JP3107117B2 - Voice input device and imaging device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice input device and an imaging device such as a camera-integrated VTR using the voice input device.

[0002]

2. Description of the Related Art For example, in a camera-integrated VTR, while photographing a subject, sounds around the subject are simultaneously recorded. In this recording, it is generally desirable to use an audio input device having a sharp directivity so as to collect only the sound from the direction of the subject facing the lens of the camera, that is, from the front of the camera.

[0003] As an example of this type of voice input device having a sharp directivity, a large number of small holes are formed in a side wall of a long tube, which is commonly called a gun microphone, for receiving voices from side and rear. It is known that the sensitivity is low and the sensitivity to a sound from the front is high.

[0004] In addition, a camera-integrated VTR generally uses a zoom lens, and can capture an image at an angle of view according to a photographer's request from telephoto to wide-angle. Moreover, recently, the magnification of the zoom lens has been increased. On the other hand, if the sound collecting means keeps a certain directivity, the consistency with the video may be deteriorated. Therefore,
There is a strong demand for changing the directivity of the audio input device according to the magnification of the video.

[0005] For this purpose, an audio input device having a zoom function capable of changing the directional characteristics from a wide directivity state to a narrow directivity state is required. Various methods for realizing this zoom function have been conventionally proposed. For example, an output signal of the above-mentioned microphone having a sharp directivity and a normal omnidirectional or unidirectional microphone is input to an arithmetic unit. A method has been proposed in which a plurality of signals are arithmetically processed by the arithmetic means and mixed appropriately to obtain zoom characteristics.

[0006]

However, the use of a long tube inevitably increases the size of the gun microphone, which makes it difficult to reduce the size of the camera-integrated VTR. In addition, even if the directivity is sharpened, the sound emitted near the microphone has a drawback that the sound is loudly collected even if the sound is incident from a direction with a low sensitivity off the main axis.

Further, as described above, an audio input device having a zoom function is used as a device for mixing an output signal of a microphone having a sharp directivity and an output signal of a normal omnidirectional or unidirectional microphone. In this case, similarly to the above, there is a disadvantage that the size becomes large, the configuration becomes complicated, and further, the control thereof becomes complicated. Further, when changing the mixing amount of the outputs of a plurality of microphones, the variable resistor is conventionally rotated by a motor, so that there is a problem that mechanical noise is easily collected.

In view of the above, it is an object of the present invention to provide a voice input device that can be easily reduced in size and can easily perform voice zooming.

[0009]

In order to solve the above-mentioned problems, a noise reduction type voice input device according to the present invention is provided with a first voice pickup device for collecting a desired voice when corresponding to reference numerals in the embodiments described later. , A directional second microphone 21 having low sensitivity in the direction of arrival of a desired sound, adaptive filter means 24 to which a sound signal of the second microphone is supplied, and an output signal of the adaptive filter means. Synthesizing means 15 for synthesizing the audio signal of the first microphone, means for adjusting the adaptive filter means 24 so that the output power of the synthesizing means 15 is minimized, the first and second microphones 11 and A signal generating means for generating a non-correlated signal having no correlation with the audio signal of the second microphone; and an adding means for adding the uncorrelated signal to the audio signal of the second microphone. And it is characterized in Rukoto.

[0010]

According to this configuration, the reference sound signal from the second microphone 21 having low sensitivity in the direction of arrival of the desired sound is:
Since the correlation with the desired sound signal from the first microphone 11 is small, the sound input device of the present invention has a configuration of an adaptive noise reduction system, and when the output power of the subtraction means is minimized, the reference sound signal becomes the second sound signal. The audio signal from one microphone 11 is removed, and only the desired audio signal is output. Therefore, a voice input device having sharp directivity in a desired voice direction is realized.

Further, by adding a non-correlated signal having no correlation between the main and reference audio signals to the reference audio signal, the reference audio reduction processing is limited. Thereby, a zoom function for audio is realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the voice input device according to the present invention will be described with reference to the drawings. In the present invention, since the concept of adaptive noise reduction processing is used, one embodiment of the present invention will be described. Before this, the adaptive noise reduction processing will be described.

FIG. 3 is a block diagram of a basic configuration of the adaptive noise reduction processing system, wherein 1 is a main input terminal, 2 is a reference input terminal, and a main input signal input through the main input terminal 1 is a delay circuit. The signal is supplied to the synthesizing circuit 4 via the line 3. The delay circuit 3 detects a time delay in the adaptive filter circuit 5 when there is no time delay between the main input signal input to the main input terminal 1 and the reference input signal input to the reference input terminal 2. The delay circuit 3 does not need to be provided.

The signal input through the reference input terminal 2 is supplied to the synthesizing circuit 4 via the adaptive filter circuit 5, and is subtracted from the signal from the delay circuit 3. And
The output of the synthesizing circuit 4 is fed back to the adaptive filter circuit 5 and is output to an output terminal 6.

In this noise reduction device, a signal obtained by adding a desired signal s and uncorrelated noise n0 to the desired signal s is input to the main input terminal 1. On the other hand, the noise n1 is input to the reference input terminal 2. This reference input noise n1
Are uncorrelated with the desired signal, but are correlated with the noise n0.

The adaptive filter circuit 5 includes a reference input noise n1
To output a signal approximating the noise n0, that is, a signal y having the same phase and the same amplitude as the noise n0. As the output signal of the adaptive filter circuit 5, a signal -y having the same phase and the same amplitude as the noise n0 can be obtained.
The synthesizing circuit 4 performs a process of subtracting the output signal of the adaptive filter circuit 5 from the output signal of the delay circuit 3 (adding when the output signal is a signal -y having a phase opposite to that of the noise n0).

The adaptive algorithm in the adaptive filter circuit 5 works to minimize the subtraction output (residual output) e output from the synthesis circuit 4. That is, now s, n
Assuming that 0, n1, y are statistically stationary and the average value is 0, the residual output e is e = s + n0-y. The expected value of squaring this is that s is n0,
Also, because it is y ^{uncorrelated, E [e 2] = E} [s 2] + E [(n0 -y) 2] + 2E [s (n0 -y)] = E [s 2] + E [(n0 - y) ² ]. Assuming that the adaptive filter circuit 5 converges,
The adaptive filter circuit 5 is adjusted so that E [e ² ] is minimized. At this time, since the E [s ^2] is not affected, and ^{Emin [e 2] = E [} s 2] + Emin [(n0 -y) 2]. That, E E by [e ^2] is minimized [(n0 -y) ^2] is minimized, the output y of the adaptive filter circuit 5 will estimate the noise n0. And
The expected value of the output from the combining circuit 4 is only the desired signal s. That is, adjusting the adaptive filter circuit 5 to minimize the total output power is equivalent to the fact that the subtraction output e becomes the least square estimation value of the desired audio signal s.

In general, the residual output e is a signal s with some noise remaining. However, since the output noise is given by n0-y, E [(n0-y) ² ] is minimized. This is equivalent to maximizing the signal-to-noise ratio of the output.

The adaptive filter circuit 5 can be realized either by an analog signal or a digital signal processing circuit. FIG. 4 shows an example in which the adaptive filter circuit 5 is realized using a digital filter. This example uses a so-called L as an adaptive algorithm.
This is an example when the MS (least mean square) method is used.

As shown in FIG. 4, in this example, an FIR filter type adaptive linear combiner 300 is used. this is,
A plurality of delay elements DL1, DL2,... DLm (m is a positive integer) each having a delay time Z ^-1 of a unit sampling time, an input noise n1, and each delay element DL1, DL
, And DLm, and a weighting circuit MX0, MX1, MX2,..., MXm for multiplying the output signals of the weighting coefficients, and an addition circuit 310 for adding the outputs of the weighting circuits MX0 to MXm. The output of the adder 310 is y (or -y).

The weighting coefficients supplied to the weighting circuits MX0 to MXm are formed on the basis of the residual signal e from the synthesizing circuit 4 by an LMS operation circuit 320 composed of, for example, a microcomputer. The algorithm executed by the LMS operation circuit 320 is as follows.

Now, the input vector X _k at time k is
As shown in FIG. 4, X _k = [x _0k x _1k x _2k ... X _mk ] ^T , the output is y _k , and the weighting factor is w _jk (j = 0, 1, 2,... M). Then, the relationship between input and output is as shown in the following Equation 1.

[0023]

(Equation 1) If the weight vector W _k at time k is _defined as W _k = [w _{0 k} w _{1 k} w _{2 k} ... W _mk ] ^T , the input / output relationship is given by y _k = X _k ^T · W _k . Here, assuming that a desired response is d _k , the residual e _k is expressed as follows. In the _{e k = d k -y k =} d k -X k T · W k LMS method, the update of the weight vector, by _{W k + 1 = W k +} 2μ · e k · X k ...... (a) becomes formula Go sequentially. Here, μ is a gain factor (step gain) that determines the speed and stability of adaptation.

Next, FIG. 1 shows a block diagram of an embodiment of the voice input device according to the present invention using the above-described adaptive noise reduction processing. In this example, the adaptive filter circuit is
Although a filter using a digital filter is used, a subtraction circuit is used as the synthesis circuit 4.

In FIG. 1, reference numeral 11 denotes a main input microphone for picking up a desired sound, and reference numeral 21 denotes a reference input microphone for picking up unnecessary sound and ambient noise in a direction to be removed as noise. In this example, the direction in which the desired sound arrives is mainly a direction from above to below in the figure (hereinafter referred to as a front direction) as shown by an arrow AR in FIG. This is an example of realizing a microphone device that prevents unnecessary sounds from being collected as noise from being collected.

In this example, the main input microphone 11 is constituted by an omnidirectional microphone as shown in FIG. On the other hand, as shown in FIG. 2, the reference input microphone 21 is a unidirectional microphone having no sensitivity in the direction of arrival of the desired sound and having sensitivity only in the back direction. The pair of microphones 11 and 21 are arranged close to each other in order to reduce the size of the device.

Due to the arrangement of the two microphones 11 and 21 as described above, both the desired sound and the unnecessary sound are mixed and input to the main input microphone 11. Meanwhile, reference input
Although unnecessary signals are input to the microphone 21, almost no desired sound is input due to the unidirectional action.
Desired voice and reference voice (unnecessary voice) have different directions of arrival,
In addition, since the sound sources are different, they are generally uncorrelated.

The audio signal collected by the main input microphone 11 and converted into an electric signal is supplied to an A / D converter 13 via an amplifier 12 and converted into a digital signal. The signal is supplied to the subtraction circuit 15 via the delay circuit 14. An unnecessary sound signal obtained by being collected by the reference input microphone 21 and converted into an electric signal is supplied to the amplifier 22 and the addition circuit 25 via the adder 25.
The signal is supplied to the -D converter 23, converted into a digital signal, and supplied to the adaptive filter circuit 24.

In this embodiment, the adaptive filter circuit 24
Is composed of an FIR filter type adaptive linear combiner 300 and an arithmetic circuit (microcomputer) 320 for adaptively controlling the linear combiner 300 as shown in FIG. Is supplied to the subtraction circuit 15 via the linear combiner 300. The output signal of the subtraction circuit 15 is fed back to the arithmetic circuit 320, returned to an analog signal by the DA converter 16, and led out to the output terminal 17.

The DA converter 16 is omitted, and the output signal of the subtraction circuit 15 is output as a digital signal.
May be derived. In addition, the delay circuit 14
This is for compensating for a time delay such as a propagation time in the adaptive filter circuit 24 and a time delay required for an operation for adaptive processing.

Basically, the adaptive filter circuit 24 is controlled so that the reference input audio signal approximates to the unnecessary audio signal included in the main input audio signal. As a result, assuming that the desired sound and the unnecessary sound in the sound collected by the main input microphone 11 are uncorrelated, the subtraction circuit 15
Then, the unnecessary audio signal of the reference input microphone 21 is subtracted and removed from the audio signal of the main input microphone 11, and only the desired audio signal is obtained from the subtraction circuit 15.

That is, in the basic configuration of this embodiment, an output audio signal of the main input microphone 11 is supplied as a main input, and noise (unwanted audio signal) as a reference input is provided.
The configuration of the adaptive noise reduction system to which the output audio signal of the reference input microphone 21 is supplied. Then, noise, in this case, an unnecessary audio signal from the back direction is selectively removed from the output terminal 17, and as a result, only the desired audio signal is output with a required quality.

As described above, in this embodiment, the desired voice and the noise are distinguished by the direction of arrival of the voice. And
The main input microphone 11 has a directional characteristic (including omnidirectionality) capable of picking up sound from a desired sound arrival direction, and has a reference input microphone 2.
Reference numeral 1 denotes a configuration in which the desired sound arrival direction has no sensitivity or has a low sensitivity directivity, and the desired sound in the sound collected by the main input microphone 11 and the reference sound collected by the reference input microphone 21 are included. Noise and no correlation.

Therefore, in this embodiment, it is only necessary to consider the directivity of the main input microphone and the reference input microphone, and it is possible to arrange both microphones close to each other.
The size can be reduced.

Further, in this embodiment, a non-correlated signal generating circuit 31 and a level adjusting circuit 32 are provided for zooming the voice, and the non-correlated signal from the generating circuit 31 is
The signal is supplied via the level adjustment circuit 32 to the addition circuit 25 inserted in the reference signal system. The attenuation of the level adjustment circuit 32 is controlled by, for example, an external control signal Scz.

The uncorrelated signal from the generating circuit 31 needs to have no correlation between the desired sound signal and the reference sound signal. For example, random noise such as white noise or colored noise is used.

Next, the audio zooming operation according to one embodiment of the present invention will be described. The power spectrum of the reference input signal of the adaptive noise reduction system is Φrr (z), the power spectrum of the uncorrelated signal added to the reference input signal (corresponding to the noise level) is Φmm (z), and the ratio between the two is B (Z) = Φmm (z) / Φrr (z), the power density ratio ρout (z) of the desired signal to the unwanted signal at the output of the system and the power density ratio ρpri ( z) is expressed by ρout (z) / ρpri (z) = {B (z) +1} / B (z).

From this equation, the power of the desired signal versus the unwanted signal at the output of the adaptive noise reduction system ρout (z)
Is, B (z) increases, i.e., the greater the power spectrum Φmm (z) is uncorrelated signal that is applied to the <br/> reference input signal at the summing circuit 25, the desired signal-to-unwanted signal at the primary input It can be seen that approaching the power density ratio ρpri (z) limits the noise (unwanted signal) reduction capability of the system.

[0039] In other words, the level adjusting circuit 32 the amount of decorrelated signal that is applied to the reference input signal in the adder circuit 25
Thus, the amount of suppression of unnecessary signals (such as background noise) can be limited, and a voice zooming function can be equivalently realized.

The uncorrelated signal leaks into the output audio signal. However, if a signal outside the audio frequency band is used as the uncorrelated signal, no problem occurs. Further, even within the audible frequency band, signals of a single frequency or the like can be easily removed using a trap circuit.

FIG. 5 shows an embodiment in which the audio input device described above is applied to the audio system of a video camera.
The configuration of the audio system 100 of this example is such that the uncorrelated signal generation circuit 3
1 is exactly the same as the voice input device of the example of FIG. 1 except for the portion of FIG.

In the video system 200 shown in FIG. 5, the subject 40 is imaged by using the zoom optical system 41, and is converted into an electric signal by the CCD image sensor 42 to obtain an image signal.
This imaging signal is supplied to a video signal processing circuit 43, for example, is converted into a color video signal of the NTSC system, and is supplied to a recording system 44. The audio signal from the DA converter 16 of the audio system 100 is supplied to the recording system 44. In the recording system 44, appropriate recording signal processing is performed, and the video signal and the audio signal are recorded on, for example, a magnetic tape.

The zoom ratio of the zoom optical system 41 is changed when the zoom motor 45 is controlled by a zoom control signal from the controller 46. The controller 46 generates a zoom control signal for controlling the motor 45 by operating the zoom operation key 47.

In this example, the adding circuit 25
A signal source such as a horizontal synchronization signal obtained by a video signal processing circuit 43 of a video camera and a drum servo signal generated by a recording system 44 is used as the decorrelation signal added to the video signal. In this example, the horizontal synchronizing signal from the video signal processing circuit 43 is used as an uncorrelated signal as the level adjustment circuit 32.
To the adder circuit 25 of the audio system 100 via. Then, the level adjustment circuit 32 is adjusted and controlled by the zoom control signal from the controller 46 in conjunction with the control of the zoom motor 45. Therefore, the sound can be zoomed up in accordance with the zoom up of the image.

In the case of this example, the uncorrelated signal is a horizontal synchronizing signal, and its frequency is as high as 15.75 kHz, so that it is inconspicuous. By providing and removing the trap circuit 48 between the device 16 and the recording system 44, no problem occurs in the reproduced sound.

As described above, in the above-mentioned example, since the existing signal sources such as the horizontal synchronizing signal and the drum servo signal can be used in the video camera, a new decorrelation signal generating circuit is not required. Well, the configuration is simple. Moreover, these signals are periodic signals and can be easily removed from the audio signal using the trap circuit.

In the above-described embodiment, the main input microphone 11 is omnidirectional. However, as shown in FIG.
The main input microphone 11 is also arranged as a single directivity with the highest sensitivity direction facing the front direction, and the unidirectional reference input microphone 21 is oriented with the highest sensitivity direction in the rear direction, for example. You may make it arrange | position.

Also, instead of using the unidirectional microphone unit alone as the main input microphone 11 and the reference input microphone 21,
A microphone using two omnidirectional microphone units may be used.

An example of realizing a unidirectional microphone using two non-directional microphone units will be described with reference to FIGS. As shown in FIG. 7, in this example, the non-directional microphone units 30 and 31
They are arranged at a distance d. Then, as shown in FIG. 8, the output audio signal of one microphone unit 30 is supplied to a subtraction circuit 32 via an amplifier (not shown). The output audio signal of the other microphone unit 31 is also supplied to an amplifier and filter circuit 3 (not shown).
3 is supplied to the subtraction circuit 32. Filter circuit 3
3 is composed of a resistor 34 and a capacitor 35 in this example. When the resistance value of the resistor 34 is R1 and the capacitance of the capacitor 35 is C1, the resistance value R1 and the capacitance C1 are selected so that C1.R1 = d / c (where c is the speed of sound). ing.

In this example, an output audio signal is derived from the output of the subtraction circuit 32 to an output terminal 37 via a frequency characteristic correction circuit 36 such as an integrator for flattening the frequency characteristic. As will be described later, the frequency characteristic correction circuit 36 is provided as needed, and need not be provided.

The operation of the microphone of this example will be described. As shown in FIG. 7, the sound source is located at an angle of θ with respect to the arrangement direction of the two microphone units 30 and 31, and the two microphone units 30 and 3
1, each unit 30, 31
^Are P0 and P1, the output P1 is P1 = ^{P0.epsilon.-j.omega. (D / c) cos .theta} . Here, ω is an angular frequency.

Since the output of the microphone unit 31 is supplied to the subtraction circuit 32 through the filter circuit 33, the output signal Pa of the subtraction circuit 32 is as shown in the following equation (2).

[0053]

(Equation 2) In Equation 2, A represents a filter function of the filter circuit 33, and ω · d / c << 1.

In Expression 2, if the following Expression 3 is satisfied, the output Pa indicates unidirectionality.

[0055]

(Equation 3)I mean,numberWhen Expression 3 is satisfied, the above Expression 2 is satisfied.Equation (1)
Is Pa = P0 · jω (d / c) (1 + cos θ), and becomes unidirectional with respect to the angle θ.

By the way, in the case of the above example, the filter function A of the filter circuit 33 is represented by A = 1 / (1 + jωC1 · R1), and C1 · R1 = d / c. A = 1 / (1 + jωd / c), and from Equation 3, it is clear that the microphone of the embodiment of FIG. 7 has unidirectionality. However, the frequency characteristic of this microphone becomes a characteristic that rises to the right (response increases as the frequency increases). In this example, the frequency characteristic correction circuit 3
6 is provided to flatten the upward-sloping characteristic.

In the example of FIG. 8, the filter circuit 3
3, subtraction circuit 32, and frequency characteristic correction circuit 36
Can also be realized by a digital filter or a processing program (software).

For example, as shown in FIG. 9, the filter circuit 33 can be constituted by a digital filter including an adder 41, a delay circuit 42, and a feedback amplifier 43 having a transfer function A.

In the above example, the voice input device of the present invention has been described as an example of a sound collecting microphone device of a camera-integrated VTR. However, the present invention is not limited to this example. That is, the present invention is applicable to all microphone devices such as professional video cameras and measurement microphone devices.

In the above example, the adaptive filter circuit 24
Although the digital filter has a digital circuit configuration, the digital filter is configured as a whole. However, the adaptive filter circuit 24 may be configured as an analog circuit and the analog circuit may be configured as a whole. Alternatively, only the adaptive filter circuit may have a digital configuration. Also,
The adaptation algorithm is not limited to the LMS method, and other methods, such as a learning similarity method, may be used.

[0061]

As described above, according to the present invention, a desired sound signal is obtained by combining a pair of microphones for picking up both main and reference sounds and a noise reduction circuit including an adaptive filter. Output, and add an uncorrelated signal, which has no correlation between the main and reference audio signals, to the reference audio signal to limit unnecessary audio signal suppression processing. Easy to do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of a voice input device according to the present invention.

FIG. 2 is a diagram illustrating an example of directivity of first and second microphones.

FIG. 3 is a block diagram showing an outline of an adaptive noise reduction device for explaining the present invention.

FIG. 4 is a diagram illustrating a configuration example of an adaptive filter circuit.

FIG. 5 is a block diagram illustrating a configuration of an embodiment of an imaging apparatus according to the present invention.

FIG. 6 is a diagram showing another example of the directivity of the first and second microphones.

FIG. 7 is a diagram for explaining an example in which a microphone having a desired directional characteristic is configured by a plurality of microphone units.

FIG. 8 is a diagram illustrating an example in which a microphone having a desired directional characteristic is configured by a plurality of microphone units.

FIG. 9 is a diagram illustrating another example of the configuration of a part of the example of FIG. 8;

[Explanation of symbols]

 Reference Signs List 11 first microphone 21 second microphone 15 subtraction circuit 24 adaptive filter circuit 25 addition circuit 31 uncorrelated signal generation circuit 32 level adjustment circuit 41 zoom optical system 43 video signal processing circuit 44 recording system 45 zoom motor 46 controller

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kaoru Gyokutoku Sony Corporation 7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-3-291098 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04R 3/00 320 H04N 5/225 H04R 1/40 320

Claims (6)

(57) [Claims] 1. A first microphone for picking up a desired sound, a second microphone having a low sensitivity in an arrival direction of the desired sound, and a sound signal of the second microphone are supplied. Adaptive filter means; synthesizing means for synthesizing the output signal of the adaptive filter means and the audio signal of the first microphone; means for adjusting the adaptive filter means such that the output power of the synthesizing means is minimized. Signal generating means for generating an uncorrelated signal having no correlation with the audio signals of the first and second microphones; and adding means for adding the uncorrelated signal to the audio signal of the second microphone. Voice input device. Wherein said signal generating means and the level adjusting circuit between said addition means are provided, Ri by <br/> this level adjustment circuits, wherein the addition amount of the decorrelated signal is variable Item 2. The voice input device according to item 1. 3. The level adjustment circuit according to claim 1 , wherein
3. The voice input device according to claim 2, wherein the voice input device is further controlled.
Place. 4. A zoom optical system, comprising: the voice input device according to claim 2 or 3; wherein an addition amount of the uncorrelated signal is controlled in conjunction with control of a zoom ratio of the zoom optical system. Imaging device. 5. An audio input device according to claim 1, wherein said uncorrelated signal is a periodic signal. 6. The imaging device according to claim 4 , wherein an output of a signal source of the imaging device is used as the decorrelation signal.