JP3607730B2 - Solid-state imaging device and driving method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a solid-state imaging device and a driving method thereof.
[0002]
[Prior art]
In general, in an XY address type solid-state imaging device that reads out signals of a pixel array in which pixels are arranged in a matrix form by an XY address method, in order to realize all-pixel independent sequential scanning, One vertical scanning circuit unit for controlling the imaging state is required. This configuration is shown in FIG. In FIG. 6, 101 is a horizontal scanning circuit, 102 is a vertical scanning circuit, 102-1 is a vertical scanning circuit unit, and 103 is a pixel. The horizontal scanning circuit 101 sequentially outputs the signals of the pixels in the rows selected by the vertical scanning circuit 102, and the vertical scanning circuit 102 sets the pixels in each row to a selected state or a non-selected state. In order to realize all pixel independent sequential scanning, it is necessary to control each pixel row independently to a selected / non-selected state. Therefore, as shown in FIG. 6, the vertical scanning circuit unit 102-1 has the number of pixels in the vertical direction. The same number is required.
[0003]
[Problems to be solved by the invention]
In the case of realizing all pixel independent sequential scanning with such a configuration, when the pixel pitch in the vertical direction is reduced, the pitch of the scanning circuit has to be reduced and a fine processing technique is required. If it is difficult to reduce the pitch of the scanning circuit to the pixel pitch, it can be realized by arranging scanning circuits on both sides of the pixel region as disclosed in Japanese Patent Application No. 4-283506. Cause an increase in area. Furthermore, as the number of pixels in the vertical direction increases, the number of scanning circuit units must increase accordingly. These have the problem of lowering the manufacturing yield of the solid-state imaging device for all-pixel independent sequential scanning as compared with the solid-state imaging device for two-line mixed interlaced scanning that can be realized by a vertical scanning circuit having half the number of vertical pixels. Further, as in a solid-state imaging device compatible with two-line mixed interlaced scanning, a method for realizing sequential scanning with a vertical scanning circuit having half the number of vertical pixels is disclosed in Japanese Patent Laid-Open No. 6-98264. However, the output signal is a two-row mixed signal, and there is a problem that the vertical resolution corresponding to the number of vertical pixels cannot be obtained.
[0004]
The present invention has been made in order to solve the above-mentioned problems in the conventional all-pixel independent sequential scanning type solid-state imaging device. The inventions according to claims 1 and 4 can reduce the number of vertical scanning circuit units in the vertical direction. It is an object of the present invention to provide a solid-state imaging device capable of realizing all-pixel independent sequential scanning readout with half the number of pixels and a driving method thereof.
[0005]
Another object of the present invention is to provide a solid-state imaging device in which the first and second switching means in the first invention can be controlled by one input clock.
[0006]
A third aspect of the present invention is to provide a solid-state imaging device according to any one of the first and second aspects, wherein the outputs from the pixels in all rows can be made uniform. And
[0007]
Furthermore, the invention described in claim 5 is a method for driving a solid-state imaging device in which a signal component independent of incident light information contained in an all-pixel independent sequential scanning readout signal can be obtained without shielding the solid-state imaging device. The purpose is to provide.
[0008]
[Means and Actions for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is a solid-state imaging device in which a readout row of a pixel array arranged in a matrix is selected by an output of a vertical scanning circuit. A vertical scanning circuit composed of a vertical scanning circuit unit corresponding to every other pixel row, and an output connected to the corresponding pixel row, and the output of each vertical scanning circuit unit in the previous stage of the pixel row corresponding to each vertical scanning circuit unit First switching means for transmitting to each pixel row; and second switching means for transmitting the output of each vertical scanning circuit unit to a pixel row in the subsequent stage of the pixel row corresponding to each vertical scanning circuit unit. The selection signal output from the scanning circuit unit is output over two consecutive horizontal scanning periods, and the first switching means includes the second switching period. Conducted in the half horizontal scanning period, non-conducted in the latter half horizontal scanning period, and the second switching means becomes non-conducted in the first half horizontal scanning period out of the two consecutive horizontal scanning periods, and in the latter half horizontal scanning period. And the switching operation of the first and second switching means is performed in a horizontal blanking period, and in the first half of the horizontal scanning period, the correspondence between the optical information signal and the dark signal of the corresponding pixel row The dark signal of the pixel row preceding the pixel row is read, and the dark signal of the corresponding pixel row and the optical information signal and dark signal of the pixel row subsequent to the corresponding pixel row are read during the second horizontal scanning period, and each pixel row The optical information signals are sequentially and independently read out.
[0009]
As described above, the selection signal output from each vertical scanning circuit unit is output over two consecutive horizontal scanning periods. In the first half horizontal scanning period, the first switching means is turned on and the second switching means is turned off. of the horizontal scanning period so that the first switching means conducts the second switching means becomes nonconductive, and the switching operation of the first and second switching means takes place in a horizontal blanking period, the first half of the horizontal In the scanning period, the optical information signal and dark signal of the corresponding pixel row and the dark signal of the previous pixel row of the corresponding pixel row are read, and in the second horizontal scanning period, the dark signal and the corresponding pixel row of the corresponding pixel row are read out. read the optical information signal and the dark signal of the subsequent pixel rows, since it is configured to sequentially independently read out the optical information signals for each pixel row, the vertical number of pixels of half the number of the vertical scanning circuit unit Accordingly, without mixing an output corresponding to the vertical direction two pixels incident light, independent pixel progressive scan readout becomes possible.
[0010]
According to a second aspect of the present invention, in the first aspect of the present invention, the second switching means is controlled by an inverted clock of the clock that controls the first switching means. As a result, the first and second switching means can be controlled by one input clock.
[0011]
According to a third aspect of the present invention, in each of the first and second aspects of the present invention, between the pixel row to which the output of each vertical scanning circuit unit is connected and the output section of the unit, A switching unit that is always in a conductive state is provided with a configuration equivalent to that of the first or second switching unit. This makes it possible to make the outputs from the pixels in all rows uniform.
[0012]
According to a fourth aspect of the present invention, in the solid-state imaging device driving method according to any one of the first to third aspects, a signal of each pixel in a pixel row selected to be in a read state by the vertical scanning circuit is nondestructive. And resetting immediately before the switching operation of the first and second switching means performed in the horizontal blanking period, and reading the light information accumulated in the pixel immediately after switching. Is. Thus, the all-pixel independent sequential scanning and reading operation is performed by the vertical scanning circuit composed of the vertical scanning circuit units, which is half the number of pixels in the vertical direction, without mixing the outputs corresponding to the incident light of the two vertical pixels. Is possible.
[0013]
According to a fifth aspect of the present invention, there is provided a solid-state imaging device in which a readout row of a pixel array arranged in a matrix is selected by an output of a vertical scanning circuit, and corresponds to every other pixel row in the vertical direction. A vertical scanning circuit including a vertical scanning circuit unit whose output is connected to the corresponding pixel row, and a first scanning line that transmits the output of each vertical scanning circuit unit to the pixel row preceding the pixel row corresponding to each vertical scanning circuit unit. 1 switching means and second switching means for transmitting the output of each vertical scanning circuit unit to a pixel row subsequent to the pixel row corresponding to each vertical scanning circuit unit, and is output from each vertical scanning circuit unit. The selection signal is output over two consecutive horizontal scanning periods, and the first switching means is turned on during the first half of the two horizontal scanning periods. The second switching means is non-conductive during the second horizontal scanning period, the second switching means is non-conductive during the first horizontal scanning period of the two consecutive horizontal scanning periods, and is conductive during the second horizontal scanning period. In the driving method of the solid-state imaging device, the switching operation of the first and second switching means is performed during the horizontal blanking period. The signal of each pixel in the pixel row selected for reading by the vertical scanning circuit is not displayed. As soon as the first and second switching means are switched during the horizontal blanking period, the light information stored in each pixel selected in the read state is reset, Then, the signal of each pixel is read out. As a result, it is possible to obtain a dark equivalent output of the solid-state imaging device without shielding the solid-state imaging device.
[0014]
【Example】
Next, examples will be described. FIG. 1 is a circuit configuration diagram showing an embodiment of a solid-state imaging device according to the present invention. In this embodiment, a solid-state imaging device having a 4 × 5 pixel configuration is assumed, but the present invention is not limited to this pixel configuration. In FIG. 1, 1 is a horizontal scanning circuit for sequentially outputting pixel signals, 2 is a vertical scanning circuit, 2-1, 2-2, 2-3 are vertical scanning circuit units, 3 is a selected row changeover switch unit, 4 is The pixels according to the incident light can be read nondestructively and are arranged in a 4 × 5 matrix. Si (i = 1 to 4) is a signal extraction line, and Gi (i = 1 to 5) is a horizontal pixel selection line. Pixels in the same row in the horizontal direction are commonly connected to one horizontal selection line, and pixels in the same column in the vertical direction are commonly connected to one signal extraction line. When the pixel is selected, the vertical scanning circuit unit reads a pixel signal when the reset clock ΦR is “L”, and outputs a selection signal that resets the charge accumulated in the pixel when the reset clock ΦR is “H”. It outputs to the pixel.
[0015]
Outputs L1, L2, and L3 of the vertical scanning circuit units 2-1, 2-2, and 2-3 are directly output to the odd-numbered horizontal pixel selection lines G1, G3, and G5, respectively. The outputs L1 and L2 of the vertical scanning circuit units 2-1 and 2-2 are output to the selection line G2 via the second and first switches 3b and 3a of the selected row changeover switch unit 3, respectively. Similarly, the outputs L2 and L3 of the vertical scanning circuit units 2-2 and 2-3 are supplied to the horizontal pixel selection line G4 of the even-numbered rows, and the second and first switches 3b and 3a of the selected row changeover switch section 3. Is output via.
[0016]
The selected row changeover switch unit 3 changes the combination of rows that transmit the outputs L1, L2, and L3 of the vertical scanning circuit units 2-1, 2-2, and 2-3 by the selected row changeover clock ΦLi. Is “H”, the output L1 of the vertical scanning circuit 2 is output to the horizontal pixel selection lines G1 and G2, the output L2 is output to the horizontal pixel selection lines G3 and G4, the output L3 is output to the horizontal pixel selection line G5, and ΦLi is When “L”, the output L1 is output to the horizontal pixel selection line G1, the output L2 is output to the horizontal pixel selection lines G2 and G3, and the output L3 is output to the horizontal pixel selection lines G4 and G5. The output Li (i = 1 to 3) of the vertical scanning circuit unit outputs a ternary pulse. The lowest level of the three values is a non-selected state, and the intermediate level is a selected state. The signal charge is reset while the highest level is selected. The highest level, that is, the timing for resetting the selected pixel corresponds to the time when the reset clock ΦR becomes “H”.
[0017]
Next, the operation of the solid-state imaging device configured as described above will be described with reference to a timing chart shown in FIG. From time t ₁ to t ₄ are horizontal pixel selection line G1 is selected. Since ΦLi is “L” from t ₁ to t ₂ , no pixel row other than the first row is selected. At t ₂ , the optical information of the pixels in the selected row is reset according to “H” of the reset clock ΦR that becomes “H” in the horizontal blanking period (HBL), and then ΦLi is set to “H”. Since ΦLi is “H” from t ₃ to t ₄ , the pixels in the first row and the second row are selected. Since the pixels in the first row are immediately after being reset at t ₂ , almost no light information is accumulated. Therefore, during the period of t ₃ , the total signal of the dark output (1d) of the pixels in the first row and the dark output (2d) of the pixels in the second row and the output (2s) according to the optical information is an output signal. Is output as At t ₄ , the optical information accumulated in the pixels in the first row and the second row is reset according to the reset clock ΦR.
[0018]
Similarly, during the period t ₅ , the dark output (2d) of the pixels in the second row, the dark output (3d) of the pixels in the third row, and the output (3s) corresponding to the light information are output, and t the ₇ period of the output corresponding to the dark output (3d) and a fourth row of dark signal (4d) and optical information of the pixels of the pixel of the third row (4s) is output, and the period t ₉ Produces a dark output (4d) for the pixels in the fourth row, a dark output (5d) for the pixels in the fifth row, and an output (5s) according to the light information. Therefore, at t ₃ , the output of the second row of pixels, t ₅ at the third row of pixels, t ₇ at the fourth row of pixels, and at t ₉ the output according to the light information of the fifth row of pixels is output independently at each row. Will be read.
[0019]
As can be seen from the above description, the read signal is the sum of the dark output for two pixels and the output corresponding to the light information for one pixel. Since the signal required as the video signal is only a signal corresponding to the optical information, the dark output for two pixels may be subtracted from the read signal in order to configure the video signal. In this case, if the dark output of each pixel is constant, a constant value may be subtracted from the read signal, but if the dark output varies from pixel to pixel and is not constant, the read signal is Even if a certain value is subtracted, it is left behind and a fixed pattern noise in the dark is generated in the video signal. The method described below is generally used to remove this dark fixed pattern noise. That is, first, the dark output is read from the imaging device, and this signal is stored in the memory. Next, the dark output of the corresponding pixel stored in the memory is subtracted from the signal read from the imaging device. The dark fixed pattern noise can be removed by the above operation.
[0020]
In order to obtain dark output from the imaging device, a signal may be read out using a mechanical or optical shutter or the like so that light does not enter the imaging device. However, the use of a mechanical or optical shutter is not desirable because it increases the number of components and causes an increase in cost and a decrease in reliability. Therefore, a method for obtaining dark output from the imaging device without shielding the imaging device will be described next.
[0021]
In the solid-state imaging device of the above embodiment, after reading a signal corresponding to the light information of the pixel in the selected state and resetting the light information, the selected row changeover switch unit is switched to change the combination of the selected rows, and the next By performing signal readout, an output corresponding to the optical information of each row is obtained. However, the timing for switching the selected row changeover switch unit is performed before resetting the optical information, so that the subsequent signal readout period can be obtained. In this case, it is possible to read the dark output without the light information of the pixels in the selected row without shielding the solid-state imaging device.
[0022]
A method for reading out the dark output will be described with reference to a timing chart shown in FIG. In reading the output when the dark, for example, time t ₄₀ in ΦLi = "L", ΦR = "H" , so, the reset level is output to the horizontal pixel selection line G2, G3, corresponding to the horizontal pixel selection line G2, G3 The signal charges of the pixels in the row to be reset are reset. Since ΦLi = “L” and ΦR = “L” at time t ₅₀ , the signal read level is output to the horizontal pixel selection lines G 2 and G 3, and the signal immediately after resetting the pixels in the row corresponding to the horizontal pixel selection lines G 2 and G 3. Is read out. In this case, in the pixels in the row corresponding to the horizontal pixel selection lines G2 and G3 selected immediately after the reset operation, the optical information is accumulated for the time from the end of the reset operation to the start of the read operation. Since this is sufficiently shorter than the optical information storage time, that is, one vertical scanning period, this storage effect can be almost ignored. Therefore, the signal read here can be treated as a dark signal.
[0023]
The above explanation was made on the assumption that the signal from the pixel is composed of an output in the dark and an output corresponding to the optical information. For example, the charge generated by the incident light is directly read out. In the case of a solid-state imaging device, the dark output is zero. In such a case, the signal from the pixel in the selected state is only the output corresponding to the light information from one pixel, and there is no need to subtract the dark output when constructing the video signal. That is, in FIG. 2, for example, at time t ₅ , the output is only (3 s).
[0024]
In the above-described embodiment, the output from the vertical scanning circuit unit is ternary and one horizontal pixel selection line is provided for each unit. However, the selection signal line and the reset signal line are independent, and 2 per row. It is also possible to use a horizontal pixel selection line.
[0025]
In the above embodiment, the operation for resetting the optical information stored in the selected pixel in response to “H” of the reset clock ΦR during the horizontal blanking period has been described. In the case of resetting the stored optical information, that is, in the case of destructive reading, this reset operation is not necessary, and the output from the vertical scanning circuit unit may be a non-selected / selected binary pulse.
[0026]
FIG. 4 shows a specific configuration example of the selected row changeover switch unit 3. In FIG. 4, the selection signals output from the vertical scanning circuit unit are the horizontal pixel selection line Gi, the source of the P channel MOS transistor Q1, the drain of the N channel MOS transistor Q2, and the source of the P channel MOS transistor Q3 and the N channel MOS transistor. Connected to the drain of Q4, P-channel MOS transistor Q1 and N-channel MOS transistor Q2 constitute a first switch 3a, and P-channel MOS transistor Q3 and N-channel MOS transistor Q4 constitute a second switch 3b. ing. ΦLi is input to the gates of the P channel MOS transistor Q1 and the N channel MOS transistor Q4, and the inverted signal / ΦLi of ΦLi is input to the gates of the N channel MOS transistor Q2 and the P channel MOS transistor Q3. Therefore, when ΦLi is “H”, the P-channel MOS transistor Q3 and the N-channel MOS transistor Q4 are turned on, and the selection signal output from the vertical scanning circuit unit is supplied to the horizontal pixel selection lines Gi and Gi + 1. When ΦLi is “L”, the P-channel MOS transistor Q1 and the N-channel MOS transistor Q2 are turned on, and the selection signal output from the vertical scanning circuit unit is supplied to the horizontal pixel selection lines Gi−1 and Gi.
[0027]
Here, the selected row changeover switch unit is the same as the field changeover switch in the solid-state imaging device compatible with two-line interlaced scanning. However, during interlaced scanning, this switch is switched during the vertical blanking period. Can take a relatively long time. In the present invention, since the selected row changeover switch section is switched within the horizontal blanking period, it is necessary to have a faster switching speed compared to the field changeover switch in the solid-state imaging device compatible with two-line mixed interlaced scanning. For this purpose, when a switch is constituted by a MOS transistor, the power supply voltage is increased, the gate width of the MOS transistor is increased, the gate length is shortened, and the clock output buffer capability for controlling the switch is increased. There are ways to increase it.
[0028]
In the present invention, since the outputs of the pixels in each row are taken out independently, it is desirable that the selection signal output from the vertical scanning circuit unit is output in the same manner to the pixels in each row. However, in the configuration of the embodiment shown in FIG. 1, the output of the vertical scanning circuit unit (selection signal) Li (i = 1 to 3) is a switch of the selected row changeover switch section for the pixels in the odd rows. Are output directly, and are output to the pixels in the even-numbered rows via the switches of the selected row changeover switch section. This configuration can cause non-uniform output between the odd-numbered pixels and the even-numbered pixels. Therefore, as in the embodiment shown in FIG. 5, each switch 3 a, which configures the selected row changeover switch unit 3, between the horizontal pixel selection lines G 1, G 3, G 5 corresponding to the pixels in the odd rows and the vertical scanning circuit unit. This problem is solved by providing the dummy switch 5 that is always in a conductive state with the same configuration as that of 3b.
[0029]
In each of the embodiments described above, the vertical scanning circuit unit is described as corresponding to the odd-numbered rows of pixels. However, the vertical scanning circuit unit is associated with the even-numbered rows and the odd-numbered rows before and after the selected row changeover switch unit. The same effect can be obtained even if the connection is made via the first and second switches. In the present invention, attention should be paid to the selection state of the pixels in the horizontal direction, so that the configuration of the horizontal scanning circuit is not limited as long as it can sequentially output the signals of the selected pixels in the horizontal direction.
[0030]
【The invention's effect】
As described above based on the embodiments, according to the first aspect of the present invention, two vertical pixels are incident by the vertical scanning circuit composed of the vertical scanning circuit units which is half the number of vertical pixels. A solid-state imaging device capable of performing all-pixel independent sequential scanning and reading without mixing outputs corresponding to light can be obtained. According to the invention described in claim 2, since the first and second switching means in the invention described in claim 1 are configured to be controlled by one input clock, the number of input terminals is reduced and driving is facilitated. A solid-state imaging device is obtained. According to a third aspect of the present invention, in each of the first and second aspects of the present invention, pixels in a row corresponding to the vertical scanning circuit unit and pixels in a row not corresponding to the vertical scanning circuit unit. Thus, a uniform signal can be extracted.
[0031]
According to the fourth aspect of the invention, the vertical scanning circuit composed of the vertical scanning circuit units, which is half the number of pixels in the vertical direction, does not mix the output corresponding to the incident light of the two pixels in the vertical direction. Thus, a method for driving a solid-state imaging device that performs all pixel independent sequential scanning and reading is obtained. According to the fifth aspect of the present invention, a driving method of a solid-state imaging device capable of obtaining a dark-time output independent of incident light information included in the all-pixel independent sequential scanning readout signal without shielding the solid-state imaging device. Can be realized.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing an embodiment of a solid-state imaging device according to the present invention.
FIG. 2 is a timing chart for explaining the driving method of the embodiment shown in FIG. 1;
FIG. 3 is a timing chart for explaining a driving method for obtaining dark output in the embodiment shown in FIG. 1;
4 is a diagram showing a configuration example of a selected row changeover switch unit in the embodiment shown in FIG. 1;
FIG. 5 is a circuit configuration diagram showing another embodiment.
FIG. 6 is a circuit configuration diagram showing a configuration example of a conventional solid-state imaging device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Horizontal scanning circuit 2 Vertical scanning circuit 2-1, 2-2, 2-3 Vertical scanning circuit unit 3 Selected row changeover switch part 3a 1st switch 3b 2nd switch 4 Pixel 5 Dummy switch

Claims (5)

In the solid-state imaging device that selects the readout row of the pixel array arranged in a matrix by the output of the vertical scanning circuit, the output is connected to the corresponding pixel row in correspondence with every other pixel row in the vertical direction. A vertical scanning circuit comprising vertical scanning circuit units, a first switching means for transmitting the output of each vertical scanning circuit unit to a pixel row preceding the pixel row corresponding to each vertical scanning circuit unit, and each vertical scanning circuit Second switching means for transmitting the output of the circuit unit to the subsequent pixel row of the pixel row corresponding to each vertical scanning circuit unit, and the selection signal output from each vertical scanning circuit unit includes two consecutive horizontal scanning periods. The first switching means conducts during the first half of the two horizontal scanning periods, and during the second horizontal scanning period. The second switching means is turned off so that the second switching means is turned off during the first half of the two horizontal scanning periods, and turned on during the second half of the horizontal scanning period. The switching operation of the means is performed in the horizontal blanking period, and in the first half horizontal scanning period, the optical information signal and dark signal of the corresponding pixel row and the dark signal of the previous pixel row of the corresponding pixel row are read, and the second half of the horizontal scanning period. In the scanning period, a dark signal of the corresponding pixel row and a light information signal and a dark signal of a pixel row subsequent to the corresponding pixel row are read, and the light information signal of each pixel row is sequentially read independently . A solid-state imaging device. The solid-state imaging device according to claim 1, wherein the second switching unit is configured to be controlled by an inverted clock of a clock that controls the first switching unit. Switching means that is always in a conductive state with a configuration equivalent to the first or second switching means is provided between the pixel row to which the output of each vertical scanning circuit unit is connected and the output section of the unit. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is provided. The solid-state imaging device driving method according to any one of claims 1 to 3, wherein a signal of each pixel in a pixel row selected to be read by the vertical scanning circuit is read nondestructively and horizontal. A driving method for a solid-state imaging device, wherein resetting is performed immediately before the switching operation of the first and second switching means performed during a blanking period, and optical information accumulated in the pixels is read immediately after switching. . A solid-state imaging device configured to select a readout row of a pixel array arranged in a matrix by an output of a vertical scanning circuit, corresponding to every other pixel row in the vertical direction, and outputting to the corresponding pixel row A vertical scanning circuit composed of vertical scanning circuit units connected to each other, a first switching means for transmitting an output of each vertical scanning circuit unit to a pixel row preceding the pixel row corresponding to each vertical scanning circuit unit, Second switching means for transmitting the output of the vertical scanning circuit unit to the subsequent pixel row of the pixel row corresponding to each vertical scanning circuit unit, and the selection signal output from each vertical scanning circuit unit is two consecutive horizontal signals. The first switching means is turned on during the first horizontal scanning period among the two consecutive horizontal scanning periods, and is output during the second horizontal scanning period. The first and second switching means are non-conductive, the second switching means is non-conductive in the first half of the two horizontal scanning periods, and non-conductive in the second horizontal scanning period. In the driving method of the solid-state imaging device, the switching operation of the means is performed in a non-destructive manner in which a signal of each pixel in the pixel row selected to be read by the vertical scanning circuit is read out in a horizontal blanking period. Immediately after performing the switching operation of the first and second switching means performed in the horizontal blanking period, the light information accumulated in each pixel selected in the readout state is reset, and then the signal of each pixel is read out. A method for driving a solid-state imaging device.

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