JP2016218428A - Imaging apparatus and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further accurately acquire an AF adjustment value for adjusting a focus detection result.SOLUTION: An imaging apparatus which has an adjustment mode for setting an adjustment value for use in adjustment of a focus detection result, to a storage unit comprises: signal generation means which stores electric charges to generate a pair of image signals for focus detection; focus detection means which detects a focus; acquisition means which acquires an adjustment value; determination means which determines whether a condition matching acquisition of an adjustment value is satisfied or not on the basis of a plurality of focus detection results; and storage control means which controls storage of electric charges in the signal generation means. In the adjustment mode, an adjustment value is acquired on the basis of a focus detection result corresponding to an image selected from among a plurality of images different by focus states if the condition matching acquisition of an adjustment value is determined to be satisfied, and the storage control means controls storage of electric charges in acquisition of the plurality of focus detection results so that the time for which the plurality of focus detection results for determination are acquired is equal to or longer than a prescribed time.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an imaging apparatus and a control method thereof, and more particularly to an imaging apparatus capable of automatic focus adjustment and a control method thereof.

  For single-lens reflex cameras, focus detection by a phase difference detection method that detects the focus state (defocus value) of the imaging optical system from the phase difference between a pair of image signals formed by light passing through the imaging optical system in the interchangeable lens The system is often installed. In such a phase difference detection method, there is a possibility that the in-focus position cannot be accurately detected due to the influence of the environment at the time of shooting, the influence of manufacturing errors of the single-lens reflex camera and the interchangeable lens, or the like. Therefore, there is an imaging apparatus having a function (AF microadjustment) for arbitrarily setting an AF adjustment value for the user to adjust the result of the automatic focus adjustment function (AF). However, in AF micro-adjustment, it is necessary to repeat the photographing and checking operations to check whether the result of fine adjustment by the user is correct.

  Therefore, a method has been proposed for allowing a user to set a desired AF adjustment value more easily. In Patent Literature 1, an AF position correction amount (AF adjustment value) is automatically set based on a focus position displacement amount associated with an image that is determined to be in focus by associating the image with a focus position displacement amount. An imaging apparatus having a function to acquire is disclosed. Specifically, the focus lens is moved by a predetermined width, and images are automatically captured sequentially at a plurality of different lens positions (focus bracket imaging). The user can easily set the AF correction amount as intended by selecting a desired focus image from a plurality of captured images.

JP 2005-109621 A

  In Patent Document 1, the focus position displacement amount is acquired according to the AF bracket step amount and the number of brackets. However, when the defocus amount is actually detected at each lens position, the above-described focus position displacement amount is caused by various error factors. May not match. Therefore, in order to obtain a more accurate AF adjustment value, it is assumed that the defocus amount is detected at each lens position, and the AF adjustment value is calculated based on the detected defocus amount.

  However, for example, when the lens or lens hood becomes hot due to the influence of direct sunlight, a local temperature gradient occurs in the air, etc., the detection error of the defocus amount may increase, and as a result, AF adjustment There is a possibility that the value includes a large error. If an AF adjustment value including such a large error is used for adjustment at the time of actual photographing, there is a problem that AF accuracy deteriorates.

  The present invention has been made in view of the above problems, and an object thereof is to obtain an AF adjustment value for adjusting a focus detection result with higher accuracy.

  In order to achieve the above object, the first aspect of the present invention is an imaging apparatus having an adjustment mode for setting an adjustment value used for adjustment of a focus detection result in a storage unit, and accumulates electric charges for focus detection. A signal generation unit that generates a pair of image signals to be used; a focus detection unit that performs focus detection based on the pair of image signals; and an acquisition unit that acquires the adjustment value used to adjust a focus detection result by the focus detection unit And determination means for determining whether the condition is suitable for acquisition of the adjustment value based on a plurality of focus detection results, and accumulation control means for controlling charge accumulation in the signal generation means, In the adjustment mode, when the determination unit determines that the condition is suitable for acquisition of the adjustment value, the acquisition unit corresponds to an image selected from a plurality of images having different focus states. The adjustment value is acquired based on a focus detection result, and the accumulation control unit is configured so that a time for acquiring the plurality of focus detection results used for determination by the determination unit is a predetermined time or more. It is characterized by controlling charge accumulation in the signal generating means when acquiring a plurality of focus detection results.

  According to a second aspect of the present invention, there is provided an imaging apparatus having an adjustment mode for acquiring an adjustment value used for adjusting a focus detection result, wherein a first pair of image signals used for focus detection by accumulating charges is generated. A signal generating means and a second signal generating means; a first focus detecting means for performing focus detection based on a pair of image signals generated by the first signal generating means; and the second signal generating means. Second focus detection means for performing focus detection based on the pair of generated image signals, acquisition means for acquiring the adjustment value used for adjusting the focus detection result by the first focus detection means, and the first Determining means for determining whether the condition is suitable for acquisition of the adjustment value based on a plurality of focus detection results by the focus detection means, and an accumulation control means for controlling charge accumulation in the first signal generating means And the tone In the mode, when the determination unit determines that the condition is suitable for acquisition of the adjustment value, the acquisition unit acquires the adjustment value based on a focus detection result of the second focus detection unit. The determination unit determines that the condition is suitable for obtaining the adjustment value when the variation in the plurality of focus detection results is within a predetermined range, and the variation is out of the predetermined range. When the image signal generated by the first signal generation unit satisfies a predetermined condition, the focus detection by the first focus detection unit and the determination by the determination unit are performed again. It is characterized by.

  According to the present invention, an AF adjustment value for adjusting a focus detection result can be acquired with higher accuracy.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment. 6 is a flowchart showing AF adjustment value setting processing in the present embodiment. FIG. 6 is a diagram illustrating an example of an AF adjustment value setting screen used in a first adjustment mode in the present embodiment. 7 is a flowchart illustrating AF adjustment value setting processing in a second adjustment mode according to the first embodiment. 6 is a flowchart illustrating a first determination process for a matching condition according to the first embodiment. 9 is a flowchart showing a second determination process of the matching condition in the first embodiment. 9 is a flowchart showing AF adjustment value setting processing in a second adjustment mode in Embodiment 2. 10 is a flowchart illustrating a third determination process for a matching condition according to the second embodiment.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. The dimensions, shapes, relative arrangements, and the like of the components exemplified in the present embodiment should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not limited.

  FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to the present embodiment. As shown in FIG. 1, a photographing lens 100 is detachably attached to the imaging apparatus 200 via a lens mounting mechanism of a mount unit (not shown). An electrical contact unit 104 is provided in the mount portion. The imaging apparatus 200 communicates with the photographing lens 100 via the electrical contact unit 104 and controls the focus lens 101 in the photographing lens 100. In FIG. 1, only the focus lens 101 is shown as a lens in the photographing lens 100, but a plurality of lenses such as a variable power lens and a fixed lens are usually provided.

  A light beam from a subject (not shown) is guided to a main mirror 201 in the imaging apparatus 200 via a photographing optical system (including a focus lens 101) in the photographing lens 100. The main mirror 201 is disposed obliquely with respect to the optical axis in the photographing optical path, and a first position (illustrated position) for guiding the light beam from the subject to the upper viewfinder optical system and a second position for retracting outside the photographing optical path. It is possible to move to the position. Further, the central portion of the main mirror 201 is a half mirror, and when the main mirror 201 is mirrored down to the first position, a part of the light beam from the subject passes through the half mirror portion. The transmitted light beam is reflected by the sub mirror 202 provided on the back side of the main mirror 201 and guided to the focus detection unit 207.

  A pair of line sensors is arranged in the focus detection unit 207 (signal generation means), and a light beam received by each line sensor is photoelectrically converted to generate a pair of image signals. In the phase difference detection method, the defocus value is detected based on the relative shift amount of the pair of image signals.

  On the other hand, the light beam reflected by the main mirror 201 forms an image on the focus plate 203 disposed at a position optically conjugate with the image sensor 209. The light (subject image) diffused by the focus plate 203 and transmitted therethrough is converted into an erect image by the penta roof prism 204. The erect image is magnified by the eyepiece 205 and can be observed by the user.

  Further, when the main mirror 201 is raised to the second position, the sub mirror 202 is also folded together with the main mirror 201 and retracts out of the photographing optical path. As a result, the light beam that has passed through the photographing lens optical system passes through the focal plane shutter 208 that is a mechanical shutter, and reaches the image sensor 209. The focal plane shutter 208 limits the amount of light incident on the image sensor 209. The imaging element 209 is configured using a photoelectric conversion element such as a CCD sensor or a CMOS sensor that photoelectrically converts an object image formed by the photographing lens 100 and outputs an electrical signal.

  The camera control unit 210 is a controller that controls various calculations and various operations in the imaging apparatus 200. The camera control unit 210 is configured using a CPU, MPU, or the like, and controls operations of circuits and the like described later. The camera control unit 210 communicates with the lens control unit 103 in the photographing lens 100 via the electrical contact unit 104. The camera control unit 210 (focus control unit) detects a defocus value, and the lens control unit 103 drives the focus lens 101 in the optical axis direction in accordance with a control signal from the camera control unit 210 to adjust the focus. The lens driving mechanism 102 for performing the above is controlled. The lens driving mechanism 102 has a stepping motor as a driving source.

  The camera control unit 210 is connected to an EEPROM 211. In the EEPROM 211, parameters that need to be adjusted to control the imaging apparatus 200, camera ID (identification) information for performing individual identification of the imaging apparatus 200, and parameters related to imaging that have been adjusted in advance using a reference lens are stored. Factory adjustment values are stored.

  Furthermore, the camera control unit 210 is connected to an operation detection unit 213 that detects an operation performed by the user on the imaging apparatus 200 and a counter 214. The operation detection unit 213 detects operations such as a release button (not shown), a selection button, and a button for selecting one of a plurality of images obtained by bracket photography described later. The counter 214 is a counter for counting the number of shootings when performing bracket shooting. The counter value of the counter 214 is reset by the camera control unit 210.

  The display unit 212 is a device that displays image data captured by the image sensor 209, items set by the user, and the like, and is generally configured using a color liquid crystal display element.

  On the other hand, the lens control unit 103 of the photographing lens 100 stores performance information such as a focal length and an open aperture value of the photographing lens 100 and lens ID (identification) information that is unique information for identifying the photographing lens 100. A memory (not shown) is provided. The memory also stores information received from the camera control unit 210 through communication. The performance information and the lens ID information are transmitted to the camera control unit 210 by initial communication when the photographing lens 100 is attached to the imaging apparatus 200, and the camera control unit 210 stores them in the EEPROM 211.

  FIG. 2 is a flowchart showing AF adjustment value setting processing in the present embodiment. In the present embodiment, a first adjustment mode for performing AF micro-adjustment in which the user arbitrarily sets an AF adjustment value, and a second adjustment mode for acquiring an AF adjustment value using micro-adjustment support (MAS). Either of these can be selected. Details of processing using AF micro-adjustment and MAS will be described later.

  First, in step S201, the camera control unit 210 determines whether or not the first adjustment mode is selected. If the first adjustment mode is selected, the process proceeds to step S205, and if the first adjustment mode is not selected, the process proceeds to step S202.

  In step S205, the camera control unit 210 controls the display unit 212 to display an AF adjustment value setting screen for performing AF micro-adjustment. FIG. 3 is a diagram illustrating an example of the AF adjustment value setting screen.

  The AF micro adjustment is a function in which the user directly sets the AF adjustment value. Based on the photographed image, the user determines the amount of focus shift from the in-focus position based on the focus detection result by the focus detection unit 207 to the desired in-focus position and its direction, and sets the AF adjustment value. . As shown in FIG. 3, in the AF micro-adjustment according to the present embodiment, the user can arbitrarily set the AF adjustment value within a range of ± 20 scales in increments of 1 scale, and according to the set AF adjustment value. The focus position based on the defocus value is shifted. The focus change amount per scale of the AF adjustment value is (1/16) × Fδ (F: the open F value of the photographing lens, δ: allowable circle of confusion diameter) in this embodiment, but is limited to this. Instead, it can be appropriately changed according to the performance of the photographing lens 100 and the imaging device 200.

  In FIG. 3, “0” is a reference position set when the imaging apparatus 200 is shipped from the factory. In the AF adjustment value setting screen shown in FIG. 3, the black triangle represents the AF adjustment value stored in the EEPROM 211. The user can change the AF adjustment value by operating the black triangle display along the scale. In the present embodiment, the AF adjustment value is stored in units of scales, for example, +1, but may be stored in units of defocus values. When the AF adjustment value setting screen is displayed, the process proceeds to step S206.

  In step S206, the camera control unit 210 determines whether or not the user has performed an operation to change the AF adjustment value using the AF adjustment value setting screen. If an operation for updating the AF adjustment value is performed, the process proceeds to step S207. If an operation for updating the AF adjustment value is not performed, the process proceeds to step S208.

  In step S207, the camera control unit 210 performs control so as to update the display of the AF adjustment value setting screen in accordance with a user operation. Here, on the AF adjustment value setting screen shown in FIG. 3, a black triangle display is displayed at a position corresponding to the user's operation.

  In step S208, the camera control unit 210 determines whether the user has determined an AF adjustment value. Here, it is determined whether or not the “SET” button has been selected on the AF adjustment value setting screen shown in FIG. If the “SET” button is not selected, the process returns to step S206 and the above processing is repeated. On the other hand, when the “set” button is selected and the AF adjustment value is determined, the process proceeds to step S209, where the camera control unit 210 ends the display of the AF adjustment value setting screen and proceeds to step S210.

  In step S210, the camera control unit 210 differs between the AF adjustment value stored in the EEPROM 211 when the first adjustment mode is selected and the AF adjustment value newly set by the processing in steps S206 to S208. Determine whether or not. If they are different, that is, if the AF adjustment value is updated, the process proceeds to step S204, where the camera control unit 210 updates the registration of the AF adjustment value stored in the EEPROM 211, and the AF adjustment value is not updated. Ends the AF adjustment value setting process.

  On the other hand, if the first adjustment mode is not selected in step S201, an AF adjustment value using MAS is calculated in the second adjustment mode in step S202. In the second adjustment mode using MAS, a plurality of images are taken while the position of the focus lens 101 is driven minutely. A desired focus image is selected from the obtained images, and an AF adjustment value is obtained based on the defocus value of the image. Details of the processing in the second adjustment mode performed in step S202 will be described later. When the AF adjustment value is calculated, the process proceeds to step S203.

  In step S203, the camera control unit 210 determines whether to update the AF adjustment value stored in the EEPROM 211 to the AF adjustment value calculated in step S202. Here, when the AF adjustment value is updated, for example, when the setting of the AF adjustment value calculated by a predetermined operation is selected, the process proceeds to step S204, and the camera control unit 210 sets the AF adjustment value stored in the EEPROM 211. Update registration. On the other hand, when the AF adjustment value is not updated, such as when the AF adjustment value setting process is canceled by a predetermined operation, the AF adjustment value setting process is terminated.

The AF adjustment value stored in the EEPROM 211 by the above processing is the focus lens at the time of AF based on the focus detection result by the focus detection unit 207 at the time of normal shooting (at the time of shooting the image for recording) by the following formula (1). This is used to correct the driving amount.
Defocus amount used to calculate the lens drive amount = defocus value + focus shift amount corresponding to the AF adjustment value (1)

  In the above formula (1), the defocus value represents a defocus value (focus detection result) detected by the focus detection unit 207. Defocus values include preset correction values such as defocus value adjustment data at the time of manufacture, temperature correction values for correcting the amount of focus deviation due to temperature, and endurance correction values for correcting focus that changes with the number of releases. And may be calculated.

  In this embodiment, one of the first adjustment mode and the second adjustment mode is selected. However, an imaging apparatus having only the second adjustment mode is also within the scope of the present invention.

  Next, the AF adjustment value setting process using MAS in the second adjustment mode performed in step S202 will be described with reference to the flowchart of FIG.

  First, in step S <b> 401, the camera control unit 210 controls the display unit 212 to display a focus bracket shooting adjustment screen. The displayed content is, for example, an operation instruction to the user. When the adjustment screen is displayed, the process proceeds to step S402.

  In step S <b> 402, the camera control unit 210 detects a defocus value for the subject used for calculating the AF adjustment value based on the pair of image signals detected by the focus detection unit 207. When the detection of the defocus value ends, the process proceeds to step S403.

  In step S403, the camera control unit 210 sends a drive instruction to the lens control unit 103 so as to move the focus lens 101 to a position (focus position) corresponding to the detected defocus value. When the driving of the focus lens 101 is completed, the process proceeds to step S404.

  In step S <b> 404, the camera control unit 210 determines whether the condition is suitable for the calculation of the AF adjustment value from a plurality of focus detection results. Details of the determination will be described later with reference to the flowchart of FIG. If the condition is met, the process proceeds to step S405. If the condition is not met, the process proceeds to step S417.

  If the condition is not met, in step S417, the camera control unit 210 controls the display unit 212 to display an error message (the fact that the error has occurred and the estimated cause of the error). When the display is completed, the process advances to step S418 to accept an instruction from the user to redo or cancel the adjustment. When redoing the adjustment, the process returns to step S402, and when canceling, the second adjustment mode is terminated.

  On the other hand, in step S405, the camera control unit 210 sends a drive instruction to the lens control unit 103 so as to move the focus lens to the focus bracket start position. Here, the focus bracket start position when the driving width of the focus lens for each shooting is s and the number of shots is m is (m−1) × s / 2 from the in-focus position calculated based on the defocus value. Only the closest side.

  In step S406, the camera control unit 210 resets the counter value n of the counter 214. The counter value n is associated with the number of shots of the focus bracket, and is set to 0 before the start of focus bracket shooting, and the process proceeds to step S407.

  In step S407, the camera control unit 210 determines from the plurality of focus detection results whether the condition is suitable for the calculation of the AF adjustment value. Details of the determination will be described later with reference to the flowchart of FIG. If the condition is met, the process proceeds to step S408. If the condition is not met, the process proceeds to step S417 to display an error message.

  In step S408, the camera control unit 210 detects a defocus value based on the pair of image signals detected by the focus detection unit 207. The defocus value detected here is finally stored in association with the image captured in step S410. When the detection of the defocus value ends, the process proceeds to step S409.

  In step S409, prior to photographing in step S410, mirror up is performed to move the main mirror 201 and the sub mirror 202 to the second position retracted from the photographing optical path. When the mirror up is completed, the process proceeds to step S410.

  In step S410, the camera control unit 210 captures an image using the image sensor 209, and stores the obtained image in association with the defocus value detected in step S408. When the photographing is finished, the process proceeds to step S411, and the mirror is moved down to move the main mirror 201 and the sub mirror 202 to the first position in the photographing optical path described above. When the mirror down is completed, the process proceeds to step S412.

  In step S412, the camera control unit 210 increments the counter value n indicating the number of shots, and proceeds to step S413. In step S413, the camera control unit 210 determines whether the value of the counter value n has reached the number of shots m. If the counter value n has not reached the number of shots m, the process proceeds to step S414, and if it has reached, the process proceeds to step S415.

  In step S414, the camera control unit 210 sends a drive instruction to the lens control unit 103 so as to move the focus lens 101 to the infinity side by the lens drive width s, and the process proceeds to step S407. By repeating steps S407 to S414, m images with the lens driving width s shifted in focus are continuously captured.

  In step S415, the user selects one image in a desired focus state from m images whose focus states are shifted by the lens driving width. In step S415, it is not always necessary to select an image. For example, when it is difficult to select a desired focused image, the image is not selected for a predetermined time, or the AF adjustment value setting process is canceled by a predetermined operation. In some cases, the second adjustment mode is terminated. On the other hand, if any image is selected, the process proceeds to step S416.

  In step S416, the camera control unit 210 calculates an AF adjustment value based on the defocus value associated with the image selected by the user in step S415. When the AF adjustment value is calculated, the second adjustment mode is terminated, and the process proceeds to step S203 in FIG.

  In the above-described example, the MAS is used in the second adjustment mode, and the user selects one image from the AF adjustment value calculation image group obtained by focus bracket shooting. However, the present invention is not limited to this, and it is not necessary to perform focus bracket photographing for calculating the AF adjustment value. For example, a plurality of temporally discontinuous images in which a defocus value and an image are associated are used as AF adjustment value calculation images, and the user selects one of them and associates it with the selected image. The AF adjustment value may be calculated from the defocus value.

  FIG. 5 is a flowchart showing the matching condition determination process performed in step S404 of FIG. 4 in the present embodiment.

  In step S <b> 501, the camera control unit 210 acquires an AF waveform (image signal) from the focus detection unit 207. When the AF waveform is acquired, the process proceeds to step S502.

  In step S <b> 502, the camera control unit 210 sets a determination threshold value for determining whether or not the matching condition is satisfied. Here, a contrast determination threshold C1 for determining whether or not the subject has sufficient contrast and a variation determination threshold σ1 for determining whether or not the variation in the focus detection result is sufficiently small are set. The contrast determination threshold C1 and the variation determination threshold σ1 are set based on at least one of the shooting environment and the setting of the imaging device 200.

  For example, for variations in focus detection results that increase due to dark subject brightness, a value close to the true value is often obtained by obtaining the average of the results of multiple focus detections. Therefore, even when the subject brightness is low, the determination threshold σ1 may be set to a relatively large value (slowly). On the other hand, even if the average of the results of multiple focus detections is acquired for the variation in focus detection results, which are high due to the high temperature (outside air temperature) and increase due to air fluctuation between the imaging device and the subject, Often not close to the value. For this reason, when the outside air temperature is higher than the predetermined temperature, the determination threshold σ1 is set smaller (so that the determination becomes stricter) than in the case where the outside air temperature is lower than the predetermined temperature.

  If the ISO sensitivity is high and there is a lot of noise in the captured image, or if the F value (aperture value) is large and the depth of focus of the captured image is deep, the selection error in image selection in step S415 becomes large. Probability is high. Therefore, it is necessary to reduce the calculation error of the defocus value associated with the image in order not to reduce the accuracy of the AF adjustment value calculated even when the image selection error is large. Therefore, when the ISO sensitivity is set higher than the predetermined sensitivity or when the F value is set higher than the predetermined value, the determination threshold C1 is larger and the determination threshold σ1 is smaller than when the ISO sensitivity is not set ( It is set so that the judgment becomes severe.

  In step S503, the camera control unit 210 determines whether the subject is suitable for calculating the AF adjustment value (applicable subject). Specifically, when the contrast of the AF waveform acquired in step S501 is less than or equal to the contrast determination threshold C1 (below the threshold), it is determined that the subject is difficult to obtain an accurate focus detection result. Further, even when the luminance is equal to or lower than the predetermined luminance, it is determined that the subject is difficult to obtain an accurate focus detection result. If at least one of the contrast and brightness of the AF waveform does not satisfy the condition, the process proceeds to step S508, and it is determined that the condition is not a conforming condition, and the process is terminated. On the other hand, if the contrast of the AF waveform is larger than the contrast determination threshold C1 and the luminance is larger than the predetermined luminance, the process proceeds to step S504.

  In step S504, the camera control unit 210 (accumulation control unit) performs accumulation setting based on the charge accumulation time of the line sensor when acquiring the AF waveform in step S501. Specifically, at least one of the number of accumulations and the accumulation interval in the line sensor is set so that the time required for multiple focus detections for variation determination in step S505 described later is equal to or longer than a predetermined time T1. The accumulation time for acquiring the AF waveform is also applied to the focus detection in step S505, and usually becomes shorter as the brightness becomes brighter.

  The variation in the focus detection result due to the air fluctuation due to the outside air temperature described above tends to be large on the time scale (about 1000 ms) for a series of bracket photographing even though it is small on a relatively short time scale (about 50 ms). There is. Therefore, if the number of accumulations and the accumulation interval for variation determination are fixed, the total focus detection time is shortened when the accumulation time required for AF waveform acquisition is short, and variations in focus detection results due to temperature rise occur. May also be determined to have small variations.

  Therefore, in this embodiment, the number of times of accumulation or the accumulation interval when continuously accumulating charges is set so that the focus detection time for variation determination is equal to or longer than the predetermined time T1. Here, the predetermined time T1 is set to an order (for example, 1000 ms) about the time required for a series of bracket shooting.

  For example, when the subject is bright and the accumulation time is as short as 1 ms, the AF waveform acquisition count is set to 1000 times. On the other hand, when the subject is slightly dark and the accumulation time is as long as 10 ms, the number of AF waveform acquisitions is set to 100 times, which is smaller than when the accumulation time is short. In this way, by setting the number of times of accumulation corresponding to the accumulation time, the variation in the result of focus detection for a predetermined time T1 or more is calculated, so that the variation in the focus detection result due to temperature rise can be detected more reliably. Can do.

  In addition, by fixing the number of accumulations and changing the accumulation interval, the time required for multiple focus detections may be set to the predetermined time T1 or more. For example, if the number of accumulations is 100, charge accumulation is performed at intervals of 10 ms when the accumulation time is 1 ms, and at shorter intervals when the accumulation time is 10 ms. In this case, since the number of times of accumulation is fixed, even if the accumulation time is very short, the number of times of accumulation does not increase enormously, heat generation due to continuous accumulation can be prevented, and variations in focus detection due to temperature rise can be suppressed. Note that both the number of accumulations and the accumulation interval may be set according to the accumulation time.

  In step S505, the camera control unit 210 performs charge accumulation and AF waveform acquisition based on the accumulation count or accumulation interval set in step S404, and calculates a defocus value each time. Then, the camera control unit 210 calculates the variation in the focus detection result from the obtained defocus values for a plurality of times. If the calculated variation is greater than or equal to the determination threshold σ1, the process proceeds to step S508, where it is determined that the conforming condition is not satisfied, and the process ends. On the other hand, if the calculated variation is smaller than the determination threshold σ1 (if it is within the predetermined range), the process proceeds to step S507, where it is determined that the condition is satisfied, and the process is terminated.

  FIG. 6 is a flowchart showing the matching condition determination process performed in step S407 of FIG. 4 in the present embodiment. The basic operations in steps S601 to S608 in FIG. 6 are the same as the operations in steps S501 to S508 described with reference to FIG. 5, and only the determination threshold value and a predetermined time value are different. Therefore, in FIG. 6, only a different part from FIG. 5 is demonstrated.

  In step S <b> 602, the camera control unit 210 sets a determination threshold value for determining whether or not the matching condition is satisfied. Here, a contrast determination threshold C2 for determining whether the subject has sufficient contrast and a variation determination threshold σ2 for determining whether the variation in focus detection is sufficiently small are set. Here, the determination thresholds C2 and σ2 are set to values that make the determination easier than the determination thresholds C1 and σ1 (values that are difficult to determine that they are not suitable subjects). Specifically, the determination threshold C2 is set smaller and the determination threshold σ2 is set larger.

  In step S604, the camera control unit 210 performs accumulation setting based on the charge accumulation time of the line sensor when acquiring the AF waveform in step S601. Specifically, at least one of the number of accumulations and the accumulation interval in the line sensor is set so that the time required for multiple focus detections for the variation determination in step S605 is equal to or longer than a predetermined time T2. The accumulation time for acquiring the AF waveform is also applied to the focus detection in step S605, and usually becomes shorter as the luminance becomes brighter. Here, the predetermined time T2 is shorter than the predetermined time T1, and is set to an order of about the time required for a series of photographing operations. As a result, it is possible to stably calculate the variation in focus detection at the time of actual shooting and more accurately determine whether or not the matching condition is satisfied.

  As described above, in this embodiment, the matching condition is determined a plurality of times. Specifically, in FIG. 4, even after it is determined in step S <b> 404 that the matching condition is satisfied before the focus bracket shooting is started, in step S <b> 407, whether or not the matching condition is satisfied is determined for each shooting of the focus bracket shooting. This cancels the calculation of AF adjustment values when the contrast of the image signal or the variation in focus detection changes significantly due to factors such as the imaging device or subject moving or the air fluctuations changing during focus bracket shooting. can do. In addition, since the image signal with higher contrast can be obtained by performing the determination before starting the focus bracket photographing at the in-focus position detected by the focus detection unit 207 (step S403), the matching subject based on the contrast can be obtained. Judgment can be made appropriately.

  In the present embodiment, the determination threshold is set to a different value depending on the timing of determination of the matching condition. Specifically, the determination threshold values C2 and σ2 used for determination during focus bracket shooting are set so that the determination is less than the determination threshold values C1 and σ1 used for determination before focus bracket shooting. As a result, once it is determined that the conforming condition is satisfied, it is difficult to determine that the conforming condition is not met due to a slight change in the condition, and it is possible to prevent the user's feeling of use from being impaired.

  The predetermined time T2 necessary for focus detection for determination during focus bracket shooting is set to be shorter than the predetermined time T1 required for focus detection for determination before focus bracket shooting. Thereby, since the adaptation condition determination during focus bracket photography is performed in a shorter time, it is possible to prevent the user's feeling of use from being impaired.

  In the method described above, the user's feeling of use is emphasized, and the adaptation condition determination during focus bracket photography is performed more slowly and in a shorter time than the adaptation condition judgment before focus bracket photography. However, with more emphasis on the accuracy of the determination, the determination related to the focus detection used for the calculation of the actual AF adjustment value, that is, the determination of the adaptation condition during focus bracket shooting is performed more strictly and over a long time. Also good. Specifically, the determination threshold values C2 and σ2 may be set to values that make determination more severe than the determination threshold values C1 and σ1. Further, the predetermined time T2 may be set to a time longer than the predetermined time T1.

  As described above, in this embodiment, it is determined whether or not the conditions are suitable for calculating the AF adjustment value based on the variation in the focus detection results of a plurality of times. By making the time required for focus detection for variation determination to be a predetermined time or more, even when the variation in focus detection results due to air fluctuations such as when the outside air temperature is high, the variation can be more accurately detected. Can be determined.

  In the first embodiment described above, the AF adjustment value is calculated based on the focus bracket captured image in the second adjustment mode. In the second embodiment, the AF adjustment value is calculated based on the defocus value calculation result of the imaging surface phase difference AF in the second adjustment mode. The AF adjustment value here is used for correcting the driving amount of the focus lens at the time of AF based on the focus detection result by the focus detection unit 207 at the time of normal photographing as in the first embodiment.

  Further, in the second adjustment mode of the first embodiment, in the matching condition determination, the matching subject determination and the focus detection variation determination are performed, and if any of the conditions is not satisfied, the AF adjustment value cannot be calculated. It was. On the other hand, in the second embodiment, the focus detection variation determination is performed, and when the condition is not satisfied, the suitable subject determination is performed. If the condition is not satisfied in the suitable subject determination, the AF adjustment value is not calculated, but if the condition is satisfied in the suitable subject determination, the focus detection variation determination is performed again. Differences from the first embodiment will be described below.

  In the second embodiment, since the imaging surface phase difference AF is used as a means for calculating the AF adjustment value, the time required for calculating the AF adjustment value is shorter than that in the first embodiment in which focus bracket shooting is performed. Therefore, the time required to acquire the AF waveform acquired for determining the focus detection variation is shorter than that in the first embodiment. In the AF waveform acquisition period that is sufficiently shorter than that of the first embodiment, when the focus detection variation is caused by air fluctuation, the amount of focus detection variation varies depending on the timing of focus detection. Therefore, when the variation in focus detection due to air fluctuation is large, the AF adjustment value can be calculated in an environment with small variation by repeatedly performing focus detection until the variation in focus detection becomes small.

  Since the configuration of the imaging apparatus is the same as that in FIG. 1, description thereof is omitted. However, in the second embodiment, the imaging device 209 has a configuration that can acquire a signal used for imaging plane phase difference AF. For example, in each of a plurality of pixel portions provided in the imaging element 209, a configuration in which a plurality of photodiodes are held under one microlens and signals for imaging and focus detection can be acquired may be used. In this case, a signal obtained by adding the signals of the two photodiodes is an imaging signal, and the signals of the individual photodiodes are a pair of image signals for focus detection. Alternatively, a configuration in which an imaging pixel and a focus detection pixel are provided in the imaging element may be used. The camera control unit 210 performs a correlation operation on the pair of image signals and detects a defocus value from the relative shift amount. In this embodiment, the camera control unit 210 is described as detecting the defocus value of the imaging plane phase difference AF, but may be performed by a signal processing unit (not shown) different from the camera control unit 210. The imaging surface phase difference AF is not described in detail because a known method is used.

  Also in this embodiment, the AF adjustment value setting process described in FIG. 2 is performed. Note that this embodiment can also be applied to an imaging apparatus having only the second adjustment mode, as in the first embodiment. The AF adjustment value setting process using the imaging surface phase difference AF in the second adjustment mode executed in step S202 of FIG. 2 will be described with reference to the flowchart of FIG.

  First, in step S <b> 701, the camera control unit 210 controls the display unit 212 to display an imaging surface phase difference AF adjustment screen. The displayed content is, for example, an operation instruction to the user. When the adjustment screen is displayed, the process proceeds to step S702.

  In step S <b> 702, the camera control unit 210 detects a defocus value for the subject used for calculating the AF adjustment value based on the pair of image signals detected by the focus detection unit 207. When the detection of the defocus value ends, the process proceeds to step S703.

  In step S703, the camera control unit 210 sends a drive instruction to the lens control unit 103 so as to move the focus lens 101 to a position (focus position) corresponding to the detected defocus value. When the driving of the focus lens 101 is completed, the process proceeds to step S704.

  In step S704, the camera control unit 210 determines from the plurality of focus detection results whether the condition is suitable for the calculation of the AF adjustment value. Details of the determination will be described later with reference to the flowchart of FIG. If the condition is suitable, the process proceeds to step S705, and if not, the process proceeds to step S710.

  If the condition is not met, in step S710, the camera control unit 210 controls the display unit 212 to display an error message (the fact that the error has occurred and the estimated cause of the error). When the display is completed, the process proceeds to step S711, and an instruction from the user to redo or cancel the adjustment is received. When redoing the adjustment, the process returns to step S702, and when canceling, the second adjustment mode is terminated.

  On the other hand, in step S705, the camera control unit 210 detects a defocus value based on the pair of image signals detected by the focus detection unit 207. When the detection of the defocus value ends, the process proceeds to step S706.

  In step S706, the camera control unit 210 moves the main mirror 201 and the sub mirror 202 to the second position retracted from the imaging optical path before detecting the defocus value in the imaging plane phase difference AF in step S707. I do. When the mirror up is completed, the process proceeds to step S707.

  In step S <b> 707, the camera control unit 210 detects the defocus value by the imaging surface phase difference AF using the imaging element 209. When the detection of the defocus value is completed, the process proceeds to step S708, and the camera control unit 210 performs mirror down to move the main mirror 201 and the sub mirror 202 to the first position in the photographing optical path. When the mirror down is completed, the process proceeds to step S709.

  In step S709, the camera control unit 210 calculates an AF adjustment value based on the defocus value detected in step S707. Specifically, the AF adjustment value is calculated based on the difference between the defocus value detected in step S705 and the defocus value detected in step S707. When the AF adjustment value is calculated, the second adjustment mode is terminated, and the process proceeds to step S203 in FIG.

  FIG. 8 is a flowchart showing the matching condition determination process performed in step S704 of FIG. 7 in the present embodiment.

  In step S <b> 801, the camera control unit 210 acquires an AF waveform (image signal) from the focus detection unit 207. When the AF waveform is acquired, the process proceeds to step S802.

  In step S <b> 802, the camera control unit 210 sets a determination threshold value for determining whether or not the matching condition is satisfied. Here, a contrast determination threshold C3 for determining whether the subject has sufficient contrast and a variation determination threshold σ3 for determining whether the variation in focus detection results is sufficiently small are set. The contrast determination threshold C3 and the variation determination threshold σ3 are set based on the shooting environment.

  In step S803, the camera control unit 210 performs accumulation setting based on the charge accumulation time of the line sensor when acquiring the AF waveform in step S801. In the first embodiment, the accumulation time is set in consideration of the time scale (about 1000 ms) required for a series of bracket photographing. On the other hand, in the present embodiment, since the AF adjustment value is acquired by the imaging plane phase difference AF, it is not necessary to consider the focus detection variation on a long time scale as in bracket shooting. Therefore, in the accumulation setting in this step, an accumulation number or accumulation interval that is convenient for focus detection is set.

  In step S804, the camera control unit 210 performs charge accumulation and AF waveform acquisition based on the accumulation count or accumulation interval set in step S803, and calculates a defocus value each time. Then, the camera control unit 210 calculates the variation in the focus detection result from the obtained defocus values for a plurality of times. When the calculation of the variation in the focus detection result is completed, the process proceeds to step S805.

  In step S805, the camera control unit 210 determines whether the variation calculated in step S804 is smaller than the determination threshold σ3. If the variation is smaller than the determination threshold σ3 (if it is within the predetermined range), the process proceeds to step S806, where it is determined that the matching condition is satisfied, and the process ends. On the other hand, if the variation is equal to or greater than the determination threshold σ3 (if outside the predetermined range), the process proceeds to step S807.

  In step S807, the camera control unit 210 determines whether the subject is suitable for calculation of the AF adjustment value (applicable subject). Specifically, when the contrast of the AF waveform acquired in step S801 is less than or equal to the contrast determination threshold C3 (below the threshold), it is determined that the subject is difficult to obtain an accurate focus detection result. Further, even when the luminance is equal to or lower than the predetermined luminance, it is determined that the subject is difficult to obtain an accurate focus detection result. If at least one of the contrast and the brightness of the AF waveform does not satisfy the condition, the process proceeds to step S808, and it is determined that the condition is not an appropriate condition, and the process is terminated. On the other hand, if the contrast of the AF waveform is larger than the contrast determination threshold C3 and the luminance is larger than the predetermined luminance, there is a possibility that there is a cause other than the subject condition, that is, a condition where there is air fluctuation. Returning, the focus detection variation is determined again.

  As described above, in this embodiment, in the determination of the matching condition, if the focus variation determination is NG regardless of the matching subject, the focus detection variation determination is performed again, so that the AF adjustment is performed as compared with the first embodiment. Opportunities for calculating values can be further increased.

  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.

200 Imaging Device 207 Focus Detection Unit 210 Camera Control Unit 211 EEPROM

Claims (23)

An imaging apparatus having an adjustment mode for obtaining an adjustment value used for adjusting a focus detection result,
Signal generating means for accumulating electric charge and generating a pair of image signals used for focus detection;
Focus detection means for performing focus detection based on the pair of image signals;
Obtaining means for obtaining the adjustment value used for adjustment of a focus detection result by the focus detection means;
Based on a plurality of focus detection results, determination means for determining whether the condition is suitable for obtaining the adjustment value;
Accumulation control means for controlling charge accumulation in the signal generation means,
In the adjustment mode, when the determination unit determines that the condition is suitable for acquisition of the adjustment value, the acquisition unit selects a focus corresponding to an image selected from a plurality of images having different focus states. Obtaining the adjustment value based on the detection result;
The accumulation control unit is configured to acquire the signal when the focus detection result is acquired a plurality of times so that a time for acquiring the focus detection result of the plurality of times used for determination by the determination unit is a predetermined time or more. An image pickup apparatus that controls charge accumulation in a generation unit.   The imaging apparatus according to claim 1, wherein acquisition of the adjustment value is limited when the determination unit determines that the condition is not suitable for acquisition of the adjustment value.   The accumulation control unit is responsive to the accumulation time of the charge for generating the image signal so that the time for acquiring the plurality of focus detection results used for determination by the determination unit is equal to or longer than the predetermined time. The imaging apparatus according to claim 1, wherein at least one of the accumulation count and the accumulation interval is changed.   The accumulation control unit sets a larger number of accumulations as the accumulation time of the charge for generating the image signal is shorter when acquiring the plurality of focus detection results used for determination by the determination unit. The imaging apparatus according to claim 3.   The accumulation control unit sets the accumulation interval longer as the accumulation time of the charge for generating the image signal is shorter when acquiring the plurality of focus detection results used for determination by the determination unit. The imaging apparatus according to claim 3.   6. The imaging apparatus according to claim 3, wherein an accumulation time of electric charge for generating the image signal is shorter as luminance is higher.   7. The determination unit according to claim 1, wherein the determination unit determines that the condition is suitable for obtaining the adjustment value when variations in the focus detection results of the plurality of times are within a predetermined range. The imaging apparatus of Claim 1.   The imaging apparatus according to claim 7, wherein the predetermined range is changed according to at least one of temperature, ISO sensitivity, and aperture value.   9. The adjustment mode according to claim 7, wherein the determination unit determines whether the condition is suitable for acquisition of the adjustment value a plurality of times, and the predetermined range varies depending on a timing of the determination. The imaging device described in 1.   10. The imaging apparatus according to claim 1, wherein the determination unit determines that the condition is not suitable for acquisition of the adjustment value when a contrast of the image signal is equal to or less than a threshold value. 11. .   The imaging apparatus according to claim 10, wherein the threshold is changed according to at least one of ISO sensitivity and an aperture value.   12. The adjustment unit according to claim 10 or 11, wherein in the adjustment mode, the determination unit determines whether the condition is suitable for acquisition of the adjustment value a plurality of times, and the threshold value differs depending on a timing of performing the determination. Imaging device.   13. The adjustment mode according to claim 1, wherein in the adjustment mode, the determination unit determines whether or not the condition is suitable for acquisition of the adjustment value a plurality of times, and the predetermined time varies depending on a timing of performing the determination. The imaging device according to any one of the above. A focus control means for controlling the position of the focus lens;
The focus control unit controls the focus lens to move to a position based on a result of adjusting a focus detection result by the focus detection unit using the adjustment value acquired in advance during normal shooting. The imaging device according to any one of claims 1 to 13. Having imaging means for imaging images;
In the adjustment mode, the focus control unit controls the focus lens to move to a plurality of different lens positions, and images are captured by the imaging unit and the focus detection is performed at each lens position of the plurality of lens positions. 15. The imaging according to claim 14, wherein focus detection is performed by a unit, and the acquisition unit acquires the adjustment value based on a focus detection result corresponding to an image selected from a plurality of the images. apparatus.   Before the imaging of the plurality of lens positions is performed, the determination unit determines whether the condition is suitable for obtaining the adjustment value at the in-focus position based on the focus detection result by the focus detection unit. The imaging apparatus according to claim 15.   The imaging apparatus according to claim 16, wherein the determination unit further determines whether or not the lens position of the plurality of lens positions is a condition suitable for acquisition of the adjustment value. A control method for an imaging apparatus having an adjustment mode for acquiring an adjustment value used for adjustment of a focus detection result, and comprising a signal generation unit that accumulates electric charges and generates a pair of image signals used for focus detection,
A focus detection step for performing focus detection based on the pair of image signals;
An acquisition step for acquiring the adjustment value used for adjusting the focus detection result in the focus detection step;
A determination step for determining whether the condition is suitable for obtaining the adjustment value based on a plurality of focus detection results;
An accumulation control step for controlling accumulation of electric charges in the signal generating means,
In the adjustment mode, when it is determined by the determination step that the condition is suitable for acquisition of the adjustment value, the acquisition step includes a focus corresponding to an image selected from a plurality of images having different focus states. Obtaining the adjustment value based on the detection result;
In the accumulation control step, the signal at the time of acquiring the plurality of focus detection results so that the time for acquiring the plurality of focus detection results used for determination in the determination step is a predetermined time or more. An image pickup apparatus control method, comprising: controlling charge accumulation in a generation unit. An imaging apparatus having an adjustment mode for obtaining an adjustment value used for adjusting a focus detection result,
A first signal generating means and a second signal generating means for accumulating electric charge and generating a pair of image signals used for focus detection;
First focus detection means for performing focus detection based on a pair of image signals generated by the first signal generation means;
Second focus detection means for performing focus detection based on a pair of image signals generated by the second signal generation means;
Acquisition means for acquiring the adjustment value used for adjustment of a focus detection result by the first focus detection means;
A determination unit that determines whether the condition is suitable for obtaining the adjustment value based on a plurality of focus detection results by the first focus detection unit;
Storage control means for controlling charge storage in the first signal generation means,
In the adjustment mode, when the determination unit determines that the condition is suitable for acquisition of the adjustment value, the acquisition unit calculates the adjustment value based on the focus detection result of the second focus detection unit. Acquired,
The determination unit determines that the condition is suitable for obtaining the adjustment value when the variation in the plurality of focus detection results is within a predetermined range, and the variation is outside the predetermined range. When the image signal generated by the first signal generation unit satisfies a predetermined condition, the focus detection by the first focus detection unit and the determination by the determination unit are performed again. An imaging device that is characterized.   The imaging apparatus according to claim 19, wherein the predetermined condition is satisfied when a contrast and a luminance of the image signal generated by the first signal generation unit are larger than a threshold value, respectively.   When it is determined by the determination means that the condition is suitable for acquisition of the adjustment value, focus detection by the first focus detection means and focus detection by the second focus detection means are performed, and the acquisition means 21. The imaging apparatus according to claim 19, wherein the adjustment value is acquired based on a difference between two focus detection results.   The image pickup apparatus according to any one of claims 19 to 21, wherein the second signal generation means is an image pickup means for generating an image pickup signal for recording. A first signal generation unit and a second signal generation unit which have an adjustment mode for acquiring an adjustment value used for adjusting a focus detection result, and which store a charge and generate a pair of image signals used for focus detection; A method for controlling an imaging apparatus comprising:
A first focus detection step for performing focus detection based on a pair of image signals generated by the first signal generation means;
A second focus detection step for performing focus detection based on a pair of image signals generated by the second signal generation means;
An acquisition step of acquiring the adjustment value used for adjustment of a focus detection result in the first focus detection step;
A determination step of determining whether or not the condition is suitable for obtaining the adjustment value based on a plurality of focus detection results obtained by the first focus detection step;
An accumulation control step for controlling accumulation of electric charge in the first signal generating means,
In the adjustment mode, when it is determined by the determination step that the condition is suitable for acquisition of the adjustment value, in the acquisition step, the adjustment value is determined based on a focus detection result by the second focus detection step. Acquired,
In the determination step, when the variation in the plurality of focus detection results is within a predetermined range, it is determined that the condition is suitable for obtaining the adjustment value, and the variation is outside the predetermined range. When the image signal generated by the first signal generation unit satisfies a predetermined condition, the focus detection is performed a plurality of times by the first focus detection step and the determination by the determination step is performed again. A control method for an imaging apparatus.

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