Electro-magnetic microphone

Details Electro-magnetic microphone Electro-magnetic microphone

2000-06-29

2004-04-13

Harvey, Minsun Oh (Department: 2644)

Electrical audio signal processing systems and devices

Having microphone

C381S111000, C381S115000, C398S132000, C398S133000

Reexamination Certificate

active

06721429

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a microphone.
Prior Art Technology
In the prior arts, a microphone is known which detects electro dynamically or electro statically displacement of a vibrated film vibrating upon sonic wave to transform electric signals, or which detects optically the displacement of the vibrated film by a laser beam.
Microphones by which the displacement of the vibrated film is detected optically by a laser beam have been proposed in U.S. Pat. Nos. 6,014,239 and 4,479,265 wherein a laser beam is radiated to the vibrated film and the reflected beam is measured by the optic detector to convert the same into electric signals.
Problems to be Solved by the Invention
A microphone for which a semi-conductor laser is used has an advantage to detect displacement by a leadless wire, while it requires a fine adjustment means to adjust finely distance between the semi-conductor laser and vibrated film and a lot of optical factors are required, which brings a complicated structure. Further, since attached things on a surface of a vibrated film cause to change characteristics of reflection of light, characteristics of the microphone are deteriorated. And especially it may impossible to receive and transmit the light in case of high humidity, and thereby the microphone ceases to function. Further, it is impossible to measure directly the frequency or phase only by an integrated logic circuit because the laser beam is light.
Measurement of the frequency of a laser beam is conducted by the method to measure difference of an optical path on the principle of constancy of light velocity by deriving the wavelength. However, this method of measurement has lower precision and requires a measuring device in larger scale. Moreover, the measurement of the optical path is not easy. Accordingly, it is difficult to provide a microphone for stable use during a long period of time if a laser beam is used.
The present invention provides a microphone with a simple structure which solves the problems mentioned above, said microphone not requiring a lead wire to detect the displacement of a vibrated film.
Means to Solve the Problems
The microphone according to the present invention is equipped with a vibrated film which vibrates upon receipt of a sonic wave and reflects an electromagnetic wave with frequency less than 10
12
Hz, a device to receive and transmit the electromagnetic wave which radiates to the vibrated film and receives the electromagnetic wave reflected by the vibrated film, and a device to measure vibrated film signals which measures signals of the electromagnetic wave received by the device to receive and transmit electromagnetic wave. Measurement of the frequency and amplitude of the electromagnetic wave reflected by the vibrated film enables to change the displacement of the vibrated film to electric signals.


REFERENCES:
patent: 5621806 (1997-04-01), Page et al.
patent: 6014239 (2000-01-01), Veligdan
patent: 6125189 (2000-09-01), Yasuno et al.
patent: 6226386 (2001-05-01), Akino
patent: 6449370 (2002-09-01), Yasuno et al.
patent: 60089783 (1985-05-01), None
patent: 61181923 (1986-08-01), None

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