JP6744933B2 - Lens part and its control method - Google Patents

Description

The present invention relates to a lens unit that is attachable to and detachable from an image pickup apparatus (or image pickup unit) having an image pickup element, and a control method thereof.

A contrast AF method and a phase difference AF method are known as automatic focus detection (AF) methods of an image pickup apparatus. Both the contrast AF method and the phase-difference AF method are AF methods often used in video cameras and digital still cameras, and there are some in which an image sensor is used as a focus detection sensor.

Since these AF methods perform focus detection using an optical image, the aberration of the optical system that forms the optical image may give an error to the focus detection result, and there is a method for reducing such an error. Proposed.

In Patent Document 1, reference correction data that defines a combination of a plurality of representative values is prepared for each of the AF frame, the focal length, the AF evaluation frequency, and the distance to the subject, and the reference correction data is interpolated according to actual conditions. A method of correcting the focus detection result with the correction data is disclosed.

Japanese Patent No. 5087077

However, the method of Patent Document 1 in which the focus detection result is corrected using the correction value suitable for the AF evaluation frequency peculiar to the camera body has a problem that the focus detection error cannot be sufficiently corrected. The focus detection error is essentially the difference between the focus state in which the observer feels that the captured image is in the best focus state and the focus state indicated by the focus detection result. However, the method described in Patent Document 1 does not consider the focus state of the captured image.

The AF evaluation frequency in Patent Document 1 represents the spatial frequency characteristic of a single frequency. However, the band actually evaluated by the focus detection has a frequency bandwidth and does not represent only a single frequency characteristic.

The present invention is directed to overcoming one or more of the problems of the prior art. Specifically, it is an object of the present invention to provide a lens unit that enables an imaging apparatus to accurately correct a focus detection error and a control method thereof.

The above-mentioned object is a lens unit that is configured to be attachable to and detachable from an image pickup unit having an image pickup element, and has a photographing optical system, and stores information regarding an MTF curve regarding an imaging position of the photographing optical system for a plurality of different spatial frequencies. Storage means and a transmission means for transmitting information to the image pickup section in response to a request from the image pickup section, and the information stored in the storage section is weighted according to the spatial frequency. Instead, the information transmitted from the lens unit to the image capturing unit is achieved by the lens unit characterized in that the image capturing unit performs weighted addition according to the spatial frequency.

With such a configuration, according to the present invention, it is possible to provide a lens unit and a control method thereof that enable the imaging device to accurately correct a focus detection error.

Flowchart showing AF operation in the embodiment Flowchart showing AF operation in the embodiment Block diagram of a digital camera as an example of an imaging apparatus according to an embodiment FIG. 3 is a diagram showing a configuration example of an image sensor according to the embodiment. The figure which shows the relationship between the photoelectric conversion area|region and exit pupil in embodiment. Block diagram of the TVAF unit 130 of FIG. The figure which shows the example of the focus detection area in embodiment. Flow chart of vertical and horizontal BP correction value (BP1) calculation processing in the embodiment FIG. 3 is a diagram for explaining a vertical/horizontal BP correction value calculation process in the embodiment. FIG. 3 is a diagram for explaining a color BP correction value (BP2) calculation process in the embodiment. The figure for demonstrating the spatial frequency BP correction value (BP3) calculation process in 1st Embodiment. The figure which shows various spatial frequency characteristics in embodiment The figure for demonstrating the spatial frequency BP correction value (BP3) calculation process in 2nd Embodiment. Flowchart for explaining the spatial frequency BP correction value (BP3) calculation processing in the third embodiment

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the embodiment has a specific and specific configuration in order to facilitate understanding and description of the invention, but the present invention is not limited to such a specific configuration. For example, an embodiment in which the present invention is applied to a lens interchangeable single-lens reflex type digital camera will be described below, but the present invention is also applicable to a lens interchangeable type digital camera and a video camera. It can also be implemented in any electronic device equipped with a camera, such as a mobile phone, a personal computer (laptop, tablet, desktop type, etc.), a game machine, or the like.

● (First embodiment)
(Description of Configuration of Imaging Device-Lens Unit)
FIG. 2 is a block diagram illustrating a functional configuration example of a digital camera as an example of the image pickup apparatus according to the embodiment. The digital camera of this embodiment is an interchangeable-lens single-lens reflex camera, and includes a lens unit 100 and a camera body 120. The lens unit 100 is attached to the camera body 120 via a mount M shown by a dotted line in the center of the figure.

The lens unit 100 has an optical system (first lens group 101, diaphragm 102, second lens group 103, focus lens group (hereinafter simply referred to as “focus lens”) 104), and a drive/control system. As described above, the lens unit 100 is a photographing lens that includes the focus lens 104 and forms an optical image of a subject.

The first lens group 101 is arranged at the tip of the lens unit 100, and is held so as to be movable in the optical axis direction OA. The diaphragm 102 functions as a mechanical shutter that controls the exposure time during still image shooting, in addition to the function of adjusting the amount of light during shooting. The diaphragm 102 and the second lens group 103 are integrally movable in the optical axis direction OA, and a zoom function is realized by moving in conjunction with the first lens group 101. The focus lens 104 is also movable in the optical axis direction OA, and the subject distance (focus distance) on which the lens unit 100 focuses is changed depending on the position. By controlling the position of the focus lens 104 in the optical axis direction OA, focus adjustment for adjusting the focusing distance of the lens unit 100 is performed.

The drive/control system includes a zoom actuator 111, an aperture actuator 112, a focus actuator 113, a zoom drive circuit 114, an aperture stop drive circuit 115, a focus drive circuit 116, a lens MPU 117, and a lens memory 118.

The zoom drive circuit 114 drives the first lens group 101 and the third lens group 103 in the optical axis direction OA using the zoom actuator 111, and controls the angle of view of the optical system of the lens unit 100. The diaphragm driving circuit 115 drives the diaphragm 102 using the diaphragm actuator 112, and controls the aperture diameter and the opening/closing operation of the diaphragm 102. The focus drive circuit 116 drives the focus lens 104 in the optical axis direction OA using the focus actuator 113, and controls the focusing distance of the optical system of the lens unit 100. Further, the focus drive circuit 116 detects the current position of the focus lens 104 using the focus actuator 113.

A lens MPU (processor) 117 performs all calculations and controls related to the lens unit 100, and controls the zoom drive circuit 114, the diaphragm drive circuit 115, and the focus drive circuit 116. Further, the lens MPU 117 is connected to the camera MPU 125 through the mount M and communicates commands and data. For example, the lens MPU 117 detects the position of the focus lens 104, and notifies the lens position information to the request from the camera MPU 125. This lens position information includes the position of the focus lens 104 in the optical axis direction OA, the position and diameter of the exit pupil in the optical axis direction OA when the optical system is not moving, and the optical axis of the lens frame that limits the luminous flux of the exit pupil. It includes information such as position and diameter in direction OA. The lens MPU 117 also controls the zoom drive circuit 114, the diaphragm drive circuit 115, and the focus drive circuit 116 in response to a request from the camera MPU 125. Optical information necessary for automatic focus detection is stored in the lens memory 118 in advance. The camera MPU 125 controls the operation of the lens unit 100 by executing a program stored in, for example, a built-in nonvolatile memory or the lens memory 118.

(Description of the configuration of the imaging device-camera body)
The camera body 120 has an optical system (optical low-pass filter 121 and image sensor 122) and a drive/control system. The first lens group 101, the diaphragm 102, the second lens group 103, the focus lens 104 of the lens unit 100, and the optical low-pass filter 121 of the camera body 120 form a photographic optical system.
The optical low-pass filter 121 reduces false color and moire in a captured image. The image sensor 122 is composed of a CMOS image sensor and peripheral circuits, and has m pixels in the horizontal direction and n pixels in the vertical direction (n and m are integers of 2 or more). The image sensor 122 of the present embodiment has a pupil division function and is capable of phase difference AF using image data. The image processing circuit 124 generates data for phase difference AF and image data for display, recording, and contrast AF (TVAF) from the image data output by the image sensor 122.

The drive/control system includes a sensor drive circuit 123, an image processing circuit 124, a camera MPU 125, a display 126, an operation switch group 127, a memory 128, a phase difference AF section 129, and a TVAF section 130.

The sensor drive circuit 123 controls the operation of the image sensor 122, A/D-converts the acquired image signal, and transmits the image signal to the camera MPU 125. The image processing circuit 124 performs general image processing performed by a digital camera, such as γ conversion, white balance adjustment processing, color interpolation processing, and compression encoding processing on the image data acquired by the image sensor 122. The image processing circuit 124 also generates a signal for phase difference AF.

The camera MPU (processor) 125 performs all calculations and controls related to the camera body 120, and includes a sensor drive circuit 123, an image processing circuit 124, a display 126, an operation switch group 127, a memory 128, a phase difference AF unit 129, and TVAF. The unit 130 is controlled. The camera MPU 125 is connected to the lens MPU 117 via the signal line of the mount M, and communicates commands and data with the lens MPU 117. The camera MPU 125 issues, to the lens MPU 117, a lens position acquisition request, a diaphragm, focus lens, and zoom drive request at a predetermined drive amount, an optical information acquisition request unique to the lens unit 100, and the like. The camera MPU 125 includes a ROM 125a that stores a program for controlling the camera operation, a RAM 125b that stores variables, and an EEPROM 125c that stores various parameters.

The display 126 is composed of an LCD or the like, and displays information about the shooting mode of the camera, a preview image before shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. The operation switch group 127 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The memory 128 as a recording unit of the present embodiment is a removable flash memory and records a captured image.

The phase difference AF unit 129 performs focus detection processing by the phase difference detection method using the focus detection data obtained by the image processing circuit 124. More specifically, the image processing circuit 124 generates, as focus detection data, a pair of image data formed by a light flux passing through a pair of pupil regions of the photographing optical system, and the phase difference AF unit 129 sets the pair of image data. The focus shift amount is detected based on the shift amount of the image data. In this way, the phase difference AF unit 129 of the present embodiment performs phase difference AF (imaging plane phase difference AF) based on the output of the image sensor 122 without using a dedicated AF sensor. The operation of the phase difference AF section 129 will be described later in detail.

The TVAF unit 130 performs a contrast focus detection process based on the TVAF evaluation value (contrast information of image data) generated by the image processing circuit 124. In the focus detection processing of the contrast method, the focus lens 104 is moved and the focus lens position at which the evaluation value reaches a peak is detected as the focus position.
As described above, the digital camera according to the present embodiment can perform both the phase difference AF and the TVAF, and can be selectively used or used in combination depending on the situation.

(Explanation of focus detection operation: phase difference AF)
The operations of the phase difference AF section 129 and the TVAF section 130 will be further described below.
First, the operation of the phase difference AF section 129 will be described.
FIG. 3A is a diagram showing a pixel array of the image sensor 122 according to the present embodiment. The two-dimensional C-MOS area sensor has six rows in the vertical direction (Y direction) and eight columns in the horizontal direction (X direction). The state observed from the unit 100 side is shown. The image sensor 122 is provided with a Bayer array color filter. The pixels in odd rows are alternately arranged with the color filters of green (G) and red (R) from the left, and the pixels in even rows are arranged in order from the left. Blue (B) and green (G) color filters are alternately arranged. In the pixel 211, a circle 211i represents an on-chip microlens, and a plurality of rectangles 211a and 211b arranged inside the on-chip microlens are photoelectric conversion units.

In the image sensor 122 of this embodiment, the photoelectric conversion units of all pixels are divided into two in the X direction, and the photoelectric conversion signals of the individual photoelectric conversion units and the sum of the photoelectric conversion signals can be read independently. Further, by subtracting the photoelectric conversion signal of one photoelectric conversion unit from the sum of the photoelectric conversion signals, a signal corresponding to the photoelectric conversion signal of the other photoelectric conversion unit can be obtained. The photoelectric conversion signal in each photoelectric conversion unit can be used as data for phase difference AF, or can be used for generating a parallax image forming a 3D (3-Dimensional) image. The sum of photoelectric conversion signals can be used as normal captured image data.

Here, a pixel signal when performing the phase difference AF will be described. As will be described later, in the present embodiment, the microlens 211i of FIG. 3A and the divided photoelectric conversion units 211a and 211b divide the exit light flux of the photographing optical system into pupils. Then, with respect to a plurality of pixels 211 arranged in the same pixel row within a predetermined range, the output of the photoelectric conversion unit 211a is connected and knitted, and the A image for AF and the output of the photoelectric conversion unit 211b are connected and knitted. Let B be an image for AF. As outputs of the photoelectric conversion units 211a and 211b, pseudo luminance (Y) signals calculated by adding outputs of green, red, blue, and green included in the unit array of the color filter are used. However, the AF A image and B image may be organized for each of red, blue, and green colors. By detecting the relative image shift amount between the AF A image and the B image thus generated by the correlation calculation, the focus shift amount (defocus amount) in the predetermined area can be detected. In the present embodiment, the sum of the output of one photoelectric conversion unit and the output of all photoelectric conversion units is read from the image sensor 122. For example, when the output of the photoelectric conversion unit 211a and the sum of the outputs of the photoelectric conversion units 211a and 211b are read, the output of the photoelectric conversion unit 211b is obtained by subtracting the output of the photoelectric conversion unit 211a from the sum. Thereby, both the A image for AF and the B image can be obtained, and the phase difference AF can be realized. Such an image sensor is publicly known as disclosed in Japanese Unexamined Patent Application Publication No. 2004-134867, and a detailed description thereof will be omitted.

FIG. 3B is a diagram showing a configuration example of the readout circuit of the image sensor 122 of this embodiment. Reference numeral 151 is a horizontal scanning circuit, and 153 is a vertical scanning circuit. Then, horizontal scanning lines 152a and 152b and vertical scanning lines 154a and 154b are wired at the boundary of each pixel, and each photoelectric conversion unit reads out a signal to the outside via these scanning lines.

The image sensor of the present embodiment has the following two types of read modes in addition to the above-described in-pixel read method. The first read mode is called the all-pixel read mode and is a mode for capturing a high-definition still image. In this case, the signals of all pixels are read out.
The second reading mode is called a thinning-out reading mode, and is a mode for only recording a moving image or displaying a preview image. In this case, since the number of pixels required is less than all the pixels, the pixel group reads only the pixels thinned out at a predetermined ratio in both the X and Y directions. Also, when it is necessary to read at high speed, the thinning-out reading mode is used similarly. When thinning out in the X direction, signals are added to improve the S/N, and in thinning out in the Y direction, the signal output of the thinned row is ignored. The phase difference AF and the contrast AF are also usually performed based on the signals read in the second read mode.

FIG. 4 is a diagram for explaining the conjugate relationship between the exit pupil plane of the photographing optical system and the photoelectric conversion unit of the image pickup element arranged near the center of the image plane at zero image height in the image pickup apparatus according to the present embodiment. The photoelectric conversion unit in the image sensor and the exit pupil plane of the photographing optical system are designed to have a conjugate relationship by an on-chip microlens. The exit pupil of the photographing optical system generally coincides with the surface on which the iris diaphragm for adjusting the light amount is placed. On the other hand, the photographing optical system of the present embodiment is a zoom lens having a variable magnification function, but depending on the optical type, when the variable magnification operation is performed, the distance and size of the exit pupil from the image plane change. FIG. 4 shows a state in which the focal length of the lens unit 100 is at the center between the wide-angle end and the telephoto end. With the exit pupil distance Zep in this state as a standard value, the shape of the on-chip microlens and the optimum design of the eccentricity parameter according to the image height (X, Y coordinates) are performed.

In FIG. 4A, 101 is a first lens group, 101b is a lens barrel member holding the first lens group, 105 is a third lens group, and 104b is a lens barrel member holding the focus lens 104. Reference numeral 102 is a diaphragm, 102a is an aperture plate that defines the opening diameter when the diaphragm is opened, and 102b is a diaphragm blade for adjusting the opening diameter when the diaphragm is narrowed down. It should be noted that 101b, 102a, 102b, and 104b that act as a member for restricting the light flux that passes through the imaging optical system represent optical virtual images when observed from the image plane. Further, the synthetic aperture in the vicinity of the diaphragm 102 is defined as the exit pupil of the lens, and the distance from the image plane is Zep as described above.

The pixel 211 is arranged near the center of the image plane, and is called the central pixel in this embodiment. The central pixel 211 is composed of the photoelectric conversion units 211a and 211b, the wiring layers 211e to 211g, the color filter 211h, and the on-chip microlens 211i from the lowermost layer. Then, the two photoelectric conversion units are projected on the exit pupil plane of the photographing optical system by the on-chip microlens 211i. In other words, the exit pupil of the photographing optical system is projected on the surface of the photoelectric conversion unit via the on-chip microlens 211i.

FIG. 4B shows a projected image of the photoelectric conversion unit on the exit pupil plane of the photographing optical system. The projected images of the photoelectric conversion units 211a and 211b are EP1a and EP1b, respectively. Further, in the present embodiment, the image pickup element has a pixel that can obtain an output of either one of the two photoelectric conversion units 211a and 211b and an output of the sum of both. The output of the sum of both is obtained by photoelectrically converting the light flux that has passed through both regions of the projection images EP1a and EP1b, which are almost the entire pupil region of the photographing optical system.

In FIG. 4A, when the outermost part of the light flux passing through the photographing optical system is indicated by L, the light flux L is regulated by the aperture plate 102a of the diaphragm, and the projected images EP1a and EP1b are vignetting by the photographing optical system. Almost no occurrence. In FIG. 4B, the light flux L of FIG. 4A is indicated by TL. Since most of the projected images EP1a and EP1b of the photoelectric conversion unit are included inside the circle indicated by TL, it can be seen that vignetting does not substantially occur. Since the light flux L is limited only by the aperture plate 102a of the diaphragm, the TL can be restated as 102a. At this time, in the center of the image plane, the vignetting states of the projected images EP1a and EP1b are symmetrical with respect to the optical axis, and the amounts of light received by the photoelectric conversion units 211a and 211b are equal.

When performing the phase difference AF, the camera MPU 125 controls the sensor drive circuit 123 so as to read the above-mentioned two types of outputs from the image sensor 122. Then, the camera MPU 125 gives information of the focus detection area to the image processing circuit 124, generates AF image A and B image data from the output of the pixels included in the focus detection area, and outputs the phase difference AF unit 129. To supply to. The image processing circuit 124 generates AF A image data and B image data in accordance with this instruction and outputs the data to the phase difference AF unit 129. The image processing circuit 124 also supplies the RAW image data to the TVAF unit 130.

As described above, the image sensor 122 constitutes a part of the focus detection device for both the phase difference AF and the contrast AF.
Note that, here, as an example, the configuration in which the exit pupil is divided into two in the horizontal direction has been described, but for some pixels of the image sensor, the exit pupil may be divided into two in the vertical direction. Further, the exit pupil may be divided into both horizontal and vertical directions. By providing the pixels that divide the exit pupil in the vertical direction, phase difference AF corresponding to the contrast of the subject in the vertical direction as well as the horizontal direction becomes possible.

(Explanation of focus detection operation: contrast AF)
Next, the contrast AF (TVAF) will be described with reference to FIG. The contrast AF is realized by the camera MPU 125 and the TVAF unit 130 working together to repeatedly drive the focus lens and calculate the evaluation value.

When the RAW image data is input from the image processing circuit 124 to the TVAF unit 130, the AF evaluation signal processing circuit 401 extracts the green (G) signal from the Bayer array signal and emphasizes the low luminance component to obtain high luminance. Gamma correction processing is performed to suppress the component. In this embodiment, the case where TVAF is performed with a green (G) signal will be described, but all signals of red (R), blue (B), and green (G) may be used. Alternatively, the luminance (Y) signal may be generated using all RGB colors. The output signal generated by the AF evaluation signal processing circuit 401 is referred to as a luminance signal Y in the following description regardless of the type of signal used.

It is assumed that the focus detection area is set in the area setting circuit 413 from the camera MPU 125. The area setting circuit 413 generates a gate signal that selects a signal within the set area. The gate signal is input to each of the line peak detection circuit 402, horizontal integration circuit 403, line minimum value detection circuit 404, line peak detection circuit 409, vertical integration circuits 406 and 410 vertical peak detection circuits 405, 407, and 411. .. The timing at which the brightness signal Y is input to each circuit is controlled so that each focus evaluation value is generated by the brightness signal Y in the focus detection area. A plurality of areas can be set in the area setting circuit 413 according to the focus detection area.

A method of calculating the Y peak evaluation value will be described. The gamma-corrected luminance signal Y is input to the line peak detection circuit 402, and the Y line peak value for each horizontal line is obtained within the focus detection area set by the area setting circuit 413. The output of the line peak detection circuit 402 is peak-held in the vertical direction in the focus detection area in the vertical peak detection circuit 405, and a Y peak evaluation value is generated. The Y peak evaluation value is an index effective for determining a high-luminance subject or a low-illuminance subject.

A method of calculating the Y integral evaluation value will be described. The gamma-corrected luminance signal Y is input to the horizontal integration circuit 403, and the integrated value of Y is obtained for each horizontal line in the focus detection area. Further, the output of the horizontal integration circuit 403 is vertically integrated in the focus detection area in the vertical integration circuit 406 to generate a Y integration evaluation value. The Y integration evaluation value can be used as an index for determining the brightness of the entire focus detection area.

A method of calculating the Max-Min evaluation value will be described. The gamma-corrected luminance signal Y is input to the line peak detection circuit 402, and the Y line peak value for each horizontal line is obtained in the focus detection area. The gamma-corrected luminance signal Y is input to the line minimum value detection circuit 404, and the minimum value of Y is detected for each horizontal line in the focus detection area. The detected line peak value and minimum value of Y for each horizontal line are input to the subtractor, and (line peak value-minimum value) is input to the vertical peak detection circuit 407. The vertical peak detection circuit 407 performs peak hold in the vertical direction within the focus detection area to generate a Max-Min evaluation value. The Max-Min evaluation value is an index effective for determining low contrast and high contrast.

A method of calculating the area peak evaluation value will be described. The gamma-corrected luminance signal Y is passed through the BPF 408 to extract a specific frequency component and generate a focus signal. This focus signal is input to the line peak detection circuit 409, and the line peak value for each horizontal line is obtained within the focus detection area. The line peak value is peak-held in the focus detection area by the vertical peak detection circuit 411, and the area peak evaluation value is generated. The area peak evaluation value has little change even when the subject moves within the focus detection area, and is therefore an index effective for restart determination for determining whether or not to shift to the processing for searching the focused point again from the focused state.

A method of calculating the total line integral evaluation value will be described. Similar to the area peak evaluation value, the line peak detection circuit 409 obtains a line peak value for each horizontal line in the focus detection area. Next, the line peak value is input to the vertical integration circuit 410 and integrated in the vertical direction within the focus detection area for all the horizontal scanning lines to generate the total line integration evaluation value. The all-line integral evaluation value is a main AF evaluation value because it has a wide dynamic range and high sensitivity due to the effect of integration. Therefore, in this embodiment, when simply described as the focus evaluation value, it means the all-line integral evaluation value.

The AF control unit 151 of the camera MPU 125 acquires each of the focus evaluation values described above, and moves the focus lens 104 through the lens MPU 117 in the predetermined direction along the optical axis direction by a predetermined amount. Then, the above-described various evaluation values are calculated based on the newly obtained image data, and the focus lens position where the total line integral evaluation value becomes the maximum value is detected.

In the present embodiment, various AF evaluation values are calculated in the horizontal line direction and the vertical line direction. As a result, focus detection can be performed on the contrast information of the subject in two directions that are orthogonal to each other horizontally and vertically.

(Explanation of focus detection area)
FIG. 6 is a diagram showing an example of the focus detection area in the shooting range. As described above, both the phase difference AF and the contrast AF are performed based on the signals obtained from the pixels included in the focus detection area. In FIG. 6, a rectangle indicated by a dotted line indicates a shooting range 217 in which pixels of the image sensor 122 are formed. Focus detection areas 218ah, 218bh, and 218ch for phase difference AF are set in the shooting range 217. In this embodiment, the focus detection areas 218ah, 218bh, and 218ch for phase difference AF are set at a total of three locations, that is, the central portion of the shooting range 217 and two locations on the left and right. Further, the focus detection areas 219a, 219b, 219c for TVAF are set so as to include one of the focus detection areas 218ah, 218bh, 218ch for phase difference AF. Note that FIG. 6 is an example of setting focus detection areas, and the number, position, and size are not limited to those shown in the figure.

(Explanation of the flow of focus detection processing)
Next, an automatic focus detection (AF) operation in the digital camera of this embodiment will be described with reference to FIGS. 1A and 1B.
After the outline of the AF process is explained, a detailed explanation will be given. In this embodiment, the camera MPU 125 first applies the phase difference AF to each of the focus detection areas 218ah, 218bh, and 218ch to obtain the defocus amount (defocus amount) and the reliability of the defocus amount. If the defocus amount having a predetermined reliability is obtained in all of the focus detection areas 218ah, 218bh, and 218ch, the camera MPU 125 moves the focus lens 104 to the closest focus position of the object based on the defocus amount. Let

On the other hand, when there is a focus detection area in which the defocus amount having a predetermined reliability is not obtained, the camera MPU 125 acquires the focus evaluation value for the focus detection area for contrast AF including the focus detection area. The camera MPU 125 determines whether there is a subject closer to the subject distance than the subject distance corresponding to the defocus amount obtained by the phase difference AF, based on the relationship between the focus evaluation value change and the position of the focus lens 104. Then, when it is determined that the subject is present on the closer side, the focus lens 104 is driven in the direction based on the change in the focus evaluation value.

If the focus evaluation value has not been obtained before, the amount of change in the focus evaluation value cannot be calculated. In that case, the camera MPU 125 focuses on the closest subject in a focus detection area in which a defocus amount larger than a predetermined defocus amount and having a predetermined reliability is obtained. The focus lens 104 is driven so that When the defocus amount having the predetermined reliability is not obtained, and when the defocus amount larger than the predetermined defocus amount is not obtained, the camera MPU 125 determines the predetermined amount irrelevant to the defocus amount. The focus lens 104 is driven. This is because when the focus lens 104 is driven based on a small defocus amount, it is highly likely that it will be difficult to detect a change in the focus evaluation value at the next focus detection.

When focus detection is completed by either method, the camera MPU 125 calculates various correction values and corrects the focus detection result. Then, the camera MPU 125 drives the focus lens 104 based on the corrected focus detection result.

The details of the AF processing described above will be described below with reference to the flowcharts shown in FIGS. 1A and 1B. The following AF processing operation is executed by the camera MPU 125 as a main body, unless another main body is specified. Further, when the camera MPU 125 drives or controls the lens unit 100 by transmitting a command or the like to the lens MPU 117, the operation subject may be described as the camera MPU 125 in order to simplify the description.
In S1, the camera MPU 125 sets the focus detection area. Here, it is assumed that three focus detection areas as shown in FIG. 6 are set for both the phase difference AF and the contrast AF.

In S2, the camera MPU 125 sets the closeness determination flag in the RAM 125b to 1.
In step S3, the camera MPU 125 exposes the image sensor 122 to read out an image signal, and the image processing circuit 124 uses the image signal for phase difference AF based on the image data in the focus detection areas 218ah, 218bh, and 218ch for phase difference AF. Is generated. Further, the RAW image data generated by the image processing circuit 124 is supplied to the TVAF unit 130, and the TVAF unit 130 calculates the evaluation value based on the pixel data in the focus detection areas 219a, 219b, 219c for TVAF. Before the image signal for the phase difference AF is generated, the image processing circuit 124 corrects the asymmetry of the exit pupil due to the vignetting of the light flux due to the lens frame of the taking lens (see JP 2010-117679 A). May be applied. The focus evaluation value calculated by the TVAF unit 130 is stored in the RAM 125b in the camera MPU 125.

In S4, the camera MPU 125 determines whether or not a reliable peak (maximum value) of the focus evaluation value is detected. If a reliable peak is detected, the camera MPU 125 advances the process to S20 to end the focus detection process. The method of calculating the reliability of the peak of the focus evaluation value is not limited, but for example, the method described in FIGS. 10 to 13 of JP 2010-78810A may be used. Specifically, it is determined whether the detected peak is the top of a mountain, the difference between the maximum value and the minimum value of the focus evaluation value, the length of the portion inclined at a certain value (SlopeThr) or more, and the inclination. Judgment is made by comparing the slopes of the parts with the respective threshold values. If all the thresholds are satisfied, it can be determined that the peak is reliable.

In this embodiment, the phase difference AF and the contrast AF are used together. Therefore, if the presence of a subject on the closer side is confirmed in the same focus detection area or another focus detection area, even if a reliable focus evaluation value peak is detected, The process may proceed to S5 without finishing the detection. However, in this case, the position of the focus lens 104 corresponding to the reliable focus evaluation value peak is stored, and when the reliable focus detection result is not obtained in the processing after S5, the stored focus is stored. The position of the lens 104 is used as the focus detection result.

In S5, the phase difference AF unit 129 calculates the shift amount (phase difference) of the pair of image signals supplied from the image processing circuit 124 for each focus detection area 218ch, 218ah, 218bh, and the phase difference is stored in advance. The defocus amount is converted using the conversion factor that is set. Here, the reliability of the calculated defocus amount is also determined, and only the defocus amount of the focus detection area determined to have the predetermined reliability is used in the AF process thereafter. Due to the influence of vignetting due to the lens frame and the like, as the defocus amount increases, the phase difference detected between the pair of image signals includes more errors. Therefore, when the obtained defocus amount is larger than the threshold value, the degree of matching between the shapes of the pair of image signals is low, or the contrast of the image signals is low, the obtained defocus amount has a predetermined reliability. It is possible to determine not to perform (reliability is low). Hereinafter, when it is determined that the obtained defocus amount has a predetermined reliability, it is expressed that “the defocus amount can be calculated”. Further, when the defocus amount cannot be calculated for some reason, or when it is determined that the reliability of the defocus amount is low, it is expressed as “the defocus amount cannot be calculated”.

In S6, the camera MPU 125 checks whether or not the defocus amount can be calculated in all of the focus detection areas 218ah, 218bh, 218ch for phase difference AF set in S1. When the defocus amount can be calculated in all the focus detection areas, the camera MPU 125 advances the process to S20, and calculates the defocus amount indicating the closest object among the calculated defocus amounts. A vertical and horizontal BP correction value (BP1) is calculated for the focus detection area. Here, the reason for selecting the closest object is that, in general, the object that the photographer wants to focus is often on the closest side. The vertical and horizontal BP correction values (BP1) are the difference between the focus detection results when focus detection is performed on the contrast of the horizontal subject and when focus detection is performed on the contrast of the vertical subject. This is the value to be corrected.

A general subject has a contrast in both the horizontal and vertical directions, and the focus state of a captured image is also evaluated in consideration of the contrast in both the horizontal and vertical directions. On the other hand, when the focus detection is performed only in the horizontal direction as in the AF of the phase difference detection method described above, an error occurs between the focus detection result in the horizontal direction and the focus state of the captured image in both the horizontal direction and the vertical direction. This error occurs due to astigmatism of the photographing optical system. The vertical and horizontal BP correction value (BP1) is a correction value for correcting the error, and is calculated in consideration of the selected focus detection area, the position of the focus lens 104, the position of the first lens group 101 indicating the zoom state, and the like. To be done. Details of the calculation method will be described later.

In S21, the camera MPU 125 calculates the color BP correction value (BP2) using the contrast information in the vertical direction or the horizontal direction for the focus detection area that is the correction value calculation target in S20. The color BP correction value (BP2) is generated by the chromatic aberration of the photographing optical system, and is generated by the difference between the color balance of the signals used for focus detection and the color balance of the signals used for the captured image or the developed image. For example, in the contrast AF of the present embodiment, the focus evaluation value is generated based on the output of the pixel (green pixel) having the green (G) color filter, so that the focus position of the green wavelength is mainly detected. Become. However, since the captured image is generated using all RGB colors, focus evaluation is performed when the focus position of red (R) or blue (B) is different from that of green (G) (when axial chromatic aberration exists). There is a deviation (error) from the focus detection result depending on the value. A correction value for correcting the error is the color BP correction value (BP2). Details of the method for calculating the color BP correction value (BP2) will be described later.

In S22, the camera MPU 125 calculates a specific spatial frequency BP correction value (BP3) for the focus detection area to be corrected using the contrast information of the green signal or the luminance signal Y in the vertical direction or the horizontal direction. .. The spatial frequency BP correction value (BP3) is generated mainly by spherical aberration of the photographing optical system, and is the difference between the evaluation frequency (band) of the signal used for focus detection and the evaluation frequency (band) when viewing the captured image. Caused by. As described above, since the image signal at the time of focus detection is read from the image sensor in the second mode, the output signals are added or thinned. Therefore, the evaluation band of the output signal used for focus detection is lower than that of the captured image generated using the signals of all pixels read in the first read mode. The spatial frequency BP correction value (BP3) is used to correct the focus detection shift caused by the difference in the evaluation band. The details of the method of calculating the spatial frequency BP correction value (BP3) will be described later.

In S23, the camera MPU 125 corrects the focus detection result DEF_B by the following equation (1) using the calculated three types of correction values (BP1, BP2, BP3), and calculates the corrected focus detection result DEF_A.
DEF_A=DEF_B+BP1+BP2+BP3 (1)

In the present embodiment, the correction value for correcting the focus detection result is divided into three stages and calculated in the order of vertical and horizontal (S20), color (S21), and spatial frequency (S22).
First, while the evaluation at the time of viewing a captured image uses the contrast information in both vertical and horizontal directions, the focus detection calculates an error caused by using the contrast information in one direction as a vertical and horizontal BP correction value (BP1).

Next, the influence of the vertical and horizontal BPs is separated, and in the contrast information in one direction, the difference between the in-focus positions due to the color of the signal used for the captured image and the color of the signal used for focus detection is calculated as the color BP correction value (BP2). Calculate as
Further, with respect to the specific color such as green or a luminance signal, which is the contrast information in one direction, the spatial frequency BP correction value ( Calculate as BP3).
In this way, by dividing and calculating the three types of errors, the amount of calculation and the amount of data stored in the lens or the camera are reduced.

In S24, the camera MPU 125 drives the focus lens 104 through the lens MPU 117 based on the corrected defocus amount DEF_A calculated by the equation (1).

In step S25, the camera MPU 125 causes the display 126 to display a display (AF frame display) indicating the focus detection area in which the defocus amount used to drive the focus lens 104 is displayed, for example, on the live view image to perform AF processing. finish.

On the other hand, if there is a focus detection area for which the defocus amount could not be calculated in S6, the camera MPU 125 advances the process to S7 in FIG. 1B. In S7, the camera MPU 125 determines whether or not the closeness determination flag is 1. The closeness determination flag is 1 when the focus lens has not been driven since the AF operation started. If the focus lens is being driven, the closeness determination flag is 0. If the closeness determination flag is 1, the camera MPU 125 advances the process to S8.

In step S8, the camera MPU 125 cannot calculate the defocus amount in all the focus detection areas, or the calculated defocus amount indicates that the defocus amount indicating the presence of the closest object is the predetermined threshold value A. In the following cases, the process proceeds to S9. In S9, the camera MPU 125 drives the focus lens by a predetermined amount on the closest side.

Here, the reason why the lens is driven by a predetermined amount in the case of Yes in S8 will be described. First, the case where there is no area in which the defocus amount can be calculated among the plurality of focus detection areas is a case where the subject to be focused is not found at the present moment. Therefore, in order to confirm the presence of a subject to be focused on all focus detection areas before determining that focusing is impossible, a predetermined amount of lens drive is performed and Be able to judge changes. Further, in the case where the defocus amount indicating the presence of the closest object in the calculated defocus amounts is equal to or smaller than the predetermined threshold value A, the focus detection area in the almost in-focus state exists at the present time. This is the case. In such a situation, in order to confirm the possibility that there is a subject that is not detected at this moment in the focus detection area where the defocus amount could not be calculated, the lens is driven by a predetermined amount, and Change in the focus evaluation value to be determined.
The predetermined amount for driving the focus lens in S9 may be determined in consideration of the F value of the photographing optical system and the sensitivity of the focus movement amount on the imaging surface with respect to the lens driving amount.

On the other hand, if No in S8, that is, if the defocus amount indicating the presence of the closest object in the calculated defocus amount is larger than the predetermined threshold A, the process proceeds to S10. In this case, there is a focus detection area for which the defocus amount can be calculated, but the focus detection area is not in focus. Therefore, in S10, the camera MPU 125 drives the lens based on the defocus amount indicating the presence of the closest object in the calculated defocus amounts.
After the lens is driven in S9 or S10, the camera MPU 125 advances the processing to S11, sets the close proximity determination flag to 0, and returns the processing to S3 in FIG. 1A.

If the closeness determination flag is not 1 (it is 0) in S7, the camera MPU 125 advances the processing to S12. In S12, the camera MPU 125 determines whether or not the focus evaluation value of the focus detection area for TVAF corresponding to the focus detection area for which the defocus amount could not be calculated has changed by a predetermined threshold value B or more before and after the lens driving. .. Although the focus evaluation value may increase or decrease, in S12, it is determined whether or not the absolute value of the change amount of the focus evaluation value is equal to or larger than a predetermined threshold value B.

Here, when the absolute value of the change amount of the focus evaluation value is equal to or larger than the predetermined threshold value B, the defocus amount cannot be calculated, but the change in the blur condition of the subject can be detected by increasing or decreasing the focus evaluation value. Means Therefore, in the present embodiment, even if the defocus amount by the phase difference AF cannot be detected, the presence of the subject is determined based on the increase or decrease of the focus evaluation value, and the AF process is continued. As a result, focus adjustment can be performed on a subject that has a large defocus amount and cannot be detected by the phase difference AF.

Here, the predetermined threshold value B used for the determination is changed according to the lens driving amount. When the lens driving amount is large, the threshold value B is set to a larger value than when the lens driving amount is small. This is because when there is a subject, the amount of change in the focus evaluation value increases as the amount of lens drive increases. The threshold value B for each lens driving amount is stored in the EEPROM 125c.

When the absolute value of the change amount of the focus evaluation value is equal to or more than the threshold value B, the camera MPU 125 advances the process to S13, and the focus detection area in which the change amount of the focus evaluation value is equal to or more than the threshold value B indicates the existence of the infinity side subject. It is determined whether or not it is only the focus detection area. The case where the focus detection area indicates the presence of an object at the infinity side means that the focus evaluation value decreases when the lens driving direction is the closest direction or the focus evaluation value increases when the lens driving direction is the infinity direction. Is.

If the focus detection area in which the amount of change in the focus evaluation value is equal to or greater than the threshold value B is not only the focus detection area indicating the presence of the subject at infinity, the camera MPU 125 advances the processing to S14 and drives the lens by a predetermined amount on the near side. To do. This is because there is a focus detection area that indicates the presence of the closest object in the focus detection area in which the amount of change in focus evaluation value is equal to or greater than the threshold value B. The reason for prioritizing the near side is as described above.

On the other hand, in S13, if the focus detection area in which the amount of change in the focus evaluation value is equal to or greater than the threshold value B is only the focus detection area indicating the presence of the subject at infinity, the camera MPU 125 advances the process to S15. In S15, the camera MPU 125 determines whether or not there is a focus detection area for which the defocus amount can be calculated. When there is a focus detection area for which the defocus amount can be calculated (Yes in S15), the camera MPU 125 processes the phase difference AF because it gives priority to the result of the phase difference AF over the existence of the infinity side subject based on the focus evaluation value. To S20 of FIG. 1A.

When there is no focus detection area for which the defocus amount can be calculated (No in S15), the information indicating the presence of the subject is only the change in the focus evaluation value. Therefore, the camera MPU 125 drives the lens by a predetermined amount toward infinity in S16 based on the change in the focus evaluation value, and returns the process to S3 in FIG. 1A.

The predetermined amount of lens driving performed in S14 and S16 may be determined in consideration of the defocus amount that can be detected by the phase difference AF. Although the defocus amount that can be detected differs depending on the subject, a lens drive amount that prevents the subject from passing by without being detected when the lens is driven from a state in which focus detection is not possible is set in advance.

When the absolute value of the change amount of the focus evaluation value is less than the predetermined threshold value B (No in S12), the camera MPU 125 advances the processing to S17, and determines whether or not there is a focus detection area in which the defocus amount can be calculated. If there is no focus detection area for which the defocus amount can be calculated, the camera MPU 125 advances the process to S18, drives the lens to a predetermined fixed point, and then advances the process further to S19 to defocus the display 126. The display is performed and the AF process is ended. This is a case where there is no focus detection area in which the defocus amount can be calculated, and there is no focus detection area in which the focus evaluation value changes before and after the lens driving. In such a case, since there is no information indicating the presence of the subject, the camera MPU 125 determines that focusing is impossible and ends the AF process.

On the other hand, if there is a focus detection area in which the defocus amount can be calculated in S17, the camera MPU 125 advances the process to S20 in FIG. 1A, corrects the detected defocus amount (S20 to S23), and combines in S24. The focus lens 104 is driven to the in-focus position. After that, the camera MPU 125 displays the in-focus state on the display device 126 in S25, and ends the AF process.

(Method of calculating vertical and horizontal BP correction values)
Next, a method of calculating the vertical and horizontal BP correction values (BP1) performed in S20 of FIG. 1 will be described with reference to FIGS. 7 to 8B. FIG. 7 is a flowchart showing details of the calculation process of the vertical and horizontal BP correction values (BP1).
In S100, the camera MPU 125 acquires vertical and horizontal BP correction information. The vertical/horizontal BP correction information is difference information between the focus position in the horizontal direction (first direction) and the focus position in the vertical direction (second direction). In this embodiment, the vertical/horizontal BP correction information is stored in advance in the lens memory 118 of the lens unit 100, and the camera MPU 125 requests the lens MPU 117 to acquire it. However, it may be stored in the nonvolatile area of the camera RAM 125b in association with the identification information of the lens unit.

FIG. 8A shows an example of vertical and horizontal BP correction information. Here, an example of the vertical/horizontal BP correction information corresponding to the center focus detection areas 219a and 218ah in FIG. 6 is shown, but the vertical/horizontal BP correction information is also stored for the other focus detection areas 219c, 218ch and 219b and 218bh. ing. However, the focus detection correction values of the focus detection areas existing at symmetrical positions with respect to the optical axis of the photographing optical system are equal in design. In the present embodiment, since the focus detection areas 219c, 218ch and 219b, 218bh satisfy such a target relationship, only one of them may store the vertical and horizontal BP correction information. If the correction value does not change significantly depending on the position of the focus detection area, it may be stored as a common value.

In the example shown in FIG. 8A, the zoom position (angle of view) and the focus lens position (focus distance) of the photographing optical system are divided into eight zones, and focus detection correction values BP111 to BP188 are stored for each zone. ing. The larger the number of divided zones, the more accurate the correction value according to the position of the first lens group 101 and the position of the focus lens 104 of the photographing optical system can be obtained. The vertical and horizontal BP correction information can be used for both the contrast AF and the phase difference AF.

In S100, the camera MPU 125 acquires the correction value corresponding to the zoom position and the focus lens position according to the focus detection result that is the correction target.
In S101, the camera MPU 125 determines whether a reliable focus detection result is obtained in the horizontal direction or the vertical direction in the focus detection area to be corrected. The method of determining the reliability of the focus detection result is as described above for the phase difference AF and the contrast AF. Since the phase difference AF of the present embodiment only performs focus detection in the horizontal direction, it is the contrast AF that can obtain reliable focus detection results in both the horizontal and vertical directions. Therefore, in the following description regarding the vertical and horizontal BP correction values, the description will be made assuming the contrast AF, but the same processing may be performed when the focus detection of the phase difference AF is performed in both the horizontal and vertical directions. When it is determined in S101 that the focus detection results in both the horizontal direction and the vertical direction are reliable, the camera MPU 125 advances the process to S102.

In S102, the camera MPU 125 determines whether or not the difference between the horizontal focus detection result and the vertical focus detection result is appropriate. This is a process performed to deal with the problem of perspective competition that occurs when a subject at a long distance and a subject at a short distance are included in the focus detection area. For example, when a distant subject has a horizontal contrast and a near subject has a vertical contrast, the absolute value is larger than the error caused by astigmatism of the photographic optical system or the sign is opposite. There may be a difference in focus detection results. When the difference between the horizontal focus detection result and the vertical focus detection result is larger than the predetermined determination value C, the camera MPU 125 determines that the difference is invalid (conflict perspective). Then, the horizontal direction or the vertical direction is selected as the direction indicating the focus detection result on the closer side, and the process proceeds to S104. For the reason described above, the determination value C may be uniquely determined to be a value that greatly exceeds the difference that may occur due to aberration or the like, or may be set using the correction information obtained in S100.

When it is determined in S102 that the difference between the horizontal focus detection result and the vertical focus detection result is appropriate, the camera MPU 125 advances the processing to S106.

On the other hand, if there is reliability in only one horizontal or vertical direction in S101, or if only one horizontal or vertical direction is selected in S102, the camera MPU 125 advances the processing to S104. In S104, the camera MPU 125 selects the direction of the focus detection result. The direction in which the reliable focus detection result is calculated or the direction in which the focus detection result corresponding to the subject closer to the closer side is calculated in the perspective competition determination is selected.

Next, the camera MPU 125 determines in S105 whether or not weighting in the horizontal direction and the vertical direction is possible. When S105 is executed, a reliable focus detection result is not obtained in both the horizontal direction and the vertical direction from the viewpoint of reliability of the focus evaluation value and perspective competition, but the vertical and horizontal BP correction values are calculated. The decision to do so is made again. The reason for this will be described in detail with reference to FIG.

FIG. 8B is a diagram showing an example of the relationship between the position of the focus lens 104 in the selected focus detection area and the focus evaluation value. Curves E_h and E_v in the figure show changes in the focus evaluation value in the horizontal direction and the focus evaluation value in the vertical direction detected by the contrast AF. Further, LP1, LP2, and LP3 indicate focus lens positions, respectively. In FIG. 8B, a case where LP3 is obtained as a reliable focus detection result from the horizontal focus evaluation value E_h and LP1 is obtained as a reliable focus detection result from the vertical focus evaluation value E_v. Is shown. Since LP1 and LP3 are greatly different from each other, it is determined that there is a perspective conflict state, and the horizontal focus detection result LP3, which is the focus detection result on the closer side, is selected in S104.

In such a situation, in S105, the camera MPU 125 determines whether or not there is a vertical focus detection result in the vicinity of the selected horizontal focus detection result LP3. Since LP2 exists in the situation as shown in FIG. 8B, the camera MPU 125 determines that weighting in the horizontal and vertical directions is possible, advances the processing to S106, and sets the correction value of the focus detection result LP3 to the focus value. The calculation is performed in consideration of the influence of the detection result LP2.

In S100, BP1_B, which is one element in FIG. 8A, is acquired as the vertical/horizontal BP correction information, and the horizontal focus evaluation value in LP3 in FIG. 8B is E_hp and the vertical focus evaluation value in LP2 is Let E_vp. In this case, in S106, the camera MPU 125 calculates the vertical/horizontal BP correction value BP1 according to the following formula (2) based on the ratio of the focus evaluation value in the direction orthogonal to the correction direction to the total focus evaluation value.
BP1=BP1_B×E_vp/(E_vp+E_hp)×(+1) (2)

In the present embodiment, since the correction value for the focus detection result in the horizontal direction is calculated, the correction value BP1 is calculated using Expression (2). However, when correcting the focus detection result in the vertical direction, the following expression is used. It can be calculated in (3).
BP1=BP1_B×E_hp/(E_vp+E_hp)×(-1) (3)

When it is determined in S102 that the difference between the horizontal focus detection result and the vertical focus detection result is appropriate, if the focus detection result on the near side is the horizontal detection result, the formula (2) is changed to the vertical direction. If the detection result is, the correction value BP1 is calculated using the equation (3).

As is obvious from the equations (2) and (3), the information that the focus evaluation value is large is determined to have a lot of contrast information included in the subject, and the vertical and horizontal BP correction values (BP1) are calculated. As described above, the vertical and horizontal BP correction information is
(Focus detection position of subject having contrast information only in vertical direction)-(Focus detection position of subject having contrast information only in horizontal direction)
Is. Therefore, the signs of the correction value BP1 for correcting the horizontal focus detection result and the correction value BP1 for correcting the vertical focus detection result are opposite. When the process of S106 ends, the camera MPU 125 ends the vertical/horizontal BP correction value calculation process.

On the other hand, when it is determined in S105 that there is no vertical focus detection result in the vicinity of the selected horizontal focus detection result LP3, the camera MPU 125 advances the processing to S103. In S103, the camera MPU 125 determines that the contrast information included in the subject is in only one direction, so BP1=0 is set, and the vertical and horizontal BP correction value calculation processing ends.

As described above, in the present embodiment, since the correction value is calculated according to the contrast information of the subject in different directions, it is possible to perform highly accurate correction value calculation according to the pattern of the subject. Note that, in FIG. 8B, the case where the subjects are competing for perspective is described. However, when one maximum value is detected in each of the horizontal direction and the vertical direction, and one of the focus detection results is unreliable. Also, the correction value is calculated in the same way.

However, the correction value calculation method in S106 is not limited to this. For example, when the focus detection can be performed only in the horizontal direction like the phase difference AF of the present embodiment, the correction value is calculated by assuming that the information amount of the contrast in the horizontal direction of the subject is the same as the information amount of the contrast in the vertical direction. You may. In that case, the correction value can be calculated by substituting E_hp=E_vp=1 in the above equations (2) and (3). By performing such processing, although the correction accuracy is reduced, the load of the correction value calculation can be reduced.

In the above description, the focus detection result of the contrast AF has been described, but similar processing can be performed on the focus detection result of the phase difference AF. The amount of change in the correlation amount calculated by the correlation calculation of the phase difference AF may be used as the weighting coefficient when calculating the correction value. This is based on the fact that the more the contrast information of the subject is, such as the case where the contrast of the subject is large or the number of edges having the contrast is large, the change amount of the correlation amount is also large. Various evaluation values may be used without being limited to the change amount of the correlation amount as long as the evaluation values can obtain the same relationship.

In this way, by correcting the focus detection result using the vertical and horizontal BP correction values, highly accurate focus detection can be performed regardless of the amount of contrast information for each direction of the subject. Further, since the correction values in the horizontal direction and the vertical direction are calculated using the common correction information as shown in FIG. 8A, the correction values are different from those in the case of storing the correction values for each direction. Information storage capacity can be reduced.

Further, when the focus detection results for each direction are greatly different, the effect of perspective competition can be reduced by not calculating the vertical and horizontal BP correction values using these focus detection results. Further, even when perspective competition is expected, more accurate correction can be performed by weighting the correction value according to the magnitude of the focus evaluation value for each direction.

(Calculation method of color BP correction value)
Next, a method of calculating the color BP correction value (BP2) performed in S21 of FIG. 1 will be described with reference to FIGS. 9A and 9. FIG. 9A is a flowchart showing details of the process of calculating the color BP correction value (BP2).
In S200, the camera MPU 125 acquires the color BP correction information. The color BP correction information is difference information between the focus position detected using the green (G) signal and the focus position detected using the signals of other colors (red (R) and blue (B)). Is. In the present embodiment, the color BP correction information is stored in advance in the lens memory 118 of the lens unit 100, and the camera MPU 125 requests and acquires the lens MPU 117, but is stored in the nonvolatile area of the camera RAM 125b. May be.

The larger the number of divided zones, the more accurate the correction value according to the position of the first lens group 101 and the position of the focus lens 104 of the photographing optical system can be obtained. Further, the color BP correction information can be used for both contrast AF and phase difference AF.

In S200, the camera MPU 125 acquires the correction value corresponding to the zoom position and the focus lens position according to the focus detection result that is the correction target.
In S201, the camera MPU 125 calculates the color BP correction value. In S200, when BP_R is acquired as one element of FIG. 9B and BP_B is acquired as one element of FIG. 9C, the camera MPU 125 calculates the color BP correction value BP2 according to the following expression (4). ..
BP2=K_R×BP_R+K_B×BP_B (4)

Here, K_R and K_B are coefficients for the correction information of each color. It is a value that correlates with the size relationship of the red (R) and blue (B) information with respect to the green (G) information included in the subject. For a subject that includes many red colors, K_R has a large value and blue. K_B takes a large value for a subject including many colors. For a subject containing a lot of green, both K_R and K_B have small values. K_R and K_B may be set in advance based on the spectral information representative of the subject. When the spectral information of the subject can be detected, K_R and K_B may be set according to the spectral information of the subject. When the calculation of the color BP correction value is completed in S202, the camera MPU 125 ends the color BP correction value calculation process.

In the present embodiment, the correction values are stored in a table format for each focus detection area as shown in FIGS. 8A and 9, but the method of storing the correction values is not limited to this. For example, coordinates are set with the intersection of the image sensor and the optical axis of the image pickup optical system as the origin, and the horizontal and vertical directions of the image pickup apparatus as the X axis and the Y axis, and the correction value at the center coordinate of the focus detection area is set to X. It may be obtained by the function of and. In this case, the amount of information to be stored as the focus detection correction value can be reduced.

Further, in the present embodiment, the correction value used for focus detection calculated using the vertical and horizontal BP correction information and the color BP correction information is calculated as not depending on the spatial frequency information of the pattern of the subject. Therefore, highly accurate correction can be performed without increasing the amount of correction information to be stored. However, the method of calculating the correction value is not limited to this. Similar to the method of calculating the spatial frequency BP correction value described below, the vertical/horizontal BP correction information and the color BP correction information for each spatial frequency may be used to calculate the correction value that matches the spatial frequency component of the subject.

(Calculation method of spatial frequency BP correction value)
Next, a method of calculating the spatial frequency BP correction value (BP3) performed in S22 of FIG. 1 will be described with reference to FIGS. 10A to 10C. FIG. 10A is a flowchart showing details of the calculation process of the spatial frequency BP correction value (BP3).
In S300, the camera MPU 125 acquires the spatial frequency BP correction information. The spatial frequency BP correction information is information on the image forming position of the photographing optical system for each spatial frequency of the subject. In this embodiment, the spatial frequency BP correction information is stored in advance in the lens memory 118 of the lens unit 100, and the camera MPU 125 requests and acquires the lens MPU 117, but is stored in the nonvolatile area of the camera RAM 125b. May be.

An example of the spatial frequency BP correction information will be described with reference to FIG. 10B showing the defocus MTF (Modulation Transfer Function) of the photographing optical system. In FIG. 10B, the horizontal axis represents the position of the focus lens 104, and the vertical axis represents the MTF intensity. The four types of curves depicted in FIG. 10B are MTF curves for each spatial frequency, and show the case where the spatial frequency changes from low to high in the order of MTF1, MTF2, MTF3, and MTF4. .. The MTF curve of the spatial frequency F1 (lp/mm) corresponds to MTF1, and similarly, the spatial frequencies F2, F3, F4 (lp/mm) correspond to MTF2, MTF3, and MTF4. Further, LP4, LP5, LP6, and LP7 indicate the focus lens 104 positions corresponding to the maximum values of the defocus MTF curves. The stored spatial frequency BP correction information is obtained by discretely sampling the curve of FIG. As an example, in the present embodiment, MTF data is sampled for 10 focus lens positions for one MTF curve. For example, for MTF1, MTF1(n) (1≦n≦10). 10 data are stored.

The spatial frequency BP correction information, like the vertical/horizontal BP correction information and the color BP correction information, has a zoom position (angle of view) and a focus lens position (focus distance) of the photographing optical system in eight zones for each position of the focus detection area. Divide and store for each zone. The larger the number of divided zones, the more accurate the correction value according to the position of the first lens group 101 and the position of the focus lens 104 of the photographing optical system can be obtained. The spatial frequency BP correction information can be used for both contrast AF and phase difference AF.

In S300, the camera MPU 125 acquires a correction value corresponding to the zoom position and the focus lens position according to the focus detection result that is the correction target.
In S301, the camera MPU 125 calculates the band of a signal used when performing contrast AF or phase difference AF in the focus detection area that is the correction target. In the present embodiment, the camera MPU 125 calculates the AF evaluation band in consideration of the influence of the subject, the photographing optical system, the sampling frequency of the image sensor, and the digital filter used for evaluation. A method of calculating the AF evaluation band will be described later.

Next, in S302, the camera MPU 125 calculates the band of the signal used for the captured image. Similar to the calculation of the AF evaluation band in S302, the camera MPU 125 calculates the captured image evaluation band in consideration of the frequency characteristics of the subject, the shooting optical system, and the image sensor, and the evaluation band of the viewer of the captured image.

Calculation of the AF evaluation band (second evaluation band) and the captured image evaluation band (first evaluation band) performed in S301 and S302 will be described with reference to FIG. In each of FIGS. 11A and 11B, the intensity is shown for each spatial frequency, the horizontal axis shows the spatial frequency, and the vertical axis shows the intensity.
FIG. 11A shows the spatial frequency characteristic (I) of the subject. F1, F2, F3, and F4 on the horizontal axis are spatial frequencies corresponding to the MTF curves (MTF1 to MTF4) in FIG. Nq represents a Nyquist frequency determined by the pixel pitch of the image sensor 122. F1 to F4 and Nq are also shown in FIGS. 11(b) to 11(f), which will be described later. In the present embodiment, the spatial frequency characteristic (I) of the subject uses a representative value stored in advance. In FIG. 11A, the spatial frequency characteristic (I) of the subject is drawn as a continuous curve, but discrete values I(n) (1≦n≦4) corresponding to the spatial frequencies F1, F2, F3, and F4. ) Has.

Further, in the present embodiment, the representative value stored in advance as the spatial frequency characteristic of the subject is used, but the spatial frequency characteristic of the subject to be used may be changed according to the subject for which focus detection is performed. By applying FFT processing or the like to the captured image signal, the spatial frequency information (power spectrum) of the subject can be obtained. In this case, although the calculation process is increased, a correction value according to the subject for which focus detection is actually performed can be calculated, so that highly accurate focus detection can be performed. In addition, several types of spatial frequency characteristics stored in advance may be used more simply depending on the magnitude of the contrast information of the subject.

FIG. 11B shows the spatial frequency characteristic (O) of the photographing optical system. This information may be obtained through the lens MPU 117 or may be stored in the RAM 125b in the camera. The information to be stored may be the spatial frequency characteristic for each defocus state or only the spatial frequency characteristic at the time of focusing. Since the spatial frequency BP correction value is calculated in the vicinity of the focus, the correction can be performed with high accuracy by using the spatial frequency characteristic at the time of focus. However, although the calculation load is increased, the focus adjustment can be performed with higher accuracy by using the spatial frequency characteristic for each defocus state. Which defocus state spatial frequency characteristic is used may be selected using the defocus amount obtained by the phase difference AF.
In FIG. 11B, the spatial frequency characteristic (O) of the photographing optical system is drawn by a continuous curve, but discrete values O(n) (1≦n≦) corresponding to the spatial frequencies F1, F2, F3, and F4. 4).

FIG. 11C shows the spatial frequency characteristic (L) of the optical low pass filter 121. This information is stored in the RAM 125b in the camera. In FIG. 11C, the spatial frequency characteristic (L) of the optical low-pass filter 121 is drawn by a continuous curve, but the discrete value L(n)(1) corresponding to the spatial frequencies F1, F2, F3, F4. ≦n≦4).

FIG. 11D shows spatial frequency characteristics (M1, M2) due to signal generation. As described above, the image sensor of this embodiment has two types of read modes. In the first read mode, that is, the all-pixel read mode, the spatial frequency characteristic does not change during signal generation, as indicated by M1. On the other hand, in the second read mode, that is, the thinned-out read mode, the spatial frequency characteristic changes at the time of signal generation as indicated by M2. As described above, the signals are added during thinning in the X direction to improve the S/N, so that a low pass effect is generated by the addition. M2 in FIG. 11D shows the spatial frequency characteristic at the time of signal generation in the second read mode. Here, the effect of addition is not taken into consideration, and the low-pass effect due to addition is shown.
In FIG. 11D, the spatial frequency characteristics (M1, M2) due to signal generation are drawn by continuous curves, but discrete values M1(n), M2(corresponding to the spatial frequencies F1, F2, F3, F4 ( n) (1≦n≦4).

FIG. 11E shows the spatial frequency characteristic (D1) showing the sensitivity for each spatial frequency when viewing the captured image and the spatial frequency characteristic (D2) of the digital filter used when processing the AF evaluation signal. Sensitivity for each spatial frequency when viewing a captured image is affected by individual differences among viewers, viewing environment such as image size, viewing distance, and brightness. In the present embodiment, the sensitivity for each spatial frequency at the time of viewing is set and stored as a representative value.

On the other hand, in the second read mode, aliasing noise (aliasing) of the frequency component of the signal occurs due to the influence of thinning. D2 shows the spatial frequency characteristic of the digital filter in consideration of the influence.
In FIG. 11E, the spatial frequency characteristic (D1) at the time of viewing and the spatial frequency characteristic (D2) of the digital filter are drawn by curves, but discrete values corresponding to the spatial frequencies F1, F2, F3, F4. D1(n) and D2(n) (1≦n≦4).

As described above, by storing various information in either the camera or the lens, the camera MPU 125 sets the evaluation band W1 and the AF evaluation band W2 of the captured image into the following formulas (5) and (6). Calculate based on
W1(n)=I(n)×O(n)×L(n)×M1(n)×D1(n) (1≦n≦4) (5)
W2(n)=I(n)×O(n)×L(n)×M2(n)×D2(n) (1≦n≦4) (6)

FIG. 11F shows the evaluation band W1 (first evaluation band) and the AF evaluation band W2 (second evaluation band) of the captured image. Quantifying the degree of influence of each spatial frequency on the factor that determines the focus state of the captured image by performing calculations such as Equation (5) and Equation (6). You can Similarly, it is possible to quantify how much the error included in the focus detection result has, for each spatial frequency.

Further, the information stored in the camera may be W1 or W2 calculated in advance. As described above, by performing the calculation for each correction, it is possible to flexibly calculate the correction value when the digital filter or the like used in the AF evaluation is changed. On the other hand, if the data is stored in advance, it is possible to reduce the storage capacity of the calculations such as Expression (5) and Expression (6) and various data.

Also, since it is not necessary to complete all the calculations in advance, for example, only the shooting optical system and the spatial frequency characteristics of the subject are calculated in advance and stored in the camera to reduce the data storage capacity and the amount of calculation. May be reduced.

In FIG. 11, in order to simplify the description, the discrete values corresponding to the four spatial frequencies (F1 to F4) are used for description. However, the larger the number of spatial frequencies having data, the more accurately the spatial frequency characteristics of the captured image and the AF evaluation band can be reproduced, and the correction value can be calculated with high accuracy. On the other hand, the amount of calculation can be reduced by reducing the spatial frequency for weighting. It is also possible to have one spatial frequency representative of the spatial frequency characteristics of the evaluation band of the captured image and the AF evaluation band, and to perform the subsequent calculations.

Returning to FIG. 10A, in S303, the camera MPU 125 calculates the spatial frequency BP correction value (BP3). When calculating the spatial frequency BP correction value, the camera MPU 125 first calculates the defocus MTF (C1) of the captured image and the defocus MTF (C2) of the focus detection signal. Using the defocus MTF information obtained in S300 and the evaluation bands W1 and W2 obtained in S301 and S302, C1 and C2 that are the first and second image formation position information are expressed by the following formula (7) and formula. It is calculated according to (8) (1≦n≦10).
C1 (n) = MTF1 (n) x W1 (1) + MTF2 (n) x W1 (2) + MTF3 (n) x W1 (3) + MTF4 (n) x W1 (4) (7)
C2 (n) = MTF1 (n) x W2 (1) + MTF2 (n) x W2 (2) + MTF3 (n) x W2 (3) + MTF4 (n) x W2 (4) (8)

In this way, the defocus MTF information for each spatial frequency shown in FIG. 10B is added based on the weighting of the captured image or AF evaluation band calculated in S301 and S302, and the defocus MTF of the captured image is added. (C1) and AF defocus MTF (C2) are obtained. The defocus MTF used when performing the weighted addition here may be used after being normalized with the maximum value of each spatial frequency (MTF1 to MTF4). In general, the defocus MTF has a different maximum value depending on the spatial frequency as shown in FIG. Therefore, in the case of weighted addition with the same weight, the influence of MTF1 becomes strong in the example of FIG. Therefore, the defocus MTF for each spatial frequency can be weighted and added by using the value standardized by the maximum value.

FIG. 10C shows the obtained two defocus MTFs C1 and C2. The horizontal axis represents the position of the focus lens 104, and the vertical axis represents the value of MTF weighted and added for each spatial frequency. The camera MPU 125 detects the maximum value position of each MTF curve. P_img (first imaging position) is detected as the position of the focus lens 104 corresponding to the maximum value of the curve C1. P_AF (second image formation position) is detected as the position of the focus lens 104 corresponding to the maximum value of the curve C2.

In S303, the camera MPU 125 calculates the spatial frequency BP correction value (BP3) by the following equation (9).
BP3=P_AF-P_img (9)
With the equation (9), it is possible to calculate a correction value for correcting an error that may occur between the focus position of the captured image and the focus position detected by AF.

As described above, the focus position of the captured image is determined by the spatial frequency characteristic of each of the subject, the photographing optical system, and the optical low-pass filter, the spatial frequency characteristic at the time of signal generation, and the spatial frequency characteristic indicating the sensitivity at each frequency at the time of viewing. , And changes depending on the image processing performed on the captured image. In the present embodiment, the focus position of the captured image can be calculated with high accuracy by calculating the spatial frequency characteristic retroactively to the generation process of the captured image. For example, the focus position of the captured image is changed by the recorded size of the captured image, the super-resolution processing performed in the image processing, the sharpness, and the like. Further, after the recording of the captured image, how much the image size and the enlargement ratio are viewed, the viewing distance at the time of viewing, and the like affect the evaluation band of the viewer. Then, as the image size increases and the viewing distance decreases, the viewer's evaluation band is set to have characteristics with emphasis on high-frequency components, so that the focus position of the captured image is also changed.

On the other hand, the in-focus position detected by AF also changes depending on the spatial frequency characteristics of the subject, the shooting optical system, and the optical low-pass filter, the spatial frequency characteristics at the time of signal generation, the digital filter spatial frequency characteristics used for AF evaluation, and so on. To do. In the present embodiment, the focus position detected by the AF can be calculated with high accuracy by calculating the spatial frequency characteristic retroactively to the process of generating the signal used for AF. For example, it is possible to flexibly deal with AF in the first read mode. In that case, the weighting coefficient may be calculated by changing the spatial frequency characteristic at the time of signal generation to the characteristic corresponding to the first read mode.

Further, since the image pickup apparatus described in the present embodiment is a lens interchangeable single-lens reflex camera, the lens unit 100 can be exchanged. When the lens unit 100 is replaced, the lens MPU 117 sends defocus MTF information corresponding to each spatial frequency to the camera body 120. Then, since the camera MPU 125 calculates the in-focus position of the captured image and the in-focus position detected by the AF, it is possible to calculate a highly accurate correction value for each interchangeable lens. The lens unit 100 may transmit not only the defocus MTF information but also information such as the spatial frequency characteristic of the photographing optical system to the camera body 120. The method of utilizing the information is as described above.

Similarly, when the camera body 120 is replaced, the pixel pitch and the characteristics of the optical low-pass filter may change. As described above, even in such a case, since the correction value that matches the characteristics of the camera body 120 is calculated, the correction can be performed with high accuracy.

Although the correction value is calculated by the camera MPU 125 in the above description, it may be calculated by the lens MPU 117. In that case, the camera MPU 125 may transmit the various information described with reference to FIG. 11 to the lens MPU 117, and the lens MPU 117 may calculate the correction value using the defocus MTF information or the like. In this case, in S24 of FIG. 1, the lens MPU 117 may correct the in-focus position transmitted from the camera MPU 125 and drive the lens.

In the present embodiment, the correction value for AF is calculated by focusing on the characteristics (vertical and horizontal, color, spatial frequency band) of the signal used for focus detection. Therefore, the correction value can be calculated by the same method regardless of the AF method. Since it is not necessary to have a correction method and data used for correction for each AF method, it is possible to reduce the storage capacity of data and the calculation load.

● (Second embodiment)
Next, a second embodiment of the present invention will be described. The main difference from the first embodiment is that the method of calculating the spatial frequency BP correction value is different. In the first embodiment, the defocus MTF information is used as a value that represents the characteristics of the imaging optical system for each spatial frequency. However, since the defocus MTF information has a large amount of data, a large storage capacity, and a large calculation load, the spatial frequency BP correction value is calculated using the maximum value information of the defocus MTF in the second embodiment. As a result, the capacity of the lens memory 118 or the RAM 125b can be saved, the amount of communication between the lens and the camera can be reduced, and the calculation load of the camera MPU 125 can be reduced.

A block diagram of the image pickup apparatus (FIG. 2), an explanatory diagram of each focus detection method (FIGS. 3A to 5), an explanatory diagram of a focus detection area (FIG. 6), focus detection processing, and various BP correction value calculation processings. The flowchart (FIG. 1, FIG. 7 and FIG. 9A) is also used in this embodiment. The flowchart of the spatial frequency BP correction value calculation process (FIG. 10A) and the explanatory diagram of each evaluation band (FIG. 11) are also used.

A method of calculating the spatial frequency BP correction value (BP3) in this embodiment will be described with reference to FIG.
In S300, the camera MPU 125 acquires the spatial frequency BP correction information.

FIG. 12 shows the position of the focus lens 104 showing the maximum value of the defocus MTF for each spatial frequency, which is a characteristic of the image-taking optical system. For the discrete spatial frequencies F1 to F4 shown in FIG. 10B, focus lens positions LP4, LP5, LP6, LP7 at which the defocus MTF has a peak (maximum value) are shown on the vertical axis. In the present embodiment, the LP4 to LP7 are stored in the lens memory 118 or the RAM 125b as MTF_P(n) (1≦n≦4). As in the first embodiment, the stored information corresponds to the position of the focus detection area, the zoom position, and the focus lens position.

In the second embodiment, in S300 of the spatial frequency BP correction value processing shown in FIG. 10A, the camera MPU 125 corresponds to the zoom position and focus lens position according to the focus detection result that is the correction target. Get the correction value.
In S301 and S302, the camera MPU 125 performs the same processing as in the first embodiment.

In S303, the camera MPU 125 calculates the spatial frequency BP correction value (BP3). When calculating the spatial frequency BP correction value, the camera MPU 125 first calculates the focus position (P_img) of the captured image and the focus position (P_AF) detected by the AF according to the following equations (10) and (11). To do. The defocus MTF information MTF_P(n) obtained in S300 and the evaluation bands W1 and W2 obtained in S301 and S302 are used for the calculation.
P_img=MTF_P(1)×W1(1)+MTF_P(2)×W1(2)+MTF_P(3)×W1(3)+MTF_P(4)×W1(4) (10)
P_AF=MTF_P(1)×W2(1)+MTF_P(2)×W2(2)+MTF_P(3)×W2(3)+MTF_P(4)×W2(4) (11)

That is, the maximum value information MTF_P(n) of the defocus MTF for each spatial frequency shown in FIG. 12 is weighted and added with the photographed images and AF evaluation bands W1 and W2 calculated in S301 and S302. Thereby, the focus position (P_img) of the captured image and the focus position (P_AF) detected by the AF are calculated.

Next, the camera MPU 125 calculates the spatial frequency BP correction value (BP3) by the following equation (9), as in the first embodiment.
BP3=P_AF-P_img (9)

In this embodiment, the spatial frequency BP correction value can be calculated more easily. In this embodiment, the accuracy of the spatial frequency BP correction value is slightly inferior to that of the first embodiment, but the amount of information stored for calculating the spatial frequency BP correction value is reduced, and the amount of communication between the lens and the camera is reduced. It is possible to reduce the load and the calculation load of the camera MPU 125.

● (Third Embodiment)
Next, a third embodiment of the present invention will be described. Also in this embodiment, the method of calculating the spatial frequency BP correction value is different from that of the above-described embodiments. In this embodiment, the spatial frequency BP correction value is not calculated when it is not necessary to calculate it, so that the communication amount between the lens and the camera is reduced and the camera MPU 125 is not reduced without degrading the accuracy of the spatial frequency BP correction value. Reduce the calculation load.

A block diagram of the image pickup apparatus (FIG. 2), an explanatory diagram of each focus detection method (FIGS. 3A to 5), an explanatory diagram of a focus detection area (FIG. 6), focus detection processing, and various BP correction value calculation processings. The flowchart (FIG. 1, FIG. 7 and FIG. 9A) is also used in this embodiment. In addition, the drawings relating to the spatial frequency BP correction value calculation processing (FIGS. 10B to 10C) are also used.

A method of calculating the spatial frequency BP correction value (BP3) in this embodiment will be described with reference to the flowchart of FIG. In FIG. 13, the same processes as those in FIG. 10A are designated by the same reference numerals, and the duplicated description will be omitted.

In S3000, the camera MPU 125 determines whether it is necessary to calculate the spatial frequency BP correction value. As can be seen from the description in the first embodiment, the more similar the evaluation band W1 of the captured image and the AF evaluation band W2 are, the smaller the spatial frequency BP correction value is. Therefore, in the present embodiment, when it is determined that the difference between the two evaluation bands is small enough not to calculate the spatial frequency BP correction value (for example, when the difference is smaller than a predetermined threshold value), the correction is performed. The calculation of the value is omitted.

Specifically, when the condition that the difference between the two evaluation bands is sufficiently small is satisfied, the calculation of the correction value is omitted. For example, when the signal used for AF is also the signal read in the first read mode, the evaluation band of the captured image is equal to the AF evaluation band. Furthermore, when a digital filter having a spatial frequency characteristic similar to the spatial frequency characteristic indicating the sensitivity for each spatial frequency when viewing a captured image is used during processing of the AF evaluation signal, the spatial frequency characteristic during viewing and the digital filter Spatial frequency characteristics become equal. Such a situation occurs when an image displayed on the display 126 is enlarged and displayed.
Similarly, it is assumed that the evaluation band of the captured image is equal to the AF evaluation band when the captured image is generated by the signal read in the second read mode. Such a situation occurs when the recorded image size of the captured image is set small.

In S3000, the camera MPU 125 determines that calculation of the correction value is unnecessary when any of such predetermined conditions is satisfied, and advances the process to S3001.
In step S3001, the camera MPU 125 does not calculate the correction value, so 0 is substituted for BP3, and the calculation process of the spatial frequency BP correction value (BP3) ends.

On the other hand, if it is determined in S3000 that the correction value needs to be calculated, the camera MPU 125 performs S300 to S303 in the same manner as in the first embodiment (or the second embodiment).

As described above, in the present embodiment, when it is determined that the calculation of the spatial frequency BP correction value is unnecessary, the calculation of the correction value is omitted, so that the amount of data stored for calculating the correction value cannot be reduced. It is possible to reduce the amount of data communication and the calculation load when calculating the correction value. It is also possible to combine with the second embodiment. In that case, not only the amount of data stored for calculating the correction value is reduced, but also the data communication amount and the calculation load when calculating the correction value are further reduced. be able to.

In the present embodiment, the omission of the spatial frequency BP correction value has been described, but the vertical and horizontal BP correction values and the color BP correction value can be omitted if it can be determined that they are unnecessary. For example, when focus detection is performed in consideration of both vertical and horizontal contrasts, calculation of the vertical and horizontal BP correction values may be omitted. If the color signal used for the captured image and the color signal used for focus detection are the same, the calculation of the color BP correction value may be omitted.

(Other embodiments)
The present invention is also realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or device via a network or various storage media, and the computer (or CPU, MPU, etc.) of the system or device reads the program. This is the process to be executed.

100... Lens unit, 104... Focus lens, 113... Focus actuator, 117... Lens MPU, 118... Lens memory, 120... Camera body, 122... Image sensor, 125... Camera MPU, 129... Phase difference AF section, 130... TVAF Department

Claims (13)

A lens unit configured to be attachable to and detachable from an image pickup unit having an image pickup element and having a photographing optical system,
Storage means for storing information on an MTF curve relating to the image forming position of the photographing optical system for a plurality of different spatial frequencies;
In response to a request from the imaging unit, a transmission unit that transmits the information to the imaging unit,
The information stored in the storage means is not weighted according to the spatial frequency,
The lens unit, wherein the information transmitted from the lens unit to the image capturing unit is subjected to weighted addition according to a spatial frequency in the image capturing unit. The information transmitted from the lens unit to the image capturing unit is related to first information regarding an evaluation frequency of a signal used for obtaining a focus detection result in the image capturing unit and an evaluation frequency of a signal used for a captured image. The lens unit according to claim 1, wherein weighted addition according to the spatial frequency is performed using the second information. The lens unit according to claim 1 , wherein the weighting is performed on information that is normalized with a maximum value for each spatial frequency. The lens unit according to any one of claims 1 to 3 , wherein the information is a discrete sample of the MTF curve. It said information lens unit according to any one of claims 1 to 3, characterized in that the information about the maximum value of the MTF curves. 6. The transmitting unit transmits the information to the newly attached image pickup unit when the image pickup unit attached to the lens unit is replaced, according to any one of claims 1 to 5. The lens part shown. The transmission unit, every time the focus detection processing by the imaging unit is carried out, the lens unit according to any one of claims 1 to 5, characterized that you send the information to the imaging unit. Said information lens unit according to any one of claims 1 to 7, characterized in that the information corresponding to the position of the focus detection area. Said information lens unit according to any one of claims 1 to 8, characterized in that the information corresponding to the zoom position and focus position of the lens unit. The imaging optical system includes a zoom lens for realizing the zoom function, the diaphragm performs the light amount adjustment, and lens unit according to any one of claims 1 to 9, characterized in that it comprises a focusing lens to perform focusing. It said transmission means performs control according to the lens unit, any one of claims 1 to 10, characterized in that the request from the imaging unit is a lens MPU to send information to the imaging unit Lens part described in. The lens MPU is electrically connected to the imaging unit via a signal line of a mount, and transmits the information to the imaging unit via the signal line in response to a request from the imaging unit. The lens unit according to claim 11 . A method of controlling a lens unit having a photographing optical system, which is configured to be detachably attached to an image pickup unit having an image pickup element,
The lens unit has a storage unit that stores information about an MTF curve of the photographing optical system for a plurality of different spatial frequencies,
The control method includes a transmitting step of reading the information from the storage unit and transmitting the information to the image capturing unit in response to a request from the image capturing unit,
The information stored in the storage unit is not weighted according to the spatial frequency, and the information transmitted from the lens unit to the imaging unit is weighted according to the spatial frequency in the imaging unit. A method of controlling a lens unit, wherein:

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