JP2014123067A - Image capturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image capturing device capable of appropriately determining a focusing condition of a focusing lens.SOLUTION: A focusing lens 103 moves from a start point A through a near point B to a far point C, and then returns to the start point A. A curve representing positional change of the focusing lens 103 is called a position curve. Contrast cyclically changes during a period in which the focusing lens 103 moves. An image capturing device determines as to whether the device focuses on an object or not and whether an in-focus direction is toward the far point or the near point in accordance with an integrated value in which a composite function obtained by combining the position curve and a contrast curve is integrated.

Description

  The present invention relates to an imaging apparatus having an autofocus function.

  2. Description of the Related Art An imaging apparatus having an autofocus function that automatically focuses a photographing lens on a subject is known. Such an imaging apparatus uses an autofocus system called a hill-climbing system. In the hill-climbing method, the focusing lens is reciprocated by a certain amount of movement in the optical axis direction to detect the focusing state, and the direction closer to the focusing state is determined as the focusing direction of the focusing lens. Then, the in-focus state is determined by moving the focusing lens in the focusing direction. This is repeated to focus the focusing lens on the subject. The amount of movement is obtained based on the aperture value or gain of the lens, and the in-focus state is determined by peak detection of the high frequency component of the luminance signal (Cited document 1).

JP 2008-170508 A

  However, in the method of obtaining the movement amount based on the aperture value or gain of the lens, the set movement amount may not be the minimum necessary movement amount. If the movement amount is not the minimum necessary, the focus lens is moved unnecessarily, and the time until focusing is increased. For this reason, there is a risk of missing a photo opportunity or recording an out-of-focus moving image. Furthermore, in the method of determining the in-focus state by peak detection of the high frequency component of the luminance signal, there is a possibility that peak detection cannot be performed appropriately.

  The present invention has been made in view of these problems, and an object thereof is to obtain an imaging apparatus capable of appropriately determining the focus state of a focus lens.

  An imaging apparatus according to the present invention uses an imaging unit that captures a subject image and outputs image data, a focusing unit that moves in a focusing direction and focuses the subject image on the imaging unit, and a contrast of the image data. A focusing unit that determines a focusing direction, and the focusing unit moves to a distant point that is a predetermined distance away from the starting point and a near point that is a predetermined distance away from the starting point. The unit outputs image data at a predetermined time interval during the period when the in-focus part is moving, and the control unit contrasts during the period during which the in-focus part is moving from the start point, the far point, and the near point. The in-focus state of the subject image in the imaging unit is determined based on an integrated value obtained by integrating a synthesis function obtained by synthesizing the change in position and the position of the in-focus portion.

  The control unit preferably determines whether or not the subject image is focused on the imaging unit.

  The control unit preferably determines the in-focus direction.

  The control unit preferably determines that the subject image is focused on the imaging unit when the integral value is within a predetermined range.

  As for the position of the in-focus part, the control unit determines the direction of the contrast from the starting point to the far point as the positive direction, the direction from the starting point to the near point as the negative direction, and the contrast as the origin from the current contrast as the origin. When the integral value is positive, the direction toward the far point can be determined as the in-focus direction, and when the integral value is negative, the direction toward the near point can be determined as the in-focus direction. preferable.

  According to the present invention, an imaging apparatus that can appropriately determine the focus state of a focus lens is obtained.

It is the block diagram which showed the imaging device roughly. It is the graph which showed the relationship between contrast and the position of a focusing lens. It is the graph which showed the relationship between a contrast curve and a lens position curve. It is the graph which showed the synthetic | combination function of a contrast curve and a lens position curve. It is the graph which showed the relationship between contrast and the position of a focusing lens. It is the graph which showed the relationship between a contrast curve and a lens position curve. It is the graph which showed the synthetic | combination function of a contrast curve and a lens position curve. It is the graph which showed the relationship between a contrast curve and a lens position curve. It is the graph which showed the composite function of a contrast curve and a lens position curve. It is the flowchart which showed the moving image recording process. It is the flowchart which showed AF standby processing. It is the flowchart which showed the drive process.

  An imaging apparatus according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a digital camera 100 that is an embodiment of an imaging apparatus. The configuration of the digital camera 100 will be described with reference to FIG.

  The digital camera 100 includes a DSP 101 that forms a control unit, an image pickup device (CCD) 102 that forms an image pickup unit, an image pickup lens 104 that includes a focusing lens 103, a diaphragm 105 that adjusts the amount of light irradiated to the image pickup device 102, and a shutter curtain 106. And mainly. The focusing lens 103 forms a focusing unit, and is driven in the optical axis direction by the lens driving unit 111 to adjust the focus of the imaging lens 104 and form a subject image on the imaging element 102. The optical axis direction is the focusing direction of the imaging lens 104.

  When the user presses the release button 107 halfway, the DSP 101 determines whether or not focus is achieved using the contrast of the image data. If the image is out of focus, the focus direction of the focusing lens 103 is determined using the contrast of the image data, and the lens driving unit 111 drives the focusing lens 103 to focus on the subject. The position of the focusing lens 103 where the subject is in focus is called the focusing position, and the current position of the focusing lens 103 is called the starting point. The direction from the starting point toward the in-focus position is referred to as the in-focus direction. The driving direction of the focusing lens 103 that focuses on a distant subject is called a far direction, and the driving direction of the focusing lens 103 that focuses on a near subject is called a near direction. A point that is a predetermined distance away from the starting point is called a far point, and a point that is a predetermined distance away from the starting point is called a near point.

  When the user fully presses the release button 107, the image sensor 102 captures a subject image and outputs image data. The image data is transmitted to the image processing circuit 108, and the image processing circuit 108 performs various image processing on the image data and transmits the image data to the DSP 101, the memory card 109, and the monitor 110. The DSP 101 performs various processes based on the image data received from the image processing circuit 108. Then, image data to be stored and left is transmitted to the memory card 109. The monitor 110 displays the image data received from the image processing circuit 108. The memory card 109 is an SD card, for example, and stores image data received from the DSP and the image processing circuit 108.

  Next, a process for focusing the subject image on the image sensor 102 during the period during which a moving image is captured will be described with reference to FIGS. When a moving image is captured, the focusing lens 103 reciprocates in the optical axis direction, the image sensor 102 captures image data at regular intervals, and the DSP 101 receives the image data and calculates contrast.

  Referring to FIG. 2, the focusing lens 103 moves from the starting point A through the near point B to the far point C and then returns to the starting point A. This movement by the focusing lens 103 is referred to as one reciprocation of the focusing lens 103. Here, the starting point A is the in-focus position, and the near point B and the far point C are points separated from the starting point A by 100.

  FIG. 3 shows the relationship between the contrast change and the position of the focusing lens 103. In FIG. 3, the left vertical axis indicates the position of the focusing lens 103, the right vertical axis indicates the contrast value, and the horizontal axis indicates the detection time. The position of the focusing lens 103 is positive in the far direction from the starting point A and negative in the near direction. The focusing lens 103 moves by −100 from the starting point A at the coordinate 0, that is, moves by 100 in the near direction and reaches the near point B, and then moves by 200, that is, moves by 200 in the far direction. Point C is reached. Then, it moves by 100 in the near direction and returns to the starting point A. A curve indicating the position change of the focusing lens 103 is referred to as a position curve. The contrast changes periodically during the period in which the focusing lens 103 moves. That is, the contrast decreases from the starting point A toward the near point B, increases as it approaches the starting point A from the near point B, decreases as it moves from the starting point A toward the far point C, and increases as it goes from the far point C to the starting point A. . A curve indicating a change in contrast is called a contrast curve.

  FIG. 4 shows a synthesis function obtained by synthesizing the position curve and the contrast curve shown in FIG. If the composite function is integrated with respect to detection times 0 to 35, the integrated value obtained is zero. Thus, it can be seen that the amount of contrast change from the starting point A through the near point B to the starting point A is equal to the amount of contrast change from the starting point A through the far point C to the starting point A. Therefore, it can be determined that the starting point A is the in-focus position. Even if the integrated value is not 0, it can be determined that the starting point A is the in-focus position when it is within a predetermined range. The predetermined range is determined based on the pixel size of the image sensor 102 or the like.

  Next, a process for focusing the subject image on the image sensor 102 in a situation where the starting point A is not at the in-focus position will be described with reference to FIGS.

  Referring to FIG. 5, the focusing lens 103 moves from the starting point A through the far point C to the near point B, and returns to the starting point A. This movement by the focusing lens 103 is referred to as one reciprocation of the focusing lens 103. Here, the starting point A is not the in-focus position, and the near point B and the far point C are points separated from the starting point A by 100.

  FIG. 6 shows the relationship between the contrast change and the position of the focusing lens 103. In FIG. 6, the left vertical axis indicates the position of the focusing lens 103, the right vertical axis indicates the contrast value, and the horizontal axis indicates the detection time. The focusing lens 103 moves by 100 from the starting point A at the coordinate 0, that is, moves by 100 in the far direction and reaches the far point C, and then moves by -200, that is, moves by 200 in the near direction. Point B is reached. Then, it moves by 100 in the far direction and returns to the starting point A. The contrast decreases from the starting point A toward the far point C, increases from the far point C through the starting point A to the near point B, and decreases from the near point B toward the starting point A.

  FIG. 7 shows a synthesis function obtained by synthesizing the position curve and the contrast curve shown in FIG. If the composite function is integrated with respect to detection times 0 to 35, the resulting integrated value is negative. Thus, it can be seen that the amount of contrast change from the starting point A through the far point C to the starting point A is not equal to the amount of contrast change from the starting point A through the near point B to the starting point A. Therefore, it can be determined that the starting point A is not the in-focus position. Further, since the integral value is negative, it can be seen that the in-focus position is in the negative direction, that is, in the near direction from the starting point A.

  Next, a process for focusing the subject image on the image sensor 102 in the actual digital camera 100 will be described with reference to FIGS. In the actual digital camera 100, since it is technically impossible to move the focusing lens 103 smoothly and continuously change the position of the focusing lens 103, the position curve and the contrast curve are shown in FIG. It does not become a continuous curve as shown in. Here, description will be made using a position curve and a contrast curve assuming the actual digital camera 100.

  Referring to FIG. 5, the focusing lens 103 moves from the starting point A through the far point C to the near point B, and returns to the starting point A. Here, the starting point A is not the in-focus position, and the near point B and the far point C are points separated from the starting point A by 100.

  FIG. 8 shows the relationship between the contrast change and the position of the focusing lens 103. In FIG. 8, the left vertical axis indicates the position of the focusing lens 103, the right vertical axis indicates the contrast value, and the horizontal axis indicates the detection time. The focusing lens 103 moves by 100 from the starting point A at the coordinate 0, that is, moves by 100 in the far direction and reaches the far point C, and then moves by -200, that is, moves by 200 in the near direction. Point B is reached. Then, it moves by 100 in the far direction and returns to the starting point A. The contrast decreases from the starting point A toward the far point C, increases from the far point C through the starting point A to the near point B, and decreases from the near point B toward the starting point A.

  FIG. 9 shows a synthesis function obtained by synthesizing the position curve and the contrast curve shown in FIG. If the composite function is integrated with respect to detection times 0 to 35, the resulting integrated value is negative. Thus, it can be seen that the amount of contrast change from the starting point A through the far point C to the starting point A is not equal to the amount of contrast change from the starting point A through the near point B to the starting point A. Therefore, it can be determined that the starting point A is not the in-focus position. Further, since the integral value is negative, it can be seen that the in-focus position is in the negative direction, that is, in the near direction from the starting point A.

  Therefore, it can be seen that the method shown in FIG.

  Next, the moving image recording process will be described with reference to FIG. The moving image recording process is a process executed by the DSP 101, and is repeatedly executed while recording a moving image.

  In the first step S101, it is determined whether or not to continue recording a moving image. If the recording is continued, the process proceeds to step S102. If the recording is not continued, the process ends.

  In the next step S102, AF standby processing is executed. The AF standby process is a process for determining the in-focus state based on the integral value, and determines the next moving direction of the focusing lens 103. The AF standby process will be described later.

  In the next step S103, AF processing is executed. The AF process is a process of driving the focusing lens 103 according to the moving direction of the focusing lens 103 determined by the AF standby process. After the AF process ends, the process returns to step S101 again.

  The AF standby process executed by the DSP 101 will be described with reference to FIG. The AF standby process is a process executed by the DSP 101 and is a process for determining the in-focus state based on the integral value. Determining the in-focus state means determining whether or not the subject image is in focus on the image sensor 102 and determining the in-focus direction.

  In the first step S111, a drive process described later is executed. The driving process is a process for obtaining an integrated value by creating a position curve and a contrast curve.

  In the next step S112, it is determined whether or not the absolute value of the integrated value obtained by integrating the integrated value obtained in step S111 is within a predetermined range. As described above, the predetermined range is determined based on the pixel size of the image sensor 102 or the like. If it is within the predetermined range, it is determined that the focusing lens 103 is in the in-focus position, and the process executes step S111 again. If it is not within the predetermined range, it is determined that the focusing lens 103 is not in the focusing position, and the process proceeds to step S113.

  In step S113, the sign of the integrated value is determined. When the sign is positive, the process proceeds to step S114, and when the sign is negative, the process proceeds to step S115.

  In step S114, the next moving direction of the focusing lens 103 is set to the far direction, and in step S115, the next moving direction of the focusing lens 103 is set to the near direction. Then, the process proceeds to step S116.

  In step S116, assuming that the next movement direction has been determined, the process ends.

  The driving process will be described with reference to FIG. The driving process is a process executed by the DSP 101, and is a process for creating an alignment value by creating a position curve and a contrast curve.

  In the first steps S121 and S122, the focusing lens 103 is moved by a predetermined movement amount at predetermined time intervals. That is, in step S121, the next position of the focusing lens 103 is acquired, and in step S122, the next position of the focusing lens 103 is transmitted to the lens driving unit 111 so that the lens driving unit 111 drives the focusing lens 103. .

  In the next step S123, image data is acquired from the image sensor 102, and contrast is calculated based on the image data. A contrast curve is created together with the contrast acquired so far.

  In step S124, the position of the focusing lens 103 is acquired from the lens driving unit 111, and a position curve is created together with the positions acquired so far.

  In step S125, a composite function of the contrast curve and the position curve is created.

  In step S126, an integrated value is calculated by integrating the composite function.

  In step S127, it is determined whether or not the focusing lens 103 has reciprocated once. If it has not made a round trip, the process returns to step S121, and steps S121 to S127 are executed again. In the case of one reciprocation, the process proceeds to step S128, and the focusing lens 103 is stopped at the current position. Then, the process ends.

  According to the present embodiment, the in-focus state of the focusing lens 103 can be appropriately determined. In addition, since the in-focus direction can be accurately predicted, the in-focus lens 103 is not driven in a direction opposite to the in-focus direction. This also allows the subject to be focused quickly. Furthermore, by using the integral value, the in-focus direction can be predicted even if the distance in which the in-focus lens 103 is reciprocated is shortened.

  In addition, although the case where the moving image is imaged has been described in the present embodiment, the processing according to the present embodiment can be executed also when the still image is imaged.

  Note that a CMOS may be used as the image sensor 102.

  Moreover, although the far direction is described as positive and the near direction is negative, the far direction may be negative and the near direction may be positive.

100 Digital camera 101 DSP
102 Image sensor (CCD)
DESCRIPTION OF SYMBOLS 103 Focus lens 104 Image pickup lens 106 Shutter curtain 107 Release button 108 Image processing circuit 109 Memory card 110 Monitor 111 Lens drive part

Claims (5)

An imaging unit that captures a subject image and outputs image data;
A focusing unit that moves in a focusing direction and focuses the subject image on the imaging unit;
A control unit that determines the in-focus direction using the contrast of the image data,
The in-focus portion moves from a starting point to a distant point away from the starting point by a predetermined distance, and from the starting point to a near point separated from the starting point by the predetermined distance,
The imaging unit outputs image data at predetermined time intervals during a period in which the focusing unit is moving,
The control unit integrates a composite function obtained by synthesizing the change in contrast and the position of the in-focus portion during a period in which the in-focus portion is moving from the starting point, the far point, and the near point. An imaging apparatus that determines a focused state of a subject image in the imaging unit based on an obtained integrated value.   The imaging apparatus according to claim 1, wherein the control unit determines whether or not a subject image is focused on the imaging unit.   The imaging device according to claim 1, wherein the control unit determines the in-focus direction.   The imaging device according to claim 1, wherein the control unit determines that a subject image is focused on the imaging unit when the integral value is within a predetermined range. With respect to the position of the focusing unit, the control unit sets the direction from the starting point to the far point as a positive direction, and sets the direction from the starting point to the near point as a negative direction, and regarding the contrast, the current contrast Is used as an origin to determine whether the contrast is positive or negative, and when the integral value is positive, the direction toward the far point is determined as the in-focus direction, and when the integral value is negative, the near point The imaging apparatus according to claim 1, wherein a direction toward the camera is determined as a focusing direction.

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