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Opto-acoustic transducer and telephone receiver
| Details |
Inventors: Edelman, Seymour;
Assignee:
Primary Examiner: Griffin; Robert L.
Assistant Examiner: Coles, Sr.; Edward L.
Attorney, Agent or Firm: Brady, O'Boyle & Gates
An optical fiber element of low density, low heat capacity, a large coefficient of thermal expansion, and a large Young's modulus varies in light transmissivity gradually between its ends from high transmissivity to opacity, whereby power modulated light transmitted through the fiber element is absorbed to cause a change in temperature of the fiber element and a resultant thermal expansion and contraction thereof. As a transducer in a telephone receiver, a light absorbing fiber element or group of such elements is coupled between the optical fiber waveguide in the receiver and a resiliently mounted acoustical diaphragm which is caused to respond over the audible range. |
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DETAILED DESCRIPTION Referring to the drawings in detail wherein like numerals designate like parts, a telephone receiver 10 includes an earpiece 11 having a customary screen 12 at the forward end of a chamber 13 in which a stiff lightweight diaphragm 14 is floatingly supported on a bellows-type spring 15 in spaced relation to the screen 12.
An optical fiber line or waveguide 16 leading into the receiver 10 terminates centrally at the rear of chamber 13 in coaxial alignment with the diaphragm 14 which is disc-like.
As depicted in FIG.
2, a single optical fiber element 17 forming a component of the waveguide 16 and preferably having a length of approximately 1 cm extends from the terminal 18 of the waveguide 16 in the receiver to a central point on the diaphragm 14 and is attached to the diaphragm at this point to form a transducer element.
Alternatively, as depicted in FIGS.
1, 3 and 4, a bundle of optical fibers 19 having approximately the same lengths as the fiber 17 can be connected between the terminal 18 of the waveguide and plural circumferentially spaced attachment points 20 on a nodal circle 21 chosen for optimum resonance.
Preferably, the radius of the nodal circle 21 is approximately equal to 0.
68 of the radius of the disc or diaphragm 14.
The optical fibers 19 are components of the optical fiber waveguide 16.
Preferably, the fibers 17 or 19 are formed from polymers although they may be glass fibers.
The desired parameters for the fibers employed are low density, low heat capacity, large coefficient of thermal expansion, and a large Young's modulus.
Suitable polymers include polyvinylidene fluoride, polyvinylchloride, and polystyrene.
Each fiber 17 or 19 is treated by a well-known technique, for example, by ultra-violet radiation, so that its light transmissivity changes smoothly and gradually in a nearly linear manner or exponentially between the terminal 18 and its point of attachment to the diaphragm 14.
More particularly, at its rear terminal 18, the optical fiber is highly transmissive of power modulated light while at its forward end adjacent to the diaphragm 14 it is opaque or non-transmissive
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Telecommunications 
