JP2002131624A - Multipoint automatic focusing camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome the problem of a prior art such that processing time gets long because a user does not know what range-finding point is prioritized to perform range-finding when an object is a moving body in a multipoint automatic focusing camera depending on the conventional technique. SOLUTION: This multipoint automatic focusing camera is equipped with an image moving arithmetic calculation part 3 calculating the moving speed and the moving direction of the moving object, a range-finding area selection part 4 selecting a range-finding area based on the maximum value and the minimum value of a moving amount and a posture detection part 43. By detecting the posture of the camera in the case of bringing the moving object into focus and shifting the range-finding area suitably in a lateral direction and in a longitudinal direction, the range-finding area along the posture of the camera is selected and the position of a subject image is detected, then estimation control is realized to perform accurate focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a focus detection device, and more particularly, to a multipoint autofocus camera equipped with a plurality of ranging points.

[0002]

2. Description of the Related Art Conventionally, many techniques for a camera having a plurality of distance measuring points have been proposed. For example, there are many cameras that perform multi-point ranging of five points obtained by adding the center part of the screen and three points on the left and right thereof and two points above and below the center, but recently, a so-called multi Focus cameras have been commercialized, and the number of ranging points tends to increase. In the future, the ranging points may be arranged on almost the entire screen. When shooting a moving subject with such a multipoint autofocus camera,
It is common to select an area in which the subject is determined to be moving as a distance measuring point, and a conventional technique in which a moving subject is photographed by a multipoint autofocus camera is known. For example, Japanese Patent Application Laid-Open No. Hei 8-29670 discloses a technique in which when a moving object cannot be predicted at a previously selected ranging point, a ranging point in the vicinity thereof is selected.

[0003]

The technique disclosed in Japanese Patent Application Laid-Open No. Hei 8-29670 for photographing a moving subject has the following problems. There is no problem if the number of ranging points is small, for example, three points. However, if the number of ranging points becomes extremely large, the number of "neighboring ranging points" increases. There is a problem that the processing time is long because it is not known whether it is enough, and no solution is suggested. Normally, when a photograph is statistically viewed, in the case of a moving subject, there are far more subjects moving in the horizontal direction than subjects running in the vertical direction. In other words, if the moving object cannot be predicted at the previously selected ranging point, the time lag is shortened if the left and right ranging points are measured more preferentially than the upper and lower ranging points.

FIG. 17A is an example of a photograph when a scene in which a train is curving a curve is taken.
(B) is a diagram showing an arrangement of distance measuring points. In an embodiment described later, an example of 25-point distance measuring is shown, but here, an example of 15-point distance measuring will be described for easy understanding. . A ~
The H line indicates the correspondence between the ranging points in the figures so that the correspondence between the ranging points is easy to understand in both figures. For example, the center ranging point P3 is located at the intersection of B and D, and the surrounding ranging points P15 are between C and H. Located at the intersection. Here, the line B at the center side will be described as an example.

In the previous distance measurement, the moving object was detected at the distance measuring point P3 and the moving object prediction distance measurement was performed.
3, when no moving object is detected, in the case of the above-described prior art, the surrounding distance measuring points P2, P4, P7, P12, and P8.
• Distance measurement is performed at P13, P9, and P14, but since there are many subjects that move sideways, the distance measurement point P2 or P
If the distance is measured preferentially, the time lag is reduced. FIG.
Has been described in the case of the horizontal position.
P8 or P13 can be preferentially measured. In this case, a switch for detecting the posture of the camera may be used.

Accordingly, the present invention provides a multi-point automatic camera which can focus on a proper subject position by shortening a time lag when a moving object is detected when a moving subject is photographed by a camera having a plurality of distance measuring points. It is intended to provide a focus camera.

[0007]

In order to achieve the above object, the present invention provides a multi-point automatic focus camera having a plurality of two-dimensionally arranged focus detection areas. And a focus detection area determining means for designating an area to be performed in a predetermined order. When focus detection is performed on a moving subject, the focus detection area determining means determines a vertical direction of the plurality of focus detection areas. The present invention provides a multi-point automatic focus camera that designates a focus detection area arranged in a lateral direction with priority over a focus detection area arranged in a multi-point automatic focus camera.

Further, in a multi-point automatic focus camera having a plurality of focus detection areas in a two-dimensional arrangement, a focus detection area determining means for designating, in a predetermined order, an area in which focus detection calculation is to be performed from the plurality of focus detection areas. And a posture detection unit that detects whether the camera is held in a horizontal position or a vertical position, and when performing focus detection on a moving subject, the focus detection area determination unit includes Provided is a multi-point auto-focus camera that designates a focus detection area arranged in a horizontal direction with respect to a direction in which a camera is held based on an output of a posture detection unit in preference to a vertical direction.

In the multi-point automatic focus camera having the above-described configuration, the order in which the regions for performing the focus detection calculation are selected from the plurality of focus detection regions by the focus detection region determining means is designated by the focus detection region arranged in the vertical direction. This is performed with priority given to the focus detection area arranged in the lateral direction over the area. At this time, the orientation of the camera is detected by the orientation detection unit, and the ranging area is shifted so as to be suitable in the horizontal and vertical directions of the camera, so that the selection of the ranging area according to the orientation of the camera can be performed. Will be implemented.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a conceptual block configuration of a distance measuring apparatus for a multipoint autofocus camera according to the present invention. The multi-point autofocus camera includes an AF sensor that outputs a focus detection signal, for example, a focus detection unit 1 including an area sensor, and a focus calculation unit 2 that performs calculations necessary for focus adjustment based on the output focus detection signal. An image movement amount calculator 3 for calculating an amount related to the image movement of the subject based on the calculation result from the focus calculator 2, and a plurality of ranging areas based on the output of the image movement amount calculator 3. A focus detection area selection unit 4 for selecting which focus detection area to focus on, a focus control unit 5 including a CPU for controlling focus of these components, and control from the focus control unit 5 A focus adjusting unit 6 drives a photographic lens (not shown) to a focused position based on a signal to achieve a focused state. The moving amount of the subject calculated by the image moving amount calculating unit 3 may be a moving speed of the subject or a moving direction of the subject.

FIG. 2 is a sectional view of a configuration example applied to a single-lens reflex camera as a multipoint autofocus camera according to the present invention. This camera includes a focus detection unit 11 for detecting a focus at a lower portion of a camera body 10. Normally, the light flux (subject image) that has passed through the photographing lens 12
Is a viewfinder 1 partially above by the main mirror 13.
The light is reflected to the fourth side, and the remaining light flux is transmitted and travels straight. The light beam reflected by the main mirror 13 is guided to a finder 14 via a pentaprism, and enters a viewer's eye as a photographing screen. On the other hand, the light beam transmitted through the main mirror 13 is reflected downward by the sub-mirror 15 integrally attached to the main mirror 13 and guided to the focus detection unit 11.

The focus detecting unit 11 includes a field mask 17 for narrowing a light beam passing through the photographing lens 12, an infrared cut filter 18 for cutting infrared light components, a condenser lens 19 for collecting the light beam, Total reflection mirror 20 for total reflection, and pupil mask 21 for restricting the amount of light beam passing
A re-imaging lens 22 for re-imaging a light beam on a photoelectric conversion element group 26 on an area sensor 23, and a photoelectric conversion element group 2
6 and an area sensor 23 comprising the processing circuit. At the time of photographing with such a camera, the main mirror 13 and the sub-mirror 15 are raised to the position indicated by the dotted line and retracted, the shutter 24 is opened for a predetermined time, and the light flux (subject image) passing through the photographing lens
5 is exposed.

FIGS. 3A and 3B schematically show an optical system including distance measurement. FIG. 3A illustrates the focus detection unit 11.
1 shows a configuration of a focus detection optical system (a phase difference detection optical system) that guides a light beam (subject image) onto a photoelectric conversion element group 26 of an area sensor 23 in FIG. I have. This focus detection optical system includes a photographing lens 12, a field mask 17 for defining a field range, a condenser lens 19, and apertures 21a, 21a arranged substantially symmetrically with respect to the optical axis of the photographing lens 12 in the optical path. And a pupil mask 21 having an opening 21b.
The re-imaging lenses 22a and 22b are respectively provided at the rear corresponding to. In FIG. 3A, the above-described total reflection mirror 20 is omitted.

In such a configuration, the taking lens 12
Of the subject that has passed through the areas Ha and Hb of the exit pupil H of the field mask 17 and the condenser lens 1
9. The photoelectric conversion of two areas 23a and 23b in which a large number of photoelectric conversion elements are arranged in the area sensor 23 while passing through the openings 21a and 21b of the pupil mask 21 and the re-imaging lenses 22a and 22b, respectively. The image is re-imaged on the element group 26. For example, if the taking lens 12 is “focused”, that is,
When the subject image 1 is formed thereon, the subject image 1
Condenser lens 19 and re-imaging lenses 22a, 22b
As a result, the image is re-imaged on the photoelectric conversion element group 26 of the area sensor 23, which is a secondary image plane perpendicular to the optical axis O, and becomes a first image I1 and a second image I2 as shown in the figure. .

Further, when the photographing lens 12 is a "front focus",
When the subject image F is formed in front of the imaging plane G, the subject images F are re-imaged perpendicularly to the optical axis O in a form closer to the optical axis O, and the first images F1, Second image F2
Becomes Further, the photographing lens 12 is shifted to the rear focus, that is, the image plane G
The subject image R is formed behind the subject image R
Are re-imaged perpendicularly to the optical axis O in a form away from the optical axis O by each other to become a first image R1 and a second image R2. Accordingly, by detecting and measuring the distance between the first image and the second image, the in-focus state of the photographing lens 12 can be detected including the front focus and the rear focus. Specifically, the light intensity distribution of the first image and the second image is
The distance between the two images can be measured by obtaining the subject image data corresponding to 3 (openings 23a and 23b).

FIG. 4 shows functional blocks including the electric control system of the camera described in FIG. 2, and the detailed configuration and operation of each unit will be described. In this configuration, the control unit 30 performs overall control of the entire camera,
An arithmetic / processing unit 31 including, for example, a CPU is provided therein.
, ROM 32, RAM 33, A / D converter 3
4 is provided.

The control unit 30 controls a series of operations of the camera according to a camera sequence program (described in detail later) stored in the ROM 32. EEPROM35
Can store and hold correction data relating to AF control, photometry, etc., as information unique to each camera body. Further, the control unit 30 includes an area sensor 23, a lens driving unit 33, an encoder 37, a photometry unit 39, a shutter driving unit 40, an aperture driving unit 41, and a film driving unit 42.
Are connected to the control unit 30 so as to be able to communicate with each other.

In such a configuration, the lens driving unit 3
6 drives the focusing lens 12a of the taking lens 12 with the motor ML38 based on the control of the control unit 30. At this time, the encoder 37 generates a pulse corresponding to the moving amount of the focusing lens 12a, and
And the lens drive is appropriately controlled. The photometer 39
Has an SPD (silicon photodiode) corresponding to the shooting area, and generates an output according to the luminance of the subject. The control unit 30 converts the photometric result of the photometric unit 39 into a digital signal by the A / D converter 34 and stores the photometric value in the RAM 33. The shutter drive unit 40 and the aperture drive unit 41 operate according to predetermined control signals from the control unit 30, and drive a shutter mechanism and an aperture mechanism (not shown) to expose the film surface. Film drive unit 4
Reference numeral 2 denotes an automatic loading, winding and rewinding operation of the film according to a predetermined control signal from the control unit 30. A first release switch (hereinafter, referred to as 1RSW) and a second release switch (hereinafter, referred to as 2RSW) are switches interlocked with a release button.
SW is turned on, and then 2R is pressed by the second stage pressing operation.
SW turns on. The control unit 30 appropriately controls each part such that photometry and AF (automatic focus adjustment) processing is performed when 1RSW is turned on, and exposure operation and film winding operation are performed when 2RSW is turned on. The posture difference detection unit 43 is a switch that detects whether the camera is held in a horizontal position or a vertical position. For example, there is a switch using mercury.

FIG. 5 shows a specific circuit configuration of the area sensor 23 described above. The pixel portion (that is, the photoelectric conversion element group 26) of the area sensor 23 is composed of a large number of pixel units 51 arranged regularly in a matrix. In this configuration, the accumulation control unit 52 controls the accumulation operation of the pixel unit according to a control signal from the control unit 30. The output V0 of each pixel unit 51 is selected by a vertical shift register 53 and a horizontal shift register 54 and input to a buffer 55. Then, the output SDATA of the buffer 55 is input to the A / D converter 34 in the control unit 30 and A / D converted.

The output VM of each pixel unit 51 is connected to the output VM of a predetermined plurality of pixel units 51 and is input to the buffer 55 via the switches MSL1 to MSLn. Then, in the distance measurement area 56, the potential of the point M to which the outputs VMn of the plurality of pixel units 51 are connected generates a potential corresponding to the peak value of the output VMn in the plurality of pixel units 51. Unit 51 is
A peak detection circuit that outputs these is configured. Therefore, when the switches MSL <b> 1 to MSLn are sequentially turned on, the potential corresponding to the peak value in each ranging area 56 can be monitored via the buffer 55.
The output VP of the buffer 55 is input to the A / D converter 34 in the control unit 30 from the terminal MDATA,
D conversion is performed.

FIG. 6 shows the pixel unit 51 described above.
Is shown below. This pixel unit 51
It comprises a photodiode 61 functioning as a photoelectric conversion element, a capacitor 62, an amplifier 63, switches 64 and 65, and an NMOS transistor 66. An amplifier 63 is connected to an output side of the photodiode 61, and a capacitor 62 is connected to an input / output terminal of the amplifier 63, and accumulates charges generated by the photodiode 61.

The output side of the amplifier 63 receives the signal X from the vertical shift register 53 and the horizontal shift register 54.
n and Yn are connected to an output terminal (output V0) via switches 64 and 65 connected in series for switching on and off, respectively. Further, the output side of the amplifier 63 is connected to the gate of an NMOS transistor 66 whose drain is connected to a fixed voltage, and the source of the NMOS transistor is connected to a monitor output terminal (monitor output VM).

In such a circuit configuration, the amplifier 63
Is changed in a direction in which the potential increases as the storage amount of the capacitor 62 increases. Since the outputs of the plurality of pixel units 51 are connected to each other in the monitor output VM, a potential indicating the peak value of the accumulated amount is generated. In this way, each pixel unit 51 performs photoelectric conversion and supplies an output as an element corresponding to the distance measurement area to the above-described image movement amount calculation unit 3.

Next, FIG. 7 shows an example of the arrangement of each of the distance measurement areas P1 to Pn constituting the focus detection area in the photographing screen. The above-described switches MSL1 to MSLn are connected to each of the distance measurement areas P
1 to Pn, respectively, for example, when one switch MSLm of the switches MSL1 to MSLn is turned on, the corresponding distance measurement area Pm
Is selected and the monitor terminal MDATA is selected.
Output to Further, for example, when a plurality of switches are turned on, peak values in the plurality of ranging areas can be monitored. For example, when all the switches MSL1 to MSLn are turned on, the peak value in the entire distance measurement area of the area sensor 23 can be output from the MDATA terminal and monitored.

The accumulation operation of the area sensor 23 will be described with reference to a time chart shown in FIG.
Here, a description will be given by taking the distance measurement areas P5, P6, and P7 in the shooting screen as an example. The control unit 30 controls the area sensor 23
After the accumulation operation is started by the accumulation start signal (INTS), the peak value is sequentially referred to for each of the distance measurement areas. At this time, priority is given to the ranging area that reaches the appropriate accumulation level the fastest, and when the peak value of the ranging area reaches the appropriate accumulation level, the accumulation end signal (INTE)
To terminate the accumulation operation for each ranging area.

That is, as shown in FIGS. 9 (a) and 9 (b), two area sensors 23 constituting an area sensor are provided.
The accumulation operation ends simultaneously for the distance measurement areas corresponding to a and 23b, for example, a5 and b5 corresponding to the distance measurement area P5. That is, accumulation operations of am, bm, (1 ≦ m ≦ n) corresponding to a certain ranging area are sequentially performed on all ranging areas. 10A and 10B linearly show the arrangement of the photodiodes 61 corresponding to one of the distance measurement areas m of am and bm.

The photodiode row am forming the right area sensor 23a has L (1), L (2), L (3),.
L (64), and the subject image signals are sequentially processed. Similarly, the photodiode array bm forming the left area sensor 23b has R (1), R (2), R (3),.
R (64), and the subject image signal is sequentially processed. Therefore, the control unit 30 controls each unit as follows to detect the subject image as data. That is, the control unit 3
When the read clock CLK is input to the area sensor 23, sensor data as a subject image signal is sequentially output from the terminal SDATA of the area sensor 23.
Therefore, the A / D converter 34 in the control unit 30
The sensor data is A / D converted and sequentially stored in the RAM 32. In this way, the control unit 30 can specify, for example, a certain ranging area and read out only the sensor data corresponding to the ranging area.

Next, the AF detection calculation based on the subject image data obtained as described above will be described. For example, in this embodiment, there is a method of performing two types of correlation calculations. One of the methods is a method in which a correlation operation is performed between the first subject image and the second subject image divided by the focus detection optical system, and a shift amount between the two images (referred to as “image shift amount”) is obtained. . The other method is a method in which a correlation operation is performed between the subject image at time t0 and the subject image at time t1 to obtain the movement amount of the subject image. (I) Correlation calculation for obtaining image shift amount: First, first
A description will be given of the correlation calculation for obtaining the image shift amount between the subject image and the second subject image. The subject image data is generally expressed by L for a pair of area sensors 23a and 23b.
(I, j) and R (i, j).

In the following description, for the sake of simplicity, a pair of ranging areas corresponding to the area sensors 23a and 23b, that is, one-dimensional subject image data are respectively represented by L (I) and R (I) (I = 1 to 1). k) (see FIG. 10). Here, in the present embodiment, assuming that k = 64, a description will be given based on the processing procedure relating to the “image shift amount detection” routine with reference to the flowchart shown in FIG.

First, initial values of variables SL, SR and FMIN are set (step S1). Here, S
L ← 5, SR ← 37, FMIN = FMIN 0 are set.

Next, 8 is input as the initial value of the loop variable J (step S2), and the correlation calculation of equation (1) is performed to obtain the correlation value F (s) (step S3). F (s) = Σ | L (SL + I) −R (SR + I) | (1) (where s = SL−SR, I = 0 to 26) where the variables SL and SR are subject image data, respectively. L
A variable indicating the head position of the block for which the correlation operation is performed among (I) and R (I), and a variable J for storing the number of shifts of the block on the subject image data R (I), and The number of data is 27.

Next, the correlation value F (s) is compared with FMIN (initial value FMIN 0 at first, and initial or updated value after the second time) (step S4). In this comparison, if F (s) is smaller (YES), FMIN is changed to F
(S) is updated, and SLM and SRM are updated to SLSR (step S5). On the other hand, according to the comparison in step S4, FMI
If N is smaller than the correlation value F (s) (NO), SR
, J are subtracted from each other to set the next block (step S6). Then, it is determined whether or not J = 0 (step S7). If it is not 0 (NO), the process returns to step S3 to repeat the same correlation calculation. As described above, the block in the object image data L (I) is fixed, and the block in the object image R (I) is shifted by one element at a time to perform the correlation operation.

On the other hand, in the determination in step S7,
If J is 0 (YES), 4 and 3 are added to the variables SL and SR, respectively, and the next block is set (step S8). Next, it is determined whether or not SL = 29 (step S9).
O), the process returns to step S2 to continue the above-described correlation calculation. However, if SL = 29 (YES), the correlation calculation ends. Thus, the subject image data L
A block for performing the correlation operation is set on (I) and R (I), and the correlation operation is repeatedly performed. As a result of the correlation calculation of each block obtained as a result, the correlation value F (s) becomes the minimum at the shift amount s = x where the correlation of the subject image data is the highest. At this time, SL and SR at the time of the minimum correlation value F (x) are stored in SLM and SRM.

Next, the following correlation values FM and FP at shift positions before and after the minimum correlation value F (x) used for calculating a reliability index described later are obtained (step S10).

[0035]

(Equation 1)

Then, a reliability index SK for determining the reliability of the correlation operation is calculated (step S11). This reliability index SK is calculated by adding the sum of the minimum correlation value F (x) and the second smallest correlation value FP (or FM) to a value (FM-F (x) or FP-F (x) corresponding to the contrast of the subject data. ))
This is a numerical value standardized by Equation (4) or Equation (5).

[0037]

(Equation 2)

Next, it is determined whether or not the reliability index SK is equal to or larger than a predetermined value α (step S12). If SK is equal to or larger than α (YES), it is determined that the reliability is low, and the detection impossible flag is set. Set (step S13). On the other hand, if SK is less than α (NO), it is determined that there is reliability, and
The image shift amount ΔZ is calculated (step S14). For example, 3
The minimum value F for continuous correlation using the point interpolation technique
The shift amount x0 that gives MIN = F (x0) is obtained by the following equation.

(Equation 3)

It should be noted that the image shift amount ΔZ can be obtained by the equation (8) using the shift amount x0. ΔZ = x0−ΔZ0 (8) (However, ΔZ0 is an image shift amount during focusing). Further, from the image shift amount ΔZ obtained by the above equation, the defocus amount ΔD of the subject image plane with respect to the expected focal plane can be obtained by the equation (9).

(Equation 4)

The defocus amount is calculated for each of the plurality of ranging areas selected in this way. Then, for example, a defocus amount indicating the shortest distance is selected from a plurality of distance measurement areas. Further, the lens driving amount ΔL is obtained from the selected defocus amount ΔD by using the equation (10).

[0041]

(Equation 5)

By driving the focus lens based on the lens drive amount ΔL, a focused state can be obtained. (II) Principle for predicting subject image position: FIG.
The principle of focus detection for a moving subject shown in (a) to (d) will be described.

Referring to FIG. 12, the relationship between the subject 66, the camera 10, and the area sensor 23 is shown in FIG.
As shown in FIG.
In the case where 6 approaches straight (in the direction of arrow G3), the first and second subject images on the first (L) and second sensors (R) are shifted from time t0 to time by the above-described principle of focus detection. They move outward from each other during t1. In this case, the movement amounts ΔXL and ΔXR of the subject image are equal.

As shown in FIG. 12B, when the subject 66 moves parallel to the camera 10 in the horizontal direction (the direction of arrow G1) perpendicular to the optical axis, the two subject images move in the same direction. I do. In this case, the moving amount ΔXL of the subject image
And ΔXR are equal.

Further, as shown in FIG. 12C, the subject 66 approaches the camera 10 toward the front left (arrow G).
In the case of four directions), the amount of movement of the first subject image (L) toward the outside due to approaching and the amount of movement to the left due to parallel movement to the left are offset, and the amount of movement is reduced.

Similarly, as shown in FIG. 12D, when the subject 66 moves to the rear left toward the camera 10,
The amount of movement of the first subject image (L) inward by moving away from the first object image (L) and the amount of movement leftward by moving in parallel to the left are offset, and the amount of movement is reduced. On the other hand, the amount of movement of the second subject image (R) toward the inside by moving away from it and the amount of movement to the left due to the parallel movement to the left are added to increase the amount of movement.

Here, based on the subject images from the time t0 to the time t1, the moving amounts .DELTA.XL and .DELTA.XR of the first and second subject images are detected by means for performing a correlation operation or the like, which will be described later, and the rightward moving When the sign of + is given, the moving amount of the subject image in the optical axis direction can be obtained by ΔXR−ΔXL, and the moving amount of the lateral subject image can be obtained by ΔXR + ΔXL. Therefore,
The movement amount ΔXR of the subject image from time t0 to time t1,
If ΔXL is obtained, the position of the subject image at time t2 can be predicted.

Assuming that the subject is moving at a constant speed, the moving speed of the subject image in the horizontal direction is constant. still,
The moving speed of the subject image in the optical axis direction is not strictly a constant speed, but may be considered as a constant speed at a minute time interval. Therefore, the predicted position of the first subject image at time t0 is
ΔX shown in Expression (11) from the subject image position at time t1
L 'has moved. That is,

(Equation 6)

Similarly, the predicted position of the second subject image is given by the equation (1)
It moves by ΔXR ′ shown in 2).

[0050]

(Equation 7)

If the image shift amount of the first and second subject images at time t1 is ΔZ, the predicted image shift amount ΔZ 'at time t2 is
Is obtained as in Expression (13).

(Equation 8)

The lens drive amount is obtained based on the predicted image shift amount ΔZ '. By setting the time t2 to the time until the start of exposure, a photograph in focus on a moving subject can be obtained. At this time, ΔXR−Δ
It is determined in advance whether the subject is approaching or moving away based on the sign of XL. If ΔXR−ΔXL> 0, the subject is approaching. Next, the correlation operation for determining the movement of the subject image and the reliability determination thereof will be described. The subject image L ′ at time t0 is described.
(I), R '(I) and the correlation blocks SLM' and SRM 'obtained by the above-described correlation operation between the two images, and the correlation coefficient S
K ′ and the image shift amount ΔZ ′ are RA
It is stored in M42. Thereafter, subject image signals L (I) and R (I) at time t1 are detected.

Next, the movement amount detection will be described with reference to the movement of the subject image shown in FIG. 13 and the flowchart shown in FIG. First, for the first subject image signal, a correlation operation is performed between the subject image signal L '(I) at time t0 and the subject image signal L (I) at time t1. this is,
In the "movement amount detection" routine for detecting the movement of the subject image, first, SLM'-10 is substituted for a variable SL (step S21). A variable J is a variable for counting the correlation range. (Step S
22). Next, the correlation output F is calculated by the correlation equation (14).
(S) is calculated (step S23).

[0054]

(Equation 9)

Subsequently, similarly to the above-described correlation calculation, F
(S) is compared with FMIN (step S24). In this comparison, if F (s) is smaller than FMIN (YES), FMI
F (s) is substituted for N, and SL is stored in SLM (step S25). In this case, the number of elements in the block to be correlated is 27, which is the same as the number of elements in the block when the image shift amount is obtained. However, if F (s) is larger than FMIN (NO), the process moves to the next step S26.

Next, 1 is added to SL, and 1 is subtracted from J (step S26). Then, it is determined whether or not J = 0. If J is not 0 (NO), the process returns to step S23 until J = 0, and the correlation equation F (s) is repeated. As described above, the correlation is obtained by changing the correlation range up to ± 10 elements. The correlation range is determined by the movement amount range to be detected. Here, when J = 0 (YE
S), the reliability is determined. That is, the correlation values FM and FP at the shift amounts before and after the minimum correlation value F (X) are obtained in the same manner as when the image shift amounts of the first and second subject images are obtained.
Is obtained by Expressions (15) and (16) (Step S)
28).

[0057]

(Equation 10)

Next, the reliability index SK is calculated using the above-mentioned equation (4).
And equation (5) (step S29). And
It is determined whether or not SK> β (step S30). When SK ≦ β in this determination (NO), it is determined that there is reliability, and
The movement amount is obtained (step S31). However, the value β is set to a value larger than the determination value α when the image shift amounts of the first and second subject images are obtained. This is because when the subject is moving, the waveform is often deformed, so that there is a high possibility that the correlation is deteriorated. Then, the movement amount ΔXL of the subject image is obtained. Similar to the calculation of the image shift amounts of the first and second subject images, the three-point interpolation method is used to obtain the values by Expressions (17) and (18).

[0059]

[Equation 11]

On the other hand, if it is determined in step S30 that SK> β (YES), it is determined that there is no reliability, and an undetectable flag is set (step S3).
2).

The details of the second subject images R (I) and R '(I) are also omitted, but a similar movement amount detection routine is executed, and the block position SRM and the movement amount ΔX having the highest correlation are executed.
Find R. The movement amounts ΔXL, Δ of the first and second object images
When XR is obtained, the image shift amount ΔZ 'at time t1 is
It is obtained from the image shift amount ΔZ at the time t0 as in Expression (19).

[0062]

(Equation 12)

At time t based on the image shift amount ΔZ at time t0
The prediction formula of the image shift amount ΔZ ″ in Equation (2) is as shown in Expression (20).

[0064]

(Equation 13)

The time t2 is obtained by a method described later, and ΔZ ″
At the time t2 by driving the lens by the amount based on
In, it is possible to focus on a moving subject. Note that the moving speed of the subject image v = (ΔXR−ΔX
If (L) / (t1−t0) is too large, the detection value is considered unreliable, and the image shift amount is not predicted. When the moving speed of the subject image is small and regarded as a detection error, the moving speed is set to zero. (III) Prediction formula of image shift amount prediction time t2: Here, a method of obtaining the time t2 at which the image shift amount is predicted will be described. As described above, at time t2
Is the image shift amount ΔZ at time t1, and the image shift amount ΔZ at time t0.
Is obtained from Equation (20) using the movement amounts .DELTA.XR and .DELTA.XL of the subject image at time t1. Now, a time t2 at which a focused state is obtained at the time of exposure is obtained by Expression (21).

[0066]

[Equation 14]

In this equation, td is the time from the time t1 to the start of lens driving, and this value includes the processing time inside the camera such as the above-described correlation operation time. Here, ke is a conversion coefficient for obtaining a lens driving time proportional to the image shift amount ΔZ ″. The lens driving amount ΔL
Are given by the equations (9) and (10) based on the image shift amount ΔZ ″.
In a region where the image shift amount ΔZ ″ is sufficiently small, the defocus amount ΔD and the lens drive amount ΔL are approximately proportional to the image shift amount ΔZ ″, so there is no problem in accuracy. te is the time from the end of lens driving to the start of exposure after the shutter curtain is opened, and includes the time for camera exposure calculation, aperture control, mirror up, and the like. By solving the equations (20) and (21), the equation (22) for obtaining the predicted image shift amount is derived as follows.

[0068]

(Equation 15)

From this ΔZ ″, equations (9) and (10)
By obtaining the lens drive amount ΔL and driving the lens, the moving subject can be brought into a focused state at the time of exposure. Next, a time t2 at which the lens is brought into focus at the end of driving the lens is obtained by Expression (23). t2 = t1 + td + ke · ΔZ ″ (23) Similarly, by solving the equations (20) and (23), the following equation (24) is derived.

[0070]

(Equation 16)

From this ΔZ ″, equations (9) and (10)
By calculating the lens drive amount ΔL and driving the lens, the moving object can be brought into a focused state at the end of the lens drive.

Next, a specific operation program in this embodiment will be described with reference to the flowchart shown in FIG. Note that the “AF detection” routine is repeatedly executed while the power of the camera is on. First, the integration operation of the area sensor 23 is performed, and when the integration is completed, subject image data (hereinafter, referred to as sensor data) is read from the area sensor 23 (step S41).

Next, it is determined whether or not the object image shift amount (hereinafter, image shift amount) has been detected (step S42). If it is not detected in this determination (NO), the image shift amount is obtained by the above-described "image shift amount detection" routine (see FIG. 11) (step S43). Here, the area sensor 2
An image shift amount is detected for a predetermined distance measuring area set in advance on 3a and 23b. However, the preset ranging area may be, for example, one ranging area selected by the photographer or all ranging areas.

Next, it is determined whether or not the detection of the image shift amount has been completed for all the predetermined distance measurement areas (step S).
44) If not completed yet (NO), the flow returns to step S43 to detect the amount of image shift in the next ranging area. On the other hand, when the image shift amount detection for all the predetermined distance measurement areas is completed (YES), the distance measurement area is selected based on a predetermined algorithm, for example, the closest selection (step S45). Hereinafter, the description will be given assuming that the selected distance measurement areas am and bm are used.

Next, it is determined whether or not the image shift amount cannot be detected, that is, whether or not all the predetermined distance measurement areas cannot be detected (step S46). In this determination, if the image can be detected (YES), the image shift amount detectable flag is set (step S47), and the image shift amount detected flag is set (step S48). On the other hand, step S
If it is determined in step 46 that all the images cannot be detected (NO), the image shift amount undetectable flag is set (step S49), and the image shift amount detected flag is cleared (step S50). After setting or clearing the image shift amount detection completed flag, the image movement amount detected flag is cleared (step S51), and the process returns to the main routine described later with reference to FIG.

In the determination in step S42,
If the image shift amount has already been detected (YES), the movement amount of the subject image with respect to time is detected for each of the first and second subject images as described below. First, the distance measuring area am selected in step S45 is set as an initial distance measuring area (step S52). Next, a correlation calculation is performed between the sensor data stored in the previous (time t0) image shift amount detection and the sensor data of the current time (time t1) for the first subject image in the distance measurement area am, and the movement amount is calculated. Is detected (step S53). This is based on the movement amount detection routine shown in FIG.

Then, it is determined whether or not the amount of movement of the first subject image has been detected (step S54). In this judgment,
If the movement amount cannot be detected (NO), the image shift amount between the first and second subject images is determined to be “0”, and all the distance measurement areas near the distance measurement area am are measured. It is determined whether an area has been set (step S5).
5). If it is determined in this determination that the shift has not been completed for all nearby distance measurement areas (NO), this time (time t1)
Is shifted in accordance with a predetermined order, and is shifted and set to the next ranging area (step S5).
6). It should be noted that the predetermined order mentioned here refers to FIGS.
As shown in (i) in order, as shown by the arrows around the initial distance measurement area an on the area sensor 23a, (b)-
In the order of (i), the ranging area is shifted in the horizontal and vertical directions near an.

The initial distance measurement area an is set after the 1RSW is turned on.
For the first distance measurement, a predetermined distance measurement area (for example, the center) is set in advance. For the second and subsequent distance measurement after the 1RSW is turned on, the area selected by the previous distance measurement is set. Set. In this case, there is a high possibility that the moving object can be detected even in the previous distance measurement.

FIGS. 16 (b) to 16 (e) show a case where the distance measurement area is shifted in the horizontal direction with an as the center, and FIGS.
(I) shifts the distance measurement area in the vertical direction around an. That is, the horizontal ranging area around an is preferentially selected over the vertical ranging area. As described above, this is because, as illustrated in FIG. 17, there are more subjects moving in the horizontal direction than subjects moving in the vertical direction of the camera. Thereafter, the process returns to step S53, and the first subject image movement amount is detected again for the new distance measurement area that has been set. Thus, the position of the first subject image is searched.

However, if it is determined in step S55 that the setting has been completed in all the neighboring distance measurement areas (YES), the process proceeds to step 59 described later. In the determination in step S54, if the position of the first object image can be detected and the movement amount from time t0 to time t1 can be detected (YES), the distance measurement area ak in which the first object movement amount can be detected is set. The movement amount of the corresponding distance measurement area bk of the area sensor 23b with respect to the second subject image is detected (step S57). This refers to the “movement amount detection” routine of FIG. At this time, the distance measurement area at time t1 when the movement amount of the first subject image can be detected is represented by a
k. Here, when a shift of the ranging area occurs, the shift amount between the ranging areas (for example,
The pixel number conversion value of the center-to-center distance) is added to ΔXL and ΔXR. When the amounts of movement of both the first and second subject images have been detected in this way, the moving speed v of the subject image in the optical axis direction is calculated from the following equation (step S58).

[0081]

[Equation 17]

Next, it is determined whether the calculated moving amount is continuous with the previously calculated moving amount (step S5).
9). That is, it is determined whether or not the subject has deviated from the distance measurement area detected last time, or is too fast to focus.
However, if it is the first distance measurement after the 1RSW is turned on, since there is no previous data, the process proceeds to step S61 without determining whether or not the distance is continuous. If it is determined that the data is continuous (YES), the process proceeds to step S61.
Move to. On the other hand, if it is determined that the
O), it is determined whether or not all the distance measurement areas are discontinuous (step S60). If they are not all discontinuous (NO), the process returns to step S56 and shifts to the next ranging area. However, if all the distance measurement areas are discontinuous (YES), the process proceeds to step S61 in order to focus on the latest distance measurement area.

In step S61, the calculated moving speed v is compared with a predetermined speed vth to determine whether or not the subject is moving in the optical axis direction. In this judgment,
If it is determined that the object is moving in the optical axis direction (moving object determination) (YES), the subject moving flag is set (step S62). However, if it is determined that the object is not moving (NO), the subject moving flag is cleared (step S63), the process returns to step S43, and the process for detecting the image shift amount is performed again.

Then, after setting the above-described subject moving flag, an image movement detected flag is set (step S64), and the process returns to the main routine.

Next, the main routine of the camera to which the multipoint autofocus camera of the present invention is applied will be described with reference to the configuration shown in FIG. 4 and the flowchart shown in FIG.
This main operation is a routine showing a control procedure of a program started by the control unit 30, and is executed when the operation of the control unit 30 starts.

First, various kinds of correction data used in the distance measurement and photometry processing stored in advance from the EEPROM 35 are read out and loaded into the RAM 33 (step S7).
1). Then, it is determined whether or not 1RSW is turned on (step S72), and if it is not on (NO),
It is determined whether a switch other than 1RSW and 2RSW is operated (step S73). If there is an operated switch (YES), a process corresponding to the operated switch is executed (step S74). Step S above
Return to 72.

On the other hand, in step S72, 1R
If the switch is on (YES), it is determined whether or not the photometry has been completed (step S75). If the photometry has not been completed, the photometry section 39 is operated to determine the amount of exposure to measure the luminance of the subject. Is performed (step S76).

Next, the aforementioned subroutine "AF detection"
Is executed (step S77). As a result of this AF operation, it is determined whether or not the image shift cannot be detected by referring to the above-described detection impossible flag (step S78). If it is determined that the image shift can be detected (NO), it is determined whether the movement amount of the subject image has been detected (step S79). On the other hand, when the image shift cannot be detected (YES), the focus lens 1
A scanning operation for searching for a lens position where AF detection is possible is performed while driving 2a (step S80), and the process returns to step S72. When this scan is performed, all flags are cleared and AF detection is restarted from the beginning.

In step S79, if the moving amount of the subject image has been detected (YES), the image shift amount is predicted. First, it is determined whether or not the 2RSW is turned on (step S81). If the 2RSW is turned on (YES), an image shift amount at the start of exposure is predicted (step S82). On the other hand, if the 2RSW is off (NO), only the AF operation is performed, so that the image shift amount at the end of the lens driving is predicted (step S8).
3) The process proceeds to the in-focus determination in step S85 described below.

If it is determined in step S79 that the moving amount of the subject image has not been detected (NO), it is determined whether the subject is moving (step S84). At this point, the image movement detected flag is cleared after the lens is driven, as will be described later. Since the subject moving flag is set after the lens is driven even if the image movement is not detected, the process proceeds to step S72. Then, the subject image movement is detected again.

On the other hand, if the image is not moving (NO), the detected image shift amount or the predicted image shift amount is converted into a defocus amount, and whether or not the image is within the focus allowable range is determined. Is determined (step S85). If it is not determined that the lens is in focus, a necessary lens drive amount is obtained, and the focus lens is driven (step S86). In the lens driving routine, the image shift detection completed flag, the image shift undetectable flag, and the image movement detected flag are cleared after the lens is driven. In this clearing process, it is considered that the subject image greatly changes after the focus lens is once driven.
This is to restart the detection from the beginning. Note that, as described above, only the subject image moving flag is not cleared here. The reason for this is to prevent the in-focus determination by the first AF detection after driving the lens and to continuously detect the movement of the subject.

If it is determined in step S85 that the camera is in focus (YES), the on / off state of the 2RSW is determined (step S87). If the 2RSW is turned on (YES), the exposure operation is performed by controlling the aperture and the shutter based on the photometric value stored in the RAM 33 (step S88). Then, the photographed film is wound up and fed to the position of the next frame (step S89), and a series of photographing operations ends. As described above, in the first embodiment, the position of the subject image is detected on the area sensor in both the image division direction and the direction perpendicular to the image division direction.
Even for a moving subject that moves vertically and horizontally, the subject image position can be detected, predictive control can be performed, and accurate focusing can be achieved.

Next, a second embodiment of the multipoint autofocus camera according to the present invention will be described. In the second embodiment, the posture detection unit 43 described with reference to FIG. 4 detects whether the camera is held in the horizontal direction or the vertical direction, and the camera is held in the horizontal direction. The priority order of selecting the ranging areas is changed between the case where the camera is held vertically and the case where the camera is held vertically. First, when the posture detection unit 43 detects that the camera is held in the horizontal direction, FIG.
The ranging areas are shifted in the order described in the section.
That is, it is the same as the first embodiment. Next, FIG. 19 shows the priority order of selecting the ranging areas when the posture detection unit 43 detects that the camera is held in the vertical direction.

The priority order of selection of the distance measurement areas shown in FIG. 19 is the same as the priority order of selection in FIG. 16 described above, and the horizontal direction is simply the vertical direction. Therefore, as shown in FIG. 19A to FIG.
The distance measuring area is shifted in the order of (b) to (i) in the order of (b) to (i) in the horizontal and vertical directions near an as shown by the arrows around the initial distance measuring area an on 3a. If the first distance measurement is performed after the 1RSW is turned on, the initial distance measurement area an is set to a predetermined distance measurement area (for example, the center) that is set in advance. For example, the area selected in the previous distance measurement is set. In this case, there is a high possibility that the moving object can be detected even in the previous distance measurement. FIG. 19B-
(E) shifts the ranging area so as to spread in the horizontal direction with an as the center, and (f) to (i) shifts the ranging area in the vertical direction with an as the center.

FIG. 20 is a flowchart showing the main routine of the second embodiment. This main routine corresponds to the routine of FIG. 18 in the first embodiment described above, and the same steps (operation, processing, judgment, etc.) are assigned the same step numbers, and detailed description thereof will be omitted. Omitted. Note that the routine for AF detection is the same as that in FIG. 15 in the first embodiment, and a description thereof will be omitted. The main routine of the second embodiment is shown in FIG.
And a step S90 of operating the attitude detection unit 43 to detect the attitude of the camera. If it is detected that the camera is held in the horizontal direction by performing this posture detection, the shift of the ranging area performed in step 56 in FIG. 15 in the AF detection in step S77 will be described with reference to FIG. It is performed in the order as described. On the other hand, if it is detected that the camera is held vertically,
In the AF detection in step S77, the shift of the distance measurement area performed in step 56 is performed in the order described with reference to FIG. Except for this step, processing is performed in the same manner as the routine in FIG.

According to the second embodiment described above, A
Since the posture of the camera is detected before the F detection is performed, it is possible to select a ranging area that is faithful to the posture. The shift order described with reference to FIGS. 16 and 19 is merely an example, and any order may be used as long as the distance measurement area in one direction can be prioritized over the other distance measurement area. In addition, modifications can be made without departing from the spirit of the present invention.
The description has been given of the example in which the present invention is applied to an L single-lens reflex camera or the like. Furthermore, although an example in which focus detection is performed by the area sensor has been described, the present invention is not limited to this.

Although the above embodiments have been described, the present invention includes the following inventions. (1) In a distance measuring method of a multi-point autofocus camera that divides a photographing screen into a number of areas and uses the divided areas as focus detection areas, a focus at a center of the photographing screen when photographing a moving subject is measured. With the detection area as a reference position, the focus detection area in the same direction as the direction of the held camera is measured with priority, and if the moving subject is not focused, the focus detection area at the center is used as the reference position. A focus detection area in a direction orthogonal to the direction of the camera, and focusing on the moving subject.

(2) In the distance measuring method for a multi-point automatic focus camera described in (1), the moving direction of the moving subject on the photographing screen is assumed by the focus detecting operation.
A ranging method for a multi-point automatic focus camera, wherein a focus detection area adjacent to the finally determined focus detection area in a moving direction is measured with the highest priority.

[0099]

As described above in detail, according to the present invention, when a moving object is photographed by a camera having a plurality of distance measuring points, a multi-point automatic focusing camera capable of shortening a time lag for detecting a moving object is provided. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conceptual block configuration in a focus detection function of a multipoint autofocus camera of the present invention.

FIG. 2 is a diagram showing a cross section of a configuration example applied to a single-lens reflex camera as a multipoint autofocus camera according to the present invention.

FIG. 3 is a diagram schematically showing an optical system including a distance measurement.

FIG. 4 is a diagram showing functional blocks including an electric control system of the camera described in FIG. 2;

5 is a diagram showing a specific circuit configuration of the area sensor shown in FIG.

FIG. 6 is a diagram showing a specific circuit configuration of a pixel unit of the area sensor.

FIG. 7 is a diagram showing an example of the arrangement of each distance measurement area forming a detection area in a shooting screen.

FIG. 8 is a time chart for explaining an accumulation operation of the area sensor.

FIG. 9 is a diagram illustrating an example of an arrangement of distance measurement areas forming two area sensors.

FIG. 10 is a diagram linearly showing an array of photodiodes corresponding to an area.

FIG. 11 is a flowchart for explaining based on a processing procedure relating to an image shift amount detection routine.

FIG. 12 is a diagram for explaining the principle of focus detection for a moving subject.

FIG. 13 is a diagram for explaining movement of a subject image.

FIG. 14 is a flowchart illustrating a movement amount detection routine.

FIG. 15 is a flowchart illustrating an AF detection routine.

FIG. 16 is a diagram for explaining a shift (lateral direction) for detecting a moving amount of a subject image in the first embodiment.

FIG. 17 is a diagram illustrating, as an example, a scene in which a train approaches a curve as a composition of a captured image.

FIG. 18 is a flowchart illustrating a main routine of the camera according to the first embodiment.

FIG. 19 is a diagram for describing a shift (vertical direction) for detecting a moving amount of a subject image in the second embodiment.

FIG. 20 is a flowchart illustrating a main routine of the camera according to the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 focus detection unit (area sensor) 2 focus calculation unit 3 image movement amount calculation unit 4 ranging area selection unit 5 focus control unit 6 focus adjustment unit

Claims (3)

[Claims] 1. A multi-point automatic focus camera having a plurality of focus detection areas in a two-dimensional arrangement, wherein a focus detection area determining means for designating, in a predetermined order, an area for performing focus detection calculation from the plurality of focus detection areas. When performing focus detection on a moving subject, the focus detection area determination means is arranged in a lateral direction than a focus detection area arranged in a vertical direction among the plurality of focus detection areas. A multipoint autofocus camera, wherein a focus detection area is designated with priority. 2. When performing focus detection on a moving subject, the focus detection area determining means includes a focus detection area arranged beside a focus detection area finally determined in a previous focus detection operation. 2. The multi-point autofocus camera according to claim 1, wherein is designated with the highest priority. 3. A multi-point automatic focus camera having a plurality of two-dimensionally arranged focus detection areas, a focus detection area determining means for designating, in a predetermined order, an area for performing a focus detection calculation from among the plurality of focus detection areas. And a posture detection unit that detects whether the camera is held in a horizontal position or a vertical position. When performing focus detection on a moving subject, the focus detection area determination unit A multi-point automatic focus camera, wherein a focus detection area arranged in a horizontal direction with respect to a direction in which the camera is held is designated with a higher priority than a vertical direction based on an output of the attitude detection unit.