JP7109297B2 - Color mode switching system - Google Patents

Description

The present invention relates to a color mode switching system using a field sequential color imaging device . More specifically, the present invention relates to a color mode switching system using a field sequential color imaging device . The present invention relates to a color mode switching system for achieving desired image quality.

In general, as a method for color imaging in an imaging device (a method based on the number of imaging elements), it is advantageous for high resolution and high sensitivity, but the optical system becomes large, and the entire camera system becomes large. A single plate type is known which is advantageous for compactness, but is disadvantageous in terms of resolution because it uses a pixel interpolation technique.
In recent years, due to the strong demand for miniaturization of the apparatus, attempts have been made to improve the resolution of the single-panel type.

A frame sequential method is known as a method of obtaining a color image without suffering a reduction in resolution due to pixel interpolation in the single-plate method (see Patent Document 1 below).
The frame sequential method is an imaging method that obtains a color image by switching the color light incident on the image pickup device for each field (color field) corresponding to each of the three primary colors, and sequentially outputting images based on RGB signals in a time division manner ( In this case, it is also called a color sequential method). For example, when trying to obtain a 60Hz color image, the image pickup device is driven at 180Hz, which is three times the frequency (switching the color fields), and the color lights R, G, and B irradiated to the image pickup device for each color field are changed. switch.

An R signal, a G signal, and a B signal are sequentially switched at 180 Hz and output from the imaging device, and a color image can be obtained by generating 60 Hz RGB signals from these signals. Unlike the color separation method (three-plate method) using on-chip color filters, the frame sequential method does not require pixel interpolation processing, so the resolution of each color signal is maintained. In order to switch the color light, generally, a rotary disc filter method (Fig. 5) is used, in which a rotary color filter is provided on the imaging lens side of the image sensor to switch RGB light, or RGB light is sequentially irradiated to the subject as illumination light. A light source switching method (FIG. 6) for imaging is used (see Patent Documents 2 to 4 below).

Japanese Unexamined Patent Application Publication No. 2007-215088 JP-A-6-121323 JP-A-2003-333608 JP-A-2006-135805

However, since the rotating disk filter method described above requires a movable part such as a rotating mechanism to be provided in the imaging apparatus, there are problems such as vibration, noise, and power consumption when dealing with a high frame rate. Further, the arrangement area of the color filters in the rotary filter, the order of color switching, etc. cannot be realized unless the physical configuration is changed by, for example, replacing the adaptive rotary filter. On the other hand, the above light source switching method requires the use of RGB switching light sources to illuminate the object, so it is difficult to perform desired photography outdoors or under conditions where illumination light is limited.

The present invention has been devised in view of the above circumstances. It is possible to take an image regardless of whether it is indoors or outdoors. In addition to the purpose of the field sequential color imaging device, it is an object of the present invention to provide a color mode switching system capable of obtaining RGB signals that can easily achieve noise reduction and sensitivity improvement for an image of a predetermined color. It is.

A first color mode switching system of the present invention comprises:
an imaging lens;
a color variable filter that sequentially time-divides subject light incident from the imaging lens into three primary color light components and outputs them;
an imaging device that sequentially receives color light components of the three primary colors time-divided by the color variable filter, converts the color light components into color signals corresponding to the color light components, and outputs the color light components according to switching of the color light components; ,
a color signal conversion unit that converts the color signal output from the imaging element into an RGB signal;
an RGB signal output unit for outputting the RGB signal output from the color signal conversion unit to the outside,
In the color variable filter, a plurality of piezoelectric dielectric layers having different refractive indices are laminated in order, and the sequential layers are sandwiched between a pair of electrode layers, at least one of which is transparent. Equipped with a frame sequential color imaging device configured to apply a voltage of
The color signal conversion unit is incorporated, performs frame interpolation processing based on the input control mode identification signal, converts the color signal from the image sensor into a predetermined RGB signal, and converts the converted RGB signal into the RGB signal. a frame interpolation processing unit that outputs to the signal output unit;
The RGB signal is input from the frame interpolation processing unit to the RGB signal output unit, and a control mode that enables desired color correction for the input RGB signal is determined based on a preset determination condition. a control mode in which the determination result is fed back to the input section of the frame interpolation processing section as the control mode identification signal, and the control mode identification signal is also output to the color variable filter driving section that drives the color variable filter; It is characterized by comprising a determination unit.

A second color mode switching system of the present invention comprises:
an imaging lens;
a color variable filter that sequentially time-divides subject light incident from the imaging lens into three primary color light components and outputs them;
an imaging device that sequentially receives color light components of the three primary colors time-divided by the color variable filter, converts the color light components into color signals corresponding to the color light components, and outputs the color light components according to switching of the color light components; ,
a color signal conversion unit that converts the color signal output from the imaging element into an RGB signal;
an RGB signal output unit for outputting the RGB signal output from the color signal conversion unit to the outside,
In the color variable filter, a plurality of piezoelectric dielectric layers having different refractive indices are laminated in order, and the sequential layers are sandwiched between a pair of electrode layers, at least one of which is transparent. Equipped with a frame sequential color imaging device configured to apply a voltage of
The color signal conversion unit is incorporated, performs frame interpolation processing based on the input control mode identification signal, converts the color signal from the image sensor into a predetermined RGB signal, and converts the converted RGB signal into the RGB signal. a frame interpolation processing unit that outputs to the signal output unit;
Based on a control mode setting signal input from the outside, a control mode that enables desired color correction for the RGB signals is determined, and a control mode identification signal that identifies the determined control mode is transmitted to the frame interpolation process. and a control mode determination section that feeds back the control mode identification signal to an input section of the control section and also outputs the control mode identification signal to a color variable filter driving section that drives the color variable filter.
One of the control modes may be a pattern set to output each light of W, R, G, and B once in each frame.

One of the control modes is to output W light twice and the first light of R, G, and B twice in one frame, and one after the one frame. so that the light of W is output twice and the second light of R, G, and B different from the first light of R, G, and B is output twice within the frame of light of W twice and a third light of R, G, and B that is different from the first light and the second light of R, G, and B are output twice within a frame of W light is output three times and the first light out of R, G, and B is output once within the frame, and W light is output in one frame after the one frame. three times, and the second light of R, G, and B is output once, and within two frames after the one frame, the light of W is output three times, and R, A pattern may be set such that the third light of G and B is output once, and these three frames are sequentially repeated.

One of the control modes is a pattern in which a predetermined one light of R, G, and B is output twice and the remaining two lights are output once each in each frame, or Within a frame of , a predetermined one of R, G, and B light is output three times, and one of the remaining two lights is output once, and within a frame after the one frame , R, G, and B are output three times, the other of the remaining two lights is output once, and these two frames are sequentially repeated. can be

According to the color mode switching system of the present invention, since the frame sequential color imaging device having the above configuration is provided, the RGB color lights from the subject incident on the imaging device are sequentially switched using the piezoelectric laminated interference filter. Color imaging is possible regardless of whether it is indoors or outdoors, and there is no need to use a movable mechanism such as a color rotation filter, which reduces vibration, noise, and power consumption associated therewith. It becomes possible to

Furthermore , according to the color mode switching system of the present invention , the following effects can be obtained. That is, the control mode is determined based on a predetermined criterion so as to obtain an RGB signal capable of achieving a desired image quality for a predetermined color. Since the signals are sent to the driving section of the filter, it is possible to easily obtain the RGB signals that can achieve the desired image quality.

1 is a block diagram showing an imaging device according to an embodiment of the present invention; FIG. 2 is a schematic diagram for explaining a conceptual configuration of a color variable filter used in the imaging device shown in FIG. 1; FIG. 5 is a graph showing spectral transmission characteristics of the color variable filter according to the embodiment; 2 is a schematic diagram showing an example of control modes ((1) to (8)) of a color variable filter used in the imaging device shown in FIG. 1; FIG. FIG. 10 is a conceptual diagram showing a conventional field-sequential-rotating-disk-filter imaging apparatus; FIG. 10 is a conceptual diagram showing a conventional imaging device of the frame sequential-light source switching system.

A color mode switching system according to an embodiment of the present invention will be described below with reference to the drawings.
First, a frame sequential color imaging apparatus according to the color mode switching system of this embodiment will be described with reference to FIGS.

The frame sequential color imaging apparatus 10 includes an imaging lens 21, a color variable filter 22, an imaging element 23, a color variable filter driving section 26, an imaging element driving section 27, a color signal conversion section (a frame interpolation processing section in this embodiment). 24A) and a color signal output section .

Here, the color variable filter 22 is configured such that spectral characteristics corresponding to each color light of R, G, and B can be switched by, for example, switching the voltage applied to the piezoelectric film laminated structure. Also, W is formed by adding all the color lights of R, G, and B.

That is, for example, as shown in FIG. 2, the color tunable filter 22 is a reflection type color tunable filter, but the principle is the same even if it is a transmission type color tunable filter. The variable element 220 is sandwiched between a pair of transparent electrode layers 222A and 222B. A predetermined voltage is applied.

All of the color light variable elements 220 are piezoelectric elements, and the compositions of PLZT layers (lead lanthanum zirconate titanate ((Pb _1-y La _y ) (Zr _1-x Ti _x )O ₃ ) having different refractive indices) are A first layer made of transparent ceramics, etc.) 221A and a second layer made of a ZnO layer 221B are alternately laminated in several tens of layers, and the thickness of these two layers 221A and B is substantially the same. The thickness of the colored light variable element 220 is, for example, several μm.

The thicknesses of the two layers 221A and 221B change according to the voltage applied from the voltage variable section 223. FIG. Since the device shown in FIG. 2 is of a reflective type, a voltage is applied that can displace the thickness (optical distance) of each of the layers 221A and 221B to a value corresponding to 1/4 wavelength of the specific color of the incident light. Then, since the specific color light satisfies the condition of enhancing each other due to the interference effect, the specific color light is emphasized and output (reflected). See the publication, however, it is important to replace the distance (thickness) of each layer with the optical distance (optical path length)).
As described above, if the light absorptance in the color variable element 220 is very small, the light transmittance of the color variable filter 22 approximately corresponds to 1 minus the light reflectance. When the reflectance is minimized (weaken each other), that is, when the thicknesses (optical distances) of the layers 221A and 221B are displaced to a value corresponding to 1/2 wavelength of the specific color light of the incident light. , the transmittance of the specific color light is maximized.
In the transmissive color tunable filter 22 used in the following embodiments, a voltage is applied between the two electrode layers 222A and 222B so as to satisfy these conditions, and the voltage is switched to output each color light. (Transparent).

In this way, the incident light carrying subject information that is incident via the imaging lens 21 can be made to output each color light component of RGB according to the voltage.
In the frame sequential system, if a color image is to be produced with a frame rate of 60, for example, it is necessary to sequentially switch the output of each color component of RGB at a speed of 1/180 (second). In the color variable filter 22, the applied voltage from the voltage variable section 223 is switched at a speed of 1/180 (second), for example.

In this embodiment, the color variable filter is of a transmissive type, and FIG. 3 shows the spectral transmission characteristics of the color variable filter 22 configured as a transmissive type.
Further, various image pickup devices such as CCD and CMOS can be adopted as the image pickup device 23 described above. In addition, in the frame sequential color imaging apparatus according to the color mode switching system of the present embodiment, a single-plate type imaging device is adopted, which eliminates the need for a color separation prism, thereby making the apparatus compact. It is

Further, the color variable filter drive section 26 described above instructs the voltage variable section 223 of the color variable filter 22 to switch the output voltage at a predetermined timing. This instruction is given by a control signal (driving signal) as shown in FIG.
In addition, the above-described imaging device driving section 27 switches each color field of the imaging frame in synchronization with the timing of color light switching of the output light from the color variable filter 22 .
A color signal conversion unit (built into the frame interpolation processing unit 24A in this embodiment) 24 converts the color signals (R/G/B/W) output from the imaging element 23 into parallel RGB signals. , and the parallel RGB signals converted thereby are output from the color signal output section 28 to the outside.

According to the frame sequential color imaging apparatus according to the color mode switching system of the present embodiment, output switching of colored light for frame sequential can be performed by controlling the voltage applied to the colored light variable element 220. Since a movable part such as a rotating disk filter for color light separation is not required, generation of vibration, noise, power consumption, etc. can be reduced. Also, there are no restrictions on lighting conditions.

The color mode switching system 10A according to the embodiment of the invention will be further described below.
As described above, the frame sequential color imaging apparatus 10 is formed from the imaging lens 21, the color variable filter 22, the imaging device 23, the color variable filter driving section 26, the imaging device driving section 27, and the color signal output section 28 shown in FIG. Further, as shown in FIG. 1, a frame interpolation processing section (including a color signal conversion section 24) 24A to which color signals (R/G/B/W) from the imaging element 23 are input, and The color mode switching system 10A according to the embodiment of the present invention can be configured by providing the control mode determination section 25 that receives the output of the frame interpolation processing section 24A and determines the control mode. The determination output from the control mode determining section 25 is fed back to the input section of the frame interpolation processing section 24A as a control mode identification signal, and is also input to the color variable filter driving section 26 as a control mode identification signal.
Based on the input control mode identification signal, the color variable filter drive unit 26 sends a control signal to the color variable filter 22 in accordance with the order of color switching in the control mode.

The color variable filter 22 described above receives the control signal from the color variable drive unit and is driven by the corresponding control pattern among the control patterns illustrated in (1) to (8) of FIG. Output color light (R, G, B, W) is switched sequentially for each field. For example, in the case of control pattern (1), W, R, G, and B, which are output colored lights, are switched in this order for each frame, and the pattern is repeated thereafter. At this time, the frequency for switching the output color light is set to four times the frame rate to be finally obtained as the video signal. For example, when trying to obtain a video signal with a frame rate of 60 Hz, color switching is performed at a frequency of 240 Hz.

As described above, the imaging element 23 is driven at the same frequency as the frequency for switching the color light of the color variable filter 22, and converts the output color light from the color variable filter 22 irradiated onto the light receiving surface into a color signal. At this time, the frame interpolation processing unit 24A receives the color signal output from the image sensor 23 and the control mode identification signal output from the control mode determination unit 25, and performs frame interpolation processing ( In each control mode, the thinned-out color signals are subjected to frame interpolation processing by calculation, averaging processing for redundant color signals, and calculation processing to convert W signals to color signals (R, G, B). etc., to generate an RGB signal with a desired frame rate.

The control mode determination unit 25 receives the RGB signals output from the frame interpolation processing unit 24A, automatically determines the control mode based on preset determination conditions, and outputs a control mode identification signal.
In this case, even if the shooting scene changes continuously, the determination can be made at high speed, so it becomes easy to switch the control mode suitable for the shooting scene for each frame.

As described above, the color variable filter drive unit 26 receives the control mode identification signal from the control mode determination unit 25, and outputs a control signal (driving signal) corresponding to the control mode to the color variable filter 22. The output color light output from the color variable filter 22 is thereby controlled.

As described above, in the color mode switching system 10A of the present embodiment, the control mode determination unit 25 determines the state of each of the RGB color signals output from the outside, and determines the control mode based on the result of this determination. A signal is fed back to the frame interpolation processing section 24A, and a control mode identification signal based on this determination result is sent to the color variable filter driving section 26. FIG. Thus, the control mode determination section 25 is set in advance with determination criteria for selecting a control mode in which the order and frequency of the color lights output from the color variable filter 22 are appropriate so that the respective RGB color signals are optimized. Thus, desired RGB color signals can be output from the color signal output section 28 .

According to the color mode switching system 10A of the present embodiment configured as described above, switching of the illumination light is not required and can be realized without installing a rotating mechanism in front of the imaging element 23. . Therefore, it is possible to solve the limitation of illumination conditions, which has been a problem in the conventional frame sequential type color imaging device, and to reduce the noise, vibration, and power consumption associated with the introduction of the rotation mechanism. In addition, it is possible to change the switching order, switching frequency, and switching timing of the colored lights without exchanging the physical filters.

In addition, by using the pattern shown in FIG. 4 as the switching pattern (control mode) of the color light output from the color variable filter 22, it is possible to shoot in different situations such as when the image is dark or when noise is conspicuous in a specific color signal. An optimum shooting mode can be selected as appropriate for each scene.
In this control mode, a plurality of selectable control modes (e.g., 8 patterns of control modes shown in FIG. 4) are stored in a storage unit (not shown) of the color variable drive unit 26, and output from the control mode determination unit 25. , a desired control mode is selected from among the stored control modes according to a control mode identification signal indicating which control mode is to be used, and the color variable filter 22 selects the desired control mode in the order of color light arrangement of this control mode. A control signal sequentially instructs the switching of the colored lights.
Advantages of each control mode (1) to (8) shown in FIG. 4 will be described below.

Control mode (1) generally functions as a normal mode, and the color variable filter 22 sequentially switches each color light of W, R, G, and B for each field (each color field of the color sequential system: the same applies hereinafter). output while The resolution of each color light signal obtained at this time does not require the pixel interpolation processing required when using an on-chip color filter, so the resolution of each color light signal is maintained. Therefore, it is possible to output color light signals with higher resolution than a single-plate imaging device using on-chip color filters.

Control mode (2) generally functions as a high-sensitivity mode, and the variable color filter 22 outputs W light three times in four fields, and outputs R, G, and B light once in 12 fields. Each outputs light. Since the W light has light of all wavelength ranges, the amount of incident light is larger than that of each of the R, G, and B lights. Therefore, even in a dark shooting scene, high-sensitivity shooting with reduced noise is possible.

Control modes (3), (4), and (5) function as modes for doubling only specific color light, and the frequency of outputting any one of R, G, and B color light is This is twice the frequency of outputting colored light. For example, in control mode (3), the frequency of outputting R light is twice the frequency of outputting B light and G light. Therefore, when only noise in a certain color signal is more noticeable than other color signals, one of the control modes (3), (4), and (5) is selected to control the output frequency of the color signal with noticeable noise. By doubling the amount of light, the amount of light that can be used to generate the color signal is doubled, and noise in the color signal can be reduced, thereby improving the image quality.

Control modes (6), (7), and (8) function as modes in which only specific colored light is tripled, and the frequency of outputting one of R, G, and B colored light is set to four fields. Since the frequency of outputting the other color light is 1 time in 8 fields, the light quantity of the specific color light irradiated to the imaging element can be made 6 times the light quantity of the other color light. In this case, since high-sensitivity photography is possible only with specific color signals, it is possible to reduce noise only with specific color signals more than in the above-described control modes (3), (4), and (5). is possible.

The control patterns shown in (1) to (8) in FIG. 4 are examples of some of the various control patterns that can be selected. For example, when the desired frame frequency is 60 Hz (one field period is 1/480 (sec), which is the same as each pattern in Fig. 4), can switch color light 8 times per frame, so more types of patterns can be set and more detailed output The frequency can be changed, and the degree of freedom of control pattern selection can be increased.

Further, in the above-described embodiment, the control mode is determined automatically by the control mode determining unit 25. However, the setting operation by the operator (for example, the 4 is directly input to the control mode determination unit 25 according to the control mode setting unit (for example, pressing operation of the control mode setting unit (for example, manual switch or remote control button)), and the control mode determined by the control mode determination unit 25 is selected. , may be sent to the frame interpolation processing section 24A and the color variable filter driving section 26 as the control mode identification signal.

The color mode switching system of the present invention is not limited to the above embodiment, and various other modifications are possible. For example, in the above embodiments, a transmission type filter is used as the color variable filter, but a reflection type filter can also be used. In the above-described embodiment, the color variable filter is composed of alternating layers composed of two kinds of layers.

In addition, the two types of piezoelectric dielectric layers that constitute the color light variable element are not limited to the PLZT layer and the ZnO layer, and other layers whose thickness can be changed to a desired value by voltage application have different refractive indices. A layer of two materials with different .
Further, although the frame sequential color imaging apparatus described above is provided with the color signal conversion section 24, the color signal conversion section 24 may perform frame interpolation processing as in the color mode switching system. .
Further, as the control mode described above, various other combinations of R, G, B, and W can be used in place of each control mode described in the embodiment. For example, within one frame, W light is output twice and the first light out of R, G, and B is output twice, and within one frame after the one frame, The light of W is output twice, the second light of R, G, and B is output twice, and the light of W is output twice within two frames after the one frame, and the light of R , G, and B are output twice.
Further, in the control mode described above, the number of color signals to be switched within one frame is not limited to four, but may be any number of three, five or more.
Also, if the proportions of R, G, B, and W included in a certain number of consecutive frames are the same, it is possible to change the chronological order of R, G, B, and W in various ways.

10, 310, 410 imaging device 10A color mode switching system 21, 321, 421 imaging lens 22 color variable filter 23, 323, 423 image sensor 24 color signal converter 24A frame interpolation processor 25 control mode determination unit 26 color variable filter drive Section 27 Imaging Element Driving Section 28 Color Signal Output Section 31 Control Mode Setting Section 220 Color Light Variable Element 221A PLZT Layer 221B ZnO Layer 222A, B Transparent Electrode Layer 223 Voltage Variable Section 320 Rotary Disc Filter 330, 430 Signal Processing Section 340 Rotation Power unit 450 RGB light emission control device 460 RGB switching light source

Claims (5)

an imaging lens;
a color variable filter that sequentially time-divides subject light incident from the imaging lens into three primary color light components and outputs them;
an imaging device that sequentially receives color light components of the three primary colors time-divided by the color variable filter, converts the color light components into color signals corresponding to the color light components, and outputs the color light components according to switching of the color light components; ,
a color signal conversion unit that converts the color signal output from the imaging element into an RGB signal;
an RGB signal output unit for outputting the RGB signal output from the color signal conversion unit to the outside,
In the color variable filter, a plurality of piezoelectric dielectric layers having different refractive indices are laminated in order, and the sequential layers are sandwiched between a pair of electrode layers, at least one of which is transparent. Equipped with a frame sequential color imaging device configured to apply a voltage of
The color signal conversion unit is incorporated, performs frame interpolation processing based on the input control mode identification signal, converts the color signal from the image sensor into a predetermined RGB signal, and converts the converted RGB signal into the RGB signal. a frame interpolation processing unit that outputs to the signal output unit;
The RGB signal is input from the frame interpolation processing unit to the RGB signal output unit, and a control mode that enables desired color correction for the input RGB signal is determined based on a preset determination condition. a control mode in which the determination result is fed back to the input section of the frame interpolation processing section as the control mode identification signal, and the control mode identification signal is also output to the color variable filter driving section that drives the color variable filter; A color mode switching system comprising a determination unit. an imaging lens;
a color variable filter that sequentially time-divides subject light incident from the imaging lens into three primary color light components and outputs them;
an imaging device that sequentially receives color light components of the three primary colors time-divided by the color variable filter, converts the color light components into color signals corresponding to the color light components, and outputs the color light components according to switching of the color light components; ,
a color signal conversion unit that converts the color signal output from the imaging element into an RGB signal;
an RGB signal output unit for outputting the RGB signal output from the color signal conversion unit to the outside,
In the color variable filter, a plurality of piezoelectric dielectric layers having different refractive indices are laminated in order, and the sequential layers are sandwiched between a pair of electrode layers, at least one of which is transparent. Equipped with a frame sequential color imaging device configured to apply a voltage of
The color signal conversion unit is incorporated, performs frame interpolation processing based on the input control mode identification signal, converts the color signal from the image sensor into a predetermined RGB signal, and converts the converted RGB signal into the RGB signal. a frame interpolation processing unit that outputs to the signal output unit;
Based on a control mode setting signal input from the outside, a control mode that enables desired color correction for the RGB signals is determined, and a control mode identification signal that identifies the determined control mode is transmitted to the frame interpolation process. and a control mode determination section that feeds back the control mode identification signal to an input section of the control section and also outputs the control mode identification signal to a color variable filter driving section that drives the color variable filter. 3. The color mode according to claim 1 , wherein one of the control modes is a pattern set to output each light of W, R, G, and B once in each frame. switching system. One of the control modes is to output W light twice and the first light of R, G, and B twice in one frame, and one after the one frame. The light of W is output twice and the second light of R, G, and B that is different from the first light is output twice within a frame of the one frame. to output light of W twice and a third light of R, G, B, different from said first light and said second light, twice in a subsequent frame; or Within the one frame, the light of W is output three times and the first light of R, G, and B is output once, and within the frame one after the one frame, W light is output three times and the second light out of R, G, and B is output once, and W light is output three times within two frames after the one frame. 3. The pattern according to claim 1 , wherein the pattern is set such that the third light of R, G, and B is output once and these three frames are sequentially repeated. color mode switching system. One of the control modes is a pattern in which a predetermined one light of R, G, and B is output twice and the remaining two lights are output once each in each frame, or Within a frame of , a predetermined one of R, G, and B light is output three times, and one of the remaining two lights is output once, and within a frame after the one frame , R, G, and B are output three times, the other of the remaining two lights is output once, and these two frames are sequentially repeated. 3. A color mode switching system according to claim 1 or 2 , characterized in that:

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