JP5315666B2 - Focus detection device, camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a focusing state for accurately performing focusing of a photographic lens even when a main subject is a person. <P>SOLUTION: A focus detecting device for detecting the focusing state of an image forming optical system 1 for a plurality of focus detecting positions set in an image surface by the image forming optical system 1 has a person detection means 8 detecting information corresponding to the person out of images formed by the image forming optical system 1, and a selection means 6 selecting at least one of the plurality of focus detecting positions based on the information detected by the person detection means 8 and the focusing state detected for the plurality of focus detecting positions. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a focus detection device that detects a focus adjustment state of a photographing lens, and a camera including the focus detection device.

Conventionally, the focus adjustment state of the photographic lens with respect to a plurality of focus detection positions set in the shooting screen, that is, the defocus amount is detected, and the defocus amounts that fall within a predetermined defocus amount range are grouped as the same group, A camera that performs focus adjustment of a photographing lens by selecting a group that is expected to capture a main subject from these groups is known (see Patent Document 1).
Japanese Patent Laid-Open No. 2-178641

  In the camera disclosed in Patent Document 1, a group that is likely to capture the main subject is selected based on the defocus amount from the group of focus detection positions classified based on the defocus amount. Therefore, it may be difficult to appropriately detect the focus adjustment state for a person who is generally likely to be a main subject.

According to a first aspect of the present invention, there is provided a focus detection apparatus for detecting a focus adjustment state of the imaging optical system with respect to a plurality of focus detection areas set in an image plane by the imaging optical system, and the plurality of focal points. Classifying means for classifying the detection area into a plurality of areas, and based on a focus detection result by the focus detection means for each of the plurality of focus detection areas, determining an adopted focus detection area for each of the plurality of areas, An area selecting means for grouping the plurality of areas into a plurality of groups and selecting a predetermined area from the areas belonging to a group selected from the plurality of groups based on the focus detection result relating to the adopted focus detection area; The person detection means for detecting a person image among the images formed by the imaging optical system and the person image exist for each of the plurality of focus detection areas. A determination means for determining whether the focus detection area is a person image presence, a calculation means for obtaining a density of the focus detection area of the person image presence for each of the plurality of areas, and the plurality of the plurality of areas based on the density A person area selecting means for selecting at least one area from the areas as a person area; one of the predetermined area and the person area is selected as an adopted area; and a focus detection area in the adopted area is selected as the imaging optical focus detection area for performing focus adjustment of the system, e Preparations and adopted area selecting means for selecting, the density of the focus detection area of the human image exists, all the focus detection areas in the area of the calculation target It is a ratio of the number of focus detection areas where the human image exists within the area to be calculated to the number .
According to a fourth aspect of the present invention, there is provided a focus detection apparatus for detecting a focus adjustment state of the imaging optical system with respect to a plurality of focus detection areas set in an image plane by the imaging optical system, and the plurality of focal points. Classifying means for classifying the detection area into a plurality of areas, and based on a focus detection result by the focus detection means for each of the plurality of focus detection areas, determining an adopted focus detection area for each of the plurality of areas, An area selecting means for grouping the plurality of areas into a plurality of groups and selecting a predetermined area from the areas belonging to a group selected from the plurality of groups based on the focus detection result relating to the adopted focus detection area; The person detection means for detecting a person image among the images formed by the imaging optical system and the person image exist for each of the plurality of focus detection areas. A determination means for determining whether the focus detection area is a person image presence, a calculation means for obtaining a density of the focus detection area of the person image presence for each of the plurality of areas, and the plurality of the plurality of areas based on the density A person area selecting means for selecting at least one area from the areas as a person area; one of the predetermined area and the person area is selected as an adopted area; and a focus detection area in the adopted area is selected as the imaging optical A focus comprising: an adopted area selection means to be selected as a focus detection area for performing focus adjustment of the system; and a reliability calculation means for calculating a person detection reliability when the person detection means detects the person image. In the detection device, the recruitment area selection means selects the person area as the adoption area when the person detection reliability is equal to or higher than a first predetermined threshold, and the focus The exit device has the person detection reliability equal to or higher than a second predetermined threshold value that is less than the first predetermined threshold value and smaller than the first predetermined threshold value, or the second predetermined threshold value. The predetermined area determined by the area selection means determined by a relationship between a first determination means for determining whether the value is less than a threshold value, and a shooting posture of a camera incorporating the focus detection device and the plurality of areas. And a second determination unit that compares the area selection reliability value when selecting the person detection reliability with the person detection reliability, and the adopted area selection unit uses the first determination unit to determine the person detection reliability. Is determined to be less than the second predetermined threshold value, the predetermined area is selected as the adopted area, and the person detection reliability is selected by the first determination means as the first predetermined threshold value. Less than the second predetermined If it is determined that the person detection reliability is greater than the area selection reliability value by the second determination means, the person area is selected as the adoption area. On the other hand, when the second determination means determines that the person detection reliability is smaller than the area selection reliability value, the predetermined area is selected as the adopted area.

  According to the present invention, it is possible to detect the focus adjustment state for correctly adjusting the focus of the photographing lens even when the main subject is a person.

  An embodiment in which the focus adjustment apparatus of the present invention is applied to a single-lens reflex camera will be described. The present invention is not limited to a single-lens reflex camera. FIG. 1 is a cross-sectional view of a camera according to an embodiment. The light from the subject that has passed through the photographing lens 1 passes through the half mirror portion of the main mirror 2, is reflected by the sub mirror 3, and is guided to the focus detection device 4. The light from the subject that has passed through the photographing lens 1 is reflected by the main mirror 2 and guided to the finder 5 at the top of the camera. The main mirror 2 and the sub mirror 3 are placed in the photographing optical path as shown before photographing, and are flipped upward and retracted from the photographing optical path during photographing.

  Part of the light from the subject guided to the finder 5 is guided to the photometric device 8. The photometric device 8 has a light receiving element in which pixels of red (R), green (G), and blue (B) are arranged in a predetermined arrangement pattern, and a photographing lens that forms an image on the light receiving element. 1 to detect the color information of the subject. This color information is output from the photometry device 8 to the control device 6 and is used when the control device 6 performs person discrimination described later. That is, the photometric device 8 detects color information corresponding to a person in the image taken by the photographing lens 1 and outputs it to the control device 6.

  The control device 6 includes a microcomputer (not shown) and peripheral components such as a memory, and performs various processes and controls. For example, based on the color information output from the photometric device 8, person determination is performed to determine a person's part from the image taken by the photographing lens 1. Further, the focus adjustment state (defocus amount) of the photographing lens 1 is obtained based on the focus detection signal output from the focus detection device 4, the lens driving device 7 is driven and controlled based on the obtained focus adjustment state, and the photographing lens. 1. Adjust the focus.

  In the focus detection device 4, 51 focus detection areas (focus detection positions) are set in the image plane of the photographing optical system as shown in FIG. 2. The focus detection areas are respectively represented as a1 to a51 in order from the upper left to the lower right as shown in FIG. Each focus detection area is provided with a focus detection optical system as indicated by 200 to 600 in FIG. In FIG. 3, a light beam incident through the region 101 of the photographing optical system 100 corresponding to the photographing lens 1 of FIG. 1 passes through the field mask 200, the field lens 300, the aperture opening 401, and the re-imaging lens 501. An image is formed on the A column of the sensor array 600. The A column of the image sensor array 600 is a one-dimensional array of a plurality of photoelectric conversion pixels that generate an output corresponding to the incident intensity. Similarly, the light beam incident through the region 102 of the photographing optical system 100 passes through the field mask 200, the field lens 300, the aperture opening 402, and the re-imaging lens 502 and is coupled onto the B row of the image sensor array 600. Image. The B column of the image sensor array 600 is a one-dimensional array of a plurality of photoelectric conversion pixels that generate an output corresponding to the incident intensity.

  A pair of subject images formed on the A and B columns of the image sensor array 600 are separated from each other in a so-called front pin state in which the photographing optical system 100 forms a sharp image of the subject before the planned focal plane, and conversely In the so-called rear pin state in which the sharp image of the subject is connected after the planned focal plane, the images approach each other, and the subject images on the A and B columns of the image sensor array 600 are predetermined at the time of the so-called in-focus state where the sharp image of the subject is just connected to the planned focal plane. It becomes the interval. Accordingly, the pair of subject images are photoelectrically converted into electric signals by the A and B columns of the image sensor array 600 and converted into electric signals, and these signals are subjected to arithmetic processing by the control device 6 to calculate the relative positional deviation amount of the pair of subject images. By determining, the focus adjustment state of the photographic optical system 100, here, the shift amount between the planned focal plane and the imaging plane and its direction (hereinafter referred to as defocus amount) can be known.

  Next, a method for adjusting the focus of the taking lens 1 from the defocus amount obtained in each focus detection area will be described. In the camera of this embodiment, the control device 6 has a person based on the color information output from the photometric device 8 for each of the focus detection areas a1 to a51 set in the shooting screen in the focus detection device 4. It is determined whether or not it is a focus detection area. That is, for each of the focus detection areas a1 to a51, it is determined whether or not the color information corresponding to the focus detection area represents a feature as a person, for example, a feature such as a face, head, or skin. If it is determined that the color information represents such a feature, it is determined that a person exists in the focus detection area. In this way, the person portion is discriminated from the image taken by the photographing lens 1 and the person is discriminated.

  Further, the control device 6 classifies the focus detection areas a1 to a51 into a plurality of blocks (sections), and selects a block (person block) based on the result of the person discrimination and a defocus amount from the plurality of blocks. A base block (AF selection block) is determined. Then, either the person block or the AF selection block is selected as the adopted block, and the driving amount (focus adjustment control) of the photographing lens 1 is based on the defocus amount detected for the focus detection area belonging to the selected block. Amount).

  As described above, the control device 6 determines the focus detection areas a1 to a51 based on the color information detected by the photometry device 8 and the defocus amounts detected for the focus detection areas a1 to a51. At least one of them is selected as a focus adjustment target area. Then, the focus adjustment control amount is determined based on the defocus amount detected in the selected target area, and the lens driving device 7 is driven and controlled according to the focus adjustment control amount, thereby adjusting the focus of the photographing lens 1. Do.

  In this way, it is possible to detect the focus adjustment state for correctly adjusting the focus of the photographing lens 1 not only when the main subject is a person but also when the main subject is not a person. Further, even if 51 points and a large number of focus detection areas are set in the shooting screen, the focus adjustment of the shooting lens 1 can be appropriately performed regardless of the number of focus detection areas.

  FIG. 4 shows an example in which the arrangement positions of the focus detection areas a1 to a51 are classified into a plurality of blocks. In this classification example, focus detection areas a1 to a51 are divided into an outer left block b1, an upper left block b2, a left block b3, a lower left block b4, a top block b5, a central block b6, a ground block b7, an upper right block b8, a right block b9, The lower right block b10 and the right outer block b11 are classified into a total of 11 blocks.

  The following focus detection areas belong to the respective blocks. Focus detection areas a1 to a3 belong to the left outer block b1. Focus detection areas a4, a9 and a14 belong to the upper left block b2. Focus detection areas a5 to a7, a10 to a12, and a15 to a17 belong to the left block b3. Focus detection areas a8, a13, and a18 belong to the lower left block b4. Focus detection areas a19, a24, and a29 belong to the top block b5. Focus detection areas a20 to a22, a25 to a27, and a30 to a32 belong to the central block b6. Focus detection areas a23, a28, and a33 belong to the ground block b7. Focus detection areas a34, a39, and a44 belong to the upper right block b8. Focus detection areas a35 to a37, a40 to a42, and a45 to a47 belong to the right block b9. The focus detection areas a38, a43, and a48 belong to the lower right block b10. Focus detection areas a49 to a51 belong to the right outer block b11.

  Since the block classification method described above is an example, the present invention is not limited to this content. Arrangement positions of arbitrary focus detection areas can be classified according to an arbitrary number of blocks.

  When the control device 6 classifies the focus detection areas a1 to a51 into the blocks b1 to b11 as described above, the control device 6 determines a person block based on the result of the person discrimination described above. Here, the density of the focus detection area where a person exists is calculated for each of the classified blocks, and the block with the highest density is determined as the person block.

  The manner in which the person block is determined will be described with reference to the example shown in FIG. In the example of FIG. 5, if there is a person in each of the focus detection areas a40, a41, a44, a45, a46, a47, a49, and a50 among the focus detection areas a1 to a51, which are shaded in the figure, Suppose that it was determined by discrimination. At this time, for example, the density of the upper right block b8 to which the focus detection area a44 belongs is calculated as 1 / 3≈0.33. It should be noted that numerator 1 represents the total number of focus detection areas where it is determined that a person exists, and denominator 3 represents the total number of focus detection areas in the block. Similarly, the density of the right block b9 to which the focus detection areas a40, a41, a45, a46 and a47 belong is calculated as 5 / 9≈0.56, and the density of the right outer block b11 to which the focus detection areas a49 and a50 belong is 2 /3≒0.67 The density of other blocks is 0. As a result, the right outer block b11 having the highest density is determined as the person block.

  As described above, the control device 6 obtains the density of the focus detection area where the person exists for each of the blocks b1 to b11, and decides the person block based on the obtained density. At this time, two or more blocks may be determined as person blocks. Also, the denominator value at the time of density calculation may be changed from the total number of focus detection areas in the actual block according to the position of the block on the screen so that the block near the center of the screen is likely to be a human block. . For example, in the example of FIG. 5, the upper right block b8 and the right outer block b11 are set to 3 without changing the denominator value, but the right block b9 closer to the center of the screen has a denominator value of 9 to 6. To change. Then, the density of the right block b9 is calculated as 5 / 6≈0.83. As a result, the right block b9 having the highest density is determined as the person block.

  Or it is good also as determining a person block by methods other than this. For example, the defocus amount of each focus detection area determined to have a person is detected, and a block including the focus detection area with the smallest detected defocus amount is determined as a person block. In addition, the person block can be determined by various methods.

  Further, when determining the AF selection block, the control device 6 selects any one of the focus detection areas belonging to each block classified as shown in FIG. 4 in each block. The focus detection area selected at this time is hereinafter referred to as an adoption area. The method for selecting the adoption area will be described in detail later.

  After selecting the adopted area for each block, the control device 6 next executes a grouping process for grouping the blocks b1 to b11 into a plurality of groups based on the defocus amount detected for each adopted area. . For example, the blocks b1 to b11 are grouped by grouping the blocks in which the defocus amount of the adopted area is within a predetermined range into the same group. The grouping process can be performed by various other methods. In this way, the control device 6 groups the blocks b1 to b11 into a plurality of groups.

  After the blocks b1 to b11 are grouped into a plurality of groups, the control device 6 next selects an optimal group that is expected to capture the main subject from the group. For example, the group to which the block indicating the closest defocus amount belongs is selected as the optimum group. The optimum group can be selected by various other methods.

  After selecting the optimum group in this way, the control device 6 next determines at least one block belonging to the optimum group as an AF selection block. For example, the block indicating the closest defocus amount among the blocks belonging to the optimum group is determined as the AF selection block. The AF selection block can be determined from the blocks belonging to the optimum group by various other methods.

  After determining the person block and the AF selection block as described above, the control device 6 selects one of them as an adopted block when determining the driving amount of the photographing lens 1. Note that a method for selecting which one of the person block and the AF selection block to be adopted will be described later in detail with reference to the flowcharts shown in FIGS. Then, based on the defocus amount detected in the adoption area of the selected adoption block, the driving amount of the photographing lens 1, that is, the focus adjustment control amount is determined, and the focus adjustment of the photographing lens 1 is performed.

  Here, a method for selecting an employment area will be described. In the camera of this embodiment, the focus detection device 4 and the control device 6 perform focus detection and focus adjustment based on the focus detection result in two stages in order to increase the accuracy of focus adjustment. The control device 6 performs focus adjustment based on the focus detection result of the first stage by the focus detection device 4, so that the photographing lens 1 can be focused to some extent. Thereafter, the control device 6 performs focus adjustment based on the focus detection result of the second stage by the focus detection device 4, whereby the photographing lens 1 can be accurately focused. There are different selection methods for the case where the control device 6 selects the adopted area in the first-stage focus detection and the case where the control device 6 selects the adopted area in the second-stage focus detection as described below. Used.

  In the first-stage focus detection, the control device 6 selects a predetermined focus detection area as an adopted area from among the focus detection areas belonging to the blocks b1 to b11 described above. An example is shown in FIG. In the example of FIG. 6, the focus detection area located at the center in each block is selected as the adoption area. That is, the focus detection area a2 in the left outer block b1, the focus detection area a9 in the upper left block b2, the focus detection area a11 in the left block b3, the focus detection area a13 in the lower left block b4, and the focus detection area in the top block b5 a24, focus detection area a26 in the center block b6, focus detection area a28 in the ground block b7, focus detection area a39 in the upper right block b8, focus detection area a41 in the right block b9, focus detection in the lower right block b10 The area a43 and the focus detection area a50 in the right outer block b11 are used areas.

  In addition, since the selection method of the employment area demonstrated above is an example, this invention is not limited to this content. A focus detection area at an arbitrary position in each block can be selected as an adopted area.

  When the control device 6 selects the adopted area in the first-stage focus detection as described above, the control device 6 calculates the defocus amount for the adopted area, thereby detecting the focus adjustment state of the photographing lens 1. That is, in the first-stage focus detection, the control device 6 calculates the defocus amount only for a total of 11 focus detection areas predetermined in each block among the 51 focus detection areas a1 to a51. I do. Thereby, only the calculation of the defocus amount necessary for focusing the photographing lens 1 to some extent can be performed, and the calculation of the unnecessary defocus amount can be omitted, so that the processing speed can be increased.

  On the other hand, in the second-stage focus detection, the control device 6 calculates the defocus amount for all 51 focus detection areas a1 to a51. Then, based on the obtained defocus amount of each focus detection area, one of the focus detection areas is selected as the adopted area in each of the blocks b1 to b11. For example, the focus detection area indicating the closest defocus amount in each of the blocks b1 to b11 is selected as the adopted area. Thereby, the focus of the photographic lens 1 can be accurately adjusted in the second stage of focus adjustment.

  Further, as described above, when selecting the adopted area from the focus detection areas belonging to each block, the control device 6 determines a predetermined reliability determination criterion for the defocus amount obtained in the focus detection area. Based on the above, the presence or absence of reliability is determined. This reliability determination method will be described in detail later. When it is determined that the defocus amount is not reliable, the focus detection area is excluded from the adopted area. That is, the control device 6 selects an adoption area based on a reliability determination criterion for determining that the defocus amounts detected for a plurality of focus detection areas are reliable.

  Note that after performing the first-stage focus detection and focus adjustment described above, the focus detection device 4 and the control device 6 may repeatedly perform the second-stage focus detection and focus adjustment a plurality of times. That is, after the control device 6 once selects the adopted area and the focus detection device performs the second-stage focus detection, the control device 6 performs the second-stage focus adjustment. After that, the control device 6 selects the adopted area again, and after the focus detection device 4 performs focus detection, the control device 6 performs focus adjustment. In this way, when selecting the employment area again, the control device 6 selects the employment area by a different selection method from the case where the previous employment area is determined, that is, when the employment area is determined in the first-stage focus detection. For example, when selecting the adoption area again, the control device 6 selects, as described above, the focus detection area indicating the closest defocus amount in each of the plurality of blocks as the adoption area.

  Further, when selecting the adoption area as described above, the control device 6 may select not only one but a plurality of focus detection areas as the adoption area in each block. That is, a part of the plurality of focus detection areas can be selected as the adopted area for each of the plurality of blocks. In this case, the average value or median value of the defocus amounts in a plurality of adopted areas may be obtained for each block, and grouping processing may be performed using the calculation result to adjust the focus of the photographic lens 1.

  Here, focus detection calculation for calculating the defocus amount will be described. The A column and B column of the image sensor array 600 shown in FIG. 3 are each composed of a plurality of photoelectric conversion pixels, and a plurality of output signal sequences α [1],. . . , Α [n], β [1],. . . β [n] is output (FIGS. 7A and 7B). The control device 6 performs correlation calculation while relatively shifting the predetermined range of data by L by a predetermined amount of data in the pair of output signal sequences. If the maximum shift number is lmax, the range of L is from −1max to + 1max. Specifically, the correlation amount C [L] is calculated by the following equation.

C [L] = Σ | a [i + L] −b [i] | (1)
In the equation (1), Σ represents the sum of i = k to r, and the first term k and the last term r are changed depending on the shift amount L as in the following equation, for example. L is an integer corresponding to the shift amount of the data string described above, and L = −lmax,. . . , -2, -1, 0, 1, 2,. . . , Lmax.

When L ≧ 0;
k = k0 + INT {−L / 2},
r = r0 + INT {−L / 2},
When L <0;
k = k0 + INT {(− L + 1) / 2},
r = r0 + INT {(−L + 1) / 2} (2)
Here, k0 and r0 are the first term and the last term when the shift amount L is zero.

  Since the relative positional deviation amount is the shift amount L when the pair of data coincides, the shift amount giving the minimum correlation amount is detected from the correlation amount C [L] thus obtained. 3 is multiplied by a constant determined by the pitch width of the photoelectric conversion pixels of the image sensor array 600 and the optical system shown in FIG. Therefore, a larger defocus amount can be detected as the maximum shift number lmax is larger.

  Incidentally, the correlation amount C [L] is a discrete value as shown in FIG. 7C, and the smallest unit of defocus amount that can be detected is the photoelectric conversion pixels of the A column and B column of the image sensor array 600. It is limited by the pitch width. Therefore, a method of performing a precise focus detection by newly calculating a true minimum value Cex by performing an interpolation operation based on the discrete correlation amount C [L] will be described. As shown in FIG. 8, this method uses a correlation amount C [Le], which is a minimum value, and correlation amounts C [Le + 1], C [Le-1] in the shift amounts on both sides of the correlation value C [Le-1]. The value Cex and the shift amount Ls that gives it are calculated by the following equation.

DL = (C [Le-1] -C [Le + 1]) / 2
Cex = C [Le]-| DL |,
E = MAX {C [Le + 1] -C [Le], C [Le-1] -C [Le]},
Ls = Le + DL / E (3)
In the formula (3), MAX {Ca, Cb} means that the larger one of Ca and Cb is selected. The defocus amount DF is calculated from the shift amount Ls by the following equation.

DF = Kf · Ls (4)
In the equation (4), Kf is a constant determined by the pitch width of the photoelectric conversion pixels of the optical system and the image sensor array 600 shown in FIG.

  It is necessary to determine whether the defocus amount obtained in this way truly indicates the defocus amount or due to the fluctuation of the correlation amount due to noise or the like. The control device 6 determines that the defocus amount is reliable when the condition shown in the following equation is satisfied.

E> E1 (5),
Cex / E <G1 (6)
In equations (5) and (6), E1 and G1 are threshold values for reliability determination criteria. The numerical value E indicates how the correlation amount changes, and is a value that depends on the contrast of the subject. The larger the value, the higher the contrast and the higher the reliability. Cex is a difference when a pair of data most closely matches and is originally 0. However, due to the influence of noise and further, parallax is generated between the area 101 and the area 102, a subtle difference occurs between the pair of subject images and does not become zero. Since the effect of the difference between the noise and the subject image is smaller as the subject contrast is higher, Cex / E is used as a numerical value representing the degree of coincidence between a pair of data. Of course, the closer Cex / E is to 0, the higher the degree of matching between a pair of data and the higher the reliability.

  In this embodiment, the defocus amount obtained in the 51 focus detection areas a1 to a51 shown in FIG. 2 is defined as Def (i) (i = 1 to 51). Further, the reliability of each defocus amount is a value E (i) depending on the contrast of the subject shown in the above equation (5), or a numerical value Cex / E ( i).

  As described above, when the contrast of the subject image in the focus detection area is low, a highly reliable defocus amount cannot be obtained. Therefore, when selecting the adopted area in each of the blocks b1 to b11, the control device 6 excludes a focus detection area having a defocus amount with low reliability. However, if the focus of the photographic lens 1 is greatly deviated, the contrast of the subject image in the focus detection area becomes low even if the contrast of the subject itself is high, and the focus detection area is excluded from the adopted area. As a result, the grouping process of the blocks b1 to b11 cannot be performed correctly.

  Therefore, in this embodiment, as described above, the control device 6 selects the adopted area in the first-stage focus detection and selects the adopted area in the second-stage focus detection. The value of the reliability determination criterion for determining that the focus amount is reliable is changed. The method will be described below.

  In the first-stage focus detection, there is a high probability that the focus of the photographic lens 1 is greatly shifted. Therefore, as shown in FIG. 6, the control device 6 determines the reliability E (i) or the reliability E (i) or the defocus amount Def1 (i) at the first stage obtained from the focus detection area determined in advance in each block. A focus detection area having a defocus amount in which Cex / E (i) satisfies the following equation is extracted. At this time, i can take only a value corresponding to a predetermined focus detection area.

E> E11 (7),
Cex / E <G11 (8)
In equations (7) and (8), E11 and G11 are threshold values for reliability determination criteria at the time of first-stage focus detection.

  As described above, in the first-stage focus detection, the control device 6 determines that the defocus amount is reliable according to the equation (7) or (8) in the predetermined focus detection area. The selected focus detection area is extracted and selected as an adopted area. Blocks b1 to b11 are grouped into a plurality of groups based on the defocus amount detected in the selected adoption area. Then, an optimum group is selected from the plurality of grouped groups, and one of the blocks belonging to the optimum group is determined as an AF selection block by the method described above.

  When the AF selection block is determined as described above, the control device 6 performs the first-stage focus adjustment. In this first-stage focus adjustment, the AF selection block is selected as it is as the adopted block without determining the person block. Based on the defocus amount detected in the focus detection area belonging to the selected adopted block in this way, the driving amount of the photographing lens 1 is determined, and the first-stage focus adjustment is performed.

  After performing the first-stage focus adjustment, the control device 6 performs the second-stage focus detection, and detects the second-stage defocus amount Def2 (i) from the 51 focus detection areas a1 to a51. At least in the second-stage focus detection, the photographing lens 1 is in focus more than in the first-stage focus detection. Therefore, the second-stage defocus amount Def2 (i) is the first-stage defocus amount Def1. The value is smaller than (i).

  Next, the control device 6 determines the reliability E (i) or Cex / E (i) from the second-stage defocus amount Def2 (i) obtained from the 51 focus detection areas a1 to a51. A focus detection area with a defocus amount that satisfies the following equation is extracted.

E> E12 (9),
Cex / E <G12 (10)
In equations (9) and (10), E12 and G12 are threshold values for reliability determination criteria at the time of focus detection at the second stage.

  Here, the control device 6 sets a value that is more easily determined to be more reliable than the threshold value of the second-stage reliability determination criterion as the threshold value of the first-stage reliability determination criterion.

E12> E11 (11),
G12 <G11 (12)
That is, a value smaller than the second-stage threshold value E12, that is, a value that is easily determined to be reliable, is set as the first-stage threshold value E11 of the reliability E. Alternatively, the first threshold value G11 of the reliability Cex / E is set to a value larger than the second-stage threshold value G12, that is, a value that is easily determined to be reliable.

  This is because the focus of the photographing lens 1 is more blurred at the time of focus detection at the first stage than at the time of focus detection at the second stage. This is to avoid misrecognizing an unreliable area due to the out-of-focus of the taking lens 1 in spite of the fact.

  As described above, in the second-stage focus detection, the control device 6 determines that the defocus amount is reliable by the formula (9) or the formula (10) out of the 51 focus detection areas a1 to a51. The determined focus detection area is extracted and selected as an adopted area. Blocks b1 to b11 are grouped into a plurality of groups based on the defocus amount detected in the selected adoption area. Then, an optimum group is selected from the plurality of grouped groups, and one of the blocks belonging to the optimum group is determined as an AF selection block by the method described above.

  When the AF selection block is determined as described above, the control device 6 performs the second-stage focus adjustment. In this second stage of focus adjustment, one of the person block and the AF selection block is selected as an adopted block by a method described later. Then, the driving amount of the photographing lens 1 is determined based on the defocus amount detected in the focus detection area belonging to the selected adopted block, and the second-stage focus adjustment is performed.

  As is clear from the equations (11) and (12), the second-stage focus detection uses the threshold value E12 or G12 of the reliability criterion that is less likely to be determined to be reliable than the first-stage focus detection. Thus, the reliability determination of each defocus amount is performed, so that in the second stage focus detection, a defocus amount with higher reliability than the defocus amount obtained by the first stage focus detection can be obtained. Since the adoption area is selected using such a highly reliable defocus amount, it is possible to select the optimum employment area and perform focus adjustment.

  However, if it is highly possible that the luminance of the image by the photographing lens 1 is lower than a predetermined value and a highly reliable defocus amount cannot be obtained, the reliability determination is performed even at the time of the second focus detection. It is preferable not to change the reference threshold value from the first stage. Thus, even in a dark shooting environment where it is difficult to correctly detect the defocus amount for the main subject, the effective defocus amount can be detected and the second-stage focus adjustment can be performed. The luminance value used for the determination at this time is set according to the situation when it is determined that the camera automatically uses the flash, for example. Note that the brightness of the image taken by the photographing lens 1 can be determined from the color information output from the photometric device 8.

  9 and 10 are flowcharts showing the focus adjustment operation of the embodiment. The controller 6 starts this focus adjustment operation when the camera is turned on. In step S10 of FIG. 9, it is confirmed whether or not a shutter button (not shown) has been half-pressed. When the shutter button is half-pressed, the process proceeds to step S20.

  In step S20, the control device 6 calculates a defocus amount for a predetermined focus detection area. At this time, the control device 6 detects the focus adjustment state of the photographic lens 1 by calculating the defocus amount with respect to a focus detection area predetermined in each block as shown in FIG.

  In step S30, the control device 6 determines whether or not the defocus amount detected in step S20 is greater than or equal to a predetermined threshold value. The defocus amount threshold value used for this determination is preset with a defocus amount corresponding to a focus adjustment state in which the first-stage focus adjustment is to be performed, that is, a state in which the photographing lens 1 is largely out of focus. . If it is determined that the defocus amount is greater than or equal to the threshold value, that is, if it corresponds to the focus adjustment state in which the first-stage focus adjustment is to be performed, the process proceeds to step S40. On the other hand, when it is determined that the defocus amount is less than the threshold value, that is, when it corresponds to the focus adjustment state in which the second-stage focus adjustment is to be performed, the process proceeds to step S90.

  When the process proceeds from step S30 to step S40, the control device 6 performs the first-stage focus adjustment in steps S40 to S80. That is, in step S40, the control device 6 selects a first-stage adoption area based on the defocus amount calculation result in step S20. At this time, the control device 6 selects, as the adopted area, the one determined to be reliable by the equations (7) and (8) among the focus detection areas for which the defocus amount is obtained in step S20.

  In step S50, the control device 6 performs block grouping based on the defocus amount obtained for the first-stage adoption area selected in step S40. In step S60, the control device 6 selects one of the plurality of groups divided in step S50 as the optimum group. In step S70, the control device 6 determines any of the blocks belonging to the optimum group selected in step S60 as an adopted block. In step S80, the control device 6 performs first-stage focus adjustment on the photographing lens 1 based on the defocus amount of the adopted area in the adopted block determined in step S70. If step S80 is performed, the control apparatus 6 will return to step S30.

  As described above, when it is determined in step S30 that the defocus amount is equal to or larger than the threshold value, the control device 6 performs the first-stage focus adjustment. Thus, a person block is selected and the person block is avoided from being adopted. That is, when the defocus amount detected with respect to the focus detection area belonging to each of the blocks b1 to b11 indicates a state in which the photographing lens 1 is largely out of focus, the control device 6 selects the adopted block. Selection of a block to which a focus detection area determined to have a person by person determination belongs is prohibited. Then, the adopted block is determined based on the defocus amount detected in step S20, and focus adjustment is performed based on the defocus amount of the focus detection area located in the adopted block.

  On the other hand, when the process proceeds from step S30 to step S90, the control device 6 performs the second-stage focus adjustment after step S90. In step S90, the control device 6 calculates defocus amounts for all focus detection areas. At this time, the control device 6 detects the focus adjustment state of the photographing lens 1 by calculating the defocus amount for all the 51 focus detection areas a1 to a51.

  In step S100, the control device 6 selects a second-stage adoption area based on the calculation result of the defocus amount in step S90. At this time, the control device 6 is determined to be reliable by the equations (9) and (10) among all the focus detection areas for which the defocus amount is obtained in step S90, and satisfies a predetermined condition in each block. Select one as the recruitment area. For example, the focus detection area indicating the closest focus adjustment state in each block is selected as the adoption area.

  In steps S110 and S120, the control device 6 executes the same processes as in steps S50 and S60, respectively. That is, in step S110, block grouping is performed based on the defocus amount obtained for the second-stage adoption area selected in step S100. In step S120, one of the plurality of groups divided in step S110 is selected as the optimum group.

  In step S130, the control device 6 determines at least one of the blocks belonging to the optimum group selected in step S120 as an AF selection block. If step S130 is performed, it will progress to step S140 of FIG.

  In step S140 of FIG. 10, the control device 6 executes a person discrimination process. At this time, the control device 6 determines whether or not each of the focus detection areas a1 to a51 is a person area, that is, a focus detection area where a person exists, based on the color information output from the photometry device 8.

  In step S150, the control device 6 calculates the reliability of the person determination process in step S140 based on the color information output from the photometry device 8. This reliability represents the accuracy with respect to the result of the person discrimination process for each focus detection area performed in step S140, and depends on the degree of coincidence with a preset person template, the brightness of the image by the photographing lens 1, and the like. Is required.

  When the brightness of the image by the taking lens 1 is lower than a predetermined value, it is preferable to set the reliability of person discrimination to a small value such as 0 in step S150. The luminance value used for the determination at this time is set according to the situation when it is determined that the camera automatically uses the flash, for example. In this way, since it is possible to avoid the execution of step S220 described later, it is possible to prohibit the person block from being selected as the adopted block. Thereby, it is possible to prevent the focus adjustment of the photographing lens 1 from being performed according to the defocus amount of the focus detection area located in the person block that is erroneously determined in the dark photographing environment where it is difficult to determine the person.

  In step S160, the control device 6 calculates the density of the person area determined to have a person in step S140 for each block. At this time, the control device 6 obtains the density of the person area of each block as described in FIG. In step S170, the control device 6 determines any block as a person block based on the density of the person area obtained in step S160. That is, the block having the highest density in the person area is determined as the person block.

  In step S170, the control device 6 may determine the person block based on the defocus amount detected for the person area in step S90 instead of the density of the person area. That is, as described above, the control device 6 can determine the block including the focus detection area in which the smallest defocus amount is detected among the focus detection areas determined to be the person area as the person block. . In this case, the control device 6 does not have to calculate the density of the person area without executing step S160.

  In step S180, the control device 6 compares the person determination reliability calculated in step S150 with a predetermined threshold A. This threshold A is set in advance to a value such as 200, for example, in accordance with a state in which the person discrimination result is sufficiently reliable. As a result of comparing the reliability of the person discrimination with the threshold A, if the reliability of the person discrimination is larger than the threshold A, the process proceeds to step S220. Otherwise, that is, the reliability of the person discrimination is the threshold A. If it is below, the process proceeds to step S190.

  In step S190, the control device 6 compares the person determination reliability calculated in step S150 with a predetermined threshold value B. The threshold value B is set to a value such as 50 in advance according to a state where the result of person discrimination is not very reliable. As a result of comparing the reliability of the person discrimination with the threshold value B, if the reliability of the person discrimination is smaller than the threshold value B, the process proceeds to step S230, otherwise, the reliability of the person discrimination is the threshold value B. If so, the process proceeds to step S200.

  If negative determinations are made in steps S180 and S190, that is, if the reliability of the person determination calculated in step S150 is within the range from the threshold value B to the threshold value A, the process proceeds to step S200. In step S200, the control device 6 determines an AF selection confidence value for determining which one of the person block and the AF selection block is selected as the adopted block. This AF selection confidence value is determined as follows, for example, according to the posture of the camera and the position of the AF selection block determined in step S130 of FIG.

  An example of a list of AF selection confidence values determined in step S200 is shown in FIG. In step S200, the AF selection confidence value is determined based on the value of the portion corresponding to the current camera posture and the position of the AF selection block among the values shown in the list. For example, assuming that the posture of the camera is a normal lateral posture and the right block b9 is an AF selection block, the AF selection confidence value at this time is determined to be 175 from the list of FIG. In the example of FIG. 11, each value of the list is set so that the AF selection block having a high possibility of the main subject having a higher AF selection reliability value.

  Since the AF selection confidence value determination method using the list of FIG. 11 described above is an example, the present invention is not limited to this. In step S200, the control device 6 can determine an arbitrary value corresponding to the posture of the camera and the position of the AF selection block as the AF selection confidence value.

  In step S210, the control device 6 compares the person determination reliability calculated in step S150 with the AF selection reliability determined in step S200. As a result, if the person determination reliability is higher than the AF selection reliability, the process proceeds to step S220; otherwise, that is, if the person determination reliability is equal to or less than the AF selection reliability, the process proceeds to step S230.

  By performing the processing of steps S180 to S210 described above, the control device 6 proceeds to either step S220 or step S230. When the process proceeds to step S220, the control device 6 selects the person block determined in step S170 as the adopted block in step S220. Thereby, the focus detection area selected as the adopted area in the person block is selected as the target area when performing the second-stage focus adjustment. On the other hand, when the process proceeds to step S230, the control device 6 selects the AF selection block determined in step S130 as the adopted block in step S230. As a result, the focus detection area selected as the adopted area in the AF selection block is selected as the target area when performing the second-stage focus adjustment. If step S220 or S230 is performed, the control apparatus 6 will progress to step S240.

  In step S240, the control device 6 performs second-stage focus adjustment on the photographic lens 1 based on the defocus amount of the adopted area in the adopted block selected in step S220 or S230. If step S240 is performed, the control apparatus 6 will complete | finish the flowchart of FIG. 9 and FIG.

According to the embodiment described above, the following operational effects can be achieved.
(1) In the camera of this embodiment, the focus detection device 4 detects the defocus amount of the photographing lens 1 with respect to a plurality of focus detection areas a1 to a51 set in the image plane by the photographing lens 1. The photometric device 8 detects color information corresponding to a person in the image taken by the photographing lens 1. The control device 6 uses at least one of the focus detection areas a1 to a51 based on the color information detected by the photometry device 8 and the defocus amount detected by the focus detection device 4 with respect to the focus detection areas a1 to a51. Is selected as a target area when the focus of the photographing lens 1 is adjusted in step S250 (steps S220 and S230). Since it did in this way, the focus adjustment state for performing the focus adjustment of the taking lens 1 correctly can be detected in consideration of whether or not the main subject is a person.
(2) The control device 6 classifies the plurality of focus detection areas a1 to a51 into a plurality of blocks b1 to b11, performs a person determination process for each of the focus detection areas a1 to a51, and a focus detection area where a person exists. Is determined based on the color information (step S140). Then, for each of the blocks b1 to b11, the density of the focus detection area where the person exists is obtained (step S160), and at least one of the blocks b1 to b11 is determined as a person block based on the obtained density (step S170). . This person block is selected as the adopted block in step S220, and the focus detection area located in the selected adopted block is selected as the focus adjustment target area. Since it did in this way, when the main subject is a person, the focus adjustment of the photographic lens 1 can be appropriately performed according to the person.
(3) Alternatively, the control device 6 selects at least one of the blocks b1 to b11 in step S170 based on the defocus amount detected for the focus detection area determined to have a person in step S140. It can also be determined. In step S220, the person block is selected as an adopted block, and a focus detection area located in the selected adopted block is selected as a focus adjustment target area. Even in this case, when the main subject is a person, the focus adjustment of the taking lens 1 can be appropriately performed according to the person.
(4) The control device 6 obtains the reliability of the person discrimination performed in step S140 for the plurality of focus detection areas a1 to a51 based on the color information (step S150). It is determined whether or not the reliability is greater than a predetermined threshold A (step S180). If it is greater, the person block to which the focus detection area determined to have a person based on the color information in step S140 belongs. In step S220, the selected block is selected. Thus, when the person is accurately identified and there is a high possibility that the main subject exists in the person block, the photographing lens 1 is set with the focus detection area in the person block as a focus adjustment target area. Can be adjusted appropriately.
(5) Further, the control device 6 determines whether or not the reliability of the person determination obtained in step S150 is smaller than a predetermined threshold B (step S190), and if so, the AF selection block is determined to be in step S230. To select as an adopted block. This prohibits selection of a person block to which the focus detection area determined to have a person in step S140 belongs. As a result, if the person identification is not performed accurately and there is a low possibility that the main subject exists in the person block, the focus adjustment target area is determined by avoiding the focus detection area in the person block. In addition, the focus of the photographic lens 1 can be adjusted appropriately.
(6) Further, when the reliability of the person determination obtained in step S150 is within the range from the threshold A to the threshold B, the control device 6 compares the reliability with the AF selection reliability value. (Step S210), it is determined which of Step S220 and Step S230 to execute according to the comparison result. Thereby, based on the reliability of person discrimination, the person block to which the focus detection area determined that the person exists in step S140 belongs, and the focus detection area determined based on the defocus amount in step S130. It was decided to determine which AF selection block to which it belongs. Since it did in this way, the focus adjustment target area can be determined in consideration of the accuracy of person discrimination, and the focus adjustment of the photographing lens 1 can be appropriately performed.
(7) When the control device 6 determines in step S30 that the detected defocus amount is equal to or greater than the predetermined value and indicates a focus adjustment state in which the first stage of focus adjustment is to be performed, the processing of steps S40 to S80 is performed. By executing the first-stage focus adjustment, the person block is prohibited from being selected as the adoption area. That is, it is determined in step S30 that the defocus amount detected in step S20 with respect to a predetermined focus detection area belonging to each of the plurality of blocks b1 to b11 indicates a state in which the photographing lens 1 is largely out of focus. In this case, step S220 is not executed, and it is prohibited to select a person block as an employment area. As described above, the focus adjustment target area is determined without considering the result of the person discrimination before capturing the subject, which is likely to be mistaken for the person discrimination because the photographing lens 1 is greatly out of focus, and the photographing lens 1 is determined. Can be adjusted appropriately.
(8) The control device 6 groups the plurality of blocks b1 to b11 into a plurality of groups based on the defocus amount (steps S50 and S110), and selects one of the plurality of groups as the optimum group. (Steps S60 and S120), an adopted block or an AF selection block is determined (Steps S70 and S130). As a result, the focus detection area located in the adopted block or AF selection block belonging to the optimum group is selected as the focus detection area based on the defocus amount, and the focus detection area is selected as the focus adjustment target area. . Since this is done, when the main subject is other than a person, the position of the main subject can be appropriately determined based on the defocus amount, and the focus of the photographic lens 1 can be adjusted according to the main subject.
(9) When the brightness of the image by the photographing lens 1 is lower than a predetermined value, the reliability of person discrimination is set to a small value such as 0 in step S150, so that step S220 is executed and the person block is set as the adopted block. It can be prohibited to be selected. In this way, it is possible to prevent the focus adjustment of the photographing lens 1 from being performed according to the defocus amount of the focus detection area located in the person block that is erroneously determined in the dark photographing environment in which person identification is difficult. Can do.

It is a figure which shows the structure of one embodiment. FIG. 6 is a layout diagram of focus detection areas set in an image plane. It is a figure which shows a focus detection optical system. It is a figure which shows the example which classified the arrangement position of the focus detection area into the some block. It is a figure which shows a mode that a person block is determined. It is a figure which shows a mode that the focus detection area located in the center in each block was selected as an adoption area. It is a figure explaining the reliability of a focus detection result. It is a figure explaining the reliability of a focus detection result. It is a flowchart which shows the focus adjustment operation | movement of one Embodiment. It is a flowchart which shows the focus adjustment operation | movement of one Embodiment. It is an example of a list of AF selection confidence values.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens 4 Focus detection apparatus 6 Control apparatus 7 Lens drive apparatus 8 Photometry apparatus

Claims (6)

Focus detection means for detecting a focus adjustment state of the imaging optical system with respect to a plurality of focus detection areas set in an image plane by the imaging optical system;
Classification means for classifying the plurality of focus detection areas into a plurality of areas;
Based on the focus detection result by the focus detection means for each of the plurality of focus detection areas, to determine the adopted focus detection area for each of the plurality of areas, based on the focus detection result for the adopted focus detection area, Area selection means for grouping the plurality of areas into a plurality of groups and selecting a predetermined area from the areas belonging to a group selected from the plurality of groups;
A person detecting means for detecting a human image out of the images formed by the imaging optical system;
For each of the plurality of focus detection areas, a determination unit that determines whether the person image is a focus detection area where a human image exists;
For each of the plurality of areas, calculating means for obtaining a density of a focus detection area of the human image presence;
A person area selecting means for selecting at least one area from the plurality of areas as a person area based on the density;
One of the predetermined area and the person area is selected as an adoption area, and a focus detection area in the employment area is selected as a focus detection area for performing focus adjustment of the imaging optical system. and means, the Bei example,
The density of the focus detection areas where the human image is present is a ratio of the number of focus detection areas where the human image exists within the calculation target area to the number of all focus detection areas within the calculation target area. A focus detection device. The focus detection apparatus according to claim 1,
The focus detection device, wherein the focus detection unit detects a defocus amount representing a focus adjustment state of the imaging optical system in the plurality of focus detection areas. The focus detection apparatus according to claim 1 or 2,
A reliability calculation means for calculating a person detection reliability when the person detection means detects the person image;
The employment area selection means selects the person area as the employment area when the person detection reliability is equal to or higher than a first predetermined threshold, and the person detection reliability is less than the first predetermined threshold. In some cases, the focus detection apparatus selects the predetermined area as the adopted area. Focus detection means for detecting a focus adjustment state of the imaging optical system with respect to a plurality of focus detection areas set in an image plane by the imaging optical system;
Classification means for classifying the plurality of focus detection areas into a plurality of areas;
Based on the focus detection result by the focus detection means for each of the plurality of focus detection areas, to determine the adopted focus detection area for each of the plurality of areas, based on the focus detection result for the adopted focus detection area, Area selection means for grouping the plurality of areas into a plurality of groups and selecting a predetermined area from the areas belonging to a group selected from the plurality of groups;
A person detecting means for detecting a human image out of the images formed by the imaging optical system;
For each of the plurality of focus detection areas, a determination unit that determines whether the person image is a focus detection area where a human image exists;
For each of the plurality of areas, calculating means for obtaining a density of a focus detection area of the human image presence;
A person area selecting means for selecting at least one area from the plurality of areas as a person area based on the density;
One of the predetermined area and the person area is selected as an adoption area, and a focus detection area in the employment area is selected as a focus detection area for performing focus adjustment of the imaging optical system. Means,
A focus detection apparatus comprising: a reliability calculation unit that calculates a person detection reliability when the person detection unit detects the person image;
The employment area selection means selects the person area as the employment area when the person detection reliability is equal to or higher than a first predetermined threshold,
The focus detection device includes:
The person detection reliability is greater than or equal to a second predetermined threshold that is less than the first predetermined threshold and less than the first predetermined threshold, or less than the second predetermined threshold. First determination means for determining whether or not
An area selection confidence value when the predetermined area is selected by the area selection means, and the person detection reliability determined by the relationship between the shooting posture of the camera incorporating the focus detection device and the plurality of areas And a second determination means for comparing
The adoption zone selection unit, when the person detection reliability by the first determination unit is determined to be less than the second predetermined threshold, selecting the predetermined area as the adoption zone, wherein When it is determined by the first determination means that the person detection reliability is less than the first predetermined threshold and is greater than or equal to the second predetermined threshold, the person is determined by the second determination means. If it is determined that the detection reliability is greater than the area selection confidence value, the person area is selected as the adopted area, while the person determination reliability is greater than the area selection reliability value by the second determination means. If it is determined that the predetermined area is smaller, the predetermined area is selected as the adopted area. In the focus detection apparatus according to any one of claims 1 to 4,
The focus detection apparatus according to claim 1, wherein when the brightness of the image by the imaging optical system is lower than a predetermined value, selection of the person area by the person area selection means is prohibited. The focus detection apparatus according to any one of claims 1 to 5,
A camera comprising: adjusting means for adjusting the focus of the imaging optical system based on the focus detection result regarding the focus detection area in the adopted area selected by the adopted area selecting means.

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