Patent Abstract:
A sound collector includes a first microphone unit and a second microphone unit having a single directivity and being pivotally supported in a manner that directions of directional axes of the units are changeable in an identical flat plane and a switch to be controlled in conjunction with the rotations of the first and the second microphone units. Output signals of the first and the second microphone units are outputted with channels of the signals being exchanged or non-exchanged by the switch in accordance with an angle formed by the directional axes.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. JP 2007-155867, filed in the Japanese Patent Office on Jun. 13, 2007, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sound collector and a sound recorder. 
     2. Description of Related Art 
     Examples of portable stereo sound recorders include those in which microphone units for collecting sounds are in an XY arrangement.  FIG. 8A  is a plan view showing the arrangement of the sound recorder of this type and the microphone units. A sound recorder  10  has the shape of a rectangular parallelepiped of approximately 70 mm (width)×150 mm (depth)×30 mm (thickness), and the front thereof is provided with a pair of microphone units  11 L and  11 R. 
     In this case, the microphone units  11 L and  11 R have uni-directivity. It is preferable if the microphone units  11 L and  11 R are arrange such that diaphragms (not shown) thereof are orthogonalized each other. However, practically it is difficult to arrange to be orthogonal, therefore the microphone units  11 L and  11 R are arranged such that the sound collecting openings of the units are sufficiently close to each other, and respective directional axes  12 L and  12 R of the units are orthogonal to each other in the identical horizontal plane. 
     With this configuration, as shown in  FIG. 8B , regions  13 L and  13 R become main sound collection ranges (directional ranges) of the microphone units  11 L and  11 R, respectively, and high sensitivity in the depth direction can be obtained, thereby attaining stereo sounds and images having impression of depth. It is therefore suitable for recording solo performance or the like. 
     As a prior art document, the following may be referred to. (Japanese Unexamined Patent Application Publication No. 2007-043510, Patent Document 1) 
     SUMMARY OF THE INVENTION 
     However, in the sensitivity characteristics shown in  FIG. 8B , the sound collection range in the right-to-left direction is somewhat narrow, and it is therefore unsuitable for sound collection of the sound source expanding to right-to-left fields, such as orchestra. For example, when recording in the situations where a train running from the left remote location gets close to a person, passes in front of the person, and then runs to the right remote location, the impression of expanding fields cannot be properly reproduced. 
     Accordingly, in an embodiment of the present invention, it is desirable to solve the issue and also solve newly caused issues. 
     The sound collector of one embodiment of the invention includes first and second microphone units having uni-directivity and being pivotally supported so that the directions of respective directional axes may be changed in an identical plane, and a switch controlled in conjunction with the rotations of the first and the second microphone units. The output signals of the first and the second microphone units are outputted by causing the switch to execute either of exchange and non-exchange of the channels of these output signals in accordance with an angle formed by the directional axes. 
     According to embodiments of the present invention, the directions of the directional axes of the first and the second microphone units can be changed and the stereo mode and the expansion field of sound can be set freely in accordance with the sound source to be recorded, whereby allowing optimum sound collection and sound recording in accordance with the sound source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing an embodiment of the present invention; 
         FIGS. 2A to 2C  are plan views for explaining the present invention; 
         FIGS. 3A to 3C  are plan views for explaining the directional properties in the present invention; 
         FIG. 4  is a schematic diagram showing an embodiment of the present invention; 
         FIGS. 5A and 5B  are plan views for explaining the use situations in an embodiment of the present invention; 
         FIGS. 6A to 6C  are diagrams for explaining an embodiment of a part of the mechanism and the circuit in the present invention; 
         FIG. 7  is a diagram for explaining other embodiment of a part of the circuit in the present invention; and 
         FIGS. 8A and 8B  are plan views for explaining the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     1A. Configuration Example 
     Description of First Half 
       FIG. 1  is a plan view showing an example of the external view when the present invention is applied to a portable stereo sound recorder. Reference numeral  20  indicates the entire sound recorder. The dot-dash line  20 C indicates the center line in the front-back direction of the recorder  20 . 
     The sound recorder  20  is configured in the shape of substantially a flat rectangular parallelepiped as a whole. A pair of microphone units  21 A and  21 B are provided at the front portion of the recorder by keeping a predetermined space, for example, 8 cm to 9 cm, between the units. 
     In this case, the directivity of the microphone units  21 A and  21 B is a uni-directivity. These microphone units  21 A and  21 B are pivotally supported by pins  24  and  24 , respectively in a rotatable manner. As shown in  FIGS. 2A to 2C , the directions of directional axes  22 A and  22 B of the units  21 A and  21 B can be changed, respectively, in the right-to-left direction in the identical horizontal plane, including the center line  20 C. 
     That is,  FIG. 2A  shows the case where the microphone units  21 A and  21 B are rotated such that the directional axes  22 A and  22 B of the microphone units  21 A and  21 B are orthogonal to each other, and the sound collecting openings of the microphone units  21 A and  21 B are sufficiently close to each other. The state shown in  FIG. 2A  corresponds to the state shown in  FIG. 8A . 
       FIG. 2B  shows the case where the microphone units  21 A and  21 B are rotated such that the directional axes  22 A and  22 B become parallel to the center line  20 C.  FIG. 2C  shows the case where the microphone units  21 A and  21 B are rotated so that the directional axes  22 A and  22 B are in the opening direction. 
     Based on the center line  20 C in the front-back direction of the recorder  20 , for example, it is assumed as follows; 
     θA is the angle formed between the directional axis  22 A and the center line  20 C. The counterclock direction is positive. 
     θB is the angle formed between the directional axis  22 B and the center line  20 C. The clock direction is positive. 
     Based on the assumptions, the three states can be expressed as follows; 
     In the state shown in  FIG. 2A , θA=θB=−45°; 
     In the state shown in  FIG. 2B , θA=θB=0 (the directional axes  22 A and  22 B are parallel); and 
     In the state shown in  FIG. 2C , θA=θB=60°. 
     Although not shown, it is arranged that the angles θA and θB can be changed continuously and independently. 
     As shown in  FIG. 1 , switches  31 A and  31 B (described later) are provided in conjunction with the microphone units  21 A and  21 B, in the recorder  20 . 
     With this configuration, when the microphone units  22 A and  22 B are in the state shown in  FIG. 2A  (θA=θB=−45°), which is the same state of that shown in  FIG. 8A , the directional properties shown in  FIG. 3A  can be obtained, as similar with the case of  FIG. 8B . Accordingly, the regions  23 A and  23 B become the main sound collection ranges of the microphone units  21 A and  21 B, respectively. Thus, because high sensitivity in the depth direction can be achieved, stereo sounds and images with an impression of depth may be obtained, thereby making the units suitable for recording solo performance or the like. 
     When the microphone units  22 A and  22 B are in the state shown in  FIG. 2B  (θA=θB=0), the directional properties shown in  FIG. 3B  can be obtained, and the regions  23 A and  23 B become the main sound collection ranges of the microphone units  21 A and  21 B, respectively. Therefore, although stereo mode is weak, very high sensitivity with respect to the sounds from the front side can be obtained, thereby making the units suitable for recording a sound of a specific sound source. 
     When the microphone units  22 A and  22 B are in the state shown in  FIG. 2C  (θA=θB=60°), the directional properties as shown in  FIG. 3C  can be obtained, and the regions  23 A and  23 B become the main sound collection ranges of the microphone units  21 A and  21 B, respectively. Therefore, stereo sounds and images having impression of expanded in right and left can be obtained, thereby making the units suitable for recording orchestra performance or the like. Alternatively, when recording the situations where a train gradually gets close from the left remote location and passes in front of a person and runs to the right remote location, impression of expansion may be properly reproduced. 
     1B. Configuration Example 
     Description of Latter Part 
     If configurations are limited to the above, the following problem in terms of audio signals (sound collection signals) outputted from the microphone units  21 A and  21 B may occur, in the case of  FIG. 2A  and in the case of  FIG. 2C  (and  FIG. 2B ). 
     That is, the state shown in  FIG. 2A  leads to the following results: 
     The output of the microphone unit  21 A is equal to the audio signal of the right channel; and 
     The output of the microphone unit  21 B is equal to the audio signal of the left channel. 
     On the other hand, the state shown in  FIG. 2C  leads to the following results: 
     The output of the microphone unit  21 A is equal to the audio signal of the left channel; and 
     The output of the microphone unit  21 B is equal to the audio signal of the right channel. Thus, the channels of the audio signals to be outputted from the microphone units  21 A and  21 B are reversed between the state shown in  FIG. 2A  and the state shown in  FIG. 2C . 
     Consequently, in the present invention, the circuit for recording audio signals has, for example, the structure as shown in  FIG. 4 . That is, audio signals SA and SB outputted from the microphone units  21 A and  21 B are supplied via preamplifiers  32 A and  32 B to A/D (analog to digital) converter circuits  33 A and  33 B to be converted into digital audio signals DA and DB, respectively. These digital audio signals DA and DB are then supplied to preprocessing circuits  41 A and  41 B, respectively. 
     In the preprocessing circuits  41 A and  41 B, the digital audio signals DA and DB are subjected to, for example, limiter processing, equalizer processing, and so-called SBM (super bit mapping, registered trademark) processing in which quantization noise is shifted to high frequency where grating on ear is avoided, by use of noise shaping technique. The preprocessing circuits  41 A and  41 B are integrated into a one-chip IC (integrated circuit)  34 , together with the following circuits  42  to  44 . 
     The preprocessed digital audio signals DA and DB are written sequentially in a buffer memory  43  by a write memory controller  42 , and the written digital audio signals DA and DB are read sequentially by a read memory controller  44 . 
     The switches  31 A and  31 B are provided to receive an on-off control in conjunction with the rotations of the microphone units  21 A and  21 B (the changes in the angle θA and the angle θB of the directional axes  22 A and  22 B), and the switch outputs are supplied to the memory controller  44  as the control signals of read addresses, respectively. 
     Subsequently, the digital audio signals DA and DB are read from the memory  43  as follows. 
     Specifically, when the directional axes  22 A and  22 B are crossed (for example, the state shown in  FIG. 2A ), these two signals are read as follows: 
     The signal DA is the digital audio signal DR of the right channel; and 
     The signal DB is the digital audio signal DL of the left channel. 
     When the directional axes  22 A and  22 B are not crossed (for example, the states shown in  FIGS. 2B and 2C ), these two signals are read as follows: 
     The signal DA is the digital audio signal DL of the left channel; and 
     The signal DB is the digital audio signal DR of the right channel. 
     The read digital audio signals DL and DR of the left and right channels are then written, namely recorded sequentially through the controller  44  into a recording media, which is a non-volatile memory  35  in this example. 
     The non-volatile memory  35  may be a memory contained in the recorder  20 , or alternatively may be a removable memory card. In either case, by employing the USB (universal serial bus) configuration, the contents of the memory  35  can be transferred to and reproduced on an external personal computer or the like. When the non-volatile memory is a memory card, the memory card can be removed from the recorder  20  and reproduced by a personal computer or the like. 
     In this manner, in the recorder  20  shown in  FIG. 4 , in accordance with the angle formed between the directional axes  22 A and  22 B of the microphone units  21 A and  21 B, the audio signals outputted from the microphone units  21 A and  21 B are classified to the digital audio signals of the left channel and the right channel, and then written in the non-volatile memory  35 . 
     Therefore, even if the microphone units  21 A and  21 B are in the state shown in  FIG. 2A  or in the states shown in  FIGS. 2B , or  2 C, the digital audio signals DA and DB of the left and right channels may be properly recorded in the non-volatile memory  35 . 
     2. Summary 
     In accordance with the recorder  20 , the correct states can be recorded in a memory by the exchange of the channels of the audio signals collected by the microphone units  21 A and  21 B between the state shown in  FIG. 2A  and the state shown in  FIG. 2C . Since the directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B can be freely and continuously changed between the state shown in  FIG. 2A  and the state shown in  FIG. 2C  (via the state shown in  FIG. 2B ), the stereo mode and the degrees of expansion can be freely set depending on the sound source to be recorded, thereby allowing optimum sound collection and sound recording. 
     For example, as shown in  FIG. 5A , when recording is performed with the recorder  20  set at the right position of a concert hall, the sounds of concert performance from musical instruments reach the microphone units  21 A and  21 B of the recorder  20  through various passages. Therefore, as shown in  FIG. 2C , when the directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B are symmetric with respect to the center line  20 C of the recorder  20 , namely when θA=θB, the microphone unit  21 B may collect and record more reflected sound components from the right wall surface than the microphone unit  21 A. 
     However, the recorder  20  allows the directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B to be set independently. Accordingly, in the case of the situation shown in  FIG. 5A , by setting directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B as those as shown in  FIG. 5B , the sound components reflected from the right wall surface may be reduced and recording with a appropriate left/right sound balance becomes possible. 
     3. Examples of Mechanism of Microphone Units and Switches, which Move in Conjunction with Each Other 
       FIGS. 6A to 6C  show one example of the mechanisms between the microphone units  21 A and  21 B and the switches  31 A and  31 B, which move in conjunction with each other. Since the relation between the microphone units  21 A and the switch  31 A is the same as the relation between the microphone unit  21 B and the switch  31 B,  FIGS. 6A to 6C  exemplify only the relation between the microphone unit  21 A and the switch  31 A. Further, directions of the directional axis  22 A of the microphone unit  21 A in  FIGS. 6A ,  6 B and  6 C corresponds to those in  FIGS. 2C ,  2 B to  2 A, respectively. 
     In  FIGS. 6A to 6C , a convex portion  211  is integrally formed with the circumferential surface of the back portion of the microphone unit  21 A along the rotating direction. At the position facing to the back portion of the microphone unit  21 A, for example, a micro switch is provided as the switch  31 A, and an actuator  311  of the switch  31 A is provided so as to correspond to the convex portion  211 . For example, the microphone switch  31 A may be a normal open switch. 
     One input terminal of a NOR circuit  32  is pulled up by a resistor R 31 , and the switch  31 A is connected between the input terminal and the grounding. The microphone unit  21 B and the switch  31 B are similarly configured and connected to the NOR circuit  32 . 
     With this configuration, in the state shown in  FIGS. 6A and 6B , that is, in the state where the directional axis  22 A of the microphone unit  21 A does not cross with the center axis  20 C (θA≧0), the convex portion  211  does not press the actuator  311 , and accordingly the switch  31 A is set to be the off state and the output voltage VA of the switch  31 A becomes “H” level. 
     On the other hand, in the state shown in  FIG. 6C , that is, in the state where the directional axis  22 A of the microphone unit  21 A crosses with the center axis  20 C (θA&lt;0), the convex portion  211  presses the actuator  311 , and accordingly the switch  31 A is set to be the on state, and the output voltage VA becomes “L” level. 
     The output voltage VB of the switch  31 B becomes either “H” level or “L” level in accordance with the angle θB of the directional axis  22 B of the microphone unit  21 B. 
     Accordingly, when the directional axes  22 A and  22 B of the microphone units  21 A and  21 B are in the state shown in  FIG. 2A , an output signal S 32  of the NOR circuit  32  becomes “H” level, whereas in the state shown in  FIG. 2B  or  2 C, the output signal S 32  of the NOR circuit  32  becomes “L” level. Thus, by supplying the NOR signal S 32  to the memory controller  44  as read control signal, as described in the 1B, the audio signals SA and SB outputted from the microphone units  21 A and  21 B may be properly recorded in the non-volatile memory  35 , as the digital audio signal DL or DR of the left or right channel. 
     4. Other Examples 
       FIG. 7  shows other example of the configuration that prevents the channels of audio signals from being reversed due to the directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B. That is, in this example, variable resistors  33 A and  33 B in conjunction with the rotations of the microphone units  21 A and  21 B, respectively are provided. The output audio signal SA of the microphone unit  21 A is supplied to one terminal (A) of each of the variable resistors  33 A and  33 B, and the output audio signal SB of the microphone unit  21 B is supplied to the other terminal B of each of the variable resistors  33 A and  33 B. 
     The output signals of the needles of the variable resistors  33 A and  33 B are extracted as the audio signals SL and SR of the left and right channels, respectively. In this example, even if the directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B are changed, channel is not reversed while reading is performed in the memory controller  44 . 
     With this configuration, when the microphone units  21 A and  21 B are in the state shown in  FIG. 2A , the signals SB and SA on the terminals (B) side of the variable resistors  33 A and  33 B are extracted as the signals SL and SR, respectively, and the extracted signals serve as the audio signals of the left and right channels, respectively. 
     When the microphone units  21 A and  21 B are in the state shown in  FIG. 2C , the signals SA and SA on the terminals (A) side of the variable resistors  33 A and  33 B are extracted as the signals SL and SR, and the extracted signals serve as the audio signals of the left and right channels. 
     When the microphone units  21 A and  21 B are in the state shown in  FIG. 2B , mixed signals consisting of the signals on the terminals (A) side and the terminal (B) side of the variable resistors  33 A and  33 B are extracted as signals SL and SR. 
     In addition, the directions of the directional axes  22 A and  22 B of the microphone units  21 A and  21 B may be continuously changed, and correspondingly the contents of the output audio signals SL and SR (the signals SA and SB) of the variable resistors  33 A and  33 B change continuously, thereby allowing the impression of expansion and stereo mode to be continuously changed. 
     5. Others 
     In the example shown in  FIG. 4 , when microphone units are in the state shown in  FIG. 2A , the controller  44  switches the addresses when the digital audio signals DL and DR are read from the memory  43 , thereby preventing the inversion of the right and left channels. Alternatively, the controller  42  may switch the addresses when the digital audio signals DA and DB are written in the memory  43 , thereby preventing the inversion of the right and left channels. Further, the inversion of the right and left channels may be prevented by switching the signal lines from the microphone units  21 A and  21 B to the controller  42 . 
     When one of the microphone units  21 A and  21 B is rotated, the directions of the directional axes  22 A and  22 B may be correspondingly changed to satisfy “θA=θB”. Further, a non-directional microphone unit may be arranged between the microphone units  21 A and  21 B, and its output audio signals may be distributed to the right and left channels, in order to avoid so-called lack of middle range. 
     Further, the directional axes  22 A and  22 B of the microphone units  21 A and  21 B may have an elevation angle or a depression angle. When the voice and sounds of an object are collected/recorded by mounting these units on a movie camera, the zooming mechanism may operate in conjunction with the rotation mechanism of the microphone units  21 A and  21 B, so that the angle of views and directional properties while capturing images match. In other words, these two units may be brought into the state shown in  FIG. 2A  at telescopic imaging, and to the state shown in  FIG. 2C  at wide-angle imaging. 
     LIST OF ABBREVIATIONS 
     A/D: Analog to Digital 
     IC: Integrated Circuit 
     SBM: Super Bit Mapping (registered trademark) 
     USB: Universal Serial Bus 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

Technology Classification (CPC): 7