JP2004070099A - Focus detecting device and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold a sufficient focus detecting function even if scenery including a high-intensity matter appears as a background. <P>SOLUTION: A focus detecting device has two or more focus detecting areas, and performs a focus detecting operation according to an output from a signal storing sensor acquired in the two or more focus detecting areas. Further, the device comprises a storing time restriction means for restricting storing time to the two or more focus detecting areas, and a night scenery imaging determination means (#103, #104, #105) for determining whether or not the scenery is night scenery. The restriction means varies ways of restrictions on the storing time according to the determination whether or not the scenery is the night scenery by the determination means (#104, #107). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a focus detection device and an improvement of a camera including the focus detection device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a camera focus detection device, a light flux from a subject passing through different exit pupil regions of a photographing lens is combined on a pair of line sensors, and a relative image signal of a pair of image signals obtained by photoelectrically converting the subject image is obtained. There is widely known an automatic focus adjustment method in which a defocus amount of a subject is detected by calculating an image shift amount, which is a positional displacement amount, by a correlation operation, and a photographing lens is driven based on the defocus amount. Further, in a camera having a plurality of focus detection areas, it is common to automatically select a focus detection area estimated to include a subject from the focus detection results in each area and detect the defocus amount. is there.
[0003]
In this case, if the reliability of focus detection is low due to low luminance or low contrast in the focus detection area in the center of the shooting screen, or if it is determined that focus detection is impossible, On the other hand, the focus detection is performed again after the auxiliary lighting is performed.
[0004]
The focus detection time is determined by the charge accumulation speed of the photoelectric conversion element formed in each focus detection area. Therefore, in this method, if the longest accumulation time is set in advance, if the time is too short, sufficient charge accumulation cannot be performed when the focus detection area including the main subject has low luminance or low contrast, It is determined that the focus cannot be detected. Conversely, if the length is too long, even if the main subject has sufficiently high brightness, if the focus detection area that is not the main subject has low brightness or low contrast, it takes time until the charge accumulation in the all focus detection areas is completed. And the responsiveness of focus detection is reduced. Therefore, in a camera having a plurality of focus detection areas and automatically selecting a main subject, the charge accumulation time of the focus detection area in which focus detection is first completed is performed within a range not exceeding a preset time. In general, the longest accumulation time for the entire focus detection area is limited so that the focus detection time does not needlessly be taken.
[0005]
For example, assuming that the preset longest accumulation time that should not be exceeded is 300 ms, and that the maximum accumulation time is up to five times the charge accumulation time of the focus detection area in which focus detection is completed first, the first focus detection area When the charge accumulation time is completed in 10 ms, the longest accumulation time is limited to 50 ms. When the charge accumulation time of the first focus detection area is completed in 60 ms to 300 ms, the longest accumulation time is 300 ms. .
[0006]
[Problems to be solved by the invention]
However, the above-described conventional focus detection device has a problem in the following night view shooting.
[0007]
When shooting a low-brightness subject such as a person against the scenery including a high-brightness point light source as shown in FIG. 5, the charge accumulation speed of the focus detection area in the center of the shooting screen including the subject includes the high-brightness point light source. It is slower than the focus detection area on the left of the shooting screen. Therefore, if the longest accumulation time for the entire focus detection area is limited based on the charge accumulation time of the focus detection area for which accumulation has been completed earlier, the focus detection area including the main subject is sufficient even if auxiliary lighting is performed. And the focus cannot be detected due to low brightness and low contrast.
[0008]
In order to solve this problem, in the apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-137161, when focus detection is performed without auxiliary illumination, the charge accumulation time of the focus detection area in which focus detection is completed first is based on the charge accumulation time. , The longest accumulation time is limited for the all-focus detection area. As a result of focus detection, if the reliability of focus detection is low due to low brightness or low contrast in the focus detection area that is likely to include the subject, or if it is determined that focus detection is impossible, auxiliary lighting is applied to the subject. After that, focus detection is performed again. For this focus detection, the longest accumulation time is determined regardless of the charge accumulation time of the focus detection area in which accumulation is completed first.
[0009]
In this method, if the subject exists in the focus detection area that is likely to include the subject, the focus can be reliably detected even if the background includes the scenery including the high brightness point light source. However, in this example, the focus detection area having a high possibility of including the subject is set at the center of the shooting screen. However, if the focus detection area is located in another focus detection area, for example, the subject is present on the right of the shooting screen, focus detection is not reliable. . However, if the focus detection area that is likely to include the subject is expanded and the subject may also be included on the right of the shooting screen, there is a possibility that auxiliary lighting will be performed even when it is not necessary to perform auxiliary lighting. Get higher. It is desirable not to use the auxiliary lighting as much as possible when it is not necessary, in terms of power consumption and not to cause discomfort when the subject is a person.
[0010]
Further, in a method of performing focus detection once without auxiliary illumination and performing focus detection again after performing auxiliary illumination based on the result, the responsiveness of focus detection is inevitably reduced.
[0011]
(Object of the invention)
A first object of the present invention is to provide a focus detection device capable of maintaining sufficient focus detection performance even in the background of a scene including a high-luminance object.
[0012]
A second object of the present invention is to provide a focus detection device capable of maintaining sufficient response performance even if focus detection is performed by performing auxiliary illumination.
[0013]
A third object of the present invention is to maintain sufficient focus detection performance even when a scene including a high-luminance object is set as a background, and to achieve a sufficient response performance even if focus detection is performed by performing auxiliary illumination. It is intended to provide a camera capable of holding the camera.
[0014]
[Means for Solving the Problems]
In order to achieve the first object, the invention according to claim 1 has a plurality of focus detection areas, and performs a focus detection operation based on a signal accumulation type sensor output obtained in the plurality of focus detection areas. A focus detection device for performing the storage, the storage time limiting means for limiting the storage time for the plurality of focus detection areas, and a night scene shooting determination means for determining whether or not the night view shooting, the storage time limiting means, The focus detection device is configured to limit the accumulation time differently depending on whether or not the night scene shooting is determined by the shooting determination unit.
[0015]
In the above-described configuration, focusing on the method of limiting the accumulation time of focus detection suitable for each of the normal shooting and the night view shooting, when the night view shooting is determined, the method of limiting the normal shooting and the accumulation time is set. I try to change it. Specifically, in normal shooting, the longest accumulation time is limited based on the sensor accumulation time of a point where the accumulation operation is completed in a plurality of focus detection areas within a range not exceeding a preset time, and This prevents the response time of focus detection from deteriorating due to an increase in accumulation time. In night scene shooting, the longest accumulation time is limited by a preset time regardless of the sensor accumulation time at the point where the accumulation operation is completed, so that sufficient charge accumulation can be performed even for a low-luminance subject such as a person. .
[0016]
In order to achieve the second object, the invention according to claim 3 has a plurality of focus detection areas, and focus detection is performed based on a signal accumulation type sensor output obtained in the plurality of focus detection areas. In a focus detection device that performs an operation, an auxiliary illumination unit that illuminates a focus detection range corresponding to a part or all of the plurality of focus detection regions, and whether or not the auxiliary illumination is required. Auxiliary lighting determining means for making a determination; and night view shooting determining means for determining whether or not night view shooting is performed, wherein the auxiliary lighting determining means determines whether the night view shooting determining means determines that night view shooting is performed. In this case, the focus detection device makes a different way of determining whether or not the auxiliary illumination is required.
[0017]
The above configuration focuses on the fact that there is a method of determining whether or not auxiliary lighting suitable for each of normal shooting and night view shooting is required. Change the method of determining whether lighting is required. Specifically, in the normal photographing, it is determined whether or not the auxiliary illumination is necessary based on the result of the focus detection performed without the auxiliary illumination, and the auxiliary illumination is not performed unnecessarily. In night view shooting, since it is determined that auxiliary lighting is necessary without performing focus detection without auxiliary lighting, the response of focus detection is not reduced, and even in a focus detection area that is less likely to include a subject. Even if a subject is present, focus detection can be reliably performed.
[0018]
Further, in order to achieve the third object, the invention according to claim 5 provides a focus detection device according to any one of claims 1 to 4 and a plurality of shooting modes including a night view shooting mode. 2. A camera comprising: a photographing mode setting unit for setting a photographing mode, wherein the night scene photographing judging unit judges that the night scene photographing is performed when the photographing mode setting unit is set to the night scene photographing mode. 4. The camera according to any one of 4.
[0019]
Similarly, in order to achieve the third object, an invention according to claim 6 has a focus detection device according to any one of claims 1 to 4, and a plurality of photometric areas, and the plurality of photometric areas. 5. The camera according to claim 1, further comprising: a calculating unit configured to calculate a photometric value obtained by using the night view photographing determining unit based on the plurality of photometric values. A camera.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments.
[0021]
FIG. 1 is a block diagram showing a circuit configuration of an interchangeable lens type single-lens reflex camera which is an example of an optical apparatus according to an embodiment of the present invention.
[0022]
In FIG. 1, reference numeral 1 denotes a lens MPU (micro processing unit) for performing all calculations and controls related to a photographing lens, 2 denotes a lens drive unit for driving a photographing lens, and 3 denotes an aperture drive unit for driving an aperture. is there. A photographing lens is constituted by the lens MPU 1 to the aperture drive unit 3.
[0023]
The taking lens is connected to the camera body via a mount indicated by a dotted line in the center of FIG. Reference numeral 4 denotes a camera MPU (micro processing unit) that performs all calculations and controls related to the camera body, is connected to the lens MPU 1 via a signal line of the mount, and drives the lens MPU 1 with a lens drive, an aperture drive, and an interchangeable lens. For example, it is possible to obtain optical information peculiar to.
[0024]
5 is a photometry unit, 6 is a defocus amount detection unit, 7 is a shutter drive unit, 8 is a film feed unit, and 9 is a dial for performing various settings (shutter speed, aperture value, shooting mode, etc.) of the camera. A unit 10 is an auxiliary lighting unit. SW1 is a switch that is turned on by the first stroke operation (half press) of the release button, and SW2 is a switch that is turned on by the second stroke operation (full press) of the release button.
[0025]
By operating the dial unit 9, various shooting modes such as a night view shooting mode, a sports mode, a portrait mode, and the like can be set. In the present embodiment, automatic focus adjustment is performed in any mode. The control of the automatic focus adjustment will be described with reference to the flowchart of FIG.
[0026]
First, in step # 101, when the switch SW1 is turned on, the process proceeds to automatic exposure in step # 102. Specifically, a part of the light beam reflected by the main mirror and passed through the focus plate is guided to the photometric unit 5 by a photometric optical system (not shown). As shown in FIG. 6, the photometric unit 5 has a photoelectric conversion element obtained by dividing a photographing screen into equal parts, and the camera MPU 4 reads out the luminance of each area as a photometric value, and comprehensively determines each photometric value for photographing. Determine the exposure. Since the automatic exposure is already widely known, and the control of the automatic exposure is not related to the present invention, further detailed description will be omitted.
[0027]
In the next step # 103, it is determined whether or not the photometric value of each photometric area measured in step # 102 is equal to or greater than EV12 in terms of film sensitivity ISO100. Then, the process proceeds to the normal focus detection in step # 104. On the other hand, if at least one of the areas is smaller than EV12, the process proceeds to step # 105, and it is determined whether the shooting mode set by the dial unit 9 is set to the night view shooting mode. In the case of the night scene photographing mode, the process proceeds to the focus detection of the night scene in step # 107, and in the case of other photographing modes, the process proceeds to step # 106.
[0028]
In step # 106, it is determined whether the maximum and minimum photometric difference (EV6 in the photographing example of FIG. 6) in the entire photometric area measured in step # 102 is equal to or greater than EV5. Then, it is determined that there is a possibility of night view photographing including a high-luminance point light source, and the process proceeds to night view focus detection in step # 107. Conversely, if it is less than EV5, the process proceeds to the normal focus detection in step # 104. That is, in the photographing example of FIG. 6, since the photometry area is less than EV12 in all photometry areas and the photometry difference in all photometry areas is EV5 or more, the process proceeds to the focus detection of the night view in step # 107 in any photography mode. become.
[0029]
Next, normal focus detection in step # 104 will be described with reference to the flowchart in FIG.
[0030]
The defocus amount (difference between the image forming position of the photographing lens and the image plane position of the photographing lens to be subjected to the photographing operation) required for the automatic focusing is formed from the subject light flux passing through different exit pupil regions of the photographing lens. It is calculated from the image shift amounts of the two images. There are a plurality of light beams of these two images, which pass through a main mirror which is a half mirror, are reflected by a sub-mirror located behind, and are guided to a defocus amount detection unit 6 by a focus detection optical system (not shown). As shown in FIG. 5, the defocus amount detection unit 6 is divided into eight focus detection areas each having a photoelectric conversion element, and the camera MPU 4 reads out the signals of these two images, performs various calculations, and performs decompression. Get the focus amount.
[0031]
Specifically, first, the process proceeds from step # 201 to step # 202, and the longest accumulation time of the photoelectric conversion element is set to a predetermined 300 ms. Then, in the next step # 203, accumulation of the photoelectric conversion elements is started. Subsequently, in step # 204, it is determined whether the longest accumulation time has elapsed, and if not, the process proceeds to step # 205, and it is determined whether any of the eight focus detection areas has completed accumulation. If the accumulation has not been completed in any of the focus detection areas, the process returns to step # 204, and the processing from step # 204 to step # 205 is repeated until the longest accumulation time has elapsed or until the accumulation is completed.
[0032]
If the accumulation has been completed in step # 205, the process proceeds to step # 206, where the image signal is read out, and in the next step # 207, it is determined whether or not the accumulation of all eight focus detection areas in this reading has been completed. If the last accumulation has not been completed, the process proceeds to step # 208, and it is determined whether the first accumulation has been completed. If the first accumulation is not completed, the process directly returns to step # 204. If the first accumulation is completed, the process proceeds to step # 209, where the longest accumulation time is reset, and the process returns to step # 204. Specifically, within a range not exceeding 300 ms, five times the accumulation time of the focus detection area in which focus detection is completed first is set as a new longest accumulation time.
[0033]
If it is determined in step # 204 that the longest accumulation time has elapsed, the process proceeds to step # 210, in which accumulation is forcibly terminated and image signals of all focus detection areas for which focus detection has not been completed are read. Before proceeding to step # 211. Similarly, when it is determined in step # 207 that the last accumulation is completed, the process proceeds to step # 211.
[0034]
In step # 211, a defocus amount in each focus detection area is obtained by calculating an image shift amount by a correlation operation. Since the amount of defocus in each focus detection area is naturally different, the amount of defocus for finally driving the photographing lens is determined from the plurality of obtained defocus amounts. Since various proposals have been made for this method and are not related to the present invention, further detailed description will be omitted.
[0035]
When the defocus amount is obtained in step # 211, the process proceeds to step # 212, and it is determined whether or not the auxiliary illumination in the current focus detection is projected. If it is determined that the auxiliary lighting is being performed, the process proceeds to step # 215, the auxiliary lighting is stopped, and the process returns to step # 216. On the other hand, when it is determined that the auxiliary lighting is not performed, the process proceeds to step # 213, and it is determined whether the auxiliary lighting is performed.
[0036]
Specifically, when the photometry value of each photometry area measured in step # 102 of FIG. 2 is less than EV12, and the reliability of focus detection is low due to low brightness and low contrast in the focus detection area at the center of the shooting screen, If it is determined that the focus cannot be detected, the process proceeds to step # 214 assuming that the auxiliary illumination is necessary, the auxiliary illumination is started, and the focus detection process from step # 202 and on is performed again. This is because, in the case of EV12 or more, if the inside of the shooting screen is sufficiently bright, there is no effect with the limited amount of auxiliary illumination, and the possibility that the subject is not included in an area other than the focus detection area at the center of the shooting screen is low. If the reliability of focus detection is low in these areas, or if focus detection cannot be performed, responsiveness deteriorates if auxiliary illumination is projected and focus detection is performed again. When it is determined that the projection of the auxiliary lighting is not necessary, the process proceeds to step # 216, and returns to the flow of FIG.
[0037]
Next, the night view focus detection in step # 107 will be described with reference to the flowchart in FIG.
[0038]
Almost the same processing as that of normal focus detection is performed. However, when it is determined that focus detection of a night view is to be performed based on the determination of the night view shooting mode in step # 105 and the determination result of the photometric difference in step # 106. The difference is that the auxiliary illumination is determined to be performed and the focus is detected by performing the auxiliary illumination from the beginning, and that the longest accumulation time is not reset.
[0039]
First, the process proceeds from step # 301 to step # 302 to start auxiliary lighting. Then, the process proceeds to a step # 303, where the longest accumulation time is set to 300 ms. In the next step # 304, the accumulation of the photoelectric conversion elements is started. In the following step # 305, it is determined whether or not the maximum accumulation time has elapsed. It is determined whether any of them has completed the accumulation. If the accumulation has not been completed for any of the focus detection areas, the process returns to step # 305, and the processing from step # 305 to step # 306 is repeated until the longest accumulation time has elapsed or until the accumulation is completed.
[0040]
If the accumulation has been completed in step # 306, the flow advances to step # 307 to read out the image signal. In the next step # 308, it is determined whether or not the accumulation of all eight focus detection areas has been completed by this readout. If not, the process returns to step # 305.
[0041]
If it is determined in step # 305 that the longest accumulation time has elapsed, the process proceeds to step # 309, in which accumulation is forcibly terminated and image signals of all focus detection areas for which focus detection has not been completed are read out. To step # 310. Similarly, when it is determined in step # 308 that the last accumulation is completed, the process proceeds to step # 310.
[0042]
In step # 310, a defocus amount is obtained by calculating an image shift amount by a correlation operation. When the defocus amount is obtained, the process proceeds to step # 311, the auxiliary lighting is stopped, and the process returns to step # 312.
[0043]
Returning to FIG. 2, if the defocus amount necessary for the automatic focus adjustment is obtained through one of the normal focus detection in step # 104 and the focus detection of the night scene in step # 107, the process proceeds to step # 108. Here, the photographing lens is driven, and the automatic focus adjustment ends in the next step # 109.
[0044]
The auxiliary illumination in the present invention can be applied to visible light from a miniature bulb, infrared light from an IRED, or flash light for intermittently emitting strobe light, regardless of the type and method of a light source. .
[0045]
According to the above-described embodiment, focusing on the method of limiting the accumulation time of focus detection suitable for each of the normal shooting and the night view shooting, if the night view shooting is determined, the normal shooting and the limitation of the accumulation time are limited. Has changed the way. Specifically, in the normal photographing, the longest accumulation time is limited based on the sensor accumulation time of a portion where the accumulation operation is completed in a plurality of focus detection areas within a range not exceeding a preset time (# 209). However, the accumulation time is not increased unnecessarily, so that the responsiveness of focus detection is not reduced. On the other hand, in night scene shooting, the longest accumulation time is limited by a preset time (in this example, 300 mS) regardless of the sensor accumulation time at the point where the accumulation operation has been completed, so that even a low-luminance subject such as a person is sufficient. Charge accumulation.
[0046]
Therefore, sufficient focus detection performance can be maintained even when a scene including a high-luminance point light source (high-luminance object) is set as a background.
[0047]
Also, focusing on the fact that there is a method of determining whether or not auxiliary lighting suitable for each of normal shooting and night view shooting is required, and when night view shooting is determined, normal shooting and auxiliary lighting are determined. I'm changing the way. Specifically, in the normal photographing, the auxiliary illumination is determined (# 213) based on the focus detection result performed without the auxiliary illumination, and the auxiliary illumination is not performed unnecessarily. In night view shooting, since the auxiliary illumination determination is performed without performing the focus detection without the auxiliary illumination, the subject is present in the focus detection area that does not decrease the responsiveness of the focus detection and is unlikely to include the subject. As a result, focus detection can be reliably performed.
[0048]
That is, even if the auxiliary illumination is performed and the focus is detected, sufficient response performance can be maintained.
[0049]
(Modification)
Although the present embodiment has been described with respect to a single-lens reflex camera, the present invention is also applicable to cameras such as video cameras and electronic still cameras and other optical devices.
[0050]
(Correspondence between invention and embodiment)
In the above embodiment, the camera MPU4 corresponds to the storage time limiting means of the present invention, the camera MPU4, the dial unit 9, or the camera MPU4 and the photometry unit 5 correspond to the night view photographing determining means of the present invention. It corresponds to the auxiliary lighting determination means of the invention.
[0051]
【The invention's effect】
As described above, according to the first aspect of the present invention, it is possible to provide a focus detection device capable of maintaining sufficient focus detection performance even when a scene including a high-luminance object is set as a background.
[0052]
Further, according to the third aspect of the present invention, it is possible to provide a focus detection device capable of maintaining sufficient response performance even if focus detection is performed by performing auxiliary illumination.
[0053]
According to the invention of claim 5 or 6, sufficient focus detection performance can be maintained even when a scene including a high-luminance object is set as a background, and focus detection is performed by performing auxiliary illumination. Thus, it is possible to provide a camera capable of maintaining sufficient response performance.
[Brief description of the drawings]
FIG. 1 is a block diagram of a camera according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation of automatic focus adjustment according to an embodiment of the present invention.
FIG. 3 is a flowchart showing a normal focus detection operation according to an embodiment of the present invention.
FIG. 4 is a flowchart illustrating an operation of focus detection of a night view according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating an example of shooting a person at night with a scene including a high brightness point light source as a background.
FIG. 6 is a diagram illustrating photometric values in night portrait photography of a person against a scene including a high brightness point light source.
[Explanation of symbols]
1 Lens MPU
2 Lens drive unit 3 Aperture drive unit 4 Camera MPU
Reference Signs List 5 Photometry unit 6 Defocus amount detection unit 7 Shutter drive unit 8 Film feed unit 9 Dial unit 10 Auxiliary lighting unit

Claims (6)

In a focus detection device having a plurality of focus detection areas and performing a focus detection operation based on a signal accumulation type sensor output obtained in the plurality of focus detection areas, an accumulation time for limiting an accumulation time for the plurality of focus detection areas Limiting means, having a night view shooting determination means to determine whether the night view shooting,
The focus detection device according to claim 1, wherein the accumulation time limiter changes the method of limiting the accumulation time depending on whether the night view shooting determination section determines that the night view shooting is performed or not. When it is determined that the image is not a night view shooting, the accumulation time limiting unit determines the accumulation time based on the sensor accumulation time at a point where the accumulation operation is completed in a plurality of focus detection areas within a range not exceeding a preset time. The longest accumulation time is limited, and when it is determined that the shooting is a night view, the longest accumulation time is limited by a preset time regardless of the sensor accumulation time of the location where the accumulation operation is completed. The focus detection device according to claim 1. In a focus detection device having a plurality of focus detection areas and performing a focus detection operation based on a signal accumulation type sensor output obtained in the plurality of focus detection areas, a part or all of the plurality of focus detection areas is provided. Auxiliary illumination means for illuminating a focus detection range corresponding to a focus detection area, auxiliary illumination determination means for determining whether or not the auxiliary illumination is required, and night scene shooting determination means for determining whether or not night view shooting is performed. Has,
The auxiliary lighting determining means makes a difference in a method of determining whether or not the auxiliary lighting is required depending on whether the night view shooting determining means determines that the night view shooting is performed or not. Focus detection device. When it is determined that the night scene shooting is not performed, the auxiliary lighting determination unit determines whether or not the auxiliary lighting is necessary based on the focus detection result performed without the auxiliary lighting, and determines that the night scene shooting is performed. 4. The focus detection device according to claim 3, wherein when it is determined that the auxiliary illumination is necessary without performing the focus detection without the auxiliary illumination. A camera comprising: the focus detection device according to claim 1; and a shooting mode setting unit configured to set an arbitrary shooting mode from a plurality of shooting modes including a night view shooting mode.
The camera according to any one of claims 1 to 4, wherein the night scene photographing determining unit determines that the night scene photographing is performed when the photographing mode setting unit is set to the night scene photographing mode. A camera comprising: the focus detection device according to claim 1; and a calculation unit having a plurality of photometry areas and calculating a photometry value obtained in the plurality of photometry areas.
The camera according to any one of claims 1 to 4, wherein the night scene shooting determination unit determines whether or not a night scene shooting is performed based on the plurality of photometric values.

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