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JPH09215086

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DESCRIPTION JPH09215086
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
stereo microphone device of a video camera which can record sound three-dimensionally well
when photographing an object.
[0002]
2. Description of the Related Art Japanese Patent Application Laid-Open No. 4-142900 discloses
an example of a stereo microphone device of a video camera capable of recording sound in three
dimensions when photographing an object.
[0003]
FIG. 5 is a perspective view showing a stereo microphone device of a video camera in the prior
art, and FIG. 6 is a block diagram for explaining the stereo microphone device of the video
camera in the prior art.
[0004]
The stereo microphone device M of the video camera in the conventional example shown in FIGS.
5 and 6 is disclosed in Japanese Patent Laid-Open No. 4-142900.
[0005]
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1
As shown in FIG. 5, in front of the camera body V, a photographing lens L with a zooming
mechanism is provided for zooming up or down the subject by operating the zooming operation
button B.
In the upper part of the camera body V, a first microphone MR showing the highest sensitivity to
the sound in the right direction, a second microphone ML showing the maximum sensitivity to
the sound in the left direction, and a first microphone MR And a second microphone MR, which is
disposed between the second microphone MR and the second microphone MR, and which
exhibits the maximum sensitivity to the direction in front of the camera.
[0006]
Here, as shown in FIG. 6, the output of the first microphone MR is output to the first gain circuit
GR, the output of the second microphone ML is output to the second gain circuit GL, and the
output of the third microphone MC is output to the third gain circuit GC. It is supplied.
[0007]
A coefficient (1-.alpha.) Is supplied to the first and second gain circuits GR and GL from the
coefficient generator ZN to multiply the outputs of the first and second microphones MR and ML
by (1-.alpha.) Respectively The coefficient α is supplied to the third gain circuit GC from the
coefficient generator ZN, and the output of the third microphone MC is controlled to be
multiplied by α.
(However, α is set to 0 <α <1.
The outputs of the first gain circuit GR and the third gain circuit GC are input to the first adder
circuit AR to obtain the combined output SR on the right side, while the outputs of the second
gain circuit GL and the third gain circuit GC are the third The left-side synthesized output SL is
input to the 2-adding circuit SL, and the right-side synthesized output SR and the left-side
synthesized output SL are recorded on a magnetic tape (not shown) at the time of recording by
the video camera.
[0008]
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2
Furthermore, the coefficient generation unit ZN is a circuit that makes the coefficient α variable
according to the zooming operation of the zoom lens L, and is constituted of, for example, a
variable resistor VR whose resistance value is variable by the movement of the zoom lens L
When the zoom lens L is on the telephoto side and a distant subject is shown in the image, the
factor α approaches 1 and when the zoom lens L is near, the factor α approaches 0. ing.
[0009]
By the way, in the above-mentioned conventional stereo microphone device M of a video camera
according to the above-mentioned prior art, an object is formed by the first microphone MR on
the right side, the second microphone ML on the left side, and the third microphone MC in the
center. While recording the sound in three dimensions, you can record noise generated near the
camera body V, such as operation sounds while the photographer is operating the video camera,
and reproduce the magnetic tape (not shown). At the same time, problems such as noise in the
vicinity of the camera body V may occur.
[0010]
In addition, although the variable resistor VR provided in the coefficient generation unit ZN can
change the coefficient α in accordance with the zooming operation of the zoom lens L, the
variable resistor VR is inferior in durability to repeated operations of a large number of times,
etc. Problems are occurring.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of the above
problems, and a first microphone exhibiting maximum sensitivity to right-handed speech and
maximum sensitivity to left-handed speech. Stereo microphone of a video camera attached to a
camera body, and a second microphone indicating a second microphone, and a third microphone
disposed between the first microphone and the second microphone and exhibiting the maximum
sensitivity with respect to the direction in front of the camera In the device, first and second gain
circuits adjust the output of the third microphone so as to reduce the gain by multiplying the
outputs of the first and second microphones by a factor β according to the subject distance and
the zoom ratio An inverting circuit for inverting the phase of the output of the third microphone,
and an object distance to the output of the third microphone whose phase is inverted by the
inverting circuit. A third gain circuit for adjusting the gain by multiplying a coefficient γ
according to the zoom ratio, a first addition circuit for adding the outputs of the first and third
gain circuits, and the second and third gain circuits And a second adding circuit for adding the
outputs. The present invention provides a stereo microphone device of a video camera
characterized by comprising:
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3
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a stereo microphone
device of a video camera according to the present invention will be described in detail below with
reference to FIGS.
[0013]
1 is a perspective view for explaining a stereo microphone device of a video camera according to
the present invention, FIG. 2 is a block diagram for explaining a stereo microphone device of a
video camera according to the present invention, and FIG. 3 is shown in FIG. FIG. 4 is a diagram
for explaining a zoom trace curve stored in a microcomputer, and FIG. 4 is a diagram for
explaining sensitivity characteristics of a stereo microphone device of a video camera according
to the present invention.
[0014]
In the stereo microphone device 1 of the video camera according to the present invention shown
in FIG. 1, the first microphone 3 showing the maximum sensitivity to the sound in the right
direction and the maximum for the sound in the left direction And a third microphone 5 installed
midway between the first microphone 3 and the second microphone 4 and showing the
maximum sensitivity with respect to the direction in front of the camera. The first and second
microphones 3 and 4 use nondirectional microphones, while the third microphone 5 uses a
superdirective microphone.
The camera body 2 also has a zoom operation button 6 for zooming up or down the subject, the
camera unit 10 for shooting the subject H, and a VTR unit 40 for recording the subject image
captured by the camera unit 10 on a magnetic tape (not shown). And are mounted with good
operability.
[0015]
Here, as shown in FIG. 2, the camera unit 10 of the video camera includes a shooting lens 12 for
shooting an object H in the lens barrel 11 projecting forward of the camera body 2 and a lens
barrel 11 for shooting. The zoom lens 13, which moves in the direction of the arrow along the
optical axis K to change the size of the subject image while adjusting the image frame of the
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subject H, the intermediate lens 14, and an iris that adjusts the light amount at the time of
shooting The focusing lens 16 moves in the arrow direction along the optical axis K of the lens
barrel 11 at the time of shooting to adjust the focus of the subject image, and the subject image
photographed by the photographing optical system 12 to 16 is optically And an imaging device
17 for photoelectrically converting the subject image.
At this time, the movable zoom lens 13 is connected to a zoom motor 22 using a stepping motor
via a gear unit 21. The zoom motor 22 zooms based on a command from the microcomputer 27
serving as drive control means. It is pulse-driven by the motor drive circuit 23.
[0016]
The movable focus lens 16 is connected to a focus motor 25 using a stepping motor via a gear
unit 24. The focus motor 25 is a focus motor based on a command from a microcomputer 27
serving as drive control means. Pulse drive is performed by the drive circuit 26.
[0017]
Further, the zoom lens 13 and the focus lens 16 which are movable in the optical axis direction
in the lens barrel 11 are provided with photosensors 28 and 29 for optically detecting the home
position in the initial state.
[0018]
By providing the photo sensors 28 and 29, after the zoom lens 13 and the focus lens 16 are
always returned to the origin position at the start of photographing, the photo sensors 28 and 29
respectively detect the origin positions of the zoom lens 13 and the focus lens 16 I'm informing
27.
Thereafter, the microcomputer 27 unilaterally sends the designated number of pulses to the
zoom motor drive circuit 23 for pulse driving the zoom motor 22 and the focus motor drive
circuit 26 for pulse driving the focus motor 25.
At this time, in the open loop control by the stepping motor, the number of pulses sent to the
zoom motor drive circuit 23 is, for example, the designated number of pulses accompanying the
zooming operation by the operation of the zooming operation button 6 connected to the
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microcomputer 27.
On the other hand, the number of pulses sent to the focus motor drive circuit 26 is the number of
pulses designated by the well-known hill-climbing servo system while referring to the zoom trace
curve (FIG. 3) described later in cooperation with the zoom operation.
[0019]
Therefore, when the zoom lens 13 and the focus lens 16 are moved after the origin positions of
the zoom lens 13 and the focus lens 16 are respectively detected by the photosensors 28 and 29,
the microcomputer 27 causes both drive circuits 23 and 26 to move as described above. Since
the designated number of pulses is transmitted unilaterally, the microcomputer 27 grasps the
current positions of the zoom lens 13 and the focusing lens 16 according to the designated
number of pulses.
[0020]
Furthermore, a plurality of zoom trace curves (FIG. 3) indicating the distance to the subject
(subject distance) based on the positions of the zoom lens 13 and the focus lens 16 are stored in
advance in the microcomputer 27, and the zoom lens 13 and the focus lens An object distance
output unit 27a1 that outputs the current object distance according to the current position 16; a
zoom output unit 27a2 that outputs the zoom ratio of the zoom lens 13; and first and second
microphones according to the object distance and zoom ratio A first coefficient unit 27b that
supplies a coefficient β for 3 and 4 and a second coefficient unit 27c that supplies a coefficient
γ for the third microphone 5 according to the subject distance and the zoom ratio.
At this time, the factor β and the factor γ described above are set so that the sound pressure in
the vicinity of the camera body at the time of telephoto is 1: 1 at the left and right, and the
subject distance and zoom ratio It is a variable that changes according to
[0021]
Here, the above-described zoom trace curve will be described with reference to FIG.
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In FIG. 3, when the moving range of the zoom lens 13 is 18 mm and this moving range is divided
into 0 to 957, the position of the zoom lens 13 (zoom lens position) is shown on the horizontal
axis, and the position of the focus lens 16 ( When the focus lens position is shown on the vertical
axis, the plurality of zoom trace curves stored in the subject distance output unit 27a1 in the
microcomputer 27 have curve characteristics depending on the case where the subject distance
is infinity (.infin.), 2 m, 1 m, and 50 cm. Although each of the zoom trace curves is different as
shown in the figure, the zoom trace curves according to the subject distance are commonly in the
locus of a bow as shown in the figure.
In each zoom trace curve, when the zoom lens position reaches the wide angle side (WIDE side),
the slope of the curve is relatively loose, and when the zoom lens position reaches the telephoto
side (TELE side), the slope of the curve is sharp It has become.
An object distance corresponding to the position of the zoom lens 13 and the position of the
focus lens 16 is stored in the object distance output unit 27a1 in the microcomputer 27.
[0022]
Therefore, when the zoom operation is performed while operating the zoom operation button 6
connected to the microcomputer 27, the focus lens 16 cooperating with the movement of the
zoom lens 13 moves along the zoom trace curve according to the subject distance. By doing this,
the focus of the subject image is adjusted.
[0023]
Next, an electrical circuit configuration for mixing the outputs from the first to third microphones
3-5, which is an essential part of the present invention, will be described.
[0024]
Returning to FIG. 2, the output of the right first microphone 3 is supplied as it is to the first gain
circuit 30.
Further, the output of the left second microphone 4 is also supplied to the second gain circuit 31
as it is.
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Furthermore, the output of the central third microphone 5 is supplied to the third gain circuit 33
through the inverting circuit 32 which inverts the phase by 180 °.
[0025]
The first and second gain circuits 30, 31 output the coefficients from the first coefficient unit
27b according to the object distance from the object distance output unit 27a1 in the
microcomputer 27 and the zoom ratio from the zoom ratio output unit 27a2. β is supplied.
Then, in the first and second gain circuits 30 and 31, the third microphone 5 is obtained by
multiplying the outputs of the first and second microphones 3 and 4 by the subject distance
based on the zoom trace curve and the coefficient β according to the zoom ratio. Is adjusted to
reduce the gain with respect to the output of. That is, the coefficient β corresponding to the
subject distance based on the zoom trace curve and the zoom ratio is set to cancel out the output
of the third microphone 5 that has passed through the inverting circuit 32 at the time of
telephoto at a ratio of about 1: 1.
[0026]
On the other hand, the third gain circuit 33 is supplied with the coefficient γ output from the
second coefficient unit 27c according to the object distance from the object distance output unit
27a1 in the microcomputer 27 and the zoom ratio from the zoom ratio output unit 27a2. It is
done. Then, in the third gain circuit 33, the gain is adjusted by multiplying the output of the third
microphone 5 passed through the inverting circuit 32 by the subject distance based on the zoom
trace curve and the coefficient γ according to the zoom ratio. At this time, when the zoom lens
13 reaches the telephoto side (TELE side), it is better to set the coefficient γ large.
[0027]
The outputs of the first gain circuit 30 and the third gain circuit 33 are input to the first addition
circuit 34 to obtain the combined output GR on the right side, while the outputs of the second
gain circuit 31 and the third gain circuit 33 are the second The left composite output GL is input
to the adder circuit 35, and the right composite output GR and the left composite output GL are
recorded on a magnetic tape (not shown) at the time of recording by the video camera.
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[0028]
At this time, the sensitivity characteristic of the stereo microphone device 1 of the video camera
according to the present invention is shown by the combined output GR on the right and the
combined output GL on the left as shown in FIG. The sound has been extinguished.
That is, the sensitivity characteristics shown in FIG. 4C are the sensitivity characteristics of the
first and second microphones 3 and 4 as shown in FIG. 4A and the sensitivity characteristics as
shown in FIG. 4B. The sensitivity characteristic by the third microphone 5 is not simply added to
the two-dot chain line state, and noise generated in the vicinity of the camera body V such as
operation sound is canceled while the photographer is operating the video camera. That is, as
described above, the ratio of the output of the first and second microphones 3 and 4 to the
output of the third microphone 5 through the inverting circuit 32 by the first and second gain
circuits 30 and 31 is approximately 1: 1. In order to cancel out.
[0029]
As a result, according to the stereo microphone device 1 of the video camera according to the
present invention, the noise generated in the vicinity of the camera body V is extinguished, and it
is possible to emphasize distant sound, and when photographing an object Recording on
magnetic tape very well.
[0030]
As described above, according to the stereo microphone device of the video camera according to
the present invention, the first microphone exhibiting the maximum sensitivity to the sound in
the right direction and the maximum sensitivity to the sound in the left direction are provided. A
second microphone, and a third microphone installed between the first microphone and the
second microphone and showing the maximum sensitivity in the forward direction of the camera
attached to the camera body, and the first and second gains In the circuit, the outputs of the first
and second microphones are multiplied by the object distance and a coefficient β according to
the zoom ratio to adjust the output of the third microphone to reduce the gain, while inverting
the phase by the inverting circuit The gain is adjusted by multiplying the output of the third
microphone by a factor γ according to the subject distance and the zoom ratio, and then the
combined output of the first and third microphones, and the second As a result, the noise
generated near the camera body is extinguished, and it is possible to emphasize sound in the
distance, so that when the subject is photographed, the sound is three-dimensional. Good
recording on magnetic tape.
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[0031]
Brief description of the drawings
[0032]
1 is a perspective view for explaining a stereo microphone device of a video camera according to
the present invention.
[0033]
2 is a block diagram for explaining a stereo microphone device of the video camera according to
the present invention.
[0034]
3 is a diagram for explaining the zoom trace curve stored in the microcomputer shown in FIG.
[0035]
4 is a diagram for explaining the sensitivity characteristics of the stereo microphone device of the
video camera according to the present invention.
[0036]
5 is a perspective view showing a stereo microphone device of the video camera in the
conventional example.
[0037]
6 is a block diagram for explaining the stereo microphone device of the video camera in the
conventional example.
[0038]
Explanation of sign
[0039]
DESCRIPTION OF SYMBOLS 1 ... stereo microphone apparatus of a video camera, 2 ... camera
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main body, 3 ... 1st microphone, 4 ... 2nd microphone, 5 ... 3rd microphone, 27 ... microcomputer,
27a1 ... subject distance output part, 27a 2 ... zoom ratio output part, 27b: first coefficient part,
27c: second coefficient part, 30: first gain circuit, 31: second gain circuit, 32: inverting circuit,
33: third gain circuit, 34: first addition circuit, 35: third 2 adder circuit.
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