ELECTROSTATIC ULTRASONIC TRANSDUCER, METHOD OF MANUFACTURING ELECTROSTATIC ULTRASONIC TRANSDUCER, ULTRASONIC SPEAKER, METHOD OF REPRODUCING SOUND SIGNAL, AND SUPER-DIRECTIVITY SOUND SYSTEM, AND DISPLAY DEVICE

Abstract

An electrostatic ultrasonic transducer includes a first electrode that has through-holes, a second electrode that has through-holes, and a vibrating membrane that is disposed such that the through-holes of the first electrode and the through-holes of the second electrode form a pair, interposed between a pair of electrodes composed of the first electrode and the second electrode, and having a conductive layer applied with a direct current bias voltage. The first electrode and the second electrode each have counter electrode portions that are formed in the through-holes to face the vibrating membrane, and a modulated wave, which is obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band, is applied between the pair of electrodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, where like numbers reference like elements.

FIGS. 1A and 1B are diagrams illustrating an example of a counter electrode portion of a cross-shaped bridge structure according to an embodiment of the invention.

FIG. 2 is a diagram illustrating an example of a counter electrode portion of a Y-shaped bridge structure according to an embodiment of the invention.

FIGS. 3A and 3B are diagrams illustrating an example of a electrode that has a counter electrode portion of a cross-shaped bridge structure.

FIG. 4 is a diagram illustrating an example of a electrode having a counter electrode portion of a Y-shaped bridge structure.

FIGS. 5A and 5B are diagrams illustrating a sectional structure of a electrode 1 shown in FIG. 3A.

FIG. 6 is a diagram illustrating an assembled state of an ultrasonic transducer according to an embodiment of the invention.

FIGS. 7A to 7C are diagrams illustrating a process for manufacturing a electrode of an ultrasonic transducer according to an embodiment of the invention.

FIGS. 8A and 8B are diagrams illustrating specifications and evaluation conditions of a counter electrode portion.

FIGS. 9A and 9B are diagrams illustrating a variation of a membrane displacement ratio of a counter electrode portion in each evaluation device.

FIG. 10 is a diagram illustrating an ultrasonic speaker using an ultrasonic transducer according to an embodiment of the invention.

FIG. 11 is a diagram illustrating a used state of a projector according to an embodiment of the invention.

FIGS. 12A and 12B are diagrams illustrating an external structure of a projector shown in FIG. 11.

FIG. 13 is a diagram illustrating an electrical structure of a projector shown in FIG. 11.

FIG. 14 is a diagram illustrating a reproducing state of a reproducing signal by an ultrasonic transducer.

FIGS. 15A and 15B are diagrams illustrating an example of a structure of an ultrasonic transducer according to the related art.

FIGS. 16A and 16B are diagrams illustrating an example of a push-pull type electrostatic ultrasonic transducer.

FIG. 17 is a diagram illustrating an aspect of arrangement of through-holes in a electrode.

FIGS. 18A to 18C are diagrams illustrating a structure of a electrode and a process for manufacturing the electrode.

Claims

1. An electrostatic ultrasonic transducer comprising: a first electrode that has through-holes;a second electrode that has through-holes; anda vibrating membrane that is disposed such that the through-holes of the first electrode and the through-holes of the second electrode form a pair, interposed between a pair of electrodes composed of the first electrode and the second electrode, and having a conductive layer applied with a direct current bias voltage,wherein the first electrode and the second electrode each have counter electrode portions that are formed in the through-holes to face the vibrating membrane, anda modulated wave, which is obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band, is applied between the pair of electrodes.

2. The electrostatic ultrasonic transducer according to claim 1, wherein the counter electrode portions have a bridge structure that builds a bridge between an outer circumferential portion and an inner portion of the through-hole.

3. The electrostatic ultrasonic transducer according to claim 2, wherein the bridge structure is a cross-shaped structure.

4. The electrostatic ultrasonic transducer according to claim 3, wherein the bridge structure is a cross-shaped structure, anda central counter electrode portion, which is wider than the bridge structure, is provided at a central portion of the cross-shaped structure.

5. The electrostatic ultrasonic transducer according to claim 2, wherein the bridge structure is a Y-shaped structure.

6. An ultrasonic speaker comprising: an electrostatic ultrasonic transducer that includes a first electrode that has through-holes, a second electrode that has through-holes, and a vibrating membrane that is disposed such that the through-holes of the first electrode and the through-holes of the second electrode form a pair, interposed between a pair of electrodes composed of the first electrode and the second electrode, and having a conductive layer applied with a direct current bias voltage, the first electrode and the second electrode each having counter electrode portions that are formed in the through-holes to face the vibrating membrane, a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band being applied between the pair of electrodes;a signal source that generates a signal wave in an audible frequency band;a carrier wave supply unit that generates a carrier wave in an ultrasonic frequency band and outputs the carrier wave; anda modulating unit that modulates the carrier wave with the signal wave in the audible frequency band output by the signal source,wherein the electrostatic ultrasonic transducer is driven by a modulated signal that is applied between the pair of electrodes and an electrode layer of the vibrating membrane and is output from the modulating unit.

7. A display device comprising: an ultrasonic speaker that includes an electrostatic ultrasonic transducer and reproduces a signal sound of an audible frequency band from sound signals supplied by a sound source, the electrostatic ultrasonic transducer including a first electrode that has through-holes, a second electrode that has through-holes, and a vibrating membrane that is disposed such that the through-holes of the first electrode and the through-holes of the second electrode form a pair, interposed between a pair of electrodes composed of the first electrode and the second electrode, and having a conductive layer applied with a direct current bias voltage, the first electrode and the second electrode each having counter electrode portions formed in the through-holes to face the vibrating membrane, a modulated wave obtained by modulating a carrier wave in an ultrasonic frequency band with a signal wave in an audible frequency band being applied between the pair of electrodes; anda projection optical system that projects an image onto a projection surface.