JP2020126184A - Imaging device - Google Patents

Abstract

To obtain an imaging device capable of tilt photographing, and with which an angle range in which the tilt angle is adjustable to an optimum angle and the accuracy of adjustment are balanced.SOLUTION: The imaging device comprises: diaphragm control means 102 for controlling the diaphragm of an image-forming optical system 101; an imaging element 103 for outputting an image signal and having an imaging plane on which light via the diaphragm is incident; tilting control means 104 for controlling a tilting angle formed by the imaging forming plane and the principal surface of the image-forming optical system; contrast evaluation value acquisition means 110 for acquiring the contrast evaluation value of a prescribed evaluation frame in the imaging plane; and control means 105 for performing a first tilting angle adjustment operation to adjust the tilting angle by the tilting control means on the basis of a contrast evaluation value when the diaphragm is set to a first diaphragm state, as well as performing a second tilting angle adjustment operation to adjust the tilting angle by the tilting control means on the basis of a contrast evaluation value when the diaphragm after the first tilting angle adjustment operation is set to a second diaphragm state that is opened larger than in the first diaphragm state.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image pickup device.

When the subject surface is tilted with respect to the optical axis of the camera optical system, the optical axis of the optical system should be tilted with respect to the image pickup surface of the image sensor to increase the depth of field along the subject surface. There has been proposed an image pickup apparatus capable of performing so-called tilt shooting.
In Patent Document 1, a contrast evaluation value on both ends of the image pickup surface of the image pickup element in a direction parallel to the tilt direction is acquired, and the tilt angle is changed to a position where the contrast evaluation value is the highest, so that a desired subject surface is obtained. There has been proposed an imaging device that performs adjustment so that it is in focus.

JP, 2017-173802, A

When the focus surface is adjusted using the method disclosed in Patent Document 1, the following problems occur. That is, in general, the darker the F value, the smaller the change in the contrast evaluation value when it deviates from the optimum tilt angle. Therefore, even if the tilt angle is adjusted in a state where the F value is dark, it is difficult to accurately obtain the optimum tilt angle.

On the other hand, when the tilt angle is adjusted while the F-number is bright, the change in contrast is large when the tilt angle deviates from the optimum angle, and therefore the optimum tilt angle can be accurately obtained. However, when the tilt angle is largely deviated from the optimum angle, the contrast evaluation value is buried in noise, and it may be difficult to obtain the optimum angle.
That is, when the method disclosed in Patent Document 1 is used, it is difficult to achieve both the angle range in which the tilt angle can be adjusted to an optimum angle and the tilt angle adjustment accuracy.
An object of the present invention is to provide an image pickup apparatus capable of achieving both an angle range in which the tilt angle can be adjusted to an optimum angle and a tilt angle adjustment accuracy.

The imaging device of the present invention is
A diaphragm control means for controlling the diaphragm of the imaging optical system,
An image pickup device that outputs an image pickup signal having an image pickup surface on which light is incident through the diaphragm,
A tilt control means for controlling a tilt angle which is an angle formed by the imaging surface and the main surface of the imaging optical system,
Contrast evaluation value acquisition means for acquiring a contrast evaluation value of a predetermined evaluation frame in the imaging surface,
The first tilt angle adjusting operation for adjusting the tilt angle by the tilt controlling means is performed based on the contrast evaluation value when the diaphragm is in the first diaphragm state, and after the first tilt angle adjusting operation. Control for performing the second tilt angle adjusting operation for adjusting the tilt angle by the tilt control means based on the contrast evaluation value when the diaphragm is set to the second diaphragm state which is opened more than the first diaphragm state And means.

According to the present invention, it is possible to obtain an image pickup apparatus capable of performing tilting shooting and achieving both an angle range in which the tilting angle can be adjusted to an optimum angle and an adjusting accuracy of the tilting angle. it can.

3 is a block diagram of the image pickup apparatus of Embodiment 1. FIG. It is a figure explaining the focus side and subject side at the time of performing a tilt photography. It is a figure explaining the relationship of the shift of a tilt angle and the gap of a focus surface. It is a figure explaining the evaluation frame of the imaging surface at the time of tilt angle adjustment. It is a figure explaining the relationship between a tilt angle and a contrast evaluation value. 3 is a flowchart of the image pickup apparatus according to the first embodiment. 9 is a flowchart of the image pickup apparatus according to the second embodiment. It is a figure explaining the relation between the tilt angle and the contrast evaluation value for each evaluation frame. 13 is a block diagram of an image pickup apparatus of Example 5. FIG. It is a figure explaining the relationship between an evaluation frame and a depth of focus. 9 is a flowchart of an image pickup apparatus according to a fifth embodiment. 13 is a flowchart of the image pickup apparatus according to the sixth embodiment. It is a figure explaining the relationship between the tilt angle and the contrast evaluation value for each evaluation frame. It is a block diagram of the monitoring system of Example 7.

Hereinafter, the image pickup apparatus according to the embodiment of the present invention will be described with reference to the drawings. In that case, components having the same function are denoted by the same numeral in all the drawings, and the repeated description thereof will be omitted.

FIG. 1 shows a block diagram of the image pickup apparatus in this embodiment. In FIG. 1, the imaging apparatus 100 includes an imaging optical system 101, a diaphragm control mechanism 102 that adjusts the diaphragm of the imaging optical system 101, an imaging element 103, and an tilt control mechanism 104 that rotates the orientation of the imaging element 103. The image pickup element 103 is, for example, a CCD type or CMOS type image pickup element, and has an image pickup surface on which light is incident through the diaphragm of the image forming optical system. The image pickup apparatus 100 also includes a control unit 105 as a control unit that controls the image pickup element 103 and each mechanism. Further, the image sensor 103 includes a contrast evaluation value acquisition unit 110 that acquires a contrast evaluation value of a predetermined area (hereinafter referred to as an evaluation frame) of the image sensor 103 from the image signal acquired by the image sensor 103.
The control unit 105 has a built-in CPU as a computer, and the CPU executes various operations of the entire apparatus based on a computer program stored in a memory (not shown).

The diaphragm control mechanism 102 is composed of a plurality of diaphragm blades, a motor, and a gear. The controller 105 controls the current flowing through the motor to move the diaphragm blades and control the size of the diaphragm aperture.
The tilt control mechanism 104 for rotating the orientation of the image sensor 103 is composed of a motor and a gear. By controlling the current flowing through the motor by the control unit 105, the orientation of the image sensor 103 can be rotated in the XZ plane. ing. The center of rotation is a straight line that passes through the intersection of the optical axis of the imaging optical system 101 and the image sensor 103 and is parallel to the Y axis. In this way, the tilt control mechanism 104 controls the tilt angle, which is the angle formed by the imaging surface of the imaging element and the principal surface of the imaging optical system. The driving of the image sensor 103 and the operation of reading an image signal from the image sensor 103 are controlled by the control unit 105.

FIG. 2 is a diagram for explaining the focus surface 107 when tilting is performed. In this embodiment, tilting is performed by controlling the tilting mechanism of the image pickup device to tilt the image pickup device, but the optical system may be tilted instead of the image pickup device.
In FIG. 2, according to the Scheimpflug principle, the image pickup surface of the image pickup element 103, the main surface 108 of the image forming optical system 101, and the focus surface 107 intersect with each other in a straight line extending in the Y-axis direction. Therefore, the focusing surface 107 is tilted with respect to the main surface 108 of the imaging optical system 101. That is, by performing the tilting photographing, the focus surface 107 can be aligned with the subject surface 109 that is inclined with respect to the main surface 108 of the imaging optical system 101. The angle b between the image pickup surface of the image pickup element 103 and the main surface 108 of the image forming optical system 101 is referred to as a tilt angle.

As shown in FIG. 2, when the angle formed by the optical axis 1140 and the focusing surface 107 is a, the distance between the image sensor 103 and the object is D, and the focal length of the imaging optical system 101 is f, the tilt angle b is It can be calculated by Equation 1.
tan(b)=f÷(D×tan(a)) (Equation 1)

In order to make the subject surface 109 desired to be observed by the user coincident with the focus surface 107, both end sides (FIGS. 2 to 2) of the imaging surface of the imaging device in a direction parallel to the tilt direction (direction along the xz plane of FIG. 2). 4 corresponding to the first evaluation frame 111 and the second evaluation frame 112.), and the tilt angle is changed so that, for example, the sum of the contrast evaluation values of both becomes the highest. With this, it is possible to perform adjustment so that a desired subject surface is brought into focus. In FIG. 2, 111 ′, 112 ′, and 113 ′ on the focus plane 107 are the first evaluation frame 111 and the second evaluation frame which are preset in the image pickup surface (effective image pickup surface) 1000 of the image pickup device. 112, a frame corresponding area corresponding to the third evaluation frame 113 is shown. In addition, as shown in FIG. 4, in the embodiment, the first evaluation frame 111 and the second evaluation frame 112 are arranged on the upper and lower end sides of the imaging surface.

FIG. 5 shows the relationship between the tilt angle and the contrast evaluation value when the F value of the imaging optical system 101 is bright and when it is dark. FIG. 5A shows a case where the F value is bright, that is, the diaphragm is relatively opened, and FIG. 5B shows a case where the F value is dark, that is, the diaphragm is relatively closed.
Generally, the resolving power of the imaging optical system is the highest near the focusing surface, and the resolving power decreases as the distance from the focusing surface increases. Specifically, when the object is sufficiently far, it decreases substantially in proportion to the reciprocal of the distance from the focus surface. Although the resolving power on the focusing surface is slightly shifted due to the influence of aberration and diffraction, it is roughly inversely proportional to the F value of the imaging optical system. Further, the proportional coefficient of the resolving power to the reciprocal of the distance from the focus surface is roughly inversely proportional to the square of the F value of the imaging optical system, although it is slightly shifted due to the influence of aberration and diffraction.

Further, in FIG. 3, the distance ΔD from the focus surface in the frame corresponding regions 111 ′ and 112 ′ corresponding to the first evaluation frame 111 and the second evaluation frame 112 is as follows when the influence of aberration and diffraction is ignored. Can be calculated as
First, the following (Equation 1) holds from the formula of imaging.

ここで、Ｓは、アオリ角度ｂ＝０の時の撮像素子１０３の有効画素領域のＸ軸方向の長さ、Δｂは最適なアオリ角度ｂからのズレ量である。
更に、数２のような近似を使用する。

Here, S is the length in the X-axis direction of the effective pixel area of the image sensor 103 when the tilt angle b=0, and Δb is the amount of deviation from the optimum tilt angle b.
Further, an approximation such as Equation 2 is used.

すると以下の数３が導かれる。

Then, the following equation 3 is derived.

従って、ピント面１０７からの距離のズレである距離ΔＤ＝ΔＤ１＋ΔＤ２は、以下の数４のようにあらわせる。

Therefore, the distance ΔD=ΔD1+ΔD2, which is the deviation of the distance from the focusing surface 107, can be expressed by the following expression 4.

From Equation 4, it can be seen that the larger the amount of deviation from the optimum tilt angle b, the larger the distance ΔD, which is the deviation from the focus surface.
As described above, the resolving power of the imaging optical system is highest near the focusing surface, and the resolving power decreases as the distance from the focusing surface increases. Specifically, when the object is sufficiently far, it decreases substantially in proportion to the reciprocal of the distance from the focus surface. Although the resolving power on the focusing surface is slightly shifted due to the influence of aberration and diffraction, it is roughly inversely proportional to the F value of the imaging optical system. Further, the proportional coefficient of the resolving power to the reciprocal of the distance from the focus surface is roughly inversely proportional to the square of the F value of the imaging optical system, although it is slightly shifted due to the influence of aberration and diffraction.
On the other hand, from Equation 4, the larger the amount of deviation from the optimum tilt angle, the greater the distance ΔD from the focus surface 107. Therefore, as shown in FIG. 5, the brighter the F value, the higher the contrast evaluation value at the optimum tilt angle, and the darker the F value, the higher the contrast evaluation value when the tilt angle deviates from the optimum tilt angle.
As a result, the following tradeoffs occur.

As shown in FIG. 5A, when the F value is bright, the degree of decrease in the contrast evaluation value is large when the F-value deviates from the optimum tilt angle. Therefore, when the tilt angle before adjustment largely deviates from the optimum tilt angle, even if the tilt angle is changed, the change in the contrast evaluation value is buried in the noise level. As a result, if the tilt angle before adjustment deviates significantly from the optimum tilt angle, it becomes difficult to search for the optimum tilt angle. In other words, when the F value is bright, the angle range 1130 in which the tilt angle can be adjusted to the optimum angle (hereinafter, referred to as “tilt angle adjustable range”) becomes narrow.

On the contrary, as shown in FIG. 5B, when the F value is dark, the contrast evaluation value when the F angle is deviated from the optimum tilt angle is higher than when the F value is bright. Therefore, the darker the F value, the larger the angle range 1130 in which the tilt angle can be adjusted.
On the other hand, when the F value is dark, there arises a problem that the deviation between the adjusted tilt angle and the optimum tilt angle becomes large. This is because when the F value is dark, the degree of decrease in the contrast evaluation value when the deviation from the optimum tilt angle is small, and the peak detection error 114 of the contrast evaluation value increases.

On the other hand, when the F value is bright, the degree of decrease in the contrast evaluation value is large when it deviates from the optimum tilt angle, and therefore the peak detection error 114 of the contrast evaluation value becomes small. That is, the brighter the F value is, the higher the adjustment accuracy of the tilt angle (hereinafter, referred to as “tilt angle adjustment accuracy”) can be.
As described above, there is a trade-off between the tilt angle adjustment range and the tilt angle adjustment accuracy. In the image pickup apparatus 100 of the present embodiment, by controlling the diaphragm control mechanism 102 of the imaging optical system 101 in accordance with the amount of angular deviation from the optimum tilt angle, both the tilt angle adjustment range and the tilt angle adjustment accuracy are compatible. It is possible. Specifically, when the amount of angular deviation from the optimum tilt angle is large, the F value is made dark to increase the tilt angle adjustment range. Adjust the tilt angle in the dark F value, and after the angle deviation from the optimum tilt angle becomes small, brighten the F value and adjust the tilt angle again to increase the tilt angle adjustment accuracy. To do. Further description will be given below.

FIG. 6 shows a flowchart of tilt angle adjustment in the image pickup apparatus 100 of the present embodiment.
In step S600, it is determined whether the contrast evaluation value is higher than a predetermined level X1 as illustrated in FIGS. 5A and 5B, and if Yes, the process proceeds to step S603 described later. The contrast evaluation value in step S600 may be the total or average value of the contrast evaluation values of the frames 111 and 112, but may be determined based on the contrast value of only one. This is because almost the same contrast value should be obtained. In the case of No, in step S601, the aperture control mechanism 102 is controlled to bring the aperture of the imaging optical system 101 into the relatively closed first aperture state (first F number).
Next, in step S602 (first tilt angle adjusting operation), the contrast evaluation value is obtained while changing the tilt angle. Then, the tilt angle is adjusted in the direction parallel to the tilt direction to maximize the total or average of the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 on both ends of the imaging surface of the image sensor. ..

Subsequently, in step S603, by controlling the aperture control mechanism 102, the aperture of the imaging optical system 101 is set to a second aperture state (second F number) that is wider than the first aperture state.
Then, in step S604 (second tilt angle adjusting operation), the contrast evaluation value is obtained while changing the tilt angle again. Furthermore, the tilt angle at which the sum or the average value of the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 on both end sides of the imaging surface of the image sensor in the direction parallel to the tilt direction becomes the largest Explore.

As described above, the darker the F value is, the larger the tilt angle adjustment range is. Therefore, in step S602 in which the tilt angle is adjusted in a dark F value (a state in which the diaphragm is closed), the tilt angle largely deviates from the optimum tilt angle. The tilt angle can be adjusted even when That is, the image pickup apparatus 100 of the present embodiment can increase the tilt angle adjustment range.
On the other hand, as the F value is brighter, the tilt angle adjustment accuracy is higher. Therefore, in step S604, the deviation between the adjusted tilt angle and the optimum tilt angle can be suppressed to be small. As described above, when the F value is bright (when the diaphragm is open), the tilt angle adjustment range becomes small. Therefore, only in step S604, when the tilt angle greatly deviates from the optimum tilt angle, Adjusting the tilt angle becomes difficult.

In the image pickup apparatus 100 of the present embodiment, in step S602, the tilt angle is once adjusted in a state where the F value is relatively dark to suppress the deviation from the optimum tilt angle. As a result, in step S604 where the tilt angle adjustment range is narrower than step S602, tilt adjustment with high tilt angle adjustment accuracy is possible.
As described above, in the image pickup apparatus 100 of the present embodiment, the tilt angle adjustment range and the tilt angle adjustment accuracy are compatible by adjusting the tilt angle as shown in the flowchart of FIG.

If the tilt angles at which the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 are the largest are different in steps S602 and S604, the average angle may be set as the optimum value of the tilt angle. Alternatively, the tilt angle may be adjusted so that the average value or the total value of the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 becomes the largest. Further, the reliability of the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 may be obtained, and the one having higher reliability may be weighted to determine the optimum tilt angle. Specifically, the one in which the number of textures that exist is large or the SN ratio of the image signal is high may be considered to have high reliability.

In order to increase the tilt angle adjustment range, it is preferable that the first diaphragm state set in step S601 has a diaphragm aperture as small as possible. Specifically, it is better to match the state in which the diaphragm aperture of the imaging optical system 101 is most narrowed. For example, a value between 16 and 64 is used for the F value with the diaphragm being in the most narrowed state. That is, it is desirable that the first diaphragm state is a state in which the diaphragm of the imaging optical system is most narrowed.
Similarly, in order to improve the tilt angle adjustment accuracy, it is preferable to open the diaphragm aperture as much as possible in the second diaphragm state set in step S603. That is, it is desirable that the second diaphragm state is a state in which the diaphragm of the imaging optical system is opened.

Since the F-number of the imaging optical system 101 is changed in step S602 and step S604, the amount of light incident on the pixel in the image sensor 103 is different. Therefore, in steps S602 and S604, the exposure amount (output signal level) is made substantially the same by controlling the storage time and sensitivity (gain) of the image sensor. Specifically, in step S604, the storage time of the image sensor is shortened or the sensitivity (gain) value is reduced in comparison with step S602. That is, the storage time of the image sensor in step S604 (second tilt angle adjustment operation) is controlled to be shorter than the storage time of the image sensor in step S602 (first tilt angle adjustment operation). Alternatively, the sensitivity of the image sensor in step S604 is controlled to be lower than the sensitivity of the image sensor in step S602.

In FIG. 6, two types of diaphragm states are used, such as performing tilt adjustment in the first diaphragm state and then performing tilt adjustment in the second diaphragm state. However, three or more types of diaphragm states may be used. As the diaphragm is closed, the tilt angle adjustment range is wider, and as the diaphragm is opened, the tilt angle adjustment accuracy is higher. Good.

As described above, as the diaphragm is closed, the resolving power of the imaging optical system 101 is less likely to be lowered when deviating from the optimum tilt angle. Therefore, when the contrast evaluation value is lower than X1, that is, when the deviation from the optimum tilt angle is large, the tilt angle is adjusted with the diaphragm relatively closed, so that the tilt angle is adjusted with the diaphragm open from the beginning. In comparison with the case, the image quality acquired during the tilt adjustment is improved.
On the other hand, as the diaphragm is opened, the resolving power of the imaging optical system 101 at the optimum tilt angle becomes higher. Therefore, when the deviation from the optimum tilt angle is small, the tilt angle is adjusted with the diaphragm relatively open, so that the tilt angle is obtained after the tilt adjustment as compared to the case where the tilt angle is adjusted until the F value is dark. The image quality is improved.
That is, according to the image pickup apparatus 100 of the present embodiment, the control unit 105 adjusts the tilt angle by the tilt control means based on the contrast evaluation value with the diaphragm of the imaging optical system in the first diaphragm state. The tilt angle adjustment operation is performed. Then, after the first tilt angle adjusting operation, the tilt control means is controlled by the tilt control means on the basis of the contrast evaluation value in a state where the diaphragm of the imaging optical system is set to a second diaphragm state which is wider than the first diaphragm state. A second tilt angle adjusting operation for adjusting the tilt angle is performed. As a result, in addition to achieving both the tilt angle adjustment range and the tilt angle adjustment accuracy, it is possible to achieve both the image quality during tilt adjustment and after the tilt adjustment.

The block configuration of the image pickup apparatus 200 (not shown) of the second embodiment is the same as that of the image pickup apparatus 100 of the first embodiment, and only the position of the evaluation frame used when adjusting the tilt angle is different. FIG. 7 is a flowchart of the second embodiment. In FIG. 7, the same reference numerals as those in FIG.
The image capturing apparatus 100 according to the first embodiment acquires the contrast evaluation values on both ends of the image capturing surface of the image sensor in the direction parallel to the tilt direction in both step S602 and step S604 of FIG. Then, the tilt angle is changed to a position where the sum or average of both contrast evaluation values is the highest.

On the other hand, as shown in FIG. 7, the imaging apparatus 200 acquires the contrast evaluation value from the imaging signal of the first evaluation frame 111 in step S702 (first tilt angle adjustment), and the contrast evaluation value becomes the highest. Change the tilt angle to the position. Then, in step S704 (second tilt angle adjustment), the contrast evaluation value is acquired from the image pickup signal of the second evaluation frame 112 in which the distance from the image pickup device to the subject surface is relatively shorter than that of the first evaluation frame. , The tilt angle is changed to the position where the contrast evaluation value is the highest. As a result, the tilt angle adjustment range can be further widened and the tilt angle adjustment accuracy can be improved with respect to the image pickup apparatus 100 of the first embodiment.

In general, when the distance to the subject is sufficiently large, the size of the circle of confusion of the imaging optical system is inversely proportional to the square of the distance. Therefore, as shown in the graph of the contrast evaluation value normalized by the peak in FIG. 8, the contrast evaluation value when the tilt angle is changed is smaller in the second evaluation frame 112 than in the first evaluation frame 111. The change will be large. That is, the tilt angle adjustment accuracy is higher when the contrast evaluation value of the second evaluation frame 112 is used. However, when the contrast evaluation value of the first evaluation frame 111 is used, the degree of decrease in the contrast evaluation value when the difference between the current tilt angle and the optimum tilt angle becomes large is small, so the tilt angle adjustment is performed. Wide range.

Therefore, the difference between the current tilt angle and the optimum tilt angle is large, and in step S702 (first tilt angle adjustment) for adjusting the tilt angle by darkening the F value, the contrast evaluation value of the first evaluation frame 111 is adjusted. Use to adjust the tilt angle. On the other hand, in step S704 (second tilt angle adjustment) for adjusting the tilt angle by brightening the F value, the tilt angle is adjusted using the contrast evaluation value of the second evaluation frame 112.
As described above, by controlling the area for obtaining the contrast evaluation value in addition to the F value of the imaging optical system 101, the tilt angle adjustment range can be further expanded and the tilt angle adjustment accuracy can be improved.

Further, in the image pickup apparatus of the third embodiment, the tilt angle adjustment is further speeded up by changing the signal reading operation from the image pickup element. This will be described below. In the following, a case will be described in which a CMOS image sensor of a method of sequentially reading image signals for each row is used as the image sensor 103.
Generally, there are three major factors that control the length of time for reading an image pickup signal for one frame from a CMOS image sensor.

The first is the driving time of the pixel circuit (hereinafter, pixel circuit driving time) for converting the light incident on each pixel into an image pickup signal and reading the image pickup signal to the vertical signal line provided for each column. The second is the time for reading the image pickup signal output from each pixel circuit with respect to the vertical signal line provided for each column at a timing shifted for each row (hereinafter, image pickup signal read time). is there. Therefore, the rate-determined time due to the second factor becomes shorter as the number of rows from which the image pickup signal is read is smaller.
The third is a time (hereinafter, an image pickup signal output time) for outputting an image pickup signal for one row, which is sequentially read for each row, to the outside of the image pickup device. Therefore, the rate-determined time due to the third factor becomes shorter as the number of columns from which the image pickup signal is read is smaller. When a CMOS image sensor having an analog-to-digital conversion function is used, there is a rate-determining factor such as the time for analog-digitalizing the image pickup signals for one column. However, this rate-determining factor becomes shorter as the number of columns from which the image pickup signal is read out is shorter, and is therefore included in the third factor.

Therefore, the length of time for reading the image pickup signal for one frame is determined by the product of the longer one of the pixel circuit drive time and the image pickup signal output time and the image pickup signal read time. The magnitude relationship between the pixel circuit drive time and the length of the image pickup signal output time depends on the image pickup element.
Even when the same image sensor is used, the magnitude relationship between the pixel circuit drive time and the length of the image signal output time differs depending on the drive mode of the image sensor. That is, when the number of columns for reading the image pickup signal is larger than the specific number of columns, the image pickup signal output time is longer, and when the number of columns for reading the image pickup signal is smaller than the specific number of columns, the pixel circuit drive is performed. The time is longer.
From the above, regardless of the image sensor to be used and the drive mode of the image sensor, the smaller the number of rows of the image signal to be read, the shorter the length of time to read the image signal for one frame. Further, depending on the image sensor to be used and the drive mode of the image sensor, the product of the number of rows of the image signal to be read and the number of columns of the image signal to be read, that is, the smaller the number of image signals to be read, the more the image signal for one frame is The read time is short.

Therefore, in the third embodiment, by reading the image pickup signal only from the range of the evaluation frame for obtaining the contrast evaluation value, the length of time for reading the image pickup signal for one frame can be shortened. The angle adjustment can be speeded up.
Specifically, the first range in which the imaging signal is read in step S702 is a partial area in the imaging surface including at least the first evaluation frame 111. That is, for example, only the image pickup signal of the first evaluation frame 111 (and the area in the vicinity thereof) is read. In addition, the second range in which the image pickup signal is read in step S704 is a partial area in the image pickup surface including at least the second evaluation frame 112. That is, for example, only the image pickup signal of the second evaluation frame 112 (and the area in the vicinity thereof) is read.
In order to read only a part of the image pickup signal from the image pickup device, a horizontal scanning circuit that drives the pixel circuit and outputs the image pickup signal to the outside of the image pickup device, and a vertical scanning circuit that reads the image pickup signal to a vertical signal line, A skip function may be provided.

In the third embodiment, the image pickup signal from the area other than the evaluation frame (and the vicinity thereof) is not read at each of the focus position adjustment and the tilt angle adjustment. However, by reading from both the evaluation frame (and its vicinity) and from other than the evaluation frame (and its vicinity), and changing the read pitches of both, the length of time for reading one frame of imaging signal is increased. May be controlled.
Specifically, in step S702, all the image pickup signals in the first evaluation frame 111 may be read, and the image pickup signals may be thinned out and read from other than the first evaluation frame 111. Further, in step S704, all the image pickup signals in the second evaluation frame 112 may be read, and the image pickup signals may be thinned out and read from other than the evaluation frame 112.

In this way, the read pitch of the image pickup signal read from other than the evaluation frame (and its vicinity) is made coarser than the read pitch of the image pickup signal read from the evaluation frame (and its vicinity). As a result, the length of time for reading the image pickup signals for one frame can be shortened as compared with the case of reading all the image pickup signals. In addition, when the image pickup signal from the area other than the evaluation frame (and its vicinity) is not read, it means that the read pitch of the image pickup signal read from other than the evaluation frame (and its vicinity) is equal to or longer than a predetermined value. Become.

That is, specifically, in the fourth embodiment, in step S702, the sampling pitch for reading the image pickup signal from outside the first range is made larger than the sampling pitch for reading the image pickup signal from the first range. Then, in step S704, the sampling pitch for reading the image pickup signal from outside the second range is made larger than the sampling pitch for reading the image pickup signal from the second range. By doing so, the image information can be acquired while speeding up the tilt angle adjustment.

It should be noted that the number of image signals to be read may be reduced (the sampling pitch may be increased) by adding or averaging a plurality of image signals without thinning the image signals, or by performing a combination of thinning and addition. The number of image pickup signals may be reduced. Note that it is preferable to add or average the plurality of image pickup signals because the SN ratio of the image is improved as compared with the case where the image pickup signals are simply thinned out.

The image pickup apparatus 300 of the fifth embodiment shown in FIG. 9 is different from the image pickup apparatus 100 of the first embodiment in that the imaging optical system 101 includes a focus control mechanism 106 for controlling the focus position. .. The focus control mechanism 106 adjusts the focus position of the imaging optical system 101 by moving the focus lens in the optical axis direction using a drive mechanism such as a stepping motor.
In the image pickup apparatus 300, not only the diaphragm of the imaging optical system but also the focus position is controlled to further expand the tilt angle adjustment range. Hereinafter, description will be made in comparison with a conventional imaging device.
In the image pickup apparatus 300 of the present embodiment, the focus position is set so that the contrast evaluation value of the second evaluation frame 112 corresponding to the subject surface closer to the image pickup apparatus than the center of the image pickup surface of the image pickup element becomes the largest. After adjusting, adjust the tilt angle.

FIG. 10 is a diagram illustrating the depth of focus depth along the optical axis direction of the imaging optical system 101 in the area of the first evaluation frame 111 and the area of the second evaluation frame 112 during tilt shooting. Is. As can be seen from FIG. 10, the depth of focus 317 of the region 112′ corresponding to the subject surface where the distance from the imaging device to the subject surface is short is the same as that of the region 111′ corresponding to the subject surface where the distance from the imaging device to the subject surface is long. The depth of focus is shallower than the depth of focus 316.
That is, when the tilt angle before adjustment deviates from the optimum tilt angle, the object plane 112 ′ corresponding to the second evaluation frame 112 is the area 111 of the object surface corresponding to the first evaluation frame 111. The contrast evaluation value is more likely to be lower than that of ′′. Therefore, if the focus position is adjusted by giving priority to the center of the image pickup surface of the image pickup device, the contrast evaluation value of the second evaluation frame 112 is below the noise level when the deviation from the optimum tilt angle is large. Adjusting the tilt angle becomes difficult.

Therefore, in the image pickup apparatus of the present embodiment, the focus position is prioritized in the second evaluation frame 112 corresponding to the area 112′ of the subject plane that is closer to the image pickup apparatus than the center of the image pickup surface of the image pickup element. adjust. Therefore, even when the deviation from the optimum tilt angle is large, the decrease in the contrast evaluation value of the first evaluation frame 111 is small, so that the tilt angle can be adjusted. That is, the tilt angle adjustment range of the image pickup apparatus of the present embodiment can be wider than that of the conventional image pickup apparatus.
FIG. 11 shows a flowchart of tilt angle adjustment using the image pickup apparatus 300 according to the fifth embodiment. First, in step S1100, it is determined whether the total or average of the contrast evaluation values of the evaluation frames 111, 112, 113 is larger than a predetermined level X1, and if Yes, the process proceeds to step S1104, and if No, the process proceeds to step S1101. .. The contrast evaluation value in step S1100 may be based on any one of the contrast evaluation values of the evaluation frames 111 to 113, or may be the sum or average of any two. In step S1101, the focus position of the imaging device 300 is adjusted so that the contrast evaluation value of the second evaluation frame 112 becomes the largest (first focus position adjusting operation). Next, in step S1102, the aperture is set to the first aperture state (first F number). After that, in step S1103 (first tilt angle adjusting operation), the tilt angle is adjusted so that the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 are maximized. By suppressing the deviation of the focus position and the tilt angle from the optimum values in steps S1101 to S1103, it is possible to adjust the tilt angle with high accuracy after step S1104.

In step S1104, the aperture opening is set to the second aperture state (second F number) that is larger than the first aperture state (large F value), and then the focus position is set again in step S1105 (second focus position adjustment). Adjust. In step S1105, unlike step S1101, the focus position is adjusted so that the contrast evaluation value of the evaluation frame (third evaluation frame 113 in FIG. 10) corresponding to the center of the imaging surface of the image sensor is maximized. Finally, in step S1106 (second tilt angle adjustment), the tilt angle is adjusted so that the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 are maximized. As described above, by controlling not only the diaphragm of the imaging optical system but also the focus position, the tilt angle can be adjusted with high accuracy while further expanding the tilt angle adjusting range.

The block configuration of the image pickup apparatus 400 (not shown) of the sixth embodiment is the same as that of the image pickup apparatus 300 of the third embodiment. However, in the image pickup apparatus 400 of the sixth embodiment, the focus position and the tilt are adjusted sequentially, and then the focus and the tilt are adjusted simultaneously.
FIG. 12 is a flowchart illustrating a flow of focus position adjustment and tilt angle adjustment using the image pickup apparatus 400 according to the sixth embodiment.
First, in step S1200, it is determined whether the sum or average of the contrast evaluation values of the evaluation frames 111 to 113 is larger than a predetermined level X1, and if Yes, the process proceeds to step S1204, and if No, the process proceeds to step S1201. The contrast evaluation value in step S1200 may be based on any one of the contrast evaluation values of the evaluation frames 111 to 113, or may be the sum or average value of any two. After the diaphragm aperture is set to the first diaphragm state (first F number) in step S1201, the contrast evaluation values of the first evaluation frame 111 and the second evaluation frame 112 are set to be the largest in step S1202. , The tilt angle is adjusted (first tilt angle adjusting operation). After that, in step S1203, the focus position is adjusted so that the contrast evaluation value of the third evaluation frame 113 at the center of the imaging surface of the image sensor becomes the highest. As described above, by suppressing the deviations of the tilt angle and the focus position from the optimum values in steps S1201 to S1203, it is possible to simultaneously adjust the focus position and the tilt angle with high accuracy after step S1204.

In step S1204, the diaphragm aperture is set to a second diaphragm state (second F value) that is wider than the first diaphragm state (large F value). After that, in step S1205, while simultaneously driving the focus lens and controlling the tilt angle, by obtaining all the contrast evaluation values of the first evaluation frame 111, the second evaluation frame 112, and the third evaluation frame 113, Adjust focus and tilt at the same time.
Specifically, the focus control mechanism and the tilt control mechanism are controlled so that the average of the contrast evaluation values of the first to third evaluation frames 111 to 113 becomes maximum. In this way, while simultaneously moving the focus control mechanism and the tilt control mechanism, by acquiring the contrast evaluation value of each evaluation frame, the focus and tilt can be adjusted at the same time, so focus and tilt can be adjusted in a short time. It will be possible.

When the focus position and the tilt angle before the adjustment are largely deviated from the optimum values, it is difficult to suddenly adjust the focus and the tilt simultaneously using steps S1204 and S125 without performing steps S1201 to S1203. .. The reason will be described below.
When the focus position and the tilt angle before the adjustment are largely deviated from the optimum values, the tilt angle at which the contrast evaluation value of the first evaluation frame 111 is maximum and the contrast evaluation value of the second evaluation frame 112 are maximum. The deviation of the tilt angle is large. Further, the difference between the tilt angle at which the contrast evaluation value of the first evaluation frame 111 is maximum, the intermediate value between the tilt angles at which the contrast evaluation value of the second evaluation frame 112 is maximum, and the optimum tilt angle is large. turn into.

FIG. 13 shows a specific example. FIG. 13 shows contrast evaluation values of the first and second evaluation frames 111 and 112 when the tilt angle is changed. As can be seen from FIG. 13, the tilt angle at which the contrast evaluation value of the first evaluation frame 111 is maximum and the intermediate value between the tilt angle at which the contrast evaluation value of the second evaluation frame 112 is maximum and the optimum tilt angle. The difference with is increasing.
Therefore, when the deviations of the focus position and the tilt angle before the adjustment from the optimum values are large, that is, when the total or average value of the contrast evaluation values of the evaluation frames 111 and 112 is lower than the predetermined level X1, the step is performed. S1201 to S1203 are performed. Then, it is necessary to suppress the deviation of the focus position and the tilt angle from the optimum tilt angle. As described above, in the imaging apparatus 400 according to the sixth embodiment, the contrast and tilt are independently adjusted in a dark F value to suppress the deviation of the focus position and tilt angle from the optimum tilt angle, and then the F value is changed. Brighten to adjust the focus position and tilt angle at the same time. As a result, in addition to achieving both the tilt angle adjustment range and the tilt angle adjustment accuracy, it becomes possible to adjust the focus and tilt in a short time.

In a seventh embodiment, a monitoring system (imaging system) 600 using the imaging device shown in the first to sixth embodiments will be described. FIG. 14 is a configuration diagram of a monitoring system (imaging system) 600 using the imaging device 500 according to the first to sixth embodiments. The imaging device and the client device 501 are connected via a network 502 so that they can communicate with each other. The client device 501 transmits various commands for controlling the imaging device 500. In response to this, the imaging device 500 transmits the response to the command and the captured image data to the client device 501. The user can select via the client device 501 whether or not to drive the imaging device 500 in the depth of field priority mode.
The client device 501 is an external device such as a PC, and the network 502 is configured by a wired LAN, a wireless LAN, or the like. Further, the power may be supplied to the imaging device 500 via the network 502.

The present invention is not limited to the above-mentioned embodiment, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.
Further, part or all of the control in this embodiment may be supplied to the image pickup apparatus and the image pickup control apparatus via a network or various storage media, a computer program realizing the functions of the above-described embodiment. Then, a computer (or a CPU, MPU, or the like) in the image pickup apparatus or the image pickup control apparatus may read out and execute the program. In that case, the program and the storage medium storing the program constitute the present invention.

100, 200, 300, 400, 500: Imaging device 101: Imaging optical system 102: Aperture control mechanism 103: Imaging device 104: Tilt control mechanism 105: Control unit 106: Focus control mechanism 107: Focus surface 108: Imaging optics Main surface 109 of system: Subject surface 110: Contrast evaluation value acquisition unit 111: First evaluation frame 112: Second evaluation frame 113: Third evaluation frame 600: Monitoring system (imaging system)
501: Client device 502: Network

Claims (14)

A diaphragm control means for controlling the diaphragm of the imaging optical system,
An image pickup device that outputs an image pickup signal having an image pickup surface on which light is incident through the diaphragm,
A tilt control means for controlling a tilt angle which is an angle formed by the imaging surface and the main surface of the imaging optical system,
Contrast evaluation value acquisition means for acquiring a contrast evaluation value of a predetermined evaluation frame in the imaging surface,
The first tilt angle adjusting operation for adjusting the tilt angle by the tilt controlling means is performed based on the contrast evaluation value when the diaphragm is in the first diaphragm state, and after the first tilt angle adjusting operation. Control for performing the second tilt angle adjusting operation for adjusting the tilt angle by the tilt control means based on the contrast evaluation value when the diaphragm is set to the second diaphragm state which is opened more than the first diaphragm state And an image pickup device. The image pickup apparatus according to claim 1, wherein the first diaphragm state is a state in which the diaphragm is most narrowed. The image pickup apparatus according to claim 1, wherein the second diaphragm state is a state in which the diaphragm is opened. 4. The accumulation time of the image sensor in the second tilt angle adjusting operation is shorter than the accumulation time of the image sensor in the first tilt angle adjusting operation. The imaging device described. 4. The gain of the image sensor in the second tilt angle adjusting operation is smaller than the gain of the image sensor in the first tilt angle adjusting operation. Imaging device. In the first tilt angle adjusting operation, the tilt angle is adjusted so that the contrast evaluation value of the predetermined first evaluation frame on the imaging surface becomes the largest, and in the second tilt angle adjusting operation, The tilt angle is adjusted so that the contrast evaluation value of the second evaluation frame in the imaging surface corresponding to the subject surface closer to the imaging device than the first evaluation frame is the largest. The image pickup apparatus according to claim 1. In the first tilt angle adjusting operation, an image pickup signal is read from a first range which is a partial area including the first evaluation frame, and in the second tilt angle adjusting operation, the second evaluation frame. The image pickup apparatus according to claim 6, wherein the image pickup signal is read out from a second range which is a partial region including the. In the first tilt angle adjusting operation, the sampling pitch for reading the image pickup signal from outside the first range is larger than the sampling pitch for reading the image pickup signal from the first range, and the second tilt angle adjusting operation is performed. In the above, the image pickup apparatus according to claim 6, wherein the sampling pitch for reading the image pickup signal from outside the second range is larger than the sampling pitch for reading the image pickup signal from the second range. A contrast evaluation value of a predetermined evaluation frame corresponding to a subject surface closer to the image pickup device than the center of the image pickup surface of the image pickup device is provided, further comprising focus control means for adjusting the focus of the imaging optical system. 6. The first tilt angle adjusting operation is performed after the first focus position adjusting operation for adjusting the focus position so as to be the largest. 6. Imaging device. After performing the first tilt angle adjusting operation, after performing the focus position adjusting operation of adjusting the focus position so that the contrast evaluation value of the evaluation frame in the center of the image pickup surface of the image pickup device becomes the largest, The image pickup apparatus according to claim 9, wherein the tilt angle adjusting operation of 2 is performed. Further, it has a focus control means for adjusting the focus position of the image forming optical system, and when performing the tilt angle adjustment in the second tilt angle adjusting operation, a third evaluation of the center of the image pickup surface of the image pickup device is performed. 9. The image pickup apparatus according to claim 1, wherein the focus position is controlled so that the contrast evaluation value of the frame becomes maximum. A monitoring system using the image pickup device according to claim 1. A computer program for causing a computer to function as each unit of the image pickup apparatus according to claim 1. A computer-readable storage medium storing the computer program according to claim 13.

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