JPH04235512A - Focus detecting device having grouping function - Google Patents

Abstract

PURPOSE:To provide a focus detecting device having a grouping function by which the result of steady focus detection can be obtained. CONSTITUTION:A focus detecting device is provided with a photographing optical system 1 for forming a subject image on a predetermined plane, a focus detecting means 2 to detect the defocus quantity of the image face of the photographing optical system 1 to the fixed face in each of plural focus detecting domains set within a photographing image plane, a weight setting means 3 to set reference defocus quantity and then a weighting coefficient in each of the focus detecting domains on a difference between the defocus quantity in the plural focus detecting domains and the reference defocus quantity, a grouping means 4 to arrange the plural focus detecting domains into plural groups on the weighting coefficient for calculating the defocus quantity of each group, and an optimal defocus quantity selecting means 5 to select the optimal defocus quantity on which the subject image to be focused is expected to have been formed among plural groups of the defocus quantities.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device for a camera or the like.

0002

[Prior Art] A camera classifies a plurality of focus detection areas into a plurality of groups based on the amount of defocus for each of a plurality of focus detection areas set within a photographic screen, and forms a subject image to be focused on from among these groups. A focus detection device is known that has a grouping function that selects an expected group and calculates an optimal defocus amount based on the defocus amount of focus detection areas belonging to this group (Japanese Patent Laid-Open No. 2-178).
(See Publication No. 641).

In this type of focus detection device, when a plurality of focus detection areas are grouped, a zone of a predetermined width is set on the defocus axis, and a zone of a predetermined width centered at the defocus amount of a certain focus detection area is set. If the defocus amount of another focus detection area is included in the zone, that area is determined to be in the same group. In other words, if the absolute value of the difference between the reference defocus amount and the defocus amount of a certain area is less than or equal to a predetermined value, that area is considered to belong to that group, and if it is larger than the predetermined value, that area is considered to belong to the same group. shall not belong. Next, from among the multiple groups created by the grouping process, one group that is likely to capture the subject intended by the photographer is selected, and the focus that belongs to the selected optimal group is An overall optimal defocus amount DEFX is calculated based on the defocus amount of the detection area.

0004

[Problems to be Solved by the Invention] However, in the conventional focus detection device described above, the absolute value of the difference between the reference defocus amount and the defocus amount in a certain area is close to a predetermined value, and the If the value becomes less than or exceeds a predetermined value, the area may or may not belong to the same group. As a result, the calculation result of the optimum defocus amount differs greatly depending on whether the object belongs to the same group or not, and there is a problem that the focus detection result becomes unstable. An object of the present invention is to provide a focus detection device having a grouping function that allows stable focus detection results to be obtained.

[0005]

[Means for Solving the Problems] The present invention will be explained with reference to FIG. 1, which is a diagram corresponding to the claims. The focus detection means 2 detects the amount of defocus of the image plane of the photographing optical system 1 with respect to a predetermined plane for each of the plurality of focus detection areas set in . weight setting means 3 for setting a weighting coefficient for each focus detection area based on the difference between the defocus amount and the reference defocus amount; Grouping means 4 for calculating group defocus amount
and an optimum defocus amount selection means 5 for selecting an optimum defocus amount at which a subject image to be focused is expected to be formed from among the defocus amounts of a plurality of groups, the above object can be achieved. achieved.

[0006]

[Operation] The weight setting means 3 sets a reference defocus amount, and each focus is detected based on the difference between the defocus amount of the plurality of focus detection areas detected by the focus detection means 2 and the reference defocus amount. A weighting coefficient is set for each area, and the grouping means 4 groups the plurality of focus detection areas into a plurality of groups based on these weighting coefficients, and calculates the amount of defocus for each group. Then, the optimum defocus amount selection means 5 selects the optimum defocus amount that is expected to form a subject image to be focused from among the defocus amounts of the plurality of groups.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an outline of a focus detection device having a grouping function according to an embodiment will be explained. The photographing optical system 1 is
A light beam from a subject is focused on a predetermined plane to form a subject image. Furthermore, some of the light flux is transmitted to a known focus detection optical system, an image sensor, a microcomputer (hereinafter referred to as CPU).
) is guided to the focus detection means 2 consisting of
As shown in FIG. 2, the focus detection means 2 detects a plurality of focus detection areas AREA(i) (i=1 to
Based on the subject image data from the image sensor corresponding to f (f=8 in FIG. 2)), a known focus detection calculation is performed to determine the defocus amount DEF(i) for each focus detection area.
Calculate.

[0008] The weight setting means 3 sets a reference defocus amount according to a grouping method to be described later, and calculates the reference defocus amount based on the difference between the defocus amount DEF(i) of each focus detection area and this reference defocus amount. A weighting coefficient H(i) is set for each focus detection area. The grouping means 4 groups a plurality of focus detection areas into a plurality of groups based on the weighting coefficient H(i), and calculates a defocus amount GDEF(j) (j=1 to e) for each group. and,
The optimum defocus amount selection means 5 selects defocus amounts GDEF(
From j), select the optimum defocus amount DEFX that is expected to form a subject image to be focused.

The configuration of an embodiment in which the focus detection device according to the present invention is applied to a single-lens reflex camera with interchangeable lenses will be explained with reference to FIG. An interchangeable lens barrel 10 is mounted on the camera body 20, and with this lens barrel 10 attached, the photographing light flux coming from the subject is transmitted to the photographing lens 10.
1 and is guided to the main mirror 21 inside the camera body 20, a part of the light flux is reflected by this main mirror 21 and guided to a finder (not shown), and another part of the light flux passes through the main mirror 21. The light is then reflected by the sub-mirror 22 and guided to the AF module 23 as a focus detection light beam.

As shown in FIG. 4, the AF module 23 includes a focus detection optical system 24 consisting of a field mass 70, a field lens 27, and two pairs of reimaging lenses 28A, 28B, 38A, and 38B, and two pairs of light receiving sections. 29A, 29B, 39
It is composed of an image sensor 25 such as a CCD consisting of A and 39B. two pairs of regions 18A, 18B symmetrical with respect to the optical axis 17 included in the exit pupil 16 of the photographic lens 11;
The light beams passing through 19A and 19B respectively pass through a field mass 70 having an aperture shape corresponding to the entire focus detection area shown in FIG.
A primary image of the subject is formed. Further, some of the light beams are transferred to the two pairs of light receiving sections 29A, 29B, 39A, 3 of the image sensor 25 by the field lens 27 and the two pairs of reimaging lenses 28A, 28B, 38A, 38B.
9B, and two pairs of secondary images are formed. and,
By detecting the relative positional relationship of these secondary images, the amount of defocus for each of the plurality of focus detection areas set on the photographing screen 9 is detected.

FIG. 5 shows the arrangement of light receiving elements on the image sensor 25. The light receiving sections 29A and 29B each consist of n light receiving elements Ap and Bp (p=1 to n), and when the photographic lens 11 is in the focused state, each of the corresponding pairs of light receiving elements (A1 and B1, A2 and B2,...) are arranged so that their outputs are equal. Furthermore, the light receiving sections 39A and 39B each have m light receiving elements Cq and Dq (m<n) (q=1
-m), when the photographic lens 11 is in focus,
Each pair of corresponding light receiving elements (C1 and D1, C2 and D2...
) are arranged so that their outputs are equal. Light receiving section 2
The light receiving elements forming 9A, 29B, 39A, 39B are:
It is composed of a charge storage type element such as a photodiode, and stores charge for a time corresponding to the illuminance on the image sensor 25, and controls the light receiving element output signal to an output level suitable for focus detection calculation described later.

Next, the sensor control section 26 shown in FIG.
Port P of FCPU (autofocus CPU) 30
The charge accumulation time of the image sensor 25 is controlled by receiving charge accumulation start and end commands from the image sensor 25 and providing control signals corresponding to the instructions to the image sensor 25. Further, a transfer clock signal or the like is given to the image sensor 25, and the light receiving element output signal is transferred to the AFCPU 30 in time series, and a synchronization signal synchronized with the start of transfer of the light receiving element output signal is sent to the port P4 of the AFCPU 30. AF
In synchronization with this signal, the CPU 30 starts A/D conversion of the light-receiving element output signal input to the port P3 using the built-in A/D converter, and obtains A/D conversion data corresponding to the number of light-receiving elements. When the A/D conversion is completed, the obtained data is subjected to data processing, which will be described later, to determine the defocus amount. That is, the respective operations of the focus detection means 2, the weight setting means 3, the grouping means 4, and the optimum defocus amount selection means 5 shown in FIG.

[0013] The AFCPU 30 connects AFC via port P5.
A display section 41 that controls the F display device 40 and indicates a front focus state according to the selected optimal defocus amount, a display section 42 that indicates a focus state, a display section 43 that indicates a rear focus state, and a focus detection impossible state. Lights up one of the display sections 44 indicating . In addition, the AFCPU 30 outputs the optimal default via port P2.
A drive signal corresponding to the sign of the amount of debris is output to control the AF motor 50. Thereby, the AF motor 50 drives the photographing lens 11 to the in-focus point via the body transmission system 51 and the lens transmission system 12. The driving amount of the AF motor 50 is transmitted to an encoder 52 such as a photointerrupter via a body transmission system 51, converted into a pulse signal by the encoder 52, and transmitted to the AFCP via port P1.
Feedback is given to U30. The AFCPU 30 controls the AF motor 50 based on this feedback pulse signal.
The amount of drive, that is, the position of the photographing lens 11 is controlled. Note that information regarding the photographic lens 11 and the like is transmitted from the lens CPU 13 provided in the lens barrel 10 to the AFCPU 30 via port P6.

The focus detection mode selection device 80 transmits information on the automatically or manually selected focus detection mode (center weighted, close-up priority, reliability priority, focus priority, etc.) to the port P.
7 to the AFCPU 30, and the AFCPU 30 performs focus detection processing based on this information.

Next, details of focus detection processing, weighting processing, grouping processing, and optimum defocus amount selection processing for a plurality of regions performed within the AFCPU 30 will be explained. <Focus Detection Process> First, the focus detection process will be described using FIGS. 6 and 7. Light receiving element Ap converted from A/D by AFCPU30
, Bp (p=1~n) and Cq, Dq (q=1~m)
The output data of ap, bp (p=1 to n) and cq
, dq (q=1 to m). Note that the output data ap,
Since similar processing is performed on bp and output data cp, dp, only the output data ap, bp will be explained. First, for the light receiving element output data ap, bp, (1)
The correlation calculation shown in the equation is performed to obtain the correlation amount C(i,L) for each focus detection area. C(i,L)=Σ|a(r+L)−b(r)|
...(1) Here,
L is an integer and is a relative shift amount (shift amount) of the pair of light receiving element output data in units of the pitch of the light receiving elements;
represents the summation for all focus detection areas i. Further, the range of the parameter r is determined as appropriate depending on the shift amount L and the focus detection area i.

The range of the parameter r in the above equation (1) is determined on the matrix of the light receiving element output data ap, bp shown in FIG. Shift amount L from -2 to +2
When the range is set to , the area surrounded by the thick line indicates the combination of light-receiving element output data to be subjected to the correlation calculation. For example, when the shift amount L is 0, the range of the parameter r in equation (1) is as shown in the following equation for each focus detection area i. When i=1: r=1~w When i=2: r=w+1~x When i=3: r=x+1~y When i=4: r=y
+1~z When i=5 r=z+1~n

...(2)

In each focus detection area, the shift amount xm(i) with the highest correlation of the light receiving element output data
is obtained by applying the three-point interpolation method disclosed in Japanese Unexamined Patent Publication No. 60-37513 by the present applicant to the calculation result of equation (1). xm(i)=x+D(i)/SLOP(i)
...(3) D and SLOP in equation (3) are the discretely calculated correlation amount C
Assuming that the minimum value of (i, L) is obtained at the shift amount L=x, it is determined by the following equation. D(i)=(C(i,x-1)-C(i,x+1)
)/2...(4) SLOP(i)=MA
X(C(i,x+1)−C(i,x),
C(i, x-
1)-C(i,x))...(5)

[0018] Also,
The defocus amount DEF(i) for each focus detection area is
It is determined by the following formula based on the shift amount xm(i) determined by formula (3). DEF(i)=KX(i)×PY(i)×xm(i
)+CZ(i)

...(6) In equation (6), PY(i) is the pitch in the arrangement direction of the light receiving elements for each focus detection area, and the value for each area is
Stored as 0. KX(i) is a coefficient determined for each focus detection area by the configuration of the focus detection optical system 24 shown in FIG. 4, and the value for each area is stored in the AFCPU 30. CZ(i) is an offset value for each area, and is a correction value determined by the amount of aberration of the photographing optical system 1 (stored in the lens CPU 13) and the position adjustment state of the AF module 23 with respect to the body 20 (for each body). E not shown
(stored in EPROM).

[0019] Also, the parameter SLO obtained by equation (5)
P(i) is an amount roughly proportional to the contrast of the subject image, and the larger the value, the deeper the depression near the minimum value of the correlation amount C(i, L), and the larger the correlation. Therefore, the reliability of the obtained defocus amount DEF(i) is high. Note that the minimum value xm(i) is not found and the defocus amount DE
When F(i) is not determined or when the defocus amount DE
Although F(i) has been found, if SLOP(i) is small and unreliable, it is determined that focus cannot be detected and the defocus amount DE is
Let F(i)=∞.

FIG. 7 is a flowchart showing the above-mentioned focus detection process. First, in step S1, the focus detection area is initialized with i=1, and in the subsequent step S2, a correlation calculation is performed in the focus detection area AREA(i), and the correlation amount C(i,
Find L). In step S3, x
Find m(i) and SLOP(i), and in step S4, x
It is determined whether m(i) has been determined. If m(i) has been determined, the process proceeds to step S5; if not, the process proceeds to step S7. When requested, in step S5, SLOP
It is determined whether (i) exceeds a predetermined value TS, that is, whether it is reliable. If it exceeds the predetermined value TS, the process proceeds to step S6; otherwise, step S
Proceed to step 7. In step S6, the defocus amount DEF(i
) and proceeds to step S8. On the other hand, in step S7, it is determined that focus detection is impossible, DEF(i)=∞, and the process proceeds to step S8. In step S8, the focus detection area number i is incremented, and in the subsequent step S9, i=9,
That is, it is determined whether the focus detection process has been performed on all focus detection areas, and when the process is completed, step S10 is performed.
The process proceeds to step S2 to perform the grouping process, and if it has not been completed, the process returns to step S2.

In the above explanation, the cross-shaped focus detection area shown in FIG. 2 is divided into eight parts, and the defocus amount of each area is detected. However, the shape of the detection area and the number of divisions are limited to the above embodiment. Not done. Furthermore, the detection areas may overlap each other, or the area boundaries may be changed depending on the intensity distribution of the subject image.

<Weighting Process and Grouping Process> Next, the weighting process and grouping process will be explained. First, a reference defocus amount is set, and the absolute value of the difference between this reference defocus amount and the defocus amount of a certain area is determined. Furthermore, depending on the absolute value of this difference, 0 to
A weighting coefficient of 1 is set and a parameter S indicating reliability is set.
Weighted averaging is performed using LOP(i) and weighting coefficients. For example, the defocus amount DEF(1), DEF(2),...,DEF of the eight focus detection areas shown in FIG.
(8), the group defocus amount GDEF and the parameter GSLOP indicating the reliability of the group are determined by the following equation. GDEF={DEF(1)*SLOP(1)*H(
1) +DEF(2)*SLO
P(2)*H(2)+...
+DEF(8)*SLOP(8)*H(8)}
/{SLOP(1)*H(1)+SL
OP(2)*H(2)+...
+SLOP(8)*H(8)}
...(7) GSLOP=SLOP
(1)*H(1)+SLOP(2)*H(2)+...
+SLOP(8)*H(8)
...(8
) Here, H(i) is a weighting coefficient.

Here, according to FIG. 8, the weighting coefficient H(i)
Explain how to set up. For example, as shown in the figure, when the absolute value of the difference between the reference defocus amount and the defocus amount of a certain area is 70 μm or less, the weighting coefficient is set to 1, and when it is 140 μm or more, the weighting coefficient is set to 0. Further, when the distance is 70 μm to 140 μm, the weighting coefficient is changed linearly from 1 to 0. In other words, if the absolute value of the difference is dD, the weighting coefficient H(k) for the area k is dD≦7
0...H(k)=1 7
0<dD<140...H(k)=1-(dD
-70)/70 140≦dD ・・
・H(k)=0
...(9). In this way, even if the absolute value of the difference varies around 140 μm, the weighting coefficient H
Since (i) is small, the group defocus amount GDEF
and the parameter GSLOP are small, and their values GDEF and GSLOP are stable.

[0024] In the above-mentioned conventional focus detection device,
As shown in FIG. 9, when the absolute value of the difference is less than 100 μm, the weighting coefficient H(i) is set to 1, and when it is larger than that, it is the same as setting it to 0. Therefore, if the absolute value of the difference varies around 100 μm for each focus detection, the weighting coefficient H(i) becomes 1 or 0, which has a large effect on the calculated defocus amount GDEF and the value of the parameter GSLOP. In other words, in the conventional method, there were only two states: "belongs to a group" and "does not belong", whereas in the present invention, "belongs to a group a little", "belongs half to a group", " There is an intermediate state in which the individual is quite part of the group.

Note that as another method of setting the weighting coefficient H(i), a triangle as shown in FIG. 10 may be used, or a triangle as shown in FIG.
As shown in FIG. 1, the weighting coefficient H(i) may vary in a curved manner. Note that hereinafter, the process of calculating the absolute value of the difference from the reference defocus amount, setting the weighting coefficient H(i), and determining whether or not they are in the same group will be referred to as group determination.

Next, a first example of grouping processing will be explained. In this grouping process, the defocus amount DEF(i) of each focus detection area is sequentially set as a reference defocus amount, and based on this reference defocus amount, other focus detection areas are grouped and weighted for each area. Coefficient H(i)
Find the group defocus amount G using equation (7).
Calculate DEF(j). According to this grouping processing method, for example, for the eight focus detection areas shown in FIG.
Groups are formed by the number of focus detection areas determined to be focus detectable.

FIG. 12 is a flowchart showing an example of this first grouping process. First, in step S21, the group number j is reset to 1, and in the subsequent step S22, the defocus amount GDEF of the j-th group is
Let (j) be infinite. In step S23, it is determined whether the defocus amount DEF(j) of the focus detection area j is infinite, that is, whether the focus cannot be detected. If the focus cannot be detected, a group is formed using the focus detection area j as a reference. Since this is not possible, the process advances to step S32; otherwise, the process advances to step S24. In step S24, the weighting coefficient H(j) of the focus detection area j is set to 1. Next, in step S25, the focus detection area number i is reset to 1,
In the following step S26, it is determined whether the focus detection area number i and the group number j are equal. If they are equal, there is no need for group determination and the process advances to step S30; otherwise, the process advances to step S27.

In step S27, it is determined whether the defocus amount DEF(i) of the focus detection area i is infinite, and if it is infinite, the focus detection area i cannot detect the focus and does not belong to any group. Therefore, the process proceeds to step S30, and if it is not infinite, the process proceeds to step S28. Step S
28, the defocus amount DD serving as the reference for group j
EF(j) and the defocus amount DEF(
Calculate the absolute value dD of the difference from i). Further step S
In step 29, the weighting coefficient H(i) is determined as described above based on the absolute value dD of the difference.

In step S30, it is determined whether or not the focus detection area number i is 8. If it is 8, it means that group determination has been completed in all focus detection areas, and the process proceeds to step S31. If not, group determination is completed. There is a focus detection area that has not been completed, so the process proceeds to step S34, where the focus detection area number i is incremented, and the process returns to step S26. In step S31, focus detection area 1 is determined by equation (7).
The defocus amount GDEF (
Calculate j). In step S32, the group number is 8.
In other words, it is determined whether calculation of the defocus amount GDEF(j) for all groups has been completed. If it has been completed, execution of the program is ended, and if not, the process advances to step S33. In step S33, the group number j is incremented and the process returns to step S22.

Next, a second example of grouping processing will be explained. In this grouping process, the same subjects such as people are spatially continuous and do not exist across focus detection areas with greatly different defocus amounts, so when determining groups, the condition that the areas are adjacent is met. , group determination is performed (however, in the example described later, group determination is performed even if there is an area in between where focus cannot be detected). In addition, in the first grouping process example, after determining the weighting coefficients H(i) of all focus detection areas,
Defocus amount DEF(i) of each area, parameter SL
Although the group defocus amount GDEF(j) was calculated at once based on OP(i) and the weighting coefficient H(i), in this second grouping processing example, group determination is performed in the order of focus detection area numbers, Based on the defocus amount GDEF(j) and parameter GSLOP(j) of the group, and the defocus amount DEF(i) and parameter SLOP(i) of the next adjacent area, defocus the new group using the following formula. Calculate the quantity GDEF(j) and the parameter GSLOP(j). GDEF(j)={DEF(i)*SLOP(i)
*HD+GDE
F(j)*SLOP(j)*HG}/
{SLOP(i)*HD+SLO
P(j)*HG}

...(10) GS
LOP(j)=SLOP(i)*HD+GSLOP(j
)*HG

...(11) Here, HD is
Defocus amount DEF(i
), and HG is a weighting coefficient for the group defocus amount GDEF(j). For these weighting coefficients HD and HG, the larger weighting coefficient of the group parameter GSLOP(j) and the focus detection area parameter SLOP(i) is set to 1,
The smaller weighting coefficient is determined according to FIG. 8 described above.

FIGS. 13 and 14 are flowcharts showing a second example of grouping processing. In step S41, group number j, focus detection area number i, and flag flag are initialized. The flag flag indicates the focus detection state of the focus detection area shown in FIG. 2. When it is 1, it indicates that there is no focus detectable area, and when it is 0, it indicates that a focus detectable area exists and a group is being formed. . In step S42, it is determined whether the defocus amount DEF(i) of the focus detection area i is infinite, and if it is infinite, it means that the focus cannot be detected, so step S49 in FIG.
Otherwise, the process advances to step S43. In step S43, it is determined whether the flag flag is 1 or not. If it is 1, it indicates that there is no focus detectable area in an area with a smaller number than the current focus detection area number i, and the defocus amount DEF(i) of the current focus detection area i is used as the reference. The process proceeds to step S52 to start group formation. If it is 0, there is an area where focus detection is possible in an area with a number smaller than the current focus detection area number i, and the group is currently being formed, so group determination is performed. In order to do so, the process advances to step S44.

First, step S for starting group formation.
The process will be explained starting from step 52. In step S52, since there is a focus detectable area, the flag flag is reset, and then the process proceeds to step S53, where the defocus amount GDEF(j) of group j and the parameter GSLOP are determined.
(j) is the defocus amount DE of the current focus detection area i.
In addition to setting F(i) and parameter SLOP(i), the defocus amount D of the current focus detection area i is set as the standard defocus amount SDEF when performing group determination.
EF(i) is set and the process advances to step S49 in FIG.

In step S44, the reference defocus amount SDEF and the defocus amount DEF(i
), and in the subsequent step S45,
Based on the absolute value dD of this difference, a weighting coefficient HD for focus detection area i and a weighting coefficient HG for group j are set. In step S46, the weighting coefficient HD or HG
Determine whether or not is 0. If either is 0, it indicates that the focus detection area i does not belong to group j, and the process advances to step S47; otherwise, the process advances to step S50. In step S47, the group number j is incremented to end the current group formation and start a new group formation. Next, in step S48, the current defocus amount DEF(i) and parameter SLOP of the focus detection area i are added to the defocus amount GDEF(j) and parameter GSLOP(j) of group j.
(i) and also set the current focus detection area i to the standard defocus amount SDEF for group determination.
The defocus amount DEF(i) is set and the process proceeds to step S49 in FIG.

If both the weighting amounts HD and HG are not 0, in step S50, the above (10), (
By formula 11), the defocus amount GDEF(
j) and the defocus amount DEF(i) of focus detection area i
The defocus amount GDEF(j) and the parameter GSLOP(j) of the new group are calculated by adding and weighting the average. In step S51, the standard defocus amount SDEF
The defocus amount DEF(i) of the focus detection area i is set to , and the process proceeds to step S49 in FIG. Note that the group defocus amount GFEF is added to the standard defocus amount SDEF.
(j) may also be set.

In step S49 of FIG. 14, it is determined whether the focus detection area number i is 8, that is, whether group determination has been completed for all areas, and if it has been completed, the execution of the program is terminated; If the process has not ended, the process advances to step S54. In step S54, it is determined whether the focus detection area number i is 5, that is, whether group determination for the focus detection area in the horizontal direction shown in FIG. In order to perform grouping processing, the process advances to step S55, and if not, the process advances to step S58. Step S
In step S55, it is determined whether or not the flag flag is 1, that is, whether or not there is a focus detectable area in the horizontal focus detection area shown in FIG. If not, there is a focus detectable area in the horizontal direction and a group is currently being formed, so the process proceeds to step S56. Step S
After setting the flag in step S56, step S57
Go to and increment the group number j. In step S58, the focus detection area number i is incremented, and the process returns to step S42 in FIG.

Next, a third example of grouping processing will be explained. In this grouping process, group determination is performed in accordance with the focus detection mode selected by the focus detection mode selection device 80 shown in FIG. For example, if the closest priority mode is selected, groups are formed based on the defocus amount that indicates the closest distance, and if the focus priority mode is selected, the group is formed based on the one with the smallest absolute value of the defocus amount. form a group. According to this processing method, since only one group is formed, the optimum defocus amount can be calculated in a short time.

FIG. 15 is a flowchart showing the third grouping process. First, in step S61, it is determined whether the focus priority mode is selected, and if the focus priority mode is selected, the process proceeds to step S62,
Otherwise, step S assumes that the mode is close priority mode.
Proceed to 63. In step S62, the area number of the defocus amount having the smallest absolute value is set in the memory S, while in step S63, the area number of the defocus amount indicating the closest distance is set in the memory S. Subsequent step S64
Then, the weighting coefficient H(s) of the focus detection area S is set to 1, and the process proceeds to step S65, where the focus detection area number i is reset. In step S66, it is determined whether the focus detection area number i is equal to the area number S. If they are equal, there is no need for group determination, and the process proceeds to step S69; otherwise, the process proceeds to step S67. In step S67, the defocus amount DEF(i) of the focus detection area i and the closest defocus amount DEF(S) with the minimum absolute value are determined.
The absolute value dD of the difference is calculated, and in the following step S68,
The weighting coefficient H(i) is determined based on the absolute value of this difference. Next, in step S69, the focus detection area number i is 8.
If it is 8, group determination has been completed for all areas, so the process advances to step S70.
If it is not 8, there remains an area for which group determination has not been completed, and the process advances to step S71. In step S70, the defocus amount G of the group is calculated using the above-mentioned equation (7).
Calculate DEF(j). In step S71, the area number i is incremented and the process returns to step S66.

<Optimal Defocus Amount Selection Process> The focus detection mode selection device 80 shown below selects the defocus amount GDEF(j) for each group calculated by the above weighting process and grouping process. The optimum defocus amount DEFX is selected depending on the mode. (1) Closest Priority Mode The rearmost focus, that is, the defocus amount GDEF(j) indicating the closest distance is set as the optimum defocus amount DEFX. (2) Focus priority mode The defocus amount GDEF(j) with the smallest absolute value, that is, the defocus amount GDEF(j) closest to the in-focus state at that time, is set as the optimal defocus amount DEFX. (3) Reliability Priority Mode The defocus amount GDEF(j) of the group with the highest reliability, that is, the group with the largest parameter GSLOP(j) indicating the reliability of the group, is set as the optimal defocus amount DEFX. As mentioned above, the AFCPU 30
According to the selected defocus amount DEFX, the focus adjustment state of the photographic lens 11 is displayed on the AF display device 40, and the AF motor 50 is controlled to drive the photographic lens 11 to the in-focus position. As a result, the subject in the focus detection area belonging to the optimum group on the photographing screen 9 can be accurately focused.

In this way, a reference defocus amount is set for the defocus amount of a plurality of focus detection areas set within the photographic screen, and this reference defocus amount and the defocus amount of each focus detection area are set. A weighting coefficient of 0 to 1 is set for each area based on the absolute value of the difference between the two areas, and based on this weighting coefficient, it is determined whether the area belongs to the same group or not, and the defocus amount of the group is calculated. As a result, the calculation result of the defocus amount does not vary greatly depending on whether a certain area belongs to the same group as in the conventional case, and a stable focus detection result can be obtained.

In the above-mentioned embodiment, the case where the plurality of focus detection areas are set in a cross shape on the screen as shown in FIG. 2 was explained as an example, but the setting shape of the plurality of focus detection areas is The detection area is not limited to the embodiment, and the detection area may be set two-dimensionally, for example. Further, the present invention is not limited to a TTL type focus detection device, but can also be applied to an external light type focus detection device. In that case, object distances can be obtained instead of defocus amounts from a plurality of focus detection areas set on the screen, and the aforementioned grouping process and optimal defocus amount selection process can be performed on them.

In the configuration of the above embodiment, the photographing lens 11 constitutes a photographing optical system, the AF module 23 constitutes a focus detection means, and the AFCPU 30 constitutes a weight setting means, a grouping means, and an optimum defocus amount selection means.

[0042]

As explained above, the focus detection device having the grouping function of the present invention sets a reference defocus amount for a plurality of focus detection areas set within the photographic screen, and A weighting coefficient is set for each area based on the difference between the defocus amount and the defocus amount of each focus detection area, and based on this weighting coefficient, multiple focus detection areas are grouped into multiple groups. Defocus amounts are calculated, and from among these defocus amounts, the optimum defocus amount that is expected to form a subject image to be focused is selected. By grouping in this way, the absolute value of the difference between the reference defocus amount and the defocus amount of a certain focus detection area is close to a predetermined value, and it becomes less than the predetermined value or less than the predetermined value for each focus detection. Even if the area exceeds 1, it does not significantly affect the determination of whether the area belongs to the same group and the calculation result of the defocus amount of the group, and a stable focus detection result can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a complaint correspondence diagram.

FIG. 2 is a diagram showing a plurality of focus detection areas set within a photographic screen.

FIG. 3 is a block diagram showing the configuration of one embodiment.

FIG. 4 is a diagram showing the configuration of an AF module.

FIG. 5 is a diagram showing the arrangement of light receiving elements on an image sensor.

FIG. 6 is a diagram showing output data of each light-receiving element on the image sensor in correspondence with a matrix.

FIG. 7 is a flowchart showing focus detection processing.

FIG. 8 is a diagram showing weighting coefficients for absolute values of differences in defocus amounts.

FIG. 9 is a diagram showing conventional weighting coefficients for absolute values of differences in defocus amounts.

FIG. 10 is a diagram showing weighting coefficients for absolute values of differences in other defocus amounts.

FIG. 11 is a diagram showing weighting coefficients for absolute values of differences in other defocus amounts.

FIG. 12 is a flowchart showing an example of a first grouping process.

FIG. 13 is a flowchart illustrating a second example of grouping processing.

FIG. 14 is a flowchart illustrating a second example of grouping processing.

FIG. 15 is a flowchart showing a third example of grouping processing.

[Explanation of symbols]

1 Photographing optical system 2 Focus detection means 3 Weight setting means 4 Grouping means 5 Optimal defocus amount selection means 9 Photographing screen 10 Lens barrel 11 Photographing lens 12 Lens transmission system 13 Lens CPU 20 Camera body 23 AF module 24 Focus detection optics System 25 Image sensor 26 Sensor control section 29A, 29B, 39A, 39B Light receiving element 30
AFCPU 40 AF display unit 50 AF motor 51 Body transmission system 52 Encoder 80 Focus detection mode selection device

Claims (1)

[Claims] 1. A photographing optical system for forming a subject image on a predetermined plane, and a defocusing system for defocusing the image plane of the photographing optical system with respect to the predetermined plane for each of a plurality of focus detection areas set within the photographing screen. and a weighting coefficient for each focus detection area based on the difference between the defocus amount of the plurality of focus detection areas and the reference defocus amount. a grouping means for grouping the plurality of focus detection areas into a plurality of groups based on the weighting coefficient and calculating a defocus amount for each group; 1. A focus detection device having a grouping function, comprising an optimum defocus amount selection means for selecting an optimum defocus amount at which a subject image to be focused is expected to be formed.