JP2016018116A - Focus adjustment device, focus adjustment method and program, and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate focus detection at high speed without a focus correction after an AF is performed, by a focus detection operation using a signal extracted from an imaging signal in any of a horizontal or vertical direction.SOLUTION: A focus adjustment device comprises: acquisition means that acquires an image signal obtained by picking up a subject image formed by a photographic optical system including a focus lens; first focus detection means that detects a focus state of the subject image in a first direction of an imaging plane using the image signal to generate first drive information on the focus lens; second focus detection means that uses a plurality of image signals corresponding to the subject image in a blur state different in a defocus amount, generates an evaluation value of the blur state having a correlation relationship with a position of the focus lens in a plurality of directions including the first direction, and generates second drive information on the focus lens on the basis of the evaluation value; and focus adjustment means that controls a drive of the focus lens using any of the first drive information and second drive information according to the evaluation value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus mounted on a digital still camera, a digital video camera, a mobile phone, or the like that performs focus adjustment using an image signal acquired by an imaging element.

  In general, there are a contrast AF (AutoFocus) detection method and a phase difference AF detection method as focus detection adjustment methods of the imaging apparatus.

  The contrast AF detection method is an AF method that is often used in digital still cameras and digital video cameras, and an image sensor is used as a focus detection sensor. Focusing on the output signal of the image sensor, particularly the contrast information of the high-frequency component, this is an AF method in which the position of the focus lens with the largest AF evaluation value is the focus position (hereinafter referred to as contrast AF).

  On the other hand, focus detection using the phase difference AF detection method is often used in single-lens reflex cameras, and is a technology that contributes to the practical application of automatic focus detection (AF) single-lens reflex cameras. For example, in a digital single-lens reflex camera, the phase difference AF detection method is performed by a focus detection unit including a secondary imaging optical system. The focus detection unit includes a pupil division unit that divides the light beam that has passed through the exit pupil of the photographing optical system into two regions, and the two-divided light beam is subjected to secondary through an optical path division unit disposed in the mirror box. An image is formed on a set of focus detection sensors by an imaging optical system. Then, by detecting the shift amount of the signal output from the focus detection sensor according to the amount of received light, that is, the relative positional shift amount in the pupil division direction, the shift amount in the focus direction of the photographing optical system is directly obtained. . Therefore, if the accumulation operation is performed once by the focus detection sensor, the amount and direction of the focus deviation can be obtained at the same time, and a high-speed focus adjustment operation is possible. At the time of photographing after focus detection, the optical path dividing unit is retracted out of the photographing light beam, and the image sensor is exposed to obtain a photographed image.

  Among the phase difference AF detection methods, the technology that provides a phase difference AF function to the image sensor and realizes high-speed AF even during electronic viewfinder observation and moving image shooting that confirms an image in real time on a display unit such as a rear liquid crystal, This is called an imaging surface phase difference AF detection method (hereinafter referred to as imaging surface phase difference AF).

  In addition, focus detection is performed when AF is performed using only the contrast change in the horizontal direction obtained from the output signal of the image sensor due to lens aberration, and when AF is performed using only the contrast change in the vertical direction. Differences may occur in the results. In other words, the focus position may shift depending on the direction of the signal to be evaluated, that is, whether the signal in the horizontal direction is evaluated or the signal in the vertical direction is evaluated.

  Among the AF methods described above, in contrast AF and imaging surface phase difference AF, in order to reduce the calculation load and increase the calculation speed, a signal extracted in only one of the horizontal and vertical directions from the output signal of the image sensor is used. Focus detection is often performed. However, since the focus position is shifted depending on the direction of the signal to be evaluated as described above, the focus detection result using the signal extracted only in one of the horizontal and vertical directions is the person who is viewing the captured image. However, there was a drawback that the camera would deviate from the out-of-focus state where it feels most focused.

  In view of this, there is one having a configuration of a focus position detection device that can correct the focus position so that a person who is viewing the captured image feels out of focus most (Patent Document 1). . In other words, the in-focus position detection apparatus of Patent Document 1 is characterized in that the subject is focused by performing focus correction after AF is completed.

JP 2006-072016 A

  However, since the correction values used in the prior art disclosed in Patent Document 1 described above differ in data for each individual lens, there is a drawback that correction cannot be performed unless the correction value is calculated for each individual lens. Furthermore, there is a case where a correction error occurs due to the pattern of the subject and the correction accuracy is deteriorated.

  The present invention has been made in view of the above-described problems, and provides an imaging apparatus having a focus detection apparatus that does not require calculation of a focus correction value for each lens that is performed after AF and can realize highly accurate focus detection. That is.

  The focus adjustment apparatus of the present invention includes an acquisition unit that acquires an image signal obtained by imaging a subject image formed by a photographing optical system including a focus lens by an imaging unit, and an imaging unit that uses the image signal. A first focus detection unit that detects the focus state of the subject image in the first direction of the surface and generates first drive information of the focus lens; and a plurality of subjects corresponding to the subject images in a blurred state with different defocus amounts Is used to generate an evaluation value of a blurred state having a correlation with the position of the focus lens for a plurality of directions including the first direction, and second driving information of the focus lens is generated based on the evaluation value And a focus adjusting means for controlling the driving of the focus lens using either the first drive information or the second drive information according to the evaluation value.

  According to the present invention, it is possible to provide a focus adjustment device that can realize high-precision focus detection and reduce a calculation load by eliminating the need for focus correction performed after AF.

1 is a block diagram of an imaging apparatus to which a focus adjustment apparatus according to a first embodiment of the present invention is applied. FIG. 3 is a block diagram of a part of a blur part of the focus adjusting apparatus according to the first embodiment of the present invention. It is a figure which shows the relationship between the power of an image signal and a focus lens position. It is a figure which shows the flowchart of AF operation | movement in the imaging device to which the focus adjustment apparatus concerning 1st Example of this invention is applied. It is a figure which shows the relationship between a defocus range and a focus lens position. It is a figure which shows the flowchart of the imaging device part AF operation | movement which applied the focus adjustment apparatus concerning 1st Example of this invention. It is a figure which shows the relationship between the blur evaluation value concerning a 1st Example of this invention, and a focus lens position. It is a figure which shows the flowchart of AF operation | movement of the imaging device to which the focus adjustment apparatus concerning the 2nd Example of this invention is applied. It is a figure which shows the flowchart of AF operation | movement of the imaging device to which the focus adjustment apparatus concerning the 2nd Example of this invention is applied.

[Example 1]
Overall Schematic Configuration of Imaging Device Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a block diagram of a digital camera as an imaging apparatus to which the focus adjustment apparatus according to the present embodiment is applied. The digital camera of this embodiment is an interchangeable lens type single-lens reflex camera, and includes a lens unit 100 and a camera body 120. The lens unit 100 is detachably connected to the camera body 120 via a mount M indicated by a dotted line in the center of the figure.

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

  The first lens group 101 is disposed at the tip of the lens unit 100 and is held so as to be able to advance and retreat in the optical axis direction OA. The aperture / shutter 102 adjusts the aperture diameter to adjust the amount of light during shooting, and also functions as an exposure time adjustment shutter when shooting a still image. The diaphragm / shutter 102 and the second lens group 103 can move forward and backward in the optical axis direction OA as one body, and realize a zoom function in conjunction with the forward / backward movement of the first lens group 101. The focus lens 104 performs focus adjustment by moving back and forth in the optical axis direction.

  The control unit of the lens unit 100 includes a zoom actuator 111, an aperture shutter actuator 112, a focus actuator 113, a zoom drive unit 114, an aperture shutter drive unit 115, a focus drive unit 116, a lens MPU 117, and a lens memory 118.

  The zoom actuator 111 performs a zoom operation by driving the first lens group 101 and the third lens group 103 forward and backward in the optical axis direction OA. The aperture shutter actuator 112 controls the aperture diameter of the aperture / shutter 102 to adjust the amount of photographing light, and controls the exposure time during still image photographing. The focus actuator 113 has a function as a position detection unit that detects the current position of the focus lens 104 by performing focus adjustment by driving the focus lens 104 forward and backward in the optical axis direction OA.

  The zoom drive unit 114 drives the zoom actuator 111 according to the zoom operation of the photographer. The shutter driving unit 115 controls the aperture of the aperture / shutter 102 by drivingly controlling the aperture shutter actuator 112. The focus driver 116 drives and controls the focus actuator 113 based on the focus detection result, and performs focus adjustment by driving the focus lens 104 forward and backward in the optical axis direction OA.

  The lens MPU 117 performs all calculations and control related to the photographing optical system, and controls the zoom driving unit 114, the shutter driving unit 115, the focus driving unit 116, and the lens memory 118. The lens MPU 117 detects the current lens position, and notifies the lens position information in response to a request from the camera MPU 125. The lens memory 118 stores optical information necessary for automatic focus adjustment.

The camera body 120 includes an optical low-pass filter 121, an image sensor 122, and a control unit described later. The optical low-pass filter 121 reduces false colors and moire in the captured image.
The image sensor 122 includes a C-MOS sensor and its peripheral part. The C-MOS sensor has a pixel array in which one photoelectric conversion element is arranged on light receiving pixels of m pixels in the horizontal direction and n pixels in the vertical direction. Have. The image sensor 122 is configured to be able to output each pixel in the pixel array independently. Some pixels are focus detection pixels, and focus detection (imaging surface phase difference AF) using the phase difference AF detection method on the imaging surface is possible.

  More specifically, the pixel array of the image sensor 122 has a plurality of shooting pixels that each receive a light beam passing through the entire exit pupil of the shooting optical system that forms the image of the subject and generate an image of the subject. . The pixel array further includes a plurality of focus detection pixels that each receive a light beam that passes through different exit pupil regions of the imaging optical system. The plurality of focus detection pixels as a whole can receive a light beam passing through the entire exit pupil of the photographing optical system, and corresponds to one photographing pixel. For example, in the pixel array, a pair of G pixels arranged diagonally out of 2 rows × 2 columns of pixels are left as shooting pixels, and R pixels and B pixels are replaced with focus detection pixels.

  The driving unit includes an image sensor driving unit 123, an image processing unit 124, a first control unit, a second control unit, and a camera MPU 125 having functions of a third control unit, a display 126, an operation switch group 127, and a memory. 128, a first focus detection unit 129, and a second focus detection unit 130.

  The image sensor driving unit 123 controls the operation of the image sensor 122, A / D converts the acquired image signal, and transmits it to the camera MPU 125. The image processing unit 124 performs γ conversion, color interpolation, JPEG compression, and the like of the image acquired by the image sensor 122.

  A camera MPU (processor) 125 having the functions of a first control unit, a second control unit, and a third control unit performs all calculations and controls related to the camera body 120. Thus, the image sensor driving unit 123, the image processing unit 124, the display 126, the operation SW 127, the memory 128, the first focus detection unit 129, and the second focus detection unit 130 are controlled.

  The camera MPU 125 having the functions of the first control unit, the second control unit, and the third control unit is connected to the lens MPU 117 via the signal line of the mount M. Thus, the lens position is acquired, a lens driving request with a predetermined driving amount is issued to the lens MPU 117, or optical information unique to the lens unit 100 is acquired.

  The camera MPU 125 having the functions of the first control unit, the second control unit, and the third control unit includes a ROM 125a that stores a program for controlling camera operation, a RAM 125b that stores variables, and an EEPROM 125c that stores various parameters. Is built-in. Further, the camera MPU 125 executes a focus detection process by loading and executing a program stored in the ROM 125a. Details of the focus detection process will be described later. The camera MPU 125 also corrects the imaging plane phase difference AF because the influence of vignetting is large and the reliability decreases when the image height at the focus detection position is large.

  The display 126 is configured by an LCD or the like, and displays information related to the shooting mode of the camera, a preview image before shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. The operation switch group 127 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The memory 128 of this embodiment is a detachable flash memory, and records captured images. The release switch also performs a first stroke (hereinafter referred to as SW1) for generating an instruction signal for starting an AE process and an AF operation performed prior to a shooting operation, and a second stroke (hereinafter referred to as an instruction signal for starting an actual exposure operation). SW2) and a two-stage switch.

  The first focus detection unit 129 performs focus detection processing by the phase difference AF method based on image signals of focus detection pixels embedded in the image sensor 122. More specifically, the first focus detection unit 129 is a pair of images (hereinafter referred to as A image and B image) formed on the focus detection pixels by the light flux passing through the pair of pupil regions of the imaging optical system. Imaging surface phase difference AF is performed based on the amount of deviation. The principle of the imaging surface phase difference AF is the same as that described in FIG. 5 to FIG. 7, FIG.

  As shown in FIG. 6 of Japanese Patent Application Laid-Open No. 2009-003122, the image pickup device 122 included in the image pickup apparatus according to the present embodiment horizontally sets the focus detection pixels for the A image among the focus detection pixels performing the image pickup surface phase difference AF. A subject image that is regularly arranged in the direction and acquired by these pixel groups is an A image. Further, the focus detection pixels for B image are also regularly arranged in the horizontal direction (long side direction), and the subject image acquired by these pixel groups is the B image. Here, the horizontal direction is perpendicular to the optical axis and extends in the horizontal direction when the image pickup apparatus is held so that the optical axis of the photographing optical system and the long side of the image pickup surface of the image pickup device are parallel to the ground. The direction along a straight line. The long side direction means a direction in which the number of pixels is large and the long side is in the shooting screen (pixel arrangement).

  As described above, the direction in which the focus detection pixels of the A image and the B image are arranged (in this example, the horizontal direction), that is, the direction evaluated by the imaging plane phase difference AF is defined as the first direction. . However, the first focus detection method performed by the first focus detection unit 129 is not limited to the imaging plane phase difference AF. It is only necessary that focus detection can be performed using the contrast in the first direction which is the in-plane direction of the image sensor 122. For example, the first focus detection method may be contrast AF. As a detailed method for calculating the focus position of contrast AF, for example, a method described in FIG. 12 of JP 2010-078810 A may be used. In other words, from the length of the portion that is inclined with a slope equal to or larger than a certain value of the curve representing the change of the contrast focus evaluation value indicating the focus state with respect to the position of the focus lens 104, and the change in the slope of the inclined portion. The peak position is calculated. Since the peak position of the contrast focus evaluation value is nothing but the in-focus position, it is possible to calculate the in-focus position. The AF method performed by the first focus detection unit 129 is hereinafter referred to as first focus detection.

  The second focus detection unit 130 performs second focus detection by a second focus detection method based on the blur evaluation value calculated from the image information obtained by the image processing unit 124. The second focus detection method uses a method called a depth from focus method (hereinafter referred to as DFD), and calculates a blur evaluation value by performing arithmetic processing on two images that differ by a predetermined defocus amount. A specific method for calculating the blur evaluation value will be described later.

  In order to obtain two images that differ by a predetermined defocus amount used for DFD, the shooting parameters such as the focus lens position, aperture amount, and focal length, which affect the blurred state of the captured image, are changed by controlling the camera MPU 125. And take a picture. Any change of the imaging parameter may be made as long as one or more parameters are changed. In this embodiment, a description will be given of a case where only the position of the focus lens is changed.

  The blur evaluation value according to the present embodiment is a value indicating the blur state of the captured image, and is a value having a correlation with the variance of the point image intensity distribution function of the photographing optical system. Here, the point spread function is a spread function after the point image passes through the lens. Further, the dispersion of the point image intensity distribution function of the photographing optical system has a correlation with the subject distance. In other words, it can be said that the dispersion of the point image intensity distribution function of the photographing optical system has a correlation with the focus lens position. From the above, it can be seen that there is a correlation between the blur evaluation value and the focus lens position. This relationship will be described in detail later.

  The focus adjustment apparatus according to the present embodiment is characterized in that the first focus detection unit 129 and the second focus detection unit 130 perform two focus detection methods. This purpose will be described later.

Description of Blur Evaluation Value Next, a method for calculating the blur evaluation value calculated by the camera MPU 125 and the second focus detection unit 130 in FIG. 1 will be described with reference to FIG. FIG. 2 is a block diagram of a unit for calculating a blur evaluation value according to the present invention. In the figure, parts similar to those in FIG.

  The second focus detection unit 130 calculates a blur evaluation value from the image signal. As described above, two image signals that differ by a predetermined defocus amount are used to calculate the blur evaluation value. Since the mechanism of this embodiment having only one image pickup device cannot pick up two images at the same time, it is necessary to pick up images in order in order to obtain two image signals that differ by a predetermined defocus amount. Here, an image captured first is referred to as image 1, and an image captured later is referred to as image 2. Image 1 and image 2 are two images that differ by a predetermined defocus amount for use in DFD.

  First, in order to acquire the luminance signal of the image 1, the image signal A / D converted by the image sensor driving unit 123 is transmitted to the MPU 125, and the image signal of the image 1 is stored in the RAM 125b.

  When the image signal of the image 1 is input to the second focus detection unit 130, the AF evaluation signal processing unit 201 converts the signal into the luminance signal Y, and then emphasizes the low luminance component to suppress the high luminance component. Gamma correction processing is performed. Further, the luminance signal Y subjected to the gamma correction processing is a three-color luminance signal of a red luminance signal (hereinafter RY), a green luminance signal (hereinafter GY), and a blue luminance signal (hereinafter BY), and RY, GY, The Y signal calculated by adding and weighting BY to a predetermined weight is included. In the following, red, green, and blue colors are referred to as R, G, and B, respectively. However, the luminance signal Y of the image 1 that is an output signal of the AF evaluation signal processing unit 201 may use any one of the RY, GY, BY, and Y signals for the purpose of noise reduction and accuracy improvement. A plurality of blur evaluation values may be calculated by combining a plurality of signals.

  Subsequently, the focus lens 104 is driven by a predetermined amount in order to change the blurring state of the image formed on the image sensor so as to obtain a luminance signal of the image 2 that differs from the image 1 by a predetermined defocus amount. The image signal of the image 2 picked up after driving is stored in the RAM 125b, and the same processing as that of the image 1 is performed through the second focus detection unit 130 to generate the luminance signal Y of the image 2. The gamma-corrected luminance signals Y of image 1 and image 2 are hereinafter referred to as luminance signal 202 (G1) of image 1 and luminance signal 203 (G2) of image 2, respectively.

  G1 and G2 are cut out from the AF evaluation range of m pixels in the horizontal direction and n pixels in the vertical direction set by the region setting 215, respectively, and set to a smaller region. Specifically, when the size of the AF evaluation range is M pixels in the horizontal direction and N pixels in the vertical direction, a term that takes into account the number of filter taps (hereinafter referred to as Tap) to be described later is added to M and N, The region is set to the direction M + Tap pixel and the vertical direction N + Tap pixel.

  Since G1 and G2 are two-dimensional signals of M + Tap rows and N + Tap columns having values in the horizontal and vertical directions, they will be expressed as G1 (i, j) and G2 (i, j), respectively, below. . However, i = 1 to M + Tap and j = 1 to N + Tap.

  G1 is input to the BPF unit 204, a specific frequency component is extracted, and is output as a signal S1. Here, the extraction of the specific frequency component includes the exclusion of the DC component and high frequency component of the subject. The purpose of passing through the BPF unit 204 is to eliminate the spatial frequency dependence of the subject.

  Calculations performed by the BPF unit 204 will be described. In the BPF unit 204, first, a convolution operation of a two-dimensional filter (BPF) is performed on G1. S1 (i, j) is obtained as shown in Equation (1) by the convolution operation. Here, a part of incorrect data is output as a result of the convolution operation depending on the size of the two-dimensional filter (BPF). This part of data that is not correctly output is called a filter tap, and the number of taps (Tap) in the row direction is obtained by the number of elements in the row direction of the filter minus one. Similarly, Tap in the column direction is obtained by -1 of the number of elements in the column direction of the filter.

  From the above, the signal S 1 (i ′, j ′) obtained by excluding the Tap signal from S 1 (i, j), which is the result of the convolution operation in order to output only correct data, is the output signal of the BPF unit 204. It becomes. However, i '= 1 to M and j' = 1 to N. As an example of the BPF used in equation (1), a two-dimensional filter as in equation (3) may be used. However, the value of the number of BPF elements may be changed according to the frequency band to be extracted.

Similarly for G2, an S1 (i ′, j ′) signal S2 is output through the BPF unit 205, excluding the Tap signal from the signal resulting from the convolution operation as shown in equation (2).

Next, the power of the image signal in the frequency space is obtained by the square calculation unit 206 and the in-region integration unit 208. For this purpose, the calculation in the frequency space is obtained by the calculation in the real space using an expression called Percival theorem. Here, Percival's theorem is a theorem that the sum of squares (integration) of a function is equal to the sum of squares (integration) of the Fourier transform. Percival's theorem is generally expressed as in equation (4), where the sum of all the energies of the waveform s (x) for all real spaces x and all frequency components of the Fourier transform S (f) of the energies of the waveforms Means the sum of f is equal.

  Hereinafter, the power of the image signal in the frequency space is referred to as P, P in the image 1 is referred to as P1, and P in the image 2 is referred to as P2.

In order to obtain P1 and P2, a square operation is first performed. Specifically, the square calculation unit 206 performs a square calculation on the output signal S1 of the BPF unit 204 as shown in equation (5) to generate a signal T1. Similarly, the square calculation unit 205 performs square calculation on the output signal S2 of the BPF unit 207 as shown in Equation (6) to generate a signal T2.

Subsequently, in order to obtain P1 and P2, the in-region integration unit 208 performs an integration operation on the output signal of the square calculation unit 206 in the regions of the horizontal direction M and the vertical direction N that are the size of the AF evaluation range. . Assuming that the output signal of the in-region integrating unit 208 is P1, P1 is obtained as shown in equation (7). Similarly, assuming that the output signal of the in-region integrating unit 209 is P2, P2 is obtained as shown in equation (8).

  However, the integration region may be narrowed or divided into a plurality of regions depending on the position of the main subject, the position of a subject other than the main subject, and the like. Further, it may be performed after calculation by a blur evaluation value calculation unit 212 described later.

  As described above, P1 is generated through the square calculation unit 206 and the in-region integration unit 208, and P2 is generated through the square calculation unit 207 and the in-region integration unit 209. Here, the relationship between the value of P and the focus lens position is shown in FIG. As shown in FIG. 3, P has a maximum value at the in-focus position. This is because the power of the image signal is the strongest because the contrast of the image is clear at the in-focus position. On the other hand, as the image is blurred toward the infinity side or the close side from the in-focus state, P gradually takes a small value. This is because the contrast of the image decreases as the image is blurred.

  The difference calculation unit 210 calculates the difference P2−P1 between the output signals P1 and P2 of the in-region integration units 208 and 209. This is for comparing the powers of signals in the frequency spaces of the image 1 and the image 2 and evaluating the difference in blur between the two images. When the degree of blur between the two images is significantly different, P2−P1 takes a large value. When the degree of blur between the two images is not so different, P2−P1 takes a small value.

The integration calculation unit 211 calculates the sum P1 + P2 of the output signals P1 and P2 of the in-region integration units 208 and 209. This is used for normalization when calculating a blur evaluation value to be described later. The blur evaluation value calculation unit 212 calculates a blur evaluation value as shown in Expression (9) by normalizing the output result of the difference calculation unit 210 with the output result of the integration calculation unit 211.

のように（Ｐ１＋Ｐ２）／２のように変更して、Ｐ１とＰ２の平均値で規格化してもよい。また、焦点検出を行い易くするために（１０）式の右辺に係数をつけてもよい。以下、本実施例においては、簡易的にボケ評価値Ｃを求める（９）式を用いて説明する。 Hereinafter, the blur evaluation value is referred to as C. The focus detection method using C will be described in detail later. In addition, Equation (9)

It is also possible to change to (P1 + P2) / 2 as in the above and normalize with the average value of P1 and P2. In order to facilitate focus detection, a coefficient may be added to the right side of equation (10). Hereinafter, in the present embodiment, description will be made using the equation (9) for simply obtaining the blur evaluation value C.

  The AF control unit 1251 in FIG. 2 takes in the blur evaluation value C, drives the focus actuator 113 based on the focus detection result through the focus drive unit 116, and performs AF control by driving the focus lens 104 forward and backward.

  With the above procedure, the second focus detection unit 130 drives the focus lens 104 with the calculated blur evaluation value C to perform second focus detection.

Description of In-Focus Position Determination Processing Operation Hereinafter, with reference to FIGS. 2 and 4, in-focus in an imaging apparatus to which the focus adjustment apparatus according to the present embodiment is executed, which is executed by the camera MPU (processor) 125 having the above-described configuration. The operation (AF operation) will be described.

  FIG. 4 is a flowchart of the AF operation of the imaging apparatus to which the focus adjustment apparatus according to the present embodiment is applied. A control program related to this operation is executed by the camera MPU 125. In FIG. 4, “S” stands for a step.

  When the area setting unit 215 included in the camera MPU 125 starts the AF operation (S400), first, an AF evaluation range for performing focus adjustment on the subject is set (S401). In the process of step S401, one ranging area is set in the image. The AF evaluation range is a range in which an image signal for focus adjustment is evaluated by an AF operation described later. The purpose of the AF operation is to adjust the focus on the subject intended by the photographer within the AF evaluation range as the focus detection area. Is to do. The AF evaluation range set here is a range for performing the first focus detection (hereinafter referred to as a first AF evaluation range), and a range for performing the second focus detection (hereinafter referred to as a second focus detection range). AF evaluation range) may or may not be set in this step. Further, when the second AF evaluation range is also set, it may not be the same as the first AF evaluation range.

  Next, the image sensor 122 is exposed (S402). Thereby, not only an output signal used for the first focus detection and the second focus detection can be obtained, but also information on a nearby subject including a focus detection region for each focus detection unit can be obtained. Further, the first focus detection and the second focus detection may be used by thinning out the number of output signals of the imaging pixels in accordance with the required focus adjustment accuracy. Further, the exposure may be performed while the focus lens is continuously moving, or may be performed while the focus lens is stopped.

  Next, the defocus amount is calculated by the first focus detection unit (S403). The defocus amount is determined from the length of the focus detection pixel row and the coefficient (K value) for converting the image shift amount into the defocus amount. A detailed calculation method is shown in FIGS. 5 to 5 of Japanese Patent Laid-Open No. 2009-003122. 7, the same as described in FIG.

  In the following description, the defocus amount calculated by the first focus detection unit is referred to as a first defocus amount. It should be noted that this step is included in both cases where the first defocus amount can be calculated and when it cannot be calculated. When the process of S403 ends, the process proceeds to S404.

  In S404, if the first defocus amount can be calculated in S403, the lens drive amount (first drive information) of the focus lens 104 corresponding to the first defocus amount is calculated, and then the process proceeds to S405. If the first defocus amount cannot be calculated in S403, the process ends without calculating the lens drive amount in S404, and the process proceeds to S405.

  In step S405, the number of exposures is determined. If the number of exposures is two or more, the process proceeds to S406 (Yes in S405), and the focus detection by the second focus detection unit and the reliability determination of the second focus detection result are performed (S406). Hereinafter, the defocus amount calculated by the second focus detection unit is referred to as a second defocus amount.

  In order to calculate the second defocus amount in S406, as described above, the image for the two exposures needs to be accumulated in the RAM 125b. This is because the luminance signals of the images 1 and 2 are used for calculating the blur evaluation value used for the second focus detection, as indicated by 202 and 203 in FIG. Therefore, when the number of exposures is 1 or less (No in S405), the second defocus amount cannot be calculated. Therefore, in order to repeat the exposure one more time, S410, which will be described later, is returned to the exposure step after execution (S402). Details of the second focus detection method and reliability determination method in S406 will be described later.

  Here, the accuracy of each of the first defocus amount calculated in S403 and the second defocus amount calculated in S406 will be described. In conclusion, for the reason described below, it can be said that the second defocus amount is more accurate as the focus detection result than the first defocus amount.

  First, as a premise, as described above, the phenomenon of defocusing depending on the direction of evaluation may occur due to the influence of aberration or the like. Further, it is generally desirable that a person who is viewing a photographed image feels most in focus, but this blurred state is not limited to only one direction, and contrast of images in a plurality of directions such as up, down, left, and right. It is determined by the situation of (edge shape). In other words, it can be said that the accuracy of the evaluation in only one direction is insufficient to obtain the out-of-focus state where the person viewing the captured image feels most focused.

  In the first focus detection method, only the blurring state in the first direction is evaluated, and thus the accuracy is insufficient. On the other hand, in the second focus detection method, information on the power of the two-dimensional edge is used as described above. Since the blur evaluation value is used, the second defocus amount is substantially equal to the evaluation of the actual picture focus state. Thus, it can be said that the second defocus amount is more accurate than the first defocus amount.

  In S406, the second defocus amount is calculated and its reliability is determined. If it is determined that the second defocus amount is reliable, the process proceeds to S408 (Yes in S407), and further the second defocus amount. Is the defocus amount at the in-focus position. If the in-focus state is determined (Yes in S108), the camera MPU 125 performs in-focus display (S409), and then ends the AF operation (S412).

  In S410, when the second defocus amount cannot be calculated (No in S405) or when the second defocus amount with low reliability is calculated (No in S407), the focus lens is driven by the first lens control. (S410). However, the first lens control is control of the focus lens drive performed by the camera MPU 125 in this step when the second defocus amount cannot be calculated or when the second defocus amount with low reliability is calculated. Point to.

  In the first lens control, the focus lens 104 is driven by the lens driving amount calculated in S404, or search driving is performed. Here, the search drive refers to driving the focus lens 104 by a predetermined amount at a predetermined speed in a preset direction (usually the closest direction). The reason why the lens driving direction is normally set to the close-up direction is that the subject to be focused on by the photographer often exists on the close-up side, but it is not limited to this direction. After the focus lens 104 is driven by the first lens control as described above, the flow returns to S402.

  In S411, when the reliable second defocus amount is calculated (Yes in S407), and the second defocus amount is not determined to be in focus (No in S408), the second lens Control is performed (S411). However, the second lens control refers to focus lens drive control performed by the camera MPU 125 in this step when it is determined that the reliability of the second defocus amount is high and the focus is not determined. In the second lens control, lens driving is performed so that exposure can be performed at a position where the position of the focus lens 104 differs by a predetermined interval. A method for determining the predetermined interval will be described later. Further, the exposure may be performed while the focus lens 104 is continuously moving, or may be performed while the focus lens 104 is stopped.

  After the focus lens 104 is driven by the second lens control as described above, the flow returns to S402.

  As can be seen from the flowchart of FIG. 4 described above, in the present embodiment, the lens is finally driven to the in-focus position using the second defocus amount instead of the first defocus amount. More specifically, when the second defocus amount can be calculated from the first defocus amount and the second defocus amount, focus detection is performed using the second defocus amount.

  If the second defocus amount is finally used, it seems that AF should always be performed using only the second focus detection unit, but the first focus detection unit must also be used in parallel. The reason for this will be described with reference to FIG. 5 from the viewpoint of the defocus amount detectable range. Hereinafter, the range of the position of the focus lens 104 capable of detecting the first defocus amount is referred to as a first defocus range, and the focus lens 104 capable of detecting the second defocus amount. The position range is referred to as a second defocus range.

  FIG. 5 is a diagram showing the relationship between the first and second defocus detection ranges and the focus lens position. The near end and the infinite end in FIG. 5 represent both ends of the limit position for driving the focus lens 104, and the position of the focus lens that is in focus is shown as the focus position.

  As shown in FIG. 5, the first and second defocus ranges always include the in-focus position. As described above, the second defocus amount is more accurate than the first defocus amount. Therefore, when the focus lens position is close to the in-focus position and the first defocus amount and the second defocus amount can be calculated, the in-focus position is calculated using the accurate second defocus detection result. I do.

  On the other hand, as shown in FIG. 5, since the second defocus detection range is narrower than the first defocus range, when the focus lens 104 is located far from the in-focus position, the first focus detection unit Is more advantageous. Therefore, when the first defocus amount can be calculated and the second defocus amount cannot be calculated, the in-focus position is calculated using the first defocus amount.

  In view of the above, the imaging apparatus needs to have both the first focus detection unit and the second focus detection unit.

  Thus, the output signal at the time of exposure in S402 may be used for either the first focus detection or the second focus detection. Therefore, for each exposure, both the first defocus amount by the first focus detection unit and the second defocus amount by the second focus detection unit are calculated. Thereby, focus detection can always be performed by both focus detection methods. However, the embodiment of the present invention is not limited to this, and only one of the focus detections may be performed for each exposure. In that case, an effect of reducing the amount of calculation required for focus detection can be obtained.

Description of Focus Detection and Reliability Determination Processing Operation by Second Focus Detection Unit Next, focus detection and reliability determination processing operation by the second focus detection unit 130 will be described with reference to FIG. FIG. 6 is a flowchart of the focus detection and reliability determination processing operation performed by the second focus detection unit, which is executed in S406 of FIG. A control program related to this operation is executed by the camera MPU 125. Also in FIG. 6, “S” is an abbreviation for a step.

  When the area setting unit 215 included in the camera MPU 125 starts the AF operation by the second focus detection (S600), the area setting unit 215 sets a second AF evaluation range for the subject (S601). In the process of step S601, one distance measurement area is set in the image. The second AF evaluation range is a range in which an image signal for focus adjustment by the second focus detection unit is evaluated. If the second AF evaluation range has already been set in S401 of FIG. 4, the process proceeds to S602 without performing the second AF evaluation range setting in this step S601. Subsequently, the blur evaluation value C is calculated from the luminance signals of the images 1 and 2 (S602). The calculation method is as described above.

  Next, a second defocus amount is calculated from the blur evaluation value calculated in S602 (S603). As described above, the blur evaluation value C has a correlation with the focus lens position. This correlation will be described with reference to FIG.

  FIG. 7A shows the relationship between the blur evaluation value C and the focus lens position. The close end and the infinite end in FIG. 7A represent both ends of the limit position for driving the focus lens 104.

  As shown in FIG. 7A, the blur evaluation value C and the focus lens position have a one-to-one correspondence relationship within the second defocus range. Of this one-to-one correspondence, the position of the focus lens corresponding to C = 0 is the in-focus position. The reason for this will be described with reference to FIGS. 3 and (9).

  According to equation (9), the blur evaluation value C is obtained by dividing the difference between the powers P1 and P2 of two images whose focus lens positions differ by a predetermined defocus amount by the sum. As shown in FIG. 3, it is assumed that the positions of the focus lenses 104 for the images 1 and 2 are L1 'and L2', respectively, and that L1 'and L2' are not in the vicinity of the in-focus position. Assume that the image powers corresponding to L1 'and L2' are P1 'and P2', and L2'-L1 'is a predetermined defocus amount necessary for performing the second focus detection. In this way, when P1 '<P2', if it is substituted into the equation (9), C> 0, so that when C = 0, it is known as the in-focus position.

  Similarly, the focus lens positions of the image 1 and the image 2 when the images 1 and 2 are obtained across the in-focus positions are L1 and L2, respectively. Assume that the powers of the images corresponding to L1 and L2 are P1 and P2, and L2-L1 is a predetermined defocus amount necessary for performing the second focus detection. As described above, P takes the maximum value at the in-focus position. Therefore, when the focus lenses of the image 1 and the image 2 are located across the in-focus position such as L1 and L2, the values of P1 and P2 are only at one place. Will have the same value. When P1 = P2, if it is substituted into the equation (9), C = 0 is obtained, so that when C = 0, the in-focus position is known.

  Hereinafter, referring back to FIG. 7A, the second defocus amount calculation method in S603 will be described. For example, when the blur evaluation value calculated in S602 is Ca, the position La of the focus lens 104 is obtained from the correlation. Since the defocus amount indicates a distance (including direction) from the in-focus position, the second defocus amount can be obtained from the blur evaluation value Ca.

  The correlation shown in FIG. 7A is stored in the ROM 125a as a table (hereinafter referred to as C table), and the second defocus amount is obtained by referring to the C table with the calculated blur evaluation value C. (S603). If the calculated value corresponding to the blur parameter C is not in the C table stored in the ROM 125a, the second defocus amount may be obtained by performing a complementary operation on the C table.

  FIG. 3 shows an example in which the left and right sides are almost symmetrical from the in-focus position, but the actual lens is not symmetrical. Even if P1 = P2 due to the fact that it is not symmetric, it will deviate from the in-focus position. Since this deviation amount can be known from the design value of the lens, the C table may be offset in advance for the deviation amount.

  Next, the lens drive amount (second drive information) of the focus lens 104 corresponding to the second defocus amount calculated in S603 is calculated (S604), and when the process is completed, the process proceeds to S605.

Next, the reliability of the second defocus amount is determined (S605). First, the reliability of the second defocus amount will be described with reference to FIG.
FIG. 7B is a diagram illustrating the relationship between the blur evaluation value C and the focus lens position. In FIG. 7B, the closest end Ls and the infinite end Lm represent both ends of the limit position for driving the focus lens 104, and Lg is a focus position.

  In FIG. 7B, the plot range of the relationship between C and the focus lens position is expanded from that in FIG. The blur evaluation value C and the position of the focus lens 104 include a part having a one-to-one correspondence and a part having a one-to-two correspondence. In FIG. 7B, there is a one-to-one correspondence between Lx and Ly, and a one-to-two correspondence between Ls and Lx and between Ly and Lm. The reason why the one-to-two correspondence is generated will be described later. Here, the one-to-two correspondence is a relation in which two focus lens positions Ls and Lx are calculated when, for example, one blur evaluation value Cx is calculated in S602 and illuminated on the C table in S603.

  The reason why the evaluation value C and the focus lens position have a one-to-two correspondence is caused by the shape of the curve representing the change of P shown in FIG. 3 and the calculation method of C shown in equation (9).

  As described above, the graph shape of P takes the maximum value at the in-focus position, and the value of P decreases as the focus is blurred toward the infinity side or the near side. Then, the inclination of P becomes 0 at the in-focus position, and increases as it is blurred toward the infinite side or the close side from the in-focus position, and approaches 0 again when the infinite end or the close end approaches. Similarly to the inclination of P, the tendency of the molecules P2-P1 on the right side of the formula (9) increases as the focus is blurred and approaches 0 again when the infinite end or the closest end approaches. That is, due to the influence of the numerator on the right side of Equation (9), the tendency of C on the left side of Equation (9) tends to increase from 0 and decrease again.

  On the other hand, the value of P1 + P2 in the denominator on the right side of the formula (9) gradually decreases from the maximum value as the focus is blurred. That is, P is normalized due to the influence of the denominator, and the tendency of C, which is the left side of equation (9), has a small value in the vicinity of the in-focus state, and tends to have a large number of blurs.

  Since C is calculated as shown in equation (9), the absolute value of C (hereinafter | C |) increases as the distance from the in-focus position increases, and decreases from a certain point. A part corresponding to 2 is generated. Based on the above, the value of C takes a value as shown in FIG.

  Returning to FIG. 7A, the reliability determination will be described. When the blur evaluation value Cx is calculated in S602, it is not possible to determine which of the Ls and Lx is the correct focus lens position simply by illuminating the C table. If the one-to-one correspondence relationship is not established, the wrong second in S603 is determined. There is a possibility of calculating the defocus amount. Therefore, when the blur evaluation value takes a value other than between Cx and Cy, it can be said that the blur evaluation value has no reliability. Since a one-to-one correspondence relationship is established within the second defocus range, it can be said that the blur evaluation value is reliable when the blur evaluation value takes a value between Cy and Cx.

  In S605, the presence or absence of reliability of the blur evaluation value as described above is determined using the value of P. For the reliability determination, either one of P1 and P2 or both of them may be used.

  Hereinafter, the reliability calculation method of the second defocus amount will be described with reference to FIG.

  The power of the image on the vertical axis in FIG. 3 takes different values depending on the contrast of the subject. However, if normalization is performed with the difference in brightness (maximum output value-minimum output value) of the captured image, Even after shooting, the graph shapes of P are almost the same. Therefore, when the value of P normalized by the light / dark difference takes a value equal to or greater than a predetermined threshold, it is determined that the second defocus amount is reliable. On the other hand, if it is less than the threshold value, it is determined that the second defocus amount is not reliable (S605), and the focus detection and reliability determination processing by the second focus detection unit is finished (S606).

  In addition, the reliability determination may be performed more simply without performing the standardization of P based on the difference in brightness. Of the threshold values used in the following determination methods, the threshold value used for P2-P1 is called a P difference threshold value, and the threshold value used for P is called a P threshold value.

  Specifically, when P2−P1 takes a value equal to or smaller than a predetermined P difference threshold and P is equal to or larger than the P threshold, it is determined that the second defocus amount is reliable, and P2−P1 is equal to the predetermined difference. When the value is equal to or smaller than the threshold value and P is equal to or smaller than the P threshold value, it is determined that the second defocus amount is not reliable. As shown in FIG. 3, there is almost no difference in the power P between the image 1 and the image 2 in the blurred state (hereinafter referred to as the large blurred state) in which the contrast of the image is greatly reduced as in the vicinity of the infinite end or the close end. . Therefore, a difference threshold is provided for the difference in power P. However, since the difference in power P is small even in the vicinity of the in-focus position, a P threshold value is further provided.

  If the number of times P2−P1 takes a value equal to or smaller than the predetermined P difference threshold is equal to or smaller than the predetermined number, the second defocus amount is determined to be reliable, and P2−P1 is equal to or smaller than the predetermined P difference threshold. The second defocus amount may be determined to be unreliable if the number of times of taking is less than or equal to a predetermined number. As shown in FIG. 3, the state in which the difference between the powers P of the image 1 and the image 2 disappears continuously in the case of a large blur, while P2−P1≈0 in the in-focus state is near the in-focus state. Take advantage of being only.

  As described above, when the reliability determination of the second defocus amount is completed in S605, the focus detection and reliability determination processing by the second focus detection unit is ended (S606).

  As described above, in this embodiment, the blur evaluation value C is calculated from the power P of the image 1 and the image 2 obtained by moving the focus lens 104 based on a predetermined defocus amount, and the second is obtained by referring to the C table. The defocus amount is calculated. At that time, by setting a threshold for the power P, the reliability of the second defocus amount can be determined.

Further, as a method for calculating the blur evaluation value C described above, when the frequency in the vicinity of the center of the frequency band extracted by the BPF unit 205 is ω, the frequency is weighted as shown in the following equation (11). 1 / ω ^ 2 may be added as a coefficient of.

  The purpose is to make the values of the plurality of blur evaluation values C coincide by normalizing with the square of the frequency when the plurality of blur evaluation values C are calculated and compared using a plurality of BPFs.

  Also, instead of using two images to obtain the second defocus amount, three images may be used. In that case, after calculating a plurality of blur evaluation values C from three images, a plurality of C may be weighted and combined for use in the second focus detection.

  As described above, in the first focus detection operation using the signal extracted from the output signal of the image sensor in only one of the horizontal and vertical directions, the second focus detection operation is performed after the first focus detection operation. It is possible to eliminate the need for focus correction performed after AF. In addition, it is possible to realize focus detection with higher accuracy than the focus correction performed after AF.

[Example 2]
Hereinafter, with reference to FIGS. 8 to 9, an image pickup apparatus to which the focus adjustment apparatus according to the second embodiment of the present invention is applied will be described. In this embodiment, the block diagram (FIG. 1) of the image pickup apparatus having the focus adjustment apparatus according to the first embodiment and the block diagram (FIG. 2) of the unit for calculating the blur evaluation value have the same configuration. Since the same operation is performed, the description is omitted. Also, a diagram showing the relationship between the power of the image signal and the focus lens position (FIG. 3) and a diagram showing the relationship between the defocus range and the focus lens position (FIG. 5) have the same configuration and will not be described.

  There are two main differences from the first embodiment. The first point is that the operation before SW1 is added to the first embodiment. The reason for this will be described later in detail. The second point is a shooting parameter that is changed in order to obtain two images that differ by a predetermined defocus amount used in the DFD that is the second focus detection method. The shooting parameters that affect the blurring state of the captured image include the focus lens position, the aperture amount, the focal length, and the like. If one or more are changed, two images that differ by a predetermined defocus amount can be obtained. In the first embodiment, two images having different blur states are obtained by changing only the focus lens position. However, in this embodiment, the second AF can be performed by moving the subject or shaking the photographer. Use the fact that the subject in the evaluation area swings. However, the direction of movement of the subject and camera shake of the photographer is assumed to be the optical axis direction OA in FIG.

  In the second embodiment, defocusing is performed in advance by performing second focus detection from two images with different blur states obtained by subject movement or camera shake of the subject with respect to the AF operation before SW1. You can know the amount.

  Hereinafter, the contents of the processing operation performed in the second embodiment will be described with reference to the flowcharts of FIGS.

Description of Focus Position Determination Processing Operation The focus operation (AF operation) according to the present embodiment, which is executed by the camera MPU (processor) 125 having the above configuration, will be described below with reference to FIG. FIG. 8 is a diagram illustrating a flowchart of the AF operation of the imaging apparatus to which the focus adjustment apparatus according to the present embodiment is applied. A control program related to this operation is executed by the camera MPU 125. In FIG. 8, “S” is an abbreviation for a step, and the same parts as those in FIG. In FIG. 8, steps other than steps S801, 802, and 803 have the same configuration as that of FIG. 1 of the first embodiment and perform the same operation, and thus the description thereof is omitted.

  According to FIG. 8, it is first determined whether SW1 is ON or OFF. If SW1 is ON, the process proceeds to S802 (Yes in S801). If it is OFF, the process proceeds to S803 (No in S802). After performing the AF operation before SW1 (S803), the flow returns to S401. Details of the AF operation before SW1 will be described later.

  In step S802, it is determined whether the second defocus amount has already been calculated. If the second defocus amount can be calculated in S802, the process proceeds to S408 (No in S802), and it is determined whether or not it is in focus. If it is determined in S408 that focus is achieved (Yes in S108), the camera MPU 125 performs focus display (S409) and ends the AF operation.

  On the other hand, if it is determined in S802 that the second defocus amount cannot be calculated, the process proceeds to S402 (Yes in S802), and the AF operation similar to that in the first embodiment is executed.

  Thus, by detecting the defocus amount in advance before SW1, it is possible to speed up the AF operation when the steps S402 to S411 performed in the first embodiment can be omitted. .

Description of AF Operation Before SW1 Hereinafter, the AF operation before SW1 executed in step S803 of FIG. 8 will be described with reference to FIG. FIG. 9 is a diagram showing a flowchart of the AF operation before SW1 (S803) in the present embodiment. In FIG. 9, “S” is an abbreviation of step, and the same parts as those in FIG. Show. A control program related to the operation of FIG. 9 is executed by the camera MPU 125.

  First, in FIG. 9, steps other than step S905 are the same as those in FIG. 4 of the first embodiment, and the same operations are performed, so that the description thereof is omitted. However, it should be noted that the steps S404 and S410 in FIG. 4 are not shown in FIG. The reason for this will be described later. Further, since it is before SW1, exposure for acquiring image signals of image 3 and image 4 is performed by control of the camera UPU 125.

  As described above, in this embodiment, a plurality of images differing by a predetermined defocus amount using the subject moving in the second AF evaluation area due to the subject moving or the camera shake of the photographer. Get the signal. However, the direction of movement of the subject and camera shake of the photographer is assumed to be the optical axis direction OA in FIG. If there is a certain amount of subject movement or camera shake in the direction other than OA, pattern matching (normalized correlation) processing or the like may be performed on the image within the AF evaluation range to perform second focus detection.

  Hereinafter, an image in a certain blurred state before the movement of the subject or the camera shake of the photographer in the optical axis direction OA is referred to as an image 3, and the image after the occurrence is referred to as an image 4.

  In S905, it is determined whether or not the second defocus interval is larger than the defocus interval threshold value. However, the second defocus interval refers to a difference between the first defocus amount obtained from the image 3 and the first defocus amount obtained from the image 4. The defocus interval threshold is a threshold used for determination with respect to the second defocus interval. In order to calculate the second defocus interval in S905, it is necessary to finish the exposure of the image 3 and the image 4. That is, if the exposure in S102 is less than once, S905 is No and the flow returns to S402 to perform exposure.

  If the second defocus interval is less than the defocus interval threshold in the case where exposure is performed twice or more with respect to the images 3 and 4 (No in S905), the flow returns to S402 to perform exposure. That is, S905, S402, and S403 are repeated until the difference between the blurring states of the image 3 and the image 4 reaches a predetermined defocus interval that is equal to or greater than the defocus threshold.

  When the second defocus interval is larger than the defocus interval threshold (No in S905), the process proceeds to S106, and the second focus detection and the reliability determination are performed using the image 3 and the image 4.

  It should be noted that the change in the defocus amount between the image 3 and the image 4 is nothing but the change in the widths of L1 ′ and L2 ′ in FIG. The blur evaluation value C also changes. In the first embodiment, the focus lens position interval is always moved at a predetermined defocus interval. However, in this embodiment, the second focus detection is performed by the defocus intervals having various values equal to or larger than the defocus threshold. (S406). Therefore, the C table to be referred to needs to be changed according to the defocus interval between the image 3 and the image 4 used for the second focus detection. Therefore, in S406, it is desirable to store a plurality of C tables in the memory.

  Further, although it is desirable not to drive the lens as much as possible before SW1, lens driving may be performed. When two images differing by a predetermined defocus amount are obtained, the case where the subject is shaken within the AF evaluation area as in the present embodiment and the focus lens position as described in the first embodiment are used. It may be used in combination with the case of using the change of the shooting parameter.

  In the first embodiment, the focus lens is used to capture two images used for the second focus detection even when the focus lens position is already close to the in-focus position at the start of the AF operation. It was necessary to drive to capture the second image. That is, there is a drawback that it is necessary to drive away from the focusing lens position. However, according to the present embodiment, it is desirable that the lens is not driven as much as possible before SW1, so that the second focus detection can be performed without driving the lens.

  As described above, in the first focus detection operation using the signal extracted from the output signal of the image sensor in only one of the horizontal and vertical directions, the second focus detection operation is performed after the first focus detection operation. It is possible to eliminate the need for focus correction performed after AF. In addition, it is possible to realize focus detection with higher accuracy than the focus correction performed after AF. Further, by adding the operation before SW1, the case where an AF result is obtained at SW2 is included, so that it is possible to realize focus detection at a higher speed.

  Further, in the processing of the above-described embodiment, a storage medium in which a program code of software that embodies each function is recorded may be provided to the system or apparatus. The functions of the above-described embodiments can be realized by the computer (or CPU or MPU) of the system or apparatus reading out and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying such a program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, or the like can be used. Alternatively, a CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like can be used.

  The functions of the above-described embodiments are not only realized by executing the program code read by the computer. Including the case where the OS (operating system) running on the computer performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized by the processing. It is.

  Furthermore, the program code read from the storage medium may be written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. After that, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms without departing from the gist of the present invention are also included in the present invention. included. Furthermore, each embodiment mentioned above shows only one embodiment of this invention, and it is also possible to combine each embodiment suitably.

Claims (15)

An acquisition means for acquiring an image signal obtained by imaging an object image formed by an imaging optical system including a focus lens by an imaging means;
First focus detection means for generating a first drive information of the focus lens by detecting a focus state of the subject image in a first direction of an imaging surface of the imaging means using the image signal;
Using a plurality of image signals corresponding to the subject images in the defocused state having different defocus amounts, evaluation values of the defocused state having a correlation with the position of the focus lens are obtained for a plurality of directions including the first direction. Second focus detection means for generating and generating second drive information of the focus lens based on the evaluation value;
Focus adjusting means for controlling the driving of the focus lens using either the first driving information or the second driving information according to the evaluation value;
A focus adjusting apparatus comprising:   The focus adjusting unit controls the driving of the focus lens using the second driving information when the evaluation value is within a predetermined range, and when the evaluation value is not within the predetermined range, the first driving is performed. The focus adjustment apparatus according to claim 1, wherein information is used to control driving of the focus lens.   The focus adjustment unit determines whether the evaluation value is within a predetermined range based on power in the plurality of directions of the image signal used by the second focus detection unit, and the power is 2. The sum of squares of image signals with respect to a direction, and the focus adjustment unit determines that the evaluation value is within a predetermined range when at least the power is equal to or greater than a predetermined threshold. 2. The focus adjustment apparatus according to 2.   4. The focus according to claim 3, wherein the second focus detection unit generates the evaluation value based on power of the image signal corresponding to the subject image in a blurred state having a different defocus amount. Adjusting device.   The second focus detection unit includes a determination unit configured to determine whether or not a difference between defocus amounts of a plurality of image signals corresponding to the subject images in a blurred state having different defocus amounts is greater than a predetermined threshold value. 5. The focus adjustment device according to claim 1, wherein the focus adjustment device controls generation of the evaluation value and generation of the second drive information according to a result of the determination. 6.   The second focus detection unit includes a conversion unit that converts the evaluation value into a defocus amount corresponding to the position of the focus lens that is correlated with the evaluation value. The second focus detection unit converts the evaluation value into the defocus amount converted by the conversion unit. The focus adjustment apparatus according to claim 1, wherein the second driving information is generated based on the first driving information.   A setting unit that sets an evaluation range for extracting an image signal used by each of the first focus detection unit and the second focus detection unit is provided, and the setting unit sets at least one of the evaluation ranges. The focus adjusting apparatus according to any one of claims 1 to 6. In the control method of the focus adjustment device,
An acquisition step of acquiring an image signal obtained by imaging a subject image formed by an imaging optical system including a focus lens by an imaging unit;
A first focus detection step of generating a first drive information of the focus lens by detecting a focus state in the first direction of the imaging surface of the imaging means using the image signal;
Using a plurality of image signals corresponding to the subject images in the defocused state having different defocus amounts, evaluation values of the defocused state having a correlation with the position of the focus lens are obtained for a plurality of directions including the first direction. A second focus detection step for generating and generating second drive information of the focus lens based on the evaluation value;
A focus adjustment step of controlling driving of the focus lens using either the first drive information or the second drive information according to the evaluation value;
A control method comprising:   A program for causing a computer to execute the control method according to claim 8.   A computer-readable storage medium storing a program for causing a computer to execute the control method according to claim 8. A taking optical system including a focus lens capable of moving back and forth in the optical axis direction
Driving means for driving the focus lens;
Imaging means for capturing an image of a subject formed by the imaging optical system and generating an image signal;
An acquisition means for acquiring an image signal obtained by imaging the subject images in different blur states formed by the imaging optical system with the imaging means;
First focus detection means for generating a first drive information of the focus lens by detecting a focus state in the first direction of the imaging surface of the imaging means using the image signal;
Using a plurality of image signals corresponding to the subject images in the defocused state having different defocus amounts, evaluation values of the defocused state having a correlation with the position of the focus lens are obtained for a plurality of directions including the first direction. Second focus detection means for generating and generating second drive information of the focus lens based on the evaluation value;
Focus adjusting means for controlling the driving of the focus lens using either the first driving information or the second driving information according to the evaluation value;
With
The focus adjustment unit controls the driving unit to drive the focus lens according to either the first driving information or the second driving information.   A plurality of image signals corresponding to the subject images in a blurred state having different defocus amounts, the imaging optical system in which the imaging parameters are changed by the changing unit; The image signal obtained by imaging the subject image formed by the imaging unit with the imaging unit, wherein the imaging parameters include at least a position of the focus lens, an aperture amount, and a focal length. The imaging device described.   Instructing means for instructing exposure to cause the imaging means to take an image of the subject image, the focus adjusting means determines whether or not the exposure is instructed by the instructing means, and according to the result of the determination The imaging apparatus according to claim 11, wherein driving of the focus lens is controlled.   Control of driving of the focus lens by the focus adjustment unit when it is determined that the exposure is not instructed by the instruction unit includes control for causing the imaging unit to capture the subject image. The focus lens drive control using the drive information, and the focus lens drive control by the focus adjustment unit when it is determined that the exposure is instructed by the instruction unit, according to the evaluation value, The imaging apparatus according to claim 13, further comprising control of driving the focus lens using either the first drive information or the second drive information.   The imaging means includes imaging pixels for generating an image of the subject image, and focus detection pixels in which a plurality of photoelectric conversion means constitute pixels corresponding to the imaging pixels, and the first focus detection The imaging apparatus according to claim 11, wherein the unit detects the focus state using an image signal from the focus detection pixel.

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