PATENT DOCUMENT

Publication Number: US-9510074-B2
Application Number: US-201414325204-A
Country: US
Kind Code: B2

Title: Grating only optical microphone

Abstract:
A micro-electro-mechanical system (MEMS) optical sensor including an enclosure having a top wall, a bottom wall and a sidewall connecting the top wall and the bottom wall. The sensor further including a compliant membrane positioned within the enclosure, which is configured to vibrate in response to an acoustic wave and having a grating formed therein. A reflector is formed directly on an inner surface of one of the bottom wall or the top wall of the enclosure. A light emitter is positioned within the enclosure along a side of the compliant membrane opposite the reflector, the light emitter is configured to transmit a laser light toward the grating and the reflector. A light detector is positioned along the side of the compliant membrane opposite the reflector, the light detector configured to detect an interference pattern of the laser light, which is indicative of an acoustic vibration of the compliant membrane.

Claims:
What is claimed is: 
     
       1. An optical microphone comprising:
 an enclosure having a top wall, a bottom wall and a sidewall connecting the top wall and the bottom wall; 
 a compliant membrane suspended within the enclosure by a suspension member, the compliant membrane configured to vibrate in response to an acoustic wave and having a grating formed therein, and wherein the suspension member is formed from a material of the compliant membrane and extends along an entire length of at least one side of the compliant membrane; 
 a reflector formed directly on an inner surface of one of the bottom wall or the top wall of the enclosure; 
 a light emitter positioned within the enclosure along a side of the compliant membrane opposite the reflector, the light emitter configured to transmit a laser light toward the grating and the reflector; and 
 a light detector positioned along the side of the compliant membrane opposite the reflector, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector, wherein the interference pattern is indicative of an acoustic vibration of the compliant membrane. 
 
     
     
       2. The optical microphone of  claim 1  wherein the suspension member is a corrugated structure formed from a material layer of the compliant membrane. 
     
     
       3. The optical microphone of  claim 1  wherein the compliant membrane comprises 1) the grating formed within a rigid frame portion of the compliant membrane and 2) a compliant outer portion that is attached to a support member. 
     
     
       4. The optical microphone of  claim 1  wherein the top wall, the bottom wall and the sidewall are integrally formed with one another from a same material, and wherein the reflector is a metal coated substrate having a top side facing the grating and a bottom side mounted directly to one of the top wall or the bottom wall. 
     
     
       5. The optical microphone of  claim 1  wherein the reflector is a metal coating applied to the inner surface. 
     
     
       6. The optical microphone of  claim 1  wherein the reflector is immovable relative to the compliant membrane. 
     
     
       7. The optical microphone of  claim 1  wherein the reflector is formed on the bottom wall and the enclosure further comprises an acoustic port formed through the top wall. 
     
     
       8. A micro-electro-mechanical system (MEMS) optical microphone comprising:
 a MEMS optical microphone enclosure having a first wall upon which a reflector is positioned and a second wall through which an acoustic port is formed; 
 a diaphragm suspended within the enclosure by a suspension member that is suspended from a diaphragm support member, the diaphragm support member extending from the first wall toward the second wall of the enclosure, the diaphragm having a grating, the grating spaced a distance above the reflector; 
 a light emitter positioned above the diaphragm, the light emitter configured to transmit a laser light toward the grating and the reflector; and 
 a light detector positioned above the diaphragm, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector, wherein the interference pattern is indicative of an acoustic vibration of the diaphragm. 
 
     
     
       9. The optical microphone of  claim 8 
 wherein the suspension member is a spring. 
 
     
     
       10. The optical microphone of  claim 8  wherein the reflector comprises a reflective plate mounted directly to an inner surface of the first wall. 
     
     
       11. The optical microphone of  claim 8  wherein the reflector comprises a reflective coating applied to an inner surface of the first wall. 
     
     
       12. The optical microphone of  claim 8  further comprising circuitry connected to the diaphragm and the reflector, the circuitry operable to apply a voltage one or more of the diaphragm and the reflector to tune the distance. 
     
     
       13. The optical microphone of  claim 12  wherein the distance is tuned by moving the diaphragm while the reflector remains stationary. 
     
     
       14. The optical microphone of  claim 8  wherein a vertical position of the reflector with respect to the first wall is fixed. 
     
     
       15. An optical microphone system comprising:
 a MEMS microphone enclosure having an acoustic port; 
 a reflector formed on an inner surface of the enclosure; 
 a diaphragm positioned within the enclosure, the diaphragm having a grating that is spaced a distance from the reflector; 
 a light emitter positioned on an inner surface of the enclosure that is different from the reflector, the light emitter configured to transmit a laser light toward the grating and the reflector; 
 a light detector positioned along the same inner surface as the light emitter, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector; and 
 circuitry connected to one or more of the diaphragm and the reflector, wherein the circuitry is operable to apply a voltage to the diaphragm to tune the distance between the grating and the reflector. 
 
     
     
       16. The system of  claim 15  wherein the reflector comprises a gold coating applied to the inner surface of the enclosure. 
     
     
       17. The system of  claim 15  wherein the distance between the diaphragm and the reflector is tuned by moving the diaphragm while the reflector remains stationary. 
     
     
       18. The system of  claim 15  wherein the voltage is used to tune the distance to any integer multiple of ¼λ of the laser light. 
     
     
       19. The system of  claim 15  wherein the reflector is fixedly attached to the inner surface of the enclosure. 
     
     
       20. The system of  claim 15  wherein the reflector is formed on the inner surface of a bottom wall of the enclosure and the light emitter and the light detector are formed on the inner surface of a top wall of the enclosure.

Description:
FIELD 
     An embodiment of the invention is directed to a micro-electro-mechanical system (MEMS) device, more specifically, a MEMS optical microphone having a single plate. Other embodiments are also described and claimed. 
     BACKGROUND 
     MEMS devices generally range in size from about 20 micrometers to about 1 millimeter and are made up of a number of even smaller components which can be formed in layers on a substrate using various MEMS processing techniques (e.g. deposition processes, patterning, lithography, etching, etc.). MEMS devices can be processed for many different applications, for example, they may be sensors or actuators. One example of a MEMS sensor is a laser microphone. A MEMS laser, or optical, microphone refers to a microphone which uses a laser beam to detect sound vibrations of an associated diaphragm. The microphone may include two essentially flat, horizontally arranged, surfaces. One of the surfaces may be a diaphragm, which can vibrate in response to sound waves, and the other surface may be a substantially stiff structure having a grating. A light emitter and a light detector may be associated with a substrate positioned below the flat surfaces. The light emitter may be a laser (e.g. a vertical cavity surface emitting laser (VCSEL)) configured to direct a light beam toward a reflective portion of the diaphragm. Typically, the substantially stiff structure having the grating is positioned between the diaphragm and the light emitter such that the light beam first passes through the grating. The light beam is diffracted by the grating and then reflected off of the reflective portion of the diaphragm back to the light detector. The light detector detects the interference pattern created by the diffracted light rays and converts the light into an electrical signal, which corresponds to an acoustic vibration of the diaphragm, which in turn provides an indication of sound. 
     SUMMARY 
     An embodiment of the invention is directed to a MEMS sensor which can be formed by MEMS processing techniques and includes a single plate suspended within the sensor to facilitate sound detection. Representatively, in one embodiment, the MEMS sensor is a very high signal-to-noise ratio (SNR) laser (or optical) microphone. Representatively, the MEMS optical sensor may include an enclosure having a top wall, a bottom wall and a sidewall connecting the top wall and the bottom wall. The sensor may further include a compliant membrane positioned within the enclosure, which is configured to vibrate in response to an acoustic wave and having a grating formed therein. A reflector is formed directly on an inner surface of one of the bottom wall or the top wall of the enclosure. A light emitter is positioned within the enclosure along a side of the compliant membrane opposite the reflector. For example, the light emitter is positioned between a side (e.g. a face) of the compliant membrane and the top wall while the reflector is positioned between another side of the compliant membrane and the bottom wall. Alternatively, the light emitter is positioned within the enclosure between a side of the compliant membrane and the bottom wall while the reflector is positioned between another side of the compliant membrane and the top wall. The emitter is configured to transmit a laser light toward the grating and the reflector. A light detector is positioned along the same side of the compliant membrane as the light emitter, the light detector configured to detect an interference pattern of the laser light, which is indicative of an acoustic vibration of the compliant membrane. 
     A further embodiment of the invention includes a MEMS optical sensor having an enclosure including a wall upon which a reflector is positioned. The sensor further includes a diaphragm positioned within the enclosure, the diaphragm having a grating, the grating spaced a distance above the reflector. A light emitter is positioned above the diaphragm, the light emitter configured to transmit a laser light toward the grating and the reflector. A light detector is positioned above the diaphragm, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector, wherein the interference pattern is indicative of an acoustic vibration of the diaphragm. 
     A further embodiment of the invention includes an optical microphone system including a MEMS microphone enclosure having an acoustic port. A reflector is formed on an inner surface of the enclosure. A diaphragm is positioned within the enclosure, the diaphragm having a grating that is spaced a distance from the reflector. A light emitter is positioned on an inner surface of the enclosure that is different from the reflector, the light emitter configured to transmit a laser light toward the grating and the reflector. A light detector is positioned along the same inner surface as the light emitter, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector. The system further including circuitry connected to one or more of the diaphragm and the reflector. The circuitry may be used to tune the distance between the diaphragm and the reflector. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  illustrates a cross-sectional side view of one embodiment of a MEMS optical microphone. 
         FIG. 2  illustrates a top plan view of a compliant membrane of the MEMS optical microphone of  FIG. 1 . 
         FIG. 3  illustrates a circuit arrangement for controlling the MEMS optical microphone of  FIG. 1 . 
         FIG. 4  illustrates one embodiment of a simplified schematic view of one embodiment of an electronic device in which the optical microphone may be implemented. 
         FIG. 5  illustrates a block diagram of some of the constituent components of an embodiment of an electronic device in which an embodiment of the invention may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  illustrates a cross-sectional side view of one embodiment of a MEMS optical microphone. Microphone  100  may include a plate such as a compliant membrane  102 , a reflector  104 , a light emitter  106 , a light detector  108  and circuitry  122  positioned within enclosure  110 . Enclosure  110  may be any type of enclosure suitable for forming a housing or packaging around the microphone components. Enclosure  110  may include at least one acoustic port  130  such that sound (S) from the ambient environment outside of enclosure  110  may enter enclosure  110 . 
     In one embodiment, enclosure  110  includes a top wall  112 , a bottom wall  114  and at least one sidewall  116 . Acoustic port  130  may be formed through any one of top wall  112 , bottom wall  114  and sidewall  116 . Sidewall  116  may connect the top wall  112  to the bottom wall  114 . Each of the top wall  112 , bottom wall  114  and sidewall  116  have an inner surface  118  and an outer surface  120 . The inner surface  118  being the surface facing the interior space within enclosure  110  and the outer surface  120  being the surface facing the ambient environment, outside of enclosure  110 . The top wall  112  and the bottom wall  114  may run substantially parallel to one another. Sidewall  116  may be substantially perpendicular to each of the top wall  112  and bottom wall  114 , or it may be slanted. In one embodiment, enclosure  110  may have a relatively low z-height (i.e. top wall  112  and bottom wall  114  are relatively close together) such that a distance between top wall  112  and bottom wall  114  is relatively small. In one embodiment, each of top wall  112 , bottom wall  114  and sidewall  116  are integrally formed with one another as one inseparable structure. In other words, enclosure  110  is a single integrally formed unit. In this aspect, each of walls  112 ,  114  and  116  may be made of the same material. For example, walls  112 ,  114 ,  116  of enclosure  110  may be formed from a plastic material. It is further contemplated that in some embodiments, one or more of walls  112 ,  114 ,  116  are formed by a substrate with electrical contacts formed therein (e.g. a printed circuit board) to facilitate electrical connections with the various microphone components discussed herein. 
     Compliant membrane  102  may be a substantially planar plate like structure that is suspended within enclosure  110  and capable of vibrating in response to sound (S). Representatively, compliant membrane  102  may also be referred to as a diaphragm or sound pick up membrane that can be used within an acoustic-to-electric transducer or sensor which converts the sound wave induced by the mechanical motion of the diaphragm to an electrical signal (e.g. a microphone). In one embodiment, compliant membrane  102  may be suspended between top wall  112  and bottom wall  114  such that it is parallel to the walls, in other words faces the walls. In addition, it is important that compliant membrane  102  be spaced a distance (d) above reflector  104 . Representatively, in one embodiment, compliant membrane  102  may be suspended above reflector  104  by suspension members  124 A and  124 B, which suspend compliant membrane  102  from support members  132 A and  132 B. In one embodiment, support members  132 A and  132 B may be posts that extend vertically upward from inner surface  118  of bottom wall  114  as shown in  FIG. 1 . In other embodiments, support members  132 A and  132 B may extend vertically downward from inner surface  118  of top wall  112 . Support members  132 A and  132 B may be integrally formed with enclosure  110 , or they may be separate structures mounted to the inner surface  118  of enclosure  110  after they are formed. 
     Suspension members  124 A and  124 B may have any size and dimension suitable for suspending compliant membrane  102  from support members  132 A and  132 B. It is further important that suspension members  124 A and  124 B be compliant or elastic members that allow for vertical movement of compliant membrane  102  (e.g. movement of compliant membrane  102  in a z-height direction) such that compliant membrane  102  can vibrate in response to sound and a distance (d) between compliant membrane  102  and reflector  104  can be tuned, in some cases, to improve a resonance of an interference pattern used to provide an indication of sound, as will be discussed in more detail below. Representatively, in one embodiment, suspension members  124 A and  124 B may be spring like structures. For example, in one embodiment, suspension members  124 A and  124 B may be springs formed by corrugations within the outer edges of compliant membrane  102 . Suspension members  124 A and  124 B may be integrally formed from the same material as compliant membrane  102 , or separately formed structures which are attached between the outer edges of compliant membrane  102  and support members  132 A and  132 B. 
     Compliant membrane  102  may include an outer frame portion  134  and a grating  128 . Outer frame portion  134  may be a rigid portion, which surrounds grating  128 . Grating  128  may be vertically aligned with reflector  104 . Grating  128  is also aligned with light emitter  106  and light detector  108  such that light emitted by light emitter  106  toward, and reflected from, reflector  104  passes through grating  128 . Grating  128  is dimensioned to form an interference pattern that can be detected by light detector  108  and used as an indicator of a movement of compliant membrane  102 . Since the pattern represents a displacement of the compliant membrane  102 , it can be used to provide an indication of sound using a diffraction based optical interferometer method or any other optical interferometric method. Representatively, in some embodiments, grating  128  may also include a reflective coating  136  to facilitate formation of the interference pattern. Reflective coating  136  may be, for example, a metallic coating (e.g. a gold coating) applied to grating  128  during a MEMS processing operation (e.g. a deposition process). 
     In some embodiments, grating  128  is integrally formed within frame portion  134  of compliant membrane  102 , such as by a MEMS processing technique (e.g. patterning, etching or the like). For example, in some embodiments, compliant membrane  102  is a substantially solid membrane having grating  128  formed within frame portion  134  such that it is within a center portion of membrane  102 . In other words, the only openings within compliant membrane  102  are those within grating  128 . Such a configuration is illustrated in more detail in  FIG. 2 . 
     Representatively,  FIG. 2  illustrates a top view of compliant membrane  102 . From this view, it can be seen that compliant membrane  102  may have, for example, a square shaped frame portion  134  within which grating  128  is formed. Alternatively, compliant membrane  102  may have any type of quadrilateral shape, or other shapes, for example, a circle, ellipse, oval or the like. Grating  128  may have a periodic structure sufficient to split and diffract light emitted from an emitter (e.g. emitter  106 ) into different beams for detection by a detector (e.g. detector  108 ). In some embodiments, the grating  128  causes the formation of an interference pattern which can be used to indicate a movement of compliant membrane  102  in response to sound waves, and in turn, as an indicator of sound. Grating  128  may be formed in a portion of compliant membrane  102  which is aligned with reflector  104 , and emitter  106 /detector  108 . In the illustrated embodiment, grating  128  is formed in a center portion of frame portion  134 . 
     Suspension members  124 A,  124 B are formed along sides of frame portion  134  of compliant membrane  102  and can be used to attach compliant membrane  102  to support members  132 A,  132 B. Suspension members  124 A,  124 B can run along an entire length of the sides of frame portion  134  or less than the entire length. Suspension members  124 A,  124 B can be made from the same material layer used to form compliant membrane  102  such that they are integrally formed with compliant membrane  102  using MEMS processing techniques. For example, the frame portion  134  of compliant membrane  102  may be wider on the side where it is desirable to have suspension members  124 A,  124 B. Corrugations  202 A,  202 B may then be formed in the extra width portion to form an elastic structure that functions as a spring. In other embodiments, suspension members  124 A,  124 B may have any structure sufficient to suspend compliant membrane  102  from support members  132 A,  132 B. For example, in other embodiments, suspension members  124 A,  124 B may be relatively narrow structures that do not extend the entire length of the edges of compliant membrane  102 . In this aspect, spaces may be formed between edges of frame portion  134  and support members  132 A,  132 B such that fluid (e.g. a gas or liquid) can flow between the structures. 
     In other embodiments, increased fluid flow through compliant membrane  102  may be accomplished by suspending grating  128  within an opening of compliant membrane  102 , for example, by springs or spoke like structures. Representatively, frame portion  134  may have a larger opening (i.e. larger than grating  128 ) and grating  128  may be suspended within the opening by springs. Compliant membrane  102 , including grating  128  and suspension members  124 A and  124 B, may be manufactured using MEMS processing techniques (e.g. deposition processes, patterning, lithography, etching, etc.). 
     Returning now to  FIG. 1 , reflector  104  may be a rigid member positioned along an inner surface  118  of enclosure  110 . Representatively, in one embodiment, reflector  104  is formed directly on inner surface  118  and compliant membrane  102  is positioned a distance (d) over or above reflector  104 . Said another way, reflector  104  is under or below compliant membrane  102 . For example, in one embodiment, reflector  104  may be a reflective substrate (e.g. a substrate with a metallic coating such as gold) which includes a top side  140  facing compliant membrane  102  and a bottom side  142  which contacts, and is mounted to, inner surface  118  of bottom wall  114 . In another embodiment, reflector  104  may be a reflective coating (e.g. a metallic coating such as gold) applied directly to inner surface  118  of bottom wall  114 . Moreover, since reflector  104  is positioned or formed directly on a wall of enclosure  110  such as by applying a metallic or reflective coating to wall  114  or by making wall  114  of a reflective material (e.g. a metallic material), and compliant membrane  102  is the only plate or membrane suspended within microphone  100  and/or formed by a MEMS processing technique, microphone  100  may be considered a “single plate” optical microphone or “single MEMS plate” microphone. Said another way, microphone  100  is considered to include only a single moving surface (i.e. compliant membrane  102 ) since, as previously discussed, reflector  104  is rigid and formed on or as part of a wall of enclosure  110 . 
     Reflector  104  is considered “rigid” relative to compliant membrane  102  in that it does not vibrate in response to sound (S) in the same manner as compliant membrane  102 . In addition, reflector  104  is considered to be in a fixed and stationary position with respect to bottom wall  114 . In other words, reflector  104  does not move (i.e. is immovable) in a vertical, a horizontal or other direction during operation of microphone  100 . It is further to be understood that although reflector  104  is shown on inner surface  118  of bottom wall  114 , reflector  104  could also be positioned on an inner surface of top wall  112 , and in some cases even sidewall  116 . For example, in one embodiment, compliant membrane  102  may be oriented within enclosure  110  such that it faces a sidewall  116  (e.g. the left sidewall) and reflector  104  could be positioned on the other sidewall  116  (e.g. the right sidewall). Reflector  104  can have any size and shape sufficient to reflect the light beam  126  emitted from light emitter  106  back toward detector  108 . 
     In addition, it is important that a distance (d) be maintained between reflector  104  and compliant membrane  102  as this area provides a resonant cavity within which light  126  can bounce back and forth between reflector  104  and compliant membrane  102 . The interference pattern created by these multiple reflections is then used by a diffraction based optical interferometer method or any other optical interferometric method to provide an indication of sound. In some embodiments, distance (d) may therefore be tuned to improve a resolution of the interference pattern created by the light reflections between reflector  104  and compliant membrane  102 . Representatively, as previously discussed, reflector  104  is at a fixed position on bottom wall  114 . In this aspect, to tune distance (d) (e.g. decrease or increase distance (d)), compliant membrane  102  can be moved either toward or away from reflector  104  to achieve a desired distance (d), while reflector  104  stays in the same position. Thus, since distance (d) can be tuned, the use of microphone  100  is not limited to an enclosure of any particular z-height. Rather, compliant membrane  102  can be moved toward or away from reflector  104  to maintain the desired distance (d) for optimal resolution. 
     In one embodiment, the distance (d) between compliant membrane  102  and reflector  104  can be tuned electrically by applying a voltage to one or more of compliant membrane  102  and reflector  104  using circuit  122 . Circuit  122  is connected to compliant membrane  102  and reflector  104  by wires  150 ,  152 , respectively. For example, in one embodiment, to tune distance (d), reflector  104  may be grounded and a voltage is applied by circuit  122  to compliant membrane  102  through wire  150 . The voltage induces an electrostatic charge between compliant membrane  102  and reflector  104 , which will in turn, draw compliant membrane  102  (and also grating  128 ) toward reflector  104 , thereby reducing distance (d). In some embodiments, distance (d) is tuned to any integer multiple of ¼ λ of the laser light  126  found suitable to improve the resolution. 
     It is further noted that distance (d) between compliant membrane  102  and reflector  104  can also help to reduce a “squeeze film” effect of microphone  100 . The squeeze film effect refers to a phenomenon that occurs when air passes between two plates in close proximity. By maintaining distance (d) between compliant membrane  102  and reflector  104 , and being able to tune this distance (d), a more open air passageway may be created. As a result, the noise penalty due to the squeeze film effect is reduced 
     Returning now to circuit  122 , circuit  122  may also be connected to emitter  106  and detector  108  by wires  154 ,  156 , respectively. Circuit  122  may receive power from an external source and provide power to one or more of compliant membrane  102 , reflector  104 , emitter  106  and/or detector  108 . In some embodiments, emitter  106  may be a light source such as a VCSEL. Emitter  106  may be configured to emit a laser light (or beam) in the direction of grating  128  and reflector  104 , for detection by detector  108 . Detector  108  may, in some embodiments, be a photo detector configured to detect a reflected light (or beam) generated by emitter  106 . The emitter  106  (e.g. VCSEL) and detector  108  (e.g. photo detector) can be off the shelf commercially available parts or custom built for a specific implementation. 
     One or more of the various components of microphone  100  (e.g. compliant membrane  102 , reflector  104 , support members  132 A,  132 B, emitter  106  and/or detector  108 ) may be formed and assembled using MEMS processing techniques (e.g. deposition processes, patterning, lithography, etching, etc.). For example, in one embodiment, support members  132 A,  132 B may be the sidewalls of a cavity formed within a substrate and compliant membrane  102  may be formed in the cavity. Representatively, a compliant membrane material and sacrificial layer may be stacked in the cavity. The compliant membrane material may then be etched or patterned to form compliant membrane  102  having suspension members  124 A,  124 B and grating  128 . The sacrificial layer may then be removed to form a space below compliant membrane  102 . This preformed MEMS structure may then be mounted within enclosure  110 , over reflector  104 , and the space will provide the distance (d) between compliant membrane  102  and reflector  104  as previously discussed. 
       FIG. 3  illustrates a circuit arrangement for controlling the MEMS optical microphone of  FIG. 1 . Representatively,  FIG. 3  illustrates a voltage source  302  which can be connected to compliant membrane  102  and reflector  104 . In one embodiment, to tune distance (d), reflector  104  is grounded and voltage V− is held at zero (or constant) while voltage V+ to compliant membrane  102  is applied (or if already applied, varied). It is further contemplated, that in some embodiments, reflector  104  may not be grounded and reflector voltage V− may instead be varied while compliant membrane voltage V+ remains constant to tune distance (d). 
       FIG. 4  illustrates one embodiment of a simplified schematic view of one embodiment of an electronic device in which a MEMS optical microphone, or other MEMS device described herein, may be implemented. As seen in  FIG. 4 , the MEMS device may be integrated within a consumer electronic device  402  such as a smart phone with which a user can conduct a call with a far-end user of a communications device  404  over a wireless communications network; in another example, the MEMS device may be integrated within the housing of a tablet computer. These are just two examples of where the MEMS device described herein may be used; it is contemplated, however, that the MEMS device may be used with any type of electronic device in which a MEMS device, for example, an optical MEMS microphone, is desired, for example, a tablet computer, a desk top computing device or other display device. 
       FIG. 5  illustrates a block diagram of some of the constituent components of an embodiment of an electronic device in which an embodiment of the invention may be implemented. Device  500  may be any one of several different types of consumer electronic devices. For example, the device  500  may be any microphone-equipped mobile device, such as a cellular phone, a smart phone, a media player, or a tablet-like portable computer. 
     In this aspect, electronic device  500  includes a processor  512  that interacts with camera circuitry  506 , motion sensor  504 , storage  508 , memory  514 , display  522 , and user input interface  524 . Main processor  512  may also interact with communications circuitry  502 , primary power source  510 , speaker  518 , and microphone  520 . Microphone  520  may be an optical microphone such as optical microphone  100  such as that described in reference to  FIG. 1 . The various components of the electronic device  500  may be digitally interconnected and used or managed by a software stack being executed by the processor  512 . Many of the components shown or described here may be implemented as one or more dedicated hardware units and/or a programmed processor (software being executed by a processor, e.g., the processor  512 ). 
     The processor  512  controls the overall operation of the device  500  by performing some or all of the operations of one or more applications or operating system programs implemented on the device  500 , by executing instructions for it (software code and data) that may be found in the storage  508 . The processor  512  may, for example, drive the display  522  and receive user inputs through the user input interface  524  (which may be integrated with the display  522  as part of a single, touch sensitive display panel). In addition, processor  512  may send an audio signal to speaker  518  to facilitate operation of speaker  518 . 
     Storage  508  provides a relatively large amount of “permanent” data storage, using nonvolatile solid state memory (e.g., flash storage) and/or a kinetic nonvolatile storage device (e.g., rotating magnetic disk drive). Storage  508  may include both local storage and storage space on a remote server. Storage  508  may store data as well as software components that control and manage, at a higher level, the different functions of the device  500 . 
     In addition to storage  508 , there may be memory  514 , also referred to as main memory or program memory, which provides relatively fast access to stored code and data that is being executed by the processor  512 . Memory  514  may include solid state random access memory (RAM), e.g., static RAM or dynamic RAM. There may be one or more processors, e.g., processor  512 , that run or execute various software programs, modules, or sets of instructions (e.g., applications) that, while stored permanently in the storage  508 , have been transferred to the memory  514  for execution, to perform the various functions described above. 
     The device  500  may include communications circuitry  502 . Communications circuitry  502  may include components used for wired or wireless communications, such as two-way conversations and data transfers. For example, communications circuitry  502  may include RF communications circuitry that is coupled to an antenna, so that the user of the device  500  can place or receive a call through a wireless communications network. The RF communications circuitry may include a RF transceiver and a cellular baseband processor to enable the call through a cellular network. For example, communications circuitry  502  may include Wi-Fi communications circuitry so that the user of the device  500  may place or initiate a call using voice over Internet Protocol (VOIP) connection, transfer data through a wireless local area network. 
     The device may include a microphone  520 . Microphone  520  may be a MEMS optical microphone such as that described in reference to  FIG. 1 . In this aspect, microphone  520  may be an acoustic-to-electric transducer or sensor that converts sound in air into an electrical signal. The microphone circuitry (e.g. circuit  122 ) may be electrically connected to processor  512  and power source  510  to facilitate the microphone operation (e.g. tilting). 
     The device  500  may include a motion sensor  504 , also referred to as an inertial sensor, that may be used to detect movement of the device  500 . The motion sensor  504  may include a position, orientation, or movement (POM) sensor, such as an accelerometer, a gyroscope, a light sensor, an infrared (IR) sensor, a proximity sensor, a capacitive proximity sensor, an acoustic sensor, a sonic or sonar sensor, a radar sensor, an image sensor, a video sensor, a global positioning (GPS) detector, an RF or acoustic doppler detector, a compass, a magnetometer, or other like sensor. For example, the motion sensor  504  may be a light sensor that detects movement or absence of movement of the device  500 , by detecting the intensity of ambient light or a sudden change in the intensity of ambient light. The motion sensor  504  generates a signal based on at least one of a position, orientation, and movement of the device  500 . The signal may include the character of the motion, such as acceleration, velocity, direction, directional change, duration, amplitude, frequency, or any other characterization of movement. The processor  512  receives the sensor signal and controls one or more operations of the device  500  based in part on the sensor signal. 
     The device  500  also includes camera circuitry  506  that implements the digital camera functionality of the device  500 . One or more solid state image sensors are built into the device  500 , and each may be located at a focal plane of an optical system that includes a respective lens. An optical image of a scene within the camera&#39;s field of view is formed on the image sensor, and the sensor responds by capturing the scene in the form of a digital image or picture consisting of pixels that may then be stored in storage  508 . The camera circuitry  506  may also be used to capture video images of a scene. 
     Device  500  also includes primary power source  510 , such as a built in battery, as a primary power supply. 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, the devices and processing steps disclosed herein may correspond to any type of optical sensor that could benefit from a single plate or membrane configuration, for example, an inertial sensor, an accelerometer, a gyrometer or the like. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20140707
Publication Date: 20161129
Grant Date: 20161129
Priority Date: 20140707
Inventors: LEE JAE H.
AGASHE JANHAVI S.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/08", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2201/003", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R23/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R23/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R23/008", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R7/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2201/003", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2201/003", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/08", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 53540850