JP2011118021A - Imaging device and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve recording performance for an image and voice data in a lens exchange type imaging system having a contrast system AF (automatic focusing) function. <P>SOLUTION: This imaging device has a function of photographing animation, and exchangeable of lenses. In photographing animation, control for automatic focusing is changed according to the class information of a mounted lens. For example, in mounting a variable focal lens which is defocussed accompanied by a change in focal distance, focal distance information on the lens is obtained (S10), a focus shifting direction and an amount are obtained (S11), and contrast AF is performed with limitation on the focus drive range (S16). When mounting a lens which is not defocussed accompanied by a change in focal distance, information on an effect that the contrast AF is not controlled is displayed (S18), and the contrast AF is performed only when an AF button is operated (S19→S16). In the manual focus controlling state, the direction of rotating a focus operating ring is displayed and informed to a photographer (S15). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a camera that can exchange lenses and has a video shooting function, and a control method thereof.

  In recent years, higher magnification of photographing lenses and higher pixels and higher density of imaging elements have been accelerated. In addition, image pickup devices that can shoot still images and moving images are widely available that can select the number of recorded pixels for still image shooting and that can capture not only the conventional television method but also the high-definition method for moving image shooting. Have been doing. In an imaging apparatus having an interchangeable lens system, as the camera and lens are released later, the imaging performance and resolution are improved, the image quality is improved, and the functionality is advanced. For example, in the early interchangeable lens system, only a silver salt photograph image was supported, but a device capable of taking a high-resolution digital still image and a high-definition moving image has been developed. As for the combination of the camera and the lens, it is desirable that various combinations can be used for taking pictures without problems in terms of marketability, merchantability, and compatibility. In other words, if the zoom function and autofocus function are not fully demonstrated in a combination where the camera is compatible with video and the taking lens is designed exclusively for still images, it will be attractive for the marketability and merchandise of the interchangeable lens system. There is a risk of damage.

  In Patent Document 1, a mounted lens is identified, and the minimum driving pitch of the lens is changed according to the resolution spatial frequency information of the camera, so that it is possible to realize a good autofocusing performance in any combination of a camera and a lens. . Japanese Patent Laid-Open No. 2004-228867 calculates an evaluation value corresponding to a contrast component of a subject from an output image signal according to a shooting situation for each lens movement position, and determines a lens driving direction, thereby performing a focus adjustment process. A method for achieving a high speed is described.

  As a control method of autofocus (hereinafter abbreviated as AF), a phase difference detection method and a contrast method are known. In the latter type of AF (hereinafter referred to as contrast AF), high-frequency components are extracted from the video signal obtained from the image sensor, and the focus is adjusted by driving the lens so that the evaluation value corresponding to the high-frequency components is maximized. To do. Patent Document 3 proposes a hybrid AF type camera using both phase difference detection type AF and contrast AF. In this camera, the correction amount is determined in advance based on the movement amount (step) that can be detected by contrast AF, and the movement amount for moving the lens by the phase difference detection AF is determined based on the correction movement amount. Focusing operation is possible.

JP 2006-178111 A JP 2002-072074 A JP 2007-108293 A

  By the way, contrast AF is used as an AF method at the time of moving image shooting. However, since this method generally takes time to focus, video data that is not in focus may be recorded at the time of moving image shooting. obtain. In addition, since the interchangeable lens for single lens reflex is designed assuming phase difference detection AF, operation sound of a motor or the like may be recorded during moving image shooting when contrast AF is performed.

Conventional interchangeable lenses for single-lens reflex cameras have a lens (varifocal lens) that is out of focus as the angle of view changes when zooming is performed. When zooming in a movie, it takes time to focus with contrast AF. It becomes a problem that it takes. Also, when the user manually adjusts the focus during moving image shooting, if the direction in which the focus operation ring should be rotated is unknown, the image data until the in-focus state may be recorded. The reason is that the user needs to rotate the focus operation ring in one direction in a trial direction and find out the in-focus direction before focusing.
Also, when a lens that does not defocus due to a change in the angle of view during zoom driving is attached to the camera, the user presses the AF button without noticing that the subject is not out of focus, and is out of focus until refocusing. The state image data may be recorded.

  An object of the present invention is to improve the recording performance of image and audio data by changing the control of automatic focus adjustment in moving image shooting according to the type of lens mounted on the camera.

  In order to solve the above problems, an apparatus according to the present invention is an imaging apparatus having a moving image shooting function and capable of exchanging lenses, and a high-frequency component extraction unit that extracts a high-frequency component of an imaging signal from an imaging element; Based on the information of the high-frequency component extraction means, a control means for controlling automatic focus adjustment related to the mounted lens is provided. The control means includes the automatic focus adjustment in shooting the moving image when a lens that is out of focus with a change in focal length is attached and when a lens that is not out of focus with a change in focal length is attached. Change the control.

  According to the present invention, at the time of moving image shooting, it is possible to improve the recording performance of image and audio data by changing the control of automatic focus adjustment according to the type of lens mounted on the apparatus main body.

1 is a block diagram illustrating a configuration example of an imaging system according to an embodiment of the present invention. It is a graph explaining the calculation method of the shift direction of a focus position and the amount of position shift. It is a flowchart which shows the example of focus control at the time of video recording.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating an example of a system configuration of an imaging apparatus capable of exchanging lenses. This apparatus has a moving image shooting function and a high-frequency component extraction function for extracting a high-frequency component of an image pickup signal, and includes a lens unit A (also referred to as an interchangeable lens) and a camera unit B (also referred to as a camera body). . The optical system 1 includes a fixed lens group including lenses 1a and 1c, a lens group (hereinafter referred to as a zoom group) 1b having a zooming function, a lens group (hereinafter referred to as a focus group) 1d having a focusing function, and an aperture amount. It is comprised by the aperture_diaphragm | restriction 2 for adjusting.

  The lens unit A includes a lens control unit 10, and the control unit is configured using an arithmetic processing device such as a microcomputer. The lens control unit 10 communicates with the camera control unit 20 of the camera unit B via the communication contact units 8 and 9, and controls the aperture drive unit 5 and the focus drive unit 7 in accordance with the command. The lens control unit 10 holds lens information about the lens unit A in a memory, and the information is sent to the camera control unit 20 of the camera unit B via the communication contact units 8 and 9.

The focal length detection unit 3 detects information corresponding to the focal length of the lens. In this example, the focal length detection unit 3 detects the focal length of the zoom group 1 b and sends detection information to the lens control unit 10. For example, a holding frame (not shown) of the zoom group 1b is provided with a brush for position detection, and the brush moves on a substrate on which a variable resistor or a gray code pattern is printed as the zoom lens moves. Slide. When the zoom encoder circuit captures the output signal at this time, focal length information is detected and captured by the lens control unit 10.
The aperture amount of the aperture stop 2 is detected by the aperture sensor 4 for detecting the aperture amount, and detection information is sent to the lens control unit 10. The lens control unit 10 sends an aperture amount control signal to the aperture driving unit 5 and adjusts the aperture amount of the aperture 2 by moving the aperture blades.

The focus group 1 d is driven by the focus driving unit 7. The focus position detection unit 6 detects position information of the focus group 1 d and sends it to the lens control unit 10. The position of the focus group 1d is detected by counting the number of pulses of the signal applied to the focus driving unit 7 by a detector (not shown) and taking it into the lens control unit 10. The focus position detection unit 6 and the focus drive unit 7 constitute a focus adjustment unit of the optical system 1.
Although FIG. 1 shows the lens group as a single lens, each lens group is actually composed of a plurality of lenses. Further, depending on the lens unit, there may be a single-focus configuration without a zoom mechanism or a lens configuration without a focus function, and the lens configuration for imaging does not matter.

  Next, the camera unit B will be described. As the image sensor 11, an element such as a CMOS that forms an image of a light beam from a subject is used. The formed subject image is photoelectrically converted by the image sensor 11, and a video signal (imaging signal) after imaging is output to a camera process circuit or the like (not shown). The video signal is supplied to the high frequency component extraction circuit 12. In this circuit, the focus voltage is detected based on the signal component due to the level of the high frequency component in the video signal that changes depending on the focus state or the sharpness of the edge of the image, and the detection result is taken into the camera control unit 20. The camera control unit 20 is configured using an arithmetic processing unit such as a microcomputer, and receives focus voltage information from the high-frequency component extraction circuit 12 to determine the in-focus state, the out-of-focus state, and the front and rear pins. Do.

  The video signal captured from the image sensor 11 is transmitted to the display control unit 13 through the camera control unit 20. Here, after conversion processing to luminance signal and color difference signal and processing such as gamma correction are performed, the video signal is sent to the display unit 14 such as a liquid crystal monitor to display an image and recorded in the recording unit 19. Is done. In response to the video signal output from the image sensor 11, the recording unit 19 periodically writes image data, and the display unit 14 displays the image in real time. In this example, a liquid crystal monitor or the like is used as the image output means.

  The camera unit B holds the lens data map 15 in a predetermined storage unit. The camera control unit 20 communicates with the lens control unit 10 of the lens unit A, identifies the type of the lens unit A, and takes in the data of the lens data map 15 corresponding to the mounted lens unit A. The camera control unit 20 compares the detection information of the focal length detection unit 3, the detection information of the aperture sensor 4, the detection information of the focus position detection unit 6 and the like acquired from the lens control unit 10 with the data of the lens data map 15. Then, the camera control unit 20 determines whether the current focus position is an in-focus position, or a front pin or a rear pin, using a method described later. Information indicating the current focus position is sent to the display unit 14 via the display control unit 13 and displayed.

  As operating elements used when the photographer operates the camera, FIG. 1 shows only the moving image / still image selection switch 16, the moving image shooting start button 17, and the AF button 18. The moving image / still image selection switch 16 is an operation means for the photographer to select moving image shooting or still image shooting, and an operation instruction by the switch is sent to the camera control unit 20. The moving image shooting start button 17 is an operation means for the photographer to instruct the camera to start moving image shooting. The photographer presses the moving image shooting start button 17 after adjusting the angle of view and focus, and starts moving image shooting. The camera control unit 20 is instructed. The AF button 18 is an operation means for instructing the camera to start AF. When still image shooting is selected by operating the moving image / still image selection switch 16, for example, still image shooting is performed by phase difference detection AF. At this time, the camera control unit 20 controls the focus driving unit 7 via the lens control unit 10 based on the detection result by a focus state detection circuit (not shown) to drive the focus group 1d. When the photographer operates the AF button 18, the camera control unit 20 calculates the driving amount of the focus group 1 d based on the focus voltage from the high frequency component extraction circuit 12, and issues a command to the lens control unit 10. The focus driving unit 7 drives the focus group 1d.

Next, a method for calculating the direction and amount of shift of the focus position in the present embodiment will be described with reference to FIG. FIG. 2 is a graph representing an example of data of the lens data map 15, and the camera unit B stores a data group of the lens data map 15 in a memory.
The vertical axis in FIG. 2 indicates the focal length (Zp), and the horizontal axis indicates from the closest position to infinity by replacing the position (Fp) on the optical axis of the focus group 1d with the position of the subject. The graph curve G (1.2) is a focus curve when the distance from the camera to the subject (subject distance) is 1.2 m, and the graph curve G (3) is a focus curve when the subject distance is 3 m. Each is shown. In the focus P0 in the figure, Zp is Z0 and Fp is F0, and at the focus P1, Zp is Z1 and Fp is F1. Further, Fp at the intersection of the straight line Zp = Z0 and the graph curve G (1.2) is G0, and Fp at the intersection of the straight line Zp = Z1 and the graph curve G (1.2) is G1. The difference X is G1-F0.

Now, assuming that the focal point at the start of moving image shooting is the point P0, that is, the zoom value Z0 and the focus value F0, the focusing curve G (1.2 m) closest to the point P0 is referred to. The When the zoom value changes to Z1 by the photographer and the zoom lens moves, according to the focus curve G (1.2) at this time, G1 indicates a value corresponding to the focus position at the time of focus. . If the focus drive range is limited to the range indicated by the difference X (= G1-F0), the focus position search range can be narrowed, and thus the time required to find the focus position is shortened. If the difference X is a positive value, the in-focus state can be obtained by moving the focus group 1d to the infinity side. Conversely, if the difference X is a negative value, the focus group 1d is moved to the near side. It can be seen that the in-focus state can be obtained by moving to.
Next, the control operation at the time of moving image shooting by the camera control unit 20 will be described in order according to the flowchart shown in FIG. The following processing is performed according to a program interpreted and executed by the camera control unit 20.

First, in S1, processing for acquiring information related to the captured image size, that is, the number of captured pixels is performed. The camera control unit 20 determines an image size (for example, an SD image or a full HD image) preset by the photographer in accordance with an operation instruction to the camera, and selects a predetermined allowable circle of confusion circle. The higher the resolution, the smaller the permissible circle of confusion.
Next, aperture value acquisition processing is performed (S2). The camera control unit 20 acquires detection information of the aperture sensor 4 through the lens control unit 10 and the communication contact units 8 and 9. And the camera control part 20 acquires the information of the focal distance (refer Z0 of FIG. 2) of a lens (S3). That is, the detection information of the focal length detection unit 3 is sent to the camera control unit 20 through the lens control unit 10 and the communication contact units 8 and 9.

In S4, the camera control unit 20 determines the allowable confusion circle based on the information acquired in S1 to 3, and calculates the depth of field based on the aperture value, the focal length, and the allowable confusion circle. The longer the focal length and the smaller the aperture value (brighter), the narrower the depth of field. In the next S5, the camera control unit 20 acquires information on the focus position (see F0 in FIG. 2) detected by the focus position detection unit 6 through the lens control unit 10 and the communication contact units 8 and 9.
In S6, the camera control unit 20 acquires lens information from the lens control unit 10, and determines whether or not the data of the lens data map 15 is held in the memory in advance by the camera unit B. As a result, when the camera unit B does not hold the data, the process proceeds to S16, but when the data of the lens data map 15 is held, the process proceeds to S7.

  In S7, the camera control unit 20 acquires data of the lens data map 15 corresponding to the mounted lens and data indicating the lens type. In the next S8, the camera control unit 20 determines whether or not zoom driving has been performed based on the operation instruction of the photographer based on the focal length information (Z0) acquired in S3. As a result, when zoom driving is performed, the process proceeds to S9, but when zoom driving is not performed, the process proceeds to S17.

  S9 is a step of determining the lens type, and the camera control unit 20 determines the mounted lens based on the lens type information acquired in S7. This is a process for discriminating between when a lens that is out of focus with a change in focal length is attached to the camera body and when a lens that is not out of focus with a change in focal length is attached to the camera body. is there. In other words, which lens is mounted on the camera unit B among a varifocal lens that is out of focus when the focal length is changed by zoom driving, a single-focus lens, and a zoom lens that does not cause out of focus even when zoom driving is performed. Is determined. As a result, if the attached lens is determined to be a varifocal lens, the process proceeds to S10, and if the determination result is determined to be any other lens, the process proceeds to S17.

  In S10, the camera control unit 20 acquires information on the focal length (see Z1 in FIG. 2) from the focal length detection unit 3, and in S11, calculates the positional deviation direction and the positional deviation amount of the focus group 1d by the method described above. To do. The information used here is the focal length acquired in S3, the difference between the focal lengths acquired in S10, the focus position F0 acquired in S5, and the lens information acquired in S7. Based on these pieces of information, a calculation process is executed as to whether the in-focus state can be obtained by moving the focus group 1d in which direction and how much.

In next S12, the difference X acquired in S11 is compared with the depth of field calculated in S4. The camera control unit 20 determines whether the magnitude of the difference X is larger or smaller than the depth of field. If the amount of positional deviation indicated by the difference X is larger than the depth of field, the process proceeds to S13. If the amount is less than the depth of field, the process proceeds to S17. In S13, the camera control unit 20 determines whether or not the camera and the lens are set to AF by the photographer's operation. If the AF is set, the process proceeds to S14. If manual focus (MF) is set for manually operating the focus operation ring, the process proceeds to S15.
In S14, the camera control unit 20 limits the focus driving range when the focus driving unit 7 moves the focus group 1d. This range is determined based on the positional deviation direction and the positional deviation amount calculated in S11.

In S15, the display unit 14 displays the direction in which the focus group 1d is moved (the rotation direction of the focus operation ring) in accordance with a command from the camera control unit 20. With respect to this direction, the positional deviation direction is calculated in S11, and the camera control unit 20 has already grasped this direction. Then, it progresses to S21.
At S16, focus control by contrast AF is performed. That is, the image signal captured from the image sensor 11 is sent to the high frequency component extraction circuit 12 for processing, and the camera control unit 20 performs communication contact units 8 and 9 and the lens control unit 10 so that the high frequency component is maximized. Then, the focus group 1d is driven via the focus driving unit 7. At this time, if the focus drive range is limited in S14, the focus group 1d is driven within the range. Then, the process proceeds to S20.

If the in-focus determination is made in S20 and the in-focus determination is made, the process proceeds to S21, but if not in focus, the process returns to S16. In the next S21, zoom drive end determination processing is performed, and the camera control unit 20 acquires detection information from the focal length detection unit 3 through the communication contact units 8 and 9 and the lens control unit 10. Then, the camera control unit 20 compares this with the focal length acquired in S10, and determines whether zoom driving is in progress. As a result, if zoom driving is being performed, the process returns to S9, but if zoom driving is not being performed, the process proceeds to S22. In S22, moving image shooting end determination processing is performed. If moving image shooting is in progress, the process returns to S8, and if the moving image ends, the series of processing ends.
In S17, it is determined whether the AF setting is the same as in S13. If the AF setting is made, the process proceeds to S18. If the manual focus (MF) is set, the process proceeds to S22.

In S18, the contrast AF stop display is performed. In this case, the AF setting is made in advance by the photographer, but the position shift of the focus group 1d due to zoom driving does not occur optically. Therefore, according to the command of the camera control unit 20, the display unit 14 notifies the user by displaying a message indicating that focus driving is not performed.
After confirming that the focus drive is not performed in S18, the camera controller 20 determines the operation state of the AF button 18 in the next S19. If the photographer operates the AF button 18 after the notification in S18, the process proceeds to S16. If the AF button 18 is not operated, the process proceeds to S22.
As described above, the image pickup apparatus according to the present embodiment changes the automatic focus adjustment control by the contrast method according to the discrimination information of the interchangeable lens at the time of moving image shooting. Thereby, it is possible to avoid recording out-of-focus image data and to record more in-focus image data. Also, when an interchangeable lens that does not shift its focus position due to zoom drive is attached to the camera body, noise (such as lens operation sound) during movie shooting is not recorded by not performing AF control. Can be prevented. Since the optimum focus control is performed for moving image shooting, power saving can be realized by not performing focus drive for focusing with such an accuracy that the photographer cannot discriminate.

  In the present embodiment, the AF state is presented to the photographer on the liquid crystal monitor. However, the present invention is not limited to this. For example, the AF information may be displayed on an organic EL monitor or a display unit in the optical viewfinder. Further, the embodiment of the present invention is not limited to a digital single-lens reflex camera, but can be applied to various imaging apparatuses having a moving image shooting function in an interchangeable lens imaging system.

DESCRIPTION OF SYMBOLS 1 Optical system 2 Aperture 3 Focal length detection part 4 Aperture sensor 5 Aperture drive part 6 Focus position detection part 7 Focus drive part 10 Lens control part 11 Imaging element 12 High frequency component extraction circuit 14 Display part 15 Lens data map 20 Camera control part

Claims (5)

An imaging device having a video shooting function and capable of exchanging lenses,
High-frequency component extraction means for extracting a high-frequency component of an imaging signal from the image sensor;
Based on the information of the high-frequency component extraction means, comprising control means for controlling automatic focus adjustment related to the mounted lens,
The control means includes the automatic focus adjustment in shooting the moving image when a lens that is out of focus with a change in focal length is attached and when a lens that is not out of focus with a change in focal length is attached. An imaging apparatus characterized by changing the control of the image pickup apparatus. Further comprising a focal length detection means for detecting information corresponding to the focal length of the mounted lens,
If the lens is a lens that is out of focus as the focal length is changed based on information acquired about the mounted lens, the control means uses information corresponding to the focal length detected by the focal length detection means. The image pickup apparatus according to claim 1, wherein the automatic focus adjustment is controlled based on the image pickup apparatus.   In the case where the mounted lens is a single focus lens or a zoom lens whose focus does not shift with a change in focal length, the auto focus adjustment is performed even if the auto focus adjustment is set by the user. The control is performed so that the automatic focus adjustment is performed when the user gives an instruction to operate the automatic focus adjustment after the notification. 2. The imaging device according to 2.   The control means, when a lens that is out of focus with a change in focal length is mounted and the automatic focus adjustment is not set, based on information corresponding to the focal length of the mounted lens, The imaging apparatus according to any one of claims 1 to 3, wherein a control is performed to display a direction in which a focus operation ring of the mounted lens is to be rotated. A method for controlling an imaging apparatus having a movie shooting function and a high-frequency component extraction function for extracting a high-frequency component of an imaging signal from an imaging device, and capable of exchanging lenses,
The control of the automatic focus adjustment in the shooting of the moving image is changed between a case where a lens that is out of focus with a change in focal length is attached and a case where a lens that is not out of focus with a change in focal length is attached. And a method of controlling the imaging apparatus.

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