JP5335492B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to a technique for providing a shooting mode in which even a beginner can easily perform zoom shooting between exposures in an imaging apparatus having a zoom lens capable of adjusting a focal length during exposure.

  The inter-exposure zoom has been widely known as an imaging technique for obtaining a special effect in which the periphery of an image flows radially. However, in order to manually perform zoom driving during exposure, a very advanced technique is required, and the skill of the photographer is required. From such a background, as disclosed in Patent Document 1, a technique for electrically moving the zoom and synchronizing it with the exposure timing is disclosed. Further, Patent Document 2 discloses a technique for photographing the main subject with high resolution by shifting the timing of the exposure start and the zoom start.

  Generally, when the focal length is changed with a zoom lens, the focus lens that performs focusing is driven and controlled following the change in the focal length of the zoom lens, and the focused state, that is, the in-focus state is maintained. Control is performed as follows. This is no exception in the process of zoom exposure during exposure, and when the focal length is changed with the zoom lens during exposure, the focus lens is driven to follow the change in focal length and keeps in focus. Is done. As a result, a sharp effect that is in focus can also be obtained with respect to a special effect obtained by zooming between exposures.

Japanese Examined Patent Publication No. 7-23949 Japanese Patent No. 3103620

However, a photographer does not always have a demand to sharply capture a special effect such as a radial flow around the image. For example, with regard to special effects, the photographer may have a request to softly focus on the background by intentionally shifting the focus and giving a predetermined amount of blur (degree of out-of-focus).
An object of the present invention is to provide an imaging apparatus in which anyone can easily set the degree of out-of-focus related to focus control for a special effect in which the periphery of an image flows radially in view of the needs of a photographer.

In order to solve the above problems, the device according to the present invention is an imaging apparatus having a function of exposure zooming photographing zooming drive during exposure, and a control means for driving the zoom lens and the focus lens during exposure And a signal processing means for processing a signal of an image captured while driving the zoom lens and the focus lens during exposure, and the control means is configured to drive the focus lens in the first mode. followed by, and driven to the focus position to focus on the subject at the position of the zoom lens driven during exposure, the control means drives the focus lens while driving the zoom lens in a second mode to time, the Four to the position to calculate the position deviated from the focusing position according to the position of the zoom lens driven during exposure Drives Surenzu, when the exposure is completed, after the control for stopping the driving of the zoom lens and focus lens, the signal processing means for processing the signals of the captured images.

  According to the present invention, it is possible for a beginner to easily set the degree of out-of-focus with respect to special effects of zoom exposure during exposure.

FIG. 6 is a block diagram illustrating a configuration example of an imaging apparatus in order to describe the embodiment of the present invention in conjunction with FIGS. 2 to 5. It is a block diagram which shows the principal part about zoom drive control and focus drive control. It is a flowchart which shows the example of a process of zoom exposure between exposures. It is the figure which illustrated the relationship between a zoom lens position and a focus lens position. 6 is a graph illustrating the relationship between the zoom lens position and the focus lens position when an out-of-focus state is intentionally generated.

  Embodiments of the present invention will be described below. FIG. 1 is a block diagram for explaining an imaging apparatus which is an example of an embodiment of the present invention. The optical system of the imaging apparatus having the function of zoom exposure during exposure is configured in three groups in this example. Hereinafter, the first group lens 101 involved in zoom control is referred to as a zoom lens, and the second group lens 103 involved in shake correction. Is called a shift lens. The third group lens 104 involved in the focus adjustment is called a focus lens.

  The zoom lens 101 can change the position along the optical axis direction, and is a lens for changing the magnification by changing the focal length. A zoom drive control unit 109 is provided to drive and control the zoom lens 101. A shutter / diaphragm 102 is disposed as an exposure unit at the subsequent stage of the zoom lens 101. A shutter / aperture drive control unit 110 that constitutes an exposure control unit is provided to drive and control the shutter / aperture 102.

The shift lens 103 is a lens that can change the position in a plane perpendicular to the optical axis and constitutes a shake correction optical system. A shift lens drive control unit 111 is provided for the shift lens 103 and controls the drive of the shift lens 103.
The focus lens 104 is a focus adjustment lens whose position can be changed along the optical axis direction. A focus drive control unit 112 that constitutes a focus control unit is provided, and drives and controls the focus lens 104 in order to determine the focus state of the subject.

  The imaging and signal processing system circuit includes an imaging element 105, an imaging signal processing unit 106, and a video signal processing unit 107. The image sensor 105 receives an optical image through the lens group and converts it into an electrical signal. The imaging signal processing unit 106 located at the subsequent stage converts the electrical signal output from the imaging element 105 into a video signal. The video signal processing unit 107 performs predetermined processing on the video signal output from the imaging signal processing unit 106 and outputs a signal that can be displayed. The display unit 108 using a liquid crystal monitor or the like constitutes an image display unit, and displays an image as necessary based on the output signal of the video signal processing unit 107. The display control unit 113 controls the imaging and signal processing system circuits, and controls the imaging operation and the display operation.

The control of the entire system is generally performed using a computer according to a program that is interpreted and executed. For example, a system control unit 118 using a CPU (Central Processing Unit) or the like controls the entire system.
The power supply unit 114 supplies a power supply voltage to each component of the system as necessary. The external input / output terminal unit 115 receives a communication signal, a video signal, and an audio signal transmitted to an external device (not shown) or outputs these signals from the terminal unit. The shutter release switch 116 is configured such that a first switch (hereinafter referred to as SW1) and a second switch (hereinafter referred to as SW2) are sequentially turned on in accordance with the push amount. Signals from these switches are sent to the system control unit 118 to determine the user's operation instructions. The zoom lever 119 is an operation means for instructing the focal length during zoom driving, and the operation instruction is sent to the system control unit 118. The storage unit 117 is used as a storage unit or a temporary storage unit for various data such as video information, audio information, time information, and setting information. The storage unit 117 further stores various programs that are interpreted and executed by the system control unit 118.

Next, the operation of the imaging apparatus having the above configuration will be described. In the shutter release switch 116, SW1 is turned on when the shutter release button is pressed about halfway, and SW2 is turned on when the shutter release button is further pushed down to the end.
First, when SW1 is turned on, the system controller 118 receives the signal and sends a control signal to the focus drive controller 112 and the shutter / aperture drive controller 110. Thus, the focus drive control unit 112 drives the focus lens 104 to perform focus adjustment, and the shutter / aperture drive control unit 110 drives the shutter / aperture 102 to set the exposure amount to an appropriate value.

  Thereafter, when SW2 is turned on, the signal is received by the system control unit 118, and image data obtained from the light image exposed to the image sensor 105 is stored in the storage unit 117 under the control of the signal. When there is an instruction to adjust the focal length using the zoom lever 119, the zoom drive control unit 109 that receives the instruction via the system control unit 118 drives the zoom lens 101 and moves the zoom lens 101 to the instructed zoom position. Let At the same time, the signal from the image sensor 105 is processed by the video signal processing unit 107 via the imaging signal processing unit 106, and the focus drive control unit 112 drives the focus lens 104 based on this processed image information to focus. Make adjustments. During zooming during exposure, zooming between exposures is started in accordance with an operation instruction of the shutter release switch 116, and driving of the zoom lens 101 and exposure to the image sensor 105 are started.

  FIG. 2 is a detailed block diagram of the zoom drive control unit 109 and the focus drive control unit 112 shown in FIG. In the zoom drive control unit 109, the zoom motor 201 is a drive unit for driving the zoom lens 101, and changes the focal length. The zoom motor drive circuit 202 is an analog circuit that drives the zoom motor 201. As a position detection unit of the zoom lens 101, a zoom reset position detection unit 203 and a zoom position detection unit 204 are provided. The zoom reset position detection unit 203 detects the reset position of the zoom lens 101 and acquires a reference position for zoom control. The zoom position detection unit 204 detects the position of the zoom lens 101.

  The zoom control unit 205 controls the amount of movement of the zoom lens 101 according to the detection signal output from the zoom position detection unit 204. The zoom motor drive circuit 202 rotates the zoom motor 201 according to the control amount, and drives the zoom lens 101. An inter-exposure zoom control unit 206 sends a control command to the zoom control unit 205 to control driving of the zoom lens 101 during exposure.

  In the focus drive control unit 112, the focus motor 207 is a drive unit for the focus lens 104. The focus motor drive circuit 208 is an analog circuit that drives the focus motor 207. A focus reset position detection unit 209 is provided as a position detection unit of the focus lens 104, and acquires a reference position for focus control. The focus position detection unit 211 detects the focus position of the focus lens with respect to the subject based on the image obtained by the image sensor 105, that is, the exposed image, and sends a detection signal to the focus control unit 210.

  Here, the zoom lens and the focus lens of the varifocal lens will be described. When a varifocal lens is used, when the zoom lens is driven to change the focal length, the focus state by the focus lens is shifted accordingly. Therefore, in order to always obtain a focused state with respect to the subject when the zoom lens is driven, the position of the focus lens needs to be corrected. At this time, the position of the focus lens that is focused at a certain subject distance at the zoom lens position can be determined in advance by optical design.

FIG. 4A is a graph showing the position of the zoom lens and the position of the focus lens at the time of focusing. The horizontal axis represents the zoom lens position (the right side is the tele side and the left is the wide side), and the vertical axis represents the focus lens position.
A graph line 1001 represents a locus of the position of the focus lens 104 that can maintain a focused state at a certain subject distance even when the zoom lens 101 is driven. That is, by following the driving of the zoom lens 101 and driving the focus lens 104 to a position along this locus, the in-focus state can always be maintained during the driving of the zoom lens 101. A graph line 1002 represents a locus of a focus lens position for maintaining a focused state at a subject distance different from that of the graph line 1001, for example, an infinite subject distance. In the actual focus control unit 210, a non-volatile storage unit holds a data table as shown in FIG. 4B, and control can be realized by referring to the data table.

  FIG. 4B shows the structure of data indicating the zoom lens position and the focus lens position at the subject distance in a tabular format. The leftmost column represents the zoom lens position, “Wide” represents the wide (wide angle) end, and “Tele” represents the tele (telephoto) end. The upper row represents the subject distance, and in this example, it is infinite, 1 m to 10 cm. Therefore, the data at the location where the row indicating the zoom lens position and the column indicating the subject distance intersect indicate the focus lens position at the time of focusing. For example, regarding the graph line 1002 shown in FIG. 4A, for the focus lens position data at an infinite subject distance, the data group included in the column 1101 in FIG. 4B is referred to according to the zoom lens position. Is required. In FIG. 4B, the numerical value is indicated by “XXXX” for the sake of convenience. This means arbitrary numerical data indicating the focus lens position, and each has a different value. In order to calculate the focus lens position at the subject distance that does not exist in the data table, interpolation calculation may be performed from the focus lens position at the subject distance between adjacent columns.

Next, a focus lens position for generating a predetermined blur amount will be described. When the focus amount in the focus range with respect to the best focus position is denoted as D, the allowable circle of confusion diameter is denoted as δ, and the aperture value (F number) F, the focus amount D in the focus range is as shown in the following equation.

If the focus lens is driven to a position deviating from the focus amount D in the focus range obtained by the above equation, an image in a state deviated from the focus state can be obtained. When the focus position of the focus lens calculated using the data table of FIG. 4B described above is denoted by G, and a coefficient (blur coefficient) indicating the degree of the out-of-focus state is denoted by K, the photographed image is blurred. The calculation formula of the focus lens position B for generating is as follows.

The two expressions (Expression 2 and Expression 3) mean the difference between whether the focus is shifted to the front side of the subject image (front pin) or the focus is shifted to the rear side (rear focus) (focusing position G is the center). Note the difference in the sign of the second term on the right side).
The blur amount of the image increases as the amount deviating from the focus amount D in the focus range increases. That is, if the value of the coefficient K is increased in the above formulas 2 and 3, the blur amount of the image is increased, and if the value of the coefficient K is decreased, the blur amount is decreased.

  Regarding the setting of the blur amount by the user operation, for example, in order for the user who is a photographer to select the blur amount, a means for displaying and setting a menu screen or the like on the display unit 108 is provided, and the coefficient K is set. What is necessary is just to set it as the structure which can change a value arbitrarily. Further, the first mode for obtaining a sharp special effect without blur in the special effect of the inter-exposure zoom shooting and the second mode for giving a predetermined blur amount can be selected on the menu screen. Also good. In that case, it can be easily handled by setting the coefficient K to zero in the first mode and setting the coefficient K to a desired value in the second mode.

FIG. 5 is a graph for explaining a focus lens position when a predetermined blur amount is generated for an infinite subject. The horizontal axis represents the zoom lens position, and the vertical axis represents the focus lens position.
A graph line 1002 is a locus of the position of the focus lens 104 that is focused on a position at infinity, as in the case of FIG. On the other hand, the focus lens 104 may be driven to the position calculated using the above-described Expression 2 or Expression 3 in order to give a predetermined amount of blur from the focused state to the out-of-focus state. A graph line 1201 represents the focus lens position calculated according to the above-described Expression 2 with respect to the graph line 1002. In order to intentionally blur the image regarding the special effect of the zoom exposure between exposures, the focus lens position corresponding to the zoom lens position follows the locus of the graph line 1201 in accordance with the driving of the zoom lens 101. The lens 104 may be driven.

Next, a flow of processing for zoom exposure during exposure in the present embodiment will be described with reference to a flowchart of FIG. Here, as a premise, it is assumed that the amount of image blur is set in advance by the user's menu operation.
First, when the mode is switched to a mode for performing zoom shooting during exposure by a user operation, the zoom drive control unit 109 moves the zoom lens 101 to the zoom start position as necessary (see S301). Thereafter, in S <b> 302, shooting preparation processing including preparation for driving the image sensor 105 and the like is performed. In step S <b> 303, the system control unit 118 determines the state of the first switch SW <b> 1 of the shutter release switch 116. As a result, when the ON state of the first switch SW1 is detected, the process proceeds to Yes, and the focusing process is performed in S304, and the focus drive control unit 112 drives the focus lens 104 to focus on the subject. . A photometric process is also performed simultaneously with this process, and an appropriate exposure amount is determined from the brightness of the subject, and an exposure time and an aperture amount are determined. On the other hand, when the ON state of SW1 is not detected in S303, the process proceeds to No and the process of S303 is repeated.

  Subsequently, in S305, the system control unit 118 determines the state of the second switch SW2 of the shutter release switch 116. As a result, when the ON state of the second switch SW2 is detected (Yes in S305), the process proceeds to the next step S306, and the inter-exposure zoom process is started. On the other hand, if the ON state of SW2 is not detected in S305, the process proceeds to No and the process of S305 is repeated.

  After the exposure is started in S306, the process proceeds to S307, and the system control unit 118 determines whether or not a predetermined time (waiting time) has elapsed since the start of exposure. This waiting time processing is performed for the purpose of refining the captured image of the main subject by performing exposure on the main subject in a focused state before driving the zoom lens 101. In this example, an exposure time for refining the image of the main subject is provided before starting the driving of the zoom lens 101. However, the exposure operation and the driving of the zoom lens 101 are started simultaneously, and the main subject is stopped after the zoom lens 101 is stopped. An exposure time for refining the image may be provided.

  When the predetermined waiting time elapses in S307, the process proceeds in the direction of Yes, and the driving of the zoom lens 101 is started in the next S308. In step S309, driving of the focus lens 104 is also started. Here, the focus lens 104 is driven in accordance with the driving of the zoom lens 101, and the above-described Expression 2 or Expression 3 is used to calculate the drive position of the focus lens. That is, the value of the coefficient K is set based on the amount of blur set in advance by a user operation, and the focus lens position B is calculated using the above-described equation 2 or 3, and the focus lens 104 is moved to this position. Is driven. Whether to use Formula 2 or Formula 3 in the position calculation here may be determined in advance. The driving of the zoom lens 101 and the driving of the focus lens 104 (including calculation of the driving position in consideration of the amount of blur) are continued until a stop process in S312 and S313 described later.

  In S310, the system control unit 118 determines whether or not the exposure time determined in S304 has elapsed. As a result, if it is determined that the exposure time has not elapsed, the process proceeds in the No direction, the determination in S310 is repeated, and an exposure time waiting process is performed. When it is determined that the exposure time has elapsed (Yes in S310), the process proceeds to S311 and the exposure ends. In step S312, the zoom drive control unit 109 stops the zoom lens 101, and in step S313, the focus drive control unit 112 stops the focus lens 104. In S314, the exposed captured image is processed, and in S315, image data recording processing is performed.

DESCRIPTION OF SYMBOLS 101 ... Zoom lens 104 ... Focus lens 109 ... Zoom drive control part 112 ... Focus drive control part 118 ... System control part 116 ... Shutter release switch 206 ... Zoom controller during exposure 211 ... Focus position detection part

Claims (5)

An image pickup apparatus having a function of zoom exposure during exposure that performs zoom driving during exposure,
Control means for driving the zoom lens and focus lens during exposure ;
Comprising signal processing means for processing a signal of an image captured while driving the zoom lens and the focus lens during exposure ;
Said control means, said focusing lens in a first mode to follow the drive of the zoom lens, is driven to the focus position to focus on the subject at the position of the zoom lens driven during exposure,
When the focus lens is driven while driving the zoom lens in the second mode , the control means calculates a position out of the focus position according to the position of the zoom lens driven during exposure. When the focus lens is driven to the position and the exposure is completed, the signal processing means processes the signal of the captured image after performing control to stop the driving of the zoom lens and the focus lens. An imaging device that is characterized.   2. The control unit according to claim 1, wherein the control unit calculates the position of the focus lens out of the focus position in the second mode by multiplying a focus amount in the focus range by a coefficient. Imaging device.   The control means calculates the position of the focus lens by setting the coefficient value to zero in the first mode and setting the coefficient value to a non-zero value in the second mode. The imaging apparatus according to claim 2, wherein the imaging apparatus is characterized.   In the second mode, the control unit drives the zoom lens after a period of time during which exposure is performed at the in-focus position of the focus lens, and moves the focus lens to a position out of the in-focus position. The imaging device according to claim 1, wherein the imaging device is driven. Control means for driving a zoom lens and a focus lens during exposure, and signal processing means for processing a signal of an image captured while driving the zoom lens and focus lens during exposure, and zoom driving during exposure A method for controlling an imaging apparatus having a function of performing zoom exposure during exposure,
The control means causes the focus lens to follow the drive of the zoom lens in the first mode, and drives the focus lens to focus at the position of the zoom lens driven during exposure,
When driving the focus lens while driving the zoom lens in the second mode, the control means calculates a position out of the focus position according to the position of the zoom lens driven during exposure. Then, when the focus lens is driven to the position and the exposure is completed, the control of stopping the driving of the zoom lens and the focus lens is performed, and then the signal of the image captured by the signal processing means is processed. A control method for an imaging apparatus.

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