JP2002072069A - Automatic multipoint focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic multipoint focus detector capable of selecting an optimum area complying with photographer's intention out of plural focus detection areas in a photographic image plane. SOLUTION: Defocus amount with a mark that a short-distance side is set as positive is obtained in plural focus detection areas in the photographic image plane respectively. After a specified value is added to the defocus amount with the mark in the focus detection area at a center part, the defocus amounts with the mark in the respective focus detection areas are compared and then any one focus detection area where the defocus amount with the mark is the largest is selected. The specified value used at such a time is decided in proportion to the f-number at open aperture of a photographing lens by a specified value deciding means. The specified value is set to the small one in the bright photographing lens and it is set to the large one in the dark photographing lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-point automatic focus detection device used for optical equipment such as a camera.

[0002]

2. Description of the Related Art In recent years, cameras provided with a multi-point automatic focus detection device having a plurality of focus detection areas in a photographing screen have been widely used. Such a multi-point automatic focus detection apparatus performs AF (auto focus) imaging by selecting an optimum focus detection area from a plurality of focus detection areas arranged in an H-shape on a shooting screen, for example, by a camera. An automatic selection mode is provided in which an automatic selection mode can be performed. In such an automatic selection mode, for example, the focus detection area having the largest defocus amount, that is, the subject is closest to the camera is selected based on the defocus amount obtained in each of the plurality of focus detection areas. For the focus detection area, a predetermined reference value is added to the defocus amount in advance, and selection is performed while giving priority to the center. Conventionally, a constant value has been used as such a reference value.

[0003]

In the above configuration, the difference ΔD0 obtained by subtracting the defocus amount of the focus detection area at the center from the defocus amount of the focus detection area to be originally selected is smaller than the reference value. In this case, that is, when the subject having the focus detection amount to be selected is slightly closer to the camera than the subject in the central focus detection area, the central area is selected. Under such circumstances, if a photograph is taken with a bright photographing lens, that is, a lens with a small open F-number, the desired subject is not focused on because the depth of focus is shallow, resulting in a rear focus. On the other hand, when there is not much difference in the subject distance between the focus detection areas in the left and right or up and down symmetric positions with respect to the focus detection area in the center, the focus detection area selected every time focus detection is performed is changed. Occurs.

The present invention has been made in view of such circumstances, that is, the present invention provides a multi-point automatic focus detection device capable of selecting an optimum subject in a photographing screen and focusing on the subject. It is another object of the present invention to provide a multi-point automatic focus detection device in which a focus detection area selected every time focus is detected does not change.

[0005]

According to the first aspect of the present invention, a defocus amount is obtained in each of a plurality of focus detection areas in a photographing screen, and the defocus amount is set to be positive on the short distance side. Converting to a signed defocus amount, selecting one of the focus detection areas based on the signed defocus amount, and controlling driving of the photographing lens based on the defocus amount of the selected focus detection area. A point automatic focus detection device, wherein a signed defocus amount obtained by a signed defocus amount is set to a first value in a focus detection region at a central portion in a shooting screen.
Automatic selection means for selecting one of the plurality of focus detection areas having the largest signed defocus amount after adding the predetermined value to the focus detection area, and setting the first predetermined value to open the photographing lens And a first predetermined value determining means for determining in accordance with the F-number, wherein the priority of the central portion is determined by the open F-number of the taking lens. Since the selection is performed in a state where the first predetermined value is added in advance to the signed defocus amount for the focus detection area in the center, the signed defocus amount in the center focus detection area is smaller than that in the other areas. However, if the difference is smaller than the first predetermined value, it is selected. On the other hand, in the focus detection area other than the central part, the difference ΔDF ₁ obtained by subtracting the signed defocus amount of the central area from the signed defocus amount of the area other than the central part is ΔDF ₁ > the first predetermined value. The first predetermined value used at this time is not selected unless the condition is satisfied. In the case where a bright lens is used in accordance with the open F-number of the taking lens, that is, in a state where the depth of focus is shallow, the first predetermined value is used. By reducing the value, ΔDF ₁ > ΔDF for satisfying the first predetermined value condition
₁ may be smaller, so that the possibility of selecting an area other than the center increases, and the object detected in the area other than the center and the object detected in the center focus detection area It is possible to prevent a subject at a shorter distance from being in focus and becoming a pin after shooting. Further, in the case of a dark lens, increasing the first predetermined value prevents an operation of selecting an area other than the center part unnecessarily in photographing that can be covered by the depth of focus, and every time focus detection is performed. The selection area is prevented from changing.

In this case, the first predetermined value determining means calculates the first predetermined value by the following definition: (first predetermined value) = (open F number) × (minimum diameter of confusion) × b b; And make it proportional to the open F-number,
It is possible to reduce the first predetermined value for a bright lens and to increase the first predetermined value for a dark lens.

The automatic selection means selects a focus detection area substantially symmetrical with respect to a center focus detection area.
Further, the signed defocus amount obtained for the focus detection area located at any one of the symmetric positions is the second value.
After adding a predetermined value, it is preferable that the priority of any one of the plurality of focus detection areas having the largest signed defocus amount is increased. For each focus detection area at the symmetric position, the selection is performed after the second predetermined value is added to the signed defocus amount of one of the focus detection areas. The possibility that either one is selected can be increased. That is, one of the regions located at the symmetric position is preferentially selected (claim 3).

In this case, the automatic selection means takes into account the position of the person's face as the subject with the normal grip of the camera, and gives priority to the upper focus detection area with respect to the focus detection area substantially vertically symmetrical. The second predetermined value is added to the signed defocus amount of the upper focus detection area so that the position of the face of the person as the subject in the vertical position grip of the camera is taken into consideration, so that the position is substantially right and left. It is preferable to add a second predetermined value to the signed defocus amount of the right focus detection area so that the right focus detection area is preferentially selected for the focus detection area at the symmetric position. 4).

It is preferable that the image forming apparatus further includes second predetermined value determining means for determining a second predetermined value used by the automatic selecting means for executing the selection in accordance with the open F number of the taking lens. For example, in the case where a second predetermined value is added to the signed defocus amount of the upper area for the focus detection area at the vertically symmetric position, the lower area is the signed defocus amount of the lower focus area. The difference ΔDF ₂ obtained by subtracting the signed defocus amount of the upper region from the amount is ΔDF ₂ > second
If the condition of the predetermined value is not satisfied, it will not be selected. However, the second predetermined value used at this time is determined in accordance with the open F-number in the case where a bright photographing lens is used, that is, in a state where the depth of focus is shallow, By reducing the predetermined value, ΔDF ₂ > ΔF for satisfying the second predetermined value condition is satisfied.
Since the DF ₂ may be smaller, the possibility that the lower region is selected increases, and the distance between the subject detected in the lower region and the subject detected in the upper region is shorter. It is less likely that the subject will not be in focus and that the subject will be out of focus as a result of shooting (claim 5).

The second predetermined value calculating means calculates the second predetermined value according to the following definition: (second predetermined value) = (open F number) × (minimum circle of confusion) × a a; Proportional to the F-number,
It is possible to reduce the second predetermined value for a bright lens and to increase the second predetermined value for a dark lens.

The priority set by the automatic selection means is the highest in the central part, and then in the focus detecting areas other than the central part of the focus detecting area. It is preferable that the focus detection area is on a straight line that extends, and then the focus detection area that is on a straight line that passes through the central focus detection area and extends in the horizontal direction of the shooting screen. For example, a face position of a person who is likely to be arranged on a vertical straight line passing through the center of the shooting screen at a normal grip position of the camera is preferentially selected (claim 7).

The relationship between the first predetermined value and the second predetermined value to be added to the signed defocus amount is such that the first predetermined value ≧ the second predetermined value so that the central focus detection area is selected with the highest priority.
It is preferably a predetermined value (claim 8).

[0013]

FIG. 1 is a block diagram showing a control system of an AF single-lens reflex camera equipped with a multipoint automatic focus detection device according to the present invention. The AF single-lens reflex camera of FIG. 1 includes a camera body 10 and an AF-compatible photographing lens (interchangeable lens) 5.
It consists of 0. Also, in FIG.
Is a CPU that performs all kinds of control of the camera, is also a focus detection unit that calculates a defocus amount based on a signal from the AF unit 28, and has a plurality of focus detection areas that exist in the shooting screen in the automatic selection mode. It is also an automatic selection means for selecting an optimum focus detection area from (area).

In FIG. 1, most of the light rays from the subject that enter the camera body 10 through the focusing lens 52 in the photographing lens 50 are reflected by the main mirror 2 and reflected by the pentaprism 8. Then, the light is emitted from an eyepiece (not shown) and guided to the light receiving surface of the photometric IC 12. The photometric IC 12 generates, for example, an electric signal obtained by logarithmically compressing a voltage value corresponding to the amount of received light, and provides information on the amount of received light to the CPU 24 via the peripheral control circuit 14. The CPU 24 executes an AE calculation (exposure calculation) based on the received light amount information and the film sensitivity information obtained from the photometric IC 12, and calculates a proper shutter speed and a proper aperture value for photographing. At the time of the photographing process, the CPU 24 controls the exposure mechanism 20 and the aperture mechanism 22 via the peripheral control circuit 14 based on the calculated appropriate shutter speed and appropriate aperture value, and performs exposure on the film. Also, the CPU 24
In the photographing process via the peripheral control circuit 14, the mirror motor 17 is driven via the motor driver IC 16 to control the up / down of the main mirror 2, and after the exposure is completed, the winding motor 18 is driven to drive the film. A process of winding up by one frame is performed.

On the other hand, a half mirror section 3 is provided on the main mirror 2, and the light beam transmitted therethrough is reflected by the sub mirror 4 and guided to the AF unit 28. The AF unit 28 is a so-called phase difference type distance measuring sensor. A
Inside the F unit 28, C
A CD line sensor is provided. The CCD line sensor includes a CCD sensor including a pair of CCD sensors for each focus detection area obtained by dividing the photographing screen into a plurality of areas. In the AF unit 28, 1 in the shooting screen
A subject light beam corresponding to one focus detection area is divided into two, and each of them is incident on each of the pair of CCD sensors corresponding to the focus detection area. Light rays incident on each CCD sensor are integrated (stored) for a predetermined time, photoelectrically converted, and transmitted to the CPU 24 as electric signals. CPU 24
Calculates a defocus amount by a phase difference method using signals obtained from a pair of CCD sensors.

The CPU 24 obtains the rotation direction and the number of rotations of the AF motor 37 for driving the focusing lens 52 and performing the focusing based on the obtained defocus amount. 3
7 is driven. The rotation of the AF motor 37 is controlled by the gear block 38, the joint 32 provided on the mount portion of the camera body 10, and the joint 6 provided on the photographing lens 50.
2 is transmitted to the gear block 54 via each of them, whereby the focusing lens 52 is driven forward and backward in the optical axis direction.

The CPU 24 includes an A / D converter 24a for converting a video signal sent from the CCD line sensor of the AF unit 28 from analog to digital.
A ROM 24b storing a program, a RAM 24c, a timer 24d, and a counter 24e for counting a pulse signal from an encoder 39 for converting the rotation of the AF motor 37 into an electric pulse are provided. The EEPROM 42 stores various constants and other information necessary for the CPU 24 to perform the AF process.

The camera shown in FIG.
Is turned on to enable operation. The photometry switch 92 is turned on by half-pressing a release button (not shown). The release switch 93 is turned on by fully pressing the release button, and the film surface is exposed by turning on this switch. The AF switch 94 is a switch for switching between an auto focus mode and a manual focus mode. When the switch is ON, the auto focus mode is set. The select switch 95 is used for selecting a plurality of focus detection areas in the shooting screen, in an automatic selection mode in which the selection is left to the camera, or in an arbitrary selection mode in which the photographer can select a desired area and perform shooting. Switch to switch between Also, the CPU 24
Display information on camera exterior display panel 2
In addition to the display on the LCD 6, various kinds of display are also performed on the display LCD 6 in the finder for performing the display in the finder.

A lens CPU 56 is provided inside the taking lens 50.
Is provided. The lens CPU 56 is connected to the peripheral control circuit 14 via a number of electrical contacts 64 and a number of electrical contacts 34 on the main body side, and transfers information about the photographing lens 50 to the CPU 24. The information transferred by the lens CPU 56 includes, for example, the open aperture value A of the photographing lens 50.
v (apex conversion value of open F value), maximum aperture value Av
(Apex conversion value of minimum aperture F value) and K value data. The K value is the number of pulses output by the encoder 39 when the AF motor 37 is driven to move the image plane formed by the photographing lens 50 by a unit length in the optical axis direction. Further, the lens CPU 56 recognizes the position of the focus adjustment lens 52 by the distance switch 58 provided for detecting the position of the focus adjustment lens 52 and transfers the information to the CPU 24.

FIG. 2 shows a photographing screen 81 and a display 82 in the finder of the camera shown in FIG. FIG. 2 also shows the arrangement of a plurality of focus detection areas provided in the shooting screen 81. As shown in FIG. 2, the photographing screen 81 in the viewfinder with a normal grip of the camera is rectangular, and the plurality of focus detection areas in the photographing screen 81 are symmetrical with respect to the central area C and the area C. Are divided and arranged in five regions, regions L and R at the position of, and regions UC and DC at the vertically symmetric position with respect to the region C. Processing for selecting an optimum area from these focus detection areas in the automatic selection mode will be described later with reference to FIGS.

FIG. 3 shows details of the display 82 in the viewfinder of FIG. When the camera of FIG. 1 is set to the automatic selection mode, in the initial state, the camera is arranged in the viewfinder display 82 corresponding to the arrangement of each focus detection area arranged as shown in FIG. All five display portions are lit and displayed (FIG. 3A), and one of the regions, for example, the region U, is selected according to the automatic selection mode.
When C is selected and focused, only the display portion corresponding to the area UC is turned on as shown in FIG. 3B, and the in-focus display 82f is turned on.

FIGS. 4 to 7 are flowcharts showing the operation of the camera executed by the CPU 24 shown in FIG. FIG. 4 shows a main routine of the camera operation, and FIG. 5 is a flowchart showing in detail the "AF process" subroutine of step S122 in FIG.
7 is a flowchart showing in detail the "defocus calculation" subroutine of step S156 in FIG.

When the main switch 91 of the camera shown in FIG. 1 is turned on, the main routine of FIG. 4 is started, and first, each control portion of the camera such as the peripheral control circuit 14 is initialized (S102). Thereafter, a power-down process for stopping power supply to each control unit and suppressing power consumption is performed (S
104), and enters a loop waiting for the photometry switch 92 to be turned on (S106). When the release button of the camera is half-pressed and the photometry switch 92 is turned on (S106:
YES), a power ON process for supplying power to each control unit of the camera is executed (S108), and a VDD loop time timer starts to enter a VDD loop (S11).
2). In the VDD loop, the photometry switch 92 is turned on once.
When the power is turned on, the power-on state is maintained for a predetermined time step S
This is a processing loop for repeatedly executing “AF processing” 122 and the like.

When a predetermined time for the VDD loop has elapsed (S124: YES), if the photometry switch 92 is ON (S126: YES), the process enters the VDD loop again, but if the photometry switch 92 is OFF (S126). : NO), and a process for maintaining the power-on state for a predetermined time (power hold time) is performed (S128 to S134).
In other words, when the process after step S128 is first entered, the power hold flag is "0" (S1
28: NO), the power hold timer is started (S130), and the power holding flag is set to "1" (S132). On the other hand, if the power hold flag has already been set to "1" (S128: Y
ES), steps S130 and S132 are skipped. If the power hold time has elapsed while the photometry switch 92 is OFF (S134: YES), the power hold flag is reset to "0" (S138).
Thereafter, the process returns to the power down process of step S104, and enters a loop waiting for the photometry switch 92 to be turned on again.

In step S106, the photometric switch 9
2 is turned on, the state of each switch is confirmed (S1).
14), various kinds of information (open aperture value Av, maximum aperture value Av, K value, etc.) regarding the taking lens 50 are acquired from the lens CPU 56 by lens communication (S116).
Next, AE calculation is performed using the photometry result by the photometry IC 12 (S118), and the optimal shutter speed, aperture value, and the like of the calculation result are displayed on the display unit 26 (S12).
0). After that, the “AF process” is executed (S12)
2).

FIG. 5 shows the details of the "AF process". In the “AF processing” of FIG.
Is turned on (S150), and the "AF"
If the photometry switch 92 is OFF when the process is entered (S150: NO), the AF lock flag is reset to "0" (S182), and the state of the viewfinder display 82 shown in FIG. Is returned to. That is, when the mode set using the select switch 95 is the automatic selection mode (S184: YE
S), all parts of the focus detection area are lit and displayed as shown in FIG. 3A (S190). On the other hand, if the mode is the optional selection mode (S184: NO), the portion corresponding to the portion selected by the photographer is lit (S186).
Thereafter, the in-focus display 82f is turned off (S188), and the process returns to the main routine.

In step S150, it is determined that the photometry switch 92 is ON (S150: YES).
The AF lock flag indicating that the F lock is being performed is "1"
If not (S152: NO), the processing from S154 is executed. If the AF lock flag is "1" in step S152 (S152: YE
S), the process returns to the main routine without executing the processes after S154. In S154, the operation of accumulating (integrating) the photoelectric conversion output of the subject image for a predetermined time is executed by using the CCD line sensor in the AF unit 28, and the integration result is taken into the CPU 24. In step S156,
The calculation of the defocus amount and the selection of the focus detection area to be subjected to the AF operation are performed using the integration result.

"Defocus calculation" in step S156
In step S15, if the calculation for the selected area is OK, that is, if an effective defocus amount is obtained,
8: YES), it is confirmed whether the defocus amount is within the focus width (S160). If the defocus amount is within the focus width, that is, if the subject is in focus (S160:
YES), the AF lock flag is set to "1" (S162).

On the other hand, if the result of the defocus calculation is NG, that is, if an effective defocus amount cannot be obtained (S158: NO), the focus display 82f is flashed (S174), and the main Return to routine.
If the defocus amount exceeds the focus width (S160: NO), the number of pulses according to the defocus amount is calculated using the K value (S176), and the number of pulses is determined according to the calculated number of pulses. The photographing lens is driven by the amount (S
178).

In step S164, it is confirmed whether the mode is the automatic selection mode. If the mode is the automatic selection mode (S164: YES), as shown in FIG. Only the optimum focus detection area selected by the processing is lit and displayed, for example, as shown in FIG. 3B (S180). Thereafter, the in-focus display 82f is lit (S172). On the other hand, if the mode is the optional selection mode (S164: NO), the process proceeds to step S172, and the in-focus display 82f is turned on.

Next, referring to FIGS. 6 and 7, "A" in FIG.
The “defocus calculation” of step S156 in the “F process” will be described in detail. Note that this "defocus calculation"
The subroutine represents a process in the automatic selection mode, and one of the plurality of focus detection regions (C, UC, DC, L, and R) optimal by the process for the automatic selection described below. Is selected. Although the “defocus calculation” subroutine in the arbitrary selection mode is not shown, in this case, the defocus calculation is performed on the area selected by the photographer, and if the defocus calculation is OK, the calculation is OK If the flag is set to “1” and the defocus calculation is NG, the calculation OK flag is reset to “0” and the subroutine ends.

In FIG. 6, when the "defocus calculation" subroutine is started, first, all the areas (C, UC, D
A defocus calculation for obtaining a defocus amount for C, L, R) is performed (S200). as a result,
The process proceeds to step S202 and thereafter unless the calculation NG is such that an effective defocus amount cannot be obtained for the entire region (S201: NO). 0 "(S220), the variable n (" selected area ") holding the selected area is cleared (S221), and the subroutine ends.

The defocus amount obtained in the defocus calculation in step S200 is an absolute value of a subject closer to the camera (near side) or farther from the camera (∞ side) with respect to the current photographing distance of the photographing lens. Although it is calculated as a large value, in step S202, when the subject image is in the ∞ direction with respect to the current shooting distance of the shooting lens, the defocus amount is set to a negative value. As a result, the defocus amount becomes a signed value, and the larger the value, the closer to the camera. In step S203, the defocus amount is set to the farthest value (negative value) for the area where the calculation was NG.

Steps S204 to S219 are processing for automatically selecting one area from all the areas (hereinafter referred to as "automatic selection processing"). In this “automatic selection process”, the focus detection area having the largest defocus amount is selected, but the area other than the central part is determined by subtracting the defocus amount of the central area C from the defocus amount of the focus detection area other than the central part. Is not selected unless the difference ΔDF obtained by subtracting the condition ΔDF ≧ predetermined amount β is satisfied. That is, the region C is selected with priority over the region other than the central portion. Step S
In 205, the predetermined amount β is determined by using the open F number of the photographing lens 50 acquired by the CPU 24, β = (open F number) × (minimum circle of confusion) × b
b: Calculated according to the definition of coefficient. Therefore, when a bright lens (a lens with a small open F number) is used as a photographing lens, the predetermined amount β is small, and when a dark lens (a lens with a large open F number) is used as the photographing lens, the predetermined amount β is small. Is a large value.

When a bright lens is used, the depth of focus is shallow, but the predetermined amount β is correspondingly small. Therefore, there is a possibility that the area other than the center portion satisfies the condition of ΔDF ≧ the predetermined amount β. As a result, the focus is not focused on a subject that is slightly closer to the subject at the center of the shooting screen, and it is possible to prevent the focus from being brought into focus after shooting. On the other hand, when a dark lens is used, the depth of focus is deep, and the range that can be covered by the depth is widened. However, the predetermined amount β is also increased accordingly. β
Is less likely to be satisfied, and unnecessary selection of a region other than the region C is prevented.

In the "automatic selection process", the area UC is set for the areas UC and DC that are vertically symmetric with respect to the center area C, and the area R is set for the areas L and R that are set symmetrically to the left and right. Selected preferentially. The predetermined amount α is used to give priority to the regions R and UC. Step S20
4, the predetermined amount α is the same definition as the predetermined amount β.
(Open F number) × (minimum circle of confusion) × a a: Calculated by definition of coefficient. For the same reason as described above with respect to the predetermined amount β, with respect to selecting one of the regions at the symmetric position, when a bright photographing lens is used, a region close to the subject is selected even if the difference is small. When the photographing lens is dark, the selection process is not performed unnecessarily.

In the "automatic selection process", each focus detection area is specified using variables (comparison code k, comparison number m) as shown in Table 1 below. Note that the reference table shown in Table 1 is stored in the EEPROM 42 of the camera body 10, and the CPU 24
This reference table is read out and used at 4c.

In the "automatic selection process", step S2
In the loop processing from 07 to S210, one of the regions L and R is selected, and one of the regions UC and DC is selected. Therefore, four regions (L, R,
UC, DC). In the loop processing of steps S213 to S216, one of the two candidates is further selected. In step S217, one region is selected from the narrowed region and the central region C, and one region is finally selected.

[0039]

[Table 1]

In step S206, the comparison code k
Is set to 2, which is the maximum value, and then, in step S20
At 7, 1 is subtracted from the comparison code k. Step S
At 208, the current comparison code k (k = 1)
The value (DF _UC +) obtained by adding a predetermined amount α to the defocus amount DF _UC of the region of the comparison number m = 1 (that is, the region UC)
α) is compared with the defocus amount DF _DC of the area with the comparison number m = 2 (that is, the area DC). (DF _UC +
α) ≧ DF _DC (S208: YES),
The area UC is held in the variable “area of comparison code k (= 1)” (S209). On the other hand, (DF _UC + α) <DF
If it is _DC (S208: NO), the area DC is held in the variable "area of comparison code k (= 1)" (S208).
211).

In step S210, the comparison code k
Is not 0 (S210: NO), the process proceeds to step S
Returning to 207, 1 is further subtracted from the comparison code k,
The comparison is performed for the area of the next comparison code k (= 0). That is, in step S208, the current comparison code k (k = 0), compared numbers m = 1 region (i.e., region R) defocus amount DF _R to a value obtained by adding a predetermined amount alpha of (DF _R + alpha) , the defocus amount DF _L comparison number m = 2 of the region (i.e. region L) are compared.
If (DF _R + α) ≧ DF _DC (S208:
YES), the area R is held in the variable “area of comparison code k (= 0)” (S209). On the other hand, (DF _R + α)
If <DF _L (S208: NO), the area L is held in the variable “area of comparison code k (= 0)” (S211).

By the above steps, the comparison code k =
In a state where one area is selected for each of 0 and the comparison code k = 1, the processing after step S212 is started. In the following, for the sake of simplicity, the description will be made assuming that the region selected for the comparison code k = 0 is the region R, and that the region selected for the comparison code k = 1 is the region UC. In step S212, the area “R” selected for the comparison code k = 0 is held in the variable “selection area n”, and 1 is set in the comparison code k in step S213.
Is added. Since the comparison code k has not reached the maximum value 2 (S214: NO), the process proceeds to step S215.

In step S215, the area UC selected for the current comparison code k = 1 is compared with the area R held in the "selected area n". That is,
A predetermined amount alpha value plus _{(DF UC} + α) to the defocus amount _{DF UC} region UC, the defocus amount of the area R DF _R
Are compared, and if (DF _UC + α) ≧ DF _R (S215: YES), the area U is stored in the variable “selection area n”.
C is held (S216). On the other hand, (DF _UC + α)
<DF in case where _R is (S215: NO), the region is held in the variable "selection area n" is left in the region R.

As described above, the vertical area (UC, DC) is preferentially selected over the horizontal area (R, L), and the area UC has priority over the areas UC, DC. Therefore, the position corresponding to the face of the person as the subject with the normal grip of the camera at the upper center position of the shooting screen corresponding to the area UC is preferentially selected. In addition, in consideration of the position of the person's face in the vertical grip of the camera, as to the regions R and L, the region R corresponding to the upper center of the shooting screen by the vertical grip is preferentially selected. .

In step S214, the comparison code k
Is 2 (S214: YES), the region R,
The process proceeds to step S217 in a state where one area is selected from L, UC, and DC. For the sake of simplicity, the following description will be made assuming that a region selected from the regions R, L, UC, and DC is the region UC.

[0046] In step S217, the value a predetermined amount β is added to the defocus amount DF _C region C, and a defocus amount DF _UC regions UC is a region which is held in the variable "selection area n" Be compared. (DF _C + β) ≧
If it is DF _UC (S217: YES), the area C is held in the variable “selection area n” (S218). On the other hand, when (DF _C + β) <DF _UC (S217:
NO), the area held in the variable “selection area n” remains the area UC. Thereafter, in step S219, the calculation OK flag is set to 1, and this subroutine ends. Finally, one area selected from all areas is
The variable “selection area n” is held. The information of the selection area held in the variable “selection area n” is stored in step S in FIG.
It will be used to execute the processing related to the selected area after 158. The operation OK flag is used in step S158 to determine whether the operation is OK.

In the above description, the focus detection areas provided in the camera body 10 are five areas of C, R, L, UC, and DC. However, when the arrangement and number of the focus detection areas are changed. Also, the present invention is applied. By changing the position of each area in Table 1, the priority of the area to be selected can be easily changed. For example, it is possible to give priority to the area L for the areas R and L and give priority to the area DC for the areas UC and DC. When a reference table in which the regions included in the comparison code k = 0 and k = 1 rows of the reference table in Table 1 are replaced is used, the region (L , R) are selected in the central area C
Can be higher than the area (UC, DC) on a straight line extending in the up-down direction.

In the "automatic selection process" shown in FIGS. 6 and 7, first, candidates are narrowed down to one candidate from regions other than the central region C, and finally the region C is By comparing, the procedure of giving the area C the highest priority was taken. Preliminarily adding a predetermined amount β in the defocus amount DF _C region C in advance by adding a predetermined amount α to the defocus amount of the area to increase the other priority, the defocus amount is the largest (the camera side The (closest) region may be extracted. In this case, by setting the predetermined amount β to a value equal to or larger than the predetermined amount α, it is possible to make the priority of the area C higher than that of the other areas.

[0049]

As described above, according to the present invention,
In the automatic selection mode in which the central portion is prioritized while selecting a close subject, the predetermined amount for giving priority to the central portion can be changed according to the brightness of the photographing lens. That is, since the predetermined amount becomes small with a bright photographing lens, it is possible to prevent a close subject from being focused on and a rear focus being set in a state where the depth of focus is shallow. Further, since the predetermined amount becomes large in the case of a dark photographing lens, it is possible to prevent the area from being unnecessarily selected in a situation where the depth of focus can be covered by the depth of focus.

Further, even if the subject distances of the regions symmetrically positioned with respect to the focus detection region at the center are almost the same, any one of the regions is prioritized, and the selected region changes each time the distance measurement is performed. Nothing. That is, the multi-point automatic focus detection device of the present invention gives priority to a close subject in photographing with a bright photographing lens, preferentially focuses on the center in photographing with a dark photographing lens, and focuses at a depth of focus. It realizes shooting without causing so-called hesitation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system of a single-lens reflex camera to which the present invention is applied.

FIG. 2 is a view showing the inside of a viewfinder of the camera shown in FIG. 1;

FIG. 3 is a view showing in detail a display in the viewfinder in the viewfinder of FIG. 2;

FIG. 4 is a flowchart illustrating a main routine of a process executed by the camera in FIG. 1;

FIG. 5 is a flowchart illustrating an AF process in detail.

FIG. 6 is a flowchart showing a defocus calculation process including an automatic selection process in detail together with FIG. 7;

FIG. 7 is a flowchart showing a defocus calculation process including an automatic selection process in detail together with FIG. 6;

[Explanation of symbols]

 2 Main mirror 4 Sub-mirror 6 Display in viewfinder LCD 8 Pentaprism 10 Camera body 12 Photometric IC 14 Peripheral control circuit 24 CPU 28 AF unit 37 AF motor 42 EEPRON 50 Shooting lens 52 Focusing lens 56 Lens CPU 81 Shooting screen 82 Viewfinder display 82f Focus display 91 Main switch 92 Photometry switch 94 AF switch

Claims (8)

[Claims] 1. A defocus amount is obtained for each of a plurality of focus detection areas in a photographing screen, and each of the defocus amounts is converted into a signed defocus amount with a plus value on the short distance side.
A multi-point automatic focus detection device that selects any one focus detection area based on the signed defocus amount, and controls driving of a shooting lens based on the defocus amount of the selected focus detection area, For the focus detection area at the center in the shooting screen, a value obtained by adding a first predetermined value to the obtained signed defocus amount is used, and the signed defocus amount among the plurality of focus detection areas is the most significant. Automatic selection means for selecting any one of the large focus detection areas; and first predetermined value determination means for determining the first predetermined value in accordance with the open F number of the photographic lens, and the open F number of the photographic lens A multi-point automatic focus detection device, wherein the priority of the central portion is determined by the following. 2. The first predetermined value determining means calculates the first predetermined value by the following definition: (first predetermined value) = (open F number) × (minimum circle of confusion) × b b; coefficient 2. The multi-point automatic focus detection device according to claim 1, wherein: 3. The automatic selection means is obtained for a focus detection area located substantially symmetrically with respect to the focus detection area in the center, and for a focus detection area located at any one of the symmetrical positions. Adding a second predetermined value to the signed defocus amount, and increasing the priority of any one of the plurality of focus detection regions having the largest signed defocus amount. The multi-point automatic focus detection device according to claim 1 or 2, wherein 4. The automatic selection means sets a signed defocus amount of a right focus detection area for a focus detection area located substantially symmetrically in a photographing screen with respect to the center focus detection area. The second predetermined value is added, and the second predetermined value is added to the signed defocus amount of the upper focus detection area for the focus detection area substantially vertically symmetrical, and The multi-point automatic focus detection device according to claim 3, wherein the priority of any one focus detection area having the largest signed defocus amount is set higher. 5. The image processing apparatus according to claim 1, further comprising a second predetermined value determining unit that determines the second predetermined value used for the selection by the automatic selecting unit according to an open F number of a taking lens. The multipoint automatic focus detection device according to claim 3 or 4. 6. The second predetermined value determining means calculates the second predetermined value by the following definition: (second predetermined value) = (open F number) × (minimum circle of confusion) × a a; The multi-point automatic focus detection device according to claim 5, wherein: 7. The automatic selection means, wherein the priority of selection is highest in the central part, and then in a focus detection area other than the focus detection area in the central part. A focus detection area on a straight line extending in the vertical direction of the shooting screen, and then a focus detection area on a straight line extending in the horizontal direction of the shooting screen passing through the focus detection area in the central portion. The multipoint automatic focus detection device according to claim 3. 8. The multi-point automatic focus detection device according to claim 3, wherein a relationship of the first predetermined value ≧ the second predetermined value is satisfied.