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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
video camera for forming a video signal, and more particularly to a video camera provided with a
microphone whose directivity characteristic is variable. [Background Art and its Problems] In
recent years, portable video cameras have become lighter and smaller, and their functions not
only form the video signal of the subject, but also incorporate the VTR device to create a
magnetic device. A mechanism for recording video (M number and audio signal [1α recording
on tape is also in practical use. By the way, when shooting with a video camera and recording the
sound signal of the shooting site at the same time (佳, of course, it is necessary to have a
recording microphone 1 (although it is integrated with a video camera as a conventional
microphone) Use a microphone, or prepare a microphone body M separately for 5 as shown in
the first row, and use this as a video camera body V K if! i! Lii SJ was using it. However, since
the microphone built in the video camera is omnidirectional or the directivity is broad even if it is
directional, the S / N becomes worse if the object to be picked up is far away There is a
drawback. Also, separately preparing a sharp directional micro-bon loses the merits of
downsizing and portability of the video camera, and in general, the directional sharp microphone
is attached to the video camera because its shape is elongated. Also in the case, there were 5
problems if only the microphone part was projected. [Purpose of this invention] This invention
has been made in such a way that cancer has been observed, and it is constructed so that the
microphone-bon incorporated in the video camera can be separated into two pieces, and its
orientation as required. The video camera is miniaturized while being able to select
characteristics. [Summary of the invention] A first microphone is attached to the main body of
the video camera, and a microphone 7 dowel is provided, which incorporates at least one or more
second microphones detachably in a part of the main body of the video camera. When the
microphone adapter is attached, the first one. By making the output of the second microphone
electrically coupled, any directional characteristics can be obtained. [Exemplary embodiment]
FIG. 2 shows an example of the appearance σ of the video camera according to the present
invention, wherein 1 is a main video camera 111S, 2 is a taking lens, and 3 is a lens finder. 4 is
the subject 11 of the video camera! 1) j1 nori; J) is the second microphone, 5 is a microphone / fcrophone adapter which is attached to and removed from the housing portion 1a formed on -frli
of the video camera, i) microphone adapter) microphone adapter 5 has at least one or more
second .sigma.) Microphones 6, and an electronic circuit shown in unit lV4. .
It is built in as shown in M e and the amplifier unit AP. The second microphone 6 and the
electronic circuit, as will be described later, can adjust the directivity characteristics to an
arbitrary one together with the first microphone 4 when the microphone 7 dovetail 5 is installed
in the hidden camera. [gamma] represents an acoustic tube for acoustically coupling the first
microphone 4 and the microphone 7 (when the microphone 5 and the speaker 5 are turned on).
In addition, illustration of each department device and operation mechanism accompanying a
video camera busy is omitted. FIG. 3 shows a circuit diagram of the microphone circuit of the
microphone-phone 7 adapter 5 and the J-th microphone 4 attached to the main part 1 of the
video camera. The output of the transformer M1 is usually converted in impedance by the FET Q
+, supplied to the amplifier A through the switch 5W (a contact), and recorded on the tape
together with the video signal. When the microphone 7 dovetail 5 is installed in the main part 1
of the video camera, the electronic circuit of the microphone 7 dovetail 5 and the microphone
circuitry in the video camera are mutually connected via the connectors C1, The S / W
switches to the illustrated state (contact b side). Therefore, the unit M □ of the first microphone
4. And a unit M2. Of the second microphone 6 accommodated in the microbon adapter 5. The
output of M3 (this microphone unit may be one or three or more) may be FETQI, Q2. Q, through
the control circuit ACC, through the control circuit ACC, the unit "ψ,". M2. The output of M3 is
calculated as described later, and is sent to the amplifier A via the switch 5W (b-contact). The
variable resistance R of the R) -R circuit ACC adjusts the directivity. The orientation of the
microphone will be briefly described with reference to the microphone main body M of FIG. In
general, spaced apart on the acoustic tube? ! It is known that when the outputs of the
microphones (-first gradient type) are connected so as to be in opposite phases electrically, a
microphone having a sharp directivity characteristic of a second-order gradient type is formed. 1)
In the microphone main body M, if the output of the unit M, and the output of the unit Mc are
also output in 3 phases, it is a distance. For a well-known wavelength (low frequency) related in
between, a narrow directional acoustic output is generated, and when the outputs of unit Mb and
unit M0 are output in reverse phase, the sound wave length (still frequency) related between
distance Dbc A narrow directional sound output is obtained.
Therefore, as shown in FIG. 4, a unit M of the first microphone 4 provided in the main part 1 of
the video camera, and a unit M2 M3 of the second microphone 6 accommodated in the
microphone adapter 5 Is calculated by the differential amplifiers OP and OP2, that is, the output
of the unit M1 and the negative phase component e of the output of the unit M3, and the
negative phase component e2 of the output of the unit M2 and the output of the unit M3 When
these outputs are supplied to the addition circuit OP3, an acoustic signal having a single
directivity characteristic sharp in high and low frequencies is obtained at the output e3.
Therefore, when the output of the output e3 and the unit M is configured to be input to the
voltage control amplifier VCA (Voltage Control Amp), the output voltage e4 of the ttt pressure
control amplifier VCA is set by the signal KK of the control terminal cant. Can be G I es K + MI (K
−)) (where 0 <K <], G is the gain of VCA), that is, by changing the signal K by the variable resistor
R) From the loop circuit ACC, an output e4 obtained by arbitrarily mixing an output signal
(cardioid characteristic) of the unit M of the first microphone 4 and an output e3 having a sharp
uni-directional characteristic is obtained. The capacitor C8 inserted in the negative feedback
circuit in FIG. 4 is for removing noise, etc. of the frequency characteristic generated in the high
frequency region, and improving the sound quality 0). In the present invention, as described
above, the first microphone 4 operates in the same manner as the built-in microphone in the
microphone (when the j-phone 7 dapter 5 is not attached) ... normal σ) video camera, When
recording, the microphone 7 dowel 5 is attached to the main part 1 of the video camera to obtain
the first one. Since the second microphones 4 and 6 form a microphone of narrow directivity, it is
possible to record the acoustic signal of the subject without deteriorating the S / N. Microphone
σ) oriented! As the temporality can be changed from the broad unidirectional temporality by the
signal KK to the narrow directional characteristic W as described above, when this is linked with
the zooming mechanism of the photographing lens 2, a more suitable recording function framing
I; It is exhibited. In the embodiment of FIG. 2, the housing place of the microphone adapter 5 is
not limited to the illustrated point, and the housing portion 1a may be provided on the side
surface or rear surface of the video camera. In addition, if the spatial distance between the first
microphone 4 and the second microphone 6 housed in the microphone 7 dovetail 5 is a
predetermined length with respect to the blue wavelength, a temporary directivity characteristic
can be obtained, as described above. The acoustic tube 7 is not necessarily required.
The microphone adapter 5 may be provided with a terminal of a connecting cord to an amplifier
or the like so that it can be used as a single directional .sigma. [Effect of Opening] According to
the present invention, as described above, the microphones for recording are t-51 and 82
microphones, the first microphone is fixed to the main part of the video camera, and the second
microphone is the video camera. Because it is detachable, it is possible to select the
characteristics of the microphone according to the recording situation. In addition, since the main
part of the hidden camera is used as the groove bottom for providing directivity, the video
camera can be formed in a compact size, which is particularly advantageous in that it can be
easily carried.
Brief description of the drawings
Fig. 3 is a perspective view showing a narrow directional microphone · body 1; part of a video
camera body and Fig. 2 is a perspective view of a video camera according to an embodiment of
the present invention, Fig. 3 FIG. 4 is a circuit diagram showing the connection of the
microphone 7 dowel and FIG. 4 is a control circuit diagram for obtaining variable directivity
In the figure, 1 is a main part of the video camera, 4 is a first microphone, 5 is a microphone
adapter, and 6 is a second microphone.
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