JP2016126232A - Imaging apparatus, method for controlling the same, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily correct the ambiguity of a recording image caused by focus detection control.SOLUTION: A camera CPU 156 corrects a defocus amount indicating a difference between a detected focusing position and the position of a focus lens group 103, according to best focus position correction information for correcting out-of-focus caused by the optical aberration of a lens group 101, to acquire the defocus amount after the correction and performs the driving control of the focus lens group, according to the defocus amount after the correction. Further, the camera CPU performs the correction processing of an image obtained in a focusing position on the basis of the best focus position correction information by an image correction part 160, to obtain the image after the correction. The camera CPU selects one of the driving control and the correction control.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus, a control method thereof, a control program, and an imaging apparatus, and more particularly, to an imaging apparatus including a focus detection apparatus that performs focus detection according to a change in contrast of a subject by moving a focus lens.

  In general, autofocus (AF) is known in which a focus state (focus state) is detected and a focus is automatically adjusted in a photographing apparatus such as a digital camera or a video camera. As AF, there is a contrast detection method in which a high-frequency component in a predetermined distance measurement area range is extracted from an image signal that is an output of an image sensor such as a CMOS image sensor, and the contrast value is calculated as a focus evaluation value. In this contrast detection method, the focus position is detected based on the focus evaluation value.

  Also, mainly during moving image shooting, a small periodic displacement is given to the focus lens group to obtain focus evaluation values in a time series (so-called wobbling control). Then, so-called hill-climbing focus position detection control is performed in which feedback control is performed so that the position of the focus lens group having the maximum focus evaluation value becomes the center position of the periodic displacement.

  By the way, in order to perform focus detection at high speed using a contrast detection method, a focus evaluation value may be obtained by thinning out image signals. When such thinning is performed, the spatial frequency band at the time of performing the contrast evaluation is converted to the low frequency side, and a difference occurs in the contrast evaluation as compared with the case of performing the contrast evaluation on the high frequency band side.

  Furthermore, if the optical aberration in the imaging optical system is large, there may be a difference between the spatial frequency band used for contrast evaluation and the spatial frequency band suitable for viewing.

  In either case, there is a difference between the position of the focus lens group (focus position) at which the focus evaluation value is determined to be the maximum in contrast evaluation and the position of the focus lens group optimal in viewing. For this reason, if focus adjustment is emphasized, a clear image cannot be recorded.

  On the other hand, there is an imaging apparatus that corrects the position of a focus lens group by setting a focus correction amount in order to prevent a shift of the focus position (see Patent Document 1).

  Furthermore, there is an imaging apparatus that corrects the focus position when the focus positions detected by a plurality of bandpass filters that extract the spatial frequency of the subject are different (see Patent Document 2).

JP 2000-19384 A JP 2009-175253 A

  The technique described in Patent Document 1 or 2 corrects the focus position by correcting the position of the focus lens group. In still image shooting, since there is an interval from the first shooting operation to the next shooting operation, the focus lens group is positioned at the position where the focus evaluation value is maximized, and then the focus is adjusted to the optimum focus position for viewing. There are few problems in correcting the position of the lens group (best focus position correction).

  The information related to the best focus position correction is stored in, for example, a memory provided in a replaceable photographing optical system or image capturing apparatus. Then, necessary information is read from the memory according to the shooting state (shooting scene) and the best focus position correction has already been performed.

  However, in moving image shooting, as described above, hill-climbing focus position detection control using wobbling control is performed.

  In such a case, in order to correct the focus position, it is necessary to offset the position of the focus lens group by the best focus position correction from the position where the focus evaluation value is maximized. Then, it is necessary to periodically shift the position of the focus lens group with the offset position as the center position.

  However, considering that the position where the focus evaluation value is maximized always changes, it is difficult to offset the position of the focus lens group in real time when focus detection is performed at high speed.

  Further, when the position displacement of the focus lens group is periodically given in the wobbling control, a phenomenon in which a slight focus change is always given when recording a moving image occurs. In order to suppress such a phenomenon, usually, wobbling control is limited to a displacement range that does not cause a problem in viewing.

  However, if the above-described offset process is performed when the displacement amount range in the wobbling control is limited, the position where the focus evaluation value is maximum does not enter the periodic displacement when the correction amount related to the best focus position is large. As a result, feedback control for searching for the maximum focus evaluation value cannot be performed.

  Accordingly, an object of the present invention is to provide an imaging apparatus, a control method thereof, and a control program that can easily correct ambiguity of a recorded image caused by focus detection control.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging optical system including a focus lens, and performs imaging by positioning the focus lens at a focus position. A focus detection unit that detects whether or not the lens is located at a focal position; and a defocus amount that indicates a difference between the focus position detected by the focus detection unit and the position of the focus lens. Drive that corrects according to the best focus position correction information for correcting the focus shift due to aberration, obtains a corrected defocus amount, and drives and controls the focus lens according to the corrected defocus amount Control means, correction control means for correcting the image obtained at the in-focus position based on the best focus position correction information and obtaining a corrected image, and presetting And selection control means for selecting either one of said drive control means and said correction control means in accordance with conditions, and having a.

  A control method according to the present invention is a control method for an imaging apparatus that has an imaging optical system including a focus lens and performs imaging by positioning the focus lens at a focus position, and the focus lens is positioned at the focus position. A focus detection step for detecting whether or not, and a defocus amount indicating a difference between the in-focus position detected in the focus detection step and the position of the focus lens is a focus caused by optical aberration of the imaging optical system. A drive control step of performing drive control of the focus lens according to the corrected defocus amount by obtaining the corrected defocus amount by correcting according to the best focus position correction information for correcting the shift; A correction control step for correcting the image obtained at the in-focus position based on the best focus position correction information to obtain a corrected image; A selection control step for selecting one of the drive control step and the correction control step in accordance with the conditions, and having a.

  A control program according to the present invention is a control program used in an imaging apparatus that has an imaging optical system including a focus lens and performs imaging by positioning the focus lens at a focus position. A focus detection step for detecting whether or not the focus lens is located at a focus position; and a defocus amount indicating a difference between the focus position detected at the focus detection step and the position of the focus lens. The focus lens is corrected according to the best focus position correction information for correcting the focus shift caused by the optical aberration of the image pickup optical system to obtain the corrected defocus amount, and the focus lens according to the corrected defocus amount An image obtained at the in-focus position based on the drive control step for controlling the drive and the best focus position correction information. A correction control step for correcting and obtaining a corrected image, and a selection control step for selecting one of the drive control step and the correction control step according to a preset condition are executed. To do.

  According to the present invention, when it is difficult to correct the position of the focus lens and maintain the best focus state, the image deterioration due to the focus shift is corrected according to the best focus position correction information. Thereby, it is possible to easily correct the ambiguity of the recorded image caused by the focus detection control.

It is a block diagram which shows the structure about an example of the imaging device by embodiment of this invention. 2A and 2B are diagrams for explaining changes in contrast evaluation values when wobbling control is performed in the camera shown in FIG. 1, in which FIG. 1A is an enlarged view of the lens group shown in FIG. 1, and FIG. The figure which shows the change of the contrast evaluation value at the time of performing wobbling control, (C) is a figure which shows the relationship between the peak position of contrast evaluation value, and the best focus position which performed focus position correction, (D) is the best focus position. It is a figure which shows determination of the peak position of the contrast evaluation value at the time of making the best focus position into the center of reciprocation of a focus lens group when the correction amount is large. It is a figure which shows an example of the imaging | photography object image | photographed with the camera shown in FIG. It is a figure for demonstrating an example of an unsharp mask filter process, (A) is a figure which shows the blur image signal which added the blurring component and the original image signal which shows the original image at the time of imaging | photography the imaging | photography object shown in FIG. (B) is a figure which shows the difference signal which shows the difference of an original image signal and a blur image signal, (C) is a figure which shows the correction | amendment image signal obtained by adding a difference signal to an original image signal. It is a figure for demonstrating the correction | amendment image signal at the time of changing an adaptation amount in an unsharp mask filter process, (A) is the original image signal and blur which showed the original image at the time of imaging | photography the imaging | photography object shown in FIG. The figure which shows the blur image signal which added the component, (B) is a figure which shows the difference signal which shows the difference of an original image signal and a blur image signal, (C) was obtained by adding a difference signal to an original image signal It is a figure which shows a correction | amendment image signal. It is a figure for demonstrating the correction | amendment image signal at the time of changing a radius in an unsharp mask filter process, (A) is the original image signal and blur component which show the original image at the time of imaging | photography the imaging | photography object shown in FIG. (B) is a diagram showing a difference signal indicating a difference between the original image signal and the blurred image signal, and (C) is a correction obtained by adding the difference signal to the original image signal. It is a figure which shows an image signal. It is a figure which shows the state from which the maximum value of the contrast evaluation value was obtained in the state which remove | deviated from the best-focus position in the case of viewing in the camera shown in FIG. It is a flowchart for demonstrating an example of the focus detection process performed with the camera shown in FIG.

  Hereinafter, an example of an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an example of an imaging apparatus according to an embodiment of the present invention.

  The illustrated imaging apparatus is, for example, a digital camera (hereinafter simply referred to as a camera), and includes a camera body 150 and an imaging optical system unit (hereinafter referred to as a lens unit) 100. The lens unit 100 can be exchanged for the camera body 150. Note that the illustrated camera is capable of shooting moving images and still images.

  The lens unit 100 includes a lens group 101, and the lens group 101 is provided with a iris diaphragm 102 and a focus lens group 103. The aperture stop of the iris diaphragm 102 is adjusted by the diaphragm diameter driving unit 104 to adjust the light amount. The focus lens group 103 is moved along the optical axis by the focus lens group driving unit 105 to adjust the focal position.

  The focus lens group driving unit 105 and the aperture diameter driving unit 104 are driven and controlled by the lens CPU 106. Then, the lens CPU 106 performs data communication with the camera CPU 156 via the camera transmission unit 151 and the lens transmission unit 109, and controls the focus lens group driving unit 105 and the aperture diameter driving unit 104 according to photometry and distance measurement evaluation described later. Control.

  The lens unit 100 includes an optical system various information memory (first memory) 107. The optical system information memory 107 stores optical characteristic information such as the F value range and the focal length of the lens unit 100 (focal length range in the case of a zoom lens), and identifies the lens unit 100. For example, identification information is stored. These optical characteristic information and identification information are called various optical system information.

  Further, the lens unit 100 includes a best focus position correction information memory (second memory) 108. The best focus position correction information memory 108 stores best focus position correction information related to various optical system information. The best focus position correction information is information for correcting the focus shift caused by the optical aberration of the lens unit 100 that varies according to the F value of the lens unit 100 and the distance of the subject.

  The lens CPU 106 transmits various optical system information and best focus position correction information to the camera CPU 156 via the lens transmission unit 103 and the camera transmission unit 151.

  The camera body 150 is, for example, a single-lens reflex digital camera body. The camera body 150 may be a digital camera body that eliminates the so-called optical viewfinder and confirms an image obtained by the image sensor 152 with an electronic viewfinder.

  In the illustrated example, mechanisms such as an optical viewfinder and a quick return mirror provided in the single-lens reflex camera are omitted. The camera shown in the figure is in a so-called live view state in which the quick return mirror is retracted from the optical axis during focus detection by contrast detection.

  The subject image (optical image) that has passed through the lens group 101 forms an image on the image sensor 152 provided in the camera body 150. The imaging element 152 is an element including, for example, a CMOS image sensor and its peripheral circuit.

  The imaging element 152 has a plurality of light receiving pixels (pixels) arranged in a two-dimensional matrix, and includes, for example, M light receiving pixels in the horizontal direction and N light receiving pixels in the vertical direction (each of M and N). Is an integer of 2 or more. In addition, a Bayer array primary color mosaic filter is formed on-chip on the image sensor 152, and constitutes a so-called two-dimensional single-plate color sensor.

  Although detailed description is omitted here, some of the plurality of light receiving pixels are used as a pair of phase difference detection pixels with different light shielding portions.

  When the image sensor 152 receives the optical image, the image signal extraction unit 153 performs A / D conversion on the output (photoelectric conversion output) of the image sensor and outputs it as an image signal. The focus detection signal extraction unit 154 extracts a signal within a range where focus detection is performed from the imaging signal in accordance with the focus detection method selected by the focus detection method selection unit 155, and generates a focus detection signal.

  At this time, the imaging signal extraction unit 153 sends the signal intensity of the imaging signal to the exposure amount determination unit 158. Then, the exposure amount determination unit 158 determines the exposure amount according to the signal intensity, and drives the image sensor driving unit 159 to adjust the gain of the image sensor 152 as described later.

  The camera CPU 156 controls the entire camera. Here, the camera CPU 156 controls the camera based on a program stored in a ROM (not shown) to execute a series of operations such as a distance measurement calculation process, a shooting process, an image formation process, and a recording process. . The exposure amount determining unit 158 receives the aperture state of the lens unit 100 and the signal intensity of a focus detection signal (to be described later) from the camera CPU 156, and performs the gain adjustment described above.

  The focus detection method selection unit 155 selects either the phase difference focus detection that is the first focus detection method (focus detection method) or the contrast focus detection that is the second focus detection method. When selecting the focus detection method, the focus detection method selection unit 155 receives, for example, the brightness and contrast of the subject in the image from the camera CPU 156, and selects the focus detection method according to the brightness and contrast. Note that the focus detection method selection unit 155 may select a focus detection method according to the setting by the user.

  Further, the focus detection method selection unit 155 obtains a focus position correction amount corresponding to the current shooting state in accordance with the above-described best focus position correction information and determines that image correction is necessary during moving image shooting. The best focus position correction amount is sent to the image correction unit 160.

  The image correction unit 160 corrects image degradation by digital signal processing. In a normal state, the image correction unit 160 outputs the image signal, which is the output of the image signal extraction unit 153, as image data without correction. On the other hand, when the best focus correction amount is received, the image correction unit 160 performs image correction processing on the imaging signal. Here, the image correction unit 160 calculates the strength and adaptive amount of the digital filter based on the best focus correction amount, and performs image correction processing according to the adaptive amount to generate image data. The image data is recorded on a recording medium (not shown) by the image recording unit 161.

  The camera CPU 156 receives the focus detection signal from the focus detection signal extraction unit 154 and sends the focus detection signal to the focus drive amount determination unit 157. The focus amount drive amount determination unit 157 calculates a focus drive amount (hereinafter simply referred to as a focus amount) based on the focus detection signal. At this time, the focus amount determination unit 157 corrects the focus amount by adding a correction amount (best focus correction amount) corresponding to the current shooting situation to the focus amount based on the best focus position correction information 108.

  Note that in the case of moving image shooting in which focus detection is performed by contrast detection, the focus amount determination unit 157 does not add a correction value to the focus amount.

  The focus drive amount determination unit 157 sends the focus amount to the lens CPU 106 via the camera transmission unit 151 and the lens transmission unit 109. The lens CPU 106 controls the focus lens group driving unit 105 according to the focus amount to drive the focus lens group 103 along the optical axis to position the focus lens group 103 at the in-focus position.

  In this way, when focus control is performed on the focus lens group 103, the focus amount is corrected using the best focus position correction information associated with the optical system information, so that the focus control is performed with high accuracy. Can do.

  In the case of still image shooting, when focus control is performed (when in focus), the camera CPU 156 performs a shooting operation. Then, the camera CPU 156 waits until the next shooting instruction is given by the release operation. On the other hand, when the moving image shooting mode or the continuous focus detection mode is set, the camera CPU 156 continuously captures the imaging signal and repeats the process from focus detection to focusing control.

  The best focus position correction information is not necessarily recorded in the lens unit 100. For example, the best focus position correction information related to the plurality of lens units 100 is recorded in the camera body 150, the lens unit 100 attached to the camera body 150 is identified, and the best focus position correction information corresponding to the identification result is used. It may be.

  FIG. 2 is a diagram for explaining a change in contrast evaluation value (that is, a focus evaluation value) when wobbling control is performed in the camera shown in FIG. FIG. 2A is an enlarged view of the lens group 101 shown in FIG. 1, and FIG. 2B is a view showing a change in contrast evaluation value when normal wobbling control is performed. FIG. 2C is a diagram showing the relationship between the peak position of the contrast evaluation value and the best focus position after the focus position correction, and FIG. 2D shows the best focus when the best focus position correction amount is large. It is a figure which shows determination of the peak position of the contrast evaluation value at the time of making a position into the center of reciprocation of a focus lens group.

  In the wobbling control, the contrast of the subject is evaluated while the focus lens group 103 provided in the lens group 101 is reciprocated slightly along the optical axis. Based on the contrast evaluation value, the position of the focus lens group 103 is corrected to the center position of the reciprocating motion at the best focus position.

  In FIG. 2B, the horizontal axis indicates the position (P) of the focus lens group 103, and the vertical axis indicates the contrast evaluation value (H). A contrast evaluation value curve C connecting the contrast evaluation values obtained by the normal wobbling control has a peak position BP.

  At the time of moving image shooting, the focus lens group 103 is moved by feedback control so that the peak position of the contrast evaluation value of the subject obtained by wobbling control becomes the center position of wobbling control.

  In the wobbling control, the range in which the focus lens group 103 is reciprocated is expanded to detect the peak position of the contrast evaluation value. Thus, even when there is a sudden change in the distance between the camera and the subject, it is possible to prevent the peak position of the contrast evaluation value from being out of the contrast detection range. Therefore, the followability at the time of focus detection can be improved.

  However, if the range of the reciprocating motion of the focus lens group 103 is excessively widened, the focus change when the focus lens group 103 is reciprocated becomes large, which may result in an unnatural image. Therefore, it is desirable to reduce the reciprocating range (also referred to as the reciprocal amount) of the focus lens group 103 during wobbling control as much as possible so that the user does not feel unnaturalness during viewing.

  Furthermore, when the peak position of the contrast evaluation value is set to the in-focus state (that is, the in-focus position), the in-focus state may not necessarily match the best in-focus state at the time of viewing the image. Such a mismatch occurs due to a geometrical optical aberration of the lens unit 100 and a blur component due to diffraction. Due to such a cause, a deviation occurs between the best focus position when viewing the image and the peak position of the contrast evaluation value.

  For example, when the contrast evaluation value is obtained by reducing the image by the addition process and the thinning process in order to speed up the calculation process of the contrast evaluation value, the frequency band changes with respect to the original image. As a result, a deviation occurs between the best focus position when viewing the image and the peak position of the contrast evaluation value.

  Further, in order to increase the calculation processing speed and increase the sensitivity of the image, for example, the contrast evaluation value is calculated using only the green pixels from the Bayer array of the image sensor 152. The shift of the focal position will not be considered.

  Furthermore, for an image containing a lot of flare components due to chromatic aberration, it may be better to shift the best focus state at the time of viewing from the peak position of the contrast evaluation value.

  For the reason described above, in order to set the best focus state at the time of viewing, the position at which the best focus state at the time of viewing is obtained from the position of the focus lens group 103 which is the peak position of the contrast evaluation value. In addition, the position of the focus lens group 103 needs to be corrected.

  That is, as described in relation to FIG. 1, the defocus amount corresponding to the focus position correction amount suitable for the current shooting situation is obtained based on the best focus position correction information recorded in the lens unit 100, and the It is necessary to obtain the position correction amount of the focus lens group 103 for obtaining the defocus amount. Then, when taking a still image, taking the position correction amount of the focus lens group 103 into consideration, the focus lens group 103 may be moved for shooting. However, the following problems arise when shooting moving images.

  With reference to FIGS. 2C and 2D, the horizontal axis indicates the position (P) of the focus lens group 103, and the vertical axis indicates the contrast evaluation value (H). A curve C represents a change in contrast evaluation value with respect to the position of the focus lens group 103, and CP represents a peak position of the contrast evaluation value. BP indicates the position of the focus lens group 103 of the best focus that is best for viewing. The best focus position is corrected in accordance with the focus position difference (defocus amount) between the peak position CP and the position BP (best focus position).

  In FIG. 2B, since the peak positions CP and BP are at the same position, the peak position BP () of the contrast evaluation value is changed even when the distance to the subject to be subjected to focus detection is changed during moving image shooting. If the position of the focus lens group 103 is controlled so as to be CP), it is possible to maintain a good in-focus state even during image viewing.

  On the other hand, in FIGS. 2 (C) and 2 (D), the best focus position correction is necessary in order to maintain a good in-focus state during image viewing. FIG. 2C shows the best focus position BP obtained by acquiring the focus position correction amount information according to the current shooting situation and performing the focus position correction from the peak position CP of the contrast evaluation value.

  As described above, in the wobbling control, the reciprocating motion of the focus lens group 103 is controlled based on the peak position of the contrast evaluation value. The reciprocation amount (reciprocating motion range) of the focus lens group 103 is desirably set to a range that does not cause a problem during image viewing.

  In the example shown in FIG. 2C, the peak position C of the contrast evaluation value and the best focus position BP exist in the reciprocating motion range. For this reason, it is necessary to control the best focus position BP to be the center position of the reciprocating motion range of the focus lens group 103 while referring to the peak position C.

  Furthermore, if the best focus position correction amount is large, the peak position of the contrast evaluation value cannot be determined when the best focus position BP is set to the center of the reciprocating range of the focus lens group 103 as shown in FIG. turn into. As a result, the wobbling control cannot be performed.

  Therefore, in order to obtain a sharp image by correcting a blurred image that becomes a problem during moving image shooting, sharp filter processing, which is one of image correction processing, is performed on the image obtained as a result of shooting.

  An example of the sharp filter process is an unsharp mask filter process. In the unsharp mask filter process, a blurred image is generated by giving a two-dimensional Gaussian distribution to an original image to be corrected. Then, the difference between the original image and the blurred image is obtained, and the difference is added to the original image to enhance the edge component.

  FIG. 3 is a diagram illustrating an example of a subject to be photographed by the camera shown in FIG.

  The subject to be photographed shown in FIG. 3 has a white bar chart subject 302 on a black background 301. Assume that the camera shown in FIG. 1 is used to photograph the object to be photographed shown in FIG.

  FIG. 4 is a diagram for explaining the unsharp mask filter processing. 4A is a diagram illustrating an original image signal indicating an original image and a blur image signal to which a blur component is added when the imaging target illustrated in FIG. 3 is captured, and FIG. 4B is an original image signal. It is a figure which shows the difference signal which shows the difference of a blur image signal. FIG. 4C shows a corrected image signal obtained by adding the difference signal to the original image signal.

  In the example shown in FIG. 4A, the signal intensity when the image signal (original image signal) obtained by photographing the subject to be photographed (hereinafter referred to as a chart) shown in FIG. 3 is scanned in the horizontal direction (X direction). The change in P is shown. 4A, OI indicates an original image signal obtained by photographing the chart shown in FIG. 3, and BI indicates a blurred image signal obtained by adding a blur component to the original image signal OI.

  Here, a difference between the original image signal OI and the blurred image signal BI is obtained, and a difference signal indicating the difference is defined as DI (see FIG. 4B).

  When the black-and-white chart shown in FIG. 3 is photographed, if the dynamic range is used up to the limit, the original image signal OI causes overexposure or underexposure and the gradation of the subject is lost. In order to prevent this, a gamma correction process for adjusting the intensity of the image signal is generally performed. Then, the difference signal DI and the original image signal OI are added to enhance the edge component of the blurred image signal. As a result, as shown in FIG. 4C, a corrected image signal HI subjected to sharp correction is obtained, and a sharp image close to the best focus state can be obtained.

  The corrected image signal HI obtained by the above processing is expressed by the following equation (1).

HI = OI + (OI-BI) = OI + DI (1)
As described above, in order to optimize the image signal after performing the unsharp mask filter process on the original image signal, the blurred image signal (that is, the additional image) DI to be added to the original image signal OI. It is necessary to select an appropriate image signal. For this reason, an adaptive variable for adjusting the filter effect is prepared when performing the unsharp mask filter processing.

  The first of the adaptation variables is an adaptation amount for adjusting how much the edge portion is subjected to contrast enhancement. The adaptation amount is obtained by multiplying the signal intensity P of the difference signal DI by a specified magnification (adjustment amount), and adding the difference signal DI whose signal intensity has been changed to the original image signal OI. This is for changing the rising component of the edge portion of the corrected image signal HI after processing.

  The second adaptive variable is a radius indicating an adjustment amount for determining the width of the edge component to be emphasized when emphasizing the edge portion. When the radius is changed, the amount of blur in the horizontal direction (X direction) is adjusted in the blur image signal BI. Therefore, by changing the radius, the blur component can be converted into the edge portion in accordance with the size of the blur portion of the original image signal. The unit of the radius is expressed in pixel pixel units.

  If the above-mentioned adaptive variables are set optimally, an image that has been unsharpened as a result of not correcting the best focus position by image processing can be made an image in which unnaturalness is suppressed during viewing. it can.

  FIG. 5 is a diagram for explaining the corrected image signal when the adaptive amount is changed in the unsharp mask filter processing. FIG. 5A is a diagram showing an original image signal indicating an original image and a blur image signal to which a blur component is added when the subject to be photographed shown in FIG. 3 is captured, and FIG. 5B is an original image signal. It is a figure which shows the difference signal which shows the difference of a blur image signal. FIG. 5C shows a corrected image signal obtained by adding the difference signal to the original image signal.

  FIG. 5A shows an original image signal and a blurred image signal BI similar to those in FIG. In the example shown in FIG. 5B, the adaptation amount is increased. As a result, the difference signal DI1 has a larger amplitude in the direction of intensity P than the difference signal DI shown in FIG. 4B. . As a result, as shown in FIG. 5C, the corrected image signal HI1 reaches the upper and lower limits of the dynamic range range by the gamma correction process with the rising and falling edges of the edge being emphasized.

  Therefore, the white portion is in a whiteout state at the boundary between the black background 301 of the chart shown in FIG. 3 and the subject 302 of the white bar chart. Furthermore, the black portion at the boundary is in a blackened state, resulting in an unnatural image with an excessively emphasized outline.

  FIG. 6 is a diagram for explaining the corrected image signal when the radius is changed in the unsharp mask filter process. FIG. 6A is a diagram showing an original image signal indicating an original image and a blur image signal to which a blur component is added when the subject to be photographed shown in FIG. 3 is captured, and FIG. 6B is an original image signal. It is a figure which shows the difference signal which shows the difference of a blur image signal. FIG. 6C shows a corrected image signal obtained by adding the difference signal to the original image signal.

  FIG. 6A shows an original image signal and a blurred image signal BI similar to those in FIG. In the example shown in FIG. 6B, as a result of increasing the radius, the difference signal DI2 is expanded in the X direction with respect to the difference signal DI shown in FIG. 4B. Thus, the image correction range is expanded with respect to the spread range of the blurred image signal.

  As a result, when the blurred state in the blurred image signal is large, it is possible to correct the edge portion where the skirt is widened due to the blur by increasing the radius. On the other hand, in the case of a blurred image signal in which the edge portion is too wide and the edge portion is adjacent, the interval between the adjacent edge portions is narrowed, and the fineness may be lost in the corrected image signal HI2.

  As described above, in the unsharp mask processing, if the adjustment amount such as the adaptation amount and the radius is appropriately set, the best focus position correction processing cannot be performed by correcting the focus position of the focus lens group 103. It is possible to correct the image.

  FIG. 7 is a diagram showing a state in which the maximum contrast evaluation value is obtained when the camera shown in FIG. 1 is out of the best focus position during viewing.

  In the illustrated example, a state in which a subject image is formed on the imaging surface IMG of the imaging element 152 when the subject OBJ is photographed by the camera shown in FIG. In this case, the maximum contrast evaluation value is obtained in a state of being out of the best focus position at the time of viewing.

  The size D of the blurred image is mainly caused by the optical aberration and diffraction of the lens group 101. If the F value (or effective F value) of the lens group 101 is known, the ray angle ω of the subject image incident on the imaging surface IMG can be derived. Therefore, the defocus amount L corresponding to the size (blur amount) D of the blurred image can be predicted. The defocus amount L is corrected in accordance with the best focus position correction information described with reference to FIG. That is, if the best focus position correction information corresponding to the various optical system information is obtained, the blur amount D can be calculated based on the light beam angle ω and the defocus amount L shown in FIG.

  Here, since the blur amount D indicates the degree of spread of the blur, the number of pixels corresponding to the blur image can be obtained according to the pixel pitch of the image sensor 152. Therefore, the number of pixels may be used as a reference value for determining the radius as the adjustment amount. Since the deterioration state of the edge component can be estimated from the blur amount D, the adaptive amount that is an adjustment value can also be estimated.

  Here, when obtaining the adjustment amount according to the best focus position correction information, the blur amount D is calculated based on the best focus position correction information. However, for example, the unfocus corresponding to the best focus position correction information is calculated. Reference data relating to the adjustment amount of the sharp mask process may be stored in advance in the memory, and the adjustment amount may be obtained based on the best focus position correction information at the time of shooting.

  In this way, when the best focus position cannot be corrected in real time by wobbling control during moving image shooting, the best focus position correction information is used as reference information for determining the adjustment amount of the image correction filter. As a result, a good image can be obtained during viewing.

  FIG. 8 is a flowchart for explaining an example of focus detection processing performed by the camera shown in FIG. Here, focus detection and focusing processing when shooting and recording a moving image will be described.

  When the focus detection process is started, the camera CPU 156 acquires shooting information indicating the focal length, the F value, and the current position of the focus lens group 103 related to the lens group 101 from the lens CPU 106 (step S101). Then, the camera CPU 156 acquires the best focus position correction value information corresponding to the shooting information from the lens CPU 106 (step S102).

  Subsequently, the camera CPU 156 determines whether or not the current focus detection method is a contrast detection method (step S103). That is, the camera CPU 156 determines whether or not the focus detection method is a preset condition. If the current focus detection method is not the contrast detection method (NO in step S103), that is, if it is the phase difference detection method, the camera CPU 156 determines the A image (first image) according to the phase difference signal that is a focus detection signal. The correlation between the image) and the B image (second image) is obtained (step S104). Then, the camera CPU 156 calculates a defocus amount according to the correlation calculation result obtained in step S104 (step S105).

  Next, the camera CPU 156 performs addition processing for adding the correction amount indicated by the best focus position correction information to the defocus amount obtained in step S105 (step S106). Then, the camera CPU 156 gives the corrected defocus amount to the focus drive amount determination unit 157. The focus drive amount determination unit 157 determines the drive amount (focus drive amount) of the focus lens group 103 based on the corrected defocus amount, and sends the focus drive amount to the lens CPU 106. The focus lens group driving unit 105 is controlled according to the lens CPU 106 focus drive amount to drive the defocus lens group 103 to the in-focus position (step S107).

  If the current focus detection method is the contrast detection method (YES in step S103), the camera CPU 156 controls the focus lens group driving unit 105 by the lens CPU 106 to perform a so-called hill-climbing focus detection operation, and the focus evaluation value is The focus lens group is moved to the maximum position (step S108).

  Subsequently, the camera CPU 156 determines an adjustment amount when performing the image correction process based on the best focus position correction information. That is, the camera CPU 156 determines the sharp filter characteristic based on the best focus position correction information (step S109). Then, the camera CPU 156 performs image correction processing using the unsharp mask processing described above, for example, by the image correction unit 160 (step S110).

  After the processing in step S107 or S110, the camera CPU 156 records an image obtained as a result of shooting by the image recording unit 161 on a recording medium (step S111). Then, the camera CPU 156 determines whether or not an image recording end operation has been performed by the user (step S112).

  If the image recording end operation has not been performed (NO in step S112), the camera CPU 156 returns to the process of step S101. On the other hand, when the image recording end operation is performed (YES in step S112), the camera CPU 156 ends the focus detection process.

  Although the case where image correction processing is performed on a moving image has been described here, the present invention can also be applied to a case where wobbling control is performed in so-called high-speed continuous shooting in which still images are continuously shot.

  As described above, in the embodiment of the present invention, when focus is performed using the contrast detection method, the adjustment amount for performing image correction is determined using the best focus position correction information recorded in the lens unit 100. Therefore, it is possible to obtain a good image that can be appreciated.

  As is clear from the above description, in the example shown in FIG. 1, the imaging signal extraction unit 153 and the focus detection signal extraction unit 154 function as focus detection means, and the camera CPU 156, the focus drive amount determination unit 157, the lens CPU 106, The focus lens group driving unit 105 functions as a drive control unit. The camera CPU 156 and the image correction unit 160 function as a correction control unit, and the focus detection method selection unit 155 and the camera CPU 156 function as a selection control unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 101 Lens group 103 Focus lens group 105 Focus lens group drive part 106 Lens CPU
152 Image Sensor 154 Focus Detection Signal Extraction Unit 155 Focus Detection Method Selection Unit 156 Camera CPU
157 Focus drive amount determination unit 160 Image correction unit

Claims (7)

An imaging apparatus having an imaging optical system including a focus lens, and performing imaging by positioning the focus lens at a focus position,
Focus detection means for detecting whether or not the focus lens is located at a focus position;
Best focus position correction information for correcting the defocus amount indicating the difference between the in-focus position detected by the focus detection unit and the position of the focus lens, and defocusing caused by optical aberration of the imaging optical system And a drive control means for obtaining a defocus amount after correction and obtaining a defocus amount after correction, and driving and controlling the focus lens in accordance with the defocus amount after correction.
Correction control means for correcting the image obtained at the in-focus position based on the best focus position correction information to obtain a corrected image;
A selection control means for selecting one of the drive control means and the correction control means according to a preset condition;
An imaging device comprising:   The selection control means uses a focus detection method used by the focus detection means as the preset condition, and selects either the drive control means or the correction control means according to the focus detection method. The imaging apparatus according to claim 1, wherein the imaging apparatus is characterized.   The selection control means selects the drive control means when the focus detection method is a phase difference detection method, and selects the correction control means when the focus detection method is a contrast detection method. The imaging device according to claim 2.   The said correction control means determines the adjustment amount which correct | amends the said image based on the said best focus position correction information using an unsharp mask process, The any one of Claims 1-3 characterized by the above-mentioned. Imaging device.   The imaging apparatus according to claim 1, wherein the selection unit selects the correction control unit when recording the corrected image. A control method of an image pickup apparatus that has an image pickup optical system including a focus lens and performs shooting by positioning the focus lens at a focus position,
A focus detection step for detecting whether or not the focus lens is located at a focus position;
Best focus position correction information for correcting the defocus amount indicating the difference between the in-focus position detected in the focus detection step and the position of the focus lens, and defocusing caused by optical aberration of the imaging optical system And a drive control step for driving and controlling the focus lens in accordance with the corrected defocus amount.
A correction control step of correcting the image obtained at the in-focus position based on the best focus position correction information to obtain a corrected image;
A selection control step for selecting one of the drive control step and the correction control step according to a preset condition;
A control method characterized by comprising: A control program used in an imaging apparatus that has an imaging optical system including a focus lens and performs imaging by positioning the focus lens at a focus position,
In the computer provided in the imaging device,
A focus detection step for detecting whether or not the focus lens is located at a focus position;
Best focus position correction information for correcting the defocus amount indicating the difference between the in-focus position detected in the focus detection step and the position of the focus lens, and defocusing caused by optical aberration of the imaging optical system And a drive control step for driving and controlling the focus lens in accordance with the corrected defocus amount.
A correction control step of correcting the image obtained at the in-focus position based on the best focus position correction information to obtain a corrected image;
A selection control step for selecting one of the drive control step and the correction control step according to a preset condition;
A control program characterized by causing