JP2010224058A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate a focusing position, in an imaging apparatus that adopts a contrast AF system. <P>SOLUTION: The imaging apparatus includes: an imaging device 101 which picks up an image by receiving subject light transmitted through a focus lens 201; an AF evaluated value arithmetic calculating section 107 which arithmetically calculates an AF evaluated value by using the image picked up by the imaging device 101; and a focusing position arithmetic calculating section 108, which arithmetically calculates the focusing position using a plurality of results by the AF evaluated value arithmetic calculating section 107 and is further provided with a focusing position arithmetic calculation start decision section 109 which decides significance of the result by the AF evaluated value arithmetic calculation section 107, based on subject information arithmetically calculated from the picked-up image from the imaging device 101 and makes a decision, to start the arithmetic calculation to the focusing position arithmetic calculation section 108, when there is significance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to an autofocus (hereinafter abbreviated as AF) technique in the imaging apparatus.

  The AF technology in the conventional digital camera is roughly classified into a TTL (Through the Lens) phase difference AF method and a contrast AF method.

  In general, the phase difference AF method is often used for AF of a lens interchangeable digital single-lens reflex camera, and there is a feature that focus detection can be performed at high speed. For this reason, it is possible to focus on a moving subject with high accuracy. This phase difference AF azimuth is provided with an AF sensor module for detecting a focus position shift in the camera body, and a focus adjustment lens (defocus amount) is detected by the focus shift amount (defocus amount) detected by the AF sensor module. Focus detection). However, this method requires a dedicated sensor, and further increases the cost of the camera by increasing the size of the camera because the optical path for shooting is divided by an optical member such as a half mirror to guide the light to the sensor. There is a problem of being connected.

  On the other hand, the compact digital camera often uses the contrast AF method, and detects the high frequency component of the subject while moving the focus lens in the optical axis direction, and performs focus detection by calculating the peak value of the contrast. The contrast AF method has a feature that the focus detection speed is not high, but high-precision focus control is possible. Since this method is performed using an image pickup device for photographing, there is no need to divide the optical path as in the phase difference AF method, and there is a great merit in terms of camera size and cost.

  “In-focus” in an image means a crisp image, which can be said to be the state in which the edge of a subject is most clear. That is, the state where the integrated value through the high-pass filter is the highest is “in focus”. Thus, in the case of the contrast AF method, the final value of focusing is generally obtained by plotting the AF evaluation value while changing the lens position (focus position) using the integrated value passed through the high-pass filter as the AF evaluation value. Calculate by interpolating the position. Hereinafter, the contrast AF method will be described with reference to FIG.

  (1) For example, assuming that the initial position (focus position) of the lens is p1, first, the AF evaluation value A1 is calculated at the focus position p1.

  (2) or (2 ') After obtaining the AF evaluation value at the focus position p1, it is not known whether the in-focus position is in the infinite direction or the closest direction. For this reason, the focus position is moved by a fixed amount in either the infinite direction (2) or the closest direction (2 '), and the AF evaluation value is calculated again there. As a result, the AF evaluation value A1 at the focus position p1 and the AF evaluation value A2 (or A0) at the focus position p2 (or p0) are compared to determine whether the focus position is either. .

  (3) Since the in-focus direction has been identified, a fixed amount of focus position is shifted toward the in-focus direction, and the AF evaluation value A3 is acquired at the focus position p3.

  (4) Further, a certain amount of focus position is shifted toward the in-focus direction, and the AF evaluation value A4 is calculated at the focus position p4. Here, when the AF evaluation value A3 at the focus position p3 and the AF evaluation value A4 at the focus position p4 are compared, A3> A4. From this, it can be determined that the peak position of the AF evaluation value, that is, the in-focus position has been passed. Therefore, the interpolation position pMax is calculated by performing interpolation with the three focus positions p2, p3, and p4 near the in-focus position and the AF evaluation values A2, A3, and A4. There are various known techniques such as linear interpolation and Lagrangian for the interpolation calculation, but linear interpolation is used if speed priority is given. If accuracy is prioritized, the number of sampling points may be increased and Lagrange interpolation, spline interpolation, or the like may be used.

  After the in-focus position pMax is calculated in this way, the focus position is returned to the calculated in-focus position pMax to stop, and the photographing operation is started.

  When the focus movement direction is reversed as in (4) to (5) and (2 ′) to (2) above, if there is backlash due to the mechanical structure of the lens, In consideration of this, it is necessary to reverse the focus movement. Specifically, the influence of the backlash can be reduced by making it go backward in the opposite direction to the in-focus direction by the amount of backlash and then returning to reverse.

  For example, FIG. 11A is an image diagram when the focus position is changed to p1_1, p1_2, and p1_3 with respect to a subject that has not moved. The AF evaluation value is calculated from the image of the AF area 11 within the shooting angle of view 10. It can also be visually determined that the degree of image sharpness, that is, the AF evaluation value is p1_1 <p1_3 <p1_2. The relationship between the focus position and the AF evaluation value in this case is as shown in the upper graph in FIG. The error between the result p1_Max obtained by interpolating the focus position from this situation (p1_1 to p1_3, A1_1 to A1_3) and the actual focus position p1_Max_T is Δp1.

  On the other hand, FIG. 11B is an image diagram when the focus position with respect to the subject is changed to p2_1, p2_2, and p2_3, similarly to FIG. 11A. This shows a case where a high-speed moving subject 13 such as an automobile moving at high speed passes behind a non-moving subject 12 and the high-speed moving subject 13 enters the AF area 11 at the focus position p2_3. . The degree of chatter of the image is p2_1 <p2_3 <p2_2. However, when the AF evaluation value is calculated, p2_1 <p2_3≈p2_2, and an error occurs in the interpolation calculation of the in-focus position. That is, the relationship between the focus position and the AF evaluation value in this case is as shown in the lower graph in FIG. An error between the result p2_Max obtained by performing the interpolation calculation of the in-focus position from this situation (p2_1 to p2_3, A2_1 to A2_3) and the actual in-focus position p2_Max_T is Δp2.

  Since the actual in-focus position p1_Max_T = p2_Max_T, the error in the lower diagram is larger than that in the upper diagram in FIG. 12, and the lens drive is stopped at the focus position where the error is large, and the image is out of focus. It will be filmed.

  As described above, the contrast AF type focus position detection requires at least three sets of images at different focus positions. In order to change the focus position, lens driving and imaging are required, and the time required for these is not short. For this reason, a moving subject (particularly in the case of a subject that moves at high speed) is likely to move during the shooting of three images, and as a result, an incorrect in-focus position is calculated.

  Furthermore, in recent years, in a lens interchangeable digital single-lens reflex camera, a technique called “live view AF” in which AF is performed while framing is performed by always displaying information on an image sensor on a rear liquid crystal. This is not new in a compact camera, but it can be said that it is groundbreaking in a single-lens reflex camera in which a light beam is not normally incident on an image sensor. However, in live view AF, since light is not guided to the phase difference sensor, the AF method has to use contrast AF. For this reason, in spite of the single-lens reflex camera, the problem that the focusing accuracy with respect to the moving object is poor is further highlighted.

  As a technique for improving the focusing accuracy in such contrast AF, there is, for example, Patent Document 1. This is to interrupt or stop the contrast AF operation when a camera shake is detected by a camera shake detection mechanism provided in the camera.

JP 2008-107665 A

  In Patent Document 1, when a camera shake is detected by a camera shake detection mechanism installed in the camera, the contrast AF operation is interrupted or stopped according to the amount of camera shake. However, in the case of image blur that causes the subject side to move at high speed, there is no camera shake information, so the contrast AF operation cannot be interrupted or stopped, and an incorrect in-focus position is calculated. .

  The present invention has been made in view of the above points, and an object thereof is to provide an imaging apparatus capable of calculating a focus position with high accuracy in the contrast AF method.

One aspect of the imaging device of the present invention is:
An image sensor for receiving and imaging subject light transmitted through the imaging optical system;
An AF evaluation value calculation unit that calculates an AF evaluation value using an image captured by the image sensor;
A focus position calculation unit that performs a focus position calculation using a plurality of results of the AF evaluation value calculation unit;
The significance of the result of the AF evaluation value calculation unit is determined based on the subject information calculated from the captured image from the imaging element, and if it is significant, the focus position calculation unit is determined to start calculation. An in-focus position calculation start determination unit,
It is characterized by comprising.

  According to the present invention, a contrast AF operation is performed only when there is no image blur that causes the subject to move at high speed by making a start determination of the AF operation of the contrast AF method based on the subject information calculated from the captured image. Therefore, it is possible to provide an imaging apparatus capable of calculating an in-focus position with high accuracy and capturing an image with less blur.

FIG. 1 is a diagram illustrating a configuration of a lens-interchangeable digital single-lens reflex camera as a first embodiment of an imaging apparatus according to the present invention. FIG. 2 is a diagram for explaining a technique for detecting a motion amount and determining a focus position calculation start using the optical flow method. FIG. 3 is a timing chart for explaining the AF operation in the camera of the first embodiment. FIG. 4 is an operation flowchart for explaining the AF operation in the camera of the first embodiment. FIG. 5 is an operation flowchart for explaining the focus position acquisition operation in the lens body. FIG. 6 is an operation flowchart for explaining the lens driving operation in the lens body. FIG. 7 is a diagram showing a configuration of a lens interchangeable digital single-lens reflex camera as a second embodiment of the imaging apparatus of the present invention. FIG. 8 is a timing chart for explaining the AF operation in the camera of the second embodiment. FIG. 9 is an operation flowchart for explaining the AF operation in the camera of the second embodiment. FIG. 10 is a diagram for explaining the contrast AF method. FIG. 11A is a diagram showing the transition of the subject image when the focus position is changed with respect to the subject that has not moved, and FIG. 11B shows the case where the subject that is moving is included. It is a figure which shows the transition of a to-be-photographed image when changing the focus position. FIG. 12 is a diagram showing the relationship between the focus position and the AF evaluation value in the cases of FIGS.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the lens interchangeable digital single-lens reflex camera as the first embodiment of the imaging apparatus of the present invention includes a camera body 100 and a lens body 200.

  Here, the lens body 200 is provided as an interchangeable lens configured to be detachable from the camera body 100, and includes a focus lens 201, a motor 202, a lens driving circuit 203, a focus encoder 204, and a lens CPU 205. , Etc.

  Here, the focus lens 201 is a photographing optical system that forms an image of a light beam from a subject, and can be adjusted in focus by being driven in the optical axis direction by a motor 202. The lens drive circuit 203 is a driver that issues a drive control signal to the motor 202. The focus encoder 204 detects the focus position of the focus lens 201 and may be a mechanical encoder that mechanically detects the position, or a potentiometer that electrically detects the position. . The lens CPU 205 communicates with the camera body 100 via the communication path 300 to control each part in the lens body 200. The lens CPU 205 adjusts the focus position of the focus lens 201 and determines the focus position detected by the focus encoder 204 by issuing a drive instruction to the lens drive circuit 203 in accordance with a command from the camera body 100. The function to transmit to 100 is provided.

  Transmission data on the communication path 300 includes a focus position (from the lens body 200 to the camera body 100), a synchronization pulse (synchronized with the focus position acquisition time) (from the lens body 200 to the camera body 100), and a lens drive amount (camera body). 100 to the lens body 200), power supply / GND, CS / Clock, and the like.

  The camera body 100 includes an image sensor 101, a motion detector 102, a recorded image processor 103, a recorded image memory 104, a display image processor 105, a display element 106, an AF evaluation value calculator 107, and a focus position calculator 108. , A focus position calculation start determination unit 109, a camera CPU 110, and the like.

  Here, the image sensor 101 receives and captures subject light that has passed through a focus lens 201 serving as a photographing optical system. The motion detection unit 102 includes a frame memory (not shown) for capturing a plurality of images picked up by the image sensor 101, and the first stage operation (hereinafter abbreviated as 1R operation) of a two-stage release button (not shown). When the distance measurement start request is made according to the above, the difference between the previous screen image captured in the frame memory and the current screen image is obtained to detect motion information of the subject, for example, a motion vector. To do.

  When a recording request is made by the second stage operation (hereinafter abbreviated as 2R operation) of the release button, the recorded image processing unit 103 captures the current screen image captured in the frame memory of the motion detection unit 102. Image processing such as image creation (demosaicing, aberration, edge enhancement, etc.), DCT frequency conversion, quantization (reducing the amount of information), multiplexing information (motion vector, differential image switching information), etc. To record in the recorded image memory 104. The recorded image memory 104 may be a built-in and fixed camera body 100 or a detachable memory.

  The display image processing unit 105 performs image creation (demosaicing, aberration, edge enhancement, etc.), thinning, DCT frequency conversion, quantization (information) on the current screen image captured in the frame memory of the motion detection unit 102. The image is picked up by the image sensor 101 by performing image processing such as motion interpolation based on multiplexing information (motion vector, difference image switching information) and displaying on the display element 106 such as a rear liquid crystal. “Live view” display in which an image is always displayed on a display element is enabled.

  The AF evaluation value calculation unit 107 includes a frame memory (not shown) for capturing an image captured by the image sensor 101, and performs sharpness extraction from the current screen image captured in the frame memory. For example, a high-pass filter The AF evaluation value is obtained by calculating the integrated value that has passed through. The in-focus position calculation unit 108 is calculated by the focus position from the lens body 200 given via the camera CPU 110 that controls each part in the camera body 100 and the AF evaluation value calculation unit 107, and starts the in-focus position calculation. An internal RAM (not shown) for storing a plurality of AF evaluation values (AF evaluation values up to the present) given through the determination unit 109 is provided, and using these two, for example, interpolation calculation is performed from information on the past three points. The in-focus position (in-focus peak) is estimated. Then, the difference (defocus amount) between the current focus position and the estimated focus position is transmitted to the lens body 200 via the camera CPU 110. The lens CPU 205 of the lens body 200 performs lens driving by the lens driving circuit 203 based on the transmitted defocus amount.

  The in-focus position calculation start determination unit 109 is based on subject information calculated from an image captured by the image sensor 101, for example, subject motion information detected by the motion detection unit 102, and the AF evaluation value calculation unit 107. The significance of the AF evaluation value obtained in step 1 is determined, and the calculation of the focus position calculation unit 108 is started or stopped. If the AF evaluation value is significant, the focus position calculation unit 108 is determined to start calculation, and a focus position (focus peak) calculation start trigger is issued. The in-focus position calculation start trigger may be bit information indicating OK / NG, or may be a form in which a pulse signal is issued only at the time of OK.

  Here, the focus position calculation start determination in the focus position calculation start determination unit 109 will be further described.

  For example, the motion information of the subject detected by the motion detection unit 102 is a basis for determining the start of the in-focus position calculation. Specifically, the motion information is the amount of motion of the subject in the AF area 11 for calculating the AF evaluation value. As a method for detecting the amount of motion, there are known techniques such as an optical flow method (block matching method, gradient method, etc.) and an inter-frame difference method, and any of them may be used.

  An example using the optical flow method in FIG. 2 will be briefly described. Two types of motion information (m1, m2) can be calculated from the three images (focus positions p2_1, p2_2, p2_3) with the focus position shifted. Looking at the motion information m1, there is a point of the person position (Xb1, Yb1) in the AF area 11, but there is no moving object, so there is no motion amount as a vector. In addition, although there is information of (Xa1, Ya1) for the automobile that is the high-speed moving subject 13, it is outside the AF area 11. Next, focusing on the motion information m2, in this case, the fast moving subject 13 enters the AF area 11, and the motion amount m_t = | (Xa2, Ya2) − (Xa1, Ya1) |.

  In the in-focus position calculation start determination unit 109, as described above, the movement amount m_t and the current position (post-movement position) P_a (Xa2, Ya2) of the current moving object (high-speed moving subject 13) corresponding thereto and From the information of the position P_b (Xa1, Ya1) before the movement of the high-speed moving subject 13, the significance of the AF evaluation value obtained by the AF evaluation value calculation unit 107, that is, the focus position calculation by the focus position calculation unit 108 is calculated. It is determined whether or not to do so. In the case of determination NG, the focus position calculation in the focus position calculation unit 108 is stopped.

An example of the situation that should be judged is as follows.
(1) When an object enters the AF area 11 from outside the AF area 11. In this case, the motion amount m_t ≠ 0, the pre-motion object position P_a is outside the AF area 11, and the post-motion object position P_b is inside the AF area 11. In the case of (1), it is determined to stop the calculation with respect to the in-focus position calculation unit, and as the determination NG, the in-focus position calculation in the in-focus position calculation unit 108 is stopped.

    (2) When an object comes out of the AF area 11 from the AF area 11. In this case, the motion amount m_t ≠ 0, the pre-motion object position P_a is in the AF area 11, and the post-motion object position P_b is outside the AF area 11. In the case of (2), it is determined to stop the calculation with respect to the in-focus position calculator, and as the determination NG, the in-focus position calculation in the in-focus position calculator 108 is stopped.

    (3) When an object moves in the AF area 11. In this case, the motion amount m_t ≠ 0, the pre-motion object position P_a is in the AF area 11, and the post-motion object position P_b is in the AF area 11. In the case of (3), the focus position calculation unit 108 is determined to start position calculation, and the determination of the focus position calculation unit 108 is continued as determination OK.

  The threshold value to be determined may vary depending on the focal length, the diaphragm, and the like.

  Hereinafter, the AF operation in the camera having the above-described configuration will be described with reference to the timing chart of FIG. 3 and the operation flowchart of FIG.

  The image sensor 101 performs an exposure operation and captures an image during the shooting period (period when the imaging timing waveform is high) (step S101). Thereafter, when there is an AF trigger by a user operation such as a 1R operation or a 2R operation (step S102), the captured image is input to the motion detection unit 102 and the AF evaluation value calculation unit 107.

  In the motion detection period (period in which the motion detection waveform is high), the motion detection unit 102 detects motion information from the previous screen image and the input current screen image (step S103). Also, the AF evaluation value calculation unit 107 calculates an AF evaluation value from the image on the original screen during the AF evaluation value calculation period (a period when the AF evaluation value calculation waveform is high) (step S104). These movement information and AF evaluation value are input to the in-focus position calculation start determination unit 109. Note that the motion detection period and the AF evaluation value calculation period do not necessarily start at the same timing.

  Thereafter, the focus position calculation start determination unit 109 performs the focus position calculation based on the motion information from the motion detection unit 102 during the focus position calculation start determination period (the period when the focus position calculation start determination waveform is high). It is determined whether or not (step S105). It is assumed that the OK / NG threshold value for determining the start of the in-focus position calculation can be changed by the focal length, aperture information, and the like. The focus position calculation start determination result is input to the focus position calculation unit 108 as bit information (flag) indicating OK / NG. Note that the pulse information may be issued only at the time of OK instead of the bit information indicating such OK / NG. The focus position calculation start determination unit 109 also inputs the AF evaluation value from the AF evaluation value calculation unit 107 to the focus position calculation unit 108.

  The AF evaluation value calculated by the AF evaluation value calculation unit 107 is directly input from the AF evaluation value calculation unit 107 to the focus position calculation unit 108 without the focus position calculation start determination unit 109. Of course, it may be.

  The focus position calculation unit 108 waits for the result of the determination of the focus position calculation start determination OK (step S106), and starts the focus position calculation (step S107). That is, in the in-focus position calculation period (the in-focus position calculation waveform is high), the AF evaluation value calculated by the AF evaluation value calculation unit 107 and the lens body 200 are sent and input via the camera CPU 110. The focus position information is used, and the in-focus position (in-focus peak) is estimated by performing interpolation calculation from the information of the past three points.

  It should be noted that the focus position necessary for the in-focus position calculation is acquired by the lens body 200 as shown in FIG. That is, when the lens CPU 205 receives a focus position acquisition request from the camera CPU 110 by data communication via the communication path 300 (step S201), the lens CPU 205 acquires the focus position using the focus encoder 204 provided in the vicinity of the focus lens 201 ( In step S202, the acquired focus position is transmitted to the camera CPU 110 by data communication via the communication path 300 (step S203). For data communication, known techniques such as clock synchronization and asynchronous are used.

  If the in-focus position calculation unit 108 estimates the in-focus position (in-focus peak) by the in-focus position calculation, it further calculates the difference (defocus amount) between the current focus position and the in-focus estimated focus position as the lens drive amount. (Step S108), and transmits it to the lens CPU 205 via the camera CPU 110 (step S109). Then, the AF evaluation value and the focus position up to now are stored in an internal RAM (not shown) (step S110).

  The lens main body 200 drives the focus lens 201 based on the lens driving amount (defocus amount) transmitted from the camera main body 100. That is, as shown in FIG. 6, when the lens CPU 205 receives the lens drive amount from the camera CPU 110 by data communication via the communication path 300 (step S211), first, the lens encoder 205 is installed in the vicinity of the focus lens 201. The current focus position is acquired by using (Step S212). Then, based on the received lens driving amount and the acquired current focus position, it is determined how much the focus lens 201 is driven in which direction, and parameters of the driving system (motor 202) necessary for the driving are determined. The lens driving circuit 203 is set (step S213). Then, the lens driving circuit 203 drives the motor 202 according to the set parameter, thereby moving the focus lens 201 by the lens driving amount instructed from the camera body 100 side (step S214).

  When the focus position calculation start determination unit 109 inputs the result of determination NG to the focus position calculation unit 108 (step S106), the focus position calculation unit 108 stores the past stored in an internal RAM (not shown). The AF evaluation value / focus position is reset, and the in-focus position calculation is not performed until three AF evaluation values / focus positions are collected again.

  However, if the two AF evaluation values / focus positions are collected, it is possible to determine the direction in which the lens is to be driven, and therefore the in-focus position until the two AF evaluation values / focus positions are collected. It is good also as what does not perform a calculation.

  The lens driving is performed every time in synchronization with the photographing timing. On the other hand, when the in-focus position calculation start determination unit 109 results in determination NG and the in-focus position calculation unit 108 interrupts the in-focus position calculation, the lens driving amount is not transmitted to the lens body 200 side. . In such a case, the lens CPU 205 performs lens driving based on the last received lens driving amount.

  The motion information detected by the motion detection unit 102 is input to the recorded image processing unit 103 and the display image processing unit 105 together with the captured image.

  The display image processing unit 105 performs image processing on the input image (step S112), and displays and outputs it on the display element 106 (step S113). At this time, it is possible to display a more easily viewable image by performing motion interpolation using the motion information in the image processing. Although not shown or described in particular, a process of displaying a captured image by performing image processing without using motion information is performed between step S101 and step S102.

  The recorded image processing unit 103 performs image processing on the input image (step S114) and records it in the recorded image memory 104 (step S115). At this time, an image with less blur can be recorded by performing motion interpolation using motion information in image processing. By recording such a captured image, it is possible to realize a preceding continuous shooting function that enables a desired image to be reliably acquired even when the shutter timing is delayed. Of course, when performing normal one-frame shooting, this image processing and recording may be performed only when the 2R operation is performed.

  According to the first embodiment of the present invention as described above, the imaging element 101 that receives and images subject light that has passed through the focus lens 201 that functions as a photographing optical system, and an image that is captured by the imaging element 101 are used. An AF evaluation value calculation unit 107 that calculates an AF evaluation value, a focus position calculation unit 108 that performs a focus position calculation using a plurality of results of the AF evaluation value calculation unit 107, and imaging from the imaging element 101 Focusing that determines the significance of the result of the AF evaluation value calculation unit 107 based on the subject information calculated from the image, and makes a determination to start the calculation with respect to the focus position calculation unit 108 if the result is significant And a position calculation start determination unit 109, so that the subject side moves at high speed by making a start determination of the AF operation of the contrast AF method based on the subject information calculated from the captured image. Since the contrast AF operation can be performed only when there is no such image blurring, it is possible to provide an imaging apparatus capable of calculating a focus position with high accuracy and capturing an image with less blur. .

  The in-focus position calculation start determination unit 109 further determines that the in-focus position calculation unit 108 stops the calculation when the result of the AF evaluation value calculation unit 107 is not significant. When there is an image blur that causes the subject to move at high speed, the contrast AF operation is not performed, so that an incorrect in-focus position is not calculated, and therefore a useless operation for driving the lens up to the in-focus position is performed. Therefore, the time to the in-focus position can be shortened.

  Further, the focus position calculation start determination unit 109 can easily determine the presence or absence of image blur that causes the subject to move at high speed by using subject movement information as the subject information.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  As shown in FIG. 7, the lens-interchangeable digital single-lens reflex camera as the second embodiment of the imaging apparatus of the present invention further includes an AF area changing unit 111 in addition to the same configuration as that of the first embodiment. .

  The AF area changing unit 111 sets an AF area 11 that is an area of a captured image in which the AF evaluation value calculation unit 107 calculates an AF evaluation value. The focus position calculation start determination unit 109 When the result becomes, an instruction to change the AF area 11 is transmitted to the AF area changing unit 111, and the AF area changing unit 111 changes the AF area 11 accordingly. Here, the change of the AF area 11 includes movement of the AF area 11 and reduction / enlargement of the area size. For example, in the situation shown in FIG. 2, the AF area 11 is reset so as to avoid the position (Xa2, Ya2) of the moving object (high-speed moving subject 13).

  Hereinafter, the AF operation in the camera having the above configuration will be described with reference to the timing chart of FIG. 8 and the flowchart of FIG.

  Here, in the present embodiment, the operation when the focus position calculation start determination by the focus position calculation start determination unit 109 results in the determination OK is the same as that in the first embodiment, and the description thereof will be given. Omitted.

  When the focus position calculation start determination unit 109 determines that the focus position calculation start determination is a result of determination NG (step S106), the focus position calculation start determination unit 109 changes the AF area 11 to the AF area change unit 111. The AF area changing unit 111 changes the AF area 11 accordingly (step S121). Then, the AF evaluation value calculation unit 107 calculates an AF evaluation value from the image of the changed AF area 11 in the original screen image during the second AF evaluation value calculation period (step S122). The AF evaluation value recalculated in this way is input to the in-focus position calculation start determination unit 109, and the in-focus position calculation start determination unit 109 adds the result to the in-focus position calculation determination result OK. Input to the arithmetic unit 108. Therefore, the in-focus position calculation unit 108 starts the in-focus position calculation, and is sent from the lens body 200 with the AF evaluation value recalculated by the AF evaluation value calculation unit 107 during the in-focus position calculation period. The focus position information input via the camera CPU 110 is used to interpolate from the past three points of information to estimate the focus position (focus peak) (step S107). Then, using the estimated focus position, the difference (defocus amount) between the current focus position and the focus estimated focus position is calculated as a lens drive amount (step S108), and this is calculated to the lens CPU 205 via the camera CPU 110. Transmit (step S109). Then, the AF evaluation value and the focus position up to now are stored in an internal RAM (not shown) (step S110).

  Therefore, in the present embodiment, lens driving based on the calculated lens driving amount is performed every time in synchronization with the photographing timing.

  According to the second embodiment of the present invention as described above, the image pickup device 101 that receives the subject light that has passed through the focus lens 201 functioning as a photographing optical system and takes an image has the same effect as the first embodiment. , An AF evaluation value calculation unit 107 that calculates an AF evaluation value using an image captured by the image sensor 101, and a focus position calculation that performs a focus position calculation using a plurality of results of the AF evaluation value calculation unit 107 The significance of the result of the AF evaluation value calculation unit 107 is determined based on the object information calculated from the captured image from the unit 108 and the captured image from the image sensor 101, and when the result is significant, the focus position calculation unit 108 An in-focus position calculation start determination unit 109 that determines the start of calculation with respect to the image, thereby determining whether to start the AF operation of the contrast AF method based on the subject information calculated from the captured image. Since the contrast AF operation can be performed only when there is no image blur that causes the subject side to move at high speed, an imaging device that can calculate an in-focus position with high accuracy and capture an image with little blurring. Will be able to provide.

  Further, when the in-focus position calculation start determination unit 109 determines that the in-focus position calculation unit 108 stops the calculation, the in-focus position calculation start determination unit 109 calculates an AF evaluation value for the AF area changing unit 111 that functions as an AF area setting unit. An instruction to change the AF area 11 that is an area of the captured image used for calculating the AF evaluation value of the unit 107 is transmitted, and the AF evaluation value calculation unit 107 changes the AF area 11 in response to the AF evaluation value again. By performing the calculation, the in-focus position calculation in the in-focus position calculation unit 108 can be continued. Accordingly, when there is an image blur that causes the subject to move at high speed, the AF area 11 is reset so as to eliminate such an image blur, and the contrast AF operation is performed, so the time to the in-focus position is further shortened. It becomes possible.

  In addition, the in-focus position calculation start determination unit 109 can easily determine the presence or absence of image blur that causes the subject to move at high speed by using subject movement information as the subject information.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

  For example, in the above-described embodiment, a lens interchangeable digital single-lens reflex camera has been described as an example. However, a compact digital camera adopting a contrast AF method, a camera-equipped mobile phone, a camera-equipped PDA, or the like may be used.

  Further, the present invention is not limited to a still camera that records still images, but can be applied to a moving image camera that records moving images. In this case, the contrast AF operation is not performed when there is an image blur that causes the subject side to move at high speed, so that an incorrect in-focus position is not calculated, and therefore it is useless for driving the lens up to the in-focus position. Since there is no operation, it is possible to record a smooth image as a video camera.

  As described above, any imaging device may be used as long as it adopts the contrast AF method.

    DESCRIPTION OF SYMBOLS 10 ... Shooting angle of view, 11 ... AF area, 12 ... Subject which does not move, 13 ... High-speed moving subject, 100 ... Camera body, 101 ... Image sensor, 102 ... Motion detection part, 103 ... Recorded image processing part, 104 ... Recorded image Memory 105: Display image processing unit 106: Display element 107 ... AF evaluation value calculation unit 108 ... In-focus position calculation unit 109 ... In-focus position calculation start determination unit 110: Camera CPU 111: AF area change 200: Lens body 201: Focus lens 202 ... Motor 203 ... Lens drive circuit 204 ... Focus encoder 205 205 Lens CPU 300 ... Communication path

Claims (4)

An image sensor for receiving and imaging subject light transmitted through the imaging optical system;
An AF evaluation value calculation unit that calculates an AF evaluation value using an image captured by the image sensor;
A focus position calculation unit that performs a focus position calculation using a plurality of results of the AF evaluation value calculation unit;
The significance of the result of the AF evaluation value calculation unit is determined based on the subject information calculated from the captured image from the imaging element, and if it is significant, the focus position calculation unit is determined to start calculation. An in-focus position calculation start determination unit,
An imaging apparatus comprising:   The focus position calculation start determination unit further makes a determination to stop calculation with respect to the focus position calculation unit when the result of the AF evaluation value calculation unit is not significant. The imaging apparatus according to 1. An AF area setting unit that sets an area of the captured image in which the AF evaluation value calculation unit calculates the evaluation value of the captured image;
When the focus position calculation start determination unit makes a determination to stop calculation with respect to the focus position calculation unit, the AF evaluation value calculation unit calculates the evaluation value with respect to the AF area setting unit. The imaging apparatus according to claim 2, wherein an instruction to change an image area is transmitted.   The imaging apparatus according to claim 1, wherein the focus position calculation start determination unit uses movement information of a subject as the subject information.

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