JP2019091067A - Lens assembly and control method thereof - Google Patents

Abstract

Kind Code: A1 A lens unit and a control method thereof are provided that enable an imaging device to accurately correct a focus detection error. A lens unit having a photographing optical system, which is detachably attached to an image pickup unit having an image sensor, and which stores information on MTF curves of the photographing optical system for a plurality of different spatial frequencies; and transmitting means for transmitting information to the imaging section in response to a request from the imaging section, wherein the information is not weighted according to spatial frequency. [Selection drawing] Fig. 2

Description

  The present invention relates to a lens unit that can be attached to and detached from an imaging device (or imaging unit) having an imaging element, and a control method therefor.

  A contrast AF method and a phase difference AF method are known as an automatic focus detection (AF) method of an imaging device. Both the contrast AF method and the phase difference AF method are AF methods that are often used in video cameras and digital still cameras, and there are systems in which an imaging device 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 an optical image may give an error to the focus detection result, and a method for reducing such an error is used. Proposed.

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

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 specific to the camera body has a problem that the focus detection error can not be sufficiently corrected. The focus detection error is originally the difference between the focus state in which the observer feels that the image is in the best focus state in the photographed image and the focus state indicated by the focus detection result. However, in the method described in Patent Document 1, the focus state of the captured image is not considered.

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

  The present invention is directed to ameliorating 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 device to accurately correct a focus detection error and a control method thereof.

  The above-described object is a lens unit configured to be attachable to and detachable from an imaging unit having an imaging element and having a photographing optical system, and storing information on MTF curves of the photographing optical system with respect to a plurality of different spatial frequencies , And transmitting means for transmitting information to the imaging unit in response to a request from the imaging unit, the information being achieved by the lens unit characterized in that weighting according to the spatial frequency is not performed. Ru.

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

Flow chart showing AF operation in the embodiment Flow chart showing AF operation in the embodiment A block diagram of a digital camera as an example of an imaging device according to an embodiment FIG. 2 is a view showing an example of the arrangement of an imaging device 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. 2 A figure showing an example of a focus detection field in an embodiment Flow chart of vertical and horizontal BP correction value (BP1) calculation process in the embodiment A diagram for explaining vertical and horizontal BP correction value calculation processing in the embodiment The figure for demonstrating the color BP correction value (BP2) calculation process in embodiment. A figure for explaining spatial frequency BP correction value (BP3) calculation processing in a 1st embodiment. The figure which shows the various space frequency characteristics in an embodiment The figure for demonstrating the spatial frequency BP correction value (BP3) calculation process in 2nd Embodiment. Flow chart for explaining the spatial frequency BP correction value (BP3) calculation process in the third embodiment

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Although the embodiments have specific and specific configurations to facilitate understanding and explanation of the invention, the present invention is not limited to such specific configurations. For example, although an embodiment in which the present invention is applied to a lens interchangeable single-lens reflex digital camera will be described below, the present invention is also applicable to a lens interchangeable type digital camera and a video camera. The present invention can also be implemented in any electronic device equipped with a camera, such as a mobile phone, a personal computer (laptop, tablet, desktop, etc.), a game console, and the like.

● (First embodiment)
(Description of Configuration of Imaging Device-Lens Unit)
FIG. 2 is a block diagram showing an example of the functional configuration of a digital camera as an example of the imaging device according to the embodiment. The digital camera of the present embodiment is a lens-interchangeable single-lens reflex camera, and has a lens unit 100 and a camera body 120. The lens unit 100 is mounted 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 (a first lens group 101, an aperture 102, a second lens group 103, a 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 disposed at the tip of the lens unit 100, and is movably held in the optical axis direction OA. The diaphragm 102 also functions as a mechanical shutter that controls the exposure time during still image shooting, in addition to the function of adjusting the light amount at the time of shooting. The diaphragm 102 and the second lens group 103 are integrally movable in the optical axis direction OA, and move in conjunction with the first lens group 101 to realize the zoom function. The focus lens 104 is also movable in the optical axis direction OA, and the subject distance (in-focus distance) at which the lens unit 100 is in focus changes according to the position. By controlling the position of the focusing lens 104 in the optical axis direction OA, focusing is performed to adjust the focusing distance of the lens unit 100.

  The drive / control system includes a zoom actuator 111, an aperture actuator 112, a focus actuator 113, a zoom drive circuit 114, an aperture 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 to control the angle of view of the optical system of the lens unit 100. The diaphragm drive circuit 115 drives the diaphragm 102 using the diaphragm actuator 112 to control 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 to control the focusing distance of the optical system of the lens unit 100. Also, 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. 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 lens position information in response to a request from the camera MPU 125. The 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 light flux of the exit pupil. It contains information such as position and diameter in the direction OA. The lens MPU 117 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. The lens memory 118 stores in advance optical information necessary for automatic focus detection. The camera MPU 125 controls the operation of the lens unit 100 by executing a program stored in, for example, a built-in non-volatile memory or lens memory 118.

(Description of Configuration of Imaging Device-Camera Body)
The camera body 120 has an optical system (optical low pass filter 121 and imaging element 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 constitute a photographing optical system.
The optical low pass filter 121 reduces false color and moiré of a captured image. The imaging device 122 is configured of a CMOS image sensor and peripheral circuits, and m pixels in the horizontal direction and n pixels in the vertical direction (n and m are integers of 2 or more) are arranged. The imaging element 122 according to the present embodiment has a pupil division function, and can perform 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 from the imaging element 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 unit 129, and a TVAF unit 130.

  The sensor drive circuit 123 controls the operation of the image sensor 122 and A / D converts the acquired image signal and transmits it 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, compression encoding processing, on the image data acquired by the imaging element 122. The image processing circuit 124 also generates a signal for phase difference AF.

  The camera MPU (processor) 125 performs all operations and controls related to the camera body 120, and the sensor drive circuit 123, image processing circuit 124, display 126, operation switch group 127, memory 128, phase difference AF unit 129, TVAF Control unit 130; 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 request for acquiring the lens position, a diaphragm with a predetermined drive amount, a focus lens, a zoom driving request, and a request for acquiring optical information unique to the lens unit 100. The camera MPU 125 incorporates a ROM 125a storing a program for controlling the camera operation, a RAM 125b storing variables, and an EEPROM 125c storing various parameters.

  The display 126 is configured of an LCD or the like, and displays information on the shooting mode of the camera, a preview image before shooting and a confirmation image after shooting, an in-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. A memory 128 as recording means of the present embodiment is a removable flash memory and records a photographed image.

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

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

(Description of focus detection operation: phase difference AF)
Hereinafter, the operations of the phase difference AF unit 129 and the TVAF unit 130 will be further described.
First, the operation of the phase difference AF unit 129 will be described.
FIG. 3A is a diagram showing the pixel arrangement of the image pickup device 122 in the present embodiment, in which a range of six rows (Y direction) and eight rows (X direction) of a two-dimensional C-MOS area sensor The state observed from the unit 100 side is shown. The image sensor 122 is provided with a Bayer-arranged color filter, and in the pixels in the odd rows, the green (G) and red (R) color filters are alternately 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 disposed inside the on-chip microlens are photoelectric conversion units.

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

  Here, the pixel signal in the case of performing phase difference AF will be described. As described later, in the present embodiment, the exit light beam of the imaging optical system is pupil-divided by the micro lens 211i of FIG. 3A and the divided photoelectric conversion units 211a and 211b. Then, for a plurality of pixels 211 in a predetermined range arranged in the same pixel row, the output of the photoelectric conversion unit 211a is connected and organized, and the AF A image and the output of the photoelectric conversion unit 211b are connected and organized. Let the thing be the B image for AF. The outputs of the photoelectric conversion units 211a and 211b use pseudo luminance (Y) signals calculated by adding the green, red, blue, and green outputs included in the unit array of the color filter. However, the AF A image and the B image may be organized for each of the red, blue and green colors. By detecting the relative image shift amount of the AF A image and the B image thus generated by correlation calculation, it is possible to detect the defocus amount (defocus amount) of the predetermined area. In this embodiment, the sum of the output of one photoelectric conversion unit and the output of all photoelectric conversion units is read out 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 out, the output of the photoelectric conversion unit 211b is obtained by subtracting the output of the photoelectric conversion unit 211a from the sum. As a result, both AF A and B images can be obtained, and phase difference AF can be realized. Such an imaging device is known as disclosed in Japanese Patent Application Laid-Open No. 2004-134867, and thus the description of the details beyond this will be omitted.

  FIG. 3B is a view showing a configuration example of the readout circuit of the image sensor 122 of the present embodiment. Reference numeral 151 denotes a horizontal scanning circuit, and reference numeral 153 denotes 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 in each photoelectric conversion unit, signals are read out via these scanning lines.

The image sensor of this embodiment has the following two types of readout modes in addition to the above-described readout method in the pixel. The first readout mode is referred to as an all-pixel readout mode, and is a mode for capturing a high definition still image. In this case, the signals of all the pixels are read out.
The second readout mode is referred to as a thinning readout mode and is a mode for performing only moving image recording or display of a preview image. In this case, since the number of pixels required is smaller than all the pixels, only the pixels thinned out to a predetermined ratio in both the X direction and the Y direction are read out. Also, when it is necessary to read data at high speed, the thinning read mode is used similarly. When thinning in the X direction, signal addition is performed to improve the S / N, and thinning in the Y direction ignores the signal output of the row to be thinned. The phase difference AF and the contrast AF are usually performed based on the signal read in the second read mode.

  FIG. 4 is a view 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 disposed near the image height zero, that is, the center of the image plane, in the image pickup apparatus of this embodiment. The photoelectric conversion unit in the image sensor and the exit pupil plane of the photographing optical system are designed to be in a conjugate relationship by the on-chip micro lens. 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, although the photographing optical system of the present embodiment is a zoom lens having a variable power function, the distance and size from the image plane of the exit pupil change when the variable power operation is performed depending on the optical type. 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, optimum design of decentration parameters according to the shape of the on-chip micro lens and the image height (X, Y coordinates) is made.

  In FIG. 4A, reference numeral 101 denotes a first lens group, reference numeral 101b denotes a barrel member for holding the first lens group, reference numeral 105 denotes a third lens group, and reference numeral 104b denotes a barrel member for holding the focus lens 104. Reference numeral 102 denotes an aperture, 102a an aperture plate for defining the aperture diameter when the aperture is open, and 102b an aperture blade for adjusting the aperture diameter when the aperture is narrowed. Note that 101b, 102a, 102b, and 104b, which function as restriction members for light fluxes passing through the photographing optical system, indicate optical virtual images when observed from the image plane. Further, the synthetic aperture in the vicinity of the stop 102 is defined as the exit pupil of the lens, and the distance from the image plane is set to Zep as described above.

  The pixel 211 is disposed in the vicinity of the center of the image plane, and is called a center pixel in the present embodiment. The central pixel 211 includes the members of the photoelectric conversion units 211a and 211b, the wiring layers 211e to 211g, the color filter 211h, and the on-chip microlenses 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 micro lens 211i. In other words, the exit pupil of the photographing optical system is projected onto the surface of the photoelectric conversion unit via the on-chip micro lens 211i.

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

  In FIG. 4A, the outermost part of the light flux passing through the photographing optical system is indicated by L, the light flux L is restricted by the aperture plate 102a of the stop, and the projected images EP1a and EP1b are vignetted by the photographing optical system. It has hardly occurred. In FIG. 4 (b), the light flux L of FIG. 4 (a) is indicated by TL. From the fact that most of the projected images EP1a and EP1b of the photoelectric conversion unit are included in the circle indicated by TL, it can be understood that vignetting is substantially not generated. Since the light beam L is limited only by the aperture plate 102a of the stop, TL can be reworded as 102a. At this time, at the center of the image plane, the vignette state of each of the projected images EP1a to EP1b is symmetrical with respect to the optical axis, and the amount of light received by each of the photoelectric conversion units 211a and 211b is equal.

  When phase difference AF is performed, the camera MPU 125 controls the sensor drive circuit 123 so as to read out the two types of outputs from the image sensor 122. Then, the camera MPU 125 supplies information of the focus detection area to the image processing circuit 124, generates AF A and B image data from the output of the pixels included in the focus detection area, and the phase difference AF unit 129 To supply to The image processing circuit 124 generates data of the A and B images for AF in accordance with this command 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 imaging element 122 constitutes a part of the focus detection apparatus for both phase difference AF and contrast AF.
Here, the configuration in which the exit pupil is divided into two in the horizontal direction has been described as an example, but the configuration may be such that the exit pupil is divided into two in the vertical direction for some pixels of the imaging device. Also, the exit pupil may be divided in both horizontal and vertical directions. By providing the pixels for dividing the exit pupil in the vertical direction, it is possible to perform phase difference AF corresponding to the contrast of the subject in the vertical direction as well as in the horizontal direction.

(Description of focus detection operation: Contrast AF)
Next, 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 cooperating to repeatedly drive the focus lens and calculate the evaluation value.

  When 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 achieve high luminance. A gamma correction process is performed to suppress the component. In the present embodiment, the case where TVAF is performed using 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.

  A 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 for selecting a signal in the set area. The gate signal is input to the line peak detection circuit 402, the horizontal integration circuit 403, the line minimum value detection circuit 404, the line peak detection circuit 409, the vertical integration circuit 406, and the 410 vertical peak detection circuits 405, 407, and 411. . Further, the timing at which the luminance signal Y is input to each circuit is controlled so that each focus evaluation value is generated by the luminance signal Y in the focus detection area. A plurality of areas can be set in the area setting circuit 413 in accordance with the focus detection area.

  The 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 determined in the focus detection area set in 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 by the vertical peak detection circuit 405 to generate a Y peak evaluation value. The Y peak evaluation value is an index that is effective for determining a high brightness subject or a low brightness subject.

  The 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 an 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 by the vertical integration circuit 406 to generate a Y integration evaluation value. The Y integral evaluation value can be used as an index for determining the brightness of the entire focus detection area.

  The 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 determined in the focus detection area. Further, 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 in the focus detection area to generate a Max-Min evaluation value. The Max-Min evaluation value is an index that is effective for determining low contrast and high contrast.

  The 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 to 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 determined in the focus detection area. The line peak value is peak-held in the focus detection area by the vertical peak detection circuit 411 to generate an area peak evaluation value. The area peak evaluation value is an index that is effective for the restart determination that determines whether or not to shift to the process of searching for the in-focus point again from the in-focus state because the change is small even if the subject moves in the focus detection area.

  A method of calculating the all 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 integration is performed on the total number of horizontal scanning lines in the vertical direction in the focus detection area to generate an entire line integration evaluation value. The all line integral evaluation value is a main AF evaluation value because the dynamic range is wide and the sensitivity is high due to the integration effect. Therefore, in the present embodiment, the case where the focus evaluation value is simply described means the entire line integral evaluation value.

  The AF control unit 151 of the camera MPU 125 obtains each of the focus evaluation values described above, and moves the focus lens 104 by a predetermined amount in a predetermined direction along the optical axis direction through the lens MPU 117. Then, the above-mentioned various evaluation values are calculated based on the newly obtained image data, and the focus lens position at which the all 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. In this way, focus detection can be performed on the contrast information of the subject in two directions, horizontal and vertical.

(Description of focus detection area)
FIG. 6 is a diagram showing an example of the focus detection area in the imaging range. As described above, both phase difference AF and 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 the imaging range 217 in which the pixels of the imaging element 122 are formed. In the imaging range 217, focus detection areas 218ah, 218bh, and 218ch for phase difference AF are set. In this embodiment, three focus detection areas 218 ah, 218 b h, and 218 ch for phase difference AF are set at a central part of the imaging range 217 and two places on the left and right. Further, focus detection areas 219a, 219b and 219c for TVAF are set to include one of focus detection areas 218ah, 218bh and 218ch for phase difference AF. Note that FIG. 6 is a setting example of the focus detection area, and the number, the position, and the size are not limited to those illustrated.

(Description of the flow of focus detection processing)
Next, with reference to FIGS. 1A and 1B, an automatic focus detection (AF) operation in the digital camera of the present embodiment will be described.
After the outline of the AF process is described, the detailed description will be made. In the present embodiment, the camera MPU 125 first applies 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 a defocus amount having 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 in-focus position of the closest subject based on the defocus amount. Let

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

  If the focus evaluation value has not been obtained before, the amount of change in the focus evaluation value can not be obtained. In that case, the camera MPU 125 focuses on the closest subject among the focus detection areas which are larger than the predetermined defocus amount and in which the defocus amount having the predetermined reliability is obtained. The focus lens 104 is driven as follows. If a defocus amount having a predetermined reliability is not obtained, and if a defocus amount larger than a predetermined defocus amount is not obtained, the camera MPU 125 determines a predetermined amount that is not related 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, there is a high possibility that it is difficult to detect a change in focus evaluation value at the time of the next focus detection.

  When focus detection is completed by any 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 focus detection result after correction.

The details of the above-described AF processing will be described below using the flowcharts shown in FIGS. 1A and 1B. The following AF processing operation is mainly executed by the camera MPU 125 unless another entity is specified. When the camera MPU 125 transmits a command or the like to the lens MPU 117 to drive or control the lens unit 100, an operation subject may be described as the camera MPU 125 in order to simplify the description.
At S1, the camera MPU 125 sets a focus detection area. Here, it is assumed that three focus detection areas as shown in FIG. 6 are set for phase difference AF and contrast AF.

At S2, the camera MPU 125 sets the close determination flag in the RAM 125b to one.
In step S3, the camera MPU 125 exposes the image sensor 122 and reads an image signal, and the image processing circuit 124 generates an image signal for phase difference AF based on image data in the focus detection areas 218ah, 218bh, and 218ch for phase difference AF. To generate In addition, the RAW image data generated by the image processing circuit 124 is supplied to the TVAF unit 130, and the TVAF unit 130 calculates an evaluation value based on pixel data in the focus detection areas 219a, 219b, and 219c for TVAF. A process of correcting the asymmetry of the exit pupil due to vignetting of the light flux by the lens frame of the photographing lens or the like in the image processing circuit 124 before generating an image signal for phase difference AF (see Japanese Patent Laid-Open No. 2010-117679) May apply. The focus evaluation value calculated by the TVAF unit 130 is stored in the RAM 125 b in the camera MPU 125.

  In S4, the camera MPU 125 determines whether or not the peak (maximum value) of the reliable focus evaluation value is detected. If a reliable peak is detected, the camera MPU 125 advances the process to step S20 to finish the focus detection process. Although the method of calculating the reliability of the peak of the focus evaluation value is not limited, for example, the method as described in FIGS. 10 to 13 of JP-A-2010-78810 may be used. Specifically, whether the detected peak is the peak of a mountain, the difference between the maximum value and the minimum value of the focus evaluation value, the length of a portion inclined at an inclination of a predetermined value (SlopeThr), and The slope of the part in question is compared with each threshold value to judge. If all the thresholds are satisfied, it can be determined that the peak is reliable.

  In the present embodiment, phase difference AF and contrast AF are used in combination. Therefore, when the presence of a closer object is confirmed in the same focus detection area or another focus detection area, the focus evaluation value peak is detected even when the reliable focus evaluation value peak is detected. The process may proceed to S5 without completing the detection. However, in this case, when the position of the focus lens 104 corresponding to the reliable focus evaluation value peak is stored, and the reliable focus detection result is not obtained in the process after S5, the stored focus The position of the lens 104 is taken 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 of the focus detection areas 218ch, 218ah, and 218bh, and stores the phase difference in advance. It converts into defocusing quantity using the conversion factor which is. Here, the reliability of the calculated defocus amount is also determined, and only the defocus amount of the focus detection area determined to have predetermined reliability is used in the subsequent AF processing. Due to the influence of vignetting due to a lens frame or the like, the phase difference detected between a pair of image signals contains more errors as the defocus amount increases. Therefore, when the obtained defocus amount is larger than the threshold, when the degree of coincidence of the shape of the pair of image signals is low, and when the contrast of the image signal is low, the obtained defocus amount has a predetermined reliability. It can be determined that it is not (unreliable). Hereinafter, when it is determined that the obtained defocus amount has a predetermined reliability, it is expressed as “the defocus amount has been calculated”. Further, when the defocus amount can not 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 can not be calculated".

  In S6, the camera MPU 125 checks whether or not the defocus amount has been calculated in all of the focus detection areas 218ah, 218bh, and 218ch for phase difference AF set in S1. If the defocus amount has been calculated in all the focus detection areas, the camera MPU 125 advances the process to S20, and the defocus amount indicating the object closest to the closest side among the calculated defocus amounts is calculated. Vertical and horizontal BP correction values (BP1) are calculated for the focus detection area. Here, the reason why the closest subject is selected is that, in general, the subject that the photographer wants to focus on is often present on the near side. The vertical and horizontal BP correction values (BP1) are the difference between the focus detection result in the case where focus detection is performed on the contrast in the horizontal direction and in the case where focus detection is performed on the contrast in the vertical direction. It is a value to be corrected.

  A general subject has contrast in both the horizontal direction and the vertical direction, and the evaluation of the focus state of a captured image is also made in consideration of the contrast in both the horizontal direction and the vertical direction. On the other hand, when focus detection is performed only in the horizontal direction as in AF of the above-described phase difference detection method, errors occur in the focus detection result in the horizontal direction and the focus state in both the horizontal direction and the vertical direction of the captured image. This error occurs due to astigmatism of the imaging optical system and the like. 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, etc. Be done. Details of the calculation method will be described later.

  In S21, the camera MPU 125 calculates a color BP correction value (BP2) using contrast information in the vertical direction or horizontal direction for the focus detection area for which the correction value has been calculated in S20. The color BP correction value (BP2) is generated due to the chromatic aberration of the photographing optical system, and is generated due to the difference between the color balance of the signal used for focus detection and the color balance of the signal used for the photographed image or the developed image. For example, in the contrast AF of this embodiment, since the focus evaluation value is generated based on the pixel (green pixel) output having a green (G) color filter, the in-focus position of the green wavelength is mainly detected. Become. However, since the captured image is generated using all RGB colors, when the in-focus position of red (R) or blue (B) is different from green (G) (when on-axis chromatic aberration exists), focus evaluation is performed This results in a deviation (error) from the focus detection result by the value. The correction value for correcting the error is the color BP correction value (BP2). Details of the method of calculating the color BP correction value (BP2) will be described later.

  At S22, the camera MPU 125 calculates a specific spatial frequency BP correction value (BP3) using the green signal or the contrast information of the luminance signal Y in the vertical direction or horizontal direction with respect to the focus detection area to be corrected. . The spatial frequency BP correction value (BP3) is mainly generated by spherical aberration of the photographing optical system, and is a difference between the evaluation frequency (band) of the signal used for focus detection and the evaluation frequency (band) at the time of viewing the photographed image. Generated by As described above, since the image signal at the time of focus detection is read out from the image sensor in the second mode, the output signal is added or thinned. Therefore, the output signal used for focus detection has a low evaluation band with respect to the captured image generated using the signals of all the pixels read out in the first readout mode. It is the spatial frequency BP correction value (BP3) that corrects the focus detection shift that occurs due to the difference in the evaluation band. 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 according to the following equation (1) using the three calculated 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 steps, and calculation is performed in order of vertical and horizontal (S20), color (S21), and spatial frequency (S22).
First, while evaluation at the time of viewing of a photographed image uses contrast information in both the vertical and horizontal directions, focus detection calculates an error caused by using contrast information in one direction as the vertical and horizontal BP correction value (BP1).

Next, by separating the influence of vertical and horizontal BP, the difference between the color of the signal used for the captured image and the color of the signal used for focus detection in the contrast information in one direction is the color BP correction value (BP2) Calculated as
Furthermore, the spatial frequency BP correction value is the difference in the in-focus position generated due to the difference between the evaluation band at the time of viewing the captured image and at the time of focus detection for one specific color such as green or luminance signal. Calculated as BP3).
As described above, by dividing and calculating the three types of errors, the amount of calculation is reduced, and the data capacity stored in the lens or the camera is 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 Equation (1).

  In step S25, the camera MPU 125 causes the display 126 to display a focus detection area (AF frame display) representing the focus detection area for which the defocus amount used to drive the focus lens 104 has been calculated superimposed on, for example, a live view image. 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 of FIG. 1B. At S7, the camera MPU 125 determines whether the close determination flag is 1. The closeness determination flag is 1 when the focus lens drive has not been performed since the start of the AF operation. If focus lens driving is performed, the close determination flag is zero. If the close determination flag is 1, the camera MPU 125 advances the process to step S8.

  When the camera MPU 125 can not calculate the defocus amount in all the focus detection areas in S8, or the defocus amount indicating the presence of the closest object on the nearest side among the calculated defocus amounts is the predetermined threshold A. In the following case, the process proceeds to S9. At S9, the camera MPU 125 drives the focus lens by a predetermined amount on the near side.

Here, in the case of Yes in S8, the reason for performing the lens drive of a predetermined amount will be described. First, among the plurality of focus detection areas, the case where there is no area for which the defocus amount can be calculated means that the subject to be focused on has not been found at the present time. Therefore, before it is determined that focusing can not be performed, a predetermined amount of lens driving is performed on all focus detection areas in order to confirm the presence of an object to be focused, and focus evaluation values to be described later are obtained. Make it possible to determine changes. In addition, when the defocus amount indicating the presence of the closest subject among the calculated defocus amounts is less than or equal to the predetermined threshold A, a focus detection area in a substantially in-focus state exists at the present time That's the case. In such a situation, a lens drive of a predetermined amount is performed in order to confirm the possibility that there is a subject not detected at this time on the near side in the focus detection area where the defocus amount could not be calculated. Change in the focus evaluation value to be determined.
Note that the predetermined amount for driving the focus lens in S9 may be determined in view of the F value of the photographing optical system and the sensitivity of the focus movement amount on the imaging surface to the lens driving amount.

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

  If it is determined in S7 that the close determination flag is not 1 (is 0), the camera MPU 125 advances the process 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 B or more before and after lens driving. . Although the focus evaluation value may increase or decrease, in S12, it is determined whether the absolute value of the change amount of the focus evaluation value is equal to or greater than a predetermined threshold B.

  Here, although the defocus amount can not be calculated when the absolute value of the change amount of the focus evaluation value is equal to or more than the predetermined threshold value B, the change of the blurred state of the subject could be detected by the increase or decrease of the focus evaluation value. Means. Therefore, in the present embodiment, even when the defocus amount due to the phase difference AF can not be detected, the presence of the subject is determined based on the increase or decrease of the focus evaluation value, and the AF processing is continued. As a result, it is possible to perform focus adjustment on an object which has a large defocus amount and can not be detected by the phase difference AF.

  Here, the predetermined threshold value B used for the determination is changed according to the lens drive amount. When the lens driving amount is large, the threshold 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 of the focus evaluation value also increases as the amount of lens drive increases. The threshold B for each lens drive amount is stored in the EEPROM 125 c.

  If the absolute value of the amount of change in focus evaluation value is equal to or greater than the threshold B, the camera MPU 125 advances the process to S13, and the focus detection area in which the amount of change in focus evaluation value is equal to or greater than the threshold B indicates the presence of an infinite distance object. It is determined whether it is only the focus detection area. When the focus detection area indicates the presence of an object at infinity, the drive direction of the lens drive is the closest direction and the focus evaluation value decreases, or the drive direction of the lens drive is the focus direction and the focus evaluation value increases. It is.

  If the focus detection area in which the amount of change in focus evaluation value is equal to or greater than the threshold B is not the only focus detection area indicating the presence of an infinite distance object, the camera MPU 125 advances the process to S14 and drives the lens by a predetermined amount on the near side. Do. This is because there is a focus detection area that indicates the presence of the near side object in the focus detection area in which the amount of change in focus evaluation value is equal to or greater than the threshold B. The reason for giving priority to the close side is as described above.

  On the other hand, if the focus detection area in which the amount of change in focus evaluation value is equal to or greater than the threshold B is only the focus detection area indicating the presence of an infinite distance object in S13, the camera MPU 125 advances the process to S15. At S15, the camera MPU 125 determines whether there is a focus detection area for which the defocus amount has been calculated. When there is a focus detection area for which the defocus amount has been calculated (Yes in S15), the camera MPU 125 processes the result of the phase difference AF in preference to the presence of the object on the infinity side by the focus evaluation value. To S20 of FIG. 1A.

  If there is no focus detection area for which the defocus amount has been calculated (No in S15), the information indicating the presence of the subject is only the change in focus evaluation value. Therefore, based on the change of the focus evaluation value, the camera MPU 125 performs a predetermined amount of lens driving to the infinity side in S16, and returns the process to S3 of FIG. 1A.

  The predetermined amount of lens drive performed in S14 and S16 may be determined in view of the defocus amount detectable by the phase difference AF. Although the detectable defocus amount differs depending on the subject, the lens drive amount is set in advance so that the subject can not be detected and not passed by the lens drive from the state where the focus can not be detected.

  If the absolute value of the change amount of the focus evaluation value is less than the predetermined threshold B (No in S12), the camera MPU 125 advances the process to S17 and determines the presence or absence of the focus detection area for which the defocus amount has been calculated. If there is no focus detection area for which the defocus amount has been calculated, the camera MPU 125 advances the process to S18, drives the lens to a predetermined fixed point, and then advances the process to S19 and causes the display 126 to be out of focus. Display and stop AF processing. This is a case where there is no focus detection area where the defocus amount can be calculated, and there is no focus detection area in which the focus evaluation value changes before and after lens driving. In such a case, since there is no information indicating the presence of the subject, the camera MPU 125 determines that the in-focus state can not be achieved and ends the AF process.

  On the other hand, if there is a focus detection area for which the defocus amount has been calculated in S17, the camera MPU 125 advances the process to S20 of FIG. 1A and corrects the detected defocus amount (S20 to S23). The focus lens 104 is driven to the in-focus position. Thereafter, the camera MPU 125 performs in-focus indication on the display 126 at S25, and ends the AF processing.

(Method of calculating vertical and horizontal BP correction value)
Next, a method of calculating the vertical and horizontal BP correction value (BP1) performed in S20 of FIG. 1 will be described using FIGS. 7 to 8B. FIG. 7 is a flowchart showing details of calculation processing of the vertical and horizontal BP correction value (BP1).
At S100, the camera MPU 125 obtains vertical and horizontal BP correction information. The vertical and horizontal BP correction information is difference information of the in-focus position in the vertical direction (second direction) with respect to the in-focus position in the horizontal direction (first direction). In the present embodiment, vertical and 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, although an example of vertical and horizontal BP correction information corresponding to the focus detection areas 219a and 218ah in the center of FIG. 6 is shown, vertical and horizontal BP correction information is stored also for other focus detection areas 219c, 218ch and 219b, 218bh. ing. However, the focus detection correction values of the focus detection areas present at symmetrical positions across 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, the vertical and horizontal BP correction information may be stored for only one of them. Further, when the correction value does not largely change 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 (field angle) of the photographing optical system and the focus lens position (focus distance) are divided into eight zones, and focus detection correction values BP111 to BP188 are stored for each zone. ing. As the number of divided zones increases, a highly accurate correction value according to the position of the first lens group 101 of the imaging optical system and the position of the focus lens 104 can be obtained. The vertical and horizontal BP correction information can be used for both contrast AF and phase difference AF.

In S100, the camera MPU 125 acquires the zoom position and the correction value corresponding to the focus lens position according to the focus detection result to be corrected.
In step S101, the camera MPU 125 determines whether a reliable focus detection result is obtained in any of the horizontal direction and 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 this embodiment only performs focus detection in the horizontal direction, it is the contrast AF that reliable focus detection results can be obtained in both the horizontal direction and the vertical direction. Therefore, in the following description of the vertical and horizontal BP correction values, contrast AF is assumed, but similar processing may be performed when focus detection of phase difference AF is performed in both horizontal and vertical directions. If it is determined in step S101 that the horizontal and vertical focus detection results are also reliable, the camera MPU 125 advances the process to step S102.

  In S102, the camera MPU 125 determines whether the difference between the horizontal focus detection result and the vertical focus detection result is valid. This is a process performed to cope with the problem of near-far conflict that occurs when a long distance subject and a close distance subject are included in the focus detection area. For example, in the case where the distant object has contrast in the horizontal direction and the close object has contrast in the vertical direction, the absolute value is larger than the error generated due to astigmatism of the imaging optical system or the like. There may be a difference in focus detection results. When the difference between the focus detection result in the horizontal direction and the focus detection result in the vertical direction is larger than a predetermined determination value C, the camera MPU 125 determines that the difference is not valid (perspective conflict). Then, the horizontal direction or the vertical direction is selected as the direction indicating the focus detection result closer to the near side, and the process proceeds to S104. Note that the determination value C may uniquely determine a value that greatly exceeds the difference that may occur due to aberration or the like, for the above-described reason, or may be set using the correction information obtained in S100.

  If it is determined in S102 that the difference between the focus detection result in the horizontal direction and the focus detection result in the vertical direction is valid, the camera MPU 125 advances the process to S106.

  On the other hand, if the reliability is in only one direction in the horizontal direction or the vertical direction in S101, or if only one direction in the horizontal direction or the vertical direction is selected in S102, the camera MPU 125 advances the process to S104. At 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 object closer to the near side is calculated in the near and far competition determination is selected.

  Next, in step S105, the camera MPU 125 determines whether weighting in the horizontal direction and the vertical direction is possible. When S105 is executed, although reliable focus detection results have not been obtained in both the horizontal direction and the vertical direction from the viewpoint of the reliability of the focus evaluation value and the near and far conflict, the vertical and horizontal BP correction values are calculated. Make another judgment to The reason is 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 indicate changes in the horizontal focus evaluation value and the vertical focus evaluation value detected by the contrast AF. Also, LP1, LP2, and LP3 indicate the focus lens positions, respectively. In FIG. 8B, LP3 is obtained as the reliable focus detection result from the horizontal focus evaluation value E_h, and LP1 is obtained as the reliable focus detection result from the vertical focus evaluation value E_v. Is shown. Since LP1 and LP3 are largely different, it is determined to be in the near and far conflict state, and the focus detection result LP3 in the horizontal direction, which is the focus detection result closer to the near side, is selected in S104.

  Under such circumstances, the camera MPU 125 determines in step S105 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 process to S106, and corrects the focus detection result LP3 with the focus value. It calculates taking into consideration the influence of the detection result LP2.

In S100, BP1_B which is one element of FIG. 8A is acquired as vertical and horizontal BP correction information, and the focus evaluation value in the horizontal direction in LP3 in FIG. 8B is E_hp, and the focus evaluation value in the vertical direction in LP2 is Suppose that it is E_vp. In this case, in step S106, the camera MPU 125 calculates the vertical and horizontal BP correction value BP1 according to the following equation (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 this embodiment, the correction value BP1 is calculated using equation (2) to calculate the correction value for the focus detection result in the horizontal direction, but when correcting the focus detection result in the vertical direction, the following equation It can be calculated by (3).
BP1 = BP1_B × E_hp / (E_vp + E_hp) × (−1) (3)

  If it is determined in S102 that the difference between the focus detection result in the horizontal direction and the focus detection result in the vertical direction is valid, if the focus detection result on the near side is the detection result in the horizontal direction, If it is the detection result of (1), 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 that the contrast information included in the subject is large, and the vertical and horizontal BP correction value (BP1) is calculated. As described above, the vertical and horizontal BP correction information is
(Focus detection position of subject having contrast information only in the vertical direction)-(Focus detection position of subject having contrast information only in the horizontal direction)
It is. Therefore, the signs of the correction value BP1 for correcting the focus detection result in the horizontal direction and the correction value BP1 for correcting the focus detection result in the vertical direction are opposite. When the process of S106 is completed, the camera MPU 125 ends the vertical and horizontal BP correction value calculation process.

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

  As described above, in this embodiment, since the correction value is calculated according to the contrast information of the subject in different directions, it is possible to calculate the correction value highly accurately according to the pattern of the subject. Although FIG. 8B illustrates the case in which the subject is in perspective competition, one maximum value is detected in each of the horizontal direction and the vertical direction, and one of the focus detection results is not reliable. 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, as in the phase difference AF of this embodiment, when focus detection can be performed only in the horizontal direction, it is assumed that the information amount of the contrast in the horizontal direction and the vertical direction of the object is the same, and the correction value is calculated. You may In that case, the correction value can be calculated by substituting E_hp = E_vp = 1 in the above-mentioned Expression (2) and Expression (3). By performing such processing, although the correction accuracy is lowered, the load of the correction value calculation can be reduced.

  In the above description, the focus detection result of contrast AF is described, but the same processing can be performed on the focus detection result of phase difference AF. The amount of change in the amount of correlation calculated by the correlation calculation of the phase difference AF may be used as a weighting coefficient in calculating the correction value. This utilizes the fact that the amount of change in the amount of correlation increases as the subject's contrast information increases, such as when the subject has a large contrast or a large number of edges with contrast. If it is an evaluation value which can obtain the same relation, various evaluation values may be used without being limited to the change amount of the correlation amount.

  As described above, 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 object. Further, since the correction values in the horizontal direction and the vertical direction are calculated using common correction information as shown in FIG. 8A, the correction value is corrected as compared to the case where each correction value is stored for each direction. The storage capacity of information can be reduced.

  In addition, when the focus detection results for each direction are largely different, the influence of the near and far conflict can be reduced by not calculating the vertical and horizontal BP correction values using these focus detection results. Furthermore, even when near-far conflict is assumed, more accurate correction can be performed by weighting the correction value based on the magnitude of the focus evaluation value for each direction.

(Method of calculating 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 calculation process of the color BP correction value (BP2).
At S200, the camera MPU 125 acquires color BP correction information. The color BP correction information is difference information of in-focus positions detected using signals of other colors (red (R) and blue (B)) with respect to the in-focus position detected using the green (G) signal. It 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

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

In S200, the camera MPU 125 acquires a correction value corresponding to the zoom position and the focus lens position according to the focus detection result to be corrected.
At S201, the camera MPU 125 calculates a color BP correction value. When BP_R as one element in FIG. 9B and BP_B as one element in FIG. 9C are acquired in S200, the camera MPU 125 calculates the color BP correction value BP2 according to the following equation (4) .
BP2 = K_R × BP_R + K_B × BP_B (4)

  Here, K_R and K_B are coefficients for correction information of each color. This value has a correlation with the magnitude relationship of red (R) and blue (B) information to green (G) information contained in the subject, and K_R takes a large value and is blue for subjects containing a large amount of red color. K_B takes a large value for an object containing many colors. For an object containing a large amount of green, both K_R and K_B take small values. K_R and K_B may be set in advance based on spectral information representative of a subject. If 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, correction values are stored in the form of a table for each focus detection area as shown in FIG. 8A and FIG. 9, but the storage method of the correction values is not limited to this. For example, with the intersection of the imaging element and the optical axis of the imaging optical system as the origin, the horizontal and vertical directions of the imaging device are set as the X and Y axes, and the correction value at the center coordinate of the focus detection area is X It may be obtained by the function of and Y. 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 object. 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 later, the correction value may be calculated according to the spatial frequency component of the object using the vertical and horizontal BP correction information for each spatial frequency and the color BP correction information.

(Method of calculating 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. 10 (a) to 10 (c). FIG. 10A is a flowchart showing details of the process of calculating the spatial frequency BP correction value (BP3).
At S300, the camera MPU 125 acquires spatial frequency BP correction information. The spatial frequency BP correction information is information on the imaging position of the imaging optical system for each spatial frequency of the subject. In the present 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. It may be

  An example of the spatial frequency BP correction information will be described with reference to FIG. 10B showing a defocusing MTF (Modulation Transfer Function) of the photographing optical system. The horizontal axis of FIG. 10B indicates the position of the focus lens 104, and the vertical axis indicates the intensity of the MTF. The four types of curves depicted in FIG. 10 (b) are MTF curves for each spatial frequency, showing the case where the spatial frequency changes from low to high in order of MTF1, MTF2, MTF3 and MTF4. . The MTF curve of the spatial frequency F1 (lp / mm) corresponds to the MTF1, and similarly, the spatial frequencies F2, F3 and F4 (lp / mm) correspond to the MTF2, MTF3 and MTF4. Also, LP4, LP5, LP6, and LP7 indicate the position of the focus lens 104 corresponding to the maximum value of each defocus MTF curve. 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 ten focus lens positions for one MTF curve. For example, MTF 1 (n) (1 ≦ n ≦ 10) for MTF 1 It stores 10 data as.

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

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

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

The 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 using FIG. FIG. 11 shows the intensity for each spatial frequency, and 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. 10 (b). Further, Nq indicates the Nyquist frequency determined by the pixel pitch of the imaging element 122. F1 to F4 and Nq are similarly shown in FIGS. 11 (b) to 11 (f) 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 object is drawn as a continuous curve, but discrete values I (n) (1 ≦ n ≦ 4) corresponding to the spatial frequencies F1, F2, F3 and F4. ).

  Further, in the present embodiment, the representative value stored in advance is used as the spatial frequency characteristic of the subject, but the spatial frequency characteristic of the subject to be used may be changed according to the subject on which the focus detection is performed. By applying FFT processing or the like to the captured image signal, spatial frequency information (power spectrum) of the subject can be obtained. In this case, although the arithmetic processing increases, since it is possible to calculate the correction value according to the subject for which the focus is actually detected, it is possible to perform focus detection with high accuracy. Also, more simply, several kinds of spatial frequency characteristics stored in advance may be used properly 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 125 b in the camera. Information to be stored may be spatial frequency characteristics for each defocus state, or may be only spatial frequency characteristics at the time of focusing. Since the spatial frequency BP correction value is calculated in the vicinity of the in-focus state, the correction can be performed with high accuracy by using the spatial frequency characteristic at the in-focus state. However, although the calculation load increases, if the spatial frequency characteristic for each defocus state is used, focusing can be performed with higher accuracy. What defocus state spatial frequency characteristic is to be used may be selected using the defocus amount obtained by phase difference AF.
The spatial frequency characteristic (O) of the photographing optical system is drawn as a continuous curve in FIG. 11B, 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 125 b in the camera. In FIG. 11C, the spatial frequency characteristic (L) of the optical low pass filter 121 is drawn as a continuous curve, but discrete values L (n) (1) corresponding to the spatial frequencies F1, F2, F3, and F4. It has ≦ n ≦ 4).

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

  FIG. 11E shows a spatial frequency characteristic (D1) indicating sensitivity for each spatial frequency when viewing a captured image and a spatial frequency characteristic (D2) of a digital filter used when processing an AF evaluation signal. The sensitivity for each spatial frequency when viewing a captured image is affected by the viewer's individual differences and the viewing environment such as the 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 characteristics 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, and F4 It has 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 of the photographed image and the AF evaluation band W2 to 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) × M 2 (n) × D 2 (n) (1 ≦ n ≦ 4) (6)

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

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

  In addition, since it is not necessary to complete all the calculations in advance, for example, only the imaging 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. The reduction of the

  In FIG. 11, in order to simplify the description, the description has been made using discrete values corresponding to four spatial frequencies (F1 to F4). However, as the number of spatial frequencies having data increases, the spatial frequency characteristics of the evaluation image of the captured image and the AF can be more accurately reproduced, and the correction value can be calculated with high accuracy. On the other hand, the amount of computation can be reduced by reducing the spatial frequency to be weighted. One spatial frequency representing the spatial frequency characteristics of the evaluation band of the photographed image and the AF evaluation band may be provided, and the subsequent calculation may be performed.

Referring back to FIG. 10A, the camera MPU 125 calculates a spatial frequency BP correction value (BP3) in S303. When calculating the spatial frequency BP correction value, the camera MPU 125 first calculates the defocus MTF (C1) of the photographed image and the defocus MTF (C2) of the focus detection signal. The first and second imaging position information C1 and C2 are expressed by the following equations (7) and (5) using the defocus MTF information obtained in S300 and the evaluation bands W1 and W2 obtained in S301 and S302. Calculated according to (8) (1 ≦ n ≦ 10).
C1 (n) = MTF1 (n) × W1 (1) + MTF2 (n) × W1 (2) + MTF 3 (n) × W1 (3) + MTF 4 (n) × W1 (4) (7)
C2 (n) = MTF1 (n) × W2 (1) + MTF2 (n) × W2 (2) + MTF 3 (n) × W2 (3) + MTF 4 (n) × W2 (4) (8)

  Thus, defocus MTF information for each spatial frequency shown in FIG. 10B is added based on the weighting of the evaluation band of the captured image or AF calculated in S301 and S302, and the defocus MTF of the captured image is added. The defocus MTF (C2) of (C1) and AF is obtained. The defocus MTF used when performing weighted addition here may be used after being normalized with the maximum value of each spatial frequency (MTF1 to MTF4). The defocus MTF generally differs in maximum value according to the spatial frequency as shown in FIG. 10 (b). Therefore, when weighted addition is performed with the same weight, the influence of MTF 1 becomes strong in the example of FIG. Therefore, the defocus MTF for each spatial frequency can be weighted and added using a value standardized at the maximum value.

  FIG. 10C shows two obtained defocus MTFs C1 and C2. The horizontal axis is the position of the focus lens 104, and the vertical axis is 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 forming position) is detected as the position of the focus lens 104 corresponding to the maximum value of the curve C2.

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

  As described above, the in-focus position of the captured image is the spatial frequency characteristics of the subject, the imaging optical system, and the optical low pass filter, the spatial frequency characteristics at the time of signal generation, and the spatial frequency characteristics , It changes with the image processing etc. which are given to a photography picture. In the present embodiment, the in-focus position of the captured image can be calculated with high accuracy by calculating the spatial frequency characteristics retroactively to the process of generating the captured image. For example, the in-focus position of the captured image is changed according to the recording size of the captured image, super-resolution processing performed in image processing, sharpness, and the like. In addition, after recording the photographed image, how much the image size and the enlargement rate are to be viewed, the viewing distance at the time of watching and the like affect the evaluation band of the viewer. Then, as the image size becomes larger and as the viewing distance becomes shorter, by setting the evaluation band of the appreciator to a characteristic with emphasis on high frequency components, the in-focus position of the photographed image is also changed.

  On the other hand, the in-focus position detected by the AF also varies with the spatial frequency characteristics of the subject, the imaging 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, etc. Do. In the present embodiment, the in-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 the AF. For example, it is possible to flexibly cope with AF in the first read mode. In that case, the weighting factor may be calculated by changing the spatial frequency characteristic at the time of signal generation to the characteristic corresponding to the first readout mode.

  Further, since the imaging device described in the present embodiment is a lens interchangeable single-lens reflex camera, the lens unit 100 can be replaced. When the lens unit 100 is replaced, the lens MPU 117 transmits 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 photographed image and the in-focus position detected by the AF, it is possible to calculate the correction value with high accuracy for each interchangeable lens. The lens unit 100 may transmit not only defocus MTF information but also information such as spatial frequency characteristics 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, the characteristics of the optical low pass filter, and the like may change. As described above, even in such a case, the correction value is calculated according to the characteristics of the camera body 120, so that correction can be performed with high accuracy.

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

  In the present embodiment, the correction value for AF is calculated paying attention to the characteristics (longitudinal, 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 data storage capacity and 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, defocus MTF information is used as a value representing the characteristic of each spatial frequency of the imaging optical system. However, the defocus MTF information has a large amount of data, and the storage capacity and calculation load become large. Therefore, in the second embodiment, the spatial frequency BP correction value is calculated using the maximum value information of the defocus MTF. As a result, the capacity of the lens memory 118 or the RAM 125 b can be saved, and the amount of communication between the lens and the camera can be reduced, and the calculation load performed by the camera MPU 125 can be reduced.

  Note that a block diagram of the imaging apparatus (FIG. 2), explanatory views of respective focus detection methods (FIGS. 3A to 5), an explanatory view of focus detection areas (FIG. 6), focus detection processing and various BP correction value calculation processing The flowcharts of (1), (7) and (9 (a)) are also used in the present 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 the present embodiment will be described with reference to FIG.
In S300, the camera MPU 125 acquires spatial frequency BP correction information.

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

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

At S303, the camera MPU 125 calculates a spatial frequency BP correction value (BP3). When calculating the spatial frequency BP correction value, the camera MPU 125 first calculates the in-focus position (P_img) of the captured image and the in-focus position (P_AF) detected by the AF according to the following equations (10) and (11) 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 local maximum value information MTF_P (n) of defocus MTF for each spatial frequency shown in FIG. 12 is weighted and added in the evaluation bands W1 and W2 of the photographed image and AF calculated in S301 and S302. Thus, the in-focus position (P_img) of the captured image and the in-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 the present embodiment, the spatial frequency BP correction value can be calculated more simply. In this embodiment, although the accuracy of the spatial frequency BP correction value is slightly inferior to that of the first embodiment, reduction of the amount of information to be stored for calculating the spatial frequency BP correction value, communication amount between lens and camera The reduction of the calculation load performed by the camera MPU 125 can be realized.

(Third Embodiment)
Next, a third embodiment of the present invention will be described. Also in the present embodiment, the method of calculating the spatial frequency BP correction value is different from the above-described embodiment. In this embodiment, the spatial frequency BP correction value is not calculated if it is not necessary to reduce the communication amount between the lens and the camera or the camera MPU 125 without reducing the accuracy of the spatial frequency BP correction value. Reduce the computational load to be

  Note that a block diagram of the imaging apparatus (FIG. 2), explanatory views of respective focus detection methods (FIGS. 3A to 5), an explanatory view of focus detection areas (FIG. 6), focus detection processing and various BP correction value calculation processing The flowcharts of (1), (7) and (9) of FIG. Also, FIGS. 10 (b) to 10 (c) regarding the spatial frequency BP correction value calculation process are also used.

  A method of calculating the spatial frequency BP correction value (BP3) in the present embodiment will be described using the flowchart of FIG. In FIG. 13, the same processes as in FIG. 10A are denoted by the same reference numerals, and redundant descriptions will be omitted.

  At S3000, the camera MPU 125 determines whether it is necessary to calculate the spatial frequency BP correction value. As understood from the description in the first embodiment, the spatial frequency BP correction value decreases as the evaluation band W1 of the photographed image and the AF evaluation band W2 are similar. Therefore, in the present embodiment, if it is determined that the difference between the two evaluation bands is small to such an extent that it is not necessary to calculate the spatial frequency BP correction value (for example, the difference is smaller than a predetermined threshold) Omit the calculation of the value.

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, if the signal used for AF is also a signal read out in the first readout mode, the evaluation band of the photographed image and the AF evaluation band become equal. Furthermore, when using a digital filter with spatial frequency characteristics similar to the spatial frequency characteristics indicating sensitivity for each spatial frequency when viewing a captured image when processing an AF evaluation signal, the spatial frequency characteristics at the time of viewing and the digital filter Space frequency characteristics become equal. Such a situation occurs, for example, when the image displayed on the display 126 is enlarged and displayed.
Also, similarly, it is assumed that the evaluation band of the photographed image and the AF evaluation band become equal even when the photographed image is generated by the signal read in the second readout mode. Such a situation occurs, for example, when the recording image size of the photographed image is set small.

The camera MPU 125 determines that calculation of the correction value is unnecessary when any of the predetermined conditions is satisfied in S3000, and advances the process to S3001.
Since the camera MPU 125 does not calculate the correction value in S3001, the camera MPU 125 substitutes 0 into BP3 and ends the process of calculating the spatial frequency BP correction value (BP3).

  On the other hand, when 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, calculation of the correction value is omitted when it is determined that calculation of the spatial frequency BP correction value is unnecessary, so the amount of data to be stored for calculation of the correction value can not be reduced. The amount of data communication and calculation load at the time of correction value calculation can be reduced. In addition, it is also possible to combine with the second embodiment, in which case the amount of data stored for calculation of the correction value is of course reduced, as well as the amount of data communication and calculation load at the time of calculation of the correction value. be able to.

  In the present embodiment, the omission of the spatial frequency BP correction value has been described, but the vertical / horizontal BP correction value or the color BP correction value can be omitted if it can be determined that it is unnecessary. For example, when focus detection is performed in consideration of the contrast in both the vertical direction and the horizontal direction, calculation of the vertical and horizontal BP correction values may be omitted. Further, when the color signal used for the photographed image and the color signal used for focus detection are equal, 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) for realizing the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU or the like) of the system or apparatus reads the program. It is a process to execute.

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

Claims (15)

A lens unit configured to be attachable to and detachable from an imaging unit having an imaging element, and having a photographing optical system,
Storage means for storing information about MTF curves of the imaging optical system for different spatial frequencies;
Transmission means for transmitting the information to the imaging unit in response to a request from the imaging unit;
The lens unit characterized in that the information is not weighted according to spatial frequency.   The lens unit according to claim 1, wherein the information transmitted from the lens unit to the imaging unit is weighted according to a spatial frequency in the imaging unit.   The lens unit according to claim 2, wherein the weighting is lower as spatial frequency is lower.   The lens unit according to claim 2, wherein the weighting is performed on information normalized with a maximum value for each spatial frequency.   The lens unit according to any one of claims 1 to 4, wherein the information is a discrete sample of the MTF curve.   The said information is information regarding the maximum value of the said MTF curve, The lens part of any one of the Claims 1 thru | or 4 characterized by the above-mentioned.   7. The image pickup unit according to claim 1, wherein the transmission unit transmits the image pickup unit to the newly mounted image pickup unit when the image pickup unit mounted on the lens unit is replaced. The lens part according to 1 or 2.   The lens unit according to any one of claims 1 to 6, wherein the transmission unit transmits the information to the imaging unit each time a focus detection process is performed by the imaging unit.   The information according to any one of claims 1 to 8, wherein the information is not transmitted to the imaging unit when the imaging unit determines that the correction value for correcting the focus detection result by the imaging unit is not calculated. The lens part as described in a term.   The lens unit according to any one of claims 1 to 9, wherein the information is information according to a position of a focus detection area.   The lens unit according to any one of claims 1 to 10, wherein the information is information according to a zoom position and a focus position of the lens unit.   The lens unit according to any one of claims 1 to 11, wherein the photographing optical system includes a zoom lens for realizing a zoom function, an aperture for adjusting a light amount, and a focus lens for adjusting a focus.   The transmission unit is a lens MPU that performs control related to the lens unit and transmits information to the imaging unit in response to a request from the imaging unit. Lens part described in.   The lens MPU is electrically connected to the imaging unit through a signal line of a mount, and transmits the information to the imaging unit through the signal line in response to a request from the imaging unit. The lens part of Claim 13. A control method of a lens unit configured to be attachable to and detachable from an imaging unit having an imaging element and having a photographing optical system,
The lens unit includes storage means for storing information on MTF curves of the imaging 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 imaging unit in response to a request from the imaging unit.
The control method of a lens unit, wherein the information is not weighted according to spatial frequency.

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