JPH03291099

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DESCRIPTION JPH03291099
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
microphones for video cameras, and more particularly to an improvement for achieving sound
recording resistant to wind noise. <Prior Art> Although the monaural method has been the
mainstream in the conventional sound pickup method for video cameras for home use, there is a
tendency toward stereo formation in the future. As a general stereo sound collection method,
there is a method of arranging two unidirectional microphone units apart from each other, but
this requires a large space from side to side, so it is suitable for video cameras that are currently
being miniaturized. Absent. On the other hand, as a stereo sound collecting method requiring
only a small space, there is a method called MS (or & (icl-Side 3 method) using one unidirectional
microphone unit and a bi-directional microphone unit. In the MS method, the unidirectional
microphone unit is disposed forward with the directivity axis facing, and the bidirectional
microphone unit is disposed with the directivity axis facing left and right. Taking the sum and the
difference, it is a stereo signal. <Problems to be Solved by the Invention> In the case of the MS
system, since the unidirectional microphone unit and the bidirectional microphone unit are
located at almost the same place, the space is not wide as described above, and thus it is suitable
for a video camera. It can be said. However, directional microphone units are more noisy when
exposed to wind or air flow because they have holes for introducing sound waves in order to give
directivity compared to nondirectional microphone units. It has an inherent disadvantage that
wind noise is generated. As a measure against this wind noise, it is conceivable to cut the low
frequency side by passing the output signals of all the directional microphone units through an
electrical fly-pass filter, but the cost increase due to the deterioration of sound quality and the
increase in parts. And it is difficult to say that it is effective. Also, as a mechanical measure, it is
conceivable to attach a strong windshield to all directional microphones to block the entry of
wind, but an effective windshield has a complicated structure and a large size, so a video camera
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Contrary to the miniaturization of the system, it also leads to a significant cost increase. An object
of the present invention is to provide a video camera having a sound collecting device which
solves the above-mentioned drawbacks of the prior art. The configuration of a video camera
according to the present invention includes a nondirectional microphone unit, a cylinder
covering the nondirectional microphone unit and having an opening in the visual field direction
of the video camera, and a video camera The bi-directional microphone unit whose directivity
axis is directed to the left and right with respect to the viewing direction, and the output signal of
both the non-directional microphone unit and the bi-directional microphone unit It is
characterized in that it comprises a combining means, and a switch means for switching between
supply and interruption of the output signal of the bi-directional microphone unit to the signal
combining means.
Note) Nondirectional microphone units inherently generate much less wind noise than directional
microphone units. In addition, if the nondirectional microphone unit is covered with the same
body, directivity occurs in the direction of the opening of the cylindrical body, and it becomes
difficult to receive the influence of wind. That is, the nondirectional microphone unit and the
cylinder covering the same produce a microphone four phone having less wind noise and
directivity. Therefore, stereo sound collection similar to that of the MS method can be performed
by the nondirectional microphone unit, the cylinder, the bidirectional microphone unit, and the
signal combining means. The switch means is for selecting the stereo sound collection system
and the monaural sound collection system. When the output signal of the bidirectional
microphone unit is supplied to the signal synthesis means by the switch means, the stereo signal
is generated according to the principle of the MS system. can get. In this case, the bi-directional
microphone unit is not strong against wind, but as described above, the non-directional
microphone unit itself is strong against wind (and the cylinder suppresses the influence of wind,
so as a whole, it is all conventional) In the case of using a static microphone unit, the generation
of wind noise is reduced. On the other hand, when the switch means cuts off the supply of the
output signal of the bidirectional microphone unit to the signal combining means, the sum and
difference signal processing becomes meaningless, and the output signal of the nondirectional
microphone unit is output as a monaural signal. Ru. In this case, since the output signal of the
weak bidirectional microphone unit is not used at all, the monaural signal has extremely less
wind noise than the stereo signal. Moreover, the directivity can be utilized. From the above, by
using switch means, when the wind is weak, the stereo sound collecting method is selected to
make the recording full of sense of presence, and when the wind is strong, the monaural sound
collecting method is selected and the wind is It becomes possible to make a recording with less
noise. Furthermore, it is also possible to switch between the stereo sound collection method and
the monaural sound collection method according to the scene to be photographed by the video
camera to make a change in recording. DESCRIPTION OF THE PREFERRED EMBODIMENTS The
present invention will be described together with its preferred embodiments with reference to
FIGS. FIG. 1 shows the whole construction of an embodiment of the present invention. In FIG. 1,
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both of the mm-oriented microphone unit 1 and the bidirectional microphone unit 10 use an
electret condenser microphone unit. The omnidirectional microphone unit 1 is mounted in the
proximal end of the cylindrical body 3 with its sound collecting surface directed into the
cylindrical body 3.
The gap between the outer periphery of the nondirectional microphone unit 1 and the inner
periphery of the cylindrical body 3 is hermetically sealed with a sealing material, and the opening
4 is opened only at the tip of the cylindrical body 3. As a result, although the microphone unit 1
originally has the non-directivity 2 represented by a two-dot chain line, covering with the
cylindrical body 3 produces a directivity 5 of a solid line in which the direction of the opening 4
is the main axis. Then, with the opening 4 of the cylindrical body 3 directed to the visual field
direction 14 so that the main axis of the directivity 5 faces the visual W (shooting) direction 14
of the video camera, eg The unit 1 is placed in front of the upper surface of the case of the video
camera 13. See Figure 2. Further, as shown in FIG. 2, the bi-directional microphone unit 10 is
also installed on the top of the case of the video camera 13 at the same place as the nondirectional microphone unit 1. However, the arrangement is arranged so that the main axis of the
tli1 direction t 1.11 ° 12 of the bidirectional microphone unit 10 is directed to the left and right
direction of the viewing direction 14. In FIG. 1, reference numeral 15 is a switch, and 16 is a
signal combining circuit. Only an output signal of the bidirectional microphone unit 10 is input to
the signal combining circuit 16 through the switch 15. As the switch 15, a slide type is used, and
when sliding toward the r 5TEREOJ side, the switch 15 is turned on and the output signal of the
bidirectional microphone unit 10 is given to the signal synthesis circuit 16, and when sliding
toward the r MONOJ side 15 turns off and shuts off the signal. As shown in FIG. 2, the switch 15
is installed on the side of the case of the video camera 13. The signal synthesis circuit 16 is
composed of two mixing amplifiers 17.degree. 18 and one inverter 19. One mixing amplifier 17
outputs the output signals of the microphone units 1, 10 both omnidirectional and bidirectional.
Input and output the sum signal. In this example, the sum signal is the left signal at the time of
stereo. The other mixing amplifier 18 receives the output signal of the omnidirectional
microphone unit 1 and the phase inversion signal of the omnidirectional microphone unit 10
through which the inverter 19 passes, so that the outputs of both microphone units 1 and 10
Output a difference signal. In the case of 乙, the difference signal is the right signal in stereo. In
the present embodiment, a volume 28 for volume control is provided between the bidirectional
microphone unit 10 and the signal synthesis circuit 16, and the mixing ratio, ie, the bidirectional
microphone unit 10 for the output signal of the nondirectional microphone unit 1. It is possible
to obtain any effective stereo effect by changing the components of the sum and the difference of
the output signals of and changing the direction of the main axis of directivity.
In addition, the main axis direction of directivity can be changed by setting the mixing amplifier
17.18 itself to have a variable mixing ratio. In FIG. 2, reference numeral 29 indicates an
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operation knob of the volume 28. The left and right audio signals obtained by the signal
synthesis circuit 16 are amplified by appropriate amplifications @ 20 and 21 and then applied to
the recording / reproducing apparatus 30 so as to be recorded here. In FIG. 1, 22 is an optical
system, 23 is an image pickup device, 24 is a video signal processing circuit, and video signals
obtained by these are given to the recording and reproducing apparatus 30 and are recorded
there. In this embodiment, the video camera 13 is built in a recording and reproducing apparatus
using an 8-width magnetic tape, but basically, the recording and reproducing apparatus 30 is a
magnetic tape, a magnetic disk, a semiconductor memory, a magneto-optical device as a
recording medium. It does not matter what you use, such as a disc or an optical disc. In addition,
whether or not to record either video signal of movie still, whether video signal and audio signal
are recorded on the same recording medium, and whether or not video camera 13 and recording
/ reproducing apparatus 30 are integrated are limited. I will not. FIGS. 3 to 6 show specific
examples of a cylinder which gives directivity to the nondirectional microphone unit 1 and also
serves as a windshield. The cylindrical body 3A of FIG. 3 has a shape in which the central portion
and the distal end portion are thinner than the proximal end portion. The cylindrical body 3B in
FIG. 4 has the same thickness (the same cross-sectional area) from the proximal end to the distal
end. The cylindrical body 3C of FIG. 5 linearly increases in thickness as it goes to the tip. The
cylindrical body 3D of FIG. 6 is such that the thickness increases in a curved manner from the
central portion to the tip portion. Although each of the cylinders 3, 3A to 3D has a circular cross
section, the cross sectional shape is not necessarily limited to a circle, and may be oval, square or
the like O and the length of the cylinders 3, 3A to 3D Since the bass region is not stereotactic, it
may be short as long as a stereo effect such as presence and stereo feeling can be obtained even
if the sound is not completely collected in stereo. This is often the case when the video camera
13 is for a movie. <Effects of the Invention> According to the present invention, since directivity
is obtained by covering the nondirectional microphone unit with a tube having an opening even
if it is short, the nondirectional microphone unit and the bidirectional microphone unit can be
obtained. It can be used to collect sound with stereo effects. In addition, it is possible to switch
between stereo sound collection and monaural sound collection by a switch, and it is possible to
easily select an effective sfF method according to the situation of the shooting scene.
In particular, in monophonic sound collection, since the directivity produces 9 directivitys by the
cylinder, it can be used uni-directionally, and wind noise due to the characteristics of the
nondirectional microphone unit itself and the windshield effect of the cylinder. Is very small.
Furthermore, since the omnidirectional microphone unit is covered and shared by a cylinder
instead of using a large number of different microphone units for stereo sound collection and
monaural sound collection, the mechanism for wind noise reduction is complicated. In addition, it
contributes greatly to the downsizing and cost reduction of video cameras.
[0002]
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Brief description of the drawings
[0003]
1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a schematic side
view of a video camera, FIG. 3, FIG. 4, FIG. 5, FIG. 5 and FIG. It is sectional drawing which shows
arrangement ¦ positioning relationship.
In the drawings, 1 is a nondirectional microphone unit, 3.3A to 3D is a cylinder, 4 is an opening,
5 is directivity, 10 is a bidirectional microphone unit, 11 and 12 are directivity, 13 is a video
camera, Reference numeral 14 denotes a viewing direction, 15 denotes a switch, 16 denotes a
signal combining circuit, and 30 denotes a recording / reproducing apparatus.
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