JP5888837B2 - IMAGING DEVICE AND IMAGING DEVICE CONTROL METHOD - Google Patents

Description

  The present invention relates to an imaging apparatus and a control method for the imaging apparatus.

  There has been proposed a zoom device having an auto zoom function for automatically controlling zoom so as to keep a subject at a certain size (see, for example, Patent Document 1). By applying the technique disclosed in Patent Document 1 to an imaging apparatus, the imaging apparatus controls zoom according to the distance to the subject, and adjusts the focus with an autofocus function or a manual focus function, thereby To focus.

Japanese Patent Laid-Open No. 7-294895

  When the imaging apparatus moves the zoom lens in order to change the focal length, a method of simultaneously controlling the focus lens so that the focus position does not shift before and after the movement of the zoom lens is conceivable.

  FIG. 7 is a diagram illustrating a method of moving the focus lens in conjunction with the zoom lens. The vertical axis of the graph shown in FIG. 7 is the focus lens position, and the horizontal axis is the zoom lens position. In FIG. 7, f11, f12, f13, and f14 are trajectories indicating the relationship between the zoom lens position and the focus lens position when the focus distance is 1 m, 2 m, 4 m, and 8 m, respectively. The image pickup apparatus stores in advance storage unit correspondence information (that is, information on each locus in FIG. 7) between each focus position, zoom lens position, and focus position. When the image pickup apparatus moves the zoom lens, the focus lens is moved according to a trajectory in which the focus distance is constant based on the correspondence information stored in the storage unit. Thereby, the imaging apparatus can change the focal length without affecting the focus distance.

  However, the method of changing the focal length without affecting the focus distance described with reference to FIG. 7 has the following problems. In other words, when auto-zoom is in operation, every time the auto-zoom operates and the distance to the subject changes, even if you try to adjust the focus appropriately with the auto-focus function or manual focus function and focus on the subject Will be out of focus. In addition, when the focus is greatly deviated, it takes time and effort to adjust the focus again.

  In view of the above-described problems, the present invention provides an image pickup apparatus that controls focus so that the subject is in focus even when the focal length changes due to the operation of auto-zoom. For the purpose of provision.

An imaging apparatus according to an embodiment of the present invention automatically captures an image of a subject formed by an imaging optical system and outputs an image signal, and automatically adjusts the subject based on the output image signal. And an automatic focus adjustment means for driving the focus lens of the imaging optical system, and the imaging optical so that the size of the subject in the imaging screen obtained based on the output image signal matches a predetermined reference size. the system of the zoom lens and auto zoom drivable zooming unit, depending especially Accordingly focal length auto zoom drive of the zoom lens is changed, based on the rate of change of the focal length not based on the focus automatic adjustment means Te, wherein calculating an adjustment amount of the focusing lens, and control means for changing the focal length by controlling the focus lens of the imaging optical system Characterized in that it obtain.

  According to the imaging apparatus of the present invention, the focus is controlled so that the subject is in focus even when the focal length is changed by operating auto-zoom on the subject in focus. be able to.

It is a figure which shows the structural example of the imaging device of this embodiment. 6 is a flowchart for explaining operation processing of the imaging apparatus according to the first embodiment. It is a figure explaining the relationship between a subject's size, a focal distance, and a zoom lens position. It is a figure which shows the correspondence of a zoom lens position and a focus lens position. 6 is a flowchart illustrating an operation process of the imaging apparatus according to the second embodiment. It is a figure which shows the correspondence of a zoom lens position and a focus lens position. It is a figure explaining the method of moving a focus lens in conjunction with a zoom lens.

  FIG. 1 is a diagram illustrating a configuration example of an imaging apparatus according to the present embodiment. The imaging device shown in FIG. 1 is a video camera, for example. The imaging apparatus includes an imaging optical system 101, an imaging measure 102, a signal processing circuit 103, a lens control circuit 104, and a CPU (Central Processing Unit) 105. The imaging apparatus also includes a recording medium 106, a recording medium control circuit 107, a monitor 108, a reproduction circuit 109, an OSD (On Screen Display) circuit 110, and operation keys 111. The imaging apparatus also includes a RAM (Random Access Memory) 112, a ROM (Read Only Memory) 113, a real-time clock 114, and an external input / output unit 115.

  The imaging optical system 101 includes at least a zoom lens that controls the focal length and a focus lens that controls the focus distance. The zoom lens and the focus lens included in the imaging optical system 101 form a subject image on the imaging surface of the imaging element 102. The zoom lens is configured to be movable in the optical axis direction, and the imaging magnification can be adjusted by moving. The focus lens has an optical axis that coincides with the optical axis of the zoom lens, is configured to be movable in the optical axis direction, and can adjust the imaging position (focal point) by moving. The image sensor 102 is a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like. The image sensor 102 converts the subject image formed on the imaging surface into an electrical signal (image signal) and outputs the electrical signal. That is, the imaging element 102 functions as an imaging unit that captures the subject image formed by the imaging optical system 101 and outputs an image signal. The signal processing circuit 103 converts the charge output from the image sensor 102 into a signal (image signal, video signal) in a predetermined format. The lens control circuit 104 controls the zoom lens and the focus lens according to instructions from the CPU 105.

  The CPU 105 controls the entire imaging apparatus. The CPU 105 obtains the size of the subject in the imaging screen based on the signal converted by the signal processing circuit 103. The CPU 105 executes the auto zoom operation as follows. The CPU 105 instructs the lens control circuit 104 to drive the zoom lens so that the size of the subject matches a predetermined reference size. That is, the CPU 105 and the lens control circuit 104 function as a zoom unit that drives the zoom lens so that the size of the subject in the imaging screen obtained based on the image signal output by the imaging unit matches the reference size. The reference size is a size serving as a reference of the subject in the auto zoom operation. The CPU 105 sets a reference size based on operation information input by the operation key 111 in accordance with a user operation, and stores the reference size in the RAM 112 before starting the auto zoom operation. The CPU 105 performs the above-described auto zoom operation when the auto zoom mode is set as the operation mode of the CPU 105. The operation key 111 sets the auto zoom mode according to the user's operation input.

  The CPU 105 and the operation key 111 function as a manual focus adjustment unit that manually drives the focus lens so that the subject is in focus. Specifically, when the user performs a focus operation using the operation key 111, the operation key 111 inputs a focus adjustment amount corresponding to the focus operation. The CPU 105 moves the focus lens to a position corresponding to the input focus adjustment amount. The CPU 105 and the operation key 111 operate as a focus manual adjustment unit when an MF (Manual Focus) mode is set as an operation mode of the CPU 105. The MF mode is an operation mode in which the CPU 105 and the operation key 111 are operated as a manual focus adjustment unit. The MF mode is set by the operation of the operation key 111 by the user.

  The CPU 105 functions as an automatic focus adjustment unit that automatically drives the focus lens so that the subject is in focus. Specifically, the CPU 105 obtains a focus adjustment amount for focusing on the subject based on the image signal output from the signal processing circuit 103. Then, the lens control circuit 104 is controlled to move the focus lens to a position corresponding to the obtained focus adjustment amount. The CPU 105 operates as an automatic focus adjustment unit when an AF (Auto Focus) mode is set as the operation mode of the CPU 105. The AF mode is an operation mode in which the CPU 105 operates as an automatic focus adjustment unit. The AF mode is set by the operation of the operation key 111 by the user.

  The CPU 105 functions as a control unit that controls the focus lens so that the focus distance changes at the same rate as the focal length change rate when the focal length changes in accordance with the driving of the zoom lens. The CPU 105 may control the focus lens so that the focus distance is inversely proportional to the subject size and proportional to the focal distance when the focal distance changes in accordance with the driving of the zoom lens.

  The RAM 112 is temporary storage means and functions as a work area for the CPU 105. The ROM 113 stores in advance a computer program used by the CPU 105 to control the imaging device. The control method of the imaging apparatus of the present embodiment is realized by the CPU 105 executing a computer program in the ROM 113. The recording medium 106 is a recording medium such as a DVD, a hard disk, or a nonvolatile memory. The recording media control circuit 107 writes a video signal to the recording media 106 in accordance with an instruction from the CPU 105. Further, the recording media control circuit 107 reads a video signal from the recording media 106 in accordance with an instruction from the CPU 105. The monitor 108 outputs an image being shot or a reproduced image in accordance with an instruction from the reproduction circuit 109. The reproduction circuit 109 causes the monitor 108 to reproduce the video signal read from the recording medium 106 by the recording medium control circuit 107.

  The OSD 110 displays an operation menu and shooting information on the monitor 108. The operation key 111 is an operation key used for the user to operate the imaging apparatus. The operation key 111 inputs operation information corresponding to a user operation. The real-time clock 114 transmits date information and time information to the CPU 105. The external input / output unit 115 outputs the captured video to an external monitor or recorder. The external input / output unit 115 receives video from an external device (for example, a video camera or a player) and inputs the video to the imaging device.

  FIG. 2 is a flowchart for explaining operation processing of the imaging apparatus according to the first embodiment of the present invention. The image pickup apparatus according to the first embodiment has the same configuration as the image pickup apparatus illustrated in FIG. After performing the focus adjustment, the image pickup apparatus according to the first exemplary embodiment causes the subject size to coincide with a predetermined reference size (keep the subject size constant) through an auto zoom operation. Then, the imaging apparatus changes the focus position in accordance with the change of the focal length accompanying this auto zoom operation.

  The CPU 105 determines whether the MF mode is set (step S1). When the AF mode is set instead of the MF mode, the CPU 105 functions as an automatic focus adjustment unit, and automatically controls the focus by AF (step S8), and proceeds to step S4. When the MF mode is set, the CPU 105 and the operation key 111 function as a focus manual adjustment unit. That is, the CPU 105 determines whether a focus operation has been performed based on the operation information input by the operation key 111 (step S2). If the focus operation has not been performed, the process proceeds to step S4. When the focus operation is performed, the CPU 105 instructs the lens control circuit 104 to move the focus lens by the operated amount (step S3). That is, the CPU 105 moves the focus lens to a position corresponding to the focus adjustment amount input by the focus operation. As a result, the subject is in focus.

  Next, the CPU 105 determines whether or not the subject size matches the reference size (step S4). FIG. 3 is a diagram for explaining the relationship between the size of the subject, the focal length, and the zoom lens position. FIG. 3A shows the size of the subject. In this example, the CPU 105 of the imaging apparatus recognizes the face of the subject using a known face recognition technique based on the signal converted by the signal processing circuit 103. The CPU 105 sets the recognized face height A as the size of the subject. If the subject size matches the reference size, the process proceeds to step S7. If the subject size does not match the reference size, the CPU 105 controls the zoom lens so that the subject size matches the reference size (step S5). For example, if the reference size value is A and the photographed subject size is A ′, the CPU 105 controls the zoom lens so that the focal length is (A / A ′) times.

  FIG. 3B shows the relationship between the focal length and the zoom lens position. The vertical axis of the graph shown in FIG. 3B is the focal length, and the horizontal axis is the zoom lens position. In the CPU 105, the locus 200 in FIG. 3B indicates correspondence information between the focal length and the zoom lens position. The CPU 105 stores correspondence information between the focal length indicated by the locus 200 and the zoom lens position in the ROM 113 in advance. Then, the CPU 105 obtains a zoom lens position such that the focal length is (A / A ′) times based on this correspondence information stored in the ROM 113, and moves the zoom lens so as to move to the obtained zoom lens position. Control.

Next, the CPU 105 controls the focus lens according to the change in the focal length accompanying the control of the zoom lens (step S6). Hereinafter, the focus lens control according to the change in the focal length accompanying the zoom lens control in step S5 will be described. In the first embodiment, the CPU 105 controls the focus lens so that the focus distance changes by the same ratio as the change rate of the focal length by the auto zoom operation. As a general focus lens control method, there is a method of controlling the focus lens position so that the focus distance does not change even when the zoom lens position, that is, the focal length changes. However, in the auto zoom mode, the focal length is changed when the distance from the imaging device to the subject changes, so it is necessary to change the focus distance in accordance with the change in the focal length. Here, when the distance to the subject (subject distance) is X, the focal length is Y, the subject size with respect to the angle of view is A, and the constant is B, the following Equation 1 is established.
X = (B / A) Y Formula 1

  Since the CPU 105 controls (B / A) to be constant during the auto zoom operation, the subject distance is proportional to the focal length. Therefore, in a state where the subject is in focus during the auto zoom operation, the state where the subject is in focus can be maintained by changing the focus distance at the same ratio as the focal length. That is, in step S5 of FIG. 2, the CPU 105 controls the focus lens position so that the focus distance changes by the rate at which the focal length changes due to the change of the zoom lens position.

  FIG. 4 is a diagram illustrating a correspondence relationship between the zoom lens position and the focus lens position in the first embodiment. The vertical axis of the graph shown in FIG. 4 indicates the focus lens position, and the horizontal axis indicates the zoom lens position. W represents the wide side and T represents the tele side. Trajectories f11 to f14 in FIG. 4 are the same as f11 to f14 in FIG. A trajectory f indicated by a bold line in FIG. 4 indicates correspondence information between the focus lens position and the zoom lens position when the CPU 105 controls the focus lens so that the focus distance changes at the same ratio as the focal length.

  When the distance from the imaging device to the subject changes from 8 m to 1 m, for example, the focal length becomes 1/8 (zoom magnification becomes 1/8) according to Equation 1. When the focal length becomes 1/8, the CPU 105 controls the focus so that the focus distance becomes 1/8. Thereby, it is possible to focus on the subject. Specifically, the CPU 105 stores correspondence information indicated by the locus f in the ROM 113 in advance. When the focal length changes with the auto zoom operation, the focus lens position with respect to the focal length is calculated based on correspondence information indicated by the locus f stored in the ROM 113. The CPU 105 controls the focus lens so that the position of the focus lens becomes the calculated focus lens position.

  Returning to FIG. 2, the CPU 105 determines whether or not the auto zoom mode is set (step S7). If the auto zoom mode is set, the process returns to step S1. If the auto zoom mode is not set, the process ends. According to the first embodiment, after the focus is adjusted to the subject by manual focus or autofocus, the distance from the imaging device to the subject is changed and the focal length is changed as the auto zoom function is operated. This makes it difficult to focus on the subject. In particular, in a state where the subject is accurately focused before the auto zoom operation is performed, it is possible to maintain the focused state even after the auto zoom operation. In addition, even when the focus is lost after zoom control, the degree can be kept small, so that it is easy to focus again by manual focus or autofocus, and the time required for focus is reduced.

  FIG. 5 is a flowchart illustrating an operation process of the imaging apparatus according to the second embodiment. The imaging apparatus according to the second embodiment also has the same configuration as the imaging apparatus illustrated in FIG. The imaging apparatus according to the second embodiment performs focus control when the reference size is changed during the auto zoom operation. The processes in steps S11, S12, S13, S15, S16, S18, and S19 in FIG. 5 are the same as the processes in steps S1, S2, S3, S4, S5, S7, and S8 in FIG.

  In step S14 of FIG. 5, the CPU 105 determines whether the reference size has been changed based on the operation information input by the operation key 111 (step S14). If the reference size has not been changed, the process proceeds to step S15. When the reference size is changed, the CPU 105 changes the reference size to a value set by operating the operation key 111, that is, a value indicated by the operation information (step S20), and the process proceeds to step S15. Then, the CPU 105 drives the zoom lens so that the subject size matches the changed reference size.

  After the processes of steps S15 and S16 are performed, the CPU 105 controls the focus lens in accordance with the change in focal length accompanying the zoom lens control (step S17). Hereinafter, the focus lens control according to the change in the focal length accompanying the zoom lens control in step S17 will be described. In this example, it is assumed that the reference size has been changed in step S20. The CPU 105 controls the focus in consideration of the change in the focal length due to the auto zoom operation and the change in the reference size. Referring to Equation 1 described above, the subject distance X is proportional to the focal length Y and inversely proportional to the subject size A (that is, the reference size) with respect to the angle of view. Therefore, the CPU 105 controls the focus lens so that the focus distance is inversely proportional to the subject size and proportional to the focal distance.

  FIG. 6 is a diagram illustrating a correspondence relationship between the zoom lens position and the focus lens position in the second embodiment. Trajectories f1, f2, and f3 in FIG. 6 indicate correspondence information between the zoom lens position and the focus lens position when the focus lens is controlled so that the focus distance is proportional to the focal length. The trajectories f1, f2, and f3 are trajectories corresponding to different subject sizes. The trajectory f2 corresponds to a size twice the size of the subject corresponding to the trajectory f1. The trajectory f2 corresponds to a size that is ½ times the size of the subject to which the trajectory f1 corresponds.

  When the size of the subject is constant, the CPU 105 controls the focus lens so that the focus lens position follows a single locus. When the size of the subject is changed, that is, when the reference size is changed, a new locus corresponding to the changed size of the subject is operated. For example, when the CPU 105 operates the focus lens along the locus f1 in FIG. 6, it is assumed that the subject size A has been changed to a double size. The CPU 105 controls the focus lens so that the focus lens position follows a locus f2, which is a locus corresponding to the double size. When the size of the subject is changed to ½ times, the focus lens is controlled so that the focus lens position follows the locus f3 which is a locus corresponding to the ½ size.

  Specifically, the CPU 105 stores correspondence information indicated by the trajectories f1 to f3 in the ROM 113 in advance. When the focal length changes with the auto-zoom operation, the CPU 105 acquires a trajectory corresponding to the subject size (reference size) at that time from the ROM 113. The CPU 105 calculates the focus lens position based on correspondence information between the focus lens position and the zoom lens position indicated by the acquired locus. Then, the CPU 105 controls the focus lens so that the position of the focus lens becomes the calculated focus lens position. According to the second embodiment, even when the size of the subject with respect to the angle of view is changed during the auto zoom operation, it is difficult for the subject to be out of focus. If the subject is in focus accurately before zoom control is performed, the in-focus state can be maintained after the auto zoom operation.

101 Imaging optical system 104 Lens control circuit 105 CPU

Claims (6)

An imaging means for imaging a subject image formed by an imaging optical system and outputting an image signal;
Automatic focus adjustment means for automatically driving the focus lens of the imaging optical system so that the subject is in focus based on the output image signal;
Zoom means capable of automatically zoom driving the zoom lens of the imaging optical system so that the size of the subject in the imaging screen obtained based on the output image signal matches a predetermined reference size;
Wherein Depending particular Thus focal length auto zoom drive is changed in a zoom lens, based on the rate of change of the focal length not based on the automatic focus adjusting means calculates the adjustment amount of the focus lens, the calculation result And a control means for controlling the focus lens of the imaging optical system to change the focus distance .   The imaging apparatus according to claim 1, further comprising a focus manual adjustment unit that drives the focus lens in accordance with a manual operation.   3. The zoom lens according to claim 2, wherein the zoom unit drives the zoom lens so that the size of the subject matches the reference size in a state where the subject is in focus by the focus manual adjustment unit. Imaging device. 4. The zoom unit according to claim 3 , wherein the zoom unit drives the zoom lens so that the size of the subject matches the reference size in a state where the subject is in focus by the automatic focus adjustment unit. Imaging device. When the reference size is changed, the zoom unit drives the zoom lens so that the size of the subject matches the changed reference size, and the control unit responds to the driving of the zoom lens. when the focal length changes, inversely proportional to the size of the focal distance is subject and, in any one of claims 1 to 4, wherein the controller controls the focus lens in proportion to the focal length The imaging device described. Capturing a subject image formed by the imaging optical system and outputting an image signal;
An automatic adjustment step of automatically driving the focus lens of the imaging optical system so that the subject is in focus based on the output image signal;
A step of automatically zooming the zoom lens of the imaging optical system so that the size of the subject in the imaging screen obtained based on the output image signal matches a predetermined reference size;
Wherein Depending particular Thus focal length auto zoom drive is changed in a zoom lens, based on the rate of change of the focal length not based on the automatic adjustment process, and calculates the adjustment amount of the focus lens, in accordance with the calculation result And a step of changing a focus distance by controlling a focus lens of the imaging optical system.

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