unit includes a piezoelectric substrate P_T, a piezoelectric substrate P_R, at least an input interdigital transducer formed on one end surface of the piezoelectric substrate P_T, and at least an output interdigital transducer formed on one end surface of the piezoelectric substrate P_R. Each piezoelectric substrates mounted on one or the other end surface of the nonpiezoelectric plate and the nonpiezoelectric plate form N bilayer zones L_Ti (i=1, 2, . . . , N), a bilayer zone L_R, and a monolayer zone between the bilayer zones L_Ti and the bilayer zone L_R. When an electric signal E_T is applied to the input interdigital transducer, an elastic wave is excited in the bilayer zone L_Ti. The elastic wave is transmitted to the bilayer zone L_R through the monolayer zone, and is transduced to an electric signal E_R. If touching a crossing point of the lanes U_Xi and U_Yi on the other end surface of the nonpiezoelectric plate, the elastic wave is intercepted at the crossing point. Therefore, the magnitude of the electric signal E_R corresponding to the crossing point decrease or disappearance. Thus, it is possible to specify the crossing point.

Claims

1. An elastic wave position-sensing device comprising:

at least two elastic wave transducing units X and Y, each thereof consisting of

a piezoelectric substrate P_T having two end surfaces running perpendicular to the direction of the thickness D thereof, and comprising N piezoelectric parts P_Ti (i=1, 2, . . . , N),

a piezoelectric substrate P_R having two end surfaces running perpendicular to the direction of the thickness D thereof,

N interdigital transducers I_Ti (i=1, 2, . . . , N), each thereof being formed on one end surface of each of said piezoelectric parts P_Ti, said thickness D of said piezoelectric substrate P_T being approximately equal to or smaller than an interdigital periodicity p of said interdigital transducer I_Ti,

an interdigital transducer I_R formed on one end surface of said piezoelectric substrate P_R and having an interdigital periodicity equal to said interdigital periodicity p, said thickness D of said piezoelectric substrate P_R being approximately equal to or smaller than said interdigital periodicity p, and

N switches C_i (i=1, 2, . . . , N), an output terminal of each thereof being connected with an input terminal of each of said interdigital transducers I_Ti ;

a nonpiezoelectric plate having two end surfaces, the thickness of said nonpiezoelectric plate being equal to or smaller than said thickness D of said piezoelectric substrates P_T and P_R, said piezoelectric substrates P_T and P_R being mounted on one or the other end surface of said nonpiezoelectric plate, said nonpiezoelectric plate comprising N nonpiezoelectric parts _Ti (i=1, 2, . . . , N) adjacent to said piezoelectric parts P_Ti, a nonpiezoelectric part _R adjacent to said piezoelectric substrate P_R, and the remaining nonpiezoelectric part;

a display panel, mounted on said one end surface of said nonpiezoelectric plate; and

a controlling system connected with said elastic wave transducing units X and Y, and said display panel,

said piezoelectric substrates P_T and P_R, and said nonpiezoelectric plate forming

N bilayer zones L_Ti (i=1, 2, . . . , N) consisting of said piezoelectric parts P_Ti and said nonpiezoelectric parts _Ti,

a bilayer zone L_R consisting of said piezoelectric substrate P_R and said nonpiezoelectric part _R, and

a monolayer zone between said bilayer zones L_Ti and said bilayer zone L_R, and consisting of said remaining nonpiezoelectric part,

said interdigital transducer I_Ti receiving an electric signal E_T with a frequency approximately corresponding to said interdigital periodicity p, exciting an elastic wave of the S_o mode and the higher order modes in said bilayer zone L_Ti, and transmitting said elastic wave, having the wavelength approximately equal to said interdigital periodicity p, to said bilayer zone L_R through said monolayer zone, the phase velocity of said elastic wave being approximately equal to the phase velocity V_fd=0, of the S_o mode elastic wave, corresponding to a condition that the product FD of the frequency F of said elastic wave and said thickness D of said piezoelectric substrate P_T is zero,

said interdigital transducer I_R transducing said elastic wave in said bilayer zone L_R to an electric signal E_R with a frequency approximately corresponding to said interdigital periodicity p,

said nonpiezoelectric plate being made of a material such that the phase velocity of the elastic wave in said nonpiezoelectric plate alone is approximately equal to that in said piezoelectric substrates P_T and P_R alone,

said controlling system turning on and off said switches C_i with a fixed period in turn, keeping a check on a magnitude of said electric signal E_R, sensing a touch with a finger or others under a fixed or more pressure on the other end surface of said nonpiezoelectric plate by a decrease or a disappearance in magnitude of said electric signal E_R, picking out one of said switches C_i turned on when said decrease or said disappearance in magnitude of said electric signal E_R happens, specifying a touch-position corresponding with the picked out switch C_i, and producing an image corresponding to said touch-position on said display panel,

said elastic wave transducing unit X having N propagation lanes U_Xi (i=1, 2, . . . , N) of the elastic wave in said monolayer zone between said bilayer zones L_Ti and L_R, two neighbors of said propagation lanes U_Xi being closed or partially overlapping each other,

said elastic wave transducing unit Y having N propagation lanes U_Yi (i=1, 2, . . . , N) of the elastic wave in said monolayer zone between said bilayer zones L_Ti and L_R, two neighbors of said propagation lanes U_Yi being closed or partially overlapping each other, said propagation lane U_Xi being vertical to said propagation lane U_Yi.

2. An elastic wave position-sensing device as defined in claim 1, wherein said nonpiezoelectric plate is made of a glass.

3. An elastic wave position-sensing device as defined in claim 1, wherein said piezoelectric substrates P_T and P_R are made of a piezoelectric ceramic, the polarization axis thereof being parallel to the direction of said thickness D thereof.

4. An elastic wave position-sensing device as defined in claim 1, wherein said piezoelectric substrates P_T and P_R are made of a piezoelectric polymer.

5. An elastic wave position-sensing device as defined in claim 1, wherein said display panel is made of a material such that the phase velocity of the elastic wave in said display panel is higher than that in said nonpiezoelectric plate alone.

6. An elastic wave position-sensing device as defined in claim 1 further comprising:

an amplifier A_X, an input terminal of said switch C_i in said elastic wave transducing unit Y being connected with an output terminal of said interdigital transducer I_R in said elastic wave transducing unit X via said amplifier A_X ; and

an amplifier A_Y, an input terminal of said switch C_i in said elastic wave transducing unit X being connected with an output terminal of said interdigital transducer I_R in said elastic wave transducing unit Y via said amplifier A_Y,

said switches C_i in said elastic wave transducing unit X, said propagation lanes U_Xi as delay elements, said amplifier A_X, said switches C_i in said elastic wave transducing unit Y, said propagation lanes U_Yi as delay elements, and said amplifier A_Y forming N oscillators H_i (i=1, 2, . . . , N).

7. An elastic wave position-sensing device comprising:

at least two elastic wave transducing units X and Y, each thereof consisting of

a piezoelectric substrate P_T having two end surfaces running perpendicular to the direction of the thickness D thereof, and comprising N piezoelectric parts P_Ti (i=1, 2, . . . , N),

a piezoelectric substrate P_R having two end surfaces running perpendicular to the direction of the thickness D thereof,

N interdigital transducers T_i (i=1, 2, . . . , N), each thereof being formed on one end surface of each of said piezoelectric parts P_Ti, each of said interdigital transducers T_i consisting of two electrodes T_i-1 and T_i-2 and having two kinds of distances between one electrode finger of said electrode T_i-1 and two neighboring electrode fingers of said electrode T_i-2, said thickness D of said piezoelectric substrate P_T being approximately equal to or smaller than an interdigital periodicity p of said interdigital transducer T_i,

an interdigital transducer R formed on one end surface of said piezoelectric substrate P_R, consisting of two electrodes R_-1 and R_-2, and having two kinds of distances between one electrode finger of said electrode R_-1 and two neighboring electrode fingers of said electrode R_-2, said thickness D of said piezoelectric substrate P_R being approximately equal to or smaller than an interdigital periodicity p of said interdigital transducer R,

N earth electrodes G_Ti (i=1, 2, . . . , N), each thereof being formed on the other end surface of each of said piezoelectric parts P_Ti,

an earth electrode G_R formed on the other end surface of said piezoelectric substrate P_R,

a phase shifter S_T including at least a coil L₁,

a phase shifter S_R including at least a coil L₂, and

N pairs of switches W_i (i=1, 2, . . . , N), each pair of switches W_i consisting of two switches W_i-1 and W_i-2, and output terminals of said switches W_i-1 and W_i-2 being connected with input terminals of said electrodes T_i-1 and T_i-2, respectively;

a nonpiezoelectric plate having two end surfaces, the thickness of said nonpiezoelectric plate being equal to or smaller than said thickness D of said piezoelectric substrates P_T and P_R, said piezoelectric substrates P_T and P_R being mounted on one or the other end surface of said nonpiezoelectric plate through said earth electrodes G_Ti and G_R, respectively, said nonpiezoelectric plate comprising N nonpiezoelectric parts _Ti (i=1, 2, . . . , N) adjacent to said piezoelectric parts P_Ti, a nonpiezoelectric part _R adjacent to said piezoelectric substrate P_R, and the remaining nonpiezoelectric part;

a display panel, mounted on said one end surface of said nonpiezoelectric plate; and

a controlling system connected with said two elastic wave transducing units X and Y, and said display panel,

said piezoelectric substrates P_T and P_R, and said nonpiezoelectric plate forming

N bilayer zones L_Ti (i=1, 2, . . . , N) consisting of said piezoelectric parts P_Ti and said nonpiezoelectric parts _Ti,

a bilayer zone L_R consisting of said piezoelectric substrate P_R and said nonpiezoelectric part _R, and

a monolayer zone between said bilayer zones L_Ti and said bilayer zone L_R, and consisting of said remaining nonpiezoelectric part,

said interdigital transducer T_i and said earth electrode G_Ti receiving an electric signal E_T1 between said electrode T_i-1 and said earth electrode G_Ti, and an electric signal E_T2 between said electrode T_i-2 and said earth electrode G_Ti via said phase shifter S_T, exciting an elastic wave of the S_o mode and the higher order modes in said bilayer zone L_Ti, and transmitting said elastic wave, having the wavelength approximately equal to said interdigital periodicity p of said interdigital transducer T_i, to said bilayer zone L_R through said monolayer zone, each of said electric signals E_T1 and E_T2 having a frequency approximately corresponding to said interdigital periodicity p of said interdigital transducer T_i, the phase difference between said electric signals E_T1 and E_T2 being 2π

y, the phase velocity of said elastic wave being approximately equal to the phase velocity V_fd=0, of the S_o mode elastic wave, corresponding to a condition that the product FD of the frequency F of said elastic wave and said thickness D of said piezoelectric substrate P_T is zero,

said interdigital transducer R and said earth electrode G_R transducing said elastic wave in said bilayer zone L_R, with wavelength approximately equal to said interdigital periodicity p of said interdigital transducer R, to an electric signal E_R1 between said electrode R_-1 and said earth electrode G_R, and an electric signal E_R2 between said electrode R_-2 and said earth electrode G_R, each of said electric signals E_R1 and E_R2 having a frequency approximately corresponding to said interdigital periodicity p of said interdigital transducer R, the phase difference between said electric signals E_R1 and E_R2 being 2π

y,

said phase shifter S_R combining said electric signals E_R1 and E_R2, and delivering a combined electric signal E_R,

said nonpiezoelectric plate being made of a material such that the phase velocity of the elastic wave in said nonpiezoelectric plate alone is approximately equal to that in said piezoelectric substrates P_T and P_R alone,

said controlling system turning on and off said pairs of switches W_i with a fixed period in turn, keeping a check on a magnitude of said electric signal E_R, sensing a touch with a finger or others under a fixed or more pressure on the other end surface of said nonpiezoelectric plate by a decrease or a disappearance in magnitude of said electric signal E_R, picking out said pair of switches W_i turned on when said decrease or said disappearance in magnitude of said electric signal E_R happens, specifying a touch-position corresponding with the picked out pair of switches W_i, and producing an image corresponding to said touch-position on said display panel,

said elastic wave transducing unit X having N propagation lanes U_Xi (i=1, 2, . . . , N) of the elastic wave in said monolayer zone between said bilayer zones L_Ti and L_R in said elastic wave transducing unit X, two neighbors of said propagation lanes U_Xi being closed or partially overlapping each other,

said elastic wave transducing unit Y having N propagation lanes U_Yi (i=1, 2, . . . , N) of the elastic wave in said monolayer zone between said bilayer zones L_Ti and L_R in said elastic wave transducing unit Y, two neighbors of said propagation lanes U_Yi being closed or partially overlapping each other, said propagation lane U_Xi being vertical to said propagation lane U_Yi.

8. An elastic wave position-sensing device as defined in claim 7, wherein x<

1/2 in a shorter distance xp of said two kinds of distances between one electrode finger of said electrode T_i-1 and two neighboring electrode fingers of said electrode T_i-2, x<

1/2 in a shorter distance xp of said two kinds of distances between one electrode finger of said electrode R_-1 and two neighboring electrode fingers of said electrode R_-2, x+y=±

1/2 in said phase difference 2π

y between said electric signals E_T1 and E_T2, and x+y=±

1/2 in said phase difference 2π

y between said electric signals E_R1 and E_R2.

9. An elastic wave position-sensing device as defined in claim 7, wherein said nonpiezoelectric plate is made of a glass.

10. An elastic wave position-sensing device as defined in claim 7, wherein said piezoelectric substrates P_T and P_R are made of a piezoelectric ceramic, the polarization axis thereof being parallel to the direction of said thickness D thereof.

11. An elastic wave position-sensing device as defined in claim 7, wherein said piezoelectric substrates P_T and P_R are made of a piezoelectric polymer.

12. An elastic wave position-sensing device as defined in claim 7, wherein said display panel is made of a material such that the phase velocity of the elastic wave in said display panel is higher than that in said nonpiezoelectric plate alone.

13. An elastic wave position-sensing device as defined in claim 7 further comprising:

an amplifier A_X, an input terminal of said phase shifter S_T in said elastic wave transducing unit Y being connected with an output terminal of said phase shifter S_R in said elastic wave transducing unit X via said amplifier A_X ; and

an amplifier A_Y, an input terminal of said phase shifter S_T in said elastic wave transducing unit X being connected with an output terminal of said phase shifter S_R in said elastic wave transducing unit Y via said amplifier A_Y,

said phase shifter S_T in said elastic wave transducing unit X, said pairs of switches W_i in said elastic wave transducing unit X, said propagation lanes U_Xi as delay elements, said phase shifter S_R in said elastic wave transducing unit X, said amplifier A_X, said phase shifter S_T in said elastic wave transducing unit Y, said pairs of switches W_i in said elastic wave transducing unit Y, said propagation lanes U_Yi as delay elements, said phase shifter S_R in said elastic wave transducing unit Y, and said amplifier A_Y forming N oscillators H_i (i=1, 2, . . . , N).