JP5230505B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus having focus detection means for detecting a focus state of an imaging optical system.

  2. Description of the Related Art In recent years, an imaging apparatus such as a camera is generally provided with an automatic focusing apparatus that performs shooting after changing an optical system to a focused state. In particular, many digital single-lens reflex cameras include a secondary imaging phase difference type focus detection device. It is also possible to perform focus detection repeatedly at time intervals of several tens of milliseconds, and to perform in-focus and out-of-focus determination more accurately and quickly than other focus detection methods such as a contrast method. It is.

  On the other hand, in recent years, there are many imaging devices that are equipped with an angular velocity sensor such as a gyro sensor and perform angular shake correction based on the detected angular velocity of the imaging device. Furthermore, in Patent Document 1, so-called translational shake in a direction orthogonal to the optical axis, which is difficult to remove by using the output of the gyro sensor, is removed by the acceleration sensor output. In addition, Patent Document 1 includes a technique that includes an accelerometer to detect a slight movement in the optical axis direction, and enables correction of shake in the optical axis direction by measuring acceleration in the optical axis direction. It is disclosed.

JP 09-080523 A

  However, in a secondary imaging phase difference type focus detection device that is often mounted on a digital single-lens reflex camera, the integration time of an AF (autofocus) sensor becomes long when the subject is dark. Therefore, the imaging state cannot always be detected in a short cycle. In addition, since the imaging state is detected discontinuously, there is an interval between focus detection and focus detection, and especially when the integration time for detecting the imaging state is long, imaging is performed by the movement of the camera body. The time when the state change cannot be recognized becomes a level that cannot be ignored.

  This problem becomes apparent when the subject deviates from the depth of field due to slight fluctuations in the optical axis direction under conditions with high imaging magnification (so-called macro imaging) such as equal magnification imaging. Therefore, an apparatus that can continuously detect the imaging state has been desired.

  Further, as in Patent Document 1, when an acceleration sensor is used as a moving object position calculating means in shake correction in the optical axis (focus) direction, the position of the moving object is obtained by second-order integration of the acceleration that is the output of the acceleration sensor. Is calculated. Therefore, the instability of calculation due to the drift of the acceleration sensor has been a problem.

(Object of invention)
The object of the present invention is to detect the in-focus state of the imaging optical system, suppress photographing in the out-of-focus state due to shake in the optical axis direction, and perform computation when obtaining shake in the optical axis direction due to acceleration. An object of the present invention is to provide an imaging device capable of suppressing divergence.

  In order to achieve the above object, the present invention provides an imaging optical system that forms an image of a subject on an imaging unit, a focus detection unit that detects a focusing state of the imaging optical system, and the imaging optical system. Optical axis direction shake calculating means for calculating the optical axis direction shake due to acceleration acting on the optical axis, and calibrating the optical axis direction shake amount so as to reset the optical axis direction shake amount calculated by the optical axis direction shake calculating means When the focus detection means detects the in-focus state, it can be photographed when the optical axis direction shake amount calculated by the optical axis direction shake calculation means is within the focus range. This is an imaging apparatus.

  According to the present invention, it is possible to detect the in-focus state of the imaging optical system, suppress photographing in the out-of-focus state due to shake in the optical axis direction, and perform computation when obtaining shake in the optical axis direction due to acceleration. An imaging device capable of suppressing divergence can be provided.

It is a block diagram which shows the outline of the imaging device which concerns on each Example of this invention. 1 is a block diagram illustrating a configuration of an imaging apparatus according to Embodiment 1. FIG. 3 is a flowchart illustrating the operation of the main part of the imaging apparatus according to the first embodiment. 3 is a timing chart for explaining the operation of the main part of the first embodiment.

  The mode for carrying out the present invention is as shown in the following examples.

  FIG. 1 is a block diagram showing an outline of an image pickup apparatus (digital single-lens reflex camera) according to an embodiment of the present invention.

  Inside the interchangeable lens 101, a focus lens 102 for focus adjustment, and a lens driving unit 103 that drives the focus lens 102 to change the imaging state of the focus lens 102 (imaging position of the subject) are provided. Yes. Further, a lens drive control unit 105 that controls the lens drive unit 103 is provided on the main board. Further, two axes included in a plane orthogonal to the optical axis 104 indicated by a one-dot chain line (the XY plane when the vertical direction in FIG. 1 is the Y direction and the vertical direction in the drawing is the X direction), and the optical axis direction An acceleration sensor 106 capable of measuring acceleration is provided. Further, an acceleration calculation unit 107 is provided on the main board to calculate the optical axis direction shake in the direction of the optical axis 104 by integrating the acceleration information measured by the acceleration sensor 106 in the second order.

  A camera main body 201 to / from which the interchangeable lens 101 is attached / detached via a lens mount is provided with a secondary imaging optical system 202. A part of the light beam that has passed through the interchangeable lens 101 is guided to the secondary imaging optical system 202. As a result, two images divided by the separator lens are formed on an AF (autofocus) sensor, which will be described later, and the in-focus state (in-focus state) of the focus lens 102 provided in the interchangeable lens 101 is determined from the amount of deviation between the two images. Movement amount) is calculated. Specifically, the imaging state of the subject, that is, the lens driving amount to the in-focus position of the focus lens 102 is calculated by the secondary imaging phase difference method.

  In the first embodiment, as will be described later, the output of the acceleration sensor 106 is further used in a form that complements the in-focus state detection operation that is intermittently performed only by the AF sensor. Thereby, it has higher time resolution and enables continuous determination of in-focus and out-of-focus rather than intermittent as in the prior art.

  FIG. 2 is a block diagram showing a configuration of main parts in the interchangeable lens 101 and the camera body 201 in the imaging apparatus having the above-described configuration, and the same parts as those in FIG.

  The release button 205 is a two-stage pressing switch mounted on the camera body 201, and the switch S1 for starting a shooting preparation operation such as focus detection is turned on by pressing up to the first stage, and the second stage is pressed. The switch S2 for starting the photographing operation is turned on by pressing until. When the switch S1 is turned on, the AF sensor 203 and the lens driving amount calculation unit 204 start focus detection (detection of the imaging state of the focus lens 102) by the secondary imaging phase difference method. Then, based on the calculated lens driving amount, lens driving which is a focus adjustment operation described later is started. After that, when the switch S2 is turned on by pressing the release button 205 up to the second stage, the photographing operation is performed by the image capturing unit 207 when the image capturing control unit 206 permits photographing as described later.

  In an actual imaging apparatus, the ON signal of the switch S1 is input to a camera microcomputer (not shown) provided in the camera body 201. Then, the AF sensor 203 performs photoelectric conversion of the subject image and accumulation operation of the signal (hereinafter simply referred to as accumulation) in accordance with an instruction from the camera microcomputer. Similarly, the lens driving amount calculation unit 204 calculates the imaging state of the focus lens 102 based on the accumulation result in accordance with an instruction from the camera microcomputer. An ON signal of the switch S2 is also input to the camera microcomputer, and the imaging control unit 206 is based on information on the shake in the optical axis direction by the acceleration calculation unit 107 that is calibrated by the calibration unit 108, which will be described later, according to an instruction from the camera microcomputer. The imaging unit 207 is caused to perform shooting. However, in FIG. 2, only the main part is shown for simplification of the drawing.

  In so-called macro photography, when the switch S1 is turned on as described above, the AF sensor 203 and the lens drive amount calculation unit 204 form an image of the subject, that is, the lens drive amount that is the amount of movement of the focus lens 102 to the focal point. Is calculated. The lens driving amount is input from the camera body 201 to the lens driving control unit 105 in the interchangeable lens 101. Then, the lens drive control unit 105 drives the focus lens 102 to the in-focus position according to the lens drive amount via the lens drive unit 103.

  In addition, an acceleration sensor 106 is provided in the interchangeable lens 101 as shown in FIG. 1, and an acceleration that varies in the direction of the optical axis 104 is always detected in accordance with an instruction from a lens microcomputer (not shown). The detected acceleration signal is output to the acceleration calculation unit 107, and the acceleration calculation unit 109 performs second-order integration of the acceleration to calculate the displacement in the optical axis direction (optical axis shake).

  When the focus lens 102 reaches the in-focus position by the lens driving, the lens driving is stopped. However, as will be described later with reference to FIG. 4, the imaging state of the subject is continuously maintained by the AF sensor 203 and the lens driving amount calculation unit 204 thereafter. Is detected. Then, it is assumed that the calibration unit 108 included in the lens microcomputer (not shown) determines that the focus lens 102 is in the in-focus range as a result of the subsequent imaging state detection. Then, the output of the acceleration calculation unit 109 at that time (information on shake in the optical axis direction) is reset as the origin of the position information of the focus lens 102. Although details will be described later, this is an operation for correcting the drift of the second-order integral value of the acceleration output in the acceleration calculation unit 109.

  Thereafter, the lens drive control unit 105 does not drive the focus lens 102 until the switch S1 is turned off and the process returns to the start stage.

  Since the acceleration calculation unit 107 performs second-order integration, there is a concern about the instability of the calculation result. However, by performing the reset operation as described above, the calculation that tends to diverge is returned to the beginning, and the calculation of the acceleration calculation unit 107 is performed. Accuracy can be stabilized.

  In addition, when it takes a long time from when the switch S1 is turned on to when the switch S2 is turned on, even if the initial reset operation is performed, the integrated calculation amount increases, and there is a concern that the calculation result by the acceleration calculation unit 107 may diverge. Is done. Therefore, even after the driving of the focus lens 102 is completed, the calibration unit 108 sequentially refers to the calculation result in the lens driving amount calculation unit 204, and when it is determined that the focus is in focus from the calculation result, the acceleration calculation unit 107. Reset the shake amount in the optical axis direction again.

  Assume that the release button 205 is further pressed, the switch S2 is turned on, and an instruction to start shooting is given. Then, after the reset operation, the imaging control unit 206 only determines that the position of the focus lens 102 is in the in-focus range from the state of shake in the optical axis direction continuously calculated by the acceleration calculation unit 107. Imaging by the imaging unit 207 is permitted. As a result, photographing becomes possible, and an imaging operation is performed by an exposure amount adjusting unit (not shown) for adjusting the exposure amount and the imaging unit 207.

  Next, the operation of the main part of the series of the imaging apparatus will be described using the flowchart shown in FIG. This flowchart starts when the main power supply of the camera body 201 is turned on and ends when the main power supply is turned off. This flowchart is repeatedly executed while the main power supply is turned on.

  The operation is started from step # 101. First, in step # 102, the state of the switch S1 is determined. If it is not turned on, it waits in this step # 102 until it is turned on. Thereafter, when the switch S1 is turned on, the process proceeds to step # 103. Then, the AF sensor 203 and the lens driving amount calculation unit 204 detect the imaging state of the subject by the secondary imaging phase difference method, that is, detect the in-focus state of the focus lens 102 based on the accumulation result. If it is not in focus, the lens drive amount to the in-focus position is calculated. In the subsequent step # 104, the lens drive control unit 105 drives the focus lens 102 to the in-focus position via the lens drive unit 103 based on the calculated lens drive amount.

  In the next step # 105, it is determined whether or not the focus lens 102 has moved to the in-focus position. If it is determined that the focus lens 102 has been reached, the process proceeds to step # 106, and the drive of the focus lens 102 is completed. In the next step # 107, a camera microcomputer (not shown) causes the AF sensor 203 to perform accumulation again, and determines the imaging state of the subject based on the accumulation result. If it can be confirmed that the position is in the in-focus position, the information on the optical axis direction shake calculated by the second-order integration is reset by the acceleration calculation unit 107 at that time.

  Although details will be described later with reference to FIG. 4, the resetting requires the accumulation time of the AF sensor 203 and the calculation time of the signal until it is determined that the focus is achieved. Then, a time delay occurs in the determination with respect to the time when the photoelectric conversion of the subject image is actually performed (average time of accumulation time). Therefore, the second-order integral value in the acceleration calculation unit 107 is reset with the past value estimated by the time delay as the origin. That is, the second-order integral value (displacement of the focus lens 102 in the direction of the optical axis 104) of the acceleration calculation unit 107 at the time of focusing is set to zero.

  In the next step # 108, it takes a long time from turning on the switch S1 to turning on the switch S2, and in order to prevent the integral calculation from diverging in the acceleration calculation unit 107, the calibration unit 108 performs the lens drive amount calculation unit. The calculation result at 204 is sequentially referred to. If the calculation result in the lens drive amount calculation unit 204 is determined to be in focus, the process proceeds to step # 109, and if it is determined to be out of focus, the process proceeds to step # 110.

  In step # 109, since the calculation result of the lens driving amount calculation unit 204 is determined to be in focus, the calibration unit 112 resets the calculation result of the acceleration calculation unit 107 again as in step 107. Then, the process proceeds to step # 110.

  In the next step # 110, it is determined whether or not the release button 205 is further pressed and the switch S2 is turned on. If not, the process returns to step # 108 and the calculation result of the acceleration calculation unit 107 drifts. Repeat the work to control. Although not shown, when the switch S1 is turned off in step # 110, the process returns to step # 102.

  Thereafter, when the switch S2 is turned on, the process proceeds from step # 110 to step # 111, and it is determined whether or not the position (focus shake amount) of the focus lens 102 continuously calculated by the acceleration calculation unit 107 is within the in-focus range. . If it is not the in-focus range, the process stays in this step. Thereafter, if it is determined that it is in the in-focus range, the process proceeds to step # 112. Done.

  FIG. 4 is a timing chart showing a series of operations including the reset operation described above. The reset operation will be described using a shake waveform in the focus direction. 4A to 4E, the horizontal axis represents elapsed time. Also, the vertical axis in FIG. 4A indicates the amount of focus shake.

  FIG. 4A shows an actual focus shake waveform 31 of the focus lens 102 and a focus shake waveform 32 that is a second-order integral value obtained by second-order integration of the output of the acceleration sensor 106 by the acceleration calculation unit 107. ing. 4B shows the photoelectric conversion and accumulation operation 33 of the AF sensor 203 and the imaging state determination timing 34 by the lens drive amount calculation unit 204, and FIG. 4C shows the drive waveform of the lens drive unit 103. 35 are shown respectively. Further, FIG. 4D shows the on / off states of the switches S1 and S2 when the release button 205 is pressed, and FIG. 4E shows the photographing availability determination 37 by the imaging control unit 206, respectively.

  Since the second-order integral value obtained by the acceleration calculation unit 107 is unstable in the low frequency region, the output drifts as described above after the focus lens 102 is driven and before focusing is confirmed. However, when the in-focus state is confirmed, the calibration unit 108 sets the second-order integration value by the acceleration calculation unit 107 at that time to zero (zero displacement in the optical axis direction), so that the acceleration second-order integration up to that point is performed. Value drift can be corrected.

  Here, the calculation of the optical axis direction shake waveform 32, which is the second-order integration result by the acceleration calculation unit 107, is started, for example, when the switch S1 is turned on by pressing the release button 205 up to the first stage. Then, accumulation is performed by the AF sensor 203, and a lens drive amount is obtained by the lens drive amount calculation unit 204 based on the accumulation result, and the focus lens 102 is driven. Thereafter, accumulation is performed again by the AF sensor 203, and focusing determination is performed by a camera microcomputer (not shown) based on the result. Then, the deviation component value D due to drift is reduced so that the second-order integral value at the timing B, which is the average time of the accumulation time of the AF sensor 203, is near zero with respect to the timing A when the in-focus is confirmed. It is said that this is reset. This is because the timing at which the focus determination is performed in the lens driving amount calculation unit 204 corrects the delay time that the AF sensor 203 has with respect to the timing at which photoelectric conversion is performed.

  In addition, in macro shooting, for example, with high shooting magnification, the time from turning on the switch S1 to turning on the switch S2 is longer than the time taken to check the focus after the focus lens 102 is driven to focus. It may be necessary. Then, after the initial focus is confirmed and reset once, there is a problem that the second-order integral value of the acceleration sensor 106 drifts again. However, even after the initial in-focus confirmation, the calibration unit 108 refers to the calculation result in the lens driving amount calculation unit 204 sequentially and repeats the reset operation to correct further drift of the acceleration second-order integral value. I can do it. In the reset operation performed between the time when the switch S1 is turned on and the time when the switch S2 is turned on, time A ′ is time A, time B ′ is time B, and drift component value D ′ is drift component. An operation similar to the above-described reset operation is performed in a form corresponding to the value D.

  Thereafter, when the switch S2 is turned on by pressing the release button 109 up to the second stage, when the second-order integral value in the acceleration calculation unit 107 becomes close to zero (in-focus range), the imaging control unit 206 Shooting is permitted, and other values are not permitted.

  Here, the expression “near zero” is because the actual in-focus range changes depending on the shooting conditions (focal length and aperture) at that time. This is because, for example, when the diaphragm is stopped, the photographing permission is determined even if the second-order integral value in the acceleration calculation unit 107 is slightly deviated from zero.

  In this way, the lens driving amount calculation unit 204 and the acceleration calculation unit 107 are configured to cooperate. Therefore, as shown in FIG. 4, for example, it is possible to perform in-focus / out-of-focus determination even after a time shorter than the sampling rate Taf for focus position detection.

  In addition, since shooting is not permitted at the time of out-of-focus, it is possible to reduce the occurrence of out-of-focus photos. Further, even if a long time is required from the switch S1 to the switch S2 being turned on, the calibration unit 108 sequentially refers to the calculation result of the lens driving amount calculation unit 204 and applies a further reset operation, whereby the acceleration calculation unit 107 The divergence of the integral calculation of can be prevented.

  In the above embodiment, the secondary imaging phase difference type AF sensor 203 and the acceleration sensor 106 capable of detecting the acceleration in the direction of the optical axis 104 are provided. Accordingly, the shake in the direction of the optical axis 104 (focus direction) can be continuously detected and used for determination of whether or not photographing is possible. Further, the effect of drift that may occur when detecting the position (fluctuation) of the focus lens 102, which is an example of a moving object, from the acceleration sensor 106 is used using the detection result of the conjugation state obtained using the AF sensor 203. It can be reduced. Therefore, an imaging device that continuously detects an imaging state, suppresses shooting in an out-of-focus state due to vibration in the optical axis direction, and suppresses divergence of computation when obtaining a moving object position detection by acceleration output. can do.

  In the above-described embodiment, the calibration unit 108 sequentially refers to the calculation result of the lens driving amount calculation unit 204 to return the calculation result of the acceleration calculation unit 107 to zero at the time of focusing determination. "Reset".

  However, the present invention is not limited to this, and as a method for the calibration unit 108 to return the calculation result of the acceleration calculation unit 107 to zero, the calculation result of the acceleration calculation unit 107 is calculated at the timing when the calculation result of the lens driving amount calculation unit 204 is calculated. A method of subtracting the bias component to be superposed is also conceivable. That is, the calculation result of the lens driving amount calculation unit 204 that calculates the output of the AF sensor 203 is compared with the calculation result of the acceleration calculation unit 107 at that time, and the difference is subtracted from the calculation result of the acceleration calculation unit 107. . Furthermore, a plurality of calibration methods such as a method in which the acceleration calculation unit 107 initializes the second-order integration of the signal of the acceleration sensor 106 and starts the calculation again at the timing when the focus is determined can be considered.

(Correspondence between Invention and Example)
The focus lens 102 corresponds to an imaging optical system that forms an image of a subject on an imaging unit (imaging unit 207) according to the present invention. The AF sensor 203 and the lens driving amount calculation unit 204 correspond to a focus detection unit that detects a focus state of the imaging optical system according to the present invention. Further, the acceleration sensor 106 and the acceleration calculation unit 107 correspond to an optical axis direction shake calculating means for calculating the optical axis direction shake due to the acceleration acting on the imaging optical system of the present invention. Further, when the lens drive control unit 105 detects the in-focus state by the focus detection unit of the present invention, the optical axis direction shake amount calculated by the optical axis direction shake calculation unit is within the focus range. This corresponds to a determination means. Further, the calibration unit 108 corresponds to a calibration unit that calibrates the optical axis direction shake amount so as to reset the optical axis direction shake amount calculated by the optical axis direction shake calculation unit of the present invention. The calibration unit 108 resets the focus shake amount at the time point before the detection delay time from the time point when the in-focus state is detected to zero.

DESCRIPTION OF SYMBOLS 102 Focus lens 106 Acceleration sensor 107 Acceleration calculating part 108 Calibration part 203 AF sensor 204 Lens drive amount calculating part 206 Imaging control part 207 Imaging part

Claims (3)

An imaging optical system for forming a subject image on the imaging means;
A focus detection means for detecting a focus state of the imaging optical system;
Optical axis direction shake calculating means for calculating optical axis direction shake due to acceleration acting on the imaging optical system;
Calibration means for calibrating the optical axis direction shake amount so as to reset the optical axis direction shake amount calculated by the optical axis direction shake calculation means,
When the focus detection unit detects an in-focus state, imaging is possible when the optical axis direction shake amount calculated by the optical axis direction shake calculation unit is within a focus range. apparatus.   The imaging apparatus according to claim 1, wherein the calibration unit calibrates the shake amount in the optical axis direction when an in-focus state is detected by the focus detection unit.   The imaging apparatus according to claim 2, wherein the calibration unit is reset by setting the shake amount in the optical axis direction at a time point before a detection delay time from a time point when the in-focus state is detected to zero. .

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