JP4460751B2 - Imaging device and imaging apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image pickup device such as a CCD and an image pickup apparatus for picking up a subject image using the image pickup device.
[0002]
[Prior art]
Imaging devices using a single-plate color imaging device are widely spread and used in various fields. On the other hand, lack of dynamic range has been pointed out, and various solutions have been proposed.
[0003]
A technique for obtaining an image with an expanded dynamic range from pixel information having the same color but different sensitivity absolute values (filter density) is known. In particular, Japanese Patent Application Laid-Open No. 2000-066941 applies to pixels in the same color block of a multi-bayer array. Are listed. This means that a four-pixel block consisting of two pixels in the vertical and horizontal directions is regarded as a unit pixel (such a unit pixel is referred to as a multiple pixel in this specification, and a row or column composed of multiple pixels is defined as a multiple row. In the image pickup device in which the double pixels constitute an RGB Bayer array, the same color filters of the four pixels constituting the double pixels are all set to different densities, or two levels of high and low in two vertical or horizontal lines. The same color filter is arranged, and pixels having different sensitivities are provided in a plurality of pixels to obtain pixel information having a wide dynamic range.
[0004]
[Problems to be solved by the invention]
However, although the conventional configuration as described above is effective, it has the following problems. In other words, pixels having different densities are different in pixel information sampling points because they have the same range of exposure amounts but have different functions. Accordingly, when image information having a high frequency with respect to the sampling frequency is input, a false signal due to aliasing (moire) is generated.
[0005]
In order to make it easier to find the fundamental difficulties, the discussion is simplified, and the case where pixels with two high and low sensitivity levels that do not overlap the exposure range are arranged in two vertical columns is taken as black (0 level) as the subject input. ) And a gray stripe (COG level) corresponding to the crossover point of the exposure amount range is arranged at the pixel pitch p of the original pixel. This is a one-dimensional wave having a period of 2p, that is, a frequency of 1 / 2p. This is shown in FIG.
[0006]
FIG. 6A shows a filter arrangement, L is a high-sensitivity (light) pixel with a low filter density, and d is a low-sensitivity d (dark) pixel with a high filter density. The arrangement of the high-sensitivity L pixels and the low-sensitivity d pixels is the same for any multiple pixel composed of two pixels in the vertical and horizontal directions. Assuming that the exposure amount ranges of the high sensitivity L pixel and the low sensitivity d pixel do not overlap as described above, the photoelectric conversion characteristics of the two high and low sensitivity pixels are as shown in FIG. .
[0007]
In this case, when the exposure amount corresponding to the subject brightness is 0 level, no significant output is produced in either the high sensitivity L pixel or the low sensitivity d pixel (below the noise level. In the case of the COG level, a saturation level output occurs on the high sensitivity L side, but the low sensitivity d side output level becomes 0 level, so that the COG level is detected. Accordingly, in this case, the output of each of the multiple pixels differs from the 0 level to the COG level due to the sampling phase shift, resulting in a false signal (moire). For example, as shown in FIG. 6B, when black is superimposed on the high sensitivity L side and gray is superimposed on the low sensitivity d side, no significant output is produced in either the L or d pixels, so the output of the multiple pixels is 0 level. Therefore, when the black and gray phases are inverted, a saturation level is generated at the L pixel. Therefore, the output of the double pixel is detected as the COG level, and the gray solid output turn into.
[0008]
In the above, the exposure range is simplified if there is no overlap. However, even if there is an overlap, the dynamic range of the two pixels is not the same (obviously, it cannot be the same for the purpose of this technique). It is clear that the same false signal is generated for the high-frequency input in the region deviating from the above range. In the case of two horizontal rows, the horizontal stripes are the same considering the horizontal stripes, and when the density is different for all four pixels, the sampling points are further reduced (the same characteristic pixel is only one pixel per multiple pixels). In both cases, the same phenomenon occurs.
[0009]
In addition, because of the use of a multiple Bayer array, sampling moire based on color coding is separately generated, and it is assumed that an optical LPF such as crystal is used to prevent this. Since it is designed corresponding to the sampling frequency, the light beam separation width (shift amount) is 2p in both the vertical and horizontal directions (trap frequency ¼p), and is invalid in the vicinity of the input frequency in question.
[0010]
The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to make it possible to expand a dynamic range without causing generation of a false signal and to achieve sufficient image quality improvement. An object is to provide an element and an imaging device.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention provides a relative spectral sensitivity of the same color to a plurality of pixels as a unit pixel block composed of a plurality of adjacent pixels, and a predetermined number of different colors for each of the plurality of pixels. A single-plate color image pickup device that is color-coded by giving the relative spectral sensitivity of the above, and gives two types of high and low sensitivities to the plurality of the same color pixels in each of the multiple pixels, and these are arranged in a checkered pattern. The color arrangement of the imaging device is a multi-Bayer arrangement in which the multi-pixel is a square 4 pixel block of 2 × 2 horizontal and the color coding arrangement is a Bayer arrangement, and the height 2 in the multi-pixel is 2 The crossing pattern of the diagonal arrangement which is the checkered arrangement of the sensitivity is changed for each of the multiple pixels .
[0012]
In this way, by arranging the two types of high and low sensitivity pixels in a double pixel, the same color pixels having different sensitivities in both the vertical and horizontal directions are arranged adjacent to each other. For this reason, even when high-frequency vertical stripes and horizontal stripes as described above are input, two types of high and low pixel outputs can be averaged to obtain a false signal (moire). In addition, although pixels with the same sensitivity are arranged side by side in the diagonal direction, the pixel pitch between the two types of pixels viewed from the diagonal direction is two types of height viewed from the vertical or horizontal direction if the pixel is a square pixel. Therefore, the generation of a false signal can be suppressed up to a certain frequency even for a fringe input in an oblique direction. Therefore, it is possible to expand the dynamic range of multiple pixels by using pixels of two types of high and low sensitivity without causing generation of false signals such as moire.
[0013]
Further, when the double pixel is a square 4 pixel block of 2 × 2 in the vertical direction and the color coding arrangement is a Bayer arrangement, the high and low 2 sensitivity checkered arrangement in the multiple pixels is used. It is preferable to change the diagonally intersecting pattern for each of the multiple pixels. In this case, the intersection pattern is the same for the same double row, and is configured to change for every adjacent double row, or the same for the same double row, so that it changes for every adjacent double row. Can be configured. With these configurations, even when viewed from an oblique direction, the arrangement of two types of sensitivity can be alternately changed for each of the plurality of pixels, and it is possible to keep the pixels having the same sensitivity in a single pixel. As in the case of vertical stripes and horizontal stripes, the generation of false signals due to the deviation of the sampling phase between multiple pixels can be sufficiently suppressed for stripes input in an oblique direction.
[0014]
Further, as the multiple Bayer array, an RGB multiple Bayer array in which the color coding array is an RGB Bayer array can be used.
[0015]
According to another aspect of the present invention, an image pickup device according to any one of claims 1 to 4 , drive means for reading the image pickup signal by driving the image pickup device, and an image signal having a predetermined format based on the image pickup signal are generated. Image signal generating means capable of generating wide dynamic range information relating to the multi-pixel based on pixel information of two types of high and low sensitivities in the multi-pixel. It is characterized by doing. According to this imaging apparatus, by using pixel information of two types of high and low sensitivities, the dynamic range of information of each multi-pixel can be expanded, and a high-quality image can be obtained. In this case, when the image signal is generated, the addition result of pixel information of two types of high and low sensitivities in the multiple pixels can be used.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of an imaging apparatus according to an embodiment of the present invention. Here, the case where it implement | achieves as a digital camera is illustrated and demonstrated.
[0017]
In the figure, 101 is an imaging lens system composed of various lenses, 102 is a lens driving mechanism for driving the lens system 101, 103 is an exposure control mechanism for controlling the diaphragm of the lens system 101, and 104 is for low-pass and infrared cut. 105, a CCD color image pickup device with a built-in color filter, 106 a CCD driver for driving the image pickup device 105, 107 a preprocess circuit including an A / D converter, and 108 a color signal generation process, A digital process circuit for performing matrix conversion processing and other various digital processes, 109 is a card interface, 110 is a memory card for recording captured images, and 111 is an LCD image display system.
[0018]
Also, 112 in the figure is a system controller (CPU) 112 for overall control of each part, 113 is an operation switch system composed of various SWs, 114 is an operation display system for displaying operation states and mode states, 115 Is a lens driver for controlling the lens driving mechanism 102, 116 is a strobe as a light emitting means, 117 is an exposure control driver for controlling the exposure control mechanism 103 and the strobe 116, and 118 is for storing various setting information and the like. A non-volatile memory (EEPROM) is shown.
[0019]
As the CCD image pickup element 105, a progressive scan (sequential scan) type and an interline structure is used. In the CCD image pickup device 105, photoelectric conversion regions (pixel portions) composed of photodiodes are arranged in a matrix of rows and columns, and a vertical transfer path is provided for each pixel portion of one column in the vertical direction. A common horizontal transfer path is provided for each of the vertical transfer paths. A signal from each pixel unit is first transferred to the vertical transfer path, then transferred to the horizontal transfer path via the vertical transfer path, and then output amplifier (floating diffusion amplifier FDA: Floating).
Diffusion Amplifier).
[0020]
The structure of the color filter of the CCD image pickup device 105 will be described in detail later with reference to FIG. 2 and later, but a multiple Bayer array is used in which 2 × 2 four-pixel blocks have the same color and the array in units of blocks is a Bayer array. It has been. In this case, in the present embodiment, in order to expand the dynamic range (D range) without causing the generation of a false signal (moire), the same color filters of high and low densities are provided in each multi-pixel composed of four pixel blocks. In a checkered pattern, that is, diagonally arranged.
[0021]
In the digital camera of the present embodiment, the system controller 112 performs all the control, and the CCD driver 106 controls the drive of the CCD image sensor 105 to perform exposure (charge accumulation) and signal readout. This is taken into the digital process circuit 108 via the preprocess circuit 107 to generate an image signal for recording in a predetermined format, and then recorded on the memory card 110 via the card interface 109.
[0022]
The system controller 112 includes a pixel addition drive control unit 112a and a wide D range information generation control unit 112b. The pixel addition drive control unit 112a is for controlling the driving of the CCD image sensor 105 using the CCD driver 106 to execute the same color addition reading. Pixel information can be added and read out from the CCD image sensor 105. The wide D range information generation control unit 112b uses the addition signal obtained by the same color addition reading or the pixel information of the two types of high and low sensitivity individually read from each of the plurality of pixels by the non-addition reading. Generate wide dynamic range information about.
[0023]
Next, the filter arrangement of the CCD image sensor 105 will be described with reference to FIG.
[0024]
FIG. 2A shows a first example of a filter array used in this embodiment. This filter array is an RGB double Bayer array with multiple pixels composed of 2 × 2 4 pixel blocks as a unit, and high and low 2 sensitivities in each double pixel (same color unit pixel block) are checked (4 pixels as shown). In this case, the configuration is diagonal).
[0025]
The R double pixel is composed of 2 × 2 4 pixels having R spectral sensitivity characteristics. Of these, 2 pixels arranged diagonally are high sensitivity pixels (LR) having a low filter density. The two diagonally arranged pixels are low sensitivity pixels (dR) having a high filter density. Similarly, the G multiple pixels are also composed of 2 × 2 4 pixels having the same G spectral sensitivity characteristic, and 2 of these diagonally arranged pixels are high sensitivity pixels (LG) having a low filter density. The two diagonally arranged pixels are low-sensitivity pixels (dG) having a high filter density. Further, the same applies to the B multiple pixels, which are composed of two high-sensitivity pixels (LB) arranged diagonally and two low-sensitivity pixels (dB) arranged diagonally. Since the array in the case of multiple pixels is an RGB Bayer array, two types of high and low sensitivity pixels (L, d) are arranged in a checkered pattern over the entire pixel array if the difference in color of the multiple pixels is ignored. It has become a format.
[0026]
In FIG. 2A, the intersection pattern of the two-sensitivity diagonal arrangement is common to all the multiple pixels, and the two low-sensitivity pixels (d) are arranged at the lower left and upper right, and the two high-sensitivity pixels (L). Are arranged in the upper left and lower right.
[0027]
By arranging the pixels (L, d) having two types of high and low sensitivity in this manner, the same color pixels (L, d) having different sensitivities are arranged adjacent to each other in both the vertical and horizontal directions. Will be. For this reason, even when high-frequency vertical stripes and horizontal stripes as described in FIG. 6 are input, two types of high and low pixel outputs can be averaged for each multiple pixel without depending on the sampling phase shift. No false signal (moire) occurs. In addition, although pixels having the same sensitivity are arranged side by side in the diagonal direction, the pixel pitch P ′ between the two types of high and low pixels viewed from the diagonal direction is vertical or horizontal as shown in FIG. Since it is narrower than the pixel pitch P between the two types of high and low pixels as seen from (P ′ = P / 2 ^1/2 ), false signals are generated up to a certain frequency even for fringes input in an oblique direction. Can be suppressed. Therefore, it is possible to expand the dynamic range of multiple pixels by using pixels of two types of high and low sensitivity without causing generation of false signals such as moire.
[0028]
FIGS. 2B to 2D show other examples of filter arrays used in this embodiment. In these arrays, even if the fringes are input in an oblique direction, the cross pattern of the two-sensitive diagonal arrangement is changed by the multiple pixels so as to sufficiently suppress the generation of false signals due to the sampling phase shift between the multiple pixels. It is an example.
[0029]
That is, FIG. 2B shows a case where the intersection pattern of the two-sensitive diagonal arrangement is the same for the same double row and is changed in units of adjacent double rows. In FIG. 2B, in the odd-numbered double row (1, 3, 5,...), The intersection pattern of the two-sensitivity diagonal arrangement is the same as in FIG. The upper left and lower right are high sensitivity L), and in the even-numbered double row (2, 4, 6,...), The cross pattern of the two sensitivity diagonal arrangement is the reverse pattern (lower left and upper right) of FIG. Is the high sensitivity L, and the upper left and lower right are the low sensitivity d). FIG. 2C is also an example in which the cross pattern of the two-sensitivity diagonal arrangement is changed in units of double lines. Here, contrary to FIG. 2B, in the even-numbered double lines, the two-sensitivity diagonal arrangement is shown. The crossing pattern is the same as in FIG. 2A, and the crossing pattern of the two-sensitivity diagonal arrangement is the reverse of that in FIG.
[0030]
FIG. 2D shows a case where the intersection pattern of the two-sensitivity diagonal arrangement is the same for the same double row and is changed in units of adjacent double rows. In FIG. 2D, in the odd-numbered double row (1, 3, 5,...), The cross pattern of the two-sensitivity diagonal arrangement is the same as in FIG. The upper left and lower right are high sensitivity L), and in the even-numbered double rows (2, 4, 6,...), The cross pattern of the two sensitivity diagonal arrangement is the reverse pattern (lower left and upper right) of FIG. Is the high sensitivity L, and the upper left and lower right are the low sensitivity d). FIG. 2E is also an example in which the cross pattern of the two-sensitivity diagonal arrangement is changed in units of double rows. Here, contrary to FIG. 2D, the even-numbered double rows have a two-sensitivity diagonal arrangement. The crossing pattern is the same as in FIG. 2A, and in the odd-numbered double columns, the crossing pattern of the two-sensitivity diagonal arrangement is the reverse of FIG. 2A.
[0031]
Next, signal processing for an image signal obtained by the image sensor 105 having the filter array as shown in FIG. 2 will be described.
[0032]
Here, in order to simplify the description, it is assumed that the exposure amount ranges of the high sensitivity L pixel and the low sensitivity d pixel do not overlap. In this case, the photoelectric conversion characteristics of the high and low sensitivity pixels L and d are as shown in FIG. By using signals from these two high and low sensitivity pixels L and d, for example, as shown by a dotted line in FIG. 3, the range of the luminance level (exposure amount) of the object that can be imaged is widened, and a wide dynamic is obtained for each of the multiple pixels. Range pixel information can be generated. The generation of wide dynamic range information can be broadly divided into two cases: using the same color addition readout and using high and low sensitivity pixel information individually read from each of the multiple pixels by non-addition readout. is there.
[0033]
First, with reference to FIG. 4, a signal processing operation when using the same color addition reading will be described.
First, the pixel addition drive control unit 112a uses the CCD driver 106 to control the drive of the CCD image pickup element 105 and execute the same color addition reading, so that each vertical pixel and horizontal pixel constituting each of the multiple pixels are read. A total of four pixels are read out (step S101). In this addition reading, vertical transfer for two lines is performed in one horizontal blanking period by driving the vertical transfer path at twice the normal speed. Thereby, two vertical pixels in each of the multiple pixels are added on the horizontal transfer path. The pixel information after vertical addition (addition average information) is sent to the output amplifier (FDA) through the horizontal transfer path. Normally, a reset pulse is supplied to the FDA at a rate of one pulse per pixel, but horizontal transfer driving or reset pulse supply timing is set so that horizontal transfer for two pixels is performed for one reset pulse. By controlling, two pixels after vertical addition adjacent in the horizontal direction are added by FDA and read out. In this manner, the addition result (addition average) of 2 × 2 4 pixels is read out from the CCD image sensor 105 as an imaging signal for each of the multiple pixels.
[0034]
The added image signal is A / D converted and sent to the digital process circuit 108. A recording image may be generated by directly applying arbitrary known signal processing such as gradation processing (γ, knee, setup) or color balance processing directly to the added image signal, In this example, prior to normal γ correction processing (step S103), processing for gradation optimization (step S102) is performed in the digital process circuit 108 under the control of the wide D range information generation control unit 112b. . The tone optimization processing (step S102) is preprocessing performed before the addition signal is input to the normal γ correction processing, and here, the original input exposure level (subject luminance) is estimated from the level of the addition signal. Based on this, the gradation correction of the added signal is performed.
[0035]
That is, since pixel information of high and low 2 sensitivity is added, the photoelectric conversion characteristics are different between the area where the high sensitivity L pixel is saturated and the area where it is not saturated, and the whole becomes a non-linear characteristic of a polygonal line. A signal (linear signal) proportional to the input exposure amount is calculated by performing a case-by-case process according to the magnitude of the output signal level. As an example of processing, the image sensor output is S ₀ (where saturation level = maximum value is S _MAX ), the corrected linear signal is S, and the sensitivity ratio of d pixel to L pixel is r (<1). For example, when
S = S ₀ / (1 + r): However, when S ₀ ≦ (1 + r) · S _MAX / 2 = (S ₀ −S _MAX / 2) / r: However, when S ₀ ≧ (1 + r) · S _MAX / 2 What should I do?
[0036]
In general, it is desirable to partially overlap the exposure amount ranges of the two pixels with different sensitivities, but the exposure amount ranges are overlapped by performing the above-described gradation optimization processing (step S102). Even in this case, it is possible to correctly obtain a linear signal proportional to the input exposure amount and apply it to the γ correction table of the γ correction process (step S103).
[0037]
Next, with reference to FIG. 5, a signal processing operation when non-additive reading is used will be described.
First, the pixel addition drive control unit 112a controls the driving of the CCD image sensor 105 using the CCD driver 106, and normal non-addition readout is performed for reading out each pixel individually (step S111). The image pickup signal read from the CCD image pickup element 105 is A / D converted and then sent to the digital process circuit 108, where an arithmetic process for obtaining wide D range information for each of the multiple pixels is performed. It is executed under the control of 112b.
[0038]
That is, processing for digitally adding signals from two pixels having the same sensitivity arranged diagonally is performed for each of the multiple pixels (step S112), whereby the addition signal between the low sensitivity pixels d and the high sensitivity pixel are processed. An addition signal between L is obtained. Next, a process of synthesizing the addition signal between the low-sensitivity pixels d and the addition signal between the high-sensitivity pixels L is performed for each multiple pixel (step S113). In this synthesis processing, for example, the high-sensitivity output side, which is an addition signal between high-sensitivity pixels L, is mainly used. The process of complementing using the side is performed. Further, in this synthesis process, gain correction processing is performed on the high-sensitivity output and the low-sensitivity output, respectively, as necessary for the purpose of obtaining a linear signal as in step S102. That is, in consideration of the sensitivity ratio r between L and d, a higher gain (relatively 1 / r times) than a high sensitivity output is given to a low sensitivity output. Then, a normal γ correction process (step S114) is performed on the combined signal, and a recorded image is generated through necessary signal processes such as knee, setup, and color balance processing.
[0039]
In addition, the following various embodiments are conceivable.
[0040]
The color arrangement of the image sensor is not limited to a multi-bayer, and any multi-color arrangement may be used. The number of constituent pixels of the multiple pixels is not limited to four, and any number can be used as long as the color arrangement and the pixel density of the image to be generated allow.
[0041]
In addition, when adding pixel information of two types of high and low sensitivities, for example, only addition of two pixels in the vertical direction may be performed inside the element, and horizontal addition may be performed by digital calculation outside the element.
[0042]
The signal processing for generating the filter array and wide D range information according to the present invention can be applied not only to a digital still camera but also to a digital movie.
[0043]
Further, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.
[0044]
【The invention's effect】
As described above, according to the present invention, the dynamic range can be expanded without causing the generation of a false signal, and the image quality can be sufficiently improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a view showing a filter structure of a solid-state imaging device used in the embodiment.
FIG. 3 is a diagram showing an example of luminance range characteristics of a high density filter and a low density filter used in the embodiment.
FIG. 4 is a view for explaining an example of signal processing for generating wide D range information applied to the embodiment;
FIG. 5 is a view for explaining another example of signal processing for wide D range information generation applied to the embodiment;
FIG. 6 is a diagram for explaining a conventional filter arrangement and its problems.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Lens system 102 ... Lens drive mechanism 103 ... Exposure control mechanism 104 ... Filter 105 ... CCD color image sensor 106 ... CCD driver 107 ... Pre-process part 108 ... Digital process part 109 ... Card interface 110 ... Memory card 111 ... LCD image display System 112 ... System controller (CPU)
112a ... Pixel addition drive control unit 112b ... Wide D range information generation control unit 118 ... Non-volatile memory (EEPROM)
LR, LG, LB: Low density filter (high sensitivity pixel)
dR, dG, dB ... high density filter (low sensitivity pixel)

Claims (6)

Color coding is performed by giving a relative spectral sensitivity of the same color to a plurality of pixels which are unit pixel blocks composed of a plurality of adjacent pixels, and giving a predetermined number of different relative spectral sensitivities to each of the plurality of pixels. a single-plate color image pickup device forms, said they were checkered arranged to impart high and low two kinds of sensitivity for a plurality of same color pixels in each multi-pixel, the color array of the imaging device, the multi-pixel Is a double Bayer array in which the pixel block is a 2 × 2 square square block and the color coding array is a Bayer array, and the cross pattern of the diagonal arrangement of the high and low 2 sensitivity checkered arrangement in the multiple pixels is An image sensor that is changed for each multiple pixel . The cross pattern is identical for the same double row, the imaging device according to claim 1, characterized in that configured to vary multiple adjacent rows. The cross pattern is identical for the same double row, the imaging device according to claim 1, characterized in that configured to vary the adjacent double row. The double Bayer array, according to claim 1 to 3 of any one imaging device, wherein said color coding sequence is RGB multi Bayer array where an RGB Bayer array. An imaging element according to any one of claims 1 to 4, a driving means for reading an image signal by driving the imaging device, capable of generating image signal generating means an image signal of a predetermined format based on the imaging signal And image signal generating means configured to generate wide dynamic range information relating to the multiple pixels based on pixel information of two types of high and low sensitivity in the multiple pixels. Imaging device. Pixel addition means for adding pixel information of two types of high and low sensitivities in the multiple pixels is further provided, and the image signal generation means outputs the wide dynamic range information based on the pixel information added by the pixel addition means. The imaging apparatus according to claim 5 , wherein the imaging apparatus is configured to generate the imaging apparatus.

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