WO2002047434A2

WO2002047434A2 - Optical microphone system and a method for forming same

Info

Publication number: WO2002047434A2
Application number: PCT/IL2001/001112
Authority: WO
Inventors: Alexander Paritsky; Alexander Kots; Sergey Smirnov
Original assignee: Phone-Or Ltd.
Priority date: 2000-12-04
Filing date: 2001-12-02
Publication date: 2002-06-13
Also published as: IL140066A0; WO2002047434A3; AU2002221021A1

Abstract

The invention provides an optical microphone system, including a microphone head including a light source, a light detector, a membrane having a first surface and a second surface and being responsive to sound pressure, the head being mounted in an enclosure having at least one opening facing the first surface, and a microphone base selected from the group of bases having means for interconnecting with the enclosure and being entirely closed, or provided with at least one aperture, facilitating the entrance therethrough of sound pressure. The invention further provides a method for forming an optical microphone.

Description

OPTICAL MICROPHONE SYSTEM AND A METHOD FOR FORMING SAME

Field of the Invention

The present invention relates to optical microphones, and more particularly, to optical microphone systems adaptable to specific uses, such as stages, studios, cellular phones, hands-free car kits, and the like. The invention further relates to a method for forming an optical microphone having a predetermined acoustic directivity response. Background of the Invention

Optical microphones are known, essentially comprising a microphone body including an optical head having a source of light, a photodetector, and a membrane onto which light is directed and which is open to free access of surrounding sound pressures. Hand-held acoustical systems (lip microphones) demand the use of figure-eight response directional microphones; at the same time, hands-free acoustical systems, wherein the microphone is meant to operate at a distance of 30-70 cm from the speaker's mouth, require a heart-shaped response directional microphone in order to achieve good results. Disclosure of the Invention

It is therefore a broad object of the present invention to provide optical microphone systems and a method for forming optical microphones which are adapted to provide the best sound pick-up results for specific uses.

It is a further object of the present invention to provide means and a method for adapting an optical microphone in order to provide acoustic directivity.

It is a yet further object of the present invention to provide an optical microphone system having heart-shaped or figure-eight-shaped sound response characteristics.

In accordance with the present invention, there is therefore provided an optical microphone system, comprising a microphone head including a light source, a light detector, a membrane having a first surface and a second surface and being responsive to sound pressure, said head being mounted in an enclosure having at least one opening facing said first surface, and a microphone base selected from the group of bases having means for interconnecting with said enclosure and being entirely closed or provided with at least one aperture facilitating the entrance therethrough of sound pressure.

The invention further provides a method for forming an optical microphone having a predetermined directivity response to sound pressure, said method comprising providing an optical microphone system as described herein, determining the required directivity response, selecting the most suitable base from said group of bases to meet the required directivity response, and interconnecting said base with the microphone enclosure. Brief Description of the Drawings

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings: Fig. 1 is a schematic, cross-sectional view of an omni-directional optical microphone according to the present invention; Fig. 2 is a schematic, cross-sectional view of a bi-directional optical microphone; Fig. 3 illustrates characteristic curves of the acoustic response of the microphone of

Fig. 2; Fig. 4 is a schematic, cross-sectional view of another embodiment of an optical microphone according to the present invention; Fig. 5 illustrates characteristic curves of the acoustic response of the microphone of

Fig. 4, and Fig. 6 is a cross-sectional view of an optical microphone construction according to the present invention. Detailed Description

Fig. 1 schematically illustrates an omni-directional optical microphone 1 consisting of a microphone head 2 including an enclosure 4 having a single opening 6, a support 8 carrying a light source 10, and light detector 12 separated from the light source 10 by a partition 14. The microphone further includes a membrane 16 having a first surface directed towards opening 6 and a second, opposite surface. The membrane 16 is responsive to impinging sound pressure. The enclosure 4 is closable from below the support 8 by a base 18. Since sound pressures can enter the microphone only from a single opening 6 and impinge upon the membrane only on one of its surfaces, the microphone is an omni-directional microphone.

Referring to Fig. 2, there is illustrated a bi-directional optical microphone 1 according to the present invention, which includes the microphone head 2. In this embodiment, however, the enclosure 4 is provided with an additional opening 20 made in the base 18, facilitating the entrance of sound waves also from another direction, to impinge on the second surface of membrane 16. As seen in Fig. 3, the microphone 1 will thus be responsive to sound pressures from more than one direction, forming a response characteristic 22 having the shape of a figure eight.

The optical microphone of Fig. 4 is similar to that shown in Fig. 2, except for the addition of an acoustical filter 24 fitted in aperture 20. Such an acoustical filter has the effect of delaying the passage of acoustic waves and of reducing their intensity, i.e., attenuating their energy, resulting, for example, in the characteristic curves shown in Fig. 5 of a heart-shaped response characteristic 26.

Fig. 6 illustrates a preferred structural embodiment of the optical microphone according to the present invention. In order to facilitate selection of the desired microphone response characteristics in accordance, e.g., with the characteristics 22 of Fig. 3 or 26 of Fig. 5, the microphone is made of two mterconnectable parts: the head 2 and further base 28, to which head 2 can be coupled. The base 28 may be closed, as shown in Fig. 1 ; it may have an aperture 20 (Fig. 2) or an aperture 20 fitted with an acoustical filter 24 (Fig. 4). For the purpose of interconnecting the two parts, base 28 may be provided with an annular rim 30 configured to allow the head 2 to be press-fitted into or around the rim. Alternatively, other mechanical means for interconnecting between the two housing parts can be provided. For example, the enclosure 4 may be press-fitted into a suitable groove made in the base 18, as illustrated in Figs. 2 and 4. Interconnectable, per se known, standard plug and socket-type electrical wiring and terminals 32 are naturally also provided.

Hence, any user may choose the most suitable base for a particular use. Whenever the microphone is used in a different mode or environment, the base may easily be changed.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. An optical microphone system, comprising: a microphone head including a light source, a light detector, a membrane having a first surface and a second surface and being responsive to sound pressure, said head being mounted in an enclosure having at least one opening facing said first surface, and a microphone base selected from the group of bases having means for interconnecting with said enclosure and being entirely closed, or provided with at least one aperture, facilitating the entrance therethrough of sound pressure.

2. The optical microphone system as claimed in claim 1, wherein said aperture is provided with an acoustic filter.

3. The optical microphone system as claimed in claim 1, wherein said enclosure and said base are provided with means for mechanical interconnection by pressure fit.

4. A method for forming an optical microphone having a predetermined directivity response to sound pressure, said method comprising: providing an optical microphone system as claimed in claim 1 or claim 2; determining the required directivity response; selecting the most suitable base from said group of bases to meet the required directivity response, and interconnecting said base with the microphone enclosure.

5. The method as claimed in claim 4, wherein the directivity response characteristic is selected from the group of omni-directional, figure-eight shaped and heart-shaped acoustic directivity responses.