JP7805766B2 - Imaging device - Google Patents

Description

The present invention relates to an imaging device equipped with a sound collection means.

Traditionally, digital still cameras have been designed primarily for capturing still images. However, in recent years, there has been a growing need for the ability to record and play back moving images. As a result, there is a demand for imaging devices that, while retaining the design of a digital still camera, are capable of capturing not only still images but also full-fledged moving images.

The lens barrel of a digital still camera is equipped with rotary or linear operating members for zooming and focusing, a motor that drives the lens in the optical axis direction, and a drive force transmission mechanism that transmits the motor's driving force to the lens, and these operations generate mechanical operating noise. Furthermore, imaging devices are equipped with operating members such as buttons and switches, which generate operating noise when operated.

Since high-quality audio recording is required when capturing moving images, it is desirable to prevent the aforementioned mechanical operating sounds generated by the imaging device from interfering with the audio to be recorded when capturing moving images as much as possible. Therefore, for example, Patent Document 1 discloses an imaging device that is equipped with a noise recording microphone that collects noise components generated inside the imaging device, and subtracts the audio (noise) collected by the noise recording microphone from the audio input to the audio recording microphone.

Japanese Patent Application Laid-Open No. 2009-253676

However, with the technology disclosed in Patent Document 1, it may not be possible to fully subtract noise when the noise is loud, and there is also a risk that the audio components that you want to record may be lost if the noise subtraction process is too strong.

The present invention aims to provide an imaging device that enables recording of audio from which noise has been removed while preventing the removal of audio components that are originally intended to be recorded.

An imaging device according to the present invention is an imaging device comprising: an imaging means, a microphone unit having a first microphone, a second microphone that acquires noise generated by a predetermined drive source, a main body portion in which the second microphone is disposed, and a correction means that corrects an electrical signal of sound collected by the first microphone using an electrical signal of sound collected by the second microphone, wherein the second microphone is disposed inside the main body portion near the drive source, the main body portion does not have a sound hole through which the second microphone collects sound from outside the imaging device, and the microphone unit is movable between a first position and a second position with respect to the main body portion. The microphone unit is movably arranged, and vibrations generated by the drive source are less likely to propagate through solids to the second position than to the first position, and the correction means sets weighting coefficients for each of the first frequency band and the second frequency band of the electrical signals obtained by the second microphone, and performs processing to remove the electrical signals obtained by the first microphone that have been weighted by the weighting coefficients from the electrical signals obtained by the second microphone, and when the microphone unit is at the second position, the weighting coefficient for the first frequency band is made smaller than when the microphone unit is at the first position .

This invention provides an imaging device that enables recording of audio from which noise has been removed while preventing the removal of audio components that are originally intended to be recorded.

1 is a perspective view of an imaging device according to an embodiment. FIG. 1 is a block diagram showing a schematic configuration of an imaging device. FIG. 2 is a perspective view of the appearance of the imaging device with the microphone unit popped up. FIG. 2 is a schematic cross-sectional view of the imaging device with the microphone unit popped up. 10A and 10B are schematic diagrams illustrating noise recorded by an NC microphone. FIG. 2 is a schematic diagram illustrating sound recorded by a microphone unit.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Figure 1 is a perspective view of an imaging device 10 according to an embodiment, with the imaging device 10 viewed from different directions in Figures 1(a) and 1(b). The imaging device 10 is a so-called digital still camera, but also has a video recording function.

The imaging device 10 is generally composed of an imaging device main body 100 (hereinafter referred to as "main body 100") and a lens unit 150 (lens barrel) that is mechanically and electrically connected to the main body 100 via a lens mount 21 provided on the front of the main body 100. The lens unit 150 is detachable from the lens mount 21, allowing the user to attach a lens unit with the desired optical characteristics to the main body 100.

The main body 100 is equipped with an operating member 103 consisting of a plurality of buttons, dials, etc. that the user uses to perform shooting operations and various settings. As part of the operating member 103, a power button 31 for switching the power on/off, a shutter button 32 for shooting operations, and a mode dial 33 for switching between shooting modes are located on the top surface (upper face) of the main body 100. Also, as part of the operating member 103, a video button 34 for shooting video and a menu button 35 for configuring various settings are located on the back surface of the main body 100. Note that the operating members 103 are not limited to those listed here.

A microphone unit 200 for recording audio is located on the top surface of the main body 100, and a rear monitor 40 (display panel) for displaying live view images, menu screens, captured images, etc. is located on the back of the main body 100.

Figure 2 is a block diagram showing the general configuration of the imaging device 10. The lens unit 150 includes an optical lens 151, an aperture 152, an in-lens image stabilization driver 153, a focus driver 154, and an aperture driver 155.

When the lens unit 150 is attached to the main body 100 via the lens mount 21, the system control unit 101 identifies the type of lens unit 150 and performs control appropriate for the attached lens unit 150. The optical lens 151 is composed of multiple lenses, including an AF lens and an image stabilization lens. The optical lens 151 may also be a fixed-focus lens or a zoom lens.

The focus driver 154 is an actuator that receives a drive signal from the distance measurement controller 123 (described below) and drives the AF lens in the optical axis direction to focus on the subject. The in-lens image shake correction driver 153 is an actuator that receives a drive signal from the in-lens image shake correction controller 124 (described below) and oscillates (displaces) the image shake correction lens in a plane perpendicular to the imaging optical axis, so as to reduce image shake caused by movement of the imaging device 10. The iris driver 155 is an actuator that receives a drive signal from the iris controller 122 (described below) and drives the iris 152, which is composed of multiple iris blades, to adjust the amount of light incident on the image sensor 111 (described below).

The main body 100 includes a system control unit 101, a shutter 120, an image sensor unit 110, an A/D conversion unit 106, an image processing unit 107, an image stabilization control unit 108, a shutter control unit 121, an aperture control unit 122, and a distance measurement control unit 123. The image sensor unit 110 includes an image sensor 111 and an in-housing image stabilization drive unit 112.

The main body 100 also includes an in-lens image stabilization control unit 124, a power supply control unit 102, an operation member 103, a fan 104, a rear monitor 40, an external I/F 160, an audio processing unit 125, a memory 170, and a speaker 130. The main body 100 also includes a microphone unit 200 housing main microphones A201 and B202 (first microphones), and a noise-canceling microphone 210 (second microphone (hereinafter referred to as "NC microphone 210")).

The system control unit 101 is a microcomputer composed of a CPU, ROM, RAM, etc. The CPU controls the overall operation of the imaging device 10 by expanding various programs stored in the ROM into the RAM and controlling the operation of each part of the imaging device 10. The shutter 120 adjusts the amount of light exposed to the image sensor 111 during imaging. The shutter control unit 121 controls the operation of the shutter 120 based on settings or the results of AE processing by the system control unit 101. The aperture control unit 122 sends a signal to the aperture drive unit 155 to drive the aperture 152 based on settings or the results of AE processing by the system control unit 101. The distance measurement control unit 123 calculates the amount of AF lens drive based on, for example, the defocus amount detected by the image processing unit 107, and sends the calculation result to the focus drive unit 154. The in-lens image shake correction control unit 124 calculates the amount of drive of the image shake correction lens to suppress image shake based on shake information of the imaging device 10 detected by a gyro sensor (not shown) or the like, and transmits the calculation result to the in-lens image shake correction drive unit 153.

The image sensor 111 is a CCD sensor, CMOS sensor, or the like, and converts the optical image formed by the focus of incident light from the lens unit 150 into an image signal consisting of an analog electrical signal, and outputs the image signal to the A/D conversion unit 106. The A/D conversion unit 106 converts the image signal transmitted from the image sensor 111 into image data consisting of a digital signal, and outputs the image data to the image processing unit 107. The image processing unit 107 performs predetermined image processing such as pixel interpolation and color conversion on the image data transmitted from the A/D conversion unit 106. The in-housing image stabilization control unit 108 calculates the drive amount of the image sensor 111 to reduce image shake based on shake information of the image capture device 10 detected by a gyro sensor (not shown), and transmits the calculated drive amount to the in-housing image stabilization drive unit 112. The in-housing image shake correction drive unit 112 is an actuator that receives a drive signal from the in-housing image shake correction control unit 108 and oscillates (displaces) the image sensor 111 in a plane perpendicular to the imaging optical axis so as to reduce image shake caused by movement of the imaging device 10. Note that the "housing" refers to the box-shaped structure that forms the overall frame of the main body unit 100.

The power supply control unit 102 is composed of a power supply detection circuit, a DC-DC converter, a switch circuit that switches between circuit blocks that supply power, and other components. It detects whether a power source such as a battery or AC adapter is installed, the type of power source, and the remaining battery charge. The power supply control unit 102 also controls the DC-DC converter based on these detection results and instructions from the system control unit 101, supplying the necessary voltage for the necessary period to various components via a storage medium (not shown) such as a memory card. The external I/F 160 is an interface that enables the transmission and reception of various data, such as audio data and image data, between the imaging device 10 and external devices. The fan 104 plays a role in suppressing temperature increases within the imaging device 10 by drawing in outside air into the imaging device 10 (main body) and releasing air heated by heat generated inside the imaging device 10 during operation to the outside. The operation member 103 and rear monitor 40 have already been described with reference to Figure 1, so a description thereof will be omitted here.

Main microphones A201, B202 and NC microphone 210 are audio input means, and different audio waveforms can be obtained by placing these microphones in different positions. NC microphone 210 is a sound collection means for obtaining audio waveforms (noise) that the user does not intend to record. Audio processing unit 125 is an audio correction means that performs noise canceling processing (hereinafter referred to as "NC processing"), such as subtracting the audio signal obtained by NC microphone 210 from the audio signal obtained by main microphones A201, B202. This makes it possible to generate audio with reduced noise. In addition to NC processing, audio processing unit 125 also generates optimal audio by setting the position of the audio waveforms obtained by main microphones A201, B202, performing compressor processing, equalizer processing, etc., and stores the generated audio data in memory 170. Furthermore, audio processing unit 125 performs audio playback processing to output the audio data stored in memory 170 from speaker 130.

Figure 3 is an external perspective view of the imaging device 10 with the microphone unit 200 in the pop-up position. A lock lever 220 is provided on the side of the main body 100 for popping up the microphone unit 200 from the main body 100. Figure 1 shows the microphone unit 200 in the storage position retracted into the main body 100. When the lock lever 220 is slid while the microphone unit 200 is in the storage position, the biasing force of the torsion spring (not shown) is released, and the microphone unit 200 moves to the pop-up position protruding from the top surface of the main body 100, as shown in Figure 3. When the top surface of the microphone unit 200 in the pop-up position is pressed down toward the main body 100, the microphone unit 200 can be returned to the storage position. In this way, the microphone unit 200 is arranged to be movable between the storage position (first position) retracted into the main body 100 and the pop-up position (second position).

Main microphones A201 and B202 are arranged inside microphone unit 200 (see Figure 4). An opening 203 (sound hole) is provided on the top surface of microphone unit 200, through which sound from around the imaging device 10 is taken into main microphones A201 and B202. One main microphone A201 is arranged directly below one of the two openings 203, and the other main microphone B202 is arranged directly below the other opening.

Figure 4 is a cross-sectional view showing the schematic configuration of the imaging device 10 when the microphone unit 200 is in the pop-up position. Here, only the details not mentioned in the previous explanations with reference to Figures 1 to 3 will be explained.

An optical low-pass filter 113 is disposed in front of the image sensor 111 (on the subject side, not shown). The optical low-pass filter 113 prevents incident light components with frequencies equal to or higher than a predetermined cutoff frequency from entering the image sensor 111. When the in-housing image stabilization drive unit 112 is driven, the optical low-pass filter 113 oscillates integrally with the image sensor 111.

A control board 114 is disposed on the rear side of the image sensor unit 110. The control board 114 is a printed circuit board on which various electronic and electrical components, including the system control unit 101, are mounted. The fan 104 is disposed on the rear side of the control board 114, and draws air into the main body 100 through the air intake 104a and exhausts it through the exhaust 104b. During this process, heat is exchanged between the air taken into the main body 100 and the control board 114, and the heated air is exhausted to the outside, thereby preventing the temperature of the control board 114 from rising.

The microphone unit 200 is rotatably supported by a swivel arm 204 at axis X, which serves as the center of rotation, and the microphone unit 200 and swivel arm 204 are biased toward the open direction by the biasing force of a torsion spring (not shown). The swivel arm 204 is rotatably supported by the main body 100 at axis Y, which serves as the center of rotation, and the swivel arm 204 and main body 100 are biased toward the open direction by the biasing force of another torsion spring (not shown). In this way, the microphone unit 200 is supported by the main body 100 via the swivel arm 204 at two axes, axis X and axis Y, and is biased to the pop-up position.

In the pop-up position, the connection between the microphone unit 200 and the main body 100 is weaker than in the retracted position, making it difficult for vibrations generated in the lens unit 150 or the main body 100 to propagate to the microphone unit 200 (a floating state).

By pushing the top surface of the microphone unit 200, which is in the pop-up position, toward the main body 100 against the biasing force of the two torsion springs, the microphone unit 200 can be returned to the stored position and held there. At this time, the microphone unit 200 and the swivel arm 204 rotate around axis X in the opposite direction to the opening direction, and the swivel arm 204 and the main body 100 rotate around axis Y in the opposite direction to the opening direction.

The NC microphone 210 is attached to the lens mount 21 attachment portion of the main body 100 in a direction parallel to the imaging optical axis. On the lens unit 150 side of the NC microphone 210 in the main body 100, an opening 211 is provided as a sound hole for capturing noise generated in the lens unit 150 into the NC microphone 210. When the lens unit 150 is attached to the lens mount 21, the opening 211 is open toward the inside of the main body 100 but not toward the outside of the main body 100. In other words, the NC microphone 210 does not have an opening as a sound hole for collecting sound toward the outside of the imaging device 10, and has sound collection directionality toward the lens unit 150 side.

With this configuration, noise generated in the lens unit 150 can be selectively collected and recorded by the NC microphone 210. The noise generated in the lens unit 150 includes the following: The operating noise of the lens drive motors of the in-lens image stabilization drive unit 153 and focus drive unit 154, and the operating noise of drive force transmission mechanisms such as gears that transmit the drive force of the lens drive motor to the optical lens 151. Other noises include the operating noise of the aperture drive motor of the aperture drive unit 155, the operating noise of drive force transmission mechanisms such as gears that transmit the drive force of the aperture drive motor to the aperture 152, and the friction noise (sliding noise) of the aperture blades that make up the aperture 152.

In the imaging device 10, these noises generated in the lens unit 150 propagate through solids to the lens mount 21, which is in close contact with the lens unit 150, and the noise that has propagated through solids to the lens mount 21 is collected and recorded by the NC microphone 210. In this case, by placing the NC microphone 210 close to a component that is in close contact with the lens unit 150, which is the source of the noise, it is possible to collect and record the noise that has propagated through solids from the lens unit 150 more effectively than if the NC microphone were placed in another location. Furthermore, by placing the NC microphone 210 close to the lens unit 150, it is possible to collect and record the noise that has been generated in the lens unit 150 and propagated through the air inside the main body 100 more effectively than if the NC microphone 210 were placed in another location.

Figure 5 is a schematic diagram illustrating noise recorded by the NC microphone 210, with the vertical axis representing signal level and the horizontal axis representing frequency on a logarithmic scale. The first frequency band 301 shown in Figure 5 is the frequency band of noise generated in the lens unit 150 and recorded by the NC microphone 210 mainly via solid propagation. The second frequency band 302 shown in Figure 5 is the frequency band of noise generated in the lens unit 150 and recorded by the NC microphone 210 mainly via air propagation. Because the transfer function from the same drive source to the NC microphone 210 differs when vibration generated by the same drive source propagates through solids and when it propagates through air, the first frequency band 301 and the second frequency band 302, which are different frequency bands, are generated.

Figure 6(a) is a schematic diagram illustrating the sound recorded when the microphone unit 200 is in the retracted position. The sound 400 to be recorded is airborne sound, such as the voice of the subject or photographer, or environmental sounds. Noise 401 is mechanical operating noise generated by the lens unit 150 mentioned above, and can be solid-borne or airborne. The main 1 microphones A201 and B202 collect noise 401 along with the sound 400 to be recorded.

On the other hand, as mentioned above, the NC microphone 210 collects noise generated by the lens unit 150 through solid propagation and air propagation. As mentioned above, the NC microphone 210 collects sound through the opening 211 provided inside the main body 100, and therefore the sound 400 to be recorded that is transmitted through the air outside the imaging device 10 is unlikely to be collected.

The audio processing unit 125 sets weighting coefficients for noise in the first frequency band 301 due to solid propagation and noise in the second frequency band 302 due to air propagation. The audio processing unit 125 then performs NC processing to remove noise collected by the NC microphone 210 and weighted by the weighting coefficient from the audio collected by the main microphones A201 and B202, thereby generating audio 402 from which noise 401 has been removed.

Depending on the amount and frequency band of noise 401, a portion of the audio 410 of the audio you want to record 400 may be removed, as shown in Figure 6(a), or some of the noise may remain without being completely processed (not shown). One way to reduce the amount of audio 410 is to use the microphone unit 200 in the pop-up position.

Figure 6(b) is a schematic diagram illustrating the sound recorded when the microphone unit 200 is in the pop-up position. When the microphone unit 200 is in the pop-up position, the distance between the main microphones A201, B202 and the lens unit 150 increases, and the coupling with the main body 100 weakens, causing the main microphones A201, B202 to appear more floating.

Main microphones A201 and B202 pick up noise 403 along with the audio 400 to be recorded, but noise 403, such as operating sounds generated by the lens unit 150, is mainly airborne noise. Therefore, the noise 403 recorded in the pop-up position is less than the noise 401 recorded in the retracted position. On the other hand, the position of the NC microphone 210 does not change whether the microphone unit 200 is in the retracted position or the pop-up position, so the NC microphone 210 picks up noise generated by the lens unit 150 through solid propagation and airborne propagation.

The audio processing unit 125 performs NC processing to remove the audio collected by the NC microphone 210 from the audio collected by the main microphones A201 and B202. This generates audio 404 from which noise 403 has been removed, as when the microphone unit 200 is in the pop-up position. At this time, the weighting coefficients set for the first frequency band 301 and second frequency band 302 of the noise collected by the NC microphone 210 are smaller than when the microphone unit 200 is in the retracted position. This makes it possible to accommodate the difference between noise 401 and noise 403 due to differences in the position of the microphone unit 200.

Specifically, by making the weighting coefficient for the first frequency band 301 smaller than the weighting coefficient for the second frequency band 302, it is possible to remove noise mainly due to air propagation. As a result, when the microphone unit 200 is in the pop-up position, it is possible to reduce the portion of sound 411 that is removed by NC processing from the sound 400 that is originally intended to be recorded, compared to when the microphone unit 200 is in the retracted position. As a result, it is possible to generate sound 404 from which noise 403 has been removed, without compromising the sound 400 that is originally intended to be recorded.

As such, using the microphone unit 200 in the pop-up position is more advantageous in terms of NC processing than using it in the retracted position. However, the photographer can selectively determine the position of the microphone unit 200 depending on the noise conditions and carrying conditions to capture video images.

The present invention has been described in detail above based on preferred embodiments, but the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the invention are also included.

For example, the NC microphone does not have to be placed near the shooting lens, but may be placed near a noise source inside the main body 100, such as the in-housing image stabilization drive unit 112 or the fan 104. In this case, in order to effectively record the noise generated by each noise source, it is desirable that the NC microphone be placed so that it has directionality with respect to the noise source. Furthermore, the number of NC microphones installed is not limited to one, and multiple NC microphones may be installed depending on the noise source.

In the above embodiment, the present invention was described as being applied to an imaging device 10 that is a digital still camera, but the present invention can be widely applied to electronic devices that have an imaging function and a driving means that generates mechanical noise.

REFERENCE SIGNS LIST 10 imaging device 21 lens mount 100 main body 125 audio processing unit 150 lens unit 200 microphone unit 201, 202 main microphone 210 NC microphone 211 opening

Claims (5)

An imaging means;
a microphone unit having a first microphone;
a second microphone for acquiring noise generated by a predetermined driving source;
a main body in which the second microphone is disposed;
a correction unit that corrects an electrical signal of the sound collected by the first microphone using an electrical signal of the sound collected by the second microphone,
the second microphone is disposed inside the main body near the drive source,
the main body does not have a sound hole through which the second microphone collects sound from outside the imaging device,
the microphone unit is disposed movably between a first position and a second position relative to the main body, and vibrations generated by the driving source are less likely to propagate through a solid to the second position than to the first position;
The correction means sets a weighting coefficient for each of a first frequency band and a second frequency band among the electrical signals obtained by the second microphone, and performs processing to remove from the electrical signals obtained by the first microphone the electrical signals weighted by the weighting coefficient of the electrical signals obtained by the second microphone, and when the microphone unit is in the second position, the weighting coefficient of the first frequency band is made smaller than when the microphone unit is in the first position . the first position is a position where the device is housed in the main body portion,
2. The imaging device according to claim 1 , wherein the second position is a position protruding from the main body. the predetermined drive source is at least one of an actuator for driving a lens and an actuator for driving an aperture, and the lens unit is detachable from the main body, the main body having a lens mount to which the lens unit is detachably attached;
the main body has a sound hole that opens toward the inside of the main body when the lens unit is attached to the lens mount,
3. The imaging device according to claim 1, wherein the second microphone collects sound through the sound hole. the sound hole opens in a direction parallel to an imaging optical axis,
The imaging device described in claim 3, characterized in that the second microphone is arranged inside the main body in a direction parallel to the imaging optical axis relative to the sound hole, and by collecting sound through the sound hole, it has sound collection directionality with respect to the lens unit. the first frequency band is a frequency band of sound generated in the lens unit and collected by the second microphone mainly through solid propagation,
5. The imaging device according to claim 3 , wherein the second frequency band is a frequency band of sound generated in the lens unit and collected by the second microphone mainly through air propagation.