JP6843558B2 - Lens control device, its control method - Google Patents

Description

The present invention relates to a lens control device that controls the drive of a focus lens. It also relates to the control method.

Conventionally, in order to realize stable AF, a technique for determining whether or not the subject to be focused has been switched has been known. In Patent Document 1, the AF frame, which is the range for focusing detection, is based on the amount of deviation between the current focus lens position calculated from the focus detection result by the phase difference detection method and the focus lens position in which the subject is in focus. It is determined whether or not the subject has been switched.

Japanese Unexamined Patent Publication No. 2006-10756

According to the method of Patent Document 1, for example, even when the subject is temporarily removed from the AF frame during panning, it is possible to determine whether or not the subject has been switched. However, especially when the distance between the image pickup device and the subject is long, if the focus detection result by the phase difference detection method varies, it may be determined that the subject has been switched to another subject even though it is the same subject. It was.

Therefore, an object of the present invention is to provide a lens control device capable of more accurately determining whether or not a subject has been switched, as compared with the prior art.

The present invention provides a focus detecting means for detecting a defocus amount based on a pair of image signals obtained by receiving and photoelectrically converting a pair of light beams having a parallax that has passed through a photographing optical system including a focus lens and the focal point. It has a control means for controlling the drive of the focus lens based on the focus detection result by the detection means, and a determination means for determining whether or not the subject has been switched based on the distance from the focus to the subject based on the defocus amount. However, in the determination means, the ratio of the distance from the focal point to the subject to the depth of view is equal to or greater than the second predetermined value based on the depth of view, and the amount of change in the distance from the focal point to the subject is the third. When it is equal to or more than a predetermined value, it is determined that the subject has been switched.

As another aspect, the present invention detects the amount of defocus based on a pair of image signals that the image pickup element receives and photoelectrically converts a pair of light beams having a parallax that has passed through a photographing optical system including a focus lens. The focus detecting means, the control means for controlling the driving of the focus lens based on the focus detection result by the focus detection means, the ratio of the defocus amount to the focus depth, and the distance from the focus to the subject based on the focus detection result. The determination means includes a determination means for determining whether or not the subject has been switched based on the above, and the determination means has a change amount of the ratio of the defocus amount with respect to the focal depth less than a second predetermined value and from the focus. When the number of times the focus detection result in which the distance to the subject is equal to or greater than the third predetermined value is detected is equal to or greater than the first predetermined number of times, it is determined that the subject has been switched.

According to the present invention, it is possible to provide a lens control device capable of more accurately determining whether or not a subject has been switched, as compared with the prior art.

Block diagram showing the configuration of a camera and a lens in this embodiment The figure explaining the pixel structure of the imaging surface phase difference detection method in this embodiment. A flowchart showing a moving image shooting process in the present embodiment Flow chart showing AF restart determination in the first embodiment of the present embodiment Flow chart showing focus feed AF processing in this embodiment Flowchart showing lens drive setting in this embodiment Flow chart showing lens drive processing in this embodiment A flowchart showing a moving body determination method in the present embodiment Table of threshold values used for moving object determination in this embodiment Flow chart showing the subject change determination method in this embodiment Table of threshold values used for subject change determination in this embodiment Flow chart showing determination of focus mode in this embodiment The figure regarding the focus mode in this embodiment Flow chart showing follow-up AF processing in this embodiment A flowchart showing a stop determination processing method in the present embodiment The figure which shows the stop determination in this embodiment

Hereinafter, an example of a mode for carrying out the present invention will be described with reference to the drawings. The embodiments described below are examples of means for realizing the present invention, and may be appropriately modified or changed depending on the configuration of the apparatus to which the present invention is applied and various conditions within the scope of the gist of the present invention. good.

[First Embodiment]
[Structure of lens 10 and camera 20]
FIG. 1 is a block diagram showing a configuration of a lens and an interchangeable lens camera body according to the first embodiment of the present invention.

As shown in FIG. 1, the present embodiment includes a lens 10 and a camera 20, and a lens control unit 106 that controls the operation of the entire lens and a camera control unit 212 that controls the operation of the entire camera provide information. I'm communicating.

First, the configuration of the lens 10 will be described. The lens 10 includes a fixed lens 101, an aperture 102, a focus lens 103, an aperture drive unit 104, a focus lens drive unit 105, a lens drive 106, and a lens operation unit 107. The fixed lens 101, the aperture 102, and the focus lens 103 are the photographing optical systems of the present embodiment. The diaphragm 102 is driven by the diaphragm drive unit 104. The lens control unit 106 controls the aperture 102 via the aperture drive unit 104 to control the amount of light incident on the image sensor 201, which will be described later. The focus lens 103 is driven by the focus lens driving unit 105. The lens control unit 106 controls the position of the focus lens 103 via the focus lens drive unit 105 to control the position of the focal point to be imaged on the image sensor 201, which will be described later. When there is a user operation via the lens operation unit 107, the lens control unit 106 performs control according to the user operation. The lens control unit 106 controls the aperture drive unit 104 and the focus lens drive unit 105 in response to control commands and control information received from the camera control unit 212, which will be described later. Further, the lens control unit 106 transmits the lens control information to the camera control unit 212.

Next, the configuration of the camera 20 will be described. The camera 20 is configured to be able to acquire an imaging signal from a luminous flux that has passed through the photographing optical system of the lens 10.

The image sensor 201 is composed of a CCD or a CMOS sensor. The luminous flux that has passed through the photographing optical system is imaged on the light receiving surface of the image sensor 201, and is photoelectrically converted into a signal charge according to the amount of incident light by the photodiode. The signal charge accumulated in each photodiode is sequentially read from the image sensor 201 as a voltage signal corresponding to the signal charge based on the drive pulse given from the timing generator 215 according to the command of the camera control unit 212.

The image pickup device 201 has two photodiodes in one pixel portion in order to perform focus detection of the image pickup surface phase difference type (FIG. 2). By separating the luminous flux with a microlens (not shown) and receiving the luminous flux having parallax with each other by these two photodiodes, two signals for imaging and AF can be taken out. The signal (A + B) obtained by adding the signals of the two photodiodes is the imaging signal, and the signals (A and B) of the individual photodiodes are the two (pair) image signals for AF. Based on the AF signal, the AF signal processing unit 204, which will be described later, performs a correlation calculation on the two image signals to calculate the amount of image shift and various reliability information.

The image pickup signal and AF signal read from the image sensor 201 are input to the CDS / AGC / AD converter 202 to perform correlated double sampling for removing reset noise, gain adjustment, and signal digitization. The CDS / AGC / AD converter 202 outputs the image pickup signal to the image input controller 203 and the AF signal to the AF signal processing unit 204, respectively.

The image input controller 203 stores the image pickup signal output from the CDS / AGC / AD converter 202 in the SDRAM 209. The image signal stored in the SDRAM 209 is displayed on the display unit 206 by the display control unit 205 via the bus 21. Further, in the mode of recording the image pickup signal, the recording medium control unit 207 records the image on the recording medium 208. Further, the ROM 210 connected via the bus 21 stores a control program executed by the camera control unit 212 and various data necessary for control. The flash ROM 211 stores various setting information and the like related to the operation of the camera 20 such as user setting information.

The AF signal processing unit 204 performs a correlation calculation based on the two image signals for AF output from the CDS / AGC / AD converter 202, and performs an image shift amount and reliability information (two-image matching degree and two-image steepness). , Contrast information, saturation information, scratch information, etc.). The calculated image shift amount and reliability information are output to the camera control unit 212. Further, the camera control unit 212 notifies the AF signal processing unit 204 of a change in the setting for calculating these based on the acquired image shift amount and reliability information. For example, when the amount of image shift is large, the area for performing the correlation calculation is set wide, or the type of the bandpass filter is changed according to the contrast information.

The face detection unit 216 performs a known face detection process on the image pickup signal to detect the face of a person on the shooting screen. The detection result is transmitted to the camera control unit 212. Based on the detection result, the camera control unit 212 transmits information to the AF signal processing unit 204 so as to add a face frame to the area including the face in the shooting screen. Here, when the faces of a plurality of people are detected from the face detection unit, there is a main face determination processing unit that prioritizes the faces according to the position of the face, the size of the face, or the instruction of the photographer. The face judged to be the most prioritized by is the main face. For example, the face selected by the photographer's instruction has the highest priority, then the closer the face position is to the center of the screen, and the larger the face size, the higher the priority. However, the method is not limited to this method as long as the face can be detected and the main face can be determined.

As the face detection process, for example, the following method is disclosed. Using a method of extracting the skin color area from the gradation color of each pixel represented by the image data and detecting the face by the degree of matching with the contour plate of the face prepared in advance, or using a well-known pattern recognition technique, the eyes, This is a method of performing face detection by extracting facial feature points such as the nose and mouth. In the present embodiment, the method of face detection processing is not limited to the above-mentioned method, and any method may be used.

The tracking processing unit 217 acquires images having different times from the image pickup signals output from the CDS / AGC / AD converter 202, extracts the feature amount of the image, searches for a region having the same feature amount, and tracks the image. At the time of initial operation in which the reference image is not registered, a partial area in the image is used as the reference image based on the information by the camera operation unit 214 and the information of the detection result of the face detection unit 216. Then, the color information is extracted from the reference image and registered as the feature amount of the subject to be tracked. Based on the extracted feature amount of the subject to be tracked, the matching process of the image of the captured signal in the current frame and the reference image is performed. Each image is extracted by a matching process as a specific region for the purpose of the region having the highest correlation with the reference image in the image of the imaging signal in the current frame. Then, it is determined whether or not the tracking is continued depending on whether or not the degree of correlation is high. Further, the tracking state based on the correlation degree is calculated as the reliability and sent to the camera control unit 212 to be used as an AF control parameter.

The camera control unit 212 controls by exchanging information with the entire inside of the camera 20. Not only the processing in the camera 20, but also various operations by the user such as power ON / OFF, setting change, recording start, AF control start, confirmation of recorded image, etc. according to the input from the camera operation unit 214. Perform various camera functions. Further, as described above, information is exchanged with the lens control unit 106 in the lens 10, control commands and control information of the lens are sent, and information in the lens is acquired.

In addition, the camera 20 has a recording medium 208 and an SDRAM 209.

[Movie shooting process]
Next, the moving image shooting process in the camera 20 of the present embodiment will be described with reference to FIG.

In the present embodiment, the moving image recording is started / stopped by pressing the moving image recording switch, but the recording may be started / stopped by another method such as a changeover switch.

When a moving image recording is instructed by the moving image recording switch or the like, in S505, the AF signal processing unit 204 performs AF area calculation processing and proceeds to S506. The AF area calculation process is a process for setting from which area on the imaging surface the signal used for focus detection is acquired.

In S506, the AF signal processing unit 204 performs focus detection processing and proceeds to S507. In the focus detection process, the defocus amount and reliability information are acquired by the focus detection of the imaging surface phase difference type. The defocus amount is detected based on the image shift amount based on the pair of image signals described above. The defocus amount of the present embodiment is information indicating how much the focus lens 103 should be controlled to be driven in the near direction or the infinite direction. The reliability information is an index showing how reliable the image shift amount is. The reliability can be defined by the steepness and the degree of coincidence between the two images of the image signals A and B, fnclvl (hereinafter, referred to as the degree of coincidence between the two images). Details of the focus detection process of the imaging surface phase difference type are described in, for example, Japanese Patent Application Laid-Open No. 2015-87704.

In S507, the camera control unit 212 refers to the responsiveness setting and the speed setting of the focus lens 103 set by the user in order to control the drive of the focus lens 103.

The user can set the speed by selecting the driving speed of the focus lens 103, for example, on the menu screen (not shown) of the camera. In the speed setting of the present embodiment, as an example, the speed is selected from 7 steps of +2 to -4. The camera control unit 212 refers to the speed parameter corresponding to the drive speed selected by the user, and sets the drive speed of the focus lens 103 using the defocus amount detected by the AF signal processing unit 204. In the present embodiment, as an example, the speed parameter is the number of vertical synchronization signals (60 Hz), and the speed can be calculated by the following formula.
Set speed [mm / s] =
Defocus amount [mm] ÷ speed parameter x 1/60 [s] (1)

As a result, the speed is changed according to the setting.

Regarding the responsiveness setting, the user can select, for example, the responsiveness of driving the focus lens 103 at the time of shooting on the menu screen (not shown) of the camera. The responsiveness is the degree of the response speed of driving the focus lens 103, and one of the indexes showing the responsiveness is the length of the response time, which is the time until the focus lens 103 is driven. The longer the response time, the lower the response, and the shorter the response time, the higher the response. In the responsiveness setting of this embodiment, as an example, a selection is made from 7 steps of +3 to -3. The camera control unit 212 refers to the response time of the focus lens 103 corresponding to the responsiveness selected by the user, until the time until the restart of S512 and the start of focusing when the subject is switched in the follow-up drive mode of S516. Change the time of.

In S508, the camera control unit 212 performs the moving object determination process. The moving object determination process is a process in which the camera control unit 212 determines whether or not the subject being photographed is moving in the optical axis direction. Details will be described later with reference to FIGS. 8 and 9.

S509 is a process in which the camera control unit 212 determines whether or not the subject has been changed. Details will be described later with reference to FIGS. 10 and 11.

In S510, the camera control unit 212 determines the focus mode to be set. Details will be described later with reference to FIGS. 12 and 13.

In S511, the camera control unit 212 determines whether or not the focus mode determined in S510 is the default, and if it is the default, the process proceeds to S512.

S512 is an AF restart determination process performed by the camera control unit 212. Details will be described later with reference to FIG.

If the focus mode is not the default in S511, the transition to S513 is performed.

In S513, when the camera control unit 212 determines that the focus mode is the focus feed mode, the process transitions to S514.

In S514, the camera control unit 212 controls AF processing in the focus feed mode. Details will be described later with reference to FIG.

If the focus mode is not the focus feed mode in S513, the process transitions to S515.

In S515, the camera control unit 212 determines the presence / absence of the subject change stop flag (described later in FIG. 10), and if the flag is off, the transition to S516 is performed, and if the flag is not off, the transition to S517 is performed.

In S517, the camera control unit 212 controls so that the lens is stopped without performing the AF process. In this way, by referring to the subject change focus stop flag, the camera control unit can control to stop the focus lens 103 drive when determining whether or not the subject has switched to another subject. .. In S516, AF processing in the follow-up mode is performed. Details will be described later with reference to FIG.

This flow is repeatedly executed until there is an instruction to stop the moving image shooting.

[Overview of focus mode]
Before explaining each subflow, the outline of each focus mode of this embodiment will be described with reference to FIG. The focus mode of this embodiment is roughly divided into three modes: "default mode", "focus feed mode", and "following mode". FIG. 13A is a diagram showing the relationship between each focus mode. FIG. 13B is a diagram showing the types and characteristics of each focus mode.

The features of each focus mode will be briefly described. The default mode (first mode, focusing stop mode) is a mode for transitioning from another focus mode when focusing is stopped (when it is determined that the focus is in focus and the driving of the focus lens 103 is stopped).

The focus feed mode (third mode) is a mode in which the drive speed of the focus lens 103, the response time and the drive speed when driving the focus lens 103 are set according to the user's specifications, and the focus lens 103 is driven according to the settings. is there. If not specified by the user, the camera control unit 212 controls to drive the focus lens 103 according to the default setting.

In the tracking mode (second mode, focus adjustment mode), when a moving object is detected as a subject, the focus lens 103 is controlled to follow the moving object, so that the driving speed of the focus lens 103 is set to the moving object. Set to the adjusted speed. In the present embodiment, as an example of drive control of the focus lens 103 according to a moving object, the camera control unit 212 variably controls the drive speed of the focus lens based on the detected defocus amount. When the detected defocus amount is relatively large, the camera control unit 212 controls to drive the focus lens faster than when it is small.

The transition of these focus modes will be described with reference to FIG. 13 (A). In the default mode, when the subject is determined to be a moving object by the moving object determination, the mode transitions to the following mode (2505). Further, in the focus feed mode, when the subject is determined to be a moving object by the moving object determination, the mode transitions to the tracking mode (2504).

In the follow-up mode, when it is determined that the subject has been changed by the subject change determination process, the mode shifts to the focus feed mode (2503).

From the default mode, when it is determined that the subject is not a moving object in the moving object determination and the subject is switched (changed) by the subject change determination, the focus feed mode is entered (2502).

When it is determined that the subject is in focus in the focus feed mode or the follow-up mode, the mode transitions to the default mode (2501,506).

[Motion judgment processing]
Next, the moving body determination process in S508 will be described with reference to FIG. In S1401, the camera control unit 212 acquires the defocus amount calculated in S506. Further, the camera control unit 212 acquires the current lens position of the focus lens 103 via the lens control unit 106.

In S1402, the target lens position is calculated from the defocus amount acquired in S1401 and the current lens position. The following formula is used for this calculation.
Drive amount [pulse] = defocus amount [mm] ÷ pulse conversion coefficient [pulse / mm]
(2)
Target lens position [pulse] = current lens position [pulse] + drive amount [pulse]
(3)

This calculation is an example of converting the amount of blur (here, the amount of defocus) on the image pickup surface of the image sensor 201 into the amount of drive of the lens of the focus lens 103. If the target lens position of the focus lens 103 can be calculated, a calculation method other than the above calculation may be used.

Even if the subject position and the position of the focus lens 103 are the same, the defocus amount calculated depending on the shooting conditions varies. Therefore, for the calculation of the target lens position of the focus lens 103, two values, a defocus value as the calculated actual value and an average of the defocus amounts for three times, are prepared. Further, the target lens position of the focus lens 103 is calculated in two patterns, one calculated using an actual value and one calculated using an average value.

In S1403, the camera control unit 212 detects the continuity of the target lens position (actual value / average value) of the focus lens 103 in the infinite direction or the closest direction. In the present embodiment, when the infinite side direction is the positive direction and the closest side direction is the negative direction, the number of consecutive increases / decreases in the infinite direction / close direction is counted.

In S1404, it is a process of setting a threshold value for the number of consecutive times. In this embodiment, as shown in FIG. 9A as an example, the threshold value is changed according to the type of value (actual value / average value) used for calculating the aperture and the target lens position.

As shown in FIG. 9A, in S1404, the smaller the aperture value, the smaller the threshold value as compared with the case where the aperture value is large. This is because when the aperture value is small, the depth of focus is shallower than when the aperture value is large, and blurring is more noticeable. By making it easier to enter the motion judgment, it is possible to reduce the occurrence of unnatural blurring, so that the quality of the moving image can be maintained. Further, when the defocus amount used for calculating the target lens position of the focus lens 103 is an actual value, the threshold value is increased as compared with the case where the average value is used. This is because stable detection is possible when the average value is used as compared with the case where the actual value is used. If the aperture value is larger than F11, the moving object is not determined. This is because the depth of focus of the subject is sufficiently deep that blurring is less likely to occur even if the moving object is not determined. For example, when the aperture value is larger than F11, the threshold value is set so that the number of consecutive times does not exceed the threshold value.

S1405 is a process for determining whether or not the number of consecutive times exceeds the threshold value. If the number of consecutive times exceeds the threshold value, the process proceeds to S1406, and if not, the process proceeds to S1413. In the present embodiment, if at least the target lens position calculated using the actual value and the target lens position calculated using the average value are equal to or greater than the threshold value set in S1404 for each, it is assumed that the subject is a moving object S1406. Proceed to. When both the target lens position calculated using the actual value and the target lens position calculated using the average value are less than the threshold value set in S1404 for each of them.
Proceed to S1413 assuming that the subject is not a moving object.

S1406 determines whether the focus is stopped (in other words, the default mode), and if the focus is stopped, the process proceeds to S1407, and if not, the process proceeds to S1409.

S1409 determines whether it is the focus feed mode, and if it is the focus feed mode, proceeds to S1410. If not, it is the follow-up mode, and thus ends the processing of this flow in order to continue the follow-up mode.

In S1407, the camera control unit 212 controls to set a fifth predetermined value as a threshold value for determining a moving object, and to set a sixth predetermined value as a threshold value for determining a moving object in S1410.

In the present embodiment, when focusing is stopped, the threshold value (here, the fifth predetermined value) is changed according to the aperture and the focal length, as shown in FIG. 9B as an example. For example, as shown in FIG. 9B, when the aperture value is small, the fifth predetermined value is smaller than when it is large. Further, when the focal length is long, the fifth predetermined value is made larger than when it is short. The shallower the depth of focus, the more noticeable the blur, so it is easier to judge the moving object in order to maintain the quality of the moving image. The smaller the fifth predetermined value is, the more agile the moving object can be determined when the moving object moves (the responsiveness of the focus lens 103 to the subject is improved). On the other hand, there may be a case where a moving object is determined for a subject that is not a moving object (the stability of tracking the focus lens 103 to the subject is reduced). Therefore, it is necessary to set this fifth predetermined value in consideration of the balance between stability and responsiveness.

Further, in the example of FIG. 9B, the aperture value and the focal length at which the moving object is not determined are set. In FIG. 9B, as an example, the moving object is not determined when the aperture value is larger than F11 and when the focal length is 24 mm or less. This is because the depth of focus of the subject is sufficiently deep that blurring is less likely to occur even if the moving object is not determined. Therefore, when the aperture value is larger than F11 and the focal length is 24 mm or less, the fifth predetermined value is set so that the defocus amount does not exceed the fifth predetermined value.

The effect of setting the sixth predetermined value in S1410 for determining the moving object in the focus feed mode will be described. For example, if a moving object is detected at a timing when the subject to be focused is not yet in focus, and the focus feed mode is immediately switched to the follow-up mode, the drive speed of the focus lens 103 suddenly changes, resulting in blurring. The state also changes suddenly. As a result, the quality of the moving image is deteriorated. Therefore, in the present embodiment, when a moving object is detected in the focus feed mode, the focus lens 103 transitions from the focus feed mode to the follow mode when the position of the focus lens 103 is near the in-focus position with respect to the subject to be focused. The camera control unit 213 controls the lens. That is, if it is less than the sixth predetermined value, it is determined that the focus lens 103 has reached the position of focusing on the target subject, and the camera control unit 212 controls the transition from the focus feed mode to the follow-up mode. As a result, the discomfort due to the change in the blur state due to the change in the drive speed of the focus lens due to the switch from the focus feed mode to the follow-up mode is reduced, and the quality of the moving image can be maintained. As for the sixth predetermined value, similarly to the fifth predetermined value, when the aperture value is small, the sixth predetermined value is set to a smaller value than when it is large. Further, when the focal length is long, the sixth predetermined value is set to a larger value than when it is short.

Further, in the focus feed mode, the threshold value is changed depending on whether or not the moving direction of the subject and the driving direction of the focus lens 103 match. When the moving direction of the subject and the driving direction of the focus lens 103 do not match, the subject and the focus lens 103 are moved and driven in directions facing each other in the optical axis direction. In this case, since both the focus lens 103 and the subject continue to move, the time for the focus lens 103 to enter the focusing range with respect to the subject becomes very short, and the time for switching from the focus feed mode to the follow-up mode. May not be enough. From this, when the moving direction of the subject and the driving direction of the focus lens 103 do not match, the sixth predetermined value is set widely to secure the switching timing. On the other hand, when the moving direction of the subject and the driving direction of the focus lens 103 match, the determination is performed with the same threshold value as that of the normal focusing stop. The threshold value is the threshold value of the focus feed mode obtained by multiplying the threshold value determined in FIG. 9B by a specified magnification. In the case of the present embodiment, as an example, when the lens and the subject are driven in opposite directions, a coefficient of 1.5 times is multiplied.

S1408 determines whether or not the defocus amount is equal to or greater than the fifth predetermined value, and if it is equal to or greater than the fifth predetermined value, the process proceeds to S1412, and if not, the process proceeds to S1413.

S1411 determines whether or not the defocus amount is less than the sixth predetermined value, and if it is less than the sixth predetermined value, the process proceeds to S1412, and if not, the process proceeds to S1413.

S1412 is a process when the subject is determined to be a moving object (a moving object is determined), and the process is terminated by turning on the moving object determination flag. In the focus feed mode, when a moving object is detected, when the defocus amount exceeds the sixth predetermined value in S1411, that is, when it is determined that the subject is in focus, the moving object is determined in S1412. Turn on the judgment flag. When the moving object flag is turned on, the focus mode determination process (FIG. 12), which will be described later, transitions to the follow-up mode. In this way, after it is determined that the subject is in focus, the mode shifts to the follow-up mode (the mode in which the focus lens 103 is controlled to follow the moving object at a speed corresponding to the moving speed of the subject), so that the focus lens 103 is suddenly out of focus. The camera control unit 212 can control the change so that it does not change. This makes it possible to improve the quality of the image when following a moving object.

On the other hand, S1413 is a process when the moving object is not determined, or when the tracking mode has already been transitioned, and the moving object determination flag is turned off to end the process. By turning off the moving object determination flag here, the driving of the focus lens 103 in the focus feed mode is continued in the focus mode determination process (FIG. 12) described later. As a result, the focus state that is not in the focused state is switched to the follow-up mode, and the camera control unit 212 can control the focus state so that the focus state does not change suddenly.

[Subject change judgment processing]
Subsequently, the subject change determination process in S509 will be described with reference to FIG. The subject change determination process is a process of determining whether or not the subject to be followed has been changed in the tracking mode.

Here, the reason why it is determined whether or not the subject has been changed only in the follow-up mode in this flow will be described. For example, when the camera control unit 212 controls the focus detection for a certain subject and causes the focus lens 103 to follow, a subject different from the subject causes the camera 20 and the focus lens to follow. It may cross between and. In this case, if the camera control unit 212 controls the drive of the focus lens 103 so that the focus lens 103 follows the crossed subject, the focus lens 103 cannot be made to follow the originally following subject. .. If the focus lens 103 is made to follow an unintentionally crossed subject, the quality of the moving image is deteriorated. Therefore, in the present embodiment, in the tracking mode, the focus lens 103 is applied to a subject different from the following subject by performing a subject change determination process for determining whether or not the subject is the subject originally being followed. It prevents the lens from being followed. For example, when a subject different from the subject being followed crosses, the camera control unit 212 controls to stop the driving of the focus lens 103 so as not to perform the following operation on the crossed subject. Details will be described later. On the other hand, even when a subject different from the originally followed subject is captured, if it can be determined that the user has intentionally changed the subject, the camera control unit 212 causes the focus lens 103 to follow. It controls the drive. Hereinafter, the flow of FIG. 10 will be described as an example of the flow for realizing this.

S2201 is a process of determining whether or not the current focus mode is the follow-up mode. In the follow-up mode, the camera control unit 212 controls to proceed to S2202 in order to determine the change of the subject. If it is not in the follow-up mode, the camera control unit 212 controls to proceed to S2217 and end the processing of this flow.

S2202 is a process of storing the defocus amount in the SDRAM 209.

In S2203, the camera control unit 212 calculates the distance from the focal point to the subject from the defocus amount calculated by the AF signal processing unit 204 in S506. The following formula is used for this calculation.
Distance from focus to subject = defocus amount x square of subject distance ÷
(Focal length squared + defocus amount x subject distance) (4)

In the present embodiment, the distance from the focal point to the subject is converted by converting the amount of defocus into the distance on the subject side indicating how far the actual subject position is from the subject position in which the subject is in focus. is there. The subject distance is the distance from the subject position in which the subject is in focus to the focus lens 103.

S2204 is a process of calculating the amount of change in the amount of defocus calculated this time and the amount of defocus calculated last time. This is to detect a large change in the subject, and can be obtained by using the following formula.
Amount of change in defocus amount DEF_Diff_NOW =
Previous defocus amount-Current defocus amount (5)

S2205 is a process in which the camera control unit 212 sets a threshold value for determining whether or not the subject has been changed. There are three thresholds.
Threshold 1 (first predetermined value): Threshold value for change in defocus amount Threshold 2 (second predetermined value): Threshold threshold 3 (third predetermined value) of the ratio of the distance from the focal point to the subject to the depth of view Value): Threshold for the distance from the focus to the subject

The threshold value 1 is a threshold value for the amount of change of the defocus amount detected this time with respect to the previously detected defocus amount. This is a threshold used to detect a sudden change in the subject. In the present embodiment, as an example, the threshold value 1 is obtained by comparing the average DEF_Diff_AVE for three times of the change amount of the defocus amount with the current defocus change amount DEF_Diff.

That is, when the following equation is satisfied, it can be determined that a sudden change in the subject has occurred.
DEF_Diff_NOW> DEF_Diff_AVE * Threshold 1 (6)

The threshold value 1 of the present embodiment is, for example, a threshold value of 1.5 times or more. This is because it is highly probable that the subject has changed when the amount of change in the defocus amount changes by 1.5 times.

The threshold value 2 is a threshold value for the ratio of the distance from the focal point to the subject to the depth of field, and is a threshold value for determining how much blurring has occurred. As the threshold value 2, a multiple of the depth of field is set. In this embodiment, as an example, the threshold value is changed as shown in FIG. 11 (A) according to the depth of focus. The smaller the aperture value, the deeper the depth of focus, and the more likely it is that the focus detection results will vary. Therefore, the deeper the depth of focus, the larger the threshold value 2 compared to other cases, resulting in variations in the focus detection results. It is possible to prevent erroneous judgment. If the distance from the focal point to the subject changes by more than twice the depth of field, it means that the subject is likely to have changed. If the depth of field is deep enough that the blur state does not change regardless of which of the subject that was originally following and the subject that crossed between the camera 20 is followed, the subject change determination should not be performed. You may. For example, as an example of the present embodiment, when the aperture value is larger than F11, the threshold value may be set so as not to perform the subject change determination. In this case, for example, the threshold value is set so that the ratio of the distance from the focal point to the subject to the depth of field does not exceed the threshold value.

The threshold value 3 is a threshold value for the distance from the focal point to the subject, and is a threshold value for detecting how far the threshold value for the distance from the focal point to the subject is. In the case of this embodiment, as an example, a distance of 1 m from the focal point to the subject is set as a threshold value. This means that if a subject that is 1 m or more away from the following subject is detected, the subject has been changed. If the threshold value 3 is increased, the followability to the originally followed subject is improved, but it becomes difficult to determine the change of the subject. That is, there is an increased possibility that it is possible to avoid performing the focusing operation on a subject (also referred to as a crossing subject) that crosses between the subject that is originally following and the camera during moving object shooting. On the other hand, if the threshold value 3 is reduced, it becomes easier to determine that the subject has been changed from the originally followed subject. There is an increased possibility that it is possible to avoid performing the focusing operation on a subject (also referred to as a crossing subject) that crosses between the subject that is originally following and the camera during moving object shooting. On the other hand, the followability of the focus lens 103 to a moving object is reduced.

If the moving speed of the subject is known in advance, the presence or absence of the change of the subject can be determined more accurately by changing the threshold value 3 of the distance from the focal point to the subject according to the moving speed. For example, when the moving speed of the subject is fast, the threshold value 3 is set larger than that when the moving speed of the subject is slower, so that it is determined that the subject is mistakenly changed even though the same subject is captured. You can prevent it from happening. When the moving speed of the subject is slow, the threshold value 3 is set smaller than that when the moving speed is faster, so that when the subject is changed, it becomes easier to follow the changed subject.

The relationship between the threshold value 2 and the threshold value 3 described above will be described with reference to FIG. 11 (C).

2301 in FIG. 11C represents the threshold value 2. 2302 (1 m in this embodiment) represents the threshold value 3. Since the threshold value 3 is the threshold value for changing the distance of the subject, it is constant regardless of the subject distance. However, as the depth of field becomes deeper, the focus detection result varies, so that a variation of 1 m or more occurs for a long-distance subject. Therefore, the threshold value 2 is also used for the determination together with the threshold value 3 in order to accurately determine the subject change even for a long-distance subject.

Since the threshold value 2 is a threshold value related to the depth of field, it changes according to the subject distance. The threshold value 2 changes like 2301, and is large on the long-distance side and small on the short-distance side. Therefore, for a long-distance subject, even if the distance from the focal point to the subject is a threshold value of 3 or more, the subject is not changed if the ratio of the distance from the focal point to the subject to the depth of field is less than the threshold value 2. The camera control unit 212 determines. As a result, it is possible to prevent erroneous determination due to variation in the focus detection result.

On the other hand, the depth of field used for the threshold value 2 becomes smaller on the short distance side. If only the threshold value 2 is set, the threshold value becomes too small with respect to the movement of the subject. Therefore, by using the threshold value 3 on the short distance side, erroneous determination can be prevented.

That is, by determining that the subject has been changed when the conditions of the threshold value 2 and the threshold value 3 are exceeded, it is possible to stably determine whether or not the subject has been changed at a long distance or a short distance.

Further, as shown by 2303 and 2304, the threshold value may be changed in an area where the subject distance is closer than a predetermined value. This will be described with reference to FIG. 11 (B).

First, the area indicated by 2303 is a distance in which the subject distance is less than 3 m (less than the seventh predetermined value) as an example in the present embodiment. If it is less than this distance, the distance between the camera and the subject is short and the influence of crossing is small. In addition, the resolution / accuracy of the distance information acquired from the lens is high, and the distance to the subject is reliable. For these reasons, the condition of the threshold value 3 may be changed depending on whether the subject distance is equal to or more than the seventh predetermined value or less than the seventh predetermined value. In this case, when the subject distance is equal to or greater than the seventh predetermined value, the threshold value 3 is set to a constant value regardless of the subject distance. When the subject distance is less than the seventh predetermined value, a value smaller than the case where the subject distance is equal to or more than the seventh predetermined value is set as the threshold value 3. Further, as in 2305, the camera control unit 212 sets the threshold value so that the threshold value 3 becomes smaller (but not 0) from the subject distance of 3 m (7th predetermined value) to (8th predetermined value). When the subject distance is less than 1 m (less than the eighth predetermined value), the subject distance is set to 1 m and the threshold value 3 is set to 0.

The area indicated by 2304 is a macro photography area in which the subject distance is 1 m (less than the eighth predetermined value). In this embodiment, the determination of this region is based on the condition that, for example, the depth of field is less than 1.5 cm (less than the tenth predetermined value). In the macro shooting area 2304, if the threshold value 3 remains 1 m, the change of the subject cannot be detected. In addition, since the depth of field becomes shallow, the conventional threshold value 2 makes it too sensitive to determine the change of the subject, resulting in an increase in erroneous determination. For the above reasons, in the macro photography area 2304, as shown in 2306, the threshold value 2 is set as a value larger than that of the other areas, and the threshold value 3 is set as a value (0 m) that has no effect.

As described above, by changing the threshold value for determining the change of the subject according to the subject distance, the depth of field, and the aperture value, stable determination becomes possible.

In the present embodiment, the case where the threshold value is set as shown in FIG. 11 is shown, but this is an example and can be changed within a range that does not deviate from the purpose.

Subsequently, in S2206, it is determined whether the amount of change in the defocus amount is the threshold value 1 or more (first predetermined value or more), and if it is the threshold value 1 or more, the process proceeds to S2207. On the other hand, if the amount of change in the defocus amount is less than the threshold value 1 (less than the first predetermined value), the process proceeds to S2209.

In S2207, is the ratio of the distance from the focal point to the subject to the depth of field a threshold value of 2 or more (second predetermined value or more) and the distance from the focal point to the subject is a threshold value of 3 or more (third predetermined value or more)? To judge. If so, it is determined that the subject has been changed, and the process proceeds to S2208. If not, the process proceeds to S2211.

In S2208, since the subject has been changed, the camera control unit 212 turns on the subject change focus stop flag and ends the process in order to control the driving of the focus lens 103 to be stopped. In S2209, it is determined whether the subject change focus stop flag is on, and if it is on, the process proceeds to S2210, and if not, the process proceeds to S2217.

In S2210, is the ratio of the distance from the focal point to the subject to the depth of field a threshold value of 2 or more (second predetermined value or more) and the distance from the focal point to the subject is a threshold value of 3 or more (third predetermined value or more)? To judge. If so, it is determined that the subject has been changed (switched) continuously, and the process proceeds to S2212. If not, the process proceeds to S2211.

In S2211, the camera control unit 212 turns off the subject change focus stop flag and ends the process in order to control the focus lens 103 to continue driving, assuming that the subject has not been changed.

In S2212, the subject change count is incremented and the process proceeds to S2213.

In S2213, it is determined whether the count is equal to or longer than the second predetermined time of the response time. If it is the second predetermined time or more, the process proceeds to S2214, and if not, the process proceeds to S2216. The second predetermined time of this response time is a value set in S507, and S2213 is a process of determining whether the count exceeds the response time.

In S2214, the subject change count is cleared and the process proceeds to S2215.

In S2215, the camera control unit 212 turns on the subject change focus drive flag and ends the process in order to control to restart the drive of the focus lens 103.

In S2216, the subject change focus stop flag is turned off to end the process.

In S2217, the subject change focus drive flag is turned off to end the process.

As described above, in the subject change determination process of the present embodiment, the ratio of the distance from the focal point to the subject to the depth of field is equal to or greater than the second predetermined value based on the depth of field, and the subject distance is the third predetermined value. In the above case, the camera control unit 212 determines that the subject has been switched. As a result, even when the distance between the image pickup device and the subject is long and the focus detection result by the phase difference detection method may vary, it is possible to more accurately determine whether or not the subject has been switched as compared with the conventional technique. Can be determined.

[Focus mode judgment]
The focus mode determination process will be described with reference to FIG. In S2401, the camera control unit 212 determines whether or not the initialization has been completed. If it has not been initialized, the focus mode is set to the focus feed mode in S2402, and the process proceeds to S2403. If not, the process proceeds to S2403 without going through S2402. The initialization process is performed each time the shooting mode or the like is switched.

In S2403, the camera control unit 212 determines whether or not the focus mode is the default mode. If it is the default mode, the process proceeds to S2404, and if not, the process proceeds to S2409.

In S2404, the camera control unit 212 determines the presence / absence of the moving object determination flag, and if the moving object determination flag is on, the process proceeds to S2405, the focus mode is set to the follow-up mode, and the control ends.

If the moving object determination flag is not on, the process proceeds to S2406, and the camera control unit 212 determines whether or not the focusing stop flag is present. If the focus stop flag is off, the process proceeds to S2407, the focus mode is set to the focus feed mode, and the control ends. If not, the focus mode is set to the default mode in S2408 and the control is terminated.

In S2409, the camera control unit 212 determines whether the focus feed mode is set, and if the focus feed mode is set, the process proceeds to S2410, and if not, the process proceeds to S2415. In S2410, the presence / absence of the moving object determination flag is determined, and if the moving object determination flag is on, the process proceeds to S2411, the focus mode is set to the follow-up mode, and the control is terminated. If not, the process proceeds to S2412 and the camera control unit 212 determines the presence or absence of the focusing stop flag. If the focusing flag is off, the process proceeds to S2413, the focus mode is set to the focus feed mode, and the control is terminated. If not, the focus mode is set to the default mode in S2414 and the control is terminated.

In S2415, since the current focus mode is the follow-up mode, it is determined whether or not the subject change focus drive flag is present. If the focus drive flag is off, the process proceeds to S2416, the focus mode is set to the follow-up mode, and the control is terminated. .. If not, the camera control unit 212 determines whether or not the follow-up stop determination flag is present in S2417, and if the follow-up stop determination flag is off, the process proceeds to S2418, the focus mode is set to the focus feed mode, and the control is terminated. If not, the focus mode is set to the default mode in S2419 and the control is terminated.

[AF restart judgment]
Next, the AF restart determination of S512 performed when the camera control unit 212 determines that the focus mode is the default mode in S511 of FIG. 3 will be described with reference to the flowchart of FIG. The AF restart determination is a process in which the camera control unit 212 determines whether or not to drive the focus lens again after focusing and stopping the focus lens.

In S701, the camera control unit 212 determines whether or not the calculated defocus amount is smaller than a predetermined multiple of the depth of focus (fourth predetermined value), and if it is less than the fourth predetermined value, the process proceeds to S702 and the fourth predetermined value. If it is equal to or more than the predetermined value, the process proceeds to S704. The threshold value of the defocus amount (fourth predetermined value) set in S701 is considered to be easy to restart when the main subject is changed and to be difficult to restart carelessly when the main subject is not changed. Let it be a value. In the present embodiment, as an example, one time of the depth of focus at which the blur of the main subject becomes visible is set as the fourth predetermined value.

In S702, it is determined whether or not the calculated reliability is a value higher than a predetermined value, and if a high value is shown, the process proceeds to S703, and if a low value is shown, the process proceeds to S704. As the reliability threshold value set in S702, for example, a value whose reliability is so low that it is difficult to trust the defocus direction is set as a value in which the main subject is considered to have changed. For example, it may be the same as the predetermined value α of S901. In this way, it is determined whether or not the main subject has changed by using the threshold values set in S701 and S702.

In S703, the AF restart counter is reset and the process proceeds to S705. In S704, the AF restart counter is added and the process proceeds to S705. As described above, if the defocus amount is larger than the predetermined value or the reliability is lower than the predetermined value, the main subject being photographed may have changed, so the AF restart counter is added in S704. And prepare to restart AF. When the detected defocus amount is less than the fourth predetermined value and the high reliability is maintained, the AF restart counter is reset in S703 in order to continuously stop the focus lens 103.

Next, in S705, the AF restart threshold value is set and the process proceeds to S706. The AF restart threshold value setting in S705 is set by the camera control unit 212 with the response time determined in S507 as a threshold value.

In S706, which proceeds after setting the AF restart threshold value in S705, it is determined whether or not the AF restart counter is equal to or higher than the AF restart threshold value, and if applicable, the process proceeds to S707, and if not applicable, the process ends. In S707, the camera control unit 212 controls to turn off the focusing stop flag, restart AF, and restart the focus lens drive to end the process.

When restarting AF in S706, the camera control unit 212 determines whether the AF restart counter added in S704 is larger than the threshold value set in S705.

[AF processing in focus feed mode]
Next, the AF process of S514 in FIG. 3 will be described with reference to the flowchart of FIG. The focus feed AF process is a process for driving the focus lens and determining whether the focus is stopped when the focus is not stopped.

In S801, it is determined whether or not the defocus amount is within the depth of focus and the reliability shows a value better than a predetermined value. If this condition is satisfied, the process proceeds to S802, and if not, the process proceeds to S803. In the present embodiment, the threshold value used in S801 is set to 1 times the depth of focus, but it may be set larger or smaller as necessary.

In S802, the camera control unit 212 turns on the focusing stop flag and ends the process.

In S803, the camera control unit 212 sets the lens drive speed and proceeds to S804. Details of the lens drive setting of S803 will be described later with reference to FIG.

In S804, the camera control unit 212 controls to perform the lens drive process, and ends the process of this flow. The details of the lens driving process of S804 will be described later with reference to FIG. 7.

[Lens drive speed setting]
Next, the lens drive speed setting of S803 of FIG. 5 will be described with reference to the flowchart of FIG.

In S901, the camera control unit 212 determines whether the reliability is less than the predetermined value α, proceeds to S902 if the reliability is lower than the predetermined value α, and proceeds to S905 if the reliability is equal to or more than the predetermined value α. The predetermined value α is set to a value at which at least the defocus direction can be determined to be reliable.

In S902, the search drive counter is added and the process proceeds to S903.

In S903, the camera control unit 212 determines whether or not the search drive transition counter is equal to or greater than the set predetermined value, and if it is equal to or greater than the predetermined value, the process proceeds to S904, and if it is not equal to or greater than the predetermined value, the process proceeds to S906. In S904, the search drive flag is turned on and the process proceeds to S906.

In S906, the camera control unit 212 determines whether the focus mode is the focus feed mode, and if it is the focus feed mode, the process proceeds to S907, and if not, the process proceeds to S912.

In S907, the camera control unit 212 determines whether or not the search flag is on, and if the search flag is on, the search speed is set in S908. In the speed setting for the search, the speed is changed stepwise according to the menu by using the information from the speed setting menu (not shown). The search drive is a focus operation performed when the defocus amount is in an unreliable and reliable state. In the search drive, the camera control unit 212 controls to set the defocus direction and drive the focus lens at the speed set in that direction regardless of the defocus amount. By adding the search drive transition counter and determining whether the search drive transition counter exceeds the specified value, search drive is performed only when it can be determined that the reliability is continuously low and the subject may be out of focus. To be able to do it. Since the search drive is a drive that does not use the defocus amount, it may cause focusing that temporarily causes a large blur. Therefore, it is possible to prevent inadvertent search drive by setting the responsiveness so that the user does not immediately shift to search drive even if the reliability becomes low.

In S909, it is determined whether or not the moving direction of the moving object in the close direction or the infinite direction and the driving direction of the focus lens match. If they do not match, the process proceeds to S910, and if they match, the process proceeds to S911. ..

In S910, the normal speed setting is performed. In normal speed setting, the speed is changed stepwise according to the menu by using the information from the speed setting menu (not shown).

In S911, when the driving directions of the moving body and the lens are the same, it is determined whether or not the set driving speed of the focus lens 103 is a speed that can catch up with the moving body. In the present embodiment, as an example, the difference between the current focus lens position and the previous focus lens position, and the current target lens position and the previous target lens position are compared. Here, the current target lens position is a current focus lens position and a target lens position based on the current focus detection result. The previous target lens position is the previous focus lens position and the target lens position based on the previous focus detection result. If the current focus lens position and the previous focus lens position are equal to or greater than the difference between the current target lens position and the previous target lens position, the camera control unit 212 determines that the speed is such that it can catch up with the moving object. If the camera control unit 212 determines that the speed is sufficient to catch up (the speed is sufficient to follow the moving object), the process proceeds to S910. If the current focus lens position and the previous focus lens position are less than the difference between the current target lens position and the previous target lens position, the camera control unit 212 determines that the speed cannot catch up with the moving object. If the camera control unit 212 determines that the speed cannot catch up (the speed is insufficient to follow the moving object), the process proceeds to S912.

In S912, the moving object is moving at a speed that cannot catch up with the currently set drive speed of the focus lens 103, so that the focus cannot be focused. Therefore, the speed setting is set faster than usual in order to catch up with the moving object.

S913 is a speed setting in the follow-up mode. In order to follow the moving body, the speed setting sets a speed that matches the speed of the moving body.

The relationship between the driving speeds of each lens in FIG. 6 is as follows.
Velocity A> Velocity C> Velocity B (Velocity D is determined according to the speed of the subject)

Since it is assumed that the subject is largely out of focus during the search drive, the camera control unit 212 controls the speed A so that the set speed is high in order to focus on the subject quickly. In the focus feed mode, if the moving object is determined to move in the closest direction or infinite direction of the subject, and if the moving object and the driving direction of the focus lens 103 match, the speeds of both are compared. Then, determine whether the focus lens can catch up with the moving object. If it is determined that the speed cannot be caught up, the speed is set to C, which is faster than the normal speed B.

[Lens drive processing]
Next, the lens drive process of S804 of FIG. 5 will be described with reference to the flowchart of FIG.

In S1001, it is determined whether the focus mode is the focus feed mode, and if it is the focus feed mode, the process proceeds to S1002, and if it is the follow-up mode, the process proceeds to S1005.

In S1002, it is determined whether or not the search drive flag is on, and if it is on, the process proceeds to S1003, and if it is off, the process proceeds to S1004. In S1003, which proceeds when the search drive flag is on, search drive is performed and the lens drive process is terminated.

Search drive processing is performed in S1003. The search drive process is a process of driving the focus lens 103 until a focus detection result that can determine that the reliability is higher than the predetermined value α is obtained when the camera control unit 212 determines that the reliability is low. The reliability threshold value α is the same as the threshold value α set in S901 of FIG. 6, and at least the direction of the defocus amount is a reliable value. If the reliability becomes better than the threshold value α, it can be determined that the subject is approaching focus, so the search drive is stopped and the control is switched to the control based on the defocus amount again. If the near end or infinite end of the lens is reached before a reliable result can be obtained, the search drive flag is turned off. If the subject cannot be specified, the search drive may be controlled to continue without turning off the search drive flag.

In S1004, the lens is driven based on the defocus amount, and the lens driving process is completed. Proceed in case of follow-up mode.

In S1005, the movement amount of the subject is predicted from the defocus amount and the lens is driven.

[Follow-up AF processing]
Subsequently, the follow-up AF process will be described with reference to FIG. The follow-up AF process is the AF process in the follow-up mode. In the follow-up AF process, in the follow-up mode, it is not simply determined whether or not the latest defocus amount is within a predetermined range (within the first range) based on the depth of focus as in S701 and S801. , The determination is made in consideration of the inverted state of the driving direction of the focus lens. Whether or not a focus detection result in which the direction in which the focus lens 103 is driven is reversed (in the opposite direction) is obtained, and the focus position is determined based on the number of times and the target lens position.

Further, in the follow-up AF process, the inversion drive is limited. Here, the inversion drive refers to the driving direction of the focus lens 103 in the closest direction based on the focus detection result (for example, the defocus amount including the information on the driving direction of the focus lens 103) that reverses the driving direction of the focus lens 103. It is a drive that reverses in the infinite direction. By limiting this inversion drive, the quality of moving images during follow-up AF is improved.

In S2601, the camera control unit 212 determines whether or not there is reverse drive, and if there is reverse drive, the process proceeds to S2609, and if not, the process proceeds to S2604. In the present embodiment, there is reverse drive when a defocus amount that reverses the drive direction of the focus lens is detected, and there is no reverse drive when a defocus amount that does not reverse the drive direction of the focus lens is detected. The camera control unit 212 determines.

In S2609, the camera control unit 212 clears the timer limiting the reverse drive, and proceeds to S2602.

In S2602, the lens drive speed is set in the same manner as in S803, and in S2603, the camera control unit 212 controls to perform the same lens drive process as in S804, and the process of this flow ends.

In S2604, the reversal timer is started and the process proceeds to S2605. The reversing timer of the present embodiment is a timer for limiting the reversing drive of the focus lens 103 by a first predetermined time (described later) when the camera control unit 212 determines that the reversing drive is performed in S2601. is there.

In S2605, the camera control unit 212 determines whether the defocus amount is equal to or greater than the fourth predetermined value. This is a process for changing the time for controlling the reversal drive by the reversal timer according to the defocus amount. In the present embodiment, as an example, the fourth predetermined value is set to be three times the depth of focus. If the defocus amount is equal to or more than the fourth predetermined value, the process proceeds to S2606, and if it is less than the fourth predetermined value, the process proceeds to S2607.

In S2606 and S2607, the camera control unit 212 sets a predetermined time (first predetermined time), which is a threshold value of the reversal timer, at the time A or the time B. The camera control unit 212 controls that the focus lens 103 is not driven until the time set as the threshold value of the inversion timer elapses. The relationship between time A and time B is as follows.
Time A <Time B

In the present embodiment, as an example, the time A is set to 0.3 seconds and the time B is set to 1 second. The reason why the time A is shorter than the time B is that when a defocus amount of 3 times or more the depth of focus is detected, the subject is likely to change direction rather than stop. .. In this case, a shorter time is set so that the focus lens 103 can be easily inverted and driven according to the movement of the subject.

On the other hand, if the defocus amount is less than 3 times the depth of focus, it is highly possible that the defocus amount is due to the variation in the focus detection result or the variation in the defocus amount when the subject stops moving. Also set B for a long time. As a result, the driving of the focus lens 103 is restricted in response to the variation in the focus detection result when the focus is stopped, and the image quality is improved. In this way, by changing the threshold value according to the driving direction, the followability to the subject that is really inverted is maintained, and when the moving subject stops, the focus lens maintains the image quality. It becomes possible to control the stop of.

In S2608, the camera control unit 212 determines whether the set first predetermined time (time A or B) has elapsed since the reversal timer was started. When the reversal timer exceeds the first predetermined time, the camera control unit 212 permits the reversal drive of the focus lens 103. If this is not the case, the camera control unit 212 controls to proceed to S2610 and perform the follow-up stop determination process. That is, the camera control unit 212 controls to stop driving the focus lens 103 until the first predetermined time is exceeded.

In S2610, the follow-up stop determination process is performed. This process will be described later with reference to FIGS. 15 and 16.

In S2611, the camera control unit 212 determines whether or not the tracking is stopped. If the follow-up is stopped, the process proceeds to S2612, the follow-up stop flag is turned on, and the camera control unit 212 controls to end the processing of this flow. If not, the process proceeds to S2613, the follow-up stop flag is turned off, and the camera control unit 212 controls to end the processing of this flow.

As described above, in the present embodiment, the camera control unit 212 controls the follow-up AF in the follow-up mode so that the drive of the focus lens 103 differs depending on whether or not there is reverse drive. In the follow-up AF in the follow-up mode, it is not determined that the focus is stopped depending on whether or not the detected defocus amount is within the depth of focus. On the other hand, if the detected defocus amount is within the depth of focus, it is determined that the focus is stopped. It is determined that the subject is in a focused state, and the focus adjustment is temporarily stopped. In order to stop the focus adjustment once, detect the moving object again, and make the focus lens follow the moving object, a time lag may occur, and blurring may occur during this period. That is, in the tracking mode of the present embodiment, the image quality when tracking a moving object can be improved by not determining that the focus is stopped depending on whether or not the detected defocus amount is within the depth of focus.

[Outline of follow-up stop judgment]
Subsequently, the follow-up stop determination of S2610 (FIG. 14) will be described with reference to FIGS. 15 and 16. FIG. 16 is a diagram for explaining the outline of the follow-up stop determination. In FIG. 16, it is assumed that the focus lens 103 reaches the vicinity of the in-focus position in the follow-up mode.

When the focus detection is performed when the focus lens 103 is located near the in-focus position, the focus detection result varies between the close and infinite directions around the in-focus position. Utilizing this feature, based on the number of times the target lens position reciprocates infinitely and close to infinity based on the focus detection result, and whether or not the subject is in focus (whether or not to stop tracking) based on each target lens position. ) Is determined by the camera control unit 212 (focus determination means).

2801 (solid line) is the actual position of the focus lens 103, and 2802 (dotted line) is the target lens position of the focus lens 103 considering the amount of defocus detected by the focus detection. Until 2803, the direction of the defocus amount detected in S506 is not inverted with respect to the driving direction of the focus lens 103, and the actual lens position and the target lens position are the same. After 2803, the direction of the defocus amount detected in S506 is reversed. In the present embodiment, when the direction of the defocus amount detected in S506 is reversed in the tracking mode, the drive of the focus lens is controlled not to be reversed for a predetermined time (first predetermined time), and the predetermined time is controlled. During that time, the actual lens position is 2805 (solid line). On the other hand, since the focus detection results vary, the actual lens position and the target lens position do not match after 2803 in FIG.

In the tracking stop determination, the camera control unit 212 makes a determination based on at least three target lens positions based on the focus detection results for at least three times. By detecting the target lens positions 2803, 2804 and 2806 and calculating the average position of these inverted target lens positions or the average position of one target lens position closest to the target lens position and one infinite target lens position, the target lens positions are calculated. Find the center position 2810. Subsequently, it is determined whether or not 2808, which is the difference between the target lens position 2804 and the target lens position 2806, is within the second range (within twice the depth of focus as an example in the present embodiment) (condition 1). Then, it is determined whether or not 2809, which is the difference between the target lens position 2807 and the center position 2810, is within the third range (within 1 times the depth of focus as an example in this embodiment) based on the latest focus detection result (condition). 2). If the above two conditions are satisfied, it is determined that the following subject has stopped.

In this embodiment, an example is shown in which the plurality of defocus amounts detected at the target lens position 2803 are defocus amounts that alternately drive the focus lens 103 in different directions. On the other hand, even if the defocus amount that drives the focus lens 103 in different directions is not continuously detected, condition 1 and condition 2 may be determined in the same manner.

[Flow of follow-up stop judgment]
FIG. 15 is a flowchart of the contents described in FIG.

In S2701, the AF signal processing unit 204 calculates the target lens position of the focus lens 103 from the defocus amount calculated in S506, and proceeds to S2702.

In S2702, the camera control unit 212 counts the reversal of the target lens position with respect to the driving direction of the focus lens 103 based on the previous focus detection result, and proceeds to S2703.

In S2703, the target lens position (also referred to as the inversion position) in which the drive direction of the focus lens 103 is inverted is stored in the SDRAM 209, and the process proceeds to S2704.

In S2704, it is determined whether or not the reversal count is the first number of times or more (three times or more in the present embodiment), and if it is the first number of times or more, the process proceeds to S2705, otherwise the process proceeds to S2709 and the follow-up stop. It is determined that this is not the case, and the process ends.

In S2705, the camera control unit 212 calculates the center position of the inverted position of the lens.

In S2706, the camera controls whether the closest target lens position and the most infinite target lens position are within the second range based on the center position (within twice the depth of focus in this embodiment). Part 212 does. If it is within the second range, the process proceeds to S2707. If it is not within the second range, the process proceeds to S2709, the camera control unit 212 determines that the follow-up stop is not performed, and the processing of this flow ends.

In S2707, the camera control unit 212 determines whether the target lens position is within a third range from the center position of the inversion position (within twice the depth of focus in this embodiment). If it is within twice, the process proceeds to S2708, the camera control unit 212 determines that the follow-up is stopped, and the process of this flow ends. If not, the process proceeds to S2709, and the camera control unit 212 determines that the follow-up stop is not stopped, and the process ends.

As described above, in the following embodiment, in the follow-up mode, the camera control unit 212 is focused in S2704 to S2707 based on the magnitude of the defocus amount and the inverted state of the drive direction of the focus lens based on the defocus amount. It is determined whether or not it is in a state. As a result, when the amount of defocus obtained as a result of focusing detection on a moving object is within the depth of focus, it is determined that the moving object is still in focus even though it is still moving, and the focus is adjusted. Can be prevented from being temporarily stopped. In this way, it is possible to improve the quality of the image when following a moving object as compared with the conventional technique.

[Other Embodiments]
In the above-described embodiment, the number of inversion counts is detected based on the focus detection result detected within the first predetermined time set in S2606 or S2607. Instead of this, it may be simply inverted whether or not the focus detection result detected within a predetermined time is detected more than the second number of times within the second range. The second number of times is the number of times that it can be determined that the subject is not moving if the focus detection result of the second number of times is continuously detected within the second range. If the focus detection result detected within the first predetermined time is detected in the second range more than the second predetermined number of times, the process proceeds to S2705, and if not, the process proceeds to S2709.

In the follow-up stop determination of the above-described embodiment, the focus lens 103 was stopped at 2805 in FIG. 16 when both S2706 and S2707 were satisfied when the inversion count was 3 times or more in S2704. .. On the other hand, the camera control unit 212 may control the focus lens 103 to stop at the position of 2807, which is the nearest target lens position. This makes it possible to focus more accurately even when the 2805 is not within the depth of focus of the actual focusing position.

Further, in the follow-up stop determination of the above-described embodiment, it is determined that the follow-up stop is performed when both S2706 and S2707 are satisfied when the reversal count is 3 times or more in S2704. On the other hand, the camera control unit 212 may determine whether or not to stop following based only on the determination of S2706 without performing the determination of S2707. In this case, since S2707 is not performed, the focus lens 103 cannot be stopped at the position of 2807, which is the nearest target lens position. However, by fixing the focus lens 103 as it is at 2805, the change in the blurred state is reduced, so that the quality of the moving image can be improved.

Further, as a method of determining whether or not the drive speed of the focus lens 103 set in S911 of FIG. 6 of the above-described embodiment is a speed that can catch up with the moving object, the previous defocus amount and the current defocus amount are used. It may be compared with the defocus amount. When the defocus amount detected this time is equal to or greater than the defocus amount detected last time, the camera control unit 212 determines that the speed cannot catch up with the moving object. If the defocus amount detected this time is less than the defocus amount detected last time, the camera control unit 212 determines that the speed is such that it can catch up with the moving object.

Further, when the subject is located on the infinite side more than a predetermined value, the determination of S911 may not be performed. The predetermined or more infinite side here is a distance at which a focus detection error occurs to an unacceptable degree in determining S911.

Further, in S2207 and S2210 of the subject change determination process (FIG. 10) described above, the ratio of the distance from the focal point to the subject to the depth of field is equal to or greater than the second predetermined value, and the distance from the focal point to the subject is the third predetermined value. If it is greater than or equal to the value, it is determined that the subject has been changed. Instead of this, it is determined whether or not the subject has been changed by determining whether or not the ratio of the defocus amount to the depth of focus is equal to or greater than the eleventh predetermined value and the defocus amount is equal to or greater than the twelfth predetermined value. You may. When the ratio of the defocus amount to the depth of focus is equal to or greater than the eleventh predetermined value and the defocus amount is equal to or greater than the twelfth predetermined value, the camera control unit 212 determines that the subject has been changed. When the ratio of the defocus amount to the depth of focus is not equal to or more than the eleventh predetermined value and the defocus amount is not equal to or more than the twelfth predetermined value, it is determined that the subject has not been changed.

Further, the result that the ratio of the distance from the focal point to the subject to the depth of field is less than the second predetermined value and the distance from the focal point to the subject is equal to or more than the third predetermined value can be obtained a third time or more. If possible, the camera control unit 212 may determine that the subject has been changed. If the ratio of the distance from the focal point to the subject to the depth of field is less than the second predetermined value and the distance from the focal point to the subject is greater than or equal to the third predetermined value, the result is less than the third number of times. It is considered that the cause is the variation in the focus detection result due to the long subject distance. Therefore, the result that the ratio of the distance from the focal point to the subject to the depth of field is less than the second predetermined value and the distance from the focal point to the subject is equal to or more than the third predetermined value can be obtained less than the third number of times. If so, it may be determined that the subject has not been changed.

The present invention also supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device read and execute the program. It can also be realized by the processing to be done. Further, it can be realized by a circuit (for example, ASIC) that realizes one or more functions.

Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various embodiments within the scope of the gist of the present invention are also included in the present invention. included. In particular, for the parts showing specific numerical values, specific numerical values are used as an example to make the explanation easy to understand, and other values may be used according to the purpose of the present embodiment. .. Further, for each of the formulas used in the above-described embodiment, another formula may be used as long as the object can be achieved.

103 Focus lens 204 AF signal processing unit (focus detection means)
212 Camera control unit (control means, determination means, setting means)

Claims (10)

A focus detection means that detects the amount of defocus based on a pair of image signals that the image sensor receives and photoelectrically converts a pair of light fluxes having parallax that have passed through a photographing optical system including a focus lens.
A control means that controls the drive of the focus lens based on the focus detection result by the focus detection means, and
It has a determination means for determining whether or not the subject has been switched based on the distance from the in-focus subject position converted from the defocus amount to the subject.
In the determination means, the ratio of the distance from the in-focus subject position to the subject to the depth of field is equal to or greater than a second predetermined value based on the depth of field, and the distance from the in-focus subject position to the subject is determined. A lens control device characterized in that when the amount of change is equal to or greater than a third predetermined value, it is determined that the subject has been switched. The ratio of the distance from the in-focus subject position to the subject to the depth of field is equal to or greater than the second predetermined value based on the depth of field, and the distance from the in-focus subject position to the subject is the third predetermined value. The lens control device according to claim 1, wherein if the above is not the case, the determination means determines that the subject has not been switched. It has a setting means for setting a threshold value and has a setting means.
The first or second aspect of the present invention, wherein when the depth of focus is deep, the setting means sets the second predetermined value to a larger amount as compared with the case where the depth of focus is shallower. Lens control device. The lens control device according to claim 3 , wherein when the subject distance is short, the setting means sets the third predetermined value to a smaller value as compared with the case where the subject distance is farther. The method according to any one of claims 1 to 4, wherein when the determination means determines that the subject has been switched, the control means controls the focus lens to stop driving. Lens control device. 5. The fifth aspect of the present invention is characterized in that, when a second predetermined time or more has elapsed after the control means controls to stop the driving of the focus lens, the control is controlled to restart the driving of the focus lens. The lens control device described. Any one of claims 1 to 6, wherein when the determination means determines that the subject has not been switched, the control means controls to continue driving the focus lens. The lens control device according to. A focus detection step that detects the amount of defocus based on a pair of image signals that the image sensor receives and photoelectrically converts a pair of light fluxes having parallax that have passed through a photographing optical system including a focus lens.
A control step that controls the drive of the focus lens based on the focus detection result in the focus detection step, and
It has a determination step of determining whether or not the subject has been switched based on the distance from the subject position in focus based on the defocus amount to the subject.
In the determination step, the amount of change in the ratio of the distance from the in-focus subject position to the subject with respect to the depth of field is equal to or greater than the second predetermined value based on the depth of field, and the in-focus subject position to the subject. A control method of a lens control device, characterized in that it is determined that the subject has been switched when the amount of change in the distance is equal to or greater than a third predetermined value. A focus detection means that detects the amount of defocus based on a pair of image signals that the image sensor receives and photoelectrically converts a pair of light fluxes having parallax that have passed through a photographing optical system including a focus lens.
A control means that controls the drive of the focus lens based on the focus detection result by the focus detection means, and
It has a determination means for determining whether or not the subject has been switched based on the ratio of the defocus amount to the depth of focus and the distance from the in-focus subject position to the subject based on the focus detection result.
The determination means obtains a focus detection result in which the amount of change in the ratio of the defocus amount to the depth of focus is less than the second predetermined value, and the distance from the in-focus subject position to the subject is greater than or equal to the third predetermined value. A lens control device characterized in that when the number of detected times is equal to or greater than the first number of times, it is determined that the subject has been switched. A focus detection step that detects the amount of defocus based on a pair of image signals that the image sensor receives and photoelectrically converts a pair of light fluxes having parallax that have passed through a photographing optical system including a focus lens.
A control step that controls the drive of the focus lens based on the focus detection result in the focus detection step, and
It has a determination step of determining whether or not the subject has been switched based on the ratio of the defocus amount to the depth of focus and the distance from the in-focus subject position to the subject based on the focus detection result.
In the determination step, a focus detection result is obtained in which the amount of change in the ratio of the defocus amount to the depth of focus is less than the second predetermined value, and the distance from the in-focus subject position to the subject is greater than or equal to the third predetermined value. A control method of a lens control device, characterized in that it is determined that the subject has been switched when the number of detected times is equal to or greater than the first number of times.

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