JP6362310B2 - IMAGING DEVICE, IMAGING SYSTEM, IMAGING DEVICE CONTROL METHOD, PROGRAM, AND STORAGE MEDIUM - Google Patents

Description

  The present invention relates to an imaging apparatus that performs autofocus control.

  2. Description of the Related Art Conventionally, in an imaging apparatus such as an electronic still camera, as a method of moving a focus lens position and focusing on a subject, autofocus control (AF control) that automatically performs a focusing operation using an image signal from an image sensor ) Is used. In addition, when adding the subject distance as camera information to the image file at the time of shooting, the subject distance is acquired based on the focus lens position when moving to the in-focus point by AF control. When such a subject distance is acquired, if an error is included in the focus lens position when the focus lens position is moved by AF control, an accurate subject distance cannot be obtained. Therefore, Patent Document 1 discloses a method for obtaining a focus position that is a theoretical value by removing an error included in the focus position. Patent Document 1 discloses an electronic camera device that corrects a focus position using a correction value for each zoom position and obtains a subject distance based on the corrected focus position.

  On the other hand, Patent Document 2 describes that there is a problem that when the aperture value is changed after the focusing operation of AF control, an out-of-focus image is taken. In order to solve this problem, Patent Document 2 discloses a camera that corrects a focus lens position according to a difference between a focus detection aperture value and a photographing aperture value that do not match.

Japanese Patent No. 4848618 JP 2008-96796 A

  However, in Patent Document 2, no consideration is given to the influence of a change in aperture value in accordance with shooting conditions. For this reason, with the configuration of Patent Document 2, it is difficult to perform highly accurate focus control.

  Therefore, the present invention provides an imaging apparatus, an imaging system, an imaging apparatus control method, a program, and a storage medium capable of highly accurate focus control.

An image pickup apparatus according to one aspect of the present invention is based on an image pickup element that photoelectrically converts an optical image obtained via a focus lens, and an image signal from the image pickup element in a state set to a first aperture value. A focus detection unit that performs focus detection, and a control unit that controls a focus position based on a focus detection signal from the focus detection unit, wherein the control unit detects the focus by the focus detection unit. If the time of photographing after setting the second aperture, the set the second diaphragm value at the time of shooting is different from the set of the first aperture when the focus detection, object The focus position is changed according to a photographing condition including at least one of a distance, a zoom position, a subject color or luminance, and a change from the first aperture value to the second aperture value.

  An imaging system as another aspect of the present invention includes a lens device including a focus lens and the imaging device.

According to another aspect of the present invention, there is provided a method for controlling an imaging apparatus, the step of photoelectrically converting an optical image obtained via a focus lens by an imaging element, the step of setting a first aperture value, In a state where the aperture value is set, a step of performing focus detection based on an image signal from the image sensor, a step of controlling a focus position based on the focus detection signal, and a photographing after performing the focus detection The second aperture value different from the first aperture value, the shooting condition including at least one of the subject distance, zoom position, subject color or brightness, and the first aperture value. Changing the focus position in response to a change to the second aperture value.

  A program according to another aspect of the present invention causes a computer to execute the method for controlling the imaging apparatus.

  A storage medium according to another aspect of the present invention stores the program.

  Other objects and features of the present invention are illustrated in the following examples.

  According to the present invention, it is possible to provide an imaging apparatus, an imaging system, an imaging apparatus control method, a program, and a storage medium capable of highly accurate focus control.

It is a block diagram which shows the structure of the imaging device in a present Example. It is a flowchart which shows operation | movement of the imaging device in a present Example. 6 is a flowchart illustrating an AF operation of the imaging apparatus according to the present exemplary embodiment. It is an example of the table of the correction value in a present Example. 4 is a flowchart illustrating a method for correcting a focus position (focus position) in the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, with reference to FIG. 1, the structure of the imaging device (camera) in a present Example is demonstrated. FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 100 in the present embodiment. In FIG. 1, 101 is a photographing lens including a zoom mechanism, 102 is an aperture and shutter for controlling the amount of light, 103 is an AE processing unit, and 104 is a focus lens. The imaging lens 101 and the focus lens 104 constitute an imaging optical system. The focus lens 104 is movable on the optical axis so that a subject image (optical image) obtained via the imaging optical system is imaged on an imaging element 107 described later. In the image pickup apparatus 100 of the present embodiment, the image pickup optical system and the image pickup apparatus main body are integrally configured, but the present invention is not limited to this. This embodiment can also be applied to an imaging system including an imaging apparatus main body (camera main body) including the imaging element 107 and a lens device (imaging optical system) that can be attached to and detached from the imaging apparatus main body.

  Reference numeral 105 denotes a motor for driving the focus lens 104, and reference numeral 106 denotes an AF processing unit. The AF processing unit 106 drives and controls the focus lens 104 using the AF evaluation value calculated from the contrast of the image. When the AF evaluation value is high, the contrast is strong. On the other hand, when the AF evaluation value is low, the contrast is weak. Reference numeral 107 denotes an image sensor, which is a light receiving means (photoelectric conversion means) that photoelectrically converts reflected light from the subject (an optical image (subject image) obtained through the focus lens 104) into an electrical signal (analog signal). An A / D converter 108 converts an analog signal into a digital signal. The A / D converter 108 includes a CDS circuit that removes output noise from the image sensor 107 and a non-linear amplifier circuit that performs amplification processing before A / D conversion. Reference numeral 109 denotes an image processing unit. The image processing unit 109 processes the image signal from the image sensor 107. Reference numeral 110 denotes a format conversion unit, and 111 denotes a DRAM (random access memory) as a high-speed built-in memory. An image recording unit 112 includes a recording medium such as a memory card and an interface thereof.

  Reference numeral 113 denotes a system control unit (control unit, CPU) that controls a system such as a shooting sequence (operation of the imaging apparatus 100). The system control unit 113 includes a focus detection unit 113a that performs focus detection based on an image signal from the image sensor 107 (image processing unit 109) in a state where the first aperture value is set. Further, the system control unit 113 includes control means 113b that controls the position (focus position) of the focus lens 104 based on a focus detection signal from the focus detection means. Further, the system control unit 113 includes a storage unit 113c (internal memory) that stores a table to be described later with reference to FIG. The focus detection unit 113a calculates a focus evaluation value indicating the contrast of the subject based on the image signal. The control unit 113b cooperates with the AF processing unit 106 to control the focus position so that the focus evaluation value is maximized.

  Reference numeral 114 denotes a VRAM (image display memory). Reference numeral 115 denotes a display unit that displays a display for assisting operation together with an image, a display of the state of the imaging apparatus 100, and a display of a shooting screen and a distance measurement area during shooting. Reference numeral 116 denotes an operation unit for operating the imaging apparatus 100 from the outside. Reference numeral 117 denotes a shooting mode switch for selecting a shooting mode such as a macro mode, a distant view mode, or a sports mode. Reference numeral 118 denotes a main switch for turning on the power to the system (imaging device 100). Reference numeral 119 denotes a switch (SW1) for performing a shooting standby operation such as AF (automatic focus detection) or AE (automatic exposure). Reference numeral 120 denotes a photographing switch (SW2) for performing photographing after the operation of the switch 119 (SW1). Reference numeral 121 denotes an angular velocity sensor unit that detects movement of the imaging apparatus 100 due to camera shake or panning. Reference numeral 122 denotes a moving object detection unit that detects a moving object from luminance information in the screen.

  The DRAM 111 (storage means) is used as a high-speed buffer that is a temporary image storage means, or as a working memory for image compression / decompression. The operation unit 116 includes a menu switch for performing various settings such as a shooting function of the imaging apparatus 100 and settings for image playback, a zoom lever for instructing a zoom operation of the shooting lens 101, an operation mode switching switch between a shooting mode and a playback mode, and the like. including. The shooting mode switch 117 is a switch for changing the distance measurement distance range, the AF operation, and the like according to the shooting mode selected by the user.

  Next, the operation (control method) of the imaging apparatus 100 in the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the imaging apparatus 100. Each step in FIG. 2 is executed based on a command from the system control unit 113.

  First, in step S201, the system control unit 113 determines the state of the switch SW1 (119). If the switch SW1 is pressed (ON), the process proceeds to step S202. On the other hand, if the switch SW1 is not pressed (OFF), step S201 is repeated. In step S <b> 202, the system control unit 113 uses the AE processing unit 103 to perform AE processing (automatic exposure processing) based on the output (image signal) of the image processing unit 109 (image sensor 107). The AE process in step S202 is executed for the subsequent AF operation (automatic focus detection operation). In step S202, the system control unit 113 performs focus correction (correction of the focus position) according to an aperture value, which will be described later, so that the aperture value (AF aperture value: first aperture value) at this time is stored in the DRAM 111. Remember.

  Subsequently, in step S <b> 203, the system control unit 113 performs an AF operation (AF processing) using the AF processing unit 106. Exposure conditions (shutter speed, aperture, sensitivity) during the AF operation are determined by the AE process performed in the immediately preceding step S202. Details of step S203 will be described later. Subsequently, in step S204, the system control unit 113 determines the state of the switch SW2 (120). If the switch SW2 is pressed (ON), the process proceeds to step S206. On the other hand, if the switch SW2 is not pressed (OFF), the process proceeds to step S205. In step S205, the system control unit 113 determines the state of the switch SW1. If the switch SW1 is pressed (ON), the process returns to step S204. On the other hand, if the switch SW1 is not pressed, the process returns to step S201.

  In step S206, the system control unit 113 determines exposure at the time of shooting. In step S 207, the system control unit 113 acquires the aperture value (second aperture value) at the time of shooting from the AE processing unit 103. As described above, when the switch SW2 (shooting switch) is pressed, the system control unit 113 sets the second aperture value. In step S208, the system control unit 113 performs focus correction (focus position correction) according to the aperture value (change between the aperture value during AF and the aperture value during shooting). Subsequently, in step S209, the system control unit 113 performs exposure control for main exposure. In step S210, the system control unit 113 performs shooting and ends this flow.

  Next, the AF operation of the imaging apparatus 100 will be described with reference to FIG. FIG. 3 is a flowchart showing the AF operation of the imaging apparatus 100, and shows details of step S203 in FIG. Each step in FIG. 3 is executed based on a command from the system control unit 113.

  First, in step S301, the system control unit 113 sets a distance measurement area (focus detection area) as a predetermined area in the screen. Subsequently, in step S302, the system control unit 113 sets a scan range corresponding to the shooting mode and the focal length. In step S303, the system control unit 113 performs initial focus driving described later. In this initial focus drive, the focus lens 104 is driven to the AF scan start position.

  Subsequently, in step S304, the system control unit 113 sets a focus speed described later. Then, the system control unit 113 starts focus driving in a predetermined direction at the focus setting speed set in step S304. Here, the predetermined direction is set to a direction opposite to the direction of the initial focus driving executed in step S303. Subsequently, in step S305, the system control unit 113 acquires a focus evaluation value in the distance measurement area set in step S301. In step S306, the system control unit 113 acquires the current position (focus position) of the focus lens 104.

  Subsequently, in step S307, the system control unit 113 determines whether or not the current position (focus position) of the focus lens 104 acquired in step S306 is within the scan range set in step S302. If the focus position is within the scan range, the process proceeds to step S305. On the other hand, if the focus position is not within the scan range, the process proceeds to step S308. In step S308, the system control unit 113 stops driving the focus lens 104.

  In step S309, the peak position of the focus evaluation value is calculated based on the focus evaluation value acquired in step S305 and the corresponding position of the focus lens 104 (focus position acquired in step S306). Subsequently, in step S310, the system control unit 113 performs in-focus determination. In step S311, the system control unit 113 drives the focus lens 104 to the peak position of the focus evaluation value calculated in step S309, and ends this flow (AF operation).

  Subsequently, a correction value for correcting the focus position will be described with reference to FIGS. FIGS. 4A to 4C are examples of correction value tables, which are stored in advance in the storage unit 113 c of the system control unit 113. In steps S202 and S207 in FIG. 2, the system control unit 113 refers to the tables in FIGS. 4A to 4C and acquires correction values corresponding to the shooting conditions.

  As shown in FIGS. 4A to 4C, in this embodiment, zooming between the wide-angle end (Wide) and the telephoto end (Tele) at each of three object distances (∞, 3 m, 50 cm). Correction values corresponding to the point (zoom position) and the aperture value Av are held. The correction value is held every 10 zoom points (zoom positions) and the aperture value Av is held every 1.0. A correction value between shooting conditions (adjacent shooting conditions) held in the table is calculated by interpolation. For example, linear interpolation is performed with respect to the aperture value direction (direction in which the aperture value Av is changed: the horizontal direction in FIG. 4), and linear interpolation is performed with the reciprocal of the distance with respect to the subject distance direction (FIGS. 4A to 4C). . As for the zoom, the same value is used until the next zoom boundary (for example, from Wide to M9).

  Hereinafter, an example in which the correction value CorVal corresponding to the shooting condition is calculated based on the interpolation formula will be described. For example, consider a case where the shooting conditions are subject distance = 1 [m], zoom position = M15, and Av value = 2.3. At this time, the interpolation formula Val1 in the aperture value direction when the subject distance is 3 [m] is expressed by the following formula (1).

  The interpolation formula Val2 in the aperture value direction when the subject distance is 50 [cm] is expressed by the following formula (2).

  The correction value CorVal is expressed as the following equation (3) using equations (1) and (2).

  In the present embodiment, the values in the tables shown in FIGS. 4A to 4C are calculated in advance by performing an optical simulation as initial values (design values). Since the optical simulation is not the main point of the present invention, the description thereof is omitted. Depending on the optical simulation result, parameters with low influence may be further thinned out for each of the subject distance, zoom point, and aperture value. Conversely, for parameters with a high degree of influence, thinning may be reduced. Further, when linear interpolation is not possible as a result of optical simulation, a correction value can be calculated using an approximate expression.

  When there is a large error for each individual with respect to the initial value (design value), adjustment is performed individually. This adjustment is performed by creating a cam table that associates the focus position with the subject distance. Since the contents of this adjustment are not the main point of the present invention, the description thereof is omitted. In order to reduce the adjustment time (cost), an adjustment value may be acquired for a predetermined subject distance, zoom position, and aperture value, and the values in the table of FIG. 4 may be rewritten according to this result. For example, when the conditions with the largest error are the open aperture and the minimum aperture at a predetermined middle position at an infinite adjustment distance, the table value closest to the condition is obtained by multiplying the focus difference by a predetermined coefficient. Rewrite the correction value so that Further, the correction value may be changed according to the color and brightness of the subject. In addition, both the adjustment value and the design value are retained, the adjustment value is adopted when it is determined that the shooting conditions are close to the environment at the time of adjustment, and the design value is determined when it is determined that the conditions are not satisfied. You may comprise so that it may employ | adopt.

  Next, with reference to FIG. 5, the focus correction (focus correction according to the change of the aperture value) in the present embodiment will be described. FIG. 5 is a flowchart showing a focus position correction method, and shows details of step S208 in FIG. Each step in FIG. 5 is executed based on a command from the system control unit 113.

  First, in step S401, the system control unit 113 acquires the aperture value AF_Av at the time of AF (the aperture value stored in step S202) from the DRAM 111. In step S402, the system control unit 113 acquires the aperture value Capt_Av at the time of shooting determined in step S207.

  Subsequently, in step S403, the system control unit 113 acquires a correction value according to the shooting conditions (subject distance, zoom position, aperture value, etc.) described with reference to FIG. That is, the system control unit 113 acquires the correction value AF_CorVal according to the shooting condition during AF and the correction value Capt_CorVal according to the shooting condition during shooting.

  Subsequently, in step 404, a value obtained by subtracting the correction value AF_CorVal according to the shooting condition at the time of AF from the correction value Capt_CorVal according to the shooting condition at the time of shooting is set as the correction value. In this way, in step S404, the system control unit 113 sets the difference between the correction value AF_CorVal and the correction value Capt_CorVal as a correction value. In step S405, the system control unit 113 subtracts the correction value calculated in step S404 from the AF in-focus position (focus position before correction) calculated in step S310 in FIG. Thereby, the focus position at the time of photographing (corrected focus position) can be acquired.

  In this embodiment, correction of the focus position with respect to the AF operation has been described. However, the present invention is not limited to this. Similarly, when the user manually focuses (MF operation), the conditions at the time of focus adjustment and the conditions at the time of photographing can be compared and corrected. At this time, the imaging apparatus 100 further includes second focus detection means for manually adjusting the position of the focus lens 104 by the user in a state where the third aperture value is set. Then, when the second aperture value set at the time of shooting is different from the third aperture value, the control unit 113b determines the focus position according to the shooting condition and the change from the third aperture value to the second aperture value. Change (correct).

  As described above, in this embodiment, the control unit 113b captures an image when the second aperture value (the aperture value at the time of shooting) set at the time of shooting is different from the first aperture value (the aperture value at the time of AF). The focus position is changed (corrected) according to the condition and the change from the first aperture value to the second aperture value. Preferably, the photographing condition is at least one of a subject distance, a zoom position, a subject color or luminance.

  In addition, preferably, the control unit 113b acquires a first correction value corresponding to the first aperture value and a second correction value corresponding to the second aperture value according to the imaging condition. Then, the control means 113b sets a value obtained by subtracting the difference between the first correction value and the second correction value from the focus position as the corrected focus position.

  In addition, preferably, the imaging apparatus 100 further includes a storage unit 113c that stores a plurality of correction values corresponding to each of the plurality of aperture values according to the shooting conditions. More preferably, when the correction value corresponding to the shooting condition is not stored in the storage unit 113c, the control unit 113b interpolates the correction value for the shooting condition using a plurality of correction values stored in the storage unit 113c. It is calculated by performing. As a result, it is not necessary to store correction values corresponding to all shooting conditions, and the memory capacity can be reduced, so that the cost can be reduced.

  Preferably, the plurality of correction values stored in the storage unit 113c differ according to individual differences of the imaging device 100.

  In addition, preferably, the control unit 113b adjusts the plurality of correction values stored in the storage unit 113c according to individual differences of the imaging device 100. More preferably, when the photographing condition satisfies a predetermined condition, the control unit 113b corrects the focus position using an adjustment value obtained by adjusting the correction value stored in the storage unit 113c. On the other hand, when the shooting condition does not satisfy the predetermined condition, the focus position is corrected using the stored correction value.

  A part of the above-described embodiments may be appropriately combined. Also, when a software program that realizes the functions of the above-described embodiments is supplied from a recording medium directly to a system or apparatus having a computer that can execute the program using wired / wireless communication, and the program is executed Are also included in the present invention. Therefore, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention on the computer can also realize the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention. In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS. The storage medium for supplying the program may be, for example, a magnetic recording medium such as a hard disk or a magnetic tape, an optical / magneto-optical storage medium, or a nonvolatile semiconductor memory. As a program supply method, a computer program that forms the present invention is stored in a server on a computer network, and a connected client computer downloads and programs the computer program.

  According to the present embodiment, it is possible to provide an imaging apparatus, an imaging system, an imaging apparatus control method, a program, and a storage medium that are capable of high-precision focus control at low cost.

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

100: Imaging device 107: Imaging device 109: Image processing unit 113: System control unit

Claims (15)

An image sensor that photoelectrically converts an optical image obtained through the focus lens;
A focus detection means for performing focus detection based on an image signal from the image sensor in a state where the first aperture value is set;
Control means for controlling a focus position based on a focus detection signal from the focus detection means,
The control means includes
A second aperture value is set at the time of shooting after the focus detection means performs the focus detection ;
If the set the second diaphragm value at the time of shooting is different from the set of the first aperture when the focus detection, object distance, zoom position, at least one of the object color or brightness An imaging apparatus, wherein the focus position is changed in accordance with an imaging condition including the first aperture value and a change from the first aperture value to the second aperture value. The control means includes
According to the photographing condition, a first correction value corresponding to the first aperture value and a second correction value corresponding to the second aperture value are acquired,
The imaging apparatus according to claim 1, wherein a value obtained by subtracting a difference between the first correction value and the second correction value from the focus position is set as a corrected focus position. .   The imaging apparatus according to claim 1, further comprising a storage unit that stores a plurality of correction values corresponding to each of the plurality of aperture values according to the photographing condition.   When the correction value corresponding to the shooting condition is not stored in the storage unit, the control unit interpolates the correction value for the shooting condition using the plurality of correction values stored in the storage unit. The imaging device according to claim 3, wherein the imaging device calculates the above.   5. The imaging apparatus according to claim 3, wherein the plurality of correction values stored in the storage unit differ depending on individual differences of the imaging apparatus.   The imaging apparatus according to claim 3, wherein the control unit adjusts the plurality of correction values stored in the storage unit according to individual differences of the imaging apparatus. The control means includes
When the shooting condition satisfies a predetermined condition, the focus position is corrected using an adjustment value obtained by adjusting the correction value stored in the storage unit,
The imaging apparatus according to claim 6, wherein when the shooting condition does not satisfy the predetermined condition, the focus position is corrected using the correction value. A second focus detection means for manually adjusting a position of the focus lens by a user in a state where the third aperture value is set;
The control means includes
A third aperture value is set at the time of shooting after the second focus detection means adjusts the position of the focus lens ;
If the set the second diaphragm value at the time of shooting is different from the positions set the third aperture when the adjustment of the focus lens, said the aperture value of the photographing condition and the third The imaging apparatus according to claim 1, wherein the focus position is changed in accordance with a change to an aperture value of 2. 8.   The image pickup apparatus according to claim 1, wherein the control unit sets the second aperture value when a photographing switch is pressed. The focus detection unit calculates a focus evaluation value indicating the contrast of the subject based on the image signal,
The image pickup apparatus according to claim 1, wherein the control unit controls the focus position so that the focus evaluation value is maximized. A lens device comprising the focus lens;
An imaging system comprising: the imaging device according to claim 1. Photoelectrically converting an optical image obtained through the focus lens by an imaging device;
Setting the first aperture value;
Performing focus detection based on an image signal from the image sensor in a state set to the first aperture value;
Controlling the focus position based on the focus detection signal;
Setting a second aperture value different from the first aperture value at the time of shooting after performing the focus detection ;
A shooting condition including at least one of a subject distance, a zoom position, a subject color or brightness, and a step of changing the focus position in accordance with a change from the first aperture value to the second aperture value. And a method of controlling the imaging apparatus. In the step of changing the focus position,
According to the photographing condition, a first correction value corresponding to the first aperture value and a second correction value corresponding to the second aperture value are acquired,
The imaging apparatus according to claim 12, wherein a value obtained by subtracting a difference between the first correction value and the second correction value from the focus position is set as a corrected focus position. Control method.   A program for causing a computer to execute the method for controlling an imaging apparatus according to claim 12 or 13.   A storage medium storing the program according to claim 14.