JP2012203207A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable focus to follow a subject even in a scene where the subject moves suddenly as in a start scene.SOLUTION: The imaging apparatus comprises: focus detecting means 101 for detecting the focusing state of a photographic lens; focusing means 107 for focusing the photographic lens according to the detected focusing state; acquisition determining means 106 for performing a focusing operation for the focusing means in a case where an amount of a change in image surface, which is an amount of change in imaging position when a focus is detected by the focus detecting means, is smaller than a preset threshold; and threshold changing means 105 for making the threshold for the acquisition determining means bigger than a preset value when a subject and the imaging apparatus are stationary as a result of satisfying a predetermined condition.

Description

  The present invention relates to an imaging apparatus such as a single-lens reflex digital camera having a focus adjusting means.

  2. Description of the Related Art Conventionally, in a camera having a focus adjustment unit, a control method for driving a photographing lens in conjunction with the movement of a moving subject is widely known in order to keep the moving subject in focus.

  The photographer performs focus adjustment by capturing (including) the subject in the focus detection area arranged on the shooting screen (on the viewfinder).

  In the focus adjustment control of the photographing lens, as a first operation, the camera performs focus adjustment according to the focus detection result on the subject. Then, focus detection is performed again, and subject capture determination is performed according to the focus detection result. If it is determined that the same subject is captured, the lens driving operation is repeated. Also, if the photographer removes the subject from the focus detection area to the background or another object such as an obstacle enters the focus detection area, it is determined that the same subject has not been captured, and the photographer In order to prevent lens driving that is different from the above intention, that is, to immediately follow another subject, a method of stopping the focus adjustment of the photographing lens for a predetermined time has been proposed.

  In the subject capture determination, as shown in FIG. 12A, the image plane position 404 obtained by observing the subject 402 with the camera when the focus has been detected in the past and the image plane position obtained by observing the subject 403a with the camera when the focus is detected this time. An image plane change amount is calculated from 405a. Then, it is determined whether or not the same subject is captured based on whether or not the calculated image plane change amount of the subject is less than a preset threshold value (hereinafter referred to as missing defocus amount). Specifically, when the image plane change amount is less than the defocus amount, it is determined that the subject whose focus is detected is captured, and focus adjustment is performed. On the other hand, when the image plane change amount at the image plane position 405b is larger than the defocus amount as shown in FIG. 12B, it is determined that a subject different from the subject whose focus is detected is captured, and focus adjustment is performed. To stop. Also, as shown in FIG. 12C, even when the current focus detection captures the background 403c, the image plane change amount of the image plane position 405c from when the subject 402 has been focus detected in the past is very large. Therefore, the defocus amount is greater than or equal to. Also in this case, it is determined that a subject different from the subject whose focus has been detected in the past is captured, and focus adjustment is stopped. In addition, as shown in FIG. 12D, the image plane change amount at the image plane position 407 may be large even when a subject 406 different from the past subject enters the front during the current focus detection. In this case also, it is determined that a subject different from the subject whose focus has been detected in the past is captured, and focus adjustment is stopped.

  With this technique, when the moving speed of the subject is high, the moving speed on the image plane position (hereinafter referred to as the image plane moving speed) also increases, and the movement change amount of the subject that is greater than the missing defocus amount is detected. For this reason, the photographic lens may not be able to follow the subject by determining that the subject is another subject. To deal with this problem, Patent Document 1 calculates the image plane moving speed based on the focus detection data of a plurality of past times, and determines whether or not the subject moves depending on whether the image plane moving speed is greater than a predetermined value. The determination is disclosed. As described above, by using the image plane moving speed for the tracking determination of the photographic lens to the subject, it is possible to determine whether the subject is a moving subject even when the image plane moving speed is high.

Japanese Patent Laid-Open No. 07-103998

  However, in the conventional technique disclosed in Patent Document 1 described above, the subject capture determination does not function well in a scene where the subject moves suddenly, such as a start scene of an athletics race or an automobile race. This is because the image plane moving speed is calculated based on the past multiple times of focus detection data, and the calculated speed does not increase immediately. Therefore, it is determined that the subject is stationary in such a scene. In addition, if the image plane moving speed is calculated from, for example, the previous and current focus detection results, it can be determined that the subject is moving, but the subject is removed from the background or an obstacle is placed in the focus detection area. Even if another subject such as a subject enters, it is erroneously determined as a moving subject. As a result, an image out of focus with respect to the subject is obtained.

(Object of invention)
An object of the present invention is to provide an imaging apparatus that can follow focus adjustment on a subject even in a scene in which the subject suddenly moves, such as a start scene of athletics or a car race.

  In order to achieve the above object, an imaging apparatus of the present invention includes a focus detection unit that detects a focus state of a photographic lens, a focus adjustment unit that performs focus adjustment of the photographic lens in accordance with the detected focus state, A capture determination unit that performs a focus adjustment operation of the focus adjustment unit when an image plane change amount that is a change amount of an image plane position when the focus is detected by the focus detection unit is less than a preset threshold; And a threshold value changing means for making the threshold value of the capture determination means larger than a preset value when the subject and the imaging device are in a stationary state by satisfying a predetermined condition. .

  According to the present invention, it is possible to follow the focus adjustment on the subject even in a scene where the subject suddenly moves, such as a start scene of athletics or a car race.

It is a block diagram which shows the concept of Example 1 of this invention. 1 is a block diagram illustrating a configuration of a single-lens reflex digital camera as Embodiment 1. FIG. It is a flowchart which shows an example of operation | movement of a subject capture determination. 12 is a flowchart illustrating another example of the subject capturing determination operation. It is a flowchart which shows the operation | movement of a capture determination means threshold value change. It is a graph which shows the camera shake amount of the yaw direction by a panning detection means. It is a graph which shows the camera shake amount of the pitch direction by a panning detection means. It is a figure which shows the rotation direction of a camera. This is a setting screen for a custom function “start scene shooting mode” that can be arbitrarily set. It is a block diagram which shows the concept of Example 2 of this invention. It is a flowchart which shows the operation | movement of the capture determination means threshold value change of Example 2. FIG. It is a figure which shows the relationship between an image surface variation | change_quantity and a to-be-photographed object movement variation | change_quantity.

  The mode for carrying out the invention is as described in Examples 1 and 2 below.

  FIG. 1 is a block diagram showing the concept of Embodiment 1 according to the imaging apparatus of the present invention.

  In FIG. 1, reference numeral 101 denotes a focus detection unit that detects the focus state of the photographic lens, that is, a defocus amount, and 107 denotes a focus adjustment unit that adjusts the focus of the photographic lens from the detected defocus amount. 106 indicates whether the same subject is captured depending on whether the image plane change amount, which is the amount of change between the current image plane position and the past image plane position, is less than the threshold value, that is, whether it is less than the missing defocus amount. It is a capture determination means for determining whether or not. Reference numeral 102 denotes panning detection means for detecting panning of the camera by a gyro sensor (angular velocity sensor), and reference numeral 103 denotes panning determination means for determining a panning state for a predetermined time (for example, 1 s) by the panning detection means 102. Reference numeral 104 denotes a stationary state determination unit that determines the stationary state of the subject from the amount of change in the image plane position and determines the stationary state of both the subject and the camera by determining the stationary state of the camera from the panning state. Is a threshold value changing means for changing the missing defocus amount which is a threshold value.

  Next, a single-lens reflex digital camera which is Embodiment 1 of the imaging apparatus of the present invention will be described. FIG. 2 is a block diagram showing the configuration of the single-lens reflex digital camera.

  Reference numeral 201 denotes a photographing lens. Reference numeral 202 denotes a shake detection unit that detects a camera shake state of a lens disposed in the lens, and specifically includes a gyro sensor (angular velocity sensor). The shake detection unit 202 is mainly used to correct the camera shake of the lens. However, in the present invention, it also serves as a panning detection unit that detects the panning of the lens.

  Reference numeral 203 denotes lens driving means. The lens driving unit 203 is configured by, for example, a DC motor or an ultrasonic motor, and focuses by changing the focus position of the photographing lens 201 under the control of the microcomputer 223. Reference numeral 204 denotes an aperture. Reference numeral 205 denotes an aperture driving unit. A diaphragm driving unit 205 drives the diaphragm 204. The amount to be driven is calculated by the microcomputer 223, and the optical aperture value is changed.

  Reference numeral 206 denotes a main mirror for switching the light beam incident from the photographing lens 201 between the viewfinder side and the image sensor side. The main mirror 206 is always arranged so as to reflect the light beam toward the viewfinder side. However, when shooting is performed, the main mirror 206 jumps upward so as to guide the light beam to the image sensor 215 and is retracted from the light beam. To do. The main mirror 206 is a half mirror so that the central part can transmit a part of the light, and is arranged in a pair of AF sensors (not shown) for focus detection (focus detection means 212). ) Is transmitted so that a part of the light beam is incident on. Reference numeral 207 denotes a sub-mirror for reflecting the light beam transmitted from the main mirror 206 to a pair of AF sensors for performing focus detection.

  Reference numeral 208 denotes a pentaprism that forms a finder. In addition, the finder includes a focus plate 209, an eyepiece 210, and the like.

  Reference numeral 211 denotes a panning detection unit that is disposed in the camera and detects panning of the camera, and specifically includes a gyro sensor (angular velocity sensor).

  Reference numeral 212 denotes a focus detection means. The light beam transmitted through the central portion of the main mirror 206 and reflected by the sub-mirror 207 reaches a pair of AF sensors for performing photoelectric conversion disposed inside the focus detection unit 212. The defocus amount indicating the focus adjustment state of the photographing lens 201 with respect to the subject is obtained by calculating the outputs of the pair of AF sensors. The microcomputer 223 evaluates the calculation result and instructs the lens driving unit 203 to drive the focus lens of the photographing lens 201.

  Reference numeral 213 denotes a focal plane shutter. Reference numeral 214 denotes shutter driving means that drives the focal plane shutter 213. The opening time of the shutter is controlled by the microcomputer 223.

  Reference numeral 215 denotes an image sensor. A CCD, CMOS sensor, or the like is used as the image sensor 215, and the subject image formed by the photographing lens 201 is converted into an electrical signal.

  Reference numeral 216 denotes a clamp circuit. Reference numeral 217 denotes an AGC circuit. The clamp circuit 216 and the AGC circuit 217 perform basic analog signal processing before AD conversion, and the microcomputer 223 changes the clamp level and the AGC reference level. Reference numeral 218 denotes an AD converter. The AD converter 218 converts the analog output signal of the image sensor 215 into a digital signal.

  A video signal processing circuit 219 is realized by a logic device such as a gate array. Reference numeral 220 denotes a memory controller. Reference numeral 221 denotes a memory. Reference numeral 222 denotes a buffer memory. The video signal processing circuit 219 performs filter processing, color conversion processing, and gamma processing on the digitized image data, and also performs compression processing such as JPEG, and outputs the result to the memory controller 220.

  The video signal processing circuit 219 can output information such as exposure information and white balance of the signal from the image sensor 215 to the microcomputer 223 as necessary. Based on the information, the microcomputer 223 instructs white balance and gain adjustment. In the case of the continuous shooting operation, the shooting data is temporarily stored in the buffer memory 222 as an unprocessed image, the unprocessed image data is read through the memory controller 220, and image processing and compression processing are performed by the video signal processing circuit 219. Perform continuous shooting. The number of continuous shots depends on the size of the buffer memory 222.

  In the memory controller 220, unprocessed digital image data input from the video signal processing circuit 219 is stored in the buffer memory 222, and processed digital image data is stored in the memory 221. Conversely, the image data is output from the buffer memory 222 or the memory 221 to the video signal processing circuit unit 219. The memory 221 may be removable.

  Reference numeral 223 denotes a microcomputer. Reference numeral 224 denotes an operation member. The operation member 224 transmits the state to the microcomputer 223, and the microcomputer 223 controls each part according to the change of the operation member. In addition, the operation member 224 has an ONESHOT mode suitable for photographing a stationary subject, an AI-SERVO mode suitable for photographing a subject whose photographing distance constantly changes, and ONESHOT to AI-SERVO depending on the state of the subject. And switching to the AI-FOCUS mode in which the camera automatically switches.

  Reference numeral 225 denotes a switch SW1. Reference numeral 226 denotes a switch SW2. The switches SW1 and SW2 are switches that are turned on / off by operating the release button, and are each one of the input switches of the operation member 224. When only the switch SW1 is on, the release button is half-pressed, and in this state, an autofocus operation or a photometric operation is performed. When the switches SW1 and SW2 are both on, the release button is fully pressed, and the release button for recording an image is on. Shooting is performed in this state. Further, a continuous shooting operation is performed while the switches SW1 and SW2 are kept on. In addition, switches such as an ISO setting button, an image size setting button, an image quality setting button, and an information display button are connected to the operation member 224, and the switch state is detected.

  Reference numeral 227 denotes a power supply unit. The power supply unit 227 supplies power necessary for each IC and drive system.

  With the camera configured as described above, the accuracy of subject capture determination is improved.

  Next, an example of the subject capturing determination operation according to the first embodiment of the present invention will be described based on the flowchart of FIG. When the switch SW1 is turned on in step # 101, an automatic focus adjustment operation is started. First, in step # 102, focus detection is performed, and the defocus amount is detected from the subject image signal. When the detection of the defocus amount is completed, a routine for changing the threshold value of the capture determination means 106 for determining whether or not the same subject is captured in the next step # 103 is executed. The routine of step # 103 will be described later using the flowchart of FIG. When the threshold value change routine of the capture determination unit 106 is completed, the process proceeds to step # 104.

  In step # 104, it is determined whether or not the same subject is captured based on whether the defocus amount detected in step # 102 and the defocus amount after a predetermined time are less than the defocus amount (threshold). To do. If it is determined that the subject is captured, the process branches to step # 105, and the focus lens is driven. When the driving of the focus lens is finished, the process proceeds to step # 108.

  If it is determined in step # 104 that the same subject has not been captured, the process proceeds to step # 106. In step # 106, the focus detection is repeated within a predetermined time in anticipation of the photographer returning the focus detection area to the same subject. If it is determined in step # 106 that the same subject has not been captured within the predetermined time, the process proceeds to step # 107a, the focus lens is stopped, and the process proceeds to step # 108.

  In the next step # 108, it is determined whether or not the switch SW1 is turned on. If it is turned on, the process returns to the focus detection in step # 102, and the flow of automatic focus adjustment is repeated until the switch SW1 is turned off. If it is determined that the camera is not turned on, the automatic focus adjustment is terminated.

  If it is determined in step # 104 that the same subject has not been captured, in addition to the method of stopping the lens, as shown in step # 107b of FIG. There is a method of performing lens driving by performing a moving object prediction calculation. Various methods for predicting a moving object for predicting a subject position from a plurality of past focus detection results have been proposed and will not be described in detail because they are not directly related to the present invention. Thereafter, the same operation as described above is repeated until the switch SW1 is turned off.

  Next, a threshold value changing operation for changing the threshold value of the capture determination means 106 for determining whether or not the same subject is captured, which is executed in step # 103 of FIGS. 3 and 4 will be described using the flowchart of FIG. To do.

  In step # 201, panning of the lens or camera is detected by the panning detection means 202 mounted on the lens or the panning detection means 211 mounted on the camera. The output value indicating the panning of the camera detected in step # 201 will be described with reference to FIG. FIG. 6A shows an output result when the panning detection means 211 arranged in the camera detects the camera shake amount in the yaw direction when the photographer holds the camera in hand and captures a stationary subject. It is. As shown in FIG. 8, the yaw direction is a direction in which the camera is rotated around the Y axis, and the camera shake amount in the yaw direction is an amount detected mainly when the camera is panned. The horizontal axis represents time, and the vertical axis represents angular velocity (deg / sec). Usually, when the camera is held by a hand and a stationary subject is captured, the output value is about −3 to 3 deg / sec and the maximum shake width is about 6 deg / sec.

  On the other hand, FIG. 6B shows a case where the panning detection means 211 arranged in the camera is a camera in the yaw direction when the photographer holds the camera while holding the camera while the user is capturing the subject while shaking the lens. It is the output result when detecting the amount of shake. In this case, the maximum fluctuation width of the output value is about 90, and the output value is larger than that when the camera is not panned.

  Further, FIGS. 7A and 7B show output results when the panning detection unit 211 arranged in the camera detects the camera shake amount in the pitch direction. The pitch direction is a direction in which the camera is rotated around the X axis as shown in FIG. 8, and the output value of the camera shake amount in the pitch direction during panning is lower than that in the yaw direction. Therefore, panning detection is performed using the detection amount around the Y axis when the camera is held at the normal position, and using the detection amount around the X axis when the camera is held at the vertical position.

  In step # 202, in accordance with the lens or camera panning detection result detected in step # 201, the panning state is determined (hereinafter referred to as panning determination) when the camera is not panned / panned. The panning determination determines that the camera is not panned if the output value output by the panning detection means is smaller than a threshold value that can be determined that the camera is not panned, and determines that the camera is panned if the output value is greater than or equal to a predetermined value. Is done. Note that the panning determination can also be performed using the panning detection means 202 that detects the panning of the lens.

  In step # 202, a predetermined time (for example, 1 s) is measured by the self-running timer of the microcomputer 223. The amount of change in the image plane during the predetermined time is a change amount (less than a predetermined value) that can be determined that the subject is stationary (the subject is stationary), and a state in which panning is not performed continues for a predetermined time (camera Is in a stationary state), the process proceeds to step # 203. The missing defocus amount (threshold value) is set larger than a preset value. When the change of the missing defocus amount (threshold value) is completed in step # 203, the process leaves the threshold value changing routine and proceeds to step # 104.

  On the other hand, if it is determined that the image plane change amount for a predetermined time is not a change amount that can be determined that the subject is stationary, or that the camera is panned within the predetermined time, it is set in advance in step # 204. Is set to the missing defocus amount (threshold value). When the setting of the missing defocus amount is completed in step # 204, the process leaves the threshold value changing routine and proceeds to step # 104.

  As described above, according to the first embodiment, in the subject capture determination, camera panning is detected from the camera or lens panning detection unit, and it is determined whether the same subject is captured in consideration of the information of the camera panning state. The threshold value of the capture determination means 104 to be changed is changed. Thereby, it is possible to improve the subject capturing accuracy in a scene such as a sudden movement of the subject.

  In the first embodiment, the omission defocus amount (threshold value) is set by operating the normal switch SW1 for performing the release. In the second embodiment of the present invention, the operation member 224 in FIG. A start scene operation means (for example, a start scene shooting button) corresponding to a proper movement is arranged. Furthermore, as shown in FIG. 9, the imaging apparatus includes a “start scene shooting mode” as a custom function that can be arbitrarily set by the photographer.

  FIG. 10 is a block diagram illustrating the concept of Embodiment 2 according to the imaging apparatus of the present invention.

  In FIG. 10, reference numeral 1101 denotes a focus state of the photographic lens 201, that is, a focus detection unit that detects a defocus amount, and 1106 denotes a focus adjustment unit that adjusts the focus of the photographic lens from the detected defocus amount. Reference numeral 1105 denotes whether or not the same subject is captured depending on whether or not the image plane change amount, which is the amount of change between the current image plane position and the past image plane position, is less than the threshold value, that is, less than the missing defocus amount. It is a capture determination means for determining Reference numeral 1102 denotes start scene operation means such as a start scene shooting button. If the start scene operation unit 1102 is operated when the start scene shooting mode is set, it is possible to determine that the camera is in a stationary state aiming at the start scene. 1103 determines a stationary state of the subject from the amount of change in the image plane position, and determines a stationary state of both the subject and the camera by determining the stationary state of the camera from the operation of the start scene operation unit 1102. Means. Reference numeral 1104 denotes a threshold value changing means for changing the missing defocus amount which is a threshold value.

  The imaging apparatus according to the second embodiment shifts to the capture determination unit threshold value changing operation (FIG. 11) after performing focus detection in the same manner as the imaging apparatus according to the first embodiment.

  In step # 301, it is determined whether the image plane change amount for a predetermined time is a change amount (less than a predetermined value) that can be determined that the subject is stationary, and whether the start scene shooting mode is on or off. Judgment is made. If it is determined in step # 301 that the image plane change amount for a predetermined time is a change amount that can be determined that the subject is stationary, and the start scene shooting mode is determined to be on, the process proceeds to step # 302. On the other hand, if it is determined that the image plane change amount during the predetermined time is not a change amount that can be determined that the subject is stationary, or that the start scene shooting mode is off, the process proceeds to step # 304. In step # 304, a default missing defocus amount (threshold value) is set, and the process leaves the threshold value changing routine and proceeds to step # 104.

  In step # 302, it is determined whether the start shooting button is on or off. If it is determined that the start shooting button is on, the missing defocus amount is set to be larger than a predetermined value, and the process leaves the threshold value changing routine and proceeds to step # 104. On the other hand, if it is determined that the start scene shooting button is OFF, the routine proceeds to the capture determination means threshold value changing routine of FIG.

  As described above, according to the second embodiment, the start scene shooting mode is validated with the change amount (less than a predetermined value) that allows the image plane change amount for a predetermined time to be determined that the subject is stationary. By turning on the start scene shooting button, the panning detection unit 102 and the panning determination unit 103 of the first embodiment are not used, and the photographer immediately takes a picture at a timing when the photographer wants to take a start scene without waiting for a predetermined time. be able to. Also, even if the start scene shooting mode is on even if the start scene shooting mode is on, the camera changes the start scene. The determination can be made automatically (without operating any operation means).

  In step # 301, it is not always necessary to turn on the start scene shooting mode.

  As mentioned above, although the 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.

101, 1101 Focus detection unit 102 Panning detection unit 103 Panning determination unit 104, 1103 Still state determination unit 105, 1104 Threshold change unit 106, 1105 Capture determination unit 107, 1106 Focus adjustment unit 1102 Start scene operation unit

Claims (7)

Focus detection means for detecting the focus state of the taking lens;
Focus adjusting means for adjusting the focus of the photographing lens according to the detected focus state;
A capture determination unit that performs a focus adjustment operation of the focus adjustment unit when an image plane change amount that is a change amount of the image plane position when the focus is detected by the focus detection unit is less than a preset threshold;
An imaging apparatus comprising: a threshold value changing unit configured to make a threshold value of the capture determination unit larger than a preset value when the subject and the imaging apparatus are in a stationary state by satisfying a predetermined condition; . Panning detecting means for detecting panning;
The threshold value changing means sets the threshold value of the capture determination means to a value that is set in advance when the unpanned state continues for a predetermined time and the image plane change amount is less than a predetermined value. The imaging apparatus according to claim 1, wherein the imaging apparatus is enlarged. It further has a start scene operation means operated when shooting the start scene,
The threshold value changing unit increases the threshold value of the capture determination unit to a value larger than a preset value when the image plane change amount is less than a predetermined value and when the start scene operation unit is operated. The imaging apparatus according to claim 1.   The imaging according to any one of claims 1 to 3, wherein the capture determination unit stops the focus adjustment operation of the focus adjustment unit when the image plane change amount is equal to or greater than a preset threshold value. apparatus.   4. The capture determination unit according to claim 1, wherein the focus adjustment unit causes the focus adjustment unit to perform a focus adjustment operation by a moving object prediction calculation when an image plane change amount is equal to or greater than a preset threshold value. The imaging device described in 1. Start scene shooting mode,
The threshold value changing unit presets the threshold value of the capture determination unit when the image plane change amount is less than a predetermined value in the start scene shooting mode and when the start scene operation unit is operated. The imaging device according to claim 3, wherein the imaging device is larger than the measured value. Panning detecting means for detecting panning;
In the start scene shooting mode, the threshold value changing unit is in a state where the panning is not performed for a predetermined time when the start scene operation unit is not operated even when the image plane change amount is less than a predetermined value. The imaging apparatus according to claim 6, wherein, when it continues, the threshold value of the capture determination unit is set larger than a preset value.

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