JP2021067704A - Imaging device - Google Patents

Abstract

To provide a structure with which it is possible to achieve an auto-focus function without utilizing luminance information.SOLUTION: While the focus position of a light-receiving lens 22 is adjusted by an adjustment mechanism 23, a point density is calculated that is equivalent to the density of points when the two-dimensional point data of a plurality of event data outputted from an imaging element 21 in a given period is plotted respectively as points to a prescribed plane. Then, when the point density is calculated, the drive of the adjustment mechanism 23 is controlled by a control unit 11 on the basis of the result of comparison of said point density with the previously calculated point density, and the focus position is thereby adjusted toward an in-focus position.SELECTED DRAWING: Figure 6

Description

The present invention relates to an imaging device.

In recent years, an event camera disclosed in Patent Document 1 below is known as a technique for generating an image of a measurement object at a higher speed. This event camera is a brightness value difference output camera developed by taking inspiration from the retinal structure of living organisms, so that it senses the change in brightness for each pixel and outputs its coordinates, time, and polarity of the change in brightness. It is configured. With such a configuration, the event camera has a feature that it does not output pixel information that does not change in brightness, that is, redundant data like a conventional camera, so that it is possible to reduce the amount of data communication and the weight of image processing. By doing so, it is possible to generate an image of the measurement object at a higher speed.

U.S. Patent Application Publication No. 2016/0227135

By the way, in the image data acquired by a normal camera, each pixel always has some kind of luminance information, and an autofocus function using the luminance information is installed in many cameras as a standard function. On the other hand, in the event camera, even if the event data corresponding to the change in the brightness can be acquired, the brightness information itself cannot be acquired, so that the autofocus function using the brightness information cannot be adopted. For this reason, even with an event camera, if the object to be measured is blurred because it is out of focus, the light of the object to be measured is dispersed and the event data cannot be obtained accurately. is there.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a configuration capable of realizing an autofocus function without using luminance information.

In order to achieve the above object, the imaging device (10) according to the invention according to claim 1 of the claims is
An image sensor (21) that outputs event data including two-dimensional point data in which the position of the pixel is specified corresponding to a pixel whose brightness has changed when light is received through the light receiving lens (22).
An adjustment mechanism (23) for adjusting the focal position of the light receiving lens, and
A control unit (11) that drives and controls the adjustment mechanism, and
With the focal position of the light receiving lens adjusted by the adjustment mechanism, the two-dimensional point data of the plurality of event data output from the image sensor within a certain period of time are plotted on a predetermined plane as points. The point density calculation unit (11) that calculates the point density corresponding to the density of the points at the time, and
With
When the point density is calculated by the point density calculation unit, the control unit drives and controls the adjustment mechanism based on the comparison result between the point density and the point density calculated in the past. It is characterized by adjusting the focal position toward the in-focus position.
The reference numerals in the parentheses indicate the correspondence with the specific means described in the embodiments described later.

In the invention of claim 1, in a state where the focal position of the light receiving lens is adjusted by the adjusting mechanism, two-dimensional point data of a plurality of event data output from the image pickup element within a certain period of time is set as a point on a predetermined plane. The point density corresponding to the density of the points when plotted is calculated by the point density calculation unit. Then, when the point density is calculated by the point density calculation unit, the adjustment mechanism is driven and controlled by the control unit based on the comparison result between the point density and the point density calculated in the past, so that the focal position is adjusted. Adjusted towards the focus position.

When two-dimensional point data of multiple event data output from the image sensor within a certain period of time is plotted on a predetermined plane as points in a state of being out of focus (a state in which the focus position is out of focus). Since the edge of the object to be measured becomes unclear, the point data tends to vary. On the other hand, two-dimensional point data of a plurality of event data output from the image sensor within a certain period of time in a focused state (a state in which the focal position matches the in-focus position) are set as points on a predetermined plane. When plotted, the edge of the object to be measured becomes clear, so that the point density of the two-dimensional point data becomes high. That is, the smaller the amount of focus shift, the higher the point density of the two-dimensional point data.

Therefore, when a comparison result is obtained in which the point density calculated this time is higher than the point density calculated in the past, the adjustment direction is maintained assuming that the focal position is adjusted toward the in-focus position. The adjustment mechanism is driven and controlled so as to be performed. If a comparison result is obtained in which the point density calculated this time is lower than the point density calculated in the past, it is assumed that the focal position is adjusted to be away from the in-focus position, and the adjustment direction is reversed. The adjustment mechanism is driven and controlled so as to switch to. In this way, since the focus position can be adjusted by using the event data, the autofocus function can be realized without using the luminance information.

In the invention of claim 2, when the point density is calculated by the point density calculation unit, the adjustment mechanism is adjusted by the control unit only when the difference between the point density and the point density calculated in the past is equal to or more than a predetermined value. Is driven and controlled. As a result, the adjustment mechanism is not driven when the difference between the point density calculated this time and the point density calculated in the past is less than the above-mentioned predetermined value, that is, for example, when the focus is almost in focus. , Unnecessary adjustment of the focal position can be suppressed.

In the invention of claim 3, the number of event data output from the image sensor is counted by the counting unit within a certain period of time, and the point density is calculated by the point density calculating unit when the counted number exceeds a predetermined number. Will be done. As a result, when the number of event data is less than the above-mentioned predetermined number, that is, when noise is detected even though the measurement target does not exist, the point density is not calculated, so that the adjustment mechanism is unnecessarily driven. It is possible to suppress unnecessary adjustment of the focal position without being done.

In the invention of claim 4, the point density calculation unit plots either one of the two-dimensional point data of the event data of the positive brightness change and the two-dimensional point data of the event data of the negative brightness change as points on a predetermined plane. The point density is calculated so as to correspond to the density of the points at the time. In the in-focus state, the two-dimensional point data of the positive brightness change and the two-dimensional point data of the negative brightness change are likely to be clustered separately, so the two-dimensional point data of the positive brightness change and the negative brightness change are two. By distinguishing from the dimension point data and calculating the point density for either one, the adjustment accuracy can be further improved.

In the invention of claim 5, the point density calculation unit divides the predetermined plane into a predetermined number of blocks, and for each block in which the number of event data is equal to or greater than the predetermined number, a value corresponding to the point density is set for each block. The point density is calculated by calculating and averaging. By calculating the value corresponding to the point density for the blocks in which the number of event data is equal to or more than the predetermined number in this way, the processing load is reduced as compared with the case of calculating the value corresponding to the point density for all the blocks. Not only that, blocks that contain only noise can be excluded from the calculation. As a result, the point density can be calculated appropriately, and the adjustment accuracy can be further improved.

It is a block diagram which shows the schematic structure of the image pickup apparatus which concerns on 1st Embodiment. It is explanatory drawing explaining the shape of the measurement object. FIG. 3A is an explanatory diagram illustrating a state in which two-dimensional point data obtained by imaging while moving the measurement object shown in FIG. 2 to the imaging device side in a state in which the focus is substantially in focus is plotted. Yes, FIG. 3 (B) is an enlarged view showing an enlarged portion X1 of FIG. 3 (A). FIG. 4A is an explanatory diagram illustrating a state in which two-dimensional point data obtained by imaging while moving the measurement object shown in FIG. 2 to the imaging device side in a state of being out of focus is plotted. Yes, FIG. 4 (B) is an enlarged view showing an enlarged portion X2 of FIG. 4 (A). It is explanatory drawing explaining the state which plotted a part of the 2D point data output by adjusting a focal position when a measurement object is not moving. It is a flowchart which illustrates the flow of the focus position adjustment process performed in the control part of an image pickup apparatus.

[First Embodiment]
Hereinafter, the first embodiment embodying the image pickup apparatus of the present invention will be described with reference to the drawings.
The imaging device 10 according to the present embodiment is a device that functions as a so-called event camera. The image pickup device 10 outputs event data so as to include two-dimensional point data in which the position of the pixel is specified corresponding to the pixel whose brightness has changed, time, and the polarity of the brightness change, and within a certain period of time. By plotting the two-dimensional point data of the plurality of output event data as points on a predetermined plane, image data obtained by capturing an image of the measurement target is generated.

As shown in FIG. 1, in addition to a control unit 11 including a CPU and the like and a storage unit 12 including a semiconductor memory and the like, the image pickup apparatus 10 responds to an input operation and a display unit 13 whose display contents are controlled by the control unit 11. It includes an operation unit 14 that outputs the operation signal to the control unit 11, a communication unit 15 for communicating with an external device, and the like.

Further, the image pickup device 10 includes an image pickup element 21, a light receiving lens 22, an adjustment mechanism 23, and the like as an image pickup unit. The image sensor 21 outputs event data including two-dimensional point data in which the position of the pixel is specified corresponding to the pixel whose brightness has changed when the light is received through the light receiving lens 22 to the control unit 11. It is configured in. That is, the image sensor 21 outputs event data (two-dimensional point data, time, polarity of brightness change) corresponding to the pixel whose brightness has changed to the control unit 11, and does not output data for the pixel whose brightness has not changed. Works for. The adjustment mechanism 23 is a known mechanism for adjusting the focal position of the light receiving lens 22, and is driven and controlled by the control unit 11 to move the light receiving lens 22 to one side (adjustment direction) along the optical axis or another. By moving it to the side, the focal position of the light receiving lens 22 is adjusted.

In the image pickup device 10 configured in this way, the focus position of the light receiving lens 22 is directed to the in-focus position by using the event data output from the image sensor 21 by the focus position adjustment process performed by the control unit 11. It will be adjusted automatically.

Hereinafter, the focal position adjustment process performed by the control unit 11 will be described in detail with reference to the drawings. Note that FIG. 2 is an explanatory diagram illustrating the shape of the measurement object R. FIG. 3A is an explanatory diagram illustrating a state in which point data obtained by imaging while moving the measurement object R shown in FIG. 2 to the imaging device 10 side in a state in which the focus is substantially in focus is plotted. Yes, FIG. 3 (B) is an enlarged view showing an enlarged X1 portion corresponding to one block of FIG. 3 (A). FIG. 4A is an explanatory diagram illustrating a state in which point data obtained by imaging while moving the measurement object R shown in FIG. 2 to the imaging device 10 side in a state of being out of focus is plotted. Yes, FIG. 4 (B) is an enlarged view showing an enlarged X2 portion corresponding to one block of FIG. 4 (A).

Since the event data output from the image sensor 21 to the control unit 11 does not include the luminance information, it is not possible to perform autofocus using the luminance information. Therefore, in the present embodiment, in the focal position adjustment process performed by the control unit 11, two-dimensional point data of a plurality of event data output from the image sensor 21 within a certain period of time is plotted on a predetermined plane as points. The point density corresponding to the density of the points is calculated, and the focal position of the light receiving lens 22 is adjusted so that the point density becomes high. The control unit 11 that performs the process of calculating the point density may correspond to an example of the “point density calculation unit”.

Specifically, for example, the predetermined plane is divided into a predetermined number of blocks, and for blocks in which the number of event data is equal to or greater than the predetermined number, the nearest neighborhood distance method is used based on the following equation (1). The average nearest neighbor distance W is calculated for each two-dimensional point data for each block, and the average value of each average nearest neighbor distance W is calculated as the point density. Then, the focal position of the light receiving lens 22 is adjusted so that the calculated point density becomes high.

The reason for adjusting the focal position of the light receiving lens 22 so that the point density calculated in this way becomes high will be described below.
Two-dimensional point data of a plurality of event data output from the image sensor 21 within a certain period of time in a state of being out of focus (a state in which the focus position is out of focus) are plotted on a predetermined plane as points. In this case, since the edge of the measurement object becomes unclear, the point data tends to vary. On the other hand, a predetermined plane with two-dimensional point data of a plurality of event data output from the image sensor 21 within a certain period of time in a focused state (a state in which the focal position matches the in-focus position) as points. When plotted in, the edge of the object to be measured becomes clear, so that the point density of the two-dimensional point data becomes high.

For example, when the light receiving lens 22 is moved to adjust the focal position, and as shown in FIG. 2, a state in which a black circular measurement object R is moving toward the imaging device 10 is imaged on a white background. Is assumed. In such an imaging state, since the black circle is imaged so as to gradually increase with respect to the white background, two-dimensional point data of a negative luminance change can be obtained at the edge portion of the measurement object R. Become. Here, when the focus is almost in focus, the edge portion of the measurement object R becomes clear, so that the line corresponding to the actual edge portion is shown in FIGS. 3A and 3B (FIG. 3). Two-dimensional point data having a relatively high point density can be obtained along the alternate long and short dash line of 3 (B). On the other hand, when the object is out of focus, the edge portion of the measurement object R becomes unclear. Therefore, as shown in FIGS. 4 (A) and 4 (B), a line corresponding to the actual edge portion ( Two-dimensional point data having a relatively low point density can be obtained so as to deviate from the alternate long and short dash line in FIG. 4 (B). That is, as can be seen from FIGS. 3 and 4, the smaller the amount of focus shift, the higher the point density of the two-dimensional point data.

Further, even when the object to be measured is not moving, the light receiving lens 22 is moved to adjust the focal position, so that the brightness changes at a position corresponding to the edge portion of the object to be measured. Event data is output according to the change. For example, when a white measurement object is imaged on a black background, as shown in FIGS. 5A to 5E, an edge portion serving as a boundary between the measurement object and the background (see reference numeral E in FIG. 5). Then, a plurality of two-dimensional point data of negative brightness change (see the black square in FIG. 5) and two-dimensional point data of positive brightness change (see the white square in FIG. 5) are obtained.

At that time, if the focus is significantly out of focus, the edge portion becomes unclear and the gray color range has a predetermined width. Therefore, as shown in FIG. 5 (A), the edge portion is in contact with the black range of the gray color range. Two-dimensional point data of minus brightness change is obtained in the part where there is, and two-dimensional point data of plus brightness change is obtained in the part in contact with the white range of the gray color range. When the focal position is adjusted toward the in-focus position, the width of the gray color range changes narrowly. Therefore, as shown in FIG. 5 (B), the two-dimensional point data of the negative luminance change. The group and the two-dimensional point data group of the plus brightness change are acquired so as to approach each other. Further, since the focal position is adjusted so as to move toward the in-focus position, as shown in FIG. 5C, the two-dimensional point data group of the negative brightness change and the two-dimensional point data group of the positive brightness change are separated. When it gets closer and the focal position almost coincides with the in-focus position, as shown in FIG. 5 (D), the two-dimensional point data group of the negative brightness change and the two-dimensional point data group of the positive brightness change are on the actual edge portion. Obtained to be located in. Then, when the focal position moves beyond the in-focus position, as shown in FIG. 5 (E), the positions of the two-dimensional point data group of the negative luminance change and the two-dimensional point data group of the positive luminance change are changed. Obtained to be swapped. In this way, even when the object to be measured is not moving, the point density of the two-dimensional point data becomes high and the focal position becomes high when the focal position almost coincides with the in-focus position (see FIG. 5 (D)). The point density of the two-dimensional point data decreases as the distance from the in-focus position increases.

Therefore, in the present embodiment, in the focus position adjustment process performed by the control unit 11, the two-dimensionality calculated when the focus position is adjusted so as to move the light receiving lens 22 by driving and controlling the adjustment mechanism 23. The adjustment direction of the light receiving lens 22 is controlled based on the point density of the point data. Specifically, when the point density calculated this time is higher than the point density calculated in the past, the adjustment direction is maintained assuming that the focal position is adjusted toward the in-focus position, and the calculation is performed this time. When the point density is lower than the point density calculated in the past, the adjustment direction is switched to the opposite side assuming that the focal position is adjusted to be away from the in-focus position.

Hereinafter, the focus position adjustment process performed by the control unit 11 will be described in detail with reference to the flowchart shown in FIG.
When the focus position adjustment process is started by the control unit 11, the light receiving lens 22 is moved in a predetermined direction (for example, one side in the adjustment direction) according to the drive control of the adjustment mechanism 23, and the focus position is adjusted (for example, one side in the adjustment direction). S101), the plot data creation process shown in step S103 is performed. In this process, two-dimensional point data of a plurality of event data output from the image sensor 21 within a certain period (for example, 100 μs) are plotted as points on a predetermined plane.

Next, the point density calculation process shown in step S105 is performed, and the average value of each average nearest neighbor distance W calculated for each block for each point plotted as described above is calculated as the point density.

Subsequently, in the determination process of step S107, it is determined whether or not the point density calculated this time is higher than the previously calculated point density stored in the storage unit 12 as will be described later. The determination process is not limited to comparing the point density calculated this time with the point density calculated last time, and may be compared with, for example, the point density calculated two times before. That is, in the above determination process, the point density calculated this time and the point density calculated in the past are compared.

Here, if the point density calculated this time is higher than the point density calculated last time (Yes in S107), it is assumed that the focal position is adjusted toward the in-focus position as described above, and the light is received. The adjustment mechanism 23 is driven and controlled so that the moving direction of the lens 22 is maintained (S109). Then, after the point density calculated this time is stored in the storage unit 12 as the previously calculated point density (S113), the process from step S103 is performed.

On the other hand, if the point density calculated this time is lower than the point density calculated last time (No in S107), it is assumed that the focal position is adjusted to be away from the in-focus position as described above, and the light receiving lens The moving direction of 22 can be switched to the opposite direction (if it is moved to one side of the adjusting direction, the other side of the adjusting direction) (S111). Then, after the point density calculated this time is stored in the storage unit 12 as the previously calculated point density (S113), the process from step S103 is performed.

By adjusting the focal position so that the point density becomes higher in this way, the focal position is in a state of substantially matching the focusing position, and the position of the light receiving lens 22 is stabilized. More precisely, the light receiving lens 22 moves slightly back and forth in a state where the focal position substantially coincides with the in-focus position.

As described above, in the image sensor 10 according to the present embodiment, in the focal position adjusting process performed by the control unit 11, the focal position of the light receiving lens 22 is adjusted by the adjusting mechanism 23 within a certain period of time. A point density corresponding to the density of points when two-dimensional point data of a plurality of event data output from the image sensor 21 is plotted on a predetermined plane as points is calculated. Then, when the point density is calculated, the adjustment mechanism 23 is driven and controlled by the control unit 11 based on the comparison result between the point density and the previously calculated point density, so that the focal position is directed to the in-focus position. Is adjusted.

That is, when a comparison result is obtained in which the point density calculated this time is higher than the point density calculated last time, the adjustment direction is maintained assuming that the focal position is adjusted toward the in-focus position. The adjustment mechanism 23 is driven and controlled as described above. If a comparison result is obtained in which the point density calculated this time is lower than the point density calculated last time, it is assumed that the focal position is adjusted to be away from the in-focus position, and the adjustment direction is reversed. The adjustment mechanism 23 is driven and controlled so as to switch. In this way, since the focus position can be adjusted by using the event data, the autofocus function can be realized without using the luminance information.

In particular, since the focus position is adjusted using the event data, it is not necessary to separately provide an optical system or the like for adjusting the focus position, so that the image pickup device 10 capable of realizing the autofocus function can be miniaturized. Further, since the amount of pixel data to be handled is smaller than that of the contrast AF of the conventional camera, the data transfer time can be shortened, so that the processing speed can be increased. Further, since it is not necessary to perform luminance conversion or luminance information acquisition for autofocus, the drive control of the adjustment mechanism 23 required for autofocus can be performed at a higher speed. Then, it is possible to secure the superiority of autofocus on a moving measurement object, which the contrast AF of the conventional camera is not good at. In the case of an event camera, the amount of data to be processed is small because only the edge peripheral information of a moving measurement object can be obtained, and the movement of the measurement object is detected due to the high frame rate that the event data is output in microsecond units. This is because the time from that to autofocus can be shortened.

Further, in the present embodiment, for the blocks in which the predetermined plane is divided into a predetermined number of blocks and the number of event data is equal to or more than the predetermined number, a value corresponding to the point density is calculated and averaged for each block. The point density is calculated with. By calculating the value corresponding to the point density for the blocks in which the number of event data is equal to or more than the predetermined number in this way, the processing load is reduced as compared with the case of calculating the value corresponding to the point density for all the blocks. Not only that, blocks that contain only noise can be excluded from the calculation. As a result, the point density can be calculated appropriately, and the adjustment accuracy can be further improved.

The present invention is not limited to the above embodiment, and may be embodied as follows, for example.
(1) In the focal position adjustment process performed by the control unit 11, two-dimensional point data of a plurality of event data output from the image sensor 21 within a certain period is plotted on a predetermined plane for convenience of explanation. The above point density is calculated, but the present invention is not limited to this, and the above point density may be calculated directly from the two-dimensional point data without plotting. Further, even if the number of event data output from the image sensor 21 within a certain period is counted by the control unit 11 functioning as a counting unit, and the point density is calculated when the counted number becomes a predetermined number or more. Good. As a result, when the number of event data is less than the above-mentioned predetermined number, that is, when noise is detected even though the measurement target does not exist, the point density is not calculated, so that the adjustment mechanism 23 is unnecessary. It is not driven, and unnecessary adjustment of the focal position can be suppressed.

(2) In the focal position adjustment process performed by the control unit 11, the above point density is calculated using the nearest neighbor distance method, but the point density is not limited to this, and other calculation methods such as the K function method and the kernel are used. The above point density may be calculated using the method. Further, in the focal position adjustment process performed by the control unit 11, the values calculated for each block with respect to the point density are averaged and calculated as the above point density, but the present invention is not limited to this, and the image sensor is not limited to this. The point density may be calculated from the two-dimensional point data of all the event data output from 21 by using the nearest neighbor distance method or the like.

(3) In the focal position adjustment process performed by the control unit 11, when the difference between the point density calculated this time and the point density calculated last time in the determination process of step S107 is equal to or greater than a predetermined value, Yes. If it is determined, the processes after step S109 may be performed. That is, when the point density is calculated by the point density calculation process, the adjustment mechanism 23 is driven and controlled only when the difference between the point density and the point density calculated in the past is equal to or greater than the predetermined value. As a result, the adjustment mechanism 23 is not driven when the difference between the point density calculated this time and the point density calculated in the past is less than the above-mentioned predetermined value, that is, for example, when the focus is almost in focus. Therefore, unnecessary adjustment of the focal position can be suppressed.

(4) In the point density calculation process in the focal position adjustment process described above, a predetermined plane is set with either one of the two-dimensional point data of the event data of the positive brightness change and the two-dimensional point data of the event data of the negative brightness change as points. The point density may be calculated so as to correspond to the density of the points when plotted in. For example, when the number of output of the two-dimensional point data of the positive brightness change is larger than the number of outputs of the two-dimensional point data of the negative brightness change, the positive brightness change is not considered without considering the two-dimensional point data of the negative brightness change. The point density is calculated so as to correspond to the density of the points when the two-dimensional point data are plotted on a predetermined plane as points. In the in-focus state, the two-dimensional point data of the positive brightness change and the two-dimensional point data of the negative brightness change are likely to be clustered separately, so the two-dimensional point data of the positive brightness change and the negative brightness change are two. By distinguishing from the dimension point data and calculating the point density for either one, the adjustment accuracy can be further improved.

10 ... Imaging device 11 ... Control unit (point density calculation unit)
21 ... Image sensor 22 ... Light receiving lens 23 ... Adjustment mechanism

Claims (5)

An image sensor that outputs event data including two-dimensional point data that specifies the position of the pixel corresponding to the pixel whose brightness has changed when the light is received through the light receiving lens.
An adjustment mechanism for adjusting the focal position of the light receiving lens and
A control unit that drives and controls the adjustment mechanism,
With the focal position of the light receiving lens adjusted by the adjustment mechanism, the two-dimensional point data of the plurality of event data output from the image sensor within a certain period of time are plotted on a predetermined plane as points. A point density calculation unit that calculates the point density corresponding to the density of the points at the time,
With
When the point density is calculated by the point density calculation unit, the control unit drives and controls the adjustment mechanism based on the comparison result between the point density and the point density calculated in the past. An imaging device characterized in that the focal position is adjusted toward the in-focus position. When the point density is calculated by the point density calculation unit, the control unit drives the adjustment mechanism only when the difference between the point density and the point density calculated in the past is equal to or more than a predetermined value. The imaging device according to claim 1, wherein the imaging device is controlled. A counting unit for counting the number of event data output from the image sensor within a certain period of time is provided.
The imaging device according to claim 1 or 2, wherein the point density calculation unit calculates the point density when the number counted by the counting unit is equal to or greater than a predetermined number. The image sensor is configured to output event data of a positive luminance change in the case of a brightening luminance change and output event data of a negative luminance change in the case of a darkening luminance change.
When the point density calculation unit plots one of the two-dimensional point data of the positive brightness change event data and the two-dimensional point data of the negative brightness change event data as points on the predetermined plane. The imaging apparatus according to any one of claims 1 to 3, wherein the point density is calculated so as to correspond to the density of the points. The point density calculation unit divides the predetermined plane into a predetermined number of blocks, calculates a value corresponding to the point density for each block for blocks in which the number of event data is equal to or greater than the predetermined number, and averages them. The imaging apparatus according to any one of claims 1 to 4, wherein the point density is calculated by the operation.

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