JP2002228920A - Main subject detector and automatic focusing camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a main subject detector capable of accurately deciding a subject intended by a photographer, and to provide an automatic focusing camera which can focus the subject intended by the photographer. SOLUTION: This main subject detecting device 140 is provided with a focusing part 142 having three or more focusing points and measuring a subject distance for every focusing point, a focusing control part 141 allowing the focusing means to perform focusing operation several times at the predetermined timing, a subject distance storage part 143 in which the subject distance is stored, and a main subject discrimination part 144 discriminating the main subject by using the subject distance. The discrimination part 144 discriminates the main subject by using the plurality of subject distances.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main subject detecting device used for an auto-focus single-lens reflex camera, a compact camera, a digital camera and the like, and an auto-focus camera.

[0002]

2. Description of the Related Art Conventionally, in an autofocus camera having a multi-point distance measuring device for measuring a distance (subject distance) between a camera and a subject at a plurality of points on a shooting screen, a subject to be focused on the camera is used. Is simply the distance between the closest subject and the camera.

[0003]

However, in the above-described conventional auto-focus camera, since the closest one of a plurality of subjects is focused, it is not always necessary to focus on the subject (main subject) intended by the photographer. There is a problem that is not always.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a main subject detecting device capable of accurately determining a subject intended by a photographer and a main subject detecting device capable of focusing on a subject intended by the photographer. It is to provide an autofocus camera.

[0005]

According to a first aspect of the present invention, there is provided a main subject detecting apparatus having three or more ranging points for measuring a subject distance at each of the ranging points, and a predetermined timing. Distance measurement control means for causing the distance measurement means to perform a plurality of distance measurement operations, and a subject distance storage means for storing the subject distance,
A main subject determining device for determining a main subject using the subject distance, wherein the main subject determining device determines a main subject using the subject distance a plurality of times. I have. According to the above configuration, the main subject is determined by using the measurement results of a plurality of times at three or more distance measuring points, so that the main subject can be accurately determined.

The main subject detecting apparatus according to a second aspect is characterized in that the main subject discriminating means discriminates a main subject by limiting to a distance measuring point including a subject distance in a movable area of the main subject. I have. According to the above configuration, the determination of the main subject is performed only at the distance measurement points having the subject distance within the movable area of the main subject, so that the processing time is shortened and the accuracy of determining the main subject is improved. Is done.

According to a third aspect of the present invention, in the main subject detecting apparatus, the main subject discriminating means is a distance difference between a latest subject distance for each of the ranging points and a latest subject distance of another ranging point. Calculate the distance difference, calculate the previous distance difference which is the distance difference between the previous subject distance and the previous subject distance of another ranging point for each of the ranging points, and calculate the latest distance difference and the previous distance. It is characterized in that a subject whose distance measurement point whose difference substantially coincides is being measured is determined to be a main subject. According to the above configuration, the main subject is often in a position and a size at which the subject distance can be measured simultaneously by a plurality of ranging points. By determining that the subject whose point is being measured is the main subject, the main subject is accurately determined. In particular, when the main subject is a moving object, the main subject is more accurately determined.

According to a fourth aspect of the present invention, in the main subject detecting apparatus, the main subject discriminating means is an object whose distance is measured at a distance measuring point at which the latest distance difference and the previous distance difference substantially coincide with each other. If there are multiple subjects, determine whether the main subject is moving away or approaching.If the main subject is moving away, determine the subject with the large subject distance as the main subject, and if the main subject is approaching Is characterized in that a subject having a small subject distance is determined as a main subject. According to the above configuration, when the main subject is moving away, the subject with the largest subject distance is determined as the main subject, and when the main subject is approaching, the subject with the smallest subject distance is determined as the main subject. Therefore, a subject having a high frequency desired by the photographer is determined to be the main subject.

According to a fifth aspect of the present invention, in the main subject detecting device, the main subject discriminating means is an object whose distance is measured at a distance measuring point at which the latest distance difference and the previous distance difference substantially match. When there are a plurality of subjects, a subject close to the center of the distance measurement range is determined to be a main subject. According to the above configuration, the subject closest to the center of the distance measurement range is determined to be the main subject, so the subject closest to the center of the frequency measurement range desired by the photographer with high frequency is determined to be the main subject.

According to a sixth aspect of the present invention, in the main subject detecting apparatus, the main subject discriminating means is an object for which the subject distance is measured at a ranging point at which the latest distance difference and the previous distance difference substantially match. If there are a plurality of subjects, it is determined whether the main subject is moving away or approaching.If the main subject is moving away, the subject whose subject distance is large and close to the center of the distance measurement range is determined as the main subject. When the main subject is approaching, a subject having a small subject distance and close to the center of the distance measurement range is determined to be the main subject. According to the above configuration, when the main subject is far, the subject distance is large and the subject close to the center of the distance measurement range is determined to be the main subject, and when the main subject is close, the subject distance is small and Since a subject close to the center of the distance measurement range is determined to be the main subject, a subject frequently desired by the photographer is determined to be the main subject.

According to a seventh aspect of the present invention, there is provided an auto-focus camera, wherein the main subject detecting device according to any one of the first to sixth aspects, a photographing optical system, and a subject distance of the main subject determined by the main subject detecting device. Lens position changing means for adjusting the position of the photographing optical system based on According to the above configuration, the main subject is accurately determined by the main subject detection device, and the subject distance of the main subject at the exposure timing is accurately calculated by the distance calculation unit. The position of the photographing optical system is adjusted based on the photographing, and photographing focused on the main subject desired by the photographer is easily performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a main subject detecting apparatus according to the present invention will be described in detail with reference to the drawings. First, FIG. 1 shows a configuration example of an autofocus single-lens reflex camera to which the main subject detection device of the present invention is applied.

At the approximate center of the camera body 100, a main mirror 111 is provided at an angle of about 45 degrees with respect to the optical axis L, and is provided at the back of the main mirror 111 and is provided at an angle of about 90 degrees with respect to the inclination of the main mirror 111. And a mirror box 110 having an auxiliary mirror 112 and the like. At the top of the mirror box 110, a reticle 121, a prism 122,
A finder 120 including an eyepiece 123, a display element 124, and the like is provided. A light emitting unit 170 for emitting flash light is provided above the viewfinder 120.

On the bottom of the mirror box 110 (the side opposite to the finder 120), there are provided a main subject detection device 140, a light control sensor 150, an automatic focus drive unit 160, and, if necessary, a relay lens 151 and the like. . The back of the mirror box 110 (the side opposite to the lens 200)
The shutter unit 130 is located between the
Is provided. Auto focus CPU 301 and wiring 30
Flexible printed circuit board 300 provided with 2 or the like
It is provided in a gap or the like of the camera body 100.

The lens 200 includes an imaging optical system 201, a lens barrel 202 for holding the imaging optical system 201, and a lens driving mechanism 203 for driving the lens barrel 202 in a direction A parallel to the optical axis L.
And the focal length and F value (open F value, open F value for automatic focusing, minimum F value, etc.) of the lens, etc.
Lens CPU 20 that outputs to the side autofocus CPU 301
4 etc. are provided. In the following description of each of the embodiments, the imaging optical system 201 of the lens 200 has an opening F equal to or smaller than a first opening F-number (for example, F6.7).
It has a value and can be auto-focused.

Note that the open F value for automatic focusing is an open F value used for automatic focus adjustment, and does not always match the actual open F value of the imaging optical system. For example, 50m for close-up
For a lens with an m / F of 2.8, F5.6 is used as the open F value for automatic focusing. Therefore, the first opening F of the imaging optical system
The value and the second open F value are broad concepts including both the open F value of the imaging optical system and the open F value for automatic focusing.

The main mirror 111 reflects a large part of the light beam from the imaging optical system 201 in the direction of the focusing screen 121 and transmits the remaining part. The auxiliary mirror 112 guides the light transmitted through the main mirror 111 to the subject detection device 140. The prism 122 inverts the left and right of the image on the focusing screen 121 and guides the image to the eyes of the photographer via the eyepiece 123.

A photometric unit 180 is provided near the exit surface of the prism 122. Photometric unit 180
Includes a condenser lens and a photoelectric conversion element such as a photodiode, and outputs a signal corresponding to the luminance of the subject 2 to an automatic focus CP.
Output to U301. The display element 124 includes a light-emitting element such as a light-emitting diode, a liquid crystal display element, and the like, and displays a state in which the lens is focused on the subject 2 (focused state), a shutter speed, an aperture value of the lens, and the like.

The light emitting unit 170 includes a capacitor (not shown) for storing light emitting energy, a charging circuit (not shown) for charging the capacitor, and discharges electric energy stored in the capacitor to light energy. An arc tube 171 for conversion, a reflector 172 for reflecting flash light from the arc tube 171 forward of the camera, and a Fresnel lens 17 for condensing or diffusing the flash light in a predetermined range.
3 and so on. The dimming sensor 150 includes, for example, a condensing lens and a photoelectric conversion element such as a photodiode, detects reflected light from the film 1 during emission of flash light by the light emitting unit 170, and automatically outputs a signal corresponding to the amount of light. Output to the focus CPU 301. Autofocus CPU 30
When determining that the exposure amount of the film 1 has reached a predetermined value based on a signal from the light control sensor 150, the light emitting unit 170 stops emitting light. The auto focus drive unit 160 includes an actuator such as a DC motor, a stepping motor, and an ultrasonic motor, an encoder that detects the rotation direction and the number of rotations of the actuator, and outputs the detected rotation direction and the number of rotations to the auto focus CPU 301. It includes a system (not shown) and is connected to the lens driving mechanism 203 via the output shaft 161. The lens driving mechanism 203 is composed of, for example, a helicoid, a gear for rotating the helicoid (not shown), and the like. Move in the direction. The moving direction and the moving amount of the imaging optical system 201 and the lens barrel 202 follow the rotation direction and the rotation speed of the actuator, respectively.

FIG. 2 is a functional block diagram of main parts of the main subject detecting device, the autofocus CPU and the autofocus unit of the present invention. The main subject detection device 140 includes a plurality of (here, 25
Distance measuring unit 142 which has the number of measurement points and measures the subject distance for each measurement point, and an imaging optical system 201 based on a predetermined timing (here, the driving amount calculated by the lens driving amount calculating unit 305). (At the timing when the adjustment of the position of the lens barrel 202 is completed) and the distance measurement control unit 141 for performing the distance measurement operation of the distance measurement unit 142, and the object distance storage unit 143 for storing the object distance measured by the distance measurement unit 142. And a main subject determining unit 144 that reads the subject distance stored in the subject distance storage unit 143 and determines the main subject.

The main subject discriminating section 144 calculates the latest distance difference, which is the distance difference between the latest subject distance and the latest subject distance at another ranging point, for each ranging point of the ranging section 142 (this section). In the embodiment, a set of two ranging points is created from the 25 ranging points, and the distance difference between the latest subject distances of the two ranging points is calculated. The distance difference between the previous subject distance and the previous subject distance at another ranging point is calculated (in the present embodiment, two ranging points are selected from 25 ranging points). Create a set of points and calculate the distance difference between the two subject distance points and the previous subject distance), and measure the ranging points where the latest distance difference and the previous distance difference are substantially the same. Is determined to be the main subject.

If a plurality of sets of measurement points exist in this determination, it is determined whether the main subject is moving away or approaching. If the main subject is moving away, the subject distance is large and the main subject is located at the center of the ranging area. The subject measured by the set of close measurement points is determined to be the main subject, and when approaching, the subject whose subject distance is small and the set of measurement points close to the center of the ranging area is measured is the main subject. Determine.

In the present embodiment, the main subject detection device 140 is composed of a distance measurement control unit 141, a distance measurement unit 142, a subject distance storage unit 143, and a main subject discrimination unit 144, as shown in FIG. The case where the distance measurement unit 141, the distance measurement unit 142, the subject distance storage unit 143, and the main subject determination unit 144 are stored in separate housings will be described. And may be arranged at different appropriate positions.

As will be described later, the auto-focus CPU 301 classifies cases according to conditions such as whether or not the current subject has low contrast (hereinafter abbreviated as low contrast). The defocus amount corresponding to the current defocus amount, the previous defocus amount, and the lens driving amount driven during that time,
A defocus speed calculation unit 303 that calculates a defocus speed using the time required from the last distance measurement to the current distance measurement, and a moving object that calculates a moving object correction drive amount when the main subject is a moving object. A lens barrel that holds the imaging optical system 201 using the correction driving amount calculation unit 304 and the defocus speed calculated by the defocus speed calculation unit 303 and the moving object correction driving amount calculated by the moving object correction driving amount calculation unit 304. A lens driving amount calculation unit 305 that calculates an amount of driving the 202 in the direction A parallel to the optical axis L. In addition,
The auto-focus driving unit 160 includes the lens driving amount calculation unit 3
Imaging optical system 2 based on the drive amount calculated by
01 and the position of the lens barrel 202 are adjusted.

FIG. 3 is a diagram for explaining the principle of a method of measuring a subject distance performed by a distance measuring unit. Here, description will be made using a phase difference detection method. A subject light flux from the subject 2 that enters through two portions of the optical system 201 forms an image on the CCD sensor CS via the condenser lens CL and the separator lens SL. The image interval between these two subject images has a predetermined value based on the distance between the subject 2 and the optical system 201. For example, when the subject 2 approaches the optical system 201 from the state of (a) to the state of (b), C
The distance between the subject images formed on the CD sensor CS becomes wider.
Therefore, the subject distance can be measured based on the interval between the subject images coupled to the CCD sensor CS.

FIG. 4 shows a CCD for measuring a subject distance.
It is an example of an arrangement diagram of a sensor. Here, CC is set so that 25 object distances, which is the number of distance measurement points, are obtained.
Twenty-five D sensors CS are arranged. The CCD sensors CS are arranged in a grid at equal intervals around the center of the photographing screen PA. The numbers representing the rows and columns are assigned to the individual CCD sensors CS in the form of (i, j). Here, i is a row number and j is a column number. For example, (2,3) is the CC of the second row and the third column.
D sensor CS. A square area having the (1,1), (1,5), (5,1), and (5,5) CCD sensors CS as vertices is the distance measurement range MA. Distance measuring range MA
And the center of the shooting screen PA substantially coincide with each other. In this embodiment, the distance measurement range MA is smaller than the photographing screen PA, but may be the same range.

FIG. 5 is a flowchart for explaining the operation of the main subject detecting device, the autofocus CPU and the autofocus unit of the present invention. First, upon receiving a command from the distance measurement control unit 141, the distance measurement operation of the distance measurement unit 142 is performed (S
1). Next, the measurement result of the subject distance by the distance measuring unit 142 is stored in the subject distance storage unit 143 (S3). Next, the main subject determining unit 144 causes the subject distance storage unit 1
The subject distance stored in 43 is read, and the main subject is determined (S5). Then, a difference between the subject distance of the current main subject and the subject distance of the previous main subject is calculated (S7). Next, the time interval between the current measurement and the previous measurement is calculated using the current measurement time and the previous measurement time (S9).

Next, as will be described later, cases are classified depending on conditions such as whether or not the current subject is a low contrast, for example, the previous defocus speed, the current defocus amount and the previous defocus amount. The defocus speed is calculated using the defocus amount corresponding to the lens drive amount driven during that time and the time required from the previous distance measurement to the current distance measurement (S11). Next, it is determined whether or not the main subject is a moving object (S1).
3). When it is determined that the main subject is a moving object, a moving object correction driving amount is calculated (S15), and a lens driving amount is calculated (S17). If it is determined that the main subject is not a moving object, calculation of the lens drive amount is performed (S19). Then, step S17 or step S
Based on the lens driving amount calculated in 19, the positions of the imaging optical system 201 and the lens barrel 202 are adjusted by the automatic focus driving unit 160 (S21). Step S2
When the process of Step 1 is completed, the process returns to Step S1, and the processes from Step S1 to Step S21 are repeated. On the other hand, when the processing in step S21 is completed, the photographer can be released (S23).

Here, a method of determining the main subject performed by the main subject determining section 144 will be specifically described with reference to FIGS. FIG. 14 is a side view when the automobile VC approaches the camera body 100 provided with the distance measuring unit 142. FIGS. 15A and 15B are explanatory diagrams illustrating a state where the subject distance of the automobile VC is measured by using 25 ranging points. FIG. 15A illustrates a state at the time of the previous ranging, and FIG.
Indicates the state at the time of the latest ranging. The subject distance between the front part of the roof of the automobile VC and the front part is simultaneously measured by the distance measuring unit 142.

When the vehicle VC is located at a position on the long distance side (the state of FIG. 15A) (during the last distance measurement), (3, 3) (4, 25) of the 25 CCD sensors CS are used. The subject distances between the front surface of the roof and the front are measured by the CCD sensors CS of B0 and A0 at the position 3), and the measured subject distances are Lb0 and La0, respectively. When the vehicle VC is in the position on the short distance side (the state of FIG. 15B) (at the time of the latest distance measurement), of the 25 CCD sensors CS, (2, 3) (4, 3) The subject distances between the front surface of the roof and the front are measured by the CCD sensors CS of B1 and A1 at the positions, respectively, and the measured subject distances are Lb1 and La1, respectively. Car V
In C, since the positional relationship between the roof front part and the front does not change, the latest distance difference (Lb1-La1) and the previous distance difference (Lb0-La0) substantially match. Therefore, the subject to be measured at the distance measuring point that measures Lb1 and La1 as the subject distance, that is, the vehicle VC
Is determined as the main subject.

FIG. 6 is an example of a flowchart of a main subject discriminating process performed by the main subject discriminating section 144. First, calculation of an area where the main subject can move (herein referred to as a movable area) using the previous defocus speed, the previous subject distance of the main subject, and the time interval between the current measurement and the previous measurement. Is performed (S31). Step S
Details of the processing performed at 31 will be described. The movable area of the main subject is given as a range of values of the distance between the main subject detection device 140 and the main subject. The upper limit of this distance is called a far side distance Lmax, and the lower limit of this distance is a near side distance Lmax.
Called min. The far side distance Lmax and the near side distance Lmin are given by the following equations. Lmax = (subject distance of previous main subject) + (previous defocus speed) × (time interval) × WdMAX1 + W
dMAX2 Lmin = (subject distance of previous main subject) − (previous defocus speed) × (time interval) × WdMIN1 + W
dMIN2 where WdMAX1, WdMAX2, WdMIN1 and WdMIN2 are constants.

Next, a distance measuring point whose subject distance is within the movable area is selected (S33). And step S
A set of two ranging points is formed for the ranging points selected in 33, a latest distance difference which is a difference between the latest ranging distances of the two ranging points, and a previous ranging distance of the two ranging points. Is calculated (S35). Next, in step S35, it is determined whether or not the latest distance difference and the previous distance difference have been calculated for all sets of two ranging points in the movable area (S37). If the calculation has not been performed for all the sets of the two ranging points, step S35 is performed.
Then, the current distance difference and the previous distance difference are calculated for a different set from the previous set. When the calculation is performed for all the pairs of the two ranging points, the difference of the distance difference is calculated for all the combinations of the latest distance difference and the previous distance difference, and the difference of the distance difference is equal to or smaller than the threshold ΔL1. In step S39, a set of distance measurement points having the latest distance difference is selected as a candidate for a distance measurement point of the main subject. Then, it is determined whether or not there is a candidate for the ranging point of the main subject selected in step S39 (S43). If there is no distance measurement point candidate of the main subject selected in step S39, the threshold ΔL
A change to increase 1 is performed (S45), and then the processing from step S39 is performed again. Note that the threshold ΔL
The initial value of 1 is given by the following equation. ΔL1 = (previous defocus speed) × Ws1 Here, Ws1 is a predetermined constant.

If it is determined in step S43 that there is a set of distance measuring points selected as candidates for the main object, the distance measuring points selected as candidates for the main object are determined. It is determined whether there are two or more pairs (S
47). If it is determined in step S47 that there are no more than two sets of distance measuring points (that is, if there is only one set of distance measuring points), the measuring point selected as a candidate for the distance measuring point of the main subject is determined. The set of distance points is selected as the distance measurement point of the main subject (S48), and the process ends.

In step S47, the set of distance measuring points is 2
If it is determined that there is more than one set, a set whose distance difference between the previous time and the present distance difference is equal to or smaller than the threshold value ΔL2 is selected as the distance measuring point of the main subject (S49). Details of the processing performed in step S49 will be described with reference to FIG. In the previous processing, the object distances of the set of distance measurement points selected as the distance measurement points of the main object are set to La0 and Lb0. Where La
0 ≦ Lb0, the value of (Lb0−La0) is called “distance difference reference value”, and described as ΔL0. Next, the upper limit is (ΔL0 + ΔL2) and the lower limit is (ΔL0−ΔL2).
Is equally divided into N regions, and each of the N regions after the division is referred to as a “distance difference small region”. Here, N is an integer of 2 or more, and N = 10 in this embodiment. Then, for each set of distance measurement points selected as the distance measurement point candidates of the main subject, the distance difference is calculated, and it is determined which small area includes the distance difference. Next, a set of distance measurement points included in the distance difference small area closest to the reference value of the distance difference is selected as the distance measurement point of the main subject. The initial value of the threshold ΔL2 is given by the following equation. ΔL2 = (previous defocus speed) × Ws2 Here, Ws2 is a predetermined constant.

In steps S39 to S43, there are two sets of distance measuring points selected as candidates for the distance measuring point of the main object, and the respective object distances are (La1, L
The processing performed in step S49 for the cases of b1) and (La2, Lb2) will be specifically described. Here, () means a set of measurement points, and ()
In the table, object distances at two focus detection points are described, and La1 ≦
It is assumed that Lb1 and La2 ≦ Lb2. As a result of calculating the distance difference of the subject distance for each set of ranging points selected as candidates for the ranging point of the main subject, as shown in FIG.
When (b1-La1) is closer to the reference value of the distance difference than (Lb2-La2), a set of ranging points corresponding to (La1, Lb1) is selected as a set of ranging points of the main subject. .

Next, it is determined whether or not there is a set of distance measuring points selected in step S49 (S5).
1). If it is determined in step S51 that there is no selected set of ranging points, a change is made to increase the threshold value ΔL2 (S53), and then the process of step S49 is performed again. If it is determined in step S51 that there is a selected set of ranging points, it is determined whether there are two or more selected pairs of ranging points (S5).
5). In step S55, if there are no more than two pairs of selected ranging points (that is, if there is only one selected pair of ranging points), the process is terminated.

If it is determined in step S55 that there are two or more sets of selected distance measuring points, the set of distance measuring points whose subject distance is smaller (or larger) than the previous object distance is determined. Is selected as the distance measuring point of the main subject (S57). Details of the processing performed in step S57 will be described with reference to FIG. First, the movable region of the main subject (the region whose upper limit is Lmax and whose lower limit is the near distance Lmin) obtained in step S31 is equally divided into M regions, and the divided M regions are referred to as “subject distances”. It is called "small area." The center of the movable area is the subject distance of the previous main subject. Here, M is an integer of 2 or more, and in this embodiment, M = 10. Then, the present subject distance is calculated for each set of the ranging points selected as the candidate of the ranging point of the main subject (for example, the average value of the subject distances of the two ranging points is calculated as the present subject distance). Then, it is determined which small area the subject distance is included in. Next, it is determined whether the main subject is approaching or moving away from the main subject detection device 140 from the previous defocus speed. If you are approaching,
A set of ranging points included in the small subject distance area close to the near side distance Lmin is selected as the ranging point of the main subject. If the subject is moving away, a set of ranging points included in the small subject distance area close to the far side distance Lmax is selected as the ranging point of the main subject.

Here, in step S49, there are two sets of distance measuring points selected as the distance measuring point candidates of the main object, and the object distances are (La1, Lb1),
In the case of (La2, Lb2), step S5
The processing performed in step 7 will be specifically described. Here, () means a set of measurement points, and () describes the subject distance of two ranging points, and it is assumed that La1 ≦ Lb1 and La2 ≦ Lb2. As a result of calculating the subject distance for each set of ranging points selected as candidates for the ranging point of the main subject, as shown in FIG. 8, (Lb1 + La1) / 2
Is closer distance Lmin than (Lb2 + La2) / 2
Is included in the small subject distance area close to. Therefore, when the main subject is approaching the main subject detection device 140, the set of ranging points corresponding to (La1, Lb1) is selected as the set of ranging points of the main subject, and the main subject is detected as the main subject. When moving away from the device 140, (La2,
The set of ranging points corresponding to Lb2) is selected as the set of ranging points of the main subject.

Next, it is determined whether or not the set selected in step S57 exists (S59). If it is determined in step S59 that there is no selected set, the set selected in step S49 is selected (S61), and the process proceeds to step S65. If it is determined in step S59 that there is a selected pair, it is determined whether there are two or more selected pairs (S6).
3). In step S63, if there are no more than two pairs of selected ranging points (that is, if there is only one selected pair of ranging points), the process ends.

In step S63, if there are two or more sets of the selected distance measuring points, a set near the center of the distance measuring range is selected as the distance measuring point of the main subject (S65). Details of the processing performed in step S63 will be described with reference to FIGS. As shown in FIG. 4, a number representing a row and a column is given in the form of (i, j) for each CCD sensor CS which is a distance measuring point. Here, i is a row number and j is a column number. Further, as shown in FIG. 9, a weighting coefficient Z (i,
j) is given. Here, the weighting coefficient Z (i,
j) is assigned a larger value as it is closer to the center of the photographing screen PA. For example, as shown in FIG. 9, “10” is assigned as the value of the weighting coefficient Z to the CCD sensor CS closest to the center of the shooting screen PA.
“6” is assigned to the CCD sensor CS at the position (2, 5) as the value of the weighting coefficient Z. That is, Z (3,3) = 10 and Z (2,5) = 6.

First, the present subject distance is calculated for each set of ranging points selected as candidates for the ranging point of the main subject (for example, the smaller one of the ranging distances of the two ranging points) Is calculated as the current subject distance), and then it is determined whether the main subject is approaching or moving away from the main subject detection device 140 from the previous defocus speed. When approaching, (subject distance) ÷
The set of ranging points having the smallest value of (weighting coefficient of ranging points) is selected as the ranging point of the main subject. When moving away, (subject distance) x (weighting coefficient of distance measurement point)
Are selected as the ranging points of the main subject. In other words, when approaching, a set of distance measurement points having a small object distance (the object is close to the main object detection device 140) and close to the center of the shooting screen PA is selected as the distance measurement point of the main object, and moves away. If there is, a set of distance measurement points having a large object distance (the object is far from the main object detection device 140) and close to the center of the shooting screen PA is selected as the distance measurement point of the main object.

Next, a method of calculating the defocus speed performed in step S11 of FIG. 5 will be described. As will be described later, the defocus speed is divided into cases depending on conditions such as whether or not the current subject is a low contrast, for example, the previous defocus speed, the current defocus amount, the previous defocus amount, It is calculated using the defocus amount corresponding to the lens driving amount driven during that time and the time required from the previous distance measurement to the current distance measurement. When calculating the defocus speed using the defocus amount obtained by the distance measurement during film winding, since the exposure period is included between the current distance measurement and the previous distance measurement, the previous The distance between the distance and the current distance measurement is a sufficiently long time. In the case where distance measurement is performed only during film winding, such as during continuous shooting, a time delay due to calculation becomes large if the defocus amount used two times before is used. When calculating the defocus speed using the defocus amount obtained by the distance measurement during film winding, the calculation is performed using the current and previous defocus amounts.

Next, the method of calculating the defocus speed shown in step S11 of FIG. 5 with reference to FIG.
This will be described more specifically. First, the distance measurement counter AFC
It is determined whether NT is smaller than 1 (S10).
1). If the distance measurement has been performed once or more, it is determined in step S103 whether the distance measurement was performed during the film winding. If it is determined in step S103 that distance measurement has not been performed during film winding, it is determined whether the distance measurement counter AFCNT is smaller than 3 (S105). When the number-of-distance-measuring counter AFCNT is 3 or more and when it is determined in S103 that ranging has been performed during film winding, it is determined whether or not the current subject is a low contrast (S107).

It is determined that the current time is not low contrast (S107).
N), when it was previously determined that the low contrast was not performed two times before (when both S109 and S111 are N), the processing A described later is performed (S113). Step S
In 107 and S109, when the low contrast is neither the last time nor the previous time, and the low contrast is obtained only two times before (Y in S111).
Is determined whether or not distance measurement was performed during film winding (S115). If it was determined that distance measurement was performed during film winding (Y in S115), processing A
Is performed, and when it is determined that the distance measurement was not performed during the film winding (N in S115), the process B is performed (S117). In step S107, it is determined that the low contrast is not performed this time. However, when the low contrast is performed last time (Y in S109), it is determined whether the low contrast was performed two times before (S119). If it is determined in step S119 that the low contrast has not been performed previously (N in S119), the process A is performed (S121). If it is determined that the previous low contrast has been performed (Y in S119), the process B is performed. (S123).

If it is low contrast this time in step S107 (Y in S107), it is determined whether or not the previous time was low contrast (S125). When it was determined that the previous time was the low contrast (Y in S125), the distance measurement counter A
Both FCNT and defocus speed Vdf are set to 0 (S129). If it is determined in step S125 that the low contrast has not been performed previously (N), processing B is performed (S127). If the distance measurement has never been performed, or if the distance measurement has not been performed twice or more and the distance measurement has not been performed during film winding (Y in S101 or Y in S105), the defocus speed Vdf. Is set to 0 (S131), and the process ends.

Next, the processing A and the processing B described in FIG. 10 will be described with reference to FIG. FIG. 11A shows process A.
Is a flowchart showing the flow of (B), and FIG.
6 is a flowchart showing the processing of FIG. Referring to (A), in process A, it is first determined whether or not it was the previous low contrast, and if it was not the previous low contrast (N in S131) and it was determined that the distance was not measured while the film was being wound (N in S113). ), The defocus speed Vdf is expressed by the following equation. Vdf = (DF3-DF1 + errdf1 + errdf
2) / (dt1 + dt2) If it is determined in step S133 that the distance is being measured while the film is being wound, the defocus speed is obtained by the following equation (S137). Vdf = (DF3−DF2 + errdf2) / dt2 When it is determined in step S131 that the low contrast has been performed last time and it is determined that the distance measurement is not being performed while the film is being wound (N in S139), the defocus speed Vdf.
Is obtained by the following equation (S141). Vdf = (DF3-DF1 + errdf1 + errdf
2 + errrdS) / (dt1 + dt2 + dtS) When it is determined that the distance is being measured while the film is being wound (S
139, Y), the defocus speed Vdf is expressed by the following equation (S143). Vdf = (DF3-DF2 + errdf2 + errdf
S) / (dt2 + dtS) After the defocus speed is obtained as described above, in any case, the previous low contrast flag is cleared (S145).

Here, dt2 indicates the current distance measurement interval, dt1 indicates the previous distance measurement interval, and dtS indicates the stored distance measurement interval. DF3 indicates the current defocus amount, DF2 indicates the previous defocus amount, and DF1 indicates the previous defocus amount. Further, errdf2 is the defocus amount due to the current driving of the lens, and errdf1 is the defocus amount due to the previous driving of the lens.
S is the stored driven defocus amount.
Vdf represents the defocus speed.

Next, the processing B will be described. In the process B, the current distance measurement interval dt2 is substituted for the stored distance measurement interval dtS, and the defocus amount errdf2 due to the current driving of the lens is stored in the stored driven defocus amount errdfS. (S1
47), the process ends.

FIG. 12 is a detailed flowchart of the calculation of the moving body correction drive amount performed in step S15 of FIG. First, the moving object correction coefficient Vhosei is calculated using the following equation (S201). Vhosei = K1 × Vdf + K2 × Vdf × Vdf where Vdf is the defocus speed, and K1 and K
2 is a constant.

Next, (moving object correction coefficient Vhosei) ×
The moving body correction drive amount H corresponding to (the previous distance measurement interval dt1)
1 is calculated (S203). Here, "the distance measurement interval T1 at the time of driving the lens" should be used instead of "the distance measurement interval dt1 at the previous time". Is unknown, so the “last distance measurement interval dt1” is used for convenience. Next, a moving body correction drive amount H2 corresponding to the current defocus amount DF3 is calculated (S205). And
The moving body correction drive amount H3 from the last distance measurement to the present is calculated (S207). Thereafter, the moving body correction drive amount H is calculated using the following equation. (Moving body correction driving amount) = H1 + H2-H3 FIG. 13 shows a lens using the movement of the main subject and the moving body correction driving amount described with reference to FIG. FIG. 9 is a diagram showing the movement of the lens when the lens is driven. Distance measurement performed at the timing of A, B
At the timing (3), processing such as discrimination of the main subject is performed, the lens driving amount is calculated, and the result is that the lens is actually driven from the timing C (current). Here, “I” on the horizontal axis is the time of the distance measurement process by the distance measurement unit 142,
“D” is the time of the process of storing the subject distance in the subject distance storage unit 143, and “Process” is the main subject determination unit 144.
Processing of the main subject by the defocus speed calculation unit 3
3 shows the time required for the defocus speed calculation process by the moving object correction amount calculating unit 304, the moving object correction amount calculation process by the moving object correction amount calculation unit 304, and the lens drive amount calculation process by the lens drive amount calculation unit 305. The moving body correction drive amount H described with reference to FIG.
1, H2, H3 and H are shown in the figure. FIG.
0 and the current distance measurement interval dt described with reference to FIG.
2, previous distance measurement interval dt1, current defocus amount DF
3, the previous defocus amount DF2, the previous defocus amount DF1, the defocus amount errdf2 due to the current driving of the lens, and the defocus amount errdf1 due to the previous driving of the lens are shown in the figure.

The present invention can take the following forms. (A) In this embodiment, the case where the phase difference detection method is used as the distance measurement method has been described. However, a form other than the phase difference detection method, for example, a triangulation method, an ultrasonic method, or the like may be applied. (B) In the present embodiment, the case where the number of distance measuring points is 25 has been described, but it is sufficient if the number of distance measuring points is three or more. The smaller the number of ranging points, the easier the process.
On the other hand, as the number of ranging points increases, the accuracy of determining the main subject improves. (C) In the present embodiment, the case where the distance measurement points are arranged in a lattice shape has been described. However, an arrangement other than the lattice shape, for example, a radial arrangement centering on the center of the distance measurement range may be performed. . Since the accuracy of determining the main subject changes depending on the arrangement of the ranging points, based on the main subject determining method,
It is necessary to consider the arrangement of ranging points. (D) In the present embodiment, in the main subject discriminating process, it is determined whether the main subject is moving away or approaching. If the main subject is moving away, a subject having a large subject distance is regarded as the main subject. When the main subject is approaching, the moving range of the main subject is determined by dividing the movable range of the main subject into a plurality in the process of determining the subject with a small subject distance as the main subject, but the main subject is far away Determines the subject with the smallest subject distance as the main subject,
When the main subject is approaching, the subject having the largest subject distance may be determined as the main subject. In this case, the subsequent processing is unnecessary, the processing is simplified, and the processing speed is improved. (E) In the present embodiment, in the main subject discriminating process, it is determined whether the main subject is moving away or approaching. If the main subject is moving away, the subject distance is large and the distance measurement range is not determined. The subject close to the center is determined as the main subject, and when the main subject is approaching, the subject whose subject distance is small and close to the center of the ranging range is determined to be the main subject. A form in which a close subject is determined to be the main subject may be used. In this case, the processing is simplified and the processing speed is improved. (F) In the present embodiment, the determination of the subject distance and the determination of the degree of separation from the center of the distance measurement range are both used in the determination processing of the main subject, but only one of the processes is used. May be used. In this case, the processing is simplified, and the processing speed is improved.

[0052]

According to the first aspect of the present invention, the main subject is determined by using a plurality of measurement results of three or more distance measuring points, so that the main subject can be accurately determined. According to the second aspect of the present invention, since the main subject is determined only at the distance measuring points having the subject distance within the movable area of the main subject, the processing time of the main subject determination is reduced, and The accuracy of determining the main subject is improved.

According to the third aspect of the present invention, since the main subject is often in a position and a size at which the subject distance can be measured simultaneously by a plurality of ranging points, the difference between the latest distance and the previous distance is different. By determining that the subject to be measured at the ranging point that substantially matches with the subject is the main subject,
The main subject is accurately determined. In particular, when the main subject is a moving object, the main subject is more accurately determined. According to the fourth aspect of the invention, when the main subject is moving away, the subject with the largest subject distance is determined to be the main subject, and when the main subject is approaching, the subject with the smallest subject distance is determined as the main subject. Since the subject is determined to be a subject, a subject frequently desired by the photographer is determined to be the main subject.

According to the fifth aspect of the present invention, the subject closest to the center of the distance measurement range is determined as the main subject.
The subject closest to the center of the distance measurement range frequently desired by the photographer is determined as the main subject. According to the sixth aspect of the present invention, when the main subject is far away, a subject having a large subject distance and close to the center of the distance measurement range is determined as the main subject, and when the main subject is approaching, the subject is determined. Since a subject whose distance is small and which is close to the center of the distance measurement range is determined to be the main subject, a subject that is frequently requested by the photographer is determined to be the main subject.

According to the seventh aspect of the present invention, the main subject is accurately determined by the main subject detection device, and the subject distance of the main subject at the exposure timing is accurately calculated by the distance calculating means. The position of the photographing optical system is adjusted based on the subject distance of the main subject in, so that the photographing focused on the main subject desired by the photographer can be easily performed.

[Brief description of the drawings]

FIG. 1 is a configuration example of an autofocus single-lens reflex camera to which the main subject detection device of the present invention is applied.

FIG. 2 is a main subject detection device and an automatic focus CPU of the present invention.
FIG. 4 is a functional configuration diagram of a main part of an automatic focusing unit.

FIG. 3 is a diagram for explaining the principle of a method of measuring a subject distance performed by a distance measuring unit.

FIG. 4 is an example of an arrangement diagram of a CCD sensor for measuring a subject distance.

FIG. 5 is a main subject detection device and an automatic focus CPU of the present invention.
4 is a flowchart for explaining the operation of the automatic focusing unit.

FIG. 6 is an example of a flowchart of a main subject determination process.

FIG. 7 is an explanatory diagram for describing a part of a main subject discrimination process.

FIG. 8 is an explanatory diagram for describing a part of a main subject discrimination process.

FIG. 9 is an explanatory diagram for describing a part of a main subject determination process.

FIG. 10 is a flowchart illustrating a part of a defocus speed calculation process.

FIG. 11 is a flowchart illustrating a part of a defocus speed calculation process.

FIG. 12 is a detailed flowchart of calculating a moving body correction drive amount.

FIG. 13 is a diagram showing the movement of the main subject and the movement of the lens when the lens is driven.

FIG. 14 is a side view when a car approaches the camera body.

FIGS. 15A and 15B are explanatory diagrams of a state in which the subject distance of the vehicle is measured by 25 ranging points, where FIG. 15A shows a state at the time of the last ranging, and FIG. 15B shows a state at the time of the latest ranging. Is shown.

[Explanation of symbols]

2 Subject 100 Camera body 140 Main subject detection device 141 Distance measurement control unit (distance measurement control unit) 142 Distance measurement unit (distance measurement unit) 143 Subject distance storage unit (subject distance storage unit) 144 Main subject determination unit (main subject determination) Means) 160 Autofocus drive unit 201 Imaging optical system 202 Lens barrel 203 Lens driving mechanism (Lens position changing means) 303 Defocus speed calculating section (Lens position changing means) 304 Moving object correction driving amount calculating section (Lens position changing means) 305 Lens drive amount calculation unit (lens position changing means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H04N 101: 00 G02B 7/11 N G03B 3/00 A F term (Reference) 2F112 AC03 CA03 CA02 CA12 FA03 FA21 FA29 FA45 2H011 AA01 AA03 BA01 BA23 BA41 BB04 2H051 AA01 AA08 BA04 BA17 BB01 BB30 CB03 CB08 CB20 CD01 CD30 CE23 CE27 DA07 DA08 DA11 DA31 DD00 DD14 EA09 5C022 AA13 AB27 AC54 AC69

Claims (7)

[Claims] 1. A distance measuring means having three or more distance measuring points and measuring a subject distance for each distance measuring point, and a measuring means for causing the distance measuring means to perform a plurality of distance measuring operations at a predetermined timing. Distance control means, subject distance storage means for storing the subject distance,
A main subject determining device that determines a main subject using the subject distance, wherein the main subject determining device determines a main subject using the subject distance a plurality of times. Main subject detection device. 2. The main subject detection device according to claim 1, wherein the main subject determination unit determines the main subject only at a distance measuring point including a subject distance in a movable area of the main subject. apparatus. 3. The main subject discriminating means calculates a latest distance difference which is a distance difference between a latest subject distance and a latest subject distance of another ranging point for each of the ranging points, and For each point, a previous distance difference that is a distance difference between the previous subject distance and the previous subject distance of another ranging point is calculated, and a distance measuring point at which the latest distance difference substantially matches the previous distance difference is calculated. 3. The main subject detection device according to claim 1, wherein the subject to be measured is determined to be a main subject. 4. The main subject discriminating means, when there are a plurality of subjects whose distance measuring points at which the latest distance difference and the previous distance difference substantially coincide with each other are subjects whose subject distance is to be measured,
It is determined whether the main subject is moving away or approaching.If the main subject is moving away, a subject with a large subject distance is determined to be the main subject. The main subject detecting device according to claim 3, wherein the main subject is determined to be a main subject. 5. The main subject discriminating means, when there are a plurality of subjects whose distance measuring points at which the latest distance difference and the previous distance difference substantially coincide with each other are subjects whose subject distance is to be measured,
The main subject detection device according to claim 3 or 4, wherein a subject near the center of the distance measurement range is determined as a main subject. 6. The main subject discriminating means, when there are a plurality of subjects whose distance measuring points at which the latest distance difference and the previous distance difference substantially coincide with each other are subject to measuring the subject distance,
It is determined whether the main subject is moving away or approaching. If the main subject is moving away, a subject having a large subject distance and close to the center of the distance measurement range is determined to be the main subject, and the main subject is approaching. 4. The main subject detecting device according to claim 3, wherein a subject having a small subject distance and close to the center of the distance measurement range is determined as a main subject. 7. A main subject detecting device according to claim 1, a photographing optical system, and a position of the photographing optical system based on a subject distance of the main subject determined by the main subject detecting device. An automatic focus camera comprising: a lens position changing unit that adjusts a distance.