JP3679298B2 - Video camera with microphone - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a video camera with a microphone, and more particularly to a video camera with a microphone capable of performing voice focusing in synchronization with image focusing.
[0002]
[Prior art]
FIG. 10 is an external view showing a schematic configuration of a conventional video camera 200 with a microphone.
A camera body 201 is provided with a lens 202 for inputting an image from a subject and a microphone 203 for inputting sound emitted from the subject.
Conventionally, a stereo microphone or a monaural microphone has been used as the microphone 203 attached to such a video camera.
The microphone attached to such a video camera can be switched to unidirectional or non-directional depending on the situation of the subject and the improvement to prevent noise generation due to wind pressure when used outdoors. Etc. have been made.
[0003]
On the other hand, the video camera is operated to focus on the subject by adjusting the lens 202 according to the distance of the subject and obtain an optimal image signal.
In addition, when a zoom lens is used, an image of a subject at a long distance can be obtained by zooming in on a short distance (zooming up) or an image of a subject at a short distance can be reduced (zoom down).
On the other hand, the microphone 203 is operated separately from the operation of the lens 202, and the surrounding sound is collected by the one-point microphone or the stereo microphone regardless of the enlargement or reduction of the image captured from the zoom lens.
In recent years, an optical microphone element has attracted attention as a small-sized microphone element. In particular, an apparatus using a vertical cavity surface emitting laser (hereinafter referred to as VCSEL) as a light emitting element can achieve further miniaturization.
[0004]
[Problems to be solved by the invention]
As described above, in the conventional video camera with a microphone, even if the subject image is enlarged or reduced by zooming, the sound recorded from the subject is not linked to this and can only capture the surrounding sound.
Therefore, a phenomenon has occurred in which sound from a subject can be heard from a distance even if an enlarged image is obtained by zooming with a camera. This is because the microphone mounted on the video camera is a unidirectional or omnidirectional microphone, and thus the sound sensitivity cannot be switched in conjunction with image zooming.
[0005]
Therefore, a video camera with a microphone needs a microphone that can be captured as a sound from a short distance when the image is enlarged, and can be captured as a sound from a long distance when the image is reduced.
The inventors have made the present invention noting that an optical microphone element using a VCSEL is suitable not only for ultra-miniaturization but also that directivity can be easily adjusted.
Accordingly, an object of the present invention is to provide a video camera with a microphone using an optical microphone element capable of zooming in and out of a microphone in conjunction with zooming in / out of an image.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a video camera with a microphone according to the present invention comprises a microphone capable of controlling directional characteristics, and in the video camera with a microphone that focuses the directional characteristics on the subject in synchronization with the focusing of the video camera on the subject. As the microphone, a vertical cavity surface emitting laser light emitting element having a substantially uniform emission intensity distribution is arranged concentrically, a substrate on which a light receiving element for receiving the emitted light of the light emitting element is arranged, and the substrate A vibration plate that is installed substantially parallel to and close to the position to be vibrated and that vibrates due to sound pressure, reflects light from the light emitting element and radiates it to the light receiving element, and supplies a driving current to the light emitting element. a light source driving circuit, a small amplification degree increases as the signal level is small, which is outputted from the light receiving element No. amplifying include circuitry, the use of a optical microphone having a negative feedback circuit that supplies to the light source drive circuit as a negative feedback signal based on the output of the small signal amplifier circuit, shows a zooming of the subject of the video camera The directivity characteristic of the optical microphone is controlled by changing the magnitude of the negative feedback signal using a zooming signal.
In the video camera with a microphone according to the present invention, the zooming signal may be a zoom amount change signal indicating a change amount of a zoom lens of the video camera.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the video camera with a microphone according to the present invention, the sound recorded from the microphone is enlarged / reduced in synchronization with the enlargement / reduction of the zoom image, thereby changing the directivity and reducing the image displayed far away. The sound corresponding to the image that is magnified and enlarged is heard from near. Furthermore, an optical microphone using a VCSEL is used as a microphone used for such a purpose.
First, prior to describing an embodiment of a video camera with a microphone according to the present invention, a basic operation and configuration of an optical microphone using a VCSEL used in the present invention will be described.
[0008]
FIG. 2 is a diagram showing a basic structure of the optical microphone element.
FIG. 2A shows a cross-sectional shape. An electronic circuit board 12 is installed on the bottom surface 8 of the container 1, and a substrate 9 on which a light emitting element and a light receiving element are arranged is attached on the substrate 12. The attachment can also be performed by electrically connecting the substrate 9 and the substrate 12 by, for example, flip chip bonding. Further, if the bottom surface 8 is formed of a semiconductor substrate such as silicon, an electronic circuit can be formed thereon, so that the electronic circuit substrate 12 can be omitted. In the example shown in FIG. 2, a vertical cavity surface emitting laser diode LD is used as a light emitting element, and a photodiode PD is used as a light receiving element. A circular surface emitting laser diode LD is arranged at the center of the substrate 9, and light receiving elements PD are arranged concentrically around the surface emitting laser diode LD.
[0009]
FIG. 2B is an enlarged plan view showing the light emitting / receiving section of the substrate 9 on which the light emitting / receiving element shown by the dotted line in FIG. 2A is mounted.
As shown in the figure, a circular light emitting element LD is arranged at the center, and light receiving elements PD1, PD2,... PDn are arranged concentrically so as to surround the light emitting element LD. A vertical cavity surface emitting laser can be used as the light emitting element LD used here.
The light emitting element LD and the light receiving element PD can be simultaneously formed on the gallium arsenide wafer by a semiconductor manufacturing process.
Therefore, since the alignment accuracy between the light emitting element LD and the light receiving element PD is determined by the accuracy of the mask used in the semiconductor manufacturing process, the alignment accuracy can be set to 1 μm or less, and the conventional light receiving / emitting element of the optical microphone element can be reduced. It can be realized with high accuracy of 1/100 or less compared with the alignment accuracy.
[0010]
In general, the vertical cavity surface-emitting light emitting device has a characteristic that the light emission intensity distribution is substantially uniform in a concentric manner. Therefore, the radiated light radiated from the light emitting element LD installed at the center toward the diaphragm 2 at a predetermined angle is reflected concentrically with the same intensity, and the diaphragm 2 vibrates by receiving the sound wave 7. As a result, the reflection angle changes and reaches the light receiving element PD concentrically.
Accordingly, the vibration displacement of the diaphragm 2 can be detected by detecting the change in the amount of light received by the light receiving elements PD1 to PDn arranged concentrically. As a result, the intensity of the incident sound wave 7 can be detected, so that it can be used as an optical microphone element.
An electrode 11 is formed for driving the light emitting element LD and the light receiving element PD or detecting the amount of incident light.
[0011]
Next, a vertical cavity surface emitting laser (hereinafter referred to as VCSEL) which is a light emitting element used in the present invention will be described.
FIG. 3 shows the emission intensity distribution of the VCSEL. As shown in the figure, the radiation intensity distribution is given as a Gaussian distribution in the nucleus.
The light emission intensity distribution P0 (θ) is expressed by equation (1).
[Expression 1]
Po (θ) = exp (−α ² θ ² ) (1)
θ: Angular displacement (per unit radians) from the vertical line on the light-emitting surface
α: Coefficient that defines the emission divergence angle (originally simplified in the calculation of “1 / α ² ”)
[0012]
When the light emission distribution coefficient α is calculated for the one-dimensional case, it is expressed by the following equation (2).
[Expression 2]
α ² = − [ln (h)] / (FAHM / 2) ² (2)
h: 1 in the relative intensity vertical direction obtained by actually measuring the light emission distribution of the laser. Half value = 0.5, 1 / e = 0.3183, 1 / e2 = 0.135335
FAHM: The full width at half maximum (FAHM) value is usually provided by the manufacturer.
If h = 0.5, FAHM = 9 degrees (with angle), rad (9/2) = 0.07854
α ² = − [(ln (0.5)] / (0.07854) ² = 112.369
Then, when this is used to calculate the emission intensity distribution for the designated direction, a distribution as shown in FIG. 3 is obtained.
[0013]
FIG. 4 is a diagram in the case where the emission intensity distribution is calculated and illustrated in two dimensions.
In this case, the two-dimensional emission intensity distribution P0 (θ) is given by equation (3).
[Equation 3]
Po (θ) = exp (−α ² θ ² ) · exp (−β ² ψ ² ) (3)
[0014]
Calculation is performed in the same way as the distribution calculation coefficients α and β in the θ direction and the ψ direction. The emission distribution coefficient α is given by equation (4), and the emission distribution coefficient β is given by equation (5).
[Expression 4]
α ² = − [ln (h)] / (FAHM / 2) ² (4)
If h = 0.5 and FAHM = 9 degrees, rad (9/2) = 0.07854
α ² = − [(ln (0.5)] / (0.07854) ² = 112.369
[0015]
[Equation 5]
β ² = − [ln (h)] / (FAHM / 2) ² (5)
If h = 0.5 and FAHM = 9 degrees, rad (9/2) = 0.07854
β ² = − [(ln (0.5)] / (0.07854) ² = 112.369
[0016]
As is apparent from the two-dimensional emission intensity distribution obtained in this way, in the vertical cavity surface emitting laser, the intensity distribution of the light emitting elements is substantially uniform in a concentric manner.
For this reason, in order to efficiently receive laser light emission as a deviation (displacement) of the diaphragm 2, it is optimal to arrange the light receiving elements concentrically. A differential signal of signals detected by light receiving elements belonging to different concentric circles arranged concentrically becomes a signal giving a change in sound pressure.
[0017]
Here, in order to limit or select the dynamic range of the received signal, it is possible to provide two or more light receiving elements concentrically.
Here, the noise reduction effect cannot be expected so much with the optical microphone shown in FIG. That is, the diaphragm 2 also vibrates due to the noise reaching the diaphragm 2, and this is superimposed on the vibration caused by the normal sound wave 7 as a noise signal.
An optical microphone having a structure as shown in FIG. 5 is known as an optical microphone that reduces the influence of noise and further reduces noise.
[0018]
In the structure shown in FIG. 5, the diaphragm 2 that vibrates by the sound wave 7 is stretched substantially at the center of the container 1. And the 1st opening part 15 and the 2nd opening part 16 are provided in the container 1 so that it may become an object position mutually with respect to the diaphragm 2.
With this configuration, the sound wave 7 enters the container 1 through any of the openings 15 and 16 and vibrates the diaphragm 2.
5 shows a structure in which the light emitting element LD and the light receiving element PD are separated for convenience of explanation, actually, the light emitting element LD and the light receiving element PD are integrally formed on the substrate 9 in FIG. The structure shown in FIG.
[0019]
When the sound pressures of the sound wave entering from the first opening 15 and the sound wave entering from the second opening 16 are equal in the optical microphone element 50 shown in FIG. The vibration plates 2 are not vibrated by canceling each other in 2b.
It is known that when two microphone elements having the same reception sensitivity are arranged close to each other and a sound wave generated at a long distance is received, the two microphone elements detect the incoming sound wave equally.
Generally, sound waves are generated from a person's mouth that is a short distance away from the microphone element. That is, sound is generated at a short distance from the microphone element. This short-distance human voice has a spherical field characteristic as indicated by a circular curve.
[0020]
On the other hand, for example, a sound wave generated by a long distance, such as noise sound, has a plane field characteristic. The acoustic intensity of a spherical wave is substantially the same along the spherical surface or collapse line and varies along the radius of the sphere, but in the case of a plane wave, the acoustic intensity is substantially the same at all points on the plane.
Accordingly, since the optical microphone element as shown in FIG. 5 can be considered as a combination of two microphone elements, when the optical microphone element is placed in the far field, the first opening 15 and the second opening 16 are almost Sound waves having the same intensity and phase characteristics arrive at the diaphragm 2 and cancel each other as described above, thereby reducing the influence.
On the other hand, since the sound wave from the near field is incident from the first opening 15 or the second opening 16 nonuniformly, the vibration plate 2 is vibrated and extracted from the light emitting element PD as a signal. In this way, an optical microphone element that can further reduce the influence of noise can be obtained by the structure of FIG.
[0021]
FIG. 6 is a diagram showing the directivity pattern of the optical microphone element shown in FIGS.
(A) shows the directivity pattern of the optical microphone element shown in FIG. 2, and has a substantially circular directivity having maximum sensitivity in the direction perpendicular to the diaphragm 2 toward the opening (left side in the figure). Has a pattern.
FIG. 5B shows the directivity pattern of the optical microphone element shown in FIG. 5, which has a substantially 8-shaped directivity pattern having maximum sensitivity in both directions of the openings 15 and 16.
Here, the directional beam pattern of the optical microphone element shown in FIGS. 2 and 5 is changed so as to extend in the axial direction indicating the maximum sensitivity as shown in FIGS. 7 and 8 and to narrow down in the direction orthogonal to the axis. Can be made.
[0022]
In order to change the directional beam pattern in this way, a part of the detection output from the light receiving element PD may be fed back to the light source driving circuit for driving the light emitting element LD using a negative feedback circuit. FIG. 9 is a diagram showing a schematic configuration of an optical microphone device using a feedback circuit 100 for changing the beam pattern as shown in FIG. 7 or FIG.
The output from the light receiving element PD is taken out through the filter circuit 18 and amplified by the amplifier 19 to become a microphone output. The filter circuit 18 is used to extract only signal components in the desired frequency range.
Here, in the optical microphone device shown in FIG. 9, a predetermined current is supplied to the light emitting element LD via a negative feedback (negative feedback dot NFB) circuit 100 for a part of the output signal taken out from the light receiving element PD, and the light emitting element LD. Is supplied as a negative feedback signal to the light source driving circuit 13 driving the.
[0023]
The negative feedback circuit 100 includes a small signal amplification circuit 10, a filter circuit 14 that extracts only a signal component in a desired frequency range from its output, and a comparator 20. A reference power supply 14 serving as a reference voltage is connected to a non-inverting input terminal of the comparator 20. The signal taken out through the filter circuit 17 is supplied to the inverting input terminal of the comparator 20.
The small signal amplifying circuit 10 amplifies only a signal below a predetermined level.
With this configuration, the comparator 20 outputs a smaller output level as the output of the filter circuit 17 is larger, and thus the light source driving circuit 13 operates so as to reduce the current supplied to the light emitting element LD.
[0024]
Here, the small signal amplifying circuit 10 amplifies the signal only when the input signal level is equal to or lower than a predetermined level, and does not amplify the signal above a certain level. Therefore, when the input signal level is higher than a certain level, the output signal level does not change and the amplification degree (gain) becomes zero. When the input signal is below a predetermined signal level, amplification is performed so that the degree of amplification increases as the signal level decreases. Furthermore, the increase rate of the output signal with respect to the input signal increases as the input signal level decreases.
[0025]
Here, since the output from the light receiving element PD is proportional to the received sound volume, the output of the small signal amplifier circuit 10 is amplified and output as the volume decreases. Since this is input to the inverting input terminal of the comparator 20 via the filter circuit 17, the output level of the comparator 20 conversely decreases with decreasing volume.
As a result, the current supplied to the light emitting element LD operates so as to decrease the light output of the light emitting element LD as the volume decreases. That is, the sensitivity of the microphone decreases with decreasing volume. Further, since a signal exceeding a predetermined level is not amplified, the optical output is not limited at the signal level. Therefore, the sensitivity of the microphone does not decrease.
[0026]
When the sound is from the axial direction perpendicular to the diaphragm and does not cause a decrease in microphone sensitivity, if the sound is shifted from the axial direction, the sensitivity gradually decreases due to the original directivity curve. To go. When the level is below a certain level, the small signal amplifying circuit 10 has an amplification factor, the supply current control of the light source driving circuit 13 is activated, and the sensitivity of the microphone further decreases.
As a result, in the optical microphone device having the negative feedback circuit 100, as shown in FIG. 7 or FIG. 8, the directional beam width of the sensitive directional pattern becomes a narrower pattern.
[0027]
7 and 8 show the directivity pattern change caused by changing the negative feedback amount.
(A) shows the directivity pattern when negative feedback is not applied. In this case, the directivity pattern is substantially circular. Next, directivity patterns when negative feedback is applied are shown in (B) and (C).
In the case of (B), the negative feedback amount is small, and in the case of (C), the negative feedback amount is large. In this way, by changing the amplification factor of the small signal amplifying circuit 10, the negative feedback amount is changed, and the directivity pattern of sensitivity is extended in the axial direction of the maximum sensitivity and is changed so as to narrow down in the direction orthogonal to the axis. Can do.
In this way, the directivity characteristic of the sensitivity of the optical microphone can be changed.
[0028]
In the sound pickup apparatus according to the present invention, the directivity characteristics of the selected microphone are changed using the optical microphone element that can change the beam pattern having such directivity.
FIG. 1 is a block diagram showing an embodiment of a video camera with a microphone according to the present invention.
In place of the microphone 203 in the conventional camera shown in FIG. 10, an optical microphone 300 including the optical microphone element 50, the light source driving circuit 13, and the negative feedback circuit 100 is used.
The configuration of the camera unit is such that a signal from a zoom amount adjusting unit 28 that adjusts a zoom amount of a lens 202 that inputs an input image 27 is extracted by a zoom amount converting unit 31 via an image detection element 29 such as a CCD and an amplifier circuit 30. .
That is, when zooming is performed on the subject by the zoom amount adjusting means 31, the zoom amount indicating the degree of enlargement or reduction is detected as a zoom amount change signal by detecting an image from the subject. 31 outputs are obtained.
[0029]
This zoom amount change signal is used as a control signal for changing the negative feedback amount of the negative feedback circuit 100.
That is, when zooming up and enlarging an image, the negative feedback amount of the negative feedback circuit 100 is increased in response to the zoom amount change signal that is an output signal from the zoom amount conversion circuit 31, and the optical microphone element 50 is directed. The beam width is sharpened to reduce the influence of surrounding sound, and only the signal from the subject is picked up and recorded.
Conversely, when the image is reduced by zooming down, the negative feedback amount is reduced or the operation of the negative feedback circuit is stopped to achieve unidirectionality, and sound collection is performed in consideration of the influence of surrounding sounds.
[0030]
In the embodiment shown in FIG. 1, the zooming amount to the subject of the video camera is obtained by the output of the zoom amount adjusting means 28 based on the image signal from the image sensor, but the method for detecting the zoom amount is limited to this. Is not to be done.
That is, it is also possible to directly detect a mechanical change of the zoom amount adjusting means 18, convert it and electrically detect it as a zoom amount change signal, and use it as a control signal for the negative feedback circuit 100.
As the optical microphone element 50 of the optical microphone 300 used in the present invention, either the structure shown in FIG. 2 or the structure shown in FIG. 5 can be used in principle. It is preferable to use the structure shown in FIG.
[0031]
【The invention's effect】
As described above in detail based on the above embodiments, in the present invention, an optical microphone using a VCSEL capable of changing the directivity characteristic with respect to sound waves is used as a microphone attached to the video camera, and the object to the subject of the video camera is used. By changing the negative feedback amount of the negative feedback circuit in response to the amount of zooming, the directivity of the microphone is changed, and the sound recording status is changed in response to the enlargement / reduction of the image. Correspondingly, it is possible to record images and sounds as if the sound was emitted in the vicinity, as if the sound was emitted in the distance with respect to the reduced image, that is, in a state close to nature.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a main configuration of a video camera with a microphone according to an embodiment of the present invention.
FIG. 2 is a diagram showing a voltage structure of an optical microphone element.
FIG. 3 is a graph showing a light emission intensity distribution of a VCSEL used in the present invention.
FIG. 4 is a diagram showing a two-dimensional calculation of the emission intensity distribution of a VCSEL used in the present invention.
FIG. 5 is a diagram showing the structure of another optical microphone element used in the present invention.
FIG. 6 is a directional characteristic pattern diagram of an optical microphone element used in the present invention.
FIG. 7 is a diagram showing a change in directivity pattern of an optical microphone element used in the present invention.
8 is a change diagram of the directivity pattern of the optical microphone element of FIG. 5. FIG.
FIG. 9 is a circuit diagram showing a schematic configuration of an optical microphone device used in the present invention.
FIG. 10 is an external view showing a schematic configuration of a conventional video camera with a microphone.
[Explanation of symbols]
2 Diaphragm LD Light emitting element PD Light receiving element 7 Sound wave 13 Light source driving circuit 28 Zoom amount adjusting means 29 Imaging element (image detecting element)
30 Amplifier 31 Zoom amount adjusting means 50 Optical microphone element 100 Negative feedback circuit 300 Optical microphone

Claims (1)

In a video camera with a microphone that includes a microphone that can control directivity, and that focuses the directivity on the subject in synchronization with focusing on the subject of the video camera.
As the microphone,
A vertical cavity surface emitting laser light emitting element having a substantially uniform emission intensity distribution in a concentric manner, and a substrate on which a light receiving element for receiving the emitted light of the light emitting element is disposed;
A vibration plate that is installed substantially parallel to and close to a position facing the substrate, vibrates due to sound pressure, and reflects light from the light emitting element to radiate to the light receiving element;
A light source driving circuit for supplying a driving current to the light emitting element;
A small-signal amplifier circuit that increases the degree of amplification as the signal level output from the light-receiving element decreases, and includes a negative feedback circuit that supplies the light source drive circuit as a negative feedback signal based on the output of the small-signal amplifier circuit Using an optical microphone
A video camera with a microphone, wherein the directivity characteristic of the optical microphone is controlled by changing the magnitude of the negative feedback signal according to a zooming signal indicating a zooming amount to a subject of the video camera.

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