JP3089312B2 - Focus adjustment device - Google Patents

Description

The present invention relates to an automatic focusing device such as a camera.

B. Prior Art As this type of automatic focus adjustment device, a relatively narrow first focus detection area and a second focus detection area wider than this are set in a shooting screen, and these focus detection areas are set. The photographer switches and selects, detects a defocus amount of the image plane of the photographing optical system with respect to a predetermined surface in the selected focus detection area, and moves the photographing optical system to a focal point based on the detected defocus amount. Automatic focusing devices are known.

Further, the one disclosed in JP-A-63-17418 is also known. In the device disclosed in this publication, a relatively narrow first focus detection area and a wider second focus detection area are set in a shooting screen, and the first focus detection area is narrowed by pressing the release halfway. Focus detection is performed, and when focus detection is not possible, a wide second focus detection area is selected. Then, a defocus amount of the image plane of the photographing optical system with respect to a predetermined surface in the selected focus detection area is detected, and the photographing optical system is moved to a focal point based on the detected defocus amount.

C. Problems to be Solved by the Invention However, the former case has the following problems when each area is selected.

When the photographer selects the first focus detection area that is relatively narrow For a stationary subject or a subject that moves slowly, a specific subject intended by the photographer is avoided by avoiding an obstructive subject because the area is small. Can always be included in the focus detection area, but it is difficult to always capture the focus detection area for a subject that moves rapidly. When the subject is removed from the focus detection area, the focus cannot be detected, and the lens is scanned unnecessarily or the object in the background is focused.

When the photographer selects a relatively wide second focus detection area It is easy to always capture the subject in the focus detection area even for a fast-moving subject. Since the area of a slow subject is large, the probability that an obstructive subject enters the area increases, and it becomes impossible to put only a specific subject intended by the photographer in the focus detection area. If another subject enters the area, the subject is in focus, and the usability is poor.

 On the other hand, the latter device has the following problems.

If the focus cannot be detected, a focus detection element such as a CCD
Since the contrast of the subject formed above is small, even if the subject shifts to the wide second focus detection area and captures the main subject, the subject is easily affected by a high-contrast subject other than the main subject, and the main subject is focused. No.

It is a technical object of the present invention to effectively shift from a narrow focus detection area to a wide focus detection area and to surely focus on a main subject.

D. Means for Solving the Problems The inventions of claims 1 and 2 will be described with reference to FIG. 1 (a) which is a diagram corresponding to claims.
Focus detection means 501 for detecting a focus adjustment state of the optical system,
Operating means 502 for starting focus detection; operating means 5
When 02 is operated, focus detection is performed by the focus detection means 501 in a predetermined area in the shooting screen, and when a predetermined time has elapsed since the operation means 502 was operated, the focus detection area by the focus detection means 501 is Including control means 503 including the predetermined area and expanding to an area wider than the predetermined area,
This solves the above-mentioned technical problem.

Further, according to the invention of claim 2, focus detection means 501 for detecting the focus adjustment state of the optical system, operation means 502 for starting focus detection, and photographing by the focus detection means 501 when the operation means 502 is operated Focus detection is performed in a predetermined area in the screen, and when the focus detection by the focus detection unit 501 is performed a predetermined number of times after the operation unit 502 is operated, the focus detection unit 50
Control means 503 for enlarging the focus detection area according to 1 to an area including the predetermined area and wider than the predetermined area is provided, thereby solving the technical problem described above.

The invention of claim 3 will be described with reference to FIG. 1 (b) which is a claim correspondence diagram. The invention of claim 3 is a focus detecting means for detecting a defocus amount according to a focus adjustment state of an optical system.
504, first control means 505 for expanding the detection area of the focus adjustment state by the focus detection means 504, and when the detection area of the focus adjustment state is expanded by the first control means 505, the focus detection means 504 And a second control unit 506 for limiting the detection range of the defocus amount according to the above.

The invention of claim 4 will be described with reference to FIG. 1 (c) which is a claim correspondence diagram. The invention of claim 4 is a focus detecting means for detecting a defocus amount according to a focus adjustment state of an optical system.
507 and a driving unit 50 that drives the optical system according to the defocus amount detected by the focus detection unit 507 to perform focus adjustment
8, a first control means 509 for expanding the detection area of the focus adjustment state by the focus detection means 507, and a driving means 508 when the detection area of the focus adjustment state is expanded by the first control means 509. There is provided second control means 510 for limiting the driving amount of the optical system, thereby solving the above-mentioned technical problem.

E. Function In the focus adjusting device according to the first aspect, when the operation means 502 for starting the focus detection is operated, the focus detection means 501 performs the focus detection in a predetermined area in the photographing screen.
When a predetermined time has elapsed after the operation of the 502, the focus detection area of the focus detection unit 501 is expanded to an area including the predetermined area and wider than the predetermined area.

In the focus adjusting device according to the second aspect, when the operation means for starting the focus detection is operated, the focus detection is performed by the focus detection in a predetermined area in the photographing screen.
When the focus detection by the focus detection unit 501 is performed a predetermined number of times after the operation of the 502, the focus detection area by the focus detection unit 501 is expanded to an area including the predetermined area and wider than the predetermined area.

In the focus adjustment device of the third aspect, when the detection area in the focus adjustment state is expanded, the detection range of the defocus amount by the focus detection unit 504 is limited.

In the focus adjusting device according to the fourth aspect, when the detection area in the focus adjustment state is enlarged, the driving amount of the optical system by the driving unit 508 is limited.

F. Embodiment An embodiment will be described with reference to FIGS.

FIG. 2 shows an embodiment in which the present invention is applied to an interchangeable lens type single-lens reflex camera, in which an interchangeable lens 10 can be detachably mounted on a camera body 20. In a state where the lens 10 is mounted, a part of the photographic light beam coming from the subject passes through the photographic lens 11 and is reflected by the main mirror 21 provided on the camera body 20 and guided to a finder (not shown). At the same time, another part of the photographing light beam is transmitted through the main mirror 21 and reflected by the sub-mirror 22, thereby being guided as a focus detection light beam to an autofocus module 23 (hereinafter, referred to as an AF module).

-Regarding the AF module 23-In Fig. 3 showing a configuration example of the AF module 23, the AF module 23 is a focus detection comprising a field mask 230, a field lens 231 and two pairs of re-imaging lenses 232A, 232B and 234A, 234B. Optical system 23A and two pairs of light receiving element arrays 233A and 23
3B and a CCD image sensor chip (hereinafter simply referred to as a CCD) 23B having 235A and 235B.

In the above configuration, the exit pupil 11 of the photographing lens 11
Two pairs of regions 111A and 111B symmetric with respect to the optical axis LX included in E
And the light flux passing through 112A and 112B form a primary image for focus detection in the vicinity shown in FIG. 5 (A) and having an aperture shape corresponding to the entire focus detection area. Two pairs of re-imaging lenses 232A, 232B and 234A, 234B
CCD23B two pairs of light receiving element arrays 233A, 233B and 235
A, 235B are formed as two pairs of secondary images.

As is well known, the defocus amount of the photographing lens can be detected by detecting the relative positional relationship of the paired secondary images in the direction in which the light receiving element arrays are arranged on the CCD 23B. Further, by detecting this positional relationship for each of a plurality of areas divided on the shooting screen as shown in FIG. 5 (A), the defocus amount can be detected for each area. In this case, the relatively narrow first focus detection area is composed of the areas 3 and 7 as shown in FIG. 5B, and the second focus detection area wider than the first focus detection area is the second focus detection area. 5 As shown in FIG. Here, the one that performs focus detection for the narrow first focus detection area is called a first focus detection system, and the one that performs focus detection for the wide second focus detection area is called a second focus detection system.

Each of the pair of light receiving element arrays 233A and 233B includes n light receiving elements Ap and Bp (i = 1 to n), and each of the pair of light receiving element arrays 235A and 235B has m light receiving elements Cp and Dp ( i =
1 to m). Each light receiving element Ap, Bp, Cp, Dp is constituted by a charge storage element such as a photodiode, and has a CCD2
By performing charge accumulation for the charge accumulation time corresponding to the illuminance on 3B, the output of the light receiving element can be set to an output level suitable for processing described later. When the primary image coincides with the film conjugate surface, the corresponding light-receiving elements (A ₁ and B _1, A ₂
, B ₂ ... An and Bn, and C ₁ and D ₁ ... Cn and Dn).

When the primary image is formed on a plane shifted from the film conjugate plane, the relative position of the pair of secondary images on the CCD 23B is determined by the shift direction of the primary image in the optical axis direction (that is, the front focus or the rear focus). The value is changed from the predetermined value in the case of the above-mentioned coincidence in accordance with the state of the pin. For example, in the case of a front focus, the positional relationship between a pair of secondary images is relatively widened, and in the case of a rear focus, it is narrow. That is, the relative positional relationship of the secondary image is determined according to the difference in the optical axis direction between the imaging plane of the subject formed by the focus detection optical system 23A and the planned focal plane unique to the focus detection optical system 23A.

-Regarding the AFCPU 30-Referring again to FIG. 2, the sensor control unit 26 receives charge accumulation start and end commands from the port P4 of the autofocus CPU (hereinafter referred to as AFCPU) 30, and sends a control signal corresponding to the commands to the CCD23B. To control the start and end of CCD23B charge accumulation. Also, the transfer clock signal
This signal is given to the CCD23B and the light-receiving element output signal is
To the port P4 of the AFCPU 30, and a generated synchronization signal synchronized with the start of the transfer of the light receiving element output signal. AFCPU
Reference numeral 30 indicates that the A / D converter is started by the built-in A / D converter in synchronization with the generated synchronizing signal, and thereafter, the output of the light receiving element is sampled at the port P3 at each cycle time of the transfer clock, and the A / D conversion is performed. In this way, after obtaining AD conversion data (2n + 2m) corresponding to the number of light receiving elements, a well-known focus detection calculation described later is performed based on this data, and a defocus amount between the primary image and the film conjugate plane is obtained.

The AF CPU 30 determines the AF display 40 based on the focus detection calculation result.
Is controlled using the port P5. For example, in the case of a front pin, a triangle display section 41, in the case of a rear pin, a triangle display section 43,
In the case of focusing, the circle display section 42 is activated, and in the case of focus detection failure, the x display section 44 is activated.

Further, the AF CPU 30 controls the driving direction and the driving amount of the AF motor 50 based on the result of the focus detection calculation as follows, and moves the photographing lens 11 to the focal point.

First, the AF CPU 30 outputs a drive signal for rotating the AF motor 50 in a direction in which the photographing lens 11 approaches the focal point from the port P2 according to the sign of the defocus amount (front focus, rear focus). The rotational motion of the AF motor 50 is transmitted to a camera-side coupling 53 provided on a mount portion of the camera body 20 and the lens 10 via a body transmission system 51 including gears and the like built in the camera body 20. . The rotational movement transmitted to the coupling 53 on the body side is further transmitted to the lens transmission system 12 composed of the coupling 14 on the lens side fitted to the coupling 53 and the gears built in the lens 10, and finally the image is taken. The lens 11 moves in the focusing direction.

The amount of drive of the AF motor 50 is detected by the amount of rotation of the gears and the like of the body transmission system 51, and the amount of rotation is converted into a pulse train signal by an encoder 52 constituted by a photo interrupter or the like, and fed back from the port P1 to the AF CPU 30. You. The AF CPU 30 controls the AF motor according to parameters such as the reduction ratio of the body transmission system 51 and the lens transmission system 12.
By counting the driving amount of 50, that is, the number of pulses fed back from the encoder 52, the taking lens 11
Can be moved by a predetermined movement amount. AFCPU30 is
Built-in pulse counter for counting the pulse signal input from port P1 and comparison register for comparing with the contents of this pulse counter. When the contents of the pulse counter and the comparison register match, an internal interrupt is activated. Has a function.

The AF CPU 30 controls the driving amount of the AF motor 50 in the following order.

First, before the driving of the AF motor 50 is started, the contents of the pulse counter are cleared, the desired number of pulses are set in the comparison register, and then the driving of the AF motor 50 is started. The encoder 52 generates a pulse by the rotation of the AF motor 50, and the pulse counter is counted up. When the content of the pulse counter matches the comparison register, an interrupt occurs,
The AF CPU 30 stops the AF motor 50 in the interrupt processing. In this way, the AF motor 50 is driven and controlled by a desired number of pulses. The AFCPU 30 has a built-in timer for measuring time, and also has a timer interrupt function that interrupts at regular intervals.

Further, in FIG. 2, a lens CPU 13 is built in the lens, and the lens CPU 13 controls a focal length necessary for the AF CPU 30 and a coupling per unit movement amount of the photographing lens 11.
The AF-related information such as the rotation speed of 14 is transmitted to the communication bus 64 on the body side via the contact 15 on the lens side and the contact 63 on the body side provided on the mount unit.

Further, reference numeral 80 denotes a release button, which is in a released state in which it is not operated, a ready state in which it is pushed in only by a first stroke (half-pressed), and a push-in button up to a second stroke larger than the first stroke. It can be operated to a release state (full press), which is an open state, and sends information of each of these states to the port P7, and performs a selection operation of the focus detection area based on this information in the released state.

The above is the outline of the configuration and operation of the embodiment in which the focus detection device according to the present invention is applied to a single-lens reflex camera.

FIG. 6 is a flowchart of an outline of the operation of the AF CPU 30.

For example, when the release button 80 is in the ready state and the AF CPU 30 is turned on, the operation of the AF CPU 30 starts from # 100.
In # 105, lens information is collected through communication with the lens CPU 13, and in # 110, it is determined whether the main mirror 21 is down. If not, the process returns to # 105 without accumulating the charge of the CCD 23B. When the mirror is down, the port P7 determines whether the release button 80 is in the released state at # 115.
If not, the sensor control unit 26 controls the charge accumulation time of the CCD 23B in # 120. When the charge accumulation is completed, in step # 125, the transferred photoelectric element output is AD-converted, and the data is stored in the memory.

In # 130, it is determined whether the first focus detection system is selected. If it is selected, the defocus amount is obtained in the first focus detection area in # 135. If it is not selected, # 14 is determined.
When 0, the defocus amount is obtained in the second focus detection area.

In step # 145, the image plane moving speed is obtained from the defocus amounts obtained by a plurality of current and past focus detections, and the defocus amount is corrected by adding a tracking correction amount predicted from the image plane moving speed.

In # 150, the display of the AF display 40 is performed according to the defocus amount. In # 155, AF motor 50 according to the defocus amount
Is performed. In # 160, wait for the drive to end,
When the driving is completed, the process returns to step # 105 to start the next focus detection cycle.

Next, details of data processing performed inside the AF CPU 30, selection of a focus detection area, tracking of a dynamic object, limitation of a range of a defocus amount, and drive control of a photographing lens optical system will be described in detail.

<Selection of Focus Detection Area> The operation state of the release button 80 and the selection of the focus detection area will be described with reference to FIGS. 7 and 8.

As shown in FIG. 7A, normally, the second focus detection system is selected, and the first focus detection system is selected by the edge at which the release button 80 changes from the release state to the ready state, and thereafter, the first focus detection system is fixed. When the time T1 has elapsed, the second focus detection system is selected again.

FIG. 8A is a flowchart of the AF CPU 30 performing the above operation.

When a change from the release state of the release button 80 to the ready state is input as an interrupt signal from the port P7, the ready state interrupt processing of # 200 is started, and the first focus detection system is selected at # 205. In # 210, the timer built in the AFCPU 30 is set to a certain time T1, and the timer is started.
The interrupt processing ends at 5, and the routine returns. Thereafter, when the timer counts a predetermined time T1, a timer interrupt occurs, and a timer interrupt process is started from # 220. In step # 225, the second focus detection system is selected. In step # 230, the timer is stopped. In step # 235, the interrupt process ends and the process returns. In this manner, the focus detection area is selected as shown in FIG. 7 (A).

 FIG. 7 (B) shows another selection method.

Normally, the second focus detection system is selected, and the first focus detection system is selected by the edge at which the release button 80 changes from the released state to the ready state. A defocus amount is obtained by the first focus detection system, and when the drive control based on the defocus amount ends, the second focus detection system is selected again, and the next focus detection is performed by the second focus detection system. .

FIG. 8B is a flowchart of the AF CPU 30 performing the above operation.

When the change from the release state of the release button 80 to the ready state is input as an interrupt signal from the port P7, the ready state interrupt processing of # 200 is started, the first focus detection system is selected in # 205, and the # 1 focus detection system is selected in # 215. Ends the interrupt processing and returns. When the drive control is completed, an internal soft interrupt is generated, and a drive end interrupt process after # 240 is started. In step # 250, the second focus detection system is selected. In step # 255, the interrupt processing is terminated and the routine returns.

FIG. 8 (C) shows a flowchart for explaining still another selection method.

In the drive interruption process shown in FIG. 8B, the focus is detected by the first focus detection system only once immediately after the release button 80 changes to the ready state. After the drive end interrupt is activated at # 240, the absolute value of the detected defocus amount is changed to the predetermined value D1 at # 245.
It is judged whether it is the following or less.
Alternatively, if the determination is negative, the interrupt processing may be terminated and returned at # 250 without changing the focus detection system. According to this configuration, the focus is switched to the second focus detection system after the first focus detection system has reached the in-focus state or near the in-focus state, so that the photographer can observe the subject without being out of focus on the viewfinder. As a result, it is possible to reliably capture the subject that the user is aiming for, and the driving stability is improved.

In addition, in the method of FIG. 7 (A) and FIG. 8 (A),
If the focus detection disable signal is output during the measurement of the predetermined time T1, the process may shift to the second focus detection area. In this case, if the main subject is captured even once within the time T1, and a focus detection impossible signal is output thereafter, the photographing lens is located at a position suitable for the main subject, and the focus shifts to the second focus detection area. Focus, it is easy to focus on the main subject.

In the above description, the predetermined time T1 and the predetermined value D1 are fixed, but these values may be changed by the photographer, or may be changed automatically according to information such as the brightness of the subject. It may be. <Focus detection calculation> The light receiving elements Ap and Bp (p = 1 to
n) and the light-receiving element output data corresponding to Cq, Dq (q = 1 to m) are ap, bp (p = 1 to n) and cq, dq (q = 1 to n).
m). For simplicity, in the following description, only the light receiving element output data ap, bp will be described, but the same applies to the light receiving element output data cq, dq.

The correlation calculation of equation (1) is performed on a pair of n pieces of light receiving element output data a _{1 to} an and b _{1 to} bn to obtain a correlation amount C (j, L).

Here, L is an integer, and the CCD image sensor chip 2
This is a relative shift amount between a pair of light receiving element output data when the light receiving element pitch arranged on 3B is one unit. In the equation (1), the range taken by the parameter r is the shift amount L
For example, they are set as shown in FIG.

When the light-receiving element output data ap, bp is made to correspond to a matrix of a matrix, for example, as shown in FIG.
Range can be determined. In FIG. 9, the shift amount L is moved in the range of -2 to +2, and a region surrounded by a thick line indicates a position on a matrix of a combination of light-receiving element output data on which a correlation operation is performed. The control shift amount is Lmin, Lmax, and the range of the shift amount L is Lmin to Lmax.
, The shift amount and the defocus amount that can be detected can be limited. Lmin in case of Fig. 9
= −2, Lmax = 2. When the shift amount L is 0, the range of the parameter r in the equation (1) is as follows for each area j.

When j = 1, r = 1 to w, when j = 2, r = w + 1 to x, when j = 3, r = x + 1 to y, when j = 4, r = y + 1 to z, when j = 5, r = z + 1 to n .. (2) The shift amount xm (j) having the highest correlation of the light-receiving element output data in each region is obtained by applying the three-point interpolation method disclosed in Japanese Patent Application Laid-Open No. 60-37513 by the present applicant to the result of equation (1) Applying it is required as follows.

 Hereinafter, the three-point interpolation method will be described.

The calculation result of the equation (1) is obtained by plotting the relative shift amount L on the horizontal axis and the correlation amount C (j, L) on the vertical axis in FIG. At the shift amount L having a high correlation, the correlation amount C (j, L) is minimized.

However, since the relative shift amount L is actually determined based on data discretely obtained from the light receiving element arrays 233A and 233B, the correlation amount C (j, L) is also discrete. Therefore, the minimum value C (j, L) _{MIN of} the correlation amount C (j, L) is not always obtained directly from the correlation amount C (j, L) obtained by the calculation.

Therefore, using the three-point interpolation method shown in FIG.
A minimum value C (j, L) _{MIN of} (j, L) is obtained.

That is, assuming that the minimum value of the discretely obtained correlation amount C (j, L) is obtained when the relative shift amount is L = x, the correlation value corresponding to the relative shift amount x−1, x + 1 before and after the relative shift amount is L = x. The quantity C (j, L) is C (j, x-1), C (j, x), C (j, x +
1). Therefore, first, the smallest correlation amount C (j, x) and the larger correlation amount (C (j, x + 1) in FIG. 11) among the remaining two correlation amounts C (j, x-1) and C (j, x + 1) ) Is drawn, and a straight line J that passes through the remaining correlation amount C (j, x−1) and has a slope opposite to the straight line H is drawn to obtain an intersection W between these two straight lines H and J.

The coordinates of the intersection W can be represented by a relative shift amount xm and its correlation amount C (j, xm), and the minimum relative shift amount xm and the minimum correlation amount in a continuous relative shift amount are represented by the coordinates. C (j, xm).

If the three-point interpolation method is expressed by an arithmetic expression, the minimum relative shift amount xm is given by the following expression: And the correlation amount C (j,
xm) can be expressed as the following equation: C (j, xm) = C (j, x) − | D (j) | (4)

Here, D (j) in the equations (3) and (4) is
Relative shift amount: Deviation between each data of x-1, x + 1 ... Can be represented by

In the expressions (3) and (4), SLOP (j) is a correlation amount C (j, x−) corresponding to the relative shift amount x−1, x, x + 1.
1) represents a larger deviation among deviations between C (j, x) and C (j, x + 1), and is expressed by the following equation: SLOP = MAX (C (j, x + 1) -C (j, x); (J, x-1) -C (j, x))... (6)

The arithmetic expressions represented by the expressions (3) to (6) indicate that the relative shift amount xm represents the relative shift amount of the output data of a pair of light receiving elements. The relative lateral shift amount SHIFT between the two formed subject images can be expressed as SHIFT = y × xm (7).

The defocus amount DEF (j) on the focal plane can be expressed by the following equation: DEF = KX × SHIFT (8)

Here, KX is a coefficient determined by the configuration conditions of the focus detection optical system shown in FIG.

The larger the value of the parameter SLOP obtained by the equation (6), the deeper the depression of the correlation amount C (j, L) shown in FIG. 10, that is, the larger the correlation.
This indicates that the reliability of DEF (j) is high. The sign of the defocus amount DEF is + when the subject position is closer to the distance than the distance set by the current imaging optical system position, that is, at the time of the rear focus, and − when it is at the far distance side, that is, at the time of the front focus. I do.

Note that the minimum value Xm (j) was not found and the defocus amount DEF
If (j) is not found or defocus amount DEF
If (j) is found but SLOP (j) is small and the reliability is low, it is determined that focus detection is impossible.

FIG. 12 shows a first example in which the defocus amount is detected by the above operation.
The operations of the focus detection system and the second focus detection system are summarized in a flowchart.

First, in # 300, it is determined whether the first focus detection system is selected. If the first focus detection system is selected, # 30 is selected.
At 5, the limit shift amount Lmin is set to -L1, Lmax = L1 (L1> 0), and at # 306, the initial value jint of the area is 3, and the final value jma of the area is #ma.
Assuming that x is 3, the defocus amount calculation subroutine is called at # 310 to determine the defocus amount in the area 3. Next, in # 315, the initial value jint of the area is set to 7 and the final value jmax of the area is set to 7, and in order to obtain the defocus amount in the area 7, the process proceeds to # 320 to call the defocus amount calculation serve routine. In step # 325, it is determined whether the defocus amounts DEF (3) and DEF (7) in the areas 3 and 7 are both undetectable. If not, the process proceeds to step # 330, and the defocus in the first focus detection area is performed. The closest defocus amount that can be detected as the amount is selected and passed to the tracking correction process. If both of them cannot be detected, the defocus amount cannot be detected in # 335, and the tracking correction processing is skipped.

If the first focus detection system is not selected in # 300, the limit shift amounts Lmin and Lmax are calculated from the preset limit defocus amounts DEFmin and DEFmax in # 340. For example, calculation is performed as in equation (9).

Lmin = INT {α × DEFmin / (PY × KX)} Lmax = INT {α × DEFmax / (PY × KX)} (9) In equation (9), α is a predetermined coefficient. Also (9)
The limit shift amounts Lmin and Lmax obtained by the formula are -L1 ≦ Lmin <L
α, DEFmin, and DEFmax are determined so that max ≦ L1. The limited defocus amounts DEFmin and DEFmax may be fixed values. In # 341, the initial value jint of the area is set to 1 and the final value jmax of the area is set to 8, and the defocus amount calculation subroutine is called in # 345 in order to obtain the defocus amount in the areas 1 to 8. In # 350, it is determined whether all the defocus amounts of the areas 1 to 8 are undetectable. If the defocus amount is detectable in at least one area, the process proceeds to # 355, and the second
Select the closest one of the defocus amounts that could be detected as the defocus amount in the focus detection area of
Get through the tracking correction process.

In this case, besides selecting the closest one, the one with the smallest absolute value of the defocus amount may be selected. When the closest object is selected, the probability that the main subject is in front is generally high, and therefore the probability of the defocus amount for the main subject also increases. When the one with the smallest absolute value of the defocus amount is selected, the in-focus subject at the current position of the lens is given priority, so that the lens does not move unnecessarily, and the driving stability can be improved. If all areas cannot be detected in # 350, the defocus amount cannot be detected in # 360, and the process proceeds to the tracking correction processing.

FIG. 13 is a flowchart of a defocus amount calculation serve routine SUBDEF.

When the subroutine of # 400 is called, the area j is set to the initial value jint of the area in # 405. In # 410, a correlation operation is performed by setting the limited shift amounts to Lmin and Lmax in the area j to obtain a correlation amount C (j, L). Xm by 3-point interpolation at # 415
(J), SLOP (j) is obtained. In # 420, it is determined whether or not Xm (j) has been obtained. If not, the process proceeds to # 435. If it has been obtained, in # 425, it is determined whether or not SLOP (j) is equal to or greater than a predetermined value TS. If there is, that is, if it is determined that there is no reliability, the process proceeds to # 435. If there is a TS or more in # 425, that is, if it is determined that there is reliability, # 430
Then, the defocus amount DEF (j) is obtained, and the flow proceeds to # 440.
On the other hand, when the process proceeds to # 435, the defocus amount cannot be detected, and the process proceeds to # 440. In # 440, it is determined whether or not j = jmax (the area ends). If j = jmax is not satisfied, # 4 is determined.
At 45, j = j + 1 and the area is updated to the next area, and # 410
And the correlation operation is performed in the next area. If j = jmax in step # 440, the flow advances to step # 450 to terminate the subroutine processing and return.

As described above, the defocus amount can be determined in the first or second focus detection area.

In the above description, the cross-shaped focus detection area shown in FIG. 5 is divided into eight, and the defocus amount of each area is detected. However, the shape and the number of divisions of the detection area are not limited to this.

<Tracking> When tracking a dynamic subject, the moving speed of the subject image is detected based on the current and past defocus amounts,
The defocus amount of the moving subject is corrected. The tracking performance for a moving subject is further improved by combining tracking correction with the automatic switching of the focus detection area described above.

 The tracking operation will be described with reference to FIG.

Assuming that the ordinate represents the defocus amount and the abscissa represents time, the trajectory of the ideal image plane with respect to the moving subject is tracked so that the detected defocus amount becomes zero. The trajectory of the surface is obtained. The actual locus of the image plane is step-shaped because the focus detection operation and the movement of the lens are performed in a time-division manner, and the lens is stopped during focus detection. During the tracking operation, the movement amount of the lens is determined according to the corrected defocus amount obtained by adding the tracking correction amount to the defocus amount. Since the defocus amount has changed by (the current defocus amount + the previous tracking correction amount) between the last and the two focus detection times Td, the moving speed Dv of the image plane is (the current defocus amount). Amount + previous tracking correction amount) / Td.

Such tracking operation will be described in detail with reference to the flowchart of FIG.

First, in # 500, it is determined whether or not focus detection cannot be performed twice consecutively. If not, the process proceeds to # 520 without performing tracking correction. If it is not impossible, the process proceeds to step # 505, and the current tracking correction amount is calculated as the current defocus amount + the previous tracking correction amount. If this step is first reached when the power is turned on, the tracking correction amount is set to 0 last time. In # 510, it is determined whether β × | previous defocus amount | <| current tracking correction amount | <γ × | previous correction defocus amount |, and if the condition is not satisfied, it is determined that the subject has not moved and tracking correction is performed. Not done # 52
Go to 0. If the condition is satisfied, it is determined that the subject is moving, and the flow proceeds to tracking correction calculation of # 515. Β is 1/10
1/1 / 1.5 and γ are set to 1.5-10. If this step is reached for the first time when the power is turned on, the previously corrected defocus amount is set to zero. In # 515, the current correction defocus amount is set to the current defocus amount + the current tracking defocus amount,
The image plane moving speed is calculated as the current tracking correction amount / the current defocus detection time Td, and the process exits to the next drive control process.

On the other hand, if the tracking correction is not performed, it is determined whether or not the focus can not be detected this time in # 520. If the focus cannot be detected, the process directly goes to the next drive control process. If it is not impossible, 0 is stored as the current tracking correction amount, the current defocus amount is stored as the current corrected defocus amount, and 0 is stored as the image plane moving speed in preparation for the next tracking process. Exit to processing. Therefore, when the tracking correction is not performed, the corrected defocus amount becomes equal to the defocus amount.

<Restriction of Defocus Amount Range> When the second focus detection system is selected, the range of the defocus amount detection range of the second focus detection system or the range of the drive amount in which the photographing lens can be driven is limited. By applying the restriction in this way, it is possible to prevent the detection of a disturbing subject other than the target subject, and to prevent the lens from being driven in response to the detection.

Here, the limited defocus amounts DEFmin and DEFmax are stored in the memory as fixed values, or the photographer manually sets,
It may be set automatically according to the magnification of the photographing optical system or the like.

A case where the limit value is set according to the magnification will be described.

 Consider a fixed focus lens with reference to FIG.

When the absolute position of the focusing lens with respect to the film surface as a reference is q, the distance from the lens to the subject is p, and the focal length of the lens is f, the magnification s is s = q / p = (q-f) / f ... (10) can be obtained. The absolute position q can be detected by an absolute position encoder, or can be detected by counting up and down relative position pulses generated by an encoder such as a photo interrupter in accordance with the driving direction based on the infinite end. The detected defocus amount may be used to correct the absolute position q when focusing on the subject. In the case of a zoom lens, the magnification s is obtained by detecting the absolute position of the zoom lens and taking this into account. Next, setting the upper limit of the speed when the subject to be tracked by the autofocus goes away is set to vf and the upper limit of the speed when approaching is set to vn (the speed when moving away is set to −), the corresponding image plane movement speed uf, un becomes uf = s × vf and un = s × vn. Assuming that the focus detection cycle time is Tc and the coefficient is c, the set defocus amounts DEFmin and DEFmax are calculated as DEFmin = c × uf × Tc DEFmax = c × uf × Tc (11)

In equation (11), time Tc may use a fixed value,
The focus detection cycle time may be directly measured and the time may be substituted. Also, the upper limit speed v of the subject may not be a fixed value but may be set manually by the photographer or automatically set according to the brightness of the subject. Further, the following equation may be used in consideration of the calculated image plane moving speed Dv.

DEFmin = (c × uf + Dv) × Tc DEFmax = (c × uv + Dv) × Tc (12) The calculated current tracking correction amount may be added to DEFmin in the equation (11).

FIG. 17 is a flowchart for performing such a limited defocus amount calculation.

First, the lens absolute position q is detected in # 600, and the magnification s is calculated from the absolute position q and the focal length f in # 605. # 610
Then, the limited defocus amounts DEFmin and DEFmax are obtained from the predetermined coefficient c, the upper limit values vf and vn of the object speed, and the magnification s. The above processing is performed before the processing of the second focus detection system or the processing of the drive control means.

When the main subject moves due to the above operation, the detected defocus amount does not change suddenly and follows, but an obstructive subject comes in front of the main subject or the main subject is detected for a moment. If the defocus amount changes suddenly due to the background deviating from the region and the defocus amount suddenly changes, the operability is improved because it does not follow.

<Lens Drive Control> The operation of the lens drive control will be described with reference to the flowchart of FIG.

In step # 700, it is determined whether or not focus detection was impossible in the current focus detection. If the focus was not detected, lens drive is not performed and the process ends with drive end detection. If it is not impossible, it is determined at # 705 whether or not the current focus is on. For example, when the absolute value of the current defocus amount is within a predetermined value and the current tracking correction amount is 0, it is determined that focusing has been achieved. If it is determined that the lens is in focus, the process exits to drive end detection without driving the lens. If it is determined that the focus is not in focus, the flow proceeds to # 710, and it is determined whether the second focus detection system has been selected this time. If the second focus detection system has not been selected, the flow proceeds to # 720. If the second focus detection system has been selected, the process proceeds to step # 715, and it is determined whether the current defocus amount is between the limited defocus amounts DEFmin and DEFmax. If not, the lens is not driven. At step # 720, the process proceeds to step # 720. In # 720, it is determined whether tracking is currently being performed (this tracking correction amount is not 0), and if tracking is not being performed, # 72 is determined.
In step 5, the lens position is controlled by a motor or the like in accordance with the current defocus amount, and the process exits to drive end detection. If tracking is in progress, the process proceeds to step # 730, where the lens position is controlled according to the corrected defocus amount this time, and the process exits to drive end detection.

As described above, when the second focus detection system is selected, the range of the defocus amount to be driven is limited, so that the detected defocus amount is abrupt as in the case where the target main subject moves. In a situation where does not change, the lens is driven according to the detected defocus amount.However, an obstructive subject comes in front of the main subject, or the main subject momentarily deviates from the focus detection area and becomes defocused. In a situation in which the focus amount changes suddenly, the main subject is not out of focus because it is not driven.

In the above embodiment, the description has been given assuming that the plurality of focus detection areas are set in a cross shape on the screen as shown in FIG. 5, but the focus detection areas may be set in other shapes.
Further, the focus detection area may be set two-dimensionally. Further, the present invention is not limited to a TTL type focus detection device, but can be applied to an external light type focus detection device. Further, the first focus detection system is selected in conjunction with the half-press operation of the release button, and then the second focus detection system is selected according to various conditions. May be linked.

G. Effects of the Invention As described above, according to the first and second aspects of the present invention, at the time of initial focus detection, a main subject intended by a photographer can be accurately captured using a narrow focus detection area. Once the main subject is captured, it is expanded to a wide focus detection area, so even if the subject moves or the photographer shakes the camera unconsciously, the main subject can be removed from the focus detection area. In addition, tracking performance and operability for the main subject can be improved.

Also, usually, even if the main subject moves, or even if the photographer shakes, the defocus amount does not change rapidly, but when the focus detection area is enlarged after capturing the main subject in a narrow focus detection area, When an obstructive subject comes in front of the main subject or when the main subject momentarily deviates from the focus detection area and captures the background, the defocus amount changes suddenly and the photographing lens is largely driven. According to the third and fourth aspects of the present invention, the detection range of the defocus amount or the drive amount of the optical system is limited, so that a sudden change in the defocus amount detection value can be avoided, and the in-focus subject and the background are focused. Therefore, it is possible to prevent the photographing lens from being largely driven.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims. 2 to 18 illustrate an example of the automatic focusing apparatus according to the present invention. FIG. 2 is an overall configuration diagram, FIG. 3 is an explanatory diagram of a focus detection optical system, and FIG. 4 is a CCD image. FIGS. 5A to 5D are explanatory diagrams of a focus detection area, FIG. 6 is a flowchart showing focus detection and focus adjustment procedures, and FIGS. 7A and 7B are first views. 8 (A) to 8 (A) to 8 (A) to 8 (C) illustrate switching of a second focus detection area.
(C) is an operation flowchart thereof, FIG. 9 is an explanatory diagram of a focus detection operation, FIGS. 10 and 11 are explanatory diagrams of a three-point interpolation operation method, and FIGS. 12 and 13 are operation flowcharts of focus detection. ,
FIG. 14 is an explanatory diagram of the tracking operation, FIG. 15 is an operation flowchart thereof, FIG. 16 is a diagram for explaining the range limitation, FIG. 17 is an operation flowchart thereof, and FIG. 18 is an operation flowchart of the lens drive control. is there. 10: Shooting lens, 13: Lens CPU 20: Camera body, 24: Focus detection optical system 25: CCD image sensor chip 30: AFCPU 40: AF display, 50: AF motor 80: Release button, 501: Shooting optical system 502 : Drive means, 503: first focus detection means 504: second focus detection means 505: selection means, 506: drive restriction means 507: restriction means, 508: judgment means 509: release operation member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/34 G03B 13/36

Claims (4)

(57) [Claims] 1. A focus detection means for detecting a focus adjustment state of an optical system, an operation means for starting focus detection, and a predetermined area in a photographing screen by the focus detection means when the operation means is operated. Control means for performing focus detection at a time point and expanding a focus detection area by the focus detection means to an area including the predetermined area and wider than the predetermined area when a predetermined time has elapsed since the operation means was operated. And a focusing device. 2. A focus detecting means for detecting a focus adjustment state of an optical system; an operating means for starting focus detection; and a predetermined area in a photographing screen by the focus detecting means when the operating means is operated. At the time when the focus detection by the focus detection means is performed a predetermined number of times after the operation means is operated, the focus detection area by the focus detection means includes the predetermined area, and And a control means for enlarging the image to a wide area. 3. A focus detection means for detecting a defocus amount according to a focus adjustment state of an optical system; a first control means for enlarging a detection area of the focus adjustment state by the focus detection means; A focus control device comprising: a second control unit that limits a detection range of the defocus amount by the focus detection unit when the detection area in the focus adjustment state is expanded by the control unit. 4. A focus detection means for detecting a defocus amount according to a focus adjustment state of the optical system, and a focus adjustment is performed by driving the optical system according to the defocus amount detected by the focus detection means. Driving means; first control means for enlarging the focus adjustment state detection area by the focus detection means; and if the focus adjustment state detection area is expanded by the first control means, the drive means A focus control device comprising: a second control unit configured to limit a driving amount of the optical system.