JP2012058357A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain an amount of communication with a lens drive means during wobbling.SOLUTION: In the imaging apparatus that performs wobbling in AF of contrast system by using the imager 110 of a CMOS sensor, if a second mode in which an area to be focused is changed is set, a camera microcomputer 130 sets a drive stop period for which the drive of a photographing optical system 152 is stopped during wobbling, longer than the case where a first mode in which the aforementioned area is fixed is set.

Description

  The present invention relates to an imaging apparatus.

  In an imaging apparatus, it is known to determine the direction in which the in-focus position is located by moving the lens in the optical axis direction (wobbling) during contrast-type autofocus (AF: automatic focus adjustment). When the image sensor is a CMOS sensor, rolling readout is performed, the lens is stopped during charge accumulation, and the lens is moved during readout. Patent Document 1 proposes a method of changing a lens driving period based on a result of comparing a lens driving period and a charge accumulation period of an AF area (AF frame) that is a focus adjustment target area.

JP 2008-111995 A

  The AF area setting includes one-point AF, multi-point AF, face AF, and the like. For one-point AF, the AF area is set to an arbitrary point. Alternatively, it can be regarded as one-point AF when it is set in a narrow area of the screen. In multi-point AF, the AF area is set to all AF points over a wide range of the screen, or set to AF points that frequently switch. In face AF, the AF area is switched according to the face detection result. In the multipoint AF and face AF, the AF area is frequently changed. However, in the method of Patent Document 1, it is necessary to instruct the lens driving means to start and end the lens driving period. Therefore, a high-cost communication environment called high-speed communication must be prepared.

  Therefore, an object of the present invention is to provide an imaging apparatus capable of suppressing the amount of communication with the lens driving unit during wobbling.

  An imaging apparatus according to one aspect of the present invention is an imaging apparatus in which a lens unit having a photographing optical system and a driving unit that drives the photographing optical system is detachable, and charge accumulation and readout are performed in units of pixel rows. An image sensor that is used in the above, a setting unit that sets a first mode in which a focus adjustment target region is fixed or a second mode in which the region fluctuates, and the lens unit and the photographing optical system via the driving unit. Based on a signal stored in the image sensor during a period in which driving of the imaging optical system is stopped during the wobbling, and communication means for performing communication to move and the imaging optical system are wobbled in the optical axis direction. An automatic focus adjusting means for moving the photographing optical system in a direction where a focusing position is present; and a driving stop period during which the driving of the photographing optical system is stopped during the wobbling. If set is characterized in that a control means for longer than the case where the first mode is set.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can suppress the communication amount with a lens drive means at the time of wobbling can be provided.

6 is a timing chart of charge accumulation and wobbling. Example 1 6 is a timing chart of charge accumulation and wobbling. (Example 2) It is a block diagram of the imaging device of a present Example.

  FIG. 3 is a block diagram illustrating a configuration of the imaging apparatus according to the present exemplary embodiment, and a broken line represents an optical axis. The imaging apparatus of the present embodiment is a lens interchangeable digital single-lens reflex camera, but the type of imaging apparatus such as a digital video camera is not limited.

  The imaging apparatus also has an automatic focus adjustment function (AF function) that determines the in-focus direction where the in-focus position (contrast peak position) is located by performing wobbling that slightly moves the imaging optical system in the optical axis direction.

  The imaging apparatus includes a main body 100 and a lens unit (interchangeable lens) 150 configured to be replaceable (detachable) with the main body 100. Mechanical attachment / detachment of the main body 100 and the lens unit 150 is performed via the mount of the main body 100 and the mount of the lens unit 150. In addition, the electrical connection and disconnection between the main body 100 and the lens unit 150 are performed via the connector of the main body 100 and the connector of the lens unit 150.

  The main body 100 includes a sub mirror 105, a focus detection circuit 107, an image sensor 110, a signal processing circuit 120, a display unit 124, a subject detection unit 126, a live view setting unit 128, a camera microcomputer (control unit) 130, a memory 140, and the like. It has a member.

  The sub mirror 105 is disposed on the optical axis together with a main mirror (not shown), and is disposed so as to be retractable on the optical path. FIG. 3 shows a non-photographing state. In this state, the main mirror reflects a part of the incident light beam to the optical finder (not shown) and transmits a part to the sub mirror 105, and the sub mirror 105 reflects the incident light beam to the focus detection circuit 107. At the time of photographing, the main mirror and the sub mirror 105 are retracted from the optical path and guide the incident light flux to the image sensor 110.

  The focus detection circuit 107 receives the light beam reflected by the sub-mirror 105 by a sensor that performs photoelectric conversion disposed inside. The defocus amount is obtained using the phase difference method by calculating the output of the sensor. The camera microcomputer 130 evaluates the calculation result and instructs the lens microcomputer 160 to move the focus lens by a predetermined amount.

  The image sensor (image sensor) 110 converts an optical image formed by the photographing optical system into an electric signal (image data), and performs charge accumulation and reading by scanning in units of pixel rows or columns (that is, rolling). (Performs) an imaging device, which is composed of, for example, a CMOS sensor. That is, in the image sensor 110, only one row is accumulated at the same time, another row is accumulated with a delay in time, and the accumulation-completed row is read during accumulation of another row. Image data from the image sensor 110 is input to the signal processing circuit 120 via the AGC / AD circuit.

  The signal processing circuit 120 is connected to the image sensor 110 and the camera microcomputer 130, and performs processing including filter processing, color conversion processing, and gamma processing compression processing on the digitized image data from the image sensor 110. Send to. The image data processed as a display image by the signal processing circuit 120 is sent to the display means driving circuit 122 and displayed as an image on the display means 124 such as an electronic viewfinder.

  The subject detection means 126 detects a subject (such as a face) that satisfies a certain condition. When the subject detection unit 126 functions as a face detection unit, face AF can be performed.

  The setting unit 128 includes a mode dial and various operation members, and sets a live view mode in which image data is continuously output from the image sensor 110 and image data is continuously displayed on the display unit 124. The setting unit 128 can also set a face AF mode in which face detection is performed by the subject detection unit 126. Furthermore, the setting unit 128 can set a one-point AF mode and a multi-point AF mode.

  In addition, the imaging apparatus can be regarded as fixing the AF area, which is a focus adjustment target area (that is, the AF area has a small fluctuation), and the AF area has a plurality of AF areas and the AF area varies. And a second mode in which the AF region varies greatly. The first mode is, for example, a one-point AF or a narrow area AF mode. The second mode is, for example, a face AF mode in which the subject detection unit 126 performs multipoint AF and face detection.

  The camera microcomputer 130 is a microcomputer (CPU, processor, control means) that is connected to the image sensor 110 and the signal processing circuit 120 and connected to the lens microcomputer 160 of the lens unit 150 via a connector (not shown). . The camera microcomputer 130 performs AF control including wobbling and image processing control. For this reason, the camera microcomputer 130 also functions as an automatic focus adjustment unit that determines the direction of the in-focus position by wobbling the photographing optical system in the optical axis direction.

  The memory 140 holds information necessary for contrast AF.

  As described above, the imaging device in which the lens unit is replaceable has an effect of suppressing the amount of communication between the main body and the lens unit during wobbling.

  In wobbling, after the lens is finely driven to an infinite position, the focus lens is first stopped and an image is captured from the image sensor 110. Next, after the focus lens is finely driven to the closest position, the lens is stopped and an image is captured from the image sensor 110.

  After determining the in-focus direction, the camera microcomputer 130 performs contrast AF by moving the focus lens of the photographing optical system in the in-focus direction. That is, the camera microcomputer 130 detects the peak position of the contrast (AF evaluation value) of the image data output from the image sensor while performing scanning that changes the relative position between the focus position formed by the focus lens and the image sensor. Do.

  The lens unit 150 includes a photographing optical system 152 that forms an optical image of a subject, a driving circuit (driving means) 155 that moves a focus lens of the photographing optical system 152 in the optical axis direction, and a lens microcomputer 160.

  The photographing optical system 152 includes a plurality of lenses that collect an optical image of a subject on the image sensor 110. Some of the plurality of lenses include a focus lens that is moved in the optical axis direction during focus adjustment.

  The drive circuit 155 includes a DC motor and a stepping motor, and moves the focus lens of the photographing optical system 152 in the optical axis direction under the control of the lens microcomputer 160.

  The lens microcomputer 160 is electrically connected to the camera microcomputer 130 and exchanges information necessary for the photographing operation. The connection between the lens microcomputer 160 and the camera microcomputer 130 includes a data line DL for performing bidirectional data communication and a vertical synchronization signal VD output from the camera microcomputer 130 to the lens microcomputer 160 (communication means).

  In contrast AF, the focus lens is moved from the current position to the peak position (focus position) of the contrast value. In order to determine the direction of the focus position from the current position of the focus lens, the focus lens is moved in the optical axis direction. Wobbling back and forth along.

  In this way, the camera microcomputer 130 moves the focus lens from the current position to the front side and the rear side, acquires the contrast value (AF evaluation value) at each position from the signal processing circuit 120 and stores it in the memory 140. Thereafter, the camera microcomputer 130 compares the AF evaluation values stored in the memory 140 and determines that the direction in which the AF evaluation value increases is the direction where the in-focus position is. Thereafter, the camera microcomputer 130 moves the focus lens in the direction where the in-focus position is located.

  At the time of wobbling, the main mirror and the sub mirror 105 are retracted from the optical path, the light beam is guided to the image sensor 110, the shutter (not shown) is opened, and images are continuously read from the image sensor 110 by a rolling readout method. Further, the camera microcomputer 130 transmits a command for driving the focus lens back and forth to the lens microcomputer 160. In response to this command, the lens microcomputer 160 issues an output signal for causing the drive circuit 155 to drive the focus lens.

  Hereinafter, operations of the camera microcomputer 130 and the lens microcomputer 160 during wobbling will be described. This operation flow (automatic focus adjustment method) is stored in the memory 140 as a program for realizing the function in the computer.

  When the live view is started, the camera microcomputer 130 acquires information such as the ID, focus sensitivity, and aperture setting of the photographing optical system 152 from the lens microcomputer 160. Next, the camera microcomputer 130 sets the wobbling width from the acquired focus sensitivity and aperture setting, and determines the wobbling time from the lens ID and the wobbling width.

  Next, the camera microcomputer 130 determines the type of the AF area. In the case of one-point AF, since the frequency of changing the AF area is low, the camera microcomputer 130 sets the contrast evaluation cycle to 2 frames (or sets the lens driving stop period to be small). On the other hand, in the case of multipoint AF, face AF, and the like, since the frequency of changing the AF area is high, the camera microcomputer 130 sets the contrast evaluation cycle to 3 frames (or sets the lens drive stop period to be large).

  Note that “2 frames” and “3 frames” are merely examples, and it is sufficient that the contrast evaluation cycle when the AF region change frequency is low is smaller than the contrast evaluation cycle when the AF region change frequency is high. Further, it is sufficient that the lens drive stop period when the AF area change frequency is low is shorter than the lens drive stop period when the AF area change frequency is high.

  Subsequently, the camera microcomputer 130 calculates a delay time T1 from the vertical synchronization signal VD to the start of charge accumulation in the AF area based on the AF area. Next, when there is a wobbling instruction, the camera microcomputer 130 starts notifying the lens microcomputer 160 of VD, wobbling width, wobbling time, T1, AF region charge accumulation period (driving stop time T2), and AF evaluation start. The timing is notified to the lens microcomputer 160.

  On the other hand, when the notification of the vertical synchronization signal VD is started, the lens microcomputer 160 starts the lens drive start timing (drive permission period T3) based on the wobbling width, the wobbling time, T1, the charge accumulation period in the AF area, and the AF evaluation start timing. Start timing). Next, the lens microcomputer 160 controls the drive circuit 155 so as to drive the focus lens of the photographing optical system 152.

  FIG. 1 is a timing chart of charge accumulation and wobbling. FIG. 1A shows a case where contrast detection (or one point AF) is performed in a narrow area of the screen, that is, a case where the frequency of changing the AF area is low. FIG. 1B shows a case where contrast detection (or multipoint AF) is performed on the entire area of the screen, that is, a case where the frequency of changing the AF area is high.

  Charge accumulation and readout are performed in accordance with the period of the vertical synchronization signal VD. The delay time T1 is a time from the vertical synchronization signal VD to the start of charge accumulation in the AF region. The lens microcomputer 160 calculates a lens driving period and a period to be stopped from the vertical synchronization signal VD and the delay time T1, and controls the driving circuit 155 to drive the focus lens as shown in FIG.

  The drive stop period T2 is a period in which the lens drive is stopped at the closest position, and charge accumulation and readout and calculation of the contrast evaluation value are performed during this period. The drive permission period T3 is a period during which the lens moves from the closest side to the infinite side for wobbling. During this period, the accumulation operation is performed while the lens is moving, so that the contrast evaluation value is not calculated. The drive stop period T4 is a period in which the lens drive is stopped at a position on the infinite side. During this period, charge accumulation and readout and calculation of a contrast evaluation value are performed. T1 to T5 are transmitted from the camera microcomputer 130 to the lens microcomputer 160 as data.

  In FIG. 1A, one cycle of wobbling is performed in four cycles of the vertical synchronization signal VD. That is, the contrast evaluation is performed once every two frames. Thereafter, the lens microcomputer 160 instructs the drive circuit 155 to drive the focus lens in the in-focus direction based on the result of the contrast evaluation value.

  FIG. 1B is different from FIG. 1A in that the period drive stop periods T2 and T4 are longer than those in FIG. This is because in the rolling readout method, the accumulation time of the portion close to the entire area is shifted little by little while the upper and lower portions of the screen overlap. In FIG. 1B, one cycle of wobbling is performed in six cycles of the vertical synchronization signal VD. That is, the contrast evaluation is performed once every three frames.

  The lens microcomputer 160 receives the information of T1 to T5 from the camera microcomputer 130, and can detect the contrast of the entire region by changing the timing of the lens driving period and the stop period. In this way, even when the AF area changes frequently as shown in FIG. 1B, if the driving method shown in FIG. 1B is selected in advance, the start and end timings of the lens driving period are driven. It is not necessary to transmit to the circuit 155, and the amount of communication can be reduced.

  FIG. 2 is a timing chart of charge accumulation and wobbling when the shutter speed is fast in FIG. That is, FIG. 2A shows a case where contrast detection is performed on a narrow area of the screen (that is, when the AF area change frequency is low) and the accumulation time of the image sensor 110 is short. FIG. 2B shows a case where contrast detection is performed on the entire area of the screen (that is, when the AF area is frequently changed) and the accumulation time of the image sensor 110 is short.

  In FIG. 2A, one cycle of the wobbling operation is performed in two periods of the vertical synchronizing signal VD. In FIG. 2B, one cycle of the wobbling operation is performed in four periods of the vertical synchronizing signal VD. It has been broken.

  The lens microcomputer 160 receives the information of T1 to T5 from the camera microcomputer 130, and can detect the contrast of the entire region by changing the timing of the lens driving period and the stop period. Even in this embodiment, even when the AF area changes frequently as shown in FIG. 2B, if the driving method shown in FIG. 2B is selected in advance, the timing of starting and ending the lens driving period can be set. It is not necessary to transmit to the drive circuit 155, and the amount of communication can be suppressed.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

  The imaging device can be applied to use for imaging a subject.

110 Image sensor 120 Signal processing circuit 128 Setting means 130 Camera microcomputer 150 Lens unit 152 Imaging optical system 155 Driving circuit (driving means)

Claims (4)

An imaging apparatus in which a lens unit having an imaging optical system and a driving unit for driving the imaging optical system is detachable,
An image sensor that performs charge accumulation and readout in units of pixel rows;
Setting means for setting a first mode in which a target area for focus adjustment is fixed or a second mode in which the area varies;
Communication means for performing communication for moving the lens unit and the photographing optical system via the driving means;
The imaging optical system is wobbled in the optical axis direction, and the imaging is performed in a direction where the in-focus position is based on a signal accumulated in the image sensor during a period in which the driving of the imaging optical system is stopped during the wobbling. Automatic focusing means for moving the optical system;
Control means for making the drive stop period during which the driving of the photographing optical system is stopped during the wobbling longer when the second mode is set than when the first mode is set. An imaging device that is characterized.   The automatic focus adjustment unit transmits information on the driving stop period set by the control unit to the lens unit, and does not transmit timings of start and end of driving by the driving unit to the lens unit. The imaging device according to claim 1.   The imaging apparatus according to claim 1, wherein the first mode is a one-point AF mode or a narrow-area AF mode.   The imaging apparatus according to claim 1, wherein the second mode is a multi-point AF mode or a face AF mode for performing face detection.