JP2004004362A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive system suitable for a digital camera capable of recording sound. <P>SOLUTION: A stepping motor is used as a focusing motor 24 which focuses a taking lens. When a still picture is taken, the focusing motor 24 is driven by a two-phase excitation drive system to enable high-speed focusing. When sound is recorded while taking a movie, the focusing motor 24 is driven by a micro step drive system so that working noise is reduced and does not affect sound-recording. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera.
[0002]
[Prior art]
A digital camera that digitally converts an image captured by an image sensor such as a CCD image sensor into image data and stores it in a storage medium such as a memory card has become widespread. Some of these digital cameras can record moving images in addition to still images, and others can record sound together with moving images.
[0003]
Many digital cameras also have an autofocus function that automatically adjusts the focus according to changes in the shooting distance, or focuses when the release button is pressed halfway when shooting a still image. I have been matching. This focusing is performed by moving a lens constituting the photographing lens with a motor along the optical axis direction.
[0004]
[Problems to be solved by the invention]
By the way, when recording a sound together with a moving image, it is necessary to prevent the operating sound of the motor at the time of focusing from being collected and recorded by a microphone built in the digital camera. On the other hand, when shooting a still image, it is necessary to focus instantaneously by driving the motor at high speed in response to half-pressing of the release button in order not to miss the shooting timing.
[0005]
However, if the motor is driven at a high speed in response to still image shooting, the operating sound becomes louder, so it is not suitable for recording sound together with moving images. On the other hand, if the operation sound is reduced by driving the motor at a low speed in consideration of recording sound, it is not suitable for taking a still image.
[0006]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a digital camera capable of driving a motor suitable for recording a still image, a moving image, and recording a sound.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a stepping motor for focusing is driven by a two-phase excitation drive method during shooting in the still image mode, and the stepping motor is micro-switched during shooting in the moving image mode. It is provided with drive means for driving in a step drive system.
[0008]
According to the second aspect of the present invention, the recording selection member for selecting whether or not to record the sound in the moving image mode and the stepping motor for focusing in the still image mode are driven by the two-phase excitation driving method. In the following shooting, when recording sound, the stepping motor is driven by a micro-step driving method, and when not recording sound, driving means for driving the stepping motor by a two-phase excitation driving method is provided. It is.
[0009]
According to a third aspect of the present invention, there is provided a drive selection member for selecting a driving method of a stepping motor for performing focusing from either a two-phase excitation driving method or a microstep driving method, and at the time of photographing in a still image mode. When the stepping motor is driven by the two-phase excitation drive method and the two-phase excitation drive method is selected by the drive method selection member in the shooting under the moving image mode, the stepping motor is driven by the two-phase excitation drive method. When the microstep driving method is selected, the stepping motor is provided with driving means for driving the stepping motor by the microstep driving method.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The front of the digital camera embodying the present invention is shown in FIG. 1, and the back is shown in FIG. On the front surface of the camera body 2, a lens barrel 4, a strobe light emitting unit 5, an objective window 6a of an optical finder 6, a recording microphone opening 7, and a release button 8 are provided. On the back side, an eyepiece window 6b of the optical finder 6, an LCD 10, an operation unit 11, a zoom button 12, and a mode knob 13 are provided. Further, a lid (not shown) of a memory slot is provided on the side surface of the camera body 2. A memory card 15 (see FIG. 3) can be mounted in the memory slot, and still image, moving image data, and audio data are recorded on the memory card 15.
[0011]
By operating the operation unit 11, it is possible to turn on / off the power, switch between the shooting mode and the playback mode, select an image under the playback mode, and instruct to delete the image. When the operation unit 11 is operated to turn on the power of the digital camera, the lens barrel 4 is extended from the retracted position to the photographing position protruding forward. The taking lens 3 is of a zoom type, and zooming is performed by pressing the zoom button 12 to the telephoto side or the wide side.
[0012]
Under the shooting mode, by operating the mode knob 13, either a still image mode for shooting a still image or a moving image mode for shooting a moving image can be selected. When the release button 8 is pressed in the still image mode, an image of one frame photographed by the CCD image sensor 16 (see FIG. 3) disposed in the back of the photographing lens 3 is captured, and the obtained still image is obtained. Are recorded and stored in the memory card 15.
[0013]
Further, in the moving image mode, when the release button 8 is pressed, the moving image shooting by the CCD image sensor 16 is started from that point, and when the release button 8 is pressed again, the moving image shooting is stopped, and the obtained moving image Image data is recorded / saved in the memory card 15. In this moving image mode, sound recording is performed along with shooting of the moving image, and the obtained sound data is recorded / saved in the memory card 15 in association with moving image data. Recording of sounds such as environmental sounds and voices under the moving image mode is performed using a microphone 18 (see FIG. 3) disposed behind the microphone opening 7.
[0014]
In the optical finder 6, the observable range changes according to zooming of the photographic lens 3, and the photographic range can be observed. The LCD 10 constitutes a so-called electronic viewfinder that displays a subject image photographed through the photographing lens 3 in real time, and is used for image reproduction and the like. Note that a speaker or the like may be provided in the digital camera so that when a moving image is reproduced on the LCD 10, the corresponding audio data can be reproduced.
[0015]
FIG. 3 shows the configuration of the digital camera. The system controller 20 controls each part of the digital camera in a predetermined sequence. The input unit 21 sends an operation signal corresponding to the operation of the release button 8, the operation unit 11, the zoom button 12, and the mode knob 13 to the system controller 20. Based on these operation signals, the system controller 20 controls each unit and executes a sequence for photographing.
[0016]
The photographing lens 3 includes a focus lens 3a, a zooming magnification lens 3b, and a diaphragm 3c. The focus lens 3a, the zoom lens 3b, and the diaphragm 3c are driven by the corresponding focus motor 24, zoom motor 25, and diaphragm motor 26, respectively, as will be described in detail later.
[0017]
As described above, the CCD image sensor 16 is disposed behind the photographing lens 3. The CCD image sensor 16 is driven by a driver 27 to convert an optical subject image into an electrical photographing signal and output it. The charge accumulation amount (exposure amount) of each light receiving element of the CCD image sensor 16 is adjusted by the electronic shutter and the diaphragm 3c.
[0018]
An imaging signal from the CCD image sensor 16 is sent to the analog processing circuit 28, and gain adjustment, γ processing, and the like are performed. The A / D converter 29 converts the photographing signal processed by the analog processing circuit 28 into RGB image data. The image data may be luminance data, color difference data, or the like. Image data from the A / D converter 29 is sent to a data processing circuit 30, an AE processing circuit 31, and an AF processing circuit 32.
[0019]
The data processing circuit 30 performs data processing such as gamma correction for LCD display, resolution change, data compression at the time of recording image data, and data expansion at the time of reading. Under the shooting mode, the processed image data is sent to the LCD driver 33. As a result, the subject image being shot is displayed on the LCD 10 as a moving image.
[0020]
The microphone 18 is operated under the moving image mode to convert the sound into an audio signal and output it. The audio signal is sent to the analog processing circuit 35. The analog processing circuit 35 performs amplification of the audio signal and automatic adjustment of the amplification factor. The A / D converter 36 converts the audio signal from the analog processing circuit 35 into audio data. The audio data from the A / D converter 36 is sent to the data processing circuit 30 and subjected to data compression and the like.
[0021]
The media controller 37 controls data input / output of the memory card 15 installed in the memory slot. When the release button 8 is pressed in the still image mode, the image data for one frame obtained immediately after that is compressed by the data processing circuit 30 and then sent to the media controller 37 and recorded on the memory card 15.
[0022]
In addition, when the release button 8 is pressed in the moving image mode, shooting is performed every 1/30 seconds, for example, during the period from immediately after that until the release button 8 is pressed. After the image data is compressed by the data compression circuit 30, it is sent to the media controller 37 and recorded on the memory card 15. Also, under this moving image mode, audio data obtained during the shooting period is also sent to the media controller 37 and recorded in association with the moving image data.
[0023]
In this example, image data and audio data are recorded in the memory card 15 attached to the digital camera. However, a memory may be built in the digital camera and recorded in the memory.
[0024]
Based on the image data output from the A / D converter 29, the AE processing unit 31 adjusts the shutter speed of the electronic shutter of the CCD image sensor 16 and the aperture 3c so that the exposure amount of the CCD image sensor 16 is appropriate. The aperture value is feedback controlled. The electronic shutter of the CCD image sensor 16 is controlled via a driver 27. The aperture value of the aperture 3c is determined by driving the aperture motor 26 via the driver 41. A stepping motor is used as the diaphragm motor 26.
[0025]
The AF processing unit 32 detects the focus state of the subject based on the image data output from the A / D converter 29, and moves the focus lens 3a so as to achieve an appropriate focus state. For example, when there is no focus, the AF processing unit 32 moves the focus lens 3a back and forth along the optical axis direction to determine the focus shift direction, and then moves the focus lens 3a to the focus position. Move. This movement of the focus lens 3 a is performed by driving the focus motor 24 via the driver 42. As the focus motor 24, a stepping motor is used in the same manner as the aperture motor 26.
[0026]
The driver 43 drives the zoom motor 25 according to the operation of the zoom button 12. The zoom lens 25 is moved along the optical axis by the zoom motor 25, so that the photographing lens 3 is zoomed. A DC motor is used as the zoom motor 25.
[0027]
Each of the motors 24 to 26 is driven in one of a high-speed drive mode in which the control speed is given priority by the corresponding drivers 41 to 43 and a mute drive mode that is excellent in silence and does not hinder voice recording. At the time of shooting a moving image, the motors 24 to 26 are driven by the mute drive mode, and the drivers 41 to 46 are controlled by the system controller 20 so as to be driven in the high speed drive mode otherwise.
[0028]
When the driving mode is the high-speed driving mode, the focus motor 24 that is a stepping motor has driving voltages of “+ V0” and “−V0” as shown in FIG. 4 showing waveforms of A-phase and B-phase driving voltages. And is driven by a two-phase excitation drive system that is periodically switched to In the mute drive mode, the focus motor 24 changes the drive voltage stepwise between “+ V0” and “−V0” as shown in FIG. Driven by the driving method. In FIG. 5, the vertical axis indicates the ratio to the voltage “V0”.
[0029]
In this example, in the mute drive mode, microstep drive is performed in which the drive voltage is changed in nine steps, and the drive voltage at each step is + 100%, + 92.4%, + 70.7%, +38 with respect to the voltage V0. .3%, 0%, -38.3%, -70.7%, -92.4%, and -100%.
[0030]
When microstep driving is performed, it is necessary to change the A-phase and B-phase driving voltages stepwise as shown in FIG. However, changing the drive voltage stepwise leads to a complicated and large scale circuit configuration of the driver. Therefore, in the driver 42 in this example, the driving voltage is substantially changed stepwise as shown in FIG. 5 by performing pulse width modulation (PWM) control on the driving voltage.
[0031]
The driver 42 includes, for example, a drive voltage output circuit that outputs a drive voltage for two-phase excitation drive, and a modulation circuit that performs pulse width modulation on the drive voltage from the drive voltage output circuit. In the two-phase excitation drive), the focus motor 24 is driven using the drive voltage from the drive voltage output circuit. In the mute drive mode (microstep drive), the drive voltage from the drive voltage output circuit is pulse width modulated by the modulation circuit. Then, the focus motor 24 is driven with this pulse width modulated drive voltage.
[0032]
FIG. 6 shows the relationship between the substantial drive voltage and the pulse voltage modulated drive voltage waveform from the driver 42. The driver 42 applies pulse width modulation with a modulation signal having a duty ratio corresponding to a required driving voltage. For example, when + 92.4% of the voltage “+ V0” is supplied to the focus motor 24 as the drive voltage, the voltage “+” is applied with the modulation signal having the on time “92.4%” and the off time “7.6%”. The output voltage of “+ V0” is modulated. On the other hand, when + 92.4% of the voltage “−V0” is supplied as the drive voltage to the focus motor 24, the modulation signal has an on time “92.4%” and an off time “7.6%”. To modulate the output voltage of -V0. A modulation signal having a sufficiently short signal period is used.
[0033]
The driving of the diaphragm motor 26 by the driver 43 is the same as the driving of the focusing motor 24 by the driver 42. That is, the zoom motor 25 is driven by the driver 43 using the two-phase excitation drive method in the high-speed drive mode and using the microstep drive method in the mute drive mode.
[0034]
In the high-speed drive mode, that is, the two-phase excitation drive method, the maximum torque of the motors 24 and 26 can be set higher because the generated torque is smaller than in the microstep drive method. In this example, in the high-speed drive mode using the two-phase excitation drive method, the speeds of the motors 24 and 26 are set higher than in the mute drive mode using the microstep drive method. Therefore, the driving voltage period in the mute driving mode is shorter than that in the high-speed driving mode.
[0035]
For the zoom motor 25 using a DC motor, in the high-speed drive mode, a drive system (hereinafter referred to as a high-voltage drive system) in which a relatively high drive voltage is supplied from the driver 43 to rotate the zoom motor 25 at a high speed is also used. In the drive mode, a drive system (hereinafter referred to as a low voltage drive system) is used in which a relatively low drive voltage is supplied from the driver 43 to rotate the zoom motor 25 at a relatively low speed.
[0036]
Next, the operation of the above configuration will be described. When the operation unit 11 is operated and the power is turned on, the mode is confirmed, and either the photographing mode or the reproduction mode is set according to the operation input from the operation unit 11. Even after branching to any mode, the operation unit 11 can be used to shift to another mode.
[0037]
Under the shooting mode, the image data of the subject image captured by the CCD image sensor 16 is continuously sent to the data processing circuit 30 and the processed image data is sent to the LCD driver 33 as in the case of the conventional digital camera. As a result, the subject image being shot is displayed on the LCD 10 as a moving image.
[0038]
As schematically shown in FIG. 7, the high-speed drive mode is set as the drive mode of each of the motors 24 to 26 in the standby state in which the operation of the release button 8 is waited for in this shooting mode.
[0039]
In this standby state, for example, when the zoom button 12 is operated to the tele side, the driver 43 drives the zoom motor 25 in the high-speed drive mode, that is, the high-voltage drive method in accordance with an instruction from the system controller 20. The zoom lens 3b is moved in the direction in which the focal length of the lens becomes longer. Conversely, when the zoom button 12 is operated to the wide side, the zoom motor 25 is driven in the high-speed drive mode by the driver 43, and the zoom lens 3b moves in a direction to shorten the focal length of the photographing lens 3.
[0040]
When the photographing lens 3 is zoomed as described above or the photographing distance changes due to a change in framing, and the AF processing unit 32 detects that the focus is not appropriate, the control of the AF processing unit 32 is controlled. Below, the focus motor 24 is driven by the driver 42, and the focus lens 3c is moved to a focus position.
[0041]
When a change in subject brightness is detected by the AE processing unit 31, the shutter speed of the electronic shutter of the CCD image sensor 16 is controlled via the driver 27 under the control of the AE processing unit 31, and the aperture The motor 26 is driven by the driver 41, and the aperture value of the aperture 3c is controlled so that an appropriate exposure amount can be obtained.
[0042]
As with the zoom motor 25, the focus motor 24 and the aperture motor 26 are set to be driven in the high-speed drive mode, so that each of the motors 24 and 26 is driven by the two-phase excitation drive method.
[0043]
As described above, zooming of the photographing lens 3 is performed in response to the operation of the zoom button 12, and focusing and adjustment of the exposure amount are always performed. Therefore, the photographer can observe an object with proper brightness and proper brightness on the LCD 10.
[0044]
For example, when a still image is shot and recorded, the mode knob 13 is operated to select the still image mode. When the release button 8 is pressed halfway in the still image mode, it is checked whether the focus is in focus or the exposure amount is appropriate. If the subject is in focus and has an appropriate exposure amount, a so-called AE lock or AF lock state is established, and the release button 8 is fully depressed.
[0045]
If the focus is not in focus, the focus lens 3c is moved to the focus position as described above. If the exposure amount is not appropriate, the shutter speed of the electronic shutter of the CCD image sensor 16 and the aperture After adjusting the aperture value of 3c to an appropriate exposure amount, the AE lock and AF lock states are established, and the release button 8 is fully depressed.
[0046]
The focus lens 3c is moved in response to the half-press of the release button 8, and the focus motor 24 and the aperture motor 26 are driven in the high-speed drive mode when changing the aperture value. Each of the apertures 3c can be driven instantaneously, and the time lag until a still image can be shortened in response to a full pressing operation of the next release button 8 can be shortened.
[0047]
When the release button 8 is further depressed to be fully depressed, one frame of image data captured immediately after this is compressed by the data processing circuit 30 and then sent to the media controller 37. Then, the image data for one frame obtained by photographing by the media controller 37 is written to the memory card 15. In this way, a still image is recorded on the memory card 15.
[0048]
On the other hand, when recording a moving image, the mode knob 13 is operated to select the moving image mode. When the moving image mode is selected, when the release button 8 is fully pressed, a moving image recording process for recording a moving image is started.
[0049]
As shown in FIG. 8, when the moving image recording process is started, first, the drive mode of each motor is set to the mute drive mode. After this, moving image and audio recording are started simultaneously. The CCD image sensor 16 shoots at 1/30 second intervals for recording a moving image, and image data of each frame obtained one after another is sent to the data processing circuit 30 and written in a buffer memory (not shown). In addition, the microphone 18 is activated to record audio, and the obtained audio data is written into the buffer memory of the data processing circuit 30.
[0050]
While moving images and audio are recorded as described above, zooming is allowed, and the focus state and exposure amount are detected. Therefore, when the zoom button 12 is operated, the zoom motor 25 is driven by the driver 43, and the photographing lens 3 is zoomed. If the focus is not achieved during shooting, the focus motor 24 is driven by the driver 43 under the control of the AF processing unit 32, and the focus lens 3a is moved to the focus position.
[0051]
Further, when the subject brightness changes, the electronic shutter of the CCD image sensor 16 is controlled by the control of the AE processing unit 31 so that the appropriate exposure is obtained, and the aperture motor 26 is driven by the driver 41 to reduce the aperture value. Is switched.
[0052]
During the shooting of this moving image, since the mute drive mode is set, the focusing motor 24 and the aperture motor 26 are both driven by the microstep drive system. The zoom motor 25 is driven at a low voltage. For this reason, each of these motors 24 to 26 is driven with a sufficiently low operating sound, and the sound is not collected by the microphone, and the sound during shooting of the moving image can be recorded in a good state.
[0053]
In general, the driving mode when driving the focus motor 24 is often intermittent, in which driving is started and stopped repeatedly in a short time. Among the operation sounds of the stepping motor, particularly loud noises include a collision sound when the motor starts and stops. This collision is caused by a collision between structures such as a lead screw, a nut, or a lens frame, and is caused by a mechanical gap (backlash). Therefore, a collision sound is generated when sudden acceleration / deceleration is performed at the start or stop of driving. However, in the microstep drive system, since smooth acceleration / deceleration can be performed, a silencing effect can be obtained during moving image shooting. Also, in the microstep drive system, camera shake is unlikely to occur because there is little vibration.
[0054]
When the release button 8 is pressed after shooting of the moving image starts, the shooting of the moving image and the recording of the sound are finished at that time. The obtained moving image data and audio data are compressed before being sent to the media controller 37 and written into the memory card 15. Thereafter, the processing returns to the standby state waiting for the operation of the release button 8, and the driving of the motors 24 to 26 is set to the high-speed driving mode.
[0055]
FIG. 9 shows an example in which the mute drive mode is set as the drive mode in the standby state waiting for the operation of the release button. In this example, the drive mode of each of the motors 24 to 26 in the standby state is set to the mute drive mode, and when the release button 8 is pressed halfway in the still image mode, the high speed drive mode is set. According to this, in the standby state, the motors 24 and 26 are driven by the micro-step drive method, which consumes less power than the two-phase excitation drive method, so that the capacity of the power supply battery can be saved. Note that the drive mode in the standby state of the zoom motor 26 may be a high-speed drive mode.
[0056]
FIG. 10 shows an example in which the presence / absence of sound recording can be selected in the moving image mode and the motor drive mode is switched according to the presence / absence of the sound recording. In this example, as shown in FIG. 10, a recording selection member 51 for selecting whether or not to record audio in the moving image mode is provided on the back side of the camera body 2.
[0057]
When the recording selection member 51 is set to the voice recording ON side, the recording mode is set, and voice recording is performed when a moving image is shot as in the first embodiment. When the recording selection member 51 is set to the OFF side, the non-recording mode is set, and only the moving image is taken without recording the sound. When the recording mode is set, as shown in FIG. 11, the motors 24 to 26 are driven in the mute driving mode during the shooting of the moving image. During shooting, the motors 24 to 26 are driven in a high-speed drive mode.
[0058]
FIG. 12 shows an example in which the motor drive mode can be manually selected in the moving image mode. In this example, a drive selection member 52 for selecting a drive mode of each of the motors 24 to 26 in the moving image mode is provided on the back side of the camera body 2. As shown in FIG. 13, when the drive selection member 52 is set to the silent side, the motors 24 to 26 are driven in the mute drive mode during moving image shooting as in the first embodiment. When the drive selection member 52 is set to the speed side, the motors 24 to 26 are driven in the high-speed drive mode during moving image shooting, and shooting with priority on zooming, focusing, and exposure control speed. Is possible.
[0059]
【The invention's effect】
As described above, according to the present invention, the stepping motor for focusing is micro-step driven when shooting a moving image and recording sound, and the stepping motor is driven by two-phase excitation when shooting a still image. As a result, when recording a sound, the stepping motor can be recorded with good operation sound, and at the same time as shooting a still image, high-speed focusing is possible, making it difficult to miss the shooting timing.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the front of a digital camera embodying the present invention.
FIG. 2 is a perspective view showing a back surface of the digital camera.
FIG. 3 is a block diagram illustrating a configuration of a digital camera.
FIG. 4 is a graph showing a waveform of a driving voltage in a two-phase excitation driving method.
FIG. 5 is a graph showing a waveform of a driving voltage of a microstep driving method.
FIG. 6 is a graph showing a relationship between a waveform of a pulse-width-modulated drive voltage and a substantially obtained drive voltage during microstep drive.
FIG. 7 is a flowchart illustrating an outline of a processing procedure under a shooting mode.
FIG. 8 is a flowchart showing an outline of a processing procedure in a moving image mode.
FIG. 9 shows an example in which a motor is driven in a mute drive mode in a standby state.
FIG. 10 shows an example of switching the motor drive mode in accordance with the presence or absence of audio recording.
11 is a flowchart showing an outline of a processing procedure in a moving image mode in the example of FIG.
FIG. 12 shows an example in which the motor drive mode can be manually selected in the moving image mode.
13 is a flowchart showing an outline of a processing procedure in a moving image mode in the example of FIG.
[Explanation of symbols]
3 Shooting lens
12 Zoom button
13 Mode knob
20 System controller
24-26 motor
41-43 drivers
31 AE processing unit
51 Recording selection member
52 Drive selection member

Claims (3)

In a digital camera that can select a still image mode for recording a still image and a moving image mode for recording a moving image together with sound, and that uses a stepping motor to focus the taking lens,
A digital camera comprising driving means for driving the stepping motor by a two-phase excitation drive method when photographing in a still image mode and driving the stepping motor by a microstep driving method when photographing in a moving image mode. In a digital camera in which a still image mode for recording a still image and a moving image mode for recording a movie can be selected and the photographing lens is focused using a stepping motor.
A recording selection member that selects whether or not to record audio under the moving image mode, and when shooting in the still image mode, the stepping motor is driven by the two-phase excitation drive method, and when recording audio during shooting in the moving image mode. A digital camera comprising driving means for driving the stepping motor by a micro-step driving system and driving the stepping motor by a two-phase excitation driving system when no sound is recorded. A digital camera that can select a still image mode for recording still images and a moving image mode for recording moving images, and can record audio when the moving image mode is selected, and uses a stepping motor to focus the photographic lens. In
A drive selection member for selecting the driving method of the stepping motor from either a two-phase excitation driving method or a micro-step driving method, and the stepping motor is driven by a two-phase excitation driving method when shooting in still image mode. When the two-phase excitation drive method is selected by the drive method selection member in the shooting under the moving image mode, the stepping motor is driven by the two-phase excitation drive method and the microstep drive method is selected. The digital camera further comprises driving means for driving the stepping motor by a microstep driving method.

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